Metallurgical furnace for producing metallic alloys

Abstract

The instant invention relates to a metallurgical furnace, comprising at least one upper stack (1), at least one lower stack (2), at least one fuel feeder positioned substantially between at least one upper stack (1) and the at least one lower stack (2), at least one row of tuy?res (3, 4) positioned in at least one of the at least one upper stack (1) and at least one lower stack (2), the at least one row of tuy?res (3, 4) providing a fluid communication between the inside of the furnace and the external environment, positioned in at least one of at least one upper stack (1) and at least one lower stack (2), and further comprising at least one permeabilizing fuel column fed through at least one hood (6), placed in the upper stack (1), which extends longitudinally through the furnace.

Claims

1. A metallurgic furnace comprising: at least an upper stack; at least a lower stack; at least one fuel feeder positioned substantially between the at least one upper stack and the at least one lower stack; at least one row of tuy?res positioned in at least one of the at least one upper stack or the at least one lower stack, and at least a row of tuy?res providing a fluid communication between the inside of the furnace and the external environment, positioned in the other of the at least one of the at least one upper stack or the at least one lower stack; and further comprising at least one permeabilizing fuel column extending longitudinally through the furnace fed by means of a hood extending longitudinally into the furnace.

2. The metallurgic furnace, according to claim 1, wherein the hood consists of a set of structured panels made of cast iron, steel or any other alloy, filled with refractory concrete and anchored in a sheet welded to the furnace structure.

3. The metallurgic furnace, according to claim 1 further comprising a filler silo system for delivering a permeabilizing material to and through the hood, wherein the filler silo system contains both an enclosed silo and an open silo.

4. The metallurgical furnace, according to claim 3, wherein the filler silo system comprises metering valves in respective discharges of the enclosed silo and the open silo.

5. The metallurgical furnace, according to claim 3, wherein the filler silo system comprises a pressure equalizing system.

6. The metallurgical furnace, according to claim 1, wherein the hood does not extend below either of the rows of tuy?res.

7. The metallurgical furnace, according to claim 1, wherein the at least one permeabilizing fuel column and the hood allow gases from the lower stack to circulate to the upper stack.

Description

DESCRIPTION OF THE FIGURES

(1) The detailed description shown below refers to the attached figures, wherein:

(2) FIG. 1 shows a furnace with a hood according to one embodiment of the instant disclosure;

(3) FIG. 2 shows a filler means according to one embodiment of the instant disclosure;

(4) FIGS. 3A and 3B show the gaseous flow obtained by the instant disclosure in relation to the gas flow of the furnaces described in the prior art.

DETAILED DESCRIPTION

(5) This description starts with one embodiment of the disclosure. Nonetheless, the disclosure is not limited to this specific embodiment, as it will be evident for a person skilled in the art.

(6) The instant disclosure provides a metallurgical furnace with innovations allowing an adequate control of the gaseous flow to enable the reduction of self-reducing agglomerates in a homogeneous way, also controlling the energy exchange between the gas and the filler, a fundamental principle of the self-reduction process.

(7) The metallurgical furnace of the instant disclosure is shown in FIG. 1, consisting essentially of an upper stack 1 where the filler (feedstock) is charged into the furnace. It is important to note that the stack may have a number of shapes such as, for example, a cylindrical shape having a circular cross-section, or a parallelepiped shape having a rectangular cross-section, inter alia. Hence, let us note that the instant disclosure is not limited to any specific shape of the furnace.

(8) In the upper stack 1 there is an assembly of at least one row of secondary tuy?res 4, which are preferably holes which allow blowing of hot or cold atmospheric air to burn CO and other combustible gases present in the ascending gas. The inflated air may optionally comprise O.sub.2 enrichment. Moreover, gaseous, liquid or solid fuel can be injected into the tuy?res 4 together with the blown air.

(9) The furnace of the instant disclosure further comprises a lower stack 2, preferably of circular or rectangular cross-section, of sufficient diameter or dimensions for solid fuel feed. The diameter or width of the cross section of the stack 2 is greater than the one of the stack 1 sufficient for positioning fuel feeders. In the feeders, located around the junction of the upper stack 1 and the lower one 2, fuel supply ducts 5 may be coupled to ensure that the fuel filler goes into the bed of the furnace, avoiding occurrences of filler drag when using thin materials. As the filler falls on the feeder, preheating, pre-drying and distillation of the volatile fractions present in solid fuels and combustible carbonaceous residues occur.

(10) The lower stack 2 has one or more rows of primary tuy?res 3 which, as well as the secondary tuy?res described above, serve to blow hot or cold air and can be enriched with O.sub.2 or not. It is also possible to inject powder, liquid or gaseous solid fuels for partial combustion of the fuel, producing gas and providing the thermal energy necessary for the reduction and/or melting of the filler.

(11) If hot air is blown in the primary and/or secondary tuy?res 4, blower assemblies 7, which can be connected with any air heating system (not shown) known from the prior art, can be used.

(12) Optionally, the lower stack 2 may have refractory lining and/or have refrigerated panels.

(13) Furthermore, the furnace according to the instant disclosure comprises at least one permeabilizer fuel column fed through at least one hood extending longitudinally through the furnace, as shown in said FIG. 1. This hood 6, which can be a vertical duct positioned in the central vertical axis of the furnace, consists of an equipment that serves to channel the gas generated countercurrent with the flow of the filler, allowing a better control of the gas distribution of the entire upper stack 1. Therefore, the instant disclosure provides an excellent control of the energy exchange between the gas and the filler, enabling the reduction of self-reducing agglomerates homogeneously and generating gains of operational stability of the process.

(14) The hood 6 is placed on top of the upper stack 1 and extends longitudinally through the furnace, preferably being limited above the secondary tuy?res 4. In one embodiment, the hood 6 preferably consists of a set of structured panels made of cast iron, steel or any other alloy, filled with refractory concrete and anchored in a sheet welded in the furnace structure. The hood 6 may also be fully or partially made of a refrigerated panel. During operation, part of the hood 6 is buried in the filler, forcing the passage of the generated gases both in the region of the primary tuy?re 3 and in the region of the secondary tuy?res 4, that is, the hood acts as a gas channeling

(15) It should be noted that there is a region, called the cohesion zone 11, where the softening and melting of the metallic filler occurs and, as a result, it is the zone of lower permeability, which considerably hinders gas passage. This difficulty in the passage of gas causes a preferential passage of the gas at specific points of the upper stack 1, making it impossible to control the gaseous flow and causing an irregular thermal exchange between the filler and the gas. The basic operating model provides for the placing of a volume of permeabilizing fuel as a fillher in the center, which not only provides thermal input, but also has the function of ensuring the passage of the gases in the cohesion zone 11, as shown in FIG. 2. When the metallic filler melts, it forms a zone of liquid and slurry material of very low permeability (cohesion zone 11). When a volume of the permeabilizing fuel is placed as a filler together with the metal charge in the upper part of the furnace, it allows the gases from the bottom vessel to reach the upper vessel easily. Thus, ideally the permeabilizer fuel is formed from at least one material which does not melt at internal temperatures of the metallurgical furnace, preferably the carbon base (C), such as, for example, metallurgical coke, petroleum coke, mineral coal, Charcoal, anthracite, briquette fuel, inter alia.

(16) Moreover, a filler means 8 is provided to enable charging of the permeabilizing fuel into the furnace. Such filler means 8 may be preferably a simple system, for examples, containing an enclosed silo 9 and an open silo 10, with metering valves in the discharge of each silo; it may optionally have a pressure equalization system to enable the charging of the permeabilizer fuel from the closed silo into the furnace. The filler means 8 together with the hood 6 enables a channeling of the gas generated in the combustion of the fuel from the lower stack 2 with the air blown by the primary tuy?res 3 and secondary tuy?res 4, more efficiently controlling the gas distribution in the furnace.

(17) FIGS. 3A and 3B show the difference in the gaseous flow of the furnace 12 of the instant disclosure with respect to the gaseous flow of the furnace 13 described in the prior art document. It is noted that in the furnace of the instant disclosure there is a channeling of the gas generated due to the area of increased permeability formed by the permeabilizer fuel charge by the filler means 8. As mentioned above, this allows a greater control of the permeability of the upper stack 1, thus controlling the energy exchange between the gas and the filler, allowing the reduction of self-reducing agglomerates in a homogeneous way generating gains of operational stability of the process.

(18) The configuration of the hood 6 defines the filler distribution in the furnace 12. Hence, the filler takes the dimensions imposed by it, that is, the width between the walls of the hood 6 is the width of the permeabilizing fuel column in the upper tub that will obey the dimensions and distances between the walls. During operation, part of the hood 6 is buried in the filler, forcing the passage of the generated gases both in the region of the primary tuy?re 3 and in the region of the secondary tuy?res 4, as shown in FIG. 5.

(19) Thus, the furnace of the instant disclosure prevents the fuel from being fully charged with the filler at the top of the stack, therefore differing from the classical manufacturing processes and minimizing carbon gasification reactions (Boudouard's reactions) and increase both of the heat and fuel consumption in the furnace.

(20) Furthermore, the furnace of the instant disclosure differs from the other prior art furnaces because permeabilizing fuel is used in small quantities in the top of the stack in order to obtain only a control of the permeability of the upper stack 1. In general, the use of this permeabilizing fuel does not affect the reduction and melting of the filler, since in this furnace self-reducing briquettes (but not just them) are used. In this case, the carbon required to reduce the filler is contained within the self-reducing briquette, thus not requiring that all the gas pass through the filler column as is the case of prior art conventional furnaces and in the classic manufacturing processes.

(21) Countless variations affecting the scope of protection of this application are allowed. Therefore, it is to be emphasized that this invention is not limited to the specific configurations/embodiments described above.