1、Process Integrated Membrane Separation - with Application to the Removal of CO2 from Natural Gas Hilde K. Engelien,22. March 2004Department of Chemical Engineering, NTNU,Definition of Given Title,Process integrated membranes: Membranes integrated into a process. Process integration techniques (proce
2、ss synthesis, modelling & optimisation).CO2 removal from natural gas: Have mainly looked at natural gas sweetening. Other applications exists.,Overview of Presentation,Membranes Principles of separation Material selection Types of membrane modules Membrane separation for CO2 removal from natural gas
3、 Applications for CO2 removal Natural gas Advantages/disadvantages Current solutions & some industrial examples Process integration Future trends & developments Concluding Remarks,Principles of Membrane Separation,(Feed),(Permeate),Phase 2,Phase 1,Driving force (C, P, T, E),Flux Selectivity,Membrane
4、 - a physical barrier from semi-permeable material that allows some component to pass through while others are held back.,Microfiltration Ultrafiltration Reverse Osmosis Molecular sieving Gas separation Membrane contactors Pervaporation,Different Membrane Structures (Selective layer),Porous membrane
5、 Non-porous membrane Carrier membranes,Size Diffusion & solubility AffinityRef: Mulder, Basic principles of separation technology),(microfiltration/ultrafiltration),(gas separation/pervaporation),(gases/liquids),Typical Membrane Structures (Gas Separation),Asymmetric membranes: very thin non-porous
6、layer - selective thick, highly porous layer - mechanical support,Asymmetric membrane structure (one type of material),Composite membrane structure (two types of materials),Nonporous layer (selectivity),Porous layer (stability),Selective layer,Asymmetric membrane,Ref. Dortmundt, 1999,Composite membr
7、anes: thin selective layer of one type polymer mounted on asymmetric membrane - support,Membranes - Material Selection,hybrid,Ref.: ethene,Polymer: poly(ethene),Polymers: most common Inorganic: more stable,Different Types of Membrane Modules,Two main categories for industrial applications: Spiral w
8、ound modules Hollow fibre modules,Ref.: Filtration Solutions Inc.,Different Types of Membrane Modules,Two main categories for industrial applications: Spiral wound modules Hollow fibre modules,Ref.: Aquilo Gas Separation,Cross section of hollow fibre,CO2 Removal from Natural Gas,Applications for CO2
9、 Removal,Separation of CO2 from gas streams are required in: Purification of natural gas (gas sweetening). Separation of CO2 in enhanced oil recovery processes (EOR). Removal of CO2 from flue gas. Removal of CO2 from biogas.Reasons for sour gas sweetening ? Impurities (CO2, H2S, H2O) Increase heatin
10、g value of natural gas - pipeline quality gas. Reduce corrosion. Prevention of SO2 pollution (formed during combustion of natural gas).Methods used in gas sweetening (removal of CO2, H2S) Absorption process using amine (conventional). Cryogenic distillation. Membranes. Hybrid process where membrane
11、is integrated with absorption unit.,Natural Gas,Natural gas: Mainly methane (CH4), ethane, propane, butane. Impurities: H2O, CO2, N2 and H2S. Natural gas treatment is the largest application of industrial gas separation. Membrane processes have 1% of this market large potentials ! (Baker, 2002) “Dis
12、posal”: Compression & re-injection of CO2 in reservoir .,Ref.: Australian Petroleum Cooperative Research Centre,Typical Natural Gas Plant - Possible Membrane Applications,Ref.: UOP,CO2 Separation Using Membranes,Mechanism of separation: diffusion through a non-porous membrane A pressure driven proce
13、ss - the driving force is the partial pressure difference of the gases in the feed and permeate.Selectivity - separation factor, (typical selectivity for CO2/CH4 is 5-30) Permeability = solubility (k) x diffusivity (D) Either high selectivity or high permeability - use highly selective thin membrane
14、s. Commercial membranes: polymer based (cellulose acetate),Selective removal of fast permeating gases from slow permeating gases. The solution-diffusion process can be approximated by Ficks law:,CO2 Removal from Natural Gas Current Membrane Solutions,Membranes (Baker, 2002): 8-9 polymer materials us
15、ed for 90 % of total gas separation membranes. Several hundred new polymers reported (academia/patents) in the last few years. Problem: maintaining properties during real operation. Most gas separation modules are hollow-fibre modules. Three markets: Low gas volumes (e.g. treatment of offgas) - bett
16、er than conventional amine absorption units. Moderate gas volumes - competitive with amine systems. Higher volumes - not competitive with current amine systems. Problem: low selectivity and flux. Hybrid solution with conventional amine absorption technology. Feed treatment - extend membrane life (co
17、ndensing liquids, particles causing blockage and well additives can harm the membrane).,CO2 Separation Using Membranes: Advantages & Disadvantages,Advantages (compared with absorption units): Simpler process solutions Smaller & lighter systems (offshore) Cleaner Less chemical additives Lower energy
18、consumption Simultaneous removal of CO2, H2S and water vapour No fire or explosion hazards Less maintenance Lower capital and operating costs (small to medium scale) Ability to treat gas at wellhead Disadvantages: Low selectivity & flux - large scale systems not economically viable (yet). Thermal st
19、ability of polymer membranes. Degradation & lifetime of membrane. Unmature technology (in industrial terms, compared with existing solutions),A better environmental solution than conventional absorption units,Natural Gas Processing Plant Qadirpur, Pakistan,In 1999: Largest membrane based natural gas
20、 plant in the world (Dortmundt, UOP, 1999). Design: 265 MMSCFD natural gas at 59 bar. CO2 content is reduced from 6.5 % to less than 2 % using a cellulose acetate membrane. Feed treatment & feed heaters. Also designed for gas dehydration. Plant processes all available gas. Plans for expansion to 400
21、 MMSCFD.,Membrane plant, Qadirpur, Pakistan,(Dortmundt, UOP, 1999),Examples of Membranes In Gas Industry,Plants using membranes for CO2 removal: Kadanwari, Pakistan - 2 stage unit for treatment of 210 MMSCFD gas at 90 bars Taiwan (1999) - 30 MMSCFD at 42 bar. EOR facility, Mexico - processes 120 MMS
22、CFD gas containing 70 % CO2 Slalm & Tarek, Egypt - 3 two-stage units each treating 100 MMSCFD natural gas at 65 bar. Texas, USA - 30 MMSCFD of gas containing 30% CO” at 42 bar.Companies with membranes for CO2 removal: NATCO Group (Cyanara membranes) Aker Kvrner Process Systems Air Liquid UOP,Process
23、 Integrated Membranes,Process Integrated Membrane: Membrane Gas/Liquid Contactors,Ref.: Aker Kvrner Process Systems,Process integrated membrane and absorption unit (developed by Kvrner Process Systems). Membrane acts as barrier & surface area. Increased mass transfer area. Used for natural gas treat
24、ment, dehydration and removal of CO2 from offgas.,There are several tests sites for this system (Falk-Pedersen) : Large laboratory unit at SINTEF. Large scale pilot unit at Krst (exhaust gas treatment from gas engine) Pilot unit at gas terminal in Scotland - testing different membranes.,Membrane Gas
25、/Liquid Contactors,Benefits: Reduction of size and weight (important offshore). Wide range of liquid and gas flows (separation of gas/liquid phase). Lower capital costs compared with alternative schemes. Reduction in energy (if membranes are integrated with the stripping unit). Reduction in solvent
26、losses. No entrainment, flooding or channelling. Performance is insensitive to motion.Santos Gas Plant, Queensland, Australia Australias largest gas producer. Novel polymide membrane facility for CO2 removal (installed Dec. 2003). Uses the gas/liquid contactor. Problem: benzene/toluene/xylene in gas
27、 stream - a dewpoint control unit is installed to ensure that BTX are at acceptable levels.,Process Integration for Membrane Applications,Design. Modelling & optimisation. Superstructure approach for optimisation.,Process synthesis and optimisation methods are important for development of efficient
28、membrane structures for specific separation tasks.,Process Integration Used in Membrane Applications,Design. Modelling & optimisation. Superstructure approach for optimisation.,Design decisions for membrane systems: Operating conditions (temperature, pressure, flow). Module configuration (parallel,
29、series, single stage, multiple stage, recyle). Membrane material (organic, inorganic, mixed, ).,Single stage scheme,Two-step scheme,Two-stage scheme,Process Integration for Membrane Applications,Design. Modelling & optimisation. Superstructure approach for optimisation.Modelling of membrane designs
30、for gas (Pettersen, Lien, 1993, 1994, 1995) : Parametric study. Algebraic model (analogous with counter-current heat exchanger). Looked at single stage and multiple stages, effects of recycle and bypass configurations. Classification modules - suitable for recovery of fast or slow permeating compone
31、nt. Common design approach: sequential procedures: Module configurations are selected a priory. Optimisation on selected module to determine the operating conditions. Resulting flowsheet may be sub-optimal.,Process Integration for Membrane Applications,Design Modelling & optimisation. Superstructure
32、 approach for optimisation.,Ref: Kookos, I.K, 2002,Membrane system design for multicomponent gas mixtures via MINLP (Qi, Henson, 2000): Superstructure Consists of: membrane units, compressors, stream mixers and splitters. Used to represent the possible network configurations of a membrane system. Ca
33、se study: CO2 and H2S separation from natural gas using spiral-wound membranes. Simultaneous optimisation of flowsheet in terms of total annual process costs.,Process Integration for Membrane Applications,Design Modelling & optimisation. Superstructure approach for optimisation.Optimal design of mem
34、brane systems (Mariott, Srensen, 2003): Detailed rigorous mathematical models for the membrane separation. Superstructure representation of the membrane system. Optimisation using generic optimisation algorithm for pervaporation pilot plant (ethanol/water). Significant improvement in design. Favoura
35、ble compared with conventional MINLP solution methods.Generic algorithms can be a basis for an effective & powerful tool for optimal design of membrane systems.,Process Integration for Membrane Applications,Design Optimisation Superstructure approachA targeting approach to the synthesis of membrane
36、networks for gas separations (Kookos, 2002): Superstructure representation. Hollow-fibre membrane system. Uses the “upper bound” trade-off curve (relationship between permeability and selectivity for membranes). Configuration and membrane properties are optimised together.Find the optimal membrane p
37、ermeability and selectivity and the optimum structure.,Future Development,Problems/Challenges,Increasing selectivity without productivity loss (flux) - larger volume application will then be possible. Maintaining membrane properties under real conditions: Loss of stability & performance at high T an
38、d high P. Maintaining membrane properties in the presence of aggressive feeds. Condensing heavy hydrocarbons - can degrade the performance of the membrane. Thermal stability (of polymer membranes) - inorganic membranes would be better. Economic competitiveness for large scale systems. Improving life
39、time of membrane. Commercialisation - getting the industry to accept membranes.,Future High Performance Membranes Selectivity vs. Permeability: Upper Bound,Upper bound for selectivity vs. permeability. Current selectivity of CO2/CH4 membranes is typically 5-30. High performance membranes will move t
40、he upper bound upwards.Higher selectivity and permeability will: reduce area (capital cost). reduce loss of methane in permeate (profit).,CO2/CH4 selectivity vs. CO2 permeability,(Ref Koros, 2000),30,Upper bound (1991),Future Trends and Developments,For improved thermal & chemical stability of polym
41、er membranes: New polymers with different side-chains or different backbones . Cross-linked polymers. Plasma treatment.New materials (move into large-scale gas separations): New polymer structures with higher selectivity & permeability. Facilitated transport membranes - high selectivity. Mixed matri
42、x materials - blends of inorganic materials (e.g. molecular sieving) domains in polymers. Combination of cross-linking and mixed matrix material. Membranes tailored for specific separation tasks. Inorganic materials.Process Integration: Rigorous models. Optimisation of whole structure (module design
43、).,Concluding Remarks,Looked at: Introduction to principles of membrane separation, material selection & types of membrane modules. Membranes for the use of CO2 removal from natural gas. Small scale: better than conventional absorption process. Medium scale: Competitive with conventional absorption
44、process. Large scale: future applications along with development of membranes. Industrial examples. Process integrated membrane gas/liquid contactor. Optimisation of membrane structures (superstructure approach). Problems and challenges. Future trends and development.Membrane technology and industri
45、al applications is a growing industry !,Future CO2 Separation: Going to Mars ?,Ref. NASA Space Research,Acknowledgements,Taek-Joong Kim, Department of Chemical Engineering, NTNU Jon A. Lie, Department of Chemical Engineering, NTNU Arne Lindbrthen, Department of Chemical Engineering, NTNU Olav Falk-P
46、edersen, Aker Kvrner Process Systems, Norway Mike Entwistle, Aker Kvrner Australia,References,Textbooks Basic Principles of Membrane Technology, Mulder, M., 2nd. Edt., Kluwer Academic Publishers, 1996 Polymer gas separation membranes, Paul, D.R., Yampolskii, Y.P., CRC Press, 1994General Papers Baker
47、, R.W., Future directions of membrane gas separation technology, Ind. Eng. Chem. Res., 2002, 41, 1393-1411 Koros, W.J., Mahajan, R., Pusing the Limits on Possibilities for Large Scale Gas Separation: Which Strategies ?, J. Membrane Science, 175, 2000, 181-196 Tabe-Mohammadi, A., A Review of the Appl
48、ications of Membrane Separation Technology in Natural Gas Treatment, Separation Science and technology, 34, 10,1999, 2095-2111 Dortmund, D., Doshi, K., Recent Developments in CO2 Removal Membrane Technology, http:/ Lee, A.L., Feldkirchner, H.L., Gamez, J.P., Meyer, H.,S., Membrane process for CO2 re
49、moval tested at Texas plant, Oil & Gas Journal, 1994, 92, 5, 90-93 Leiknes, T.O., Gas transfer and degassing using hollow fibre membranes, Dr. ing. thesis, Department of Hydraulic and Environmental Engineering, NTNU, Norway, ISBN 82-471-5391-2. Hagg, M.B., Membrane purification of chlorine gas, Dr.
50、ing. thesis, Department of Chemical Engineering, NTNU, Norway, ISBN Ali, S., Boblak, P., Capili, E., Milidovich, S., Membrane Separation and Ultrafiltration,Laboratory for Process and Product Design, University of Illinois, , http:/vienna.che.uic.edu/teaching/che396/sepProj/FinalReport.pdf Lindbrthe
51、n, A., Otty, M., Natural Gas Dehydration and Purification by Membranes, Report, 1999, Telemark Tekniske Industrielle Utviklingssenter. Drioli, E., Romano, M., Progress and new perspectives on integrated membrane operation for sustainable industrial growth, Ind. Eng., Chem. Res., 2001, 40, 1277-1300,
