DE401904C - Process for the production of pure oxygen and nitrogen in a single operation - Google Patents

Description

ISSUED
ON SEPTEMBER 12, 1924

REICH PATENT OFFICE

PATENT LETTERING

JVi 401904 CLASS 17g GROUP

(B 94922 Ijijg)

E. Barbet & FiIs & Cie. in Paris.

Patented in the German Empire on July 6, 1920.

The purpose of the invention is to

in a continuous rectification complete purity of nitrogen and To reach oxygen and to remove even the noble gases.

The one set up by E. Barbet since 1890 Continuous alcohol rectification theory is general and consists of the following.

ίο The refining of a volatile product does not happen in the capacitor, regardless of the contrivances and complicated ones Constructions one likes to take refuge.

Rather, the refining takes place on the plates of the rectification column, but below Contribution of the return from the condenser. The condensed liquid that is on the uppermost plate flows back and which must be pure, effects the washing of the rising one Fumes. This washing liquid, which has been taken from the product that has already been cleaned, is gradually and systematically displaced all less volatile constituents towards the lower parts of the device allows only the most volatile constituents to pass through.

The heavy ones, d. H. little volatile vapors

condense in the liquid on the plates and evaporate in their place corresponding weight of more volatile vapor, so decomposition occurs. When the fumes contain a very small amount of an impurity that is very volatile, so goes this component passes through the boiling liquid of the plate without being held there and as if the vapor passage plate were not there. He can namely do not condense and in its place a liquid evaporate, the less is fleeting than himself.

In the invention, these are applicable to the decomposition of the usual liquids and effectively tested principles of liquid air have been adapted.

The adjustment is given for the plate column. One can almost indiscriminately use all types of plates commonly used with alcohol, benzene, etc.

The heating in the lower part of the rectifying column is also easy to imagine. If you want to bring a liquid to the boil, its boiling point is around -190 ° the outside air is sufficient to form a very effective heat source.

By far the hardest part of the solution is in the top of the rectifying column to obtain a reflux of liquid nitrogen and its volume easily to a constant hourly weight to regulate in order to get a constant cleaning.

The solution to the problem has already been attempted in the following direction: The above Nitrogen escaping at -194 ° is in divided into two parts. One forms the commercial product, the other serves as a return and must consequently be condensed and returned to the plates.

This solution, which already provides a nitrogen] of a certain purity, but still not enough, because the air when j also contains only small amounts of gases that are even more difficult than condensed nitrogen such. B. neon, hydrogen and helium. So the nitrogen would not really be pure.

The procedure followed in the case of alcohol rectification, the final removal of the last Traces of aldehyde-like impurities of the order of a millionth possible has, by virtue of a special adaptation, allows the complete cleaning of the Nitrogen. The process is called pasteurization of alcohol by Barbet and is very easy. It is based in turn on the fractionation ability of the j Plates and not on contrivances at the! Condensation. ',

I The nitrogen return cannot be completely chemically pure, no matter how the condensation is carried out because, as a result of the sudden occurrence of condensation 6f absorbed everything that was present in vapor form, namely nitrogen, neon, hydrogen and helium. You leave that All flow back to the top plate, where this liquid passes through the bubbles Nitrogen vapor is again brought to the boil. According to the laws of boiling, the most volatile The body is first converted back into vapor form, i.e. after it has been traversed by vapor bubbles on one or two plates have been, the return is released from them provided that a derivation is made somewhere.

Even if the nitrogen vapors rising from the lower plates themselves very much Containing small amounts of neon, hydrogen and helium can cause their vapors, since they are more volatile than nitrogen, do not condense to make the less volatile Vaporize nitrogen in their place. ; The liquid on the plate remains as full constantly pure, and it is enough to have this liquid. however not the steam from this plate, in 'Subtract the desired amount in order to chemically ge; to get pure nitrogen. If you- the Automatically brings the liquid to the boil again with an even if impure vapor, this gives the benefit of a pure product.

After the above, the present invention is that which is subjected to such air to be separated a continuous rectification in a column apparatus, that in order to complete removal of the noble gases of the air escaping from the top of the column nitrogen to \ ^r erflüssigung by expansion of the contained rare gases freed and is introduced into the rectification column in the liquid state at the top, on the upper plates of which it is cleaned by repeated boiling of the refluxes and drawn off in the liquid state at one of the uppermost plates. The argon is ι in the liquid state at the point υ its highest concentration near the middle of the column subtracted. The oxygen is partially withdrawn in the liquid state in the lower part of the column for the purpose of removing the rare gases contained therein, while the pure oxygen is discharged in gaseous form at a slightly higher point.

One can proceed in such a way that only part of the in the rectifying column returned liquid nitrogen, about half, in the pure state of one of the

top plates of the column is derived.

The purity of the withdrawn nitrogen is regulated by the circulation speed, which he by changing the course of the gaseous nitrogen for the purpose of liquefaction compressing pump receives.

A device suitable for the process is shown schematically in the drawing in Fig. Ι for example shown.

AA ' is a plate column. In the upper part A the nitrogen is rectified, in the lower part A that of the oxygen. At P it becomes uninterrupted

Liquid and gaseous air is supplied. the end cold gaseous nitrogen escapes from an upper outlet pipe of the column, its Volume is approximately twice the intended production of useful nitrogen.

This gaseous nitrogen escaping above must be completely liquefied in order to form the reflux entering at η, half of which is withdrawn a little lower at m and forms the pure nitrogen of the trade, while the other half continues to flow down from plate to plate to avoid the rising vapors to wash and disassemble.

The known means for condensing a gas consists of compression and cooling. The nitrogen is accordingly compressed by a pump / to a pressure of 2 to 3 kg; However, before it gets to this pump, it has to exchange its cold content with the nitrogen coming from the compression. The compressed nitrogen coming from / loses its heat of compression in a water cooler K ^{fed by a line 5 1} and then passes through the exchange device //, where it absorbs the cold content of the nitrogen sucked in by the pump, this exchange being very precise because the weights the amounts of nitrogen flowing in both directions are equal. So that none of the cold content of the sucked in nitrogen is lost, it runs through a coiled pipe K ' when it exits H , where it cools the water circulating in K and intended to absorb the compression heat from the pump by a few degrees. A compressed nitrogen is thus obtained which, apart from radiation losses, has almost the same temperature as the upper part of column A when it emerges from H at /; but the nitrogen must now be liquefied.

The pasteurized nitrogen is withdrawn at m in the liquid state, but it must be released in the gaseous state and at normal temperature. This is an important source of latent and recoverable cold, but the weight of this withdrawn amount is barely half that of the gaseous nitrogen just compressed. The latent heat of vaporization of this nitrogen can therefore liquefy only about half of what is required in a heat exchange device B.

The remainder is liquefied in an adjacent tube cooler / is

ι but completely secured there because of this

^! Tubular cooler the total amount, which in a boiler E, as will be discussed, takes up liquefied air. The liquefied nitrogen goes through a float-equipped separator b, which prevents the passage of the uncondensed components, while the liquid nitrogen rises as a result of the pressure to the top plate of A at η.

The pasteurized nitrogen has become gaseous again in B. This very cold gas enters an exchange device C at the bottom and then into a water-cooled coiled tube D ' . Its volume is measured by a gas meter M , and the outlet tap d is regulated by hand so that only the desired amount emerges. From there the nitrogen finally reaches the gasometer.

The cold content of the gaseous pasteurized nitrogen is used to provide a certain weight of very cold air, which is also used to feed the rectification column. This air is compressed in a container R and enters an exchange device D, which is fed with water through a pipe S ' , then into the tubular cooler C and is cooled there by contact with the gaseous nitrogen. λ'οη there it gets into the tubular body of E, where it liquefies as a result of its pressure

' will.

A derivative has to be made for the three more volatile than nitrogen impurities, namely neon, hydrogen and helium. Characterized in that the liquid nitrogen reflux is again brought to the boil on the top plates, these three gases are \ ^r on again so that the compression pump / nitrogen containing reaching again evaporated, more thereof; nevertheless, the condensation of these gases in B occurs because they are entrained. The total liquid ¹¹ S

'' ■ gets into the separator b before it reaches the

^: upper plate of the column descends. This separator can be of the automatic type

^: Cleaners must be set up that are used at the outlet end of steam coils. The incoming liquid is still under pressure, but as soon as it passes through the outlet valve

til has passed through, it is only below the atmospheric pressure prevailing in the upper part of the column y4, so that it undergoes sudden relaxation and consequently partial evaporation and the remaining liquid is instantaneously reduced to yg ° abs. Temp, is cooled. This cooling is the result of a partial gasification, which is nothing more than a distillation. ίο The general law of distillation reappears, according to which the vapors developed are much richer in volatile impurities than the liquid. The latter has already accumulated neon, hydrogen and helium on the two or three upper plates of the column through repeated boiling. The vapors developed therefrom as a result of the expansion are therefore much richer in impurities, and one only needs to subtract a very moderate proportion of them at N to be sure that as much noble gases are removed as are always added by the influx of new quantities of atmospheric air are fed to the device.

The absolute noble gas content of this withdrawn gas is of little importance. It is sufficient that the total amount flowing out is exactly the same as the inflow, and this results in the proportion to be withdrawn. It can be fairly easily limited to ¹ ½ to ₃ % of the air going to the rectification.

From this explanation of the induction of a vigorous reflux of liquid nitrogen it is readily apparent that one has the ability to increase its relative amount. You just have to run the pump / faster. At M , the same amount of finished, pure nitrogen is still withdrawn, but since a greater weight of reflux is allowed to flow back, the volume of nitrogen emerging from A is increased by exactly the same amount, and the process proceeds as before without any disturbance. The method thus makes it possible to carry out refining as far as the technology requires, since the degree of purification, according to the principles set out, is directly dependent on the proportion of the washing liquid, i.e. the return flow.

You have to heat the lower part of the rectifier the more, the more Return one lets enter at the top, because then one around. so greater fluid weight too is evaporating.

In the lower part of Ä , however, a heat source is required, which is formed by the tubular boiler B, which is used to evaporate the pure, i.e. nitrogen-free oxygen, as required by technology and the residue remaining in the lower part of the rectification column Liquid is formed. Compressed air is introduced here, which has previously been freed from carbon dioxide and moisture. \ This air which has been compressed in the container B at about 4 kg of printing has been heated by this compression. You j first cool it in G with cold water! from which is fed at S ". From G reaches the compressed air in a tube chiller F whose tubes they lapped while these gaseous, but very cold oxygen of about 93 ⁰ abs. Temp, are flowed through, which consists Ä at Ox It should be remembered that the air contains 23 parts by weight of oxygen to about Tj parts of nitrogen, and it follows immediately that the recovery of the cold content of 23 kg of oxygen is the cooling of the air necessary for the production of this 23 kg of oxygen can't go very far.

The air cooled in F and still under pressure finally reaches the tube bundle of E, while in these tubes there is liquid oxygen of 93 ° abs. Temp, as the last outflow from the column ^ 'is located. As a result of its pressure, the air, instead of being at 83 ° abs. Temp, to be liquefied, at about 99 ⁰ abs. Temp, to be liquefied. The liquid oxygen of 93 ° abs. Temp, so it can condense by: being vaporized by itself. This pure oxygen vapor supplies, on the one hand, the gaseous oxygen continuously diverted at Ox and, on the other hand, causes the boiling process on all plates of the column AA ' .

The gaseous oxygen withdrawn at Ox reaches the after passing through the coolers F, G and the counter M '. Gasometer.

The pressurized liquid air produced in E is not simply conducted to the feed plate α by means of an automatic cleaning device e , but its pressure is used to let its total amount rise into the tube chamber of / 110. It represents the liquid air previously mentioned as a supplemental liquefier for the nitrogen return.

In FIG. 7, the liquid air begins to boil and, in the process, turns into gaseous form with enrichment in nitrogen, specifically in the ratio that is necessary to complete the liquefaction of the nitrogen. All of the excess remains in a liquid state, and the liquid and gas come together to the feed plate a.

One can readily see that if the ratio of the nitrogen return in the upper part of A is increased, the amount of liquid air evaporated in I is increased, while the boiling caused in the lower part of A by the heating in B remains constant. So there is a lot of rectifying steam in A, as is absolutely necessary, which

ίο exactly to evaporate the further amount-; the liquid nitrogen return is increased. So the process goes smoothly and automatically, without laborious regulation j being necessary. ;

For the purpose of replacing the radiation losses, a tube cooler U is arranged next to the rectification column, in whose tube chamber liquid air is circulated, which is used for its production.

ao the compression pump comes from. The I liquid air enters at y , and the very cold I vaporized air exits at u and returns from there to the condensing pump. j On the other hand, one passes ν through a pipe

as a certain amount of steam from the rectifier ■ column from that taken at a height! becomes where there is already a fairly high oxygen level is available. These vapors can therefore be liquefied at an absolute temperature that is higher than that of liquid air without the need for compression. They liquefy and come back in a liquid state on the same plate, where they are taken:

have been. In order to measure the cooling achieved in this way, a sensitive pointer thermometer t is attached at the desired height, according to which the additional cold supply is regulated.

Like nitrogen, oxygen contains certain impurities. These are the argon, which at - abs 187 ⁰ = 86 °. Temp, boils, so at a temperature between the boiling point of Sauer- I

W substance and nitrogen, furthermore the cryp- ' clay and xenon, which are considerably less volatile than oxygen.

The removal of these three impurities can be achieved very easily if one on the theory of Barbet about the un-; interrupted alcohol rectification! falls back. Namely, it turns out that the j argon that is released from the upper plates by j the returns are displaced and from the lower j

Part of the device through the boiling | gang is driven out, must accumulate on a central plate. So you only need to attach a tap Ar at the height of its greatest concentration, which is provided with an immersed elbow pipe on the inside, so that liquid and not gas can be drawn off. The cock is set so that about V ₄ to ¹ ^ ₃ percent is drawn off, so that no trace of argon is found in either the oxygen or the nitrogen.

The krypton and xenon continue to be forced into the lower part of the rectifying device and into the tubular body B and accumulate there when the gaseous oxygen is withdrawn at Ox , ie a few plates above the lowest part of the device. A disruptive increase in their amount is prevented by continuously withdrawing a small amount of liquid at X which, depending on the result of the examination of the oxygen, which must be chemically pure, can in turn be V ₄ , V ₂ or even 1 percent. The three impurities argon, krypton and xenon are thus removed without the need for special condensation or any other trick.

The device designed in this way is therefore completely adaptable and can meet all requirements with regard to purity and other properties of the products to be achieved. The pure nitrogen and oxygen, after it has been brought to the outside temperature, goes through gas meters M, M, by means of which the ratio of these gases can be regulated very precisely.

It is important to remember that the air to be compressed is completely exhausted first Their carbonic acid must be freed by passing them through a solution of caustic soda or soda, and then of its moisture by letting it pass through sulfuric acid at 50-55 ° Be.

The device is controlled by pressure gauges, electrical or other thermometers and Cold insulation agents, which must be very effective, completed.

The overall arrangement shown in Fig. 1 for the liquefaction of the nitrogen return is only an example.

Another example is shown schematically in Fig. 2.

The compression pump / presses the nitrogen slightly higher than in the previous example. The double volume of nitrogen emerging from the upper part of the column exchanges its cold content with the same nitrogen strongly compressed in / for example to 5 to 6 kg pressure. The compressed nitrogen cooled in H is still gaseous. Instead of liquefying it as in the previous arrangement, it is fed into the tubular chamber of E, where it is completely liquefied. Since the weight of this nitrogen is greater than that of the air introduced into E according to Fig. 1, there is a greater

gassing of oxygen, so a higher boiling capacity of the rectifying device and therefore better refinement.

The nitrogen completely liquefied in E passes through separator e and rises from there to n, where it goes to the top plate of the column and provides an ample nitrogen return. At e , the expansion of the liquid nitrogen takes place

ίο and consequently the automatic gasification, by virtue of which one can subtract the light gases neon, hydrogen and helium at N.

The pasteurized nitrogen is again drawn off in the liquid state at m . It is gasified in B , where it liquefies an approximately equal amount of air, which from here passes through the separator T to the feed point of the rectification column. The nitrogen continues on its way through exchangers C and D and then to meter M.

When the gaseous oxygen is withdrawn at Ox nothing changes, apart from the fact that the air, which absorbs the cold content of the pure oxygen escaping from Ox , only has an extremely low overpressure of at most 0.2 kg and therefore no longer needs a water cooler. P and G are two exchange devices, and the pure oxygen escapes through the meter M. The air cooled in G and F , but which cannot be liquefied, rises to Q and supplements the supply of the device there. There is thus a mixed feed by about _^3/4 of the necessary amount as liquid air to enter at P, while the remainder cooled to be very strong but enters gaseous air through Q.

As can be seen from the foregoing, there are a very large number of heat exchange devices required, and these devices must act very vigorously so that the cold content of the exiting pure gases in favor of those entering the device for liquefaction and rectification Fresh air is used.

Fig. 3 of the drawing shows the design, for example, in a vertical section an exchange body that enables the result mentioned.

The extraordinarily long bundle of tubes is not straight. In a small distance from each of the tube plates 1 and 2, the \ tubes 3 are guided to toward the center, so that they fit into a cylinder 4, whose cross section is considerably smaller than that of the tube plates. As a result, from this point onwards, the passage cross-section for the gases becomes very much smaller and therefore their speed increases. The limit is reached when you close the tubes so tightly ^; collapse so that they touch; then the passage cross-section is considerably smaller than that of the interior of the tube.

If you want a larger passage cross-section, you solder on it ! Tubes 3 a copper wire or a small copper strip at certain intervals 5, the strength of which is calculated as. that all tubes are equidistant from each other to have. The attachment points of these fastening rings are offset so that can never touch two of them, which doubles the distance between the tubes would be. This gives the means to get the gases exactly the one you want To give speed outside the tubes. There is still a structural trick required to enable this arrangement. This can be achieved in several ways, one of which is the following is shown in the drawing.

The whole tube bundle is first drawn into the narrow cylinder 4 by the The pipes protrude about 50 cm above the lower flange 6. The ends of the tubes 3 are made bendable by heating by hand. Then bring the tubular plate ι and put the tubes in rows one after the other in the holes of the Plate a. The distance by which each tube protrudes from the plate is approx Brought 2 to 3 cm, and the tubes are then rolled in in a known manner. On that the plate and the tubes can be pushed into the enlarged part 7 of the jacket and then rivets the edge of the tube plate in place. * ° o

The tube jacket ends here at 8, and the entire upper cylindro-conical part is separated from it. The jacket 4 ends in a threaded, soldered bronze ring 9. A flange 10 is screwed onto 9. As soon as the flange 10 is above the Ring 9 is screwed over, it can be moved on the cylinder 4. Simultaneously it becomes possible to move the entire cylindro-conical part 11 on top to 4, until all tubes protrude 60-80 cm.

The process described for the tube plate 1 at the lower end is then repeated. The plate 2 is applied, and the pipes are sets row by row into it einge- ^X1 5, by allowing them to survive a few centimeters. The tubes are then rolled in, and after this has been done, the entire cylindro-conical part 11 is pulled up and even brought into a somewhat higher position than the correct one. The flange 10 is then put back in place and so on

Claims (9)

screwed wide so that it cuts off with the top of 9. The part 11 is brought into contact with the flange lo by tightening the connecting bolts. You then only need to rivet the edge of the tube plate 2 to the jacket, and the tube bundle is ready. The complete seal on the outer sides of the two tube plates ι and 2 is made in the usual way ίο by a tin solder bath. It can be seen that the gases entering through a pipe socket 12 can easily distribute themselves evenly between the pipes, since the pipes are quite far apart at this point. The gases then crowd to circulate in the very narrow channels that are cleared by the tubes in the narrowed portion of the jacket. ■ Patent claims: 1. Process for the production of pure oxygen and nitrogen in one single operation, characterized in that the air to be broken down is an uninterrupted rectification in one Column apparatus is subjected in such a way that for the purpose of complete removal of the noble gases from the upper Part of the column escaping nitrogen after liquefaction by expansion freed from the rare gases contained therein and in a liquid state above in the rectifying column is initiated, on the upper plates of which he is repeated Boiling the return flows is cleaned and drawn off in a liquid state on one of the top plates, while the Argon in the liquid state withdrawn at the point of its highest concentration near the center of the column and the oxygen in the lower part of the column for the purpose of removing the rare gases contained therein partly in withdrawn in the liquid state, the pure oxygen, on the other hand, is discharged in gaseous form at a slightly higher point. 2. The method according to claim 1, characterized in that only a part of the liquid nitrogen returned to the rectification column, about half, in the pure state of one of the uppermost plates of the column is derived in the liquid state. 3. The method according to claim 1, characterized in that the purity of the withdrawn Nitrogen is regulated by the rate of circulation, which the nitrogen by changing the course of the gaseous nitrogen; receives compressing pump for the purpose of liquefaction. 4. Apparatus for carrying out the method according to claim 1 to 3, characterized in that the column in its upper part with a feed (s) for the liquid nitrogen serving as reflux and underneath with a discharge line (m) for the pure liquid utility nitrogen, approximately in the middle with a discharge line (Ar) for liquid argon and in its lower part with two discharge lines, through one of which (Ox ¹ ) liquid oxygen with the total content of xenon and krypton and through the other higher-lying (Ox) purer gaseous Oxygen is withdrawn. 5. Apparatus according to claim 4, characterized in that a device (b) for separating neon, hydrogen and helium by expanding the compressed nitrogen is switched on between the discharge line (As) for the distilled nitrogen and the feed (n). 6. Apparatus according to claim 4, characterized in that in the discharge line (Ox ¹ ) for the liquid oxygen, a tap (X) is switched on for drawing off xenon and krypton-containing oxygen. 7. Apparatus according to claim 4, characterized in that a branch line (v) is provided approximately in the middle of the column, which leads part of the gases through an auxiliary cooler (U) . 8. Heat exchange device for the \ * orrichtungen according to claim 4 to 7, characterized in that a bundle of ¹ Oo very long tubes of very small cross-section lies in the middle in a narrow jacket which widens at both ends to form chambers of large cross-section, in which the ends of the tubes of each bundle spread out. 9. Heat exchange device according to claim 8, characterized in that the tubes in the center of the device are ringed at intervals that keep them at a certain distance from each other. 1 sheet of drawings.