17:15 〜 19:15
[SGC37-P13] Origin of gases emitted during coal waste self-heating in Upper Silesia, Poland and Czechia – laboratory simulation data
キーワード：coal waste, self-heating, volatile pollutants, Upper Silesian Coal Basin, hydrous and dry pyrolysis, oxidation laboratory experiment
Coal wastes deposited in improperly constructed dumps may undergo self-heating processes. Due to the limited availability of oxygen within the dump, besides the burning, pyrolysis processes occur. Both processes result in emissions of pollutants (mostly volatile) and have been developed in several heaps in the Polish (PL) and Czech (CZ) parts of the Upper Silesian Coal Basin (USCB).
To examine the amount, molecular and stable isotope composition of volatile compounds produced during self-heating, in relation to organic matter content and maturity, four samples in the Polish part of the USCB were collected: two from the Janina Mine (J1, J2) (Rr ca. 0.5%) and two from the Marcel Mine (M1, M2) (Rr ca. 0.9%). The Rock-Eval data indicate 1.8, 27.3, 2.3 and 24.1 wt. % TOC, respectively and the presence of the gas-prone kerogen in all samples. Self-heating simulations were conducted in closed reactors in conditions: pyrolysis, without (DP) and with water (HP) in temperatures of 250, 360 and 400oC for 72 h, and oxidation with air (OXI) in temperatures of 250 and 400oC for 72 h.
The gases from thermally active heaps in Hermanice (HER, CZ) and Bytom (BYT, PL) were collected and analysed (molecular and isotopic composition of volatile products) to compare with artificially produced gases during HP, DP, and OXI experiments. The rock material stored there has a different coal rank: in BYT it is sub-bituminous coal (comparable to J1 and J2 samples), while in HER wastes with coking coal particles (as in M1 and M2) were deposited. Sampling was carried out in the winter 2022/23, spring 2023, autumn 2023, and autumn 2024 campaigns at the same test points located at the emanations of volatile pollutants. Gases were sampled at each point directly from the chimney where the outflow of gas/vapour was visible. Surface temperature measurements in these spots were up to 345 °C (HER) and 158 °C (BYT). The molecular composition of experimentally-generated gases and collected from heaps (i.a., HCs (C1-C8), CO, CO2, H2, H2S, organic S-compounds) and stable isotope composition of selected volatile compounds (δ13C(CH4, CO2), δ2H(CH4)) were determined.
During all OXI experiments, only traces of HCs were produced. The concentration of HCs in HP and DP runs increases with temperature increase up to 58.4 mol%. The δ13C values of CO2 from all experiments vary from -25.7 to +0.3‰ and strongly depend on carbonate content and process conditions. The δ13C(CH4) from J1 and J2 have values -34.5±2‰ independent of temperature and process type. A strong temperature-increase, from -45 to -31.6‰ is observed for δ13C(CH4) values from HP and DP experiments of M1 and M2 samples. The δ2H(CH4) values of HP runs are statistically lower than DP runs and amount, on average, -315 and -280‰, respectively.
During the study period (2022-2024), significant changes in gas concentrations were recorded indicating fire movement within both heaps. The δ13C(CH4) values vary from -43.0 to -17.7‰, δ13C(CO2) range from -25.6 to -16.5‰ and δ2H(CH4) from -291 to -143‰ indicating the thermogenic origin of all gases. Most of the collected gases from both dumps have isotope signatures (δ13C(CH4, CO2), δ2H(CH4)) similar to gases generated during conducted HP, DP and OXI experiments, but methane of some gases evidence heavier C & H isotope composition. Based on visible trends of δ13C(CH4) values generated during laboratory experiments, we can conclude that these gases were generated at temperatures higher than 400oC, probably occurring in deeper parts of studied dumps. The data presented here show that the stable isotope composition analysis of gases is a good tool for the evaluation of generated gases origin and fire tracking in thermally active coal waste dumps.
This study was financed by the AGH University of Krakow as a part of the programme Excellence Initiative – Research University, Action 4, Grant No. 4113 and the National Science Centre, Poland, grant No 2017/27/B/ST10/00680.
To examine the amount, molecular and stable isotope composition of volatile compounds produced during self-heating, in relation to organic matter content and maturity, four samples in the Polish part of the USCB were collected: two from the Janina Mine (J1, J2) (Rr ca. 0.5%) and two from the Marcel Mine (M1, M2) (Rr ca. 0.9%). The Rock-Eval data indicate 1.8, 27.3, 2.3 and 24.1 wt. % TOC, respectively and the presence of the gas-prone kerogen in all samples. Self-heating simulations were conducted in closed reactors in conditions: pyrolysis, without (DP) and with water (HP) in temperatures of 250, 360 and 400oC for 72 h, and oxidation with air (OXI) in temperatures of 250 and 400oC for 72 h.
The gases from thermally active heaps in Hermanice (HER, CZ) and Bytom (BYT, PL) were collected and analysed (molecular and isotopic composition of volatile products) to compare with artificially produced gases during HP, DP, and OXI experiments. The rock material stored there has a different coal rank: in BYT it is sub-bituminous coal (comparable to J1 and J2 samples), while in HER wastes with coking coal particles (as in M1 and M2) were deposited. Sampling was carried out in the winter 2022/23, spring 2023, autumn 2023, and autumn 2024 campaigns at the same test points located at the emanations of volatile pollutants. Gases were sampled at each point directly from the chimney where the outflow of gas/vapour was visible. Surface temperature measurements in these spots were up to 345 °C (HER) and 158 °C (BYT). The molecular composition of experimentally-generated gases and collected from heaps (i.a., HCs (C1-C8), CO, CO2, H2, H2S, organic S-compounds) and stable isotope composition of selected volatile compounds (δ13C(CH4, CO2), δ2H(CH4)) were determined.
During all OXI experiments, only traces of HCs were produced. The concentration of HCs in HP and DP runs increases with temperature increase up to 58.4 mol%. The δ13C values of CO2 from all experiments vary from -25.7 to +0.3‰ and strongly depend on carbonate content and process conditions. The δ13C(CH4) from J1 and J2 have values -34.5±2‰ independent of temperature and process type. A strong temperature-increase, from -45 to -31.6‰ is observed for δ13C(CH4) values from HP and DP experiments of M1 and M2 samples. The δ2H(CH4) values of HP runs are statistically lower than DP runs and amount, on average, -315 and -280‰, respectively.
During the study period (2022-2024), significant changes in gas concentrations were recorded indicating fire movement within both heaps. The δ13C(CH4) values vary from -43.0 to -17.7‰, δ13C(CO2) range from -25.6 to -16.5‰ and δ2H(CH4) from -291 to -143‰ indicating the thermogenic origin of all gases. Most of the collected gases from both dumps have isotope signatures (δ13C(CH4, CO2), δ2H(CH4)) similar to gases generated during conducted HP, DP and OXI experiments, but methane of some gases evidence heavier C & H isotope composition. Based on visible trends of δ13C(CH4) values generated during laboratory experiments, we can conclude that these gases were generated at temperatures higher than 400oC, probably occurring in deeper parts of studied dumps. The data presented here show that the stable isotope composition analysis of gases is a good tool for the evaluation of generated gases origin and fire tracking in thermally active coal waste dumps.
This study was financed by the AGH University of Krakow as a part of the programme Excellence Initiative – Research University, Action 4, Grant No. 4113 and the National Science Centre, Poland, grant No 2017/27/B/ST10/00680.