A low-energy low-pressure adsorption PSA air separation nitrogen production process

Abstract

The application provides a low-energy-consumption low-pressure adsorption PSA air separation nitrogen production process, and belongs to the technical field of air separation. The process comprises the following steps: air is compressed to 0.2-0.5 MPa, and then water is removed through gas-liquid separation; the compressed air is sent into a first adsorption tower for adsorption, product nitrogen is discharged from the top of the first adsorption tower and is pressurized to greater than or equal to 0.6 MPa; after adsorption is stopped, upper pressure equalization is performed, and then upper and lower pressure equalization is performed; then the compressed air is sent into a second adsorption tower for adsorption, product nitrogen is discharged from the top of the second adsorption tower, the first adsorption tower is simultaneously vented and vacuumized to regenerate the adsorbent; after the second adsorption tower stops adsorption, subsequent operations are the same as those of the first adsorption tower, and the process is cyclic; after product nitrogen is discharged, the product nitrogen is pressurized to greater than or equal to 0.6 MPa. The application adopts the mode of reducing adsorption pressure and pressurizing product nitrogen twice to produce nitrogen, significantly reduces the energy taken away by vented gas, and can reduce energy consumption by more than 10%-20%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of air separation, and particularly relates to a low-energy-consumption low-pressure adsorption PSA air separation nitrogen production process. BACKGROUND

[0002] At present, there are mainly two kinds of air separation nitrogen production processes, one is a low-temperature method, called cryogenic air separation, and the other is a pressure swing adsorption process, also called a PSA method. The commonly used small and medium flow nitrogen in industrial production is generally realized by using air as raw gas through the PSA pressure swing adsorption technology.

[0003] The pressure swing adsorption air separation nitrogen production process generally compresses air to 0.7-1.0 MPa, and after drying and purification, the air is introduced into a PSA device for nitrogen-oxygen separation. The adsorption amount of the adsorbent increases with the increase of the gas pressure, so the pressure used in the pressure swing adsorption air separation nitrogen production is generally 0.8-1.0 MPa, and in some high-pressure occasions, even 1.5-2.5 MPa of adsorption pressure is selected. The adsorbent for the pressure swing adsorption air separation nitrogen production is carbon molecular sieve, the adsorption of oxygen by the carbon molecular sieve is speed-type adsorption, the oxygen molecules are small, and can enter the carbon molecular sieve micropores faster than nitrogen, and with the extension of the adsorption time, the adsorption amount of nitrogen also increases, so the adsorption time is generally controlled to be 40-60 s. The air / nitrogen (Air / N2) ratio is generally used in the industry to measure the energy-saving effect of the equipment, and under the same conditions, the lower the Air / N2, the more energy-saving. Taking 99.5% purity nitrogen as an example, under 0.7 MPa, the Air / N2 is generally 2.6, that is, 1 of 99.5% purity nitrogen can be produced for every 2.6 of air, and with the increase of the nitrogen concentration, the Air / N2 also increases.

[0004] Under the traditional process, 2.6 Nm 3 Air is raised to 0.7 MPa, and finally only 1 Nm 3 Nitrogen is produced, and the remaining 1.6 Nm 3 Air is all naturally discharged (referred to as "air discharge"). This part of the air discharge is compressed from normal pressure to 0.7 MPa, and then directly discharged into the air, causing a large amount of energy waste.

[0005] Generally, the energy-saving effect of the pressure swing adsorption air separation nitrogen production system depends on the adsorption performance of the carbon molecular sieve. The performance breakthrough of the carbon molecular sieve as an adsorption material is a long and slow process, and it is currently difficult to significantly reduce the energy consumption of the pressure swing adsorption nitrogen production process by improving the adsorption material.

[0006] Therefore, it is necessary to provide an improved technical solution for the above-mentioned deficiencies of the prior art. SUMMARY

[0007] The present application aims to provide a low-energy low-pressure adsorption PSA air separation nitrogen process, which can reduce energy loss during venting, to solve the problem of high energy consumption of the existing PSA air separation nitrogen process.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0009] A low-energy low-pressure adsorption PSA air separation nitrogen process comprises the following steps:

[0010] Step one, compress air to 0.2-0.5 MPa, then perform gas-liquid separation to remove liquid water;

[0011] Step two, send the compressed air after gas-liquid separation into the first adsorption tower for adsorption for a certain time to obtain product nitrogen, which is discharged from the top of the first adsorption tower;

[0012] Step three, after the first adsorption tower stops adsorption, connect the top of the first adsorption tower with the top of the second adsorption tower to perform up equalization, after a certain time of up equalization, connect the bottom of the first adsorption tower with the bottom of the second adsorption tower to perform up-down simultaneous equalization;

[0013] Step four, after the up-down simultaneous equalization is completed, send the compressed air obtained in step one into the second adsorption tower for adsorption for a certain time to obtain product nitrogen, which is discharged from the top of the second adsorption tower, and at the same time, vent the first adsorption tower, and then perform vacuumization after venting;

[0014] Step five, after the second adsorption tower stops adsorption, connect the top of the second adsorption tower with the top of the first adsorption tower to perform up equalization, after a certain time of up equalization, connect the bottom of the second adsorption tower with the bottom of the first adsorption tower to perform up-down simultaneous equalization, then vent the second adsorption tower, and perform vacuumization after venting, and execute step two;

[0015] In steps two and four, after the product nitrogen is discharged, pressurize to ≥0.6 MPa.

[0016] Preferably, the first adsorption tower and the second adsorption tower are filled with adsorbents, and the adsorbents are carbon molecular sieves.

[0017] Preferably, the first adsorption tower and the second adsorption tower are further filled with drying agents.

[0018] Preferably, the drying agent is aluminum oxide.

[0019] Preferably, in step two, the adsorption time is 20-60 s.

[0020] Preferably, in step three, the up equalization time is 1-5 s, and the up-down simultaneous equalization time is 1-5 s.

[0021] Preferably, in step four, the adsorption time is 20-60s.

[0022] Preferably, in step four, the vacuum is drawn to an absolute pressure of ≤0.05MPa.

[0023] Preferably, in step five, the up-pressure equalization time is 1-5s, and the up-down simultaneous pressure equalization time is 1-5s.

[0024] Preferably, in step two, the adsorption time is 35-40s; and in step four, the adsorption time is 35-40s.

[0025] Beneficial effects:

[0026] (1) The present application uses a method of reducing the adsorption pressure and secondary pressurizing the product nitrogen to produce nitrogen, which reduces the pressure of the vented gas from above 0.6MPa to below 0.3MPa, significantly reducing the energy taken away by the vented gas, and under the same product nitrogen flow, the power of the air compression equipment can be reduced, thereby achieving energy saving and consumption reduction.

[0027] (2) In the pressure equalization process, the present application uses an "up-pressure equalization + up-down simultaneous pressure equalization" pressure equalization method, so that the product nitrogen remaining at the top of the adsorption tower after adsorption enters another adsorption tower, the pressure at the top of the other adsorption tower is higher than that at the bottom, at this time the product nitrogen reverses through the adsorbent and is further purified, the nitrogen after further purification enters the bottom, and is mixed with the air entering the bottom in the up-down simultaneous pressure equalization process, through the above process, the nitrogen concentration in the gas at the bottom of the other adsorption tower at the beginning of adsorption is higher than that of air, which can improve the purity of the product nitrogen produced.

[0028] (3) When the adsorption tower is vented, the air at the bottom is discharged to the outside without passing through the adsorbent bed, this part of air does not need to pass through the adsorbent bed to remove water, and in the existing process, the raw air needs to pass through a cold dryer for drying, the vented air at the bottom also consumes the power of the cold dryer, so the energy utilization rate of the present application is higher in the drying process of the raw air. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the application, and together with the description of the exemplary embodiments of the application given below, make an explanation of the application, and do not constitute an improper limitation of the application. Among them:

[0030] Figure 1 The process flow chart of the present application examples 1-4.

[0031] Figure 2 The process flow chart of the present application comparative examples 1-4.

[0032] 100, low-pressure blower; 200, gas-liquid separation tank; 301, first adsorption tower; 302, second adsorption tower; 303, nitrogen buffer tank; 401, booster; 402, high-pressure nitrogen tank; 301a, first bottom valve; 301b, first top valve; 302a, second bottom valve; 302b, second top valve; 304a, first equalizing valve; 304b, second equalizing valve; 305a, first vent valve; 305b, second vent valve; 305c, third vent valve; 306a, stop valve; 306b, vacuum pump. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0034] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as a limitation on the present application, which indicates or implies that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation.

[0035] In the description of the present application, the meaning of several is one or more, and the meaning of multiple is more than two. Greater than, less than, more than, etc. are understood as not including the number, and above, below, etc. are understood as including the number. If it is described as first, second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the sequence of indicated technical features.

[0036] In addition, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include one or more features.

[0037] The present application will be described in detail below with reference to the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0038] The present application is aimed at the problems existing in the current pressure swing adsorption air separation nitrogen production process, and provides a low-energy-consumption low-pressure adsorption PSA air separation nitrogen production process. The process comprises the following steps:

[0039] Step one, compress air to 0.2-0.5MPa (for example 0.21MPa, 0.25MPa, 0.30MPa, 0.35MPa, 0.40MPa, 0.45MPa, 0.49MPa), then carry out gas-liquid separation, remove liquid water;

[0040] Step two, send the compressed air after gas-liquid separation into the first adsorption tower for adsorption for a certain time, obtain product nitrogen gas, and the product nitrogen gas is discharged from the top of the first adsorption tower;

[0041] Step three, after the first adsorption tower stops adsorption, the top of the first adsorption tower is communicated with the top of the second adsorption tower, and the upper equalization is carried out, after a certain time, the bottom of the first adsorption tower is communicated with the bottom of the second adsorption tower, and the upper and lower simultaneous equalization is carried out;

[0042] Step four, after the upper and lower simultaneous equalization is finished, the compressed air obtained in step one is sent into the second adsorption tower for adsorption for a certain time, product nitrogen gas is obtained, the product nitrogen gas is discharged from the top of the second adsorption tower, and the first adsorption tower is vented, and then vacuumized;

[0043] Step five, after the second adsorption tower stops adsorption, the top of the second adsorption tower is communicated with the top of the first adsorption tower, and the upper equalization is carried out, after a certain time, the bottom of the second adsorption tower is communicated with the bottom of the first adsorption tower, and the upper and lower simultaneous equalization is carried out, then the second adsorption tower is vented, and then vacuumized, and step two is executed;

[0044] In steps two and four, after the product nitrogen gas is discharged, pressurize to ≥0.6MPa (for example 0.6MPa, 0.61MPa, 0.63MPa, 0.65MPa, 0.70MPa).

[0045] In the preferred embodiment of the present application, the first adsorption tower and the second adsorption tower are filled with adsorbents, and the adsorbents are carbon molecular sieves.

[0046] In the preferred embodiment of the present application, the first adsorption tower and the second adsorption tower are further filled with drying agents, and the drying agent bed is located below the adsorbent bed, and after the compressed air enters the first adsorption tower and the second adsorption tower, it is dried by the drying agent bed first, and then adsorbed by the adsorbent bed.

[0047] In the preferred embodiment of the present application, the drying agent is alumina.

[0048] In step two, the adsorption time is 20-60s (for example 21s, 23s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 59s).

[0049] In the preferred embodiment of the present application, in step three, the upper equalizing time is 1-5s (for example, 1.5s, 2.0s, 2.5s, 3.0s, 3.5s, 4.0s, 4.5s), and the upper and lower simultaneous equalizing time is 1-5s (for example, 1.5s, 2.0s, 2.5s, 3.0s, 3.5s, 4.0s, 4.5s).

[0050] In the preferred embodiment of the present application, in step four, the adsorption time is 20-60s (for example, 21s, 23s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 59s).

[0051] In the preferred embodiment of the present application, in step four, the vacuum extraction is to an absolute pressure of ≤0.05MPa (for example, 0.05MPa, 0.04MPa, 0.03MPa, 0.02MPa, 0.01MPa).

[0052] In the preferred embodiment of the present application, in step five, the upper equalizing time is 1-5s (for example, 1.5s, 2.0s, 2.5s, 3.0s, 3.5s, 4.0s, 4.5s), and the upper and lower simultaneous equalizing time is 1-5s (for example, 1.5s, 2.0s, 2.5s, 3.0s, 3.5s, 4.0s, 4.5s).

[0053] In the preferred embodiment of the present application, in step two, the adsorption time is 35-40s (for example, 36s, 37s, 38s, 39s); and in step four, the adsorption time is 35-40s (for example, 36s, 37s, 38s, 39s).

[0054] The process of the present application reduces the inlet pressure, increases the humidity of the compressed air, and if a traditional process is used, the compressed air needs to be cooled to a lower temperature, which undoubtedly increases the power consumption of the cold dryer, which is not conducive to energy saving. Therefore, the present application uses a gas-liquid separation tank to preliminarily remove water from the compressed air, and adds a drying agent to the adsorbent to further dry the nitrogen. Neither the gas-liquid separation tank nor the adsorbent produces energy consumption, and when the adsorbent is regenerated by vacuum extraction, the drying agent is also regenerated and can be recycled.

[0055] The low-energy-consumption low-pressure adsorption PSA air separation nitrogen production process of the present application will be described in detail below through specific examples.

[0056] The low-energy-consumption PSA air separation nitrogen production process used in the following examples is as follows: Figure 1The PSA air separation nitrogen device shown in the embodiment, specifically, the device comprises an air inlet device, an adsorption device and a pressurizing device, wherein: the air inlet device comprises a low-pressure fan 100 and a gas-liquid separation tank 200 arranged in series; the adsorption device comprises first and second adsorption towers 301 and 302 arranged in parallel, and a nitrogen buffer tank 303 is arranged downstream of the first and second adsorption towers 301 and 302; the downstream of the nitrogen buffer tank 303 is the pressurizing device, and the pressurizing device comprises a pressurizing machine 401 and a high-pressure nitrogen tank 402.

[0057] Specifically, the outlet pipeline of the gas-liquid separation tank 200 is divided into two branches, and enters the bottoms of the first and second adsorption towers 301 and 302 respectively, a first bottom valve 301a is arranged on the branch connected to the first adsorption tower 301, and a second bottom valve 302a is arranged on the branch connected to the second adsorption tower 302; first and second top valves 301b and 302b are arranged on the top pipelines of the first and second adsorption towers 301 and 302 respectively.

[0058] The top pipelines of the first and second adsorption towers 301 and 302 are connected through an upper equalizing pipeline, and a first equalizing valve 304a is arranged on the upper equalizing pipeline.

[0059] First and second vent valves 305a and 305b are arranged on the vent pipelines of the first and second adsorption towers 301 and 302 respectively, the outlet pipelines of the first and second vent valves 305a and 305b are combined and then divided into two branches, one branch is a vent branch and is provided with a third vent valve 305c, and the other branch is a vacuum pumping branch and is provided with a stop valve 306a and a vacuum pump 306b.

[0060] The vent pipelines of the first and second adsorption towers 301 and 302 are also connected through a lower equalizing pipeline, and a second equalizing valve 304b is arranged on the lower equalizing pipeline.

[0061] Embodiment 1

[0062] The embodiment provides a low-energy-consumption low-pressure adsorption PSA air separation nitrogen process, which is used for preparing nitrogen gas with a purity of 99.5% and a pressure of ≥0.6 MPa, and a design nitrogen production capacity of 1000 Nm 3 / h, and steps of the process are as follows:

[0063] Step one, raw material air treatment: air is compressed to 0.4 MPa by a low-pressure fan 100, and then the compressed air is sent to a gas-liquid separation tank 200 for gas-liquid separation to remove liquid water;

[0064] Step two, one tower adsorption: open the first tower bottom valve 301a, the first tower top valve 301b, and send the compressed air after gas-liquid separation into the first adsorption tower 301 to adsorb for 40 seconds to obtain product nitrogen, which is discharged from the top of the first adsorption tower 301 and enters the nitrogen buffer tank 303;

[0065] Step three, one tower pressure equalization: after the first adsorption tower 301 stops adsorption, close the first tower bottom valve 301a and the first tower top valve 301b, open the first pressure equalization valve 304a to connect the top of the first adsorption tower 301 with the top of the second adsorption tower 302 for upward pressure equalization, and after 3 seconds of upward pressure equalization, open the second pressure equalization valve 304b to connect the bottom of the first adsorption tower 301 with the bottom of the second adsorption tower 302 for simultaneous upward and downward pressure equalization, and the time for simultaneous upward and downward pressure equalization is 2 seconds.

[0066] Step four, two tower adsorption: after the simultaneous upward and downward pressure equalization is completed, close the first pressure equalization valve 304a and the second pressure equalization valve 304b, open the second tower bottom valve 302a and the second tower top valve 302b, and send the compressed air after gas-liquid separation into the second adsorption tower 302 to adsorb for 40 seconds to obtain product nitrogen, which is discharged from the top of the second adsorption tower 302 and enters the nitrogen buffer tank 303, at the same time, open the first vent valve 305a and the third vent valve 305c to vent the first adsorption tower 301, after venting, close the third vent valve 305c, open the stop valve 306a and the vacuum pump 306b to vacuumize the first adsorption tower 301 to regenerate the adsorbent therein, after vacuumization is completed, close the stop valve 306a and the vacuum pump 306b, and the first adsorption tower 301 is standby.

[0067] Step five, two tower pressure equalization: after the second adsorption tower 302 stops adsorption, close the second tower bottom valve 302a and the second tower top valve 302b, open the first pressure equalization valve 304a to connect the top of the second adsorption tower 302 with the top of the first adsorption tower 301 for upward pressure equalization, and after 3 seconds of upward pressure equalization, open the second pressure equalization valve 304b to connect the bottom of the second adsorption tower 302 with the bottom of the first adsorption tower 301 for simultaneous upward and downward pressure equalization, and the time for simultaneous upward and downward pressure equalization is 2 seconds, after the simultaneous upward and downward pressure equalization is completed, execute step two, at the same time, open the second vent valve 305b and the third vent valve 305c to vent the second adsorption tower 302, after venting, close the third vent valve 305c, open the stop valve 306a and the vacuum pump 306b to vacuumize the second adsorption tower 302 to an absolute pressure ≤0.05 MPa to regenerate the adsorbent.

[0068] The adsorbent in the first adsorption tower 301 and the second adsorption tower 302 is carbon molecular sieve, and the loading amount is 5000 kg, and alumina is also filled in the first adsorption tower 301 and the second adsorption tower 302 as a drying agent, and the loading amount is 200 kg, and the drying agent bed is located below the adsorbent.

[0069] In the above process, the nitrogen gas entering the nitrogen gas buffer tank 303 has a pressure of about 0.3 MPa to 0.35 MPa, is pressurized to 0.6 MPa by the booster 401, and is sent to the high-pressure nitrogen gas tank 402 for temporary storage.

[0070] In the above process, the average flow rate of the raw material air is 2586 Nm 3 / h, the average flow rate of the product nitrogen gas is 994 Nm 3 / h, the gas consumption ratio is 2.60, and the purity of the product nitrogen gas is ≥99.5% and ≤99.9%.

[0071] In this embodiment, the total power consumption of the low-pressure blower 100, the vacuum pump 306b, and the booster 401 is 245 kW.

[0072] Embodiment 2

[0073] This embodiment provides a low-energy-consumption low-pressure adsorption PSA air separation nitrogen production process, which is used for producing nitrogen gas with a purity of 99.5% and a pressure of ≥0.6 MPa, and has a design nitrogen production capacity of 1500 Nm 3 / h. The steps of the process are as follows:

[0074] Step one, raw material air treatment: the air is compressed to 0.4 MPa by the low-pressure blower 100, and then the compressed air is sent to the gas-liquid separation tank 200 for gas-liquid separation to remove liquid water;

[0075] Step two, one-tower adsorption: the first tower bottom valve 301a and the first tower top valve 301b are opened, the compressed air after gas-liquid separation is sent to the first adsorption tower 301 for adsorption for 35 seconds to obtain product nitrogen gas, and the product nitrogen gas is discharged from the top of the first adsorption tower 301 and enters the nitrogen gas buffer tank 303;

[0076] Step three, one-tower pressure equalization: after the first adsorption tower 301 stops adsorption, the first tower bottom valve 301a and the first tower top valve 301b are closed, the first pressure equalization valve 304a is opened, the top of the first adsorption tower 301 is communicated with the top of the second adsorption tower 302, and the upper pressure equalization is performed, after 3.5 seconds of upper pressure equalization, the second pressure equalization valve 304b is opened, the bottom of the first adsorption tower 301 is communicated with the bottom of the second adsorption tower 302, and the upper and lower pressure equalization is performed simultaneously, and the time for the upper and lower pressure equalization is 2 seconds;

[0077] Step four, two-tower adsorption: after the end of the up-down simultaneous equalization, the first equalization valve 304a and the second equalization valve 304b are closed, the second tower bottom valve 302a and the second tower top valve 302b are opened, the compressed air after the gas-liquid separation is sent into the second adsorption tower 302, and adsorption is performed for 35 seconds to obtain the product nitrogen gas, the product nitrogen gas is discharged from the top of the second adsorption tower 302 and enters the nitrogen gas buffer tank 303, at the same time, the first vent valve 305a and the third vent valve 305c are opened to vent the first adsorption tower 301, after the venting, the third vent valve 305c is closed, the stop valve 306a and the vacuum pump 306b are opened to vacuumize the first adsorption tower 301 to regenerate the adsorbent in the first adsorption tower 301, after the vacuumization, the stop valve 306a and the vacuum pump 306b are closed, and the first adsorption tower 301 is standby;

[0078] Step five, two-tower equalization: after the second adsorption tower 302 stops adsorption, the second tower bottom valve 302a and the second tower top valve 302b are closed, the first equalization valve 304a is opened to connect the top of the second adsorption tower 302 with the top of the first adsorption tower 301 to perform up equalization, after the up equalization for 3.5 seconds, the second equalization valve 304b is opened to connect the bottom of the second adsorption tower 302 with the bottom of the first adsorption tower 301 to perform up-down simultaneous equalization, the time for the up-down simultaneous equalization is 2 seconds, after the up-down simultaneous equalization, step two is performed, at the same time, the second vent valve 305b and the third vent valve 305c are opened to vent the second adsorption tower 302, after the venting, the third vent valve 305c is closed, the stop valve 306a and the vacuum pump 306b are opened to vacuumize the second adsorption tower 302 to an absolute pressure of ≤0.05 MPa to regenerate the adsorbent.

[0079] The adsorbent in the first adsorption tower 301 and the second adsorption tower 302 is carbon molecular sieve, and the loading amount is 7500 kg, and the first adsorption tower 301 and the second adsorption tower 302 are also filled with alumina as a drying agent, and the loading amount is 500 kg, and the drying agent bed is located below the adsorbent.

[0080] In the above process, the nitrogen gas entering the nitrogen gas buffer tank 303 has a pressure of 0.3 MPa to 0.35 MPa, is pressurized to 0.6 MPa by the booster 401, and is sent into the high-pressure nitrogen gas tank 402 for temporary storage.

[0081] In the above process, the average flow rate of the raw material air is 3879 Nm 3 / h, the average flow rate of the product nitrogen gas is 1486 Nm 3 / h, the gas consumption ratio is 2.61, the product nitrogen gas purity is ≥99.5% and ≤99.9%.

[0082] In this embodiment, the total power consumption of the low-pressure blower 100, the vacuum pump 306b and the booster 401 is 362 kW.

[0083] Example 3

[0084] The embodiment provides a low-energy-consumption low-pressure adsorption PSA air separation nitrogen production process, which is used for producing nitrogen with a purity of 99.9% and a pressure of greater than or equal to 0.6 MPa, and a design nitrogen production capacity of 1000 Nm 3 / h. Steps of the process are as follows.

[0085] Step one, raw material air treatment: air is compressed to 0.4 MPa by a low-pressure fan 100, and then the compressed air is sent to a gas-liquid separation tank 200 for gas-liquid separation to remove liquid water;

[0086] Step two, one-tower adsorption: a first tower bottom valve 301a and a first tower top valve 301b are opened, the compressed air after gas-liquid separation is sent to a first adsorption tower 301 for adsorption for 40 seconds, product nitrogen is obtained, the product nitrogen is discharged from a tower top of the first adsorption tower 301 and enters a nitrogen buffer tank 303;

[0087] Step three, one-tower pressure equalization: after the first adsorption tower 301 stops adsorption, the first tower bottom valve 301a and the first tower top valve 301b are closed, a first pressure equalization valve 304a is opened, a tower top of the first adsorption tower 301 is communicated with a tower top of a second adsorption tower 302 to perform upper pressure equalization, after upper pressure equalization for 4 seconds, a second pressure equalization valve 304b is opened, a tower bottom of the first adsorption tower 301 is communicated with a tower bottom of the second adsorption tower 302 to perform upper and lower simultaneous pressure equalization, and the upper and lower simultaneous pressure equalization lasts for 2 seconds;

[0088] Step four, two-tower adsorption: after the upper and lower simultaneous pressure equalization is completed, the first pressure equalization valve 304a and the second pressure equalization valve 304b are closed, a second tower bottom valve 302a and a second tower top valve 302b are opened, the compressed air after gas-liquid separation is sent to the second adsorption tower 302, adsorption lasts for 40 seconds, product nitrogen is obtained, the product nitrogen is discharged from a tower top of the second adsorption tower 302 and enters the nitrogen buffer tank 303, meanwhile, a first vent valve 305a and a third vent valve 305c are opened, the first adsorption tower 301 is vented, after venting, the third vent valve 305c is closed, a stop valve 306a and a vacuum pump 306b are opened, the first adsorption tower 301 is vacuumized to regenerate adsorbent in the first adsorption tower 301, after vacuumization is completed, the stop valve 306a and the vacuum pump 306b are closed, and the first adsorption tower 301 is standby;

[0089] Step five, two towers equalization: after the second adsorption tower 302 stops adsorption, the second bottom valve 302a and the second top valve 302b are closed, the first equalization valve 304a is opened, the top of the second adsorption tower 302 is communicated with the top of the first adsorption tower 301, and the upper equalization is performed. After the upper equalization for 4 seconds, the second equalization valve 304b is opened, the bottom of the second adsorption tower 302 is communicated with the bottom of the first adsorption tower 301, and the upper and lower equalization is performed. The time of the upper and lower equalization is 2 seconds. After the upper and lower equalization is finished, step two is executed, and the second vent valve 305b and the third vent valve 305c are opened at the same time. The second adsorption tower 302 is vented, and after the venting, the third vent valve 305c is closed, the stop valve 306a and the vacuum pump 306b are opened, and the second adsorption tower 302 is vacuumized to an absolute pressure ≤0.05 MPa, so that the adsorbent is regenerated.

[0090] The adsorbent in the first adsorption tower 301 and the second adsorption tower 302 is carbon molecular sieve, and the loading amount is 6600 kg. Alumina is also loaded in the first adsorption tower 301 and the second adsorption tower 302 as a drying agent, and the loading amount is 460 kg. The drying agent bed is located below the adsorbent.

[0091] In the above process, the nitrogen gas entering the nitrogen gas buffer tank 303 has a pressure of 0.3 MPa-0.35 MPa, is pressurized to 0.6 MPa by the booster 401, and is sent to the high-pressure nitrogen gas tank 402 for temporary storage.

[0092] In the above process, the average flow rate of the raw material air is 3478 Nm 3 / h, the average flow rate of the product nitrogen gas is 1023 Nm 3 / h, the gas consumption ratio is 3.4, the purity of the product nitrogen gas is ≥99.9% and ≤99.99%.

[0093] In this embodiment, the total power consumption of the low-pressure blower 100, the vacuum pump 306b and the booster 401 is 329 kW.

[0094] Embodiment 4

[0095] The embodiment provides a low-energy-consumption low-pressure adsorption PSA air separation nitrogen production process, which is used for producing nitrogen gas with a purity of 99.99% and a pressure of ≥0.6 MPa. The design nitrogen production capacity is 1000 Nm 3 / h, and the steps of the process are as follows:

[0096] Step one, raw material air treatment: the air is compressed to 0.4 MPa by the low-pressure blower 100, and then the compressed air is sent to the gas-liquid separation tank 200 for gas-liquid separation to remove liquid water;

[0097] Step two, one tower adsorption: open the first tower bottom valve 301a, the first tower top valve 301b, send the compressed air after gas-liquid separation into the first adsorption tower 301 and adsorb for 40 seconds to obtain product nitrogen, the product nitrogen is discharged from the top of the first adsorption tower 301 and enters the nitrogen buffer tank 303;

[0098] Step three, one tower pressure equalization: after the first adsorption tower 301 stops adsorption, close the first tower bottom valve 301a, the first tower top valve 301b, open the first pressure equalization valve 304a, connect the top of the first adsorption tower 301 with the top of the second adsorption tower 302, and carry out the upper pressure equalization, after 5 seconds of upper pressure equalization, open the second pressure equalization valve 304b, connect the bottom of the first adsorption tower 301 with the bottom of the second adsorption tower 302, and carry out the upper and lower simultaneous pressure equalization, the time of upper and lower simultaneous pressure equalization is 5 seconds.

[0099] Step four, two tower adsorption: after the upper and lower simultaneous pressure equalization is completed, close the first pressure equalization valve 304a and the second pressure equalization valve 304b, open the second tower bottom valve 302a and the second tower top valve 302b, send the compressed air after gas-liquid separation into the second adsorption tower 302, and adsorb for 40 seconds to obtain product nitrogen, the product nitrogen is discharged from the top of the second adsorption tower 302 and enters the nitrogen buffer tank 303, at the same time, open the first vent valve 305a and the third vent valve 305c, vent the first adsorption tower 301, after venting, close the third vent valve 305c, open the stop valve 306a and the vacuum pump 306b, and vacuumize the first adsorption tower 301 to regenerate the adsorbent in the first adsorption tower 301, after vacuumization is completed, close the stop valve 306a and the vacuum pump 306b, and the first adsorption tower 301 is standby.

[0100] Step five, two tower pressure equalization: after the second adsorption tower 302 stops adsorption, close the second tower bottom valve 302a and the second tower top valve 302b, open the first pressure equalization valve 304a, connect the top of the second adsorption tower 302 with the top of the first adsorption tower 301, and carry out the upper pressure equalization, after 5 seconds of upper pressure equalization, open the second pressure equalization valve 304b, connect the bottom of the second adsorption tower 302 with the bottom of the first adsorption tower 301, and carry out the upper and lower simultaneous pressure equalization, the time of upper and lower simultaneous pressure equalization is 5 seconds, after the upper and lower simultaneous pressure equalization is completed, execute step two, at the same time, open the second vent valve 305b and the third vent valve 305c, vent the second adsorption tower 302, after venting, close the third vent valve 305c, open the stop valve 306a and the vacuum pump 306b, and vacuumize the second adsorption tower 302 to an absolute pressure ≤0.05 MPa to regenerate the adsorbent.

[0101] The adsorbent in the first adsorption tower 301 and the second adsorption tower 302 is carbon molecular sieve, and the loading amount is 11000 kg, and alumina is also filled in the first adsorption tower 301 and the second adsorption tower 302 as a drying agent, and the loading amount is 800 kg, the drying agent bed is located below the adsorbent.

[0102] In the above process, the nitrogen gas entering the nitrogen gas buffer tank 303 has a pressure of 0.3 MPa to 0.35 MPa, is pressurized to 0.6 MPa by the booster 401, and is sent to the high-pressure nitrogen gas tank 402 for temporary storage.

[0103] In the above process, the average flow rate of the raw material air is 4724 Nm 3 / h, the average flow rate of the product nitrogen gas is 978 Nm 3 / h, the gas consumption ratio is 4.83, and the purity of the product nitrogen gas is ≥99.99%.

[0104] In this embodiment, the total power consumption of the low-pressure blower 100, the vacuum pump 306b, and the booster 401 is 429 kW.

[0105] Comparative Example 1

[0106] This comparative example provides a PSA air separation nitrogen production process for producing nitrogen gas with a purity of 99.5% and a pressure of ≥0.6 MPa, and the design nitrogen production capacity is 1000 Nm 3 / h. The process is implemented using the device as shown in Figure 2 , and the steps are as follows:

[0107] Step 1, raw material air treatment: the air is compressed to 0.7 MPa by the air compressor 501, and then the compressed air is sent to the cold dryer 502 for drying;

[0108] Step 2, one-tower adsorption: the first tower bottom valve 301a and the first tower top valve 301b are opened, the compressed air after gas-liquid separation is sent to the first adsorption tower 301 for adsorption for 40 seconds to obtain product nitrogen gas, and the product nitrogen gas is discharged from the top of the first adsorption tower 301 and sent to the high-pressure nitrogen gas tank 402 for temporary storage;

[0109] Step 3, one-tower pressure equalization: after the first adsorption tower 301 stops adsorption, the first tower bottom valve 301a and the first tower top valve 301b are closed, and the first pressure equalization valve 304a and the second pressure equalization valve 304b are opened, so that the top of the first adsorption tower 301 is communicated with the top of the second adsorption tower 302, and the bottom of the first adsorption tower 301 is communicated with the bottom of the second adsorption tower 302, and the upper and lower parts are simultaneously equalized in pressure until the pressure of the first adsorption tower 301 and the second adsorption tower 302 is balanced, and the time for simultaneous equalization of the upper and lower parts is 2 seconds;

[0110] Step four, two-tower adsorption: after the end of the up-down simultaneous equalization, the first equalization valve 304a and the second equalization valve 304b are closed, the second tower bottom valve 302a and the second tower top valve 302b are opened, the compressed air after gas-liquid separation is sent into the second adsorption tower 302, and adsorption is performed for 40 seconds to obtain product nitrogen, the product nitrogen is discharged from the top of the second adsorption tower 302 and temporarily stored in the high-pressure nitrogen tank 402, and at the same time, the first vent valve 305a is opened to vent the first adsorption tower 301 so that the adsorbent in the first adsorption tower 301 is regenerated, and after venting, the first vent valve 305a is closed, and the first adsorption tower 301 is standby;

[0111] Step five, two-tower equalization: after the second adsorption tower 302 stops adsorption, the second tower bottom valve 302a and the second tower top valve 302b are closed, and at the same time, the first equalization valve 304a and the second equalization valve 304b are opened to connect the top of the first adsorption tower 301 with the top of the second adsorption tower 302 and to connect the bottom of the first adsorption tower 301 with the bottom of the second adsorption tower 302, and up-down simultaneous equalization is performed until the pressure of the first adsorption tower 301 and the second adsorption tower 302 is balanced, and the up-down simultaneous equalization time is 2 seconds; after the up-down simultaneous equalization is completed, step two is performed, and at the same time, the second vent valve 305b is opened to vent the second adsorption tower 302 so that the adsorbent in the first adsorption tower 301 is regenerated, and after venting, the second vent valve 305b is closed, and the second adsorption tower 302 is standby.

[0112] The adsorbent in the first adsorption tower 301 and the second adsorption tower 302 is carbon molecular sieve 3570 kg, and no drying agent is loaded.

[0113] In the above process, the pressure of the product nitrogen entering the high-pressure nitrogen tank 402 is 0.65 MPa-0.7 MPa, and the output pressure is 0.6 MPa.

[0114] In the above process, the average flow rate of the raw material air is 2765 Nm 3 / h, the average flow rate of the product nitrogen is 1017 Nm 3 / h, the gas consumption ratio is 2.72, the purity of the product nitrogen is ≥99.5% and ≤99.9%.

[0115] In the present comparative example, the total power consumption of the air compressor 501 and the cold dryer 502 is 278 kW.

[0116] Comparative Example 2

[0117] The present comparative example provides a PSA air separation nitrogen production process for producing nitrogen with a purity of 99.5% and a pressure of ≥0.6 MPa, and the design nitrogen production capacity is 1500 Nm 3 / h, the steps of the process refer to Comparative Example 1, carbon molecular sieve adsorbent is used, and the difference lies in that the adsorbent loading amount is 5300 kg, the adsorption time is 40 s, and the up-down simultaneous equalization time is 2 s.

[0118] In the above process, the product nitrogen pressure entering the high-pressure nitrogen tank 402 is 0.65-0.7 MPa, and the output pressure is 0.6 MPa.

[0119] In the above process, the average flow rate of the raw material air is 4116 Nm 3 / h, the average flow rate of the product nitrogen is 1502 Nm 3 / h, the gas consumption ratio is 2.74, and the product nitrogen purity is ≥99.5% and ≤99.9%.

[0120] In the present comparative example, the total power consumption of the air compressor 501 and the cold dryer 502 is 436 kW.

[0121] Comparative Example 3

[0122] The present comparative example provides a PSA air separation nitrogen production process for producing nitrogen with a purity of 99.9% and a pressure of ≥0.6 MPa, and the design nitrogen production capacity is 1000 Nm 3 / h, the steps of the process refer to Comparative Example 1, and a carbon molecular sieve adsorbent is used, with the difference being that the adsorbent loading amount is 5128 kg, the adsorption time is 40 s, and the simultaneous equalization time is 2 s.

[0123] In the above process, the product nitrogen pressure entering the high-pressure nitrogen tank 402 is 0.65-0.7 MPa, and the output pressure is 0.6 MPa.

[0124] In the above process, the average flow rate of the raw material air is 3874 Nm 3 / h, the average flow rate of the product nitrogen is 1001 Nm 3 / h, the gas consumption ratio is 3.87, and the product nitrogen purity is ≥99.9% and ≤99.99%.

[0125] In the present comparative example, the total power consumption of the air compressor 501 and the cold dryer 502 is 411 kW.

[0126] Comparative Example 4

[0127] The present comparative example provides a PSA air separation nitrogen production process for producing nitrogen with a purity of 99.99% and a pressure of ≥0.6 MPa, and the design nitrogen production capacity is 1000 Nm 3 / h, the steps of the process refer to Comparative Example 1, and a carbon molecular sieve adsorbent is used, with the difference being that the adsorbent loading amount is 9090 kg, the adsorption time is 40 s, and the simultaneous equalization time is 2 s.

[0128] In the above process, the product nitrogen pressure entering the high-pressure nitrogen tank 402 is 0.65-0.7 MPa, and the output pressure is 0.6 MPa.

[0129] In the above process, the average flow of raw air is 5314 Nm 3 / h, the average flow of product nitrogen is 997 Nm 3 / h, the gas consumption ratio is 5.33, and the purity of product nitrogen is ≥ 99.99%.

[0130] In the present comparative example, the total power consumption of the air compressor 501 and the cold dryer 502 is 562 kW.

[0131] The data of Examples 1-4 and Comparative Examples 1-4 are as follows:

[0132] Table 1: Data summary of Examples 1-4 and Comparative Examples 1-4

[0133]

[0134] As shown in Table 1 above, under the same design capacity and purity conditions, the energy consumption of Examples 1-4 is significantly lower than that of Comparative Examples 1-4, wherein the total energy consumption of Example 1 is reduced by 11.87% compared to Comparative Example 1, the total energy consumption of Example 2 is reduced by 12.43% compared to Comparative Example 2, the total energy consumption of Example 3 is reduced by 19.95% compared to Comparative Example 3, and the total energy consumption of Example 4 is reduced by 23.67% compared to Comparative Example 4; and by comparing the energy saving effects of Examples 1-4, it is found that the greater the nitrogen production and the higher the purity, the higher the energy utilization rate of the nitrogen production process provided by the present application, and the more obvious the energy saving effect.

[0135] At the same time, by comparing Examples 1-4 and Comparative Examples 1-4, it can be seen that the nitrogen production process provided by the present application has a lower gas consumption ratio than Comparative Examples 1-4 under the same nitrogen purity and production, and has higher process efficiency and energy utilization efficiency.

[0136] In summary, the present application provides a PSA air separation nitrogen production process with higher process efficiency and energy utilization efficiency, which can be used to produce nitrogen with a purity of 99.5% or higher. Compared with existing nitrogen production processes, it has the advantages of low gas consumption ratio and low average energy consumption, can significantly reduce the energy consumption of the nitrogen production process, and can produce greater economic and environmental benefits.

[0137] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A low-energy-consumption, low-pressure adsorption PSA air separation nitrogen production process, characterized in that, Includes the following steps: Step 1: Compress the air to 0.2-0.5 MPa, and then perform gas-liquid separation to remove liquid water; Step 2: The compressed air that has undergone gas-liquid separation is sent into the first adsorption tower for adsorption for a certain period of time to obtain product nitrogen gas, which is discharged from the top of the first adsorption tower. Step 3: After the first adsorption tower stops adsorption, connect the top of the first adsorption tower to the top of the second adsorption tower for upper pressure equalization. After upper pressure equalization for a certain period of time, connect the bottom of the first adsorption tower to the bottom of the second adsorption tower for upper and lower pressure equalization simultaneously. The upper pressure equalization time is 1 to 5 seconds, and the upper and lower pressure equalization time is 1 to 5 seconds. Step 4: After the pressure equalization of the upper and lower parts is completed, the compressed air obtained in Step 1 is sent into the second adsorption tower. After adsorption for a certain period of time, product nitrogen is obtained. The product nitrogen is discharged from the top of the second adsorption tower, and the first adsorption tower is vented at the same time. After venting, a vacuum is drawn. Step 5: After the second adsorption tower stops adsorption, connect the top of the second adsorption tower to the top of the first adsorption tower for upper pressure equalization. After upper pressure equalization for a certain period of time, connect the bottom of the second adsorption tower to the bottom of the first adsorption tower for simultaneous upper and lower pressure equalization. Then, vent the second adsorption tower, evacuate it, and then execute Step 2. The upper pressure equalization time is 1-5 seconds, and the simultaneous upper and lower pressure equalization time is 1-5 seconds. In steps two and four, after the nitrogen gas from the product is released, the pressure is increased to ≥0.6MPa.

2. The low-energy-consumption, low-pressure adsorption PSA air separation nitrogen production process as described in claim 1, characterized in that, The first and second adsorption towers are filled with adsorbent, which is a carbon molecular sieve.

3. The low-energy-consumption, low-pressure adsorption PSA air separation nitrogen production process as described in claim 2, characterized in that, The first and second adsorption towers are also filled with desiccant.

4. The low-energy-consumption, low-pressure adsorption PSA air separation nitrogen production process as described in any one of claims 3, characterized in that, The desiccant is aluminum oxide.

5. A low-energy-consumption, low-pressure adsorption PSA air separation nitrogen production process as described in any one of claims 1 to 4, characterized in that, In step two, the adsorption time is 20–60 seconds.

6. A low-energy-consumption, low-pressure adsorption PSA air separation nitrogen production process as described in any one of claims 1 to 4, characterized in that, In step four, the adsorption time is 20–60 seconds.

7. A low-energy-consumption, low-pressure adsorption PSA air separation nitrogen production process as described in any one of claims 1 to 4, characterized in that, In step four, a vacuum is drawn until the absolute pressure is ≤0.05MPa.

8. The low-energy-consumption, low-pressure adsorption PSA air separation nitrogen production process as described in claim 5, characterized in that, In step two, the adsorption time is 35–40 s; in step four, the adsorption time is 35–40 s.

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