Mining processes have always been brutal on control equipment, with abrasive and corrosive slurries and chemicals present throughout the facility.
Our article in the September 2024 issue of North American Mining, titled “How advanced control valves, regulators and relief valves improve mining operations,” is the first installment in a two-part series on the challenges involved in six common processing steps. Part one covers the first four steps: crushing/grinding/ball mills, digestion/autoclaves, flotation/thickening, and leaching/solvent extraction.
To isolate and extract the desired mineral, the raw ore must first be crushed and ground into a fine powder.
Raw ore is typically transferred via conveyors through a series of crushing/grinding steps to break up the ore into fine particles. Later steps in this process often use enormous SAG and/or ball mills to reduce the ore to a very fine, granular consistency.
In some mills, water is added to keep the fine particles in suspension and to help keep downstream screens clean. This water tends to carry suspended solids that can create scale, and the feed stream may have significant pressure drops. Large-bore, V-ball valves, such as Emerson’s Fisher Vee-Ball V150 and V300 Rotary Control Valves, are a good option for this service. If cavitation is an issue, anti-cavitation accessories, like Emerson’s Fisher Cavitrol Hex Trim, can be added.
Grinding/milling equipment depends on the oil lubrication system, which must be designed with redundant pumps and reliable pressure regulators. Backpressure regulators (like the Fisher MR98, MR108, LR128, and 63EG) and pressure-reducing regulators (like the MR95, MR105, LR125, and 1098) may be needed, depending on pressure and flow requirements.
The lube oil system is critical for crushing/grinding/milling operations and must utilize high-tier regulators and controls to ensure very reliable performance. (Emerson Fisher models LR128, MR95/98, MR108 and LR125 shown left to right.)
After pulverization, some minerals, such as alumina, require further processing at high temperatures and pressures to make extraction possible.
Alumina digester and flash tank pressure relief are particularly challenging applications. Materials tend to scale and stick to the internals of the vessel, either plugging lines or rendering them inoperable.
An Anderson Greenwood 500 series pilot-operated relief valve is a capable choice, particularly when a high-pressure steam purge is installed below the valve to prevent minerals from scaling and plugging the valve inlet.
In flotation, pulverized ore is mixed with chemicals and aerated, which separates the ore into lighter elements that float and heavier elements that sink. This process may require oxygen and/or brine, both of which require carefully-specified equipment.
Fisher GX and Fisher easy-e EZ control valves constructed with Monel alloy are suitable for regulating oxygen feeds, while brine feeds may require a Baumann valve made with Duplex, Ferralium, Super Duplex, or Avesta to prevent corrosion.
Following flotation, each exit stream typically passes through a thickener to recover water for reuse. In most flotation and thickening applications, multiple low-pressure valves divert feeds, underflow, and overflow slurry streams. Precise requirements vary by process, but zero-leakage, high-performance knife gate valves, such as the Clarkson KGA and KGD, are often needed.
Knife gate valves are common around the floatation and thickener areas. The best valves are tight shutoff, full ported and reversible valves, such as the Clarkson KGA Heavy Slurry Knife Gate Valve (left) and the higher-pressure rated Clarkson KGD Wafer Slurry Knife Gate Valve (right). Both offer zero leakage, replaceable sleeves and handle a range of process pressures.
Leaching is a common unit operation in many mine processing areas in which a solvent is poured over pulverized ore, dissolving the target mineral to remove it from the rest of the ore. Because the solvent is typically caustic or acidic, the best valves for these applications will have protective linings that prevent direct contact with process media—Neotecha NeoSeal butterfly valves, for instance.
While the best choice of control equipment will vary by specific application, many mines face similar challenges that can be overcome with thorough application understanding and knowledge of equipment options.
With extensive experience and successful installations in a broad range of mining applications worldwide, Emerson has the equipment and expertise to help mine operators reach their goals.
Visit the Industrial Process Valves & Instruments section on Emerson.com to know how you can achieve modernized processes, safety improvements, and Net Zero goals with process valves that control, protect and isolate.
The post Advanced Control Valves, Regulators, and Relief Valves Address Common Challenges in Mining Operations appeared first on the Emerson Automation Experts blog.