Choosing the right spray dryer is significant for your production efficiency and cost control. This article will guide you on how to choose a spray dryer, helping you consider more comprehensively and match your production requirements better.
Understand the Feature of Your Material
To find an efficient spray dryer, the first step is to have a clear understanding of the characteristics of your materials, so that the spray dryer can be matched with your production successfully. The following points can be considered.
Heat Sensitivity
You may think that heat-sensitive materials cannot be handled by spray dryers, but this is not true. Due to the extremely short drying time, spray drying is actually an ideal method for handling heat-sensitive materials if the temperature is controlled correctly.
For materials that are not sensitive to heat, there is no strict temperature limit during the drying process. These materials can usually be dried at 200–300°C for fast and efficient drying.
Heat-sensitive materials, such as milk powder, probiotics, and vitamins, can be damaged at high temperatures.
Therefore, heat-sensitive materials should use a co-current spray drying design. An electric heating spray dryer is also a better choice, which can control the temperature more accurately.
If your material is a common heat-sensitive material, use a temperature of 150-200°C. For highly heat-sensitive materials like probiotics, it is best to choose a low-temperature drying spray dryer with a temperature between 50-120°C.
Viscosity
- Low-viscosity liquids (like water): You can choose a pressure spray dryer, which needs less energy and makes larger powder particles. But the nozzle hole is very small, so the liquids need to be filtered well, or the nozzle can easily be blocked.
- Medium- and high-viscosity liquids (like yogurt): A centrifugal spray dryer is usually the best choice. The high-speed spinning disc can atomize thick liquids into fine droplets and is less likely to clog.
- Very high-viscosity materials (like paste or thick slurry): A Two-fluid spray dryer is usually the only choice. It have high-speed air to break the liquid into droplets, but it uses much more energy, usually 4–8 times more than the other types.
You can also use different pumps, such as hose pumps, plunger pumps, and screw pumps. These pumps have strong feeding power and good anti-blocking performance.
Powder Specifications Requirements
You can choose the right spray dryer according to the powder size you want to make.
Pressure Spray Dryer
Particle size: Usually 60–500 microns (μm), or even larger.
Features: A pressure spray dryer can make large and strong powder particles, similar to laundry detergent powder. The powder also flows very well.
Centrifugal Spray Dryer
Particle size: Usually 10–200 microns (μm).
Features: This is the most common spray dryer used in industrial production. It cannot make very large particles, but the particle size is uniform, and the powder shape is round and uniform.
Two-Fluid Spray Dryer
Particle size: Usually 1–30 microns (μm).
Features: If you want to produce very fine powder, especially 20 microns or smaller, a two-fluid spray dryer is a good choice. But it cannot produce large powder particles.
Spray Dryer Processing Capacity
You need to choose a spray dryer with the right production capacity that matches your production needs.
If the production capacity is too small, the production efficiency will be poor. If the production capacity is too large, the machine may lead to unused production capacity, and increased costs—especially for centrifugal spray dryers, which cannot maintain a stable atomization effect under low feed flow rate conditions.
Here is a table below for your reference:
| Category | Water Evaporation Capacity | Processing Capacity | Features & Applications |
| Laboratory Spray Dryer | 0.5 – 5 kg/h | Approx. 5 – 50 kg/h | Minimum sample volume as low as 200 mL;
Adjustable process parameters; Suitable for formulation screening and process development. |
| Pilot-Scale Spray Dryer | 5 – 200 kg/h | Approx. 50 – 2,000 kg/h | Be used for pilot testing and small-scale production.
Support continuous operation for long production runs. Precise parameter control to reduce scale-up risks. |
| Medium-Scale Spray Dryer | 200 – 1,000 kg/h | Approx. 2,000 – 10,000 kg/h | Designed for large-scale continuous production.
Supports multiple nozzles or multiple atomizing discs. Explosion-proof systems, inert loop systems, and solvent recovery systems are available if needed. |
| Large-Scale Industrial Spray Dryer | 1,000 – 3,000+ kg/h | Approx. 10,000 – 30,000+ kg/h | Ultra-high capacity, designed for large chemical plants and industrial parks;
Fully customizable (corrosion-resistant, explosion-proof, CIP/SIP). |
Energy Source and Operating Costs Of Spray Dryer
Steam-Heated Spray Dryer
Steam-heated spray dryers use steam generated by boilers to heat the air. It has low running costs. With typical temperatures usually below 160°C, they are suitable for heat-sensitive materials. They are the most widely used spray dryers in large-scale industry production.
Electrically-Heated Spray Dryer
Electrically-heated spray dryers heat air with electricity directly, with a rapid temperature rise and accurate temperature control. The equipment is relatively simple and produces less pollution. However, the running cost is higher. It is suitable for laboratories and testing or R&D work that needs strict temperature control.
Gas-Heated Spray Dryer
Gas-fired spray dryers burn natural gas to produce heat. Its running cost is moderate, and it can reach very high temperatures (500–600°C) for efficient drying. They are often used in chemical and ceramic production that needs high-temperature processing.
Oil-Heated Spray Dryer
An oil-heated spray dryer burns diesel fuel to produce heat. Because it creates a large amount of pollution during production, it is now mostly outdated and rarely used.
Spray Dryer Circulation System
Open-Cycle Spray Dryer
An open-cycle spray dryer uses air as the drying medium. After drying, the air is released outside directly. The system is simple and low-cost.
Closed-Cycle Spray Dryer
A closed-cycle spray dryer uses inert gas (such as nitrogen) in an extremely sealed system. This equipment is more complex and relatively expensive. The gas can be reused repeatedly. This helps prevent the explosion and oxidation risks.
The type of spray dryer you choose depends on the solvent used in your material.
- If your material uses water as the solvent, you can choose the open-cycle spray dryer. This is the standard spray drying system, and the cost is easier to control.
- If your material uses organic solvents, such as ethanol, acetone, or hexane, you should choose the closed-cycle spray dryer. The nitrogen protection system can not only help prevent explosions but also recover the solvent. Although the investment cost is higher, the system is safer.
- If your material is easily oxidized by air, you can also choose a closed-cycle spray dryer. The nitrogen environment keeps oxygen away and helps protect product quality.
Typical Cases Of Selecting Spray Dryers
Now, here are some common examples of how to choose the right spray dryer. You can think about the material, production size, safety, and heating method together.
Case 1: Milk Powder Factory
The material is a milk solution with water as the solvent.
The factory needs large-scale production and already has a steam boiler.
A good choice is:
- Open-cycle spray dryer
- Centrifugal atomization
- Steam heating
This is a common setup with good efficiency and lower running costs.
Case 2: Pharmaceutical Factory with Alcohol
The material is a traditional Chinese medicine extract that contains ethanol.
This is an organic solvent and can easily catch fire or explode.
The material contains small particles.
A good choice is:
- Closed-cycle spray dryer with nitrogen protection
- Centrifugal atomization
- Steam heating
This setup helps improve safety and also allows solvent recovery.
Case 3: Laboratory Testing
The material is a variety of small test samples with low production volume.
A good choice is:
- Open-cycle spray dryer
- Two-fluid atomization
- Electric heating
This setup is flexible for different materials and makes temperature control easier.
FAQ
Are There Any Special Requirements for Spray Dryers in The Food and Pharmaceutical Industries?
The spray dryers in the pharmaceutical industry have the strictest requirements. It should follow GMP standards. All parts that contact the material must use 316L stainless steel. The system should also include CIP (clean-in-place) and SIP (sterilization-in-place) systems.
The spray dryers in the food industry mainly focus on food safety standards and low-temperature drying. By controlling the inlet air temperature (usually ≤160°C, or 80–120°C for heat-sensitive materials), it can keep the food’s flavor, color, and nutrients.
How Should I Choose a Spray Dryer If My Production Materials Are Corrosive?
If your material is corrosive, all parts that touch the material and the exhaust gas need protection. This includes the atomizer disc, the inner wall of the tower, the pipes, etc.
For normal corrosion (like salt solution or weak acid), 316L stainless steel is enough.
For strong acids or strong alkalis, the atomizer disc should be changed to ceramic or PEEK. The inner wall of the tower should be coated with Teflon (PTFE) coating.
When you customize the spray dryer equipment, you should tell the manufacturer about your material clearly.
What is the Difference Between Co-Current And Counter-Current Spray Dryers?
Co-current spray dryer: Hot air and droplets flow downward from the top of the tower in the same direction. This design is preferred for heat-sensitive materials, as the product does not experience high temperatures during drying. It is suitable for heat-sensitive materials such as milk powder, probiotics, and Chinese herbal extracts. It is also the most commonly used design in industry.
Counter-current spray dryer: Hot air moves upward from the bottom of the tower, and the droplets fall downward from the top, traveling in opposite directions. This method offers higher drying efficiency. However, the product will touch the high-temperature inlet air, so it is suitable only for heat-resistant materials.
What is the Minimum Sample Volume for a Laboratory Spray Dryer for Small-Batch Testing?
The minimum sample volume for laboratory spray dryers is typically 10 ml to 200 ml. Common models include:
- YC-015 Lab Spray Dryer: Only 30ml (related to factors such as the solid content of the material) of material is needed to complete an experiment.
- YC-500 Mini Spray Dryer: It can be placed directly on the experimental bench. Only 10-20ml (related to factors such as the solid content of the material) of material is needed to complete an experiment.
- YC-018 Milk Spray Dryer: The recovery rate is high, up to 92%, it’s suitable for sugary materials. Only 100ml (related to factors such as the solid content of the material) of material is needed to complete an experiment.
What is the Difference in Operating Cost Between Electric-Heated Spray Dryers and Steam-Heated Spray Dryers for Large-Scale Production?
For large-scale production (such as milk powder factories), the operating cost is
very different between the two types of spray dryers.
The steam-heated spray dryers has 30%-50% lower operating costs than electric heating.
Electrically-heated spray dryers can offer rapid temperature rise and precise control, but the operating cost is higher, and they are more suitable for small batches.
If your factory already has a steam boiler, choosing the steam-heated spray dryer can save a lot of operating costs.
Final Thoughts
The essential points to selecting a spray dryer are matching the appropriate system type, atomization method, and heating solution according to material characteristics. Pilotech offers various spray dryers from laboratory to industrial scale, supporting flexible combinations of open/closed cycle systems, centrifugal/pressure/airflow atomization, and electric/steam/gas heating options. If you have any questions, please feel free to contact us. We look forward to cooperating with you!