Terry Norgate

Selection and operation of high pressure grinding rolls circuits for minimum energy consumption

Abstract Results obtained from a laboratory-scale high pressure grinding rolls show that the specific energy consumption of the rolls increases linearly as the applied grinding force increases, but this is not accompanied by a linear increase in the size reduction achieved. Instead the latter increases at a gradually reducing rate, which is shown to be best described by a power-law equation. It is also shown that increasing the applied grinding force reduces the Bond Work Index of the rolls product and hence the energy required for any subsequent comminution. Using a computer simulation model of a comminution circuit incorporating a high pressure rolls in pre-grinder mode ahead of a ball mill, it is shown how the specific energy consumption of the rolls, ball mill and overall circuit changes as the applied grinding force of the rolls increases, for both a zinc and gold ore. Because of the conflicting effects of applied grinding force on the rolls and ball mill specific energies, there may be an optimum applied grinding force at which the overall circuit specific energy is a minimum. This optimum is largely ore dependent as illustrated in the paper. The effect of operating a number of rolls in series on the specific energy consumption is also described in the paper.

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.

Pure zircon process for removing radionuclides from zircon concentrates

Abstract The presence of U and Th as impurities in zircon makes it radioactive. Provided the U and Th levels are below 500 ppm, or 70 Bq g-1 activity, the limits that allow transportation of the material as a non-radioactive substance, it is acceptable as a commercial product. However, some zircon sands contain radioactivity levels well above this limit. A new process (the pure zircon process) is described for the removal of radioactivity from zircon. Tests to identify the best flux addition, calcination temperature and time, and leaching conditions indicated that by grinding a zircon sample containing 1059 ppm U + Th to a particle size of about 15–20 μm, calcining it with 15 wt-% calcium borate (colemanite) at 1200°C for 4 h and leaching the calcine with up to 1M HCl at 80°C for 30 min gave a product with <500 ppm U + Th. While the grade of Zr of the final product was slightly increased, the levels of major impurities, Al, Fe, Ti and P were decreased. Operating costs for the pure zircon process using the optimum conditions were estimated to be A

Rock Smelting of Copper Ores with Waste Heat Recovery

243/t leach product.

Assessing the environmental impact of metal production processes

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.