EP4018143A1

EP4018143A1 - Method for operating a heat exchanger, arrangement with a heat exchanger, and system with a corresponding arrangement

Info

Publication number: EP4018143A1
Application number: EP20767968.9A
Authority: EP
Inventors: Stefan Lochner; Ralph Spöri; Axel Lehmacher; Pascal Freko; Paul Heinz; Felix RÖßLER
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2019-08-23
Filing date: 2020-08-18
Publication date: 2022-06-29
Also published as: JP2022544643A; CA3143868A1; US20220316811A1; WO2021037391A1; AU2020339214A1; CN113966453A

Abstract

The invention relates to a method for operating a heat exchanger (1), in which a first operating mode is carried out in first time periods, and a second operating mode is carried out in second time periods that alternate with the first time periods; in the first operating mode a first fluid flow (A) is formed at a first temperature level, is fed into the heat exchanger (1) in a first region (2) at the first temperature level, and is partially or completely cooled in the heat exchanger (1); in the first operating mode a second fluid flow (B) is formed at a second temperature level, is fed into the heat exchanger (1) in a second region (3) at the second temperature level, and is partially or completely heated in the heat exchanger (1); and in the second operating mode the feeding of the first fluid flow (A) and of the second fluid flow (B) into the heat exchanger (1) is partially or completely halted. In the second time period the second region (12) is cooled by using cooling fluid that is conducted through passages in or on the heat exchanger (1) in the second region (12) but not in the first region (11) which comprises the terminal 30% at the warm end of the heat exchanger (1). A corresponding arrangement (10) and a system (100) with such an arrangement (10) are also covered by the present invention.

Description

description

Method for operating a heat exchanger. Arrangement with heat exchanger and

System with a corresponding arrangement

The present invention relates to a method for operating a heat exchanger, an arrangement with a correspondingly operable heat exchanger and an installation with a corresponding arrangement according to the preambles of the respective independent claims.

State of the art

In a large number of areas of application, heat exchangers (more technically correct: heat exchangers) are operated with cryogenic fluids, i.e. fluids with temperatures well below 0 ° C, in particular well below -50 ° C or -100 ° C. In the following, the present invention is mainly described with reference to the main heat exchangers of air separation plants, but it is basically also suitable for use in other areas of application, for example for plants for storing and recovering energy using liquid air or natural gas liquefaction or plants in the petrochemical industry.

For the reasons explained below, the present invention is also particularly suitable in plants for liquefying gaseous air products, for example gaseous nitrogen. Corresponding systems can, in particular, be supplied with gaseous nitrogen by air separation systems and liquefy it. The liquefaction is not followed by a rectification as in an air separation plant. Therefore, when the problems explained below are overcome, for example when there is no need for corresponding liquefaction products, these systems can be completely switched off and kept on standby until the next use.

For the construction and operation of main heat exchangers in air separation plants and other heat exchangers, please refer to the relevant specialist literature, for example H.-W.

Häring (Ed.), Industrial Gases Processing, Wiley-VCH, 2006, in particular Section 2.2.5.6, "Apparatus". Details on heat exchangers are general for example the publication "The Standards of the Brazed Aluminum Plate-Fin Heat Exchanger Manufacturers'Association", 2nd edition, 2000, in particular Section 1.2.1, "Components of an Exchanger".

Without additional measures, heat exchangers in air separation plants and other heat exchangers through which warm and cryogenic media flow, achieve temperature equalization and heat up when the associated plant is shut down and the heat exchanger is shut down, or the temperature profile that forms in a corresponding heat exchanger in stationary operation can be in such a Case not be held. If, for example, cryogenic gas is then fed into a heated heat exchanger when it is restarted, or vice versa, there are high thermal stresses as a result of different thermal expansion due to differential temperature differences, which in the long term can lead to damage to the heat exchanger or require a disproportionately high cost of materials and manufacturing to avoid such damage.

In particular, when a heat exchanger is shut down before it heats up as a whole, the temperatures at the previously warm end and at the previously cold end are equalized due to the good heat conduction (longitudinal heat conduction) in its metallic material. In other words, the previously warm end of the heat exchanger becomes colder over time and the previously cold end of the heat exchanger becomes warmer until the temperatures mentioned are at or near an average temperature. This is also illustrated again in the attached FIG. The temperatures, which were around -175 ° C or +20 ° C at the time of shutdown, equalize over several hours and almost reach an average temperature.

This behavior is observed in particular when, when an air separation plant is switched off, the main heat exchanger, which is housed insulated from the cold, is blocked together with the rectification unit, ie when no more gas is supplied from the outside. In such a case, typically only gas that arises due to thermal insulation losses is blown off cold. The same applies if a system for liquefying a gaseous air product, for example liquid nitrogen, is switched off. If warm fluid is subsequently fed in at the cooled, warm end of the heat exchanger when it is restarted, the temperature there rises suddenly. Correspondingly, the temperature at the heated, cold end drops suddenly when the system is restarted if the corresponding cold fluid is fed in there. This leads to the material stresses already mentioned and thus possibly to damage.

DE 10 2014018412 A1 discloses a method for operating a liquefaction process for liquefying a hydrocarbon-rich stream, in particular natural gas. During commissioning, and as long as the hydrocarbon-rich stream to be liquefied cannot be delivered in accordance with the specifications, at least one partial refrigerant stream from a refrigerant circuit, which is at a suitable temperature level, is passed through at least one heat exchanger in an amount that is controlled during commissioning instead of the hydrocarbon-rich stream to be liquefied and which, when normal operation is reached, is dimensioned in such a way that it compensates for the amount of heat introduced into the refrigeration circuit by the hydrocarbon-rich stream to be liquefied during normal operation.

US 2015/226094 A1 and EP 2 880 267 A2 describe the generation of electrical energy in a combined system comprising a power plant and an air treatment system. In a first operating mode, a storage fluid is produced and stored in the air treatment system from feed air. In a second operating mode, the storage fluid is evaporated or pseudo-evaporated under superatmospheric pressure and a gaseous high-pressure fluid formed in the process is expanded in a gas expansion unit of the power plant. In the second operating mode, gaseous natural gas is liquefied or pseudo-liquefied against the evaporating or pseudo-evaporating storage fluid.

CN 102 778 105 A describes a quick start of an oxygen generator in which, on the one hand, feed air is expanded in a turboexpander before it is liquefied and fed into the main rectification column, and in which, on the other hand, liquid argon, which is stored in a storage tank, is used in a refrigeration cycle is used to cool the feed air. US 2012/1617616 A1 or EP 2 449 324 B1 discloses a method for operating a liquefaction system for gas liquefaction using a main heat exchanger. A refrigerant compression circuit is provided, of which a low-pressure part conducts evaporated refrigerant from the main heat exchanger to a compressor and a high-pressure part returns the compressed and cooled refrigerant from the compressor to the main heat exchanger. The pressure within the condensing system is controlled by regulating the amount of vaporized refrigerant in either or both of the low pressure and high pressure parts of the condensing system.

The object of the present invention is to specify measures which enable a corresponding heat exchanger, in particular in one of the aforementioned systems, to be restarted after a long period of shutdown without the aforementioned disadvantageous effects occurring.

Disclosure of the invention

Against this background, the present invention proposes a method for operating a heat exchanger, an arrangement with a correspondingly operable heat exchanger and a system with a corresponding arrangement with the features of the respective independent claims.

First, some terms used to describe the present invention are explained and defined below.

As used herein, a "heat exchanger" is an apparatus which is designed for the indirect transfer of heat between at least two fluid flows, for example, which are guided in countercurrent to one another. A heat exchanger for use in the context of the present invention can be formed from a single or a plurality of heat exchanger sections connected in parallel and / or in series, for example from one or more plate heat exchanger blocks. A heat exchanger has “passages” which are set up to guide fluid and which are separated from other passages by separating plates or only connected on the inlet and outlet side via the respective headers. The passages are separated from the outside by means of side bars.

The passages mentioned are hereinafter referred to as "heat exchanger passages" designated. In the following, the two terms "heat exchanger" and "heat exchanger" are used synonymously in accordance with common usage. The same applies to the terms “heat exchange” and “heat exchange”.

The present invention relates in particular to the apparatus referred to in the German version of ISO 15547-2: 2005 as plate-fin heat exchangers. If a “heat exchanger” is used below, this should therefore be understood in particular as a rib-plate heat exchanger. A fin-plate heat exchanger has a large number of flat chambers or elongated channels lying one above the other, which are separated from one another by corrugated or otherwise structured and interconnected, for example soldered plates, usually made of aluminum. The panels are stabilized by means of side bars and connected to one another via these. The structuring of the heat exchanger plates serves in particular to enlarge the heat exchange surface, but also to increase the stability of the heat exchanger. The invention particularly relates to brazed fin and plate heat exchangers made of aluminum. In principle, however, corresponding heat exchangers can also be made from other materials, for example from stainless steel, or from various different materials.

As mentioned, the present invention can be used in air separation plants of a known type, but also, for example, in plants for storing and recovering energy using liquid air. The storage and recovery of energy using liquid air is also known as Liquid Air Energy Storage (LAES). A corresponding system is disclosed, for example, in EP 3 032 203 A1. Systems for liquefying nitrogen or other gaseous air products are also known from the specialist literature and are also described with reference to FIG. In principle, the present invention can also be used in any further systems in which a heat exchanger can be operated accordingly. It can be, for example, plants for natural gas liquefaction and separation of natural gas, the LAES plants mentioned, plants for air separation, liquefaction cycles of all kinds (especially for air and nitrogen) with and without air separation, ethylene plants (i.e. especially separation plants that process gas mixtures Steamerackern are set up), systems in which Cooling circuits, for example with ethane or ethylene at different pressure levels, and systems in which carbon monoxide and / or carbon dioxide circuits are provided act.

At times of high electricity supply, air is compressed, cooled, liquefied and stored in an insulated tank system in a first operating mode in LAES systems with corresponding electricity consumption. At times when the electricity supply is low, the liquefied air stored in the tank system is heated in a second operating mode, in particular after a pressure increase by means of a pump, and thus converted into the gaseous or supercritical state. A pressure flow obtained in this way is expanded in an expansion turbine which is coupled to a generator. The electrical energy obtained in the generator is fed back into an electrical network, for example.

Corresponding storage and recovery of energy is fundamentally not only possible using liquid air. Rather, other cryogenic liquids formed using air can also be stored in the first operating mode and used in the second operating mode to generate electrical energy. Examples of corresponding cryogenic liquids are liquid nitrogen or liquid oxygen or component mixtures which predominantly consist of liquid nitrogen or liquid oxygen. In corresponding systems, external heat and fuel can also be coupled in to increase efficiency and output power, in particular using a gas turbine whose exhaust gas is expanded together with the pressure flow formed from the air product in the second operating mode. The invention is also suitable for such systems.

Classic air separation systems can be used to provide the corresponding cryogenic liquids. If liquid air is used, it is also possible to use pure air liquefaction systems. The term "air processing systems" is therefore also used below as the generic term for air separation systems and air liquefaction systems.

The present invention can in particular also be used in a so-called nitrogen liquefier. Also systems for liquefaction and / or Decomposition of gases other than air benefit from the measures proposed according to the invention.

Advantages of the invention

In principle, cold gas from a tank or exhaust gas from the stationary system can flow through a heat exchanger during a shutdown of the associated system in order to avoid heating or to maintain the temperature profile developed in stationary operation (i.e. in particular the usual production operation of a corresponding system) . Such an operation, in which the usual, also normal operation, passages are used accordingly, can, however, only be implemented with great effort in conventional methods.

In certain cases, as proposed, for example, in US Pat. No. 5,233,839 A, heat from the surroundings can also be introduced there via thermal bridges in order to avoid the cooling of the warm end of a corresponding heat exchanger. If there is no process unit downstream of the heat exchanger with a significant buffer capacity for cold (e.g. no rectification column system with the accumulation of cryogenic liquids), such as in a pure air liquefaction system, excessive thermal stresses can occur when hot process streams are suddenly supplied to the warm end of the Recommissioning can be reduced.

In this case, for example, the warm process streams supplied after restarting can be at least partially relaxed in an expansion machine after exiting the cold end of the heat exchanger and as cold streams (which in this case, however, do not yet have the low temperature as they would later in normal operation present at the cold end) can be returned via the cold end to the warm end. In this way, the heat exchanger can be slowly brought to its normal temperature profile by Joule-Thomson cooling.

However, the present invention relates less to this case, i.e. less to processes in which, after restarting, the cold end of the heat exchanger is not directly connected to cold process streams (on the one that is present in normal operation Final temperature), but rather the case that cryogenic fluids are available from the start of restarting, which are to be heated by the heat exchanger, and which are therefore fed to the heat exchanger at the cold end from the restart.

If, as can be the case within the scope of the present invention, a process unit with a significant buffer capacity for cold is located downstream of the heat exchanger (e.g. a rectification column system with an accumulation of cryogenic liquids, as is the case in an air separation plant), one can use the above-described Measures to minimize the occurrence of thermal voltages at this point, however, at the simultaneously heated cold end, the sudden onset of the flow of colder fluid can lead to the occurrence of thermal voltages due to impermissibly high (temporal and local) temperature gradients. Keeping the warm end warm even promotes the formation of higher temperature differences at the cold end and thus the occurrence of increased thermal stresses. Therefore, in such cases, cooling or keeping the cold end of the heat exchanger cold is desirable or advantageous.

As mentioned, the present invention relates in particular to the case just explained. In other words, within the scope of the present invention, the case is considered that (in addition to the always possible heating at the warm end of the heat exchanger) the cold end of the heat exchanger is cooled down or kept cold during standstill phases.

To cool or keep the cold end of a corresponding heat exchanger cold, as proposed in US Pat. No. 5,233,839 A, the area to be cooled can be equipped with additional cooling passages that can be applied to the outside of the heat exchanger (block) in particular. By arranging corresponding passages with different densities (which can also be formed by a single, meandering pipe in the form of corresponding pipe sections), it is possible to dose the heat dissipated (or, in physically incorrect terminology, the cold introduced). Alternatively, it is also possible to use passages of the heat exchanger that are used during normal operation, at least in part, for cooling or keeping the cold end cold. Against this background, the present invention proposes a method for operating a heat exchanger. As will also be explained in detail below, the heat exchanger can in particular be part of a corresponding arrangement, which in turn can be designed as part of a larger system. The present invention can be used in particular in air processing systems of the type explained in detail above and below. In principle, however, it can also be used in other areas of application in which a flow through a corresponding heat exchanger is prevented during certain times and the heat exchanger heats up during these times or a temperature profile formed in the heat exchanger is equalized. In particular, the present invention can be used in an air separation plant, since in a corresponding air separation plant there is a buffer capacity for cold fluid at the cold end of the heat exchanger and it is therefore desirable to keep the cold end cold during standstill phases.

However, the present invention also relates in embodiments to those measures which avoid excessive thermal stress on the warm end of a heat exchanger. Such measures can be combined within the scope of the present invention with the measures proposed according to the invention, which are aimed at reducing thermal stresses at the cold end of the heat exchanger.

The present invention is based in one embodiment (hereinafter referred to as "first" embodiment) on the knowledge that cooling using an in particular cryogenic liquid that is evaporated in evaporation passages on or in the heat exchanger, but not previously, offers particular advantages. By using the measures proposed according to the invention, it is possible, in particular, to dispense with expensive pumps for providing a cooling flow. The operation of the heat exchanger proposed according to the invention offers advantages because it reduces both the consumption of cold fluids and the corresponding hardware and control and regulation technology does not have to be made available in a complex manner. A further advantageous embodiment of the invention (hereinafter referred to as “second” embodiment) is based on the knowledge that it can also offer particular advantages if gas is used as the cooling fluid, this but not through the entire heat exchanger, but only over a section at the cold end through its heat exchanger passages.

The first embodiment is explained below.

According to the first embodiment, the cooling at the cold end of a corresponding heat exchanger is carried out with liquid, for example with liquid nitrogen, which is taken from a container. The container can, in particular, be fed with a corresponding liquid during regular operation. The liquid is withdrawn in liquid form from the container and evaporation passages are fed into or on the heat exchanger. The evaporation passages can also be formed by line sections of a line provided in a suitable arrangement on or in the heat exchanger. The use of passages, which are also used in the regular operation of a corresponding heat exchanger for cooling and / or heating fluids, as corresponding evaporation passages is also possible in principle.

The corresponding liquid is removed from the container and fed into the evaporation passages in particular when a maximum temperature is exceeded at the cold end of the heat exchanger. In particular, the liquid in the container is at or near its boiling point. The container can be fed from another container or tank or from another source (e.g. the low-pressure column of an air separation plant).

As the temperature begins to equalize in the heat exchanger through conduction, heat is withdrawn from the refrigerant and evaporation occurs. The arrangement in the first embodiment of the present invention is such that a gas formed during the evaporation of the liquid (partially or completely) flows back into the tank (circulation principle). In particular, a pressure regulator at a gas phase outlet of the container can be used to set a defined container pressure in order to set the desired evaporation temperature level of the refrigerant. This is in particular a limit temperature for the cold end of the heat exchanger to be kept cold. In the first embodiment of the present invention, the arrangement is overall such that, due to the evaporation of the liquid, a driving pressure gradient and thus a natural circulation are established. The supply of the liquid to the container can also be regulated in that, for example, a metal temperature measurement on the heat exchanger determines the flow of refrigerant into the container.

Aspects of the second embodiment of the invention have already been or will be explained in more detail below.

In addition to the measures proposed according to the invention (i.e. both in the first and in the second embodiment), heat can be introduced at the warm end of the heat exchanger, for example by means of convective heat supply, heat supply by radiation or electro-thermal resistance heating. Details are explained below.

The cooling provided according to the invention at the cold end can in particular be matched to a heating power input at the head end. Adequate adjustment of the amount of heat supplied and removed results in a defined temperature gradient due to the longitudinal heat conduction in the metallic heat exchanger, which is determined by the conductive cross-sectional area, effective thermal conductivity and other geometry and process parameters. By coordinated regulation of the cooling and, if necessary, the heating, the almost linear temperature gradient is adjusted so that the steady-state temperature levels of the metallic heat exchanger at the warm and cold ends are maintained during the system shutdown. The coordination of the heating and cooling capacities with the equipment and process boundary conditions can take place in all embodiments of the invention, for example on the basis of the measurement of current and metal temperatures of the heat exchanger.

In contrast to temperature control of the warm and cold ends of a corresponding heat exchanger using measures as disclosed in the previously mentioned US Pat. No. 5,233,839 A, the method proposed according to the invention according to the first embodiment can have the advantage that the liquid supply of the The liquid used for cooling or keeping cold is the drainable The amount of heat is greater and refrigerant can be saved. According to the second embodiment, particularly targeted cooling can take place at the cold end of the heat exchanger.

In summary, the present invention proposes performing the method in first time periods in a first operating mode and in second time periods, which alternate with the first time periods, in a second operating mode. The first time periods and the second time periods do not overlap within the scope of the present invention. The first periods of time or the first operating mode carried out in a first period corresponds within the scope of the present invention to the production operation of a corresponding plant, i.e. in the case of an air separation plant that is the focus of the invention, to that operating mode in which liquid and / or gaseous air products flow through Air separation can be provided. Correspondingly, the second operating mode, which is carried out in the second operating time periods, represents an operating mode in which corresponding products are not formed. Corresponding second periods of time or a second operating mode are used in particular to save energy, for example in systems for liquefying and re-evaporation of air products for energy generation or in the previously mentioned LAES systems.

As already mentioned, the heat exchanger is preferably not flowed through in the second operating mode or is flowed through to a significantly lesser extent than in the first operating mode. However, the present invention does not fundamentally rule out that certain quantities of gases are also passed through a corresponding heat exchanger in the second operating mode. The amount of fluids passed through the heat exchanger in the second operating mode is always well below the amounts of fluids that are passed through the heat exchanger in a regular first operating mode. The amount of fluids passed through the heat exchanger in the second operating mode is, in the context of the present invention, for example, no more than 20%, 10%, 5%, or 1% or 0.1%, based on that in the first operating mode through the heat exchanger amount of fluid carried.

In the context of the present invention, as mentioned, the first operating mode and the second operating mode alternate in the respective time periods carried out, ie on a respective first period in which the first operating mode is carried out, there always follows a second period in which the second operating mode is carried out and the second period or the second operating mode is followed by a first period of time with the first operating mode, etc. In particular, however, this does not rule out that further time periods with further operating modes can be provided between the respective first and second time periods, for example a third period with a third operating mode. In the context of the present invention, in the case of a third operating mode, the following sequence results in particular: first operating mode - second operating mode - third operating mode - first operating mode, etc.

In the context of the present invention, in the first operating mode, a first fluid flow is formed at a first temperature level, fed into the heat exchanger in a first area at the first temperature level, and partially or completely cooled in the heat exchanger. In the context of the present invention, a gas mixture to be broken down by a gas mixture decomposition method, for example by air, which is decomposed in an air separation plant, can be used as a corresponding first fluid flow.

Furthermore, in the first operating mode, a second fluid flow is formed at a second temperature level, fed into the heat exchanger in a second region at the second temperature level and partially or completely heated in the heat exchanger. The formation of the second fluid flow can in particular represent the formation of a return flow in an air separation plant in the form of an air product or a waste flow.

The second temperature level corresponds in particular to the temperature at which a corresponding return flow is formed in one. It is preferably at cryogenic temperatures, in particular from -50 ° C. to -200 ° C., for example from -100 ° C. to -200 ° C. or from -150 ° C. to -200 ° C. In contrast, the first temperature level is at the first fluid stream is formed and fed to the heat exchanger in the first region, preferably at bypass temperature, but in any case typically at a temperature level well above 0 ° C, for example from 10 ° C to 50 ° C. If it is said here that a first or second fluid flow is formed at the first or second temperature level, it is of course not excluded that further fluid flows are formed at the first or second temperature level. Corresponding further fluid flows can have the same or different composition as or than the fluid of the first or second fluid flow. For example, a total flow can initially be formed from which the second fluid flow is formed by branching off.

Furthermore, within the scope of the present invention, several fluid flows can optionally also be formed and then combined with one another and used in this way to form the second fluid flow.

If it is said here that a fluid flow in the heat exchanger is "partially or completely" cooled or heated, this is understood to mean that either the entire fluid flow is passed through the heat exchanger, either from a warm end or an intermediate temperature level to the cold one End or an intermediate temperature level or vice versa, or that the corresponding fluid flow in the heat exchanger is divided into two or more partial flows which are taken from the heat exchanger at the same or different temperature levels. Of course, it is also possible to feed a further fluid flow to the respective fluid flow in the heat exchanger and to further cool or heat a collective flow formed in this way in the heat exchanger. In any case, however, a corresponding fluid flow is fed into the heat exchanger, specifically at the first or second temperature level, and this is cooled or heated in the heat exchanger (alone or together with other flows as explained above).

It is also understood that in addition to the first and second fluid streams, further fluid streams can also be cooled or heated in the heat exchanger, namely to the same or different temperature levels and / or starting from the same or different temperature levels as the first or second fluid stream . Corresponding measures are customary and known in the field of air separation, so that reference can be made in this regard to the relevant specialist literature, as cited at the beginning. In the second operating mode, within the scope of the present invention, the feeding of the first fluid flow and the second fluid flow into the heat exchanger and the respective cooling or heating in the heat exchanger are partially or completely suspended. For example, instead of the first fluid flow, which is passed through the heat exchanger in the first operating mode and is cooled in the heat exchanger, no fluid can be passed through the heat exchanger. The heat exchanger passages of the heat exchanger, which are used in the first operating mode to cool the first fluid flow, therefore remain impervious to flow in this case. However, it is also possible, instead of the first fluid flow, which is passed through the heat exchanger and cooled in the first operating mode, to pass a different fluid flow through the heat exchanger, in particular in a significantly smaller amount. The same also applies to the second fluid flow, which can be replaced by another gas in the second operating mode, but without causing cooling at the cold end of the heat exchanger, i.e. the mentioned second area, within the scope of the present invention.

If the cold end of the heat exchanger is being cooled, this occurs in particular to the second temperature level at which this cold end is present in the first operating mode.

According to the invention, it is now provided that using cooling fluid that is passed through passages in or on the heat exchanger in the second area, but not in the first area, which according to the invention comprises the terminal 30% of the heat exchanger at the warm end, the second area is cooled in the second period. As mentioned, the first and second configurations, for which important aspects have been explained above, are particularly advantageous here. To avoid misunderstandings, it should be emphasized that the first area is arranged at the warm end and the second area is arranged at the cold end of the heat exchanger, or the first area starts out from the warm end in the direction of the cold end of the heat exchanger and the second area starts out from the cold end End extends towards the warm end of the heat exchanger.

In the first embodiment, the passages are evaporation passages through which the flow in the second region of the heat exchanger (but not in the first region). It can be applied separately to the heat exchanger Passages, but also sections of passages that are used for regular heat exchange. These passages or sections can in particular run on or in a region of the heat exchanger which, starting from the second, cold end, extends a maximum of 50%, 40%, 30% or 20% in the direction of the first, warm end. As mentioned, however, these are not arranged on or in the first area, which comprises the terminal 30% of the heat exchanger at the warm end. In the first embodiment, the second area is cooled by evaporating a liquid, which is used as the cooling fluid, in evaporation passages which are in thermal contact with the second area. The liquid used here, as mentioned in particular liquid nitrogen, is taken from a container, gas formed in the evaporation is (partially or completely) returned to the container, and the liquid is through a pressure built up by the evaporation of the gas in the container through the Pressed evaporation passages. In this way, natural circulation is established and the amount of refrigerant used is reduced.

In contrast to methods according to the prior art, in the first embodiment the evaporation temperature and the cooling temperature can be set in particular by setting the pressure in the entire system, in particular using a pressure control and corresponding blowing off gas from the container. Because, within the scope of the first embodiment of the present invention, a liquid medium is made to evaporate for cooling, the amount of heat dissipated can be significantly increased compared to known methods in which a gas is used, with a reduced refrigerant requirement.

In the method according to the invention, according to the first embodiment, an amount in which the liquid is evaporated in the evaporation passages is advantageously set by feeding the liquid into the container, wherein the feeding of the liquid into the container can be regulated in particular by means of a temperature control. In this way, too, the temperature at which the second end of the heat exchanger is cooled can be adjusted accordingly. In the second embodiment of the invention, a gaseous cooling fluid is used. The passages used for cooling are each sections of heat exchanger passages which run in the heat exchanger between the first end and the second end, and which in particular in the first operating mode for normal heat exchange, in particular for the first and / or second fluid flow or further fluid flows, be used. A section can in particular be formed by appropriate (intermediate) removal options, for example page headers. The passages in which corresponding partial stretches are formed can in particular also comprise only a part, for example less than 50%, of the total number of passages.

In the second embodiment, the sections have a length of no more than 50%, 40%, 30% or 20%, for example 5 to 15%, of a total length of the heat exchanger passages, in particular between the first (warm) end and the second (cold) The End. As mentioned, however, these are not arranged on or in the first area, which according to the invention comprises the terminal 30% of the heat exchanger at the warm end. With such a design of the partial sections, in particular the second area or the cold end of the heat exchanger can be cooled in a targeted manner without causing (undesired) heat dissipation in the first area or in the warm end.

As already mentioned, in the present invention, in both embodiments, heat can be supplied to the first area in the second time period in that this heat is provided by means of a heat source and is transferred from outside the heat exchanger to the first area. In the simplest case, a corresponding heat source can be ambient heat, which by means of suitable measures, for example, can be introduced into a corresponding area of a coldbox or led to the first area of the heat exchanger. However, the heat source can also be an active heating device, as will also be explained in more detail below.

For example, this heat can be provided by means of the heat source and transferred to the first region via a gas space located outside the heat exchanger, or this heat can be via a heat exchanger contacting component, for example via metallic or non-metallic supports, suspensions or fastenings, are fed to the heat exchanger block. In the context of the present invention, electrical heating tapes with solid contact can also be used. The heat transfer takes place in the configuration in which the heat is transferred via the gas space, predominantly or exclusively without solid body contact, ie predominantly or exclusively in the form of heat transfer in the gas space, ie without or predominantly without heat transfer by solid heat conduction. The term "predominantly" here denotes a proportion of the amount of heat of less than 20% or less than 10%. In the case of the use of other heating devices such as electrical heating strips, these ratios naturally differ accordingly.

In this embodiment, the present invention therefore provides for active heating of the warm end of a corresponding heat exchanger to be carried out in the second period of time or for passive heating to be permitted via heat conduction. The term “outside of the heat exchanger” distinguishes the present invention from alternatively likewise possible heating by means of a targeted fluid flow through the heat exchanger passages. In this embodiment, the heating does not take place by transferring heat from a fluid guided through the heat exchanger passages.

In this context, it should be pointed out in particular that when a "region" of a heat exchanger (the first region or the second region) is mentioned, such regions do not refer to the direct feed point of the first or second fluid flow into the heat exchanger must restrict, but that these areas can also in particular represent terminal sections of a corresponding heat exchanger, which can extend a predetermined distance in the direction of the center of the heat exchanger. Corresponding areas can in particular include the terminal 10%, 20% or 30% of a corresponding heat exchanger, the first area according to the invention being understood to mean the terminal 30% at the warm end. Corresponding areas are typically not structurally delimited from the rest of the heat exchanger. In the context of the present invention, the heat can be transferred to the heat exchanger from outside the heat exchanger passages by means of the heat source by solid-state heat conduction via a heat conducting element contacting the first region. This can be done, for example, as already mentioned, via supports or metallic or non-metallic elements as heat conducting elements which contact the heat exchanger and which in turn are heated, for example, by means of a resistive or inductive heater. A corresponding arrangement can basically be designed as proposed in US Pat. No. 5,233,839 A.

As an alternative to heat transfer by solid-state heat conduction, the heat provided by the heat source can also be transferred to the first area via a gas space located outside the heat exchanger, as explained, namely at least partially convectively and / or at least partially radiatively, i.e. by thermal radiation.

The present invention in the embodiment in which heat is transferred from the heating device via the gas space located outside the heat exchanger to the first area, the particular advantage that, for example, in contrast to the aforementioned US Pat. No. 5,233,839 A, no suspension of a corresponding area is required, which is provided there for the transfer of heat. The present invention thus allows temperature control in this embodiment even in cases in which a heat exchanger block is stored in other areas, for example at the bottom or in the middle, in order in this way to relieve the stresses on the lines that connect a corresponding heat exchanger to the environment reduce. The method presented in the prior art, on the other hand, can only be used if a corresponding heat exchanger block is suspended from the top. Another disadvantage of the method described in the mentioned prior art compared to the mentioned embodiment of the invention is that heat is only introduced there to a limited extent at the supports and not over the entire surface of a heat exchanger in a corresponding area. This can, for example, lead to icing at the sheet metal jacket transitions of a corresponding heat exchanger. In contrast, the present invention in the mentioned embodiment enables an advantageous introduction of heat and in this way an effective temperature control without the disadvantages described above. In particular, within the scope of the present invention, as mentioned, it can be provided that the heat is transmitted at least partially convectively and / or radiatively to the first region via the gas space. In particular, gas turbulence can be induced for convective heat transfer so that heat build-up can be avoided. In contrast, pure radiant heating can act directly on the first area of the first heat exchanger via the corresponding infrared radiation.

As mentioned several times, the method of the present invention is particularly suitable for use in the context of a gas separation process, for example within the framework of a process for the low-temperature separation of air or natural gas, in which a correspondingly liquefied gas mixture is fed to a separation. In the first operating mode, the first fluid stream is therefore advantageously at least partially fed to a rectification after the partial or complete cooling in the heat exchanger. In other words, the gas separation process provides for the first fluid flow to be at least partially liquefied and, in particular, to be broken down into fractions of different material compositions. Certain changes, albeit slight changes compared to decomposition, can also result from the liquefaction itself due to the different condensation temperatures.

The present invention extends to an arrangement with a heat exchanger, the arrangement having means which are configured to carry out a first operating mode in first periods of time and to carry out a second operating mode in second periods of time which alternate with the first periods of time, in which first operating mode to form a first fluid flow at a first temperature level, to feed it into the heat exchanger in a first region at the first temperature level, and to cool partially or completely in the heat exchanger, in the first operating mode furthermore to form a second fluid flow at a second temperature level, in feed a second region at the second temperature level into the heat exchanger, and partially or completely heat it in the heat exchanger, and partially or completely shut off the feeding of the first fluid flow and the second fluid flow into the heat exchanger in the second operating mode etting. According to the invention, passages are provided in or on the heat exchanger in the second area, but not in the first area, which according to the invention comprises the terminal 30% at the warm end of the heat exchanger, and means are also provided which are set up for the second To cool the region in the second time period using cooling fluid which can be guided through the passages in or on the heat exchanger in the second region, but not in the first region.

In the first embodiment mentioned, which also relates to the arrangement according to the invention, the passages are used as evaporation passages through which the flow in the second area of the heat exchanger (but not in the first area), and a container is provided which can accommodate a cryogenic Liquid is set up as the cooling fluid. Means are provided which are designed to remove the liquid from the container and to evaporate it in the evaporation passages, these means being arranged to return gas formed during the evaporation into the container, and the liquid by means of a pressure built up by the evaporation of the gas in the container through the evaporation passages.

In a corresponding arrangement, as already mentioned, the evaporation passages are provided in particular separately from passages formed inside the heat exchanger on an outside of the heat exchanger.

In the second embodiment, the passages are each partial sections of heat exchanger passages that run in the heat exchanger, in particular between the first (warm) end and the second (cold) end, the partial sections having a length of no more than 50% or 40%, in particular not more than 30% or 20% and in particular more than 5% or 10%, of a total length of the heat exchanger passages, in particular between the first (warm) end and the second (cold) end, and wherein the cooling fluid can be provided in gaseous form and through the sections the heat exchanger passages can be guided. As mentioned, the sections mentioned are not formed in the first area, which includes the terminal 30% of the heat exchanger at the warm end. According to an advantageous embodiment, a heat source, in particular a heating device, is also provided, which is set up to supply heat to the first area in the second period by providing the heat by means of the heat source and transferring it from outside the heat exchanger to the first area.

For further aspects of an arrangement according to the invention and its advantageous configurations, express reference is made to the above explanations relating to the method according to the invention and its configurations. The arrangement according to the invention benefits from the advantages that have been described for corresponding methods and method variants.

In the context of the present invention, the heat exchanger is advantageously arranged in a coldbox, a gas space through which the heat can be transferred being formed by an area within the coldbox that is free of insulating material. In this case, the first area of the heat exchanger can be arranged in the gas space within the coldbox in particular without suspensions contacting the first area. Reference is also made to the above explanations regarding the advantage in this regard.

In the context of the present invention, the heat source can in particular be designed as a heating device in the form of a radiant heater, which can be heated electrically or using heating gas, for example. The heating device can, however, also be designed, in particular, as a resistive or convective heating device which heats up a heat-conducting element contacting the first region of the heat exchanger.

The present invention also extends to a plant, which is characterized in that it has an arrangement as it has been explained above. The system can in particular be designed as a gas mixture separation system. It is also distinguished in particular by the fact that it is set up to carry out a method, as was previously explained in embodiments. The invention is explained in more detail below with reference to the accompanying drawings, which show an embodiment of the invention and corresponding heat exchange diagrams.

Brief description of the drawings

Figure 1 illustrates temperature profiles in a heat exchanger after shutdown without the use of measures according to an embodiment of the present invention.

Figure 2 illustrates an arrangement with a heat exchanger according to a particularly preferred embodiment of the invention.

FIG. 3 illustrates an arrangement with a heat exchanger according to a further particularly preferred embodiment of the invention.

FIG. 4 illustrates an air separation plant which can be equipped with an arrangement according to an embodiment of the invention.

In the figures, elements that are identical or functionally or meaningfully corresponding to one another are indicated with identical reference symbols and are not explained repeatedly for the sake of clarity.

Detailed description of the drawings

FIG. 1 illustrates temperature profiles in a heat exchanger after shutdown (through which there is no flow) without the use of measures according to advantageous embodiments of the present invention in the form of a temperature diagram.

In the diagram shown in FIG. 1, a temperature labeled F1 at the warm end of a corresponding heat exchanger and a temperature labeled C at the cold end are shown in ° C on the ordinate versus a time in hours on the abscissa. As can be seen from FIG. 1, the temperature H at the warm end of the heat exchanger at the start of shutdown, which still corresponds to the temperature in regular operation of the heat exchanger, is approx. 20 ° C and the temperature C at the cold end is approx. -175 ° C . Over time, these temperatures increasingly converge. The high thermal conductivity of the materials built into the heat exchanger is responsible for this. In other words, here heat flows from the warm end towards the cold end. Together with the heat input from the environment, this results in an average temperature of approx. -90 ° C. The significant increase in temperature at the cold end is largely due to the internal temperature equalization in the heat exchanger and only to a lesser extent due to external heat input.

As mentioned several times, strong thermal stresses can arise in the case shown if the warm end of the heat exchanger is exposed to a warm fluid of approx. 20 ° C. in the example shown after regeneration for some time without further measures. Correspondingly, however, thermal stresses can also arise if a system downstream of the heat exchanger immediately supplies cryogenic fluids again, for example cryogenic liquids from a rectification column system of an air separation system. However, the present invention relates to plants in which the latter problem occurs less or not at all.

In FIG. 2, an arrangement with a heat exchanger according to a particularly preferred embodiment of the present invention is illustrated and denoted as a whole by 10. The configuration according to FIG. 2 essentially corresponds to the previously explained first configuration.

The heat exchanger is provided with the reference number 1. It has a first area 11 and a second area 12, which here are not structurally differentiated from the rest of the heat exchanger 1. The first area 11 and the second area 12 are characterized in particular by the feeding in and removal of fluid flows.

In the example shown, two fluid flows A and B are passed through the heat exchanger 1, with the fluid flow A previously being the first fluid flow and the fluid flow B previously referred to as the second fluid stream. The first fluid flow A is cooled in the heat exchanger 1, whereas the second fluid flow B is heated. The routing of the fluid flows A and B through the heat exchanger typically takes place only during normal operation, that is to say during the first time period or operating mode explained above. On the other hand, the cooling explained below takes place in a second period or operating mode.

For further details, reference is made to the explanations above. It should be emphasized in particular that in the second operating mode, explained several times, the heat exchanger is not flowed through by the corresponding fluid flows A and B, or not to the same extent as in the first operating mode. For example, in the second operating mode, other than the fluid flows A and B or the fluid flows A and B can be used in a smaller amount.

The heat exchanger 1 can be accommodated in the arrangement 10 in a cold box (not shown), which can in particular be partially filled with an insulating material, for example perlite. An area free of the insulating material, which at the same time represents a gas space surrounding the first area 11 of the heat exchanger 1, is indicated by G.

A heating device 3 is provided in the arrangement 10, which heats the first region 11 of the heat exchanger 1 during certain periods of time in the second operating mode or during the entire second operating mode. For this purpose, heat F1, illustrated here in the form of a plurality of arrows, can be transferred to the first end 11 or the first region 11 of the heat exchanger 1 by means of the heating device 3 in the arrangement 10. Although the transfer of the heat via the gas space G is illustrated here, this can in principle also take place via a, for example, metallic heat-conducting element, if the heating device 3 is designed accordingly. In the first operating mode, there is typically no corresponding heat transfer. The second region 12 of the heat exchanger is cooled in accordance with the embodiment of the invention illustrated here, or heat is actively dissipated from it, as explained below.

In the embodiment of the present invention illustrated here, the second region 12 of the heat exchanger 1 is converted into by an evaporation of a liquid Evaporation passages 13, which are in thermal contact with the second region 12, are cooled. The liquid is withdrawn from a container 2, and the gas formed during the evaporation is partially or completely returned to the container 2. In the embodiment of the invention illustrated here, the liquid is forced through the evaporation passages 13 by a pressure of the gas in the container 2 that has built up as a result of the evaporation. So there is a natural cycle.

In the arrangement according to FIG. 2, an amount in which the liquid is evaporated in the evaporation passages 13 is set by feeding the liquid into the container 2 via a feed line F. The feeding of the liquid into the container 2 is regulated by means of a temperature control TC on the basis of a value recorded by means of a temperature transmitter TI.

In the embodiment illustrated here, the pressure built up in the container 2 by the evaporation of the gas is set by blowing gas out of the container 2, for which purpose a pressure control PC with a pressure transducer is used here. This acts on a valve in an off-gas line O, which is not specifically designated. The evaporation temperature and thus the cooling temperature are also set by means of a corresponding pressure setting.

In Figure 3, an arrangement with a heat exchanger according to a particularly preferred embodiment of the present invention is illustrated. The configuration according to FIG. 3 essentially corresponds to the previously explained second configuration.

Here, too, the arrangement is denoted overall by 10. The heat exchanger is again provided with the reference number 1. It has a first area 11 and a second area 12. Reference is made to the explanations relating to FIG. 2 for further details.

In the example shown here, too, two fluid flows A and B are passed through the heat exchanger 1, the fluid flow A previously being referred to as the first fluid flow and the fluid flow B being previously referred to as the second fluid flow. The first fluid flow A is cooled in the heat exchanger 1, whereas the second fluid flow B is heated. The routing of the fluid flows A and B through the heat exchanger typically takes place only during normal operation, that is to say during the first time period or operating mode explained above. On the other hand, the cooling explained below takes place in a second period or operating mode.

In the heat exchanger 1, only indicated heat exchanger passages 14 run between the first end 11 and the second end 12. The passages each have sections 14 'which are no more than 20% of a total length of the heat exchanger passages 14 between the first end 11 and the second end 12. A cooling fluid C is provided in gaseous form and passed through the sections 14 ′ of the heat exchanger passages 14.

FIG. 4 illustrates an air separation plant with an arrangement with a heat exchanger, which can be operated using a method according to an advantageous embodiment of the present invention.

Air separation plants of the type shown are, as mentioned, often described elsewhere, for example at H.-W. Häring (Ed.), Industrial Gases Processing, Wiley-VCH, 2006, in particular Section 2.2.5, "Cryogenic Rectification". For detailed explanations of the structure and mode of operation, reference is therefore made to the relevant specialist literature. An air separation plant for using the present invention can be designed in the most varied of ways. The use of the present invention is not restricted to the embodiment according to FIG.

The air separation plant shown in FIG. 4 is denoted by 100 as a whole. It has, among other things, a main air compressor 101, a pre-cooling device 102, a cleaning system 103, a post-compressor arrangement 104, a main heat exchanger 105, which can represent the heat exchanger 1 as explained above and in particular is part of a corresponding arrangement 10, an expansion turbine 106, a throttle device 107 , a pump 108 and a distillation column system 110. In the example shown, the distillation column system 110 comprises a classic double column arrangement comprising a high pressure column 111 and a low pressure column 112 as well as a crude argon column 113 and a pure argon column 114. In the air separation plant 100, a feed air flow is sucked in and compressed by means of the main air compressor 101 via a filter (not designated). The compressed feed air stream is fed to the pre-cooling device 102 operated with cooling water. The pre-cooled feed air stream is purified in the cleaning system 103. In the cleaning system 103, which typically comprises a pair of adsorber containers used in alternating operation, the precooled feed air stream is largely freed of water and carbon dioxide.

Downstream of the cleaning system 103, the feed air flow is divided into two partial flows. One of the partial flows is completely cooled down to the pressure level of the feed air flow in the main heat exchanger 105. The other partial flow is recompressed in the booster arrangement 104 and also cooled in the main heat exchanger 105, but only to an intermediate temperature level. After cooling to the intermediate temperature level, this so-called turbine stream is expanded to the pressure level of the completely cooled partial stream by means of the expansion turbine 106, combined with it and fed into the high-pressure column 111.

An oxygen-enriched liquid bottom fraction and a nitrogen-enriched gaseous top fraction are formed in the high-pressure column 111. The oxygen-enriched liquid bottom fraction is withdrawn from the high pressure column 111, partly used as a heating medium in a bottom evaporator of the pure argon column 114 and fed in defined proportions into a top condenser of the pure argon column 114, a top condenser of the crude argon column 113 and the low pressure column 112. Fluid evaporating in the evaporation chambers of the top condensers of the crude argon column 113 and the pure argon column 114 is likewise transferred to the low-pressure column 112.

The gaseous nitrogen-rich top product g is withdrawn from the top of the high-pressure column 111, liquefied in a main condenser, which creates a heat-exchanging connection between the high-pressure column 111 and the low-pressure column 112, and fed in portions as a return to the high-pressure column 111 and expanded into the low-pressure column 112. An oxygen-rich liquid bottom fraction and a nitrogen-rich gaseous top fraction are formed in the low-pressure column 112. The former is partially pressurized in liquid form in the pump 108, heated in the main heat exchanger 105, and made available as a product. A liquid nitrogen-rich stream is withdrawn from a liquid retention device at the top of the low-pressure column 112 and discharged from the air separation plant 100 as a liquid nitrogen product. A gaseous nitrogen-rich stream withdrawn from the top of the low-pressure column 112 is passed through the main heat exchanger 105 and provided as a nitrogen product at the pressure of the low-pressure column 112. From the low-pressure column 112, a stream is also withdrawn from an upper region and, after heating, in the

Main heat exchanger 105 is used as what is known as impure nitrogen in the pre-cooling device 102 or, after heating by means of an electric heater, in the cleaning system 103.

Claims

1. A method of operating a heat exchanger (1), in which

- a first operating mode is carried out in first periods of time and a second operating mode is carried out in second periods of time that alternate with the first periods of time,

- In the first operating mode, a first fluid flow (A) is formed at a first temperature level, is fed into the heat exchanger (1) in a first area (11) at the first temperature level, and is partially or completely cooled in the heat exchanger (1),

- In the first operating mode, a second fluid flow (B) is formed at a second temperature level, is fed into the heat exchanger (1) in a second region (12) at the second temperature level, and is partially or completely heated in the heat exchanger (1), and

- In the second operating mode, the feeding of the first fluid flow (A) and the second fluid flow (B) into the heat exchanger (1) is partially or completely suspended, characterized in that

- The second area (12) in the second period using cooling fluid that is in the second area (12), but not in the first area (11), which comprises the terminal 30% at the warm end of the heat exchanger (1) Passages in or on the heat exchanger (1) is cooled.

2. The method according to claim 1,

- wherein the passages in the second region (12) of the heat exchanger (1) are evaporation passages (13) through which flow occurs, and wherein the cooling fluid is a liquid which is taken from a container (2) and evaporated in the evaporation passages,

- Gas formed during the evaporation of the liquid (13) being returned to the container (2), and

- wherein the liquid is forced through the evaporation passages (13) by a pressure of the gas in the container (2) built up by the evaporation of the liquid.

3. The method according to claim 2, in which an amount in which the liquid is evaporated in the evaporation passages (13) is set by feeding the liquid into the container (2).

4. The method according to claim 2 or 3, wherein the pressure built up by the evaporation of the gas in the container (2) is adjusted by blowing gas from the container (2).

5. The method according to claim 1,

- wherein the passages are each partial sections (14 ') of heat exchanger passages (14) which run in the heat exchanger (1),

- wherein the sections comprise a length of not more than 50% or 40% of a total length of the heat exchanger passages (14), and

- The cooling fluid being provided in gaseous form and being guided through the sections (14 ') of the heat exchanger passages (14).

6. The method according to any one of the preceding claims, in which a transfer of heat (Fl) to the first region (11) is carried out in the second period of time.

7. The method according to claim 6, wherein the heat (Fl) by means of a heat source (3) arranged outside the heat exchanger (1) provides the transfer the heat (H) is made from outside the heat exchanger (1) to the first region (11).

8. The method according to claim 7, in which the transfer of the heat (H) provided is carried out by solid-state heat conduction via a heat-conducting element contacting the first region (11).

9. The method according to claim 7, in which the transfer of the provided heat (Fl) via a gas space (G) located outside the heat exchanger (1) is transferred to the first area (11), the heat (W) via the gas space ( W) is transmitted at least partially convectively and / or radiatively to the first region (11).

10. The method according to any one of the preceding claims, in which the heat exchanger (1) is operated as part of a gas separation process and in which, in the first operating mode, the first fluid stream (A) is at least partially fed to a rectification after partial or complete cooling in the heat exchanger becomes.

11. The method according to any one of claims 2 to 4, is used as the evaporation passages (13) at least a part of passages of the heat exchanger (1), the first fluid flow (A) and / or the second fluid flow (B) in the first Lead operating mode, or separately to passages within the heat exchanger (1) on an outside of the heat exchanger (1) formed passages are used.

12. Arrangement (10) with a heat exchanger (1), the arrangement (10) having means which are set up for

- to carry out a first operating mode in first periods of time and to carry out a second operating mode in second periods of time which alternate with the first periods of time, to form a first fluid flow (A) at a first temperature level in the first operating mode, in a first area (2) on the first Feed the temperature level into the heat exchanger (1) and partially or completely cool it down in the heat exchanger (1),

- to form a second fluid flow (B) at a second temperature level in the first operating mode, to feed it into the heat exchanger (1) in a second area (3) at the second temperature level, and to partially or completely heat it in the heat exchanger (1), and

- in the second operating mode, partially or completely suspend the feeding of the first fluid flow (A) and the second fluid flow (B) into the heat exchanger (1), characterized in that

- in the second area (12), but not in the first area (11), which comprises the terminal 30% at the warm end of the heat exchanger (1),

Passages are provided in or on the heat exchanger (1), and

Means are provided which are set up for the second area (12) in the second time period using cooling fluid which is in the second area (12) but not in the first area (11) through the passages in or on the heat exchanger (1) is feasible to cool.

13. Arrangement according to claim 12,

- wherein the passages are provided as evaporation passages (13) through which the second region (12) of the heat exchanger (1) flows,

- wherein a container (2) is provided which is set up to receive a cryogenic liquid as the cooling fluid, and wherein means are provided which are set up to remove the liquid from the container (2) and in the evaporation passages (13) to evaporate, - wherein the means are set up to return gas formed during the evaporation into the container (2) and to press the liquid through the evaporation passages (13) by a pressure of the gas in the container (2) built up by the evaporation.

14. Arrangement (10) according to claim 12, wherein the passages each sub-sections (14 ') of

Are heat exchanger passages (14) which run in the heat exchanger (1), wherein the sections comprise a length of not more than 50%, 40%, 30% or 20% of a total length of the heat exchanger passages (14), and wherein the cooling fluid can be provided in gaseous form and can be guided through the sections (14 ') of the heat exchanger passages (14).

15. Plant (100), characterized by an arrangement (10) according to one of claims 12 to 14, wherein the plant (100) is designed as a gas separation plant, in particular as an air separation plant.