Bleaching equipment, batch

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. 

A comparison of typical bleaching recipes of cotton fabric for batch bleaching in different equipment with hydrogen peroxide is summerised in Table 7.1. When making-up a bleaching bath, naturally the quality of cotton, degree of pre-treatment, liquor ratio, equipment used and temperature must all be taken into account. 

The soap phase, which contains the precipitated, nonhydratable phos-phatides, and other oil-insoluble material, is then separated from the oil phase. The oil is water washed to reduce the soap concentration to less than 50 ppm. A small amount of citric acid or phosphoric acid may be added to the washed oil to "split" remaining traces of soap. This improves the efficiency of subsequent bleaching. The oil is then dried. Most of the industry uses continuous process equipment, but batch process installations are also still in use. 

In the 1800 s small batch type oil extraction systems were common in Europe. The same vessel was used for both extraction and meal desolventizing. Today, only extraction of specialty and high value oils and recovery of oil from spent bleaching clay are carried out in batch extractors. A rotating drum and a vertical cylindrical kettle equipped with a vapor tight cover and a low-speed agitator are two popular batch type extractor designs. 

Chem. Descrip. Mixt. of polyfunctional org. and inorg. substances Uses Peroxide bleach bath stabilizer, dispersant, chelating agent for bleaching cel-lulosic fibers and their blends in pad-steam, long liquor, or cold-pad batch applies. dispersant promoting suspension and flushing of silicates for reduction/prevention of silicate deposits on fiber and equip. 

Use Level 5-10 g/l (cold pad batch) 6-10 g/l (continous knit equip ) 2-4 g/l (conventional hydrogen peroxide bleach)... 

Features Nonsilicate useful in both batch and continuous processes provides telly bleached fabrics without chem. buildup in equip. eliminates need for seques-trants economical stable to most chems. used in scouring Properties Brn. liq. mild odor readily sol. in water dens. 8.4 Ib/gal pH essentially neutral... 

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