CN114688828A - Air separation device and system based on LNG cold energy utilization - Google Patents

Air separation device and system based on LNG cold energy utilization Download PDF

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Publication number
CN114688828A
CN114688828A CN202210441590.6A CN202210441590A CN114688828A CN 114688828 A CN114688828 A CN 114688828A CN 202210441590 A CN202210441590 A CN 202210441590A CN 114688828 A CN114688828 A CN 114688828A
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air
tower
nitrogen
outlet
cooling tower
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Inventor
郑少雄
薛志恒
赵鹏程
赵杰
张朋飞
吴涛
孟勇
王伟锋
赵永坚
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Xian Thermal Power Research Institute Co Ltd
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Xian Thermal Power Research Institute Co Ltd
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Priority to CN202210441590.6A priority Critical patent/CN114688828A/en
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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
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04157—Afterstage cooling and so-called "pre-cooling" of the feed air upstream the air purification unit and main heat exchange line
    • 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
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04048—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams
    • F25J3/0406—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams of nitrogen
    • 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
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04048—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams
    • F25J3/04066—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams of oxygen
    • 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
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04254—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using the cold stored in external cryogenic fluids
    • F25J3/0426—The cryogenic component does not participate in the fractionation
    • F25J3/04266—The cryogenic component does not participate in the fractionation and being liquefied hydrocarbons
    • 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
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/30—Processes or apparatus using other separation and/or other processing means using a washing, e.g. "scrubbing" or bubble column for purification purposes
    • F25J2205/32—Processes or apparatus using other separation and/or other processing means using a washing, e.g. "scrubbing" or bubble column for purification purposes as direct contact cooling tower to produce a cooled gas stream, e.g. direct contact after cooler [DCAC]
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/30—Processes or apparatus using other separation and/or other processing means using a washing, e.g. "scrubbing" or bubble column for purification purposes
    • F25J2205/34—Processes or apparatus using other separation and/or other processing means using a washing, e.g. "scrubbing" or bubble column for purification purposes as evaporative cooling tower to produce chilled water, e.g. evaporative water chiller [EWC]

Abstract

The invention provides an air separation device and system based on LNG cold energy utilization, comprising an air separation pretreatment system and an air separation fine distillation system; the air pretreatment system comprises an air compression unit, an air pre-cooling unit and an air purification unit; the outlet of the air compression unit is connected with the inlet at the bottom of the air cooling tower, the bottom of the air cooling tower is connected with a self-circulating water system, the middle part of the air cooling tower is connected with a low-temperature waste nitrogen cooling system, and the outlet at the top of the air cooling tower is connected with an air purification unit; the air separation rectification system comprises a rectification tower, wherein a condensation evaporator K1 and an air fractionation tower are arranged in the rectification tower, an outlet of an air purification unit is connected with an inlet at the bottom of the rectification tower, an outlet at the top of the condensation evaporator K1 is led into a liquid nitrogen collector, and an outlet at the bottom of the rectification tower is connected with a high-purity liquid oxygen collector. The invention realizes the separation of nitrogen and oxygen. The invention solves the defects of complex flow, huge equipment, complex operation, higher operation cost and the like of the traditional air separation process.

Description

Air separation device and system based on LNG cold energy utilization
Technical Field
The invention belongs to the technical field of air separation, and particularly relates to an air separation device and system based on LNG cold energy utilization.
Background
LNG cold energy is used in various ways as an important subsidiary industry of the LNG industry. The method mainly comprises the following steps: air separation, low-temperature power generation, low-temperature refrigeration, raw and cold crushing of waste rubber, light hydrocarbon separation, gas turbine inlet air cooling technology and the like. The technology of low-temperature freezing (cold water air conditioning, refrigeration house and ice making) is relatively mature; at present, industrialization of indirect utilization of LNG cold energy in waste rubber cryogenic grinding projects is realized, but direct utilization of LNG cold energy in the projects is not realized, and corresponding pilot-scale research is being carried out domestically.
Oxygen and nitrogen are not only important production raw materials in chemical industry, but also have very wide application in the fields of medical treatment, electronics, metallurgy, aviation, environmental protection and the like. With the rapid development of the scientific technology and the economy in the world, the demand of various industries on oxygen and nitrogen is rapidly increased, the consumption is more and more, and the development of the air separation technology is promoted. Although the traditional voltage-condensation refrigeration air separation technology can obtain oxygen, nitrogen and the like required by various industries, the pharmaceutical industry and the aviation industry, the energy consumption is very high, and the demand for electric energy is very large. Therefore, the development of energy-saving and efficient air separation technology gradually becomes the development direction of air separation industry. Meanwhile, with the gradual development of the liquefied natural gas cold energy utilization industry, a new process route is brought to the air separation technology, and a new research direction is provided for the development of the air separation technology. Currently, there are four main methods of air separation: chemical absorption, pressure swing adsorption, membrane permeation, and cryogenic rectification.
The existing air separation process mainly has the defects of complex flow, huge equipment, complex operation, higher operation cost and the like, so that the LNG air separation process can only be developed in a large LNG receiving station and cannot be comprehensively popularized and implemented.
In summary, a reasonable LNG air separation system is urgently needed to be provided, the economic feasibility of the whole set of LNG air separation cold energy comprehensive utilization scheme is improved, and the problems of dependence on space and insufficient development and popularization of an LNG air separation process can be solved by miniaturized and skid-mounted equipment, so that the investment cost of engineering is reduced.
Disclosure of Invention
The invention aims to provide an air separation device and system based on LNG cold energy utilization. The device of the invention realizes the separation of nitrogen and oxygen in the air so as to obtain high-purity nitrogen and high-purity oxygen.
In order to achieve the purpose, the invention adopts the following technical scheme:
an air separation device based on LNG cold energy utilization comprises an air separation pretreatment system and an air separation fine distillation system;
the air pretreatment system mainly comprises an air compression unit, an air precooling unit and an air purification unit; the air pre-cooling unit comprises an air cooling tower, an outlet of the air compression unit is connected with an inlet at the bottom of the air cooling tower, the bottom of the air cooling tower is connected with a self-circulation water system, the middle part of the air cooling tower is connected with a low-temperature waste nitrogen cooling system, and an outlet at the top of the air cooling tower is connected with an air purification unit;
the air separation distillation system comprises a rectifying tower, wherein a condensation evaporator K and an air fractionating tower are arranged inside the rectifying tower, an outlet of an air purification unit is connected with the bottom inlet of the rectifying tower, an outlet of the top of the condensation evaporator K is led into a liquid nitrogen collector, and an outlet of the bottom of the rectifying tower is connected with a high-purity liquid oxygen collector.
As a further improvement of the invention, the air compression unit comprises a self-cleaning air filter and an air compressor, one end of the self-cleaning air filter is externally connected with air, the other end of the self-cleaning air filter is connected with the air compressor, and an outlet of the air compressor is connected with an inlet at the bottom of the air cooling tower.
As a further improvement of the invention, the self-circulation water system comprises a water storage tank and a first booster pump, wherein the water storage tank is connected with a heat exchange water inlet at the bottom of the air cooling tower through the first booster pump.
As a further improvement of the invention, the low-temperature waste nitrogen cooling system comprises a water cooler and a second booster pump, wherein heat exchange media of the water cooler are cooling water and waste nitrogen, and a gas outlet of the water cooler is connected with a heat exchange water inlet in the middle of the air cooling tower through the second booster pump.
As a further improvement of the invention, the air purification unit comprises a first molecular sieve adsorber and a second molecular sieve adsorber, and the first molecular sieve adsorber and the second molecular sieve adsorber are connected in parallel; the parallel inlets of the first molecular sieve absorber and the second molecular sieve absorber are connected with the outlet at the top of the air cooling tower, and the parallel outlets are connected to the air storage tank through a mixer.
As a further improvement of the present invention, the air purification unit further comprises a waste nitrogen heating unit, the waste nitrogen heating unit comprises a heating tank, a power supply, a switch and an electric heater, the electric heater is arranged in the heating tank, and the power supply, the switch and the electric heater are electrically connected; the top of the heating tank is provided with a waste nitrogen inlet, the bottom of the heating tank is provided with a waste nitrogen outlet, and the waste nitrogen outlet is connected with a parallel inlet;
the parallel inlets of the first molecular sieve adsorber and the second molecular sieve adsorber are respectively provided with a first regulating valve and a second regulating valve.
As a further improvement of the invention, the first molecular sieve adsorber and the second molecular sieve adsorber both have adsorption beds of alumina gel and molecular sieve.
As a further improvement of the invention, a nitrogen branch pipe is also arranged on a pipeline leading the outlet at the top of the condensation evaporator K into the liquid nitrogen collector and is connected to an air fractionating tower at the top of the rectifying tower.
As a further improvement of the invention, a waste nitrogen outlet of the air fractionation tower is connected with the low-temperature waste nitrogen cooling system.
A separation method of an air separation device based on LNG cold energy utilization comprises the following steps:
raw material air enters an air compression unit to be compressed, the temperature of an outlet of the air compression unit is increased, and then the raw material air enters an air pre-cooling unit to cool the air;
the compressed air exchanges heat with normal temperature water from a circulating water system at the lower part of the air cooling tower, and then passes through the packing layer to rise to the upper part of the air cooling tower to exchange heat with cooling water;
cooling water at the upper part of the air cooling tower is generated by a low-temperature waste nitrogen cooling system in the water cooling tower, and compressed air enters an air purification unit after being washed and cleaned of harmful substances in the air in the heat exchange of the air cooling tower;
the air after compression and precooling temperature reduction sequentially passes through an adsorption bed of an air purification unit to remove moisture, acetylene, carbon dioxide and hydrocarbons and then enters an air separation fine distillation system;
air is rectified from the lower part of the lower tower of the rectification system, and the separation of nitrogen and oxygen in the air is realized through multiple air partial condensation and liquid-air partial evaporation processes.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides an air separation device based on LNG cold energy utilization, wherein raw material gas sequentially passes through an air compression unit, an air precooling unit and an air purification unit, impurities such as dust, moisture, acetylene, carbon dioxide, hydrocarbons and the like are removed through a pretreatment system, and after the raw material gas is cooled to the saturation temperature under the separation pressure in a heat exchange system, the raw material gas is fed from the lower part of a lower tower of a rectification system for rectification. The invention combines the existing mature LNG cold energy utilization technology to complete air separation pretreatment and air separation fine distillation. Firstly, air separation pretreatment is carried out, raw material gas is subjected to impurity removal such as dust, moisture, acetylene, carbon dioxide and hydrocarbons through a pretreatment system, and is cooled to the saturation temperature under the separation pressure in a heat exchange system, and then the raw material gas is fed from the lower part of the lower tower of a rectification system for rectification. The nitrogen flowing out of the top of the lower tower is condensed into liquid nitrogen in a condensing evaporator, and is divided into two strands after being led out, one strand of nitrogen is used as reflux liquid to provide cold energy for steam rising in the upper tower from the downward flow of the top of the upper tower, so that a liquid product with higher purity can be obtained; introducing the other strand into a liquid nitrogen collector for storage; high-purity liquid oxygen is obtained from the bottom of the upper tower and is guided into a liquid oxygen collector for storage, so that the separation of nitrogen and oxygen is realized. The invention solves the defects of complex flow, huge equipment, complex operation, higher operation cost and the like of the traditional air separation process.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below; it is obvious that the drawings in the following description are some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
FIG. 1 is a schematic diagram of an air separation pretreatment system based on LNG cold energy utilization according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an air separation fine distillation system based on LNG cold energy utilization according to an embodiment of the present invention.
1. A self-cleaning air filter; 2. an air compressor; 3. an air cooling tower; 4. a water storage tank; 5. a first booster pump;
6. a water cooler; 7. a second booster pump; 8. a first regulating valve; 9. a second regulating valve; 10. a first molecular sieve adsorber; 11. a second molecular sieve adsorber; 12. a mixer; 13. a power source; 14. a switch; 15. an electric heater; 16. an air storage tank.
K1, condensation evaporator; c1, C2 air fractionation columns; LN2And liquid nitrogen; LO2And liquid oxygen.
Detailed Description
In order to make the technical solutions of the present invention better understood, 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 obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The existing problem is that air is a multi-component complex gas mixture mainly composed of oxygen, nitrogen and other gases, and besides oxygen and nitrogen components, the air also contains gas impurities such as argon, carbon oxides, nitrogen oxides, sulfides, water vapor, hydrocarbons, acetylene, a small amount of dust and the like. The air separation device can be damaged due to the direct entering of natural air which is not subjected to purification treatment, and small particle impurities contained in the natural air can enter equipment such as a compressor, a cooler and the like along with the air, so that the cooling effect of the equipment can be influenced, and even serious consequences such as the abrasion of equipment parts and the blockage of the equipment, a gas pipeline and the like can be caused; the water vapor and the carbon dioxide in the air can be frozen and gathered in the equipment due to low temperature, so that the equipment and the gas pipeline are blocked, and the quality and the yield of the product are reduced or the whole air separation production line stops production; in the air separation unit, if hydrocarbons such as acetylene enter, there is a possibility of occurrence of a combustion or explosion accident, and the hydrocarbons such as acetylene cause friction, impact, electrostatic discharge, or the like with the oxygen-containing medium in the air separation unit to induce an emergency. Therefore, only if the impurities in the air are removed, the long-term safe and reliable operation of the air separation system can be effectively ensured.
The air pre-treatment system mainly comprises air compression, air precooling and air purification, and aims to remove impurities contained in air and purify the air so that the air can reach the optimal state before rectification, the air separation is more smooth, the purity of the prepared product is higher, the energy consumption is less, and the long-term safe and reliable operation of an air separation system is ensured.
The invention provides an air separation device based on LNG cold energy utilization. The raw material gas is cleaned of impurities such as dust, moisture, acetylene, carbon dioxide, hydrocarbons and the like by a pretreatment system, and is cooled to the saturation temperature under the separation pressure in a heat exchange system, and then the raw material gas is fed from the lower part of the lower tower of a rectification system for rectification. The rectification of the air is completed through the processes of partial condensation of the air and partial evaporation of the liquid air for many times, so that the separation of the nitrogen and the oxygen in the air is realized, and the high-purity nitrogen and the high-purity oxygen can be obtained conveniently.
As shown in FIG. 1, the air separation plant based on LNG cold energy utilization comprises an air separation pretreatment system and an air separation fine distillation system.
The air pretreatment system mainly comprises an air compression unit, an air precooling unit and an air purification unit; the air pre-cooling unit comprises an air cooling tower 3, an outlet of the air compression unit is connected with an inlet at the bottom of the air cooling tower 3, the bottom of the air cooling tower 3 is connected with a self-circulation water system, the middle part of the air cooling tower 3 is connected with a low-temperature waste nitrogen cooling system, and an outlet at the top of the air cooling tower 3 is connected with an air purification unit;
the air separation distillation system comprises a rectifying tower, wherein a condensation evaporator K1 and an air fractionating tower are arranged in the rectifying tower, an outlet of an air purification unit is connected with the bottom inlet of the rectifying tower, and an outlet at the top of the condensation evaporator K1 introduces Liquid Nitrogen (LN)2) The outlet at the bottom of the rectification column is connected with high-purity Liquid Oxygen (LO)2) A collector.
The air pretreatment system mainly comprises air compression, air precooling and air purification, and aims to remove impurities contained in air and purify the air so that the air can reach the optimal state before rectification, the air separation is more smooth, the purity of the prepared product is higher, the energy consumption is less, and the long-term safe and reliable operation of the air separation system is ensured;
according to the air separation rectification distillation system, the rectification of air is completed through multiple air partial condensation and liquid air partial evaporation processes, so that the separation of nitrogen and oxygen in the air is realized, and high-purity nitrogen and high-purity oxygen can be obtained.
Specifically, the air separation pretreatment system comprises main components such as a self-cleaning air filter 1, an air compressor 2, an air cooling tower 3, a water storage tank 4, a first booster pump 5, a water cooler 6, a second booster pump 7, a first regulating valve 8, a second regulating valve 9, a first molecular sieve adsorber 10, a second molecular sieve adsorber 11, a mixer 12, a power supply 13, a switch 14, an electric heater 15, an air storage tank 16 and the like.
The air compression unit comprises a self-cleaning air filter 1 and an air compressor 2, wherein one end of the self-cleaning air filter 1 is externally connected with air, the other end of the self-cleaning air filter 1 is connected with the air compressor 2, and an outlet of the air compressor 2 is connected with an inlet at the bottom of the air cooling tower 3.
The self-circulation water system comprises a water storage tank 4 and a first booster pump 5, wherein the water storage tank 4 is connected with a heat exchange water inlet at the bottom of the air cooling tower 3 through the first booster pump 5.
The low-temperature waste nitrogen cooling system comprises a water cooler 6 and a second booster pump 7, heat exchange media of the water cooler 6 are cooling water and waste nitrogen, and a gas outlet of the water cooler 6 is connected with a heat exchange water inlet in the middle of the air cooling tower 3 through the second booster pump 7.
When the air purifier is used, raw material air is compressed in the air compressor 2 after small-particle solid impurities such as dust and the like are removed through the self-cleaning air filter 1, the air pressure is compressed, the outlet temperature is increased, and then the air enters the precooling system to be cooled.
In the precooling system, compressed air exchanges heat with normal-temperature water from a circulating water system at the lower part of the air cooling tower 3, then passes through the packing layer and rises to the upper part of the air cooling tower 3 to exchange heat with cooling water, and further the cooling effect is achieved.
The cooling water on the upper part of the air cooling tower 3 is generated by cooling low-temperature waste nitrogen in the water cooling tower, and besides, the compressed air is further washed and cleaned by harmful substances such as dust, hydrogen sulfide and ammonia in the air in the heat exchange of the air cooling tower 3 and then enters a purification system.
In the molecular sieve purifier, compressed, precooled and cooled air passes through an adsorption bed filled with alumina gel and molecular sieve successively to remove impurities such as moisture, acetylene, carbon dioxide, hydrocarbon and the like and enters the next system.
The air purification unit comprises a first molecular sieve adsorber 10 and a second molecular sieve adsorber 11, and the first molecular sieve adsorber 10 and the second molecular sieve adsorber 11 are connected in parallel; the parallel inlets of the first molecular sieve adsorber 10 and the second molecular sieve adsorber 11 are connected with the top outlet of the air cooling tower 3, and the parallel outlets are connected with an air storage tank 16 through a mixer 12.
As a preferred embodiment, the air purification unit further comprises a waste nitrogen heating unit, the waste nitrogen heating unit comprises a heating tank 17, a power supply 13, a switch 14 and an electric heater 15, the electric heater 15 is arranged in the heating tank 17, and the power supply 13, the switch 14 and the electric heater 15 are electrically connected; the top of the heating tank 17 is provided with a waste nitrogen inlet, the bottom of the heating tank is provided with a waste nitrogen outlet, and the waste nitrogen outlet is connected with a parallel inlet;
the parallel inlets of the first molecular sieve adsorber 10 and the second molecular sieve adsorber 11 are respectively provided with a first regulating valve 8 and a second regulating valve 9.
Wherein, the first molecular sieve adsorber 10 and the second molecular sieve adsorber 11 both have adsorption beds of alumina gel and molecular sieve.
Based on the above arrangement, two adsorbers are used alternately, one adsorber adsorbs impurities in the air, the other adsorber is heated by the electric heater 15, water and carbon dioxide which are used for heating and desorbing the adsorbent are heated and desorbed to regenerate the adsorbent, and the waste nitrogen is discharged into the atmosphere through the silencer.
The air separation fine distillation system comprises a condensation evaporator K1 and air fractionation columns C1 and C2. The raw material gas is cleaned of impurities such as dust, moisture, acetylene, carbon dioxide, hydrocarbons and the like by a pretreatment system, and is cooled to the saturation temperature under the separation pressure in a heat exchange system, and then the raw material gas is fed from the lower part of the lower tower of a rectification system for rectification. The saturated temperature of raw material air with oxygen content of 20.9% under the separation pressure, air in lower tower pre-rectifying, with steam gradually rising, as rising gas, its nitrogen content gradually increases, pure gas nitrogen (containing 99.99% nitrogen) in the top of lower rectifying tower is condensed into liquid nitrogen in condensation evaporator K1, and as reflux liquid, it flows downwards from the top of lower tower.
The temperature of the reflux liquid at the top of the lower tower of the rectifying tower is lower than the temperature of the rising steam at the bottom of the tower, and the reflux liquid at the top of the tower meets the rising gas with higher temperature in the reflux process, so that part of the reflux liquid is evaporated due to the temperature rise, and part of the rising gas is condensed due to the temperature reduction. Oxygen as a less volatile component of air will condense more readily during condensation than the more volatile component nitrogen, so the concentration of nitrogen in the ascending gas is increased. During gasification, also because oxygen is the less volatile component and nitrogen is the more volatile component, nitrogen evaporates more than oxygen and the concentration of oxygen in the remaining liquid is increased. Repeated condensation and evaporation, the oxygen-enriched liquid with more liquid oxygen components is gathered at the bottom of the lower tower, and the nitrogen is gathered at the top of the lower tower. The nitrogen content of the rectifying tower is still increased layer by layer from bottom to top, and the temperature of the filler is gradually reduced. The liquid oxygen at the bottom of the upper tower exchanges heat with the gas nitrogen at the top of the upper tower and is condensed into liquid, and high-purity nitrogen (containing 99.99 percent of nitrogen) is obtained at the top of the lower tower and the upper tower.
The nitrogen flowing out of the top of the lower tower is condensed into liquid nitrogen in a condensation evaporator K1, the liquid nitrogen is divided into two strands after being led out, and one strand of the nitrogen is used as reflux liquid to provide cold energy for steam rising from the upper tower from the downward flow of the top of the upper tower so as to obtain a liquid product with higher purity; the other strand was introduced into a liquid nitrogen accumulator and stored. High-purity liquid oxygen (containing 99.80 percent of oxygen) obtained at the bottom of the upper tower is guided into a liquid oxygen collector to be stored at the saturation temperature of the separation pressure, thereby realizing the separation of nitrogen and oxygen.
As a preferred embodiment, the top outlet of the condensation evaporator K1 introduces Liquid Nitrogen (LN)2) And a nitrogen branch pipe is also arranged on the pipeline of the collector and is connected to the air fractionating tower at the top of the rectifying tower. And a waste nitrogen outlet of the air fractionating tower is connected with the low-temperature waste nitrogen cooling system.
The invention also provides a separation method of the air separation device based on LNG cold energy utilization, which comprises the following steps:
raw material air enters an air compression unit to be compressed, the temperature of an outlet of the air compression unit is increased, and then the raw material air enters an air pre-cooling unit to cool the air;
the compressed air exchanges heat with normal temperature water from a circulating water system at the lower part of the air cooling tower 3, and then passes through the packing layer to rise to the upper part of the air cooling tower 3 to exchange heat with cooling water;
cooling water at the upper part of the air cooling tower 3 is generated by a low-temperature waste nitrogen cooling system in a water cooling tower, and compressed air enters an air purification unit after being washed and cleaned of harmful substances in the air in the heat exchange of the air cooling tower 3;
the air after compression and precooling temperature reduction sequentially passes through an adsorption bed of an air purification unit to remove moisture, acetylene, carbon dioxide and hydrocarbons and then enters an air separation fine distillation system;
the air is rectified from the lower part of the lower tower of the rectification system, and the separation of nitrogen and oxygen in the air is realized through multiple air partial condensation and liquid-air partial evaporation processes.
The invention is described in further detail below with reference to the accompanying drawings:
referring to fig. 1, a schematic diagram of an air separation pretreatment system based on LNG cold energy utilization according to an embodiment of the present invention. The normal-temperature raw material air is subjected to dust and other small-particle solid impurities removal through the self-cleaning air filter 1, then enters the air compressor 2 for compression, and then enters the precooling system for cooling the air. In the precooling system, compressed air exchanges heat with normal-temperature water from a circulating water system at the lower part of the air cooling tower 3, then passes through the packing layer and rises to the upper part of the air cooling tower 3 to exchange heat with cooling water, and further the cooling effect is achieved; cooling water at the upper part of the air cooling tower 3 is generated by cooling low-temperature waste nitrogen in a water cooling tower; the compressed air enters a purification system after being further washed and cleaned of harmful substances such as dust, hydrogen sulfide and ammonia in the air in the heat exchange of the air cooling tower 3. In a molecular sieve purifier, compressed, precooled and cooled air passes through an adsorption bed filled with alumina gel and a molecular sieve successively to remove impurities such as moisture, acetylene, carbon dioxide, hydrocarbon and the like and enters the next system. The two adsorbers are used alternately, one adsorber is used for adsorbing impurities in air, the other adsorber is used for heating the waste nitrogen from the rectifying tower through the electric heater 15, water and carbon dioxide which are used for heating and desorbing the adsorbent are heated to regenerate the adsorbent, and the waste nitrogen is discharged into the atmosphere through the silencer.
Referring to fig. 2, a schematic diagram of an air separation fine distillation system based on LNG cold energy utilization according to an embodiment of the present invention. The raw material gas is cleaned of impurities such as dust, moisture, acetylene, carbon dioxide, hydrocarbons and the like by a pretreatment system, and is cooled to the saturation temperature under the separation pressure in a heat exchange system, and then the raw material gas is fed from the lower part of the lower tower of a rectification system for rectification. The air is pre-rectified in the lower tower, gradually rises along with the steam, is used as ascending gas, the nitrogen content of the ascending gas is increased layer by layer, pure gas nitrogen (containing 99.99 percent of nitrogen) is arranged at the top of the lower tower, and the pure gas nitrogen is condensed into liquid nitrogen in a condensation evaporator K1 and flows down from the top of the lower tower as reflux liquid. The nitrogen content of the rectifying tower is still increased layer by layer from bottom to top, and the temperature of the filler is gradually reduced. The liquid oxygen at the bottom of the upper tower exchanges heat with the gas nitrogen at the top of the upper tower and is condensed into liquid, and high-purity nitrogen (containing 99.99 percent of nitrogen) is obtained at the top of the lower tower and the upper tower. The nitrogen flowing out of the top of the lower tower is condensed into liquid nitrogen in a condensation evaporator K1, the liquid nitrogen is divided into two strands after being led out, and one strand of the nitrogen is used as reflux liquid to provide cold energy for steam rising from the upper tower from the downward flow of the top of the upper tower so as to obtain a liquid product with higher purity; the other strand is introduced into Liquid Nitrogen (LN)2) The collector is stored; high purity Liquid Oxygen (LO) is obtained from the bottom of the upper column2) And is guided into a liquid oxygen collector for storage, thereby realizing the separation of nitrogen and oxygen.
The invention combines the existing mature LNG cold energy utilization technology to complete air separation pretreatment and air separation fine distillation. Firstly, air separation pretreatment is carried out, raw material gas is subjected to impurity removal such as dust, moisture, acetylene, carbon dioxide and hydrocarbons through a pretreatment system, and is cooled to the saturation temperature under the separation pressure in a heat exchange system, and then the raw material gas is fed from the lower part of a tower of a rectification system for rectification. The nitrogen flowing out of the top of the lower tower is condensed into liquid nitrogen in a condensation evaporator K1, the liquid nitrogen is divided into two strands after being led out, and one strand of the nitrogen is used as reflux liquid to provide cold energy for steam rising from the upper tower from the downward flow of the top of the upper tower so as to obtain a liquid product with higher purity; introducing the other strand into a liquid nitrogen collector for storage; high-purity liquid oxygen (containing 99.80 percent of oxygen) is obtained at the bottom of the upper tower and is guided into a liquid oxygen collector for storage, thereby realizing the separation of nitrogen and oxygen. The invention solves the defects of complex air separation flow, huge equipment, complex operation, higher operation cost and the like in the traditional air separation process.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (10)

1. An air separation device based on LNG cold energy utilization is characterized by comprising an air separation pretreatment system and an air separation fine distillation system;
the air pretreatment system mainly comprises an air compression unit, an air precooling unit and an air purification unit; the air pre-cooling unit comprises an air cooling tower (3), an outlet of the air compression unit is connected with an inlet at the bottom of the air cooling tower (3), the bottom of the air cooling tower (3) is connected with a self-circulation water system, the middle part of the air cooling tower (3) is connected with a low-temperature waste nitrogen cooling system, and an outlet at the top of the air cooling tower (3) is connected with an air purification unit;
the air separation distillation system comprises a rectifying tower, wherein a condensation evaporator K1 and an air fractionating tower are arranged in the rectifying tower, an outlet of an air purification unit is connected with the bottom inlet of the rectifying tower, and an outlet at the top of the condensation evaporator K1 introduces Liquid Nitrogen (LN)2) The outlet at the bottom of the rectification column is connected with high-purity Liquid Oxygen (LO)2) A collector.
2. The LNG cold energy utilization-based air separation device according to claim 1, wherein the air compression unit comprises a self-cleaning air filter (1) and an air compressor (2), the self-cleaning air filter (1) is externally connected with air at one end, the other end is connected with the air compressor (2), and an outlet of the air compressor (2) is connected with a bottom inlet of the air cooling tower (3).
3. The LNG cold energy utilization-based air separation device as claimed in claim 1, wherein the self-circulating water system comprises a water storage tank (4) and a first booster pump (5), and the water storage tank (4) is connected with a heat exchange water inlet at the bottom of the air cooling tower (3) through the first booster pump (5).
4. The LNG cold energy utilization-based air separation device is characterized in that the low-temperature waste nitrogen cooling system comprises a water cooler (6) and a second booster pump (7), heat exchange media of the water cooler (6) are cooling water and waste nitrogen, and a gas outlet of the water cooler (6) is connected with a middle heat exchange water inlet of the air cooling tower (3) through the second booster pump (7).
5. The LNG cold energy utilization-based air separation device according to claim 1, characterized in that the air purification unit comprises a first molecular sieve adsorber (10) and a second molecular sieve adsorber (11), the first molecular sieve adsorber (10) and the second molecular sieve adsorber (11) are connected in parallel; the parallel inlets of the first molecular sieve adsorber (10) and the second molecular sieve adsorber (11) are connected with the top outlet of the air cooling tower (3), and the parallel outlets are connected with the air storage tank (16) through the mixer (12).
6. An LNG cold energy utilization based air separation plant according to claim 5, characterized in that the air purification unit further comprises a dirty nitrogen heating unit, the dirty nitrogen heating unit comprises a heating tank (17), a power supply (13), a switch (14) and an electric heater (15), the electric heater (15) is arranged in the heating tank (17), and the power supply (13), the switch (14) and the electric heater (15) are electrically connected; the top of the heating tank (17) is provided with a waste nitrogen inlet, the bottom of the heating tank is provided with a waste nitrogen outlet, and the waste nitrogen outlet is connected with a parallel inlet;
the parallel inlets of the first molecular sieve adsorber (10) and the second molecular sieve adsorber (11) are respectively provided with a first regulating valve (8) and a second regulating valve (9).
7. An LNG cold energy utilization based air separation plant according to claim 1, characterized in that the first molecular sieve adsorber (10) and the second molecular sieve adsorber (11) each have an adsorption bed of alumina gel and molecular sieve.
8. The LNG cold energy utilization-based air separation plant of claim 1, wherein a top outlet of the condensing evaporator K1 introduces Liquid Nitrogen (LN)2) And a nitrogen branch pipe is also arranged on the pipeline of the collector and is connected to the air fractionating tower at the top of the rectifying tower.
9. The LNG cold energy utilization-based air separation plant of claim 1, wherein a waste nitrogen outlet of the air fractionation tower is connected to the cryogenic waste nitrogen cooling system.
10. A separation method of an LNG cold energy utilization based air separation plant according to any of claims 1 to 9, characterized by comprising the steps of:
raw material air enters an air compression unit to be compressed, the temperature of an outlet is increased, and then the raw material air enters an air pre-cooling unit to cool the air;
the compressed air exchanges heat with normal temperature water from a circulating water system at the lower part of the air cooling tower (3) and then passes through the packing layer to rise to the upper part of the air cooling tower (3) to exchange heat with cooling water;
cooling water at the upper part of the air cooling tower (3) is generated by a low-temperature waste nitrogen cooling system in a water cooling tower, and compressed air enters an air purification unit after being washed and cleaned of harmful substances in the air in the heat exchange of the air cooling tower (3);
the air after compression and precooling temperature reduction sequentially passes through an adsorption bed of an air purification unit to remove moisture, acetylene, carbon dioxide and hydrocarbons and then enters an air separation fine distillation system;
the air is rectified from the lower part of the lower tower of the rectification system, and the separation of nitrogen and oxygen in the air is realized through multiple air partial condensation and liquid-air partial evaporation processes.
CN202210441590.6A 2022-04-25 2022-04-25 Air separation device and system based on LNG cold energy utilization Pending CN114688828A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003021457A (en) * 2001-07-09 2003-01-24 Hitachi Ltd Internal pressurization type low-temperature air separation equipment
CN104406365A (en) * 2014-11-27 2015-03-11 苏州制氧机股份有限公司 Double-expander medium-pressure liquid device
US20150354888A1 (en) * 2013-01-27 2015-12-10 Nanjing Reclaimer Environmental Teknik Co., Ltd. Air Separation Apparatus for Isobaric Separation and Production of Oxygen and Nitrogen
CN106123489A (en) * 2016-06-29 2016-11-16 苏州制氧机股份有限公司 A kind of mixing column method for producing oxygen through
CN109163506A (en) * 2018-08-02 2019-01-08 杭州福斯达深冷装备股份有限公司 With the device for assisting lower tower low energy consumption to produce low purity oxygen and high pure oxygen product simultaneously

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003021457A (en) * 2001-07-09 2003-01-24 Hitachi Ltd Internal pressurization type low-temperature air separation equipment
US20150354888A1 (en) * 2013-01-27 2015-12-10 Nanjing Reclaimer Environmental Teknik Co., Ltd. Air Separation Apparatus for Isobaric Separation and Production of Oxygen and Nitrogen
CN104406365A (en) * 2014-11-27 2015-03-11 苏州制氧机股份有限公司 Double-expander medium-pressure liquid device
CN106123489A (en) * 2016-06-29 2016-11-16 苏州制氧机股份有限公司 A kind of mixing column method for producing oxygen through
CN109163506A (en) * 2018-08-02 2019-01-08 杭州福斯达深冷装备股份有限公司 With the device for assisting lower tower low energy consumption to produce low purity oxygen and high pure oxygen product simultaneously

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