Rugged equipment reliably serves in a Texas in-situ recovery mine.
by Mike Bjorkman
02/03/2015

In 2010, a rare-mineral exploration, development and production company opened an in-situ recovery (ISR) mine in South Texas. This was the first new ISR mine in the U.S. in five years. The facility extracts raw minerals from a sandstone formation and ships them to a nearby processing plant where they are refined.

Image 1. The rugged construction and careful design of this slurry pump make it well suited for heavy applications. (Images courtesy of BJM Corp.)
During the ISR mining at the site, on-site groundwater fortified with gaseous oxygen is pumped into injection wells that are drilled deep into the sandstone. The solution dissolves minerals from the host rock. Then it is recovered and brought back to the surface through production wells. At the surface, the solution—with the minerals in suspension—is pumped into ion-exchange columns, also called concentration tanks, where the mineral is stripped from the solution and loaded onto millions of resin beads. The resin-mineral material is then pumped into tanker trucks for shipment offsite. At every concentration tank, a sump collects a combination of process water and rainwater. Most of the process water comes from washing of the socks—large, fine-mesh cotton bags that are installed on transfer hoses to filter sand, mud and other grit from the solution before and after it is pumped into the injection wells (see Image 4, page 44). The water in the sumps—loaded with debris from the socks and surrounding soil—must be pumped to a wastewater system in which any solids are filtered out before the water is transported to a deep disposal well for reclamation. Until 2011, the facility used two small submersible pumps that were not up to the job. Insufficiently powered, the pumps had rubber wear plates and other components that failed under heavy use and the barrage of abrasive solids suspended in the mining solution.

The Solution

A pump distributor worked closely with the facility to arrive at a solution. After reviewing the application’s challenges in detail, a heavy-duty submersible slurry pump was selected. Engineered for maximum service life, the pump type offers robust construction and superior solids-handling capabilities. The 5-horsepower pumps have built-in agitators that fluidize solids into a slurry for complete pumping. They also have hardened components—including high-chrome iron agitators, wear plates and an impeller—to resist abrasive materials. Key features include:
Image 2. The sandstone is transported to a local processing plant where extraction of the rare minerals can begin.
  • Optimum wear resistance—All wetted parts are constructed of abrasive resistant 28 percent chrome iron (600 Brinell, 71 Rockwell C) for maximum wear life. In addition, a replaceable hardened wear plate is located on the suction side, where erosion would cause a loss of pump performance.
  • Maximum solids handling capability—An integral agitator fluidizes settled solids into a slurry making them easier to pump with less chance of clogging. The semi-open impeller handles abrasive solid concentrations as high as 70 percent by weight.
Image 3. Sandstone containing the rare minerals must first be mined and crushed into smaller pieces.
Design features for maximum service life of these pumps include the following:
  • Class H motor insulation and built-in, full load amperage and temperature overload protection
  • Double silicon carbide mechanical seals in a separate, oil-filled seal chamber
  • Heavy-duty lip seal that provides additional protection for the mechanical seals
  • Stainless steel shaft and shaft sleeve that provide maximum wear and corrosion protection
  • Pump volutes cast from hardened ductile iron (300 Brinell hardness), which is twice as abrasive resistant as standard ductile iron with walls that are extra thick at the point where pumped slurry enters the discharge
Image 4. Socks made of large, fine-mesh cotton bags must be washed after filtering sand, mud and other grit out of the solution. After washing, the solid-laden water is pumped from the sump.
The semi-open impeller constructed of 28 percent chrome works with the agitator to easily pass aggregate through the pump and out the discharge. The agitator keeps solids suspended in the fluid being pumped so that the entry remains clear and pumping action continues without fail. The top discharge, slim-line design of this agitator pump ensures optimum wear resistance along the discharge path. Further, the pumped fluid cools the pump’s internal motor functions as it passes. The vertical design allows for the sump to be pumped down to within inches of the bottom (see Image 5).
Image 5. The slurry pump can pump down to inches from the bottom of the sump.
The pumps have run reliably since their installation, resisting the grit and keeping up with the demand even during heavy rainstorms. By early 2012, the company was using four of these pumps at the facility and specified this model as the standard pump for the sumps in its operations.

Mikael Bjorkman is vice president of BJM Corp. and has more than 30 years of experience in the pump industry. He serves as marketing and information technology director for BJM Pumps LLC and All Test Pro LLC, both subsidiaries of BJM Corp. BJM Pumps supplies electrical submersible pumps to industrial and municipal markets throughout the U.S., Canada and South America. Bjorkman may be reached at 860-399-5937. Visit bjmpumps.com for more information.

Issue

February 2015