EP3759255A1 - High heat flux regime coolers - Google Patents
High heat flux regime coolersInfo
- Publication number
- EP3759255A1 EP3759255A1 EP19841627.3A EP19841627A EP3759255A1 EP 3759255 A1 EP3759255 A1 EP 3759255A1 EP 19841627 A EP19841627 A EP 19841627A EP 3759255 A1 EP3759255 A1 EP 3759255A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- copper
- cooler
- casting
- pipe
- heat flux
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/42—Constructional features of converters
- C21C5/46—Details or accessories
- C21C5/4646—Cooling arrangements
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B7/00—Blast furnaces
- C21B7/10—Cooling; Devices therefor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B1/00—Shaft or like vertical or substantially vertical furnaces
- F27B1/10—Details, accessories, or equipment peculiar to furnaces of these types
- F27B1/24—Cooling arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B14/00—Crucible or pot furnaces
- F27B14/08—Details peculiar to crucible or pot furnaces
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D1/00—Casings; Linings; Walls; Roofs
- F27D1/12—Casings; Linings; Walls; Roofs incorporating cooling arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D9/00—Cooling of furnaces or of charges therein
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D9/00—Cooling of furnaces or of charges therein
- F27D2009/0002—Cooling of furnaces
- F27D2009/0018—Cooling of furnaces the cooling medium passing through a pattern of tubes
- F27D2009/0021—Cooling of furnaces the cooling medium passing through a pattern of tubes with the parallel tube parts close to each other, e.g. a serpentine
Definitions
- the present invention relates to copper coolers used in the walls and roof of furnace crucibles, and more
- FEA alone cannot account for chemical corrosion and mechanical erosion aspects at a so-called "hot face".
- FEA can be used to estimate a temperature distribution within a casting, as well as for any material in front of the cooler, i.e., for specified constant surface temperature, applied heat flux, and other boundary conditions. Mechanical stresses are then calculable from the thermal results.
- CFD Computational fluid dynamics
- RANS Reynolds averaged Navier-Stokes models
- DNS direct numerical simulations
- Typical coolers are formed as burner coolers, launders, tuyeres, staves, wall coolers, roof coolers, transition coolers, casting molds, electrode clamps, tap-hole coolers, and hearth anodes.
- Most modern pyro-metallurgical furnaces use some kind of cooling system to stabilize the relentless erosion of wall, roof and hearth refractories.
- Coolers are arranged in a variety of ways in the walls, roofs and hearths of cylindrical furnaces, oval
- furnaces blast furnaces, Mitsubishi-style flash smelting and converting furnaces, IsaSmelt furnaces, Ausmelt furnaces, fuming furnaces, electric arc furnaces (EAF) , both AC and DC, basic oxygen furnaces (BOF) , electric slag cleaning furnaces, rectangular furnaces, Outokumpu flash smelting and converting furnaces, Inco flash smelting furnaces, slag cleaning
- Coolers can very easily be stacked vertically, horizontally, or tilted in layers, with alternating courses of refractory.
- a wear resisting barrier of metal, refractory brick and/or castable refractory is sometimes used as a lining on the hot face of a cooler.
- Such hot faces can be smooth, or can include pins, deep pockets and/or grooves that are machined on after or cast-in before.
- a serious problem develops when the cooling pipes to be embedded and the metal castings they are embedded in are two different materials. Different materials have different coefficients of thermal expansion. If the differences are large, sufficient bonding between the pipe coils and castings will be stymied during the heating and cooling of the casting process. Or the strength of the bonding afterward between the pipe coils and the castings will be inadequate to survive the service they must perform.
- Monel-400 pipes have been cast in copper coolers for many years. (Monel-400 is a trademark brand for an alloy of about 63% nickel and 31% copper.) Unfortunately, published failure analyses have shown that the copper coolers were never bonded or in complete contact with the Monel-400 pipe when they left the copper mold. Many defects are seen in testing and evaluation of the Monel-to-copper casting bond. The bonding defects found were sufficient to reduce the thermal transfer efficiency and introduce significant unknowns for modelling for the overall furnace-cooling patterns. [0013] Prior art copper cooler designs were manufactured from copper billets drilled with longitudinal holes for water passages. Extruded holes have also been used for the water passages, but some of these have been well-known failures. Transverse drill holes with internal plugs have also been tried in forming internal cooling-water circuits. The drilled and extruded designs normally include plugs to be installed in all the open drill ends around the edges of the billet
- the internal water passage layout is often very constrained by having to build up the water passages from combinations of interconnected drill bores.
- cast coolers can be made in a wide variety of cooler shapes and sizes, and almost any layout is possible with the internal piping. Cast copper coolers can normally be used with much larger heat loads, compared to drilled and plugged coolers.
- Such molds are typically made from sand that has been mixed with a bonding agent.
- the original model shapes are made from wood and other easily formed materials before being pressed in the sand.
- the pipe coils are securely placed inside the sand mold into the exact positions that were calculated and modeled by CFD and FEA to be optimum. But very few, if any, go the bother of CFD and FEA for both thermal and stress analyses because of the expense of modelling time and software.
- differential coefficient of expansion must also be such that high heat flux and constant thermal cycling can be tolerated over the operational lifetime without cracking or other materials failures.
- a furnace-cooling block comprised a UNS C70600 90%, C71300 75%, C71500 70%, C71640 66%, or UNS C70600 Schedule-40 water pipe cast inside a pour of high purity (99%-Wt) copper UNS-type C11000 de-oxidized during the casting process to produce a high-purity copper approximating UNS-type C81100.
- a resulting fusion of the pipe to the casting was such that the differential coefficient of expansions of the two copper alloys involved did not exceed the yield strength of the casting copper anticipated during operational thermal cycling in service.
- the melting point of the copper alloy I used in the pipe was such that a relatively thin-wall pipe could be used with a sand packing during the melt.
- a high heat flux furnace cooler embodiment of the present invention comprises a CuNi pipe coil cast inside a pour of high purity (99%-Wt) copper de-oxidized during the casting process, or that was melted in an inert environment.
- the depth and position relative to a hot face that the pipe coil must finish at is derived from iterative computational fluid dynamics (CFD) and/or finite element analysis (FEA) analyses and modelling.
- CFD computational fluid dynamics
- FEA finite element analysis
- the finished position of the pipe coil is then fixed inside a copper casting mold by a sacrificial scaffolding of supports, spacers, wire ties and other devices each all a copper, a stainless steel, or a nickel alloy comprising at least 20%-Wt copper, or copper alloy and at least 10%-Wt nickel.
- a resulting fusion of the pipe coil to the casting is such that the differential coefficient of expansions of the two copper alloys involved does not ever exceed the yield strength of the casting copper during operational thermal cycling.
- Fig. 1 is a functional block diagram of a high heat flux pyrometallurgical furnace for the production of at least one of molten metal, metal alloy, matte, or slag, and that comprises high heat flux coolers alternatively and
- the pipe coils are diagramed as being disposed inside each high heat flux cooler relative to any surface and at a depth and a position derived from an intelligence results obtained for a particular design and a specific application of the high heat flux cooler using iterative computational fluid dynamics (CFD) and/or finite element analysis (FEA) analyses and modelling;
- CFD computational fluid dynamics
- FEA finite element analysis
- Fig. 2 is a functional block diagram of one of the coolers in Fig. 1, a hot face surface of the cooler faces a high level heat flux from the reactions occurring within the furnace crucible and every input to it;
- Fig. 3 is a cross sectional diagram of a mold patterned to produce the coolers of Figs. 1 and 2, the CuNi pipe coils of Fig. 4 are fully prepared for casting by welding of several copper-nickel, Monel-400, nickel, or stainless steel straps of Figs. 5A-5C. It should be noticed in this case that the coolers' hot face faces down during casting;
- Fig. 4A is a perspective view diagram, as seen from a hot face surface, of one arrangement of four independent CuNi pipe coils nested within others that work in tandem in a stave cooler embodiment.
- the CuNi pipe coils shown herein are prepared for casting, for example by welding on of several copper-nickel straps like in Figs. 5A-5C;
- Fig. 4B is a perspective view diagram, as seen from a hot face surface, of one arrangement of the four independent CuNi pipe coils of Fig 4A nested within others that work in tandem in a stave cooler embodiment such as in Figs. 6A-6D.
- the CuNi pipe coils shown herein fully prepared for casting, and are permanently attached by welding of several copper- nickel rods that bury their ends in the sand mold;
- Figs. 5A-5C are perspective view diagrams of one appliance that can be used as a casting chaplet.
- straps like these are not the best way to fixate the pipe coils in the casting mold because such straps can twist or warp in ways the pipe coils will move in the heat of the pour.
- Better devices are however proprietary to the leading foundries, and they employ trade secret rods, spacers, chaplets, and wires.
- the straps here can inhibit the pipe coils from cooperatively expanding and contracting with the casting as the molten copper pours in and wets the surfaces, bonds to the CuNi, and shrinks during cooling and solidification. Independent support of each pipe may be better;
- Fig. 6A is an elevation view diagram of the backside of a stave cooler embodiment that stand up vertically in service and can measure ten feet tall, four feet wide, and two feet thick and is principally made of cast copper weighing 3,000 kg;
- Figs. 6B, 6C, 6D are cross sectional view diagrams of cross-sections A-A, B-B, C-C of the stave cooler of Fig.
- Fig. 7 is a flowchart diagram of a method embodiment of the present invention for designing, computer modelling with CFD and FEA, casting, and foundry finishing coolers like those of Figs. 1 and 2;
- Fig. 8A is a perspective view diagram of a transition cooler embodiment as would be used in an Outokumpu or Inco Flash furnace, or any furnace with a gas offtake through the roof.
- a perspective view diagram of a pipe coil circuit-A is shown as a ghost inside the copper casting;
- Fig. 8B is a perspective view diagram of a pipe coil circuit-B extracted from the transition cooler copper casting of Fig. 8A. Both pipe coil circuit-A and pipe coil circuit-B fit together inside the same transition cooler;
- Fig. 8C is a perspective view diagram of pipe coil circuit-A and coil circuit-B nested together and from the cooler of Figs 8A and 8B with the transition cooler copper casting shown as ghost;
- Fig. 8D is a cross sectional view diagram of the transition cooler of Figs. 8A-8C.
- Fig. 1 represents a high heat flux pyrometallurgical furnace 100 comprising any furnace for the production of one or more of molten metal, metal alloy, matte, or slag.
- the types of furnaces and applications further may include plasma furnace, rotary holding, smelting, converting, or refining, direct reduced iron furnaces, furnaces with gas and/or concentrate injection such as a Vanyukov, tilting stations and granulators, gasifier roaster shaft furnace, etc.
- Furnace 100 comprises a crucible 102 formed of refractory 104. These are, in turn, cooled by several high heat flux coolers 106, 108. These are each dimensionally formed and finished into a shape suitable for service as a launder, a runner, a cooler, a wall cooler, a roof cooler, a burner block, a tuyere, a casting mold, an electrode clamp, a tap cooler, off gas or fume hoods and ducts, feed and
- the several high heat flux cooler coolers 106, 108 each comprise high purity (99%-Wt) copper castings in which CuNi pipe coils 110, 112, 114, and 116 are embedded during a pour of liquid copper into a mold.
- a steel containment shell 120 typically encloses furnace 100. In blast furnace
- the steel containment shell 120 is gas-tight in order to prevent the uncontrolled escape of toxic process gases.
- Fig. 2 represents a high heat flux cooler 200 in more detail than coolers 106, 108 in Fig. 1.
- High heat flux cooler 200 principally comprises a high purity (99%-Wt) copper casting 202. Inside casting 202 are positioned one or more CuNi pipe coils 204. These are supplied with coolant through one or more pipe coil inlet ends 206 and outlet ends 208, typically through heavy duty industrial hoses with pipe threads, brazed, or welded couplings.
- the high heat flux cooler 200 has at least one surface, i.e., a hot face 210, that faces and receives a high heat flux 212.
- the high heat flux cooler 200 absorbs and disposes of the high heat flux 212 that passes in and through hot face 210, casting 202, and CuNi pipe coils 204 into the coolant exhausted at outlet ends 208.
- the portions of high purity (99%-Wt) copper casting 202 between hot face 210 and CuNi pipe coils 204 must be especially free of copper crystal defects and contaminates.
- the depth of CuNi pipe coils 204 inside casting 202 from hot face 210 must neither be too shallow nor too deep. If too deep, hot face 210 can melt under sudden increase or high heat flux 212. If too shallow, hot face 210 can heat unevenly sufficient to create ripples of stress that can crack the copper crystal or produce high shear stresses locally. This assumes the coolant flow and heat transport out are adequate.
- the correct depth to set CuNi pipe coils 204 inside casting 202 from hot face 210 is determined from iterative computation fluid dynamics (CFD) and/or finite element
- FSA analysis
- Fig. 3 exemplifies a copper casting method 300 that employs a steel flask cope 302A and drag 302B, each with both top and bottom openings.
- Steel cope flask 302A is placed over a first half of a 3D-pattern for a cooler 106, 108, 202.
- a cope mold 304 is formed by packing sand over a cooler pattern inside the steel flask 302.
- Steel drag flask 302B is placed over a second half of a 3D-pattern for a cooler 106, 108, 202.
- a drag mold 306 is formed by packing sand over the cooler pattern inside the steel drag flask 302B.
- the two 3D-patterns are removed and the CuNi pipe coils 400 of Fig. 4 are laid into cope mold 304.
- Cope mold 304 and drag mold 306 are joined together with CuNi pipe coils 400 inside.
- the CuNi pipe coil's 400 pipe inlet and outlet ends must be oriented facing up and protruding out the top through the cope mold 304.
- the drag mold 306 includes any deep surface patterning required in the hot face. For example, horizontal ribs and channels to retain refractory bricks, brick inserts, metal inserts, or pockets to retain shotcrete or other
- ASTM Schedule-40 pipe, or thinner can therefore be used for any UNS C70600 90%, C71300 75%, C71500 70%, C71640 66%, or UNS C70600 copper-nickel alloy pipe coils. And, tighter water passage spacing is made possible.
- the commercial cost UNS C70600 90%, C71300 75%, C71500 70%, C71640 66%, or UNS C70600 copper-nickel alloy pipe is less than Monel-400 pipe.
- the finished copper castings will run cooler, because of the higher thermal conductivity compared to Monel-400. Shear stresses at the interface of the CuNi alloy pipe to cast around copper is also less than with Monel-400 because of the better match in coefficients of expansion.
- preformed pipe coils of Fig. 4 should be packed internally with a mixture of sand and organic binders to stiffen and shore up the pipe coils from collapsing during the casting process .
- the pipe coils are not reinforced inside with sand, they may sag in sections that allow loops to bend closer to the hot face. (In the mold, the hot face is face down.)
- all embodiments of the present invention seek to strike a balance between the differential melting points, and the differential coefficients of expansion of the materials comprising the pipe coils and the copper casting. Large sufficient differential melting points means the pipe coil will not melt or soften during casting, and easily formed thin-wall pipes can be used with confidence.
- Copper alloys are, in general, preferred for the pipe coils and casting materials because of their superior thermal conductivity compared to material costs.
- respective copper-alloys used in the pipe and casting must be sufficiently different to result in maximal differential melting points, and sufficiently the same to result in a minimal differential coefficient of expansion.
- the material yield strengths of the pipe coils and castings both reduce proportionately as the copper content of the respective alloys increases.
- the maximum copper casting stress at the pipe coil interface is almost linearly proportional from 8000 PSI if 30%-Wt copper to 2000 PSI if 100%-Wt copper.
- the maximum pipe stress is almost linearly proportional from 14000 35 PSI if 30%-Wt copper to 2000 PSI if 100%-W copper.
- Pipe coils can be made of one piece of smooth-wall pipe bent to the desired shapes, or by welding in segments. If the required pattern is not practical, then pipe fittings are needed. The fittings must be welded-on, and any sharp edges should be ground smooth. Otherwise, the pipe joints will collect occlusions in the casting and/or generate voids.
- UNS C70600 90%, C71300 75%, C71500 70%, C71640 66%, or UNS C70600 copper alloy is less likely to be contaminated by handling and storage than Monel-400
- the same precautions and cleaning procedures conventional for Monel-400 are preferably used in making any embodiments of the present invention.
- the pipe coils should not be handled with bare hands, and should be laid out on clean dry
- a set of CuNi pipe coils 400 is comprised of a set of four separate and
- Each CuNi pipe coil 400 must not shift of float inside cope mold 304 during casting.
- CuNi pipe coils 400A, 400B, 400C, 400D are
- cope mold 304 positioned in proper relation to another, and the whole in proper relation to the inside of cope mold 304.
- Fig. 4B represents an alternative to straps.
- a pipe coil 420 comprises the same independent CuNi pipe coils 400A, 400B, 400C, 400D of Fig. 4A. But they are connected together and prepared for casting with rods that are welded to their backsides.
- a top lateral rod 422 includes a top footer 424 and 426.
- a rod chaplet 428 does not penetrate the sand mold.
- a mid lateral rod 430 similarly has two rod chaplets 432 and 434.
- a bottom lateral rod 436 includes two rod chaplets 438 and 440 and a bottom footer 442 and 444.
- Figs. 5A-5C represent chaplet straps 402, 404, and 406 in more detail.
- a pair of z-folded legs 402A-402B, 404A- 404B, 406A-406B on the ends of each chaplet strap are
- the chaplet straps 402 and 406 further include top strut spacers 402C and 402D, and bottom strut spacers 406C and 406D.
- Inside cope mold 304 these set the in-service up-down relative position of CuNi pipe coils 400A, 400B, 400C, 400D.
- the CuNi pipe coils 400A, 400B, 400C, 400D operate stood up and vertical.
- the hot face is laid on its face. And in-service, the hot face is vertical and facing into the furnace .
- any chaplets, straps, rods, supports, spacers, stabilizers, and wire ties that were necessary to position and hold the metal pipe coils in an optimal place relative to the hot face during the casting process are preferred to each substantially comprise a copper, a stainless steel, or a nickel alloy that comprises at least 20%-Wt copper, or copper alloy and at least 10%-Wt nickel.
- Figs. 6A-6D represent a stave cooler 600 in an embodiment of the present invention that stands up vertically in service and can measure ten feet tall, four feet wide, and two feet thick.
- An example copper casting 602 is principally made of cast copper weighing 3,000 kg.
- the pipe coils 400 of Fig. 4 are cast into casting 602 using the molding method and equipment illustrated in Fig. 3.
- the cooling capacity of cooler 600 is split amongst four pipe coils 400A, 400B, 400C,
- the copper cover in the hot face may need an
- Copper is required between the pipe coils and the hot face in case of an intense heat load which could melt the surface.
- the copper acts as a thermal buffer to help
- the front half of the pipe coils typically absorb about 70% of the heat load if it is properly set back from the hot face. If the pipe coils are too close a hot face, then there is a risk of film boiling of the fluid coolant inside the pipe due to insufficient distribution of the heat load.
- the usual stresses at the interfaces of pipe coil surfaces with the cast copper do not exceed the yield stresses for the cast copper. This must be confirmed in FEA with three-dimensional finite element thermo-mechanical stress analyses. With FEA, it is practical to pre-qualify cyclic loading applications.
- the coefficient of thermal expansion for UNS C70600 90%, C71300 75%, C71500 70%, C71640 66%, or UNS C70600 copper-nickel alloy is about 9.0 x lCr 6 in/in/°F, and 9.8 x lCr 6 in/in/°F for UNS C81100 cast copper.
- the differential then is only 0.8 x lCr 6 in/in/°F. With the yield strength of cast copper being about 9.0 ksi, and 30-40 ksi for Monel-400.
- Embodiments of the present invention pour hot liquid copper from a melting furnace into a ladle.
- a de-oxidant must be added-in if the copper was melted down in a non-inert environment. Any oxide slag is skimmed off. Oxygen can be readily picked up by molten copper transferring from the melting station to the casting mold. A sufficient superheat of the copper over its melting point is used to prevent the copper from prematurely solidifying during handling or
- Liquefied copper from the ladle must be sufficiently fluid to fill the mold, and readily flow completely cover the pipe coils, and up inside to the top of its risers. Any gas bubbles are intended to rise high up to the top of the flooded surface.
- the deoxidized copper is poured into the mold from the ladle, the casting is allowed to cool until it has completely solidified. Any risers and gating systems are mechanically removed. Any excess material is machined or cut away, and additional hot face grooves and/or pockets are formed or finished to retain shotcrete, inserts, bricks, etc.
- coolers On the outside surfaces of newly cast and machined coolers, bolt holes are drilled and tapped to help with locating, mounting, or cooler lifting due to relatively low yield stress of the copper it is often necessary to embed helicals or metal to get the require strength around the threads.
- the coolers can be very large and very heavy. Any mating surfaces between coolers are machined. The amount of machining needed is dependent on the end use for the cooler. Surface imperfections are repaired by grinding, welding, and machine smoothing.
- the completed coolers are visually inspected, x- rayed, sent through infrared-thermal inspection, and then hydrostatic or pneumatic pressure tested for coolant leaks flow tested for pressure drop before and after casting. A ball test verifies none of the pipes has collapsed or other serious defect developed. Electrical conductivity testing is used to indirectly verify that the cooler's copper metal purity and thermal conductivity meets minimum standards. Pipe welds are normally inspected prior to casting using x-rays and/or liquid dye penetrants.
- Coolers with steel and/or iron pipes and tubes cast inside the copper have several advantages. Pipe coil can be inexpensive and very easy to manufacture, bend, weld, and join with fittings. Steel and iron pipe coils do not come close to melting when the molten copper is poured into the mold. The resulting coolers will then have well-defined water passages.
- Cast copper can not form a good metallurgical bond with the outside surfaces of steel and iron pipes.
- Destructive testing proves steel and iron pipes always separate easily from the cast copper. If they had fused and bonded, it would be difficult to separate afterwards. Destructive testing samples are usually sliced up 0.25 to 1.00 inches thick to fully expose the pipe coils' cross-sections. Just cutting across through the slice will show that such pipes are not mechanically locked-in. This is usually sufficient to confirm a poor steel-to-copper bond. Steel and iron pipes will often just fall out on their own, even before being touched by a pneumatic chisel.
- Stainless steel pipes or tubes with copper cast around them have a unique set of advantages.
- Stainless steel pipe coil is somewhat more expensive than steel or carbon pipe, but is relatively easy to manufacture, bend, weld, and make fittings.
- the stainless steel pipe coils will not melt when molten copper is poured around them in a mold.
- Stainless steel does not contaminate the copper.
- These coolers can also have well-defined water passages.
- Monel-400 pipes and tubes cast inside copper coolers are advantageous in that the Monel-400 does not melt when molten copper is poured into the mold. Its melting point is substantially higher. So the resulting coolers can always be expected to have retained the well-defined water passages of the pipe provided the pipe does not soften and collapse.
- Molten copper also wets Monel-400 very well. Nickel and copper have a high affinity for one another. So the pipe coil and copper casting are predisposed to forming tight, intimate interfaces .
- a pneumatic chisel can usually manage to separate them from copper cast bodies in destructive tests. On close inspection of the separated pieces, copper particles amounting to less than 10% of the total surface area cover the Monel-400 pipe. That means 90% of the surface area of a typical Monel-400 pipe section will remain not bonded, both mechanically and metallurgically . Any interface of pipe to copper is normally clearly visible on an x-ray. When using ultrasonic testing, there is normally an echo at the outside of the pipe, which reveals a lack of pipe bonding.
- Monel-400 pipe coil is an expensive pipe coil commercially used with cast copper, due to its high nickel content it is much more difficult to manufacture. Monel-400 pipes used in coolers made with them represent about 30% of the cost of the casting. This is due in part to cost of standard returns and fittings in Monel-400, and are more difficult to obtain than their counterparts in stainless steel, carbon steel, or iron pipe. In summary, cast copper does not easily form good metallurgical bonds with the outside of the Monel-400 pipes. Pure nickel is even more expensive than Monel-400, but pure nickel does not bond any better.
- the coefficient of thermal expansion for Monel-400 is about 7.7x10-6 in/in/" F., compared to 9.8x10-6 in/in/" F. for UNS C81100 cast copper.
- Monel-400 pipe in cast copper coolers can be expected to deliver good service if used in near steady- state operations. I.e., limited thermal cycling.
- Pure-copper pipe coil is attractive because it is much less expensive than Monel-400, albeit still more
- the pure-copper pipe coils soften too much, and even melt if used in large castings. A catastrophic melt-through of the pipe is possible, particularly near the corners. So the pure copper pipe coils must have coolants run through inside them during the casting pour. Experience also shows that when coolants are run through they generate strong vibrations inside just when the cooling liquid copper pour needs to be very still. The coolants generate vibrations when they swirl, cavitate, film boil, and even pulse due to steam generation. The vibrations interfere with proper copper crystal grain formation.
- Copper pipe coils especially those plated with nickel, are far better than those with iron. That is when it comes to limiting the adverse formation in the copper casting of gas bubbles, porosity, gaps, a lack of metal fusion, and contamination. If too much cooling of the pipe coils is applied during the casting pour, good metallurgical bonds to the outside of the pipe are inhibited. But, if too little cooling is applied, spot melt-throughs in the walls of the copper pipe will develop.
- sand-cores have also been used to define water passages within a copper casting.
- the loose sands are blended with organic binders that dry and agglomerate temporarily into the required core shapes.
- pieces of agglomerated sand can nevertheless break off and wander around during casting, and thus ruin any water containment.
- the sand is easily knocked loose after the liquid copper has cooled and solidified.
- the sand-core techniques are much less expensive than using any internal pre-formed metal pipe coils.
- the coolers resulting from sand-core castings can enjoy very well-defined water passages.
- the cooling water will be in intimate contact with the cast copper cooler, and that maximizes heat transfer. Best of all, no pipes in-between that need to be bonded.
- designing water passages with sand- cores is much less flexible than using preformed pipe coils because the sand-cores must be mechanically supported with spacers, struts, wire ties, and other devices up until the liquid copper sufficiently freezes around them.
- the sand-core type copper castings can finish permeated with gas bubbles if not vented during the casting.
- the cores must be supported up until the cast copper cools and freezes, because they would sag otherwise. Any steel
- vent/support pipes in the sand-cores must be sealed with plugs and/or welds to make them gas-tight.
- a presence of steel pipes is a significant source of porosity, and through-thickness defects. Without pipes, the defects can cause leakage.
- Coils of thick-walled copper pipes patterned into shape are conventionally arranged inside a mold, and molten copper is poured from above directly into the mold.
- a few variations on copper alloys have been tried over the years. As always, intimate bonding of the cast copper cooler to the cooling pipes inside is the goal necessary to realizing adequate cooler thermal efficiencies. A slight, very shallow skin melting of the thick-walled pipes is promoted to occur briefly during the pouring to reach fusion.
- Embodiments of the present invention comprise thermal modelling.
- the heat removal characteristics of high heat flux cooler coolers 106, 108 can be estimated using finite element analysis (FEA) computer modelling.
- FEA finite element analysis
- FEA can be used to estimate the temperature distribution within the casting in operation, as well as any material in front of the hot faces, i.e., for constant surface temperature, applied heat flux, and other specified boundary conditions.
- a three-dimensional (3D) finite element model can be built for various alternatives, i.e., (A) Pipe coil material: copper, NiCu (UNS N04400); and
- Hot face pattern smooth face, rectangular grooves, rectangular pockets, pins, etc.
- One computer model can be used for each case.
- the heat in must equal the heat out.
- Choices of pipe materials do not have much affect on this because the pipe walls are relatively thin. But a loss of bonding can have a dramatic impact. Bonding losses can be approximated in mathematical modelling.
- the FEA models can be run as steady state. Thermal conductivities can be varied with temperature. Based on FEA modelling, temperatures inside the pipe coils did not vary significantly with changes in either the type of pipe (copper or NiCu) or whether the hot face pockets or grooves were filled with either castable or pure copper.
- pipe coils 110, 112, 114, 116 should comprise a copper-nickel (CuNi) of at least 70%-Wt copper, and the copper cast bodies of high heat flux cooler coolers 106, 108, should be a copper alloy of at least 50%-Wt copper.
- the pipe coils should not be cooled during casting. Alternatively, the pipe coils coils should be packed with sand.
- the pipe coils 110, 112, 114, 116 should comprise UNS C70600 90%, C71300 75%, C71500 70%, C71640 66%, or UNS C70600 copper alloy, and the copper cast bodies of high heat flux cooler coolers 106, 108, should start as high purity copper (99%-Wt) that finishes as an approximation of UNS C81100.
- a maximum wall thickness equivalent to ASTM Schedule-40 was determined to be
- inventions comprise a casting of liquid high purity (99%-Wt) copper with only a deoxidant added during a casting process and that is three-dimensionally formed to fit a
- At least one hot face is included and intended to face a substantial heat flux during use that is severe sufficient to threaten significant cracking, wear, and/or melting of the hot face.
- a metal pipe coil that is substantially comprised of copper in an alloy, is oriented and disposed relative to the hot faces within the casting. Such is configured that an inlet end and an outlet end of the metal pipe coil are externally accessible for the circulation of a coolant.
- a metallurgical bond is important to achieve that is a skin fusion of a substantial portion of the outside surfaces of the metal pipe coil with the casting.
- the thickness of the walls of the metal pipe coil are reduced near to a minimum necessary that avoids spot softening and collapse during a casting pour of the casting in a mold. This may need to be empirically determined.
- the alloy used in the walls of the metal pipe coil has a near minimally different and higher melting point that sidesteps spot softening and collapse during a casting pour of the casting in the mold.
- the supports, spacers, stabilizers, and wire ties are preferred to each substantially comprise a copper, a stainless steel, or a nickel alloy of at least 20%-Wt copper, or copper alloy, and at least 10%-Wt nickel.
- the pyrometallurgical furnaces applications herein include any furnace for the production of one or more of molten metal, metal alloy, matte, or slag.
- the coolers are dimensionally formed and finished in shapes variously suitable for service as a launder, a runner, a cooler, a wall cooler, a roof cooler, a burner block, a tuyere, a casting mold, an electrode clamp, a tap cooler, or a stave cooler.
- the metal pipe coil is substantially comprised of copper in a copper-nickel alloy (CuNi) .
- the metal pipe coil is substantially comprised of UNS C70600 90%, C71300 75%, C71500 70%, C71640 66%, or UNS C70600 schedule-40 water pipe that has been cast inside a pour of liquid high purity (99%-Wt) copper.
- the casting is poured from liquid high purity (99%-Wt) copper comprising a minimum of 99%-Wt copper.
- the metal pipe coil must be oriented and disposed at a depth relative to the hot face according to an intelligence result obtained for a particular design and a specific application of the cooler using
- CFD computational fluid dynamics
- FOA finite element analysis
- the coolers must at a minimum be dimensionally formed and finished in a shape suitable for service as a launder, a runner, a cooler, a wall cooler, a roof cooler, a burner block, a tuyere, a casting mold, an electrode clamp, a tap cooler, or a stave cooler in a
- pyrometallurgical furnace for the production of at least one of molten metal, metal alloy, matte, or slag, and comprising a pipe coil disposed inside the cooler relative to any surface and at a depth and a position derived from an intelligence obtained for a particular design and a specific application of the cooler using iterative computational fluid dynamics (CFD) and/or finite element analysis (FEA) analyses and modelling.
- CFD computational fluid dynamics
- FFA finite element analysis
- One pipe coil is the minimum, additional pipe coils, all similar to, separate and independent from the first pipe coil, can also be added-in as a failsafe backup to the first pipe coil.
- additional pipe coils all similar to, separate and independent from the first pipe coil, can also be added-in as a failsafe backup to the first pipe coil.
- Four such pipe coils and the grouping are shown in Figs. 4 and 6.
- coolers are not normally required below a steady state heat flux of 5 kW/m 2 . Above that, the
- refractory will typically tend to wear.
- coolers are not placed within a metal zone, or superheated low grade copper matte, or nickel matte. Notwithstanding, it was been done. Coolers that were designed for a direct to blister furnace to produce blister copper metal, using a composite furnace module design (it included horizontal tapered pins which had not been done before) . Those worked very well, and continue to do so.
- Fig. 7 represents a method 700 for manufacturing a particular type cooler for an application in a particular type furnace that will be subject to an estimated high level heat flux greater than 25 kW/m 2 average, and that further involves the casting of CuNi pipe coils in a copper casting.
- the method 700 comprises a step 702 for patterning a sand casting mold with a 3D-pattern for a a furnace cooler with a shape suitable for service as a launder, a runner, a cooler, a roof or wall cooler, a tuyere, a casting mold, an electrode clamp, a tap cooler, or a stave cooler in a pyrometallurgical furnace for the production of at least one of molten metal, metal alloy, matte, or slag.
- a step 704 places inside the sand casting mold, a pipe coil comprising a UNS C70600 90%, C71300 75%, C71500 70%, C71640 66%, or UNS C70600 Schedule-40 water pipe or equivalent.
- a step 706 is for pouring into the mold and flooding around the pipe coil a liquefied molten high purity (99%-Wt) copper during the casting process to produce a high- purity copper casting approximating UNS-type C11000 .
- the pour may need to have a deoxidant added.
- a step 708 is for cooling a resulting casting, removing it from the mold, and machining and otherwise finishing it and testing for its service by an end user. This all is such that a resulting internal separation of the pipe coil at substantially every and all points of its outer surfaces to any cold face exceeds 5/16" after the casting process is complete.
- a step 710 is for stabilizing an optimal position of the pipe coils relative to any hot face of the cooler during the casting process with strapping, rods, chaplets, and other devices with materials comprising stainless steel of alloys of copper having melting points substantially exceeding that of UNS C70600 90%, C71300 75%, C71500 70%, C71640 66%, or UNS C70600 copper.
- a step 712 is for determining what is the optimal position of the pipe coils relative to any hot face of the cooler during the casting process with iterative CFD and FEA computer modelling.
- Embodiments of the present invention provide solutions for high average heat flux above 25 kW/m 2 .
- conventional coolers and casting methods are performing well.
- the present Method then includes a large safety margin that can accommodate a long lasting steady state furnace upset. So the Method begins by multiplying the given average heat flux by a factor of four to set the minimum capability of the cooler, i.e., 100 kW/m 2 if the starting condition is 25 kW/m 2 .
- the front facing hemispheres of the individual pipes in the pipe coils can be assumed to absorb 70% of the incoming heat flux. Film boiling inside the pipe coils of the pipe coil can occur if this lopsided heat absorption phenomenon is not recognized and the pipe coils are unknowingly set too close to the hot face.
- the lopsided heat absorption phenomenon also causes shear forces to develop at the pipe surface interfaces with the casting, and if that gets too severe, the pipe coils will de-bond and the thermal resistance will increase
- Every cooler may be subjected to wear. Some more than others.
- a starting condition for the rate of wear must be given, i.e., one millimeter per year. So for a campaign life of five years, wear will have reduced the hot face closer to the pipe coils by five millimeters.
- CFD and FEA computer modelling must confirm in their final iterations that the cooler can perform properly with the hot face reduced by (wear rate) x (campaign years) .
- the pipe coils should not ever get closer than 5/16" inside the casting to any cold face.
- Liquid copper during the casting process must have good sufficient access to fill all voids and without letting the copper to freeze to quickly.
- the grains of copper that crystalize during cool down will be too small if the freeze occurs too quickly. Large crystals take time to grow.
- grains that are 1/4" (6 mm) in size need to be allowed to form to minimize crystal grain defects.
- CFD and FEA computer modelling must confirm in their final iterations that the cooler can perform properly with this 5/16" minimum inside cold face separation allowance.
- Figs. 8A-8D represent a high heat flux transition cooler 800 as would be used in an Outokumpu or Inco Flash furnace, or any furnace with a gas offtake through the roof.
- cooler 800 depends on two, essentially parallel pipe coil circuits A and B, 802 and 804 to carry heat out. It is important that each evenly cool the whole of cooler 800 throughout to avoid the unnecessary development of thermal stresses.
- Figs. 8A-8D represent a practical cooler 800 in an embodiment in which the two pipe coil circuits A and B, 802 and 804, actually were modelled with CFD and FEA to have satisfied these goals in a practical and real-world
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Abstract
Description
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Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
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US201862701832P | 2018-07-22 | 2018-07-22 | |
US16/101,418 US10364475B2 (en) | 2011-03-30 | 2018-08-11 | Wear-resistant, single penetration stave coolers |
US201962808857P | 2019-02-22 | 2019-02-22 | |
US16/290,922 US10954574B2 (en) | 2010-03-30 | 2019-03-03 | Water pipe collection box and stave cooler support |
US16/422,909 US20190276906A1 (en) | 2011-03-30 | 2019-05-24 | High heat flux regime coolers |
PCT/US2019/038752 WO2020023169A1 (en) | 2018-07-22 | 2019-06-24 | High heat flux regime coolers |
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EP3759255A1 true EP3759255A1 (en) | 2021-01-06 |
EP3759255A4 EP3759255A4 (en) | 2021-12-01 |
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EP19841627.3A Withdrawn EP3759255A4 (en) | 2018-07-22 | 2019-06-24 | High heat flux regime coolers |
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IT202000025735A1 (en) * | 2020-10-29 | 2022-04-29 | Danieli Off Mecc | COOLING DEVICE FOR AN ELECTRIC OVEN OR SIMILAR |
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DE29611704U1 (en) * | 1996-07-05 | 1996-10-17 | MAN Gutehoffnungshütte AG, 46145 Oberhausen | Cooling plate for metallurgical furnaces |
US6280681B1 (en) * | 2000-06-12 | 2001-08-28 | Macrae Allan J. | Furnace-wall cooling block |
CN1145705C (en) * | 2000-08-04 | 2004-04-14 | 冶金工业部鞍山热能研究院 | Casting-cooling wall with buried pipes and its material |
US6460598B1 (en) * | 2000-11-27 | 2002-10-08 | Ceramic Process Systems Corporation | Heat exchanger cast in metal matrix composite and method of making the same |
US8268233B2 (en) * | 2009-10-16 | 2012-09-18 | Macrae Allan J | Eddy-free high velocity cooler |
-
2019
- 2019-06-24 EP EP19841627.3A patent/EP3759255A4/en not_active Withdrawn
- 2019-06-24 WO PCT/US2019/038752 patent/WO2020023169A1/en active Search and Examination
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