At integrated steelworks, after the blast furnaces have been tapped, liquid pig iron is conveyed in torpedo cars to the steel shop where it will be treated in several ways. Throughout this movement, both pig iron and steel lose a large amount of heat. To avoid this loss, plants resort to two kinds of procedure.

One of them consists of using rice straw, which is thrown onto the bath's surface, forming a coating that will go on burning, producing energy and, as a result, maintain the temperature of the liquid metal. This procedure is at present going out of use for three reasons. The first is the cost factor: the price of rice straw is making this practice economically impracticable. The second is based on the fact that the density of rice straw is very low which means that large amounts of material are moved about, leading to operating difficulties at the plants, not to mention critical control of the moistness of the rice straw. Besides, this practice is quite inefficient. The third reason, and the most serious one, is the fact that burning rice straw produces ash which is almost entirely made up of silica. Besides being a reagent, this silica is classed as extremely fine grain, which makes it an important cause of silicosis, so endangering the health of the employees working in the area. Added to this is the fact that, being very fine, this ash overheats the exhaust filter during desulfurizing.

The other procedure, and one used increasingly, consists of raising the temperature of the run from the blast furnace to make up for energy lost while the liquid metal is on the move. This means an increase in fuel, the result of which is a rise in the final product cost. On the other hand, it is well known that all plants, in particular steelworks, produce several kinds of industrial spoils that present serious risks to the environment and are the

great challenges these companies have to face and solve, since the laws concerning environmental pollution are becoming stricter daily.

Acknowledging the importance of both reducing industrial costs and finding solutions for recycling the plants'spoils, we have devised a new process which, in addition to being economically feasible, will mean a contribution towards lessening pollution of the environment.

This process consists of agglomerating alumina-based ore in the form of pellets or briquettes mixed with some industrial spoils, such as blast furnace sludge, and coke or charcoal fines, thereby producing a high melting point, low-density mixture. These agglomerates will serve as a coating for the surface of the pig iron or liquid steel, where they will carry out their functions. Right after they have been cast onto the surface of the liquid bath, the coke or charcoal fines contained in the agglomerates will go into combustion, providing heat and thereby performing their first function.

Straight after combustion, the agglomerates will become porous, and settle all over the bath's surface, thereby accomplishing their second role, that of a heat insulator.

In view of their rounded format, the pellets will mobilize all over the bath's surface, thereby making distribution of the liquid metal bath coating easier, particularly in the torpedo cars. The balls'diameter will be determined as a function of the need to obtain more or less packing of the layer to be formed or the surface to be coated. The briquettes, in their turn, will be used when the area to be applied does not require their being highly mobile.

Transfer of energy due to firing of coke or charcoal fines in contact with the bath will produce the porosity needed for them to work as a heat insulator. The capacity of the insulating coating will be a function of two factors: the agglomerate's geometric shape, which will determine how good or bad packing is, and the agglomerate's density.

In view of the melting point of the agglomerates, they will stay on the surface of the bath without melting, and thereby not contaminate the metal until it is finally treated.

In this process, the initial stages consist of selecting the raw materials, which may be bauxite, clays or kaolin. Industrial spoil can be sludge from the blast furnace or the steelworks, besides coke or charcoal fines. By means of phase diagrams, the mixture, whose melting temperature is higher than 1350°, is chosen. After selection, the mixture agglomerates in the form of pellets or briquettes. These agglomerates'mechanical strength should be higher than 70 kilos per pellet or 150 kilos per briquette, that is, they should be strong enough to stand any handling without producing fines.

The agglomerates should also remain unharmed by thermal shock at 1200°.

Having passed these tests, the agglomerates'technical state is such that they can concurrently play a dual role as both a supplier of energy for the liquid metal and a heat insulator.