The Process and Applications of a Roll Compactor

Roll Compacters are also called dry granulators. In many industries which work with powder formed or granulated products they face various problems like, powder does not flow and cannot be dosed, or a problem with dust, the solubility is not appropriate, segregation occurs or the density is too low etc.

To solve these problems we need granules produced by Roll Compacters. Roller compactors are used for particle size enlargement.

From the laboratory machine for processing a few hundred gramsto the high production machine producing more than 5.000 kilograms per hour. The application area of this technology is vast; it ranges from pharmaceuticals and cosmetic to chemical Industries or from colours swatches and tabletsto right up to the flavours for food production.

How It Works :

In roller compactor fine powders are forced between two counter rotating rolls and the raw material is pressed into a solid compact or sheet, which are called flakes.These flakes are then milled and reduced in size to the desired grain size according to the requirements.

Detailed Explanation of Process:

There are three main parts in Roller Compactor:

1. Feeding Unit : It conveys the powder to the compaction area between the rolls
2. Compaction Unit: In this unit powder is compacted between two counter rotating rolls to a ribbon by applying a pressure.
3. Size Reduction Unit: In this unit the flakesare milled to the desired particle size.

The most important parameter in the dry granulation process is the force applied on the powder compacted between two rolls. The applied force is expressed in kN/cm, being the force per cm roll width.

The roller compactor compresses the material into flakes. The adjustable speed rolls determine theholding time of the product within the compaction area. The necessary compaction pressure is, which is infinitely variable within a range is transmitted to the rolls via the hydraulic system. Constant roll pressure is maintained by the hydraulic unit,At a given force, depending on the amount of powder sent to the rolls, the powder will be compressed to a predefined ribbon thickness. To form a homogenous ribbon, uniformity of granule thickness and size is maintained with precise process control.

There are two main types of Roll Compactors: Variable and Fixed Gap

Roller compactors can be divided into two categories: One is with a fixed gap, the other one with a floating gap.

In fixed gap the amount of powder gathered in into the compaction area between the rolls is consistent, which leads to different forces to be applied to the powder. Like in slugging, this can cause difference in the ribbon and granulate properties.

In floating gap the distance between the rolls is varies according to the amount of powder provided. Where the force applied to the powder remains constant. Property fluctuations in the granules are reduced to a minimum.

In manufacturing of capsules and tablets on high speed production equipment we require better flowing material with relatively bigger particle size which is achieved through Drygranulation and also, for bonding the particles of various substances together during the compaction process we need dry granulation. Thus Roller compacters are very important machinery for various industries.

Katharine Hurley works with Cemach Limited, The India based manufacturer and exporter of pharmaceutical machineries company offers Roll Compactor, Tablet Press Machine etc.