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Technical features of fluid bed granulator

Views: 7     Author: Site Editor     Publish Time: 2024-05-16      Origin: Site


The fluid bed granulator (commonly known as one-step granulator in China) is a product developed abroad. China has introduced it since the early 1970s and has been used in pharmaceutical factories for nearly 40 years. Boiling granulation technology is a technology that integrates mixing, granulation, and drying in a fully enclosed container. Compared with other wet granulation methods, it has the characteristics of simple process, short operation time, low labor intensity, and reduces material handling. times and shorten the time required for each process, thereby reducing pollution to materials and the environment.

Boiling granulation technology has the advantages of fast heat transfer, high heat transfer efficiency, uniform particle size, low density, good fluidity, and good compression formability. Little or no migration of soluble ingredients occurs between particles, reducing the possibility of uneven tablet content.

At present, the technology of fluid bed granulator is being used more and more widely. This article briefly explains the technical characteristics of fluid bed granulator. At the same time, it analyzes some problems that arise in the production and use of fluid bed granulator and proposes targeted solutions. Improve the method permanently to improve the production practicality of the fluid bed granulator.

1.Introduction to the structure and working principle of fluid bed granulator

The main structure of the fluid bed granulator is shown in the figure. Put the powdery materials for granulation into the fluidized bed (i.e. raw material container). The hot air flow is sucked under the negative pressure of the induced draft fan. After being filtered by the primary and medium-efficiency filters, it is dehumidified by the surface cooler and then heated by the heater. After being filtered by the high-efficiency filter to meet the cleanliness level requirements, the air volume is adjusted by the air inlet valve. , from the air flow distribution plate into the fluidized bed through the air inlet duct. The hot air flow agitates and suspends the medicinal powder (such as Chinese herbal medicine powder, extract powder, etc.) in the granulation chamber into a fluidized state (also known as "boiling" state), and then dries in the fluidized bed. At this time, the liquid material (such as traditional Chinese medicine extract or adhesive, coating liquid, etc.) is sent to the nozzle through the conveying pipe, and then the liquid material is atomized into fine droplets by compressed air and sprayed into the fluidized bed to form a boiling powder. When wet, the powders build up bridges with each other and aggregate into particles. After the material is dried, it will be discharged from the discharge port, and the waste gas will be discharged from the exhaust pipe on the top of the fluid bed granulator.

During the boiling drying process, part of the powder rises with the air flow and is carried to the filter chamber by the air flow. The dry powder is captured by the bag. When a certain amount is captured, the fan stops working and the bag shaking system starts to work. The material is shaken off into the fluidized bed, and then the fan is restarted.


2.Problems and solutions that arise in actual production

2.1 Improvement of air volume and pressure control

The original air volume and pressure of our equipment is adjusted and controlled by the public frequency induced draft fan (exhaust pipe section) and the regulating damper (air inlet pipe section). During the granulation process, because the powder particles are initially fine and light, even if the air valve is closed to the set minimum opening, the powder particles are still blown to the filter collection bag by the strong hot air. Powder particles cannot achieve good boiling and drying in the ebullating bed, and the particles tend to gather together to form cakes and agglomerates. To this end, the air volume and air pressure adjustment should be modified accordingly. The regulating damper in the air inlet section should be cancelled. The original public frequency fan in the exhaust section should be replaced with a variable frequency fan of the same power. An air pressure meter should be installed in the exhaust duct. The air pressure parameters can be used to control the air volume and air pressure. The speed of the fan is adjusted to improve the boiling effect of the material.

2.2 Add airflow guide plate to improve airflow distribution

When the air flow guide plate is not installed, the air flow directly hits the front end of the hot air chamber, reducing the wind pressure and speed, and it is easy to form an air flow blind spot at the rear end of the hot air chamber, affecting the boiling granulation effect. In order to guide the air flow and distribute it evenly, several sets of air flow guide plates are installed in the hot air chamber to adjust the angle of the air flow, so that the air flow blown into the ebullating bed is more uniform and a better fluidized drying effect is obtained.

2.3 Inlet air temperature precision control modification

According to relevant process regulations, the temperature difference in the ebullated bed during drug production should not exceed ±3°C. Since the original and only temperature sensor of our domestic equipment is located in the middle of the ebullated bed, when it detects the temperature change in the fluidized bed, Control the opening of the heat exchanger steam valve to adjust the temperature. Since the temperature measurement point is far from the air inlet, there is a certain delay in detecting changes in the inlet air temperature, resulting in a temperature difference control range that often exceeds ±10°C. Due to the large temperature deviation, the quality of the product is seriously affected. When the inlet air temperature is high, the adhesive (liquid material) evaporates quickly, which reduces the ability of the adhesive to wet and penetrate the powder particles, resulting in the resulting granulated semi-finished product having small particle size, loose density, and high brittleness, which is not conducive to compression. Sheet forming. When the inlet air temperature is too low, the powder particles in the ebullating bed will dry too slowly. The moist powder particles will continue to stick to each other and aggregate, causing the material to stick to the sieve or cake and agglomerate in large areas, making it impossible for the material to dry normally in the ebullating bed. Fluidized drying ultimately leads to low production yield or even failure to produce normally, causing the entire batch to be reworked.

Due to the manufacturing level of domestic equipment, it is impossible to improve the control temperature accuracy range. After consultation with the equipment manufacturer and equipment verification, a temperature sensor was added to the connection between the bottom of the ebullating granulator and the air inlet pipe, and used in conjunction with the original temperature sensor (that is, simultaneously detecting the internal temperature of the ebullating bed and the inlet temperature). The temperature of the air outlet), and at the same time modify the temperature control system control program so that the entire system can process the detected temperature change data in a more timely manner, so that the equipment can effectively adjust the opening of the steam valve in the shortest time and reduce the temperature range deviation. Keep the working temperature of the fluid bed granulator stably within the allowable range.

2.4 Improved handling of the "drip liquid" problem

"Drip liquid" means that in actual production, the liquid material ejected from the nozzle is often linear and does not form a mist spray, resulting in poor boiling drying effect. The particles in the stroke after granulation are coarser, and the tablets are squeezed out in the subsequent tableting process. Finished product has spots. This is mainly due to the fact that the boiling and rising powder particles condense with the liquid material at the nozzle and stick to the nozzle.

Therefore, the fixed nozzle is changed to a nozzle with flexible rotation function. The nozzle faces downward when spraying. After spraying, the nozzle turns upward to prevent powder particles from sticking to the nozzle. In addition, a constant temperature heating system is added to the liquid material storage barrel to prevent the material from becoming too viscous due to the temperature drop.

2.5 Improved treatment of the problem of collection bag falling off

The collection bag is made of anti-static, non-fiber shedding cloth, which is not easy to generate static electricity. The collection bag is hoisted as a whole and tied to a stainless steel screw hook. During the fluidized bed boiling drying process, the collection bag shakes frequently due to the long operation time, so the collection bag rope tied to the stainless steel screw hook will often fall off, and the stainless steel screw buckle will occasionally loosen due to long-term shaking. causing the collection bag to fall off. The fallen collection bag is scattered on the upper part of the air sealing ring, and a lot of material fine powder accumulates inside and cannot be shaken off and returned to the silo. Since the collection bag falls off and is not easily noticeable from the outside, when the machine is shut down after a production batch is completed, the air seal shrinks and the scattered collection bag can easily enter the gap between the sealing ring and the boiling body. When the fluidized bed is started again, the air sealing ring will no longer be able to seal, which will cause a large loss of material. The manufacturer recommends that when disassembling and cleaning the collection bag, unbuckle the collection bag from the stainless steel screw hook. In fact, in operation, it is very inconvenient to install, remove and wash each rope buckle. It takes at least 30 minutes to complete a circle of 50 buckles, and it takes at least 50 minutes to install them after cleaning.

Solution: Improve the fixation method of the collection bag

Try changing the lanyard to a lanyard type, and add steel wire to the lanyard and then nail it to increase the wear resistance of the lanyard. Change the stainless steel belt buckle hook to a stainless steel spring hook. The stainless steel spring hook will not fall off due to vibration and wind flow generated inside the equipment during work, and is easy to operate, replace and clean for each batch of disassembly and assembly.

2.6 Improvement of silo cart

The dried granules will enter the general mixer through the lifting and reversing granulator in the next process. In this way, when the empty silo is returned to the silo cart, the space for entering the trough is too narrow, making it difficult to hang the silo arm. When entering the trough, the operator always adjusts the position of the silo cart. If the position is slightly wrong, the silo cannot be placed on the cart. In daily work, 5 to 8 silo displacement operations are required for each batch of materials. If the silo cannot be lowered to the correct position, it cannot be placed on the silo trolley, and the silo cannot be returned to the boiling bed, which is a problem for the work. caused inconvenience.

In order to facilitate the silo hanging arm to be put into place, a 45-degree arc slope is polished on both sides of the contact point, so that the silo can be easily inserted into the slot. When the silo is slowly lowered, just drop the cart onto the arc section. It will be driven to the correct position, which greatly saves operating time and improves work efficiency.

2.7 Improvement of heat energy saving in fluid bed granulator

The energy consumption during the operation of the fluid bed granulator is mainly the electric energy consumed by the fan and the steam heat energy consumed by the heat exchanger.

In terms of power saving, it has been mentioned above that the original public frequency fan is installed with an inverter for frequency conversion control, which has a good effect of saving power.

In terms of heat energy saving, it is necessary to improve the thermal efficiency of the fluid bed granulator and reduce heat energy loss through the following ways.

Approach 1: Recover the heat from the exhaust outlet airflow of the fluid bed granulator and reuse the exhaust heat.

The exhaust air temperature of the fluid bed granulator is higher than the temperature of the inlet air, so the heat energy of the exhaust air is exchanged to the inlet air through the heat exchanger for preheating, and the initial temperature of the inlet air is increased to achieve the purpose of reducing steam usage. At the same time, the exhaust pipes are insulated to reduce heat energy consumption.

Method 2: Dehumidify the incoming air.

When the air humidity in Beijing is high in summer, the inlet air should be dehumidified to reduce the humidity of the fresh air, thereby improving the ability to carry moisture, shortening the drying and granulating time, and achieving energy saving.

Approach 3: Reasonably control drying time and air inlet temperature.

The boiling granulation process can usually be divided into three stages: preheating stage, constant speed drying stage, and reduced speed drying stage. The air temperature at the air inlet should be reasonably set according to the different characteristics of the three stages. The preheating stage should use a low air temperature of 30℃---50℃ (because the moisture content of the powder is relatively high in the initial stage of startup. If the air temperature is too high, the chemical components in the powder will melt and the powder will agglomerate and cannot boil well. ). When the powder particles are fully boiled and reach a good fluidized state, the air temperature is raised to above 80°C (set differently according to different drug varieties). After entering the speed-reducing drying stage, the air temperature is reduced to about 60°C. The time of drying operation is greatly affected by the operation of preheating stage and constant speed drying stage. It should be controlled so that most of the moisture in the powder particles is removed in the constant speed stage with higher drying rate. This can greatly reduce the drying time and achieve energy saving purpose.


There is still a certain gap between domestic fluid bed granulator and the world's advanced equipment, and there is still a lot of room for development and improvement. By improving the technical details of production equipment such as greater control and automation of operations, the service life of the equipment has been extended. The service life improves the practicality of the fluid bed granulator, the convenience of operation, the stability of product quality, reduces energy loss, reduces labor intensity, improves product yield, and avoids unnecessary material loss. The modified fluid bed granulator is easy to use and has stable process parameters, and the production efficiency has been greatly improved.

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