The impact of the combination of phytic acid and citric acid metal chelating agents on coal spontaneous combustion

This study investigates the influence of the metal chelating agents phytic acid,citric acid,and their combination on the spontaneous combustion of coal. Thermal analysis and infrared spectroscopy were employed to analyze the characteristic spontaneous combustion temperature points of coal samples and the changes in the content of active groups in coal after the addition of chelating agents. Furthermore,the inhibitory effects of the different chelating agents on coal spontaneous combustion were compared and analyzed. The results indicate that phytic acid,citric acid,and their combination exhibit inhibitory effects on coal spontaneous combustion. The ignition temperature of the coal sample treated with citric acid increased from 351. 10 ℃ to 360. 85 ℃,an increase of 9. 75 ℃. Additionally,infrared spectroscopy revealed that the contents of methyl,methylene,carboxyl, and hydroxyl groups in the coal were lower than those in the raw coal sample,indicating that the coal sample becomes more resistant to activation at room temperature, thereby inhibiting spontaneous combustion. The ignition temperature of the coal sample treated with phytic acid increased from 351. 10 ℃ to 383. 05 ℃,reflecting an increase of 31. 95 ℃. The overall decrease in the content of active groups in the coal was more pronounced than that observed in the citric acid-treated samples,suggesting that phytic acid is more effective in inhibiting spontaneous combustion. The ignition temperature of the coal sample treated with a combination of phytic acid and citric acid rose from 351. 10 ℃ to 394. 59 ℃,an increase of 43. 49 ℃. The content of active groups in this mixed treatment was further reduced compared to the individual treatments,demonstrating that the combined use of phytic acid and citric acid significantly enhances the inhibition of coal spontaneous combustion. Furthermore,an analysis was conducted on the complexation capabilities of the two chelating agents and their effects on the coal matrix. The interplay between the mixed chelating agents enhances their inhibitory effect on the spontaneous combustion of coal,producing a notable synergistic effect.