Decentralized drying-gasification scheme of sewage sludge with torrefied biomass as auxiliary feedstock

Abstract

A drying-autothermal gasification scheme with torrefied biomass as auxiliary feedstock was proposed for the first time in order to realize the decentralized treatment of sewage sludge in wastewater treatment plant. Thermodynamic equilibrium and energy flow balance for the proposed system were evaluated. A non-stoichiometric thermodynamic equilibrium model was applied to evaluate the effect of adding ratio of torrefied biomass on the autothermal gasification performance. A novel dual-check algorithm was developed to determine the molar numbers of syngas components and the injected air. The energy utilization ratio for the whole process was introduced to measure the ratio of the energy used in the whole system to the total input energy. High adding ratio of torrefied biomass was favor of lifting the cold gas efficiency, but it would lead to low energy utilization ratio in terms of sewage sludge treatment.