Stewardship of our natural resources seems to be a leading topic of conversation for many industries in the United States. This is especially true for the aggregates mining and processing sector, where our industry faces stringent environmental regulations and tough construction specifications. Within our industry's stewardship discussion are the topics of water and fuel conservation, both of which play a considerable environmental and economic role.

Water conservation

For years, washing has been the industry standard for classifying manufactured and natural materials. The process, while very effective, often generates one saleable product and a considerable amount of sludge, a non-saleable, semi-solid residue resulting from a number of air or water treatment processes.

It is within these stewardship discussions that many pits and quarries have begun to see the value of "dry" processing of fines. Where a dry fines processing system has been implemented, aggregate producers have effectively reduced the amount of sludge they produce. Some applications have even eliminated the need for a traditional wash plant and sludge pond.

According to Fisher Industries Sales Manager Curt Kittelson, one such quarry – Carolina Sunrock's Butner Quarry in North Carolina – went from producing 50,000 tons of sludge per year to a mere 2,500 tons. Kittelson said the site did this by adding a Fisher Air Separator, a dry fines processing system, to its operation. "That is a 95 percent reduction in fines going into the sludge pond," Kittelson said.

In addition to aggregate mining applications, asphalt producers recognize the value of a dry fines processing system. They cite reduced fuel costs as a key benefit. When dry material enters an asphalt drum, less time and energy is needed to manufacture the asphalt. "Because of this cost savings, several asphalt producers have even been willing to pay more for aggregates processed using a dry system," Kittelson said.

Two saleable products

"Quarries that have utilized the Fisher Air Separator to dry process their fines have not only conserved water and fuel costs, but have been generated a second saleable product, as well," Kittelson added.

A Fisher Air Separator at a Hanson operation.

He said dry fines from limestone, granite, and sand and gravel applications fill a variety of niche markets and have been sold as aglime, mineral fillers for fertilizer, concrete filler and pipe bedding. "We've even had some quarries sell their dry fines for use in composite shingles," he added.

"Without a doubt, managing fines via dry processing is something we think more and more quarries will consider and asphalt producers will endorse, particularly where water is in short supply and while fuel prices continue to rise," Kittelson said. "We believe a key component to the success of dry processing fines will be the portability and adaptability of the dry fines processing system."

The 13-ft. diameter Fisher Air Separator effectively removes unwanted fines from aggregate products, bringing otherwise rejected material into specification. It requires minimal maintenance and can process up to 150 tph.

"Our air separator has been designed with the mobile contractor in mind," Kittelson said. Portable units set up in as little as two hours, are easily transported, and feature triple axel assembly with brakes and suspension and a heavy-duty beam chassis.

"The Air Separator is field proven in abrasive and nonabrasive applications," according to Kittelson, "and has achieved successful separation of unwanted fines in limestone, granite, trap rock, basalt, silica, sand and gravel operations," he added.

Its ability to dry process materials and remove excess fines promotes an efficient and clean operation. "It has met or exceeded the expectations of countless aggregate processing facilities throughout the United States, helping them achieve their goals of water conservation, reducing fuel costs and creating a second saleable product," Kittelson said.

Fisher Industries, http://www.fisherind.com/