Study On The Trend Of Safety Characteristic Parameters Of Toluene Nitration Involving Mixing Effect

Toluene nitration is widely used in modern industry.The reaction happens in a liquid-liquid heterogeneous system with large heat release and high risk of thermal runaway,and it is easy to be affected by the mixing effect.In terms of the thermal safety of batch reactions,the maximum accumulation and Maximum temperature of systhesis reaction（MTSR）are important safety parameters.These two safety parameters are susceptible to operating conditions and mixing effects.However,there is no quantitative study on the variation of these two safety parameters.Therefore,this topic quantitatively focuses on studying the variation of maximum accumulation and MTSR of toluene nitration with operating conditions on the premise of considering the effects of mixed effects.First,the kinetic parameters of the toluene nitration reaction were solved by a set of isothermal calorimetry experiments,and the Hatter number（Ha）of the reaction was calculated.As a result,it was verified that the reaction system was a diffusion controlled liquid-liquid heterogeneous reaction.Secondly,the dimensionless mathematical model of the reaction was established.The effects of five model parameters(dimensionless adiabatic temperature riseΔτ_ad,dimensionless reaction rate constant v_ADaRE,dimensionless activation energyγ,feed volume ratioε,reaction order)on the maximum accumulation and MTSR of reaction were studied by numerical simulation.It was found that the MTSR showed an"S"shape with temperature for the reaction with high activation energy or high heat release.In order to judge the variation law of MTSR with process temperature,the MTSR increment criterion was theoretically derived,and the validity of the criterion was verified by numerical calculation and calorimetry experiments.Finally,by changing the stirring rate,the effect of mixing effect on the maximum accumulation and MTSR of toluene nitration was studied.The results of numerical calculation and calorimetry experiments show that the maximum accumulation and MTSR decrease rapidly in the initial stage of the stirring rate increasing from zero;after the stirring rate increases to a certain extent,the increase of the stirring rate has little effect on the maximum accumulation and MTSR.According to the MTSR incremental criterion proposed in this paper,the process temperature can be adjusted to make the reaction operate in a safer and higher conversion rate condition.This criterion applies not only to the toluene nitration reaction,but also to other heterogeneous diffusion controlled reactions.