Synergetic effect during co-pyrolysis/gasification of biomass and sub-bituminous coal

In this work, the co-pyrolysis of Indonesian coal (sub-bituminous) and two types of biomass, rice straw and Leucaena leucocepha wood, was studied using a drop tube fixed-bed reactor. The gasification reactivity of the obtained co-pyrolyzed char with steam was examined using a rapid heating thermobalance reactor. In the co-pyrolysis, a synergetic effect, in terms of higher gas yield and lower tar and char yields, was manifested especially at a biomass and coal ratio of 1:1. This synergetic effect could be explained by the transferring of active OH and H radicals from the biomass to the coal as well as the catalytic role of potassium (K) from the biomass. In the steam gasification, the in situ pyrolyzed char from the coal/biomass blend exhibited a higher reactivity than that from the coal or the biomass. This could be related to the increased surface area and pore volume of chars from the blend as well as the influence of volatile K released from the biomass. In addition, the biomass type appeared to have a significant influence not only on the magnitude of the synergetic effect during the co-pyrolysis but also on the reactivity of the resultant chars.