PULVERIZED COAL INJECTION AT BF N5 DURING CAMPAIGN EXTENSION PERIOD ARCELORMITTAL SOUTH AFRICA, NEWCASTLE WORKS

摘要

After a planned maintenance stop in April 2005, Blast furnace N5 (ArcelorMittal South Africa, Newcastle Works) started up a pulverized coal plant for the first time, joining the cost reduction revolution that swept the global steel industry. Newcastle experienced a perfect start-up and phenomenal ramp-up to 160kg/thm in five months. This was achieved with good replacement ratios, despite a burden that consists of 40% lump ore. The success was short lived however. The high rate of unprepared burden, inadequate raw material quality and an aging hearth started to take its toll. With a hearth replacement in sight, the coke rate was increased to reduce hearth wear and still maintain decent hot metal production, leading to a disappointing low PCI rate of 100kg/thm. With the lower than expected PCI rate, other means of cost savings were needed. Taking a financial decision, the local, lower quality coal in the coke blend was increased finding a balance between cost of quality and value in use. After the planned hearth replacement in May /June 2008 the injection coal rate of 160kg/thm will be targeted again. A higher prepared burden rate and better coke quality should make this sustainable. Due to the low-cost local supply of high volatile, medium ash coals, few changes in PCI blend have been made over the past few years. Only during the commissioning of a new coalmine near Newcastle (July 2007) did it become feasible to partially replace the coal in use. Plant scale tests proved to be successful creating a further cost saving with shorter coal transport distances.