Evaluating the efficiency of the enhanced ultrasonic–assisted hydrogen peroxide degradation of low–rank coal biogenic gas

Abstract

ABSTRACT The efficiency of biogas formation from low-rank coal was improved through ultrasonic-assisted hydrogen peroxide degradation. We investigated various aspects of this process, including the mass of the small-molecule organic matter, changes in the composition of biogas components in three systems, and alterations in the microscopic morphology of coal before and after biogas formation. Our analytical methods included UV-vis spectrophotometry, drainage gas collection method, gas chromatography, infrared spectroscopy, and scanning electron microscopy. Optimal pretreatment conditions were identified with an ultrasonic power of 400 W, a reaction time of 90 min, and a reaction temperature of 60°C. The biogenic methanogenic cycle was delineated into three stages, with the raw coal and filtrate systems exhibiting fast and slow gas production stages during the first and second stages, respectively. In contrast, the residual coal system displayed slow and fast gas production stages during these stages. Methane yields were measured at 270.72 μmol g−1 (raw coal), 303.50 μmol g−1 (residual coal), and 293.43 μmol g−1 (filtrate). Pretreated coal exhibited biomethane yields (residual coal and filtrate) approximately 120% higher than untreated raw coal. Notably, the gas-forming potential of the filtrate should not be underestimated. Ultrasonic-assisted hydrogen peroxide pretreatment disrupted the macromolecular reticulation structure within the raw coal, resulting in the opening of a portion of the aromatic ring structure. This innovative approach offers a novel strategy for augmenting biomethane production from low-rank coal and furnishes a scientific foundation for advancing industrial applications.