MXPA06009962A - Plate-type heat-exchanger - Google Patents

Abstract

A plate-shaped heat exchanger (20, 120) for a heat exchange unit (40) of a chemical reactor (60), that advantageously presents a thermal insulation obtained in an unusually simple and reliable manner, has a substantially flattened box-like structure (22), with a substantially parallelepiped, rectangular configuration, defining an internal chamber (24), and comprises an inlet connection (28) and an outlet connection (29) of a heat exchange operating fluid into and from said chamber (24), and a distributor pipe (10, 110) of said operating fluid inside saidchamber (24), extended in said structure (22) at a long side (22a) of it, said distributor pipe (10, 110) comprising a first tube (30, 130) and a second tube (32, 132), positioned one inside the other, between said tubes, respectively external tube (30) and internal tube (32, 132), an interspace (30a) being defined in fluid communication, on one side, with said chamber (24) through a plurality of openings (26) provided in the external tube (30, 130) of said distributor pipe (10, 110), and, on the other side, with the internal tube (32, 132) of the same distributor pipe (10, 110), said internal tube (32, 132) being hydraulically connected to said inlet connection (28) for the heat exchange operating fluid.

Description

HEAT EXCHANGER OF TYPE OF PLATES DESCRIPTION Field of the invention The present invention, in its most general aspect, refers to a heat exchanger for a heat exchange unit of a chemical reactor.

In particular, the invention relates to a heat exchanger in the form of plates having substantially a flattened box-like structure, with a substantially parallelepiped and rectangular configuration, defining an internal chamber and comprising an inlet connection and an outlet connection for a fluid operative of heat exchange in and from said chamber and a distributor conduit of said fluid operating in said chamber, extended in said structure on a long side thereof.

The invention also relates to a heat exchange unit comprising a plurality of heat exchangers in the form of plates of the type mentioned above.

State of the art It is known that to obtain an optimal conclusion of endothermic or exothermic chemical reactions, such as, for example, synthesis reactions of ammonia, methanol, formaldehyde or, respectively, styrene, the heat must be removed, or respectively supplied to a reaction environment , generally to a catalytic bed, in order to control the temperature in a restricted range around a previously calculated theoretical value.

It is also known, that for this purpose, a heat exchange unit is used, comprising a plurality of heat exchangers in the form of plates, said unit being disposed in said catalytic bed; the heat exchangers in the form of plates are internally crossed by an operating heat exchange fluid for example in a radial or axial direction.

The operating heat exchange fluid, incoming from an input connection, feeds a distributor conduit; The operating fluid is then collected by a collecting duct, which ends in an outlet connection.

It is also known that for a good operation of the heat exchange unit it is preferred that the abovementioned distributor and collector ducts are thermally insulated, in order to prevent the so-called parasitic heat exchange between the heat exchange operating fluid that crosses the ducts above and the reactive fluid outside the heat exchangers in the form of plates.

Such a parasitic heat exchange causes, for example in an exothermic reaction, unwanted heating of the heat exchange operating fluid flowing through the distributor conduit, creating a non-uniform temperature profile along the total length of the sides lengths of the heat exchanger in the form of plates, whose length can sometimes be considerable, and consequently create a non-uniform temperature profile in the catalytic bed. In other words, the parasitic heat exchange influences the heat exchange operating fluid that enters the heat exchanger in the form of plates so that the fluid has different temperatures at different heights of the heat exchanger in the form of plates, of this way worsening the efficiency in the reaction.

In addition, as regards the parasitic heat exchange, the influence of fluid speed must also be considered. In the case of an exothermic reaction, the operating fluid of heat exchange in the distributor conduit is heated by the outer fluid of the exchanger in the form of plates as it proceeds progressively. This effect is stronger the further away the inlet connection of the distributor conduit or the outlet connection of the collector conduit is left, due to the reduction in fluid velocity of the fluid crossing the conduit in question.

Therefore, due to said reduction in the speed of fluid flowing inside the distributor and collector ducts, a non-uniform heat exchange occurs in the areas of the catalytic beds surrounding these tubes, avoiding the desired temperature control in these areas.

In the state of the art, in order to achieve this thermal insulation, it has been proposed to cover the collector and distributor conduits with a layer of a cover of low thermal conductivity. Generally ceramic coatings are used, with a base of substances such as zirconium, yttrium, alumina, cerium, magnesium oxides and their mixtures.

The heat exchangers in the form of plates of a heat exchange unit of a chemical reactor made in accordance with the aforementioned schematic description provide excellent thermal insulation which perfectly solves the purpose. On the other hand, in many cases, it has also proved to be too perfect against the operational needs for a correct operation of the heat exchanger.

SUMMARY OF THE INVENTION The underlying problem of the present invention is to provide a heat exchanger in the form of plates for a heat exchange unit of a chemical reactor capable of satisfying the aforementioned requirement, while at the same time simplifying the way of doing things and mentioned drawbacks described in relation to the state of the art.

This problem is solved, in accordance with the present invention, by a heat exchanger of the aforementioned type, and characterized in that said distributor conduit comprises a first and second tube, positioned one inside the other, an interspace between said tubes is defined, external and internal respectively, in fluid communication, on one side, with said chamber through a plurality of openings provided in the external conduit of said distributor conduit, on the other side, with the inner tube of the same distributor conduit, said inner tube being hydraulically connected to said inlet connection for the heat exchange operating fluid.

Further features and additional advantages of the heat exchanger in the form of plates for a heat exchange unit of a chemical reactor in accordance with the present invention will be clear from the description of one embodiment thereof, written below with reference to the drawings. attachments, given as indicative but not limiting examples.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 schematically represents a longitudinal sectional view of a chemical reactor equipped with a heat exchange unit, comprising heat exchangers in the form of plates in accordance with the present invention.

Fig. 2 schematically represents an enlarged perspective view of a heat exchanger in the form of plates of the heat exchange unit of Fig. 1.

Fig. 3 schematically represents a sectional view from above of a detail of Fig. 2.

Fig. 4 schematically represents a sectional view from above of an element from which it is possible to obtain a component of a variant embodiment of a heat exchanger in the form of plates according to the invention.

FIG. 5 schematically represents a sectional view from above of a component of the heat exchanger in the form of plates obtained from the element of FIG. 4.

Fig. 6 schematically represents a sectional view from above of a distributor conduit included in the variant mode of the heat exchanger, the component of Fig. 5 is used in said distributor conduit, shown during the assembly stage.

FIG. 7 schematically represents a sectional view from above of the distributor conduit of FIG. 6, in a working position.

DETAILED DESCRIPTION OF A MODALITY OF THE INVENTION With reference to the figures, a heat exchanger in the form of plates, according to the present invention and globally indicated with the number 20, for a heat exchange unit 40 of a chemical reactor 60 is shown.

The chemical reactor 60 comprises a cylindrical shell 62, closed at its opposite ends with their respective bottoms, lower 63 and upper 64. Within the shell 62 a reaction environment 69 is provided comprising an annular catalytic bed 50, known per se, open at the top, and with the side walls having holes for a reactive fluid to cross the same, in a radial or axial-radial direction.

In the reaction environment 69, and more precisely within the catalytic bed 50, the heat exchange unit 40 is held, in a conventional manner per se, intended to be immersed in a mass of an appropriate catalyst, not shown in the drawing. . Said heat exchange unit 40 has a substantially cylindrical configuration and comprises a plurality of heat exchangers in the form of plates 20, placed side by side next to each other in a radial arrangement.

Each heat exchanger in the form of plates 20 comprises a flattened box-shaped element 22, with a rectangular parallelepiped configuration, defining an internal chamber 24, and comprises an inlet connection 28 and an outlet connection 29 for an exchange operating fluid of heat, in and from said chamber 24.

A distributor duct 10 and a conductive duct 11 are provided on the long sides 22a and 22b of said element 22, in fluid communication, from one side with said chamber 24a through respectively, a plurality of inlet 26 and outlet 27 openings and , on the other side, with the outside of the heat exchanger in the form of plates 20 through, respectively, said inlet 28 and outlet 29 connections.

It should be highlighted, that as an alternative, only one of the two conduits mentioned above distributor and collectors can be provided.

The short sides of the element 22 are indicated with 22c and 22d. More particularly, each heat exchanger in the form of plates 20 is preferably constituted by a pair of metal plates 20a and 20b in juxtaposition, reciprocally joined, in a pre-established separate relationship, by means of perimetric welding 20c, so that said chamber is defined among them.

The inlet connections 28 and outlet 29 of said heat exchange operant fluid are in turn connected to the openings 66 and 67, respectively, provided in the bottom 64 of the reactor 60.

In accordance with an aspect of the present invention, said distributor conduit 10 and said collector conduit 11 each comprise a first tube 30, 31 and a second tube 32, 33 one being positioned within the other. In particular, the distributor conduit 10 and the collector conduit 11 comprise an outer tube, 30 and 31 respectively, in fluid communication with said chamber 24 through said plurality of inlet openings 26 and respective outlet openings 27, and an inner tube. 32 and 33, respectively.

The inner tube, 32 and 33, is positioned inside said outer tube 30 and 31, respectively, so as to define an interspace therewith (the interspace between the inner tube 32 and the outer tube 30 with the number 30a in the figures). The inner tube 32 and 33 is in fluid communication with the respective interspace through a plurality of additional openings 34 and 35 distributed in said inner tubes 32 and 33, respectively, and this is in fluid communication with the outside of the heat exchanger in plate shape 20 through said respective inlet connection 28 and outlet connection 29 for said heat exchange operating fluid.

Preferably the outer tubes 30 and 31 and the inner tubes 32 and 33 are substantially rectilinear.

In the example shown in Figure 3, the inner tube 32, for example with smooth walls, has a substantially oval section in the portion below the inlet connection 28, and is inserted into the outer tube 30, which has a shape generally substantially of mandrel, in other words, having a shape similar to that of the intersection of two circles with equal diameters and with a distance between the centers that is smaller than said diameter. For example, the internal oval duct 32 can be made by pressing a circular tube or using tubes with an ellipsoid section, available in the market. It should be noted that alternatively, as an internal conduit 32, a single circular sectional tube can also be used that one that is not oval.

The openings 34 provided in the inner tube 32 are generally circular and have such a diameter to ensure good distribution of heat exchange operating fluid. Advantageously, the diameter of the openings 34 can vary along the length of the inner tube 32, to balance the pressure loss of the fluid flowing in the inner tube 32.

The external dimensions of the inner tube 32 are slightly smaller than the space enclosed by the outer tube 30. In other words, the interspace 30a is formed between said mandrel-shaped outer tube 30 and said inner tube 32 of oval shape. More precisely, the inner tube 32 and the outer tube 30, substantially placed in a coaxial position, are constrained in the direction transverse to the axis.

The transverse tie is constituted by opposite depressions 36 on the inner surface of the outer tube 30, made, for example, by embossing the outer tube with a punch that is pushed from the outside towards the outer tube 30. The depressions 36 are preferably 4, for example, all at the same height of the outer tube 30, preferably in the four zones of minimum distance between the inner oval tube 32 and the mandrel-shaped external tube 30. It should be noted that this set of four depressions 36 are preferably repeated at different heights of the outer tube 30, for example in each meter of the outer tube 30. Alternatively, the depressions 36 are provided with different heights of the outer tube 30, appropriately staggered, in a substantially helical arrangement.

Naturally, advantageously, the structure of the collecting duct 11 is completely similar to the aforementioned structure, which is related to the distributor duct 10.

Figures 4, 5, 6, 7 show a heat exchanger in the form of plates 120, in accordance with a variant embodiment of the present invention, in particular with a collector conductor 110 of said heat exchanger in the form of plates 120 being represented.

It should be noted that in said variant, the elements that are structurally or functionally similar to those of the heat exchanger in the form of plates 20 are indicated with the same reference number and that the detailed description thereof is not repeated for a shorter brevity. .

The plate-shaped heat exchanger 120 comprises the distributor conduit 110 which includes an outer tube 130 in fluid communication with said chamber 24 through said plurality of inlet openings 26, and an inner tube 132 positioned within said outer tube 130. and in fluid communication with the outside of the heat exchanger in the form of plates 120 through said inlet connection 28 for said heat exchange working fluid, a plurality of generally circular openings 34 are distributed in said inner tube 132.

Also in this case, the inner tube 132 has substantially oval external dimensions and is inserted into the outer tube 30, having a substantially mandrel-shaped section.

However, in this variant the inner tube 132 is made starting from a circular tube, equipped with group of depressions 138 (figure 4), from which the set of ports is removed (figure 5), at least partially, on two sides opposite, for example by a filing step that creates two opposite flattened faces 132a and 132b.

In the rest of the description and the following claims, the term "group of ports" generally refers to a projection part projecting from the external surface of said circular tube along its perimeter, preferably said projection part is annular in shape. of disk.

The external dimensions of the inner tube 132 are slightly smaller than the space provided by the outer tube 130. In other words, an interspace 30a is formed between said mandrel-shaped tube 130 and said inner oval tube 132; more precisely, by positioning the internal oval tube 132 coaxial with the outer mandrel-shaped tube 30, the minimum distance between the inner tube 132 and the outer tube 130 is approximately a few millimeters.

The inner tube 132 and the outer tube are constricted in the direction transverse to the axis.

The transverse tie is constituted by a constricted union. More precisely, the inner tube 132 is inserted into the outer tube 130 with the two flat faces 132a and 132b positioned substantially parallel to the direction of the widest dimension of the mandrel of the outer tube 130 (FIG. 6), or in other words, parallel to the string defined by the two intersecting points of the two circumferential arcs that form the mandrel. After said insertion, the inner tube 132 is preferably rotated at an angle of about 90 ° (Fig. 7), until the opposite areas 132c and 132d of the inner tube that are still completely finned, is blocked against the inner walls of the inner tube. outer tube 130, preferably in a direction orthogonal to that of the aforesaid broader dimension of the mandrel.

Naturally, advantageously, a collector conduit structure that can be used in the heat exchanger 120 is completely similar to the structure mentioned, which refers to the distributor conduit 110.

The operation of the heat exchanger in the form of plates of a heat exchange unit of a chemical reactor, according to the present invention, is described below.

A reactive fluid enters the chemical reactor through an opening 70 in the upper bottom 64 and reaches the catalytic bed 50. Here the plurality of heat exchangers in the form of plates 20 provide or absorb heat respectively in accordance with endothermic or exothermic reactions, supporting the moving chemical reaction in the catalytic bed 50. The products of the reaction leave the reactor through an opening 71 in the bottom bottom 63.

Each heat exchanger in the form of plates 20 is provided with an operant heat exchange fluid from an opening 66, through the inlet connection 28 until it reaches the distributor conduit 10.

Said heat exchange working fluid, after having crossed the heat exchange chamber 24 internally, is collected by the collecting duct 11 and, through the outlet connection 29, reaches an exit opening 67 for the operating fluid of heat exchange.

The thermal insulation of the distributor conduit 10 and collector 11 of the heat exchanger in the form of plates of the invention is obtained due to the interspace formed between the inner tube (32,33) and the outer tube (30,31) of said collecting ducts and dealers.

As previously indicated, the inner tube is inserted into the outer tube and is constricted therein in the transverse position; The above is carried out above all to prevent damage caused by vibrations of the inner tube towards the internal walls of the external tube.

It is worth mentioning that the inner tube must freely enter the external tube, due to the fact that both elements are generally made of austenitic steel, if a certain separation is not available, it can easily happen that assurance occurs between the two tubes during the insertion of the internal tube inside. of the external tube.

It should also be emphasized that, by using tubes of elliptical cross-section as an inner tube, the mandrel shape of the outer tube is exploited in an optimal manner.

The main advantage achieved by the heat exchanger in the form of plates for a heat exchange unit of a chemical reactor, in accordance with the present invention, is the fact that thermal insulation is obtained in an unusually simple and reliable manner.

Another considerable advantage is the fact that the external surface of the outer tube of the collector and distributor conduits is completely used as a heat exchange area between the heat exchange operating fluid flowing in the plate-shaped heat exchanger and the catalyst reaction. In factby directing the openings equipped in the inner tube to the outer edge of the heat exchanger in the form of plates, the operating heat exchange fluid, to flow into said plate exchanger, must flow through the surrounding interspace the inner tube, in this way exchanging heat correctly with the reaction fluid outside the heat exchanger in the form of plates and at the same time protecting the operant heat exchange fluid inside the inner tube.

Obviously, to meet specific and incidental needs, a person with ordinary skill in the art can apply numerous variants and modifications to the heat exchanger in the form of plates described above, all of which, however, remain within the scope of protection of the present invention as defined in the following claims.

Claims (22)

1. A heat exchanger in the form of plates (20, 120) for a heat exchange unit (40) of a chemical reactor (60), having a substantially flat box-like structure (22), with a substantially parallelepiped rectangular configuration, defining an internal chamber (24), and comprising an inlet connection (28) and an outlet connection (29) for an operating fluid heat exchange in and from said chamber (24), and a distributor conduit (10,110) of said fluid operating in said chamber (24), extended in said structure (22) on a long side (22a) thereof, characterized in that said distributor conduit (10,110) comprises a first tube (30,130) and a second tube (32, 132). ), positioned one inside the other, external tube (30,130) and inner tube (32, 132) respectively between said tubes being defined an interspace, an interspace (30a) is provided in fluid communication, on one side, with said chamber (24). ) through a plurality of openings (26) provided in the external tube (30, 130) of said distributor conduit (10, 110), and, on the other side, with the internal tube (32,132) of the same distributor conduit (10, 110) , said inner tube (32, 132) being hydraulically connected to said inlet connection (28) for the operating heat exchange fluid.

2. A heat exchanger in the form of plates (20, 120) according to claim 1, characterized in that the interspace (30a) communicates with the inner tube (32, 132) of the distributor conduit (10, 110) through a plurality of additional openings (34) provided therein.

3. A heat exchanger in the form of plates (20, 120) according to claim 2, characterized in that said additional openings (34) provided in the inner tube (32, 132) are circular.

4. A heat exchanger in the form of plates (20, 120) according to claim 3, characterized in that the diameter of the additional openings (34) varies along the length of the inner tube (32, 132).

5. A heat exchanger in the form of plates (20, 120) according to claim 2, characterized in that said openings (26) and said additional openings (34) are distributed along the entire length of the respective external (30, 130) and internal (32, 132).

6. A heat exchanger in the form of plates (20, 120) according to claim 1, characterized in that said outer tube (30,130) and said inner tube (32, 132) are substantially rectilinear.

7. A heat exchanger in the form of plates (20, 120) according to claim 1, characterized in that said inner tube (32,132) has a substantially oval section.

8. A heat exchanger in the form of plates (20, 120) according to claim 1, characterized in that said external tube (30, 130) has a section substantially in the form of a mandrel.

9. A heat exchanger in the form of plates (20, 120) according to claim 1, characterized in that said inner tube (32, 132) has a circular section.

10. A heat exchanger in the form of plates (20, 120) according to claim 1, characterized in that it is equipped with a collecting duct (11) for the operating fluid, extended on the other long side (22b) of said structure ( 22) and comprising a first (31) and second (33) tube, positioned one inside the other, between said tubes, external (31) and internal (33) respectively, an interspace being defined in fluid communication, on one side, with said chamber 24 through a plurality of openings (27) provided in the external tube (31) of said collecting duct (11) and, on the other side, with the internal tube (33) of the same collecting duct (11), said inner tube (33) being hydraulically connected to said outlet outlet (29) of heat exchange operating fluid.

11. A method for carrying out a heat exchanger in the form of plates (20,120) according to claim 1, characterized in that said inner tube (32,132) and said external tube (30,130), substantially coaxially positioned, are reciprocally constrained in the direction transversal to the axis.

12. A method in accordance with the claim 11, characterized in that said inner tube (132) is made starting from a circular tube, equipped with a group of fins (138), said group of fins being removed, at least in part, on two opposite sides.

13. A method in accordance with the claim 12, characterized in that said removal of a portion of fins is performed by a filing step to create two opposite and parallel planar faces (132a, 132b).

14. A method in accordance with the claim 13, characterized in that said inner tube (132) is inserted into the outer tube (130), with the two flat faces (132a, 132b) positioned substantially parallel to the direction of the widest dimension of the mandrel of the outer tube ( 130), said inner tube (132) then being rotated at an angle of about 90 °, until the opposite sides (132c, 132d) of the inner tube (132) that is still fully flapped, are locked against the inner walls of the inner tube (132). outer tube (30).

15. A heat exchanger in the form of plates (20) made in accordance with the method of claim 11, characterized in that said transverse tie is constituted by opposed depressions (36) of the internal surface of the outer tube (30).

16. A heat exchanger in the form of plates (20) according to claim 15, characterized in that said depressions (36) are four in number, all positioned at the same height of the external tube (30).

17. A heat exchanger in the form of plates (20) according to claim 16, characterized in that said set of four depressions (36) are repeated at different heights of the external tube.

18. A heat exchanger in the form of plates (20) according to claim 15, characterized in that said depressions (36) are arranged at different heights of the outer tube (30),. staggered appropriately in a substantially helical array.

19. A heat exchanger in the form of plates (120) made in accordance with the method of claim 12, characterized in that the transverse tie is constituted by a constrained connection.

20. A heat exchange unit (40) of a chemical reactor (60), characterized in that it comprises a plurality of heat exchangers in the form of plates (20, 120) according to claim 1.

21. A chemical reactor (60) of the type comprising a cylindrical shell (62) closed at its opposite ends with its respective bottoms, lower (63) and upper (64), inside the shell provides a reaction environment, comprising a bed catalytic (50) wherein a heat exchange unit is positioned, characterized in that in said heat exchange unit (40) comprises a plurality of heat exchangers in the form of plates (20, 120) in accordance with claim 1 .

22. A chemical reactor (60) according to claim 22, characterized in that said heat exchange unit (40) has a substantially cylindrical configuration and comprises a plurality of heat exchangers in the form of plates (20, 120) located side by side. side one next to another in a radial arrangement.