Spray Granulation Spray Granulation Gives Solid Materials Customized Properties

Author / Editor: Dr. Michael Jacob / M.A. Manja Wühr

Flowability, dustlessness and easy dosing — these are some of the plus points of granulates produced by fluidized or spouted bed technology. The product design can be specifically influenced by process engineering.

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The principle of spray granulation: Convective drying or solidification and particle development take place in a single process step.
The principle of spray granulation: Convective drying or solidification and particle development take place in a single process step.
(Picture: Glatt)

Whether for subsequent use as solid compounds in washing agents, food or feed products or to increase the stability of chemical substances, e.g. reduction of the decomposition risk, or for volume reduction to make transport and storage easier, or for the production of stable multi-component systems, e.g. ceramics or catalysts, or also to minimise risk potentials — a variety of industrial applications require a conversion of one or more raw materials or substances being available in form of liquids to a long-term stable solid product form with exactly defined properties.

Spray granulation processes using fluidized or spouted bed technology provide processing options for the production of free-flowing granulates directly from the liquid. This process can be used for a variety of material systems, applications and industries as the product properties can be varied by the selection of specific process parameters and technical apparatus configurations. Spray-granulated products are typically characterised by the following properties:

  • Dustlessness, good abrasion resistance
  • Roundness, narrow grain size distribution
  • Very good pourability and flowability
  • Excellent dosing properties
  • Compact structure, frequently with an almost closed surface
  • Low hygroscopicity due to a lower specific surface compared to powders or agglomerates
  • High bulk density compared to powders or agglomerates
  • Versatility in the application

These product properties are required in nearly all industries. In the food industry, phosphates, stabilizers, additives, sweeteners, fatty acids or flavouring agents are spray-granulated, for example. The chemical industry uses the same process for detergent components, fragrance, silicates, diverse salts or salt mixtures and special chemicals with a high purity.

In the fertilizer industry, very innovative products can be efficiently produced, e.g. multi-component-products or special fertilizers. Also very complex material systems such as plant protection products, ceramics, catalysts, glass components are dried by spray granulation. Further applications fields for the process include the treatment of thermally sensitive products such as enzymes, proteins, yeasts or micro-organisms.

For this, the spouted bed technology (ProCell design) is preferably used as it allows users to work with considerably shorter residence time in the apparatus in contrast to the classic fluidized bed. Furthermore, spray granulation can be used for actives or additives of various types and origin. Active ingredients for pharmaceutical applications can be processed to granules directly after the upstream chemical synthesis, for example.