A quenching heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas

Abstract

The present application relates to heat exchanger technical field, specifically to a kind of quenching heat exchanger for preventing high-temperature pyrolysis gas outlet coking, including pyrolysis gas box, upper water header, lower water header and heat exchange tube module, heat exchange tube module includes inner tube, outer tube, inlet pipe, upper connector and lower connector, inner tube is arranged in outer tube;Pyrolysis gas box has multiple extension pipes, extension pipe is worn with adjusting column, adjusting column is inserted into inner tube, and the depth of adjusting column inserted into inner tube is adjustable, adjusting column is sealingly fixed between adjusting column and extension pipe, the outside of the section of adjusting column in inner tube is provided with helical flow guide structure, so that the flow of pyrolysis gas close to outlet end changes from straight line to spiral line, reduce the laminar layer between fluid and inner wall of inner tube, improve heat exchange coefficient, adjusting column occupies the space of inner tube, so that the flow rate of pyrolysis gas is accelerated, and the deeper adjusting column is into inner tube, the faster pyrolysis gas flows in inner tube, so that the flow rate of pyrolysis gas is adjustable, reduce the coking of outlet end.

Description

Technical Field

[0001] This invention relates to the field of ethylene cracking equipment technology, and more specifically to a quench heat exchanger for preventing coking at the outlet of high-temperature cracked gas. Background Technology

[0002] Besides the pyrolysis furnace, another crucial piece of equipment in a pyrolysis unit is the linear quench heat exchanger. The linear quench heat exchanger consists of an inlet connector, double-tube heat exchange units, a water header, and a pyrolysis gas header. The specific structure is as follows: Each double-tube heat exchange unit includes concentric inner and outer tubes. Each double-tube heat exchange unit is connected to a pyrolysis furnace outlet tube via an inlet connector. Multiple double-tube heat exchange units are arranged in parallel in a single or multiple rows, connected to the water header and the pyrolysis gas header. The inner tube contains high-temperature cracked gas, with the temperature at the inlet connection reaching 800-900℃. Upon entering the quench heat exchanger, the temperature drops to approximately 400℃ (depending on the feedstock) within a very short time (generally less than 0.1 seconds; 0.03-0.07 seconds for gas cracking and 0.02-0.06 seconds for distillate oil cracking). Thus, the quench heat exchanger differs from ordinary heat exchangers in that it has high thermal intensity and extremely harsh operating conditions, requiring the inside and outside of the tube to withstand both high temperature and pressure differences simultaneously.

[0003] Existing quench heat exchangers such as Figure 1 As shown, the system includes a pyrolysis gas chamber 1, an upper water manifold 2, a lower water manifold 3, and multiple heat exchanger tube modules arranged in parallel. Each heat exchanger tube module includes an inner tube 4, an outer tube 5, an inlet pipe 6, an upper connecting pipe 7, a lower connecting pipe 8, an upper connector 9, and a lower connector 10. The inner tube 4 is concentrically inserted inside the outer tube 5. One opening of the upper connector 9 and the lower connector 10 is welded to the outer tube 5, and the other opening is welded to the inner tube 4, so that the channel between the outer wall of the inner tube 4 and the inner wall of the outer tube 5 connects the upper connector 9 and the lower connector 10. The upper connector 9 is connected to the upper water manifold 2 through the upper connecting pipe 7, and the lower connector 10 is connected to the lower water manifold 3 through the lower connecting pipe 8. In use, the inlet pipe 6 is connected to the outlet of the external pyrolysis furnace. High-temperature pyrolysis gas flows from the inner tube 4 to the pyrolysis gas chamber 1. The cooling medium enters the lower connector 10 from the inlet of the lower water manifold 3, and then flows to the channel between the outer wall of the inner tube 4 and the inner wall of the outer tube 5 for heat exchange, reaching the upper water manifold 2. The high-temperature medium flows from the outlet of the pyrolysis gas box 1 to the subsequent process.

[0004] When the cracking gas is cooled in the inner tube, a part of high-boiling-point hydrocarbons will be condensed inevitably. Thus, a part of the condensate is taken away by the cracking gas, and another part is attached to the wall of the inner tube. With the production going on, the hydrocarbon condensate attached to the wall of the inner tube will undergo dehydrogenation reaction under the action of the cracking gas, and at the same time, condensation reaction will occur. In particular, the aromatic hydrocarbons will be further condensed after dehydrogenation, which will eventually lead to coke formation. Generally speaking, due to the difference in the properties of the cracking raw materials, especially the difference in the group composition, the coking condition of the quenching heat exchanger is also different. When naphtha or light diesel oil is used as the raw material for cracking, the most common phenomenon is that coke is formed at the outlet end of the inner tube of the quenching heat exchanger, and the coke is mainly formed by condensation, dehydrogenation and condensation reaction, and is accompanied by secondary reaction coking. The coking affects the heat exchange effect, and even causes blockage. In addition, the flow rate of the high-temperature cracking gas in the existing quenching heat exchanger is uncontrollable, or can only be indirectly controlled by controlling the flow rate of the cracking gas at the outlet of the cracking furnace. Under the condition that the flow rate of the cracking gas at the outlet of the cracking furnace is constant, the flow rate of the high-temperature cracking gas in the quenching heat exchanger cannot be adjusted, which cannot meet the increasingly high and flexible production requirements. SUMMARY

[0005] In view of the above technical problems existing in the prior art, the present application provides a quenching heat exchanger for preventing coking at the outlet of high-temperature cracking gas, which can adjust the cracking gas speed of the inner tube and reduce the coking of the inner tube.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] The present application provides a quenching heat exchanger for preventing coking at the outlet of high-temperature cracking gas, which comprises a cracking gas tank, an upper water header, a lower water header and a plurality of heat exchange tube modules arranged side by side, each heat exchange tube module comprising an inner tube, an outer tube, an inlet tube, an upper connecting pipe and a lower connecting pipe, the inner tube being concentrically arranged in the outer tube, the upper end of the inner tube being communicated with the cracking gas tank, and the lower end of the inner tube being communicated with the inlet tube; the lower water header, the lower connecting pipe, the annular channel between the outer wall of the inner tube and the inner wall of the outer tube, the upper connecting pipe and the upper water header are sequentially communicated to form a cooling water flow channel.

[0008] A plurality of extension pipes are arranged on the top of the cracking gas tank, the extension pipes are through the cracking gas tank, the extension pipes are aligned with the inner tubes of the heat exchange tube modules, and part or all of the extension pipes are provided with adjusting columns, the adjusting columns are inserted into the inner tubes through the cracking gas tank, the depth of the adjusting columns inserted into the inner tubes is adjustable, the adjusting columns and the extension pipes are sealingly fixed, and the outer side of the section of the adjusting column located in the inner tube is provided with a spiral flow guide structure.

[0009] As a further improvement of the quenching heat exchanger of the present application, a plurality of positioning columns are arranged on the outer side of the adjusting column along the length direction of the adjusting column.

[0010] As a further improvement of the quenching heat exchanger of the present application, a plurality of positioning columns are arranged helically along the length direction of the adjusting column.

[0011] As a further improvement of the quenching heat exchanger of the present application, the longitudinal section of the positioning column is in the shape of a water droplet with a narrow lower part and a wide upper part.

[0012] As a further improvement of the quenching heat exchanger of the present application, the outer side of the adjusting column is covered with a ceramic layer or a paint layer.

[0013] As a further improvement of the quenching heat exchanger of the present application, the helical flow guide structure is a helical groove opened on the outer side of the adjusting column, and the helical groove is arranged in a single helix, a double helix or a multi-helix.

[0014] As a further improvement of the quenching heat exchanger of the present application, the helical flow guide structure is a helical fin fixed to the outer side of the adjusting column, and the helical fin is arranged in a single helix, a double helix or a multi-helix.

[0015] As a further improvement of the quenching heat exchanger of the present application, the adjusting column is threadedly connected with the extension pipe, so as to realize the sealing and fixing between the adjusting column and the extension pipe, and adjust the depth of the adjusting column inserted into the inner pipe.

[0016] As a further improvement of the quenching heat exchanger of the present application, the outer diameter of the segment of the adjusting column located in the inner pipe gradually decreases from top to bottom, or is stepwise reduced.

[0017] As a further improvement of the quenching heat exchanger of the present application, the outer diameter of the segment of the adjusting column located in the inner pipe is adjustable.

[0018] The present application has the following advantages:

[0019] Compared with the prior art, the quenching heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas has the following advantages:

[0020] 1) The adjusting column is inserted into the inner pipe, the adjusting column occupies the space of the inner pipe, the path of the flow of the pyrolysis gas is reduced, so as to accelerate the flow rate of the pyrolysis gas, and the deeper the adjusting column is inserted into the inner pipe, the larger the space of the inner pipe is occupied, and the faster the pyrolysis gas flows in the inner pipe, so as to realize the adjustment of the flow rate of the pyrolysis gas and reduce the coking at the outlet end;

[0021] 2) The faster the flow rate of the pyrolysis gas is, the shorter the time of indirect heat conduction with the cooling water flow channel is, and the higher the temperature of the pyrolysis gas when flowing into the pyrolysis gas tank is, that is, by adjusting the flow rate of the pyrolysis gas, the temperature of the pyrolysis gas after heat exchange can be adjusted, so as to meet the flexible and variable production requirements;

[0022] 3) The accelerated flow rate of the pyrolysis gas can flush the impurities on the inner wall of the inner pipe, so as to reduce the coking of the inner pipe, especially the segment of the inner pipe close to the pyrolysis gas tank;

[0023] 4) The spiral guide structure changes the linear flow of the cracking gas into spiral flow, and the flow of the cracking gas near the outlet end is changed from linear to spiral by rotating the flow channel, which reduces the laminar flow between the fluid and the inner wall of the inner tube, increases the heat exchange coefficient, and more impacts the impurities in the inner tube, reduces the coking at the outlet end, and even avoids coking.

[0024] In addition:

[0025] 5) The positioning column on the outside of the adjusting column can reduce the vibration caused by the impact of the cracking gas, and prevent the adjusting column from coking due to vibration of the inner tube;

[0026] 6) The water droplet-shaped positioning column allows the cracking gas to enter from below and exit from above, preventing the high-temperature cracking gas from forming deposits on its surface and causing coking;

[0027] 7) The outside of the adjusting column is covered with a ceramic layer or a paint layer, which separates the metal material of the adjusting column base from the high-temperature cracking gas, avoids the reaction between the metal material and the high-temperature cracking gas, and prevents the metal base of the adjusting column from being eroded by the carbon in the cracking gas, thereby improving the service life of the adjusting column;

[0028] 8) The outer diameter of the adjusting column gradually decreases from top to bottom, or is stepwise reduced, or is stepwise adjustable, so that the flow area of the inner tube near the outlet end is smaller, and the flow rate of the high-temperature cracking gas is faster, further reducing the coking at the outlet end. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a structure schematic diagram of the existing technology of the quenching heat exchanger.

[0030] Figure 2 It is a structure schematic diagram of the quenching heat exchanger for preventing coking of high-temperature cracking gas at the outlet in the embodiment.

[0031] Figure 3 It is a shape schematic diagram of the adjusting column in another embodiment.

[0032] Figure 4 It is a shape schematic diagram of the adjusting column in another embodiment.

[0033] Figure 2 Reference numerals:

[0034] Cracking gas tank 10, inner tube 20, outer tube 30, inlet pipe 40, upper connecting pipe 50, lower connecting pipe 60;

[0035] Extension pipe 70, adjusting column 80, positioning column 90. DETAILED DESCRIPTION

[0036] The present application will be described in detail below in conjunction with specific embodiments and drawings.

[0037] The quenching heat exchanger of the embodiment for preventing coking at the outlet of high-temperature pyrolysis gas comprises a pyrolysis gas tank 10, an upper water header, a lower water header and a plurality of heat exchange tube modules arranged in parallel, as shown in Figures 1 to 4 each heat exchange tube module comprises an inner tube 20, an outer tube 30, an inlet tube 40, an upper connecting tube 50 and a lower connecting tube 60, the inner tube 20 is concentrically arranged in the outer tube 30, the upper end of the inner tube 20 is communicated with the pyrolysis gas tank 10, and the lower end of the inner tube 20 is communicated with the inlet tube 40. The lower water header, the lower connecting tube 60, the annular channel between the outer wall of the inner tube 20 and the inner wall of the outer tube 30, the upper connecting tube 50 and the upper water header are sequentially communicated to form a cooling water flow channel. As an improvement, a plurality of extension tubes 70 are arranged on the top of the pyrolysis gas tank 10, the plurality of extension tubes 70 penetrate the pyrolysis gas tank 10, the plurality of extension tubes 70 are aligned with the inner tubes 20 of the plurality of heat exchange tube modules, and part or all of the extension tubes 70 are provided with adjusting columns 80, the adjusting columns 80 are inserted into the inner tubes 20 through the pyrolysis gas tank 10, the depth of the adjusting columns 80 inserted into the inner tubes 20 is adjustable, the adjusting columns 80 are sealingly fixed between the extension tubes 70, and the outer side of the section of the adjusting column 80 located in the inner tube 20 is provided with a spiral flow guide structure.

[0038] Compared with the prior art, the following advantages are achieved:

[0039] 1) The adjusting column 80 is inserted into the inner tube 20, the adjusting column 80 occupies the space of the inner tube 20, the path of the pyrolysis gas flow is reduced, so that the flow rate of the pyrolysis gas is accelerated, and the deeper the adjusting column 80 is inserted into the inner tube 20, the greater the space of the inner tube 20 is occupied, and the faster the pyrolysis gas flows in the inner tube 20, so that the flow rate of the pyrolysis gas is adjustable, and the coking at the outlet end is reduced;

[0040] 2) The faster the flow rate of the pyrolysis gas, the shorter the time of indirect heat conduction with the cooling water flow channel, and the higher the temperature of the pyrolysis gas when flowing into the pyrolysis gas tank 10, that is, by adjusting the flow rate of the pyrolysis gas, the temperature of the pyrolysis gas after heat exchange can be adjusted, and the flexible production requirements can be met;

[0041] 3) The flow rate of the pyrolysis gas is accelerated, which can flush the impurities on the inner wall of the inner tube 20, so that the coking of the inner tube 20 is reduced, especially the section of the inner tube 20 close to the pyrolysis gas tank 10;

[0042] 4) The spiral flow guide structure changes the straight flow of the pyrolysis gas into spiral flow, and changes the straight flow of the pyrolysis gas close to the outlet end into spiral flow through the rotating flow channel, reduces the laminar layer between the fluid and the inner wall of the inner tube, improves the heat exchange coefficient, more impacts the impurities of the inner tube, reduces the coking at the outlet end, and even avoids coking.

[0043] In the embodiment, the adjusting column 80 is threadedly connected with the extension tube 70, which on the one hand realizes the sealing and fixing between the adjusting column 80 and the extension tube 70, and on the other hand adjusts the depth of the adjusting column 80 inserted into the inner tube 20 by rotating up and down.

[0044] In the embodiment, the outer side of the adjusting column 80 is provided with a plurality of positioning columns 90, which are arranged helically along the length direction of the adjusting column 80, so that the space of the radial deviation of the adjusting column 80 is small, the large vibration caused by the impact of the cracking gas can be reduced, and the coking caused by the vibration of the adjusting column in the inner tube can be prevented. The longitudinal section of the positioning column 90 is in the shape of a water droplet with a narrow lower part and a wide upper part, the cracking gas enters from the lower part and exits from the upper part, and the coking caused by the deposition of the high-temperature cracking gas on the surface thereof is prevented.

[0045] In the embodiment, the outer side of the adjusting column 80 is covered with a ceramic layer or a paint layer, so that the metal material of the adjusting column base body is isolated from the high-temperature cracking gas, the reaction of the metal material with the high-temperature cracking gas is avoided to prevent coking, the metal base body of the adjusting column 80 can be prevented from being eroded and corroded by the carbon in the cracking gas, and the service life of the adjusting column 80 is improved.

[0046] In the embodiment, the spiral flow guide structure is a threaded groove opened on the outer side of the adjusting column 80 or a spiral fin fixed to the outer side of the adjusting column 80, and the spiral of the threaded groove and the spiral fin is single helix, double helix or multi-helix arrangement.

[0047] In practice, it can be further improved by combining Figure 3 As shown in the figure, the outer diameter of the segment of the adjusting column 80 located in the inner tube 20 gradually decreases from top to bottom, so that in the case that the adjusting column 80 extends into the inner tube 20 by the same length, the segment of the inner tube 20 closer to the cracking gas tank 10 is higher, and the flow rate of the cracking gas is faster, so that the coking is reduced in a targeted manner, and the effect is more obvious. Or it can be changed to the adjusting column 80 shown in the figure, which is gradually reduced in stages, that is, it is divided into a plurality of segments with gradually reduced diameters from top to bottom. Figure 4 As shown in the figure, the adjusting column 80 is gradually reduced in stages, that is, it is divided into a plurality of segments with gradually reduced diameters from top to bottom.

[0048] In practice, it can be further improved that the outer diameter of the segment of the adjusting column 80 located in the inner tube 20 can be adjusted, so as to change the form of the outer diameter of the adjusting column to change the way of occupying the space of the inner tube 20, and to adjust the flow rate of the cracking gas. The outer diameter adjustment structure of the adjusting column can be a thickened sleeve welded on the outer side of the adjusting column 80.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited to the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A rapid cooling heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas, comprising a pyrolysis gas housing, an upper water manifold, a lower water manifold, and multiple heat exchange tube modules arranged in parallel, each heat exchange tube module comprising an inner tube, an outer tube, an inlet pipe, an upper connecting pipe, and a lower connecting pipe, the inner tube being concentrically inserted inside the outer tube, the upper end of the inner tube being connected to the pyrolysis gas housing, and the lower end of the inner tube being connected to the inlet pipe; the lower water manifold, the lower connecting pipe, the annular channel between the outer wall of the inner tube and the inner wall of the outer tube, the upper connecting pipe, and the upper water manifold are sequentially connected to form a cooling water flow channel; characterized in that: Multiple extension pipes are erected on the top of the pyrolysis gas box. The extension pipes are connected to the pyrolysis gas box and aligned with the inner tube of the heat exchange tube module. Some or all of the extension pipes are fitted with adjustment columns. The adjustment columns are inserted into the inner tube through the pyrolysis gas box and the depth of the adjustment columns inserted into the inner tube is adjustable. The adjustment columns and extension pipes are sealed and fixed. A spiral guide structure is provided on the outside of the section of the adjustment column located in the inner tube.

2. A quench heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas according to claim 1, characterized in that: Multiple positioning posts are provided on the outside of the adjusting column, and the multiple positioning posts are arranged along the length of the adjusting column.

3. A quench heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas according to claim 2, characterized in that: Multiple positioning posts are spirally arranged along the length of the adjusting post.

4. A quench heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas according to claim 2, characterized in that: The longitudinal section of the positioning post is teardrop-shaped, narrow at the bottom and wide at the top.

5. A quench heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas according to claim 1, characterized in that: The outer side of the regulating column is covered with a ceramic layer or a paint layer.

6. A quench heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas according to claim 1, characterized in that: The spiral guide structure is a threaded groove on the outside of the regulating column, and the threaded groove can be arranged as a single spiral, double spiral or multiple spirals.

7. A quench heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas according to claim 1, characterized in that: The spiral guide structure consists of spiral fins fixed to the outside of the regulating column, and the spiral fins are arranged in a single spiral, double spiral, or multiple spiral configuration.

8. A quench heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas according to claim 1, characterized in that: The adjusting column and the extension tube are threaded together to achieve a sealed fixation between the adjusting column and the extension tube, as well as to adjust the depth of the adjusting column inserted into the inner tube.

9. A quench heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas according to claim 1, characterized in that: The outer diameter of the section of the regulating column located in the inner tube gradually decreases from top to bottom, or decreases in stages.

10. A quench heat exchanger for preventing coking at the outlet of high-temperature pyrolysis gas according to claim 1, characterized in that: The outer diameter of the section of the regulating column located in the inner tube is adjustable.

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