Rotary Atomizer Spray Dryer

Spray Dryer Working Principle

The operating process of a rotary atomizer spray dryer consists of three main stages.

Liquid Atomization

This is the first stage. The pumping system delivers the feed solution to the rotary atomizer. This atomizer contains a centrifugal atomizer disc/wheel, which typically operates at 10,000–30,000 RPM. Using the centrifugal force and shear stress generated by high-speed rotation, the rotary atomizer instantly propels the feed solution outward and breaks it into micron-sized droplets.

This is why this type of atomizer is recommended for viscous materials. It is not limited by physical orifices, which helps reduce clogging. Furthermore, this process significantly increases the material’s surface area to volume ratio, thereby accelerating the drying rate. Therefore, it is also suitable for applications where efficiency is a priority.

Gas-Droplet Contact and Evaporation

After the air is heated by the heating system to the preset inlet temperature, it is introduced into the drying chamber in a spiral, uniform, and steady flow via the hot air distributor. When the atomized droplets come into contact with the hot air, the moisture or solvent evaporates instantly in just a few seconds due to their enormous surface area.

Powder Separation and Collection

After the moisture or solvent evaporates, a dry powder is formed. Some of the dry powder falls to the bottom of the drying tower. The remaining powder is carried by the exhaust air into the cyclone separator and bag filter. These devices separate the powder from the air, helping you minimize product loss. The hot, moist exhaust air is then discharged by an induced draft fan.

You Can Use Our Rotary Atomizer Spray Dryer for:

Pharmaceutical and Biotechnology

The rotary atomizer spray dryer does not require high-pressure pumps or intense shear forces, so it does not damage the biological structure of macromolecules. Furthermore, the moisture in the highly atomized droplets can evaporate rapidly, and particle temperature can be maintained at a relatively low outlet temperature. This helps preserve the activity of heat-sensitive substances.

Therefore, it is well suited for processing materials containing herbal extracts, enzymes, antibiotics, and other substances.

Advanced Materials and Technical Ceramics

Battery anode and cathode materials, as well as ceramic slurries, have high solid content and are highly abrasive, making traditional nozzles extremely prone to wear or clogging. The rotary atomizer features a wide flow channel design that allows for the smooth processing of slurries with solid content as high as 50%–60%. Combined with carbide or ceramic liners, it can withstand the erosion caused by highly abrasive materials.

Furthermore, the droplets ejected by centrifugal force form highly uniform spherical particles due to surface tension. The resulting powder exhibits excellent flowability and high bulk density, which facilitates subsequent sintering or electrode coating.

Food Industry

Flavoring and fragrance microcapsules, dairy products, and natural pigments are prone to volatilization and flavor distortion during the drying process. Additionally, high sugar or fat content can lead to sticking, caking, and poor solubility.

But rotary atomization can create uniformly coated microencapsulation, effectively sealing in volatile flavor compounds or active pigments. The microspheres produced by a rotary atomizer spray dryer also feature a dense microporous structure internally, offering rapid dispersion and instant dissolution upon contact with water. You can use this process to treat pigments, high-sugar food flavorings, and similar products.

Fine Chemicals and Organic Solvents

The processing of materials such as polymer resins often involves the use of organic solvents like ethanol and acetone, which pose flammable and explosive risks.

The rotary atomizer spray dryer’s low-pressure operating characteristics allow for perfect integration with a closed-loop system, guaranteeing the safe drying of flammable solvents. This design also reduces air pollution, improves material utilization, and saves you costs.

Furthermore, the centrifugal atomizing head has no vulnerable slits, enabling long-term, high-intensity, continuous, and stable operation during chemical R&D and pilot-scale testing.

Rotary Atomizers VS Pressure Nozzles

Pressure nozzles are also one of the common atomization methods used in the spray dryer machine. However, they operate on completely different principles and are used in different applications from a rotary atomizer. Understanding the differences between them and making the right choice can help you improve the efficiency of experiments and save high costs.

Working Principle

A rotary atomizer relies on centrifugal force to form droplets. In contrast, a pressure nozzle uses a high-pressure pump (typically operating at 2–30 MPa) to generate extremely high kinetic energy, forcing the feed liquid through a nozzle with extremely small orifices, where it is broken up into fine droplets.

Due to the physical limitations imposed by the small orifice, this atomization method is strongly discouraged when processing high-viscosity or high solids content feed liquids.

Particle Size Adjustment

For centrifugal atomizers, particle size is primarily determined by the tip speed of the atomizing disc. Without the need to shut down the machine or disassemble any components, you can precisely fine-tune the average particle size and particle size distribution simply by adjusting the motor speed (RPM) on the control panel.

However, if you are using a pressure nozzle, adjusting the droplet size requires shutting down the machine, disassembling the nozzle, and replacing the nozzle core or orifice disc with one of a different aperture size. You also need to readjust the operating pressure of the high-pressure pump.

This method offers limited flexibility and is prone to affecting the feed flow rate. If you need to adjust the particle size frequently, we recommend you choose a rotary atomizer.

Product Features

Droplets ejected by centrifugation form regular spheres due to surface tension. Furthermore, the feed solution contains fewer air bubbles during the ejection process, resulting in denser particles during drying, lower dust generation, and reduced static electricity buildup. These particles exhibit high solid content, high bulk density, and good flowability.

During the high-pressure spraying process, air is easily entrained into the droplets along with the high-pressure fluid, resulting in large internal cavities within the particles after drying. Therefore, the final products processed by a pressure nozzle are typically microporous hollow spheres. These spheres have a low bulk density and extremely high solubility, making them suitable for products such as instant coffee and powdered milk.

Suitable Materials

The rotary atomizer is suitable for processing high-viscosity, high-solids-content, and heat-sensitive materials. Because the centrifugal atomizer disc features a wide-channel design, reduce risk of physical slot blockage. At the same time, low-pressure feeding prevents localized heating caused by high-pressure friction, thereby protecting heat-sensitive materials.

Pressure nozzles have extremely small orifices, typically measuring only a few tenths of a millimeter. Even the tiniest crystals, suspended particles, or high-viscosity clumps can cause severe clogging or wear on the nozzle. Therefore, they are best suited for handling low-viscosity, clear solutions and liquids with low solid content that are free of particles or contain only minute amounts of them.

How Effective Is the Scaling Up of the Atomizer Spray Dryer?

Process Parameters Scale-Up

Scaling up the process parameters for a rotary atomizer spray dryer is relatively simple. The key factor for scaling up centrifugal atomization is the tip speed of the atomizing disk. By using the disk tip speed as a primary scaling reference alongside optimized feed rate, drying air flow, and more, key particle metrics can be seamlessly transitioned from lab testing to pilot production.

Thermodynamic and Chamber Geometry Scale-up

As the tower diameter increases, the air pattern changes. Laboratory equipment primarily relies on anti-adhesion measures on the chamber walls and rapid particle settling. While in large-scale industrial towers, the particle residence time increases.

During scale-up, it is necessary to ensure that the spray pattern radius does not exceed the radius of the chamber wall to prevent wall sticking. If conditions permit, you can use CFD simulations to make precise predictions.

How to Maintain Your Rotary Atomizer Spray Dryer?

Cleaning and Inspection

After each operation, you must thoroughly rinse the feed lines and the interior of the rotary atomizing disc with warm water or a specific cleaning solution. Make sure that no material residue remains inside the atomizing disc’s flow channels to prevent severe mechanical vibrations caused by mass eccentricity during the next startup, which could disrupt production.

Dynamic Balance and Mechanical Checks

Please check the dynamic balance of the rotary atomization head regularly. In addition, check the lubrication of the high-speed bearings and inspect and replace any worn gearbox drive belts or wear sleeves.

Seals and Ducting Maintenance

The equipment’s seal integrity affects drying results. You need to regularly inspect the mechanical seals and rubber O-rings on the centrifuge head to prevent the feed solution from seeping into the motor or lubricating oil from contaminating the material. You should also check the seals on the drying tower door and at the cyclone separator connections to prevent air leaks that could reduce drying efficiency.

Calibration and Filter Replacement

Calibrate the inlet and outlet air temperature sensors and the tower pressure transmitter regularly. Clean or replace the inlet HEPA filter and exhaust bag filters regularly to keep the differential pressure remaining within safe design limits.