CN114588737A - Cascade utilization LNG cold energy recovery VOC system suitable for LNG power crude oil carrier - Google Patents
Cascade utilization LNG cold energy recovery VOC system suitable for LNG power crude oil carrier Download PDFInfo
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- 239000010779 crude oil Substances 0.000 title claims abstract description 13
- 238000011084 recovery Methods 0.000 title claims abstract description 13
- 239000000446 fuel Substances 0.000 claims abstract description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 29
- LYCAIKOWRPUZTN-UHFFFAOYSA-N ethylene glycol Natural products OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 7
- 125000003827 glycol group Chemical group 0.000 claims description 4
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims description 4
- 239000013535 sea water Substances 0.000 claims description 4
- 239000007864 aqueous solution Substances 0.000 claims description 3
- 239000000969 carrier Substances 0.000 claims description 2
- 239000012855 volatile organic compound Substances 0.000 abstract description 50
- 238000001816 cooling Methods 0.000 abstract description 19
- 239000007791 liquid phase Substances 0.000 abstract description 13
- 238000009833 condensation Methods 0.000 abstract description 12
- 230000005494 condensation Effects 0.000 abstract description 12
- 238000000926 separation method Methods 0.000 abstract description 12
- 208000001034 Frostbite Diseases 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 238000004064 recycling Methods 0.000 abstract description 2
- 230000009977 dual effect Effects 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 44
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 39
- 239000003949 liquefied natural gas Substances 0.000 description 27
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 27
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 22
- 239000003921 oil Substances 0.000 description 15
- 239000001273 butane Substances 0.000 description 13
- 229930195733 hydrocarbon Natural products 0.000 description 13
- 150000002430 hydrocarbons Chemical class 0.000 description 13
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 13
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 12
- 229910052757 nitrogen Inorganic materials 0.000 description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 10
- 239000001301 oxygen Substances 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 10
- 125000000383 tetramethylene group Chemical group [H]C([H])([*:1])C([H])([H])C([H])([H])C([H])([H])[*:2] 0.000 description 10
- 239000012071 phase Substances 0.000 description 8
- 239000007788 liquid Substances 0.000 description 7
- 238000000034 method Methods 0.000 description 7
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 239000001294 propane Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 4
- 239000004215 Carbon black (E152) Substances 0.000 description 3
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 2
- IAQRGUVFOMOMEM-UHFFFAOYSA-N butene Natural products CC=CC IAQRGUVFOMOMEM-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000002309 gasification Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000003507 refrigerant Substances 0.000 description 2
- 230000029058 respiratory gaseous exchange Effects 0.000 description 2
- 239000000779 smoke Substances 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000007539 photo-oxidation reaction Methods 0.000 description 1
- -1 propylene, butylene Chemical group 0.000 description 1
- 210000002345 respiratory system Anatomy 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/002—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
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N5/00—Exhaust or silencing apparatus combined or associated with devices profiting by exhaust energy
-
- 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
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D3/00—Devices using other cold materials; Devices using cold-storage bodies
- F25D3/10—Devices using other cold materials; Devices using cold-storage bodies using liquefied gases, e.g. liquid air
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
- B01D2257/708—Volatile organic compounds V.O.C.'s
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Separation By Low-Temperature Treatments (AREA)
Abstract
The invention discloses a VOC (volatile organic compound) recycling system by utilizing LNG cold energy in a stepped mode, which is suitable for an LNG power crude oil carrier. Has the beneficial effects that: VOC condensation in this application is through the level four cooling, the temperature reduces step by step, the cold energy of the different gradients of make full use of, through the one-level separation after every level of cooling, obtain four kinds of products and the tail gas of ultra-low VOC concentration, tail gas VOC volume content after condensation recovery processing is reduced to below 1% by 20%, make liquid phase product and tail gas aftercooling obtain recycle, the product and the tail gas that obtain are close to the normal atmospheric temperature, the low temperature frostbite risk to personnel and equipment has been avoided, the liquid phase product of retrieving simultaneously can be used as dual fuel engine fuel, thereby save navigation LNG fuel consumption, clean tail gas directly discharges up to standard.
Description
Technical Field
The invention relates to the technical field of marine environment protection, in particular to a VOC (volatile organic compound) recycling system for cascade utilization of LNG (liquefied natural gas) cold energy, which is suitable for an LNG (liquefied natural gas) power crude oil carrier.
Background
In a ship for transporting crude oil, when the steam pressure of the crude oil exceeds the allowable pressure of an oil tank, oil gas volatile gas (VOC) is discharged into the atmosphere through a safety valve. The VOC contains hydrocarbons such as methane, ethane, propane, butane, pentane, propylene, butylene and the like. The methane is a greenhouse gas with stronger greenhouse effect than carbon dioxide, and the rest gases and nitric oxides are subjected to a photo-oxidation reaction under the action of sunlight to generate ozone smoke, so that the environment is harmed. In addition, excessive ozone smoke can damage the respiratory system of people, and even cause life danger when reaching a certain concentration. Therefore, the emission of VOC not only causes environmental pollution and influences safe production and personnel health, but also wastes energy. With the stricter air pollution control standards, the shipping industry is concerned with the emission of VOC from oil tanker carriers. MARPOL 73/78 convention VI specifies: if the contracting country decides to control the cargo steam, the wharf and the ship used need to be provided with a steam discharge control system approved by the governing body of the safety standard of the steam discharge control system, and the liquid cargo ship required to control the cargo steam needs to be provided with a steam discharge collection system approved by the governing body of the MSC/circ.585.
VOC generated from crude oil ships mainly come from cargo handling and ship sailing. The method specifically comprises 'big breathing' caused by pressure change in the cargo hold during loading and unloading and 'small breathing' caused by temperature pressure change during sailing. Where the VOC produced during loading has the greatest proportion but can be disposed of using an onshore oil and gas recovery system. The measures currently taken by VOC released by 'small breath' in the navigation process are generally to inhibit the generation of VOC through technical means, and the application of VOC condensation and recovery is less. The suppression of the production of VOC can only reduce the amount of the produced to a limited extent, and the concentration of the finally discharged atmosphere is high. The known cold source for VOC condensation and recovery mainly comprises nitrogen and propane, and the process needs to be provided with an independent refrigerant circulating device and uses equipment such as a compressor, an expander and the like, so that the equipment investment and the energy consumption are large. Due to the reasons of long investment return period, large occupied ship space and the like, the method is greatly limited in the process of popularization and application.
An effective solution to the problems in the related art has not been proposed yet.
Disclosure of Invention
Aiming at the problems in the related art, the invention provides a system for recovering VOC (volatile organic compound) by using LNG cold energy in a cascade mode, which is suitable for an LNG power crude oil tanker, so as to overcome the technical problems in the prior related art.
The technical scheme of the invention is realized as follows:
the system comprises a storage tank, wherein the storage tank is connected with a primary cooler, the primary cooler is connected with a primary separator, a circulating water outlet of the primary cooler is connected with a circulating pump, the circulating pump is connected with a multi-stream plate type heat exchanger, the primary cooler is connected with the multi-stream plate type heat exchanger, a cold stream outlet of the multi-stream plate type heat exchanger is connected with a fuel system, one end of the primary separator is connected with the multi-stream plate type heat exchanger, the other end of the primary separator is connected with a secondary cooler, the secondary cooler is connected with a secondary separator, one end of the secondary separator is connected with the multi-stream plate type heat exchanger, the other end of the secondary separator is connected with a tertiary cooler, and the tertiary cooler is respectively connected with a ventilating mast and a tertiary separator, one end of the third-stage separator is connected with the multi-flow-strand plate heat exchanger, the other end of the third-stage separator is connected with a fourth-stage cooler, the fourth-stage cooler is connected with the second-stage cooler, the fourth-stage cooler is connected with a fourth-stage separator, the fourth-stage separator is connected with the third-stage cooler, and the other end of the fourth-stage separator is connected with the multi-flow-strand plate heat exchanger.
Further, the temperature range of the first-stage cooler and the first-stage separator is 0-5 ℃, the temperature of the second-stage cooler and the second-stage separator is in the second temperature range, the temperature of the second temperature range is 55-65 ℃ lower than that of the first temperature range, the temperature of the third temperature range of the third-stage cooler and the third-stage separator is 20-30 ℃ lower than that of the second temperature range, and the temperature of the fourth temperature range of the fourth-stage cooler and the fourth-stage separator is 40-50 ℃ lower than that of the third temperature range.
Further, the primary cooler adopts low-temperature circulating water, the temperature of the circulating water is 0-20 ℃, the circulating water is preferably glycol water solution or seawater, the secondary cooler adopts LNG secondary heat exchange, the tertiary cooler adopts clean tail gas, and the quaternary cooler adopts LNG primary heat exchange.
Further, the multi-strand plate heat exchanger has one hot stream and four cold streams, and the hot stream is circulating water.
The invention provides a system for recovering VOC (volatile organic compounds) by using LNG cold energy in a cascade mode, which is suitable for an LNG power crude oil carrier and has the following beneficial effects:
(1) the application utilizes the cold energy condensation VOC that produces among the LNG power ship fuel gasification process, the VOC condensation passes through the level four cooling, the temperature reduces step by step, make full use of the cold energy of different gradients, through the one-level separation behind every stage of cooling, obtain the tail gas of four kinds of products and ultra-low VOC concentration, tail gas VOC volume content after condensation recovery processing is reduced to below 1% by 20%, make liquid phase product and tail gas aftercold obtain recycle, the product and the tail gas that obtain are close to the normal atmospheric temperature, the low temperature frostbite risk to personnel and equipment has been avoided, the liquid phase product of retrieving simultaneously can be used as engine fuel, thereby save navigation LNG fuel consumption, clean tail gas directly discharge to reach standard.
(2) The temperature range of the first-stage cooler and the first-stage separator is 0-5 ℃, the temperature of the second-stage cooler and the second-stage separator is in a second temperature range, the temperature of the second temperature range is 55-65 ℃ lower than that of the first temperature range, the temperature of the third temperature range of the third-stage cooler and the third-stage separator is 20-30 ℃ lower than that of the second temperature range, and the temperature of the fourth temperature range of the fourth-stage cooler and the fourth-stage separator is 40-50 ℃ lower than that of the third temperature range.
(3) The primary cooler adopts low-temperature circulating water, the temperature of the circulating water is 0-20 ℃, the circulating water is preferably glycol water solution or seawater, the secondary cooler adopts LNG secondary heat exchange, the tertiary cooler adopts clean tail gas, and the quaternary cooler adopts LNG primary heat exchange.
(4) The multi-strand plate heat exchanger has one hot stream and four cold streams, and the hot stream is circulating water.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a flow chart of a cascade LNG cold energy recovery VOC system suitable for an LNG-powered crude carrier according to an embodiment of the present invention.
In the figure:
1. a storage tank; 2. a primary cooler; 3. a first stage separator; 4. a circulation pump; 5. a multi-strand plate heat exchanger; 6. a secondary cooler; 7. a secondary separator; 8. a tertiary cooler; 9. a ventilated mast; 10. a third stage separator; 11. a four-stage cooler; 12. a fourth stage separator; 13. a fuel system.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.
The invention is further described with reference to the following drawings and detailed description:
the first embodiment is as follows:
referring to fig. 1, the system for recovering VOC by using cold energy of LNG in a cascade manner, according to an embodiment of the present invention, includes a storage tank 1, the storage tank 1 is connected to a primary cooler 2, the primary cooler 2 is connected to a primary separator 3, a circulating water outlet of the primary cooler 2 is connected to a circulating pump 4, the circulating pump 4 is connected to a multi-stream plate heat exchanger 5, the primary cooler 2 is connected to the multi-stream plate heat exchanger 5, a cold stream outlet of the multi-stream plate heat exchanger 5 is connected to a fuel system 13, one end of the primary separator 3 is connected to a cold stream inlet of the multi-stream plate heat exchanger 5, the other end of the primary separator 3 is connected to a secondary cooler 6, the secondary cooler 6 is connected to a secondary separator 7, one end of the secondary separator 7 is connected to the multi-stream plate heat exchanger 5, the other end of the second-stage separator 7 is connected with a third-stage cooler 8, the third-stage cooler 8 is connected with a ventilating mast 9 and a third-stage separator 10 respectively, one end of the third-stage separator 10 is connected with the multi-strand plate heat exchanger 5, the other end of the third-stage separator 10 is connected with a fourth-stage cooler 11, the fourth-stage cooler 11 is connected with the second-stage cooler 6, the fourth-stage cooler 11 is connected with a fourth-stage separator 12, the fourth-stage separator 12 is connected with the third-stage cooler 8, and the other end of the fourth-stage separator 12 is connected with the multi-strand plate heat exchanger 5.
According to the scheme, the step cooling separation process is adopted, cold sources with different temperatures are fully utilized, corresponding products and clean tail gas under different temperature intervals are obtained, wherein the VOC-containing oil gas is cooled to four temperature intervals through the first-stage cooler 2, the second-stage cooler 6, the third-stage cooler 8 and the fourth-stage cooler 11, the VOC-containing oil gas in the four temperature intervals is subjected to gas-liquid separation through the first-stage separator 3, the second-stage separator 7, the third-stage separator 10 and the fourth-stage separator 12, each stage is located in one temperature interval and comprises one cooler and one separator, the cooling and the separation are carried out firstly, and the first product mainly comprises hydrocarbon components such as hexane, pentane, butane, butene and the like; the second product mainly comprises hydrocarbons such as pentane, butylene, hexane, butane and the like, a small amount of water, a small amount of nitrogen and oxygen; the third product mainly comprises hydrocarbons such as butylene, butane, pentane, hexane and the like and trace moisture, nitrogen and oxygen; the fourth product mainly comprises hydrocarbons such as butylene, butane, pentane and propane, trace nitrogen and oxygen, the VOC condensation in the application is cooled by four stages, the temperature is reduced step by step, and the cold energy of different gradients is fully utilized. Four products and tail gas with ultralow VOC concentration are obtained through first-stage separation after each stage of cooling, the volume content of VOC in the tail gas subjected to condensation recovery treatment is reduced from 20% to below 1%, so that residual cold of the liquid-phase product and the tail gas is recycled, the obtained product and the tail gas are close to normal temperature, the risk of low-temperature frostbite on personnel and equipment is avoided, meanwhile, the recycled liquid-phase product can be used as fuel of a dual-fuel engine, the fuel consumption of navigation LNG is saved, and the clean tail gas directly reaches the standard and is discharged.
Example two:
as shown in fig. 1, a primary cooler 2 is connected to the storage tank 1, a primary separator 3 is connected to the primary cooler 2, a circulating water outlet of the primary cooler 2 is connected to a circulating pump 4, the circulating pump 4 is connected to a multi-stream plate heat exchanger 5, the primary cooler 2 is connected to the multi-stream plate heat exchanger 5, a cold stream outlet of the multi-stream plate heat exchanger 5 is connected to a fuel system 13, one end of the primary separator 3 is connected to a cold stream inlet of the multi-stream plate heat exchanger 5, the other end of the primary separator 3 is connected to a secondary cooler 6, the secondary cooler 6 is connected to a secondary separator 7, one end of the secondary separator 7 is connected to the multi-stream plate heat exchanger 5, the other end of the secondary separator 7 is connected to a tertiary cooler 8, and an air-permeable mast 9 and a tertiary separator 10 are connected to the tertiary cooler 8, one end of the third-stage separator 10 is connected with the multi-flow-strand plate-type heat exchanger 5, the other end of the third-stage separator 10 is connected with a fourth-stage cooler 11, the fourth-stage cooler 11 is connected with the second-stage cooler 6, the fourth-stage cooler 11 is connected with a fourth-stage separator 12, the fourth-stage separator 12 is connected with the third-stage cooler 8, the other end of the fourth-stage separator 12 is connected with the multi-flow-strand plate-type heat exchanger 5, the temperature interval of the first-stage cooler 2 and the first-stage separator 3 is 0-5 ℃, the temperature of the second-stage cooler 6 and the second-stage separator 7 is in a second temperature interval, the temperature of the second temperature interval is 55-65 ℃ lower than that of the first temperature interval, the temperature interval of the third-stage cooler 8 and the third-stage separator 10 is 20-30 ℃ lower than that of the second temperature interval, the temperature interval of the fourth-stage cooler 11 and the fourth-stage separator 12 is 20 ℃ lower than that of the third temperature interval The temperature is 40-50 ℃;
example three:
as shown in fig. 1, a primary cooler 2 is connected to the storage tank 1, a primary separator 3 is connected to the primary cooler 2, a circulating water outlet of the primary cooler 2 is connected to a circulating pump 4, the circulating pump 4 is connected to a multi-stream plate heat exchanger 5, the primary cooler 2 is connected to the multi-stream plate heat exchanger 5, a cold stream outlet of the multi-stream plate heat exchanger 5 is connected to a fuel system 13, one end of the primary separator 3 is connected to a cold stream inlet of the multi-stream plate heat exchanger 5, the other end of the primary separator 3 is connected to a secondary cooler 6, the secondary cooler 6 is connected to a secondary separator 7, one end of the secondary separator 7 is connected to the multi-stream plate heat exchanger 5, the other end of the secondary separator 7 is connected to a tertiary cooler 8, and an air-permeable mast 9 and a tertiary separator 10 are connected to the tertiary cooler 8, one end of the third-stage separator 10 is connected with the multi-flow strand plate heat exchanger 5, the other end of the third-stage separator 10 is connected with a fourth-stage cooler 11, the fourth-stage cooler 11 is connected with the second-stage cooler 6, the fourth-stage cooler 11 is connected with a fourth-stage separator 12, the fourth-stage separator 12 is connected with the third-stage cooler 8, the other end of the fourth-stage separator 12 is connected with the multi-flow strand plate heat exchanger 5, the first-stage cooler 2 adopts low-temperature circulating water, the temperature of the circulating water is 0-20 ℃, the circulating water is preferably glycol aqueous solution or seawater, the second-stage cooler 6 adopts secondary heat exchange of LNG, the third-stage cooler 8 adopts clean tail gas, and the fourth-stage cooler 11 adopts primary heat exchange of LNG;
example four:
as shown in fig. 1, a primary cooler 2 is connected to the storage tank 1, a primary separator 3 is connected to the primary cooler 2, a circulating water outlet of the primary cooler 2 is connected to a circulating pump 4, the circulating pump 4 is connected to a multi-stream plate heat exchanger 5, the primary cooler 2 is connected to the multi-stream plate heat exchanger 5, a cold stream outlet of the multi-stream plate heat exchanger 5 is connected to a fuel system 13, one end of the primary separator 3 is connected to a cold stream inlet of the multi-stream plate heat exchanger 5, the other end of the primary separator 3 is connected to a secondary cooler 6, the secondary cooler 6 is connected to a secondary separator 7, one end of the secondary separator 7 is connected to the multi-stream plate heat exchanger 5, the other end of the secondary separator 7 is connected to a tertiary cooler 8, and an air-permeable mast 9 and a tertiary separator 10 are connected to the tertiary cooler 8, one end of the third-stage separator 10 is connected with the multi-flow-strand plate heat exchanger 5, the other end of the third-stage separator 10 is connected with a fourth-stage cooler 11, the fourth-stage cooler 11 is connected with the second-stage cooler 6, the fourth-stage cooler 11 is connected with a fourth-stage separator 12, the fourth-stage separator 12 is connected with the third-stage cooler 8, the other end of the fourth-stage separator 12 is connected with the multi-flow-strand plate heat exchanger 5, the multi-flow-strand plate heat exchanger 5 has a hot stream and four cold streams, and the hot stream is circulating water.
In practical application, the method adopts a graded cooling separation process, fully utilizes cold sources with different temperatures, and obtains corresponding products and clean tail gas in different temperature intervals, wherein the VOC-containing oil gas is cooled to four temperature intervals through a first-stage cooler 2, a second-stage cooler 6, a third-stage cooler 8 and a fourth-stage cooler 11, the VOC-containing oil gas is subjected to gas-liquid separation through a first-stage separator 3, a second-stage separator 7, a third-stage separator 10 and a fourth-stage separator 12 respectively, each stage is positioned in one temperature interval and comprises one cooler and one separator, the cooling is firstly carried out and then the separation is carried out, and the first product mainly comprises hydrocarbon components such as hexane, pentane, butane, butene and the like; the second product mainly comprises hydrocarbons such as pentane, butylene, hexane, butane and the like, a small amount of water, a small amount of nitrogen and oxygen; the third product mainly comprises hydrocarbons such as butylene, butane, pentane, hexane and the like and trace moisture, nitrogen and oxygen; the fourth product mainly comprises hydrocarbons such as butylene, butane, pentane and propane, and trace nitrogen and oxygen, and in the application, the VOC condensation is cooled by four stages, the temperature is reduced step by step, and the cold energy of different gradients is fully utilized. Four products and tail gas with ultralow VOC concentration are obtained through first-stage separation after each stage of cooling, the volume content of VOC in the tail gas subjected to condensation recovery treatment is reduced from 20% to below 1%, so that residual cold of the liquid-phase product and the tail gas is recycled, the obtained product and the tail gas are close to normal temperature, the risk of low-temperature frostbite on personnel and equipment is avoided, meanwhile, the recycled liquid-phase product can be used as fuel of a dual-fuel engine, the fuel consumption of navigation LNG is saved, and the clean tail gas directly reaches the standard and is discharged.
Example five concrete application examples:
the embodiment provides a 15.8-million-load heavy-ton oil tanker VOC recovery scheme. The discharge amount of VOC-containing oil gas in the oil cargo hold is about 1600kg/h, and the VOC content is about 881 kg/h. After being discharged from the oil gas collecting system of the oil cargo tank, the VOC oil gas is firstly cooled to 5 ℃ by the primary cooler 2, and low-temperature circulating water is adopted as cooling cold energy and is ethylene glycol aqueous solution. And cooling the mixture, and then feeding the cooled mixture into a primary separator 3, wherein the operating pressure of the primary separator 3 is 110-115 KPa, the liquid phase is a first separated product, and the product mainly contains hydrocarbon components such as hexane, pentane, butane and butylene. The gas phase material flow goes to a secondary cooler 6 to be continuously cooled.
And the gas-phase material flow of the primary separator 3 enters a secondary cooler 6 for cooling, the cooled cold energy comes from the secondary heat exchange of LNG, and the required amount of the LNG is about 950 kg/h. After cooling, the temperature is-55 ℃, and the gas and the liquid enter a secondary separator 7 for gas-liquid separation. The secondary separator 7 is operated at a pressure of 108-112 KPa. Separating to obtain a second product, wherein the second product mainly comprises hydrocarbons such as pentane, butylene, hexane, butane and the like, and a small amount of water, trace nitrogen and oxygen. The gas phase flows to a three-stage cooler 8 to be continuously cooled.
The gas phase material flow of the second-stage separator 7 enters a third-stage cooler 8 for cooling, the cooled cold energy comes from the gas phase material flow of the fourth-stage separator 12, and the temperature after cooling is-80 ℃. Then enters a three-stage separator 10 for gas-liquid separation. The tertiary separator 10 operates at a pressure 105 and 110 KPa. The third product is separated out and mainly comprises hydrocarbons such as butylene, butane, pentane, hexane and the like, and trace moisture, nitrogen and oxygen. The gas phase flows to a downstream four-stage cooler 11 to be continuously cooled.
The gas phase material of the third-stage separator 10 flows into a fourth-stage cooler 11 to be continuously cooled, the cooled cold energy comes from the primary heat exchange of LNG, and the cooled temperature is-120 ℃. After the temperature is reduced, the gas and the liquid are separated in the four-stage separator 12, and the operation pressure of the four-stage separator 12 is 101-110 KPa. Separating out the fourth product, which mainly comprises hydrocarbons such as butylene, butane, pentane, propane and the like, and trace nitrogen and oxygen. The unliquefied gas phase is composed mainly of nitrogen, oxygen and trace amounts of methane, ethane, propane, etc.
This embodiment LNG provides 107KW of cold for VOC condensation, meaning 107KW of steam heat can be saved in fuel gasification. The embodiment recovers 10KW of medium-grade low-temperature cold below-65 ℃ from clean tail gas for condensing VOC, thereby avoiding the use of other refrigerants. This embodiment retrieves 41 KW's cold volume from the liquid phase product and is used for cooling low temperature circulating water, has solved the problem that cooling needs the cold source behind the circulating water cooling VOC, simultaneously, makes the liquid phase VOC of retrieving reach the combustion temperature requirement behind the fuel system more easily. In this embodiment, 230kg/h of the first recovered product, 585kg/h of the second recovered product, 40kg/h of the third recovered product and 21kg of the fourth recovered product were recovered, respectively. The total recovery of VOC liquid phase products is 876kg/h, the effective liquefaction rate of VOC is up to 99.4%, and the VOC tail gas can reach the standard of the ventilating mast and be discharged. The embodiment adopts a dual-fuel engine of a ship type, and liquid-phase products are used as fuel under the condition of ensuring that the consumption of LNG is not lower than 950kg/h according to the requirement of sailing fuel. This embodiment utilizes oil gas discharge pressure, chooses for use low pressure drop equipment, guarantees that the pressure of discharging terminal clean tail gas satisfies the emission requirement, does not set up supercharging equipment such as compressor, draught fan.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (4)
1. The VOC system is recovered by utilizing LNG cold energy in a gradient manner and is suitable for an LNG power crude oil carrier, and comprises a storage tank (1) and is characterized in that the storage tank (1) is connected with a primary cooler (2), the primary cooler (2) is connected with a primary separator (3), a circulating water outlet of the primary cooler (2) is connected with a circulating pump (4), the circulating pump (4) is connected with a multi-stream plate type heat exchanger (5), the primary cooler (2) is connected with the multi-stream plate type heat exchanger (5), a cold stream outlet of the multi-stream plate type heat exchanger (5) is connected with a fuel system (13), one end of the primary separator (3) is connected with a cold stream inlet of the multi-stream plate type heat exchanger (5), the other end of the primary separator (3) is connected with a secondary cooler (6), and the secondary separator (7) is connected with the secondary cooler (6), one end of the second-stage separator (7) is connected with the multi-flow strand plate type heat exchanger (5), the other end of the second-stage separator (7) is connected with a third-stage cooler (8), the third-stage cooler (8) is connected with an air-permeable mast (9) and a third-stage separator (10) respectively, one end of the third-stage separator (10) is connected with the multi-flow strand plate type heat exchanger (5), the other end of the third-stage separator (10) is connected with a fourth-stage cooler (11), the fourth-stage cooler (11) is connected with the second-stage cooler (6), the fourth-stage cooler (11) is connected with a fourth-stage separator (12), the fourth-stage separator (12) is connected with the third-stage cooler (8), and the other end of the fourth-stage separator (12) is connected with the multi-flow strand plate type heat exchanger (5).
2. The system for recovering the VOC by using the cold energy of the LNG in the cascade suitable for the LNG power crude oil carrier is characterized in that the temperature range of the primary cooler (2) and the primary separator (3) is 0-5 ℃, the temperature of the secondary cooler (6) and the secondary separator (7) is in the second temperature range, the temperature of the second temperature range is 55-65 ℃ lower than that of the first temperature range, the temperature of the third temperature range of the tertiary cooler (8) and the tertiary separator (10) is 20-30 ℃ lower than that of the second temperature range, and the temperature of the fourth temperature range of the quaternary cooler (11) and the quaternary separator (12) is 40-50 ℃ lower than that of the third temperature range.
3. The system for recovering the VOC through the cold energy of the LNG suitable for the LNG powered crude oil carrier in the cascade mode is characterized in that the primary cooler (2) adopts low-temperature circulating water with the temperature of 0-20 ℃, the circulating water is preferably glycol aqueous solution or seawater, the secondary cooler (6) adopts secondary heat exchange of the LNG, the tertiary cooler (8) adopts clean tail gas, and the quaternary cooler (11) adopts primary heat exchange of the LNG.
4. The system for the cascade utilization of LNG cold energy recovery VOC suitable for LNG powered crude oil carriers according to claim 1 wherein the multi-stream plate heat exchanger (5) has one hot stream and four cold streams and the hot stream is circulating water.
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