The Characteristics And Kinetic Mechanisms Of Coal Residue Pyrolysis In The Different Atmosphere

Coal residue is one of the most quantity industrial solid residues,with the characteristics of lower volatile, high ash, lower heat value and hard-to-burn. So, the large scale utilization of coal residue is limited. Co-combustion of low caloric gas and coal residue could improve the combustion efficiently. In the combustion, the component of low caloric gas influence the characteristics of coal residue pyrolysis greatly. Pyrolysis in the appropriate atmosphere is important to the combustion efficiency. So far, research in this field is limitted and the characteristics and mechanisms of coal residue pyrolysis in different atmosphere are covered and un-recognized, which hindering the further utilization and development. So, it is necessary to study the characteristics and mechanisms of coal residue pyrolysis in different atmosphere.Based on the deeply analysis of the status of utilization and the situation of coal residue and low caloric gas, the characteristics of coal residue was analyzed. The experiments of coal residue pyrolysis have been investigated on 4 kinds of different coal residues by non-isothermal thermogravimetric method, researching the effects of experiment parameters, such as different heat rate, different sample diameter, different pressure and different gas mixture of CO2 or CH4 with N2 with the concentration of 10%, 30%, 60%, 100%, to the pyrolysis characteristics, then analyzing the kinetic characteristics. The main conclusions are as follow:(1) The component of different coal residues changed. The content of volatile is 9.69%～13.26%, the content of Fixed Carbon is 6.35%～30.3%, the content of Ash is 54.67%～82.4%. The content of constituent is Carbon 39%～55%,Hydrogen 1.1%～2.3%,Oxygen 1.9%～6.5%.(2) With the rise of the temperature, coal residues pyrolysis experienced three stages: low temperature weight loss stage; main decomposes stage and second release gas stage. Temperature is the main factor to influence the coal residue pyrolysis.(3) The primary pyrolysis temperature, (dw/dt)max and its temperature, quality number D vary with different coal residues, sample diameter, heat rate, pressure and atmosphere.(4) The influence of atmosphere is different at respective pyrolysis phases.ΔW =ΔW N 2 ?ΔWatmosphere is used for judging the degree of percent conversion. (5) A most optimum pyrolysis temperature phase△Topt exists in the pyrolysis process in the CH4 atmosphere. Before the carbon deposition temperature, CH4 improves the pyrolysis,ΔW CH4could express that.(6) The coal residue pyrolysis is very complicated in the different atmosphere; the whole process can not be described by one step reaction. The results show that in the first stage, the pyrolysis reaction obeys the mechanism of three-dimensi onal spherical diffusion(D4); In the second stage, the reaction obeys the liquefaction reaction and the progression of chemical reaction is 2(F2);in the third stage, the pyrolysis of high Carbon coal residues still obeyed F2, but the lower Carbon's(C<10%) obeyed the chemical reaction with the progression of 1(F1).(7) In the different atmosphere, the activation energy is lower in the fist and third stage, the higher in the second stage. The same stage of different coal residues have the different activation energy.(8) In CO2 atmosphere, the activation energy is higher and higher with the higher CO2 concentration in the first and second stage, but lower in the third stage. Whereas, in the CH4 atmosphere, the activation energy is lower and lower with the higher CH4 concentration in the first stage and higher in the second stage.The conclusion from above experiments and analysis of coal residue pyrolysis in the different atmosphere are helpful to the development of co-pyrolysis of coal residue and low caloric gas and supply valuable reference data for more research in this field.