As the mining industry uses large volumes of water under greater environmental scrutiny, operators are finding innovative ways to more efficiently strain, treat, and reuse water that accumulates in pits, sumps, and wash bays.
In Canada and Upper Midwest states like Wisconsin, Michigan and North/South Dakota, mining heavy equipment washdowns are a major source of water use. Wash processes are used to clean mud, clay, and other corrosives off mining machinery, trucks, and other heavy-duty equipment. The wastewater is typically collected in a service bay or sump and must be sufficiently strained and treated before reuse.
When rainwater washes over equipment and open pit mine sites, it can also generate water mixed with dirt and sediment that is typically collected in a large sump or pit nearby. In underground mines, groundwater infiltration and condensation can cause a similar effect to that of rain.
No matter how the water is generated, any dirt and debris must be removed before it can be used, further treated, recycled, or discarded. Due to the volume of water used, the mining industry is increasingly seeking new ways to reuse water through more efficient filtration, treatment and recycling efforts.
Toward this end, the mining industry in Canada and Upper Midwest states is finding that automated scraper strainers are one of the simplest, most cost-effective methods to remove both micron-sized particles and oversized dirt and debris. This is helping to streamline water straining for immediate re-use. It also provides a critical first step in multi-step water treatment systems that can reduce clogging, fouling, and maintenance while increasing production.
One example is the automatic scraper strainer from Acme Engineering, a North American manufacturer of industrial self-cleaning strainers. The motorized unit is designed to continually remove both very large and very small (100 micron) suspended solids from water that can accumulate in a mine, pit, or sump. Cleaning is accomplished by a spring-loaded blade and brush system, managed by fully automatic controls.
Four scraper brushes rotate at 8 RPM, resulting in a cleaning rate of 32 strokes per minute. The scraper brushes get into wedge-wire slots and dislodge resistant particulates and solids. This approach enables the scraper strainers to resist clogging and fouling when faced with large and high solids concentration. It ensures a complete cleaning.
Blowdown occurs only at the end of the intermittent scraping cycle when a valve is opened for a few seconds to remove solids from the collector area. Liquid loss is well below 1% of total flow.
The technology is even being used to filter and reuse water from a virtually unused resource – accumulated water at the bottom of mines, which until now has mostly been an impediment to efficient production.
“Automated scraper strainers are being used to remove rocks and suspended solids from the water that usually collects at the bottom of mines. The filtered water is then pumped back to the surface for continual reuse,” says Robert Presser, Vice President of Acme Engineering, an ISO 9001:2015 certified manufacturer of environmental controls and systems with integrated mechanical, electrical and electronic capabilities.
According to Presser, to increase reliability in rugged mining conditions, the industry is using the automatic scraper strainer in an innovative way with an eductor, a type of pump that does not require any moving parts.
“Mine operators are using an eductor at the bottom of the strainer to pressurize the blow down line to send the evacuated solids [from the strainer] relatively far away. Since the eductor has no moving parts, operators don’t have to worry about small bits of rock and particles damaging an impeller like they would on a typical pump,” explains Presser. He adds that operators must use a ¾-inch low flow water line at about 75 PSI to inject motive water into the eductor to move the solids down the blowdown line.
As mining operators in Canada and the Upper Midwest seek to comply with environmental standards and do more with less, those that take advantage of advanced strainers to most efficiently reuse their existing water will cost effectively achieve both these aims while improving their process.
For more info, visit Acme Engineering Prod. Inc. at acmeprod.com or in the U.S.; phone Robert Presser, Vice President at: 518-236-5659; fax: 518-236-6941; mail Acme at Trimex Building, Route 11, POB 460 PMB 10, Mooers, New York 12958. In Canada phone: 514-342-5656; fax: 514-342-3131; mail them at 5706 Royalmount Ave., Montreal, Quebec, H4P 1K5.