Coal char characteristics variation in the gasification process and its influencing factors

Abstract

Underground coal gasification is a burgeoning coal exploitation technique that coal is directly converted into gaseous fuel by controlled combustion. In this paper, the gasification experiments of Inner Mongolia lignite, Xinjiang subbituminous coal, and Hancheng medium volatile bitumite were conducted respectively by using the tube furnace coal gasification experiment system. The gasification process was conducted under 3°C/min increment within the range of 600–900°C. The gas composition was analyzed by gas chromatography and the pore structure of the coal char was detected by low-temperature N2 adsorption. The results show that the gasification temperature, gasification agent, and coal type have an important influence on the gasification reaction. With the increase of gasification temperature, the effective component, gas calorific value, and gas production rate increase. When CO2 is used as the gasifying agent, the effective components in the gas are mainly CO. When H2O(g) is used as the gasifying agent, the effective component of gas is H2. The coal gasification performance with low thermal maturity is obvious better than the high rank coal with higher coalification. N2 adsorption–desorption experiments show that the pore is mainly composed by transition pore and the micropores, the specific surface area is chiefly controlled by a pore size of 2–3 nm. With the increase of coalification degree, the adsorption amount, specific surface area, and total pore volume show a decreasing trend. The gasifying agent has a great influence on the pore structure of the coal char. The gasification effect of H2O (g) is significantly better than that of CO2. Analyzing the gasification characteristics and pore changes of different coal rank coals under different gasification agents, we found that Inner Mongolia lignite is more conducive to the transport of gasification agents and gaseous products in coal.

Biocoal Characterization as an Environmentally Friendly Alternative Energy Innovation Composite Variations of Gasified Char with Coconut Shell Charcoal

“…After char characterization result by proximate analysis, it is found that char experiences an increase in Gross Calorific Value grades from 5,804 cal/gr to 6,183 cal/gr and a significant decrease in sulfur levels from 1.18% to 0.38% and also a significant decrease of inherent moisture from 16.10% to 12%. Changes in quality for the better because the coal (lignite type) used is suitable as a raw material, The coal gasification performance with low thermal maturity is obvious better than the high rank coal with higher coalification [29]. The results of the briquette characterization can be seen in Table 9.…”

Influence of the Heating Rate on the Quality of Metallurgical Coke

“…To explain the difference in the reactivity values of coals, it is also necessary to consider the coal rank. It is known that the coke reactivity increases with the decreasing of coal rank. , Another factor to consider is the alkalinity index (AI) of the ashes. This was calculated from the ash chemical composition using the ratio of the total content of the basic oxides (Fe 2 O 3 , CaO, MgO, Na 2 O, and K 2 O) to the total content of acidic oxides (Al 2 O 3 and SiO 2 ) according to X-ray fluorescence (XRF) analysis (Table ).…”

Pyrolysis characteristics and microstructure evolution of different coal types

“…The pyrolysis solid product coal char of different final pyrolysis temperatures (600°C,750°C, and 900°C) was crushed into 60-80 meshes at and dried for 48 h. The pore variation was measured by ASAP2000; this instrument uses the principle of gas adsorption (typically nitrogen) (Li et al 2020, Yin et al 2020).…”