System for preparing nitrogen by deep freezing method

Abstract

The utility model belongs to the technical field of air separation, and particularly relates to a deep freezing method nitrogen making system. Comprising a filter, the filter is connected with a compressor, the compressor is connected with a high-purity nitrogen preparation unit and an instrument compressed air preparation unit through a compressed air conveying pipeline and an instrument compressed air pipeline, and the high-purity nitrogen preparation unit comprises a molecular sieve purifier, an expansion machine and a rectifying tower which are sequentially connected. The instrument compressed air preparation unit comprises an alumina gel dryer, a dryer gas outlet pipeline is arranged at the top of the alumina gel dryer, a dryer discharge pipeline is arranged at the bottom of the alumina gel dryer, an oxygen-enriched waste gas pipeline is arranged in the middle of the rectifying tower, and the oxygen-enriched waste gas pipeline is respectively connected with the alumina gel dryer and the molecular sieve purifier through a regeneration gas treatment mechanism. According to the utility model, the oxygen-enriched waste gas generated in the high-purity nitrogen preparation unit is further utilized as the regeneration gas of the dryer and the purifier, so that the consumption of compressed air can be reduced by 8-12%, and meanwhile, the regeneration effect of the dryer can be improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of air separation, and in particular relates to a nitrogen production system using a deep freezing method. Background Art

[0002] Compressed air is usually used to prepare high-purity nitrogen and compressed air for instruments. High-purity nitrogen is usually produced by deep freezing, which is a mature industrial gas separation technology. The process of separating air by deep freezing is as follows: compressed air enters the expander, and the temperature is reduced through the adiabatic expansion process to liquefy. After the air is liquefied, it is distilled and separated by using the different boiling points of oxygen and nitrogen. Since the boiling point of nitrogen (-195.8℃) is lower than that of oxygen (-183.0℃), nitrogen evaporates before oxygen and is collected from the top of the tower as the main product. Liquid nitrogen can be collected from the bottom of the tower as a by-product. The oxygen-rich waste gas that cannot be completely separated during the distillation process, including part of the oxygen and nitrogen, is directly discharged.

[0003] In the prior art, compressed air is usually passed through a molecular sieve purification device to remove impurities and water, and a portion of it continues to enter a nitrogen production device for separation and purification to produce high-purity nitrogen, while the other portion is directly used as compressed air for instruments. The compressed air entering the nitrogen production device requires a dew point less than -65°C, while compressed air for instruments usually only needs a dew point less than -40°C to meet the demand. If only compressed air for instruments is prepared and purified using a molecular sieve purification device, the cost is too high, resulting in waste. In addition, the filler in the purification device absorbs moisture in the air and needs to be regenerated. Usually, compressed air from the compressor outlet is used for regeneration, but the moisture content in the compressed air is high, the analysis effect is poor, and the compressor consumes a lot of electricity to prepare compressed air, resulting in an increase in production costs. While the nitrogen production device produces nitrogen, it also separates oxygen-rich waste gas, which is usually directly discharged, resulting in a waste of resources. Utility Model Content

[0004] The utility model provides a deep freezing method nitrogen making system to solve the problems that oxygen-rich waste gas cannot be reasonably utilized and the production cost of compressed air for instruments is high.

[0005] In order to solve the above problems, the technical solution of the utility model is:

[0006] The deep freezing method nitrogen making system described in the utility model comprises a filter, the filter is connected to a compressor, the compressor is connected to a high-purity nitrogen preparation unit and an instrument compressed air preparation unit through a compressed gas transport pipeline and an instrument compressed gas pipeline respectively, the high-purity nitrogen preparation unit comprises a molecular sieve purifier, an expander and a distillation tower connected in sequence, the instrument compressed air preparation unit comprises an aluminum gel dryer, a dryer air outlet pipeline is provided at the top of the aluminum gel dryer, and a dryer discharge pipeline is provided at the bottom, an oxygen-enriched waste gas pipeline is provided in the middle of the distillation tower, a high-purity nitrogen pipeline is provided at the top, and a liquid nitrogen pipeline is provided at the bottom, and the oxygen-enriched waste gas pipeline is respectively connected to the aluminum gel dryer and the molecular sieve purifier through a regeneration gas processing mechanism.

[0007] The utility model sets up a separate production line for compressed gas used for instruments, uses an aluminum gel dryer for processing, thereby extending the service life of the molecular sieve and reducing the cost.

[0008] Furthermore, the regeneration gas processing mechanism includes a blower, which is connected to the heating furnace after merging with the oxygen-rich exhaust gas pipeline through a pipeline. The heating furnace is connected to the aluminum gel dryer and the molecular sieve purifier through the dryer regeneration gas transport pipeline and the molecular sieve regeneration gas transport pipeline respectively.

[0009] The utility model further utilizes the oxygen-rich waste gas generated in the high-purity nitrogen preparation unit as the regeneration gas for the dryer and the purifier, and does not use compressed gas as the regeneration gas. The energy consumption of the compressor to produce compressed gas is high, and the water content in the compressed gas is high, resulting in poor regeneration effect.

[0010] The oxygen-rich waste gas recycled by the utility model has a certain pressure and a low temperature, and has a better effect in the cold blowing process in the latter part of the regeneration process. In the thermal desorption stage, the air of the blower and the oxygen-rich waste gas are mixed and used to reduce the heating burden of the heating furnace. In the cold blowing stage, the oxygen-rich waste gas is used alone, which can achieve a better cold blowing effect and make the regeneration more thorough.

[0011] Furthermore, the diameter of the oxygen-enriched exhaust gas pipeline after being merged with the blower pipeline is smaller than the diameter of the oxygen-enriched exhaust gas pipeline and the blower pipeline before being merged.

[0012] After the oxygen-rich waste gas and the gas pipeline from the blower are merged, the pipe diameter is reduced, and the automatic pressurization function is realized, so that the regeneration gas pressure is further increased and the regeneration effect is improved.

[0013] Furthermore, the aluminum glue dryer is a first aluminum glue dryer and a second aluminum glue dryer in parallel. The first aluminum glue dryer and the second aluminum glue dryer are respectively provided with a first dryer air outlet pipeline and a second dryer air outlet pipeline.

[0014] During the regeneration process of the first aluminum glue dryer, the second aluminum glue dryer is switched to carry out the normal production process to ensure the uninterrupted production process.

[0015] Furthermore, the molecular sieve purifier is a first molecular sieve purifier and a second molecular sieve purifier in parallel.

[0016] Purifier discharge pipelines are provided at the bottom of the first molecular sieve purifier and the second molecular sieve purifier.

[0017] During the regeneration process of the first molecular sieve purifier, the second molecular sieve purifier is switched to carry out the normal production process to ensure that the production process is uninterrupted.

[0018] Furthermore, the air outlet of the compressor is connected to the air outlet of the filter through a pipeline, and the filter is back-flushed with pressurized gas, which has a better cleaning effect.

[0019] Working principle:

[0020] After the air passes through the filter to remove dust and mechanical impurities, it is compressed by a compressor and transported to the instrument compressed air preparation unit and high-purity nitrogen preparation unit through the instrument compressed air pipeline and the compressed air transport pipeline for further processing.

[0021] The compressed air in the compressed gas transport pipeline enters the first molecular sieve purifier to remove water, carbon dioxide and hydrocarbons, and then is cooled and liquefied by the expander and enters the distillation tower for distillation. The high-purity nitrogen separated at the top of the tower is transported to the user through the high-purity nitrogen pipeline. The small amount of by-product liquid nitrogen obtained at the bottom of the tower is transported through the liquid nitrogen pipeline, and the oxygen-rich waste gas obtained in the middle of the tower is transported through the oxygen-rich waste gas pipeline.

[0022] The compressed air in the compressed air pipeline for instruments enters the first aluminum glue dryer for drying and dehydration, and then is transported to the user through the first dryer outlet pipeline.

[0023] The oxygen-rich waste gas in the oxygen-rich waste gas pipeline is used as the regeneration gas of the first aluminum glue dryer. After the oxygen-rich waste gas is mixed with the air generated by the blower and enters the heating furnace for heating, it enters the first aluminum glue dryer through the dryer regeneration gas transport pipeline for thermal regeneration to desorb the water adsorbed by the aluminum glue. At this time, the heating system of the heating furnace is turned off and the blower is stopped, so that the low-temperature oxygen-rich waste gas directly enters the first aluminum glue dryer to cold-blow the desorbed water and discharge it from the dryer discharge pipeline at the bottom of the first aluminum glue dryer. During the regeneration process of the first aluminum glue dryer, the second aluminum glue dryer is switched to carry out the normal production process to ensure that the production process is uninterrupted.

[0024] The dryer regeneration gas transport pipeline is also provided with a molecular sieve regeneration gas transport pipeline, and the oxygen-rich waste gas is transported to the first molecular sieve purifier through the molecular sieve regeneration gas transport pipeline for use as the molecular sieve regeneration gas. The oxygen-rich waste gas regenerates the molecular sieve after passing through the heating furnace, and the desorbed impurity gas is discharged through the purifier discharge pipeline. During the regeneration process of the first molecular sieve purifier, the second molecular sieve purifier is switched to carry out the normal production process to ensure that the production process is uninterrupted. After the thermal desorption is completed, the heating system of the heating furnace is turned off, and the low-temperature oxygen-rich waste gas is used for cold blowing.

[0025] If the filter is clogged after long-term use, a branch line is opened through the compressed gas transport pipeline to connect the outlet end of the filter, and the filter is back-blown with compressed air. The impurities back-blown out are discharged through the bottom of the filter. Back-blowing the filter with pressurized compressed gas has a better cleaning effect.

[0026] The beneficial effects of the utility model are as follows:

[0027] 1) The utility model sets up a separate production line for compressed gas used for instruments and uses an aluminum gel dryer for processing, thereby extending the service life of the molecular sieve and reducing the cost.

[0028] 2) The utility model further utilizes the oxygen-rich waste gas generated in the high-purity nitrogen preparation unit as the regeneration gas for the dryer and purifier, which can reduce the consumption of compressed air by 8-12%, and at the same time improve the regeneration effect of the dryer and reduce the consumption of the heating furnace. Compressed air is no longer used as regeneration gas. The energy consumption of the compressor to produce compressed air is high, and the water content in the compressed air is high, resulting in poor regeneration effect.

[0029] 3) Oxygen-rich waste gas itself has a certain pressure, does not contain water, has a dew point below -65°C, and has a low temperature, so it has a better effect in the cold blowing process in the latter part of the regeneration process. In the thermal desorption stage, the air from the blower and the oxygen-rich waste gas are mixed to reduce the heating burden of the heating furnace. In the cold blowing stage, the oxygen-rich waste gas is used alone to achieve a better cold blowing effect, making the regeneration more thorough.

[0030] 4) The utility model uses pressurized compressed gas to back-blow the filter, which has a better cleaning effect.

[0031] 5) After the oxygen-rich exhaust gas of the utility model is combined with the gas pipeline from the blower, the pipe diameter is reduced, and the function of automatic pressurization is realized, so that the pressure of the regenerated gas is further increased, thereby improving the regeneration effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0033] Figure 1 This is a schematic diagram of the structure of the deep freezing method nitrogen production system of the utility model;

[0034] In the figure: 1. filter; 2. compressor; 3. first molecular sieve purifier; 4. second molecular sieve purifier; 5. expander; 6. distillation tower; 7. high-purity nitrogen pipeline; 8. oxygen-enriched waste gas pipeline; 9. liquid nitrogen pipeline; 10. blower; 11. heating furnace; 12. compressed gas pipeline for instruments; 13. first aluminum gel dryer; 14. second aluminum gel dryer; 15. dryer regeneration gas transport pipeline; 16. first dryer outlet pipeline; 17. second dryer outlet pipeline; 18. dryer discharge pipeline; 19. purifier discharge pipeline; 20. molecular sieve regeneration gas transport pipeline; 21. compressed gas transport pipeline. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below in conjunction with the embodiments.

[0036] Example 1

[0037] like Figure 1 As shown, a deep freezing method nitrogen production system includes a filter 1, the filter 1 is connected to a compressor 2, the compressor 2 is connected to a high-purity nitrogen preparation unit and an instrument compressed air preparation unit through a compressed gas transport pipeline 21 and an instrument compressed gas pipeline 12, respectively, the high-purity nitrogen preparation unit includes a molecular sieve purifier, an expander 5 and a distillation tower 6 connected in sequence, the instrument compressed air preparation unit includes an aluminum gel dryer, a dryer gas outlet pipeline is provided at the top of the aluminum gel dryer, and a dryer discharge pipeline 18 is provided at the bottom, an oxygen-enriched waste gas pipeline 8 is provided in the middle of the distillation tower 6, a high-purity nitrogen pipeline 7 is provided at the top, and a liquid nitrogen pipeline 9 is provided at the bottom, and the oxygen-enriched waste gas pipeline 8 is connected to the aluminum gel dryer and the molecular sieve purifier through a regeneration gas processing mechanism.

[0038] In this embodiment, a separate production line is set up for compressed gas for instruments, and an aluminum gel dryer is used for processing, thereby extending the service life of the molecular sieve and reducing the cost.

[0039] It can be understood that the regeneration gas processing mechanism includes a blower 10, which is connected to a heating furnace 11 after merging with an oxygen-rich exhaust gas pipeline 8 through a pipeline. The heating furnace 11 is connected to an aluminum gel dryer and a molecular sieve purifier through a dryer regeneration gas transport pipeline 15 and a molecular sieve regeneration gas transport pipeline 20, respectively.

[0040] In this embodiment, the oxygen-rich waste gas generated in the high-purity nitrogen preparation unit is further utilized as the regeneration gas for the dryer and the purifier, and compressed gas is not used as the regeneration gas. The energy consumption of the compressor 2 in producing the compressed gas is high, and the water content in the compressed gas is high, resulting in poor regeneration effect.

[0041] The oxygen-rich waste gas recycled in this embodiment has a certain pressure and a relatively low temperature, and has a better effect in the cold blowing process in the latter part of the regeneration process. In the thermal desorption stage, the air of the blower 10 and the oxygen-rich waste gas are mixed and used to reduce the temperature rise burden of the heating furnace 11. In the cold blowing stage, the oxygen-rich waste gas is used alone, which can achieve a better cold blowing effect and make the regeneration more thorough.

[0042] It can be understood that the diameter of the oxygen-enriched exhaust gas pipeline 8 after being merged with the pipeline of the blower 10 is smaller than the diameter of the oxygen-enriched exhaust gas pipeline 8 and the pipeline of the blower 10 before being merged.

[0043] In this embodiment, after the oxygen-rich exhaust gas and the gas pipeline from the blower 10 are combined, the pipe diameter is reduced, and the automatic pressurization function is realized, so that the regeneration gas pressure is further increased, and the regeneration effect is improved.

[0044] It can be understood that the aluminum glue dryer is a parallel first aluminum glue dryer 13 and a second aluminum glue dryer 14. The first aluminum glue dryer 13 and the second aluminum glue dryer 14 are respectively provided with a first dryer air outlet pipeline 16 and a second dryer air outlet pipeline 17.

[0045] During the regeneration process of the first aluminum gel dryer 13, the second aluminum gel dryer 14 is switched to perform a normal production process to ensure that the production process is uninterrupted.

[0046] It can be understood that the molecular sieve purifier is a first molecular sieve purifier 3 and a second molecular sieve purifier 4 in parallel. A purifier discharge pipeline 19 is provided at the bottom of the first molecular sieve purifier 3 and the second molecular sieve purifier 4.

[0047] During the regeneration process of the first molecular sieve purifier 3, the second molecular sieve purifier 4 is switched to carry out the normal production process to ensure that the production process is uninterrupted.

[0048] It can be understood that the air outlet of the compressor 2 is connected to the air outlet of the filter 1 through a pipeline. The filter 1 is back-flushed with pressurized gas to achieve a better cleaning effect.

[0049] Working principle:

[0050] After the air passes through the filter 1 to remove dust and mechanical impurities, it is compressed by the compressor 2 to produce compressed air, which is transported to the instrument compressed air preparation unit and the high-purity nitrogen preparation unit through the instrument compressed air pipeline 12 and the compressed air transport pipeline 21 for further processing.

[0051] The compressed air in the compressed gas transport pipeline 21 enters the first molecular sieve purifier 3 to remove water, carbon dioxide and hydrocarbons, and then is cooled and liquefied by the expander 5 and enters the distillation tower 6 for distillation. The high-purity nitrogen separated at the top of the tower is transported to the user through the high-purity nitrogen pipeline 7. The small amount of by-product liquid nitrogen obtained at the bottom of the tower is transported through the liquid nitrogen pipeline 9, and the oxygen-rich waste gas obtained in the middle of the tower is transported through the oxygen-rich waste gas pipeline 8.

[0052] The compressed air in the compressed air pipeline 12 for instruments enters the first aluminum glue dryer 13 for drying and dehydration, and then is transported to the user through the first dryer outlet pipeline 16 for use.

[0053] The oxygen-rich waste gas in the oxygen-rich waste gas pipeline 8 is used as the regeneration gas of the first aluminum gel dryer 13. After the oxygen-rich waste gas is mixed with the air generated by the blower 10, it enters the heating furnace 11 for heating, and then enters the first aluminum gel dryer 13 through the dryer regeneration gas transport pipeline 15 for thermal regeneration to desorb the water adsorbed by the aluminum gel. At this time, the heating system of the heating furnace 11 is turned off, and the blower 10 is stopped, so that the low-temperature oxygen-rich waste gas directly enters the first aluminum gel dryer 13 to cold-blow the desorbed water and discharge it from the dryer discharge pipeline 18 at the bottom of the first aluminum gel dryer 13. During the regeneration process of the first aluminum gel dryer 13, the second aluminum gel dryer 14 is switched to carry out the normal production process to ensure that the production process is uninterrupted.

[0054] The dryer regeneration gas transport pipeline 15 is also provided with a molecular sieve regeneration gas transport pipeline 20, and the oxygen-rich waste gas is transported to the first molecular sieve purifier 3 through the molecular sieve regeneration gas transport pipeline 20 for use as the molecular sieve regeneration gas. The oxygen-rich waste gas regenerates the molecular sieve after passing through the heating furnace 11, and the desorbed impurity gas is discharged through the purifier discharge pipeline 19. During the regeneration process of the first molecular sieve purifier 3, the second molecular sieve purifier 4 is switched to carry out the normal production process to ensure that the production process is uninterrupted. After the thermal desorption is completed, the heating system of the heating furnace 11 is turned off, and the low-temperature oxygen-rich waste gas is used for cold blowing.

[0055] After long-term use, the filter 1 is clogged. A branch line is opened through the compressed gas transport pipeline 21 to connect the outlet end of the filter 1, and the filter 1 is back-blown with compressed air. The impurities back-blown are discharged through the bottom of the filter 1. Back-blowing the filter with pressurized compressed gas has a better cleaning effect.

Claims

1. A deep freezing nitrogen production system, characterized in that: The invention comprises a filter (1), wherein the filter (1) is connected to a compressor (2), and the compressor (2) is connected to a high-purity nitrogen preparation unit and an instrument compressed air preparation unit through a compressed gas transport pipeline (21) and an instrument compressed gas pipeline (12), respectively. The high-purity nitrogen preparation unit comprises a molecular sieve purifier, an expander (5) and a distillation tower (6) which are connected in sequence, and the instrument compressed air preparation unit comprises an aluminum gel dryer, wherein a dryer gas outlet pipeline is provided at the top of the aluminum gel dryer, and a dryer discharge pipeline (18) is provided at the bottom. An oxygen-enriched waste gas pipeline (8) is provided in the middle of the distillation tower (6), a high-purity nitrogen pipeline (7) is provided at the top, and a liquid nitrogen pipeline (9) is provided at the bottom. The oxygen-enriched waste gas pipeline (8) is connected to the aluminum gel dryer and the molecular sieve purifier through a regeneration gas processing mechanism.

2. The deep freezing nitrogen production system according to claim 1, characterized in that: The regeneration gas processing mechanism comprises a blower (10), which is connected to a heating furnace (11) after merging with an oxygen-rich waste gas pipeline (8) through a pipeline. The heating furnace (11) is connected to an aluminum gel dryer and a molecular sieve purifier through a dryer regeneration gas transport pipeline (15) and a molecular sieve regeneration gas transport pipeline (20), respectively.

3. The deep freezing nitrogen production system according to claim 2, characterized in that: The diameter of the oxygen-enriched waste gas pipeline (8) after being merged with the pipeline of the blower (10) is smaller than the diameter of the oxygen-enriched waste gas pipeline (8) and the pipeline of the blower (10) before being merged.

4. The deep freezing nitrogen production system according to claim 1, characterized in that: The aluminum glue dryer is a first aluminum glue dryer (13) and a second aluminum glue dryer (14) arranged in parallel.

5. The deep freezing nitrogen production system according to claim 1, characterized in that: The molecular sieve purifier is a first molecular sieve purifier (3) and a second molecular sieve purifier (4) which are connected in parallel.

6. The deep freezing nitrogen production system according to claim 1, characterized in that: The air outlet end of the compressor (2) is connected to the air outlet end of the filter (1) through a pipeline.

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