Spray granulation is an advanced process widely used in the pharmaceutical, food, and chemical industries. If you are looking for the right particle engineering process for your production, please read this article. This article will introduce the spray granulation process in detail.
What is the Spray Granulation Process?
Spray granulation is a particle formation process in which a liquid feed, solution, suspension, or binder is atomized into droplets and combined with powder particles under controlled drying conditions, allowing particles to agglomerate and grow into larger granules.
The Process of Spray Granulation
Among different spray granulation technologies, fluidized-bed spray granulation is one of the most widely used systems in the pharmaceutical, food, and chemical industries because it integrates mixing, granulation, and drying into a single process.
Standard fluidized-bed spray granulation involves four core steps.
Fluidized Powder Bed
Preheated air enters the unit from the bottom through a distribution plate and flows upward through the powder bed, causing the powder particles to become suspended and move in a boiling motion. This fluidized motion ensures thorough separation and circulation of the powder, thereby increasing the contact area for wetting and drying. The fluidized state also prevents the powder from clumping into large lumps.
Atomization and Spraying
The nozzle atomises the liquid material (a solution, suspension, or melt containing solids) into fine droplets, which are sprayed onto the fluidized particles. The droplets wet the particle surfaces, forming temporary “liquid bridges” between the particles and initiating the agglomeration process.
Drying and Granulation
Hot air continuously flows through the particle bed, causing the solvent in the droplets to evaporate rapidly. The liquid bridge then solidifies, firmly bonding the particles together, and stable particles begin to form.
Discharge
When the particles reach the target moisture content, particle size range, and flow characteristics, the process is stopped. Particles that have reached the target size are automatically discharged through air classification. Smaller particles that have not reached the target size remain in the bed for further granulation. In continuous operation mode, granulation and discharge occur at the same time.
Spray Granulation Process vs Spray Drying Process
Main Difference
Simply put, the most fundamental difference between spray granulation and spray drying is the final product.
Spray drying directly converts liquids into fine powder particles, typically ranging from several microns to a few hundred microns in size, such as infant formula and protein powder.
In spray granulation, the liquid is converted into larger particles (50 μm–5 mm). The particles grow layer by layer in a fluidized bed, resulting in larger granules with improved bulk density, reduced dust generation, and excellent flowability. Such as laundry detergent, pharmaceutical granules.
Limitations of Spray Drying
- Dust issues: Fine particles in the powder can generate dust, which may pose a safety hazard.
- Need further processing: Powders obtained through spray drying often require an additional agglomeration step to produce larger particles.
Types of Spray Granulation Process
Based on the location of the nozzle within the fluidized bed equipment, the most common spray granulation systems used in industrial applications can be classified into three types.
Top Spray
The nozzle is located at the top of the fluidized bed and sprays liquid downward onto the powder bed. This is the most widely used granulation method. It is primarily used for the agglomeration of fine powders and particle growth, transforming fine powders into free-flowing granules. Granules produced by top-spray granulation have good porosity.
Bottom Spray
The nozzle is located at the bottom of the fluidized bed, and the liquid is sprayed along with the rising gas stream. Bottom spray systems are primarily used for particle coating and layering applications, especially in pharmaceutical sustained-release, taste-masking, and functional coating processes. This configuration enables more uniform droplet distribution across the particle surface.
Tangential Spray
The nozzles are arranged tangentially along the walls of the fluidized bed cylinder, creating a rotating flow field inside the equipment. This method improves particle sphericity, producing denser, more uniform particles. You can use it to prepare high-density pellets or sustained-release micro-pellets.
Other Spray Granulation Technologies
In addition to fluidized-bed spray granulation, industrial particle engineering also includes other granulation technologies such as spray-drying granulation, melt granulation, rotary atomization granulation, and prilling processes. However, fluidized-bed spray granulation is the most widely used method.
Advantage of Spray Granulation Process
Integrated Process
Multiple steps, such as mixing, granulation, and drying, are completed within a single machine. This helps you reduce equipment demands and reduce potential issues associated with product transfer.
Precise and Controllable Particle Size
You can precisely control parameters such as particle size, residual moisture, and bulk density based on process parameters and equipment configuration to achieve a wide range of product characteristics.
Good Particle Quality
The granule produces minimal dust, has high sphericity, a uniform particle size distribution, high bulk density, excellent flowability, is easy to measure, and has good solubility.
Protect Thermally Sensitive Substances
Although hot air is used, rapid solvent evaporation can help maintain relatively low particle temperatures, making the process suitable for many heat-sensitive materials.
High Production Efficiency
Spray granulation supports continuous operation and can achieve high industrial throughput, from several kilograms to multiple tons per hour, making it suitable for large-scale production.
Drawback of Spray Granulation Process
Higher Investment
Fluidized-bed spray granulation equipment is relatively precise, requires strict process control, and results in a higher upfront investment.
Complex Control of Process Parameters
Parameters such as inlet air temperature, spray rate, droplet size, and airflow must be precisely adjusted and monitored, which places high technical demands on operators.
Risk of Sticking to the Walls
If the process parameters are set incorrectly, wet particles may adhere to the inner walls of the equipment or the distribution plates, affecting operational stability and product collection.
High Standards for Raw Materials
Spray granulation has certain requirements regarding the solid content and viscosity of the feed solution. Solid content that is too high or too low may affect granulation.
Applications of the Spray Granulation Process
Food and Animal Feed Industry
The spray granulation process is suitable for functional food ingredients, vitamins, dietary supplements, and protein products. It is also commonly used for granulating instant coffee, instant tea, and seasonings. Additionally, it can be used for granulating animal feed additives and pet food. If you need to convert liquid nutrients into dry, stable solid granules, this process is an excellent choice.
Pharmaceutical and Health Products Industry
Spray granulation is broadly applied in pharmaceutical formulation processes to produce granules containing active pharmaceutical ingredients and excipients for subsequent tableting and capsule filling. It can also be used for the granulation of plant extracts and functional health supplements.
Chemical Industry
You can use spray granulation for the granulation of industrial chemicals and fine chemical products. Such as the production of catalyst granules and the pelletization of plastic additives and polymer granules. It can also be used for the preparation of battery materials.
Ceramics and Powder Metallurgy
The spray granulation process can be used for the spray granulation of ceramic powders, including alumina, zirconia, and silicon nitride. It improves powder flowability and particle uniformity for ceramic pressing, sintering, and powder metallurgy applications.
Fertilizers and Agrochemicals
Spray granulation can be used for the production of fertilizer granules as well as the preparation of powder forms of pesticides and crop protection products. It helps produce uniform fertilizer granules with improved storage stability, reduced dust generation, and better application performance.
Detergents and Household Chemicals
The spray granulation process can also be used to produce washing powder granules, surfactants, and other products. Spray granulation produces free-flowing detergent granules with controlled particle size, improved solubility, and reduced powder dust during packaging.
FAQ
Which Key Parameters Affect the Final Particle Size In the Spray Granulation Process?
In the spray granulation process, inlet air temperature, fluidizing air velocity, spray rate, and binder properties are the key parameters that influence particle size. The average particle size increases with rising binder viscosity and spray rate, while it decreases with increasing fluidizing air velocity and inlet air temperature.
Which Process Consumes More Energy? Spray Granulation or Spray Drying?
In many applications, spray granulation process typically consumes less energy than spray drying. Spray drying typically involves a solid content of 30%–50%, requiring the evaporation of large amounts of water, which results in higher energy consumption. While spray granulation adds only the amount of water necessary for particle growth, resulting in minimal evaporation.
Which Materials Are Not Suitable for Spray Granulation Process?
Spray granulation poses challenges when processing materials with high sugar, high fat, or high viscosity. High-sugar materials tend to melt at high temperatures and adhere to the inner walls of equipment. While high-fat materials may compromise the hardness and wear resistance of the granules.
For such materials, you should first conduct feasibility tests to optimize the formulation and process parameters. If necessary, add anti-caking agents before spray granulation production.
How Can Dust Emissions in Exhaust Gases Be Addressed During Spray Granulation Production?
Industrial spray granulation production lines are typically equipped with high-efficiency dust collection systems. The pharmaceutical and chemical industries commonly use dust collectors specifically designed for granulation and fluidized-bed drying to filter dust from exhaust gases and discharge clean air.
A well-designed exhaust gas treatment system not only meets environmental emission requirements but also enables material recovery to reduce waste.
How to Choose a Binder For Spray Granulation Process?
Common binders used in the spray granulation process include starch slurry, maltodextrin solutions, polyvinylpyrrolidone (PVP), and other polymer-based binder solutions. A suitable binder should be compatible with the material and should not affect the product’s activity or purity. It should also have moderate viscosity to facilitate atomization. Furthermore, the solid bridges formed after drying should be sufficiently strong to make the granules wear-resistant.
Final Thoughts
Choosing the right production equipment for a product is crucial. Pilotech is an experienced spray dryer manufacturer in China. We hold more than 50 patents, 5 software copyrights, and CE certification. We will provide you with excellent equipment quality and professional services. Welcome to contact us!