CN110354637B - Method for enriching easily-adsorbed gas by pressure swing adsorption method - Google Patents
Method for enriching easily-adsorbed gas by pressure swing adsorption method Download PDFInfo
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- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
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- B01D53/047—Pressure swing adsorption
Abstract
The invention provides a method for enriching easily-adsorbed gas by a pressure swing adsorption method, which comprises the following steps: (1) the raw material gas enters a first adsorption tower, and the adsorption operation is carried out until the adsorbent is saturated; (2) carrying out pressure equalizing operation on the first adsorption tower after adsorption; (3) introducing the product gas into the adsorption tower to replace unadsorbed gas, and blowing the replaced gas into other adsorption towers; (4) carrying out pressure equalizing operation on the replaced first adsorption tower again; (5) carrying out vacuum desorption on the first adsorption tower to obtain product gas; (6) and pressurizing the desorbed first adsorption tower. The invention adopts the working procedures to match a plurality of adsorption towers, realizes the enrichment of the gas easy to be adsorbed, particularly takes the product gas as the replacement gas, and leads the replaced gas to enter other adsorption towers, and carries out the pressure equalizing operation after replacement, thereby not only improving the replacement effect, but also improving the concentration and the recovery rate of the component easy to be adsorbed.
Description
Technical Field
The invention belongs to the technical field of gas adsorption, relates to a method for enriching an easily-adsorbed gas by a pressure swing adsorption method, and particularly relates to a method for enriching an easily-adsorbed gas by a pressure swing adsorption method containing product gas replacement.
Background
Pressure swing adsorption is a common gas separation mode in the chemical industry, and is widely applied industrially due to the advantages of strong flexibility, low operation cost, good separation effect and the like. If necessary, the gas that is easily adsorbed can be recovered after adsorption separation, the remaining gas that is difficult to adsorb can be recovered, or both can be recovered. The adsorbent is one of factors influencing the separation effect, and the design optimization of the adsorption process is also important for improving the separation effect.
At present, the flow of gas adsorption separation generally includes the steps of adsorption, pressure equalization, desorption and final charging, and the replacement is also one of the common operations in the adsorption flow, and can be used for improving the product concentration to a certain extent, but when the replacement operation is performed, the gas in the adsorption tower also has a part of product gas besides the impurity gas, the direct discharge of the replaced gas can cause the loss of the target product gas, the product recovery rate is reduced, and the pollution can be caused, and if the replaced gas is conveyed back to the raw material tank, the gas treatment capacity of the adsorbent can be reduced. In addition, when gas separation is performed under high pressure, low-pressure replacement is generally adopted, and the low-pressure replacement operation not only has a limited effect on enrichment of the product gas, but also causes gas desorption due to reduction of the partial pressure of the target gas, thereby reducing the treatment capacity and the enrichment effect of the target gas.
CN 107694284A discloses a method for concentrating methane in a gas layer by multi-tower replacement vacuum pressure swing adsorption, which mainly comprises pressurization and CH4Adsorption, CO2The method comprises the steps of replacement, pressure reduction, adsorbent vacuum desorption, vacuum purging and the like, pressure equalizing operation is not adopted before replacement, the pressure of replacement gas is higher, unadsorbed gas in a replacement tower can be replaced, methane can also be replaced, the gas separation effect is poor, and CO is adopted2Other impurity gases can be introduced during replacement, which is not beneficial to the thickening of methane in the coal bed gas. CN 102350171a discloses a gas separation method using a displacement method, wherein at least 6 adsorption towers are combined together to realize cyclic adsorption, each adsorption tower completes the cyclic processes of adsorption, pressure reduction, evacuation, displacement, vacuum pumping, pressure increase and pressure increase in sequence, and each adsorption tower completes one process at the same time.
In view of the above, there is also a need to find more optimized process steps for the separation of components in the mixed gas and the enrichment of the readily adsorbable gas to substantially increase the concentration and recovery of the product gas.
Disclosure of Invention
The invention aims to provide a method for enriching an easily-adsorbed gas by a pressure swing adsorption method, which adopts the pressure swing adsorption method, utilizes selective adsorption of an adsorbent on a target component, enables the gas displaced in the gas adsorption separation process to enter other adsorption towers, and adopts pressure equalizing operation after displacement, thereby greatly improving the concentration and recovery rate of product gas while enhancing the displacement effect.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for enriching an easily-adsorbed gas by a pressure swing adsorption method, which comprises the following steps:
(1) the raw material gas enters a first adsorption tower, wherein the easily-adsorbed components are adsorbed by the adsorbent, the difficultly-adsorbed components flow out, and the adsorption operation is carried out until the adsorbent is saturated;
(2) carrying out pressure equalizing operation on the first adsorption tower and the third adsorption tower after adsorption in the step (1);
(3) introducing the product gas into the first adsorption tower after pressure equalization in the step (2), replacing unadsorbed gas, and blowing the replaced gas into the third adsorption tower in the step (2);
(4) carrying out pressure equalizing operation on the first adsorption tower and the fourth adsorption tower after replacement in the step (3);
(5) vacuumizing the first adsorption tower after pressure equalization in the step (4), and desorbing the easily-adsorbed components adsorbed in the step (1) to obtain product gas;
(6) and (3) pressurizing the gas and the external source gas which are replaced by the fourth adsorption tower in the first adsorption tower desorbed in the step (5), and performing the operation of the step (1) again.
According to the invention, selective adsorption of the target component by the adsorbent is utilized, a set of adsorption process is completed in the adsorption tower, after the easily-adsorbed component in the raw material gas is adsorbed, the pressure is reduced through pressure equalizing operation, then the unadsorbed gas in the adsorption tower is replaced, the replaced gas enters other adsorption towers which are arranged in parallel, and the recovery rate of the product gas can be improved while the purity of the product gas is improved through the pressure equalizing and vacuum desorption steps after replacement; after desorption, the gas replaced by other adsorption towers is introduced for pressurization and final pressurization, so that the recovery rate of the gas easy to adsorb is further improved, the whole operation procedure is completed, and then the operation is carried out in a circulating manner.
The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.
As a preferred technical scheme of the invention, the method needs at least 5 adsorption towers to complete the cyclic adsorption.
Preferably, the steps of adsorption, pressure equalization, replacement, pressure equalization, desorption and pressurization are completed in each adsorption tower.
According to the invention, at least 5 adsorption towers are arranged in parallel according to the operation procedures in each adsorption tower and the inlet-outlet relation of gas between the adsorption towers, so that in the process that one adsorption tower completes one operation process, other adsorption towers can start from different nodes and can complete one cycle in the same sequence, the mutual matching of a plurality of adsorption towers is realized, and the treatment rate of the feed gas is improved.
In the invention, "first", "third", "fourth", etc. before the adsorption tower are used for distinguishing the adsorption towers which are arranged in parallel, and the distinguishing mode is not fixed, if one of the adsorption towers is taken as the first adsorption tower, the pressure of the adsorption tower in the step (2) is not necessarily equalized with that of the third adsorption tower, the pressure of the adsorption tower is only corresponding to the process, the first adsorption tower needs to be depressurized, and the other adsorption tower which is subjected to the pressure boosting process after desorption just meets the requirement, but not limited to the third adsorption tower, namely, different adsorption towers are in different stages in the adsorption cycle at the same time, and are different from each other, and the number of the adsorption towers is related to the stage division number of the operation process in the adsorption cycle; the key point of the invention is that the working procedures of a plurality of adsorption towers are matched, so that all the adsorption towers can complete one cycle of adsorption at the same time.
As a preferable technical scheme of the invention, the raw material gas in the step (1) comprises an easily-adsorbed component and a difficultly-adsorbed component, wherein the easily-adsorbed component comprises methane.
Preferably, the volume fraction of the readily adsorbable component in the feed gas is 2 to 60%, such as 2%, 5%, 10%, 20%, 30%, 40%, 50%, or 60%, but not limited to the recited values, and other values not recited in this range are equally applicable.
Preferably, the non-adsorbable component comprises any one or a combination of at least two of nitrogen, oxygen, carbon monoxide or an inert gas, typical but non-limiting examples of which are: combinations of nitrogen and oxygen, oxygen and carbon monoxide, nitrogen, carbon monoxide and inert gases, and the like.
The raw gas which can be treated in the invention needs to meet the requirement that a specific adsorbent has obvious difference on the adsorptivity of different components so as to separate and purify the easily adsorbed components by utilizing the strong adsorbability of the easily adsorbed components. The methane in the raw gas treated by the method is an easily-adsorbed component, and comprises medium-low concentration coal bed gas, industrial methane tail gas and the like.
In the step (1), raw material gas enters from the bottom of the adsorption tower, easily-adsorbed components are enriched in the adsorption tower, the bottom of the methane concentration in the adsorption tower is firstly raised, then the upper part of the methane concentration in the adsorption tower is raised, namely the front end of a methane concentration distribution curve is continuously moved upwards, the methane concentration at the outlet of the adsorption tower is measured in real time, when the methane concentration starts to obviously increase, the adsorption bed starts to penetrate, and the raw material gas is stopped to be introduced.
As a preferred technical scheme of the invention, the adsorbent in the step (1) comprises any one of activated carbon, molecular sieve or ionic liquid zeolite or a combination of at least two of the activated carbon, the molecular sieve and the ionic liquid zeolite, and typical but non-limiting examples of the combination are as follows: a combination of activated carbon and molecular sieve, a combination of molecular sieve and ionic liquid zeolite, a combination of activated carbon, molecular sieve and ionic liquid zeolite, and the like, preferably ionic liquid zeolite.
In a preferred embodiment of the present invention, the adsorption pressure in step (1) is 0.1 to 1.0MPa, for example, 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.8MPa or 1.0MPa, but the adsorption pressure is not limited to the above-mentioned values, and other values not shown in the above-mentioned value range are also applicable.
In the present invention, the adsorption pressure is selected mainly according to the concentration of the easily adsorbable component in the feed gas, and when the easily adsorbable component is contained in the feed gas, such as methane, the oxygen content determines the explosion limit, and the adsorption pressure is also influenced by the oxygen content based on the safety consideration.
In the invention, when the concentration of methane in the feed gas is lower, normal pressure operation is generally good, so that the safety is ensured, and when the concentration of methane is higher, pressurization operation can be adopted, so that the gas stripping treatment capacity is improved.
Preferably, the adsorption temperature in step (1) is-10 to 60 ℃, for example-10 ℃, 0 ℃, 10 ℃, 20 ℃, 30 ℃, 40 ℃, 50 ℃ or 60 ℃, but not limited to the recited values, and other values not recited within the range of values are equally applicable, preferably 20 to 30 ℃.
As a preferable technical scheme of the invention, the pressure equalizing operation in the step (2) and the step (4) is at least one stage independently.
In the invention, the pressure in the adsorption tower is higher after the adsorption in the step (1) is finished, the adsorption tower is communicated with other low-pressure adsorption towers for pressure balance, and the impurity gas and a small amount of unadsorbed methane enter another adsorption tower, so that the reduction of the methane recovery rate caused by direct discharge is avoided; the pressure equalizing stage number is determined according to the replacement pressure of the next step.
Preferably, the displacement pressure in step (3) is 80 to 1000kPa, such as 80kPa, 100kPa, 150kPa, 200kPa, 300kPa, 400kPa, 500kPa, 600kPa, 800kPa, or 1000kPa, but is not limited to the recited values, and other values not recited in the range of values are also applicable.
In the invention, unadsorbed gas still exists in the adsorption tower after adsorption and pressure equalization, the unadsorbed gas is replaced by the product gas, the methane partial pressure in the product gas is higher, the impurity gas adsorbed on the surface of the adsorbent is desorbed by competitive adsorption effect and enters another adsorption tower needing pressure boosting along with the unadsorbed gas in a sweeping mode, the methane gas proportion in the adsorption tower is greatly improved, the recovery rate loss caused by the direct outflow of the methane gas is reduced, and the replacement time is adjusted according to the required methane concentration and recovery rate in the product gas.
Preferably, the pressure after equalizing the pressure in step (2) and step (4) is 5 to 100kPa lower than the substitution pressure, for example, 5kPa, 10kPa, 20kPa, 30kPa, 40kPa, 50kPa, 60kPa, 80kPa, 100kPa, etc., but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
In the invention, the pressure of the adsorption tower is higher after the product gas is replaced, pressure equalizing operation can be carried out, the tower pressure is reduced, the higher energy consumption in the desorption stage is avoided, and part of impurity gas can be discharged, so that the purity of methane obtained by desorption is improved.
As a preferable embodiment of the present invention, after the evacuation in the step (5), the pressure in the first adsorption column is 10 to 35kPa, for example, 10kPa, 15kPa, 20kPa, 25kPa, 30kPa or 35kPa, but the pressure is not limited to the above-mentioned values, and other values not specified in the above-mentioned range of values are also applicable.
In the invention, the vacuum pump is adopted to carry out vacuum treatment on the adsorption tower, wherein the adsorbed gas can be desorbed, and the regeneration of the adsorbent is realized at the same time.
In addition, in the present invention, unless otherwise specifically mentioned, the pressure refers to an absolute pressure.
Preferably, after the desorption in the step (5), the first adsorption tower is subjected to pressure equalizing operation.
Preferably, the pressure equalizing operation is at least one stage, and preferably, the pressure equalizing operation is performed by adopting a third adsorption tower and a fourth adsorption tower in sequence.
Preferably, after the pressure equalization operation, the pressure in the first adsorption column is lower than the displacement pressure by 5 to 100kPa, for example, 5kPa, 10kPa, 20kPa, 30kPa, 40kPa, 50kPa, 60kPa, 80kPa, or 100kPa, but not limited to the recited values, and other values not recited in the range of the recited values are also applicable.
In the invention, the pressure of the adsorption tower is lower after vacuum desorption, pressurization is needed, pressure equalization can be carried out firstly by utilizing the cooperation between the adsorption towers in order to avoid the need of excessive external source gas, and the gas containing a small amount of methane is introduced while the pressure is increased, so that the methane recovery rate is improved.
As a preferable technical scheme of the invention, the step (6) further comprises a pressure equalizing operation again after the gas replaced by the fourth adsorption tower is adopted for pressurization.
In the invention, the replacement operation exists after the adsorption of the adsorption tower, and the purged gas enters other adsorption towers needing to be boosted, so when the adsorption tower is in a boosting stage, the adsorption tower which carries out the replacement operation can be arranged at the same time according to the matching among the adsorption towers, the purged gas is introduced into the adsorption tower, the tower pressure is further increased, and the gas is transferred among the adsorption towers, thereby being beneficial to the improvement of the methane recovery rate; after introducing the gas displaced by the other adsorption column, if the difference from the adsorption pressure is still large, the pressure equalization can be performed again, and generally, the difference between the two is not large.
As a preferred technical scheme of the invention, the exogenous gas in the step (6) comprises a purge gas and/or a raw material gas, and is preferably a purge gas.
Preferably, the pressure of the exogenous gas is the same as the adsorption pressure in step (1).
Preferably, the purge gas is counter-pressurized, in a direction opposite to the flow of the feedstock in step (1).
Preferably, the purge gas comprises nitrogen and oxygen, preferably the non-adsorbable component exiting the adsorption operation in step (1).
In the invention, at the end of the cyclic adsorption process, the gas is finally pressurized to the adsorption pressure, the cyclic adsorption is started, the purified gas is preferentially adopted to reversely pressurize the adsorption tower, generally, the purified gas is blown from the top of the tower to the bottom of the tower, the methane concentration distribution curve can be compressed, and the methane treatment capacity of the adsorbent per unit volume is improved.
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) the raw material gas enters a first adsorption tower, wherein easily-adsorbed components are adsorbed by an adsorbent, difficultly-adsorbed components flow out, and the adsorption operation is carried out until the adsorbent is saturated, wherein the adsorption pressure is 0.1-1.0 MPa, and the adsorption temperature is-10-60 ℃;
(2) carrying out pressure equalizing operation on the first adsorption tower and the third adsorption tower after adsorption in the step (1), wherein the pressure equalized is 5-100 kPa lower than the replacement pressure in the step (3);
(3) introducing the product gas into the first adsorption tower after pressure equalization in the step (2), replacing unadsorbed gas, wherein the replacement pressure is 80-1000 kPa, and blowing the replaced gas into the third adsorption tower in the step (2);
(4) carrying out pressure equalizing operation on the first adsorption tower and the fourth adsorption tower after replacement in the step (3), wherein the pressure equalized is 5-100 kPa lower than the replacement pressure in the step (3);
(5) vacuumizing the first adsorption tower after pressure equalization in the step (4) until the pressure is 10-35 kPa, and desorbing the easily-adsorbed components adsorbed in the step (1) to obtain product gas;
(6) equalizing the pressure of the first adsorption tower desorbed in the step (5) with a third adsorption tower and a fourth adsorption tower in sequence;
(7) and (3) pressurizing the pressure-equalized first adsorption tower obtained in the step (6) by adopting the gas and the external source gas replaced by the fourth adsorption tower, wherein the pressure of the external source gas is the same as the adsorption pressure in the step (1), and then performing the operation in the step (1) again.
Compared with the prior art, the invention has the following beneficial effects:
(1) the method realizes the enrichment of the gas easy to adsorb by the processes of adsorption, pressure equalization, replacement, pressure equalization, desorption and pressurization, particularly uses the product gas as the replacement gas, and leads the replaced gas to enter other adsorption towers, thereby not only improving the replacement effect, but also improving the concentration and the recovery rate of the components easy to adsorb;
(2) the invention carries out pressure equalizing operation after replacement, which can further reduce the concentration of impurity gas in the adsorption tower, thereby improving the concentration of methane in the product gas; the energy consumption in the vacuum desorption operation process is reduced by reducing the pressure of the adsorption tower;
(3) in the method, a plurality of adsorption towers are matched, and the gas transfer among the towers avoids the direct discharge of unadsorbed target components, so that the product recovery rate is improved, and the treatment rate of the feed gas can be improved by simultaneously operating the adsorption towers.
Drawings
FIG. 1 is a schematic view of a structural connection of an adsorption apparatus provided in example 1 of the present invention;
FIG. 2 is a schematic view showing the operation of an adsorption apparatus provided in example 1 of the present invention;
FIG. 3 is a schematic view of the structural connection of an adsorption apparatus provided in example 2 of the present invention;
wherein, 101A-a first adsorption tower, 101B-a second adsorption tower, 101C-a third adsorption tower, 101D-a fourth adsorption tower, 101E-a fifth adsorption tower, and 201-a product gas storage device.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is defined by the claims.
The following are typical but non-limiting examples of the invention:
example 1:
the embodiment provides a method for enriching methane by a pressure swing adsorption method, which is operated by a device composed of 5 adsorption towers arranged in parallel, the structural connection schematic diagram of the device is shown in fig. 1, the device comprises a first adsorption tower 101A, a second adsorption tower 101B, a third adsorption tower 101C, a fourth adsorption tower 101D, a fifth adsorption tower 101E, a feeding line, an equalizing line, a replacing line, a desorption line and a final filling line, each pipeline is independently connected with 5 adsorption towers and is provided with a valve; the replacement line and the desorption line are connected with a product gas storage device 201.
In this embodiment, a 5-tower operation flow is taken as an example to specifically describe an operation procedure for enriching methane; wherein the adopted adsorption pressure is 120kPa, the desorption pressure is 20kPa, taking the first adsorption tower 101A as an example, the method comprises 20 operation flows, which respectively comprise: 1. adsorption; 2. adsorption; 3. adsorption, 4, adsorption; 5. vacant; 6. pressure equalizing; 7. replacement; 8. vacant; 9. pressure equalizing; 10. vacant; 11. vacant; 12. vacant; 13. desorbing; 14. desorbing; 15. desorbing; 16. desorbing; 17. pressure equalizing; 18. pressure equalizing; 19. introducing the displaced gas; 20. final charging; the other adsorption towers respectively carry out 20-step circulation according to the same sequence and different nodes, and the operation flow diagram of the device is shown in figure 2 and operates according to the numbering sequence of the flow.
The following description will specifically describe the operation flow of 20 steps by taking the first adsorption tower 101A as an example:
1-4, adsorption: opening valves 101A and 102A, feeding the raw material gas into the first adsorption tower 101A, and contacting with adsorbent at adsorption pressure of 120kPa, wherein the methane which is a component easy to adsorb is enriched in the adsorption tower, and the component difficult to adsorb, such as N, is enriched in the adsorption tower2、O2And CO flows out of the tower top to a tail gas tank, the concentration of methane at the outlet of the adsorption tower is measured in real time, and the introduction of the feed gas is stopped after the adsorption of the adsorbent is saturated.
5. Vacant: the valves 101A and 102A were closed, and the first adsorption column 101A was not subjected to any operation, and the pressure was maintained at 120 kPa.
6. Pressure equalizing: and opening valves 104A and 104C, communicating the first adsorption tower 101A with the third adsorption tower 101C, releasing the pressure of the first adsorption tower 101A, boosting the pressure of the third adsorption tower 101C, and keeping the pressures of the two towers to be 92kPa after pressure equalization.
7. And (3) replacement: the valve KV13 is opened, the unadsorbed gas in the first adsorption tower 101A is replaced with product gas (105kPa), and purged into the third adsorption tower 101C, the replacement gas has a higher methane partial pressure, and the impurity gas adsorbed on the adsorbent surface is desorbed and purged out of the tower.
8. Vacant: the valves 104A, 104C and KV13 were closed, and the pressure was maintained at 105kPa without any operation on the first adsorption column 101A.
9. Pressure equalizing: and opening valves 104A and 104D, communicating the first adsorption tower 101A with the fourth adsorption tower 101D, releasing the pressure of the first adsorption tower 101A, boosting the pressure of the fourth adsorption tower 101D, and keeping the pressure of the two towers to be 65kPa after pressure equalization.
10-12, vacant: the valves 104A and 104D were closed, and the first adsorption tower 101A was not operated at all, and the pressure was maintained at 65 kPa.
13-16, desorption: and opening the valve 108A, communicating the first adsorption tower 101A with a vacuum pump, vacuumizing the first adsorption tower 101A to obtain a purified methane product and regenerating the adsorbent, wherein the desorption vacuum degree is 20 kPa.
17. Pressure equalizing: and closing the valve 108A, opening the valves 104A and 104C, communicating the first adsorption tower 101A with the third adsorption tower 101C, pressurizing the first adsorption tower 101A, decompressing the third adsorption tower 101C, and keeping the pressures of the two towers 65kPa after pressure equalization.
18. Pressure equalizing: and closing the valve 104C, opening the valve 104D, communicating the first adsorption tower 101A and the fourth adsorption tower 101D, pressurizing the first adsorption tower 101A, and depressurizing the fourth adsorption tower 101D, wherein the pressures of the two towers after pressure equalization are 92 kPa.
19. Introduction of displaced gas: the valve KV43 is opened, the fourth adsorption tower 101D is replaced with the product gas, the replaced gas is purged to the first adsorption tower 101A, and the first adsorption tower 101A is further pressurized to 105 kPa.
20. Final charging: the first adsorption tower 101A is reversely and finally charged with the purified gas (120kPa), so that the first adsorption tower 101A is pressurized, and the next cycle is started.
The operation process and the operation conditions are adopted to enrich the methane in the raw material gas, the raw material gases with different methane concentrations are used for carrying out a plurality of experiments, and the volume fractions of each component of the three raw material gases are respectively as follows: 5.7% of methane and 94.3% of nitrogen; 15.6% of methane and 84.4% of nitrogen; 25.3 percent of methane and 74.7 percent of nitrogen. After 30 times of the above-mentioned circulation process, the methane concentration and the methane recovery rate in the product gas were measured, and the results are shown in table 1.
Table 1 results of cycle adsorption experiment of raw material gas having different methane concentrations in example 1
Example 2:
the embodiment provides a method for enriching methane by a pressure swing adsorption method, which is operated by adopting a device consisting of 5 adsorption towers arranged in parallel, the structural connection schematic diagram of the device is shown in figure 3, the overall structure and the connection relation are basically consistent with those of the embodiment 1, and the difference is that: the operation pipeline comprises a feeding line, an equalizing line, a replacing line, a desorption line and a final charging line, and also comprises a pressure reducing line.
In this embodiment, a 5-tower operation flow is taken as an example to specifically describe an operation procedure for enriching methane; wherein the adopted adsorption pressure is 550kPa, the desorption pressure is 25kPa, taking the first adsorption tower 101A as an example, the method comprises 18 operation flows, which are respectively as follows: 1. adsorption; 2. adsorption; 3. adsorption, 4, adsorption; 5. vacant; 6. pressure equalizing; 7. replacement; 8. vacant; 9. pressure equalizing; 10. pressure equalizing; 11. vacant; 12. vacant; 13. desorbing; 14. desorbing; 15. desorbing; 16. desorbing; 17. pressure equalizing; 18. pressure equalizing; 19. introducing the displaced gas; 20. final charging; and other adsorption towers respectively carry out 20 steps of circulation according to the same sequence and different nodes.
The following description will specifically describe the operation flow of 20 steps by taking the first adsorption tower 101A as an example:
1-4, adsorption: opening valves 101A and 102A, feeding the raw material gas into the first adsorption tower 101A, and contacting with adsorbent at 550kPa, wherein the methane which is a component easy to adsorb is enriched in the adsorption tower, and the component difficult to adsorb, such as N, is enriched in the adsorption tower2、O2And CO flows out of the tower top to a tail gas tank, the concentration of methane at the outlet of the adsorption tower is measured in real time, and the introduction of the feed gas is stopped after the adsorption of the adsorbent is saturated.
5. Vacant: the valves 101A and 102A were closed, and the first adsorption column 101A was not subjected to any operation, and the pressure was maintained at 550 kPa.
6. Pressure equalizing: and opening valves 104A and 104C, communicating the first adsorption tower 101A with the third adsorption tower 101C, releasing the pressure of the first adsorption tower 101A, boosting the pressure of the third adsorption tower 101C, and enabling the pressures of the two towers to be 390kPa after pressure equalization.
7. And (3) replacement: the valve KV13 is opened, the unadsorbed gas in the first adsorption tower 101A is replaced with product gas (395kPa), and purged into the third adsorption tower 101C, the replacement gas has a higher methane partial pressure, and the impurity gas adsorbed on the adsorbent surface is desorbed and purged out of the tower.
8. Vacant: the valves 104A, 104C and KV13 were closed, and the pressure was maintained at 395kPa without any operation of the first adsorption column 101A.
9. Pressure equalizing: and opening valves 104A and 104D, communicating the first adsorption tower 101A with the fourth adsorption tower 101D, releasing the pressure of the first adsorption tower 101A, boosting the pressure of the fourth adsorption tower 101D, and enabling the pressures of the two towers to be 220kPa after pressure equalization.
10. Pressure equalizing: and (3) closing the valves 104A and 104D, opening the valve KV14, and equalizing the pressure with the empty buffer tank, wherein the pressure is 101kPa after equalizing the pressure.
11-12, vacant: the valve KV14 was closed, and the pressure was maintained at 101kPa without any operation of the first adsorption column 101A.
13-16, desorption: and opening the valve 108A, communicating the first adsorption tower 101A with a vacuum pump, vacuumizing the first adsorption tower 101A to obtain a purified methane product and regenerating the adsorbent, wherein the desorption vacuum degree is 25 kPa.
17. Pressure equalizing: and closing the valve 108A, opening the valves 104A and 104C, communicating the first adsorption tower 101A with the third adsorption tower 101C, pressurizing the first adsorption tower 101A, decompressing the third adsorption tower 101C, and keeping the pressures of the two towers to be 220kPa after pressure equalization.
18. Pressure equalizing: and closing the valve 104C, opening the valve 104D, communicating the first adsorption tower 101A and the fourth adsorption tower 101D, pressurizing the first adsorption tower 101A, and decompressing the fourth adsorption tower 101D, wherein the pressures of the two towers after pressure equalization are 390 kPa.
19. Introduction of displaced gas: the valve KV43 is opened, the fourth adsorption tower 101D is replaced with the product gas, the replaced gas is purged to the first adsorption tower 101A, and the first adsorption tower 101A is further pressurized to 395 kPa.
20. Final charging: the first adsorption tower 101A is reversely and finally charged with the hardly-absorbed component (550kPa) flowing out in the adsorption stage, so that the first adsorption tower 101A is pressurized, and the next cycle is started.
The operation process and the operation conditions are adopted to enrich the methane in the raw material gas, two raw material gases with different methane concentrations are used for carrying out experiments, wherein in one mixed gas, the volume fractions of the components are respectively as follows: 40.2% of methane, 11.6% of oxygen, 48.0% of nitrogen and 0.2% of other gases; in another mixed gas, the volume fractions of the components are respectively as follows: 31.1% of methane, 11.8% of oxygen, 56.8% of nitrogen and 0.3% of other gases; after 30 times of the above-mentioned circulation process, the methane concentration and the methane recovery rate in the product gas were measured, and the results are shown in table 2.
Table 2 results of cycle adsorption experiment of raw material gas having different methane concentrations in example 2
| Experiment number | 1 | 2 |
| Concentration of methane in raw gas (%) | 40.2 | 31.3 |
| Methane concentration in product gas (%) | 99.6 | 96.8 |
| Oxygen concentration in product gas (%) | 0.1 | 0.5 |
| Methane recovery (%) | 97.4 | 96.1 |
Example 3:
the embodiment provides a method for enriching methane by a pressure swing adsorption method, which adopts a device consisting of 5 adsorption towers arranged in parallel for operation, and the overall structure and the connection relation are basically consistent with those of the embodiment 1, and the difference is that: the operation pipeline comprises a feeding line, an equalizing line, a replacing line, a desorption line and a final charging line, and also comprises a pressure reducing line.
In this example, the operation procedure for enriching methane is the same as that of example 2, taking the operation procedure of 5 towers as an example.
The following description will specifically describe the operation flow of 20 steps by taking the first adsorption tower 101A as an example:
1-4, adsorption: opening valves 101A and 102A, feeding the raw gas into the first adsorption tower 101A, and contacting with adsorbent at adsorption pressure of 950kPa, wherein the methane which is a component easy to adsorb is enriched in the adsorption tower, and the component difficult to adsorb, such as N, is enriched in the adsorption tower2、O2And CO flows out of the tower top to a tail gas tank, the concentration of methane at the outlet of the adsorption tower is measured in real time, and the introduction of the feed gas is stopped after the adsorption of the adsorbent is saturated.
5. Vacant: the valves 101A and 102A were closed, and the first adsorption column 101A was not subjected to any operation, and the pressure was maintained at 950 kPa.
6. Pressure equalizing: and opening valves 104A and 104C, communicating the first adsorption tower 101A with the third adsorption tower 101C, releasing the pressure of the first adsorption tower 101A, boosting the pressure of the third adsorption tower 101C, and enabling the pressures of the two towers to be 699kPa after pressure equalization.
7. And (3) replacement: the valve KV13 is opened, the unadsorbed gas in the first adsorption tower 101A is replaced with product gas (750kPa), and purged into the third adsorption tower 101C, the replacement gas has a higher methane partial pressure, and the impurity gas adsorbed on the adsorbent surface is desorbed and purged out of the tower.
8. Vacant: the valves 104A, 104C and KV13 were closed, and the pressure was maintained at 750kPa without any operation on the first adsorption column 101A.
9. Pressure equalizing: and opening valves 104A and 104D, communicating the first adsorption tower 101A with the fourth adsorption tower 101D, releasing the pressure of the first adsorption tower 101A, boosting the pressure of the fourth adsorption tower 101D, and keeping the pressure of the two towers to be 408kPa after pressure equalization.
10. Pressure equalizing: and (3) closing the valves 104A and 104D, opening the valve KV14, and equalizing the pressure with the empty buffer tank, wherein the pressure is 101kPa after equalizing the pressure.
11-12, vacant: the valve KV14 was closed, and the pressure was maintained at 101kPa without any operation of the first adsorption column 101A.
13-16, desorption: and opening the valve 108A, communicating the first adsorption tower 101A with a vacuum pump, vacuumizing the first adsorption tower 101A to obtain a purified methane product and regenerating the adsorbent, wherein the desorption vacuum degree is 30 kPa.
17. Pressure equalizing: and closing the valve 108A, opening the valves 104A and 104C, communicating the first adsorption tower 101A with the third adsorption tower 101C, pressurizing the first adsorption tower 101A, decompressing the third adsorption tower 101C, and keeping the pressures of the two towers 408kPa after pressure equalization.
18. Pressure equalizing: and closing the valve 104C, opening the valve 104D, communicating the first adsorption tower 101A and the fourth adsorption tower 101D, pressurizing the first adsorption tower 101A, and decompressing the fourth adsorption tower 101D, wherein the pressures of the two towers after pressure equalization are 699 kPa.
19. Introduction of displaced gas: the valve KV43 is opened, the fourth adsorption tower 101D is replaced with the product gas, the replaced gas is purged to the first adsorption tower 101A, and the first adsorption tower 101A is further pressurized to 750 kPa.
20. Final charging: the first adsorption tower 101A is reversely and finally charged with purified gas (950kPa), so that the first adsorption tower 101A is pressurized, and the next cycle is started.
The operation process and the operation conditions are adopted to enrich the methane in the raw material gas, two raw material gases with different methane concentrations are used for carrying out experiments, wherein in one mixed gas, the volume fractions of the components are respectively as follows: 25.2% of methane and 74.8% of nitrogen; in another mixed gas, the volume fractions of the components are respectively as follows: 36.0% of methane and 74.0% of nitrogen; after 30 times of the above-mentioned circulation process, the methane concentration and the methane recovery rate in the product gas were measured, and the results are shown in Table 3.
Table 3 results of cycle adsorption experiment of raw material gas with different methane concentrations in example 3
| Experiment ofNumbering | 1 | 2 |
| Concentration of methane in raw gas (%) | 25.2 | 36.0 |
| Methane concentration in product gas (%) | 92.5 | 99.1 |
| Methane recovery (%) | 98.2 | 98.1 |
The results of the examples show that the range of initial concentration of methane in the raw material which can be processed by the invention is wide, in the examples, different pressures are adopted for adsorption in a safe range according to different concentrations of methane, and especially when the mixed gas contains oxygen, the selection of the adsorption pressure needs to consider the concentration of oxygen content and explosion limit; the concentration of the thickened methane has controllability, and the recovery rate can reach more than 80 percent and can reach more than 98 percent at most.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above methods, i.e. it does not mean that the present invention must rely on the above methods for its implementation. It will be apparent to those skilled in the art that any modifications to the invention, equivalents of the materials used, additions of auxiliary materials, and operations, and selection of particular means, are within the scope and disclosure of the invention.
Claims (22)
1. A method for enriching an easily-adsorbed gas by a pressure swing adsorption method is characterized by comprising the following steps:
(1) the raw material gas enters a first adsorption tower, wherein the easily-adsorbed components are adsorbed by the adsorbent, the difficultly-adsorbed components flow out, and the adsorption operation is carried out until the adsorbent is saturated; the adsorption pressure is 0.1-1.0 MPa; the volume fraction of the easily-adsorbed component in the feed gas is 2-60%, and the easily-adsorbed component is methane;
(2) carrying out pressure equalizing operation on the first adsorption tower and the third adsorption tower after adsorption in the step (1);
(3) introducing the product gas into the first adsorption tower after pressure equalization in the step (2), replacing unadsorbed gas, and blowing the replaced gas into the third adsorption tower in the step (2);
(4) carrying out pressure equalizing operation on the first adsorption tower and the fourth adsorption tower after replacement in the step (3);
(5) vacuumizing the first adsorption tower after pressure equalization in the step (4), and desorbing the easily-adsorbed components adsorbed in the step (1) to obtain product gas;
(6) pressurizing the gas and the external source gas which are replaced by the fourth adsorption tower in the first adsorption tower desorbed in the step (5), and performing the operation of the step (1) again;
the method needs at least 5 adsorption towers to complete the cyclic adsorption, and each adsorption tower completes the steps of adsorption, pressure equalization, replacement, pressure equalization, desorption and pressurization.
2. The method of claim 1, wherein the non-adsorbable component comprises any one or a combination of at least two of nitrogen, oxygen, carbon monoxide, or an inert gas.
3. The method of claim 1, wherein the adsorbent of step (1) comprises any one of activated carbon, molecular sieve or ionic liquid zeolite or a combination of at least two thereof.
4. The method of claim 3, wherein the adsorbent of step (1) is an ionic liquid zeolite.
5. The method according to claim 1, wherein the adsorption temperature in step (1) is-10 to 60 ℃.
6. The method according to claim 5, wherein the adsorption temperature in the step (1) is 20-30 ℃.
7. The method according to claim 1, wherein the pressure equalizing operation of step (2) and step (4) is independently at least one stage.
8. The method according to claim 1, wherein the displacement pressure in the step (3) is 80 to 1000 kPa.
9. The method according to claim 1, wherein the pressure after equalizing the pressure in the step (2) and the step (4) is 5 to 100kPa lower than the displacement pressure.
10. The method according to claim 1, wherein after the evacuation in the step (5), the pressure in the first adsorption tower is 10 to 35 kPa.
11. The method according to claim 1, wherein after the desorption in the step (5), the first adsorption tower is subjected to a pressure equalization operation.
12. The method of claim 11, wherein the pressure equalization operation is at least one stage.
13. The process according to claim 12, wherein the pressure equalizing operation employs a third adsorption column and a fourth adsorption column, which are sequentially pressure equalized.
14. The method according to claim 11, wherein after the pressure equalizing operation, the pressure in the first adsorption column is 10 to 100kPa lower than the displacement pressure.
15. The method according to claim 1, wherein the step (6) further comprises a re-equalizing operation after the pressurizing with the gas displaced by the fourth adsorption column.
16. The method of claim 1, wherein the exogenous gas of step (6) comprises a purge gas and/or a feed gas.
17. The method of claim 16, wherein the exogenous gas of step (6) is a purge gas.
18. The method of claim 1, wherein the pressure of the source gas of step (6) is the same as the adsorption pressure of step (1).
19. The method of claim 17, wherein the purge gas is counter-pressurized to counter the flow of the feedstock in step (1).
20. The method of claim 17, wherein the purge gas comprises nitrogen and oxygen.
21. The method as claimed in claim 17, wherein the purge gas is a poorly adsorbed component discharged from the adsorption operation in step (1).
22. The method according to any one of claims 1-21, characterized in that the method comprises the steps of:
(1) the raw material gas enters a first adsorption tower, wherein easily-adsorbed components are adsorbed by an adsorbent, difficultly-adsorbed components flow out, and the adsorption operation is carried out until the adsorbent is saturated, wherein the adsorption pressure is 0.1-1.0 MPa, and the adsorption temperature is-10-60 ℃;
(2) carrying out pressure equalizing operation on the first adsorption tower and the third adsorption tower after adsorption in the step (1), wherein the pressure equalized is 5-100 kPa lower than the replacement pressure in the step (3);
(3) introducing the product gas into the first adsorption tower after pressure equalization in the step (2), replacing unadsorbed gas, wherein the replacement pressure is 80-1000 kPa, and blowing the replaced gas into the third adsorption tower in the step (2);
(4) carrying out pressure equalizing operation on the first adsorption tower and the fourth adsorption tower after replacement in the step (3), wherein the pressure equalized is 5-100 kPa lower than the replacement pressure in the step (3);
(5) vacuumizing the first adsorption tower after pressure equalization in the step (4) until the pressure is 10-35 kPa, and desorbing the easily-adsorbed components adsorbed in the step (1) to obtain product gas;
(6) equalizing the pressure of the first adsorption tower desorbed in the step (5) with a third adsorption tower and a fourth adsorption tower in sequence;
(7) and (3) pressurizing the pressure-equalized first adsorption tower obtained in the step (6) by adopting the gas and the external source gas replaced by the fourth adsorption tower, wherein the pressure of the external source gas is the same as the adsorption pressure in the step (1), and then performing the operation in the step (1) again.
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