What Are The Important Influencing Factors In Fluidized Bed Technology?

Fluidized bed systems have many different advantages – good heat transfer, efficient drying and thorough mixing. These are all due to the free movement of the particles during the fluidization process, thereby increasing the contact surface area with the process air and the granulation liquid. However, in order to give full play to the advantages of the fluidized bed, it is necessary to choose a suitable method in the actual operation process and pay attention to the influence of some important parameters.

The key components of the fluidized bed system are the fluidized bed processor, the process air treatment system and the exhaust gas treatment system. In order to achieve as precise a process control as possible, the system development can also focus on concepts such as the optimization of air flow, efficient feeding and discharging. This will enable higher throughput, faster processes and ensure repeatable quality of the final product.

So how does a fluidized bed work? In order to fluidize the product, the process gas flow passes directly below the distribution plate. The tangential air flow from the distribution plate allows for a uniform movement of the product, ensuring efficient use of energy; this also leads to a more uniform product quality in the subsequent spraying process. An integrated filtration system also cleans the process air before it leaves the system. There are a number of different options for this, including single-chamber filter systems, dual-chamber filter systems and cartridge filter systems.

Depending on the situation, the downstream exhaust gas can also be treated with static redundant back-up filters, cleanable filter systems or recirculating operation with solvent recovery.

The Fluidization Process Determines The Particle Shape

In the fluidized bed process, different operating methods will have an impact on the final particles and process. For example, spray granulation can be achieved by top spray system or tangential spray system, while bottom spray method is used for pellet or microtablet coating. Each method has its own advantages and disadvantages. Top spraying can produce finer and more porous particles, but the resulting particles are less regular in shape. Also, the top spray method requires a higher spray pressure (at least 0.75 bar) due to the ‘whisker effect’ (i.e. product sticking to the nozzle). However, this method offsets its disadvantages by requiring less powder flow characteristics than the bottom spray method. In addition, the bottom spray method produces larger particles.

One of the advantages of the tangential spray method is the reduced time required for the granulation process. In the tangential spray method, the granulating liquid is fed through a binary nozzle that is tangential to the bottom of the material container wall. As a result, the granulation solution can be sprayed into the area where the powder particles are moving at the highest speed (which is also the area with the longest drying path due to the circular motion of the product). As a result, the drying process efficiency of the tangential spray method is greatly improved, and the spray rate is higher (30% higher) than the other two methods, and the spray time is also shorter. Furthermore, the tangential spray method is not sensitive to over-wetting of the particles. In the production process, the tangential spray method often requires the use of a smaller amount of granulation liquid in order to achieve a specific target particle size. The tangential spray method also helps to produce coarser particles; during the drying process, the pressure (droplet size) of the nozzle can be adjusted to obtain the desired particle state, such as when the nozzle pressure is lower, coarser particles will be obtained. particles.

Parameters Affecting The Fluidization Process

In addition, there are many other factors that should be taken into consideration by pharmaceutical companies as they also have an important impact on the fluidization process. For example, equipment should be resistant to shock stress and a certified safety concept should be applied; processes should be carried out in a reproducible and automated manner and require a short set-up time.

When producing highly active substances, the systems should not only meet special containment standards, but also incorporate comprehensive cleaning concepts from WIP (Cleaning in Place) to CIP (Cleaning in Place). In addition, an online quality control system, such as an integrated process analytical technology (PAT) system, and compliance with GAMP 5 standards are also basic requirements for the system.

There are also many parameters that affect the fluidization process. Such as inlet temperature – the higher the temperature, the finer the particles; if the inlet temperature is lowered, the system will produce coarser particles at the same spray rate. Conversely, the higher the air humidity, the coarser the particles produced and the longer they will take to dry.

The position of the nozzle also plays a decisive role in the fluidization process. In the top spray method, the optimal nozzle height should ensure that the spray can cover the entire fluidized bed surface. If the nozzle is too close to the fluidized bed, the bed surface will be completely wetted, but this will result in coarser particles. Conversely, if the nozzle is positioned too high, the binder dries before it comes into contact with the powder particles (due to the spray drying effect), resulting in finer agglomerates.

The size of the nozzle is also an important influencing parameter. According to a well-known general rule in the industry – the higher the atomization pressure, the finer the droplet size. From this, it can be known that when the nozzle size is larger, the droplets produced will be larger (under the same pressure).

Improve Production Safety And Reliability

From the above, it can be seen that there are many factors affecting the fluidized bed process, so a lot of experience is needed to maintain the balance of all aspects of the fluidized bed process to ensure that the performance of the final product can be optimized. The safety and reliability of technology are important, but the guarantee work of the whole process cannot be ignored. Increased throughput, faster processes and reproducible end product quality can only be ensured if the air flow, the feeding and discharge concept and the granulation process are all perfectly coordinated with each other. That’s why Diosna offers a wide variety of optional components for CAP fluid bed processors. These components include granulation liquid containers, cleaning stations, granulator, lifting columns and vacuum conveying systems. All components of the equipment can be integrated into the overall control system and play a key role. Diosna internally develops the necessary hardware and software solutions for CAP fluid bed processors on the basis of recognized standard systems. The software used is 21 CFR Part 11 compliant and offers a wide range of options for bulk data acquisition and documentation, also utilizing PAT technology. Also very important: Diosna designed the software with intuitive user guidance and a step-by-step recipe creation system to ensure safe and reliable operation of the system and to keep the entire fluidized bed process perfectly balanced in all aspects.