Study On Tabacco Stem Pyrolysis And Microwave Expansion

A lot of tobacco stems that are by-products from tobacco production are abandonded every year. It not only wastes available resources, but also causes environmental pollution. So it is significant to study industrial application of tobacco stems in terms of environmental protection and raising farmers'income.Tobacco stem prolysis characteristics were studied with thermal analysis instrument and pyrolysis kineticses were investigated based on thermal data. For secking suitable ways, tobacco stem prolysis and microwave expansion were studied experimentally, which provides some fundamental datas for industrial application of tobacco stems.The thermal analysis experiments were performed up to 700℃at heating rates of 5, 15, 25,and 35℃/min in a dynamic nitrogen flow of 60mL/min.According to TG and DTG, there were three weight loss stages in the pyrolysis process, and weight lost remarkly during 150~480℃. Pyrolysis activation energies at different particle sizes calculated by FWO and Popescu methods respectively were approximately identical, and activation energies increased as reaction conversion increased.Results of tobacco stem prolysis indicated that the optimum condition for maximum liquid yiely was particle diameter 18-40 mesh, prolysis temperature 500℃. And the maximum yield of liquid was 35%. MgO and attapulgite can increase liquid yield.The liquid yield was reduced with CaO. Dolomite had no influence on liquid yield. Gas products mainly consists of H2, CO, CH4, CO2 and liquid products mainly consisted of nicotine, acid, ketone, aldehyde and heterocyclic compounds et al,according to analysis by GC and GC-MS respectively.Results of tobacco stem microwave expansion indicated that water content had a considerable effect on expanding rate and the best water content was about 20%. The best time was about 80s. Besides, temperature changed remarkabely in the process and tobacco stems expanded remarkabely when temperature is between 85 and 95℃. It improved expanding rate and quality of expanded tobacco steams adding an appropriate amount of expanding agent and the optimum concentration of this expanding agent is 10%.