CN113606865A - Device and method for preparing liquid nitrogen through air separation - Google Patents
Device and method for preparing liquid nitrogen through air separation Download PDFInfo
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- CN113606865A CN113606865A CN202110900661.XA CN202110900661A CN113606865A CN 113606865 A CN113606865 A CN 113606865A CN 202110900661 A CN202110900661 A CN 202110900661A CN 113606865 A CN113606865 A CN 113606865A
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- 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
- F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
- F25J3/0423—Subcooling of liquid process streams
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- 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
- F25J3/04472—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 the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages
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- 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
- F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
- F25J3/04193—Division of the main heat exchange line in consecutive sections having different functions
- F25J3/04206—Division of the main heat exchange line in consecutive sections having different functions including a so-called "auxiliary vaporiser" for vaporising and producing a gaseous product
- F25J3/04212—Division of the main heat exchange line in consecutive sections having different functions including a so-called "auxiliary vaporiser" for vaporising and producing a gaseous product and simultaneously condensing vapor from a column serving as reflux within the or another column
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- 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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- 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
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- 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
- F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
- F25J3/04872—Vertical layout of cold equipments within in the cold box, e.g. columns, heat exchangers etc.
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- 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
- F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
- F25J3/04872—Vertical layout of cold equipments within in the cold box, e.g. columns, heat exchangers etc.
- F25J3/04884—Arrangement of reboiler-condensers
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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
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
- F25J2200/54—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column in the low pressure column of a double pressure main column system
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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
- F25J2210/00—Processes characterised by the type or other details of the feed stream
- F25J2210/40—Air or oxygen enriched air, i.e. generally less than 30mol% of O2
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- 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
- F25J2215/00—Processes characterised by the type or other details of the product stream
- F25J2215/42—Nitrogen or special cases, e.g. multiple or low purity N2
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- 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
- F25J2215/00—Processes characterised by the type or other details of the product stream
- F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2
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Abstract
The invention relates to a device and a method for preparing liquid nitrogen by air separation. The device for preparing liquid nitrogen by air separation comprises a lower tower, an upper tower, a lower tower top condensation evaporator arranged in the bottom of the upper tower, an upper tower top condensation evaporator and a subcooler; the raw materials provides the device and is connected with lower tower, and lower tower is connected with lower top of the tower condensation evaporimeter, still is connected with the upper tower through the cold ware, and lower top of the tower condensation evaporimeter is connected with lower tower, upper tower respectively, and the upper tower is connected with upper top of the tower condensation evaporimeter, still is connected with upper top of the tower condensation evaporimeter through the cold ware, and upper top of the tower condensation evaporimeter is connected with upper tower, liquid nitrogen user respectively. The method comprises the following steps: air and liquid air are sent into a lower tower for rectification, the obtained liquid air is sent into an upper tower for rectification, the obtained nitrogen is condensed into liquid nitrogen and then sent into the upper tower for rectification, and the nitrogen obtained by rectification in the upper tower is liquefied and then sent to a liquid nitrogen user. The invention can improve the rectification extraction rate and can also improve the yield of liquid nitrogen products.
Description
Technical Field
The invention relates to the technical field of air separation, in particular to a device and a method for preparing liquid nitrogen in an air separation mode.
Background
The existing scheme for preparing liquid nitrogen in an air separation mode is mainly to directly send raw material air into each rectifying tower for rectification respectively, and the scheme has the defects that: the distillation extraction rate is relatively low, the liquid nitrogen yield is low, and the requirements of customers are difficult to meet.
Disclosure of Invention
The invention aims to provide a device and a method for preparing liquid nitrogen by air separation, which can improve the rectification extraction rate and the liquid nitrogen yield.
In order to achieve the purpose, the invention adopts the technical scheme that:
an apparatus for preparing liquid nitrogen by air separation, which is used for preparing liquid nitrogen by separating air and liquid air provided by a raw material providing device and providing the liquid nitrogen to a liquid nitrogen user, wherein the apparatus for preparing liquid nitrogen by air separation comprises: the system comprises a lower tower, an upper tower, a lower tower top condensation evaporator, an upper tower top condensation evaporator and a subcooler, wherein the lower tower top condensation evaporator, the upper tower top condensation evaporator and the subcooler are arranged in the bottom of the upper tower; the lower tower is provided with an air inlet, a liquid-air inlet, a nitrogen outlet, a liquid-air outlet and a liquid nitrogen inlet, the upper tower is provided with a liquid-air inlet, a liquid nitrogen inlet, a nitrogen outlet and an oxygen-enriched liquid-air outlet, the condensing evaporator at the top of the lower tower is provided with a nitrogen inlet and a liquid nitrogen outlet, and the condensing evaporator at the top of the upper tower is provided with a nitrogen inlet, an oxygen-enriched liquid-air inlet, a liquid nitrogen outlet and an oxygen-enriched gas outlet;
the raw material supply device is respectively connected with the air inlet and the liquid air inlet of the lower tower, the nitrogen outlet of the lower tower is connected with the nitrogen inlet of the condensing evaporator at the top of the lower tower, the liquid-air outlet of the lower tower is connected with the liquid-air inlet of the upper tower through the subcooler, the liquid nitrogen outlet of the condensing evaporator at the top of the lower tower is divided into two paths and is respectively connected with the liquid nitrogen inlet of the lower tower and the liquid nitrogen inlet of the upper tower, the nitrogen outlet of the upper tower is connected with the nitrogen inlet of the upper tower top condensing evaporator, the oxygen-enriched liquid air outlet of the upper tower is connected with the oxygen-enriched liquid air inlet of the upper tower top condensing evaporator through the subcooler, and a liquid nitrogen outlet of the upper tower top condensation evaporator is divided into two paths and is respectively connected with the liquid nitrogen inlet of the upper tower and the liquid nitrogen user, and an oxygen-enriched gas outlet of the upper tower top condensation evaporator is connected with a position required by the process.
And a liquid nitrogen outlet of the lower tower top condensation evaporator is connected with a liquid nitrogen inlet of the upper tower through the subcooler.
And an oxygen-enriched gas outlet of the upper tower top condensation evaporator is connected with a position required by the process through the subcooler.
The device for preparing the liquid nitrogen through the air separation further comprises a cold box, and the lower tower, the upper tower, the lower tower top condensation evaporator, the upper tower top condensation evaporator and the subcooler are all arranged in the cold box.
The device for preparing liquid nitrogen through air separation further comprises a first throttling valve arranged between the liquid-air outlet of the lower tower and the liquid-air inlet of the upper tower.
The device for preparing the liquid nitrogen through the air separation further comprises a second throttling valve arranged between a liquid nitrogen outlet of the condensing evaporator at the top of the lower tower and a liquid nitrogen inlet of the upper tower.
The device for preparing the liquid nitrogen through the air separation further comprises a third throttle valve arranged between the oxygen-enriched liquid air outlet of the upper tower and the oxygen-enriched liquid air inlet of the condensing evaporator at the top of the upper tower.
The device for preparing the liquid nitrogen through the air separation further comprises a fourth throttling valve arranged between a liquid nitrogen outlet of the upper tower top condensation evaporator and the liquid nitrogen user.
The device for preparing the liquid nitrogen through the air separation further comprises a main heat exchanger, the raw material supply device is respectively connected with the air inlet and the liquid air inlet of the lower tower through the main heat exchanger, and the oxygen-enriched gas outlet of the condensation evaporator at the top of the upper tower is connected with the position required by the process through the main heat exchanger.
A method for preparing liquid nitrogen by air separation, which adopts the device for preparing liquid nitrogen by air separation and is used for preparing liquid nitrogen by separating air and liquid air provided by a raw material providing device and providing the liquid nitrogen for a liquid nitrogen user, and the method for preparing liquid nitrogen by air separation comprises the following steps:
step 1: respectively sending the air and the liquid air into the lower tower for rectification to obtain oxygen-enriched liquid air and nitrogen;
step 2: supercooling the liquid air obtained in the lower tower, sending the liquid air into the upper tower for rectification to obtain oxygen-enriched liquid air and nitrogen, sending the nitrogen obtained in the lower tower into a condensation evaporator at the top of the lower tower for condensation to obtain liquid nitrogen, and sending the liquid nitrogen obtained in the condensation evaporator at the top of the lower tower into the lower tower and the upper tower respectively for rectification;
and step 3: and respectively sending the oxygen-enriched liquid air and the nitrogen obtained in the upper tower into the condensation evaporator at the top of the upper tower for heat exchange to respectively obtain oxygen-enriched gas and liquid nitrogen, sending the oxygen-enriched gas obtained by the condensation evaporator at the top of the upper tower to a position required by the process, and respectively sending the liquid nitrogen obtained by the condensation evaporator at the top of the upper tower to the upper tower and a liquid nitrogen user.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the invention can improve the rectification extraction rate, can also improve the yield of liquid nitrogen products and meets the requirements of users.
Drawings
FIG. 1 is a schematic diagram of an apparatus for producing liquid nitrogen by air separation according to the present invention.
In the above drawings: c1, lower tower; c2, feeding into a tower; k1, a lower tower top condensation evaporator; k2, an upper tower top condensation evaporator; e2, subcooler.
Detailed Description
The invention will be further described with reference to examples of embodiments shown in the drawings to which the invention is attached.
The first embodiment is as follows: as shown in FIG. 1, an air separation liquid nitrogen making apparatus for separating air and liquid air supplied from a raw material supply apparatus and supplying the separated air to a liquid nitrogen user comprises a lower column C1, an upper column C2, a lower column top condensing evaporator K1, an upper column top condensing evaporator K2 and a subcooler E2 (liquid air liquid nitrogen subcooler E2), wherein the lower column top condensing evaporator K1 is disposed in the bottom of the upper column C2.
The lower tower C1 is provided with an air inlet, a liquid air inlet, a nitrogen outlet, a liquid air outlet and a liquid nitrogen inlet, wherein the air inlet is positioned at the middle lower part of the lower tower C1 and is used for feeding air into the lower tower C1, the liquid air inlet is positioned at the middle part of the lower tower C1 and is used for feeding liquid air into the lower tower C1, the liquid air outlet is positioned at the bottom of the lower tower C1 and is used for feeding the oxygen-enriched liquid air collected at the bottom of the lower tower C1 out of the lower tower C1, the nitrogen outlet is positioned at the top of the lower tower C1 and is used for feeding the nitrogen generated by rectification out of the lower tower C1, and the liquid nitrogen inlet is positioned at the top of the lower tower C1 and is used for feeding the liquid nitrogen into the lower tower C1. The upper tower C2 is provided with a liquid air inlet, a liquid nitrogen inlet, a nitrogen outlet and an oxygen-enriched liquid air outlet, wherein the liquid air inlet is positioned in the middle of the upper tower C2 and used for feeding the oxygen-enriched liquid air into the upper tower C2, the liquid nitrogen inlet is positioned at the upper part of the upper tower C2 and used for feeding the liquid nitrogen into the upper tower C2, the liquid nitrogen inlets can be provided with a plurality of liquid nitrogen inlets for feeding liquid nitrogen from different sources, the nitrogen outlet is positioned at the top of the upper tower C2 and used for feeding the nitrogen generated by rectification out of the upper tower C2, and the oxygen-enriched liquid air outlet is positioned at the bottom of the upper tower C2 and used for feeding the oxygen-enriched liquid air collected at the bottom of the upper tower C2 out of the lower tower C1. The lower tower top condensation evaporator K1 is provided with a nitrogen inlet and a liquid nitrogen outlet, the nitrogen inlet is positioned at the top of the lower tower top condensation evaporator K1 and used for sending nitrogen into the lower tower top condensation evaporator K1 for heat exchange, and the liquid nitrogen outlet is positioned at the bottom of the lower tower top condensation evaporator K1 and used for sending the liquid nitrogen condensed into nitrogen out of the lower tower top condensation evaporator K1. The upper tower top condensation evaporator K2 is provided with a nitrogen inlet, an oxygen-enriched liquid air inlet, a liquid nitrogen outlet and an oxygen-enriched gas outlet, the nitrogen inlet is positioned at the upper part of the upper tower top condensation evaporator K2 and is used for sending nitrogen into the upper tower top condensation evaporator K2 for heat exchange, the oxygen-enriched liquid air inlet is positioned at the bottom of the upper tower top condensation evaporator K2 and is used for sending the oxygen-enriched liquid air into the upper tower top condensation evaporator K2 for heat exchange, the liquid nitrogen outlet is positioned at the lower part of the upper tower top condensation evaporator K2 and is used for sending liquid nitrogen condensed into nitrogen out of the upper tower top condensation evaporator K2, and the oxygen-enriched gas outlet is positioned at the top of the upper tower top condensation evaporator K2 and is used for sending the oxygen-enriched gas formed by heating the oxygen-enriched liquid air out of the upper tower top condensation evaporator K2. The subcooler E2 has a plurality of heat exchange lines therein.
The raw material supply device is respectively connected with an air inlet and a liquid air inlet of a lower tower C1, a nitrogen outlet of the lower tower C1 is connected with a nitrogen inlet of a lower tower top condensing evaporator K1, a liquid air outlet of the lower tower C1 is connected with a liquid air inlet of an upper tower C2 through a cooler E2, a liquid nitrogen outlet of the lower tower top condensing evaporator K1 is divided into two paths and is respectively connected with a liquid nitrogen inlet of the lower tower C1, the liquid nitrogen inlet of the upper tower C2 is connected, the nitrogen outlet of the upper tower C2 is connected with the nitrogen inlet of the upper tower top condensing evaporator K2, the oxygen-enriched liquid air outlet of the upper tower C2 is connected with the oxygen-enriched liquid air inlet of the upper tower top condensing evaporator K2 through a cooler E2, the liquid nitrogen outlet of the upper tower top condensing evaporator K2 is divided into two paths and is respectively connected with the liquid nitrogen inlet of the upper tower C2 and a liquid nitrogen user, and the oxygen-enriched gas outlet of the upper tower top condensing evaporator K2 is connected with the position required by the process. Wherein, the liquid nitrogen outlet of the lower tower top condensation evaporator K1 is connected with the liquid nitrogen inlet of the upper tower C2 through a cooler E2, and the oxygen-enriched gas outlet of the upper tower top condensation evaporator K2 is connected with the position required by the process through a cooler E2.
The device for preparing the liquid nitrogen by air separation further comprises a cold box, a first throttling valve, a second throttling valve, a third throttling valve, a fourth throttling valve and a main heat exchanger.
The lower tower C1, the upper tower C2, the lower tower top condensation evaporator K1, the upper tower top condensation evaporator K2 and the subcooler E2 are all arranged in the cold box. The main heat exchanger is typically located outside the cold box. The raw material supply device is respectively connected with an air inlet and a liquid air inlet of the lower tower C1 through a main heat exchanger, and an oxygen-enriched gas outlet of the upper tower top condensation evaporator K2 is connected with the position required by the process through the main heat exchanger.
The first throttle valve is arranged between the liquid air outlet of the lower tower C1 and the liquid air inlet of the upper tower C2, in particular between the subcooler E2 and the liquid air inlet of the upper tower C2. The second throttling valve is arranged between a liquid nitrogen outlet of the lower tower top condensation evaporator K1 and a liquid nitrogen inlet of the upper tower C2, in particular between a subcooler E2 and a liquid nitrogen inlet of the upper tower C2. The third throttle valve is arranged between the oxygen-enriched liquid air outlet of the upper tower C2 and the oxygen-enriched liquid air inlet of the upper tower top condensation evaporator K2, in particular between the subcooler E2 and the oxygen-enriched liquid air inlet of the upper tower top condensation evaporator K2. The fourth throttle valve is arranged between the liquid nitrogen outlet of the upper tower top condensation evaporator K2 and a liquid nitrogen user. The first, second, third and fourth of the first throttle, the second throttle, the third throttle and the fourth throttle are only used for distinguishing different throttles and are not used for indicating the sequence among the throttles.
Based on the device for preparing liquid nitrogen by air separation, the method for preparing liquid nitrogen by air separation comprises the following steps:
step 1: respectively feeding air and liquid air into a lower tower C1 for rectification to obtain oxygen-enriched liquid air and nitrogen;
step 2: supercooling the liquid air obtained in the lower tower C1, then sending the liquid air into the upper tower C2 for rectification to obtain oxygen-enriched liquid air and nitrogen, sending the nitrogen obtained in the lower tower C1 into a lower tower top condensation evaporator K1 for condensation to obtain liquid nitrogen, and then sending the liquid nitrogen obtained in the lower tower top condensation evaporator K1 into the lower tower C1 and the upper tower C2 respectively for rectification;
and step 3: and respectively sending the oxygen-enriched liquid air and the nitrogen obtained in the upper tower C2 into an upper tower top condensation evaporator K2 for heat exchange to respectively obtain oxygen-enriched gas and liquid nitrogen, sending the oxygen-enriched gas obtained by the upper tower top condensation evaporator K2 to a position required by the process, and respectively sending the liquid nitrogen obtained by the upper tower top condensation evaporator K2 to an upper tower C2 and a liquid nitrogen user.
The method for preparing the liquid nitrogen by air separation comprises the following specific processes: the compressed air supplied from the raw material supply device is cooled to a certain temperature in the main heat exchanger, and is sent into the lower column C1 from the bottom of the lower column C1, and participates in rectification as ascending gas in the lower column C1. The other feed to the bottom of lower column C1 was a liquid void obtained at the bottom of the main heat exchanger, which in this case also served as part of the feed supply to lower column C1. After rectification by a lower tower C1, oxygen-enriched liquid air with certain concentration is obtained at the bottom of the lower tower C1, and nitrogen is obtained at the top of the lower tower C1. Oxygen-enriched liquid air obtained from the bottom of the lower tower C1 is sent to the top of the upper tower C2 after being subjected to cold throttling, the oxygen-enriched liquid air is used as reflux liquid at the top of the upper tower C2 to participate in rectification, oxygen-enriched liquid air with a certain concentration is obtained from the bottom of the upper tower C2, and nitrogen is obtained from the top of the upper tower C2. Nitrogen obtained from the top of the lower tower C1 enters a lower tower top condensation evaporator K1, is condensed into liquid nitrogen by oxygen-enriched liquid air obtained from the bottom of the upper tower C2, part of the liquid nitrogen flows back to the top of the lower tower C1 and participates in rectification of the lower tower C1 as reflux liquid, and in addition, part of the extracted liquid nitrogen is sent to the top of the upper tower C2 after being subjected to cold throttling and participates in rectification as reflux liquid at the top of the upper tower C2. The oxygen-enriched liquid air at the bottom of the upper tower C2 is sent to an upper tower top condensation evaporator K2 after cold throttling, and the nitrogen at the top of the upper tower C2 is also sent to an upper tower top condensation evaporator K2. In the condensing evaporator K2 at the top of the upper tower, the oxygen-enriched liquid air and the nitrogen exchange heat, the oxygen-enriched liquid air is heated into oxygen-enriched gas and sent out to the position required by the process, and the nitrogen is condensed into liquid nitrogen and sent out. A small amount of liquid nitrogen flows back to the top of the upper tower C2 to be used as reflux liquid to participate in rectification, and most of the liquid nitrogen is sent out of the cold box as a product and is provided for a liquid nitrogen user (for example, sent to a low-temperature storage tank of the liquid nitrogen user).
The flow of preparing liquid nitrogen by separating air by the double towers is characterized in that: 1. liquid and air participate in rectification for multiple times; 2. the extraction efficiency is high, and the liquid nitrogen yield is high; 3. a double condensing evaporator process is adopted.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. An apparatus for preparing liquid nitrogen by air separation, which is used for preparing liquid nitrogen by separating air and liquid air provided by a raw material providing device and providing the liquid nitrogen to a liquid nitrogen user, and is characterized in that: the device for preparing liquid nitrogen by air separation comprises: the system comprises a lower tower, an upper tower, a lower tower top condensation evaporator, an upper tower top condensation evaporator and a subcooler, wherein the lower tower top condensation evaporator, the upper tower top condensation evaporator and the subcooler are arranged in the bottom of the upper tower; the lower tower is provided with an air inlet, a liquid-air inlet, a nitrogen outlet, a liquid-air outlet and a liquid nitrogen inlet, the upper tower is provided with a liquid-air inlet, a liquid nitrogen inlet, a nitrogen outlet and an oxygen-enriched liquid-air outlet, the condensing evaporator at the top of the lower tower is provided with a nitrogen inlet and a liquid nitrogen outlet, and the condensing evaporator at the top of the upper tower is provided with a nitrogen inlet, an oxygen-enriched liquid-air inlet, a liquid nitrogen outlet and an oxygen-enriched gas outlet;
the raw material supply device is respectively connected with the air inlet and the liquid air inlet of the lower tower, the nitrogen outlet of the lower tower is connected with the nitrogen inlet of the condensing evaporator at the top of the lower tower, the liquid-air outlet of the lower tower is connected with the liquid-air inlet of the upper tower through the subcooler, the liquid nitrogen outlet of the condensing evaporator at the top of the lower tower is divided into two paths and is respectively connected with the liquid nitrogen inlet of the lower tower and the liquid nitrogen inlet of the upper tower, the nitrogen outlet of the upper tower is connected with the nitrogen inlet of the upper tower top condensing evaporator, the oxygen-enriched liquid air outlet of the upper tower is connected with the oxygen-enriched liquid air inlet of the upper tower top condensing evaporator through the subcooler, and a liquid nitrogen outlet of the upper tower top condensation evaporator is divided into two paths and is respectively connected with the liquid nitrogen inlet of the upper tower and the liquid nitrogen user, and an oxygen-enriched gas outlet of the upper tower top condensation evaporator is connected with a position required by the process.
2. The device for preparing liquid nitrogen through air separation according to claim 1, characterized in that: and a liquid nitrogen outlet of the lower tower top condensation evaporator is connected with a liquid nitrogen inlet of the upper tower through the subcooler.
3. The device for preparing liquid nitrogen through air separation according to claim 1, characterized in that: and an oxygen-enriched gas outlet of the upper tower top condensation evaporator is connected with a position required by the process through the subcooler.
4. The device for preparing liquid nitrogen through air separation according to claim 1, characterized in that: the device for preparing the liquid nitrogen through the air separation further comprises a cold box, and the lower tower, the upper tower, the lower tower top condensation evaporator, the upper tower top condensation evaporator and the subcooler are all arranged in the cold box.
5. The device for preparing liquid nitrogen through air separation according to claim 1, characterized in that: the device for preparing liquid nitrogen through air separation further comprises a first throttling valve arranged between the liquid-air outlet of the lower tower and the liquid-air inlet of the upper tower.
6. The device for preparing liquid nitrogen through air separation according to claim 1, characterized in that: the device for preparing the liquid nitrogen through the air separation further comprises a second throttling valve arranged between a liquid nitrogen outlet of the condensing evaporator at the top of the lower tower and a liquid nitrogen inlet of the upper tower.
7. The device for preparing liquid nitrogen through air separation according to claim 1, characterized in that: the device for preparing the liquid nitrogen through the air separation further comprises a third throttle valve arranged between the oxygen-enriched liquid air outlet of the upper tower and the oxygen-enriched liquid air inlet of the condensing evaporator at the top of the upper tower.
8. The device for preparing liquid nitrogen through air separation according to claim 1, characterized in that: the device for preparing the liquid nitrogen through the air separation further comprises a fourth throttling valve arranged between a liquid nitrogen outlet of the upper tower top condensation evaporator and the liquid nitrogen user.
9. The device for preparing liquid nitrogen through air separation according to claim 1, characterized in that: the device for preparing the liquid nitrogen through the air separation further comprises a main heat exchanger, the raw material supply device is respectively connected with the air inlet and the liquid air inlet of the lower tower through the main heat exchanger, and the oxygen-enriched gas outlet of the condensation evaporator at the top of the upper tower is connected with the position required by the process through the main heat exchanger.
10. A method for producing liquid nitrogen by air separation, which is used for producing liquid nitrogen by separating air and liquid air supplied from a raw material supply device and supplying the liquid nitrogen to a liquid nitrogen user, according to the apparatus for producing liquid nitrogen by air separation as claimed in claim 1, characterized in that: the method for preparing liquid nitrogen by air separation comprises the following steps:
step 1: respectively sending the air and the liquid air into the lower tower for rectification to obtain oxygen-enriched liquid air and nitrogen;
step 2: supercooling the liquid air obtained in the lower tower, sending the liquid air into the upper tower for rectification to obtain oxygen-enriched liquid air and nitrogen, sending the nitrogen obtained in the lower tower into a condensation evaporator at the top of the lower tower for condensation to obtain liquid nitrogen, and sending the liquid nitrogen obtained in the condensation evaporator at the top of the lower tower into the lower tower and the upper tower respectively for rectification;
and step 3: and respectively sending the oxygen-enriched liquid air and the nitrogen obtained in the upper tower into the condensation evaporator at the top of the upper tower for heat exchange to respectively obtain oxygen-enriched gas and liquid nitrogen, sending the oxygen-enriched gas obtained by the condensation evaporator at the top of the upper tower to a position required by the process, and respectively sending the liquid nitrogen obtained by the condensation evaporator at the top of the upper tower to the upper tower and a liquid nitrogen user.
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| CN113606866A (en) * | 2021-08-06 | 2021-11-05 | 苏州市兴鲁空分设备科技发展有限公司 | Device and method for preparing nitrogen by air separation |
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