CN105749728B - Method and apparatus for capturing carbon dioxide - Google Patents

Abstract

The invention discloses a method for capturing carbon dioxide. The method adopts a chemical absorption method based on a catalytic reaction process, and utilizes fractal-dimensional heat exchange and vapor recompression process enhancement technologies to capture carbon dioxide. The invention also discloses a carbon dioxide capture device for the above method, which comprises an absorption tower, a desorption tower, a mixed steam separation system and a reboiler system. The invention captures carbon dioxide by using the catalytic desorption method, the fractal heat exchanger and the vapor recompression process enhancement technology, which not only improves the reaction rate, but also reduces the energy consumption, and can be widely used in natural gas, shift gas, flue gas or synthetic gas. _CO2 capture and separation purification in gases such as gas.

Description

Carbon dioxide capture method and device

technical field

The invention relates to the field of energy and chemical industry, in particular to the technical field of carbon capture, and more particularly to a method for capturing carbon dioxide. of carbon dioxide. The invention also relates to a carbon dioxide capture device for use in the method.

Background technique

Chemical absorption technology is one of the most active, mature, and easily industrially scaled or commercialized carbon capture technologies at this stage. The so-called chemical absorption gas separation method refers to a method of selectively removing components easily soluble in the absorption liquid from the gas phase by chemical reaction using an absorbent solvent. The essence of removing CO ₂ by chemical absorption method is to use the alkaline absorbent solution to contact with CO ₂ in the mixed gas and chemically react to form unstable salts, and the salts will decompose in reverse to release CO ₂ under certain conditions. So as to achieve the purpose of separating and enriching CO ₂ from the mixed gas.

One of the cores of chemical absorption technology to capture carbon dioxide is the development of high-efficiency absorbents. Existing absorbents mainly include monoethanolamine (MEA), diethanolamine (DEA), N-methyldiethanolamine (MDEA), diisopropanolamine (DIPA) and other solvents or their mixed systems. The Chinese invention patent with publication number CN 103381330A proposes an absorbent for carbon capture, which is composed of ionic liquid 1-butyl-3-methylimidazole acetate and an amine solution. The Chinese invention patent with publication number CN 102974203A proposes an absorbent with a special structure of active amine compound aqueous solution. The active amine molecule contains two functional groups, primary amine and tertiary amine, and the primary amine mainly plays the role of accelerating the absorption rate. , the tertiary amine can increase the absorption and reduce the desorption temperature, and the two types of amines can play a role in promoting activation. The active amine aqueous solution is contacted with the gas to be treated to achieve the purpose of purifying the gas. From the analysis of the characteristics of absorbent research at home and abroad, the conventional absorption system has not solved a series of problems such as solvent degradation, equipment corrosion and high desorption energy consumption.

The desorption process of chemical absorption carbon dioxide capture technology requires a lot of heat (the energy consumption of the desorption process of MEA carbon capture is about 3.5GJ/t CO ₂ ), which directly affects the economy and application of the technology. Using heat pump technology or vapor recompression technology, through the state change and phase change of the working fluid, the low-grade thermal energy can be upgraded to a high-grade temperature region, which can greatly reduce the energy consumption of the carbon capture chemical absorption desorption process. The Chinese invention patent with publication number CN 102869426A proposes a carbon dioxide gas recovery device, the recovery device has a heat pump, so that the heat generated by the exothermic reaction when the absorption liquid absorbs carbon dioxide in the absorption tower is moved through the heat medium to act as a It is used as a heat source for the endothermic reaction when carbon dioxide is separated from the rich absorption liquid in the regeneration tower. The Chinese invention patent publication number CN 101464072A proposes a waste steam condensation heat recovery system of a coal-fired power plant, including: a high-temperature heat pump device for absorbing heat from the spent steam of the coal-fired power plant, and improving the high-temperature heat pump through the heat pump cycle. Working medium temperature; carbon dioxide capture device, which uses the high-temperature heat pump working medium to heat the MEA absorbent used to capture carbon dioxide in flue gas to complete the desorption process; transcritical carbon dioxide heat pump device is used to absorb heat from the exhausted steam of coal-fired power plants , the temperature of the carbon dioxide heat pump working medium is increased through the heat pump cycle; the district heating heat device uses the carbon dioxide heat pump working medium to heat regional domestic water and district heating hot water.

The heat exchanger is the key equipment in carbon capture. Optimizing its design to improve its heat exchange efficiency is one of the important ways to save energy and reduce consumption in the carbon capture process. In order to improve the heat exchange efficiency of the heat exchanger, the current measures to enhance heat transfer mainly include: changing the shape of the tube bundle or designing the thread shape and corrugated shape inside and outside the tube, that is, through the transformation of the tube bundle shape or surface configuration to enhance the heat transfer. Heat; the fluid space outside the tube bundle is designed with a baffle-type structure. These enhanced heat transfer methods make the fluid generate continuous local turbulence in the flow heat transfer area, increase the fluid turbulence intensity, and then improve the heat transfer efficiency, but lead to an increase in the flow resistance of the system. In addition, the existing heat exchange tube bundle design lacks consideration of the optimization of the fluid transport path, and the structural design has the problems of unreasonable fluid transport path, increased flow resistance and mismatched heat transfer performance in the heat exchange tube bundle. Therefore, it is urgent to carry out the optimal design of the heat exchange tube bundle structure in the heat exchanger to achieve efficient heat exchange. The Chinese utility model patent with publication number CN202304505U proposes a Cantor set fractal structure heat exchanger. The heat exchange tube bundle of the shell and tube heat exchanger is designed with fractal structure features to make full use of the shell space and increase the flow heat exchange. In order to improve the comprehensive performance of flow heat transfer of the heat exchanger, that is, to maximize the thermal effectiveness (heat exchange/pump work) of the heat exchanger, and then achieve the purpose of efficient heat exchange and energy saving. The Chinese invention patent with publication number CN 102032828B proposes a new type of heat exchange tube with fractal surface structure features, and a special-shaped fluid-disturbing heat exchange tube is inserted in its tube, the heat exchange tube can improve the flow heat exchange field in the heat exchange tube Synergy to achieve efficient heat exchange and energy saving purposes.

SUMMARY OF THE INVENTION

One of the technical problems to be solved by the present invention is to provide a carbon dioxide capture method, which can reduce the energy consumption of the carbon capture process.

In order to solve the above technical problems, the carbon dioxide capture method of the present invention adopts a chemical absorption method based on a catalytic reaction process, and utilizes fractal-dimensional heat exchange and vapor recompression process enhancement technologies to capture carbon dioxide.

The main steps of the method include:

1) Absorb carbon dioxide gas from a gas source containing carbon dioxide using a chemical absorption medium to generate a rich absorption liquid;

2) desorb carbon dioxide from the rich absorbing liquid, and generate the lean absorbing liquid;

3) Separation of carbon dioxide from other vapors through vapor recompression process enhancement technology.

Among them, a solid base catalyst is used in the process of absorbing carbon dioxide, and a solid acid catalyst is used in the process of desorbing carbon dioxide.

The vapor recompression process enhancement technology includes the steps of: compressing and increasing the pressure of the mixed vapor, condensing and exchanging heat to form high-pressure liquid, throttling, and changing into a mixture of low-pressure and low-temperature saturated vapor and saturated liquid, and separating carbon dioxide gas and condensate .

The second technical problem to be solved by the present invention is to provide a carbon dioxide capture device based on the above method, which is more efficient and energy-saving.

In order to solve the above-mentioned technical problems, the carbon dioxide capture device of the present invention includes:

The absorption tower is used to absorb carbon dioxide gas from a gas source containing carbon dioxide by using a chemical absorption medium to generate a rich absorption liquid;

a desorption tower for separating the carbon dioxide from the rich absorption liquid to regenerate the chemical absorption medium to generate a lean absorption liquid;

A mixed steam separation system, used for exporting and cooling the mixed steam containing the carbon dioxide gas from the desorption tower, separating the carbon dioxide gas and the condensate, and transporting the condensate back to the desorption tower;

The reboiler system is used for exporting and heating the chemical absorption medium that has absorbed the carbon dioxide from the desorption tower, and then transporting it back to the desorption tower; the reboiler system includes a heat exchanger.

The mixed vapor separation system includes a vapor recompression device, and the vapor recompression device mainly consists of a compressor, a condenser, a throttle valve and an evaporator to form a closed system. The mixed steam of carbon dioxide, the condenser is used to condense the mixed steam compressed and boosted by the compressor into a high-pressure liquid, and the throttle valve is used to convert the high-pressure liquid into a mixture of low-pressure and low-temperature saturated steam and saturated liquid, The evaporator is used to separate carbon dioxide gas and condensate from the mixture of saturated steam and saturated liquid. The vapor recompression device realizes the upgrading of low-grade thermal energy to a high-grade temperature region through the state change and phase change of the working medium.

The reboiler system includes a vapor recompression device, the vapor recompression device includes a throttle valve, an evaporator and a compressor, the throttle valve is used for decompression, the evaporator is used for separating vapor and condensate, and the compressor is used for It is used to compress the vapor into high temperature and high pressure gas and return it to the desorption tower.

The condenser and the heat exchanger are fractal heat exchangers, and the fractal heat exchanger has a Cantor set fractal structure, which can increase the flow heat exchange area, thereby improving the overall flow heat exchange performance of the heat exchanger.

By using the catalytic desorption method, the invention improves the reaction rate, reduces the residence time, reduces the operating temperature of the device, and reduces the energy consumption; by using the fractal heat exchanger to increase the flow heat exchange area, and the vapor recompression process enhancement technology, The energy utilization efficiency of the system is improved, the process energy consumption is reduced, and it can be widely used in the capture, separation and purification of CO ₂ in natural gas, shift gas, flue gas or synthesis gas.

Description of drawings

FIG. 1 is a schematic diagram of the system structure of the carbon dioxide capture device according to Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram of the system structure of the carbon dioxide capture device according to the second embodiment of the present invention.

The reference numerals in the figure are explained as follows:

1, 26: Mixed gas source containing carbon dioxide gas

2, 27: raw material gas

3, 28: Decarbonization purification gas

4, 5, 6, 29, 30, 31: rich absorbent

7, 8, 9, 11, 12, 20, 21, 22, 23, 32, 33, 34, 37, 38, 42, 43, 44, 46, 47: lean absorption liquid

10, 45: Supplementary Absorbent

13, 48: Carbon dioxide and steam mixture

14, 41: High temperature and high pressure steam

15: High pressure liquid

16, 39: Vapor-liquid mixture

17, 50: carbon dioxide gas

18, 19, 51: Condensate

24, 35: External heat source (input)

25, 36: External heat source (output)

40: Low temperature and low pressure steam

49: Mixed liquid containing carbon dioxide

52: Condensate (input)

53: Condensate (output)

1001, 2001: Absorption tower

1002, 2002: Desorption tower

1003, 2003: Fans

1004, 2004: Rich Absorbent Pump

1005, 2005: Rich and poor absorption liquid heat exchanger

1006, 2012: Lean Absorbent Pump

1007, 2013: Coolers

1008, 2011: Compressors

1009, 2014: Condensers

1010, 2009: Throttle valve

1011, 2010, 2015: Gas-liquid separator

1012, 1013, 2006, 2008: Circulating Pumps

1014, 2007: Reboiler System Heat Exchanger

Detailed ways

In order to have a more specific understanding of the technical content, features and effects of the present invention, the detailed description is as follows in conjunction with the illustrated embodiments. Production devices and process methods that are not described in detail in the examples all adopt existing known production devices and process methods.

Example 1

As shown in FIG. 1 , the carbon dioxide capture device of this embodiment includes: an absorption tower 1001 , a desorption tower 1002 , a mixed vapor separation system, a reboiler system, a vapor recompression device, and the like.

The mixed gas source 1 containing carbon dioxide gas is fed into the absorption tower 1001 through the fan 1003, flows through the absorption tower 1001 from bottom to top, and forms a countercurrent contact with the lean absorption liquid 12 entering the tower from the top, so that the carbon dioxide is removed. The purified decarburized purified gas 3 is discharged from the top of the absorption tower 1001 . The rich absorbing liquid 4 that has absorbed carbon dioxide is pumped into the lean-rich absorbing liquid heat exchanger 1005 through the rich absorbing liquid pump 1004 for heat exchange with the desorbed lean absorbing liquid 8 with a higher temperature, and then enters the desorption tower 1002 after absorbing heat. The rich absorption liquid 6 enters from the upper part of the desorption tower 1002, and the lean absorption liquid 7 after desorbing carbon dioxide flows out from the bottom of the desorption tower 1002. Enter the absorption tower 1001. The carbon dioxide and steam mixture 13 discharged from the top of the desorption tower 1002 enters the vapor recompression device, and is compressed into high temperature and high pressure steam by the compressor 1008. 1011 separates the condensate 18 and the carbon dioxide gas 17, the condensate 18 is transported back to the desorption tower 1002 by the circulating pump 1012, and the separated carbon dioxide gas 17 enters the subsequent compression process. The lean absorbing liquid 20 at the bottom of the desorption tower 1002 is pumped into the reboiler system by the circulating pump 1013, and after the heat exchange and temperature rise in the condenser 1009 of the vapor recompression device, it enters the reboiler system heat exchanger 1014, and then returns to the desorption tower 1002. The heat source of the reboiler system heat exchanger 1014 is provided from outside (eg, saturated steam).

Example 2

As shown in FIG. 2 , the carbon dioxide capture device of this embodiment includes: an absorption tower 2001 , a desorption tower 2002 , a mixed vapor separation system, a reboiler system, a vapor recompression device, and the like.

The mixed gas source 26 containing carbon dioxide gas is fed into the absorption tower 2001 through the fan 2003, flows through the absorption tower 2001 from bottom to top, and forms a countercurrent contact with the lean absorption liquid 47 entering the tower from the top, so that the carbon dioxide is removed. The purified decarburized purified gas 28 is discharged from the top of the absorption tower 2001 . The rich absorbing liquid 29 that has absorbed carbon dioxide is pumped into the lean-rich absorbing liquid heat exchanger 2005 through the rich absorbing liquid pump 2004 for heat exchange with the desorbed lean absorbing liquid 43 with a higher temperature, and then enters the desorption tower 2002 after absorbing heat. The rich absorption liquid 31 enters from the upper part of the desorption tower 2002 . Part of the lean absorption liquid after desorbing carbon dioxide enters the reboiler system, enters the reboiler system heat exchanger 2007 through the circulating pump 2006, and then returns to the desorption tower 2002, and the heat source of the reboiler system heat exchanger 2007 is provided by the outside (such as , saturated steam); the other part enters the vapor recompression device, passes through the circulating pump 2008, and then decompresses through the throttle valve 2009, then enters the gas-liquid separator 2010, and the low-temperature and low-pressure steam 40 is compressed into the high-temperature and high-pressure steam 41 by the compressor 2011 and returns In the desorption tower 2002, the lean absorbing liquid 42 enters the absorption tower 2001 after heat exchange and cooling by the lean liquid pump 2012, the lean and rich liquid heat exchanger 2005, and the cooler 2013. The carbon dioxide and steam mixture 48 discharged from the top of the desorption tower 2002 enters the mixed steam separation system, and after heat exchange in the condenser 2014, the liquid phase returns to the desorption tower 2002 through the gas-liquid separator 2015, and the separated carbon dioxide gas 50 enters the subsequent Compression handler.

In the absorption process and the desorption process of the above two embodiments, a catalytic reaction is introduced to reduce the energy consumption of the reaction and desorption. Solid base catalysts are used in the absorption process, and solid acid catalysts are used in the desorption process.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. The technical solutions of the present invention are modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention. within the scope of the claims.

Claims (3)

1. The carbon dioxide trapping method is characterized in that a chemical absorption method based on a catalytic reaction process is adopted, and a fractal dimension heat exchange and steam recompression process strengthening technology is utilized to trap carbon dioxide; the method comprises the following steps:

1) absorbing carbon dioxide gas from a carbon dioxide-containing gas source by using a chemical absorption medium to generate a rich absorption liquid; using a solid base catalyst in the absorption of carbon dioxide; the rich absorption liquid is pumped into the lean absorption liquid heat exchanger through a rich absorption liquid pump to exchange heat with the desorbed lean absorption liquid with higher temperature, and the lean absorption liquid enters the desorption tower after absorbing heat;

2) desorbing carbon dioxide from the rich absorption liquid and generating a lean absorption liquid; using a solid acid catalyst in the desorption of carbon dioxide; part of the lean absorption liquid after the carbon dioxide desorption enters a reboiler system, enters a reboiler system heat exchanger through a circulating pump and then returns to the desorption tower, and a heat source of the reboiler system heat exchanger is provided by the outside; the other part of the absorption liquid enters a steam recompression device, is decompressed by a circulating pump and a throttle valve, then enters a gas-liquid separator, low-temperature and low-pressure steam is compressed into high-temperature and high-pressure steam by a compressor and returns to a desorption tower, and lean absorption liquid enters an absorption tower after being subjected to heat exchange and cooling by a lean liquid pump, a lean and rich liquid heat exchanger and a cooler;

3) and (3) the mixture of the carbon dioxide and the steam discharged from the top of the desorption tower enters a mixed steam separation system, the heat is exchanged by a condenser, a gas-liquid separator is used for separating the carbon dioxide gas, the liquid phase returns to the desorption tower, and the separated carbon dioxide gas enters a subsequent compression treatment procedure.

2. A carbon dioxide capture device for use in the method of claim 1, comprising:

the absorption tower is used for absorbing carbon dioxide gas from a gas source containing carbon dioxide by adopting a chemical absorption medium to generate rich absorption liquid; the rich absorption liquid is pumped into the lean absorption liquid heat exchanger through a rich absorption liquid pump to exchange heat with the desorbed lean absorption liquid with higher temperature, and the lean absorption liquid enters the desorption tower after absorbing heat;

a desorption tower for separating the carbon dioxide from the rich absorption liquid to regenerate a chemical absorption medium to produce a lean absorption liquid; one part of the lean absorption liquid after the carbon dioxide desorption enters a reboiler system, the other part of the lean absorption liquid enters a steam recompression device, the lean absorption liquid enters a gas-liquid separator after being subjected to pressure reduction through a circulating pump and a throttle valve, low-temperature and low-pressure steam is compressed into high-temperature and high-pressure steam through a compressor and returns to a desorption tower, and the lean absorption liquid enters an absorption tower after being subjected to heat exchange and cooling through a lean liquid pump, a lean-rich liquid heat exchanger and a cooler;

a mixed vapor separation system for conducting a mixed vapor containing the carbon dioxide gas out of the desorption tower, cooling the mixed vapor, separating the carbon dioxide gas from the condensate, and returning the condensate to the desorption tower;

a reboiler system for leading the chemical absorption medium having absorbed the carbon dioxide out of the desorption tower, heating the chemical absorption medium, and returning the heated chemical absorption medium to the desorption tower; the reboiler system comprises a heat exchanger.

3. The apparatus of claim 2, wherein the condenser and heat exchanger are fractal heat exchangers having a constantan set fractal structure.

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