WO2003089863A1

WO2003089863A1 - A method for manufacturing a cooling element and a cooling element

Info

Publication number: WO2003089863A1
Application number: PCT/FI2003/000293
Authority: WO
Inventors: Petri Jokinen
Original assignee: Outokumpu Oyj
Priority date: 2002-04-19
Filing date: 2003-04-15
Publication date: 2003-10-30
Also published as: AR039417A1; FI20020750A0; FI20020750A; PE20031006A1; AU2003222853A1

Abstract

The invention relates to a method for manufacturing a cooling element (1, 11, 17) to be used in a pyrometallurgical reactor, said cooling element being composed of at least two elements, said elements being made by continuous casting of a highly heat-conductive metal, so that in at least one of the elements there is arranged a flow channel for the cooling liquid; and that the elements are joined together by electron beam welding. In addition, the invention relates to a cooling element (1, 11, 17) used in a pyrometallurgical reactor, said cooling element being composed of at least two elements, said elements being manufactured by continuous casting of a highly heat-conductive metal, so that in at least one of said elements there is arranged at least one flow channel for the cooling liquid, and that the elements are joined together by electron beam welding.

Description

A METHOD FOR MANUFACTURING A COOLING ELEMENT AND A COOLING ELEMENT

The invention relates to a method, defined in the preamble of claim 1 , for manufacturing a cooling element used in a pyrometallurgical reactor. The invention also relates to a cooling element.

In connection with industrial reactors, such as flash smelting furnaces, blast furnaces and electric furnaces particularly used in the manufacturing of metals, there are employed massive cooling elements that are generally made of copper. Typically the cooling elements are water-cooled and thus provided with a cooling channel system. In pyrometallurgical processes, the cooling elements are used for protecting the reactor masonry, so that the heat directed to the surface of the masonry as a result of the cooling is transferred to water through the cooling element, and consequently the wearing of the lining is essentially reduced in comparison with a reactor that is not cooled at all. The reduction in the wearing is achieved by a so-called autogenous lining solidified at the surface of the fireproof lining, said autogenous lining being generated from slag and other materials separated from the molten phases.

On the surface of the cooling element, there often is arranged a ceramic lining, for instance made of fireproof bricks. The working conditions in a reactor are extremely hard, and the cooling elements are subjected to strong corrosion and erosion strain caused among others by the furnace atmosphere and contacts with the molten material. For an effective operation of the cooling element, it is important that the joint between the fireproof bricks and the cooling element is good, in which case an effectively heat-transferring contact is achieved.

According to the prior art, cooling elements can be manufactured by sand casting, where in a mold made in sand there is installed a cooling pipework made of a highly heat-conductive material such as copper, and during the casting around said pipework, the pipework is cooled by air or by water. The element to be cast around the pipework is likewise made of some highly heat- conductive material, advantageously copper. This manufacturing method is described for instance in the GB patent 1386645. A drawback in said method is that the pipe system serving as the flow channel is unevenly attached to the surrounding casting material, because part of the pipes may be completely detached from the element cast around it, and part of the pipe may be completelely melted and thus damaged. If a metallic bond is not created between the cooling pipe and the other element cast around it, the heat transfer is not efficient. On the other hand, if the pipe system is completely melted, it prevents the circulation of the cooling water.

There also is known a method according to which in the mold of the cooling element, there is placed a glass pipework having the shape of the flow channel, which glass pipework is then broken after casting, so that a flow channel is formed inside the element. The US patent 4,382,585 specifies a widely used method for manufacturing a cooling element, according to which the element is made for instance of a rolled or forged copper plate by drilling the required flow channels therein. There also is known a method for manufacturing cooling elements by casting perforated profile as a continuous casting, i.e. slip casting, through a mandrel.

Cooling elements are typically made of copper and provided with for instance longitudinal and/or transversal channels where the cooling agent circulates. In a known fashion part of the perforations that constitute the channel system of the cooling element are plugged, so that in the element there is left only a necessary number of inlet apertures, through which the cooling agent is conducted into the element, and outlet apertures, through which the cooling agent is conducted out of the element. According to a known plugging method, the cooling element is provided with a plug that is arranged in the hole to be plugged by a compression joint, said plug being on the outside welded to the housing of the cooling element. Prior to welding, the workpieces are preheated to a high temperature. At the preheating stage, the oxidizing risk of the plug joint is high, and therefore the plug joint according to the prior art is relatively susceptible for instance to damages caused by corrosion. For example an atmosphere prevailing in the furnace space of a flash smelting furnace and containing, among others, S0 gas, causes corrosion that proceeds as a sulphatizing reaction. In order to avoid the damage risks of the plug joint and possibly resulting cooling agent leakages, it has been necessary to replace the cooling elements fairly often.

The object of the present invention is to avoid the drawbacks of the prior art and to realize a novel method for manufacturing cooling elements. Another object of the invention is a compact cooling element that has a long working life.

The invention is characterized by what is set forth in the characterizing part of claim 1. Other preferred embodiments of the invention are characterized by what is set forth in the other claims.

Several advantages are achieved by using the solution according to the invention. The invention relates to the manufacturing of a cooling element used in a pyrometallurgical reactor, said cooling element being formed of at least two pieces that are made by continuous casting of a highly heat-conductive metal; at least in one of said pieces, there is arranged at least one flow channel for the cooling liquid, such as water, and the pieces are interconnected by electron beam welding. When electron beam welding is used in the joints of metallic cooling elements, such as copper elements, there is obtained a compact and durable structure in the cooling element. In electron beam welding, the object to be welded need not be preheated at all. The electron beam is focused on the surface of the cooling element, or somewhat below the surface. The welding heat is created when the electron beam having an extremely high power density strikes the object. The electron beam is generated in a so-called electron beam gun, where a hot cathode emits electrons that are accelerated by high voltage to a high speed. Welding takes advantageously place in a vacuum space that provides protection for the welding. In electron beam welding, there are not needed any additive agents, and consequently the heat transfer capacity of the cooling element is not weakened. Other advantages of welding are its extremely low heat input in the object to be welded, a deep penetration, a narrow side penetration, accuracy, cleanliness and its capacity to be easily automated in order to produce various different weld results.

Cooling element channels can also be made by working, for instance by drilling holes in the object in the desired direction, for instance horizontally or vertically. According to a preferred embodiment of the invention, the cooling element constitutes a housing and two auxiliary elements that are interconnected advantageously by electron beam welding, so that a closed flow channel system is formed in the cooling element. The flow channel system is created by connecting the drilled holes, i.e. channels, to each other, and said flow channel system includes inlet and outlet apertures for the cooling liquid. According to another preferred embodiment of the invention, the auxiliary element is at the edge on the side facing the junction designed so that when the auxiliary element is connected to the housing, there are created brackets at the flow channel system. The measures of said brackets are designed to be suitable for the flow channel system. Now a thicker weld seam is obtained at the flow channel system, and the cooling liquid is prevented from possibly entering the reactor space. Thus the plugging of the extra holes is advantageously avoided altogether, because the flow channel system can be closed by means of the auxiliary elements to be welded to the housing element. At least in one element, for instance in the housing, there is drilled an inlet aperture and an outlet aperture for the cooling liquid.

According to a preferred embodiment of the invention, the pieces forming the cooling element are interconnected by electron beam welding at a desired angle, so that two separate flow channel systems are created in the cooling element. Now the two channel systems have different cooling liquid circulations. According to another embodiment, both pieces have a separate flow channel system, and the pieces are interconnected at essentially right angles. In this way, there is obtained a cooling element to be used for instance in a corner of the reactor or in the ceiling. According to a preferred embodiment, the flow channel systems are created so that the cooling liquid circulates between two separate pieces, and the pieces are interconnected essentially at an angle of 180 degrees.

The invention is described in more detail below with reference the appended drawings.

Figure 1a A cooling element according to a preferred embodiment of the invention.

Figure 1 b Figure 1 a seen from the side.

Figure 2 A cooling element according to another preferred embodiment of the invention.

Figure 3 A cooling element according to a preferred embodiment of the invention.

Figures 1 a and b illustrate a cooling element 1 manufactured according to the method of the invention, said cooling element including a housing 2 and auxiliary elements 3 and 4. The housing is a copper plate made by continuous casting, and in said copper plate, there is worked a flow channel system 5 for the cooling water, so that holes, i.e. channels, are drilled in the plate both in the vertical and horizontal direction. In addition, in the housing 2 there is drilled an inlet aperture 8 and an outlet aperture 9 for the cooling water. In the flow channel system, the cooling water circulates in the direction indicated by the arrow. In said apertures, there can be welded pipes for the flowing cooling liquid. The auxiliary elements 3 and 4 are connected to the housing 2 by electron beam welding, so that the flow channel system is closed and the water circulates inside the housing. The auxiliary elements are welded at both ends of the housing at the welding seams 10, so that water cannot come out except at the inlet and outlet apertures. The auxiliary elements 3 and 4 are essentially worked at the edges 7 to be welded, so that suitable brackets 6 are formed at the flow channel system. Said brackets are placed at such spots of the housing where the flow channel system 5 runs. The elements 2, 3 and 4 constituting the cooling element 1 are connected together so that the housing 2 and the auxiliary elements 3 and 4 are arranged adjacently, meeting surfaces facing each other, advantageously in a vacuum, so that a protection is achieved for the welding. The electron beam is developed in a so-called electron beam gun, and the electrons are accelerated by high voltage to a high speed towards the object to be welded. Welding is conducted to proceed along the welding seam 10, so that the elements are put together in a compact way.

Figure 2 illustrates a cooling element according to another preferred embodiment of the invention, said cooling element 11 being formed of continuously cast sheet-like copper elements 15 and 16. In said elements, there are drilled flow channel systems 13 and 14 for the cooling water, and thus each element has its own water circulation, i.e. an own inlet and outlet aperture. Water proceeds in the cooling element in the directions indicated by the arrows. According to the method of the invention, the elements 15 and 16 are interconnected at the seam 12 by means of electron beam welding, so that a compact and durable structure is achieved. The elements 15 and 16 are placed at right angles with respect to each other. The cooling element 11 can advantageously be used for instance as a corner element in a reactor.

Figure 3 illustrates an embodiment of the invention, according to which the cooling element 17 is made of two continuously cast sheet-like copper elements 22 and 23 that are interconnected at the seam 18 by means of electron beam welding. Prior to welding, in the elements 22 and 23, there are drilled both horizontal and vertical holes, and the flow channel systems 20 and 21 are formed by joining the elements together at said holes. The elements are identical, and they are interconnected at an angle of 180 degrees. The elements 22 and 23 are joined together so that the flow channels are joined as extensions of each other, i.e. the cooling liquid proceeds from one element to the other through the flow channel systems. In the flow channel systems, the cooling water proceeds in the direction indicated by the arrow. Prior to joining the elements together, at least one of them is provided with sleeves 19 that are attached at the flow channels in order to reinforce the joint and advantageously prevent any possible contact between the cooling water and the molten material.

For a man skilled in the art, it is obvious that the various embodiments of the invention are not restricted to the above described examples only, but may vary within the appended claims.

Claims

1. A method for manufacturing a cooling element (1 , 11 , 17) to be used in a pyrometallurgical reactor, said cooling element being composed of at least two elements, said elements being made by continuous casting of a highly heat-conductive metal, so that in at least one of the elements there is arranged a flow channel for the cooling liquid, characterized in that the elements are joined together by electron beam welding.

2. A method according to claim 1 , characterized in that the flow channels are made by drilling.

3. A method according to claim 1 or 2, characterized in that the cooling element (1) is composed of three elements, a housing (2) and two auxiliary elements (3, 4), which are interconnected so that a closed flow channel system (5) is created in the cooling element.

4. A method according to claim 3, characterized in that the auxiliary element (3, 4) is at the edge (7) facing the junction designed so that when connecting the auxiliary element to the housing, there are created brackets (6) at the flow channel system.

5. A method according to claim 1 - 4, characterized in that in at least one of the elements, there is drilled an inlet aperture (8) and an outlet aperture (9) for the cooling liquid.

6. A method according to claim 1 or 2, characterized in that the elements forming the cooling element are interconnected so that two separate flow channel systems (13, 14, 20, 21) are created in the cooling element (11 , 17).

7. A method according to claim 1 , 2 or 6, characterized in that both elements (15, 16) have a separate flow channel system (13, 14).

8. A method according to claim 6 or 7, characterized in that the elements (15, 16) are joined together essentially at right angles.

9. A method according to claim 1 , 2 or 6, characterized in that the flow channel systems (20, 21) are formed so that the cooling liquid proceeds between two different elements (22, 23).

10. A method according to claim 8 or 9, characterized in that the elements (22, 23) are joined together at an angle of essentially 180 degrees.

11. A method according to claim 1 - 10, characterized in that the elements ( 2, 3, 4, 15, 16, 22, 23) forming the cooling element (1 , 11 , 17) are made of copper.

12. A cooling element (1 , 11 , 17) used in a pyrometallurgical reactor, said cooling element being composed of at least two elements, said elements being manufactured by continuous casting of a highly heat-conductive metal, so that in at least one of said elements there is arranged at lest one flow channel for the cooling liquid, characterized in that the elements are joined together by electron beam welding.