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Research into the Characteristics of Cross-flow Rotating Packed Bed and Application in Polymer Devolatilization

Author: LiuZhenHe
Tutor: LiuYouZhi
School: University of North
Course: Chemical Engineering
Keywords: Rotating packed bed(RPB) cross-flow pressure drop mass transfer urea formaldehyde resin(UF) free formaldehyde
CLC: TQ051
Type: Master's thesis
Year: 2007
Downloads: 64
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Abstract


The polymer devolatilization equipments and polymer devolatilization intensifying methods were summarized briefly. A cross-flow rotating packed bed(RPB) was designed and manufactured for polymer devolatilization.The comparison experiment for gas pressure drop was studied between sealed cross-flow rotating packed bed(RPB) and opened cross-flow RPB by change it’s inner sealed structure. The mass transfer characteristics was investigated in sealed cross-flow RPB.A mathematical model was developed for it.which made a solid foundation for polymer devolatilization.The application for polymer devolatilization was studied in sealed cross-flow RPB with urea formaldehyde resin(UF) by air-stripping.A cross-flow RPB was optimization designed according to the characteristics of surface film renewal polymer devolatilization equipment which has short time heating polymer,high liquid film revnew and big area of heating and mass transfer.The liquid collector,the sealed ring and preserve heatting system of the shell were set for cross-flow RPB.The pressure drop of the two types cross-flow RPB was studied based on air-water system by change it’s inner seal structure. The experimental data showed that the effect of rotating speed upon the type RPB pressure drop had obvious difference. The nondimensional number of higee factor(β) and rotation-flow ratio(ψ) is evaluate the influence RPB rotating speed upon gas pressure drop for the sealed and opened RPB respectively.The pressure in sealed cross-flow decrease with increasing of higee factor(β). However,it decreased decrease with increasing of rotation-flow ratio(ψ<30) is augmented first, then it increased with increasing of rotation-flow ratio(ψ>30) in opened cross-flow RPB.The same rules of pressure drop in the two type cross-flow RPB is the pressure drop increase with gas flow rate goes up under low speed or high gas flow rate.It decrease first then increase with increasing gas flow rate under high rotating speed and low gas flux. It increased with increasing liquid flow rate.The gas-film controlled mass transfer characteristic was investigated in sealed cross-flow rotating packed bed,where the CO2 in the air(y=0.5~0.1) was absorbed by NaOH solution(CNaOH=0.926mol/L).The experimental data showed that the CO2 removal efficency decreased with increasing of gas flux;it increase with higee factor(β) is speed up; it increase with liquid flux is enhanced under rotating speed high than 1000rpm;however ,it decrease with liquid flux is enhanced under higee factor(β) more than 60. A mathematical model was developed for gas film controlled mass transfer in sealed cross-flow RPB.The calculate values from mathematical model accord with the experimental values well.The application for polymer devolatilization was investigation in RPB. The formaldehyde in air pollutant was mainly come from the panel which made from urea formaldehyde resin(UF), high content of formaldehyde in air is harmfull to people. The rotating packed bed(RPB) was used for devolatilized free formaldehyde in liquid UF with air-stripping, The influences of free Formaldehyde removal efficiency was studied under different feed temperature,RPB speed, gas flux and the liquid flux. The Orthogonal experiment data showed that the RPB speed is key factor for free formaldehyde removal efficiency in liquid UF with air-stripping.The free formaldehyde removal efficiency in UF high than 80% under the operation conditions that the feed temperature:80℃,gas-liquid ratio:800~1100. higee factor(β):60~130. The application of air-stripping free formaldehyde from UF in RPB has high removal efficiency, low energy consumption,simple techniques and convenient for shutdown and start working, and so on.The techniques of polymer devolatilization by RPB has broad applied perspective.

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