Evaporation materials handling

In order to make a multipurpose plant even more versatile than module IV, equipment for unit operations such as soHd materials handling, high temperature/high pressure reaction, fractional distillation (qv), Hquid—Hquid extraction (see Extraction, liquid-liquid), soHd—Hquid separation, thin-film evaporation (qv), dryiag (qv), size reduction (qv) of soHds, and adsorption (qv) and absorption (qv), maybe iastalled. 

A chemical process consists of four reactors, 25 pumps, and a number of compressors, distillation columns, mixing tanks, evaporators, filter presses, and other materials handling and separation units. Each individual unit either requires or releases energy. 

Spiral-Conveyor Devices Figure 11-60 illustrates the major adaptations of this widely used class of material-handling equipment to indirect heat-transfer purposes. These conveyors can be considered for heat-transfer purposes as continuously agitated kettles. The adaptation of Fig. ll-60cf offers a batch-operated version for evaporation duty. For this service, all are package-priced and package-shipped items requiring few, if any, amdliaries. 

A number of different evaporator designs are illustrated in Fig. 8, and the variations based upon these concepts are many. Often, physical properties and materials handling considerations for the feed or the bottom streams (e.g., solids content, viscosity, heat sensitivity) will indicate that one evaporator type will be better suited for the duty than other types. 

Initially, 0.5 g (1 mmole) Rb2[Pt(CN)4] 1.5H204 is added to 15 mL H20 with heating (approx. 70°) and stirring. Approximately 1 mL liquefied chlorine gas, cooled in an acetone/dry ice bath, is added cautiously. ( Caution. Chlorine gas is a hazardous material. Handle with care ) The mixture is then stirred for 20 minutes to drive off the excess chlorine, and then an additional 2.5 g (5 mmole) Rb2[Pt(CN)4] 1.5H20 is added. The solution is allowed to stir for another 15 minutes and then evaporated by boiling to 10 mL and finally cooled in an ice bath. The resulting crystals are isolated. An X-ray diffraction powder pattern demonstrates that the crystals are monoclinic Rb 175 [Pt(CN)4] 1.5H20. 

The source material should be carefully cleaned and handled since, on heating, the volatile impurities and surface contaminants are the first materials to be vaporized. In some cases, the evaporant materials should be cleaned before they are used. Materials should be handled with metallic instruments since abrasive transfer can contaminate surfaces in contact with polymers. The source and source material can be outgassed and premelted prior to film deposition. 

The reactor effluent, containing 1—2% hydrazine, ammonia, sodium chloride, and water, is preheated and sent to the ammonia recovery system, which consists of two columns. In the first column, ammonia goes overhead under pressure and recycles to the anhydrous ammonia storage tank. In the second column, some water and final traces of ammonia are removed overhead. The bottoms from this column, consisting of water, sodium chloride, and hydrazine, are sent to an evaporating crystallizer where sodium chloride (and the slight excess of sodium hydroxide) is removed from the system as a soHd. Vapors from the crystallizer flow to the hydrate column where water is removed overhead. The bottom stream from this column is close to the hydrazine—water azeotrope composition. Standard materials of constmction may be used for handling chlorine, caustic, and sodium hypochlorite. For all surfaces in contact with hydrazine, however, the preferred material of constmction is 304 L stainless steel. 

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