Continuous vacuum bleaching

Figure 24. Standard continuous vacuum bleaching system. (Diagram Courtesy LFC Lochem B. V.) (This figure is available in full color at http //www.mrw.interscience.wiley.com/biofp.)...

Fig. 2. Continuous vacuum bleaching system (LURGI). Adapted from Appelqvist and Ohison (1972).

Procedure—The three most common types of contact bleaching methods are batch atmospheric, batch vacuum, and continuous vacuum. Although vacuum... 

The bleaching process is relatively straightforward—refined and/or degummed soybean oil is mixed with the appropriate dosage of earth, heated to a bleaching temperature, and then filtered. The three most common types of contact bleaching methods are batch atmospheric, batch vacuum, and continuous vacuum. This sequence is also the chronological order in which the methods were developed ... 

In operation, the oil is charged to the kettle and heated to about 70-80°C, the clay is added, and heating continued to about 95-105°C. About 0.5-1.5% clay is required depending on oil quality and product specifications. Contact time of 10-20 min is allowed at the maximum temperature before filtering is started. Filters may be of a variety of designs, but plate-and-frame type filters, rather than tank filters, are often used because they are somewhat easier to manipulate. In vacuum bleaching these operations are performed with the bleaching vessel under reduced pressure. 

Wear breathing apparatus, eye protection, laboratory coat, and butyl rubber gloves. Cover spill with 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand.8 For each 1 mL of iron pentacarbonyl, place 45-50 mL of household bleach (about 5% sodium hypochlorite solution) in a plastic bucket equipped with a stirrer and located in a fume hood. Dilute the bleach with three times its volume of water and, to this solution, slowly add the contaminated spill mix while stirring. Continue the stirring for a period of 48 hours, and then filter the slurry using vacuum filtration. The... 

Used engine oils can be reused. Sometimes, all that is needed is removal of particles by filtration or centrifugation. In others, it may be necessary to remove volatile acids and water by heating, followed by treatment with sulfuric acid, then lime, and, sometimes, bleaching clay. A final distillation under vacuum completes the rerefining.63 Another system uses propane at ambient temperature in a continuous process.64 The additives and impurities precipitate and settle out, after which the propane is flashed off and the... 

Vacuum Drying— Water-washed oil must be vacuum-dried if it is to be stored for any period of time. This is usually accomplished with a continuous spray drier, operating at 50 mm Hg absolute pressure. The vacuum-drying step is not required when the washed soybean oil is coupled directly to bleaching or silica purification (Farr, 2000). 

Bleaching powder, also known as chloride of lime, is produced by reacting hydrated lime with chlorine. It consists of a mixture of calcium hypochlorite (Ca(OCl)2 — the active ingredient), calcium chloride, calcium hydroxide and water. Some processes convert 40 % of the calcium hydroxide, giving about 25 % of available chlorine . Others continue chlorination to completion, which corresponds to 60% conversion and about 36% of available chlorine [31.3]. The reaction (31.1) is surprisingly complex. It is exothermic and drives off excess water. The product is dried under vacuum at temperatures below 85 °C. 

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