Oslo type crystallizer

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. 

All the CSD data examined in this work are those obtained by CEC (Crystal Engineering Corp.) style Krystal-Oslo type crystallizer (Figure 5), except sample no.22 by DTB type crystallizer. Figure 6 and Table III illustrate some examples of... 

In fact, reality shows that the increase of the average retention time r leads to different results in the basic types of crystallizers. The dotted lines in Figure 11.7 show the typical deviation from the linear dependence of growth on the average retention time in DTB and FC crystallizers. Only products from the Oslo-type crystallizer with its suspension not in contact with the impeller pump follow the... 

Due to their easier operation and their more compact design, the suspension-type crystallizers are selected wherever possible the FC crystallizers for all applications with moderate claims toward particle sizes (90% of all crystallizers worldwide are of FC-type) and the DTB crystallizers for all applications up to a (RRSB distribution) of 2.5 mm (about 8%). The rest of the applications above the d of 2.5 mm use the Oslo-type crystallizer (about 2%). 

A quadmple-effed evaporative crystallization is chosen as the adequate process (Figure 16.18). Whereas FC-type crystallizers are selected for the production of PDV salt with the desired average particle size of around 0.4 mm, a Messo Oslo-type crystallizer is chosen to produce the granular salt with the average particle size of... 

The question of the salt retention time for the Oslo-type crystallizer can be left open until the start-up. The need to clarify the entire recirculation completely leads to a crystallizer diameter allowing any retention time between more than 10 h and lower than 20 h (easily achievable just by decreasing or increasing the crystal bed mass inside the crystallizer by simply opening or closing the salt withdrawal for a longer time). 

The feed point of the concentrated brine is the receiver tank B (Figure 16.19). The only crystallizer fed from here is the Oslo crystallizer. While the concentrated brine in this receiver is still undersaturated, the Oslo crystallizer can be fed with crystal-free solution all the time - the absolute precondition for the granular production in the Oslo-type crystallizer. 

The feed brine not taken to feed the Oslo-type crystallizer leaves the receiver tank B to receiver tank C by overflow. The fines-containing centrates and the hydro-cydone overflows from the separation stations are collected in the receiver tank C, too, where the still existing undersaturation redissolves the fines, before the resulting mixture is fed in parallel to the FC-type crystallizers. 

Figure 16.20 Granular sodium chloride from the Oslo-type crystallizer. Note the rounding of the crystals due to attrition.

Mg - %Ca. The Oslo-type crystallizer was able to produce an average particle size of above 2 mm, fluctuating between 1.8 and 3.5 mm. The period between two maxima was 2 days. While with increasing length of the operation the fluctuation became dampened, the uniformity of the salt bed was reduced. 

The Messo Oslo-type crystallizer reached runtimes of around 3 weeks between washouts without any disturbance from scaling. This was a breakthrough in the Oslo crystallizer history for salt crystallization and the approved consequence of the inversion of the internal recirculation. The process required about 11 t/h of heating steam and evaporated 34 t of water per houn... 

Another type of crystallizer is the Oslo-type unit shown in Figure 24. In units of this type, the object is to form a supersaturated solution in the upper chamber and then reHeve the supersaturation through growth in the lower chamber. The use of the downflow pipe in the crystallizer provides good mixing in the growth chamber. 

The reactants can be mixed in the circulation piping of a forced-circulation-type crystallizer, or Oslo crystallizer (Figure... 

Whereas the FC-type crystallizer is designed to safely avoid spontaneous nucleation only, additional measures and tools are integrated in the larger DTB and Oslo crystallizers to make their retention time longer leading to coarser crystals. 

In the growth types of crystallizers, DTB and Oslo-type, these interrelationships have all been taken into account. In the designs intended to produce coarser granularity via the longer retention times, these measures are taken in order to keep the energy input into the suspension smaller than that in the FC crystallizer with its short retention time. For this reason, the crystallizer designs differ from one another mainly with respect to the layout and location of the circulation pumps (whether these are inserted in the suspension or in clarified solution cf. Figure 11.2). 

An Oslo surface-cooled crystallizer is illustrated in Fig. 18-71. Supersaturation is developed in the circulated liquor by chilling in the cooler H. This supersaturated liquor is contacted with the suspension of ciystals in the suspension chamber at E. At the top of the suspension chamber a stream of mother hquor D can be removed to be used for fines removal and destruction. This feature can be added on either type of equipment. Fine ciystals withdrawn from the top of the suspension are destroyed, thereby reducing the overall number of ciys-tals in the system and increasing the particle size of the remaining product ciystals. 

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)...

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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