Study On Variation Law Of Chahasu No.3 Coal Pore Characteristics Under Low Temperature Oxidation

Coal mine fire is one of the five major disasters in coal mine,according to statistics,In coal mine fires,coal spontaneous combustion is one of the main factors.During the whole process of spontaneous combustion of coal,the specific structural changes of coal have not yet been clearly explored,and the low temperature oxidation process is the initial stage of spontaneous combustion.The whole process of coal has changed a lot in both macro and micro,including coal strength,calorific value,oxygen uptake,output gas,pore structure,a series of changes in functional groups,etc.,which are closely related to the pore structure of coal.Due to the long formation of coal and the huge differences of coal geological and environmental conditions,resulted in the diversity of coal and non-uniformity in the internal structure of coal pore.There are many methods to measure the porosity parameters.Among them,mercury intrusion is one of the most commonly used equipment.In this paper,the porosity characteristics of Chahasu No.3 coal after different oxidation treatment are studied by mercury porosimeter.In order to study the porosity characteristics of coal samples under low temperature oxidation,four kinds of coal with different diameter were selected from Chahasu No.3 long flame coal,the coal belongs to non-caking coal(BN31)and small amount of long flame coal(CY41),then used mercury porosimeter to measure pore structure,the main research contents:(1)Study on the pore volume characteristics of coal with different temperature and time oxidation treatment;(2)Characteristics of pore specific surface area of coal treated by oxidation at different temperatures and times(3)Variation of fractal dimension of Chahasu No.3 Coal at low temperature oxidation.The experimental results show that the results of the study are as follows:(1)With the increase of temperature,the pores in the coal sample are further developed and the pore volume increased with the temperature increasing;(2)Analyzed the change of the pore volume ratio with the temperature,four different types of holes,the variation trend of small holes and large holes is opposite.The pore size of coal samples is mainly distributed with small holes and large holes,(3)The total specific surface area of coal increased with the increase of the temperature.The influence of the total specific surface area of coal samples is mainly transitional pore and micropores,and the change tendency of the two is the opposite;(4)The fractal dimension of four coal sample changed with temperature,it is concluded that the fractal dimension of coal sample increases with temperature at 25~50 ? and decreases at 50~75 ? stage,Indicating that the surface of the coal first rough,and then become smooth.