CN111677653B - Air separation system for recycling waste heat of compressed air, pre-dehumidifying and pre-cooling - Google Patents
Air separation system for recycling waste heat of compressed air, pre-dehumidifying and pre-cooling Download PDFInfo
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- 238000001816 cooling Methods 0.000 title claims abstract description 106
- 238000000926 separation method Methods 0.000 title claims abstract description 54
- 239000002918 waste heat Substances 0.000 title claims abstract description 24
- 238000004064 recycling Methods 0.000 title description 2
- 238000007906 compression Methods 0.000 claims abstract description 72
- 230000006835 compression Effects 0.000 claims abstract description 63
- 238000005057 refrigeration Methods 0.000 claims abstract description 40
- 238000007791 dehumidification Methods 0.000 claims abstract description 27
- 238000000746 purification Methods 0.000 claims abstract description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 43
- 239000002808 molecular sieve Substances 0.000 claims description 6
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 6
- 230000009467 reduction Effects 0.000 claims description 4
- 238000005188 flotation Methods 0.000 claims description 2
- 239000002994 raw material Substances 0.000 abstract description 12
- 238000005265 energy consumption Methods 0.000 abstract description 6
- 230000000694 effects Effects 0.000 abstract description 5
- 239000003570 air Substances 0.000 description 266
- 239000000498 cooling water Substances 0.000 description 13
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 description 12
- 239000007789 gas Substances 0.000 description 11
- 238000010521 absorption reaction Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 4
- 230000008020 evaporation Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- MSSNHSVIGIHOJA-UHFFFAOYSA-N pentafluoropropane Chemical compound FC(F)CC(F)(F)F MSSNHSVIGIHOJA-UHFFFAOYSA-N 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 101100238302 Caenorhabditis elegans morc-1 gene Proteins 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000012080 ambient air Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B41/00—Pumping installations or systems specially adapted for elastic fluids
- F04B41/06—Combinations of two or more pumps
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
- F01D15/08—Adaptations for driving, or combinations with, pumps
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
- F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K27/00—Plants for converting heat or fluid energy into mechanical energy, not otherwise provided for
- F01K27/02—Plants modified to use their waste heat, other than that of exhaust, e.g. engine-friction heat
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
- F04B39/06—Cooling; Heating; Prevention of freezing
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
- F04B39/16—Filtration; Moisture separation
-
- 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
- F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
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- Engineering & Computer Science (AREA)
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- General Engineering & Computer Science (AREA)
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Abstract
The invention discloses an air separation system for recovering waste heat of compressed air and carrying out pre-dehumidification and pre-cooling, which comprises an air flow path, a purification module, a dehumidification loop and an organic Rankine-steam compression refrigeration cycle loop, wherein the air flow path is connected with the purification module; the organic Rankine-steam compression refrigeration cycle loop comprises a first-stage high-temperature evaporator, a second-stage high-temperature evaporator, a third-stage high-temperature evaporator, a first condenser, a working medium pump, an expander, a first-stage low-temperature evaporator, a second-stage low-temperature evaporator, a third-stage low-temperature evaporator, a compressor, a second condenser and a throttling element. The air cooling unit and the organic Rankine-steam compression refrigeration cycle system are combined, and the organic Rankine-steam compression refrigeration cycle system has the cooling effect on compressed air, so that the state of compressed air at the outlet of the compression module basically meets the state required by the outlet of the existing air separation system after being processed by the air cooling unit, and the existing air cooling unit is used for pre-cooling and pre-dehumidifying the inlet raw material air, thereby further saving the compression energy consumption and achieving the purpose of saving energy.
Description
Technical Field
The invention relates to an industrial air pretreatment system, in particular to an air separation system for recovering waste heat of compressed air, pre-dehumidifying and pre-cooling.
Background
Air separation technology, i.e. an industrial technology for separating each component gas in air and producing gases such as oxygen, nitrogen and argon, has been developed for over one hundred years. Is widely applied to the processes of industrial production, medical treatment and the like. The air separation equipment mainly comprises an air compressor, an air cooling system, a purification system, a heat exchange system, an expander, a rectification system and part of auxiliary systems in sequence.
At present, the flow organization form of air in an air compressor, an air cooling system and a purification system is generally as follows: firstly, air obtained in the external environment passes through a filter to roughly filter larger particle pollutants; secondly, performing multi-stage compression by a plurality of air compressors to obtain air with higher pressure; then, the air enters an air cooling tower to be cooled and washed, and saturated air with lower temperature is obtained; and finally, the air enters a purification system, the water and other gas impurities in the air are removed by utilizing the adsorption action of the alumina and the molecular sieve, and finally the high-pressure and pure air is obtained and sent into a rectification system for rectification.
In a general air separation process, before air enters an air compressor, the relative humidity of the air is the same as that of ambient air, generally 60% -90%, and the compression work of the air compressor on water vapor in the air belongs to useless work; in addition, along with the compression process of the air compressor, a large amount of high-grade heat energy can be generated, the air can be heated to about 110 ℃, at present, water circulation cooling is adopted to take away the heat energy, the air is cooled to about 40 ℃, the energy is wasted, and before entering the next-stage air compressor, the air temperature is still high, the number of stages of the compressor is increased, and the cost is increased.
The Chinese patent publication No. CN106958987A discloses an air pre-dehumidification and pre-cooling system for air separation, which utilizes an organic Rankine-vapor compression refrigeration cycle to recover the waste heat of compressed air and utilizes a lithium bromide absorption system to pre-dehumidify and pre-cool raw material air. The chinese patent publication No. CN107940801A discloses an air separation system for recovering waste heat of compressed air, which utilizes two lithium bromide absorption systems to recover waste heat of compressed air and pre-treat raw air. The Chinese patent publication No. CN109539693A discloses a gas cooling system and a gas cooling method, which simplify the Chinese patent publication No. CN107940801A, remove the part of lithium bromide for air pretreatment and dehumidification, and only consider that an absorption system is used for recovering the waste heat of partial compressed air. However, the above device adopts the lithium bromide absorption/dehumidification system, and the lithium bromide is highly corrosive, so that the device is easily damaged, and meanwhile, the lithium bromide absorption system is bulky and is not beneficial to the interstage arrangement of the air compressor.
Disclosure of Invention
The invention provides an air separation system for recovering waste heat of compressed air and carrying out pre-dehumidification and pre-cooling, which can realize that an air cooling unit behind a compression module in the traditional air separation is used for pre-dehumidification and pre-cooling of inlet raw material air, and meanwhile, the compressed air can be pre-cooled again while the waste heat of the compressed air is effectively recovered by utilizing an organic Rankine cycle-steam compression refrigeration cycle, so that the energy is fully utilized, and the purpose of saving the cost is achieved.
An air separation system for recovering waste heat of compressed air and carrying out pre-dehumidification and pre-cooling comprises an air flow path, a purification module, a dehumidification loop and an organic Rankine-steam compression refrigeration cycle loop; the dehumidification loop comprises an air cooling tower and a water cooling tower;
the air flow path comprises an air cooling tower, a primary air compressor, a compressed air precooling flow path of a primary high-temperature evaporator, a first water cooler, a compressed air cooling channel of a primary low-temperature evaporator, a secondary air compressor, a compressed air precooling flow path of a secondary high-temperature evaporator, a compressed air cooling channel of a second water cooler and a secondary low-temperature evaporator, a tertiary air compressor, a compressed air precooling flow path of a tertiary high-temperature evaporator, a third water cooler and a compressed air cooling channel of a tertiary low-temperature evaporator which are sequentially communicated, and finally the air cooling tower, the primary air compressor, the compressed air precooling flow path of the primary high;
the organic Rankine-vapor compression refrigeration cycle loop comprises a first-stage high-temperature evaporator, a second-stage high-temperature evaporator, a third-stage high-temperature evaporator, a first condenser, a working medium pump and an expander of the organic Rankine cycle, and a first-stage low-temperature evaporator, a second-stage low-temperature evaporator, a third-stage low-temperature evaporator, a compressor, a second condenser and a throttling element of the vapor compression refrigeration cycle;
in the organic Rankine-steam compression refrigeration cycle loop, a part of cycle working medium exchanges heat with compressed air in a first-stage high-temperature evaporator, a second-stage high-temperature evaporator and a third-stage high-temperature evaporator, the heated gaseous working medium enters an expander to do work, the working medium cooled and decompressed by the expander enters a first condenser, the working medium enters a working medium pump after absorbing heat, and the working medium enters the three high-temperature evaporators again after being boosted to finish the organic Rankine cycle; meanwhile, the expander drives the compressor in the vapor compression refrigeration cycle to work, so that the other part of working medium is compressed, the compressed working medium enters the second condenser, enters the throttling element for cooling and pressure reduction again after being cooled, enters the first-stage low-temperature evaporator, the second-stage low-temperature evaporator and the third-stage low-temperature evaporator for heat exchange with compressed air again, and enters the compressor again after the compressed air is cooled to a lower temperature, so that the vapor compression refrigeration cycle is completed.
The controls and components typically employ valve devices.
In order to improve the purification effect, preferably, the purification module adopts a molecular sieve.
The system can pre-cool air before the air compression at the lower stage by utilizing the waste heat generated in the air compression process, so that the temperature of the air processed by the air compressor is reduced, meanwhile, the temperature and the moisture content of the air at the outlet of the low-temperature evaporator reach the temperature requirement of the compressed air at the outlet of the hollow cold unit in the air separation process in the prior art, and the air cooling unit in the existing air separation equipment can be used for pre-cooling and pre-dehumidifying the raw material air, so that the compression power consumption of the air compressor is remarkably reduced, and meanwhile, the damage to the air compressor caused by liquid-carrying compression of the air compressor is avoided due to the reduction.
In the air flow path, air in the environment firstly passes through an air cooling tower, and the air is dehumidified, washed and cooled by chilled water and cooling water in the air cooling tower; then, the air enters a primary air compressor to be compressed to obtain air with higher temperature and pressure; then the air enters a compressed air precooling flow path of the primary high-temperature evaporator to provide heat for the organic Rankine cycle, and the temperature of the compressed air is reduced; compressed air at the outlet of the first-stage high-temperature evaporator exchanges heat through a first water cooler; and then the compressed air enters a compressed air cooling channel of the first-stage low-temperature evaporator, is cooled by using cold energy provided by a vapor compression refrigeration cycle refrigeration circulation loop, then enters a second-stage air compressor for secondary compression, the compressed air sequentially passes through a compressed air precooling flow path of the second-stage high-temperature evaporator, and compressed air cooling channels of the second water cooler and the second-stage low-temperature evaporator, then enters a third-stage air compressor for compression after being cooled, and then sequentially passes through a compressed air precooling flow path of the third-stage high-temperature evaporator, a compressed air cooling channel of the third water cooler and the third-stage low-temperature evaporator, and finally enters a molecular sieve for purification.
Preferably, the organic Rankine cycle-vapor compression refrigeration cycle loop uses R245fa working medium. R245fa has the advantages of strong stability, low evaporation pressure, incombustibility, large evaporation latent heat and specific heat and the like, and is widely applied to organic Rankine cycles and refrigeration cycles. The organic Rankine cycle-vapor compression refrigeration cycle working medium can also be R134a, R600 and the like.
In order to improve the dehumidification efficiency and the heat exchange effect, preferably, the air cooling tower and the water cooling tower are packed towers.
For convenience of manufacture and use, the first condenser and the second condenser are preferably cooled by water cooling.
In order to improve the heat exchange effect, preferably, the first-stage low-temperature evaporator, the second-stage low-temperature evaporator and the third-stage low-temperature evaporator adopt dividing wall type heat exchange.
In order to improve the heat exchange efficiency, preferably, the first-stage high-temperature evaporator, the second-stage high-temperature evaporator and the third-stage high-temperature evaporator adopt dividing wall type heat exchange.
In order to improve the efficiency of the organic Rankine-vapor compression refrigeration cycle, preferably, the expander and the compressor adopt a coaxial air flotation structure.
In order to improve the efficiency of the organic Rankine-vapor compression refrigeration cycle, preferably, the working medium pump adopts a plunger pump.
In the dehumidification loop, the waste nitrogen enters the lower part of the water cooling tower, is fully contacted with cooling water in the water cooling tower for heat exchange and then is discharged, and the cooling water is cooled into chilled water in the process. The chilled water enters the top of the air cooling tower and is in full contact with the other part of cooling water and raw material air from the bottom side of the tower to exchange heat, so that the temperature of the raw material air is reduced and pre-dehumidification is carried out at the same time. The heated chilled water and cooling water flow out from the bottom of the air cooling tower. The pre-cooled and dehumidified air flows out of the top of the air cooling tower and enters a primary air compressor.
The air cooling unit and the organic Rankine-steam compression refrigeration cycle system are combined, and the organic Rankine-steam compression refrigeration cycle system has the cooling effect on compressed air, so that the state of compressed air at the outlet of the compression module basically meets the state required by the outlet of the existing air separation system after being processed by the air cooling unit, and the existing air cooling unit is used for pre-cooling and pre-dehumidifying the inlet raw material air, thereby further saving the compression energy consumption and achieving the purpose of saving energy.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention utilizes the waste heat generated by the air compressor in the compression process in the air separation process as a heat source to cool the air entering the next-stage air compressor, and the air is not cooled by simply utilizing cooling water, thereby saving energy.
(2) According to the organic Rankine-steam compression refrigeration cycle system, through the organic Rankine-steam compression refrigeration cycle, the air entering the next-stage air compressor is precooled by taking the waste heat of the air compressor as a heat source, the temperature of the air processed by the air compressor is reduced, and the purposes of improving the performance of the air compressor and reducing the compression power consumption are achieved.
(3) According to the invention, the temperature of compressed air is reduced by using the organic Rankine-steam compression refrigeration cycle system, so that the temperature of the compressed air at the outlet of the compression module basically meets the requirement of the gas at the outlet of the air cooling unit in the existing air separation process, the air cooling unit can be used for pre-cooling and pre-dehumidifying the inlet raw material air, absorbing moisture in the air, dehumidifying and washing the air, and the work consumed by compressing water vapor by the air compressor is reduced; in addition, the air moisture is reduced, so that the damage to the air compressor caused by liquid-carrying compression of the air compressor is avoided.
Drawings
FIG. 1 is a schematic diagram of a prior art air separation system;
FIG. 2 is a schematic structural diagram of an air separation system for recovering waste heat of compressed air, pre-dehumidifying and pre-cooling according to an embodiment of the present invention;
FIG. 3 is a diagram of an organic Rankine-vapor compression refrigeration cycle T-s in an embodiment of the invention.
Detailed Description
The invention will be described in further detail below with reference to the drawings and examples, which are intended to facilitate the understanding of the invention without limiting it in any way.
As shown in fig. 1, in the air separation system in the prior art, raw air after large particles are coarsely filtered by a filter firstly enters a primary air compressor 3, enters a first water cooler 5 after being heated and pressurized, enters a secondary air compressor 7 after being cooled to about 40 ℃ for continuous compression, compressed air at an outlet of the secondary air compressor enters a second water cooler 9, is cooled to about 40 ℃ and enters a tertiary air compressor 11, high-temperature and high-pressure gas at an outlet of the tertiary air compressor 11 enters an air cooling tower 1 for cooling and dehumidification to become saturated gas with the temperature of about 15 ℃, and then enters a molecular sieve 15 to complete subsequent steps.
Wherein, a part of cooling water in the air cooling tower 1 is pumped to the middle part of the tower by an external water supply through a first solution pump 22, and the other part of cooling water is pumped to the top part of the tower by a water cooling tower 2 through a second solution pump 23. The air cooling tower and the water cooling tower are called as an air cooling unit.
As shown in fig. 2, the air separation system for recovering the residual heat of the compressor and performing pre-dehumidification and pre-cooling in the present embodiment includes an air flow path, a dehumidification loop, and an organic rankine-vapor compression refrigeration cycle loop, wherein:
the air flow path comprises an air cooling tower 1, a primary air compressor 3, a compressed air precooling flow path of a primary high-temperature evaporator 4, a first water cooler 5, a compressed air cooling channel of a primary low-temperature evaporator 6, a secondary air compressor 7, a compressed air precooling flow path of a secondary high-temperature evaporator 8, a compressed air cooling channel of a second water cooler 9 and a compressed air cooling channel of a secondary low-temperature evaporator 10, a compressed air precooling flow path of a tertiary air compressor 11, a compressed air precooling flow path of a tertiary high-temperature evaporator 12, a compressed air cooling channel of a tertiary water cooler 13 and a compressed air cooling channel of a tertiary low-temperature evaporator 14, a molecular sieve 15 and subsequent processes which are.
The working process is as follows: raw material air enters an air cooling tower 1, enters a primary air compressor 3 after being cooled and dehumidified to become high-temperature high-pressure gas, then enters a primary high-temperature evaporator 4, and is absorbed by a working medium in the primary high-temperature evaporator 4 to provide heat for an organic Rankine cycle loop. Compressed air at the outlet of the first-stage high-temperature evaporator 4 enters a first water cooler 5, and heat is taken away by cooling water. Then enters a first-stage low-temperature evaporator 6 to exchange heat with a refrigeration working medium, and enters a second-stage air compressor 7 after being cooled. The high-temperature and high-pressure gas at the outlet of the secondary air compressor 7 enters the secondary high-temperature evaporator 8 again, and then enters the tertiary air compressor 11 after being cooled by the second water cooler 9 and the secondary low-temperature evaporator 10. The high-temperature high-pressure gas at the outlet of the tertiary air compressor 11 enters the tertiary high-temperature evaporator 12 again, and then is cooled by the third water cooler 13 and the tertiary low-temperature evaporator 14. The air temperature is about 15 ℃, and the air cooling unit outlet air requirement is basically met, so the air separation system can eliminate the air cooling unit.
In the dehumidification loop, a part of cooling water in the air cooling tower 1 is pumped to the middle part of the tower by an external water supply through a first solution pump 22, and the other part of cooling water is pumped to the top part of the tower by a water cooling tower 2 through a second solution pump 23. Raw material air enters from the bottom side of the air cooling tower 1, flows out from the top of the tower, and is cooled and dehumidified by cooling water and chilled water in the air cooling tower 1. The air cooling tower and the water cooling tower are called as an air cooling unit.
In the organic Rankine-steam compression refrigeration cycle loop, a part of working medium exchanges heat with compressed air in the primary high-temperature evaporator 4, the secondary high-temperature evaporator 8 and the tertiary high-temperature evaporator 12, the heated gaseous working medium enters the expander 19 to do work, the working medium cooled and depressurized by the expander 19 enters the first condenser 20, the working medium enters the working medium pump 21 after being absorbed by cooling water, and the working medium enters the high-temperature evaporator again after being pressurized, so that the organic Rankine cycle is completed. At this time, the expander 19 is operated by coaxially driving the compressor 18 in the vapor compression refrigeration cycle, so that another part of the working fluid is compressed. The compressed working medium enters a second condenser 17, enters a throttling element 16 for cooling and pressure reduction again after being cooled, enters a first-stage low-temperature evaporator 6, a second-stage low-temperature evaporator 10 and a third-stage low-temperature evaporator 14 for heat exchange with compressed air again, and enters a compressor 18 again after being cooled to a lower temperature, so that the steam compression refrigeration cycle is completed.
The specific calculation is as follows:
according to the actual situation and the experience, 60000Nm3An/h air separation system is taken as an example. The raw material air temperature T1 is 25 ℃, the moisture content d1 is 16g/kg, the pressure P1 is 101.325kPa, the air cooling tower outlet air temperature T11 is 15 ℃, and the moisture content d2 is 5g/kg (primary air compressor inlet air state). The isentropic efficiency of the first-stage air compressor, the second-stage air compressor and the third-stage air compressor is eta which is 0.85. The outlet pressure of the primary air compressor, the outlet pressure of the secondary air compressor and the outlet pressure of the tertiary air compressor are respectively P12-202 kPa, P22-346 kPa and P32-600 kPa.
In the existing air separation system, the outlet air temperature of the first water cooler and the outlet air temperature of the second water cooler is T4-40 ℃.
In the air separation system designed by the invention, the outlet air temperature of the first, second and third water coolers is T4 ═ 30 ℃. The temperature of compressed air at the outlet of the first-stage, second-stage and third-stage high-temperature evaporators is Tbout 60 ℃. The isentropic efficiency η 1 of the expander is 0.85, the mechanical efficiency η 2 of the expander is 0.96, and the isentropic efficiency η 3 of the compressor is 0.85. The evaporation temperature Tbsat of the first-stage, second-stage and third-stage high-temperature evaporators is 55 ℃, and the superheat degree of an outlet is 5 ℃. The evaporation temperature Tesat of the first-stage, second-stage and third-stage low-temperature evaporators is 10 ℃, and the superheat degree of an outlet is 3 ℃. The condensation temperature Tc of the first condenser and the second condenser is 30 ℃, and the outlet supercooling degree is 5 ℃. The throttling process of the throttling element is insulated. The isentropic efficiency eta 4 of the working medium pump is 0.85. As shown in fig. 3, the organic rankine-vapor compression refrigeration cycle T-s is illustrated.
Mass flow of air
ma＝600000/0.21*1.29/3600＝106.2kg/s
Calculating air enthalpy value by using humid air enthalpy value formula
h＝1.006(T-273.15)+(2501-1.86(T-273.15))d
Compression process formula of air compressor of existing air separation system
Wherein T12/T12' is the temperature of the compressed air at the outlet of the primary air cooling tower.
Compression process formula of primary air compressor of air separation system in the invention
Compression power consumption of primary air compressor of existing air separation system
W1＝ma*(h12-h1)
The air separation system primary air compressor in the invention has compression power consumption
W1′＝ma*(h12′-h11)
The primary air compressor of the air separation system saves energy consumption
ΔW1＝W1-W1′
Also, two-stage and three-stage air compressors have
Compression process formula of secondary air compressor of existing air separation system
Wherein T22/T22' is the temperature of the compressed air at the outlet of the primary air cooling tower.
Compression process formula of secondary air compressor of air separation system in the invention
Compression power consumption of two-stage air compressor of existing air separation system
W2＝ma*(h22-h21)
Compression power consumption of secondary air compressor of air separation system in the invention
W2′＝ma*(h22′-h21′)
The air separation system secondary air compressor saves energy consumption
ΔW2＝W2-W2′
Compression process formula of three-stage air compressor of existing air separation system
Wherein T32/T32' is the temperature of the compressed air at the outlet of the primary air cooling tower.
Compression process formula of three-stage air compressor of air separation system in the invention
Compression power consumption of two-stage air compressor of existing air separation system
W3＝ma*(h32-h31)
Compression power consumption of three-stage air compressor of air separation system in the invention
W3′＝ma*(h32′-h31′)
The air separation system secondary air compressor saves energy consumption
ΔW3＝W3-W3′
The air separation system in the invention can save compression power consumption
ΔW＝ΔW1+ΔW2+ΔW3
Meanwhile, the evaporator comprises a first-stage, a second-stage and a third-stage high-temperature evaporator and a first-stage, a second-stage and a third-stage low-temperature evaporator
Qb1＝morc1*(h6-h5)＝ma*(h12′-hbout)
Qb2＝morc2*(h6-h5)＝ma*(h22′-hbout)
Qb3＝morc3*(h6-h5)＝ma*(h32′-hbout)
Qe1＝mvcr1*(h1-h4)＝ma*(h4′-h21′)
Qe2＝mvcr2*(h1-h4)＝ma*(h4′-h31′)
Qe2＝mvcr3*(h1-h4)＝ma*(h4′-hout′)
Expander and compressor relation
Wexp*η2＝Wcom
The enthalpy value of the working medium in the above formula is obtained by looking up a physical table.
Combining the above formulas, the final Δ W is 914kW 4.8E6kWh
Tout＝14.2℃
From the calculation, the air separation system designed by the invention uses the air cooling unit for pre-cooling and pre-dehumidifying raw material air, and combines the organic Rankine-steam compression refrigeration cycle to recover compression waste heat and cool the compressed air, and finally the air state at the outlet of the compression module completely meets the air state parameters processed by the existing air cooling unit, thereby indicating that the system in the invention is completely feasible. Meanwhile, the system of the invention realizes that the compression energy consumption is saved by 4.8E6kWh every year, and has great significance for saving energy of the air separation system. Meanwhile, the air cooling unit and the organic Rankine-steam compression refrigeration system are stable in operation, simple to operate and long in service life, and cost can be greatly saved.
The embodiments described above are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present 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 present invention.
Claims (10)
1. An air separation system for recovering waste heat of compressed air and carrying out pre-dehumidification and pre-cooling comprises an air flow path and a purification module, and is characterized by further comprising a dehumidification loop and an organic Rankine-vapor compression refrigeration cycle loop; the dehumidification loop comprises an air cooling tower and a water cooling tower;
the air flow path comprises an air cooling tower, a primary air compressor, a compressed air precooling flow path of a primary high-temperature evaporator, a first water cooler, a compressed air cooling channel of a primary low-temperature evaporator, a secondary air compressor, a compressed air precooling flow path of a secondary high-temperature evaporator, a compressed air cooling channel of a second water cooler and a secondary low-temperature evaporator, a tertiary air compressor, a compressed air precooling flow path of a tertiary high-temperature evaporator, a third water cooler and a compressed air cooling channel of a tertiary low-temperature evaporator which are sequentially communicated, and finally the air cooling tower, the primary air compressor, the compressed air precooling flow path of the primary high;
the organic Rankine-vapor compression refrigeration cycle loop comprises a first-stage high-temperature evaporator, a second-stage high-temperature evaporator, a third-stage high-temperature evaporator, a first condenser, a working medium pump and an expander of the organic Rankine cycle, and a first-stage low-temperature evaporator, a second-stage low-temperature evaporator, a third-stage low-temperature evaporator, a compressor, a second condenser and a throttling element of the vapor compression refrigeration cycle;
in the organic Rankine-steam compression refrigeration cycle loop, a part of cycle working medium exchanges heat with compressed air in a first-stage high-temperature evaporator, a second-stage high-temperature evaporator and a third-stage high-temperature evaporator, the heated gaseous working medium enters an expander to do work, the working medium cooled and decompressed by the expander enters a first condenser, the working medium enters a working medium pump after absorbing heat, and the working medium enters the three high-temperature evaporators again after being boosted to finish the organic Rankine cycle; meanwhile, the expander drives the compressor in the vapor compression refrigeration cycle to work, so that the other part of working medium is compressed, the compressed working medium enters the second condenser, enters the throttling element for cooling and pressure reduction again after being cooled, enters the first-stage low-temperature evaporator, the second-stage low-temperature evaporator and the third-stage low-temperature evaporator for heat exchange with compressed air again, and enters the compressor again after the compressed air is cooled to a lower temperature, so that the vapor compression refrigeration cycle is completed.
2. The air separation system for recovering the waste heat of the compressed air and performing pre-dehumidification and pre-cooling as claimed in claim 1, wherein the purification module employs a molecular sieve.
3. An air separation system for recovering the afterheat of compressed air and pre-dehumidifying and pre-cooling as claimed in claim 1, wherein the air cooling tower is a packed tower.
4. An air separation system for recovering the afterheat of compressed air and pre-dehumidifying and pre-cooling as claimed in claim 1, wherein the water cooling tower is a packed tower.
5. The air separation system for recovering the waste heat of the compressed air and performing pre-dehumidification and pre-cooling as claimed in claim 1, wherein the working medium adopted by the organic Rankine-vapor compression refrigeration cycle loop is R245 fa.
6. The air separation system for recovering the waste heat of the compressed air and performing pre-dehumidification and pre-cooling as claimed in claim 1, wherein the first condenser and the second condenser are cooled by a water cooling method.
7. The air separation system for recovering the waste heat of the compressed air and performing pre-dehumidification and pre-cooling as claimed in claim 1, wherein the first-stage low-temperature evaporator, the second-stage low-temperature evaporator and the third-stage low-temperature evaporator use dividing wall type heat exchange.
8. The air separation system for recovering the waste heat of the compressed air and performing pre-dehumidification and pre-cooling as claimed in claim 1, wherein the first-stage high-temperature evaporator, the second-stage high-temperature evaporator and the third-stage high-temperature evaporator use dividing wall type heat exchange.
9. The air separation system for recovering the waste heat of the compressed air and performing pre-dehumidification and pre-cooling as claimed in claim 1, wherein the expander and the compressor are of a coaxial air flotation structure.
10. The air separation system for recovering the waste heat of the compressed air and performing pre-dehumidification and pre-cooling as claimed in claim 1, wherein the working medium pump is a plunger pump.
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| CN102563987A (en) * | 2012-03-01 | 2012-07-11 | 浙江大学 | Vapor-compression refrigerating plant driven by organic Rankine cycle and method |
| CN104454048A (en) * | 2014-10-18 | 2015-03-25 | 杭州哲达科技股份有限公司 | ORC expansion recycling method and device of waste heat of air compressor set |
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| CN107702429B (en) * | 2017-06-20 | 2019-12-17 | 丁玉龙 | Energy efficiency improving device and method for liquid air energy storage system |
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| CN109163475A (en) * | 2018-08-30 | 2019-01-08 | 浙江大学 | The remaining heat recovery refrigerating system and method coupled based on expanding machine and compressor |
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