Shell and tube heat exchange assembly, fluidized bed heat exchanger, and method for preventing and controlling tube fouling

Abstract

The present application provides a shell and tube heat exchange component, a fluidized bed heat exchanger and a method for preventing scaling of the tube side. The heat exchanger includes a lower tube box, heat exchanger tubes, an upper tube box, a liquid-solid separation box, a downcomer, a solid particle tank, a liquid storage tank, a liquid circulation pump, a three-pronged bracket, a propeller, a first sieve plate, a second sieve plate, a spring pile hammer and an elliptical elbow. The heat exchanger tubes are connected to the upper tube box, and the upper part of the upper tube box is connected to the liquid-solid separation box. The solid particles enter the solid particle tank through the downcomer and then enter the lower tube box together with the liquid flowing from the liquid storage tank under the action of the liquid circulation pump. The technical solution of the strongly distributed self-cleaning fluidized bed heat exchanger can better solve the technical problems in the traditional technology that the tube side of the constant pressure reduction device top heat exchanger is prone to scaling and the heat exchange effect is significantly reduced after long-term use. It can be used to extend the operating cycle of the constant pressure reduction device top heat exchanger.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry, and more specifically to the field of long-cycle operation of chemical heat exchange equipment, and relates to a shell and tube heat exchange component, a fluidized bed heat exchanger and a method for preventing and controlling tube scaling. Background Art

[0002] Heat exchangers are widely used in the petrochemical industry. However, after long periods of use, scaling will inevitably form inside the heat exchanger, significantly increasing the heat transfer resistance inside the heat exchanger, greatly reducing the heat transfer efficiency, and seriously affecting the normal operation of the heat exchanger.

[0003] The development of a fluidized bed heat exchanger with self-cleaning and descaling capabilities can effectively reduce the thermal resistance inside the heat exchanger, thereby preventing the heat exchange efficiency of the heat exchanger from decreasing, and further extending the service life of the heat exchanger equipment within one cycle, which has significant economic benefits. Document US005676201A discloses an external circulation fluidized bed heat exchanger, but the fluidized bed heat exchanger fails to fully consider the uniform distribution of solid particles, so its ability to maintain high heat transfer efficiency under long-term use is not strong. Document CN202709856U discloses a horizontal liquid-solid circulating fluidized bed heat exchanger using a Kenics static mixer, but the circulation and distribution effects of the circulating fluidized bed heat exchanger are not good, and its Kenics static mixer can only be used for horizontal heat exchangers, and its use is not wide. Document CN20160710754 discloses an external circulation fluidized bed heat exchanger with a spherical float and arc-shaped baffles. This fluidized bed heat exchanger fails to fully consider the uniform distribution of the heat exchanger tubes, resulting in poor heat transfer efficiency over long periods. Document CN106595350A discloses a liquid-solid circulating fluidized bed heat exchanger with a distribution box and a distribution plate. This heat exchanger has good particle distribution, but fails to fully consider the issue of particle circulation, resulting in low heat transfer efficiency.

[0004] In summary, solving the problem of uniform distribution and sufficient circulation of solid particles is one of the key technologies to maintain high heat transfer efficiency of fluidized bed heat exchangers over a long period of time, but existing technologies have failed to fully solve the above problems. Summary of the Invention

[0005] In response to the above-mentioned problems in the prior art, the present application proposes a shell-and-tube heat exchange assembly, a fluidized bed heat exchanger and a method for preventing and controlling tube scaling. By using structures such as double sieve plates, a three-pronged bracket with a propeller and a spring pile hammer, the problem of uniform distribution and sufficient circulation of solid particles in the fluidized bed heat exchanger is achieved, thereby solving the above-mentioned technical problems in a targeted manner.

[0006] In the first aspect, the present application provides a shell and tube heat exchange assembly, comprising a lower tube box, an upper tube box, and a heat exchanger tube array arranged between the lower tube box and the upper tube box, wherein a propeller, a first sieve plate and a second sieve plate are arranged in the lower tube box, wherein the first sieve plate is arranged in the middle of the lower tube box to divide the lower tube box into a first space at the top and a second space at the bottom, the second sieve plate is arranged in the first space, the blades of the propeller are arranged between the first sieve plate and the second sieve plate, and the first sieve plate and the second sieve plate can be opened and closed to pass and block solid particles respectively.

[0007] In one embodiment of the first aspect, it further includes: a three-pronged bracket, which is arranged in the second space of the lower tube box, and one of the brackets passes through the sieve holes of the first sieve plate to support the propeller, and the other two brackets are supported on the inner wall of the lower tube box.

[0008] In one embodiment of the first aspect, the wall surface of the second sieve plate at the installation contact point with the first sieve plate and the lower pipe box is hollow, and the first sieve plate and the second sieve plate are both composed of two identical semicircular sieve plates, and the two semicircular sieve plates can be driven by the outside to move perpendicularly to the inner wall surface of the lower pipe box in the opposite direction toward the hollow part of the inner wall surface to the outside of the lower pipe box, thereby realizing the opening and closing of the sieve plate.

[0009] In one embodiment of the first aspect, the first sieve plate and the second sieve plate are circular, and have a pore size of 0.6 to 0.8 times the diameter of the solid particles and a thickness of 5 to 10 cm.

[0010] In one embodiment of the first aspect, the cross-sectional shape of the first sieve plate and the second sieve plate is one of a flat type, an upward convex type, a downward convex type, a convex transparent type, and a concave transparent type.

[0011] In one embodiment of the first aspect, the first sieve plate and the second sieve plate are made of one of polyurethane, carbon steel, stainless steel, and manganese steel.

[0012] In one embodiment of the first aspect, the three brackets of the tripod bracket are exactly the same in length and diameter, the length of the bracket is 20 to 50 cm, and the diameter is 0.4 to 0.6 times the length of the heat exchanger tube. The angles between the three brackets are 120° to each other, two of the brackets are respectively fixed on opposite sides of the second space of the lower tube box, and the other bracket passes through the hole at the center of the first sieve plate and is perpendicular to the ground.

[0013] In one embodiment of the first aspect, the installation position of the tripod bracket is approximately 1 / 4 of the height of the lower tube box from the bottom of the lower tube box.

[0014] In one embodiment of the first aspect, the propeller is a fixed-pitch propeller with three or four blades, the diameter of the propeller is 0.5 to 0.7 times the diameter of the lower tube box, and the rotation speed of the propeller is between 60 and 120 r / min.

[0015] In one embodiment of the first aspect, the cross-sectional shape of the propeller blade is one of round-back type, wing type or crescent type.

[0016] In one embodiment of the first aspect, the lower tube box is semi-cylindrical and its height is 0.4 to 0.6 times the tubes of the heat exchanger, and the installation position of the second sieve plate is 5 to 10 cm away from the upper interface of the lower tube box.

[0017] In the second aspect, the present application also provides a self-cleaning fluidized bed heat exchanger including a shell and tube heat exchange assembly of the first aspect and its embodiments, which also includes a liquid-solid separation box, a downcomer, a solid particle tank, a liquid storage tank and a liquid circulation pump, wherein the liquid-solid separation box is connected to the downcomer and the liquid storage tank respectively, the downcomer is connected to the solid particle tank, the liquid in the liquid storage tank is transported to the downcomer box through the liquid circulation pump, and the solid particles in the solid particle tank are mixed with the liquid through an elliptical elbow and then flow into the downcomer box.

[0018] In one embodiment of the second aspect, a spring pile hammer is provided at the inner top of the liquid-solid separation box, and the spring pile hammer is installed at the central axis of the liquid-solid separation box. The maximum extension length of the spring pile hammer is 1.1 to 1.3 times that of the liquid-solid separation box, and its shortest compression length is 0.3 to 0.5 times the maximum extension length. The pile hammer at the bottom of the spring pile hammer is circular, with a diameter of 0.7 to 0.9 times the diameter of the down pipe and a height of 5 to 10 cm. The spring pile hammer has a settling speed of 100 to 200 mm / min.

[0019] In one embodiment of the second aspect, the liquid-solid separation box is a gravity sedimentation separator or a cyclone separator.

[0020] In a third aspect, the present application provides a method for preventing tube-side scaling in a self-cleaning fluidized bed heat exchanger utilizing the second aspect and its embodiments, wherein crude oil is circulated in the heat exchanger tubes and water is circulated in the shell side. The method comprises: passing crude oil from a liquid storage tank through a liquid circulation pump, together with inert solid particles flowing out through an elliptical elbow, into a lower tube box; the solid particles pass through an open first sieve plate and are blocked by a closed second sieve plate, wherein the solid particles between the first and second sieve plates are fully and uniformly mixed and fluidized during this residence time under the stirring of a propeller; and closing the first sieve plate to prevent solid particles that have not been fully mixed from entering the heat exchanger tubes. The second sieve plate is opened to allow the fully and evenly mixed solid particles to enter the heat exchanger tubes. The fully and evenly mixed particles will repeatedly flush the wall of the heat exchanger tubes. Under the flushing of the solid particles, dirt is not easy to adhere to and aggregate on the wall of the heat exchanger tubes. After all the fully and evenly mixed particles have entered the heat exchanger tubes, the first sieve plate is opened again and the second sieve plate is closed to perform a circulation operation. The crude oil in the tube side and the water in the shell side complete the heat exchange, and the solid particles and water are separated in the liquid-solid separation box. The spring pile hammer installed on the top of the liquid-solid separation box will accelerate the sedimentation speed of the particles in the downcomer. Finally, the solid particles and water circulate in the self-cleaning fluidized bed heat exchanger.

[0021] In one embodiment of the third aspect, the bulk density of the solid particles is greater than the density of the circulating liquid and does not react with the medium used in the application.

[0022] In one embodiment of the third aspect, the average diameter of the solid particles is 2 to 3 mm, and the average mass solid content of the solid particles in the self-cleaning fluidized bed heat exchanger is 3% to 7%.

[0023] In one embodiment of the third aspect, the solid particles are one or more of zirconium silicate beads, corundum balls, porcelain balls, steel balls, and engineering plastics.

[0024] In one embodiment of the third aspect, the flow rate of the crude oil in the heat exchanger tubes of the self-cleaning fluidized bed heat exchanger is in a range of 2 m / s to 4 m / s.

[0025] In one embodiment of the third aspect, the second screen plate is opened after the first screen plate is closed for a preset time period.

[0026] Compared with the existing technology, the self-cleaning fluidized bed heat exchanger provided in this application can make solid particles evenly distributed and fully circulated in the fluidized bed heat exchanger, so that the fluidized bed heat exchanger can maintain high heat exchange efficiency over a long period of time. It has the advantages of uniform particle distribution and strong circulation capacity.

[0027] The above technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings, wherein:

[0029] Figure 1 It shows a structural schematic diagram of a self-cleaning fluidized bed heat exchanger according to an embodiment of the present invention;

[0030] Figure 2 A schematic structural diagram of a lower tube box of a self-cleaning shell-and-tube heat exchange assembly according to an embodiment of the present invention is shown;

[0031] Figure 3 Shows a top view and a cross-sectional schematic diagram of a sieve plate of a shell and tube heat exchange assembly according to an embodiment of the present invention;

[0032] Figure 4 A schematic structural diagram of a three-pronged bracket of a shell-and-tube heat exchange assembly according to an embodiment of the present invention is shown;

[0033] Figure 5 A schematic structural diagram of a propeller of a shell-and-tube heat exchange assembly according to an embodiment of the present invention is shown.

[0034] List of reference numerals:

[0035] 100-shell-and-tube heat exchange assembly; 200-fluidized bed heat exchanger; 1-lower tube box; 2-heat exchanger tubes; 3-upper tube box; 4-liquid-solid separation box; 5-down pipe; 6-solid particle tank; 7-liquid storage tank; 8-liquid circulation pump; 9-trident bracket; 10-propeller; 11-first sieve plate; 12-second sieve plate; 13-spring pile hammer; 14-elliptical elbow.

[0036] In the drawings, like reference numerals are used for like parts, but the drawings are not necessarily true to scale. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings.

[0038] Figure 1 FIG. 2 is a schematic structural diagram of a strongly distributed self-cleaning fluidized bed heat exchanger 200 of the present invention. Figure 1 As shown, the strongly distributed self-cleaning fluidized bed heat exchanger 200 consists of a lower tube box 1, heat exchanger tubes 2, an upper tube box 3, a liquid-solid separation box 4, a downcomer 5, a solid particle tank 6, a liquid storage tank 7 and a liquid circulation pump 8. Among them, the lower tube box 1, the heat exchanger tubes 2 and the upper tube box 3 constitute a tube-and-tube heat exchange assembly 100. And as shown Figure 2As shown, the lower tube box 1 includes a tripod bracket 9, a propeller 10, a first sieve plate 11 and a second sieve plate 12. The first sieve plate 11 is installed in the middle of the lower tube box 1 to divide the lower tube box 1 into two spaces. The base of the tripod bracket 9 is installed in the lower part of the lower tube box. The propeller 10 is installed at the tail of the tripod bracket 9 and is located in the upper space divided by the first sieve plate 11. The second sieve plate 1 is installed in the upper part of the lower tube box 1 to separate the lower tube box 1 from the heat exchanger tube 2, and the heat exchanger tube 2 from the upper tube The upper part of the upper pipe box 3 is connected to the liquid-solid separation box 4. A spring pile hammer 13 is installed on the top of the liquid-solid separation box 4. The liquid-solid separation box 4 is divided into two routes. The solid phase in the lower route is connected to the solid particle tank 6 through the downcomer 5, and the liquid phase in the upper route flows into the liquid storage tank 7. The upper entrance is equipped with a sieve plate to prevent solid particles from passing through. The liquid in the liquid storage tank 7 is connected to the lower pipe box 1 through the liquid circulation pump 8. The solid particles in the solid particle tank 6 are mixed with the liquid through the elliptical elbow 14 and then flow into the lower pipe box 1.

[0039] In a preferred embodiment of the present invention, the lower tube box 1 is semi-cylindrical and has a height of 0.4 to 0.6 times that of the heat exchanger tubes 2. The installation position of the second sieve plate 12 is 5 to 10 cm away from the upper interface of the lower tube box 1, and the installation position of the first sieve plate 11 is on the middle line of the lower tube box 1; the wall surface of the installation contact point between the second sieve plate 12, the first sieve plate 11 and the lower tube box 1 is hollow; the installation position of the tripod bracket 9 is approximately 1 / 4 of the height of the lower tube box 1 from the bottom of the lower tube box 1.

[0040] In another embodiment, the first sieve plate 11 and the second sieve plate 12 have exactly the same size specifications, and their diameters are the same as the diameter of the lower tube box 1, wherein the center of the first sieve plate 11 is provided with a hole for the passage of the tripod bracket 9, and the diameter of the hole is 1.1 to 1.3 times the diameter of the tripod bracket; the first sieve plate 11 and the second sieve plate 12 are both composed of two identical semicircular sieve plates, and the two semicircular sieve plates can be driven by the outside to move perpendicularly to the wall of the lower tube box 1 in the opposite direction toward the hollow part of the wall to the outside of the lower tube box, thereby realizing the opening and closing of the sieve plate; the aperture of the sieve plate is 0.6 to 0.8 times the diameter of the solid particles, the thickness is 5 to 10 cm, the front structure is circular, and the side structure is flat, one of the upper convex type, the lower convex type, the convex transparent type, and the concave transparent type (see Figure 3 ), the sieve plate is made of polyurethane, carbon steel, stainless steel, or manganese steel. The first sieve plate 11 and the second sieve plate 12 are switched on and off at regular intervals controlled by an external device; the switching states of the two sieve plates are completely opposite, and each switching state lasts for 3 to 5 seconds.

[0041] In the above technical solution, refer to Figure 4The three brackets of the tripod bracket 9 are exactly the same in length and diameter. The length of the bracket is 20 to 50 cm, and the diameter is 0.4 to 0.6 times the heat exchanger tube 2. The angles between the three brackets are 120°. Two of the brackets are respectively fixed to the left and right sides of the lower part of the lower tube box 1, and the other bracket passes through the hole at the center of the first sieve plate 11 and is perpendicular to the ground.

[0042] Preferably, the propeller 10 is a fixed-pitch propeller with three or four blades, and the shape of the blades is one of a round back section, an airfoil section or a crescent section, such as Figure 5 As shown; the diameter of the propeller is 0.5 to 0.7 times the diameter of the lower tube box 1, and the speed of the propeller is between 60 and 120 r / min.

[0043] Optionally, the liquid-solid separation box 4 is a gravity sedimentation type or a cyclone separator, and the spring pile hammer 13 is installed at the central axis of the separation box 4. The maximum extension length of the spring pile hammer 13 is 1.1 to 1.3 times that of the liquid-solid separation box 4, and the shortest length is 0.3 to 0.5 times the maximum length. The pile hammer at the bottom of the spring pile hammer 13 is circular, with a diameter of 0.7 to 0.9 times the diameter of the downcomer 5 and a height of 5 to 10 cm. The settling speed of the spring pile hammer 13 is 300 to 400 mm / min.

[0044] It should be understood that the bulk density of the inert solid particles used in the strongly distributed self-cleaning fluidized bed heat exchanger is greater than the density of the circulating liquid and does not react with the medium used in the application. Preferably, one or more of zirconium silicate beads, corundum balls, porcelain balls, steel balls, and engineering plastics are used; the average diameter of the solid particles used is 2 to 3 mm; and the average mass solid content of the solid particles in the strongly distributed self-cleaning fluidized bed heat exchanger is 2% to 4%.

[0045] In the method for preventing tube-side scaling using a strongly distributed self-cleaning fluidized bed heat exchanger provided by the present invention, crude oil circulates in the tubes of the strongly distributed self-cleaning fluidized bed heat exchanger, and cooling water circulates in the shell side.

[0046] In the above method, crude oil flows from the liquid storage tank 7 through the liquid circulation pump 8 and then enters the lower pipe box 1 together with the inert solid particles flowing out through the elliptical elbow 14. The particles first pass through the open first sieve plate 11 and are blocked by the closed second sieve plate 12. At this time, the particles between the first sieve plate 11 and the second sieve plate 12 will be fully and evenly mixed and fluidized under the stirring of the propeller 10 during this residence time; the first sieve plate 11 will be closed (preferably closed for a preset time period, such as 5 minutes or 10 minutes) to prevent the particles that are not fully mixed from entering the heat exchanger tubes 2; then the second sieve plate 12 will be opened to allow the fully mixed particles to enter Enter the heat exchanger tube 2; after all the fully and evenly mixed particles have entered the heat exchanger tube 2, the first sieve plate 11 will be opened again and the second sieve plate 12 will be closed again to perform a circulation operation; the fully and evenly mixed particles will repeatedly flush the wall of the heat exchanger tube 2. Under the flushing of the solid particles, dirt is not easy to adhere to the wall of the heat exchanger tube 2; the crude oil in the tube side and the water in the shell side complete heat exchange; the solid particles and water are separated in the liquid-solid separation box 4, and the spring pile hammer 13 installed on the top of the liquid-solid separation box 4 will accelerate the sedimentation speed of the particles in the downcomer 5. Finally, the solid particles and water circulate in the strongly distributed self-cleaning fluidized bed heat exchanger.

[0047] In the above method, solid particles circulate in a strongly distributed self-cleaning fluidized bed heat exchanger, and the liquid crude oil can be partially extracted from the liquid storage tank and sent to a subsequent system, or it can be left unextracted and all used to complete the cycle.

[0048] In the above method, the flow rate of the crude oil in the heat exchanger tubes 2 of the strongly distributed self-cleaning fluidized bed heat exchanger is in the range of 2 m / s to 4 m / s.

[0049] In the technical solution and method of the present invention, the heat transfer coefficient is calculated based on the temperature difference between the inner wall temperature and the mainstream temperature and the heat flux, and the scaling condition of the tube is judged based on the change pattern of the heat transfer coefficient over time, thereby serving as a basis for judging the ability to maintain the heat transfer effect over a long period of time.

[0050] By adopting the technical solution of the present invention, a strongly distributed self-cleaning fluidized bed heat exchanger consisting of a lower tube box 1, a heat exchanger tube array 2, an upper tube box 3, a liquid-solid separation box 4, a downcomer 5, a solid particle tank 6, a liquid storage tank 7, and a liquid circulation pump 8 is provided. A tripod bracket 9, a propeller 10, and a first sieve plate 11 and a second sieve plate 12 are installed in the lower tube box 1, and a spring pile hammer 13 is installed in the liquid storage tank 7. The heat transfer coefficient of the highly distributed self-cleaning fluidized bed heat exchanger is maintained at 94% of the original after 200 days of continuous operation.

[0051] The present invention is further described below by way of examples and comparative examples, but the method of the present invention is not limited thereto.

[0052] [Example 1]

[0053] use Figure 1 The strongly distributed self-cleaning fluidized bed heat exchanger shown is used in the top heat exchanger of a certain factory's constant pressure reduction device. 208 heat exchanger tubes are arranged inside the strongly distributed self-cleaning fluidized bed heat exchanger. Each tube is 2000mm long and has a diameter of Φ25×2.5mm. The tube bundles are arranged in a right triangle. The lower tube box is 1000mm high and 700mm wide. The solid particles are zirconium silicate with an average particle size of 2.5mm. The average volume solid content of the solid particles in the strongly distributed self-cleaning fluidized bed heat exchanger is 4%. The liquid phase is crude oil with a flow rate of 2.5m / s. The double sieve plate is made of polyurethane. The second sieve plate is 50mm away from the upper interface of the lower tube box. The thickness of the two plates is 5cm, and the side structure is Figure 3 The plane type shown has a switching cycle of 4s. The length of the tripod is 40cm and the diameter is 15mm. The propeller used is Figure 5 The four-blade circular back section shown has a propeller diameter of 500 mm and a rotational speed of 100 rpm. The liquid-solid separation chamber uses gravity settling, with a spring hammer of 80 mm in diameter and 6 cm in height, a settling rate of 100 mm / min, and a downpipe diameter of 100 mm. Under these conditions, the heat transfer coefficient remained at 93% of its original value after 180 days of continuous operation.

[0054] [Example 2]

[0055] The same strongly distributed self-cleaning fluidized bed heat exchanger as in Example 1 was used in the top heat exchanger of a certain factory's atmospheric and vacuum unit. The solid particles were corundum balls with an average particle size of 4 mm. The average volume solid content of the solid particles in the strongly distributed self-cleaning fluidized bed heat exchanger was 5%. The liquid phase was crude oil with a flow rate of 3.5 m / s. The double sieve plates were made of stainless steel. The second sieve plate was 70 mm from the upper interface of the lower tube box. The thickness of the two plates was 8 cm. The side structure was Figure 3 The convex type shown has a switching cycle of 5s. Figure 4 ) is 35cm long and 15mm in diameter, and the propeller used is Figure 5 The three-bladed airfoil section shown has a propeller diameter of 600 mm and a rotational speed of 120 rpm. The liquid-solid separation chamber uses gravity settling, with a spring hammer of 90 mm in diameter and 4 cm in height, a settling rate of 150 mm / min, and a downpipe diameter of 100 mm. Under these conditions, the heat transfer coefficient remained at 95% of its original value after 210 days of continuous operation.

[0056] [Comparative Example 1]

[0057] A fluidized bed heat exchanger was used as the top heat exchanger in a factory's atmospheric and vacuum unit. This fluidized bed heat exchanger was similar to the highly distributed, self-cleaning fluidized bed heat exchanger in Example 1, except that the sieve plate, tripod support, propeller, and spring hammer were omitted. The solid particles used were zirconium silicate with an average particle size of 3 mm. The average volume solids content of the solid particles within the highly distributed, self-cleaning fluidized bed heat exchanger was 5%. The liquid phase was crude oil at a flow rate of 3 m / s. Under these conditions, the heat transfer coefficient was reduced to 69% of the original value after 180 days of continuous operation.

[0058] [Comparative Example 2]

[0059] A fluidized bed heat exchanger was used as the top heat exchanger for a factory's atmospheric and vacuum unit. This fluidized bed heat exchanger was similar to the highly distributed, self-cleaning fluidized bed heat exchanger in Example 1, featuring the same three-pronged support and propeller configuration, but without the double sieve plates and spring hammer. The solid particles used were zirconium silicate with an average particle size of 3 mm. The average volume solids content within the highly distributed, self-cleaning fluidized bed heat exchanger was 5%. The liquid phase was crude oil at a flow rate of 3 m / s. Under these conditions, the heat transfer coefficient decreased to 77% of the original value after 200 days of continuous operation.

[0060] [Comparative Example 3]

[0061] A fluidized bed heat exchanger was used as the top heat exchanger of a factory's atmospheric and vacuum unit. This fluidized bed heat exchanger was similar to the highly distributed, self-cleaning fluidized bed heat exchanger in Example 1, equipped with double sieve plates of the same specifications, but without the tripod support, propeller, and spring hammer. The solid particles used were zirconium silicate with an average particle size of 2.5 mm. The average volume solids content of the solid particles within the highly distributed, self-cleaning fluidized bed heat exchanger was 5%. The liquid phase was crude oil at a flow rate of 2.5 m / s. Under these conditions, the heat transfer coefficient was 73% of the original value after 210 days of continuous operation.

[0062] In the description of the present invention, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "back", "inside", "outside", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention.

[0063] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A tube-and-tube heat exchange assembly, comprising a lower tube box (1), an upper tube box (3), and heat exchanger tubes (2) arranged between the lower tube box (1) and the upper tube box (3), characterized in that: A propeller (10), a first sieve plate (11) and a second sieve plate (12) are provided in the lower tube box (1), wherein the first sieve plate (11) is provided in the middle of the lower tube box (1) to divide the lower tube box (1) into an upper first space and a lower second space, the second sieve plate (12) is provided in the first space, the blades of the propeller (10) are provided between the first sieve plate (11) and the second sieve plate (12), the first sieve plate (11) and the second sieve plate (12) can be alternately opened and closed to respectively pass and block solid particles, and the first sieve plate (11) and the second sieve plate (12) can be closed simultaneously so that the solid particles between the first sieve plate (11) and the second sieve plate (12) are fully and uniformly mixed and fluidized under the stirring of the propeller (10) during the residence time; The wall surface at the installation contact point between the first sieve plate (11), the second sieve plate (12) and the lower tube box (1) is hollow, and the first sieve plate (11) and the second sieve plate (12) are both composed of two identical semicircular sieve plates, and the two semicircular sieve plates can be driven by the outside to move perpendicularly to the inner wall surface of the lower tube box (1) and in the opposite direction toward the hollow part of the inner wall surface to the outside of the lower tube box (1), thereby realizing the opening and closing of the sieve plates; The solid particles are one or more of zirconium silicate beads, corundum balls, porcelain balls, steel balls, and engineering plastics.

2. The shell and tube heat exchange assembly according to claim 1, characterized in that: The first sieve plate (11) and the second sieve plate (12) are circular, and have an aperture of 0.6 to 0.8 times the diameter of the solid particles, and a thickness of 5 to 10 cm.

3. The shell and tube heat exchange assembly according to claim 2, characterized in that: The cross-sectional shape of the first sieve plate (11) and the second sieve plate (12) is one of a flat type, an upward convex type, a downward convex type, a convex transparent type, and a concave transparent type.

4. The shell and tube heat exchange assembly according to claim 3, characterized in that: The first sieve plate (11) and the second sieve plate (12) are made of one of polyurethane, carbon steel, stainless steel, and manganese steel.

5. The shell and tube heat exchange assembly according to any one of claims 1 to 4, characterized in that: Also includes: A three-pronged bracket (9) is arranged in the second space of the lower tube box (1), and one bracket thereof passes through the through hole of the first screen plate (11) to support the propeller, and the other two brackets thereof are supported on the inner wall of the lower tube box (1).

6. The shell and tube heat exchange assembly according to claim 5, characterized in that: The three brackets of the tripod bracket (9) are identical in length and diameter. The length of the bracket is 20 to 50 cm, and the diameter is 0.4 to 0.6 times the length of the heat exchanger tube (2). The angles between the three brackets are 120 degrees. Two of the brackets are fixed on opposite sides of the second space of the lower tube box (1), and the other bracket passes through the hole at the center of the first sieve plate (11) and is perpendicular to the ground.

7. The shell and tube heat exchange assembly according to claim 6, characterized in that: The installation position of the tripod bracket (9) is 1 / 4 of the height of the lower tube box (1) from the bottom of the lower tube box (1).

8. The shell and tube heat exchange assembly according to any one of claims 1 to 4, characterized in that: The propeller (10) is a fixed-pitch propeller having three or four blades, the diameter of the blade being 0.5 to 0.7 times the diameter of the lower tube box (1), and the rotation speed of the propeller being between 60 and 120 r / min.

9. The shell and tube heat exchange assembly according to claim 8, characterized in that: The cross-sectional shape of the blades of the propeller (10) is one of a round-back type, an airfoil type, or a crescent type.

10. The shell and tube heat exchange assembly according to claim 9, characterized in that: The lower tube box (1) is semi-cylindrical and its height is 0.4 to 0.6 times that of the heat exchanger tubes (2). The installation position of the second sieve plate (12) is 5 to 10 cm away from the upper interface of the lower tube box (1).

11. A fluidized bed heat exchanger comprising the shell and tube heat exchange assembly according to any one of claims 1 to 10, characterized in that: It also includes a liquid-solid separation box (4), a downcomer (5), a solid particle tank (6), a liquid storage tank (7) and a liquid circulation pump (8), wherein the liquid-solid separation box (4) is connected to the downcomer (5) and the liquid storage tank (7) respectively, the downcomer (5) is connected to the solid particle tank (6), the liquid in the liquid storage tank (7) is transported to the downcomer box (1) through the liquid circulation pump (8), and the solid particles in the solid particle tank (6) are mixed with the liquid through the elliptical elbow (14) and then flow into the downcomer box (1).

12. The fluidized bed heat exchanger according to claim 11, characterized in that A spring pile hammer (13) is provided on the inner top of the liquid-solid separation box (4). The spring pile hammer (13) is installed at the central axis of the liquid-solid separation box (4). The maximum extension length of the spring pile hammer (13) is 1.1 to 1.3 times that of the liquid-solid separation box (4), and the shortest compression length thereof is 0.3 to 0.5 times the maximum extension length. The pile hammer at the bottom of the spring pile hammer (13) is circular, with a diameter of 0.7 to 0.9 times the diameter of the down pipe (5) and a height of 5 to 10 cm. The spring pile hammer (13) has a settling speed of 100 to 200 mm / min.

13. The fluidized bed heat exchanger according to claim 12, characterized in that The liquid-solid separation box (4) is a gravity sedimentation separator or a cyclone separator.

14. A method for preventing tube-side scaling using a fluidized bed heat exchanger according to any one of claims 11 to 13, characterized in that: Crude oil is circulated in the heat exchanger tubes (2), and water is circulated in the shell side. The method comprises: The crude oil is passed from the liquid storage tank (7) through the liquid circulation pump (8) and then enters the lower pipe box (1) together with the inert solid particles flowing out through the elliptical elbow (14); The solid particles pass through the opened first sieve plate (11) and are blocked by the closed second sieve plate (12). During this residence time, the solid particles between the first sieve plate (11) and the second sieve plate (12) are fully and uniformly mixed and fluidized under the stirring of the propeller (10); Closing the first sieve plate (11) to prevent solid particles that are not fully mixed from entering the heat exchanger tubes (2); The second sieve plate (12) is opened to allow the fully and evenly mixed solid particles to enter the heat exchanger tubes (2). The fully and evenly mixed particles will repeatedly flush the wall surface of the heat exchanger tubes (2). Under the flushing of the solid particles, dirt is not easy to adhere to the wall surface of the heat exchanger tubes (2); After all the fully and evenly mixed particles have entered the heat exchanger tubes (2), the first sieve plate (11) is opened again and the second sieve plate (12) is closed to perform a circulation operation; and The crude oil in the tube side and the water in the shell side complete heat exchange, the solid particles and water are separated in the liquid-solid separation box (4), the spring pile hammer (13) installed on the top of the liquid-solid separation box (4) will accelerate the sedimentation speed of the particles in the downcomer (5), and finally the solid particles and water circulate in the fluidized bed heat exchanger.

15. The method according to claim 14, characterized in that The bulk density of the solid particles is greater than the density of the circulating liquid and does not react with the medium used in the application.

16. The method according to claim 15, characterized in that The average diameter of the solid particles is 2-3 mm, and the average mass solid content of the solid particles in the fluidized bed heat exchanger is 3%-7%.

17. The method according to claim 16, wherein The flow rate of crude oil in the heat exchanger tubes (2) in the fluidized bed heat exchanger ranges from 2 m / s to 4 m / s.

18. The method according to claim 14, characterized in that After the first screen plate (11) is closed for a preset period of time, the second screen plate (12) is opened.

Images