Process Introduction
Calsmelt Pty Ltd was established to pursue research activities to produce aluminium via an alternative carbothermic production route.
During the last few years, Calsmelt has successfully completed a “concept proof” stage for its ThermicalTM carbothermic process. While the Thermical™ process is classified as a carbothermic process for aluminium smelting, in detail it is fundamentally different when compared with previously proposed carbothermic processes.
In the Thermical™ approach, metal is produced in a highly reactive medium with much lower kinetic barriers, and at significantly lower temperatures. By comparison, due to its lower temperature of operation, the ThermicalTM process does not exhibit the difficult challenges that have plagued previous approaches.
The Thermical™ process is capable of meeting today’s aluminium industry demands and of replacing current aluminium cell technology. The process will insure a competitive future for the aluminium industry by drastically reducing the costs and environmental footprint. Capital costs will be reduced by 77% to 80% and the operational cost will be lowered by about 40%. Power consumption will be about 40% lower. Fluoride emissions will be completely eliminated and the quantity of generated gases will be significantly lower. Thus, the Global Warming Potential (GWP) of the Thermical™ process is 40-60% lower than in the electrochemical process.
The Thermical™ process may also offer significant potential for the reduction of those raw material preparation problems evident in the prior bauxite refining stage that produces the smelting starting product, smelting grade alumina.
Calsmelt believes that the Thermical™ process has the potential to benefit the different parties that operate across the aluminium industry in different ways.
At present, Calsmelt’s major goal is to very cost effectively replace the electrolytic cell process. This goal will serve aluminium-producing companies due to its significant cost cutting results and environmental benefits. However, the successful operation of the Thermical™ process will also open windows to tackle raw material preparation problems in the alumina refining process, so providing a substantial advantage for alumina refineries.
Not least, the dramatic capital cost reductions may also provide tangible advantages to governments with respect to any perceived political problems related to investment in infrastructure (e.g., any major new power generation facilities).
The technology for the ThermicalTM process comprises two stages: charge production and metal production. In recent work, conducted by Calsmelt, it has been demonstrated that each stage of the process functions effectively, and according to theoretical expectation.
Therefore, following the completion of the “concept proof” stage, a detailed book has been written to provide a reasonably complete formal record of the theoretical, modeling and experimental results produced to date. Furthermore, this book also contains consideration of proposed process options and outlines the overall technological feasibility of the process in some detail.
Comparison of Thermical™ and Conventional Processes
It is well established that an aluminium carbothermic process has great economic and productivity advantages (at least theoretically) over the existing Hall-Heroult electrochemical process. In Table 1 below, the Thermical™ process and conventional carbothermic processes (including ARP) are compared with the data (Norgate T E, Rankin W J., 2001) on the Hall-Heroult process.
Based on the data shown in Table 1, it is apparent that the advantages of either conventional carbothermic processes (or the Thermical™ process) over the Hall-Heroult process are huge and sufficiently commanding to warrant process and technology change, should a deliverable carbothermic technology be available.
In Table 1, the differences between the Thermical™ and conventional carbothermic processes were calculated based on the different process requirements including:
i. The first stage of the Thermical™ process requires significantly lower temperature and does not produce any gas. Therefore, unlike the Alcoa carbothermic smelting process, there is no requirement for a separate fume collection and treatment system at this stage;
ii. the second stage operates at a lower temperature than for the conventional carbothermic processes, therefore there is a much lower cost of gas collection and treatment and a lower carbon content occurs in the produced metal; and,
iii. lower energy and carbon consumption occurs in the Thermical™ process than in other conventional carbothermic processes for aluminium smelting.
Clearly, the advantages of the Thermical™ process over the various conventional processes are appreciable. But, these economical and environmental advantages alone are not the prime reason to pursue the Thermical™ process. It is the fact that the Thermical™ process also uniquely overcomes the remaining critical process and technical deficiencies found with the various, previously considered, carbothermic processes, to the point that carbothermic smelting of aluminium becomes feasible and economically viable.
The significant advantages of the Thermical™ process over conventional carbothermic processes relate to the process and technological problems inherent to those conventional processes at very high temperatures. However, in the Thermical process, these problems are simply reduced by the lower temperature requirements of this new carbothermic approach. The Thermical™ process involves the production of metal in a highly reactive medium with much lower kinetic barriers.
Differences between the processes and foreseeable advantages of the Thermical™ process, relative to conventional processes, are summarized in Table 2.