FR2739304A1 - Compressed air purification, esp. prior to distillation - Google Patents

Abstract

The removal of CO and H2 traces from freshly compressed air, which also contains CO2 and H2O impurities, involves: (a) contacting the compressed air stream, at the compressor delivery temp., with a bed of CO oxidation catalyst; (b) cooling the resulting intermediate air stream to ambient temp.; (c) contacting the stream with an adsorbent to adsorb CO2 and H2O; and (d) contacting the stream with a H2-trapping adsorbent to obtain dry pure compressed air at ambient temp.. Also claimed are: (i) the methods of distilling air under pressure, esp. for producing ultra-pure nitrogen, the process involving preliminary compressed air purification by the above process; and (ii) the compressed air purification plant for carrying out the above process, comprising a catalytic treatment zone (5) having an oxidation catalyst particle bed (10); a cooling zone having a heat exchanger (6); and an adsorption zone (7) having a first bed (8a', b') for adsorbing H2O and CO2 and a second bed (8a", b") for adsorbing H2. The catalyst in (a) comprises copper or a platinum gp. metal (selected from Os, Ir, Pd, Rh, Ru and Pt), pref. supported on alumina, silica or zeolite particles. The adsorbent in (c) is selected from alumina, silica or zeolites and molecular sieves. The adsorbent in (d) is selected from Os, Ir, Pd, Rh, Ru and Pt, pref. supported on alumina, silica or zeolite particles.

Description

 The present invention relates to an air purification process intended to reduce its content of residual impurities (essentially CO, H2, CO2, and H2O) at a rate of the order of a few tens of ppb, or even of ppb (parts per billion).

 Many gases of industrial interest can be obtained from air by various separation processes. Thus, nitrogen and argon are widely used as an inert atmosphere to perform delicate manipulations. They are generally obtained by cryogenic distillation of pressurized air, after the carbon dioxide CO 2 and the water vapor H 2 O have been removed from the air by prior adsorption.

 However, the carbon monoxide CO and the hydrogen H2 contained in the air are found in the distillation products, with the exception of the addition of an additional distillation column for hydrogen. is particularly expensive.

 This is the reason why we proceed to a pre-treatment of the air, after compression and before sending to the distillation device. Currently, the treatment consists in putting the air in the presence of a CO and / or H2 oxidation catalyst based on noble metals such as platinum and palladium, or copper for the oxidation of CO, in conditions achieving both high temperature oxidation of CO to CO2 and H2 to H2O by means of oxygen in the air. However, these catalysts are sensitive to the presence of water vapor in the air to be purified and end up being deactivated as and when they are used. This is why air is generally desiccated before the catalytic treatment. However, oxidation reactions in turn produce carbon dioxide and water which must be removed at the end of the treatment.

 Thus, EP-A-0 438 282 proposes a process for cleaning air with carbon monoxide, carbon dioxide, water vapor and hydrogen, in which water vapor and dioxide are first removed. adsorption carbon at ambient or lower temperature, then carbon monoxide and hydrogen are oxidized in the presence of suitable catalysts, and the water and carbon dioxide produced by the oxidation are removed by adsorption before subjecting the resulting air to cryogenic distillation.

 This method has the disadvantage of generating during treatment impurities already removed, and consequently require the implementation of an additional desiccation / decarbonation bed for trapping the additional water and carbon dioxide produced by the double oxidation.

 The object of the present invention is to provide an easy-to-use CO 2, CO 2, H 2 and H 2 air purification process in economical simplified apparatus and under conditions allowing high purity to be attained. final, compatible with technological applications requiring perfectly inert gases.

To this end, the subject of the invention is a process for the purification of traces of carbon monoxide CO and hydrogen H 2 in compressed raw air leaving a compressor, comprising, as other impurities CO 2 and H 2 O, characterized in that it includes the steps of
(i) bringing a stream of raw compressed air at the discharge temperature of the compressor into contact with a bed of CO 2 oxidation catalyst to provide an intermediate air flow;
(ii) cooling the intermediate air stream to ambient temperature,
(iii) contacting the cooled intermediate air stream with at least one adsorbent material to remove CO 2 and H 2 O adsorption to provide a desiccated and decarbonated air stream,
(iv) bringing the decarbonated desiccated air stream at ambient temperature into contact with a hydrogen scavenging adsorbent material, at the end of which dry, substantially pure compressed air is obtained at room temperature.

 In the present description, "raw air" is understood to mean air that has not undergone any purification operation, in particular desiccation or decarbonation.

 In the process of the present invention, the first stage (i) of catalytic oxidation therefore uses a moist air stream, ie with traces of water vapor, and "hot", that is, ie that was warmed during its initial compression.

 According to the subsequent needs, the pressure at which the raw air to be purified is compressed can be very varied, in particular it can be from 2.105 to 106 Pa, especially from 6.105 to 8.105 Pa for distillation applications. These pressures are absolute pressures.

 The discharge temperature of a compressor producing compressed air for industrial operations depends on many parameters, in particular the initial temperature of the air (which depends on the season, the air source being atmospheric air) and the pressure difference applied to the atmospheric air.

To fix ideas, the discharge temperature of a compressor is generally 80 to 150 ° C, preferably 110 to 130 OC for industrial applications, including distillation.

 The water content of the compressed air treated in step (i) depends in particular on the climatic conditions when the air is taken from the atmosphere. For low humid air, this content amounts to about 1 g of water per Nm3. The moisture content of moist air is generally 5 to 15 g H2O / Nm3. In the present description, the unit of volume Nm3 represents the volume in cubic meters (m3) occupied by a gas at 0 C and under 105 Pa.

 The air to be purified usually has before treatment less than 40 ppm, more generally less than 10 ppm, very commonly of the order of 1 to several ppm of carbon monoxide, and equivalent contents of hydrogen.

 In step (i), the flow of air discharged by the compressor is brought into contact with a CO oxidation catalyst at 002. Several CO oxidation catalysts can be used according to the present invention, in particular a catalyst comprising copper or a platinum family metal selected from osmium, iridium, palladium, rhodium, ruthenium and platinum.

 Preferably, this catalyst is supported on mineral particles, in particular of a material chosen from alumina, silica and natural or synthetic zeolites.

 In the present invention, it has unexpectedly been found that the effectiveness of a CO oxidation catalyst in CO 2 is not affected by the content of the CO-containing gas in impurities such as water vapor or carbon dioxide. Thus, the "wet" raw compressed air discharged by the compressor can circulate continuously in a bed of CO oxidation catalyst without any noticeable loss of catalyst activity, and therefore without a notable drop in the efficiency of the catalyst. oxidation of CO to CO2, for a period comparable to the normal duration of use of the catalyst in the absence of these impurities. It seems that at the discharge temperature of a compressor, the water vapor contained in the air to be purified adsorbs little on the catalyst and does not deactivate it for this type of oxidation.

 After passing over the catalytic bed, the intermediate air flow contains only a small amount of CO, of the order of a few tens of ppb or even a few ppb, and still contains water vapor, CO 2 and hydrogen. The intermediate air stream resulting from the catalytic treatment is then cooled to room temperature in step (ii), before being subjected to an adsorption step (iii) to substantially remove CO 2 and H 2 O.

 Step (iii) can be carried out using at least one conventional adsorbent, chosen in particular from alumina, silica, natural or synthetic zeolites, and molecular sieves. If the raw compressed air further contains hydrocarbon impurities, the latter will also be stopped by the mass of adsorbent. The materials currently available have been considerably developed and allow almost quantitative purification in CO2 and H2O.

Step (iii) will therefore be conducted in a conventional manner for those skilled in the art to provide a flow of dried air and decarbonated.

 After step (iii) desiccation / decarbonation, the airflow contains no more impurity as significant as hydrogen. The latter is removed from the decarbonated desiccated gas at ambient temperature by adsorption on an adsorbent material capable of trapping hydrogen, under conditions in which the hydrogen is not oxidized in water. In this way, the separation of hydrogen in the process of the invention does not produce additional impurity in the final step.

 Preferably, the hydrogen adsorbent material of step (iv) consists of particles comprising an adsorbent metal selected from osmium, iridium, palladium, rhodium, ruthenium and platinum. By way of example, among these metals having a good affinity for hydrogen, a preferred metal is palladium which is capable of adsorbing a volume of hydrogen greater than 3000 times its initial volume.

Given the low hydrogen content present in the air to be purified, a very small amount of metal is therefore necessary to carry out the purification of the present invention. Thus, the adsorbent material is preferably in the form of particles comprising a support on which the metal is deposited, this support being able to be chosen from conventional supports, in particular alumina, silica and natural or synthetic zeolites.

 The content of said adsorbent metal in the adsorbent particles is preferably 0.3 to 2.5% by weight, in particular 0.5 to 2% by weight, most preferably about 1% by weight.

 The temperature at which the adsorption process is carried out is generally room temperature, in particular 20 to 40 ° C.

 During the adsorption stages (iii) and (iv), the adsorbent materials are progressively loaded with water, carbon dioxide and hydrogen, possibly until drilling. In order to be able to carry out the purification process in a continuous manner, it is possible to use in each step alternately one or the other of two masses of adsorbent (s) put in parallel, one of which operates in adsorption while the other works in regeneration. Regeneration of the adsorbent mass can be carried out by increasing the temperature (TSA process), by lowering the pressure (PSA process), by sweeping and eluvium by a so-called regeneration gas, or by a combination of at least two of these ways.

 Preferably, for step (iv), the adsorbent mass operating in regeneration is eluted by oxygen-enriched air whose temperature is higher than the ambient temperature (the purified air temperature). This causes both desorption by heat, elution by a purge gas and a partial oxidation of H2 adsorbed H2O which is eluted / desorbed itself by the hot gas. This mode of regeneration makes it possible to ensure an adsorption capacity close to the maximum capacity of initial adsorption, for a period of several months, possibly one or more years.

 The adsorption operations are then conducted cyclically, a cycle consisting of an adsorption operating period followed by the same operating period in regeneration of the same mass of adsorbent.

 The duration of a cycle is variable and depends in particular on the degree of pollution of the charge to be treated, the charge rate, the temperature, and the quality of the regeneration obtained.

 This last parameter depends in particular on the regeneration rate, namely the ratio of the flow rate of the regeneration gas to the flow rate of the treated gas. According to the present invention, a high regeneration rate is desirable, preferably greater than 40%, for example of the order of 60%.

 It also depends on the temperature of the regeneration gas (TSA process or elution). The latter is advantageously greater than room temperature, but less than about 200 ° C, for example from 110 to 1300C.

 The skilled person is able to set the various operating parameters, particularly in the preferred ranges proposed above, to obtain the degree of purification corresponding to its requirements. In general, with a standard adsorbent material, it is possible to guarantee a hydrogen content of the order of a few ppb in a dry and decarbonated air during successive cycles, by carrying out the regeneration at high temperature, preferably greater than or equal to 120 ° C, under a high regeneration rate, preferably greater than or equal to 40%.

 The air obtained at the end of step (iv) of the process of the invention is of sufficient desiccation and decarbonation quality to be able to be engaged without risk of clogging in a cryogenic distillation operation, intended for example to produce ultra-pure nitrogen, for example for the electronics semiconductor industry. The invention therefore also relates to a process for the distillation of air under pressure, characterized in that it comprises a step of purifying the compressed air before the preliminary cooling to the distillation, according to the method described above.

 The process can operate continuously, using in steps (iii) and (iv) alternately one or the other of two masses of adsorbent (s), one of which works in adsorption while the other operates in regeneration. Regeneration of said adsorbent mass may be provided by scavenging with oxygen-enriched air from the vaporization of the oxygen-rich liquid (so-called "rich liquid") separated as the liquid residue from the subsequent distillation. Alternatively, the elution may also be provided by means of nitrogen gas containing some traces (t) of oxygen from the vaporization of the overhead fraction of the distillation.

The invention also relates to a device for carrying out the compressed air cleaning method described above. This device is characterized in that it comprises
a catalytic treatment zone comprising a bed of particles of a CO2 CO 2 oxidation catalyst, provided with means for supplying compressed raw air intended to be connected to the discharge of a compressor, and means for evacuating an intermediate air flow resulting from the treatment,
a cooling zone comprising a heat exchanger supplied with hot fluid by said means for evacuating the intermediate air flow,
an adsorption zone comprising a first bed of at least one water-adsorbing material and CO2 and a second bed of at least one hydrogen-adsorbing material, provided with feed means for the flow of water; intermediate air cooled in the exchanger.

 The invention also relates to an air distillation plant, characterized in that it comprises a compressed air purification device installed upstream of the distillation column. In the case of a continuously compressed air purification device, it further comprises means for sampling and vaporizing residual distillation liquid and means for circulating the residual vaporized liquid connected to said gas supply means. regeneration.

An exemplary embodiment of the invention will now be described with reference to Figures 1 and 2 of the accompanying drawings, in which:
- Figure 1 is a diagram showing a facility for producing ultra-pure nitrogen by air distillation according to the invention;
- Figure 2 is a diagram showing an air distillation plant according to the invention.

 The pressures discussed below are absolute pressures.

 The installation shown in FIG. 1, intended to produce ultra-pure nitrogen by air distillation, essentially comprises a compressor 1 for supplying air, a device 2 for cleaning the compressed air, an exchanger 3, and a distillation column 4. The air purification device 2 comprises a catalytic oxidation reactor 5, a refrigerant 6 and a continuous adsorption zone 7 comprising two adsorption columns 7a and 7b filled with material 8a and 8b adsorbing CO2, 1 'H2O and H2.

 The installation works as follows.

 Atmospheric air is compressed by the compressor 1 under a pressure of 6.105 to 8.105 Pa. The compression is accompanied by an increase in the air temperature between about 80 and about 15000 depending on the initial temperature. The flow of compressed air delivered by the compressor 1 is conveyed via a gas supply duct 9 to the purification device 2. The catalytic oxidation reactor 5 is supplied with air to be purified through the supply duct. 9. Within the catalytic reactor, the compressed raw air stream flows through a catalyst bed 10, preferably in the form of a compact filler. At the outlet of the catalytic reactor, the air is substantially purified with CO, and is charged with CO2, H2O and H2. This intermediate air stream is conveyed via a gas supply pipe 11 to the refrigerant 6, to be there. The refrigerant 6 may be of any known type, advantageously a simple water cooler, and this cooled intermediate air stream is then conveyed via a line 12 to the zone of cooling. adsorption 7.

 This zone comprises two identical adsorption columns 7a and 7b filled with the same adsorbent comprising a first bed 8a 'and a second bed 8a ", respectively 8b' and 8b", each supplied with air to be purified via gas supply lines. 13a and 13b connected to the pipe 12 by a three-way valve 14.

Each of the columns is provided, at the end opposite the gas supply to be purified, of a gas supply line 15a, respectively 15b, connected by a three-way valve 16 to an air production line. The columns 7a and 7b are furthermore equipped with regeneration gas supply lines 18a, 18b respectively, connected via a three-way valve 19 to a gas supply line 20, as well as ducts 21a. respectively 21b, used regeneration gas evacuation.

 In operation, in a first stage, the three-way valves 14, 16 and 19 are operated so that the cooled intermediate air flow circulates via the lines 12 and 13a through the column 7a from which it leaves via the pipe 15a. to open into the pipe 17, while the regeneration gas flows via the lines 20 and 18b through the column 7b which it is discharged via the pipe 21b. This circulation of gases is maintained as long as the absorbent materials 8a 'and 8a "are capable of absorbing a sufficient quantity of CO2, H2O and H2.After a determined duration, in particular according to the composition of the air at the pressure of the compressed raw air and the temperature of the cooled air, the positions of the three-way valves 14, 16 and 19 are reversed, so that the column 7a operates in regeneration and the column 7b adsorption In this second time, the cooled intermediate air flow circulates via the pipes 12 and 13b through the column 7b, which it leaves via the pipe 15b to open into the pipe 17, while the regeneration gas flows via the pipes 20 and 18a through the column 7a from which it is discharged via the pipe 21a.This circulation of gases is maintained for the same duration as that of the previous operation.After these two operations, an "adsorption / regeneration" cycle is effec The continuous treatment of the gas to be purified, intended to be distilled in column 4, implements a number of necessary cycles, which can last a total of several months, possibly one or more years.

 The purified air flows in the production line 17 to the heat exchanger 3 where it is cooled to a temperature corresponding to its dew point at the discharge pressure of the compressor. For a delivery pressure of about 6.105 Pa, this temperature is about -160 C. The purified air thus cooled is conveyed via the air supply line 22 to the lower part of the distillation column 4. In this column the cold air circulates against the current of a liquid rich in oxygen which condenses at the foot of the column, while one recovers at the head of column a gas composed of pure nitrogen. The reflux of the column 4 is provided by a top condenser 23, which uses as refrigerant the rich liquid collected at the bottom of the column, expanded to an intermediate pressure. For this, the rich liquid is taken at the bottom of the column via the sampling pipe 24, expanded in the valve 25 and supplies the condenser 23 via the pipe 26.

 The ultrapure nitrogen from the distillation is taken at the top of the column via the pipe 27 and is heated to room temperature in the heat exchanger 3.

 The rich vaporized liquid in the overhead condenser 23 is conveyed via a gas supply pipe 28 to the heat exchanger 3 in which the vaporized rich liquid (LRV) is heated. To ensure the cold resistance of the apparatus, the LRV is heated in the exchanger 3 to an intermediate temperature at which it is expanded in a turbine 31 at atmospheric pressure and returned to the exchanger 3 (at point 32 ) at a colder temperature level from which it is warmed. The vaporized rich liquid is conveyed via a gas supply pipe 29 on which an electric heater 30 is installed, to the purification device 2, where it feeds the pipe 20 after having been heated to a temperature of 80 to 150 ° C. C.

 According to the variant shown in FIG. 2, the air purification device 2 can be put in place in an air distillation plant intended to produce nitrogen and pure oxygen, this installation being similar to the installation shown in FIG. 1 except that column 4 is replaced by a double distillation column with intermediate reflux by vapor condenser. In this case, the regeneration of the adsorbent in the adsorption zone 7 may be performed as previously by means of rich liquid taken this time at the bottom of the column 4 and vaporized, or with substantially pure nitrogen gas having some traces of separated oxygen at the head of the double column and then conveyed via a pipe of fed to the exchanger 3, where it is warmed to ambient and then heated as previously in the heater 30.

 Due to the particular arrangement of the various elements of the purification device 2, and the operating conditions chosen, that is to say the absence of refrigerant downstream of the compressor 1 and upstream of the catalytic reactor 5 to treat air relatively hot compressed crude (at the discharge temperature of the compressor 1), the air distillation plants described above can be operated continuously for very long periods, to obtain distillation products of high purity.

 The performance of the method and the purification device according to the invention will now be illustrated by the following exemplary embodiments.

EXAMPLES
Compressed air at a pressure of 6.105 Pa absolute, heated in the compressor at a temperature of 120 ° C, and having a water content of 10 g / Nm3, a CO content of 1 to 2.5 ppm and a hydrogen content up to 4 ppm, is treated in a device of the type shown in Figures 1 and 2.

 The CO oxidation catalyst consists of palladium supported on 0.5% Pd / Al 2 O 3 alumina.

 The refrigerant cools the intermediate air stream to a temperature of 20 to 40 ° C.

The adsorbent material intended to block H20,
CO2 and H2, consists of three superimposed adsorbent masses, the lower mass being composed of alumina, the intermediate mass being a 13X molecular sieve and the upper mass consisting of palladium supported on alumina at 1 or 2% Pd / Al 2 O 3 . The three adsorbents are in respective proportions of 24 kg, 28 kg and 5.6 kg. The adsorption is carried out continuously, over several cycles (adsorption / regeneration), the regeneration being carried out by means of a hot gas at 1200C.

 The following examples show the purification results according to the process of the invention with various operating conditions.

Example 1
The flow rate of the air load being 110
Nm3 / h, the catalytic treatment is carried out as indicated above, the intermediate air stream is cooled to 20 ° C and the adsorption at 20 C is carried out with cycles of 3.36 hours of adsorption followed by 3 , 36 hours of regeneration with hot air (120 C) with a regeneration rate of 40%.

The adsorption of hydrogen is carried out on two types of adsorbent: palladium on alumina at 1%
Pd / Al 2 O 3 and palladium on alumina at 2% Pd / Al 2 O 3.

 The results obtained under these conditions with air at 1 ppm H2 and 3 ppm H2 are shown in Table I.

Example 2
The flow rate of the air load being 190
Nm3 / h, the operating conditions of Example 1 were repeated with shorter cycles of 2 hours of adsorption followed by 2 hours of purification.

 The results obtained with air at 1 ppm H2 and at 3-4 ppm H2 are shown in Table I.

Example 3
Example 2 is exactly repeated except that the regeneration of the adsorbent is carried out with air enriched with oxygen (content of 2 = 30%).

 The results obtained with air at 1 ppm H2 and at 3-4 ppm H2 are shown in Table I.

Example 4
Example 3 is repeated with a regeneration rate of 60% instead of 40% but the regeneration of the adsorbent is carried out with hot air (120 ° C.).

 The results obtained with air at 1 ppm H2 and at 3-4 ppm H2 are shown in Table I.

Example 5
The flow rate of the feed being 197 Nm3 / h, the catalytic treatment is carried out as above, the intermediate air stream is cooled to 40 ° C and the adsorption at 40 C is carried out with cycles of 51 min adsorption followed by 51 minutes of regeneration with hot air (120 C) with a regeneration rate of 70%.

 The results obtained with air at 1 ppm H2 and at 3-4 ppm H2 are shown in Table I.

 In all cases the air is purified with water and carbon dioxide in the usual proportions.

The purified air can be engaged in a cryogenic distillation operation without danger of clogging due to the condensed and solidified material.

During all these tests, the catalyst placed downstream of the compressor oxidized continuously, and at this temperature level (temperature approximately equal to 120 C), the
CO at a rate of less than or equal to 2 ppb.

Example <SEP> Q <SEP> Content <SEP> in <SEP> Temperature <SEP> Load <SEP> in <SEP> Time <SEP> Number <SEP> Gas <SEP> of <SEP> Rate <SEP> Composite
H2 <SEP> (ppm) <SEP> ture <SEP> of ad- <SEP> Pd <SEP> on <SEP> of <SEP> of <SEP> regeneration <SEP> of <SEP> tion <SEP> of <SEP> the air
<tb> Nm3 / h <SEP> sorption <SEP> adsorbent <SEP> cycle <SEP> cycles <SEP> tion <SEP> Regenerated <SEP> purified
<tb>(<SEP> C) <SEP> H2 <SEP> (h <SEP> + <SEP> h) <SEP> ration <SEP> H2 <SEP> residual
<tb> (% <SEP> weight <SEP> (%)
<tb> Pd / Al2O3)
<tb> 1 <SEP> 1 <SEP> 1 <SEP> 25 <SEP> nd *
<tb> 110 <SEP> 1 <SEP> 20 <SEP> 2 <SEP> 3.36 + 3.36 <SEP> 25 <SEP> air <SEP> 40 <SEP> nd
<Tb>

3 <SEP> 1 <SEP> 25 <SEP><SEP> 100 <SEP> ppb
<tb> 3 <SEP> 2 <SEP> 25 <SEP> nd
<Tb>

2 <SEP><<SEP> 1 <SEP> 1 <SEP> 25 <SEP> nd
<Tb>

190 <SEP><<SEP> 1 <SEP> 20 <SEP> 2 <SEP> 2 <SEP> + <SEP> 2 <SEP> 25 <SEP> air <SEP> 40 <SEP> nd
<Tb>

3-4 <SEP> 1 <SEP> 25 <SEP><SEP> 150 <SEP> ppb
<tb> 3-4 <SEP> 2 <SEP> 25 <SEP> nd
<Tb>

3 <SEP> 1 <SEP> 1 <SEP> 5 <SEP> air <SEP> nd
<Tb>

190 <SEP> 1 <SEP> 20 <SEP> 2 <SEP> 2 <SEP> + <SEP> 2 <SEP> 5 <SEP> enriched <SEP> 40 <SEP> n / a
<Tb>

3-4 <SEP> 1 <SEP> 5 <SEP> (30 <SEP>% <SEP><SEP> 50 <SEP> ppb
<tb> 3-4 <SEP> 2 <SEP> 5 <SEP> O2) <SEP> nd
<Tb>

4 <SEP> 1 <SEP> 1 <SEP> 5 <SEP> nd
<Tb>

190 <SEP> 1 <SEP> 20 <SEP> 2 <SEP> 2 <SEP> + <SEP> 2 <SEP> 5 <SEP> air <SEP> 60 <SEP> nd
<Tb>

3-4 <SEP> 1 <SEP> 5 <SEP><<SEP> 50 <SEP> ppb
<tb> 3-4 <SEP> 2 <SEP> 5 <SEP> nd
<Tb>

<SEP> 1 <SEP> 1 <SEP> 51 <SEP> min <SEP> 50 <SEP> nd
<Tb>

197 <SEP> 1 <SEP> 40 <SEP> 2 <SEP> + <SEP> 50 <SEP> air <SEP> 70 <SEP> n / a
<Tb>

3-4 <SEP> 1 <SEP> 51 <SEP> min <SEP> 50 <SEP> nd
<Tb>

3-4 <SEP> 2 <SEP> 50 <SEP> n / a
<Tb>

* nd means not detected, which corresponds to an H2 content <5 ppb
It appears from these results that the process according to the invention makes it possible to eliminate CO and H2 up to contents of the order of ppb.

 The elimination of H2 in ppb is possible in all cases with a support impregnated with 2% Pd.

 When the air is heavily polluted with H2 (content of 3 to 4 ppm), the purification remains very satisfactory with a support impregnated with 1% of Pd.

When the air has a classic H2 pollution (approximately 1 ppm), the support impregnated with 1% of
Pd is sufficient in all the examples.

 Example 2 shows that the process can be applied to the treatment of high air loads in a relatively short time.

 Examples 3 and 4 show the advantage of carrying out the regeneration with enriched air (Ex.

3) or air with a high regeneration rate (Ex.

4) to obtain a better purification.

 In Example 5, despite a higher temperature favoring less adsorption, very good purification is achieved through a high rate of regeneration.

Claims (19)

 1- Process for the purification of traces of carbon monoxide CO and H2 hydrogen in compressed raw air leaving a compressor, containing as other impurities CO2 and H20, characterized in that it comprises the steps of:  i) supplying a stream of raw compressed air at the discharge temperature of the compressor into contact with a bed of CO2 CO 2 oxidation catalyst to provide an intermediate air flow;  ii) cool the intermediate air stream to room temperature,  iii) contacting the cooled intermediate air stream with at least one adsorbent material to remove adsorption Co2 and H2O, to provide a desiccated and decarbonated air stream,  iv) bringing the decarbonated desiccated air stream at ambient temperature into contact with a hydrogen-trapping adsorbent material, at the end of which dry, substantially pure compressed air is obtained at room temperature.  2- Method according to claim 1, characterized in that the raw air to be purified is compressed at a pressure of 2.105 to 106 Pa.  3- Method according to claim 1 or 2, characterized in that the discharge temperature of the compressor is 80 to 150 ° C, preferably 110 to 130 C.  4. Process according to any one of claims 1 to 3, characterized in that the compressed raw air treated in step (i) has a water content of 5 to 15 g / Nm3.  5. Process according to claim 1 or 4, characterized in that the catalyst of stage i) comprises copper or a platinum group metal selected from osmium, iridium, palladium, rhodium, ruthenium and platinum.  6. Process according to any one of claims 1 to 5, characterized in that the catalyst of step i) is supported on particles of a material selected from alumina, silica and zeolites.  7- Process according to any one of claims 1 to 6, characterized in that one chooses the (s) material (s) adsorbent (s) of step iii) among alumina, silica, zeolites and molecular sieves.  8- Process according to any one of claims 1 to 7, characterized in that the hydrogen adsorbent material of step iv) consists of particles comprising an adsorbent metal selected from osmium, iridium, palladium , rhodium, ruthenium and platinum.  9- Process according to claim 8, characterized in that the particles comprise a support selected from alumina, silica and zeolites.  10- Method according to one of claims 8 or 9, characterized in that the content of said adsorbent metal absorbent particles is 0.3 to 2.5% by weight.  11- A method according to any one of claims 1 to 10, characterized in that step iv) is carried out continuously by means of alternately one or the other of two masses of adsorbent (s) whose one works in adsorption while the other operates in regeneration.  12- The method of claim 11, characterized in that the regeneration is carried out hot (temperature above 80 ° C) by circulating a regeneration gas in said mass of adsorbent with a regeneration rate, expressed by the ratio of flow rate of the regeneration gas at the treated gas flow, greater than 40%.  13- Method according to claim 11, characterized in that the mass of adsorbent operating in regeneration is eluted by oxygen-enriched air whose temperature is greater than room temperature.  14. Process for the distillation of air under pressure, especially for the production of ultra-pure nitrogen, characterized in that it comprises a step of purifying the compressed air before the preliminary cooling to the distillation, according to a process according to any one of claims 1 to 13.  15. Process for the distillation of air under pressure, in particular for the production of ultra-pure nitrogen, characterized in that it comprises a step of purifying the compressed air before the preliminary cooling to the distillation, according to a process continuously according to claim 11, the regeneration of said adsorbent mass being ensured by scanning with oxygen-enriched air from the vaporization of the separated rich liquid in the distillation of the air.  16- Device (2) for purifying compressed air characterized in that it comprises a catalytic treatment zone (5) comprising a bed (10) of particles of a CO oxidation catalyst in CO2, provided with means (9) supplying compressed raw air intended to be connected to the discharge of a compressor (1), and means (11) for evacuating an intermediate air flow resulting from the treatment, a cooling zone comprising a heat exchanger (6) supplied with hot fluid by the means (11) for evacuating the intermediate air flow, an adsorption zone (7) comprising a first bed (8a ', 8b' ) of at least one water-adsorbing material and CO2 and a second bed (8a ", 8b") of at least one hydrogen-adsorbing material, provided with means (12, 14, 13a, 13b) of feeding the intermediate air stream cooled in the exchanger.  17- Device according to claim 16 characterized in that it comprises two identical adsorption zones (7a, 7b) each comprising a first bed (8a ', 8b') and a second bed (8a ", 8b") of adsorbent, each zone being provided with supply means (13a, 13b) in the intermediate air stream cooled in the compressed air purification exchanger and feed means (18a, 18b) in a gas of regeneration.  18- air distillation plant comprising a compressor (1) aspirating atmospheric air, a heat exchanger (3) and an air distillation column (4) supplied with air cooled in the exchanger, characterized in it further comprises a device (2) for purifying compressed air according to claim 16 or 17 connected to the discharge of the compressor (1) and means (17) for supplying the exchanger (3) in air purified to cool.  19- air distillation plant comprising a compressor (1) sucking atmospheric air, a heat exchanger (3) and an air distillation column (4) fed with air cooled in the exchanger, characterized in it further comprises a device (2) for purifying continuous compressed air according to claim 17, means for sampling (28, 31) vaporization (3) residual distillation liquid and means (29) circulation of vaporized residual liquid connected to said regeneration gas supply means (20).