Energy-saving nitrogen-making device and nitrogen-making method thereof

Abstract

The invention discloses an energy-saving nitrogen-making device and a nitrogen-making method thereof.The energy-saving nitrogen-making device comprises a gas compressor, a freezing dryer, a purifier and a cold box which are connected in sequence; a main heat exchanger, and a rectifying tower, a subcooler, a main condensation evaporator and an expansion machine which are connected with the main heat exchanger are arranged in the cold box; gas is introduced into the freezing dryer through the gas compressor, dried and cooled by the freezing dryer, purified by the purifier and then introduced into the cold box for nitrogen generation treatment, and gas led out from the upper end of the rectifying tower in the cold box is compressed by the gas compressor and then led out. The invention discloses an energy-saving nitrogen-making device, which reduces the rectification pressure, improves the rectification efficiency, and improves the extraction rate and the reliability of stable operation. And the single-time investment cost and the long-term maintenance cost are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of nitrogen production equipment, and in particular to an energy-saving nitrogen production device and a nitrogen production method thereof. Background Art

[0002] Nitrogen is an inert gas that is colorless, odorless and non-toxic. Because of this characteristic, it is often used as a protective gas in many industries, such as food, medical, electronics, etc. There are three types of nitrogen production: 1. Air separation cryogenic production; 2. Membrane separation production; 3. Pressure swing adsorption production. For large-scale factory gas use, air separation cryogenic nitrogen generators are generally selected.

[0003] Among the conventional nitrogen generator processes, the simplest and most commonly used is the single-tower reflux nitrogen production process. When a certain process is selected, the general extraction rate is determined. For the single-tower reflux nitrogen production process, the conventional extraction rate is about 51~55%. If you want to seek energy saving and consumption reduction in a given process, the conventional ideas are: One idea is to consider increasing the number of plates in the distillation tower to improve the extraction rate of the distillation tower. However, when the number of plates in the distillation tower increases to a certain number, the extraction rate of nitrogen will approach a fixed value infinitely. Moreover, as the number of plates in the distillation tower increases, the resistance value of the tower also increases, requiring higher pressure raw gas, increasing energy consumption; on the other hand, as the tower becomes taller, the tower's cold storage box will also become taller and larger, and the cost of sorting, manufacturing and transportation will also increase at the same time.

[0004] Another idea is to change the process type, such as replacing the single-tower reflux nitrogen production with a double-tower nitrogen production process with a pump. However, this brings another problem, that is, more dynamic and static equipment will be involved in the process, and the investment cost of the equipment will be greater. In addition, the overall floor space of the equipment will also increase, and the land cost of the manufacturer will increase. In addition, as the number of dynamic and static equipment increases, the maintenance cost of the equipment will also increase. More uncertainty and instability are also increasing.

[0005] Another way to improve the extraction rate without changing the process is to reduce the pressure of the product nitrogen. By reducing the operating pressure, the components with higher volatility in the mixture will evaporate more easily, and the components with lower volatility will be more easily condensed. The higher the condensation and evaporation efficiency, the better the separation effect. Reducing the pressure of the product nitrogen is the most direct and effective method. However, the disadvantage is that the pressure of nitrogen is the pressure required by the manufacturer. Once it is reduced, it will not meet the requirements of the process. Therefore, this solution is obviously even less feasible.

[0006] For the three main solutions to improve the extraction rate mentioned above, only the third solution can retain the original process and significantly increase the extraction rate. How can we improve the extraction rate while ensuring the pressure required by users? In the process of single-tower reflux nitrogen production, if you want to increase the pressure of nitrogen, there are only two conventional modes. First, use an expander with a booster end, and replace the commonly used expander with an expander with a booster. Its characteristic is that the equipment does not change much, and only a number of automatic and manual valves need to be added to the booster end. Relatively speaking, this solution is more economical. Second, add a nitrogen compressor at the outlet of the product nitrogen to directly increase the pressure of nitrogen. However, the energy consumption of the nitrogen compressor is very high, and a nitrogen compressor with good quality and high efficiency is also expensive. Choosing a high-efficiency and high-quality nitrogen compressor will require a higher equipment investment cost for the enterprise. This solution improves the extraction rate of cryogenic air separation nitrogen production and reduces energy consumption, while adding a new dynamic equipment nitrogen compressor, which brings in more energy consumption, and the energy consumption does not decrease but increases. Summary of the invention

[0007] The present invention overcomes the deficiencies of the prior art, provides an energy-saving nitrogen production device and a nitrogen production method thereof, reduces the distillation pressure, improves the distillation efficiency, improves the extraction rate and the reliability of stable operation; and reduces the single investment cost and long-term maintenance cost.

[0008] To achieve the above object, the technical solution adopted by the present invention is: an energy-saving nitrogen production device, comprising a gas compressor, a cold dryer, a purifier and a cold box connected in sequence; a main heat exchanger, a distillation tower, a subcooler, a main condenser evaporator and an expander connected to the main heat exchanger are arranged in the cold box; the gas is introduced into the cold dryer through the gas compressor, and after being dry-cooled by the cold dryer and purified by the purifier, it is introduced into the cold box for nitrogen production treatment, and the gas drawn out from the upper end of the distillation tower in the cold box is compressed by the gas compressor and then discharged.

[0009] In a preferred embodiment of the present invention, the secondary compressed gas from the gas compressor is introduced into a cold dryer, dried by the cold dryer, introduced into a purifier, purified by the purifier, introduced into a main heat exchanger in a cold box, and then introduced into a distillation tower.

[0010] In a preferred embodiment of the present invention, the gas drawn out from the upper end of the distillation tower is introduced into a gas compressor for three-stage compression and then discharged after heat exchange in a main heat exchanger.

[0011] In a preferred embodiment of the present invention, the air inlet end of the gas compressor is also connected to a filter, and the external gas is introduced into the gas compressor after being filtered by the filter.

[0012] In a preferred embodiment of the present invention, the liquid collecting area at the bottom of the distillation tower is connected to the inlet of the subcooling pipeline 1 of the subcooler, and the outlet of the subcooling pipeline 1 of the subcooler is connected to the condensing pipeline 1 of the main condensing evaporator. After condensation by the main condensing evaporator, it is returned to the subcooling pipeline 2 of the subcooler, and is introduced into the expander through the subcooling pipeline 2 and discharged, and fed back to the purifier.

[0013] In a preferred embodiment of the present invention, the gas branched out from the upper end of the distillation tower is introduced into the condensation pipeline 2 of the main condenser evaporator, and after being led out through the condensation pipeline 2, it returns to the interior of the distillation tower.

[0014] In a preferred embodiment of the present invention, the liquid collecting area of ​​the distillation tower is connected to the residual liquid evaporator. And / or, the main condenser evaporator is also connected to the residual liquid evaporator.

[0015] In a preferred embodiment of the present invention, the purifier includes adsorption cylinder 1 and adsorption cylinder 2, and the pipelines leading out of the cold dryer are respectively introduced into adsorption cylinder 1 and adsorption cylinder 2 through branches and valves, and the outlets of adsorption cylinder 1 and adsorption cylinder 2 are then introduced into the inlet of the distillation tower of the cold box through branches and valves.

[0016] In a preferred embodiment of the present invention, the purifier further comprises an electric heater, the inlet end of the electric heater is connected to the outlet of the expander of the cold box; the outlet end of the electric heater is respectively connected to the first adsorption cylinder and the second adsorption cylinder through a reflux pipeline and a reflux valve; the gas discharged from the expander is heated by the main heat exchanger and then heated by the electric heater before being introduced into the purifier; And / or, the gas compressor, purifier, expander, electric heater and main heat exchanger are connected to the silencer.

[0017] In a preferred embodiment of the present invention, a nitrogen production method of an energy-saving nitrogen production device comprises the following steps: Step S1, external gas is filtered through a filter and then introduced into a gas compressor; Step S2, the filtered external gas enters the first-stage air compressor of the gas compressor for primary compression; and then is introduced into the second-stage air compressor for secondary compression; Step S3, dry-cooling the gas after secondary compression through a cold dryer. Step S4, introducing the dry cooled gas into a purifier for purification; Step S5, introducing the purified gas into a cold box for nitrogen production; Step S6, the nitrogen discharged from the cold box is returned to the third-stage compressor of the gas compressor for compression before being discharged.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The energy-saving nitrogen production device disclosed in the present invention reduces the distillation pressure, improves the distillation efficiency, improves the extraction rate and the reliability of stable operation; and reduces the single investment cost and long-term maintenance cost.

[0019] 1. Reduce the distillation pressure, essentially improve the distillation efficiency and the extraction rate.

[0020] 2. On the basis of the original equipment layout area, no additional equipment floor space is required, which saves energy and reduces costs while maintaining the original land cost.

[0021] 3. Not only does it not require a nitrogen compressor, it can also meet the nitrogen production requirements. The single investment cost and long-term maintenance cost of the equipment are reduced.

[0022] 4. The pressure of the raw gas at the outlet of the air compressor is reduced, and the operating pressure level of the downstream supporting equipment is also reduced. The load and design pressure of the dynamic and static equipment are reduced, the wall thickness requirements of the equipment are reduced, and the investment in the equipment is also significantly reduced.

[0023] 5. When the outlet pressure of the air compressor is reduced, the pressure level of the supporting pipes, flanges and other equipment accessories at the rear end can be reduced, further saving costs.

[0024] 6. In terms of production safety, the higher the pressure during the operation of the equipment, the greater the possibility of leakage, and the secondary disasters will also be aggravated. When the pressure during the operation of the equipment is reduced, the reliability of the equipment will increase, and the safety will also be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0026] Figure 1 It is a structural schematic diagram of an energy-saving nitrogen production device in a preferred embodiment of the present invention; Figure 2 It is a structural schematic diagram of a cold dryer in an energy-saving nitrogen production device in a preferred embodiment of the present invention; Figure 3 It is a schematic diagram of the working process of three-stage compression of the air compressor in the preferred embodiment of the present invention; Figure 4 This is a comparison table of energy consumption between the energy-saving nitrogen generator in the preferred embodiment of the present invention and the typical nitrogen generator in the prior art; Among them, 1-filter, 2-gas compressor, 3-purifier, 31-electric heater, 32-adsorption cylinder 1, 33-adsorption cylinder 2, 34-instrument gas bearing gas system, 4-cold dryer, 5-cold box, 51-main heat exchanger, 52-main condenser evaporator, 53-distillation tower, 54-subcooler, 55-expander, 56-cooler, 6-residual liquid evaporator, 7-muffler, 8-exhaust pipeline. DETAILED DESCRIPTION

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances. Embodiment 1

[0029] like Figure 1 , Figure 2 As shown, an energy-saving nitrogen production device includes a gas compressor 2, a cold dryer 4, a purifier 3 and a cold box 5 connected in sequence; a main heat exchanger 51, a distillation tower 53, a subcooler 54, a main condenser evaporator 52 and an expander 55 are arranged in the cold box 5; wherein the main heat exchanger 51 is connected with the distillation tower 53, the subcooler 54, the main condenser evaporator 52 and the expander 55; the gas is introduced through the gas compressor 2, and after being dry-cooled by the cold dryer 4 and purified by the purifier 3, it is introduced into the cold box 5 for nitrogen production treatment, and the gas drawn out from the upper end of the distillation tower 53 in the cold box 5 is compressed by the gas compressor 2 and then led out. The cold dryer 4 adopts the cold dryer equipment in the prior art.

[0030] Specifically, the purifier 3 includes an adsorption cylinder 1 32 and an adsorption cylinder 2 33. The pipelines leading out of the cold dryer 4 are respectively introduced into the adsorption cylinder 1 32 and the adsorption cylinder 2 33 through branches and valves. The outlets of the adsorption cylinder 1 32 and the adsorption cylinder 2 33 are then introduced into the main heat exchanger 51 of the cold box 5 through branches and valves, and then introduced into the inlet of the distillation tower 53.

[0031] Specifically, a main heat exchanger 51, a distillation tower 53, a subcooler 54, a main condenser evaporator 52 and an expander 55 are arranged in the cold box 5; wherein the main heat exchanger 51 is connected with the distillation tower 53, the subcooler 54, the main condenser evaporator 52 and the expander 55.

[0032] Furthermore, the secondary compressed gas of the gas compressor 2 is introduced into the cold dryer 4, and after being cold-dried by the cold dryer 4, it is introduced into the purifier 3. The outlets of the adsorption cylinder 1 32 and the adsorption cylinder 2 33 of the purifier 3 are introduced into the inlet of the distillation tower 53 of the cold box 5 through the branch and the valve. Then, after being purified by the purifier 3, it is introduced into the distillation tower 53 in the cold box 5. The gas drawn out from the upper end of the distillation tower 53 passes through the tertiary compression passage of the gas compressor 2 and is then led out through the exhaust pipeline 8. Embodiment 2

[0033] like Figure 1 , Figure 2 As shown, an energy-saving nitrogen production device includes a gas compressor 2, a cold dryer 4, a purifier 3 and a cold box 5 connected in sequence; a main heat exchanger 51, a distillation tower 53, a subcooler 54, a main condenser evaporator 52 and an expander 55 are arranged in the cold box 5; wherein the main heat exchanger 51 is connected with the distillation tower 53, the subcooler 54, the main condenser evaporator 52 and the expander 55. External air is introduced through the gas compressor 2, and after being dry-cooled by the cold dryer 4 and purified by the purifier 3, it is introduced into the cold box 5 for nitrogen production treatment, and the gas drawn out from the upper end of the distillation tower 53 in the cold box 5 is compressed by the gas compressor 2 and then led out. Furthermore, the cold dryer 4 adopts the cold dryer equipment in the prior art, and the specific selection and selection are not repeated here one by one, as long as the dry cooling treatment of the compressed air can be basically achieved.

[0034] Specifically, the cold box 5 is provided with a main heat exchanger 51, a distillation tower 53, a subcooler 54, a main condenser evaporator 52 and an expander 55; wherein the main heat exchanger 51 is connected with the distillation tower 53, the subcooler 54, the main condenser evaporator 52 and the expander 55. External air is introduced through the gas compressor 2, and after being dry-cooled by the cold dryer 4 and purified by the purifier 3, it is introduced into the main heat exchanger 51 of the cold box 5. The gas cooled by the main heat exchanger 51 enters the distillation tower 53 for nitrogen production.

[0035] Furthermore, the distillation tower 53 adopts the distillation nitrogen production tower body in the prior art. Nitrogen is extracted from the top of the distillation tower 53 and enters the main heat exchanger 51; while the raw air is cooled by the main heat exchanger 51, the nitrogen extracted from the top of the distillation tower 53 is reheated and then led out of the cold box 5; the reheated nitrogen is further compressed by the three-stage compression passage of the gas compressor 2 and then led out through the exhaust pipe 8.

[0036] Furthermore, a part of the gas drawn out from the upper end of the distillation tower 53 is introduced into the condensation pipeline 2 of the main condensation evaporator 52, and after being drawn out through the condensation pipeline 2, it returns to the inside of the distillation tower 53. After distillation in the distillation tower 53, oxygen-rich liquid air is obtained at the bottom. The liquid collecting area at the lower part of the distillation tower 53 is connected to the inlet of the subcooling pipeline 1 of the subcooler 54, and the outlet of the subcooling pipeline 1 of the subcooler 54 is connected to the condensation pipeline 1 of the main condensation evaporator 52. After condensation in the main condensation evaporator 52, it is returned to the subcooling pipeline 2 of the subcooler 54, and is introduced into the expander 55 through the subcooling pipeline 2 for export, and fed back to the purifier 3. The expansion end of the expander 55 is connected to the purifier 3 through the main heat exchanger 51. The liquid air at the bottom of the distillation tower 53 is throttled into the main condenser evaporator 52 for evaporation. After the oxygen-enriched air is cooled by the subcooler 54, it is reheated in the main heat exchanger 51 and enters the expansion end of the expander 55. The expanded low-temperature air enters the main heat exchanger 51 to cool the raw air, and after being reheated to the ambient temperature, it exits the cold box 5 as the regeneration gas of the purifier 3. The expansion end of the expander 55 is arranged in the cold box 5, and the expansion end is connected to the outside of the cold box 5. Furthermore, a cooler 56 connected to the boosting end of the expander 55 is also arranged outside the cold box 5. After being pressurized by the boosting end of the expander 55, the nitrogen is cooled by the subcooler 56 and output as product nitrogen, thereby meeting the output requirements of the product.

[0037] Specifically, the purifier 3 includes an adsorption cylinder 1 32 and an adsorption cylinder 2 33. The pipelines drawn from the cold dryer 4 are respectively introduced into the adsorption cylinder 1 32 and the adsorption cylinder 2 33 through a branch and a valve. The outlets of the adsorption cylinder 1 32 and the adsorption cylinder 2 33 are then introduced into the inlet of the distillation tower 53 of the cold box 5 through a branch and a valve. The purifier 3 also includes an electric heater 31, which is connected to the outlet pipeline of the expansion machine 55, and the outlet pipeline is connected to the inlet end of the electric heater 31 after passing through the main heat exchanger 51. The outlet end of the electric heater 31 is respectively connected to the adsorption cylinder 1 32 and the adsorption cylinder 2 33 through a reflux pipeline and a reflux valve. Furthermore, in the present embodiment, the pipeline leading out from the cold dryer 4 is connected to the adsorption cylinder 1 32 and the adsorption cylinder 2 33 respectively through a pair of parallel branches and valves, and the other ends of the adsorption cylinder 1 32 and the adsorption cylinder 2 33 are connected to the main heat exchanger 51 of the cold box 5 through a pair of parallel branches and valves, that is, the adsorption cylinder 1 32 and the adsorption cylinder 2 33 are connected in parallel between the main heat exchanger 51 and the cold dryer 4, and the two ends of the adsorption cylinder 1 32 and the adsorption cylinder 2 33 are respectively connected to the two ends of the electric heater 31 through a pair of parallel return pipes and return valves.

[0038] Furthermore, the gas compressor 2 uses a three-stage compressor. The secondary compressed gas of the gas compressor 2 is introduced into the cold dryer 4, and after being cold-dried by the cold dryer 4, it is introduced into the purifier 3. The outlets of the adsorption cylinder 1 32 and the adsorption cylinder 2 33 of the purifier 3 are introduced into the inlet of the distillation tower 53 of the cold box 5 through a branch and a valve. Then, after being purified by the purifier 3, it is introduced into the main heat exchanger 51 of the cold box 5 and then introduced into the distillation tower 53. The gas drawn out from the upper end of the distillation tower 53 passes through the main heat exchanger 51 and is introduced into the three-stage compression passage of the gas compressor 2 and then is led out. Embodiment 3

[0039] On the basis of the second embodiment, the air inlet end of the gas compressor 2 is further connected to a filter 1 , and the external air is introduced into the gas compressor 2 after being filtered by the filter 1 .

[0040] Specifically, the front end of the gas compressor 2 is connected to the filter 1, and the external air (raw air) enters the gas compressor 2 after the dust is removed by the filter 1. The air compressed by the gas compressor 2 passes through the cold dryer 4 to dry the raw air after preliminary compression, and then enters the purifier 3 to adsorb and remove residual moisture, carbon dioxide and hydrocarbons. Embodiment 4

[0041] On the basis of the third embodiment, the liquid collecting area at the bottom of the distillation tower 53 and the main condenser evaporator 52 are further connected to the residual liquid evaporator 6. The low-temperature liquid produced by the distillation tower 53 and the main condenser evaporator 52 can be gasified through the residual liquid evaporator 6 and then discharged into the atmosphere. Embodiment 5

[0042] On the basis of the fourth embodiment, the gas compressor 2, the purifier 3, the expander 55, the electric heater 31 and the main heat exchanger 51 are connected to the muffler 7. That is, the muffler 7 is connected to the pipeline of each device to discharge the gas to the atmosphere. There will be noise when the gas is discharged, and the muffler 7 is used for noise reduction. Among them, the muffler 7 adopts the muffler of the SIL-601 / 602 model in the prior art, but is not limited to this. In other embodiments, other muffler products in the prior art can be selected according to actual use requirements.

[0043] In other embodiments, the gas introduced into the main heat exchanger 51 by the purifier 3 is directly introduced into the instrument gas bearing gas system 34, which is used to detect the composition of the gas purified by the purifier 3. The instrument gas bearing gas system 34 adopts the instrument gas bearing gas system in the prior art, and the specific models are not described and listed one by one here, as long as the gas component content detection can be basically achieved. Embodiment 6

[0044] Based on the fourth embodiment, Figure 1~Figure 3As shown, an energy-saving nitrogen production device disclosed in this embodiment, the gas compressor 2 adopts a three-stage compressed air gas compressor, and the gas compressor 2 is divided into two parts. The air is first compressed to a lower pressure by using the first-stage compression and the second-stage compression of the air compressor. After the air at a lower pressure enters the distillation tower 53, it will be easier to distill and more nitrogen will be extracted. After the nitrogen after reheating is completed, it flows back into the third stage of the gas compressor 2 for compression, and finally a nitrogen product with the pressure required by the user is obtained. This embodiment is different from the traditional supercharging method. The traditional supercharging uses a supercharging expander for supercharging, but the actual supercharging effect is low (up to 1.24 times the outlet pressure). In this embodiment, it can be increased to more than 2 times the outlet pressure. This embodiment reduces the pressure entering the tower. After the pressure is reduced, the efficiency of the distillation tower 53 is significantly improved. The effect of double energy saving is achieved. In terms of energy saving, a qualitative improvement has been formed.

[0045] The gas compressor 2 used for air separation nitrogen production is a centrifugal air compressor. In this embodiment, the centrifugal air compressor is selected as follows: Figure 3 The three-stage compression centrifugal air compressor shown in the figure. The single-tower nitrogen production process is to first pressurize the ambient atmosphere to about one kilogram higher than the product pressure, and then go through cooling-dehydration-adsorption-distillation to finally obtain product nitrogen gas about one kilogram lower than the air pressure provided by the raw material air compressor. Therefore, when the nitrogen pressure is determined, the discharge pressure of the air compressor is basically determined.

[0046] The characteristic of the technical solution in this embodiment is that the three-stage compression of the air compressor is split, and the pressure of the raw air entering the cold box of the distillation tower is reduced without adding new equipment, thereby improving the extraction rate of the distillation tower 53 and obtaining more product nitrogen. After the nitrogen returns to the three-stage compression of the gas compressor 2, nitrogen that meets the customer's requirements is obtained. This process does not add any dynamic equipment or static equipment, changes the direction and sequence of the process, and can achieve the effect of energy saving and cost reduction. Embodiment 7

[0047] On the basis of Example 6, Figure 1~Figure 3 As shown, take the nitrogen generator project implemented as an example. Specifically, in this embodiment, the raw gas 5300Nm 3 / HThrough the primary and secondary compression of the gas compressor 2, the pressure rises from normal pressure to 0.5MPa(G), then enters the purifier 3 to adsorb excess impurities such as carbon dioxide and water, and then enters the distillation tower 53 for distillation. The pressure of the product nitrogen in the distillation tower 53 is 0.4MPa(G) at this time. This part of the product nitrogen will enter the third stage of the gas compressor 2 for compression again, and finally obtain 0.85MPa(G) product nitrogen. From the original conventional energy consumption of 0.31KW.H / Nm 3 N, after using the new solution, the energy consumption is directly reduced to 0.24KW.H / Nm3 N. This nitrogen generator project is 2400Nm 3 / H, based on 8,000 working hours per year, the electricity consumption can be saved by about 1.344 million KW per year. The effect of energy saving and cost reduction is considerable.

[0048] The energy consumption of this equipment is compared with that of the typical nitrogen production equipment in the prior art. Figure 4 As shown. Pressure is a very important factor in the performance of the distillation tower 53. Under the same feed conditions, the temperature at the top of the tower decreases due to the decrease in pressure, so that the intersection point of the distillation fraction composition moves downward, and the reflux ratio of the distillation tower 53 increases; as the pressure decreases, the pressure drop of the tower plate will also decrease. At the same gas flow rate, the liquid film thickness and liquid film velocity required to meet the phase equilibrium will decrease, and the density of the gas and liquid phases will also decrease, resulting in a decrease in the tower plate pressure drop; the lower the pressure, the closer the gas-liquid equilibrium is to the ideal state. The greater the difference in equilibrium gas and liquid phase concentrations, the better the separation effect. Embodiment 8

[0049] Based on the seventh embodiment, the device configuration includes: Gas compressor 2, i.e. air / nitrogen compressor: 1 unit; inlet temperature 30°C; atmospheric pressure 101.3KPa; exhaust volume 5300Nm 3 / h; exhaust pressure is 0.5MPa (G); motor power is 670kW; nitrogen inlet temperature is 40℃; nitrogen inlet pressure is 0.4MPa; exhaust volume is 2400Nm 3 / h; exhaust pressure is 0.85MPa (G); cooling water consumption is 60T / h.

[0050] Cold dryer 4: 1 unit. Processing air volume is 5300Nm 3 / hr; working pressure is 0.5Mpa; air inlet temperature of the cold dry unit is ≤38℃; air outlet temperature of the cold dry unit is ~33℃; refrigerant is R407C; cooling water consumption is 16.5t / hr; motor power is 16.6kW.

[0051] Purifier 3: 1 unit; Model: HXK-5300 / 1.0; Air processing volume: 5300Nm 3 / h; working pressure: 0.5MPa(G); air inlet temperature: ~33℃; air outlet temperature: ~41℃; CO in purified air 2 Content: ≤1ppm; H 2 O content: ≤1ppm; adsorption time: 4h; regeneration heating gas inlet adsorption tube temperature: ≥180℃; regeneration heating gas outlet adsorption tube temperature: ≥80℃; regeneration gas volume: 1203Nm 3 / h; adsorbent: 13X-APG molecular sieve 4×8V type; adsorbent capacity includes, molecular sieve: 1700kg / cylinder; activated alumina: 800kg / cylinder; inert alumina: 400kg / cylinder; electric heater power: 132kW; main equipment includes: 2 adsorption cylinders; 1 electric heater.

[0052] Cold box 5 includes: distillation tower: 1; model: FN-2400; processed air volume: ~5200Nm 3 / h; Output: Nitrogen 2400Nm 3 / h; Purity: Nitrogen ≤ 2ppmO 2 ; Pressure: Nitrogen ≥ 0.4MPa (G); Main equipment: Main heat exchanger: 1 set; Distillation tower: 1 unit; Condenser evaporator: 1 unit; Subcooler: 1 unit; Turbine expander: 2 units; Shell: 1 unit.

[0053] The instrument air bearing air system 34 includes: instrument air filters: 2 sets; instrument filter system: 1 set; expansion end bearing gas cabinet: 1 set. Embodiment 9

[0054] A nitrogen production method of an energy-saving nitrogen production device is implemented by the energy-saving nitrogen production device in Example 6 or Example 7, and the nitrogen production method comprises the following steps: Step S1, external gas is filtered by filter 1 and then introduced into gas compressor 2, Specifically, the front end of the gas compressor 2 is also connected to a filter 1 , and the raw air enters the gas compressor 2 after dust is removed by the filter 1 .

[0055] Step S2, the filtered external gas enters the first-stage air compressor of the gas compressor 2 for primary compression; and then is introduced into the second-stage air compressor for secondary compression.

[0056] Specifically, the gas drawn out from the upper end of the distillation tower 53 passes through the main heat exchanger 51 and is introduced into the tertiary compression passage of the gas compressor 2 and then discharged.

[0057] Step S3, dry-cooling the gas after secondary compression through the cold dryer 4.

[0058] Specifically, the air compressed by the gas compressor 2 passes through the cold dryer 4 to dry the raw air, and then enters the purifier 3 to adsorb and remove residual moisture, carbon dioxide and hydrocarbons.

[0059] Step S4, introducing the dry cooled gas into the purifier 3 for purification.

[0060] Specifically, the outlets of the adsorption cylinder 1 32 and the adsorption cylinder 2 33 of the purifier 3 are introduced into the inlet of the distillation tower 53 of the cold box 5 through a branch and a valve. Then, after being purified by the purifier 3, they are introduced into the distillation tower 53 in the cold box 5. Specifically, the pipelines led out of the cold dryer 4 are respectively introduced into the adsorption cylinder 1 32 and the adsorption cylinder 2 33 through a branch and a valve, and the outlets of the adsorption cylinder 1 32 and the adsorption cylinder 2 33 are then introduced into the inlet of the distillation tower 53 of the cold box 5 through a branch and a valve. The inlet end of the electric heater 31 of the purifier 3 is connected to the outlet of the expander 55 of the cold box 5, and the outlet end of the electric heater 31 is respectively connected to the adsorption cylinder 1 32 and the adsorption cylinder 2 33 through a reflux pipeline and a reflux valve.

[0061] Step S5, introducing the purified gas into the cold box 5 for nitrogen production treatment.

[0062] Specifically, the main heat exchanger 51 in the cold box 5 is connected to the distillation tower 53, the subcooler 54, the main condenser evaporator 52 and the expander 55. The gas cooled in the main heat exchanger 51 enters the distillation tower 53. Nitrogen is extracted from the top of the distillation tower 53 and enters the main heat exchanger 51. While the main heat exchanger 51 cools the raw air, it reheats itself and exits the cold box 5. More specifically, a part of the gas drawn out from the upper end of the distillation tower 53 is branched and passed through the main condenser evaporator 52, condensed into liquid nitrogen in the main condenser evaporator 52, and returned to the inside of the distillation tower 53. After distillation in the distillation tower 53, oxygen-rich liquid air is obtained at the bottom. The expansion end of the expander 55 is connected to the purifier through the main heat exchanger 31, and the liquid air at the bottom of the distillation tower 53 is throttled into the main condenser evaporator 52 for evaporation. After the oxygen-enriched air is cooled by the subcooler 54, it is reheated in the main heat exchanger 51 and enters the expansion end of the expander 55. The expanded low-temperature air enters the main heat exchanger 51 to cool the raw air, and after being reheated to the ambient temperature, it exits the cold box 5 as the regeneration gas of the purifier 3. The expansion end of the expander 55 is arranged in the cold box 5, and the expansion end is led out of the cold box 5. A cooler 56 connected to the boosting end of the expander 55 is also arranged outside the cold box 5. After the nitrogen is boosted by the boosting end of the expander 55, it is cooled by the supercooler 56 and output as product nitrogen, thereby meeting the output requirements of the product. In addition, the distillation tower 53 and the main condenser evaporator 52 are also connected to the residual liquid evaporator 6. The low-temperature liquid produced by the distillation tower 53 and the main condenser evaporator 52 can be discharged into the atmosphere after being gasified by the residual liquid evaporator 6.

[0063] Step S6, the liquid nitrogen or nitrogen gas discharged from the cold box 5 is returned to the third-stage compressor of the gas compressor 2 for compression before being discharged.

[0064] Specifically, it is exported after passing through the three-stage compression passage of the gas compressor 2.

[0065] The working principle is: The energy-saving nitrogen production device disclosed in the present invention reduces the distillation pressure, improves the distillation efficiency, and improves the extraction rate; and reduces the single investment cost and long-term maintenance cost.

[0066] Without adding any equipment, the present invention reduces the raw air pressure from the original three-stage supercharging to the two-stage supercharging, thereby reducing the distillation pressure, substantially improving the distillation efficiency, and significantly improving the extraction rate to nearly 60%. Compared with the highest extraction rate of 55% in the existing single-tower nitrogen production process, it can still be increased by 5%. The present invention does not add any dynamic and static equipment. If it is conventional, a nitrogen compressor needs to be added. According to this process, not only is a nitrogen compressor not required, but the nitrogen production requirements can also be met. The single investment cost and long-term maintenance cost of the equipment will also be lower.

[0067] The raw gas pressure at the outlet of the air compressor of the present invention is reduced, the use pressure of the downstream supporting equipment is also reduced, and the design pressure can also be reduced at the same time. The load and design pressure of the dynamic equipment and the static equipment are reduced at the same time, the wall thickness of the equipment will be reduced, and the investment in the equipment is also significantly reduced. When the outlet pressure of the air compressor is reduced, the pressure level of the supporting pipes, flanges and other accessories at the rear end can be reduced, and 10% of the cost can be saved.

[0068] The invention is applicable to production safety, such as pressure vessels and pressure pipes. If the pressure is higher, the possibility of leakage will be greater, and the secondary disasters will be aggravated. When the process pressure is reduced, the reliability of the equipment will increase, and the safety will also be improved.

[0069] Based on the ideal embodiment of the present invention, through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. An energy-saving nitrogen production device, characterized in that: It comprises a gas compressor (2), a cold dryer (4), a purifier (3) and a cold box (5) which are connected in sequence; The cold box (5) is provided with a main heat exchanger (51), and a distillation tower (53) connected to the main heat exchanger (51), a subcooler (54), a main condenser evaporator (52) and an expander (55); The gas is introduced into the cold dryer (4) through the gas compressor (2), and after being dry-cooled by the cold dryer (4) and purified by the purifier (3), is introduced into the cold box (5) for nitrogen production. The gas drawn out from the upper end of the distillation tower (53) in the cold box (5) is compressed by the gas compressor (2) and then discharged.

2. An energy-saving nitrogen production device according to claim 1, characterized in that: The secondary compressed gas of the gas compressor (2) is introduced into the cold dryer (4), and after being cold-dried in the cold dryer (4), is introduced into the purifier (3), and then after being purified by the purifier (3), is introduced into the main heat exchanger 51 in the cold box (5), and then introduced into the distillation tower (53).

3. An energy-saving nitrogen production device according to claim 2, characterized in that: The gas drawn out from the upper end of the distillation tower (53) is subjected to heat exchange in the main heat exchanger (51), introduced into the gas compressor (2), compressed in three stages, and then discharged.

4. An energy-saving nitrogen production device according to claim 3, characterized in that: The air inlet end of the gas compressor (2) is also connected to a filter (1), and external air is filtered by the filter (1) and then introduced into the gas compressor (2).

5. An energy-saving nitrogen production device according to claim 4, characterized in that: The liquid collecting area at the bottom of the distillation tower (53) is connected to the inlet of the subcooling pipeline 1 of the subcooler (54), and the outlet of the subcooling pipeline 1 of the subcooler (54) is connected to the condensing pipeline 1 of the main condensing evaporator (52). After condensation in the main condensing evaporator (52), the liquid is returned to the subcooling pipeline 2 of the subcooler (54), and is introduced into the expansion machine (55) through the subcooling pipeline 2 to be discharged and fed back to the purifier (3).

6. An energy-saving nitrogen production device according to claim 5, characterized in that: The gas branched out from the upper end of the distillation tower (53) is introduced into the condensation pipeline 2 of the main condensation evaporator (52), and after being led out through the condensation pipeline 2, it returns to the interior of the distillation tower (53).

7. An energy-saving nitrogen production device according to claim 6, characterized in that: The liquid collecting area of ​​the distillation tower (53) is connected to the residual liquid evaporator (6). And / or, the main condenser evaporator (52) is also connected to the residual liquid evaporator (6).

8. An energy-saving nitrogen production device according to claim 7, characterized in that: The purifier (3) comprises an adsorption cylinder 1 (32) and an adsorption cylinder 2 (33). The pipelines leading out of the cold dryer (4) are respectively introduced into the adsorption cylinder 1 (32) and the adsorption cylinder 2 (33) through branches and valves. The outlets of the adsorption cylinder 1 (32) and the adsorption cylinder 2 (33) are then introduced into the inlet of the distillation tower (53) of the cold box (5) through branches and valves.

9. An energy-saving nitrogen production device according to claim 8, characterized in that: The purifier (3) further comprises an electric heater (31), the inlet end of the electric heater (31) being connected to the outlet of the expander (55) of the cold box (5); the outlet end of the electric heater (31) being connected to the first adsorption cylinder (32) and the second adsorption cylinder (33) respectively via a reflux pipeline and a reflux valve; the gas discharged from the expander (55) is heated by the main heat exchanger (51) and then heated by the electric heater (31) before being introduced into the purifier (3); And / or, the gas compressor (2), the purifier (3), the expander (55), the electric heater (31) and the main heat exchanger (51) are connected to the muffler (7).

10. A nitrogen production method for an energy-saving nitrogen production device, characterized in that: The nitrogen production method is realized by any energy-saving nitrogen production device in claim 1 to claim 9, and comprises the following steps: Step S1, external gas is filtered by a filter (1) and then introduced into a gas compressor (2); Step S2, the filtered external gas enters the first-stage air compressor of the gas compressor (2) for primary compression; and then is introduced into the second-stage air compressor for secondary compression; Step S3, dry-cooling the gas after the secondary compression through a cold dryer (4). Step S4, introducing the dry cooled gas into a purifier (3) for purification; Step S5, introducing the purified gas into a cold box (5) for nitrogen production; Step S6, the nitrogen discharged from the cold box (5) is returned to the third stage compressor of the gas compressor (2) for compression before being discharged.

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