Spray drying, which produces a dry powder from a liquid or slurry, is one of the most popularly-used continuous drying processes. A liquid including solutions, emulsions, wet slurry and suspensions is sprayed via a spray nozzle or a rotary atomizer into a drying chamber. Continuously feeding heated gas while increasing the surface area of sprayed droplets rapidly dries and makes granules. Therefore, degeneration of the powder is exceptionally low and the process can be the preferred process of thermally sensitive materials. Dried granules are highly close to spherical in shape and have excellent fluidity. For foods and pharmaceuticals, they will be easily soluble in water. For inorganic materials such as metallurgical powders and fine ceramics, high-density molds can be obtained.
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- Aluminum oxide
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- Oligosaccharide
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- Silicon carbide
The process of spray drying produces stable spherical granules and a sharp particle distribution.
Applicable fields
Spray dryers are used in a variety of industries. Below are some of the fields that we have been involved with.
| Food |
| Industrial materials |
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| Chemicals and Pharmaceuticals |
| Steel and Metals |
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Process design
Our specially designed rotary atomizers are suited for the particle size range of 20 – 200μm. The particle size can be controlled by disc shapes and rotating speed. Compared to other atomization modes, a rotary atomizer is able to create granules with a sharp particle size distribution and high fluidity. The capacity of spray dryers is generally measured by water evaporation volume. However, we believe that the most important aspect is to target both powder formation and production efficiency. Even if two spray dryers have the same water evaporation capacity, the process design will differ depending on the material characteristics and operating conditions. Our engineering specialists provide spray dryers that exactly match your needs by carrying out unique testing, evaluation, and process designing for each project based on our expertise and technical knowhow accumulated over many years. We also take environmental and safety requirements seriously. In order to save energy, our unique heat exchanging process allows you to reduce both CO2 and energy costs. Our technologists also design the most suited process to meet your strict safety requirements and legal regulations.
Process flows
Open-cycle system
Closed-cycle system
For water solvents, an open-cycle system (where atmospheric air is used) is generally selected. For flammable solvents as well as oxygen-sensitive materials, a closed-cycle system (where an inert gas, e.g., nitrogen, is used) is normally selected. If required, an open cycle system for flammable organic solvents such as ethanol can be selected. As a safety measure, the spray dryer is controlled at below 25% of the lower explosion limit of the gas concentration. The evaporated solvent is discharged after the catalyst or the heating decomposition process.
Atomization modes
Rotary atomizer
Our specially designed rotary atomizers are suited for the particle size range of 20 – 200μm. The particle size can be controlled by disc shapes and rotating speed. Compared to other atomization modes, a rotary atomizer is able to create granules with a sharp particle size distribution and high fluidity.
Rotary atomizer
As our design principle, a motor direct link system is applied as a standard feature in order to obtain a long lifespan and easy maintenance. Currently, we are carrying out various technical developments such as the use of non-contact seal, reduction of mechanical noise and further simplification of maintenance.
Disc
We have developed our unique disc design in order to reduce the rotational speed even if the same particle size is targeted. It allows for a lifetime much longer than high speed rotating atomizers. A variety of materials such as stainless steel, fine ceramics and coated materials are also available.
| Model | PR-015K | PR-10K | PR-15K | PR-22K | PR-37K | PR-55K |
|---|---|---|---|---|---|---|
| Rotational speed | 20000rpm | 20000rpm | 20000rpm | 12000rpm | 12000rpm | 12000rpm |
| Capacity | ～10kg/h | ～100kg/h | ～150kg/h | ～300kg/h | ～600kg/h | ～1000kg/h |
| Power | 0.15kW | 1.0kW | 1.5kW | 2.2kW | 3.7kW | 5.5kW |
| Model | PR-005-D | PR-005-B | PR-015-D | PR-015-B | PR-075-B | PR-250-B |
|---|---|---|---|---|---|---|
| Rotation speed | 30000rpm | 30000rpm | 30000rpm | 24000rpm | 18000rpm | 18000rpm |
| Capacity | ~500kg/h | ~500kg/h | ~1500kg/h | ~1500kg/h | ~7500kg/h | ~25000kg/h |
| Power | 5.0kW | 5.0kW | 15.0kW | 15.0kW | 75.0kW | 250.0kW |
*D:Motor direct drive model B:Belt drive model
Nozzles
The most appropriate nozzle can be selected depending on the liquid’s characteristics and operating conditions. A variety of materials such as stainless steel, fine ceramics, special alloys and coated materials are available.
Two-fluid nozzle
Two-fluid nozzle atomization is suited for granules below the particle size of 20μm. One fluid is the liquid to dry and the other one is compressed gas to impact the liquid to be atomized. By controlling the liquid concentration, viscosity and gas-liquid ratio, it is possible to target single-micron particles. Our own unique nozzle is specially designed to prevent clogging even for high-concentration and high-viscosity fluids.
Single-fluid nozzle (Pressure nozzle)
A single-fluid nozzle atomizes by the kinetic energy of the liquid pressure. As the pressure increases, the flow through the nozzle increases, and the size of droplets decreases. A variety of nozzle orifices can be selected to meet suitable material properties and operating conditions. By creating the condition of universal-joint nozzles, a smaller drying chamber can be designed in situations of a limited footprint.
Powder collections
Dual collection method
The powder is collected at two points: beneath the drying chamber and the cyclone. Spherical powder with good fluidity can be collected from the drying chamber and fines are collected from the cyclone. This method therefore can be beneficial for grading the powder.
Cyclone collection method
A cyclone separates particles from the gas stream by its centrifugal force. It is generally used for producing light or fine powders. A multi-stage cyclone is also available for specific requirements.
Bag filter collection method
Fabric filters in the bag-house separate powders from the gas stream. It is suited for collecting extra fine particles where efficient collection cannot be achieved by a cyclone. A variety of filter materials including pre-coated filters can also be selected.
* Please contact us for further information, as there are other methods available.
Materials
As a standard feature, SUS(AISI)304 with buff #300 finishing is used in powder contacting part. Depending on the material characteristics, other materials, such as SUS (AISI) 316, SUS (AISI)316L, fluororesin coating and higher buff finishing levels can be selected.
Heat sources
A variety of heat sources including electricity, steam, LNG, LPG, kerosene, heavy oil, exhaust heat sources within a factory, and a combination thereof can be selected. Depending on the cleanliness of the operation, the heat source can be selected from either a direct heating or indirect heating system. HEPA filters can also be selected. In case of indirect heating, a high level of energy saving can be achieved by circulating the exhaust heat of the heat exchanger.
Energy-saving system
By recycling the heat of exhaust gas that would normally be wasted, a high level of energy efficiency can be achieved. With our unique environmentally friendly system, not only the operating cost, but the CO2 emissions can also be reduced.
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