This system requires more equipment and control, but Trost believes it gives a more consistent mix.
“We are required to use the system for any HMA produced for IDOT, but we are so convinced of the benefits of this system that we use it for 100 percent of the mixes we produce,” he says. “In addition to the consistency of mix, the equipment runs more reliably when we use it continuously.”
New Joliet plant
While improvements have been made to the existing plants in Thornton and Bourbonnais, the Gallagher Joliet plant was recently upgraded. The Joliet plant and property was originally purchased by Gallagher in the 1970s. In 1990, a 350 ton per hour (tph) Astec Double Barrel plant was purchased to replace the original batch plant. This site is in Will County, an area that had seen rapid growth throughout the 1990s and early-mid 2000s.
Struggling to keep up with product demand, Gallager upgraded the facility to a 500-tph Astec Double Barrel plant. “The new facility was planned and designed starting with a clean sheet of paper. Our key considerations throughout the process were safety, productivity, reliability and being environmentally friendly all while keeping the initial cost within budget,” Trost says.
With the changes, Gallagher now had a larger drier/mixing drum and burner system for an increased production rate. The burner is capable of firing on natural gas or used oil. The new plant also includes a greater aggregate storage capacity including eight cold feed bins and two RAP bins.
“Previously we only had six cold feed bins and a single RAP bin,” Trost says. “The two RAP bins also gave us the capability to incorporate RAS into our mixes. We have five, 350-ton HMA silos with the new plant set up for long-term storage that gives us lots of capacity to store mix and get ahead of crews on high-production days.”
The new Joliet plant has two 900-barrel fines silos that can store fines collected from the bag house or store virgin mineral filler to be added to mixes. The fines feed system includes two sizes of vane feeders to cover a large range of flow required by different types of mixes and a range of production rates.
The plant includes a new tank farm with concrete secondary containment for the three 35,000-gallon liquid asphalt storage tanks, one 20,000 gallon used oil burner fuel tank, and a skid-mounted AC pump system, calibration tank, additive tank, hot oil system and burner fuel pre-heater system.
A lot of effort was put into the design of the plant to be flexible yet as simple as possible, with a big emphasis on noise reduction.
“We put the plant in a different area of the yard at Joliet so we could improve the traffic flow in the yard, and also to allow us to complete the construction of the plant while maintaining the operation of the existing plant,” Trost says. “We began construction in late 2008, and during the 2009 season we had both plants running until we could complete the IDOT certification process for the new plant. Then in 2010, we dismantled the old plant and sold it.”
Several design improvements of the new plant focused on reducing noise. “Our Joliet facility is located with a mixture of residential and industrial neighbors,” Trost says. “With the old plant, we occasionally received complaints from our neighbors about the noise during the operation of the plant. As a result, we worked hard with Astec in the design phase of the project to eliminate this concern for our neighbors.”
One area of noise complaint originated with the slat conveyors associated with the HMA silo storage system. As with HMA plants, the big conveyor is always running as were all four transfer conveyors on top of the silo system giving the operator the ability to divert material from one silo to another when changing mixes or filling silos.
“You had five conveyors running, plus the chain drive system that would generate a lot of noise,” Trost says. “With the new plant we installed a rotating batcher system. We have the main conveyor drive chain in a sealed housing and an oil bath to keep the chain lubricated and running quiet.”