Long-Lasting Lining
Published by Alfie Lloyd-Perks,
Editorial Assistant
World Cement,
The design and shape of the vertical bull nose in preheater cyclones is critical for directing the gas flow and optimising material separation efficiency within the cyclone. However, this area can present significant challenges for refractory linings due to its inherent vulnerability.
The bull nose area is subjected to intense abrasion from turbulent, high-velocity air currents and passing raw meal particles, particularly in lower-stage cyclones where peak temperatures often exceed 900 – 1000°C. The sharp angles of the bull nose structure, combined with mechanical loads from the airflow, further increase the risk of cracking and spalling of the lining, necessitating frequent repairs or relining. These harsh conditions are exacerbated by alkali and other chemical attacks, which are intensified by the increased use of alternative fuels (AFs).
Relining the bull nose area poses additional complications due to its elevated position within the cyclone, requiring extensive scaffolding for access. Castable solutions demand precise, labour-intensive moulding to accommodate the sharp angles, while gunning materials, though faster to apply, may have limited durability due to higher open porosity. Although precast solutions involve a higher initial cost, they can be a viable alternative to achieve longer lifetimes in these demanding and potentially fragile vertical bull nose areas of the lower-stage cyclones.
Only 12 months of service life
A 4000 tpd cement plant in Australia, operating on a fuel mix of 70% coal and 30% AFs, faced persistent challenges with the refractory lining in the vertical bull nose zones of its lower-stage cyclones. The used gunning material failed to withstand the harsh conditions, necessitating frequent repairs.
The vertical bull nose lining, subjected to severe abrasion and temperatures up to 950°C, cracked at the leading edge of the bull nose, resulting in a short service life of 12 months and relining needed every year. This not only consumed significant man-hours and material costs but also required complex scaffolding, further adding both time and costs to the maintenance plan. Seeking a more durable refractory solution, the plant aimed to extend the lining's lifespan, thereby minimising downtime and overall maintenance costs.
Tailored curved precast solution
As an alternative to in-situ cast and gunning solutions, HASLE Refractories proposed a precast solution based on its Modular Lining concept.
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Read the article online at: https://www.worldcement.com/special-reports/20012025/long-lasting-lining/
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