WO2023226287A1

WO2023226287A1 - Heat exchanger having double-ended tie rod assembly

Info

Publication number: WO2023226287A1
Application number: PCT/CN2022/126340
Authority: WO
Inventors: 陈孙艺
Original assignee: 茂名重力石化装备股份公司
Priority date: 2022-05-27
Filing date: 2022-10-20
Publication date: 2023-11-30
Also published as: CN114909928A

Abstract

The present invention relates to the technical field of shell-and-tube heat exchangers, and in particular to a heat exchanger having a double-ended tie rod assembly, comprising a tube shell, a tube bundle, and bonnets. The tube bundle comprises a left tube plate, a right tube plate, a plurality of internal plates (baffle plates or supporting plates), and a plurality of heat exchange tubes; the tube bundle further comprises a plurality of tie rods arranged in parallel with the heat exchange tubes; a same tie rod is divided into a left tie rod fixed to the left tube plate and a right tie rod fixed to the right tube plate; the left tie rods and the right tie rods are aligned one by one and are tightened and fixedly connected; the internal plates are firmly positioned at fixed positions on the tube bundle. The overall strength and stiffness of the tube bundle are significantly improved; the impact of a medium flowing from left to right can be withstood under reinforcement by the left tie rods, and the impact of a medium flowing from right to left can also be withstood under reinforcement by the right tie rods; compared with a conventional one-way tie rod tube bundle, the internal plates and the tie rods do not vibrate to wear the heat exchange tubes, or bend to become unstable, under the impact of a reversely flowing medium, and the tube bundle has a simple structure, high quality, and a long service life.

Description

A heat exchanger with a double-ended tie rod assembly

Technical field

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

Background technique

In the existing technology, shell and tube heat exchangers are the most widely used heat exchangers. Shell and tube heat exchangers are also called tube heat exchangers or tube condensers and are widely used in chemical industry, petroleum industry, etc. Convection heat transfer of "liquid-liquid", "vapor-vapor", "vapor-liquid" heat exchange in the fields of medicine, food, light industry, metallurgy, coking, etc., as well as steam condensation and liquid evaporation heat transfer Wait for the heat exchange and condensation process.

The usual structure of a shell-and-tube heat exchanger in the prior art is shown in Figure 1, which is mainly composed of main components such as a tube bundle 1, a shell 2, and a tube box 3. The tube bundle 1 is the core component of the shell-and-tube heat exchanger. , the tube bundle 1 usually consists of heat exchange tubes 1-1, support plates (or baffles) 1-2, fixed distance tube tie rod assemblies 1-3 and tube plates 1-4. Rows of heat exchange tubes 1-1 pass through The support plate (or baffle) is supported by 1-2, and its two ends penetrate into the tube holes of the tube plate and are fixedly connected to the tube plate to ensure the sealing and strength of the joint. The two ends of the heat exchange tube are connected to the tube. box.

As can be seen from Figure 1, the traditional tube bundle only has a tie rod fixed to the tube plate at one end, and there is no fixed tie rod to the tube plate at the other end. The tie rod only serves to position the baffle or support plate when assembling the tube bundle. As the name suggests, the tie rod only has the function of bearing axial tension. When subjected to axial pressure, this slender round rod can easily bend.

technical problem

On the one hand, with the development of social economy, the scale of construction of petrochemical equipment is getting larger and larger. The National Development and Reform Commission specifically issued the "Strict Energy Efficiency Constraints in Key Petrochemical and Chemical Industries to Promote Energy Saving and Carbon Reduction Action Plan (2021-2025)" for the petrochemical and chemical industry. Year)", it is strictly prohibited to build new normal and vacuum plants with a capacity of less than 10 million tons/year, and naphtha cracking to produce ethylene with a capacity of less than 800,000 tons/year. There are similar requirements for the lower production capacity limits of other petrochemical plants. The structural size of the new heat exchanger not only breaks through the limit of the nominal diameter not exceeding 4000mm in the GB/T 151-2014 "Heat Exchanger" standard, but is also integrated with the reactor to form an ethylene oxide reactor and a propylene oxide reactor. Wait, the processing volume is getting bigger and bigger. The processing capacity of the old heat exchanger of the old device is sometimes overloaded. The heat exchanger tube bundle vibrates under the impact of the large flow and strong fluid medium on the shell side. The vibration impact not only produces noise and pollutes the environment, but also wears and damages the heat exchange tubes. It will cause internal leakage in the equipment, thus affecting the production and quality of chemical products, and even leaking outside to pollute the environment.

On the other hand, with the development of energy-saving and environmental protection technology, the temperature of deep processing of petrochemical processes is getting higher and higher, and the indicators for full utilization of waste heat recovery are becoming more and more stringent. Thin tube sheets have replaced thick-walled large forged tubes in lightweight design. Plates are becoming more and more common, but thin tube plates lack the pressure-bearing capacity and require special structural strengthening.

Another point is that the reverse flow of petrochemical equipment has raised new requirements for the intrinsic safety of heat exchangers. First, in order to maintain the operating effect of the heat exchanger, annual shutdown and maintenance are traditionally carried out to remove impurities and dirt that have been deposited in the corners of the structure for a long time. Now, in order to reduce or avoid the economic loss of shutdown, a set of process called process reverse flushing has been explored and promoted. With the cleaning technology, the equipment does not need to be dismantled. The original inlet and outlet functions are interchanged. The flushing fluid is sent in reverse circulation several times to loosen most impurities and dirt and be brought out of the equipment. The effect is good. Second, the technical transformation of some installations and facilities may require changing the original inlet to an outlet, and the outlet to an inlet, but the pipe bundle in the shell is difficult to transform. Third, when the outlet pipeline of the heat exchanger shell is operated improperly or unexpectedly, the original forward-flowing medium will cause reverse flow water hammer when encountering a suddenly closed valve or obstacle, which will have a strong impact on the tube bundle, just like a highway brake. The same applies to the shaking of passengers. In order to avoid damage to the harness, a harness "seat belt" should be added.

Therefore, it is of engineering significance to improve the problems existing in the above-mentioned prior art.

Technical solutions

In view of the above technical problems in the prior art, the present invention provides a heat exchanger with a double-ended tie rod assembly.

In order to achieve the above objects, the present invention provides the following technical solutions:

Provides a heat exchanger with a double-ended tie rod assembly, including a tube shell, a tube bundle and a tube box. The tube bundle includes a left tube plate, a right tube plate, multiple inner plates and multiple heat exchange tubes. The left tube plate and the right tube plate They are fixed at both ends of the tube shell and together form the shell side. The left tube plate and the right tube plate are respectively fixed with different tube boxes and together form the tube side. Multiple heat exchange tubes are located side by side in the shell side and pass through them. The left tube plate and the right tube plate are connected to the tube side behind; the inner plate is one of the baffle plate and the support plate or both coexist, and multiple inner plates are distributed along the length direction of the heat exchange tube; its characteristics are: The tube bundle also includes multiple tie rods arranged in parallel with the heat exchange tubes. The same tie rod is divided into a left tie rod fixed on the left tube plate and a right tie rod fixed on the right tube plate. The left tie rod and the right tie rod are aligned one by one and tightened to fix the connection. , multiple inner plates are fixedly connected to the left tie rod or the right tie rod.

As a further specific solution, a flower basket bolt is provided between the left tie rod and the right tie rod, so that the left tie rod and the right tie rod pull and tighten each other.

As a further specific solution, a rigid block is welded between the left tie rod and the right tie rod, so that the left tie rod and the right tie rod can be welded and tightened to each other.

As a further specific solution, the connection methods between the end of the left tie rod and the shell side of the left tube plate, and between the end of the right tie rod and the shell side of the right tube plate are: threaded connection, welding, or both. The combination.

As a further specific solution, the number of left tie rods and right tie rods is multiple, the ends of the multiple left tie rods are distributed along the full circle area or non-full circle area corresponding to the left tube plate, and the ends of the multiple right tie rods are distributed along the right Full circle area distribution or non-full circle area distribution of the tube plate.

As a further specific solution, the tie rod is a full-length entire structure, or the tie rod is a segmented combined structure.

As a further specific solution, the cross-sectional shape and size of the tie rod change along the length direction, and the cross-section of the tie rod increases toward the direction of the left tube plate/right tube plate.

As a further specific solution, the heat exchange tube is a straight tube bundle, and the two ends of the heat exchange tube are respectively connected to the tube boxes at both ends of the tube shell; or the heat exchange tube is a U-shaped tube bundle, and the heat exchange tube passes through the left tube plate in a roundabout way. and the right tube plate and connected to the same tube box, so that the two straight tube sections of the heat exchange tube are located in the same tube shell; or the heat exchange tube is a U-shaped tube bundle, and the two straight tube sections of the heat exchange tube are located in different tubes. in the shell.

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

As a further specific solution, the pull rod sleeve is provided with multi-section distance tubes; or the pull rod is a rod body without a distance tube, and a distance piece is provided in the tube shell, and the distance piece passes through multiple inner plates and its two ends Connect the left tubesheet and right tubesheet respectively.

beneficial effects

The heat exchanger with a double-ended tie rod assembly of the present invention has the following advantages compared with the traditional one-way tie rod tube bundle:

(1) The inner plate (baffle plate or support plate) has strong vibration resistance. The same baffle or support plate is tightened by the left tube plate and the right tube plate at the same time, and the inner plate is firmly positioned at a position on the tube bundle.

(2) The overall strength and stiffness of the tube bundle is high. There are tie rods connected to the tube plates at both ends of the tube bundle. The tie rod connected to the tube plate at the left end tightens the inner plate to the left. The tie rod connected to the tube plate at the right end tightens the inner plate to the right. The left tie rod and the right tie rod tighten each other. It forms an integral tie rod that is equivalent to a full length connecting from the left tube plate to the right tube plate, but is better than the integral tie rod. The inner plate tightened by both ends significantly improves the overall strength and stiffness of the tube bundle. During the loading and unloading process of the tube bundle, The original structural dimensional accuracy can be better maintained during the process of assembly into the casing or extraction for maintenance.

(3) Tube bundles are suitable for a wide range of applications, and are especially suitable for thin tube sheets.

First, the fluid state is suitable for medium impact. It can not only withstand the impact of the medium flowing from left to right with the reinforcement of the left tie rod, but also withstand the impact of the medium flowing from right to left with the reinforcement of the right tie rod. The inner plate and tie rod will not be affected by the impact of the reverse flow medium. Vibration wears the heat exchange tube or causes bending and instability.

Second, it is structurally suitable for heat exchanger structures such as steam generators, waste heat boilers, and coolers with large shell diameters, thin tube plates, and ultra-long heat exchange tubes. The two-way tie rod assembly composed of the left tie rod and the right tie rod supports the tube plate equivalent to the support of the heat exchange tube to the tube plate. Therefore, it can significantly reduce the imaginary circle diameter for calculating the tube plate thickness in the tube plate layout area. According to the imaginary circle diameter The thickness of the tube sheet is reduced in the same proportion as the reduction.

Third, the process is suitable for situations with large flow rates on the shell side, unsteady flow regimes, and gas-liquid mixed two-phase flow or high elasticity of the gas flow.

(4) The tube bundle has high-temperature self-tightening function. When the tube side temperature of the tube bundle is higher than the shell side temperature, the thermal elongation of the heat exchange tube is slightly longer than the thermal elongation of the tie rod made of similar steel. The two-way tie rod is driven by the heat exchange tube and has relative displacement to both ends of the tube bundle. trend, resulting in the effect of tightening the baffles or support plates. On the contrary, when the tube side temperature of the tube bundle is lower than the shell side temperature, the two-way pull rod has the effect of pushing the baffle or support plate tight.

(5) Discipline is cost-effective. The tube bundle only adds some common traditional parts such as tie rods to achieve good performance and has the characteristics of simple structure, high quality and long service life.

Compared with the full-length integral tie rod, the double-ended tie rod assembly that is first separated into two sections and then connected together has the following advantages:

1. It not only functions as a frame to assemble the tube sheet and inner plate, but also tightens the inner plate, and can achieve two-way tightening to fix the inner plate in the same position.

2. The tie rod is divided into a left tie rod and a right tie rod. When connected together, they are equivalent to the tie braces in Appendix L of the GB/T 150-2014 "Heat Exchanger" standard, which can strengthen the space between the tube sheets at both ends. The connection fixes the various parts of the tube bundle together to form a tight whole, improving the structural strength and rigidity. Even thin-walled and thick tube plates are suitable for working conditions with high shell pressure.

3. The two ends of the tie rod do not need to pass through the thickness of the tube plate, and there is no damage to the overall strength of the tube plate. The tube plate is suitable for working conditions with high pressure.

4. When the tube bundle operates at high temperature of the shell, the internal components have a thermal self-tightening effect and the sealing is reliable. It is suitable for large-diameter petrochemical heat exchangers.

Description of the drawings

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

Figure 2 is a first structural schematic diagram of a tube bundle of a heat exchanger with a double-ended tie rod assembly in this application.

Figure 3 is a second structural schematic diagram of a tube bundle of a heat exchanger with a double-ended tie rod assembly according to the present application.

Figure 4 is a third structural schematic diagram of the tube bundle of a heat exchanger with a double-ended tie rod assembly in this application.

Embodiments of the invention

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

The heat exchanger with a double-ended tie rod assembly in this embodiment includes a traditional structure: a tube shell, a tube bundle, and a tube box. The tube bundle includes a left tube plate, a right tube plate, multiple inner plates, and multiple heat exchange tubes. The left tube plate The right tube plate and the right tube plate are fixed at both ends of the tube shell and together form the shell side. The left tube plate and the right tube plate are fixed to different tube boxes respectively and form the tube side together. Multiple heat exchange tubes are located side by side on the shell side. The heat exchange tube is welded and fixed to the left and right tube plates, and the heat exchange tube passes through the inner plate with a gap fit. The inner plate is either a baffle plate or a support plate or both. Multiple inner plates are distributed along the length of the heat exchange tube. Each inner plate is arranged along the radial direction of the tube shell or is inclined relative to the axis of the tube shell. layout. What this application improves is:

As shown in Figure 2, the tube bundle also includes a plurality of tie rods arranged in parallel with the heat exchange tubes 14. The same tie rod is divided into two sections: a left tie rod 131 fixed to the left tube plate 11 and a right tie rod fixed to the right tube plate 12. The tie rod 132, the plurality of left tie rods 131 and the plurality of right tie rods 132 are aligned one by one and tightened and fixedly connected. The plurality of inner plates 16 are fixedly connected to the left tie rod 131 or the right tie rod 132, so that each inner plate 16 is connected by the left tube plate 11 By tightening the left tie rod 131 and the right tube plate 12 through the right tie rod 132, the inner plate 16 is firmly positioned at a fixed position on the tube bundle. The bidirectionally tightened tube plate and inner plate significantly improve the overall strength and strength of the tube bundle. The stiffness can not only withstand the impact of the medium flowing from left to right under the reinforcement of the left tie rod 131, but also can withstand the impact of the medium flowing from right to left under the reinforcement of the right tie rod 132. Compared with the traditional one-way tie rod tube bundle, the inner plate 16 will not vibrate, wear out the heat exchange tubes or bend and become unstable under the impact of the reverse flow medium. The tube bundle has the characteristics of simple structure, high quality and long service life.

The double-ended tie rod strengthens the tube bundle structure shown in Figure 2. The tube side fluid enters the heat exchange tube 14 from the direction of the arrow on the left end. After exchanging heat in the heat exchange tube 14, it leaves the tube bundle in the direction of the arrow on the right end. The left end of the left tie rod 131 in the figure is threaded or It is welded and fixed on the shell side of the left tube plate 11 and can withstand the impact of the shell side fluid from left to right. The right end of the right tie rod 132 is fixed on the shell side of the right tube plate 12 and can withstand the impact of the shell side fluid from right to right. The impact effect on the left side can also withstand the axial vibration of the shell side fluid.

The connection method of each left tie rod 131 and the corresponding right tie rod 132: a flower basket bolt 15 as an intermediate piece is provided between the left tie rod 131 and the right tie rod 132, so that the left tie rod 131 and the right tie rod 132 can pull and tighten each other; or change A rigid block is welded between the left tie rod 131 and the right tie rod 132, so that the left tie rod 131 and the right tie rod 132 are welded and tightened to each other.

In practice, the connection methods between the end of the left tie rod 131 and the shell side of the left tube plate 11 and between the end of the right tie rod 131 and the shell side of the right tube plate 12 are: threaded connection, welding or both connections. The combination of methods, that is, partial tie rod welding and partial tie rod threaded connection, is determined according to the working conditions of different locations. The connection between the tie rod and the tube plate is usually threaded. As shown in Figure 2, the connection between the tie rod 131/132 with a distance tube and the inner plate 16 can be tightened with end threads. Figures 3 and 4 are shown without a distance tube. The connection between the tie rod 133/134 and the inner plate 16 can be welded.

In practice, the number of left tie rods 131 and right tie rods 132 in Figure 2 is multiple. The ends of the multiple left tie rods 131 are distributed along the full circular track or non-full circle area corresponding to the left tube plate 11. The multiple right tie rods 132 The ends are distributed along the full circle area or non-full circle area of the right tube plate 12, depending on the pipe routing area on the tube plate.

During actual manufacturing, the tie rod has a full-length structure, or the tie rod has a segmented combined structure. Only one end of the entire length of the tie rod needs to pass through the tube plate at the end with relatively good working conditions to the side of the pipe and then welded and fixed. The tie rod at the other end with relatively poor working conditions does not need to pass through the tube plate. . The segmented composite structure is connected together through middle parts or welding, and the middle parts can tighten the two sections of tie rods. The ends of the left and right tie rods are tightened together through flower basket bolts in the middle. If necessary, stronger rigid parts are provided to weld the ends of the left and right tie rods together to form a full-length connection from the left tube plate to the right Integral tie rod for tube sheet.

What can actually be further optimized: the cross-sectional shape and size of the tie rod changes along the length direction, and the cross-section of the tie rod increases toward the left tube plate/right tube plate. The thickness of the left tubesheet and the right tubesheet located at both ends of the tube shell are unequal, making the tube bundle a flexible thin tubesheet or a stretched tubesheet. The thin tubesheet is suitable for the end with a large fluid temperature difference on both sides of the tubesheet, and the thick tube The plate is suitable for the end where the fluid temperature difference on both sides of the tube sheet is smaller.

As an optional solution, as shown in Figures 2 and 3, the heat exchange tubes are straight tube bundles, and the two ends of the heat exchange tubes 14 pass through the left tube plate 11 and the right tube plate 12 respectively to connect to the tube boxes at both ends of the tube shell; Or as shown in Figure 4, the heat exchange tubes are U-shaped tube bundles. The heat exchange tubes pass through the left tube plate 11 and the right tube plate 12 and the ports are connected to the same tube box, so that the two straight tube sections of the heat exchange tube 14 located in the same shell. Or the heat exchange tubes may be changed to U-shaped tube bundles, and the two straight tube sections of the heat exchange tubes may be located in different tube shells. As shown in Figure 4, the equivalent right tube plate 12 in the figure is actually equivalent to a thicker baffle or support plate. Since the tube plate spacer 17 has sufficient strength and rigidity, the equivalent right tube plate 12 can also be used as a right tube plate. The tie rod 134 tightens the foundation of the inner panel.

As an optional solution, as shown in Figure 2, a multi-section spacer pipe is provided on the outside of the tie rod, and spacers are provided between two adjacent inner plates 16, and between the inner plate 16 and the left tube plate 11/right tube plate 12. The pipe phase is fixed, and the end of the distance pipe is threaded or welded; or as shown in Figure 3 or 4, the pull rod is a polished rod body without a distance pipe, and a distance piece 17 is additionally provided in the pipe shell, and the distance piece passes through multiple The inner plate 16 of the block and its two ends are connected to the left tube plate 11 and the right tube plate 12 respectively.

In the prior art, some other types of heat exchangers have entire tie rods between tube sheets to facilitate maintenance. Compared with this type of heat exchanger, this application has the following obvious advantages:

1. The purpose of this application is to improve the operating efficiency and safety of the heat exchanger, which is different from the existing technology's purpose of facilitating maintenance.

2. The double-ended tie rod of this application plays the role of assembling the tube plate and the inner plate (baffle plate or support plate).

3. The double-ended pull rod of this application can tighten any baffle or support plate toward the tube sheets at both ends, preventing the baffle or support plate from vibrating under the action of the shell side medium.

4. The double-ended tie rod of this application is threaded or welded to the shell side of the tube sheet, or only one end needs to pass through the end of the tube sheet with relatively good working conditions to the tube side and then welded and fixed, and the welding sealing performance is reliable.

5. During the application process of the heat exchanger of this application, when the medium on the shell side is under low temperature and high pressure conditions, the double-ended tie rod assembly tightens the tube sheet, which has good resistance to the high internal pressure of the tube sheet. Strengthening effect. When the pressure of the shell-side refrigerant rises in the existing technology, which installs tie rods for ease of maintenance, the periphery of the end mounting plate deflects toward the head and deforms. The seals at both ends of the tube bundle periphery will loosen, and the heat medium on the shell-side side will be in contact with the tube-side. Pass-through leakage will occur between the cold media on both sides.

6. The tube bundles and tube shells of this application can be manufactured simultaneously into large-volume parts, and then assembled together. In the existing technology, if the tube plate and the tie rod are fixed by nuts, there are assembly disadvantages: after the tube bundle parts are processed, it is difficult to assemble effectively alone. It is necessary to wait until the tank body is manufactured and then assemble with the support of the tank body, especially when the ends of the tie rod are When the nuts are not tightened tightly, there will be leakage between the end of the pipe bundle and the mounting plate. However, when the nuts at both ends of the tie rod are tightened too much, the distance between the two mounting plates will be shortened by the tie rod, and the periphery of the mounting plate will also deflect and deform toward the head. , it will also cause leakage between the end of the pipe bundle and the mounting plate, which is a contradiction that the nut tightening force cannot be adjusted.

In short, the heat exchanger with a double-ended tie rod assembly in this application is a baffle or support plate with strong vibration resistance, high overall strength and rigidity of the tube bundle, and the tube bundle is suitable for a wide range of applications and is especially suitable for thin tube plates. The tube bundle has a high-temperature self-tightening function and is a new technology with high cost performance.

本申请具有双头拉杆组件的管束可行性分析：Feasibility analysis of the pipe bundle with double-ended tie rod assembly in this application:

When the tube bundle of a traditional one-way tie rod assembly operates at high temperatures, the thermal expansion and elongation of the heat exchange tubes will only be restrained by the shell and not by the tie rods. There is freedom between the heat exchange tubes and tie rods.

However, in the tube bundle of this embodiment, the heat exchange tubes and the tie rods are mutually constrained, as shown in Figure 2 . Inside the tube bundle, the temperature of the heat exchange tube is slightly higher than that of its adjacent tie rods, and the thermal expansion of the two is basically coordinated. If the temperature of the heat exchange tube is much higher than that of its adjacent tie rods, the thermal expansion of the heat exchange tube will be limited by the adjacent tie rods. , in addition to its own thermal expansion and elongation, the tie rod is also elongated by the thermal expansion and elongation of the heat exchange tube, so the reliability of the thermal self-tightening should be checked. At the same time, structural self-tightening caused by thermal expansion and thermal stress verification are two aspects of protection design. From the perspective of technical reliability, the thermal stress of the two structures should still be checked. If the thermal stress is large and the check can be passed, the requirements of both aspects should be met. If the thermal stress is large and the check cannot be passed, the requirements should be met. Take measures to reduce thermal stress.

1).Safety check of tie rod

After the tube bundle is assembled at room temperature of 20°C, the difference in thermal expansion and elongation between the heat exchange tube and its adjacent tie rod at the average operating temperature is:

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

In the formula: △ L - the maximum thermal expansion difference between the heat exchange tube and the tie rod with the full length L during operation, mm;

B _m —The linear expansion coefficient of the heat exchange tube at the average operating temperature. For carbon steel and chromium-molybdenum steel, it is taken to be 1.324×10 ^-5 mm/(mm·℃) when operating at the rare extreme high temperature of 350°C;

△ T _m —The difference between the average operating temperature of the heat exchange tube and its manufacturing and assembly temperature (generally 20°C), 330°C;

L _m —maximum expansion of heat exchange tube, mm;

B _j —The linear expansion coefficient of the tie rod at the average operating temperature. For high temperatures of carbon steel and chromium-molybdenum steel, assume that the temperature of the tie rod is 20°C lower than that of the heat exchange tube next to it. When operating at 300°C, take 1.29×10 ^{- 5} mm/(mm·℃);

△ T _j —The difference between the average operating temperature of the tie rod and its manufacturing and assembly temperature (generally 20°C), 280°C;

L _j —minimum expansion amount of tie rod, mm.

Substitute the relevant values into equation (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 expansion difference △ L divided by L is the thermal strain ε =7.572×10 ^-4 mm/mm. Then the compressive stress to withstand all thermal strains is: σ _y = ε E (3)

In the formula: σ _y —The thermal strain tensile stress borne by the tie rod, MPa;

ε —Thermal strain, taken as 7.57×10 ^-3 mm/mm;

E - elastic modulus of tie rod material, take 1.83×10 ⁵ MPa for carbon steel and chromium-molybdenum steel when operating at high temperature of 300°C;

Substitute the relevant values into equation (3) to calculate:

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

Because thermal stress is self-limiting and local, the stress will drop immediately once it yields. The allowable value of carbon steel can be relaxed here, taking

3[σ] ^t _r =3×90=270MPa (5)

The tensile stress in formula (4) is only half of the allowable stress value of the tie rod of 270MPa, while the allowable value of chromium-molybdenum steel is higher. Therefore, the elastic elongation of the tie rod can eliminate the influence of the thermal stress, the tie rod will not be broken, and the tie rod is safe.

2).The influence of the extension of the tie rod on the displacement of the baffle

The commonly used heat exchange tube length L is approximately 6000mm. Substitute into equation (2) to calculate the thermal expansion elongation difference between the heat exchange tube and its adjacent tie rod:

△ L =7.572×10 ^-4 ×6000≈4.5mm (6)

On the one hand, the usual spacing between baffles or support plates is 400mm. For heat exchange tubes with a length L of about 6000mm, at least five baffles or support plates are set up to form six equal intervals. The average spacing between them is 1000mm. Even for a heat exchange tube with a length of 12000mm, the average spacing between baffles or support plates will not increase accordingly. Each two baffles or support plates need to be coordinated and digested. The difference in thermal expansion and elongation is:

Because the baffles or support plates are not flat during the assembly of the tube bundle, the tie rods are not straight enough, and there are gaps between the parts, this small difference in thermal expansion and elongation is easily digested through displacement coordination within the 1000mm length of each interval. There will be a phenomenon that the baffle plate or support plate is stretched and deformed by the tie rod distance tube.

On the other hand, the calculation and verification results according to equation (4) show that the elastic elongation of the tie rod can also coordinate the influence of the thermal displacement, and the tie rod will not be broken. In short, the baffle plate or the support plate will not be broken. The phenomenon that the tie rod spacer tube is stretched and deformed.

3). Countermeasures to control the difference in thermal expansion and elongation between the heat exchange tube and its adjacent tie rod

First of all, it is necessary to make full use of the objective existence of the thermal expansion and elongation difference between the heat exchange tube and its adjacent tie rod under operating conditions to achieve the main purpose of tightening the overall structure of the tube bundle. Secondly, it is necessary to control the thermal expansion and elongation difference when the thermal expansion and elongation difference is too large through calculation and verification. Harmful.

If the difference in thermal expansion and elongation between the heat exchange tube and its adjacent tie rod is large, a material with a larger linear thermal expansion coefficient than the heat exchange tube can be used to make the tie rod to reduce the difference in thermal expansion and elongation.

Structural countermeasures can be taken, such as canceling the distance tube and only using tie rods, so that the tie rods are more directly in contact with the shell side medium, absorbing heat from the heat transfer of the medium and the radiation of adjacent heat exchange tubes to increase the temperature, and also reduce thermal expansion and elongation. Difference.

An elastic washer can also be added between the fastening nut at the end of the tie rod and the baffle or support plate, so that the deformation of the elastic washer can coordinate and digest the difference in thermal expansion and elongation.

4). Countermeasures to control the average temperature difference between the heat exchange tube and its adjacent tie rods

Based on the principle of Equation (2), the countermeasure to reduce the thermal expansion tensile stress of the heat exchange tube on the tie rod is not only to control the thermal expansion elongation difference between the heat exchange tube and its adjacent tie rods, but also to control the average temperature difference between the heat exchange tube and its adjacent tie rods. . Specifically, we use the stress allowable value of equation (5) as a basis to back-calculate the stress calculation value of equation (4), then back-calculate the strain calculation value of equation (3), and finally back-calculate the temperature difference calculation value of equation (2). Adjust the flow rate, flow rate or tube bundle and heat exchange tube structure to control the temperature difference.

Generally speaking, in general petrochemical process technology, the benefits of two-way tie rods are obvious, and the harmful effects are small or even non-existent.

During actual manufacturing, for fixed tube plate heat exchangers, the tube bundles that have been assembled and inspected as shown in Figures 2 and 3 should be fed into the tube shell from the right end of the tube plate with a slightly smaller outer diameter than the left end. After one end is exposed, the outer circle of the right end tube plate is welded to the tube shell to form a sealed shell side; for a floating head heat exchanger, a floating head cover is assembled on the outer circle of the right end tube plate.

For U-shaped tube bundle heat exchangers, just send the U-shaped section at the right end of the assembled and inspected tube bundle into the heat exchanger shell.

In the description of the present invention, unless otherwise expressly stipulated and limited, the terms "installation", "connection", "connection" and "fixing" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection. , or integrated; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two elements or an interaction between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood on a case-by-case basis.

The standard parts used in the present invention can be purchased from the market, and the special-shaped parts can be customized according to the instructions and drawings. The specific connection methods of each part are all mature bolts, rivets, welding, etc. in the existing technology. Conventional means, machinery, parts and equipment all adopt conventional models in the prior art, and circuit connections adopt conventional connection methods in the prior art, which will not be described in detail here.

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

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art will understand that , the technical solution of the present invention may be modified or equivalently substituted without departing from the essence and scope of the technical solution of the present invention.

Claims

A heat exchanger with a double-ended tie rod assembly, including a tube shell, a tube bundle and a tube box. The tube bundle includes a left tube plate, a right tube plate, multiple inner plates and multiple heat exchange tubes. The left tube plate and the right tube plate are fixed at both ends of the tube shell and together form the shell side. The left tube plate and the right tube plate are respectively fixed with different tube boxes and together form the tube side. Multiple heat exchange tubes are located side by side in the shell side and pass through the left The tube plate and the right tube plate are connected to the tube side behind; the inner plate is one of the baffle plate and the support plate or both coexist, and multiple inner plates are distributed along the length direction of the heat exchange tube; its characteristics are: tube bundle It also includes multiple tie rods arranged side by side with the heat exchange tubes. The same tie rod is divided into a left tie rod fixed on the left tube plate and a right tie rod fixed on the right tube plate. The left tie rod and the right tie rod are aligned one by one and tightened to fix the connection. Multiple inner plates are fixedly connected to the left tie rod or the right tie rod.
A heat exchanger with a double-ended tie rod assembly according to claim 1, characterized in that: a flower basket bolt is provided between the left tie rod and the right tie rod, so that the left tie rod and the right tie rod pull and tighten each other.
A heat exchanger with a double-ended tie rod assembly according to claim 1, characterized in that a rigid block is welded between the left tie rod and the right tie rod, so that the left tie rod and the right tie rod are welded and tightened to each other.
A heat exchanger with a double-ended tie rod assembly according to claim 1, characterized in that: between the end of the left tie rod and the shell side of the left tube plate, between the end of the right tie rod and the shell side of the right tube plate The connection methods are: threaded connection, welding or a combination of these two connection methods.
A heat exchanger with a double-ended tie rod assembly according to claim 1, characterized in that: the number of left tie rods and right tie rods is multiple, and the ends of the multiple left tie rods are distributed along the entire circular area of the left tube plate. Or distributed in a non-complete circle area, the ends of the multiple right tie rods are distributed along the complete circle area or non-complete circle area of the right tube plate.
A heat exchanger with a double-ended tie rod assembly according to claim 1, characterized in that: the tie rod is a full-length entire structure, or the tie rod is a segmented combined structure.
A heat exchanger with a double-ended tie rod assembly according to claim 1, characterized in that: the cross-sectional shape and size of the tie rod change along the length direction, and the tie rod moves toward the left tube plate/right tube plate direction. The cross section increases.
A heat exchanger with a double-ended tie rod assembly according to claim 1, characterized in that: the heat exchange tube is a straight tube bundle, and the two ends of the heat exchange tube are respectively connected to the tube boxes at both ends of the tube shell; or the heat exchange tube is a straight tube bundle. The heat exchange tube is a U-shaped tube bundle, and the heat exchange tube passes through the left tube plate and the right tube plate and is connected to the same tube box, so that the two straight tubes of the heat exchange tube are located in the same tube shell; or the heat exchange tube It is a U-shaped tube bundle, and the two straight tube sections of the heat exchange tube are located in different tube shells.
A heat exchanger with a double-ended tie rod assembly according to claim 1, characterized in that: the thickness of the left tube plate and the right tube plate are unequal.
A heat exchanger with a double-ended pull rod assembly according to claim 1, characterized in that: the pull rod sleeve is provided with multiple sections of fixed distance tubes; or the pull rod is a rod body without a fixed distance tube, and the tube shell is provided with a fixed distance tube. The distance piece passes through multiple inner plates and its two ends are connected to the left tube plate and the right tube plate respectively.