Recycler uses atomized dust suppressionPublished 15/4, 2015
Reclaimed Aggregates, a leading west coast recycler of asphalt and concrete, has employed an atomized mist dust suppression system to control air quality in and around its Chula Vista plant in southern California.
Reclaimed Aggregates, a subsidiary of Pavement Recycling Systems operates one of the largest pavement salvage and reclaimed asphalt pavement production facilities in the region. 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.
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 receiving area and moved by front loader to the crusher or into stock piles. The offloading process creates a tremendous amount of dust, and that was causing issues for our neighbours who run large vehicle salvage lots, said Reclaimed Aggregates 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 discovered the DustBoss series of suppression equipment from Dust Control Technology. They chose the DB-45, as the unit is able to throw its atomized plume 46m to deliver effective dust control over a 1,115m2 area. When equipped with optional 359° oscillation, the design can cover as much as 16,875m2 from a single location.
The DustBoss made an immediate impact, said Erautt. 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. We leave the machine running most of the day if it isnt raining. We havent had a single call from our neighbours about dust from the day we added it.
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, said DCT president Laura Stiverson. In most applications, fugitive particles are generally around 50-100 microns in size, but water droplets from a sprinkler are much larger, often 2000 to 6000 microns. 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 addition to cold milling, pavement preservation and soil stabilization, Pavement Recycling Systems also provides cold in-place recycling. The process involves a train of several different machines, which together handle the milling of existing asphalt pavement. The milled material is removed and added to a crusher with its own integrated dust suppression, which reduces the material to a 25mm minus aggregate. The aggregate is transferred to a machine that mixes the material with an asphalt-based emulsified recycling agent in an engineered mix design. The cold recycled asphalt is installed, compacted to specific depths and then overlaid with a thin layer of virgin asphalt. Sometimes asphalt slurry can be spread over the recycled asphalt as a preservation tool.
A road project can involve thousands of truck loads carrying asphalt out and bringing material in, causing a lot of dust and traffic, said Erautt. The cold in-situ recycling 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%-80%. In addition, the work is done faster, the cost of the process plummets and the finished product is just as good. Our goal is to reduce as much material going into landfills as possible. Recycling material is just good business, but it shouldnt come at the expense of air quality. At our processing centres or out on site, a clean and efficient operation that includes dust control keeps the community and clients happy. Its good for everyone in the end.