Research On Influence Of Preheating Buffer Of Homogeneous Feedstocks On Gas Production Characteristic

China is a large agricultural country in the world with abundant agricultural resources and materials.It has always been a major concern of the people’s livelihood to ensure national food security.However,with the improvement of people’s living standards and the continuous expansion of the scale of farming in rural areas,the total amount of various kinds of wastes is constantly increasing.Anaerobic fermentation technology is an important way to solve the problems of rural garbage and livestock manure.At present,there are some problems in the pre-mixing stage of anaerobic fermentation,such as the blockage of the mixture transportation and the inconspicuous mixing effect,the slow heating rate of the mixture,the restriction of the methane yield and the long fermentation period.On the basis of the existing vertical premixing equipment,in view of the above existing problems,The main research contents,methods and results are as follows:（1）The relationship between the axial velocity of the mixture and the structural parameters of the vertical spiral stirring blade radius was derived by the kinematic and mechanical analysis of the mixture using cow dung and corn straw as the raw materials,determining the optimum range of mixed speed.Under the conditions of different mixing speeds and different mixing times,the determination of the optimal mixing uniformity was carried out.The results show that when the rotating speed is 85 r/min and the mixing time is 12 min,the mixing uniformity of the raw materials is the highest,that is,the mixing uniformity is 88.4%.When the mixing time is 10min and the rotating speed is 95 r/min,the mixing uniformity of the raw materials is the highest,that is 90.5%.The quadratic polynomial regression model shows that the first term of mixing speed and mixing time has significant effect on mixing uniformity（P<0.05）,however,the interaction terms of mixing speed and mixing time has no significant effect on mixing uniformity（P>0.05）.By using Design-Expert 8.0 software and repeated experiments,the mixing degree of raw materials is the best when the mixing speed is 87 r/min and the mixing time is 10 min,that is,the mixing uniformity reaches 85.4%.（2）The pre-fermentation buffer device was designed between the front-end premix equipment and the fermentation device of the terminal equipment,and the key parts of the pre-fermentation buffering device were designed and selected,including heat transfer analysis and design calculation of the preheating and buffering device,design and calculation of the heating ring,insulation material selection and solar panel selection and so on.Then the equipment is processed and trial-produced.（3）On the basis of the trial production of the above-mentioned equipment,the methane production performance of anaerobic wet fermentation of cow dung and corn straw was tested by preheating and buffering,when the temperature reached the target temperature of medium temperature anaerobic fermentation,the mixture was put into the fermentation device,and the anaerobic environment was used to produce methane by anaerobic fermentation.The results show that the preheating treatment can further degrade some insoluble organic matter into organic matter which can be utilized by Methanogens,and accelerate the hydrolysis process of anaerobic fermentation,thus shortening the whole fermentation cycle.Preheating treatment can increase methane production,and the cumulative methane production of preheating group is 1.18times that of non-preheating group.The preheating treatment can accelerate the gas production rate and improve the gas production efficiency.The methane production rate of the preheating group after 3 days is 29%higher than that of the non-preheating group.Gompertz equation can simulate the process of anaerobic digestion of cow manure and corn straw.The maximum methane production rate of preheating group is 3.75,which is 42.59%higher than that of non-preheating group（2.63）.（4）After verifying the feasibility analysis of preheating buffer,the experiment of methane production by anaerobic fermentation of mixed materials is carried out with different ratio as the experimental factor.The results show that when the VS mixing ratio of cow dung and corn straw is 2:1,the methane production performance is the best,and the treatment group C1 has the highest cumulative methane production of 1737 ml,compared with the VS mixing ratio of cow dung and corn stalk 1:1 and 1:2,the cumulative methane production increased by 34.52%and70.87%respectively.The maximum daily methane production rate is 11.32 m L·g^-1on the 5th day of the experiments,which is 33.33%higher than that of the treatment group and 1.51 times higher than that of the treatment group C3.When the VS mixing ratio of cow dung and corn straw is 2:1,there is little difference between the theoretical methane yield P and the experimental methane yield,the absolute percentage deviation is only 6.9%.In this paper,the research status of anaerobic fermentation pretreatment technology,premixing equipment and influencing factors at home and abroad are summarized,which provided a basic idea for this research.The dynamic analysis and experimental study of the mixture are carried out,the preheating and buffering methods are puting forward to study the preheating of the mixture,and the corresponding experimental results and conclusions are obtained,which can provide a reference for the follow-up research.