DE10152356A1 - Recovering argon in a low temperature decomposition comprises removing an oxygen fraction deficient in volatile components from an intermediate point of a rectification section and fed to a pure oxygen column - Google Patents

Abstract

Providing a process for recovering argon in a low temperature decomposition. Process for recovering argon in a low temperature decomposition comprises: (a) feeding an argon-rich oxygen fraction (25) into a first rectification section (26, 28); (b) introducing an oxygen-deficient gas (32) from the first rectification section into a second rectification section (29); and (c) removing crude argon from the second rectification section; an oxygen fraction deficient in volatile components being removed from an intermediate point of the first rectification section and fed to a pure oxygen column (49), and pure oxygen being removed from the pure oxygen column. An Independent claim is also included for an apparatus for recovering argon in a low temperature decomposition. Preferred Features: The first rectification section is arranged in a first container and a second container. The argon-enriched oxygen fraction is fed to the first container and then to the second container from the upper region of the first container. A liquid fraction (36) is removed from the lower region of the second container and a first partial stream of the liquid fraction is injected into the upper region of the first container as run-back liquid. The oxygen fraction deficient in volatile components which is fed to the pure oxygen column consists of a second partial stream of the liquid fraction from the second container.

Description

The invention relates to a process for the production of argon by low-temperature Decomposition in which an argon-enriched oxygen fraction into a first Rectification section is initiated, an oxygen-depleted gas from the first Rectification section is introduced into a second rectification section in which it is further depleted of oxygen, from the second rectification section Raw argon is taken.

"Rectification section" here means an area in which countercurrent Mass exchange takes place, which means in particular mass exchange elements such as has ordered and / or disordered packing and / or mass transfer trays. On Rectification section can be in one container or in several gas and liquid side containers connected in series. It can be about a distillation column, but in particular also a pure reinforcement column and / or act purely a power column. Is a rectification section in more than arranged in a container, preferably prevails essentially in all containers the same pressure. This is achieved in that in the gas line between the No pressure-changing measures are carried out on containers. The first" and the "second" rectification section in the sense of the invention are different Containers arranged.

Such a method and a corresponding device are described in EP 628777 B1 (= US 5426946). Here is the usual form of crude argon rectification in two rectification sections connected in series, each in a own containers are arranged.

The invention is based on the object, in such a system additionally to obtain highly pure oxygen.

This object is achieved in that from an intermediate point of the first Rectification section a depleted in less volatile constituents  Oxygen fraction is removed and introduced into a pure oxygen column, and that highly pure oxygen is taken from the pure oxygen column.

Such a procedure is known from EP 299364 B1 (= US 4824453) known. However, their teaching cannot be easily compared with that of EP 628777 B1 because the latter relates to crude argon rectification, the is equipped with packing, in particular ordered packing. EP 299364 B1 (= US 4824453), however, the withdrawal of an intermediate fraction requires few soils above the bottom of the crude argon rectification. Such a deduction is with one packed column not possible with reasonable equipment expenditure. opposite however, these concerns address a combination of the teachings of the invention made both documents mentioned.

Two variants are available for the implementation of the invention The following are explained in more detail.

In a first variant of the invention, the section of crude argon rectification, the to retain the less volatile components from the highly pure The oxygen product is placed in a separate container by the first one Rectification section in a first container and in at least a second container is arranged, the argon-enriched oxygen fraction in the first container introduced and gas from the top of the first container into the second Container is introduced, further a liquid fraction from the lower part of the taken from the second container, a first partial flow of the liquid fraction as Return liquid is fed into the upper area of the first container and the on less volatile constituents depleted oxygen fraction, which in the Pure oxygen column is introduced through a second partial flow of liquid Fraction from the second container is formed.

In this way, all parameters of the two subsections of the first Rectification section can be optimized independently, for example Diameter, spatial arrangement and / or type of used Mass transfer elements. The first container can be as efficient as possible Depletion of less volatile components are designed, the second Container on the oxygen-argon separation.  

It is advantageous if the first container is a mass transfer tray and the second Containers pack, especially ordered pack, has. Preferably contains the first container only floors, for example three to 15, preferably about ten practical floors. The second container can also be combinations of pack and have floors; it preferably contains only an ordered pack.

In a further embodiment of the first variant of the invention, the first container at least partially higher than the pure oxygen column. For example the first container immediately above the pure oxygen column or the second Be placed container. This allows the residual fraction from the first container, the usually liquid in the swamp, without additional conveyors such as Example, a pump removed from the first rectification section and, for example one step for further processing. If the argon and Pure oxygen extraction on a two-column system for low-temperature separation is connected by air, the liquid fraction flows solely due to the geodetic Slope back into the low pressure column. In this case, it is advantageous if the first container is placed higher than the intermediate point of the low pressure column to which the liquid fraction flows back.

The first and the second partial flow of the liquid fraction from the lower area of the second container can be transported by means of a common conveyor become. As a result, the - which is required anyway in the case of a divided crude argon column - Pump at the same time for transporting or lifting the depleted oxygen-depleted components.

In a second variant of the invention, the first rectification section is in one only container arranged below the intermediate point at which the depleted oxygen fraction depleted of less volatile constituents, Mass transfer trays and packing above this intermediate point, in particular orderly pack. In this way it is also possible to part of the first rectification section, which is used to hold back the less volatile Components can be realized in a particularly cost-effective manner without the To influence argon-oxygen separation significantly.  

Both variants of the invention are fundamentally independent of the source of the argon-enriched oxygen fraction. They are preferably related applied with a low temperature air separation plant. Here, feed air is in disassembled a two-column system that has at least one high-pressure column and one Has low pressure column, at least a portion of the feed air in the High pressure column is introduced and the argon-enriched oxygen fraction, which is introduced into a first rectification section, from the low pressure column is subtracted.

With both variants, too, it is favorable if the pure oxygen column passes through indirect heat exchange with a feed air stream or with a gas fraction the high pressure column is heated.

The invention also relates to a device for the production of argon Claim 9.

The invention and further details of the invention are described below of exemplary embodiments illustrated in the drawings. in this connection demonstrate

Fig. 1 shows a first embodiment for the first variant of the invention with bake of the pure oxygen column with nitrogen from the head of the high-pressure column,

Fig. 2 shows another embodiment for the first variant of the invention with bake of the pure oxygen column by means of a gas fraction from the lower portion of the high-pressure column,

Fig. 3 shows a third embodiment for the first variant of the invention with heating the pure oxygen column by means of feed air and

Fig. 4 shows an embodiment for the second variant of the invention.

In the process of Fig. 1, compressed, cleaned and cooled to about dew point feed air is introduced into the high pressure column 2 of a two-column system for nitrogen-oxygen separation, which also has a low-pressure column 3 and a main condenser 4 , via which the two Columns are in a heat-exchanging connection.

A first part 6 of the gaseous top nitrogen 5 of the high pressure column 2 is liquefied in the main condenser 4 against evaporating bottom liquid of the low pressure column 3 . The condensate 7 obtained in this way is fed into the high-pressure column and is used there for the first part as a return. A second part of the liquid nitrogen 7 from the main condenser 4 is fed via line 8 , a subcooling countercurrent 9 , line 10 and throttle valve 11 as a return to the low-pressure column 3 or withdrawn via line 12 as a liquid nitrogen product.

Liquid crude oxygen is obtained in the sump of the high-pressure column 2 . This is also led via line 13 to the supercooling counterflow 9 . A portion 15 of the supercooled raw oxygen 14 is throttled directly into the low-pressure column 3 ( 16 ).

In addition to the liquid nitrogen 12 already mentioned, gaseous nitrogen 17 , 18 , impure nitrogen 19 , 20 , gaseous oxygen 21 and liquid oxygen 22 , 23 are withdrawn as products from the low-pressure column 3 , if appropriate after passage through the supercooling counterflow 9 . The purity of the oxygen products 21 , 23 is, for example, 99.5 to 99.6 mol%. If necessary, a portion 24 of the top nitrogen 5 of the high pressure column 2 can be obtained directly as a gaseous pressure product.

An argon-enriched oxygen fraction is introduced via line 25 from an intermediate point of the low-pressure column into the lower region of a sieve plate column 26 . Residual liquid 27 from the bottom of the sieve tray column 26 flows back to the same location of the low-pressure column 3 . The sieve tray column contains only trays as mass transfer elements, for example three to 15, preferably about ten practical trays. These soils retain less volatile components such as hydrocarbon, krypton, xenon and carbon dioxide from the rising steam.

The sieve tray column 26 together with a first crude argon column 28 forms the "first rectification section" in the sense of the invention ("first container" 26 and "second container" 28 ). The "second rectification section" is implemented by a second crude argon column 29 . These three containers form the crude argon rectification, in that gas 30 is passed from the top of the sieve tray column 26 via line 31 to the sump of the first crude argon column 28 and the top gas 32 of the first crude argon column 28 flows on to the sump of the second crude argon column 29 , in each case without pressure-changing measures in lines 30 , 31 and 32 . In the opposite direction, the bottom liquid 33 , 35 of the second crude argon column 29 is applied to the top of the first crude argon column 28 and liquid 36 , 38 , 39 forms the return for the sieve tray column 26 . The pumps 34 and 37 serve to overcome the corresponding static height.

The return liquid for the entire crude argon rectification ( 29 , 28 , 26 ) is generated in the top condenser 40 of the second crude argon column 29 . For this purpose, part 41 of the supercooled raw oxygen 14 is evaporated from the high-pressure column 2 in the evaporation space of the top condenser 40 . Gas 42 formed in the process is conducted to the low-pressure column 3 . Raw argon is withdrawn in gaseous form via line 43 from the second raw argon column 29 or the top condenser and fed to a pure argon column 44 at an intermediate point. A nitrogen-rich residual gas 55 is drawn off at the top thereof, and liquid pure argon 45 is obtained in the sump. In a top condenser 46 and a bottom evaporator 47 , return liquid or rising vapor is generated in the known manner.

To obtain high-purity oxygen, part of the bottom liquid 36 , 38 of the second crude argon column 28 is applied to the top of a pure oxygen column 49 as an oxygen fraction 48 depleted in less volatile constituents, where it is separated from more volatile components such as argon and nitrogen and partly from CO. Highly pure oxygen product 50 is withdrawn from the bottom of the pure oxygen column 49 . It has a significantly higher purity than the oxygen product 21 , 22 , 23 of the low pressure column 3 , namely for example 99.9999 mol%. The highly pure oxygen product can also be drawn off in whole or in part in gaseous form (not shown). Residual steam 51 from the top is returned together with gas from the top of the sieve tray column 26 into the first crude argon column 28 . The pure oxygen column 49 has a bottom evaporator 52 which is operated with top nitrogen 5 , 53 from the high pressure column 2 . Liquid nitrogen 54 from the bottom evaporator 52 is returned to the high pressure column 2 .

The sieve plate column 26 is arranged in such a way that its sump is at a greater height than the mouth of the lines 25 or 27 into the low-pressure column 3 . In the example, it is built up above the pure oxygen column 49 . The pure oxygen column 49 is placed in such a way that no additional pumps are required for its operation. The pump 37 - which is required anyway in the case of a divided crude argon column - is used in common for introducing the return liquid into both columns 26 , 49 . The residual liquid 27 of the sieve plate column 26 , like the liquid 54 generated in the sump evaporator 52 , flows back to the two-column system solely on account of the geodetic gradient.

The number of trays in the sieve tray column can be easily attributed to the contamination of the Adapt ambient air with less volatile components without this Influence on the other rectification steps.

The heating of the pure oxygen column 49 with nitrogen shown in FIG. 1 is to be preferred with regard to the separation efficiency. Figs. 2 and 3 show alternatives for the choice of heating medium for the bottoms evaporator 52; otherwise they do not differ from FIG. 1.

In Fig. 2, is withdrawn from the lower region of the high-pressure column 2 and passed into the evaporation space of the bottoms evaporator 52 via conduit 253 a gaseous fraction, which has approximately the composition of the feed air. 1 The condensate 254 formed there flows back to the high pressure column 2 .

Fig. 3 differs therefrom in that a partial stream of the feed air 1 is used as a heating medium for the bottoms evaporator of 52 353, which is upstream of the high pressure column 2 diverted air from the high pressure column. The liquefied air 354 flows back to the high-pressure column 2 .

The second variant of the invention is shown in FIG. 4. Only the differences from the system of FIG. 1 are described below.

The mass transfer trays 426 , which are accommodated in the sieve tray column 26 in FIG. 1, are located in FIG. 4 in addition to the packing section 455 in the first crude argon column 428 . The "first rectification section" is thus arranged in a single container. (The combination of packings and trays in a raw argon column is known per se from US 5019144, but here a completely different purpose is pursued.) Two pumps are necessary here. A ( 437 ) conveys the oxygen fraction 436 depleted of less volatile constituents, which is removed in liquid form above the sieve trays 426 , to the top of the pure oxygen column 49 ; a second pump ( 456 ) lifts the residual liquid 427 in order to be able to feed it into the low-pressure column 3 .

The bottom evaporator 52 of the pure oxygen column 49 is heated in FIG. 4 as in FIG. 1 with high-pressure column nitrogen 53 . Alternatively, heating with a fraction from the high-pressure column (as in FIG. 2) or with feed air (as in FIG. 3) is possible.

Claims (9)

1. A process for the production of argon by low-temperature decomposition, in which an argon-enriched oxygen fraction ( 25 ) is introduced into a first rectification section ( 26 , 28 , 426 , 455 ), an oxygen-depleted gas ( 32 ) from the first rectification section into a second rectification section ( 29 ) is introduced in which it is further depleted of oxygen, crude argon ( 43 ) being removed from the second rectification section ( 29 ), characterized in that an intermediate point of the first rectification section ( 26 , 28 , 426 , 455 ) is used less volatile components depleted oxygen fraction (36, 38, 48, 436) is removed and is introduced into a pure oxygen column (49), and that is removed from the pure oxygen column (49), high purity oxygen (50). 2. The method according to claim 1, characterized in that the first rectification section is arranged in a first container ( 26 ) and in at least a second container ( 28 ), that the argon-enriched oxygen fraction ( 25 ) is introduced into the first container ( 26 ) and gas ( 30 , 31 ) from the upper region of the first container ( 26 ) is introduced into the second container ( 28 ), that a liquid fraction ( 36 , 38 ) is further removed from the lower region of the second container ( 28 ), a first partial flow of the liquid fraction is fed as reflux liquid ( 39 ) into the upper region of the first container ( 26 ) and that the oxygen fraction depleted in less volatile constituents, which is introduced into the pure oxygen column ( 49 ), through a second partial stream ( 48 ) of the liquid fraction ( 36 , 38 ) is formed from the second container. 3. The method according to claim 2, characterized in that the first container ( 26 ) mass transfer trays and / or the second container ( 28 ) packing, in particular ordered packing. 4. The method according to claim 2 or 3, characterized in that the first container ( 26 ) is arranged higher than the pure oxygen column ( 49 ). 5. The method according to any one of claims 2 to 4, characterized in that the first and the second partial flow of the liquid fraction ( 36 ) from the lower region of the second container ( 28 ) are transported by means of a common conveyor ( 37 ). 6. The method according to claim 1, characterized in that the first rectification section ( 426 , 455 ) is arranged in a single container ( 428 ), below the intermediate point at which the depleted oxygen fraction ( 436 ) is removed, mass transfer trays ( 426 ) and above this intermediate point pack, in particular ordered pack ( 455 ). 7. The method according to any one of claims 1 to 6, characterized in that feed air ( 1 ) is broken down into a two-column system which has at least one high-pressure column ( 2 ) and one low-pressure column ( 3 ), at least part of the feed air is introduced into the high-pressure column ( 2 ) and the argon-enriched oxygen fraction ( 25 ), which is introduced into a first rectification section ( 26 , 28 , 428 ), is withdrawn from the low-pressure column ( 3 ). 8. The method according to any one of claims 1 to 7, characterized in that the pure oxygen column ( 49 ) is heated by indirect heat exchange with a feed air stream ( 353 ) or with a gas fraction ( 53 , 253 ) from the high pressure column ( 2 ). 9. Apparatus for the production of argon by cryogenic decomposition with an argon transfer line ( 25 ) for introducing an argon-enriched oxygen fraction into a first rectification section ( 26 , 28 , 426 , 455 ), with a gas line ( 32 ) for introducing an oxygen-depleted gas from the first Rectifying section into a second rectifying section ( 29 ) for further oxygen depletion and with a raw argon removal line ( 43 ) for removing raw argon from the second rectifying section ( 29 ), characterized by a line ( 36 , 38 , 48 , 436 ) for removing one wherein the pure oxygen column (49) depleted in less volatile components oxygen fraction from an intermediate point of the first Rektifizierabschnitts (26, 28, 426, 455) which is connected to a pure oxygen column (49) includes a product line (50) for withdrawing high purity oxygen.