DTB Crystallizer
Draft Tube Baffle Type (DTB) Crystallizers are suitable for vacuum cooling and processes with moderate evaporation rate. Due to the small amount of additional heat required in the process phase, it has a positive effect on operating costs.
(DTB) Crystallizers are generally used in the chemical and fertilizer industries to produce crystalline products such as ammonium sulfate, potassium chloride, monoammonium phosphate.
DTB Crystallizers operate with low supersaturation, which is a limitation for crystal growth; very large crystals can only be produced by dissolving the fines. In processes when re-dissolution of fine crystals is not necessary or desirable, the rate of crystallizator internal circulation is adjusted so that it has minimal nucleation effect on the suspension.
To ensure effective crystallization process control, it is important to control the retention time and crystal mass to achieve optimum conditions for the crystal-specific surface and the fastest possible growth. The mass flow around the crystallizer needs to be managed for settling by gravity to remove the crystal gruel and to achieve a crystal slurry density.
The DTB Crystallizers have an internal or external circulator that pushes the solution upwards in a draft tube, and there is an annular settling area outside the crystallizer. The solution in the crystallizer moves upwards at very low speed. This allows large crystals to return through the draft tube to the main circulation, while only fine crystals below a certain grain size re-dissolve with temperature, thus creating an additional supersaturation point.
