DE1265724B - Process for the enrichment of oxygen in air - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

COIb

German KL: 12 i-13/02

Number: 1265 724

File number: F 33107IV a / 12 i

Filing date: February 1, 1961

Open date: April 11, 1968

Today, the distillation of liquefied atmospheres is mainly used to obtain oxygen Air applied. This process is used to produce oxygen and nitrogen in large part pure state. Is a gas required to carry out a process that is opposite to the atmospheric? Air has only a certain enrichment of the oxygen content, as in newer processes in the iron and steel industry or, in the case of oxidation processes, in the chemical industry, that is the usual practice Mix air with appropriate amounts of distilled oxygen.

The production of oxygen as a by-product in the electrolysis of aqueous solutions is also known. Because of the high energy requirement, this process is used to carry out electrolytic processes Obtaining other products bound, and the resulting oxygen can often because of high transport costs of the compressed gas cannot be used economically.

Furthermore, methods are also known for producing oxygen in a purely chemical way using oxygen compounds of lead, manganese, barium and other elements. Thus, for example barium oxide combined at 500 to 600 ⁰ C with the oxygen of the atmospheric air to barium peroxide, which is converted back at 800 ° C under reduced pressure in oxygen and barium oxide. Because of the high heat demand, these processes are no longer of industrial importance.

There has also been no lack of attempts, different ones Use isothermal physical processes for a partial decomposition of the atmospheric air. So you have the separation in the gravitational field of gas centrifuges, the diffusion through Membranes, absorption in aqueous solutions and other liquids, and finally adsorption applied to surfactants. For example, according to British patent specification 365 092 Oxygen, nitrogen, hydrogen and other gases are adsorbed on silica gel, which is followed by fractionated Desorb minor separation effects achieved. However, the process works with 20 to 120 atmospheres Overpressure and is therefore uneconomical.

The ability of crystalline zeolites to transform molecules in dependence on adsorb their molecular size and shape differently. The term molecular sieve for this special silicates can be found for the first time in the reference Kolloid Z., 40 (1926), p. 4.

Only after the work of Barrer, z. B. Quarterly Reviews, III (1949), pp. 293-330, employs methods of enrichment
of oxygen in air

Applicant:

Paint factories Bayer Aktiengesellschaft,
5090 Leverkusen

Named as inventor:

Dr. Gerhard Heinze, 5072 Schildgen

However, technology is increasingly focusing on this special property of zeolite. For example, US Pat. No. 2,882,243 describes that a molecular sieve of the Na zeolite A type adsorbs 24.8 percent by weight of oxygen at -196 ° C., but only traces of nitrogen. At -78 ° C, the loading with oxygen under comparable conditions is only 4.8 percent by weight, whereas with nitrogen it is 10.6 percent by weight. A technical use of these effects occurring at low temperatures is ruled out because of the required cooling effort. According to US Pat. No. 2,843,219, nitrogen can be separated from natural gas using zeolites. The process is preferably carried out at 0 ° C. or lower temperatures and at overpressures of a few atmospheres. The loaded molecular sieve is regenerated by heating to 100 to 200 ° C. US Pat. No. 2,944,627 describes an adiabatic adsorption process for removing an adsorbable component from a gas stream, for example using molecular sieves. In a system of two containers filled with adsorbents, the starting gas is passed under a constant overpressure of a few atmospheres through the one container connected to adsorption and only part of the enriched gas escaping is fed to the consumer, while the other part, which is quite considerable in its quantity is expanded to atmospheric pressure and used to regenerate the adsorbent of the second container and is thus lost. A special application of this known method relates to the production of O ₂ -enriched air, the columns being filled with molecular sieves with pore sizes of 5 Å or 13 Å units. If, however, a molecular sieve with a pore size of 4 Å units is used, a nitrogen-enriched gas is not obtained from air. Finally, there is another method from French patent specification 1223 261

809 538/507

for the separation of oxygen and nitrogen with necessary for the implementation of the process Molecular sieves known. In this procedure there is prerequisites. Such a zeolite is made from e.g. oxygen-rich gas obtained by expanding one in the zeolite A when the negatively charged lattice adsorption column about two thirds of the aluminosilicate framework is enclosed under increased pressure its gas. The regeneration takes place 5 through Ca ions and one third through Na ions Evacuate to pressures from 0.5 to 1 torr. Which are saturated. . Compression work to be expended is therefore very high. To carry out the procedure, turn The above statements show that the separation of the zeolite expediently in granulated form and of oxygen and nitrogen with zeolites basically filling one at the ends with inlet and outlet it is possible to use an economical process, however, with an elongated adsorption column provided with a valve. Of the to a large extent of the special zeolite and especially zeolite is common in molecular sieve zeolites also depends on the process conditions. Assign by heating adsorbed water

The subject of the present invention is a liberate. Before the first loading, the column is opened Process for the enrichment of oxygen evacuated by a pressure of, for example, 100 Torr, selective removal of nitrogen from the atmosphere. Then dried through the inlet valve shear air with molecular sieve zeolites of type A, air enter until the pressure is equalized and opens in which 30 to 80% of the negatively charged grid- then also the exhaust valve to dry air provide the aluminosilicate framework by calcium or atmospheric pressure flowing through the column Strontium are occupied, characterized in that «The zeolite is mainly saturated with at temperatures between about -30 and + 40 ° C 20 nitrogen, so that at the end of the column an oxygen-following periodically changing work steps with rich gas flows out. As soon as the oxygen one Duration of minutes or fractions of the concentration of the exiting gas below the ge-minutes expire: the desired amount has decreased, you close that

_{x.,,, Λ,,,,.} , ", ..,. Outlet valve and activates the zeolite again

a) pumping of the molecular sieve zeolite corresponds _Ver Braden _through the column with a vacuum pump holding system to a pressure of not _{moderate pumping the nitrogen-free} surfaces adsorbate. The less than 50 Torr (regeneration), adjustment of the AdsorptionsgMchgewichte takes place

b) Setting a pressure over the molecular sieve so quickly that the work cycles of the overflow Zeolite of around atmospheric pressure by pumping in and pumping out quickly, just minutes or flow of dried air and 30 fractions of minutes alternating between

c) Obtaining oxygen-rich gas by tracing.

'Passing dried air over the mole-. ^{In ner e} 'j jsdsnsa embodiment of the method

kularsieb-Zeolite at approximately constant pressure with ^the _f ^Sau _ ^Ie ™ * tompnnuwter air is filled and

a flow rate of 120 to while maintaining at most a few Atmo-600 l / h, based on an inner diameter of 35 spheres of excess pressure of air through

the adsorption column of 46 mm. flows, whereby the escaping gas emen in turn

has a higher oxygen content than the injected one

Not all molecular sieves, compressed air of the composition of the atmospheric

which see sufficient air at ordinary temperature, After exhaustion of the effectiveness of the adsorption capacity for permanent gases such as O ₂ 40, the zeplith becomes by relaxing the in the column

or N ₂ are suitable. It was namely the over- column enclosed gas to normal pressure re-

surprising observation made that such moles generated, with a nitrogen-rich gas mixture ent

Kular sieve types that give way thanks to one. This embodiment is particularly then

large pore radius the adsorption of O ₈ - and of economic importance, if this is _{equally possible with N 2} molecules, gas enriched with oxygen in terms of 45 oxygen in any case in compressed

the selectivity towards both types of molecules is required for the form,

There are large differences between the normal temperature - It is also a combination of the two working methods. There is also no connection between possible, in that the overflow of the air in the weight unit or 1 mole relative to spherical air takes place with the production of oxygen, the own adsorption capacity for, for example, N ₂ and the gas rich in pressure, which is followed by for Degree of selective preference for N ₂ over regeneration find the column at normal pressure or the adsorption of O _2. For an explanation, it is sufficient to consider that atmospheric pressure creates an even higher absorption certain differences in the radii or other capacities of the zeolite for nitrogen, mechanical and electrical properties of the 55 The following examples serve to describe the O ₂ - or Take into account N ₂ molecules, not just to explain the principle of the method in more detail and to make it out, since the adsorbent shows differently from substance to substance which oxygen concentrations are obtained under the selectivity found, a specific contribution to the various test conditions. can. Although certain zeolites, for example an Sr = ZeO — The above-mentioned Na zeolite A is just like different 60 lith A, give even better separation effects, the various ion exchange products of zeolite A are selected in the examples so that they can be compared with one commercially available Sodium, for example, zeolite obtainable by potassium or magnesium, the Ca-containing zeolite A, is replaced, can be carried out for the implementation of the invention, according to the method hardly suitable, since with these:

Molecular sieves only insignificant separation effects heob * 65 ■, example! be respected. In contrast fulfill molecular sieves of the A at the ends with taps provided glass tube type A, in which at least a part of the sodium yon 700 mm length and 46 mn clear width (space ion by calcium or strontium is replaced, the content-about-1.150 ml) was with 800 g by baking out

Ca-laden molecular sieve zeolite freed from adsorbed water filled in granule form. At room temperature (20 to 22 ⁰ C) the column was evacuated in three experiments (a), (b), (c) to a pressure of (a) 380 Torr, (b) 190 Torr and (c) 95 Torr, Then dried tuft was let in until the pressure was equalized and further air was blown through the column at normal pressure of about 760 Torr at a flow rate of 600 l / h. From the one emerging at the end of the column. The first, second and third liters of gas were collected separately and the oxygen content was determined by analysis. The following Cv contents were found depending on the vacuum set:

Set pressure

a) 380 torr

b) 190 torr

c) 95 torr

Volume percentage

Eg game 3

A valved steel pipe from the the same dimensions as the column used in Examples 1 and 2 was also 800 g granulated, Ca-loaded molecular sieve Zeo-i lithA filled. At room temperature (20 to 22 ° C) was used in two experiments (a) and (b) compressed air up to a: Overpressure of (a) 1 atm and (b) 3 atm presses and flows through the column at a constant pressure of 120 l / h. The regeneration between the individual experiments were carried out by releasing the pressure to normal pressure, the analysis of the first 61 of the at Flowing through the column at the end of the exiting gas mixture resulted in a function of the set Overpressure the following Cv contents:

first liter

23.9
35.1
51.2

second liter

24.8 37.8 41.8

third liter

26.5 31.0 29.3

Hired
pressure

Example 2

The same column as in Example 1 was cooled in a chamber filled with water and as Eisstiicken bath to 0 ⁰ C. Then again as in Example 1 to a pressure of (a) 380 Torr, (b) 190 Torr and (c) 95 Torr, the column was filled with air at normal pressure and 6001 air per hour continued to flow through it.

The analysis of the first, second and third liters shows the following O ₂ contents:

a) latü

b) 3 atü

Volume percent O ₂

first and
second liter

23.42
30.0

third and
fourth liter

23.4
31.6

fifth and sixth liter

23.6
29.1

Example 4

Set pressure

Volume percent O ₂

a) 380 torr

b) 190 torr

c) 95 torr

third liter

26.3 34.5 40.1

35

40 The same pressure column as in Example 3 was in six experiments (a) to (f) in the same way by compressed air at room temperature (20 to 22 ⁰ C) with a constant pressure of (a), (c) and (e) 1 atü and (b), (d) and (f) 3 atü flows through. For regeneration, the pressure was released to normal pressure and by pumping out additional amounts of gas up to a pressure of (a) and (b) 380 Torr, (c) and (d) 190 Torr, (e) and (f) 95 Torr an increased capacity for Created nitrogen. The first 71 of the gas obtained during the overflow were analyzed. The Cv contents achieved with the various vacuum-pressure combinations were as follows:

Set pressures

first liter second liter

Volume percent O ₂

fourth and
fifth liter

third liter

sixth and
seventh liter

a) 1 atm / 380 Torr 25.4

b) 3 atm / 380 Torr 27.2

c) 1 atm / 190 Torr 34.7

d) 3 atm / 190 Torr 38.7

e) 1 atm / 95 Torr 48.2

f) 3 atm / 95 Torr 51.9

Example 5

This example describes the continuous generation of oxygen-enriched air.

In an apparatus according to the figure, three adsorption towers, each with a capacity of 8 liters (internal diameter 94 mm, height 1150 mm) are filled with the same zeolite as in Examples 1 to 4. The towers each carry three solenoid valves a, b and c (see the illustration), which are controlled by a switching drum that can be regulated in terms of its rotational speed. On the exit side there are check valves that close when the towers are evacuated.

The air to be separated flows along the strongly drawn out path. It occurs, for example, through entry 27.4
33.0
39.2
46.4
50.2
54.0

26.8
34.0
37.5
44.5
41.8
48.8

28.2
33.9
31.4
37.2
30.4
37.6

25.0
29.7
24.3
29.8
23.7
29.1

valve c of the first tower and flows through it at normal pressure, while the inlet valves c of the other two towers remain closed. After a specified switching time, which can be selected between 5 and 30 seconds, the inlet valve of the first tower closes and that of the second tower opens. After a further, equally long time interval, the air is passed through the third column and then again through the first. During the two switching intervals in which air does not flow through a column, it is first connected to the vacuum pump by opening one of the valves α and evacuated to pressures between 0.05 and 0.2 ata, with N ₂ -rich gas being supplied to the Atmosphere is given off.

In the second switching interval, dried air is allowed to flow in through the relevant valve b until the pressure is equalized with the atmosphere. The column is then ready to be switched on again as a separation column in the continuous air flow in the following work cycle.

The device marked E in the schematic drawing is an expansion machine that uses the pressure difference that exists when air at normal pressure flows into the evacuated towers for energy recovery.

In the test series in the following table, the sequence of switching pulses was set to 9, 12, 15 or 18 seconds in each case. The throughput was increased from 4 m ³ / h to 10 m ³ / h. The temperature of the zeolite was 15 to 17 ° C in all experiments. To determine the average O ₂ content, the sampling extended over several minutes by continuously branching off a small partial flow and collecting it into a collective sample, which was then determined by gas analysis.

In _; Depending on the switching time and thus on the vacuum reached during the pumping period on the one hand, and on the other hand on the amount of air passed over during the working period, the gas obtained had the following oxygen content in percent by volume:

30th

35

-

9 Switching time (seconds) 15th 18th Achieved vacuum (ata) 0.08 0.06 12th 0.13 0.18 48.7 47.1 - 44.0 46.4 Throughput - 43.9 42.3 42.7 4m ³ / h ... 40.6 39.5 40.1 40.4 5m ³ / h ... 38.4 39.3 37.5 38.4 6m ³ / h ... 37.4 38.1 37.1 - 7m ^s / h ... 37.8 35.3 35.1 - 8m ³ / h ... 35.0 34.7 9m ³ / h ... 34.7 10m ³ / h ...

The linear flow rate (based on empty space) when passing over the zeolite during the working period was ^{16 cm / sec at 4 m 3} throughput per hour and 40 cm / sec at 10 ^{m 3} / h. The duration of a complete working cycle was 3 · 9 = 27 seconds for the shortest switching time and 3 · 18 = 54 seconds for the longest switching time.

Claims (2)

Patent claims: 1. A process for the enrichment of oxygen by selective removal of nitrogen from atmospheric air with molecular sieve zeolites, type A, in which 30 to 80 ° / _{0 of} the negatively charged lattice sites of the aluminosilicate framework are occupied by calcium or strontium, characterized in that At temperatures between about -30 and +40 ⁰ C, the following periodically changing work steps take place over a period of minutes or fractions of minutes: a) Pumping the system containing the molecular sieve zeolite down to a pressure of not less than 50 Torr (regeneration), b) Setting a pressure over the molecular sieve zeolite of approximately atmospheric pressure by the influx of dried air and c) Obtaining oxygen-rich gas by passing dried air over the Molecular sieve zeolite at approximately constant pressure with a flow rate from 120 to 600 l / h, based on an internal diameter of the adsorption column of 46 mm. 2. The method according to claim 1, characterized in that the selective removal of the Nitrogen under increased pressure of about 1 to 5 atm and the regeneration under relaxation can run at normal pressure. Considered publications:
French Patent No. 1 223 261. 1 sheet of drawings 309 538/507 4.68 ® Bundesdruckerei Berlin