Fluidized-bed co-gasification of residual biomass/poor coal blends for fuel gas production

Abstract

Experiments involving the co-gasification of residual biomass/poor coal blends and gasification of individual feedstocks used in the blends were performed in a bench scale, continuous fluidized-bed working at atmospheric pressure. Two types of blends were prepared, mixing pine chips (from Valcabadillo, Spain) with black coal, a low-grade coal from Escatrón, Spain, and Sabero coal, a refuse coal from Sabero, Spain, in the ratio range of 0/100–100/0. Experimental tests were carried out using as a gasification agent mixtures of air and steam with dew points of 74–85°C at gasification temperatures of 840–910°C and superficial fluidized gas velocities of 0.7–1.4 m/s. Feasibility studies were very positive, showing that blending effectively improved the performance of fluidized-bed co-gasification of the low-grade coal, and the possibility of converting the refuse coal to a low-Btu fuel gas. This study indicates that a blend ratio with no less than 20% pine chips for the low-grade coal and 40% pine chips for the refuse coal are the most appropriate. The dry product gas low heating value augments with increasing blend ratio from 3700 to 4560 kJ/N m 3 for pine chips/low-grade coal, and from 4000 to 4750 kJ/N m 3 for pine chips/refuse coal. Dry product gas yield rises with the increase of the blend ratio from 1.80 to 3.20 N m 3/kg (pine chips/low-grade coal), and from 0.75 to 1.75 N m 3/kg (pine chips/refuse coal), respectively. About 50% co-gasification process overall thermal efficiency can be achieved for the two types of blend.