Pinch White Paper (Rev 3) 2012

Pinch white paper (2012) rev 3 Page 1 of 21 © J D Kumana, 4/2012

PINCH ANALYSIS - WHAT, WHEN, WHY, HOW

Kumana & Associates, Consulting Engineers 3642 Robinson Road, Houston, TX 77459

Tel (281) 437-5906, [email protected] In the early 1980s, against a background of the “energy crisis”, Pinch Technology emerged as a tool for the design of heat exchange networks. Its key feature was to give the engineer simple concepts to use interactively, enabling him to stay in control. Applying Pinch Analysis (as it is now called), the engineer could calculate the “target” energy requirement for any process, and produce thermally efficient and industrially acceptable designs which took account of operability, plant layout, safety, start up etc. The basic concept is simple: the performance of any system is always limited by a single constraint – the Pinch – just as the strength of a chain is determined by the strength of the weakest link. If one needs a stronger chain, Pinch Analysis teaches that the most cost-effective strategy is not to replace the chain with a new one, but to increase the strength of the existing chain by selectively replacing the weakest link(s). Pinch Analysis achieved almost instant acceptance as a superior approach to the design of optimum Heat Exchanger Networks (HENs), with proper account being taken of capital costs and payback requirements. Typical fuel savings were 20% or more compared to the existing or previous best design. In the next major advance, Pinch Analysis was extended to the analysis of on-site utilities, such as boilers, turbines, heat pumps, and refrigeration systems, and techniques were developed for optimum design of Combined Heat and Power (CHP) systems. Over the past 25 years, Pinch Analysis has evolved from this specialized tool for energy efficiency improvement into a broad-based methodology for reducing capital costs, minimizing environmental pollution (NOx, SOx, VOC, wastewater), freshwater conservation, wastewater treatment system design, batch process scheduling, capacity debottlenecking in both processes and utilities, and site development planning. The most recent applications have been in management of chemical species, such as hydrogen and sulfur in oil refineries, and in conservation of electrical power. A key feature of Pinch Analysis is the setting of targets before design. The “target” level of heat recovery represents the optimum economic trade-offs between costs for steam (fuel), cooling water, refrigeration, shaftwork, HEN capital, CHP capital, and maintenance. No matter what the current cost of energy, Pinch Analysis provides the optimum design for that cost. Since constraints of safety, reliability, and operability are factored in as well, the final design is not only practical, but is guaranteed to meet the payback criterion specified by the plant owner. Of course, the magnitude of savings realized will depend upon the payback stipulated. The longer the acceptable payback, the bigger the savings, as in Figure 2.


Figure 1: (a) Traditional design approach (b) Targeting before design

Figure 2: Typical Relationship of Potential Energy Savings to Payback

The project workflow using the pinch approach is shown in Figure 3. The problem is first transposed into the pinch format, which plots “composite curves” of resource (energy, water, etc) demand and availability. Then targets are set and a broad set of pinch design rules used to approach the target as closely as economically and practically possible. Working in this transposed environment gives the engineer a simple visualization of even the most complex problems and enables quick assessment of alternatives, including outline economics. Constraints can easily be considered and


either overcome or accepted. Finally, the pinch environment is transposed back to ‘PFD’ form, and the final stages of simulation, feasibility checking and detailed design are completed.

Figure 3: Project Workflow with Pinch Analysis It should be kept in mind that Pinch Analysis does not give the final optimum HEN design immediately. What it does do is help the design engineer to systematically organize the process demands, and then provide heuristic rules to identify 3-4 near-optimal flowsheet structures. This can be called the “structural optimization” stage. This must be followed up with “parametric optimization” to pick the best design for that particular site, using conventional flowsheet simulation/optimization tools, keeping in mind constraints of safety, operability, reliability, and of course economics. Thermal Energy Efficiency and Design of Heat Exchanger Networks All chemical manufacturing processes require energy in the form of heat and power. Power is consumed both for shaftwork and for cooling. The individual process heating duties can be combined into a single “cold composite curve” drawn on a temperature-enthalpy (T-H) diagram; it represents the enthalpy demand profile of the process. Similarly, all the cooling duties can be combined into a single “hot composite curve”, which represents the enthalpy availability profile of the process. When both curves are plotted on the same T-H diagram, as in Figure 4, they show the opportunity for heat recovery as well as the minimum net heating and cooling requirements. The point of closest approach, where available temperature driving forces between hot and cold streams are at a minimum, is called the process pinch. It separates the overall process into two distinct thermal domains: (a) a net heat sink above the pinch temperature, meaning that hot utility must be supplied, and (b) a net heat source below the pinch temperature, meaning that cooling must be provided. The temperature difference between hot and cold streams at the pinch is called the Minimum Approach Temperature (MAT). For each value of MAT, there are corresponding values of minimum heating and cooling requirements (Qh)min and (Qc)min. These are the energy targets.


Figure 4: Composite Curves (a) without heat recovery (b) with heat recovery

In order to achieve the targets, the HEN design must satisfy three conditions:

1. No hot utilities used below the pinch temperature 2. No cold utilities used above the pinch temperature 3. No heat transfer from hot streams above the pinch to cold streams below the pinch

From these fundamental rules, it is possible to derive a number of useful design guidelines. For example: • Heat engines must not cross the pinch, i.e., the supply and exhaust temperatures should both be

either entirely above or entirely below the process pinch temperature. • Heat pumps must be placed across the pinch, i.e., the supply temperature must be below the

pinch, and the exhaust temperature must be above the pinch. • Distillation and evaporation operations must not cross the pinch. These and other rules help the engineer to design the process for maximum overall efficiency, achieving the optimum balance between capital costs, energy consumption, operating flexibility, and environmental emissions. Electrical Power Conservation and Recovery Energy has two primary manifestations – heat and power. Process integration concepts for heat recovery are well established, but the techniques for power conservation and recovery are relatively new. How does one recover power? Indirectly, through expansion of a high pressure gas or vapor through a turbine. In many chemical plants, high pressure gases are let down through an expansion valve, which wastes the potential energy in the fluid. The high pressure gas/vapor should instead be expanded through a turbine that drives a pump or compressor or generator. Power conservation and recovery can be accomplished in many ways, e.g.

• Reduce process flows by minimizing recycles • Reduce pressure drop through piping network and control system modifications • Use of direct “pressure exchangers”, if a certain amount of liquid mixing can be tolerated • Load management for pumps, compressors, and steam/gas turbines • Load shifting between multiple refrigeration levels


• Adjustable speed drives (eg. variable frequency motors). • Pressure recovery through gas/vapor expanders and hydraulic turbines • Pressure recovery through ejectors and thermo-compressors • Inlet gas heating for turbo-expanders • Use of inlet-cooled turbo-expanders for refrigeration • Reduce the inlet temperature of gas/vapor to a compressor • Increase the inlet temperature to a backpressure steam turbine or gas turbine (expansion

section) These all could have an impact on the process heat and material balance, which usually means that the heat exchanger network may have to be modified as well. Recent results have shown that power and thermal pinch analysis, when done in tandem, can yield spectacular savings, up to 40%.

Figure 5: Incorporating Electrical Power Savings into Thermal Pinch Analysis CHP System Design using Total Site Energy Profiles In Total Site analysis, the objective is to optimize the energy interactions between multiple process units at a site. The residual heating and cooling duties (after heat recovery) are extracted from the “grand composite curves” of individual process units and combined together in a Total Site profile, which gives a graphical representation of the total site Combined Heat and Power (CHP) system, as in Figure 6. This construction enables the experienced engineer to understand the integration possibilities between processes through utilities, appropriate steam levels and loads, cooling water duty, refrigeration levels and duties, optimum cogeneration strategy, fuel use, etc. There is usually a large potential for improvement in overall site efficiency through inter-unit integration via utilities, typically 10-20% at a 2-yr payback.


Figure 6: Construction of Total Site Energy Source-Sink Curves

Figure 7: Optimum CHP System Configuration Derived from Total Site Profiles

The economics of existing and proposed CHP configurations are then modeled by simulation, eg. using an electronic spreadsheet (Figure 8), to confirm the steam/power balance, and to calculate economics. The model calculates the true marginal costs of steam consumption and power generation, and is a very useful tool for evaluating energy conservation projects in the global context. The simulation model is also useful for “what-if” analyses of alternative scenarios, such as different production rates, different operating strategies, different fuel and electric supply contracts, etc. The simulation model is also very useful for determining the true marginal value of steam savings, which is not a fixed number, but changes with generating rate (Figure 9).


Figure 8: Superstructure for CHP System Simulation Model

Figure 9: Typical Marginal Steam Cost Variation with Generation Rate


Water Conservation and Wastewater Minimization Each water related process operation can be considered as having input and output water streams, and a composite of water demand (input streams) and water sources (output streams) can be constructed. Figure 10 shows such a Water Pinch construction, which graphically depicts the water sources and demands in a process, on purity vs flow axes. This identifies a pinch, the area in the process which is most constrained. The area of overlap (shaded) shows the scope for water reuse. As with Energy Pinch, rigorous design rules must be followed to evolve the optimum “distributed effluent treatment” design.

Figure 10: Water Pinch Approach: Basic Representation

Although the targeting concept is simple, optimizing a water network involving reuse, recycling and treatment options can become very complex, especially when one must deal with multiple contaminants. The design algorithm requires powerful mathematical programming techniques and software. The Water Pinch approach uses these mathematical tools for optimization, and composite curves for graphical visualization and interpreting the results. Integrated Process Debottlenecking Expanding production of process units will eventually lead to capacity bottlenecks. The capacity pinch may occur in the piping system, in a distillation column, in the heat recovery network, or in the utility system (eg. fired furnace, boiler, cooling tower, wastewater treatment). Traditionally, independent teams are set up to redesign the various parts of a process such as columns, to achieve the desired throughput. This often results in missed opportunities to exploit differences in “capital efficiency” between different areas of the plant. Pinch Analysis provides an integrated design approach in which cost-benefit trade-offs can be intelligently and easily made across design disciplines and plant areas.


The tools include combined hydraulic/thermodynamic analysis, Column Targeting, and pressure drop vs heat recovery network design. Examples of applying this approach are: • 8% debottleneck in column capacity achieved at much lower cost by adding side condenser,

instead of the original solution of increasing by 5% through retraying. • Use of extra heat exchange area and parallel trains to overcome bottlenecks on both pumps and

furnace. Oil refinery Hydrogen and Sulfur Optimization The trend in the oil refining industry, worldwide, is towards more sour and heavier crude oils as feedstock, and lower demand for fuel oil. Coupled with lower sulfur and aromatics specifications for gasoline, refiners are facing a need for dramatic increases in hydrotreating capacity. Optimizing the recovery, distribution, and utilization of hydrogen has become an important issue, the only alternative being loss of operating flexibility and further erosion of already tight profit margins.

Gas flow: MMscf/d Hydrogen NetworkVol% H2

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Figure 11: Simplified H2 Network Model

Hydrogen management using the techniques of Pinch Analysis helps find solutions that lead to reduced capital outlay, lower operating costs, lower emissions, improved product quality, and increased yields/capacity. The tools include H2 surplus diagrams, short-cut simulations, and LP- optimization.


H2 surplus diagrams set targets for fresh hydrogen consumption, identify bottlenecks of the distribution system, and highlight opportunities for improved utilization through redistribution and recovery. Short-cut modeling is used to produce overall H2 balances and LP tools are used for network optimization. Typical savings are 5-10% of fresh hydrogen consumption. A similar approach could be applied to refinery sulfur management. Benefits The benefits of Pinch Analysis, when retrofitting an existing plant include: • Lower energy consumption, due to better thermal integration • Lower energy costs, due to lower consumption as well as shifting load from higher to lower cost

utilities • Lower emissions of combustion products (eg. NOx, SOx, CO2) • Lower emissions of CHP system wastes such as boiler and cooling tower blowdown. • Capacity debottlenecking of energy utilities such as boilers, furnaces, cooling towers, and

refrigeration systems • Capacity debottlenecking of distillation columns and batch processes • Reduced freshwater consumption and wastewater effluent flow • Capacity debottlenecking of wastewater treatment system (with attendant capital cost savings) • Improved hydrogen utilization and profitability in oil refining operations Figure 12 shows the documented results for reduction in the corporate energy efficiency index for a major national oil company in the middle-east, using process-integration techniques on a company-wide basis, despite low energy costs and high capital costs.

Figure 12: Actual Energy Efficiency Improvement for a Mid-East Oil Company

The implemented projects will save the equivalent of about 34 MBD of oil. Total economic potential for energy savings from identified projects is around 92 MBD oil equivalent (18,500 TPD of CO2


emissions reduction), which can be expected to rise as the valuation for energy rises relative to capital costs. In new plant designs or plant expansions, it is possible to reduce capital costs by 5-10% compared to the “base-case” designs typically proposed/offered by EPC contractors, and to compress the design/construction schedule by 1-2 months. While this may sound counter-intuitive, upon careful analysis the reasons become apparent (see Figure 13 and Table 1).

Figure 13: Petrochemical Unit Flowsheets (a) original - top (b) optimized - bottom

When is the right time to incorporate process integration (Pinch Analysis) into the design? As early as possible (see Figure 14). Published industry statistics show that 80% of long-term economics for a new process plant are locked in at the conceptual design stage – when barely 2% of the engineering budget has been spent (~ 0.2% of the project budget).


A recent study by the Construction Industry Institute of 53 major projects showed that those who spent the most effort on FEED (front-end engineering design) optimization averaged 20% lower operating costs, 39% schedule compression, and 15% higher capacity/utilization compared to the group that spent the least effort on pre-project planning.

Table 1: Economic Comparison of Original vs Optimized Petrochemical Unit Flowsheets

Figure 14: The Right Time for Process Optimization


Track Record Pinch Analysis burst onto the scene in the mid-1980s as a novelty, but within a few years quickly became accepted as mainstream “best practice”, especially in the chemical and petroleum industry. The larger companies with multiple plants have established in-house teams of Pinch specialists, but for the majority of small-medium size companies, the optimum strategy is to retain consultants specializing in Pinch Analysis to support their energy programs. In the early days, governmental agencies like the US Dept of Energy and ETSU in the UK, trade organizations such as EPRI and GRI, and utility companies sponsored over 50 case studies in the early 1990s to prove the technology (see Table 2) and to share the results and implementation history.

Table 2: Summary of Demonstration Study Results

% Cost Savings Payback Industry # of Plants Avg Range Range, yr Oil Refining 9 29 10 - 40 0.6 - 2.8 Chemicals 17 32 15 - 40 0.9 - 4.3 Food & Beverage 18 25 7 - 45 0.7 - 3.9 Pulp & Paper 9 18 10 - 35 0.8 - 2.4 Textiles & Fibers 4 12 3 - 25 1.1 - 4.7 Iron & Steel 2 31 11 - 50 0.9 - 1.5 59

Figure 15: Payback on Energy Saving Projects Ranges from

1 to 3 years, even with low energy prices Savings generally stem from a variety of sources – heat recovery optimization (HEN revamp), CHP system optimization, process modifications, equipment upgrades, and improved operational practices. The use of on-line performance monitoring using Energy Efficiency Indices and other metrics has proved to be a particularly valuable tool.


Pinch Analysis has been successfully used across the full spectrum of the chemical process industries.

• Oil refining & gas processing • Distilleries & Breweries • Petrochemicals • Pharmaceuticals • Fertilizers & Pesticides • General Organic Chemicals • Polymers & Fibers • Inorganic Chemicals • Pulp & Paper • Synthetic Fuels from Coal • Food Processing • Minerals & Metals

The electric utility industry in the US has been particularly active in encouraging large industrial customers to apply Pinch Analysis for a variety of reasons, including: a) Load retention – an efficient plant is more likely to be economically competitive, and to expand

production in the future. b) To gain an understanding of the customer’s CHP system – whether it is a candidate for heat

engines, heat pumps, load leveling via demand side dispatching (of cogeneration capacity), etc. c) To develop better working relationships and potential partnerships with major industrial

customers. d) To help reduce local environmental emissions. Barriers to more rapid and widespread acceptance of Pinch Analysis are mostly due to the following common misconceptions and fears in the minds of technical managers: • The existing process has already been “optimized” for heat recovery, so there could be no further

scope for energy cost savings. • Additional heat recovery will not be economic unless fuel prices are “high”. • A high degree of integration will cause problems with operating flexibility and product quality. • If a consultant finds big opportunities for performance improvement in my facility, it will reflect

poorly on our plant engineers. • Optimizing a new plant at the design stage will cause schedule delays and cost over-runs. First and foremost, it is important to understand that there are two kinds of optimization - structural and parametric. In parametric optimization, the process configuration itself is fixed, and the focus is on selecting the best combination of parameter values (flow rates, temperatures, compositions) that result in the lowest operating cost. This is the traditional way. Pinch Analysis, on the other hand, addresses the process structure itself, and determines the optimum equipment configuration to start with. This is called structural optimization. Typically, the gains in efficiency from structural optimization are in the range of 15-35% compared to 3-7% for parametric optimization. Structural and parametric optimization are complementary; for best results one should use both. Second, when done correctly, the relative costs of capital and energy (or water) are already built into the equation, so the issue of high or low energy costs does not even arise. The design will always be optimum for the prevailing site-specific economic conditions. Third, a “high” degree of integration is not necessarily the correct design. In a good design there is a balance between capital costs and operating costs that include not only energy but also productivity (eg. downtime due to fouling, quality loss due to control excursions, maintenance costs, etc) and safety/reliability issues. Pinch Analysis offers a way to quantify these impacts in a systematic


manner. The ultimate design decision is still in the hands of the engineer and project manager, as it should be. Only a bad carpenter blames his tools. Comparable results have been obtained in the other areas to which pinch analysis has been applied, although the track record is not as extensive because the methodology is more recent. Water conservation and wastewater minimization projects have so far been completed in the oil refining, petrochemical, chemical, and pulp/paper industries. Flow savings have ranged from 20-50%. Integrated capacity debottlenecking projects have been completed for oil refining, petrochemicals, and specialty chemical (batch) plants. Capacity increases of 10-30%, without significant new capital investment, have been identified. Making It Happen • How do I identify candidate sites for a pinch study?

The attached Checklist will help take you through the logic of when, where, and how to use Pinch Analysis effectively.

• How is a Pinch study different from a conventional energy audit? A conventional audit looks at how the existing plant operation can be brought closer to “best practices” with respect to insulation, tracing, steam condensate recovery, boiler efficiency, controls, and opportunistic heat recovery. A pinch study, by contrast, looks not at equipment features, but the site as a whole. It takes a systems approach, as opposed to a component approach. The focus is on exploiting the synergy between components that is unique to the particular site. From fundamental thermodynamic analysis, the absolute minimum energy consumption target and the absolute maximum power generation potential can be identified. It provides a site-specific benchmark of performance, rather than questionable comparisons with competitive plants which may have completely different economic parameters - plant size and vintage, raw material quality, product mix, local utility costs, weather conditions, labor costs, etc. In short, a pinch study significantly complements and augments a conventional energy audit.

• What will it cost?

The scope and costs of a pinch study vary widely, from US$40K to 350K, depending on the complexity of the process, the objectives of the analysis, availability of necessary data, and who does the work. Although some large multinational industrial firms have developed in-house capability to perform pinch analyses, most have found it more cost-effective to hire outside consultants. The consultant’s fee can be reduced by 40-50% if the responsibility for data collection and reconciliation is borne by plant personnel.

• How much effort will it take to compile usable heat and material balance data?

Most oil refineries and petrochemical plants tend to maintain up-to-date flowsheets and reliable heat/material balances. For them the incremental effort for a pinch study would be minimal. However, if the plant does not have flowsheets and heat/material balances, as is common in many industries, about 1-2 man-months would be required.

• What software tools are available commercially?

Several companies offer Pinch Analysis software, with varying capabilities and cost. High end software with full design capability (capital/energy tradeoffs, multiple utilities optimization, interactive HEN design, distillation column analysis, total site CHP integration, exergy targeting) leases for between US$25-40K per year, including technical support. Low end software with only basic energy targeting capability can be purchased for under $10K. Commercial-grade software for modeling water systems and wastewater optimization is also available.


• Where can I get training in Pinch Analysis and the use of the software?

The primary sources of training for the general public are introductory 1-4 day courses offered through the University of Manchester Institute of Science and Technology (England), and the American Institute of Chemical Engineers (New York). Customized training is also available through software vendors (IHI/ESDU, KBC, Aspen) and consulting firms specializing in process integration, eg. Kumana & Associates.

Additional Reading and References 1. “Debottlenecking of Refinery Units using Pinch Technology”, Karp, Rutkowski, and Wells,

Energy Processing Canada, (Jul/Aug 1989).

2. “Putting the Pinch on Energy Costs”, EPRI Journal, (July/Aug 1991).

3. “The Goal”, 2nd ed, Goldratt, North River Press, Great Barrington, Massachusetts (1992)

4. “Use Process Integration to Improve Process Designs and the Design Process”, Morgan, Chem Eng Prog, (Sep 1992)

5. “Optimum Dispatching of Plant Utility Systems to Minimize Cost and Local NOx Emissions”, Nath, Kumana & Holiday, ASME Proc: Ind Power Conference, New Orleans (1992).

6. “Optimization of Total Site Energy and Utility Systems using Pinch Analysis Concepts”, Skelland and Petela, Kemia-Kemi, Vol 20, no.4 (1993).

7. “Pinch Analysis – A State-of-the-Art Overview”, Linnhoff, Trans I Chem E, Vol 71, part A (Sept 1993).

8. “Pinch Technology: Optimizing Process Efficiency and Minimizing Capital Costs”, EPRI publication no. BR-102466 (1994).

9. “User Guide on Process Integration for the Efficient Use of Energy”, Linnhoff et al, Gulf Publishing Co, Houston (1994).

10. “Use Pinch Analysis to Knock Down Capital Costs and Emissions”, Linnhoff, Chem Eng Prog, (Aug 1994).

11. “Chemical Process Design”, Smith, McGraw-Hill Inc, New York (1995).

12. “Heat Exchanger Network Synthesis”, Shenoy, Gulf Publishing Co, Houston (1995).

13. “Process Integration: Planning your Total Site”, Rudman, Chemical Technology Europe, (Jan/Feb 1995).

14. “Waste Minimization through Process Design”, Rossiter (ed), McGraw-Hill, New York (1995).

15. “Make your Process Water Pay for Itself”, Dhole et al, Chem Eng, (Jan 96).

16. “Freshwater and Wastewater Minimization: Concepts, Software and Results”, Buehner and Kumana, Chemputers Conference proceedings, Houston, TX, (Mar 1996).

17. “Water Conservation and Wastewater Minimization through Process Integration”, Kumana, Paper 57m, presented at 5th World Chemical Engineering Congress, San Diego, CA (Jul 1996)

18. “Pollution Prevention through Process Integration”, El-Halwagi, Academic Press (1997)

19. “Process Water Reduction using Water Pinch Technology”, EPRI publ no. TA-114453 (1999).


20. “Hydrogen Network Management – A Systems Approach”, Linnhoff, Tainsh, and Wasilweski, paper presented at European Refinery Technology Conference, Paris, France (Nov 1999).

21. “Refinery Hydrogen Management”, a series of technical briefs published by Aspen Technology Inc., Boston, Mass.

22. “Thermodynamically Rigorous Approach to CHP System Design”, Kumana, Proc. of 21st Industrial Energy Technology Conference, Houston, Tx (May 1999).

23. “A Critical Comparison of Alternative Methods for HEN Retrofit Design“, Kumana, 51st Canadian Congress of Chemical Engineering, Halifax, Nova Scotia (Oct 14-17, 2001).

24. “Fuel and Power Conservation Opportunities in Gas Processing”, Kumana, Rumaih, and Juaidan, Gas Processors Assn Technical Conference, Muscat, Oman (May 21, 2003).

25. “Optimization of Process Topology Using Pinch Analysis”, Kumana and Qahtani, Proc of First International Symposium on Exergy, Energy and Environment, Izmir, Turkey (July 13-17, 2003); edited version republished in Saudi Aramco Journal of Technology (Winter 2004), pp 13-23.

26. “Pinch Analysis: A Practical Tool for Effective Water Management”, Kumana, Petrotech 2003 Conference, Bahrain (Sep 29 – Oct 1, 2003).

27. “Chemical Process Design and Integration”, Smith, John Wiley & Sons Ltd, England (2005).

28. “Electrical Power Savings In Pump And Compressor Networks Via Load Management”, Kumana and Aseeri, Proc of 27th Industrial Energy Technology Conference, New Orleans, La (May 2005); edited version republished in Saudi Aramco Journal of Technology (Fall 2005), pp 39-43.

29. “Power Savings via Load Management at Rabigh Refinery”, Kumana, Qahtani, and Farsi, presented at 2nd Saudi Arabian Energy Conservation Forum, Dammam, KSA (Nov 28-29, 2006).

30. “Meaningful Energy Efficiency Performance Metrics for the Process Industries”, Kumana, Proc of 31st Industrial Energy Technology Conference, New Orleans, La (May 12-15, 2009).

31. “Corporate Energy Management Programs: A Case Study”, Kumana, Chemical News (November 2010).


PINCH CHECKLIST for ENERGY SYSTEMS Yes No 1. Base Case energy consumption > $500K/yr 2. At least 4 streams with heating or cooling duties > 100 KBtu/h each If you answered No to either 1 or 2, you should attempt to design the heat

recovery system by inspection, using intuition and experience. The potential energy savings would probably be too small to justify the cost and effort of a formal pinch analysis study. Else, continue

3. Do either of the following conditions describe the situation at your plant? a) pressure from top management to reduce energy costs b) production capacity limited by energy utilities (eg. steam, CW) supply If you answered No to both 3a and 3b, it might be premature to propose a

pinch analysis at your site at this time. If you answered Yes to either, conduct a scoping study to determine energy targets and savings potential. For this you will need to perform the following tasks:

• Develop simplified process flowsheets • Develop consistent heat and material balance • Prepare overall site utilities balance, reconciled vs meters • For batch operations, prepare detailed activity schedules for each item of

equipment, production line, and/or product

• Assemble cost data - utilities, equipment capital, payback criteria • Data extraction • ∆Tm optimization • Identify potentially beneficial process modifications • Composite curves • Determine energy targets, with and without process mods • Calculate savings potential Some of these tasks will require specialized pinch software. 4. Savings scope, including simple process modifications, >15% If No, potential savings may be too small to justify further work. Else,

proceed with detailed pinch design study, consisting of

• Appropriate placement of distillation & evaporation operations w.r.t. pinch • Time average and Time slice models (for batch processes) • Identify HEN design/retrofit projects • Identify CHP design/retrofit projects • Techno-economic feasibility analysis 5. Number of process units on site >2? 6. Is the optimum CHP system configuration significantly different than the

existing or base case (if new plant) design?

7. Are there any plans to add new units or shut down existing process units that could have a significant impact on steam/fuel demand?

8. Are there any plans to replace or expand the existing utility system? 9. a) Do you currently co-generate electrical power? b) If not, are you considering it? 10. Do you have at least one condensing steam turbine?


If you answered Yes to any of questions 5 - 10, then conduct a Total Site

Analysis, including the appropriate combination of the following tasks:

• development of a CHP simulation model • site-wide source sink profiles • shaftwork (power generation) targeting • optimization of steam header pressures and loads • optimization of refrigeration levels and loads • CO2 emissions targets


PINCH CHECKLIST for CAPACITY DEBOTTLENECKING 1. Where are the bottlenecks? Continuous processes Yes No a distillation capacity b evaporation capacity c pumps d compressors e fired heaters f boilers g cooling tower h refrigeration system i vacuum system

Batch operations Yes No a reactor b heater c cooler d pump e dryer f holding vessel/tank g furnace h boiler i cooling tower j refrigeration system k vacuum system

2. Appropriate action if you answered Yes to any of the above: Process Type Item# Recommended Action Continuous a Column targeting, thermal/hydraulic analysis b Reduce flow, reduce line ∆P (eg. ASDs), or replace pump/motor c-f Energy pinch analysis, Exergy analysis (for refrigeration) g Parallel equipment; shift load between vac pump & steam jets Batch a-f Decompose activities into external, possibly additional, equipt Try to overlap activities, concurrent vs sequential Process mods such as changing reactor temp, adding catalyst, adjusting

reactant ratio, improved mixing, column pressure “crash” activities on the critical path, through selective additional

equipment in parallel, or using higher grade utilities g-k Energy pinch analysis - time average & time slice models Utility load leveling through better scheduling of activities, using Time-

Event charts


PINCH CHECKLIST for WATER & WASTEWATER FLOW MINIMIZATION

Yes No 1. Average plant water intake > 100 gpm 2. At least 4 water users of > 10 gpm each If you answered No to either one of the above, you should attempt to design a

water reuse strategy by inspection, matching wastewater sources with water users by intuition and experience. The potential water savings would probably be too small to justify the cost and effort of a rigorous pinch analysis study. Otherwise, continue.

3. Do any of the following conditions describe the situation at your plant? a) potential for water supply restriction in foreseeable future b) production capacity expansion limited by existing water supply c) pressure from top management to reduce sewer charges or on-site

wastewater treatment costs

d) regulatory compliance order to reduce wastewater flow to outfall e) reduced flow will eliminate need to expand/upgrade wastewater treatment

facility to match planned production capacity increase or to meet tighter effluent criteria.

If you answered No to all (3a-e), pinch analysis, while applicable, is not for you at this time. If you answered Yes to any one, conduct a scoping study to determine water consumption targets and savings potential. For this you will need to perform the following tasks:

• Develop simplified flowsheet of the water system • Develop water balance, reconciled vs meters • Select 3, or at most 4, contaminants to describe system. Suggested

“components” are BOD, COD, TOC, pH, salts, ions, TSS, etc.

• Data extraction - stream selection • Assign contaminant concentrations to selected streams. If unknown,

guess, reasonable value.

• Run Water Pinch software to plot composite curves and to determine targets based on simple reuse.

• Estimate savings potential 4. Savings scope from simple reuse achieves desired flow objective If Yes, finish up design of water reuse system, as indicated by software.

If No, you have to explore the feasibility of relaxing “design” concentration specifications, introducing regeneration options, etc as called for by pinch analysis. This is major undertaking, requiring a very high degree of expertise in the methodology.

Documents

Pinch White Paper (Rev 3) 2012