Study on the Fire Prevention and Extinguishing Performance of Ammonium Polyphosphate-Reinforced Coal Cangue Slurry for Goaf Grouting and Filling
Abstract
1. Introduction
2. Experiment
2.1. Materials
2.2. Preparation of Coal Gangue Slurry
2.2.1. Analysis of the Slurry-Forming Performance of Coal Gangue Slurry
2.2.2. Settling Velocity and Critical Stabilization Time Tests
2.2.3. Plasticity Index Test
2.2.4. Viscosity Coefficient
2.3. Thermal Stability Test of Coal Gangue Slurry
2.4. Study on the Oxidation Characteristics of Coal Gangue After Grouting Backfill
- (1)
- Six grouting thicknesses (0 cm, 5 cm, 7 cm, 9 cm, 11 cm, and 13 cm) and three heating temperatures (100 °C, 200 °C, and 300 °C) were used.
- (2)
- The reactor liner was stacked with different thicknesses of gangue blocks and then we injected gangue blocks of gangue slurry so they were just submerged. The mixture was placed at room temperature for 24 h to dry for the next operation.
- (3)
- The dried specimens were placed in the reaction vessel and evacuated using a vacuum pump.
- (4)
- Dry air was introduced, and the programmed temperature controller was set to heat the vessel to the target temperature.
- (5)
- After stabilizing at the target temperature, gas sampling bags were used to collect reaction products.
- (6)
- The gases were collected and immediately introduced into the gas chromatograph. Thereafter, the O2, N2, CO, and CO2 compositions of the gases were examined in three batches and averaged.
- (7)
- The detected data were compared with standard gas samples to determine the proportional content of each gas. To investigate the effects of additives on the oxidation performance of backfilled coal gangue, additional tests were conducted using a coal-based solid waste backfill fire prevention platform. These tests focused on coal gangue with additives and a grouting thickness of 9 cm.
3. Results Analysis
3.1. Slurry-Forming Performance of Coal Gangue Slurry
3.2. Influence of Heating Duration on the Thermal Stability of Coal Gangue Slurry
3.3. Influence of Grouting Thickness on the Thermal Stability of Coal Gangue Slurry
3.4. Influence of Heating Temperature on the Thermal Stability of Coal Gangue Slurry
3.5. Comprehensive Evaluation of the Thermal Stability of Coal Gangue Slurry Under Different Conditions
3.6. Evaluation of the Oxidation Performance of Coal Gangue
3.6.1. Gas Content After the Oxidation of Coal Gangue
3.6.2. Influence of Additive Type on Oxidation Reaction of Coal Gangue Slurry
3.6.3. Influence of Additive Dosage
4. Fire Suppression Mechanisms
5. Conclusions
- The coal gangue slurry of this type exhibited no solid–liquid interface separation, with a plasticity index consistent with the requirements of standard grouting materials. The stable slurry-forming performance indicates its suitability as a grouting backfill material.
- With increasing heating duration, the central, maximum, and minimum surface temperatures of the coal gangue slurry followed polynomial growth functions (R2 > 0.99). As the grouting thickness increased, the surface temperature initially rose and then declined, peaking at a thickness of 10 cm. Additionally, the central, maximum, and minimum surface temperatures displayed an overall ascending trend as the heating temperature increased.
- When the heating temperature increased from 100 °C to 300 °C, the CO and CO2 concentrations progressively rose. At grouting thicknesses of 9–12 cm, CO and CO2 gases were only detected at 300 °C during coal gangue oxidation, with their concentrations decreasing as grouting thickness increased. The oxidation reaction rate, reflected by CO and CO2 concentrations, demonstrated that CO levels initially increased and then decreased as grouting thickness rose from 0 cm to 13 cm, reaching a maximum at 5 cm. Comparative analysis of additives with identical mass fractions revealed that the coal gangue slurry modified with ammonium polyphosphate (APP) released significantly lower amounts of CO and CO2 than the control group or slurries modified with zinc borate or magnesium hydroxide, confirming APP’s superior inhibitory effect.
- Increasing APP dosage progressively reduced CO and CO2 emissions from the coal gangue slurry, with maximum reductions of 70.0% and 83.2%, respectively, compared to the control group, markedly enhancing fireproofing performance. Mechanistic analysis indicates that APP decomposes upon heating, generating non-volatile phosphorus oxides and polyphosphoric acid that coat the coal gangue surface to isolate oxygen. Under high temperatures, APP dehydrates to form polyphosphoric or metaphosphoric acid, which scavenges free radicals such as -OH and inhibits combustion, as well as being a strong dehydrating agent. This promotes carbonization with char-forming substances, generating an expanded carbon layer reinforced by non-combustible gases, thereby effectively isolating air and blocking fire propagation. The fire prevention and suppression system based on the synergistic interaction between coal gangue slurry and APP not only meets the grouting requirements for coal mine goafs but also extends to other coal-bearing solid waste accumulation scenarios such as open-pit mines and abandoned mine backfilling, offering a universal solution for ecological restoration and fire hazard control in mining areas.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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Number | Mass Concentration (%) | Heating Time (min) | Heating Temperature (°C) | Grouting Thickness (cm) |
---|---|---|---|---|
1 | 68 | 0, 12, 20, 30, 40, 50, 60 | 140 | 10 |
2 | 68 | 40 | 100, 120, 140, 160, 180, 200 | 10 |
3 | 68 | 40 | 140 | 5, 10, 15, 20 |
Parameter | Coarse Particles (1–3 mm) Content (%) | Water-to-Binder Ratio | Mass Concentration (%) | Settling Velocity (mm/min) | Critical Stabilization Time (min) | Plasticity Index | Viscosity Coefficient (mPa·s) |
---|---|---|---|---|---|---|---|
Value | 20 | 0.471:1 | 68 | 0 | 0 | 7.43 | 551 |
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Wu, R.; Liu, X.; Wang, S.; Song, X.; Yu, H.; Guo, Z. Study on the Fire Prevention and Extinguishing Performance of Ammonium Polyphosphate-Reinforced Coal Cangue Slurry for Goaf Grouting and Filling. Fire 2025, 8, 213. https://doi.org/10.3390/fire8060213
Wu R, Liu X, Wang S, Song X, Yu H, Guo Z. Study on the Fire Prevention and Extinguishing Performance of Ammonium Polyphosphate-Reinforced Coal Cangue Slurry for Goaf Grouting and Filling. Fire. 2025; 8(6):213. https://doi.org/10.3390/fire8060213
Chicago/Turabian StyleWu, Rui, Xiangyu Liu, Shi Wang, Xuepeng Song, Haigen Yu, and Zhiguo Guo. 2025. "Study on the Fire Prevention and Extinguishing Performance of Ammonium Polyphosphate-Reinforced Coal Cangue Slurry for Goaf Grouting and Filling" Fire 8, no. 6: 213. https://doi.org/10.3390/fire8060213
APA StyleWu, R., Liu, X., Wang, S., Song, X., Yu, H., & Guo, Z. (2025). Study on the Fire Prevention and Extinguishing Performance of Ammonium Polyphosphate-Reinforced Coal Cangue Slurry for Goaf Grouting and Filling. Fire, 8(6), 213. https://doi.org/10.3390/fire8060213