Size enlargement processes

Size enlargement operations serve various purposes in the powder processing industry. These include improving handling and flow, reducing losses, producing specific shapes, minimizing dust, enhancing product uniformity, and boosting appearance. Several processes contribute to size enlargement, including compaction, granulation, encapsulation, pelletizing, and agglomeration. While some of these terms may refer to similar operations, they are typically applied across different industries.

Size enlargement processes can be categorized into two main groups:

  1. Processes that aim to control functional properties, such as granulation.
  2. Processes that focus on producing defined forms, such as tablets and pellets.

Granulation for Enhanced Functional Properties of Solids

To control or change the functional properties of solids, we use a size enlargement process called granulation, also known as tumbling agglomeration. Granulation transforms powder materials into larger entities, resulting in aggregates that are significantly larger and possess a porous structure.

The basic method for granulation is the tumble/growth size enlargement method, which produces approximately spherical agglomerates by building up fine particulate solids during tumbling. These resulting granules are often weak and require a binder material to enhance their formation and achieve adequate final strength.

Benefits of Granulation

Compared to the parent powder materials, these larger granules flow more freely and produce less dust. Additionally, granular materials are typically easier to handle and facilitate dosing. Granulation also prevents segregation of powder mixtures since the individual particles of different compositions cannot move freely.

Key Factors in Granulation

In tumbling granulation/agglomeration, the quantity of binder liquid added to the process is crucial for obtaining resistant and functional agglomerates. Moreover, the rotation speed of the granulation unit plays a significant role. An optimal rotation speed ensures sufficient time for particle-particle interactions, facilitating the size enlargement process.

Granulation processes effectively address dustiness issues in various industries. In the food industry, granules with an open structure promote optimal dispersion characteristics for fine food powders, leading to instant products. During granulation in a disc pelletizer, minimal shear forces are applied to the sample materials, resulting in granules with a relatively open structure. These granules exhibit properties such as low mechanical strength, greater shape flexibility, and reduced pressure drop.

High-Shear Granulation

In contrast, high-shear granulation yields denser granules with distinct properties. Depending on the requirements, we can tailor specific characteristics such as granule size, porosity, and hardness for optimal performance in desired applications, including instant products. Our high-shear granulation equipment features a high-accuracy dosing system that effectively disperses the binder liquid, ensuring the production of high-quality granules with uniform properties.

Pressure Agglomeration: A Distinct Size Enlargement Method

A distinct size enlargement method exists called pressure agglomeration, also known as tabletting. This process enables the production of products that meet specific size requirements. Often, these products can form without the need for binder materials, acquiring immediate strength due to plastic deformation.

Pressure agglomeration processes serve various purposes, including easier handling, improved consumption, and controlled release in the food, pharmaceutical, and agricultural industries. Additionally, this method can reduce stickiness when products are in tablet form. Pressure agglomeration can also function as a pre-treatment for analytical measurements, such as Scanning Electron Microscopy (SEM).

Equipment for Granulation and Pressure Agglomeration

In our field testing area, we have different setups for both granulation and pressure agglomeration. Granulation can be executed using high-shear granulation equipment, low-shear rotating drums, and low-shear disc pelletizers. Pressure agglomeration is performed using various hydraulic presses and different tabletting molds.

Analytical Measurements Post-Process

After the size enlargement process, several analytical measurements can determine the density and porosity of the resulting granules and tablets. Techniques such as helium pycnometry, mercury porosimetry, and gas physisorption provide valuable insights. Additionally, a tablet hardness tester and rotating drum can evaluate the strength and attrition loss of the granules and tablets.

 

4o mini