CN109855389B - Method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process - Google Patents
Method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process Download PDFInfo
- Publication number
- CN109855389B CN109855389B CN201910008842.4A CN201910008842A CN109855389B CN 109855389 B CN109855389 B CN 109855389B CN 201910008842 A CN201910008842 A CN 201910008842A CN 109855389 B CN109855389 B CN 109855389B
- Authority
- CN
- China
- Prior art keywords
- lng
- cold energy
- tower
- cooling
- nitrogen
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Abstract
The invention relates to a method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process, belonging to the field of air separation-LNG utilization. The method comprises the following steps: the method comprises a purification step, a cooling step, a rectification step and an LNG cold energy conversion step. The method adopts a single-tower rectification process of a main rectifying tower and an argon tower to produce liquid oxygen, liquid nitrogen or gas nitrogen, cold energy of condensation at the top of the main rectifying tower, condensation of the gas nitrogen and precooling of air comes from the processes of evaporation, heat exchange, compression, heat exchange and condensation of a refrigerant, and the refrigerant fully recovers low-temperature full-range cold energy released during normal-pressure gasification of LNG as cold energy required by an air separation process. The circulation process of the refrigerant is simple and convenient, and the refrigerant can recover more than 90% of cold energy released by LNG gasification; the method can obtain gas nitrogen and liquid nitrogen with the purity of more than 99.999 percent and the pressure of more than 0.5MPa, liquid oxygen with the purity of more than 99.6 percent and the pressure of more than 0.5MPa, and the power consumption of the liquid oxygen and nitrogen is less than 300 KW/t; the production of the conventional air separation gas product with the same scale can be finished by using small-specification equipment.
Description
Technical Field
The invention relates to the field of air separation-LNG (liquefied natural gas) utilization, in particular to a method for producing liquid oxygen and liquid nitrogen by utilizing LNG cold energy and a single-tower rectification process.
Background
Distributed LNG gas supply has become an important component in the clean energy structure of China. Stored in Liquefied Natural Gas (LNG), Liquid Nitrogen (LN)2) Liquid Oxygen (LO)2) The medium-low temperature cold energy is a precious resource obtained by consuming a large amount of electric energy, and the maximum energy efficiency of the medium-low temperature cold energy is supposed to be exerted. The external cooling air separation technology breaks through the technical development bottleneck of the industry for decades, and the new energy-saving and emission-reducing way of the LNG normal-pressure gasification low-temperature cold energy recycling technology is provided and practiced. At present, the cold energy recycling potential in the fields of air separation and LNG is huge, and the investment income is remarkable.
The novel technology of 'LNG conventional air separation and pressure gasification high-temperature cold energy recycling' and 'LNG air separation and normal-pressure gasification low-temperature cold energy recycling' which are universal at home and abroad and are promoted by large-scale coastal LNG receiving stations has the following technical advantages and is remarkable in energy saving and efficiency improvement:
(1) realizing deep utilization of cold energy: the new technology LNG cold energy utilization temperature range is-160 ℃ to the ambient temperature, and the high-quality low-temperature cold energy is completely recovered; in the traditional technology, LNG is conveyed at high pressure, the cold energy utilization temperature range is only-70 ℃ to the ambient temperature, so that a large amount of high-quality low-temperature cold energy is lost, and only a low-quality high-temperature cold energy part can be recovered;
(2) the air separation energy consumption is further reduced: the unit energy consumption of the new technology product is reduced by about 30 percent, namely, the new technology product is advanced by the current world level of 0.42KWh/m3(O2) Reduced to 0.3KWh/m3(O2) The following;
(3) the cold energy recovery rate is high: the recovery rate of cold energy of the new technology is more than 90 percent, namely 2Kg of liquid oxygen-nitrogen product can be produced by gasifying 1Kg of LNG; the traditional technology can only produce less than 0.5kg, and the recovery rate is only 20-30%;
(4) the product cost is low: the new technology directly produces 300-400 yuan/ton liquid oxygen nitrogen, while the traditional technology is 600-700 yuan/ton, which is reduced by more than 40%;
(5) the total investment is low, the occupied area is small: according to the calculation of unit liquid product, compared with the traditional technology, the new technology reduces the investment of the device by more than 30 percent and saves the occupied area by more than 30 percent;
(6) the process design is flexible: the production scale of the new technology can be adjusted within the range of 5-3000 tons/day, and the new technology can be used for constructing a large-scale continuous operation device and realizing small-scale production and can be stopped along with start.
Chinese patent CN 101943512a discloses an air separation method using cold energy of liquefied natural gas, which transfers LNG cold energy to an air separation unit through circulating pressure liquid nitrogen and circulating cooling liquid, wherein the circulating formation process of the circulating pressure liquid nitrogen is as follows: a strand of low-temperature and low-pressure nitrogen (208) is pumped out from the low-pressure nitrogen (104) in the middle of the main heat exchanger (4) and is compressed by a low-temperature nitrogen compressor unit to form pressure nitrogen (702), the method comprises the steps that pressure nitrogen (702) enters an LNG-nitrogen heat exchanger (12) to exchange heat with LNG (601) pressurized to the conveying pressure, the pressure nitrogen after heat exchange and pressure nitrogen (703) flowing back from high-pressure supercooling liquid nitrogen (710) are converged and then enter a low-temperature nitrogen compressor unit to be compressed to form medium-pressure nitrogen (704), the medium-pressure nitrogen (704) enters the LNG-nitrogen heat exchanger (12) to exchange heat with the LNG (601) pressurized to the conveying pressure, the pressure nitrogen after heat exchange and medium-pressure nitrogen (705) flowing back from the high-pressure supercooling liquid nitrogen (710) are converged, the compression and heat exchange steps are circulated until the high-pressure supercooling liquid nitrogen (710) is formed, and one stream is extracted to serve as circulating pressure liquid nitrogen (708). The circulating cooling liquid (802) cooled by the LNG-cooling liquid heat exchanger (14) enters all parts of the system needing cooling. The recycling process of the circulating pressure liquid nitrogen of this patent is complicated, and is low to the recycle ratio of LNG cold energy, the LNG quantity: the yield of oxygen and nitrogen products was 2.24.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the technical problems of complex process and low utilization rate of LNG cold energy in the air separation method using LNG cold energy in the prior art, thereby providing a method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process. The specific technical scheme is as follows:
a method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process comprises the following steps:
purifying, namely filtering and pressurizing air, and then purifying the air to obtain purified air and impurities, wherein the impurities are discharged outside;
a cooling step, wherein the purified air is cooled by a refrigerant to obtain precooled air;
a rectification step, wherein pre-cooled air is rectified and separated to obtain a tower top gas phase and a tower bottom liquid phase, the tower bottom liquid phase is liquid oxygen, and the tower top gas phase is cooled by a refrigerant to obtain liquid nitrogen;
the LNG cold energy conversion step, wherein the cold energy provided by the refrigerant is cold energy provided by the LNG, and the LNG and the heat medium are subjected to cold energy exchange to obtain NG and the refrigerant; and the refrigerant is converted into the heat medium after cooling the purified air and the gas phase at the top of the tower and exchanges cold energy with new LNG again.
Further, the method for producing the liquid oxygen and the liquid nitrogen by utilizing the LNG cold energy and the single-tower rectification process also comprises the following steps,
in the rectification step, the gas phase containing argon is extracted and subjected to secondary rectification separation to obtain an argon-rich gas phase and a residual liquid, the residual liquid returns to the rectification step, and the argon-rich gas phase is emptied or further purified into a liquid argon product;
in the rectification step, dirty nitrogen is extracted as a condensate for condensing the argon-rich gas phase, which is returned to the cooling step after condensing the argon-rich gas phase.
Further, the method for producing the liquid oxygen and the liquid nitrogen by utilizing the LNG cold energy and the single-tower rectification process also comprises the following steps,
in the cooling step, the purified air is cooled by a first cooling unit and a second cooling unit which are arranged in parallel, and then enters a third cooling unit again for secondary cooling, so that the precooled air is obtained;
condensing the waste nitrogen after the argon-rich gas phase to be used as a cooling medium of the first cooling unit, cooling the purified air flowing through the first cooling unit, and returning to the purification step;
the refrigerant is used as a cooling medium of the third cooling unit, the purified air flowing through the third cooling unit is cooled and then is used as a cooling medium of the second cooling unit again, and the purified air flowing through the second cooling unit is compressed and converted into the heat medium to exchange cold with LNG.
Further, the method for producing the liquid oxygen and the liquid nitrogen by utilizing the LNG cold energy and the single-tower rectification process also comprises the following steps,
in the purification step, a first purification unit and a second purification unit are arranged in parallel, and the purification units alternately perform purification operation and regeneration operation;
in the regeneration operation, the waste nitrogen after condensing the argon-rich gas phase cools the purified air flowing through the first cooling unit and then returns to the purification step for impurity replacement and restoration of the purification unit.
Further, in the LNG cold energy conversion step, the LNG is evaporated and heat exchanged in sequence to release cold energy to obtain NG;
after the purified air flowing through the second cooling unit is cooled by the cooling medium serving as the second cooling unit, the compressed and evaporated LNG exchanges heat and is converted into the heat medium to exchange cold with new LNG, the new LNG completes the evaporation process, and the heat medium absorbs the cold of the new LNG and is converted into the refrigerant.
Further, in the rectification step, the gas phase at the top of the tower is sequentially condensed and recooled at the top of the tower and then converted into liquid nitrogen, and the refrigerant is used as a condensing medium condensed at the top of the tower, compressed and subjected to heat exchange, and converted into the heat medium to perform cold exchange with new LNG;
the refrigerant is used as the sub-cooled cooling medium, cools the liquid nitrogen condensed at the top of the tower, and then is mixed with the cooling medium flowing out of the third cooling unit, and is used as the cooling medium of the second cooling unit to cool the purified air flowing through the second cooling unit.
Further, the first cooling unit, the second cooling unit and the third cooling unit are respectively a heat exchanger I, a heat exchanger II and a heat exchanger III.
Further, the first purification unit and the second purification unit are an air purifier I and an air purifier II, respectively.
Further, in the purification step, air is pressurized to 0.5-1.2 MPa; in the cooling step, the moisture content of the precooled air is 15-40%;
further, the refrigerant is a single-component gas or a multi-component gas with low-temperature characteristics.
Further, the refrigerant includes single-component gas and multi-component gas with low temperature characteristics, such as nitrogen, oxygen, argon, air, nitrogen argon, nitrogen oxygen, oxygen argon, and the like.
The technical scheme of the invention has the following advantages:
1. the invention provides a method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process, wherein the single-tower rectification process of a main rectification tower and an argon tower is adopted to produce liquid oxygen, liquid nitrogen or gas nitrogen, the cold energy of condensation at the top of the main rectification tower, condensation of gas nitrogen and precooling of air comes from the processes of evaporation, heat exchange, compression, heat exchange and condensation of a refrigerant, and the refrigerant fully recovers low-temperature whole-course cold energy released during normal-pressure gasification of LNG as cold energy required by the air separation process; the process method can be used for obtaining gas nitrogen and liquid nitrogen with the purity of more than 99.999 percent and the pressure of more than 0.5MPa, liquid oxygen with the purity of more than 99.6 percent and the pressure of more than 0.5MPa, the extraction rate of the liquid oxygen is more than 99.6 percent, and the power consumption of the liquid oxygen nitrogen is less than 300 KW/t; gasifying 1 ton LNG can produce 2 ton liquid oxygen nitrogen, and the cold energy released by LNG gasification is fully utilized.
2. The production of air separation products can be completed, and liquid oxygen, liquid nitrogen, gas nitrogen and liquid argon products with different purities can be flexibly produced by adjusting the flow of the refrigerant serving as the condensing medium at the tower top;
the liquid argon can be flexibly produced or not produced by emptying or further purifying the argon-rich gas phase; the proportion of oxygen and nitrogen products is flexibly adjusted by adjusting the produced quantity of the waste nitrogen in the rectification step, the oxygen-nitrogen ratio can be increased by the large produced quantity of the waste nitrogen, and vice versa, and the optimal oxygen-nitrogen ratio is 1: 1.2-2.0.
The proportion of the oxygen and nitrogen products is flexibly adjusted by adjusting the extraction amount of the waste nitrogen in the rectification step
3. The production of electronic grade air separation products can be completed, and the production of electronic grade liquid nitrogen or gas nitrogen with the content of more than 99.99999 percent and electronic grade liquid oxygen with the content of more than 99.99 percent can be realized.
4. The method adopts a pressurized air rectification process, realizes the production of liquid or gas air products under the pressure of 0.5-1.2MPa, and can realize the production of conventional air separation gas products of the same scale by using small-specification equipment; the expansion-free machine refrigeration process can save production energy consumption to the maximum extent.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a flow chart of a process for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process according to the invention;
wherein, 1-air filter; 2-an air compressor; 3-air purifier I; 4-air purifier II; 5-a heater; 6-heat exchanger I; 7-heat exchanger II; 8-heat exchanger III; 9-main rectifying column condenser; 10-main rectification column; an 11-argon column condenser; 12-an argon column; 13-refrigerant compressor I; 14-heat exchanger IV; 15-heat exchanger V; 16-refrigerant compressor II; 17-heat exchanger VI; 18-LNG compressor; 19-LNG vaporizer.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The apparatus is not indicated by manufacturers, and is a conventional product commercially available.
The air compression and air purification (or purification) system is a conventional process in the air separation field, and is not specifically limited by the embodiment of the invention;
the air rectification system and the heat exchange system of the process are conventional processes, and the embodiments of the invention do not specifically limit the processes.
Example 1
The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process, which has a flow chart shown in figure 1, comprises the following steps:
(1) purification step
Air at normal temperature and normal pressure is filtered by an air filter 1 and then enters an air compressor 2 to be pressurized to 0.8 MPa; impurities in the pressurized air are removed through a purifier I3, and the purified air reaches the standard allowed by an air separation process; meanwhile, the purifier II 4 carries out regeneration operation; when the purifier I3 adsorbs impurities in the air and is saturated, the purifier I3 is switched to the regenerated purifier II 4 to continue purifying the air, and the purifier I3 starts regeneration operation; the purifier I3 and the purifier II 4 alternately carry out purification operation and regeneration operation for air purification circulation operation;
(2) step of Cooling
The purified air is cooled by a heat exchanger I6 and a heat exchanger II 7 which are arranged in parallel, and then enters a heat exchanger III 8 again for secondary cooling to obtain precooled air, wherein the moisture content of the precooled air is 35%;
(3) step of rectification
The precooled air enters a main rectifying tower 10 from the middle part, the gas nitrogen at the top of the tower is partially condensed by a condenser 9 at the top of the main rectifying tower, the condensed liquid phase automatically flows back to the main rectifying tower 10, and the uncondensed gas phase is condensed into liquid nitrogen by a condenser 15 and is sent out of the device to a liquid nitrogen storage tank;
liquid-phase waste nitrogen is extracted from the upper part of the main rectifying tower 10 and serves as a cold source of the argon tower top condenser, argon-containing gas phase is extracted from the lower part of the main rectifying tower 10 and sent to the argon tower 12 to finish rectification, argon-rich gas at the top of the argon tower is condensed by the tower top condenser 11, the condensed liquid phase automatically flows back into the argon tower 12, the uncondensed argon-rich gas phase is further purified into a liquid argon product, and the liquid phase at the bottom of the tower returns to the main rectifying tower 10 from the lower part; the waste nitrogen flowing through the condenser at the top of the argon tower passes through a heat exchanger I6 and a heater 5 and then is used for regenerating a purifier I3 and a purifier II 4 (regeneration, which comprises replacing impurities with hot nitrogen and recovering a molecular sieve with cold nitrogen, namely, the waste nitrogen heated by the heater 5 is regenerated and cooled by unheated waste nitrogen for later use);
liquid oxygen is extracted from the bottom of the main rectifying tower 10 and sent to a liquid oxygen storage tank;
(4) LNG cold energy conversion step
The cold energy that the refrigerant provided provides for LNG, LNG carries out cold energy exchange with hot-medium and obtains NG and the refrigerant specifically includes:
LNG is gasified into gas-phase NG by the evaporator 19, the gas-phase NG is reheated to normal temperature by the heat exchanger VI 17, and the normal-temperature NG is pressurized by the LNG compressor 18 and then is sent to an NG pipe network;
one path of the refrigerant from the evaporator 19 is used as a cooling medium of the heat exchanger III 8 and the overhead condenser 9 of the main rectifying tower for cooling purified air and overhead gas nitrogen, and the other path of the refrigerant is used as a cooling medium of the nitrogen condenser 15 for cooling an uncondensed gas phase at the top of the main rectifying tower 10; the refrigerant flowing through the nitrogen condenser 15 and the heat exchanger III 8 is mixed to be used as a cooling medium of the heat exchanger II 7 and converted into the heat medium, the heat medium is pressurized by a refrigerant compressor II 16, and the cold energy of the gas-phase NG is further recovered by a heat exchanger VI 17; the refrigerant flowing through the condenser 9 at the top of the main rectifying tower further recovers the cold energy of the refrigerant through a heat exchanger IV 14 and a refrigerant compressor 13; and the refrigerant flowing through the heat exchanger IV 14 and the heat exchanger II 7 exchanges cold energy with new LNG again, so that the recycling of the refrigerant is realized. In the present embodiment, the refrigerant is nitrogen, and the gas nitrogen condensation and the refrigerant gasification constitute a gas nitrogen condensation system.
Through the rectification process of the main rectification tower, gas nitrogen with the purity of more than 99.999 percent is separated from the top of the main rectification tower and sent to a liquid nitrogen condensation system, and liquid oxygen with the purity of 99.6 percent is separated from the bottom of the main rectification tower.
The main parameters, consumption and capacity of the present example using LNG cold energy and air separation in a single column rectification process are shown in table 1:
TABLE 1 utilization of LNG Cold energy and air separation for Single column rectification Process Main parameters, consumption and Capacity
The embodiment realizes the production of liquid or gas air products under the pressure of 0.5-1.2MPa, and is suitable for the cold energy recycling of medium and small vaporization quantities of urban LNG vaporizing stations, industrial park LNG vaporizing stations and the like.
Comparing the results of a 600t/d cold energy air separation unit of the LNG-cold energy air separation process flow in the patent CN 101943512A, the results are shown in the following table 2:
table 2 comparison of example 1 with the results obtained by air separation in patent CN 101943512a
The present example and the comparative example clearly show that: the contrast case is far less than this embodiment to the recycle rate of LNG cold energy, and the LNG according to this embodiment: oxygen nitrogen product ratio, for LNG vaporization amount of 1344t/d, this example is capable of producing 968t/d liquid oxygen, 1983t/d liquid nitrogen.
Example 2
The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process, which has a flow chart shown in figure 1, comprises the following steps:
(1) purification step
Air at normal temperature and normal pressure is filtered by an air filter 1 and then enters an air compressor 2 to be pressurized to 500 KPa; impurities in the pressurized air are removed through a purifier I3, and the purified air reaches the standard allowed by an air separation process; meanwhile, the purifier II 4 carries out regeneration operation; when the purifier I3 adsorbs impurities in the air and is saturated, the purifier I3 is switched to the regenerated purifier II 4 to continue purifying the air, and the purifier I3 starts regeneration operation; the purifier I3 and the purifier II 4 alternately carry out purification operation and regeneration operation for air purification circulation operation;
(2) step of Cooling
The purified air is cooled by a heat exchanger I6 and a heat exchanger II 7 which are arranged in parallel, and then enters a heat exchanger III 8 again for secondary cooling to obtain precooled air, wherein the moisture content of the precooled air is 15%;
(3) step of rectification
The precooled air enters a main rectifying tower 10 from the middle part, the gas nitrogen at the top of the tower is partially condensed by a condenser 9 at the top of the main rectifying tower, the condensed liquid phase automatically flows back to the main rectifying tower 10, and the uncondensed gas phase is condensed into liquid nitrogen by a condenser 15 and is sent out of the device to a liquid nitrogen storage tank;
liquid-phase waste nitrogen is extracted from the upper part of the main rectifying tower 10 and serves as a cold source of the argon tower top condenser, argon-containing gas phase is extracted from the lower part of the main rectifying tower 10 and sent to the argon tower 12 to finish rectification, argon-rich gas at the top of the argon tower is condensed by the tower top condenser 11, the condensed liquid phase automatically flows back into the argon tower 12, the uncondensed argon-rich gas phase is further purified into a liquid argon product, and the liquid phase at the bottom of the tower returns to the main rectifying tower 10 from the lower part; the waste nitrogen flowing through the condenser at the top of the argon tower passes through a heat exchanger I6 and a heater 5 and is used for regenerating a purifier I3 and a purifier II 4;
liquid oxygen is extracted from the bottom of the main rectifying tower 10 and sent to a liquid oxygen storage tank;
(4) LNG cold energy conversion step
The cold energy that the refrigerant provided provides for LNG, LNG carries out cold energy exchange with hot-medium and obtains NG and the refrigerant specifically includes:
LNG is gasified into gas-phase NG by the evaporator 19, the gas-phase NG is reheated to normal temperature by the heat exchanger VI 17, and the normal-temperature NG is pressurized by the LNG compressor 18 and then is sent to an NG pipe network;
one path of the refrigerant from the evaporator 19 is used as a cooling medium of the heat exchanger III 8 and the overhead condenser 9 of the main rectifying tower for cooling purified air and overhead gas nitrogen, and the other path of the refrigerant is used as a cooling medium of the nitrogen condenser 15 for cooling an uncondensed gas phase at the top of the main rectifying tower 10; the refrigerant flowing through the nitrogen condenser 15 and the heat exchanger III 8 is mixed to be used as a cooling medium of the heat exchanger II 7 and converted into the heat medium, the heat medium is pressurized by a refrigerant compressor II 16, and the cold energy of the gas-phase NG is further recovered by a heat exchanger VI 17; the refrigerant flowing through the condenser 9 at the top of the main rectifying tower further recovers the cold energy of the refrigerant through a heat exchanger IV 14 and a refrigerant compressor 13; and the refrigerant flowing through the heat exchanger IV 14 and the heat exchanger II 7 exchanges cold energy with new LNG again, so that the recycling of the refrigerant is realized.
And in the rectification process of the main rectification tower, gas nitrogen with the purity of more than 99.999 percent is separated from the top of the main rectification tower and is sent to a liquid nitrogen condensation system, and liquid oxygen with the purity of 99.6 percent is separated from the bottom of the main rectification tower and is sent out of the device to a liquid oxygen storage tank.
Example 3
The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process, which has a flow chart shown in figure 1, comprises the following steps:
(1) purification step
Air at normal temperature and normal pressure is filtered by an air filter 1 and then enters an air compressor 2 to be pressurized to 1.2 MPa; impurities in the pressurized air are removed through a purifier I3, and the purified air reaches the standard allowed by an air separation process; meanwhile, the purifier II 4 carries out regeneration operation; when the purifier I3 adsorbs impurities in the air and is saturated, the purifier I3 is switched to the regenerated purifier II 4 to continue purifying the air, and the purifier I3 starts regeneration operation; the purifier I3 and the purifier II 4 alternately carry out purification operation and regeneration operation for air purification circulation operation;
(2) step of Cooling
The purified air is cooled by a heat exchanger I6 and a heat exchanger II 7 which are arranged in parallel, and then enters a heat exchanger III 8 again for secondary cooling to obtain precooled air, wherein the moisture content of the precooled air is 40%;
(3) step of rectification
The precooled air enters a main rectifying tower 10 from the middle part, the gas nitrogen at the top of the tower is partially condensed by a condenser 9 at the top of the main rectifying tower, the condensed liquid phase automatically flows back to the main rectifying tower 10, and the uncondensed gas phase is condensed into liquid nitrogen by a condenser 15 and is sent out of the device to a liquid nitrogen storage tank;
liquid-phase waste nitrogen is extracted from the upper part of the main rectifying tower 10 and serves as a cold source of the argon tower top condenser, argon-containing gas phase is extracted from the lower part of the main rectifying tower 10 and sent to the argon tower 12 to finish rectification, argon-rich gas at the top of the argon tower is condensed by the tower top condenser 11, the condensed liquid phase automatically flows back into the argon tower 12, the uncondensed argon-rich gas phase is further purified into a liquid argon product, and the liquid phase at the bottom of the tower returns to the main rectifying tower 10 from the lower part; the waste nitrogen flowing through the condenser at the top of the argon tower passes through a heat exchanger I6 and a heater 5 and is used for regenerating a purifier I3 and a purifier II 4;
liquid oxygen is extracted from the bottom of the main rectifying tower 10 and sent to a liquid oxygen storage tank;
(4) LNG cold energy conversion step
The cold energy that the refrigerant provided provides for LNG, LNG carries out cold energy exchange with hot-medium and obtains NG and the refrigerant specifically includes:
LNG is gasified into gas-phase NG by the evaporator 19, the gas-phase NG is reheated to normal temperature by the heat exchanger VI 17, and the normal-temperature NG is pressurized by the LNG compressor 18 and then is sent to an NG pipe network;
one path of the refrigerant from the evaporator 19 is used as a cooling medium of the heat exchanger III 8 and the overhead condenser 9 of the main rectifying tower for cooling purified air and overhead gas nitrogen, and the other path of the refrigerant is used as a cooling medium of the nitrogen condenser 15 for cooling an uncondensed gas phase at the top of the main rectifying tower 10; the refrigerant flowing through the nitrogen condenser 15 and the heat exchanger III 8 is mixed to be used as a cooling medium of the heat exchanger II 7 and converted into the heat medium, the heat medium is pressurized by a refrigerant compressor II 16, and the cold energy of the gas-phase NG is further recovered by a heat exchanger VI 17; the refrigerant flowing through the condenser 9 at the top of the main rectifying tower further recovers the cold energy of the refrigerant through a heat exchanger IV 14 and a refrigerant compressor 13; and the refrigerant flowing through the heat exchanger IV 14 and the heat exchanger II 7 exchanges cold energy with new LNG again, so that the recycling of the refrigerant is realized.
And in the rectification process of the main rectification tower, gas nitrogen with the purity of more than 99.999 percent is separated from the top of the main rectification tower and is sent to a liquid nitrogen condensation system, liquid oxygen with the purity of 99.6 percent is separated from the bottom of the main rectification tower, and argon-containing gas is extracted from a side line of the main rectification tower and is sent to an argon tower.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (8)
1. A method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process is characterized by comprising the following steps:
purifying, namely filtering and pressurizing air, and then purifying the air to obtain purified air and impurities, wherein the impurities are discharged outside;
a cooling step, wherein the purified air is cooled by a refrigerant to obtain precooled air;
a rectification step, wherein pre-cooled air is rectified and separated to obtain a tower top gas phase and a tower bottom liquid phase, the tower bottom liquid phase is liquid oxygen, and the tower top gas phase is cooled by a refrigerant to obtain liquid nitrogen;
the LNG cold energy conversion step, wherein the cold energy provided by the refrigerant is cold energy provided by the LNG, and the LNG and the heat medium are subjected to cold energy exchange to obtain NG and the refrigerant; the refrigerant is converted into the heat medium after cooling the purified air and the gas phase at the top of the tower and exchanges cold energy with new LNG again;
wherein the content of the first and second substances,
in the rectification step, the gas phase containing argon is extracted and subjected to secondary rectification separation to obtain an argon-rich gas phase and a residual liquid, the residual liquid returns to the rectification step, and the argon-rich gas phase is emptied or further purified into a liquid argon product;
in the rectification step, effluent nitrogen is extracted as condensate for condensing the argon-rich gas phase, and the condensed argon-rich gas phase returns to the cooling step;
in the cooling step, the purified air is cooled by a first cooling unit and a second cooling unit which are arranged in parallel, and then enters a third cooling unit again for secondary cooling, so that the precooled air is obtained;
condensing the waste nitrogen after the argon-rich gas phase to be used as a cooling medium of the first cooling unit, cooling the purified air flowing through the first cooling unit, and returning to the purification step;
the refrigerant is used as a cooling medium of the third cooling unit, the purified air flowing through the third cooling unit is cooled and then is used as a cooling medium of the second cooling unit again, and the purified air flowing through the second cooling unit is compressed and converted into the heat medium to exchange cold with LNG.
2. The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process as claimed in claim 1, further comprising,
in the purification step, a first purification unit and a second purification unit are arranged in parallel, and the purification units alternately perform purification operation and regeneration operation;
in the regeneration operation, the waste nitrogen after condensing the argon-rich gas phase cools the purified air flowing through the first cooling unit and then returns to the purification step for impurity replacement and restoration of the purification unit.
3. The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process as claimed in claim 1,
in the LNG cold energy conversion step, the LNG is evaporated and heat exchanged in sequence to release cold energy to obtain NG;
after the purified air flowing through the second cooling unit is cooled by the cooling medium serving as the second cooling unit, the compressed and evaporated LNG exchanges heat and is converted into the heat medium to exchange cold with new LNG, the new LNG completes the evaporation process, and the heat medium absorbs the cold of the new LNG and is converted into the refrigerant.
4. The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process as claimed in claim 3,
in the rectification step, the tower top gas phase is sequentially subjected to tower top condensation and re-cooling and then converted into liquid nitrogen, and the refrigerant serving as a condensation medium condensed at the tower top condenses the tower top gas phase and then is converted into a heat medium for cold exchange with new LNG through compression and heat exchange;
the refrigerant is used as the sub-cooled cooling medium, cools the liquid nitrogen condensed at the top of the tower, and then is mixed with the cooling medium flowing out of the third cooling unit, and is used as the cooling medium of the second cooling unit to cool the purified air flowing through the second cooling unit.
5. The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and a single-tower rectification process as claimed in claim 1, wherein the first cooling unit, the second cooling unit and the third cooling unit are a heat exchanger I, a heat exchanger II and a heat exchanger III respectively.
6. The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process according to claim 2, wherein the first purification unit and the second purification unit are respectively an air purifier I and an air purifier II.
7. The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process as claimed in any one of claims 1-4, wherein in the purification step, air is pressurized to 0.5-1.2 MPa; in the cooling step, the moisture content of the pre-cooled air is 15% -40%.
8. The method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process as claimed in any one of claims 1-4, wherein the refrigerant is a single-component gas or a multi-component gas with low temperature characteristics.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910008842.4A CN109855389B (en) | 2019-01-04 | 2019-01-04 | Method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910008842.4A CN109855389B (en) | 2019-01-04 | 2019-01-04 | Method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109855389A CN109855389A (en) | 2019-06-07 |
| CN109855389B true CN109855389B (en) | 2020-11-13 |
Family
ID=66894036
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910008842.4A Active CN109855389B (en) | 2019-01-04 | 2019-01-04 | Method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109855389B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113587552B (en) * | 2021-07-14 | 2022-11-18 | 四川空分设备(集团)有限责任公司 | Air separation system and air separation method utilizing LNG cold energy |
Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5495552U (en) * | 1977-12-16 | 1979-07-06 | ||
| DE3528374A1 (en) * | 1985-08-07 | 1987-02-12 | Linde Ag | METHOD AND DEVICE FOR PRODUCING NITROGEN WITH OVER-ATMOSPHERIC PRESSURE |
| JPH0252980A (en) * | 1988-08-18 | 1990-02-22 | Kobe Steel Ltd | Air separating device |
| CN2766203Y (en) * | 2005-04-15 | 2006-03-22 | 林福粦 | Air separator for recovering cold energy of liquefied natural gas |
| CN1873357A (en) * | 2005-04-25 | 2006-12-06 | 林福粦 | Air separation system for recycling cold energy of liquified natural gas |
| CN101839612A (en) * | 2010-04-06 | 2010-09-22 | 浙江大学 | Backward flow type air separation system and method based on cold energy utilization of LNG (Liquefied Natural Gas) satellite station |
| CN101846436A (en) * | 2010-05-27 | 2010-09-29 | 中国海洋石油总公司 | Full-liquid air separation device using cold energy of liquefied natural gas (LNG) |
| CN201653068U (en) * | 2010-04-06 | 2010-11-24 | 浙江大学 | Reverse filling type air separation system based on utilization of cold energy of LNG satellite stations |
| CN102472575A (en) * | 2009-07-24 | 2012-05-23 | 大阳日酸株式会社 | Air liquefaction and separation method and device |
| CN103988037A (en) * | 2011-12-05 | 2014-08-13 | 普莱克斯技术有限公司 | Air separation method and apparatus |
| CN205262061U (en) * | 2015-12-16 | 2016-05-25 | 新疆天辰气体有限公司 | High pure nitrogen air separation device |
| CN108224900A (en) * | 2018-01-24 | 2018-06-29 | 北京拓首能源科技股份有限公司 | A kind of oxygen nitrogen and argon piece-rate system using cold energy of liquefied natural gas |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001141359A (en) * | 1999-11-17 | 2001-05-25 | Toshiba Corp | Air separator |
| US7549301B2 (en) * | 2006-06-09 | 2009-06-23 | Praxair Technology, Inc. | Air separation method |
| US8601833B2 (en) * | 2007-10-19 | 2013-12-10 | Air Products And Chemicals, Inc. | System to cold compress an air stream using natural gas refrigeration |
| CN201532078U (en) * | 2009-06-04 | 2010-07-21 | 中国海洋石油总公司 | Air separating system using liquefied natural gas cold energy |
-
2019
- 2019-01-04 CN CN201910008842.4A patent/CN109855389B/en active Active
Patent Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5495552U (en) * | 1977-12-16 | 1979-07-06 | ||
| DE3528374A1 (en) * | 1985-08-07 | 1987-02-12 | Linde Ag | METHOD AND DEVICE FOR PRODUCING NITROGEN WITH OVER-ATMOSPHERIC PRESSURE |
| JPH0252980A (en) * | 1988-08-18 | 1990-02-22 | Kobe Steel Ltd | Air separating device |
| CN2766203Y (en) * | 2005-04-15 | 2006-03-22 | 林福粦 | Air separator for recovering cold energy of liquefied natural gas |
| CN1873357A (en) * | 2005-04-25 | 2006-12-06 | 林福粦 | Air separation system for recycling cold energy of liquified natural gas |
| CN102472575A (en) * | 2009-07-24 | 2012-05-23 | 大阳日酸株式会社 | Air liquefaction and separation method and device |
| CN101839612A (en) * | 2010-04-06 | 2010-09-22 | 浙江大学 | Backward flow type air separation system and method based on cold energy utilization of LNG (Liquefied Natural Gas) satellite station |
| CN201653068U (en) * | 2010-04-06 | 2010-11-24 | 浙江大学 | Reverse filling type air separation system based on utilization of cold energy of LNG satellite stations |
| CN101846436A (en) * | 2010-05-27 | 2010-09-29 | 中国海洋石油总公司 | Full-liquid air separation device using cold energy of liquefied natural gas (LNG) |
| CN103988037A (en) * | 2011-12-05 | 2014-08-13 | 普莱克斯技术有限公司 | Air separation method and apparatus |
| CN205262061U (en) * | 2015-12-16 | 2016-05-25 | 新疆天辰气体有限公司 | High pure nitrogen air separation device |
| CN108224900A (en) * | 2018-01-24 | 2018-06-29 | 北京拓首能源科技股份有限公司 | A kind of oxygen nitrogen and argon piece-rate system using cold energy of liquefied natural gas |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109855389A (en) | 2019-06-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109838975B (en) | Low-energy-consumption liquid nitrogen preparation device and process | |
| CN108061428B (en) | Pure nitrogen preparation device and process | |
| CN101538040B (en) | Method for coproducing or singly producing food grade carbon dioxide and industrial grade carbon dioxide by utilizing industrial waste gas | |
| CN203375800U (en) | Deep cooling air separation oxygen generation system by adoption of synthesis ammonia process | |
| CN113405318B (en) | Application method of device for producing pure nitrogen by using single rectifying tower | |
| CN101264862B (en) | Method for preparing heavy water and deuterium gas | |
| CN101846436A (en) | Full-liquid air separation device using cold energy of liquefied natural gas (LNG) | |
| CN111238166A (en) | Refrigeration cycle system and method in carbon dioxide rectification separation process | |
| CN110207460A (en) | A kind of recyclable device and its recovery method of integrated High Purity Nitrogen and argon gas | |
| CN109855389B (en) | Method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process | |
| CN111238165A (en) | Carbon dioxide rectification device and rectification method based on tail gas cold energy utilization | |
| CN101943513B (en) | Method for lowering liquid space division energy consumption | |
| CN1952569A (en) | Process and equipment for liquefying air-containing coal-bed gas | |
| CN207123117U (en) | A kind of new double tower nitrogen device for making | |
| CN204718303U (en) | A kind of air-separating plant preparing pressure oxygen | |
| CN211226357U (en) | Device for preparing dry ice and recovering dry ice tail gas to produce food-grade carbon dioxide | |
| CN115540499A (en) | Device and method for producing high-purity nitrogen and ultrapure oxygen by low-temperature pressurization circulation of flash evaporation waste gas | |
| CN213335168U (en) | Refrigeration cycle system in carbon dioxide rectification separation process | |
| CN211782271U (en) | Carbon dioxide rectifying device based on tail gas cold energy utilization | |
| CN212842469U (en) | Single-tower cryogenic rectification argon recovery system with argon circulation and hydrogen circulation | |
| CN114963691A (en) | Low pressure CO 2 Low-temperature gas separation method and device | |
| CN104964515B (en) | Synthetic ammonia tailgas comprehensive utilization process and device | |
| CN103539603A (en) | Method for preparing liquefied methane by using synthesis ammonia vent gas and purge gas | |
| CN207831794U (en) | A kind of adipic acid tail gas purifies the device of liquid laughing gas processed | |
| CN109357475B (en) | System for cascade utilization LNG cold energy prepares liquid oxygen liquid nitrogen |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| TR01 | Transfer of patent right | ||
| TR01 | Transfer of patent right |
Effective date of registration: 20210730 Address after: 207.201, 2f, Shihua Hotel, No. 14, Xiba hedongli, Chaoyang District, Beijing 100028 Patentee after: Zhongke Huizhi (Beijing) Technology Co.,Ltd. Address before: 100192 room 1301, unit 2, building 14, chenjiaying, Dongxiaokou, Changping District, Beijing Patentee before: Cao Jianxi |