Bulk Separation and Purification of Coal Gas by Using Pressure Swing Adsorption

Bulk separation and purification of coal gas by using pressure swing adsorption

Young Woo You^a, Dong Geun Lee^a, Seung Moon Lee^b, Ki Hyun Kim^b, Seong Man Kim^b and Chang-Ha Lee^a, *

^aDepartment of Chemical and Biomolecular Engineering, Yonsei University, Seoul, Korea

^bIron making Research Group of Technical Research Laboratories, POSCO, Pohang, Korea

^*E-mail: leech@yonsei.ac.kr, Tel: +82-2-2123-2762

Global warming, resulting from greenhouse gases emissions especially CO₂, is a big issue facing the earth. And the steel and iron industry is known as one of major global warming gas emission industries. One of the options for solving the global warming problem in steel and iron industry is to recover H₂ from coal gas as a clean energy resource. However, coal gas from iron and steel processes contains relatively low H₂ fraction (38 vol.%) and high CO₂ fraction (50% vol.%) compared with reforming gas or coke oven gas. Therefore, bulk separation and purification of coal gas should be performed to use hydrogen as a combustion fuel or fuel for fuel cell.

In this study, layered two-bed and four-bed PSA processes were investigated experimentally and theoretically for the H₂ recovery from coal gas (H₂/CO/CO₂/CH₄/N₂; 38 H₂ vol.%). The four-bed PSA process could produce H₂ with purity of 96-99.5% and recovery of 71-85%. The recovered H₂ product for fuel cell should contain carbon monoxide below 10 ppm because of CO poison on anode catalysts.

Therefore, purification by using PSA and PVSA processes with single adsorbent bed or layered bed were performed experimentally to remove CO and recover high purity H₂ (less than 10 ppm CO) from hydrogen-rich mixture. Two types of feed were used in this study: Feed1 is 99% H₂ mixture containing 0.1% CO concentration (H₂/CO/CO₂/N₂ mixture), Feed2 is 95% H₂ mixture containing 0.3% CO concentration (H₂/CO/CO₂/CH₄/N₂ mixture). In the PSA experiments using activated carbon, carbon monoxide in the feed could be removed to 1.1 ppm in the product with 99.99%+ H₂ purity and 80.0% recovery in Feed 1 and 6.7 ppm with 99.96% H₂ purity and 78.4% recovery in Feed 2 under 6.5 bar adsorption pressure. In addition, the effects of P/F ratio and adsorption pressure were investigated experimentally. PVSA process applied to Feed1 gave higher performance result than PSA process, but the vacuum cost should be evaluated.

References

 ADDIN EN.REFLIST [1] J.J. Lee, M.K. Kim, D.G. Lee, C.H. Lee, Heat-Exchange Pressure Swing Adsorption Process for Hydrogen Separation, AIChE J, 54 (2008), 2054-2064.

[2] J.G. Jee, S.J. Lee, M.B. Kim, C.H. Lee, Three-bed PVSA process for high-purity O₂ generation from ambient air, AIChE J., 51 (2005), 2988-2999.

[3] J.Y. Yang, C.H. Lee, Adsorption dynamics of a layered bed PSA for H₂recovery from coke oven gas. AIChE J., 44 (1998), 1325–1334.