Chemical Processing March 2011

2009

Conservation efforts arebecoming a sustainability

imperative at plants

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RC

H 2

01

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Effectively Clean Tanks and Reactors

Select the Right Instrument-SystemValve

Clamp-On Flow Meter Gains Firm Hold

Keep Out of Hot Water

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5 CHEMICALPROCESSING.COM ● MARCH 2011

MARCH 2011 | VOLUME 74, ISSUE 3

Chemical Processing (ISSN 0009-2630) is published monthly by Putman Media Inc., 555 West Pierce Road, Suite 301, Itasca, IL 60143. Phone (630) 467-1300. Fax (630) 467-1109. Periodicals postage paid at Itasca, IL, and additional mailing offi ces. POSTMASTER: Send address changes to Chemical Processing, P.O. Box 3434, Northbrook, IL 60065-3434. SUBSCRIPTIONS: Qualifi ed reader subscriptions are accepted from operating management in the chemical processing industries at no charge. To apply for a qualifi ed subscription, fi ll in the subscription card. To nonqualifi ed subscribers in the United States, subscriptions are $68 per year. Single copies are $14. Canadian and foreign annual subscriptions are accepted at $115 surface per year. Single copies are $16. Canada Post International Publications Mail Product Sales Agreement No. 40028661. Canadian Mail Distributor information: Frontier/BWI, PO Box 1051, Fort Erie, Ontario, Canada, L2A 5N8. Copyright 2011 Putman Media Inc. All rights reserved. The contents of this publication may not be reproduced in whole or in part without the consent of the copyright owner. REPRINTS: Reprints are available on a custom basis. For price quotation, contact Foster Reprints, (866) 879-9144, www.fostereprints.com also publishes Control, Control Design, Food Processing, Pharmaceutical Manufacturing and Plant Services. Chemical Processing assumes no responsibility for validity of claims in items reported.

CONTENTS

3630

COLUMNS7 From the Editor: Is Water the New

Carbon?

9 Chemical Processing Online: Learn By Osmosis.

11 Field Notes: Keep Out of Hot Water.

19 Energy Saver: Optimize Your Steam System, Part I.

21 Compliance Advisor: EPA Expands Endocrine Disruptor Testing.

46 Plant InSites: Consider More � an Static Mixers.

50 End Point: EU Carbon Trading Gets Hacked.

DEPARTMENTS12 In Process: Converting Heat to Electricity

Gets Easier | Toluene O� ers Golden Oppor-tunity | Piloting Begins for Polyol Process

44 Process Puzzler: Choose Cleaning Sol-vent Wisely

47 Product Spotlight/Classifi eds

49 Ad Index

COVER STORY 22 Water Turns Green Global constraints on the supply of fresh water, declin-

ing water quality and increasingly stringent regulations on discharges are forcing chemicals companies to rethink how they manage and use their water resources. Optimization has become a corporate mantra.

FEATURES MAINTENANCE AND OPERATIONS

30 Effectively Clean Tanks and Reactors Automated clean-in-place systems o� er many bene� ts and,

so, their use has increased rapidly. However, determining the best cleaning equipment can be hard. � is article o� ers some guidelines to help you choose the most appropriate unit for your operation.

INTRUMENTATION AND CONTROL

36 Select the Right Instrument-System Valve A variety of choices exist for instrument-system valves. To

make the best choice, � rst ask: What do I want the valve to do? � is article reviews the basic types of valves, how they work, what functions they ful� ll, and what to think about when choosing one over another.

MAKING IT WORK

42 Clamp-on Flow Meter Gains Firm Hold Eastman Chemical’s site in Kingsport, Tenn., features a wide

range of piping carrying various chemicals. Seeking to improve � ow monitoring capabilities, the company investigated recent advances in � ow metering. Here, Eastman explains why it chose an ultrasonic device.

22

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7 chemicalprocessing.com march 2011

From The eDiTor

“Water is a

local, rather than

global, manage-

ment issue”

The rising cost and tighter regulation of water, coupled with concerns about long-term availability in many regions, is prompting many chemical companies to treat water conservation as an imperative in their sus-tainability efforts, as our cover story, p. 22, highlights.

“State of Green Business 2011,” a report released in early February by GreenBiz.com, trumpets the trend. In a section titled “Water Footprinting Makes a Splash,” it notes: “Water has been rising as a sustainability issue… we’ve referred to it as ‘the new carbon’ due to its parallels to companies’ efforts with their greenhouse gas foot-print: understanding and measuring it, reducing it, even offsetting it to the point of being ‘neutral.’”

Yet, the report points out that accounting for wa-ter can be even tougher than accounting for carbon. The amount of water used to make a product can vary significantly depending up where a plant is located and the process it uses. In addition, analyses should consider the source and quality of the water.

Nevertheless, it stresses: “Despite the complex-ity, companies are finding that conducting a water footprint analysis can help them seek opportunities for efficiency and optimization. It can also lead to innovation.” The report adds: “Growing pressures to disclose water footprints — much as companies have done with their carbon footprint — will lead many companies to dive in.”

Some of that pressure stems from an initiative of the Carbon Disclosure Project (CDP), London (which around 3,000 organizations from 60 countries use as a conduit for disclosing their greenhouse gas emissions). In 2010, it launched CDP Water Disclosure.

Paul Dickinson, CDP’s executive director, sum-marizes the thinking behind the effort: “So is water the new carbon? In the sense that water presents an equally pressing challenge to the long-term sustainability of business, yes it is, and the need for greater transparency and access to high quality information to inform and improve decision-making is just as vital. As companies have repeatedly demonstrated with carbon, what they measure they manage. Thinking about challenges in a strategic way will enable them to mitigate risks and identify opportunities, putting companies in a far stron-ger position to navigate a water-constrained world than would otherwise be the case.

“In other respects water is very different from car-bon. Whereas sustainable alternatives to carbon do exist, for water there is no substitute. The challenge therefore lies in managing what we have among competing users,

be they businesses, communities or ecosystems. Those competing users... are linked by the geography and politics of their local water systems, making water a local rather than a global management issue, even if its im-pacts can be felt across the world through the displace-ment of populations and higher commodity prices.

“CDP Water Disclosure’s goal is to make meaningful, systematic and comparable reporting on water a standard corporate practice globally, en-abling investors, companies themselves, governments and other stakeholders to put this data at the heart of their decision-making.”

The group sent questionnaires to 302 of the world’s 500 largest companies (according to the Financial Times’ “Global 500” rankings), and got 175 responses. “The strong response rate in this inaugural year is indicative of the high level of importance being placed on water by global corporations across sectors and geographies,” notes the report summarizing the findings (available at https://www.cdproject.net/CDPResults/CDP-2010-Water-Disclosure-Global-Report.pdf).

All ten chemical companies surveyed (a group that includes Akzo Nobel, BASF, Dow and DuPont) provided inputs, compared to 17 of 21 pharmaceuti-cal firms and just 15 of 51 oil and gas outfits. Besides presenting data, the report highlights best practices from companies in a number of industries.

Risks cited by chemical companies include: tougher regulation of water withdrawals and discharge quality, coupled with better contaminant-detection techniques, will boost treatment and management costs and make obtaining production licenses more difficult; and falling levels of both surface and groundwater will limit opera-tion and expansion of some facilities.

On the positive side, the companies see opportuni-ties to contribute to overall water availability through better water- and wastewater-treatment chemicals, water-efficient fertilizers, and processes and products to produce and recycle water.

In this green thrust one point is clear: How efficient-ly and sustainably a chemical firm uses water ultimately will affect whether it sinks or swims economically.

Mark rosenzweig, Editor in Chief

[email protected]

is water the new Carbon?Companies face increasing pressure to disclose, as well as optimize, water use

CP1103_07_Edit.indd 7 2/24/11 9:26 AM

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E-mail: [email protected]/Customer Service:(888) 644-1803 or (847) 559-7360

EDITORIAL STAFF

Mark Rosenzweig, Editor in Chief, x478

[email protected]

Amanda Joshi, Managing Editor, x442

[email protected]

Traci Purdum, Senior Digital Editor, x428

[email protected]

Seán Ottewell, Editor at Large

[email protected]

CONTRIBUTING EDITORS

Andrew Sloley, Troubleshooting Columnist

Lynn L. Bergeson, Regulatory Columnist

Ven Venkatesan, Energy Columnist

Dirk Willard, Columnist

DESIGN & PRODUCTION

Stephen C. Herner, Group Art Director, x312

[email protected]

Brian Hertel, Associate Art Director, x413

[email protected]

Rita Fitzgerald, Production Manager, x468

rfi [email protected]

EDITORIAL BOARD

Vic Edwards, Aker SolutionsTim Frank, Dow Chemical

Ben Paterson, Eli LillyRoy Sanders, Consultant

Ellen Turner, Eastman ChemicalBen Weinstein, Procter & Gamble

Jon Worstell, ConsultantSheila Yang, Bayer

ADMINISTRATIVE STAFF

John M. Cappelletti, President/CEOJulie Cappelletti-Lange, Vice President

Rose Southard, IT DirectorJerry Clark, Vice President of Circulation

Jack Jones, Circulation Director

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9 CHEMICALPROCESSING.COM MARCH 2011

CHEMICAL PROCESSING ONLINE

Learn By OsmosisIndustry leaders offer you insights via free webinars

WHEN I learned about osmosis in grade school I started fantasizing about how cool it would be to apply that theory to learning. If only I could place my text-books under my pillow and have the knowledge that lay within seep through to my brain during my sleep.

Trust me when I tell you it doesn’t work that way. To learn via osmosis I had to re� ne my technique. What I did � nd useful to help prepare for exams was to play tapes while I was doing simple chores. For example, while I was weeding the ower beds I also was learning how to conjugate verbs in French. (Écouter (to listen to): écoute, écouterai, écoutais, écoutant – See, I can still do it!)

Using the same theory, I have learned so much from Chemical Processing’s free Webinars and online panel discussions. I serve as moderator for these events and can’t help but pick up things.

Our production team does a terri� c job of rounding up top-notch speakers who are a part of the chemical processing community. From these folks I have learned the � ner points of energy-e� cient synchronous belt drives as well as how to pinpoint problems within steam and process-heating systems during the “Energy E� ciency” panel discussion.

I’ve also listened in as experts on the European Union’s REACH (Registra-tion, Evaluation, Authorization and Restriction of Chemical substances) mandate discussed compliance requirements across supply chains — from procurement to manufacturing to distribution — during “� e Impact of REACH & GHS on Your Supply Chain/Manufacturing Processes” Web event.

And speaking of the supply chain, during the “Best Practices In Inven-tory Optimization And Supply Chain Planning” event I learned how Eastman Chemical Co. balances supply with demand to ensure reliable and sustainable order ful� llment across complex chemicals environments.

I also was fortunate enough to sit in on the “Dust Control” panel discussion with several experts that I have met with in person to gain a better understanding of the risks involved with powder and dust in the manufacturing process. In addition to this event, ChemicalProcessing.com will soon be launch-ing a three-part video series on explosion protection featuring interviews I did with Guy Colonna, P.E., division manager, National Fire Protection Association. (Guy was one of the panelists on the Dust Control discussion.)

We have a great panel-discussion series set up for the rest of the year including emissions, alarm management and process safety. More information on these upcoming and on-demand events is located online at www.chemicalprocessing.com/webinars. And the videos I just mentioned will be avail-able at http://www.chemicalprocessing.com/cp_videos.

I bet you could learn a thing or two from our edu-cational o¢ erings. And if you have anything you’d like to teach, let me know. We’re always looking for good presenters.

TRACI PURDUM, Senior Digital Editor

[email protected]

I bet you could

learn a thing or

two from our

educational

offerings.

VISIT THE CARTOONGALLERY

All work and no play makes for a very dull day! Be sure to visit the Comical Processing cartoon gallery to get a much-needed chuckle.

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field notes

Keep Out of Hot WaterSome simple steps can ease heat exchanger commissioning

I KneW we were in trouble. The client, despite protests from me and operators with a few hun-dred years of experience, decided to run the heat exchanger without flushing the cooling tower. The water was sludge. We wasted a day cleaning out the plates.

Commissioning heat exchangers poses all sorts of dangers. Let’s review the basics so you don’t col-lect similar anecdotes.

A walk-through is essential and is the starting point for a successful commissioning. First, collect the data sheet on the exchanger and the drawings. Next, check the punch list to confirm pressure testing and cleaning have been completed. Verify that at least a visual inspection, especially of the tubesheet, tubes or plates, was done at the shop.

During the walk-through: 1) Ensure all inlets and outlets are fitted for temperature and pressure gauges; 2) Check foundation bolts — they should be loose at one end, preferably in a pipe sleeve for easy adjustment; 3) Allow space for equipment removal — four feet or so is necessary to take out a floating head or plates (You need a plan for safe maintenance); 4) Look at vent cocks and relief devices — they should be sized correctly and vented to a safe spot; 5) Verify the exchanger can be drained easily and hazardous waste is confined by a dike around the unit; 6) Make certain flow through new pipe to the unit goes through a filter or, at a minimum, a strainer; 7) Confirm all unused nozzles are blocked and flanges and other joints have correct and new gaskets; and 8) Check that relief valves are installed where they should be for thermal expansion of liquids — if liquids flow through the exchanger.

After the walk-through, consider a pneumatic leak test. Soap all joints and tighten as required. The ASME code only allows testing up to maxi-mum allowable working pressure or 50 psig — whichever is lower. The leak rate for N2 is 52 times that for water, so this is a good test before initial startup; helium is only about 1.12 times N2 and hydrogen is 2.2 (assuming laminar flow). Leak testing will help drive out moisture. However, the test won’t find a tubesheet leaking into a shell — that’s the shop’s job.

Now it’s time to go over the job safety analy-sis for the startup procedure. Ensure all safety equipment is in place and all instrument loops

are functioning, and review contingency plans for safety and environmental problems.

The type of heat exchanger to some degree affects the initiation procedure. Exchangers with fixed tubesheets offer the greatest challenge. With fixed tubesheets: 1) Start hot f low first with a condensing gas (e.g., steam) in the shell; or 2) Begin both f lows simultaneously when using liquids in both the shell and tubing. Otherwise, for other fixed tubesheet configurations (U-tubes, packed f loating heads, packed f loating tubesheets and internal f loating heads) start cold f low first, then hot.

Shutdowns are the opposite of startups. For example, with a U-tube heat exchanger, gradu-ally close off the hot flow, then shut the cold flow. There is one difference though: drain all steam condensate — slowly! It’s not a good idea to leave an exchanger full and unused even if only for a few weeks; corrosion and freezing can cause damage, especially to delicate tubing. So, either drain an idle exchanger and purge it with dry gas or peri-odically circulate fluids.

Make an allowance for venting, especially if an exchanger is full of inert gas or where condensing steam could pull a vacuum on tubing or a shell not rated for full vacuum. And don’t forget to vent to a safe location. Adjust all flows slowly and once the exchanger reaches desired operating temperature keep it there! Heat exchangers containing long thin tubes don’t handle thermal shock well — so avoid cycling them!

Your job doesn’t end once the exchanger is operating. Don’t forget to close the vents! Tighten bolts loosened for thermal expansion. Identify any potential maintenance problems, such as water hammer, poorly supported pipe, and relief lines that don’t allow for condensation drainage. Pinch points have been one of the leading dangers in working with heat exchangers lately and have led to at least one fatal accident. Workers have been crushed aligning a head or tubesheet. Review heat exchanger installation and make it easier and safer.

After commissioning the exchanger take the time to document the process. Practice makes perfect. dIrK WIllard, Contributing Editor

[email protected]

A walk-through is

essential and is

the starting point

for a successful

commissioning.

CP1103_11_FieldNotes.indd 11 2/23/11 11:50 AM

March 2011 cheMicalprocessing.coM 12

in process

Converting Heat to Electricity Gets EasierDevelopment promises to enable plants to produce electricity directly from waste heat

By dispErsinG nanocrystals of rock salt into lead telluride, researchers at Northwestern Uni-versity, Evanston, Ill., have created a material that can generate electricity directly from heat far more efficiently than previously possible.

The researchers say the material boasts a high “thermoelectric figure of merit” — the material can convert up to 14% of waste heat to electricity.

“It has been known for 100 years that semicon-ductors have this property that can harness elec-tricity,” explains Mercouri Kanatzidis, professor of chemistry at Northwestern’s Weinberg College of Arts and Sciences. “To make this an efficient process, all you need is the right material, and we have found a recipe or system to make this material.”

Chemical plants producing high grade heat could make their systems more efficient by using this new technology, Kanatzidis notes. However, applicability isn’t limited to industrial sites. “Thermoelectric technol-ogy is scalable. So you can make small and portable gen-erators. It can be very attractive where other technologies are not suitable, e.g, [for handling] vehicle exhaust.”

Past attempts at nanoscale inclusions increased the scattering of electrons, which reduced overall conductivity. The Northwestern team overcame this problem by using, for the first time, nanostructures in lead telluride (PbTe) to reduce electron scattering, while still increasing the material’s energy conversion efficiency. More details appear in a recent article in Nature Chemistry by Kanatzidis and his coworkers.

“We can put this material inside of an inexpensive device with a few electrical wires and attach it to some-thing like a light bulb,” says Vinayak Dravid, professor of materials science and engineering at Northwestern’s McCormick School of Engineering and Applied Science and a co-author of the paper. “The device can make the light bulb more efficient by taking the heat it generates and converting part of the heat, 10 to 15%, into a more useful energy like electricity.”

Within the next year the team hopes to boost the thermoelectric figure of merit to 2 from its cur-rent 1.7; ultimately, it might reach 2.5 to 3, notes Kanatzidis.

In addition, the team already is working with private industry to commercialize the material, a process which Kanatzidis expects should take two to four years. Industrially, the technology could be implemented via direct contact with a hot waste stream or contact with a heat-transfer fluid heated by the waste stream.

“One challenge remaining is the full scale-up on the multi-kilogram and ton scale. Another is the demonstration of long-term stability … to high temperatures and thermal cycling,” says Kanatzidis. “It is stable over the timescale of months and years, but we do not know about tens of years.”

Material developer

Figure 1. Northwestern University professor Mercouri Kanatzidis and fellow researchers have developed a material that can generate electricity directly from heat. Source: Northwestern University.

Jan 10 Feb 10 Mar 10 Apr 10 May 10 June 10 July 10 Aug 10 Sep 10 Oct 10 Nov 10 Dec10

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61000

Economic snapshot

Both shipments and capacity utilization continued to rise.Source: American Chemistry Council.

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Toluene OffersGolden OpportunityA NEW catalyst enables solvent-free low-tempera-ture selective oxidation of toluene to benzyl benzoate at high yield, report researchers at Cardi� University, Cardi� , U.K., and Lehigh University, Bethlehem, Pa. � e catalyst — gold/palladium nanoparticles on a carbon support — boasts turnover numbers around 30 times higher than other heterogeneous catalysts for the reaction. “� is opens up the possi-bility of using hydrocarbon feedstocks in a new way to form intermediates and � nal products for use in the chemical, pharmaceutical and agricultural busi-ness sectors,” notes Graham Hutchings, a professor in the Cardi� School of Chemistry who was on the research team.

� e catalyzed reaction at 160°C produces benzyl alcohol, benzaldehyde, benzoic acid and benzyl benzo-ate but no carbon dioxide. Selectivity to the benzoate exceeds 94%. “Catalyst activity could be higher, but it is usable,” notes Hutchings, who adds that the next step in the development is to increase catalyst activity.

� e nanoparticles are 2–5 nm in size and were

prepared by sol immobilization. � ey contain gold and palladium at about a 1:1 ratio by weight — the addition of palladium signi� cantly enhances the con-version — and are stable and reusable, the researchers say. More details appear in a report in Science.

� e catalyst now is in the form of a powder but could be made into pellets, adds Hutchings, who fore-sees use in either a stirred-pot or continuous � ow reactor.

Catalyst Researcher

Figure 2. Prof. Graham Hutchings of the Cardiff School of Chemistry was part of the research team. Source: University of Cardiff.

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in process

Piloting Begins For Polyol ProcessBayer Technology Services, Leverkusen, Germany, has started up a kilogram-scale pilot plant at Chempark Leverkusen that uses carbon dioxide to make polyols, a key raw material for polyurethane. The process promises to provide an outlet for CO2, whose emissions contribute to global warming, while also supplanting petroleum for polyol production, notes the company.

The key to the process is a catalyst discovered by researchers at Bayer and the CAT Catalyst Center, which Bayer and RWTH Aachen University, jointly run, that enables efficient use of the CO2.

RWE Power is supplying the pilot plant with CO2 recovered via a scrubber from flue gas at its lignite power plant in Niederaussem.

Bayer MaterialScience now is testing the poly-ols, which are used primarily to make soft and rigid foams, at one of its existing plants.

Meanwhile, RWTH Aachen University is con-ducting ecological and economic studies of all stages of the process and comparing it with conventional processes and products.

The process stems from the “Dream Production” project. This brought together Bayer, RWE, RWTH Aachen University and the CAT Catalyst Center.

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energY saVer

Optimize your Steam System, Part IA simple four-step approach can improve steam efficiency

FOr mOSt process plants, steam systems are so vital they could be compared with the human body’s blood circulating system. Hence, consider steam system losses just as life-threatening as a severe blood loss in our own bodies.

Maintaining an efficient and reliable steam system is very critical for the plant’s process integrity and financial health. Recently, I came across a plant that survived market recessions successfully simply because it optimized its steam system costs when market conditions were good. In this two-part series, we will review four steps for steam system optimization.

Step 1: Review your steam generation systems. First, we have to ask ourselves, ”Did we convert our purchased fuels into steam at the best pos-sible efficiency?” Reviewing parameters for stack temperature and stack oxygen content could help identify deviations and the best possible efficiency levels. The parameters relevant to cost optimization include fuel costs and unutilized waste, such as heat steam generation.

At many sites I visit, one of the most common areas in need of steam system efficiency improve-ments is the steam generator or boiler. The two combustion optimization efforts — excess air control and additional heat recovery that we discussed in our first two columns, “Take a Fresh Look at Your Process Heaters” — Part I and II (www.chemicalprocessing.com/articles/2011/fresh_look_at_process_heaters.html and www.chemicalprocessing.com/articles/2011/take-fresh-look-process-heaters-part-2.html), are also applicable to the fired boilers.

Boilers offer additional opportunities for efficiency improvements. One is the blowdown control. Though well-established, automatic blowdown systems are still not available in many operating boilers. Depending upon the boiler’s feed water quality, blowdown losses could change from insignificant to significant levels. Adding an automatic blowdown controller could easily reduce and maintain the blowdown losses, instead of depending on manual control only. Even with an automatic blowdown system in service, it is necessary to regularly monitor the feed water and drum water qualities to maintain the desired blowdown levels.

Another common efficiency improvement op-

portunity is the blowdown heat recovery. If there is no blowdown heat recovery system in place at your plant, consider adding one that would recover f lash steam and sensible heat separately to conserve feed water and reduce waste water.

Step 2: Perform a critical evaluation of the steam distribution system. Steam distribution systems commonly suffer from both visible and invisible losses. Continuous f low of high-pres-sure steam to a lower pressure header through a pressure reducing valve (PRV) is one of the invisible losses. Supplying steam from higher-than-required pressure to a user is another kind of invisible loss.

[For details about the use of models to provide insights, including for dealing with upsets and transient conditions, see “Consider Dynamic Simulation for Steam System Design,” www.ChemicalProcessing.com/articles/2010/186.html.]

The concept of cogeneration is to recover the mechanical energy in reducing the high-pressure steam into low-pressure steam and then utilize the latent heat for process heating. It may be worth running some pumps or blowers with steam, if there is a constant f low of high pressure steam through a PRV.

Space heating during winter months and most tank farm heating require only low-pressure steam. If you notice a high-pressure steam supply to such users at your site, reconsider supplying low-pressure steam to them.

Failed steam traps in closed condensate col-lection systems are another kind of invisible dis-tribution system loss. Whenever there’s excessive backpressure in the condensate return system or excessive venting at the collection tank, the most probable cause is typically failed steam traps. A systematic steam trap survey could identify the problem.

Leaks and missing insulation are some of the visible losses in a steam distribution system. Standardized methods already exist to fix these visible losses and so do not delay in taking these obvious actions.

Next month, in Part II, we will cover steps three and four. Ven V. VenkateSan, Energy Columnist

[email protected]

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compliance advisor

EPA Expands Endocrine Disruptor Testing Agency mandates screening of more chemicals and issues guidance

On nOvEmbEr 17, 2010, the U.S. Environmental Protection Agency (EPA) announced the second list of chemicals for which EPA intends to issue test orders under the Endocrine Disruptor Screening Program (EDSP). EPA also released its draft policies and proce-dures for requiring Tier 1 screening under the EDSP, and a new guidance document outlining weight-of-evidence (WoE) policies. This column explains why the issuance of the second list of EDSP screening chemicals, and the proposed policies and procedures for obtaining testing, are important developments.

nEw ADDiTiOns

The second list of chemicals includes pesticides, per-fluorocarbon compounds (PFC), pharmaceuticals, and those used as plasticizers or in the production of phar-maceutical and personal care products. The chemicals include a significant number of Toxic Substances Con-trol Act (TSCA) chemicals that EPA has identified as priorities under the Safe Drinking Water Act (SDWA) and that may be found in sources of drinking water.

PuTTing iT in PErsPEcTivE

The draft policies and procedures are intended, ac-cording to EPA, to supplement policies and procedures published in April 2009. The policies and procedures address both substantive and administrative issues.

EPA’s draft, “Weight-of-Evidence Guidance Docu-ment: Evaluating Results of EDSP Tier 1 Screening to Identify Candidate Chemicals for Tier 2 Testing,” is intended “to set forth some general principles, criteria and considerations EPA generally believes to be relevant using a WoE approach to evaluate data submitted as part of EPA’s EDSP” Tier 1 screening assays.

EPA summarizes the EDSP as a “two-tiered paradigm for screening and testing chemicals with the potential to interact with the endocrine system.” Tier 1 screening identifies substances that have the potential to interact with the estrogen, androgen or thyroid hor-monal systems. Tier 2 testing aims to identify further and characterize chemical-induced interactions with estrogen, androgen or thyroid hormonal systems for risk assessment. EPA states that it expects the diversity in en-docrine endpoints within the Tier 1 screening assays to provide corroborating information and support a WoE evaluation to yield a decision as to whether the chemical identified in Tier 1 requires additional testing in Tier 2.

The guidance itself notes that this approach is not meant to be any different in its application to the

endocrine program than from other areas of scientific assessment where EPA utilizes a WoE approach. It is interesting that this announcement acknowledges that the approach will be used to evaluate “other scientifically relevant information” — which has been a controversial element of EPA’s endocrine testing program. Many interested parties insist that if EPA fairly and fully evaluates the body of existing data already developed and submitted to EPA, the need for the now-required “lower-tier” endocrine effect tests would not be justified.

DiscussiOn

This list builds on the earlier requirements originating under the 1996 Food Quality Protection Act. EPA’s endocrine testing program first broadened to include chemicals used in pesticide formulations that other-wise would be subject to TSCA testing. This latest list expands EPA’s domain from pesticide and toxics programs to chemicals in other EPA program areas such as drinking water.

Expansion of the endocrine program’s domain indi-cates that EPA may intend to use its authority to address concerns with other chemicals arising out of other pro-grams and agencies; and to compensate, to some degree, for the shortcomings in testing authority found in other statutes administered by both EPA and other federal agencies. The latest list, for example, incorporates phar-maceuticals that have drinking water exposures as EPA believes they may present endocrine effect risks. This lets EPA take the lead from the Food and Drug Administra-tion in this regard. EPA’s approach could greatly expand the number of chemicals subject to testing orders.

Chemical manufacturers and downstream users of these chemicals should monitor this program care-fully. Although a chemical’s inclusion in the second list doesn’t mean the substance is an endocrine disruptor, certain inferences will nonetheless be drawn and manu-facturers and users of chemicals subject to screening could be subject to deselection or other adverse com-mercial consequences. Stakeholders should monitor the docket, be aware of comments submitted, and watch for new developments as to chemicals of concern. Lynn bErgEsOn, Regulatory Editor

[email protected]

Lynn is managing director of Bergeson & Campbell, P.C., a Wash-

ington, D.C.-based law firm that concentrates on chemical industry

issues. The views expressed herein are solely those of the author.

Chemical manu-

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downstream

users of these

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CP1103_21_Comp.indd 21 2/23/11 11:52 AM

MARCH 2011 CHEMICALPROCESSING.COM 22

PRESSURE TO reduce water consumption and switch to other, often lower-quality, sources is prompting a major rethink about how chemical companies manage and use their water resources. Optimization has become a corporate mantra.

“An increasing challenge is water scarcity and ensuring that the population has enough for their needs, so we are seeing increasing restrictions on where industry can get water — plus increasing cost. Industry is also seeing signi� cant increases in waste-water sewer fees — disproportionately so compared with homes,” notes Derek Miller, North American industrial water manager, Air Products and Chemi-cals, Bethlehem, Pa.

“Our customers are facing three pinches in terms of their water utility footprints,” says Glen Messina, global business leader, chemical monitoring solutions

Conservation efforts arebecoming a sustainabilityimperative at plants

By Seán Ottewell,Editor at Large

Water TurnsGreen business — water and process

technologies for GE Power & Water, Trevose, Pa. First, global constraints on the

supply of fresh water are growing: regulations now are beginning either to prevent companies

from using municipal fresh water or taking more from rivers.

Second, companies face declining water qual-ity — for example, plants more and more must take discharge water from municipal treatment plants.

� ird, increasingly stringent regulations worldwide govern discharges, even sometimes banning them. Traditional tailing ponds are being closed down, so new ways are needed to recondition the water.

VENDORS RESPOND

“Between 2006 and 2010, we doubled our investment in the technologies in these areas and we expect this to double again in the next three to � ve years. We think we have a signi� cant advantage here because of the breadth of our portfolio,” notes Messina.

� e company has launched an advanced system for cooling water. � is comprises GenGard anti-fouling and anti-corrosion treatment coupled with the TrueSense automation and control platform that allows continuous monitoring and dosing of the cooling water.

GE also o� ers a broad portfolio of � ltration systems, including basic paper cartridges, reverse

CP1103_22_29_CoverStory.indd 22 2/24/11 3:59 PM


osmosis (RO), ultra� ltration, membrane bioreactors (MBRs), electrodi-alysis, electrodialysis reversal and electrodeionization.

“� ese systems allow us to take a raw discharge and convert it into drinking water quality. Industrial users today want to meet regulatory standards for either discharge or recycling back into the front end of their processes,” explains Messina.

In addition, the � rm has established an integrated water solutions group to help customers look at the water utility footprint of existing plants and to o� er engineering services for new plant construction. “…More than a dozen of the Fortune top 50 companies have approached us to carry out an evaluation of their existing water utility footprints,” he notes.

GE Power & Water has dramatically decreased its own water usage. In 2008 the company set a goal of a 20% reduction (versus a 2006 baseline) by 2012. It achieved a 30% cut by the end of 2009 and is now working on the next benchmark.

“Each application is customized for each of our plants: there is no cookie-cutter solution. At the same time it is important to remember that some of these improvements are based on changing operations. For example, a simple re-routing of water pipes reduced usage at one site. So cold water � ow redesign can be very important while not be-

ing a major capex [capital expenditure].” Looking to the future, Messina points to the challenges posed by the need to remove heavy metals such as mercury. In some countries,

the legal requirement is for � ve parts per trillion: “� is is a very complex demand to deal with and there’s no one magic solution: a

combination of technologies will be needed to achieve this.”Dow Water & Process Solutions, Edina, Minn., is focused on

the twin requirements of reduced costs and increased sustainability.“Industry generally will have to be very, very much more

e¢ cient so that water use can be focused on using it for drinking and food production. Reducing water use and then reusing it in

the system is therefore becoming more important for the forma-tion of long-term, sustainable enterprises,” says Snehal Desai, global marketing director.

One major technology focus for the company is a new fouling-resistant (FR) series of � lters for waste treatment centers. “� is is particularly important in

the production of chloralkalis, which requires a lot of water. Standard RO technology was used by one customer to recycle the water, but they wanted to increase the times between � lter clean-ings,” notes Desai.

Customers increasingly are talking about the net energy footprint to treat water (Figure 1), too, prompting Dow to develop low energy technologies that, for example, need less pressure drop across � lters. A low energy FR technology is due to be launched later this year.

MBRs are � nding greater use to reduce the organic and suspended load in water streams, which then can be polished further with an RO system. Desai points to the new M20 series of MBR technologies as


being crucial for users that need to produce water that can be re-used again in the process stream.

He also cites geographic challenges. “Companies on the Houston Ship Channel have big issues with fouling because the surface water can be very dirty

there. On the Gulf Coast, the challenge is to provide cost-e� ective desalination technol-ogy. In China it also depends on sector and location of the plant, but the government is being very aggressive now in pushing water cleanliness.”

Dow Water & Process Solu-tions is focusing its R&D e� orts on three main areas: improved rejection of salt from water, lower energy use and better fouling resistance.

Typically, required salt rejec-tion is 99.5–99.7% but ultrapure water, which is a rapidly growing market, demands even better performance — this often involves RO coupled with ion exchange. One of the big costs here is resin regeneration; the company now is actively working on this.

Work also is advancing on nano� ltration. � is is important where divalent ions such as cal-cium and sulfate must be rejected. For example, in oil production, injecting water with a high sulfate level increases scaling in wells.

PLANT INITIATIVE

Bayer HealthCare aims to reduce water consumption at its Berkeley, Calif., site by 10% by 2015 from a 2010 baseline. “We know exactly what our total water consumption is and the volume of our waste stream, so we can drill down and see exactly how much water is used in each process, each building and so on,” says � omas Daszkowski, vice president, BTS Process Tech-nology (BTS). BTS is the tech-nological backbone of the Bayer group worldwide, developing and implementing process and plant optimization for the company.

One of the major uses of water at Berkeley is in cleaning opera-tions. � ey rely on high purity water also known as water-for-injection (WFI). Such water is expensive because it has to be puri� ed by processes such as RO or distillation and then stored and distributed at high temperature. So reducing its use also pares site demand for natural gas and electricity. “Our evaluation has

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showed us that all our resources are linked, and making a conscious effort to reduce one resource can help reduce our overall consumption as well,” notes Daszkowski.

Operations are benefiting from a new skid, de-signed by the Berkeley site’s PAT [process analyti-cal technology] group, to minimize over-cleaning. “This skid includes many of the types of analytics such as a total organic carbon (TOC) analyzer, dual wavelength UV analyzer, a pH analyzer, and conductivity analyzers that are used for cleaning validation, all packaged together in a real-time, inline process monitoring tool,” says Chris Wil-liams, BTS PAT manager. Early use of the skid points to a number of pluses, including an average water consumption reduction of up to 50%.

Pipeline projects are reaping benefits too. “The project team has looked at many other water savings through redesign of old systems. The RO system in one of our buildings sends close to 8 million gallons of water a year into our drains. Repiping the drain to our cooling towers lowered our consumption of city water and helped us re-duce site consumption by approximately 7%,” says Arun Nedungadi, sustainability engineer.

Another project reuses tower water that cools clean steam condensate, saving about 2.5 million gallons of water annually. “In addition, 1.5 million gallons of condensate that was being sent to drain is now being redirected to our main steam plant where a redesign of oversized pumps has halted excessive water-hammering,” adds Nedungadi.

“Overall, these projects have helped cut water consumption at the Berkeley facility by 12 mil-

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Figure 1. Companies are paying increasing attention to the net energy footprint to treat water. Source: Dow.


lion gallons, approximately 10% of the total in 2010 — this is a major step forward in helping us realize our 2015 goals,” explains Ron Roberts, principal engineer, central utilities.

A key aspect of sustaining these changes is to engage company employees in the conservation ef-forts. “We will be looking to include employees in identifying and implementing projects by having dedicated energy teams for our mission-critical buildings on site,” says David Woodard, principal, health environment & safety group.

WASTEWATER FOCUS

As part of its overall sustainability goals, Air Products is committed to cutting its water con-sumption by 10% by 2015 versus 2009, and is promoting water reuse.

In addition, the company is helping its indus-trial clients improve wastewater treatment: “For industrials that have wastewater treatment plants, they can face challenges meeting production capacity changes. The desire to increase treatment capacity without major capital investment is a

good application for oxygen,” explains Miller. Retrofitting pure oxygen onto existing processes that rely on air and activated sludge can double treatment capacity (Figure 2), while adding high efficiency mixers at the same time can reduce power consumption by up to 50%, he notes.

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Figure 2. Switching from air to oxygen for wastewater treatment can double capacity. Source: Air Products and Chemicals.


Air Products also is helping customers to reuse their own wastewater, especially when signi cant quantities of organics or nutrients are present and use of oxygen is a good t. � ere’s a strong focus on MBRs because they are high-intensity, have a small footprint and produce very high quality water that can be reused in a number of on-site applications such as cooling-water makeup.

“However, while you get a lot more treatment/volume with an MBR, the use of high sludge concentrations can lead to limitations getting su� cient oxygen into the wastewater using conventional air-based aeration. So we believe that the optimum MBR design would run on pure oxygen. We have a couple of these up and running

now in industrial applications and are close to commercializ-ing a further optimized system,” he reveals.

Overall, the company sees an increasing drive from industry to do more wastewater treatment in less space, reduce waste disposal costs and extract value in the form of water reuse and energy. “We are working to make our oxygen technologies more e� cient and, with part-ners, are developing complete treatment systems designed to take advantage of the bene ts of oxygen,” he says.

REDUCING INTAKE

At its Rotterdam site in the Netherlands, Akzo Nobel has cut fresh water consumption while increasing the concentration of saline water that its treatment

Figure 3. Australian refi nery no longer discharges wastewater and uses treated sewage water. Source: BP.

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plant can handle. Salt concentration has risen from its original maximum concentration of 2% as process in-tensi� cation and expansion projects took place.

“Our � rst choice, an anaerobic biological system, did not work. But we found we could use an aerobic system instead. By slowly creating and maintaining a biomass that was adjusted to the higher salt concen-trations, we were able to operate at 3% salts. Large water savings were realized and we could operate the installation at a higher total capac-ity,” notes a spokeswoman.

At its Delfzijl, the Netherlands, site, Akzo has installed an efficient co-generation plant to generate steam for a multi-effect evapora-tion process, with condensate puri-fied and reused in a continuous recycling system.

Half a world away, the BP re� nery in Kwinana, Australia, (Figure 3) now sends its wastewater to a water recycling plant instead of discharging it into the Cockburn Sound. In addition, the company is taking in treated sewage water from a nearby e� uent plant. � is water, treated by intense micro� ltration and RO, is so pure that it would leach metal from standard piping. So BP has installed glass-reinforced epoxy pipelines.

A Safl ex™ 2000 system cleans tube bundles twice as fast as manual water jetting. Index the fl exible lances manually, or from a distance using an optional X-Y manipulator with wireless controls.

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RELATED CONTENT ONCHEMICALPROCESSING.COM

“Wastewater Analysis Center,” www.ChemicalProcessing.com/knowledge_centers/hach/index.html

“Cooling Water Treatment Provides Sound Results,” www.ChemicalProcess-ing.com/articles/2010/090.html

“What’s On Tap for Water,” www.ChemicalProcessing.com/ar-ticles/2008/133.html

“Better Water Technology is On Tap,” www.ChemicalProcessing.com/articles/2007/112.html

“Optmize Water Use,” www.Chemi-calProcessing.com/articles/2005/571.html



TANKS, REACTORS and other vessels can be cleaned in many ways. However, use of automated clean-in-place systems has increased rapidly. � at’s because automated devices clean more thoroughly than other methods, dramatically reducing or eliminating risk of cross-contamination caused by product or cleaning-chemical residue.

Automated cleaning provides other bene� ts as well:

• faster return to service of vessels — downtime can be reduced by as much as 90%;

• decreased water and chemical use;• lowered wastewater disposal costs;• improved safety because workers no longer

have to enter tanks; and • better sta productivity because people can

be deployed to other tasks.� e decision to automate is easy — a plant usu-

ally can recoup the cost of an automated system in the � rst few months of operation through reduced chemical and water costs and increased produc-tion. However, determining the best cleaning equipment can be hard. If vessels are large, have

obstructions such as mixing paddles, and con-tain sticky, � ammable or toxic residues, selection can get challenging. So, this article o ers some guidelines to help you choose the most appropriate equipment for your operation.

THE STARTING POINT

Before you begin evaluating cleaning equipment, you must understand your cleaning requirements.

Residue. First, assess the residue to determine what’s required to remove it. Is the substance sticky or easily cleaned? Can a cleaning liquid dissolve it? If not, what level of impact is needed to break it up and wash it away?

(If you’re not sure how to remove the residue, a cleaning equipment vendor can use computational � uid dynamics modeling to determine the � ow rate, operating pressure, coverage and the position of the spray head for complete cleaning of the ves-sel and any permanently installed equipment.)

Cleaning agents. Once you understand the resi-due’s characteristics, you can sort out which clean-ing agents to use. Chemical additives typically are

Effectively CleanTanks and Reactors

Choose the right equipment to avoid costly contamination problems

By Anthony Wood, Spraying Systems Co.

CP1103_30_35_Maint.indd 30 2/23/11 11:36 AM


employed to remove contaminants, improve tank wetability and reduce foam. Heat can boost the cleaning action of many water-based detergent chemicals.

Vessel size. Interior surface area and distance between the walls substantially a� ect selection. Evaluate the spray distance, usually measured in terms of the vessel diameter, but also consider vessel length and height. For example, for a 20-ft.-dia., 40-ft.-long vessel, use two vessel cleaners that each can handle up to 20 ft. or a single vessel cleaner that can handle up to 40 ft. You many need multiple nozzles if the spray can’t reach a part of the vessel due to internal obstructions such as an agitator (Figure 1).

Impact. � e level of impact needed to thor-oughly clean vessels depends on the residue, cleaning chemicals and water temperature. Hard-to-clean residues require greater impact. � e theo-retical spray impact, I, equals K Q P½ where K is a constant, Q is � ow rate and P is liquid pressure.

If you’re not certain how much impact is needed, a cleaning equipment vendor should be able to provide guidance and impact data. Some manufacturers will conduct tests in their spray labs with your speci� c residue to optimize cleaning performance. Another option is a short-term lease on a pumping system and vessel cleaner, so you can evaluate the equipment in your production en-vironment. Some vendors also o� er no-obligation equipment trials.

Safety. Is the residue, cleaning solvent or environment toxic or � ammable? � e answer will signi� cantly in� uence the type of equipment you choose.

Once you understand your cleaning require-ments, the next step is to evaluate the cleaning equipment. So, let’s look at what’s available and the pros and cons of each option.

THE TYPE OF POWER

� e � rst decision is whether to use a machine pow-ered by � uid or a motor.

• Fluid-driven cleaning machines use � uid to spin a turbine that powers a gear set (Figure 2). � e nozzle assembly rotates as the hub revolves around its central axis. � e higher the liquid pres-sure and � ow, the faster the rotation.

• Motor-driven cleaning machines rely on an external electric or air motor to drive the nozzle as-sembly (Figure 3). � e nozzles revolve around the central axis of the nozzle assembly.

Both machines operate at high pressures, provide 360° cleaning coverage and suit large vessels (up to 100 ft. dia.). � ey often o� er comparable cleaning performance. However, there are several operational di� erences.

Clogging. A � uid-driven machine is more prone to clogging. As � uid passes through the device, debris can accumulate in the internal � ow passages or get caught in the gears. When this happens, the machine stops working because the gears no longer can rotate. Verifying operation is crucial but can be challenging — it’s di� cult to visually observe the inside of a large vessel.

need multiple nozzles if the spray can’t reach a part of the vessel due to internal obstructions such as an

manufacturers will conduct tests in their spray labs

equipment. So, let’s look at what’s available and the

OPTIMIZE CLEANINGSix steps may provide significant benefits:

1. Reduce use of heated water. Hot water is costly but frequently is viewed as a necessary evil to remove some residues. However, increas-ing impact often can often get the job done and cut or eliminate the need for hot water.

2. Minimize “striping.” Vessel cleaners pro-vide 360° coverage. However, the solid stream sprays don’t overlap as they rotate, so there’s a small distance between the sprays and thus a so-called striping effect. The greater the dis-tance the nozzles are from the vessel walls, the greater the distance between the sprays. The best way to minimize striping is to use a four-nozzle hub rather than the standard two-nozzle hub. This will cut striping in half.

3. Change spray head position. Use an ad-justable ball fitting to clean vessels in sections. Clean the top half of the vessel, then lower the device and clean the bottom half of the vessel or change the angle to clean difficult locations.

4. Decrease the number of cleaning cycles. Simple adjustments to pressure and flow may enable a reduction in the number of cycles needed for thorough cleaning. To increase impact and cleaning efficiency it’s far more effective to increase flow than pressure. Doubling flow rate boosts impact as much as 100%; doubling pressure only provides 40% more impact.

5. Recirculate. Do you spray and drain? Check into recycling your cleaning solution if you aren’t using hazardous materials and your water is debris free.

6. Activate cleaning with the flip of a switch. Hard piping your vessel cleaner in place can save time and reduce labor costs. Consider permanently installing the device if the material or its temperature won’t damage the cleaning equipment.

CP1103_30_35_Maint.indd 31 2/23/11 11:37 AM


A motor-driven machine will continue to oper-ate even with debris in the nozzles. The external motor ensures continued rotation and cleaning. Plus, you easily can hear the sound from the motor and verify operation without having to inspect the vessel.

If you’re using less than pristine water and it’s difficult to see inside your vessel, a motor-driven machine is a better choice.

Cleaning cycle time. If short cleaning cycles are a priority, consider a motor-driven unit. Using an electric motor, cycle times remain constant regard-less of operating pressure and flow rate. With an

air motor, you can increase air pressure to make the nozzle hub rotate more quickly.

Fluid-driven machines can achieve comparable cycle times to motor-driven machines by raising pressure. However, operating at higher pressures increases wear of internal parts and results in more frequent maintenance.

Sparking or explosion risks. Explosion-proof electric motors are available or you can use an air motor. Or you may be able to change cleaning solvents to eliminate the explosion hazard without negatively impacting cleaning. Other options in-clude increasing humidity in the vessel to mini-

Fluid-driven Machine

Motor-driven Cleaner

Figure 2. Rotational speed depends upon liquid pres-sure and flow.

Figure 3. Electricity or air can power the motor.Figure 1. The size of a vessel or internal obstructions may require use of multiple nozzles for effective cleaning.

Multiple Nozzles

CP1103_30_35_Maint.indd 32 2/23/11 11:37 AM



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mize the risk of static electricity, prevent complete drying of the residue and ease residue removal.

OTHER CONSIDERATIONS

Fluid-driven machines generally cost less than mo-tor-driven ones, although the cost depends upon the size of the machine. However, fluid-driven machines have many internal parts and disassem-bly, replacement and reassembly of worn parts can be time-consuming. In some cases, maintenance requires a special tool kit. Factory refurbishing usually is recommended based on hours of use.

Motor-driven machines require minimal maintenance and are serviced easily by the user. The motors are positioned outside the tank, ensur-ing long life and minimal exposure to harmful solvents.

Which is a better choice? Fluid-driven ma-chines usually cost less. Motor-driven machines are less expensive to operate and maintain. The specifics of your operation such as water quality and hours of use will determine which is more cost-effective.

If you’ve determined that a motor-driven cleaner is your best choice, you must select between two types:

1. Machines with nozzles in a fixed position. These can be permanently installed or moved from vessel to vessel but the cleaning head is in a fixed position on the unit. Maximum operating pressure is 5,000 psi. Various types of motors are available and users specify extension length, flange size and a two- or four-nozzle hub.

2. Machines with retractable nozzles. These permanently installed units offer a higher level of automation (Figure 4). A pneumatic mechanism inserts and retracts the extension and the clean-ing head. A control panel allows setting multiple stopping points between full insertion and full re-traction to position the nozzles where more impact is required or to clean around obstructions. The control panel can be located away from the vessel for convenience or safety. Maximum operating pressure is 4,000 psi.

The properties of the residue or the cleaning agents and your desired level of automation will determine which option is best for your operation.

PERFORMANCE VALIDATION

Once you’ve selected and installed a new cleaning machine, how do you know if it’s doing its job?

Visual inspection is one option. Monitor the machine to make sure it’s working and inspect the

Retractable Head

Figure 4. Cleaning head can be set at any position from zero to full extension.

CP1103_30_35_Maint.indd 34 2/23/11 11:37 AM

inside of the vessel when the cleaning cycle is com-plete. Swab or ribo� avin tests are common ways to verify cleanliness. Of course, the viability of these approaches depends on the size and location of your vessel.

Another option is using an acoustic monitoring device (Figure 5). A sensor mounted to the exterior of the tank “listens” to the performance of the cleaning equipment and identi� es variations from a pre-determined baseline. It instantly can detect rotation failure and changes in rotation speed or spray pressure and can notify operators via audible or visual alarms. � e monitoring device also transmits performance documentation for qual-ity control and record keeping. It obviates visual monitoring and post-cleaning tests.

ANTHONY WOOD is a tank cleaning specialist at Spray-

ing Systems Co., Wheaton, Ill. E-mail him at Anthony.wood@

spray.com.

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Acoustic Monitoring Device

Figure 5. Unit mounted on onside of vessel detects loss of rotation and variations in rotation speed and fl uid pressure.

CP1103_30_35_Maint.indd 35 2/23/11 11:38 AM


Picking a valve for an instrument system means sorting through what may seem an overwhelm-ing number of choices. Just to name a few, there are ball, diaphragm and bellows valves, as well as check, excess flow, fine metering, gate, multi-port, needle, plug, rising plug, relief and safety valves. And each of these comes in many sizes, configu-rations, materials of construction and actuation modes.

To make the best choice, it’s always good prac-tice to first ask: What do I want the valve to do?

Most valves fulfill one of five primary func-tions — on/off, flow control, directional flow, over-pressure protection and excess flow protection. Matching valve type to function is the first and most important selection step. It’s not unusual to

see misapplied valves, such as a ball valve used for throttling flow. In some cases, the mismatch can be catastrophic, say, if a ball valve were in a high-pressure oxygen system. With a source of ignition, the sudden burst of oxygen — enabled by the fast opening of the valve — could lead to a fire.

So, here, we’ll review the basic types of valves, how they work, what functions they fulfill, and what to think about when choosing one over another.

On/OFF VaLVES

On/off control — stopping and restarting system fluid flow — is the most basic valve function. Pri-mary on/off options are ball, gate, diaphragm and bellows valves.

Select the Right instrument-System ValveStart by matching valve type to desired function

By Michael Adkins, Swagelok Company

CP1103_36_41_Instru.indd 36 2/23/11 11:41 AM


Perhaps the most common of all valve types, ball valves (Figure 1) are designed for on/off con-trol. Quarter-turn actuation starts or stops flow by rotating a metallic ball with a large hole through its center. Straight-through flow occurs when the hole is lined up with the flow path. When the hole is turned 90° from the flow path, flow stops. If you’re seeking an on/off valve with quick shutoff and high flow capacity, a ball valve is a good choice. The position of its handle provides a quick indication of whether the valve is open or closed; ball valves are easy to lock out and tag for safety purposes. They are most practical and economical at sizes between ¼ in. and 2 in.

Typically used for process control rather than instrumentation applications, gate valves commonly are chosen for on/off control — particularly for lines above 2 in. They also frequently serve as the first valve off the process line for instrumentation, often in a double-block-and-bleed configuration. Among the oldest types of on/off valves, they usu-

ally are specified in general industrial applications, such as large process or transmission lines. Some can exceed 100 in. Multiple rotations of the handle lower or raise a sealing mechanism in or out of a straight flow path. Shutoff is gradual.

Packing surrounds the stem, the cylindrical part connecting the handle (or actuation) with the inner mechanism, preventing system media from escaping to atmosphere where the stem meets the valve body. Valves that seal to atmosphere with metal-to-metal seals are referred to as “packless” because they don’t contain soft packing material, e.g., gaskets and O-rings, normally found around the stem in other valves.

All stem seals or packing are subject to wear, which can lead to leakage. Valves with packing re-quire servicing or replacement at regular intervals, although some types of packing, such as the two-piece chevron design, create more effective seals and last longer than others.

Unlike packed valves, diaphragm valves (Figure

on/off Valves

Valve Type Flow pathVisual indication

of shutoff?shutoff speed

packing or packless? Typical Use

Ball straight Yes rapid packing Very broad, suitable for many applications —practical and economical

gate straight no gradual packing general industrial use — typically for large pro-cess or transmission lines

Diaphragm globe Yes rapid packless applications, often high-purity, requiring rapid shutoff, precise actuation speeds and high cycle life

Bellows globe sometimes gradual packless services where a high-integrity seal to atmosphere is critical and access for maintenance is limited

Flow control Valves

Valve Type Flow pathprecision of

Flow controlshutoff

capability? Typical Use

needle globe excellent Yes applications requiring precise flow control and leak-tight shutoff — often used for high-temperature applications and with lighter, less viscous fluids

Fine metering globe excellent sometimes applications, frequently in laboratory settings, requiring the most precise flow control

Quarter-Turn plug

straight good Yes economical utility valves typically chosen for low-throttling applications

rising plug straight good Yes services where the valve needs to be cleaned out, such as when system media can coagulate and clog valve

Selection Guidelines

Table 1. Each valve type has basic characteristics that suggest it for particular applications.

CP1103_36_41_Instru.indd 37 2/23/11 11:41 AM


2) are packless. � ey provide rapid shuto and precise actuation speeds and, in some cases, also may deliver consistent quantities of process � uid. Diaphragm valves typically are employed in high purity applications. � ey o er the highest cycle life of any valve type, thanks their highly engi-neered anatomy. Each valve contains a thin metal or plastic diaphragm that � exes up and down, creating a leak-tight seal over the inlet. � is ro-bust valve usually is small, with the largest ori� ce or internal pathway typically less than 2 in.

Bellows valves also are packless, making them a good choice when the seal to atmosphere is critical and access for maintenance is limited. � ey frequently are speci� ed for the contain-ment area in nuclear power plants. A welded seal divides the lower half of the valve, where the system media resides, from the upper parts of the valve, where actuation is initiated. � e stem, which is entirely encased in a metal bellows, moves up and down (without rotating), sealing over the inlet.

Bellows and diaphragm valves are said to have a globe-like � ow path. In globe valves, � uid doesn’t � ow straight through on a level plane as in a ball valve. Instead, it enters the valve under the seat and exits above the seat. Globe valves have lower � ow rates than straight-through-� ow-path valves of the same ori� ce size.

FLOW CONTROL VALVES

� ese enable an operator to increase or decrease � ow by rotating a handle. Once adjusted to a desired � ow rate, the valve will hold that � ow rate reliably. Some � ow control valves also pro-vide very reliable shuto , but many turns of the handle are necessary to move from the fully open to the fully closed position.

� e most common � ow control valves are

KEEP FIVE POINTERS IN MIND1. Know your application. When choosing a

valve, you must have on hand certain pieces of information, including the chemical composition of the system media and the full range of pressures and temperatures the valve may experience over its life. Make sure your valve choice can accommodate these parameters. Don’t go with hunches or ap-proximations. Consult the product data.

2. Check for material compatibility. It’s possible to have the right valve but the wrong materials of construction. Valves often come in a standard set of materials, but others often are available. Always check the product catalog to identify temperature and pressure ranges, as well as compatibility with different system media (chemicals). When in doubt, consult your manufacturer’s representative.

3. Factor in the maintenance schedule. Differ-ent valves have different maintenance schedules. Your system parameters, including the number of times the valve is cycled, will affect this schedule. Your maintenance team must be able to manage the schedule. This seems like an obvious point but it’s often overlooked. Are you willing to ser-vice that valve once every 20 days when it’s 100 feet in the air?

4. Understand pressure drops. Almost every valve or other component produces a drop in pres-sure. You must check the cumulative pressure drop, to avoid risks of ending up with too little pressure at a certain point in the line. Every valve is rated with a fl ow coeffi cient, Cv, which describes the relationship between the pressure drop across an orifi ce, valve or other assembly and the corresponding fl ow rate. The higher the Cv, the lower the pressure drop. Ball and needle valves of the same size will produce very different pressure drops — very little for the ball valve but signifi cant for the needle valve (or other globe valves).

5. Consider cost of ownership. The true cost is the purchase price plus the expenses of owning and maintaining or replacing a valve over time. To calculate the cost of ownership, you must know how long the valve will operate in your particular system between maintenance checks. Maintenance costs should include replacement parts, labor and down-time. Some valves are much easier to maintain than others; some can be serviced in place, while others must be removed from the process line. Also, given your valve choice, what are the chances of unsched-uled maintenance and downtime?

Ball Valve

Figure 1. Quarter-turn actuation and straight-through fl ow path suit this valve for many on/off applications.

CP1103_36_41_Instru.indd 38 2/23/11 11:41 AM

needle, fine metering, quarter-turn plug and rising plug.

Needle valves (Figure 3) of-fer excellent f low control and, depending on design, leak-tight shutoff. They consist of a long stem with a highly engineered stem-tip geometry (e.g., vee- or needle-shaped) that fits pre-cisely into a seat over the inlet. The stem is finely threaded, enabling precise f low control. Stem packing provides the seal to atmosphere.

Some designs feature a metal-to-metal seat seal; consequently, needle valves are a good choice for high-temperature applica-tions. However, flow is limited because of the globe-style flow path. Needle valves also suit lighter, less viscous fluids.

For the most precise flow control, consider fine metering valves. Typically found in labora-tory settings, these are a type of needle valve with a long, fine stem that lowers through a long, narrow channel. This makes for a pronounced globe pattern, ideal for marking fine gradations of flow. Some fine metering valves aren’t designed for shutoff.

Quarter-turn plug valves are economically priced utility valves. Quarter-turn actuation rotates a cylindrical plug with an orifice in a straight-through flow path. Plug valves commonly are used for low-pressure throt-tling applications in addition to shutoff.

Rising plug valves, like needle valves, lower a tapered element into an orifice to reduce flow. They differ from needle valves in their flow path, which is straight-through rather than globe pat-terned. Because of the straight path, the valve isn’t as effective at providing fine gradations of flow. The rising plug is roddable —

Figure 2. Benefits include rapid shutoff, precise actuation speeds and unrivalled cycle life.

Figure 3. Finely threaded stem enables excel-lent flow control; some designs offer leak-tight shutoff.

Diaphragm Valve Needle Valve

CP1103_36_41_Instru.indd 39 2/23/11 11:42 AM

and so it’s a good choice if there’s a risk of clogging with system media.

DIRECTIONAL FLOW VALVES

A third function of valves is to direct flow.Check valves (Figure 4) ensure flow

in only one direction. In most designs, the upstream fluid force pushes a spring-loaded poppet open, allowing flow. An increase in downstream or back-pressure force drives the poppet back into the seat, stopping reverse flow. Check valves are available with fixed or adjustable cracking pressures.

Some ball and diaphragm valves are designed with multiple ports. In most multi-port valves (Figure 5) fluid enters through a single inlet but may exit through one of several outlets, depending on the position of the actuator. Multi-port valves may or may not have a shutoff position.

OVER-PRESSURE PROTECTION

VALVES

These devices prevent buildup of system pressure beyond a certain setting. They come in two types: relief valves and rupture discs.

One type of relief valve is a propor-tional relief valve (Figure 6). It contains a vent to atmosphere that opens when system pressure exceeds a set point. A spring-loaded poppet enables the mea-sured release of fluid. The vent closes when pressure returns to a point below the set point.

A safety relief valve is designed to open very quickly, releasing a large amount of system media. Safety codes

require use of such valves in certain applications.

Don’t use safety relief and propor-tional relief valves interchangeably with check valves — the three serve different functions.

Rupture discs are found mainly on sample cylinders to protect against over-pressurization, which may occur, for example, when temperatures rise during transport. Like relief valves, rupture discs vent to atmosphere. A metal diaphragm bursts when pressure reaches a value preset by the manufac-turer. Once activated, the rupture disc must be replaced. A rupture disc is an economical choice where transportation codes require equipping compressed gas cylinders with a pressure relief device.

EXCESS FLOW VALVES

Designed to stop uncontrolled release of system media if a downstream line ruptures, excess flow valves use a spring to hold a poppet in the open position under normal conditions. When excess flow arises downstream, the poppet moves to a tripped position, prevent-ing almost all flow. When the system is corrected, the valve returns to its open position. These valves are available with fixed tripping values.

A GOOD START

Once you have matched valve type to function, you’re well on your way to selecting the right valve for your instru-ment system. However, you still must grapple with many details, including:

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CP1103_36_41_Instru.indd 40 2/23/11 11:42 AM

• installation issues, maintenance schedules and access;

• safety and code requirements; and• system parameters, such as pressure, tempera-

ture, � ow rates and system media.Ultimately, you’ll need to determine:• valve size and type of actuation; and• materials of construction (including O-rings

and seals), which must be compatible with the chemical composition of the system media, pressures and temperatures.

A valve manufacturer’s representative as well as product catalogs and product test reports can be valuable resources in re ning your choice.

MICHAEL ADKINS is product manager, general industrial

valves, for Swagelok Co., Solon, Ohio. E-mail him at michael.

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Figure 5. Some ball and diaphragm valves can direct fl ow to one of several outlets.

Figure 6. When actuated by over-pressurization, this valve provides a measured release of fl uid.

Multiple-port Valve Proportional Relief Valve

CP1103_36_41_Instru.indd 41 2/23/11 11:43 AM


Making it work

Eastman ChEmiCal’s main facility in King-sport, Tenn., is a huge challenge for anyone responsible for monitoring flow in its miles of pipe. Started in 1920, the complex now stretches over 4,000 acres and contains 550 buildings. The main plant site alone covers 900 acres. The facility makes a wide range of products to support Eastman’s five business segments. So, not surprisingly, it boasts every type of piping imaginable, carrying gases, slurries and an incredible number of industrial chemicals.

Because we have such a variety of piping and prod-ucts, we periodically reassess our measurement capabili-ties. In 2009, we decided to thoroughly investigate flow metering to see if we could benefit from recent advances.

Much of my job as an environmental and process analytics chemist is to use portable devices to ensure ac-curacy of installed flow meters, to troubleshoot process upsets and to do flow checks on unmetered lines. Ac-curacy is my main concern. So, I try my best to keep up with the latest technology.

The need for accurate, representative flow data that we could archive and access has been increasing exponentially, but nothing in place could provide all the information we required. Several internal develop-ment and engineering groups had looked independently into earlier-generation clamp-on ultrasonic flow meters with data logging capability and had varying degrees of success with them. For the most part these meters were collecting dust on a shelf. The problem was accuracy. I often heard things such as: “We’ve had a clamp-on ul-trasonic for years and I’ve never had much luck with the thing” or “Clamp-on meters are very frustrating to use. You never know if they are giving you accurate readings, if you actually get any readings at all.” I believed such meters had vast potential but hadn’t lived up to it. So, I resolved to see if there had been any advances.

I called every clamp-on ultrasonic flow meter manufacturer I could identify. My intent was to get these meters in-house and test each of them on process and utilities pipes. I selected 20 points throughout the site; several are in our coal gasification plant, which transports gases and liquids as well as slurries of chang-ing consistency and temperature.

hOW UltRasOniC WORKs

The technique most ultrasonic flow meters use is called transit-time difference. The meter sends ultrasonic pulses through the medium, one in the flow direction and one against it. Transducers alternate as emitters and receivers. The transit time of the signal going with the flow is shorter than the one going against. The meter measures transit-time difference and determines the average flow velocity of the medium. Because ultrasonic signals propagate in solids, you can mount the meter directly on a pipe and measure flow non-invasively, eliminating any need to cut the pipe.

The tests. One of my first tests for all the meters was in a parking lot where we have a 30-in. water line. Aside from accuracy, I focused on ease of installation. After all, I have to go all over the plant measuring flow and I don’t want to waste time setting up. I also was looking for reliability, data logging capability, diagnostic tools and good battery life.

The water line provided telling results. If a meter took too long to set up or didn’t give adequate accu-racy on such an easy task, there was no point trying it at the other test sites. Some meters didn’t make it out of the parking lot.

Clamp-on Flow meter Gains Firm holdSite finds ultrasonic device provides easy

installation and accuracy

By Greg Harper, Eastman Chemical Co.

CP1103_42_43_MIW.indd 42 2/23/11 11:46 AM


MAKING IT WORK

And the winner is… I’m not going to name those meters or, for that matter, the others I didn’t ultimately select — some were good products with good accuracy and I don’t want to make them look bad. But, at the end of six months, one meter met all of my standards, especially for ease of set up and accuracy. It was from Flexim.

It had two distinct advantages over the others. First, it is a combination gas/� uid meter; so I only had to buy one meter, not two. Second, its instal-lation is a snap. e main problem with the others was installation. Flexim has a xed frequency on its transducers. Regardless of what’s being measured, they keep that frequency. e others use a sweep frequency — it takes quite a bit of time to set up their transducers and put them on the pipe. en you have to nd a “sweet spot” and, even after you’ve found the spot, you still have to adjust the transducers to get an accurate measurement.

ere are many ways of getting a signal to a pipe. Lots of meters rely on multiple transducers that operate at di� erent frequencies to cope with the various types and wall thicknesses of pipes and diverse liquids. Flexim uses the same transducer for everything but lters the transmission pattern and either increases the transducer voltage (which can range from 15 V to 90 V), or breaks up the pattern of transmissions to adapt to real-world conditions. e meter sends approximately 1,000 pulses back per second in 500 pairs; the system automatically recognizes a change in liquid consistency. Not even coal slurries are a big challenge. e system, through a combination of software, clever trans-ducers and signal processing, automatically realizes it’s losing signal and boosts power to the transduc-ers. It can monitor anything from ¼-in. tubing to a 30-ft. penstock.

I think it’s safe to say that ultrasonic � ow meters nally have achieved their potential. I have taken more than 600 readings — including on pipes containing acids, water, gases, and slurries at several hundred degrees — with this portable meter and my success rate is 99.8%. ( e photo shows me checking a 42-in.-dia. line.) At the end of the day, I collect all the data dumps from the built-in data logger and export them to a spreadsheet.

Our internal customers have gained faith in ultrasonics and have bought ultrasonic units to replace their older meters. Concerns about accuracy are a thing of the past. One of our clients was run-ning an addition process and having some problems with the feed rates. An ori ce plate � ow meter on the line wasn’t giving consistent measurements. I

took the portable over there and spent three days. e client liked the results but wasn’t sure about the accuracy. So, I brought the Flexim meter to our metrology group, which has a Coriolis � ow meter set-up, and we bench tested the portable against it. e correlation was 0.9999.

NEXT STEPS

We currently have ve ultrasonic meters in our group — four Fluxus F601 liquid units and one Fluxus G601 gas unit, which actually can measure liquids as well. Most applications we have are for liquid measurements but with a plant this size the ability to measure gas � ows from outside the pipe is de nitely a plus. e G601’s speci cations give a 100-psi minimum requirement to measure gas � ows. e lowest-pressure line I’ve personally attempted to measure is 140 psi; that particular application was for a nitrogen header and the meter worked well.

At the present time our Flow Measurements Group consists of three people (two utility opera-tors and me). All across the site, people are clamor-ing for us to come over with the clamp-on meters. is has prompted us to do some “creative schedul-ing,” but that’s a good problem to have. Ultimately, we may add people to the group.

We continually are nding new applications for this technology. When we rst started using the devices we were doing straightforward chores — basically chemical-addition-type measurements expressed as gal/min or lb/min. We also did a fair amount of checking and troubleshooting existing � ow meters. We have begun to expand our rep-ertoire by adding heat � ow (BTU) type measure-ments. e meters are dual channel and con gured for temperature inputs, allowing us to measure sup-plies and returns simultaneously. We never had this energy meter functionality before and it’s already starting to pay o� . It’s de nitely something we’ll keep our eyes on.

Where I used to hear “Ultrasonics might as well be Ouija boards,” now all I hear is “What’s my � ow?” Ultrasonic is de nitely the way to go today.

GREG HARPER is an environmental and process analytics chem-

ist and leads the Flow Measurement Group at Eastman Chemical’s

facility in Kingsport, Tenn. E-mail him at [email protected].


“Ultrasonic Flow Meter is Portable, Fast and Reliable,”www.ChemicalProcessing.com/vendors/products/2009/262.html

CP1103_42_43_MIW.indd 43 2/23/11 11:47 AM


process puzzler

`SCRUTINIZE THE SOLVENT

Check the Kb [Kari-butanol] value and check the toxicity [for the solvent] before you go further.

Guy Weismantel, presidentWeismantel International, Kingwood, Texas

USE ACETONE

Isohexane is very harmful to the environment and health. Methanol is also very toxic. So, I suggest using acetone for f lushing as it is clean and less hazardous to the environment and health.

Wikipedia notes: “According to a report by the Cornucopia Institute, hexane is used to extract oil from grains as well as protein from soy, to such an extent that in 2007, grain proces-sors were responsible for more than two-thirds of hexane emissions in the United States. The report also pointed out that the hexane can persist in the final food product created; in a sample of processed soy, the oil contained 10 ppm, the meal 21 ppm and the grits 14 ppm hexane. The adverse health effects seem specific to n-hexane; they are much reduced or absent for other isomers. There-fore, the food oil extraction industry, which relied heavily on hexane, has been considering switch-ing to other solvents, including isohexane.”

Some notes about acetone usage from Wiki-

pedia: “Acetone has been studied extensively and is generally recognized to have low acute and chronic toxicity if ingested and/or inhaled. Inhalation of high concentrations (around 9,200 ppm) in the air caused irritation of the throat in humans in as little as 5 min. Inhalation of concentrations of 1,000 ppm caused irritation of the eye and throat in less than 1 hr; however, in-halation 500 ppm of acetone in the air caused no symptoms of irritation in humans even after 2 hr of exposure. Acetone is not currently regarded as a carcinogen, a mutagenic chemical or a concern for chronic neurotoxicity effects. Acetone can be found as an ingredient in a variety of consumer products ranging from cosmetics to processed and unprocessed foods. Acetone has been rated as a GRAS (Generally Recognized as Safe) substance when present in beverages, baked goods, desserts, and preserves at concentrations ranging from 5 to 8 mg/L. Additionally, a joint U.S-European study found that acetone’s ‘health hazards are slight.’”

Amr Hatem Rashed, production engineerAbu Qir Fertilizers & Chemical Industries,

Alexandria, Egypt

WHICH SOLVENT WORKS BEST?

For safety, the case that methanol or acetone is “safer” is weak. Commonly accepted values for f lash point, lower explosion limit (LEL) and upper explosion limit are: isohexane, -9°F, 1.0 v%, 7.4 v%; acetone, -4°F, 2.5 v%, 12.8 v%; methanol, 54°F, 6.0 v%, 36 v%. All are heavier than air and vapor clouds will tend to travel along the ground (though methanol is just a little bit heavier). All will be used at temperatures far in excess of the f lash point. Methanol has a higher f lash point and higher LEL but a much wider range for potential explosive mixtures. Isohexane has the lowest f lash point and the lowest LEL but also the narrowest explosive range. Acetone lies in between on all of the criteria here. Toxicity and exposure data are also mixed. It’s difficult to say which is the safer solvent here.

From the question, it’s apparent that both isohexane and methanol are available in the plant. However, both also appear to have some con-taminants in them. No mention was made of the

Choose Cleaning Solvent WiselyReaders raise a variety of issues to consider

THIS mONTH’S pUZZLER

at our batch specialty chemicals plant the production manager wants us to use waste isohexane as a cleaning solvent. he proposes pumping the isohexane, which is available from a nearby process, into our columns prior to cleaning for startup. The commissioning engineer opposes using it on the grounds that a safer cleaning solvent, such as spent methanol or acetone, could be available. he suggests using methanol because it’s cleaner. We’re cleaning two knockout pots and two distil-lation columns that have been used for several months in the produc-tion of fish oil (eicosapentaenoic acid and docosahexaenoic acid). The material safety data sheet for fish oil shows the following: closed-cup flash point, 149°c; auto-ignition point, unknown; and conditions to avoid, “oxygen.” The columns each contain one 8-ft. bed of structured packing. normally, the columns operate at a maximum of 100-torr with electric thermosiphon reboilers. The condensers use chilled glycol. (The cleaning process proposed by the production manager appears online at www.chemicalprocessing.com/articles/2011/vanquish-vexing-vent-ing.html.) What do you think of the commissioning engineer’s objec-tion? is there a better approach for cleaning the process?

CP1103_44_45_Puzzler.indd 44 2/23/11 12:01 PM


process puzzler

availability of acetone. There is a big advantage in using something already present. Safety data, permitting, training, and experience in han-dling the solvent are already in place. The steps outlined look reasonable but the specific details will count. Details such as temperatures and hold times and specific steps need to be worked into a true procedure for operations.

The real question that needs to be answered is which solvent works best for the process require-ments and gets the equipment clean? A shorter time spent using the more effective solvent could easily give a safer operation than more time required when using a less effective solvent. With-out knowing which solvent will work better, you can’t come to a decision.

Andrew W. Sloley, principal engineerCH2M HILL, Bellingham, Wash.

CONSIDER VARIOUS HAZARDS

Isohexane poses an unseen hazard. A typical material safety data sheet shows it contains a mix-ture of branched butanes and pentanes, e.g., 2, 2 di-methyl butane. Butanes are considered more dangerous than propanes and natural gas because they tend to evaporate easily at room temperature and then recondense somewhere you don’t want them to be. That’s why the American Petroleum Institute’s “Recommended Practice for Classifica-tion of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Divi-sion 1 and Division 2” (API-500) recognizes this exceptional hazard by labeling butanes as “highly volatile liquids.”

Although API’s “Protection Against Igni-tions Arising Out of Static, Lightning, and Stray Currents” (API-RP-2003) and the National Fire Protection Association’s “Recommended Practice

on Static Electricity” (NFPA-77) don’t provide convenient reference for comparing solvents, I found a useful article on the web: http://www.chilworthpacific.com/pdfs/Vahid_Ebadat_cv.pdf. Ebadat shows clearly that acetone would be the best choice based on lower minimum ignition energy (MIE) alone: 0.3 micro-Joules (mJ) for hydrocarbons, 0.14 mJ for alcohols and 1.15 mJ for acetone.

This is not the whole picture, though. The dangers of static electricity are measured by ac-cumulated energy and voltage. A low MIE and high accumulated energy are the worst for risk of explosion and high voltage is a risk to personnel. Energy is directly proportional to accumulated voltage and the liquid dielectric constant. Metha-nol has a higher dielectric constant than either acetone or isohexane: 34 vs. 21 vs. 2 at about 77oF. In other words, with methanol you have the lowest threshold with the highest capacity for producing energy. Methanol is a bad choice; how-ever, isohexane appears to have gained in stature because, for a given f luid velocity, the accumu-lated energy and volts are much lower than for acetone. The auto-ignition temperatures and f lash points also favor acetone over isohexane.

Now, let’s consider the cleaning method. Fish oil exposed to oxygen forms aldehydes and ketones, so purging and avoiding high tempera-ture is crucial. Operating at a high temperature is a poor idea, so is vacuum. I would lower the temperature of the columns down to about 50°C and increase pressure to atmospheric. The KOH may saponify much above 7–8 pH. Before using the cleaning procedure it would be a good idea to test it in the laboratory.

Dirk Willard, senior process engineerMiddough Engineering, Holland, Ohio

MAY’S PUZZLERWe heat heavy oil with steam before sending it to a reac-tor. The oil, which is pumped through the shell of the heat exchanger, enters at 100°F and exits at 250°F; 125-psig steam goes through the tubes. The old exchanger had four shell passes and eight tube passes. someone at corpo-rate engineering mistakenly ordered a heat exchanger with three shell passes and six tube passes. The new shell is rated for 250 psig. The oil/steam overall external heat transfer coefficient is 100 BTu/lb-hr-°F. is there anything we can do to use this unit so we don’t have to order a new heat exchanger and delay production?

send us your comments, suggestions or solutions for this question by april 15, 2010. We’ll include as many of them as possible in the may 2011 issue and all on cp.com. send visuals — a sketch is fine. e-mail us at [email protected] or mail to process puzzler, Chemical Processing, 555 W. pierce road, suite 301, itasca, il 60143. Fax: (630) 467-1120. please include your name, title, loca-tion and company affiliation in the response.

and, of course, if you have a process problem you’d like to pose to our readers, send it along and we’ll be pleased to consider it for publication.

CP1103_44_45_Puzzler.indd 45 2/23/11 12:02 PM


plant insites

Consider More Than Static MixersA number of technologies can handle pipeline mixing

The TerM “pipeline mixing” covers mixing of materials in a flowing line downstream of a junc-tion. The mixing may involve miscible liquids, immiscible liquids and multi-phase mixtures. Op-tions include just letting materials mingle naturally, using pipe fittings to spur contact, and installing static mixers, spray nozzles or spargers. Static mixers now dominate pipeline mixing — but that doesn’t mean they’re always the best choice.

Let’s consider a recent case that involved choosing a better pipeline mixer for a liquid/liquid service that included mixing both miscible and im-miscible liquids.

This application has two mixing steps: 1) mix-ing two miscible liquid reactants; and 2) adding the reactants to an immiscible liquid catalyst. Some reactions take place at the interface. Others occur inside the catalyst phase after the reactants dissolve into the catalyst. The catalyst-to-reactants ratio is roughly 1:1 by volume; the catalyst has the same volume as the total reactants in the system. Neither the reactant phase nor the catalyst phase is well defined as either a continuous phase or a discon-tinuous phase.

The idea was to improve yields by more-thorough reactant/reactant and reactants/catalyst mixing. This would increase inter-phase surface area, which would help both types of reaction mechanisms. The current setup relies on a simple pipe junction upstream of the reactors. We evalu-ated a spray nozzle, a sparger and a static mixer as a possible replacement.

Conventional spray nozzles accelerate a liquid to create a jet. The liquid then breaks up into smaller droplets. The major types of spray nozzles that might be used here are based on (1) rotating flow in a chamber that exits 90° from the liquid inlet, (2) swirl imparted by an internal vane or (3) a narrow stream cut by a spiral blade (pig tail).

These nozzles form droplets primarily through a combination of liquid ligament breakup and slicing of liquid sheets leaving the nozzle. Both mecha-nisms vary with liquid velocity, surface tension between phases and other physical properties. Jet instability is a key factor in making lots of drops. The little data available show most mixing veloc-ity is shed within 12 in. to 18 in. of the nozzle. No significant droplet formation occurs because the original liquid ligaments or sheets don’t form.

A sparger is a pipe with multiple holes that cre-ate a pressure drop forcing flow to distribute across the holes. (This pressure drop only is imposed on the liquid being injected, not the entire stream.) With the sparger installed into the main line, the injected flow of one stream would enter the second stream. The sparger could be aligned either across a larger pipe (at 90°) or along the same flow line as the larger pipe.

As with a spray nozzle, enhanced liquid mixing comes from local turbulence created by injecting a high velocity liquid into a second liquid. The mixing is likely at least as good as that of a spray nozzle. Design and installation of a liquid sparger typically is both cheaper and simpler.

Static mixers have become dominant for good reason. They use vanes or blades as elements. This enables mixing to occur at relatively low pressure drop, as little as 10% or 20% that of a sparger. The only potential downsides are that a static mixer often requires a longer straight pipe run for instal-lation and pressure drop is applied to the entire stream.

Overall, the sparger and the static mixer are the best technical choices. Both have proven track records. In contrast, the spray nozzle, which is designed for liquid injection into gas, rarely is used in liquid/liquid services and should be avoided.

Despite this, the plant has opted for spray-noz-zle injection for both mixing tasks. It considered spray nozzles proven technology because they have been used in this process by other plants. Here, though, hydraulic constraints limit the pressure drop to a fraction of that at other units; so results may not be as good.

Not agreeing with a decision doesn’t free an engineer of the responsibility to help the site derive the most benefit possible from its choice. So, we recommended use of pig-tail-type nozzles. These mechanically “cut” a solid liquid stream into sheets but don’t form as uniform droplets as the other types in conventional services. However, their me-chanical design is guaranteed to at least do some-thing. The cutting action will improve liquid/liquid mixing somewhat. Also, the cutting edge acts as a minor mixing element in its own right. andrew Sloley, Contributing Editor

[email protected]

The sparger and

the static mixer

are the best

technical choices.

CP1103_46_Insites.indd 46 2/23/11 11:48 AM

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enD poinT

EU Carbon Trading Gets HackedCyber criminals view emission allowances as a gold mine

FollowinG THE January theft of emissions allowances worth €7 million ($9.4 million) from an account in the Czech Republic — plus hacked trad-ing accounts in Austria, Poland, Greece and Estonia — the European Commission (EC) has temporarily suspended the national registries that manage its emissions trading scheme (ETS).

Launched in 2005, the ETS encourages compa-nies to invest in low-polluting technologies by making the firms buy allowances to cover their annual emis-sions. Each country within the European Union (EU) is allocated a certain quantity of permits which are then issued to companies. More efficient companies profit by selling or banking unused allowances. Sales last year reached €90 billion ($124 billion).

Henry Derwent, president and CEO of the International Emissions Trading Association (IETA), Geneva, Switz., outlined why criminals are attracted to the registries in an interview with National Public Radio on January 22.

“It is essentially an allowance. This piece of paper allows my company to emit a ton of carbon diox-ide through a combustion process. So it has value. Companies that produce less carbon than they’re permitted can sell what’s left of their allowance to companies that produce more than they should. There’s actually a market where these allowances are traded electronically. Over the past few months, but especially in the last week, criminals have been able to break into one of the registries where those carbon allowances were recorded and change who owns what. If you make sure that it’s transferred to an ac-count that you own and you sell it very quickly, then you’ve essentially got something for nothing, sold it for a lot, and you get out of town with all the dollars in your bag.”

What the theft proves, he added, is that carbon emission allowances are now seen as commodities like gold or wheat — and, if not defended by good security, are likely to be targeted by criminals.

Eleven months prior to the attacks, the IETA sent a letter to Jos Delbeke, deputy director general at the EC’s directorate general for the environment, Brussels, concerning an earlier value-added-tax fraud associated with the scheme. Among the six measures urged in the letter were: new anti-phishing con-trols, a centralized monitoring/EU registry system, comprehensive anti-fraud measures, and continuous evaluation of ETS.

In a letter to the EC on January 20, IETA pointed out that the thefts could have been avoided if these recommendations had been implemented properly.

The letter adds: “We would like to invite the Com-mission and member states to be aware of the damage that this situation is inflicting on market participants. We therefore call on the Commission to urgently and thoroughly close this security gap by reviewing re-quirements to access accounts, by ensuring the actual implementation of stringent IT security checks by a set date, and by clarifying liability issues once and for all in case of a theft of emission allowances. There must be a deadline by when security upgrades have to occur and progress of implementation must be closely monitored.”

Before compiling its letter, the IETA canvassed the views of its own members on a number of issues relating to the registry suspension. It asked, “What mandatory security tests should be used to determine whether registries can re-open?” More than 20 mem-bers — including industrial companies — replied.

Most respondents considered it necessary for registries to have second authentication in place — in addition to ID and password — for all accounts where a transaction can be initiated. Such authentication, they said, could include electronic certificates, elec-tronic ID cards, one-time passwords via short message service (SMS), or tokens.

It was also emphasized that the e-tokens used for second authentication shouldn’t restrict operational arrangements. In practice, each designated user of an account should get an e-token for second authentication.

There was much less support for two-person authorization procedures. Here, each access to an account where a transaction can be initiated (or each transaction) would be initiated by one authorized rep-resentative through ID and password, then confirmed by a different authorized representative with a differ-ent ID and password.

Overall, respondents felt that registry security should respect the following requirements: strong passwords, changed on a monthly basis; personal ac-counts and follow up of inactive accounts; confirma-tion of a transaction by both parties before it becomes effective; and encrypted and secure connection to the web server. SEán oTTEwEll, Editor at Large

[email protected]

Hackers target

emissions trad-

ing due to lax

security.

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Chemical Processing March 2011