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New drum at Terex
Like Gencor,
Terex Roadbuilding has doubled efforts
to improve RAP ingestion. Terex engineers have been developing a replacement
since mid-2004 for what CMI called its TRIPLE-DRUM plant. Now available
under the E3 drum name, the new design has been field tested at a site near
the Texas gulf coast, Terex says.
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| Terex’s new E3 drum, which replaces the Triple-Drum,
features an exclusive early-entry RAP system. |
Featuring the CMI-exclusive early-entry RAP system,
the new drum more efficiently preheats RAP and virgin aggregate at lower
temperatures by adding RAP into the drum prior to the combustion point.
Integral to the drum’s continuous steel shell, stainless-steel heat transfer
panels in the combustion zone optimize material heating, while a new series
of teepee-shaped flights in between the heat transfer panels protects the
shell and reduces required drum maintenance, Terex says.
The new design also incorporates popular features
from Terex’s Magnum line of portable and relocatable drum mixers. The mixing
zone includes Magnum-style flights for improved mixing and coating of the
aggregate with binder. The new drum also borrows from the tire-mount design
for longer, more reliable operation.
Terex says its new E3 counterflow drum is available
for portable, re-locatable, and stationary plant designs. Production
capacities range from 300 to 500 tons per hour for portable designs to 300
to 700 tons per hour for re-locatable and stationary plants. The E3 is
available as a field retrofit for the hundreds of existing TRIPLE-DRUM plant
installations.
Astec’s updates
At Astec, officials have substantially updated the
Six Pack portable hot-mix plant. “We’ve devoted a great deal of time and
energy to updating the entire plant,” says Smith. “We started this proj-ect
with an ambitious goal of improving every component, and I am satisfied that
we have accomplished this goal.” (The plant was originally called a Six Pack
because it could be loaded onto six semi-trailers, Smith says, but
additional components, such as a polymer tank, now bring the total to eight
trailer loads.)
Astec plants are designed to run high RAP content.
“When you run more recycled pavement, you need to screen your RAP,” says
Smith. “You need to have two recycle bins versus one RAP bin, so we build
most of the portable plants with two RAP bins. Customers fractionate the RAP
into finer and coarse RAP, and by the way you feed in RAP, you can run
higher percentages of it.”
In the current redesign of the Six Pack portable
plant, Smith says the Phoenix Talon burner leads the list of updates. The
burner features a premix gas design and air-atomized oil-burning technology.
Variable frequency drives replace traditional dampers in the Phoenix Talon,
which significantly reduces noise during operation. Variable frequency
drives also control oil and airflow, eliminating oil control valves and air
dampers.
Astec redesigned the entire plant layout. The
Self-Erecting Bin and Control Center fit onto individual trailer loads.
Trucks can now drive from the self-erecting bin directly to the Control
Center window, which simplifies the ticketing process and allows plant
operators to move more trucks into and out of the facility each day. Astec’s
engineers have restructured both the self-erecting bin and control center
loads to minimize transportation costs and to simplify plant tear-down and
set-up.
Other updates have been made to the portable
baghouse. “Many of our customers now want to burn waste oil, so we’re
adapting our equipment to that fact,” says Smith. That’s why Astec baghouses
now come standard with anti-corrosive stainless-steel top doors — to resist
the corrosion of the high sulfur content in waste oils.
Two significant updates have been made to Astec’s
portable drag conveyor to increase wear resistance and to lower maintenance
costs. The drag inlet hopper is now lined with ceramic tiles for maximum
abrasion resistance. The new drag liner, built with overlapping 1-inch-thick
steel, eliminates bolts and increases the wear life of the steel.
ADM’s strategy
Asphalt Drum Mixers Inc., a manufacturer of asphalt
plants and related equipment since 1974, began the design and manufacturing
of the Milemaker series in the early 90s. The company’s goals for hav-ing
separate drums for drying and mixing are reduced emissions, the use of high
percentages of RAP and exceptional mix quality. And the company wanted a
plant that was quiet, so as standard equipment ADM uses a sealed-in burner
for low noise. Another area of improvement was to simplify the RAP en-try
process and eliminate, if possible, the high maintenance attributed to
running high percentages of RAP without sacrificing the heat transfer from
the superheated aggregate.
With the mixing chamber separate from the drying
process, there is no blue smoke contamination in the baghouse. Temperature
of the final mix or any variety of additives presents no threat to baghouse,
so emissions are no longer a concern for the plant, regardless of the
location. “We developed a plant that can do it all,” says Mark Simmons, vice
president of ADM.”
Just one of the company’s most recent improvements
to the Milemaker series plants includes increased dryer drum diameters. For
example, the company increased the Milemaker 325 drum diameter from 96 to
102 inches. Similarly, the drum diameters of the Milemaker 225 and the 160
were both increased. (In all cases, the model number is the rated
tons-per-hour capacity of the plant.)
Plant conversions
While Stansteel Asphalt Plant Products builds
complete hot-mix asphalt plants — either batch plants or drum-mix plants —
the company specializes in helping asphalt producers convert their existing,
outdated plants to the latest technology.
“Customers can keep many of their existing
components, such as their cold feed bins, asphalt tanks, and the like,” says
Lennie Loesch, Stansteel’s chief executive. “We can modify their plants and
add some components to let them have the latest in production technology,
components to run stone matrix asphalt, and more. They can leverage their
existing investment.”
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Some Gencor plants have
run up to 50% RAP while making 600 tons per hour of mix.
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For example, one Colorado customer experienced a
major increase in demand, and wanted to boost production capacity of its 35-
to 40-year-old batch plant. “Our analysis allowed him to keep his dryer, his
cold feed equipment, his baghouse, his silo, and his slat conveyor,” says
Loesch. “The recommended upgrade included a custom-designed, rotary recycle
mixer that allowed them to increase production from 150 to 320 tons per
hour.
“We took the batch tower out and converted it to a
continuous mixing process that could run 35% recycle, or more, compared to
10% recycle in the old batch plant,” says Loesch. “They had a
100-million-BTU burner, and a 65,000-cubic foot per minute baghouse, so the
heating and drying capacity was present. We basically inserted a rotary
mixer between the aggregate dryer and the bottom of the slat conveyor. In
the rotary mixer, the hot aggregate is mixed with liquid AC, fines from the
baghouse, and recycled asphalt. The rotary mixer is sized to create a
continuous flow process.
“The owner kept three-fourths of his existing
equipment, and he probably saved $1.5 million to $2 million, compared to
buying an all-new asphalt plant,” says Loesch. “What we did for them cost
about $650,000, and he got a 320-ton per hour counterflow drum mixing unit
with state-of-the-art technology — including added silo capacity. And it
was much easier to modify the air quality permit, as opposed to a new source
emissions application.”
Stansteel commonly converts parallel-flow drums into
counterflow drums. “We prefer to convert the parallel flow drum to a
counterflow drum and insert the rotary mixer between the dryer discharge and
the slat conveyor,” says Loesch. “Often these parallel flow drums are having
blue smoke emissions. The stone matrix and Superpave mixes require higher
temperatures of the mix, and the parallel flow plants have a hard time doing
that.”
So whether you need a new plant, a conversion, or
just want to update a component or two, a wide range of equipment is
available. |
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