En construction

Different types of crystallization units can be proposed:

  • Crystallization by concentration

This process concerns firstly products having a solubility which does not vary appreciably with the temperature: sodium chloride, ammonium sulphate, sodium carbonate, citric acid, …

Another application concerns the recovery – or elimination – of products from liquid effluents, often very dilute : eluates, residual substances from reaction tanks, solution stripped in absorption towers, ….

In most cases, the actual crystallisation unit is combined with a pre-concentration stage.

  • Crystallization by cooling

When the solubility curve varies with the temperature (direct solubility), the technique of crystallisation by cooling may be applied. The operating temperature is usually obtained by applying a vacuum to the hot concentrated feed solution, or by indirect heat exchange with a cold source (water or thermal fluid). Due to the risk of solids build-up on the heat exchange surfaces, the vacuum cooling solution is retained in most cases. This technique is applied for example in the production of boric acid, melanin, ammonium molybdate, glauber salt, …

  • Cristallization by reaction or by equilibrium displacement

Crystallisation and chemical reaction are two single operations which may occasionally be combined.

Kestner (backed by its experience gained in the manufacture of synthetic products such as ammonium sulphate, ammonium perchlorate or ammonium phosphate) can offer equipment which combine these two features. In most of the cases mentioned here, the question of energy efficiency often becomes a major factor and a specific study is devoted to the integration of the crystalliser in the process as a whole, for each project.

For each one of these processes, we are able to provide different technologies:

  • DTB,
  • Oslo,
  • Forced circulation,
  • Induced circulation.

We deeply analyze our customers’ final product specific requirements like granulometry, purity… in order to propose the most suitable solution. GEA Kestner also offers complete packages that include solids / liquids’ separation such as centrifugation, filtration, drying.

Kestner has also an in-depth experience in the design of elutriation legs which covers:

  • Classification of crystals in the leg, to produce a narrow crystal size.
  • Cooling of the crystals by contact with cold mother liquor, to get less suspension flashing in the dewatering equipment.
  • Increase in crystals purity by replacement of mother liquor by a feed stream to displace the impurities sticking to the crystals.