Process Safety Aspects in Water-Gas-Shift (WGS) Catalytic Membrane Reactors Used for Pure Hydrogen Production

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Kazantzis and Yi Hua Ma Mary Kay O Connor Process Safety Center International Symposium

1 Process Safety Aspects in Water-Gas-Shift (WGS) Catalytic Membrane Reactors Used for Pure Hydrogen Production Reyyan Koc, Nikolaos K. Kazantzis and Yi Hua Ma Mary Kay O Connor Process Safety Center International Symposium October 26-28, 2010 / Texas Center for Inorganic Membrane Studies (CIMS) Worcester Polytechnic Institute Department of Chemical Engineering

2 Outline Introduction Pd-Based Membrane Reactor H 2 Transport Through Pd-Based Membrane Pd/Alloy Membrane Reactors in IGCC Plants Safety Analysis for Pd/Alloy Membrane Reactors Objective Modeling Results [T feed, W catalyst, H 2 O:CO Ratio, Driving for H 2 permeation ( P H2 )] Safety Aspects HAZOP [Feed flow rate, Reaction side pressure, Impurities] Conclusions 2

Pd-Based Membrane Reactor Applications of catalytic membrane reactors to refinery products [10] : Dehydrogenation & hydrogenation reactions Conversion of remote natural gas to syngas and liquid fuels

3 Pd-Based Membrane Reactor Applications of catalytic membrane reactors to refinery products [10] : Dehydrogenation & hydrogenation reactions Conversion of remote natural gas to syngas and liquid fuels Steam reforming Water gas shift reaction Retentate: Mostly CO 2 + H 2 O CO + H 2 O CO 2 + H 2 ΔH 298K = kJ/mol 1 & 3. Inert packing 2. Reaction /Shell side 4. Permeate/Tube side GE Syngas r 2 r1 4 H 2 Pd-based membrane HT WGS catalyst WPI Pd/Alloy Membranes Pd supported on porous Inconel (media grade 0.1 µm) Prepared by Electroless Plating Excellent long term H 2 /He selectivity ½'' OD 2.5'' Long 4 in 2 (25 cm 2 ) 3

4 H 2 Transport Through Pd-Based Membrane Solution diffusion mechanism Sieverts Law Interstitial diffusion of H atom in Pd lattice [8] 4

http://sequestration.mit.edu/pdf/lfe_2005-002_wp.

5 Pd/Alloy Membrane Reactors in IGCC Plants Table 1. Syngas compositions 100% 98% 91% 80% X CO & R H2 60% 40% 20% 20% 44% 42% 60% 0% GE Gasifier Highest H 2 O:CO ratio Shell 1 Shell 2 Gasifier Type GE CO Conversion H2 Recovery P shell = 220 & P Tube,MR = 15 psia F feed =1.1 scfh, T Rxn =450 C Highest X CO and R H2 Lowest H 2 S +COS concentration

Safety Analysis for Pd/Alloy Membrane Reactors - Objective Performance target levels: X CO = 98% & R H2 = 95% Isothermal Case: P shell = 220 & P Tube,MR = 6 psia F Dry feed =1.

6 Safety Analysis for Pd/Alloy Membrane Reactors - Objective Performance target levels: X CO = 98% & R H2 = 95% Isothermal Case: P shell = 220 & P Tube,MR = 6 psia F Dry feed =1.1 scfh, T Rxn =400 C H 2 O:CO X CO [%] R H2 [%] MR PBR F H2 Ratio MR / PBR 1.2 Membrane reactor limitations: 1. Reaction side temperature:@ T 300 C for Pure Pd H 2 embrittlement T 550 C intermetallic diffusion and permeance decline 2. Impurities : Poisoning of the Pd membrane due to H 2 S in the feed The standard principles of Hazard and Operability (HAZOP) analysis were followed to identify and prevent potential process risks to personnel, environment, equipment integrity and/or the efficiency or economics of the process [5.6]. 6

7 Feed flow rate[sccm] Feed Temperature P Shell = 15 atm, P Tube = 1 atm, H 2 O:CO = 2 and 100% ρ Bulk,max T Rxn,Max = 500 C &T Rxn,Min = 300 C for pure Pd membranes T MAX R H [a] T Feed [ C] [b] T Feed [ C] T feed 300 C to protect the membrane, however X CO = 95% and R H2 = 89% The target levels of X CO = 98% and R H2 = 95% were not achieved 7

8 Feed flow rate[sccm] W catalyst & H 2 O:CO T Feed = 300 C, P Shell = 15 atm, P Tube = 1 atm [a] Percentage of the ρ Bulk,max [%] H 2 O:CO = 2 - T max =530 C X CO = 93% - R H2 = 86% 40% ρ Bulk,max is sufficient enough and the contact area is increased 2 1 X CO [b] T Rxn >500 C H 2 O:CO = 4 - T max =470 C X CO = 98% - R H2 = 82% Use excess steam to reduce the T Rxn and also shift the Rxn to the products side 2 H 2 O:CO Mole Ratio 1 X CO

9 Process Safety Aspects: F Feed F Feed Causes Consequences Prevention & Repair More (Above the nominal level) Less (Below the nominal level) No (no flow) Malfunction of the flow control instruments Inappropriate adjustment and/or failure of the valves and pressure regulators (same causes with More and) Plugging of the lines Leaks on the feed line Da>1 Da>>1 Da<1 Da<<1 Hot spots Membrane damage Catalyst sintering Reduced X CO & R H2 Decreased T Rxn and variations Insignificant changes Decreased T Rxn due to reduced H Rxn Reduced H 2 production rates Pressure increase in the feed line due to plugging Pressure decrease due to leaks Oxidation of the membrane Regular maintenance and inspection of the control instrument, valves and pressure regulators A backup line before the reactor entrance Fast responsive temperature recorders and controllers Relief valves Poisonous gas detectors on both reaction and permeate sides Regeneration / substitution of the membrane 9

CO Conversion and H 2 Recovery Process Safety Aspects: H 2 O:CO In addition to the same effects with F feed : H 2 O:CO Causes Consequences Prevention & Repair More (above the nominal level) Less

10 CO Conversion and H 2 Recovery Process Safety Aspects: H 2 O:CO In addition to the same effects with F feed : H 2 O:CO Causes Consequences Prevention & Repair More (above the nominal level) Less (blow the nominal level) No ( no steam ) X CO & R H2 100% 95% 90% 85% 80% An error in the ratio controller Failure of the water pump CO Conversion Decreased T Rxn Reduced X CO & R H2 Increased T Rxn Coke formation (H 2 O:CO<2) Reduced X CO & R H2 Pressure built up due to, plugging of the pipelines and/or the membrane reactor Equilibrium Back up lines Relief valves Fast responsive pressure recorders and controller Regeneration / substitution of the membrane and catalyst Membrane appearance after removal from the reactor** 75% 70% H 2 Recovery Run Time [min] Run Time (min) **WPI-CIMS from Unpublished data by A. S. Augustine 10

11 Feed flow rate[sccm] 95.6 % 92.7 % 94.7 % Increase ΔP H2 : Driving force for H 2 permeation T Feed = 300 C, H 2 O:CO =4 and 40% ρ Bulk,max P Shell 45atm P Tube 0.5 atm R H % 97.6 % 97 % R H [a] P Shell [atm] (P Tube = 1 atm) 50 [b] P Tube [atm] (P Shell = 20 atm) T max = C - X CO 98% - R H2 95% 11

12 Reaction side Pressure [psia] R H2 [%] Process Safety Aspects: P shell H 2 Recovery Feed pressure Due to coke formation in the syngas feed line and plugging of line** **WPI-CIMS from Unpublished data by A. S. Augustine Run Time [min] More Less P Shell Causes Consequences Prevention & Repair Malfunction of the compressor and back pressure regulators Plugging or closing of the valves as well as connections at the zones before/after the membrane exit Increased T Rxn Increased X CO & R H2 Decreased T Rxn Decreased X CO & R H2 Back up lines Relief valves Fast responsive pressure recorders and controller Excess steam Recording the changes in permeate flow rate 12

Remained Permeance F/F o [%] Process Safety Aspects: Impurities Pure Pd foil Pd/Au alloy coupon 8 wt% Au 10 μm 5 μm 10 μm 20 ppmv H 2 S/ 320⁰C/ 120 h Mundschau et al.

Repair C H2 S > 0 Malfunction of the gas cleaning unit Pure Pd membrane: Decreased selectivity and even demolished [3] Pd-Cu and Pd-Au: Reduced permeance [4] Catalyst poisoning

13 Remained Permeance F/F o [%] Process Safety Aspects: Impurities Pure Pd foil Pd/Au alloy coupon 8 wt% Au 10 μm 5 μm 10 μm 20 ppmv H 2 S/ 320⁰C/ 120 h Mundschau et al. [9] 55 ppmv H 2 S/ 400⁰C/ 24h Chen & Ma [3] H 2 S Concentration [ppm]** **WPI-CIMS from unpublished data by Pomerantz & Chen [3-4] F Impurity Causes Consequences Prevention & Repair C H2 S > 0 Malfunction of the gas cleaning unit Pure Pd membrane: Decreased selectivity and even demolished [3] Pd-Cu and Pd-Au: Reduced permeance [4] Catalyst poisoning Corrosion Regular maintenance of the gas cleaning units Placement of the gas composition analyzers Regeneration/substitution of the membrane and catalyst Recording the changes in permeate flow rate 13

14 Conclusions A standard Hazard and Operability (HAZOP) analysis was pursued to identify potential hazards as well as failure modes and hopefully prevent potential risks In particular, the effect of variations in the total feed flow rate and temperature, catalyst loading, H 2 O:CO ratio, reaction and permeate side pressures and purity of the feed on the process state in the form of possibly adverse process excursions/deviations from normal operating conditions were considered. The absence of adequate control of the reactor temperature as well as the purity of the feed which may cause hot spots and decline in the permeance and selectivity were identified and classified as critical for the operation of the WGS membrane reactor. Utilization of excess steam together with the application of vacuum on the permeate side was found to be the most effective method of reducing the temperature rise in the reaction zone without decreasing the overall CO conversion and H 2 recovery. If the suggested precautionary measures are taken, the membrane reactor could be operated safely without compromising the high performance target levels of 98% CO conversion and 95% extra pure ( %) H 2 recovery. 14

Cicero Project Officer: Jason C. Hissam Disclaimer: This report was prepared as an account of work supported by an agency of the United States Government.

15 Acknowledgements U.S. Department of Energy Award No. DE-FC26-07NT43058 Composite Pd and Pd Alloy Porous Stainless Steel Membranes for Hydrogen Production and Process Intensification DOE Project Manager: Daniel Driscoll Technology Manager: Daniel C. Cicero Project Officer: Jason C. Hissam Disclaimer: This report was prepared as an account of work supported by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific otherwise does not necessarily constitute or imply its endorsement, recommendation, or opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. 15

16 References 1. Khan FI, Abbasi SA, J Loss Prev Process Ind ;10(4): Chiappetta G, Clarizia G, Drioli E., /10;193(1-3): Chen CH, Ma YH., J Memb. Sci., 2010, In press. 4. Pomerantz N, Ma YH., Ind Eng Chem Res 2009; /23/; 04/15/;48(8): Chiappetta G, Clarizia G, Drioli E., /10;193(1-3): Khan FI, Abbasi SA., J Loss Prev Process Ind ;10(4): J. Voelkl, G. Alefeld, Topics in Applied Physics, 28 (1978). 9. Mundschau MV, Xie X, Evenson IV CR, Sammells AF,Catalysis Today 118 (2006) Armor JN, J Memb. Sci., 147, 1998, Thanks for your attention Questions? 16

17 1 & 3. Inert packing 2. Reaction /Shell side 4. Permeate/Tube side Pd-based membrane Backup slide Retentate: Mostly CO 2 + H 2 O GE Syngas Composition (Dry): 45% CO + 38% H % CO 2 GE Syngas r 2 r HT WGS catalyst 4 H 2 Properties of Pd/Inconel Membrane: Q o = ft 3.μm/(ft 2.h.psi 0.5 ) Pd Thickness = 10 μm E p = 15.6 kj/mol Selectivity (H 2 /He) = Mass balance equations at the unsteady state conditions: Reaction side (1) Permeate side (2) Energy balance equation in the reaction side at the unsteady state conditions (3)

Conference: Advanced Coal-Fired Power Systems '96 Review Meeting

Paper Number: DOE/METC/C-97/7257 Title: Testing and Analysis of METC10 Sorbent Authors: R.V. Siriwardane Conference: Advanced Coal-Fired Power Systems '96 Review Meeting Conference Location: Morgantown,