Microscopic mechanism of oxygen consumption inhibitor delaying the oxidation of coal

Abstract

In order to inhibit the coal-oxygen complex that triggers spontaneous coal combustion, a retardant consisting of sodium alginate solution, sodium bicarbonate, inorganic salt MgCl₂ and deoxidiser that can achieve multiple effects of hysteresis and oxygen depletion was developed. Taking the sulfur-containing side-chain reactive group of coal molecule -CH₂-SH as the object of study, the Gaussian 16W procedure and density-functional-transfer theory (DFT) were applied to investigate the electrostatic potential and reaction tendency, oxygen adsorption capacity, front-line orbitals, natural bonding capacity, and oxygen adsorption capacity of the reactive group before and after the formation of the complexes with Na⁺ and Mg²⁺, using the solvation effect at the level of B3LYP/6-31G(d, p), respectively. The changes of electrostatic potential and reaction tendency, oxygen adsorption, front orbitals, natural bonding orbitals and charge transfer before and after the formation of complexes between -CH₂-SH reactive groups and Na⁺, Mg²⁺, respectively. Comparative analysis of the interaction with oxygen before and after the formation of coordination blocking structure of coal and inorganic salts in gaseous environment, aqueous environment and retarded oxygen-depleting sodium alginate blocking solution environment, respectively. The calculated results show that the side chain of the aromatic ring of the raw coal is the active site for easy adsorption of oxygen, and the stability of the coordination blocking structure is significantly enhanced under the environment of hysteretic oxygen-depleting sodium alginate gel blocking agent, and the adsorption of oxygen before and after the coal molecule combines with Na⁺ and Mg²⁺ is the weakest under the environment of hysteretic oxygen-depleting sodium alginate gel blocking agent; The absolute value of the HOMO orbital energy increases the most, and the energy level difference (E_LUMO - E_HOMO) of the complexes increases the most; the natural bonding orbital analysis reveals that the lone pair of electrons of S atoms in -CH₂-SH under the environment of hysteresis oxygen depletion sodium alginate gel blocker has a strong coordination effect with Na⁺ and Mg²⁺. In the hysteresis oxygen depletion sodium alginate gel resist environment, the stability of the coordination blocking structure is strengthened due to the moderateness of the dielectric constant, and its oxygen depletion also reduces the number of O₂ molecules, which further reduces the adsorption and collision chances between the two, and a more desirable blocking effect can be obtained. The results reveal the micro-mechanism of the hysteresis oxygen depletion inhibitor in preventing spontaneous combustion of coal, which can provide a reference for further improving the inhibition effect of the inhibitor.