Views: 8 Author: Site Editor Publish Time: 2023-11-08 Origin: Site
Adjust the air inlet volume to make the materials in the container boil and fully mixed, and the boiling layer will not easily exceed the nozzle. The initial air volume of fluid bed dry granulator should not be too large, otherwise the powder will boil too high and adhere to the surface of the filter bag, causing air flow obstruction. When adjusting the air volume, it is better that the inlet air volume is slightly larger than the exhaust air volume. Generally, after the air volume is determined, you only need to adjust the exhaust air volume to achieve a suitable boiling state. When starting the fan, the damper needs to be closed. After the fan is running, the exhaust damper can be gradually increased to create an ideal material boiling state.
If the inlet air temperature of fluid bed granulation is too high, the particle size will be reduced, and if it is too low, the material will be over-wetted and form agglomerates. Therefore, it is very important to control the temperature during boiling granulation.
Steam enters the heater, causing the air to be heated as it passes through. Since the temperature rises and falls over a certain period of time when the steam is heated, it is necessary to pay attention to advance control and prediction when setting and adjusting. Personal experience, when using production equipment, when steam heating is heating up, there will be a buffer zone of about ten degrees, that is, the set temperature is 60°C, the temperature may rise to 70°C, and then gradually decrease and stabilize to 60°C, then if it is during the granulation process To adjust the temperature, you need to turn off the air inlet briefly in advance, or set the temperature about 10°C lower than the ideal temperature, and then adjust after it is relatively balanced.
When the temperature reaches the requirements, spray granulation can be carried out. At this time, the flow and pressure of the compressed air and the flow and velocity of the adhesive should be controlled. At the same time, the backflushing (blow-up) function of the filter bag needs to be turned on. Blowback every few seconds.
The bed pressure fluctuation is generally within ±3%. If the pressure fluctuation exceeds ±10%, the fluidization may not be ideal.
The flow rate and pressure of the compressed air and the flow rate and flow rate of the adhesive need to be appropriate to ensure the appropriate particle size distribution of the product.
During the spraying process, the material temperature and air outlet temperature drop. When they drop to a certain value, the spraying should be stopped to prevent wall sticking or sedimentation. When the temperature of the material returns to the original value, spraying begins again, and this cycle is repeated until the adhesive is sprayed out. It is necessary to pay attention to the maximum viscosity temperature of different adhesives, and adjust the retention time of the material temperature at the maximum viscosity temperature according to the needs of the product.
In the spray chamber, the material is affected by the gas and the shape of the container, causing upward and downward circulation movements from the center to the surroundings. The adhesive is sprayed from the spray gun. The powder material is adhered by the adhesive droplets, aggregates into particles, and is heated. The air flow takes away moisture, and the change in outlet temperature should be controlled. Wet particles tend to stick together and form cakes. There are other reasons for the formation of cake: too much loading, so you need to ensure that the loading is appropriate; the particles are too wet, and the moisture content of the particles needs to be reduced; if there is dead volume, dry part of the material first and then add the remaining wet particles or make noise to shake the particles.
The filling volume should be appropriate, not too much or too little. Generally, the filling volume is about 60%-80% of the container volume of the fluid bed granulator. Too much or too little will affect the boiling state and granulation effect.
The container of fluidized bed granulator is generally equipped with a static elimination device. The static electricity generated by powder friction can be eliminated in time. Some manufacturers equip the static elimination device with a separate probe, which needs to be manually inserted during use. Pay attention to it during use and must not forget it. Static electricity is the main cause of fine powder adsorption and collection bags, thus affecting pressure difference, fluidization state, uneven granulation, etc. (Interlude: During another pilot test, because the equipment was newly purchased, I forgot to insert the electrostatic probe when using it. During the material preheating process, I found that the material was getting less and less. Repeated observation found that most of the material was adsorbed on the collection bag)
The collection bag has not shaken for a long time, and there is too much powder adsorbed on the bag; the boiling height is too high, the state is intense, the bed negative pressure is too high, and the powder is adsorbed on the collection bag. The air duct is blocked and the air inlet and outlet is not smooth.