WO2018042296A1

WO2018042296A1 - Systems and methods for electrode cooling in an electric arc furnace using wastewater

Info

Publication number: WO2018042296A1
Application number: PCT/IB2017/055113
Authority: WO
Inventors: Yousef Ahmed AL SMAIL; Othman AL-ZEGHAIBI; Ahmed Hussein AL-NAZR; Hesham A. HANAFY; Hesham H. AL-AHMED; Tariq T. AL-SHAHEEN; Mohamed Bahgat SADDIK
Original assignee: Sabic Global Technologies B.V.
Priority date: 2016-08-30
Filing date: 2017-08-24
Publication date: 2018-03-08

Abstract

Systems and methods for cooling an electric arc furnace (EAF) using wastewater. Some methods include heating a material disposed with an interior volume an EAF by supplying power to one or more electrodes of the EAF, each being at least partially disposed within the interior volume, and cooling the one or more electrodes using wastewater by transferring heat from the one or more electrodes to the wastewater. Some methods include passing the wastewater through a filter to reduce a total suspended solids content of the wastewater.

Description

SYSTEMS AND METHODS FOR ELECTRODE COOLING IN AN ELECTRIC ARC

FURNACE USING WASTEWATER

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Application No. 62/381,411, filed August 30, 2016, which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field of Invention

[0002] The present invention relates generally to systems and methods for cooling electric arc furnaces, and more specifically, but not by way of limitation, to systems and methods for cooling electric arc furnaces (e.g., electrodes thereof) using wastewater.

2. Description of Related Art

[0003] In the steelmaking industry, an electric arc furnace (EAF) is often used to melt iron, steel, and/or the like. An EAF is a furnace that operates by generating electric arcs between furnace electrodes and metal within the furnace to melt the metal. An EAF can generate a large amount of heat; for example, in certain industrial applications, temperatures within an EAF can reach 1800 degrees Celsius or higher. While the body and lid of an EAF can comprise a refractory material that is capable of withstanding such temperatures, electrodes of the EAF must be made of a material that permits electric arc generation. As a result, electrodes are often consumed over time during use of an EAF.

[0004] In order to slow the rate of electrode consumption and protect components coupled to the electrodes, many EAFs employ a water-based cooling system. Such water- based cooling systems may use a relatively large amount of water to cool EAF electrodes, which, in many instances, comes from fresh water sources. SUMMARY

[0005] Cooling of EAF electrode(s) may not require high-quality water, such as fresh water and/or water that has been purified (e.g., via one or more chemical and/or biological processes) for the purpose of removing certain contaminants, such as ammonia, cyanide, phenols, and/or the like; therefore, using such high-quality water to cool EAF electrode(s) may be wasteful and/or unnecessarily expensive. Some embodiments of the present disclosure can avoid the use of such high-quality water for cooling EAF electrode(s) via, for example, including a cooling system that is configured to cool the electrode(s) with wastewater. Such wastewater can be produced by other steelmaking equipment, such as, for example, a direct-reduced iron (DRI) furnace, blast furnace, smelter, and/or the like (which may be located onsite with the EAF), during, for example, cooling associated with the other steelmaking equipment. In some embodiments, such wastewater can be filtered (e.g., via physical filtration) for the purpose of reducing a total suspended solids (TSS) content of the wastewater, which may mitigate clogging of the cooling system.

[0006] Some embodiments of the present methods comprise: heating a material disposed within an interior volume of an EAF by supplying power to one or more electrodes of the EAF, each being at least partially disposed within the interior volume, and cooling the one or more electrodes using wastewater by passing the wastewater through a filter to reduce a TSS content of the wastewater and transferring heat from the one or more electrodes to the wastewater.

[0007] In some methods, the transferring heat from the one or more electrodes to the wastewater comprises contacting a portion of at least one of the one or more electrodes that is disposed outside of the interior volume with the wastewater. In some methods, the transferring heat from the one or more electrodes to the wastewater comprises spraying the wastewater onto at least one of the one or more electrodes.

[0008] In some methods, the wastewater comprises water that was used to cool a DRI furnace, a blast furnace, and/or a smelter. Some methods comprise heating a material disposed within a chamber of a DRI furnace by supplying reduction gas to the chamber and cooling the material and/or the DRI furnace using water by transferring heat from the material and/or the DRI furnace to the water, thereby producing the wastewater.

[0009] In some methods, the TSS content of the wastewater before passing through the filter is between approximately 50 PPM and approximately 200 PPM. In some methods, the TSS content of the wastewater after passing through the filter is less than approximately 10 PPM. In some methods, the wastewater, after passing through the filter, comprises at least one of: greater than 35 mg/1 of ammonia and greater than 0.5 mg/1 of cyanide.

[0010] Some embodiments of the present systems comprise: an EAF comprising a body, a lid configured to be coupled to the body such that the lid is movable relative to the body between an open position and a closed position in which the lid and the body cooperate to define an interior volume, and one or more electrodes configured to heat a material disposed within the interior volume, and a cooling system configured to cool the one or more electrodes using wastewater by transferring heat from the one or more electrodes to the wastewater. In some systems, the cooling system comprises the wastewater. In some systems, the wastewater comprises at least one of: greater than 35 mg/1 of ammonia and greater than 0.5 mg/1 of cyanide.

[0011] In some systems, the cooling system comprises one or more sprayers configured to spray at least one of the one or more electrodes with the wastewater.

[0012] Some systems comprise a filter configured to reduce a TSS content of the wastewater before heat is transferred from the one or more electrodes to the wastewater. In some systems, the filter is configured to reduce the TSS content of the wastewater to less than approximately 10 PPM.

[0013] In some systems, the system comprises a DRI furnace, a blast furnace, and/or a smelter and the cooling system is configured to receive, as the wastewater, water that has been used to cool the DRI furnace, the blast furnace, and/or the smelter. [0014] The term "wastewater" is defined as water that has been adversely affected in quality by anthropogenic influence. Examples of wastewater include: (1) water that has been used for cooling in a DRI furnace, a blast furnace, and/or a smelter; (2) water having a TSS content that is between approximately 50 PPM and approximately 200 PPM (e.g., before filtering); (3) water having greater than 35 milligram per liter (mg/1) of ammonia and/or greater than 0.5 mg/1 of cyanide; (4) water having a total dissolved solids (TDS) content that is greater than 100 mg/1; and/or (5) water having greater than 50 mg/1 alkalinity.

[0015] As used herein, "water" and "wastewater" includes liquid water and liquid wastewater, respectively, that has transitioned to a gaseous phase.

[0016] The term "coupled" is defined as connected, although not necessarily directly, and not necessarily mechanically; two items that are "coupled" may be unitary with each other. The terms "a" and "an" are defined as one or more unless this disclosure explicitly requires otherwise. In any disclosed embodiment, the term "approximately" can be substituted with "within [a percentage] of what is specified, where the percentage includes .1, 1 , 5, and 10 percent. [0017] Further, a device or system that is configured in a certain way is configured in at least that way, but it can also be configured in other ways than those specifically described.

[0018] The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), and "include" (and any form of include, such as "includes" and "including") are open-ended linking verbs. As a result, an apparatus that "comprises," "has," or "includes" one or more elements possesses those one or more elements, but is not limited to possessing only those one or more elements. Likewise, a method that "comprises," "has," or "includes," one or more steps possesses those one or more steps, but is not limited to possessing only those one or more steps. [0019] Any embodiment of any of the apparatuses, systems, and methods can consist of or consist essentially of - rather than comprise/have/include - any of the described steps, elements, and/or features. Thus, in any of the claims, the term "consisting of or "consisting essentially of can be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open- ended linking verb.

[0020] The feature or features of one embodiment may be applied to other embodiments, even though not described or illustrated, unless expressly prohibited by this disclosure or the nature of the embodiments.

[0021] In the context of the present invention, the present invention relates in embodiment 1 to method including the step of heating a material disposed within an interior volume of an electric arc furnace (EAF) by supplying power to one or more electrodes of the EAF, each being at least partially disposed within the interior volume; and cooling the one or more electrodes using wastewater by passing the wastewater through a filter to reduce a total suspended solids (TSS) content of the wastewater; and transferring heat from the one or more electrodes to the wastewater. Embodiment 2 is the method of embodiment 1, wherein the transferring heat from the one or more electrodes to the wastewater comprises contacting a portion of at least one of the one or more electrodes that is disposed outside of the interior volume with the wastewater. Embodiment 3 is the method of embodiments 1 or 2, wherein the transferring heat from the one or more electrodes to the wastewater comprises spraying the wastewater onto at least one of the one or more electrodes. Embodiment 4 is the method of any of embodiments 1, 2 or 3, wherein the wastewater comprises water that was used for cooling in a direct-reduced iron (DRI) furnace, a blast furnace, and/or a smelter. Embodiment 5 is the method of any of embodiments 1 to 3, including the step of heating a material disposed within a chamber of a DRI furnace by supplying a reduction gas to the chamber; and cooling the material and/or the DRI furnace using water by transferring heat from the material and/or the DRI furnace to the water, thereby producing the wastewater. Embodiment 6 is the method of any of embodiments 1 to 5, wherein the TSS content of the wastewater after passing through the filter is less than approximately 10 parts per million (PPM). Embodiment 7 is the method of any of embodiments 1 to 6, wherein the TSS content of the wastewater before passing through the filter is between approximately 50 PPM and approximately 200 PPM. Embodiment 8 is the method of any of embodiments 1 to 7, wherein the wastewater, after passing through the filter, comprises at least one of: greater than 35 milligrams per liter (mg/1) of ammonia and greater than 0.5 mg/1 of cyanide.

[0022] Embodiment 9 provides a system, the system including an EAF having a body; a lid configured to be coupled to the body such that the lid is movable relative to the body between an open position and a closed position in which the lid and the body cooperate to define an interior volume; and one or more electrodes configured to heat a material disposed within the interior volume; and a cooling system configured to cool the one or more electrodes using wastewater by transferring heat from the one or more electrodes to the wastewater. Embodiment 10 is the system of embodiment 9, wherein the cooling system comprises one or more sprayers configured to spray at least one of the one or more electrodes with the wastewater. Embodiment 11 is the system of embodiments 9 or 10, wherein the cooling system comprises a filter configured to reduce a TSS content of the wastewater before heat is transferred from the one or more electrodes to the wastewater. Embodiment 12 is the system of embodiment 11, wherein the filter is configured to reduce the TSS content of the wastewater to less than approximately 10 PPM. Embodiment 13 is the system of any of embodiments 9 to 12, wherein the system includes a DRI furnace, a blast furnace, and/or a smelter; and the cooling system is configured to receive, as the wastewater, water that has been used for cooling in the DRI furnace, the blast furnace, and/or the smelter. Embodiment 14 is the system of any of embodiments 9 to 13, wherein the cooling system comprises the wastewater. Embodiment 15 is the system of embodiments 9 to 14, wherein the wastewater includes at least one of: greater than 35 mg/1 of ammonia and greater than 0.5 mg/1 of cyanide.

[0023] Some details associated with the embodiments are described above, and others are described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following drawings illustrate by way of example and not limitation. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which that structure appears. Identical reference numbers do not necessarily indicate an identical structure. Rather, the same reference number may be used to indicate a similar feature or a feature with similar functionality, as may non-identical reference numbers.

[0025] FIG. 1 is a schematic of an electric arc furnace coupled to one embodiment of the present wastewater cooling systems. [0026] FIG. 2 is a cross-sectional side view of a direct-reduced iron furnace that may be suitable for use as a source of wastewater for some embodiments of the present wastewater cooling systems.

DETAILED DESCRIPTION

[0027] Referring now to FIG. 1, shown is an EAF 100 coupled to a first embodiment 104 of the present wastewater cooling systems. EAF 100 can include a body 112 and a lid 118 configured to be coupled to the body such that the lid is movable relative to the body between an open position and a closed position (FIG. 1) in which the lid and the body cooperate to define an interior volume 122. Interior volume 122 can be configured to receive a material (e.g., 126) for melting, such as, for example, iron (e.g., DRI, pig iron, scrap iron, and/or the like), steel (e.g., scrap steel), and/or the like. Lid 118 can be coupled to body 112 in any suitable fashion, such as, for example, via a pivotal, hinged, slidable, removable and/or the like connection. Body 112 and lid 118 can each comprise one or more refractory materials, such as, for example, alumina, silica, magnesia, lime, a fire clay, and/or the like, configured to withstand high temperatures within EAF 100. [0028] EAF 100 can include one or more electrodes 134 configured to heat a material (e.g., 126) disposed within interior volume 122. For example, each of electrode(s) 134 can be coupled to lid 118 such that, when the lid is in the closed position, the electrode can be at least partially disposed within interior volume 122. When power is supplied to electrode(s) 134, the electrode(s) can generate electric arcs between the electrode(s) and a material (e.g., 126) disposed within interior volume 122 in order to heat and melt the material. Electrode(s) 134 can comprise any suitable material that is capable of generating an electric arc and is resistant to high temperatures within an EAF (e.g., 100), such as, for example, graphite. Electrode(s) (e.g., 134) of an EAF (e.g., 100) are typically consumed over time, due to, for example, sublimation, oxidation, and/or the like, and the rate of electrode consumption can increase with electrode temperature.

[0029] FIG. 1 also depicts a first embodiment 104 of the present wastewater cooling systems. Cooling system 104 can be configured to cool electrode(s) 134 using wastewater, thereby decreasing the rate of electrode consumption. Transfer of heat from electrode(s) 134 to the wastewater can be accomplished in any suitable fashion, whether directly (e.g., via bringing the wastewater into contact with one or more of the electrode(s), using, for example, one or more sprayers) and/or indirectly (e.g., via passing the wastewater through one or more fluid conduits that are directly coupled to one or more of the electrode(s), via passing the wastewater and a working fluid that is in thermal communication with one or more of the electrode(s) through a heat exchanger, and/or the like).

[0030] Such wastewater can come from any suitable source (e.g., 138). For example, such wastewater can be produced by other steelmaking equipment, such as, for example, a DRI furnace (e.g., 182, described in more detail below), a blast furnace, a smelter, and/or the like (which may be located onsite with the EAF), during, for example, cooling associated with the other steelmaking equipment. Depending on the source, such wastewater can comprise a TSS content that is between approximately 50 PPM and approximately 200 PPM and/or at least one of: greater than 35 mg/1 ammonia and greater than 0.5 mg/1 of cyanide. [0031] While not required in all embodiments, cooling system 104 comprises a filter 142 configured to reduce the TSS content of the wastewater. For example, filter 142 can comprise a membrane, media, screen, mesh, mat, and/or the like through which fluid flow is permitted and through which passage of suspended solids is physically restricted. Filter 142 can be configured to reduce the TSS content of the wastewater to less than approximately 10 PPM (e.g., less than approximately 1 PPM). By filtering the wastewater, filter 142 can remove suspended solids from the wastewater, which might otherwise clog cooling system 104. Cooling system 104 can be used alone and/or in conjunction with other cooling systems, including those that do not use wastewater.

[0032] FIG. 2 depicts a DRI furnace 182 that may be suitable for use as a source (e.g., 138) of wastewater for some embodiments (e.g., 104) of the present wastewater cooling systems. DRI furnace 182 can include a chamber 186 within which DRI precursor (e.g., iron oxide pellets, lump ores, and/or the like) can be heated and exposed to reducing gas (e.g., natural gas, reformed gas, syngas, coke oven gas, hydrogen, carbon monoxide, and/or the like) to produce DRI. DRI precursor can be provided to chamber 186 via a hopper 190.

[0033] DRI furnace 182 can include a reducing gas circuit 194 configured to control flow of reducing gas through chamber 186. To illustrate, an input feed of gas, such as natural gas, along with reducing gas in circuit 194, can be passed through a reformer 196 to produce reducing gas. Reducing gas from reformer 196 can be directed by circuit 194 through chamber 186 (e.g., counter to the flow of DRI precursor through the chamber) to produce DRI from DRI precursor. Gas exiting chamber 186 can be cooled and cleaned of carbon dioxide, sulfur, and/or the like, using, for example, a scrubber, before being reintroduced by circuit 194 into the chamber.

[0034] In one example, the reduced material from chamber 186 can be directed to a cooling zone 202 to be cooled (e.g., by a flow of cooling gas) in order to produce cold DRI. In another example, the reduced material can be hot-discharged into one or more briquetting machines 206 in order to produce hot briquetted iron. In yet another example, the reduced material can be hot-discharged into a transport system 210 to be directly charged into an EAF (e.g., 100).

[0035] Operation of DRI furnace 182 can involve the use of water. For example, water can be used to cool DRI furnace 182, material within the DRI furnace, and/or the like, to clean and/or cool reducing gas in circuit 194, to reform gas in reformer 196, and/or the like. During such use(s), contaminants (e.g., ammonia, cyanide, phenols, and/or the like), suspended solids, dissolved solids, and/or the like can be introduced to the water, thereby producing wastewater. Before disposing of and/or purifying such wastewater, it can be provided to a cooling system (e.g., 104).

[0036] Wastewater cooling systems (e.g., 104) of the present disclosure can be used to cool component(s) of an EAF (e.g., 100) other than (e.g., in addition to) electrode(s) (e.g., 134). For example, in some embodiments of the present wastewater cooling systems (e.g., 104), at least one of a body (e.g., 112) and a lid (e.g., 118) of an EAF (e.g., 100) can comprise one or more fluid conduits (e.g., 228) (e.g., forming part of one or more water-cooled panels), and the cooling system can be configured to cool at least one of the body and the lid by passing wastewater through the one or more fluid conduits.

[0037] Some embodiments of the present methods comprise heating a material (e.g., 126) disposed within an interior volume (e.g., 122) of an EAF (e.g., 100) by supplying power to one or more electrodes (e.g., 134) of the EAF, each being at least partially disposed within the interior volume, and cooling the one or more electrodes using wastewater by passing the wastewater through a filter (e.g., 142) to reduce a TSS content of the wastewater and transferring heat from the one or more electrodes to the wastewater.

[0038] In some methods, transferring heat from the one or more electrodes to the wastewater comprises contacting a portion of at least one of the one or more electrodes that is disposed outside of the interior volume with the wastewater. In some methods, the transferring heat from the one or more electrodes to the wastewater comprises spraying (e.g., with sprayer(s)) the wastewater onto at least one of the one or more electrodes.

[0039] In some methods, the wastewater comprises water that was used for cooling in a DRI furnace (e.g., 182), a blast furnace, and/or a smelter. Some methods comprise heating a material disposed within a chamber (e.g., 186) of a DRI furnace (e.g., 182) by supplying a reduction gas to the chamber and cooling the material and/or the DRI furnace using water by transferring heat from the material and/or the DRI furnace to the water, thereby producing the wastewater.

[0040] In some methods, the TSS content of the wastewater before passing through the filter is between approximately 50 PPM and approximately 200 PPM. In some methods, the wastewater, after passing through the filter, comprises at least one of: greater than 35 mg/1 of ammonia and greater than 0.5 mg/1 of cyanide.

[0041] The above specification and examples provide a complete description of the structure and use of illustrative embodiments. Although certain embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention. As such, the various illustrative embodiments of the methods and systems are not intended to be limited to the particular forms disclosed. Rather, they include all modifications and alternatives falling within the scope of the claims, and embodiments other than the one shown may include some or all of the features of the depicted embodiment. For example, elements may be omitted or combined as a unitary structure, and/or connections may be substituted. Further, where appropriate, aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples having comparable or different properties and/or functions, and addressing the same or different problems. Similarly, it will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments.

[0042] The claims are not intended to include, and should not be interpreted to include, means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) "means for" or "step for," respectively.

Claims

1. A method comprising:

heating a material disposed within an interior volume of an electric arc furnace (EAF) by supplying power to one or more electrodes of the EAF, each being at least partially disposed within the interior volume; and

cooling the one or more electrodes using wastewater by:

passing the wastewater through a filter to reduce a total suspended solids (TSS) content of the wastewater; and

transferring heat from the one or more electrodes to the wastewater.

2. The method of claim 1, wherein the transferring heat from the one or more electrodes to the wastewater comprises contacting a portion of at least one of the one or more electrodes that is disposed outside of the interior volume with the wastewater.

3. The method of claim 1 or 2, wherein the transferring heat from the one or more electrodes to the wastewater comprises spraying the wastewater onto at least one of the one or more electrodes.

4. The method of any of claims 1 or 2, wherein the wastewater comprises water that was used for cooling in a direct-reduced iron (DRI) furnace, a blast furnace, and/or a smelter.

5. The method of any of claims 1 or 2, comprising:

heating a material disposed within a chamber of a DRI furnace by supplying a reduction gas to the chamber; and

cooling the material and/or the DRI furnace using water by transferring heat from the material and/or the DRI furnace to the water, thereby producing the wastewater.

6. The method of any of claims 1 or 2, wherein the TSS content of the wastewater after passing through the filter is less than approximately 10 parts per million (PPM).

7. The method of any of claims 1 or 2, wherein the TSS content of the wastewater before passing through the filter is between approximately 50 PPM and approximately 200 PPM.

8. The method of any of claims 1 or 2, wherein the wastewater, after passing through the filter, comprises at least one of: greater than 35 milligrams per liter (mg/1) of ammonia and greater than 0.5 mg/1 of cyanide.

9. A system comprising:

an EAF comprising:

a body;

a lid configured to be coupled to the body such that the lid is movable relative to the body between an open position and a closed position in which the lid and the body cooperate to define an interior volume; and one or more electrodes configured to heat a material disposed within the interior volume; and

a cooling system configured to cool the one or more electrodes using wastewater by transferring heat from the one or more electrodes to the wastewater.

10. The system of claim 9, wherein the cooling system comprises one or more sprayers configured to spray at least one of the one or more electrodes with the wastewater.

11. The system of claim 9 or 10, wherein the cooling system comprises a filter configured to reduce a TSS content of the wastewater before heat is transferred from the one or more electrodes to the wastewater.

12. The system of claim 11, wherein the filter is configured to reduce the TSS content of the wastewater to less than approximately 10 PPM.

13. The system of any of claims 9 or 10, wherein:

the system comprises a DRI furnace, a blast furnace, and/or a smelter; and

the cooling system is configured to receive, as the wastewater, water that has been used for cooling in the DRI furnace, the blast furnace, and/or the smelter.

14. The system of any of claims 9 or 10, wherein the cooling system comprises the wastewater.

15. The system of claim 14, wherein the wastewater comprises at least one of: greater than 35 mg/1 of ammonia and greater than 0.5 mg/1 of cyanide.