Crystallizers Oslo-Krystal

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.

Figure 8.45. Oslo-Krystal evaporator types a) waisted, (b) and (c) monolithic. A and B, circulating liquor outlet and inlet C, vapour outlet D, crystal magma outlet E, liquor overflow. After Bamforth, 1965)...

The principles of the Oslo-Krystal process, already referred to above in connection with cooling crystallizers, can also be applied to evaporative crystallization. Three forms of the Oslo-Krystal evaporating crystallizer are shown in Figure 8.45. The construction of these crystallizers, commonly used in multiple-effect systems, is of the closed form, i.e. the vaporizer is directly connected with the crystallizer body to form a sealed unit. 

Bamforth (1965) has given operating details of several Oslo-Krystal plants producing ammonium sulphate. Oslo-Krystal evaporating crystallizers have also been used for the manufacture of ammonium nitrate, borax, boric acid, sodium chloride, sodium dichromate and oxalic acid. In the case of sodium chloride, this type of crystallizer can, when operated under appropriate conditions, also produce spherical crystals of a median size 2-3 mm as opposed to the <0.5 mm cubic crystals normally produced in a conventional forced circulation evaporating crystallizer. An example of this interesting and commercially useful crystalline form is shown in Figure 8.46 where a microscopic inspection of... 

As described above, the Oslo-Krystal unit is a fluidized-bed agitated crystallizer in which the gentle action minimizes secondary nucleation and allows large crystals to grow. Oslo-Krystal vacuum crystallizers can be of the open Figure 8.51) or closed Figure 8.45) types. In the former the crystallization zone is at atmospheric pressure. In the latter all parts of the equipment are under reduced pressure. 

Figure 8.51. An Oslo-Krystal vacuum crystallizer showing two different methods of operation a) classified suspension, b) mixed suspension. After Saeman, 1956)...

CVs in the range 30-50%, although sodium chloride appeared consistently to be lower (20-30%). Industrial CV data have also been reported by Palmer (1970) for a large number of substances crystallized in Oslo-Krystal units. 

Palmer, K. (1970) Product size performance from Oslo-Krystal crystallizers. In Industrial Crystallization, Institution of Chemical Engineers Symposium, London, 190-201. Pamplin, B.R. (1980) Crystal Growth, 2nd edn., Pergamon, Oxford. 

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

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 circulating-liquor crystallizers, such as the Krystal-Oslo unit, supersaturation is created in what is essentially clear liquor. This clear liquor is then transported to the crystal bed where the supersaturation is released. 

This type of crystallizer is generally known as the Krystal or Oslo" unit and was developed in Norway by Isaacssen and Jeremiassen [54]. Figure 8.21 illustrates disgrammatically the use of forced circulation in conjunction with this design of crystallizer for ammonium sulfate production. 

The best-known representative of the group of fluidized bed crystallizers is the Oslo crystallizer [7]. Today, there are two known versions (Figure 11.16). The original design was developed in the 1920s by a Arm called Krystal A/S in Oslo, which explains the name. This design is susceptible to malfunctions in the case of products that tend to produce incrustations, as falling crusts can block the annular gap at the entrance to the fluidized bed. In the case of the crystallization of sodium chloride. 

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