Real-time performance investigation of a downdraft gasifier fueled by cotton stalks in a batch-mode operation

•Dynamic behavior of a downdraft gasifier.•Internal heating of air.•Real-time measurements of temperature and analysis of the produced gas.•Wider range of air flow rates.•Channeling problem. The gasification of agricultural biomass wastes is considered to be a promising technique for energy recovery from a renewable energy source. The dynamic behavior and performance of an Imbert downdraft gasifier integrated with internal heating of the gasifying agent is investigated. The gasifier is operated by a batch of cotton stalks as the feedstock and using air as the gasifying agent. The air flow rate was changed from 60 up to 200 l/min which is corresponding to equivalence ratio (ER) between 0.305 and 0.195. The real-time measurements of the temperature along the reactor and the analysis of the produced gas during the gasification process were used to study the behavior of the gasification system. The process was evaluated in terms of the lower heating value (LHV), gasification efficiency, carbon conversion efficiency, and the gas yield. The obtained results showed that the gasifier achieved high energy conversion efficiency of cotton stalks compared to the results reported in the literature. An optimum average LHV, gas yield, and cold gas efficiency of 4.61 MJ/m3, 1.94 m3/kg, and 57.4%, respectively, were obtained at ER of 0.235. Besides, the detailed study of the actions inside the gasifier showed the interaction between the different gasification zones and shed the light on the channeling problem of the Imbert gasifier.