Study On Reflowed Aqua Ammonia Explosion Pretreatment For Corn Stover

Under the energy and environment pressure, people begin to find alternatives to fossil fuels. Biomass energy is preferred due to its widespread and low-carbon availability, but it is of high cost and immature technology. As a key technology for biomass energy conversion, Pretreatment is payed much more attention. In this paper, a set of reflowed aqua ammonia explosion pretreatment (RAAEP) equipment was developed based on the ammonia pretreatment principle. The related factors, such as temperature, pretreatment time, moisture of corn stover and the ammonia flow rate which impacted pretreatment effect were studied by the orthogonal experiments plan.The experimental results showed that RAAEP for corn stover which length is about 2-3cm was highly effective to separating cellulose and hemicellulose from lignin. And the enzyme contact area with cellulose and hemicellulose was increased.The reaction temperature was the first key factor of the corn stover pretreatment. The cellulose content was increased by 17.13% and lignin content was decreased by 17.73% when the reaction temperature varying from 60℃to 90℃. The X-ray diffraction data confirmed that the crystallinity degree of the corn epidermis dropped from 0.5674 to 0.5611 and that of the corn cob rised from 0.4268 to 0.5435 at the pretreatment temperature 90℃because of the removal of the amorphous portion of biomass. The glucan and xylan enzymatic digestibility was 75.2% and 90.0% respectively at the temperature point.The effect of pretreatment are unconspicuous for the short pretreatment time, but the glucan digestibility reduced for too long treatment time. With the treatment time prolonged from 9 min to 12 min, the glucan digestibility and xylan digestibility decreased by 15.4% and 4.61% respectively. And the optimal treatment time was 9min in this study.The initial moisture content of the corn stover caused an obvious variety of the hemicellulose content. With the increase of moisture content in stover, the hemicellulose content was increased, but the xylan enzymatic digestibility was reduced by 12.67% when the moisture of corn stover rised from 80% to 120%. Aqueous ammonia flow rate was positive to delignification of the cornstover. With the aqueous ammonia flow rate increased from 1.5 L/min to 4.5L/min, the lignin content decreased from 14.02% to 13.30% correspondingly. When the aqueous ammonia flow rate was 0, 1.5, 3 and 4.5L/min, the cellulose content was 42.26%,45.14%,42.14% and 44.36% respectively, which was disorderly. However, the maximum of the glucan digestibility was 76.8% for the null flow rate of aqueous ammonia.Considering synthetically the cellulose content and the glucan conversion, the optimized reflowed aqua ammonia explosion pretreatment condition was achieved, which is the cornstover moisture content 80%, reaction temperature 90℃, residence time 9 min and aqueous ammonia flow rate 1.5L/min.Under the operation condition, the cellulose content of pretreated corn stover was 50.45% and the glucan enzymatic digesbility was 75.61%.