CN117346564A - Composite heat exchanger and carbon capture pressure increasing system thereof - Google Patents

Abstract

The invention belongs to the technical field of carbon capture, and particularly relates to a composite heat exchanger and a carbon capture pressure increasing system thereof, wherein the composite heat exchanger consists of a fixed tube plate type heat exchange structure, a spiral plate type sleeve heat exchange structure and a support plate for connecting the fixed tube plate type heat exchange structure and the spiral plate type sleeve heat exchange structure; the fixed tube-sheet type heat exchange structure comprises a sealing plate with an enclosure structure, four tube-sheet type heat exchanger cylinders which are uniformly distributed are arranged in the sealing plate, and heat insulation plates are arranged between the adjacent tube-sheet type heat exchanger cylinders; the spiral plate type sleeve heat exchange structure comprises an outer pipe and an inner pipe sleeved inside the outer pipe. According to the invention, the lean-rich liquid heat exchanger, the gas cooler, the lean liquid precooler and the condenser are integrated into a composite heat exchanger, and the heat and pressure energy contained in the carbon capture pressure increasing system are recycled, so that the utilization rate of energy in the unit can be improved, the energy consumption of the unit is reduced, and the COP of the unit is improved.

Description

A composite heat exchanger and its carbon capture and pressure boosting system

Technical field

The invention belongs to the technical field of carbon capture, and in particular relates to a composite heat exchanger and its carbon capture and pressure boosting system.

Background technique

Currently, the carbon capture and pressure boosting system shown in Figure 1 can be used to capture and recover CO ₂ in mixed gases such as chemical exhaust gas, power plant gas tail gas, cement roasting flue gas, etc., and can be directly used for CO ₂ pressure boosting. In the carbon capture and thermal pressure boosting of CO ₂ in industrial fields such as chemical industry, cement, steel, natural gas, coal and electricity, it can significantly reduce equipment investment and operating costs, and has high economic and social value.

However, there is much room for process optimization and equipment integration in the above process of the carbon capture and pressure boosting system. For example, the heat contained in the low-pressure flue gas is not utilized before entering the fan. The compression and pressure increase of the high-temperature flue gas increases the power consumption of the fan; the low-pressure steam passes through the temperature and pressure reduction device before entering the reboiler, and this part of the heat energy is not used. Utilization; The mixture of CO ₂ and water vapor desorbed from the top of the desorption tower has a high temperature, and this part of the heat energy is not utilized, but directly enters the condenser, and the cooling capacity required for condensation is also large; the current process system Before the medium-rich liquid is sent to the desorption tower, the heat contained in the lean liquid flowing out from the bottom of the desorption tower is recovered only through the lean-rich liquid heat exchanger. Moreover, the lean liquid flowing out of the desorption tower needs to be throttled and decompressed by the pressure reducing valve before entering the absorption tower. The throttling and decompression increases the entropy of the high-pressure lean liquid and reduces the working capacity. This part of the high-pressure energy is not utilized.

In addition, in the current process system, the low-pressure flue gas and lean liquid before entering the absorption tower, as well as the CO ₂ and water vapor mixture desorbed from the top of the desorption tower, need to be cooled through a gas precooler, a lean liquid precooler and a condenser respectively. Condensation, this part of the cooling and condensation needs to take away the heat through the circulating water in the public project. The heat taken away by this part of the circulating water needs to be released to the atmosphere through the subsequent air cooling tower, which increases the power consumption of the air cooling tower. In summer, the temperature of the circulating water is high, and it is difficult to ensure that the low-pressure flue gas and lean liquid before entering the absorption tower, as well as the CO ₂ and water vapor mixture desorbed from the top of the desorption tower, can be cooled and condensed to the temperature required by the process. , it is impossible to ensure that the process system is in optimal operating condition.

Therefore, we proposed a composite heat exchanger and its carbon capture and pressure boosting system to solve the above problems.

Contents of the invention

In order to solve the above problems, a composite heat exchanger and its carbon capture and pressure boosting system are provided.

The above purpose is achieved through the following preparation process:

A composite heat exchanger, which consists of a fixed tube plate heat exchange structure, a spiral plate casing heat exchange structure located above the fixed tube plate heat exchange structure, and two connecting tubes connecting the fixed tube plate heat exchange structure and the spiral plate casing heat exchange structure. Composed of support plates;

The fixed tube plate heat exchange structure includes a sealing plate with an enclosure structure. There are four evenly distributed tube plate heat exchanger cylinders inside the sealing plate, and there is a space between adjacent tube plate heat exchanger cylinders. There is an insulating plate, and each tube plate heat exchanger cylinder is provided with head pipe boxes at the upper and lower ends. The four tube plate heat exchanger cylinders are connected in sequence through pipes to the upper and lower end head pipe boxes to form a series structure. ;

The spiral plate casing heat exchange structure includes an outer tube and an inner tube placed inside the outer tube. The outer tube and the inner tube are divided into four areas by three partitions, and the inner tube in each area has There are outer spiral plates on the outside, and inner spiral plates are provided on the inside of the inner tube. The flow of the shell side of each tube plate heat exchanger enters the four areas of the outer tube after being discharged. It forms a counter-current to the flow inside the inner tube.

As a further improvement of the above technical solution: the tube plate heat exchanger barrel is provided with a number of vertical heat exchange tubes, and the heat exchange tubes are connected to the upper and lower head tube boxes.

As a further improvement of the above technical solution: the tube plate heat exchanger barrel is also provided with interlaced transverse baffles for fixing the heat exchange tubes.

As a further improvement of the above technical solution: both ends of the outer tube are provided with head plates.

As a further improvement of the above technical solution: the shell side of the four tube plate heat exchanger cylinders respectively flows four kinds of heat streams, and the tube sides of the four tube plate heat exchanger cylinders sequentially flow into the rich liquid before the desorption tower. liquid, the four hot streams are discharged from the shell side of the tube plate heat exchanger barrel and enter the four areas of the outer tube. The inner tube flows with cold water, and the cold water is in contact with the four areas of the outer tube. The hot streams flowing inside form a countercurrent.

A carbon capture and pressure boosting system, including a fan, an absorption tower, a solution pump, a desorption tower, a reboiler, a gas-liquid separation tank and a lithium bromide refrigerator, and also includes a solution turbine and the above-mentioned composite heat exchanger;

The low-pressure flue gas containing CO ₂ enters the composite heat exchanger as H4 and then enters the absorption tower through the fan and is absorbed by the lean liquid to form a rich liquid;

The rich liquid enters the desorption tower after passing through the solution pump and the composite heat exchanger. After desorption, the mixture of CO ₂ and water vapor coming out of the top of the tower is used as H3, and the lean liquid flowing out from the bottom of the tower is used as H2. The H3 passes through the composite heat exchanger. After the exchanger, it enters the gas-liquid separation tank, and the H2 enters the absorption tower after passing through the composite heat exchanger and the solution turbine;

After the low-pressure steam passes through the lithium bromide refrigerator, part of it enters the reboiler. The condensate from the reboiler is used as H1 and is discharged after passing through the composite heat exchanger. The other part is passed through the composite heat exchanger as cold water and returns after absorbing heat. Lithium bromide refrigerator performs re-refrigeration cycle;

Among them, the temperature magnitude of H1-H4 is specifically H4>H3>H2>H1.

As a further improvement of the above technical solution: the solution turbine is driven by H2 to provide power for the fan.

The beneficial effects of the present invention are:

(1) The heat contained in the low-pressure flue gas, the mixture of CO ₂ and water vapor desorbed from the top of the desorption tower, the lean liquid flowing out from the bottom of the desorption tower, and the condensate coming out of the reboiler is used to treat the incoming Preheating of rich liquid before desorption tower. It can reduce the heat required for desorption in the desorption tower and reduce the energy consumption of the desorption tower.

(2) Use the heat originally wasted by low-pressure steam in the temperature and pressure reduction device to drive the potassium bromide refrigerator and produce cold water instead of circulating water to meet the cooling and condensation needs in the above process system. It not only ensures that the process system is in the best operating condition in summer, but also recycles the heat originally wasted by low-pressure steam in the temperature and pressure reduction device. At the same time, it replaces circulating water and reduces the energy consumption of public utilities.

(3) The lean liquid flowing out of the desorption tower is changed from throttling and decompressing the pressure reducing valve to driving a solution turbine to drive the rotation of the fan and to supercharge the low-pressure flue gas.

(4) The composite heat exchanger integrates the rich-liquid heat exchanger, gas cooler, lean-liquid precooler and condenser into one device. It can reduce the cost of equipment and pipelines and greatly reduce the footprint of the unit.

Description of drawings

Figure 1 is a schematic diagram of the overall flow of the carbon capture and pressure boosting system in the prior art;

Figure 2 is a schematic front view of the overall simple structure of the composite heat exchanger in the present invention;

Figure 3 is a schematic side view of the structure of the composite heat exchanger in the present invention;

Figure 4 is a partial structural schematic diagram of the structure of the composite heat exchanger in the present invention;

Figure 5 is a schematic diagram of the overall flow of the carbon capture and pressure boosting system in the present invention.

Illustration: 1. Fixed tube plate heat exchange structure; 11. Sealing plate; 12. Tube plate heat exchanger cylinder; 13. Insulation plate; 14. Heat exchange tube; 15. Head tube box; 16. Baffle ; 2. Spiral plate casing heat exchange structure; 21. Outer tube; 22. Inner tube; 23. Outer spiral plate; 24. Inner spiral plate; 25. Partition plate; 26. Head plate; 3. Support plate.

Detailed ways

The present application will be described in further detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific embodiments are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application. Those skilled in the field can refer to The above application contents make some non-essential improvements and adjustments to this application.

Example 1

As shown in Figure 2-4, the composite heat exchanger of this embodiment is composed of upper and lower parts. The upper part is a spiral plate casing heat exchange structure 2, and the lower part is a fixed tube plate heat exchange structure 1. The part is fixed to the lower part through the support plate 3.

The fixed tube plate heat exchange structure 1 includes a sealing plate 11 with an enclosure structure. There are four evenly distributed tube plate heat exchanger cylinders 12 inside the sealing plate 11, and the adjacent tube plate heat exchanger cylinders 12 are There are insulating plates 13 in between, and head tube boxes 15 are provided at the upper and lower ends of each tube plate heat exchanger cylinder 12. A number of vertical heat exchange tubes 14 are provided inside the tube plate heat exchanger cylinder 12. The heat exchange tubes 14 are connected to the upper and lower head tube boxes 15. The tube plate heat exchanger barrel 12 is also provided with interlaced transverse baffles 16 for fixing the heat exchange tubes 14.

The four tube plate heat exchanger cylinders 12 are connected to the upper and lower head pipe boxes 15 in sequence through pipes to form a series structure. From Figure 2, the details are: the upper head pipe of the first tube plate heat exchanger cylinder 12 The box 15 is connected to the upper end head tube box 15 of the second adjacent tube plate heat exchanger cylinder 12 through a pipeline, and the lower end head tube box 15 of the second tube plate heat exchanger cylinder 12 is connected to the adjacent third tube box 15 through a pipeline. The lower end head pipe box 15 of the first tube plate heat exchanger cylinder 12, the upper end head pipe box 15 of the third tube plate heat exchanger cylinder 12 is connected to the adjacent fourth tube plate heat exchanger cylinder through a pipeline. 12, and the upper and lower head pipe boxes 15 of each tube plate heat exchanger cylinder 12 are connected with heat exchange tubes 14, that is, the exchange tubes of the four tube plate heat exchanger cylinders 12 are connected. The heat pipe 14 has a tube side, so the four tube plate heat exchanger cylinders 12 form a tube side (passing through the heat exchange tube 14) in series, and the tube side takes the cold stream - rich liquid (before entering the desorption tower); four The shell side of the tube plate heat exchanger barrel 12 (outside the heat exchange tube 14) respectively carries four heat streams (low-pressure flue gas, the mixture of CO ₂ and water vapor desorbed from the top of the desorption tower, and the mixture flowing out from the bottom of the desorption tower. lean liquid, condensate coming out of the reboiler), and the four hot streams flow out and enter the spiral plate casing heat exchange structure 2 and flow out. Therefore, a shell is formed between the four tube plate heat exchanger barrels 12 process in parallel.

The spiral plate casing heat exchange structure 2 includes an outer tube 21 and an inner tube 22 that is sleeved inside the outer tube 21. Both ends of the outer tube 21 are provided with head plates 26. There are three sections between the outer tube 21 and the inner tube 22. The partition 25 is divided into four areas. In each area, an outer spiral plate 23 is provided on the outside of the inner tube 22, and an inner spiral plate 24 is provided on the inside of the inner tube 22. The shell side of each tube plate heat exchanger barrel 12 is After being discharged, the material flows into the four areas of the outer tube 21 and forms a counter-current with the material (cold water) flowing inside the inner tube 22 .

The outer tube 21 carries the heat streams (H1~H4), and adjacent heat streams are separated by partitions 25. The temperatures in the hot stream are H1, H2, H3, and H4 from low to high. H1~H4 exchange heat with cold water in sequence, forming a pure countercurrent efficient heat exchange. At the same time, the hot stream and cold water are guided by the inner and outer spiral plates. A spiral flow is formed and the direction of the spiral flow is opposite, making the heat exchange more efficient. There are corresponding pipeline connections between the above parts, and the streams (rich liquid, hot streams H1~H4, cold water) flow through the pipelines. Finally, the hot streams (H1~H4) and rich liquid pass through the composite heat exchanger to complete the heat exchange, and then return to their respective process flows.

The above-mentioned composite heat exchanger also integrates a rich-liquid heat exchanger, a gas cooler, a lean-liquid precooler and a condenser into one device. The cost of equipment and pipelines is greatly reduced, and the footprint of the unit is reduced.

As shown in Figure 5, the carbon capture and pressure boosting system of this embodiment includes a fan, an absorption tower, a solution pump, a desorption tower, a reboiler, a gas-liquid separation tank and a lithium bromide refrigerator. It also includes a solution turbine and a composite type heat exchanger;

The low-pressure flue gas containing CO ₂ enters the composite heat exchanger as H4 and then enters the absorption tower through the fan and is absorbed by the lean liquid to form a rich liquid;

The rich liquid enters the desorption tower after passing through the solution pump and the composite heat exchanger. After desorption, the mixture of CO ₂ and water vapor coming out of the top of the tower is used as H3, and the lean liquid flowing out from the bottom of the tower is used as H2. H3 passes through the composite heat exchanger. After entering the gas-liquid separation tank, H2 passes through the composite heat exchanger and the solution turbine before entering the absorption tower;

After the low-pressure steam passes through the lithium bromide refrigerator, part of it enters the reboiler. The condensate from the reboiler is used as H1 and is discharged after passing through the composite heat exchanger. The other part is passed through the composite heat exchanger as cold water and returns after absorbing heat. The lithium bromide refrigerator performs a re-refrigeration cycle.

The lower part of the composite heat exchanger is used to transfer the hot streams H1~H4 (low-pressure flue gas, the mixture of CO ₂ and water vapor desorbed from the top of the desorption tower, the lean liquid flowing out from the bottom of the desorption tower, and the condensed water coming out of the reboiler). The heat contained in the liquid) is used to preheat the rich liquid before entering the desorption tower. The heat contained in these hot streams H1~H4 is recycled and passed through the upper part, where it is further cooled and condensed to the temperature required by the process by the cold water from the lithium bromide refrigerator. The cold water flowing out of the lithium bromide refrigerator is produced by low-pressure steam drive.

In addition, the lean liquid H2 flowing out of the desorption tower will be changed from throttling and decompressing the original pressure reducing valve to driving a solution turbine to drive the rotation of the fan and supercharge the low-pressure flue gas.

The above recycling of heat and pressure energy contained in the process system can improve the utilization rate of the internal energy of the unit, reduce the energy consumption of the unit, and improve the COP of the unit. The heat originally wasted by low-pressure steam in the temperature and pressure reduction device is used to drive the potassium bromide refrigerator and produce cold water instead of circulating water to meet the cooling and condensation needs in the above process system. It not only ensures that the process system is in the best operating condition in summer, but also recycles the heat originally wasted by low-pressure steam in the temperature and pressure reduction device. At the same time, it replaces circulating water and reduces the energy consumption of public utilities.

The above-mentioned embodiments only express several implementation modes of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the patent scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims (7)

1. A composite heat exchanger, characterized in that it consists of a fixed tube plate heat exchange structure (1), a spiral plate casing heat exchange structure (2) located above the fixed tube plate heat exchange structure (1), and a connected and fixed heat exchanger. The tube plate heat exchange structure (1) and the spiral plate casing heat exchange structure (2) are composed of two sets of support plates (3); The fixed tube plate heat exchange structure (1) includes a sealing plate (11) with an enclosure structure, and four evenly distributed tube plate heat exchanger cylinders (12) are provided inside the sealing plate (11), and Insulation plates (13) are provided between adjacent tube plate heat exchanger cylinders (12), and head tube boxes (15) are provided at the upper and lower ends of each tube plate heat exchanger cylinder (12). ), the four tube plate heat exchanger cylinders (12) are connected in sequence to the upper and lower end head tube boxes (15) through pipes to form a series structure; The spiral plate casing heat exchange structure (2) includes an outer tube (21) and an inner tube (22) sleeved inside the outer tube (21). The outer tube (21) and the inner tube (22) are connected by Three partitions (25) are divided into four areas. In each area, an outer spiral plate (23) is provided on the outside of the inner tube (22), and an inner spiral plate (23) is provided on the inside of the inner tube (22). 24), the flow in the shell side of each tube plate heat exchanger barrel (12) enters the four areas of the outer tube (21) after being discharged, and forms with the flow inside the inner tube (22) countercurrent. 2. The composite heat exchanger according to claim 1, characterized in that a plurality of vertical heat exchange tubes (14) are provided inside the tube plate heat exchanger barrel (12), and the heat exchanger The pipe (14) communicates with the upper and lower head pipe boxes (15). 3. The composite heat exchanger according to claim 2, characterized in that the tube plate heat exchanger barrel (12) is also provided with interlaced transverse baffles for fixing the heat exchange tubes (14). Plate (16). 4. The composite heat exchanger according to claim 1, characterized in that, both ends of the outer tube (21) are provided with head plates (26). 5. The composite heat exchanger according to claim 1, characterized in that four heat streams flow on the shell side of the four tube plate heat exchanger barrels (12) respectively, and the four tube plate heat exchangers The rich liquid before entering the desorption tower flows sequentially from the tube side of the tube plate heat exchanger barrel (12). The four hot streams are discharged from the shell side of the tube plate heat exchanger barrel (12) and then enter the outer tube (21). In the four areas, cold water flows in the inner tube (22), and the cold water forms a countercurrent with the hot streams flowing in the four areas of the outer tube (21). 6. A carbon capture and pressure boosting system, including a fan, an absorption tower, a solution pump, a desorption tower, a reboiler, a gas-liquid separation tank and a lithium bromide refrigerator, characterized in that it also includes a solution turbine and claim 5 The composite heat exchanger; The low-pressure flue gas containing CO ₂ enters the composite heat exchanger as H4 and then enters the absorption tower through the fan and is absorbed by the lean liquid to form a rich liquid; The rich liquid enters the desorption tower after passing through the solution pump and the composite heat exchanger. After desorption, the mixture of CO ₂ and water vapor coming out of the top of the tower is used as H3, and the lean liquid flowing out from the bottom of the tower is used as H2. The H3 passes through the composite heat exchanger. After the exchanger, it enters the gas-liquid separation tank, and the H2 enters the absorption tower after passing through the composite heat exchanger and the solution turbine; After the low-pressure steam passes through the lithium bromide refrigerator, part of it enters the reboiler. The condensate from the reboiler is used as H1 and is discharged after passing through the composite heat exchanger. The other part is passed through the composite heat exchanger as cold water and returns after absorbing heat. Lithium bromide refrigerator performs re-refrigeration cycle; Among them, the temperature magnitude of H1-H4 is specifically H4>H3>H2>H1. 7. The carbon capture and pressure boosting system according to claim 6, wherein the solution turbine is driven by H2 to provide power for the fan.