Exergy Analysis On The Process Of Enhancing The Anaerobic Fermentation Of Corn Straw Pretreated By Mixed Microbes

The energy utilization of agricultural wastes such as straws can reduce environmental pollution and reduce the waste of resources.Microbial pretreatment can reduce the high degree of incorporation of cellulose,lignin,and hemicellulose in the straw,facilitate the hydrolysis process of anaerobic fermentation,and increase the rate of methane production.In the process of converting lignocellulose to biomethane,the pretreatment process used to destroy the solid structure of lignocellulosic raw materials requires energy and chemicals.The choice of optimal pretreatment conditions cannot be determined by the number of products alone,but also depends on the process.The thermodynamic properties.In this paper,the exergy balance model of compound bacteria pretreatment and anaerobic fermentation process is established through exergy-based thermodynamic analysis method,and the exergy efficiency of compound bacteria pretreatment combined with anaerobic fermentation is optimized through genetic algorithm,and the pretreatment based on exergy efficiency is obtained.The matching conditions of pretreatment and anaerobic fermentation process.The main results of the research are as follows.Firstly,the lignocellulosic and temperature changes of corn stalks pretreated by compound bacteria under different straw particle size,ventilation,and pretreatment temperature were explored.The results show that:after 360 hours of pretreatment,when the straw crushed particle size is 20-40 mesh,the pretreatment ventilation rate is 2.5 L/min,and the pretreatment temperature is 35?,the corresponding corn stalk has the lowest lignocellulosic content,and the degradation effect is maximized.Good;the heat production in the pretreatment process of the compound bacteria is different under different treatment conditions,and the pretreatment time corresponding to the maximum material temperature is between 144h and 216h.Secondly,combining the pretreatment with composite bacteria and the results of the anaerobic fermentation test,the calculation results of the exergy efficiency show that the three treatment conditions affect the pretreatment exergy efficiency as follows:ventilation>pretreatment temperature>crushed particle size.In the pretreatment time of 144h?216h,the material has higher heat exergy,and the suitable range of corresponding pretreatment conditions are:particle size(10?60 mesh),ventilation(0?1.5 L/min),pretreatment The suitable range of temperature(30?35?)and pretreatment time is(144h?216h).By calculating the effects of different stirring rates and fermentation temperature after pretreatment on the methane production rate and exergy efficiency of anaerobic fermentation,the appropriate range of anaerobic fermentation processing conditions is determined as follows:stirring rate(40-50 r/min),fermentation temperature(30?40?);Finally,based on the genetic algorithm to solve the multi-factor influence of the pretreatment combined anaerobic fermentation exergy efficiency results show that the optimal value of the exergy efficiency of the overall process is between 18-20%.At the pretreatment temperature of 33?,straw particle size 0.50 mm,ventilation rate of 0.8 L/min,the temperature of the anaerobic fermentation process is 38?,the stirring rate is 48 r/min,the degradation degree of wood fiber after 170h pretreatment is:fiber The nutrient content is 23.52%,the hemicellulose content is 21.36%,the lignin content is 12.28%,the methane production rate is 121 mL/g,the total exergy efficiency is 19.25%,and the relative error compared with the optimized value is 3.27%.