CN116899362A - Variable density packed bed system and method for capturing low-temperature carbon - Google Patents
Variable density packed bed system and method for capturing low-temperature carbon Download PDFInfo
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- CN116899362A CN116899362A CN202311078734.7A CN202311078734A CN116899362A CN 116899362 A CN116899362 A CN 116899362A CN 202311078734 A CN202311078734 A CN 202311078734A CN 116899362 A CN116899362 A CN 116899362A
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- 238000000034 method Methods 0.000 title claims abstract description 36
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 33
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 33
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 106
- 239000003546 flue gas Substances 0.000 claims abstract description 106
- 239000007789 gas Substances 0.000 claims abstract description 93
- 238000010926 purge Methods 0.000 claims abstract description 67
- 239000000945 filler Substances 0.000 claims abstract description 58
- 238000001816 cooling Methods 0.000 claims abstract description 32
- 230000008569 process Effects 0.000 claims abstract description 23
- 238000009825 accumulation Methods 0.000 claims abstract description 16
- 238000011049 filling Methods 0.000 claims abstract description 15
- 230000005012 migration Effects 0.000 claims abstract description 8
- 238000013508 migration Methods 0.000 claims abstract description 8
- 230000000694 effects Effects 0.000 claims abstract description 5
- 238000012856 packing Methods 0.000 claims description 60
- 239000010410 layer Substances 0.000 claims description 59
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 38
- 239000000779 smoke Substances 0.000 claims description 38
- 239000013078 crystal Substances 0.000 claims description 25
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 19
- 239000001569 carbon dioxide Substances 0.000 claims description 19
- 238000000859 sublimation Methods 0.000 claims description 19
- 230000008022 sublimation Effects 0.000 claims description 18
- 238000000926 separation method Methods 0.000 claims description 15
- 239000012530 fluid Substances 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 7
- 238000005485 electric heating Methods 0.000 claims description 5
- 238000012544 monitoring process Methods 0.000 claims description 5
- 239000011229 interlayer Substances 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 229910001369 Brass Inorganic materials 0.000 claims description 3
- 229910000906 Bronze Inorganic materials 0.000 claims description 3
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 3
- 239000010951 brass Substances 0.000 claims description 3
- 239000010974 bronze Substances 0.000 claims description 3
- 239000000919 ceramic Substances 0.000 claims description 3
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical compound [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 claims description 3
- 238000009413 insulation Methods 0.000 claims description 3
- 229910001220 stainless steel Inorganic materials 0.000 claims description 3
- 239000010935 stainless steel Substances 0.000 claims description 3
- 238000004781 supercooling Methods 0.000 claims description 3
- 238000010408 sweeping Methods 0.000 claims description 3
- 230000003213 activating effect Effects 0.000 claims description 2
- 239000002440 industrial waste Substances 0.000 claims 1
- 238000005057 refrigeration Methods 0.000 claims 1
- 238000001926 trapping method Methods 0.000 abstract description 4
- 239000000047 product Substances 0.000 description 14
- 238000013461 design Methods 0.000 description 4
- 238000011084 recovery Methods 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 239000002826 coolant Substances 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000003517 fume Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000010257 thawing Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000012263 liquid product Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- 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
- B01D53/002—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 condensation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D7/00—Sublimation
- B01D7/02—Crystallisation directly from the vapour phase
-
- 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
Abstract
The invention discloses a variable density packed bed system and a trapping method for trapping low-temperature carbon, wherein the variable density packed bed system comprises a flue gas precooler, a cooling device, a flue gas pressurizing buffer tank, a variable density packed bed and CO 2 The gas product storage tank, the cold energy recoverer, the gas chromatograph and the purge gas pressurizing buffer tank are connected through a plurality of pipelines and valves; the variable-density packed bed is provided with two inlets and two outlets, a plurality of cold accumulation fillers are filled in a filler area of the variable-density packed bed, and the filling density of the cold accumulation fillers is gradually reduced along the flow direction of the flue gas. According to the invention, the desublimation carbon is captured by adopting the variable-density cold accumulation filler matched with the migration characteristic of the frost layer in the desublimation process, so that the risks of excessive flow resistance and freeze blockage in the desublimation process are relieved, and the system is stable in operation, high in heat exchange efficiency and compact in structure; meanwhile, in the trapping method, the CO is further improved by a residual flue gas purging method 2 Gaseous productThe trapping purity is good, and the technical effect is good.
Description
Technical Field
The invention belongs to the technical field of carbon dioxide trapping, and particularly relates to a variable density packed bed system and a trapping method for low-temperature carbon trapping.
Background
Currently, CO 2 The trapping technology mainly comprises the following steps: absorption, adsorption, membrane separation and cryogenic separation. Compared with other methods, the low-temperature separation method utilizes the phase transition temperature difference between gas components to realize the separation of CO 2 Physical removal is carried out, the system does not involve chemical reaction during operation, and the trapped CO 2 The product has higher purity, does not cause secondary pollution to the environment, and has the advantages of long service life, high reliability and the like.
The low-temperature separation method can be classified into a desublimation separation method and a liquefaction separation method according to the phase change process. CO 2 Is 216.55K, the three-phase pressure is 0.518MPa, the critical point temperature is 304.25K, and the critical point pressure is 7.38MPa. The liquefaction separation method adopts a compression and condensation method to trap liquid products and combines CO 2 As can be seen from the phase diagram data, this method generally requires the CO to be processed 2 Compressed to a higher pressure. And CO 2 The sublimation phase change can occur under normal pressure, the trapping is completed in a solid form, compression equipment is not required to be introduced, and the operation energy consumption is low, so that the method has a wider application prospect.
The Chinese patent publication No. CN 114087897A discloses a desublimation heat exchanger for capturing low-temperature carbon and a working method thereof, wherein a coolant is introduced into the heat exchanger to pre-cool the heat exchanger, and CO 2 De-sublimation occurs in the heat exchanger, and the reciprocating motion of the linear sliding rail assembly drives the magnet assembly on the heat exchanger body to move, so that the scraper assembly moves back and forth under the action of magnetic force to scrape CO 2 Frost crystal, but equipment damage is easily caused by a mechanical scraping mode, the service life of a system is reduced, when carbon capture is carried out on multi-component mixed gas, purge replacement is not carried out on gas which does not undergo phase change, and residual gas and CO are not carried out 2 The frost crystals enter the collection area together, resulting in a reduced product purity.
Chinese patent publication No. CN 213668629U discloses a boiler low-temperature cooling carbon capturing system, in which a cooling medium circulation pipeline is arranged in a low-temperature cooler, and flue gas is cooled and desublimated in the cooler after desulfurization and denitrification treatment, and CO 2 The heat exchange with the cooling medium is carried out by dividing wall type through the pipeline, and the heat exchange is increasedAnd the heat exchanger is designed to meet the size requirement, the system needs to be continuously cooled in the running process, and the system is difficult to be applied to an industrial cold energy recovery scene of intermittent cooling.
Foreign scholars propose a design of adopting a packed bed to carry out low-temperature desublimation carbon trapping, and carry out analysis and research from the aspects of operation energy consumption and economy, but the packed bed system disclosed so far adopts fillers with uniform size, and the arrangement mode of the internal fillers is not considered by combining the frost front migration behavior in the desublimation trapping process, so that the current packed bed system has larger flow resistance in operation and has the risk of frost accumulation and freeze blocking.
In summary, the prior art mainly has the following disadvantages: the system for capturing the sublimated carbon by adopting the dividing wall type heat exchange increases the design size requirement of the heat exchanger, and the requirement of continuous cooling is difficult to be effectively matched with an intermittent cold source; the packing arrangement in the packed bed system adopting contact heat exchange does not consider the migration behavior of frost front, and the risk of freezing and blocking exists; the mechanical defrosting means is easy to cause equipment damage and reduce the service life of the system; meanwhile, the current desublimation carbon trapping system lacks a perfect purging method which can carry out displacement purging on residual impurity gas in heat exchange equipment, so as to lead to trapped CO 2 The purity of the product is reduced.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a variable density packed bed system and a trapping method for low-temperature carbon trapping, which realize efficient heat exchange, compact design, stable operation and high-purity trapping of a low-temperature desublimation carbon trapping system.
A variable density packed bed system for capturing low-temperature carbon comprises a flue gas precooler, a cooling device, a flue gas pressurizing buffer tank, a variable density packed bed and CO 2 A gaseous product storage tank, a cold energy recoverer, a gas chromatograph and a purge gas pressurizing buffer tank;
the hot fluid channel of the flue gas precooler is connected with a first air inlet of the flue gas pressurizing buffer tank through a pipeline provided with an incoming flue gas first stop valve;
the filling area of the variable-density filling bed is filled with a plurality of cold accumulation filling materials, and the filling density of the cold accumulation filling materials is gradually reduced along the flowing direction of the flue gas;
the variable density packed bed is provided with two inlets and two outlets; the first outlet of the variable density packed bed is divided into two paths after passing through a first outlet stop valve of the packed bed, and one path is sequentially connected with a purifying flue gas stop valve, a cold fluid channel of a cold energy recoverer and a gas chromatographic analyzer; the other path is sequentially connected with a precooling working medium second stop valve, a cold fluid channel of the smoke precooler, a cooling device and the precooling working medium first stop valve, and is used as a precooling working medium feeding pipeline; the gas outlet pipeline of the flue gas pressurizing buffer tank provided with the inflow flue gas second stop valve is arranged in parallel with the precooling working medium feeding pipeline and is connected with the first inlet of the variable density packed bed through the first inlet stop valve of the packed bed;
the second outlet of the variable density packed bed is divided into two paths after passing through a second outlet stop valve of the packed bed, and one path is connected with a second air inlet of the pressurizing buffer tank through a pipeline provided with a second purge gas stop valve; another way is connected with CO in sequence 2 Stop valve, CO 2 The gaseous product storage tank, the first stop valve of the purge gas, the hot fluid channel of the cold energy recoverer, the purge gas pressurizing buffer tank and the second inlet stop valve of the packed bed are connected with the second inlet of the variable density packed bed.
Further, the cold accumulation filler adopts three spherical fillers with different particle diameters, a high-density filler layer, a medium-density filler layer and a low-density filler layer are sequentially arranged in a filler zone along the flow direction of the flue gas, and each density filler layer is internally provided with a temperature sensor for monitoring the precooling effect of the packed bed;
the incoming smoke entering from the first inlet of the variable density packed bed is firstly cooled by the high density packing layer, the temperature is rapidly reduced to be below the carbon dioxide frost point temperature, and then desublimation and frosting occur in the upper areas of the medium density packing layer and the low density packing layer; under the heating of the inflow flue gas, the surface temperature of the filler gradually rises, frost crystals initially condensed on the surface of the filler sublimate, and the frost crystals are sublimated after being cooled by the filler in the lower area, so that the whole frost crystals migrate downwards until the maximum trapping limit of the filler bed is reached;
the packing layers with three packing densities respectively play different functions: the incoming smoke is rapidly cooled, carbon dioxide desublimation sites are provided, and frosting sites for desublimation again are provided by downward migration after sublimation of carbon dioxide desublimation.
Optionally, the cold accumulation filler adopts spherical fillers with different particle sizes and vertical or wave-shaped cold accumulation plates with fins with different arrangement intervals.
Optionally, the cold accumulation filler is made of one or more of stainless steel, ceramic, phosphor bronze and brass.
Further, the flue gas pressurizing buffer tank has a buffer function on pressure fluctuation generated in the mixing process of the purge gas and the inflow flue gas, and a diaphragm or an air bag is arranged in the tank to pressurize the mixed flue gas.
Further, the flow direction of the first inlet and outlet stream of the variable density packed bed is opposite to the flow direction of the second inlet and outlet stream; the first inlet stop valve of the packed bed, the first outlet stop valve of the packed bed, the second inlet stop valve of the packed bed and the second outlet stop valve of the packed bed are all one-way valves.
Further, the variable density packed bed sequentially comprises a heat insulation layer, a vacuum interlayer, an electric heating layer and a packing area from outside to inside; and after the residual flue gas is purged and replaced, starting an electric heating layer to heat the carbon dioxide frost crystal, so that the carbon dioxide frost crystal sublimates and is trapped in a gaseous product form.
Optionally, the flue gas precooler and the cold energy recoverer are plate-fin heat exchangers or shell-and-tube heat exchangers.
Optionally, the cooling device comprises an external energy driven refrigerating system or a heat exchange system for recovering industrial residual cold, and the cold energy recovery working medium comprises LNG, liquid nitrogen, air separation byproducts and other low-temperature fluids.
The method for capturing the low-temperature carbon dioxide uses the variable-density packed bed system for capturing the low-temperature carbon, and specifically comprises the following steps of:
step1, in the pre-cooling process, a pre-cooling working medium first stop valve and a packed bed first inlet stop valve are firstly opened, and the rest are openedThe valve is kept in a closed state, and the precooling working substance cools the filling material in the variable-density filling bed to cool the filling material to CO 2 The temperature is lower than the frost point temperature and reaches the supercooling temperature at the same time; the temperature sensor of the packing area monitors the temperature of the packing of different density layers in the packed bed in real time and is used as a basis for judging the precooling process;
after the temperature of the filling material is reduced to a set working temperature zone, opening a first outlet stop valve of the filling bed and a second stop valve of the precooling working medium, and closing other valves; the precooling working medium flows into a smoke precooler to precool incoming smoke, and then flows into a cooling device to recover precooling capability;
step2, in the desublimation separation process, a first stop valve of incoming smoke is opened, precooled smoke enters a smoke pressurizing buffer and is mixed with purge gas, a second throttle valve of the incoming smoke, a first inlet stop valve of a packed bed, a first outlet stop valve of the packed bed, a stop valve of purified smoke are opened, and the rest valves are closed; the flue gas pressurizing buffer presses the flue gas into the variable density packed bed to carry out desublimation carbon trapping;
the flue gas flows through the high-density packing layer, the medium-density packing layer and the low-density packing layer in sequence, and the flue gas is rapidly cooled to CO in the high-density packing layer 2 Below the frost point, then desublimation occurs in the upper regions of the medium and low density filler layers; with the continuous progress of the trapping process, under the heating of the inflow flue gas, the surface temperature of the filler gradually rises, frost crystals initially condensed on the surface of the filler sublimate, and after being cooled by the filler in the lower area, the frost crystals are sublimated, and the whole is downwards moved until the maximum trapping limit of the packed bed is reached;
CO in flue gas 2 Frosting on the surface of the filler to finish desublimation and separation and remove CO 2 The purified flue gas enters a cold energy recoverer for rewarming, then enters a gas chromatograph, and continuously monitors CO 2 Concentration;
step3, a small amount of CO is adopted in the process of sweeping gas treatment 2 When the purified flue gas flows out of the variable density packed bed, a first stop valve of the purge gas is opened, and the purge gas enters the purge gas after being cooled in the cold energy recovererA gas pressurizing buffer tank;
step4, purging, when the packed bed reaches the maximum trapping limit, monitoring CO in the gas chromatograph 2 Stopping introducing the flue gas into the variable density packed bed when the concentration exceeds the allowable working limit; opening a second inlet stop valve of the packed bed, a second outlet stop valve of the packed bed and a second stop valve of the purge gas, and closing the rest valves; the purge gas pressurizing buffer tank presses the gas into the variable density packed bed, residual flue gas is replaced, and the residual flue gas flows into the flue gas pressurizing buffer tank together with the purge gas;
step5, in the sublimation collection process, after residual flue gas in the packed bed is removed, a stop valve of a second outlet of the packed bed is kept in an open state, and CO is opened 2 Stop valve, closing the rest valves, starting the electric heating layer of the variable density packed bed, CO 2 Sublimation of frost crystals into CO 2 A gaseous product storage tank, which completes trapping in the form of gas.
Compared with the prior art, the invention has the following beneficial effects:
1. the design of the variable density filler effectively matches CO in the desublimation and trapping process 2 The migration characteristic of the frost layer realizes rapid cooling of incoming smoke by the sectional effect, and the frost forming sites provided on the surface of the filler are fully utilized for trapping.
2. The invention adopts a small amount of CO 2 The product is used as purge gas to replace residual flue gas in the packed bed, so that the trapping purity of the product is improved, and meanwhile, the purge gas is cooled to the vicinity of frost point by using purified flue gas, so that CO caused by purging is avoided 2 Sublimating frost crystals in advance; the sublimation mode of electric heating overcomes the damage of mechanical defrosting to the system and prolongs the service life of the system.
3. In the invention, the flowing smoke and the filler are in direct contact heat exchange, so that the heat transfer resistance is reduced, and the system is more compact; the filler with the cold accumulation function overcomes the defect of intermittent cold supply in a cold energy recovery scene, and can further reduce the trapping cost by combining industrial residual cold recovery.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a variable density packed bed system for cryogenic carbon capture according to the present invention;
FIG. 2 is a schematic view showing the internal structure of a variable density packed bed according to an embodiment of the present invention;
FIG. 3 is a flow chart of a purge method for a variable density packed bed system in accordance with an embodiment of the present invention.
In the figure: 1-a flue gas precooler; 2-a cooling device; 3-an incoming smoke first stop valve; 4-a smoke pressurizing buffer tank; 5-an incoming smoke second stop valve; 6-precooling a working medium first stop valve; 7-a packed bed first inlet shutoff valve; 8-a variable density packed bed; 9-a high density packing zone temperature sensor; 10-a medium density packing zone temperature sensor; 11-a low density packing zone temperature sensor; 12-a packed bed first outlet shutoff valve; 13-a purified flue gas stop valve; 14-precooling a working medium second stop valve; 15-a packed bed second inlet shutoff valve; 16-packed bed second outlet shutoff valve; 17-a purge gas second shut-off valve; 18-CO 2 A stop valve; 19-CO 2 A gaseous product storage tank; 20-a purge gas first shut-off valve; 21-a cold energy recoverer; 22-gas chromatograph; 23-a purge gas boost buffer tank; 801-packed bed first inlet; 802-insulating layer; 803-vacuum interlayer; 804 an electrically heated layer; 805-a packed bed first outlet; 806-a packed bed second inlet; 807-a low density filler layer; 808-a medium density filler layer; 809—a high density filler layer; 810-packed bed second outlet.
Detailed Description
The invention will be described in further detail with reference to the drawings and examples, it being noted that the examples described below are intended to facilitate the understanding of the invention and are not intended to limit the invention in any way.
As shown in fig. 1 and 2, a variable density packed bed system for cryogenic carbon capture includes a pre-cooling unit, a flue gas pressurization buffer unit, a carbon dioxide capture unit, and a purge gas treatment unit.
The precooling unit includes: the device comprises a flue gas precooler 1, a cooling device 2, a precooling working medium first stop valve 6, a precooling working medium second stop valve 14, a high-density packing region temperature sensor 9, a medium-density packing region temperature sensor 10 and a low-density packing region temperature sensor 11. The hot fluid inlet and outlet of the flue gas precooler 1 are respectively connected with the flue gas and incoming flue gas first stop valve 3, and the cold fluid inlet and outlet are respectively connected with the precooling working medium second stop valve 14 and the cooling device 2; the cooling device 2 cools the pre-cooling working medium after temperature rise to restore the pre-cooling capacity; the precooling working medium first stop valve 6 is connected with the cooling device 2 and the packed bed inlet first stop valve 7; the high-density packing region temperature sensor 9, the medium-density packing region temperature sensor 10 and the low-density packing region temperature sensor 11 are arranged in the packing layer and are used for monitoring the precooling effect of the packed bed.
The flue gas pressurization buffer unit includes: the device comprises an inflow smoke first stop valve 3, a smoke pressurizing buffer tank 4, an inflow smoke second stop valve 5 and a purge gas second stop valve 17. The flue gas pressurizing buffer tank 4 is provided with two air inlets which are respectively connected with the incoming flue gas first stop valve 3 and the purge gas second stop valve 17, and impurity gas blown out before sublimation of the packed bed is mixed with the incoming flue gas and pressurized; the incoming flow smoke second stop valve 5 is communicated with the exhaust port of the smoke pressurizing buffer tank 4.
The carbon dioxide capture unit includes: a packed bed first inlet stop valve 7, a variable density packed bed 8, a packed bed first outlet stop valve 12, a packed bed second inlet stop valve 15, a packed bed second outlet stop valve 16, CO 2 Stop valve 18, CO 2 A gaseous product reservoir 19. The variable density packed bed 8 is provided with two inlets and two outlets which are respectively connected with a packed bed first inlet stop valve 7, a packed bed second inlet stop valve 15, a packed bed first outlet stop valve 12 and a packed bed second outlet stop valve 16, and CO 2 The sublimated frosting is separated from other gas components in the packed bed, and after residual flue gas is removed by purging, sublimation operation is started, and the residual flue gas is trapped in a gaseous form; CO 2 The stop valve 18 connects the packed bed second outlet stop valve 16 and CO 2 A gaseous product reservoir 19.
The purge gas treatment unit includes: the device comprises a purified flue gas stop valve 13, a purge gas first stop valve 20, a cold energy recoverer 21, a gas chromatograph 22 and a purge gas pressurizing buffer tank 23. The hot fluid inlet and outlet of the cold energy recoverer 21 are respectively connected with a purge gas first stop valve 20 and a purge gas pressurizing buffer tank 23, the cold fluid inlet and outlet are respectively connected with a purified flue gas stop valve 13 and a gas chromatograph 22, the purge gas exchanges heat with the purified flue gas, and the cold energy of the purified flue gas is recovered while the purge gas is cooled.
The internal structure of the variable density packed bed 8 includes: a packed bed first inlet 801, a thermal insulation layer 802, a vacuum interlayer 803, an electrical heating layer 804, a packed bed first outlet 805, a packed bed second inlet 806, a low density packing layer 807, a medium density packing layer 808, a high density packing layer 809, and a packed bed second outlet 810.
The variable density packed bed 8 adopts a material with good cold accumulation performance as cold accumulation filler, and adopts a direct contact mode for heat exchange between precooling working medium, incoming smoke and spherical filler in a precooling stage and a carbon dioxide capturing stage. The cold accumulation filler comprises any one or more of stainless steel, ceramic, phosphor bronze, brass and the like.
Referring to fig. 1 to 2, the carbon dioxide capturing flow of the present invention is as follows:
s01, in the pre-cooling process, firstly, a pre-cooling working medium first stop valve 6 and a packed bed first inlet stop valve 7 are opened, and the rest valves are kept in a closed state, so that the pre-cooling working medium cools the packing in the variable density packed bed 8 to cool the packing to CO 2 The temperature below the frost point reaches a certain supercooling temperature; the temperature sensor 9 of the high-density packing area, the temperature sensor 10 of the medium-density packing area and the temperature sensor 11 of the low-density packing area monitor the temperature of the packing of different density layers in the packed bed in real time and serve as the basis for judging the precooling process.
After the temperature of the filling material is reduced to a set working temperature zone, opening a first outlet stop valve 12 of the filling bed and a second stop valve 14 of the precooling working medium, and closing other valves; the precooling working medium flows into the flue gas precooler 1 to precool the inflow flue gas and then flows into the cooling device 2, and precooling capacity is recovered through an external energy driven refrigerating system or a heat exchange system for recovering industrial residual cold.
S02, in the desublimation separation process, opening a first stop valve 3 of incoming smoke, mixing the precooled smoke with purge gas in a smoke pressurizing buffer 4, opening a second throttle valve 5 of the incoming smoke, a first inlet stop valve 7 of a packed bed, a first outlet stop valve 12 of the packed bed, a stop valve 13 of purified smoke, and closing other valves; the membrane or bladder in the fume pressurization buffer 4 presses fume into the variable density packed bed 8 for desublimation carbon capture.
The flue gas flows through the high density filler layer 809, the medium density filler layer 808 and the low density filler layer 807 in sequence, and the flue gas is rapidly cooled to CO in the high density filler layer 809 2 Below the frost point, subsequent desublimation occurs in the upper regions of the middle density filler layer 808 and the low density filler layer 807; with the continuous progress of the trapping process, under the heating of the inflow flue gas, the surface temperature of the filler gradually rises, frost crystals initially condensed on the surface of the filler sublimate, and after being cooled by the filler in the lower area, the frost crystals are sublimated, and the whole is downwards moved until the maximum trapping limit of the packed bed is reached; the packing layers with three packing densities respectively play different functions: the incoming smoke is rapidly cooled, carbon dioxide desublimation sites are provided, and frosting sites for desublimation again are provided by downward migration after sublimation of carbon dioxide desublimation.
CO in flue gas 2 Frosting on the surface of the filler to finish desublimation and separation and remove CO 2 The purified flue gas enters a cold energy recoverer 21 for rewarming, then enters a gas chromatograph 22 for continuous monitoring of CO 2 Concentration.
S03, adopting a small amount of CO in the process of sweeping gas treatment 2 When the purified flue gas flows out of the variable density packed bed 8, a first stop valve 20 of the purge gas is opened, and the purge gas enters a pressurizing buffer tank 23 of the purge gas after being cooled in a cold energy recoverer 21;
s04, purging, when the packed bed reaches the maximum trapping limit, the CO detected in the gas chromatograph 22 2 Stopping introducing the flue gas into the packed bed when the concentration exceeds the allowable working limit; opening a packed bed second inlet stop valve 15, a packed bed second outlet stop valve 16 and a purge gas second stop valve 17, and closing the rest valves; the membrane or the air bag in the purge gas pressurizing buffer tank 23 presses the gas into the variable density packed bed 8, the residual flue gas is replaced, and the residual flue gas flows into the flue gas pressurizing buffer tank 4 together with the purge gas;
s05, in the sublimation collection process, after residual flue gas in the packed bed is removed, a second outlet stop valve 16 of the packed bed is kept in an open state, and CO is opened 2 Shut-off valve 18, closing the remaining valves, activating electrically heated layer 804 of variable density packed bed 8, co 2 Sublimation of frost crystals into CO 2 A gaseous product reservoir 19, in the form of a gas, completes the trapping.
Referring to FIG. 3, an embodiment of the present invention provides a purge method for a variable density packed bed system for cryogenic carbon capture, comprising the steps of:
step1, the pre-cooled flue gas is further cooled in a variable density packed bed 8, and CO in the flue gas 2 The desublimation and frosting occur, and the low-temperature carbon trapping of the inflow smoke is completed;
step2, removal of CO 2 The purified flue gas after passing through the packed bed first outlet stop valve 12 and the purified flue gas stop valve 13 in sequence exchanges heat with the purge gas in the cold energy recoverer 21.
CO 2 The gaseous product tank 19 releases a small amount of clean gas as purge gas before sublimation of frost crystals in the variable density packed bed 8, and the purge gas first shutoff valve 20 is opened, and the purge gas is cooled by the purified flue gas in the cold energy recoverer 21 and then stored in the purge gas pressurizing buffer tank 23.
step3, the purified flue gas after temperature rise enters a gas chromatograph 22, and CO is continuously monitored 2 The concentration, along with the progress of the trapping process, the temperature in the packed bed gradually rises, the frost layer on the surface of the packing becomes thick, the packed bed loses the ability of desublimation and trapping after a period of time, and CO in tail gas 2 The concentration rises sharply, and the flue gas is stopped from being introduced into the packed bed.
step4, stopping the continuous introduction of the flue gas into the variable density packed bed 8, and before the system is changed from the sublimation carbon trapping mode to the sublimation mode, leaving a small amount of flue gas which is not trapped in the packed bed, and directly sublimating frost crystals to reduce the trapping purity, so that pure CO needs to be utilized before sublimation 2 The gas sweeps the residual flue gas.
Opening the second inlet stop valve 15 of the packed bed and the second outlet of the packed bedThe port shut-off valve 16 closes the packed bed first inlet shut-off valve 7, the packed bed first outlet shut-off valve 12, and the purge gas first shut-off valve 20, and uses the purified CO after cooling 2 The gas sweeps the variable density packed bed 8, and the cooled CO 2 The temperature should be as low as possible to avoid CO caused by sublimation of frost crystals in advance due to heat exchange 2 The trapping amount decreases.
step5, open the purge gas second shutoff valve 17, close CO 2 And the stop valve 18 allows the purge gas and the residual flue gas to enter the flue gas pressurizing buffer tank 4 together to complete purging operation of the packed bed, and when the system is in a desublimation working mode, the purge gas in the flue gas pressurizing buffer tank 4 and the inflow flue gas enter the variable-density packed bed 8 together to perform low-temperature desublimation carbon trapping.
The foregoing embodiments have described in detail the technical solution and the advantages of the present invention, it should be understood that the foregoing embodiments are merely illustrative of the present invention and are not intended to limit the invention, and any modifications, additions and equivalents made within the scope of the principles of the present invention should be included in the scope of the invention.
Claims (9)
1. A variable density packed bed system for capturing low-temperature carbon is characterized by comprising a flue gas precooler (1), a cooling device (2), a flue gas pressurizing buffer tank (4), a variable density packed bed (8) and CO 2 A gaseous product storage tank (19), a cold energy recoverer (21), a gas chromatograph (22) and a purge gas pressurization buffer tank (23);
the hot fluid channel of the flue gas precooler (1) is connected with a first air inlet of the flue gas pressurizing buffer tank (4) through a pipeline provided with an incoming flue gas first stop valve (3);
a packing region of the variable-density packed bed (8) is filled with a plurality of cold accumulation packing materials, and the packing density of the cold accumulation packing materials is gradually reduced along the flow direction of the flue gas;
the variable density packed bed (8) is provided with two inlets and two outlets; the first outlet of the variable density packed bed (8) is divided into two paths after passing through a first outlet stop valve (12) of the packed bed, and one path is sequentially connected with a purified flue gas stop valve (13), a cold fluid channel of a cold energy recoverer (21) and a gas chromatograph (22); the other path is sequentially connected with a precooling working medium second stop valve (14), a cold fluid channel of the smoke precooler (1), a cooling device (2) and a precooling working medium first stop valve (6) to be used as a precooling working medium feeding pipeline; an air outlet pipeline of a flue gas pressurizing buffer tank (4) provided with an incoming flue gas second stop valve (5) is arranged in parallel with a precooling working medium feeding pipeline, and is connected with a first inlet of a variable density packed bed (8) through a packed bed first inlet stop valve (7);
the second outlet of the variable density packed bed (8) is divided into two paths after passing through a second outlet stop valve (16) of the packed bed, and one path is connected with a second air inlet of the pressurizing buffer tank (4) through a pipeline provided with a second purge gas stop valve (17); another way is connected with CO in sequence 2 Stop valve (18), CO 2 The gaseous product storage tank (19), the first stop valve (20) of the purge gas, the hot fluid channel of the cold energy recoverer (21), the purge gas pressurizing buffer tank (23) and the second inlet stop valve (15) of the packed bed are connected with the second inlet of the variable density packed bed (8).
2. The variable density packed bed system for low temperature carbon capture according to claim 1, wherein the cold storage packing adopts three spherical packing with different particle diameters, a high density packing layer (809), a medium density packing layer (808) and a low density packing layer (807) are sequentially arranged in the packing area along the flow direction of the flue gas, and a temperature sensor is respectively arranged in each density packing layer for monitoring the precooling effect of the packed bed;
incoming flue gas entering from the first inlet of the variable density packed bed (8) is first cooled by the high density packing layer (809), the temperature is rapidly reduced below the carbon dioxide frost point temperature, and then desublimation and frosting occur in the upper regions of the medium density packing layer (808) and the low density packing layer (807); under the heating of the inflow flue gas, the surface temperature of the filler gradually rises, frost crystals initially condensed on the surface of the filler sublimate, and the frost crystals are sublimated after being cooled by the filler in the lower area, so that the whole frost crystals migrate downwards until the maximum trapping limit of the filler bed is reached;
the packing layers with three packing densities respectively play different functions: the incoming smoke is rapidly cooled, carbon dioxide desublimation sites are provided, and frosting sites for desublimation again are provided by downward migration after sublimation of carbon dioxide desublimation.
3. The variable density packed bed system for cryogenic carbon capture of claim 1, wherein the cold storage packing is spherical packing with different particle sizes, vertical or wave-shaped cold storage plates with fins of different arrangement pitch.
4. The variable density packed bed system for cryogenic carbon capture of claim 1, wherein the cold storage filler material is one or more of stainless steel, ceramic, phosphor bronze, brass.
5. A variable density packed bed system for cryogenic carbon capture according to claim 1, characterized in that the flow direction of the first inlet and outlet stream of the variable density packed bed (8) is opposite to the flow direction of the second inlet and outlet stream; the first inlet stop valve (7), the first outlet stop valve (12), the second inlet stop valve (15) and the second outlet stop valve (16) are all one-way valves.
6. The variable density packed bed system for cryogenic carbon capture according to claim 1, wherein the variable density packed bed (8) comprises, in order from the outside to the inside, a thermal insulation layer (802), a vacuum interlayer (803), an electrical heating layer (804) and a packing region; and after the residual flue gas is purged and replaced, starting an electric heating layer (804) to heat the carbon dioxide frost crystal, so that the carbon dioxide frost crystal sublimates and is trapped in a gaseous product form.
7. The variable density packed bed system for cryogenic carbon capture of claim 1, wherein the flue gas precooler (1) and the cold energy recoverer (21) are plate-fin heat exchangers or shell-and-tube heat exchangers.
8. Variable density packed bed system for cryogenic carbon capture according to claim 1, characterized in that the cooling device (2) comprises an external energy driven refrigeration system or a heat exchange system for recovering industrial waste cold.
9. A method for capturing carbon dioxide at a low temperature, characterized by using the variable density packed bed system for capturing carbon at a low temperature according to any one of claims 1 to 8, comprising the steps of:
step1, in the pre-cooling process, a pre-cooling working medium first stop valve (6) and a packed bed first inlet stop valve (7) are opened, the rest valves are kept in a closed state, and the pre-cooling working medium cools the filler in the variable density packed bed (8) to cool the filler to CO 2 The temperature is lower than the frost point temperature and reaches the supercooling temperature at the same time; the temperature sensor of the packing area monitors the temperature of the packing of different density layers in the packed bed in real time and is used as a basis for judging the precooling process;
after the temperature of the filling material is reduced to a set working temperature zone, opening a first outlet stop valve (12) of the filling bed and a second stop valve (14) of the precooling working medium, and closing other valves; the precooling working medium flows into a smoke precooler (1) to precool incoming smoke, and then flows into a cooling device (2) to recover precooling capability;
step2, in the desublimation separation process, a first stop valve (3) of incoming smoke is opened, precooled smoke enters a smoke pressurizing buffer (4) to be mixed with purge gas, a second throttle valve (5) of the incoming smoke, a first inlet stop valve (7) of a packed bed, a first outlet stop valve (12) of the packed bed, a stop valve (13) of purified smoke are opened, and other valves are closed; the flue gas pressurizing buffer (4) presses the flue gas into the variable density packed bed (8) to carry out desublimation carbon trapping;
the flue gas flows through the high-density packing layer (809), the medium-density packing layer (808) and the low-density packing layer (807) in sequence, and the flue gas is rapidly cooled to CO in the high-density packing layer (809) 2 Below the frost point, subsequent desublimation occurs in the upper regions of the medium density filler layer (808) and the low density filler layer (807); with the continuous capturing process, the temperature of the surface of the filler is gradually increased under the heating of the incoming smoke, and frost crystals initially condensed on the surface of the filler sublimate and are separated by the lower areaThe filler is sublimated after cooling, and the whole is expressed as downward migration of frost crystals until the maximum trapping limit of the packed bed is reached;
CO in flue gas 2 Frosting on the surface of the filler to finish desublimation and separation and remove CO 2 The purified flue gas enters a cold energy recoverer (21) for rewarming, then enters a gas chromatograph (22), and continuously monitors CO 2 Concentration;
step3, a small amount of CO is adopted in the process of sweeping gas treatment 2 When the purified flue gas flows out of the variable density packed bed (8), a first stop valve (20) of the purge gas is opened, and the purge gas enters a pressurizing buffer tank (23) of the purge gas after being cooled in a cold energy recoverer (21);
step4, purging, when the packed bed reaches the maximum capture limit, the CO detected in the gas chromatograph (22) 2 Stopping introducing the flue gas into the variable density packed bed (8) when the concentration exceeds the allowable working limit; opening a packed bed second inlet stop valve (15), a packed bed second outlet stop valve (16) and a purge gas second stop valve (17), and closing the rest valves; the purge gas pressurizing buffer tank (23) presses the gas into the variable density packed bed (8), residual flue gas is replaced, and the residual flue gas flows into the flue gas pressurizing buffer tank (4) together with the purge gas;
step5, in the sublimation collection process, after residual flue gas in the packed bed is removed, a second outlet stop valve (16) of the packed bed is kept in an open state, and CO is opened 2 A stop valve (18), closing the rest of the valves, activating the electrically heated layer (804), CO, of the variable density packed bed (8) 2 Sublimation of frost crystals into CO 2 A gaseous product tank (19) for completing the trapping in the form of a gas.
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