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​Critical Parameters and Design of Roll Compactor for Dry Granulation

Jun. 25, 2022

The efficiency of a roll compactor machine for dry granulation is dependent two things; the design of the machine and the operating parameters.

Also, the operating parameters tend to have a significant impact on the whole process of dry granulation.

The parameters can affect the feasibility of the process, the compact quality, the flowability of granules and the blend uniformity.

Critical Parameters and Design of Roll Compactor for Dry Granulation

Roller compactor for dry granulation

So what are the critical parameters and design of roll compactor for dry granulation?

► Compaction Force

Compaction occurs when pressure is exerted on the two counter-rotating rollers.

This force is what is known as the compaction force it has to suffice for the process of compaction to be effective.

Understand that during compaction, the force exerted on the rollers facilitates densification and bonding of particles.

This is what consequently leads to the transformation of powders into compacted ribbons, flakes and sometimes the sheets.

So, when you increase the compaction force to an absolute limit, the density of the compact also increases.

It also increases the particle size as well as the flowability of granules.

When the compaction force is put at its optimal level, the quality of granule increases depending on the mixture of material.

Excessive roller pressure, nonetheless, will lead to the breaking of the compact material, thus compromising the quality of granules.

Besides, when the pressure is beyond the optimum, it can lead to an increase in temperature, thus affecting granulation of heat sensitive materials.

► Roll Gap

The roll gap is the shortest distance between the two counter-rotating rollers of a roll compactor machine.

Interestingly, this is the most critical parameter of roll compaction and the one that needs to be stabilized by the other settings above and below.

Roller gap has a significant effect on the density of compacts and flowability of granules.

This also tends to impact compact’s hardness and blend uniformity.

The effect of the gap majorly arises as a result of the amount of force applied to the rolls and the amount of material that passes between them.

Generally, the compaction force tends to increase as the roller gap decreases and vice versa.

► Roll speed

Thisbasically refers to the amount of time it takes for the material to be compacted and it has a significant impact on the density of compacts.

The speed of the rollers should be set and changed according to the screw speed and the flow of materials.

Note that a higher roller speed leads to inadequate compaction of materials.

It also can also lead to blend segregation and consequently loss of blend uniformity.

► Screw speed

The feeder screw speed is another critical parameter of roll compactor for dry granulation.

Like the roll speed, feeder screw speed is dependent on:

● Flow of material

● Roller speed

● Roller gap.

A low screw speed can cause inadequate deposition of material into the nip region.

This can result in the formation of weak compacts.

A high screw speed, on the other hand, can lead to an increase in temperature within the roller unit.

This can lead to melting or caking of particles during movement.

Please note;

Using high screw speeds won’t solve an inadequate flow of materials.

You should always maintain an optimum speed for the horizontal and vertical screw.

This will help you to achieve homogenous compaction for your materials.

Also, always remember to keep the screw speed equal to the roller speed.

► Milling

If you want to reduce the size of densified materials, you need to apply more compaction force.

Steadily increasing the pressure can help you achieve the desired size of granules, uniformity of blends and good flowability of materials.

The sieve in the milling system can also affect the particle size distribution which can also impact the granule uniformity.

Excessive fines generated in the milling process can densify the blend and affect flowability.

This can also affect the uniformity of blends as well as compact hardness during compression.

Main Technical Specifications of Roll Compactor

The technical specification of any machine determines its capability to perform its intended functions.

In this case, they help determine the ability of a roll compactor machine to process specific products.

Note that that unlike most features of an industrial machine, technical specifications like the name suggests are usually specific to a particular model.

And, understanding the technical specification of a roll compactor imagine can help you understand its suitability for your products and processes.

Keeping this in mind, here is a table indicating the main technical specifications of roll compactor machines.

ModelType of machine based on manufacturer’s product line. For instance, at SaintyCo we have RC-150C and RC-5B series
Feed screw speedRPMThe speed at which the feed screw rotates.
Roll  speedRPMThe speed of a step pulley drive
Roll drive motorKW or HPPower consumption
Feed screw drive motorMotor power consumption
Type of rollKW/HPThis describes the surface of the roll which may be smooth or corrugated
Roll forceKg or tonsMaximum compaction force
Roll diametermm or cmSize of the roll
OutputKg/hourThe quantity of processed material the machine produces per hour

There are other specifications that we’ve not mentioned in this table. But like I said, each model has its specs.

And these are just the main ones that you should be looking for when buying a roll compactor machine.

Critical Parameters and Design of Roll Compactor for Dry Granulation

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