JP2584550B2 - Heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger, and more particularly to a shell and tube type heat exchanger using a so-called bayonet tube.

[0002]

2. Description of the Related Art A shell-and-tube heat exchanger using a bayonet-type tube as shown in FIG. Compared with the heat exchanger of the mold type, one end of the tube is not fixed, so that the generation of thermal stress is extremely small. However, the joint between the main tube plate at one end of the first shell surrounding the main space where heat is exchanged and the open end of the outer tube is most likely to fail due to the influence of heat and pressure. For the inspection and repair, it is necessary to remove the inner pipe from the intermediate space, but conventionally, the inner pipe was sufficiently pulled out over its entire length. However, this has a problem that a space corresponding to the entire length of the inner tube must be secured on the side of the second shell, and the time required for pulling out, (re) assembling, and the like cannot be ignored.

[0003] Further, the shell side of this type of heat exchanger is filled with a catalyst for reaction to form a catalyst bed, a first fluid is used as a reaction raw material, and a second fluid is used as a heat removal or heating medium. Often used as.

Conventionally, as a reactor, a general,
There are widely known ones in which a reaction stream flows in parallel to the axial direction of the reactor, and an axial reactor in which a catalyst bed is provided between the inner and outer double tubes. However, such an axial flow reactor has a problem that a high pressure loss is caused by a reaction flow flowing in parallel to the axial direction of the reactor.

In order to solve such a problem, the inventors of the present invention disclosed in Japanese Patent Application Laid-Open No. 55-149640 and the like a method in which a radial-flow reactant between a center and an outer periphery perpendicular to a reactor axis is parallel to the reactor axis. In view of the difficulty of countermeasures against tube thermal expansion by using a straight tube as a cooling tube in this type of reactor, a reactor that removes heat with a cooling tube has been proposed, for example, in JP-A-59-162942. A type of reactor in which cooling is performed by a bayonet tube with a radial flow is proposed. Although such a reactor has excellent performance, according to further studies by the present inventors, it becomes necessary to make the tube sheet extremely thick when the reactor is large. There is a problem that it is difficult to remove the catalyst from the part, and improvement thereof has been desired.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made based on the above-mentioned demand, and it is easy to secure the opening of an intermediate space of a heat exchanger using a bayonet tube. Is fixed from the upper side to the lower side, an opening for extracting the catalyst is provided in the center of the tube sheet, and the opening serves also as a reinforcing member for the tube sheet, so that the required wall thickness of the tube sheet is reduced. The present invention provides a reactor for an exothermic reaction in which an extension part in the intermediate drum can be easily removed and reassembled.

That is, according to the present invention, there is provided a cylindrical first shell having a main tube plate at one end, the main tube plate having a number of closed tubes, ie, outer tubes, projecting toward the other end in the shell. It has a sub tube plate outside the main tube plate and a body that closes the intermediate space between the two tube plates, and the sub tube plate projects from the sub tube plate into each outer tube, and is generally substantially coaxial with the corresponding outer tube. The secondary tubesheet has a number of tubes or inner tubes opening near the tip of the tube, and the secondary tubesheet also has a second shell closing the space opposite the intermediate space or internal tube space with the secondary tubesheet. An inlet for the first fluid and an outlet for the fluid from within the shell, a first opening communicating with the intermediate space and passing the second fluid, and a second fluid communicating with the inner tube space. A second opening through which the first opening, the intermediate space, the annular space between the outer tubes, the inner tube, the inner tube space, and the second opening are arranged in this order; The first fluid flowing through the first shell between the inlet and the outlet and the second fluid flowing between the first and second openings are indirectly heated via the outer tube. In the heat exchanger to be exchanged, most of the inner space of the inner tube in the intermediate space is made detachable, or the inner tube is made freely attachable and detachable to and from the sub tube plate. The inner tube can be pushed into the outer tube by the length that the inner tube protrudes into the intermediate space and fixed to the main tube plate (or outer tube), so that the inner tube does not need to be pulled out from the outer tube over the entire length. Is a heat exchanger capable of removing most of the portion in the intermediate space, in particular, the first shell is filled with a catalyst for an exothermic reaction, and a first fluid as a raw material for the reaction is charged into the first shell, and the charged catalyst is filled in the first shell. The exothermic reaction is caused to flow in the order of the catalyst layer and the outlet formed by the above, and a second fluid serving as a cooling medium flows between the first and second openings. The heat exchanger for removing the reaction heat of the reaction, the heat exchanger having means for flowing the first fluid in the first shell in a radial direction substantially perpendicular to the axis of the first shell; The heat exchanger, wherein the first shell is upright, and further, the first shell has the other end as a top,
Having a catalyst extraction opening at the center of the main tube plate, this opening communicates with the extraction opening at the center of the second shell by an extraction tube, and supports the lower end of the catalyst layer so as to be positioned higher toward the outer periphery thereof; The above heat exchanger having a downwardly projecting catalyst guide bottom penetrated by a lower portion of the outer tube and having an extraction opening at the lowermost portion.

Hereinafter, the case where the heat exchanger of the present invention is used as a reactor for exothermic reaction will be mainly described with reference to the accompanying drawings.

FIG. 1 is a schematic longitudinal sectional view of a heat exchanger of the present invention used as a reactor for an exothermic reaction.

In the example shown in FIG. 1, the upper and lower ends of a heat exchanger serving as a reactor are closed, and a catalyst 12 is provided on a shell 10 having a cylindrical portion with a vertically long annular layer as will be understood later. Has formed.

The reaction gas which has entered the outer peripheral space of the guide cone 30 in the top space 15 from the gas inlet 14 enters the outer peripheral guide space 17 through the circumferentially arranged introduction pipes 16 and has a gas-permeable outer peripheral catalyst support as an inner wall thereof. Through the cylinder of the screen 18, the catalyst layer 12
Flows radially in the radial direction, reacts exothermically during this time, passes through the ventilation portion of the center pipe 20 supporting the inner catalyst, that is, the center pipe screen 22, enters the center pipe inner space 24, ascends and is taken out from the recovery port 26. . The gas flow may be reversed.

The bayonet tube 32 mainly includes an outer tube 34 and an inner tube 36 disposed coaxially inside the outer tube 34. The upper end of the outer tube 34 is closed, and the upper end of the inner tube 36 is opened therein.

The lower end of the outer tube 34 is joined to a main tube plate (tube plate for outer tube) 38. The main tube plate 38 has a catalyst extraction opening 39 at the center.
The opening 39 and the lower end of the outer peripheral screen 18 are connected by an inverted truncated cone side peripheral catalyst extraction guide bottom 40. Outer screen 18
The lower surface is a circular bottom between the lower end of the outer peripheral guide space 17 and the inner surface 9 of the shell.
Closed at 42.

A guide bottom 40 extends through the lower portion of the bayonet tube 32. 44 is the guide. A member 46 that supports the lower end of the center pipe is also connected to the guide bottom 40. The lower part of the member 46 is a plurality of legs arranged on the circumference, so that when the catalyst is extracted as described later, the guide bottom is formed by gravity.
The movement of the catalyst particles gathered at the extraction opening 39 is not hindered by 40.

The discharge opening 39 communicates with a discharge external opening 52 at the center of the bottom 50 of the reactor shell by a discharge pipe 48.

The heat exchanger, which is the reactor of this embodiment, is assumed to be used for methanol synthesis.
FW) from the inlet 54 to the inlet header space 56 between the vessel bottom 50 and the sub tube plate 58, the guide tube (inner tube extension member) 60, and the joining means 62 to be used in the present invention. Upward, and enters the outer tube at the upper end and turns downward to remove the heat of reaction from the catalyst layer 12 to become a steam / water mixture or steam, and the outlet header space or intermediate space 66 between the main tube plate 38 and the sub tube plate 58.
And is taken out from the steam exit 68.

Reference numeral 28 denotes a catalyst inlet and upper manhole, and reference numeral 70 denotes a lower manhole. Guide bottom 40, annular bottom 42 and main tube plate 38
Between them is a dummy space 71. The dummy space is a waste of space at first glance, but is effective for efficiently discharging the catalyst from the catalyst extraction opening 39. At first glance, the connection between the catalyst extraction opening 39 and the extraction external opening 52 by the extraction tube 48 is complicated, but it is sufficiently compensated by the reduction in thickness of the main tube plate described later.

That is, since the upper tube sheet supports the reaction pressure, if this support is not dispersed to the shell bottom 50 via the extraction pipe 48 as in the present invention, the reaction pressure is 90.0 kg / cm ² G・ Temperature: 330 ° C ・ Assuming a methanol yield of 2500t / day, use of expensive tube sheet
It requires a thickness of 50 mm and a thickness of about 560 mm, but in the present invention, it is possible to make the thickness about 300 mm with the same diameter. This thickness difference of about 260 mm corresponds to a weight of about 21.0 ton.

In the present invention, in order to inspect and repair the joint between the outer tube 34 and the tube sheet 38 where the trouble is most likely to occur, the inner tube 36 is used.
Since the operator can enter the exit header space 66 from the manhole 70 without pulling out the full length of the bottom and without removing the bottom 50 and the sub tube plate 58, the total length of the inner tube together with the bottom 50 and the tube plate 58 can be taken at once. This eliminates the great practical disadvantage of having to pull out with a great deal of trouble and to prepare a space for this under the reactor.

FIGS. 2 to 5 show the removal of the bayonet type cooling pipe from the space between the inner tube plate, ie, the space between the auxiliary tube plate and the outer tube plate, without removing the inner tube from the outer tube. Here is an example for making the structure possible.

In FIG. 2, the weld overlay 381 where the outer tube 34 is joined to the main tube plate 38 is a portion where trouble is likely to occur. The junction above it is made by a typical tube expansion.

The inner tube 36 is fixed to the outer tube via a stay 361 by welding or the like. The upper end of the guide tube 60 of the guide sleeve 601 is pressed against the upper end of the lower part of the inner tube 36 slightly protruding from the lower end of the outer tube via the gasket ring 603 to seal between the two tubes.

When removed, the guide tube 60 has a length that provides a space of a thickness that allows easy work by humans. The guide tube has a female screw that engages with a male thread portion near the lower end of the guide tube 60. These screws and tapered screws 611 having different pitches are joined to the sub tube plate 58 by bushings 609 which are engaged with the sub tube plate 58.

When the two pipes are joined, the screw is screwed into the tube sheet 58 when the bush 609 is turned, and at the same time, the inner pipe is screwed.
36 is cut to push up, and the reverse is turned
When turning 9 is complete, the guide tube 60 falls down. Guide tube 60
Does not fall below the tube sheet 58, but protrudes mostly downward to allow work in the space 66.

In the example shown in FIG. 3, no guide tube is used. When the reactor is used, the lower end screw portion 605 of the inner tube is screwed into a female screw hole cut in the sub tube plate 58, and the lock nut 613 secures the fixation and the seal. When performing inspection and repair, loosen the lock nut 613, remove it from the sub tube plate 58, lift it up, and use the upper side of the threaded portion 605 to cut into the portion 365 cut as a female screw at the lower end of the outer tube engaged with it. The space 66 is released by screwing.

In the example shown in FIG. 4, the inner tube is fixed to the outer tube as in FIG. 2, the seal joint between the guide tube 60 and the lower end of the inner tube is made the same, the joint with the sub tube plate 58 is made without a lock nut, This is only the engagement between the male screw portion 605 at the lower end of the tube and the female screw cut in the tube plate 58.

In the example shown in FIG. 5, the guide tube 60 is pushed up by a lock nut 582 which engages with the screw portion 605 to seal and join with the inner tube outside the figure as in the example of FIG. Sealing is performed with a tape gasket 581.

[0028]

As is apparent from the above description, the heat exchanger usable in the exothermic reaction reactor of the present invention has the following remarkable effects.

(1) The use of a bayonet tube eliminates the need for measures against thermal expansion of the tube, and in the case of use as a reactor, fixing the bayonet tube at the bottom of the vessel creates a free space at the top of the reactor, facilitating catalyst filling.

(2) By making the channel, that is, the inner tube inside the intermediate space removable, inspection and repair of the tube welded portion can be performed with the catalyst filled.

(3) By making the inner tube inside the channel removable, it is not necessary to secure a space for pulling out the entire inner tube bundle, which had to be considered in the past. Especially in the case of the vertical type, upward facing bayonet structure used in heat exchangers used in conventional axial flow reactors, the installation position of the main body was increased due to this removal allowance, and the cost of the frame etc. was considerable. Such a problem does not occur.

(4) In a preferred embodiment used as a reactor, the wall thickness of the tube sheet can be significantly reduced by using the opening for extracting the catalyst also as a reinforcing member for the tube sheet.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a heat exchanger of the present invention used as a reactor for an exothermic reaction.

FIG. 2 shows a structure for removing a bayonet-type cooling pipe from the space between the inner-tube tube plate, that is, the auxiliary tube plate and the outer-tube plate, without removing the inner tube from the outer tube. It is a figure showing an example.

FIG. 3 shows a structure for removing a bayonet-type cooling pipe from an inner pipe tube, that is, a space between a sub-tube sheet and an outer pipe sheet, without removing the inner pipe from the outer pipe. It is a diagram showing an example

FIG. 4 shows a structure for removing a bayonet type cooling pipe from an inner pipe tube, that is, a space between a sub pipe sheet and an outer pipe sheet, without removing the inner pipe from the outer pipe. It is a diagram showing an example

FIG. 5 is a view showing a structure for removing a bayonet-type cooling pipe from an inner pipe tube, that is, a space between a sub-tube sheet and an outer pipe sheet, without removing the inner pipe from the outer pipe. It is a diagram showing an example

FIG. 6 is a schematic longitudinal sectional view showing the concept of a shell and tube type heat exchanger using a bayonet type tube.

[Explanation of symbols]

 a first shell b main tube sheet c outer tube d sub tube sheet e body f inner tube g second shell h first fluid inlet i first fluid outlet j second fluid first opening k Second opening of second fluid x Intermediate space y Inner tube space z First shell

Claims (5)

(57) [Claims] 1. A cylindrical first shell having a main tube plate at one end, the main tube plate having a number of closed tubes, that is, outer tubes, projecting toward the other end in the shell, the outer tube being provided with a main tube plate. It has a sub tube sheet on the outside and a body that closes the intermediate space between the two tube sheets, and the sub tube sheet projects a number of tubes, i.e., inner tubes, projecting from the sub tube plate into each outer tube and opening near the tip of the outer tube. The secondary tube sheet also has a second space that closes the space opposite the intermediate space, that is, the internal tube space together with the secondary tube plate.
A first fluid inlet into the first shell and an outlet therefrom for the fluid, a first opening communicating with the intermediate space and passing the second fluid, and an inner tube. A second opening communicating with the space and allowing the passage of the second fluid, and thus the first opening;
Intermediate space, annular space between outer tubes, inner tube, inner tube space,
And the second opening communicate in this order, a first fluid flowing through the first shell between the inlet and the outlet, and a second fluid flowing between the first and second openings. In the heat exchanger in which heat is exchanged indirectly via the outer tube, the inner tube is made detachable with a large part of the inner space of the intermediate space, or the inner tube is made detachable with the sub tube plate. When the inner tube is removed from the sub tube plate , the inner tube is pushed into the outer tube by a length substantially protruding into the intermediate space, and the connecting portion provided on the inner tube and the main tube plate or
Is connected to the joint provided on the outer tube, and the inner tube is pushed into the outer tube.
A heat exchanger that can be fixed in the inserted state without removing the inner tube from the outer tube over its entire length and can remove most of the inner space of the inner tube. 2. A catalyst for an exothermic reaction is filled in a first shell, and a first fluid as a raw material for the reaction flows through an inlet, a catalyst layer formed by the filled catalyst, and an outlet in this order. The heat exchanger according to claim 1, wherein the reaction is performed, and a second fluid serving as a cooling medium is circulated between the first and second openings to remove reaction heat of the reaction. 3. The heat exchanger according to claim 1, further comprising means for flowing the first fluid in the first shell in a radial direction substantially perpendicular to the axis of the first shell. 4. The heat exchanger according to claim 1, wherein the first shell is upright. 5. The first shell has the other end as a top and has a catalyst extraction opening at the center of the main tube plate, and this opening communicates with the extraction opening at the center of the second shell by an extraction pipe. The catalyst guide according to any one of claims 1 to 4, wherein the lower end of the catalyst layer is supported by the lower portion of the outer tube, and the lower portion of the outer tube is supported by the lower portion of the catalyst layer. The heat exchanger according to claim 1.