Numerical Simulation Of Nonisothermal Amplification Effect And Optimization Of Amplification Number In Stirred Tank

Low viscosity liquid polymer products often experience from laboratory scale gradually exaggerated to industrial scale expansion process,while the production unit(stirred tank)amplifier amplification effect can make the industrial scale production of a security risk,therefore,the research on characteristics of producing device and the control of the amplification effect is of great significance to realize industrialization production safety.Taking the amplification of the polymerization reaction stirred tank as the research object,through the use of COMSOL software.Combined with the similarity theory and the case study of the polymerization reaction,the optimization of the amplification number of stirred tank,the similar conditions of mass transfer and heat transfer before and after amplification and the safety risks of non-isothermal effects of the polymerization reaction were studied.Finally,the amplification criterion with better comprehensive effect of mass transfer is optimized,and the parameters of the amplification criterion of non-isothermal heat transfer are optimized from the Angle of changing the coil structure of stirred tank,and the correlation formula of convective heat transfer outside the coil is fitted,which provides guidance for solving the non-isothermal amplification effect of stirred tank and the design of the amplification parameters of stirred tank.After a lot of simulation research,the main conclusions are as follows:(1)Based on the similarity theory,the scale-up criteria,which are power consumption per unit volume(P/V),blade end velocity(u_tip),blade discharge per unit volume(V/Q_c)and Reynolds number(Re),are obtained,which are used as the scale-up criteria for the next study of mass transfer and heat transfer in the stirred tank.The corresponding scale-up criteria are recorded as benchmark 1?benchmark 4.(2)The amplification effect of mass transfer process in stirred tank is compared with the time mixing characteristics and spatial mixing characteristics before and after amplification under different standards.The change rules of relevant parameters under different amplification standards are obtained.The mixing time relationship is the benchmark 3=reference kettle<benchmark 1<benchmark 2<benchmark 4,the power consumption per unit volume is the benchmark 3>benchmark 1=reference kettle>reference 2>benchmark4.The mixing time is long and it is not suitable for the design of agitator amplification.The mixing time closest to the reference kettle can be obtained by enlarging the equal cycle time.By comparing the mixing characteristics of time and space,the power consumption per unit volume(P/V)is taken as the amplification benchmark,which can satisfy the good mixing effect,and also ensure the economy,which is better than the other three amplification standards.(3)The heat transfer process in the stirred tank with coil is the result of the coupling of the fluid-thermal physical field,and the non-isothermal heat transfer phenomenon exists.The5 m³ stirred tank with a fine chemical polymerization reaction of non-isothermal process simulation results show that stirred tank heating stage and the polymerization of the early nonisothermal effects can lead to the main reaction is out of control and security risks of thermal gathered in local high temperature,polymerization time about 50s early intermittent warming helps control by-products and thermal runaway,At the same time,through safety risk analysis,the necessity of thermal similarity of control system in stirred tank amplification research is proposed.(4)The parameter design is suggested to optimize the amplification criterion of non-isothermal heat transfer by changing the coil pitch of stirred tank.The larger the ratio of coil pitch to coil diameter(Sc/dt)is,the smaller the convection heat transfer coefficient outside the coil is.When the geometric similarity of the reference tank is doubled,the thermal similarity between the amplification tank and the reference tank can be achieved when the Sc/dt value is between 1.68 and 1.8.