CN-121986176-A - Method and system for producing low-carbon ferrochrome by chromite ore and low-carbon ferrochrome produced by same

Abstract

The present invention relates to a method and system for recovering low carbon ferrochrome from a feed material comprising chromite ore and aluminium particles by an aluminothermic smelting process using an inert gas, such as argon, in an electric arc furnace hearth. The aluminothermic smelting process produces a pool of molten low carbon ferrochrome metal on which molten slag floats in the chamber. The molten low carbon ferrochrome metal and molten slag are separately extracted and processed to provide a solidified low carbon ferrochrome metal product and a solidified slag particle product, respectively. A method for recycling, recovering and reusing the inert gas, and a system for achieving recycling, recovering and reusing the inert gas.

Inventors

• Daniel. Shaw
• Adrian Jacobs Van der Mewe
• Ottomar Alois Lange

Assignees

• 美国MM金属有限公司

Dates

Publication Date

20260505

Application Date

20240731

Priority Date

20230802

Claims (20)

1. 1. A system for producing low carbon ferrochrome from chromite ore, said system comprising: An aluminum particle source having a low magnesium and copper content; Forging a lime source; a source of chromite ore containing chromite and iron oxide; An argon source; A conveyor configured to convey the aluminum particles, the wrought lime, and the chromite ore as a feed material mixture to a chamber of a Direct Current (DC) plasma arc furnace via a feed material injection system, the proportion of the feed material of the mixture as determined by thermochemical calculations for reducing the chromium oxide and iron oxide to form low-carbon ferrochrome metal; A conduit configured for delivering the argon gas into the chamber via a feed material injection system; The Direct Current (DC) plasma arc furnace includes a single transferred arc electrode or cathode electrode, an anode electrode, a Direct Current (DC) power source, and a support for holding the single transferred arc cathode electrode extending into and above the anode electrode, the DC power source configured to provide power to the DC arc cathode electrode when the argon gas is in the chamber to produce a plasma arc to heat the feed material in the chamber to a temperature in the range of about 1660 ℃ to 1850 ℃, wherein the aluminum in the aluminum particles acts as a reductant to produce an exothermic reaction to reduce the chromium oxide and iron oxide in the chromite ore to produce a molten material pool in the chamber above the anode electrode, the molten material pool comprising molten low carbon ferrochrome metal with molten slag floating on top of the molten low carbon ferrochrome metal.
2. 2. The system of claim 1, wherein the single transferred arc electrode or cathode is formed of graphite, and wherein the anode comprises an outer anode system formed of copper and an inner anode system formed of a conductive refractory material.
3. 3. The system of claim 2, wherein the DC plasma arc furnace is configured such that the argon acts as a carrier gas to inject the feed material mixture into the chamber.
4. 4. The system of claim 3, wherein the support holding the single transferred arc graphite electrode or cathode is configured to move the single transferred arc graphite electrode or anode such that a portion extends into the chamber, the support being capable of controlling a height for establishing the single transferred arc graphite electrode or cathode relative to the feed material until a desired power is established to create the pool of molten material in the chamber, the power varying with a feed rate at which the feed material is introduced into the chamber by the argon gas.
5. 5. The system of claim 1, wherein the DC plasma arc furnace comprises a tap hole from which the molten low carbon ferrochrome metal may be caused to flow, and wherein the system further comprises an ingot caster having a plurality of molds configured to cast the molten low carbon ferrochrome metal into a plurality of ingots.
6. 6. The system of claim 5, further comprising a crusher device for crushing and crushing the ingot into smaller pieces of low carbon ferrochrome metal.
7. 7. The system of claim 1, wherein the DC plasma arc furnace comprises a tap hole from which the molten slag may be caused to flow, and wherein the system further comprises a water chiller configured to quench the molten slag into quenched slag particles.
8. 8. A system according to claim 3, wherein the argon is provided into the chamber at a pressure above atmospheric pressure to prevent air from entering the chamber.
9. 9. The system of claim 1, wherein the system further comprises an apparatus configured to receive gas from the chamber to produce recovered argon from the chamber and to provide the recovered argon for reintroduction into the chamber.
10. 10. The system of claim 9, wherein the apparatus comprises a scrubber.
11. 11. The system of claim 1, wherein the electric arc furnace comprises a hood and associated conduits for collecting furnace off-gas and other solid material ejected from the chamber and for conveying the solid material via the scrubber to a dust recovery bin or other collector.
12. 12. The system of claim 1, further comprising a dryer for drying the chromite ore.
13. 13. The system of claim 1, further comprising a main argon supply tank and a recovery argon supply tank, each of the main argon supply tank and the recovery argon supply tank configured to provide the argon to the system.
14. 14. The system of claim 1, wherein the DC plasma arc furnace comprises a ferrochrome tap hole and a slag tap hole, the molten low carbon ferrochrome metal can be caused to flow from the ferrochrome tap hole and the molten slag can be caused to flow from the slag tap hole, and wherein the DC plasma arc furnace is mounted on a tiltable mount configured to allow tilting of the DC plasma arc furnace relative to a vertical axis to enable controlled emptying of the contents of the chamber.
15. 15. A system for recovering ferrochrome metal or another ferroalloy in a chamber of an electric arc furnace using a aluminothermic smelting process, wherein the aluminothermic smelting process is performed in the presence of an inert gas introduced into the chamber, whereby furnace off-gases comprising the inert gas and dust particles are produced during the smelting process, the system comprising: A main inert gas supply tank; An exhaust gas conduit configured to be coupled to the electric arc furnace and form an upstream component of a gas flow path from the electric arc furnace, whereby the furnace exhaust gas is conveyed into the gas flow path through the exhaust gas conduit; a primary damper located in the gas flow path downstream of the exhaust duct and coupled to a vent in communication with ambient atmosphere; a dust separation cyclone apparatus located in the gas flow path downstream of the main damper and configured to cool the furnace off-gas from the main damper and configured to remove dust particles from the furnace off-gas; A heat exchanger located in the gas flow path downstream of the dust separation cyclone apparatus for further cooling the furnace exhaust gas from the dust separation cyclone apparatus, thereby producing cooled furnace exhaust gas; A buffer tank having an interior at atmospheric pressure and an outlet coupled to the interior of the buffer tank, the buffer tank being located in the gas flow path downstream of the heat exchanger for receiving the cooling furnace exhaust gas from the heat exchanger; An induced draft fan located in the gas flow path between the heat exchanger and the buffer tank for drawing cooled furnace off-gas from the heat exchanger and providing cooled furnace off-gas to the interior of the buffer tank whereupon the inert gas drips to a bottom portion of the interior of the buffer tank and exits from the outlet; A pressurized tank located in the gas flow path downstream of the buffer tank, the pressurized tank having an inlet and an outlet, and A gas compressor located in the gas flow path between an outlet of the buffer tank and an inlet of the pressurization tank, the gas compressor configured to compress cooled furnace gas from the outlet of the buffer tank to a desired pressure to produce compressed cooled inert gas and to deliver the compressed cooled inert gas to the pressurization tank, the pressurization tank coupled to the main inert gas supply tank for receiving inert gas from the main inert gas supply tank, whereupon the inert gas supplements the compressed cooled furnace gas in the pressurization tank to produce pressurized reclaimed inert gas, the pressurization tank coupled to the furnace to deliver the pressurized reclaimed inert gas from the pressurization tank back to the electric arc furnace.
16. 16. The system of claim 15, wherein the inert gas is argon, and wherein the system further comprises a feed material source comprising chromite ore, aluminum particles, and wrought lime, the feed material being fed into the chamber along with the argon.
17. 17. The system of claim 15, wherein the exhaust conduit is water cooled.
18. 18. The system of claim 15, wherein the dust separation cyclone apparatus is water cooled.
19. 19. The system of claim 15, wherein the main damper is configured to control a furnace port pressure by restricting gas flow downstream of the furnace and is configured to prevent all gas downstream of the furnace from flowing to the dust separation cyclone apparatus.
20. 20. The system of claim 15, wherein the heat exchanger is a tube cooler.

Description

Method and system for producing low-carbon ferrochrome by chromite ore and low-carbon ferrochrome produced by same Cross Reference to Related Applications The present PCT application claims priority under 35 u.s.c. ≡120 of application serial No. 18/756,430 filed on 27 of 2024, which is in turn a continuation of PCT/US2020/035842 entitled "method and system for producing low carbon ferrochrome from chromite ore and low carbon ferrochrome produced thereby", and which is in turn a continuation of U.S. patent application serial No. 18/229,467 entitled "method and system for producing low carbon ferrochrome from chromite ore" filed on 10 of 2021, 11, and which is in turn a continuation of U.S. patent application serial No. 17/523,087 entitled "method and system for producing low carbon ferrochrome from chromite ore" filed on 3 of 2020, 6, and which is in turn a continuation of PCT/US2020/035842 entitled "method and system for producing low carbon ferrochrome from chromite ore and low carbon ferrochrome produced thereby", and which is entitled "method and system for producing low carbon ferrochrome from chromite ore and low carbon ferrochrome produced thereby" filed on 27 of 2019, which is filed on 27 of US, and which is published in U.s.s. patent application serial No. 17 of No. 16, which is filed on 2019, and which is hereby incorporated by reference. Technical Field The present invention relates generally to alloy forming and, more particularly, to a method and system for producing low carbon ferrochrome from chromite ore and the low carbon ferrochrome produced thereby. Description Background Low carbon ferrochrome ("LC FeCr") is a versatile, commodity product, the most common use of which is for "trimming" high chromium content steels in ladle furnaces where carbon introduction from high carbon ferrochrome is unacceptable. Several low carbon ferrochrome with different contents of carbon, silicon and nitrogen can be produced from chromite. LC FeCr can be manufactured from chromite ore by a variety of processes, such as the pelin process and duplex steelmaking process, the seprilex process, etc., all of which use silicon as a reducing agent in the form of ferrosilicon (FeSi) and metallic silicon (SiMet). Aluminum has been used as an alternative reducing agent rather than silicon. By using aluminum (rather than carbon) as a reducing agent, a metal alloy low carbon ferrochrome containing about 70% chromium can be produced. However, from an economic and environmental standpoint, the conventional carbon reductant smelting process for producing LC FeCr from chromite is far from satisfactory. Thus, there is a need for an economical and environmentally friendly system and method for producing low carbon ferrochrome from chromite ore. The present invention addresses this need. Disclosure of Invention One aspect of the invention is a system for recovering low carbon ferrochrome metal from chromite ore. The system includes an aluminum particle source, a wrought lime source, a chromite ore source, an argon source, a conveyor, a conduit, and a Direct Current (DC) plasma arc furnace. The aluminum particles have low magnesium and copper content. Chromite ore contains chromium oxide and iron oxide. The conveyor is configured to convey aluminum particles, wrought lime, and chromite ore as a feed material mixture to a chamber of a Direct Current (DC) plasma arc furnace via a feed material injection system. The proportion of the feed material of the mixture is determined by thermochemical calculations for the reduction of chromium oxide and iron oxide to form low carbon ferrochrome metal. The conduit is configured for delivering argon into the chamber via the feed material injection system. A DC plasma arc furnace includes a single transferred arc electrode or cathode electrode, an anode electrode, a Direct Current (DC) power source, and a support that holds the single transferred arc cathode electrode extending into the chamber and over the anode electrode. The DC power supply is configured to provide power to the DC arc cathode electrode while argon is in the chamber to generate a plasma arc to heat the feed material in the chamber to a temperature in the range of about 1660 ℃ to 1850 ℃, wherein aluminum in the aluminum particles acts as a reducing agent to generate an exothermic reaction to reduce chromium oxide and iron oxide in chromite ore to generate a pool of molten material in the chamber above the anode electrode. The molten material pool includes molten low carbon ferrochrome metal with molten slag floating on top of the molten low carbon ferrochrome metal. According to a preferred aspect of the system of the present invention, the single transferred arc electrode or cathode is formed of graphite, and wherein the anode comprises an external anode system formed of copper and an internal anode system formed of a conductive refractory material. According to another preferred aspect of the system of the present invention,