5:15 PM - 6:45 PM
[SGC32-P09] Properties of the volatile products released during coal waste self-heating in Upper Silesia, Poland and Czech Republic
Keywords:Upper Silesian Coal Basin, coal waste, self-heating, volatile pollutants, carbon stable isotopes, CSIA
The coal wastes deposited in dumps are a typical element of the industrially-changed landscape of the Polish and Czech parts of the Upper Silesian Coal Basin. Within the improper protected/constructed heaps, due to air and water infiltration, the self-heating and self-burning processes may develop, resulting in the emission of volatile (gaseous and solid) pollutants. These processes have developed in several landfills in Poland and the Czech Republic. Volatile products of thermal transformations often precipitate on the surface of the deposit in the form of secondary minerals (Nadudvari et al., 2024).
Heaps in Hermanice (HER, CZ) and Bytom (BYT, PL), where thermal processes are developed, were selected for the study of emission intensity, molecular and isotopic composition of volatile self-heating products. The rock material stored there has a similar mineral composition, but the coal rank is different: in Bytom it is sub-bituminous coal while in Hermanice it is coking coal. Sampling were carried out in the winter 2022/23, spring 2023 and autumn 2023 campaigns at the same test points located at the emanations of volatile pollutants. Gases were sampled at each point twice: directly from the chimney where the outflow of gas/vapour was visible (sample SURF) and after sticking the probe into the ground (sample DEEP). Polycyclic aromatic hydrocarbons (PAHs), emitted into the atmosphere with particulate matter (PM) during waste self-burning were collected on glass fibre filters using a Senya high-flow aspirator. Surface temperature measurements in these spots ranged from 3 to 345 °C, and at the probe depths (50-100 cm), from 63 to 363 °C; statistically, higher temperatures were recorded at the heap in Hermanice.
The molecular composition of collected gases (N2, O2, hydrocarbons (HC), CO, CO2, H2 and S-compounds) and δ13C values of selected gases was determined. The concentrations and δ13C values of individual PAHs associated with PM were obtained using gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) and compound-specific isotope analysis (CSIA), respectively.
During the study period, significant changes in gas concentrations were recorded. In general, SURF gases were richer in pollutants (HC, CO, CO2, H2 and S-compounds) than DEEP gases at all sites. This may suggest that the gases flowing out of chimneys are generated in significantly greater depths than those reached with the sampling probe. The δ13C(CH4), δ13C(C2H6), and δ13C(CO2) values indicate the thermogenic origin of almost all gases. Only in one gas from BYT the δ13C(CH4) = -52.9‰ suggest its at least partial microbial origin. The highest concentrations of CO2 (19.17%), CO (0.67%), HC (2.43%), H2 (6.26%) and S-compounds (844 ppm) were recorded in gas flowing out of the pipe penetrating the HER dump to a depth of 12m (temperature ca. 350oC). The periodical sampling made it possible to follow the thermal processes in the heaps.
In extracts of PM obtained by ultrasonic extraction, phenanthrene and fluorene predominate regardless of subsurface temperature or season. PAHs emissions depend on the stage of self-burning. The highest PAHs emissions are related to DEEP temperatures ranging from 200 to 250 °C. At lower (initial stage) and high temperatures (final stage) of burning, PAHs are released in low concentrations. The δ13C values of phenanthrene and fluorene might be helpful to distinguish the stage of the process due to their isotopic depletion with temperature increase. As a result, CSIA might help evaluate the progress of the self-heating process at coal waste heaps.
The data presented here show that the molecular and isotopic composition analysis of gases and PAHs are good tools for tracking processes 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.
Nadudvari A., et al., 2024. https://doi.org/10.1016/j.coal.2023.104403
Heaps in Hermanice (HER, CZ) and Bytom (BYT, PL), where thermal processes are developed, were selected for the study of emission intensity, molecular and isotopic composition of volatile self-heating products. The rock material stored there has a similar mineral composition, but the coal rank is different: in Bytom it is sub-bituminous coal while in Hermanice it is coking coal. Sampling were carried out in the winter 2022/23, spring 2023 and autumn 2023 campaigns at the same test points located at the emanations of volatile pollutants. Gases were sampled at each point twice: directly from the chimney where the outflow of gas/vapour was visible (sample SURF) and after sticking the probe into the ground (sample DEEP). Polycyclic aromatic hydrocarbons (PAHs), emitted into the atmosphere with particulate matter (PM) during waste self-burning were collected on glass fibre filters using a Senya high-flow aspirator. Surface temperature measurements in these spots ranged from 3 to 345 °C, and at the probe depths (50-100 cm), from 63 to 363 °C; statistically, higher temperatures were recorded at the heap in Hermanice.
The molecular composition of collected gases (N2, O2, hydrocarbons (HC), CO, CO2, H2 and S-compounds) and δ13C values of selected gases was determined. The concentrations and δ13C values of individual PAHs associated with PM were obtained using gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) and compound-specific isotope analysis (CSIA), respectively.
During the study period, significant changes in gas concentrations were recorded. In general, SURF gases were richer in pollutants (HC, CO, CO2, H2 and S-compounds) than DEEP gases at all sites. This may suggest that the gases flowing out of chimneys are generated in significantly greater depths than those reached with the sampling probe. The δ13C(CH4), δ13C(C2H6), and δ13C(CO2) values indicate the thermogenic origin of almost all gases. Only in one gas from BYT the δ13C(CH4) = -52.9‰ suggest its at least partial microbial origin. The highest concentrations of CO2 (19.17%), CO (0.67%), HC (2.43%), H2 (6.26%) and S-compounds (844 ppm) were recorded in gas flowing out of the pipe penetrating the HER dump to a depth of 12m (temperature ca. 350oC). The periodical sampling made it possible to follow the thermal processes in the heaps.
In extracts of PM obtained by ultrasonic extraction, phenanthrene and fluorene predominate regardless of subsurface temperature or season. PAHs emissions depend on the stage of self-burning. The highest PAHs emissions are related to DEEP temperatures ranging from 200 to 250 °C. At lower (initial stage) and high temperatures (final stage) of burning, PAHs are released in low concentrations. The δ13C values of phenanthrene and fluorene might be helpful to distinguish the stage of the process due to their isotopic depletion with temperature increase. As a result, CSIA might help evaluate the progress of the self-heating process at coal waste heaps.
The data presented here show that the molecular and isotopic composition analysis of gases and PAHs are good tools for tracking processes 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.
Nadudvari A., et al., 2024. https://doi.org/10.1016/j.coal.2023.104403