| The rapid development of modern industry requires increased performance requirements of polymeric materials,and there is an urgent need for research on polymer devolatilization.As a typical chemical process intensification device,the rotating packed bed can effectively disperse viscous fluid into smaller liquid micro-elements by the centrifugal force generated by the high-speed rotation of the rotor.The liquid micro-elements can rapidly update the liquid surface through continuous breaking and coalescence to strengthen the gas-liquid mass transfer process.A pre-distributor device for viscous fluid feed is firstly proposing in this paper.The combination of experimental and simulation studies was used to investigate its initial dispersion effect on viscous fluids;Then,experimental research was conducted on the devolatilization performance of the CMC acetone system in a rotating bed;Finally,the packing structure is reasonably simplified,and the modified eddy cell mass transfer model is coupled to build three-dimensional CFD model of gas-liquid flow and mass transfer process,and the hydrodynamics and mass transfer characteristics of non-Newtonian fluid in the bed were studied.The main research results are as follows:(1)Three different structures of pre-distribution disks were compared by visualization experimental observation,and the one with slope and dispersion sheet was preferably selected,and CFD simulation was used to study the dispersion performance of non-Newtonian fluids.The results show that the distribution disk can maintain dispersion characteristics in a wider operating range(liquid volume flow rate Q from 30 to 210 L/h and zero-shear viscosityμ0 from 61 to 12865 mPa·s).The liquid holding capacity(εL)in the turntable area is positively correlated with Q and apparent viscosity(μ)and negatively correlated with rotational speed(N).The specific surface area of the liquid in the cavity(aP)is positively correlated with N and negatively correlated with Q and μ εL ap are empirically correlated as follows:εL=1.59q0.446 Re-0.174 W e-0.001 ap·R=604.4q-0.204 Re0.094W e-0.069(2)The results of the experimental study on devolatilization showed that the devolatilization rate(E)and the total volume mass transfer coefficient of the liquid phase(KLa)increased with rotational speed,but when the speed exceeds 600 rpm,the trend slows down.Increasing volume rate is beneficial for E,but unfavorable for KLa.Increasing CMC mass fraction(M)is both detrimental both E and KLa.The vacuum degree plays a decisive role in the devolatilization process,and higher vacuum degree will obtain higher degreasing efficiency.The main reason is that the vacuum degree changes the driving force.The maximum one stage devolatilization rate can reach 45%,and the acetone removal rate can rise to 74%after the fourth stage devolatilization.(3)The modified eddy cell mass transfer model was used to construct a three-dimensional CFD model of the mass transfer process.The simulation results show that the errors between the simulated and experimental results of the devolatilization rate are within±25%.There is a flow end effect zone on the inner side of the packing layer.Increasing Q and CM is benificial for the effective interface area(ae),but not for aP;both ae and aP increases with the increase of N.The effect of N on εL exhibits a non monotonic relationship;the liquid phase volumetric mass transfer coefficient(kLa)gradually increases along the radial direction,while the mass transfer rate gradually decreases along the radial direction,indicating that the concentration gradient has a greater impact on the mass transfer rate than kL;it was found that the mass transfer rate on the surface of the film adhered to the filler and the liquid droplets in the filler gap was faster,while the mass transfer rate near the large liquid block was lower;and the value of kLa is within 0.5 to 4 s-1. |
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