The current disclosure relates to a cooling unit for a metallurgical furnace, the cooling unit comprising a cooling body and at least one cooling conduit leading through the cooling body, wherein a cooling liquid can be conducted via the at least one cooling conduit. Furthermore, the current disclosure relates to a metallurgical furnace comprising a heat source, a furnace wall, a furnace roof and a cooling unit and a method for manufacturing a cooling unit for a metallurgical furnace.

Due to high operating temperatures and harsh chemical and mechanical conditions metallurgical furnaces are, in general, lined with refractory materials. In addition, furnace zones which experience particularly high refractory wear due to very high temperatures or chemical or mechanical stress, can be supplied with cooling units. This can help to reduce said high refractory wear in those zones and thus helps to increase the total lifetime of the refractory lining and reduce furnace downtimes. A cooling unit comprises a cooling body for conducting heat away from the furnace and cooling lines. Cooling liquid flows through the cooling lines to dissipate the heat from the cooling body.

Inexpensive cooling bodies can be made of welded steel, which leads to low material costs but considerable welding costs. If the cooling body comprises welded cooling body parts, cooling lines can be formed between said welded cooling body parts. So, the cooling lines are defined by said welded cooling body parts and cooling liquid flows directly within the cooling body without additional cooling conduits. However, the corresponding welding seams are potential weak spots, carrying the risk for cooling liquid leakage. Also, those cooling lines usually have a polygonal, e.g., rectangular, cross section which, compared to a circular cross section, has several potential disadvantages, such as pressure loss and inhomogeneous flow speed, flow turbulences and/or flow interruption of the cooling liquid. Also, often linear flow of the cooling liquid is not possible due to geometric limits of welded cooling lines. To prevent this, cooling lines in the form of cooling conduits can be provided, wherein copper cooling bodies can be cast around the (steel) cooling conduits. Cooling units comprising cast copper cooling bodies and cooling conduits within said cooling bodies are waterproof and have no limitations regarding the inside and outside design. Copper has a relatively high thermal conductivity compared to steel but is much more expensive.

Also, cooling conduits can be drilled into solid copper cooling bodies, which still leads to high material costs. To drill cooling conduits into the copper cooling bodies drill holes in the surface of said copper cooling bodies are produced and have to be sealed by screws or by welding - which again are potential weak spots and might lead to cooling liquid leakage.

Alternatively, cast steel or (grey) cast iron cooling bodies can be used instead but are difficult to manufacture due to the high melting point of steel or iron, which requires high energy effort and the use of refractory molds that can withstand those high temperatures. As the cooling conduits are usually also made of steel, cast steel or cast iron cannot easily be cast around said steel cooling conduits as said cooling conduits might melt without any additional refractory surface coating.

It is therefore an object of the invention to provide a cooling unit which is inexpensive and waterproof.

This object has been achieved by the cooling body comprising a casing and a core material, said casing having an inner space filled with said core material, said core material at least partially embedding the at least one cooling conduit, wherein the material of the casing has a melting point of at least 100°C higher, preferably of at least 200°C higher, than the core material. The cooling unit according to this disclosure in comparison to welded cooling lines prevents cooling liquid leakage as a number of cooling conduits is used, whose outside surface is at least partially embedded into the core material. The cooling unit according to this disclosure can be used with various furnaces, e.g., copper flash smelting furnaces, copper flash converting furnaces, FeTi Electric furnaces, Ilmenite DC furnaces, FeCr DC furnaces, TKSE DRI Smelter etc. A metallurgical furnace might comprise a heat source, a furnace bottom, a furnace wall and a furnace roof and a cooling unit according to this disclosure. The cooling unit as disclosed herein can be mounted on the furnace roof or the furnace wall. Heat generated by the heat source is conducted through the casing to the core material and further through the cooling conduits to the cooling liquid and is further dissipated by the cooling liquid flowing through the cooling conduits.

All temperatures (e.g., melting points, boiling points etc.) in this disclosure are referred to as being under standard atmospheric conditions (i.e., at a pressure of 1 atm or 101 .3 kPa). If is used in connection to temperatures or thermal conductivity, a deviation of plus minus 5% is included.

A cooling unit for a furnace as disclosed herein can be manufactured by providing a casing comprising a bottom and an inner space, wherein cooling conduits are provided within the inner space and wherein liquid core material is cast into the inner space to at least partly embed the cooling conduits, wherein the material of the casing has a melting point of at least 100°C higher, preferably of at least 200°C higher, than the core material. The liquid core material is cooled down to solidify and then represents the core material. Preferably, a bottom of the casing is aligned horizontally during casting.

The cooling conduits preferably also have a melting point at least 100°C higher, preferably at least 200°C higher, than the core material. Due to the lower melting point of the core material compared to the material of the casing and the cooling conduits, the core material can be cast into the casing and around the cooling conduits, at least partially embedding said cooling conduits without damaging the cooling conduits by the heat of the core material during the casting.

A casing having an upper opening can be provided, wherein the liquid core material is cast into the inner space through the upper opening. The upper opening can be closed after casting the core material. This leads to a closed casing, which prevents leakage of the core material if said core material melts during operation. Preferably the provided casing comprises side walls with a number of apertures. The casing is immersed into a bath of liquid bulk core material - so that said liquid bulk core material fills the inner space. Afterwards the casing is removed from said bath of liquid bulk core material, such that excess liquid bulk core material flows out of the inner space through the apertures and the remaining liquid bulk core material represents the liquid core material. After the core material is solidified, it extends to the edge of the apertures closest to the bottom of the casing and represents the core material. This process allows easy manufacturing as the bulk core material can be molten easily before casting into the inner space. Preferably the bottom of the casing is aligned horizontally during removal from said bath of liquid bulk core material and during solidification of the core material.

Preferably the casing comprises cast steel, and/or (grey) cast iron and/or cast copper. The casing might also comprise steel plates, e.g., welded steel plates. Steel has a melting point of 1425°C to 1540°C (depending on the steel grade), grey cast iron has a melting point of -1150°C, copper has a melting point of ~1083°C, copper-tin alloy has a melting point of -1150°C to -1160°C and copperzinc alloy (brass) has a melting point of 960°C to 1050°C (depending on the exact composition of the alloy).

(Grey) cast iron has a thermal conductivity of -55 W/(m*K) which is higher than the thermal conductivity of steel (up to 50 W/(m*K). Also (grey) cast iron has the advantage of ensured leak proofness over welded steel plates and therefore prevents leakage of the core material during production and/or operation.

On the other hand (welded) steel plates as wells as cast steel have the advantage of easier modification, e.g., application of attaching means, e.g., by welding.

Copper has a high thermal conductivity of -400 W/(m*K) and also allows modifications, e.g., application of attaching means, wherein screwing or milling is preferred over welding.

Preferably the casing is closed which prevents leakage of the core material if said core material melts during operation. The casing can, for example, have the shape of a tub, e.g., having a bottom and side walls. The bottom and side walls can form a cuboid with an opening at the top, wherein a top surface can be omitted to form said opening. Preferably the casing has a side wall thickness and/or a bottom thickness of 10 to 30 mm, preferably 20 mm.

Preferably the core material has a melting point from 200°C to 900°C, preferably from 400°C to 700°C. Preferably the core material has a thermal conductivity of at least 50 W/(m*K). It is preferred when the casing has a thermal conductivity of at least 40 W/(m*K) but heat resistant steel casings might also have a lower thermal conductivity, e.g., of about 20 W/(m*K). If the thermal conductivity of the core material is sufficiently high (e.g., at least 40 W/(m*K)), the thermal conductivity of the cooling body altogether is still sufficient, even when the thermal conductivity of the casing is relatively low. Of course, still high thermal conductivity of the casing and the core material is preferred.

Preferably the core material comprises one or more of the following materials: zinc, tin, aluminum, copper. Preferably a copper alloy and/or aluminum alloy is used as core material. Zinc has a melting point of 420°C and a thermal conductivity of 1 10 W/(m*K), tin has a melting point of 232°C and thermal conductivity of 67 W/(m*K), aluminum has a melting point of 660°C and a thermal conductivity of 160 W/(m*K). As those core material choices are inexpensive, the production cost of the cooling unit is kept low.

The thermal expansion coefficients of the core material and the casing preferably differ by a maximum of 0.5 K ^-1 . Aluminum has a thermal expansion coefficient of 2.39 K ^-1 wherein stainless steel (e.g., steel type 1 .4841 usable for temperature of 1050°C to 1 100°C) has a thermal expansion coefficient of 1 .9 K ^-1 - therefore, e. g., the casing comprising stainless steel and the core material comprising aluminum (e.g., being an aluminum alloy) is a beneficial combination of materials, as corrosion is reduced, and the lifetime is extended.

Also, a casing comprising stainless steel and a core material comprising zinc and/or tin (e.g., being a tin alloy) might be used. It might also be beneficial to use a casing comprising copper and a core material comprising aluminum. A casing comprising copper can also be combined with a core material comprising zinc (e.g., being a zinc alloy) and/or tin (e.g., being a tin alloy).

It might also be beneficial to use a casing comprising (grey) cast steel (e.g., steel type 1 .4848 or 2.4879) and a core material comprising aluminum. A casing comprising (grey) cast steel can also be combined with a core material comprising zinc (e.g., being a zinc alloy) and/or tin (e.g., being a tin alloy).

The material of the casing and/or the core material can each be made of a metal or can comprise a metal being alloyed in such a way that corrosion is prevented. Preferably the core material is made of zinc or aluminum or tin or a zinc alloy, an aluminum alloy or a tin alloy.

The number of cooling conduits can comprise steel, stainless steel, nickel, copper etc. but preferably have a higher melting point, preferably by 100°C or 200°C, than the core material. The number of conduits can also be coated with refractory material, in particular if the conduit material has a melting point close to the core material. If aluminum is used as core material, cooling conduits comprising stainless steel are preferred to prevent corrosion. Monel, an alloy comprising copper and nickel, might also be used as material for the number of cooling conduits as the melting point of Monel is ~1350°C which is higher than of copper (~1083°C).

The number of cooling conduits may have a circular or oval cross section which leads to improved cooling liquid flow and little pressure loss of the cooling liquid.

The core material can be chosen such that after mounting the cooling unit at a metallurgical furnace and during operation of said furnace the core material does not melt. This is in particular preferential if the cooling unit is mounted vertically but can also be preferential for mounting horizontally. If the core material is not to melt during operation, the melting point of the core material should be higher than a maximum expected temperature of the core material during operation of a metallurgical furnace. This maximum expected temperature can for instance be 400°C which would allow zinc (melting point of 420°C) or aluminum (melting point of 660°C) but would exclude tin (melting point of 232°C) - if the core material should not melt during operation of the furnace. Also differences of density between the liquid state and the solid state can be disregarded if the core material is solid during operation of the metallurgical furnace. Melt indication means can be provided to detect unwanted melting of said core material and an alert can be triggered.

Melt indication means can comprise thermoelements and/or objects which sink into the core material when melting, wherein said sinking and therefore melting is detected.

The core material can also be chosen such that after mounting the cooling unit at a metallurgical furnace and during operation of said furnace the core material can melt during operation. This can increase heat dissipation from the furnace to the cooling conduits. A low melting point of the core material is beneficial for easier manufacturing of the cooling unit. In this case preferably the core material should not reach its boiling point during operation of the metallurgical furnace, because of material reduction due to evaporation and/or generation of poisonous gas.

Preferably the boiling point (at standard atmospheric pressure of 1 atm or 101 .3 kPa) of the core material is above 900°C, preferably above 1650°C. Aluminum has a boiling temperature of 2470°C, zinc has a boiling temperature of 907°C and tin has a boiling temperature of 2602°C. Boiling tin leads to evaporation of poisonous gas. However, this is not an issue for the cooling unit described as the core material should not reach temperatures in the boiling temperature range of tin.

After mounting the cooling unit in a metallurgical furnace, during operation the core material might reach temperatures of up to 900°C on the hot side, wherein temperatures of the core material of about 40 to 60°C are reached in areas of the cooling conduits if the cooling function of the cooling unit works properly. To prevent boiling of the core material even in case of failure of the cooling function of the cooling unit, which might lead to higher temperatures of the core material, core materials with higher boiling temperatures are preferred. Even when a failure of the cooling function of the cooling unit arises and the core material melts, said melting of the core material will absorb heat in the amount of the melting heat of the core material, which leads to an emergency cooling effect.

The cooling unit for a metallurgical furnace can also comprise a cooling body and at least one cooling conduit leading through the cooling body, wherein a cooling liquid can be conducted via the at least one cooling conduit, wherein the cooling body comprises a casing and a core material, said casing having an inner space filled with said core material, said core material at least partially embedding the at least one cooling conduit, wherein the core material comprises zinc and/or tin and/or aluminum, wherein the material of the casing comprises steel and/or cast (grey) iron and/or copper.

Connection ports at the ends of the number of cooling conduit can be provided for conducting cooling liquid, i.e., as input and/or output for said cooling liquid.

A plurality of cooling conduits leading through the cooling body can be provided, which leads to better temperature distribution and dissipation. If the plurality of cooling conduits is constructed separately from each other, redundancy is provided which ensures the cooling system still is (partially) operational if a cooling conduit fails. Also, a plurality of cooling conduits can provide a large area covered by cooling conduits if said plurality of cooling conduits are meandered as the curve radius of cooling conduits should not be below a minimum curve radius.

The number of cooling conduits has an outer surface. Preferably at least part of the outer surface of the number of cooling conduits is uncovered by the core material. Preferably at least part of an outer surface of the number of cooling conduits facing away from a bottom of the casing is uncovered by the core material. This leads to reduced weight and cost of the cooling unit as less core material is used. E.g., the part of the outside surface of the number of cooling conduits facing the bottom can be covered by the core material, wherein the part of the outside surface of the number of cooling conduits facing away from the bottom can be uncovered by the core material - at least in sections where the cooling conduits are parallel to the bottom. If for instance the number of cooling conduits have a circular cross section, the lower half of the surface is facing the bottom and the upper half is facing away from the bottom. Therefore, the lower half can be covered by the core material while the upper half is uncovered by the core material - at least in sections where the cooling conduits are parallel to the bottom. If the number of cooling conduits have a polygonal cross-section the lower half of the outer surface of the conduits can be covered by the core material while the upper half is uncovered by the core material - at least in sections where the cooling conduits are parallel to the bottom. The height of the core material and therefore the coverage of the cooling conduits by the core material during operation can be determined by CFD simulations.

Preferably an outer surface of the number of cooling conduits is uncovered by the core material, in a region from 30% to 70% along the height of the cooling conduits, the height being measured along a direction normal to the bottom. Preferably an outer surface of the number of cooling conduits is uncovered by the core material, along at least 80% of the length of any respective number of cooling conduits in a region from 30% to 70% along the height of the cooling conduits, the height being measured along a direction normal to the bottom.

The number of cooling conduits can be mainly covered by the core material, preferably at least in sections where the cooling conduits are parallel to the bottom. This can lead to better cooling compared to cooling conduits being partially or completely uncovered by the core material. Preferably connection ports at the end of the number of cooling conduits are uncovered for easier access to the cooling liquid.

Side walls of the casing can comprise a number of apertures, preferably an even number of apertures, preferably two, four or eight apertures, wherein the core material fills the inner space up to an edge of said number of apertures closest to a bottom of the casing. This can be the case due to the manufacturing process, as described below. Side walls of the casing may also comprise mounting means for mounting the cooling unit at a furnace roof and/or a furnace wall. These mounting means allow secure mounting of the cooling unit. Mounting means might comprise holes, hooks, bolts, screws, threads or any other suitable mounting means. Preferably the side walls of the casing comprise at least 2 mounting means. If three mounting means are used, wiggling can be prevented (inverted tripod-effect).

A bottom of the casing can comprise a number of, e.g., at least two, attaching means. The number of attaching means can be used for attaching a number of refractory bricks. The attaching means can comprise a dovetail shape for attaching a number of refractory bricks having equivalent recesses (e.g., inverted dovetail shaped). This leads to secure connection but also to a high contact surface between the attaching means and the refractory bricks and therefore to high temperature distribution from the refractory bricks to the casing and further to the core material.

It is also possible to provide a cooling unit for a metallurgical furnace, the cooling unit comprising a cooling body and at least one cooling conduit leading through the cooling body, wherein a cooling liquid can be conducted via the at least one cooling conduit, wherein the cooling body comprises a casing and a core material, said casing having an inner space filled with said core material, said core material at least partially embedding the at least one cooling conduit, wherein the core material comprises carbon, the core material being pasty. In this case the melting point of the core material can also be less than 100°C higher, or equal or lower compared to the melting point of the material of the casing, in particular if the core material is pasty.

Figs. 1 to 4 show exemplary, schematic, and non-limiting advantageous embodiments of the invention wherein

Fig. 1 shows a casing for a cooling body,

Fig. 2 shows the casing with cooling conduits, Fig. 3 shows a cooling body comprising the casing partially filled with a core material, wherein the cooling conduits are partially embedded into said core material and thus shows a cooling unit comprising said cooling body and said cooling conduits,

Fig. 4 shows the cooling unit having attaching means at the outside surface of the bottom.

Fig. 1 shows a casing 20 for a cooling body 2 for a cooling unit 1 . The casing 20 has an inner space I, defined by a bottom B and side walls S and preferably comprises cast steel and/or cast copper and/or cast iron. The casing 20 might also comprise, e.g., welded, steel plates or copper plates. The casing 20 depicted by way of example has a rectangular bottom B and perpendicular side walls S, while having an upper opening O opposite of the bottom B. Of course, other shapes of the bottom B and/or the side walls S and/or the upper opening O are possible. The casing 20 by way of example also has mounting means M. The mounting means M can be used for furnace roof mounting and/or furnace wall mounting. The side walls S of the casing 20 by way of example comprise a number of apertures A, preferably being distanced from the bottom B of the casing 20.

For manufacturing a cooling unit 1 for a furnace, at least one cooling conduit 3 is provided within the inner space I, the at least one cooling conduit 3 configured to conduct a cooling liquid, e.g., water. Fig. 2 shows the casing 20 from Fig. 1 wherein two meandered and intertwined cooling conduits 3 are provided. The at least one cooling conduit 3 has an outer surface 31 and connection ports 30 at the end for conducting the cooling liquid, i.e., as input and/or output for said cooling liquid.

Also, an optional fastening unit 4 is provided, to keep the cooling conduits 3 in place during the casting process and during operation, wherein in Fig. 2 the fastening unit 4 by way of example is embodied as rods mounted across the cooling conduits 3 and connected to the side walls S. The fastening units 4 might also be embodied as clamps. The clamps can be attached, e.g., welded, to the bottom B of the casing 20. To further manufacture the cooling unit 1 , liquid core material, having a melting point at least 100°C lower, preferably 200°C lower than the material of the casing, is cast into the inner space surrounding the cooling conduits 3, e.g., through the upper opening O and solidifies to form the core material 21 . The cooling body 2 therefore comprises the casing 20 and the core material 21 , wherein the cooling unit 1 comprises the cooling body 2 and the cooling conduits 3 leading through the core material 21 of said cooling body 2. The core material 21 can be chosen such that the boiling point of the core material 21 is above 900°C, preferably above 1650°C. Preferably the core material 21 is chosen such that its melting point is between 200°C and 900°C, preferably between 400°C and 700°C. Preferably the core material 21 comprises one or more of the following materials: zinc, tin, aluminum.

For manufacturing the cooling unit 1 the casing 20 can also be immersed into a bath of liquid bulk core material and then removed from the bath of liquid bulk core material, such that excess liquid bulk core material flows out of the inner space I through the apertures A and the remaining liquid bulk core material represents liquid core material, after solidifying representing the core material 21 . After manufacturing the cooling unit 1 the core material 21 fills the inner space I up to the edge of said number of apertures A closest to the bottom B of the casing 20.

Fig. 3 shows a cooling body 2 comprising a casing 20 and a core material 21 , wherein the casing 20 is partially filled with said core material 21 , such that in sections where the cooling conduits 3, by way of example having a circular cross section, are parallel to the bottom B, the outer surface 31 of the number of cooling conduits 3 facing away from the bottom B of the casing 20 is uncovered by the core material 21 and the outer surface 31 of the number of cooling conduits 3 facing the bottom B is covered by the core material 21 . So, Fig. 3 depicts a cooling body 2 comprising the casing 20 partially filled by the core material 21 , wherein the cooling conduits 3 are partially embedded into said core material 21 and thus Fig.3 3 depicts a cooling unit 1 comprising said cooling body 2 and said cooling conduits 3. So, the lower half of the outer surface 31 of said conduits 3 is facing the bottom B and the upper half of the outer surface 31 is facing away from the bottom B. The casing 20 could also be filled with the core material 21 , such that the number of cooling conduits 3 are mainly covered by the core material 21 , wherein preferably the connection ports 30 at the end of the number of cooling conduits 3 are uncovered for easier accessing the cooling liquid.

Fig. 4 shows the cooling unit 1 from Fig. 3 comprising attaching means 5 provided at the outside surface of the bottom B for attaching refractory bricks 6. Here the attaching means 5 are dovetail shaped by way of example. The cooling unit 1 can be mounted at a roof or at a wall of a metallurgical furnace. If mounted on a roof of a metallurgical furnace preferably the cooling unit 1 is mounted horizontally. In this case the core material 21 can also be in a liquid state during normal operation of the metallurgical furnace. If the cooling unit 1 is mounted on a wall, it might be mounted vertically or inclined, in which case it is preferable if the core material 21 is not in a liquid state during normal operation of the metallurgical furnace.