DEVELOPMENT OF A DYNAMIC MODEL OF A PALLADIUM MEMBRANE REACTOR FOR WATER GAS SHIFT

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1 DEVELOPMENT OF A DYNAMIC MODEL OF A PALLADIUM MEMBRANE REACTOR FOR WATER GAS SHIFT Angelo Rossi, Giacomo Lamonaca, STRUTTURA INFORMATICA, Florence (IT), Pietro Pinacci, Francesca Drago, RSE, Milan, (IT) 6th Trondheim Conference on CO2 Capture, Transport and Storage, June

STRUTTURA INFORMATICA, a Software and Process Engineering Solutions provider, focuses on the study and development of dynamic simulation models of thermal power plants and related technologies

RICERCA SISTEMA ENERGETICO RSE carries out research into the field of electrical energy with special focus on national strategic projects funded through the Fund for Research into Electrical Systems.

2 STRUTTURA INFORMATICA, a Software and Process Engineering Solutions provider, focuses on the study and development of dynamic simulation models of thermal power plants and related technologies addressing both renewable and conventional sources. RICERCA SISTEMA ENERGETICO RSE carries out research into the field of electrical energy with special focus on national strategic projects funded through the Fund for Research into Electrical Systems. RSE is a total publicly-controlled Company: the sole shareholder is GSE S.p.A. The activity covers the entire supply system with an application-oriented, experimental and system-based approach. RSE has a unique heritage of human resources, experience and innovation, essential to the continuity and revival of innovation in this important sector for the country.

3 STRUTTURA INFORMATICA Action fields: - CC e IGCC plant (Combined Cycle e Integrated Gasifier CC); - Concentrating Solar Power (CSP); - Gasification plant (carbone e biomasse) - Clean Coal Technologies (CCT); - Carbon Capture & Storage (CCS); - Hydrogen separation. Modelling activities: - process study and their formulation; - mathematical model definition; - model development and validation; - integration of models or tasks by means of dynamic solutors. The software platform: - ISAAC Dynamics: development system for dynamic simulations (time depending); - Support tools: Stargate (web-based access tool), Alexandria (document system).

4 Summary 1. Foreword 2. Process description & phenomena 3. Model Description 4. ISAAC DYNAMICS simulation platform 5. Experimental apparatus and results 6. Simulation and comparison with experimental results 7. Conclusions & Developments

1.Foreword Palladium and palladium alloy membranes have been extensively studied in bench-scale tests at several R&D institutes throughout the world.

In a membrane reactor, CHEMICAL REACTION, MASS TRANSFER and HEAT TRANSFER occur simultaneously However dynamic models able to follow the time evolution of the main process parameters have been not

5 1.Foreword Palladium and palladium alloy membranes have been extensively studied in bench-scale tests at several R&D institutes throughout the world. Studies are now focusing on specific applications in a membrane reactor both for the WGS reaction and for steam reforming. In a membrane reactor, CHEMICAL REACTION, MASS TRANSFER and HEAT TRANSFER occur simultaneously However dynamic models able to follow the time evolution of the main process parameters have been not yet developed. Simplest models MONO- DIMENSIONAL STEADY STATE CONSIDER EQUILIBRIUM CONDITIONS CHEMICAL REACTIONS AND SEPARATION ARE CONSIDERED AS SEQUENTIAL STEPS Latest models Consider kinetics of the WGS reaction and include a more detailed description of the membrane structure. In this paper the basis of a new dynamic model of a palladium membrane reactor for the Water Gas Shift Reaction are described and their preliminary validation through experimental data is presented.

6 2. Process description and phenomena The water gas shift is an exothermic reaction where the CO is converted into CO 2, thus producing H 2 : CO + H 2 O CO 2 + H 2 ΔH (298 K )= 41.2 kj mol 1 The temperature affects the reaction kinetics positively The conversion is promoted by lowering the temperature. In industrial applications, the water gas shift reaction is carried out in several steps: usually, in order to achieve high conversions this process takes place in two reactors operating at high and low temperatures.

2. Process description and phenomena http://www.netl.doe.

html The WGS reaction can take advantagefrom the use of membrane

permits removal of one of the reaction products, thus moving the

7 2. Process description and phenomena The WGS reaction can take advantagefrom the use of membrane reactors The use of a membrane selectively permeable to hydrogen permits removal of one of the reaction products, thus moving the conversion beyond the thermodynamic equilibrium according to the well-described shift effect. Thin dense Pd-based membranes allow both high H2 fluxes and selectivity Under these conditions THE SHIFT EFFECT CAN BE MAXIMIZED

through the porous support Simplified model of a palladium membrane. The hydrogen flux through the membrane is evaluated considering the Pd layer and the multilayered support as resistances in series.

8 3. Model description The models developed by Struttura Informatica are: Pd based membrane: Extended model of a palladium membrane. This model takes into account: Chemical/ physical phenomena involved in the H 2 permeation through the Pd; Flux of H 2 and other gases through defects in the Pd layer Flux of H 2 and other gases through the porous support Simplified model of a palladium membrane. The hydrogen flux through the membrane is evaluated considering the Pd layer and the multilayered support as resistances in series. Further this model takes into account the flux of H 2 and of other gases through defects of the Pd layer. WGS reactor. Its main features are: The model is fully dynamic (time depending); Kinetics of the WGS reaction is considered; WGS reaction and separation occur simultaneously in a single cell;

9 3. Model description The membrane reactor model is composed by: A. Pd based membrane (simplified model) B. WSG Reactor A. Pd based membrane simplified This module simulates: Feed flux shell side incoming; Hydrogen diffusive flux inside the Pd; Other gaseous component flux through defects of Pd layer; Hydrogen and other components flux through the multilayered support (2 layers) permeate current flux (rich in H2) flowing in the inner side of the membrane..and calculates: The hydrogen amount permeating through the membrane; The out going gas flow rates (unp/per side) and their correlated compositions; Temperature variations during the separation process; Pd temperature variation during the above mentioned process; Pressure changes inside the cells.

10 H 2 flux through the membrane is: J = J + J + H 2 S KH 2 VH 2 3. Model description J Where: J Js is the H 2 flux through the Pd layer S Pe n n = ( Pf Pp ) 0.5 < n < 1 L Sieverts Law and Pe = Pe0e E a RT Arrhenius J KH2 is the diffusion component (Knudsen); J KH = F ( P P 2 KH 2 f P ) FK = f (r pores, PM) J VH2 is the viscous component (Poiseuille) J VH = F P ( P P 2 VH 2 av f P ) F = f (µ) V

11 3. Model description B. WSG Reactor Model main features assumption Fixed bed tubular catalytic reactor (Plug Flow Reactor); Fe/Cr catalyst. Thermal Model : Chemical model: Well stirred reactor; The reaction takes place on the catalyst surface the gaseous phase; Kinetic parameters depend on the catalyst; The interaction between catalyst and gaseous mixture is neglected. Kinetic and potential energies are neglected; Reaction heat is considered; The thermal exchange catalyst/gas/reactor wall is taken in account; The heat exchange between reactor wall and external atmospheres is considered. Hydralic Model: In the mass balance, the diffusion term is neglected.

12 3. Model description Reactor kinetic equation: Simplified description based on a semi-empirical model TD equilibrium constant Weakly influenced by pressure and decreases while temperature increases.

3. Model description WSG membrane reactor : Modelling techiniques The model has

has been built connecting in series the WGS reactor module and the Pd membrane

To reach a better degree of accouracy we have divided the longitudinal axis of

13 3. Model description WSG membrane reactor : Modelling techiniques The model has been realized in two different steps: Firtst step : The WGS membrane reactor has been built connecting in series the WGS reactor module and the Pd membrane module. To reach a better degree of accouracy we have divided the longitudinal axis of the reactor and the membrane in n - axial cells (e.g. five). CO-Shift reactor FEED GAS INLET PERMEATE OUTLET UNP. OUTLET PERMEATE INLET Metallic membrane

3. Model description WSG membrane reactor : Modelling techiniques Second step : Combining the equations forming the mathematical models of the two modules we

In this way the WGS reaction and H 2 separation occur simultaneously in a single cell.

14 3. Model description WSG membrane reactor : Modelling techiniques Second step : Combining the equations forming the mathematical models of the two modules we have got a single module able to represent, in detail, the behaviuor of a WSG membrane reactor both from the hydraulic, thermal and chemical point of view. In this way the WGS reaction and H 2 separation occur simultaneously in a single cell. Also in this case the reactor can be splitted in one or more axial cells CO, H 2 O CO 2 Catalytic bed Pd layer H 2 This dynamic model is able to follow the time evolution of the main process parameters until steady state is reached.

15 4.ISAAC DYNAMICS simulation platform Isaac Dynamics 2.1 is a complete instrument designed for the studying, modelling and running dynamic simulations of integrated and compelx systems. It allows an easy and effective development of accurate, detailed dynamic models by means of its innovative technical features: modular architecture; a friendly graphical user interface; an auto learning component connection tool; maximum portability indipendence from sw platforms; and functionalities: sound and effective solver, based on the Newton-Raphson, operates in double precision; capabiliity of generating external autonomous applications; wide component library addressing the market sectors of interest: Concentrating Solar Power (CSP), Carbon Capture and Storage (CCS), Combined Cycle (CC) plants.

5.Experimental set - up @ RSE Laboratory pilot loop Mass flow controllers;

housed; On-line gas chromatograph for dry gases analysis; Acquisition and

TEST SECTION Consisting of a 316 L stainless steel reactor (20mm I.D.

non-porous end of the membrane support to the reactor.

16 5.Experimental set - RSE Laboratory pilot loop Mass flow controllers; Electrically heated oven where process gases are heated and the test section is housed; On-line gas chromatograph for dry gases analysis; Acquisition and control system of the process parameters, interfaced with a computer. TEST SECTION Consisting of a 316 L stainless steel reactor (20mm I.D.) where the membrane is housed; gas tight sealing is insured by welding the non-porous end of the membrane support to the reactor. Pd - MEMBRANE Obtained by electroless plating on SS macroporous support Pd layer Thickness µm Ref. Cat. Today 156 (2010)

17 6. Simulation and comparison of results Membrane module validation Permeation test with pure gas C4 membrane thickness 12 µm 310 C no sweep experimental model - without defects model - with defects H2 flux [Nl/h] E E E E E+05 P [Pa]

18 6. Simulation and comparison of results Membrane module validation Permeation test with pure gas- membrane C4 -no sweep C4 - no sweep 60 experimental 400 C model 400 C experimental 310 C model 310 C H2 Flux [Nl/h] C 310 C ,0E+00 1,0E+05 2,0E+05 3,0E+05 4,0E+05 Pressure difference [Pa]

19 6. Simulation and comparison of results Membrane module Validation C4 membrane at 400 C experimental model experimental model no sweep sweep H2 flux [Nl/h] E E E E E E+05 P [Pa]

20 6. Simulation and comparison of results Membrane module validation Permeation test with pure gas-t= 400 C no sweep 60 Membrane Thickness (mm) H 2 flux [Nl/h] C3 29 C4 12 experimental C3 model C3 experimental C4 model C4 C4 15 C E E E E E+05 P [Pa]

21 6. Simulation and comparison of results Membrane module validation 1 C3 membrane 0.8 He 400 C Flux [Nl/h] CO C E E E E E E E E+05 P [Pa]

22 6. Simulation and comparison of results Membrane module validation C3-400 C WGS mixture 8 6 CO 7.6% H 2 O 27.2% H % CO % H 2 Flux [Nl/h] 4 2 experimental model 0 0.0E E E E E+05 Feed Pressure [Pa]

23 6.Simulation and comparison of the results WGS membrane reactor module validation Experimental data Test performed in a pilot loop at C P feed = bar GHSV =1580 h- 1 Sweep gas = N 2 P sweep =atmospheric Counter-current mode Reactor geometrical data Internal diameter [mm] 20 Length filled with catalyst [mm] 85 Membrane external diameter [mm] 10 Membrane internal diameter [mm] 6 Membrane active surface [cm 2 ] 23 Feed composition [%vol] FEED 1 FEED2 CO H2O H CO CO conversion % MR feed 1 MR feed 2 Eq TD feed 1 Eq TD feed 2 TR feed 1 TR feed 2 H2O/CO E E E E E E+05 P feed ( Pa)

24 6. Simulation and comparison of results 100 Feed 1 CO conversion [%] TD equilibrium Experimental MR Experimental TR Model TR Model MR Feed pressure [bar]

25 6. Simulation and comparison of results Feed CO Conversion [%] TD Equilibrium Experimental MR Experimental TR Model TR Model MR Feed Pressure [bar]

26 7. Conclusions & developments H 2 permeation through a Pd based membrane is well represented by the membrane model. WGS reaction is also satisfactory described by the model, although not yet totally validated. The MRWGS model slightly overestimates experimental data: mismatch between calculated and experimental data increases while increasing feed pressure. This can be due to the following main factors, not considered in the model: concentration polarization of the feed, becoming stronger while increasing H 2 recovery (feed pressure); gas distribution at reactor inlet; uncertainty about some data regarding catalyst kinetic. Developments model improvement by considering polarization effects; investigate gas distribution and its influence on the reaction by experimental tests

More Info Contact: angelo.rossi@strutturainformatica.it Phone +39 055 4379027 www.

27 More Info Contact: Phone Acknowledgements Preliminary validation of the model has been performed in a national project financed by the Research Fund for the Italian Electrical System under the Contract Agreement between RSE and the Ministry of Economic Development

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