Fluid bed processing is an important technology in the pharmaceutical industry. It is widely used in various processes and offers unique advantages. Understanding fluid bed processing will help you select the right fluid bed machines and optimize your production. This article will introduce you to fluidized bed processing.
3 Types of Fluid Bed Processing of Pharmaceuticals
Fluid Bed Drying
Fluid bed drying is a method used to dry wet particles or powder. Particles treated with fluid bed drying have a uniform moisture content, making them ideal for tablet production applications where strict requirements are placed on the final moisture content.
Procedure
The steps involved in fluidized bed drying are mainly as follows.
- First, the particles or powder to be dried are loaded into the fluid bed dryer.
- Then, hot air is blown into the chamber. Once a certain air velocity is reached, the particles become suspended, entering a fluidized state. They will continuously tumble and rise. During this process, the moisture in the particles evaporates, and the moist air is exhausted from the equipment.
- Finally, you will get dried particles.
Fluid Bed Granulation
Fluidized bed granulation is an integrated process that simultaneously performs mixing, granulation, and drying within a single unit. It is also known as the one-pot method.
This process transforms powders into granules with improved flowability and less dust generation. And they typically feature a porous surface and pore structure. These characteristics make them suitable for tablet and capsule manufacturing. Tablets produced using these granules also exhibit greater content uniformity.
Procedure
- First, load the powder to be processed into the fluid bed granulator, then introduce hot air to create a fluidized state.
- Next, spray the liquid binder onto the surface of the fluidized particles, causing them to adhere to each other and agglomerate, gradually increasing in size.
- Finally, continue to introduce hot air to evaporate the moisture, and you will get dry granules.
Fluid Bed Tablet Coating
Fluid bed coating is a technique that involves applying a uniform film to the surface of tablets or granules by a spray process. This film can be used to mask taste, protect against moisture, control drug release, prevent oxidation, or block light.
Coatings are widely used in the pharmaceutical industry. In addition to protecting the drug and improving the patients’ medication experience, you can also strengthen brand identification by designing the appearance of the coating.
Procedure
- As in the process described above, hot air keeps the particles suspended. The airflow velocity should be higher than the minimum fluidization velocity to ensure that the particle surfaces are fully exposed, allowing the subsequent coating to adhere evenly.
- The second step is to spray the coating solution onto the particle surfaces to form an initial film. In this step, you need to control the droplet size to ensure that particles are uniformly coated.
- Continue to introduce hot air to remove the solvents or moisture from the coating solution. Eventually, a continuous, uniform film forms on the particle surfaces. Each layer is dried as it is sprayed, and this process is repeated multiple times until the film thickness meets your needs.
Advantages of Fluid Bed Processing of Pharmaceuticals
Multiple Uses
A fluid bed processor can be used for drying, granulation, and coating. This is the most significant advantage of fluid bed processors. It helps reduce material transfer during production, improves production efficiency, and lowers the risk of pharmaceutical contamination.
You also avoid the need to purchase multiple pieces of equipment and can save costs. The factory’s floor space is also saved.
Improved Product Uniformity
Since the granules being processed are suspended within the equipment, their surfaces are almost completely exposed. So drying, granulating, and coating can be carried out more uniformly.
Allows for Precise Control
You can precisely control parameters such as airflow rate, spray rate, inlet temperature, and humidity to produce products that meet your requirements. Precise control also helps minimize variations between batches.
Suitable for Heat-Sensitive Ingredients
Fluid beds perform well when processing heat-sensitive materials. For example, probiotics and some APIs. Fluid bed systems provide efficient heat transfer and shorter processing times, helping reduce thermal stress on heat-sensitive materials. And as the material is suspended by the air flow, each particle is heated more uniformly, reducing the risk of thermal degradation.
3 Types of Fluid Bed Processors for Pharmaceuticals
Top Spray
Top spray is the most basic type of fluidized bed processor. The material is loaded into the equipment, and hot air is blown upward from the bottom to fluidize the material. Nozzles are positioned above the bed and spray adhesive or coating solution downward.
Top spraying is the first choice in the granulation process. But it does not provide the same level of spray precision as bottom spraying. If you need functional coatings, such as enteric coatings, top spraying is not the best choice for you.
Bottom Spray
Bottom spray is also called the Wurster process. The core design is a flow guide cylinder (known as a Wurster tube) installed at the center of the bottom of the equipment. The nozzle is at the bottom of the flow guide cylinder and sprays upward.
Procedure
The particles carried by the air flow rise rapidly from inside the tube and enter the spraying area. Upon reaching the top, they fall onto the exterior of the tube, where they slowly settle and dry before being drawn back into the flow tube, creating a continuous, cyclical coating path. The particles are coated with an extremely thin layer of coating with each cycle. After multiple cycles, a dense coating is achieved.
Pros and Cons
Bottom-spray coating systems allow for more precise control of film thickness and produce a more uniform coating. However, this type of equipment is expensive and more complex to set up. This process also has restrictions on raw materials. If your product is a fine powder or large granules, it is not suitable for you.
Tangential Spray
The tangential spray nozzles are at the side of the equipment, and the liquid is sprayed from the side. There is a rotating turntable at the bottom of the equipment. Carried by the airflow and the rotating turntable, the material moves in a spiral or circular pattern along the equipment walls. So that they are evenly coated as they rotate.
Tangential spray is ideal for applications involving particles that need to be rounded and those requiring multi-layer coating. However, if your particles are flat, this method isn’t suitable. It is also more difficult to clean.
FAQ
How Can Nozzle Clogging Be Prevented in a Fluidized Bed System?
Make sure the viscosity of the feed liquid is not too high, and filter it before use to effectively prevent nozzle clogging. You can also choose anti-bearding cap nozzles. They can prevent fine powder from accumulating and clumping at the nozzle opening. It is also important to clean the fluid bed processors regularly.
What Is the Difference Between a Fluid Bed Dryer and a Fluid Bed Processor?
Fluid bed dryers are typically used only for drying. While fluid bed processors can perform not only drying but also processes such as granulation and coating. Manufacturers also refer to equipment with granulation and coating capabilities as fluid bed systems or fluid bed granulators. You had better clarify the functions of the equipment before placing an order.
What Are the Material Requirements for the Fluid Bed Processor?
The most critical point of the fluidized bed processor is achieving a fluidized state for the material. This requires that the material not be too large and too heavy, as it may fail to fluidize. For drying, fluidized bed dryers cannot directly dry liquids. They cannot effectively dry particles with high sugar content or high viscosity either.
How Can Particle Agglomeration Be Prevented during Fluid Bed Coating?
You need to strike the right balance between the spray rate and the inlet air temperature. If the spray rate is too high, the bed will become overly wet, leading to agglomeration. If the spray rate is too low and the temperature is too high, the droplets may dry into powder before reaching the particle surface.
Are Fluidized Bed Processors More Suitable for Continuous Production or Batch Production?
Both modes have their own advantages. You can choose based on your needs. Batch production offers high flexibility and is suitable for small-batch production of multiple product varieties. Continuous production is suitable for the large-scale production of a single product. Most pharmaceutical fluid bed processors are designed for batch production, while continuous systems are available for specific large-scale manufacturing applications.
Final Thoughts
Are you planning to order fluid bed processors? Pilotech is an experienced fluid bed processor manufacturer in China. We have fluid bed dryers, fluid bed granulators, and fluid bed coaters. We can also provide verification services for a variety of materials if you need. Welcome to contact us!