Blast furnace flue dust co-processing in cement kiln - A pilot study

An integrated steel plant generates a large amount of blast furnace flue dust - about 18-22 kg/t of hot metal - as a by-product of the production process. The major component of this flue dust is iron oxides and coke fines. The recovery and reuse of this iron and coke is very important with increasing price of conventional resources. Cement plants on the other hand are looking for alternative fuel and raw materials as a substitution to the traditional fuel and raw materials, thus co-processing of the flue dust is a solution for both the industries. The study gauges the potential of flue dust utilization in a cement plant in India, using an experimental trial of one month and also analyses the techno-economic feasibility of the co-processing route. Since flue dust contains iron which is a limiting constituent in the limestone deposit of this plant, feasibility of reducing the iron content in the flue dust was evaluated through the magnetic separation route. The objective was to utilize maximum quantum of flue dust with acceptable iron content and high energy content. It was observed that the magnetic separation does not effectively segregate the iron present in the flue dust and neither increases the energy content. The cost analysis of the usage of flue dust also revealed that flue dust can be used effectively by the cement industry if its cost ranges in an acceptable range of USD 35-39 (approximately).