Heat transfer block type heat exchanger

Abstract

This invention provides a heat transfer block type heat exchanger that can maintain heat exchange capacity while suppressing sludge accumulation and extending the lifespan of the heat exchange function without requiring major design changes. [Solution] The diameter R1 of the process fluid inlet pipe 13a that introduces the process fluid L1 into the heat transfer block or heat transfer block group 11 is the same size as the maximum arrangement diameter of the multiple process fluid flow passages formed on the process fluid inlet side of the heat transfer block or heat transfer block group 11, and the length of the process fluid inlet pipe 13a that has a diameter R1 is a predetermined length D1 such that the flow velocity of the process fluid L1 is uniform.

Description

Technical Field

[0001] The present invention relates to a heat transfer block type heat exchanger that can suppress sludge deposition and extend the life of the heat exchange function while maintaining the heat exchange capacity without major design changes.

Background Art

[0002] Generally, hydrochloric acid or sulfuric acid is used as the process fluid for pickling in the production line of thin steel sheets, and this process fluid fills the line tank through which the thin steel sheet passes. In order to keep the temperature of this process fluid constant, the line tank and the heat exchanger are connected by pipes, and the process fluid is constantly circulated. As a heat exchanger for the pickling line of thin steel sheets, a heat transfer block type heat exchanger in which a plurality of heat transfer blocks are stacked and arranged in a shell container is common. The heat transfer block of the heat transfer block type heat exchanger has a structure in which a heat medium passes through a plurality of heat medium flow paths, and a process fluid passes through a process fluid flow path that intersects orthogonally with this, so that the heat medium and the process fluid exchange heat (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, while pickling removes scale formed on the surface of steel plates, the removed scale remains in the process fluid as sludge. Process fluid containing sludge has the characteristic of easily adhering to the walls of pipes, and the slower the flow velocity of the process fluid, the more easily it adheres. As sludge accumulation progresses, it can clog the process fluid passages and hinder the circulation of the process fluid. If the process fluid passages of a heat transfer block become clogged with sludge, the heat exchange capacity decreases, resulting in the inability to maintain a constant temperature of the process fluid.

[0005] Generally, the diameter of the process fluid piping connecting a heat transfer block type heat exchanger and the line tank is smaller than the diameter of the heat transfer block, and a header block is installed immediately before the heat transfer block to enlarge the flow path. As a result, the flow velocity in the process fluid passages formed on the outer periphery of the heat transfer block is slower than that in the central area, and blockage by sludge is more likely to occur in the process fluid passages formed on the outer periphery.

[0006] In Patent Document 1, the cross-sectional area of ​​the process fluid passages in the heat transfer block is made larger than that of the central region of the heat transfer block. This makes the flow velocity of all process fluid passages uniform, thereby suppressing blockage of the process fluid passages by sludge and maintaining the heat exchange function over a long period of time.

[0007] In this Patent Document 1, the diameter of the central region of the process fluid passage is reduced, which decreases the heat exchange capacity due to the reduction in the surface area within the process fluid passage. Therefore, increasing the number of process fluid passages can be considered as a solution, but this reduces the spacing between adjacent process fluid passages and thins the process fluid passage walls, leading to a shorter lifespan for the heat transfer block, or making it difficult to manufacture due to insufficient strength.

[0008] Another option is to increase the diameter of the outer periphery of the process fluid passages, but this would reduce the number of passages for both the process fluid and the heat transfer medium, thus decreasing the heat exchange capacity. In this case, if we try to maintain the number of process fluid passages, the spacing between adjacent passages will become narrower, leading to thinner walls and a shorter lifespan for the heat transfer block, or it may become difficult to manufacture due to insufficient strength.

[0009] In any case, maintaining the heat exchange capacity would require either increasing the number of heat transfer blocks or increasing the diameter of the heat transfer blocks. Both of these would involve redesigning the entire heat exchanger and the piping connected to it, resulting in a major modification.

[0010] The present invention has been made in view of the above problems, and aims to provide a heat transfer block type heat exchanger that can maintain heat exchange capacity while suppressing sludge accumulation and extending the lifespan of the heat exchange function without major design changes. [Means for solving the problem]

[0011] To solve the above-mentioned problems and achieve the objective, the heat transfer block type heat exchanger according to the present invention is a heat transfer block type heat exchanger that houses a heat transfer block or a group of heat transfer blocks in which a plurality of process fluid flow passages for passing a process fluid and a heat transfer medium flow passage perpendicular to the process fluid flow passages for passing a heat transfer medium, in a shell container, the heat transfer block having a plurality of process fluid flow passages for passing a process fluid and a heat transfer medium perpendicular to the process fluid flow passages, or the heat transfer block group having a plurality of heat transfer blocks connected in a multi-stage manner in the direction of process fluid flow such that the process fluid flow passages are in communication, and performs heat exchange between the process fluid and the heat transfer medium, wherein the diameter of the process fluid inlet pipe that allows the process fluid to flow into the heat transfer block or the group of heat transfer blocks is the same as the maximum arrangement diameter of the plurality of process fluid flow passages formed on the process fluid inlet side of the heat transfer block or the group of heat transfer blocks, and the length of the process fluid inlet pipe having the above diameter is a predetermined length such that the flow velocity of the process fluid is uniform.

[0012] Furthermore, in the heat transfer block type heat exchanger according to the present invention, a tapered surface is formed in the process fluid flow passage on the process fluid inlet side of the heat transfer block or the group of heat transfer blocks, which tapers in a way that is aligned with the flow direction of the process fluid.

[0013] Furthermore, the heat transfer block type heat exchanger according to the present invention is characterized in that a taper is provided between adjacent process fluid flow passages by forming the tapered surface.

[0014] Furthermore, in the heat transfer block type heat exchanger according to the present invention, the tapered surface is formed by machining to widen the process fluid flow passage of the heat transfer block toward the process fluid inlet side.

[0015] Furthermore, in the heat transfer block type heat exchanger according to the present invention, a flow passage corresponding to the process fluid flow passage is formed in the heat transfer block or the heat transfer block on the process fluid inlet side of the heat transfer block group, and a tapered perforated plate with the tapered surface is attached. [Effects of the Invention]

[0016] According to the present invention, it is possible to maintain heat exchange capacity while suppressing sludge accumulation and extending the lifespan of the heat exchange function without making major design changes. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a schematic diagram showing an overview of a pickling system in a thin steel sheet manufacturing line to which a heat transfer block type heat exchanger, which is an embodiment of the present invention, is applied. [Figure 2] Figure 2 is a schematic diagram showing the general configuration of a heat transfer block type heat exchanger. [Figure 3] Figure 3 shows the configuration of one of the heat transfer blocks within the heat transfer block group. [Figure 4] Figure 4 shows the configuration of the bottom heat transfer block. [Figure 5]Figure 5 is a cross-sectional view of part A in Figure 4. [Figure 6] Figure 6 is a view showing a part of the tapered surface formed in the process fluid flow path of the lowermost heat transfer block. [Figure 7] Figure 7 is a view showing an example of the formation of the tapered surface. [Figure 8] Figure 8 is a view showing another example of the formation of the tapered surface. [Figure 9] Figure 9 is an explanatory view comparing the present embodiment with the conventional example. [Figure 10] Figure 10 is a view showing the change in pump pressure with respect to the amount of steel sheet processed by the heat transfer block type heat exchanger according to the conventional and present embodiments.

Mode for Carrying Out the Invention

[0018] The heat transfer block type heat exchanger according to an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments, and the constituent elements in the following embodiments include those that can be replaced and are easy for those skilled in the art, or those that are substantially the same.

[0019] <Pickling System> Figure 1 is a schematic view showing an overview of a pickling system 1 in a production line of a thin steel sheet 3 to which a heat transfer block type heat exchanger 6 according to an embodiment of the present invention is applied. As shown in Figure 1, in the pickling system 1 in the production line of the thin steel sheet 3, a process fluid L1 for pickling, such as hydrochloric acid or sulfuric acid, is filled in the line tank 2. The scale formed on the surface of the thin steel sheet 3 has cracks, and when the thin steel sheet 3 passes through the process fluid L1, pickling treatment is performed to dissolve the base metal with acid and detach the oxide scale (sludge) from the steel sheet surface. Note that this sludge remains in the process fluid L1.

[0020] [[ID=I32]] To maintain a constant temperature for the process fluid L1, the line tank 2 and the heat transfer block type heat exchanger 6 are connected by process fluid piping 4, which continuously circulates the process fluid L1. A circulation pump 5 for circulating the process fluid L1 is provided in the process fluid piping 4.

[0021] <Heat transfer block type heat exchanger> Figure 2 is a schematic diagram showing the general configuration of a heat transfer block type heat exchanger 6. Figure 3 shows the configuration of heat transfer block 11a, which is one of the heat transfer block group 11 (11a to 11f). Figure 4 shows the configuration of the bottom heat transfer block 11g. As shown in Figure 2, the heat transfer block type heat exchanger 6 is housed in a cylindrical shell container 10 with multiple heat transfer blocks 11a to 11g (heat transfer block group 11) stacked on top of each other. Note that there may be only one heat transfer block 11g.

[0022] As shown in Figures 2 and 3, each heat transfer block 11a to 11g is a cylinder made of carbon with good heat exchange efficiency, and has multiple process fluid passages 20 extending in the Z direction to allow the process fluid L1 to pass through, and a heat medium passage 21 extending in a direction perpendicular to the process fluid passages 20 (Y direction), intersecting the process fluid passages 20, to allow the heat medium L2 to pass through. The process fluid passages 20 are arranged in rows in the Y direction and in multiple rows in the X direction. The heat medium passages 21 are arranged in rows in the Z direction and in multiple rows in the X direction, flanking the rows of process fluid passages 20. Each heat transfer block 11a to 11g has positioning members 23 extending in the Z direction protruding from both ends in the X direction, so that when the heat transfer blocks 11a to 11g are stacked, the process fluid passages 20 are connected.

[0023] A heat transfer medium inlet pipe 12a for introducing the heat transfer medium L2 is provided in the +Y direction of the uppermost heat transfer block 11a, and a heat transfer medium outlet pipe 12b for discharging the heat transfer medium L2 is provided in the -Y direction of the lowermost heat transfer block 11g. Here, a partition member 14 is provided between each heat transfer block 11a to 11g and the shell container 10. The heat transfer medium L2 that flows in from the heat transfer medium inlet pipe 12a moves in a zigzag pattern to the lower heat transfer blocks sequentially through the heat transfer medium flow passages 21 of each heat transfer block 11a to 11g, as shown by the dashed line, and then flows out from the lowermost heat transfer block 11g through the heat transfer medium outlet pipe 12b. The partition member 14 has a semi-ring or semi-cylindrical shape and is provided on one side in the Y direction of each heat transfer block 11a to 11g, forming a flow path that moves the heat transfer medium L2 in a zigzag pattern.

[0024] On the other hand, a process fluid inlet pipe 13a for introducing process fluid L1 is provided in the -Z direction of the lowest heat transfer block 11g, and a process fluid outlet pipe 13b for releasing process fluid L1 is provided in the +Z direction of the uppermost heat transfer block 11a.

[0025] <Process fluid inlet piping> The diameter R1 of the opening of the process fluid inlet pipe 13a is the same size as the maximum arrangement diameter of the process fluid flow passage 20 of the heat transfer block 11g, and the process fluid inlet pipe 13a maintains this diameter R1 for a predetermined length D1 at which the flow velocity of the process fluid L1 becomes uniform. The process fluid inlet pipe 13a is connected to the process fluid pipe 4, which is the process fluid pipe 13c, via a bellows 13d. Since the diameter of the process fluid pipe 13c is smaller than the diameter R1 of the process fluid inlet pipe 13a, the pipe diameter of the process fluid inlet pipe 13a on the bellows 13d side is set to the pipe diameter of the process fluid pipe 13c.

[0026] The maximum diameter of the process fluid passage 20 is the diameter of the outermost part of the process fluid passage 20. That is, it is the diameter from the outermost process fluid passage 20 to the outermost process fluid passage 20 on its diagonal, and is the diameter of the circumscribed circle that includes all the process fluid passages 20. By making the diameter R1 of the process fluid inlet pipe 13a the same size as the maximum diameter of the process fluid passage 20 of the heat transfer block 11g, the process fluid L1 that reaches the heat transfer block 11g will flow almost uniformly. This suppresses the low flow velocity in the outer peripheral region of the heat transfer block that occurred when a header block was conventionally used, and reduces the accumulation rate of sludge contained in the process fluid L1. Note that a uniform flow may vary depending on the flow rate (average flow velocity), but it refers to a state where the difference between the maximum flow velocity and the minimum flow velocity is within 0.6 m / s.

[0027] The diameter R1 of the process fluid inlet pipe 13a is preferably 0 mm to 10 mm greater than the maximum arrangement diameter of the process fluid passage 20, because if it is too large, a low-velocity section will be generated. The predetermined length D1 can be determined by the diameter of the heat transfer block 11g and the flow velocity of the process fluid L1, for example, 300 mm to 1000 mm. The diameter of the heat transfer blocks 11a to 11g is 602 mm, and the height is 482 mm. Each heat transfer block 11a to 11g is provided with 295 process fluid passages 20. The maximum arrangement diameter of the process fluid passage 20 is 530 mm. The diameter of the process fluid passage 20 is 16 mm.

[0028] On the other hand, the diameter of the process fluid outlet pipe 13b is the same as the diameter of the process fluid pipe 4, and the header block 26 narrows the maximum arrangement diameter of the process fluid flow passage 20 of the heat transfer block 11a to the diameter of the process fluid pipe 4.

[0029] <Formation of tapered surface> Here, if the surface of the heat transfer block 11g on the process fluid inlet side has a flat portion perpendicular to the inflow direction of the process fluid L1, the process fluid L1 will collide with this flat portion, reducing its flow velocity and making it easier for sludge to accumulate.

[0030] Therefore, in this embodiment, a tapered surface 24S is formed in the process fluid flow passage 20 on the process fluid inlet side of the heat transfer block 11g, which tapers in the direction of the flow of the process fluid L1 (see Figures 2 and 4(b)).

[0031] Figure 5 is a cross-sectional view of section A in Figure 4. Figure 6 shows a portion of the tapered surface 24S formed in the process fluid flow passage 20 of the lowest heat transfer block 11g. By forming the tapered surface 24S shown in Figures 5 and 6, the decrease in flow velocity when the process fluid L1 collides with the heat transfer block 11g can be suppressed. This further reduces the rate of sludge accumulation, extending the lifespan of the heat transfer block type heat exchanger 6.

[0032] The cross-section of the tapered surface 24S shown in Figures 5 and 6 has a linear slope, but it may also have a curved slope. Furthermore, as shown in Figure 6, the formation of the tapered surface 24S creates a taper between adjacent process fluid passages 20. Figure 5 is also a cross-sectional view of line BB in Figure 6. The tapered surface 24S is formed by machining the process fluid passage 20 of the heat transfer block 11g to widen it toward the process fluid inlet side. For example, the heat transfer block is cut into a conical shape around the axis of the process fluid passage 20. The angle of the tapered surface 24S is, for example, 30° to 120°, and preferably 60° to 90°.

[0033] Figure 7 shows an example of the formation of the tapered surface 24S. In Figure 6, a flat region E remains on the process fluid inlet side surface of the heat transfer block 11g, but in order to avoid a decrease in flow velocity, it is more preferable for the tip of the process fluid inlet side of the heat transfer block 11g to be narrowly pointed in a triangular shape. Therefore, as shown in Figure 7, it is preferable to have the tapered surfaces 24S overlap between all adjacent process fluid passages 20 so that the tips of the process fluid inlet side are narrowly pointed.

[0034] Figure 8 shows another example of tapered surface formation. Figure 8(b) is a cross-sectional view along line CC of Figure 8(a). The tapered surface 24S described above was formed by directly cutting the heat transfer block 11g, but as shown in Figure 8, a flow passage corresponding to the process fluid flow passage 20 may be formed on the heat transfer block 11g, which does not have a tapered surface 24S, and a tapered perforated plate 30 with a tapered surface 24S may be attached. In this case, the material of the tapered perforated plate 30 should be the same as that of the heat transfer blocks 11a to 11g, or a material with a thermal expansion coefficient equivalent to that of the heat transfer blocks 11a to 11g.

[0035] Figure 9 is an explanatory diagram comparing this embodiment with a conventional example. Figures 9(a) and 9(b) show a conventional heat exchanger with heat transfer blocks, in which a header block 27 for connecting process fluid piping 4 is provided on the process fluid inlet side. In this case, since the diameter R2 of the process fluid piping 4 is smaller than the diameter of the heat transfer block group 11, the flow velocity of the process fluid L1 on the outer circumference side of the heat transfer block group 11 decreases (Figure 9(a)). Also, since the surface S on the process fluid inlet side of the heat transfer block group 11 is a plane in which the process fluid flow passage is formed, the process fluid L1 collides with surface S, and this collision reduces the flow velocity of the process fluid L1 (Figure 9(b)).

[0036] In contrast, in this embodiment, as shown in Figure 9(c), a process fluid inlet pipe 13a is provided, and the diameter R1 of the process fluid inlet pipe 13a is set to be the same as the maximum arrangement diameter of the multiple process fluid flow passages formed on the process fluid inlet side of the heat transfer block group 11. By setting the length of the process fluid inlet pipe with diameter R1 to a predetermined length D1, the flow velocity of the process fluid L1 becomes uniform, and the decrease in flow velocity is suppressed. Furthermore, since a tapered surface 24S is formed on the process fluid inlet side of the heat transfer block 11g, the process fluid L1 does not collide with the heat transfer block 11g, and the decrease in the flow velocity of the process fluid L1 can be suppressed. By installing this process fluid inlet pipe 13a and forming the tapered surface 24S, the decrease in process fluid L1 can be significantly suppressed, and the rate of sludge accumulation can be suppressed.

[0037] <Verification Results> Figure 10 shows the change in pump pressure with respect to steel sheet processing volume using conventional and this embodiment heat transfer block type heat exchangers. Conventional heat transfer block type heat exchangers, as shown in Figures 9(a) and 9(b), have process fluid L1 flowing in via a header block 27 and do not have a tapered surface 24S. The heat transfer block type heat exchanger 6 of this embodiment has a process fluid inlet pipe 13a and a tapered surface 24S. Other common features include, as described above, the diameter of the heat transfer block is 602 mm, the height is 482 mm, and each heat transfer block is provided with 295 process fluid passages 20. The maximum arrangement diameter of the process fluid passages 20 is 530 mm. The diameter of the process fluid passages 20 is 16 mm. The angle of the tapered surface at the inlet is 90°. The predetermined length of the process fluid inlet pipe 13a is 1000 mm. The process fluid L1 is hydrochloric acid with a concentration of 4-6% and a flow rate of 200 m³. 3 At / h, the hydrochloric acid temperature in line tank 2 is maintained at 90-95°C. The heat transfer medium is steam at a pressure of 0.4 MPa.

[0038] Here, as blockage of the heat transfer block by sludge progresses, the pump pressure increases, so the pump pressure is used as an indicator of the degree of blockage, and the lifespan is defined as the point at which the pump pressure reaches 0.3 MPa, at which point the temperature of line tank 2 can no longer be maintained at 90-95°C. Since the amount of sludge generated affects the blockage of the heat transfer block, the weight of the steel plates that have passed through line tank 2, i.e., the amount of steel plates processed (tons) in the production facility, is used as an indicator of the lifespan.

[0039] The approximate characteristic curves LN11 to LN14 shown in Figure 10 represent the results of four processing trials for a conventional block-type heat exchanger, where the pump pressure increases linearly with increasing steel sheet processing volume. On the other hand, approximate characteristic curve LN1 represents the processing results for the block-type heat exchanger of this embodiment, where the pump pressure remains constant up to a certain steel sheet processing volume, and after exceeding that volume, the pump pressure increases linearly with increasing steel sheet processing volume, similar to the conventional method.

[0040] As shown in Figure 10, the average lifespan (average of 4 cycles) of a conventional heat transfer block type heat exchanger was 13.6 thousand tons, while the lifespan of the heat transfer block type heat exchanger of this embodiment was 18.6 thousand tons. As a result, the lifespan of the heat transfer block type heat exchanger of this embodiment is approximately 1.4 times that of a conventional heat transfer block type heat exchanger, demonstrating a significant improvement in lifespan.

[0041] In the heat transfer block heat exchanger of this embodiment, the pump pressure remains constant up to a specific steel sheet processing volume, for example, 14,000 tons, after which the pump pressure increases, as in conventional heat transfer block heat exchangers. It is thought that sludge is less likely to adhere during this period when the pump pressure is constant, and once sludge begins to adhere, the accumulation of sludge starts to progress. In other words, the heat transfer block heat exchanger of this embodiment has a structure that makes it difficult for sludge to adhere up to a specific steel sheet processing volume, and by suppressing sludge adhesion up to this specific steel sheet processing volume, it can be said that the lifespan is extended.

[0042] The heat transfer block type heat exchanger according to the present invention has been specifically described above with respect to embodiments and modifications for carrying out the invention. However, the spirit of the present invention is not limited to these descriptions and must be interpreted broadly based on the claims. Furthermore, it goes without saying that various changes and modifications based on these descriptions are also included in the spirit of the present invention. [Explanation of Symbols]

[0043] 1. Pickling System 2-line tank 3 Thin steel plate 4 Process fluid piping 5. Circulation pump 6. Heat transfer block type heat exchanger 10 Shell containers 11 Heat transfer block group 11a~11g Heat transfer block 12a Heat medium inlet piping 12b Heat medium outlet piping 13a Process fluid inlet piping 13b Process fluid outlet piping 13c Process fluid piping 13d bellows 14 Partition members 20 Process fluid flow channels 21 Heat medium flow path 23 Positioning member 24S Tapered Surface 26,27 Header Block 30 Tapered perforated plate D1 predetermined length E flat area L1 Process Fluid L2 heat medium LN1,LN11~LN14 Approximate characteristic curve R1, R2 diameter S side

Claims

1. A heat transfer block type heat exchanger that houses a heat transfer block in a shell container, the heat transfer block having a plurality of process fluid flow passages for passing a process fluid and a heat transfer medium flow passage perpendicular to the process fluid flow passages for passing a heat transfer medium, or a group of heat transfer blocks in which the heat transfer blocks are connected in multiple stages in the flow direction of the process fluid such that the process fluid flow passages are in communication with each other, and performs heat exchange between the process fluid and the heat transfer medium, A heat exchanger of the heat transfer block type, characterized in that the diameter of the process fluid inlet piping that introduces the process fluid into the heat transfer block or the group of heat transfer blocks is equal to the maximum arrangement diameter of a plurality of process fluid flow passages formed on the process fluid inlet side of the heat transfer block or the group of heat transfer blocks, and the length of the process fluid inlet piping that has the aforementioned diameter is a predetermined length such that the flow velocity of the process fluid is uniform.

2. The heat transfer block type heat exchanger according to claim 1, characterized in that a tapered surface is formed in the process fluid flow passage on the process fluid inlet side of the heat transfer block or the group of heat transfer blocks, which tapers in the direction of the flow of the process fluid.

3. The heat transfer block type heat exchanger according to claim 2, characterized in that a taper is provided between adjacent process fluid flow passages by forming the tapered surface.

4. The heat transfer block type heat exchanger according to claim 2, characterized in that the tapered surface is formed by cutting to widen the process fluid passage of the heat transfer block toward the process fluid inlet side.

5. The heat exchanger of the heat transfer block type according to claim 2, characterized in that a flow passage corresponding to the process fluid flow passage is formed in the heat transfer block or the heat transfer block on the process fluid inlet side of the group of heat transfer blocks, and a tapered perforated plate with the tapered surface is attached to it.

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