CN1221643A - PSA process and system - Google Patents
PSA process and system Download PDFInfo
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- CN1221643A CN1221643A CN 98123070 CN98123070A CN1221643A CN 1221643 A CN1221643 A CN 1221643A CN 98123070 CN98123070 CN 98123070 CN 98123070 A CN98123070 A CN 98123070A CN 1221643 A CN1221643 A CN 1221643A
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Abstract
A PSA process involving the storage of products of various purities in segregated storage tanks for subsequent usage is disclosed. Products of increasing purities, admitted at the product end of the bed, are used during purification and repressurization steps. In addition, different composition streams collected at the feed end of the bed during the countercurrent depressurization step are admitted at the feed end of the bed, in the order of increasing product component content, during the rising pressure step(s). This cycle gives higher recovery and lower bed size factor than prior art PSA cycles.
Description
The present invention relates to transformation absorption (PSA) method and system.The present invention relates more specifically to be equipped with hydrogen through transformation absorption (PSA) legal system.
Known existence prepares the whole bag of tricks of hydrogen.Some example comprises as follows: (1) natural gas or naphtha steam-reforming, (2) hydrocarbon is as gasoline or fuel oil catalyzed conversion and (3) heavy oil or gas by partial oxidation of natural.In the said method, the natural gas steam-reforming may be the method that is widely used in Hydrogen Preparation most.Fig. 1 represents that methane steam reforming prepares the basic technology unit of hydrogen.With reference to Fig. 1, raw material such as natural gas via compress, and send into purification unit to remove the compound of desulfuration.Desulfurization material mixes with superheated steam then, and sends into converter and tentatively produce H
2And CO.The converter effluent fluid is sent into heat recovery units, sends into displacement converter (shift converter) then to obtain extra hydrogen.Displacement converter effluent is sent into purification unit (for example PSA) with the preparation high-purity hydrogen then by cooling processing and heat recovery unit.Below providing some the prior art method that is used to prepare hydrogen briefly introduces.
People such as Sircar at United States Patent (USP) 4,077, in 779, set forth four hydrogen PSA of a kind of improvement method; Wherein, before each adsorbent bed decompression operation, adopt the following current displacement stage, be commonly referred to the high-pressure wash stage.By before adsorbent bed decompression operation, adopt the high-pressure wash stage to reach the rate of recovery that improves light component.In addition,, cleaning and adopting between the pressure period again and bleed the stage according to this invention, just can be with high-recovery (96.5%) from 75%H
2And 25%CO
2Raw material production high-purity H
2(99.99%).
People such as Fuderer at United States Patent (USP) 5,553, in 981, disclose the method that a kind of combination by displacement conversion, washing and PSA improves the hydrogen rate of recovery.Carbon dioxide is mainly removed by washing.Then by the PSA purified hydrogen.The waste part of PSA system turns back to the displacement conversion unit, improves the hydrogen rate of recovery.In the example, the raw material typical case is hydrogeneous about 97% after the methanation, finally can be with H by PSA
2Be purified to 99.99%.If the 80%PSA waste material turns back to the displacement converter, 15% turns back to partial oxidation unit and 5% discharges as fuel gas, and the rate of recovery can reach 99%.
People such as Fong at United States Patent (USP) 5,152, in 975, disclose a kind of method for preparing high-purity hydrogen.This method comprises following basic step: (1) partial oxidation hydrocarbon gas raw material, preparation H
2With the CO synthesising gas mixture, (2) make synthesising gas mixture with steam reaction CO be changed into tentatively to contain CO
2And H
2Raw gas mixture and (3) make raw gas mixture handle produce high-purity hydrogen and a kind of discarded gaseous impurity mixture by PSA.
People such as Kapoor at United States Patent (USP) 5,538, in 706, disclose a kind of method for preparing hydrogen and carbon monoxide from hydrocarbon.It comprises that partial oxidation, PSA separate and as a kind of low temperature distillation of possibility.This system separates and the minimizing raw material by improving PSA, and preferable performance is provided.Partial oxidation reactor produces high-purity hydrogen and carbon monoxide.By PSA and distillation integrated processes, or may only pass through the PSA method, hydrogen is separated with admixture of gas (containing carbon dioxide, methane and steam etc.) with carbon monoxide.At least the admixture of gas stream that is rich in hydrocarbon (with steam etc.) will turn back to reactor.The preferred embodiment of PSA system comprises the adsorption zone (or bed of zeolite 5A or zeolite 13X) that some polyphones connect, and at each adsorption zone, carbon monoxide absorption is poorer than hydrocarbon, carbon dioxide and steam, but stronger than hydrogen.According to this invention, adopt PSA to circulate substantially, and reduce pressure/the desorption phase separated into two parts: the medium decompression of first, this process top bed stand countercurrent depressurization, and bottom bed stands the following current decompression, and carbon monoxide is discharged between two adsorbent beds; Second portion is the normal countercurrent depressurization to two beds.This method can prepare the hydrogen and the carbon monoxide of purity at least 98% just as claimed in claim, and the gas that enters the PSA unit contains the 55%H that has an appointment
2And 42%CO.
People such as McCombs at United States Patent (USP) 4,263, in 018, disclose a kind of pressure swing adsorption method, utilize at least two adsorbent beds and a storage tank, storage tank or be dead slot or be packed bed.Storage tank is used to store the even depressed gas at a top, and it will be used for even boost phase subsequently to another pressurization.This invention has implemented to reflux successively strategy, and the void gas that wherein even decompression phase is collected improves order at even boost phase according to purity and returns.In addition, this disclosure of the Invention at the bottom of the use-the even stage of bottom, wherein, accept evenly the boost bed of gas of bottom and also accept feed, the i.e. continual feed of the even phase process of the end-bottom simultaneously.
People such as Yamaguchi at United States Patent (USP) 5,258, in 059, have set forth a kind of PSA method, and it has adopted three adsorbent beds at least, with the disposal tower (storage tank that separates) of a charging/discharging program control type.This disposal tower is used to store the void gas that the following current decompression phase of circulation reclaims.The regeneration stage that this gas is used to circulate is then cleaned adsorbent bed.This disposal tower is specially designed for avoiding gas to mix, and promptly has the impurity concentration gradient in this disposal tower.This invention is limited at least three adsorbent beds of employing and a disposal tower is used to store the following current depressed gas, and this gas is used for cleaning subsequently.This invention does not illustrate, and this disposal tower how can be in advanced person's PSA circulation have not only been supplied with purge gas but also supplying products gas-pressurized.
People such as Baksh at United States Patent (USP) 5,565, in 018, disclose and have adopted the extraneous gas storage tank that separates to store different purity gas, so that improve the cleaning that order is used for the PSA circulation by purity after a while, evenly boost and the product pressure period.Utilize this novel PSA circulation, reached the obvious reduction of bed size factor and power consumption.
Although to basic PSA circulation after deliberation many improvement and change, and be applied to commercial processing, as be used for preparing hydrogen from forming gas, compare with other method, concerning big plant produced high-purity hydrogen, the PSA method still is invalid and uneconomic.Particularly, PSA method (as above-mentioned those disclosed) is all produced a kind of enriched products at present, and its purity is average in whole " preparing product " stage, and has several intrinsic problems.
For example, in the even stage of top-top bed, be subjected to the product gas of purity reduction through the bench grafting of even boost phase.Therefore, at this even boost phase end, the gas that purity is minimum is the product end that is in bed.So in preparing product stage subsequently, product purity glides, when whole production work-in-process purity mean time, product purity descends.In addition, the gas that is used to clean, the normally gas that reduces from another purity that obtains in the preparing product stage.If this purge gas is obtained by storage tank, then fixedly the gas of purity is used for cleaning.Similar problem (using the product that reduces purity) also is present in the PSA circulation that utilizes the product pressure period, and in this PSA circulation, product gas is to obtain in the production phase from another bed.
The typical case is, at prior art H
2PSA circulation in, the product gas that reduced by purity through the bench grafting of even boost phase.Therefore, at this even boost phase end, the gas that purity is minimum is the product end that is in bed.In addition, the gas that is used for the adsorbent bed cleaning is to be obtained by the even decompression phase in the second level, and reduces order by purity and use.Equal even wash phases is stated, to gases used same being suitable for of the PSA circulation that utilizes the product pressure period.In addition, in the even stage of the end-bottom, the gas that the bench grafting that is pressurizeing is reduced by hydrogen concentration, the beginning hydrogen concentration equals feed concentration, and with the continuation in even stage of the end-bottom, a bed material feeding end hydrogen concentration reduces because of the heavy ends desorb.
Above-mentioned concentration is successively decreased, and promptly is being used to reflux and gas that the hydrogen concentration of pressurization again reduces, causes the irreversibility and the losses by mixture of process, i.e. the diminishing efficiency of PSA method.For example, at wash phase and even stage of the end-bottom, H
2The gas that concentration reduces is being used for refluxing.In the even stage of the end-bottom, when evenly beginning, H
2Molar fraction is about 0.7403 (identical with forming gas feed concentration), and in the even process in the end-end was carried out, bed material feeding end hydrogen mole fraction dropped to about 0.65 from about 0.74.Therefore, in the prior art PSA cycles for keeping desired product purity, produce and evenly decompression phase must reach than bed and penetrate required time and earlier stop.This causes making full use of adsorbent bed.
Moreover, for example to clean and the pressure period product that uses purity to reduce again, the extra pollution of bed product end is owing to adopted the minimum product gas of purity at the refluxing stage end.This additional pollution of bed product end causes the obvious reduction of preparing product stage initial production purity.This causes the reduction of product average purity, or specifies purity product (light component) rate of recovery obviously to reduce.In addition, the product gas that uses purity to descend, the mass-transfer zone expansion strengthens.Finally, in order to comprise mass-transfer zone and to keep product purity, need more adsorbent, bed size factor is higher more expensive with the PSA method as a result.
Therefore, the purpose of this invention is to provide a kind of efficient PSA method, the mixed feeding (as forming gas) that is used for from hydrogen prepares a large amount of high-purity hydrogens, compares H with prior art PSA cycles
2The rate of recovery is higher, and power needs with bed size factor lower.Another object of the present invention is that preparation can be used for PSA circulation different phase, or is used for the multiple purity product of special time in the stage.
The present invention preferably includes a kind of PSA method, and this method relates to stores the different purity product in order to using subsequently in the storage tank that separates.The purity of receiving in bed product termination improves product, can be used for cleaning and pressure period again.In addition, the various combination logistics of concentrating in the bed material feeding end in the countercurrent depressurization stage is pressed product content increase order at boost phase and is received at the bed material feeding end.This circulation is compared with the prior art PSA cycles that does not have the concentration counter-rotating, has provided higher product recovery rate and lower bed size factor.
By following preferred embodiment explanation and accompanying drawing, will represent other purpose of the present invention, feature and advantage to those skilled in the art.Wherein:
Fig. 1 is how the conversion of expression steam/methane combines with PSA, is used to prepare the process chart of high-purity hydrogen.
Fig. 2 is the PSA adsorption tower schematic diagram that contains three layers of adsorbent.
Fig. 3 is four PSA method schematic diagrames that adopt counter-rotating bed two ends CONCENTRATION DISTRIBUTION.
Fig. 4 adopts to have a preferred process of the present invention schematic diagram of four PSA tower circulations of two ends concentration counter-rotating.
Fig. 5 does not adopt four PSA tower circulation schematic diagrames that separate storage tank or multiple-grooved.This is outside the scope of the invention.
Fig. 6 describes to adopt the PSA analog result of Fig. 5 PSA circulation.A PSA cyclic process bed product end pressure and hydrogen concentration distribution have been described.
Fig. 7 describes to adopt the PSA analog result of Fig. 5 PSA circulation.PSA cyclic process bed material feeding end pressure and hydrogen concentration distribution have been described.
Fig. 8 describes to adopt the PSA analog result of this invention (see figure 4) PSA circulation (as Fig. 4).A PSA cyclic process bed product end pressure and hydrogen concentration distribution have been described.
Fig. 9 describes to adopt the PSA analog result of this invention (see figure 4) PSA circulation (as Fig. 4).PSA cyclic process bed material feeding end pressure and hydrogen concentration distribution have been described.
Figure 10 describes another embodiment that the present invention adopts double bed PSA method, adopts the counter-rotating purity profile at bed product end.
Figure 11 describes one of the present invention and comprises double bed PSA tower circulation embodiment, adopts the counter-rotating purity profile at bed product end.
Figure 12 describes one of the present invention and comprises double bed PSA method embodiment, adopts the counter-rotating purity profile at the bed two ends.
Figure 13 describes one of the present invention and comprises double bed PSA tower circulation embodiment, adopts the counter-rotating purity profile at the bed two ends.
This invention discloses the efficient PSA method that is used to prepare hydrogen by reducing irreversibility that exists in the prior art PSA method and the gas losses by mixture of following.
The present invention has following characteristics:
(1) backflows that continue at the bed two ends adopted in new PSA circulation, and promptly product (light component) improves order by purity and refluxes at bed product end, and the gas that hydrogen (this light component) concentration improves refluxed at material feeding end in the pressure period again that PSA circulates;
(2) separate storage tank by adopting, reduce the irreversibility and the gas losses by mixture of method;
(3) new PSA circulation will continue to reflux and be used for double bed and four PSA methods;
(4) increase H
2The rate of recovery and productive rate and
(5) it is even to have in bed two ends concentration counter-rotating top-top and bottom-end, promptly adopts the separation storage tank at the bed two ends.
In order to bring into use the minimum gas of hydrogen purity in backflow, then at the gas that cleans and the pressure period is used the hydrogen purity raising again, must the multiple hydrogen concentration product of preparation.According to the present invention, the pure gas of be used for refluxing (clean and top-top bed even) uses at last, and H
2The gas that concentration improves is in that the pressure period also is used for material feeding end again.Therefore, our H that need reverse at two ends
2Concentration promptly adopts at the bed two ends and separates storage tank.
Need multiple purity product because clean and pressurize again,, and it is contemplated that several operator schemes so the PSA circulation becomes more complicated inherently.For example, if require the hydrogen concentration counter-rotating of bed two ends, then can adopt two to separate storage tank, each one at the every end of bed.Typical separate storage tank design can be people such as Yamaguchi at United States Patent (USP) 5,258, type described in 059 maybe can be the container that adsorbent or inert material layer are housed, or the void tower that suppresses mixing baffle is housed.Be attached in the PSA circulation by separating storage tank, we can store multiple hydrogen concentration gas, can improve order by hydrogen concentration and use it for cleaning and pressurization again.For example, evenly the gas of decompression phase collection is stored in the separation storage tank.When evenly boost phase begins, at first consume and separate the minimum gas of storage tank moderate purity, the product that just uses purity to improve later on.Therefore, the product that reduces in even decompression phase purity enters the separation storage tank, and leaves storage tank at even boost phase with opposite order (product purity raising).Similarly, adopt another storage tank at the bed material feeding end, the gas that the decompression phase material feeding end is collected, even boost phase improves the order use by hydrogen concentration the end-end of at.
For ease of the counter-rotating of bed two ends purity, in the PSA circulation, add and separate storage tank, circulating to compare with prior art makes the method flexibility bigger, and efficient improves.Particularly,, add at the bed two ends according to the present invention and to separate storage tank known PSA circulation, the result clean and again the pressure period as even stage of top-top and bottom-bottom, H
2The rate of recovery is than the PSA that the does not utilize hydrogen concentration counter-rotating high 10-15% that circulates.
The preferred embodiment of the invention comprises utilizing and separates the storage tank different purity gas that storage is obtained by the bed one or both ends in the PSA circulation.Then, the gas of these purity variations is used for cleaning and pressurization again by the order of concentration raising.
For example, in the even stage of the end-bottom, the gas that hydrogen concentration is minimum is used for material feeding end and pressurizes in early days again, and then, the gas that hydrogen content improves up to feed concentration is used for pressurizeing the later stage again.Therefore, even boost phase end, the end-end, bed material feeding end concentration and feed gas concentration are coincide.In feed stage subsequently, bed material feeding end concentration accurately meets supplied materials concentration, therefore, has reduced PSA method process irreversibility and losses by mixture.
In addition, bed product end H
2The gas that purity improves is used for cleaning and pressurization again.Should see that the employing of bed two ends concentration counter-rotating is very different with prior art PSA cycles.In those circulations, the product that fixedly purity product, or purity reduces (being obtained by another production phase) is used for a top backflow, and H
2The gas that concentration reduces is used for the end-end in the even stage.Therefore, add and separate storage tank, can prepare multiple purity gases by the various requirements that reflux and pressurize again at the bed two ends.Add the separation storage tank by employing and collect high pressure absorption phase different purity gas, this method also can provide the ability of each purity gases requirement of supply, to satisfy the demand of client to product.
PSA method of the present invention describes with particularly preferred embodiment with reference to the accompanying drawings.The feed of this PSA method is a forming gas, and its composition is about 74%H2,22.5%CO
2CO, CH with trace
4, N
2And H
2O.
Fig. 2 represents to contain the PSA adsorption tower of three layers of adsorbent, is used for removing impurity to produce high-purity hydrogen from forming gas.Ground floor (B1) is tentatively removed H from forming gas
2O, adsorbent are alumina, or zeolite-Y, or the alumina of same zeolite-Y mixing.The second layer (B2) is commonly referred to the body portion abscission zone, tentatively removes CO from forming gas
2, adsorbent is active carbon or zeolite.The 3rd layer (B3) is basic adsorbent zeolite, removes residual impurity, produces the high-purity hydrogen as required product.
Basic characteristics of the present invention can prepare H by forming gas by narration
2Four layers of PSA method operate and describe.Should see that the scope of the invention is not limited to Hydrogen Preparation, and main feature of the present invention also can be applied to other PSA separation process, as with zeolite as the adsorbent separation of air with preparation oxygen, or use O
2Selective absorbent prepares N from air
2This systems approach and equipment also can be used for various purifying processing, prepare the ultra-high purity argon as the crude argon purifying.In addition, though characteristics of the present invention are to prepare H with four PSA methods from forming gas
2Describe, but this method also can be less than or adopt more than four modes.
Four hydrogen circulations, preferred total cycle time is about 16 minutes of about 2-, preferably 2-8 minute.The hydrogen purity that reclaims is preferably the about 99.9999 volume % hydrogen of about 99-, best 99.99 volume %.The preferred product rate of recovery is about 80-about 95%, best 95%.
Fig. 3 is four PSA method schematic diagrames, comprises four adsorbent beds, and feed compressor or pressure fan separate storage tank (ST1, ST2 and ST3) with three, and intermediate connection tube line and valve.
In order more specifically to set forth the present invention, preferred feature will be by preparing H with four PSA methods from forming gas
2Example describe.All valves among the figure all are that machine system and logical program carry out the electric control operation as calculated.
Think and finished product pressurization (PP) beginning that circulates after the stage at bed B.With reference now to Fig. 3-4,, below with the stage order of preferred operation mode narration bed B process.Note AD=absorption; The pressurization of PP=product; EQD=evenly reduces pressure; PPG=provides purge gas; BD=emptying; PG=cleans; EQU=evenly boosts.
Stage I: (AD): feed gas (as forming gas) is introduced in the bed bottom, and product is discharged from the top.In our example, valve 12,42,77 and 78 (see figure 3)s are opened and are made feed gas flow through adsorbent bed.
Stage II: (AD and PP): valve 12,42,77 and 78 stayed open as the stage 1.In addition, valve 43 is opened.This provides the product gas-pressurized for bed C.
Stage III: (EQD): valve 12,42,43,77 and 78 is closed; Valve 32,62,71 and 75 is opened.Make the decompression of bed part.Valve 32 and 75 makes evenly No. 3 separating tanks of container (ST3) of a gas pressurized bottom, B bottom.Valve 62 and 71 makes a B top gas No. 1 separating tank of even container (ST1) that pressurizes.These hold-up vessels such as United States Patent (USP) 5,258,059 people such as (, 1993) Yamaguchi are described, be circulation with baffled.
Stage IV: (PPG): valve 32,62,71 and 75 is closed; Valve 52 and 73 is opened.Bed continues decompression, simultaneously the product purge gas is supplied with the bottom of No. 2 separating tanks of clean container (ST2).This hold-up vessel still as previously mentioned, be communicated with and have a deflection plate.
Stage V: (BD): valve 52 and 73 is closed; Valve 22 is opened.Bed continues decompression combustion furnace gas is supplied with the steam methane converter, till the bed pressure reaches minimum.
Stage VI: (PG): valve 22 stays open; Valve 52 and 73 is opened.Gas with cleaning hold-up vessel (ST2) bottom cleans from bed top adverse current.
Stage VII: (EQU): valve 52 and 73 is closed; Valve 32,62,71 and 75 is opened.Bed pressurizes simultaneously with both uniform gas of the even container in top and bottom (ST1 and ST3).
The stage VIII: (PP) valve 32,62,71 and 75 is closed; Valve 41 is opened.Continue to be forced into maximum operating pressure with the product that is in absorption phase bed A supply.
Table 1 and 2 provides the operating condition example and adopts the PSA method operating characteristics of three layers of adsorbent (for example Fig. 2: alumina is at bed material feeding end (B1), and the person of connecing is active carbon (B2), and the Na-Y zeolite is at bed product end (B3) then).In the table 1, the result adopts separating tank to finish that bed two ends are cleaned and pressure period concentration counter-rotating and obtaining again by the present invention.Correction data is by identical PSA circulation in the table 2, but obtains under without any concentration counter-rotating situation.For the sake of clarity, be used for acquisition table 2 result's PSA cyclic representation in Fig. 5.Should see that Fig. 4 and Fig. 5 unique difference in the PSA circulation is to adopt separating tank to reach a two ends among Fig. 4 and clean and pressure period concentration counter-rotating again.
Symbol has following implication in the table: kPa 1000Pa=pressure criteria international unit (1.0 atmospheric pressure=101.325kPa), s=chronomere, second, m=rice and NCFH=standard cubic meter/hour.
Table 1: Fig. 2-4 has described the non-limiting example that the present invention and three layers of adsorbent are used in four PSA methods.Result shown below is by adopting forming gas (dry basis: 74.03%H
2, 22.54%CO
2, 0.36%CO, 2,16%CH
4And 0.91%N
2) obtain as the PSA simulation of feed.Feed typically contains the 1500ppmH that has an appointment
2O.
Alumina consumption: 97.663Kg/ bed
Charcoal consumption: 900kg/ bed
Layer 3 adsorbent: Na-Y zeolite
Layer 3 bed height 0.1270m
Zeolite consumption: 514kg/ bed
Circulation timei (s): 960
High pressure: 1187.53kPa
Low pressure: 144.57kPa
Delivery rate: 184.1NCFH
Hydrogen purity: 99.55%
The hydrogen rate of recovery: 80.11%
Temperature (K): 300
Table 2: Fig. 5 has described example that three layers of adsorbent are used in four PSA methods, does not adopt separating tank, and promptly each end of bed does not adopt the concentration counter-rotating.Result shown below is by adopting forming gas (dry basis: 74.03%H
2, 22.54%CO
2, 0.36%CO, 2.16%CH
4And 0.91%N
2) obtain as the PSA simulation of feed.Feed typically contains the 1500ppmH that has an appointment
2O.
Alumina consumption: 97.663Kg/ bed
Charcoal consumption: 900kg/ bed
Layer 3 adsorbent: Na-Y zeolite
Layer 3 bed height 0.1270m
Zeolite consumption: 514kg/ bed
Circulation timei (s): 960
High pressure: 1187.53kPa
Low pressure: 144.57kPa
Delivery rate: 156.70NCFH
Hydrogen purity: 99.6%
The hydrogen rate of recovery: 71%
Temperature (K): 300
By table 1 and 2 as seen, four PSA methods that adopt the present invention to carry out concentration counter-rotating (table 1) with separating tank are separated the situation that storage tank carries out the concentration counter-rotating, H than not adopting
2The rate of recovery is wanted high (80.11 pairs 71%).
In addition, Fig. 6 and 7 represents bed product end and material feeding end respectively, is cleaning with the pressure period is not carried out the PSA circulation of carrying out concentration counter-rotating (being that the gas that product purity reduces is used for refluxing) with separating tank, purity decline again.For example, Fig. 6 shows wash phase and top-even stage of top bed, H
2The gas that concentration reduces is being used for refluxing.Fig. 7 shows even stage of the end-bottom, H when evenly beginning
2Molar fraction is 0.7403 (identical with feed concentration), and along with the hydrogen mole fraction that carries out of even process is reduced to about 0.64 by 0.7403.
Therefore, for keeping the desired product purity of prior art PSA cycles, produce with even decompression phase and must penetrate the more Zao end of required time than bed; So adsorbent bed does not make full use of.In addition,, use the minimum product gas of purity, cause a product end additionally to pollute because of the refluxing stage end for example at the product that evenly boosts and wash phase uses purity to reduce.This additional pollution of bed product end can bring the obvious reduction of product purity in early days in the preparing product stage, and causes the product average purity to reduce.In addition, the product gas that uses purity to reduce increases the expansion of mass-transfer zone.As a result,, need more adsorbent, cause higher bed size factor and more expensive PSA method for comprising mass-transfer zone and keeping product purity.
In order to bring into use the minimum gas of hydrogen purity in backflow, subsequently at the gas that cleans and the pressure period is used the hydrogen purity raising again, just must the multiple hydrogen concentration product of preparation.According to the present invention, bed product purity that end requires distributed as shown in Figure 8 to the time; Wherein, the highest gas of purity that is used for backflow (cleaning and top-top bed are evenly) uses at last.Therefore, as shown in Figure 8, for implementing invention described herein, the product gas that need utilize purity to improve.So our purity order that need reverse, and prepare multiple purity product promptly needs to adopt and separates storage tank.
Fig. 9 represents that the required hydrogen concentration of a material feeding end is to time distribution map.From Fig. 9 as seen, enter a bed bottom gas concentration at even boost phase end, match with feed concentration.Yet, do not implement the PSA method that concentration is reversed at material feeding end, the even stage of the end-bottom begins H
2Concentration is coincide with feed concentration, then as shown in Figure 7, and along with even continuation H
2Concentration descends.
Because reflux and product add the multiple purity product of pressure request, thereby PSA circulates and just becomes more complicated inherently, and it is contemplated that several operator schemes.For example, if require the hydrogen concentration counter-rotating of bed two ends, then can adopt two to separate storage tank, each one at the every end of bed.Typical separate storage tank design can be people such as Yamaguchi at United States Patent (USP) 5,258, type described in 059 maybe can be the container that adsorbent or inert material layer are housed, or simply is that the void tower that prevents mixing baffle is housed.
Incorporate into PSA circulation into by separating storage tank, we can store multiple hydrogen concentration gas, improve order by hydrogen concentration and can use it for cleaning and pressurization again.For example, the gas in evenly decompression phase collection is stored in the separation storage tank.Evenly boost phase begins, and at first consumes the minimum gas of purity that separates storage tank, and the product that purity improves uses later on.
Should be noted that this example (see Table 1 and Fig. 3,4 and Fig. 8 to Fig. 6) in, evenly the product gas that reduces of decompression phase purity enters the separation storage tank, and leaves storage tank at even boost phase by reversed sequence (product purity raising).Similarly, separate storage tank by adopt another at the bed material feeding end, the gas that the decompression process material feeding end is collected improves order by hydrogen concentration and is used for even boost phase (seeing Fig. 3,4 and 9 couples of Fig. 7)
The PSA circulation is convenient to a two ends purity counter-rotating in conjunction with separating storage tank, compares with prior art PSA cycles, make that the method flexibility is bigger, and efficient improves.Particularly,, add according to the present invention and to separate storage tank (seeing Table 1) known PSA circulation, with the same PSA that cleans and the concentration counter-rotating is not adopted at pressure period bed two ends again circulate (seeing Table 2) compare H as a result
2The rate of recovery improves 10-15%.
Figure 10 and 11 represents respectively with a kind of replaceable operator scheme, the double bed hydrogen PSA method of i.e. bed product end employing counter-rotating purity profile on the top, and stage order.Referring now to Figure 10 and 11 this double bed of explanation PSA methods, relate to an A.
The stage I: (FP and EQU): feed gas is (as H
2Forming gas) introduces in bed A bottom, introduce at bed A top from the uniform gas of bed B.In our example, valve 11,61 and 62 (see figure 10)s are opened.Bed B is in even decompression phase.
Stage II: (AD): valve 61 and 62 is closed.Valve 11 stays open as the stage I.In addition, valve 51,73 and 74 is opened.This makes product flow through this bed.Bed B reduces pressure, and supplies with uniform gas to separating storage tank (ST1).
Stage III: (AD): valve 11,51,71 and 74 stays open, and bed A is in absorption.In addition, valve 61 and 62 is opened, and this supplies with bed B with purge gas.Bed B is in wash phase.
Stage IV: (AD): valve 61 and 62 is closed. Valve 11,51,71 and 74 stays open, and bed A is in absorption.Bed B is in even boost phase, accepts to separate the gas of storage tank (ST1 and ST2).
Stage V: (EQD): valve 11,52,73 and 74 is closed; Valve 61 and 62 is opened.A is partly even with bed B for bed.Bed B is in feed pressurization and even boost phase.
Stage VI: (EQ): valve 62 is closed; Valve 61 stays open.In addition, valve 71 is opened.This bed continues decompression, supplies with uniform gas to separating tank (ST1) simultaneously.Bed B is in absorption phase.
Stage VII: (PG): valve 71 is closed.Valve 61 stays open, and additional valves 62 and 21 is opened.Bed A cleans with bed B product, and waste fluid is got back to the steam methane converter as the combustion furnace pneumatic transmission.Bed B is in absorption phase.
Stage VIII: (PP): valve 21 and 62 is closed.Valve 61 stays open.Valve 71 is opened.By accepting the uniform gas of separating tank (ST1), bed A stands part pressurization again.Bed B is in absorption phase.
Figure 12 and 13 represents respectively with the alternative operator scheme of another kind, is bed product end and material feeding end at two ends, adopts the double bed hydrogen PSA method of counter-rotating purity profile, and the stage order.Referring now to Figure 12 and 13 this double bed of explanation PSA methods, relate to an A.
The stage I: (FP and EQU): feed gas is (as H
2Forming gas) introduces in bed A bottom, introduce at bed A top from the uniform gas of bed B.In our example, valve 11,61 and 62 (seeing Figure 12) are opened.Bed B is in even decompression phase.
Stage II: (AD): valve 61 and 62 is closed.Valve 11 stays open as the stage I.In addition, valve 51,73 and 74 is opened.This makes product flow through this bed.Bed B reduces pressure, and separates storage tank (ST1 and ST2) with the bottom to the top and supplies with uniform gas.
Stage III: (AD): valve 11,51,71 and 74 stays open, and bed A is in absorption.In addition, valve 61 and 62 is opened, and this supplies with bed B with purge gas.Bed B is in wash phase.
Stage IV: (AD): valve 61 and 62 is closed. Valve 11,51,71 and 74 stays open, and bed A is in absorption.Bed B is in even boost phase, accepts storage tank (ST1 and ST2) separated at the top with the bottom gas.
Stage V: (EQD): valve 11,52,73 and 74 is closed; Valve 61 and 62 is opened.A is partly even with bed B for bed.Bed B is in feed pressurization and even boost phase.
Stage VI: (EQ): valve 62 is closed; Valve 61 stays open.In addition, valve 31,71 and 72 is opened.This bed continues decompression, supplies with uniform gas to top and bottom separating tank (ST1 and ST2) simultaneously.Bed B is in absorption phase.
Stage VII: (PG): valve 31,71 and 72 is closed.Valve 61 stays open, and additional valves 62 and 21 is opened.Bed A cleans with bed B product, and waste fluid is got back to the steam methane converter as the combustion furnace pneumatic transmission.Bed B is in absorption phase.
Stage VIII: (PP): valve 21 and 62 is closed.Valve 61 stays open.Valve 31,71 and 72 is opened.By accepting the uniform gas of top and bottom separating tank (ST1 and ST2) simultaneously, bed A stands part pressurization again.Bed B is in absorption phase.
According to above-mentioned PSA circulation, can make several improvement and change one or more stages, and not depart from the application or invent total feature.For example, top-top and bottom-end again the pressure period can occur successively, rather than as above-mentionedly occur simultaneously.
In addition, because will collect the multiple purity product of different amounts, the time in each stage of PSA cycling distributes and the process control key.Utilize the PSA circulation that separates storage tank further to improve, also comprise PSA the overlapping of each stage of circulating to reduce total cycle time, select operating condition (high pressure, low pressure, evenly reduce pressure end pressurization etc.), distribute the order that each stage of each time in stage and circulation finishes.
In the another kind of operator scheme, separate even groove (as ST1) and can remove, and all even depressed gas directly go to other bed, promptly allow directly bed-bed evenly from this method.Yet, this operator scheme, bed-bed is evenly in the stage, is subjected to the product gas that purity reduces (product that we will improve with purity among the present invention) through the bench grafting of even boost phase.When finishing even boost phase, this is in the product pressurization of production phase bed with another, or stands the feed pressurization, or stands product and feed pressurization simultaneously.
Though products of separated storage tank (ST1, ST2 and ST3) is adopted in invention described herein, can design multistage storage tank, wherein the different time eluting gas is directly delivered to corresponding storage tank the preparation of product stage.The present invention also is not limited to adopt at top and bottom and has saucer type head and the mobile vertically cylindrical shape adsorbent bed of gas, promptly can adopt other design.For example, can adopt radial bed reaching the reduction pressure loss, and follow the reduction power consumption.In addition, can adopt each layer of bed diverse location filling mixed adsorbent the layer mixed bed.For example, can place at the bed material feeding end and to mix with alumina and make spherical Na-Y zeolite, to remove to water in the materials flow and carbon dioxide, then, each layer carries out forming gas and separates after placing on the alumina zeolite compositions, to prepare the product of hydrogen enrichment.
In addition, adopt multistage storage tank can make the flexibility of method bigger.For example, the independent stage of each of circulation shown in Figure 3 needn't take cycle regular time.So, can be advantageously used in determining to distribute to time in each stage as physical descriptors such as pressure and components; Therefore, the variation with temperature, pressure and different product demand comes method of adjustment.Since do not need bed-bed gas to transmit when adopting when adding storage tank, each just can isolated operation so, and can look the set that this method is single bed unit.Yet concerning suitable size and shared compressor and vavuum pump, the complete cycle of each must have some synchronous with other circulation.
At last, narrate though the PSA circulation prepares hydrogen with regard to forming gas, wherein special embodiment explains, and having openly, improved other embodiment of feature all is considered as within the scope of the invention.Above-mentioned embodiment and the improvement that comprises also can be used for other PSA separation process.Although super-atmospheric pressure circulation that PSA described herein is recycling also should be seen, the PSA circulation is not limited to super-atmospheric pressure transformation absorption (PSA) circulation, also can adopt and stride atmospheric pressure or sub-atmospheric pressure PSA circulation.In addition, PSA method of the present invention also can be used to separate other mixture (as air), with preparation oxygen or nitrogen, or oxygen and nitrogen accessory substance.
The present invention can make the highest gas of purity use at last, or at the product that evenly boosts, cleaning and product pressure period use purity to improve, rather than as the reversed sequence of prior art.In addition, the present invention allows the PSA method to operate in such a way, and promptly at the even stage end of the end-bottom, bed material feeding end concentration and feed concentration are coincide.Should see that the prior art PSA process is in the even stage of the end-bottom, bed material feeding end concentration, heavy ends concentration raises when evenly carrying out the end-bottom of because of, and has departed from feed concentration.
Therefore, the present invention separates storage tank counter-rotating concentration at bed top and bottom two ends through adopting, the purity of can reversing order, and by proper order use multiple product purity, to eliminate the intrinsic problem of prior art PSA cycles.Moreover because of the multiple purity product of needs, adsorbent bed is fully used, and promptly bed can keep online before the heavy ends of bed outflow end have just penetrated.
The concrete feature of the present invention is only represented in one or more accompanying drawings for convenient, because these features can combine with further feature by the present invention.Other embodiment will be familiar with by those skilled in the art, and wishes to be included in the scope of this claim.
Claims (1)
1. one kind is used for from the method for one or more the alternative absorbed component of admixture of gas separation that comprise relatively poor selective absorption component, wherein admixture of gas contacts one or more fixed bed of sorbent that contain the selective absorption agent material, to adsorb this one or more alternative absorbed component, the cycle stage of employing comprises:
(a) absorption, this stage admixture of gas is by above-mentioned one or more fixed bed of sorbent, under higher adsorptive pressure, contact with adsorbent, and above-mentioned one or more alternative adsorbed components in the selective absorption admixture of gas, and its relatively poor selective absorption component is from the product end recovery of above-mentioned one or more fixed bed of sorbent; With
(b) decompression, this stage disconnects the path of admixture of gas to above-mentioned one or more fixed bed of sorbent, and make a pressure be reduced to lower desorption pressures from higher adsorptive pressure, so that from one or more fixed bed of sorbent desorbs and one or more alternative adsorbed components of recovery;
Wherein:
ⅰ) a part of relatively poor selective absorption component, by one or more fixed bed of sorbent, be passed into one or more external discrete gas storage tanks that gas mixes that are suitable for preventing to feed, it is higher degree that the product gas that is passed into said external divided gas flow storage tank begins, be product gas afterwards, directly be passed into another without any product gas from one or more fixed bed of sorbent in the adsorption system than low-purity;
ⅱ) from the product gas of external discrete gas storage tank, the initial product end that under lower desorption pressures, is passed into one or more fixed bed of sorbent, so that be pressurized to middle pressure again than the low-purity product gas with what extraneous gas separation storage tank fed at first, feed the product gas of higher degree then, in one or more like this fixed bed of sorbent, just have the product gas that purity is carried De Genggao at its product end;
ⅲ) stage (b) is used to clean the relatively poor selective absorption component of a part of one or more fixed bed of sorbent, reclaim from the product end of one or more fixed bed of sorbent, and by the product end of one or more fixed bed of sorbent, be passed into one or more external discrete gas storage tanks that gas mixes that are fit to prevent to feed, the gas that is passed into external discrete gas storage tank is higher degree at first, be product gas afterwards, directly be passed into another without any product gas from one or more fixed bed of sorbent in the adsorption system than low-purity;
ⅳ) with stage ⅱ) simultaneously, reclaim gas from one or more fixed bed of sorbent material feeding ends, and will be from the gas of one or more fixed bed of sorbent material feeding ends recovery, feed one or more external discrete gas storage tanks that gas mixes that are fit to prevent to feed, the gas that feeds external discrete gas storage tank is higher degree at first, be product gas afterwards than low-purity, in the adsorption system without any product gas from one or more fixed bed of sorbent directly feed the road another;
ⅴ) from the gas in the external discrete gas storage tank by one or more fixed bed of sorbent material feeding ends recovery, the initial material feeding end that under lower adsorptive pressure, is passed into one or more fixed bed of sorbent, so that with being forced into middle pressure from what external discrete gas storage tank fed again than the low-purity product gas at first, feed the product gas of higher degree then, in one or more like this fixed bed of sorbent, just have the product gas that purity is carried De Genggao at its material feeding end.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 98123070 CN1221643A (en) | 1997-12-09 | 1998-12-07 | PSA process and system |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/987,791 | 1997-12-09 | ||
| CN 98123070 CN1221643A (en) | 1997-12-09 | 1998-12-07 | PSA process and system |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100581645C (en) * | 2002-12-24 | 2010-01-20 | 普莱克斯技术有限公司 | Process and apparatus for hydrogen purification |
| CN101898069A (en) * | 2010-08-16 | 2010-12-01 | 西南化工研究设计院 | Pressure swing adsorption pressured regeneration method for preparing methanol synthesis gas |
| CN104519977A (en) * | 2012-06-04 | 2015-04-15 | 乔治洛德方法研究和开发液化空气有限公司 | Process for producing hydrogen with various levels of purity by H2PSA |
-
1998
- 1998-12-07 CN CN 98123070 patent/CN1221643A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100581645C (en) * | 2002-12-24 | 2010-01-20 | 普莱克斯技术有限公司 | Process and apparatus for hydrogen purification |
| CN101898069A (en) * | 2010-08-16 | 2010-12-01 | 西南化工研究设计院 | Pressure swing adsorption pressured regeneration method for preparing methanol synthesis gas |
| CN101898069B (en) * | 2010-08-16 | 2013-04-10 | 西南化工研究设计院 | Pressure swing adsorption pressured regeneration method for preparing methanol synthesis gas |
| CN104519977A (en) * | 2012-06-04 | 2015-04-15 | 乔治洛德方法研究和开发液化空气有限公司 | Process for producing hydrogen with various levels of purity by H2PSA |
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