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This document provides an overview of heterogeneous reactors and application areas. It outlines the course objectives which are to review basic multiphase reaction engineering, develop relationships between transport effects and kinetics, derive performance equations for various reactor types, and present case studies. The document then discusses various reactor types including mechanically agitated tanks, bubble columns, trickle beds, and loop reactors. It provides examples of industrial multiphase catalytic processes and emerging technologies.
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- 1. 1 ChE 512 Transport Effectsin Chemical Reactors PART 2 Module 1 Introduction to Heterogeneous Reactors and Application Areas P.A. Ramachandran rama@wustl.edu
- 2. 2 Topical Outline • Introduction •Kinetic models • Transport effects • Gas-solid reactions • Gas-liquid reactions • Three Phase Reactors • Biochemical reactors • Electrochemical reactors
- 3. 3 Course Objectives Course Objectives •Review basic multiphase reaction engineering reactor types and applications in petroleum processing, fine chemicals, and specialty chemicals. • Develop basic relationships that describe the coupling between transport effects and kinetics for multiphase systems on a local level. • Derive the basic performance equations for integral reactor performance using ideal flow patterns for the various phases. • Present case studies or examples where the theory is put into practise.
- 4. 4 Module 1 Outline •Industrial Applications and Examples • Review of Common Reactor Types • Guidelines for Reactor Selection
- 5. 5 Starting References Starting References 1.Doraiswamy L.K. and Sharma. M. M. Heterogenous Reactions, 2. P. A. Ramachandran and R. V. Chaudhari, Three-Phase Catalytic Reactors, Gordon & Breach, London (1983). 3. P. L. Mills, P. A. Ramachandran, and R. V. Chaudhari, Reviews in Chemical Engineering, 8, pp. 1-192 (1992). 4. P. L. Mills and R. V. Chaudhari, “Multiphase catalytic reactor engineering and design for pharmaceuticals and fine chemicals,” Catalysis Today, 37(4), pp. 367-404 (1997).
- 6. 6 Multiphase Catalytic Reactions MultiphaseCatalytic Reactions Reactants Products Catalyst Δ • Gases • Liquids • Solids • Solvent • Gases • Liquids • Solids • Solvent Homogeneous Heterogeneous Enzyme Bacteria Cells Present Future
- 7. 7 Classification Based onNumber of Phases • Gas-Solid Catalytic • Gas-Solid Non-Catalytic • Gas-Liquid • Gas-Liquid Solid Catalytic • Gas-Liquid with Solid Reacting • Liquid-Liquid • Gas-Liquid-Liquid-Solid
- 8. 8 Some Examples of SomeExamples of Multiphase Catalytic Processes Multiphase Catalytic Processes • Hydrogenation of specialty chemicals • Oxidation of glucose to gluconic acid • Oxidation of n-paraffins to alcohols • Methanol synthesis • Fischer-Tropsch (FT) synthesis • Hydrodesulfurization (HDS) of heavy residuals • Adiponitrile synthesis • Production of animal cells • Fermentation processes
- 9. 9 Other Emerging Other Emerging MultiphaseCatalytic Technologies Multiphase Catalytic Technologies • Catalysis by water soluble metal complexes in biphasic and nonionic liquid media • Reactions in supercritical fluid media • Asymmetric catalysis for chiral drugs/agrichemicals • Polymerization with precipitating products (e.g., Polyketones) • Phase transfer catalysis • Catalysis by adhesion of metal particles to liquid-liquid interfaces • Catalysis by nano-particles and encapsulation of metal complexes
- 10. Multiphase Reactor TechnologyAreas Multiphase Reactor Technology Areas Petroleum Refining Polymer Manufacture Environmental Remediation Syngas & Natural Gas Conversion Bulk Chemicals Fine Chemicals & Pharmaceuticals HDS, HDN, HDM, Dewaxing, Fuels, Aromatics, Olefins, ... MeOH, DME, MTBE, Paraffins, Olefins, Higher alcohols, …. Aldehydes, Alcohols, Amines, Acids, Esters, LAB’s, Inorg Acids, ... Ag Chem, Dyes, Fragrances, Flavors, Nutraceuticals,... Polycarbonates, PPO, Polyolefins, Specialty plastics De-NOx, De-SOx, HCFC’s, DPA, “Green” Processes .. P. L. Mills NASCRE 1, Houston, Jan 2001 Value of Shipments in $US billions http://www.eia.doe.gov/ 350 150 450 250 1987 1989 1995 1997 1991 1993
- 11. 11 The Global ChemicalIndustry CR&D Chemical Sciences & Engineering P. L. Mills CS&E • Generates > $2 trillion gross income - 70,000 products - 1000 corporations (many small ones) • Largest contributor to GDP • Distribution: European Union 35% USA 27% Asia 15% Japan 13% Balance 10%
- 12. 12 Multiphase Catalytic Reactions MultiphaseCatalytic Reactions - - Business Drivers Business Drivers - - • Increased globalization of markets • Societal demands for higher environmental performance • Financial market demands for increased profitabilty and capital productivity • Higher customer expectations • Changing work force requirements Technology Vision 2020, The US Chemical Industry, Dec. 1996 http://www.eere.energy.gov/industry/chemicals/pdfs/chem_vision.pdf
- 13. 13 Cost Breakdown forChemical Production Cost Breakdown for Chemical Production • For large-scale processes, research must focus on reducing cost of raw materials and/or capital • Small-scale processes can benefit from almost any improvement 0 10 20 30 40 50 60 70 Small Scale Product Large Scale Product < 10 MM lb/yr * * Adapted from Keller & Bryan, CEP, January (2000) > 100 MM lb/yr
- 14. 14 Process Development Methodology ProcessDevelopment Methodology Lerou & Ng, CES, 51(10) (1996)
- 15. 15 Oxidation of Oxidation ofp p- -Xylene Xylene to Terephthalic Acid to Terephthalic Acid • G-L (homogeneous) catalytic oxidation with precipitating solid product. • Oxygen mass transfer limitation, starvation of oxygen (due to safety limits) and exothermicity are key issues in reactor performance • Undesired impurity 4-CBA in ppm level requires a separate hydrogenation step (g-l-s reaction) to purify TPA • Involves dissolution of impurities, hydrogenation and re-crystallization to achieve purified TPA • Selection of suitable multiphase reactors has been a major challenge CH3 COOH CH3 CH3 CH3 COOH CHO COOH COOH COOH O2 cat I O2 cat I O2 cat I H2 cat II p-xylene 4-CT 4-CBA TPA 4-CT Oxidation: Cat I: Co-Mn-Br Temp.: 190-205°C PO2: 1.5-3.0 MPa Hydrogenation: Cat II: Pd/support Temp.: 225-275°C
- 16. 16 Key Multiphase ReactorTypes Key Multiphase Reactor Types • Mechanically agitated tanks • Multistage agitated columns • Bubble columns • Draft-tube reactors • Loop reactors Soluble catalysts & Powdered catalysts Soluble catalysts & Tableted catalysts • Packed columns • Trickle-beds • Packed bubble columns • Ebullated-bed reactors
- 17. 17 Classification of Multiphase Classificationof Multiphase Gas Gas- -Liquid Liquid- -Solid Solid Catalyzed Reactors Catalyzed Reactors 1. Slurry Reactors Catalyst powder is suspended in the liquid phase to form a slurry. 2. Fixed-Bed Reactors Catalyst pellets are maintained in place as a fixed-bed or packed-bed. K. Ostergaard, Adv. Chem. Engng., Vol. 7 (1968)
- 18. 18 Modification of theClassification for Modification of the Classification for Gas Gas- -Liquid Liquid Soluble Soluble Catalyst Reactors Catalyst Reactors 1. Catalyst complex is dissolved in the liquid phase to form a homogeneous phase. 2. Random inert or structured packing, if used, provides interfacial area for gas-liquid contacting.
- 19. 19 Common types ofgas-solid reactors • Packed bed • Fluid bed • Monolith • Riser and Downer
- 20. 20 Multiphase Reactor Types MultiphaseReactor Types at a Glance at a Glance Middleton (1992)
- 21. 21 Mechanically Agitated Reactors MechanicallyAgitated Reactors - -Batch or Semi Batch or Semi- -Batch Operation Batch Operation- - (a) Batch (b) Semi - Batch “ Dead - Headed “ Gas Gas P G
- 22. 22 Mechanically Agitated Reactors MechanicallyAgitated Reactors - - Continuous Operation Continuous Operation - - G G G L G L G Multistage Agitated Column for the Synthesis of Vitamin “carbol” (Wiedeskehr, 1988)
- 23. 23 Mechanically Agitated Reactors MechanicallyAgitated Reactors - - Pros and Cons Pros and Cons - - Pros Cons • Small catalyst particles • Catalyst handling • High effectiveness factor • Catalyst fines carryover • Highly active catalysts • Catalyst loading limitations • Well-mixed liquid • Homogeneous reactions • Catalyst addition • Pressure limitations • Nearly isothermal • Temp. control (hot catalysts) • Straightforward scale-up • Greater power consumption • Process flexibility • Large vapor space Source: P. L. Mills, R. V. Chaudhari, and P. A. Ramachandran Reviews in Chemical Engineering (1993).
- 24. 24 The BIAZZI HydrogenationReactor The BIAZZI Hydrogenation Reactor G G M ¾ Inefficient cooling ¾ Catalyst deposition in low turbulence area ¾ Sealing problems ¾ Poor mixing and non- homogeneous conditions in low turbulence area ¾ Inefficient heat and mass transfer ¾ Powerful gas dispersion and recirculation: high mass transfer ¾ No heat transfer limitations (up to 20 m2 /m3 ) ¾ Negligible fouling ¾ Safer than the conventional reactors ¾ Easy catalyst recycling Conventional Reactor BIAZZI Reactor
- 25. 25 Multistage Agitated Columnfor Synthesis Multistage Agitated Column for Synthesis “Carbol” “Carbol”- -Pharmaceutical Intermediate Pharmaceutical Intermediate • Continuous reactor system with a cascade column and multistage agitator ensures good mixing, long mean residence time and narrow residence time distribution • Gas phase voidage is minimum, hence safer for acetylene handling • High productivity/smaller volume Chem. Eng. Sci., 43, 1783, 1988 R O + (i) aq. KOH (ii) NH3, -5oC R OH (iii) H2SO4 α,β-unsaturated ketone Carbol
- 26. 26 Bubble Column Reactors BubbleColumn Reactors at a Glance at a Glance Tarhan (1983)
- 27. 27 Key Types ofBubble Columns Key Types of Bubble Columns G G G G G G L L L L L L (a) Empty (b) Plate (c) Packed Semi - Batch Continuous Semi - Batch or Continuous or Continuous
- 28. 28 Bubble Column Reactors BubbleColumn Reactors - - Pros and Cons Pros and Cons - - Pros Cons • Small catalyst particles • Catalyst handling • High effectiveness factor • Catalyst fines carryover • Highly active catalysts • Catalyst loading limitations • Well-mixed liquid • Homogeneous reactions • Nearly isothermal • Selectivity Control • Lower power consumption • No guidelines for internals • High pressure operation • More complex scaleup Source: P. L. Mills, R. V. Chaudhari, and P. A. Ramachandran Reviews in Chemical Engineering (1993).
- 29. 29 Draft Tube andLoop Reactors Draft Tube and Loop Reactors Internal Circulation External Circulation
- 30. 30 Venturi Venturi Loop Reactors LoopReactors Cramers et al. (1994)
- 31. 31 O O O OH HO O O O O2 H2O H2 n-C4Maleic anhydride Maleic acid Tetrahydrofuran Example: DuPont Butane to THF Process Example: DuPont Butane to THF Process Pilot Plant Reactor Ponca City, OK n-C4 Oxidation Reactor Maleic acid Hydrogenation Reactor Purification Train Commercial Plant Asturias, Spain $$$$ $ $$
- 32. 32 Other Types ofLoop Reactors Other Types of Loop Reactors Internal External Jet Loop with Recirculation Recirculation External Recirculation
- 33. 33 Jet Loop RecycleReactors Jet Loop Recycle Reactors Batch Operation Continuous Operation • Excellent mass & heat transfer performance • Uniform catalyst distribution and mixing • Commercially used in hydrogenation, alkylation, oxidation, amination, carbonylation and bio-catalytic reactions • Higher Productivity/ Throughput • Lower Catalyst Consumption • Safer Operation • Higher Yields & Selectivity • Lower Power Consumption Source : Davy Process Technology
- 34. 34 Gas Gas- -lift and LoopReactors lift and Loop Reactors - - Pros and Cons Pros and Cons - - Pros Cons • Small catalyst particles • Catalyst handling • High effectiveness factor • Catalyst fines carryover • Highly active catalysts • Catalyst loading limitations • Well-mixed liquid • Homogeneous reactions • Nearly isothermal • Selectivity control • High pressure operation • Possible pressure limitations (Gas-lift reactor) (Loop reactor) • Process flexibility • Greater power consumption (Loop reactor) • Modular design • Catalyst attrition Source: P. L. Mills, R. V. Chaudhari, and P. A. Ramachandran Reviews in Chemical Engineering (1993).
- 35. 35 Fixed Fixed- -Bed Multiphase Reactors BedMultiphase Reactors L L L L L G G G G G L G Semi-Batch or Continuous Operation; Inert or Catalytic Solid Packing (a) Trickle - Bed (b) Trickle - Bed (c) Packed - Bubble Flow Cocurrent Countercurrent Cocurrent downflow flow upflow
- 36. 36 Trickle Bed Reactors TrickleBed Reactors - - Advantages Advantages - - • Plug flow of gas and liquid • High catalyst / liquid ratio • Stationary catalyst • Minimal catalyst handling problems • Operating mode flexibility • High pressure operation • Heat of reaction used to volatize liquid • Large turndown ratio • Low dissipated power • Lower capital and operating costs
- 37. 37 • Larger particles,low catalyst effectiveness • Possible poor liquid - solid contacting • High crushing strength required for small particles • Potential for reactor runaway • Long catalyst life required • Inability to handle dirty feeds • Potential for liquid maldistribution • More difficult to scale - up Trickle Bed Reactors Trickle Bed Reactors - - Disadvantages Disadvantages - -
- 38. 38 Packed Bubble FlowReactors Packed Bubble Flow Reactors - - Advantages Advantages - - • Complete liquid - solid contacting • Higher liquid holdup • Better temperature control • Less problems with liquid maldisdribution • Higher heat and mass transfer rates
- 39. 39 Packed Bubble FlowReactors Packed Bubble Flow Reactors - - Disadvantages Disadvantages - - • Higher dissipated power than in TBR • Throughput limited by bed fluidization velocity • Increased potential for runaway • Promotion of undesired homogeneous reactions • Greater pressure drop
- 40. 40 Bioreactor Types Bioreactor Types (AfterBailey and Ollis, 1986) Mechanical agitation External pumping Gas agitation
- 41. 41 Commercial or PlannedBioprocesses Commercial or Planned Bioprocesses High Volume Products High Volume Products Product Carbon source Production, t/year Lactic acid corn syrup, whey permeate, agric. waste 300,000 Citric acid molasses, glucose 550,000 Amino acids molasses, glucose, corn syrup 250,000 lysine, glutamic acid Ethanol molasses, corn syrup, cellulose, agric. waste 28,000,000a Single cell protein methane 50,000b 1,3 Propane diol corn syrup NA Penicillin glucose, corn steep liquor 25,000 Detergent enzymesc glucose, maltose, starch a for fuels only (US production 14.5x106 t/year in 1996) b a target of 500,000 t/year is projected for Europe for 2010 c yearly product value in excess of 109 US$ Leib, Pereira & Villadsden, NASCRE 1, Houston 2001
- 42. 42 Biological Biological vs vs ChemicalSystems Chemical Systems • Tighter control on operating conditions is essential (e.g., pH, temperature, substrate and product concentrations, dissolved O2 concentration) • Pathways can be turned on/off by the microorganism through expression of certain enzymes depending on the substrate and operating conditions, leading to a richness of behavior unparalleled in chemical systems. • The global stoichiometry changes with operating conditions and feed composition; Kinetics and stoichiometry obtained from steady-state (chemostat) data cannot be used reliably over a wide range of conditions unless fundamental models are employed • Long term adaptations (mutations) may occur in response to environment changes, that can alter completely the product distribution Leib, Pereira & Villadsden, NASCRE 1, Houston 2001
- 43. 43 Complex Reactor example: ComplexReactor example: para para- -Amino Phenol Amino Phenol by 4 by 4- -Phase Hydrogenation Phase Hydrogenation • Single step process • Intermediate phenylhydroxylamine rearranged by interfacial reaction to para-aminophenol • Selectivity determined by competing hydrogenation in organic phase and & interfacial rearrangement with aqueous acid catalyst PhNH3 + Aq. Phase Org. Phase Pt/C Gas phase PhNO2 PhNHOH PhNH2 PhNHOH 4-PhNH2(OH) H+ H+ PhNH2 4-PhNH3 +(OH) H+ H2 H2 H+ PhNH3 + H+ H2 NO2 NHOH NH2 NH2 OH H2 Pt/C Phenyl hydroxyl amine p-Amino phenol Aniline R.V. Chaudhari et al., CES, 56, 1299, 2001 An intermediate used in the manufacture of several analgesic and antipyretic drugs, e.g., paracetamol, acetanilide, & phenacetin P. L. Mills, CAMURE-5, June 2005
- 44. 44 Complex Reactor: Example2 Complex Reactor: Example 2 Phenyl Acetic Acid by 3 Phenyl Acetic Acid by 3- -Phase Hydroformylation Phase Hydroformylation CHO CHO Products Reactant CO H2 Rh P SO3Na SO3Na SO3Na P NaO3S NaO3S NaO 3S P SO3Na SO3Na SO3Na OC H Rh/TPPTS Catalyst Gas Phase Aor Bor Eor Por Ag Bg Organic Phase Aqueous Phase Aaq Baq Eaq Paq Gas - Organic Phase Interface Aqueous- Organic Phase Interface Soluble catalyst Cl CO/H2 Pd-Catalyst OH O Benzyl chloride Phenyl acetic acid Wan & Davis, 1993 Gas Gas- -Liquid Liquid- -Liquid w/Soluble Catalyst Liquid w/Soluble Catalyst
- 45. 45 Electrochemical Reactors • Electrolyticproduction of chlorine and NaOH; Chloralkali industry. • Aluminum production (Halls process) • Fuel cells • Monsanto adiponitrile process • Paired electrosynthesis • Pollution prevention; Metal recovery
- 46. 46 Strategies for MultiphaseReactor Selection Strategies for Multiphase Reactor Selection • Maximize yield • Ease of scale-up • High throughput • Low pressure drop • Lowest Capital cost • Other requirements Process Requirements Reactor ? Reactants • Intrinsically safe • “Green” processing • Zero emissions • Sustainable Desired Products Undesired Products Unconverted Reactants Environmental and Safety ) “Wish List”
- 47. 47 Summary: Distinguishing Features Summary:Distinguishing Features of Multiphase Reactors of Multiphase Reactors • Efficient contacting of reactive phases and separation of product phases is key to safety, operability and performance • Various flow regimes exist, depending on phase flow rates, phase properties, operating conditions, and geometry • Reaction and interphase transport time-scales, and phase flow patterns dictate reactor type, geometry and scale • Gradual scale-up over several scales may be required for reliable commercialization
- 48. 48 Three Three- -Level Strategy forReactor Selection Level Strategy for Reactor Selection Level I Level I Level II Level III Catalyst Design Reactant & Energy Injection Strategies Hydrodynamic Flow Regimes • Analyze process on three levels • Make decisions on each level Use fundamentals, data, & basic models for screening of various reactor alternatives
- 49. 49 Multiphase Transport Multiphase Transport- -KineticInteractions Kinetic Interactions ) T , C ( R ) C ( L I b I b I I I b I η = ∑ − = j I b I b I j I j R I b I h ) T , C ( R ) H ( ) T ( L I j η Δ ( ) I Phase in transport & kinetics f I j = η I 0 I 0 I 0 P , C , T Time & Length Scales Reactor Eddy or Particle Molecular II 0 II 0 II 0 P , C , T ) T , C ( R ) C ( L II b II b II II II b II η = ∑ − = j II b II b II j II j R II b II h ) T , C ( R ) H ( ) T ( L II j η Δ ( ) II Phase in transport & kinetics g II j = η I I I P , C , T II II II P , C , T Phase II Phase I I e Q I, Phase II e Q II, Phase II in Q II, Phase I in Q I, Phase Reactor Performance Determines Raw Material Utilization, Separations, Recycle Streams, Remediation, and Hence Process Economics & Profitability