HIGH TEMPERATURE REMOVAL OF H{sub 2}S FROM COAL GASIFICATION PROCESS STREAMS USING AN ELECTROCHEMICAL MEMBRANE SYSTEM
A bench scale set-up was constructed to test the cell performance at 600-700 C and 1 atm. The typical fuel stream inlet proportions were 34% CO, 22% CO{sub 2}, 35% H{sub 2}, 8% H{sub 2}O, and 450-2000 ppm H{sub 2}S. The fundamental transport restrictions for sulfur species in an electrochemical cell were examined. Temperature and membrane thickness were varied to examine how these parameters affect the maximum flux of H{sub 2}S removal. It was found that higher temperature allows more sulfide species to enter the electrolyte, thus increasing the sulfide flux across the membrane and raising the maximum flux of H{sub 2}S removal. The results identify sulfide diffusion across the membrane as the rate-limiting step in H{sub 2}S removal. The maximum H{sub 2}S removal flux of 1.1 x 10-6 gmol H{sub 2}S min{sup -1} cm{sup -2} (or 3.5 mA cm{sup -2}) was obtained at 650 C, with a membrane that was 0.9 mm thick, 36% porous, and had an estimated tortuosity of 3.6. Another focus of this thesis was to examine the stability of cathode materials in full cell trials. A major hurdle that remains in process scale-up is cathode selection, as the lifetime of the cell will depend heavily on the lifetime of the cathode material, which is exposed to very sour gas. Materials that showed success in the past (i.e. cobalt sulfides and Y{sub 0.9}Ca{sub 0.1}FeO{sub 3}) were examined but were seen to have limitations in operating environment and temperature. Therefore, other novel metal oxide compounds were studied to find possible candidates for full cell trials. Gd{sub 2}TiMoO{sub 7} and La{sub 0.7}Sr{sub 0.3}VO{sub 3} were the compounds that retained their structure best even when exposed to high H{sub 2}S, CO{sub 2}, and H{sub 2}O concentrations.
- Research Organization:
- Georgia Tech Research Corp. (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FG26-99FT40586
- OSTI ID:
- 823016
- Resource Relation:
- Other Information: PBD: 1 Jun 2003
- Country of Publication:
- United States
- Language:
- English
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