Research On Corn Straw Pretreatment And Its Anaerobic Fermentation For Biogas Production

Anaerobic fermentation is an important way to utilize crop straw resources.With the development of renewable energy technology,biogas technology and engineering of crop straw have made great progress.Due to the dense structure of the wood fiber in the straw,it is not easy to be degraded.During the anaerobic fermentation process,to improve the gas production performance of the straw,it is necessary to pretreat the straw.In this research,the effects of three combined pretreatment methods of urea and pulverization,urea and hydrothermal,urea and ultrasonic on the gas production performance of straw anaerobic fermentation were studied,and the pretreatment conditions were optimized.The anaerobic fermentation parameter of pretreated corn straw was analyzed by kinetic study.The research provides a scientific reference for the promotion and application of straw biogas.In the combined pretreatment test of urea and pulverization,three-level factor of response surface optimization pretreatment was selected.The independent variables are pretreatment time(5 d,10 d,15 d),urea mass concentration(45 g/L,50 g/L,55 g/L),corn straw particle size(0.8 mm,3.3 mm,5.8 mm).The pre-treated corn straw accumulated biogas production was used as the response value,and then analysis the effects of different pretreatment conditions on biogas production from corn straw.The results show that urea and pulverization pretreatment can improve the biogas production performance of corn straw.The optimized pretreatment conditions are that pretreatment time is 10.82 d,urea concentration is 48.67 g/L,and corn straw particle size is less than 12 mesh.The cumulative biogas production in the verification test is 693.3 mL/g VS,which is close to the model's predicted value of 707.314 mL/g VS.The relative error is 1.98%,and the highest methane content in the verification test reached 73.11%.In the combined pretreatment test of urea and hydrothermal,the three factors of urea concentration,pretreatment temperature and pretreatment time were selected for corn straw pretreatment,and the model fitting and kinetics of biogas production by pretreatment of corn straw were studied.The effects of different pretreatment conditions on biogas production from corn straw were analyzed.The results show that the effect of pretreatment temperature on the biogas production of corn straw is higher than that of urea concentration and pretreatment time.Considering the pretreatment cost,the optimal combination of pretreatment conditions is that urea mass concentration is 44.05 g/L,pretreatment temperature is 40 °C and the pretreatment time is 29 h.The cumulative gas production of the test group 19 is the highest,reaching 527.31 mL/g VS,which is an increase of 195.6% compared with the anaerobic fermentation cumulative biogas production of the untreated corn straw in the control group of 178.37 mL/g VS.In the experimental study of urea and ultrasonic pre-combination treatment,the effects of combined pretreatment urea concentration,pretreatment temperature and pretreatment time on the biogas production of corn straw are analyzed by single factor experimental design.The results showed that with the increase of urea concentration and pretreatment time,and with the decrease of pretreatment temperature,the total biogas yield of pretreated corn straw increased.The anaerobic fermentation of pretreated corn straw is better than the other two combined pretreatments.When urea concentration is 50 g/L,pretreatment temperature is 50 °C,and pretreatment time is 80 min,the total gas production of corn straw anaerobic fermentation is the highest 5018.50 mL.In this paper,the optimal conditions of the above combined pretreatment were obtained and the biogas production characteristics of anaerobic fermentation of corn straw after pretreatment were explored,which provided a scientific reference for the pretreatment of straw.