CN114909928A

CN114909928A - Heat exchanger with double-end pull rod assembly

Info

Publication number: CN114909928A
Application number: CN202210593313.7A
Authority: CN
Inventors: 陈孙艺
Original assignee: Challenge Petrochemical Machinery Corp
Current assignee: Challenge Petrochemical Machinery Corp
Priority date: 2022-05-27
Filing date: 2022-05-27
Publication date: 2022-08-16
Also published as: WO2023226287A1

Abstract

The invention relates to the technical field of shell-and-tube heat exchangers, in particular to a heat exchanger with a double-head pull rod assembly, which comprises a shell, a tube bundle and a tube box, wherein the tube bundle comprises a left tube plate, a right tube plate, a plurality of inner plates (baffle plates or support plates) and a plurality of heat exchange tubes, the tube bundle also comprises a plurality of pull rods which are arranged in parallel with the heat exchange tubes, the same pull rod is divided into a left pull rod fixed on the left tube plate and a right pull rod fixed on the right tube plate, the left pull rod and the right pull rod are aligned one by one and tightened and fixedly connected, the inner plates are firmly positioned at fixed positions on the tube bundle, the integral strength and rigidity of the tube bundle are obviously improved, the impact of a flowing medium from left to right can be borne under the reinforcement of the left pull rod, and the impact of the flowing medium from right to left can be borne under the reinforcement of the right pull rod, compared with the traditional one-way pull rod tube bundle, the inner plates and the pull rods cannot vibrate and abrade the heat exchange tubes or bend unstably under the impact of the flowing medium in the reverse direction, the tube bundle has simple structure, high quality and long service life.

Description

Heat exchanger with double-end pull rod assembly

Technical Field

The invention relates to the technical field of shell-and-tube heat exchangers, in particular to a heat exchanger with a double-head pull rod assembly, which is specially used for heat exchange of petrochemical industry, coal chemical industry, chemical fertilizer industry, air-conditioning refrigeration and electric power facilities.

Background

In the prior art, a shell-and-tube heat exchanger is the most widely used heat exchanger, and is also called a shell-and-tube heat exchanger or a shell-and-tube condenser, and is widely applied to heat exchange and condensation processes of heat exchange of liquid-liquid, vapor-vapor and vapor-liquid in the fields of chemical industry, petroleum, medicine, food, light industry, metallurgy, coking and the like, and heat exchange and condensation processes of vapor condensation, liquid evaporation and heat transfer and the like.

A common structure of a shell-and-tube heat exchanger in the prior art is shown in fig. 1 and mainly comprises a tube bundle 1, a shell 2, a tube box 3 and other main components, wherein the tube bundle 1 is a core component of the shell-and-tube heat exchanger, the tube bundle 1 usually comprises heat exchange tubes 1-1, support plates (or baffle plates) 1-2, distance tube pull rod assemblies 1-3 and tube plates 1-4, rows of the heat exchange tubes 1-1 are supported by the support plates (or baffle plates) 1-2, and two ends of the heat exchange tubes penetrate into tube holes of the tube plates and are fixedly connected with the tube plates, so that the sealing performance and the strength of a joint are ensured, and two ends of the heat exchange tubes are communicated with the tube box.

As shown in fig. 1, only one end of the tube plate of the conventional tube bundle is fixed with a pull rod, and the other end of the tube plate is not fixed with a pull rod. As the name suggests, the pull rod only has the function of bearing axial tension, and when the pull rod is under the action of axial pressure, the slender round rod is easy to bend.

On the one hand, along with the development of social economy, the construction scale of petrochemical plants is getting bigger and bigger, national development committee specially issues a strict energy efficiency constraint promotion energy-saving and carbon reduction action scheme (2021) in key industries of petrochemical industry for the petrochemical field, atmospheric pressure reduction below 1000 ten thousand tons per year is strictly forbidden to be newly built, naphtha cracking below 80 ten thousand tons per year is used for preparing ethylene, and similar requirements are also provided for the lower limit of the capacity of other petrochemical plants. The structural size of the newly-built heat exchanger not only breaks through the limitation that the nominal diameter does not exceed 4000mm in the GB/T151-2014 heat exchanger standard, but also is integrated with a reactor to form an ethylene oxide reactor, a propylene oxide reactor and the like, and the treatment capacity is increased more and more. The processing capacity of an old heat exchanger of an old device is required to be operated in an overload mode sometimes, a heat exchanger tube bundle vibrates under the impact of a large-flow strong fluid medium in a shell pass, vibration impact not only produces noise to pollute the environment, but also abrades and destroys a heat exchange tube to cause internal leakage of equipment, so that the production and the quality of chemical products are influenced, and even the environment is polluted by outward leakage.

On the other hand, with the development of energy-saving and environment-friendly technology, the deep processing temperature of the petrochemical technology is higher and higher, the index of fully utilizing waste heat is stricter and stricter, and the thin tube plate is more and more common in lightweight design to replace a thick-wall large-forging-price tube plate, but the pressure bearing capacity of the thin tube plate is deficient, and the structure needs to be specially strengthened.

And the reverse flow of the petrochemical device raises new requirements on the intrinsic safety of the heat exchanger. First, in order to maintain heat exchanger operation effect, traditionally practice the annual shutdown and overhaul, clear away the impurity dirt of long-term deposit in the structure corner, now for reducing or avoid the economic loss who parks, explore and promoted a set of clean technique called flow backwash, equipment needn't tear out, original import, export function exchange, send into the washing liquid reverse circulation and circulate a plurality of times, just can erode most impurity dirt not hard up, take out of the equipment outside, respond well. Secondly, the original inlet can be changed into the outlet and the original outlet can be changed into the inlet by technical transformation of some devices and facilities, but the tube bundle in the shell is difficult to transform. Thirdly, when the outlet pipeline of the heat exchanger shell is not operated properly or is unexpected, the media flowing forwards originally meet a suddenly closed valve or a barrier to generate a water hammer flowing reversely, so that the tube bundle is impacted strongly, like the shaking of passengers caused by the braking of a high-speed highway, and in order to avoid damaging the tube bundle, a tube bundle safety belt is additionally arranged.

It is therefore of engineering interest to improve upon the problems of the prior art described above.

Disclosure of Invention

In view of the above technical problems in the prior art, the present invention provides a heat exchanger with a dual-head drawbar assembly.

In order to achieve the purpose, the invention provides the following technical scheme:

the heat exchanger with the double-head pull rod assembly comprises a shell, a tube bundle and tube boxes, wherein the tube bundle comprises a left tube plate, a right tube plate, a plurality of inner plates and a plurality of heat exchange tubes; the inner plates are one or both of the baffle plate and the support plate, and the inner plates are distributed along the length direction of the heat exchange tube; the method is characterized in that: the tube bundle further comprises a plurality of pull rods arranged in parallel with the heat exchange tubes, the same pull rod is divided into a left pull rod fixed on the left tube plate and a right pull rod fixed on the right tube plate, the left pull rod and the right pull rod are aligned one by one and are fixedly connected, and the inner plates are fixedly connected with the left pull rod or the right pull rod.

As a further specific scheme, a turn buckle is arranged between the left pull rod and the right pull rod, so that the left pull rod and the right pull rod are mutually pulled and tightened.

As a further specific scheme, a rigid block is welded between the left pull rod and the right pull rod, so that the left pull rod and the right pull rod are welded and tightened.

As a further specific scheme, the connection mode between the end part of the left pull rod and the shell side of the left tube plate and the connection mode between the end part of the right pull rod and the shell side of the right tube plate are as follows: threaded connections, welding or a combination of both.

As a further specific scheme, the number of the left pull rods and the right pull rods is multiple, the end parts of the left pull rods are distributed along a full circle area or a non-full circle area of the corresponding left tube plate, and the end parts of the right pull rods are distributed along a full circle area or a non-full circle area of the right tube plate.

As a further specific scheme, the pull rod is of a full-length whole-strip structure, or the pull rod is of a segmented combined structure.

As a further specific solution, the cross-sectional shape and size of the tie rods varies along the length direction and the cross-section of the tie rods increases toward the direction close to the left tube sheet/right tube sheet.

As a further specific scheme, the heat exchange tube is a straight tube bundle, and two ends of the heat exchange tube are respectively connected with tube boxes at two ends of a tube shell; or the heat exchange tube is a U-shaped tube bundle, and the heat exchange tube bypasses through the left tube plate and the right tube plate and is communicated with the same tube box, so that two straight tubes of the heat exchange tube are positioned in the same tube shell; or the heat exchange tube is a U-shaped tube bundle, and two sections of straight tubes of the heat exchange tube are positioned in different tube shells.

As a further specific scheme, the thicknesses of the left tube plate and the right tube plate are not equal.

As a further specific scheme, the pull rod sleeve is provided with a plurality of sections of distance pipes; or the pull rod is a rod body without a distance tube, a distance piece is arranged in the tube shell, the distance piece penetrates through the inner plates, and the two end parts of the distance piece are respectively connected with the left tube plate and the right tube plate.

The invention has the beneficial effects that:

compared with the traditional one-way draw bar tube bundle, the heat exchanger with the double-head draw bar assembly has the following advantages:

(1) the inner plate (baffle plate or support plate) has strong vibration resistance. The same baffle or support plate is simultaneously tensioned by the left tube sheet and the right tube sheet, and the inner plate is securely positioned in a position on the tube bundle.

(2) The tube bundle has high overall strength and rigidity. The tube plates at the two ends of the tube bundle are connected with pull rods, the inner plates are tensioned to the left by the pull rods connected with the tube plates at the left end, the inner plates are tensioned to the right by the pull rods connected with the tube plates at the right end, the left pull rods and the right pull rods are mutually tightened together to form an integral pull rod which is equivalent to a full length and is connected to the right tube plate from the left tube plate, but the integral pull rod is superior to the integral pull rod, the integral strength and rigidity of the tube bundle are obviously improved by the double-head tensioned inner plates, the tube bundle is in the loading, hoisting and unloading processes, and the original structural size precision can be better maintained in the assembling process of entering the shell or extracting and overhauling.

(3) The tube bundle has wide application range and is particularly suitable for thin tube plates.

First, the flow regime is suitable for media impingement. The left pull rod and the right pull rod can bear the impact of flowing media from left to right under the reinforcement of the left pull rod, and can also bear the impact of flowing media from right to left under the reinforcement of the right pull rod, and the inner plate and the pull rod cannot vibrate to wear the heat exchange tube or bend unstably under the impact of reverse flowing media.

And secondly, the heat exchanger is structurally suitable for heat exchanger structures such as a steam generator, a waste heat boiler, a cooler and the like with a large-diameter shell, a thin tube plate and an ultra-long heat exchange tube. The two-way pull rod assembly consisting of the left pull rod and the right pull rod is equivalent to the support of the heat exchange tube to the tube plate on the support of the tube plate, so that the diameter of an imaginary circle for calculating the thickness of the tube plate in the tube plate distribution area can be obviously reduced, and the thickness of the tube plate is reduced in the same proportion according to the reduction degree of the diameter of the imaginary circle.

And thirdly, the method is technically suitable for the occasions of large shell-side flow, unstable flow state and high elasticity of gas-liquid mixed two-phase flow or airflow.

(4) The tube bundle has a high-temperature self-tightening function. When the tube pass temperature of the tube bundle is higher than the shell pass temperature, the thermal elongation of the heat exchange tube is slightly longer than that of the pull rod made of the same steel, and the bidirectional pull rod is driven by the heat exchange tube to have the tendency of relative displacement towards the two ends of the tube bundle respectively, so that the effect of tensioning the baffle plate or the support plate is generated. Conversely, when the tube side temperature of the tube bundle is lower than the shell side temperature, the bidirectional pull rod has the effect of pushing the baffle plate or the support plate tightly.

(5) The tube bundle has high cost performance. The tube bundle can obtain good performance only by adding a plurality of pull rods which are common traditional parts, and has the characteristics of simple structure, high quality and long service life.

Two sections of double-end pull rod assemblies that connect together again of separating earlier, compare in whole pull rod of full length, the advantage lies in:

the inner plate can be tensioned, bidirectional tensioning can be realized, and the inner plate is fixed at the same position.

And the tie rod is divided into a left tie rod and a right tie rod which are connected together, and then the tie rod is equivalent to a tension brace in appendix L in GB/T150-2014 Heat exchanger standard, so that the tube plates at two ends can be connected in an enhanced manner, all parts of the tube bundle are fixed together to form a fastened whole, the structural strength and the rigidity are improved, and the tie rod is also suitable for the working condition of high shell pressure even if the tube plate with thin wall thickness.

And the two ends of the pull rod do not need to penetrate through the thickness of the tube plate, so that the overall strength of the tube plate is not damaged, and the tube plate is suitable for working conditions with high pressure.

And fourthly, when the tube bundle runs at high temperature of the shell, the internal parts have a thermal self-tightening effect, the sealing is reliable, and the tube bundle is suitable for a large-diameter petrochemical heat exchanger.

Drawings

Fig. 1 is a schematic structural diagram of a shell-and-tube heat exchanger in the prior art.

FIG. 2 is a first schematic view of a tube bundle of a heat exchanger having a tie rod assembly according to the present application.

FIG. 3 is a schematic view of a second configuration of a tube bundle of a heat exchanger having a tie rod assembly according to the present application.

Fig. 4 is a schematic view of a third configuration of a tube bundle of a heat exchanger having a tie rod assembly according to the present application.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and the accompanying drawings.

The heat exchanger with the double-head pull rod assembly comprises the following conventional structures: the tube bundle comprises a left tube plate, a right tube plate, a plurality of inner plates and a plurality of heat exchange tubes, the left tube plate and the right tube plate are fixed at two ends of the tube bundle and jointly enclose a shell pass, the left tube plate and the right tube plate are respectively fixed with different tube boxes and jointly enclose a tube pass, the plurality of heat exchange tubes are located in the shell pass in parallel and penetrate through the left tube plate and the right tube plate to be communicated with the tube pass, the heat exchange tubes are welded and fixed with the left tube plate and the right tube plate, and the inner plates are penetrated through the heat exchange tubes in a clearance fit mode. The inner plates are one or both of the baffle plates and the support plates, the inner plates are distributed along the length direction of the heat exchange tube, and each inner plate is arranged along the radial direction of the tube shell or is obliquely arranged relative to the axis of the tube shell. The improvement of this application is:

as shown in fig. 2, the tube bundle further includes a plurality of tie rods arranged in parallel with the heat exchange tubes 14, and the same tie rod is divided into two segments: the left pull rod 131 fixed on the left tube plate 11 and the right pull rod 132 fixed on the right tube plate 12 are aligned one by one and tightened and fixedly connected, the left pull rods 131 and the right pull rods 132 are fixedly connected with the inner plates 16, so that the inner plates 16 are tensioned left and right by the left tube plate 11 through the left pull rods 131 and the right tube plate 12 through the right pull rods 132, the inner plates 16 are firmly positioned at fixed positions on the tube bundle, the overall strength and rigidity of the tube bundle are obviously improved by the tube plate and the inner plates which are tensioned bidirectionally, and the impact of flowing media from left to right can be borne under the reinforcement of the left pull rod 131, and the impact of flowing media from right to left can be borne under the reinforcement of the right pull rod 132. Compared with the traditional one-way draw bar tube bundle, the inner plate 16 can not vibrate to wear the heat exchange tube or bend and lose stability under the impact of a reverse flowing medium, and the tube bundle has the characteristics of simple structure, high quality and long service life.

In the double-end pull rod reinforced tube bundle structure shown in fig. 2, a tube pass fluid enters the heat exchange tube 14 from the arrow direction of the left end, and leaves the tube bundle from the arrow direction of the right end after heat exchange through the heat exchange tube 14, the left end of the left pull rod 131 in the figure is screwed or welded and fixed on the shell side of the left tube plate 11, so that the impact effect of the shell pass fluid from left to right can be borne, and the right end of the right pull rod 132 is fixed on the shell side of the right tube plate 12, so that the impact effect of the shell pass fluid from right to left can be borne, and the axial vibration of the shell pass fluid can be borne.

The connection mode of each left pull rod 131 and the corresponding right pull rod 132 is as follows: a turnbuckle 15 serving as an intermediate piece is arranged between the left pull rod 131 and the right pull rod 132, so that the left pull rod 131 and the right pull rod 132 are pulled and tightened with each other; or a rigid block is welded between the left pull rod 131 and the right pull rod 132 instead, so that the left pull rod 131 and the right pull rod 132 are welded and tightened with each other.

In practice, the connection between the end of the left tie rod 131 and the shell side of the left tube plate 11 and the connection between the end of the right tie rod 131 and the shell side of the right tube plate 12 are as follows: the screw thread connection, the welding or the combination of the two connection modes, namely the welding of a part of the pull rod and the screw thread connection of a part of the pull rod are determined according to the working conditions of different positions. The tie rods are usually screwed to the tube sheet, the tie rods 131/132 with spacers can be screwed to the inner plate 16 with their ends screwed together as shown in fig. 2, and the tie rods 133/134 without spacers can be welded to the inner plate 16 as shown in fig. 3 and 4.

In practice, the number of the left and

right tie rods

131 and 132 in fig. 2 is plural, the ends of the left tie rods 131 are distributed along the circular track or non-circular area of the corresponding left tube plate 11, and the ends of the right tie rods 132 are distributed along the circular area or non-circular area of the right tube plate 12, depending on the tube arrangement area on the tube plate.

In actual manufacturing, the pull rod is of a full-length whole-strip structure or a segmented combined structure. Only one end of the whole pull rod needs to penetrate through the tube plate at the end with relatively good working condition to be welded and fixed to one side of the tube pass, and the pull rod at the end with relatively bad working condition at the other end does not need to penetrate through the tube plate. The segmented composite structures are connected together through an intermediate piece or welding, and the intermediate piece can tighten two segments of the pull rod. The ends of the left pull rod and the right pull rod are tightened together through a turn buckle, and if necessary, a stronger rigid part is arranged to weld the ends of the left pull rod and the right pull rod together, so that an integral pull rod with the whole length connected from the left tube plate to the right tube plate is formed.

Actually, it can be further optimized: the cross-sectional shape and size of the tie rods varies along the length and increases in cross-section towards the tie rods closer to the left/right tube sheet. The left tube plate and the right tube plate at the two ends of the tube shell have unequal thicknesses, so that the tube bundle belongs to a flexible thin tube plate or a tension tube plate, the thin tube plate is suitable for the end with larger fluid temperature difference at the two sides of the tube plate, and the thick tube plate is suitable for the end with smaller fluid temperature difference at the two sides of the tube plate.

As an alternative, as shown in fig. 2 and 3, the heat exchange tubes are straight tube bundles, and two ends of the heat exchange tube 14 respectively penetrate through the left tube plate 11 and the right tube plate 12 to communicate with tube boxes at two ends of the tube shell; or as shown in fig. 4, the heat exchange tubes are U-shaped tube bundles, and the heat exchange tubes pass through the left tube plate 11 and the right tube plate 12 in a circuitous way and have ports communicated with the same tube box, so that two straight tubes of the heat exchange tubes 14 are located in the same tube shell. Or the heat exchange tube is changed into a U-shaped tube bundle, and two sections of straight tubes of the heat exchange tube are positioned in different tube shells. As shown in fig. 4, the equivalent right tube plate 12 is actually equivalent to a thicker baffle or backing plate, and the tube plate spacers 17 are strong and rigid enough to allow the equivalent right tube plate 12 to serve as a foundation for the right tie rods 134 to tension the inner plate.

As an alternative scheme, as shown in fig. 2, a plurality of distance tubes are arranged on the outer side of the pull rod in a penetrating manner, the two adjacent inner plates 16, the inner plate 16 and the left tube plate 11/right tube plate 12 are fixed through the distance tubes, and the ends of the distance tubes are connected or welded in a threaded manner; or as shown in fig. 3 or 4, the pull rod is a polished rod body without a distance tube, and a distance piece 17 is additionally arranged in the shell, penetrates through a plurality of inner plates 16 and is connected with the left tube plate 11 and the right tube plate 12 at two ends respectively.

Among the prior art, some other types of heat exchangers set up whole pull rod between the tube sheet for the convenience of maintaining, and this application compares in this type of heat transfer, has following obvious advantage:

1. this application aim at improves the operating efficiency and the security of heat exchanger, and is different with the maintenance purpose of being convenient for of prior art.

2. The double-ended tie rod of the present application serves to assemble the tube sheet and the inner plate (baffle or backing plate).

3. The double-end pull rod can pull any baffle plate or support plate in the direction of the tube plates at two ends, and can prevent the baffle plate or support plate from vibrating under the action of a shell side medium.

4. The double-end pull rod is connected with the shell side of the tube plate in a threaded mode or welded, or only one end of the double-end pull rod needs to penetrate through the tube plate with the relatively good working condition to be welded and fixed to the tube side, and the welding sealing performance is reliable.

5. The application of the heat exchanger is that when the shell side medium is the low temperature high pressure working condition, the double-end pull rod assembly has a good reinforcing effect on the pipe plate to resist high internal pressure under the tensioning effect of the pipe plate. In the prior art, when the pressure of a shell pass refrigerant is increased in the technique of arranging the pull rod for maintenance, the periphery of the end mounting plate deflects and deforms towards the end socket, the seals at two ends of the periphery of the tube bundle are loosened, and the heat medium at the shell pass side and the cold medium at the tube pass side are communicated and leaked.

6. The tube bundle and the tube shell of the present application can be manufactured separately and simultaneously as a large number of parts, which are then assembled together. And prior art if the tube sheet passes through the nut with the pull rod fixed, then there is the equipment drawback: the pipe bundle parts are difficult to be independently and effectively assembled after being processed, the pipe bundle parts need to be assembled under the support of the tank body after the tank body is manufactured, especially, when nuts at two ends of the pull rod are not screwed tightly, the end parts of the pipe bundle and the mounting plates can leak, but when the nuts at two ends of the pull rod are screwed tightly, the distance between the two mounting plates is shortened by the pull rod, the periphery of the mounting plates can deflect and deform towards the end socket, the end parts of the pipe bundle and the mounting plates can leak, and the contradiction that the screwing force of the nuts cannot be adjusted is also caused.

In a word, the heat exchanger with the double-end pull rod assembly is a novel technology that the baffle plate or the supporting plate has strong vibration resistance, the integral strength and rigidity of the tube bundle are high, the tube bundle is wide in application occasions and particularly suitable for thin tube plates, the tube bundle has a high-temperature self-tightening function, and the cost performance of the tube bundle is high.

This application has double-end pull rod assembly's tube bank feasibility analysis:

the thermal expansion extension of the heat exchange tube in the high-temperature operation of the tube bundle of the traditional one-way pull rod assembly is only restrained by the shell and cannot be restrained by the pull rod, and the heat exchange tube and the pull rod are free.

However, in the tube bundle of the present embodiment, the heat exchange tubes and the tie rods are mutually constrained, as shown in fig. 2. In the tube bundle, the temperature of the heat exchange tube is slightly higher than that of the adjacent pull rod, the thermal expansion of the heat exchange tube and the adjacent pull rod is basically coordinated, if the temperature of the heat exchange tube is much higher than that of the adjacent pull rod, the thermal expansion of the heat exchange tube is limited by the adjacent pull rod, the pull rod is not enough except for the thermal expansion elongation of the pull rod, and the thermal expansion elongation of the heat exchange tube is also prolonged, so that the reliability check is carried out on the thermal self-tightening. Meanwhile, the structural self-tightening and the thermal stress check caused by thermal expansion are two aspects of the protection design. From the technical reliability, the thermal stress of the two structures should be checked, if the thermal stress is large and the check can pass, the requirements of the two aspects are met at the same time, and if the thermal stress is large and the check cannot pass, a countermeasure for reducing the thermal stress should be taken.

1) Safety check of tie rod

After the tube bundle is assembled at the normal temperature of 20 ℃, the thermal expansion extension difference between the heat exchange tube and the adjacent pull rod at the average operating temperature is as follows:

△L＝L _m -L _j ＝β _m ×△T _m ×L－β _j ×△T _j ×L (1)

in the formula: delta L is the maximum thermal expansion difference in operation between the heat exchange tube with the full length of L and the pull rod, and is mm;

β _m the linear expansion coefficient of the heat exchange tube at the average operating temperature is 1.324 multiplied by 10 when the heat exchange tube operates at the rare extreme high temperature of 350 ℃ for carbon steel and chromium molybdenum steel ^-5 mm/(mm·℃)；

△T _m -the difference between the average operating temperature of the heat exchanger tube and the temperature at which it is manufactured and assembled (generally taken to be 20 ℃), 330 ℃;

L _m -maximum expansion of the heat exchange tubes, mm;

β _j the linear expansion coefficient of the pull rod at the average operating temperature is 1.29 multiplied by 10 when the pull rod is set to be lower than the temperature of the heat exchange tube beside the pull rod by 20 ℃ for the high temperature of the carbon steel and the chromium molybdenum steel and the operation is carried out at 300 DEG C ^-5 mm/(mm·℃)；

△T _j The difference between the average operating temperature of the tie-rod and the temperature at which it is manufactured and assembled (generally taken at 20 ℃), 280 ℃;

L _j minimum expansion of the tie rod, mm.

The relevant numerical values are substituted into the formula (1) to calculate:

△L＝[1.324×10 ^-5 (350-20)L]－[1.29×10 ^-5 (300-20)L]

＝(436.92-361.2)10 ^-5 L

＝7.572×10 ^-4 L (2)

no matter how long the heat exchange tube is, the thermal strain epsilon obtained by dividing the thermal expansion difference Delta L by L is 7.572 multiplied by 10 ^-4 mm/mm, the compressive stress to which it is subjected to all thermal strains is:

σ _y ＝εE (3)

in the formula: sigma _y -the thermal strain tensile stress to which the tie rod is subjected, MPa;

ε -thermal strain, 7.57X 10 ^-3 mm/mm；

E-elastic modulus of the pull rod material is 1.83 multiplied by 10 when the carbon steel and the chromium molybdenum steel run at the high temperature of 300 DEG C ⁵ MPa; substituting the relevant numerical value into the formula (3) to calculateObtaining:

σ _y ＝7.572×10 ^-4 ×1.83×10 ⁵ ＝138.6MPa (4)

since the thermal stresses are self-limiting and localized, the stresses drop immediately upon yielding, it being possible here to relax the permissible value of the carbon steel, taking

The tensile stress of the formula (4) is only half of the allowable stress value 270MPa of the pull rod, and the allowable value of the chromium-molybdenum steel is higher. Therefore, the elastic extension of the pull rod can eliminate the influence of the thermal stress, the pull rod cannot be broken, and the pull rod is safe.

2) Influence of extension of the tie rod on the displacement of the cross-flow plate

The length L of the commonly used heat exchange tube is about 6000mm, and the thermal expansion elongation difference between the heat exchange tube and the adjacent pull rod is calculated by substituting formula (2):

△L＝7.572×10 ^-4 ×6000≈4.5mm (6)

on the one hand, the typical spacing between the baffles or support plates is 400mm, for a heat exchange tube with a length L of about 6000mm, at least five baffles or support plates are arranged to form six equal intervals, the average spacing between the baffles or support plates is 1000mm, even for a heat exchange tube with a length of 12000mm, the average spacing between the baffles or support plates will not increase, and the difference in thermal expansion elongation to be harmoniously digested between every two baffles or support plates is:

4.5/6≈0.75mm (7)

because the baffle plate or the supporting plate is uneven, the pull rod is not straight enough and gaps exist among parts when the tube bundle is assembled, the tiny thermal expansion extension difference is easily coordinated and digested by displacement within the range of 1000mm of each interval, and the phenomenon that the baffle plate or the supporting plate is pulled by the pull rod distance tube to be distorted and deformed can not occur.

On the other hand, as a result of the calculation and check of equation (4), it is found that the influence of the thermal displacement can be coordinated with the elastic extension of the tie rod, and the tie rod is not broken, and in short, the baffle plate or the support plate is not distorted by the tie rod spacer.

3) Control of the difference in thermal expansion elongation between the heat exchange tube and its adjacent tie rod

Firstly, the objective existence of the thermal expansion extension difference between the heat exchange tube and the adjacent pull rod under the operation state is fully utilized to achieve the main purpose of fastening the integral structure of the tube bundle, and secondly, the harmfulness when the thermal expansion extension difference is overlarge is controlled through calculation and check.

If the thermal expansion extension difference between the heat exchange tube and the adjacent pull rod is large, the pull rod can be made of a material with a linear thermal expansion coefficient larger than that of the heat exchange tube so as to reduce the thermal expansion extension difference.

Structurally, countermeasures can be taken, such as elimination of a distance tube and adoption of a pull rod only, the pull rod is enabled to be in contact with a shell side medium more directly, heat is absorbed from medium heat transfer and radiation of an adjacent heat exchange tube, the temperature is increased, and the thermal expansion elongation difference is also reduced.

An elastic washer can be additionally arranged between the fastening nut at the end part of the pull rod and the baffle plate or the supporting plate, and the deformation of the elastic washer is used for coordinating the thermal expansion elongation difference of digestion.

4) Strategy for controlling the average temperature difference between a heat exchange tube and its adjacent tie rod

Based on the principle of the formula (2), the strategy for reducing the action of the heat exchange tube thermal expansion tensile stress on the pull rod can control the thermal expansion elongation difference between the heat exchange tube and the adjacent pull rod, and also can control the average temperature difference between the heat exchange tube and the adjacent pull rod. Specifically, on the basis of the stress allowable value of the formula (5), the stress calculation value of the formula (4) is reversely deduced, then the strain calculation value of the formula (3) is reversely deduced, and finally the temperature difference calculation value of the formula (2) is reversely deduced, so that the temperature difference is controlled by adjusting the flow rate, the flow velocity or the structure of the tube bundle and the heat exchange tube.

In general, in general petrochemical process technology, the two-way pull rod has remarkable advantages and little or no harmful effect.

During actual manufacturing, for the fixed tube-plate heat exchanger, the tube bundle which is assembled in the figures 2 and 3 and is qualified in inspection is conveyed into the tube shell from one end, the diameter of the excircle of the tube plate at the right end of the tube bundle is slightly smaller than that of the excircle at the left end of the tube bundle, and the excircle of the tube plate at the right end of the tube bundle is welded with the tube shell to form a sealed shell pass after the other end of the tube shell is exposed; for the floating head type heat exchanger, the floating head cover can be assembled on the excircle of the tube plate at the right end.

For the U-shaped tube bundle heat exchanger, the tube bundle which is assembled and qualified in inspection is conveyed into the heat exchanger shell by one end of the U-shaped section at the right end of the tube bundle.

In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The standard parts used in the invention can be purchased from the market, the special-shaped parts can be customized according to the description of the specification and the accompanying drawings, the specific connection mode of each part adopts conventional means such as bolts, rivets, welding and the like mature in the prior art, the machines, the parts and equipment adopt conventional models in the prior art, and the circuit connection adopts the conventional connection mode in the prior art, so that the detailed description is omitted.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A heat exchanger with a double-head pull rod assembly comprises a tube shell, a tube bundle and tube boxes, wherein the tube bundle comprises a left tube plate, a right tube plate, a plurality of inner plates and a plurality of heat exchange tubes; the inner plates are one or both of the baffle plate and the support plate, and the inner plates are distributed along the length direction of the heat exchange tube; the method is characterized in that: the tube bundle further comprises a plurality of pull rods arranged in parallel with the heat exchange tubes, the same pull rod is divided into a left pull rod fixed on the left tube plate and a right pull rod fixed on the right tube plate, the left pull rod and the right pull rod are aligned one by one and fixedly connected in a tightening mode, and the inner plates are fixedly connected with the left pull rod or the right pull rod.

2. The heat exchanger with the double-ended draw rod assembly of claim 1, wherein: a turn buckle is arranged between the left pull rod and the right pull rod, so that the left pull rod and the right pull rod are pulled and tightened mutually.

3. The heat exchanger with the double-ended draw rod assembly of claim 1, wherein: a rigid block is welded between the left pull rod and the right pull rod, so that the left pull rod and the right pull rod are welded and tightened.

4. The heat exchanger with the double-ended draw rod assembly of claim 1, wherein: the connection modes between the end part of the left pull rod and the shell side of the left tube plate and between the end part of the right pull rod and the shell side of the right tube plate are as follows: threaded connections, welding or a combination of both.

5. The heat exchanger with the double-ended draw rod assembly of claim 1, wherein: the quantity of left pull rod and right pull rod is many, and the tip of many left pull rods distributes along the whole circle regional distribution or the non-whole circle regional distribution of left tube sheet, and the tip of many right pull rods distributes along the whole circle regional distribution or the non-whole circle regional distribution of right tube sheet.

6. The heat exchanger with the double-ended draw rod assembly of claim 1, wherein: the pull rod is of a full-length whole-strip structure, or the pull rod is of a segmented combined structure.

7. The heat exchanger with the double-ended draw rod assembly of claim 1, wherein: the cross-sectional shape and size of the tie rods varies along the length and increases in cross-section towards the tie rods closer to the left/right tube sheet.

8. The heat exchanger with the double-ended draw rod assembly of claim 1, wherein: the heat exchange tubes are straight tube bundles, and two ends of each heat exchange tube are respectively connected with tube boxes at two ends of the tube shell; or the heat exchange tube is a U-shaped tube bundle, and the heat exchange tube bypasses through the left tube plate and the right tube plate and is communicated with the same tube box, so that two straight tubes of the heat exchange tube are positioned in the same tube shell; or the heat exchange tube is a U-shaped tube bundle, and two sections of straight tubes of the heat exchange tube are positioned in different tube shells.

9. The heat exchanger with the double-ended draw rod assembly of claim 1, wherein: the thickness of the left tube plate is unequal to that of the right tube plate.

10. The heat exchanger with the double-ended draw rod assembly of claim 1, wherein: the pull rod sleeve is provided with a plurality of sections of distance pipes; or the pull rod is a rod body without a distance tube, a distance piece is arranged in the tube shell, and the distance piece penetrates through the plurality of inner plates and the two end parts of the inner plates to be respectively connected with the left tube plate and the right tube plate.