Removal Process Of Benzene Series By Paraffin Oil With Aspen Plus

With the rapid development of industry in China in recent years,the issue of air pollution becomes more and more serious.Especially the VOCs from industrial production,has become a theat to environment and human health.In this work,the VOCs(mainly focused on benzene series in exhaust gas)removal via absorption by paraffin oil was studied.Using the rate-based model in Aspen Plus,the absorption-desorption process of benzene series was developed.A certain desorption model was firstly chosen according to equilibrium model,and then the whole process was built based on packed tower.Moreover,to add-in the rotating packed bed(RPB)into the simulation in Aspen Plus,external Fortran program was applied.Further,the absorption-desorption process of VOCs by paraffin oil in RPB can be simulated and further validated by published experimental data.The conclusions are as follows:1 According to the distillation curve of paraffin oil,paraffin oil in Aspen Plus was divided into several components,and the properties model of UNIFAC was set.The model of methylbenzene absorption by paraffin oil in packed tower was further developed.The simulation showed that the absorption efficiency decreased as temperature of liquid feeding increased.The temperature of gas feeding had no significant influence on absorption process.Besides,the absorption efficiency increased as the pressure in tower top increased,and atmospheric pressure was well enough to meet the demand of absorption.When the concentration of methylbenzene was 500ppm,temperature was 20 ? and gas/liquid rate was 100,the removal rate of methylbenzene would reach 99.99%2 The whole process simulation of methylbenzene absorption-desorption was developed.Three different desorption methods of distillation desorption,stripping desorption and nitrogen desorption by equilibrium model were selected.The unit energy consumption was 8.35 GJ,1.37 GJ and 1.3 GJ per kg methylbenzene,respectively.Therefore,the nitrogen desorption was chosen due to its lowest energy consumption.3 The effects of various packing,specific surface area,packing layer height,tower top operating pressure,gas and liquid feeding temperature and flow rate on absorption were investigated based on non-equilibrium model.The results showed that the packing of MELLAPAK 350Y could meet the absorption requirement.The optimal value of tower top operating pressure was 1atm,packing layer height was 1m,liquid feeding was 5L/h,and the unit energy consumption was 0.351 GJ per kg benzene series.In addition,the benzene series components were simulated separately and mixedly,showing that there was no synergistic effect among benzene series components.Moreover,the distributions of benzene series mass fraction,pressure drop in the column,liquid holdup and HETP were analyzed in absorption tower based on rate-based model.4 Based on packing volume conservation and cross section area conservation with packed tower,rotating packed bed(RPB)was built by Aspen Plus.The empirical correlations of mass transfer coefficient from Rao et al and mass transfer area from Luo et al were employed in RPB model validated by published experimental data.Furthermore,the effects of operating conditions of RPB,such as feeding concentration,temperature,flow rate,rotational speed on benzene series absorption were analyzed.The results showed that the absorption efficiency increased as rotational speed increased.In addition,the comparison of mass transfer efficiency between RPB and packed tower was discussed,and the whole process simulation of absorption-desorption using RPB was developed.Finally,the mass transfer results of the RPB and PB were compared and analyzed,under the conditions of the same packing volume and operating conditions,the removal efficiency of methylbenzene in the PB and RPB were 87.02%and 92.35%,the RPB modeling could provide basis for further study of RPB application to the removal of VOCs.