Studies on the cement-bonded briquettes of iron and steel plant by-products as burden material for blast furnaces

Abstract: During the various stages of iron and steel production a number of iron bearing by-products are generated. These by-products can be made into cement- bonded agglomerates for use as burden material for blast furnaces. In order to improve the quality of agglomerates, the effect of various processing parameters on the properties of cement-bonded briquettes has been studied. It has been found that the room-temperature properties of briquettes depend upon various processing parameters like solid / water ratio, vibration time, briquetting force, compression time and particle size distribution of the raw material. The study has also shown that the strength of briquettes decreases after heating in a nitrogen environment and after reduction. The strength of briquettes can be increased by increasing the amount of pre-reduced / flaky components, increasing the amount of cement and decreasing the particle size of the raw material. Under certain reducing conditions, the cement-bonded briquettes exhibit a tendency to swell catastrophically. This happens especially during the reduction of wustite to iron at 950oC using CO as the reducing gas. The briquettes that contain coarse pellet-fines particles are specially prone to swelling since the pellet-fines contains a large percentage of under-fired and weak fraction of the pellets. This swelling can be controlled by grinding the raw material finely, increasing the cement content, and adding calcium oxide / magnesia / silica or alumina to the cement. A model to describe the swelling process has also been propounded.