Spray drying and microprilling are common techniques for particle preparation. There are obvious differences between them, such as applicable materials, particle shape, dissolution performance, and production efficiency.
This article will help you understand these two processes and find solutions suited to your products.
What is Microprilling?
Microprilling is also known as spray congealing, spray cooling, or spray chilling. It is a granulation technology that converts molten materials into uniform spherical particles. The particles produced by this method have large diameters, and less dust escapes. It is often used for processing fatty substances, waxes, and some fusible chemicals.
What is Spray Drying?
Spray drying can turn liquid materials into powder. You’ll see it in the food, pharmaceutical, chemical, and new materials industries. It consists of an atomizer, drying tower, cyclone separator, and powder collection system. You can handle heat-sensitive materials through this technology and realize continuous, large-scale production.
Difference Between Spray Congealing and Spray Drying
1. Process Mechanism
- Microprilling: After the materials are heated to the molten state, they are dispersed into droplets by microporous or vibrating nozzles. Subsequently, these droplets rapidly cool and solidify in the cold air, forming solid particles. The whole process is achieved through cooling granulation, without solvent evaporation. So there is no loss in quality.
- Spray Drying: Liquid material is dispersed into fine droplets via an atomizer and enters a drying chamber, where it comes into contact with hot air. Within just a few seconds, the moisture or solvent in the material is removed, ultimately yielding dry powder.
2. Applicable Material
- Microprilling: The process needs to solidify the molten material and then produce granules. Thus, the material must be hot-melt, with a defined melting point and good flowability. Such as fatty acids, waxes, hydrogenated vegetable oils, and hot melt adhesives. If you want to protect the active ingredient of the product, it can also be mixed with a lipid carrier and coated by this process.
- Spray Drying: It is ideal for most liquid materials and pumpable medium to low viscosity slurries. As long as your raw materials can be made into solutions, suspensions or emulsions, spray drying machines can handle them.
3. Particle Shape
- Microprilling: Particles produced via spray congealing are spherical. During this process, the material is directly cooled and solidified without any solvent evaporation; so, the resulting particles have a denser internal structure and a smoother surface finish.
- Spray Drying: This type of drying also produces spherical pellets, but in a variety of forms. As the moisture is spilled, it gives the granules a hollow or porous structure with a slightly concave surface. Of course, you can adjust the spray dryer’s inlet temperature and the solids content of the formulation to adjust the particle size.
4. Particle Size Range
- Microprilling: The particle size of the granules is generally larger than that produced by spray drying, usually ranging from 20 to 500 μm or even reaching millimeter size.
It is attributed to the high viscosity of the molten material, which makes it difficult for the atomizer to break it into fine droplets. This also helps mitigate dust explosions to some extent.
While you can adjust the particle size by regulating the atomization pressure, nozzle diameter and material viscosity, the overall particle size is still relatively large.
- Spray Drying: Spray dryers can produce extremely fine powder particles, ranging from 1 to 150 μm. You can precisely control particle size by changing atomizers—such as pressure nozzles, two-fluid nozzles, or centrifugal atomizers. If you wish to obtain larger particles, you need to increase the solid content of the material or integrate it with a fluidized bed.
5. Bulk Density & Flowability
- Microprilling: It produces denser and smoother particles, so the bulk density is higher and the flowability is better. It facilitates your subsequent packaging and transportation.
- Spray Drying: The particles produced by this are porous and lightweight, with a lower bulk density. The fluidity of the powder is not as good as that of spray congealing. In practical production, you can enhance the fluidity of the particles by performing secondary granulation or adding anti-agglomeration agents
6. Solubility
- Microprilling: Particles often dissolve in water with difficulty and very slowly. This is because the carrier materials—typically fats or waxes—are hydrophobic. Fortunately, you can utilize this characteristic to formulate sustained-release pharmaceuticals or other controlled-release products.
- Spray Drying: Loose, porous granular powders dissolve very quickly, and water can quickly penetrate and dissolve the powder. You can use spray drying for instant food, beverages, and pharmaceutical powders.
7. Encapsulation Efficiency
- Microprilling: The embedding rate of this technology is extremely high, reaching up to 95%. Through cooling and solidification, the core components can be firmly encapsulated within the substrate, with very little loss of activity.
- Spray Drying: It can be used for microencapsulation; however, its encapsulation efficiency is influenced by the specific formulation and wall materials. And it is generally less efficient than spray congealing, hovering around 85%. Wall materials include gum arabic, maltodextrin, and various proteins.
8. Production Capacity
- Microprilling: Suitable for medium-scale production. Although the output per volume is usually higher than spray drying, the heating of the material and subsequent cooling are required, thus its production pace is slower.
- Spray Drying: It is well-suited for continuous large-scale industrial production. Depending on the model, the hourly output ranges from 500ML for the lab type to several tens of tons for the industrial type. However, the larger the capacity, the higher the dryer tower will be.
9. Energy Efficiency
- Microprilling: High energy efficiency. Energy consumption primarily stems from heating the material and cooling the air. Since it does not require the extensive evaporation of water or solvents, its energy consumption is about one-quarter that of spray drying.
- Spray Drying: It uses a lot of heat to evaporate water, resulting in low energy efficiency. You can improve it by installing a heat recovery system that brings waste heat back into the system to preheat the incoming air.
10. Equipment and Operational Costs
- Microprilling: The system is simple, with a compact structure, so the equipment investment is low. And the operating costs mainly lie in the heating and cooling system. The operation costs are also lower.
- Spray Drying: Spray dryers are highly integrated and require accompanying components such as tall drying towers, powder collection systems, and exhaust gas treatment units, leading to higher initial investment costs.
For materials that are flammable or explosive, an inert closed-loop circulation system is required, further increasing costs. However, when processing large volumes of material over the long term, the comprehensive cost becomes more economical.
11. Applications
- Microprilling: Commonly used in slow-release drugs, flavor coating, sulfur or wax coating of fertilizers, masking the taste, adhesive granulation, ruminant feed additives, and spherical catalysts.
- Spray Drying: It is widely used in milk powder, instant coffee, protein powder, fruit powder, laundry detergent, chemical pigments, fine ceramics, battery materials, and herbal extracts.
Microprilling VS Spray Drying: Comparison Table
| Aspects | Microprilling | Spray Drying |
| Process Mechanism | Molten material is atomized, then cooled and solidified, yielding solid particles | Liquid material is atomized into fine droplets and dried to produce powder |
| Applicable Material | Molten materials, lipids, waxes | Liquid material or pumpable slurry, like solutions, suspensions, emulsions |
| Particle Shape | Uniform spherical particles with smooth surfaces | Hollow powder or spherical powder |
| Particle Size Range | Larger, 20-500μm even higher | Smaller, 1-150μm |
| Bulk Density & Flowability | Higher | Lower |
| Solubility | Slower | Excellent |
| Encapsulation Efficiency | Excellent | Good |
| Production Capacity | Moderate | Large |
| Energy Efficiency | High | Low |
| Equipment and Operational Costs | Medium | High |
| Applications | Pharmaceutical granules, waxes, and controlled-release particles | Milk powder, coffee, flavors, enzymes, pharmaceuticals, and chemical powders |
Which is Better, Microprilling or Spray Drying?
When to Select Microprilling
Molten Materials: Your raw materials have a low melting point and can be directly melted, such as lipids, waxes, or polymers.
Pursuing Extremely High Particle Uniformity: Microprilling can produce spherical particles with a narrow particle size distribution. You will end up with consistent, dense granules—no weird shapes or rough edges.
Downstream Process Requirements: Micro-powder granules flow easily and pack densely, so capsule filling gets faster and more accurate. That’s less hassle on your production line.
Manufacturing Functional Coatings: Microprilling can keep coating thickness even, save on coating material, and boost your controlled-release stability. You will get better performance for less waste.
Low-Dust Environments: Microprilling generates less dust and larger particle sizes. It is a lifesaver in places where dust-free production is a must.
When to Choose Spray Drying？
Liquid Feed Material: If your material is a solution, emulsion, suspension, or pumpable slurry, spray drying can be applied to convert it into powder.
Requirement for Rapid Dissolution: Particles produced via spray drying are hollow and spherical, offering rapid dissolution rates. Also, the process can manufacture amorphous solid dispersions, thereby enhancing the bioavailability of your pharmaceutical products.
Ultra-Fine Particle Sizes: You can make extremely small powder particles, such as inhalants, with a spray dryer while flexibly adjusting the particle size.
FAQ
Can Spray Drying Replace Microprilling?
In some applications, spray drying can replace microprilling. It dries liquids fast, turns them into fine powders, and works well for microencapsulation. But when you need large-sized, highly uniform spherical particles, microprilling is a better option.
What Are the Main Limitations of Microprilling?
Microprilling has high requirements for material. If your substance only melts at a very high temperature or falls apart when heated, microprilling won’t work. It’s a cooling process that turns liquid into solid spheres, but it doesn’t let you tweak porosity much. Spray drying gives you more control there.
Which Technology Is More Effective for High-Sugar or Highly Hygroscopic Materials？
Spray drying is more effective. Spray dryers can evaporate water from materials, and by adding maltodextrin, they can prevent high-sugar materials from sticking to the walls and forming lumps. Sugar-based materials are likely to decompose in a molten state, so they are not suitable for microprilling.
Which Technology Is Better for Heat-Sensitive Materials？
Spray drying. Although the inlet air temperature is higher, drying is typically completed in a few seconds, bringing in very little thermal damage to the active ingredients. Microprilling, on the other hand, requires heating the material to a molten state, a temperature exceeding its melting point, which can easily degrade heat-sensitive components.
How Do the Powders from Both Processes Perform in Downstream Tableting?
Microprilling produces larger, well-formed particles that are uniformly filled and molded for tabletting. Spray-dried particles are smaller and easier to mix. Sometimes, need extra steps—like adding flow aids or doing a second round of granulation—to stop clumping or cracking.
Accelerate Your R＆D with Pilotech Lab Spray Dryer
Microprilling and spray drying have their advantages. But if you’re still testing and changing your formula, spray drying is usually your best bet. It’s flexible, easy to adjust, and provides the data you need for scaling up.
Pilotech laboratory spray dryer helps you fine-tune your formula, improve the particle structure, and provide data support for your subsequent large-scale production.
Contact us now to get a custom spray drying solution.
More Resources:
The Spray Dryer Blueprint: A Practical Guide for Your Business