Optimization of Pulverized Coal Injection (PCI) Rate in an Ironmaking Blast Furnace By an Integrated Process Model

Abstract

Pulverized coal injection (PCI) is generally used in modern blast furnace (BFs) ironmaking to reduce coke consumption by burning cheaper coal. This paper presents a numerical study on the effects of PCI on the inner states and overall performance of a 5000-m 3 industrial BF. This is based on a recently developed integrated BF model that simulates an entire BF, including the raceway and hearth regions. The model is extended to consider the interaction between the raceway and the remaining BF region, the layered burden structure, and the hydrogen related reactions. After validation, it is used to study the effect of PCI rate and its interaction with oxygen enrichment and top burden distribution. The results are analyzed in detail in terms of raceway combustion characteristics, inner flow and thermochemical behavior, and overall performance. A maximum operable PCI rate is identified under given blast and burden conditions, beyond which relatively low coal-coke replacement ratio, high pressure drop, and low hot metal (HM) temperature are observed. With increasing PCI rate, the indirect reduction rate by CO increases to a maximum and then decreases; however, that by H 2 increases linearly. Consequently, the total indirect reduction rate increases first and then slows down. The maximum PCI rate is further improved with appropriate oxygen-enriched operation combined with suitable burden distribution. Too high oxygen enrichment increases the coke rate to compensate for the cooling effect of coal injection. The results suggest that this integrated model can be used as a cost effective tool to understand, quantify and optimize PCI effects on BF performance under different bottom and top operations.