Simulation Study On The Process Of PMIDA Oxidation In An Oscillating Flow Reactor

Glyphosate?PMG?is a sterile organophosphorus herbicide.With the extensive cul-tivation of genetically modified crops.It is currently the most widely used and most pro-ductive pesticide.N-phosphonomethyliminodiacetic acid?PMIDA?oxidation is a key step in the preparation PMG.The oxidation of PMIDA to get PMG is a series reaction,in which the target product PMG is the intermediate product of the series reaction.PMG may be further oxidized to produce AMPA,which is a by-product.The backmixing of materials will not be conducive to the formation of PMG.The reactor form and operation have a decisive impact on the yield of PMG.Oscillating flow reactor?OFR?was used as the reactor.The external periodic oscillation is applied to improve the radial mixing,and baffles are set up to reduce the axial backmixing.The flow characteristics of OFR and the results of the reaction were simulated by computational fluid dynamics?CFD?software and process simulation software.The suitable oscillation conditions,process conditions and reactor structure were explored to realize the plug flow with smaller Reynolds num-ber and the higher product yield.The specific work is as follows:1.The experimental device and transfer model of OFR were established.The math-ematical model describing the flow characteristics of the reactor was established by geo-metric modeling and meshing,using Euler-Euler model and periodic oscillation boundary conditions in CFD software.The numerical simulation results were compared with the experimental results to determine the reliability of the model.The average relative errors for predicting the concentration of PMIDA and PMG at the outlet of OFR were 7.64%and 7.41%,respectively.The errors were acceptable in engineering applications.2.In order to explore the relationship between the flow characteristics of the reactor and the oscillation operating parameters,the development of the standard cell vortex was simulated,and the influence of oscillation parameters on the residence time distribution?RTD?was studied under the oscillation conditions of 0-6 mm amplitude and 0-3.0 Hz frequency.The results show that under certain oscillation conditions,the radial mixing in the reactor is enhanced,and the RTD variance is smaller when the amplitude is small.The influence of oscillation conditions on flow characteristics is usually expressed by dimen-sionless oscillation Reynolds number Re_o and Strauhal number St.It is found that when the St was 3.891 and Re_o was 842.1,the RTD variance was only 0.0115.The flow pattern was the close to the plug flow.In this study,the RTD variance is correlated with the os-cillating Re_o under different St.The fitting results can predict the RTD variance to a cer-tain extent.3.The effects of oscillation conditions on the PMIDA oxidation were investigated on the basis of flow field study.The concentrations of PMIDA and PMG at the outlet of the reactor and the axial distribution in the reactor were simulated.When the concentra-tion reached oscillating stability,the concentration oscillated periodically,but the average value remained unchanged.When the amplitude was 1 mm,the frequency was 2.4 Hz,and the number of reactor cells is 80,the maximum concentration of PMG is 0.02297 mol L^-1 and the yield is 45.94%.Under the studied feeding conditions,the yield of PMG of the plug-flow reactor and the mixed-flow reactor were calculated to be 47.42%and 34.42%respectively.The evaluation of the effect of the OFR showed that the results were closer to the plug-flow reactor under certain oscillating conditions.4.In order to develop an optimized process for continuous PMIDA oxidation,ac-cording to the result of CFD,the flow pattern under different oscillation conditions was correlated by deviation degree coefficient a,and the real PMIDA oxidation was simulated by RPlug module in Aspen Plus combined with deviation degree coefficient a.Using the process simulation process,the concentration of PMIDA and PMG at the outlet with os-cillating operating parameters of 1 mm and 2.4 Hz was optimized.The optimized varia-bles were the length of the reactor with fixed diameter,reaction temperature and reaction pressure.The overall optimization of the yield of glyphosate at the outlet of the reactor was carried out with multiple parameters.The optimum values were as follows:the reac-tor length was 7.25 m,the reaction temperature was 48?,and the reaction pressure was 0.28 MPa.The maximum yield was 62.94%.The results of this study can well simulate and optimize the process,and provide a reference for the optimization design of the con-tinuous PMIDA oxidation.