The Benefits of Adding A Pin Mixer to a Limestone Disc Pelletizing System

This article was co-authored by:

Chris Kozicki
Agglomeration Expert

Carrie Carlson
Technical Writer

A pin mixer can be an incredibly valuable tool in a limestone pelletizing system, offering several benefits to both the process and the product.

Made up of Calcium Carbonate and typically crushed prior to use, limestone intended for use as a soil amendment is processed to a very fine powder. And while highly effective for use on soils, crushed limestone is dusty, resulting in a product that is difficult to handle, and yields high amounts of waste due to wind carrying the powder away from the target field.

To combat this problem, producers began pelletizing limestone powder on a disc pelletizer, or pan granulator into easy-to-handle limestone granules. This has shown to be a highly effective method, but producers are now discovering that the addition of a pin mixer to the pelletizer plant can bring significant value to the operation.

Why Add A Pin Mixer to a Disc Pelletizing System

Adding a pin mixer to a disc pelletizing system serves multiple purposes. The major advantages that this brings are as follows:

  • De-dusting

    Disc pelletizers are referred to as an “open system,” meaning the material is not contained, and therefore is free to escape into the air. As a dusty material, pelletizing limestone in an open system creates a messy, dusty, and potentially hazardous environment.

    The introduction of a pin mixer allows the fine powder to be de-dusted prior to entering the pelletizer. This is done by pre-blending the material with a majority of the required product moisture and binder. The material becomes virtually dust free before it is fed onto the disc pelletizer.

  • Increased Production

    Adding a pin mixer to the pelletizer plant also allows for increased production. Because moisture must be gradually added on a pan pelletizer, reaching the desired moisture level on this piece of equipment can take a good amount of time. With a pin mixer, however, the majority of the moisture can be added to the process and uniformly blended, before it even hits the pan. This means the limestone can spend significantly less time on the pan pelletizer, and the rate of production is then considerably increased.

  • Densification / Reduced Binder Usage

    The mechanical energy of the pins rotating in a pin mixer naturally creates an increase in product density, yielding a stronger product. Because this densification is created through energy and not through added binder, less binder is required to reach the same density result. This translates into less cost for binder.

  • Blending

    Because a pan pelletizer is not intended to mix materials on the pan, often the distribution of binder throughout the material can be uneven. Adding a pin mixer prior to the pan pelletizer allows for thorough mixing of the binder with the material, resulting in more uniform pellets. This is particularly noted in final crush strength; relying on the pan pelletizer to mix the binder yields varying crush strengths due to uneven distribution of binder. When material and binder are pre-blended in a pin mixer, end crush strength is much more uniform.

Click the image below to view our infographic on limestone soil amendments
Limestone and Gypsum Soil Amendment Infographic

Though many limestone producers still rely on the disc pelletizing system for processing limestone, the advantages that the addition of a pin mixer can add to the process have proven to be highly beneficial.

FEECO has been custom engineering pin mixers for over 60 years. We have helped several agricultural limestone producers to create a product that meets their needs, on a system that is efficient and built to last. For more information on our agglomeration equipment and technology, contact us today!

About the Authors . . .

Chris Kozicki is a Process Sales Engineer and agglomeration expert.

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Carrie Carlson is a technical writer and visual designer.

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