Study On The Kinetics Of Fluidized Combustion Reaction Of Oil Shale Semicoke

Oil shale semi-coke is a hazardous waste product formed during thermal processing of the oil shale,which has a certain calorific value.The way of burning not only uses the residual heat of the semi-coke,but also reduces its harm to the environment.Based on the related research of the semi-coke characteristics of oil shale in the previous period,this article adopts the kinetic analysis method,toke the combustion characteristics of activated carbon particles as a reference,and applied different combustion devices to conduct in-depth research.The general rule of combustion is obtained by analyzing the influence of different heating rate and different final temperature.The kinetic parameters of the sample were calculated to obtain the characteristics of the activation energy of the sample as a function of conversion.The AKTS software was sent to draw the constant temperature combustion curve by simulation and prediction,which compared the results of weight loss curve at constant temperature in fluidized bed and fixed bed.At the same time,the characteristics of fluidized combustion were obtained by analyzing the gas release characteristics of the semi-coke fluidized combustion under different combustion conditions.Thermogravimetric analyzer was used to study the combustion characteristics of activated carbon and Longkou semi-coke from the heating rate.The TG-DTG curve showed that the semi-coke combustion process was divided into two stages,while the activated carbon combustion process has only one stage.With the increase of heating rate,each peak of weight loss gradually broadened,the peak became larger,and the combustion curve moved to the high temperature segment.At the same time,the ignition and the burnout temperature rose when the reaction rate per unit time increased,which resulted each combustion evaluation index value going up.The FWO method and Friedman method were used to study the kinetics of activated carbon and Longkou semi-coke.The results showed that the two algorithms presented the same rule.The Popescu method inferred that the activated carbon combustion conforms to the anti-Jander three-dimensional diffusion model,and the semi-coke combustion corresponds to the Avrami-Erofeev model.The constant temperature combustion test of activated carbon and semi-coke were carried out using a batch fluidized bed and a self-made U-tube fixed bed.The results showed that the activation energy of non-isothermal combustion of activated carbon could be used as a reference for the initial stage of fluidized combustion,while the thermostatic constant temperature combustion had a certain degree of correlation with U-tube fixed-bed combustion.For semi-coke,the activation energy obtained by fluidized combustion and fixed-bed combustion were smaller than the activation energy of non-isothermal combustion of thermogravimetry.From the comparison between the predicted weightlessness curve and the weight loss curves of different burners,it could be concluded that the fixed-bed combustion curve of activated carbon had strong correlation with the prediction,and the semi-coke fluidized combustion curve had better agreement with the predicted value.It provides an important theoretical basis for predicting fluidized bed and fixed bed combustion by using thermogravimetry combustion.Based on the study of semi-coke fluidized bed combustion characteristics,the NO_x and SO₂release characteristics in different combustion processes were analyzed.The resulted show that with the increasing of bed temperature and air flow,the instantaneous peak emission of gas decreased.While the particle size were arose,the peak value of instantaneous emission of SO₂ is opposite to the trend of NO_x.Under different influencing factors,air flow has the greatest effect on NO and NO_x,followed by particle size.For SO₂,the influence of bed temperature was greater than that of particle size and air flow,combustion time had the least effect on gas release.