Kinetics of Catalyzed Steam Gasification of Low-Rank Coals to Produce Hydrogen. Final Report for the Period Ending March 31, 1986

摘要

The principal goal of coal char-steam gasification research at the University of North Dakota Energy Research Center (UNDERC) is to establish the feasibility of low-rank coal gasification for hydrogen production. The program has focused on determining reaction conditions for maximum product gas hydrogen content and on evaluating process kinetics with and without catalyst addition. The high inherent reactivity of lignites and subbituminous coals, compared to coals of higher rank, make them the probable choice for use in steam gasification. An extensive matrix of char-steam gasification tests was performed in a laboratory-scale thermogravimetric analyzer (TGA) at temperatures of 700 deg, 750 deg, and 800 deg C. Four low-rank coals and one bituminous coal were included in the TGA test matrix. Catalysts screened in the study included K sub 2 CO sub 3 , Na sub 2 CO sub 3 , trona, nahcolite, sunflower hull ash, and lignite ash. Results showed uncatalyzed North Dakota and Texas lignites to be slightly more reactive than a Wyoming subbituminous coal, and 8 to 10 times more reactive than an Illinois bituminous coal. Several catalysts that substantially improved low-rank coal steam gasification rates included pure and mineral (trona and nahcolite) alkali carbonates. The reactivity observed when using trona and nahcolite to catalyze the steam gasification was the highest, at nearly 3.5 times that without catalysts. The use of these inexpensive, naturally-occurring alkalis as gasification catalysts may result in elimination of the need for catalyst recovery in the hydrogen-from-coal process, thereby simplifying operation and improving process economics. The study included evaluations of temperature and catalyst loading effects, coal and catalyst screening, and determinations of the apparent activation energies of the steam gasification reaction. 11 refs., 23 figs., 9 tabs. (ERA citation 11:047149)