The feasibility of air classification of dusts from the iron and steel industry

In this paper, the feasibility of air classification of dusts from iron and steel production for improved recycling is investigated. By air classification a dust can be separated into a coarse fraction and a fine fraction. According to literature data some components which are usually unwanted in recycled material like alkali chlorides and the heavy metals Zn and Pb are enriched in the fine dust fraction. Therefore, air classification of dust before recycling would allow recycling of an increased amount of dust and reduce landfill. However, the benefits have to be measured against the cost of air classification. In order to be able to study the feasibility of such treatment the investment costs and the operating costs of a classification facility were calculated for three different dust treatment capacities. The results show that the three main factors affecting the feasibility of such a treatment are the capacity of the unit, the cost of landfill of the respective dust and the fraction of dust which can be recycled after the treatment. A cost curve per ton of processed dust is presented and shown for annual capacities of 2.370, 7.000 and 23.000 t. For the higher capacities it is shown that good feasibility is probable even if rather low landfill costs are assumed.