| Coal spontaneous combustion causes mine gas explosion and coal dust explosion,which threatens human health and life,cause serious waste of resources and destruction of ecological environment.Coal oxidation spontaneous combustion is a complex physical and chemical process,which has experienced different oxidation stages of low temperature physical oxygen absorption and high temperature chemical oxygen absorption.Therefore,developing an inhibitor to inhibit the whole process of coal oxidation is an effective technical means to prevent and control coal spontaneous combustion.Phosphorus containing compounds have high flame retardant efficiency and good compatibility,which are often used as acid source and other flame retardant elements to form multi-source integrated flame retardant.Sodium alginate has good biodegradability and stable chemical properties,which is easy to form a gel film.Based on this,on the basis of previous research results,a “threesource integrated” chemical inhibitor based on phosphorous compound was developed,a multifunctional physical inhibitor based on sodium alginate was developed by using the basic theories of thermodynamics and materials science.A compound inhibitor with self activation performance and physical and chemical retardation was developed by optimizing the ratio,and its performance and synergistic retardation characteristics were studied.Gas chromatography experiment,gas production and cross point temperature of coal retarded by different phosphorus compounds were evaluated by temperature-programmed.The results indicate that,phytic acid(PA)has good inhibition effect on coal spontaneous combustion,and it is determined to be the base material for the development of chemical inhibitor.The concentration changes of Ca,Fe,Mn and other metal elements after treated with deionized water and PA were analyzed by XRD and ICP-MS.The results indicate that,PA has strong chelation on metal elements that catalyze spontaneous combustion of coal,especially Fe.Using PA as acid source,a "three-source integrated" PA/CS/TA chemical inhibitor was developed by introducing carbon source and air source using aqueous molecular self-assembly technology.With the conductivity as the index,the optimal concentration of each component was determined by single factor and orthogonal experiment,phytic acid(PA)was 0.7wt%;chitosan(CS)was 1wt%;tannic acid(TA)was0.5wt%.It is found that PA/CS/TA inhibitor has obvious expansion characteristics through thermal oxidation experiments.By means of Fourier infrared spectroscopy,the migration characteristics of coal functional groups were analyzed,and the microscopic mechanism of PA/CS/TA retarder inhibiting coal spontaneous combustion was revealed.A multifunctional and efficient gel which as a physical inhibitor to Inhibit spontaneous combustion of coal(SA/GEL/PVA/GL)was developed.The fluidity,mechanical properties and water retention and water absorption capacity of the gel were evaluated by determining the viscosity,tensile strength,elongation at break,water loss rate and water absorption ratio of the gel,the optimal ratio of each component was determined.The results show that,Sodium alginate has the greatest effect on the fluidity of gel base solution.The concentration of crosslinker has significant effect on the mechanical properties of the gel system,When the concentration of crosslinker was 2%,the mechanical properties of gel were the best,the tensile strength was 6.25 MPa and the elongation at break was 286.07%.Gel has a lower water loss rate under different temperature conditions.With the increase of the concentration of crosslinker,the water loss rate of gel decreased obviously.When the concentration of crosslinker was 2%,the gel lost water was only 38.5% at 90℃,that indicate the gel had excellent water retention and heat resistance.The double cross-linked network structure formed in the gel by chemical crosslinking makes the gel dry film have the properties of reabsorbing water and swelling,and the maximum water absorption ratio was 37.73g/g.Based on the pressure difference method,the oxygen permeability coefficient of the crosslinked gel decreased by 76% compared with the pure sodium alginate,indicating that the oxygen isolation ability of the gel was significantly improved.The gel has strong selfhealing ability,which can self-repair the damage in about 1min,prolonging the resistance life,and has good environmental adaptability.The effect of gel on pore structure of coal was compared and analyzed by using low temperature liquid nitrogen adsorption method.Gel can significantly reduce the number of micropores,pore volume and pore specific surface area in coal,and reduce the oxygen adsorption capacity of coal.The index gas,characteristic temperature point and apparent kinetics of raw coal samples retarded with composite inhibitors(SA/GEL/PVA/GL-PA/CS/TA),PA/CS/TA and PA were measured,and the inhibition characteristics of different inhibitors on spontaneous combustion of coal were analyzed.The CO production and initial release temperature were significantly reduced and delayed by composite inhibitors.The characteristic temperature points of different oxidation stages were increased,the heat release of coal oxidation process was reduced obviously by composite inhibitors.The peak endothermic temperature of coal retarded with composite inhibitors was increased 41.9℃,27℃,20.3℃ compared to the lignite,coal sample retarded with PA,coal sample retarded with PA/CS/TA.The activation energy of water evaporation stage and oxygen absorption weight gain stage were increased67.84 k J/mol 和 87.14 k J/mol compared to the lignite.The results show that,the inhibition effect of compound inhibitor on lignite and gas coal is obviously better than that of single inhibitor PA/CS/TA and PA.Inhibition effect on coal at low temperature oxidation stage has been significantly improved and at high temperature oxidation stage also shows a good inhibition effect.The whole process of coal spontaneous combustion from low temperature to high temperature is realized.Figure 94;Table 36;Reference 184... |
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