Modeling of Blast Furnace with Layered Cohesive Zone
- PDF / 1,631,974 Bytes
- 20 Pages / 593.972 x 792 pts Page_size
- 46 Downloads / 233 Views
ronmaking blast furnace (BF) is a multiphase reactor involving counter-, co- and/or, cross-current flows of gas, powder, liquid, and solid phases.[1] In this process, iron-bearing materials and coke are charged at the top of the furnace. Hot gas (blast) enters the furnace through the tuyeres in the lower part and combusts carbonaceous materials (coal, coke) to form reducing gas. As this gas ascends, it reduces and melts the ironbearing materials to form liquid iron and slag in the cohesive zone (CZ). The liquid percolates through the coke bed to the hearth. If pulverized coal injection or other injection technology is practiced, then unburnt coal (or other injectants) may leave the raceway region at high injection rates through gas entrainment as a distinct powder phase.[2] These characteristics demonstrate the complexity of the BF operation and the difficulties in understanding the physical and chemical phenomena in a BF. Since the 1960s, intensive research has been undertaken to characterize the internal state of a BF with different techniques such as dissection studies, in situ measurements, physical experimentation, and mathematical modeling. Among them, numerical modeling demonstrates an increasing capability to provide detailed information about fluid flow, heat and mass X. F. DONG, Research Associate, and A. B. YU, Federation Fellow and Scientia Professor, are with the Lab for Simulation and Modelling of Particulate Systems, School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia, Contact e-mail: [email protected] S. J. CHEW, Principal Research Engineer, and P. ZULLI, Senior Principal Research Engineer, are with BlueScope Steel Research, P.O. Box 202, Port Kembla, NSW 2505, Australia. Manuscript submitted February 17, 2009. Article published online January 5, 2010. 330—VOLUME 41B, APRIL 2010
transfer, as well as chemical reactions throughout the furnace. One-, two-, and three-dimensional continuumbased mathematical models have been developed in sequence, as summarized in recent reviews.[3–5] The development of numerical models originated from the understanding of macroscopic phenomena at the early stage toward the simulation of critical operational conditions and flow phenomena on a microscale. Corresponding to this trend, the CZ has attracted much attention in recent years. Through dissection studies, the existence of the CZ as a layered structure where burden materials undergo dramatic physiochemical change has been demonstrated. Within the CZ, the iron-bearing materials experience softening and melting and react with the reducing gases to produce wustite and iron. Therefore, this zone comprises alternate layers of coke and semifused masses of slag and iron. Through this zone, the layered structure of solid ore and coke in the upper part of the BF gradually transits to the lower zone where only the solid coke remains alongside gases and liquids. The resistance to upward gas flow is great in the CZ because the ore layers are relatively impermeable, which results in most
Data Loading...
