Crystallizations

ATR designs and supplies crystallizer units made of glass in various sizes from laboratory, pilot plants size up to relatively small scale productions units. Various proposed theories and model concepts can be applied to the solution of crystallization problems, but actual results obtained in laboratory or pilot plant units are necessary for the design of full-scale units, in particular of the available data are incomplete. For these tests, ATR supplies crystallizers which are distinguished by universal corrosion resistance and have simple facilities for visually monitoring the course of the test. Due to our modular system, the units can be readily adapted to different test conditions.

Crystallization by supersaturation of solutions by means of evaporation and/or cooling is an important process in thermal process engineering.

Depending on the specifications for the end products such as-

  • Particle size
  • Particle size distribution
  • Product purity

A wide range of crystallizer types is available for coping with manifold crystallization problems. The criteria for selecting the crystallization process are the physical properties of the solutions and products and also economic considerations.

To obtain crystals from a less than, saturated solution, it is necessary for the solubility curve to pass from the single-phase region into the two-phase region (solution + salt).

The crystallization installations including the test units are designed in such a way that it can be used without modifications or with only minor modifications (interchangeable parts) for working on diverse evaporation problems and crystallization problems. It consists essentially of the actual crystallizer, a heat exchanger, the feed system and product removal system and the vapour condensation part.

The crystallization installation consists of universal crystallizer element, which is the core unit. The crystallizer can come with options such as external circulation or internal and external forced circulation. Both the internal and the external circulation are infinitely controllable. In this way, the supersaturation can be varied and adapted within wide limits.

The feed solution is in a temperature-controlled stirred vessel. The feed is introduced via a graduated and heated measuring vessel by means of a speed-controlled hose pump upstream of the heat exchanger.

The crystallized product (crystals+ mother liquor) is discharged from the system via a graduated and heated vessel. By means of a speed-controlled pump with an half open impeller, the solution is delivered from the crystallizer to the heat exchanger. This consists of a vertical shell and tube heat exchanger and it can either be cooled with cooling water, brine or another coolant or it can be heated with steam, hot water or other heating media. Since there are several tubes, the unit can be run with a relatively high vaporisation rate or cooling rate. Moreover in corrosion tests and incrustation tests, several tubes of different materials can be investigated at the same time.

The condensate system consists of a condenser, a vacuum connection and a graduated measuring vessel. Depending on the particular coolant and vacuum system, the unit can thus run under the appropriate vacuum. The unit can be fitted with all the requisite measuring points and controls so that it can run under stable conditions (in equilibrium) for a prolonged period.