Study On Two-phase Anaerobic Fermentation Method With High Efficient Temperature Increase

Temperature is an important factor affecting the survival and metabolism of anaerobic fermentation microorganisms.In the cold regions of our country,the temperature and low temperature difference is large,and the long-term constant temperature fermentation of the system consumes too much energy and the economic benefit is low.How to achieve variable temperature control to reduce energy consumption becomes an urgent problem to be solved.In this experiment,cow dung was used as the fermentation substrate and activated sludge as the inoculum.The two-phase anaerobic fermentation experiment was carried out with different warming methods for the acid-producing phase and the constant temperature of the methanogenic phase to explore the best performance and the best economic benefits.The warming method.Then select different parameter conditions and analyze the influence of these factors on the performance of acid production and gas production in the fermentation process,and optimize the anaerobic fermentation process parameters under the optimal temperature increase condition.It provides some theoretical value and reference significance for improving the problems faced by biogas fermentation projects in cold regions.This article contains two phases of experimental research.Firstly,three different heating methods(5 ℃/2 d,2.5 ℃/d,4 ℃,9 ℃,2 ℃ every two days in order)are selected for the acid-producing phase.The warming method with the best performance for acid production and gas production;and a set of acid-producing phase constant temperature fermentation at 35 °C to compare energy consumption values,and then select the warming method with the best economic benefit;secondly,perform two warming methods under the best warming method.Phase anaerobic fermentation experiment,the total solids(TS)mass fraction(6%,8%,10%),the mass ratio of the methanogenic phase anaerobic sludge to the fermentation substrate dry matter(10%,20%,30%),Fermentation experiments of different factors with the ratio of cow manure and corn stalks(10:0,7:3,1:1,3:7),analyze the reasons and get the optimal fermentation conditions under the best warming method.conclusion as below:(1)The fermentation system of the acid-producing phase can achieve the best acid-producing effect under the conditions of 5 ℃/2 d of temperature increase,and the gas production rate and gas production of the methane-producing phase are also the best,with a cumulative gas production of 6720 m L;The difference between system energy consumption and production capacity is 632.75 k J,which is the smallest of the three groups and is much smaller than the constant temperature group.(2)Factor optimization and mechanism analysis: Under the conditions of5 ℃/2 d of temperature increase,the total solid mass fraction is 8%,the mass ratio of the anaerobic sludge of the methane-producing phase to the dry matter of the fermentation substrate is 30%,When the ratio of manure to corn stalks was 7:3,both the acid-producing phase and the methane-producing phase could reach their respective optimal conditions.The ratio of cow manure to corn stalks is 7:3 and 10:0.Compared with 10:0,there are more types of methanogens and higher density of methanogens;the dominant microbial flora of fermentation broth with different composition is also different,but they are all kinds of microorganisms.Work together to complete the anaerobic fermentation of the methane production phase.In summary,the best warming method is 5 ℃ /2 d.Under the best warming method,the total solid mass fraction is 8%,and the mass ratio of the anaerobic sludge of the methane-producing phase to the dry matter of the fermentation substrate is30.%.When the ratio of cow dung to corn stover is 7:3,the fermentation effect is excellent.