Crystallization forced circulation crystallizer

Fig. 2. Forced circulation evaporators (a) submerged-tube, shown as circulating magma crystallizer (b) submerged-tube, shown as suspension type...

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. 

Crystallizers with Fines Removal In Example 3, the product was from a forced-circulation crystallizer of the MSMPR type. In many cases, the product produced by such machines is too small for commercial use therefore, a separation baffle is added within the crystallizer to permit the removal of unwanted fine crystalline material from the magma, thereby controlling the population density in the machine so as to produce a coarser ciystal product. When this is done, the product sample plots on a graph of In n versus L as shown in hne P, Fig. 18-62. The line of steepest ope, line F, represents the particle-size distribution of the fine material, and samples which show this distribution can be taken from the liquid leaving the fines-separation baffle. The product crystals have a slope of lower value, and typically there should be little or no material present smaller than Lj, the size which the baffle is designed to separate. The effective nucleation rate for the product material is the intersection of the extension of line P to zero size. 

FK . 18-64 Forced -circulation (evaporative) crystallizer, (Swenson Process Equipment, Inc.)... 

In the forced-circulation-type crystallizer (Fig. 19-43) primaiy control over particle size is exercised by the designer in selecting the circulating system and volume of the body. From the operating standpoint there is little that can be done to an existing unit other than supply external seed, classify the discharge ciystals, or control the shiny... 

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 3.3 Agitated crystallizers (/) Swenson DTB Draft tube and baffle), (ii) Forced circulation (a) with and (b) without external heat exchange, in) Krystal Oslo a) circulating liquor b) circulating slurry...

Figure 9.17 Forced-circulation hatch crystallizer after Rohani, 2001)...

Figure 9.18 Continuous crystallizers, a) draft-tube and baffle (DTB), (b) single effect forced-circulation evaporative, (c) Oslo or Krystal type after Rohani, 2001)...

Forages, as ruminant feed, 10 863 Foraminifera, 17 690 Forastero cocoa beans, 6 353 Forced air cooling, of food, 21 560 Forced circulation crystallizer, 8 136 Forced-circulation evaporators, in sodium chloride solution mining, 22 803, 804 Forced convection, 13 245 Forced drainage experimental procedure, 12 12... 

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.

Natural circulation evaporators like those shown on Figure 8.16 may be equipped for continuous salt removal and thus adapted to crystallization service. For large production rates, however, forced circulation types such as the DTB crystallizer of Figure 16.10(g), with some control of crystal size, are the most often used. The lower limit for economic continuous operation is l-4tons/day of crystals, and the upper limit in a single vessel is 100-300 tons/day, but units in parallel can be used for unlimited capacity. 

Crystallizers (IFP, Chemical Engineers Handbook, p. 19.40) External forced circulation ... 

The forced-circulation crystallizer is a simple unit designed to provide high heat-transfer coefficients in either an evaporative or a cooling mode. Figure 12 shows a... 

FIGURE 12 Schematic diagram of a forced-circulation evaporative crystallizer. 

In the saturator process (see Figure 12.7), neutralization and crystallization are carried out in the same vessel. The sulfuric acid is delivered to the suction side and the ammonia to the pressure side of the forced circulation pump. Crystallization of the metastable solution gives particle sizes generally between 0.5 and 3 mm. The salt is continuously discharged at the lower end of the saturator. The salt is separated in centrifuges, dried, and cooled. The mother liquor is returned to the saturator. Impurities in the sulfuric acid can adversely affect crystallization. Small quantities of phosphoric acid, urea, or inorganic salts are added to promote crystal growth295. 

The circulating-magma design describes equipment in which crystals are intentionally transported with the liquor to the region where supersaturation is being created. Swenson-Walker, Wulff-Bock, and doublepipe crystallizers are examples of this type. Forced-circulation design is common. 

Newman and Bennett applied dimensional analysis in order to compare forced-circulation and draft-tube crystallizers. The first variables... 

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