Design And Optimization Of A Microwave Reactor With Interlayer

The preparation of biodiesel by microwave enhanced esterification is a very efficient technology,but at present,the preparation scale of microwave reactor is generally small,which can only meet the needs of laboratory research.In order to promote the large-scale and industrial production of biodiesel,it is necessary to design the microwave reactor.According to the characteristics of traditional microwave reactor and the structure characteristics of existing microwave reactor,a pilot scale microwave reactor with interlayer is proposed in this paper.In order to optimize the design of the reactor,the Maxwell equation,the heat transfer equation and the flow equation are coupled in this paper.The electric field,the flow field and the temperature field are simulated and analyzed in the way of numerical simulation.The corresponding improvement measures are proposed by studying the influence of various factors on the microwave heating effect.Finally,the microwave heating control system is designed according to its heating characteristics.The main research contents and conclusions are as follows:(1)Structure optimization of microwave reactor.The Maxwell equation and the heat transfer equation are coupled for transient simulation to analyze the microwave heating effect of different reactors.The results show that the position of waveguide and the thickness of interlayer have significant influence on the microwave heating effect.Then,by response surface analysis,considering the heating efficiency and heating uniformity,the optimal reactor structure is 344 mm waveguide height and 20 mm interlayer thickness.(2)Analysis of the influence factors of microwave heating effect.Through the optimized structure,the influence of material dielectric properties,microwave frequency and material quantity on the microwave heating effect is explored.It is found that the microwave heating efficiency is high when the material dielectric value is high,the uniformity is good when the material dielectric value is low and the material quantity is large;High efficiency and uniformity of microwave heating at high frequency but when low frequency is not.(3)Effect of stirring on microwave heating uniformity.Based on the electromagnetic thermal model,the flow equations are coupled to explore the influence of different factors on the power consumption of stirring and the uniformity of microwave heating.Through response surface analysis,it is found that the primary and secondary order of the factors influencing the microwave heating effect is stirring speed > impeller diameter > clearance from the bottom,and there is an interaction between the different factors;From two aspects of stirring power consumption and heating uniformity,when impeller diameter is 133.6 mm,clearance from the bottom is 55.0 mm and mixing speed is 300.0 rpm,the stirring effect is the best.(4)Design and construction of microwave heating control system.Based on the heating characteristics of the reactor,a PLC temperature control system is designed.After experimental debugging,the system can achieve the purpose of heating materials in the reactor and constant temperature control.