EP2986924A1

EP2986924A1 - Retrofittable device for low-temperature separation of air, retrofitting system, and method for retrofitting a low-temperature air separation system

Info

Publication number: EP2986924A1
Application number: EP14715547.7A
Authority: EP
Inventors: Tobias Lautenschlager
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2013-04-18
Filing date: 2014-04-03
Publication date: 2016-02-24
Anticipated expiration: 2034-04-03
Also published as: EP2986924B1; WO2014169989A1; PL2986924T3; CN105264317A; CN105264317B

Abstract

The retrofittable device for low-temperature separation of air comprises a distillation column system, which has a high-pressure column (3), a low-pressure column (4), and a first raw argon column (6). Said device comprises supply lines (101, 102) for connecting the first raw argon column (6) to a second raw argon column (41), wherein the supply lines pass through the outer wall of the first cold box (1), which encloses the high-pressure column (3), the low-pressure column (4), and the first raw argon column (6). The invention further relates to a retrofitting system, which comprises a second cold box (40), a second raw argon column (41), and corresponding supply lines (201 to 205), and to a method for retrofitting the device mentioned first.

Description

description

Retrofittable device for cryogenic separation of air, retrofit system and method for retrofitting a cryogenic air separation plant

The invention relates to a method according to the preamble of patent claim 1.

"Gas inlet" and "liquid return" form the so-called argon transition. They may be formed as separate lines or as a common line. In the second case, the corresponding line must have a relatively large cross section, so that the gas flow and the liquid flow in the opposite direction do not interfere and thus the functions of gas supply and

Liquid return can be met together.

A "cold box" is here understood to mean an insulating casing which comprises a heat-insulated interior completely with outer walls; in the interior of equipment to be isolated parts are arranged, for example, one or more

Separation columns and / or heat exchangers. The insulating effect can be through

corresponding configuration of the outer walls and / or be effected 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.

Methods and devices for the cryogenic decomposition of air are known, for example, from Hausen / Linde, Tiefftemperaturtechnik, 2nd edition 1985, Chapter 4 (pages 281 to 337). The distillation column system can be designed as a two-column system (for example as a classical Linde double column system), or as a three or more column system for nitrogen-oxygen separation.

If there is no need for a cryogenic production of argon, energy-optimized plants for nitrogen and / or oxygen production would like to do so called dummy argon column used ("first crude argon column"), as described for example in EP 540900 A1. This dummy argon column is equipped with about 25 theoretical plates and produces no marketable argon product, but an argon-rich residual gas, which consists of about 86% argon, 12% oxygen and 2% nitrogen. The production of an argon-rich residual gas improves the

Oxygen yield of the plant.

If such a plant later with an argon, in particular a pure argon extraction, as shown for example in EP 1 03772 A1,

be retrofitted, is associated with the previously known methods and devices high effort.

The invention is therefore an object of the invention to provide a device that can be retrofitted without much conversion with an argon, and a corresponding method for retrofitting and a retrofit system that requires a relatively small amount of equipment.

This object is solved by the entirety of the features of claim 1. The basic invention is to equip the device so that they can be retrofitted without opening the coldbox (s) with a full argon production (or at least with a full crude argon column) and thereby the existing first crude argon column can be reused by later a first part the argon-oxygen separation is carried out in the first crude argon column and (only) the remainder of the argon-oxygen separation in the second crude argon column to be upgraded. For this purpose, the corresponding "Vorsorgeleitungen" provided, passed through the outer wall of the cold box and there in particular with

Connection devices such as flanges provided. The

"Vorsorgeleitungen" remain in normal operation of the (not yet) retrofitted

Device out of service and have appropriate for this case

Shut-off devices that are suitable for being opened during retrofitting.

This differs significantly from the teaching of the above-mentioned EP 1 103772 A1. In particular, there is no "precaution line" between a first and a second one Rohargonsäule as defined above, but merely a conventional compound of two parts of a split crude argon column, which passes through no Coldboxwand. Also with regard to retrofitting an air separation plant without crude argon column by an additional argon module is not disclosed that

any lines as "precautionary line" as defined above

would be trained. Even then, the person skilled in the art would not infer from this the indication that the lines between the first and the second crude argon columns are designed as "precaution lines." The connecting lines are connected in such a way that after the retrofitting it is possible to connect the first and second crude argon columns as a series connection

Operate distillation sections, that is like two sections of a single distillation column, which are arranged one above the other or among each other. This can basically be realized in two different ways, namely:

- first variant: first crude argon column "under" the second crude argon column

- second variant: first crude argon column "over" the second crude argon column "below" and "above" does not refer to the spatial arrangement of the columns, but to their procedural interconnection. A first column is in this procedural sense "under" a second column, when in operation of the plant, the head vapor of the first column is introduced into the sump region of the second column and, conversely, the sump liquid of the second column flows to the head of the first column. A first column is located in the procedural sense "over" a second column, when the head vapor of the second column is introduced into the bottom region of the first column and the bottom liquid of the first column flows to the head of the second column during operation of the plant. The first variant of the invention is described in claim 2. It has the advantage that it works with a relatively small number of precautionary lines.

The first crude argon top condenser is shut down in this variant of retrofitting usually, but is replaced by a retrofitted second Rohargon- top condenser at the top of the retrofitted second Rohargonsäule. Alternatively, the first raw argon overhead condenser may be after retrofitting

continue to be operated, so to speak as an intermediate evaporator.

It is advantageous if another Vorsorgeleitung for the of (in the second

Rohargon overhead condenser) vaporized cooling fluid is provided in a central region of the low-pressure column. In addition, further supply lines for the introduction (in the second crude argon overhead condenser) of non-evaporated cooling fluid into a middle region of the low-pressure column and / or for the introduction of residual gas from a pure argon column may be provided in a middle region of the low-pressure column.

Claim 4 describes the second variant of the invention. In this case, the continued operation of the first crude argon top condenser after retrofitting is made possible. There is no need to retrofit a second crude argon top condenser, or at any rate only a relatively small one. The return for the first and the second crude argon column after retrofitting is generated exclusively or at least in large part by the first crude argon top condenser, which in principle continues to operate in the same way as before retrofitting. To connect a pure argon column and a pure argon column overhead condenser during retrofitting can be provided in the context of the second variant further Vorsorgeleitungen, as listed in claim 5. Alternatively, in the case of the first variant, an argon end product can also be obtained directly from the second crude argon column if the second crude argon column contains a corresponding number of theoretical plates and the final argon final product has some theoretical or practical trays below the head (or top condenser). the second crude argon column is arranged as described in US 5235816 for a one-piece crude argon column; in the second variant, these features are realized according to the first crude argon column.

In principle, the features of both variants of the retrofittable

Device are combined. Then both alternatives of retrofitting are possible. The selection can then be made at the time of retrofitting. The invention also relates to a retrofit system according to claims 6 to 9 for retrofitting a device of the type described above (main plant). Their connecting lines are preferably arranged so that they end at the level of the connections of the Vorsorgeleitung. In the best case, the coldbox of the retrofit system must be placed only next to the coldbox (s) of the main system and the corresponding connections are connected to each other directly or via short pipes.

Thirdly, the invention relates to a method according to claim 10 for retrofitting a cryogenic air separation plant with an argon production.

The retrofit system described above and the method for retrofitting can also be used if the main system is not or not completely designed for retrofitting. In this case, of course, the main system must be internally adapted. The retrofit system can still be delivered completely pre-assembled in a coldbox, if their size allows it.

The invention and further details of the invention are explained below with reference to embodiments schematically illustrated in the drawings. Hereby show:

Figure 1 shows an embodiment of the first variant of the invention and

Figure 2 shows an embodiment of the second variant of the invention.

With reference to FIG. 1, the main plant will first be described below, a cryogenic air separation plant without argon recovery, whose

Distillation column system is housed in the example in a single cold box 1 in the example. Alternatively, the columns and condensers of the distillation column system may also be arranged in two or more separate cold boxes.

Not shown are the compression, precooling and cleaning of the feed air and the refrigeration by work-performing relaxation of one or more process streams and the cooling of the feed air in a main heat exchanger. The main heat exchanger is used for cooling of feed air in indirect Heat exchange with recycle streams from the distillation column system. It can be composed of a single or several parallel and / or serially connected

Heat exchanger sections may be formed, for example, from one or more plate heat exchanger blocks. The main heat exchanger can be housed in the same cold box 1 with the distillation column system or in a separate coldbox.

A first, gaseous feed air stream 2 is in the sump area of a

High-pressure column 3 introduced. This is part of the distillation column system, which also has a low pressure column 4, a main condenser 5, a first

Rohargonsäule 6 and a first crude argon head capacitor 7 has. The main condenser is designed as a condenser-evaporator, in particular as a multi-storey bath evaporator (cascade evaporator). Alternatively, a could

one-storey bath evaporator or a falling film evaporator can be used. As crude argon top condenser 7 here single-storey bath evaporator is used, which also has a condenser-evaporator with evaporation space and

Liquefaction space forms.

A second, predominantly liquid feed air stream 8 is fed to the high-pressure column 3 at an intermediate point. At least a part of the liquid air is over

Receded line 9, cooled in a subcooling countercurrent 10 and fed via line 11 of the low pressure column 4 at an intermediate point.

The bottoms liquid 12 of the high-pressure column is also cooled in the subcooling countercurrent 10 and the lines 13 and 14 the

Evaporation space of the first raw argon top condenser supplied. The line 14 represents a "refrigerant line for introducing a cooling fluid into the evaporation space of the first crude argon top condenser". Via line 15, an impure liquid nitrogen flow from another

Subtracted intermediate point of the high-pressure column 3, supercooled (10) and abandoned via line 16 to the head of the low-pressure column 4.

A first part 17 of the gaseous top nitrogen of the high-pressure column 3 is introduced into the liquefaction space of the main condenser 5. In the main capacitor generated liquid nitrogen 18 is fed to a first part 19 as reflux to the top of the high pressure column. A second part 20 can be obtained after supercooling 10 via line 21 as a liquid product. A second part 22 of the gaseous nitrogen head of the high-pressure column 3 can be led directly to the main heat exchanger and then recovered as a gaseous pressure product.

From the bottom of the low pressure column liquid oxygen 23 is withdrawn and by means of a pump 24 to a first part 25 in the evaporation chamber of the

Main capacitor 5 transports. Gaseous oxygen 26 produced in the main condenser, like a flushing liquid 27, becomes the bottom of the

Low pressure column returned. From the top of the low-pressure column 4 gaseous impure nitrogen 28 is withdrawn, warmed in the subcooling countercurrent and fed via line 29 to the main heat exchanger. An intermediate point of the low-pressure column communicates via a gas feed line 30 and a liquid return line 31 with the bottom region of the first crude argon column 6.

Top gas 32 of the first crude argon column 6 is largely liquefied in the first crude argon top condenser. The liquefied portion flows via line 33 back to the top of the first crude argon column 6 and is used there as a liquid reflux. The gaseous remaining portion 34 is withdrawn from a first Rohargon line 34 and warmed in the main heat exchanger, either in their own passages or together with the impure nitrogen 29th

From the evaporation space first raw argon overhead condenser produced there vapor 34 and unevaporated liquid 35 are withdrawn and the

Low pressure column 4 is supplied at a suitable intermediate point. In that regard, the embodiment within the coldbox 1 corresponds to a conventional air separation plant without argon recovery, but with discharge of argon.

In the context of the invention, additional supply lines are provided for the retrofitting of an argon production. The embodiment of Figure 1 has the following Vorsorgeleitungen, which are shown in dashed lines in the drawing: a supply line 101 for discharging a gaseous overhead product of the first

crude argon,

a second supply line 102 for introducing liquid into the upper region of the first crude argon column,

a third supply line 103 for removing cooling fluid from the distillation column

System,

a fourth supply line 104 for introducing vaporized cooling fluid into a middle region of the low-pressure column,

a fifth supply line 105 for introducing non-evaporated cooling fluid into a middle region of the low-pressure column and optionally and

a sixth supply line 106 for introducing non-evaporated cooling fluid into a middle region of the low-pressure column. These supply lines pass through the outer wall of the first cold box 1 and each have a flange for connection to a pipeline. Before retrofitting, the supply lines are not in operation, but closed off.

If argon production is required at a later point in time, then a retrofit system is added as part of the method according to the invention for retrofitting, which has a second coldbox 40 in which a second crude argon column 41 has suitable connection lines.

In the embodiment of Figure 1, the retrofit system also has a second crude argon overhead condenser 42 and a pure argon column 43 with pure argon overhead condenser 44 and bottom evaporator 46. The connection lines 201, 202, 203, 204, 205 and 206 are fluidly connected to the corresponding supply lines 101 to 106. The lines 14 and 34 are shut off and put out of service.

Subsequently, the retrofitted system works like a normal one

Air separation plant with argon recovery in a split crude argon column. The divided crude argon column consists of a "lower portion" formed by the first crude argon column 6 and an "upper portion" with top condenser 42 formed by the second crude argon column 42. The first raw argon Top condenser is no longer operated; but his evaporation chamber should either be completely emptied or constantly flushed with a small stream.

The top gas of the first crude argon column 6 is passed via the lines 101 and 201 into the bottom region of the second crude argon column 41; in the opposite direction flows the

Bottom liquid of the second crude argon column 41 via a pump 45 and the lines 202 and 102 back to the top of the first crude argon column. 6

The supercooled bottoms liquid 13 from the high-pressure column 4 no longer flows to the first crude argon top condenser 7, but via the lines 103 and 203 in the retrofit system. After release of sensible heat in bottom evaporator 46 of the pure argon column, the further supercooled stream is split into two substreams 47 and 48, which are fed to the evaporation chambers of the two condenser-evaporators 42 and 44. The evaporated portion 49/50 becomes from there becomes over the

Lines 204 and 104, the remaining liquid fraction via the lines 205 and 105 and 206 and 106 fed into the low-pressure column 4. A portion 51 of the bottom liquid of the pure argon column 43 is withdrawn as liquid argon product. In the top condenser 44 non-liquefied residual gas 52 is discharged into the atmosphere (ATM).

Figure 2 shows an embodiment of the second variant of the invention. in the

Only the differences to FIG. 1 will be described below. Otherwise the same applies to FIG. 1. The operation of the main plant of FIG. 2 without argon recovery (cold box 1) does not differ from FIG. 1. However, the device has different precaution pipes:

a seventh supply line 301 for discharging gas from a middle section of the low-pressure column,

an eighth supply line 302 for introducing liquid into a middle one

Section of the low-pressure column,

a ninth supply line 303 for introducing gas into the lower region of the first crude argon column, a tenth supply line 304 for discharging liquid from the lower one

Area of the first crude argon column,

an eleventh supply line 305 for discharging a gaseous top product of the first crude argon column,

- A twelfth Vorsorgeleitung 306 for discharging cooling fluid from the

Distillation column system,

a thirteenth supply line 307 for introducing vaporized cooling fluid into a middle region of the low pressure column and

a fourteenth supply line 308 for introducing non-evaporated cooling fluid into a middle region of the low-pressure column.

The retrofit system in the coldbox 40 differs only by the lack of second Rohargon-Kopfkondenstor, the additional pump 60 and a correspondingly different interconnection of the connecting lines 401 to 409 of that of Figure 1.

After retrofitting, the entire plant of Figure 2 works like a conventional air separation plant with argon production in a split crude argon column. The divided crude argon column consists of a "lower portion" formed by the second crude argon column 42 and an "upper portion" with top condenser 7 formed by the first crude argon column 6.

Claims

claims

Apparatus for the cryogenic separation of air with a distillation column system, which has a high pressure column (3), a low pressure column (4) and a first crude argon column (6) and is arranged in at least one first coldbox (1), and with

- A gas supply line (30) for the introduction of gas from a central portion of

Low-pressure column (4) into the first crude argon column (6),

- A liquid return line (31) for introducing liquid from the

Rohargonsäule (6) in a middle section of the low-pressure column (4),

- A first raw argon top condenser (7) for generating

Reflux liquid for the first crude argon column (6), which is designed as a condenser-evaporator with liquefaction space and evaporation space,

- A coolant line (14) for introducing a cooling fluid in the

Evaporation space of the first crude argon top condenser (7) and with

- A first crude argon line (34) for removing a gaseous

Overhead product of the first crude argon column (6) from the distillation column system,

marked by

- means for shutting off the first Rohargonleitung and

- Vorsorgeleitungen (101, 102, 301, 302) for connecting the first

Rohargonsäule (6) with a second crude argon column, wherein the

Lead supply lines through the outer wall of the first coldbox (1) and are formed so that the first and second crude argon column can be operated as a sequential distillation sections.

Apparatus according to claim 1, characterized by

Means for shutting off the coolant line (14) to the first raw argon

Top condenser (7),

a first supply line (101) for discharging a gaseous overhead product of the first crude argon column (6),

- A second supply line (102) for introducing liquid into the upper

Area of the first crude argon column (6) and

- A third supply line (13) for discharging cooling fluid from the

Distillation column system. Apparatus according to claim 2, characterized by

a fourth supply line (104) for introducing vaporized cooling fluid into a middle region of the low-pressure column (4),

and particularly,

- A fifth supply line (105) for introducing unevaporated cooling fluid in a central region of the low-pressure column (4) and optionally and / or

- A sixth Vorsorgeleitung (106) for introducing unevaporated cooling fluid of a top condenser of a pure argon column in a central region of the low-pressure column (4).

Device according to one of claims 1 to 4, characterized by

Means for shutting off the gas supply line (30) to the first crude argon column (6),

- means for shutting off the liquid return line (31) from the first

Crude argon column (6),

- A seventh Vorsorgeleitung (301) for discharging gas from a middle

Section of the low-pressure column (4),

an eighth supply line (302) for introducing liquid into a middle one

Section of the low-pressure column (4),

a ninth supply line (303) for introducing gas into the lower one

Area of the first crude argon column (6) and

- A tenth supply line (304) for discharging liquid from the

lower portion of the first crude argon column (6).

Device according to one of claims 1 to 4, characterized in that characterized by

an eleventh supply line (305) for discharging a gaseous overhead product of the first crude argon column (6),

- A sixth Vorsorgeleitung (306) for discharging cooling fluid from the

Distillation column system,

- A twelfth Vorsorgeleitung (307) for the introduction of vaporized cooling fluid in a central region of the low-pressure column (6) and in particular

- A thirteenth Vorsorgeleitung (308) for introducing unvaporized cooling fluid from the top condenser of a pure argon column in a central region of the low-pressure column (4). Retrofit installation for retrofitting a device according to one of claims 1 to 4, characterized by

a second crude argon column (41),

- A second coldbox (40), in which the second crude argon column (41) is arranged and through

- Connecting lines (201 - 205) for connecting the second crude argon column with the Vorsorgeleitungen (101 - 105) of the device, wherein the

Pass connecting lines through the outer wall of the second cold box (2),

- Wherein the connecting lines (201 - 205) for connection to the

Vorsorgeleitungen (101 - 105) are formed.

Retrofit installation according to claim 6 for retrofitting a device according to one of claims 2 or 3, characterized by

- One or two connecting lines (201, 202) for connecting the lower

Area of the second crude argon column (41) to the first and the second

Connecting line (101, 102),

- A second raw argon overhead condenser (42) for generating

Return liquid for the second crude argon column (41), which is designed as a condenser-evaporator with liquefaction space and evaporation space, and

- A connecting line (203) for connecting the evaporation space of the second raw argon overhead condenser (42) with the third Vorsorgeleitung (103) and

- In particular by a connecting line (204) for introducing

vaporized cooling fluid from the evaporation space of the second Rohargon- head capacitor (42) in a central portion of the low-pressure column (4).

Retrofit installation according to claim 6 or for retrofitting a device according to one of claims 4 or 5, characterized by

one or two connecting lines for connecting the lower region of the second crude argon column (41) to the seventh and eighth precursor lines (301, 302), - One or two connecting lines for connecting the lower portion of the second Rohargonäule (41) to the ninth and tenth Vorsorgeleitung (303, 304).

Retrofit installation according to one of claims 6 to 8 for retrofitting a

Device according to one of the claims 4, characterized by a

Pure argon column (43) with a pure argon column overhead condenser (44).

A method for retrofitting a cryogenic air separation plant without argon production, characterized in that a retrofit installation according to one of claims 6 to 9 is placed next to a main plant without argon production and the connecting lines are connected to the main plant.