DE1187248B - Process and device for the production of oxygen gas with 70 to 98% O-content - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

F25j

German KL: -17 g -2/01

Number: 1187 248

File number: G 373911 a / 17 g

Filing date: March 29, 1963

Opening day: February 18, 1965

The invention relates to a method and a device for the production of oxygen gas with 70 to 98% O ₂ content by low-temperature air separation in a double rectifier, in particular in connection with regenerators for the heat exchange between decomposition air and decomposition products, with evaporation of the liquid from the sump Product removed from the low-pressure column with the aid of a partially condensing fraction of the decomposition air exiting in gaseous form from a pre-washing column, the non-condensed portion of which is passed on to the pressure column of the double rectifier and the liquefied portion of which is returned as washing liquid to the pre-washing column, while the washing liquid draining from the pre-washing column is returned to the low-pressure column Sump liquid is introduced from the pressure column.

With the described method, the energy consumption advantage is reduced compared to normal Double column rectification with an increase in the oxygen content in the oxygen-rich end product.

It is also known to take a small amount of a concentrate enriched with krypton and xenon to be taken from the bottom of the low-pressure column and to be further evaporated to obtain krypton and xenon. The main amount of the oxygen to be obtained is one or more floors above the Taken from the column bottom without further enrichment. However, this increases the energy requirements of the system in no way diminished.

The invention has set itself the task on the basis of the method described above also for higher oxygen purities up to about 98% the decomposition pressure and thus the energy requirement to decrease further.

This is achieved by passing the product taken from the bottom of the low pressure column represents a precursor with a lower O ₂ content as the final product, which intermediate product prior to the evaporation by Zwischeneindampfung under partial condensation of another of the Vorwaschsäule to pressure column guided fractionation air fraction to the O ₂ content of the end product is brought, the vapors developed from the intermediate product during the intermediate evaporation are returned to the foot of the low-pressure column.

According to a further feature of the invention it is possible to achieve the intermediate evaporation effect to reinforce that the liquid precursor removed from the low pressure column by rectification by means of the methods and equipment for extraction formed during the intermediate evaporation

of oxygen gas

with 70 to 98% O ₂ content

Applicant:

Society for Linde's ice machines

Corporation,

Wiesbaden, Hildastr. 2-10

Named as inventor:
Max Seidel, Munich-Solln

Vapors are enriched with oxygen before it is subjected to the intermediate evaporation.
Depending on the required purity of the generated oxygen, the heating of the intermediate evaporation and the end product evaporation are now switched on differently in the path of the air fraction coming from the prewash column in order to heat the three evaporation points, namely the bottom of the low-pressure rectification column, intermediate evaporation and end product evaporation To achieve condensation pressures, i.e. the lowest possible pressure of the separation air.
To heat the low-pressure column, nitrogen is condensed from the top of the pressure column in the usual way. The condensation pressure of this nitrogen depends on the pressure in the bottom of the low-pressure column and on the oxygen content of the liquid to be evaporated. The bottom liquid of the low-pressure column has the same oxygen content as the intermediate product removed for intermediate evaporation.

A lower boiling temperature is associated with the lower oxygen content of the evaporating liquid. Since for the enrichment of the liquid on the lower oxygen content less rectification path and so that less column resistance is required, there is a lower pressure with the lower oxygen purity connected in the column sump, which leads to a further lowering of the boiling temperature of the evaporating Liquid leads. At the lower boiling point of the liquid to be evaporated in the bottom of the low-pressure column An equally lower condensation temperature of the nitrogen heating the column is sufficient from the top of the pressure column and thus a correspondingly lower condensation pressure.

The boiling point of the intermediate product evaporation and the end product evaporation is due to the

509 509/87

3. 4th

higher oxygen contents higher than the boiling temperature - with oxygen contents of the end product below 90%

door in the column sump of the low pressure column. This is due to the higher boiling point at the final

Intermediate product evaporation takes place in reverse order to product evaporation.

Oxygen content of the liquid equal to the oxygen - first the final evaporation and with the remaining

content of the end product and under a pressure, the 5 slightly less oxygenated vapors

heated in the case of the interposition of enrichment steam. By whole or partial

rectification around the resistance of the enrichment return of the heating of intermediate

rectification between the low-pressure column and intermediate evaporation and evaporation of the end product

evaporation is higher than the pressure above the sump.

the low pressure column. It follows that the boiling point content of the air frac-

temperature of the intermediate evaporation is higher than the tion can be influenced. Not to the prewash column

Boiling temperature of the sump liquid of the low-pressure recirculated partial condensate quantities are

Rectifying column. in this case together with the non-condensed

In order to heat the air fraction used for heating with the same decomposition part to the pressure or with only a pressure resistance of 15 feet to the pressure column,
In all cases, the oxygen enrichment of the condensed liquid can be increased, as in the case of heating the low-pressure column, from the pressure column to the low-pressure column from the bottom of the pressure column to the low-pressure column, if a portion of the condensate has to be increased, according to the Invention in the form of the air fraction coming out of the prewash column of the decomposition air passed through the prewash column, ao between the end product evaporator and the intermediate evaporator, an oxygen content of the schene evaporator or branched off before both and the evaporating liquid, which in the combined pressure column bypassing one or both settlement equilibrium with the vapors of the Endpro evaporators below the point of introduction for the product, z. B. in the evaporators due to partial condensation of acid

80 '/. OrGdUUt in the vaporous end product ^ ξ ^ depleted residual vapors of the

'"approx. 94 ° / O final evaporation or the intermediate evaporation

90o / _e O, r content in the vaporous end product ^ ^end ? ^e ° ^A "^ ^{ls de} _Q ^{r air} / ^r £ ^{ktion is} introduced.

^{/ e} * Due to the higher oxygen enrichment of the

ν _approx. 970 / ο Due to the higher oxygen enrichment of the

oao / r "n ^ oU;". ' ^ «". «Η * ™ ,, -» ». Bn ^ JinH the pressure column is rectified in the

98 ° / «(Jo-Cienait in the vaporous final product,,,",, ".,., ..

_t Qg ₀ , Q 30 low pressure column relieved. It won't just be that

² "Amount of the transferred from the foot of the prewash column

The with the - compared to the evaporated end- oxygen-rich liquid is reduced, without the

product - increased Og content associated temperature amount of the running down from the foot of the pressure column

The increase in temperature does not come into its own because the liquid increases in the same degree, but rather

Evaporation of the end product below a low level - it will be in the upper section of the low pressure column

higher pressure is carried out than the evaporation also requires less scrubbing nitrogen from the pressure column

of the preliminary product in the bottom of the low-pressure column is required to get out of the reduced amount of column vapor

and the evaporation of the intermediate product. To wash out the oxygen. As a consequence

End product vapors only have to withstand the resistance of the remaining a larger amount of nitrogen for the working

Heat exchanger with the separation air, but no expansion for cold production; so results

Overcoming resistance to rectification. an increased oxygen yield.

Taking into account the influences of composition, the FIGS. 1, 2 and 3 show, for example, the equilibrium of the scheme and the evaporation pressure result in the production of oxygen of 80, 90 and, if Te is the boiling point at the end product-98% purity according to the process. In order to make the wall evaporation and Tz the boiling point at the 45 lungs of the process for different intermediate oxygen evaporation more visible, the material content of the end product was consciously different for the variation of the ratio of Tz: Te, namely omitted essential details.

Generation of 90% igeni oxygen (Fig. 1)

^{102 700 Nm 3 of} air with a pressure of about 4.0 ata are fed in through line 1 every hour, in the regenerators 2, 4, 6 and in the next switching phase in the regenerators 3, 5, 7 and cooled down from there H ₂ O and CO ₂ purified. The amount of air remaining after deducting the switching losses of 100,000 Nm ³ / Therefore at about 90% O _a content of the end hour then flows through the line 8 into the preliminary product, the condensation sides of the intermediate washing column 9, which is dampened with some rectification trays 10 and End product evaporator is provided in parallel. In this it is wired by the. 60 heating of the final evaporator 20 and the intermediate in-With oxygen content of the end product over 90% evaporator 100 accumulating condensate washed. The washing liquid fraction running out of the pre-washing column 9 with the air coming from the pre-washing column is first the higher boiling temperature from -35,000 Nm ³ / hour, the approximately converging intermediate product evaporation and the settlement equilibrium with the gas that has occurred after the separation of the resulting oxygen-65 gene air is and an oxygen content of about rich partial condensate remaining slightly oxygen-43% ^carbonate, is withdrawn, the final evaporation column through the line 11 to the bottom of this material poorer vapors and filled through the preferably heated silica gel, alternately driven adsorbers

Oxygen content
of the end product Boiling temperatures Less than 90% Ο ₈
About 90% og
Over 90% O, Tz lower than Te
Tz equals Te
Tz greater than Te

12 α and 12 b out and there freed from the residual impurities washed out of the total air, in particular from carbon dioxide and hydrocarbons.

The purified liquid is then passed through the line 13 via the heat exchanger 14 and the Relaxation valve 17 at point 18 in the low-pressure column 16 of the double rectifier, in the pressure of about 1.3 ata prevails.

The washed air fraction withdrawn in gaseous form from the top of the prewash column 9 through line 19 has an oxygen content of approximately 14%. A portion of this air fraction is partially liquefied through line 19 a in the final evaporator 20 in heat exchange with the evaporating liquid end product supplied through line 21 from the intermediate evaporator 100 and fed into the separator 22 .

The other parallel partial flow of the air fraction coming from the prewash column is fed through line 106 to the intermediate evaporator 100 and partially liquefied in heat exchange with the partially evaporating liquid product fed through line 53 from the rectification column 102 and fed into the separator 101 . In the separators 22 and 101 , the liquefied fractions are separated off and fed together through the line 23 as washing liquid with an oxygen content of about 21% into the head of the prewash column 9; the gaseous proportions of a total of about 65,000 Nm ³ / hour with about 9% oxygen content are removed with the lines 24a and 2Ab from the top of this separator and together with the line 24 into the pressure column 15 of the which is under a pressure of about 3.7 ata Double rectifier introduced. The liquid that collects in the sump of this column, about 21100 Nm ³ / hour with about 21% oxygen content, is removed via line 25, subcooled in heat exchanger 26 and via the expansion valve 27 at point 28 above the introduction point 18 of the liquid from the prewash column 9 introduced into the low-pressure column 16. ^{About 20,400 Nm 3 of} liquid nitrogen per hour are taken from the upper part of the pressure column 15 through the line 29, supercooled in the heat exchanger 30 and, after expansion in the valve 31, introduced into the low-pressure column 16 as scrubbing liquid at the top through the line 32. Gaseous nitrogen is removed from the top of the pressure column through line 33 and warmed up somewhat in heat exchanger 34.

About 23,500 Nm ³ / hour of this nitrogen are then passed through the line 35 into the turbine 36, expanded in this work-performing and then together with about 54,500 Nm ³ / hour nitrogen, which still has a content of about 2% oxygen and the withdrawn through the line 38 from the top of the low-pressure column 16 and then heated in the heat exchangers 30 and 26, passed through the heat exchanger 14. About 78,000 Nm ³ / hour of nitrogen are then passed through line 37 to regenerators 3 and 5 or 2 and 4 and heated in these to ambient temperature, whereupon they leave the system through line 39.

A part of the slightly warmed nitrogen in the heat exchanger 34 is through the line 40 the Heat exchanger 41 supplied, heated in this countercurrent to itself to ambient temperature, then compressed in the dry-running compressor 42 to, for example, 15 ata, then in the heat exchanger 41 cooled again and liquefied in the heat exchanger 34, relaxed in the control valve 43 and via valve 44 a of the pressure column 15 or that of the pressure column 15 via the heat exchanger 30 supplied to the low pressure column 16 flowing liquid nitrogen stream.

When the apparatus is cold, the nitrogen liquefied in the heat exchanger 34 and expanded in the control valve 43 is fed to the prewash column 9 via valve 44b and separator 101 in order to initiate the prewashing of the air before the liquid end product is produced.

In the bottom of the low-pressure column 16, liquid oxygen with an oxygen content of about 80% collects as a preliminary product, is withdrawn through line 52 and fed to the enrichment rectification column 102 as reflux liquid. The outflowing precursor, which is further enriched with oxygen, is fed through the line 53 from the foot of this column to the intermediate evaporator 100 and is enriched to a purity of the end product of about 90%. The vapors developed in the intermediate evaporator 100 are brought into mass transfer with the preliminary product running off in the enrichment rectification column 102, and the gaseous residue with about 53% oxygen content withdrawn from the top of this column is introduced through the line 54 into the low-pressure column 16. The intermediate evaporator is shown as a circulation evaporator. The liquid part remaining during the circulation of the evaporating liquid is fed back to the intermediate evaporator through the line 53 with the intermediate product flowing into the intermediate evaporator. The 90% liquid end product passes from the intermediate evaporator 100 through the line 21 into the final evaporator 20. In this it is evaporated. In the subsequent separator 45, the liquid part remaining during the circulation of the evaporating liquid, which contains about 97% oxygen in the composition equilibrium with the 90% oxygen-containing vapors, is separated off and removed from the base of the separator through line 46 and transferred via an adsorber 47 of the im constant circulation of evaporating liquid supplied again. The gaseous end product, about 22,000 Nm ³ / hour 90% oxygen, consisting of 19,200 Nm ³ / hour pure oxygen and 2800 Nm ³ / hour air, is removed through line 48 from the top of separator 45, in regenerator 7 Ambient temperature warmed and leaves through line 49 the system.

The function of the regenerator pairs 2/3, 4/5 and 6/7 is periodically interchanged in a known manner. The position of the valve groups 50a to 50c on the warm side of the regenerators and of the groups of check valves 51α to 51c on their cold side results from the current curve drawn in the regenerators.

As far as the possible variants of the method already mentioned are concerned, under certain circumstances the nitrogen cycle via the heat exchangers 34 and 41, as well as the compressor 42 and expansion valve 43 can be dispensed with. This would be the valves 44 a and 44 δ and their connections are also omitted.

In this case, either the pressurized nitrogen to be supplied to the expansion turbine 36 can be

heating coils preheated in a pair of regenerators or a regenerator pair receives a center tap, from which two alternate operated adsorber each a fraction of air via an expansion turbine in the low-pressure column is initiated. In the last-mentioned procedure, the expansion of pressurized nitrogen would as There is no need for regenerator purging gas.

Generation of 80% oxygen (Fig. 2)

^{After deducting the switching losses, 100,000 Nm 8 of} 102,500 Nm ^a / hour of air with a pressure of 3.6 ata enter the prewash column 9 every hour and the liquid part with about 28% oxygen content is returned to the top of the prewash column 9. The washing liquid running out of the prewash column, about 29,000 Nm ³ / hour with about 43% oxygen content, is fed into the ao low-pressure column 16, in which there is a pressure of 1.3 ata. From the in Endverdampf he 20 remaining uncondensed -. About 71 000 Nm ⁸ / hour with about 12% oxygen - Per hour 31 000 ⁸ Nm unteiek the end of the supplied under a pressure of 3.2 ata standing pressure column 15 The remaining 40,000 Nm ³ / hour are partially condensed in the intermediate evaporator 100 and the gas-liquid mixture with about 9% oxygen content in the gas and 22% oxygen content in the liquid at a suitable point above the feed point of the non-condensed partial flow from the final evaporator 20 nrÄ pressure column 15 headed. ^{27,200 Nm 8 of} gaseous nitrogen for the expansion turbine 36 are withdrawn from the head of the pressure columns 15 every hour. 16 500 Nm ⁸ / hour of liquid nitrogen pass from the upper part of the pressure column 15 as scrubbing liquid into the low pressure column 16. From the bottom of the pressure column 15, 27 300 Nm ⁸ with about 28% oxygen content are drawn off every hour and introduced into the low pressure column 16 at a suitable point. From the top of the low-pressure column 16, about 48,000 Nm ^{3 of} nitrogen, which still has a content of about 1% oxygen, are drawn off every hour.

The approximately 70% oxygen obtained in the bottom of the low-pressure column 16 is enriched to approximately 80% in the enrichment rectification column 102 and in the intermediate evaporator 100 and then passed to the final evaporator 20. The gaseous end product forms 25 200 Nm '/ hour of 80% oxygen, consisting of 18 800 Nm ^a / hour pure oxygen and 6400 Nm ⁸ / hour air.

Generation of 98% oxygen (Fig. 3)

From 103,000 Nm ⁸ / hour of air at a pressure of about 4.1 ata, after deduction of the switching losses, 100,000 Nm * per hour get into the prewash column 9. From the air fraction with about 20.6% oxygen content withdrawn from the top of the prewash column 9 every hour about ^{31,200 Nm 8 led} directly to the lower end of the pressure column 15, which is under a pressure of 3.8 ata, and 71,300 Nm ^{8 was} partially liquefied in the intermediate evaporator 100. The liquid part with about 36.5% oxygen content is returned to the top of the prewash column 9. The washing liquid flowing out of the prewash column, about 1120 Nm ^a / hour with about 43% oxygen content, is passed into the low-pressure column 16, in which there is a pressure of 1.3 ata. The part not condensed in the intermediate ^{evaporator 100, 57 500 Nm 3} / hour with about 17% oxygen content, is partially liquefied in the final evaporator 20 and the gas-liquid mixture with about 10.5% oxygen in the gas and about 25% oxygen in the liquid Introduced into the pressure column 15 at a suitable point above the feed point of the partial flow coming from the head of the prewash column 9. ^{22,300 Nm 3 of} gaseous nitrogen for the expansion turbine 36 are withdrawn from the head of the pressure column every hour. 800 Nm ³ / hour of liquid nitrogen with about 9% oxygen content pass from the upper part of the pressure column as scrubbing liquid into the low-pressure column 16. From the bottom of the pressure column 15, about 600 Nm ³ with about 33% oxygen content are drawn off every hour and at a suitable point in the low-pressure column 16 initiated. From the top of the low-pressure ^{column 16, about 58,700 Nm 3 of} nitrogen, which still has an O ₂ content of about 3.5%, are drawn off every hour. The approximately 82% oxygen obtained in the bottom of the low-pressure column is enriched to approximately 98% in the enrichment rectification column 102 and in the intermediate evaporator 100 and then passed to the final evaporator. The gaseous end product forms about 000 Nm ^s / hour 98% oxygen, consisting of about 18 600 Nm ³ / hour pure oxygen and Nm ^s / hour air.

Claims (20)

Patent claims: 1. Process for the production of oxygen gas with 70 to 98% CV content by low-temperature air separation in a double pectifier, especially in connection with regenerators for the heat exchange between separation air and separation products, with evaporation of the liquid from the bottom of the low-pressure column with the help of a Prewashing column exiting partially condensing air fraction in gaseous form, the non-condensed fraction of which is passed on to the pressure column of the double rectifier and whose liquefied fraction is returned as washing liquid to the prewashing column, while the washing liquid flowing out of the prewashing column is introduced into the low-pressure column below the inlet point of the pressure liquid from the sump characterized in that the product removed from the bottom of the low-pressure _{column is an intermediate product with a lower O 2} content than the end product, which intermediate product before evaporation d By intermediate evaporation with partial condensation, another fraction of the air from the prewashing column to the _{pressure column is brought to the O 2} content of the end product, with the vapors developed from the preliminary product during the intermediate evaporation being returned to the base of the low-pressure column. 2. The method according to claim 1, characterized in that the liquid from the low pressure column removed intermediate product by rectification by means of the intermediate evaporation Vapors are enriched with oxygen before it is subjected to intermediate evaporation will. 3. The method according to claim 1 or 2, characterized in that a first part of the from the prewash column exiting gaseous air fraction is led directly to the foot of the pressure column and the other part for heating the intermediate evaporation and the final evaporation of the product is used and then above the introduction point of the first part is introduced into the pressure column (Fig. 3). 4. The method according to one or more of claims 1 to 3, characterized in that the Condensate formed during the intermediate evaporation from the non-condensed fraction of the fractionation air separated and fed to the prewash column as washing liquid. 5. The method according to one or more of claims 1 to 3, characterized in that a Part of the condensates formed during the intermediate evaporation and final evaporation of the product to an ao point corresponding to its composition in the lower part of the pressure column. 6. The method according to one or more of claims 1 to 5, characterized in that for the recovery of oxygen gas with about 90% O ₂ content, the intermediate evaporation and the final evaporation is effected by two parallel partial flows of the air fraction emerging from the prewash column ( Fig. 1). 7. The method according to one or more of claims 1 to 5, characterized in that for the recovery of oxygen gas with less than 90% O ₂ content, the air fraction exiting the prewash column first to heat the final evaporation and after separation of the condensate formed Heating of the intermediate evaporation with further partial condensation is used (FIG. 2). 8. The method according to one or more of claims 1 to 5, characterized in that for the recovery of oxygen gas with more than 90% O ₂ content, the air fraction emerging from the prewash column first to heat the intermediate evaporation and after separation of the condensate formed Heating of the final evaporation is used with further partial condensation (FIG. 3). 9. The method according to any one of claims 5 to 8, characterized in that the product intermediate evaporation the condensate formed from the air fraction used for heating is fed to the prewash column as washing liquid, while that in the final evaporation of the product from the air fraction used for heating formed condensate of the pressure column of the double rectification at one of its composition corresponding Body is forwarded (Fig. 3). 10. The method according to any one of claims 5 to 8, characterized in that the final evaporation of the product condensate formed from the air fraction used for heating as washing liquid is fed to the prewash column, while that in the intermediate product evaporation from the air fraction used for heating formed condensate of the pressure column of the double rectifier at one of its composition corresponding Body is forwarded (Fig. 2). 11. The method according to claim 1, characterized in that that the intermediate evaporation is carried out as a circulation evaporation, the at with each circulation, non-evaporated liquid is separated and partially from the resulting vapors passed on as a liquid end product for final evaporation and the remaining amount together with the pre-product of the further evaporation removed from the low-pressure rectification column is subjected. 12. Device for performing the method according to claim 1, characterized by a Intermediate evaporator (100), the evaporation side to the bottom of the low pressure column (16) for Charging with liquid to be evaporated and connected for recirculation of the vapors developed is and the heating side on the one hand with the head of a prewash column (9) for loading with an air fraction to be partially condensed and, on the other hand, with the lower one Part of the pressure column (15) for discharging at least part of the air fraction used for heating communicates. 13. Device according to claim 12, characterized by the inclusion of an enrichment rectification column (102) in the liquid and vapor path between the evaporation side of the intermediate evaporator (100) and the sump of the Low pressure column (16). 14. Device according to claim 12 or 13, characterized by the formation of the intermediate evaporator (100) as a circulation evaporator with vapor separation to the low-pressure column (16) and Liquid discharge to the final evaporator (20) from the circulation line from the vapor separator to the Radiator. 15. Device according to claim 12, characterized by condensate separator (22, 101) in the discharges of the intermediate product evaporator (100) and final evaporator (20) in part condensed air fraction with an upper connection to the lower part of the pressure column (15) and lower Connection to the head of the prewash column (9). 16. Device according to claim 12, characterized by a condensate separator (101 or 22) in the derivation of the intermediate product evaporator (100) or final evaporator (20) partially condensed air fraction with an upper connection to the lower part of the pressure column (15) and lower connection to the head of the prewash column (9), while the outlet nozzle for the partially condensed air fraction from one of the two mentioned evaporators (20, 100) directly is connected to the lower part of the pressure column (15) (Figs. 2 and 3). 17. Device according to claim 12, characterized by a direct line with a throttle element between the head of the prewash column (9) and the foot of the pressure column (15) and through a parallel line to this, in whose way the heating jackets of the intermediate product evaporator (100) and final evaporator (20) are switched on (Fig. 3). 18. Device according to claim 17 for the method according to claim 6, characterized by Parallel connection of the heating jackets of the product intermediate evaporator (100) and final evaporator (20; Fig. 1). 19. Device according to claim 17 for the method according to claim 7, characterized by Series connection of the heating jackets of the product 509 S09 / 87 Intermediate evaporator (100) and final evaporator (20) in contrast to the evaporation sequence (Fig. 2). 20. Device according to approached 17 for the method according to approach, characterized by Series connection of the heating jackets of the product Intermediate evaporator (100) and final evaporator (20) in cocurrent to the evaporation sequence (Fig. 3). Considered publications:
German Auslegeschriften No. 1 099 564, 1 135 935. 1 sheet of drawings 509 509/87 2.65 © Bundesdruckerei Berlin