Back pressure flash separator

In order to reduce the time-consuming open-column chromatographic processes, conventional methods of hydrocarbon-group-type separation have been replaced by MPLC and HPLC. Flash column chromatography is a technique less commonly applied than open-column version, but several applications have been described [2,24—27]. The common technique version is to use a silica-gel-filled column for example, 230 to 400 mesh 20 X 1 cm column size with a back pressure of 1.5 X 10 Pa of an ambient gas such as nitrogen. Solvents are similar to the ones apphed in the case of open-column chromatography fractionations. 

Equipment. All of the catalysts were tested in continuous flow, fixed-bed pilot plants equipped for both liquid and gas recycle operation and continuous distillation of products. Hydrocarbons boiling above the desired product end point were recycled to extinction, that is, to 100 conversion of fresh feed. The product was cooled and passed into a high pressure phase separator. Here, hydrogen-rich recycle gas was flashed from the hydrocarbon product and recycled back to the reactor inlet. Electrolytic hydrogen make-up was added on demand to maintain constant system pressure. 

Hot, rich glycol at reduced pressure generates flash gas that can be used as a fuel gas to the regenerator reboiler or as a stripping gas or for both. Excess flash gas is normally vented to the flare system. The flash separator pressure is maintained through a back-pressure control valve on the gas outlet line from the separator. The liquid flow is maintained through a level-control valve. 

Sidestream compressors are used in refrigeration processes where, for economy, the refrigerant is flashed off at different pressure levels. Ideally, separate compressors could be used to successively compress the gas back up to the condensing pressure level. The pressure ratio for each stage is low enough to enable this to be done with only one or two impellers in each section. Because of this, compressors can be made with all sections in one casing so that mixing of the streams takes place intern.ll I v. 

Tearing or distortion of a moulded rubber product at the line of separation of the two mould halves (the spew line) due to the sudden release, on opening the mould, of the high pressures developed by the thermal expansion of the heated rubber other names are suck back, flash back and retracted spew. 

A typical configuration for a methanol carbonylation plant is shown in Fig. 1. The feedstocks (MeOH and CO) are fed to the reactor vessel on a continuous basis. In the initial product separation step, the reaction mixture is passed from the reactor into a flash-tank where the pressure is reduced to induce vapourisation of most of the volatiles. The catalyst remains dissolved in the liquid phase and is recycled back to the reactor vessel. The vapour from the flash-tank is directed into a distillation train which removes methyl iodide, water and heavier by-products (e.g. propionic acid) from the acetic acid product. 

In the case of flash degassing, the polymer solution is first heated under pressure to above the boiling point of the volatile components and decompressed directly into the ZSK. The polymer and solvent (monomer) spontaneously separate from each other inside the ZSK and the majority of the volatile components are released via the back venting system. Depending on the pressure and the temperature, up to 90% of the solvent can be removed in this way. Efficiency depends on the temperature of the polymer solution at the feed intake, the pressure drop in the back vent, and the material properties of the feeding system. The back vent is located upstream from the polymer or polymer solution feeding port (see Fig. 10.2). In this case, there is no melt in the screw channel so that the entire screw cross-section is available for the removal of gas or vapors. 

Ethylene, isobutane, comonomer and catalyst are continuously fed to the loop reactor where polymerization occurs at temperatures lower than 100°C and pressures of approximately 40 kg/cm2 and residence times of approximately one hour. Ethylene conversion exceeds 97% per pass. Reactor effluent is flashed to separate the solid resin from the gaseous stream (3). Polyethylene powder is purged (4) with nitrogen to remove traces of hydrocarbons and pneumatically conveyed to the extrusion area for stabilization and pelletizing. The gaseous stream is compressed, purified and recycled back to the reactor. 

The reactor effluent leaving the air cooler is separated into hydrogen-rich recycle gas, a sour water stream, and a hydrocarbon liquid stream in the high-pressure separator. The sour water effluent stream is often sent to a plant for ammonia recovery and for purification so water can be recycled back to the hydrocracker. The hydrocarbon rich stream is pressure reduced and fed to the distillation section after light products are flashed off in a low-pressure separator. 

Vapor produced in the condenser is compressed back to column bottom pressure before entering the column. Figure 17.13 shows the application of this scheme to the propylene-propane separation problem. The bottoms liquid is flashed to 72psia to remove the required heat in the condenser. Additional heat added during isentropic compression is insufficient to make up the difference between reboiler and condenser duties. Therefore, the auxiliary steam-heated reboiler is needed. 

Operation of the virgin and modified AI2O3 manbrane was compared by the separation of an oil-water emulsion, which consisted of 20 engine oil (1 g/L), Tween 80 (0.5 g/L), Span 80 (0.5 g/L), and distilled water. Stable oil-water emulsion had an average droplet size of 1.79 pm, and 90% of the oil droplets were between 0.67 and 7.4 pm. Filtration tests were conducted at the transmanbrane pressure of 0.16 MPa, feed flow rate of 5 m/s, and at an operating temperature of SO C. The membrane was back-flashed at the interval of 10 min. For the virgin AljOj manbrane, the flux declined sharply in the first 60 min, from 446 to 159 L/m h. The steady flux was only about 30% of the initial flux, implying that the AljOj membrane was seriously fouled. However, the flux of the modified membrane quickly reached a constant in 10 min. The flux declined from 506 to 441 L/m h, which is 88% of the initial flux. 

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