Summary
The method described has been carried out in a 3-ton rotating furnace at Domnarfvet Iron and Steel WorkS. It has, the following characteristic features.
The molten iron is brought into intimate contact with powdered burnt lime by treatment in a rapidly rotating furnace.
The treatment has to take place under strongly reducing conditions, which can be made in a simple way by keeping the furnace tightly closed during the process.
The lime must be maintained in the fine powdered form during the whole treatment, which is made possible both by avoiding a temperature in excess of 1350° to 1400°C and by the addition of a suitable amount of coke powder to the lime.
By carrying out the process in this way it has been found possible to desulphurize hot metal down to very low sulphur contents in a few minutes even from relatively high starting values, and with a high lime yield.
Owing to the short time of treatment and the small lime addition necessary, the drop of temperature during the process has been very small, with the consequence that external heat supply and its associated disadvantages have been avoided.
The rotation speed normally has been the maximum of the furnace, 40 rpm. Lower speeds have also been tried, but with unsatisfactory results. No inconveniences, with the high speed have been encountered.
The advantages of the method can thus be summarized as follows
1—A very rapid and complete desulphurization can be obtained. The sulphur content can in one operation be brought down to very low values even with high starting content in the iron and with high lime yield.
2—The desulphurizing material is cheap and can be obtained everywhere. After the treatment it may be used for other purposes.
3—No formation of molten slag is taking place, with the result that attack on the lining of furnace and ladle is avoided. The furnace is of a simple construction and can advantageously be lined with ordinary fire clay.
4—The iron during the tapping can be separated easily from the lime.
5—No dangerous smoke is formed during the process.
The first plant for commercial production is in operation at Surahammar Iron and Steel Works, Surahammar, Sweden.
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Discussion on this paper, TP 3109C, may be sent, 2 copies, to AIME by Oct. 1, 1951. Manuscript, Feb. 27, 1951. St. Louis Meeting, February 1951.
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Kalling, B., Danielsson, C. & Dragge, O. Desulphurization of Pig Iron with Pulverized Lime. JOM 3, 732–738 (1951). https://doi.org/10.1007/BF03397384
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DOI: https://doi.org/10.1007/BF03397384