Improved technology for obtaining biogas taking into account thermal and biotechnological stabilization in biogas installation reactors
DOI:
https://doi.org/10.31548/energiya2018.05.172Abstract
In any biotechnological process, biological agent - microorganisms, its nature and physiological and technological properties plays a major role. At the same time, the temperature of the fading mass is a very important factor in the effective process of fermentation.
The analysis of recent researches and publications has shown that one of the promising directions for increasing the efficiency of biogas plants operation is also the development of highly efficient technology, which provides for more intensive processing of different types of substrates in biogas plants.
The purpose of the study is to develop a highly efficient technology for obtaining maximum volumes of biogas by preparing input substrates with the optimal dosage of special impurities, as well as for balanced use of excess heat energy of the cogeneration unit in the summer.
One of the ways to improve the energy efficiency of the BSU's work is to reduce the cost of energy for ensuring its technological processes while increasing the amount of the initial product (biogas) that can be provided by optimal dosage and destructive (cavitation) treatment of various types of raw materials, optimal heating and mixing with the required loading intensity The substrate, which will ensure the efficient use of the entire volume of the BSU reservoir, excludes the formation of "dead" zones, the stratification of the sediment, from Taeda mineralized sediment and appearance peel and promote the equalization of temperature field and improves gas.
The process of intensifying the digestion is that the flow of different types of raw materials in the rotary-pulsating apparatus of the BSU is shredded to the required microscopic level and homogenized. In the course of processing, the bonds of long fibers (lignin, cellulose), which diminish in sizes up to 0,1 microns, are torn. Therefore, bacteria that are involved in the process of biogas production, it is easier to spread biogenic materials. As a result, methane content in biogas increases to 70-75%.
In the summer and autumn transition to the thermophilic fermentation regime, with the same volume of methane, the biogas output will increase by at least 1.5-2 times, which additionally leads to a decrease in the cost of 1 kW of installed capacity.
The energy used to heat the reactor for 12 hours, in all other equal conditions, during its operation in the thermophilic mode should be: in the winter period, 0.83 MW·h., In the summer - 0.52 MW·h.
It was established that an increase in the thickness of the thermal insulation layer by 50 mm helps to reduce heat loss through the surface of the reservoir by 15 ... 20 %, which in turn leads to a reduction in energy consumption, which, according to the mesophilic operating mode, is 3.6% or 21 kW·year/m³. The payback period of the event - less than 6 months.
The working time of the cogeneration unit, which should be (provided that the new portion of the biomass is warmed up) is calculated: for 1 hour - in the first and in the second variant - 0.8 hours; in 12 hours: 0.35 hours in the first version, and 0.22 hours in the second one.
It is shown that the nominal thermal power of the cogeneration unit is sufficient to cover the heat load and to transfer the operation of the reactors of the BSU from thermotolerant to the thermophilic regime even during the cold period of the year.
It has been found that energy expenditures on the intensification of anaerobic fermentation of biomass for the climatic conditions of the Kiev region can reach up to 250 kWh/year for 1 m³ of mesophilic regime and nearly 400 kWh/year for 1 m³ for the thermophilic regime of the BSU.
The application of highly efficient technology for biogas production on the basis of destructive (cavitation) treatment of various types of raw materials with the optimal dosage of special impurities does not allow the foam formation and floating crust in the upper part of the bioreactor and promotes more efficient use of the entire volume of the reactor BSU.
Keywords: biogas, substrate, methane tank, temperature conditions, energy-saving technology
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