May 1, 2018 - Furnace refractories are an essential consideration in thermal process equipment operations for optimizing efficiency, productivity, and performance as well as cutting operating costs.
To optimize furnace refractory lining, operational factors must be considered, such as furnace type, alloy composition, operating temperatures and melt rate, type of fuel used and charging and drossing practices. Furnace design is also critical, with factors including equipment type, static or tilting, capacity, desired casting temperature and position of freeze plane.
The service life of a furnace refractory lining is typically between four to 15 years, depending on the type of furnace and other variables including alloy type, melt rate, combustion system, scrap charging size and furnace practice. Contributing factors to refractory failure include corundum growth, mechanical damage, metal penetration, thermal shock, erosion and chemical attack.
Since 1974, the Pyrotek TAB Refractory Services team, based in Warrington, UK, has developed lining compositions and materials that can withstand harsh environments. The systems are pre-fired to 932°F (550°C), which eliminates water to allow for faster commissioning. A strong ceramic bond is developed and firing shrinkage is allowed that results in less stress relief cracking. Installation is not affected by ambient temperatures. Big-block systems can also be combined with castable or brick furnace linings, and to maximize service life, the company provides “zoned” refractory linings consisting of both cast-in-place and precast monolithic blocks. Employing the most suitable refractory materials for each different area of the furnace extends the lining’s durability and reduces furnace maintenance and downtime.
Figure 1. Big-block linings improve furnace performance and productivity
Examples of the work illustrate the key issues and routes to effective refractory relines. Here are recent projects where the company has provided refractory technology input:
The company’s global refractory team and engineering centers work with aluminum operations to select the optimal refractory design and materials for their particular applications. In some cases, upgrading from brick to a non-wetting, corundum-resistant lining in smelting furnaces can increase ingot and billet casting capability. After a 5-year period, some customers reported that furnace downtime due to refractory repairs was reduced by up to 65 percent. Total furnace availability increased by up to 12.6 percent, and output increased by up to 26 percent. Refractory costs per pound of aluminum produced were reduced by up to 22.8 percent.
Furnace relines and maintenance for major aluminum companies around the world have been carried out with over 1,100 completed projects in more than 30 countries.
Sponsored by: ACRI (The Association of China Refractories Industry), Tangshan YinNaiLian E-Business Co., Ltd.
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