High quality syngas production from catalytic coal gasification using disposable Ca(OH)2 catalyst

This study works on the production of high H2/CO mole ratio and CH4-rich syngas suitable for methane synthesis from catalytic coal gasification using inexpensive and disposable Ca(OH)2 in a fluidized bed with a continuous coal feeding rate of 1.2 kg/h. Experiments conducted at atmospheric pressure demonstrated that carbon conversion and gas yield increased markedly after loading Ca(OH)2 into lignite, while CH4 yield was almost constant. Increasing excess oxygen ratio (ER), steam to carbon mole ratio (S/C) and catalytic gasification temperature could increase carbon conversion but went against CH4 production. At atmosphere pressure, CH4 was mainly derived from coal pyrolysis and raising carbon conversion thus led to the reduction of CH4 content in syngas. Elevating gasification pressure exhibited a significant effect in raising carbon conversion and encouraging CH4 formation. Increasing S/C and pressure as well as reducing ER and gasification temperature were beneficial to raise H2/CO mole ratio in syngas. At 1.5 MPa, under conditions of ER = 0.050, S/C = 1.00 and gasification temperature of 800 °C, catalytic coal gasification achieved good results with carbon conversion of about 70.0% and CH4 yield of 0.142 N m3/kg-coal. And its producer gas, with the best H2/CO mole ratio of about 3.0, was highly rich in CH4 with its content of 10.1 vol.% well matched in terms of SNG production.