METHOD OF OPERATING AN ELECTRIC ARC FURNACE AND STEEL MILL

Abstract

The disclosure discloses a method of operating an electric arc furnace, the method comprising capturing, from at least one facility of a steel mill, a heated metallurgical gas comprising water and carbon monoxide; conducting, by a reactor supply line, said metallurgical gas to a reactor; transforming, by a treatment of said metallurgical gas within said reactor, the carbon monoxide and water into hydrogen and carbon dioxide according to a water-gas shift reaction; and subsequently separating said hydrogen by a separation device. The method is characterized in that it further comprises providing an iron-bearing material, which comprises iron mainly in the form of iron oxide, to the electric arc furnace; at least partially melting the iron-bearing material to obtain a molten bath; conducting, by a furnace supply line, said hydrogen to the electric arc furnace, which is arranged downstream of the furnace supply line; and injecting, by a plurality of hydrogen injection devices, said hydrogen into said electric arc furnace, such that said hydrogen reacts as a reducing agent for reducing iron oxide in the molten bath during a smelting operation of the electric arc furnace.

Claims

1. A method of operating an electric arc furnace, the method comprising: capturing a heated metallurgical gas comprising water and carbon monoxide, from at least one facility of a steel mill; conducting said metallurgical gas to a reactor through a reactor supply line; transforming the carbon monoxide and water into hydrogen and carbon dioxide according to a water-gas shift reaction, by a treatment of said metallurgical gas within said reactor, and subsequently separating said hydrogen by a separation device; providing an iron-bearing material, which comprises iron mainly in the form of iron oxide, to the electric arc furnace; at least partially melting the iron-bearing material to obtain a molten bath; conducting said hydrogen through a furnace supply line to the electric arc furnace, which is arranged downstream of the furnace supply line; and injecting said hydrogen into the molten bath in said electric arc furnace by means of a plurality of hydrogen injection devices such that said hydrogen acts as a reducing agent for reducing iron oxide in the molten bath during a smelting operation of the electric arc furnace.

2. The method according to claim 1, wherein the heated metallurgical gas has a temperature in a temperature range of 20? ? C. to 100? C.

3. The method according to claim 1, wherein the water-gas shift reaction is performed in presence of a catalyst.

4. The method according to claim 1, wherein the method further comprises conducting said hydrogen via a storage supply conduct to a hydrogen storage tank and discharging said hydrogen from said hydrogen storage tank via the furnace supply line to the electric arc furnace.

5. The method according to claim 1, wherein the method further comprises heating said hydrogen upstream of the electric arc furnace, such that said hydrogen has a temperature in a range of 25? C. to 700? ? C. when said hydrogen is injected into said electric arc furnace.

6. The method according to claim 1, wherein the plurality hydrogen injection devices comprises at least one supersonic gas lance for injecting at least a part of said hydrogen supplied to the electric arc furnace into said furnace.

7. The method according to claim 6, wherein hydrogen injected via the supersonic gas lance has a throughput in the range of 10 m.sup.3/min to 500 m.sup.3/min.

8. The method according to claim 1, wherein the method further comprises injecting oxygen into the electric arc furnace through a plurality of oxygen injection devices.

9. The method according to claim 1, wherein the method further comprises introducing lime into the electric arc furnace by a lime introduction device.

10. The method according to claim 1, wherein the method further comprises inserting a material in the electric arc furnace, wherein the material comprises at least one of the following: iron oxide, pre-reduced iron ore pellets, a direct reduced iron, hot briquette iron briquettes, blast furnace grade, DR grade iron ore pellets or fines or mixtures thereof.

11. The method according to claim 1, wherein the method further comprises operating said electric arc furnace with electric energy obtained from a renewable energy source.

12. A steel mill comprising an electric arc furnace and being adapted to: capture a heated metallurgical gas comprising water and carbon monoxide, from at least one facility of the steel mill; conduct said metallurgical gas to a reactor through a reactor supply line; transform the carbon monoxide and water into hydrogen and carbon dioxide according to a water-gas shift reaction, by a treatment of said metallurgical gas within said reactor, and subsequently separate said hydrogen by a separation device; provide an iron-bearing material, which comprises iron mainly in the form of iron oxide, to the electric arc furnace; at least partially melt the iron-bearing material to obtain a molten bath; conduct said hydrogen through a furnace supply line to the electric arc furnace arranged downstream of the furnace supply line; and inject said hydrogen into the molten bath in said electric arc furnace by means of a plurality of hydrogen injection devices such that said hydrogen acts as a reducing agent for reducing iron oxide in the molten bath during a smelting operation of the electric arc furnace.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Embodiments of the disclosure are now described by way of example and with reference to the attached drawings, wherein

[0056] FIG. 1: is a schematic view illustrating the method, the electric arc furnace and the steel mill according to the disclosure;

[0057] FIG. 2: is a schematic view illustrating the electric arc furnace according to the disclosure.

DETAILED DESCRIPTION

[0058] FIG. 1 illustrates a schematic view of the method as well as the electric arc furnace and the steel mill 100 according to the disclosure. The steel mill 100 comprises a facility 12 consisting of a blast furnace 12 emitting heated metallurgical gases comprising water and carbon monoxide. The gas from blast furnace has a temperature in a range of approximately 200? ? C. to 300? C. The metallurgical gas may be cleaned by a scrubber and stored in a gas holder (not shown). As shown on FIG. 1, the metallurgical gases emitted by the blast furnace 12 are captured and guided by/through the reactor supply line 14 to the reactor 16. The metallurgical gas has to be pre-heated for the hydrogen production process, for instance by mixing the metallurgical gas with steam (not shown), wherein the steam provides the heat and the water necessary for the water gas shift reaction.

[0059] Further devices (not shown), such as a temperature sensor, a pressure sensor, a flow meter and (automatic) valves may be arranged on and/or or within the reactor supply line 14. These further devices may be connected to a control unit, such as for example a computer (not shown). The control unit may be configured to determine process parameters related to the metallurgical gas, such as for example the temperature of the metallurgical gas, the pressure of the metallurgical gas and/or the velocity of the metallurgical gas. Depending on these process parameters, the control unit may determine by means of a software whether a valve arranged within the reactor supply line 14 should be fully opened, partially opened or closed.

[0060] The metallurgical gas conducted through said reactor supply line 14 is introduced in the reactor 16, wherein the carbon monoxide and water compounds in the metallurgical gas are transformed into carbon dioxide and hydrogen. The transforming of carbon monoxide and water into hydrogen and carbon dioxide is based on a water-gas shift reaction in presence of a catalyst, such as e.g. a nickel-based catalyst (not shown). Before the metallurgical gas is treated in the reactor, further steps may be carried out upstream of the reactor in order to heat the gas and/or to separate substances, such as e.g. gaseous sulphur compounds, from the metallurgical gas that would otherwise harm the catalyst (not shown).

[0061] After the gas has been treated in the reactor, the gas is conducted to the separation device 18 wherein said hydrogen is separated from the other compounds of the metallurgical gas. In a subsequent step, said hydrogen is either led directly by a furnace supply line 20 to the electric arc furnace arranged downstream of said furnace supply line 20, or via a supply conduct 22 to a hydrogen storage tank 24. In order to operate the passage of said hydrogen towards the tank 24 and/or the electric arc furnace 10, (automatic) valves are arranged within the supply conduct 22 and the furnace supply line 20 (not shown). The valves comprise actuators that are operated by the computer. Additionally, both, the furnace supply line 20 and the supply conduct 22, comprise each a pressure sensor, a flow meter and a temperature sensor (not shown) connected to the computer. Said hydrogen is conducted depending on the requirements of the electric arc furnace 10 either directly into said furnace or into the storage tank 24. In case said hydrogen is stored in the tank 24, said hydrogen may be released at a predetermined rate and/or volume into the electric arc furnace. As can be further derived from FIG. 1, a discharge line 23 for discharging said hydrogen is in fluid communication to the furnace supply line 20. The discharge line 23 comprises a temperature sensor, a flow meter, a pressure sensor and an (automatic) valve, wherein each of these elements is connected to and operated by the control unit (not shown).

[0062] In addition, the furnace supply line 20 may comprise an optional heating arrangement (not shown), wherein the heating arrangement is likewise controlled by the computer. The heating arrangement allows to heat up said hydrogen upstream of the electric arc furnace, such that said it has a temperature in a range of 25? C. to 700? C. when it is injected into said electric arc furnace.

[0063] Said hydrogen is injected into the electric arc furnace 10 through/by a plurality of injection devices 26, as is shown in more detail in FIG. 2. The two dashed horizontal lines inside the furnace symbolize the boundaries between a slag area 34 and a liquid metal area 36. During the operation of the electric arc furnace, a slag layer 34 forms at the surface in proximity to the electrode(s) (not shown). Beneath the slag layer 34, a liquid metal layer 36 is generated after the electric arc furnace 10 is operated for a certain time. The electrode(s) of the EAF are protruding from an upper section, respectively from a furnace hat (not shown), into the slag. In other words, the electrodes are at least partially submerged in the slag.

[0064] The plurality of hydrogen injection devices 26 comprise also a supersonic gas lance 28, which protrudes from an upper section of the furnace, respectively the furnace cover, into the liquid metal area 36. During the operation of the EAF, hydrogen is injected via the supersonic gas lance 28 in a rate which is preferably in the range of 10 m.sup.3/min to 500 m.sup.3/min.

[0065] In addition, the electric arc furnace 10 is also provided with a plurality of oxygen injection devices 30, respectively lances, for injecting oxygen into the electric arc furnace 10. The oxygen injection devices 30 are spaced apart from said hydrogen injection devices 26 and the supersonic gas lance 28. It should be noted that also the oxygen injection devices 26 may comprise or consist of a supersonic gas lance.

[0066] As further shown in FIG. 2, a lime introduction device 32 is protruding into the liquid metal area 32 of the electric arc furnace respectively at the interface between the liquid metal area 32 and the slag area 34. The lime introduction device 32 provides a jet of lime during the operation of the electric arc furnace.

[0067] During the operation of the electric arc furnace, material is inserted in the hearth of the furnace. The material may comprise at least one of the following: scrap iron, iron oxide, pre-reduced iron ore pellets, a direct reduced iron (DRI), hot briquette iron briquettes (HBI), blast furnace grade, DR grade iron ore pellets or fines or mixtures thereof. The electric arc furnace is powered by electric energy, wherein said electric energy is obtained from a renewable energy source.

[0068] The injected hydrogen is used to reduce iron oxides (for example FeO) into iron (Fe) and water according to the following reaction equation:

FeO+H.sub.2.Math.Fe+H.sub.2O.

[0069] In addition, the injected hydrogen is further used to react with oxygen whilst releasing heat according to the following equation:

H.sub.2+?O.sub.2.fwdarw.H.sub.2O.

[0070] The injected oxygen is used to oxidize iron (Fe) according to the following equation:

Fe+?O.sub.2.fwdarw.FeO.

[0071] As can be understood from FIG. 2, the amount of carbon dioxide is totally or at least significantly reduced during the operation of the electric arc furnace 10.

[0072] The discussed embodiments are examples of the disclosure. The described components of each respective embodiment represent each individual features of the disclosure which are to be considered independently of each other. The features are thus also to be regarded as components of the disclosure individually or in a combination other than the combination shown. Furthermore, the described embodiments may also be supplemented by further features of the disclosure already described.

[0073] Further features and embodiments of the disclosure result for the skilled person in the context of the present disclosure and the claims.