The catalytic effects of single and mixed catalysts

i.e.

single 3%Ca and 5%Na-BL(black liquor) catalysts and mixed 3%Ca+5%Na-BL catalyst

on carbon conversion

gasification reaction rate constant and activation energy

relative amount of harmful pollutant like sulphur containing gases have been investigated by thermogra-vimetry in steam gasification under temperature 750℃ to 950℃ at ambient pressure for three high-metamorphous anthracites (Longyan

Fenghai and Youxia coals in Fujian Province). The mixed catalyst of 3%Ca+5%Na-BL increases greatly the carbon conversion and gasification rate constant by accelerating the gasification reaction C+H

2

O→CO+H

2

due to presence of alkali surface compounds [COM

]

[CO

2

M

]

and exchanged calcium phenolate and calcium carboxylate (COO)

2

. By adding CaCO

3

into BL catalyst in gasification

in addition to improving the catalyst function and enhancing the carbon conversion

the effective desulphurization is also achieved

but the better operating temperature should be below 900℃. The homogenous and shrinking core models can be successfully employed to correlate the relations between the conversion and the gasification time and to estimate the reaction rate constant. The reaction activation energy and pre-exponential factor are estimated and the activation energy for mixed catalyst is in a range of 98.72-166.92 kJ·mol

-1

much less than 177.50-196.46 kJ·mol

-1

for

non-catalytic steam gasification for three experimental coals.