Low energy consumption single column nitrogen generation device with low temperature supercharging turbine expander and method

Abstract

The application discloses a low-energy-consumption single-tower nitrogen production device with a low-temperature supercharged turbine expander and a method thereof. The device comprises an air compressor, an air pre-cooling unit, a molecular sieve purification device, a main heat exchanger, a rectifying tower, a multi-channel condensation evaporator, a low-temperature supercharged turbine expander and a super-cooler. In the application, the low-temperature supercharged turbine expander is used, the pressurized gas is a low-temperature gas, and the pressurization ratio is greatly improved. Compared with a single-tower backflow expansion nitrogen production device, the extraction rate is increased by about 15%, and the energy consumption is reduced by about 20%. Compared with a double-tower nitrogen production device with a liquid nitrogen pump, only one rectifying tower is needed, and a liquid nitrogen pump is not needed, so that the demand for moving equipment is reduced, the failure rate is lowered, the manufacturing cost is reduced, the land area occupied by the cold box is reduced, and the extraction rate is comparable to that of the double-tower nitrogen production device with the liquid nitrogen pump.

Description

TECHNICAL FIELD

[0001] The application relates to a low-energy-consumption single-tower nitrogen production device with a low-temperature supercharging turboexpander and a method thereof, and belongs to the technical field of air separation devices. BACKGROUND

[0002] China has attached great importance to energy saving and consumption reduction work, and has successively introduced a number of energy saving and consumption reduction policies and measures, and has continuously strengthened the system, mechanism, legality and capacity building of energy saving and emission reduction, and has effectively promoted energy saving and consumption reduction in key fields such as industry, building and transportation, and has promoted China's energy development into a new stage through the ways of accelerating industrial adjustment, eliminating backward production capacity, optimizing energy structure and promoting the construction of an energy-saving society. Therefore, energy consumption indicators are increasingly valued.

[0003] At present, common pure nitrogen equipment on the market includes single-tower nitrogen production and double-tower nitrogen production. Although the single-tower nitrogen production has a simple structure, the extraction rate is low, the product unit consumption is high, and it is not suitable for large-scale nitrogen demand. The double-tower nitrogen production can produce normal pressure or low pressure nitrogen, the device has a high extraction rate, and the energy consumption is lower than that of the single-tower nitrogen production, but the product pressure is low, and the nitrogen product needs to be compressed by a nitrogen compressor to meet the requirements of users on the nitrogen pressure. SUMMARY

[0004] In view of the deficiencies of the prior art described above, the application provides a low-energy-consumption single-tower nitrogen production device with a low-temperature supercharging turboexpander and a method thereof. In the case of reducing the demand for moving equipment, an extraction rate comparable to that of a double-tower nitrogen production device with a liquid nitrogen pump is obtained.

[0005] To achieve the above-mentioned application purposes, the application provides the following technical solutions:

[0006] A low-energy-consumption single-tower nitrogen production device with a low-temperature supercharging turboexpander comprises an air compressor, an air pre-cooling unit, a molecular sieve purification device, a main heat exchanger, a rectifying tower, a multi-channel condenser evaporator and a low-temperature supercharging turboexpander.

[0007] The air compressor, the air pre-cooling unit, the molecular sieve purification device, the main heat exchanger and the rectifying tower are sequentially connected through pipelines, the upper end of the rectifying tower is connected with the multi-channel condenser evaporator through a pipeline, the upper end outlet of the multi-channel condenser evaporator is connected with the inlet of the supercharging end of the low-temperature supercharging turboexpander, and the outlet of the supercharging end of the low-temperature supercharging turboexpander is connected back to the bottom of the rectifying tower.

[0008] The single-tower nitrogen production device further comprises a supercooler, and the supercooler is connected with the multi-channel condenser evaporator and the low-temperature supercharging turboexpander through pipelines.

[0009] The molecular sieve purification device comprises at least two groups of molecular sieve purifiers, and the at least two groups of molecular sieve purifiers can work alternately.

[0010] The single-tower nitrogen production device further comprises an electric heater, which is connected with the at least two groups of molecular sieve purifiers respectively.

[0011] As another aspect of the application, a process for producing nitrogen by using the device is also provided, and the specific steps are as follows:

[0012] After the large-particle impurities in the air are filtered, the air is sent to an air compressor, and the air compressor pressurizes the air and sends it to an air pre-cooling unit; the pre-cooled air enters a molecular sieve purification device to adsorb water, CO2, C2H2 and other harmful impurities in the air; the air further purified by the molecular sieve purification device enters a main heat exchanger, is cooled by return flow gas and then directly enters a rectification tower for rectification; high-purity nitrogen is obtained at the top of the rectification tower, and the high-purity nitrogen is divided into two paths, one of which is reheated by the main heat exchanger and then sent to a customer end as product nitrogen, and the other of which enters a multi-channel condenser evaporator, and liquid nitrogen obtained by condensing and liquefying is re-entered into the rectification tower as reflux liquid; part of liquid air is extracted from the middle and lower parts of the rectification tower, throttled by a throttle valve and then enters the multi-channel condenser evaporator as a cold source to exchange heat with the nitrogen at the top of the tower; the low-temperature air vaporized enters a pressurizing end of a low-temperature booster turbine expander to be pressurized, and the low-temperature air pressurized is cooled by the main heat exchanger and then re-enters the bottom of the rectification tower to participate in rectification.

[0013] The single-tower nitrogen production device further comprises a super-cooler; during rectification, liquid air is extracted from the bottom of the rectification tower, is super-cooled by the super-cooler, is throttled by a throttle valve and then enters a multi-channel condenser evaporator as a cold source to liquefy nitrogen gas. The oxygen-enriched gas vaporized enters an expansion end of a low-temperature booster turbine expander in sequence through the super-cooler and the main heat exchanger, and the low-temperature expanded oxygen-enriched gas re-enters the main heat exchanger and is vented.

[0014] The molecular sieve purification device comprises at least two groups of molecular sieve purifiers, which can work alternately; the single-tower nitrogen production device further comprises an electric heater, which is connected with the at least two groups of molecular sieve purifiers respectively; the low-temperature expanded oxygen-enriched gas re-enters the main heat exchanger and is divided into two paths, one of which is vented to the outside, and the other of which enters the electric heater to be heated and then enters the at least two groups of molecular sieve purifiers to be reactivated.

[0015] Compared with the prior art, the application has the following beneficial effects:

[0016] 1. Currently, domestic air separation manufacturers with design and manufacturing capabilities all use ambient temperature gas pressurization or blower braking for the booster end of the expander. This invention uses a low-temperature booster turbine expander, with the booster gas being a low-temperature gas (~-150 to -190℃), which greatly improves the pressure ratio. The structure and working principle of the low-temperature booster turbine expander have been described in the applicant's prior patent application (application number CN2021101323325), and will not be repeated here.

[0017] 2. Compared with nitrogen generation equipment with single-tower reflux expansion, the extraction rate is increased by about 15% and energy consumption is reduced by about 20%.

[0018] 3. Compared with a dual-tower nitrogen generator with a liquid nitrogen pump, only one distillation tower is needed, eliminating the need for a liquid nitrogen pump, reducing the demand for moving equipment, lowering the failure rate, reducing manufacturing costs, and reducing the footprint of the cold box; while the extraction rate is comparable to that of a dual-tower nitrogen generator with a liquid nitrogen pump. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the present invention; Detailed Implementation

[0021] The technical solutions in specific embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figure 1 As shown, the nitrogen generation device in this embodiment includes an air compressor (AC), an air precooling unit (RU), a molecular sieve purification device, a main heat exchanger (E1), a distillation column (C1), a multi-channel condenser-evaporator (K1), a low-temperature booster turbine expander (ET), a subcooler (E2), and an electric heater (EH).

[0023] The air compressor (AC), the air pre-cooling unit (RU), the molecular sieve purifying device, the main heat exchanger (E1) and the rectifying tower (C1) are sequentially connected by pipelines, the upper end of the rectifying tower (C1) is connected with the multi-channel condensing evaporator (K1), the upper end outlet of the multi-channel condensing evaporator (K1) is connected with the pressurizing end inlet of the low-temperature pressurized turbo expander (ET), and the pressurizing end outlet of the low-temperature pressurized turbo expander (ET) is connected back to the bottom of the rectifying tower (C1). The side outlet of the multi-channel condensing evaporator (K1) is connected with the super-cooler (E2), the outlet of the super-cooler (E2) is connected with the expansion end inlet of the low-temperature pressurized turbo expander (ET), and the expansion end outlet of the low-temperature pressurized turbo expander (ET) is connected to the main heat exchanger (E1).

[0024] The molecular sieve purifying device comprises two groups of molecular sieve purifiers (MS1, MS2) working alternately, and the electric heater (EH) is connected with the two groups of molecular sieve purifiers (MS1, MS2) by pipelines respectively.

[0025] After the large-particle impurities in the air are filtered, the air is sent to the air compressor (AC), the air compressor (AC) pressurizes the air and sends the air to the air pre-cooling unit (RU). The pre-cooled air enters the molecular sieve purifiers (MS1, MS2) to adsorb the moisture, CO2, C2H2 and other harmful impurities in the air. The air further purified by the molecular sieve purifiers (MS1, MS2) enters the main heat exchanger (E1), is cooled by the return flow of air and directly enters the rectifying tower (C1) for rectification. High-purity nitrogen is obtained at the top of the rectifying tower (C1), the high-purity nitrogen is divided into two paths, one path is reheated by the main heat exchanger (E1) and sent to the customer end as product nitrogen, and the other path enters the multi-channel condensing evaporator (K1), is condensed and liquefied to obtain liquid nitrogen which reenters the upper part of the rectifying tower (C1) as a reflux liquid. Part of the liquid air is extracted from the middle and lower parts of the rectifying tower (C1), throttled by the throttle valve (V1) and enters the multi-channel condensing evaporator (K1) as a cold source to exchange heat with the nitrogen at the top of the tower. The low-temperature air vaporized enters the pressurizing end of the low-temperature pressurized turbo expander (ET) for pressurization, the pressurized low-temperature air is cooled by the main heat exchanger (E1) and then reenters the bottom of the rectifying tower (C1) to participate in rectification. During the rectification process, the liquid air is extracted from the bottom of the rectifying tower (C1), is super-cooled by the super-cooler (E2), is throttled by the throttle valve (V2) and enters the multi-channel condensing evaporator (K1) as a cold source to liquefy the nitrogen. The oxygen-enriched gas vaporized in sequence passes through the super-cooler (E2) and the main heat exchanger (E1) and then enters the expansion end of the low-temperature pressurized turbo expander (ET), the low-temperature expanded oxygen-enriched gas reenters the main heat exchanger (E1) and is divided into two paths, one path is vented to the outside, and the other path is heated by the electric heater (EH) and then enters the molecular sieve purifiers (MS1, MS2) to activate the molecular sieve purifiers (MS1, MS2).

[0026] The low-energy-consumption single-tower nitrogen production device with low-temperature supercharging turbine expander and the method provided by the application are described in detail above, and the structure and working principle of the application are described by using specific examples. The above examples are only used to help understand the method and core idea of the application. It should be pointed out that, for ordinary skilled persons in the technical field, some improvements and modifications can be made to the application without departing from the principle of the application, and these improvements and modifications also fall within the protection scope of the claims of the application.

Claims

1. A low-energy-consumption single-tower nitrogen production device with a cryogenic turboexpander, characterized in that: Includes air compressors, air precooling units, molecular sieve purification devices, main heat exchangers, distillation columns, multi-channel condenser-evaporators, and low-temperature booster turbine expanders; The air compressor, air precooling unit, molecular sieve purification device, main heat exchanger, and distillation column are connected sequentially via pipelines. The upper end of the distillation column is connected to the pipeline of the multi-channel condenser-evaporator. The upper outlet of the multi-channel condenser-evaporator is connected to the inlet of the pressure boosting end of the cryogenic turboexpander. The outlet of the pressure boosting end of the cryogenic turboexpander is connected back to the bottom of the distillation column. A portion of liquid air is extracted from the middle and lower part of the distillation column, throttled, and then enters the multi-channel condenser-evaporator as a cold source to exchange heat with the nitrogen at the top of the column. The vaporized cryogenic air enters the pressure boosting end of the cryogenic turboexpander for pressurization. After being cooled by the main heat exchanger, the pressurized cryogenic air enters the bottom of the distillation column to participate in distillation.

2. The single-tower nitrogen generator according to claim 1, characterized in that: The single-tower nitrogen generator also includes a subcooler, which is connected to the multi-channel condenser-evaporator and the low-temperature booster turbine expander pipeline.

3. A single-tower nitrogen generator according to claim 1 or 2, characterized in that: The molecular sieve purification device includes at least two sets of molecular sieve purifiers, which can work alternately.

4. A single-tower nitrogen generator according to claim 3, characterized in that: The single-tower nitrogen generator also includes an electric heater, which is connected by pipeline to the at least two sets of molecular sieve purifiers.

5. A method for producing nitrogen gas, characterized in that... The single-tower nitrogen generator according to any one of claims 1-4 is characterized in that: large particulate impurities in the air are filtered and then introduced into an air compressor, which pressurizes the air and sends it to an air precooling unit; the precooled air enters a molecular sieve purification device to adsorb harmful impurities in the air; the air further purified by the molecular sieve purification device enters the main heat exchanger, is cooled by reflux gas, and then directly enters a distillation column for distillation; high-purity nitrogen is obtained at the top of the distillation column, and the high-purity nitrogen is divided into two streams. One stream of nitrogen is reheated in the main heat exchanger and sent to the customer as product nitrogen. The other stream enters the multi-channel condenser-evaporator, where it is condensed and liquefied to obtain liquid nitrogen that re-enters the upper part of the distillation column as reflux liquid. A portion of liquid air is extracted from the middle and lower parts of the distillation column, throttled by a throttling valve, and then enters the multi-channel condenser-evaporator as a cold source to exchange heat with the nitrogen at the top of the column. The vaporized low-temperature air enters the pressurization end of the low-temperature booster turbine expander for pressurization. After being cooled by the main heat exchanger, the pressurized low-temperature air re-enters the bottom of the distillation column to participate in distillation.

6. The method according to claim 5, characterized in that: The single-tower nitrogen generation device also includes a subcooler. During the distillation process, liquid air is drawn from the bottom of the distillation column, subcooled by the subcooler, and then throttled by the throttling valve before entering the multi-channel condenser-evaporator, which also serves as a cold source for liquefied nitrogen. The vaporized oxygen-enriched gas passes through the subcooler and the main heat exchanger in sequence before entering the expansion end of the cryogenic booster turbine expander. The oxygen-enriched gas after cryogenic expansion re-enters the main heat exchanger and is then vented.

7. The method according to claim 6, characterized in that: The molecular sieve purification device includes at least two sets of molecular sieve purifiers, which can work alternately.

8. The method according to claim 7, characterized in that: The single-tower nitrogen generator also includes an electric heater, which is connected by pipeline to the at least two sets of molecular sieve purifiers.

9. The method according to claim 8, characterized in that: After the oxygen-enriched gas expands at low temperature, it re-enters the main heat exchanger and splits into two paths: one path is vented to the outside, and the other path enters the electric heater to be heated before entering the at least two sets of molecular sieve purifiers for regeneration and activation.

10. The method according to any one of claims 5-9, characterized in that: The harmful impurities include moisture, CO2, and C2H2.

Images