The Studies On Henry Coefficient And Devolatilization Process In High-Speed Dispersion Reactor

In the production of polymers,devolatilization is an important unit operation,that is,the process of separating low molecular weight components from the polymer system.These low-molecular-weight components are collectively referred to as "volatiles",and their content is usually an important indicator of polymer quality.The presence of volatiles not only reduce the quality of products,but also cause ham to users and the environment.Devolatilizer is the main equipment in the devolatilization process.It usually achieves the goal of devolatilization by means of achieving larger gas-liquid contact area and destroying the phase equilibrium between gas and liquid.The Henry's coefficient is the most basic parameter in the gas-liquid equilibrium.In this paper,the Henry's coefficient of volatiles in the binary system of PDMS/n-alkane is first measured,and the influence of different operating conditions on the Henry's coefficient are discussed.The results show that with the increase of the experimental temperature,the Henry's coefficient gradually increases,analogous to the Arrhenius equation,and the fitting formula is (?).As the number of carbon atoms in the n-alkanes increases,the Henry's coefficient of the volatiles gradually decreases.The relationship is In H =-0.937nc+18.330.The viscosity of the polymer has little effect on the Henry's coefficient.Under the same volatile conditions,the viscosity increases from 50 cst to 5000 cst,and the maximum increase rate of Henry's coefficient is only 5%.The Henry's coefficient under different conditions is compared with the Flory-Huggins theory and the difference was not more than 10%.Based on the binary system,the Henry's coefficient of the volatile matter in the ternary system under different conditions was studied.In the PDMS/ISO thirty alkane/alkanes three element system,the Henry coefficient of the volatile fraction gradually decreases with the increase of the mass fraction of isothirty alkanes in the PDMS-ISO thirty alkane mixed solvent.As with the binary system,the Henry's coefficient of volatiles increases with increasing temperature.The relationship is (?).The Henry's coefficient of volatiles in the ternary system also decreases with increasing number of carbon atoms.The fitting result is In H =-1.105nc+18.802.In the three element system of PDMS/n-pentane/n-heptane,the greater the mass ratio of n-heptane to n-pentane,the smaller the Henry coefficient of the volatile matter,and the n-heptane and n-pentane as the volatile matter,which have less influence on each other and belong to the ideal mixture.In the three element system of PDMS/hexane/n-octane,the greater the mass ratio of n-octane and n-hexane,the smaller the Henry coefficient of the volatile in the polymerization solution,and the larger the decrease.Based on the Henry's coefficient and other basic data measured in the experiment,a diffusion devolatilization mass transfer model was established based on the mass conservation equation and the solute permeation theory.The relative error between the model value and the experimental value was within ±10%,and the model can describe the diffusion devolatilization process of volatiles in polymer solution well.