BLOW LANCE ASSEMBLY FOR METAL MANUFACTURING AND REFINING

Abstract

The instant invention relates to a blow lance assembly for metal manufacturing and refining, developed so as to control slag formation and oxidation, as well as the heat capacity of the reactor, and the conservation of the operational conditions during charging and blowing, having, in its lower part, two groups of gas outlets which determine two blowing conditions, the first group consisting of oxygen passage nozzles having a converging-diverging shape, main responsible for the oxidation reactions and for the conveyance of the basic solid material, mainly calcium oxide, for initial slag formation, and dephosphorization at the final stages during batch refining; the second group consisting of secondary jets with various functions during each blowing stage, the first function, at the beginning of the process as an afterburning agent, through the reaction of oxygen with carbon monoxide generated by the main jets, and the second function being that of accelerating the reaction with carbon by increasing oxygen jet speed, accelerating scrap melting in the early stages and, finally, incrementing the oxidation of the elements of the metal bath, iron, in order to reduce the phosphorus content in the final stages of batch refining.

Claims

1. A blow lance assembly for manufacturing and refining metals, comprising a lower afterburning module (114) built into a copper nozzle (101), and including secondary outlets for lower oxygen (116) and combustible gases (117), which surround a converging-diverging primary oxygen outlet (115), and in which a main oxygen pipe (105) contains in its interior a pulverized solid material injection pipe (119).

2. The blow lance assembly, according to claim 1, in which said assembly has secondary outlets for oxygen (116) and combustible gases (117), with independent control of primary oxygen.

3. The blow lance assembly, according to claim 1, in which injection of the pulverized solid material through the pipe (119) is carried out continuously.

4. The blow lance assembly, according to claim 1 in which oxygen is the carrier gas.

5. The blow lance assembly, according to claim 1, in which, during injection intervals, when fractioned addition is carried out, an inert gas is used as conductor of the particulate material.

6. The blow lance assembly, according to claim 5, in which the inert gas is argon.

7. The blow lance assembly, according to claim 5, in which the inert gas is nitrogen.

8. The blow lance assembly, according to claim 1, in which the powdered solid material injection pipe (119) extends to the copper nozzle side (101).

9. The blow lance assembly, according to claim 1, including a flow driver adapted at the powdered solid material outlet (119).

10. The blow lance assembly, according to claim 1, in which the powdered solid material injection pipe (119) works at injection rates ranging from 50 kg/min to 1500 kg/min.

11. The blow lance assembly, according to claim 1, in which the lower oxygen secondary outlet (116), ring- or point-shaped, is connected with the main oxygen pipe (105).

12. The blow lance assembly, according to claim 1, in which the lower oxygen secondary outlet (116), ring- or point-shaped, is connected with an auxiliary gas-supply chamber (117).

Description

DESCRIPTION OF THE INVENTION

[0021] In its lower part, the lance has two groups of gas outlets which determine two blow conditions. The first group consists of oxygen passage nozzles with converging-diverging shape, primarily responsible for oxidation reactions and for the transport of basic solid material, mainly calcium oxide, for the initial formation of slag and dephosphorization in the final stages during batch refining. The second group consists of secondary supersonic jets with varied functions at each stage of the blowing process. The first function, early in the process, as afterburning agent, through the reaction of oxygen with carbon monoxide generated by the main jets. The second function, contributing to accelerate the reactions with carbon by increasing the oxygen jet speed, accelerating the scrap melting in the initial stages, and ultimately increasing the oxidation of the metal bath elements, iron, in order to reduce the phosphorus in the final stages during batch refining.

[0022] In order to illustrate the metal refining process, FIG. 1 shows a side section of an oxygen furnace, the furnace consisting of an external container, a metallic housing (201), open at the top, in the mouth of the furnace (207), wherein the oxygen furnace is internally coated with refractory bricks (202) of which the function is to protect the metallic housing (201) from the extreme refining conditions during the oxygen blowing process. During the metal production process, the furnace contains four different materials: liquid metal (301), scrap (302), slag (303) resulting from oxidation of the liquid metal elements and adding slag-forming agents, and gases (305) from the refining reactions. During the blowing process, a mixture of metal (301), slag (303) and gases (305), called emulsion, is formed, which occupies a large volume of the furnace. Above the furnace, there is a dust removal duct (208) for capturing gases (305) and smokes generated in the refining process, with an opening, or dome (209) for the passage of the lance (100) inside the oven to begin the liquid metal refining process. To start the refining process, the lance (100) is positioned at a certain distance above the metal bath, said distance being called LBDlance-bath distance (401) in relation to the height of the static bath (400) During the refining process, scrap (302) is melted gradually, incorporating the metal bath (301). Oxygen (300) reacts with the metal bath (301) initiating the formation of slag (303) and generating gases (305), forming an emulsion region (402). The lance (100) is immersed in the emulsion (402), which causes its adhesion to the lance or the formation of a lance scale (403). The same occurs in the region of the furnace cone (206) and the furnace mouth (207), resulting in the formation of a mouth scale (404), caused both by the emulsion (402) and by the projection of slag and metal (203) as splashes or scattering. Further layers of lance scale (403) adhere to the lance (100), compromising its passage through the lance dome (209), which makes necessary to stop the production in order to carry out cleaning and, in many cases, replacement by a clean lance (100). The same phenomenon occurs in the region of the cone (206) and mouth (207) of the furnace, and it is necessary to stop production activities in order to clean the area, facilitating the charging of scrap (302) and metallic bath (301).

[0023] FIG. 2 shows a sectional view of a state of art lance (100), comprising a copper nozzle (101) having, at its end, the oxygen outlets through a varying number of holes and angles with the vertical axis, the main oxygen pipe (105), intermediate pipe (106), the outer pipe (107), in general all made of steel, wherein this lance (100) has also an coolant inlet (108). The liquid, generally water (304), travels to the copper nozzle (101) returning through the outer pipe (107) to the lance outlet (109). The good performance of the lance (100) depends on the water ability to extract heat from the nozzle (101) and from the outer pipe (107).

[0024] FIG. 3 is a sectional view of the lower afterburning module (114) embedded in the copper nozzle (101) and comprising secondary outlets of lower oxygen (116), which surround the convergent-divergent outlet of main oxygen (115). An injection pipe of powdered solid material (119) is inserted inside the main oxygen pipe (105). Unlike the state of art practice, the injection of pulverized solid material through this pipe (119) is carried out by continuous injection, and in this case, oxygen is the carrier gas (300). In case of fractional addition, similarly to the state of art practice, during non-injection intervals, an inert gas (307), generally argon or nitrogen, is used. The powdered solid material injection pipe (119) is brought close to the copper nozzle (101) in order to prevent the formation of suspended material in the main oxygen pipe (105). At the outlet of the pulverized solid material pipe (119) there may be a flow driver adapted to convey the pulverized solid towards the main oxygen (115) outlets, suitably sized to transport gases and solids. The powdered solid material injection pipe (119) can work with injection rates ranging from 50 kg/min to 1500 kg/min, and may extend to the surface of the copper nozzle (101) in order to unload the material intended for the converter environment.

[0025] In the configuration shown, the lower oxygen secondary outlet (116), ring- or point-shaped, is connected to the main oxygen pipe (105) and aims at achieving an afterburning which facilitates scrap (302) melting in the initial moments of blowing, and may also be connected with the auxiliary gas-supply chamber (117). For large amounts of scrap placed into the furnace, the insertion of an auxiliary gas-supply chamber (117) is provided, which can be crossed by oxidizing gases, such as oxygen itself (300), and combustible gases (305), contacting the furnace environment (200) through the secondary gases outlet (118). The auxiliary gas-supply chamber (117) is intended to enable individual control of pressure and flow conditions. Therefore, if this camera is used for oxygen (300) passage, early in the refining process, the condition of intermediate pressure and flow favors the scrap (302) melting, and afterburning results in the formation of initial slag (303), rich in iron oxide, favoring the dissolution of other slag-forming agents. Subsequently, during the decarburization step, the condition changes to high pressure and flow, contributing to an increase in carbon removal rate during the refining process of the metal bath (301). Finally, at the end of processing, the condition of low flow and pressure and of increased slag (303) oxidation occurs, contributing to phosphorus retention. In cases of extremely high temperatures, inert gases with coolant properties or even purging agents may be used to prevent the closure of the secondary gas outlets (118).