Effect Of Fe、Ca、Al On Structural Thermal Evolution And Spontaneous Combustion Tendency Of Shengli Lignite

Taking Shengli lignite as the research object,the effects of Fe,Ca and Al on the thermal evolution and spontaneous combustion tendency of Shengli lignite structure were investigated.Firstly,the experimental coal samples were pyrolyzed at different temperatures and inert gas atmospheres to make structural thermal evolution.Then,the combustion performance experiments of coal/coke were carried out in a fixed-bed reactor by temperature-programmed and isothermal gradient isothermal experiments.Using FT-IR,Raman,XRD and other characterization methods to determine the coal/coke structure changes and spontaneous combustion tendency.For the Fe-containing coal/coke:The coking temperature ranges from room temperature to 400℃.Fe can significantly increase the combustion performance of Shengli lignite,and the structure of the char no significant changes have been made;The coking temperature ranged from 400℃ to 700℃,and various oxygen-containing functional groups in coal gradually disappeared as the coking temperature increased.The main structure of coal char changes from low polyaromatic structure to high polyaromatic structure;The coking temperature ranged from 700℃ to 900℃.The coal char structure gradually evolved from a high polyaromatic structure to a carbon microcrystalline structure,and the degree of graphitization of coal coke increased rapidly.FT-IR showed that the vibrational absorption peak of the C=C skeleton of the benzene ring in coal was significantly weakened at 700℃,and the benzene ring skeleton was broken.Fe can not only increase the spontaneous combustion tendency of low-temperature coke for Shengli lignite,but also increase the spontaneous combustion tendency of high-temperature coke for Shengli lignite.The experiment of Ca-containing coal/coke shows that the coking temperature is in the range of room temperature to 400℃.Ca promotes the combustion of high polyaromatic structure in coal,and the main structure of coal char does not change greatly.The coking temperature ranged from 400℃ to 700℃.The composition of low polyaromatic structure in coal gradually evolved toward high polyaromatic structure.The coking temperature ranged from 700℃ to 900℃,The high polyaromatic structure evolves towards the carbon microcrystal structure,and Ca can slow down the graphitization process of the high temperature coke of the Shengli lignite and inhibit the evolution of the high polyaromatic structure to the carbon microcrystal structure.FT-TR showed the vibration absorption peak and aroma of the benzene ring C=C skeleton in coal at 700℃.The ring’s stretching vibration absorption peak rapidly weakens.Ca can significantly slow down the graphitization process of the high-temperature coke of the lignite.There are still about 50%of the high-polyaromatics structure in SL~+-Ca-900.Ca can significantly increase the spontaneous combustion tendency of Shengli lignite coke.The experimental results of aluminum-containing coal/coke show that:The coking temperature ranged from room temperature to 400℃,and the various structure in the coal became more difficult to burn under the influence of Al.The structure of the coal sample did not change significantly within this temperature range;the coking temperature was between 400℃ and 700℃,the main structure of coal char changes from the low polyaromatic structure to the high polyaromatic structure;the coking temperature is in the range of 700℃ to 900℃,and the main structure of char is evolved from a highly clustered structure toward a carbon microcrystal structure.Al can reduce the spontaneous combustion tendency of low-temperature coke in Shengli lignite,and increase the tendency of spontaneous combustion of high-temperature coke in Shengli lignite.