Factors affecting fluidized bed granulation need to be emphasized

Fluidized bed granulation is also called one-step granulation, which is mainly a method in which three steps of mixing, granulating and drying of conventional wet granulation are completed in a closed container. Fluidized bed granulation allows the drug powder to remain in a suspended fluidized state under the action of a bottom-up gas stream, which will be sprayed from the upper or lower portion into the fluidization chamber, and the powder reaggregates into particles.

Fluidized bed granulation has many advantages. For example, dry mixing, wet mixing, stirring, pellet forming and drying of materials are all done in the same fluidized bed equipment, which reduces a lot of operation and saves production. practice. Fluidized bed granulation also allows production to be carried out in a sealed environment, which not only prevents external contamination of the drug, but also reduces the operator's chances of contact with irritating or toxic drugs and excipients.

In addition, the particle size obtained by the fluidized bed granulation technique is uniform, and the fluidity and colloidal formability are good. It is also possible to distribute the drug having a very low content in the component more uniformly in the obtained granules. It is worth mentioning that the fluidized bed can also produce many layers and multi-phase functional particles.

Although fluidized bed granulation has many advantages, it is a relatively complicated process and is also affected by many factors. For example, equipment factors, in the fluidized bed granulator, the movement of the air splitter and the container army particles has an impact. Among them, the material and shape of the container have a greater impact on particle motion.

If the operator is using a top-spray fluidized bed, the position of the nozzle will affect the uniformity of the spray and the degree of wetting of the material, and in order to make the particle size distribution as narrow as possible, the spray area should be adjusted as much as possible to the surface area of ​​the wet bed. Because if the position is too high, the distance from the nozzle to the material is longer, which increases the volatilization of the liquid medium, and the material cannot be completely wetted, showing a phenomenon of spray drying.

When the nozzle position is too low, the adhesive cannot be sufficiently contacted with the material after being atomized, the particle size of the obtained particles is not uniform, and the nozzle leading edge is also prone to ejection failure. Some experts have suggested that the structure of the mixer will also have a great influence on the granulation when using the rotary cutting fluidized bed granulation.

Another example is the prescription factor, including the nature of the material, the choice of binder, and so on. The author understands that in fluidized bed granulation, the particle size and particle size distribution are the more important physical properties of the material. The smaller the particle size of the material powder, the larger the surface area of ​​the material and the greater the amount of binder required.

When granulating with a hydrophilic material, the powder and the binder are mutually soluble, and the particles are easily condensed, so that fluidized bed granulation is suitable. The particles of the hydrophobic material need to be bonded together by the bridging action of the binder, and the solvent is evaporated to form particles.

When the material is a water-absorbing substance, such as starch, the surface of the powder may not be completely wetted due to the water absorption of the material, and the flow rate of the binder should be increased. Because even the same material, the flow rate of the binder should not be the same due to the difference in water content, and the larger the water content of the material under the same binder flow rate, the larger the pellet produced.

The choice of binders also needs attention. Fluidized bed granulation experts say that the role of the binder is to form a solid bridge between the powders. The type, concentration and method of addition of the binder have a great influence on the granulation. . “The choice of binder is the key to the entire fluidized bed granulation process. The ideal binder should have a good affinity with the surface of the material powder to facilitate wetting and adhesion to each other.” The expert said .

In general, the fluidized bed granulation has the advantages of uniform particle strength, fluidity, compression formability, and a relatively low content of the components in the particles, which is more uniform in the particles and saves production time. However, although the advantages of fluidized bed granulation are numerous, there are many influencing factors, and relevant personnel need to consider carefully when using technology or equipment.

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