Atmospheric bleaching

Color and peroxide values (PV) have been compared for tallows bleached at atmospheric pressure and under vacuum at several temperatures (67). At 90°C, atmospheric bleaching gave better color than bleaching under vacuum, but peroxide values were lower for the vacuum bleached product (PVs of 2 versus 16, respectively). At higher temperatures, color was better and peroxide values were lower. A bleaching temperature of 90°C to 110°C was recommended for beef tallow. 

Trace metals in the crude oil are removed in the refining and, primarily, in the bleaching steps (27-32). Inadequate bleaching of the oil can leave trace metals at high concentration in the oil. This can promote autoxidation in the fryer. In addition, atmospheric bleaching, poor vacuum in the vacuum bleacher, high temperature in the bleacher, or poor vacuum in the deodorizer can produce free radicals in the fresh oil (33). These free radicals can rapidly oxidize the oil in a fryer. 

Sulfurization of unsaturated compounds and meicaptans is normally carried out at atmospheric pressure, in a mild or stainless steel, batch-reaction vessel equipped with an overhead condenser, nitrogen atmosphere, an agitator, heating media capable of 120—215°C temperatures and a scmbber (typically caustic bleach or diethanolamine) capable of handling hydrogen sulfide. If the reaction iavolves the use of H2S as a reactant or the olefin or mercaptan is a low boiling material, a stainless steel pressurized vessel is recommended. 

Sulfurchlorination of unsaturated compounds or mercaptans is normally carried out at atmospheric pressure in a glass-lined reaction vessel because of the potential to Hberate HCl during the reaction. The sulfurchlorination vessel is equipped with a cooling jacket or coils (very exothermic reaction), a nitrogen or dry air sparging system, an overhead condenser, and a caustic or bleach scmbber. If one of the reactants (olefin or mercaptan) is alow boiling material, ie, isobutylene, a glass-lined pressure vessel is recommended. 

Besides readings of Earth s surface temperatures taken with standard glass thermometers, direct readings of atmospheric temperatures have been taken with satellites and weather balloons. In addition to direct measurements of Earth s recent temperatures, proxy measurements of temperatures from farther in the past can be derived from borehole temperature measurements, from historical and physical evidence regarding the e xtent and mass of land and sea ice, and from the bleaching of coral reefs. 

OPEN PAN SULFITATION (OPS) A sugar cane mill process wherein sugar solutions are concentrated by boiling in an open pan at atmospheric pressure, rather than under a vacuum, and bleached (see SULFITATION) to produce a white sugar product. 

WASTE DISPOSAL METHOD All decontaminated material should be collected, contained and chemically decontaminated or thermally decomposed in an EPA approved incinerator, which will filter or scrub toxic by-products from effluent air before discharge to the atmosphere. Any contaminated protective clothing should be decontaminated using HTH or bleach and analyzed to assure it is free of detectable contamination (3X) level. The clothing should then be sealed in plastic bags inside properly labeled drums and held for shipment back to the DA issue point. Decontamination of waste or excess material shall be accomplished in accordance with the procedures outlined above with the following exception ... 

Reduced sulfur fuel, 18 667 Reducing agents, 9 687, 688-689 Reducing atmospheres, reaction of photoholes with, 19 84-85 Reducing bleaches, 4 63-64 bleaching mechanism, 4 47 Reducing chemistry, in water treatment, 23 222-226... 

Ozone. An unstable, pale-blue gas, and a sibling of oxygen existing in the form of O3. Ozone can be formed in the atmosphere by subtle electrical transfers, especially from pollutants or by shock from lightening. As an industrial gas, it is used as bleach and purification of water due to its reactivity. 

Information regarding death in humans exposed to atmospheres of chlorine dioxide is limited to a single case in which a bleach tank worker died after being exposed to an airborne chlorine dioxide concentration of 52 mg/m (18.5 ppm) for an unspecified amount of time (Elkins 1959). 

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