Research On Dehydration And Quality Improvement Of Low-rank Coal Based On Instantaneous Release Of High Pressure Steam

With society’s continued growth,greater emphasis has been placed on the development and utilization of low-rank coal.However,the low-rank coal has a high water content and its direct utilization calorific value is low.beside it also brings a lot of inconvenience to storage and transportation.In this paper,the method of instantaneous release of high pressure steam was used to study the dehydration of two low-rank coals of lignite and non-caking coal with different particle sizes to obtain the law of moisture removal,pore structure and functional group changes with test parameters;and the differences were investigated.The law of moisture resorption of samples with different pressures of the same size and the same size at different Pressures and humidity,the effect of instantaneous release pressure and sample particle size on moisture resorption characteristics is explained,and a suitable isotherm adsorption model is selected to analyze the resorption process.The main conclusions are as follows:(1)The release of the high pressure steam instantaneous can remove moisture from low-rank coal.For the 13-6 mm particle size,the moisture removal rates of lignite and non-stick coal are 62.04% and 42.35%,respectively;instantaneous pressure has an significant effect on moisture removal.As the test pressure rises,the moisture content of lignite and non-stick coal steadily decreases and the moisture removal rate increases;the pressure holding time has an effect on the moisture removal,and the moisture content of the test sample becomes first as the pressure holding time increases.The tendency to increase after decreasing.The two low-rank coals have the highest free water content.After high pressure steam instantaneously releases,more free water and capillary water can be removed,and the combined water is also reduced to a certain extent.The moisture of lignite and non-stick coal is mainly stored in the small pores,the micropores are secondary,and the middle and large pores have less water,and the instantaneous release of high pressure steam has a better effect on the removal of water in the small,middle and large pores.(2)The instantaneous discharge of high-pressure steam can expand the pores of low-rank coals.With the increase of instantaneous discharge pressure and holding time,the proportion of pores and large pores in the sample increases after the test,and the pressure and time are positively correlated with the pore size.Comparing the samples before and after the test,there is little difference in the content of functional groups,and the impact of instantaneous release of high pressure steam on the functional groups is small.(3)With the increase of instantaneous discharge pressure,the moisture resorption rate of each sample increases gradually at equilibrium,and the time to reach moisture resorption equilibrium decreases;as the particle size of the sample decreases,the shorter the time required for moisture adsorption to reach adsorption equilibrium,the shorter the time to reach moisture resorption equilibrium.The resorption Pressure and relative humidity have a significant effect on the resorption of the two low-rank coals.The equilibrium moisture content gradually increases with the increase of the resorption Pressure,and the time to reach the equilibrium moisture resorption decreases;the relative humidity of the resorption increases,and for the samples of two kinds of lowrank coals,the equilibrium moisture resorption rate of each sample of rank coal increases,and the time to reach equilibrium decreases;(4)Both low-rank coals belong to type II adsorption.The Dent model has a good adsorption fitting effect on the two coal samples.The coal samples are divided into two layers of adsorption.The adsorption capacity of the first layer increases with the increase of relative pressure.The low relative pressure section increases rapidly;the middle and high relative pressure section,the second layer of adsorption plays a leading role.There are 48 figures,6 tables and 98 references in the thesis.