Factors to be considered in the selection of granulation method

Granulation is a process affected by many factors. The following factors should be considered when selecting an appropriate granulation method:

1. Characteristics of raw materials. For the selection of raw material characteristics, it is necessary to check whether the powder has enough fineness to ensure the rolling granulation; If extrusion granulation is selected, whether the plasticity of raw materials kneaded with water is sufficient; If it is the slurry product of wet grinding or liquid phase synthesis, whether it is easy to atomize; If shotcrete granulation is adopted, what is the thermal sensitivity of raw materials.

2. Processing capacity requirements The unit time processing capacity of different granulation methods varies greatly, so equipment investment and processing cost must be considered.

3. The product particle size distribution varies greatly with different granulation methods. For example, the particle size of shotcrete granulation is small, while the particle size of compressed granulation can be large. The granulation method should be selected according to the required granulation.

4. The products obtained by the methods of stirring, mixing, granulation and fluidization granulation are spherical particles with irregular shape; Rolling into a ball can obtain a smooth sphere; For the preparation of regular particles with special shape, compression and extrusion granulation are required. The selection of product particle formation shall consider the requirements and convenience of subsequent processes.

5. Under the condition that the particle strength of the product does not require high particle strength or is not expected to be too high (such as instant food), the method of early separation by spraying can be used; If the particle strength is required to be very high, compression granulation, adhesive addition and even sintering after forming are required, such as the production of grinding medium particles.

6. The porosity and density of the product particles also directly affect the strength of the product in these two indicators. For example, for the production of catalyst carrier particles, it is a contradiction to improve the porosity and strength at the same time. The porosity and density can be adjusted by process operation parameters.

7. The choice of dry/wet production process will inevitably lead to dust generation, so it is not suitable for the granulation of toxic or other dangerous powders. On the other hand, the wet rule requires drying after granulation and wastes some solvents. Some drugs cannot contact with water, or recrystallize to form other structures during drying, which is not suitable for wet process.

8. Space limitation The space occupied by equipment with different granulation methods varies greatly. This problem must be considered from the perspective of saving civil engineering investment.

While paying attention to the above factors, it should also be considered that one machine can be used for multiple purposes to select granulation and reaction at the same time. For example, the drum type rolling granulation equipment is also suitable for simultaneous operation with the presence of solid phase reactants or the chemical reaction process of producing solid phase products. The fluidization granulation method completes the drying of particles at the same time.