DE102013018664A1 - Process for the cryogenic separation of air and cryogenic air separation plant - Google Patents

Abstract

The method and apparatus are used for cryogenic separation of air with a multi-strand plant having at least two air separation strands, both of each of the two air separation strands having a coldbox containing a distillation column system comprising a first high pressure column (101), a first low pressure column (102). and a first main capacitor (103) formed as a condenser-evaporator and having an evaporation space and a liquefaction space. A first nitrogen gas stream (104, 114) from the first high pressure column (101) is introduced into the liquefaction space of the first main condenser (103). A first liquid nitrogen stream (105) from the liquefaction space of the first main condenser (103) is introduced into the first high-pressure column (101). A first oxygen gas stream (108) from the vaporization space of the main condenser (103) is introduced into the first low pressure column (102). The distillation column system of both air separation strands also has a second high pressure column (201) and a second low pressure column. The first high pressure column (101) and the second high pressure column (201) of the distillation column systems of each of the two air separation lines have the same size. The first low-pressure column and the second low-pressure column of the distillation column systems of each of the two air separation strands have the same size. The first and second low pressure columns (102, 202) of the distillation column systems of each of the two air separation strands contain mass transfer elements formed in at least a portion of the respective low pressure column (102, 202) by an ordered packing made of folded metal sheets the ordered packing has a specific surface area of more than 1000 m2 / m3, in particular 1200 m2 / m3 or more.

Description

The invention relates to a method for the cryogenic separation of air according to the preamble of patent claim 1.

The basics of cryogenic separation of air in general and the construction of two-column plants in particular are in the Monograph "Tiefftemperaturtechnik" by Hausen / Linde (2nd edition, 1985) and in one Review by Latimer in Chemical Engineering Progress (Vol. 63, No.2, 1967, page 35) described. The heat exchange relationship between the high-pressure column and the low-pressure column of a double column is usually realized by a main condenser in which head gas of the high-pressure column is liquefied against vaporizing bottom liquid of the low-pressure column.

The distillation column system of the invention is designed as a classic two-column system. In addition to the separation columns for nitrogen-oxygen separation, it can have other devices for obtaining other air components, in particular noble gases, for example argon recovery.

The main capacitor is formed in the invention as a condenser-evaporator. The term "condenser-evaporator" refers to a heat exchanger in which a first condensing fluid stream undergoes indirect heat exchange with a second evaporating fluid stream. Each condenser-evaporator has a liquefaction space and an evaporation space, which consist of liquefaction passages or evaporation passages. In the liquefaction space, the condensation (liquefaction) of a first fluid flow is performed, in the evaporation space the evaporation of a second fluid flow. Evaporation and liquefaction space are formed by groups of passages that are in heat exchange relationship with each other.

In this case, the main capacitor as a bath evaporator, in particular as a cascade evaporator (for example, as in EP 1287302 B1 = US Pat. No. 6,748,763 B2 described), or be designed as a falling film evaporator. It can be formed by a single heat exchanger block or by a plurality of heat exchanger blocks, which are arranged in a common pressure vessel.

The distillation column system of an air separation plant is arranged in one or more cold boxes. A "cold box" is here understood to mean an insulating casing which comprises a heat-insulated interior completely with outer walls; in the interior are arranged to be isolated plant parts, for example, one or more separation columns and / or heat exchangers. The insulating effect can be effected by appropriate design of the outer walls and / or by the filling of the gap between system parts and outer walls with an insulating material. In the latter variant, a powdery material such as perlite is preferably used. Both the distillation column system for nitrogen-oxygen separation of a cryogenic air separation plant and the main heat exchanger and other cold plant parts must be enclosed by one or more cold boxes. The outer dimensions of the coldbox usually determine the transport dimensions of the package in prefabricated systems.

The invention relates to a multi-stranded plant having at least with respect to the distillation column system two basically independent strands (Trains). The two or more distillation column system strands are regularly built the same in their interior; but one or more strands can also be configured differently from the others. The process steps upstream and downstream of the distillation column system may be single-stranded or also multi-stranded, wherein the number of strands in the different serial steps may be the same or different. In a specific example, a three-stranded main air compressor is associated with single-stream air pre-cooling and purification, and the purified air is introduced into a three-strand cold section, each of the cold strands containing a main heat exchanger and a distillation column system.

Multi-stranded methods of the type mentioned and corresponding devices are made WO 2013093305 A1 . WO 2013104840 A1 . WO 2009024672 A2 and EP 1666823 A1 = US 7516626 B2 known.

In the case of a transport limitation (usually 4.8 m in the column diameter), the amount of product obtained per unit (strand) is severely limited. Therefore, many lines of equipment (trains) are often needed to deliver the required amount of product, for example, to oxygen to customers. The limitation of the column diameter also means that the columns of multi-strand systems in the cold box are equipped with packages with a very low specific surface area (for example 350 m ² / m ² ); The same applies to single-strand systems of very large capacity. This is favorable in that, with limited column diameter, a particularly high capacity per column is achieved. The columns are particularly high and there is also the need for use of cryogenic transfer pumps (either a Liquid nitrogen pump for stacking the columns one above the other or a liquid oxygen transfer pump for adjacent columns). In addition to an increase in the total costs, this also negatively influences the complexity and the energy requirement of the system.

The invention has for its object to provide such a method and a corresponding device, which have high capacity, relatively low investment costs and a relatively small space requirement with favorable energy consumption.

This object is solved by the characterizing features of claim 1.

Contrary to the previous practice with restrictions on the column diameter, the invention uses an ordered packing of particularly high density in the low-pressure columns. In this case, a part of the mass transfer region of each of the two low-pressure columns may be filled with a particularly dense packing (and the remainder for example by packing of lower density or else by a combination of packing and conventional rectification trays), or all mass transfer elements are formed by the particularly dense packing. In the high-pressure column either be a structured packing, preferably with more than 1000 m ² / m ^3, or sieve trays, or a combination of these two types of mass transfer elements used. Due to the inventive pairwise parallel connection of columns, a particularly high product capacity (per strand) can be achieved despite a limited column diameter; the base area required for this purpose and the cold box height remain relatively small, namely comparable to a distillation column system with a single double column which is filled with very low specific surface area packings (for example 350 or 500 m ² / m ² ).

The high-pressure columns and the low-pressure columns of a strand according to the invention in pairs the "same size" on. This is understood here to mean that the corresponding column heights and diameters do not differ from one another by more than 10%, in particular not more than 5%. The comparison relates in pairs to the mutually corresponding sections of the first and second high-pressure columns or of the first and the second low-pressure columns

The use of a particularly dense packing initially seems to be counterproductive for a particularly high capacity, because this reduces the capacity of the corresponding column with a limited column diameter. In the context of the invention, however, it has surprisingly been found that such a configuration is more favorable if a distillation column system strand is formed by two parallel two-column systems, in particular if a common main capacitor is used for both. A single strand is of course more complex in terms of apparatus; however, a surprisingly significantly increased capacity can be achieved as compared to a classical distillation column system strand.

Due to the inventive pairwise parallel connection of columns within a strand, a particularly high product capacity (per strand) can be achieved despite a limited column diameter; the required footprint and the height of the coldbox remain relatively small. For example, in the context of the invention, the capacity for oxygen production can be increased by 20 to 30% compared to a conventional design.

Out US 6128921 Although it is known to operate two parallel double columns next to each other in a common coldbox; However, this document refers only to a single-stranded system and aims to make the two twin columns different. One skilled in the art would not consult this publication if he is looking to improve multi-strand systems; In any case, he does not take any suggestion as to how a multi-stranded system of the type mentioned at the outset could be modified in the sense of the task described above.

The advantages of the method according to the invention are particularly noticeable in very large systems that are multi-stranded, wherein at least two strands or all strands of the overall system according to the invention are formed. By increasing the capacity per strand, for example, with a four-strand plant according to the invention, a total capacity can be achieved which corresponds to a conventional five-strand plant; For example, in a plant that would have to be designed conventionally with six strands, five strands of the invention suffice.

The invention is realized by a two-stranded or multi-stranded plant, wherein at least two air separation strands are formed by distillation column systems with the four columns each. Each distillation column system is enclosed by its own cold box or several cold boxes and forms a single strand. 4 , which is explained below, shows an example of a four-stranded embodiment.

In a first variant of the invention, the four columns are in the form of two double columns arranged side by side, as described in claim 2 in detail. The two double columns can be prefabricated in the workshop and then transported to the site, the critical transport dimensions, for example, a maximum of 4.8 m diameter are met and still a high capacity of the distillation column system strand is achieved. At the construction site, the two double columns are installed in an insulation, preferably in a common cold box.

In a second variant, at least four, in particular all five, of said elements of the distillation column system are arranged one above the other, as shown in claims 3 and 4. An arrangement of two elements "one above the other" is understood here to mean that the upper end of the lower of the two elements is at a lower geodetic height than the lower end of the upper of the two elements and the projections of the two elements overlap in a horizontal plane. For example, the two elements are arranged exactly one above the other, that is, the axes of the two columns run on the same vertical line. Preferably, all elements arranged one above the other have the same vertical axis.

In a preferred embodiment of the invention, the first main capacitor is arranged in the bottom region of the first low-pressure column. By this is meant that the main condenser is below the mass transfer elements of the first low-pressure column in the same container as this. The main capacitor is used for the operation of all four columns. This arrangement can be applied to both variants of the invention.

Alternatively, the main condenser is arranged in a separate container from the first low-pressure column, which is located, for example, between the first low-pressure column and the first high-pressure column or adjacent to these two columns.

In principle, the first and the second high-pressure column can be supplied separately with air via two strands. Preferably, however, both are supplied via a common air line, which delivers a total compressed air flow, which is branched into at least two compressed air streams, wherein the first compressed air sub-stream is introduced into the first high-pressure column and the second compressed air sub-stream in the second high-pressure column. The air separation train formed by the four columns of the distillation column system then has only a single strand for air compression, purification and cooling.

It is also advantageous if the second low-pressure column, the first low-pressure column, the main condenser, the first high-pressure column and the second high-pressure column are arranged in a common coldbox.

In the invention, a single main condenser can supply all four columns with reflux liquid. In this way, a reduction in the expenditure on equipment and a particularly high flexibility in the installation of the individual column, which can be used for a space-saving arrangement of the columns. The columns are connected in pairs in parallel, resulting in a particularly high capacity with limited column diameter. This embodiment can be applied to both variants of the invention; it is particularly advantageous in the second variant. Alternatively, in both variants, a separate second main capacitor for the second high-pressure column and the second low-pressure column can be used, which is arranged for example in the bottom of the second low-pressure column.

Of course, the evaporation space of a common first main capacitor must also be charged with liquid. This is done in the invention, for example, by the fact that both a first liquid oxygen stream from the first low-pressure column and a second liquid oxygen stream from the second low-pressure column are introduced into the evaporation space of the main capacitor.

• – Eintritt des Verdampfungsteilraums eines Blocks verbunden mit nur einer der beiden Niederdrucksäulen oder mit beiden Niederdrucksäulen
• – Austritt des Verdampfungsteilraums eines Blocks verbunden mit nur einer der beiden Niederdrucksäulen oder mit beiden Niederdrucksäulen
• – Eintritt des Verflüssigungsteilraums eines Blocks verbunden mit nur einer der beiden Hochdrucksäulen oder mit beiden Hochdrucksäulen
• – Austritt des Verflüssigungsteilraums eines Blocks verbunden mit nur einer der beiden Hochdrucksäulen oder mit beiden Hochdrucksäulen

If the main condenser consists of several parallel blocks, there are various possibilities of connection between the entrances and exits of the evaporation and liquefaction partitions of the blocks, which basically can be combined as desired:

• - Entry of the evaporation compartment of a block connected to only one of the two low-pressure columns or with both low-pressure columns
• - Exit the evaporation compartment of a block connected to only one of the two low-pressure columns or with both low-pressure columns
• - Entry of the liquefaction compartment of a block connected to only one of the two high-pressure columns or with both high-pressure columns
• - The outlet of the liquefaction compartment of a block connected to only one of the two high pressure columns or with both high pressure columns

The invention also relates to a device according to claim 8 or 9. The device according to the invention can be supplemented by device features which correspond to the features of the dependent method claims.

The invention and further details of the invention are described below with reference to two in the Drawing schematically illustrated embodiments explained in more detail. In the drawings, only the most important elements are shown, in particular those with which the system of the invention differs from conventional air separation systems. Hereby show:

1 A first embodiment of a distillation column system according to the first variant of the invention,

2 A second exemplary embodiment of a distillation column system in the context of the first variant of the invention,

3 an embodiment of a distillation column system in the second variant of the invention and

4 the representation of a multi-strand system according to the invention.

In the 1 to 3 in each case only one distillation column system of one strand is shown, each with four columns. Each of the strands can be constructed, for example, in parallel in four or five times identical copy and then forms a multi-stranded system according to the invention. The main air compressors, cleaning devices and main heat exchangers, not shown, are also four- or five-stranded in these embodiments.

The distillation column system of the embodiment of the 1 has a first high pressure column 101 , a second high pressure column 201 , a first low-pressure column 102 , a second low-pressure column 202 , a first main capacitor 103 and a second main capacitor 203 on. Both main capacitors 103 . 203 are formed in the example by a six-stage or two three-stage cascade evaporator. The columns are arranged in the form of two double columns.

Each double column can be controlled substantially independently. The pressure in the low-pressure columns, for example, can be set and controlled separately. Through this decoupling, the overall control effort is made easier and any manufacturing tolerances in both double columns can be better compensated.

Via a common air line is a total compressed air flow 1 introduced. This was, as usual in the air separation, compressed in a main air compressor, cleaned in a cleaning device and cooled in a main heat exchanger to about dew point. (These steps are not shown in the drawing.) The total compressed air flow 1 is in a first compressed air sub-stream 100 and a second compressed air sub-stream 200 branched. The first compressed air partial flow 100 gets into the first high-pressure column 101 , the second compressed air sub-stream 200 in the second high-pressure column 201 initiated.

The main capacitor 103 has in the embodiment a uniform liquefaction space and a uniform evaporation space, that is these spaces are not - as in other embodiments of the invention - divided into one or more liquefaction subspaces and / or evaporation subspaces.

A first nitrogen gas stream 104 . 114 from the first high-pressure column 101 is in the liquefaction space of the first main capacitor 103 initiated. In the liquefaction space of the first main capacitor 103 becomes liquid nitrogen 115 generated at least to a first part as a first liquid nitrogen stream 105 to the first high-pressure column 101 is directed.

A second nitrogen gas stream 204 . 214 from the second high pressure column 201 is in the liquefaction space of the second main capacitor 203 initiated. In the liquefaction space of the second main capacitor 203 becomes liquid nitrogen 215 generated at least to a first part as a second liquid nitrogen stream 205 to the second high-pressure column 201 is directed.

A first liquid oxygen stream 106 from the first low-pressure column 102 flows from the bottom of the bottom mass transfer layer 107 the first low-pressure column 102 and thereby becomes the evaporation space of the first main capacitor 103 initiated. In the evaporation chamber of the first main capacitor 103 gaseous oxygen is formed. It becomes at least a first part as the first oxygen gas stream 108 in the first low-pressure column 102 initiated by placing it from below into the bottom mass transfer layer 107 the first low-pressure column 102 flows; a second part can be used directly as gaseous if required Obtained oxygen product and warmed in the main heat exchanger.

A second liquid oxygen stream 206 from the second low-pressure column 202 flows from the bottom of the bottom mass transfer layer 107 the second low-pressure column 202 and thereby becomes the evaporation space of the second main capacitor 203 initiated. In the evaporation chamber of the second main capacitor 203 gaseous oxygen is formed. It becomes at least a first part as a second oxygen gas stream 208 in the second low-pressure column 202 initiated by placing it from below into the bottom mass transfer layer 207 the second low-pressure column 202 flows; if necessary, a second part can be obtained directly as a gaseous oxygen product and heated in the main heat exchanger.

The return liquids 109 . 209 for the two low-pressure columns 102 . 202 each by a nitrogen-enriched liquid 20 formed on both high-pressure columns 101 . 201 is deducted from an intermediate or directly from the head. From the top of both low-pressure columns 102 . 202 becomes impure nitrogen 110 . 210 withdrawn and passed as residual gas through a subcooling countercurrent to the main heat exchanger (both not shown).

Also not shown is how from both high pressure columns 101 . 201 each withdrawn an oxygen-enriched bottoms liquid stream, in the subcooling countercurrent 23 is cooled and introduced into the evaporation space of the top condenser or the head condensers at least one crude argon column. The bottoms can either be run separately or mixed before the supercooling countercurrent and then split. Over the lines 111 . 211 becomes the low pressure columns 102 . 202 Liquid air fed at an intermediate point. This liquid air comes from the main heat exchanger, in the liquid pressurized oxygen 41 evaporated from the low pressure columns or pseudo-evaporated (if the oxygen pressure is supercritical).

The main product of the distillation column system is liquid oxygen 141 . 241 from the evaporation spaces of the main capacitors 103 . 203 deducted, merged and over line 14 fed to an internal compression, not shown. The liquid oxygen is pumped to a high product pressure, vaporized or pseudo-evaporated under this high product pressure, warmed to about ambient temperature and finally stripped off as gaseous pressure oxygen product.

Another product of the distillation column system is pressurized nitrogen directly from the top of the high pressure columns 101 . 201 withdrawn (lines 104 . 142 and 204 ), together via management 42 led to the main heat exchanger, warmed there and finally recovered as gaseous pressure nitrogen product. In addition, one part each 143 . 243 in the main capacitors 103 . 104 produced liquid nitrogen supplied to an internal compression and recovered as a high-pressure gaseous nitrogen product.

If Argon is to be produced as a product, can over the line pairs 113 . 114 . 213 . 214 a common classical argon production or a separate first and a second argon production be connected, wherein the line pairs 113 . 213 are connected to the lower portion of a crude argon column or each one of two parallel Rohargonsäulen. The internal structure and mode of operation of such a classic argon recovery are, for example, in DE 2325422 A . EP 171711 A2 . EP 377117 B2 (= US 5019145 ) DE 4030749 A1 . EP 628777 B1 (= US 5426946 ) EP 669508 A1 (= US 5592833 ) EP 669509 B1 (= US 5590544 ) EP 942246 A2 . EP 1103772 A1 . DE 19609490 (= US 5669237 ) 8th . EP 1243882 A1 (= US 2002178747 A1 ) and EP 1243881 A1 (= US 2002189281 A1 ). If the oxygen product must be delivered argon-free, a crude argon column can be connected in a similar manner, which then serves only for the discharge of argon. The crude argon column (s) and optionally the pure argon column (s) can be housed in separate cold boxes or in a common cold box with one or both double columns.

In a concrete example, the mass transfer elements in the two low-pressure columns 102 . 202 formed exclusively by ordered packing. The oxygen sections of the two low-pressure columns 102 . 202 (Area below the lines 113 / 213 are provided with an ordered packing with a specific surface area of 700 m ² / m ³ or alternatively 1200 m ² / m ³ , in the remaining sections the packing has a specific surface area of 500 m ² / m ³ . In addition, the two low-pressure columns 10 . 202 have a nitrogen section above the mass transfer sections shown in the drawing; this is then filled with a packing having a specific surface area of 500 m ² / m ³ or, alternatively, 1200 m ² / m ³ . By way of derogation, it is possible to combine ordered packing of different specific surface area within each of said sections.

In the high pressure columns 101 . 201 the mass transfer elements are formed exclusively by ordered packing with a specific surface area of 1200 m ² / m ³ . Alternatively, some of the mass transfer elements could be in one or both high pressure columns 101 . 201 be formed by conventional distillation trays, for example by sieve trays.

2 is different from this 1 in that the mass transfer elements of the high-pressure columns 101 . 201 are formed exclusively by sieve plates. In addition, the main capacitors are designed as six-stage cascade evaporator. Alternatively, it is also possible to use two three-stage cascade evaporators.

The embodiment of 1 and 2 can be modified by replacing 2 each with 3-stage main capacitors 103 . 203 or in each case a six-stage main capacitor 103 . 203 a common main capacitor is used, which is formed for example as a two-block six-stage cascade evaporator (as it is analogous in 3 is shown). This is then preferably not in the container of one of the low-pressure columns 102 . 202 arranged but outside in a separate container.

In 3 [= single drawing of IC1131a] is an example of a strand of an embodiment according to the second variant of the invention shown. The above too 1 and 2 The same applies analogously, as far as applicable.

The distillation column system of 3 has a first high pressure column 101 , a second high pressure column 201 , a first low-pressure column 102 , a second low-pressure column 202 and a "first", single main capacitor 103 which is formed by a six-stage cascade evaporator.

Via a common air line is a total compressed air flow 1 introduced. This was, as usual in the air separation, compressed in a main air compressor, cleaned in a cleaning device and cooled in a main heat exchanger to about dew point. (These steps are not shown in the drawing.) The total compressed air flow 1 is in a first compressed air sub-stream 100 and a second compressed air sub-stream 200 branched. The first compressed air partial flow 100 gets into the first high-pressure column 101 , the second compressed air sub-stream 200 in the second high-pressure column 201 initiated.

The main capacitor 103 has here a uniform liquefaction space and a uniform evaporation space, that is these spaces are not - as in other embodiments of the invention - divided into one or more liquefaction subspaces and / or evaporation subspaces.

A first nitrogen gas stream 104 from the first high-pressure column 101 and a second nitrogen gas stream 204 from the second high pressure column 201 be over line 114 into the liquefaction space of the main condenser 103 initiated. In the liquefaction space of the main condenser 103 becomes liquid nitrogen 115 generated. From the liquid nitrogen 115 become a first liquid nitrogen stream 105 to the first high-pressure column 101 and a second liquid nitrogen stream 205 to the second high-pressure column 201 diverted.

A first liquid oxygen stream 106 from the first low-pressure column 102 flows from the bottom of the bottom mass transfer layer 107 the first low-pressure column 102 and is thereby in the evaporation space of the main capacitor 103 initiated. In addition, via a line, not shown, a second liquid oxygen stream from the bottom of the second low-pressure column 202 in the evaporation space of the main capacitor 103 introduced. In the evaporation space of the main capacitor 103 gaseous oxygen is formed. It becomes a first part as the first oxygen gas stream 108 in the first low-pressure column 102 initiated by placing it from below into the bottom mass transfer layer 107 the first low-pressure column 102 flows. A second part is via a line as a second oxygen gas stream 208 in the second low-pressure column 202 introduced.

The return liquids 109 . 209 for the two low-pressure columns 102 . 202 be through a nitrogen-enriched liquid 20 formed by means of a pump 21 through a subcooling countercurrent 22 and a line 23 is pressed. The nitrogen-rich liquid 20 is at both high-pressure columns 101 . 201 subtracted from an intermediate or directly from the head and then merged (not shown). From the top of both low-pressure columns 102 . 202 becomes impure nitrogen 110 . 210 subtracted and over the residual gas lines 31 . 32 through the subcooling countercurrent 22 led to the main heat exchanger, not shown.

Also not shown is how from both high pressure columns 101 . 201 each withdrawn an oxygen-enriched bottoms liquid stream, in the subcooling countercurrent 23 is cooled and introduced into the evaporation space of the top condenser or the head condensers at least one crude argon column. The bottoms can either be run separately or mixed before the supercooling countercurrent and then split. Over the lines 111 . 211 becomes the low pressure columns 102 . 202 Liquid air fed at an intermediate point. This liquid sluice comes from the main heat exchanger, in the liquid pressurized oxygen 41 evaporated from the low pressure columns or pseudo-evaporated (if the oxygen pressure is supercritical).

The main product of the distillation column system is liquid oxygen 41 from the evaporation space of the main capacitor 103 withdrawn and fed to an internal compression, not shown. The liquid oxygen is pumped to a high product pressure, vaporized or pseudo-evaporated under this high product pressure, warmed to about ambient temperature and finally stripped off as gaseous pressure oxygen product.

Another product of the distillation column system is pressurized nitrogen via line 42 directly from the head of the high-pressure columns 101 . 201 withdrawn, warmed in the main heat exchanger and recovered as a gaseous pressure nitrogen product. In addition, a part 43 in the main capacitor 103 produced liquid nitrogen supplied to an internal compression and recovered as a high-pressure gaseous nitrogen product.

If Argon is to be produced as a product, can over the line pairs 113 . 114 . 213 . 214 a common classical argon production or a separate first and a second argon production be connected, wherein the line pairs 113 . 213 are connected to the lower portion of a crude argon column or each one of two parallel Rohargonsäulen. The internal structure and the mode of operation of such a classical argon recovery are, for example, in are, for example, in DE 2325422 A . EP 171711 A2 . EP 377117 B2 (= US 5019145 ) DE 4030749 A1 . EP 628777 B1 (= US 5426946 ) EP 669508 A1 (= US 5592833 ) EP 669509 B1 (= US 5590544 ) EP 942246 A2 . EP 1103772 A1 . DE 19609490 (= US 5669237 ) 8th . EP 1243882 A1 (= US 2002178747 A1 ) and EP 1243881 A1 (= US 2002189281 A1 ). If the oxygen product must be delivered argon-free, a crude argon column can be connected in a similar manner, which then serves only for the discharge of argon. The crude argon column (s) and optionally the pure argon column (s) can be housed in one or more separate cold boxes or in a common coldbox with the four other columns.

In a concrete example, the mass transfer elements in the two low-pressure columns 102 . 202 formed exclusively by ordered packing. The oxygen sections of the two low-pressure columns 102 . 202 (Area below the lines 113 / 213 is equipped with an ordered packing with a specific surface area of 700 m ² / m ³ or alternatively 1200 m ² / m ³ , in the remaining sections the packing has a specific surface area of 500 m ² / m ³ . In addition, the two low-pressure columns 10 . 202 have a nitrogen section above the mass transfer sections shown in the drawing; this is then filled with a packing having a specific surface area of 500 m ² / m ³ or, alternatively, 1200 m ² / m ³ . By way of derogation, it is possible to combine ordered packing of different specific surface area within each of said sections.

In the high pressure columns 101 . 201 the mass transfer elements are formed exclusively by ordered packing with a specific surface area of 1200 m ² / m ³ . Alternatively, some or all of the mass transfer elements will be in one or both high pressure columns 101 . 201 formed by conventional distillation trays, for example through sieve trays.

According to 4 is a multi-stranded plant by two or more distillation column systems according to one of 1 to 3 educated. In the example, there are four strands (Trins) Tr1 to Tr4. Each distillation column system is of its own coldbox 301 enclosed and forms a strand of a distillation column system. In the example, all four air separation strands are constructed identically; alternatively, individual or all strands could be designed differently. (Contrary to the schematic drawing, each distillation column system is designed as shown in FIG 1 is shown.) Each strand has an inlet filter 302 for atmospheric air (AIR), a main air compressor 303 , an air pre-cooling 304 an air purification 305 (usually formed by a pair of molecular sieve adsorbers), an air compressor 306 (Booster Air Compressor - BAC) with aftercooler 307 and a main heat exchanger 308 in a separate coldbox 309 on; These devices are each independent of the other strands. The in the reboiler 306 After-compressed air is in the main heat exchanger 308 liquefied (or - if its pressure is supercritical - pseudo-liquefied) and via pipe 311 the distillation column system in the coldbox 300 forwarded and there in the streams 111 and 112 from 1 branched. The further from the main heat exchanger 308 outgoing electricity 1 and the warm end of the main heat exchanger 308 inflowing fluids 41 . 42 . 32 are like in 1 numbered. The liquid oxygen 32 is vaporized or pseudo-evaporated in the main heat exchanger under high pressure (internal compression). All return streams are warmed in the main heat exchanger to about ambient temperature and withdrawn via the product lines P.

alternative to 4 For example, the hot part (air compression, pre-cooling and air purification) and / or the main heat exchanger may have a different number of strands than the distillation column system. For example, one distillation column system strand could be supplied by two main air compressor strands or two distillation column system strands from four main air compressor strands. The concept of the invention can also be applied to a process without air recompression 306 / 307 (For example, with compression of the total air to more than 5 bar above the highest of the operating pressures of the two high-pressure columns) or in processes with other elements such as a nitrogen cycle can be applied.

The refrigeration is in 4 not shown. Any known type of turbine circuit can be chosen, with one, two or more turbines. The distillation column system is in 4 deviating from the 1 to 3 shown without argon recovery; but it can - as in the 1 to 3 - Have an argon recovery, or even a column for the discharge of argon to improve the rectification.

Compared to a classical system, with a given product capacity, for example gaseous pressure oxygen, the number of distillation column system strands can be reduced by the invention, for example from six to five or from five to four.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

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• US 6748763 B2 [0005]
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• WO 2013104840 A1 [0008]
• WO 2009024672 A2 [0008]
• EP 1666823 A1 [0008]
• US 7516626 B2 [0008]
• US 6128921 [0016]
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• US 5592833 [0047, 0062]
• EP 669509 B1 [0047, 0062]
• US 5590544 [0047, 0062]
• EP 942246 A2 [0047, 0062]
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• EP 1243881 A1 [0047, 0062]
• US 2002189281 A1 [0047, 0062]

Cited non-patent literature

• Monograph "Tiefftemperaturtechnik" by Hausen / Linde (2nd edition, 1985) [0002]
• Review by Latimer in Chemical Engineering Progress (Vol. 63, No.2, 1967, page 35) [0002]

Claims (10)

A process for the cryogenic separation of air with a multi-stranded plant having at least two air separation strands, each of the two air separation strands having a coldbox containing a distillation column system comprising a first high-pressure column ( 101 ), a first low-pressure column ( 102 ) and a first main capacitor ( 103 ), which is designed as a condenser-evaporator and having an evaporation space and a liquefaction space, wherein - a first nitrogen gas flow ( 104 . 114 ) from the first high-pressure column ( 101 ) into the liquefaction space of the first main capacitor ( 103 ), - a first liquid nitrogen stream ( 105 ) from the liquefaction space of the first main capacitor ( 103 ) in the first high-pressure column ( 101 ) and - a first oxygen gas stream ( 108 ) from the evaporation space of the main capacitor ( 103 ) in the first low-pressure column ( 102 ), characterized in that - the distillation column systems of both air separation strands also have a second high pressure column ( 201 ) and a second low-pressure column, but have no further separation columns for nitrogen-oxygen separation, - the first high-pressure column ( 101 ) and the second high pressure column ( 201 ) of the distillation column systems of each of the two air separation strands have the same size, - the first low pressure column and the second low pressure column of the distillation column systems of each of the two air separation strands have the same size, - the first and the second low pressure column ( 102 . 202 ) of the distillation column systems contain each of the two air separation strands mass transfer elements, which in at least a portion of the respective low pressure column ( 102 . 202 ) are formed by an ordered packing made of folded metal sheets, the ordered packing having a specific surface area of more than 1000 m ² / m ³ , in particular 1200 m ² / m ³ or more. Method according to claim 1, characterized in that - the first high-pressure column ( 101 ) and the first low-pressure column ( 102 ) of the distillation column systems of each of the two air separation strands are arranged one above the other and form a first double column. The second high pressure column ( 201 ) and the second low-pressure column of the distillation column systems of each of the two air separation strands are superimposed to form a second double column and - the first double column and the second double column of the distillation column systems of each of the two air separation strands are juxtaposed. A method according to claim 1, characterized in that the following elements of the distillation column systems of each of the two air separation strands are arranged one above the other in the following order from top to bottom: - second low-pressure column - first low-pressure column ( 102 ) - first main capacitor ( 103 ) - first high-pressure column ( 101 ) Method according to one of claims 1 or 3, characterized in that the following elements of the distillation column system are arranged one above the other in the following order from top to bottom: - first low-pressure column ( 102 ) - first main capacitor ( 103 ) - first high-pressure column ( 101 ) - second high pressure column ( 201 ) Method according to one of claims 1 to 4, characterized in that the first main capacitor ( 103 ) in the bottom region of the first low-pressure column ( 102 ) is arranged. Method according to one of claims 1 to 5, characterized in that via a common air line, a total compressed air flow ( 1 ) supplied in at least two partial compressed air streams ( 200 . 200 ) is branched, wherein the first compressed air sub-stream ( 100 ) in the first high-pressure column ( 101 ) and the second compressed air sub-stream ( 200 ) in the second high-pressure column ( 201 ) is initiated. Method according to one of claims 1 to 6, characterized in that the second low-pressure column ( 202 ), the first low-pressure column ( 102 ), the main capacitor ( 103 ), the first high-pressure column ( 101 ) and the second high pressure column ( 201 ) are arranged in a common coldbox. Method according to one of claims 1 to 7, characterized in that - a second nitrogen gas stream ( 204 . 114 ) from the second high pressure column ( 201 ) into the liquefaction space of the main condenser ( 103 ), - a second liquid nitrogen stream ( 205 ) from the liquefaction space of the main condenser ( 103 ) in the second high-pressure column ( 201 ), - a second oxygen gas stream ( 208 ) from the evaporation space of the main capacitor ( 103 ) is introduced into the second low-pressure column, Cryogenic air separation plant with a multi-strand plant with at least two air separation strands, each of the two air separation strands having a coldbox, the one Distillation column system containing a first high pressure column ( 101 ), a first low-pressure column ( 102 ) and a first main capacitor ( 103 ), which is designed as a condenser-evaporator and having an evaporation space and a liquefaction space, and having - means for introducing a first nitrogen gas stream ( 104 . 114 ) from the first high-pressure column ( 101 ) into the liquefaction space of the first main capacitor ( 103 ), Means for introducing a first liquid nitrogen stream ( 105 ) from the liquefaction space of the first main capacitor ( 103 ) in the first high-pressure column ( 101 ) and means for introducing a first oxygen gas stream ( 108 ) from the evaporation space of the main capacitor ( 103 ) in the first low-pressure column ( 102 ), characterized in that - the distillation column system of both air separation strands also a second high pressure column ( 201 ) and a second low-pressure column, but have no further separation columns for nitrogen-oxygen separation, - the first high-pressure column ( 101 ) and the second high pressure column ( 201 ) of the distillation column systems of each of the two air separation strands have the same size, - the first low pressure column and the second low pressure column of the distillation column systems of each of the two air separation strands have the same size, - the first and the second low pressure column ( 102 . 202 ) of the distillation column systems contain each of the two air separation strands mass transfer elements, which in at least a portion of the respective low pressure column ( 102 . 202 ) are formed by an ordered packing made of folded metal sheets, the ordered packing having a specific surface area of more than 1000 m ² / m ³ , in particular 1200 m ² / m ³ or more. Cryogenic air separation plant according to claim 9, wherein - the first high pressure column ( 101 ) and the first low-pressure column ( 102 ) of the distillation column systems of each of the two air separation strands are arranged one above the other and form a first double column. The second high pressure column ( 201 ) and the second low-pressure column of the distillation column systems of each of the two air separation strands are superimposed to form a second double column and - the first double column and the second double column of the distillation column systems of each of the two air separation strands are juxtaposed.

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