Study On The Risk Assessment Of Semibatch Homogeneous Runaway Reactions

In recent years,frequent accidents of runaway reactions have attracted extensive social attentions.Therefore,developing available risk assessment methods of runaway reactions is of high importance.However,the existing theories and experiment methods have some limitations.This paper will systematically study several important questions and parameters of risk assessmen of runaway reactions,including research methods for hazardous reactions,the maximum temperature of the synthesis reaction(MTSR),the time to maximum rate under adiabatic condition(TMRad);And this paper proposes an isoperibolic calorimetry-based method to identify the autocatalytic behavior,a new method to calculate TMRad,and a runaway criterion for semibach homogeneous reactions on the basis of operation condition and reaction kinetics.Firstly,this paper proposes an isoperibolic calorimetry-based method to identify the autocatalytic behavior for homogeneous reactions.Through this method,the autocatalytic behavior and the corresponding kinetic parameters could be determined by comparing the fitting performances of autocatalytic model and second order model with experimental data.To validate the method,the calorimetric experiments of esterification between acetic anhydride and methanol are conducted.The results show that: the autocatalytic model fits better with the experimental data than second order model and the reaction enthalpy calculated by autocatalytic model is closer to the experimental value of reaction enthalpy than second order model,which validate the autocatalytic behavior of the esterification and method.Secondly,based on numerical calculations of dimensionless mathematic model of homogeneous semibatch reactors and calorimetric experiments,this paper investigates the variation of accumulation and MTSR.The numerical calculation results indicate that with some values of model parameters,MTSR may increase following an “S” shape as reaction temperature increases.A semi-empirical criterion is proposed to judge when this tendence appears.Calorimetric experiments of esterification between propionic anhydride and 2-butanol are conducted to validate the criterion.Thirdly,due to the runaway reaction or the complexity of reaction mechanism,the measured exothermic curves by ARC often don't give the final exothermic temperature.The existing methods to calculate TMRad with adiabatic calorimetry results are not appliable to this scenario.Hence this paper proposes a new method,which is applicable to not only this scenario but also the exothermic curves with final exothermic temperature.Two adiabatic calorimetric tests of nitro compound and mixture of DTPB/toluene are conducted to validate the new method.Finally,on the basis of the non-linear analysis of mathematic model of the semibatch homogeneous reactors,this paper also proposes a new online runaway criterion,namely adiabatic criterion.Both numerical simulations and experiments demonstrate that this adiabatic criterion is suitable for not only isoperibolic mode but also isothermal mode.In addition,this criterion is able to identify the critical accumulation.