Sharif Jahanshahi

CSIRO’s multiphase reaction models and their industrial applications

The status and ongoing work on a multiphase reaction model developed at the Commonwealth Scientific & Industrial Research Organization are outlined in this article. The package enables metallurgists to simulate reactions in pyrometallurgical processes with respect to equilibrium between various phases and to calculate slag viscosity at elevated temperatures. The models have been validated against measurements on physico-chemical properties of melts and solid phases produced in industrial processes. A number of examples of the application of the package to ferrous and non-ferrous smelting and refining processes are presented.

Determination of the chemical diffusion of oxygen in liquid iron oxide at 1615 °c

The chemical diffusion of oxygen in liquid iron oxide has been studied by the oxidation of a melt in a long capillary at 1615 °C. When pure oxygen was used as the oxidizing agent, the surface composition of the slag was found to be in close agreement with the expected gas-slag equilibrium, suggesting that diffusion is the controlling step. This was not the case when air, 5 pct oxygen in argon or pure CO2 was used to oxidize the slag. The deviation of the surface composition from the expected equilibrium was in accordance with a mechanism of mixed control by both the gas-slag reaction and diffusion in the bulk. The average value of the chemical diffusivity of oxygen (or iron) in liquid iron oxide with Fe2+/FeT between 0.25 and 0.77 was established to be 3(±1) × 10-7 m2/s. This value is one to two orders of magnitude higher than those from earlier studies. There seems to be a reasonable correlation between the chemical and the ionic self-diffusivities through the Darken equation. A quantitative analysis in this respect and on the role of electron hole migration depends on the availability of data on the ionic conductivity and the tracer diffusivities.

Current Status and Future Direction of Low-Emission Integrated Steelmaking Process

In 2006 the Australian steel industry and CSIRO initiated an R&D program to reduce the industry’s net greenhouse emission by at least 50%. Given that most of the CO2 emissions in steel production occur during the reduction of iron ore to hot metal through use of coal and coke, a key focus of this program has been to substitute these with renewable carbon (charcoal) sourced from sustainable sources such as plantations of biomass species. Another key component of the program has been to recover the waste heat from molten slags and produce a by-product that could be substituted for Portland cement.

Utilization of biomass as an alternative fuel in ironmaking

Abstract Raw biomass is unsuitable for ironmaking applications. However, after pyrolysis, the resultant chars can substitute for conventional nonrenewable fuels and reductants. Provided that the renewable fuels are produced sustainably, they have great potential to lower net CO2 emissions from an integrated steel plant without the need for significant capital expenditure. Charcoal properties can be tailored for optimal performance, and applications in cokemaking, sintering, and the blast furnace are presented. Potential applicability to alternate and emerging ironmaking processes is discussed. This chapter discusses recent R&D for the 10 applications identified and also presents progress toward a versatile large-scale pyrolysis process.

Silica Activity and Raman Spectra of the CaO-SiO2-TiOx System

The thermodynamic activity of SiO 2 in CaO-SiO 2 -TiO x slags was measured by the slag-metal-gas equilibrium method. Slags containing up to 43 mol% TiO x , were equilibrated with molten copper in molybdenum crucibles in H 2 -H 2 O-Ar gas atmosphere. The oxygen partial pressure and temperature were maintained at ∼10 -12 atm and 1873 K, respectively. In the equilibrated slags, the proportion of titanium in the reduced Ti 3+ state ranged from 16% to 54% of total Ti by mass. Results showed that at a given CaO/SiO 2 ratio, the activity coefficient of SiO 2 increases with increasing TiO x concentration. Samples of CaO-SiO 2 -TiO x slags were also examined by Raman spectroscopy. Raman spectra obtained for oxidised and reduced CaO-SiO 2 -TiO x slags show that the Ti 4+ ion has a tetrahedral coordination, while the coordination of Ti 3+ appears to be predominantly octahedral. These findings are consistent with the observed effect of titania on the silica activity in the CaO-SiO 2 -TiO x slags.

Rock Smelting of Copper Ores with Waste Heat Recovery

It is generally recognised that the grades of metallic ores are falling globally. This trend can be expected to increase the life cycle-based energy requirement for primary metal production due to the additional amount of material that must be handled and treated in the mining and mineral processing stages of the metal production life cycle. Rock (or whole ore) smelting has been suggested as a possible alternative processing route for low grade ores with a potentially lower energy intensity and environmental impact than traditional processing routes. In this processing route, the beneficiation stage is eliminated along with its associated energy consumption and greenhouse gas emissions, but this is partially offset by the need for more solid material to be handled and heated up to smelting temperatures. A life cycle assessment study was carried out to assess the potential energy and greenhouse gas benefits of a conceptual flowsheet of the rock smelting process, using copper ore as an example. Recovery and utilisation of waste heat in the slag (via dry slag granulation) and offgas streams from the smelting step was also included in the study, with the waste heat being utilised either for thermal applications or electricity generation.