Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/513927
Solving Fines Problems OPERAT F ilter presses have been used in aggregate opera- tions in Europe for some time, but they were most commonly found in waste wa- ter treatment plants in the United States…until recently. Now that the technology has been introduced to the aggregates industry in North America, things have been changing. "Over the past three or four years, fi lter presses have really taken off in the United States," says Cory Jenson, general manager – Environmen- tal Division, McLanahan Corp. "We think the trend here in the U.S. is moving the same way it happened in Europe," he says, "and for us, it's growing very fast. There are more and more people considering fi lter presses and putting them in." Though there are several factors that have helped fi lter presses gain interest in the aggregates industry, many producers see them as a way to reduce the number of settling ponds they have at their operation or eliminate them altogether. This might be due to a lack of space, diffi culty in acquiring a settling pond permit, or the extra expense and time spent cleaning out a settling pond. "We don't have an abundance of room for multiple settling ponds, and we don't have an abundance of room to clean out the settling ponds and lay the clay material out to dry," says Jason Voss, quarry operations man- ager at Stevens Creek Quarry, which had a fi lter press installed on site two and a half years ago. Though the name suggests that water is pressed out of the fi nes slur- ry, that's not what actually happens. A fi lter press consists of a series of recessed plates that are hollowed out on each side. When the plates are put together, they form a chamber between the plates. Each chamber is lined with fi lter media so that, when the plates are put together and the fi nes material is fed into the chamber, the pressure from the slurry does the dewatering. Once the chambers are full of solids, they open, and the dry material falls out in cakes. "The dry cakes that come out of the fi lter press look like a big thick mud fl ap, like what you'd fi nd on a truck," says Bryan Pfohl, current pres- ident and chairman of Carolina Sun- rock LLC and Sunrock Group Holdings Corp. "What comes out of the press is a clean, fi nished product, so to speak, and has the possibility to be used for other purposes." Jenson agrees. "Sometimes, depending on the material, the location, and the market, the cakes can become a saleable product for an operation," he says. "Everybody's tailings are different, so it depends on what it consists of as to what it can potentially be sold for." AGGREGATES MANAGER Over the past three or four years, the fi lter press has gained interest among aggregate producers who see it as a way to reduce the number of settling ponds they have at their operations or to eliminate them altogether. The desire might arise from a lack of space for a pond, diffi culty in acquiring a settling pond per- mit, or the expense and time involved in cleaning out the pond, not to mention plant downtime during the clean out process. The fi lter press system is a closed-loop system that recycles the water. As the solids are removed from the slurry, the water is sent back to water tanks for storage and reused in the processing plant, as need- ed. Settling ponds lose a lot of water to evaporation because of their openness, as well as when they are cleaned out. Only a small amount of water is lost through the fi lter press' closed-loop system, which is what is left on the fi nished products. 1 Out with the old settling pond 4 Water is recirculated