Abstract
The ninth International Conference on ‘Molten slags, fluxes and salts (MOLTEN12)’, organised by CSM (The Chinese Society for Metals) and USTB (University of Science and Technology Beijing), was held in Beijing, China on 27–31 May 2012. More than 300 people from 25 countries around the world (179 from abroad and more than 120 from China) attended the conference. Nine plenary lectures were given on 28 May 2012, and 156 lectures in 28 parallel sessions and 27 posters were given on 29–30 May 2012. An exhibition with suppliers was also organised in the same conference building.
The quality of the lectures was extremely high with presentations from universities, institutes, industry and thermodynamic software developers. The conference clearly demonstrated the state of the art in five areas: molten slags; molten salts and applications; transport/interfacial phenomena and foaming; industrial applications in extraction, smelting and refining; and recovery and utilisation of slags, wastes or byproducts of the metallurgical industry.
The conference plenary lectures highlighted that as in the last decade the centre of gravity of the metals industry has shifted eastwards towards China, so the slags and fluxes literature has followed with reference to numbers of papers published per annum. This has been well evidenced by the number of papers, attendees and organisations attending the MOLTEN12 conference from China. Despite this it was clear that the Chinese steel industry suffers, alongside the rest of the global steel industry, with intensive competition, overcapacity and high raw materials prices leading to weak or non-existent profits.
European Union countries still have big impact on the research of slags. In particular, 40 people from Sweden attended this conference presenting a number of high quality papers. The research from KTH Stockholm in particular was notable for number of high quality papers. South America was less well represented with only one person from Chile and nobody from either Argentina or Brazil.
An increased attention on sustainable metals production (including recycling of valuable metals and reuse of slags as cement or construction material) was reflected in the papers. Minimisation of slag production per unit of metal produced is another trend triggering innovative production process development. In Japan, two schemes under consideration to solve the issue of steelmaking slag utilisation were presented, the first is to decrease volume of slag generation via ‘multiphase flux refining’ and the second is to use the mixture of steelmaking slag and soil for the recovery of coastal environment.
The developers of thermodynamic packages Factsage, Thermocalc and Pandat reported their recent development. Some interesting examples of the development and application are: FactSage – CaO–CaF2 system and P2O5 containing steelmaking slag system; Pandat – V2O3–TiO2 system. One paper discussed the applicability of different thermodynamic packages in steel refining slags and paper from ArcelorMittal Global R&D, France, McGill University, Canada and CSIRO, Australia reviewed the main thermostatistical models of metallurgical slags in terms of theory and applications.
A new experimental design to simulate the lime dissolution in slag was developed by KTH via CFD and water modelling simulation. The mechanism of lime dissolution in converter slag revealed by this work is similar to results previously published from 6 t pilot plant and 320 t industrial converters, presented by Tata Steel R&D in this conference. In discussion, it was postulated that the dicalcium silicate layer normally observed in laboratory tests, was not present in industrial samples, due to the extreme turbulent conditions in the converter. Thermodynamic modelling of 
Fundamental research was reported by the academics from the University of Tokyo, Japan on producing H2 by using the heat and FeO in steelmaking slag. Currently in Japan the heat associated with the slags is not utilised. The amount of waste heat from converter slag is estimated to be 2·4×1016 J, which is equivalent to the annual energy consumption of 570 000 families in Japan. Therefore, this unharnessed energy should be efficiently recovered and utilised in the steelmaking industry or in society for the reduction in total energy consumption and CO2 emission. Converter slag contains 15–30 mass-% of FeO normally, and thus the function of FeO as a reducing agent of H2O gas is expected: 2FeO (in slag)+H2O (g) = Fe2O3 (in slag)+H2 (g). Since the above reaction is exothermic, the supply of heat energy for operation of this process would either be unnecessary, or only a little heat supply would be required. Therefore, the necessary heat energy could be supplied via discharged converter slag at molten state. Exhaust gas analysis by a quadrupole mass spectrometer confirmed the generation of H2 gas. On a similar topic, JFE Steel Corporation, Japan reported a feasibility study on a rational steelmaking slag recycling system by phosphorus separation and collection. Phosphorus was enriched by reducing steelmaking slag with carbon under high temperature conditions (1373–1873 K). Calculations showed that phosphorus was enriched in slag to be >30 mass-%P2O5 by dephosphorisation of high phosphorus hot metal (1·05 mass-%P).
Research on stainless steel production included a laboratory study on desulphurisation of stainless steel by using CaO–Al2O3 based slags during secondary metallurgy. For the process studied, the slag carryover from EAF was removed before adding CaO–Al2O3 based flux. A paper from Carnegie Mellon University studied the beneficial effects of molten silicates, or mould fluxes, on the oxidation of type 304 stainless steel under slab reheating conditions. It is claimed that a plant trial is being carried out to use molten silicates to suppress the formation of subscale of type 304 stainless steel during heating before hot rolling.
A paper from KTH, Sweden discussed the possibilities to control impurity elements and inclusion characteristics during ladle refining. It was particularly pointed out that, practical aspects such as steel sampling for suitable inclusion characteristics need to be considered and it is essential to study methods for rapid determinations of inclusions such as the OES/PDA and the LA–ICP–MS techniques. Offline methodologies such as the electrolytic extraction method, were shown in combination with metallographic methods, to determine more in-depth information with respect to the specific inclusion characteristics.
Experimental technique development also featured in the programme with a paper from Wuhan University of Science and Technology, China and Institute of Iron and Technology, Germany reported their work on the accuracy of viscosity measurement using rotation viscometer. Out of various factors, instable side movement of spindle is the main effect to generate error, especially in low viscosity fluid. Water modelling and mathematical modelling experiments were presented on an investigation into the open eye size in a gas stirred ladle under two regimes of thin and thick slag layers.
Overall this conference remains one of the most international and well attended in the steel processing calendar, with good interaction between academia and industry from across the world. The plenary lectures in particular gave an opportunity to reflect on the progress of research in this field since this conference series started and it is encouraging to note the developments that have taken place over that time. The one major change over this time has been the increasing emphasis on research to address environmental, CO2 and waste concerns, as well as the major process issues of cost and quality. The next Molten conference will be held in North America in 2016, where it is expected that this trend will continue.