Failure Mechanism and Material Requirements for Coal Lance in Blast Furnace Original Research Article

Pulverized coal injection (PCI) is a key technology in modern ironmaking by blast furnace (BF) and the life of injection lance has a great influence on PCI operation and on normal running of blast furnace. It is found that the main reasons for the failure of the lances are their outer surface oxidation and the inner surface erosion through monitoring some lances used in BF. The outer surface oxidation of the lances made of lCr18Ni9Ti is inevitable under high hot blast temperature condition through thermodynamics analysis. A mathematical model for calculating the temperature of common monocular coal lance had been developed according to the principles of mass and energy balance. Increasing temperature and flow velocity of the hot blast would cause a rise in the lance temperature. The influence of hot blast temperature is more obvious. The lance temperature would decline when compressed air flux increases. Conveying technology of dense phase pulverized coal is beneficial to extending lanceʹs life because decreasing solid-gas ratio would intensify erosion and burning loss. The anti-oxidation temperature of lance materials needs to be over 1000 °C for BF intensified smelting. In order to increase the resistance to oxidation of the coal lanceʹs outer surface, oxidation-resistant steel or Al coating stainless steel is the appropriate material for BF use. Employing the metal surface treatment technology to enhance the hardness of the coal lanceʹs internal surface could prolong the service life of coal lance.