Operations focus: Made of the mist

Features - Operations Focus

A Chicago-area C&D recycler is operating a safer, cleaner workplace since introducing a dust collection system into its daily recycling process.

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March 16, 2015

Chicago is going through a building boom, sparked in part by the addition of 19 new hotels to its skyline—more than 3,000 rooms—slated to open by 2016. The boom isn’t limited to hospitality, as all categories of construction have seen growth, from residential to commercial and mixed-use. One result is improved volumes for local construction and demolition (C&D) recyclers.

In 2012, two mid-sized Chicagoland recycling companies—Lakeshore Waste Services and Recycling Systems Inc.—merged to become Lakeshore Recycling Systems (LRS). The company has since acquired two additional locations, allowing the firm to raise its production to 1.5 million tons of debris processed annually. LRS, headquartered in Morton Grove, Illinois, says it is now the largest provider of construction material disposal containers in the Chicago area.

Along with that increased volume, a greater amount of dust has been created at the recycling centers, which has the potential to affect air quality and worker safety. Thus, LRS officials wanted to take a proactive approach to dust suppression.

“Although we have residential pickup, our main source of material is from C&D projects,” explains Mark Sredin, longtime production manager for LRS. “We receive concrete, wood, drywall, cardboard, glass and paper. All of these materials create their own particulates, along with the years of dust they may have collected prior to demolition.”
 

Dusty process

Sales of raw separated material contribute to a large portion of the company’s revenue, along with tipping fees and container rentals/transport. In most cases, the company drops off one or more containers at a demolition site, where it is up to the contractors to control any fugitive material and dust. When LRS picks up the full container, it’s covered with a tarp to contain dust during transport and hauled to one of the three locations.

Asphalt applications

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. By upgrading its dust suppression system operators report a substantial air quality improvement in the material receiving area.

Dozens of dump trucks daily deliver recovered pavement from projects in the San Diego area to the company’s Chula Vista, California, facility. Material is offloaded onto a 200-foot by 200-foot 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,” says 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 from Dust Control Technology (DCT), Peoria, Illinois. They chose the DB-45 based on its range, which is well suited to the size of the area requiring dust management. The unit is able to throw its atomized plume 150 feet to deliver effective dust control over a 12,000 square foot area. When equipped with optional 359-degree oscillation, the design can cover as much as 74,000 square feet from a single location.


 

“The size range is critical to avoid the ‘slipstream’ effect that large droplets from sprinklers have on airborne dust particles,” says DCT President Laura Stiverson.

The atomized mist system creates droplets that are closer in size to the dust particles, which encourages 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.

In all, hundreds of vehicles—including the 55 company-owned waste collection trucks—arrive daily to deliver recyclable materials from LRS’ more than 6,000 commercial and municipal customers. Each incoming vehicle is weighed upon entry and exit to determine its disposal fee.

The recycling process begins when a front loader pushes the bulk material into a 25,000-square-foot, three-walled, open-air structure. The debris is loaded onto a tipping floor leading to a large steel screen with 2-inch openings. Industrial vibrators shake the screen, set at a 7-degree slope, moving the material slowly down the incline. Small debris such as dirt and aggregate falls through the holes and onto a lower conveyor belt to be transported to the landfill, whereas the remaining larger debris is conveyed to a sorting area.

Once separated, the screened debris drops onto a 5-foot-wide conveyor belt and is then transferred onto another curved conveyor feeding the large material picking line to be sorted. Wood, glass, steel, cardboard, brick and concrete are removed. Sorted material is then sold to various vendors for repurposing.

Sredin says sorting the recyclable material also involves a staff of people evaluating and separating the debris, then placing larger pieces in bins. This requires a safe work area, with dry floors and adequate air quality, he says. With all of the mechanical agitation, the process creates large volumes of fugitive dust and a need for dust suppression.
 

Successful system

LRS started with a large sprinkler system for dust management, which is common in many bulk handling applications. But Sredin and his team soon realized that it wasn’t adequate alone.

“It saturated the material and caused pooling water under the sprayer and around heavy machinery,” Sredin recalls. “It not only made the material hard to handle, it didn’t address the dust issue.”

Company officials performed a detailed search in trade magazines and online for a better solution, eventually contacting Dust Control Technology, Peoria, Illinois, to investigate the company’s family of atomized mist dust suppression units. Impressed by what they learned, the firm purchased its first DustBoss DB-30 for its California Avenue location in Chicago, with the intention of replacing the ineffective sprinkler system.

Initial testing proved successful and operators reported a substantial improvement in air quality along the debris sorting line, as well as dramatically reduced pooling and runoff. Based on that experience, the company has now installed a unit in each of its facilities, creating a safer and more efficient workplace for its more than 350 employees, according to Sredin.

Sredin’s team chose the DB-30 because of its rugged construction and long warranty, he says.

“We initially tried it in multiple positions and areas in the plant,” he continues. “Due to its long range, we found that mounting the DustBoss on the deck over the main conveyor and away from the picking line was the best way to suppress it before it reached employees, letting the mist cover the rest of the conveyor system.”

The DB-30 uses a 7.5-horsepower fan delivering 9,200 CFM (cubic feet per minute) to project a 100-foot cone of dust-trapping mist. With an adjustable throw angle of 0-to-50 degrees in height, the unit has a coverage area of up to 31,000 square feet when equipped with optional 359-degree oscillation.

A three-sided building poses a unique challenge, Sredin says. Even though it is an enclosed space, operators still have to contend with the elements such as wind, rain and severely low temperatures.

According to Sredin, swirling wind within the complex is addressed by merely adjusting the unit’s spray angle. “Our DustBoss is on all day, every day. When it rains or snows, there’s less dust, so we simply turn off the atomizer and allow the strong fan to clear the air. It’s very versatile,” he says.
 

Previous pooling

Pooling and runoff are among the biggest concerns when using dust suppression, especially near walkways, as they are a potential cause of slips and falls.

While large sprinklers can apply 500 gallons per minute (GPM) or more, the DB-30 uses just 3 GPM. “Even running the atomizer all day long, there is no pooling,” Sredin says, adding, “Also, our water bill has gone down considerably.”

When LRS acquired its South Side Chicago location, “For dust suppression they were using a garden hose with a spray nozzle you would buy at the hardware store. It wasn’t doing anything to the dust, and the floor was wet all the time,” says Sredin.

“We immediately brought in the DB-30 and mounted it in a fashion similar to our primary facility. The safer workplace and higher air quality was an instant morale booster for everyone,” he adds.

In 2014, the company purchased Heartland Recycling in Forest View, Illinois, which had installed three small atomizers that didn’t contain adequate fans. “The mist just fell to the floor and pooled, without capturing much dust,” Sredin recalls. “I think the previous owners had the right idea, but with low coverage and no oscillation, the units didn’t do much. We installed one DB-30 to replace all three units and solved both the pooling and the dust problems at the same time.”
 

Increasing incentives

The city of Chicago, in partnership with LRS, has concentrated on recycling programs involving C&D materials by offering incentives to businesses that reduce service charges for keeping materials out of landfills. According to Chicago officials, “C&D debris accounts for 30 percent of all solid waste produced [in the Chicagoland area].”

The city’s incentive plan has increased the volume of recycled C&D debris. It now accounts for 85 percent of all recycled material, with approximately 500,000 tons recycled each year, according to the city of Chicago’s website, www.cityofchicago.org. A large percentage of that material is processed by LRS.

A company spokesperson says LRS is predicting that it will stay on pace for its expansion with gradually increasing volumes of recyclable debris. According to Sredin, with each new facility, there is anticipation of dust suppression using a DustBoss product.

“They’ve done a great job, exceeding all of our expectations,” he concludes of the dust suppression system.



This article was submitted on behalf of Dust Control Technology, Peoria, Illinois. More information is available at www.dustboss.com