Experimental Study On The Process Of Dry Anaerobic Digester Heated By Solar Energy

The large number of agricultural waste and livestock manure in China is beyond the removal ability of land,it will not only pollute the environment but also cause loss large amounts of energy.The anaerobic fermentation in the treatment of organic waste under certain conditions can be transformed into efficient green manure and produce a large amount of methane.At present,the anaerobic fermentation is divided into wet and dry fermentation,the technology of dry fermentation can not only solve low the utilization rate of organic waste and the pollution of fermentation residue,it has good adaptability for raw materials,easy processing load,consuming less water and leftovers is not bad for environment.But the dry fermentation has acidifying problem because of mass and heat transfer is difficult,so this paper studied the influenc ing factors of fermentation and fermentation device to solve the problem of dry heat and mass transfer,and realized the maximal capacity of fermentation process for the same system.The combination of fermentation and solar energy to solve the prolem that single renewable energy can be affected by climate and other natural conditions to achieve normal operation all year.In this paper cow dung and straw are as raw materials,the effects of temperature and inoculation amount for gas production were investig ated by static fermentation（without stirring）,and the optimal group was found.The new fermentation equipment was designed to operate with the fermentation conditions（with stirring）,and the external mixing device was designed to design a solar mixed dr y fermentation system.The main research results are as follows:Under static fermentation conditions,Total Solid is 15% and 20%,the experiments with the inoculation amount of 20% to 40% can successfully start.Compared with the fermentation under the th ermophilic temperature（37 ℃）,the experiments was active at mesophilic temperature（52 ℃）and have strong decomposition force on the fermentation substrate.The production rate of biogas is fast but the daily biogas production is unstable.When Total Solid is 15%,the inoculation amount is 40% at 37 ℃.TS and VS removal rate are 23.9% and 21.5%,and the inoculation amount is 40% under the condition of 52℃,the speed of peak is fast and the peak value is high.The average methane content is 31.9.05 L·kg^-1TS.With the increasing in the amount of inoculation,the rate of fermentation is increasing and the total gas production is increasing.TS gas production rate reaches 365.15 L·kg^-1TS,while the average methane production reaches 54.5%,The removal rates of TS and VS are 25.1% and 22.9%.When Total Solid is 20%,with 37℃ under this conditions of each experimental group can be successfully started,inoculation of 40% of the experimental group in the starting speed and gas production is better than other groups a nd gas production rate is 157 L·kg^-1TS,The average of methane content is 52.3%,the removal rates of TS and VS are 17.3% and 15.8% respectively.At 52 ℃,the all experiments can start smoothly.The optimal experiments that the inoculation amount is 40% TS h as 286.6 L Kg^-1TS for the rate of gas production,the average methane content reaches 52.6%,removal rates of TS and VS are 27.6% and 31.5%,respectively.The optimum conditions of static gas production are applied to the dynamic fermentation process.The operating condition is 37℃ and the amount of 18 Lwith inoculation ratio of 40%,the experiment can start successfully.A total biogas production is 648.53 L of gas.The total biogas production reaches from the first day to the 43 rd day 93.8% of the total biogas production.The biogas production is 11.18 L in every day.For the total methane content the number of days that the whole fermentation process is more than 50% is 26 days,accounting for 44.83% of the total fermentation days.The total methane producti on is 342.2L,the daily methane production is 5.9L,ratio of methane is 52.77%.The biogas production rate for cosuming 1kg total solid is 1.5 times for static fermentation experiment under the same conditions.The external mixing device is combined with t he solar energy to experiment.The supply of heat and the material of dry fermentation need heat for the temperature are matched to the enough of solar collectors.The device is designed to handle 15 t of organic waste at a 600 cm,a height of 260 cm and a wi dth of 240 cm device.External use15 cm insulation layer and with 16 sets of 40 tube solar collectors for heating,in the external temperature of-7℃ under the conditions the temperature of fermentation can be maintained at 37℃.The innovation of subject lies in:（1）In this paper,cow dung and straw is more common for the agricultural waste,is used as raw material to study the performance of biogas production under different conditions of high total solid,temperature and inoculation amount,which provides the basis for further improving the yield of dry fermentation.（2）Design the dry fermentation reactor with external stirrer to solve the problem of heat and mass transfer of dry fermentation at the same time to ensure the system is easy operation.And the dry fermentation reactor combines with solar collector to achieve thermostatic fermentation.