CN118022490B - Low-pressure flue gas CO2Energy-saving trapping process - Google Patents
Low-pressure flue gas CO2Energy-saving trapping process Download PDFInfo
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 49
- 239000003546 flue gas Substances 0.000 title claims abstract description 49
- 230000008929 regeneration Effects 0.000 claims abstract description 78
- 238000011069 regeneration method Methods 0.000 claims abstract description 78
- 238000010521 absorption reaction Methods 0.000 claims abstract description 58
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000005516 engineering process Methods 0.000 claims abstract description 31
- 230000002745 absorbent Effects 0.000 claims abstract description 30
- 239000002250 absorbent Substances 0.000 claims abstract description 30
- 230000006835 compression Effects 0.000 claims abstract description 25
- 238000007906 compression Methods 0.000 claims abstract description 25
- 238000003795 desorption Methods 0.000 claims abstract description 20
- 239000002918 waste heat Substances 0.000 claims abstract description 20
- 238000005265 energy consumption Methods 0.000 claims abstract description 15
- 238000010438 heat treatment Methods 0.000 claims abstract description 13
- 238000004064 recycling Methods 0.000 claims abstract description 11
- 238000005191 phase separation Methods 0.000 claims abstract description 10
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- 230000008859 change Effects 0.000 claims abstract description 9
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- 239000000428 dust Substances 0.000 claims abstract description 4
- 239000007788 liquid Substances 0.000 claims description 77
- 239000007789 gas Substances 0.000 claims description 42
- 239000012071 phase Substances 0.000 claims description 36
- 238000010992 reflux Methods 0.000 claims description 10
- 239000000945 filler Substances 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 238000005086 pumping Methods 0.000 claims description 5
- 238000013461 design Methods 0.000 claims description 4
- 238000012546 transfer Methods 0.000 claims description 4
- 125000004122 cyclic group Chemical group 0.000 claims description 3
- 238000001704 evaporation Methods 0.000 claims description 3
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- 239000012535 impurity Substances 0.000 claims description 3
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- 238000004519 manufacturing process Methods 0.000 claims description 3
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- 238000009834 vaporization Methods 0.000 claims description 3
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- 230000010485 coping Effects 0.000 abstract description 2
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- 238000005457 optimization Methods 0.000 abstract description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 18
- 229910002092 carbon dioxide Inorganic materials 0.000 description 9
- 239000001569 carbon dioxide Substances 0.000 description 9
- 238000007789 sealing Methods 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1456—Removing acid components
- B01D53/1475—Removing carbon dioxide
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1418—Recovery of products
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1425—Regeneration of liquid absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/18—Absorbing units; Liquid distributors therefor
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/50—Carbon dioxide
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B27/00—Machines, plants or systems, using particular sources of energy
- F25B27/02—Machines, plants or systems, using particular sources of energy using waste heat, e.g. from internal-combustion engines
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/50—Carbon oxides
- B01D2257/504—Carbon dioxide
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
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- B01D2258/0283—Flue gases
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Abstract
The invention relates to the technical field of CO 2 energy-saving trapping and purifying, and discloses a low-pressure flue gas CO 2 energy-saving trapping process, which comprises a flue gas waste heat recycling system, a split-phase energy-saving system and an energy-saving regeneration system, and is used for realizing water washing dust fall and cooling (to 40 ℃) of high-temperature low-pressure flue gas (more than 150 ℃), flue gas CO 2 absorption, CO 2 desorption and absorbent regeneration, and specifically comprises the following steps: s1, after the temperature of the outside water is raised by a flue gas heat exchanger, the outside water is used as a low-temperature heat source (70-90 ℃) to drive a compression heat pump to generate high-temperature steam, and heat energy is provided for a tower bottom reboiler of the regeneration tower. The invention combines the compression heat pump technology, the phase separation technology and the interstage heating technology, and aims to remarkably improve the efficiency of CO 2 trapping and greatly reduce the energy consumption and the operation cost. Through the deep integration and optimization of various technologies, the energy efficiency improvement and the energy consumption reduction of the CO 2 capturing process are successfully realized, and a more economic and environment-friendly solution is provided for coping with global climate change.
Description
Technical Field
The invention relates to the technical field of energy-saving CO 2 trapping and purifying, in particular to an energy-saving low-pressure flue gas CO 2 trapping process.
Background
As is well known, with the continuous development of world economy, the greenhouse effect affecting climate abnormal changes is becoming serious in recent decades, natural disasters frequently occur in the global area, and life threat and property loss brought to people are huge. As CO 2 is one of the main greenhouse gases, with the continuous development of domestic industry, fossil energy, whether it is the total annual consumption or the proportion occupied in primary energy, is continuously rising, so that a large amount of carbon dioxide gas is discharged into the atmosphere, and thus the influence on global climate is receiving wide attention from all countries of the world.
In 1997, in order to alleviate global warming and protect humans from climate warming, the united nations climate change framework convention participating state signed the "kyoto protocol" in japan, requiring developed countries to bear obligations to reduce carbon emissions since 2005, and some european countries have implemented carbon tax collection policies to control emissions. The developing country starts to bear relief from 2012, and China also implements preferential policies for encouraging recovery. Each country has carbon dioxide relief, and how to effectively reduce CO 2 emissions has become an important political economic issue in countries around the world, and is a difficult task facing the world today.
In industrial production, a large amount of CO 2 is discharged as waste gas, so that the ecological environment is destroyed, bad influence is brought to the survival of human beings, the valuable resource CO 2 is wasted, the resource CO 2 is captured and developed and utilized, waste is changed into valuable, and the method has good economic and social benefits and has no wider market prospect. In the field of CO 2 capturing and utilizing, a CO 2 capturing, utilizing and sealing technology (CCUS) provides a powerful technical support for reducing CO 2 emission and realizing recycling and large-scale utilization of CO 2, and can be used for recycling CO 2 in a large scale from waste gas of enterprises such as refining, cement, coal-fired thermal power generation, steelmaking and the like.
Under the current background of increasingly severe global climate change and environmental issues, the CO 2 capture technology has gained widespread attention by the scientific research and industry as an important means to reduce greenhouse gas emissions and to cope with global warming. Although the traditional carbon dioxide capturing process can realize the separation and sealing of carbon dioxide to a certain extent, the problems of high energy consumption, low efficiency, high running cost and the like limit the large-scale application of the traditional carbon dioxide capturing process. Therefore, the existing process is optimized and perfected, and the novel energy-saving trapping and purifying process for CO 2 is urgent.
Disclosure of Invention
The invention aims to solve the problems of high energy consumption, low efficiency, high operation cost and the like of the traditional carbon dioxide trapping process in the prior art, which can realize the separation and the sealing of carbon dioxide to a certain extent, and provides the low-pressure flue gas CO 2 energy-saving trapping process.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
The low-pressure flue gas CO 2 energy-saving trapping process comprises a flue gas waste heat recycling system, a split-phase energy-saving system and an energy-saving regeneration system, and realizes the water washing dust fall and cooling (to 40 ℃) of high-temperature low-pressure flue gas (more than 150 ℃), the absorption of flue gas CO 2, the desorption of CO 2 and the regeneration of an absorbent, and specifically comprises the following steps:
S1, after the temperature of the outside water is raised by a flue gas heat exchanger, the outside water is used as a low-temperature heat source (70-90 ℃) to drive a compression heat pump to generate high-temperature steam, and heat energy is provided for a tower bottom reboiler of a regeneration tower;
S2, enabling the flue gas subjected to water washing treatment to flow into an absorption tower, and carrying out chemical reaction with a CO 2 absorbent sprayed from the tower top to change an absorbent lean solution without CO 2 into an absorbent rich solution loaded with CO 2, so as to complete absorption of CO 2 in the flue gas;
S3, after the treatment of the absorption tower, extracting an absorbent rich solution rich in CO 2 from the bottom of the absorption tower, and pumping the absorbent rich solution into a subsequent working section through a rich solution pump;
S4, adding a phase separator between the absorption tower and the regeneration tower to separate the rich liquid, re-refluxing the upper dilute phase to the absorption tower, and pumping the lower rich phase into the regeneration tower, so that on one hand, the regeneration volume is reduced, the regeneration energy consumption is reduced, and on the other hand, the utilization rate of the absorbent is improved through the dilute phase reflux, and the production cost is greatly reduced;
s5, utilizing the hot water waste heat of the reboiler to heat the middle section solution of the regeneration tower for the second time, so that on one hand, the desorption amount of the rich solution is increased, and on the other hand, the energy utilization rate of the system is greatly improved;
In the step S1, a flue gas waste heat recycling system mainly adopting a compression heat pump technology is adopted; the compression heat pump comprises a compressor, an evaporator, a condenser and a throttle valve, wherein the low-temperature low-pressure heat pump cycle working medium is subjected to isobaric absorption to change the heat of a low-temperature low-pressure heat source into high-temperature low-pressure gas, the high-temperature high-pressure gas is subjected to adiabatic compression by the compressor, the high-temperature high-pressure gas is subjected to isobaric heat release in the condenser and is finally changed into low-temperature high-pressure liquid, the low-temperature low-pressure cycle working medium is subjected to adiabatic throttling by the throttle valve, and the liquid cycle working medium flows through the evaporator to start a new cycle process;
in the step S2, a phase-splitting energy-saving system mainly adopting a phase-splitting technology is adopted; the whole absorption tower adopts a filler tower structural design, and five sections of fillers are sequentially arranged from top to bottom;
after the rich liquid in the step S4 is subjected to phase separation, the upper dilute phase is mixed with the lean liquid at the bottom of the regeneration tower under the pushing of a dilute phase pump and is pumped into an absorption tower again for cyclic absorption;
The lower layer of rich phase is separated into cold and hot two streams to enter the regeneration tower under the pushing of a rich phase pump;
In the step S5, an energy-saving regeneration system mainly adopting an inter-stage heating technology is adopted, and the system consists of a regeneration tower, an inter-stage heater and an MVR heat pump;
The MVR heat pump is arranged at the bottom of the regeneration tower, the desorbed lean solution enters the flash tower for flash evaporation, and a large amount of liquid is gasified instantly due to the pressure reduction in the flash tower, so that a large amount of steam (namely secondary steam) is generated, and the vaporization latent heat of the liquid is converted into the sensible heat of gas to be extracted;
the regenerated lean solution is pressurized by a lean solution pump and then enters a lean-rich solution heat exchanger for heat exchange, and the lean solution (60-65 ℃) after heat exchange is cooled by a lean solution cooler and then enters an absorption tower for circulating absorption.
In the step S1, the high-temperature hot water flowing out of the flue gas heat exchanger in the evaporator is changed into low-temperature hot water (30-50 ℃) after being evaporated and absorbed by the circulating working medium, and flows into the hot rich liquid preheater to preheat the hot rich liquid before the regeneration tower.
In the step S1, outside water (25 ℃) is converted into high-temperature steam (120 ℃) to flow into a gas-liquid separator after high-temperature high-pressure gas fluidization heat release in a condenser, and lower-layer hot water (80 ℃ -90 ℃) flows into a cold rich liquid preheater to preheat cold rich liquid before a regeneration tower; the upper steam flows into a steam mixing tank, is mixed with the outside steam and flows into a reboiler, and provides heat energy for the CO 2 desorption process in the regeneration tower.
Furthermore, in step S2, in order to reduce the damage degree of the tail gas to the environment, the solution is extracted below the first section of filler at the top of the tower for washing, so that the impurity content of the tail gas is further reduced, and the tail gas at the top of the tower meets the direct emission requirement.
Further, in the step S2, in order to better and fully complete the absorption of CO 2, a part of rich liquid (10% -20%) is extracted below the fourth-stage filling material to be cooled and refluxed, and the rich liquid is cooled to 40 ℃ -45 ℃ by an inter-stage cooler and then enters the absorption tower again, so that the solution load is increased, and the absorption efficiency of the absorbent on CO 2 is improved.
Further, in the step S2, a gas distributor is additionally arranged at the bottom of the tower, so that the flue gas entering the tower is uniformly distributed on the section of the whole tower, and gas-liquid mass transfer with the liquid phase of the absorption tower is facilitated.
Further, in the step S4, a small part of rich liquid (20% -30%) is preheated by a cold rich liquid preheater and then flows into the top of the desorption tower as cold rich liquid; most of the rich liquid (70% -80%) is subjected to heat exchange through a lean rich liquid heat exchanger, is further heated through a hot rich liquid preheater, and finally flows into the top of the regeneration tower as hot rich liquid.
Further, in step S5, an interstage heater is disposed in the middle section of the regeneration tower, lean liquor flowing into the regeneration tower is heated and regenerated by a reboiler, then interstage heating is performed on rich liquor by using residual heat of condensed water, temperature drop caused by chemical reaction and heat loss is supplemented, and the rich liquor is kept in a proper temperature range, so that the desorption capability of CO 2 of the rich liquor is ensured;
the tower top of the regeneration tower is provided with a compression heat pump system, the waste heat of the gas produced from the tower top is used as a low-temperature heat source, high-temperature steam is produced through the compression heat pump, and the high-temperature steam flows into a steam mixer to supply heat for the regeneration tower;
The regenerated gas flowing out of the compression heat pump enters a gas-liquid separator through a regenerated gas cooler, and dilute solution from the bottom part of the separator is pressurized by a reflux pump and returns to a regeneration tower to maintain the solution balance of the system;
the CO 2 product gas coming out from the upper part of the separator enters the subsequent process, thereby completing the whole CO 2 capturing process.
Compared with the prior art, the invention has the following beneficial effects:
1. In the invention, the compression heat pump technology is adopted to drive the compressor by using a small amount of electric energy, so that the low-temperature waste heat in the flue gas is lifted and used for driving the trapping process of CO 2 under the condition of lower energy consumption, and the heat transfer from low temperature to high temperature is realized, thereby reducing the energy consumption of the whole trapping process.
2. In the invention, the phase separation technology is adopted to mainly utilize the density difference of the rich phase and the dilute phase in the rich liquid absorbent to realize that the rich phase absorbent flows into the regeneration tower for regeneration, and the dilute phase absorbent flows back into the absorption tower for absorption again. The technology can not only improve the utilization rate of the CO 2 absorbent, but also greatly reduce the energy consumption in the regeneration process by reducing the volume of the rich liquid entering the regeneration tower, and has important significance for realizing the low-energy-consumption trapping of CO 2.
3. In the invention, the interstage heating technology is adopted, which has important significance for increasing the desorption rate of the rich liquid and improving the whole energy utilization rate of the trapping process. In the traditional CO 2 regeneration process, high-temperature steam directly flows out of the boundary after heat exchange by a tower bottom reboiler, so that a large amount of low-temperature heat energy is wasted. The interstage heating technology carries out secondary temperature rise on the middle section solution of the regeneration tower by recovering and recycling the waste heat, thereby greatly reducing the energy utilization rate of the whole trapping process.
In general, the invention integrates the heat pump system, the phase separation system and the inter-stage cooling system in a coupling way, thereby not only realizing high-efficiency carbon dioxide trapping, but also obviously reducing energy consumption, having important environmental protection and economic benefits, and compared with the traditional CO 2 trapping technology, the invention greatly improves the utilization rate of the absorbent, reduces the trapping energy consumption and saves investment and operation cost. In the future, with the further development and improvement of the process, more efficient and energy-saving carbon dioxide capturing and sealing are expected to be realized.
Drawings
FIG. 1 is a process flow diagram of an energy-saving capture process for low-pressure flue gas CO 2 of the present invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention discloses an exemplary embodiment of the invention provides a low-pressure flue gas CO 2 energy-saving trapping process, as shown in figure 1, the whole process flow consists of a flue gas waste heat recycling system, a split-phase energy-saving system and an energy-saving regeneration system, and the method comprises the following steps of water washing, dust reduction and cooling (to 40 ℃) of high-temperature low-pressure flue gas (more than 150 ℃), flue gas CO 2 absorption, CO 2 desorption and absorbent regeneration, and specifically comprises the following steps:
S1, adopting a flue gas waste heat recycling system mainly based on a heat pump technology: after the temperature of the outside water is raised by the flue gas heat exchanger, the outside water is used as a low-temperature heat source (70-90 ℃) to drive the compression heat pump to generate high-temperature steam, so as to provide heat energy for a tower bottom reboiler of the regeneration tower;
Firstly, the isobaric absorption low-temperature low-pressure heat pump cycle working medium of low temperature low pressure changes into high-temperature low-pressure gas by the isobaric absorption low-temperature low-pressure heat source heat quantity, then the high-temperature high-pressure gas is changed into high-temperature high-pressure gas after adiabatic compression by a compressor, finally the high-temperature high-pressure gas in a condenser releases heat by isobaric pressure and becomes low-temperature high-pressure liquid, finally the low-temperature low-pressure cycle working medium is changed into the low-temperature low-pressure cycle working medium after adiabatic throttling by a throttle valve, and the liquid cycle working medium flows through an evaporator to start a new cycle process;
in the evaporator, the high-temperature hot water flowing out of the flue gas heat exchanger is changed into low-temperature hot water (30-50 ℃) after being evaporated and absorbed by the circulating working medium, and flows into the hot rich liquid preheater to preheat the hot rich liquid before the regeneration tower;
In the condenser, outside water (25 ℃) is converted into high-temperature steam (120 ℃) to flow into the gas-liquid separator after high-temperature high-pressure gas liquid heat release, and lower-layer hot water (80 ℃ -90 ℃) flows into the cold rich liquid preheater to preheat the cold rich liquid before the regeneration tower;
the upper steam flows into a steam mixing tank, is mixed with the outside steam and flows into a reboiler, so as to provide heat energy for the CO 2 desorption process in the regeneration tower;
S2, enabling the flue gas subjected to water washing treatment to flow into an absorption tower, and carrying out chemical reaction with a CO 2 absorbent sprayed from the tower top to change an absorbent lean solution without CO 2 into an absorbent rich solution loaded with CO 2, so as to complete absorption of CO 2 in the flue gas;
The whole absorption tower adopts a filler tower structural design, and five sections of fillers are sequentially arranged from top to bottom;
In order to reduce the damage degree of tail gas to the environment, extracting solution below the first section of filler at the top of the tower for washing, and further reducing the impurity content of the tail gas, so that the tail gas at the top of the tower meets the direct emission requirement;
In the middle section of the absorption tower, in order to better and fully complete the absorption of CO 2, a part of rich liquid (10% -20%) is extracted below the fourth section of filling material for cooling reflux, and the rich liquid is cooled to 40 ℃ -45 ℃ by an inter-stage cooler and then enters the absorption tower again, so that the solution load is increased, and the absorption efficiency of the absorbent on CO 2 is improved;
a gas distributor is additionally arranged at the bottom of the tower, so that the flue gas entering the tower is uniformly distributed on the section of the whole tower, and gas-liquid mass transfer with the liquid phase of the absorption tower is facilitated;
S3, after the treatment of the absorption tower, extracting an absorbent rich solution rich in CO 2 from the bottom of the absorption tower, and pumping the absorbent rich solution into a subsequent working section through a rich solution pump;
S4, adopting a phase-splitting energy-saving system mainly based on a phase-separation technology: a phase separator is additionally arranged between the absorption tower and the regeneration tower to carry out phase separation on the rich liquid, the upper dilute phase is refluxed to the absorption tower again, and the lower rich phase is pumped into the regeneration tower, so that on one hand, the regeneration volume is reduced, the regeneration energy consumption is reduced, and on the other hand, the utilization rate of the absorbent is improved through the reflux of the dilute phase, and the production cost is greatly reduced;
after the rich liquid is subjected to phase separation, the upper dilute phase is mixed with the lean liquid at the bottom of the regeneration tower under the pushing of a dilute phase pump and is pumped into an absorption tower again for cyclic absorption;
the lower layer of rich phase is separated into cold and hot two streams to enter the regeneration tower under the pushing of the rich phase pump. A small part of rich liquid (20% -30%) flows into the top of the desorption tower as cold rich liquid after being preheated by a cold rich liquid preheater; most of the rich liquid (70% -80%) is subjected to heat exchange through a lean rich liquid heat exchanger, then is further heated through a hot rich liquid preheater, and finally flows into the top of the regeneration tower as hot rich liquid;
s5, adopting an energy-saving regeneration system mainly adopting an interstage heating technology: the system consists of a regeneration tower, an interstage heater and an MVR heat pump, and utilizes the hot water waste heat of a reboiler to carry out secondary heating and heating on the middle section solution of the regeneration tower, so that on one hand, the desorption amount of rich liquid is increased, and on the other hand, the energy utilization rate of the system is greatly improved;
The MVR heat pump is arranged at the bottom of the regeneration tower, the desorbed lean solution enters the flash tower for flash evaporation, and a large amount of liquid is gasified in the moment due to the pressure reduction in the flash tower, so that a large amount of steam (namely secondary steam) is generated, and the vaporization latent heat of the liquid is converted into the sensible heat of gas to be extracted. The regenerated lean solution is pressurized by a lean solution pump and then enters a lean-rich solution heat exchanger for heat exchange, and the lean solution (60-65 ℃) after heat exchange is cooled by a lean solution cooler and then enters an absorption tower for circulating absorption;
An interstage heater is arranged in the middle section of the regeneration tower, lean liquid flowing into the regeneration tower is heated and regenerated by a reboiler, then interstage heating is carried out on rich liquid by utilizing condensate water waste heat, temperature reduction caused by chemical reaction and heat loss is supplemented, and the rich liquid is kept in a proper temperature range, so that the CO 2 desorption capability of the rich liquid is ensured;
the tower top of the regeneration tower is provided with a compression heat pump system, the waste heat of the gas produced from the tower top is used as a low-temperature heat source, high-temperature steam is produced through the compression heat pump, and the high-temperature steam flows into a steam mixer to supply heat for the regeneration tower;
The regenerated gas flowing out of the compression heat pump enters a gas-liquid separator through a regenerated gas cooler, and dilute solution from the bottom part of the separator is pressurized by a reflux pump and returns to a regeneration tower to maintain the solution balance of the system;
the CO 2 product gas coming out from the upper part of the separator enters the subsequent process, thereby completing the whole CO 2 capturing process.
The invention creatively provides a flue gas waste heat recycling system based on a compression heat pump technology, high-temperature steam is generated by the compression heat pump for the desorption process of CO 2, the breakthrough technology not only optimizes the traditional CO 2 desorption method, but also realizes the remarkable improvement of the energy utilization rate and the reduction of the operation cost by the high-efficiency energy conversion characteristic of the compression heat pump. The application range of the heat pump technology in the field of industrial gas treatment is widened, and a new thought and possibility are provided for realizing a low-carbon and energy-saving CO 2 capturing and separating process.
The invention innovatively provides a phase-splitting energy-saving system mainly based on a phase separation technology, and by introducing a phase separator between a CO 2 absorption tower and a desorption tower, the separation of a dilute phase and a rich phase of lean solution is realized, a traditional mode of regenerating all lean solution is broken through, only the rich phase rich in CO 2 is regenerated, and the relatively clean dilute phase is directly returned to the absorption tower, so that the volume of regenerated rich solution is obviously reduced, the energy efficiency ratio of a CO 2 capturing process is optimized, and important theoretical support and practical guidance are provided for the economy and sustainability of a carbon capturing and sealing technology.
The invention creatively provides an energy-saving regeneration system mainly based on an interstage heating technology, and the interstage heater is arranged at the middle section of the CO 2 regeneration tower, so that the waste heat of condensed water flowing out of a reboiler is fully utilized, the efficiency of the regeneration process is improved, waste heat resources in the process are utilized to the maximum extent, and the recovery and the reutilization of energy are realized.
In summary, the invention designs an energy-saving trapping process for low-pressure flue gas CO 2, which combines an advanced compression heat pump technology, a phase separation technology and an interstage heating technology, and aims to remarkably improve the efficiency of CO 2 trapping and greatly reduce the energy consumption and the operation cost. Through the deep integration and optimization of various technologies, the energy efficiency improvement and the energy consumption reduction of the CO 2 capturing process are successfully realized, and a more economic and environment-friendly solution is provided for coping with global climate change.
The foregoing has shown and described the basic principles and main features of the present invention and the advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (7)
1. The low-pressure flue gas CO 2 energy-saving trapping process is characterized in that the whole process flow consists of a flue gas waste heat recycling system, a split-phase energy-saving system and an energy-saving regeneration system, and the low-pressure flue gas water washing dust fall of which the temperature is higher than 150 ℃ is realized, the temperature is reduced to 40 ℃, the flue gas CO 2 absorption, the CO 2 desorption and the absorbent regeneration are realized, and the method specifically comprises the following steps:
S1, after the temperature of the outside water is increased by a flue gas heat exchanger, the outside water is used as a low-temperature heat source with the temperature of 70-90 ℃ to drive a compression heat pump to generate high-temperature steam, and heat energy is provided for a reboiler at the bottom of a regeneration tower;
S2, enabling the flue gas subjected to water washing treatment to flow into an absorption tower, and carrying out chemical reaction with a CO 2 absorbent sprayed from the tower top to change an absorbent lean solution without CO 2 into an absorbent rich solution loaded with CO 2, so as to complete absorption of CO 2 in the flue gas;
S3, after the treatment of the absorption tower, extracting an absorbent rich solution rich in CO 2 from the bottom of the absorption tower, and pumping the absorbent rich solution into a subsequent working section through a rich solution pump;
S4, adding a phase separator between the absorption tower and the regeneration tower to separate the rich liquid, re-refluxing the upper dilute phase to the absorption tower, and pumping the lower rich phase into the regeneration tower, so that on one hand, the regeneration volume is reduced, the regeneration energy consumption is reduced, and on the other hand, the utilization rate of the absorbent is improved through the dilute phase reflux, and the production cost is greatly reduced;
s5, utilizing the hot water waste heat of the reboiler to heat the middle section solution of the regeneration tower for the second time, so that on one hand, the desorption amount of the rich solution is increased, and on the other hand, the energy utilization rate of the system is greatly improved;
In the step S1, a flue gas waste heat recycling system mainly adopting a heat pump technology is adopted; the compression heat pump comprises a compressor, an evaporator, a condenser and a throttle valve, wherein the low-temperature low-pressure heat pump cycle working medium is subjected to isobaric absorption to change the heat of a low-temperature low-pressure heat source into high-temperature low-pressure gas, the high-temperature high-pressure gas is subjected to adiabatic compression by the compressor, the high-temperature high-pressure gas is subjected to isobaric heat release in the condenser and is finally changed into low-temperature high-pressure liquid, the low-temperature low-pressure cycle working medium is subjected to adiabatic throttling by the throttle valve, and the liquid cycle working medium flows through the evaporator to start a new cycle process;
in the step S2, a phase-splitting energy-saving system mainly adopting a phase-splitting technology is adopted; the whole absorption tower adopts a filler tower structural design, and five sections of fillers are sequentially arranged from top to bottom;
after the rich liquid in the step S4 is subjected to phase separation, the upper dilute phase is mixed with the lean liquid at the bottom of the regeneration tower under the pushing of a dilute phase pump and is pumped into an absorption tower again for cyclic absorption;
The lower layer of rich phase is separated into cold and hot two streams to enter the regeneration tower under the pushing of a rich phase pump;
In the step S5, an energy-saving regeneration system mainly adopting an inter-stage heating technology is adopted, and the system consists of a regeneration tower, an inter-stage heater and an MVR heat pump;
The MVR heat pump is arranged at the bottom of the regeneration tower, the desorbed lean solution enters the flash tower for flash evaporation, a large amount of liquid is gasified instantly due to the pressure reduction in the flash tower, a large amount of secondary steam is generated, and the vaporization latent heat of the liquid is converted into the sensible heat of gas to be extracted;
the regenerated lean solution is pressurized by a lean solution pump and then enters a lean-rich solution heat exchanger for heat exchange, and the lean solution with the temperature of 60-65 ℃ after heat exchange is cooled by a lean solution cooler and then enters an absorption tower for circulating absorption;
In the step S5, an interstage heater is arranged at the middle section of the regeneration tower, lean liquor flowing into the regeneration tower is heated and regenerated by a reboiler, then interstage heating is carried out on rich liquor by utilizing condensate water waste heat, temperature reduction caused by chemical reaction and heat loss is supplemented, and the rich liquor is kept in a proper temperature range so as to ensure the CO 2 desorption capability of the rich liquor;
the tower top of the regeneration tower is provided with a compression heat pump system, the waste heat of the gas produced from the tower top is used as a low-temperature heat source, high-temperature steam is produced through the compression heat pump, and the high-temperature steam flows into a steam mixer to supply heat for the regeneration tower;
the regenerated gas flowing out of the compression heat pump enters a gas-liquid separator through a regenerated gas cooler, and dilute solution from the bottom part of the separator is pressurized by a reflux pump and returns to a regeneration tower to maintain the solution balance of the system;
the CO 2 product gas coming out from the upper part of the separator enters the subsequent process, thereby completing the whole CO 2 capturing process.
2. The energy-saving trapping process of low-pressure flue gas CO 2 according to claim 1, wherein in the step S1, in the evaporator, high-temperature hot water flowing out of the flue gas heat exchanger is evaporated by the circulating working medium to absorb heat and then becomes low-temperature hot water with the temperature of 30-50 ℃, and the low-temperature hot water flows into the hot rich liquid preheater to preheat the hot rich liquid before the regeneration tower.
3. The energy-saving trapping process of low-pressure flue gas CO 2 according to claim 1, wherein in the step S1, after the outside water with the temperature of 25 ℃ is gasified and released by high-temperature high-pressure gas in a condenser, high-temperature steam with the temperature of 120 ℃ is changed into high-temperature steam, and the hot water with the temperature of 80-90 ℃ at the lower layer flows into a cold rich liquid preheater to preheat the cold rich liquid before a regeneration tower; the upper steam flows into a steam mixing tank, is mixed with the outside steam and flows into a reboiler, and provides heat energy for the CO 2 desorption process in the regeneration tower.
4. The energy-saving trapping process for low-pressure flue gas CO 2 according to claim 1, wherein in step S2, in order to reduce the damage degree of the tail gas to the environment, the solution is extracted below the first section of filler at the top of the tower for washing, so that the impurity content of the tail gas is further reduced, and the tail gas at the top of the tower meets the direct emission requirement.
5. The energy-saving capturing process of low pressure flue gas CO 2 according to claim 1, wherein in step S2, in order to better and more fully complete the absorption of CO 2, 10% -20% of rich liquid is extracted below the fourth section of packing for cooling and refluxing, and the rich liquid is cooled to 40 ℃ -45 ℃ by an inter-stage cooler and then enters the absorption tower again, so that the solution load is increased, and the absorption efficiency of the absorbent on CO 2 is improved.
6. The energy-saving trapping process for low-pressure flue gas CO 2 according to claim 1, wherein in the step S2, a gas distributor is additionally arranged at the bottom of the tower, so that the flue gas entering the tower is uniformly distributed on the whole section of the tower, and gas-liquid mass transfer with the liquid phase of the absorption tower is facilitated.
7. The energy-saving capturing process of low pressure flue gas CO 2 according to claim 1, wherein 20% -30% of the rich liquid in the step S4 flows into the top of the desorption tower as cold rich liquid after being preheated by a cold rich liquid preheater; 70% -80% of the rich liquid is subjected to heat exchange through a lean rich liquid heat exchanger, is further heated through a hot rich liquid preheater, and finally flows into the top of the regeneration tower as hot rich liquid.
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