Study On Kinetics And Runaway Risk Criterion Models Of Hazardous Chemical Reactions

While the chemical industry benefits human life,various safety problems make human society suffer huge losses as well.Chemical safety has become a worldwide issue.In recent years,more and more scholars at home and abroad have devoted to the field of chemical process safety,and the relevant research has made great progress as well.For the risk criterion models of hazardous chemical reactions and its application,further research and improvement are still needed.Taking the heterogeneous hazardous chemical reaction systems common in the fine chemical and pharmaceutical industry as the research objects,this paper will systematically study the reaction kinetic models,the thermal runaway and thermal behavior criterion models,as well as the optimization algorithms of thermally safe operation conditions.Firstly,for the catalytic hydrogenation reaction with carbon dioxide generation,an on-line measurement combined with the off-line measurements are employed to establish the characterization method of the apparent kinetics.Linear fits are performed between the experimental data measured by off-line HPLC and in-situ ReactIR,and the fitting performances are used to determine the validity of experimental data collected by in-situ ReactIR.At the same time,the absorption intensities of infrared characteristic peaks are converted to concentrations.Based on the experimental data at different temperatures,the kinetic parameters of the desired reaction are calculated by the least square method.The rationality of the kinetic parameters is indicated by the comparison between the experimental and calculated reaction rate curves.Finally,the kinetic model of the reaction is established.The results show that:for the studied reaction system,in-situ ReactIR can be used to accurately track the reaction process within a certain temperature range;the calculated curves of reaction rate are highly close to the experimental ones,confirming the validity of this method and the rationality of the apparent kinetic equation.Secondly,for the isoperibolic semi-batch liquid-liquid heterogeneous reaction systems,given the variations of heat transfer capacity of the system during the dosing period,the extreme assumption of US is proposed.Combined with the traditional ideal assumption and taking into account the normal operation and cooling failure scenarios,the mathematic model of the desired reaction is established based on the equations of mass balance and energy balance.The maximum temperature of the synthesis reaction under the completely cooling failure scenario(MTSR)as well as the corresponding time(θMTSR)are studied by numerical simulation.Based on θMTSR,a more general criterion,used for thermal behavior(including inherent safety,non-ignition,thermal runaway and QFS)determination,is established.Based on this criterion,a series of boundary diagrams are established.Due to the limitation of boundary diagrams,the novel adiabatic temperature diagrams are proposed.Employing boundary diagrams combined with adiabatic temperature diagrams,thermal behaviors of the isoperibolic semi-batch liquid-liquid heterogeneous reactions can be effectively determined on the premise of taking into account the desired reaction,secondary reaction and technical limits of the equipment.Thirdly,in essence,thermal behavior recognition can be regarded as a pattern recognition issue,including "feature"(used to characterize thermal behaviors)extraction and recognition.Traditional criteria usually use single feature,which may lead to the omission of important information and cause the different results.In this paper,from the perspective of pattern recognition,multiple features are extracted for the isoperibolic semi-batch liquid-liquid heterogeneous system,and the features of different dimensions are then identified through several pattern recognition algorithms.The results show that the combination of the 5-D features{f2,f3,f5,f4,f6)and the support vector machine(SVM)yields the highest recognition accuracy,which is then determined as the final multi-feature pattern recognition criterion,MFR criterion.On this basis,from the perspective of inherent safety,an improved generalized inherently safe region is constructed by introducing the thermally safe upper limit τj,MAT combined with MFR criterion.Compared with the traditional criteria,the effectiveness and superiority of MFR criterion are verified.Finally,based on the θMTSR criterion and MFR criterion,the optimization algorithms for the thermally safe operating conditions of hazardous chemical reactions are established.Based on the detailed introductions of the establishment process of optimization algorithms,the effectiveness and practicability of the criteria and the optimization algorithms are verified through the case studies,which can better guide the practical applications.