Research On Semi-dry Anaerobic Fermentation Process And Equipment Based On Fresh Cow Dung

With the rapid development of the livestock and poultry breeding industry in my country,the effective treatment and resource utilization of livestock and poultry manure has become an urgent problem to be solved at the moment,and anaerobic fermentation technology is one of the effective ways to realize the efficient use of livestock and poultry manure.Based on the basic properties of fresh cow dung(TS concentration 15%～20%),this subject has developed a semi-dry anaerobic fermentation process and equipment suitable for fresh cow dung.Through the research of fermentation temperature,inoculum ratio,stirring method and other fermentation processes,a suitable semi-dry anaerobic fermentation process is determined.Using the process conditions,the self-made star-shaped horizontal three-axis cyclone stirred reactor and the purchased CSTR type Reactor comparison test to determine a suitable semi-dry anaerobic reactor;through the optimization test of the stirring parameters,the stirring parameters are determined,and then the 300m~3 biogas engineering design is carried out on the star-shaped horizontal three-axis swirling vertical cylindrical reactor,and the main components are The force and the flow field of the material are simulated and analyzed,and the anaerobic fermentation operation test of the completed biogas project is carried out.The main research content and results are as follows:(1)The effect of fermentation temperature on the gas production performance of anaerobic fermentation of fresh cow dung showed that the cumulative gas production was 4994.6ml,10943.3ml,10619.0 ml,under the experimental conditions of 25℃,35℃and 55℃respectively.Based on energy-saving considerations,the semi-dry anaerobic fermentation temperature of fresh cow dung is 35℃.(2)The test of the influence of the proportion of inoculum on the gas production performance of anaerobic fermentation of fresh cow dung showed that the gas production rate of the five groups of the five experimental groups was 127.93ml/g TS,131.91ml/g TS,152.42ml/g TS,140.75ml/g TS and 139.69ml/g TS when the inoculation ratios were 10%,20%,30%,40%,and 50%.That is,the dry matter ratio of the inoculum the test group is 30%.The test group has the best gas production performance,so the proportion of inoculum for semi-dry anaerobic fermentation of fresh cow dung is 30%.(3)The effect of mixing method on the gas production performance of fresh cow dung anaerobic fermentation showed that the cumulative gas production of the non-stirring test group,the 10r/min intermittent agitation test group and the 10r/min continuous agitation test group were 6817.5ml,respectively,11048.4ml and 8996.1ml,so it is more appropriate to choose low-speed intermittent stirring in the semi-dry anaerobic fermentation of fresh cow dung.(4)The effect of different anaerobic fermentation reactors on the gas production performance of dry cow dung anaerobic fermentation showed that the cumulative gas production of the self-developed star-shaped horizontal three-axis swirling vertical cylindrical reactor can be increased by 13.05%compared with the CSTR reactor of the same volume,and the degradation rate of cow manure is also 10.42%higher than that of the CSTR reactor.Therefore,the self-developed star-shaped horizontal three-axis swirling flow stirring vertical cylindrical reactor can be selected for large-scale processing of fresh cow dung.(5)The optimization test of the stirring parameters of the star-shaped horizontal three-axis swirl stirring vertical cylindrical fermentation equipment shows that when the fixed stirring interval is 4h and the stirring time is 2min,the adjustment speed is 5r/min,10r/min,15r/min,the cumulative gas production is the highest when the stirring speed is 10r/min;the fixed stirring speed is 10r/min,the stirring time is 2min,and the stirring interval is set to 3h,4h,5h respectively,when the stirring interval is 4h,the cumulative gas production is the highest.Therefore,the stirring speed of 10r/min,the stirring interval of 4h,and the stirring time of 2min are suitable stirring parameters for the semi-dry anaerobic fermentation of fresh cow dung.(6)The design and force simulation analysis of a 300m~3 star-shaped horizontal three-axis swirling vertical cylindrical reactor:the structure and parameters of the reactor tank and stirring device are designed through calculation,and the Solid Works software is used to complete the three-dimensional construction.The simulation analysis of the force of the tank and the mixing device is carried out through the Solid Works Simulation software,which meets the design requirements.(7)Numerical simulation of the flow field of a 300m~3star-shaped horizontal three-axis swirling vertical cylindrical reactor:the designed 300m~3 star-shaped horizontal three-axis agitating vertical cylindrical tank is optimized for the stirring parameter conditions The fluid simulation analysis of the movement state of the material is carried out.Through the analysis of the velocity vector diagram and the turbulence trajectory diagram,the complete mixing of fresh cow dung can be realized at a speed of 10r/min.(8)Production and operation test of 300m~3 star-shaped horizontal three-axis swirling vertical cylindrical tank reactor:The test of heat insulation effect and gas production performance shows that the temperature increase effect can meet the design temperature,and The heat preservation effect is good;in the whole fermentation cycle,the cumulative gas production can reach 6443.86m~3,and the average volumetric gas production rate is1.07m~3/(m~3·d),which can realize the stable operation of semi-dry biogas project with high efficiency and low energy consumption.Have a good promotion value.