Study On Pyrolysis And Chemical Looping Combustion Reaction Mechanism Of Three Ningdong Bituminous Coals

Coal pyrolysis is the most important process in coal processing and the key technology to realize the efficient utilization of coal.To explore the influence of pyrolysis characteristics on coal pyrolysis process and control the distribution of pyrolysis products can achieve classification and high value utilization.Ningdong area of Ningxia is an important coal base in China.Deepening the understanding of the pyrolysis reaction mechanism of Ningdong coal can make more effective use of the rich coal resources in the western region,which is conducive to promoting the economic development and improving the ecological environment of the western region.In this paper,three kinds of Ningxia bituminous coal were taken as the research object to explore the reaction characteristics of low-temperature pyrolysis,and the change law of pyrolysis reaction was analyzed from vitrinite structure by using a variety of characterization methods.Two kinetic models,coats Redfern and DAEM,were used to reveal the pyrolysis mechanism.Finally,the combustion characteristics of vitrinite and CuFe2O4 OC of Ningdong bituminous coal were studied by chemical looping combustion technology,and the mechanism of chemical looping combustion was revealed by analyzing the changes of three kinds of coal coke.The main contents are as follows:(1)The vitrinite of hongshiwan coal,Qinghua coal and Zaoquan coal were separated and then pyrolyzed by TG.The results showed that the total weight loss rate of coal pyrolysis decreased.Using Coats-Redfern kinetic model,the activation energy E of three main pyrolysis stages was calculated,and it was found that the activation energy of coal pyrolysis increased with the increase of temperature.The Vadf of HSW vitrinite is higher than that of QH and ZQ vitrinite,so it has lower activation energy.(2)Three kinds of coal vitrinite were pyrolyzed by TG-MS at different heating rates of 5,10 and 15℃/min,and the pyrolysis reaction characteristics of vitrinite were investigated.The results show that the higher the heating rate is,the lower the weight loss rate is,and the temperature corresponding to the maximum weight loss rate moves to a higher temperature.With the increase of heating rate,DTG peak area and weight loss rate decrease,which indicates that higher heating rate can not fully react in the pyrolysis process of coal,resulting in partial structure can not be completely decomposed.The mass spectra show that with the increase of heating rate,the corresponding temperature peaks of the four pyrolysis gases shift to the high temperature direction,and the gas escape shows an upward trend.DAEM kinetic analysis shows that the activation energy of HSW coal ranges from 59.85 to 328.24 kJ/mol when the pyrolysis conversion is 0.1～0.9.The activation energy range of ZQ coal is from 63.24 to 440.28 kJ/mol and the activation energy of QH coal ranges from 78.41 to 540.33 kJ/mol.The kinetic parameters calculated by the two models are quite different,mainly due to the compensation effect of activation energy and pre exponential factor.The correlation coefficient R2 shows that DAEM is more suitable for coal pyrolysis kinetic analysis than coats Redfern model.(3)The oxygen carrier of CuFe2O4 was prepared and characterized,and the chemical chain combustion characteristics of vitrinite were studied under the φ of 1.The results show that the weightlessness rates of HSW,ZQ and QH vitrinite with CuFe2O4 OC are 8.06,6.97 and 6.14%respectively,the maximum weightlessness rates are 0.61,0.39 and 0.37%/min,respectively,which indicates that the reaction between HSW with CuFe2O4 OC is more intense.Finally,the char produced after chemical chain combustion of vitrinite is analyzed.The difference between vitrinite char and primary vitrinite after chemical chain combustion is revealed by XRD and XPS.The results show that the chemical chain combustion makes the lamellar spacing of the micro component char significantly reduced,and the stacking height and diameter of the microcrystalline structure of the aromatic layer increased significantly.There are same attribution peaks in the surface of coke structure before and after HSW and QH chemical chain combustion,while there are four kinds of C 1s in ZQ coal,but only three belong peaks after the chemical chain combustion,and can not found-COOH.