Study on inhibition of coal spontaneous combustion by ethylenedia mine tetraacetic acid microcapsule

The frequent occurrence of coal spontaneous combustion poses a serious threat to the safety of coal mine production. Inhibitors have played an important role in preventing and controlling spontaneous combustion of coal. Microcapsule material is a composite fire extinguishing material with good effect of preventing spontaneous combustion of coal. In this paper,polyethylene glycol 6 000 (PEG6000) is selected as the wall material and ethylenediaminetetraacetic acid (EDTA) as the core material,and the core-to-wall ratios of 1∶2,1∶3,1∶4,1∶5 microencapsulated EDTA. The surface morphology of the microcapsules was characterized by SEM. The results showed that PEG6000 was effectively coated on the surface of EDTA,and a new type of PEG6000-EDTA inhibitor microcapsules was successfully prepared. The effects of different core wall specific inhibitor microcapsules on the spontaneous combustion characteristics of coal samples were studied by thermal analysis experiments. The phased characteristics of the inhibited coal samples and the heat release law of the characteristic temperature points were mastered. Combined with thermokinetic parameters,the inhibition mechanism of microcapsules with different core wall ratio on coal spontaneous combustion was analyzed. The results show that the thermal reactivity and inhibition mechanism of microcapsules with different core wall ratio are different,and the effect is the best when the core wall ratio is 1∶3. It is determined that ethylenediamine tetraacetic acid microcapsule inhibitor has chemical inhibition effect on coal spontaneous combustion. It can reduce the weight loss rate of coal,increase the T1 and T3 temperatures by 12 ℃ and 34 ℃ respectively,and greatly reduce the heat release in the range of 30-200 ℃ and 325-683 ℃. The calculation of apparent activation energy shows that in P1 and P3 stages,the activation energy of inhibited coal samples is 22.96 kJ/mol and 54.98 kJ/mol respectively,which is 4.14 kJ/mol and 13.04 kJ/mol higher than that of raw coal respectively. It is proved that the inhibition microcapsule can effectively improve the activation energy and inhibit the spontaneous combustion of incoming coal. The research shows that EDTA microcapsule inhibitor has a good inhibitory effect on coal samples and can effectively inhibit the process of coal spontaneous combustion reaction.