Study On Combined Pretreatment Of Corn Stover By Microwave And Steam Explosion

Biomass energy is one of the widely concerned renewable energy sources. The key technologies of biomass energy utilization focus on the pretreatment stage. In this study, a new corn pretreatment system with advantages of microwave method, which is of high efficiency and removal some lignin, and steam explosion technology with good pretreatment effect was designed, manufactured and installed. By orthogonal experiments, contrasted and single-factor ones, the results of the corn stover pretreatment effect was developed.It was found that the pretreatment of the corn stover by microwave and steam explosion methods was feasible. The new experimental apparatus is of reliable safety, simple operation and non-pollution. The impact factors of corn stover pretreatment were in turn microwave radiation time, explosion pressure, radiation power, water content, corn stalk length and pressure holding time. And the more lignin and hemicellulose were removed in the new approach in the nature of the microwave and steam explosion pretreatment, which was compared with microwave pretreatment, hemicellulose decreased by 5% and lignin decreased by 2%, with steam explosion method, hemicellulose decreased by 3% and lignin decreased by 4%. However, the combined method could not reduce the relative crystallinity of the corn stover. Instead, the relative crystallinity increased, which was 9% higher than microwave method and 1% lower than steam explosion pretreatment.Explosion pressure had a great effect on the pretreatment results. The relative crystallinity of the corn stover increased gradually with explosion pressure. Magnifying crystallite size was conducive to the process of enzymatic reaction. Byproducts increased gradually with explosion pressure homodromously. When explosion pressure was lower than 2.0MPa, the byproducts generated less. When explosion pressure was higher than 2.0MPa, byproducts increased dramatically. The cellulose hydrolysis rate increased gradually with explosion pressure. When explosion pressure was 2.0MPa and 2.3MPa, the cellulose hydrolysis rate was 89% and 88%, respectively.From the point of the effect of byproducts and the cellulose hydrolysis rate, the optimal pretreatment conditions were cornstalk length 2~3cm, explosion pressure 2.0MPa, pressure holding time 15min, microwave power 470~500W, microwave irradiation time 3min and water content 20%. Under the operation conditions, the cellulose hydrolysis rate reached 89%, which was 24% higher than microwave pretreatment and 19% higher than steam explosion pretreatment.