Influence of feedstock composition in fluidised bed co-gasification of mixtures of lignite, bituminous coal and sewage sludge

Energy recovery from sewage sludge can be achieved by several thermochemical processes, including its co-processing with other fuels. In this work, co-gasification of mixtures of sewage sludge with two types of coal (bituminous and lignite) was performed in a laboratory-scale fluidised bed reactor. The influence of the feedstock composition on key parameters of gasification—such as gas heating value and yield, cold gas efficiency and tar generation—was determined. Whereas some of these results can be explained as the sum of individual contributions of each feedstock component, some synergistic effects were also identified. Among these, the decrease of tar yield and the increase of H2 and CO in the gas suggest that co-gasification of sewage sludge with certain types of coal may be energetically advantageous and improve the process performance.

► Design of experiments to study effect of sewage/coal blends on co-gasification.
► Co-gasification produces synergistic effects on product composition (tar).
► Improved LHV and gas yields (d.a.f. + air) with addition of sewage sludge.