Design And Performance Of Composite Dust Suppressant Based On The Molecular Structure Of Bituminous Coal

Coal resources as China’s primary energy sources in the largest proportion of consumption sources,its status will remain difficult to replace.Coal dust control in coal mining has always been an important challenge affecting safe coal mining.For hydrophobic bituminous coal,traditional physical dust suppression methods are less effective and can hardly meet the mine’s requirements for coal dust suppression.It is found that surfactants can effectively wet the surface of coal dust,thus providing some dust suppression effect.Therefore,in recent years,chemical dust suppression methods have become one of the hot methods for coal dust control because they can significantly improve coal dust prevention and control effects,and their dust suppression mechanisms and technologies have also attracted the attention of coal industry dust control research.However,the existing chemical dust suppressants still have problems such as high cost and poor applicability to strongly hydrophobic coal dust.Based on the above,the surface microscopic molecular structure information of coal is obtained by combining industrial analysis of coal samples,Fourier infrared spectroscopy（FTIR）,nuclear magnetic resonance carbon spectroscopy(¹³C NMR),X-ray photoelectron spectroscopy（XPS）and other characterization test methods to build a molecular structure model of coal.The strong correlation factors between the molecular structure of coal dust surface and wettability are systematically analyzed by measuring contact angle,settling time and free energy of coal surface.The dust suppressant source material is improved through experimental studies,and molecular simulations are combined with indoor experiments to further investigate the coal dust surface wetting mechanism from the molecular scale.The widely used,natural and non-hazardous biomass xanthan gum with excellent performance is chosen as the main raw material for the binder.A biomass-modified binder is prepared by modifying xanthan gum with organic modifications.Six anionic and nonionic surfactants are compounded to determine the optimal ratio of wetting agents.Further,the wetting agent and binder are used as the main components of the composite dust suppressant,which makes the compound dust suppressant set wetting,bonding,cohesion and other functions in one,and has better environmental and economic benefits.In addition,the compound dust suppressant research method provides technical guidance and research ideas for scientific and efficient dust suppression in mines.The main results are as follows:（1）The microstructural characteristics of bituminous coal are revealed,and the molecular structure model of bituminous coal is constructed by the analysis of fine characterization means.The molecular structure of bituminous coal from Pingdingshan mine is dominated by hydrophobic aromatic hydrocarbons,with an aromatic bridge carbon to perimeter carbon ratio of 0.167,and the main aromatic units are benzene,naphthalene and anthracene.The aromatic carbon ratio is 76.89%,and the aromatic structure is a typical bituminous coal with benzene,naphthalene and anthracene as the main carbon skeleton.The fat structure exists in the form of methyl and methylene groups,and the ratio of the main hydrophilic groups C-O（ether bond and hydroxyl group）,carboxyl group and carbonyl group is about 8:1:2.The molecular structure model constructed to match the actual characteristics of the test coal sample has the molecular formula C179H142N2O12S.（2）The influencing factors of surfactant wetting of coal dust are obtained,and the wetting mechanism involved in the coal-surfactant-water system is revealed.Anionic and nonionic surfactants can achieve effective modulation of bituminous coal surface wettability,with nonionic surfactants having stronger wettability than anionic surfactants for bituminous coal dust.The shortest settling time is obtained for the nonionic surfactant tralatone X-100,with a critical micelle concentration（CMC）of about 0.2%.The adsorption of surfactants on the coal surface can significantly increase the polar component of free energy on the surface of bituminous coal,and the same type of surfactant can be used to determine its wetting ability on coal dust byΔG_sl^{A B}.（3）Based on the molecular structure of bituminous coal and the wetting mechanism of the hydrophobic structure of surfactant,a composite dust suppressant molecule rich in polyhydroxyl groups and containing aromatic rings is designed,and the surfactant compound formulation is preferred.The compounding solutions between the nonionic surfactant fatty alcohol polyoxyethylene ether JFC,isooctanol polyoxyethylene ether JFC-E and octylphenyl polyoxyethylene ether X-100 produce a wetting synergistic effect at a mass ratio of 2:2.The solution viscosity required for coal dust agglomeration is achieved with 0.04%and 0.06%modified xanthan gum（XGTCS）solutions,while ensuring the solution fluidity.The compound dust suppressant formulation is determined to be 0.2%JFC-E+0.2%X-100+0.06%XGTCS.The time required for wetting and settling 100 mg of coal dust in 25 ml solution is 23 s,the viscosity of the solution is 11.7 m Pa·s,and the average evaporation rate of water is 0.18g-m^-2-s^-1,which indicates that it has good wetting,bonding and water retention properties and meets the actual needs of dust suppression on site.