DP17

ExxonMobil ProprietarySection Page

PLANT ENVIRONMENTAL CONSIDERATIONS XVII 1 of 20

DESIGN PRACTICES February, 2004

ExxonMobil Research and Engineering Company – Fairfax, VA

CONTENTSSection Page

SCOPE .......................................................................................................................................................2

REFERENCES...........................................................................................................................................2

INTRODUCTION........................................................................................................................................3

REGULATORY ISSUES ............................................................................................................................................4General.......................................................................................................................................................................4Air ...............................................................................................................................................................................4Water ..........................................................................................................................................................................5Solid and liquid Waste ................................................................................................................................................5Site Remediation ........................................................................................................................................................6Noise ..........................................................................................................................................................................6

EMISSION AND CONTAMINATION SOURCES.......................................................................................6

EMISSION REDUCTION GUIDANCE .......................................................................................................6

GENERAL PRACTICES ............................................................................................................................................6

PROCESS AND EQUIPMENT RECOMMENDATIONS.............................................................................................7Alkylation ....................................................................................................................................................................7Amine Treating, Sour Water Stripping, Sulfur Recovery.............................................................................................7Catalytic Reforming ....................................................................................................................................................8Caustic Treating .........................................................................................................................................................9Coking ........................................................................................................................................................................9Desalting.....................................................................................................................................................................9Fired Heaters............................................................................................................................................................10Fluid Catalytic Cracking............................................................................................................................................10Hydrogen Manufacture .............................................................................................................................................11Ketone Dewaxing .....................................................................................................................................................11MTBE........................................................................................................................................................................11Process Contact Steam Condensate........................................................................................................................12Sewers......................................................................................................................................................................12Tankage....................................................................................................................................................................12

TABLESTable 1: Approach To Manufacturing Plant Environmental Control ......................................................................13Table 2: References To Major Environmental DP Sections...................................................................................14Table 3: List Of Major Emission Sources...............................................................................................................15Table 4: Types Of Site Contamination...................................................................................................................16Table 5: Components Of An Emission Reduction Program....................................................................................17Table 6: Emission Control Guidance .....................................................................................................................18

REVISION MEMOFebruary 2004 Many minor editorial changes and updates

Changes shown by ➧


XVII 2 of 20 PLANT ENVIRONMENTAL CONSIDERATIONSFebruary, 2004 DESIGN PRACTICES


SCOPEThe Plant Environmental Considerations DP provides an overview of environmental control technology, types ofcontamination, and environmental control recommendations for specific process units. References for additionalenvironmental guidance, including other DP sections, are listed below.

REFERENCES1. Highlights of New and Proposed Air Toxics Regulations, EE.3E.91.2. Site Remediation Regulatory Review, EE.42E.923. MEFA: Minimum Emissions Facilities Assessment, EE.12E.924. MEFA: Minimum Emissions Facilities Assessment - Phase 2, EE.123E.925. Rittmeyer, Robert W., Waste Minimization–Part 1: Prepare an Effective Pollution Prevention Program, Chemical

Engineering Progress, May 1991, 56–62.6. Guidelines for Preparing a Cost-Effective Environmental Assessment, 88 ECS2 79, August 26, 19887. Responsible Waste Management Practices, Version 2, Environmental Coordinators Network Best Practice,

May 15, 20038. No Oil to Sewer Catalog, EE.76E.20029. Operations Integrity Management System (OIMS) Elements 3.4, 7.2, Facilities Design and Construction10. Onsite Process Units, Wastewater Source Load Study, Environmental Control Toolmaking Project, February 21,

1975, by F.A. Devine, et. al., Correspondence no. 5001211. Urban, D.B, R. R. Goodrich, "Refinery Process Unit Wastewater Load Factors-Final Report," EE.086E.86,

October, 198612. Wastewater Management- Preferred Operating Practices, EE. 99E.9813. Waste Preferred Operating Practices, EE. 82E. 9714. Environmental Performance Indicators, Exxon Mobil Corporation Manual, 2002 EPI Manual, November, 200215. Best Practice for Managing Risk with the use of Third Party Waste Disposal Facilities, Air, Water, Waste

Best Net16. Environmental Business Planning Web

http://emcorp.na.xom.com/she/corporate/docs/EBP%20Ref%20Guide%20-%20Dec.doc17. Energetics, Inc. AICHE, US Dept of Energy, "Waste Reduction Priorities in Manufacturing", a DOE/CWRT

Workshop, August 1, 199418. F. H Vaughan, J. B. Wilkinson, "Safety and Environmental Procedures for Projects", TMEE 082, EE.72E.98,

Dec. 199819. Environmental Procedure for Processing Challenged Crudes Web

http://emre.na.xom.com/waterwst/SRADOCS_s00/ChalCrude/EnvPtc/EnvPtc.htm20. Global Best Practice for Processing Opportunity Crudes Web

http://emre.na.xom.com/waterwst/SRADOCS_s00/ChalCrude/EnvPtc/REI.htm21. Refining Project Systems Manual, TMEE 0112, EE.49E.2002, June 2002





INTRODUCTIONIncorporating environmental considerations into plant operations and project design is essential due to continuouslyexpanding regulations that affect the petroleum and petrochemical industries. Trends in regulatory requirements aremoving beyond control of gross emissions and discharges, focussing more on targeted constituents and individualcompounds. These regulations cover discharges to the air, water and ground, the generation of noise and odors, andthe remediation of contaminated sites. Worker and community exposure, as well as impact on the environment mustbe evaluated as part of project planning and preparation of environmental impact assessments.In addition to strict adherence to local environmental and health regulations, ExxonMobil has additional guidelines toassure that corporate environmental policy and operations integrity are considered. In many cases these may bemore restrictive than local regulations. The effects of our plants on the environment play a major role in the public'sperception of our operations. Good community relations is a valuable asset, and attention to plant discharges whichmay be of concern plays a major part in maintaining local support.Good business sense suggests a stepwise approach when factoring environmental considerations intomanufacturing plant expansions or new projects. The approach is summarized below, with a more completedescription and examples contained in Table 1.

• Eliminate/Minimize Sources of Emissions or Wastes by using alternative processes/equipment• If Wastes/Emissions cannot be eliminated, Recycle or Reduce them• If Wastes/Emissions cannot be reduced, Treat them cost-effectively• If Wastes cannot be treated, Dispose of them properly

With reference to the ExxonMobil Refining Project System, environmental impacts should be identified andconsidered prior to Gate 1 in the business planning stage. A set of possible alternatives should be explored whereenvironmental impacts are significant. A more extensive evaluation is needed during engineering screening studiesdone prior to Gate 2, as facility bases are prepared, compared and cost estimates developed.It is important that environmental impacts are identified, and alternatives assessed in parallel with economicconsiderations. This early assessment within the planning process allows project management to make more-informed decisions when evaluating project alternatives and their impacts. A team of process and environmentalengineers, along with regulatory compliance specialists should be consulted in the early stages of the project toidentify environmental considerations.In some cases, operating permits may need to be re-opened and re-negotiated with government authorities. In othercases, small incremental investments in low emission alternatives can result in large waste reductions or emissioncredits. These credits may be used with governmental authorities to gain more flexible operating permits, regulatoryrelief in other areas, or intangible, but important public perception credits.Economic evaluation should consider all costs in the life cycle of the project and net environmental impacts shouldbe identified. Design Practices XVIII through XX provide details on recommended procedures and controlrequirements for specific situations. This section provides an overview of the major environmental regulatory issues,a listing of emission sources and types of site contamination, and environmental considerations for specificequipment and process units.Table 2 may be used as a guide to locate sections containing information on a particular environmental control topic.Specific technology is arranged by environmental media (e.g. air, water, waste) and key contaminants.The ExxonMobil Corporation Environmental Performance Indicators (EPI) Manual explains the EPIs that are trackedfrom different regions and segments of the business. Examples include effluent water discharge oil and biochemicaloxygen demand (BOD5) in tonnes per year, and a number of air emissions, including VOCs, SOx, NOx and GHGs.These indicators and corporate targets should be considered when assessing plant environmental facility needs.The EPIs, and Emission Estimating Guide (EEG) and the guidance manual for Environmental Business Plans aretools that can be used to assess facility needs at the manufacturing plant.




REGULATORY ISSUES

General

The environmental laws and regulations which affect ExxonMobil's operations continue to become more stringent andcomplicated. These regulations are usually specific to a particular country, state, or province and each location willhave its own unique set of requirements which need to be met. It is of primary importance to be aware of current andpotential environmental laws and regulations in order to maintain compliance and to prepare for future requirements.Sometimes minor modifications of existing facilities can cause a re-opening of an existing operating permit. In somecases there is opportunity for negotiation in setting both the quantity and concentration of permitted emissions, or siteclean-up/remediation requirements. A recent trend is for regulators to accept “risk-based” solutions rather than strictadherence to numerical standards. Favorable changes in the details and implementation of regulations aresometimes possible if it can be demonstrated that regulations are unnecessarily excessive based upon humanhealth considerations, environmental risk assessment (show negative net environmental benefit), and a cost versusbenefit analysis. . In addition, the new trend in regulation is to provide flexibility in achieving goals. This may allowalternative approaches such as an emission 'bubble' over the entire manufacturing plant, or emissions trading withother manufacturing plants which result in similar emission reductions at reduced cost, to be considered.The charter of most environmental regulatory agencies is to provide for the protection of the community, plantworkers, and the environment. Protection levels for the surrounding community and ExxonMobil personnel aredocumented in government and industry standards and ExxonMobil Biomedical Sciences (EMBSI) publications.These allowable levels are periodically revised, and care should be taken in obtaining the latest limits and in theiruse. Consultation with the plant Industrial Hygienist (IH) is recommended to clarify appropriate long and short termpersonnel exposure limits. In some locations, limits on emissions or clean-up requirements are also set to preservethe “quality of life". This includes such intangibles as the effects on vegetation and animal species as well as odor andnoise annoyances.In most locations, there is a need to obtain a “permit or license" before starting construction or as a condition of beingable to operate the facility. These permits usually set out the allowable emissions from the operation and maydocument the required equipment deemed necessary for control. Various impact analyses may be required in orderto determine ambient concentrations resulting from plant emissions. The most stringent regulatory agencies are likelyto require risk assessments which fully document emissions to all media and consider combined effects of differentemissions on the surrounding community. These analyses involve emission estimates, dispersion modeling, watereffluent estimates and population density and land use considerations (e.g. schools, health care facilities). For siteremediation, clean-up requirements may be based on fixed regulatory contaminant concentrations or may be derivedfrom a risk analysis.

Air

There are several different types of emissions to the air which may be a concern. These include the products ofcombustion, volatile organic compounds, hazardous air pollutants, and particulate matter. Regulation of combustionprocesses has historically focused on the emission quantity and concentration of oxides of sulfur and particulatesbased on respiratory concerns. More recently, oxides of nitrogen have received increased attention due to both acidprecipitation and ozone formation. Particulate emissions have also received additional focus due to the heavy metalswhich may be present in the particulate phase and the potential effects of fine particulate matter. The ambientconcentration of fine particulate matter (less than 2.5 micron), which is generally emitted in aerosol form fromcombustion operations and atmospheric interactions, is now being regulated. The other recent expansion of controlson combustion emissions relates to the so called “greenhouse" effect (global warming) and limits carbon dioxide andmethane emissions (greenhouse gases).Controls on the emissions of volatile organic compounds (VOCs) and on air toxics significantly affect facilityoperations. In many locations, the concentration of ozone (urban smog) is above health based standards. Althoughemissions from mobile sources contribute significantly to these high ozone levels, controls are focused on industrialsources of VOCs and nitrogen oxides (NOx). Addressing concerns about emissions of air toxics and other potentiallyhazardous releases and their effects on the surrounding community is one of the most active regulatory areas. Airemissions from fugitives (valves, pumps, etc.), tanks, waste water treating, loading operations and vents are receivingincreased attention and, in some locations, controls requiring ninety percent or greater reduction in emissions arebeing required. Leak detection and repair programs (LDAR) are becoming prevalent, requiring measurement and





correction of fugitive emissions. Emissions of polynuclear aromatics (PNAs) and heavy metals on particulates fromsources such as landfarms, unpaved roads and site remediation operations are also receiving increased attention.Planning for and mitigating the effects of accidental releases of hazardous vapors has been a major focus of recentregulation. New dispersion models are used to determine the potential affected areas in the result of a spill and alsoto evaluate the effectiveness of various controls. Incidental releases of VOCs and toxics are often the cause ofcommunity odor complaints which are sometimes regulated to protect the “quality of life."There is an increasing trend toward international agreements to address air pollution concerns since in many casesthe effects of emissions are evident large distances from the sources. Reduction of acid precipitation was part of anagreement between Canada and the United States. More recently, the Montreal Protocol, an international agreementto halt production of certain chlorofluorocarbons, was negotiated to mitigate the depletion of stratospheric ozone.

Water

Quality requirements for industrial wastewater effluents have changed significantly worldwide since the passing of theClean Water Act in the United States in 1975. Past regulations focused on conventional contaminants such as oil andgrease, biochemical oxygen demand (BOD5) and suspended solids (TSS). In many locations, regulatory authoritiesare continuing to reduce the allowable concentrations and mass limits of these indicator parameters of pollution. Inthese regulations and many others worldwide, additional emphasis is on the control of toxic compounds. Specificeffluent concentration and/or quantity limits are being imposed on industrial facilities for compounds such asphenolics, benzene, and metals. In many locations regulatory agencies are placing limits on nutrient (nitrogen andphosphorus) discharges which may cause uncontrolled algae or vegetative growth (eutrification) in receiving bodiesof water. The vegetative growth, if escalated to an undesirable stage, can reduce the intended uses of the waterresource, negatively impact wildlife, change the aesthetic appearance or quality, or increase the cost of pretreatingthe water for industrial, domestic or agricultural uses. Regulatory limits for acute and chronic toxicity to aquaticorganisms has become more common, and can affect the selection of WWTP equipment considered in plant design.Many environmental agencies are requiring more consistent compliance and more frequent monitoring and reportingfor established effluent limits. The capability of new analytical methods to measure very low concentrations is creatingthe need for increased emphasis on reducing toxic contaminants. In locations that require maximum water reuse,concerns focus on avoiding excessive concentration of the contaminants that need to be treated prior to discharge.Also, new projects are changing the types and quantities of compounds entering the wastewater system. The needfor more consistent compliance has introduced other challenges to the WWTP operation. Sparing philosophy has tobe considered since there will likely be no scheduled WWTP turnaround for a significant period of time, much longerthan typical refinery petroleum process equipment. Therefore, all WWTP equipment has to be designed for removalfrom service with part or all of the facility in operation, while continuing to meet all discharge requirements.New regulations are starting to consider the tendency of certain compounds to bio-accumulate in aquatic organisms.The protection of larger systems, such as watersheds, is also under regulatory consideration and may requireextensive sampling, analysis and modeling of wastewater effluent discharges into these water bodies.An understanding of current and projected air emission requirements at the WWTP is essential, as it will impacttreatment plant equipment selection, since certain types of equipment are not amenable to retrofitting to meet morestringent air emission standards.

Solid and liquid Waste

Until the mid 1970s, solid and liquid waste disposal consisted mainly of biological treatment via landfarms and burialin landfills. Increasing concerns over protection of human health and the environment have led many countries toplace restrictions on the disposal of these "hazardous" wastes. New regulations have been enacted to protect thequality of ground and surface waters, the air, and land from contamination by solid waste. Today, in many countries,biomass is classified as "hazardous or dangerous" waste.A solid or liquid waste may be deemed hazardous based on its quantity, concentration, physical or chemicalproperties . Wastes may be classified as hazardous if they may cause, or significantly contribute to, a substantialpresent or potential hazard to human health or the environment when improperly treated, stored, transported, ordisposed. A solid waste is usually classified as hazardous when it exhibits characteristics of ignitability, corrosivity,reactivity, or toxicity. In many locations, specific manufacturing by–products or process streams have been classifiedas hazardous. The definition of hazardous may differ between states, provinces, or countries.The trend in solid/hazardous waste regulation focuses on the “cradle to grave" concept of hazardous wastemanagement. This approach involves comprehensive tracking procedures and full documentation of waste




generation, shipment, storage, treatment and disposal. Several regulatory bodies now limit the transport of hazardouswastes to other jurisdictions for disposal. ExxonMobil regions and operating affiliates have plans for managingwastes properly to meet company and government needs. This approach is clearly communicated in OIMS 6.5,which requires a system be in place to track emissions and wastes, to evaluate pollution prevention steps, and tocontrol emissions and wastes consistent with policy, regulatory requirements, and business objectives. ExxonMobilmaintains a list of Approved Hazardous Waste Sites, which are periodically audited to ensure that potential liability tothe company is minimized (refer to ExxonMobil Waste Disposal Site Audit List). If certain wastes cannot be acceptedat these audited sites, treatment facilities may need to be installed on-site.

Site Remediation

Regulations covering the remediation of contaminated sites are focused on reducing the volume, toxicity and/ormobility of the contaminants. These regulations are often focused on protecting groundwater quality. Historically,regulations have addressed clean-up of current or recent contamination. More recently, regulations mandate theremediation of older spills, leaks and disposal sites.Clean-up levels are often fixed by regulation, but may be negotiated based on general guidelines and riskassessments of site specific conditions. Separate surface and sub–surface clean-up levels may be used, reflectingdifferent exposure pathways and potential health risks. In most locations, remediation requirements are based onspecific contaminants of concern as well as general parameters such as the total hydrocarbon present. There is atrend toward setting levels based on risk to humans and ecological receptors. Since many of ExxonMobilmanufacturing facilities have been in operation for over 50 years, project planners need to factor in the cost ofcontaminated soil handling and disposal during the construction of new projects or revamp of existing facilities wheresoil excavation and removal is planned.

Noise

Regulations to control noise are based on protection from hearing damage as well as mitigating annoyance topreserve “quality of life." In addition, limits are sometimes set to ensure clear communications in control rooms.Standards for worker safety have been established and appropriate noise levels for industrial, commercial andresidential areas need to be checked for the particular local jurisdiction. Currently, there are workplace andcommunity noise limits in most countries.Noise sources which may be regulated include blowers, gas turbines, fired heaters, construction equipment, motorsand engines as well as intermittent noise sources such as flares, safety relief valves, and other flow induced noise.Options for controlling the generation of noise and thus mitigating its effects include purchasing low–noise equipmentand installing noise control devices such as enclosures, pipe insulation and silencers.

EMISSION AND CONTAMINATION SOURCESTable 2 lists the major sources of plant emissions along with the pollutants usually associated with each source.Table 3 lists the types of site contamination. Air emissions estimating procedures are included in the ExxonMobilmanual at the following website: http://emre.na.xom.com/tmee046/contents_sra/tmee046.htm

EMISSION REDUCTION GUIDANCE

GENERAL PRACTICES

There are usually a number of ways in which emissions of various pollutants can be reduced. In some cases thereare technical limitations, but most often cost is the major consideration. The first part of this section is focused onreducing the generation of wastes rather than treating or controlling them with “end of pipe" methods. These activitieshave been referred to as “pollution prevention" or “source control". The second part of this section provides specificrecommendations for emissions reduction in manufacturing plant operations. A key activity to evaluate emissionsand potential reduction is to prepare a flow sheet and material balance on the particular facility or project underconsideration. Air Emission estimating tools are on the SHE website (http://emcorp.na.xom.com/she/) and in theEmission Estimating Guide and water/wastewater estimation guidance can be found in the Environmental DesignPractices.

http://emre.na.xom.com/tmee046/contents_sra/tmee046.htm

http://emcorp.na.xom.com/she/





Table 4 describes a hierarchy of environmental control. At the top of the list is waste minimization and at the bottomof the list is disposal. In most cases, the preference in cost effective and responsible waste management is toaddress emissions using techniques near the top of the hierarchy listing.The components of an emission reduction program are listed in Table 5. The most cost-efficient time to incorporateemission reduction opportunities is during process development or facilities design.In application of emission reduction technologies, the effects on other media should be considered. Sometimes, anaction that results in a reduction of one type of emission results in creating a problem in another media. In general,the transfer of a pollutant from one media to another doesn't eliminate the problem, but ideally results in a moretechnically and economically feasible control alternative. Examples of transfers include the control of air pollutantsthat results in the generation of water or solid wastes; removal of wastewater dissolved metals creating a wastesludge; and disposal of sludge to landfill creating potential liability due to contamination of the ground water or soil.

PROCESS AND EQUIPMENT RECOMMENDATIONS

Table 6 summarizes emission reduction options. Additional details on low emission design considerations andemission reduction strategies for selected process areas are summarized below. An in–depth discussion of theseconcepts is available in references 3 and 4.

Alkylation

Sulfuric Acid Alkylation: From an environmental aspect, a key emission issue from the alky plant is low pH material tothe sewer. Biological treatment systems can be severely affected with an acid spill. Low pH (4 or less) in a BIOX unitcan completely kill the microorganisms used for treatment. Therefore, special precautions must be taken in thealkylation unit as well as in the sulfuric acid loading and unloading areas. At the alky plant, a neutralization pit isprovided to allow acid or caustic to be added to neutralize what is in the pit before discharge to sewer. The pit shouldbe designed with reliability in mind. Redundant pH meters should be provided, and corrosion resistant materials mustbe used to prevent leakage to the sewer. At loading and unloading areas, a containment sump should be provided incase of spillage. Fugitive emissions from alky units can be an issue due to use and recovery of isobutane, as well asthe propylene and butylene feedstocks. Alkylation units are provided with their own flare knock-out (KO) drums tokeep acid out of the main refinery flare system. Alkylation plants may include a caustic wash system for propane,which generates spent caustic. This spent caustic can typically be reused in the WWTP if it is metered in the systemat a controlled rate.Hydrofluoric (HF) Acid Alkylation: HF alkylation introduces additional concerns over those of sulfuric acid alkylation,due to the additional safety and IH issues of HF. Fluoride is typically regulated in the WWTP effluent, and limeaddition facilities are typically used to precipitate fluorides from spills and other excursions. While lime can controleffluent fluoride, the calcium added can result in precipitation and scaling in the WWTP primary separationequipment, and in some cases may result in reliability issues in Dissolved Air Flotation units (DAFs) due to solidsdeposition. HF alkylation units also generate sludges which contain fluorides and must be managed responsibly.

Amine Treating, Sour Water Stripping, Sulfur Recovery

In order to limit the sulfur in fuel gas, feedstocks to certain process units, and certain products, refineries removehydrogen sulfide by amine scrubbing. MEA (mono-ethanol amine)and DEA (di ethanol amine)are the most commonamines, but other amines are sometimes used. Amine selection can impact air (primarily SOx) emissions from firedheaters. Amine entrainment from scrubbers, losses from process equipment leaks and excess water purge fromregenerator overhead can all contribute to amine losses. Amine lost will typically end up in the WWTP, andrepresents both BOD and organic nitrogen load. Effective amine unit design should always strive to minimize aminelosses, due to the cost of replacing the amines and their impact on the WWTP. Foaming in amine systems createsmajor upsets, both in the sulfur recovery unit and in the WWTP. All amine scrubbers should be provided with towerdifferential pressure (DP) measurement with high DP alarms in the control center to alert for an amine loss. Oilskimming facilities should be provided in the regenerator overhead accumulator. The rich amine flash drum shouldbe provided with reliable oil separation and removal capability, ideally where no amine/hydrocarbon interfaceinstrumentation is needed (See DP Section V-B). Facilities to inject antifoam at the inlet to the regenerator should beprovided. Activated carbon columns should either be included or stub outs included for future installation. MEAreclaimers generate a high nitrogen sludge, which must be managed. The sludge can put a heavy load on theWWTP, and must be considered in the WWTP design. The preferred alternative is to send the reclaimer sludge to athird party reclaimer or waste disposal site.




Regeneration of the amine produces an H2S rich gas stream that is routed to the sulfur recovery plant. Sulfur plantproblems can result in diversion of high H2S gas stream to an H2S flare. To minimize odor issues with an acid gasflare, fuel gas injection facilities into the acid gas flare should be provided to improve H2S combustion. New designsshould provide facilities to minimize use of the acid gas flare for startups and shutdowns.Sour water streams from many different processes are routed to sour water strippers to remove H2S and NH3. Froman environmental standpoint, it is preferable to use a steam reboiler for heating rather than live steam injection, tokeep stripped sour water volume to a minimum. Fixed valve trays are preferable over sieve trays for better resistanceto fouling and better reliability. Startup and shutdown facilities should include a startup line that recycles effluent backto the feed tank, feed drum, or slop tankage. This allows time to test the wastewater before sending water to theWWTP or desalter. For better ammonia removal, consideration should be given to installing a stripper where theupper section is used for H2S and gross NH3 removal, and the bottom 4-6 trays operate at a higher pH (by injectingcaustic) to achieve 10-15 ppm effluent ammonia levels. Consideration should also be given to provide pH control onthe bottoms from the sour water stripper, since this wastewater is typically reused in the desalter. Lower pH water (pH6-7) is preferred for use in the desalter to greatly improve oil- water separation and prevent oil undercarry in thedesalter washwater discharge to WWTP.Sulfur recovery is usually accomplished in a Claus plant. There are some process options which affect recovery, suchas how many reactors to use (typically 3), and whether to use hot gas bypass to heat the reactor inlets or to use firedreheaters. While hot gas bypass is easier to operate, recoveries are higher with fired reheaters. However, with highefficiency FLEXSOR tail gas units, the hot gas bypass Claus plant might be more desirable. The off–gas from aClaus plant, referred to as tail gas, consists of SO2, H2S, CO2, N2 and water vapor. While most locations used toroute tail gas to an incinerator, most locations now route the tail gas to a hydrogenator followed by a tail gas clean-upunit. The hydrogenator converts all the SO2 to H2S, then the tail gas unit scrubs out the H2S. Essentially all new tailgas units employ ExxonMobil proprietary Flexsorb technology, where the tail gas is scrubbed by an amine solution,which is then regenerated, and the H2S off gas is sent back to the sulfur recovery unit. Flexsorb SE technology canreduce tail gas H2S emissions to less than 5 ppm. It is a very environmentally friendly, totally enclosed system withvery few operating issues, and very minor solvent losses.

Catalytic Reforming

Emissions from reforming can be divided into those from “on–oil" operation and those from catalyst regeneration. The“on–oil" emissions are mostly hydrocarbons in the form of fugitive emissions, water condensates, and as adsorbedmaterial on disposed sludges and media from traps, dryers, and adsorbers. The presence of benzene in thesestreams increases the need for controls. Emissions which occur during regeneration include hydrocarbons,combustion products, and chlorine and sulfur compounds. These species can be found in the reactor purges andscrubber waters, and on spent catalyst, traps, dryers and adsorbers. Some work has shown the potential for very lowtrace levels of dioxin emissions from continuous catalytic reforming (CCR)units and not from Powerformers. Hence,if dioxins are an issue in the particular location, this info may be helpful in identifying the type of reforming unit thatshould be considered for the project.DP XVIII–A2 provides guidance for reducing fugitive emissions. Dealing with the air emissions from the catalystregeneration step is sometimes difficult. One option is to precede the inert gas purge with a hot hydrogen sweep tothe fuel gas system or to send the purge stream to the flare or other vapor control. The latter option is likely not to bean economic alternative.Primary water emissions during regeneration can be minimized by using hot rather than cold flue gas regeneration. Inthe latter, the regeneration gas is scrubbed with water to prevent the recirculation of undesirable chemical speciessuch as HCl and H2S. Alternatively, hot flue gas regeneration minimizes the formation of condensates, but requiresthat the pollutants be controlled as air emissions in a dryer or adsorber. The drier or adsorber will then requireregeneration.In locations where wastewater streams result from wet scrubbing of the on–oil recycle gas or the use of cold gasregeneration, the wastewater stream should be kept isolated to minimize the volume of waste water containingbenzene. In some locations, these benzene waste containing streams may need to be treated separately. For thesame reasons, as well as to reduce the load on the wastewater plant, sludge formed in the separator drums shouldbe kept out of the sewers.





Caustic Treating

Spent caustic is generated after caustic washing of various streams to remove H2S and mercaptans. When H2S isthe only component, the spent caustic can be used at the WWTP for pH control. Spent caustics containing highconcentrations of mercaptans, cresylic acids and/or naphthenic acids must be handled differently. These causticswere at one time reused in the pulp and paper industry, but increased regulations have led to essentially no outletsfor spent caustic from refining. MERICHEM (www.merichem.com) used to and still does reclaim spent caustic in theirprocess at a cost, but those costs have increased dramatically. New projects which generate spent caustic shouldcarefully evaluate whether a waste will need to be sent out for disposal.

Coking

Fluid and Flexicokers: Cokers are a source of combustion products and sour water. Combustion emissions can becontrolled using standard technology. It is not uncommon to combine off gas from Coking units with FCCU offgas.Coker offgas contains basically the same contaminants as described later for an FCCU. Coker wet gas is also similarto FCCU in terms of contaminants and processing requirements. Sour water is generated in Coking units thatcontains H2S and NH3, in addition to phenols and thiocyanate. Typically, the sour water is routed to a sour waterstripper. At locations where it is allowable, coker sour water is used as coke quench. If sour water as quench is notallowed, stripped sour water is an excellent source of quench water, rather than fresh water. Use of stripped sourwater reduces fresh water usage and reduces contaminant load to the WWTP. Coker sour water can also be used tosupplement FCCU circulation water to reduce corrosion in the FCCU. Coke particles, similar to other suspendedsolids that enter the refinery sewers generate up to 10 times their weight in wet sludge, which is costly to dispose of.Sumps at Cokers to collect coke, and coke settling basins or separators, before it gets mixed with other sewercontaminants should be considered. Coke storage facilities can have particulate emissions, and bag filters aretypically specified to reduce particulate emissions. Truck or rail car loading facilities should also focus on minimizingparticulate emissions. Fluid and Flexicokers are an excellent place to reuse sludges generated in refining. However,sludge rerun impacts unit capacity, so this should be considered in new designs. Typical sludge generation per 100kBD of crude capacity is about 150-250 B/D, and additional capacity to handle this should be incorporated into newcoker designs.Delayed Cokers: Delayed cokers generate a wet gas and sour water. Wet gas and sour water considerations arethe same as Fluid/Flexi cokers and FCCUs. In addition, delayed cokers generate spent water from coke cuttingoperations. This water is typically routed to the process sewer, and can contain coke fines. Good design of cokerecovery facilities save sewer cleaning costs later. Sludges are also reused in delayed cokers and new designsshould include facilities to handle the sludge rerun.

Desalting

Crude oil desalters tend to impact wastewater treatment plant operation more frequently than any other piece ofequipment in the refinery. Problems associated with desalting include emulsions, gross free oil, and oily solids. Theproper design and operation of the desalter and brine handling system is imperative for good WWTP operation.While the purpose of the desalter is to control crude unit overhead corrosion and heater fouling by removing saltsfrom the crude oil, the brine quality is equally as important as the desalted crude quality.Crude oil selection flexibility provides a major competitive advantage for any site. However, opportunity crudes makedesalter operation more challenging, and oftentimes the resulting desalter brine quality limits how much of a specificcrude can be processed. Highly water-soluble crude oil contaminants, such as methanol and glycol, partition with thedesalter brine and may pose a concern based on the facility's capacity to handle these contaminants in the WWTP.More information is available in the Environmental Procedure for Processing Challenged Crudes, described in thereference section of this document. The Environmental Procedure is part of the Global Best Practice for ProcessingOpportunity Crudes, also described in the reference section.The desalter handbook and Operating Guide (EETD 085) includes many considerations for desalter design,focussing primarily on maximizing salt removal from the crude. With current trends in crude quality, it is also prudentto pre-invest for crude that is heavier and more viscous than expected when specifying a desalter.Listed below are the most important desalter design considerations from a brine quality standpoint:

1. Use of EMRE mudwash design maximizes water residence time in the desalter, which keeps oil carryunderto a minimum. This extends desalter runlength to allow uninterrupted operation between turnarounds.




2. Use of the three AGAR probe level control design, or the next-generation On-line Water Level (OWL) designprovides maximum desalter level control and allows effective monitoring of emulsion band. Early responsecan prevent grid short circuit and/or wide emulsion band, either of which can result massive oil carryunder.

3. Selection of proper wash water and/or pH control facilities so that desalter brine pH can be maintained at7.0 or below. Higher pH significantly reduces the coalescing efficiency in the desalter.

4. Include facilities to add demulsifier and wetting agent , locating demulsifier injection point far from desalter toallow good contacting.. Wetting agents reduce/prevent buildup of solids stabilized emulsions at theinterface, and also reduce the oil content of the desalter brine solids.

5. Keep water injection to the preheat train upstream of the desalter to no more than 1% on crude. Excesswater injected can result in more difficult to break emulsions in the desalter.

6. When specifying the desalter brine handling system, consider that solids in the brine will foul heat exchangeequipment, and contribute significantly to sludge buildup in downstream brine storage or equalization tanks.

7. For a new desalter, brine oil content should be specified to be less than 250 ppm. Bilectric type desalters,made by PETRECO have very good oil removal capability.

8. All desalter control parameters (mix valve, demulsifier injection, level control) should be in the DCS system.Consistent operation from a manually controlled desalter is not possible.

9. Consider water reuse options for desalter wash water. Use of stripped sour water can reduce the overallBOD and phenol load to the WWT because of phenolic compound removal across the desalter (up to 90%of SWS phenols removed). Use of other process contact condensate can reduce oil levels in the sewer(See DP Section XIX-B).

Desalter brine contributes a large portion of the total benzene that goes to refinery wastewater treating. In the U.S.,benzene removal from desalter brine is typically necessary, requiring a benzene stripper or Induced Gas Flotationunit (IGF). Even at some locations outside the U.S., flotation units have been installed to remove crude solids fromdesalter brine before they get to the WWTP. Solids removal from desalter brine significantly improves WWTPoperation.With the increased concerns about exposure to benzene vapor in workspaces, desalters should be designed to beeffectively cleared prior to entry to avoid need for self contained breathing apparatus. Strategically placed nozzlescan allow circulation of chemicals that will absorb benzene.

Fired Heaters

Fired heaters are being required to use low NOx burners to minimize NOx emissions.. More and more pressure isbeing applied to use gas fuel versus liquid fuel because of greater potential for lower emissions. Instrumentation istypically required which allows furnace heat duty and efficiency to be readily calculated. It is typical to have permitlimits based on furnace heat duty. Furnace SOx emissions are also tightly controlled, but typically managed via fuelgas treatment for H2S removal. However, SOx emission limits may restrict use of waste gas burners in furnaces ifthe waste gas contains significant amount of H2S, mercaptans, or other reduced sulfur species.

Fluid Catalytic Cracking

Air contaminants from fluid catalytic cracking are present in both the reactor product gas and in the regenerator fluegas. The reactor product gases can be purified by merox processes, caustic washing, and/or amine scrubbing. TheFCCU is usually the largest producer of fuel gas in the refinery. FCCU fuel gas can be high in H2S, CO, COS, andmercaptans, and is typically treated with amine. A water wash is sometimes installed before the amine scrubber toremove CO, COS, and other impurities prior to contact with amine. This treating procedure can reduce aminedegradation and improve removal of other reduced sulfur compounds aside from H2S. The source of wash watercould be from wastewater source such as stripped sour waters or pipestill condensate, thus providing a potentialwater reuse opportunity.Regenerator flue gas contains SOx, NOx, CO, CO2 and catalyst fines. There are many control technologiesapplicable to reducing emissions of particulates, sulfur oxides, nitrogen oxides, and carbon monoxide. Reduction ofcatalyst fine emissions has been achieved through a combination of catalyst physical property enhancements, reactordesign considerations, and changes in operating conditions. Present catalysts are coarser, denser and more attrition





resistant and have been combined with significant improvements in cyclone design. Equipment for control ofparticulate emissions include electrostatic precipitators, fabric filters, and wet scrubbing. Additional details areavailable in DP sections XVIII–A3 through XVIII–A6. Approaches to reduce SOx emissions include hydrotreating thefeed, the use of De–SOx transfer additives, flue gas desulfurization, and wet gas scrubbing. SOx emission controltechniques include dry sorbents, and gas scrubbing (dry or wet). NOx emission control methods include selectivenon–catalytic reduction (SNCR) (ExxonMobil's Thermal DeNOx Process and urea based reduction processes), andselective catalytic reduction (SCR). For low temperature (partial burn) regenerators, a CO boiler is used both as a COemissions control device and as a steam generator. It has been found operating the regenerator at full burn(complete conversion of CO to CO2) may result in lower NOx emissions .The FCCU generates the large majority of sour water in refineries. To control corrosion by cyanide, makeup water issometimes added to promote contacting with the gas stream. Ammonium Polysulfide is added to FCCUs to convertcyanide to thiocyanate. Thiocyanate from FCCU can represent a large non-NH3 nitrogen load to the WWTP. TheFCCU Sour water contains phenolic compounds, H2S, and NH3, and is usually routed to the sour water stripper toremove NH3 and H2S. The stripped FCCU sour water typically requires biological treatment to reduce the BOD levelprior to discharge.FCCUs use large amounts of catalyst, and can generate several tons per day of waste catalyst fines when they arewithdrawn. Spent catalyst can sometimes be sold as equilibrium catalyst to another FCCU plant or resid cracker,sent back to the manufacturer to be reclaimed, or disposed of as a non-hazardous industrial waste. FCCU fines alsosettle in the Cat Bottoms stream storage tanks, which need to be periodically cleaned out and generate a wastesludge. FCCU catalyst from loading/unloading operations can contribute significantly to sewer solids if facilities arenot adequately designed. When these solids enter the sewer and get mixed with other solids, the options forhandling are reduced, costs increase, and sludge volume increases due to increase in moisture content.

Hydrogen Manufacture

Hydrogen plants use steam reforming to produce hydrogen from hydrocarbons. A concentrated CO2 stream isemitted from hydrogen plants to the atmosphere. An amine solvent is used to remove CO2 from the hydrogen.Typically catacarb or MDEA is used to scrub the CO2. Catacarb contains Vanadium, which can contribute to thewastewater effluent, so the amounts must be checked versus permit limits. Both catacarb and MDEA contain organicnitrogen and BOD load that can overwhelm a WWTP when spilled. Certain shift catalysts can contribute to highmethanol vapor emissions from hydrogen plants.

Ketone Dewaxing

Solvent losses from ketone dewaxing can be as much as half of a refinery's total toxic emissions. Sources of solventloss include ketone stripper tower bottoms to sewer, residual solvent in the products, fugitive leaks, solventcontaminated drain system, and the blanket gas purge vent. Solvent lost in products is destroyed when the lubeshydrotreater is downstream the ketone dewaxer, and in those cases, is not ultimately released to the environment.Options to reduce emissions focus on improving the operation of the existing equipment as much as possible beforeintroducing new technology or making investment.Ketone stripper tower bottoms losses to the sewer can be reduced by increasing tower bottoms temperature,increasing tower feed temperature, equalizing feed rate by continuous feed of sump water, improving control logic tobetter anticipate load swings, reducing sand fouling of tower internals, increasing the number of effective stages, andinstalling an analyzer to measure solvent loss. Residual solvent in products can be reduced by installation of ananalyzer to monitor solvent loss, and debottlenecking product stripping towers. The above options have the potentialto reduce emissions by about 60 percent.ExxonMobil proprietary Cat Dewaxing doesn’t use a solvent, but doesn’t produce a wax stream either, which canhave a significant environmental benefit and value.

MTBE

Much of the environmental impact of the MTBE synthesis process is due to the use of a large quantity of water whichis needed to remove catalyst threatening contaminants from the hydrocarbon feed stream. Spent water may containacetronitrile, ammonia, methanol, and other organics present in the feed. These can be minimized by reducing theuse of process water and/or finding a suitable disposition for the spent water other than wastewater treatment. Somepotential process changes include recycling spent water, using it in cooling services, as desalter wash water or as




boiler feedwater. Recycling requires treatment such as steam stripping, ion exchange, or chlorination. Methanol isused to make MTBE, and is infinitely water soluble and can represent a large BOD load to a WWTP. Therefore,methanol emissions to refinery sewers must be controlled. MTBE plants should be provided with an isolated sewersump inside the MTBE unit, which is not released to the sewer until methanol levels are measured and low enoughnot to present a problem.

Process Contact Steam Condensate

A significant source of wastewater (in terms of both flow and contaminant level) to a refinery treatment plant iscondensed steam. Non-contact condensed steam should be recovered in the plant, and ideally returned to the boilerfeedwater system. At a minimum, non-contact steam condensate should be recovered in the cooling tower returnwater. Options for reducing steam consumption generally offer improved energy efficiency, lower water treatingcosts, and environmental credits.Steam usage can be reduced in vacuum pipestills by specifying mechanical vacuum pumps instead of steam jetejectors, use of recycled overhead gas as the stripping medium, and optimizing the coil/stripping steam ratio. Insidestream strippers, specifying high efficiency (structured) packing instead of trays or random packing can reducesteam use. Effective design of FCCUs should minimize steam needed to enhance catalyst circulation, to promotecatalyst/hydrocarbon contacting, and reactor stripping steam. Use of reboilers in sour water strippers instead ofdirect steam injection significantly reduces the amount of stripped sour water generated.

Sewers

New designs should consider installing a 3 sewer system consisting of:

- Clean water that does not require wastewater treatment (rainwater, demineralizer waste)

- Contaminated rainwater that requires wastewater treatment (can be diverted to earthen basin or rainwaterstorage tank)

- Process contact sewer water that requires wastewater treatment, preferably in an aboveground system

Tankage

A large semi- continuous source of oil in refinery sewers is from tank water draws that go directly to sewer. Moderndesigns should pipe all crude water draws to a dedicated crude water draw tank. The oil is then returned to crudetanks, so no product downgrade is necessary.Water draws from intermediates, products and imported gasoil tanks also need to be captured. Water draws fromthese tanks should be piped to an offspec slop tank that is designed for oil/water separation. From there the oil canbe sent to a Coker, FCCU or Pipestill.





Table 1: Approach To Manufacturing Plant Environmental Control

*See Note Below

ELIMINATION/MINIMIZATIONThe reduction or elimination at the source, usually within a process.

Measures include process modifications, feedstock substitution,improvements in feedstock quality, improvements in housekeeping and

management practices, and recycling within a process.

RECYCLE/REUSEThe use or reuse of a waste stream as an effective substitute for acommercial product or as an ingredient or feedstock in an industrialprocess. It can occur on or off site and includes the reclamation ofuseful constituent fractions within a waste material, use of a waste

stream after removal of certain contaminants, water reuse, or the useof a waste stream as a fuel supplement or fuel substitute.

TREATMENTAny method, technique, or process that changes the physical,

chemical, or biological character of any waste stream in a way thatneutralizes the waste, recovers energy or material resources from

the waste, or renders such waste less hazardous, safer to manage,amenable for recovery or reuse, amenable for storage, or reduced in

volume.

DISPOSALThe discharging, depositing, injecting, dumping, spilling, leaking, orplacing of waste into or on any land or water so that such waste orany constituents can enter the air or be discharged into any water,

including ground water.

* As a practical matter, there will always be some trace air andwastewater emissions and disposal of wastes at an industrial facility.Source reduction and recycling should be considered in projects onlyto the extent that they are cost-effective or strategically justified, and

do not cause problems to other plant operations. For example, aflare gas recovery compressor can significantly reduce flaring.

However, if excessive nitrogen is in the flare gas, the low BTU fuelgas can cause firing problems (flame impingement, failure to meet

temperature targets, etc) at site heaters. Careful consideration mustbe given to ensuring reliability of affected unit operations resulting

from source reduction/recycling efforts.




Table 2: References To Major Environmental DP Sections

MEDIA POLLUTANT OR CONCERN CONTROL TOPIC SECTION

Air Hydrocarbons Fugitives/Tanks/Waste Water/Loading XVIII–A2

Toxics Industrial HygieneEquipment/Practices

XVIII–B, B1XVIII–A2

Particulates CyclonesBag FiltersScrubbers/DemistersElectrostatic Precipitators

XVIII–A3XVIII–A4XVIII–A5XVIII–A6

Combustion Products(SOx, NOx, CO, Particulates)

XVIII–A, A5, A8

Dispersion Impact Modeling XVIII–A1

Noise Flow InducedCombustionMachinery

DevicesDevicesDevices

XVIII–C, C1XVIII–C, C2XVIII–C

Water NH3, H2S Sour Water Strippers XIX-A10

Oil API SeparatorsFlotation Units

XIX–A1XIX–A2

Suspended Solids Media FiltrationClarification/Thickeners/ FlocculationFlotation Units

XIX–A3XIX–A4, XX–A2XIX–A2

Dissolved Organics/ Phenols/Oil andrelated contaminant indicators, such asBOD5, COD, TOC, Aquatic Toxicity

Biological TreatmentActivated Carbon TreatersChemical Oxidation

XIX–A5, A6, A7XIX–A8XIX-A11

Fresh Water Resources Water Reuse XIX-B

Waste Sludge DewateringIncinerationStabilizationBiotreatment

XX–A1, A2, A3XX–A5XX–A6XX–C1

Spent Caustic Treatment/Disposal/Reuse XX–C4

SiteRemediation

Groundwater Containment XX-B2

Remediation & Monitoring XX-B3

Risk Assessment XX-B1

Soil Containment XX-B2

Treatment XX-B4, XX-C1

Risk Assessment XX-B1

Free-Phase Product Treatment, Recovery XX-B6

Ponds & Lagoons Treatment XX-B5





Table 3: List Of Major Emission Sources

SOURCE CONTAMINANTS COMMENTS

Alkylation Acids, sludges, butadiene

Boiler Feedwater Production Treating chemicals Need to choose biocides, scale inhibitors and dosages carefully toavoid impact on biotreatment, effluent nutrients and toxicity

Catalytic Reforming Benzene, chlorine Benzene leakage from valves.

Coking CO, CO2, SOx, NOx, particulates,metals, cyanide, sulfur, nitrogen andphenolic compounds in wastewater

Sludge receptor.

Combustion CO, SOx, NOx, CO2, toxics,particulates

Large collective source of total plant primary air pollutants.Emissions are taxed in some locations.

Cooling Tower VOCs, several biocides, antiscalingand dispersant chemicals used

Improved leak detection for VOCs. Choice of chemical additives tocontrol microbe biofouling growth and scale formation, particularlywhen cycles are increased for water conservation

Desalting Waste water, benzene, oil, sludge,emulsions

Large volume (50–60%) of benzene contaminated oily water.Large cost to control.

Flares HCs, SO2, combustion products Emissions may be reportable.

Fluid Cat Cracking CO, CO2, SOx, NOx, particulates,metals, cyanide, sulfur, nitrogen andphenolic compounds in wastewater

Largest volume of primary air pollutants from single processsource. Regulatory pressure even for tightly controlled units.

Gas Treating H2S, solvent leaks (organic nitrogen,BOD5)

Gas Turbines NOx

Hydrocarbon Steam Stripping Sour water, benzene water Largest source of sour water.

Hydrocracking Spent catalysts, NH3, H2S

Hydrotreating Spent catalysts, NH3, H2S

Isomerization Spent catalysts

Ketone Dewaxing Ketone leaks, waste water Large source toxic emissions from single process unit.

Loading/Unloading VOCs Potentially large source of VOCs. Many locations require controls

Lubes Processing Solvents (organic nitrogen, BOD5)

MTBE Plant MTBE, methanol

Process Fugitives VOCs, benzene Large contributor of VOCs.

Product Treating Spent caustic Typical industrial disposal outlets disappearing. Upsets in WWTP.

Spent Catalyst Metals Traditional landfill not viable. Most metal bearing catalysts arereturned to vendor.

Sulfur Plant SO2, H2S Sulfur plant reliability a key issue.

Tankage Water draws, VOCs, sludges Large source of waste water, VOCs and sludge.

Wastewater Treating VOCs, benzene, metals, inorganicand biosludges, NH3, phenols,COD/BOD, nitrate

Many source reduction opportunities. Sophisticated treatmentprocess units may be required. Biological systems are typicallythe most cost-effective for organics, metal and toxicity removal.




Table 4: Types Of Site Contamination

SOURCE TYPICAL CONTAMINANTS

Accidental Spills- Leaking tanks- Tank Overfills- Acid/Caustic Spills- Piping Failures/flange leaks- Fires

CrudeProductsChemicalsCatalystsAdditivesWastes

Disposal Practices- Landfarms- Landfills-Tank Sludges- Lagoons/Pits/Impoundments- Dredged Spoils- Oily Water Discharges





Table 5: Components Of An Emission Reduction Program

EVALUATE THE WASTE STREAMSConduct emissions inventoryPrepare waste and wastewater flow and contaminant material balances (requires sampling and lab analysis)Characterize waste (Toxicity, Quantity, Regulatory Impact)Management costsSafety and health risksPotential for successPotential environmental liability

IMPLEMENT LOW COST/OPERATIONS IMPROVEMENT ITEMSSegregation of wastes (optimize treatment efficiency)Improved material handling (to reduce material quantities)Reuse/substitution/operational changesPreventative maintenance

TECHNICAL EVALUATIONProduct qualityProduct safetyWorker health and safetyMaintenance requirementsSpace requirementsInstallation scheduleProduction downtimeReliability/Proven performanceCommercial availabilityPermitting requirements/Community acceptanceRegulatory constraintsEffects on other environmental mediaPersonnel skills requirements

ECONOMIC EVALUATIONCapital requirementsReturn on investmentOperating and maintenance costsLife Cycle Cost AnalysisConsider Third Party Operation of Facilities (Most effective is solid waste sludge dewatering and disposal)




Table 6: Emission Control Guidance

SOURCE CONTROL OPTIONS

Alkylation • Improved pumps and valves to reduce fugitive emissions• Flood systems/dikes to reduce impact of HF release.• Detectors to provide early warning of HF release.

• HF process/storage vents to water–spray scrubbers.

CatalyticReforming

• Ventless regeneration system.• Isolate wastewaters.• Use hot flue gas regeneration.

Coking • Enclosed structures for coke handling and storage.• Reduce sour water production by minimizing steam use.

• Improved COS removal from FLEXICOKING gas.

Combustion • Ultra low NOx (ULNB) burners can achieve 25 ppm in boiler flue gas.

• Addition of SCR (Selective Catalytic Reduction) can achieve 5 ppm NOx, but at 3 to 4 xincremental cost.

• Reduce emissions at individual sources.• Sub–micron particulate removal options

Desalting � Use of EMRE mudwash design.� Use of the three AGAR probe design for desalter level control� Proper wash water selection and/or pH control facilities� Add demulsifier as far upstream as possible.� Keep water injection to the preheat train upstream of the desalter to no more than 1% on

crude.� Consider solids issues when designing the desalter brine handling system,� Use bielectric desalter design� For a new desalter, specify brine oil content to be less than 250 ppm.� All desalter instrumentation should be in the DCS system.� Consider water reuse options for desalter wash water.

Dewaxing • Condense blanket gas vapors.• Improve packing and maintenance.• Seal legs on drains.• Reduce hazard of emissions.� Temperature control of deketonizer.

Dimersol • Spent caustic contains Ni and Al. Do not reuse at WWTP.

FCC • ESP for particulate control.• Wet Gas Scrubber is most cost effective if particulates and SOx control needed.

• DeSOx additives offer moderate control at low cost.

• Other credits needed to make feed desulfurization attractive.• Thermal DeNOx for moderate control, SCR (Selective Catalytic Reduction) for greater

NOx control.

• Control critical parameters that impact emissions.• CO boiler for CO control.

Flares • Recover vapor vents.� Reuse water as flare seal drum makeup• Flare gas recovery compressors

Hydrocracking/Gofining

• Water wash streams should use recycled water from another process





Table 6 (Cont)


IntermittentReleases

• Use closed purge sampling systems where practical.• Coordinate sample volumes with test requirements.• Restock unused paint.• Drain process vessels to closed system or fract tanks for separation before going to

sewer.� Offsite disposal of MEA reclaimer sludge� Include clearing headers in design of process units to route flush material to a closed

system to keep out of sewer.

Loading • Absorption• Adsorption• Vapor balancing.• Thermal oxidation.• Catalytic oxidation.• Carbon adsorption.• Refrigeration

MTBE • Replace wash water recycle loop with individual loops for methanol extraction/recoveryand feed washing.

� May not be easily stripped or removed by conventional treatments• Use of a feed treater instead of a feed wash tower.• Alternates to wastewater treatment for feed wash water.

Process ContactSteam Condensate

• Dry vacuum distillation.• VPS vacuum pumps vs. steam jet ejectors.• Recycle VPS overhead gas as stripping medium.• Replace sidestream stripper trays with packing.

Process Fugitives • 75–90 percent reduction of uncontrolled emissions achievable via practice changes -annual inspections, graphite packing replacement.

• Enhanced (“smart") inspections, which target the few significant sources, are cost–effective step.

• Use 5–ring valve packing with three low density graphite sealing rings and braided orcomposite rings.

• Use ESVP (Extended Stem Valve Packing) for Reformer MOVs (Motor Operated Valves).• Use rupture disks with pressure relief valves.• Consider sealless (mag drive, canned) pumps as replacements, or install double seals.• Consider environmental impact in equipment selection.

Product Treating(Spent Caustic)

• Cascaded reuse in less severe service.• Wash or condense Merox vents to remove sulfur compounds.• Replace caustic treating with regenerable treating (e.g. Merox, amine).• Regenerate spent caustic.

SOx Management(overall)

• Optimum priority for control is: (1) sulfur plant, (2) combustion controls, and (3) FCCcontrols.

Spent Catalyst • Cascaded reuse in less severe service.• Use as filler in construction materials (e.g. cement, asphalt, and brick).• Offsite total recovery systems (e.g. CRI–MET).• Onsite integrated treatment and recycle (e.g. MAGNACAT, DEMET).• Upgrade feed quality.• Minimize inventory.• Reuse spent phosphoric acid polymerization catalyst as biox nutrient.• Increase catalyst life.




Table 6 (Cont)


Sulfur Recovery • Consider adding a third stage Claus catalytic reactor.• Catalyst selection for destruction of other sulfur species� Add tail gas clean-up unit (TGCU).

Tankage • Double rim seals on external floating roof tanks.• Liquid mounted in place of vapor mounted seals.• Slotted guide pole sleeves• Internal floating roofs on fixed roof tanks.• Tankage minimization.• Tankage vapor recovery systems.• Route tank water draws to separate oil/water separation equipment.� Mixers on crude tanks to minimize sludge deposition

WWTP • Major troublesome sources of oily water are desalter and tank water draws.• Steam stripping is major source of sour water., but stripping essential to remove sour H2S

and NH3 to acceptable levels prior to further treatment• Inadequate housekeeping, practices still a major contributor.• Water flow (versus oil content) is key parameter for facility sizing and impact� Reduction in soluble , non-biodegradable organics, where possible to reduce BOD /COD

load. Use light napthas vs. aromatic oils for diluents• Trend towards closed, above ground treatment facilities (including sewers).• Segregate streams for upstream treatment.• Reuse water within process or in another process.; example reuse stripped sour waters

(SWS bottoms) for desalter feed makeup (reduces phenols)• Reduce sludge volume via sewer segregation, wastewater reduction, feed to cokers.

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