A solution that sticks for global roofing industry
Compact, high-efficiency heat exchangers create better adhesion in shingle-making process
Author: Jamie Zachary
Analysts are pegging the global asphalt shingle market to grow by 5.8% from 2018 to 2023 due to the product’s cost-effectiveness, durability and applications in residential repair and remodelling projects across developed regions.
Where does that leave manufacturers?
“As the demand for asphalt shingle production increases, plant operators will face increased competition, as well as the need to improve the efficiency of their operations,” says Albert Bedell, regional director, Asia Pacific for Solex Thermal Science.
“Indirect heating technology represents one of the most cost-effective solutions to manufacturing a better-quality shingle that can also cost less to produce.”
What goes into a shingle?
Asphalt, or composite, shingles are made up of three main components: a thin membrane, asphalt and ceramic-coated opaque mineral granules.
- Membrane: Constructed from recycled paper and wood or fibreglass, the membrane looks like a continuous sheet of paper – or a roll that you’re used to see feeding a printing press.
- Asphalt: This is a thick hydrocarbon substance that is comes from oil refining. Unlike road asphalt, roofing asphalt is mixed with crushed limestone rock to create a filled coating.
- Granules: These crushed and screened rocks are covered with a speciality ceramic coating. Granules can come in different sizes and colours, depending on the specifications, and are meant to provide mechanical protection for the asphalt.
During the shingle-making process, a thin paper-like membrane will be stretched out like a conveyor belt covered with the mixed asphalt. The granules are then applied evenly on top of the asphalt before a thermally activated sealant is applied to hold the bond.
Lastly, a release film might be applied to the backs to prevent shingles from sticking together while in storage.
The ‘why’ behind heating
Prior to being applied to the asphalt, granules are typically stored outside – meaning they need to be heated up to stick to the surface.
“If the granules are too cold, they won’t actually settle. You will end up having most of the granules just fall off the paper,” says Bedell. “Imagine if you had an ice cube and sprinkled some sand on it. It’s just going to sit on top. But if you heated up that sand, then it’s going to melt into the surface of the ice and stick.”
On the flip side, if the granules are too hot, they can settle too far down into the asphalt – like a hot rock in snow. By displacing the asphalt, the granules compromise that impermeable layer, which could lead to a water path that tracks to the paper and eventually into the home.
“You’re really trying to hit this Goldilocks temperature where it’s hot enough that it just settles into the tar, and not so hot that it just falls through or too cold that it bounces off,” says Bedell.
The Solex advantage
Traditionally, shingle manufacturers would pre-heat the granules with direct-fired rotary driers or even blow torches. The challenge with a process that uses blow torches is it creates a high degree of temperature variability – meaning some granules could be too hot, others too cold.
And while rotary driers can create consistent heat, they also consume high amounts of energy, are bulky and contain a number of moving parts that lead to higher long-term maintenance costs.
The Solex heat exchanger can provide uniform and precise temperature to the granules immediately before they are applied to the asphalt. The vertical units use indirect plate heating and a countercurrent flow of thermal oil through the plates to heat bulk solids material by conduction.
Solex thermal modeling capabilities guarantee even temperature profiles for the finished product, including controls that allow operators to adjust to different process speeds.
“If the process stops for a little while, you don’t have burnt particles falling out the way you would if you were just blowing a torch across the top of it,” says Beddel. “You’re able to more carefully modulate the temperature.”
The mass flow discharge feeder creates uniform product velocity and regulates product flow rate, thereby creating consistent applications while reducing abrasion or degradation to the unit.
Case study: Slate chip heater
The plant’s objective was to improve heating during the shingle production process. Cold granules entering the facility were heated using blow torches, creating uneven temperatures and resulting in high energy consumption costs.
The plant installed Solex’s indirect heating technology. The heater’s small, vertical orientation meant it could be easily integrated into the existing facility. Installed in 2017, it was successfully able to heat a mass flow of granules from colder ambient conditions to a high-temperature setting by using a countercurrent flow of thermal oil.
Based on the success of this slate chip heater, the customer now plans to install additional Solex heaters on other production lines within their plant.
Did you know?
“Stickiness” is not the only benefit that the Solex heat exchanger offers during the roofing production process. Pre-heating raw materials that are used in shingles can also increase production capacity without compromising quality and improve energy efficiency by as much as 90%.
Ready to talk specifics? Contact a Solex team member today.