DTB CRYSTALLIZER

DTB crystallizer is for the production of large-size crystalline materials such as ammonium sulfate, potassium chloride and diammonium phosphate.

WORKING PRINCIPLE

The Draft Tube Baffle Crystallizer (DTB) consists of five basic elements:

Crystallizer vessel.
Circulation pumping propeller
Baffles
The circulation pump.
The heat exchanger.

It is specially designed to produce coarse crystals with narrow size distribution. The DTB can produce large size particles (up to 3mm) due to its gentle agitation of growing crystals with very limited breakage. It has a controlled residence time for optimal growth and a long operating cycle with limited encrustations.

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Particular features:

Low secondary nucleation due to low mechanical energy input (internal circulation)
Removing of fines (d < dcritical) from the internal baffle
Efficient fines destruction due to heating and/or dilution
Production of large size crystals (up to 3mm)
No or little heat make-up (fine dissolution)
Controlled residence time for optimal growth
Long operating cycle with limited encrustation
Appropriate for vacuum cooling (no external loop) and evaporative crystallization (moderate capacities)
Compact arrangement

Basic Principles of the DTB Crystallizer

Growing crystals are brought to the boiling surface where supersaturation is most intense, and growth is most rapid.
The baffle permits separation of unwanted fine crystals from the suspension of growing crystals, thereby affecting control of the product size.
Sufficient seed surface is maintained at the boiling surface to minimize harmful salt deposits on the equipment surfaces.
Low head loss in the internal circulation paths makes large flows at low power requirements feasible.

APPLICATION INDUSTRIES

Inorganic chemical

Ammonium sulfate, Nickel sulfate, Peroxodisulfuric sodium, Alum, potassium chloride Barium chloride, Sodium nitrate, Soda ash, Silver nitrate , Sodium hydrogen carbonate , Potassium carbonate, Sodium Phosphate, Boric acid, etc

Organic chemical

Bisphenol-A, Caprolactam, Acrylamide, Hydroquinone, Adipic acid, Ammonium adipic acid Fumaric acid, Trehalose, Aspartame, Amino acid, etc

MODELS AND TECHNICAL SPECIFICATIONS

Key Specifications & Design Parameters
Parameter	Typical Range	Impact on Crystallization	Remarks
Impeller Speed	50–300 RPM	Higher speed = smaller crystals (more nucleation)	Design on Request
Draft Tube Diameter Ratio (D/Tank D)	0.3–0.6	Affects circulation efficiency	Design on Request
Residence Time	1–6 hours	Longer time = larger crystals	Design on Request
Supersaturation Control	ΔC = 1–10%	Critical for crystal growth vs. nucleation	Design on Request
Cooling/Evaporation Rate	Depends on solute	Faster cooling = more nucleation	Design on Request
Slurry Density	20–40% solids	Higher density = more collisions (attrition)	Design on Request
Advantages vs. Other Crystallizers
Feature	Draft Tube	Scraped Surface	Stirred Tank
Crystal Size Control	Excellent	Good	Poor
Fouling Resistance	Moderate	Best	Poor
Energy Use	Medium	High	Low
Scalability	Industrial-scale	Limited by scraping mechanism	Easy
Shear Sensitivity	Low-Medium	High (scraping)	Medium