The Drying Characteristics Of Low-rank Coal Under Different Conditions

With the continuous developing of economy and society,coal is still dominant in the application of energy in our country,but coal is non-renewable resource,the reserves of high-rank coal with better quality is becoming more lower,the resource’ shortage problem has become a global hot issue.People have turned their attention to lignite that is abundant reserves,easy to mine and with low price,but its high water content has restricted its extensive use.Drying technology is an effective method to solve the lignite’s high moisture content problem effectively,we dried lignite by using heat of flue gases,not only improving the quality of lignite,but also can effectively utilize heat of flue gases,improve boiler efficiency and reduce flue gas emissions,the purpose of energy saving and profit increasing is achieved.The flue gas circulation can also take the water vapor away,and then the water resources can be recovered and utilized by condensation,which is of great significance to the arid areas of our country.In this paper,drying lignite by simulating flue gases was proposed.After drying,the dried samples were reabsorbed and characterized by FT-IR,SEM,BET and so on.The conclusions are as follows:(1)The oxygen groups(carboxyl and phenolic hydroxyl groups)in the surface decide moisture absorption of Zhundong coal after drying,physical structure of coal’s has little influence on its moisture absorption.(2)The drying of low rank coal can increase the maturity of organic matter of coal and improve the coal rank.In the oxidizing environment,the reactivity of the coal sample increases more than that in the inert atmosphere.(3)In the drying process of low rank coal,the main functional groups mainly based on decomposition in inert atmosphere,and the changes of functional groups is relatively complex in the oxidizing atmosphere,functional groups is mainly oxidized in low temperature stage and decomposed in the high temperature stage,which produce noncondensable gas and solid products.In infrared spectra,the hydroxyl groups in 3600-3000cm-1 are similar in two different drying environments.(4)The bond energy of aliphatic structure is weaker than aromatic structure,so it is easy to change.In an inert atmosphere,aliphatic structure is the first to break with heat energy.In an oxidizing environment,oxygen atoms first attack aliphatic compounds and take place oxidation reactions.