Project Status: Complete
Project Participants: CSIRO, BlueScope Steel, OneSteel
Project Leader: Dongsheng Xie (CSIRO)
Historically, iron-making slag is either air cooled in large pits or water granulated. Water granulation has the advantage of producing a slag product suitable as a low greenhouse gas cement clinker substitute, albeit with significant environmental disadvantages – in particular the high water consumption, formation of acid mist, and the need to dry the granulated slag. Previous CSIRO research has demonstrated at laboratory and pilot scale that dry granulation produces a slag suitable as cement substitute; and that the heat released from the slag can be captured by a small volume of air – making the process suitable for high grade heat recovery. The project aimed to further develop dry granulation technology, with particular emphasis on using it as a means to capture the waste heat released from slag cooling; and to develop know-how for scale-up from pilot to industrial scale. This work formed part of the Australian steel industry’s contribution to the WorldSteel Association’s CO2 Breakthrough Program.
The overall objective of the project was to develop a dry granulation process that produces a high value slag and enables capture/recovery of the waste heat released from slag cooling, whilst demonstrating its techno-economic, energy and sustainability benefits at pilot scale. The project also aimed to scale up the technology and demonstrate it through plant trials.
The concept of integrated dry granulation and heat recovery has been successfully demonstrated through the prototype pilot facility at CSIRO. The designed process has performed well, delivering smooth operation under variable conditions and high slag tapping rates. Many tests have been carried out using industrial blast furnace slags and the granulated products were collected. The products were characterised and assessed with respect to cementitious properties. Further assessment by a third party laboratory found that the dry granulated slags have good cementitious properties and are suitable for cement production.
A techno-economic evaluation indicated that dry slag granulation has significant advantages over the wet granulation process in terms of both capital and operating cost. Plant visits were made to collect data on casting rates and measure temperatures of slag and hot metal from the blast furnaces at OneSteel’s Whyalla steelworks and BlueScope Steel’s Port Kembla. These data were further assessed in relation to implementation of dry granulation and the results were documented in a report.
Advanced Computational Fluid Dynamics (CFD) modelling of the dry granulation process was successfully carried out. A CFD model for heat transfer and fluid mechanics in the spinning disc atomisation process was assembled and the model validated using experimental data from the pilot plant at CSIRO.
A draft business plan for the subsequent stages of the project has been developed. Industry engagement and promotion of the new process continued through visits and meetings with potential investors and collaborators.