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What is the role of a crystallizer?

Date:28 July, 2021   |   No Comments   |   Posted By Team Alaquainc

A crystallizer is heating equipment that transforms amorphous PET into a semi-crystalline state from virgin, post-process or scrap PET.

Processors who produce or use considerable amounts of scrap or recycled PET material need crystallizers. Because processing converts virgin PET to amorphous PET, which cannot be reprocessed in high concentrations, those who must re-use this material have only two choices:

  • Process a small percentage of amorphous PET regrind (10% or less) with virgin PET, or blend a small percentage of amorphous PET regrind (10% or less) with virgin PET before processing.
  • Using a crystallizer, “re-crystallize” the amorphous PET regrind to a semi-crystalline form (similar to virgin PET).


What is the function of a crystallizer?

A crystallizer raises the temperature of granulated amorphous PET to slightly below its melting point, but above its glass transition temperature. Infact, when heated PET reaches its “crystallization” temperature, the amorphous PET molecules rapidly change state: Hence, crystalline structures develop and align inside the molecules and the material transitions from an amorphous to a semi-crystalline state.

Next, when the transformation is complete, the “crystallized” PET is ready for drying (if necessary) and processing in the same way that virgin PET is. So, when amorphous materials are heated during drying, they tend to clump together since they haven’t crystallized. Several issues arise from agglomerated materials: 1) They cause insufficient residence time for some materials by disrupting smooth mass flow through a drying hopper. 2) Large agglomerated clumps resist drying, retaining undesirable moisture due to their size. 3) Agglomerated clumps can become caught or bridged in downstream processes, resulting in a slew of other material handling problems.

Your crystallizer equipment can perform crystallization either in a continuous or batch process, depending on its capabilities. Typically, sizing for crystallizers is based on the hourly capacity for crystallizing materials.


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What are the types of crystallizers?

Majorly the crystallizers are of two types mentioned below:

  • Hot-air hopper Crystallizers
  • Infrared Drum (IRD) Crystallizers

Hot-air hopper Crystallizers-

Crystallizers, much like dryers, feed material into a hopper, heat it to a precise temperature using warmed air, and then discharge it into a downstream process. A hopper-type crystallizer and a dryer, on the other hand, have numerous key functional differences:

Crystallizers use ambient air-

Use heated ambient air in open loop crystallizer. Note: Crystallization doesn’t control moisture as effectively as drying. Ensure PET is thoroughly dry before use if damp.

Crystallizer hoppers use an agitator-

For seamless material flow in amorphous PET, mechanically agitate the hopper to prevent clumps during and after crystallization.

Infrared Drum (IRD) Crystallizers-

Infrared Drum (IRD) crystallizers differ from hopper-type crystallizers in several ways:

Infrared Heat Source-

An infrared emitter, located in the drum’s middle, heats material directly as it rotates in the drum, eliminating the need to inject heated air.

Rotating Horizontal Drum-

Instead of a vertical hopper, the IRD employs a horizontal rotating drum. Continuous rotation prevents clumping, ensures thorough material mixing, eliminating the need for agitators in vertical crystallizer hoppers.

Can Simultaneously Crystallize and Dry-

Cool air swiftly removes moisture as the infrared source heats pellets, making them rise rapidly. IRD crystallizers remove over 90% of material moisture but lack the precision of a desiccant dryer for moisture control.

Alaqua is the best crystallizer supplier in the USA along with other processing equipment such as the evaporator, solvent recovery, and other equipment to serve various industrial requirements. Alaqua supplies processing equipment such as crystallizers made in the USA worldwide for various food processing, pharmaceutical, and various chemical industries. To know more contact us today!

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