Advanced Membrane Reactors for Carbon-Free Fossil Fuel Conversion

Transcription

1 Advanced Membrane Reactors for Carbon-Free Fossil Fuel Conversion Daniel Jansen, Wim Haije, Michiel Carbo, Virginie Feuillade, Jan Wilco Dijkstra,Ruud van den Brink

2 Contents The project Objectives R&D results ECN Reactor design System analysis Materials science Catalyst testing Conclusions

3 Advanced Membrane Reactors in Energy Systems Development of novel membranes for membrane reactors. Objective: The purpose of this project is to develop and CO 2 membranes to allow combinations of natural gas reforming or WGS with or CO 2 separation in separation enhanced reactors, i.e. membrane reactors, for carbon-free hydrogen production or electricity generation.

4 The ECN GCEP project layout overall efficiencies economics experimental results system studies reactor requirements patents IP membrane & catalyst development reactor design reactor tests fundamental knowledge characterization desired specifications IP publications materials research new developments Task 1. Task 2. Task 3. Task 4. Task 5. System analysis and thermodynamic evaluations Hydrogen membrane research & development CO 2 membranes research & development Catalyst screening Reactor modelling and design Executed by ECN Executed by TUD Executed by ECN+TUD Executed by ECN Executed by ECN

5 Application: Steam Reforming NGCC with CO 2 membrane reformer reactor Natural gas O Pre-reformer Steam reformer membrane reactor / CO 2 Steam sweep Combined Cycle Advantages compared to membrane reformer: eliminating the requirement of water gas shift reactors: cost reductions offering higher conversion efficiencies at lower temperatures rich stream remains at elevated pressure and temperature CO inhibition of membrane not foreseen no need for CO 2 cleaning section

6 Application: O IGCC with CO 2 membrane water gas shift reactor Coal O G-E gasifier Cooler T=300 o C Pre-shift Water gas shift membrane reactor Combined Cycle O 2 G-E product gas (around 1300 o C) CO 2 Steam sweep Advantages compared to membrane WGS reactor: eliminating the requirement of LT water gas shift reactor: cost reduction incomplete CO conversion in WGS does not reduce the IGCC efficiency but lowers CO 2 capture ratio rich stream remains at elevated pressure and temperature CO inhibition of membrane not foreseen no need for CO 2 cleaning section

7 Reactor Design/System analysis CO 2 versus selective membranes Main Question Membrane application: Everybody agrees on the fact that either or CO 2 selective membranes are viable options for carbon capture technologies But..: Nobody cares or dares to look into the process boundary conditions: Are both membranes equally fit to operate in a certain process??

8 Reactor Design/System analysis CO 2 versus selective membranes: Reforming Steam Reforming Natural gas O Pre-reformer Steam reformer membrane reactor / CO 2 Steam sweep Combined Cycle Membrane reformer: Residual partial pressure of permeating compontent in retentate as a function of conversion. 8.0 Conversion relatively easy enhanced by separation of favourable kinetics H2 and CO 2 retentate partial pressure (bar) CO 2 membrane membrane CO 2 selective membranes show a too low conversion and are therefore not suitable, as opposed to selective membranes Overall conversion 600 o C, 40 bar, S/C = 3,Sweep: steam 5 bar, 600 o C, Sweep flow/feed flow = 0.11 (mole/mole) See poster

9 Reactor Design/System analysis O CO 2 versus selective membranes: IGCC Coal O G-E gasifier Cooler T=300 o C Pre-shift Water gas shift membrane reactor Combined Cycle Partial pressure and CO 2 in retentate (bar) O 2 25,0 20,0 15,0 10,0 5,0 0,0 G-E product gas (around 1300 o C) CO 2 membrane membrane WGS conversion (relative to product gas) (%) CO 2 Steam sweep permeation results in better CO 2 recovery and CO conversion but CO 2 permeation does not perform much worse Complete system and exergy analysis needed to really determine all pros and o C, 42.2 bar, S/C just enough to complete water gas shift, excess catalyst, Sweep: steam 17 bar, 300 o C See poster

10 Reactor Design/System analysis IGCC with WGS Membrane Reactor Quench Gas N 2 Syngas IP Steam Air Pulverized Coal O 2 HP Steam Gas Cleaning Section IP Steam WGS -WGS Membrane Reactor O Cryogenic Distillation CO 2 Liquefaction, CO, IP Steam Slag BFW O, CO 2 N 2 CO,, N 2, CH 4 CO 2 N 2, N 2 Stack ASU Dry-fed Coal Gasifier Gas Cooler Air Gas Turbine HRSG Steam Turbine

11 Reactor Design/System analysis IGCC with CO 2 WGS Membrane Reactor Quench Gas N 2 Syngas IP Steam CO 2 -WGS Membrane Reactor CO 2 Liquefaction HP Steam CO 2, O IP Steam Air Pulverized Coal O 2 Gas Cleaning Section WGS CO 2 LP Steam, CO, IP Steam Slag BFW O, CO 2 O CO 2 Stack N 2, N 2 ASU Dry-fed Coal Gasifier Gas Cooler Air Gas Turbine HRSG Steam Turbine

12 Reactor Design/System analysis CO 2 versus selective membranes: Exergy analysis IGCC 4 Losses due to CO 2 capture Efficiency reduction (% points) 3,5 3 2,5 2 1,5 1 0,5 0 CO2 compression CO-Shift Lost GT-work CO2 separation Case Output Efficiency Carbon Membrane Sweep Capture Area Steam [MW e ] [-] [-] [m 2 ] [kg/s] IGCC Base Case IGCC Selexol (HT- & LT-WGS) IGCC H2-selective WGS-MR IGCC CO2-selective WGS-MR Sensitivity analysis on CO 2 permeation: see poster

13 Reactor Design/System analysis: Conclusions Reactor modeling Membrane reformer for CO 2 capture in NGCC - CO 2 selective membranes show a too low CH 4 conversion and are therefore not suitable for CO 2 capture in NGCC power plants Water gas shift membrane reactor for CO 2 capture in IGCC - CO 2 selective membranes give CO conversions in IGCC comparable to separating membranes and offer therefore a viable alternative System analysis IGCC - Coal gasifiers always produce /CO 2 -ratios higher than unity, resulting in a higher partial pressure, which is beneficial in membrane permeation - The steam sweep flow applied in CO 2 -selective WGS-MR results in higher efficiency penalty for CO 2 capture compared to -selective WGS-MR

14 Materials Science-Catalysis Stability test of commercial catalyst 70 CH4 Conversion [%] Noble metal catalyst Vendor A Ni-catalyst Vendor A Noble Metal catalyst Vendor B Noble metal catalyst Vendor C Noble metal catalyst ECN CH 4 2.9% O 17.5% N % Flow 25 sccm T = 500 C P = 1 atm Time [hr]

15 Hydrotalcite general formula: Mg 6 Al 2 (OH) 16 CO 3 4 O Materials Science-assumption Mg/Al OH - O CO -- 3 CO 2 transport channel?? Rhombohedral system: R3 m a=b 3Å c 23Å

16 Materials Science-composition SEM-EDX result hydrothermally synthesized sample (starting materials: 90/10 Mg/Al-nitrate): Impurity phase Impurity phase Main phase

17 Materials Science-composition 25/75 90/10 50/50 ND very suitable to see a) Light elements C, O, H b) Difference between Mg and Al Diffraction experiment on GEM at ISIS, UK

18 Materials Science-composition Materials: Rather poor crystallinity, esp. impurities 50/50 sample relatively pure: refinable (GSAS) Results: Composition Mg 0.64 Al 0.36 (OH) 2 (CO 3 ) O Mg< 0.64: Boehmite impurity (Al rich) Mg> 0.64: Hydromagnesite impurity (Mg rich)

19 Materials Science-composition 20 o C In-Situ XRD under N 2 /CO 2 / O o C o C 500 Lin (Cps) Interlayer water out: 1.5 Å 350 o C 300 o C o C Theta - Scale There is no structural memory effect!!! File: MG 50 pellet 100 N2 CO2.raw - Start: End: Step: Step time: 2. s File: MG 50 pellet 300 N2 H2O.raw - Start: End: Step: Step time: 38. s File: MG 50 pellet 350 N2 H2O.raw - Start: End: Step: Step time: 2. s File: MG 50 pellet 400 N2 H2O.raw - Start: End: Step: Step time: 2. s File: MG 50 pellet 450 N2 H2O.raw - Start: End: Step: Step time: 2. s File: MG 50 pellet RT N2 after heattreatments.raw - Start: End: Step: Step time: 4. s (C) - Hydrotalcite, syn - (Mg0.667Al0.333)(OH)2(CO3)0.167(H2O)0.5 - Rhombo.H.axes - a b c alpha beta gamma Primitive - R-3m (166)

20 Materials Science-material stability Hydrotalcite TGA/MS 1. Adsorbed o C C 240 C 310 C 450 C 0,018 O(ad) O(g) weight (mg) ,008 sample H2O CO2 2. Interlayer o C O(abs) O(g) 3. o C 0-0,002 Mg(OH) 2 MgO + O(g) time (s) 4. o C Mg(OH) 2 + MgCO 3 2MgO +CO 2 (g) + O(g) First tentative working hypothesis

21 Materials Science-CO 2 transport Dense membrane produced using cold isostatic pressing under 2000 bar sliced to about 2,4 mm thick discs. Rest porosity about 15% Permeancy measured of CO 2 and He Permeancy No significant difference between He and CO 2 (Knudsen-like) At 250 o C the material deteriorates and permeancy goes up Ln(Flow) 5,50 4,50 3,50 2,50 1,50 He CO2 1,50E-03 2,00E-03 2,50E-03 3,00E-03 3,50E-03 1/T

22 Materials Science-Conclusions Hydrotalcites Hydrotalcites exist in a small compositional window around Mg/Al=0.64/0.36=1.8 Hydrotalcites are not stable above 200 o C - dense HTC membranes are not feasible in the T,p window of the applications - porous HTC membranes not first choice - search for alternative hydroxidic materials or porous supports impregnated with hydroxides Catalyst Four (pre)commercial pre-reforming catalysts have been tested. Cheap Ni-catalyst is promising and could do the job in reformers with CO 2 selective membranes.

23 Summary Reactor Design/System analysis CO 2 selective membranes show a too low CH 4 conversion - driving force for CO 2 permeation to low to enhance reform reaction CO 2 selective membranes for WGS give CO conversions comparable to separating membranes and offer therefore a viable alternative - from efficiency point of view steam sweep should be as low as possible Materials Science Hydrotalcites are not stable above 200 o C - Dense HTC membranes are not feasible in the T,p window of the foreseen applications - porous HTC membranes not first choice - search for alternative hydroxidic materials or porous supports impregnated with hydroxides

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