143 / 2023-06-29 20:38:52

Study on the influence of different thermal coals on the mixed-burning characteristics of Ventilation air methane and Pulverized coal

Ventilation air methane;,NO emission characteristics,species of thermal coal;,ignition temperature;,CH4 conversion;

The greenhouse effect of methane is about 21 times that of carbon dioxide, making it the "main contributor" to the global greenhouse effect. Ventilation air methane (VAM) has the characteristics of low CH₄ concentration (0.1%.vol to 0.75%.vol), large concentration fluctuation range, and large amount, making it difficult to directly utilize. Direct emissions not only cause energy waste, but also exacerbate the greenhouse effect. The utilization of VAM containing ultra-low concentrations of CH₄ is still in the research and development stage. The current technological solutions mainly include thermal storage oxidation technology and as auxiliary fuel. Although the research on thermal storage oxidation technology is relatively mature, its processing capacity for VAM with CH₄ concentration below 0.2vol% is low, and it cannot adapt to the characteristics of high flow rate of VAM. As an auxiliary fuel, combustion technology is an oxidation heating technology that combines VAM and ambient air into gas turbines, gas internal combustion engines, or coal-fired boilers. It not only reduces CH₄ emissions and fully utilizes them, but also achieves the goal of reducing environmental pollution and increasing economic benefits. Due to the fact that the pithead power plant is a supporting facility for coal mines, only 1-2 kilometers away from the return air wellhead, it has the convenience and foundation for industrial application. So VAM can be introduced into the power plant boiler for mixed combustion.

However, there are significant differences in the characteristics of steam coal in different regions, which increases the probability of problems occurring during the combustion process, leading to significant differences in the mixed combustion characteristics of steam coal and VAM in power plant boilers.

In order to explore the impact of different coals on the characteristics of VAM and coal-fired co combustion, three kinds of steam coals, namely, Chifeng lignite in Inner Mongolia, Hami long flame coal in Xinjiang and Anthracite in Yangquan, Shanxi, were used as experimental coal samples. Through the establishment of a VAM and coal-fired co combustion test system, the impact of the addition of three kinds of steam coals on the ignition temperature, CH₄ conversion rate and NO emission characteristics of VAM and coal-fired co combustion system was studied.

Experiments show that the coupling system of lignite and VAM has the lowest ignition temperature, which is most conducive to the combustion of the coupling system; the addition of anthracite has the strongest catalytic effect on the transformation of CH₄ in the VAM; the concentration peak of NO in the VAM-lignite coupling system is the highest, and the lowest in the VAM-anthracite coupling system. More importantly, CH₄ in the VAM has a reducing effect on the NO produced during the mixed-burning process, and the higher the concentration of CH₄, the stronger the reducing effect. The results of this study can not only lay the foundation for the industrial application of mixed combustion of VAM and thermal coal, but also have great significance for improving the combustion efficiency of pulverized coal and the stability of boiler operation of coal-fired boilers, and solving the practical problems brought about by the change of boiler coal types.