Rapid Mixture Granulator(RMG); Working and Principle

A Rapid mixture granulator (RMG) is used in mixing, agitation, and shear mixing (to break internal molecular force). It is used in pharmaceuticals to make granules. The components of the RMG (impeller and chopper) are highly responsible for the wet granulation process.

Components of RMG:

Rapid mixture granulator components are as follows:

1. Mixing chamber
2. impeller
3. Chopper
4. Discharge port
5. Filter
6. Pursuing air and port provided for solution inlet.
7. Motor

The impeller and chopper are responsible for mixing and breaking the granule’s mass. 

Discharge points are connected horizontally at the lower part of RMG. The discharge point is operated automatically with the help of a pneumatic pump( required 3-5 kg/cm2 compressed air pressure)

The filter is placed with a vent air filter to remove purging air and retained granules inside. 

Purging air is supplied below from the impeller to prevent stickiness in the granules to the impeller and also helps prevent contamination.

Pursing Air Pressure ranges from 5-6 kg.

There are two motors, one for the impeller and another one for the chopper

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Working Principle of RMG:

Rapid mixture granulator works on agitation and tumbling. The impeller is responsible for uniformly mixing wet granules, and the chopper helps in breaking or reducing particle size. At the starting process or during binder addition, the impeller and chopper generally operate at low speed. Then after the formation of wet mass, they are operated at high speed to make the desired granule size.

Dry mixing is done at high speed after adding all dispensed materials into RMG.

During batch validation, all the dry and wet mixing time parameters are set and applied in the batch manufacturing records (BMR). All the parameters are set differently for every product, although it takes 3-5 minutes to mix the dry granules and 5-10 minutes for wet mixing to get the desired 0.5 mm to 1.5 mm sized granules.

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Working behind of impeller:

The impeller is designed at the bottom of the S.S. grade 316 dome-shaped bowl. The impeller mixes the dry powder uniformly and prepares a wet mass after the addition of the binder. It consists of two large blades ( responsible for mixing the dispensed materials) and two small blades( responsible for lifting the dispensed materials ) that are operated at a lower speed during binder addition. Then it operated at a speed of 200 rpm or as given in batch manufacturing records.

Speed – 200 RPM (impeller rotates in an anti-clockwise direction).

Working behind chopper:

The chopper is designed at the lower side of RMG, which helps break down a large mass of granules into tiny granules. A chopper is used whenever required and operated at a speed of 1440-2880 rpm. The chopper does not have any advantage on the size of granules when the impeller speed is high (it’s about 200 rpm).

The process of convert wet mass into granules is called Kneading.

Wet milling of Granules:

After the wet mixing process is completed, the powder mixtures are passed through the multi-mill, and wet granules are transferred to the FBD bowl.

Calculation For a working capacity of the Rapid mixture granulator?

For this, first, calculate the bulk density of powder to be mixed, then it is multiplied by the capacity in liters (provided by the vendor), for, eg.

The working capacity in a liter is 600 liters, and its working volume is 80% means 480 liters and bulk density is 0.5; then capacity in kgs is 480X0.5= 240 kg. so we can make a batch of 240 kg materials in a modal of 600 liters RMG.

Process variable in RMG:

• Time was taken during the mixing process.
• Speed of impeller
• Speed of chopper
• Binder solution quantity

The Endpoint in Rapid Mixture Granulator:

A simple method for detecting endpoints is:

• Take wet granules in hand and close the fist, then open and break it throughout the thumb, called a banana breaking method.
• Ampere load method ampere load on the impeller and chopper is displayed on PLC with amp unit.

Advantage:

• Easy to operate from a PLC panel
• Requires less time for cleaning and is easy to clean
• Safety is adequate
• Standardized according to GMP
• Self-discharge
• Mixing can be performed at a large scale in less time
• Can produce Homogenous mass and later on granules in less time.

Disadvantage:

• High noise level
• Required ample space to install
• During the process, temperature becomes high because of friction force between granules.
• High in cost
• Working height is higher, so it requires more effort to add materials.