How neighborly of them

Bill Wilson / December 28, 2000

Asphalt plant managers aren’t getting fat off pies, cakes and cookies

Asphalt plant managers aren’t getting fat off pies, cakes and cookies.

Lets face it, few welcome the new addition to the neighborhood if it’s constantly inviting noisy trucks and smelling like fresh asphalt. Forget about that annual invitation to the block party, too.

But the local snub could start to wear off in the near future. Asphalt plants are here to stay, and there is a continuous effort to build a kinder, gentler facility as far as the environment is concerned.

"We’ve kinda had to build a plant you can’t see, you can’t hear and you can’t smell," Don Brock, CEO of Astec Industries, told ROADS & BRIDGES. "Obviously, that’s not reachable, but I think you have to strive for that and that’s what the public wants."

Astec has thrown out a few ideas, including putting a plant inside a bigger building.

"You create problems in the building with truck fumes and ventilation, and you have to sprinkle the building if you put liquid asphalt inside of it," he said. "We’re still striving to come up with a way of doing it."

Solutions are in high demand. The asphalt industry is still trying to master the design and production of Superpave mixes, and Brock believes recycled asphalt is an appealing component.

"If you screen it and process it, and add another recycle bin, you can often times get as much as 40% recycled asphalt in the Superpave mixes," he said. "I think recycled asphalt will become more important as the price

for asphalt keeps going up. I think there will be more emphasis in the coming years in increasing the amount of recycle."

Taking on tough

California, here we clean. That’s the claim coming out of Astec Industries Inc., Chattanooga, Tenn. The manufacturer has a stationary plant near Anaheim, Calif., outfitted with a special natural gas burner which meets and exceeds stringent California emission standards.

The plant also is equipped with gas recirculation and blue smoke packages, and two 200-ton storage silos are designed to Seismic 4 requirements.

The liquid asphalt is stored in two Heatec vertical asphalt tanks and kept up to temperature by a 2 million BTU helical coil hot oil heater. A 100-gal. calibration tank is part of the liquid asphalt package.

Astec also provided a dry additive system for rubber, including a 3-ton calibration tank, and a 2,000-gal. liquid additive tank with its own calibration tank and metering package.

Astec’s newest Turbo Six Pack portable asphalt plant has 400 tons per hour capacity and is lighter in weight, according to the company.

A new baghouse load has shrunk over 10 ft in length while its ground clearance has increased from 14 to 24 in. Performance has been maintained by installing a higher number of lower profile filter modules and increasing the length of the baghouse section while reducing overall length of the load.

Kingpin loads of the baghouse and the Turbo Double Barrel mixer have been reduced. The Double Barrel mixer load lost approximately 20,000 lb of its total weight while keeping every ton of operating capacity.

Ultra competitive

Taking Gencor Industries Inc., Orlando, Fla., everywhere it has to be is the Portable Ultraplant, which comes with an Ultradrum and burner, self erect silos and conveyors, a portable baghouse, a giraffe recycle system, a turbocoil hot oil heater and a portable AC tank.

The Ultradrum and burner is equipped with a blue smoke capture system, a self-cleaning recycled asphalt pavement (RAP) inlet that allows up to 50% RAP in the mixture without clogging, adjustable veiling flights and sweeping material inlet flights.

Self-erect silos come in two options: one-piece portable or two-piece self-erect. The one-piece portable SE silo is available in 70- and 100-ton capacities, while the two-piece is offered in 120- and 170-ton capacities. No crane is needed for the erection of the silos, which contain built-in hydraulic controls.

Two-plant conversion

Need a batch plant? Turn to the Rotary Mixer Conversion. Need a drum mix plant? Make another turn to the Rotary Mixer Conversion. The apparatus, manufactured by GenTec Equipment Co., Louisville, Ky., converts a batch plant into a drum mix plant on demand.

Production rate can reach up to 300 tons per hour while using up to 50% RAP.

Once aggregate moves through electronic metering devices on the cold feed storage bins and weight belt scales and is fed into the dryer, it is then sent to a bucket elevator. A divert chute at the top of the elevator directs the aggregate into the rotary mixer.

RAP is placed directly into the rotary mixer, where it is melted into the heat of the aggregate and blended into the mix without exposure to the burner flame.

Triple action

The Triple-Drum High Production Counterflow Hot Mix Asphalt Plant, a product of CMI Corp., Oklahoma City, Okla., combines three distinct drying and heating zones in a single drum resulting in higher production capacities for virgin and high ratio RAP mixes, according to the company.

A highlight of the triple drum’s design is a mid-drum, variable length high temperature radiating combustion zone. The feature includes overlapping heat reflector/transfer elements, and CMI believes it provides the following five advantages to hot mix production and recycling: It enhances total fuel combustion through a high temperature radiant zone, prevents RAP and virgin aggregates from interfering with the combustion process, provides conductive, convective and radiant heat to RAP and virgin aggregate in the combustion, blending and mixing zones of the drum, prevents high shell losses in the combustion zone of the drum and provides efficient incineration/oxidation of gaseous emissions from the mixing and blending section of the drum without affecting the combustion process.

Production capacities can reach 600 tons per hour for portable triple drum models and 750 tons per hour for stationary models.

Plant miles

Asphalt Drum Mixers Inc. (ADM), Huntertown, Ind., is dotting the country with its Milemaker Series, a line of portable and stationary counterflow asphalt plants producing 160 to 450 tons per hour.

Designed to deliver the mix quality required to meet Superpave specifications, process up to 40% RAP, add and blend additives and modifiers and meet present environmental standards, the series comes with a self-erect silo and the company’s 380-tons-per-hour slat conveyor consisting of a 6-in. pitch drag chain with optional chrome carbide liners.

Also included is a counterflow drying drum, ranging from 40 to 50 ft long. The longer drying drum ensures that the aggregate moisture levels are the lowest possible and thorough mixture of the aggregate, additives and asphalt cement, according to the company.

Other features are an Eco-Star burner with pre-heated air reducing fuel consumption and NOX emissions and a reverse-pulse baghouse.

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