Blending process in pharmaceutical industry is a critical unit operation to ensure the homogenous mixture of API and excipients. Here we briefly discuss about purpose, types, principle and occupancy of blending operation.

Purpose of blending in pharmaceutical industry

In pharmaceutical manufacturing blending is a vital part to ensure the product quality. During this step different ingredients (including API and excipients) are mixed together to make the final blend and the main purpose of this step is to ensure the adequacy of mixing of ingredients.


Importance of blending in pharmaceutical industry

  • The necessities of blending or mixing are as follows:
  • To ensure blend uniformity
  • To ensure content uniformity
  • To ensure proper lubrication


Different types of mixing in pharmaceutical industry

  • Mixing of solids: Double cone blender, V blender, Bin blender, Mass Mixer, High Speed Mixer, Fluid bed dryer etc.
  • Mixing of semi-solids:Sigma blade mixer, Planetary mixer etc.
  • Mixing of liquids:Impellers, Air-jets, Fluid-jets and Baffle mixers.


Read also: Mixing in Pharmaceutical Engineering


Factors to be taken into consideration while selecting a mixing equipment include:

  • Physical properties of materials to be mixed such as density, viscosity and miscibility
  • Speed range and accuracy of mixer
  • Capacity and the size of the mixing vessel
  • Operating temperature and operating range 
  • Economic considerations – operating efficiency, cost and maintenance


Different types of blenders in pharmaceutical industry

  • Double Cone Blender: two-thirds of the volume of the cone blender is filled to ensure proper mixing of dry ingredients and granules.
  • Octagonal Blender: used for efficient mixing of dry ingredients and granules.
  • V-type Blender: widely used in pharmaceutical and chemical industryfor efficient mixing of dry ingredients and granules
  • Vertical blender: excellent technique for processing heat-sensitive formulations without worrying about thermal degradation.
  • Mass Blender: for dry, wet, and lumpy mass.


Difference between octagonal blender and double cone blender

Octagonal blender

  • The octagonal blender is designed to process a larger volume with less power consumption. 
  • It occupies less space compared to other similar blenders.
  • Requirement of RPM is less due to its design.

Double cone blender

  • Two-thirds of the volume of the cone blender is filled to ensure proper mixing.
  • The conical shape at both ends enables uniform mixing and easy discharge.
  • The cone is statically balanced to avoid any excessive load on the gear box and motor.


Double cone blender principle

In this type of blender, mixing takes place axially, as a result of the powder moving through the different sections. Where fragile homogenous particles of dry powder and granules of different sizes and forms are mixed together. Mixing is thorough but it depends on the rotating speed. The mixture is discharged through a hermetically closing butterfly valve which can be operated manually or automatically.The highly efficient machine comes with a special PLC programming which has high safety features and longer service life.


Octagonal blender working principle

Octagonal blender is an octagonal shaped blender design to process larger volume of materials. It occupies less space compared to other similar blenders like ‘V’ and Double Cone and results in less power consumption. The materials come from all sides due to the octagonal shape of the product container, hence requirement of blender RPM is less. It manages to stay well balanced even in higher capacities.


Bin blender working principle

Bin blender is used in tablet and capsule manufacturing with a single step transfer system. The granules transfer into IBC containers in the granulation area for blending. The blending process is done through a dust-free connection. Inside the container, an intensive mixing principle is developed due to the cutting effect caused by its square shape. This geometry, added to high speeds, ensures a great homogeneity among raw material with cohesive nature.


Blender size calculation

Let the target batch size is 250 kg.
Where, bulk density of powder/granules found 0.50 g/ml and blender occupancy is 70%.
Then the blender size to be = 250/0.5 = 500/0.7 = 714 = 700 L


Dry mixing in pharmaceutical industry

Dry mixing is an important step before the granulation. Once both the ingredients (intra and extra granular) are dispensed, API and intra-granular excipients are mixed together through dry mixing. But extra-granular excipients do not add withthis mixture; instead, they are added after the granulation as blending or lubrication material.


Difference between mixing and blending in Pharmaceuticals

The terms blending and mixingare often used interchangeably, but technically they are slightly different. 

  • Blending is a process of combining materials uniformly with relatively gentle process compared to mixing.
  • Mixing is a process of combining materials vigorously.

  • In terms of the phase of material, blending is the process of solid-solid mixing or mixing of bulk solids with small quantity of liquid. 
  • Where mixing is more closely associated with liquid-liquid, gas-liquid, and viscous materials. 


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