Experimental Study On The Tendeney Of Spontaneous Combustion Of Lignite

China is rich in lignite resources. Clean and highly-efficient utilization of low rank coal, such as lignite is more and more widely attention now. However, lignite is low degree of carbonization, good reactivity and easy spontaneous combustion. Thus the study on the tendency of spontaneous combustion of lignite has important significance for the clean and efficient utilization of lignite.In this paper the tendency of spontaneous combustion of Ximeng lignite, Indonesia lignite and several kinds of lignite from Xinjiang is mainly studied by a series of experiments, including coal quality analysis, scanning electron microscope(SEM), nitrogen adsorption, thermogravimetric analysis, static oxygen absorption test. The results are contrasted with Datong bituminous coal, Pingdingshan bituminous coal, Shenhua low ash bituminous coal and Yangquan anthracite. Finally some rules of the tendency of spontaneous combustion of lignite are summarized.It is found by scanning electron microscope that lignite has loose surface, well developed porosity and large surface area. So oxygen is easy to contact with the surface of coal, causing oxidation and spontaneous combustion of coal. Nitrogen adsorption experiment showed that the pore structure of lignite, such as Ximeng lignite, is mainly composed by medium-sized pores. The distribution of total pore volume and ratio surface area of coal decreases with the increase of coal rank. There is no direct relation between the aperture and the low-temperature oxidation of coal.By analyzing the TG and DTG curves, the whole process from coal oxidation to coal combustion could be divided into six stages:physical adsorption, water evaporation with losing weight, absorption of oxygen with increasing weight, thermal decomposition, combustion and burning out.And the characteristic temperatures of every stage were obtained. Analysis showed that the tendency of spontaneous combustion of the two lignite above mentioned was significantly greater than the other four bituminous coal and anthracite. Coats-Redfern integral method was used to analyze samples’ oxidative combustion dynamic characteristics. Activation energy of six coal samples was calculated to analyze the tendency of spontaneous combustion of coal. Calculations showed that the oxidation process of the six coal samples belonged to the first-order reaction, and the tendency of spontaneous combustion of the two lignite was greater. The tendency of spontaneous combustion of Ximeng lignite was influenced by particle size and oxygen density. Analysis showed that the smaller the particle size, the stronger the tendency of spontaneous combustion; the greater the oxygen density, the stronger the tendency of spontaneous combustion in general.With the increase of coal rank, the oxygen consumption during coal low temperature oxidation decreases. As temperatures rise, the oxygen consumption of Ximeng lignite increase significantly. And before100℃, oxygen consumption increases as temperature rises dramatically, after100℃, oxygen consumption increases slowly with the increase of temperature. The oxygen consumption of Ximeng lignite in low temperature oxidation increases with the increase of oxidation time. But when oxidation time is up to60min (just for this experimental conditions), oxygen consumption increases less significantly than before, explaining Ximeng lignite in this environment has been fully oxidized.