Improved Roofing Granule Production through Engineered Equipment

This article was authored by:

Shane Le Capitaine
Thermal Processing Expert

Asphalt shingles are the leading choice for residential roofing in the United States. They are affordable, durable, low maintenance, versatile, and have proven effective in the roofing industry for almost 100 years. A large part of their effectiveness, however, lies in the the roofing granules adhered to them, and quality roofing granules rely on robust roofing granule production equipment.

Processing Roofing Granules

While roofing granules may not look like much more than rocks, they are actually a highly engineered product – the result of advanced processing techniques that work to create a premium roofing granule product. A typical process of transforming rock into roofing granule is outlined and illustrated below.

Click on the image to view larger


Traditional roofing granules are composed of graded particles of igneous rock, such as granite. At the mine site, rock is mined and ground to the desired size granule. This ground rock is first dried in a rotary dryer, or rock dryer. This initial drying step reduces the moisture content, which increases the efficiency of the kiln downstream.

The pre-dried rock is then sent to storage until it is needed for processing.


The dried rock is pre-heated in a low temperature, direct-fired rotary dryer. The rock is heated in order to prepare it for coloring.

The pre-heating unit provides high capacity processing capabilities. As such, it is not uncommon to split the process into two identical lines after the pre-heater to maximize plant throughput.

Image: 3D FEECO Direct-Fired Rotary Dryer (Click on the image to view larger)


The heated material exits the pre-heating unit and is fed to a coating drum. Pigment is sprayed onto the bed of material as the drum rotates. This rotational movement serves to evenly coat the granules with the pigment. Additional additives may also be included in the mixture to improve product performance. No heat is applied in this step.

Image: 3D FEECO Coating Drum (Click on the image to view larger)

High Temperature Curing

After the granules are coated, a rotary kiln is used to cure the coating onto the rock base. This chemically binds the pigment (and any other coatings) to the rock.

This process is carried out in a direct-fired rotary kiln, where the material is heated to about 1000º F for a set retention time to produce the desired results.

Image: 3D FEECO Direct-Fired Rotary Kiln (Click on the image to view larger)


Material exiting the rotary kiln is fed to a direct-fired cooler where it is cooled to around 200º F for subsequent handling and storage and to prevent sticking of the material.

Image: 3D FEECO Direct-Fired Rotary Cooler (Click on the image to view larger)

Rotary Drums: The Standard in Roofing Granule Production

Known for their high throughput, robust build, and lifelong reliability, it’s no surprise that rotary drums are the industry standard for processing roofing granules into a premium product.

It is often said that rotary equipment designed around the unique characteristics of the material to be processed will produce the best results, and roofing granule production is a prime example of this; materials of construction must be carefully selected to withstand the constant heavy loads and abrasion that are typical of this industry.

“Roofing granule production is a demanding process,” says Shane Le Capitaine, FEECO Process Engineer. “Producers need equipment they can rely on despite harsh processing conditions, and that’s what we can provide.”

Many of the roofing granule industry’s top producers rely on FEECO for the best in custom, heavy-duty processing equipment. In addition to individual pieces of equipment, we can provide the complete processing line, including the rock dryer, pre-heater, coating drum, rotary kiln, and cooler, along with all of the necessary material handling equipment to support the process.

FEECO also offers a unique testing center – The Innovation Center – where we can run feasibility tests and aid in process and product development around roofing granule production.

For more information on our roofing granule production capabilities, contact us today!

About the Author . . .

Shane Le Capitaine is a Process Sales Engineer and thermal processing and fertilizer production expert.

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