Changes in the Distribution of Temperature in a Coal Deposit and the Composition of Gases Emitted during Its Heating and Cooling
Abstract
:1. Introduction
2. Materials and Methods
2.1. Materials
- −
- 0 < G ≤ 0.0025—no actions needed, no fire risk;
- −
- 0.0025 < G ≤ 0.0070—enhanced scrutiny of the atmosphere, more frequent collections of gas samples;
- −
- 0.0070 < G ≤ 0.0300—preventive actions;
- −
- G > 0.0300—firefighting;
2.2. Methods
3. Results and Discussion
3.1. Temperature Changes
3.2. Simulation of Heating Process
3.3. Gas Concentration Changes
3.4. Analysis of Fire Indices
4. Conclusions
- Changes in temperature in the vicinity of a heating and cooling hot spot were analyzed. The percentages of coal in the reactor for given temperatures were calculated. By comparing the percentages of coal for the same temperature in the hot spot, for the heating phase and cooling phase, significant differences in the distribution of given percentages of coal were observed. For all the coals, the average temperature during the cooling phase was higher at each of the sensors.
- Changes in the concentrations of gases during heating and cooling were analyzed. The dynamics of changes in the concentrations of gases for the tested coals were determined. For samples 1 and 5, the lowest increases were measured for ethane, propane, and carbon dioxide, while the highest were measured for ethylene, propylene, hydrogen, and carbon monoxide. For samples 1, 2, and 4, the lowest increases were measured for ethane and propane and the highest were measured for ethylene, carbon monoxide, and hydrogen. Background values during heating and cooling, i.e., concentrations of gases at the virgin temperature of rocks, were determined. Ethylene was chosen as one of the most characteristic gases, especially for assessing the cooling of coal.
- Changes in the values of fire indices were analyzed. The Graham index during heating was similar for all the tested coals. Hence, the use of the Graham index criteria during heating is perfectly justified. Yet, using the criteria during cooling leads to incorrect conclusions. During cooling, the Litton index assumes the value of 1 (cooling down to the ambient temperature) within the temperature range of 200–100 °C, i.e., it prematurely informs about cooling down. Use of the index based on the ethylene concentration was proposed. During the cooling phase, the index changes linearly.
- It is impossible to assume common criteria to assess the fire hazard for the heating phase and cooling phase. Hence, for the accurate determination of the temperature in the cooling hot spot, it is necessary to conduct model tests for each of the coals and select proper limits.
Author Contributions
Funding
Conflicts of Interest
Appendix A
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Sample 1 | Sample 2 | Sample 3 | Sample 4 | Sample 5 | ||||||
---|---|---|---|---|---|---|---|---|---|---|
g | % | g | % | g | % | g | % | g | % | |
>2 mm | 3 | 1.1 | 6 | 2.0 | 2 | 0.7 | 8.5 | 2.8 | 7.5 | 2.3 |
2–1 mm | 100.5 | 36.5 | 106.5 | 35.5 | 99.5 | 36.4 | 110 | 36.3 | 119.5 | 36.9 |
1–0.7 mm | 57 | 20.7 | 55.5 | 18.5 | 60.5 | 22.2 | 53 | 17.5 | 60 | 18.5 |
0.7–0.5 mm | 40.5 | 14.7 | 46.5 | 15.5 | 39 | 14.3 | 49.5 | 16.3 | 53.5 | 16.5 |
0.5–0.35 mm | 22.5 | 8.2 | 25.5 | 8.5 | 20 | 7.3 | 30.5 | 10.1 | 38 | 11.7 |
0.35–0.25 mm | 10.5 | 3.8 | 18 | 6 | 15 | 5.5 | 20.5 | 6.8 | 20 | 6.2 |
0.25–0.125 mm | 18 | 6.5 | 18 | 6 | 17 | 6.2 | 15 | 5.0 | 13.5 | 4.2 |
<0.125 mm | 23 | 8.4 | 25 | 8 | 20 | 7.3 | 16 | 5.3 | 12 | 3.7 |
Sample No | Transient Moisture Wex PN-G-04511:1980 pt. 2.1 | Moisture Content of Sample Wa PN-G-04560:1998 | Ash Content Aa PN-G-04560:1998 | Volatile Matter Content Va PN-G-04516:1998 | Total Carbon Content Ca PN-G-04571:1998 | Total Sulfur Content Sta PN-G-04571:1998 | Total Hydrogen Content Hta PN-G-04584:2001 | Nitrogen Content Na PN-G-04571:1998 | Oxygen Content Oa PN-G-04571:1998 | Activation Energy A PN-93/G-04558 | Coal Autoinfla-mmability Index Sza PN-93/G-04558 | Autoinfla-mmability Group PN-93/G-04558 |
---|---|---|---|---|---|---|---|---|---|---|---|---|
% Weight | % Weight | % Weight | % Weight | % Weight | % Weight | % Weight | % Weight | % Weight | kJ/mol | °C/min | ||
1 | 2.8 | 2.2 | 6.9 | 29.5 | 81.9 | 0.68 | 4.55 | 1.33 | 6.85 | 61 | 77 | II |
2 | 7.1 | 8.0 | 5.4 | 34 | 69.5 | 0.75 | 4.8 | 1.1 | 11.42 | 47 | 125 | V |
3 | 1.2 | 0.8 | 4.2 | 23 | 87.8 | 0.48 | 3.2 | 1.13 | 8.3 | 60 | 42 | II |
4 | 3.8 | 4.4 | 5.6 | 33.7 | 74.5 | 0.88 | 3.98 | 1.21 | 9.75 | 62 | 83 | III |
5 | 8.8 | 9.2 | 4.9 | 34.1 | 70.6 | 1.10 | 4.72 | 0.79 | 12.28 | 47 | 135 | V |
Ranges of Temperature in Reactor | Temperature in Hot Spot | ||||
---|---|---|---|---|---|
Heating Phase | Cooling Phase | ||||
100 °C | 200 °C | 300 °C | 200 °C | 100 °C | |
up to 50 °C | 96% | 66% | 55% | 62% | 89% |
50–100 °C | 4% | 27% | 34% | 29% | 10% |
100–150 °C | - | 5% | 6% | 5% | - |
150–200 °C | - | 2% | 3% | 2% | - |
200–250 °C | - | - | 1% | 1% | - |
250–300 °C | - | - | 1% | - | - |
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Więckowski, M.; Howaniec, N.; Postnikov, E.B.; Chorążewski, M.; Smoliński, A. Changes in the Distribution of Temperature in a Coal Deposit and the Composition of Gases Emitted during Its Heating and Cooling. Sustainability 2018, 10, 3587. https://doi.org/10.3390/su10103587
Więckowski M, Howaniec N, Postnikov EB, Chorążewski M, Smoliński A. Changes in the Distribution of Temperature in a Coal Deposit and the Composition of Gases Emitted during Its Heating and Cooling. Sustainability. 2018; 10(10):3587. https://doi.org/10.3390/su10103587
Chicago/Turabian StyleWięckowski, Marek, Natalia Howaniec, Eugene B. Postnikov, Mirosław Chorążewski, and Adam Smoliński. 2018. "Changes in the Distribution of Temperature in a Coal Deposit and the Composition of Gases Emitted during Its Heating and Cooling" Sustainability 10, no. 10: 3587. https://doi.org/10.3390/su10103587