Long-tube evaporators

Costs for forced circulation evaporators, long tube evaporators, and agitated falling-film evaporators are presented in Figs. 15-26 and 15-27. Information on purchased cost of specialized heaters is given in Figs. 15-28 and 15-29, while Figs. 15-30 and 15-31 present costs for process furnaces and direct-fired heaters. 

Evaporator Continuous Evaporator—long tube, thin film, wiped film... 

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... 

Fig. 1. Natural ckculation evaporators where C = condensate, E = entrainment return, F = feed, N = noncondensibles vent, P = product or concentrate, S = steam, V = vapor, and M = knitmesh separator (a) horizontal-tube, (b) short-tube vertical, (c) propeUer calandria, and (d) long-tube reckculating.

Fig. 3. Film-type evaporators (a) long-tube vertical, (b) falling film, and (c) horizontal tube. Terms are defined in Figure 1. M represents end view of (a).

FIG. 11-122 Evaporator types, a) Forced circulation, (h) Siibmerged-tiihe forced circulation, (c) Oslo-type crystallizer, (d) Short-tube vertical, (e) Propeller calandria. (f) Long-tube vertical, (g) Recirculating long-tube vertical, (h) Falling film, (ij) Horizontal-tube evaporators. G = condensate F = feed G = vent P = product S = steam V = vapor ENT T = separated entrainment outlet. 

FIG. 11-123 Temperature variations in a long-tube vertical evaporator. 

Best applications of long-tube vertical evaporators ... 

Major evaporator designs include forced-circulation, long-tube vertical (both rising and falling film), and calandria-type evaporators. The economics of a particular process will dictate the evaporator style and model best suited to a particular application. Forced-circulation and calandria evaporators are required for processes where crystals are formed. These evaporators are designed to keep crystals suspended in solution to prevent scaling of the equipment. Long-tube vertical evaporators are used to concentrate a liquid that does not have solids present. 

Figure 5. Natural circulation, long tube film evaporator.

Long tube vertical evaporators with either natural or forced circulation are most popular. Tubes are 19-63 mm dia and 12-30 ft long. 

Figure 10.32. Long-tube evaporators (a) Rising film (b) Falling film...

Over-all heat transfer coefficients54 Long tube evaporators... 

Brooks, C. H. and Badger, W. L. Trans. Am. Inst. Chem. Eng. 33 (1937) 392. Heat transfer coefficients in the boiling section of a long-tube, natural circulation evaporator. 

This is a process mainly used in power plants for separation of dissolved matters by evaporation of the water. Multistage flash distillation, multiple-effect vertical long-tube vertical evaporation, submerged tube evaporation, and vapor compression are effective process equipment. It may require pH adjustment. The process removal efficiency is about 100%. 

Although equipment such as long-tube evaporators, thermosiphon reboilers, and tubular steam generators has been used for many years, rela-... 

Figure 8.16. Some types of evaporators, (a) Horizontal tube, (b) Calandria type, (c) Thermocompressor evaporator, (d) Long tube vertical, (e) Falling film, (f) Forced circulation evaporator-crystallizer, (g) Three types of Oslo/Krystal circulating liquid evaporator-crystallizers.

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