Water is a important part for practically all mining operations. Sadly, most mining operations are positioned in areas the place water is scarce, so this useful resource should be fastidiously conserved and recycled as a lot as doable.
On this article, KeeChong Lee, Emerson Business Gross sales Supervisor, focuses on two of the bigger water customers in a mine, grinding/classification and flotation. Lee has 19 years of numerous expertise at Emerson, specialising in each technical and advertising and marketing roles for Fisher™ FIELDVUE™ merchandise. He at the moment focuses on driving innovation.
KeeChong Lee, Emerson Business Gross sales Supervisor
Each processes require tight management of water circulate to optimise efficiency, however that water is commonly closely recycled and accommodates abrasive sediments, and even small rocks. Correct collection of the management valves on this utility is important to realize most effectivity, throughput, and reliability.
As soon as the ore has been faraway from the mine, it undergoes two main course of steps in preparation for mineral extraction. Step one is crushing/classification, the place the ore is first crushed, after which floor into even finer-sized particles in preparation for the extraction steps downstream. Water is used to move the particles (within the type of a slurry), and hydrocyclones are used to separate and classify the particles, with bigger particles being returned to the mill for additional grinding.
Lee: “Water addition to the mill feed and sumps should be fastidiously regulated utilizing management valves to keep up a constant circulation of slurry density and permit correct hydrocyclone operation. Tight management of those water flows is troublesome as a result of abrasive particles current within the recycled water.”
As soon as the ore has been correctly floor and categorised to the right vary of particle dimension, the slurry is fed to the flotation part. Flotation tanks use entrained air to bubble up by way of the ore slurry and separate the extractable minerals from the tailings. The configuration of the tanks will fluctuate by ore sort, with the product both floating to the highest or sinking to the underside.
As soon as separated, each the tailings and focus are thickened to take away water, with the latter recycled again to the method. The flotation course of requires water addition on the conditioning tank and on the pump field, with flows regulated by the management valves. Lee feedback: “Flotation separation effectivity is strongly depending on a really tightly managed mixture of slurry density and chemical focus. Any variation considerably impacts the method and may end up in product loss by way of the tailings stream.”
He continues: “As indicated above, optimised course of management of the grinding and flotation areas is essentially depending on tight water circulate management. Sadly, this activity is just not so simple attributable to complicating components, together with water high quality, circulate variation, and strain drops. Course of water in most mining operations is closely recycled. In consequence, it normally accommodates important portions of sediment, and even small rocks and gravel, all of which may be punishing to valve internals. Pipe sizes are usually fairly giant (see article title picture) and the flows variable, making it troublesome to dimension the valves for a selected utility. Sizing is additional sophisticated when giant strain drops are concerned as a result of these are inclined to create valve cavitation at low flows, a situation which might additional erode the valve internals, and trigger harm to downstream piping.”
Lee says giant pipe sizes are inclined to favour butterfly valves attributable to their inherent price benefit at increased pipe diameters. Nevertheless, this worth distinction may be shortly erased attributable to lower than optimum efficiency past its management vary. “Butterfly model valves have restricted turndown and may solely management throughout a small vary of flows (25-50%), so they’re ailing fitted to purposes like grinding and flotation processes that should precisely throttle water at low, medium, and excessive flows. Butterfly model valves will sometimes trigger cavitation when dealing with giant strain drops, creating valve and pipe harm. In consequence, the valves and downstream piping might require routine alternative or restore in all these excessive strain drop purposes.”
Emerson gives a greater physique model that it says is way more fitted to this utility. The eccentric plug v-ball design (see beneath) is a ball valve model with a modified ball that gives tight circulate management over a much wider vary, together with very tight shut off, in all these scaling/sediment purposes.
Eccentric v-ball valves present correct circulate management over a much wider vary of flows than butterfly valves
The valve internals may be long-established from hardened trim designs, and the wiping motion of the eccentric ball permits this valve model to persistently obtain very tight shutoff, even with entrained sediment and scaling within the course of media. The V-shaped ball offers tremendously improved turndown and management at low flows, permitting this valve model to throttle throughout a much wider management vary than a butterfly valve.
Lee: “One of many massive benefits of the eccentric v-ball design is the power to put in anti-cavitation trim. Such trim allows the valve to deal with very excessive strain drops with minimal cavitation. The massive ports move greater particles and sediments, and the trim may be constructed from a excessive hardness R31233 alloy for lengthy lasting service, even in very erosive circumstances.”
V-ball valves with Fisher™ Cavitrol™ Hex Trim from Emerson present giant bore, anti-cavitation trim. These trims cut back cavitation throughout the total vary of flows and may be long-established from very excessive hardness alloys for lengthy service life
Anti-cavitation trim protects each the valve and downstream piping, permitting the valve to raised deal with and management circulate in excessive strain drop purposes, the place a butterfly valve would are inclined to carry out badly.
A mine website was combating poor management and brief service lifetime of their grinding and flotation water addition valves. Excessive strain drops have been creating cavitation circumstances that decreased the typical valve service life to about three months.
After consulting with an Emerson Accredited Service Supplier, the location determined to interchange their 42 current butterfly valves with Fisher™ CV500 Eccentric Plug Valves, and so they observed instant enhancements in each course of management and repair life. The broad circulate management vary of the v-ball valves offered far superior water circulate management, permitting the system to tightly management slurry densities. This instantly translated to raised product restoration and better course of effectivity.
Along with the numerous course of enhancements, the service lifetime of the brand new valves was lengthened significantly. Whereas the butterfly valves required alternative each three months, the brand new valves have been pulled after 12 months in service and confirmed minimal indicators of injury.
Regardless of the upper preliminary funding within the new valves, the challenge paid for itself within the first 12 months of service. The brand new valves offered:
- Diminished operational price attributable to higher management, which decreased recycle flows and pumping power consumption.
- Diminished upkeep prices with valve service life prolonged from three months to over a 12 months, and counting.
- Improved course of management, leading to density management enhancements, which elevated product restoration and yields, whereas lowering tailing processing prices.
- Diminished water utilization attributable to higher upstream management, which prevented flooding of downstream filters, whereas enhancing water restoration.
Lee concludes: “In case your mining operation is combating poor slurry density management and brief service life attributable to points with water addition valves, it could be time to judge a valve alternative challenge. Whereas eccentric v-ball valves have a better buy price than butterfly valves, that worth distinction is greater than justified by the numerous positive factors in course of enhancements and repair life.”
