Heat exchange block, its manufacturing method, heat exchanger including said block, and its mounting method

Abstract

The heat exchanger block (1) comprises a body (10), vertical channels (20) intended for the flow of a process fluid and horizontal channels (60) intended for the flow of a service fluid. According to the invention, at least one bottom part (2), in particular the upstream bottom part, defines a central bowl part (3) defining a central surface (S3), a peripheral seat part (4) defining a peripheral reference surface (S4), a transition part (5) and a distance (h4) between the nearest horizontal channel (60a) and the peripheral surface (S4) that is substantially greater than the distance (h3) between the nearest horizontal channel (60a) and the central surface (S3). The thermal stresses generated in the block of the invention are much lower than in the prior art, which results in a significantly longer service life for both the block and the heat exchanger than in the prior art.

Description

[Technical field]

[0001] The present invention relates to the technical field of block-type heat exchangers, in particular to a heat exchanger block with an improved shape with respect to both thermal and mechanical issues, and also to a heat exchanger equipped with such a heat exchanger block. [Background technology]

[0002] Various heat exchangers are known, inter alia, plate, tube or fin type heat exchangers. The invention is particularly concerned with block type heat exchangers. The latter generally firstly comprise an inlet and an outlet for the so-called process fluid, both arranged along the main axis of the heat exchanger. In addition, the casing of the heat exchanger is provided with lateral inlets and outlets, both for the so-called service fluid. The process fluid is, for example, an acid and the service fluid is a heat transfer fluid such as water.

[0003] The casing houses at least one heat exchanger block, typically a number of heat exchanger blocks stacked one above the other. Each block is made of a heat conducting material. The invention relates more particularly to process fluids that are corrosive to metals. In this respect, said material is typically graphite, optionally combined with an additive, for example of polymer type. It is noted that the blocks may be parallelepipedal or cylindrical, the invention more particularly contemplating cylindrical blocks.

[0004] Two series of flow passages are cut out in the block for the circulation of a process fluid and a service fluid, respectively: a first flow passage is elongated, extends continuously between the bottom surfaces of the body and opens at said bottom surfaces, and a second flow passage is elongated, extends continuously between the opposing lateral surfaces of the body and opens at said lateral surfaces.

[0005] Block-type heat exchangers of the above known type are described, for example, in EP 0 196 548 A1 and WO 2006 / 081965 A1.

[0006] However, the prior art block type heat exchangers as disclosed above are not satisfactory, especially with regard to mechanical problems. In fact, some material failures have been observed, which shorten the life of the heat exchanger. These failures occur especially at the periphery of the bottom part of the block, which is upstream with respect to the flow of the hot process fluid.

[0007] US 3,391,016 describes a process for manufacturing a heat exchange element formed by annular bodies of graphite. US 2,821,369 discloses a heat exchanger comprising a plurality of hollow cylindrical graphite blocks arranged in axial alignment to form a column with a central hollow interior. These two documents deal with a type of heat exchange block that is substantially different from the type aimed at by the present invention. In fact, due to the annular shape of the block, the lateral channels do not extend continuously between the lateral faces of the block.

[0008] Finally, GB 1078868 discloses a heat exchanger provided with several graphite blocks but without an external casing. Each of said blocks is formed by two separate parts fixed to each other by a clamp. This further document does not relate to a heat exchanger block of the type according to the invention, since this block does not include longitudinal and transverse channels. In fact, in this British document, both the process fluid and the service fluid flow in two series of channels opening at the bottom of the block. Nevertheless, one of the objects of the present invention is to provide a heat exchanger block making it possible to remedy the drawbacks associated with the prior art mentioned above.

[0009] It is a further object of the present invention to provide a block which ensures both satisfactory thermal and mechanical performance for the heat exchanger in which it is mounted.

[0010] A further object of the invention is to provide a heat exchanger which has a relatively simple structure, in particular with regard to the channels cut out in the blocks belonging to said heat exchanger, and which can be manufactured without any particular risk of mechanical breakage. Summary of the Invention

[0011] One of the objects of the present invention is a heat exchanger block (1; 501; 1001, 2001, 3001), a body (10), in particular made of graphite and in particular having a cylindrical shape with a circular cross section; - first so-called longitudinal channels (20) formed in said body along the longitudinal direction (L1) of said block, each longitudinal channel extending continuously between two opposing bottom parts (2, 6; 502, 506; 1002, 1006, 2002, 2006, 3002, 3006) of said body and opening at said bottom parts, said longitudinal channels intended for the flow of a first so-called process fluid; - second so-called transverse channels (60; 560) formed in the body along a transverse direction, each of which extends continuously between two opposing transverse faces (7, 8) of the body and opens in said transverse faces, said transverse channels intended for the flow of a second so-called service fluid, At least one bottom part (2;502;1002,1006,2002,2006,3002,3006) a central so-called homogenizing bowl section (3; 503; 1003, 1103, 2003, 2103, 3003, 3103) which defines a so-called central reference surface (S3; S503) and is intended to homogenize the temperature of the constituent material of said block; a peripheral seat (4; 504) defining a so-called peripheral reference surface (S4; S504), projecting upstream relative to the central bowl section along said longitudinal direction and adapted to receive a sealing means; a transition portion (5; 505) extending between said peripheral seat portion and said central bowl portion; a so-called peripheral distance (h4; h504) between the so-called opposing wall (61; 561) of the nearest transverse channel (60a; 560a) and the peripheral surface (S4; S504), which is substantially greater than the so-called central distance (h3; h503) between said wall (61; 561) of the nearest transverse channel (60a) and the central surface (S3; S503), said distances (h3; h503) and (h4; h504) being considered to be along the longitudinal direction of the block, The heat exchange block is characterized in that a recess (22; 522) is provided in the bottom surface portion so as to separate the heat exchange block from the outside.

[0012] According to advantageous features of the heat exchanger block according to the invention: the ratio of the outer periphery distance to the central distance (h4 / h3) is greater than 1.2, preferably greater than 2; The outer perimeter distance (h4) is greater than d60a, in particular greater than 2×d60a, where −d60a is the diameter of the nearest lateral channel (60a). The center distance (h3) is greater than t26, preferably greater than 2*t26, where -t26 is the minimum material thickness between the longitudinal channel (20) and the transverse channel (60). the so-called transition angle (a5) between the reference plane (S5) of the transition section and the reference plane (S3) of the bowl section is between 30° and 90°; - only the upstream bottom portion (2; 502) of the base portions is provided with the bowl portion (3; 503), while the opposing downstream bottom portion (6; 506) is substantially flat or is provided with a fluid distribution chamber, the depth of which (D903) is sufficiently smaller than the depth of the bowl portion (D3 / D503). The bowl portions (1003, 1103, 2003, 2103, 3003, 3103) are provided on both the upstream bottom portion and the downstream bottom portion, respectively.

[0013] A further subject of the present invention is a method for producing a heat exchanger block as defined above, comprising the steps of: - providing a preform, in particular a standard heat exchanger block, comprising a preform body and first so-called vertical channels formed in the preform body along a longitudinal direction of the preform, opening at two opposite, both substantially flat, bottom sides of the preform, and second so-called transverse channels formed in the preform body along a transverse direction, opening at two opposite, lateral sides of the preform, - removing material of said preform, in particular by machining or a similar process, to form said bowl portion (3) and said transition portion (5).

[0014] A further subject of the invention is a heat exchanger (I; II; III), a housing having a lower cover (310; 1310), an upper cover (320; 1320) and an outer casing (330; 1330); at least one heat exchange block (1, 101, 201; 501; 1001, 2001, 3001) arranged between said lower cover and said upper cover, Each of the blocks comprises: -The main body, - first so-called longitudinal channels formed in the body along the longitudinal direction of the block, opening at two opposite bottom parts of the body, said longitudinal channels intended for the flow of a first so-called process fluid; - second so-called transverse channels formed in the body along a transverse direction and opening at two opposite transverse faces of the body, said transverse channels intended for the flow of a second so-called service fluid, The heat exchanger comprises: - first means (322; 1332) for the first fluid to enter the first flow path; - second means (336; 1336) for introducing said second fluid into said second flow path; - first means (312; 1312) for the first fluid exiting the first flow path; - second outlet means (337; 837; 1337) for the second fluid from the second flow path, a heat exchanger, characterized in that at least one heat exchanger block (1; 501; 1001, 2001, 3001) is a heat exchanger block as defined above.

[0015] According to advantageous features of the heat exchanger according to the invention: - the heat exchanger comprises one heat exchange block (1; 501) as defined above, said one block being the so-called upstream block located closest to said first inlet means (322), said one block (1; 501) being provided with one bowl part (3; 503) located on said so-called upstream bottom part (2; 502) directed towards said first inlet means; the distance (d561) between the opposing wall (561) of the nearest horizontal passage (560a) and the upper wall (838) of the second outlet means (837) of the second fluid, considered along the longitudinal direction of the block, is smaller than 20 mm, in particular smaller than 10 mm, the wall (561) of the nearest horizontal passage (560a) being advantageously closer to the first inlet means than the upper wall (838). some, preferably all, of the heat exchanger blocks are heat exchanger blocks (1001, 2001, 3001) as defined above.

[0016] A further subject of the invention is a method for implementing a heat exchanger as defined above, in which the first and second fluids are circulated in the first and second flow paths to enable heat exchange therebetween, and in which the first fluid, if gaseous, flows through the heat exchanger in a single phase without significant condensation, the first fluid entering the first inlet means at a temperature, in particular higher than 80°C, while the second fluid entering the second inlet means at a temperature, in particular between -20°C and +35°C.

[0017] According to a feature of the invention, the first fluid may enter the first inlet means at a temperature greater than 200°C.

[0018] A further subject of the invention is a method for implementing a heat exchanger as defined above, wherein the first and second fluids are circulated in the first and second flow paths to enable heat exchange therebetween, the first fluid passing through the heat exchanger and being subjected to condensation, the inlet temperature of the first fluid being in particular between +80°C and +300°C, while the outlet temperature of the first fluid being in particular between -15°C and +60°C, and the inlet temperature of the second fluid being in particular between -20°C and +35°C, while the outlet temperature of the second fluid being in particular between -15°C and +45°C. [Brief description of the drawings]

[0019] The invention will now be described with reference to the accompanying drawings, given as non-limiting examples. [Figure 1] FIG. 1 is a vertical sectional view showing a heat exchanger provided with a block according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective, partially cut away view of a block according to the present invention. [Diagram 3] FIG. 3 is a longitudinal section similar to FIG. 1, showing the upstream end of the block of FIG. 2 and the heat exchanger of FIG. 1 in more detail. [Figure 4] FIG. 4 is a longitudinal section similar to FIG. 3, showing the upstream end of a block according to the prior art and a heat exchanger provided with such a block. [Diagram 5] FIG. 5 is an enlarged vertical cross-sectional view of the upstream end of the block of FIG. [Figure 6] FIG. 6 is a graph showing the variation of both thermal and mechanical stresses of blocks of the invention with representative ratio values ​​of the blocks. [Figure 7] FIG. 7 is a longitudinal section similar to FIG. 1, showing, on an enlarged scale, a portion of a heat exchanger provided with a block according to a second embodiment of the invention. [Figure 8] FIG. 8 is a vertical cross-sectional view similar to FIG. 3, showing the portion VIII of FIG. 7 in greater detail on an enlarged scale. [Figure 9] FIG. 9 is a schematic front view of the heat exchanger of FIG. 1, particularly showing the lateral flow passages in the block portion of the heat exchanger and the flow of fluid in the flow passages. [Figure 10] FIG. 10 is a schematic front view of the heat exchanger of FIG. 7, particularly showing the lateral flow passages in the block portion of the heat exchanger and the flow of fluid in the flow passages. [Figure 11] FIG. 11 is a schematic front view of a block according to another modified example of the present invention. [Figure 12] FIG. 12 is a longitudinal section similar to FIG. 1, showing a heat exchanger provided with a block according to a third embodiment of the invention. [Figure 13] FIG. 13 is a graph that illustrates, in schematic form, the variation of graphite temperature along a major dimension of a prior art heat exchanger for two different cases. [Figure 14] FIG. 14 is a graph that illustrates generally the change in graphite temperature for the prior art heat exchanger and the heat exchanger of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The following reference symbols are used in this specification: I. Heat exchanger according to a first embodiment of the present invention 1. Upstream block according to the present invention 10 Block 1 Body 12 Baffle section above 10 L1 Block vertical direction 2. Bottom surface of upstream side of block 1 The center of C2 P2 outer periphery 20 Longitudinal channel 22 Recess in bottom portion 2 3. Central bowl of bottom part 2 h3 Distance between S3 and 61 4 Seat of bottom part 2 h4 Distance between S4 and 61 41 Shoulder 5. Transition between bowl portion 3 and seat portion 4 S3, S4, S5 3, 4, 5 reference planes a5 Angle between S3 and S5 6. Downstream bottom of block 1 7,8 Upstream and downstream surfaces of the lateral flow passage 60 Cross flow path T26 Material thickness between 20 and 60 d60 60 diameter 60a Upstream side lateral flow channel d60a Diameter of flow channel 60a 61 60a wall 60b to 60e: Flow paths directly below the flow path 60a DZ Dead Zone 101,201 Block of heat exchanger I according to the prior art 102,202 Upstream face of blocks 101,201 106,206 Downstream faces of blocks 101,201 310 Lower cover of heat exchanger I 312 Opening in 310 320 Heat Exchanger I Top Cover 322 Opening in 320 324 Space within 320 326 Color Section 328 Spring 330 Casing of Heat Exchanger I 335 Periphery Chamber 336,337 Inlet and outlet pipes IV. Prior art heat exchangers 401 Upstream Block 402 Bottom part of 401 h402 Distance between 402 and 460a Center of C' 402 The outer periphery of P'402 460 Cross flow path h460 Distance between two channels 460 460a Upstream side lateral passage 420 Cover Loading zone for R 420 II. Heat exchanger according to a second embodiment of the present invention 501 and onwards: Same as 1 and onwards, but with 500 added 838 Client pipe 837 wall d561 Distance between walls 561 and 838 903 / D903 Distribution chamber and its depth (Fig. 11) III. Heat exchanger according to a third embodiment of the present invention 1001 and onwards: Same as 1 and onwards, but with 1000 added 1103 Second bowl portion of block 1001 2001 Second block according to the present invention 2003, 2103 Bowl portions on each end of block 2001 3001 Third block according to the present invention 3003, 3103 Bowl portions on each end of block 3001

[0021] Figure 1 shows a heat exchanger according to a first embodiment of the invention, generally referenced I. This heat exchanger firstly comprises a number of heat exchanger blocks 1, 101, 201. Block 1 is according to the invention and blocks 101, 201 are according to the prior art, as will be explained in more detail below. In this example, three blocks are shown stacked one on top of the other, it being understood that a different number of blocks may be envisaged. Preferably, whatever the number of blocks, only one block according to the invention is provided.

[0022] These different blocks 1, 101, 201 are made of any suitable material, in particular one compatible with corrosive environments, such as graphite. Each block has a body, referenced 10 for block 1. Said body has a typical cylindrical shape, with a circular cross section. What are known as baffle sections 12, as shown in particular in figures 2 and 5, are provided on the outer periphery of this body 10.

[0023] L1 refers to the main or longitudinal axis of each block, which is parallel to the main axis of the heat exchanger. In a manner known per se, each block is hollowed out with different channels to allow the flow of the two fluids intended to be placed in heat exchange with each other.

[0024] A first series of channels 20, called longitudinal channels, which are parallel to the axis L1, open out in opposing bottom parts 2, 6 of each block. With respect to the direction of fluid flow along the longitudinal channels, each bottom part 2 is called the upstream side and each opposing bottom part 6 is called the downstream side.

[0025] Furthermore, the second series of lateral channels 60 run obliquely, in particular perpendicular to the axis L1, and open into the opposite lateral faces 7, 8 of each block. In operation, the two fluids circulating in the first and second series of channels, respectively, are placed in a heat exchanger. These channels 20, 60 are separate from one another, i.e. do not open into one another.

[0026] Apart from the blocks 1 to 201, the heat exchanger I also comprises a lower cover 310, an upper cover 320 and an outer casing 330. In the upper cover 320 an opening 322 is cut out for the first so-called process fluid inlet into the longitudinal passages of all three blocks. This inlet is connected to a supply source of this fluid arranged upstream and not shown. Said opening leads to a space 324 provided in the underside of the cover.

[0027] Additionally, the bottom cover 310 is cut out with an opening 312 for the outlet of the first fluid out of the vertical flow passage, which is connected to suitable downstream equipment such as piping, the latter as such is known, not shown.

[0028] The casing 330 defines, together with the opposing walls of the blocks, an outer circumferential bowl section 335 intended for the circulation of a second, so-called service fluid, intended to be in heat exchange with the process fluid in the blocks 1-201. For this purpose, the casing is provided with a pipe with a respective inlet 336 for the second fluid and an outlet 337 connected to other suitable downstream equipment, such as further pipes. The latter, also known as such, are not shown.

[0029] Said space 324 defines a peripheral collar 326 which rests on the upstream block 1 in use. It is important to ensure a tight seal between the conductive wall of the block 1 and the collar 326 to avoid any contact between the two fluids. For this purpose, the interface between said block and said collar is provided with sealing means which are known and are not shown in detail. Furthermore, the top cover 320 is provided with pressing means adapted to exert a controlled compressive force on the block and said sealing means. In the example shown, these pressing means are formed by springs 328 which are known as such.

[0030] In this embodiment, the downstream bottom part 6 of the upstream block 1 and both bottom parts 102, 106, 202, 206 of the other blocks 101, 201 are manufactured according to the prior art. In other embodiments, in particular in one of the figures 12-14, both bottom parts may be provided with respective chambers, as will be explained in more detail below.

[0031] Returning to FIG. 1, the general structure of said exemplary faces is known per se and will not be described in detail here. It is sufficient to state that these bottom parts 6, 102, 106, 202, 206 are substantially flat. By "flat" we mean that said bottom parts are formed generally at the same height relative to the main longitudinal axis of the block. In this respect, each bottom part may be completely flat or may be hollowed out with at least one groove of shallow depth suitable for forming, for example, a seat for an O-ring type sealing member.

[0032] The upstream bottom part 2 of the upstream block 1 is, on the one hand, manufactured according to the invention. In fact, it is not flat, but is provided with a central recess 22, the depth of which is considerable and thus defines: - a central bowl portion 3 which opens into a space 324 provided in the cover; - a peripheral seat 4 radially surrounding the bowl portion; and a transition portion 5 extending between the peripheral seat portion and the central bowl portion;

[0033] In this embodiment, the central bowl section 3 is flat and defines a so-called central reference plane S3. Alternatively, this bowl section may not be flat and may, for example, have a wavy shape. In this case, the reference plane is defined by the average height of the bowl section.

[0034] The seat 4 projects upstream relative to the central bowl part 3 along a longitudinal direction L1. It defines a so-called peripheral reference surface S4, which in this embodiment is flat. In some variants, this seat is not flat but is provided with, for example, grooves adapted to receive several seals. Surface S4 is then defined by the average height of the seat, similar to surface S3 above. In use, collar part 326 of top cover 320 rests on seat 4 and exerts a compressive effect on this seat by means of spring 328.

[0035] It should be noted that in this embodiment, the seat 4 is provided at its radially inner end with a shoulder 41, the function of which is generally to maintain the annular seal and has no mechanical effect.

[0036] The transition portion 5 is in this embodiment linear when viewed in cross section in Fig. 5. Alternatively, this portion may have another shape, for example defining a step. The portion 5 is associated with a transition surface S, which is defined in a similar manner to the surfaces S3, S4.

[0037] In the following some important typical dimensions of the upstream bottom part 2 of the block 1 are specified: - the so-called perimeter distance h4 between the wall 61 of the nearest horizontal channel 60a and the perimeter surface S4 along the longitudinal direction of the block, said wall 61 being called the "upper side" with respect to its position in the figure, but also the "opposite side" since it is oriented towards the process fluid inlet. - the so-called centre distance h3 between said wall 61 and the centre surface S3 of the nearest transverse channel along the longitudinal direction of the block.

[0038] According to an important feature of the invention, which will be explained in detail below, said distance h4 is much greater than said distance h3. In this respect, it is emphasized that the applicant has identified an explanation regarding the shortcomings of the prior art and the importance of said essential features.

[0039] Reference is now made to Figure 4, which shows a heat exchanger IV according to the prior art, in which mechanical elements similar to those of heat exchanger I are given the same reference numbers, increased by 400.

[0040] First, we refer to the so-called rest zone R, where the top cover 420 rests on the upstream graphite block 401. In this zone, minimal clamping force is applied, which induces significant compressive stresses in the area of ​​the graphite column on which the cover 420 is supported. Compressive loading against the rest zone R results in tensile stresses approaching the maximum allowable tensile stresses. This problem is exacerbated by the presence of the upstream lateral channel 460a, which passes under the surface supporting the cover.

[0041] To ensure mechanical performance, prior art heat exchangers are provided with a significant material thickness forming a flat bottom 402. In other words, as shown in Fig. 4, the distance h402 separating the bottom 2 from the upstream lateral channel 460a is much larger than the distance h460 between the lateral channels of two adjacent series. This makes it possible to reduce the stresses borne by the graphite material in the region of the first layer of horizontal channels.

[0042] While this design is theoretically advantageous as far as mechanical considerations are concerned, it does create problems with undesirable thermal stresses, the latter of which, shown in Figure 4, is particularly severe when the process fluid enters the heat exchanger at high temperatures.

[0043] At the center C' of the bottom portion 402, the graphite surface first comes into contact with the incoming hot process fluid. Moreover, it is far away from the first cooling flow passage due to the large value of h402. At the periphery P' of this bottom portion, the graphite surface also comes into contact with the incoming hot process fluid. However, unlike the center C', this periphery P' is also very close to the service fluid, which has a temperature significantly lower than the process fluid.

[0044] As a result, the temperature in the center T C’ is the temperature of the outer periphery T P’ As a result, the volume of graphite near the center expands more than the volume of graphite near the periphery, causing thermal stresses throughout the heat exchanger. These stresses are likely to cause some material failure, especially in the periphery region P'.

[0045] The latter is in fact subjected to a combination of mechanical stresses due to the clamping forces and thermal stresses due to the temperature gradient through the graphite block. This failure phenomenon is particularly likely to occur in the transient mode, when the heat exchanger starts to receive hot process fluid after having been idle for a long enough time to have a uniform and low temperature. In summary, the applicant has identified that even if prior art heat exchanger blocks are provided with a significant material thickness at the upstream end, this adversely results in mechanical weakness.

[0046] As mentioned above, one of the important features of the invention is to significantly increase the ratio h4 / h3. In this respect, Figure 6 shows the variation of both mechanical and thermal stresses versus the ratio h4 / h3. In the graph of Figure 6, the x-axis corresponds to said ratio. Furthermore, the dashed and dotted line shows the variation of the parameter M representative of the mechanical stress of the block, the dashed line shows the variation of the parameter T representative of the thermal stress of the block, and the solid line shows the global stress G, i.e. the sum of the stress values ​​M and T. The lower the values ​​of both M and T, the better the behavior.

[0047] As shown in Figure 6, the thermal stress decreases as the ratio h4 / h3 increases. Furthermore, the mechanical stress increases as the ratio h4 / h3 increases. Surprisingly, however, the decrease in the thermal stress is much more significant than the increase in the mechanical stress. As a result, the value of the overall stress G tends to decrease with the increase in the ratio h4 / h3.

[0048] Theoretically, an increase in this ratio h4 / h3 can be achieved by increasing the value of h4 and / or decreasing the value of h3. In practice, it is desirable to keep h4 at a value similar to that of the prior art blocks. In this respect, h4 is advantageously set such that the stress exerted by the clamping force through the top cover is compatible with the mechanical properties of the material. Due to the particular shape of the bottom part 2 of the block, the clamping force is borne mainly by the annular seat 4 and secondarily by the transition part 5.

[0049] On the other hand, h3 is significantly reduced to reach a value that is significantly smaller than in the prior art. In other words, the central part of the bottom part is made much thinner than the periphery of the block. Moreover, surprisingly, this reduction in h3 is not detrimental to the overall mechanical behavior. This allows for a much lower thermal stress with respect to the prior art blocks with a flat bottom part as shown in FIG. 4. Thus, h3 can advantageously be set to a very low value without considering mechanical stress due to the clamping force. This low value is favorable for an efficient heat exchange between the top surface of the bowl part 3 and the layer of the horizontal channels 60a directly below, which are close to each other.

[0050] When compared to the prior art, there is an improved heat exchange between the top of the column, which is in contact with the hot process fluid, and the flow passages of the first layer, which are in contact with the cold service fluid. As a result, the central portion C of the bottom part 2 shown in Figure 3 has a lower temperature in use than the central portion C' of the prior art shown in Figure 4. The temperature gradient T P -T C Therefore, the gradient T of the prior art P’ -T C’ is significantly reduced relative to

[0051] As a result, the thermal stresses generated by this temperature gradient are much lower than in the prior art, which results in a much longer life span of both the block 1 and the heat exchanger according to the invention than in the prior art. This reduction in block breakage results in a reduction in the overall volume of impregnated graphite produced. Furthermore, less waste of such impregnated graphite is handled. These advantages are illustrated in the comparative examples at the end of this specification.

[0052] In summary, the present invention stands for removing graphite material in a target zone, which allows improving thermal performance by this local thinning while maintaining high mechanical performance. Thus, surprisingly, removing material is not detrimental to the overall mechanical behavior.

[0053] Returning to the graph of FIG. 6, a person skilled in the art would be in a position to select an appropriate value of the ratio h4 / h3 in order to obtain a significant reduction in the overall stress G and thus a substantial improvement in the overall behavior of the block and of the entire heat exchanger.

[0054] This improvement is due to the technical effect of temperature homogenization over the entire block, the degree of which increases with the value of the ratio h4 / h3 mentioned above. The ratio at which this technical effect becomes noticeable is called the threshold ratio. According to the general scope of the invention, this threshold ratio h4 / h3 is advantageously greater than 1.2, preferably greater than 2.

[0055] Moreover, the person skilled in the art will select this ratio so as to maintain the overall mechanical strength of the block and the heat exchanger. In this respect, said ratio h4 / h3 is advantageously less than 50, preferably less than 15.

[0056] With particular reference to FIG. 5, in an advantageous embodiment: h4 is greater than d60a, preferably greater than 2×d60a, where d60a is the diameter of the flow passage 60a. In this regard, h4 may be, for example, greater than 8 mm (millimeters). -h4 is smaller than 10 x d60a, preferably smaller than 5 x d60a. In this respect, h4 is, for example, smaller than 100 mm, in particular smaller than 50 mm. h3 is greater than t26, preferably greater than 2×t26, where −t26 is the material thickness between the channels 20, 60. In this figure 5, the walls of one channel 20 are shown diagrammatically by dashed lines. In this respect, h3 is, for example, greater than 1 mm. -h3 is smaller than 0.8 x h4, preferably smaller than 0.4 x h4. In this regard, h3 is, for example, smaller than 20 mm.

[0057] Returning to FIG. 5, reference is made to the angle a5 between the reference plane S5 of the portion 5 and the surface S3. Typically, said angle a5 is between 30° and 90°. In the example shown, said portion is rectilinear. However, said portion 5 may also be formed with a different shape, in particular stepped. In this case, the reference plane is a line passing through the bottom point and the top point of said portion 5.

[0058] The block 1 may be manufactured starting from a standard block according to the prior art, the opposing bottom parts of which are substantially flat. In this respect, a recess 22 is provided in one of these bottom parts. This step may generally be carried out by a machining process. Once said recess is provided, this results in the formation of both the central bowl part 3 and the transition part 5. Generally, no material is removed at the periphery of said standard block, at the level of the seat part 4. Such a manufacturing method is advantageous, since it makes it possible to retrofit a typical heat exchanger block.

[0059] Considering the use of the heat exchanger I described above, the process and service fluids enter in a known manner via the inlets 322, 336. The heat exchanger I is more particularly adapted for a so-called cooling operation corresponding to a substantially single-phase flow of the process fluid. In this respect, said process fluid may be liquid and, if gaseous, does not undergo any significant condensation.

[0060] In a typical manner, the inlet temperature of the process fluid is greater than 80° C. As will be explained in more detail below, the present invention also encompasses the possibility of deeper bowl sections than bowl section 3 of this embodiment. With this in mind, block 1 and heat exchanger I are provided specifically for processing process fluids having inlet temperatures below 200° C. In this temperature range, the particular shape of this first embodiment is advantageous with respect to prior art designs with regard to thermal considerations. Furthermore, the block is convenient to manufacture due to its relatively shallow bowl section.

[0061] The inlet temperature of the service fluid, on the other hand, is typically between -20°C and +35°C. When these two fluids enter the heat exchanger they are subjected to heat exchange in the usual way. The cooled process fluid leaves through outlet opening 312 at a typical temperature between -15°C and +60°C, whilst the warmed service fluid leaves through outlet pipe 337 at a typical temperature between -15°C and +45°C.

[0062] Figures 7, 8 and 10 show a heat exchanger II and a block 501 according to a second embodiment of the invention. In these figures, mechanical elements similar to those of the first embodiment are given the same reference numbers, increased by 500. Figure 7 shows an upstream block 501 according to the invention and an adjacent block 601 according to the prior art.

[0063] The heat exchanger block 501 of this second embodiment differs from the block 1 described above mainly in that it is provided with a deeper bowl section 503. In a more detailed aspect, for blocks of the same overall size, the upstream lateral channels 560a are located further below the lateral channels 60a. In other words, the blocks 501 are provided with fewer lateral channels relative to the blocks 1 in the upstream parts of these blocks. Schematic diagram 10 of the block 501 compared to FIG. 9 shows that the block 501 no longer includes the upper channels 60a, 60b of the block 1.

[0064] Returning to figure 8, reference is made to the wall 838 of the tube 837, which is in contact with the exhaust service fluid. This wall 838 is conventionally called the upper wall, since it is oriented towards the inlet of the process fluid. According to this second embodiment, the distance d561 between the upper wall 561 of the channel 560a and the above-mentioned upper wall 838 is advantageously smaller than 20 mm, in particular smaller than 10 mm.

[0065] The present invention includes the possibility of the top wall 561 being located below the top wall 838 of the tube. However, this closest possibility is less preferred since it adds more complexity to the manufacture and reduces the heat transfer area while providing no additional thermal benefits.

[0066] The values ​​of some other characteristic parameters of this second embodiment are similar to those of the first embodiment described above: in fact, h504 is similar to h4, h503 is similar to h3, the ratio h504 / 503 is similar to the ratio h4 / h3, and the angle a505 is similar to the angle a5.

[0067] This second embodiment, provided with a so-called deep bowl section 503, is more particularly adapted to cooling operation of heat exchangers with high process fluid inlet temperatures, typically higher than 200° C. The Applicant has discovered that for these process fluid inlet temperature values, a bowl section like bowl section 3 of the first embodiment does not ensure a completely satisfactory temperature homogenization.

[0068] The applicant has in particular found that the flow of the service fluid has particular characteristics in the most upstream part of the block 1. In the schematic diagram 9, apart from the line of the upstream flow passage 60a, other adjacent lines of flow passages are shown 60b-60d. In this case, the applicant recognizes that much less service fluid flows along these four lines of the upper flow passages 60a-60d of the block 1 according to the first embodiment, it being noted that the number of these lines may be different.

[0069] These upper lines of channels 60a-60d therefore form a so-called dead zone, referenced DZ in Fig. 9, in which, as explained above, little service fluid flows and, moreover, at a very low speed. The discovery of this phenomenon led the Applicant to the conclusion that the risk of graphite breakage in the most upstream part of the block 1 is particularly high. Indeed, in this zone, considerable vaporization is likely to occur, constituting the main graphite breakage risk.

[0070] As a result, the excavation of a deeper bowl 503 allows for an improved technical effect of temperature homogenization while reducing the dead zone phenomenon explained above. In this respect, the particular advantages associated with the block 501 provided with a deeper bowl according to this second embodiment are illustrated by the comparative examples given at the end of this specification.

[0071] It should also be noted that even though the manufacturing process of block 501 is less convenient than that of block 1, block 501 is still satisfactory in terms of mechanical strength.

[0072] Fig. 11 shows another variant of the invention that can be added to block 1 or block 501. According to this variant, the upstream bottom part 2 / 502 of block 1 / 501 is provided with the bowl part 3 / 503 described above, while the downstream bottom part 6 / 506 of the block is provided with a chamber 903 according to the general prior art described in US Patent Application Publication No. 3391016, US Patent Application Publication No. 2821369 and GB Patent Application Publication No. 1078868. This chamber ensures only the function of fluid distribution between block 1 / 501 and the adjacent block (not shown) and has a depth D903 that is significantly smaller than the bowl part D3 / D503. Typically, the ratio of D3 / D503 to D903 is greater than 1.3.

[0073] The two above-mentioned embodiments of the invention, provided for cooling operation, refer to a heat exchanger I / II provided with one block 1 / 501 according to the invention. Said block, provided upstream with respect to the flow of the process fluid, is provided with one bowl section 3 / 503 oriented towards the process fluid inlet. Indeed, during such cooling, the graphite temperature tends to decrease substantially linearly from the upper surface S3 or S503 of the block towards the process fluid outlet. As a result, the need for temperature homogenization is especially required in the upstream part of the upstream block, which explains the provision of this single bowl section.

[0074] Alternatively, the heat exchanger may be provided with a so-called neutral block on the upstream side. This neutral block, as it is known, does not ensure the heat exchange function, but an auxiliary function such as fluid distribution. In this respect, a single block according to the invention is located upstream, next to said neutral block.

[0075] Figure 12 shows a heat exchanger III according to a third embodiment of the invention, in which mechanical elements similar to those of the first embodiment are given the same reference numbers increased by 1000.

[0076] This third embodiment of the heat exchanger III differs from the above described heat exchangers I and II mainly in that it is provided with blocks 1001, 2001, 3001 essentially according to the invention, each of which is further provided with two temperature homogenizing bowls located respectively in its respective bottom part.

[0077] In a more detailed embodiment, upstream block 1001 is provided with upstream bowl portion 1003 on upstream bottom surface portion 1002, and downstream bowl portion 1103 on downstream bottom surface portion 1006. Further, intermediate block 2001 is provided with upstream bowl portion 2003 on upstream bottom surface portion 2002, and downstream bowl portion 2103 on downstream bottom surface portion 2006. Finally, downstream block 3001 is provided with upstream bowl portion 3003 on upstream bottom surface portion 3002, and downstream bowl portion 3103 on downstream bottom surface portion 3006.

[0078] In a typical embodiment, the bowl sections 1003, 1103, 2003, 2103, 3003, 3103 described above have the same depth, which advantageously corresponds to the depth of the bowl section 3 of the first embodiment. In particular, it is less preferred to provide a deeper bowl section such as the bowl section 503 of the second embodiment. It should be noted that while Figure 12 shows three heat exchange blocks stacked one on top of the other, this number may be different.

[0079] The heat exchanger III of this embodiment is particularly adapted for condensing operation corresponding to a two-phase flow of a process fluid. In this respect, said process fluid is a gas subjected to full or partial condensation. By way of example, the inlet temperature of the process fluid is between +80°C and +300°C, while its outlet temperature is between -15°C and +60°C. Furthermore, the inlet temperature of the service fluid is between -20°C and +35°C, while its outlet temperature is between -15°C and +45°C.

[0080] With reference to FIG. 13, during condensation the evolution of the graphite temperature across the heat exchanger I is much different than during cooling operation. FIG. 13 summarises two curves C, C' which show this graphite temperature GT along the main dimension Zexch of the heat exchanger. In a first zone Z1, Z'1 close to the inlet, the temperature slowly decreases as during cooling operation, but when condensation occurs it increases significantly, this corresponds to zone Z2, Z'2. Finally, the temperature returns to a gradual decrease in zone Z3, Z'3 close to the outlet.

[0081] Moreover, the location of zones Z2, Z'2 may vary from one heat exchanger to another, depending on several parameters such as the type of fluid as well as the operating conditions. In this regard, the solid curve in Fig. 13 shows zone Z2 close to the process fluid inlet, while in this same Fig. 13, the dashed curve shows zone Z'2, which is near the process fluid outlet.

[0082] As a result, the need for temperature homogenization in the condensation case is required throughout the heat exchanger and not just in the upstream portion as in cooling operation. This realization by the applicant explains the advantage of providing a bowl section at the bottom of each of these blocks, rather than just at every block.

[0083] Figure 14 shows the modelling of the technical effect brought about by the invention during condensation. The solid curve shows the variation of the graphite temperature GT along the main dimension Zexch of the heat exchanger for a prior art heat exchanger without a bowl section, while the dashed curve shows the same temperature variation at the same spot of the heat exchanger for a heat exchanger III with multiple bowl sections.

[0084] It should be noted that gas condensation causes a significant temperature rise DT, which in the prior art would likely damage or at least weaken the graphite, whereas with the present invention there is almost no temperature rise in zone dt, which is favorable for the mechanical integrity of the heat exchanger. Moreover, the two curves above are intermixed in the most upstream and downstream parts of the heat exchanger.

[0085] In the embodiment of FIG. 12, all blocks are provided with opposing bowl sections. In theory, the invention may also include a variant in which at least one block is provided with one bowl section or no bowl sections at all. This variant may be suitable in certain cases where the location of condensation can be precisely identified. However, such a variant is much less preferred, since it does not ensure temperature homogenization in the various zones of the heat exchanger.

[0086] Finally, in the three main embodiments of the invention, the heat exchanger extends vertically with an upper inlet for the process fluid and a lower outlet for said process fluid. Alternatively, said process fluid may flow from bottom to top. As yet another variation, the heat exchanger may extend horizontally or in an oblique configuration.

[0087] In summary, the invention is based on the identification of the bowl section's function, which allows homogenizing the graphite temperature over at least a portion of the heat exchanger. Furthermore, depending on the different applications, several embodiments, as detailed above, may be considered. During cooling, one bowl section is preferred, especially a deeper bowl section when the inlet temperature of the process fluid is high. During condensation, multiple bowl sections are preferred in each bottom section of each block.

[0088] It should be noted that the bowl provided in the bottom part of the block according to the invention is different from the chambers provided in the blocks disclosed in the above mentioned US Pat. No. 3,391,016, US Pat. No. 2,821,369 and GB Pat. No. 1,078,868. Indeed, in these prior art arrangements, said chambers ensure only the function of fluid distribution between two adjacent blocks. On the other hand, these chambers, due to their very shallow depth, are not adapted to perform the prominent function of temperature homogenization. In any case, these documents do not concern this homogenization function.

[0089] Comparative Example The following examples illustrate the benefits and technical effects provided by features according to two main embodiments of the present invention.

[0090] First, a prior art heat exchange block 401 is provided. With reference to FIG. 4, the characteristics and dimensions of this block are as follows: -Overall height: 482mm - Overall diameter: 602mm - Number of process channels: 295 -Diameter of each process channel: 16mm -Number of service channels: 464 -Diameter of each service channel: 10mm -Distance h460:5mm -Distance h402:26mm

[0091] To form a heat exchanger, ten blocks according to the prior art were housed one above the other in a housing similar to that of FIG.

[0092] Secondly, a block 1 according to the first embodiment of the present invention is provided. This block 1 differs from the block 401 according to the prior art, essentially as follows. - distance h4 (see figure 5) is 24.4 mm. - distance h3 (see also figure 5) is 5mm.

[0093] This block 1 was housed in an enclosure along with other prior art blocks similar to block 401.

[0094] Thirdly, a block 501 according to a second embodiment of the present invention is provided. This block 501 is different from the block 1 according to the first embodiment of the present invention, and is essentially as follows. - Distance h504 (see Figure 8) is 54.4 mm. The distance h503 (see FIG. 8) is 5 mm. There are fewer lateral service channels 560. In fact, in this block 501, the two upper lateral channels 60a-60b of the block 1 are not provided.

[0095] This block 501 was housed in an enclosure along with other prior art blocks similar to block 401 .

[0096] Three heat exchangers IV, I, II, each equipped with the above-mentioned blocks 401, 1, 501 as upstream blocks, were subjected to the same mounting method. For each heat exchanger, gaseous chloric acid HCl was fed to the process flow path with a flow rate of 3142.8 kg / h, at a temperature of 1335° C. and at a pressure of 3.20 barg. At the same time, a service fluid, typically water, was fed to the service flow path 460 with a flow rate of 87000 kg / h, at a temperature of 63.6° C. and at a pressure of 4.25 barg.

[0097] During these implementations, for each heat exchanger, several parameters were measured and are summarized in the following table: -T1max is the maximum temperature of the water entering the fluid flow path. With reference to Figure 8, the location of T1max corresponds to the top end of flow path 560a, close to wall 561. -T2max is the maximum temperature of the graphite skin of the heat exchanger. Referring to FIG. 8, the location of T2max corresponds to the graphite wall 561. - T3max is the maximum temperature of the graphite skin of the heat exchanger. Referring to Figure 8, the location of T3max corresponds to the graphite surface S503.

[0098] JPEG2024523028000002.jpg32156

[0099] As shown by the different simulation values, the invention allows to substantially reduce the temperatures of different characteristics of the implementation with respect to the prior art, in particular the heat exchanger II and block 501 according to the second embodiment of the invention provide a further reduction of these temperatures with respect to the heat exchanger I and block 1 according to the first embodiment.

[0100] This comparative example clearly shows the advantages of the present invention with regard to thermal issues. Moreover, as explained above, this thermal technical effect does not result in a significant mechanical weakening of the heat exchanger according to the invention.

Claims

1. A heat exchange block (1; 501; 1001, 2001, 3001), comprising: A main body (10), particularly made of graphite, and particularly having a cylindrical shape with a circular cross-section; A first so-called longitudinal flow path (20) formed in the main body along the longitudinal direction (L1) of the block, each longitudinal flow path continuously extending between two opposing bottom surfaces (2, 6; 502, 506; 1002, 1006, 2002, 2006, 3002, 3006) of the main body and opening at the bottom surfaces, and the longitudinal flow path being intended for the flow of a first so-called process fluid; A second so-called transverse flow path (60; 560) formed in the main body along the transverse direction, each transverse flow path continuously extending between two opposing transverse surfaces (7, 8) of the main body and opening at the transverse surfaces, and the transverse flow path being intended for the flow of a second so-called service fluid; At least one bottom surface (2; 502; 1002, 1006, 2002, 2006, 3002, 3006) defines: A central so-called homogenization bowl portion (3; 503; 1003, 1103, 2003, 2103, 3003, 3103) intended to homogenize the temperature of the constituent material of the block, defining a so-called central reference plane (S3; S503); A peripheral seat portion (4; 504) defining a so-called peripheral reference plane (S4; S504), protruding upstream of the central bowl portion along the longitudinal direction and adapted to receive sealing means; A transition portion (5; 505) extending between the peripheral seat portion and the central bowl portion; A so-called peripheral distance (h4; h504) between the so-called opposing wall (61; 561) of the closest transverse flow path (60a; 560a) and the peripheral surface (S4; S504), being substantially larger than the so-called central distance (h3; h503) between the wall (61; 561) of the closest transverse flow path (60a) and the central surface (S3; S503), and the distances (h3; h503) and (h4; h504) being considered along the longitudinal direction of the block; A heat exchange block, characterized in that a recess (22; 522) is provided in the bottom surface so as to partition the above.

2. The heat exchange block according to claim 1, wherein: The ratio (h4 / h3) of the outer peripheral portion distance to the central portion distance is greater than 1.2, preferably greater than 2, in the heat exchange block.

3. In the heat exchange block according to claim 1, When d60a is the diameter of the closest cross-flow path (60a), the outer peripheral portion distance (h4) is greater than d60a, particularly greater than 2 × d60a, in the heat exchange block.

4. In the heat exchange block according to claim 1, When t26 is the minimum material thickness between the longitudinal flow path (20) and the cross-flow path (60), the central portion distance (h3) is greater than t26, preferably greater than 2 × t26, in the heat exchange block.

5. In the heat exchange block according to claim 1, The so-called transition angle (a5) between the reference plane (S5) of the transition portion and the reference plane (S3) of the bowl portion is between 30° and 90°, in the heat exchange block.

6. In the heat exchange block according to claim 1, The bowl portion (3; 503) is provided only on the upstream bottom surface portion (2; 502) of the bottom surface portion, while the opposing downstream bottom surface portion (6; 506) is substantially flat or a fluid distribution chamber is provided on the downstream bottom surface portion, The depth (D903) of the chamber is sufficiently smaller than the depth (D3 / D503) of the bowl portion, in the heat exchange block.

7. In the heat exchange block according to claim 1, The bowl portions (1003, 1103, 2003, 2103, 3003, 3103) are provided on both the upstream bottom surface portion and the downstream bottom surface portion, respectively, in the heat exchange block.

8. In the method for manufacturing the heat exchanger block according to claim 1, A step of providing a preform, particularly a standard heat exchanger block, wherein the preform has a preform body and openings at both bottom surface portions that are substantially flat on both opposing sides of the preform, and a first so-called longitudinal flow path formed in the preform body along the longitudinal direction of the preform, and a second so-called cross-flow path formed in the preform body along the transverse direction and opening at two opposing transverse surface portions of the preform. A method for forming the bowl portion (3) and the transition portion (5), particularly including the step of removing the material of the preform by machining or a similar process.

9. A heat exchanger (I; II; III), comprising a housing having a lower cover (310; 1310), an upper cover (320; 1320) and an outer peripheral casing (330; 1330), and at least one heat exchange block (1, 101, 201; 501; 1001, 2001, 3001) disposed between the lower cover and the upper cover, each said block comprising a main body, a first so-called longitudinal flow path formed in the main body along the longitudinal direction of the block, opening at two opposing bottom surfaces of the main body, and the longitudinal flow path being intended for the flow of a first so-called process fluid, the first so-called longitudinal flow path, a second so-called transverse flow path formed in the main body along the transverse direction, opening at two opposing transverse surfaces of the main body, and the transverse flow path being intended for the flow of a second so-called service fluid, the second so-called transverse flow path, the heat exchanger further comprising first inlet means (322; 1332) for the first fluid into the first flow path, second inlet means (336; 1336) for the second fluid into the second flow path, first outlet means (312; 1312) for the first fluid from the first flow path, and second outlet means (337; 837; 1337) for the second fluid from the second flow path, characterized in that at least one heat exchange block (1; 501; 1001, 2001, 3001) is a heat exchanger block according to any one of claims 1 to 7.

10. In the heat exchanger according to claim 9, comprising one heat exchange block (1; 501) according to claim 6, said one block being a so-called upstream block located closest to the first inlet means (322), and said one block (1; 501) being provided with one bowl portion (3; 503) located on a so-called upstream bottom surface (2; 502) directed towards the first inlet means.

11. In the heat exchanger according to claim 10, The distance (d561) between the opposing wall (561) of the nearest transverse flow path (560a), which is considered to be along the vertical direction of the block, and the upper wall (838) of the second outflow means (837) of the second fluid is less than 20 mm, particularly less than 10 mm. The wall (561) of the nearest transverse flow path (560a) is preferably closest to the first inflow means than the upper wall (838), a heat exchanger characterized thereby. **Claim 12** In the heat exchanger according to claim 9, A heat exchanger in which some, preferably all, of the heat exchange blocks are the heat exchange blocks (1001, 2001, 3001) according to claim 7. **Claim 13** A method of implementing the heat exchanger according to claim 11, The first and second fluids are circulated in the first and second flow paths to enable heat exchange therebetween, When the first fluid is a gas, it flows through the heat exchanger in a single-phase state without significant condensation, A method in which the first fluid flows into the first inflow means at a temperature particularly higher than 80°C, while the second fluid flows into the second inflow means at a temperature particularly between -20°C and +35°C. **Claim 14** In the method of implementing a heat exchanger according to claim 13, A method in which the first fluid flows into the first inflow means at a temperature higher than 200°C. **Claim 15** A method of implementing the heat exchanger according to claim 12, The first and second fluids are circulated in the first and second flow paths to enable heat exchange therebetween, The first fluid is exposed to condensation through the heat exchanger, the inlet temperature of the first fluid being particularly between +80°C and +300°C, while the outlet temperature of the first fluid is particularly between -15°C and +60°C, The inlet temperature of the second fluid is particularly between -20°C and +35°C, while the outlet temperature of the second fluid is particularly between -15°C and +45°C.

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