Process and apparatus for the direct reduction of iron oxides in an electrothermal fluidized bed and resultant product

Abstract

A method and an apparatus (50) for producing direct reduced iron (37) from dry pellets (25) composed of iron oxide and carbonaceous material. A mixture of pellets (25) and free coke particles (38) with weight relation from 3:1 to 5:1 is fed into the top of an electrothermal fluidized bed (32) that is fluidized by nitrogen. By exposing pellets (25) in the electrothermal fluidized bed (32) to temperatures of between approximately 850-1,100° C. for an average period of between approximately 15-60 minutes, the volatiles are removed and the pellets (25) metallized. Reduced pellets (37) mixed with free coke (38) are discharged from the bottom of fluidized bed (32) and cooled. The reduced iron pellets (37) are physically separated from any free coke (38) and the free coke (38) is recycled back into the fluidized bed (32).

Description

BACKGROUND [0001] This invention relates to a process for the chemical reduction of iron oxides into metallic iron at temperatures below the melting point of iron (1,530° C.), commonly known as “direct reduction.” More specifically, the present invention is directed to a process for the direct reduction (“DR”) of iron ores using solid carbon as the reductant in which the heat needed for the reduction reactions is provided by resistively heating the reactant materials while they are in a fluidized bed formed by a mixture of reactant materials and free carbonaceous particles. The invention additionally provides a unique direct reduced iron (DRI) product as a result of the inventive process. [0002] Iron ores of various types are found in enormous amounts throughout the world. Most iron ores are oxides of iron, mainly hematite (Fe2O3). To make metallic iron, the ore is chemically reduced using agents that are in most cases derived from coal or natural gas (methane). The reduction of iro...

AI Technical Summary

Benefits of technology

[0020] Another aspect of the invention, the fluidized bed portion of the furnace, is designed so as to include two distinct zones, namely, an upper zone with vertical walls and a generally constant cross-sectional area and a lower zone of a reduced cross-sectional area that terminates in an inverted conical section in which the fluidizing gas distributor is located. This design provides for active fluidization in the top zone of a particulate mixture having a high concentration of granular carbon and green DRI pellets and a low concentration of reduced DRI pellets. A mixture of reduced DRI pellets with a low content of granular carbon is fluidized in the lower zone. To prevent particle agglomeration and deposition formation on the interior of the furnace, the furnace is designed without any interior horizontal surfaces. More particularly, all internal surfaces are at an angle equal to or greater than the angle of repose for the reduced pellets. The electrodes that enter the fluidized bed to enable current flow therethrough are positioned to be in contact only with the upper fluidized bed zone that is rich in granular carbon. This minimizes the possibility of heating the iron-rich pellets to a temperature above the melting point of metallic iron, which would cause uncontrolled agglomeration of iron onto the surface of the electrodes and other internal surfaces.

Problems solved by technology

This minimizes the possibility of heating the iron-rich pellets to a temperature above the melting point of metallic iron, which would cause uncontrolled agglomeration of iron onto the surface of the electrodes and other internal surfaces.

Images