WO2024254702A1

WO2024254702A1 - Waste ferrous slag cleaning method, furnace, and system

Info

Publication number: WO2024254702A1
Application number: PCT/CA2024/050808
Authority: WO
Inventors: Sa GE; Ian Archibald Cameron; Kyle Turas CHOMYN
Original assignee: Hatch Ltd.
Priority date: 2023-06-14
Filing date: 2024-06-14
Publication date: 2024-12-19

Abstract

A method, system, and furnace for cleaning slag produced by a steelmaking or oxidizing process. The method comprising, receiving into a slag cleaning furnace an input slag with a high FeO content and adding reductant to the slag cleaning furnace to produce molten iron and a cleaned slag with a lower FeO content compared to the input slag. The method may further comprise cooling and/or granulating the cleaned slag. The system comprising an input for receiving steelmaking slag from a steelmaking process, a reductant addition component, and optionally, a slag cooling or granulating component and, an off-gas output.

Description

WASTE FERROUS SLAG CLEANING METHOD, FURNACE, AND SYSTEM

FIELD

[0001] The present invention relates to steelmaking and cement manufacture and more specifically to processing slag produced from steelmaking, including for the use in the manufacture of cement.

BACKGROUND

[0002] Blast furnaces (BF) have conventionally been used for making pig iron which is then converted to steel. A by-product of using blast furnaces to make pig iron is blast furnace slag. Blast furnace slag may comprise for example SiO2, AI2O3, CaO and MgO and may be repurposed for use in other industries.

[0003] Blast furnace slag may be used, for example, as raw material in the manufacture of cement. Cement manufacturers have resorted to using the slag from blast furnace plants as raw materials in making cement. This blast furnace slag is an alternative to the conventional, and carbon and energy intensive, lime calcination processes to produce cement. However, the steel making industry is moving towards lower CO2 emission processes for making steel. Blast furnaces are significant contributors to CO2, accordingly there is an effort in the industry to cease using blast furnaces.

[0004] As the steelmaking industry moves away from the use of blast furnaces, it is expected that the industry will adopt other steelmaking routes. Steelmaking furnaces produce a waste product slag that is not useable in making cement however. Conventionally, steelmaking slag is disposed of as solid waste on land around the plants as stockpiles or used in low value applications like road bed material etc. These stockpiles are expected to grow at unprecedented rates as the use of alternate steelmaking routes surpasses the use of traditional blast furnace technology.

BRIEF DESCRIPTION OF THE FIGURES

[0005] FIG. 1 shows an embodiment of a slag cleaning process and system as disclosed herein.

[0006] FIG. 2 shows an electric slag cleaning furnace in accordance with an embodiment of the present disclosure. [0007] FIG. 3 shows a process for making steel and cleaning the resulting slag with an electric slag cleaning furnace in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0008] The invention as disclosed herein comprises a method and system for cleaning slag produced by a steelmaking or oxidizing process. The steelmaking or oxidizing process may comprise, for example, an electric arc furnace (EAF), electric smelting furnace (ESF), basic oxygen furnace (BOF), or any other steelmaking or oxidizing process or furnace that produces a slag with a high or substantial FeO content. A high or substantial FeO content may comprise, for example, an FeO content of 10% or more, 12% or more, 15% or more, or 20% or more, by weight. The system comprises a slag cleaning furnace. The slag cleaning furnace may be an ironmaking or reducing furnace. The slag cleaning furnace may be downstream of the steelmaking or oxidizing process. The slag cleaning furnace may comprise the same type or a different type of furnace compared to the upstream steelmaking or oxidizing furnace. The slag cleaning furnace may produce a molten iron and an iron making slag. The iron making slag may be repurposed downstream of the slag cleaning furnace, for example, the iron making slag may be used as a product downstream, for example in the manufacture of cement, for example as a clinker substitute, or as road aggregates. The process comprises providing an input slag, for example from an upstream steelmaking or oxidizing process, into a slag cleaning furnace. The input slag may be in a molten state or may be in a solid state. The process of cleaning the input slag to produce a cleaned slag, according to the present disclosure may be beneficial in helping reduce greenhouse gas emissions that are emitted during cement manufacturing by providing the cement manufacturers with useable slag and avoiding the carbon intensive lime calcination process that would have otherwise needed to be employed due to the lack of blast furnace slag. It is expected that due to more stringent caps on GHG emissions, the use of blast furnaces in the steelmaking industry will decrease significantly. Reduction of blast furnaces will reduce the amount of blast furnace slag or iron making slag available and suitable for cement replacement being generated and sold to cement manufacturers.

[0009] EAF steelmaking accounts for approximately 30% of the global steel production. The slag from EAF steelmaking has typically been stockpiled in proximity to the steelmaking plant as a solid waste. In the foreseeable future however, as more iron and steel making plants replace blast furnaces with lower carbon emission steelmaking processes such as EAF, ESF, etc., the amount of slag (and solid waste) produced from these processes is expected to increase by approximately an order of magnitude causing these stockpiles to grow exponentially.

[0010] The slag cleaning furnace and method as disclosed herein may be used to process an input slag received from a steelmaking or oxidizing process, for example from an electric steelmaking furnace or a basic oxygen steelmaking furnace. In an example, the slag cleaning furnace and method may be used to produce the raw material for the cement industries as well as iron as a by-product. The slag cleaning furnace and method may produce a cleaned slag with a low FeO content compared to the input slag. The process may also increase the overall iron yield of the steel plant by extracting further iron that may have been remaining in the input slag (i.e. the slag received from the steelmaking or oxidizing process). The possibility of recycling the slag produced from steelmaking or oxidizing process in accordance with the present invention can significantly reduce the slag waste that would otherwise be stockpiled or end up in landfills from these processes.

[0011] In an aspect of the invention as disclosed herein, a method is provided for processing slag produced from a steelmaking or oxidizing process. The method may comprise receiving into a slag cleaning furnace, an input slag with a high FeO content. The steelmaking or oxidizing process may comprise an ESF, an EAF or a BOF, for example. The slag cleaning furnace may comprise an ESF or BF, for example. In an example, the process may comprise providing slag from a first ESF to a second ESF. The first ESF may be a steelmaking ESF while the second ESF may be a slag cleaning ESF. Cleaning the input slag in accordance with this process and system may produce molten iron and a cleaned slag with a lower FeO content as compared to the input slag. The cleaned slag may be an iron making grade slag, for example the cleaned slag may be considered equivalent, similar or at least comparable to an iron making slag.

[0012] The FeO content in the input slag may be for example, greater than or equal to 10% by weight, for example greater than or equal to 12% by weight, or greater than or equal to 15% by weight, or greater than or equal to 20% by weight, or greater than or equal to 30% by weight, or greater than or equal to 50% by weight. The high FeO content in the input slag may result in significant iron recovery in the slag cleaning furnace. In further examples, the input slag may be received from any one or more of, an upstream electric furnace, a steelmaking furnace, a ladle metallurgy facility, or any other facility for producing a slag with a high or substantial FeO content. The input slag may comprise a high basicity. For example, the high basicity may be a basicity (B2) of 2, 3, 4, 5, or more, or for example any basicity (B2) greater than 2. Basicity B2 is calculated according to the following formula: CaO/SiO2. The basicity (B2) of slag may be for example the ratio of CaO to silica (SiCh). In an example, the high basicity input slag may be a steelmaking slag. Steelmaking slag (which is typically regarded as a waste) tends to have a higher basicity and a higher iron/FeO content as compared to iron making slag. In addition, the slag cleaning furnace may be fed with other iron bearing slag or solid wastes produced by a basic oxygen furnace (for example, BOF dust slag), other metallurgical processes such as a ladle metallurgical furnace (LMF), or a different steelmaking or oxidizing process. Iron bearing solid wastes may comprise for example, skulls, dusts, sludge, and may include any other solids or legacy solids found stockpiled at or by iron and steel making plants.

[0013] The cleaned slag produced by the slag cleaning furnace may be an iron making slag. The cleaned slag may be useable to make cement or road aggregates. The cleaned slag may comprise FeO in an amount less than the FeO content of the input slag. For example, the cleaned slag may comprise an FeO content of 5% or less by weight, for example less than or equal to 3% by weight or less than or equal to 1% by weight, or none or almost negligible FeO. The cleaned slag may comprise a low basicity. For example, the cleaned slag may comprise a basicity (B2) that is lower than the basicity of the input slag, for example a basicity (B2) of less than or equal to 2.5, for example a basicity (B2) of 1, 1.3, 1.5, 2, 2.3 or 2.5. The lower basicity cleaned slag for example may comprise a basicity that is lower relative to the input slag received by the slag cleaning furnace. In another example, the cleaned slag may comprise a higher basicity or the same or similar basicity, as compared to the input slag.

[0014] The process may comprise adding a reductant to the input slag received by the slag cleaning furnace. The reductant may be added to the slag in the slag cleaning furnace, upstream of the slag cleaning furnace, simultaneously with the introduction of input slag to the slag cleaning furnace or at a separate time before or after the addition of the input slag to the slag cleaning furnace. The process may further comprise heating the input slag with the added reductant in the slag cleaning furnace to produce molten iron and a molten cleaned slag with a lower FeO content as compared to the input slag. The input slag may be heated to a temperatures of at least 1200 degrees Celsius to become molten. The input slag may be heated up to a temperature of about 1800 degrees Celsius. Once the input slag is molten, the iron separates from the remainder of the slag materials within the furnace to form a molten cleaned slag layer floating on top of a molten iron layer. The molten cleaned slag layer may then be tapped to extract the cleaned slag in a molten form, while leaving the molten iron layer. The cleaned slag may comprise a changed basicity as compared to the input slag. The reductant may be for example carbon or a bio-carbon. The reductant may react with the unconditioned input slag to turn FeO into Fe. For example, the reductant may be added in a select amount to produce molten iron (Fe) by reducing FeO. In an example the reductant may be any one or more of anthracite, coke, coal, biochar, biomass, synthetic carbon black, products from pyrolysis or any form of industrial carbon.

[0015] The process may further comprise the addition of a slag component or slag components, to the slag cleaning furnace. The slag component may be a slag additive. The slag additive may be added to the slag cleaning furnace independently of any reductant. For example, slag additives may be added before, simultaneously with or after the addition of reductant. The slag additives may for example be fluxes. Fluxes may be used to further condition the slag. For example, fluxes may be used to modify the basicity of the cleaned slag. Fluxes may be added in an amount sufficient to condition the cleaned slag to be suitable for downstream use. For example, fluxes may be added in an amount sufficient to bring the cleaned slag to a suitable level and/or quality for the manufacture of cement. In an example, fluxes may be used to adjust properties of the cleaned slag to match requirements of the cement industry. Fluxes may be any one or more of, but are not limited to, an additive containing SiC>2 (for example gravel), and/or AI2O3, and/or MgO, for adjusting basicity, for example for reducing or increasing basicity, and adjusting other slag properties. For example, fluxes may include bauxite for alumina, and/or dolomitic lime for adjusting MgO.

[0016] The process may further comprise capturing off-gas from the slag cleaning furnace. Off-gas may be used as fuel for a steelmaking plant, combusted in a waste heat boiler or other device to generate steam, or sent for further processing. For example, off-gas may comprise CO, and CO may be recycled back to the slag cleaning furnace or to the steelmaking production plant upstream of the slag cleaning furnace, or to any other plant, as desired. In another example, captured CO may be combusted in a waste heat boiler or other device to generate steam. Generating steam from off-gas may reduce fossil fuel use and may be integrated into the remainder of the steelmaking or oxidizing plant or any other plant or process for use. The process as disclosed herein may further comprise sending captured CO to a further carbon capture, utilization and storage step.

[0017] Molten iron and cleaned slag produced by the slag cleaning furnace may be sold, recycled or re-used in the same plant, in a different plant, or in a different industry, such as the cement industry. Molten iron may be used in a number of other applications. For example, molten iron may be sold directly as a product (for example, as cast pig iron or granulated pig iron), and/or may be recycled upstream of the slag cleaning furnace, for example to the upstream steelmaking or oxidizing process or other steelmaking furnace, ladle metallurgy facility, or any other facility for producing iron and/or steel. The molten iron may additionally or alternatively be sent downstream of the slag cleaning furnace to other steelmaking operations such as a steelmaking plant or other plant for increasing iron yield in the plant.

[0018] The cleaned slag produced from the slag cleaning furnace may be cooled and/or granulated downstream of the slag cleaning furnace. In an example, the cleaned slag may be conditioned to be suitable for the cement industry by cooling and/or granulating the cleaned slag to be used to produce a clinker substitute for use in the manufacture of cement. The clinker substitute may be provided or sold to cement manufacturers for use in the manufacture of cement. Iron and steel plants may use the process and system disclosed herein to process and recycle their ESF, BOF, EAF or other steelmaking or oxidizing furnace slag, or other high FeO slag, in order to continue producing saleable slag and serving the steelmaking and other industries. For example, in order to continue serving cement industry clients.

[0019] FIG. 1 shows a slag cleaning furnace system 100 for processing an input slag received from a steelmaking or oxidizing process. The slag cleaning furnace system 100 comprises a slag cleaning furnace 102 that may be powered by an electrical supply 104 providing electricity to the furnace. The slag cleaning furnace 102 receives an input slag, such as waste solids 106 from stockpiles of steelmaking facilities, and/or molten steelmaking slag 108, or any other high FeO content slag, from an upstream process or facility, for example from an upstream or coupled continuous reduced iron steelmaking process (CRISP) or basic oxygen furnace or other electric furnace such as an EAF or ESF. The input slag 106/108 may comprise a high FeO content, for example an FeO content of 10% or more by weight. In an example, the input slag may have a high basicity, such as a basicity (B2) of 2 or more. The slag cleaning furnace may be further fed with other components 110 such as reductants and/or fluxes or other iron bearing solids. Reductants may be for example carbon in an amount sufficient to produce molten iron by reducing FeO in the input slag. Flux may comprise any one or more of, but are not limited to, an additive containing SiO2 and/or AI2O3, and/or MgO, for adjusting basicity, bauxite for alumina, and dolomitic lime for adjusting MgO. Iron bearing solids may include, for example, skulls, dusts, sludge, and may include any other solids or legacy solids found stockpiled at or by iron and steel making plants. The electric supply 104 may be used to provide electricity to one or more electrodes residing within the slag cleaning furnace 102 to drive an endothermic reaction. The endothermic reaction in the slag cleaning furnace 102 heats the slag to help produce a cleaned slag with lower FeO content compared to the input slag. The endothermic reaction may be further driven by chemical energy from added reductants. The cleaned slag may comprise a modified basicity (B2) compared to the input slag, for example, the basicity (B2) of the cleaned slag may be similar to, higher or lower than the input slag, or in another example, the basicity (B2) may be unchanged. The cleaned slag comprises a lower FeO content as compared to the input slag, for example an FeO content of less than about 5% by weight. The slag cleaning furnace 102 according to the invention produces molten iron 112 and a low FeO content molten cleaned slag 114, as well as an off gas 116. The molten iron 112 may be tapped from the slag cleaning furnace 102 in a molten state. The molten iron 112 may be sent to further processing downstream, for example, molten iron may be sent to a steel or other production plant 118. In another example, the molten iron may be provided back into the system upstream of the slag cleaning furnace, into another steelmaking furnace, a ladle metallurgy facility, or any other facility for producing steel. Optionally, the molten iron may be provided as a final product, for example as cast pig iron or granulated pig iron. The molten cleaned slag 114 may be tapped from the slag cleaning furnace 102 in a molten state. The cleaned slag may be further cooled or granulated 120 for example to produce a clinker substitute or other aggregate before being sent to a downstream slag handling process 122. In an example, the downstream slag handling process may comprise selling/providing the cleaned slag to or for use by cement manufactures to be used in the manufacture of cement. The off-gas 116 from the slag cleaning furnace 102 may be captured. The off-gas 116 may comprise for example CO, and the captured CO may be recycled, combusted or further processed as previously discussed.

[0020] In an aspect of the invention, the slag cleaning process comprises transferring molten slag (as input slag) from a steelmaking or oxidizing vessel to a slag cleaning furnace in batches. In another example, the input slag may be provided to the slag cleaning furnace continuously. Reductant may be added directly to the slag cleaning furnace and/or to the input slag, whether prior to entering the slag cleaning furnace, simultaneously on entering the slag cleaning furnace, or after entering the slag cleaning furnace, to reduce the FeO contained in the input slag and produce molten iron and cleaned slag with a lower FeO content, within the slag cleaning furnace. Flux may also be added to create properties in the cleaned slag which allow for iron recovery and which may make the slag suitable for use in other industries such as, for example, in cement manufacture. Electric energy may be added to the furnace as electricity provided to one or more electrodes to provide the energy necessary to drive the endothermic reactions and to heat the slag to a temperature that facilitates tapping the molten cleaned slag and molten iron from the slag cleaning furnace. Molten iron may then be fed back into the steelmaking or oxidizing vessel upstream of the slag cleaning furnace, to increase the amount of iron ultimately extracted from the same amount of input. Alternatively or additionally, the molten iron may be sent downstream for further use in other plants, industries or as a saleable product. Cleaned slag may be tapped from the slag cleaning furnace and cooled or granulated to produce a material suitable for other industries, for example, suitable for the cement industry. Off-gas from the cleaning furnace may be collected and cleaned to capture CO. CO may be used as a fuel at steelmaking plants, reducing the reliance on purchased fossil fuels or, alternatively or additionally, can be combusted in a waste heat boiler or other device to generate steam to be integrated into the steelmaking or other plant and reduce fossil fuel use in the generation of steam.

[0021] In an aspect of the invention, iron containing material from a steelmaking or oxidizing furnace may be sent to an iron making or reducing furnace for processing. The iron containing material may be a by-product of a steelmaking or oxidizing process such as steelmaking slag. The iron containing material may comprise a high FeO content. A high FeO content may be for example, an FeO content of 10% by weight or more. Processing may comprise cleaning the iron containing material, for example to produce a cleaned slag with lower FeO content, for example an FeO content of less than 5% by weight, and an iron by-product. The steelmaking or oxidizing furnace may be, for example, an electric smelting furnace, an electric arc furnace, a blast oxygen furnace, a ladle metallurgy facility or any other facility for producing a slag with a high FeO content. In an example, the steelmaking or oxidizing furnace may be a combination of furnaces and/or facilities that produce a slag with a high FeO content. The iron making or reducing furnace may be, for example, a dedicated electric smelting furnace, an ironmaking electric smelting furnace, or a reducing electric smelting furnace. In an example, one or more iron making or reducing furnaces may be used as slag cleaning furnaces.

[0022] The slag cleaning method and system as described herein may be used to convert waste slag comprising a high FeO content into a material suitable for use in other industries. In an example, cleaned slag may be used as cement replacement or road aggregates. The method and system may help reduce CO2 emissions from conventional carbon intensive manufacture process, such as cement manufacture, as well as recovering iron from the slag as a value added product.

[0023] In another aspect, a method for producing iron and cement-useable slag is disclosed herein. The method may comprise providing direct reduced iron (DRI) to a steelmaking or oxidizing furnace and melting the DRI to produce a molten steel and a slag. The steelmaking or oxidizing furnace may be electric. The slag may comprise a high FeO content such as an FeO content of 10% or more by weight. The steelmaking or oxidizing furnace may be, for example, an EAF, an ESF or a BOF. The method further comprises reducing the slag with the high FeO content from the steelmaking furnace in an iron making or reducing furnace to produce a molten iron and a slag with a lower FeO content. The lower FeO content may be, for example, and FeO content that is relatively lower than the FeO content of the slag from the steelmaking furnace, for example, and FeO content of 5% by weight or less. The iron making or reducing furnace may be electric. The iron making or reducing furnace may be, for example, an electric smelting furnace, or blast furnace. In addition, the method may comprise separating the molten iron from the slag with the lower FeO content and producing from the slag with the lower FeO content a clinker substitute for use in the manufacture of cement. In an example, the molten iron may be sold as a product or used in other upstream or downstream steelmaking or iron making projects. Off-gas produced from the iron making or reducing furnace may be captured. Off-gas may include for example, carbon monoxide (CO). Captured CO may be used as fuel or may be combusted in a waste heat boiler or other device to generate steam, or may be further processed, for example as previously discussed in this disclosure. The method may further comprise the addition of pellet fines and/or other FeO-bearing slag and wastes, and/or steel scrap with the DRI to the iron making or reducing furnace as additional feed material. The additional feed material may be received for example, from legacy stockpiles at iron and steelmaking plants. [0024] A slag cleaning furnace system as disclosed herein may comprise one or more of a dedicated ESF, an ironmaking ESF, or a reducing ESF. The system may be for example, its own facility or may be added to an existing furnace, such as, for example as an addition to a continuous reduced iron steelmaking process (CRISP) plant. A CRISP plant is a type of steelmaking technology which uses a stationary electric furnace to continuously melt and decarburize DRI and other metallic materials to produce steel. When added to an existing plant, such as a CRISP plant, accumulated or fresh slag from the existing plant may be directly added to the slag cleaning furnace and recovered as useable slag and molten iron. The molten iron may be cast into products or returned back into the system, while the slag can be sold or provided to other industries, for example, for cement or road aggregates.

[0025] In an aspect of the invention, a slag cleaning furnace for converting a steelmaking slag into an iron making grade slag is provided herein. The slag cleaning furnace may be a non-tiling electrical furnace. The slag cleaning furnace may comprise an input connection for receiving the steelmaking slag in solid or molten form from a steelmaking process, a reductant addition component and/or a flux addition component. The slag cleaning furnace may also comprise a crucible or hearth wherein the molten slag and molten iron collect as a molten bath, and one or more electrodes for receiving electricity and providing heat to the bath to melt the input slag. The electricity may be provided to the electrode(s) by an electric energy supply or source. The slag cleaning furnace system may further comprise a slag cooling and/or granulating component, and off-gas output. The slag cleaning furnace may also comprise an off-gas capture component. The furnace may comprise and be operated by an electric energy supply or source. The steelmaking process upstream of the input connection may be a continuous reduced iron steelmaking process. The slag cleaning furnace may comprise tap holes for tapping molten iron and/or slag. The tap hole(s) for molten iron may be connected or directed in some way to a molten iron recycle stream back to the steelmaking process or to other downstream uses. The tap hole(s) for cleaned slag may be connected or directed in some way, for example via a slag transport, to further downstream uses, such as for example to a cement manufacturing or road aggregate manufacturing facility or process.

[0026] The method and system as disclosed herein may provide cement makers and other industries access to usable slag as a low-GHG raw material as an alternative to using limestone calcination which is highly GHG-intensive. Waste can be significantly reduced by turning the non-useable slag from CRISP or other steelmaking processes and facilities into a useable product. Iron units may also be recovered which can boost the overall iron yield, and reduce the need for raw materials. The system and process may further provide opportunities for iron and steelmaking plants to recycle legacy solid waste material which is currently stockpiled.

[0027] FIG. 2 shows an electric slag cleaning furnace 200 in accordance with an embodiment of the present disclosure. The furnace 200 may be a fixed, non-tilting, type furnace. The furnace 200 may be a type of electrical smelting furnace (ESF). The furnace 200 comprises a crucible or hearth 210 wherein the molten bath of material resides and is retained. The furnace 200 also comprises an electrode 212 for providing electrical energy to the materials within the bath so as to heat and render the materials molten. The electrode 212 may comprise a plurality of electrodes in a particular configuration. For example, there may be three electrodes arranged in a circular-shaped configuration. Alternatively, there may be six electrodes arranged in an in-line configuration. Input slag 214 is received in the furnace 200 through the top. The input slag 214 may be in solid form 214A and/or molten form 214B. The input slag 214 is from a steel making process. The input slag 214 may be received directly from a BOF, for example. Or the input slag 214 may be from a stockpile that had been created from the slag created by a steelmaking process that occurred some time ago. The input slag 214 may also be from an electric arc furnace (EAF) that was configured to produce steel. Reductant 216 is also provided into the furnace 200. Once there is input slag 214 and reductant 216 in the furnace 200, electricity is provided to the electrode(s) 212. The electrode(s) 212 generates heat within the materials in the furnace by electric arc heating and/or electric resistance heating. The materials within the furnace 200 melt so as to turn molten. Once molten, a majority of the iron material within the input slag 214 separates and sinks to the bottom of the furnace, while the cleaned slag floats to the top of the furnace 200. This creates a molten slag layer 220, and a molten metal layer 222. Additives may be provided to the molten materials to achieve the desired basicity and composition for use downstream of the furnace 200 including in the cleaned slag for use in the manufacture of cement. Once the molten materials have stratified within the furnace 200 and have the correct chemistry, the cleaned molten slag is extracted from the side of the furnace 200 by tapping the side wall of the furnace 200 at the correct level to create a cleaned slag taphole 224 on the vertical face through which the molten slag passes for extraction. The molten iron metal layer 222 may also be extracted from the furnace via tapping a metal taphole 226. By having tap holes in this fashion, the molten cleaned slag and/or the molten iron may be extracted from the furnace continuously. In this way, input slag may be provided into the slag cleaning furnace 200 continuously, the input slag may be cleaned continuously, and the cleaned slag may be extracted continuously, such that the occurrence of any one of these steps does not interrupt the occurrence of any of the other steps and the slag cleaning process may continue indefinitely and not in a batch fashion. Since there are separate tapholes for the molten iron and the cleaned slag, each of those molten materials may be extracted from the furnace as needed and independent of the other molten material. A nontilting type furnace is a furnace wherein the crucible rests permanently or is affixed to the ground. The non-tilting type furnace cannot be moved and cannot be tilted so as to pour out the contents therein. To extract the molten slag within the furnace, the taphole in the vertical face of the furnace is used. The non-tilting type furnace arrangement can help with processing a high volume of input slag, including as a result of allowing for the continuous operation of the furnace. Generally, a tilting-type furnace must necessarily only be operated in a batch or quasi-continuous method because the furnace must be periodically tilted to pour out the contents of the furnace via the top of the furnace. During that pouring phase, no additional materials may be added to the furnace and typically the electrodes must be removed from the furnace as well. A tilting-type furnace is also generally limited in the amount of materials it can smelt at one time because the furnace is suspended and there are weight limitations in suspended furnaces. By contrast, a non-titling furnace rests on the ground and accordingly does not have the same weight limitations as a tilting-furnace. With less weight limitations, the non-tilting type furnace may be significantly larger and can hold a greater amount of material for smelting at a single time. Furthermore, the slag cleaning furnace in accordance with the present disclosure may not foam the cleaned slag and may intentionally avoid or inhibit the foaming of the cleaned slag. In such an embodiment, the slag cleaning furnace may be provided with feed piles comprising the input slag to be cleaned. The feed piles are composed of solid input slag and may reside below and/or above the molten slag. The feed piles may partially cover the top of the molten slag. In an embodiment of the present disclosure, the input slag to be cleaned may be fed into the furnace 200 such that it is deposited in solid and/or molten form directly on top of the existing cleaned slag. [0028] FIG. 3 shows a process 300 for making steel and cleaning the resulting slag with an electric slag cleaning furnace 302 in accordance with an embodiment of the present disclosure. The process 300 comprises making steel in one of two methods. In a first method 304, ferrous feed (which may comprise ore based metallics or DRI) and/or ferrous scrap is provided to an electric arc furnace (EAF). The EAF heats the feed to render molten and produces steel. The EAF also produces an EAF steelmaking slag. That EAF steelmaking slag comprises a high FeO content such that it would not be useable in a cement making process. In a second method 306, ferrous feed is provided to a basic oxygen steelmaking furnace (BOF). The ferrous feed may be molten pig iron received from an electric smelting furnace (ESF) or any other ironmaking furnace The BOF produces steel and also produces BOF steelmaking slag. The BOF steelmaking slag also comprises a high FeO content such that it would not be useable in a cement making process. The EAF steelmaking slag is provided to the slag cleaning furnace 302. The BOF steelmaking slag is provided to the slag cleaning furnace 302. The slag cleaning furnace 302 receives the steelmaking slag, receives a reductant, and smelts the materials using electric energy, The slag cleaning furnace 302 reduces the FeO in the steelmaking slag to produce a cleaned slag that is useable for manufacturing cement 308. The slag cleaning furnace 302 also produces iron 310.

Claims

CLAIMS:

We claim:

1. Method for processing slag, the method comprising, a) receiving into a non-tilting slag cleaning furnace an input slag with an FeO content equal to or greater than 10% by weight, the input slag produced by a steelmaking process; b) adding a reductant to the slag cleaning furnace; c) heating the input slag with the reductant in the slag cleaning furnace with an endothermic reaction using electricity provided to electrodes in a circular or in-line configuration to produce a molten iron layer beneath a molten cleaned slag layer in the slag cleaning furnace, wherein the cleaned slag has an FeO content that is lower than the FeO content of the input slag, and wherein the basicity B2 of the cleaned slag is equal to or less than 2.5; d) tapping the molten cleaned slag from a taphole in the vertical face of the slag cleaning furnace in a molten state; d) granulating the molten cleaned slag; and e) providing the granulated cleaned slag downstream for use in the manufacture of cement.

2. The method of claim 1 , wherein the slag cleaning furnace is a dedicated electric smelting furnace (ESF), an ironmaking ESF, a reducing ESF.

3. The method of claim 1 or 2, further comprising using the granulated cleaned slag in the manufacture of cement.

4. The method of any one of claims 1 to 3, further comprising using the granulated cleaned slag to produce a clinker substitute for use in the manufacture of cement.

5. The method of any one of claims 1 to 4, wherein the input slag has a high basicity.

6. The method of any one of claims 1 to 5, wherein the cleaned slag has a basicity (B2) that is lower than the basicity (B2) of the input slag.

7. The method of any one of claims 1 to 6, wherein the FeO content of the input slag is greater than or equal to 20% by weight.

8. The method of any one of claims 1 to 7, wherein the FeO content of the cleaned slag is less than the FeO content of the input slag.

9. The method of any one of claims 1 to 8, further comprising receiving the input slag from an upstream electric furnace.

11. The method of any one of claims 1 to 10, further comprising receiving in the slag cleaning furnace, skulls, dust, sludges, and/or other iron bearing solids from a steelmaking or oxidizing process.

12. The method of any one of claims 1 to 11, wherein the reductant is added in a select amount to the slag cleaning furnace to produce the molten iron by reducing the FeO content of the input slag.

13. The method of claim 1, further comprising providing the molten iron into a steel production plant.

14. The method of any one of claims 1 to 13, further comprising adding a slag component to the slag cleaning furnace.

15. The method of claim 14, wherein the slag component comprises flux.

16. The method of claim 15, wherein the flux is added as the slag component in an amount sufficient to condition the cleaned slag to a suitable level and/or quality for the manufacture of cement.

17. The method of claim 16, wherein the flux comprises any one or more of an additive containing SiO2 and/or AI2O3 and/or MgO and/or CaO for adjusting basicity and slag properties.

18. The method of any one of claims 1 to 17, further comprising receiving the input slag from an upstream steelmaking furnace, a ladle metallurgy facility, or any other facility for producing a slag with an FeO content of 10% by weight or more.

19. The method of claim 1 , further comprising using chemical energy from the reductant to drive the endothermic reactions.

20. The method of any one of claims 1 to 19, wherein the reductant comprises any one or more of anthracite, coke, coal, biochar, and biomass.

21. The method of any one of claims 1 to 20, further comprising collecting the input slag from a stockpile of slag produced by the steelmaking process, and providing the input slag into the slag cleaning furnace.

22. The method of any one of claims 1 to 21, wherein the circular configuration comprises three electrodes, and wherein the in-line configuration comprises six electrodes.

23. The method of any one of claims 1 to 22, further comprising capturing off-gas from the slag cleaning furnace.

24. The method of claim 23, wherein the off-gas comprises CO, and the CO is (i) recycled back to the slag cleaning furnace or iron I steel production plant, (ii) combusted in a waste heat boiler to generate steam, (iii) sent to a further carbon capture, utilization and storage step, or (iv) flaring CO gas to the atmosphere.

25. A method for producing iron and cement-usable slag, comprising: a) providing DRI into a steelmaking or oxidizing furnace; b) smelting the DRI with the steelmaking or oxidizing furnace to produce molten steel and a slag with a high FeO content; c) reducing the slag with the high FeO content in an electric iron making or reducing furnace comprising electrodes to produce a molten iron and a cleaned slag with a lower FeO content; d) separating the molten iron from the slag with the lower FeO content; and e) producing from the slag with the lower FeO content, a clinker substitute for use in the manufacture of cement.

26. The method of claim 25, wherein the slag with a high FeO content has an FeO content of 10% by weight or more.

27. The method of claim 25, further comprising providing the molten iron to the steelmaking or oxidizing furnace.

28. The method of claim 25, further comprising capturing carbon monoxide (CO) from the iron making or reducing furnace.

29. The method of claim 28, further comprising using the CO as fuel or combusting in a waste heat boiler to generate steam.

30. The method of any one of claims 25 to 29, further comprising providing pellet fines and/or other FeO-bearing slag and wastes, and/or steel scrap with the DRI to the iron making or reducing furnace.

31. The method of claim 25, further comprising using the clinker substitute in the manufacture of cement.

32. A slag cleaning furnace for converting a steelmaking slag into an iron making grade slag, the furnace comprising, an input connection for receiving the slag in solid or molten form from a steelmaking process; a reductant addition component; an electrical supply; electrodes arranging in a circular or in-line configuration for receiving electricity from the electrical supply and providing heat to the steelmaking slag as an endothermic reaction; a non-tilting crucible for holding the molten slag and the molten iron; a taphole in the vertical face of the crucible for extracting the molten slag therethrough; a slag cooling or granulating component; and, an off-gas output.

33. The furnace of claim 32, wherein the electrode is arranged within the furnace to contact the materials within the crucible to generate heat.

34. The furnace of claim 32 or 33, further comprising a molten iron recycle stream for providing molten iron from the slag cleaning furnace to the steelmaking process.

35. The furnace of any one of claims 32 to 34, further comprising a tap hole in the vertical face of the furnace wall through which the cleaned molten slag is extracted.

36. The furnace of claim 35, further comprising a connection with a cement manufacturing facility, wherein the cleaned slag is used to manufacture cement.

37. The furnace of any one of claims 32 to 36, wherein the steelmaking process is a continuous reduced iron steelmaking process or a process comprising a BOF.

38. The furnace of any one of claims 32 to 37, further comprising a flux addition component.

39. The furnace of any one of claims 32 to 38, further comprising an iron bearing solid waste addition component. 40. The furnace of any one of claims 32 to 39, wherein when arranged in a circular configuration there are three electrodes, and wherein when arranged in an in-line configuration there are six electrodes.