Pilot-scale study on downdraft gasification of municipal solid waste with mass and energy balance analysis

Abstract

The current study investigated the gasification of heterogeneous feedstock with municipal solid waste fed into a downdraft gasifier. The air from the blower for the combustion zone entered the hearth through the six nozzles. The whole combustion zone was supplied with air at a rate of 150 kg/h, based on an equivalence ratio of 0.3 to 0.5. The proposed gasifier was designed with a capacity of around 100 kg/h, and could be operated at 0.035 bar atmospheric pressure to generate product gas. The experimental findings were effectively described by a theoretical mass and energy balance. Air flow rates of 140 to 150 kg/h were used to produce good product gas quality. For 8 h, each test was run in continuous operation and steady condition. The maximum gas of 250 kg/h was generated with an equivalence ratio of 0.35 and an energy content value of 1380 kcal/Nm3. Cold gas efficiency was found to be 89.31% at an optimum equivalence ratio of 0.35. With more efficient hot gas generation from the gasifier, the cost of thermal energy using the factory's energy consumption could be significantly reduced. Although a traditional downdraft gasifier has a throat at the bottom, the adopted design had no throat and the gasification agent was supplied on the reactor downside. The heat and mass balance discrepancy of 2% between energy intake and output was minimal and could be explained by several factors not considered in the balance, such as heat loss to the environment, less tar, and unburned carbon in the ash.