Studies On The Process Of Structure Change And Reactivity Of Zhundong Coal Char By Microwave Pyrolysis

Coal pyrolysis is an important technology of the clean utilization of coal, andthe original and coupled reaction of combustion and gasification. However，Therehas been so many disadvantages such as low efficiency of energy utilization，lots ofenvironment pollution, poor quality of chars with the conventional method of coalpyrolysis. It has been proved that coal microwave pyrolysis technology canabsolutely take place of the conventional pyrolysis by reseachers in future. Butprevious research are mainly involved in the temperature rise property of themicrowave field, oil and gas production ratio, and less in the characteristics of thesolid char by microwave pyrolysis, not to mention the change of the char structureand chemical reactivity. Base on this background, this paper focus on the changeregularity of the char during microwave pyrolysis and the combustion andgasification reactivity, compared to the conventional pyrolisis. Hope that this papercan provides theoretical basis and data support for the future microwave pyrolysisresearch.Firstly the Zhundong coal has been selected to make the char in the horizontalfurnace and microwave experiment furnace at different temperatures. It has beendiscussed that the change of the surface functional groups of coal char in theprocesses of the different pyrolysis with the method of the FTIR. Thethermostability of different oxygen functional groups in both microwave pyrolysisand conventional pyrolysis are C-O<-COOH<C=O<-OH. MW char has a shortaverage chain length than RP char and a smaller aromatic content.Then it has been discussed that the change of pore structure of coal char in theprocesses of the different pyrolysis with the method of N2adsorption and SEM. Theaverage pore diameter of RP char at different temperature changes a lot. The porevolume and specific surface area of MW char and RP char increase first, thendecrease and finally increase and they are larger than ZD raw. RP char has a largerpore volume than MW char at different pyrolysisi temperatures, and specific surfacearea varies with the pyrolysis temperature changes. This paper come up a totallynew coal pyrolysis model, which can explain the every step of the microwavepyrolysis. MW char pore structure is simple, with lots of cylindrical pore and littlecracks.Finally the reaction of combustion and gasification of MW char and RP charhas been discussed. The reasons have been analyzed that MW char has a smallerignition temperature and larger burnout temperature than RP char. The combustionreaction activation energy of different char has been calculated and it shows that the combustionreactivity of MW char is superior to RP char. The reasons have beenanalyzed that the fixed carbon conversion and specific gasification reaction rate ar elarger than RP char. The gasification reaction activation energy of different char hasbeen calculated and it shows that the gasification reactivity of MW char is superiorto RP char. The difference of the gasification reactivity of char in the same pyrolysisat different temperature has been discussed, and the activation energy of differentchar show: RP700>RP900>RP800，MW700>MW900>MW800.