DE1551583A1 - Rectifying column of an air separation plant - Google Patents

Description

Rectifying Column of an Air Separation Plant The invention relates to to a rectification column of an air separation system, which air after the low temperature process liquefies and taking advantage of the difference between the boiling points the elementary Constituents of the air rectified and broken down into their main components, i.e. nitrogen, Oxygen and some noble gases decomposed. The usual rectifying column in an air separation plant consists of a first container into which air is introduced in saturation and there is also liquefied to liquid air and liquid nitrogen, what is called pre-separation who calls air; a second container which holds liquid nitrogen and liquid Air supplied to it from the first container into oxygen and nitrogen with predetermined degrees of purity below one almost equivalent to that of the atmosphere Decomposed pressure, and a main capacitor that is between the first and the second Container is arranged and the air supplied from the first container by means of cold liquefies and cools the liquid oxygen in the second container has been rectified. The rectifying column is one immediate device for separating air into nitrogen, oxygen and some Noble gases, so that the quality of this device is essentially all the efficiency of the air separation system, which is why enormous effort and expense of construction and manufacturing of this device.

In addition, the larger the system is made, the more difficult the problems become, and this to a multiplied extent. The drawing illustrates the prior art and some exemplary embodiments of the invention; 1 shows an overview plan showing the flow in the air separation plant to which the invention relates; Fig. 2 shows a rectifying column belonging to the plant of Fig. 1, in a vertical section through the main part of the rectifying column, which conventionally consists of a known linear tube type main condenser; 3 shows an exemplary embodiment of the rectifying column according to the invention in a vertical section through the main part of the rectifying column, in which a helical main condenser is installed; Zig. 4 shows a vertical partial section of the rectifying column according to FIG. 3; Figure 5 shows another embodiment of the invention with a vertical, schematic section through the main part of the rectification column, having a main capacitor outside of this column. 6 shows a vertical partial section of the rectifying column according to FIG. 5; 7, 8, 9 and @ 10 each show a vertical partial section, with which practical exemplary embodiments of the rectifying column according to the invention are given; and FIG. 11 is a property diagram of the rectifying column according to the invention showing the relationship between the depth of liquid oxygen and the saturation temperature. Fig. 2 shows a conventional rectifying column which contains the most popular linear tube type main condenser. To form the so-called main condenser, the rectifying column of this type comprises a first vessel 13, a second vessel 14, a lower plate 19 which separates the first from the second vessel, and a plurality of straight tubes 20 which are perpendicular to the lower plate 19 and attached to an upper plate 22 which supports a domed end plate 21. Accordingly, as the apparatus becomes larger in size and in the amount of air and liquid circulating, the lower and upper plates 19 and 22 become larger in diameter, thereby creating a need for the molded materials to be larger in size and heavier in weight .

However, it is difficult to not only use a plate as large as e.g. from about 4 to 6 m in diameter, technically castable, but also a majority of straight pipes to be welded and held to it, taking into account both mass and heat loss considerations are crucial. The weakest point of the rectifying column of this type lies in the fact that when the capacity is increased, the flow of air and of the liquid conveyed through the straight tubes 20 which make up the main condenser is capable of entering an unstable state, the so-called flooding state, to pass within the fluctuation range in which the amount to be treated is relatively small.

In such a case, the main capacitor cannot be cheap Cope with heat exchange, and in the worst case scenario, it turns out to be so severe Consequence that the operation of the device ceases completely.

In other words, according to the main condenser of this type, the nitrogen gas in the first container 1 "is cooled by liquid oxygen on the outside of the straight tubes while it rises in the straight tubes 20, and after being partially liquefied, it runs along the inner surfaces of these tubes down in the opposite direction to the upward flowing gas, ie in the direction of gravity, so that although the air and liquid are treated effectively in the device to some extent, once the amount of air and The invention is therefore based on the object of overcoming these deficiencies and proposing a new rectifying column which has a main condenser of relatively small dimensions and low pressure loss with stable properties and improved heat exchange efficiency and with the suitability for a large capacity air separation plant ice. This object is achieved in a rectifying column of an air separation plant with a main condenser between a first container and a second container, which liquefies the air for the purpose of rectification and separation into its components according to the low-temperature process, in that the main condenser has a plurality of helical shaped tubes that the nitrogen gas of the first container is introduced outside the helical shaped tubes and liquid oxygen of the second container is introduced into the helical shaped tubes, whereby a heat exchange takes place between them. In this way, not only is liquid oxygen in the helical tubes made to spontaneously circulate by the bubble pumping action, but nitrogen gas outside the tubes is also liquefied and flows in the direction equivalent to the flow of the gas. A plurality of the helical shaped tubes are attached to the periphery of the housing of the main capacitor.

The end of each helical tube is expediently on the circumference of the housing of the main capacitor attached via at least one annular plate, and one Core tube with two openings at both ends is in the middle of the group of helical shaped tubes arranged, wherein the upper opening of the core tube is at the upper part of the helical tube group and the lower opening rests on the plate of the first container.

The end of each helical tube is expediently on the circumference of the housing attached and arranged the housing below the second container. A manifold is expediently arranged at the lower socket of the housing, and a hydrocarbon absorption separator is connected at one point between the manifold and the second tank, liquid oxygen circulating in this separator.

Both ends of a plurality of helical shaped tubes are zwecii7) -_ L.'Lg over the upper and lower plates on the-. Housing fixed, the upper and the lower manifold to ( ': arranged ieäen plates, the manifold and the lower part of the second container connected to one another and the upper and the lower part of helical shape pipe group of the casing with the upper part of the first container is connected.

The pipe distributors and the poorer part of the second container are expediently connected to one another via the hydrocarbon absorption separating device.

A building material circulation device is expediently connected in series in the circuit in which the hydrocarbon absorption separating device is connected. Finally, it is expediently provided that the depth of the liquid oxygen in the second container is limited to approximately 2.m.

The features of the invention mentioned are explained in connection with the exemplary embodiments illustrated in the drawing.

According to FIG. 1 , the air is introduced from a feed coil 1 in order to flow on through a filter device 2 to remove fine dust, then the pressure is increased to a predetermined yaw rate by means of an air compressor 3.

The air heated by the pressure increase treatment is cooled by means of a flooding column 4 and then passed through a shuttle valve 5 into a cold storage device 6.

A plurality of cold storage devices are arranged in series , which hold the cold of the oxygen returned from the separation system, and switch to one another in a predetermined rhythm.

The air is exposed to the aforementioned cold effect, so that it is liquefied by the low-temperature process.

On the other hand, the water of the flooding column 4 absorbs the Heat the air after compression, and its. Temperature is increased by so that it must be cooled.

To cool the water by means of the cold of nitrogen flowing from is returned to the separation plant, an evaporator cooling device 7 is arranged for this.

The so by the evaporator cooling device 7 to a predetermined Temperature cooled water is returned to a water tank 8 and through a Pump 9 circulated.

The air from said cold storage devices 6 is partially Introduced into an expansion device 11 via an automatic control valve 10 and, after their temperature is further lowered by the Joule-Thomson effect, transferred into a second container 14 of the rectification column 12.

The remaining air thus divided is fed into the second container 14 introduced.

Having heat between the rectified and separated air in the Column exchanged and nitrogen from the first Container 13 is removed by a second capacitor 15, explosives such as acetylene and the like, removed by an acetylene separator 16.

After the oxygen leaves the "acetylene separator 16" it takes its temperature by releasing cold to the cold storage device 6 again and is then transferred to the consumption system.

It will also become liquid air after getting the lower part of the first Container was removed into the second container 14 via a liquid air filter device 17 and a strong cooling device 18 introduced.

The rectification column 12 is an immediate device for separation the air into nitrogen and oxygen, and therefore determines the quality of this facility the efficiency of the whole air separation system, so that a highly efficient rectifying column is required.

The rectifying column according to the invention fulfills these requirements and is shown in FIGS. 3-6.

3 and 4 represent a schematic overview and illustration of the parts of the rectifying column, the main condenser according to the invention being arranged directly under the lower part of the second vessel at a position between the second vessel 14 and the first vessel 13. FIGS. 5 and 6 each show a schematic overview of an image or of the parts of the rectification column, wherein the main capacitor is arranged between reasonable according to the invention in series with the first container and the second container at a location.

. With reference to Figures 3 and 4 it should be noted that reference numeral 23 denotes a hollow core tube; while a lower opening 24 of the core tube connected to a plate 25 of the first container 13 and an upper opening 26 positioned so that it protrudes from a group 27 of helical form tubes, and a plurality of spiral shaped pipes 28 is the concomitant use of a spacer 29 in a plurality of layers wrapped around the core tube , the helical form tubes are wrapped around the core tube 24 in such a way that the length of each tube is equal to one another, and both ends of these tubes are then welded to upper and lower annular plates 31 and 32 which extend around the circumference of the Housing 30 of the main capacitor attached end.

The circulation resistance of the spiral-shaped tubes is dimensioned so that it is almost equal to one another over their entire length. If : the thickness of the housing 30 is solid enough to attach the helical shape 28 to it, one can use the annular plates. Save 31 and 32. As for the socket, it is possible to fix the lower end of each helical tube 28 to the circumference of the housing in the radial direction through the annular plate 31 and to attach the upper end of the tube to a cover piece 33. @ `° 'to be Gk 33 aasgebildet sufficiently strong to form the spiral tubes 28 to be able to attach thereto: k:; in this case, the Cover B must..

Then the welding operation in the circumferential direction is reduced by one circumferential part when comparing this structure with that of the ring-shaped plate 32.

The word "circumference" in this invention means the outer peripheral surface and encompasses both the housing 30 and the cover 33.

The housing 30 and the cover 33 can be shaped by embossing.

In order to prevent liquid oxygen from entering the first container 13 oozes out, the lower edge of the housing 30 is hermetic to the periphery of the upper one Edge of the first container 13 is welded.

The nitrogen gas which has risen in the first container 13 is introduced into the housing 30 through the upper opening 26 after flowing through the core tube 23. During this process, the nitrogen gas is passed through the Y @ a? - 'rrohr 23 @@ e leads that it is to the upper part of the helical tube group On the other hand, each helical tube 28 in the housing 30 is filled with liquid oxygen from the lower part of the second container 14. Accordingly, the nitrogen gas introduced into the casing 30 is liquefied by absorbing cold of the liquid oxygen in the tubes in the course of passing through the helical tube group 27 from the upper side to the lower side.

Nitrogen transformed into liquid droplets slowly sinks into the space outside these pipes in the same direction as the nitrogen gas, so that there is no eddy current, i.e., a washout phenomenon as in the case of the conventional main condenser with straight tubes. On the other hand will liquid oxygen in the tubes is heated and partly by the nitrogen gas or mostly gasified, so that it is within the helical tubes through the Blow pump effect moves in the opposite direction to nitrogen gas.

In other words, liquid oxygen from the lower is annular Plate 31 sucked through the upper annular plate 32 into the second container 14 transferred and put into circulation spontaneously without a special circulation pump is required.

The deeper the depth of the liquid oxygen in the second container 14 is made, the easier the spontaneous circulation becomes and the higher the heat exchange efficiency increases; however , there is another problem involved , so that this effect is limited.

As the depth of the liquid oxygen is increased , the greater the pressure on the testicle of the column of the second container 14 and the higher the degree of saturation of liquid oxygen.

This relationship is shown in Figure 11; the saturation temperature of liquid oxygen varies inversely proportional to the rise of the liquid depth.

On the other hand, in order to rectify liquid air with the rectifying column and decompose it into oxygen and nitrogen , it is necessary to have a difference of approximately 200 between the liquid oxygen of the sliding vessel 14 and the nitrogen gas of the first vessel 13.

This means that the depth of the liquid oxygen is limited to some extent and , depending on the capacity of the device, usually remains within a range of up to approximately 1 meter. Ba has been shown by experiments that the temperature of the nitrogen gas of the first container in the rectification column remains at a level of approximately 96.65 ° K during operation, so that the temperature of the lower surface of the liquid oxygen at the lower end of the tented container does not exceed 94, 65 ° K and, taking into account the information on FIG. 11 mentioned, the depth of the liquid oxygen will be approximately 2 m according to the temperature mentioned.

Accordingly, the depth in the case of spontaneous circulation m limited to a level of approximately. 2

In the embodiment shown in FIGS. 5 and 6 , in order to introduce the nitrogen gas of the first container 13 into a housing 34, the housing and the first container 13 are connected to one another by the conduit 35, and are also connected to the to introduce liquid oxygen of the second container 14 into each helical tube 28 , the upper plate 36 and the lower plate 36 (not shown) to which the helical tubes are fixed at both ends, and the second container 14 through the conduits 37 and 38, are connected.

Here, an upper pipe distributor 39 and a lower pipe distributor 40 are arranged on the upper and the lower plate, respectively. The introduced from the conduit 35 into the housing 34, nitrogen gas is by means of cold receiving during the transit passage liquefied between the helical shape pipes 27, and introduced by I the conduit 38 back into the first container 13, and on the other hand, liquid oxygen in the tubes is partly or for the most part gasified, circulates spontaneously in the pipes by means of the bladder pump eßbktes and is then reintroduced into the second container 14 through the pipe 37 similar to the structure in FIGS. 3 and 4. FIG. 7 shows an example of the structure according to FIG. 4, in order to avoid explosive substances, such as 8. Acetylene and the like, which are present in the liquid oxygen in the second container 14, a hydrocarbon absorption separator 41 is arranged in the circuit of the liquid oxygen.

In other words , the hydrocarbon absorption separator $ 1 is located outside the container, connected at a point between the manifold 42 and with the periphery of the lower "annular plate 31 of the housing 30 in the second container 14 and the lower part of the second container 14 through the conduits 43 and 44. Hydrocarbons such as acetylene and the like contained in the liquid oxygen in the lower part of the second container 14 are continuously removed by the hydrocarbon absorption separator 4 1 , so that it is possible to remove oxygen from the second container 14 to be drawn directly from the system as the end product without the need for a second condenser 15 and / or an acetylene removal device 16, which is (are) usually present in the liquid oxygen discharge line , which has the advantage that there is no pressure loss as in the previous device , the pressure of the sour fabric product directly from the conventional value, 100 to 500 mm water column, to 1500 to 2000 mm water column (working pressure of second container '_4) is increased and it is possible that the Start-up of the air compressor and the liquid gas compressor to @;. ._. @ ,. . Fig. 6 shows an example of the rectifying column shown in FIG. 6. Here are explosive substances such as acetylene or the like., That are present in the liquid oxygen through the hydrocarbon-Absorptiontrenneinriehtung 41 similar to the structure of FIG. 7 is removed.

-In Fig. 9 is provided a small Saueratoffumlaufeinrichtung k5 which generates such a circulation force as the hydrocarbon Absorptionstrenneinriehtung corresponds to the circulation resistor 41, which is arranged in the circuit of flUseigen oxygen.

The T Sauerstoffumlaufeinriehtung is constructed similar to the main capacitor according to Fig. 6.

Thus, the absorption power of oxygen is greater than that of FIG. 7, and the amount of liquid oxygen, which is introduced into the hydrocarbon-absorbing separating device is greatly increased, so that hydrocarbons are effectively removed from the liquid oxygen.

Heat is exchanged between the nitrogen gas, which is introduced through the pipe 46 into the first container 13 , and liquid oxygen in the course of the descent between the helical tube group 27 of the building material circulation device 45, so that by means of the reintroduction of the nitrogen gas into the first container 13 through the pipe 47, the nitrogen gas is further liquefied by cryogenic processes. "Also, liquid oxygen introduced from the conduit 48 into the helical shaped tubes 28 @ is heated and gasified by the nitrogen gas and then reintroduced into the second container 14 through the conduit 49.

Fig. 10 shows a rectifying column in which the first vessel 13 and the second container 14 are arranged separately from one another.

In this case, one end plate 51 and the upper part are the first Container connected to each other via the pipe 52, so that the nitrogen gas in the first container 13 is inserted into a housing 50, and an end plate 54 and the upper part of the first container 13 are also via the conduit pipe 53 connected to one another, so that in the housing 50 liquefied nitrogen again is introduced into the first container 13 as a reflux liquid.

The lower part of the second container 14 and a lower annular one Plate 56 are interconnected so that liquid oxygen of the lower part of the second container-is inserted into the spiral-shaped tubes 28, and the lower Part of the second container 14 and an upper annular plate 58 are also included Connected to one another via the conduit 59, so that they are in the helical shaped tubes @ 28 gasified oxygen is reintroduced into the second container 14.

A manifold 60 is attached to the upper annular plate 58 and a manifold 61 is attached to the lower annular plate 56. --- For spontaneous circulation of liquid oxygen and liquid nitrogen, the first container 13, the case 50 and the second container 14 are constructed to be predetermined. Height differences hl and h2 according to FIG. 10; However, if in this case liquid nitrogen and liquid oxygen are forced to circulate by means of a pump, the parts can be arranged at the same height.

As explained above, when the first tank 13 and the second tank 14 are separated from each other , the height of the rectifying column is considerably decreased, earthquake resistance is favorably maintained, and the height of the cold storage tank is decreased with the same refrigeration capacity. Accordingly , this configuration facilitates the manufacture of the cold storage tank or the installation and operation of each device.

Claims (1)

Claims J Rectilizing column of an air separation plant with a main condenser between a first container and a second container, which liquefies the air for the purpose of rectification and separation into its components according to the animal temperature process, characterized in that the main condenser (12) has a plurality of helical tubes (28 ) up, has since introduced # ßtiokatoftgas of the first container (13) outside the wendeltormrohre and introduced liquid Sauerstott the second container (14) into the spiral-shaped tubes, a heat exchange takes place thereby between them. 2. Rectifying column according to claim 1, characterized in that liquid oxygen circulates in the tubes by the bubble pumping action, the nitrogen gas outside the tubes (28) is liquefied with the aid of cooling and liquid nitrogen thus flows in the same direction as the 8tiokstoffgas. j. Rektitisierkolonne according to claim 1, characterized in that, since & the = talking a plurality of the spiral shaped pipes (28), which liquid oxygen from the lower part of the second container (I @) engage in the tubes, corresponding to the periphery of the housing (30) of the main capacitor (12 ) are distributed and the nitrogen gas from the first container (13) into the space outside the group (27) of tubes, which is composed of the helical tubes (28) , is conducted , whereby the heat exchange between the nitrogen gas and the liquid oxygen results in the pipes. 4. Rectifying column according to claim 3, characterized in that the tube ends via at least one annular plate (31 or 32) are attached to the housing circumference (30) and that a core tube (23) with two end openings (24,26) in the middle of the Group of helical tubes (28) is arranged, wherein the upper opening (26) is arranged at the upper part of the helical tube group (27) and the lower opening (24) is carried by the plate (25) of the first container (13). @. Rectifying column according to Claims 3 and 4, characterized in that the main condenser housing (30) is located below the second container (14). .. b. Rectifying column according to Claim 3 and subsequent claims, characterized in that a manifold (40 or 42) is attached to the lower socket part of the helical shaped pipes (28) and a hydrocarbon absorption separating device (41) is arranged at a place between the manifold and the second container (14) is so that liquid oxygen passes through the separator (41). 7. Rectifying column according to claim 1, characterized in that both ends of a plurality of the helical shaped tubes (28) are attached to the housing (34) via an upper and lower plate (36) and an upper and a lower manifold (39 and 40, respectively) are attached to the upper or lower plate (36,36) that furthermore the pipe manifolds and the lower part of the second container (14) are connected to one another and the upper and lower part of the group of helical tubes (28) of the housing (34) are correspondingly connected to the upper part of the first container (13). B. rectifying column according to claim 6 and 7, characterized in that the two manifolds (39, 40) and the lower part of the second container (14) are connected to one another via the hydrocarbon absorption separating device (41). 9. Rectifying column according to claim 8, characterized in that an oxygen circulation device (45) is connected in series with the circuit in which the hydrocarbon absorption separation device (41) is present for the purpose of removing the liquid oxygen in the lower part of the second container (14) Hydrocarbons is located, which allows compensation for the circulation resistance of the separator (41). 10. rectifying column according to claim 1, characterized in that the depth of the liquid oxygen in the lower part of the second container (14) is about 2 m.