Plasma and Oxygas Fired Furnace

Abstract

The present disclosure concerns an apparatus suitable for smelting and separating metals in flexible oxido-reduction conditions. More particularly, it concerns an apparatus for smelting metallurgical charges comprising a bath furnace susceptible to contain a molten charge up to a determined level, characterized in that the furnace is equipped with: at least one non-transfer plasma torch for the generation of first hot gases; at least one oxygas burner for the generation of second hot gasses; and, submerged injectors for injecting said first and second hot gases below said determined level.

Claims

1-10. (canceled)

11. Apparatus for smelting metallurgical charges comprising a bath furnace susceptible to contain a molten charge up to a determined level, characterized in that the furnace is equipped with: at least one non-transferred plasma torch for the generation of first hot gases; at least one oxygas burner for the generation of second hot gasses; and, submerged injectors for injecting said first and second hot gases below said determined level.

12. The apparatus according to claim 11, wherein said at least one burner and at least one torch are located below said determined level.

13. The apparatus according to claim 11, wherein the ratio of a total nominal enthalpy expressed as MJ/s of the oxygas burner(s) to that of the plasma torch(es) is from 1:5 to 5:1.

14. The apparatus according to claim 11, wherein the ratio of the total nominal gas flow rate expressed as Nm̂/s, susceptible to be fed into the oxygas burner(s) to that susceptible to be fed into the plasma torch(es) is from 1:10 to 10:1.

15. The apparatus according to claim 11, wherein the furnace has a generally cylindrical shape, having a circular bottom with a diameter d, and sidewalls with a height h, the ratio of h to d being more than 4.

16. A process for smelting metallurgical charges using the apparatus according to claim 11, comprising: feeding a metallurgical charge including transition metals and slag formers to the furnace; smelting the charge using the oxygas burner(s) as primary enthalpy source, thereby forming an alloy comprising a first part of the transition metals and a slag comprising a second part of the transition metals; treating the slag in strongly reducing conditions using the plasma torch(es) as primary enthalpy source, thereby forming an alloy enriched in transition metals and a slag depleted in transition metals by transferring said second part of the transition metals from the slag to the alloy; and, separating the alloy and the depleted slag by tapping.

17. The process according to claim 16, wherein the submerged injectors are located so as to inject said first and second hot gases into the slag.

18. A process for smelting metallurgical charges using the apparatus according to claim 11, comprising: feeding a metallurgical charge including transition metals and slag formers to the furnace; smelting the charge using the oxygas burner(s) as primary enthalpy source, thereby forming a first alloy comprising a first part of the transition metals and a slag comprising a second part of the transition metals; separating the first alloy by tapping, leaving the slag in the furnace; treating the slag in strongly reducing conditions using the plasma torch(es) as primary enthalpy source, thereby forming a second alloy enriched in transition metals and a slag depleted in transition metals by transferring said second part of the transition metals from the slag to said second alloy; and, separating the second alloy and the depleted slag by tapping.

19. The process according to claim 18, wherein the submerged injectors are located so as to inject said first and second hot gases into the slag.

20. A process for smelting metallurgical charges using the apparatus according to claim 11, comprising the steps of: feeding a metallurgical charge including transition metals and slag formers to the furnace; smelting the charge in strongly reducing conditions using the plasma torch(es) as primary enthalpy source, thereby forming an alloy comprising transition metals and a first slag depleted in transition metals; separating the first slag by tapping, leaving the alloy in the furnace; treating the alloy using the oxygas burner(s) as primary enthalpy source, thereby forming an alloy partially depleted in transition metals and a second slag enriched in transition metals by transferring part of the transition metals from the alloy to the second slag; and, separating the enriched alloy and the second slag by tapping.

21. The process according to claim 20, wherein the submerged injectors are located so as to inject said first and second hot gases into the slag.

Description

EXAMPLE: CU—NI—FE SEPARATION IN A FURNACE EQUIPPED WITH OXYGAS BURNER AND PLASMA Torch

[0029] A batch of 6 tons of roasted Cu—Ni—Fe concentrate with composition according to Table 1 is processed in an open bath furnace to valorize Cu and Ni in an economical and efficient way. The bath furnace is equipped with a 3 MW non-transferred plasma torch connected to a submerged tuyere on one hand, and another submerged tuyere in which a 1.5 MW oxygas burner resides. The inner diameter of the furnace is 1.5 m and the useable height (bottom to feed port) is 7 m.

TABLE-US-00001 TABLE 1 Composition of the feed (wt. %) Cu Ni Fe CaO SiO.sub.2 Al.sub.2O.sub.3 MgO 2.5 5 22 3.8 40 3.8 4

[0030] In a first step, mildly reducing conditions are imposed at 1200° C. with an oxygas burner to reduce much of the Cu present in the concentrate and collect Ni and Fe in a slag phase. In a batch process of 12 h, the abovementioned concentrate is charged at 0.5 ton/h together with 0.1 ton/h of limestone as fluxing agent. To maintain the heat balance of the furnace with a bath temperature of 1200° C. and appropriate lambda of 0.7, the oxygas burner injects 200 Nm.sup.3/h natural gas and 240 Nm.sup.3/h oxygen into the bath. After a 12 h batch, about 160 kg of a first alloy is formed, and 5.8 tons of a Ni—Fe bearing slag. The respective compositions are shown in Tables 2 and 3.

TABLE-US-00002 TABLE 2 Composition of the first alloy (wt. %) Cu Ni Fe 94 1.8 4

TABLE-US-00003 TABLE 3 Composition of the slag (wt. %) Cu Ni Fe CaO SiO.sub.2 Al.sub.2O.sub.3 MgO 0.025 5 22.5 15 41 3.9 4.1

[0031] The alloy is tapped, the oxygas burner is shut down, maintaining a safety flow of nitrogen through tuyere, and the plasma torch is started to heat the slag bath to 1500° C. for Ni and Fe recovery. After a 3 h batch, about 1.6 tons of a Fe—Ni second alloy is obtained, and 4.1 ton of a cleaned slag. The respective compositions are shown in Tables 4 and 5.

TABLE-US-00004 TABLE 4 Composition of the second alloy (wt. %) Cu Ni Fe 0.09 18.5 81.4

TABLE-US-00005 TABLE 5 Composition of the cleaned slag (wt. %) Ni Fe CaO SiO.sub.2 Al.sub.2O.sub.3 MgO 0.02 0.3 30 58 5.5 5.8

[0032] The plasma torch is operated at strongly reducing conditions with 700 Nm.sup.3/h air as plasma gas, and 500 Nm.sup.3/h natural gas to obtain a mean lambda of 0.3 for the injected gases. The electric power to the plasma torch in this process step is 2.3 MW. To maintain a liquid slag, 0.2 ton/h of limestone is added during the slag cleaning step. The example illustrates the use of both heating technologies according to different metals to be recovered.