| The anaerobic fermentation of solar energy temperature control has a broad application prospect,and has become a hot research spot at home and abroad at present.The commonly used heating mode in biogas engineering is to allocate the heat sources such as biogas boiler,power generation waste heat,ground source heat pump and so on reasonably,to carry on the joint warming,which can save energy and environmental protection,but also reduce the waste of resources.However,at present,the research at home and abroad has been mainly focused on the process of solar temperature control and wet fermentation,and there is no research on the anaerobic dry fermentation process of solar temperature control.This subject takes the solar temperature-controlled dry and wet anaerobic fermentation system as the research object.The dry and wet fermentation solid mass fraction(TS)is 20%and 8%,respectively.The fermentation temperature is set to 37±1? in summer and 26 in winter When±1? and the inoculum ratio is 30%,batch test research was carried out under the actual working conditions in summer and winter respectively.The daily heating rate of dry and wet fermentation tanks,fermentation temperature fluctuation,fermentation tank heat loss,typical Changes in solar temperature control capability and daily gas production and other parameters under the weather.In order to ensure the smooth progress of the test,the system energy balance and solar collector area calculations were carried out in the early stage,and were verified during the test.The conclusions of the summer study are as follows:(1)During the startup phase,the daily heating rate of the wet fermentation tank is better than that of dry fermentation.The fluctuation rate of the temperature increase rate of wet fermentation on a rainy day is greater than that of dry fermentation because the TS value of wet fermentation is lower and the integrated heat transfer coefficient is higher than that of dry fermentation,so the heat dissipation of the fermentation tank is higher than that of dry fermentation.It can be seen from the fact that the temperature difference between the inlet and the outlet of the wet fermentation tank in the first 3 days is higher than that of dry fermentation.The heat transfer effect between the feed liquids of the wet fermentation tank on cloudy or rainy days is still better than that of dry fermentation.More heat,so the rate of temperature increase in wet fermentation is faster.(2)During the test period,the average ambient temperature varies from 15.2 to 27.5?.After the dry and wet fermentation enters the period of stable gas production,the solar collector can output high-temperature hot water of 59.1-94.4? to the outside of the system while maintaining the fermentor at a constant temperature of 37±1?.After the system has undergone frequent changes in weather conditions,the temperature of the fermentor can still be maintained at 37±1?.It can be seen that the all-glass evacuated tube solar collector can increase the temperature of the fermenter with an effective volume of 3 m3 The temperature control ability of the device is strong(3)During the start-up process,the temperature of the wet fermentation liquid and the heat dissipation loss of the fermentor have been higher than that of the dry fermentation.The heat dissipation loss of the wet fermentation tank is 0.084?0.556 kW·h,and the heat dissipation loss of the dry fermentation tank is 0.053?0.478 kW·h.The average heat loss is 16.3%?58.5%higher than dry fermentation.Compared with the heat dissipation loss of the fermenter in the warming stage,the heat dissipation loss of the fermenter during the stable operation period is slightly larger than that of the fermenter in the initial heating period During the fermentation cycle,the cumulative gas production of dry and wet fermentation is 51.38 and 40.3 m3,respectively,and the peak daily gas production of dry and wet fermentation is 2.20 and 1.90 m3.When the total amount of dry and wet fermentation materials is the same,the TS value of wet fermentation is lower,the dry matter content is less than that of dry fermentation,and the amount of organic matter that eventually enters the gas production stage is low,so the cycle of wet fermentation gas production is relatively short.The conclusions of the winter study are as follows:(4)The average ambient temperature during the temperature increase of the test was-9.2?-1.7?,and the lowest ambient temperature was-15.1?.On the second day of temperature increase,the daily heating rate of wet fermentation reached a maximum of 5.1?,and dry fermentation reached a maximum of 3.9? on the third day of temperature increase The wet fermentation ended at the 9th day and entered the stage of stable gas production.The dry fermentation lags behind the wet fermentation for 5 days.The reason why the wet fermentation ended earlier due to the lower TS value and the higher water content in the fermenter than the dry fermentation.When the fermentation raw materials,inoculation amount and insulation layer thickness are the same,the comprehensive heat transfer coefficient of the wet fermentation feed liquid is higher than that of dry fermentation Large,the heat transfer effect between the cow dung,inoculum,and water in the fermenter is better than that of dry fermentation,which makes the wet fermenter heat up faster.(5)During the test,the average ambient temperature is mainly concentrated at-5±1.5?,the minimum value of the solar hot water temperature for dry and wet fermentation is 27.7 and 29.9?,and the highest value is 72.5 and 73.4?,which ensures that the solar collector can continue to ferment.The tank provides heat.The solar temperature-controlled dry and wet fermentation system can achieve a constant temperature fermentation of 26±1? even in the winter and cold weather conditions.The system has strong anti-interference ability in bad weather(6)During system start-up,the heat loss of wet fermentation is 0.319?1.058 kW-h,the dry fermentation start time is slightly longer,and the heat loss is 0.288?1.112 kW-h;when both the dry and wet fermentation tanks are in the warming stage,the wet fermentation tank dissipates heat every day The amount is 10.8%to 13.4%higher than the dry fermentation tank.During the experiment,the first gas production peak of wet fermentation was 1.54 m3,and the first gas production peak of dry fermentation was 2.36 m3.The cumulative gas production of dry fermentation is 61.4 m3;the cumulative gas production of wet fermentation is 43.12 m3.Due to the low TS value and low dry matter content in wet fermentation,the gas production cycle is relatively shortThrough experimental research,it can be concluded that during the test,the solar-controlled dry-wet anaerobic fermentation system has a low TS value,a high water content,and a good internal heat transfer effect.The daily heating rate is better than that of dry fermentation,and the average daily heat loss is always higher than that of dry fermentation;when the system is running stably,the heat loss of the fermentation tank is slightly higher than the temperature increase process.When the system experiences continuous rainy/snowy days,the solar collector can still maintain the fermentor 37±1/26±1?constant temperature fermentation,and the gas production is good,indicating that the solar temperature-controlled anaerobic fermentation system is relatively stable and reliable Dry-wet fermentation due to different solid mass fractions,gas production time is also different,wet fermentation due to lower solid mass fraction,gas production time is shorter than dry fermentation. |
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