CN112710176A

CN112710176A - Tube nest heat exchange assembly, fluidized bed heat exchanger and method for preventing tube side scaling

Info

Publication number: CN112710176A
Application number: CN201911025321.6A
Authority: CN
Inventors: 罗城静彦; 顾军民; 裴义霞; 张斌
Original assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Current assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Priority date: 2019-10-25
Filing date: 2019-10-25
Publication date: 2021-04-27

Abstract

The application provides a tube array heat exchange assembly, a fluidized bed heat exchanger and a method for preventing tube pass from scaling, the heat exchanger comprises a lower tube box, a heat exchanger tube array, an upper tube box, a liquid-solid separation box, a downcomer, a solid particle groove, a liquid storage tank, a liquid circulating pump, a three-fork support, a propeller, a first sieve plate, a second sieve plate, a spring pile hammer and an oval elbow, wherein the heat exchanger tube array is connected with the upper tube box, the upper part of the upper tube box is connected with the liquid-solid separation box, solid particles enter the solid particle groove through the downcomer, and then enter the lower tube box together with liquid flowing from the liquid storage tank under the action of the liquid circulating pump.

Description

Tube nest heat exchange assembly, fluidized bed heat exchanger and method for preventing tube side scaling

Technical Field

The invention relates to the field of chemical engineering, in particular to a tubular heat exchange assembly, a fluidized bed heat exchanger and a method for preventing and controlling tube side scaling, belonging to the field of long-period operation of chemical heat exchange equipment.

Background

Heat exchangers are widely used in the field of petrochemical industry. However, after long-term use, the phenomenon of adhesion and scaling inevitably occurs inside the heat exchanger, so that the heat transfer resistance inside the heat exchanger is greatly increased, the heat exchange efficiency of the heat exchanger is greatly reduced, and the normal use of the heat exchanger is seriously affected.

The fluidized bed heat exchanger with the self-cleaning descaling capacity is developed, so that the thermal resistance in the heat exchanger can be effectively reduced, the reduction of the heat exchange efficiency of the heat exchanger is prevented, the service life of the heat exchanger equipment in one cycle is prolonged, and the fluidized bed heat exchanger has great economic benefit. Document US005676201A discloses an external circulating fluidized bed heat exchanger, which however fails to adequately take into account the problem of uniform distribution of solid particles and is therefore not capable of maintaining high heat transfer efficiency over long periods of use. Document CN202709856U discloses a horizontal liquid-solid circulating fluidized bed heat exchanger using a Kenics static mixer, however, the circulating fluidized bed heat exchanger has poor circulation and distribution effects, and the Kenics static mixer can only be used for a horizontal heat exchanger, and the application range is not wide. Document CN20160710754 discloses an external circulation type fluidized bed heat exchanger with a spherical floating plug and an arc baffle, which fails to fully consider the problem of uniform distribution of tube passes of the heat exchanger, and thus has poor heat exchange effect under a long period. Document CN106595350A discloses a liquid-solid circulating fluidized bed heat exchanger with a distribution box and a distribution plate, which has a good particle distribution effect, so that the problem of particle circulation cannot be fully considered, and the heat transfer efficiency of the heat exchanger is low.

In summary, solving the problems of uniform distribution and sufficient circulation of solid particles is one of the key technologies for maintaining high heat transfer efficiency of a fluidized bed heat exchanger for a long period of time, and the prior art fails to sufficiently solve the problems.

Disclosure of Invention

Aiming at the problems in the prior art, the application provides a tube nest heat exchange assembly, a fluidized bed heat exchanger and a method for preventing tube side scaling, which aim to solve the technical problems by realizing the uniform distribution and sufficient circulation of solid particles in the fluidized bed heat exchanger through structures such as double sieve plates, a trident bracket with a propeller, a spring pile hammer and the like.

In a first aspect, the application provides a tube nest heat transfer unit, be in including lower tube case, upper tube case and setting lower tube case with heat exchanger tube nest between the upper tube case be provided with propeller, first sieve and second sieve in the lower tube case, wherein, first sieve sets up the middle part of lower tube case is in order with the first space of lower tube case partition part and the second space of lower part, the second sieve sets up in the first space, the paddle of propeller set up in first sieve with between the second sieve, first sieve with the second sieve can be opened and close in order to pass through respectively and block solid particle.

In one embodiment of the first aspect, the method further comprises: and the three-fork bracket is arranged in the second space of the lower channel box, one bracket penetrates 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 channel box.

In an embodiment of the first aspect, a wall surface of a mounting contact position of the second screen plate with the first screen plate and the lower tube box is hollow, the first screen plate and the second screen plate are both composed of two identical semicircular screen plates, and the two semicircular screen plates can be driven by the outside to respectively be perpendicular to an inner wall surface of the lower tube box and perform translational motion towards the hollow position of the inner wall surface in a reverse direction to the outside of the lower tube box, so that the screen plates are opened and closed.

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

In an embodiment of the first aspect, a cross-sectional shape of the first screen plate and the second screen plate is one of a planar type, a convex-upward type, a convex-downward type, a convex-through type, and a concave-through type.

In one embodiment of the first aspect, the first screen deck and the second screen deck are made of one of polyurethane, carbon steel, stainless steel, manganese steel.

In one embodiment of the first aspect, the three supports of the three-prong support have the same length and diameter, the length of the support is 20-50 cm, the diameter of the support is 0.4-0.6 times of that of the heat exchanger tube array, the angles between the three supports are 120 ° with each other, two of the three supports are respectively fixed on the opposite sides of the second space of the lower tube box, and the other support passes through a hole at the center of the first screen plate and is perpendicular to the ground.

In one embodiment of the first aspect, the three-prong support is mounted at a location that is about 1/4 the height of the lower header tank from the bottom of the lower header tank.

In one embodiment of the first aspect, the propeller is a fixed pitch propeller, and has three or four blades, the diameter of the propeller is 0.5 to 0.7 times the diameter of the lower header, and the rotating speed of the propeller is between 60 and 120 r/min.

In one embodiment of the first aspect, the blades of the propeller have a cross-sectional shape of one of a dorsal, aerofoil or crescent.

In one embodiment of the first aspect, the lower tube box is semi-cylindrical and has a height of 0.4 to 0.6 times of the heat exchanger tubes, and the second screen plate is installed at a distance of 5 to 10cm from an upper interface of the lower tube box.

In a second aspect, the present application further provides a self-cleaning fluidized bed heat exchanger including the tube nest heat exchange assembly of the first aspect and the embodiment thereof, and further includes a liquid-solid separation tank, a downcomer, a solid particle tank, a liquid storage tank and a liquid circulation pump, wherein the liquid-solid separation tank is respectively connected to the downcomer and the liquid storage tank, the downcomer is connected to the solid particle tank, the liquid in the liquid storage tank is conveyed to the downcomer through the liquid circulation pump, and the solid particles in the solid particle tank flow into the downcomer after being mixed with the liquid through an elliptical bend.

In an embodiment of the second aspect, a spring pile hammer is arranged at the top of the inner side of the liquid-solid separation box, the spring pile hammer is arranged at the central shaft of the liquid-solid separation box, the maximum extension length of the spring pile hammer is 1.1-1.3 times of that of the liquid-solid separation box, the shortest compression length of the spring pile hammer is 0.3-0.5 times of the maximum extension length, the pile hammer at the bottom of the spring pile hammer is circular, the diameter of the pile hammer is 0.7-0.9 times of the diameter of the downcomer, the height of the pile hammer is 5-10 cm, and the settling speed of the spring pile hammer is 100-200 mm/min.

In one embodiment of the second aspect, the liquid-solid separation tank is a gravity settler separator or a cyclone separator.

In a third aspect, the present application provides a method for preventing tube-side scaling using the self-cleaning fluidized bed heat exchanger of the second aspect and embodiments thereof, wherein crude oil is circulated in the heat exchanger tubes and water is circulated in the shell side; the method comprises the following steps: crude oil passes through a liquid circulating pump from a liquid storage tank and then enters a lower pipe box together with inert solid particles flowing out through an elliptic elbow; the solid particles pass through the opened first sieve plate and are blocked by the closed second sieve plate, and the solid particles between the first sieve plate and the second sieve plate are fully and uniformly mixed and fluidized under the stirring of a propeller during the residence time; closing the first screen plate to prevent solid particles which are not sufficiently uniformly mixed from entering the heat exchanger tubes; the second sieve plate is opened so that the fully and uniformly mixed solid particles enter the heat exchanger tube array, the fully and uniformly mixed particles can repeatedly scour the wall surface of the heat exchanger tube array, and dirt is not easy to adhere and agglomerate on the wall surface of the heat exchanger tube array under the scouring of the solid particles; after the fully and uniformly mixed particles completely enter the heat exchanger tube nest, opening the first sieve plate again and closing the second sieve plate to perform circulating operation; and the crude oil in the tube pass and the water in the shell pass complete heat exchange, solid particles and water are separated in the liquid-solid separation box, a spring pile hammer arranged at the top of the liquid-solid separation box can accelerate the settling velocity of the particles in the descending tube, and finally the solid particles and the water circulate in the self-cleaning fluidized bed heat exchanger.

In one embodiment of the third aspect, the solid particles have a bulk density greater than that of the fluid flowing through and are non-reactive with the media used in the application.

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

In an 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.

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

In one embodiment of the third aspect, the second screening deck is opened after the first screening deck is closed for a preset period of time.

The application provides a self-cleaning formula fluidized bed heat exchanger compares in prior art, can make solid particle evenly distributed and abundant circulation in fluidized bed heat exchanger, lets fluidized bed heat exchanger keep high heat exchange efficiency's technical characterstic under long period, has that the particle distribution is even, advantage that the circulation ability is strong.

The features mentioned above can be combined in various suitable ways or replaced by equivalent features as long as the object of the invention is achieved.

Drawings

The invention will be described in more detail hereinafter on the basis of embodiments and with reference to the accompanying drawings. Wherein:

FIG. 1 shows a schematic structural view of a self-cleaning fluidized bed heat exchanger according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a lower tube box of the self-cleaning tube nest heat exchange assembly according to the embodiment of the invention;

FIG. 3 shows a top view and a schematic cross-sectional view of a screen deck of a tube and tube heat exchange assembly according to an embodiment of the invention;

FIG. 4 shows a schematic structural diagram of a trifurcated rack of a tube array heat exchange assembly according to an embodiment of the invention;

fig. 5 shows a schematic structural diagram of a propeller of the tube array heat exchange assembly according to the embodiment of the invention.

List of reference numerals:

100-tube array heat exchange assemblies; 200-a fluidized bed heat exchanger; 1-a lower tube box; 2-heat exchanger tubes; 3, feeding a tube box; 4-liquid-solid separation tank; 5-a downcomer; 6-solid particle tank; 7-a liquid reservoir; 8-liquid circulation pump; 9-a three-prong stent; 10-a propeller; 11-a first screen deck; 12-a second screen deck; 13-spring pile hammer; 14-elliptical elbow.

In the drawings, like parts are provided with like reference numerals. The drawings are not to scale.

Detailed Description

The invention will be further explained with reference to the drawings.

Fig. 1 is a schematic structural diagram of a strong distribution self-cleaning fluidized bed heat exchanger 200 according to the present invention. As shown in fig. 1, the strong distribution self-cleaning fluidized bed heat exchanger 200 is composed 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 circulating pump 8. Wherein, lower tube box 1, heat exchanger tube array 2 and upper tube box 3 constitute shell and tube heat exchange assembly 100. And as shown in fig. 2, the lower tube box 1 comprises a three-way support 9, a propeller 10, and 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 three-way support 9 is installed in the lower portion of the lower tube box, the propeller 10 is installed at the tail portion of the three-way support 9 and located in the upper space divided by the first sieve plate 11, the second sieve plate 1 is installed at the upper portion of the lower tube box 1 to separate the lower tube box 1 from the heat exchanger tubes 2, the heat exchanger tubes 2 are connected to the upper tube box 3, the upper portion of the upper tube box 3 is connected to the liquid-solid separation box 4, the top of the liquid-solid separation box 4 is provided with a spring pile hammer 13, the liquid-solid separation box 4 is divided into two paths, the lower path is connected to the solid particle tank 6 by the solid phase through the descending tube 5, the liquid in the liquid storage tank 7 is connected to the lower header 1 by the liquid circulation pump 8, and the solid particles in the solid particle tank 6 are mixed with the liquid by the elliptical elbow 14 and then flow into the lower header 1.

In a preferred embodiment of the invention, the lower tube box 1 is semi-cylindrical, the height of the lower tube box is 0.4-0.6 times of that of the heat exchanger tubes 2, the installation position of the second sieve plate 12 is 5-10 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 part of the second sieve plate 12, the first sieve plate 11 and the lower pipe box 1 is hollow; the three-prong support 9 is mounted at a position about 1/4 of the height of the lower channel 1 from the bottom of the lower channel 1.

In another embodiment, the first sieve plate 11 and the second sieve plate 12 have the same size and specification, and the diameters of the first sieve plate and the second sieve plate are the same as the diameter of the lower pipe box 1, wherein a hole for the three-fork support 9 to pass through is arranged at the center of the circle of the first sieve plate 11, and the diameter of the hole is 1.1-1.3 times of the diameter of the three-fork support; 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 respectively move in a translational manner perpendicular to the wall surface of the lower pipe box 1 and reversely towards the hollow part of the wall surface to the outside of the lower pipe box, so that the sieve plates are opened and closed; the aperture of the sieve plate is 0.6-0.8 times of the diameter of the solid particles, the thickness of the sieve plate is 5-10 cm, the front structure is circular, the side structure is planar, convex downward, convex and concave (see figure 3), and the sieve plate is made of one of polyurethane, carbon steel, stainless steel and manganese steel. The first sieve plate 11 and the second sieve plate 12 are controlled by the outside to be switched on and off at regular time; the opening and closing states of the two sieve plates are completely opposite, and the duration time of each opening and closing state is 3-5 s.

In the above technical solution, referring to fig. 4, the three supports of the three-prong support 9 have the same length and diameter, the length of the support is 20-50 cm, the diameter is 0.4-0.6 times of that of the heat exchanger tube array 2, the angles between the three supports are 120 ° with each other, two of the supports are respectively fixed on the left and right sides of the lower portion of the lower tube box 1, and the other support passes through a hole at the center of the first sieve plate 11 and is perpendicular to the ground.

Preferably, the propeller 10 is a fixed-pitch propeller, and has three or four blades, and the shape of the blades is one of a circular back type tangent plane, a wing type tangent plane or a crescent type tangent plane, as shown in fig. 5; the diameter of the propeller is 0.5-0.7 times of that of the lower pipe box 1, and the rotating speed of the propeller is 60-120 r/min.

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

It is understood that the bulk density of the inert solid particles used by the strong distribution self-cleaning fluidized bed heat exchanger is larger than that of the circulating liquid, and the inert solid particles do not react with the used medium of the used occasion, and one or more of zirconium silicate beads, corundum balls, ceramic balls, steel balls and engineering plastics are preferably selected; the average diameter of the used solid particles is 2-3 mm; the average mass solid content of the solid particles in the strongly distributed self-cleaning fluidized bed heat exchanger is 2-4%.

In the method for preventing tube side scaling by adopting the strongly distributed self-cleaning fluidized bed heat exchanger, crude oil circulates in the tube of the strongly distributed self-cleaning fluidized bed heat exchanger, and cooling water circulates in the shell side.

In the method, crude oil passes through a liquid circulating pump 8 from a liquid storage tank 7 and then enters a lower pipe box 1 together with inert solid particles flowing out through an elliptic elbow 14, the particles firstly pass through an opened first sieve plate 11 and are blocked by a closed second sieve plate 12, and the particles between the first sieve plate 11 and the second sieve plate 12 are fully and uniformly mixed and fluidized in the retention time under the stirring of a propeller 10; the first screen plate 11 will be closed (preferably for a preset period of time, such as 5min or 10min) to prevent insufficiently uniformly mixed particles from entering the heat exchanger tubes 2; then the second sieve plate 12 is opened, so that the fully and uniformly mixed particles enter the heat exchanger tube array 2; after the fully and uniformly mixed particles completely enter the heat exchanger tube array 2, the first sieve plate 11 is opened again, and the second sieve plate 12 is closed again for cycle operation; the particles which are fully and uniformly mixed can repeatedly wash the wall surface of the heat exchanger tube array 2, and dirt is not easy to adhere and agglomerate on the wall surface of the heat exchanger tube array 2 under the washing of solid particles; the heat exchange between the crude oil in the tube pass and the water in the shell pass is completed; solid particles and water are separated in the liquid-solid separation box 4, the spring pile hammer 13 arranged at the top of the liquid-solid separation box 4 can accelerate the sedimentation speed of the particles in the descending pipe 5, and finally the solid particles and the water circulate in the strongly-distributed self-cleaning fluidized bed heat exchanger.

In the method, the solid particles circulate in the strongly distributed self-cleaning fluidized bed heat exchanger, and the liquid-phase crude oil can be partially pumped out from the liquid storage tank and is sent to a subsequent system, or can not be pumped out, and all the liquid-phase crude oil is used for completing circulation.

In the method, the flow velocity range of the crude oil in the heat exchanger tube 2 in the strongly distributed self-cleaning fluidized bed heat exchanger is between 2m/s and 4 m/s.

In the technical scheme and the method, the heat transfer coefficient is calculated by the temperature difference between the inner wall temperature and the main stream temperature and the heat flux, and the tube side scaling condition is judged according to the change rule of the heat transfer coefficient along with time, so that the judgment basis for maintaining the heat transfer effect capability under a long period is provided.

By adopting the technical scheme of the invention, the strongly distributed self-cleaning fluidized bed heat exchanger comprises 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 groove 6, a liquid storage tank 7 and a liquid circulating pump 8, wherein a three-fork support 9, a propeller 10, a first sieve plate 11 and a second sieve plate 12 are arranged in the lower tube box 1, and a spring pile hammer 13 is arranged in the liquid storage tank 7, so that the better technical effect that the heat transfer coefficient is still 94% of the original heat transfer coefficient after the continuous operation for 200 days is achieved.

The invention is further illustrated by the following examples and comparative examples, without however being limited thereto.

[ example 1 ]

The strong distribution self-cleaning fluidized bed heat exchanger shown in FIG. 1 is applied to a top heat exchanger of an atmospheric and vacuum distillation plant of a certain plant, 208 heat exchanger tubes are arranged in the strong distribution self-cleaning fluidized bed heat exchanger, each tube is 2000mm long, the tube diameter is phi 25 multiplied by 2.5mm, and the tube bundles are arranged in a regular triangle. The height of the lower pipe box is 1000mm, and the width of the lower pipe box is 700 mm. The solid particles adopt zirconium silicate, the average particle size is 2.5mm, and the average volume solid content of the solid particles in the strongly distributed self-cleaning fluidized bed heat exchanger is 4%. The liquid phase was crude oil and the flow rate was 2.5 m/s. The double sieve plates are made of polyurethane, the distance between the second sieve plate and the upper interface of the lower pipe box is 50mm, the thickness of the two sieve plates is 5cm, the side structure is a plane type shown in figure 3, and the switching period is 4 s. The length of the three-fork support is 40cm, the diameter of the three-fork support is 15mm, the used propeller is a four-blade round back type tangent plane shown in fig. 5, the diameter of the propeller is 500mm, and the rotating speed is 100 r/min. The liquid-solid separation box adopts a gravity settling type, the diameter of the spring pile hammer is 80mm, the height of the spring pile hammer is 6cm, the settling speed is 100mm/min, and the pipe diameter of the downcomer is 100 mm. Under this condition, the heat transfer coefficient after 180 days of continuous operation was 93%.

[ example 2 ]

The same strongly distributed self-cleaning fluidized bed heat exchanger as in example 1 was used for the top heat exchanger of an atmospheric and vacuum distillation plant of a certain plant, the solid particles were corundum balls, the average particle size was 4mm, and 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 and the flow rate was 3.5 m/s. The double sieve plates are made of stainless steel, the distance between the second sieve plate and the upper interface of the lower tube box is 70mm, the thicknesses of the two sieve plates are 8cm, the side surface structure is a convex type shown in figure 3, and the switching period is 5 s. The length of the three-fork support (figure 4) is 35cm, the diameter is 15mm, the propeller is a three-blade wing type tangent plane shown in figure 5, the diameter of the propeller is 600mm, and the rotating speed is 120 r/min. The liquid-solid separation box adopts a gravity settling type, the diameter of the spring pile hammer is 90mm, the height of the spring pile hammer is 4cm, the settling speed is 150mm/min, and the pipe diameter of the downcomer is 100 mm. Under the condition, the heat transfer coefficient after the continuous operation for 210 days is 95 percent of the original heat transfer coefficient.

Comparative example 1

The fluidized bed heat exchanger is applied to a top heat exchanger of an atmospheric and vacuum device of a certain plant. The fluidized bed heat exchanger refers to a strong distribution self-cleaning fluidized bed heat exchanger as in example 1, except that no sieve plate, no three-fork bracket, no propeller and no spring pile hammer are arranged. The solid particles adopt zirconium silicate, the average particle size is 3mm, and the average volume solid content of the solid particles in the strongly distributed self-cleaning fluidized bed heat exchanger is 5 percent. The liquid phase is crude oil, and the flow velocity is 3 m/s. Under the condition, the heat transfer coefficient is 69 percent after the continuous operation for 180 days.

Comparative example 2

The fluidized bed heat exchanger is applied to a top heat exchanger of an atmospheric and vacuum device of a certain plant. The fluidized bed heat exchanger refers to the same strongly distributed self-cleaning fluidized bed heat exchanger as in example 1, and is provided with the same three-fork bracket and propeller but no double sieve plate, and spring pile hammer. The solid particles adopt zirconium silicate, the average particle size is 3mm, and the average volume solid content of the solid particles in the strongly distributed self-cleaning fluidized bed heat exchanger is 5 percent. The liquid phase is crude oil, the flow rate is 3m/s under the condition, and the heat transfer coefficient is 77 percent of the original heat transfer coefficient after continuous operation for 200 days.

Comparative example 3

The fluidized bed heat exchanger is applied to a top heat exchanger of an atmospheric and vacuum device of a certain plant. The fluidized bed heat exchanger refers to a strong distribution self-cleaning fluidized bed heat exchanger as in example 1, and is provided with double sieve plates with the same specification, but is not provided with a three-fork support, a propeller and a spring pile hammer. The solid particles adopt zirconium silicate, the average particle size is 2.5mm, and the average volume solid content of the solid particles in the strongly distributed self-cleaning fluidized bed heat exchanger is 5 percent. The liquid phase was crude oil and the flow rate was 2.5 m/s. Under the condition, the heat transfer coefficient after the continuous operation for 210 days is 73 percent of the original heat transfer coefficient.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "bottom", "top", "front", "rear", "inner", "outer", "left", "right", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the present invention.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.

Claims

1. A 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 screen deck (11) and a second screen deck (12) are arranged in the lower tube box (1), wherein the first screen deck (11) is arranged in the middle of the lower tube box (1) to divide the lower tube box (1) into a first space on the upper portion and a second space on the lower portion, the second screen deck (12) is arranged in the first space, blades of the propeller (10) are arranged between the first screen deck (11) and the second screen deck (12), and the first screen deck (11) and the second screen deck (12) can be opened and closed to pass and block solid particles, respectively.

2. The tubular heat exchange assembly according to claim 1, wherein the wall surface of the first screen plate (11) and the installation contact position of the second screen plate (12) and the lower tube box (1) is hollow, the first screen plate (11) and the second screen plate (12) are both composed of two identical semicircular screen plates, and the two semicircular screen plates can be driven by the outside to respectively perform translational motion perpendicular to the inner wall surface of the lower tube box (1) and reversely towards the hollow position of the inner wall surface to the outside of the lower tube box (1), so that the screen plates are opened and closed.

3. The tube array heat exchange assembly according to claim 2, wherein the first sieve plate (11) and the second sieve plate (12) are circular, and have a pore diameter of 0.6-0.8 times the diameter of the solid particles and a thickness of 5-10 cm.

4. The tube array heat exchange assembly according to claim 3, wherein the cross-sectional shape of the first screen plate (11) and the second screen plate (12) is one of a plane type, a top convex type, a bottom convex type, a convex transparent type and a concave transparent type.

5. The tube array heat exchange assembly according to claim 4, wherein the first screen deck (11) and the second screen deck (12) are made of one of polyurethane, carbon steel, stainless steel, manganese steel.

6. The tube bank heat exchange assembly of any one of claims 1 to 5, further comprising:

-a three-pronged bracket (9) arranged in the second space of the lower channel (1) and one of which supports the propeller through the through hole of the first screen deck (11) and the other two of which are supported on the inner wall of the lower channel (1).

7. The tube array heat exchange assembly according to claim 6, wherein the three supports of the three-fork support (9) have the same length and diameter, the length of the support is 20-50 cm, the diameter of the support is 0.4-0.6 times of that of the heat exchanger tube array (2), the angles between the three supports are 120 degrees, two supports are respectively fixed on the opposite sides of the second space of the lower tube box (1), and the other support passes through a hole at the circle center of the first screen plate (11) and is perpendicular to the ground.

8. The tube heat exchange assembly according to claim 7, wherein the three-way bracket (9) is mounted at a position which is about 1/4 of the height of the lower tube box (1) from the bottom of the lower tube box (1).

9. The tube array heat exchange assembly according to any one of claims 1 to 5, wherein the propeller (10) is a fixed pitch propeller, and has three or four blades, the diameter of the propeller is 0.5 to 0.7 times of the diameter of the lower tube box (1), and the rotating speed of the propeller is 60 to 120 r/min.

10. The tube array heat exchange assembly according to claim 9, wherein the blades of the propeller (10) have a cross-sectional shape of one of a circular-back type, a wing type or a crescent type.

11. The tube array heat exchange assembly according to claim 10, wherein the lower tube box (1) is semi-cylindrical and has a height of 0.4-0.6 times of the heat exchanger tube array (2), and the second screen plate (12) is installed at a distance of 5-10 cm from the upper interface of the lower tube box (1).

12. A fluidized bed heat exchanger comprising the tube bundle heat exchange assembly as claimed in any one of claims 1 to 11, further comprising a liquid-solid separation tank (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 tank (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), liquid in the liquid storage tank (7) is conveyed to the lower tube box (1) by the liquid circulation pump (8), and solid particles in the solid particle tank (6) are mixed with liquid by an elliptic bend (14) and then flow into the lower tube box (1).

13. The fluidized bed heat exchanger according to claim 12, wherein the liquid-solid separation box (4) is provided with a spring pile hammer (13) at the top of the inner side, 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 1.1-1.3 times of the liquid-solid separation box (4), the shortest compression length thereof is 0.3-0.5 times of the maximum extension length, the pile hammer at the bottom of the spring pile hammer (13) is circular, the diameter thereof is 0.7-0.9 times of the diameter of the downcomer (5), the height thereof is 5-10 cm, and the settling velocity of the spring pile hammer (13) is 100-200 mm/min.

14. Fluidized bed heat exchanger according to claim 13, wherein the liquid-solid separation tank (4) is a gravity settler separator or a cyclone separator.

15. A method of preventing tube-side fouling using a fluidized bed heat exchanger as claimed in any one of claims 12 to 14, wherein crude oil is circulated in the heat exchanger tubes (2) and water is circulated in the shell-side, the method comprising:

crude oil passes through a liquid circulating pump (8) from a liquid storage tank (7) and then enters a lower pipe box (1) together with inert solid particles flowing out through an elliptic elbow (14);

the solid particles pass through the opened first sieve plate (11) and are blocked by the closed second sieve plate (12), and 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 a propeller (10) during the residence time;

closing the first sieve plate (11) to prevent insufficiently and uniformly mixed solid particles from entering the heat exchanger tubes (2);

the second sieve plate (12) is opened so that the fully and uniformly mixed solid particles enter the heat exchanger tube array (2), the fully and uniformly mixed particles can repeatedly scour the wall surface of the heat exchanger tube array (2), and dirt is not easy to adhere and agglomerate on the wall surface of the heat exchanger tube array (2) under the scouring of the solid particles;

after the fully and uniformly mixed particles completely enter the heat exchanger tubes (2), opening the first sieve plate (11) again and closing the second sieve plate (12) for circulating operation; and

the heat exchange between the crude oil in the tube pass and the water in the shell pass is completed, the solid particles and the water are separated in the liquid-solid separation box (4), the settling speed of the particles in the descending tube (5) can be accelerated by a spring pile hammer (13) arranged at the top of the liquid-solid separation box (4), and finally the solid particles and the water circulate in the self-cleaning fluidized bed heat exchanger.

16. The method of claim 15, wherein the solid particles have a bulk density greater than that of the fluid flowing therethrough and are non-reactive with the media of use in the application.

17. The method of claim 16, wherein the solid particles have an average diameter of 2-3 mm and an average mass solid content of 3-7% in the self-cleaning fluidized bed heat exchanger.

18. The method of claim 17, wherein the solid particles are one or more of zirconium silicate beads, corundum balls, porcelain balls, steel balls and engineering plastics.

19. The method according to claim 18, characterized in that the flow velocity of the crude oil in the heat exchanger tubes (2) in the fluidized bed heat exchanger ranges between 2 and 4 m/s.

20. A method according to claim 15, characterised by opening the second screening deck (12) after closing the first screening deck (11) for a preset period of time.