Double-pipe wall surface efficient strip falling devolatilization device and heat transfer method

Abstract

The invention relates to a double-pipe wall efficient strip-falling devolatilization device and a heat transfer method.The double-pipe wall efficient strip-falling devolatilization device comprises a gas-liquid separation chamber and a heat exchanger, the heat exchanger comprises a shell and a plurality of inner pipes arranged in the shell, the inner pipes are sleeved with outer pipes, annular gaps between the inner pipes and the outer pipes are open, and the annular gaps are used for circulation of polymer materials; the first heating medium flows back in the inner pipe, the second heating medium is arranged between the outer pipe and the shell, and the annular space is communicated with the gas-liquid separation chamber. By setting the sizes of the inner pipe and the outer pipe, the thickness of the annular gap can be adjusted. When the content of a light phase in a fed material is low, a small annular gap thickness can be adopted, and the ultrathin polymer annular liquid film is adopted at the moment. When the content of light phases in fed materials is high, the large annular gap thickness can be adopted, liquid can flow along falling films of the inner pipe wall and the outer pipe wall respectively, equipment can be normally operated completely, and the heat transfer effect is better. The devolatilization device and the devolatilization method are not only suitable for devolatilization working conditions of polymers with small productivity or in laboratories, but also can be used for devolatilization processes of large polymers.

Description

Technical Field

[0001] The invention relates to the technical field of efficient heat transfer, and in particular to a double-tube wall efficient strip devolatilization device and a heat transfer method. The device is suitable for the devolatilization process of polymers with large thermal resistance and high viscosity. Background Art

[0002] The heat transfer problem of high viscosity and high thermal resistance material system has always been the difficulty of heat transfer. For example, in the production process of polymers, whether it is resin or polymer plastic, it generally involves the problem of devolatilization. However, the heat transfer in the devolatilization process is difficult and the light phase content of the product is high, which has always restricted the development of similar processes.

[0003] There are generally two types of heat transfer equipment and methods in the current devolatilization process. One is static devolatilization, which mainly increases the heat transfer driving force by increasing the heat transfer temperature difference of the heat transfer equipment, such as flash devolatilization, traditional tube-and-tube strip devolatilization, etc. Although the heat transfer can be enhanced to a certain extent by unilaterally increasing the heat transfer driving force, it is limited by the high thermal resistance and high viscosity of the polymer itself. If the heat transfer distance is large, taking tube-and-tube heat transfer as an example, it is still difficult for the heat to reach the center of the fluid in the tube far away from the heating wall. The Chinese patent with announcement number CN116753750B discloses a devolatilization preheating device and preheating method suitable for high-viscosity polymers. It is based on the traditional fin strip devolatilizer. The heat transfer method of this type of devolatilizer is to use the heating medium in the tube as the primary indirect heat source and the fin as the secondary direct heat source to heat the polymer. The heat transfer distance is only half of the fin thickness, which solves the problem of the large heat transfer distance of the traditional tube-and-tube. However, the premise for the normal operation of this type of devolatilizer is that the middle chamber of the devolatilizer must be completely filled, which requires strict matching of the temperature of the heating medium and the viscosity of the material. Therefore, it is generally only used for devolatilization of materials containing less than 15% of light weight. In addition, due to the influence of the heat transfer efficiency of the fins, the central chamber in the traditional fin strip devolatilizer is generally large, and there is also the disadvantage of clogging and difficulty in cleaning. Another method of enhancing heat transfer for devolatilization is dynamic devolatilization, that is, forcibly disturbing the high-viscosity fluid through stirring components such as stirring paddles, scrapers, screws, etc. Although this heat transfer method increases the heat transfer efficiency to a certain extent, it has many disadvantages such as polymer wall adhesion, local high-temperature thermoplasticity, small processing volume during application, high manufacturing and maintenance costs, and difficulty in increasing the processing volume. It has not fundamentally solved the problem of polymer heat transfer.

[0004] Therefore, it is very important to develop a new structure of a strip devolatilizer with simple structure and efficient mass transfer for the production of polymers. Summary of the invention

[0005] The purpose of the present invention is to provide a double-tube wall high-efficiency strip devolatilization device and a heat transfer method to solve the problems of the existing polymer devolatilizers with complex structure, low adaptability and low devolatilization efficiency.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In the first aspect, the present invention provides a double-tube wall high-efficiency strip devolatilization device, including a gas-liquid separation chamber and a heat exchanger, wherein the heat exchanger includes a shell and a plurality of inner tubes arranged in the shell, an outer tube is arranged outside the inner tube, and an annular gap between the inner and outer tubes is open, and the annular gap is used for the circulation of polymer materials, a first heating medium refluxes in the inner tube, a second heating medium is arranged between the outer tube and the shell, and the annular gap is connected to the gas-liquid separation chamber.

[0008] Furthermore, the heat exchanger further comprises an upper tube sheet, a middle tube sheet and a lower tube sheet arranged from top to bottom, the upper end of the inner tube is fixed on the upper tube sheet, a head is arranged above the upper tube sheet, the space between the head and the upper tube sheet is an inner tube compartment, a partition is arranged in the inner tube compartment, an inlet and outlet of the first heating medium are arranged on both sides of the partition, the first heating medium in the inner tube enters from the inlet, and flows out from the outlet after heat exchange in the inner tube;

[0009] An outer tube is arranged between the middle tube plate and the lower tube plate, and the area between the middle tube plate and the upper tube plate is the outer tube compartment;

[0010] A raw material inlet is arranged on the side wall of the outer tube compartment;

[0011] A shell side inlet and a shell side outlet for the second heating medium to enter and exit are arranged on the shell in the area where the outer tube is located;

[0012] The lower tube plate is fixedly connected to the gas-liquid separation chamber, and the gas-liquid separation chamber is provided with a polymer outlet d and a light phase outlet e.

[0013] Furthermore, the height of the outer tube compartment is 0.5-1.5 times the overall diameter of the heat exchanger; the polymer is at least one of polyolefin elastomer POE, polystyrene butadiene SBR, thermoplastic elastomer SEBS, ethylene-vinyl acetate copolymer EVA or polypropylene PP.

[0014] Furthermore, a baffle is arranged in the space in the area where the outer tube is located.

[0015] Furthermore, the inner tube is a U-shaped tube, or a tube array with a cap at one end.

[0016] Furthermore, the width of the annular gap is 2-10 mm, and there is no spoiler in the annular gap.

[0017] Furthermore, the first heating medium is the same as or different from the second heating medium. Preferably, the first heating medium is heat transfer oil and the second heating medium is steam.

[0018] In a second aspect, the present invention provides a heat transfer method using the device, the process of the heat transfer method is:

[0019] The first heating medium A with a certain temperature and pressure enters the inner tube compartment on one side from the inlet on the inner tube compartment, flows downward along the inner tube, turns, flows upward into the inner tube compartment on the other side, and flows out from the outlet on the inner tube compartment;

[0020] The second heating medium B with a certain temperature and pressure enters from the shell side inlet, transfers heat to the material in the annular gap through circumferential flow, and the condensed second heating medium is discharged from the shell side outlet;

[0021] The polymer material to be heated enters from the raw material inlet on the side wall of the outer tube compartment, and is initially distributed in the liquid phase under the disturbance of the inner tube, then enters the annular space between the inner tube and the outer tube, moves downward, and finally enters the gas-liquid separation chamber;

[0022] In the process of the material moving downward along the annular gap, due to the setting of the annular gap, the second heating medium on the outer tube side and the first heating medium on the inner tube side heat the annular gap material from both the outer and inner directions, making it easier to reach the center of the material, thereby obtaining the heat required for vaporization of a large amount of light phase substances in the material, providing the possibility for complete vaporization of the light phase liquid; when the material liquid enters the gas-liquid separation chamber from the annular gap, the space suddenly expands, the gas phase separates from the liquid phase matrix and flows out from the light phase outlet, and the liquid phase falls to the bottom of the gas-liquid separation chamber under the action of gravity and is discharged from the material outlet.

[0023] Preferably, when the light phase content in the feed is within 10wt%, the annular gap width is 2-6mm;

[0024] When the light phase content in the feed is greater than 10wt%, the annular gap width is 6-10mm.

[0025] In a third aspect, the present invention provides a devolatilization process, wherein the process uses the device, and preferably adopts multi-stage devolatilization, including three stages: pre-devolatilization, primary devolatilization and fine devolatilization.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1 The present invention can use different heating media according to physical parameters, which is more energy-efficient; when the outer tube is heated by steam, the heat transfer coefficient of the equipment is higher, the temperature is easier to control, and the cost of steam can be greatly reduced. The inner tube is heated by heat transfer oil with a higher temperature, which uses less and can better prevent the material from being blocked inside the tube and outside the tube at the end of the inner tube.

[0028] 2 High applicability; by setting the size of the inner and outer tubes, the thickness of the annular gap can be adjusted.

[0029] When the light phase content in the feed is small and the material viscosity is high, a small annular gap thickness can be used. At this time, the ultra-thin polymer annular liquid film provides a guarantee for more efficient devolatilization. Under certain working conditions, the light phase in the final product can be reduced to below 200PPM.

[0030] When the light phase content in the feed is high and the material viscosity is low, a large annular gap thickness can be used, and the liquid can flow along the inner and outer tube walls respectively, and the equipment can operate normally with better heat transfer effect. Under this condition, the fin strip devolatilizer cannot achieve normal operation.

[0031] 3. Low processing and manufacturing cost. The heat transfer effect of the present invention has no direct relationship with the diameter of the inner tube, but is only related to the thickness of the annular gap. Traditional tube-in-tube strip devolatilizers generally require small diameter heat exchange tubes and internal plug-ins, which are high in manufacturing cost and easy to clog.

[0032] 4 Small amplification effect. The present invention is not only applicable to the devolatilization of polymers with small production capacity or in laboratories, but also to the devolatilization of large-volume polymers. This is because the tubular double-wall heating has a controllable number of tubes, a larger heat transfer area, a more compact volume, and no amplification effect. Traditional tube-in-tube strip devolatilizers are generally more suitable for small production capacity, while fin strip devolatilizers require finned tubes to enclose the material space, so they are not very suitable for laboratories or small production capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a schematic cross-sectional structure diagram of a double-tube wall surface high-efficiency strip devolatilization device according to an embodiment of the present invention.

[0034] Figure 2 It is a partial enlarged schematic diagram of the inner tube and the outer tube.

[0035] In the figure, 1 is an inner tube compartment, 2 is an outer tube compartment, 3 is an inner tube, 4 is an outer tube, 5 is an annular gap, 6 is a baffle, 7 is an upper tube sheet, 8 is a middle tube sheet, 9 is a lower tube sheet, 10 is a gas-liquid separation chamber, 11 is a partition, a is a heat transfer oil inlet, b is a heat transfer oil outlet, c is a raw material inlet, d is a polymer outlet, e is a light phase outlet, f is a steam inlet, and g is a condensate outlet. DETAILED DESCRIPTION

[0036] The present invention is further explained below in conjunction with the embodiments and drawings, but this is not intended to limit the scope of protection of the present application.

[0037] Example 1

[0038] This embodiment of the double-tube wall surface high-efficiency strip devolatilization device (see Figure 1 ), the device includes a heat exchanger and a gas-liquid separation chamber;

[0039] The heat exchanger comprises an inner tube box, an outer tube box, inner tubes and outer tubes for heat transfer, an upper tube plate, a middle tube plate and a lower tube plate.

[0040] The inner tube is preferably a U-shaped tube, the upper end of which is connected to the upper tube sheet 7, the outer diameter of the inner tube is slightly smaller than the inner diameter of the outer tube, and is embedded in the outer tube 4; the two ends of the outer tube 4 are respectively connected to the middle tube sheet 8 and the lower tube sheet 9, the inner diameter of which is slightly larger than the outer diameter of the inner tube, and is sleeved outside the inner tube;

[0041] The outer tube 4 is concentric with the inner tube 3, and the width of the annular gap 5 between the two concentric circles corresponding to the inner diameter of the outer tube and the outer diameter of the inner tube is controlled to be about 2-5 mm. The upper end of the annular gap is connected to the outer tube compartment 2, and the lower end of the annular gap is connected to the gas-liquid separation chamber 10, forming the main channel for polymer circulation and heat transfer;

[0042] The upper tube sheet 7 and its upper end cap form an inner tube compartment 1; a partition 11 is provided in the inner tube compartment 1, and the partition divides the inner tube compartment into two independent chambers, which are respectively connected to the heat transfer oil inlet a and the heat transfer oil outlet b;

[0043] The upper tube sheet 7 is at a certain distance from the middle tube sheet 8 and forms an outer tube compartment 2 with the heat exchanger shell; a raw material inlet c is arranged on the side wall of the outer tube compartment;

[0044] The middle tube sheet 8 is spaced a certain distance from the lower tube sheet 9, and together with the outer tube 4 and the shell, forms a shell side of the heat exchanger, and a steam inlet f and a condensed water outlet g are provided on the side wall of the shell side;

[0045] The lower tube sheet 9 is connected to the gas-liquid separation chamber 10 through an equipment flange; the gas-liquid separation chamber is provided with a polymer outlet d and a light phase outlet e.

[0046] The heat transfer process is:

[0047] The first heating medium A (preferably heat transfer oil) with a certain temperature and pressure enters the inner tube compartment on one side from the heat transfer oil inlet, flows downward along the inner tube, turns through the U-shaped tube, flows upward into the inner tube compartment on the other side, and flows out of the equipment from the heat transfer oil outlet;

[0048] The second heating medium B (preferably steam) with a certain temperature and pressure enters the devolatilizer from the steam inlet of the shell side, transfers heat to the material in the annular gap through bypass flow, and condensed water is discharged from the condensed water outlet;

[0049] The polymer material to be heated enters from the material inlet on the side wall of the outer tube compartment, and is initially distributed in the liquid phase under the disturbance of the inner tube (because the inner tube is evenly distributed in the outer tube compartment and plays a disturbing role), then enters the annular space between the inner tube and the outer tube, moves downward, and finally enters the gas-liquid separation chamber.

[0050] In the process of the material moving downward along the annular gap, in this embodiment, since the width of the annular gap is controlled at 2-5mm, the latent heat of the steam on the outer tube side and the sensible heat of the heat transfer oil on the inner tube side can more easily reach the center of the material, thereby obtaining the heat required for the vaporization of a large amount of light phase substances in the material, and providing the possibility for the complete vaporization of the light phase liquid. When the liquid enters the gas-liquid separation chamber from the annular gap, the space suddenly expands, the gas phase separates from the liquid phase matrix and flows out from the light phase outlet, and the liquid phase falls to the bottom of the gas-liquid separation chamber under the action of gravity and is discharged from the material outlet.

[0051] Example 2

[0052] In this embodiment, a baffle is provided in the space in the area where the outer tube is located, heat transfer oil flows in the inner tube, polymer raw materials flow in the annular gap, steam is used for heating between the outer tube and the shell, the material is heated and devolatilized from both the inside and the outside, and the steam flows around the baffle for heat exchange.

[0053] Example 3

[0054] In this embodiment, the inner tube and the outer tube can also use the same fluid with different temperatures for heat exchange, and the specific temperature difference can be determined according to the actual situation. The height of the outer tube compartment can be determined according to the processing volume, and the height of the outer tube compartment is 0.5-1.5 times the overall diameter of the heat exchanger. Preferably, it is 0.5-1.0 times.

[0055] Example 4

[0056] In this embodiment, the inner tube adopts a tube array with a lower head. The lower head end of the inner tube is placed under the lower tube plate, and the upper end of the inner tube is fixed to the upper tube plate. The heating medium entering one side of the inner tube compartment enters the lower head of the inner tube through the inner tube, and flows out from the outlet on the other side of the inner tube compartment after reversing.

[0057] Example 5

[0058] In this embodiment, the polymer is a polyolefin elastomer POE (it can also be any one of high viscosity systems such as polystyrene butadiene SBR, thermoplastic elastomer SEBS, ethylene-vinyl acetate copolymer EVA, polypropylene PP, etc.). The POE efficient devolatilization process includes three sections: pre-devolatilization, primary devolatilization and fine devolatilization, wherein both the primary devolatilization and fine devolatilization sections can be devolatilized using the device described in Example 1.

[0059] Example 6

[0060] The heat exchanger shell of this embodiment has a diameter of 200 mm, an outer tube compartment height of 100 mm, an outer tube inner diameter of 38 mm, an inner tube inner diameter of 32 mm, and an annular gap width of 3 mm, which can achieve efficient devolatilization of 1-5 kg / hour of polymer in the laboratory.

[0061] In the description of this specification, the specific features, structures, materials or characteristics described in the embodiment are included in at least one embodiment of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments and features of the different embodiments described in this specification without contradicting each other.

[0062] In the drawings of the embodiments disclosed in the present invention, only the structures related to the embodiments disclosed in the present invention are involved, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

[0063] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0064] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A double-tube wall surface high-efficiency strip devolatilization device, comprising a gas-liquid separation chamber and a heat exchanger, wherein the heat exchanger comprises a shell and a plurality of inner tubes arranged in the shell, characterized in that: An outer tube is arranged outside the inner tube, and the annular gap between the inner and outer tubes is open. The annular gap is used for the circulation of polymer materials. The first heating medium refluxes in the inner tube. The second heating medium is arranged between the outer tube and the shell, and the annular gap is connected with the gas-liquid separation chamber.

2. The device according to claim 1, characterized in that The heat exchanger further comprises an upper tube sheet, a middle tube sheet and a lower tube sheet arranged from top to bottom, the upper end of the inner tube is fixed on the upper tube sheet, a head is arranged above the upper tube sheet, the space between the head and the upper tube sheet is an inner tube compartment, a partition is arranged in the inner tube compartment, and an inlet and outlet of the first heating medium are arranged on both sides of the partition, the first heating medium in the inner tube enters from the inlet, and flows out from the outlet after heat exchange in the inner tube; An outer tube is arranged between the middle tube plate and the lower tube plate, and the area between the middle tube plate and the upper tube plate is the outer tube compartment; A raw material inlet is arranged on the side wall of the outer tube compartment; A shell side inlet and a shell side outlet for the second heating medium to enter and exit are arranged on the shell in the area where the outer tube is located; The lower tube plate is fixedly connected to the gas-liquid separation chamber, and the gas-liquid separation chamber is provided with a polymer outlet d and a light phase outlet e.

3. The device according to claim 2, characterized in that The height of the outer tube compartment is 0.5-1.5 times the overall diameter of the heat exchanger; the polymer is at least one of polyolefin elastomer POE, polystyrene butadiene SBR, thermoplastic elastomer SEBS, ethylene-vinyl acetate copolymer EVA or polypropylene PP.

4. The device according to claim 2, characterized in that A baffle is arranged in the space in the area where the outer tube is located.

5. The device according to claim 1, characterized in that The inner tube is a U-shaped tube or a tube array with a cap at one end.

6. The device according to claim 1, characterized in that The width of the annular gap is 2-10 mm, and there is no spoiler in the annular gap.

7. The device according to claim 1, characterized in that The first heating medium is the same as or different from the second heating medium. Preferably, the first heating medium is thermal oil and the second heating medium is steam.

8. A heat transfer method using the device according to any one of claims 1 to 7, characterized in that: The process of the heat transfer method is: The first heating medium A with a certain temperature and pressure enters the inner tube compartment on one side from the inlet on the inner tube compartment, flows downward along the inner tube, turns, flows upward into the inner tube compartment on the other side, and flows out from the outlet on the inner tube compartment; The second heating medium B with a certain temperature and pressure enters from the shell side inlet, transfers heat to the material in the annular gap through circumferential flow, and the condensed second heating medium is discharged from the shell side outlet; The polymer material to be heated enters from the raw material inlet on the side wall of the outer tube compartment, and is initially distributed in the liquid phase under the disturbance of the inner tube, then enters the annular space between the inner tube and the outer tube, moves downward, and finally enters the gas-liquid separation chamber; In the process of the material moving downward along the annular gap, due to the setting of the annular gap, the second heating medium on the outer tube side and the first heating medium on the inner tube side heat the annular gap material from both the outer and inner directions, making it easier to reach the center of the material, thereby obtaining the heat required for vaporization of a large amount of light phase substances in the material, providing the possibility for complete vaporization of the light phase liquid; when the material liquid enters the gas-liquid separation chamber from the annular gap, the space suddenly expands, the gas phase separates from the liquid phase matrix and flows out from the light phase outlet, and the liquid phase falls to the bottom of the gas-liquid separation chamber under the action of gravity and is discharged from the material outlet.

9. The heat transfer method according to claim 8, characterized in that: When the light phase content in the feed is within 10wt%, the annular gap width is 2-6mm; When the light phase content in the feed is greater than 10wt%, the annular gap width is 6-10mm.

10. A devolatilization process, characterized in that: The process uses the device described in any one of claims 1-7.

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