Hydrothermal Treatment Technology Of Cassava Residue Based On Cellulosic Ethanol Production

Cassava is an economically feasible and the most widely used raw material for the production of non-grain fuel ethanol, however, in the whole process when obtaining 1 ton of fuel ethanol, about 400 kg of cassava residue is produced. Cassava residue is the solid waste during the process of fuel ethanol production, which primarily contains cellulose(20 wt%), hemicellulose(5 wt%) and lignin(18 wt%). Currently, cassava residue is used to produce biogas by bio-fermentation, but cellulose and hemicellulose components can not be fully used. Generally, anaerobic residue is used as fertilizer or burned after drying, which is a great loss of resource. Making high value-added use of cassava residue gains significant concerns in the cassava fuel ethanol industrial production. In this paper, cassava residue was treated by hydrothermal reaction. Combined with the development of the common metabolic technology of pentose and hexose, utilization program of cellulose and hemicelluloses in the form of sugar was put forward and the quality of the residual lignin was improved. Thus the full utilization of raw cassava materials efficiently based on fuel ethanol production was realized.Firstly, full components analysis of cassava alcohol residue and cassava anaerobic residue was performed, and the fermentability of raw materials was also analysed by SEM and XRD. The results showed that the crystallinity of cassava alcohol residue, and cassava anaerobic residue were 28.3 and 18.9, respectively. Compared with the crysallinity of corn stover, it turned out that the cassava residue possessed a loose structure, and the cellulose had a lower crystallinity index, which was easier to ferment.The research of hydrothermal reaction technology was based on the two kinds of raw materials: cassava alcohol residue and cassava anaerobic residue. The effects of reaction temperature, reaction time, and the ratio of solid and liquid on the yield of xylose and glucose, and the production of acetic acid, furfural, and HMF were systematically and comprehensively analyzed in the hydrothermal reaction process. Then, the optimal hydrothermal process conditions based on the yield of xylose and enzymatic digestibility were both analysed.The suitable hydrothermal reaction condition areas of two kinds of raw materials were determined based on the study of hydrothermal treatment technology. The production of ethanol produced by fermentation of xylose and glucose was taken into consideration as the optimal target, the multifactor experiments for the treatment technology of cassava residue and anaerobic residue were designed and conducted by the response surface method, and the Box-Behnken design model was selected on the key factors influencing the production of ethanol best level research. Finally, the optimal conditions of the hydrothermal treatment of two kinds of cassava residue were obtained, the deviation between the optimal value and the experimental value was less than 3%. Therefore, the optimal method is reliable and feasible. The hydrothermal reaction treatment conditions of two kinds of cassava residue were optimized in this thesis. The specific optimization results are as follows:The optimized conditions of cassava alcohol residue: reaction temperature is 193 ?, the ratio of solid and liquid is 0.115, reaction time is 51 min, the production of ethanol would reach 70.6 mg/g. The relationship between the three factors and the production of ethanol is nonlinear. The degree of influence is as follows: reaction temperature> reaction time> solid-liquid ratio.The optimized conditions of cassava anaerobic residue: reaction temperature is 163 ?, the ratio of solid and liquid is 0.095, reaction time is 59 min, the production of ethanol would reach 19.5 mg/g. The relationship between the three factors and the production of ethanol is also nonlinear. The degree of influence is as follows: reaction temperature> reaction time> solid-liquid ratio.