Experimental Study On Microwave Pretreatment Of Biomass

It is clear that growing biomass is an excellent method by which atmosphericcarbon dioxide can be sequestered, minimizing the effect of greenhouse gases on theEarth’s atmosphere. It is a source of sustainable energy and has potential to play animportant role in the future around the world. But its relatively high moisture content,low calorific value and other shortcomings mean that it is less attractive as a fuel thancoal which have much higher energy densy. Microwave technology has been shownto be an energy-efficient method for chemical processing and has become widelyaccepted as a mild and controllable processing tool. Low temperature microwavepretreatment has rarely been reported and the objective of this research is to explorethe low temperature microwave pretreatment of cotton stalk and sawdust. Thefeasibility of biomass pretreatment by characterizing solid products for succeedingprocess to generate renewable fuels.Two processes were evaluated: drying and pyrolysis. In microwave drying,temperature is the most important factors affecting microwave drying characteristics,biomass is treated in the temperature range of80°C–140°C, the higher dryingtemperature, the faster the drying rate, and microwave drying can also enrichbiomass pore structure, effectively increase the specific surface area of the materials.In low temperature microwave-induced pyrolysis, biomass is treated with nitrogen,at150°C–400°C. This process happened with the release of CO, CO2, CH4non-condensable gas, and liquid product mainly contains the acid, alcohol, aldehydewhich are the products of hemicellulose decomposition. In addition, this processproduced a solid product with enhanced fuel value, which get the same value neededtemperature40℃lower than the conventional torrefaction. Low temperaturemicrowave-induced pretreatment of biomass could be a competitive technology toemploy the least energy and to retain the most bioenergy. Meanwhile, due to theshedding of oxygen containing functional groups and the escape of gas and liquidcontaining oxygen, the O/C ratios of solid product is very low. Integrated technology and economy of low temperature microwave-induced pyrolysis, this article gives asuggestion: low temperature microwave-induced pyrolysis conditions do not exceed250℃, about20min.It was studied that using thermogravimetric analyzer on biomass pyrolysischaracteristics before and after low temperature microwave-induced processing, Itwas found100℃microwave drying have little impact on pyrolysis characteristicsof cotton stalk. But rising temperatures can cause that thermal decompositionweightlessness is more obvious, and it is good for biomass pyrolysis of cellulose andhemicellulose, cotton stalk pyrolysis index is bigger and bigger. Maximum weightloss rate increases with the increase of microwave pyrolysis temperature first andthen decrease for the solid product of low temperature microwave-induced pyrolysis,when250℃is maximum.