Miscella concentration

Listed in sequence are miscella concentration, pressure, temperature, and feed velocity. DPE, dimethyi poiysiioxane elastomers. 

Sweet Chili Miscella - Concentrates were prepared at reduced pressure only. Initial attempts to use the miscella as obtained from the supplier were unsuccessful. When the miscella was combined with distilled water and the mixture was heated with stirring, an intractable gel formed. Subsequently, a hexane fraction was first distilled from the starting material at reduced pressure. Pepper volatiles entrained in this distillate were later reclaimed by careful fractional re-distlllatlon of the hexane fraction. The residue from this fractional distillation was combined with the heptane-extracted material obtained with the steam distillation-extraction head. 

Flakes of oilseeds were most fi equently used for the solvent extraction studies. Sometimes, ground oilseed kernels through a specified sieve size was used. Residual oil content in the extracted flakes after a certain specified extraction condition or oil content in miscella (mixture of oil and solvent) was examined and the percentage of total oil extracted was calculated. The total extractable oil of flakes was determined by four hours Soxhlet extraction. Wan et al. used a precision densitometer to determine the miscella concentration (percent of oil in miscella by weight) after a given time of extraction from which the per-... 

Screw-pressed oil is aUowed to stand to settle out suspended soUds, filtered through plate filter presses, and then pumped to storage. The oil-rich solvent (miscella) from the solvent-extraction process is filtered or clarified, and most of the solvent is removed in a long tube evaporator. FinaUy, the concentrated oil passes through a stripping column where sparging steam is injected to remove the residual solvent. A metric ton of cottonseed yields ca 91... 

In the process, miscella leaves the extractor at about 30-35 percent oil and is concentrated to approximately 65 percent oil by evaporation. The FFA in the concentrate then is reacted with alkali (sodium hydroxide solution) to produce soaps that are removed with other water-soluble compounds by centrifugation. Next, the solvent is removed from the miscella-refined oil by further evaporation, and the soapstock is spread on the meal in the DT to recover its solvent. Hexane vapors from the miscella and the DT are condensed, and the solvent is recycled to the extractor for reuse. The noncondensable gases are passed through a mineral oil stripper to recover the last traces of hexane. 

If the miscella flux rate is significantly reduced for a given prepared oleaginous material, the miscella can partially discharge into a later, undesired miscella collection receptacle. This will cause concentration contamination caused by mixing of the extractor washes and reduce the efficiency of the extractor. 

As the temperature of the miscella exiting the first stage evaporator is low, it is a good heat sink for heat recovery. In various facilities, heat from hot finished oil, heat from steam ejector exhausts, or recovered flash steam is used to preheat the miscella to approximately 75°C in temperature. The preheated, concentrated miscella is then typically heated to 110°C in a steam-heated exchanger prior to entering the second rising film evaporator. 

Smith studied the effect of boiling point differences of various cuts of hexane on miscella (218). Smith also determined the vapor pressure of hexane-soybean oil solutions at high solvent concentrations (211). When making stripping calculations, one should be aware that the last portions of solvent to vaporize consist of higher boiling constituents in that particular cut of solvent. 

For oleaginous materials having a low oil content (18-20%), such as soybean and rice bran, solvent extraction is often applied for oil recovery. Hexane is widely accepted as the most effective solvent used today. Most of the extractors currently used are designed as countercurrent flow devices. The solid material flows in an opposite direction of solvent-oil miscella with an increasing oil concentration. The miscella containing around 25-30% oil after extraction is subjected to solvent distillation to recover the oil. The extracted solid material, commonly known as white flakes, is also conveyed to the desolventizing process. 

According to Wu and Lee [24], in an experiment using the UF of miscella of crude soybean oil by a porous ceramic membrane, it was found that the polarization of concentration... 

The effect of pressure on rise of the permeate flux, decreases after a certain time of filtration previously reported by Wu and Lee [24] enter into agreanent with the results obtained by Kim et al. [21] in degumming of crude soybean oil by a PI UF membrane. According to these authors, the gel layer represented by the precipitation of solute on the membrane surface makes the permeate flux independent of pressure, and an increase in pressure resulted in a layer of solute denser and thicker. Initially, with the increase in the work pressure, the rate of permeation of oil miscella in hexane increased. However, up to 3 kg cm , the rate of permeation of miscella tended to become constant, which is a behavior usually observed in UF membranes. This trend was observed in three concentrations of miscella analyzed (20%, 30%, and 40%, m m ). This is attributed to the fact that the phospholipid layer due to the polarization of concentration retained on the membrane surface can control the permeation rate above the critical pressure. From this stage, therefore, the permeation rate is not more related to a function of the pressure. 

Kim et al. [21] reported that the increase in the concentration of miscella leads to a drop in permeate flux. These authors attributed this result to the fact that higher concentrations of solutes promote fouling. The transport of solutes to the membrane by convection causes a steep concentration gradient within the boundary layer, leading to the transport of solutes back into the interior due to diffusion phenomena. No more solute molecules can be accommodated due to the close arranganent and increased mobility of smaller molecules. This increase in concentration leads to precipitation and, therefore, the plugging or fouling in the membrane. 

Pagliero et al. [53] evalnated the recovery of solvent in miscella degummed snnflower oil/hexane with concentrations of oil between 25% and 45% (w/w). Manbranes were synthesized from PVDF, prepared by the process of phase inversion, and evaluated for their flow and selectivity toward the oil. Tests were performed in a 400 mL filtration unit, with an effective area of membrane equal to 31.66.10 m and agitation of 750 rpm. The best separation was achieved at pressures between 4 and 6 bar, and a tanperature of 50 C and 25% oil in miscella (w/w), corresponding to a flow of 30 L m h. 

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