CN1040844C - Pressure swing adsorption/desorption process with multiple countercurrent depressurization steps - Google Patents
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Abstract
The present invention discloses a PSA method which adopts standard PSA circulation. The method of the present invention comprises an adsorption step, at least one forward flow pressure reducing step which is used for balancing or providing cleaning gas, a counterflow pressure reducing step, a counterflow cleaning step and a repressurization step. The method of the present invention also comprises an additional counterflow desorption step which is carried out together with a first counterflow desorption step which is higher than the atmospheric pressure and the counterflow cleaning step which is carried out approximately at an adsorbent temperature. Compared with a PSA method which has only one counterflow pressure reducing step or does not additionally contain the counterflow cleaning step, the present invention can provide increased capacity and a recovery rate.
Description
What present invention relates in general to is transformation absorption (PSA) method, particularly be to separate or the improved PSA method of Purge gas, wherein adopted a plurality of countercurrent depressurization steps that combine with the adverse current cleaning step.
The PSA method provides the means of efficient and cost-effective for the separation that has the multi-component gas stream of two kinds of gases at least, and described gas has different characterization of adsorptions.Easily the gas of absorption can be impurity, and it is removed from the gas that is difficult for absorption, and the latter discharges as product gas, and perhaps, easily the gas of absorption can be required product, and it is separated from the gas that is difficult for absorption.For example, can remove carbon monoxide and light hydrocarbon to produce (99+%) hydrogen stream of purifying from hydrogeneous feed stream, be used for hydrocrack or other catalysis process, wherein these impurity can have a negative impact to catalyst or reaction.Similarly, easily the gas of absorption such as ethene can reclaim from feed stream to produce the product of ethylene-rich.
In the PSA method, be typically at least one that multicomponent gas is delivered to one group of adsorption zone, under elevated pressure, adsorb at least a component effectively, promptly easy adsorbed components, at least a other component of while promptly is difficult for absorbed component and therefrom passes through.In the time that limits, termination is sent into feed stream to absorber, and adsorption zone is reduced pressure by one or more following current depressurization steps, wherein said pressure is reduced to a limit value, permission will still be present in a kind of component that separated, difficult absorption or the various ingredients discharge of adsorption zone under this pressure, not have the easily absorbed component of remarkable concentration in the described component.By a countercurrent depressurization steps adsorption zone is reduced pressure then, the pressure of adsorption zone is further reduced, wherein by being the gas of discharging desorb inversely with the feed stream direction.At last, adsorption zone cleans and pressurization again.The PSA method of this class is at US-A-3, and 430,418; US-A-3, open in 564,816 and US-A-3,986,849, and narrate in these patents, the content of these documents is introduced here as reference, and the PSA method generally circulates with sequential process in comprising each bed of PSA system and carries out.
By with the adsorbent bed countercurrent depressurization to desorption pressures, from adsorbent bed, remove easily adsorbed components, i.e. adsorbate.Preferred lower desorption pressures can be in desorption procedure the more thorough adsorbate of removing.Lower desorption pressure also can provide bigger capacity difference between the adsorption and desorption state, thereby has increased the capacity of this process.Yet, seldom use very low desorption pressures, promptly pressure below atmospheric pressure is because technical complexity and relative expense, for example vavuum pump and analog.In addition, in hydrogen purification, often need under pressure that is suitable for entering the fuel gas house steward such as 20-100psia (138 to 690kPa), provide the desorb off-gas flows, be also referred to as tail gas.Accordingly, when adopting vavuum pump in psa process, discharge pressure is typically to be kept or is higher than fuel gas pressure.When not adopting vavuum pump, PSA hydrogen process is typically and adopts the desorption pressures that is greater than or equal to fuel gas pressure.
EP-B-15413 discloses a kind of pressure swing absorption process, has wherein adopted two stage adverse current desorption procedure to remove absorbed component, and described component can reach and be lower than an atmospheric pressure.This patent disclosure be that injector produces desorption pressures by means of air jet system, also disclose and pressure is higher than desorption pressures and is that gas or the admixture of gas that forms in the process of this method is used as driving force, promptly be used for the power gas of air jet system.The example of this driving force comprises: absorption effluent stream, feed stream and from the effluent stream of the first adverse current desorption procedure.
US-A-4,813,980 disclose a kind of multitower pressure swing absorption process, are used for producing ammonia synthesis gas and carbon dioxide simultaneously from reformer tail gas, described tail gas contains hydrogen, nitrogen and the carbon dioxide as key component, and with trace methane, carbon monoxide and argon gas impurity.The feature of this PSA system is that two groups of attached beds of absorption, wherein CO are arranged
2At first group is to be adsorbed in the adsorbent in the A bed, does not have CO substantially
2Effluent gases discharge that to deliver to second group be the adsorbent of B bed, remove trace impurity, discharge H simultaneously
2/ N
2Content is NH
3The effluent gases of synthetic chemical formula metering.CO by first group of adsorbent recovery
2Be high-purity, can be used to react and produce urea with ammonolysis product.First group of adsorbent bed adopted two stage adverse current desorption procedure, wherein extremely makes the adsorbent bed decompression near environmental pressure in the phase I by discharging contained gas.Be rich in CO at second desorption procedure adsorbent bed of finding time to being lower than an atmospheric pressure, further removing
2Effluent stream.
The problem that two stage desorption procedure of prior art exist is not have to be provided with the adverse current cleaning step that combines with two desorption procedure.Thereby, two adverse current desorption procedure on function similar in appearance to a continuous adverse current desorption procedure.The normal adverse current cleaning step that adopts is with further desorb adsorbate from adsorbent bed in the PSA method, and removes the adsorbate in the space that still remains in adsorbent bed after the adverse current desorption procedure.Compare with the PSA sorption cycle that does not adopt the adverse current cleaning step, the PSA sorption cycle of employing adverse current desorption procedure and adverse current cleaning step is typically and has improved purity, capacity and the rate of recovery.For example, US-A-3,430,418 and US-A-3,986,849 disclose the method for using the adverse current cleaning step in the PSA sorption cycle.In fact, US-A-4,813,980 disclose two adverse current desorption procedure have been arranged in the A bed, also disclose at the B bed and have used the adverse current cleaning step, but only be and the coupling mutually of single stage adverse current desorption procedure.
Thereby, seek improved PSA method, its adopts a plurality of desorption procedure be additional to the adverse current cleaning step, and wherein first countercurrent depressurization steps can carry out being higher than under the atmospheric pressure.Further also to seek improved method, wherein the adverse current cleaning step or near carrying out under the adsorption temp, and be in by the tail gas that this method obtained and be enough to be used as under the tail gas pressure of fuel gas.
By the invention provides the PSA method that is suitable for the isolated or purified feed stream, it has adopted a plurality of adverse current desorption procedure except that the adverse current cleaning step.This method can provide to the rate of recovery of the raising of non-absorbed component with to the capacity of adsorbate component.Preferred two adverse current desorption procedure and adverse current cleaning step between two desorption procedure of adopting.First adverse current desorption procedure is being higher than under the atmospheric pressure and is carrying out carrying out under the temperature of adsorption step.Further preferably will be used as power gas by the desorb effluent air-flow that first desorption procedure produces, drive the injector that operational contact is arranged with another adsorbent bed that carries out second desorption procedure, so that the tail gas stream under the tail gas pressure that is between first and second desorption pressures to be provided.
One aspect of the present invention provides the PSA method of separating first component from feed stream, described feed stream contains described first component and at least a other component, a plurality of adsorbent beds have wherein been adopted, and each described adsorbent bed all experiences the circulation of repetition, this circulation may further comprise the steps: (a) feed stream is delivered to and contained first adsorbent bed that its component is had the adsorbent of adsorption capacity, this is under the effective adsorption conditions that comprises adsorptive pressure and temperature, and shifts out the product air-flow that is rich in described first component with respect to feed stream from first adsorbent bed; (b) the first adsorbent bed following current is decompressed to equalizing pressure, this pressure is lower than adsorptive pressure, and the effluent that will discharge is thus being delivered to second adsorbent bed of pressurization again; (c) with first adsorbent bed countercurrent depressurization to the first desorption pressures, this pressure is higher than atmospheric pressure and is lower than intermediate pressure, with other component of desorb effectively, and discharges the first desorb effluent air-flow that contains described other component; (d) with charging first adsorbent bed is carried out adverse current with the cleaning that contains first component under about adsorption temp and clean, and discharge the cleaning effluent stream that contains other component; (e) with (d) step simultaneously or thereafter, to further countercurrent depressurization to the second desorption pressures of first adsorbent bed, this pressure is lower than first desorption pressures, and can be effectively further other component of desorb, and discharge the second desorb effluent stream that contains described other component; And (f) first adsorbent bed is forced into adsorptive pressure again.
As another aspect of the present invention, the PSA method of separating described first component from the feed stream that contains first component and at least a other component is provided here, a plurality of adsorbent beds have wherein been adopted with feed end and product end, each described adsorbent bed all experiences the circulation of repetition, this circulation may further comprise the steps: the feed end of (a) feed stream being delivered to first adsorbent bed, this adsorbent bed contains the adsorbent that other component is had effective adsorption capacity, and this is under the effective adsorption conditions that comprises adsorptive pressure and temperature, and discharges the product air-flow that is rich in first component with respect to feed stream from the product end of this first adsorbent bed; (b) the first adsorbent bed following current is decompressed to equalizing pressure, this pressure is lower than adsorptive pressure, and thus the effluent air-flow is delivered to the product end of second adsorbent bed of pressurization just again; (c) with first adsorbent bed countercurrent depressurization to the first desorption pressures, this pressure is higher than atmospheric pressure and is lower than equalizing pressure, and effective other component of desorb of energy, discharges the first desorb effluent air-flow that contains other component from the feed end of first adsorbent bed; (d) under about adsorption temp, first adsorbent bed is carried out adverse current with charging with the cleaning that contains first component and clean, and discharge the cleaning effluent air-flow that contains other component from the feed end of this first adsorbent bed; (e) with the adverse current cleaning while or thereafter, further with first adsorbent bed countercurrent depressurization to the second desorption pressures, this pressure be lower than first desorption pressures and can be effectively further other component of desorb, and discharge the second desorb effluent air-flow that contains other component from the feed end of first adsorbent bed, wherein by will be simultaneously just at least a portion first desorb effluent air-flow of the 3rd adsorbent bed of countercurrent depressurization to the first desorption pressures through having the injector of operational contact to flow out with first adsorbent bed, carry out further countercurrent depressurization; (f) first adsorbent bed is forced into adsorptive pressure again.
Figure 1 shows that the sorption cycle sketch that the PSA method of 10 adsorbent beds is arranged according to of the present invention.
Figure 2 shows that the sorption cycle sketch that the PSA method of 4 adsorbent beds is arranged according to of the present invention.
Figure 3 shows that the flow direction between the adsorbent bed of particular moment of circulation shown in Figure 2 connects.
The invention relates to the PSA method of from the feed stream that contains first component and at least a other component, separating described first component. According to the present invention, the component of the non-adsorbable or difficult absorption of " first component " representative in feed stream. The adsorbate of " other component " representative in feed stream, the component of namely easily adsorbing.
The method can be used for carrying out body portion from or purifies and separates, and the corresponding feed stream that can be applicable to wide range. Suitable incoming flow is that those are gaseous state under adsorption conditions. When using the present invention when coming the hydrogeneous feed stream of isolated or purified, suitable feed stream be those contained density of hydrogen preferably 10 to 90mol%. The adsorbate that exists in the feeding gas material, be that other component typically comprises one or more of the following stated, for example, light hydrocarbon such as methane and ethane, carbon monoxide, carbon dioxide, water, hydrogen sulfide, ammonia, nitrogen and oxygen. Feed stream can contain other adsorbate, for example C sometimes3-C
6The hydrocarbon of scope, alcohol, ether, amine, mercaptan, aldehyde, ketone and analog. First component depends on existing other component, adsorption conditions in the charging and the adsorbent that adopts. Thereby, the situation that above-mentioned adsorbate is first component may appear. For example, when separation of nitrogen from methane, nitrogen is adsorbate, and methane reclaims as the product of non-absorption. What form contrast is that in the hydrogen purification method, methane often is adsorbate.
Thereby method of the present invention is not limited to concrete feed stream, can be used to implement various separation, for example, for example, isolates hydrogen from the feed stream that contains hydrogen, methane, carbon monoxide and nitrogen, and wherein hydrogen is not adsorbed; By absorption nitrogen air separation is become nitrogen and oxygen; By absorbing carbon dioxide separating carbon dioxide and non-acid gases such as nitrogen, hydrogen and methane; With by absorption normal butane separate normal butane and iso-butane.
The typical feed stream of handling according to the present invention derives from oil plant, natural gas, air and chemical plant.The example in charging source comprises reformation waste gas, synthesis gas and the natural gas of light hydrocarbon or methanol recapitalization.
Corresponding to feed stream, the product correspondence that obtains by method of the present invention various purposes are arranged.For example, can carry out PSA hydrogen process provides very highly purified hydrogen, as 99
+Mol.% is used as industrial chemicals.Also can, in the hydrogen product air-flow, provide certain adsorbate concentration with this method, for example, when the ammonia synthesis gas with 3 mol of hydrogen/mole nitrogen is provided, product will contain the hydrogen of the 75mol.% that has an appointment.When the separating butane feed stream when obtaining the iso-butane product, iso-butane can be used as raw material for alkylation or gasoline blending ingredients.
In fact the present invention can anyly have the sorbent material of capacity to implement to absorbed component in adsorbent bed by using.Known and the commercially available suitable adsorbent of prior art comprises crystal molecule sieve, active carbon, activated clay, silica gel, activated alumina and analog.Molecular sieve comprises for example US-A-4,440,871; US-A-4,310,440 and US-A-4,567,027 disclosed various forms of silicoaluminophosphates and aluminate or phosphates also comprise zeolite molecular sieve, above-mentioned document is introduced here as reference.
The zeolite molecular sieve of calcined form can be represented by following general formula;
Me
2O∶Al
2O
3∶XSiO
2∶yH
2O
Wherein Me is a cation, and the value of X is about 2 to infinity, and n is the cation valence mumber, and the value of y is about 2 to 10.
Operable typical known zeolite comprises, chabasie is also referred to as zeolite D, clinoptilolite, and erionite, faujasite also is called X zeolite and zeolite Y, iron zeolite (ferrier-ite), modenite, zeolite A and zeolite P.Other zeolite that is suitable for according to the present invention is that those have high silicon dioxide content, and promptly wherein the ratio of silica and aluminium oxide is typically greater than 100 greater than 10.One of this class high silica zeolites is silica zeolite (silicalite), and this speech here uses and comprises US-A-4, polycrystalline silica (silicapolymorph) and US-A-4 in 061,724, the F-silicate in 073,865.
PSA of the present invention circulation comprises known absorption, one or more equilibrium step, adverse current desorb, cleaning and pressurized circulation step again.The step of circulation is typically with reference to them to be described with respect to the direction of adsorption step.Thereby the circulation step that wherein airflow direction is identical with the adsorption step direction is called " following current " step.Similarly, circulation step be called opposite of airflow direction " adverse current " step wherein with adsorption step.Feed stream is delivered to adsorbent bed with the adsorptive pressure that has raise so that adsorbate absorption in adsorption step, and the product air-flow that is rich in first component with respect to feed stream is provided.In equilibrium step, preferably following current discharges the pressure in the decompression bed, the thus obtained effluent air-flow that preferably is rich in first component, and deliver to another adsorbent bed that pressurizes just again with countercurrent direction.Typically when equilibrium step finishes, provide the step of purge gas to begin, the wherein further following current decompression of adsorbent bed is impure relatively purge gas to provide with regard to first component, thereby is applicable to as purge gas.Choose wantonly,, can be used to provide purge gas with a part of product gas or from the gas of one of equilibrium step gained for replacement provides the step of purge gas.When the step that purge gas is provided finishes, if adopt, with the adsorbent bed countercurrent depressurization to desorption pressures with the desorb adsorbate.When desorption procedure finishes, use the purge gas that obtains from another adsorbent bed that adsorbent bed is carried out the adverse current cleaning.At last, use balanced gas to make adsorbent bed be forced into adsorptive pressure again with charging or product gas then earlier from other adsorbent bed.Also can adopt to well known to a person skilled in the art other additional step, for example, the following current cleaning step wherein carries out following current with the purge flow that contains adsorbate to adsorbent bed and cleans under elevated pressure such as adsorptive pressure.
What the present invention is directed to is improvement to above-mentioned basic PSA circular order, has wherein comprised additional adverse current desorption procedure in this circulation, i.e. depressurization steps.By being decompressed to second desorption pressures with countercurrent direction and realizing the second adverse current desorption procedure by bed, described second desorption pressures is lower than first desorption procedure pressure at the end, i.e. first desorption pressures.
In order to obtain advantage of the present invention, must comprise an adverse current cleaning step that combines with two adverse current desorption procedure.Preferably before the second adverse current desorption procedure or with its simultaneously, carry out the adverse current cleaning step.Therefore, in some cases, before beginning, the second adverse current desorption procedure finishes the adverse current cleaning step.Under the other situation, at least a portion adverse current cleaning step and the second adverse current desorption procedure take place simultaneously.Certainly after the second adverse current desorption procedure, carry out the adverse current cleaning step.Be not subjected under any concrete theoretical condition that limits, believe that if after the first adverse current desorption, carry out the adverse current cleaning step this cleaning can help to make the adsorbate forward position to become clear and concentrate adsorbate in the place that the feed end of adsorbent bed is promptly introduced feed stream in adsorbent bed.Accordingly, when carrying out the second adverse current desorption procedure after certainly, can discharge more adsorbate when not comprising the adverse current cleaning step.Preferably, the purge gas that effective dose is provided in the adverse current cleaning process is to provide the adsorbate component concentrations that has improved at the feed end of adsorbent bed with respect to product end.More preferably, the purge gas of effective dose is the purge gas of feed stream 0.5 to 2 volume of every volume, further the more preferably purge gas of charging 0.5 to 1 volume of every volume.
By any means, for example vavuum pump can be implemented in the pressure decline in the second countercurrent depressurization steps process, but according to the present invention preferably, use an injector to realize second countercurrent depressurization steps.The suitable injector of using according to the present invention also is that prior art is known, as jet pump or fluid delivery pump, all these are all operated according to following principle: the dynamic air-flow under the pressure that has improved is by nozzle decompression, the increase of the molecular velocity in nozzle place power gas, thereby momentum raises.Molecule in the power gas of Jia Suing is carried away the molecule of medium then secretly with the form that sucks by the Momentum Transfer in blending space in this manner.Kinetic energy partly transforms and is back to compression energy in diffuser, and the pressure of the mixed airflow that is produced is between the reset pressure of the medium of the reset pressure of power gas and suction.About the design and the details of operation of injector it is well known to those having skill in the art that.
When the present invention adopted injector, being used to drive the power gas that injector and generation obtain the required suction of second desorption pressures can be from the available any fluid air flow of factory, no matter it derives from psa process or from other process.Yet preferably, power gas produces from psa process, further more preferably, it contains from the adverse current desorb effluent air-flow of first desorption procedure and/or purgative gas charging or with the second adverse current desorption procedure and carries out the effluent air-flow of another adsorbent bed of described step simultaneously.This is not to provide the step of power gas to carry out simultaneously with second desorption procedure fully, but only some must carry out simultaneously.In fact, the power gas from two or more process steps or bed can be used for driving injector in single second desorption procedure.The example of operable other dynamic air-flow comprises feed stream, adsorption production effluent air-flow and is used for the countercurrent depressurization effluent air-flow of balance.
Those skilled in the art may appreciate that many used according to the present invention preferred power gas because the pressure of decompression adsorbent bed descends and consequent flow velocity descends, can experience unsettled flox condition.Thereby many under these conditions injectors can not resemble common good operation design drawing marked, and the power gas in the described design drawing provides under pressure stable and flow velocity.Corresponding with it, need two or more injectors are installed, each is optimized processing by the concrete flox condition that it can experience.For example, when first countercurrent depressurization steps began, the pressure and the flow velocity of power gas were higher, preferably adopted than the power gas that is used in adverse current desorption procedure terminal point, be the higher larynx footpath and the nozzle area ratio of injector of low-pressure and low flow rate of gas.Also can, provide variable larynx footpath and nozzle area ratio to adapt to the power gas condition of variation.
Furtherly, suction one side of injector must be directly connected to according to the present invention and just carry out on the adsorbent bed of second desorption phase simultaneously.As one aspect of the present invention, be to provide the appropriate time of a container in the PSA circulation to store and transmit the suction benefit of injector as what substitute.Like this, suction one side of injector is connected to the pressure that reduces when the fooled dynamic gas of this container can utilize wherein.In the subsequent step of this circulation, when the suction benefit that is necessary to adopt injector reduces the pressure of adsorbent bed, just this container is connected on the described bed that just carries out second desorption phase its pressure is descended, and cause the pressure of reservoir vessel to rise.The circulation subsequent step again or in circulation subsequently, injector reduces the pressure of reservoir vessel again.
When method of the present invention was used for hydrogen purification, preferably the effluent from injector was that tail gas contains the desorb effluent stream from the first and second adverse current desorb effluent streams, and provides with the tail gas pressure that is enough to allow to be incorporated into the fuel gas house steward.The pressure that typical fuel gas reaches the tail gas that obtains thus is 20 to 100Psia (138 to 690kPa), is preferably 20 to 50Psia (138 to 345kPa).
The temperature of using in adsorption method of the present invention is not harsh, and it depends on feed stream and required separating, though generally speaking this method is isothermal basically.For hydrogen purification, typical temperature range is about-100 to 700 (73 to 371 ℃), preferred-18-150 ℃, more preferably 50 to 200 (10 to 93 ℃), more preferably 50 to 150 (10 to 66 ℃).According to the above-mentioned adverse current cleaning step of the present invention with the approximately identical temperature of adsorption step under carry out, preferably in 50 °F (10 ℃), more preferably in 20 °F (6.7 ℃).But should be appreciated that,, can give meter and be accompanied by the temperature that absorption and the fuel factor of heat of desorption have to a certain degree and raise and reduction though this method generally speaking is an isothermal.
Similar, the absolute pressure value that adopts in the PSA procedure is not harsh, as long as the pressure differential of absorption and desorption procedure is enough to make the adsorbate composition loading on adsorbent to change, thereby provides the load of effective separating feed air-flow poor (delta loading).In adsorption step, typical force value is 100 to 2000psia (698 to 13790kPa), preferred 350 to 13790kPa, 200 to 1000psia (1396 to 6895kPa) more preferably, further 400 to 1000Psia (1758 to 6895kPa) more preferably, force value at the terminal point of second desorption procedure is 1 to 500psia (6.9 to 3448kPa), more preferably about 5 to 50Psia (34 to 345kPa).Should be understood that the pressure in equilibrium step, the step that purge gas is provided, the first adverse current desorption procedure and adverse current purgative gas step is the median of the absorption and second desorption procedure.According to the present invention, be higher than an atmospheric pressure at the pressure of the first desorption procedure terminal point.
As hydrogen purification, preferably combine and select second desorption pressures in some cases so that required tail gas pressure to be provided with first desorption pressures.Thereby second desorption pressures can be higher or lower than atmospheric pressure.For example, if beginning first desorption procedure under elevated pressures, and the first desorb effluent is used as power gas in injector, then can obtain a lower pressure at the terminal point of second desorption procedure, and still can be provided at the tail gas pressure between the initial power gas pressure and the second desorption terminal pressure, and this pressure is still enough high to deliver to the fuel gas house steward.
The required time of whole each steps of promptly implementing the PSA circulation on the whole Xun Huan total time is 3 to 30 minutes, more preferably 4 to 20 minutes.At least need two adsorbent beds for implementing each equilibrium step, be typically the product gas source that provides stable and need at least 4 adsorbent beds.Preferably adopt about 4 to 14 adsorbent beds, more preferably from about 7 to 14, most preferably from about 10 to 12 according to the present invention.
10 circulations are routine substantially
Use is commonly used to design the computer simulation model of commercial psa process, and the psa process with 10 adsorbent beds that all has three absorbers to be in adsorption step and three equilibrium steps at arbitrary given time is simulated.The basis of simulation is that above-mentioned psa process should be able to be handled 60MMSCFD (1.7 * 10
6m
3) to have 20 moles of % methane surpluses at 600psia (4137kPa) be the feed stream of the composition of hydrogen.This circulation is included in the adsorption step under the 600psia (4137kPa), three equilibrium steps and the step that purge gas is provided, pressure at the terminal point of the step that purge gas is provided is 145psia (1000kPa), then be the adverse current desorption procedure with reach pressure 25Psia (172kPa), purgative gas quantity is the adverse current cleaning step of the about 0.6 volume purgative gas of every volume charging, pressurize again with balanced gas and product gas then.
This Simulation result is shown in Table 1 in first hurdle that is entitled as " single phase desorb ".
Table 1
| Condition | The single phase desorb | The desorb of two stages | |
| Do not have and clean | Cleaning is arranged | ||
| The first desorption pressures Psia (kPa), second desorption pressures Psia (kPa) the purgative gas quantity purgative gas volume feed volume capacity1The rate of recovery 2Productive rate 3 | 25(172) - 0.6 82.5 84.4 69.5 | 25(172) 11(76) - 87.4 85.4 74.6 | 25(172) 11(76) 0.6 91.5 87.0 79.6 |
| 1Capacity=(feed volume/adsorbate volume) * 105 hours -1 2The rate of recovery=H 2Product molal quantity/H 2Time material molal quantity * 100 3Productive rate=capacity * the rate of recovery/100 | |||
As can be seen, the capacity that above-mentioned circulation produces is 82.5, and hydrogen recovery rate is 84.4%, and productive rate is 69.5.
Have two countercurrent depressurization steps
10 sorption cycle
Second simulation implementing is similar to above-mentioned circulation, and difference is that the step that provides purge gas or adverse current to clean is not provided.The pressure that this process is simulated to obtain at the first desorption procedure terminal point is 25psia (172kPa).Comprise one second desorption procedure in addition, adopted an injector in second desorption procedure, pressure to be reduced to 11psia (76kPa) thus.Obtain being used to drive the power gas of injector by another adsorbent bed that just carries out first desorption procedure.With general single phase injector performance figure is the performance of basis simulation injector, simulation at be that larynx footpath is 10 with nozzle area ratio, have 25% additional accidental error, this is because the beginning of the first adverse current desorption procedure and operation of unstable state at the end and non-best area ratio.This simulation shows that the adsorbent bed that just carries out second desorption procedure can reduce to 8psia (55kPa), however for considering because the resistance that pressure drop causes adds 3Psia (21kPa), i.e. 11Psia (76kPa) to the final desorption pressures that is reached.
Second hurdle that is entitled as " two stage desorbs one do not have clean " by table 1 acceptance of the bid makes capacity factor measure increase to 87.4 owing to increased by second desorption procedure as can be seen.Also have the rate of recovery to increase by 1% and reach 85.4%, productive rate increases to 74.6%.This improvement major part is because the maximum pressure increase of the pressure change of the minimum pressure of desorption procedure extremely at last from charging of global cycle.This new circulation allows exhaust gas pressure to reduce to 11Psia (76kPa), and this value is inaccessiable in the circulation of the embodiment 1 that does not have second desorption procedure.
Two adverse current desorption procedure and an adverse current are arranged
10 circulations of cleaning step
Figure 1 shows that 10 circulations adopting the inventive method, wherein provide two adverse current desorption procedure to combine with a contrary cleaning step.The order of this circulation is described similar with 2 to embodiment 1.For example, end-around carry according to bed (1) can see that bed (1) carries out an adsorption step earlier, and what follow then is three equilibrium steps, the effluent that wherein therefrom obtains is delivered to adsorbent bed 5,6 and 7 respectively, and each described equilibrium step is designated as E1, E2 and E3 in the reasonable time scope.The single step of purge gas that provides in the step that purgative gas is provided of bed (1) experience a series of PP1 of being designated as, H and PP2 then, they and embodiment 1 described circulation is equal to.Provide among the step PP1 of purge gas at first, resulting effluent is delivered to the bed 9 that just carries out first cleaning step.The time period that is designated as H is represented a maintenance stage, and wherein this bed is independently.In second that the is designated as PP2 step that purge gas is provided, the effluent that therefrom obtains is delivered to bed 9 in the time range that is designated as PR, and in this time phase, the valve of bed 9 feed ends cuts out, with the beginning sequence of pressurizeing again.Also can, in this time range, still make the bed 9 feed ends valve be in the breakdown state so that second cleaning step to be provided.For the present invention, provide to determine cleaning in the cleaning step or pressurize again not to be crucial, can make decision by those skilled in the art second.Second the step of cleaning is provided after, adsorbent bed (1) countercurrent depressurization to pressure in being designated as the time phase of D1 is 25Psia (172kPa).According to the present invention at this moment adsorbent bed (1) use from just carrying out the gas that cleaning is provided that first adsorbent bed that step of purge gas is provided (3) obtains at the time phase that is designated as P1 and carry out adverse current and clean.When adverse current was cleaned end, the further countercurrent depressurization of bed (1) was to about 11Psia (76kPa).This second decompression power step realizes described injector and adsorbent bed (2) binding operation that just carries out first depressurization steps by using an injector.After second desorption phase finished, adsorbent bed (1) used effluent gas that obtains from adsorbent bed (3), (5), (6), (7) and the outflow product gas that obtains from least one adsorbent bed (8), (9) or (10) to pressurize again in time phase PR, E3, E2, E1 and R.Get in touch adsorbent bed (9) as mentioned previously in being designated as the time phase of PR, adsorbent bed (1) can also clean for the second time.The time phase that cleans corresponding to adsorbent bed among the time phase of P1, D2 and PR among Fig. 1 and the embodiment 1 is equal to.
Be shown in title " two stage desorbs one the do not have clean " hurdle 3 of table 1 to carry out Simulation result according to method of the present invention.As can be seen, by outside second desorption procedure, increasing the adverse current cleaning performance of this method is significantly improved.For example, can see that capacity factor measure increases to 91.5, hydrogen recovery rate increases to 87.0, and productive rate increases to 79.6%.Though not shown in table, even when adopting significant flushing dose, as every volume charging 14 volume purgative gas, the performance of the circulation of embodiment 3 simulations has been compared improvement with the performance that the circulation of embodiment 1 simulation obtains.As in embodiment 3, the pressure change that improved circulation has increased global cycle obtains income on the productive rate with the lower waste gas body pressure that reaches 11psia (76kPa).
Four circulations
Figure 2 shows that sorption cycle flow chart according to PSA method of the present invention with 4 adsorbent beds.In this one side of the present invention, the second adverse current desorption procedure and adverse current cleaning step carry out simultaneously.Have, carry out the adsorbent bed of the first adverse current desorption procedure, this step preferably provides the power gas that drives injector, and the decompression of following current simultaneously is to provide purge gas.Such step is known as both-end (dual-end) decompression in the PSA field.Comprising an adsorption step that is designated as A with reference to bed (1) this circulation among Fig. 2, then is the equilibrium step in the time phase E1 process, and effluent gas is wherein delivered to the adsorbent bed (3) that just carries out equilibrium step.This following current and countercurrent depressurization are to provide the purge gas and the first desorb effluent gas then.After first desorb/provide purgative gas step finished, this is further countercurrent depressurization and clear Xian of adverse current simultaneously in being designated as the time phase of D2/P.After second desorb/cleaning step finished, this adsorbent bed is pressurization again in E1 and R time phase.
Figure 3 shows that in sorption cycle shown in Figure 2 the mobile annexation that when about 3 minutes, is engraved between adsorbent bed.Can see that bed (1) is just carrying out adsorption step, wherein feed stream is delivered to the feed end of this adsorbent bed, and the effluent air-flow is discharged from the product end of this adsorbent bed.Part effluent air-flow is discharged as product, and remainder is delivered to the adsorbent bed (2) that pressurizes just again.Adsorbent bed 3 carries out adverse current simultaneously and cleans and countercurrent depressurization to the second desorption pressures.Suction one side of delivering to injector by the second desorb effluent stream that will be designated as " D2 gas " realizes that described pressure reduces.The purge gas that obtains from the product end of bed (4) is used for adverse current and cleans adsorbent bed (3).Adsorbent bed (4) is just carrying out the two ends depressurization steps with the purge gas that is provided for cleaning adsorbent bed (3) with what be used as that power gas drives injector is the first desorb effluent gas that is designated as " D1 gas ".The tail gas air-flow that contains the first and second desorb effluent air-flows is discharged from injector and is removed from this process.
Those skilled in the art may appreciate that, can make many changes to the foregoing description within the scope of the invention.For example, for reaching the number that required result can change adsorbent bed, the number of equilibrium step, connection and similar factor between the bed.Have again, can adopt many group adsorbent beds, adverse current desorb and cleaning step are appeared at independently in the absorber group, rather than in one group.Furtherly, the power gas that comes from an absorber group can be used to drive the injector that operational contact is arranged with the adsorbent bed of another absorber group.Similar again, as mentioned above, various air-flow can be used to drive injector except that the first adverse current effluent and purge gas.For example, feed stream can be used as power gas drives operational contact with the bed that just carries out the adverse current desorption procedure injector.Substitute effluent gas by discharging in this process, the charging limit that the effluent of injector can be back to another adsorbent bed is used as and flows purge gas.Also have, this method is narrated, can adopt adverse current desorption procedure in the method for the invention more than two though should be understood that the top reference first and second adverse current desorption procedure.In this case, preferably before final adverse current desorption procedure, carry out described adverse current cleaning step.It shall yet further be noted that and do not specialize as here introducing as reference with reference to all patents introduced and publication list of references.
Claims (11)
1. one kind is used for from the pressure swing absorption process of feed stream separation first component, described feed stream contains described first component and at least a other component, wherein adopted a plurality of adsorbent beds, and each described adsorbent bed all experiences the repetitive cycling that may further comprise the steps:
(a) feed stream is delivered in first adsorbent bed that contains adsorbent, described adsorbent is comprising the adsorption capacity that has under effective adsorption conditions of adsorptive pressure and temperature described other component, and has discharged with respect to the feed stream enrichment product gas flow of described first component from first adsorbent bed;
(b) the first adsorbent bed following current is decompressed to the equalizing pressure that is lower than adsorptive pressure, and with effluent from delivering to just again second adsorbent bed of pressurization here;
(c) with first adsorbent bed countercurrent depressurization to the first desorption pressures, this pressure is higher than atmospheric pressure and is lower than equalizing pressure and effective described other component of desorb, and shifts out the first desorb effluent that contains described other component;
(d) under about adsorption temp, first adsorbent bed is carried out adverse current with the purgative gas charging that contains described first component and clean, and discharge the cleaning effluent that contains described other component;
(e) clean simultaneously with described adverse current or after, further with first adsorbent bed countercurrent depressurization to the second desorption pressures, this pressure be lower than first desorption pressures and also can be effectively further described other component of desorb, and discharge the second desorb effluent air-flow that contains described other component; And
(f) first adsorbent bed that pressurizes again.
2. method as claimed in claim 1, it is characterized in that making at least a portion first desorb effluent to pass through an injector from step (c), this injector has operational contact with the 3rd adsorbent bed that just carries out step (e), makes the 3rd adsorbent bed be decompressed to second desorption pressures thus.
3. method as claimed in claim 1 is characterized in that after step (b) first adsorbent bed being carried out the pressure that following current is decompressed to provides cleaning, and this pressure is lower than equalizing pressure and is higher than first desorption pressures, and discharges the purge flow that contains wash feed.
4. method as claimed in claim 3 is characterized in that making at least a portion purge flow by an injector, and this injector has operational contact with the 3rd adsorbent bed that just carries out step (e), makes the 3rd adsorbent bed be decompressed to second adsorptive pressure thus.
5. method as claimed in claim 1, wherein second desorption pressures is lower than an atmospheric pressure.
6. method as claimed in claim 1, wherein adsorption conditions comprise 350kPa-13790kPa adsorptive pressure and-adsorption temp of 18-150 ℃.
7. method as claimed in claim 1, wherein said first component is a hydrogen, described other component is selected from methane, ethane, carbon monoxide, carbon dioxide, ammonia, nitrogen, hydrogen sulfide and water.
8. method as claimed in claim 1, wherein said first component is a nitrogen, described other component is selected from methane, ethane, carbon monoxide, carbon dioxide, ammonia, hydrogen sulfide and water.
9. method as claimed in claim 1, wherein said first component is a methane, described other component is a nitrogen.
10. method as claimed in claim 1, wherein said first component is an oxygen, other component is a nitrogen.
11. method as claimed in claim 1, wherein first component is an iso-butane, and other component is a normal butane.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN93105685A CN1040844C (en) | 1993-04-19 | 1993-04-19 | Pressure swing adsorption/desorption process with multiple countercurrent depressurization steps |
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| Application Number | Priority Date | Filing Date | Title |
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| CN93105685A CN1040844C (en) | 1993-04-19 | 1993-04-19 | Pressure swing adsorption/desorption process with multiple countercurrent depressurization steps |
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| CN1040844C true CN1040844C (en) | 1998-11-25 |
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| US8435328B2 (en) * | 2011-01-11 | 2013-05-07 | Praxair Technology, Inc. | Ten bed pressure swing adsorption process operating in normal and turndown modes |
| NL2007218C2 (en) * | 2011-08-03 | 2013-02-05 | Stichting Energie | Regeneration of gas adsorbents. |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4070164A (en) * | 1976-02-18 | 1978-01-24 | Toray Industries, Inc. | Adsorption-desorption pressure swing gas separation |
| US4077779A (en) * | 1976-10-15 | 1978-03-07 | Air Products And Chemicals, Inc. | Hydrogen purification by selective adsorption |
| EP0015413A1 (en) * | 1979-02-16 | 1980-09-17 | Linde Aktiengesellschaft | Pressure swing adsorption process for the decomposition or purification of gas mixtures |
| US4717397A (en) * | 1985-08-12 | 1988-01-05 | Linde Aktiengesellschaft | Adsorbate recovery in PSA process |
| US5203888A (en) * | 1990-11-23 | 1993-04-20 | Uop | Pressure swing adsorption process with multiple desorption steps |
-
1993
- 1993-04-19 CN CN93105685A patent/CN1040844C/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4070164A (en) * | 1976-02-18 | 1978-01-24 | Toray Industries, Inc. | Adsorption-desorption pressure swing gas separation |
| US4077779A (en) * | 1976-10-15 | 1978-03-07 | Air Products And Chemicals, Inc. | Hydrogen purification by selective adsorption |
| EP0015413A1 (en) * | 1979-02-16 | 1980-09-17 | Linde Aktiengesellschaft | Pressure swing adsorption process for the decomposition or purification of gas mixtures |
| US4717397A (en) * | 1985-08-12 | 1988-01-05 | Linde Aktiengesellschaft | Adsorbate recovery in PSA process |
| US5203888A (en) * | 1990-11-23 | 1993-04-20 | Uop | Pressure swing adsorption process with multiple desorption steps |
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| CN1094329A (en) | 1994-11-02 |
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