Reforming options for H 2 and SNG manufacture via steam gasification

Transcription

1 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

2 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

3 Introduction 3

4 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

5 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

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 6

7 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

8 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

9 Target process 9

10 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/

11 Reforming options for thermochemical SNG manufacture

12 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 850 C) 0.89 kg/kg for steam reforming (10 % CH4 850 C) Steam SOUR SHIFT Feed gas Cooling Cooling COS HYDROLYSIS Bypass stream 15/04/

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16 Reforming options for thermochemical hydrogen manufacture

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18 15/04/ 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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21 Gasifier performance and the effect of pressure

22 Gasification pressure vs. compression work (methanation at 15 bar pressure) 15/04/

23 Gasification pressure vs. district heat output 15/04/

24 Gasification pressure vs. district heat output 15/04/

25 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/

26 TECHNOLOGY FOR BUSINESS

27 Additional slides 15/04/

28 Air reforming

29 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/

30 Comparison of - O 2 gasifier with O 2 reformer - Steam gasifier with O 2 reformer

31 Simulated gas compositions 15/04/

32 Simulated gas compositions 15/04/