Pretreatment of anaerobic fermentation feedstock in a vortex layer apparatus: Effect of the working chamber ferromagnetic core on biogas production

Abstract

Currently, the volume of waste generation is growing at a high rate. Anaerobic digestion is an effective way to process organic waste to produce biogas. To increase the bioavailability and efficiency of mass transfer between feedstock particles and microorganisms, it is advisable to pretreat organic waste using various methods. One of the most promising and energy-efficient methods for preparing a feedstock for anaerobic bioconversion is its processing in a vortex layer apparatus (VLA). However, there are some limitations in the VLA operation. Therefore, to exclude the stagnant central zone from the volume of the VLA working chamber and increase the magnitude of the magnetic field in the VLA working chamber, a ferromagnetic core in the form of a steel pipe was coaxially mounted. Thus, the purpose of this work is to experimentally study the effect of the ferromagnetic core of the VLA working chamber on the production of biogas during anaerobic bioconversion of a model of organic waste from the agricultural sector. To achieve this goal, an experimental plant was developed and created. The experimental data obtained suggest the high efficiency of pretreatment of the feedstock in VLA with a ferromagnetic core in the working chamber before anaerobic bioconversion. The developed anaerobic bioconversion system made it possible to increase the methane production rate by 287 % at hydraulic retention time (HRT) of 4 days and by 3.5 times at HRT of 2 days compared to the control. At the same time, the methane yield at HRT of 4 days increased by 43 %, and at HRT of 2 days it decreased by 14 %. The hydrogen sulfide content in biogas also increased more than three times, while no hydrogen was detected in the biogas. Thus, pretreatment of the feedstock in VLA with a ferromagnetic core to produce biohythane in a one-stage anaerobic bioconversion system at 55.1 °C is impractical.