To overcome the disadvantages of the rotating bed available in open literature, a novel kind of high gravity device-rotating zigzag bed (RZB) was developed, which exhibits many superior features owing to its unique rotor combining a rotational part with a stationary one. The outstanding characteristics of RZB are its capability of middle-feed and easily realizing multirotor configuration in one unit by simply installing multiple rotors along the same axis. Thus one unit of RZB can be applied to continuous distillation processes with a higher mass transfer capacity. A preliminary test of mass transfer performance of the RZB in a pilot-scale system using methanol-water was carried out in this study. Experimental results show its excellent mass transfer behavior with an acceptable pressure drop. Comparison with rotating packing bed (RPB) shows that RZB provides equivalent mass transfer efficiency to RPB but exhibits excellent operability with a higher turndown ratio than that of RPB. Comparison with valve tray indicates that the baffle efficiency of RZB is slightly lower than the plate efficiency of valve tray. But if the difference between the tray space and baffle space is taken into consideration, RZB provides much higher efficiency than that of valve tray. Therefore the RZB is a kind of high efficiency gas-liquid contactor and a promising alternative in chemical process industries.
The CD spectra of chiral 4,4'-biphenylene-silicas were measured and simulated using time-dependent density functional theory and a chiral sensor for silicas was developed.
ABSTRACT:We prepared polyetherimide (PEI) hollow fiber membranes using polyvinylpyrrolidones (PVP) with different molecular weights (PVP 10,000, PVP 40,000, and PVP 1,300,000) as additives for oil/water separation. Asymmetric hollow fiber membranes were fabricated by wet phase inversion technique from 25 wt % or 30 wt % solids of 20 : 5 : 75 or 20 : 10 : 70 (weight ratio) PEI/PVP/N-metyl-2-pyrrolidone (NMP) solutions and a 95 : 5 NMP/water solution was used as bore fluid to eliminate resistance on the internal surface. Effects of PVP molecular weights on morphology, oil-surfactant-water separation characteristics, mechanical, and thermal properties of PEI/PVP hollow fiber membranes were investigated. It was found that an increase in PVP molecular weight and percentage in PEI/PVP dope solution resulted in the membrane morphology change from the finger-like structure to the spongy structure. Without sodium hypochlorite posttreatment, hollow fiber membranes with higher PVP molecular weights had a higher rejection but with a lower water flux. For oil-surfactant-water emulsion systems (1600 ppm surfactant of sodium dodecylbenzenesulfonate and 2500 ppm oil of n-decane), experimental results illustrated that the rejection rates for surfactant, total organic carbon, and oil were 76.1 Ϸ 79.8%, 91.0 Ϸ 93.0%, and more than 99%, respectively. Based on the glass transition temperature values, PVP existed in hollow fiber membranes and resulted in the hydrophilicity of membranes. In addition, using NaOCl as a posttreatment agent for membranes showed a significant improvement in membrane permeability for PVP with a molecular weight of 1300 K, whereas the elongation at break of the treated hollow fiber membranes decreased significantly.
Developed from rotating zigzag bed
(RZB), the counterflow concentric-ring
rotating bed uses a rotor composed of stationary–rotating discs,
a set of concentric circular rotating rings with perforations, and
a liquid distribution at the eye of the rotor, preserving the outstanding
characteristics of RZBs consisting of intermediate feeding and multirotors
coaxially installed in series in a casing. A mass-transfer model was
proposed from which the local gas- and liquid-side mass-transfer coefficients,
gas–liquid effective interfacial area, and height equivalent
to theoretical plate (HETP) can be calculated. Total reflux distillation
experiments were conducted in a counterflow concentric-ring rotating
bed at atmospheric pressure using an ethanol–water system,
and the mass-transfer end effects were also investigated. The experimental
values of overall volumetric gas-side mass-transfer coefficient and
HETP agree with the calculated values very well. Obvious end effects
exist in the distillation process, and a correlation which takes inner
and outer end effects into consideration is given. Compared with RZB,
the counterflow concentric-ring rotating bed has lower mass-transfer
efficiency, but it has gas–liquid throughput at least 5.576
times greater than that of RZB. Compared with rotating packed bed,
the concentric-ring rotating bed has a much higher local gas-side
mass-transfer coefficient.
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