The De-Sulphurization at Blast Furnaces
Blast furnace is the main equipment in ferrous metallurgy production, and it has an important position when it comes to technology and machinery. During the reduction process at the blast furnace, sulfur generated from the sulfur-containing material will cause the blast furnace to produce more impurities in the steel, reducing the quality of the steel, and influencing the economic efficiency of the process. Therefore, the de-sulphurization of blast furnaces has become the development direction of blast furnace technology for its great disadvantage of related equipment, pollution and so on. The goal of this process is that sulfur content in the liquid iron should be controlled between 0.1% and 0.3% for better quality steel. The current way of de-sulphurization is mainly done by injection of de-sulphurizers into blast furnace, through the use of oxidation or reduction of the sulfur-containing materials, forming a reaction to convert the sulfur in the material into sulfur oxide, and the sulfur oxide was then removed through the slag.
To make the de-sulphurization process more effective, different ways of injection materials could be considered in practice, including concentrated lime stones, pyrite, bastnasite and etc. When injecting concentrated lime stones, the lime and calcium silicate combine with the sulfur dioxide and nitrogen dioxide to form calcium sulfate and calcium nitrate which are easy to settle in the slag and remove the sulfur dioxide. Pyrite is a mineral with high sulfur content, and its chemical reaction could help to remove sulfur and nitrogen. Additionally, injection of bastnasite could be an effective way to improve the sulfur content. This mineral is a mixed mineral composed of iron, calcium, cerium, lanthanum, yttrium and other substances. The iron in it can combine with the hydrogen to form water, so as to reduce the carbon monoxide entering the furnace, thus reduce the amount of sulfur.
Moreover, the use of water injection treatment has been reported recently. In this process, water spray is injected on the high temperature reductive zone to cool the surface, promoting the oxidation and reactions of the sulfur-containing materials which helps to reduce the sulfur content of blast furnace. In addition, the use of oxygen injection technology has been widely used to improve the de-sulphurization efficiency. This involves the directly injection of oxygen-enriched air into the furnace during the explosion phase, which can increase the partial pressure of oxygen to improve the de-sulphurization efficiency.
All in all, the de-sulphurization at blast furnaces is an important part of the steelmaking process and the use of different injection materials and oxygen injection technology has made it possible for blast furnaces to continuously improve the quality of steelmaking. With the deeper understanding of the steelmaking process, more technologies and methods of de-sulphurization will come up in future and more effective ways to reduce sulfur content of the blast furnace will be developed, helping to greatly increase production efficiency.
