Analysis Of Factors Affecting The Fragmentation Of Lignite In Drying Process

China’s lignite resources are about 130 billion tons of geological reserves,and it has severely limited the widespread application of lignite due to its high moisture content of 25-65%.Therefore,drying technologies has become the key to the efficient utilization of lignite.Among those technologies,there are different degrees of fragmentation and pulverization.In this paper,the effects of temperature(final drying temperature and heating rate),particle size and drying time on the fragmentation of lignite in fixed bed were studied.The causes of fragmentation were analyzed based on the physical factors such as moisture,particle strength and mineral composition contents of lignite.This paper explores the fragmentation characteristics of Mengdong(MD),Xiaolongtan(XLT),and Zhaotong(ZT)lignite at a temperature of 100°C-200°C,a particle size of 13-2mm,a heating rate of 1-10°C/min,and a drying time of 0-90 min.The results showed that the fragmentation rates of different lignite were ZT>XLT>MD,but the content of total pulverization rate was less.The content of fine particles of MD lignite was more compared with that of XLT and ZT.With the increase of temperature,particle size and drying time,the partice size change rate of MD and XLT decreases and fragmentation rate increases.Similiarly,the fragmentation degree of ZT increases with the increase of temperature and drying time.However,as the particle size increasing,the particle size change rate increases and the fragmentation rate decreases.The point load test revealed the change of compressive strength of lignite particles.The results showed that with the increase of drying time and temperature,the compressive strength of particles gradually decreased,and there was a negative correlation between compressive strength and fragmentation rate of lignite.By analyzing the relationship between loss of moisture and fragmentation,it is found that there is a positive relationship between fragmentation rate and dewatering moisture.Based on this,the distribution of initial moisture content in pores is explored.It indicates that the moisture in macropores is mianly responsible for the fragmentation and the effect of moisture in micropores on fragmentation is negligible.Comparing the fragmentation rate of lignite with different density,it can be found that the fragmentation degree of high-density lignite is small,and the pulverization rate of lignite at each density level is lower than 0.5%.XRD was used toanalyze minerals with different densities of lignite.The results showed that the main mineral compositions of different density lignite were quartz,kaolinite,gypsum,muscovite,feldspar and hematite.XRF was used to analyze the main mineral element composition of different density lignite.It showes the proportion of main mineral elements in different lignite was different and the variation trend of the main mineral elements in the same lignite with density was also different.This paper based on the analysis of the main elements content of lignite minerals,combined with the physical properties of the minerals(moisture content,ash content)to infer the mathematical prediction model of lignite fragmentation characteristics.