| In the distribution of energy resources in China that are rich in coal,poor in oil,and low in gas,coal occupies an important position in energy consumption.With the improvement of safety awareness,coal mine safety accidents are decreasing year by year,but coal mine explosion accidents are still prone to causing a large number of casualties and severe property losses.Suppression of explosion is one of the methods to prevent and control explosion accidents,and it is also an effective means to reduce the serious consequences of explosions.The performance of explosion suppression materials in explosion suppression devices has a very important impact on the suppression effect of explosions.Bentonite,as a material with a large specific surface area and rich pore structure,can adsorb free radicals during the explosion reaction process.However,in the humid environment of mines,bentonite is prone to absorbing water and solidifying into blocks,unable to fully react with the substances during the explosion process,resulting in poor explosion suppression effect.Using calcium-based bentonite as the raw material,different types of spatial levitation enhanced explosion suppression bentonite materials were prepared through three modification methods:silane coupling agent surface modification,silica encapsulation modification,and quaternary ammonium salt intercalation modification.The changes in characteristics,anticaking performance,and explosion suppression performance of these three modified bentonite materials were explored.First,three different technical routes of anticaking modification were selected,and silane coupling agent KH560 with different concentrations was selected for surface modification.Tetraethyl silicate and ethanol solution were used as solvents,dilute hydrochloric acid as catalyst,and silica sol prepared in different proportions was coated and modified by sol-gel method.Different amounts of didodecyldimethylammonium chloride were added to prepare modified bentonite by intercalation,and it was analyzed and characterized using instruments such as Fourier transform infrared spectroscopy and scanning electron microscopy.The results showed that the modified bentonite obtained by different modification methods showed significantly different modification effects with changes in the concentration or proportion of the modifier.When the concentration of silane coupling agent KH560 is 4 wt%,the number of hydroxyl groups on the surface of modified bentonite decreases,hydrophobicity increases,interlayer spacing slightly increases,and spatial levitation is good;When tetraethyl silicate:ethanol=1:12.5,the particle size uniformity decreases and the particle size increases,but a hydrophobic covering layer is formed on its surface,which is beneficial for improving the anticaking effect of modified bentonite;When the addition amount of dodecyl dimethyl ammonium chloride reaches 0.5 times,the particle size distribution of the modified bentonite is uniform,and the agglomeration phenomenon is significantly weakened,showing a good anticaking effect.When the addition amount is 0.75 times,the infrared spectrum shows that the intercalation modifier has fully entered the bentonite layer.Secondly,three kinds of modified bentonite prepared under different modification conditions were placed in the laboratory normal temperature and humidity environment（20℃,30%RH）and humid environment（20℃,80%RH）respectively,and their spatial levitation rate was tested using the laboratory self-made spatial levitation test device,and the effect of different modification methods on the spatial levitation of bentonite was analyzed.The results showed that in laboratory and humid environments,the spatial levitation of modified bentonite in silica encapsulated silica solution with TEOS:Et OH:H2O=2:20:0.5 increased by 166.89%and 355.36%,respectively.In quaternary ammonium salt intercalation modification,the spatial levitation of modified bentonite increased by 146.62%and 269.64%when the amount of modifier added was 1.0 times,When the concentration of silane coupling agent in surface modification is 2 wt%,the spatial levitation of modified bentonite is improved by 14.86%and 88.06%,respectively.Finally,taking the results of pipeline explosion suppression test,differential scanning calorimetry and thermogravimetric analysis as evaluation indicators,the preparation method of modified explosion suppression bentonite used in coal mine was selected by combining the characterization results,spatial levitation,and other factors of the three modified bentonites.Compare and analyze the thermogravimetric test data on the effects of different modified bentonite on flame length,flame development time,and flame peak velocity in explosion suppression experiments.The results showed that with the increase of bentonite concentration,the flame length,maximum flame time,flame propagation speed,and flame peak speed of silane coupling agent surface modified bentonite improved,and the explosion suppression effect gradually increased;With the increase of bentonite concentration,the maximum flame length and peak flame velocity decrease slightly,and the explosion suppression effect is not significant;The quaternary ammonium salt intercalation modified bentonite gradually enhances its explosion suppression effect with the increase of bentonite concentration,and its suppression effect on the maximum flame length is very obvious.By comparing three types of modified bentonite,it can be concluded that using calcium-based bentonite with a cation exchange capacity of 0.75times that of dodecyl dimethyl ammonium chloride for intercalation modification can obtain modified explosion suppression bentonite materials that are suitable for coal mine environments and have good spatial levitation effects.This modified bentonite material helps to improve the effectiveness of bentonite explosion suppressants in the underground explosion suppression process of coal mines,and better ensures coal mine safety.There are 45 figures,12 tables and 97 references in this thesis. |
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