Simulation Of The Flow Field In The Falling Film Liquid-liquid Fast Mixing Reactor

There are problems of incomplete reaction and emulsion between the mixture of siloxane and the hydrochloric acid existing in the dimethyldichlorosilane hydro-lysis process.One kind of mixed reactor was designed in this paper using the ideas of falling film.CFD software was used to simulate the water-oil falling film on the plate.The comparison between the experiment and the simulation results showed that the use of film board within the reactor could effectively increase the contact areas between water and oil.The hydrolysis reaction was complete and there was no emulsified phenomenon in the new reactor.Works were as following:Based on the problems such as emulsification,polymerization,the too long residence time and uncompleted reactions,a new mixed reactor was developed in this paper.The experiment and the simulation showed that the oil and the water mixed quickly on the plate,and there was less emulsification in the device,There was a gap between the inner and the outside cylinder,so the gas generated in the reaction could be guided by the gap.The demister was put in the annular gap to reduce the entrainment.Based on various geometric models,the relationship between meshing quality and simulation results was studied and compared.The results showed that the computational results were stable with equisize skew and aspect ratio of models less than 0.85 and 5,respectively.By using the Geo-Reconstruction in the VOF models,the interface between the water-air and the water-oil was simulated successfully.Because of the density difference,the oil droplet floated to the free interface causing the interface deformation and fluctuation.The fluctuation destroyed the stability of the falling film.The CCD and computers were used to measure the film thickness on the inclined plate,and the results showed that:inclined angle 30°,spraying density 10m3/m2·h,separation 45mm,the experimental data and the simulation results were identical.The error was less than 13%.The coalesce of oil droplets and free interface led to the deformation of the gas-liquid interface;The smaller angle notch on the inclined plate there was,the less big wave were generated;Splash occurred after the fluid flowed through the rectangular groove with different sizes;The falling film was smooth and stable if the trapezoid size was big;The high intensity turbulence was generated if the value of peak/wavelengths was larger;The hemicycle shaped grooves,the rectangular grooves,the trapezoidal grooves,and the notch grooves were made on the plate,and the falling film conditions on these plates were compared.The results showed that the waves on the plate grooved by the hemicycle shapes were obvious.The water and the oil mixed better,and the flow speed on the plate was smaller.It could avoid the emulsification.