Classifications

• • 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
• • 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
• • 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
• • 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
• • 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
  • F27D2009/0056—Use of high thermoconductive elements
  • F27D2009/0062—Use of high thermoconductive elements made from copper or copper alloy
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D1/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators
  • F28D1/02—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid
  • F28D1/04—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid with tubular conduits
  • F28D1/047—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid with tubular conduits the conduits being bent, e.g. in a serpentine or zig-zag
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
  • F28D2021/0019—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for
  • F28D2021/0056—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for for ovens or furnaces
  • F28D2021/0057—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for for ovens or furnaces for melting materials

Definitions

• the present invention relates to stave coolers for circular furnaces with steel containment shells, and more particularly to cast-iron and cast-copper stave coolers with a single
• Integrated steelworks use blast furnaces to supply
• the average thermal load levels a stave cooler will be subjected to depends on where it will be positioned within a blast furnace and how the furnace is operated. See Fig. 1. Cast- iron staves can still be successfully used in the less demanding middle and upper stack areas of blast furnaces, but the much higher average heat loads below in the lower stack, Belly, Bosh, Tuyere Level, and Hearth all require the use of higher
• Cast iron staves are less efficient at cooling than are copper staves because the cast iron metal is relatively much lower in thermal conductivity. Their inherent thermal resistance allows heat to pile up too high if too much loading is
• Stave coolers can also be used in reduction vessels for the production of direct reduced iron (DRI) .
• DRI direct reduced iron
• a stave comprising an outer housing, an inner pipe circuit comprising individual pipes housed within the outer housing, wherein the individual pipes each has an inlet end and an outlet end and wherein each pipe may or may not be mechanically connected to another pipe, and a manifold, integral with or disposed on or in the housing; wherein the inlet and/or outlet ends of each individual pipe is disposed in or housed by the manifold.
• the manifold may be made of carbon steel while the housing may be made of copper.
• Todd Smith further adds, "Each of the inlet and outlet ends of each individual pipe may be surrounded in part by cast copper within a housing of the manifold.”
• each conventional coolant connection must have a corresponding penetration or access window in the shell in order to complete the hose
• each stave cooler must be bolted to or otherwise mechanically attached to the steel containment shell to provide vertical support to itself and the refractory brick lining it supports and cools on its hot face.
• the hot smelting inside the furnaces produces very hot, toxic, and often flammable process gases that will find escape paths between the refractory bricks, and between the stave coolers and out through any openings in the containment shell.
• Stave coolers like those described by Todd Smith, have many independent circuits of coolant piping inside, and each produces pairs of coolant connection ends that must be passed out back and through the containment shell.
• Todd Smith describes a "manifold" that can be made of carbon steel on the back of a housing that may be made of copper. He points out that his stave 100 provides for ease of installation since it reduces the number of access holes or apertures required in the furnace shell 51 necessary for the inlet/outlet piping 108 to and from 100 through furnace shell 51. And he says, at paragraph [0094], that stave 100 is of very strong construction to provide much of the support necessary for installation of the stave 100 on furnace shell 51. The effects of stave expansion/contraction due to temperature changes in the furnace are minimized since individual pipe connections to furnace shell have been eliminated. And, stave 100 reduces weld breaches in pipe connections with furnace shell 51 since such connections have been eliminated.
• Todd Smith says further that his stave 100 reduces the importance/criticality of any support bolts needed to help support stave 100 on furnace shell 51 since such bolts are no longer relied upon to independently support stave 100 since manifold 106 carries much of the load required to support stave 100 on furnace shell 51.
• a stave cooler that has one-only through-bulkhead neck that is always collared in an appropriate steel is needed in the industry to control process gas sealing and containment. All of the coolant piping from all the coolant circuits within a single rectangular copper body must pass through in a single tight group to then connect externally outside the steel containment shell. This minimizes the adverse effects of thermal expansion and contraction to manageable levels. Tightly grouping the individual pipe connections through the furnace shell limits the deteriorating forces at work.
• stave coolers must depend entirely for their vertical mechanical support by a single hanging of the through-bulkhead in a single corresponding penetration of the containment shell. Carrying only "much of the load" leaves the door open to more than one penetration of the steel containment shell per stave cooler.
• the two jobs of supporting the stave cooler's weight, and connecting all the coolant piping, must always be shared in a single through-bulkhead neck.
• cast-iron and cast-copper stave cooler embodiments of the present invention have all of the stave cooler's weight supported inside a furnace containment shell by a single gas- tight steel collar on the backside. All the coolant piping in each cooler has every external connection collected and routed together through the one steel collar.
• a wear protection barrier is disposed on the hot face. Such is limited to include at least one of horizontal rows of ribs and channels that retain metal inserts or refractory bricks, or pockets that assist in the retention of castable cement and/or accretions frozen in place from a melt, or an application of an area of hardfacing that is welded on in bead, crosshatch, or weave patterns.
• Fig. 1 is a cross sectional view diagram of a vertically orientated metal smelting or converting furnace embodiment of the present invention with a steel containment shell that has only one penetration per stave cooler for liquid coolant
• Fig. 2 is a cross sectional view diagram of a middle section of a furnace like that of Fig. 1, and represents the way stave cooler embodiments of the present invention seal out the escape of process gases with steel-to-steel welds around steel collars on the protruding necks, and have castable refractory cement packed in behind them. Bricks are inserted into tapered grooves. When pockets are provided instead, the pockets are filled with refractory castable or ram. The steel containment shell is penetrated only once per stave cooler, and all piping for liquid coolant circulation is gathered together in a single group to pass through the protruding necks inside their
• Figs. 3A-3C are cold face, side, and bottom edge view diagrams of a stave cooler embodiment of the present invention.
• Fig. 4 is a cross sectional diagram of a copper casting mold useful in making the stave coolers of Figs. 1, 2, 3A, 3B, and 3C;
• Fig. 5 is a perspective view diagram of a stave cooler embodiment of the present invention like that of Figs. 1, 2, and 3A-3C
• Fig. 6 is a perspective view and cutaway diagram of a stave cooler embodiment of the present invention like that of Figs. 1, 2, and 3A-3C mounted and welded inside a steel containment shell ;
• Fig. 7 is a functional block diagram in a schematic type view of a cooling system embodiment of the present invention that is intrinsically safe from boiling liquid expanding vapor explosion (BLEVE) should any of its liquid, water-based coolant escape or leak into a pyrometallurgical furnace;
• BLEVE boiling liquid expanding vapor explosion
• Fig. 8 is a cross sectional view diagram of a stave cooler embodiment of the present invention hanging inside a steel containment shell. This view details the location of a
• Fig. 9A is a plan view diagram of a hot face of a stave cooler fitted with pockets and hardfacing welding overlays.
• Fig. 9B is a cross-sectional view of one pocket of Fig. 9A taken along line 9B-9B.
• Iron smelting furnaces operate in highly reducing
• Carbon monoxide is a compound that has a reactive oxygen species that has a reactive oxygen species.
• CO carbon monoxide
• monoxide is produced from the partial oxidation of carbon- containing compounds. It forms when there is not enough oxygen to produce carbon dioxide (CO 2) , such as when smelting iron. In the presence of atmospheric concentrations of oxygen, carbon monoxide burns with an invisible blue flame, producing carbon dioxide .
• CO 2 carbon dioxide
• Copper is highly preferred over cast iron for stave coolers because the thermal conductivity of copper is so much better than cast iron. But copper is relatively soft and easily
• FIG. 1 represents a typical blast furnace 100 in which various stave cooler embodiments of the present invention have been installed inside a steel containment shell.
• Fig. 6 shows the novel way these mount and assemble in detail.
• the typical blast furnace 100 includes a steel containment shell 102 with several essential zones of operation inside: a stack 104, a belly 106, a Bosch 108, a Tuyere level 110, and a hearth 112.
• the average operating temperatures are much more severe in the lower elevated stack 104 and below, and therefore heat loading is more demanding on its stave coolers. Compared to those in the middle stack 104 and above.
• a liquid-cooled, cast iron type stave cooler embodiment of the present invention is therefore used in the middle stack 104 and above.
• Such cast iron stave coolers are referred to herein by the general reference numeral 114.
• Cast iron material offers superior abrasion resistance, but is not as thermally conductive as copper. Its inherent thermal resistance is problematic and iron stave are prone to cracking.
• a cast copper type stave cooler embodiment of the present invention is therefore used in the lower stack 104 and below.
• Such cast copper stave coolers are referred to herein by the general reference numeral 116.
• High quality copper material offers superior thermal conductivity, but is easily abraded by the agitation and churning of the materials inside the furnace, and therefore must include an abrasion resistant facing incorporated into the entire outside surface area of the hot faces of each cast copper stave cooler.
• Fig. 2 represents a section of an iron-smelting furnace 200 in an embodiment of the present invention that uses either cast iron stave coolers 114 (Fig. 1), or cast copper stave coolers 116.
• cast iron stave coolers 114 Fig. 1
• cast copper stave coolers 116 cast copper stave coolers 116.
• containment shell 202 are lined with copper stave coolers 204. These each have a single protrusion 206, and each such
• protrusion 206 is jacketed in a steel-to-steel welding collar 208.
• a completed annular steel-to-steel weld 210 secures the mounting of each copper stave coolers 204 and prevents the uncontrolled escape of process gases 212.
• a castable refractory cement 214 is packed in behind each copper stave cooler 204, in front of the inside walls of the steel containment shell 202, to further prevent any uncontrolled escape of process gases 212.
• Cast copper stave coolers require an abrasion resistant facing or layer incorporated into their hot faces if their campaign lives are to exceed ten years. Cast iron stave coolers do not because the cast iron itself is very wear resistant.
• the hot faces of the copper stave coolers 204 can therefore be finished in a number of different ways to accommodate
• a conventional technique has been to horizontally groove the hot faces to retain rows of refractory brick, castable refractory cement, or even cast iron metal inserts.
• the hot faces include a weld overlay or spray coating of abrasion resistant metal or ceramic.
• abrasion resistant metal or ceramic For example, nickel and chromium for the weld overlay and metal spray coatings. Silicon dioxide is useful for the ceramic spray coatings .
• a further option that will increase abrasion resistance involves machining vertical or horizontal grooves into the hot faces for the later insertion of matching metal inserts during installation .
• Fig. 2 simplified a range of possible abrasion resistant facing types by its showing rows of refractory bricks 216 inserted into horizontal grooves on the hot faces. Such bricks would ordinarily continue over to cover the copper lips of the grooves. Alternatively, the entirety of the hot faces of the stave coolers can be deeply dimpled or pocketed to better retain castable refractory cement, instead of grooving or slotting.
• Smelting furnace coke 218 will helpfully form a layer of accretion 220 as it chills on the hot faces of the copper stave coolers 204.
• accretion includes condensed gases, slag, and metal.
• An internal arrangement of liquid coolant piping 222 inside the copper stave coolers 204 are all routed in a single group for external connection with hoses 224 outside the steel containment shell 202. They must all pass through the one, single protrusion 206 of their respective stave cooler 204.
• monoxide gas is very toxic, odorless, colorless, and can burn very hot in ordinary air with an invisible flame. These are why it's so hazardous.
• Embodiments that require welding a steel collar to a drilled billet are not preferred due to an inherent high probability of weld failure.
• a solid copper stave body is cast in a flattened and rectangular shape. They may also be curved slightly to fit better in
• stave coolers are typically about 2.5 meters tall, 1.0 meter wide, and 120 mm thick. So in general, embodiments like liquid-cooled stave coolers 114, 116, and 204 are substantially taller than they are wide, and are substantially wider than they are thick.
• Figs. 3A-3C represent a cast copper cooler stave 300 in a typical embodiment of the present invention. All corners and edges are finished eased and rounded. (Sharp edges adversely concentrate mechanical stresses in the castable refractory cement.)
• a copper body 302 is cast over preformed and pre-shaped independent circuits of coolant piping 304 and 306.
• a single, protruding neck 308 is collared completely by a steel collar 310.
• Steel collar 310, copper neck protrusion 308, and copper body 302 will not bond together very well in a steel-to-copper weld. A much more secure and gas tight attachment is needed. So steel collar 310 is preferably embedded into the copper of neck 308 and body 302 during casting. See Fig. 4.
• steel collar 310 may be fabricated in two parts. A first part, e.g., of stainless steel, cast into the copper stave, and then the second part, e.g., carbon steel, only attached to the first part by specialty welding after such casting is completed.
• first part e.g., of stainless steel
• second part e.g., carbon steel
• the copper in neck 308 is a continuous part of the copper casting of body 302. Such copper casting in neck 308 may not completely fill the spaces inside the distal end of steel collar 310. And so those spaces left can be stuffed with a packing material to impede any wayward process gases that get as far as inside neck 308.
• Figs. 3A-3C are intended to illustrate that all the
• independent circuits of coolant piping in a stave cooler must be grouped together and terminate only within neck 308. These independent circuits are then externally connectable, e.g., with flexible coolant hoses 224 (Fig. 2,) outside steel containment shell 202.
• neck 308 on the cold face of body 302 is critical. This one point provides all the
• Stave cooler 300 should hang straight on its own like a picture frame does on a single hook on a wall, as in Fig. 3A. However, with respect to Fig. 3B, it may be necessary for the bottom to tilt in or out toward the inside of containment shell 102, 202, relative to the top, in order to follow the inside profile and contours of the furnace.
• a number of bolts or struts may be disposed on the cold face for attachment to or standoff from the steel containment shell. These can help set any top or bottom forward tilt of the liquid-cooled stave cooler needed to push away from its
• the stave cooler 300 will hang the straightest if neck 308 is disposed close to the top edge and straddles an imaginary lateral middle line. If the construction of stave cooler 300 is symmetrical about this imaginary lateral middle line, its center of gravity (COG) will be bisected.
• COG center of gravity
• Neck 308 and steel collar 310 are shown in Figs. 3A-3C as nearly square with rounded corners. But they can also be
• Fig. 4 represent a method 400 for casting and fabricating, for example, copper cast stave coolers 300. Copper casting methods are both ancient and well known. Therefore many of the conventional details of copper casting need not be described here .
• a mold 402 is split open to receive a network 404 of pre shaped and pre-formed pipes and fittings.
• a steel-to-steel welding collar 406 is prepositioned inside of the top of mold 402, and enclosing the coupling ends of pipe network 404.
• Mold 402 is positioned flat and level with steel-to-steel welding collar 406 pointing up and proud of the mold.
• a molten liquid flow of copper 408 is desired to come up and rise gently and evenly from under the center. Feeding from the edges would promote one sided shrinkage.
• the pour rises up inside and around to embed the steel-to-steel welding collar 406 and completely immerse and bond with pipe network 404.
• the pour is continued up to a particular level 410, and then the whole allowed to cool slowly and solidify.
• a pure crystalline formation of the copper during casting is not preferred because such copper castings will not bond well with the coolant piping.
• a small grain copper is best, but not at the expense of electrical conductivity quality control measures that fall below a minimum of 80% of International
• IACS Annealed Copper Standard
• An open space 412 may be deliberately left inside steel-to- steel welding collar 406.
• the steel-to-steel welding collars here should have a tight seal with the protruding necks. (To prevent errant escaping process gases.)
• a practical way to construct these steel-to- steel welding collars is to use a length of structural steel tubing with rounded corners and no seams or welds. Large
• the steel used in the structural steel tubing comprises a type of steel that has a thermal coefficient of expansion that matches the thermal coefficient of expansion of the steel of which the steel
• containment shell is comprised.
• the casting of copper inside a steel-to-steel welding collars of carbon steel may not result in a clean joint between the two. It may be better to use a stainless steel or nickel alloy here for the collar if that is a problem.
• the level of liquid molten copper that is flooded into the steel-to-steel welding collar from below during casting can be limited to filling the bottom half only.
• the inside of the top half can be stuffed later with some suitable packing to prevent errant escaping process gases.
• Each liquid-cooled stave cooler embodiment includes at least two independent circuits of coolant piping all of which are disposed as flat loops in a single common layer. One loop can often be laid inside another loop. All such independent circuits of coolant piping are arranged inside the solid copper stave bodies to be uniform, parallel, and proximate to the insides of the hot faces.
• Each end of each independent circuit of coolant piping are all turned up together in a single group inside and through both the protruding neck and inside the steel-to-steel welding collar.
• Anchors 813 Fig. 8 added to the steel collars would help to increase any mechanical locking with the cast copper. This requirement will frustrate drilling in billet methods because too many plugs become necessary to be practical.
• a liquid-cooled stave cooler for smelting furnaces with steel containment shells comprises a single, copper casting of a stave body that is rectangular in shape with a top edge, a bottom edge, left and right side edges, a hot face, and a cold face.
• a stave body is substantially taller than it is wide, and that is substantially wider than it is thick.
• Each stave may be straight or curved in plan, or straight, bent, or curved when viewed from the sides.
• the staves are configured to be cemented to the inside of a steel
• containment shell of a smelting furnace e.g., to seal the escape of process gases.
• An abrasion resistant facing is often incorporated into the entire outside surface area of the hot face of copper stave coolers.
• a shield material with a higher abrasion resistance than copper to the churning and roiling of material inside a furnace is needed. It is placed to environmentally protect the copper casting of the stave body. If a copper stave coolers is not protected with an abrasion resistant facing, then the copper stave cooler must be sufficiently liquid-cooled to always chill and maintain for itself a protective layer of frozen accretion on its hot face.
• Copper stave cooler embodiments of the present invention will therefore invariably have a single, protruding elongated neck of the single copper casting is disposed proximate to the middle of the top edge and on the cold face of the stave body.
• a steel-to-steel welding collar completely jackets the end of the protruding elongated neck.
• Such preferably comprises a prefabricated material similar to structural steel tubing having rounded corners and no seams or welds .
• Each end of each independent circuit of coolant piping are all turned up together in a single group inside and through the protruding elongated neck jacketed by the steel-to- steel welding collar.
• Some stave cooler embodiments of the present invention will include an abrasion resistant facing incorporated into the entire surface area of the hot face can include a number of horizontal and parallel grooves cast into the solid copper stave body to retain one of refractory brick, castable refractory cement, and metal inserts.
• abrasion resistant facings may alternatively include a grid pattern of deep rectangular surface pockets or dimples cast into the solid copper stave body to retain castable
• Any abrasion resistant facing incorporated into the entire surface area of a hot face may further alternatively include a deposited layer of weld metal on copper material.
• the correct tilting and angular set of heavy stave coolers inside the containment seals into wet castable refractory cement during construction can be assisted by placing a number of struts or bolts on their backsides as spacers to the steel containment shell. Castable refractory material is placed after the stave coolers are installed, and these devices can maintain a standoff and tilt of the liquid-cooled stave cooler it would otherwise not assume.
• annular steel-to-steel weld of matching types of steel is required between the outside of the steel-to-steel welding collar and the inside of a corresponding penetration of the steel containment shell.
• the independent circuits of coolant piping used in copper stave cooler embodiments comprise pipes of flexible tubing cast in liquid molten copper inside a mold which was flooded from the bottom.
• the liquid molten copper is allowed to slowly rise up and slowly cool inside the steel-to-steel welding collar .
• a number of rows of parallel and horizontal grooves may be alternatively disposed on the entirety of the hot face. These assist in an attachment of refractory bricks or castable refractory cement.
• stave cooler embodiments of the present invention are finished to be eased and rounded. Such assures that fewer thermal stresses will be imposed on any castable refractory cement in contact with such points .
• Fig. 5 represents a stave cooler 500 in an embodiment of the present invention. Such is illustrated as a flat panel, but it may be advantageous to work in some convex or concave
• stave cooler 500 comprises a flat panel body 502 of either cast iron or cast copper. If cast copper, a hot face 504 can include horizontal grooving 506 to lock in and hold conventional refractory bricks (not shown) . Cast copper wears and abrades more easily than cast iron, so cast copper stave coolers need the protection afforded by conventional refractory bricks and other abrasion resistive materials.
• Cast copper embodiments of stave cooler 500 comprise a small grain copper with a balance of factors like molten metal heat, cooling rate after the pour, alloys added to improve strength and control grain sizes, deoxidants, optimized pipe bonding with the casting, and not falling below an electrical conductivity of 80% IACS so its thermal conductivity will be relatively free of thermal resistance and gradients.
• Stave cooler 500 further comprises a numbers of liquid coolant pipe loops or tubing embedded with the flat panel body 502 just inside hot face 504. These circulate liquid coolant that is pumped in and pulled out through a single external piping connection group 510 which is all collected together through a single steel collar 512.
• the single steel collar 512 is embedded into the flat panel body 502 during iron or copper casting and includes an annular flare 514, anchors, or other device to mechanically lock the pieces together, since simple bonding between dissimilar metals can be inadequate in these severe applications.
• stave cooler embodiments of the present invention can be improved by circulating liquid coolants within them that are water-based but nevertheless intrinsically safe from boiling liquid expanding vapor explosion (BLEVE) .
• BLEVE boiling liquid expanding vapor explosion
• stave cooler 500 Every corner and edge of stave cooler 500 is eased and blunted to reduce cracking and separation of castable cement that is typically packed around and behind stave coolers to prevent outflows of hazardous process gases past them.
• Fig. 6 represents the advantageous and novel way that stave cooler 500 mounts inside a circular furnace 600 with a steel containment shell 602. Only one penetration hole 604 is provided in steel containment shell 602 for each stave cooler 500. Steel collar 512 passes through and is continuously, and gas-tight welded all around with a steel-steel-steel weld 606. Such weld 606 must provide a long life, high reliability gas seal to keep internal hazardous process gases, like carbon monoxide (CO), from escaping. The full weight of stave cooler 500 is borne by the simple hanging of steel collar 512 inside the one penetration hole 604. Weld 606 and castable cement all around stave cooler 500 keep it from slipping off inside.
• CO carbon monoxide
• Water makes an excellent choice as a coolant because its low viscosity makes it easy to pump and its high specific heat means that coolant pumping volumes and speeds can be kept as low as is possible. A balanced combination of these considerations means the pumps in water-based cooling systems can be
• Fig. 7 represents a water-based cooling system 700 in an embodiment of the present invention that is intrinsically safe from BLEVE.
• a heat transfer fluid mixture 702 comprises water, glycol alcohol, and corrosion inhibitors in a homogeneous solution that are circulated around in a closed loop by a liquid pump 704.
• the percentage of water used in the heat transfer fluid mixture 702 has both high and low limits. In general, water can in this use can range from 10% to 50%.
• the minimum percentage of water that can be used is limited by the adverse impacts of increasing viscosity and reduced specific heat that bear on the acquisition and operating costs of liquid pump 704. As viscosity increases, it requires a greater pumping effort and a stronger liquid pump 704 to maintain a minimum coolant velocity 706. And as the specific heat of heat transfer fluid mixture 702 is decreased by diluting the water, the greater will be the pumping effort required of a larger capacity liquid pump 704 to maintain a higher, minimum level coolant velocity 706 that will compensate for the
• the heat transfer fluid mixture must have a room-temperature viscosity of less than 20 mPa.s. And the heat transfer fluid mixture 702 must have a specific heat greater than 2.3 kJ/kg.K. Otherwise, the requirements for a suitable pump 704 become unreasonable and/or unmanageable.
• the maximum percentage of water that can be used safely is limited by the risks of BLEVE . Short of that threshold, the mixed coolant blend 702 will burn, and not BLEVE, if it escapes from a cooler 708 with a steel collar 709 into a high heat ferrous or non-ferrous pyrometallurgical furnace 710. All the coolant circulation for each stave cooler 708 passes through in a single grouping within its respective steel collar 709. Stave cooler 708 is essentially the same as stave coolers 114, 116,
• Intermolecular bond types determine whether any two chemicals are miscible, that is, whether they can be mixed together to form a homogeneous solution.
• the water and glycol in the heat transfer fluid mixture 702 easily join together in a homogeneous solution.
• the bonds holding the molecules of each chemical together must break, and new bonds must form between the two different kinds of molecules. For this to happen, the two must have compatible intermolecular bond types. Water and MEG glycol do. The more nearly equal in strength the two intermolecular bond types are, the greater will be the
• miscibility of the two chemicals usually there is a limit to how much of one chemical can be mixed with another, but in some cases, such as with CH 3 OH (MEG) and 3 ⁇ 40 (water) , there is no limit and any amount of one is miscible in any amount of the other .
• the percentage of water in the heat transfer fluid mixture 702 will have a practical range between 10% and 50%.
• the optimum percentage of water plus corrosion inhibitors in the heat transfer fluid mixture 702 is generally about 25%. No excess water is left unabsorbed to support a BLEVE .
• the heat transfer fluid mixture 702 is circulated in a closed system and pressurized by a pressurization system 712. Typical pressures run 2-7 bar. Raising the pressure inside the closed system raises the boiling point of the heat transfer fluid mixture 702. The minimum boiling point of the heat
• transfer fluid mixture 702 under pressure should be no less than 175° C.
• a particulate filter 714 is used to remove rust particles, exfoliated mineral scale, and other solid contaminants from the heat transfer fluid mixture 702 as it circulates.
• a chiller or heat exchanger 720 is used to remove and dispose of the heat gained by the heat transfer fluid mixture 702 in circulation, e.g., a cooler 708 inside furnace 710. Such chillers and heat exchangers are conventional.
• Fig. 7 shows only a stave cooler 708, such could just as well be a panel cooler, or a cooling jacket for a top submerged lance (TSL) , torch, or Tuyere to receive the benefits of intrinsically safe operation from BLEVE.
• TSL top submerged lance
• Fig. 8 concerns itself with the characteristics of various metals to alloy or not alloy with other metals. Associated with that is how well metals will physically bond with other metals.
• a stave cooler installation 800 in an embodiment of the present invention mounts a cast-iron or cast-copper stave cooler 802 inside a carbon-steel containment shell 804.
• a single steel collar 806 embedded at one end into stave cooler 802 provides the entire support of the weight by hanging from a single penetration 808 in containment shell 804.
• a carbon-steel-to- carbon-steel weld 810 stoppers process gas inside from passing through penetration 808.
• Anchors 813 can be added to the steel collar 806 to improve its mechanical lock with the stave body casting.
• Embodiments of the present invention join together a carbon-steel collar part 814 to a stainless-steel or nickel alloy collar part 816 with a "specialty weld" 818 that together serve as steel collar 806.
• Collar part 816 typically comprises either a 300-series austenitic stainless steel or a nickel alloy.
• Type-304 and type- 316 are both acceptable, as are type-309 and type-310. Referring to these as "300-series austenitic stainless” is a bit clearer to most.
• the 400-series martensitic stainless steels have a coefficient of thermal expansion close to the low carbon steel used in steel shell plate, but such can easily suffer from embrittlement during the casting process.
• Duplex grades, those half way between the 300-grades and 400 grades of stainless steel, could also be used effectively for collar part 816.
• a dirty interface and porosity 812 will be avoided with the use of collar part 816 because the copper contacts only the stainless steel or a nickel alloy. However, the bonding of stainless steel or nickel alloy with copper, is no better than for carbon steel.
• Stainless Steel Association (Sheffield, UK) says dissimilar metal welds involving stainless steels can be done using most full fusion weld methods, including tungsten inert gas (TIG) and metal inert gas (MIG) . Welds using consumable fillers allow for better control of joint corrosion resistance and mechanical properties .
• TIG tungsten inert gas
• MIG metal inert gas
• the joint (at weld 818) is considered to be stainless, rather than the carbon steel.
• Over-alloyed fillers e.g., with increased nickel content, can avoid dilution of the alloying elements in the fusion zone of the parent stainless steel.
• stainless steel include plain carbon or low alloy structural grades and austenitic stainless steel grades such as 1.4301 (304) or 1.4401 (316) . Carbon and alloy steels less than 0.20% C do not normally need a preheat when being welded to austenitic stainless steels. Carbon and alloy steels with carbon levels over 0.20% may require a preheat. High restraint joints, where the material thickness is over thirty millimeters, should also be preheated. Temperatures of 150° C are usually adequate.
• Standard 308 type filler can be used for joining a stainless steel to carbon steel, and the more highly alloyed fillers, such as the 309 type (23 12L to BS EN 12072) are preferred. Cracking in the weld dilution zone can be a problem if a 308 type (19 9L to BS EN 12072) filler is used, because there can be too little ferrite, and martensite may form on cooling.
• a hard facing 830 of abrasion resistant material can be applied as a thin layer on the hot face of stave cooler 802 to protect the stave cooler from wear and increase its campaign life.
• an intermediate layer 832 may be needed to improve bonding and durability .
• Hard facing 830 here comprises an alloy of nickel and chromium, and/or molybdenum, and/or niobium.
• Alloy 625 is an austenitic type of crystalline structured nickel- chromium-molybdenum-niobium alloy with outstanding corrosion resistance and high strength over a wide range of temperatures from cryogenic to 1800°F (982°C) .
• Alloy 625 derives from a solid-solution hardening of the nickel-chromium matrix in the presence of molybdenum and niobium. Precipitation-hardening treatments are not required.
• Alloy 625 is outstanding in a variety of severe operating environments in its resistance to pitting, crevice corrosion, impingement corrosion, intergranular attack, oxidation and carburization in high temperature service, and is practically immune to cracking caused by chloride stress corrosion.
• Alloy 625 can be easily welded to copper and processed by standard shop fabrication practices.
• Coolers principally cast from pure copper and that
• Wear in these furnaces is a combination of abrasion, impacts, metallic, corrosion, heat and other effects.
• Castable cement slathered on the hot face surfaces of copper stave coolers can protect the copper from wear during use.
• the relatively cool surfaces precipitate and freeze jackets of accretion from the melt, and these form a principal wear barrier .
• nickel-chrome alloys suited for abrasion resistance include Alloy-122, Alloy-622, Alloy-82, and Alloy-686. Some nickel-chrome alloys particularly suited for corrosion
• minimum nickel content should be 55%
• minimum chrome content 18% should be 6%.
• Metal and refractory brick inserts are also conventional ways that copper stave coolers have been shielded from wear. But the machining needed to finish off the grooves, ribs, and channels needed to retain the metal and refractory brick inserts is expensive. It is also very challenging to keep the inserts in tight firm contact with the stave cooler. Any looseness in the fit will allow the inserts to get too hot and that will
• the refractory bricks illustrated in Todd Smith ' s Fig. 3 do not keep tight hold of the ribs and channels embedded in the stave cooler hot faces (as illustrated in Todd Smith ' s Fig. 4 and 5) . These refractory bricks do appear to have an advantage of being directly insertable, rather than needing to be slid in from the stave coolers' sides. Sliding in may not always be possible, especially in vertically oriented cylindrical
• Figs. 9A and 9B represent applications in which copper stave coolers 900 and their hot faces 902 especially cannot be protected with refractory brick or metal inserts for practical or economic reasons.
• a number of pockets 904 are distributed on hot face 902.
• a hard facing weld overlay 906 is applied in bead, crosshatch, or weave patterns on the more exposed raised
• Fig. 8 represents a hard facing 830 that is applied over a buffer or intermediate layer 832. Depending on the materials used in the hard facing 830, it may not be necessary to include any buffer or intermediate layer 832.
• the hard facing 830 can be applied by welding beads 906 in groups in those portions of the hot face surface more subject to wear than others. In some cases, that will mean the entire surface will require a weld overlay, e.g., no pockets.
• An improved copper stave cooler embodiment of the present invention has increased wear resistance to at least one of abrasion, impact, metal-to-metal contact, heat, and corrosion on an included hot face surface.
• a hardfacing comprising at least one alloy of nickel and chromium is fused on by welding.
• the hardfacing is typically applied as a weld overlay of molten metal in an inert shield gas.
• these copper stave coolers 900 can be further improved by including a plurality of castable cement retention pockets 904 disposed across the surface of the hot face 902.
• Each such pocket 904 includes inwardly tilting, shallow walls and footings 908 that operate to better retain a castable cement filling when in use.
• a perimeter of raised and more exposed copper base material surrounds each of the
• the copper base material to receive welding overlays is the equivalent of UNS C12000 if wrought or UNS C81100 if cast, which includes deoxidants and low residual phosphorous that promote good welds, reduced copper grain size, an electrical conductivity of at least 80% IACS, and improved embrittlement resistance during welding.

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• 2018
  • 2018-09-14 KR KR1020207015947A patent/KR102304132B1/ko active IP Right Grant
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