Application of a Coal Combustion Model in the Design of Blast Parameters for an Ironmaking Blast Furnace

Abstract

With significant economic drivers to reduce consumption of expensive coking coal, Pulverized Coal Injection (PCI) commenced at BlueScope Steel in 2002, at injection rates ranging between 100 and 150 kg-coal/tonne of liquid iron. The key limitation to injection rates is associated with the reduction in packed bed permeability via additional char load into the furnace. The coal is injected via a simple co-axial lance, consisting of an inner pipe (for coal and carrier gas) and an outer annulus (for cooling gas to protect the lance from the high furnace temperatures). The cooling gas can be compressed air, natural gas or pure oxygen. Depending on the choice of cooling gas, the oxygen-to-carbon ratio of the system will change. In this paper, the application of a validated three-dimensional numerical model of the blowpipe/tuyere/raceway is described. The model is used for various plant-specific investigations of blast parameters such as oxygen enrichment, blast temperature and atomic oxygen-to-carbon ratio. The model results show the sensitivity of coal burnout to different operating parameters and confirm that burnouts higher than 80% are difficult to obtain due to the short residence times of the coal.