Investigation of Coal-Gasification Catalysis Reaction Mechanisms. Quarterly Technical Progress Report, October-December 1981

摘要

This report presents gasification rate data obtained with CO sub 2 and steam gasification of char prepared from Illinois No. 6 coal. Catalysts included alkali metal carbonates, alkali metal chlorides, and CaO. KNCO and K sub 2 SO sub 4 were also included among the catalysts because partial conversion of K sub 2 CO sub 3 to these salts has been observed in partially gasified chars. Except for tests involving the effect of variations in K sub 2 CO sub 3 loading and the use of CaO, all catalysts were employed in amounts to yield the same atomic metal cation to carbon ratio (M/C = 0.04). The same order of activity among the alkali metal carbonates, Cs exp + > K exp + > Na exp + > Li exp + , was found for both CO sub 2 and steam gasification. CaO is a less effective catalyst than K sub 2 CO sub 3 . Reactivity of CaO-catalyzed chars decreases with increasing pressure of CO sub 2 or steam, while the opposite is true when alkali metal carbonates are used. K sub 2 SO sub 4 and KNCO display less activity than K sub 2 CO sub 3 in CO sub 2 gasification. The alkali metal chlorides are much less effective catalysts than the alkali metal carbonates in both steam and CO sub 2 gasification. Tests with mixtures of catalyzed and noncatalyzed chars have shown that the K sub 2 CO sub 3 catalyst is mobile during steam and CO sub 2 gasification, while CaO shows no evidence of mobility. Product gas compositions from steam gasification have been interpreted by the calculation of pseudoequilibrium constants for major gasification reactions. These constants are compared with thermodynamic values. The results indicate that the gas reactions occur mainly within the char particles with lesser degrees of reaction as the gases traverse the hot retort after leaving the char sample zone. Different reaction mechanisms for CH sub 4 formation are indicated for catalyzed and noncatalyzed chars. (ERA citation 07:049009)