Sorption characteristic of coal as regards of gas mixtures emitted in the process of the self-heating of coal

Abstract

Abstract. One of the most challenging tasks in the coal mining sector is the detection of endogenous fire risks. Under field conditions, the distance between the points where samples for the analyses are collected and the actual place where coal self-heating takes place may be quite remote. Coal is a natural sorbent with a diverse character of pore structures which are surrounded by fractures and cleavage planes constituting ideal spaces for the flow and adsorption of gases. The gases (methane, ethane, ethylene, propane, propylene, acetylene, carbon dioxide, carbon monoxide, hydrogen) released from the source of fire migrate through the seam and may be subject to adsorption, or they may cause the desorption of gases accumulated in coal. Therefore, the values of reference sample concentrations may be overstated or understated, respectively. The objective of this experimental study was to investigate the adsorption phenomena accompanying the flow of a multi-component gas mixture through a coal bed which may occur in situ. The research was conducted by means of a method based on a series of calorimetric/chromatographic measurements taken to determine the amount of gases released during coal heating at various temperatures under laboratory conditions. Based on the results obtained in the course of the experiments, it was concluded that the amount of gas adsorbed in the seam depends on the type of coal and the gas. Within the multi-component gas mixture, hydrocarbons demonstrated the largest sorption capacity, especially as concerns propylene.

Analysis of metamorphism and tendency of black coals to spontaneous combustion

“…Similar results ( Fig. 3) are obtained by processing other experimental data [19][20][21][22][23][24][25][26]. This indicates a different transformative effect of pressure, temperature, and time factors at individual stages of metamorphism.…”

“…1, c). TECHNOLOGY [19][20][21][22][23][24][25][26]: а -the ratio between the carbon content and a mixture of other components (О 0 , Н 0 , N 0 ); b -the ratio between the content of carbon and oxygen; c -the ratio between the content of carbon and hydrogen; d -the ratio between the carbon content and nitrogen; I, II, III, IV -ranges of changes in the properties of coal; 1 -linear interpolation of experimental data; 2 -the boundaries of the change in components; • -experimental data…”

“…The interdependence of the content of hydrogen (H 0 ) and oxygen (O 0 ) in the organic (combustible) mass of coal according to[19][20][21][22][23][24][25][26] : 1 -the boundaries of the change in the considered parameters; • -experimental data…”

Research on a Gas Index Reflecting the Sorption Process on Carbon Materials in Coal Mines

“…While Figure 3a-c,e represents the values at the outlet of the sorption column at the temperatures of 323 K, 373 K, 423 K, 473 K and 523 K, respectively. In the case of samples with number 1-9, the sorption indices were calculated based on the results obtained and published in earlier papers [20][21][22], but in this study these results were used in the context of the sorption index (SG). Based on the results drawn for individual samples at the inlet of the sorption column, it was established that the sorption indices of combustion products attained mostly have a value below 3.…”

Profile of CO2, CO, and H2 Emissions from Thermal Oxidation of Polish Coals

“…The gas can originate from sources other than the self-heating process, i.e., natural content, acid mine water neutralization, machines with diesel-fueled engines working underground or the injection of carbon dioxide into a sealed area as an inert gas [24,32]. Additionally, studies on the fire gases sorption on coal also showed that carbon dioxide is easily absorbed on coal surface due to its small kinetic diameter (0.33 mm), a linear structure and a high quadruple moment of molecules [28,33,34]. This phenomenon may result in underestimating the value of the gas concentration at the monitoring station, especially when the distance between the source of fire and the sampling point is long.…”