External heat removal system for adjusting two-stage regeneration heat removal load

Abstract

The utility model discloses an external heat removal system for adjusting two-section regeneration heat removal load, which comprises a first regenerator, a second regenerator and an external heat remover, the first regenerator and the second regenerator are coaxially arranged from top to bottom and are communicated, the external heat remover is parallel to the regenerators, and the upper portion of the external heat remover is communicated with the first regenerator through a catalyst inlet inclined pipe. Two catalyst outlets are formed in the lower part of the external heat remover, one catalyst outlet is communicated with the lower part of the second regenerator through a second re-return inclined pipe, and a second re-return one-way slide valve is arranged on the second re-return inclined pipe; the other catalyst outlet is communicated with the first regenerator or is communicated with the middle upper part of the second regenerator through a steering return inclined pipe, a return lifting pipe and a return inlet pipe which are communicated in sequence; and a steering return one-way slide valve is arranged on the steering return inclined pipe. According to the utility model, the heating load and the scorching temperature of the first regenerator and the second regenerator can be more effectively adjusted and controlled, and the long-period production requirement of the device is met.

Description

Technical Field

[0001] This utility model relates to an external heat extraction system in the field of regenerative heat extraction, specifically to an external heat extraction system that adjusts the regenerative heat extraction load of two stages. Background Technology

[0002] Catalyst regeneration is a common process in oil refining and chemical plants. When the quality of the feedstock is relatively stable, the regeneration effect of the catalyst not only affects the activity of the regenerated catalyst, but also the depth of the feed reaction, thereby affecting the properties of the reaction products and the yield of the target product, which has a significant impact on the economic benefits of the plant.

[0003] In early wax oil catalytic cracking units, the reaction and regeneration processes were typically in thermal equilibrium, meaning the heat released during catalyst regeneration and coking was in balance with the heat required for the reaction. However, with the decline in the quality of catalytic cracking (or catalytic pyrolysis) feedstock, heavier or even inferior feedstocks significantly increased the coking rate during the reaction. The heat released during coking and regeneration far exceeded the heat required for the reaction. Measures needed to remove some of this heat to prevent overheating during regeneration, which could lead to hydrothermal deactivation of the catalyst and affect the regeneration effect. Simultaneously, measures needed to prevent carbonization of the regenerator internals due to overheating during regeneration. The heat generated by the high-temperature catalyst can be used to produce medium- or high-pressure steam, serving as the main steam supply source for the entire plant. The installation of external heat exchangers not only ensured that the regenerator did not overheat but also fully utilized the excess heat from coking, becoming an important heat regulation measure in catalytic cracking units or exothermic process units.

[0004] In early catalytic cracking units, internal heat extraction technology was used to remove excess heat from the regeneration of coke. The internal heat extractor has a simple structure, mainly consisting of vertical or coiled heat extraction tube bundles. It does not require a catalyst circulation system or a fluidizing air system, resulting in lower investment. However, it has disadvantages such as difficulty in adjusting the heat load, low heat extraction efficiency, and maintenance difficulties.

[0005] Compared to internal heat exchangers, external heat exchangers are located outside the regenerator and connected to it via a catalyst inlet and return pipe. The external heat exchanger contains several heat-extracting tube bundles. Steam and water circulate within the tube bundles, while the catalyst circulates outside. Heat is removed by exchanging heat between the lower-temperature deoxygenated water or other low-temperature medium inside the tube bundles and the higher-temperature catalyst outside. A single-acting slide valve on the inclined tube returning the catalyst to the regenerator regulates the catalyst circulation rate and heat load. This heat exchange structure not only improves the heat exchanger's efficiency but also adapts to changes in the regenerator's coking load caused by variations in feed weight. Due to the high catalyst heat transfer coefficient, excellent heat extraction effect, and flexible operation, external heat exchangers are widely used in the oil refining and chemical industry. Currently, in large-scale oil refining and chemical plants, external heat exchangers have replaced internal heat exchangers as the most commonly used heat extraction method. External heat exchange systems and their associated medium- and high-pressure steam systems are crucial for the stable operation of the plant, reduced energy consumption, and overall plant economic benefits.

[0006] Most current external heat exchangers are structured as follows: hot catalyst is drawn from the upper or lower dense phase bed of the regenerator, enters the external heat exchanger through inclined tubes, and the cooled catalyst flows out from the side or bottom of the external heat exchanger, returning to the lower or upper part of the regenerator via the external heat exchanger return pipe and a single-acting slide valve. This heat exchange method is suitable for single-stage regenerators. For two-stage or multi-stage regeneration processes, an external heat exchanger with only one return path for the cooled catalyst cannot extract heat from two or more regenerators. It can only control the heat load of one stage of regeneration, and the heat load of other stages of regenerator cannot be effectively and timely regulated. Utility Model Content

[0007] To address the issues of uneven heat extraction in the two-stage regeneration bed and unstable fluidization in the external heat exchanger bed, this invention provides an external heat exchange system that adjusts the heat extraction load of the two-stage regeneration bed.

[0008] The external heat exchange system for adjusting the heat exchange load of two regeneration stages provided by this utility model includes a first regenerator and a second regenerator arranged coaxially and connected from top to bottom, and an external heat exchanger arranged parallel to the regenerators. The upper part of the external heat exchanger is connected to the first regenerator through an upwardly inclined catalyst inlet tube, and the lower part of the external heat exchanger is provided with two catalyst outlets. One catalyst outlet is connected to the lower part of the second regenerator through a downwardly inclined secondary regeneration return tube, and the secondary regeneration return tube is provided with a secondary regeneration return one-way slide valve. The other catalyst outlet is connected to the first regenerator or to the upper middle part of the second regenerator through a sequentially connected diverting return inclined tube, a return riser tube, and a return inlet tube. The diverting return inclined tube is arranged downwardly and is provided with a diverting return one-way slide valve. The return riser tube is arranged vertically. An external heat exchange tube bundle parallel to the axial direction of the external heat exchanger is arranged inside the external heat exchanger.

[0009] To prevent the catalyst at the catalyst inlet from eroding the external heat exchange tube bundle and lining, and to increase the length of the external heat exchange tube bundle to increase the heat exchange load of the external heat exchanger, a triangular inlet guide plate is installed at the end of the inclined tube at the catalyst inlet, and an anti-impact plate is installed on the outside of the external heat exchange tube bundle directly opposite the catalyst inlet.

[0010] Fluidizing air is introduced at the bottom of the external heat exchanger. Two fluidizing air distribution rings, a main fluidizing air distribution ring and a secondary fluidizing air distribution ring, can be installed at the bottom of the external heat exchanger to adjust the catalyst density in the secondary return inclined tube, the diverting return inclined tube, or the return riser entering the external heat exchanger and returning to the regenerator, preventing catalyst bridging or accumulation and ensuring that the catalyst reaches the optimal fluidization state. A return riser fluidizing air ring can also be installed at the bottom of the return riser.

[0011] As an improvement, the end of the return inlet pipe returning to the first or second regenerator is equipped with a catalyst distributor located inside the first or second regenerator. One end of the catalyst distributor is equipped with a conveying air supply to ensure that the catalyst is evenly sprayed into the regenerator, avoiding local accumulation of catalyst in the regenerator, which would affect the fluidization and temperature imbalance of the regenerator. The catalyst distributor can be configured as a straight pipe section, a Y-shaped pipe, or a ring pipe.

[0012] The two catalyst outlets at the bottom of the external heat exchanger can both be located on the lower side of the external heat exchanger; or one can be located on the lower side of the external heat exchanger and the other at the center of the bottom of the external heat exchanger.

[0013] The external heat extraction system of this utility model changes the heat transfer coefficient by adjusting the fluidizing air volume and changes the catalyst circulation volume by controlling the opening of the one-way slide valve at the outlet of the external heat exchanger, thereby affecting the heat transfer temperature difference and adjusting the heat extraction load. Therefore, the air volume of the fluidizing air and the lifting air and the opening of the one-way slide valve must be adjusted in coordination.

[0014] The flow path of the catalyst within the external heat exchange system of this invention is as follows: A portion of the catalyst in the first regenerator enters the external heat exchanger through the catalyst inlet inclined tube and exchanges heat with the low-temperature deoxygenated water medium in the external heat exchange tube bundle. The cooled catalyst, after heat exchange, returns to the regenerator in two paths. One path returns to the lower part of the second regenerator through the secondary return inclined tube, while the other path returns to the first regenerator or the upper part of the second regenerator through the diverting return inclined tube, diverting riser, and return inlet pipe. A portion of the catalyst in the second regenerator enters the first regenerator from bottom to top. Pressurized lifting air is introduced into the return riser to transport the catalyst. This lifting air, along with the cooled catalyst, returns to the first or second regenerator to participate in the catalyst regeneration and coking process.

[0015] The difference between this utility model's external heat exchange system and conventional external heat exchangers lies in the fact that it has two channels for the cold catalyst to return to the regenerator, and the amount of catalyst circulating back to the regenerator is controlled by two one-way slide valves.

[0016] When the catalyst enters from the first regenerator, and the amount of coke burned in the first regenerator increases and the temperature rises, the opening of the slide valve returning the catalyst to the first regenerator in the external heat exchanger is increased to control the amount of catalyst circulating back to the first regenerator. The booster airflow is adjusted accordingly to remove more heat, preventing overheating of the first regenerator and damage to internal components, catalyst deactivation, etc. By increasing the booster airflow and the slide valve opening returning to the first regenerator, the heat load of the first regenerator is increased, indirectly preventing excessive heat extraction from the second regenerator by the external heat exchanger. This avoids excessively low coking temperatures in the second regenerator bed, which would affect the coking effect, lead to incomplete combustion of coke adhering to the regenerator, and ultimately reduce catalyst activity. Furthermore, when the heat load is high, the amount of catalyst circulating in the external heat exchanger increases, approaching the total catalyst circulation volume. The inclusion of a channel for the cooled catalyst to return to the first regenerator allows for more flexible operation and adjustment of the semi-regeneration circulation pipe, resulting in more stable unit operation.

[0017] When the catalyst enters the second regenerator, and the amount of coke burned and the temperature rise in the second regenerator increase, the opening of the slide valve returning the catalyst to the second regenerator is increased to control the amount of catalyst circulating back to the second regenerator. The fluidizing air volume of the mains air is also adjusted to remove more heat, preventing the second regenerator from overheating and causing damage to internal components or catalyst deactivation. Increasing the opening of the slide valve returning to the second regenerator increases the heat load of the second regenerator. To increase the heat load of the first regenerator, the opening of the slide valve returning to the first regenerator and the lift air flow rate of the return riser pipe should be increased.

[0018] This utility model has the following beneficial effects:

[0019] 1) This allows for more effective regulation and control of the heat load and coking temperature of the first and second regenerators, while preventing excessively high regeneration temperatures in either the first or second regenerator from affecting the service life of the internal components and meeting the long-cycle production requirements of the equipment.

[0020] 2) The heat load adjustment range is larger, which is beneficial for adjusting the storage capacity of the first and second regenerators and adjusting the coking intensity in the two regenerators in real time, thereby improving the overall coking effect. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the first structure of the external heat extraction system of this utility model.

[0022] Figure 2 This is a schematic diagram of the second structure of the external heat extraction system of this utility model.

[0023] Figure 3This is a schematic diagram of the third structure of the external heat extraction system of this utility model.

[0024] In the diagram: 1-Catalyst inlet inclined tube, 2-Anti-impact plate, 3-Inlet guide plate, 4-External heat exchanger, 5-External heat exchanger tube bundle, 6-Main fluidizing air distribution ring, 7-Secondary fluidizing air distribution ring, 8-Secondary recirculation return inclined tube, 9-Secondary recirculation return one-way valve, 10-First regenerator, 11-Flue gas distribution plate, 12-Second regenerator, 13-Return riser, 14-Diverting return inclined tube, 15-Diverting return one-way valve, 16-Return riser fluidizing air ring, 17-Return riser riser air, 18-Return inlet pipe, 19-Catalyst distributor. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] Figure 1 A structural schematic diagram of one embodiment of this utility model is provided. In the diagram, "A" and "connection opening A" indicate that the pipelines are connected as a single unit. As shown in the diagram: the first regenerator 10 and the second regenerator 12 are coaxially connected from top to bottom, forming a single unit. A flue gas distribution plate 11 is provided at the connection point between the two. The external heat exchanger 4 is arranged parallel to the regenerators. The upper part of the external heat exchanger 4 is connected to the first regenerator 10 through an upwardly inclined catalyst inlet pipe 1. An inlet guide plate 3 is provided at the end of the catalyst inlet pipe 1. An external heat exchange tube bundle 5 parallel to the axial direction of the external heat exchanger 4 is provided inside the external heat exchanger 4, and an anti-impact plate 2 is provided on the outside of the external heat exchange tube bundle 5. A mainstream fluidized air distribution ring 6 and a secondary fluidized air distribution ring 7 located below the mainstream fluidized air distribution ring 6 are provided at the lower part of the external heat exchanger 4. Two catalyst outlets are located on the lower wall of the external heat exchanger 4. One catalyst outlet is located between the main fluidizing air distribution ring 6 and the secondary fluidizing air distribution ring 7, and is connected to the lower part of the second regenerator 12 via a downward-sloping secondary recirculation return pipe 8 with a secondary recirculation return one-way valve 9. The other catalyst outlet is located below the secondary fluidizing air distribution ring 7, and is connected to the first regenerator 10 via a downward-sloping diversion return pipe 14 with a diversion return one-way valve 15, a return riser pipe 13 connected to the diversion return pipe 14, and a return inlet pipe 18 connected to the return riser pipe 13. A catalyst distributor 19 located inside the first regenerator 10 is located at the end of the return inlet pipe 18, and a conveying air is provided at one end of the catalyst distributor 19. The return inlet pipe 18 is located above the catalyst inlet pipe 1. A return riser fluidizing air ring 16 is located at the bottom of the return riser pipe 13, and the return riser air 17 is introduced into the return riser pipe 13 through the return riser fluidizing air ring 16.

[0027] Figure 2 A second structural schematic diagram of this utility model is provided. (Compared to...) Figure 1 The difference is that the return inlet pipe 18 is located below the catalyst inlet inclined pipe 1.

[0028] Figure 3 A schematic diagram of a third structure of this utility model is provided. (Compared to...) Figure 1 and Figure 2 The difference is that the return inlet pipe 18 is connected to the upper part of the second regenerator 12.

[0029] The following is combined with Figure 1 The working process of this utility model is described as follows:

[0030] When the catalyst to be generated enters from the first regenerator 10 and the catalyst to be regenerated flows out from the second regenerator 12, the catalyst enters the external heat exchanger 4 through the catalyst inlet inclined tube 1 from the first regenerator 10. During the process of entering the external heat exchanger 4, the catalyst is guided by the inlet guide plate 3 and buffered by the anti-impact plate 2, which avoids the catalyst from eroding the external heat exchanger tube bundle 5 and the lining. The bottom of the external heat exchanger 4 is provided with a mainstream fluidizing air distribution ring 6 and a secondary fluidizing air distribution ring 7, through which fluidizing air is introduced. The catalyst reaches a fluidized state from top to bottom in the external heat exchanger cylinder 4 and exchanges heat with the medium in the external heat exchanger tube bundle 5. The lower part of the external heat exchanger 4 is provided with two catalyst outlets. One catalyst outlet returns to the lower part of the second regenerator 12 through the secondary return inclined pipe 8 and the secondary return one-way slide valve 9. Part of the catalyst in the second regenerator 12 enters the first regenerator 10 from bottom to top through the flue gas distribution plate 11. The other catalyst outlet enters the return riser 13 through the diverting return inclined pipe 14 and the diverting return one-way slide valve 15. The return riser 17 is introduced into the return riser 13 through the return riser fluidizing air ring 16. The return riser 17 is used as pressurized air to transport the catalyst. The lifted catalyst and fluidizing air enter the first regenerator 10 through the return inlet pipe 18 and the catalyst distributor 19.

Claims

1. An external heat extraction system for regulating the heat extraction load of two-stage regeneration processes, characterized in that: The device includes a first regenerator and a second regenerator arranged coaxially and connected from top to bottom, and an external heat exchanger arranged parallel to the regenerators. The upper part of the external heat exchanger is connected to the first regenerator through an upwardly inclined catalyst inlet tube, and the lower part of the external heat exchanger is provided with two catalyst outlets. One catalyst outlet is connected to the lower part of the second regenerator through a downwardly inclined secondary regeneration return tube, which is equipped with a secondary regeneration return one-way slide valve. The other catalyst outlet is connected to the first regenerator or to the upper middle part of the second regenerator through a sequentially connected diverting return inclined tube, a return riser tube, and a return inlet tube. The diverting return inclined tube is arranged downwardly and is equipped with a diverting return one-way slide valve. The return riser tube is arranged vertically. An external heat exchanger tube bundle parallel to the axial direction of the external heat exchanger is arranged inside the external heat exchanger.

2. The external heat extraction system according to claim 1, characterized in that: An inlet guide plate is provided at the end of the catalyst inlet inclined tube.

3. The external heat extraction system according to claim 1, characterized in that: An anti-impact plate is installed on the outside of the external heat extraction tube bundle directly opposite the catalyst inlet.

4. The external heat extraction system according to claim 1, characterized in that: The lower part of the external heat exchanger is provided with a mainstream air distribution ring.

5. The external heat extraction system according to claim 4, characterized in that: A secondary fluidization air distribution ring is provided below the main fluidization air distribution ring.

6. The external heat extraction system according to claim 1, characterized in that: The end of the return inlet pipe is equipped with a catalyst distributor located in the first regenerator or the second regenerator.

7. The external heat extraction system according to claim 6, characterized in that: The catalyst distributor is a straight pipe section, a Y-shaped pipe, or a ring pipe.

8. The external heat extraction system according to claim 1, characterized in that: The bottom of the return riser is provided with a return riser fluidizing air ring.

9. The external heat extraction system according to claim 4, characterized in that: The bottom of the return riser is provided with a return riser fluidizing air ring.

10. The external heat extraction system according to any one of claims 1 to 9, characterized in that: The two catalyst outlets at the bottom of the external heat exchanger are both located on the lower side of the external heat exchanger; or one is located on the lower side of the external heat exchanger and the other is located at the center of the bottom of the external heat exchanger.

11. The external heat extraction system according to any one of claims 1 to 9, characterized in that: The return inlet pipe that returns to the first regenerator is located above or below the catalyst inlet inclined pipe.

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