MATHEMATICAL MODELING AND ALGORITHM OF TEMPERATURE CONTROL IN THE BIOGAS FUEL PROCESS
DOI:
https://doi.org/10.26577/EJE208830226Abstract
This article is a study on the identification of effective processing of organic waste from wastewater and the production of high–quality biogas fuel, through optimal mathematical modeling and expression of an algorithm for automatic control of temperature transitions between mesophilic (35-40 ° C) and thermophilic (50-55 °C), during anaerobic digestion (AC) from wastewater. with a productive volume of 10 m3/day in a small biogas plant with methane output. For anaerobic digestion, a substrate with a mixture of primary and secondary precipitation from a sewage treatment plant located for construction in the city of Kokshetau (Kazakhstan) with connection to the urban sewerage network is used. This substrate has cod values of 2500 - 3000 mg/l and contains organic substances of 60-80% of the dry matter. The kinetic model is constructed with the inclusion of four independent inhibitory functions, such as temperature (Mono-Arrhenius), pH, free ammonia (NH3) and volatile fatty acids (VFA). The control algorithm is implemented by five priority levels with a protective cooling period of 15 days, with a temperature change rate of 5 days. The results were verified according to 34 criteria with indicators of 100% compliance with (Verein Deutscher Ingen, 2016; IEA Bioenergy, 2023; Metcalf & Eddy, et al. 2014; Mao et. al. 2015). At this capacity, the biogas plant provided electrical power generation in the mesophilic mode of 1.5 – 2 kW and in the thermophilic mode it reached 2.4 kW with an increase of 33%. Precipitation of a substrate with a high content of protein nitrogen when working according to this algorithm ensures timely prevention of ammonia inhibition and thereby ensures uninterrupted and uniform operation of biogas plants with high-quality methane output.
Keywords: anaerobic digestion, sewage sludge, thermophilic regime, mesophilic regime, high-quality biogas, mathematical modeling, automatic control, volatile fatty acids, ammonia, biogas plant.
