CN112629160A - Air separation natural reheat overhauling method - Google Patents
Air separation natural reheat overhauling method Download PDFInfo
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- CN112629160A CN112629160A CN202011522494.1A CN202011522494A CN112629160A CN 112629160 A CN112629160 A CN 112629160A CN 202011522494 A CN202011522494 A CN 202011522494A CN 112629160 A CN112629160 A CN 112629160A
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- 238000000926 separation method Methods 0.000 title claims abstract description 104
- 238000000034 method Methods 0.000 title claims abstract description 21
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000010926 purge Methods 0.000 claims abstract description 29
- 238000003303 reheating Methods 0.000 claims abstract description 20
- 238000010438 heat treatment Methods 0.000 claims abstract description 18
- 238000012423 maintenance Methods 0.000 claims abstract description 15
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 14
- 239000007788 liquid Substances 0.000 claims abstract description 13
- 238000009413 insulation Methods 0.000 claims abstract description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000001301 oxygen Substances 0.000 claims abstract description 6
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 6
- 238000002309 gasification Methods 0.000 claims abstract description 4
- 238000000746 purification Methods 0.000 claims description 26
- 238000001816 cooling Methods 0.000 claims description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 19
- 239000000498 cooling water Substances 0.000 claims description 18
- 230000000694 effects Effects 0.000 claims description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 7
- 239000007789 gas Substances 0.000 claims description 5
- 230000003203 everyday effect Effects 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 4
- 239000001569 carbon dioxide Substances 0.000 claims description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 3
- 230000006835 compression Effects 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 3
- 238000005194 fractionation Methods 0.000 claims description 3
- 239000012528 membrane Substances 0.000 claims description 3
- 239000002808 molecular sieve Substances 0.000 claims description 3
- 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 3
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 2
- 239000002994 raw material Substances 0.000 claims 3
- 230000008878 coupling Effects 0.000 claims 1
- 238000010168 coupling process Methods 0.000 claims 1
- 238000005859 coupling reaction Methods 0.000 claims 1
- 238000009434 installation Methods 0.000 claims 1
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 229910052786 argon Inorganic materials 0.000 description 3
- 238000013211 curve analysis Methods 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 238000010792 warming Methods 0.000 description 3
- OLBVUFHMDRJKTK-UHFFFAOYSA-N [N].[O] Chemical compound [N].[O] OLBVUFHMDRJKTK-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 235000011089 carbon dioxide Nutrition 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
- F25J3/04763—Start-up or control of the process; Details of the apparatus used
- F25J3/04769—Operation, control and regulation of the process; Instrumentation within the process
- F25J3/04854—Safety aspects of operation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
- F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
- F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
- F25J3/04763—Start-up or control of the process; Details of the apparatus used
- F25J3/04769—Operation, control and regulation of the process; Instrumentation within the process
- F25J3/04812—Different modes, i.e. "runs" of operation
- F25J3/04824—Stopping of the process, e.g. defrosting or deriming; Back-up procedures
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J5/00—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Separation By Low-Temperature Treatments (AREA)
Abstract
The invention discloses an air separation natural reheat maintenance method, which comprises the steps of cold insulation shutdown, cold insulation shutdown of a cold box, and gasification oxygen discharge system pressure during shutdown; fully draining, namely opening a bypass valve on the air separation tower to fully drain the air separation tower; naturally reheating, standing the air separation device for naturally reheating, and slowly raising the temperature of the air separation device; maintaining the pressure of the cold box, and periodically filling hot nitrogen into the cold box to maintain the pressure; and heating and purging, wherein when the next thermal state is started, the purging pipe is used for continuously purging the air separation device, so that the one-time reheating shutdown of the air separation device is reduced. When the air separation unit is shut down again, the air separation unit is shut down according to a cold insulation shut-down method, then liquid is discharged comprehensively, the air separation unit is stood for natural re-heating, the cold box is periodically filled with hot nitrogen to maintain pressure, the temperature in the cold box naturally re-heats and rises to a certain temperature before the next hot start, and when the hot start is carried out, the air separation unit is heated and blown again, so that the time for restarting the air separation unit after being shut down is greatly shortened, the power consumption is reduced, a large amount of cost is saved, and the economic benefit is improved.
Description
Technical Field
The invention relates to the technical field of IGCC units, in particular to an air separation natural reheating maintenance method.
Background
After the IGCC unit is operated for a long time, after long-term operation, ice, dry ice or mechanical powder deposition can be generated on a low-temperature container and a pipeline of the fractionating tower by the air separation unit, the resistance is gradually increased, the temperature difference of a heat exchange end of the plate is increased, the yield of oxygen and nitrogen is reduced, the purity of oxygen and nitrogen is reduced, and under the condition, the air separation unit needs to be shut down by reheating to remove the deposits, so that the negative influence on the unit is reduced. If the resistance of the heat exchanger and the resistance of the rectifying tower are increased during operation, the gas inlet amount of the rectifying tower is reduced, and the temperature difference of the heat exchange end of the plate is increased, so that the specified indexes on yield and purity are not reached, the reheating machine is stopped in advance.
And a reheating stopping step, namely stopping the product delivery, stopping the oxygen-nitrogen pump and then stopping the expander. Then the special step of reheating shutdown is carried out, the fractionating tower discharges liquid, the system is heated, and the booster compressor is stopped after the high-temperature exchange heating is finished. And stopping the air compressor after all the equipment in the tower is heated. The reheating shutdown generally needs 60 hours, if the operation of the argon system before the shutdown, the argon tower is difficult to heat, and the shutdown time needs about 72 hours. All temperature measuring points of an argon column, main cooling and the like are normal temperature, the air separation device is heated after frost on a blow-off valve on site disappears, the air separation device is shut down in a reheating mode, the time is long, the energy consumption is high, and energy is not saved.
Disclosure of Invention
The invention aims to provide an air separation natural reheat maintenance method to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme: an air separation natural reheat maintenance method comprises the following steps:
s1, performing cold insulation shutdown on the cold box, and discharging the pressure of the oxygen system through gasification when the cold box is shut down;
s2, fully draining liquid, namely opening a bypass valve on the air separation tower, and fully draining liquid to the air separation tower;
s3, naturally reheating the air separation device to stand for naturally reheating, so that the temperature of the air separation device slowly rises;
s4, maintaining the pressure of the cold box, and periodically filling hot nitrogen into the cold box to maintain the pressure;
and S5, heating and purging, wherein when the next thermal state is started, the purging pipe is used for continuously purging the air separation device, so that the one-time reheating shutdown of the air separation device is reduced.
In a preferred embodiment, the cold box is provided with equipment to be operated at a low temperature, the air separation unit comprises an air compressor for pressurizing, pre-cooling and purifying raw air, the air compressor is connected with a water cooling tower through a pipeline, the water cooling tower is connected with a purification system, the purification system is connected with a heat exchanger and a supercharger, and the heat exchanger and the supercharger are connected with the air separation tower through a pipeline system.
In a preferred embodiment, the purification system is a molecular sieve purification system or a membrane purification system, etc. for removing impurities, water, carbon dioxide, etc. from air, and the air separation column comprises an upper column and a lower column, and the upper column and the lower column are connected through an evaporator.
In a preferred embodiment, in step S1, after the pressure relief is performed in the shutdown, the pressure in the upper column of the air separation column is controlled to be 30 KPa; in step S2, the lower column of the fractionation tower is drained first, and the upper column of the air separation tower is drained.
In a preferred embodiment, in step S3, the natural reheat is increased by 5.6 degrees per day on average in the first ten days, and then the rate of temperature rise is slowed down and the temperature in the tower reaches-100 ℃ fifteen days after the liquid discharge.
In a preferred embodiment, in step S4, the hot nitrogen is introduced through the cold box feed gas line, maintaining the cold box pressure at 30 KPa.
In a preferred embodiment, in step S5, one end of the purge tube is connected to the purification system, the other end of the purge tube is directly connected to the heat exchanger and the air separation column, the air compressor compresses the raw air, the pressure is increased to 3-6 barg, the raw air is pre-cooled by the water cooling column, the raw air is cooled to 14-15 ℃ and then is input to the purification system, the air at the outlet of the purification system is clean dry air with the temperature of 22-25 ℃, so that the air separation device is rapidly purged before hot start, and the restart time of the air separation device after shutdown is greatly shortened.
In a preferred embodiment, the purging pipe is connected with the inlet end of the supercharger through a heating pipe 7, the outlet end of the supercharger is connected with the heat exchanger and the air separation tower through a pipeline, the clean air is further compressed through the supercharger, the pressure is continuously increased to 15-60 barg, the purging and heating effects are further improved through the compressed hot air, and the restarting time is saved.
In a preferred embodiment, a cooler is installed on an outlet end pipeline of the supercharger to cool the temperature of the air flow and improve the energy efficiency of the compressor, the cooler utilizes cooling water flowing in a cooling water loop to realize a cooling function, the cooling effect depends on the flow and the temperature of the cooling water, the temperature of the cooling water is 20-30 ℃, the flow is adjusted through a water return valve arranged on the cooling water loop, when the opening degree of the water return valve is reduced, the flow of the cooling water is reduced, the cooling effect is reduced, and correspondingly, the temperature of the output air flow is increased.
In a preferred embodiment, the purge pipe and the warming pipes 7 at two ends of the supercharger are both provided with pressure reducing valves, the pressure reducing valves ensure that the air pressure after pressurization of the purge pipe and the supercharger does not exceed the design pressure of the air separation column, and the outlet ends of the pressure reducing valves are refluxed to the inlet ends of the superchargers through pipelines, so that energy consumption is reduced.
Compared with the prior art, the invention has the beneficial effects that: after the GCC unit realizes long-period operation, the space division start-stop interval is longer. When the air separation unit is shut down again, the air separation unit is shut down according to a cold insulation shut-down method, then the liquid is discharged completely, the air separation unit stands still for natural re-heating, and the cold box is periodically filled with hot nitrogen to maintain the pressure. And before the next hot state is started, the temperature in the cold box naturally reheated to a certain temperature, the temperature is averagely increased by 5.6 ℃ every day in the first ten days after liquid discharge according to data curve analysis, then the temperature increase rate is reduced, the temperature can reach-100 ℃ in the tower about fifteen days, if the shutdown time is long enough, the temperature can be naturally reheated to-40 ℃, and if nitrogen is intermittently charged, the temperature can be reheated to a higher temperature. When the air separation device is started in a hot state, the air separation device is heated and blown together, so that the time for restarting the air separation device after being stopped can be greatly shortened, the power consumption is reduced, a large amount of cost is saved, and the economic benefit is improved.
Drawings
FIG. 1 is a schematic view of the structure of the present invention.
In the figure: 1. an air compressor; 2. a water cooling tower; 3. a purification system; 4. a purge tube; 5. a supercharger; 6. a cooler; 7. a warming tube; 8. a heat exchanger; 9. an air separation column; 91. descending the tower; 92. and (5) feeding into the tower.
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, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the invention provides a technical solution of an air separation natural reheat maintenance method, which includes the following steps:
s1, performing cold insulation shutdown on the cold box, and discharging the pressure of the oxygen system through gasification when the cold box is shut down;
s2, fully draining, namely opening a bypass valve on the air separation tower 9, and fully draining the air separation tower 9;
s3, naturally reheating the air separation device to stand for naturally reheating, so that the temperature of the air separation device slowly rises;
s4, maintaining the pressure of the cold box, and periodically filling hot nitrogen into the cold box to maintain the pressure;
and S5, heating and purging, wherein when the next thermal state is started, the purging pipe 4 is used for continuously purging the air separation device, so that the one-time air separation device reheating shutdown is reduced.
After the IGCC unit realizes long-period operation, the air separation start-stop interval is longer. When the air separation unit is shut down again, the air separation unit is shut down according to a cold insulation shut-down method, then the liquid is discharged completely, the air separation unit stands still for natural re-heating, and the cold box is periodically filled with hot nitrogen to maintain the pressure. And before the next hot state is started, the temperature in the cold box naturally reheated to a certain temperature, the temperature is averagely increased by 5.6 ℃ every day in the first ten days after liquid discharge according to data curve analysis, then the temperature increase rate is reduced, the temperature can reach-100 ℃ in the tower about fifteen days, if the shutdown time is long enough, the temperature can be naturally reheated to-40 ℃, and if nitrogen is intermittently charged, the temperature can be reheated to a higher temperature. When the air separation device is started in a hot state, the air separation device is heated and blown together, so that the time for restarting the air separation device after being stopped can be greatly shortened, the power consumption is reduced, a large amount of cost is saved, and the economic benefit is improved.
Further, in the above-mentioned case,
furthermore, equipment which needs to operate at low temperature is installed in the cold box, and the air separation device can reach the low temperature of-150 ℃ to-180 ℃ when in operation, so that the low-temperature equipment is arranged in the heat-insulating cold box, the air separation device comprises an air compressor 1 for pressurizing, precooling and purifying raw air, the air compressor 1 is connected with a water cooling tower 2 through a pipeline, the water cooling tower 2 is connected with a purification system 3, the purification system 3 is connected with a heat exchanger 8 and a supercharger 5, and the heat exchanger 8 and the supercharger 5 are connected with an air separation tower 9 through a pipeline system.
Further, the purification system 3 is a molecular sieve purification system or a membrane purification system, etc. for removing impurities, water, carbon dioxide, etc. in the air, and the air separation column 9 includes an upper column 92 and a lower column 91, and the upper column 92 and the lower column 91 are connected by an evaporator.
Further, in step S1, after the pressure reduction is stopped, the pressure in the upper column 92 of the air separation column 9 is controlled to 30 KPa; in step S2, the lower column of the air separation column 9 is discharged first and the upper column of the air separation column is discharged again to ensure the pressure of the air separation column 9.
Further, in step S3, natural reheating is performed at an average of 5.6 degrees per day for the first ten days, and then the temperature rise rate is slowed down, and the temperature in the tower reaches-100 ℃ fifteen days after the liquid drainage.
Further, in step S4, hot nitrogen gas is introduced through the cold box feed gas line, maintaining the cold box pressure at 30 KPa.
Further, in step S5, one end of the purging pipe 4 is connected with the purification system 3, the other end of the purging pipe is directly connected with the heat exchanger 8 and the air separation tower 9, raw air is compressed by the air compressor 1 and is boosted to 3-6 barg, precooling is carried out by the water cooling tower 2, the raw air is input into the purification system 3 after being cooled to 14-15 ℃, air at an outlet of the purification system is clean dry air with the temperature of 22-25 ℃, and therefore the air separation device is rapidly purged before hot start, and the time of restarting the air separation device after shutdown is greatly shortened.
Further, sweep the entry end that pipe 4 passes through warming up 7 connection booster compressor 5, and booster compressor 5's exit end passes through pipe connection heat exchanger 8 and air separation column 9, further compresses clean air through booster compressor 5, continues to step up to 15 ~ 60barg, further improves through the hot-air after the compression and sweeps the effect of heating, saves the restart time.
Furthermore, the heating gas is introduced into the corresponding heating channel line, the heat exchanger 8, the upper tower 92 and the lower tower 91 are respectively purged, and then the purged impurities are discharged into the atmosphere.
Further, a cooler 6 is installed on an outlet end pipeline of the supercharger 5 to cool the temperature of the air flow and improve the energy efficiency of the compressor, the cooler 6 achieves a cooling function by using cooling water flowing in a cooling water loop, the cooling effect depends on the flow and the temperature of the cooling water, the temperature of the cooling water is 20-30 ℃, the flow is adjusted by a water return valve arranged on the cooling water loop, when the opening degree of the water return valve is reduced, the flow of the cooling water is reduced, the cooling effect is reduced, and accordingly the temperature of the output air flow is increased.
Furthermore, the air separation device is subjected to purging temperature rise through the purging pipe 4 to serve as a first temperature rise stage, when the temperature of the air separation device is about 0 ℃, the completion of a first temperature rise state is marked, and then hot air is subjected to temperature rise again through the compression stroke of the supercharger 5.
In a preferred embodiment, pressure reducing valves are respectively installed on the heating pipes 7 at the two ends of the purging pipe 4 and the supercharger 5, the pressure reducing valves ensure that the air pressure after the purging pipe 4 and the supercharger 5 are pressurized does not exceed the design pressure of the air separation tower 9, and the outlet end of the pressure reducing valve is refluxed to the inlet end of the supercharger 5 through a pipeline, so that energy consumption is reduced.
The working principle is as follows: when the invention is used, after the GCC unit realizes long-period operation, the space division start-stop interval is longer. When the air separation unit is shut down again, the air separation unit is shut down according to a cold insulation shut-down method, then the liquid is discharged completely, the air separation unit stands still for natural re-heating, and the cold box is periodically filled with hot nitrogen to maintain the pressure. And before the next hot state is started, the temperature in the cold box naturally reheated to a certain temperature, the temperature is averagely increased by 5.6 ℃ every day in the first ten days after liquid discharge according to data curve analysis, then the temperature increase rate is reduced, the temperature can reach-100 ℃ in the tower about fifteen days, if the shutdown time is long enough, the temperature can be naturally reheated to-40 ℃, and if nitrogen is intermittently charged, the temperature can be reheated to a higher temperature. When the air separation device is started in a hot state, the air separation device is heated and blown together, so that the time for restarting the air separation device after being stopped can be greatly shortened, the power consumption is reduced, a large amount of cost is saved, and the economic benefit is improved.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. An air separation natural reheat maintenance method is characterized by comprising the following steps:
s1, performing cold insulation shutdown on the cold box, and discharging the pressure of the oxygen system through gasification when the cold box is shut down;
s2, fully draining, namely opening a bypass valve on the air separation tower (9) and fully draining the air separation tower (9);
s3, naturally reheating the air separation device to stand for naturally reheating, so that the temperature of the air separation device slowly rises;
s4, maintaining the pressure of the cold box, and periodically filling hot nitrogen into the cold box to maintain the pressure;
and S5, heating and purging, wherein when the next thermal state is started, the purging pipe (4) is used for continuously purging the air separation device, so that the one-time air separation device reheating shutdown is reduced.
2. An air separation natural reheat maintenance method according to claim 1, characterized in that: the installation needs the equipment of low temperature operation in the cold box, air separation plant includes air compressor (1) of raw materials air pressurization, precooling, purification, air compressor (1) is through tube coupling water cooling tower (2), purification system (3) is connected in water cooling tower (2), heat exchanger (8) and booster compressor (5) are connected in purification system (3), air separation tower (9) is connected through the tube system in heat exchanger (8) and booster compressor (5).
3. An air separation natural reheat maintenance method according to claim 2, characterized in that: the purification system (3) is a molecular sieve purification system or a membrane purification system and the like and is used for removing impurities, water, carbon dioxide and the like in the air, the air separation tower (9) comprises an upper tower (92) and a lower tower (91), and the upper tower (92) is connected with the lower tower (91) through an evaporator.
4. An air separation natural reheat maintenance method according to claim 1, characterized in that: in step S1, after the pressure relief is carried out after the stop, the pressure in an upper tower (92) of an air separation tower (9) is controlled to be 30 KPa; in step S2, the lower column of the fractionation column (9) is drained first and the upper column of the air fractionation column is drained second.
5. An air separation natural reheat maintenance method according to claim 1, characterized in that: in step S3, the natural re-heating is averagely increased by 5.6 degrees every day in the first ten days, then the temperature rise rate is reduced, and the temperature in the tower reaches-100 ℃ in fifteen days after the liquid drainage.
6. An air separation natural reheat maintenance method according to claim 1, characterized in that: in step S4, the hot nitrogen gas is introduced through the cold box feed gas line, maintaining the cold box pressure at 30 KPa.
7. An air separation natural reheat maintenance method according to claim 1, characterized in that: in the step S5, one end of the purging pipe (4) is connected with the purification system (3), the other end of the purging pipe is directly connected with the heat exchanger (8) and the air separation tower (9), raw material air is compressed by the air compressor (1), the pressure is increased to 3-6 barg, precooling is carried out by the water cooling tower (2), the raw material air is input into the purification system (3) after being cooled to 14-15 ℃, and air at the outlet of the purification system is clean dry air with the temperature of 22-25 ℃, so that the air separation device is rapidly purged before hot start, and the time for restarting the air separation device after shutdown is greatly shortened.
8. An air separation natural reheat maintenance method according to claim 7, characterized in that: sweep the entry end that pipe (4) are connected booster compressor (5) through heating tube (7), the exit end of booster compressor (5) passes through pipe connection heat exchanger (8) and air separation column (9), further compresses clean air through booster compressor (5), continues to step up to 15 ~ 60barg, further improves through the hot-air after the compression and sweeps the effect of heating, saves the restart time.
9. An air separation natural reheat maintenance method according to claim 8, characterized in that: the energy-saving compressor is characterized in that a cooler (6) is mounted on a pipeline at the outlet end of the supercharger (5) to cool the temperature of air flow and improve the energy efficiency of the compressor, the cooler (6) achieves a cooling function by utilizing cooling water flowing in a cooling water loop, the cooling effect depends on the flow and the temperature of the cooling water, the temperature of the cooling water is 20-30 ℃, the flow is adjusted through a water return valve arranged on the cooling water loop, when the opening degree of the water return valve is reduced, the flow of the cooling water is reduced, the cooling effect is reduced, and accordingly the temperature of the output air flow is increased.
10. An air separation natural reheat maintenance method according to claim 8, characterized in that: all install the relief pressure valve on the warming-up pipe 7 at purge tube (4) and booster compressor (5) both ends, guarantee through the relief pressure valve that the air pressure after purge tube (4) and booster compressor (5) pressure boost can not surpass air separation column (9) design pressure, and pass through the entry end that the pipeline flows back booster compressor (5) with the exit end of relief pressure valve, reduce the energy loss.
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