Kremneva K. Increasing effectiveness of two-stage processof highly-dispersedbiomass gasification for low capacitycogeneration plants

The dissertation investigates the two-stage highly-dispersed biomass gasifications process for low capacity cogeneration plants based on internal combustion engines. The new technology of obtaining gas with low tar has been developed. The possibility of reducing consumption of fossil fuels, including natural gas, is demonstrated. On the basis of experimental studies, it was found that stable process of oxidative pyrolysis of biomass in a dense bed in filtration incineration mode with the front up 800oС provided specific air flow in the amount 25,0...55,0 m3/(m2h). It was experimentally established that the speed of the inverse heat wave in oxidative pyrolysis of highly-dispersed biomass in the dense bed is determined by the thickness of a biomass particle and constitutes: 11,4...18,2 cm/h for walnut shells; 45,0...90,0 cm/h for sunflower husk. Mathematical model for oxidative pyrolysis of highly-dispersed biomass in the dense bed has been improved. Additionally, the research took into account the empirical values of the movement rate of the reverse thermal wave, the coke volume change regarding the initial biomass and the temperature of the front incineration, which allowed for the first time to get the relationship for tar in pyrolysis gas and the time of its contact with coke residue at 500…670oC. It was determined that the process of resin decomposition is completed in the contact time of 1,5...3,1 sec. On the basis of theoretical and experimental studies, it was found that the amount of heat required to start the process of oxidative pyrolysis of highly-dispersed biomass in a dense bed in the filtration incineration mode is 2,60...3,46 MJ per kg of feedstock. Technological schemes for cogeneration plants based on a two-stage process of biomass gasification were developed on the basis of gas ICE with air or air-steam gasification of coke and effective modes of their work have been proposed. The effectiveness of the schemes is confirmed by the results of the exergy and technical-economic analysis.