Claims
- 1. A method for improving the control and efficiency of a combustion reaction in a flash smelting furnace, comprising the steps of:
- a. mixing a first oxidizing gas having a first oxygen concentration with solid particles consisting of at least one combustible component and at least one incombustible component;
- b. directing said mixture of solid particles and oxidizing gas into a combustion chamber of said flash smelting furnace;
- c. burning said mixture of solid particles and oxidizing gas in a first flame portion to provide for the heat release capable of converting at least part of said particles into liquid droplets;
- d. directing an auxiliary fuel into said combustion chamber to surround said first flame portion;
- e. directing a second oxidizing gas having a second oxygen concentration into said combustion chamber to surround said first flame portion and mix with said auxiliary fuel;
- f. burning said auxiliary fuel and said second oxidizing gas to create a second flame portion surrounding said first flame portion; and
- g. controlling the flow of said first and second oxidizing gases and said auxiliary fuel to provide a temperature gradient between said first flame portion and said second flame portion for maintaining a desired temperature of said particles during smelting.
- 2. The method of claim 1, which further includes the steps of:
- a. directing a third oxidizing gas having a third oxygen concentration into said first flame portion in said combustion chamber; and
- b. controlling the flow of said third oxidizing gas to maintain a desired temperature in the said first flame portion.
- 3. The method of claim 1, which further includes the steps of:
- a. collecting a residue produced by the smelting of said particles inside said furnace in a furnace residue collecting volume; and
- b. directing a fourth oxidizing gas having a fourth oxygen concentration toward said furnace residue collecting volume to further oxidize said residue.
- 4. The method of claim 1, which further comprises the steps of:
- a. collecting a residue produced by the smelting of said particles inside said furnace in a furnace residue collecting volume; and
- b. introducing fluxing materials into said residue.
- 5. The method of claim 1, which further includes the step of introducing fluxing material into said mixture of solid particles and oxidizing gas.
- 6. A method of claim 1, which further includes the steps of:
- a. collecting a residue produced by the smelting of said particles; and
- b. introducing solid material into said residue through an opening in said furnace wall.
- 7. The method of claim 2, wherein at least one of said oxidizing gases is selected from the group consisting of pure oxygen, air, and oxygen-enriched air.
- 8. The method of claim 3 wherein at least one of said oxidizing gases selected from the group consisting of pure oxygen, air and oxygen-enriched air.
- 9. The method of claim 1, wherein at least one of the combustible components of said solid particles is carbon.
- 10. The method of claim 1, wherein at least one of the combustible components of said solid particles is sulfur.
- 11. The method of claim 1, which further includes the step of controlling the ratio of the amount of total combustible material to total oxygen introduced into said combustion chamber.
- 12. The method of claim 1, wherein said particles contain at least one metallic component.
- 13. The method of claim 12, wherein said metallic component is copper.
- 14. A method for improving the control and efficiency of a combustion reaction in a flash smelting furnace, comprising the steps of:
- a. mixing a first oxidizing gas having a first oxygen concentration with solid particles consisting of at least one combustible component and at least one incombustible component;
- b. directing said mixture of solid particles and oxidizing gas into a combustion chamber of said flash smelting furnace;
- c. burning said mixture of solid particles and oxidizing gas in a first flame portion to provide for the smelting of said solid particles;
- d. directing an auxiliary fuel into said combustion chamber to surround said first flame portion;
- e. directing a second oxidizing gas having a second oxygen concentration into said combustion chamber to surround said first flame portion and mix with said auxiliary fuel;
- f. burning said auxiliary fuel and said second oxidizing gas to create a second flame portion surrounding said first flame portion;
- g. directing a third oxidizing gas having a third oxygen concentration into said first flame portion in said combustion chamber; and
- h. controlling the flow of said first, second, and third oxidizing gases and said auxiliary fuel to provide a temperature gradient between said first flame portion and said second flame portion for maintaining a desired temperature of said particles during smelting.
- 15. A flash smelting apparatus for the treatment of solid particles having at least one combustible component and at least one incombustible component which comprises:
- a. a combustion chamber receivably attached to a burner;
- b. first means for separately introducing said particles to said burner;
- c. second means for separately introducing a first oxidizing gas to said burner, said first oxidizing gas mixing with said particles within said burner to create a first flame portion within the combustion chamber;
- d. third means for separately introducing an auxiliary fuel preferably through a plurality of holes in said burner such that said auxiliary fuel surrounds said first flame portion in said combustion chamber; and
- e. fourth means for separately introducing a second oxidizing gas preferably through a plurality of holes in said burner such that said second oxidizing and said auxiliary fuel mix within said combustion chamber to create a second flame portion that surrounds said first flame portion.
- 16. The apparatus of claim 15, which further comprises means for separately directing a third oxidizing gas having a given oxygen concentration into said burner such that said third oxidizing gas mixes with said particles and said first oxidizing gas in said first flame portion.
- 17. The apparatus of claim 15, which further comprises:
- a. means for collecting a residue created by the combustion of said particles in said combustion chamber; and
- b. means for separately directing a fourth oxidizing gas having a given oxygen concentration toward said residue.
- 18. The apparatus of claim 15, which further comprises means for introducing fluxing material into said first flame portion.
- 19. The apparatus of claim 15, which further comprises:
- a. means for collecting a residue created by the combustion of said particles in said combustion chamber; and
- b. means for introducing fluxing material into said residue.
- 20. The apparatus of claim 15, which further comprises:
- a. means for collecting a residue created by the combustion of said particles in said combustion chamber; and
- b. means for introducing solid material into said residue.
- 21. The apparatus of claim 15, which further comprises means for controlling the flow rate of said particles, said first and second oxidizing gases, and said auxiliary fuel.
- 22. A flash smelting apparatus for the treatment of solid particles having at least one combustible component and at least one incombustible component which comprises:
- a. a combustion chamber receivably attached to a burner;
- b. first means for separately introducing said particles to said burner;
- c. second means for separately introducing a first oxidizing gas to said burner, said first oxidizing gas mixing with said particles within said burner to create a first flame portion within the combustion chamber;
- d. third means for separately introducing an auxiliary fuel preferably through a plurality of holes in said burner such that said auxiliary fuel surrounds said first flame portion in said combustion chamber;
- e. fourth means for separately introducing a second oxidizing gas preferably through a plurality of holes in said burner such that said second oxidizing gas and said auxiliary fuel mix within said combustion chamber to create a second flame portion that surrounds said first flame portion; and
- f. fifth means for separately introducing a third oxidizing gas preferably through a plurality of holes in said burner such that said third oxidizing gas mixes within said particles and said first oxidizing gas in said first flame portion.
BACKGROUND OF THE INVENTION
This is a continuation-in-part of U.S. patent application No. 07/199,248 filed on May 26, 1988 U.S. Pat. No. 4,890,562.
The present invention relates to an apparatus and method of flash smelting. More particularly, the invention relates to a method of controllable oxidation of the combustible components of dispersible particles in a smelting apparatus to provide for improved control over the heat release and temperature distribution during the flash smelting process.
Flash smelting furnaces are used in the extraction of metals to alter the physical and chemical properties of solid ore particles or concentrates to allow separation of their components. The particles are partially or completely melted to change their physical properties and their combustible components are partially or completely oxidized to change their chemical properties. When utilized in a primary metal industry, a flash smelting process extracts a metal, such as copper, from its sulfur-containing ore by passing finely ground ore or concentrates through a high-temperature flame, which melts the concentrates and oxidizes the sulfur. The molten matte is then separated from the molten slag. Frequently, additional fluxing material, such as silica, is mixed with the ore particles prior to their introduction into the flash furnace.
An ore is suitable for a flash smelting process if the energy given off by the oxidation of the combustible components satisfies the sustained high-temperature requirements of the process. Thus, it is desirable to burn ores rich in sulfur, such as copper, in a highly concentrated oxygen stream, such as pure oxygen or oxygen-enriched air, because a major fraction of the heat utilized for flash smelting is generated in situ by the exothermic oxidation reactions. This flash smelting process allows for a significant reduction in the amount of auxiliary energy necessary to smelt the ore compared to reverberatory type furnaces.
Because sulfur sublimates at a very low temperature, it is easy to oxidize gaseous sulfur during the limited time available inside the flame. However, a substantial sulfur content of the particles is essential for conducting the flash smelting process.
The efficiency and stability of a flash smelting process depends in part on the amount of heat being released and transferred to the particles within the flash burner flame envelope prior to their accumulation in the molten bath. This amount, in turn, depends in part on the rate that heat is released from the oxidation reactions occurring in the flash burner flame envelope. When the amount of heat being transferred to the particles, while they are resident in the flash burner flame envelope, decreases, the average temperature of particles heated in the flame decreases. The resulting lower molten bath temperature, in the case of copper ore smelting, reduces the rate of reaction inside the melt, slows the rate of separation of the matte from the slag, and produces deposits of solidified magnetite slag within the furnace. This slag build-up contributes to a further deterioration of the heat transfer properties within the furnace. Eventually, if this cycle continues, the smelting process must be interrupted and the furnace cleaned.
Thus, to prevent unnecessary interruptions in the continuous flash smelting process, the stability of the process must be maintained. This stability can be challenged by reduced ore concentrate feed rates when the concentrate feed system fails, by deviations in the physical or chemical properties of the concentrates, or by an uneven oxidizing gas flow. There have been many attempts to solve this problem.
Some flash smelting furnaces provide for injection of coke with the ore concentrates along with additional oxygen flow to introduce additional fuel and oxidizer into the flame envelope during such upset conditions. Unfortunately, this procedure typically results in the discharge of excessive carbon monoxide and soot into the flue gas treatment train because of the short retention time available for the carbon particles to be oxidized in the flame envelope.
Other smelting furnaces employ additional burners to heat the molten bath and the flash smelting furnace interior. Such use of auxiliary burners enhances the process performance by reducing the dependency of the process on the energy released within the flame envelope, especially when the smelting process is temporarily interrupted by failures upstream or downstream from the smelting furnace. Unfortunately, the use of auxiliary burners does not contribute directly to the heating and melting of the solid particles inside the flash burner flame envelope. Furthermore, the use of auxiliary burners does not control the flash burner flame temperature and, therefore, does not control the amount of heat lost from the flash burner flame to the furnace environment. Therefore, the advantage of the these auxiliary burners is limited to the partial maintenance of the overall furnace interior temperature. This auxiliary energy input does not have a substantial effect on the processes taking place within the flash burner flame envelope.
Although more sulfur in the ore concentrates could be oxidized to increase the heat transferred to the solid particles within the flame envelope, excessive oxidation of the sulfur results in reduced concentrations of sulfur in the matte. This lowered concentration can create a heat deficiency when the matte is oxidized in the converter. The use of carbon particles as an auxiliary fuel is capable of only marginally reducing the share of heat needed from sulfur oxidation inside of the flash smelting burner.
Therefore, a need exists for an improved flash smelting method and apparatus to maintain better control over the temperature distribution inside the flash flame burner envelope by use of an auxiliary fuel capable of rapid oxidation inside the flame envelope of the flash burner. Furthermore, there is a need for a method and apparatus that provides improved control over the combustion reactions occurring and the heat transfer properties of the flash burner flame envelope.
The use of carbon-bearing particles as an auxiliary fuel, introduced by mixing with concentrates, is limited because of the relatively slow rate of carbon oxidation compared to sulfur inside the flash burner flame. For solid dispersible material containing carbon as a major or sole combustible component, the use of existing flash smelting processes cannot be effectively implemented due to a limited rate of carbon oxidation inside the flash burner flame. Because of the difficulties inherent in flash smelting carbon-bearing solids, there also exists a need for a method and apparatus that efficiently flash smelts these solids with the use of an auxiliary fuel that can be easily oxidized inside the flash burner flame envelope.
The use of an existing flash smelting process cannot be recommended to thermally decontaminate carbon-bearing dispersible materials containing a hazardous component. The main reason for the non-suitability of an existing flash smelting apparatus for thermal decontamination purposes is the possibility of incomplete decontamination and leachability of hazardous components from the solid residue generated in the flash smelting chamber. However, many hazardous solid wastes having substantial carbon and/or sulfur content may be converted, at least partially, into melt using the flash smelting method. Incineration of cyanide contaminated spent pot liner from the primary aluminum industry is one such example. This waste has typically more than 30% of carbon and should be converted to unleachable slag to become environmentally safe. Therefore, there exists a need for a flash incinerating method and apparatus capable of converting carbon and/or sulfur-bearing wastes into environmentally safe slag and environmentally safe exhaust gases.
US Referenced Citations (3)
Continuation in Parts (1)
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Number |
Date |
Country |
| Parent |
199248 |
May 1988 |
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Patent Grant
5042964
