Study on reaction characteristics of co-gasification of sludge and biomass

The gasification technology can convert biomass and municipal sludge into H2, CO, and CH4. It can meet the demands for municipal sludge and biomass reduction, harmlessness, and resource recovery. This paper studied the co-gasification reaction characteristics of biomass (chili pepper stalks and cigarette rods) and municipal sludge. The gasification reactivity, product composition, and distribution variation were investigated by changing the mixing ratio of biomass and sludge. The carbon conversion efficiency gradually improved with increasing biomass proportion, and the sludge–cigarette rods mixture reached a carbon conversion of 100%, confirming the prominent positive synergism that facilitated pyrolysis and gasification. At a biomass mixing ratio of 40%, the syngas (H₂ and CO) yield increased by 76.98 and 73.40% for sludge mixed with chili pepper stalks and tobacco stalks, respectively. Meanwhile, the calorific value of combustible gas was increased from 2048.53 to 3310.09 kcal/kg (CPS) and 3181.18 kcal/kg (CR). Sludge with a high ash content contains abundant alkali and alkaline earth metals (AAEMs), which can selectively catalyze the cracking and structural rearrangement of high-content biomass volatiles and drive the conversion of light volatile fractions into heavy tar components. The tar yield increased from 31.57 to 42.54% after cigarette rod incorporation, and more than 90% of the tar components were heavy fractions with boiling points above 230 °C.