Gary Catlett, Astec industrial products director who did some of the design work on the Phoenix Coal burner and served as team director on the Grand Junction installation, says the different operating procedure Bryan was alluding to has been the only adjustment required in switching from oil to coal.
"We recommended that they (United) ramp down on the coal feed and ramp up on the oil feed at the end of the day, as well as ramp down on the dryer feed (aggregate coming into the drum) in order to clean out any residual coal in the system," Catlett says.
With United being the first customer to install the modified Phoenix burner, which is configured to burn coal, waste oil or #2 oil, the fuel source options and the transition from one fuel source to another is easier to control. Astec is adding the natural gas-burning option to it 100 MMBTU/hr Phoenix Coal burner.
"The (coal) burner requires a base flame source (fired by waste oil or natural gas) to heat up the dryer and ignite the (pulverized) coal as it is fed into the burner," Catlett says.
As for the efficiency and low emissions of the coal-fired burner, Catlett says the burner only uses 16 pounds of coal to produce one ton of HMA. The ash produced by burning coal is minimal — approximately 1.25 pounds per one ton of HMA — and does not affect the quality of the mix.
Catlett is optimistic about the potential for the coal-fired burner technology.
"Astec built a coal-fired burner in the '80s and was ready to launch the product, but by the time the product was available oil prices dropped and the market was no longer interested in a coal-fired burner," he notes. "The current rise of oil prices has renewed that interest and for (HMA) producers who have access to coal, the technology may provide an economical alternative to their current fuel sources.
Bryan, in particular, will evaluate the advantages of firing his Grand Junction plant with coal, and then decide if United's other five production facilities could benefit as well. Time will tell, but Bryan adds, "If fuel prices, including used oil, continue to rise, and we anticipate they will, we expect to save even more by burning coal."