Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Sulfur or sulfur containing component
Reexamination Certificate
1998-03-06
2001-03-06
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Sulfur or sulfur containing component
C423S243040, C502S004000, C210S679000, C095S045000, C095S049000
Reexamination Certificate
active
06197269
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for the removal of gaseous oxidisable constituents from, a gas phase.
BACKGROUND OF THE INVENTION
It is known to absorb gaseous constituents from a gas phase using conventional contact techniques and conventional contact equipment, such as packed columns.
However, this technique has the disadvantage in that it is possible to operate only within a restricted range of gas/liquid flow rate ratios because otherwise operational problems occur, such as, for example, “flooding” or the entrainment of liquid. The consequence of this is, in particular, that when removing components at low concentration levels it is necessary to work outside the optimum operating conditions of the equipment used (gas/liquid ratio 100:1-1:100) and/or with a liquid flow rate higher that is strictly necessary, in order to obtain an optimum loading and/or in order to be able to remove the components effectively.
Said known techniques are therefore not suitable for the removal of gaseous impurities which are present in low to very low concentrations (i.e. below 1 mg/m
3
). Even in those cases where the gaseous impurities can be removed by means of the conventional absorption techniques, said techniques will not be cost-effective or will be barely cost-effective because of the high liquid flow rates required.
Furthermore, in the case of said known contact techniques absorption usually proceeds via an acid/base reaction, as a result of which the field of application is restricted to gaseous constituents which can be absorbed via a mechanism of this type. The use of redox reactions in the absorption of gaseous constituents has not been described to date.
SUMMARY OF THE INVENTION
A first aim of the invention is, therefore, to provide an efficient and cost-effective process by means of which gaseous, oxidisable impurities can be removed from a gas stream in a simple manner, especially in low concentrations.
It has now been found, surprisingly, that a system of this type can be provided by the use of membrane gas absorption techniques using oxidative liquid phases, that is to say liquid phases which contain an oxidising agent.
A second aim of the invention is, therefore, to render membrane gas absorption techniques applicable to and/or to adapt said techniques for use with, such oxidative liquid phases. Further aims and advantages of the invention will become apparent from the text which follows.
Membrane gas absorption techniques, as well as the equipment used for these, have been disclosed in the prior art.
Thus, Netherlands Patent Applications 9400438 and 9401233 in the name of the Applicant, which are not prepublished, describe methods for the absorption of acidic gaseous impurities, such as CO
2
and SO
2
, from a gaseous stream by means of membrane gas absorption, the gas stream containing the acidic impurities to be removed being brought into contact with a liquid stream which absorbs the components to be removed. During this process the gas stream and the liquid stream are kept separate by means of a porous or non-porous (“closed”) membrane, so that said streams are not mixed with one another.
It is also, for example, known from International Patent Applications 94-01204 and 91-15284 to absorb water vapour from a gas stream by means of membrane gas absorption, in which method a highly hygroscopic liquid absorbent is used.
In the case of the procedures in the cited publications, the absorption of the gaseous component to be absorbed proceeds by means of absorption into the liquid phase, via an acid/base reaction or by means of hygroscopic interaction.
The use of oxidation/reduction reactions in membrane gas absorption for the absorption of oxidisable gaseous impurities has to date neither been described nor suggested. On the contrary, to date it has been assumed that membrane gas absorption could not be carried out on the basis of oxidation/reduction reactions, especially because it was thought that the absorption process—that is to say the absorption of the uncharged gaseous, frequently organic, impurities to be absorbed into the liquid phase and/or the envisaged redox reactions in the liquid phase—would proceed too slowly (i.e. low transfer because of low solubility in water) and/or would be insufficiently stable (because of, for example, attack on the membrane). It will be clear that problems of this type do not arise, or rarely arise, with small polar acidic or basic molecules, such as CO
2
or SO
2
, or with water (vapour)—which to date have been removed using membrane gas absorption.
The present invention is based, inter alia, on the surprising discovery that the combination of absorption of the gaseous constituents and the subsequent oxidation/reduction reactions proceed so rapidly that a membrane gas absorption system based on said redox reactions gives adequate mass transfer to enable it to be used in practice.
The invention is further based on the discovery that it is possible to carry out membrane gas absorption using an oxidising liquid absorbent without the membranes being used in this operation being attacked, the membrane starting to leak or any pores present becoming clogged.
Furthermore, it has been found that the membrane gas absorption according to the invention is particularly suitable for the removal of low to very low concentrations of impurities which are impossible to remove, extremely difficult to remove or cannot be removed economically using alternative methods from the prior art—such as, for example, catalytic oxidation, an ozone scrubber, gas washing without the separating action of membranes, or filtration using an oxidising agent such as potassium permanganate. Finally, the method according to the invention gives a high loading capacity of the liquid absorbent.
The invention provides, in particular, methods for the removal of mercury vapour, ethene or H
2
S from a gas stream in very low concentrations, these being methods for which a need has already existed for a long time.
REFERENCES:
patent: 3911080 (1975-10-01), Mehl et al.
patent: 4101631 (1978-07-01), Ambrosini et al.
patent: 4115514 (1978-09-01), Ward, III
patent: 4147754 (1979-04-01), Ward, III
patent: 4174374 (1979-11-01), Matson
patent: 4187086 (1980-02-01), Walmet et al.
patent: 4516984 (1985-05-01), Warner et al.
patent: 4750918 (1988-06-01), Sirkar
patent: 5135547 (1992-08-01), Tsou et al.
patent: 5749941 (1998-05-01), Jansen et al.
patent: 9416800 (1994-08-01), None
patent: 0 634 204 (1995-01-01), None
patent: WO 94/16800 (1994-08-01), None
Feron Paul Hubert Maria
Jansen Albert Edward
Browdy and Neimark
Griffin Steven P.
Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk On
Warn Elin A
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