Study On Surface Hydrophobic Modification And Slurribility Of Coal By Paraffin And Paraffin Emulsion

Coal-water slurry(CWS),a kind of liquid fuel,can be conveniently stored and transported,and can also improve the utilization efficiency of coal resources and reduce environmental pollution.It is well known that low-rank coal,such as lignite,accounts for a large proportion of global coal resources.Therefor,the applacations of low-rank coal for preperation becomes a key topic.However,because of containing a large number of oxygen-containing functional groups,low-rank coal is highly hydrophilic and with rather high internal water content.Moreover,the developed pore structure of low-order coal will cause a severe resorption phenomena of the free water in the pulping process.These two factors lead to the poor slurryability of low-rank coal,limiting its development and utilization.In this dissertation,the surface modification of the Inner Mongolia coal was carried out by means of the combination of microwave dewatering and surface physical coating modification,compared with the Binchang coal with higher coal rank.The surface properties of the two modified coal particles were analyzed,and the pulp properties of both were measured.First,the ground coal sample with a certain particle size distribution was put into a microwave oven to dehydrate until the mass was constant.Then the dried coal samples were modified with paraffin petroleum ether solution,cationic emulsified paraffins,anionic emulsified paraffins,and non-ionic emulsified paraffins,respectively.The determination results show that each modifier can be adsorbed on the surfaces of two kinds of coal particles.The Inner Mongolia Coal has the best adsorption effect with paraffin petroleum ether solution,and the adsorption film thickness is 4.85 nm,while the adsorption filmthickness of non-ionic emulsified paraffin on the Bingchang coal is the maximum of 1.82 nm.Secondly,the surface properties of the coal particles before and after modification were determined by means of contact angle measuring instrument,zeta potential analyzer,specific surface area analyzer and constant temperature and humidity chamber,and the results show that the coal characteristics of each coal particle after modification has different degree of improvement compared To that of raw coal particle.Among them,the Inner Mongolia Coal modified by paraffin has the most obvious improvement effect in contact angle,porosity and water absorption rate,etc.,compared to that of raw coal,and the Bingchang coal modified by non-ionic emulsified paraffin has the most obvious improvement effect in surface properties.Finally,the CWSs of all of the above coal particles were prepared in the presence of naphthalene sulfonate dispersant,respectively.The slurryabilities and stabilities of the slurries were analyzed by rheometer and stability analyzer,etc.The results show that the slurryability and stability of the Inner Mongolia Coal modified by of paraffin wax are the most obviously improved,and its maximum pulp concentration increases from 55.0% to 62.0%,increasing 7 percent.While the Bingchang coal modified by non-ionic emulsified paraffin has the best slurryability and stability as well as its maximum slurry concentration increases from 62.5% to 66.0%,increasing 3.5 percent.In conclusion,in this dissertation,the coals,especially low-rank coal,have certain improvement effects in surface property and slurryability.It will pave the way for the improvement of coal characteristics and the development of CWS technology.