Cooling plate

Abstract

A cooling plate for refractory-lined shaft furnaces includes a first cooling plate element facing the inside of the furnace and a second, rear cooling plate element, where in the cooling plate elements are welded together. A cooling channel is formed between the first and second elements of the cooling plate. Pipe elements are connected to the coolant inlet and coolant outlet. The first cooling plate element is a bloom with a plane front side facing the inside of the furnace, and the cross-sectional area of the cooling channel is larger in the end regions thereof than in the center region, as viewed along the longitudinal extent of the cross-section.

Description

The invention concerns a cooling plate for refractory-lined shaft furnaces, especially blast furnaces, with a first rolled cooling plate element facing the inside of the furnace and a second rolled cooling plate element facing to the rear, which are welded together, with a cooling channel formed between the first and the second elements of the cooling plate, and with pipe sections connected to the coolant inlet and coolant outlet. Both the first and second cooling plate elements consist of copper or a low-alloy copper. In addition, the invention concerns a cooling system.

A cooling plate of this general type is described in German Patent Application 100 00 987.5, which discloses a cooling plate for refractory-lined shaft furnaces with cooling channels into which coolant can be admitted, in which (cooling plate) at least the front side facing the inside of the furnace consists of a bloom that contains grooves for receiving refractory material and is preferably made of copper or a low-alloy copper; in which two trough-shaped rolled sections, each with the trough facing to the outside, are welded together; in which bores for receiving the ends of pipe connection fittings, which are welded in, are produced in the rolled section or supplementary section on the rear side; and in which the free ends of the rolled sections are sealed by caps.

The bending of the first cooling plate element or shield and the production of grooves in the bent shield is difficult from the standpoint of manufacturing engineering. Moreover, the more or less “lens-shaped” cross section of the cooling channel resulting from the trough-like shape of the two cooling plate elements has been found to be unfavorable from the standpoint of fluid mechanics. While the amount of heat flowing from the lateral fins of the shield towards the cooling water channel is the greatest, it is precisely in the corners of the “lens” that the flow rate of the cooling water is the lowest. The low flow rate leads to a low heat-transfer coefficient α from the inner surface of the cooling channel to the cooling water. In addition, the volume of water flowing past there may experience an unacceptably high degree of heating.

Therefore, the objective of the invention is to develop a cooling plate of the general type described above with improved characteristics from the standpoint of manufacturing engineering, fluid mechanics and cooling engineering.

This objective is achieved by a cooling plate with the features of claim 1 and by a system with the features of claim 12. Advantageous modifications are described in the dependent claims.

In accordance with the essential concept of the invention, the first cooling plate element or the shield of the cooling plate or stavelet is no longer designed as an arched structure, but rather is designed as a bloom with a plane front side facing the inside of the furnace, i.e., with a plane hot side, and the cross-sectional area of the cooling channel formed between the first and second cooling plate elements is larger in the end regions than in the center region, as viewed along the longitudinal extent of the cross-sectional area. The end regions of the cooling channel cross section are the regions near the joint lines or weld seam of the two cooling plate elements. The end regions may have any desired shape, as long as they have a larger cross-sectional area than the center region. The effect of the cross-sectional shape in accordance with the invention is that the greatest volume of the cooling water no longer flows in the center region, but rather in the thermally stressed end regions of the cooling channel, which results in greater flow rates and thus more favorable values of the heat-transfer coefficient. In this regard, the cross section in the center region should be designed in proportion to the cross section in the end regions in such a way that the smaller amounts of heat that develop there can be efficiently eliminated.

All together, a cooling plate with improved flow characteristics of the cooling water and thus improved cooling characteristics is created in this way. The temperature on the hot side, i.e., the side facing the inside of the furnace, becomes more uniform. Furthermore, a significant advantage is gained with respect to manufacturing engineering, because the first cooling plate element now has a plane design and no longer needs to be curved. In addition, it is much easier to produce grooves in a plane cooling plate than in a curved cooling plate, e.g., by milling or roll forming.

In accordance with an especially preferred embodiment, the end regions of the cooling channel cross section bulge out on one or both sides. Taking the center region into consideration as well, this results in a cooling channel cross section that is shaped something like a bone or like a half-bone cut along its longitudinal axis. This shape results in an especially good ratio of the flow rate of the cooling water to the heat loads that arise.

To obtain a cooling channel with this type of bone-like shape, various design combinations are proposed. For a cross section that is shaped more or less like a half-bone, either a first cooling plate element with recesses produced in its rear side facing the water is used, or a second cooling plate element with a double trough-like shape that bulges out towards the wall of the furnace is used. A first cooling plate element of this type is combined with a more or less plane second cooling plate element; a trough-shaped second cooling plate element is combined with a first cooling plate element with a plane rear side facing the water. To obtain a bone-shaped cross section, a first cooling plate element with recesses is combined with a corresponding second cooling plate element with recesses or with a double trough-shaped second cooling plate element.

The recesses, which preferably run parallel to the longitudinal axis of the cooling plate, are produced by roll forming or by milling. The trough-shaped second cooling plate element, which is designed thinner than the first cooling plate element, is produced by roll forming or bending.

Both the first and the second cooling plate element are made of copper or a copper alloy.

In accordance with a preferred embodiment, the trough-shaped second cooling plate element has variable material thickness across its width. It is formed thicker at its edges than in its center region. This has the advantage that, in the region of greater heat flow, i.e., in the edge region, more copper material is available for the conduction of heat. Due to the reinforced edge regions, the weld for joining the two elements with each other can also be made more massive. This contributes to the mechanical stability of the cooling plate and thus to further improvement of the cooling characteristics of the system.

A second cooling plate element can be welded with the edges of the first cooling plate element; in accordance with a preferred embodiment, it is welded to the rear side of the first cooling plate element as a supplementary section with its longitudinal edges bent towards the rear side of the first cooling plate element. To prevent waviness of the edges of the first cooling plate element due to a nonuniform temperature distribution, it is proposed that slits be produced at regular intervals in the edge regions of the first cooling plate element perpendicularly to the longitudinal axis of the cooling plate.

In a preferred embodiment, the free ends of the two joined cooling plate elements are sealed with caps, and the pipe sections for the coolant intake and discharge extend through bores in the second cooling plate element on the rear side. To reduce pressure losses on the water side in the vicinity of the coolant inlet and outlet, the first cooling plate element, which is provided with cooling channel recesses, is hollowed out at the level of the pipe sections, e.g., by milling out the copper. A ramp-like transition from the inlet and outlet regions that have been enlarged in this way to the cooling channel recesses is produced by gradually reducing the depth of the hollow in the direction of the cooling channel recesses. The reason for the smaller pressure losses is the smoother transition that now exists from the round pipe section to the cooling channel cross section of the invention with its larger end regions and smaller center region.

Aside from a flange-and-bracket connection for mounting the cooling plate on the furnace wall of the shaft furnace, it is proposed that the cooling plate have at least two suspension points, such that a first suspension point is designed as a fixed connection in the upper part of the cooling plate, preferably above the pipe section to the coolant inlet or outlet, and a second suspension point is designed as a loose connection in the lower part of the cooling plate, preferably just above the pipe section to the coolant inlet or outlet. This advantageous suspension with loose attachment points, which are preferably designed as hangers, allows the lower part of the cooling plate to undergo thermal expansion.

Further details and advantages of the invention are evident from the dependent claims and from the following description, in which the embodiments of the invention illustrated in the drawings are explained in greater detail. In this regard, besides the combinations of features enumerated above, features on their own or in different combinations are also intrinsic parts of the invention.

FIG. 1 shows a cross section of a cooling plate in accordance with a first embodiment.

FIG. 2 shows a cross section of a cooling plate in accordance with a second embodiment.

FIG. 3 shows a preferred design of a second cooling plate element in accordance with FIG. 2.

FIG. 4 shows a longitudinal section of a cooling plate mounted on the wall of a shaft furnace.

FIG. 5 shows a partial segment of a longitudinal section of a preferred design of a first cooling plate element in accordance with FIG. 1.

FIG. 6 shows a side view of a cooling plate with a preferred design of the first cooling plate element.

FIG. 7 shows a segment of a cooling system mounted on a furnace wall.

FIG. 8 shows the longitudinal section A-A of a cooling plate in accordance with FIG. 7.

FIG. 9 shows an enlarged view of the upper partial segment shown in FIG. 8.

FIG. 10 shows enlarged views of the partial segments shown in FIG. 8.

FIG. 1 shows a cooling plate 1 or stavelet with a first cooling plate element 2 facing the inside O_i of the furnace and a second, rear cooling plate element 3, which are welded together. The weld seams 4 are located on the protected, cold side of the cooling plate or stavelet. Between the rear, water side 5 of the first cooling plate element 5, which is designed as a rolled copper bloom, and the water side 6 of the second cooling plate element 3, a cooling channel 7 is formed, which is supplied with a coolant, preferably cooling water. Pipe sections 8, 9 for water intake and discharge are mounted in bores in the second cooling plate element 3. The cooling plate 1 is mounted on the furnace wall 10, for example, by means of a flange 11, which is inserted into a bracket 12 mounted on the furnace wall and secured by a bolt 13 (see FIG. 4). The first cooling plate element 2 is designed as a massive bloom with a plane—in the sense of being noncurved—front side 14, in which grooves 15 are produced, which run transversely to the longitudinal axis of the cooling plate 1 and facilitate the application of refractory ramming mix or injection molding compound after completion of the mounting.

Two recesses 16, 17 that run parallel to the longitudinal axis of the cooling plate 1 at some distance from each other are produced on the rear, water side 5 of the first cooling plate element 2 or shield. Each of these recesses has a more or less semicircular cross section. The cooling channel 7 is sealed on the rear side, i.e., towards the furnace wall, with an approximately plane or slightly outwardly curved second cooling plate element 3 as a supplementary element. This results in the formation of a cooling channel 7 with a cross-sectional area, such that the end regions 18, 19, as viewed along the longitudinal extent of the cross-sectional area (x-direction), have a larger cross-sectional area than the center region 20.

FIG. 2 shows another preferred embodiment of a cooling plate 101 with a cooling channel cross section claimed in accordance with the invention. In this embodiment, the desired cross section of the channel 107—here the cross section perpendicular to the longitudinal axis of the cooling plate—is determined by the shape of the second cooling plate element 103, which is shaped to form a double trough. The desired cooling channel cross section with larger end regions 118, 119 relative to the center region 120 of the cross section is created by the curvature of the troughs 121, 122 and the formation of a center region 123, which, in the case shown here, is short, but may also be longer.

To achieve mechanical stability of a cooling plate 101 of this type, the trough-shaped second cooling plate element 203 or the copper sheet is reinforced, i.e., made thicker, in its edge regions 324, 325, as shown in FIG. 3. This may be accomplished, for example, by roll forming.

FIG. 4 shows the longitudinal section of a cooling plate 1 in its mounted position on the furnace wall, for example, the wall of a blast furnace. After the cooling plate has been secured by the flange-and-bracket principle, the remaining space between the cooling plate 1 and the furnace wall 10 is filled with backfill compound 26. The pipe sections 8 and 9 are welded (27) with the second cooling plate element 3. The free ends of the cooling channel 7 are sealed by caps 28, 29.

FIG. 5 shows another preferred embodiment of the cooling plate 1 based on the embodiment shown in FIG. 1. The massive first cooling plate element 1 is further hollowed out (hollows 30) in the regions facing the pipe sections 8, 9 for the water intake and discharge, so that the inlet and outlet regions are enlarged. This cross-sectional enlargement is gradually adapted—in ramp-like fashion—to the curvature of the cooling channel recesses 16, 17. This has the positive effect of reducing the cooling water pressure losses.

Due to the fact that the second cooling plate element 3 is mounted on the rear side of the first cooling plate element 2 in such a way that the edge regions 2a, b (or fin regions) are not covered, there is the danger of waviness developing in the first cooling plate element. This is prevented by producing slits 31 in the edge regions 2a, b transversely to the longitudinal axis of the cooling plate. These slits extend from the edge 32 approximately as far as the second cooling plate element 3. The slits allow the edge regions to undergo thermal expansion without stress when the furnace is charged.

The cooling plates of the invention are combined into a cooling system. For example, they may be installed immediately adjacent to one another, and their stability can be supported by a spring-and-groove principle in the first cooling plate elements. Alternatively, the edge regions of the first cooling plate elements can also be installed in overlapping fashion.

FIG. 7 shows a segment of this type of cooling system 33, which comprises several cooling plates 1 or stavelets. FIG. 7 also reveals another preferred system for mounting the stavelets on the furnace wall 10. To this end, each cooling plate 1 or stavelet has several suspension points 34-39, six each in the present case, such that the two upper suspension points 34, 35 are designed as fixed suspension points, and the suspension points 36-39 located below them are designed as loose attachment points.

A fixed connection between the cooling plate 1 and the furnace wall 10 is produced at the fixed points 34, 35 (see FIG. 8 and especially FIG. 9) by screwing in a screw 40 from above. For this purpose, a projection 41 is attached—preferably by welding—to the furnace wall 10, and a corresponding projection 42 is attached on the rear side of the cooling plate 1 outside the region of the cooling channel. The projections have aligned bores, through which the screw 40 is inserted to join the two projections. The loose attachment points 36-39 have a design comparable to that of a door suspension, as is shown in detail in FIG. 10. For this purpose, at suitable places on its rear side, the cooling plate has projections 43, each of which is provided with a bore. Each of the projections 43 is suspended on a pin 44, which is held by a projection 45 extending out from the furnace wall. These loose attachment points 36-39 allow the cooling plate 1 to undergo thermal expansion in the downward direction. To prevent the space required for the expansion on the suspensions or loose attachment points from being blocked by backfill compound, a throw-away part 46 made of plastic, preferably Styropor, is inserted at this site during assembly.

All together, the proposed cooling channel cross section results in a stavelet with optimum characteristics with respect to the fluid mechanics and cooling effect. In addition, the stavelet of the invention has advantages over the previously known stavelet from the standpoint of manufacturing engineering. Compared to the previously known Cu staves, large savings of material and weight are realized with these stavelets due to their smaller thickness, which, in addition, is accompanied by a greater useful volume of the furnace region.

Claims

1. Cooling plate (1, 101) for refractory-lined shaft furnaces, with a first cooling plate element (2, 102) facing the inside (Oi) of the furnace and a second, rear cooling plate element (3, 103), which are welded together, with a cooling channel (7, 107) formed between the first and the second elements of the cooling plate, and with pipe sections (8, 9) connected to the coolant inlet and coolant outlet, wherein the first cooling plate element (2, 102) is designed as a bloom with a plane front side (14) facing the inside (Oi) of the furnace, and that the cross-sectional area of the cooling channel is larger in the end regions (18, 19; 118, 119) than in the center region (20; 120), as viewed along the longitudinal extent of the cross-section.

2. Cooling plate in accordance with claim 1, wherein the end regions (18, 19; 118, 119) bulge out on one or both sides.

3. Cooling plate in accordance with claim 1, wherein, on its side facing the furnace interior (Oi), the cooling channel cross section is formed by the first cooling plate element (2) with at least two recesses (16, 17) that run along its rear side (5).

4. Cooling plate in accordance with claim 1, wherein the cooling channel cross section is formed on its rear side by a second cooling plate element (103) that has an at least double trough-like shape with bulges that project towards the furnace wall.

5. Cooling plate in accordance with claim 3, wherein the cooling channel cross section is formed on the rear side by a more or less plane second cooling plate element (3).

6. Cooling plate in accordance with claim 4, wherein the edge region (324, 325) of the second cooling plate element (103) is formed thicker than its center region.

7. Cooling plate in accordance with claim 1, wherein the second cooling plate element (3, 103) is welded by its longitudinal edges to the rear side (5) of the first cooling plate element (2, 102).

8. Cooling plate in accordance with claim 7, wherein the second cooling plate element (3) is welded to the rear side of the first cooling plate element (2) at some distance from the edges (2a, b) of the first cooling plate element, and that at least one slit (31) is produced in the edges regions (2a, b) of the first cooling plate element (2) perpendicularly to the longitudinal axis of the cooling plate.

9. Cooling plate in accordance with claim 3, wherein the pipe sections (8, 9) for the coolant intake and discharge extend through bores in the second cooling plate element (3) at the rear of the cooling plate, and that, at the level of these pipe sections (8, 9), the first cooling plate element (2) is hollowed out, and the depth of the hollow (39) was intended decreases in ramp-like fashion towards the cooling channel recesses (16, 17).

10. Cooling plate in accordance with claim 1, wherein the cooling plate (1, 101) has at least two suspension points (34, 38) for mounting the cooling plate on the furnace wall (10) of the shaft furnace, such that a first suspension point (34) is designed as a fixed connection in the upper part of the cooling plate, and a second suspension point (38) is designed as a loose connection in the lower part of the cooling plate.

11. Cooling plate in accordance with claim 10, wherein the first suspension point (34) comprises a screw connection as the fixed connection, and that the second suspension point (38) comprises a hung connection as the loose connection.

12. System (33) for cooling refractory-lined shaft furnaces, which comprises a large number of cooling plates (1, 101) of the types specified in claim 1, which are made of rolled copper or a rolled copper alloy and are installed side by side or in an overlapping fashion.