2004 Volume 83 Issue 11 Pages 932-938
This study was made to obtain basic knowledge of conversion biobriquettes composed of low rank coals contiaining large amount of ash and sulphur and biomass like agricultural and forest waste into clean gaseous fuels. Three Chinese bituminous coals and three kinds of biomass were heat-treated at 1173K in nitrogen after into biobriqettes. Each biobrigette char obtained was subsequently gasified with steam at 1073-1273K and 0.12-0.68MPa partial pressures of H2O to measure the reactivity. For comparision, steam gasification of the corresponding coal char was conducted under the same conditions.
It was found that coal chars had low reactivities, while gasification rate of biobriquette chars with and without Ca (OH) 2 acting as desulphurization agent were greatly enhanced to the same level of that for a subbituminous coal. The enhancement of the rate for biobriquette chars without calcium can be explained by such a situation that the portion of biomass would be preferentially gasified, thereby the contact area between unreacted coal char and steam could be increased, in addition of the catalytic effect of biomass ash. For the composition of gases evoluved, it depended on the ratio of coal/biomass in weight, gasification temperature, and the partial pressure of steam, indicated the control of the ratio of H2/CO by selecting these operating factors.
