Rate of reduction of FeO in slag by Fe-C drops
- PDF / 811,666 Bytes
- 9 Pages / 603.28 x 783.28 pts Page_size
- 38 Downloads / 147 Views
I.
INTRODUCTION
THE rate of reaction between FeO in slag and carbon in iron plays an important role in many iron and oxygen steelmaking (OSM) processes. In OSM, the reaction is responsible for decaburization, and in the blast furnace, it is responsible for producing some of the iron. There is renewed interest in this reaction due to the development of bath smelting processes. In these processes, coal, ore, and oxygen are added directly to the reactor. The ore dissolves into the slag and is reduced by carbon in the coal char and by carbon in iron droplets in the slag. It has been demonstrated, ]~,21 that the reaction between iron-carbon droplets in the slag is responsible for about half of the reduction. It has been known for many years that in processes such as O S M , [3,41 the slag-metal emulsion contains a large quantity of iron droplets and the reaction of these drops play an important role because of their large surface area as compared to the normal bath surface area. Similarly, in iron bath smelting, the fast reaction rates could only be possible because there is a large quantity of metal droplets in the slag. There have been numerous investigations of the reaction in question. Those relevant to the present investigation will be discussed. Mulholland e t al. fs] conducted an X-ray fluoroscopy study of the reaction between ironcarbon drops and slag composition relevant to OSM and demonstrated the existence of a gas halo surrounding the metal drop as it reacted with the slag. Gore and Hazeldean t6~ made similar observations and measured the rate of decarburization. They found there was a short induction period of a slow rate followed by a fast reaction period and finally a slow reaction. Gaye and R i b o u d [71 made kinetic measurements for metal drops and D.-J. MIN, formerly with Carnegie Mellon University, is Research Engineer with the Research Institute of Science and Technology, Pohang, Korea. R.J. FRUEHAN, Professor, is with the Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University, Pittsburgh, PA 15213. Manuscript submitted February 8, 1991. METALLURGICAL TRANSACTIONS B
found that sulfur in the metal decreased the rate. Sommerville e t al. tSj reacted slags containing less than 5 wt pct FeO with iron carbon melts in a special crucible such that the metal was not in contact with carbon. They showed that the rate was first order with respect to FeO. The rates were of the same magnitude expected if the rates were controlled by the rate of decarburization of iron by CO2. In the comparison it was necessary to assume a sulfur content of the metal, which was unfortunately not measured. Belton r9j also interpreted Gaye and Riboud's rates as being controlled by the dissociation of CO2 on the iron surface. Based on the above studies and others, it is generally agreed the reaction between FeO in the slag with iron carbon droplets occurs v i a a two-step reaction, with COCO2 acting as gas intermediates, as shown schematically in Figure 1. At the slag-gas interface, CO reduces
Data Loading...
