Characteristics And Kinetics Of Pyrolysis Inferior Lignite

Yunnan is one of the main producers of lignite in our country, and more of that is the young lignite which has big moisture、more ash and low utilization rate, so the study of the inferior lignite pyrolysis characteristics of coal in power plant has very important guiding significance.This paper mainly study the three kinds of lignite which is xiaolongtan A,xiaolongtan B and xianfeng coal, which investigates the influences of pyrolysis characteristics as the different reaction conditions.Firstly, this paper does pyrolysis experiment of three kinds of lignite by using the thermal gravimetric analyzer in different heating rate (10k/min, and k/min,30k/min), coal particle size (0.074mm,0.15mm and0.37mm) and reaction atmosphere (nitrogen atmosphere and air atmosphere),which get that the maximum pyrolysis rate has significantly increased with with the increase of heating rate; the final weight loss is reduced with the increase in the particle size of pulverized coal; the generation amount of the pyrolysis product is increased as the increase of pyrolysis temperature and the generation amount of the pyrolysis product is the fastest between400℃to600℃and the pyrolysis is the most intense; The pyrolysis characteristics from good to bad is Xiaolongtan coal B, Xianfeng coal and Xiaolongtan A coal.Secondly, we derive that the derivation of the Coast-Redfern integration method and Ozawa integral method have the premise which is that the activation energy E and reaction mechanism function f (a) does not change. Therefore, these two integral method can only be applied to the reaction which the activation energy and reaction mechanism function does not change. While differential method of Kissinger method is although simple operation and has good data reproducibility, but it needs to be involved for the maximum reaction rate in the calculation, so it is suitable for the treatment of the DTA and the DSC curve instead of TG curve.Thirdly, We calculate the three coal samples reaction mechanism functions in pyrolysis of30K/min heating rate, then we get that Xiaolongtan A coal and Xianfeng B coal is three-dimensional diffusion-reaction mechanism model in the low temperature range, and the reaction mechanism functions is f(a)=3/2(1-α)4/3((1-α)-1/3-1)-1.Also the model is two-stage chemical reaction mechanisms model in the high-temperature, and the reaction mechanism is f(α)=(1-α)2. Xionglongtan B coal is three-dimensional diffusion-reaction mechanism model in high temperature section and the low-temperature range.At last, We solve the three coal pyrolysis reaction kinetics model in the case of the known reaction mechanisms function and verified the results of the solution. Then we get that the activation energy of Xiaolongtan A coal is53.71kJ/mol in the low temperature range, and the activation energy of Xiaolongtan A coal is47.32kJ/mol in the high temperature range; The activation energy of Xiaolongtan B coal is50kJ/mol in the all temperature range; The activation energy of Xianfeng coal is66.76kJ/mol in the low temperature range, and the activation energy of Xianfeng coal is39.26kJ/mol in the high temperature range.