TW202117025A - A partition wall of a reducing furnace - Google Patents

Abstract

The present invention relates to a method for smelting metal- and metal oxide containing wastes and side streams, such as slags, dust, scales and sludges genereated in stainless steel and ferrochrome manufacturing processes. The invented method is a physical separation process of liquid metals produced in a combined ferrochrome and stainless steel slags cleaning furnace. Metal streams are separated mainly for usability and value reason.

Description

Partition wall of reduction furnace

The present invention relates to a cooling refractory wall inside a slag cleaning furnace used for FeCr and steelmaking workshop (SMS) slag reduction and precipitation. The wall allows the metal droplets present in the molten slag input feed to be partially separated from the metal droplets produced during the reduction reaction. This allows one furnace to simultaneously produce two metal products with different chemical contents. The main driving factor is to provide the possibility of producing high and low nickel chromium iron from the slag flow mentioned above.

At present, according to the current advanced technology level, the slag from the production of ferrochrome is allowed to cool, and the metal particles are separated from the cold slag by mechanical separation methods, usually by winnowing, thick coal separation, and magnetic separation. In these types of recovery processes, the total yield of chromium is usually less than 50%, because the slag phase contains a large amount of chromium oxide that has not been separated by the methods mentioned. Depending on the smelter process and the grade of chromite used, the slag can contain 5% to 10% FeCr metal and 5% to 20% chromium oxide.

Under the current advanced technology level, the slag from stainless steel production is currently processed by allowing it to cool, reducing the particle size of the slag, and separating the metal particles into individual streams using screens or magnets. The total yield of nickel in these processes usually exceeds 95%, because nickel is usually present in the slag only in metal particles.

One of the known methods for combined liquid slag treatment has been described in the Finnish Patent Application No. 20195153 of Parviainen and Vallo, "Combined smelting of molten slag and residue from stainless steel and ferrochrome plants (Combined Smelting of molten slags and residuals from stainless steel and ferrochromium works)". This application describes a furnace or converter method for processing the above-mentioned slag stream in a furnace to recover precious iron, nickel and chromium units from oxides of their metals by carbothermal reduction. However, the nickel units present as droplets in the stainless steel slag are diluted to the total metal flow of oxides and droplets, thereby reducing the product nickel composition. Typically, ferrochromium with high nickel content is of great value to austenitic stainless steel manufacturers, and low-nickel ferrochromium is suitable for manufacturing high-grade iron stainless steel grades.

In the present invention, a method for producing high and low nickel FeCr products using a single furnace is disclosed.

The present invention is defined by the content disclosed in the independent claim. The preferred embodiments are described in the attached claims.

According to the present invention, the metal droplets present in the slag stream fed to the furnace are separated into two dissimilar metal pools by a wall made of suitable refractory material. The metal particles produced during the carbothermal reduction process of metal oxides are partially separated into pools on respective sides of this wall. A part of these droplets will settle into the first pool. Another part of these droplets will settle into the second pool. The separated metals have different compositions: the first pool will have a high nickel content, and the second pool will have a near zero nickel content. The chromium content in pool two is slightly higher than that in pool one because there is no dilution effect of nickel. The actual metal composition in the two pools is related to the characteristics of the feed material and the metal relative to the metal oxide content.

Concentrating nickel to a lower metal volume will increase its value. Typically, the value of iron-nickel alloys is rated based on their nickel content. The higher the nickel content, the greater the benefit provided by the material flow. This innovation allows a high separation rate of nickel, thereby increasing the total value of its composition and the material produced.

The present invention relates to a method for smelting metal and metal oxide wastes and side streams such as slag, dust, scale and sludge generated in the manufacturing process of stainless steel and ferrochrome. The method of the present invention is a physical separation process of liquid metal produced in a combined ferrochrome and stainless steel slag cleaning furnace. The separation of the metal flow is mainly due to availability and value reasons.

The embodiment of the present invention relates to a method for cleaning molten slag. For the purposes of this specification, the term slag includes all metal-containing and metal scraps and side streams such as, for example, slag, dust, fouling, and sludge produced during the manufacturing of stainless steel and ferrochrome. In the process of the present invention, the molten slag is fed into the furnace 100 from one side. On the opposite side of the furnace 100, purified slag is discharged 20 from the furnace 100. A refractory wall 200 is provided in the lower part of the furnace 100, which generates two metal pools 30, 50 under the slag layer 70 flowing from the inlet to the outlet 20. The wall 200 is high enough to separate the metal pools 30, 50, but low enough to allow the slag layer 70 other than metal to move freely from the inlet side 10 toward the outlet side 20 above the wall 200. In the furnace 100, the bottom on each side of the refractory wall 200 is a discharge arrangement 40, 60 for liquid metal.

Therefore, in one embodiment, a method for cleaning one or more slags in a furnace 100 includes the following steps: feeding one or more slags into the furnace 100 through one or more inlets 10 to form Flow through the slag layer 70 of the furnace 100; Gravity separation of metal droplets present in the slag from the slag into the first metal collection pool 30; Self-melting of other metal droplets formed in the metal oxide reduction process The slag is gravity separated into the second metal collection pool 50, which is separated from the first metal collection pool 30 by the refractory wall 200; the metal is recovered from the first metal collection pool 30 through the outlet 40; and the metal is recovered from the first metal collection pool 30 through the outlet 60 The second metal collection tank 50 recovers metal; and the cleaned slag is recovered through the outlet 20.

In a suitable embodiment, one or more of the inlets 10 are slag feed launders. In certain embodiments, one or more of the inlets 10 are adapted to feed molten stainless steel slag into the furnace 100. In other embodiments, one or more of the inlets 10 are adapted to feed molten ferrochrome slag.

In some embodiments, the slag fed into the furnace 100 is rich in nickel. For the purposes of this specification, the term nickel-rich slag should be understood to mean that the slag contains nickel compounds. In a particular embodiment, the nickel-rich slag has a nickel compound to non-nickel metal compound ratio of at least 1:1, for example a nickel compound to chromium compound ratio of at least 1:1, preferably 3: 2. Appropriately 2:1.

In the metal pool closer to the slag feed, the first metal collection pool 30, nickel-rich metal accumulates because the metal droplets present in the slag stream settle into the pool. In the second metal collecting pool 50, which is closer to the outlet for discharging the purified slag, the material that mainly originates from the reduction reaction of metal oxides and has a very low nickel content will settle.

Therefore, in one embodiment, the metal recovered from the second metal collection tank is substantially different from the metal recovered from the first metal collection tank.

Solid slag made of stainless steel can be used as a raw material to increase metal production or adjust the chemical properties of slag. If the solid slag or metal oxide stream from stainless steel production is used as the raw material input of the furnace, the feed should be directed to the area where the nickel recovery of the first metal collection tank 30 is highest, that is, in the first metal collection tank 30 Above, it is preferably close to the slag feeding side of the first metal collection tank 20 to allow the material to melt completely. Here, the slag melt and nickel oxide are reduced to nickel metal in the slag layer, and the nickel-containing droplets settle into the first metal collection pool 30. Therefore, in one embodiment, the one or more slags contain nickel oxide.

In other embodiments, the one or more slag contains chromium oxide. The solid ferrochrome production slag can be used as a raw material to increase metal production or to adjust the chemical properties of the slag. In order to maximize the chromium content of the second metal collection tank 50, the feeding area of the solid slag or metal oxide stream from ferrochrome production should be close to or higher than the refractory wall side of the second metal collection tank 50, for example, downstream of the refractory wall. Here, the slag melt and its iron oxide and chromium oxide are reduced to ferrochrome metal in the slag layer, and the metal droplets settle to the second metal collection pool 50. Therefore, in one embodiment, one or more slags are fed into the furnace through the slag inlet 10 to a position downstream of the refractory wall 200 to bypass the first metal collection pool 0. In other embodiments, one or more slags are fed into the furnace through the inlet 10 to a position upstream of the refractory wall 200 for separating nickel from the first metal collection pool 30.

The slag fed into the furnace 100 may be solid in various embodiments and may be liquid in other embodiments. In still other embodiments, the slag fed into the furnace 100 may include a combination of both liquid slag and solid slag.

Other embodiments relate to a furnace 100 for cleaning one or more molten slag. In one embodiment, the furnace 100 includes: one or more inlets 10 for feeding molten slag into the furnace to form a flowing slag layer 70; a first metal collection tank 30 configured to collect and flow The metal droplets separated by the slag layer 70 by gravity; the second metal collection pool 50, which is located downstream of the first metal collection pool, the first metal collection pool 30 and the second metal collection pool 50 are physically separated by the refractory wall 200; and One or more outlets 20, which are used to remove cleaned slag from the furnace. In one embodiment, the slag layer 70 flows directly above the metal collection pool. In one embodiment, one or more outlets 20 may be slag discharge launders.

In other embodiments, the first metal collection tank 30 includes one or more outlets 40 for metal recovery. In one embodiment, such an outlet 40 may be a tap adapted to discharge liquid metal. In other embodiments, the one or more outlets 40 may include one or more discharge holes and launders.

Similarly, in one embodiment, the second metal collection tank 50 includes one or more outlets 60 for recovering metal. Again, in one embodiment, such an outlet may be a tap adapted to discharge the liquid metal. In other embodiments, the one or more outlets 60 may include one or more discharge holes and launders.

In other embodiments, the furnace 100 further includes one or more electrodes 80 positioned between the one or more inlets 10 and the one or more outlets 20. The electrode 80 is needed to supply electrical energy to heat the material flow up to the reaction temperature-1600°C to 1650°C, and to provide heat to the actual reduction reaction.

In one embodiment, the one or more inlets 10 comprise one or more slag feed launders. In other embodiments, the one or more outlets 20 comprise slag discharge launders.

Depending on the composition of the slag to be fed into the furnace 100, the inlet 10 is positioned relative to the first metal collection tank 30 and the second metal collection tank 50. In one embodiment, one or more inlets 10 are positioned upstream of the first metal collection tank 30 and the second metal collection tank 50. In other embodiments, one or more inlets 10 are located downstream of the first metal collection tank 30.

The actual position of the refractory wall 200 depends on the furnace operating temperature, the difference in metal and slag density, and the slag viscosity at the operating temperature. Therefore, in one embodiment, the refractory wall is positioned to optimize the nickel separation ability. If the wall is too close to the entrance end or too far away from the entrance end, the nickel separation may be damaged.

The refractory wall 200 can be internally cooled by a suitable cooling medium to increase its service life. Suitable cooling media are, for example, non-fuel oil or air. The use of water may cause safety issues.

The structure of the refractory wall 200 can be independent of the furnace refractory to avoid design problems related to the thermal expansion of the refractory.

In the alternative, the refractory wall 200 may be designed as a functional part of the furnace refractory to avoid design issues related to the buoyancy effect of different densities of refractories, metals, and slag.

The purpose of the refractory wall 200 is to divide the metal pool in the furnace into two sections 30, 50, one section with high nickel and one section with low nickel.

Other embodiments describe the use of a furnace. In one embodiment, the furnace 100 described above is used in a method for cleaning one or more slags. In other embodiments, the furnace 100 described above is used in the method described above.

FIG. 1 illustrates an embodiment in which molten FeCr and stainless steel (SS) slag is fed to a rectangular one-line six self-baking furnace 100 through a feed inlet 10. The electrode configuration in the figure is exemplary.

The combined slag layer 70 flows through the furnace 100 where the purified slag is discharged to, for example, the slag pot 20.

Inside the furnace 100, metal droplets present in the feed slag settle down to the first metal pool 30 due to gravity. From the first metal pool 30, the metal is discharged from the furnace 100 through the discharge hole and the launder 40.

Inside the furnace 100, the metal droplets produced by the metal oxide reduction process can settle to both the metal pools 30 and 50 due to gravity. If the feed of the chromium-rich solid feed material is arranged to the downstream side of the refractory wall 200, the deposited metal will not dilute the nickel content in the first metal collection tank 30. The chromium oxide present in the molten slag feed will enter the two pools. The nickel oxide present in the solid feed material should be fed to the upstream side of the furnace 100 to enhance the nickel recovery of the first metal collection tank 30. From the second metal collection tank 50, similar to the first metal collection tank 30, the metal is discharged from the furnace through the discharge hole and the launder 60.

no

The present invention will be explained in more detail with reference to the accompanying drawings, in which: [Figure 1] Schematically shows a rectangular furnace with electrodes and refractory wall metal spacers according to the present invention. In a rectangular furnace, the metal pool inside the furnace is divided into two sections, one section has droplet sedimentation, and one section is used for the metal from the oxidation-reduction reaction.

10: entrance/entrance side

20: Outlet/outlet side/slag tank/discharge/first metal collection tank

30: Metal pool/first metal collection pool/section

40: Discharge configuration/outlet/discharge hole and launder for liquid metal

50: Metal Pool/Second Metal Collection Pool/Section

60: Discharge configuration/outlet/discharge hole and launder for liquid metal

70: Slag layer/flowing slag layer

80: Electrode

100: furnace

200: Refractory Wall

Claims (17)

A method for cleaning one or more slags in a furnace (100), which includes the following steps: Feeding one or more slags into the furnace (100) via one or more inlets (10) to form a slag layer (70) flowing through the furnace (100), Gravity separation of metal droplets present in the slag from the slag into a first metal collection pool (30), The other metal droplets formed in the metal oxide reduction process are gravity separated from the slag into a second metal collection pool (50), the second metal collection pool is connected by a refractory wall (200) and the first The metal collection tank (30) is separated, Metal is recovered from the first metal collection tank (30) through an outlet (4), Recover metal from the second metal collection tank (50) through an outlet (60), and The cleaned slag is recovered through an outlet (20). The method of claim 1, wherein the metal recovered from the second metal collection tank (50) is substantially different from the metal recovered from the first metal collection tank (30). The method of claim 1 or 2, wherein the one or more slags contain chromium oxide. The method of any one of the preceding claims, wherein the one or more slags comprise nickel oxide. Such as the method of any one of claims 1 to 3, wherein the one or more slags are fed into the furnace via the slag feed launder (10) to a position downstream of the refractory wall (200) to bypass the The first metal collection tank (30). The method according to any one of the preceding claims, wherein the one or more slags are fed into the furnace via the slag feed launder (10) to a position upstream of the refractory wall (200) for the purpose of removing nickel from The first metal collection tank (30) is separated. A furnace (100) for cleaning one or more molten slag, which contains: One or more inlets (10) for feeding molten slag into the furnace to form a layer of flowing slag (70), A first metal collection tank (30) configured to collect metal droplets separated by gravity from the flowing slag layer (70), A second metal collection tank (50) located downstream of the first metal collection tank, the first metal collection tank (30) and the second metal collection tank (50) are physically separated by a refractory wall (200) ,and One or more outlets (20) for removing cleaned slag from the furnace. Such as the furnace (100) of claim 7, wherein the first metal collection tank includes one or more outlets (40) for metal recovery. Such as the furnace (100) of claim 7 or 8, wherein the second metal collection tank includes one or more outlets (60) for metal recovery. Such as the furnace (100) of any one of claims 7 to 9, which further comprises one or more electrodes (80) positioned between the one or more inlets (10) and the one or more outlets (20) ). Such as the furnace (100) of any one of claims 7 to 10, wherein the one or more inlets (10) include one or more slag feeding launders. Such as the furnace (100) of any one of claims 7 to 11, wherein the one or more outlets (20) comprise a slag discharge launder. Such as the furnace (100) of any one of claims 7 to 12, wherein the one or more outlets (40, 60) for recovering metal include discharge holes and launders. Such as the furnace (100) of any one of claims 7 to 13, wherein one or more inlets (10) are positioned upstream of the first metal collection tank and the second metal collection tank (30, 50). For example, the furnace (100) of any one of claims 7 to 14, wherein one or more inlets (10) are located downstream of the first metal collection tank (30). A use of the furnace (100) according to any one of claims 7 to 15, which is used in a method for cleaning one or more slags. A furnace (100) used in the method of any one of claims 1 to 6.

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