Vacuum pans, batch and continuous types (VKT)

BMA’s continuous vacuum pan „VKT“ (Verdampfungs-Kristallisations-Turm) is based on a proved design principle: the vertical cylindrical crystallization chamber of the batch plan. It allows the use of mechanical circulators ensuring excellent circulation and mixing of the massecuite. The VKT consists of superimposed crystallization chambers, i.e. it is a cascade of stirring vessels, where the massecuite flows from top to bottom under its own gravity. The forced circulation practiced, in conjunction with constantly low massecuite levels, allows the use of low-pressure heating steam, as the hydrostatic pressure of the massecuite column in a continuously operating unit is much lower than in a conventional pan.

Versions
The preferred VKT version has four super-imposed chambers. It can be employed for all sugar varieties such as 1st and 2nd white (refined and basic), raw and low-grade, at beet and cane sugar factories and in refineries. For cleaning purposes, one chamber each of the white and raw sugar units can be bypassed via appropriate pipelines. The design of the 4-chamber pan can be such to permit retrofitting a 5th chamber to increase its capacity. Low-grade and raw sugar VKTs have an external overflow system.
  If the space occupied by an existing station equipped with modern, well-preserved batch pans shall be utilized for continuous operation, a horizontally cascaded unit (VKH) can also be used. All batch pans used should be similar in design and should have stirrers installed.

Operation
The seed produced in a special pan seeding unit as described above is fed into the first crystallization chamber. Feed solution continuously fed into all chambers, intermixing between the chambers being excluded. The dry substance content and, consequently, the crystal content of the massecuite increases from chamber to chamber and reaches its maximum in the final chamber. Where a low-grade VKT is concerned, the optimum nonsugar/water ratio for subsequent cooling crystallization can be set in the final chamber.
Each VKT chamber can be adjusted separately, a fact which ensures safe and continuous operation and brings about technological advantages such as

• uniform tapping of heating steam from evaporators,
• uniform tapping of feed solution,
• uniform vapor tapping and condenser loading,
• uniform massecuite discharge.

Brochure page 10 (PDF 855 KB)

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