Study On Calculation Deviation Of Traditional Methods For Time To Maximum Rate Under Adiabatic Condition

Time to maximum rate under adiabatic condition(TMR_ad)is a quiet important parameter used to evaluate the possibility of heat risk under adiabatic conditions in the chemical process risk assessment.The traditional methods of calculating TMR_ad are based on the N-order model:the first method is based on the kinetic parameters using the analytical formula to calculate TMR_ad,the second method is extrapolated by the linear relationship between ln(TMR_ad)and 1/T to obtain the TMR_ad at the lower temperature.However,the chemical reaction process is very complicated and the test results often affected by the thermal correction coefficient?,the evaluation results calculated by traditional methods without consider the type of reaction may cause large deviation or even incorrect assessments,which especially for the autocatalytic reaction.Therefore,it is quiet necessary to clarify the influence of the reaction type and?on the traditional methods TMR_ad evaluation and try to propose a solution.Firstly,the traditional methods are used to analyze the TMR_add calculation deviations of different reaction types:the adiabatic process is simulated based on numerical calculation method to obtain the theoretical true values and exothermic characteristic of different types of reactions,use two kinds of traditional methods to analysis and then compare with the theoretical true values to obtain the calculation deviations.The analysis shows that if the reaction involves only single-step N-order reaction,the deviation of T_D24 is within 14?under the calculation conditions,which indicates that the traditional methods evaluations are reliable.If the reaction involves autocatalysis,the T_D24 deviation reaches 300?under the calculation conditions,the traditional methods evaluations are unreliable and the evaluation at lower temperature is more risky,this is because the single-step N-order reaction model is not suitable for the analysis of autocatalytic reaction.Secondly,the traditional methods TMR_ad calculation deviations under different?show that the traditional methods T_D24 evaluation deviation of single-step N-order reaction under small?is within 3?,the evaluation results are reliable.With the increase of?,the exothermic curve may deformed severely and it cannot reflect the decomposition characteristics of the sample,the kinetic analysis results have no reference value and the evaluation of TMR_ad assessment is not reliable.Forautocatalytic reactions,the evaluation results of traditional methods under different?are always deviated.Therefore,it is recommended to increase the sample mass and reduce?to obtain a more valuable exothermic curve and analyze it with a suitable model.Finally,the analysis of the reasons why the traditional methods are not suitable for the autocatalytic reaction indicate that the difference of the analyze model may cause the deviation of the kinetic parameters(the activation energy of the autocatalytic reaction initiation phase E_a1is smaller than the activation energy of single-step N-order E_a),then according to the parameter sensitivity analysis,the evaluation based on autocatalytic model is more conservative at low temperature and the model calculation results are quite different.The evaluation based on autocatalytic model at high temperature is more dangerous,however the overall reaction rate are very fast and the deviation is not obvious.According to the above analysis results,the proposed numerical calculation method based on the reaction model has strong applicability,which is verified by the analysis of 20%DTBP toluene solution and CHP.It is recommended to determine the reaction type of substances with several tests and analytical method,then evaluate TMR_add and T_D2424 in this method.In addition,the TMR_ad analytic solutions of autocatalytic reaction can approximate the iterative results of autocatalytic reaction Berlin model,this formula also verifies by the analysis of CHP.This proposed formula also provides a new solution for the simplified calculation of the autocatalytic reaction.