Nitrogen generator adopting combined condensation evaporator

Abstract

The utility model discloses a nitrogen generator adopting a combined condensing evaporator. The nitrogen generator comprises a rectifying tower and two condensing evaporators, the first condensation and evaporation device is of a plate-fin type, the second condensation and evaporation device is of an immersion bath type, and the first condensation and evaporation device and the second condensation and evaporation device are integrated together and share a nitrogen-rich steam inlet, a nitrogen-rich steam distribution part, a nitrogen-rich liquid guide-out part and a nitrogen-rich liquid outlet. The nitrogen generator provided by the utility model is simple in structure and convenient to manufacture; the space and the cost are saved; a nitrogen-rich steam distribution part and a nitrogen-rich liquid leading-out part are integrated to generate a synergistic effect; and the steam with higher oxygen content is evaporated, so that the safety coefficient is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a nitrogen generator adopting double condensing evaporators, in particular to a nitrogen generator with combined double condensing evaporators. BACKGROUND

[0002] The nitrogen generator adopting double condensing evaporators has high nitrogen yield and purity, and its process and equipment are disclosed in CN202648307U and US005711167A.

[0003] In the prior art, the two condensing evaporators are both immersion type and arranged in two mutually isolated containers, which results in high cost and large space occupation.

[0004] Therefore, how to design a combined condensing evaporator to enable one gas to exchange heat with multiple liquids at the same time so as to make the equipment more compact, lower in manufacturing cost and higher in safety factor is an urgent issue to be solved by those skilled in the art. SUMMARY

[0005] The utility model aims at providing a nitrogen generator adopting double condensing evaporators, which is more compact and lower in cost while ensuring safety and heat exchange performance.

[0006] In one aspect, the equipment of the utility model comprises: a rectifying tower for separating a supply air stream into nitrogen-rich vapor and oxygen-rich liquid air and a device for delivering the supply air stream to the rectifying tower; a main heat exchanger for interacting with the rectifying tower to cool the supply air stream. A first plate-fin condensing evaporator capable of airifying the oxygen-rich liquid air by indirectly exchanging heat with the total nitrogen-rich vapor to be condensed to form nitrogen-rich liquid and a first gas-liquid mixed stream. A second gas-liquid separator receiving the first gas-liquid mixed stream, which separates a top second gas-liquid separator gas phase and a bottom second gas-liquid separator liquid phase; a device for delivering the second gas-liquid separator liquid phase to a second condensing evaporator; a device for extracting the second gas-liquid separator gas phase and delivering it to a recycle compressor. The second condensing evaporator comprises a second heat exchanger core immersed in the second gas-liquid separator liquid phase, which is capable of forming nitrogen-rich liquid and oxygen-rich exhaust stream by indirectly exchanging heat with the total nitrogen-rich vapor to be condensed; a device for extracting the oxygen-rich exhaust stream and delivering it to a heat exchanger. A recycle compressor for compressing the second gas-liquid separator gas phase; a device for delivering the compressed second gas-liquid separator gas phase to the rectifying tower; and a device for delivering a part of the nitrogen-rich vapor to the main heat exchanger for warming; the first plate-fin condensing evaporator and the second condensing evaporator are integrated together and placed in the same shell.

[0007] In yet another aspect, the device of the present application further comprises: an expansion device and a device for sending the oxygen-enriched waste gas stream into the expansion device after being partially warmed in the main heat exchanger.

[0008] In yet another aspect, the device of the present application further comprises: a first gas-liquid separator for receiving the oxygen-enriched liquid air and separating to obtain a first gas-liquid separator gas phase at the top and a first gas-liquid separator liquid phase at the bottom, and a device for transporting the first gas-liquid separator liquid phase to the first plate-fin condensation evaporator.

[0009] In yet another aspect, the integrated first plate-fin condensation evaporator and second condensation evaporator are separated by a partition plate; the first plate-fin condensation evaporator is a closed structure, and the second condensation evaporator is a semi-open structure.

[0010] In yet another aspect, the integrated first plate-fin condensation evaporator and second condensation evaporator share one nitrogen-enriched vapor distribution part and one nitrogen-enriched liquid leading-out part, and the total nitrogen-enriched vapor to be condensed is condensed from top to bottom in the gas distribution part and then leaves from the nitrogen-enriched liquid leading-out part.

[0011] In another aspect, the first plate-fin condensation evaporator has a first liquid distribution part at the top and a first gas-liquid mixed flow leading-out part at the bottom, and the flow directions of the first gas-liquid separator liquid phase and the nitrogen-enriched vapor are the same.

[0012] Compared with the prior art, the technical scheme provided by the present application has the following advantages:

[0013] 1. Simple structure, easy to manufacture;

[0014] 2. Save space and cost;

[0015] 3. The nitrogen-enriched vapor distribution part and the nitrogen-enriched liquid leading-out part are integrated, producing a synergistic effect;

[0016] 4. The second condensation evaporator immersed in the kettle liquid is equivalent to a bath-type heat exchanger. It is used to evaporate a flow with a higher oxygen content, thereby improving the safety factor. BRIEF DESCRIPTION OF DRAWINGS

[0017] The advantages and spirits of the present application can be further understood through the following detailed description and drawings, and those skilled in the art know that the drawings and examples do not limit the present application in any way. The same reference signs in the drawings correspond to the same or equivalent components.

[0018] Figure 1 is a flow chart of a nitrogen generator using double condensation evaporators for Comparative Example 1;

[0019] Figure 2 is a schematic diagram of replacing double condensation evaporators with a combined condensation evaporator in Example 1;

[0020] Figure 3 is a three-dimensional front view of a heat exchanger core of the combined condensing evaporator of Example 1;

[0021] Figure 4 is a side sectional view of the combined condensing evaporator of Example 1 taken along the stacking direction of the heat exchanger core slabs;

[0022] In the figure: 100 - combined condensing evaporator; 2 - supply air stream; 3 - oxygen enriched liquid air; 3a - first gas-liquid separator liquid phase; 3b - first gas-liquid separator gas phase; 4 - first condensing section liquid phase; 4a - first gas-liquid mixture stream; 4b - second gas-liquid separator gas phase; 5 - recirculation stream; 6 - oxygen enriched exhaust air stream; 7 - gaseous nitrogen product; 8 - liquid discharge; 10 - main heat exchanger; 11 - first pressure reduction device; 12 - second pressure reduction device; 13 - first gas-liquid separator; 14 - second gas-liquid separator; 15 - first liquid distribution section; 16 - first gas-liquid mixture stream outlet section; 20 - rectification column; 21 - second part of the nitrogen enriched vapor; 22 - total condensed nitrogen enriched liquid; 23 - liquid nitrogen product; 25 - separation plate; 26 - nitrogen enriched vapor inlet; 27 - nitrogen enriched liquid outlet; 28 - nitrogen enriched vapor distribution section; 29 - nitrogen enriched liquid outlet section; 30 - first bath type condensing evaporator; 30' - first plate fin type condensing evaporator; 31 - first part of the nitrogen enriched vapor; 32 - first part of the nitrogen enriched liquid; 35 - nitrogen condensing channel; 36 - first evaporation channel; 37 - second evaporation channel; 40 - second condensing evaporator; 41 - total nitrogen enriched vapor to be condensed; 42 - second part of the nitrogen enriched liquid; 50 - first heat exchanger core; 60 - second heat exchanger core; 70 - recirculation compressor; 80 - expansion device. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present application more clear, the technical scheme of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0024] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "assembly", "connection" mean that two or more parts form a component sealed for fluid such as liquid, gas, etc. The assembly and connection mode includes welding connection, flange connection, bolt connection, adhesion or one-piece forming, etc. The terms "connected", "communicated" mean a state that liquid, gas and other fluids can flow between two or more parts.

[0025] The terms "downstream", "upstream" are relative to the direction of liquid or gas flow. The process of liquid or gas flowing from the inlet to the outlet is the process of flowing from upstream to downstream.

[0026] The terms indicating the orientation, such as "below", "above", "parallel to the horizontal plane", "perpendicular to the horizontal plane" are corresponding to the orientation of the combined condenser evaporator in the normal use scene.

[0027] In addition, the limiting words similar to "one" appearing in this text are not limited to the quantity, but describe the technical features that have not appeared in the preceding text. Similarly, unless the noun is modified by a specific quantity quantifier, it should be considered to include both singular and plural forms in this text, that is, the technical solution can include a single technical feature or multiple technical features.

[0028] It should be understood that in the present application, "at least one" means one or more, and "multiple" means two or more. "And / or" is used to describe the association between the associated objects, which means that there can be three kinds of relationships, for example, "A and / or B" can represent three cases: only A, only B, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects. "At least one of the following" or similar expressions means any combination of these items, including any combination of single or multiple items. For example, at least one of a, b or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0029] Comparative Example 1 discloses a nitrogen generator using a dual-condenser evaporator in the prior art. The supply air stream 2, after compression, precooling, and purification (not shown), is cooled in the main heat exchanger 10 and fed into a distillation column 20. After distillation, total nitrogen-rich vapor 41 to be condensed and gaseous nitrogen product 7 are generated at the top of the column, and oxygen-rich liquid air 3 is generated at the bottom. In the first immersion condenser 30, the oxygen-rich liquid air 3, depressurized by the first pressure reducing device 11, indirectly exchanges heat with the first portion of nitrogen-rich vapor 31. The former partially evaporates to generate a recirculation stream 5, which is discharged from the top; the latter condenses to obtain the first portion of nitrogen-rich liquid 32. The liquid phase 4 in the first condensation section, after being depressurized by the second pressure reducing device 12, is fed into the second condenser 40, where it indirectly exchanges heat with the second portion of nitrogen-rich vapor 21. The former partially evaporates to generate an oxygen-rich waste gas stream 6, which is discharged from the top; the latter condenses to obtain the second portion of nitrogen-rich liquid 42. The first part of nitrogen-rich liquid 32 and the second part of nitrogen-rich liquid 42 are mixed to obtain the total condensed nitrogen-rich liquid 22. A portion of this liquid is taken out of the distillation column 20 as liquid nitrogen product 23, and the other portion is returned to the upper part of the distillation column 20 as reflux liquid. The recirculation stream 5 is compressed in the recirculation compressor 70, partially cooled in the main heat exchanger 10, and then sent back to the distillation column 20. The oxygen-rich waste gas stream 6 is first partially reheated in the main heat exchanger 10, then expanded in the expansion device 80, and finally fully reheated in the main heat exchanger 10 before being discharged. The gaseous nitrogen product 7 is also taken out after being fully reheated in the main heat exchanger 10.

[0030] The first immersion evaporator 30 and the second immersion evaporator 40 are both immersion evaporators. The first heat exchanger core 50 and the second heat exchanger core 60 are generally semi-open plate-fin structures. The liquid in the kettle circulates repeatedly in the evaporation channel of the heat exchanger core through the thermosiphon effect, and evaporates continuously. When evaporating the kettle liquid with a high oxygen content, it has the beneficial effect of reducing the deposition of flammable hydrocarbons and improving safety.

[0031] Example 1 is an example of replacing the dual condenser evaporator with a combined condenser evaporator 100 in this invention (see Example 1). Figure 1 (The area within the dashed box). Figure 2 In this embodiment, the first plate-fin condenser-evaporator 30' is a closed type, realizing the function of the first immersion condenser-evaporator 30 in Comparative Example 1; the second heat exchanger core 60 remains unchanged. The first plate-fin condenser-evaporator 30' and the second heat exchanger core 60 are integrated, and two gas-liquid separators are added to further optimize the process.

[0032] The oxygen enriched liquid air 3 from the bottom of the column is depressurized by the first pressure reducing device 11 and forms a gas-liquid mixture stream due to flash evaporation. The stream is separated in the first gas-liquid separator 13 and a first gas-liquid separator liquid phase 3a is obtained. The 3a enters the first liquid distribution section 15 at the top of the first plate-fin condensing evaporator 30'. The first gas-liquid separator 13 is not necessary but it can remove the gas phase components from the oxygen enriched liquid air 3 completely. Without the disturbance of the gas bubbles, the pure liquid first gas-liquid separator liquid phase 3a is distributed more evenly into the evaporating channels in the first liquid distribution section 15 and the performance of the heat exchanger is improved.

[0033] The first gas-liquid separator liquid phase 3a exchanges heat indirectly with the total nitrogen enriched vapor to be condensed 41 from the top of the rectification column 20 in the evaporating channels and a first gas-liquid mixture stream 4a is obtained after partial evaporation. The first gas-liquid mixture stream 4a exits from the first gas-liquid mixture stream exit section 16 and is sent into the second gas-liquid separator 14. The first condensed section liquid phase 4 is obtained after separation in the second gas-liquid separator 14. The first condensed section liquid phase 4 is depressurized by the second pressure reducing device 12 and is sent into the shell of the combined condensing evaporator to replenish the tank liquid. The gas phase 3b from the first gas-liquid separator combines with the gas phase 4b from the second gas-liquid separator and can be sent back to the rectification column 20 as the recirculation stream 5.

[0034] The second heat exchanger core 60 of the second condensing evaporator 40 is fully immersed in the tank liquid. The tank liquid exchanges heat indirectly with the total nitrogen enriched vapor to be condensed 41 from the rectification column 20 in the second heat exchanger core 60 by the thermosyphon effect. The partially evaporated tank liquid forms the oxygen enriched exhaust stream 6 at the top of the condensing evaporator. The total nitrogen enriched vapor to be condensed 41 is condensed and the total condensed nitrogen enriched liquid 22 is obtained. To prevent the accumulation of flammable impurities in the tank liquid, the condensing evaporator of the present application also produces the liquid discharge 8 periodically.

[0035] Figure 3 A three-dimensional view of the combined condensing evaporator of embodiment 1 is shown. The closed first plate-fin condensing evaporator 30' and the semi-open second heat exchanger core 60 are completely separated by the partition plate 25. From the top of the first plate-fin condensing evaporator 30' to the bottom of the second heat exchanger core 60, the oxygen enriched liquid air 3 enters the first liquid distribution section 15 at the top of the first plate-fin condensing evaporator 30', the first gas-liquid mixture stream 4a exits from the first gas-liquid mixture stream exit section 16, the first condensed section liquid phase 4 enters the second liquid distribution section 17 at the top of the second heat exchanger core 60, the second condensed section liquid phase 5 exits from the second condensed section liquid phase exit section 18, and the liquid discharge 8 exits from the liquid discharge exit section 19. Figure 3 As can be seen from the figure, both the first plate-fin condensing evaporator 30' and the second heat exchanger core 60 are stacked by multiple channels. In the first plate-fin condensing evaporator 30', the channels are the nitrogen condensing channels 35 and the first evaporating channels 36 arranged alternately; in the second heat exchanger core 60, the channels are the nitrogen condensing channels 35 and the second evaporating channels 37 arranged alternately.

[0036] The first plate-fin condensing evaporator 30' is characterized by its complete isolation from the tank liquid in the liquid storage container. This isolation can be achieved by a complete and continuous shell or by the combination of the shell and the seal. The top and the bottom of the first plate-fin condensing evaporator 30' have components for distributing or collecting the liquid and its partially evaporated products. Figure 3In the middle, the top of the first plate-fin condensing evaporator 30' is provided with a first liquid distribution part 15, and the bottom is provided with a first gas-liquid mixed flow outlet part 16.

[0037] The second heat exchanger core 60 is characterized in that the condensing channel therein is completely not connected with the kettle liquid in the liquid storage container, and the second evaporation channel 37 therein is completely connected with the kettle liquid in the liquid storage container at the top and the bottom. The sealing of the condensing channel can be realized by applying a sealing strip on the top, bottom and side; while the sealing of the second evaporation channel 37 is realized by applying a sealing strip only on the side. Such design makes the first plate-fin condensing evaporator 30' equivalent to a "single-pass" heat exchanger, and the second heat exchanger core 60 equivalent to a "immersion" heat exchanger. Therefore, the advantages of two different heat exchange modes are integrated in one combined heat exchanger.

[0038] On the side, preferably but not necessarily on the same side, the nitrogen-rich vapor distribution part 28 and the nitrogen-rich liquid outlet part 29 are arranged across the first plate-fin condensing evaporator 30' and the second heat exchanger core 60. Among them, the nitrogen-rich vapor distribution part 28 and the nitrogen-rich vapor inlet 26 are arranged on the upper edge of the side, and the nitrogen-rich liquid outlet part 29 and the nitrogen-rich liquid outlet 27 are arranged on the lower edge of the side. Since the gas to be condensed in the closed first plate-fin condensing evaporator 30' and the semi-open second heat exchanger core 60 is nitrogen-rich vapor, they can share a nitrogen-rich vapor distribution part 28 and a nitrogen-rich liquid outlet part 29, which reduces the manufacturing difficulty and cost, and embodies the synergistic advantage of combining different types of condensing evaporator equipment.

[0039] Figure 4 is a side view cross-sectional view of the combined condensing evaporator in Example 1. The heat exchanger core is preferably of a plate-fin structure. The plate-fin structure has the advantages of compact structure, large heat exchange area and small pressure drop. It is composed of a group of parallel plates, and corrugated or wavy structures or other intermediate elements can be inserted between the plates to form fin-shaped heat exchange structures. A stack of plate blocks forms a stack of plane channels for different fluids to enter into heat exchange relationship. In the manufacturing process, the plate pieces, fin partitions and other exchanger components are stacked and extruded together, and then brazed together in a vacuum furnace at a temperature of 550-900°C.

[0040] Figure 4 In the middle, it can be seen that the nitrogen condensing channel 35, the first evaporation channel 36 and the second evaporation channel 37 are roughly parallelly distributed and substantially perpendicular to the horizontal direction.

[0041] The preferred embodiments in the specification are only the preferred embodiments of the utility model, and the above embodiments are only used to illustrate the technical scheme of the utility model and not to limit the utility model. Unless clearly indicated to the contrary, each aspect or embodiment defined herein can be combined with any other one or more aspects or one or more embodiments. In particular, any indicated preferred or advantageous features can be combined with any other indicated preferred or advantageous features. Any technical scheme that can be obtained by logical analysis, reasoning or limited experiments by those skilled in the art according to the concept of the utility model should be within the scope of the utility model.

Claims

1. A nitrogen generator employing a combined condensing evaporator, comprising: - providing a feed air stream, (1) a rectifier column for separating said feed air stream into a nitrogen-rich vapor and an oxygen-rich liquid air and means for feeding said feed air stream to said rectifier column; (2) a main heat exchanger for interacting with a rectifier column generated stream to cool the feed air stream; (3) a first plate-fin condensing evaporator capable of airifying said oxygen-rich liquid air by indirect heat exchange with the total nitrogen-rich vapor to be condensed to form a nitrogen-rich liquid and a first gas-liquid mixture stream; (4) a second gas-liquid separator receiving said first gas-liquid mixture stream and separating into a second gas-liquid separator vapor phase at the top and a second gas-liquid separator liquid phase at the bottom; (5) means for feeding said second gas-liquid separator liquid phase to a second condensing evaporator; (6) means for extracting said second gas-liquid separator vapor phase and feeding it to a recycle compressor; (7) a second condensing evaporator comprising a second heat exchanger core immersed in said second gas-liquid separator liquid phase capable of forming a nitrogen-rich liquid and an oxygen-rich exhaust stream by indirect heat exchange with said total nitrogen-rich vapor to be condensed; (8) means for extracting said oxygen-rich exhaust stream and feeding it to said main heat exchanger; (9) said recycle compressor for compressing said second gas-liquid separator vapor phase; (10) means for passing said compressed second gas-liquid separator vapor phase to said rectifier column; and (11) means for feeding a portion of said nitrogen-rich vapor to said main heat exchanger for warming; characterized in that said first plate-fin condensing evaporator and said second condensing evaporator are integrated together and placed in the same housing. Said nitrogen generator further comprises expansion means and means for feeding said oxygen-rich exhaust stream after being partially warmed in the main heat exchanger to said expansion means.

2. The nitrogen generator employing a combined condenser evaporator as claimed in claim 1 wherein, Said nitrogen generator further comprises a first gas-liquid separator receiving said oxygen-rich liquid air and separating into a first gas-liquid separator vapor phase at the top and a first gas-liquid separator liquid phase at the bottom, and means for feeding said first gas-liquid separator liquid phase to a first plate-fin condensing evaporator.

3. The nitrogen generator employing a combined condenser evaporator as claimed in claim 2 wherein, Said integrated first plate-fin condensing evaporator and said second condensing evaporator are separated by a partition; said first plate-fin condensing evaporator is a closed structure and said second condensing evaporator is a semi-open structure.

4. A nitrogen generator employing a combined condensing evaporator according to any one of claims 1-3, characterized in that, Said integrated first plate-fin condensing evaporator and said second condensing evaporator share a nitrogen-rich vapor distribution section and a nitrogen-rich liquid outlet section, said total nitrogen-rich vapor to be condensed is condensed from top to bottom in the gas distribution section and exits from the nitrogen-rich liquid outlet section.

5. The nitrogen generator employing a combined condenser evaporator as claimed in claim 4 wherein, Said first plate-fin condensing evaporator has a first liquid distribution section at the top and a first gas-liquid mixture outlet section at the bottom, said first gas-liquid separator liquid phase and said nitrogen-rich vapor have the same flow direction.

6. The nitrogen generator employing a combined condenser evaporator as claimed in claim 3 wherein, ​

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