Tatsuo Kabata

Technology for removing carbon dioxide from power plant flue gas by the physical adsorption method

Abstract Research into technology for removal of CO 2 considered to be the major cause of global warming, was applied to electric power plant flue gas. Our method was to use zeolite as adsorbent for physical adsorption, progressing from the previously used PSA (Pressure Swing Adsorption) method to the more advanced PTSA (Pressure and Temperature Swing Adsorption) method. We have been conducting basic research since the 1980s, and in 1991 built a 1000m 3 N/h scale pilot plant, where we are continuing research through trial operation. Trial operation of the pilot plant has been mainly for acquisition of scale up data, as well as improvement in the decrease in the power consumption of PTSA units. As a result, we have seen a better than 20% improvement in that area. In addition, the pilot plant completed 2000 hours of continuous operation without incident between October and December, 1994. The total hours of operation of the plant have topped 4000 hours, but we have seen no decrease in the effectiveness of the CO 2 adsorbent. The SOx in the flue gas was trapped in the lower part of desiccant in PSA-H 2 O before the process. Some of desiccant reacts to that, but we have prevented any ill effects on the process that might be caused by main units. At this point we would like to report on the results of our research, as well as outline our plants for the future.

Gas Transport Impedance in Segmented-in-Series Tubular Solid Oxide Fuel Cell

Gas phase transport is a very important electrode process in practical solid oxide fuel cells. In this study, we have identified gas conversion impedance and gas diffusion impedance in the Mitsubishi segmented-in-series tubular solid oxide fuel cell. Gas conversion impedance is caused by the weak convection transport in the gas flow channel. It is observed that both the insufficient anode and cathode gas flow rates can result in the gas conversion impedance. Gas conversion impedance appears at less than 0.1 Hz, and its magnitude strongly depends on the gas flow rates. It disappears when the gas flow rates of both the anode and cathode are improved sufficiently. Anode gas diffusion through the porous substrate appears at ~0.5 Hz and dominates the overall diffusion impedance. Cathode gas diffusion through the porous current collecting layer appears at ~3 Hz, which significantly contributes to the overall gas diffusion impedance under low cathode oxygen partial pressures.