Simulation And Process Optimization Of Coal Tar Chemical Chain Pyrolysis System Based On Aspen Plus

Chemical looping technology is a multipurpose technology attracting great attention due to its three distinguished advantages,such as high energy utilization ratio,low pollutant emission as well as CO₂ inherent separation.Based on the principle of chemical looping technology,the chemical looping flameless combustion idea was put forward by our project group creatively to be applied to the pyrolysis of liquid hydrocarbon fuel coal tar with non-expensive oxygen carrier,and a new carbon black production craft was proposed.Compared with the traditional carbon black production process,the chemical looping pyrolysis of coal tar to produce carbon black has great potentials for the characteristics of low energy consumption,low pollution.In the previous researches of our project group,some achievements on the reaction mechanism have been obtained,but there are still some blanks in the design and optimization of fluidized bed fuel reactor and air reactor that needs comprehensive research.In this paper,further exploration is carried out on the optimization of the process of preparing carbon black by chemical looping pyrolysis of coal tar.The main research contents and results are as follows:Firstly,a single fluidized bed fuel reactor model was established in Aspen Plus,and the pyrolysis reactions between coal tar and oxygen carrier in fluidized bed were calculated.The results show that,it is most favorable for the production of carbon black when reaction temperature is 900°C,reaction time is 2 s,and the oxygen carrier/coal tar mole ratio is 2.5.At this time,the carbon black yield and the energy conversion efficiency in the reactor are high.These operating conditions provide guidance for the following experiment.Secondly,a laboratory-scale fluidized bed fuel reactor was built up,and the coal tar pyrolysis experiments were carried out using Fe₂O₃ prepared by the impregnation method as the compound oxygen carrier of Fe/Al.The experimental data was compared with the simulation results of coal tar chemical looping pyrolysis constructed and analyzed in Aspen Plus to further optimize the operating parameters.The influence of operating conditions on system performance?carbon black yield,energy conversion efficiency,etc.?was investigated.The results show that the reaction temperature and oxygen carrier/coal tar mole ratio in the fuel reactor had a great influence on the pyrolysis performance,while the reaction time had little effect.The simulation results were in good agreement with the experimental data.Applying the outlet parameters of the fuel reactor to be the inlet data of air reactor in Aspen Plus,the regeneration reaction of the oxygen carrier in the air reactor was simulated,and the influence of reaction temperature and air/oxygen carrier ratio on regeneration efficiency was analyzed.Taking the entire system that consists of a fuel reactor and an air reactor and some other devices as the research object,the energy balance and mass balance were calculated,and some efforts were made to investigate whether the system was endothermic or not.Finally,the heat exchanger design for waste heat recovery in the simulation process is carried out for the purpose of self-heating of the entire system.The high temperature regenerated oxygen carrier particles and flue gas and sand at the outlet of the air reactor were used as the heat source for the reaction in Fuel reactor.By changing the sand/oxygen carrier mole ratio and reducing the heat loss of the exhaust gas,the operating conditions for the self-heating of air reactor also are obtained,and the thermal efficiency of the entire system is improved.In this paper,through the combination of numerical simulation and fluidized bed experiments both in cold and hot states,the experiment are guided by the simulation results,and then the simulation parameters are corrected by experimental data.From the perspective of system optimization,the performance of each reactor are investigated in the system of coal tar chemical looping pyrolysis to prepare carbon black,and the equipment combination and operating parameters of self-heating system were obtained,which has important guiding significance for the establishment of practical process.