CN1168192A

CN1168192A - Separation of gases

Info

Publication number: CN1168192A
Application number: CN96191442A
Authority: CN
Inventors: 克里斯托弗·约翰·布罗恩; 伊恩·戴维·赫德森
Original assignee: British Nuclear Fuels PLC
Current assignee: Sellafield Ltd
Priority date: 1995-11-17
Filing date: 1996-11-15
Publication date: 1997-12-17
Also published as: EP0804795A1; KR19980701355A; WO1997019454A1; GB9523517D0; CA2206453A1; JPH10512808A

Abstract

A method for the separation of at least one constituent gas from a gas mixture containing the at least one constituent gas and at least one other gas species is described, the method comprising the steps of: providing a stream of the gas mixture to a first membrane of a zeolite material under conditions of pressure and temperature such that the required gas is selectively adsorbed onto a first face of the zeolite material membrane and diffusion through the zeolite membrane towards a second face is promoted; retaining and containing the permeate gas emerging from said membrane second face and passing a retentate of said gas stream not passed through said zeolite membrane either back to the first face of the first zeolite membrane or to a first face of a second zeolite membrane; and, repeating said method steps until a content of the required gas in the gas mixture is reduced to a desired level.

Description

Gas separates

The present invention relates to a kind of method that is used for isolating each component gas from molecular gas potpourri or monatomic gas and molecular gas potpourri.

People wish and can before they are discharged into the atmosphere, isolate the radioactivity noble gas, as krypton for example from other gas such as oxygen and nitrogen.For example, usually need to isolate the radioactive isotope of noble gas from waste gas stream, these isotopes are produced by nuclear reaction in this fuel.The noble gas that also may need to be used as inert carrier gas in the gas-phase reaction (as gas shift reaction) separates and recycle.Also wish from the molecular gas potpourri, to isolate each component gas, as from rock gas, isolating carbon dioxide or from air, isolating carbon dioxide.

Utilize the zeolitic material bed to select absorption krypton and xenon, this is known, in case noble gas is adsorbed in the zeolitic material, temperature and/or pressure condition then are conditioned, make and from zeolitic material, discharge gas, and further handle, contain and preservation in some mode.Such method is batch method substantially and uses many adsorption systems.The case description of these methods is in U.S. Pat-A-4447353 and European patent EP 0658364.

Once advised some other methods based on continuous processing rather than batch method.The polymeric membrane that these technology using gases piece-rate systems that propose are used.In this method, gas molecule " dissolving " and is diffused into a low-pressure area by it in polymeric matrix.The shortcoming of this method is that the maximum temperature of inlet air flow is limited in about 100 ℃.Also relate to the radiolysis problem of polymeric film material.But major defect is, because gas is very low by the flow of film, so require the area of polymer film very big, makes this method expensive like this.In addition, owing to a pressure reduction need be arranged,, like this, the people is thrown doubt upon to the economy of this gas separating method so will require pressurization again between each step of polyphone to drive diffusion technique.

The object of the invention is, a kind of continuous processing that is used for separating from a gas stream one or more desirable gas is provided, the shortcoming of some polymer film methods that it did not once propose.

According to the present invention, a kind of gaseous mixture of containing at least a component gases and at least a other gas (other gas species) from a kind of of being used for is proposed, the method of separating this at least a component gases, this method comprises following all steps: first film that a described gaseous mixture stream is sent to a zeolitic material under certain pressure and temperature conditions, make that described at least a component gases is selected to be adsorbed on first of described zeolitic material film, and impel it through described film to second diffusion, contain and keep the enrichment of emitting from described film second face described at least a component gases see through gas; With the residual gas (retentate gas) by described zeolite membrane not in the described gas stream, or flow to described first of described first zeolite membrane, or flow to first of one second zeolite membrane; And, repeat the above steps of described method, reduce to a desirable value until the content of the described at least a component gases in described gaseous mixture.

Zeolitic material is meant aluminosilicate molecular sieves, but title " zeolite " is also made a general reference crystalline molecular sieve sometimes.General molecular sieve is made a general reference in word in this instructions " zeolite ", comprises the mutation after being replaced by metal as silicate, aluminate or phosphate (gallium phosphate), phosphoric acid gallium (gallium phosphate) and these materials.

Proprietary name used herein " contain and keep " (containing and retaining) is to show that seeing through gas is retained or contains so that perhaps storage or bottling or suitable words only are put in the atmosphere.Seeing through gas can further handle with method of knowing in the prior art or device, and then the understanding of the implication that proprietary name " is contained and reservation " should be not restricted.

At least a component gases can be a kind of monatomic gas, as a kind of noble gas (noble gas) (for example krypton gas), or but a kind of molecular gas, as carbon dioxide.Like this, potpourri (xenon at this moment can be separated from krypton), monatomic gas and the molecular gas of the monatomic gas of gaseous mixture a kind of as xenon and krypton, perhaps, can be a kind of only be the potpourri of molecular gas.But, two or more gas is arranged in this potpourri.

In following total description to method, specifically mentioned krypton, still, this is just to using for example.Here the krypton of mentioning is construed as other noble gas that comprises as xenon and radon, perhaps as the molecular gas of carbon dioxide.

In foregoing invention, the permeation parts in the air-flow is by zeolite membrane and with respect to that part of the noble gas that contains higher proportion in the unstripped gas; Residue then is not pass through that part of of zeolite membrane in the flow of feed gas.The relative scale of all components of a kind of gaseous mixture by zeolite membrane is considered for " separation coefficient ", is defined as two kinds of ratios that see through thing by the gas of film.

Residue or be recycled in the original flow of feed gas, and by first zeolite membrane first perhaps, are directed to second zeolite membrane that is connected in series with first film.In a suitable stage, when the radgas content of residue reduces to a License Value, residue is discharged in the atmosphere.

According to the degree of separating krypton from flow of feed gas, see through thing and can or keep and/or contain, perhaps self be sent to a zeolite membrane again, make further raising separation degree.

Zeolite membrane can comprise just like the base material of the porous of sintering metal or pottery and the zeolite membrane that one deck forms thereon.Importantly, zeolite membrane should be flawless basically, does not make not " pin hole " or areola to the size whole thickness similar or bigger, that run through film in the hole of zeolitic material itself.This film of describing in international monopoly WO94/01209 is applicable to this purposes.

The shape of film can be plane or cylindrical shape, is fit to be installed in the process equipment to contain and the guiding gas stream.

As everyone knows, it is molecular screen material that zeolitic material often is construed to, by composition and the manufacturing of controlling them, can make its structure contain the conduit and the cavity of many tool specific dimensions, so that have required maximum sized atom and molecule is filtered effectively and/or is adsorbed into.In addition, zeolitic material also can be made into has required electric polarization characteristic, and like this, polar molecule or easily polarized atom or molecule can optionally be attracted on zeolitic material.So, size selectivity (this is that hole because of zeolitic material has with conduit is similar to molecular dimension) and control to the electrical characteristics of zeolitic material are combined, just can be to attracting in controlling with the gaseous species that is adsorbed on the film.

The zeolite membrane material can elect, and atom that its crystalline texture can be made wish separated gas or molecule can be attracted to the inside, and can spread by material.

In some cases, preferably, first and all zeolitic material films of back comprise a kind of electropolarized zeolitic material, the example of this zeolitic material is a chabazite.Why this wishes, is because noble gas, especially krypton gas are more polarized, thereby is attracted to the zeolitic material of polarization, so, has improved the speed that just is adsorbed to when krypton begins on the zeolite membrane material.In case the krypton atom is inhaled in the film, the conduit size of this zeolitic material can make as nitrogen molecular and can not diffuse through thus, like this, be adsorbed onto this control of speed that film gets on, just improved the efficient of method greater than the rate of adsorption of other kind gas in the gaseous mixture by making krypton.

When containing the radioactivity noble gas that is hopeful it is separated in the air-flow, this raw gas mixture often comprises the multiple gases molecule, as water (H except as krypton (Kr) and the xenon (Xe) ₂O), carbon dioxide (CO ₂), nitrogen oxides (NO _x), organic hydrocarbon (HC), oxygen (O ₂) and nitrogen (N ₂).Before raw gas mixture flows to first zeolite membrane, wish from this gaseous mixture stream, to isolate other kind gas as much as possible.Before relying on first zeolite membrane separation krypton, wish from unstrpped gas, to remove H ₂O, CO ₂, NO _xAnd HC.Some polar molecules will especially easily be attracted in the film like this, and can block all holes, have reduced rate of propagation, thereby have reduced the separation coefficient of krypton by film, and have reduced the efficient of this method.To this, preferably, gaseous mixture is flowed by separating device at first at first to remove these big molecular gass and/or polar molecule gas.For realizing this purpose, can earlier air communication be crossed just like silicon zeolite (silicalite) nonpolar zeolitic material.Because this zeolite is nonpolar, all polar molecules of not wanting are eliminated by pottery, and krypton and nitrogen are passed through from it; Also have, other big molecule also is blocked as HCs.Or, because the polymer gas diffusion barrier can stop polar molecule to pass through effectively, so also can use this film.Like this, just dream up a kind of method in the present invention, this method adopts a nonpolar zeolite membrane or a polymer film to remove as water and NO _x, and one or more polarity zeolite membrane is isolated krypton with following current.

Although Gai Shu the inventive method is for example understood by separate the noble gas krypton from a gas in the above, this method can be used for separating many other and gases not of the same race from a gas stream.Particularly, made imagination to remove carbon dioxide from rock gas, wherein carbon dioxide has reduced the calorific value of the rock gas that acts as a fuel, and causes this useless material has also been done transportation.Also conceived: the inventive method can be used to produce carbon dioxide from air.Also imagine separating carbon dioxide from the flue gas of power house, make final energy reduce the amount that this " greenhouse " gas enters atmosphere.

The special advantage of the inventive method is, with compare with gas isolating polymer film method, it utilizes a kind of zeolitic material film and has increased gas flow greatly, although and its separation coefficient of polymer film method also can be compared with of the present invention, its gas flow is said so very little relatively.

For enabling to understand more fully the present invention, with reference to the accompanying drawings some examples are made an explanation.Wherein accompanying drawing is:

Fig. 1 is the curve of expression from the mixture separation krypton of nitrogen and krypton, demonstrates gas flow by a zeolite membrane to the relation of temperature;

Fig. 2 is the cross-sectional view by the zeolite membrane of a signal;

Fig. 3 is the illustrative figure corresponding to crossing current (cross-flow) type filter scheme of this film of conceiving among the present invention;

Fig. 4 is the process flow diagram of an embodiment of expression the inventive method;

Fig. 5 is the process flow diagram of second embodiment of expression the inventive method;

All curve maps among Fig. 6 to 11 are to be illustrated in to relate to the separation of multiple gases under the said condition in the following example 1 to 6 that will say.

See all accompanying drawings now, each identical feature indicates with same label respectively among the figure.

Fig. 1 represents that several gases are by the flow of a silicon zeolite membrane and the relation of temperature. Can find out, encircle approximately The border temperature is namely during about 300 ° of K, and the separation between krypton and the nitrogen is about 1.5, and namely krypton diffuses through the amount of this film Than nitrogen about 1.5 times. The zeolitic material of this moment is non-polar silicon zeolite. The thickness of this zeolite membrane is 40-50 μ m, it is that porous sintered stainless steel substrate at a thick 3mm generates.

Fig. 2 represents that one is equipped with the cross section of the schematic structure 10 of a cylindrical shape zeolite membrane. This structure comprises one Cylindrical shape separating member 12, this member 12 comprise one at a porous sintered stainless steel or aluminum oxide base material 16 The zeolite membrane 14 of upper formation. Member 12 is comprised in the cylindrical housing 18, and all annular seal are arranged 20 to prevent Leakage Gas. Shell 18 has an inlet duct 22, in order to from then on to enter gas (such as arrow Shown in 24); Also have two

outlet conduits

26 and 28, respectively in order to export enrichment krypton see through gas (as Shown in the arrow 30) and krypton by dilution residual gas (as shown in arrow 32). Pipeline 22,26 and Be provided with the pressure-regulating device that is fit to such as choke valve and/or force (forcing) pump or vavuum pump on 28, and signal Property is indicated with

label

34,36 and 38. One device that is suitable for can comprise a plurality of as shown in Figure 2, flat The unit that row connects relies on the air inlet side to pass film with ordering about through air-flow through the pressure reduction between the side. Residual gas Body is ended by zeolite membrane and makes pottery and eliminate, and this is can not enter the hole of this structure because its molecule is too big, perhaps Because electrode polarization or other are former thereby made pottery and eliminate.

In all accompanying drawings of back, will indicate the mistake of describing among Fig. 2 by the schematic model shown in Fig. 3 Stream film (cross-flow membrane) structure. All relevant label among the figure is similar. But, The personnel that are familiar with this technical field will appreciate that: simple and easy illustrated all unit 10 shown in all accompanying drawings in the back Also will comprise the essential technology controlling and process characteristic that all are described in Fig. 2.

Fig. 4 expresses all unit 10 and connects into a series winding mode being purified to a desirable water through gas Flat, residual gas 32 wherein is recycled to the import 24 of each preceding step.

Fig. 5 represents is the process chart of a device, and the method comprises that one is used for except depolarization/macromolecular First separating step. This device comprises a first separative element 40, and there is the zeolite shown in a Fig. 2 this unit 40 Film 42, this zeolite comprise non-polar silicon zeolite. The effect of this film 42 be with greatly/polar molecule and some oxygen Repel in residual gas 44 with nitrogen, and allow krypton, most of nitrogen and oxygen pass and to seeing through in the gas 46. Removed such as water, nitrogen dioxide and HC₃See through the import 24 that gas is then delivered to first separative element 10, In order to from nitrogen and oxygen, separate krypton. The residual gas of unit 10 and see through gas then by described in conjunction with Fig. 4 Process.

Zeolite membrane shown in Figure 5 can comprise the polarity zeolite just like chabasie, in order to improve from input gas The ability of separating krypton.

Provide some below under the pressure and temperature condition described in each example, to including separate instance in the specific gas potpourri of several gases of described ratio.

Example 1

The unstrpped gas that a kind of general pressure is 100KPa, contain krypton and nitrogen under 303 ° of K temperature by a silicon zeolite membrane.The molfraction of krypton changes between 0 and 1 in nitrogen.As can be seen from Figure 6, separation coefficient is 1.6 and favourable to krypton, and is constant basically in whole krypton concentration range in nitrogen.Like this, can find out zeolite membrane be to specific gas effectively rather than separation coefficient depend in part on the relative scale of all component gases.

Example 2

Fig. 7 expresses the curve of the relation of the temperature of two unstrpped gas systems and separation coefficient, and the nitrogen that two unstripped gas system wherein comprises and the ratio of krypton are respectively 50%-50%, 75%-25% and 95%-5%.The general pressure of this gaseous mixture system is 100KPa, and this mixture systems is by a silicon zeolite membrane in 175 ° of K temperature ranges.Can find out: the temperature range that can obtain best separation coefficient is from about 325 ° of K to about 350 ° of K, and the optimum temperature of all three kinds of gaseous mixture systems overlaps basically.Usually, find that from about 275 ° of K to about 400 ° of K are optimum temperature ranges, and wherein the most desirable temperature range is from about 325 ° of K to about 375 ° of K.The best result that is reached is 1.8 and favourable to krypton from coefficient.Equally, can find out that can obtain best result forms irrelevant with gaseous mixture from the optimum temperature of coefficient largely.

Example 3

Fig. 8 expresses the curve of relation of the general pressure of the piece-rate system of krypton and nitrogen and raw gas mixture system.Gas temperature remains on 303 ° of K, passes through a silicon zeolite membrane at pressure under 100KPa to 600KPa situation.Used the gaseous mixture unstripped gas of three kinds of nitrogen and krypton, the nitrogen that it contains and the ratio of krypton are respectively 50%-50%, 75%-25% and 95%-5%.Can find out from curve map: maximum separation coefficient 1.8 is that the minimum pressure 100KPa condition of using all examples is issued to.Although it is basic identical that nitrogen-krypton ratio is respectively the separation coefficient of gaseous mixture under each pressure of 50%-50% and 75%-25%, rarer 95%-5% gaseous mixture demonstrates the highest separation coefficient under each pressure.

Example 4

The unstrpped gas that a kind of general pressure is 100KPa, contain krypton and carbon dioxide under 303 ° of K temperature by a silicon zeolite membrane.As what can find out from the horizontal axis of Fig. 9, the molfraction of krypton in carbon dioxide from 0 to 1 changes.Fig. 9 left vertical axis is represented the flow of every kind of gas by the silicon zeolite membrane, the separation coefficient that the right side vertical axis reaches when then being illustrated in each concentration.The maximum separation coefficient is 2.7, and is favourable to carbon dioxide.

Example 5

The carbon dioxide of 50%-50% and krypton mixed gas are to pass through a silicon zeolite membrane under 303 ° of K conditions in temperature, and unstripped gas air inlet general pressure is increased to 450KPa from 100KPa.Figure 10 expresses a curve map, and the relation between the general pressure of the gas flow of a kind of carbon dioxide and krypton-85 gas potpourri and gaseous mixture is represented in the left side of this curve; And the relation between the general pressure of separation coefficient and gaseous mixture is represented on the right side of curve.As can be seen from Figure 10, when minimum gaseous tension 100KPa, the optimum separation factor that helps carbon dioxide is 2.4.Although total flow increases and obviously improves with total gas pressure, separation coefficient reduces with the raising of gaseous tension.

Example 6

A kind of gaseous mixture that contains the carbon dioxide that krypton that pressure is 50KPa and pressure is 50KPa is by a silicon zeolite membrane, and temperature is increased to 675 ° of K from 200 ° of K.As can be seen from Figure 11, the maximum separation coefficient during 200 ° of K is 20, helps CO ₂Along with the rising of temperature, separation coefficient sharply reduces.Carry out krypton and CO with this method ₂The optimum temperature range that separates is that 200 ° of K are to about 300 ° of K.

Example 7

A kind ofly contain the CO that pressure is 50KPa ₂With pressure be the gaseous mixture of nitrogen of 50KPa when 303 ° of K of temperature by a silicon fiml zeolite.Observe and help CO ₂Separation coefficient be 3.7.

Claims

1. one kind is used for the gaseous mixture that contains at least a component gases and at least a other gas from a kind of, the method of separating this at least a component gases, this method comprises following all steps: first film that described gaseous mixture stream is sent to a zeolitic material under certain pressure and temperature conditions, make that described at least a component gases is selected to be adsorbed on first of described zeolitic material film, and impel it through described film to second diffusion; Contain and keep a kind of enrichment of emitting from described film second face described at least a component gases see through gas; With the residual gas by described zeolite membrane not in the described gas stream, or flow to described first of described first zeolite membrane, or flow to first of one second zeolite membrane; And, repeat above steps, reduce to a desirable value until the content of the described at least a component gases in described gaseous mixture.

2. the method for claim 1 is characterized in that, described at least a component gases is a kind of noble gas.

3. method as claimed in claim 2 is characterized in that described noble gas comprises a kind of radgas.

4. the method for claim 1 is characterized in that, described at least a component gases is a kind of molecular gas.

5. method as claimed in claim 4 is characterized in that described molecular gas is a carbon dioxide.

6. as each described method in the claim 1 to 3, it is characterized in that described at least a other gas is a kind of molecular gas.

7. as each described method in the claim 1,4 or 5, it is characterized in that described at least a other gas is a kind of monatomic gas.

8. as arbitrary described method in claim 1 to 3 or 6, it is characterized in that described at least a component gases is a krypton.

9. method as claimed in claim 8 is characterized in that, described at least a other gas is nitrogen.

10. method as claimed in claim 9 is characterized in that, is separating in 200 ° K to 450 ° K temperature range.

11. method as claimed in claim 8 is characterized in that, described at least a other gas is carbon dioxide.

12. method as claimed in claim 11 is characterized in that, separation is being carried out in 200 ° K to 375 ° K temperature range.

13. the method for claim 1 is characterized in that, the each component gas that described at least a other gas is air, and separation is being carried out in 200 ° K to 450 ° K temperature range.

14. the method for claim 1 is characterized in that, described at least a component gases is a carbon dioxide, and described at least a other gas is nitrogen.

15., it is characterized in that described zeolitic material is silicon zeolite (silicalite) as each described method in above-mentioned all claims.

16., it is characterized in that described zeolitic material is a chabazite as each described method in the claim 1 to 14.

17., it is characterized in that as each described method in the claim 1 to 3, also comprise a step, promptly at first with described gas stream by a primary separating device, make the molecule that one of from described gas stream, separates in water outlet, carbon dioxide, NOx and the hydrocarbon at least.

18. method as claimed in claim 17 is characterized in that, described primary separating device is a nonpolar zeolitic material film.

19. method as claimed in claim 17 is characterized in that, described primary separating device is a polymer film.

20., it is characterized in that the described described at least first zeolitic material film comprises a kind of polarity zeolitic material as each described method in above-mentioned all claims.

21. the method for claim 1 is characterized in that, described at least a component gases is an xenon, and described at least a other gas is krypton.