Preparation And Performance Research Of New Inhibitor For Preventing Coal Spontaneous Combustion

Mine fire is an important disaster accident of coal mine accidents in our country,which is mainly caused by coal oxidation spontaneous combustion,and The frequent occurrence of coal spontaneous combustion accidents and high tendency of coal seam spontaneous combustion in our country seriously threaten the safe and efficient mining of coal in our country,resulting in significant casualties and economic losses.With the continuous study on the mechanism of low temperature oxidation and spontaneous combustion of coal,scholars have gradually formed methods of prevention and treatment,such as grouting,inert gas,foam,gel,inhibitor and so on.Inhibitors,especially salt,are widely used owing to its wide sources?low cost?simplicity and practicality.However,problems such as easy to erosion?the single resistance effect?short service life?requires repeated spraying and plagued are troubling the safety production of coal in China.Therefore,it is particularly important to develop a new type of green and environmental protection inhibitors which are compound?synergistic?long inhibitory cycle and high efficiency.Based on the basis of previous research on the mechanism of coal spontaneous combustion theory,three kinds of coal samples with different metamorphic degrees were selected as the research objects,the preparation and application of flame retardant materials for preventing spontaneous combustion of coal seam and the optimization of flame retardant technology are the basic points of the study.The polyvinyl acetate emulsion was prepared,which was compounded with typical physical retardant superabsorbent polymer?SAP?and new chemical retardant Mg-Al layered double hydroxides to produce emulsion composite inhibitors.The microcapsule technology and aerosol atomization technology in the polymer flame retardant method were used as reference.Through the ZRJ-1 coal spontaneous combustion detector,programmed temperature gas chromatography,synchronous thermal analyzer and Fourier transform in-situ infrared spectrometer,the variation characteristics of oxygen uptake,crossing point temperature,oxygen consumption rate,exothermic intensity,formation rate of CO?CO₂?CH₄ and characteristic temperature point before and after treatment were explored.The inhibition rate and activation energy were used as measure to quantitatively investigate the inhibition performance of different concentration of inhibitors.Finally,the flame retardant mechanism of inhibitors to inhibit coal oxidation spontaneous combustion was deduced by combining the infrared spectra of coal samples and peak-splitting software.The experimental results show that:1)In the process of temperature programmed,the oxygen consumption rate,exothermic strength,CO?CO₂ and CH₄ production of coal samples with different concentration are far lower than that of raw coal samples.Compared withtheabovemacro-parametersofcoalspontaneouscombustion characteristics,it shows that the newly prepared inhibitor can well encapsulate coal,delay the reaction rate of coal oxygen,effectively prevent coal oxidation,and has a good inhibition effect for coal;The characteristic temperature points of coal samples after inhibition treatment are higher than that of raw coal,The activation energy of each temperature section of the flame retarded coal sample is greatly increased,and the whole process of oxidation spontaneous combustion is greatly delayed.Whether it is at the stage of low temperature oxygen absorption and weight gain or at the stage of high temperature thermal decomposition and combustion;the flame retardant with 20%concentration has excellent ability to inhibit the spontaneous combustion of coal.2)The inhibitor treated coal sample whether free hydroxyl,alcohol,phenol,the hydroxy carboxylic acid,hydroxyl hydrogen bond association,or fat on the side chain of methyl and methylene content decreased and The rate of lively methyl and methylene participating in coal-oxygen complex reaction at low temperature greatly reduced,which effectively prevents the oxidation of methyl and methylene,and increases the structural stability of coal molecule.As the temperature increases,the methylene peak shifts to the right obviously,leading to the hysteresis of coal reaction chains.LDHS can adsorb and complex with acid functional groups such as-COOH in coal macromolecule to form stable precipitation,which can improve the stability of C=O group in-COOH and delay the oxidation and decomposition of C=O and C-H functional groups.These mechanisms work together to improve the inhibiton effect of the inhibitor.