Experimental investigation of energy consumption for the process of initial heating of a substrate for the use of electric heat-mechanical system
Authors: Zablodskiy Nikolay , Spodoba Mykhailo , Spodoba Alexander 
Published: May 2022

Purpose. Experimental determination of energy consumption for the process of initial heating of the substrate to the temperature of anaerobic digestion in a biogas reactor using an electrothermal-mechanical system with automatic control to assess the energy efficiency of the process of heating the substrate and the profitability of further processing of the resulting biogas into thermal and electrical energy.

Methodology. Experimental studies of the dynamics of temperature changes in an heating cable placed in an electrothermal-mechanical system, determining the duration of the process and the energy consumed by the initial heating of the substrate, processing and analysis of the obtained data arrays, summarizing the results obtained.

Findings. Biogas technologies play an important role in the formation of a modern energy system, the profitability of which directly depends on the energy efficiency of anaerobic digestion intensification. The process of digestion of waste is long, so one of the main methods of intensification of biogas production is the mixing of waste in the process of anaerobic fermentation. There is a need to improve the energy efficiency of anaerobic digestion intensification and the profitability processing of biogas into heat and electricity. Ways to improve energy efficiency mainly consist in reducing the time of heating the substrate in a biogas reactor, reducing the consumption of electrical energy for the process of thermal stabilization of anaerobic digestion, structural combination of energy-efficient systems for mixing and heating raw materials in reactors, and introducing automatic production systems. The implementation of these actions will make it possible to establish the optimal geometric dimensions of an electrothermal-mechanical system with automatic control for mixing and heating the substrate in a biogas reactor and significantly increase the energy efficiency of biogas plants and the subsequent processing of the resulting biogas into thermal and electrical energy.

Originality. As a result of the experimental study and analysis of the data obtained, it was found that with the same power of the heating sections, the change in the temperature of the electric cable in each blade does not occur in the same way. The authors found that the average value of the temperature of the sections of the electric heating cable of the lower blades is 12.9% higher compared to the upper blades of the electrothermal-mechanical system. In the course of experimental studies, the authors found that when using a heating system made of an electric heating cable mounted in the blades of a two-tier paddle mixer, it consumes J, on the process of initial heating of the substrate from  before °С in a biogas reactor with a volume of 40 liters. The duration of the heating itself is 300 minutes. In the course of experimental studies, the authors established the energy efficiency from dividing the electrothermal-mechanical system into heating sections, when each blade is a separate section with its own automatic temperature control of the electric heating cable mounted in the corresponding section, while the consumption of electrical energy is reduced by 27.9%.

Practical value. The results obtained can be used in the design, construction and modernization of biogas production intensification systems, namely, mixing and heating of the substrate in biogas plants. This will improve the energy efficiency of the biogas formation process and the profitability of its processing into heat and electricity.