During the operation of spray dryers, wall sticking problems are very common. Not only can it adversely affect product quality and production efficiency, but it can also lead to safety hazards. The following will analyze the main causes of sticking to the wall, and give corresponding solutions and summary suggestions.
I. Main reason for sticking to the wall
1. Characteristics of the material itself
- High viscosity or low melting point: Materials such as sugars, gums, and proteins tend to melt during drying, and then adhere to the walls of the drying chamber.
- High humidity or high solids: The material entering the dryer has high humidity or high solids, which will cause the droplets to come into contact with the wall without sufficient drying.
- Improper particle size: Oversized particles tend to settle on the wall surface when drying, while ultra-fine particles may adhere to the wall due to electrostatic adsorption.
2. Improper setting of operating parameters
- Low inlet air temperature: Too low inlet air temperature will cause the material to not dry in time, which will increase the risk of sticking to the wall.
- Poor atomization effect: The atomizer is clogged or the pressure is insufficient, which will make the droplet particle size too large, shorten the residence time of the droplet in the drying chamber, and the drying is not sufficient.
- Feed speed too fast: Feeding too fast will make the material in the drying chamber dry for a short time, resulting in the material sticking to the wall before it is completely dry.
- Uneven air distribution: There are vortex or short circuits in the air flow in the drying room, which makes the material in some areas unable to dry sufficiently.
3. Equipment design and structural defects
- Unreasonable structure of drying chamber: The cone angle of the drying chamber is too small or the transition area is not properly designed, which is easy to make materials accumulate on the wall.
- Inner wall is not smooth enough: The inner wall is rough or scratched, which will make it easier for the material to adhere to it.
- Electrostatic adsorption: When drying insulating materials, it is easy to generate static electricity, resulting in adsorption of materials on the metal wall.
4. Other factors
- System air leakage: System air leakage will make the temperature and humidity in the drying room unstable, affecting the drying effect of the material.
- Untimely cleaning: If the equipment is not cleaned for a long time, the residual material will form scale on the wall.
II. Solution
1. Handling of material characteristics
- Add anti-sticking agent: You can add anti-sticking agents such as silica and magnesium stearate to reduce the viscosity of the material.
- Adjust the formulation: Reduce the proportion of highly viscous components in the material, or mix the material with other ingredients to improve its drying properties.
- Pretreatment materials: Spray granulation or pre-drying of materials to reduce their initial humidity.
2. Optimize operating parameters
- Increase the inlet air temperature: On the premise of ensuring that the material does not decompose, appropriately increase the inlet air temperature to speed up the drying speed of the material.
- Improve atomization effect: Regularly clean and maintain the atomizer to ensure its normal operation; Adjust the atomization pressure and flow rate to make the droplet size uniform.
- Reduce the feeding speed: According to the drying characteristics of the material, adjust the feeding speed reasonably to ensure that the material has enough drying time.
- Optimize airflow distribution: By adjusting the angle and position of the air sparger, the airflow in the drying chamber is evenly distributed, avoiding vortex and short circuits.
3. Improve equipment design
- Optimize the structure of the drying chamber: appropriately increase the cone angle of the drying chamber to avoid the accumulation of materials on the wall; Improved design of transition areas for smoother material flow.
- Use a smooth inner wall material: Choose polished stainless steel or a coated material (such as Teflon) as the inner wall material for the drying chamber to reduce material adhesion.
- Install static elimination device: For materials that are prone to static electricity, you can install an electrostatic elimination device, such as an ionizing fan, to reduce electrostatic adsorption.
4. Strengthen system maintenance and management
- Sealing System: Inspect and seal all connections of the system to prevent air leakage and keep the temperature and humidity in the drying room stable.
- Regular cleaning: Develop a strict cleaning plan and regularly clean the drying room, atomizer, pipeline and other components to prevent material residue.
- Monitoring key parameters: Real-time monitoring of key parameters such as inlet air temperature, outlet air temperature, atomization pressure, feed speed, etc., and timely adjustment of operations to ensure the stable operation of the system.
III. Summary and suggestions
1. Prevention first
- Before production, the characteristics of the material are fully evaluated, and the appropriate anti-sticking agent and formulation adjustment plan are selected according to the characteristics of the material.
- Operate in strict accordance with the operation manual of the equipment, and reasonably set the inlet air temperature, atomization pressure, feeding speed and other parameters to avoid the problem of sticking to the wall due to improper operation.
2. Quick Response
- Once the sticking phenomenon is found, stop the machine in time for inspection, analyze the cause of sticking to the wall, and take corresponding measures.
- Slight sticking of the wall can be solved by adjusting the operating parameters; For severe sticky walls, the equipment needs to be cleaned and maintained.
3. Continuous Improvement
- Regularly summarize and analyze the production process, collect relevant data on sticking problems, and continuously optimize process parameters and equipment design.
- Pay attention to new technologies and methods in the industry, and apply them to production in a timely manner to improve the performance and stability of spray dryers.
By comprehensively considering the material characteristics, operating parameters, equipment design and system maintenance and other factors, and taking targeted measures, we can effectively solve the problem of sticking to the wall of the spray dryer, improve product quality and production efficiency, and ensure production safety.
