| Coal spontaneous combustion affects seriously the safety of coal mining,threatens staffs health,and also be able to cause the waste of coal resources.Spraying inorganic salt inhibitor is a coal spontaneous combustion prevention technology which has the characteristics of economic,practical,easy operation and wide application.The research main line of the technology is improving inhibitor property on the premise of controling the production cost.At present,the action mechanism of inhibitor has a few of researches.In this paper,the mechanism of Zn2+restraining the oxidation of ?-thiophenol structure in coal is analysed thoroughly,which lay a foundation for selection and optimization of inhibitor.The coal of Dongqu,Malan and Tunlan were selected as the experimental coal sample,ZnCl2 is used as the experimental inhibitor,and MgCl2 is used as reference inhibitor.The effect of ZnCl2 solution restraining coal oxidation and spontaneous combustion was analysed comparatively through thermogravimetric experiment.The results of thermogravimetric experiment show that the MgCl2 solution is better than the ZnCl2 solution in the effect of maintaining coal moisture.But in the effect of restraining coal adsorbing O2,ZnCl2 solution is far higher than that of MgCl2 solution.Using the Gaussian 03 program,the coordination and stability between Zn2+ and?-thiophenol structure in coal are analyzed contrastively with the coordination and stability between Mg2+ and ?-thiophenol structure in coal by using density functional theory(DFT)method at the B3LYP/6-31G(d,p)level.The results show that the coordination between Mg2+and ?-thiophenol structure in coal is very weak,while the coordination bond is unstable and easy to be destroyed when O2 close to coordination complex[MgSH8C10]2+.However,the coordination between Zn2+ and ?-thiophenol structure in coal belongs to ionic bond,which can be able to hinder ?-thiophenol structure in coal interacting with O2,and it is steadily.Then this paper analysed the mechanism of Zn2+restraining ?-thiophenol structure in coal C10H7SH reacting with O2 at the same level.The calculation results show that the process of ?-thiophenol structure in coal C10H7SH reacting with O2 has roughly the same isomerization course with the process of coordination complex[ZnSH8C10]2+reacting with O2.Under the Zn2+ coordination,the heat are decreased 14.92 kJ·mol-1 which release from ?-thiophenol structure in coal C10H7SH adsorbing O2 by van der Waals interaction,and the activation energy of the whole reaction are increased 47.62 kJ·mol-1.At the same time,all chemical potential barriers in the reaction prosess have also been improved.The first chemical potential barrier that the oxidation reaction with Zn2+coordination need overcome is higher 32.70 kJ·mol-1 than that without Zn2+coordination,and the second chemical potential barrier is increased 30.79 kJ·mol-1,and the third chemical potential barrier is increased 9.28 kJ·mol-1.Consequently,Zn2+ has inhibition mainly in the adsorption and oxidation phase of ?-thiophenol structure in coal reacting with O2,and gradually lose with the reaction process. |
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