Project Status: Complete
Project Participants: CSIRO, CRC Salinity
Project Leader: David Langberg (CSIRO)
The substitution of fossil carbon by “renewable” carbon from biomass (such as charcoal) has the potential to radically reduce the net carbon dioxide emissions from metallurgical processes. This project built on the work of foundation project “Biomass as Fuel and Reductant for Modern Smelting Processes” (4C1) which demonstrated that charcoals produced from oil mallee trees are suitable reductants for use in rotary kilns (Becher process), and for bath smelting processes (HIsmelt process).
Australia faces a growing problem of increasing soil salinity due to the rising water table in areas where deep rooted perennial vegetation has been replaced by shallow rooted crops, such as the wheat belt of Western Australia. A program of replanting native mallee trees, which can be harvested on a short rotation cycle, has been initiated in Western Australia. This will produce large quantities of woody biomass, which could potentially supply charcoal to the metallurgical industry and at the same time improve returns for farmers.
During this project, samples of two species of mallee leaf/twig biomass from four locations were charred. Part of the material from each location had previously been subjected to a steam stripping procedure to remove the oils. The ash compositions of the raw materials and resulting charcoals and the carbon dioxide reactivities of the charcoals were determined. Two of the charcoals were used as reductants for ilmenite reduction in a rotary drum test developed at CSIRO Minerals. The economics of using biomass as a fuel and reductant depends upon the cost of the mallee charcoal, which is in turn strongly dependent on the cost of the mallee biomass. This project has shown that the lowest cost material – the leaf/twig fraction – produced charcoal with quite attractive properties for metallurgical applications (very high reactivity, high lime content in ash, high phosphorous and alkalis).