Key Components of Wet Granulators

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Key Components of Wet Granulators, wet granulators are essential in converting powdered raw materials into particles of specific size, shape, and density. The excellent performance of wet granulators includes high volume production, refined and even particle size, and the ability to change the mesh diameter to adjust the particle size arbitrarily while complying with the standards of reasonable pharmaceutical GMP. Therefore, this paper will discuss the optimization of wet granulators to help readers improve granulation performance and create better-quality products.

Key Components of Wet Granulators


Critical Components of Wet Granulators

A wet pelletizer consists of several components that produce uniform and dense pellets. Understanding these components and their functions is essential to optimizing granulation performance.

  • Mixer: It homogenizes powders, liquids, and binders to form a moist mass.
  • Pelletizer: A high-shear rotating disk that disperses the liquid in the wetted material into tiny droplets and facilitates the formation of particles.
  • Pelletizing Drum: A cylindrical container that surrounds the pelletizing disk and provides an enclosed space for the formation and growth of pellets.
  • Feeder: feeds powders and liquids evenly into the mixer.
  • Outlet: Allows the pellets to exit the granulation drum after formation.
  • Air Handling System: Provides hot or cold air to control the Temperature and humidity of the pellets.
  • Control System: monitors and regulates various parameters of the pelletizer, such as Temperature, humidity, and rotation speed.


Operating Principle of Wet Granulator

A wet granulator is a kind of equipment that utilizes a liquid binder to coagulate powder particles; its operation principle is as follows:

  1. Wetting: Powder raw materials are mixed with a liquid binder, and the liquid is evenly distributed on the surface of the powder, forming wet particles.
  2. Coalescing: The liquid binder forms liquid bridges, which bond the powder particles to form larger particles.
  3.  Rolling: The particles roll over and collide with each other in the pelletizing machine to promote further growth of the particles.
  4.  Drying: After pelletizing, the wet pellets are dried to remove moisture and form a dry, stable granular product.

Key parameters in a wet granulator: Properties of the liquid binder: viscosity, surface tension, solubility, etc. Characteristics of the powder particles: particle size distribution, shape, surface properties, etc. Operational parameters of the granulator: roller speed, Temperature, humidity, etc.


Critical Parameters in a Wet Pelletizer

The pelletizing performance of a wet pelletizer depends on the optimization of several critical parameters, including:

Raw material characteristics

  • Particle size distribution: affects moistening, pelletizing, and drying processes.
  • Fluidity: affects particle interaction and homogeneous mixing.
  • Surface properties: affects moistening, adhesion, and subsequent processing steps.

Process Parameters

  • Adhesive Type and Concentration: Determines the adhesion strength and structure of the particles.
  • Adhesive addition method: affects the homogeneity and porosity of the granules.
  • Mixing speed and time: Controls the rate of granule formation and size distribution.
  • Temperature: affects the binder’s solubility, the granules’ drying speed, and the product’s stability.

Equipment Design

  • Mixer type: affects the shape and size uniformity of the granules.
  • Vessel shape and size: affects the flow of raw materials, mixing efficiency, and quality of the granules.
  • Drying conditions affect the granules’ moisture content, stability, and subsequent processability.

Monitoring and control

  • Particle size distribution monitoring: ensures that the product meets specifications.
  • Humidity control: Prevents excessive drying or humidity, which can affect the stability of the pellets.
  • Temperature control optimizes process efficiency and ensures product quality.

Critical Parameters in a Wet Pelletizer

Raw Material CharacteristicsProcess ParametersEquipment DesignMonitoring and control
· particle size distribution

· Mobility

· Surface Properties

· Adhesive type and concentration

· Addition method of binder

· Mixing speed and time

· Temperature

· Blender Types

· Container shapes and sizes

· drying conditions

· Particle Size Distribution Monitoring

· Humidity Control

· Temperature Control


Advantages and Limitations of Wet Granulators

Wet granulator is widely used in pharmaceutical, food, chemical, and other fields, with the following advantages:


  1. Good homogeneity: Wet granulators can mix the powdered raw materials evenly to form particles with uniform particle size and distribution.
  2. Controlled porosity: Wet granulators can maintain the porosity and surface area of the granules by adjusting the solvent amount and drying conditions to meet different application requirements.
  3. Improved solubility: Wet granulators can increase the solubility of drugs or other active ingredients by increasing the dissolution surface area of the granules, improving bioavailability.
  4. Improved flowability: Wet granulators can convert powdered particles into particles with better flowability, simplifying subsequent handling and packaging.


  1. Solvent use: Wet granulators require solvents, which can pose environmental and safety concerns, especially when using organic solvents.
  2. Time-consuming drying: wet granulation requires pellet drying, which may extend the production cycle.
  3. High equipment investment: Wet pelletizer equipment is expensive and requires professional operation and maintenance.
  4. Risk of cross-contamination: Wet granulators risk cross-contamination when handling different products, which requires strict cleaning and sterilization measures.

Therefore, when choosing a wet granulator, it is necessary to consider its advantages and limitations and weigh them according to specific applications and production requirements.


Solvent Selection in Wet Granulators

The choice of solvent is critical to the operation of a wet granulator as it affects the characteristics of the granules and the overall process efficiency. The following factors need to be considered when selecting the proper solvent:

  1. Solvency: The solvent must dissolve the material to be granulated and form a homogeneous solution.
  2. Volatility: The solvent should have suitable fluctuations to ensure that the volatilization rate during the granule drying process is appropriate and does not result in shrinkage or breakage.
  3. Toxicity: Solvents should be low toxicity and meet GMP regulations and FDA standards to ensure process safety and product quality.
  4. Viscosity: The solvent’s viscosity should suit particle formation and flowability.
  5. Cost and availability: Solvent cost and availability must also be considered to ensure process economics.

Common wet granulator solvents include water, ethanol, isopropanol, and toluene. Water has lower solvency but has the advantages of low toxicity, low cost, and easy availability; ethanol has good solvency and volatility but is more costly; isopropanol has lower volatility than ethanol but better solvency; toluene has the highest solvency and volatility but has higher toxicity and is more expensive. Therefore, when selecting solvents, it is necessary to make a comprehensive evaluation based on process characteristics and solvent properties.

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In short, wet granulators are vital in the pharmaceutical, food, and chemical industries. Users can optimize pelleting performance and produce high-quality, uniformly sized pellets by understanding the key components, principles of operation, critical parameters, benefits and limitations, and the importance of solvent selection.

Wet granulators have become indispensable in many industries due to their high volume production capabilities, granule fineness, and ease of cleaning. Compliance with cGMP regulations and FDA standards ensures the production process’s safety and the product’s quality. The wet granulator is worth your consideration if you are looking for an efficient and reliable pelletizing solution.



What are the advantages of a wet granulator?

  • Advantages of a wet granulator include: – Large scale production capacity – Fine and uniform sized pellets – Adjustable pellet size – Easy to clean.

What are the main parameters of a wet granulator?

  • The main parameters of a wet pelletizer include: – Mixing blade design and speed – Granule bed temperature – Flow, and viscosity of the binding liquid.

What are the criteria for solvent selection in a wet granulator?

  • Criteria for solvent selection in a wet granulator include: – Compatibility with raw materials – Volatility – Solubility – Safety and regulatory compliance.
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