Wear Protection
average ash and silica content of 42 per cent and 62 per cent respectively. Tis can be considered typical of many coal-fired power stations in India. Te historical lifetime of NiHard IV rolls at this site was approximately 1,000 running hours (RHs) with a maximum wear of 50mm.
wear resistance offered by Xwin and Neox not only provides Indian coal-fired power stations longer running life of the grinding elements and increased maintenance cycles but the prolonged grinding profile consistency maintains the overall pulveriser efficiency for longer and its impact on all the downstream influences such as combustion performance and backend emissions.
Fig. 2. Xwin Grinding Roll @ 5,200 RHs.
In recent years large advances have been made in wear resistant products, namely ceramic composite materials also known as metal matrix composites, in which ceramic of specific properties is combined with a high chromium alloy. Te result is a composite material that provides the extreme wear resistance of ceramic but maintains the mechanical properties of the high chromium base metal. One such product is Xwin by Magotteaux. Xwin
grinding rolls were installed on the mills at the power station in West Bengal beginning in 2010 with a guaranteed lifetime of 5,000 RHs. Since that date the Xwin rolls have achieved an average lifetime of 5,268 RH’s with a maximum wear of 51 mm; a 4x improvement over NH4. Tese results correlate closely with results obtained at other Xwin locations in India. In 2011 an advanced ceramic technology called Neox, also by Magotteaux, was installed at the site in West Bengal. Performance results of the Neox rolls have projected a lifetime in excess of 10,500 RHs which is 9x better than NH4 and 2x better than Xwin. Like Xwin the performance results of Neox rolls at other locations in India are correlating closely. Te Xwin and the Neox ceramic metal matrix composite technologies have advanced the wear resistance of pulveriser grinding elements far beyond the wear resistance offered by NH4, high chromium alloys or high chrome hard-surfacing. Te increased
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As a result of the introduction of ceramic based metal matrix composite technology in the Indian pulverised coal-fired power generation market all vertical spindle roller mills in this market, with the exception of E mills, have converted the grinding elements to these products such as Xwin and Neox. Additionally other coal-fired power markets such as China, Europe, South Africa, South-East Asia and the USA are recognising the advantages that this technology offers and are switching to Xwin or Neox. ●
For more information ✔ at
www.engineerlive.com/ipe Fig. 4. Typical grinding roll lifetime.
Fig. 3. Neox Grinding Roll @ 8,040 RHs Projected Life: >10,500 RHs.
Ken Birchett, PE is Product Manager with Magotteaux Inc, USA
www.magotteaux.com
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