Chemical Process Design Subject 3. Overview of Process Synthesis Javier R. Viguri Fuente CHEMICAL ENGINEERING AND INORGANIC CHEMISTRY DEPARTMENT UNIVERSITY OF CANTABRIA [email protected] License: CreaNve Commons BY‐NC‐SA 3.0 Waste treatment network 4.Hierarchical decomposition ...Criteria for Assessing preliminary design 3...INDEX 1.Process Integration and Intensification • Case Study: application of hierarchical decomposition .Superstructure optimization * Examples: HEN.Representing Alternatives .Basic Steps in flowsheet synthesis .Further Reading and References 2 .Generation of flowsheets .Gathering Information . Distillation.Preliminary Process Synthesis 2. P. connected + integration. phase.1. task . T. 3 . composition.Synthesis Steps: Eliminate property differences between raw materials and products organized alternatives into a synthesis tree. where operations are combined in Unit Processes. form of solid phase. well defined properties as µ. MW or color). ..Process Operations: Basic operations.Chemical State: Raw material and product specifications (Mass.Preliminary Process Synthesis Raw materials PROCESS FLOWSHEET ? Desired Product Process synthesis problem Steps in process synthesis: Process operations Flowsheets . Preliminary Process Synthesis SYNTHESIS STEP PROCESS OPERATIONS SYNTHESIS TREE ..Mixing -Eliminate differences in composition . phase change .Unit operations 4 . P.1.T. P and phase .Integrate task .Separation .Chemical reaction .Distribute the chemicals by matching sources and sinks .Eliminate differences in T.Eliminate differences In molecular types . utilities and subproducts.Basic Steps in flowsheet synthesis .2.. Chemical prices 5 .Gathering Information and Database creation • Basic thermo-physical properties for all chemicals considered • Information about reaction and conditions • Yield • Product purity • Raw materials • Process bounding (restrictions) • Utilities • Environmental Impact and toxicity of components • Cost of equipment. . * OTHER REPRESENTATIONS: Useful to think about the design problem. minimum heat and cool utilities. reaction. T.Representing Alternatives • AGREGATION IN A SINGLE OBJECT • EQUIPMENT AGREGATION REPRESENTING A FUNCTION OF HIGHER LEVEL as: Feed preparation. Process Flow Diagram (PFD). Comp. 6 . Flowsheet Unit operations .Block Flow Diagram (BFD).) Batch Processes where the all tasks are developed in the same equipment but at different times * MORE SPECIALISED REPRESENTATIONS (Process Subsystems): T vs. * REPRESENTATION OF THE PROCESS TRANSITIONS IN THE SPACE OF CHEMICAL COMPOSITION: Useful to synthesis of reactor networks and non-ideal separation processes. Allow to obtain alternatives to the heat exchange between streams.Basic Steps in flowsheet synthesis . * COMPLETE FLOWSHEET : Equipment and inter-conexión . Transfered Heat amount. etc.. recovery. separation. Describe design alternatives.Task Diagram (Change of P.2. in the HEN (Heat Exchange Networks). FLEXIBILITY Requires manufacture of specified products in spite of variations in the feeds it handles.Criteria for Assessing preliminary design ECONOMIC EVALUATION Need Equipment and utilities Cost. Oil Refinery: Earnings = F(capacity of process different oils at different time + scheduling) CONTROLLABILITY Ability of operate the process satisfactorily while undergoing dynamic changes in operation conditions or while recovering from disturbances 7 . HAZOP Analysis.Basic Steps in flowsheet synthesis . Mass and heat balances solved ENVIRONMENTAL CONCERNS Need Satisfy regulations / EIA / LCA. ( $.. heat transfer coeff. SAFETY ANALYSIS Determine whether any reasonable combination of events leads to unsafe situations. T cooling water. supply).2. RCO2) POF approaches: . Yokohama and Ito. 2006. 2001. 2009. 2006.Process systems: Mele at al.Power Plants: Li et al...Basic Steps in flowsheet synthesis . GillenGosalbez and Grossmann.. 2011.. Bernier et al. Favrat. F2(EI99. GWP100. D. 3117–3134 Unfeasible Solutions (Impossible) Pareto Optimal Frontier 8 .. F. Energy 31. Pelster et al.. Marechal.Criteria for Assessing preliminary design: Pareto Optimal Frontiers (POF)... NPV). 1995 . Burer.2... M. Gerber et al. 2010. H. 2010. Feasible Solutions (Suboptimal) Li. 2011. F1(Costs. Multiobjective optimization of an advanced combined cycle power plant including CO2 separation options. Hierarchical Decomposition: .Obtaining flowsheets to apply optimization .Superstructure optimization: .Optimize superflowsheet that contains all alternatives .3.Interactions between levels can be considered systematically (with more powerful strategies).Tends to ignore some strong interactions between the levels .Successive Refinement. 9 .Generation of flowsheets: How to generate flowsheets? Exhaustive enumeration may involve 103 – 106 flowsheets Methods to reject non-viable alternatives easy and quickly .. . 10 . Reduced energy consumption .Generation of flowsheets: Integrated Chemical Processes Feed Level 1 Level 2 Level 3 Level 4 Level 5 BatchContinuous Input-output structure Recycle structure Separation Synthesis Heat Recovery Product DESIGN: Hierarchical decomposition approach. Integrated approach • Process Integration of unit operations to design multifunctional integrated chemical manufacturing systems. • Examples: .Higher productivity . Separation Process + Chemical reactions (reactive distillation). • Advantages of process integration .3. Mechanical Unit Opeartions + Chemical reactions (Reactive extrusion) 11 . Heat Transfer + Chemical reactions (fuel cell with internal reforming). non-integrated units (systems). the steadystate and the dynamic operating behavior of integrated process unit (system) is much more complex than the behahvior of single.Improved operational safety .Heat and Power Integration.Higher selectivity ..Improved ecological harmlessness by avoidance of auxiliary agents and chemical wastes * Due to he interaction of several process steps in one apparatus (system). Methyl isocyanate (MIC-Bhopal accident) generated and immediately converted to final pesticide in process with a total inventory <10 kg MIC.Equipments: heat exchanger in the form of the printed circuit/diffusion bonded unit.Generation of flowsheets: Process Intensification F e e d Level 1 BatchContinuo us Level 2 Inputoutput structure Level 3 Recycle structure •The aim of Process Intensification is to optimize capital. supercritical fluids. structured packed columns. to bring dramatic improvements in manufacturing and processing. supersonic gas liquid reactor. to bring dramatic improvements in manufacturing and processing. energy..Methodologies: reactive distillation. or waste production • Advantages of process intensification Development of novel apparatuses and techniques. Use of ultrasound. oscillating flows in reactors. . . . microchannel heat exchangers. reactive extraction.70% plus reduction in energy usage and hence substantial reduction in operating cost .Just-in-time manufacture becomes feasible with ultra-short residence times. fuel cells.99. energy consumption. • Examples: . membrane separations.3. as compared to the present state-of-art. energy consumption. 12 . or waste production.Industrial applications: Small intensely stirred reactors and microchannel reactors in Organic Nitration (nitroglycerine). Level 4 Separatio n Synthesis Level 5 Produc t Heat Recovery DESIGN: Hierarchical decomposition approach. centrifugal fields. leading to inherently safe operation. microwave. washing. substantially decreasing equipment size/production-capacity ratio. Smaller inventories lead to improved intrinsic safety. as compared to the present state-of-art.99% reduction in impurity levels Better product quality more valuable . . dewatering and drying in styrene-butadiene rubber. 60% capital cost reductions . .Lower waste levels reduce downstream purification costs. membrane reactions.Distributed (rather than centralised) manufacture more economic. Environmental and safety benefits by radical reduction in the physical size of the plant. substantially decreasing equipment size/production-capacity ratio. isothermal reactor crystallizer in Phosphoric acid. heat exchange reactor.Better control of process irreversibilities can lead to lower energy use. Integrated approach • Development of novel apparatuses and techniques.8% reduction in reactor volume for a potentially hazardous process. extrusion. . single equipment to coagulation of latex. Remove heat exchangers.3.Application of Hierarchical decomposition: 5 Levels . to discover alternatives 1. Lump entire process Level 2 – Input-output structure Memo 1 is to obtain Base Case Flowsheet 13 .Recycle structure 4. Aggregate structure separation Level 3 .To interpret a given flowsheet in terms of hierarchy (proceed in reverse).Generation of flowsheets: Case Study . pumps 2. Group all liquid + vapor separators Level 4 – Separation synthesis 3.. C3 and H1. 1 Task in 1 Equipment State-Equipment Network (SEN) 2 kind of Nodes: State and Equipment. C2 Example 2: Wastewater treatment network Example 3: Synthesis of ammonia plant 14 .3. C2.Generation of flowsheets . • Useful with high number of alternatives State-Task Network (STN) 2 kind of Nodes: State and Task. Example 1: Heat exchange of H1 with C1. H2 with C1. Several Tasks in 1 Equipment.Superstructure Optimization • Representation that contains all the alternatives to be considered for a design.. 1990) C2 H2-C1 H2-C1 C2-HU H2-CU H2 H2-C2 H2-C2 15 .1986) STAGE 1 STAGE 2 H1-C1 H1-C1 H1-CU H1 C1-HU Superstructure H1-C2 H1-C2 C1 (Yee and Grossmann. C2. C3 and H1..Example 1: Heat exchange of H1 with C1. H2 with C1. C2 Superstructure (Floudas et al. BATs MbB SpB 16 . MbH MbS Solid BATs Sp S MbI MbO MbB Wastewater 1 Sw1 MbH SpH HM.Example 2: Wastewater treatment network Super-structure for the industrial waste waters treatment. BATs MbB MbI Wastewater 2 MbI MbO Sw2 Inorg. BATs Sw3 SpO MbB Biorg. organic compounds unsuitable for biological treatment. inorganic salts. heavy metals. eliminating suspended solid. bioorganic compounds. BATs SpI MbO Final wasterwater to discharge MbB Final Mixer MbO Wastewater 3 Org. 1998. BATs Sw2 Final Mixer MbI Sw3 Inorg.Example 2: Wastewater treatment network Sw1 MbS Solid BATs Sp S MbH SpH HM. 17 . heavy metals and inorganic salts (Galan and Grossmann. 2011). eliminating suspended solid. BATs Sp I Super-structure for the industrial waste waters treatment. 1997) 18 .Example 3: Synthesis of ammonia plant Superstructure (Biegler et al.. .Optimal design of real world industrial wastewater treatment networks..R. M.C. Grossmann. Georgiadis and A. L. 1998. B. Grossmann. R. Optimal design of distributed wastewaters treatment networks. 19 . Prentice Hall. I. • Smith. Westerberg.M.A.. 1988. E. • Galán. • Floudas. T.F.Further Reading and References • Biegler. pp. Conceptual Design of Chemical Processes. • Douglas.E. 32 (2). I. I.E. Systematic Methods of Chemical Process Design.. Grossmann.. A. 2011... Pistikopoulos. J. Grossmann. Kokossis (Editors). 1986. 2005. 37 (10).. European Symposium on Computer-Aided Process Engineering ESCAPE-21. C. John Wiley & Sons • Yee.N. Ciric. B. AIChE Journal. 4036-4048. Heat exchangers networks synthesis. Simultaneous optimization models for heat integration-II.. McGraw-Hill. 1997.C. pp. 1165-1184..E. Chemical Process: Design and Integration. pp. Computers and Chemical Engineering 14 (10). I... 1990.4. 276-290 • Galan. I.... A. Grossmann. Industrial and Engineering Chemistry Research.M.E. Automatic synthesis of optimum heat exchanger network configurations.
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