CEE Jul-Sep-2012

- shell temperatures and long a campaign life based on the premise that lining protection is achieved by a solidified layer in the bosh, belly and lower stack. However, it is observed that copper stave cooler designs have a limited 'anchoring' functionality and this could result in exposure of the copper stave coolers to the abrasive and erosive descend burden and ascend of gases. Copper has a limited resistance against abrasion and erosion and wear of the copper ribs will catalyze further loss of anchoring functionally. The 'Hoogovens' bosh design comprises a dense pattern of machined copper plate coolers and (semi) graphite and a 20+ year campaign has been achieved in 2006. The 'Hoogovens' bosh design is the optimum solution to secure a stable bosh profile and to allow high productivity levels. This first bosh design was installed at Hoogovens IJmuiden in the early '70's and performed very well. Figure 5 shows the bosh of Hoogovens IJmuiden Blast Furnace No. 4 after 8 years of operations. The bosh of IJmuiden Blast Furnace No.6 has been commissioned in 1986 and is operating at very high productivity levels for many years. One of the principal advantages of a high conductive plate cooler design relates to the 'solidified layer adhesion' capability and this is also clearly observed in Figure 2. Figure 2: Protection by Solidified Layer Advanced bosh, belly and stack designs To design philosophies have survived into the 21 51 century and share a similar engineering philosophy based on the 'thermal solution'. Reference is made to Figure 3 illustrating advanced cooper plate cooler design. Both designs include cast iron stave coolers in the upper stack. The 'Hoogovens' copper plate cooler and copper stave design. Both designs include cast iron stave coolers in the upper stack. The 'Hoogovens' copper plate cooler design includes high-conductive graphite refractory in the bosh, belly, lower and middle stack. This graphite provides thermal protection to the embedded SiC refractory courses. The SiC provides protection ' ) I J L.·-----> Figure 3: Advanced bosh, belly and stack designs against abrasion and erosion and this design provides a synthesis of thermal and mechanical components. Copper stave coolers also have a high cooling– efficiency but cannot survive all process conditions. Exposing conventional copper stave coolers to fluctuating high-temperature process condition can result in leaking cooling channels due to expansion issues (cracking) and abrasion/erosion. This has been observed at various plants on different continents and prohibits low-cost hot metal production. Additional refractory protection is required such as graphite and SiC inserts vis-a-vis the plate cooler design. This off-sets, however, typical copper stave cooler advantages proclaimed in industry such as reduced CAPEX and increased working volume. Furthermore, stave cooler designs require long shut– downs if repairs are required. In addition, copper plate coolers are always required in the (lower) bosh to permit high coal injection rates and to protect tuyere-coolers. This area is exposed to a variety of loadings (Figure 4): • Heat (Raceway Gases and Impinging Metal and Slag) • Erosion and Abrasion (Solids, Gases and Liquids) • Oxidation (Water Leakages, FeO) • Alkali's, Zinc, Lead 13 .....