This technology can tackle basic dewatering applications and precise electrowinning processes.
by Greg Duncan
February 11, 2015

The early stages of mine development—including identifying the lodes and extracting the earth that surrounds them—are rugged operations that require equipment that can withstand long, hard days of work and function reliably in extreme weather conditions. This equipment includes both the heavy machinery that works the mine and ancillary equipment that optimizes the mining process. Industrial pumps are a key component in the mining production chain and are used to perform critical duties during mine construction, from dewatering applications to waste-oil transfer. These important duties require pumps that are rugged enough to handle slurries consisting mostly of mud and rocks.

Rough and Delicate

While the overriding image of mining is one centered on brute force, the industry has a delicate side as well. Sometimes mine operators hit a rich lode that is easily extractable, but the process is not usually that simple. Precise, exacting processes are required to optimize extraction. Electrowinning helps meet these requirements.

Electrowinning is the extraction of metals and minerals from ores that have been put in solution through a process known as leaching. While the word “electrowinning” has a space-age sound, it is actually the world’s oldest industrial electrolytic process. It was discovered by English chemist Humphry Davy in 1807 and patented commercially in 1865 by James Elkington in Wales. The first commercial electrowinning plant in the U.S. was established in 1883 in Newark, New Jersey.

In the electrowinning process, a current is passed from an inert anode through the liquid solution so that the metal or mineral is deposited onto the cathode via an electroplating process. Electrowinning is commonly used for the extraction of copper, gold, silver, platinum, zinc, aluminum, cobalt, manganese and many minerals.

The electrowinning process requires the introduction of various types of harsh, corrosive or hazardous chemicals into the mining operation. Cyanide, for example, is used when electrowinning for gold. These chemicals are introduced into the ore during the leaching process, which helps separate the minerals or metals from the ore before a second chemical process pulls the commodity out during electrowinning.

Electrowinning enables the recovery of minute, but valuable, metal or mineral particles. As an example, as much as 20 tons of soil are required to extract one pound of platinum.

The Common Denominator

The link between the rough and tumble of mine excavation and the precise operation of electrowinning is the industrial pumps that are required to optimize both processes. One type of pump—air operated double diaphragm (AODD)—has been proven in the field to be flexible enough to offer ruggedness and reliability for operations such as mine dewatering and for handling corrosive chemicals during electrowinning operations. Invented in 1955 by Jim Wilden, AODD pump technology has been proven to excel when used in the entire array of mining applications.

AODD pumps can perform effectively at both ends of the mining spectrum because the method of operation allows them to easily handle variable flow rates and pressures. They also are dry-run capable and nimble enough to transfer liquids that are shear-sensitive or high-viscosity, as well as slurries laden with rocks, pebbles and other particulates.

The simple design of the AODD pump features few moving parts, which simplifies maintenance. The pump’s sealless design results in fewer leaks, which is a critical consideration when handling hard-to-seal or hazardous liquids. AODD pumps are available in both metal and plastic housing constructions. A wide array of elastomers can be used in the diaphragms, which eliminates many chemical compatibility concerns.

The wide variety of AODD pump configurations provides operational flexibility that can also result in optimized efficiency at many levels. The ability to feature AODD pumps in a wide range of applications, from basic general-use to delicate electrowinning processes, allows the operator to more cost-effectively outfit a mine. AODD pumps can also be less costly to operate, especially those models that are outfitted with next-generation mechanically actuated air distribution systems (ADS). And, at their most basic, AODD pumps excel in the typical rugged and harsh operating atmospheres found in mines, which reduces breakdown incidents along with corresponding downtime and repair costs.

Because AODD pumps do not require electricity to operate, they also help improve mine safety, especially when used in potentially explosive environments. Over the years, mine safety has taken great leaps forward, which was proven in 2013 when the Mine Safety and Health Administration (MSHA) reported that the fatality rate in U.S. mines was its lowest ever in 2012, based on the number of man-hours that were worked during the year. The MSHA also reported that actual work-related fatalities in mines totaled 36 for the year, which was just one more than the lowest fatality total of 35 in 2009. This improvement in safety is a positive development not only for mine personnel but also for surrounding communities and the environment.

One pump company offers metal and plastic AODD pumps, which can be used for both dewatering operations and chemical transfer in electrowinning processes. Clamped metal AODD pumps incorporate many design enhancements that make them a good choice for various mine operations. Chief among these are a shock-absorbing polyurethane screen base that absorbs the impact from constant assault by solid particles, resulting in maximized durability. These pumps also feature an integrated suction strainer, with the option of plumbed suction, if needed.