Reforming options for H 2 and SNG manufacture via steam gasification VETAANI Final seminar, April 9 th 2014, Helsinki Ilkka Hannula VTT Technical Research Centre of Finland
Table of Contents Introduction to the topic Target parameters for indirect steam gasification plants The effect of reforming choises on SNG production The effect of reforming choises on H 2 production The effect of pressure on steam gasification plants Summary and conclusions 15/04/2014 2
Introduction 3
Main alternatives for large scale gasification of woody biomass PRESSURISED O 2 GASIFIER Pros - High output/size - Can be pressurised - Single trains up to 300 MW? - Technically proven at precommercial scale Cons - Requires oxygen Biomass ATM. STEAM GASIFIER Pros - No oxygen needed Cons - Complicated design - Difficult to pressurise - Single trains only up to 100 MW? Steam Air 15/04/2014 4
Main alternatives for large scale gasification of woody biomass Up to 98 % of carbon to product gas and tars Biomass Steam Air 15/04/2014 5
Main alternatives for large scale gasification of woody biomass Up to 98 % of carbon to product gas and tars ~80 % of carbon to product gas and tars Fluegas Biomass Steam Air 15/04/2014 6
Main alternatives for large scale gasification of woody biomass Up to 98 % of carbon to product gas and tars ~80 % of carbon to product gas and tars Fluegas Biomass Steam Air 15/04/2014 7
Baseline assessment for indirect steam gasification Pressure control difficult and compression savings minimal ---> Suitable for use with relatively low pressure syntheses Large steam input drives water-gas shift ---> Suitable for uses where high H 2 /CO ratios are required No need for oxygen ---> Suitable for scales where oxygen uneconomic Conclusion: Small-scale SNG and H 2 good match with steam gasification! 15/04/2014 8
Target process 9
Targeted operating parameters based on experimental data from Vetaani project Product gas 820 C Hot-filtration 820 C Fluegas Steam/O 2 reforming Steam/O 2 = 0.7 kg/kg 95 % CH 4 conv. = 957 C 35 % CH 4 conv. = 850 C Biomass Steam Steam/Bio > 0.8 kg/kgdry Air 880 C Indirect steam reforming Steam/C > 4.3 mol/mol (all steam thru gasifier) 10 % CH 4 conv. = 850 C 15/04/2014 10
Reforming options for thermochemical SNG manufacture
H 2 /CO = 3 achieved without shift reactor with following steam/biomass ratios in the gasifier: 0.86 kg/kg for O 2 reforming (35 % CH4 conversion @ 850 C) 0.89 kg/kg for steam reforming (10 % CH4 conversion @ 850 C) Steam SOUR SHIFT Feed gas Cooling Cooling COS HYDROLYSIS Bypass stream 15/04/2014 12
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Reforming options for thermochemical hydrogen manufacture
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15/04/2014 18 Source: Hufton, J., 2011, Advanced Hydrogen and CO2 Capture Technology for Sour Syngas, Gasification Technology Council Gasification Technology Conference, Oct 31st Nov 3 rd, Washington, D.C., Air Products
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Gasifier performance and the effect of pressure
Gasification pressure vs. compression work (methanation at 15 bar pressure) 15/04/2014 22
Gasification pressure vs. district heat output 15/04/2014 23
Gasification pressure vs. district heat output 15/04/2014 24
Summary and conclusions SNG manufacture Shift reactor not necessarily required. Reforming choises have small impact of overall efficiency Steam reforming delivers 5 /MWh lower production cost than oxygen reforming H 2 manufacture Sulphur separation capability of pressure swing adsorption an important topic Oxygen reforming allows more flexibility and higher H 2 yields Steam reforming delivers 5 /MWh lower production cost than oxygen reforming Gasification pressure Changes in syngas and combustion air compression cancel out each other between 1 5 bar Pressures below 3 bar significantly restrict DH output potential 15/04/2014 25
TECHNOLOGY FOR BUSINESS
Additional slides 15/04/2014 27
Air reforming
Conclusions on air reforming in SNG/H2 production SNG Air reforming only a theoretical possibility as N 2 can t be separated by condensation CH 4 concentration in SNG 60 vol% H 2 N 2 can be separated by H2PSA However, H 2 concentration at H2PSA inlet 54/46 vol% (at min/max CH 4 conversion) too low? If workable: then performance little below O 2 reforming but similar economics 15/04/2014 29
Comparison of - O 2 gasifier with O 2 reformer - Steam gasifier with O 2 reformer
Simulated gas compositions 15/04/2014 31
Simulated gas compositions 15/04/2014 32