J. Phys. IV France 09 (1999) Pr3-343-Pr3-348
A reactive redox system of metal oxide for a two-step thermochemical cycle for converting coal to upgraded chemical fuels of CO/H2T. Kodama, T. Shimizu, A. Aoki and Y. Kitayama
Department of Chemistry and Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181, Japan
A two-step thermochemical process using a redox system of metal oxides for converting coal to CO and H2 with H2O/CO2 was studied for the propose of utilizing solar high-temperature heat below 1173 K. In the first step, metal oxide was reacted with coal as an oxidant to produce CO and H2 : metal oxide + CHn(coal)→metal + xCO + (1-x)CO2 + n/2H2. The metal so formed was reoxidized with H2O or CO2 to generate H2 or CO in the second step. A number of coal-metal oxide systems were thermodynamically examined and demonstrated at 1173 K. The coal-In2O3 and coal-SnO systems yielded 82 and 62% respectively. With iron-based oxides, the In(III)-, Ni(II)- and Sn(II)-doped ferrites yielded 60-70% of coal conversions. In these coal-ferrite systems, magnetic separation of recovered ferrite from coal ashes can be expected. The proposed two-step process using In(III)-ferrite could be repeated with highly coal conversion of 60-90%. Our two-step process is superior to the conversions of coal and H2O/CO2 to H2 and CO below 1173 K by the direct single-step reactions, CHn + H2O → CO + (n/2+1)H2 and CHn + CO2 → 2CO + n/2H2.
© EDP Sciences 1999