A leading west coast recycling facility of asphalt and concrete material from large demolition and road projects has successfully employed an atomized mist dust suppression system to control air quality in and around its Chula Vista, CA plant.
Reclaimed Aggregates Inc. (RAI) occupies five acres in Southern California, operating one of the largest pavement salvage and reclaimed asphalt pavement (RAP) production facilities in the region.
The mid-sized DB-45 dust suppression machine throwing mist 45 meters.
By upgrading the dust suppression from a sprinkler system to a DustBoss DB-45, operators report a substantial air quality improvement in the material receiving area.
RAI was formed as a subsidiary of Pavement Recycling Systems (PRS) in 2005, with its first two locations in Colton and Lancaster. In 2009, the company’s Chula Vista facility was added and acts as its largest processing location, receiving and processing concrete and asphalt recovered from multiple road and construction demolition projects.
Since opening, the business has expanded its scope to service hundreds of contractors and companies, as well as local and state government projects.
DAMPENING ASPHALT AND CONCRETE DUST AT TRUCK DUMP
Dozens of dump trucks per day deliver recovered pavement from projects all over the San Diego area to the Chula Vista site. Material is offloaded onto a 200'x200' dry earth receiving area and immediately moved by front loader to the crusher or into storage piles.
“The offloading process creates a tremendous amount of dust, and that was causing issues for our neighbors who run large vehicle salvage lots,” said Facilities Manager Robert Erautt. “At first, we tried to reduce the amount of dust with a sprinkler system. It just saturated the material, creating a lot of mud, but the dust still remained an issue.”
Company officials reviewed the options and during their investigation discovered the DustBoss series of suppression equipment. They chose the DB-45 mist cannon based on its range, which is well suited to the size of the area requiring dust management.
"Recycling material is just good business, but it shouldn't come at the expense of air quality."
Robert Erautt - Facilities Manager
The unit is able to throw its atomized plume 150 feet to deliver effective dust control over a 12,000 square foot (1,115 square meter) area. When equipped with optional 359° oscillation, the design can cover as much as 74,000 square feet (16,875 square meters) from a single location.
The mist is created by a stainless steel manifold with 18 atomizing nozzles delivering 80+ PSI (5.52 BAR) of pressure, propelling millions of droplets with an 18,000 CFM (510 CMM), 15 HP industrial fan. The DB-45 delivers a dense curtain of water droplets atomized to a 50-200 micron size range, which creates the greatest attraction to most dust particles.
The size range is critical to avoid the ‘slipstream’ effect that large droplets from sprinklers have on airborne dust particles. In most applications, fugitive particles are generally around 50 to 100 microns in size, but water droplets from a sprinkler are much larger, often 2000 to 6000 microns.
Trucks dump aggregates into the into the receiving area where a front loader moves it to the crusher or into stockpiles.
The velocity of the large sprinkler droplet affects the airflow and when an airborne particle approaches it, the flow often deflects the particle without a collision between dust and droplet.
In contrast, the atomized mist dust suppression system creates droplets that are much closer in size to the dust particles, which encourages the necessary contact to bring dust particles to the ground.
The sheer number of these miniscule droplets also increases the surface area available to contact airborne particles, without over-saturating the debris. While large sprinklers can apply 500 gallons per minute or more, the DB-45 puts out just 11.3 GPM at 100 PSI inlet pressure, helping RAI prevent mud and minimize runoff.
“The DustBoss made an immediate impact,” Erautt said. “On hot dry days — which we get a lot of around here — a little breeze can carry dust a long way. We just turn on the atomizer and you can see the mist pull the dust out of the air. The unit is on a metal carriage, so we can adjust its position if the wind changes, but generally it stays in one place."
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"We leave the machine running most of the day if it isn't raining. We haven't had a single call from our neighbors about dust from the day we added it."
Robert Erautt - Facilities Manager
SUSTAINABLE ROAD PRODUCTION
Prior to material recycling, California roads were constructed with aggregate and sand pulled from local quarries. To replace these roads, thousands of tons of existing asphalt, concrete and base were removed and transported to landfills, while virgin material was trucked in.
Reclaimed Aggregates has made it possible to minimize the use of new materials by recycling road and construction debris into its Class II base CMB (crushed miscellaneous base), meeting CalTrans specifications. RAI primarily produces a Recycled Class II base, as well as various products and materials for use in pavement preservation using 100 percent recycled asphalt.
"We just turn on the atomizer, and you can see the mist pull the dust out of the air. The unit is on a metal carriage, so we can adjust its position if the wind changes, but generally it stays in one place."
Robert Erautt - Facilities Manager
In addition to cold milling, pavement preservation and soil stabilization, PRS also provides cold in-place recycling (CIR or CIPR). The process involves a “train” of several different machines, which together handle the milling of existing asphalt pavement. It is then removed from the roadbed and added to a crusher with its own integrated dust suppression, which reduces the material to a 1-inch minus aggregate.
The aggregate is transferred to a machine that mixes the cold milled material with an asphalt-based emulsified recycling agents in an engineered mix design. The cold recycled asphalt is installed, compacted to specific depths and then overlaid with a thin section of virgin asphalt. Sometimes a RAP slurry can be installed over the recycled asphalt as a preservation tool, depending on the project specs.
“A road project can involve thousands of truck loads carrying asphalt out and bringing material in, causing a lot of dust and traffic,” Erautt said. “The CIR process only requires the engineered emulsion to be shipped in, reducing truck traffic 40:1 and lowering the carbon footprint of most projects by about 70 to 80 percent. In addition, the work is done faster, the cost of the process plummets and the finished product is just as good.”
Erautt called it an engineered approach using sustainable solutions.
The push for greener, more environmentally sound construction methods is not just a trend; it has become a key component of lean and efficient business models for companies across the country. RAI is doing on-site recycling in projects from coast to coast, and dust suppression is a primary objective.
“Our goal is to reduce as much material going into landfills as possible,” Erautt said. “Recycling material is just good business, but it shouldn’t come at the expense of air quality. At our processing centers or out on a project site, a clean and efficient operation that includes dust control keeps the community and clients happy. It’s good for everyone in the end.
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