Wear protection
Coal quality influences the type and magnitude of wear experienced within the grinding zone. Lower quality coals, such as lignite coals or brown coals, tend to be more aggressive and require high throughput.
Fig. 3. CE683 Test Site: High Chrome Hardsurfacing
Standard Xwin Superiority vs. HiCr Hardsurfacing Bowl segments
Grinding rolls
4 times better 1.3 to 1.5 times better
Xwin® concentrated design Superiority vs. HiCr Hardsurfacing
Grinding rolls 4 times better
2x improvement to the grinding roll that better matches the lifecycle of the segments.
Vertical Mill design also plays a factor; namely the orientation or position of the grinding elements relative to the throat vanes and the pulverised coal and primary air (PA) velocity vectors. Te table is generally positioned at or below the centreline of the PA throat vanes thus the primary wear mechanism on the table is from compression and the sliding friction of the coal across the table.
Te orientation of the tyres is generally above
the centreline of the throat, thus in addition to compression, the tyres are exposed to abrasion as they rotate in the mill. More abrasive coals have a greater influence on
the tyres, thus explaining why the table to tyre wear life ratio is 2:1 or even 3:1 in some applications. It is important to consider the design of the table and the tyre separately. Xwin tyres and tables allow such a consideration.
Fig. 6. Increased wear resistance.
Fig. 7. Improved uniform wear across grinding surface (Primary Purpose of Xwin Concentrated Design). Grinding Elements
Xwin, a composite material of high-chrome alloy and granularised ceramic, has a composite hardness of 2100 Vickers, well above the ceiling that exists with mono- metal high chrome and hard-surfaced high chrome alloys.
Top: Standard Xwin Roll - 13 months.
Bottom: Xwin Roll Concentrated Design - 34 months.
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Xwin grinding elements offer a longer lifetime and the ability to maintain a proper grinding profile for a longer period. Tis translates to Xwin grinding elements assisting in maintaining mill efficiency and maximising the optimum operating campaign between maintenance cycles. Depending upon the VM type, the overall lifetime improvement using Xwin versus HiCr or hardfaced grinding elements ranges from two to three times better or more.
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