EP1544559A1 - Process and device for the cryogenic separation of air - Google Patents

Abstract

First and second air separation units (ASU Train 1, ASU Train 2") deliver liquid oxygen streams (F1,F2) at high pressure into a tank (T1") from which it may be pumped (P1",P2") through a heat exchanger (V1") to provide gaseous oxygen (GOX). The identical assemblies may be in multiple connections.

Description

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

The basics of cryogenic decomposition of air in general 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.

Multi-strand air separation plants have so far become as independent as possible operated by each other to keep your redundancy as high as possible.

The invention is based on the object, a process of the type mentioned to find that is economically particularly favorable, in particular by relatively low Equipment costs.

This object is achieved in that two corresponding streams of first and the second cryogenic air separation plant together the be supplied similar step.

The common method step may be one or more of the The following described process stages act:

For example, a portion of the feed air may be for the first and second cryogenic air separation plants or the entire feed air for both cryogenic air separation plants be compressed together from the atmospheric pressure.

Downstream of a common or separate compression, a joint pre-cooling of the feed air for the first and the second cryogenic air separation plant be provided, for example in a common Heat exchanger, in a common direct contact cooler or in separate

Direct contact coolers, from cooling water from the same evaporative cooler be charged.

In combination with it or independently of it can be a common adsorptive Purification of the feed air for the first and the second cryogenic air separation plant be performed, for example, in a pair of Molecular sieve adsorbers, or in more than two parallel adsorber containers.

Is ever a stream in the first and in the second cryogenic air separation plant densified and / or recirculated, the corresponding post-compression can or cycle compaction are also carried out together.

Also, the pressure increase in the liquid state of each product or Intermediate stream from the first and second cryogenic air separation plant can be carried out together within the scope of the invention become.

If ever a liquid product stream from the first or second Cryogenic air separation plant to be introduced into a common tank, this is also an implementation of the invention, as well as the evaporation each of a liquid product stream from the first and second cryogenic air separation plant in a common evaporator.

Another realization of the invention would be the sharing of one Main heat exchanger for the cooling of feed air for both cryogenic air separation plants. This would be especially true when using Regenerators useful, for example, those with steel hurdles, as in WO 99/42773 are described.

The invention also relates to a method and a device for generating a gaseous print product by cryogenic separation of air according to the The preamble of claim 3 or claim 9.

The recovery of a gaseous printed product by pressure increase in the liquid Condition and subsequent evaporation (at subcritical pressure) or pseudo-evaporation (at supercritical pressure) is also referred to as internal compression. In this case, at least one of the products becomes liquid from one of the separation columns of a Cryogenic air separation plant or one with one of these columns deducted connected capacitor. (For a two-pillar system, it can be for example, nitrogen from the high-pressure column of a two-column system or to act on oxygen from the low pressure column.) This liquid product is now in liquid state brought to an elevated pressure, in indirect heat exchange evaporated with a heat transfer fluid or (at supercritical pressure) pseudo-evaporated and finally recovered as gaseous pressure product. When Heat transfer fluid can be used, for example, feed air or nitrogen become.

The pressure increase in the liquid can be by any known means be carried out, for example by means of a pump, the use of a hydrostatic potential and / or pressure build-up evaporation on a tank. At the Most commonly pumps are used. The "means for pressure increase" can in The simplest case can be formed by a single cryogenic pump. In all Usually, however, you set two or more in parallel and / or switchable Pumping to a certain redundancy and thus a significantly increased Resilience to achieve. Common are, for example, pump pairs, where in Normal operation only one pump is in operation. When using three parallel pumps Each of the pumps can be designed for a capacity of 50% Normal operation always two of the three devices are in operation.

Such internal compression methods are known, for example, from DE 830805, DE 901542 (= US 2712738 / US 2784572), DE 952908, DE 1103363 (= US 3083544), DE 1112997 (= US 3214925), DE 1124529, DE 1117616 (= US 3280574), DE 1226616 (= US 3216206), DE 1229561 (= US 3222878), DE 1199293, DE 1187248 (= US 3371496), DE 1235347, DE 1258882 (= US 3426543), DE 1263037 (= US 3401531), DE 1501722 (= US 3416323), DE 1501723 (= US 3500651), DE 2535132 (= US 4279631), DE 2646690, EP 93448 B1 (= US 4555256), EP 384483 B1 (= US Pat. No. 5,036,672), EP 505812 B1 (= US Pat. No. 5,263,328), EP 716280 B1 (= US Pat. No. 5,644,934), EP 842385 B1 (= US Pat. No. 5,954,937), EP 758733 B1 (= US Pat. No. 5,845,517), EP 895045 B1 (= US 6038885), DE 19803437 A1, EP 949471 B1 (= US 6185960 B1), EP 955509 A1 (= US 6196022 B1), EP 1031804 A1 (= US 6314755), DE 19909744 A1, EP 1067345 A1 (= US 6336345), EP 1074805 A1 (= US 6332337), DE 19954593 A1, EP 1134525 A1 (= US Pat. No. 6,477,860), DE 10013073 A1, EP 1139046 A1, EP 1146301 A1, EP 1150082 A1, EP 1213552 A1, DE 10115258 A1, EP 1284404 A1 (= US 2003051504 A1), EP 1308680 A1 (= US Pat. No. 6,612,129 B2), DE 10213212 A1, DE 10213211 A1, EP 1357342 A1 or DE 10238282 A1.

The invention particularly relates to multi-strand internal compression processes, ie those in which two or more cryogenic air separation plants are in parallel be operated in the same place. In many cases, the different strands (trains) identical to each other, but it is also possible, different Cryogenic air separation plants operate in this way in parallel. The Cryogenic air separation plants of the invention may be used, for example, as be formed classical double column system, but also as a one-, three- or Multi-pillar system. They can be used in addition to the columns for nitrogen-oxygen separation other devices for obtaining other air components, in particular of noble gases, for example an argon production.

A method and a device of the type mentioned are out WO 03016804 A2. Here, oxygen is obtained as a printed product. The liquid oxygen product of each individual cryogenic air separation plant is brought separately by means of a pump liquid pressure and evaporated. The gaseous Print product of the multi-strand system is finally merged.

The invention is based on the object, such a process and a to find corresponding device which are economically particularly favorable, especially by relatively low investment costs and particularly high Reliability.

This object is achieved in that the first and the second liquid product stream be mixed at least partially before the pressure increase. Preferably the two liquid products are brought together completely to an elevated pressure. This saves a pump set. Although the pump set is now double Having capacity, it is less expensive than two sets of simple capacity. In addition - with constant redundancy - the number becomes more rotating Machines diminished; This leads to increased reliability and reduced Maintenance and service costs.

Of course, the invention can also be applied to systems with more than two Cryogenic air separation plants are applied. For a four-stranded one Plant can, for example, the inner-compaction product of all four Cryogenic air separation plants brought together and through a common Means be brought to increased pressure. Alternatively, two can each Plants share a means to increase the pressure.

In the simplest case, the two liquid product streams are after their deduction from the Separation column of the respective cryogenic air separation plant in one Total product line merged and through this total product line to Pressure increase conducted in the liquid state.

Alternatively or additionally, the two liquid product streams are before Pressure increase initiated in a common liquid reservoir and from the the pressure increase in the liquid state is charged.

In many cases, the system already has such a liquid reservoir in order to in case of failure of the or one of the cryogenic air separation plants in the short term product to deliver by external evaporation (emergency supply, backup system). In In this case, it is favorable to use the means used for internal compression for Pressure increase also for this emergency supply to use. In addition to a special high availability at relatively low equipment and maintenance costs thereby a continuous operation of the pumps when switching to Emergency supply possible, and there is a reduction in the response time of the Emergency supply and less wear of the pumps.

Downstream of the pressure increase, the high pressure product, for example, in separate heat exchangers, for example in two each one of the two cryogenic air separation plants associated main heat exchanger system are evaporated. For this purpose, from the common product stream downstream of the pressure increase in the liquid state, a first partial flow and a second partial flow branched off. Of the first partial flow is in indirect heat exchange with a first heat transfer fluid stream brought the downstream of the indirect heat exchange at least partially introduced into a separation column of the first cryogenic air separation plant becomes. The second substream is in indirect heat exchange with a second Heat transfer fluid flow brought downstream of the indirect Heat exchange at least partially in a separation column of the second Cryogenic air separation plant is initiated.

Alternatively or additionally, the high pressure product in a heat exchanger vaporized, which is assigned to two cryogenic air separation plants, by the common product stream downstream of the pressure increase in the liquid Condition at least partially in indirect heat exchange with a common Heat transfer fluid flow is brought to a first part of the common Heat transfer fluid flow downstream of the indirect heat exchange in a Separation column of the first cryogenic air separation plant is initiated and a second part of the common heat transfer fluid stream downstream of the indirect Heat exchange in a separation column of the second cryogenic air separation plant is initiated.

Figur 1 eine erste viersträngige Tieftemperatur-Luftzerlegungsanlage,

Figur 2 eine zweite viersträngige Tieftemperatur-Luftzerlegungsanlage und

Figur 3 ein Ausführungsbeispiel der Erfindung.

The invention and further details of the invention are explained in more detail below with reference to the drawings. Hereby show:

FIG. 1 shows a first four-stranded cryogenic air separation plant,

Figure 2 shows a second four-stranded cryogenic air separation plant and

Figure 3 shows an embodiment of the invention.

FIG. 1 shows a system with four cryogenic air separation plants (ASU Train 1 to ASU Train 4; ASU = air separation unit). Each of these four strands has one complete system with coldbox, main heat exchanger, rectification system, lines, Machines and valves on. In the example, all four are cryogenic air separation plants constructed identically in their interior. The rectification system each preferably consists of two columns, a high-pressure column and a Low-pressure column, which has a main condenser in heat exchanging connection stand. Each of the four cryogenic air separation plants has its own Pump set P1 to P4. Each pump set has three separate ones in the examples Pumps on the liquid oxygen ("liquid product stream") from the Low pressure column of the respective strand are fed. Each of these pumps has a nominal throughput, which is half of the nominal product quantity corresponds internally compressed oxygen of the respective strand. In normal operation run two pumps per pump set P1 to P4; the third is turned on, if one of the other two fails. Alternatively, one, several or all Pump sets, for example, each consist of two pumps.

The outlet of each pump set is with the main heat exchanger system of respective cryogenic air separation plant connected. There it will be on high Pressure pumped oxygen either vaporized in the known way and heated (at subcritical pressure) or warmed (at supercritical pressure) and finally via the lines G1 to G4 as gaseous pressure product (GOX-gaseous oxygen) deducted. As a heat transfer fluid is a part of the feed air, High pressure nitrogen or another suitable fluid used.

At least temporarily, a portion of the liquid oxygen from the Low-pressure columns of the four cryogenic air separation plants not the Pump sets P1 supplied to P4, but via the lines L1 to L4 as Liquid product (LOX - liquid oxygen) deducted. This liquid is in the Example of Figure 1 in a double oxygen tank T1 / T2 trained Liquid reservoir directed, part of an emergency system (backup system) is. The emergency supply system also has another pump set P5 and a steam-heated water bath evaporator V on. If one or more of the Cryogenic air separation plants wholly or partially off, is the missing GOX product quantity supplemented by evaporation of liquid oxygen in the Backup System.

In Figure 2, only four pump sets are needed instead of the five pump sets of Figure 1. This is achieved by internal compaction and emergency supply in each 4 low-temperature air separation plants are integrated. Here is in every strand the entire liquid oxygen from the low-pressure column into an oxygen tank T1 ' initiated to T4 '. This is with the entry of the respective pump set P1 'to P4' connected. The outlet of the pump set is on the one hand with the inner compression heat exchanger for evaporation of the pressure oxygen against the heat transfer fluid connected in normal operation. On the other hand, the exit of each pump set is also each with a water bath evaporator V1 'connected to V4', with the aid of analogous to Figure 1 an emergency supply can be ensured. Through this integration of the Emergency supply system in the individual strands is the number of pump sets of reduced to four and greatly shortened the length of the fluid lines.

In the embodiment of Figure 3 according to the invention are in contrast only two pump sets P1 "and P2" needed. The following are the two in the Drawing left arranged cryogenic air separation plants described However, both shown on the right are identical. The reference numerals are accordingly identical except for the indices.

All the liquid oxygen in the low pressure column of the first Cryogenic air separation plant (ASU Train 1) is obtained from Figure 1, flows via a first liquid product line F1 into an oxygen tank T1 ", which as common liquid reservoir for the first and the second cryogenic air separation plant is being used. Accordingly, the liquid oxygen also becomes the second cryogenic air separation plant via a second Liquid product line F2 is introduced into the tank T1 "directly from this tank will now the pump set P1 "via one or (as shown) a plurality of liquid lines LX1 loaded according to the invention together for the first and the second Cryogenic air separation plant is used. In normal operation, the High-pressure oxygen, which emerges from the pump set P1 ", in each case half over the Partial flow lines TL1 and TL2 to the respective cryogenic air separation plant returned to there evaporated against the heat transfer fluid and / or warmed to become. The thus obtained gaseous pressure product leaves the Cryogenic air separation plants via the lines G1 and G2.

In emergency mode, at least one of the lines TL1 or TL2 is closed. The corresponding amount of high-pressure oxygen then flows to the Water bath evaporator V1 "and thus ensures the emergency supply.

Claims (14)

Process for the low-temperature decomposition of air, in which a first feed air stream of a first cryogenic air separation plant having at least one separation column is supplied, a second feed air stream is supplied to a second cryogenic air separation plant having at least one separation column, at least one first process stream, which is assigned to the first cryogenic air separation plant, and at least one second process stream, which is assigned to the second cryogenic air separation plant, are subjected to a similar method step, and the first and the second process stream are formed at least by at least one substream of the feed air, a product stream or an intermediate product stream of the first or second cryogenic air separation plant, characterized in that the two streams are fed together to the similar process step. A method according to claim 1, characterized in that the similar method step is formed by at least one of the following steps: joint compression of at least part of the feed air for the first and the second cryogenic air separation plant, co-cooling at least a portion of the feed air for the first and second cryogenic air separation plants downstream of a common or separate compression, jointly adsorptive cleaning of at least part of the feed air for the first and the second cryogenic air separation plant, joint recompression of at least part of the feed air for the first and the second cryogenic air separation plant downstream of a common or separate compression, combined compression of each product or intermediate product stream from the first or second cryogenic air separation plant, which is guided as a circulating stream, common pressure increase in the liquid state of each product or intermediate product stream from the first or second cryogenic air separation plant, Introduction of a respective liquid product stream from the first or second cryogenic air separation plant into a common tank, Vaporization of a respective liquid product stream from the first or second cryogenic air separation plant in a common evaporator, Cooling of feed air for the first and the second cryogenic air separation plant in a common main heat exchanger. A process for producing a gaseous print product by cryogenic separation of air, in which a first feed air stream of a first cryogenic air separation plant having at least one separation column is supplied, a second feed air stream is supplied to a second cryogenic air separation plant having at least one separation column, a first liquid product stream is removed from a separation column of the first cryogenic air separation plant, pressurized in the liquid state, and vaporized and / or heated by indirect heat exchange with a heat transfer fluid and subsequently recovered as a first portion of the gaseous print product; a second liquid product stream is taken from a separation column of the second cryogenic air separation plant, brought to an elevated pressure in the liquid state and vaporized and / or heated by indirect heat exchange with a heat transfer fluid and subsequently recovered as a second part of the gaseous print product,
characterized in that the first and second liquid product streams are at least partially mixed prior to the pressure increase. A method according to claim 3, characterized in that the first liquid product stream is withdrawn from the separation column of the first cryogenic air separation plant via a first liquid product line, the second liquid product stream is withdrawn from the separation column of the first cryogenic air separation plant via a second liquid product line, the first and the second liquid product line open into a total product line and the first and the second liquid product stream are conducted together over the entire product line for pressure increase in the liquid state. A method according to claim 3, characterized in that the first and the second liquid product stream are introduced into a common liquid reservoir and supplied from the liquid reservoir from the pressure increase in the liquid state. A method according to claim 5, characterized in that an emergency supply system for the evaporation of liquid product from the liquid reservoir is provided independently of the indirect heat exchange with the heat transfer fluid, said emergency supply system can be charged via a downstream of the pressure increase in the liquid state arranged branching with liquid product. Method according to one of claims 3 to 6, characterized in that from the common product stream downstream of the pressure increase in the liquid state, a first partial flow and a second partial flow are branched off, the first substream is brought into indirect heat exchange with a first heat transfer fluid stream, which downstream of the indirect heat exchange is at least partially introduced into a separation column of the first cryogenic air separation plant and the second substream is brought into indirect heat exchange with a second heat transfer fluid stream which is at least partially introduced into a separation column of the second cryogenic air separation plant downstream of the indirect heat exchange. Method according to one of claims 3 to 7, characterized in that the common product stream downstream of the pressure increase in the liquid state is at least partially brought into indirect heat exchange with a common heat transfer fluid stream, a first portion of the common heat transfer fluid stream is introduced downstream of the indirect heat exchange in a separation column of the first cryogenic air separation plant and a second portion of the common heat transfer fluid stream downstream of the indirect heat exchange is introduced into a separation column of the second cryogenic air separation plant. Device for producing a gaseous printed product by cryogenic separation of air, with a first cryogenic air separation plant, which is connected to a first feed air line and has at least one separation column, a second cryogenic air separation plant, which is connected to a second feed air line and has at least one separation column, a first liquid product line for removing a liquid product from a separation column of the first cryogenic air separation plant, wherein the first liquid product line via means for increasing the pressure in the liquid state with a heat exchanger for evaporation and / or heating of the product flow brought liquid to an elevated pressure by indirect heat exchange with a heat transfer medium Fluid is connected, a second liquid product line for removing a liquid product from a separation column of the second cryogenic air separation plant, wherein the second liquid product line via means for increasing the pressure in the liquid state with a heat exchanger for evaporation and / or heating of the liquid to an elevated pressure product stream by indirect heat exchange with a heat transfer medium Fluid is connected,
characterized in that the first and second liquid product lines are connected to the same pressure increasing means. Apparatus according to claim 9, characterized in that the first and the second liquid product line lead into a total product line and are connected via this total product line with the entrance of the means for increasing the pressure. Apparatus according to claim 9, characterized in that the first and the second liquid product line are connected to a common liquid reservoir and that the liquid reservoir is connected via a further liquid line with the inlet of the means for increasing the pressure. Device according to one of claims 9 to 11, characterized by an emergency supply system with means for evaporating liquid product from the liquid reservoir independently of the indirect heat exchange with the heat transfer fluid, said emergency supply system with the outlet of the means for pressure increase in the liquid state is connectable. Device according to one of claims 9 to 12, characterized in that the outlet of the means for increasing the pressure is connected to a first and a second partial flow line, the first partial flow line leads to means for indirect heat exchange with a first heat transfer fluid flow and means are provided for introducing the first heat transfer fluid flow downstream of the indirect heat exchange into a separation column of the first cryogenic air separation plant, and the second partial flow line leads to means for indirect heat exchange with a second heat transfer fluid flow and means are provided for introducing the first heat transfer fluid flow downstream of the indirect heat exchange into a separation column of the second cryogenic air separation plant. Device according to one of claims 9 to 13, characterized in that the outlet of the means for increasing the pressure is connected to a common product flow line, the common product flow line leads to means for indirect heat exchange with a common heat transfer fluid flow and both means for introducing a portion of the common heat transfer fluid stream downstream of the indirect heat exchange into a separation column of the first cryogenic air separation plant and means for introducing a portion of the common heat transfer fluid flow downstream of the indirect heat exchange into a second cryogenic separation column; Air separation plant are provided.

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