Direct bath smelting process for managing peripheral cold zone at metal-slag interface

Abstract

An improved direct smelting vessel includes a smelting reduction vessel (SRV) and optionally a cyclone converter (CCF). The SRV provides means for promoting metal mixing in an area beneath a slag layer adjacent a vessel wall of the direct smelting vessel. The device for promoting metal mixing may include a layered refractory hearth having two refractory base plate layers, a refractory hearth having one or more gas bubbling devices, and / or at least one pair of solids injection guns (or other devices) that provide alternating solids injection at any given time. The device for promoting metal mixing reduces the stagnation zone capable of supporting a semi-solid slag layer that limits metal-slag heat transfer. The means for promoting metal mixing maintain an effective temperature difference between the metal flowing out of the forehearth and the metal at the vessel wall not greater than 40 DEG C.

Description

[0001] Priority Statement under 35 U.S.C. § 119

[0002] This application claims priority to U.S. Provisional Application No. 63 / 352,492, filed on June 15, 2022, entitled “A Direct Bath Smelting Process with Management of Peripheral Cold Zones at the Metal-Slag Interface,” and U.S. Non-Provisional Patent Application No. 18 / 204,683, filed on June 1, 2023, entitled “A Direct Bath Smelting Process with Management of Peripheral Cold Zones at the Metal-Slag Interface,” both of which are assigned to the present assignee and are hereby expressly incorporated herein by reference. Technical Field

[0003] The present invention relates to a method and an apparatus for direct smelting of metal-containing materials. Background Art

[0004] Two known methods of direct smelting of metalliferous materials which rely primarily on a molten bath as the smelting medium are generally referred to as HIsmelt and HIsarna. Summary of the invention

[0005] The present invention relates to an improved direct smelting vessel comprising a smelting reduction vessel (SRV) and optionally a cyclone converter (CCF). In particular, the direct smelting vessel may be an enclosed vessel having a top, a refractory hearth zone in the bottom of the vessel for containing a molten bath, and a gas zone between the molten bath and the top. Means are provided for promoting metal mixing (e.g., passive mixing and / or active mixing) in a region adjacent to the periphery of the vessel at the metal-slag interface (e.g., a cold shoulder region). For example, providing improved metal mixing in this region reduces stagnant zones that can support a semi-solid slag layer that limits metal-slag heat transfer. In particular, the means for providing metal mixing maintains an effective temperature difference between tapped metal and metal at the vessel wall of no more than 40°C (72°F).

[0006] In some embodiments of the invention, the apparatus for promoting metal mixing may include a layered refractory furnace having two refractory floor layers, a refractory furnace utilizing one or more gas bubbling devices, and / or at least one pair of solids injection lances, wherein at any given time (e.g., immediately or after a period of time) prior to switching to a second opposing lance of the pair, a first opposing lance of the pair provides all of the injected feed solids to the pair.

[0007] For a layered refractory hearth, the device provides a primary layer having a depth that improves molten metal mixing, which plays a key role in metal-slag heat transfer. In addition, the SRV provides a secondary layer having a different depth (e.g., deeper than the primary layer depth) that provides a safety function related to preventing slag from blowing out of the forehearth. The depth of the layered refractory hearth will be described in further detail herein.

[0008] For refractory furnaces utilizing one or more gas bubblers, the gas bubblers promote metal convection by injecting gas (eg, argon or the like) into the region beneath the slag layer adjacent the vessel wall of the direct smelting vessel.

[0009] For at least one pair of solids injection lances, the injection lances provide injection plumes strong enough to promote metal convection at opposing walls of the vessel. Alternating between opposing lances (e.g., with respect to a given pair of lances) in a regular cycle based on the time required for hot metal to cool near the vessel wall can be used to promote metal convection that limits the creation of a semi-solid slag layer at the metal-slag interface.

[0010] It should be appreciated that other means for promoting metal mixing near the metal wall may be passively or actively utilized to reduce the semi-solid slag layer described herein.

[0011] One embodiment of the present disclosure includes a method for direct smelting metalliferous material and producing molten metal in a direct smelting vessel. The method includes injecting solid carbonaceous material through at least one injection lance extending into the direct smelting vessel such that the solids at least partially penetrate into a molten metal layer in the direct smelting vessel, wherein a slag layer floats on the molten metal layer. The method also includes promoting metal mixing in an area below the slag layer proximate a vessel wall of the direct smelting vessel.

[0012] In further accordance with embodiments, metal mixing reduces the volume occupied by stagnant zones that are cool enough to support a semi-solid slag layer that limits heat transfer from the metal slag.

[0013] In other embodiments, the metal mixing maintains an effective temperature difference between the metal flowing out of the forehearth and the metal at the vessel wall of no more than 40°C.

[0014] In still other embodiments, a direct smelting vessel is used to promote metal mixing, the direct smelting vessel comprising a layered refractory floor having two refractory floor layers, the two refractory floor layers comprising a first layer and a second layer, the first layer having a first depth that supports a first metal depth, and the second layer having a second depth that supports a second metal depth. The second metal depth is greater than the first metal depth. The first depth that supports the first metal depth promotes metal mixing by convection of metal into and out of an area below the slag layer adjacent to a vessel wall.

[0015] In still other embodiments, the first layer comprises at least 70% of the cross-sectional area of ​​the layered refractory floor.

[0016] In other embodiments, the first depth supports a first metal depth of no greater than 900 mm.

[0017] Further in accordance with an embodiment, the first depth supports a first metal depth of no greater than 700 mm.

[0018] In other embodiments, the first depth supports a first metal depth of no greater than 600 mm.

[0019] In still other embodiments, the second depth supports a second metal depth that is at least 300 mm greater than the first metal depth.

[0020] In still other embodiments, metal mixing is promoted by injecting gas into the direct smelting vessel using one or more gas bubbling devices to promote convection of metal to the area below the slag layer adjacent the vessel wall.

[0021] In other embodiments, the gas includes argon or nitrogen.

[0022] According to further embodiments, metal mixing is facilitated by using one or more pairs of solids injection lances in the direct smelting vessel, wherein one branch of a pair of solids injection lances provides at least a majority of the injected feed solids for the pair of solids injection lances at any given time.

[0023] In other embodiments, injection of feed solids through one branch of the pair of solids injection lances is reversed to an opposite branch of the pair of solids injection lances either immediately after injection through one branch or after a period of time.

[0024] Another embodiment of the present disclosure includes an apparatus for direct smelting metal-bearing materials and producing molten metal and molten slag. The apparatus includes a direct smelting vessel, the direct smelting vessel including at least one of the following: a layered refractory hearth, a refractory hearth with one or more gas bubbling devices, or one or more pairs of solid injection lances. The layered refractory hearth with two refractory floor layers includes a first layer and a second layer, the first layer having a first depth that supports a first metal depth, and the second layer having a second depth that supports a second metal depth. The second metal depth is greater than the first metal depth. One or more pairs of solid injection lances utilize a branch of a pair of solid injection lances that provides at least a majority of the injected feed solids to the pair of solid injection lances at any given time. The layered refractory hearth, one or more gas bubbling devices, or one or more pairs of solid injection lances promote metal mixing at a region below the slag layer adjacent to the vessel wall of the direct smelting vessel.

[0025] In further accordance with embodiments, metal mixing reduces stagnant zones that can support a semi-solid slag layer that limits metal-slag heat transfer between the molten metal and the molten slag.

[0026] In other embodiments, the metal mixing maintains an effective temperature difference between the metal flowing out of the forehearth and the metal at the vessel wall of no more than 40°C.

[0027] In still other embodiments, the direct smelting vessel comprises a tiered refractory furnace.

[0028] In yet other embodiments, the first layer comprises at least 70% of the cross-sectional area of ​​the refractory floor, wherein the first depth supports a first metal depth of no greater than 900 mm, and wherein the second depth supports a second metal depth at least 300 mm greater than the first metal depth.

[0029] In other embodiments, the direct smelting vessel comprises a refractory furnace having one or more gas bubbling devices.

[0030] In still other embodiments, the direct smelting vessel includes one or more pairs of solids injection lances.

[0031] To achieve the above and related purposes, one or more embodiments of the present invention include the features fully described and particularly pointed out in the claims below. The following description and the accompanying drawings set forth certain illustrative features of one or more embodiments. However, these features are indicative of only a few of the various ways in which the principles of the various embodiments may be employed, and this description is intended to include all such embodiments and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention is further described by way of example with reference to the accompanying drawings, in which:

[0033] Figure 1A is a cross-sectional side view of a direct smelting vessel having an SRV using a shallow pool concept to achieve metal mixing in the cold shoulder region in accordance with an embodiment of the present disclosure.

[0034] Figure 1B According to the embodiments of the present disclosure Figure 1A A cross-sectional top view of a direct smelting vessel.

[0035] Figure 2A is a cross-sectional side view of a direct smelting vessel having an SRV using stirring gas injection to achieve metal mixing in the cold shoulder region in accordance with an embodiment of the present disclosure.

[0036] Figure 2B According to the embodiments of the present disclosure Figure 2A A cross-sectional top view of a direct smelting vessel.

[0037] Figure 3 A process flowsheet for direct smelting utilizing a direct smelting vessel having an SRV employing means for providing metal mixing in a cold shoulder region in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION

[0038] Embodiments of the invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments shown herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0039] The term "smelting" is understood herein to mean a thermochemical process in which chemical reactions that reduce metal oxides occur to produce carbonaceous molten metal. These smelting reactions occur only at sufficiently low oxygen potentials and are highly endothermic, requiring a large supply of heat to maintain a constant process temperature.

[0040] Two processes for direct smelting metalliferous materials rely primarily on a molten bath as the smelting medium and are generally referred to as the HIsmelt process and the HIsarna process. As will be discussed in further detail herein, the HIsmelt process utilizes an SRV, while the HIsarna process utilizes an SRV and a CCF located above the SRV.

[0041] The HIsmelt process involves directly smelting metal-containing materials in the form of iron oxide and producing molten iron. The process includes forming a molten iron bath and slag in a vessel (e.g., an SRV). Materials are injected into the bath, including metal-containing materials (e.g., iron oxide, etc.) and solid carbonaceous materials (e.g., coal, etc.), which act as a reducing agent for the iron oxide and a source of energy for forming a molten metal bath within the vessel.

[0042] The HIsmelt process also includes post-combustion of reaction gases (such as CO and H2 released from the molten pool) with oxygen-containing gas (usually hot oxygen-enriched air or technical pure cold oxygen) in a generally gas-continuous space above the molten pool (e.g., referred to as the head space). The heat generated by the post-combustion reaction is transferred to the molten pool to meet the thermal energy required for smelting the metal-containing material.

[0043] The HIsmelt process also includes forming a transition zone above the nominal quiescent surface of the molten pool. In this zone, there are a large number of rising and falling droplets, splashes or streams of molten metal and / or slag, which provide an effective medium to transfer most of the heat energy generated by the post-combustion reaction gases above the molten pool to the molten pool. The plume transfers heat from the headspace where the heat is generated (e.g., at a relatively high oxygen potential) to the molten pool used for smelting purposes (e.g., at a relatively low oxygen potential). Therefore, the plume effectively acts as a heat pump.

[0044] In the HIsmelt process, metal-bearing material and solid carbonaceous material are injected into a molten bath by a plurality of solid injection lances. The lances may be inclined relative to the vertical so as to extend downwardly and inwardly through the sidewalls of the direct smelting vessel and into the lower region of the vessel, thereby delivering at least a portion of the solid material into the molten metal layer in the bottom of the vessel. In order to promote post-combustion of the reaction gases in the upper portion of the vessel, a stream of hot air, which may be enriched with oxygen, is injected into the upper region of the vessel by one or more downwardly extending gas injection lances. Exhaust gases resulting from the post-combustion of the reaction gases in the vessel are discharged from the upper region of the vessel through an exhaust gas duct. The sidewalls and top of the vessel also include slag-coated water cooling plates through which water is circulated in a continuous loop.

[0045] The molten metal product is withdrawn from the smelting reduction vessel (SRV) via a forehearth. The forehearth is a siphon overflow device connected to the molten metal pool in the SRV through an opening near the bottom of the metal pool (the "forehearth connection"). The forehearth allows molten metal to be withdrawn from the SRV in a continuous manner during operation while maintaining the metal level in the SRV for safe operation (e.g. keeping large pieces of metal away from water cooling elements).

[0046] With respect to the SRV, the HIsarna process has the same or similar physical components and layout as the HIsmelt process and operates in the same or similar manner. The difference between the two is that in the HIsarna process, the incoming iron ore is not sprayed into the molten pool, but is heated, partially pre-reduced, and substantially melted in a smelting cyclone (e.g., within a CCF) that is directly connected to the gas outlet at the top of the SRV. Substantially molten, partially reduced iron ore droplets fall from the smelting cyclone into the SRV slag and are smelted from there (e.g., primarily carbon-rich metal reacts with FeO in the slag). Carbonaceous material is still sprayed into the molten pool as previously described to carburize the metal and produce splashing, fountain plumes and mixing within the SRV.

[0047] In both HIsmelt and HIsarna processes, the heat transfer process from the headspace combustion zone to the molten pool is effectively carried out in two steps. The first step is the heat transfer from the gas space to the slag in the upper zone of the SRV, and the second step is the heat transfer from the slag to the metal in the lower zone. There are actually two fountains in the SRV, namely the first is mainly a slag fountain that splashes into the headspace to obtain heat from the hot combustion gases, and the second is a metal fountain that splashes into the slag layer to obtain heat from the hot slag and carry it to the metal pool.

[0048] A previously unrecognized mechanism that limits metal-slag heat transfer is referred to herein as a "cold shoulder." When slag splashes onto a water-cooled plate, an intermediate semi-solid layer forms between the frozen layer of solidified slag and the bulk of molten slag. This semi-solid layer can move downward under the action of gravity until it encounters the metal-slag interface near the vessel wall. If the molten metal temperature at this location is low enough, the semi-solid slag can float inward from the vessel wall toward the center. Therefore, the semi-solid slag layer can occupy a portion of the cross-section of the molten pool, thereby inhibiting the free movement of metal and slag across this horizontal interface. This limits metal-slag heat transfer, thereby impairing SRV productivity. The term "cold shoulder" refers to the metal temperature at the periphery of the molten pool, the lower its temperature, the easier it is for the semi-solid slag to float inward (resulting in more limited metal-slag heat transfer).

[0049] Ideally, the temperatures of the metal and slag will be fairly close, with the slag being slightly hotter than the metal. A typical metal forehearth temperature target is 1400-1450°C (2252-2642°F). A nominal temperature drop of 20°C (36°F) across the forehearth means that the actual metal temperature in the primary splash zone is about 1420-1470°C (2588-2678°F). The slag temperature in the primary splash zone will be slightly higher than this, ideally 1430-1500°C (2606-2732°F), such as measured as the slag is tapped through the tap chute. The stronger the cold shoulder effect, the greater the temperature difference between the metal and slag. A suitable (practical) target for efficient SRV process operation is a temperature difference of no more than about 70°C (126°F) between the tap hole temperature and the forehearth metal temperature. This equates to a metal-slag temperature difference of about 50°C (90°F) inside the SRV.

[0050] The present invention relates to improvements in metal-slag heat transfer based on an apparatus for improving metal mixing (e.g., passive or active) at a region below a slag layer adjacent to a vessel wall of a direct smelting vessel (e.g., a cold shoulder region). For example, providing improved metal mixing in this region reduces stagnant zones that can support a semi-solid slag layer that limits metal-slag heat transfer. In particular, the apparatus for providing metal mixing maintains an effective temperature difference between metal flowing out of a forehearth and metal at the vessel wall of no more than 40°C (72°F) (or in some embodiments no more than 30°C, i.e., 54°F, or no more than any value between 30-40°C).

[0051] In some embodiments of the invention, the means for promoting metal convection may include a layered refractory furnace having two refractory floor layers. The effective depth of the metal bath of the first layer provides passive metal convection in the cold shoulder region of the SRV while maintaining the safety function around the forehearth using the second deeper layer, as will be described in further detail herein.

[0052] In other embodiments of the invention, the means for promoting metal convection may include a refractory furnace utilizing one or more gas bubbling devices.

[0053] Other devices may include at least one pair of solids injection lances, wherein a first opposing lance of the pair provides the pair with injected feed solids (e.g., all, a majority, etc.) at any given time (e.g., immediately or some time later) before switching to a second opposing lance of the pair. These devices are described in further detail herein.

[0054] In the HIsmelt pilot plant, a vertical SRV was operated with a metal bath depth of about 250-400 mm (about 10-16 inches) in a furnace with an inner diameter of 2.7 m (about 8.9 feet). The metallurgical properties in this HIsmelt process enable high heat transfer rates between the metal and the slag, so that up to about 30 MW of useful heat can be transferred to the metal bath. The net result is a process in which 15 t / h of wet ore (with an iron content of 62.8%) is converted into 8.5 t / h of hot metal (with a carbon content of 4%). In operation, the pilot plant SRV was found to be highly responsive to changes in the coal and ore injection rates. The temperature difference between the outflowing metal and the outflowing slag (tapped slag) is modest, typically between about 0°C and about 40°C (72°F). However, it is difficult to measure the temperature difference within the SRV with high accuracy. During testing, it was found that increasing the amount of coal and ore injection resulted in increased spatter (e.g. both slag in the gas and metal in the slag), which in turn resulted in increased heat transfer to the bath. The pilot plant SRV was therefore judged to be operating at the process "sweet spot", which was subsequently used as a justification for building a commercial scale demonstration plant, i.e. a 6m (approximately 19.7 ft) SRV.

[0055] One of the practical issues associated with the Pilot Plant SRV (2.7m) is that due to the relatively shallow metal pool, the height of liquid metal to provide a liquid seal on top of the forehearth connection is small (typically 150-250mm / 6-10 inches). If the back pressure control valve fails, the Pilot Plant SRV pressure may increase momentarily, blowing the slag out of the forehearth. This creates a potential hazard and forces the process to be stopped.

[0056] The practical response was that all subsequent SRVs (e.g., the 6m SRV, etc.) were designed to operate in a deeper metal pool to minimize the potential for slag blowout. Subsequent designs used metal pools of approximately 1200-1500mm (approximately 47 to 59 inches) in depth in the 6m SRV and approximately 850-1000mm (approximately 34-39 inches) in depth in the 2.7m pilot plant SRV. While this increase in metal depth was very effective in reducing the potential for slag blowing through the forehearth connection, it was considered to have unintended, potentially negative consequences. That is, during the commissioning of the 6m SRV, heat transfer from gas to slag was very efficient (e.g., slag was heated to 1500-1550°C / 2732-2822°F), but heat transfer from slag to metal pool was not very effective (e.g., metal was only approximately 1400°C / 2552°F). Furthermore, improving heat transfer from slag to metal pool was difficult to remedy. The temperature difference between the tap metal and the tap slag is typically about 100-150°C (about 180-270°F), and in some cases 200°C (360°F) or more. As a result, the heat of the molten pool is limited, which greatly reduces productivity and efficiency. The underlying cause is believed to be a function of the solid injection lance configuration, but changes in lance arrangement (e.g., from 8 lances to 2 "giant lances") have only slightly alleviated these problems, which remain essentially unresolved.

[0057] A 6m SRV was subjected to a tapping test, which involved opening the tap hole through the side wall at the metal-slag interface while the SRV was operating normally, and then measuring the temperature and sampling the metal and slag flowing out. The results showed that the metal / slag temperature at the tap hole location was about 150°C (about 270°F) lower than normal tapping (e.g., at the higher tap trough), and about 50°C (about 90°F) lower than the metal flowing out of the front furnace. Samples of the rapidly quenched slag taken from both the tap trough and the tap were subjected to morphological analysis. Samples taken from the tap trough (the higher, the hotter) showed a uniform (fully molten) morphology, while samples taken from the tap showed the presence of a crystalline phase, indicating that the material temperature at this location was significantly below its liquidus temperature. The analysis confirmed the presence of unexpectedly cold metal and slag at the periphery of the 6m SRV directly below the slag layer.

[0058] The slag thrown at the water-cooled elements in the SRV forms a frozen layer that is typically 20-30 mm (0.79-1.18 inches) thick. As described above, there is a transition zone between the solid slag in the frozen layer and the hot, fully liquid slag further away from the frozen layer. The transition zone is expected to contain a highly viscous semi-solid slag (e.g., a mixture of solid slag and sticky slag) containing a crystalline phase consistent with a bulk slag precipitate. It is further expected that this type of semi-solid slag can slowly migrate downward along the wall under the action of gravity, eventually reaching the metal-slag interface. At this location, it may effectively float on the molten metal. It is believed that the material sampled in the slag removal test was taken from the semi-solid slag located at the metal-slag interface.

[0059] The presence of semi-solid slag at the metal-slag interface represents a more significant potential problem, since the temperature of the metal immediately adjacent to the semi-solid slag is also lower than the desired temperature. Thus, the estimated bulk metal temperature in the molten pool (e.g., the temperature measured at the forehearth plus an estimated heat loss of about 20°C (36°F) across the forehearth itself) is about 70°C (126°F) higher than the metal in the semi-solid slag adjacent to the tapping location. This means that the uppermost portion of the metal pool, at the periphery near the vessel wall, is about 70°C (126°F) cooler than the bulk metal (e.g., molten mixed metal) in the center (e.g., central zone) of the SRV.

[0060] Metal-pool hydrodynamic analysis shows that metal depth and mixing in the cold shoulder region appear to be interrelated. The ejection of solids results in an upwelling of more or less central metal into the central fountain region, with an associated region of turbulence surrounding the central jet activity. For continuity, any metal moving upward in the central region of the SRV is locally displaced by metal flowing in from elsewhere. If the metal pool is deep, this metal displacement flow can come from the sides and from below, consistent with normal liquid flow in a large body of liquid. In this case, the upper periphery, the cold shoulder region, does not necessarily participate in mixing and therefore may become a stagnant “dead spot” (i.e. little or no mixing). With little metal moving into and out of this cold shoulder region, natural heat losses from the refractory wall may result in some localized metal cooling and is therefore a potential cause of the observations made during the deslagging tests.

[0061] In a shallow metal pool, such as in a pilot plant SRV (i.e. a 2.7 m SRV), metal replacement cannot come more from below (e.g. because the floor is in the way) but is forced to flow in more strongly from the sides. As a result, in the pilot plant SRV, the liquid turbulence zone associated with the injection plume is "squeezed" from below and, therefore, naturally the metal turbulence zone is likely to expand in the lateral direction towards the vessel wall. As a result, metal convection entering and leaving the cold shoulder zone is significantly stronger, resulting in an increase in the metal temperature in this area. Therefore, a high viscosity cold semi-solid slag (e.g. with solid slag and sticky slag) in the transition zone moving down the wall will encounter a significantly hotter metal layer relative to the slag liquidus temperature.

[0062] As described above, the semi-solid slag (e.g., sticky slag with solid slag) that arrives at the metal-slag interface, if it remains cool enough, can form a slag layer that floats on the molten metal and penetrates as far as possible toward the center of the SRV. At some point along a radial line from the wall to the center, the metal mixing and temperature rise sufficiently that the slag layer with semi-solid slag will be broken up, melted, and moved away (e.g., by convection or mixing). Thus, the slag layer will be in a dynamic equilibrium in the form of a donut-shaped ring (in plan view) with a given average size. The outer diameter of the ring is defined by the SRV wall, and the inner diameter of the ring is defined by the local metal mixing and the temperature across the metal-slag interface.

[0063] Such a slag layer (e.g., donut-shaped, etc.) can provide a barrier that effectively reduces heat transfer from the metal to the slag. Within the "slag radius" in the outer region, the barrier effectively restricts the free movement of the liquid metal and slag in both the upward and downward directions. The smaller the slag radius, i.e., the distance from the outer wall to the radial point where the slag breaks up, melts, and moves away, the easier it is for the bulk metal and bulk slag layer in the SRV to interact and exchange heat. This is believed to be the reason why the pilot plant SRV (i.e., 2.7 m) performs better in terms of slag-to-metal heat transfer than the 6 m SRV.

[0064] A key issue identified is that stagnant metal in the cold shoulder region can cause localized cooling, which in turn can cause the dross layer to grow more than would otherwise occur. To improve metal-to-slag heat transfer efficiency in larger SRVs (e.g., deep metal SRVs), metal mixing should be promoted (e.g., passively and / or actively) in the cold shoulder region. As described herein, mixing in the cold shoulder region can be improved in a variety of ways by different means. However, the core objective is to bring a sufficient amount of hot bulk molten metal into the cold shoulder region to break up, mix and melt the dross layer and to expand the central "active core" region to allow for free metal-to-slag mixing and heat transfer.

[0065] As described herein, an apparatus for promoting metal mixing (e.g., passive mixing and / or active mixing) in a cold shoulder region may include (i) a layered refractory furnace having two refractory floor layers, (ii) a refractory furnace utilizing one or more gas bubbling devices, and / or (iii) at least one pair of solids injection lances, wherein at any given time prior to switching to a second opposing lance of the pair, a first opposing lance of the pair provides injected feed solids to the pair.

[0066] For the layered refractory furnace, passive radial metal mixing is promoted by making the majority of the SRV metal pool shallow enough (based on the pilot plant's 2.7m SRV), while retaining a deep pool area adjacent to the forehearth connection and end discharge taphole for safety.

[0067] Alternatively or additionally, additional stirring gas may be intentionally injected into the molten pool by using appropriate means in order to enhance metal mixing near the walls and achieve the desired heat transfer effect.

[0068] Furthermore, alternatively or additionally, the process may include the deliberate use of pairs of single-sided solids injection lances whose injection plumes are sufficiently strong to promote the necessary level of convection in the metal layer at the opposing walls. Thus, a strategy of alternating between opposing lances (in a given pair) in a regular cycle may be used to control the dross layer, using a relatively long time constant associated with the hot metal in the wall region to allow for sufficient cooling before the dross layer can reestablish itself in a meaningful manner.

[0069] With reference to the accompanying drawings, Figure 1A A side cross-sectional view of a direct smelting vessel 101 is shown, the direct smelting vessel forming part of an apparatus particularly suitable for carrying out the HIsarna process described herein. Figure 1B Shows Figure 1A A top cross-sectional view of the direct smelting vessel 101 is shown. Figure 1A As shown, a layer of molten slag 102 is located above a layer of molten metal 103 , supported by a refractory lined furnace 104 within the SRV 120 .

[0070] The direct smelting vessel 101 injects coal and additives into the molten metal pool using two solid injection lances 105 to penetrate the molten metal layer 103 and form a turbulent injection zone 106. The bottom of the injection zone 106 is determined by the conditions at the outlet of the injection lances 105 and is typically located about 200-300 mm (about 7.9-11.8 inches) below the static metal layer in the SRV 120.

[0071] Figure 1AThe furnace bottom shown in comprises two different layers. For example, a main layer (otherwise described as the first layer) comprising 60, 65, 70, 75, 80, 85, 90, 95 or a series of percentages (e.g., falling within, outside or overlapping these values) of the planar area (cross-sectional area) of the refractory furnace can have a higher floor layer. In a specific embodiment, the area of ​​the main layer with a higher floor layer is preferably at least 70%. In other embodiments, the area of ​​the main layer with a higher floor layer is between about 75-85%, and preferably about 80% in some embodiments. The remaining percentage of the furnace floor area is a secondary layer (otherwise described as the second layer) adjacent to the forehearth connection 109, which is deeper than the main layer. In a specific embodiment, the percentage of the secondary layer is between 15-25% of the refractory furnace floor area, and preferably about 20% in some embodiments. The floor height in the main layer can be selected so that the working metal depth 107 is not greater than about 2 times the metal injection depth calculated from the spray gun spray plume. In practice, this translates to a metal pool depth of about 400-600 mm (about 15.7-23.6 inches) in a commercial size SRV (e.g., a 6 m SRV, etc.). It will be appreciated that the pool depth may vary depending on the diameter of the refractory hearth (e.g., scaled with changes in diameter). Thus, the depth ratios described herein may be used to scale the depths of different SRVs having different diameters.

[0072] The floor height of the secondary layer can be set to meet safety requirements for maintaining a sealed forehearth (e.g., 1200-1500 mm, or 47.2 to 59.1 inches for a commercial-scale 6 m SRV). The secondary layer can be sized to act as a metal sump, accommodating both the forehearth connection 109 and one or more end discharge tapholes 110. In this type of refractory arrangement, vigorous lateral metal mixing will occur naturally (e.g., passively from the perspective of the equipment operator) in the cold shoulder area. This will provide the necessary "melt back" to keep the dross layer small and allow free metal-slag interaction for heat transfer. In turn, this leads to reduced FeO content in the slag, increased productivity, increased efficiency, and reduced costs. For slag formulations where high amounts of foaming are a potential problem (e.g., iron ore containing 2-6% titanium dioxide), this will also reduce the foaming potential, making the operation of the SRV more reliable.

[0073] Figure 2A and Figure 2B An SRV 201 is shown with its refractory floor configured in a conventional manner, having a metal bath depth of approximately 1200-1500 mm (approximately 47.2 to 59.1 inches) across the diameter of the 6 m SRV.

[0074] like Figure 2A and Figure 2BAs shown, in some embodiments of the present invention, in order to mix the molten metal in the SRV, especially to promote mixing at the cold shoulder area, a series of downwardly angled bubbler lances 202 can be used. The bubbler lances 202 direct a bubbling stirring gas (e.g., argon, etc.) into the metal pool, which promotes gas stirring in the molten metal (e.g., similar to using gas bubbling to promote mixing in a ladle).

[0075] The gas bubblers 202 (e.g., argon bubblers, etc.) are typically thick-walled stainless steel tubes of about 5 mm (about 0.20 inches) inner diameter (ID), lined with an outer alumina layer about 5-15 mm (about 0.20-0.59 inches) thick. These bubblers are designed so that if back pressure is lost for any reason, the molten metal will attempt to push back up into the bubbler but will freeze there (e.g., due to the thermal mass of the tube wall relative to the liquid metal). In this way, an inherently fail-safe design can be achieved, in the event of a bubbler failure, this will not affect the rest of the refractory lining.

[0076] These bubblers provide active metal mixing pulses to the otherwise stagnant cold shoulder region, achieving similar benefits to those described with respect to the primary and secondary layers of a layered refractory furnace.

[0077] In some embodiments, pairs of single-sided solid injection lances are used, whose injection plumes are strong enough to promote convection in the metal layer at the opposite wall. Therefore, the dross layer can be controlled using a strategy of alternating between opposite lances (in a given pair) in a regular cycle, using a relatively long time constant associated with the hot metal in the wall region to cool sufficiently before the dross layer can re-establish itself in a meaningful way. Therefore, at least one pair of opposite solid injection lances can be used, and at any given time (e.g., at least 50% of the total time in normal operation), substantially all of the molten pool injection feed solids assigned to each pair are fed through one branch of the pair. Then, feed through one branch of each pair of lances and then reverse to the other branch, either immediately after the previous branch cycle or at some later time. Therefore, this asymmetric lance injection and metal thermal inertia can be used to achieve benefits similar to those described with respect to the primary and secondary layers of the above-mentioned layered refractory furnace and / or gas bubbler. It should be understood that providing substantially all of the feed solids can include all or all negligible amounts of feed solids from the opposite lances. Additionally, in some embodiments, a majority of the feed solids may be allocated to one of a pair of opposing lances. Thus, in some embodiments, the feed solids provided by one branch of a pair of opposing lances may include 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 85, 80, 75, etc. percent of the feed solids of the pair of opposing lances.

[0078] In some embodiments, different means for promoting metal mixing in the cold shoulder region may be used in combination. For example, the means may include one or more SRVs having relative Figure 1A and Figure 1B The primary and secondary layers described herein use bubblers 202 to provide improved melting in the cold shoulder region, use at least one pair of opposed solids injection lances and alternately feed solids between each lance of the pair, and / or use other similar devices not specifically described herein.

[0079] Figure 3 A molten bath based process is provided for the direct smelting of metalliferous material, such as iron oxide, and for producing molten metal in a direct smelting vessel. Figure 3 As shown in block 310 of , metal-bearing material (eg, ore, such as iron ore fines, etc.) is injected into the SRV 120 and / or into the smelting cyclone 130 using the solids injection lance 105 and then enters the SRV 120 from the smelting cyclone.

[0080] In some embodiments, an ore pre-processing unit, such as an ore dryer or an ore pre-heater, may be used to dry and / or heat the solid metalliferous material before it is injected into the SRV 120 through the injection lance 105 or before it is injected into the smelting cyclone 130. In addition, a metalliferous material dispensing / metering unit may be used for the pre-processed metalliferous material to control the time and amount of metalliferous material used.

[0081] Figure 3 Block 320 shows that solid carbonaceous material (e.g., coal, etc.) is injected into the molten pool in SRV 120 through at least one injection lance (e.g., extending downward and inward, etc.) such that the injected solids at least partially penetrate the molten metal layer. In addition, a carbonaceous material dispensing / metering unit can be used for the carbonaceous material to control the timing and amount of carbonaceous material used.

[0082] Figure 3 Controlling the slag layer as described herein using a means for promoting mixing of metal in a cold shoulder region near the wall and below the slag layer is further shown in box 330. The means for promoting mixing of metal is used to maintain the temperature of the metal at the cold shoulder region at no greater than 40° C. (72° F.), or other temperature as described herein, which is lower than the temperature of the metal in the forehearth of the SRV.

[0083] As shown in block 330, the apparatus includes promoting passive radial metal mixing while retaining a deep melt pool region adjacent to a forehearth connection using the layered refractory hearth described herein.

[0084] Alternatively or additionally, the apparatus includes intentionally injecting additional stirring gas into the molten pool, such as via a gas bubbler, which enhances metal mixing near the SRV walls to achieve slag-metal heat transfer.

[0085] Alternatively or additionally, the apparatus includes the deliberate use of pairs of single-sided solids injection lances whose injection plumes are sufficiently strong to promote convection in the metal layer at the opposing walls. By alternating between opposing lances of a given pair in a regular cycle, the formation of the dross layer can be controlled by using a relatively long time constant associated with the molten iron in the wall region being sufficiently cooled before the dross layer can be reestablished in a meaningful manner.

[0086] To supplement the present disclosure, the present application also incorporates the following references in their entirety by reference:

[0087] 1. U.S. Patent No. 6,989,042 “Direct Smelting Process and Apparatus”, priority date April 17, 2000

[0088] 2. US Patent No. 8221675 “Direct Smelting Vessel and Cooler Therefor”, priority date May 18, 2006

[0089] 3. U.S. Patent US 9175907 “Direct Smelting Process and Apparatus”, priority date February 9, 2010

[0090] 4. Australian Patent AU 2011301784 (WO 2012 / 034184) “Direct Smelting Process”, priority date September 15, 2011

[0091] 5. U.S. Patent US 9359656 “Direct Smelting Process”, priority date February 9, 2012

[0092] 6. PCT / AU2012 / 000293 (WO2012 / 126055) “Direct Smelting Process for High Sulphur Feed”, priority date 21 March 2012

[0093] 7. PCT / AU2012 / 001486 (WO2013 / 082658) “Starting a Smelting Process”, priority date 6 December 2011

[0094] 8. PCT / AU2012 / 001481 (WO2013 / 082653) “Starting a Smelting Process”, priority date 6 December 2011

[0095] 9. PCT / AU2012 / 001487 (WO2013 / 082659) “Starting a Smelting Process”, priority date 6 December 2011

[0096] 10. CT / AU2014 / 001098 (WO2015 / 081376) “Smelting Process and Apparatus”, priority date December 4, 2014

[0097] 11. PCT / AU2014 / 001146 (WO2015 / 089563) “Smelting Process and Apparatus”, priority date December 19, 2014

[0098] Specific embodiments of the present invention are described herein. With the benefit of the teachings provided in the foregoing description and the associated drawings, those skilled in the art to which the present invention pertains will recognize many modifications and other embodiments of the present invention set forth herein. Therefore, it should be understood that the present invention is not limited to the specific embodiments disclosed, and modifications and other embodiments and combinations of embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein, they are used only in a general and descriptive sense and not for the purpose of limitation.

Claims

1. A method for direct smelting metalliferous material and producing molten metal in a direct smelting vessel, the method comprising: injecting solid carbonaceous material through at least one injection lance extending into the direct smelting vessel such that solids at least partially penetrate into a layer of molten metal in the direct smelting vessel, wherein a slag layer floats on the layer of molten metal; and Metal mixing is promoted in a region beneath the slag layer immediately adjacent a vessel wall of the direct smelting vessel.

2. The method of claim 1 wherein the metal mixing reduces the volume occupied by stagnant zones that are cool enough to support a semi-solid slag layer that limits metal-slag heat transfer.

3. The method of claim 1 wherein the metal mixing maintains an effective temperature difference between the metal flowing out of the forehearth and the metal at the vessel wall of no more than 40°C.

4. The method of claim 1 wherein the metal mixing is facilitated using the direct smelting vessel, the direct smelting vessel comprising: a layered refractory floor having two refractory floor layers, the two refractory floor layers comprising a first layer and a second layer, the first layer having a first depth that supports a first metal depth and the second layer having a second depth that supports a second metal depth; wherein the second metal depth is greater than the first metal depth; and The first depth wherein the first metal depth is supported promotes mixing of the metal by convection of metal into and out of an area beneath the slag layer adjacent the vessel wall.

5. The method of claim 4, wherein the first layer comprises at least 70% of the cross-sectional area of ​​the layered refractory floor.

6. The method of claim 4, wherein the first depth supports the first metal depth of no greater than 900 mm.

7. The method of claim 4, wherein the first depth supports the first metal depth of no greater than 700 mm.

8. The method of claim 4, wherein the first depth supports the first metal depth of no greater than 600 mm.

9. The method of claim 4, wherein the second depth supports the second metal depth being at least 300 mm greater than the first metal depth.

10. The method of claim 1 wherein the metal mixing is promoted by injecting gas in the direct smelting vessel using one or more gas bubbling devices to promote convection of metal to a region beneath the slag layer adjacent the vessel wall. The method of claim 10 , wherein the gas comprises argon or nitrogen.

12. The method of claim 1 wherein the metal mixing is facilitated by using one or more pairs of solids injection lances in the direct smelting vessel, wherein one branch of a pair of solids injection lances provides at least a majority of the injected feed solids to the pair of solids injection lances at any given time.

13. The method of claim 12, wherein the injection of the feed solids through the one branch of the pair of solids injection lances is reversed to an opposite branch of the pair of solids injection lances immediately after injection through the one branch or after a period of time.

14. An apparatus for direct smelting of metalliferous material and producing molten metal and molten slag, the apparatus comprising: A direct smelting vessel comprising at least one of: (a) A layered refractory furnace having two refractory floor layers, comprising: a first layer having a first depth supporting a first metal depth; and a second layer having a second depth supporting a second metal depth, wherein the second metal depth is greater than the first metal depth; (b) a refractory furnace having one or more gas bubbling devices; or (c) one or more pairs of solids injection lances, wherein one branch of a pair of solids injection lances provides at least a majority of the feed solids injected to the pair of solids injection lances at any given time; wherein the stratified refractory furnace, the one or more gas bubbling devices, or the one or more pairs of solids injection lances promote metal mixing at a region below a slag layer adjacent a vessel wall of the direct smelting vessel.

15. The apparatus of claim 14, wherein the metal mixing reduces stagnant zones capable of supporting a semi-solid slag layer that limits metal-slag heat transfer between the molten metal and the molten slag.

16. The apparatus of claim 14, wherein the metal mixing maintains an effective temperature difference between the metal flowing out of the forehearth and the metal at the vessel wall of no more than 40°C.

17. The apparatus of claim 14 wherein the direct smelting vessel comprises the tiered refractory furnace.

18. The apparatus of claim 17, wherein the first layer comprises at least 70% of the cross-sectional area of ​​the refractory floor, wherein the first depth supports the first metal depth of no greater than 900 mm, and wherein the second depth supports the second metal depth of at least 300 mm greater than the first metal depth.

19. The apparatus of claim 14 wherein the direct smelting vessel comprises the refractory furnace having one or more gas bubbling devices.

20. The apparatus of claim 14 wherein the direct smelting vessel comprises the one or more pairs of solids injection lances.

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