Operational Aspects Typical: Processes are designed & optimized based on given (fixed) data (flowrates, temperatures, pressures, etc.) But: Processes (and Heat Exchanger Networks) are: −often operated “off” design (above/below) −subject to disturbances −to be started up and shut down The Result: The Process Engineer will over-design before the Control Engineer adds new Units for Manipulation T. Gundersen OPER 01 Various Topics for Heat Exchanger Networks Process, Energy and System

T. Gundersen Various Operational Aspects Controllability  Property of the Process, not the Control System  Ability to handle operational Variations Flexibility  Ability to cope with different Operating Conditions Start-Up and Shut-Down  Starting up from “Cold” Conditions is challenging “Switchability”  Change Operation from one Condition to another Environmental Aspects Safety Maintenance “RAMS”  Reliability, Availability, Maintainability, Safety Various Topics for Heat Exchanger Networks Process, Energy and System OPER 02

T. Gundersen Two important Aspects of Operability Controllability of Processes  “Ability to handle Short Term Variations”  Withstand (unwanted) Disturbances  Stability Issues  Follow (wanted) Set-Point Changes  On-line Optimization Flexibility of Processes  “Ability to handle Long Term Variations”  Undesirable Variations  Fouling (or Scaling) in Heat Exchangers  Deactivation of Catalysts  Desirable Variations/Changes  New Raw Materials and/or new Products  Changes in Production Volume Various Topics for Heat Exchanger Networks Process, Energy and System OPER 03

T. Gundersen Similarities/Analogies between Synthesis of Processes and Control Systems Levels Structure Parameters Various Topics for Heat Exchanger Networks Process, Energy and System OPER 04 Production Site Process Equipment Choice of Units Matching Sequences Pressures Temperatures Flowrates Optimizing Advisory Basic Control Manipulators Pairing Controller Types Gain Integral Time Derivative Time ProcessControl

WS-1: Heat Integration T. Gundersen StreamT s T t mCp ΔH °C°CkW/°C kW H H C Steam280280(var) Cooling Water 15 20(var) Specification: ΔT min = 20°C Find: Q H,min, Q C,min T pinch, U min U min,MER and Network Notice: 1) H1 and H2 provide as much heat as C1 needs (800 kW) 2) T s (C1) T t (C1) + 20° Heat Integration − Introduction Process, Energy and System OPER 05

WS-1: What about Controllability? T. Gundersen Heat Integration − Introduction Process, Energy and System OPER 06 mCp (kW/°C) H1 H2 C1 200°C 250°C 50°C 100°C 300°C 180°C C I III II 200ºC H 217.5°C55°C 186.7ºC MER Design with Q H = Q H,min, Q C = Q C,min, U = U min,MER Consider: Disturbance for H1 inlet T, while controlling H2 outlet T

Flexibility in Heat Exchanger Networks C2 290° 115° C1 120° H2 450° 280° H1 310° 50° 280° 240 kW 20 kW 330 kW 10 kW 290° C 285° 40° mCp T. Gundersen Various Topics for Heat Exchanger Networks Process, Energy and System OPER 07

C2 290° 115° C1 120° H2 450° 280° H1 310° 50° 169.5° 240 kW 241 kW109 kW 231 kW 179.7° C 395.5° 40° mCp T. Gundersen Various Topics for Heat Exchanger Networks Process, Energy and System Flexibility in Heat Exchanger Networks OPER 08

C2 290° 115° C1 120° H2 450° 280° H1 310° 50° 234.5° 240 kW 111 kW239 kW 101 kW 227.8° C 330.5° 40° mCp T. Gundersen Various Topics for Heat Exchanger Networks Process, Energy and System Flexibility in Heat Exchanger Networks OPER 09

In Summary: The Network Structure was Flexible (Resilient) for the Cases when mCp was 1.0 and 1.85 for Stream H1, but did not work when mCp was 1.35 even with infinite Heat Transfer Area. The Reason: The Problem is Non-Convex, which happens when: −the Pinch point changes −there is a change in Mass Flowrates T. Gundersen Various Topics for Heat Exchanger Networks Process, Energy and System Flexibility in Heat Exchanger Networks OPER 10

T. Gundersen WS-5: Design for Flexibility Q: How to handle Fouling ? 4 175° 20° 3 175° 2 155° 90° 1 200° 115° 138° 170° ° 20° H22 84° Time (months) U 1 (W/m 2 K) Exchanger 1 has fouling above 125°C Ref.: Kotjabasakis and Linnhoff, Oil & Gas Jl., Sept. 1987Kotjabasakis 73° Various Topics for Heat Exchanger Networks Process, Energy and System OPER 11

T. Gundersen WS-5: Fouling in Heat Exchangers 1: The Traditional Approach 4 175° 20° 3 175° 2 155° 90° 1 200° 115° 138° 170° ° 20° H ° New Area: 148 m 2 Energy Usage: Constant (the same) 73° Various Topics for Heat Exchanger Networks Process, Energy and System OPER 12

T. Gundersen WS-5: Fouling in Heat Exchangers 2: An alternative Solution 4 175° 20° 3 175° 2 155° 90° 1 200° 115° 138° 170° ° 20° H22 84° New Unit: Heater on Stream 3 Energy Usage: From 1850 to 2140 kW H 73° Various Topics for Heat Exchanger Networks Process, Energy and System OPER 13

T. Gundersen WS-5: Fouling in Heat Exchangers 3: Use Network Interactions 4 175° 20° 3 175° 2 155° 90° 1 200° 115° 138° 170° ° 20° H22 84° New Area: 103 m 2 Energy Usage: 15% Reduction !! 73° Various Topics for Heat Exchanger Networks Process, Energy and System OPER 14

T. Gundersen WS-5: Fouling in Heat Exchangers Summary “Method/Approach”ΔAreaΔEnergy Traditional Approach148 m 2 0 Alternative SolutionNew Heater+ 13% Network Interactions103 m % Best Result obtained by using a “Systems Approach” Various Topics for Heat Exchanger Networks Process, Energy and System OPER 15

T. Gundersen Summary of Operability Plant Operation is often “Off-Design” Controllability (Short Term Variations) Flexibility (Long Term Variations) A new Design Strategy for Fouling The importance of Topology (Flowsheet or Network Structure) has been proven Process Integration has a Focus precisely on the Structural Aspects of Process Plants Various Topics for Heat Exchanger Networks Process, Energy and System OPER 16

T. Gundersen EXP 01 Process, Energy and System Expansions of Process Integration Expansions of PA & PI Objectives  from Energy Cost  to Equipment Cost  to Total Annualized Cost  and also Operability, including  Flexibility  Controllability  Switchability  Start-up & Shut-down  New Operating Conditions  and finally Environment, including  Emissions Reduction  Waste Minimization

T. Gundersen EXP 02 Process, Energy and System Expansions of Process Integration Scope  from Heat Exchanger Networks  to Separation Systems, especially  Distillation and Evaporation (heat driven)  to Reactor Systems  to Heat & Power, including  Steam & Gas Turbines and Heat Pumps  to Utility Systems, including  Steam Systems, Furnaces, Refrigeration Cycles  to Entire Processes  to Total Sites  to Regions Expansions of PA & PI

T. Gundersen EXP 03 Process, Energy and System Expansions of Process Integration Plants  from Continuous  to Batch and Semi-Batch Projects  from New Design  to Retrofit  to Debottlenecking Thermodynamics  from Simple 1st Law Considerations  to Various 2nd Law Applications  Exergy in Distillation and Refrigeration Expansions of PA & PI

T. Gundersen EXP 04 Process, Energy and System Expansions of Process Integration Methods  Pinch based Methodologies from Analogies  from Heat Pinch for Heat Recovery and CHP in Thermal Energy Systems  to Mass Pinch for Mass Transfer / Mass Exchange Systems  to Water Pinch for Wastewater Minimization and Distributed Effluent Treatment Systems  to Hydrogen Pinch for Hydrogen Management in Oil Refineries  Other Schools of Methods  was discussed on a previous slideprevious slide Expansions of PA & PI

T. Gundersen EXP 05 Process, Energy and System Expansions of Process Integration Detailed Engineering Strategic Planning Conceptual Design Heat Integration Pinch Analysis Optimization Methods Combined Methods Expansions in Process Integration Process Integration is much more than Pinch Analysis for Heat Exchanger Networks

T. Gundersen EXP 06 Process, Energy and System Expansions of Process Integration Stages and Analogies in Methods Heat Pinch Mass Pinch Water Pinch Hydrogen Pinch Data Extraction Analysis Design Optimization Modeling T Q Heat Pinch Graphical Diagrams Representations and Concepts Performance Targets ahead of Design Pinch Decomposition

T. Gundersen Process, Energy and System Water Pinch Demonstration Wastewater Minimization Topic:Efficient Use of Wastewater R euse, Regeneration and Recycling - both Targets and Design Methods:Water Pinch (discussed here) Mathematical Programming Ref.:Wang and Smith “Wastewater Minimization”, Chem. Engng. Sci., vol. 49, pp , 1994 EXP 07

T. Gundersen Process, Energy and System Water Pinch Demonstration Wastewater Minimization Graphical Representation H T Δ H = mCp ΔT mass/heat analogy C Δm = m H2O Δ C m C pr,in C pr,out C out,max C in,max EXP 08

T. Gundersen SUM 01 Process, Energy and System Final Summary Main Results from Pinch Analysis The Concept of Composite Curves  Applicable whenever an “Amount” has a “Quality”  Heat & Temperature, Mass & Concentration, etc. A Two Step Approach: Targets ahead of Design A fundamental Decomposition at the Pinch T H C m Heat Pinch Water Pinch Q C,min Q H,min Water min

T. Gundersen SUM 02 Process, Energy and System Final Summary Objectives for using Process Integration Minimize Total Annual Cost by optimal Trade- off between Energy, Equipment and Raw Material Within this trade-off: minimize Energy, improve Raw Material usage and minimize Capital Cost Increase Production Volume by Debottlenecking Reduce Operating Problems by correct rather than maximum use of Process Integration Increase Plant Controllability and Flexibility Minimize undesirable Emissions Add to the joint Efforts in the Process Industries and Society for a Sustainable Development