US20240377131A1

US20240377131A1 - Plant and process for low-temperature fractionation of air

Info

Publication number: US20240377131A1
Application number: US18/687,650
Authority: US
Inventors: Stefan Lochner
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2021-09-01
Filing date: 2022-08-26
Publication date: 2024-11-14
Also published as: WO2023030683A1; EP4396509A1; TW202316070A; WO2023030682A3; CN117980678A; US20240377129A1; TW202311683A; KR20240059622A; CN117980679A; KR20240057420A; EP4396508A2; WO2023030682A2

Abstract

The invention relates to a plant for low-temperature fractionation of air, having a rectification column system comprising a high-pressure column, a divided low-pressure column and an argon column, and a coldbox system comprising a first coldbox, a second coldbox and a third coldbox. The high-pressure column is disposed beneath the lower section of the low-pressure column. The high-pressure column together with the lower portion of the low-pressure column is disposed in the first coldbox, and the top portion of the low-pressure column in the second coldbox. It is proposed that the argon column or one or more sections of the argon column be disposed in the third coldbox. The pure oxygen column is disposed in the second coldbox. The present invention likewise provides a corresponding process.

Description

The present invention relates to a plant and a method for low-temperature air separation according to the preambles of the independent claims.

PRIOR ART

The production of air products in the liquid or gaseous state by cryogenic separation of air in air separation plants is known and described, for example, in H.-W. Häring (editor), Industrial Gases Processing, Wiley-VCH, 2006, in particular Section 2.2.5, “Cryogenic Rectification.”
Air separation plants have rectification column systems which can be designed as two-column systems, in particular as classical Linde double-column systems, but also as triple-column or multi-column systems. In addition to rectification columns for obtaining nitrogen and/or oxygen in the liquid and/or gaseous state, i.e., rectification columns for nitrogen-oxygen separation, rectification columns for obtaining further air components, in particular of argon, can be provided.
The rectification columns of the mentioned rectification column systems are operated at different pressure levels. Known double-column systems have what is known as a high-pressure column (also referred to as a pressure column, medium-pressure column, or lower column) and what is known as a low-pressure column (also referred to as an upper column). The high-pressure column is typically operated at a pressure from 4 to 14 bar, in particular at approximately 5.3 bar, or at approximately 11 bar. The low-pressure column is typically operated at a pressure in a pressure range from 1 to 4 bar, in particular at about 1.4 bar, but also at 3 bara. In certain cases, higher pressures can also be used in the low-pressure column which can also be operated at 2-4 bara and the pressure column at 9-14 bara. The specific pressures cited here and below are absolute pressures at the top of the respective indicated rectification columns.
In known methods and plants for low temperature separation of air, an oxygen-enriched, nitrogen-depleted liquid is formed in a lower region of the high-pressure column and withdrawn from the high-pressure column. This liquid, which in particular also contains argon, is at least partially fed into the low-pressure column and further separated there. Before being fed into the low-pressure column, it can be at least partially evaporated, wherein optionally evaporated and unevaporated fractions can be fed into the low-pressure column at different positions.
In order to extract argon, air separation plants with crude and pure argon columns can be used. An example is illustrated in Häring (see above) in FIG. 2.3A and described starting on page 26 in the section “Rectification in the Low-pressure, Crude and Pure Argon Column” and also starting on page 29 in the section “Cryogenic Production of Pure Argon.” As explained there, argon accumulates in corresponding plants at a certain height in the low-pressure column. At this or at another favorable point, optionally also below the argon maximum, argon-enriched gas with an argon concentration of typically 5 to 15 mole percent can be withdrawn from the low-pressure column and transferred into the crude argon column. A corresponding gas typically contains about 0.05 to 100 ppm of nitrogen and otherwise substantially oxygen. It should be expressly emphasized that the indicated values for the gas drawn off from the low-pressure column represent only typical example values.
The crude argon column serves substantially to separate off the oxygen from the gas withdrawn from the low-pressure column. The oxygen separated off in the crude argon column or a corresponding oxygen-rich fluid can be returned to the low-pressure column in liquid form. The oxygen or the oxygen-rich fluid is typically fed into the low-pressure column several theoretical or practical plates below the feed point for the oxygen-enriched, nitrogen-depleted, and optionally at least partially evaporated liquid withdrawn from the high-pressure column. A gaseous fraction which remains in the crude argon column during the separation and contains substantially argon and nitrogen is further separated in the pure argon column to obtain pure argon. The crude and the pure argon column have top condensers which can be cooled in particular with a part of the oxygen-enriched, nitrogen-depleted liquid withdrawn from the high-pressure column, which partially evaporates during this cooling. Other fluids can also be used for cooling.
In principle, a pure argon column can also be dispensed with in corresponding plants, wherein it is typically ensured here that the nitrogen content at the argon transition is below 1 ppm. However, this is not a mandatory prerequisite. Argon of the same quality as from a conventional pure argon column is in this case withdrawn from the crude argon column or a comparable column, typically slightly further down than the fluid conventionally transferred into the pure argon column, wherein the plates in the section between the crude argon condenser, i.e., the top condenser of the crude argon column, and a corresponding withdrawal serve in particular as barrier plates for nitrogen. The present invention can be used with such an arrangement without a pure argon column. Since the crude argon column or a comparable column in such an arrangement is already used for pure argon production and not for crude argon production, an “argon column” is also referred to below. An argon column can therefore be a conventional crude argon column (which is used with or without a pure argon column) or a corresponding crude argon column modified for pure argon production.
In order to improve the construction height of a corresponding air separation plant and its prefabricability, EP 2 965 029 B1 proposes the division of the low-pressure column into a base part (base section) and a top part (top section), wherein the base section of the low-pressure column remains installed with the high-pressure column as in a conventional double-column arrangement, but the top section of the low-pressure column is stored in a separate cold box. In addition, it is proposed here to carry out a division of the crude argon column into a base part (base section) and a top part (top section) and to accommodate these sections in separate co-boxes. Liquid from a lower region of the top section of the low-pressure column and a lower region of the base section of the crude argon column is returned to the base section of the low-pressure column by means of a common pump.
The object of the present invention is to further improve corresponding arrangements in particular with regard to the construction effort and costs.

DISCLOSURE OF THE INVENTION

Against this background, the present invention proposes a plant and a method for the low-temperature separation of air having the features of the independent claims. Preferred embodiments form the subject-matter of the dependent claims and of the following description.
Prior to explaining the features and advantages of the present invention, some of the principles of the present invention will be explained in greater detail, and terms used below will be defined.
The devices used in an air separation plant are described in the cited technical literature, for example in Häring (see above) in Section 2.2.5.6, “Apparatus.” Unless the following definitions differ, reference is therefore explicitly made to the cited technical literature with respect to terminology used within the framework of the present application.
Liquids and gases may, in the terminology used herein, be rich or poor in one or more components, wherein “rich” can refer to a content of at least 75%, 90%, 95%, 99%, 99.5%, 99.9%, or 99.99%, and “poor” can refer to a content of at most 25%, 10%, 5%, 1%, 0.1%, or 0.01% on a mole, weight, or volume basis. The term “predominantly” can correspond to the definition of “rich.” Liquids and gases may also be enriched in or depleted of one or more components, wherein these terms refer to a content in a starting liquid or a starting gas from which the liquid or gas has been extracted. The liquid or the gas is enriched if it contains at least 1.1 times, 1.5 times, 2 times, 5 times, 10 times, 100 times, or 1000 times the content, and depleted if it contains at most 0.9 times, 0.5 times, 0.1 times, 0.01 times, or 0.001 times the content of a corresponding component, based on the starting liquid or the starting gas. If, by way of example, reference is made here to “oxygen,” “nitrogen,” or “argon,” this is also understood to mean a liquid or a gas which is rich in oxygen or nitrogen but need not necessarily consist exclusively of it. With plants according to embodiments of the present invention, for example, purities in the range of 0.05 ppb oxygen in nitrogen, 0.2 ppb oxygen in argon and 0.2 ppb argon in oxygen can be achieved.
The present application uses the terms “pressure range” and “temperature range” to characterize pressures and temperatures, which means that corresponding pressures and temperatures in a corresponding plant do not have to be used in the form of exact pressure or temperature values in order to realize the inventive concept. However, such pressures and temperatures typically fall within certain ranges that are, for example, +1%, 5%, or 10% around an average. In this case, corresponding pressure ranges and temperature ranges can be in disjoint ranges or in ranges which overlap one another. In particular, pressure ranges, for example, include unavoidable or expected pressure losses. The same applies to temperature ranges. The values indicated here in bar relating to the pressure ranges are absolute pressures.
A “condenser evaporator” refers to a heat exchanger in which a first, condensing fluid stream enters into indirect heat exchange with a second, evaporating fluid stream. Each condenser evaporator has a liquefaction chamber and an evaporation chamber. The liquefaction and evaporation chambers have liquefaction or evaporation passages. Condensation (liquefaction) of the first fluid stream is carried out in the liquefaction chamber, and evaporation of the second fluid stream in the evaporation chamber. The evaporation and liquefaction chambers are formed by groups of passages, which are in a heat-exchanging relationship with one another. The so-called main condenser is a condenser evaporator via which a high-pressure column and a low-pressure column of a plant for low-temperature separation of air are coupled to one another in a heat-exchanging manner.
The term “subcooling heat exchanger” is intended here to denote a heat exchanger in which subcooling of one or more material flows which are transferred between the rectification columns of a rectification column system of the type used here is carried out. In a counterflow thereto, in particular one or more material flows discharged from the rectification column system and the entire plant can be heated. The subcooling heat exchanger is present in addition to the so-called main heat exchanger which is characterized in that at least the predominant share of the air supplied to the rectification column system is cooled therein. The air separation plant of the invention can in principle also be designed without a subcooling heat exchanger.
The term “cold box” is understood here to mean a temperature-insulating enclosure in which process engineering apparatuses operated at low, in particular cryogenic temperatures are installed. A plant for the low-temperature separation of air can comprise one or more corresponding cold boxes and, in particular, can be produced in a modular manner from corresponding cold boxes, as is also the case within the scope of the present invention. In a cold box, several plant parts, i.e., for example, separating apparatuses such as columns and the associated heat exchangers, can also be fastened together with the piping to a supporting steel frame, which is covered on the outside with sheet-metal plates. The interior of the enclosure formed in this way is filled with insulating material, such as perlite, in order to prevent heat input from the environment. A partial or complete prefabrication of cold boxes with the corresponding apparatuses at the factory is also possible, so that they have to be finished at the construction site or only connected to each other as needed. For connection, line modules that are temperature-isolated and, possibly, accommodated in cold boxes can be used. In typical cold boxes, the plant parts are usually installed at a minimum distance from the wall, in order to ensure sufficient insulation. The piping in a cold box is preferably designed without flange connections, i.e., completely welded, or with suitable transition components according to the invention, in order to avoid the formation of leaks. Due to the temperature differences that arise, expansion bends can be present in the piping. Components susceptible to maintenance are typically not arranged in the cold box, so that the interior of the cold box is advantageously maintenance-free. Valves can be designed, for example, as so-called “corner valves” in order to enable repair from outside. In this case, the valve is located in the cold box wall; the pipeline is guided to the valve and back again. Pipelines and apparatuses are made of aluminum or stainless steel, the latter in particular, but not exclusively, at very high operating pressures. The transition component according to the invention makes it possible to connect such materials. The painting of the cold box is quite often in white, but also in other bright colors. The penetration of moisture from the ambient air, which would freeze at the cold plant parts, can for example be prevented by a continuous flushing of the cold box with, for example, nitrogen.
The relative spatial terms “upper,” “lower,” “over,” “under,” “above,” “below,” “adjacent to,” “next to,” “vertical,” “horizontal,” etc. here refer to the spatial orientation of the rectification columns of an air separation plant or other components in normal operation. An arrangement of two components “one above the other” is understood here to mean that the upper end of the lower of the two components is located at a lower geodetic height than or the same geodetic height as the lower end of the upper of the two components, and the projections of the two apparatus parts overlap in a horizontal plane. In particular, the two components are arranged exactly one above the other, that is to say the axes of the two components run on the same vertical straight line. However, the axes of the two components do not have to lie exactly perpendicular one above the other, but can also be offset relative to one another, in particular if one of the two components, for example a rectification column or a column part with a smaller diameter, is to have the same distance from the sheet metal jacket of a cold box as another with a larger diameter. Terms such as “functionally below” or “functionally above” in the case of a rectification column designed in multiple parts refer to the arrangement of partial columns which would have them if the rectification column were formed in one piece.

Advantages of the Invention

The present invention relates to a plant for low-temperature separation of air which has a rectification column system with a high-pressure column, a low-pressure column and a argon column, wherein the low-pressure column and optionally also the argon column are (each) divided at least into a base section and a top section, as already described, for example, in the cited EP 2 965 029 B1. Furthermore, the plant optionally has a pure oxygen column.
If present, the pure oxygen column serves to obtain high-purity or ultra-high purity oxygen with a residual content of foreign components of up to typically 0.05 ppb or 1 ppb methane, argon, krypton, xenon, nitrogen, hydrogen, carbon monoxide, carbon dioxide, etc., but optionally also more or less. If present, the pure oxygen column is supplied with liquid from an intermediate point of the argon column which is introduced at the top of the pure oxygen column. In the optionally present two-part argon column, this intermediate point is in particular in its base section and in any case in particular above a lowermost separation section which serves to separate components having a higher boiling point than oxygen, in particular hydrocarbons, carbon dioxide, krypton and xenon.
The argon column can in particular be a crude argon column which is used in addition to a pure argon column. Instead of a crude argon column and a pure argon column, a single column for obtaining an argon product which partially combines the functions of a raw and pure argon column with one another by having a further section provided for separating off nitrogen. If an argon column is subsequently mentioned, this can in particular be a crude argon column which is present in addition to a pure argon column, but also a correspondingly modified crude argon column, next to which there is no pure argon column.
The transfer of fluids between the columns and partial columns, which are used according to the invention, is summarized below only for clarification. Thus, the sump fluid of the pressure column, optionally after use as a cooling medium in a top condenser of the argon column and optionally a pure argon column, if present, is fed into the top section of the low-pressure column. The top gas of the pressure column is condensed into parts in a main condenser connecting the pressure column and the base section of the low-pressure column while exchanging heat and recirculated to the pressure column and discharged as product from the air separation plant. The sump liquid of the base section of the low-pressure column is at least partially discharged from the air separation plant as a product. Top gas of the base section of the low-pressure column is fed into the top section of the low-pressure column, in particular below the lowermost rectification section. Further top gas of the base section of the low-pressure column is fed into the argon column, in particular below the lowermost rectification section, or its base section if it is correspondingly subdivided. Top gas of the base section of the argon column, if the argon column is correspondingly divided, in particular below the lowermost rectification section, is fed into the top section of the argon column. Sump liquid from the top section of the argon column is fed into the base section of the argon column if the argon column is correspondingly subdivided, in particular above the uppermost rectification section, for which purpose a pump is used in particular.
The terms “base section” and “top section” denote in each case the sections of the columns that are correspondingly divided and therefore designed in two parts, which correspond in their function, in particular with regard to the fractions or flows arising there, to the lower or upper sections of conventional, one-part columns. A base section has, for example, a sump tank, a top section has a top condenser, for example. The top section is therefore the part of the columns which is connected to a corresponding condenser, and in which a return flow is fed to the corresponding columns. In a low-pressure column of known air separation plants designed in one piece, an oxygen-rich liquid fraction is obtained In the sump, which can be drawn off as an oxygen product. This is therefore also carried out in a sump or lower region of a base section of a low-pressure column designed in two parts. A gaseous nitrogen product can accordingly be drawn off at the top of a one part low-pressure column of known air separation plants, provided this is correspondingly equipped, or so-called impure nitrogen. The same applies to the upper region of a top section of a low-pressure column designed in two parts. At the top of a single-part argon column (with regard to the term “argon column,” see the above explanations), and accordingly at the upper region of a top section of a two-part argon column, a crude argon stream or an argon product stream is drawn off, from the sump of a single-piece argon column, and correspondingly from a lower region of a base section of a two-part argon column, the arising sump product is fed back into the low-pressure column.
In the context of the present invention, the division of the low-pressure column into the top section and base section is carried out in particular above the so-called oxygen section. As set out in Haring (see above) with reference to FIG. 2.4A, although argon is contained in atmospheric air with a content of less than 1 mole percent, it exerts a strong influence on the concentration profile in the low-pressure column. The separation in the lowermost rectification section of the low-pressure column, which typically comprises 30 to 80 theoretical or practical plates, can therefore be regarded as a substantially binary separation between oxygen and argon. This rectification section is the mentioned oxygen section. Only starting at the discharge point for the gas transferred into the crude argon column or in the division carried out above the oxygen section in accordance with the invention, the separation changes within a few theoretical or practical plates into a ternary separation of nitrogen, oxygen, and argon.
The term “rectification section” should here denote any section within a rectification column or partial column of a multipart rectification column which is set up to carry out rectification and is designed for this purpose in particular with corresponding mass transfer structures such as separating plates or ordered or disordered packings. In particular, fluid outlets or inlets, for example side outlets, can be provided between rectification sections. Below a (functionally) lowermost rectification region, the “base” of the rectification column is located above the (functionally) upper rectification region, its “top.”
The present invention proposes overall a plant for low-temperature separation of air which has a rectification column system with a high-pressure column, a low-pressure column and an argon column, as well as a cold box system with a first cold box, a second cold box, and a third cold box. Further cold boxes are possible, for example a total of four cold boxes, wherein the low-pressure column is divided into at least a base section and a top section and a main heat exchanger box may additionally be provided.
In the context of the present invention, the base section and the top section of the low-pressure column are arranged side by side in such a way that an orthogonal projection of the base section of the low-pressure column onto the horizontal plane does not intersect with an orthogonal projection of the top section of the low-pressure column onto the horizontal plane. In particular, there is a cross-sectional plane which intersects the base section and the top section of the low-pressure column.
Optionally, in the context of the present invention, the argon column can likewise be divided at least into a base section and a top section, wherein the base section and the top section of the argon column are arranged side by side in such a way that an orthogonal projection of the base section of the argon column onto the mentioned horizontal plane does not overlap with an orthogonal projection of the top section of the argon column onto the horizontal plane. In particular, a cross-sectional plane is present which intersects the base section and the top section of the low pressure column.
In contrast to this, in the context of the present invention, the high-pressure column is arranged below the base section of the low-pressure column such that that an orthogonal projection of the high-pressure column onto the horizontal plane overlaps with the orthogonal projection of the base section of the low-pressure column onto the horizontal plane, wherein the longitudinal axes of the high-pressure column and of the base section of the low-pressure column lie in particular along a common main axis, or a vertical axis is present which intersects the high-pressure column and the base section of the low-pressure column.
In the context of the present invention, the high-pressure column is arranged together with the base section of the low-pressure column in the first cold box, and the top section of the low-pressure column is arranged in the second cold box. According to the invention, the argon column or one or more sections of the argon column is/are in the first cold box and/or the second cold box. Alternatively, the argon column or all parts of the argon column are accommodated in a third cold box. As a further alternative, there is a separate box for the base section and for the top section of the argon column.
The arrangement proposed according to the invention results in particular in simple constructability with small transport dimensions and enables the lowest possible box height (not higher than the church tower or in the vicinity of the airport . . . ). A “cold plant part” is understood here to mean an apparatus or an apparatus part which, during regular operation of the plant, is operated at low temperatures, in particular below −50° C.
In one embodiment of the invention, in which a correspondingly subdivided argon column is provided, the base section of the argon column can be arranged in particular in the first cold box and the top section of the argon column can be arranged in particular in the second cold box or vice versa, i.e., the base section of the argon column can also be arranged in the second cold box and the top section of the argon column can also be arranged in the first cold box.
As mentioned, the argon column can be designed as a crude argon column, in which case in particular a pure argon column can be provided. The pure argon column can be arranged in the first cold box or the second cold box, in particular in the cold box, in which is arranged, in the case of a corresponding embodiment or subdivision, the top section of the argon column designed as a crude argon column.
In the invention, the pure oxygen column is arranged in one of the cold boxes, namely in the same cold box as the argon column or a first section of the argon column.
The pure oxygen column and the argon column or a first section (for example the base section) of the argon column are arranged side by side in the plant used according to the invention such that an orthogonal projection of the pure oxygen column or of an upper part of the pure oxygen column onto the horizontal plane does not intersect with the orthogonal projection of the argon column or of the first section onto the horizontal plane. The upper part can be a part of the pure oxygen column which is not taken up by a sump evaporator arranged in the sump of the pure oxygen column. Due to its dimensioning, the latter can also assume a space which is significantly greater in cross section than the upper part of the pure oxygen column, and can be optionally arranged eccentrically (relative to a central axis of the upper part). In this case, the orthogonal projection of the lower part of the pure oxygen column with the sump evaporator onto the horizontal plane can also partially overlap with the orthogonal projection of the base section of the argon column onto the horizontal plane.
Furthermore, the top section of the low-pressure column and the pure oxygen column or an upper section of the pure oxygen column are preferably arranged side by side in such a way that an orthogonal projection of at least the pure oxygen column or an upper section of the pure oxygen column onto the horizontal plane does not overlap with the orthogonal projection of the top section of the low-pressure column or the first section of the argon column onto the horizontal plane.
As already stated in other words, if present in a corresponding embodiment, the pure oxygen column is fed at a feed point with a first transfer liquid which is removed from the argon column or its base section at an extraction point. The cited columns or column parts are therefore equipped with corresponding extraction and feed points. As mentioned, the extraction point from the argon column or its base section is in particular above a rectification section which serves to discharge hydrocarbons. The extraction point for the first transfer liquid is in particular 1 to 30 theoretical plates above a sump of the argon column or the base section thereof.
The first transfer liquid transferred into the pure oxygen column therefore has in particular an oxygen content of 50 to 95 mole percent, an argon content of 10 to 50 percent, a nitrogen content of 0.1 ppm to 500 ppm, preferably of 0.1 ppm to 100 ppm, and a content of other components having a higher boiling point than oxygen of 0.01 ppb to 25 ppm.
The pure oxygen column and the argon column or its base section are advantageously arranged in such a way that the extraction point for the transfer liquid from the argon column or its base section is geodetically above the feed point for the transfer liquid into the pure oxygen column. In this way, the transfer liquid can run into the pure oxygen column, in particular without using a pump, which on the one hand saves the effort for a corresponding pump and, on the other hand, avoids possible contaminations by a corresponding pump. The feed point of the transfer fluid into the pure oxygen column is in particular above an uppermost rectification section of the pure oxygen column.
In one embodiment of the invention with a correspondingly divided argon column, it is provided in particular that the base section of the argon column is fed with a second transfer liquid at a feed point located in particular below a lowermost rectification section in the base section of the argon column, which transfer liquid is withdrawn from the top section of the low-pressure column at an extraction point located in particular below a lowermost rectification section in the top section of the low-pressure column. The cited columns or column parts are therefore equipped with corresponding extraction and feed points.
In this embodiment, the top section of the low-pressure column and the base section of the argon column can be arranged in such a way that the extraction point for the second transfer liquid from the top section of the low-pressure column is geodetically above the feed point for the further transfer liquid into the base section of the argon column. In this way, the sump liquid from the base section and sump liquid from the top section of the low-pressure column can be combined in the base section of the argon column and fed back to the base section of the low-pressure column using just one (i.e., using a common) pump, which ideally has a redundant design.
Preferably, an empty section is arranged in the base section of the argon column or its base section. An empty section is located inside the shell of a column and extends over a vertical sub-region of the column. There are no mass transfer elements in an empty section, which therefore does not affect the mass transfer. At first it seems counterproductive to provide such a section, as the column shell becomes more expensive. However, in the context of exchanging one or more transfer fluids, it is operationally expedient in the invention to place the mass transfer region of the top section of the low-pressure column relatively high (above the empty section) and the sump relatively low (below the empty section). In particular, the empty section is arranged in the lower region of the column, in particular directly above the lower end of the column shell.
If a corresponding system has a subcooling heat exchanger, it can be arranged in one of the cold boxes. In the just explained embodiment, the subcooling heat exchanger can in particular be arranged below the top section of the low-pressure column.
In this embodiment of the invention, it can therefore in particular be provided that the top section of the low-pressure column is arranged geodetically above a subcooling heat exchanger. If the sump liquid of the top section of the low-pressure column is to be drainable into the sump from the base section of the argon column from above a corresponding rectification section into the pure oxygen column, it must be positioned sufficiently high. In this case, the sump of the base section of the argon column can be extended downwards by a so-called “blank,” i.e., an empty region or empty section so that it can be simultaneously ensured that, in a corresponding embodiment, liquid can drain from the top section of the low-pressure column into the sump of the base section of the argon column. As a result, the low-pressure column can be arranged as low as possible, and the box height of the cold box in which the low-pressure column is located can be reduced.
Alternatively to the just mentioned embodiment, it can also be provided that the top section of the low-pressure column is fed at a feed point, which is located in particular below a lowermost rectification section in the top section of the low-pressure column, with a second transfer liquid which is removed from the base section of the argon column at an extraction point, in particular located below a lowermost rectification section in the base section of the argon column. The cited columns or column parts are therefore equipped with corresponding extraction and feed points. In this embodiment, the base section of the argon column and the top section of the low-pressure column are arranged such that the extraction point for the further transfer liquid from the base section of the argon column is geodetically above the feed point for the further transfer liquid into the top section of the low-pressure column. In this way, the sump liquid in the low-pressure column and sump liquid of the base section of the argon column can be combined in the top section of the low-pressure column and returned to the base section of the low-pressure column by means of only one pump.
In a corresponding system which has a subcooling heat exchanger, said heat exchanger can be arranged in particular below the base section of the argon column in the just explained embodiment.
It can in particular be provided that the top section of the low-pressure column and the top section of the argon column are arranged side by side in such a way that the orthogonal projection of the top section of the low-pressure column onto the horizontal plane does not overlap with the orthogonal projection of the top section of the argon column onto the horizontal plane. A cross-sectional plane is correspondingly present which intersects the top section of the low-pressure column and the top section of the argon column.
In the context of the present invention, in particular, cold box heights of 35 to 50 meters, in particular approximately 43 meters, can be maintained. The high-pressure column can in particular have a height of 15 to 30 meters, in particular 25.8 meters, and the base section of the low-pressure column in particular can have a height of 7 to 20 meters, for example 14.8 meters. The height of the base section of the low-pressure column is defined in particular from the height of the main condenser and the separating devices accommodated therein and of the so-called oxygen section which can both in particular lie at 5 to 14 meters, for example at 7.4 meters. The diameter can in particular be 1.5 to 4 meters, for example approximately 2.8 meters. The base section of the argon column has, for example, a height of 25 to 45 meters, in particular approximately 39 meters.
The top section of the low-pressure column has in particular a height of 18 to 30 meters, for example of 23 meters (with a diameter of 2.4 to 3 meters, for example of about 2.6 meters) or a height of 25 to 30 meters, for example of about 27 meters (with a diameter of 1.2 to 4.0 meters, for example of about 2.45 meters). The dimensions depend in particular on the utilized packing density. The top section of the argon column can have an expedient dimensioning.
The proposed arrangements and embodiments thereof according to the invention enable against this backdrop in particular, a compact design.
As in known systems, the base section of the low-pressure column is connected to the high-pressure column via a condenser evaporator for reciprocal heat exchange, and the base section of the low-pressure column and the high-pressure column are arranged in particular in a common column shell or in several shell-connected column shells, in particular in the form of a known Linde double column (but without the top section of the low-pressure column).
The subcooling heat exchanger can in particular have a vertical space requirement of up to 45 meters, for example of approximately 8 meters, if it is mounted upright. If the top section of the argon column comprises a corresponding top condenser (crude argon condenser), it has a height of typically 30 to 40 m like the base section of the argon column. The above-explained arrangement variants for the subcooling heat exchanger are particularly advantageous because they are associated with a space-saving arrangement. Other arrangement variants of the subcooling heat exchanger, for example in a heat exchanger box, etc., can also be advantageous.
(A) The pure oxygen column can be arranged next to the high-pressure column, the base section of the low-pressure column and the base section of the argon column (with a corresponding subdivision) in the first cold box, such that an orthogonal projection of at least an upper part (for reasons and further explanations, see above) of the pure oxygen column onto the horizontal plane does not overlap with the orthogonal projection of the high-pressure column onto the horizontal plane and the orthogonal projection of the base section of the low-pressure column onto the horizontal plane as well as the orthogonal projection of the base section of the argon column. The connecting pipelines are thereby minimized.
If this arrangement (A) can no longer be transported due to its dimensions, the HDS can be relocated with the lower part of the LDS into a separate box. Ideally, the upper part of the low-pressure column is then in a second cold box with the argon column. The reboiler of the pure oxygen column can be located in the shadow of the low-pressure column and arranged asymmetrically. The argon column or its sections are arranged in a third cold box. The height arrangement is important here.
In the context of the present invention, the base section of the argon column (with a corresponding subdivision thereof) can be set up in particular for separating high-boiling components, but also other impurities, in particular also to avoid enrichment.
In the context of the present invention, in particular a lower region of the top section of the low-pressure column and a lower region of the base section of the argon column (with a corresponding division) can be fluidically coupled via a pump to an upper region of the base section of the low-pressure column.
Merely for clarification, it should be mentioned again here that the plant proposed according to the invention advantageously has means which are configured to feed the high-pressure column with cooled compressed air, means which are configured to feed the low-pressure column with fluid from the high-pressure column, and means which are configured to feed the argon column with fluid from the low-pressure column.
Finally, the present invention also extends to a method for the low temperature separation of air; with regard to its features, express reference is made to the corresponding independent patent claim. In particular, a plant is used in such a method as has previously been explained in different embodiments. For features and advantages of the proposed method and possible embodiments, reference is therefore expressly made to the explanations relating to the plant according to the invention.
The invention is explained in more detail below with reference to the accompanying drawings, which illustrate embodiments of the present invention and embodiments not according to the invention.

DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a plant for low-temperature separation of air, which can be based on an embodiment of the invention, in the form of a simplified process flowchart.

FIG. 2 illustrates an arrangement of components of a plant designed according to an embodiment of the invention for the low temperature separation of air in a side view and in a simplified representation.

FIG. 3 illustrates an arrangement of components of a plant designed according to an embodiment of the invention for the low temperature separation of air in a plan view and in a simplified representation.

FIG. 4 shows a modification of FIG. 2 in which an empty section is used.

If plant components of a plant for low-temperature separation of air (hereinafter also referred to as “air separation plant”) are described below, the corresponding explanations also apply to a method carried out thereby and vice versa.

EMBODIMENTS OF THE INVENTION

FIG. 1 schematically shows an air separation plant which is set up to obtain an argon product and a pure oxygen product and is denoted overall by 100.
The air separation plant 100 has a rectification column system 10 which comprises a high-pressure column 11, a low-pressure column divided into a base section 12 and a top section 13, a (crude) argon column also divided into a base section 14 and a top section 15, and a pure argon column 20. A pure oxygen column is designated by 18. A block designated with 1 comprises the customary components present in an air separation plant of the illustrated type for compression, purification and cooling of the feed air, in particular also a main heat exchanger of known type. A subcooling heat exchanger is designated with 17.
The base section 12 and the top section 13 of the low-pressure column and the base section 14 and the top section 15 of the argon column are structurally separated from one another and are arranged next to one another in the sense explained above. The base section 12 and the top section 13 of the low-pressure column together functionally correspond to a conventional low-pressure column of a double column. The high-pressure column 11 and the base and top section 12, 13 of the low-pressure column therefore form a rectification column system for nitrogen-oxygen separation of a type known per se, to which is connected an argon system consisting of the base section 14 and the top section 15 of the argon column and the pure argon column 20.
In the shown exemplary embodiment, cooled and compressed feed air in the form of two material flows a, b is fed into the high-pressure column 11 or the top section 13 of the low-pressure column. The air separation plant 100 can be designed for internal compression and can be designed as desired in the frame shown here. Further compressed feed air is conducted in the form of a material flow c through a sump evaporator, not designated separately, of the pure oxygen column 18, at least partially condensed there, and then likewise, now referred to as d, fed into the top section 13 of the low-pressure column. The specific type of air feed into the column arrangement is not essential to the invention and can be designed in any desired manner (with/without a choked flow, with/without air feed into the low-pressure column or its top section 13, etc.). This also applies to the provision of turbines for cold generation, which may or may not be provided.
The high-pressure column 11 and the base section 12 of the low-pressure column are connected via a condenser evaporator 19, the so-called main condenser, to exchange heat and are designed as a structural unit. However, the invention can in principle also be used in systems in which the high-pressure column 11 and the low-pressure column (or their base section 12) are arranged separately from one another and have a separate condenser evaporator 19, i.e., not integrated into the columns.
The operation of the air separation plant 100 is directly evident from the representation according to FIG. 1 . Reference is therefore made to the technical literature cited at the outset.
In particular, the base section 12 and the top section 13 of the low-pressure column are in this case fluidically coupled to one another in that head gas is transferred from an upper region of the base section 12 of the low-pressure column in the form of a material flow e to a lower region of the top section 13 of the low-pressure column. As also explained with reference to FIG. 2 , the arrangement of the top section 13 of the low-pressure column and of the base section 14 of the argon column in the shown example is such that sump liquid in the form of a material flow f can run from a lower region of the top section 13 of the low-pressure column into a lower region of the base section 14 of the argon column, in which a further section of the top gas is also fed from the upper region of the base section 12 of the low-pressure column in the form of a material flow g. In this way, sump liquid is collected from the top section 13 of the low-pressure column and the base section 14 of the argon column in the sump om of the base section 14 of the argon column and can be pumped back into an upper region of the base section 12 of the low-pressure column by means of a common pump 110 in the form of a material flow h. A reverse arrangement is also possible, as mentioned.
The top gas of the base section 14 of the argon column is transferred into a lower region of the top section 15 of the argon column, and liquid is correspondingly pumped back with a pump 120. The incorporation of the pure argon column 20 can substantially correspond to that which is routine in the art. The argon column consisting of the base section 14 and the top section 15 is therefore fluidically connected in parallel to the low-pressure column or its base section 12 and top section 13 such that corresponding top gas from an upper region of the base section 12 of the low-pressure column is also transferred into a lower region of the base section 14 of the argon column, and the sump liquid is returned from the lower region of the base section 14 of the argon column into the upper region of the base section 12 of the low-pressure column. In particular, the same pump is used, which is also used to return the sump liquid from the lower region of the top section 13 of the low-pressure column into an upper region of the base section 12 of the low-pressure column.
Furthermore, the base section 14 and the top section 15 of the argon column are fluidically coupled to one another in that top gas is transferred from an upper region of the base section 14 of the argon column into a lower region of the top section 15 of the argon column and, by means of a (further) pump, sump liquid is recirculated from a lower region of the top section 15 of the argon column into an upper region of the base section 14 of the argon column.
The pure oxygen column 18 is fed here at a feed point 18 a with a transfer liquid in the form of a material flow t, which is removed from the base section 14 of the argon column at an extraction point 14 a. The pure oxygen column 18 and the base section 14 of the argon column are arranged in such a way that the extraction point 14 a for the transfer liquid from the base section 14 of the argon column is geodetically above the feed point 18 a for the transfer liquid into the pure oxygen column 18, as a result of which it can be transferred into the pure oxygen column 18 without a pump.
The base section 14 of the argon column is furthermore fed at a feed point 14 b with a further transfer liquid in the form of the material flow f already mentioned, which is removed from the top section 13 of the low-pressure column at an extraction point 13 b, wherein the top section 13 of the low-pressure column and the base section 14 of the argon column in the example illustrated here are arranged in such a way that the extraction point 13 b for the further transfer liquid from the top section 13 of the low-pressure column is above the feed point 14 b for the further transfer liquid into the base section 14 of the argon column.
Integration of the components of the air separation plant 100 into cold boxes is illustrated in FIG. 2 in the form of a simplified side view, wherein the components of the air separation plant 100 are indicated with identical reference signs as explained above with respect to FIG. 1 . As shown in FIG. 1 , these are shown in side view, but even more greatly simplified. The fluid connections are not shown, but are evident corresponding to the representation according to FIG. 1 . Two cold boxes 110 and 120 are illustrated, which, as explained below, contain components of the air separation plant 100 and thermally insulate them.
The base section 12 and the top section 13 of the low-pressure column are arranged in this case next to one another in such a way that an orthogonal projection of the base section 12 of the low-pressure column onto a horizontal plane H does not overlap with an orthogonal projection of the top section 13 of the low-pressure column onto the horizontal plane H, and the base section 14 and the top section 15 of the argon column are likewise arranged side by side in such a way that an orthogonal projection of the base section 14 of the argon column onto the horizontal plane H does not overlap with an orthogonal projection of the top section 15 of the argon column onto the horizontal plane H.
In contrast, the high-pressure column 11 is arranged below the base section 12 of the low-pressure column such that an orthogonal projection of the high-pressure column 11 onto the horizontal plane H overlaps with the orthogonal projection of the base section 12 of the low-pressure column onto the horizontal plane H.
The pure oxygen column 18 and the base section 14 of the argon column are arranged side by side such that an orthogonal projection of at least one upper part (further explanations above) of the pure oxygen column 18 onto the horizontal plane H does not overlap with the orthogonal projection of the base section 14 of the argon column onto the horizontal plane H,
Furthermore, in the air separation plant 100, the top section 13 of the low-pressure column and the top section 15 of the argon column are arranged side by side in such a way that the orthogonal projection of the top section 13 of the low-pressure column onto the horizontal plane H overlaps with the orthogonal projection of the top section 15 of the argon column onto the horizontal plane H.
The high-pressure column 11, the base section 12 of the low-pressure column and the base section 14 of the argon column and the pure oxygen column 18 are arranged in the first cold box 110, and the top section 13 of the low-pressure column and the top section 15 of the argon column are arranged in the second cold box 120, just like the pure argon column 20. This results in the advantages of a corresponding embodiment according to the invention.
As illustrated in dashed lines here, the subcooling heat exchanger 17 can in particular be arranged below the top section 13 of the low-pressure column in the second cold box 120 such that an orthogonal projection of the subcooling heat exchanger 17 onto the horizontal plane H overlaps with the orthogonal projection of the top section 13 of the low-pressure column onto this horizontal plane H in particular.
As explained, the top section 13 of the low-pressure column can be designed with a lower packing density than the top section 15 of the argon column, and
the base section 14 of the argon column can be configured to separate methane. As explained above and in detail in FIG. 1 , here as well, a lower region of the top section 13 of the low-pressure column and a lower region of the base section 14 of the argon column can also be fluidically coupled to an upper region of the base section 12 of the low-pressure column via a (common) pump.
FIG. 3 illustrates the components shown in FIG. 2 in plan view, wherein the horizontal plane H lies parallel to the paper plane, and reference is expressly made to the explanations relating to FIG. 2 for further details.
FIG. 4 corresponds to FIG. 2 except for the empty section 14 a of the base section 14 of the argon column. The column shell extends uninterrupted over the entire length of the column (i.e., including the empty section 14 a shown in dashed lines). Only above the empty region 14 a are mass transfer elements installed, such as structured packings. The liquid drips from the lower end of the mass transfer elements through the empty section into the column sump at the lower end of the empty section 14 a.

Claims

1. A plant for low-temperature separation of air, having

a rectification column system having a high-pressure column, a low-pressure column, an argon column and a pure oxygen column, and a cold box system, wherein

the pure oxygen column and the argon column or a base section of the argon column are arranged side by side such that an orthogonal projection of at least one upper part of the pure oxygen column onto the horizontal plane (H) does not overlap with the orthogonal projection of the argon column or the base section of the argon column onto the horizontal plane (H),

the pure oxygen column has a feed point for a first transfer liquid and the argon column or the base section of the argon column has an extraction point for the first transfer liquid, wherein the pure oxygen column and the base section of the argon column are arranged such that the extraction point for the first transfer liquid is geodetically above the feed point for the first transfer liquid,

wherein

the low-pressure column is divided into at least a base section and a top section,

the base section and the top section of the low-pressure column are arranged next to one another in such a manner that an orthogonal projection of the base section of the low-pressure column onto the horizontal plane (H) does not intersect with an orthogonal projection of the top section of the low-pressure column onto the horizontal plane (H),

the high-pressure column is arranged below the base section of the low-pressure column in such a manner that an orthogonal projection of the high-pressure column onto the horizontal plane (H) intersects with the orthogonal projection of the base section of the low-pressure column onto the horizontal plane (H),

the pure oxygen column and the argon column or the base section of the argon column are arranged side by side such that an orthogonal projection of at least one upper part of the pure oxygen column onto the horizontal plane (H) does not overlap with the orthogonal projection of the argon column or the base section of the argon column onto the horizontal plane (H),

the cold box system has a first cold box, a second cold box and a third cold box,

the high-pressure column-together with the base section of the low-pressure column is arranged in the first cold box,

the top section of the low-pressure column is arranged in the second cold box,

the argon column or one or more sections of the argon column is or are arranged in the third cold box, and

the pure oxygen column is arranged in the second cold box.

2. The plant according to claim 1, wherein the argon column is divided at least into a base section and a top section, wherein the base section and the top section of the argon column are arranged next to one another in such a manner that an orthogonal projection of the base section of the argon column onto the horizontal plane (H) does not intersect with an orthogonal projection of the top section of the argon column.

3. The plant according to claim 1, wherein the argon column is designed as a crude argon column and further a pure argon column is provided, wherein the pure argon column is arranged in the first cold box or the second cold box, in particular in the cold box in which the top section of the argon column designed as a crude argon column is arranged.

4. The plant according to claim 1, wherein the extraction point for the first transfer liquid is 1 to 30 theoretical plates above a sump of the base section of the argon column.

5. The plant according to claim 1, wherein the base section of the argon column has a feed point for a second transfer liquid, and the top section of the low-pressure column has an extraction point for the second transfer liquid, wherein the top section of the low-pressure column and the base section of the argon column are arranged such that the extraction point for the second transfer liquid is above the feed point for the second transfer liquid.

6. The plant according to claim 1, wherein an empty section of the argon column or in the base section of the argon column is arranged.

7. The plant according to claim 1, having a subcooling heat exchanger which is arranged in the first or second cold box, in particular in the second cold box below the top section of the low-pressure column.

8. The plant according to claim 1, wherein the top section of the low-pressure column has a feed point for a second transfer liquid, and the base section of the argon column has an extraction point for the second transfer liquid, wherein the base section of the argon column and the top section of the low-pressure column are arranged in such a way that the extraction point for the second transfer liquid is above the feed point for the second transfer liquid.

9. The plant according to claim 8, having a subcooling heat exchanger which is arranged below the base section of the argon column.

10. The plant according to claim 1, in which all cold apparatus parts are arranged in the first or the second cold box and no third cold box is used.

11. The plant according to claim 1, wherein the first section of the crude argon column is formed by the base section thereof.

12. A method for the low-temperature separation of air, wherein a plant according to claim 1 is used.