Optimization of the technological process of the farm biogas plant

Biomass is considered to be one of the most promising alternative sources of energy today. One of the most effective methods of purification and processing any livestock is methane fermentation with the production of biogas. At the same time, the issue of environmental protection is being resolved. Biogas technology makes it possible to obtain natural biofertilizer with the help of anaerobic fermentation, which contains biologically active substances with trace elements, using accelerated methods. The issue of using methane fermentation is relevant. Therefore, the purpose of the research is to determine the optimal duration of manure fermentation in the bioreactor of the farm installation. For the study, a farm-type biogas plant with a total reactor volume of 51,3 m3 was used, where the volume of liquid manure in the reactor was 40,8 m3 . The study of the bioreactor operation process was carried out in 4 operating modes: I - operating mode: - loading dose – 2,5 m3 /day, - duration of fermentation - 16 days; II - mode of operation: - loading dose - 4 m3 / day, - duration of fermentation - 10 days; III - mode of operation: - loading dose – 5,5 m3 /day, - duration of fermentation - 7 days; VI - mode of operation: - loading dose - 7 m3 /day, - duration of fermentation - 6 days. For all operating modes: - fermentation temperature - 32 o C; -- excess pressure of biogas in the reactor – 0,005 MPa; - loading frequency – 1 time/day. According to the results of the research, the following indicators of the quality of the technological process for 4 operating modes were obtained: I - mode of operation: biogas output – 16 m3 /day, maximum possible biogas output (theoretical) – 20,4 m3 /day, specific biogas output per unit volume of the loaded mass – 6,4 m3 /m3 ; II - operating mode: biogas output – 28,5 m3 /day, maximum possible biogas output (theoretical) – 36,7 m3 /day, specific biogas output per unit volume of loaded mass – 7,1 m3 /m3 ; III - operating mode: biogas output – 34,5 m3 /day, maximum possible biogas output (theoretical) – 42,3 m3 /day, specific biogas output per unit volume of loaded mass – 6,3 m3 /m3 ; VI - operating mode: biogas output – 35,5 m3 /day, maximum possible biogas output (theoretical) – 44,5 m3 /day, specific biogas output per unit volume of loaded mass – 5,1 m3 /m3 . The dependence of biogas output on the dose of dry organic substance (DOS) loading of the bioreactor was determined: I mode of operation: daily loading dose – 1,75 kg of DOS /m3 reactor, - actual biogas output – 0,22 m3/kg SOF, - maximum possible biogas output (theoretical) – 0,28 m3 /kg DOS; II - mode of operation: daily loading dose – 3.19 kg of DOS /m3 reactor, - actual biogas output – 0.21 m3/kg DOS, - maximum possible biogas output (theoretical) – 0,27 m3 /kg DOS; ІІІ - operating mode: daily loading dose – 4,18 kg DOS /m3 reactor, - actual biogas output – 0.19 m3 /kg DOS, - maximum possible biogas output (theoretical) – 0.23 m3 /kg DOS; ; VI - mode of operation: daily loading dose – 5.95 kg DOS /m3 reactor, - actual biogas output – 0.15 m3 /kg DOS, - maximum possible biogas output (theoretical) – 0.19 m3 /kg DOS. The obtained data on the daily output of biogas at the four studied loading modes indicate that with the given characteristics of the manure loaded into the reactor, more efficient operation of the installation is ensured at daily loading doses of 10-13% of the volume of raw materials in the bioreactor, that is, at the daily loading of the reactor 4.0-5.5 m3 of manure with a fermentation duration of 10-7 days. In practice, the duration of fermentation is chosen depending on the temperature: at 25-40 o C (32 o C) in the following intervals from 10 to 20 days. The results of the study make it possible to recommend that at a temperature of 32 °C, the duration of fermentation should be reduced from 10 to 20 days to 7-10 days, which increases the productivity of the biogas plant by the mass of fermented manure. Key words: biogas plant, bioreactor, biogas, biofertilisers, farm waste, biomass, methane fermentation.