| Coal resource plays a leading role in Chinese primary energy.The basis for developing efficient pyrolysis technology of coal are comprehensive understanding of coal pyrolysis process,accurate description of coal pyrolysis characteristics and improvement of coal pyrolysis theory.The objects of study in this paper are LY bituminous coal of metallurgical power and QX lignite of industrial gasification.Thermogravimetric analysis is used to conduct non-isothermal experiments on two kinds of coal samples with heating rates of 5K/min,10K/min and 15K/min,respectively.According to the TG-DTG curve of thermogravimetric analysis experiment,the pyrolysis process of the two kinds of coals is studied,the weight loss of temperature intervals are divided reasonably,and the weight loss of each temperature interval is calculated.Then,the reasons for the formation of products in the pyrolysis process are analyzed.The kinetic parameters of different temperature ranges are calculated by Coats-Redfern method.According to the calculation results,the group with the highest fitting correlation coefficient is selected to determine the reaction mechanism of different temperature ranges and establish the kinetic model of pyrolysis reaction.The results show that the pyrolysis of LY bituminous coal at 150-300 ℃ and650-850℃ conforms to the spherically symmetric three-dimensional diffusion model,and the pyrolysis reaction level at 300-650℃ is 2.5.QX lignite is 150-300℃,the reaction series is 1,300-650℃,the reaction series is 2.5,and 650-850℃ conforms to the one-dimensional diffusion model.The self-designed fixed bed device is used to conduct the isothermal rapid pyrolysis experiment of coal at 850℃.The purpose is to analyze the distribution characteristics of the products generated during rapid pyrolysis of coal samples.CPD model is used to simulate the pyrolysis of two kinds of coal.CPD model is used to obtain the distribution characteristics of each product simulated by CPD,and the difference between CPD simulated data and fast pyrolysis experimental data is analyzed.The results show that the difference between the pyrolysis product yield of LY bituminous coal CPD simulated semi-coke,tar and gas and the fixed bed experiment ranged from 1.8% to 7.38%,and the difference of QX lignite ranged from1.42% to 18.19%.The simulated semi-coke values of the two coal samples are in good agreement with the experimental results,but there is a certain difference in the yield of tar and gas.This is that the secondary cracking of tar at high temperatures is not considered in the CPD model.The simulated value of tar is higher than theexperimental value,while the simulated value of gas production is lower than the experimental value.The difference between the simulated semi-coke data and the experimental data of the two coal samples is that the influence of ash content is not considered in the CPD modified model.Combining with the experimental results of the rapid pyrolysis of two samples in this paper,the modified function is fitted on the basis of CPD simulation results,which is convenient for industrial application. |
