Fluidized bed granulation experience sharing
Fluidized bed granulation has made a certain summary of fluidized bed granulation through the development of the project and the reading of related materials, and shared it with everyone, I hope to help everyone. The entire summary is divided into
1. Equipment articles
A complete fluidized bed facility consists of an air handling unit, material tank, expansion tank, filter bag, spray system (adhesive preparation tank, peristaltic pump, spray gun) and control system. Be explained:
Air treatment unit: The air used for fluidized bed granulation must be filtered and dehumidified (humidified). Especially the dehumidification (humidification) device is emphasized here. The humidity of the air will have a significant effect on the granulation effect of the fluidized bed. In different seasons, the humidity of the air is significantly different. The 1 degree dew point in winter is equivalent to 4 grams of water per kg of air, while the 20 degree dew point in summer is equivalent to 15 grams of water per kilogram of water. If there is no humidification or dehumidification equipment, then It may result in poor reproducibility of the process. Dew point temperature is not as low as possible, low material is easy to produce static electricity, and the final yield will also lead to low LOD; too high will prolong the drying time. It is generally recommended to control the inlet dew point at 8-10 degrees, 10 degrees. The dew point temperature is equivalent to 8 grams of water per kg of air. For materials with a very high fine powder rate, a dew point temperature of about 15 degrees can be seen, which can effectively reduce static electricity and ensure fluidization.
Material tank: The material accounts for 35-90% of the total volume of the material tank. The bulk density of the pellets obtained after powder granulation and the starting powder will increase slightly, but the difference is not large, so as long as the starting amount is guaranteed to be The material is super-excellent in the volume range. The opening ratio of the material tank is very important, which determines the pressure difference when the material is fluidized. The opening ratio is generally 12%, and the diameter of the chassis is generally 100μm. The spray gun: the volume of the liquid diffuses about 1000 times after being atomized. The size of the nozzle generally does not have much effect on the granulation effect. Small-caliber nozzles are recommended for solution-based adhesives. Large-aperture nozzles are recommended for suspensions and starches. There are three types of nozzles: single nozzle type, three nozzle type and six nozzle type. However, it should be noted that the spray range of each nozzle cannot overlap when the multi-nozzle type is used, otherwise the adhesive will be partially excessive. Filter bag: polyester material is usually used, generally 20μm transmittance, and Zui can reach 3-5μm. Currently, there is also a metal filter. The granules are backflushed by compressed air during granulation, each filter. They are equipped with a flushing nozzle for online cleaning.
2. Materials
I mainly want to introduce the adhesive used in fluidized bed granulation.
(1) Starch pulp: In the fluidized bed granulation, the concentration of starch slurry is generally recommended to be 8%. It is necessary to pay special attention to the difference in viscosity of starch slurry at different temperatures, so when using a peristaltic pump to spray liquid The rate will be different. There is a parameter for your reference. It is recommended to stop heating when the starch slurry is heated to 82-86 degrees. The temperature is always greater than 60 degrees during the whole granulation process. If the viscosity of the starch slurry is low, a mixed binder such as 6% starch slurry + 3% PVP can be used.
(2) Pregelatinized starch: It can be partially dissolved in cold water. The recommended concentration is 5-8%. It can also be directly added to the formulation in powder form, and water is used as a wetting agent to granulate, but it is the same as the liquid form. The bonding effect needs 2-4 times
(3) PVPK30: soluble in water or ethanol, the concentration range is 5-30%, and the concentration in the fluidized bed is usually 20%. It can also be directly added to the powder formulation, and granulated with water or ethanol as a wetting agent, but the same viscosity is achieved. The amount required for the combined effect needs to be greatly increased. The use of PVP as a binder requires special attention. Two-fold, tablets containing PVP usually harden after storage, so they are suitable for effervescent tablets or chewable tablets, but PVP has strong hygroscopicity, if it is to be avoided In this regard, derivatives of PVP such as BASF's VA64 and ISP's S630, which have the same viscosity as PVPK30, can be used, but the hygroscopicity is greatly reduced.
(4) PVPK90: The commonly used concentration is 3-5%. The dissolution rate is slower during preparation. The prepared particles have large particle size and high hardness, which is not particularly common.
(5) HPMC: Low-viscosity models are commonly used. Commonly used are Dow E3 and E5, Japan's Shin-Etsu pharmacoat 603 and 606, commonly used water or water/ethanol as solvent, commonly used concentration of 10-15%, if water is used as solvent The HPMC can be first dispersed in 80-90 degrees hot water, stirred evenly and then dissolved in cold water. The water/ethanol mixed solvent can be first dispersed in ethanol and diluted in water to dissolve. 3. Craft articles
The whole granulation process of the fluidized bed is mainly divided into four steps: preheating of materials, spraying, drying and cooling. The processes are described as follows: (1) Preheating of materials: In fact, there is still an empty preheating before the materials are preheated.
There are two main purposes for emptying the air:
First, the initial inlet air volume of the fluidized bed is generally unstable. After the equipment is operated for a certain period of time, it can ensure that the parameter tends to be stable, avoiding the instability of the parameters and adversely affecting the preheating of the subsequent materials. By preheating the machine, the material warm-up time can be greatly reduced and the efficiency can be improved.
Suggestion for parameter setting of material preheating stage: Since the starting material has a very high fine powder rate and a large static electricity, it is recommended to use a lower inlet air volume in the fluidized state of the material, and the shaking bag frequency of the fluidized bed is as high as possible. With the material temperature as the jump point of the program, the material temperature of the jump point is slightly different depending on the nature of the product and the production batch, which is generally 45-50 degrees. (2) Spraying liquid: It is recommended to perform a liquid spray test before each fluidized bed is used, especially when using a first adhesive for the first time, and record the spray liquid curve, that is, the spray rate corresponding to the number marked on the peristaltic pump; Observe the atomization state of the adhesive under the set atomization pressure. Judging the standard: When atomizing the liquid spray, the palm and the liquid spray direction pass through the entire spray surface vertically, so that there is no obvious moist feeling on the palm.
Suggestion of parameter setting in the spraying stage: at the beginning of the spraying stage, the particle size of the material gradually becomes larger and larger. In order to ensure the fluidized state, the air volume of the inlet air can be adjusted accordingly (the air volume is from small to large); the bag of the filter bag The frequency can be set relatively high when the liquid starts to be sprayed, and the frequency and time of shaking the bag can be reduced when the material is gradually formed into particles. The spray phase is generally based on time as a jump point. If it is in the process exploration stage, it is recommended to regularly sample from the fluidized bed sampling port to observe the particle state, especially to prevent the particles from being too wet. In addition, in order to ensure the particle quality and improve the production efficiency, it is recommended to divide the whole liquid spraying process into several pieces. (Generally 2-3) The spray rate is subjected to gradient granulation. Timing recording system related parameters (including inlet air volume, inlet air temperature, exhaust air temperature, material temperature, spray rate, atomization pressure, material pressure difference, filter bag pressure difference, filter bag shaking bag frequency and time, etc.) A good fluidized bed process has a plateau at each spray rate gradient, ie all of the above parameters remain stable. If the parameters of the system are constantly changing throughout the spray state, even if the particles prepared by Zui are better, it does not necessarily mean that your process is superior, especially the reproducibility is likely to be poor.
(3) Drying: After the spraying is finished, the material is dried. The drying temperature is generally not too high, otherwise it is easy to cause over-drying. In the process of the process, it is generally necessary to sample at a certain material temperature to determine the LOD of the particles. When the LOD is Drying is finished within the set range. If the LOD value should be reached, the average film is generally recommended to be 1%-1.5%. The LOD of some products has also been set. The methods that can be used include: reducing the inlet air volume, Increasing the spray rate and reducing the atomization pressure are more effective, but the premise is that the adhesive (wetting agent) must have a good atomization state.
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