Catalytic Activity of the Black Liquor and Calcium Mixture in CO2 Gasification of Fujian Anthracite*

CO2 gasification of Fuijian high-metamorphous anthracite with black liquor (BL) and/or mixture of BL and calcium stuff (BL+Ca) as catalyst was studied by using a thermogravimetry under 750–950°C at ambient pressure. When the coal was impregnated with an appropriate quantity of Ca and BL mixture, the catalytic activity of CO2 gasification was enhanced obviously. With a loading of 8% Na-BL+2%Ca, the carbon conversion of three coal samples tested reaches up to 92.9%–99.3% at 950°C within 30min. The continuous formation of alkali surface compounds such as ([-COM], [-CO2M]) and the presence of exchanged Ca, such as calcium phenolate and calcium carboxylates (COO)2Ca, contribute to the increase in catalytic efficiency, and using BL+Ca is more efficient than that adding BL only. The homogeneous model and shrinking-core model were applied to correlate the data of conversion with time and to estimate the reaction rate constants under different temperature. The corresponding reaction activation energy (Ea) and pre-exponential factor of three anthracites were estimated. It is found that Ea is in the range from 73.6 to 121.4kJ · mol−1 in the case of BL+Ca, and 74.3 to 104.2kJ · mol−1 when only BL was used as the catalyst, both of which are much less than that from 143.5 to 181.4kJ · mol−1 if no catalyst used. It is clearly demonstrated that both of BL+Ca mixture and BL could be the source of cheap and effective catalyst for coal gasification.