EP3587971A1 - Method for operating a heat exchanger, assembly with a heat exchanger and air processing installation with such an assembly - Google Patents

Abstract

The invention relates to a method for operating a heat exchanger (1), in which, in a first operating mode, one or more first fluids to be cooled are fed to a heat exchange area (10) at a first end (11) at a first temperature level and to the second end (12) through the Heat exchange area (10) is or are performed and one or more second fluids to be heated is or are supplied to the second end (12) at a second temperature level below the first temperature level and to the first end. It is provided that the first operating mode is carried out in a first operating period interrupted by a second operating period, the supply of the first and second fluid or fluids is prevented in the second operating period, and in one or more partial periods of the second operating period in a second Operating mode the first end (11) of the heat exchange area (10) by applying one or more third fluids, which is or are fed to the heat exchange area (10) at the first end (11) and guided in the direction of the second end (12), is tempered to the first temperature level or a third temperature level that differs from this by no more than 80 Kelvin. A corresponding arrangement (100) and a system with such an arrangement (100) are also the subject matter of the present invention.

Description

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

State of the art

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

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

For the construction and operation of main heat exchangers in air separation plants and other heat exchangers, 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 about 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 " refer to.

Without additional measures, the heat exchangers of air separation plants and other heat exchangers through which warm and cryogenic media flow flow compensate for the temperature and heat up when the associated plant is at a standstill and the decommissioning of the heat exchanger, or the temperature profile that develops in a corresponding heat exchanger in stationary operation can occur in such a way Case cannot be held. If, for example, cryogenic gas is subsequently fed into a heated heat exchanger when it is put back into operation, or vice versa, there are high thermal stresses due to different thermal expansion due to differential temperature differences, which can damage the heat exchanger or require a disproportionately high amount of material or production.

In particular, when a heat exchanger is decommissioned before it heats up overall, due to the good heat conduction (longitudinal heat conduction) in its metallic material, the temperatures at the previously warm end and at the previously cold end are equalized. In other words, the previously warm end of the heat exchanger becomes colder over time and the previously cold end of the heat exchanger warmer until the temperatures mentioned are at or close to an average temperature. This is also attached in the Figure 1 illustrated again. The temperatures, which were around -175 ° C or +20 ° C at the time of decommissioning, converge over several hours and reach almost a medium temperature.

This behavior is observed in particular when the main heat exchanger, which is housed in a cold-insulated manner, is blocked together with the rectification unit when an air separation plant is switched off, ie when no more gas is supplied from the outside. In such a case, typically only gas that is caused by thermal insulation losses is blown off cold. The same also applies if a system for liquefying a gaseous air product, for example liquid nitrogen, is switched off.

If hot fluid is subsequently fed into the cooled, warm end of the heat exchanger when it is restarted, the temperature suddenly increases there. Accordingly, the temperature at the heated cold end drops suddenly when restarting, if corresponding cold fluid is fed in there, suddenly. This leads to the material stresses already mentioned and thus possibly to damage.

The present invention therefore has the task of specifying measures which enable a corresponding heat exchanger, in particular in one of the aforementioned systems, to be put into operation again after a prolonged decommissioning without the disadvantageous effects mentioned 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.

In the parlance used here, a "heat exchanger" is an apparatus which is designed for the indirect transfer of heat between at least two fluid streams, for example 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 for fluid guidance and are fluidically separated from other passages by separating plates or are only connected on the input and output sides via the respective headers. The passages are separated from the outside by side bars. The passages mentioned are referred to below as "heat exchanger passages". In the following, the terms "heat exchanger" and "heat exchanger" are used synonymously. The same applies to the terms "heat exchange" and "heat exchange".

The present invention relates in particular to the apparatuses designated as fin-plate heat exchangers in accordance with the German version of ISO 15547-2: 2005. If the term "heat exchanger" is used below, this should in particular be understood to mean a fin-plate heat exchanger. A fin-plate heat exchanger has a large number of superimposed flat chambers or elongated channels, each of which is usually corrugated or otherwise structured and connected to one another, for example soldered plates. made of aluminum, are separated from each other. The plates are stabilized by means of side bars and connected to each other via them. The structuring of the heat exchanger plates serves in particular to increase the heat exchange area, but also to increase the stability of the heat exchanger. The invention relates in particular to brazed aluminum fin-plate heat exchangers. 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 referred to as Liquid Air Energy Storage (LAES). A corresponding system is for example in the EP 3 032 203 A1 disclosed. Plants for the liquefaction of nitrogen or other gaseous air products are also known from the specialist literature and also with reference to the Figures 8A and 8B described. In principle, the present invention can also be used in any other systems in which a heat exchanger can be operated accordingly. For example, these can be plants for liquefying natural gas and separating natural gas, the aforementioned LAES plants, plants for air separation, all types of liquefaction circuits (in particular for air and nitrogen) with and without air separation, ethylene plants (in particular separation plants that process gas mixtures) Steam crackers are set up), systems in which cooling circuits are used, for example with ethane or ethylene at different pressure levels, and systems in which carbon monoxide and / or carbon dioxide circuits are provided.

At times of high electricity supply, air is compressed, cooled, liquefied and stored in an insulated tank system in a first operating mode in a first operating mode. At times of low electricity supply, 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 stream 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.

Appropriate 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 to generate electrical energy in the second operating mode. 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 in order to increase the efficiency and the output power, in particular using a gas turbine, the exhaust gas of which is expanded together with the pressure stream formed from the air product in the second operating mode. The invention is also suitable for such systems.

Classic air separation plants can be used to provide appropriate cryogenic liquids. If liquid air is used, it is also possible to use pure air liquefaction systems. The term “air treatment plants” is therefore also used below as a generic term for air separation plants and air liquefaction plants.

Advantages of the invention

In principle, cold gas from a tank or exhaust gas from the stationary system can flow through a heat exchanger while the associated system is at a standstill, in order to avoid heating or that in the stationary system Operation (ie in particular the usual production operation of a corresponding system) to maintain a temperature profile. However, such an operation can only be implemented with great effort in conventional methods.

In particular in the case of small amounts of corresponding cold gases or low flow velocities in the heat exchanger, incorrect distribution within a heat exchanger block and, in particular, over several heat exchanger blocks cannot be ruled out. In principle, however, it is desirable to keep the gas quantities used low, for example in order to avoid product losses or the consumption of appropriate cryogenic media.

The present invention is based on what appears at first glance to be paradoxical the knowledge that when a heat exchanger used to provide cryogenic fluids is taken out of operation, it is particularly advantageous to supply it with a warm fluid for a corresponding period of time. Against the background of the efforts usually made to thermally insulate a corresponding heat exchanger to avoid additional heat input, this appears to be of little use, for example using cold boxes and the like. In the context of the present invention, however, it was recognized that the temperature control proposed according to the invention, or the "keeping warm" of the heat end of the heat exchanger to a certain extent within the scope of the present invention, can be achieved by introducing warm fluids, which include a possible temperature loss and thus outweigh any increased energy requirements.

Because when a warm fluid is fed back into the warm end of the heat exchanger due to the temperature control of the warm end proposed according to the invention, the temperature difference between the warm fluid and the warm end of the heat exchanger is less than in the conventional case explained at the beginning, extreme temperature jumps or temperature gradients become excessive short time here at least significantly reduced. By using the present invention, the material stresses that occur during corresponding load changes can therefore also be greatly reduced and the service life of a corresponding heat exchanger, which is largely defined by the number of such load changes, can be significantly increased.

As explained in the below Figure 2 illustrated, to which reference is made briefly at this point, if the warm end of the heat exchanger is brought to a temperature level by application of one or more fluids, at which the warm end at the beginning of the decommissioning or in the regular operating mode is present, or to a temperature level close to this temperature level, the warm end is kept close to the temperature level at which the warm end is at the beginning of the decommissioning or in the regular operating mode. This makes it possible to apply warm fluid to the warm end again during a subsequent recommissioning without excessive thermal stresses occurring at the warm end. Since cold fluid is typically not yet available at the cold end at a corresponding point in time due to the temporary decommissioning of the associated system or a corresponding temperature gradient can be smoothed here, as also proposed in embodiments of the present invention, temperature control of the second (cold) Do not end up at a correspondingly low temperature level. This heats up accordingly. Alternatively, however, the cold end of the heat exchanger can be appropriately tempered.

In the context of the present invention, the temperature profile in a heat exchanger during the downtime of a corresponding system can be very well controlled and calculated in further configurations, which are also explained in detail below, and the number of possible load changes (switching on and switching off) can thus be determined , Alternatively, if a required number of starts and stops and the respective downtime are known, the amount of feed gas (temperature control fluid) required and how, for example, optimal time or sensor-based control can be carried out. This is particularly advantageous if a corresponding system or its heat exchanger is frequently put into and out of operation, for example in the case of a system for storing and recovering energy, a system for liquefying a gaseous air product such as nitrogen or another of the ones explained above other plants.

Overall, the present invention proposes a method of operating a heat exchanger with a heat exchange area extending between a first end and a second end.

In the parlance used here, a "heat exchange area" is an area in which heat exchange takes place between two or more fluids in a corresponding heat exchanger. A corresponding heat exchange area can extend over the entire length of a corresponding heat exchanger or heat exchanger block. However, it is also possible for fluids to be supplied and / or removed from a corresponding heat exchanger at an intermediate temperature level. In this case, a heat exchange area for corresponding fluids only extends over the area in which one or more such fluids are subjected to heat exchange, ie not over the entire length of the heat exchanger or heat exchanger block. If a first or warm end of a heat exchanger (and not specifically a heat exchange area) or a second or cold end of a heat exchanger (and not specifically the heat exchange area) is mentioned above and below, this also includes the first or second end of a corresponding one Understand heat exchange area.

In the context of the present invention, in a first operating mode, one or more first fluids to be cooled are supplied to the heat exchange region at the first end at a first temperature level and are guided through the heat exchange region from the first end to the second end. The "first end" of the heat exchange area (which, as mentioned, can also be one end of the heat exchanger as a whole) is the aforementioned so-called warm end. Accordingly, the "second end" is the aforementioned cold end. In the context of the present invention, in the first operating mode, one or more second fluids to be heated are also supplied to the heat exchange area at the second end at a second temperature level below the first temperature level and are guided through the heat exchange area from the second end to the first end.

The first and second temperature levels depend in particular on the use of a corresponding heat exchanger. As explained several times, comes the present invention in particular in connection with the production or treatment of cryogenic fluids for use, for example in connection with the cryogenic air separation or the liquefaction of gaseous air products. Here, the first temperature level is in particular 0 to 100 ° C, for example 0 to 50 ° C and the second temperature level in particular is -100 to -200 ° C, for example -125 to -175 ° C. A corresponding heat exchanger is typically for operation at a superatmospheric pressure level, for example at 1 to 50 bar abs., In particular at 5 to 20 bar abs. may be set up. As explained, a corresponding heat exchanger is, in particular, a preferably brazed, at least partially made of aluminum, fin-plate heat exchanger of a known type. As mentioned, the use of alternative materials is also possible.

Within the scope of the present invention it is provided that the first operating mode is carried out in a first operating period, which is interrupted by a second operating period. The first operating mode corresponds to the regular stationary operation, for example a production operation of a corresponding system, in which the latter, for example, produces a desired product. This is interrupted when a corresponding system comes to a standstill, namely in the second operating period. It goes without saying that the first and second periods can alternate with one another several times over the entire service life of a corresponding system or if a corresponding method is carried out over longer periods of time. By using the present invention, the resulting loads on a heat exchanger can be reduced, particularly in the case of frequent changes, since the warm end is tempered.

This is achieved in the context of the present invention in that in the second operating period, in which the supply of the first fluid or fluids and the second fluid or fluids to the heat exchange region is prevented and the first operating mode is not carried out, in one or more partial periods of the second operating period in a second operating mode, the first end of the heat exchange area is acted upon by the application of one or more third fluids, which is or are supplied to the heat exchange area at the first end and is guided towards the second end through at least part of the heat exchange area, to the first temperature level or on third Temperature level that differs by no more than 80 Kelvin from the first temperature level is tempered. A corresponding temperature control can in particular also take place in such a way that the third temperature level does not differ from the first temperature level by more than 60, 40 or 20 K.

A corresponding temperature control process can also take place in particular over a certain period of time, during which the temperature level of the first end of the heat exchange area can also deviate from the first temperature level by more than 80 K at times. This can be the case in particular if the first operating mode has been ended for a long time and the second operating mode is only carried out after a longer time within the second operating period. In this case, however, the present invention can enable slow temperature control or heating of the first end of the heat exchanger, so that it can then be subjected to a corresponding warm first fluid again in the first operating mode. In this case, the second operating mode essentially serves to prepare for the subsequent first operating mode. However, it can also be provided that the first end of the heat exchange area is kept at the first or the third temperature level over the entire second operating period. This can be the case in particular if the second operating period is only comparatively short compared to the first operating period.

In other words, it can be provided within the scope of the present invention that the second operating period comprises a first partial period and a second partial period lying after the first partial period, the second operating mode being carried out during the second partial period. In particular, it can be provided that the second operating mode is not carried out in the first partial period and instead a different operating mode than the first and second operating modes is carried out or a corresponding system is completely shut down. In particular, the second operating mode can follow the first operating mode resumed subsequently in the second partial period, it being understood that between the second operating mode in the second partial period and the "subsequent" first operating mode, a switching operation or a switching period is carried out in the first operating period can be present. In any case, however, the first and second operating periods are operating periods that do not overlap each other. In other words, the first and the second operating mode are not carried out simultaneously.

If it is said here that the second operating mode is carried out “in one or more partial periods” of the second operating period, this can in particular also be understood to mean an intermittent second operating mode. In particular, this may include initiating the second operating mode at specific time intervals, for example on the basis of a time specification or on the basis of one or more temperature measurements. For example, the second operating mode can be initiated in preparation for the first operating mode at a predetermined time interval before the first operating mode is to be initiated again.

Provision can also be made for the second operating mode to be carried out in the second operating period, for example in a specific cycle. In this way, for example, an excessive drop in the temperature at the first end of the heat exchange area can be avoided, so that the first operating mode can subsequently be resumed more quickly. It is also possible, for example, whenever a determined temperature at the first end of the heat exchange area falls below a predetermined value, to start the second operating mode and to end it again when the determined temperature at the first end of the heat exchange area then again exceeds a certain predetermined value increases.

A corresponding intermittent operation, or, more generally, operation only during one or more partial periods during the second operating period, can be used in the context of the present invention in particular to reduce an amount of the third fluid or fluids that are used to temper the first end of the heat exchange area. In this way, the use of the invention results in a particularly resource-efficient method.

If it is said here that the third fluid or fluids supplied to the heat exchange region at the first end are guided "in the direction" of the second end "through at least part of the heat exchange region", this can in particular also mean that the heat exchange region is one or more first . has sections adjoining the first end of the heat exchange region and one or more second sections adjoining the second end, the third fluid or fluids being guided through the first section or sections but not through the second section or sections.

For example, a corresponding fluid can thus be drawn off from the heat exchange area after passing through a section, in particular via a suitable side header. In a corresponding variant of the present invention, the first end of the heat exchange region is tempered in this way, but in this case the third fluid or fluids do not act on the entire heat exchange region. In this way, any undesired heating of the second end of the heat exchange area can be prevented. In this way, an additional expenditure of energy for the subsequent cooling of the temperature at the cold end can be reduced.

Preferably, the one or more fluids in the second operating mode are supplied to the first end of the heat exchange region at the first or the third temperature level. However, it can also be provided that different temperatures are used, provided that this means that the first end of the heat exchange region is supplied by the application of the third fluid or fluids or that to the heat exchange region at the first end and in the direction of the second end at least part of the heat exchange area is or are brought to the first temperature level or the third temperature level.

In one embodiment of the present invention, a corresponding method comprises that in the first operating mode only the first fluid or fluids is or are guided from the first end to the second end through the heat exchange region, and that in the second operating mode only the second fluid or fluids are passed from the first end to the second end through the heat exchange area is or will be. In other words, in the first operating mode, no more fluids than the first fluid or fluids are passed through the heat exchange area from the first end to the second end, and in the second operating mode no fluids other than the fluid or third fluid are passed through the heat exchange area from the first end to the second end guided. A first total of the one (s) in the first Operating mode (in particular based on a time unit) from the first end to the second end through the heat exchange region is greater than a second total amount of the one or more in the second operating mode (in particular based on the same time unit) from the first end to the second end through the heat exchanger guided second fluids.

The method proposed according to the invention can also be carried out in a particularly resource-saving manner by a corresponding reduction in quantity. The risk of incorrect distribution or maldistribution of the naturally warm third fluid or fluids in one or more heat exchangers or heat exchanger blocks is significantly lower than in the case of a cold fluid. The second total can therefore be chosen to be extremely small. In embodiments of the invention, the second total amount (in particular based on a unit of time) can be, for example, 0.01 to 0.1, 0.1 to 1, 1 to 5, 5 to 10 or 10 to 50 percent of the first total amount (in particular based on the same) Unit of time).

In a corresponding method it can in particular be provided that in the second operating mode the second end of the heat exchange area is also tempered by applying the third fluid or fluids that are or are fed to the heat exchanger at the first end. This can take place in particular in that no fluid is fed to the second end in the second operating mode and the temperature control therefore acts on both ends.

The present invention can be used in various configurations, in particular in connection with the cryogenic air separation. The production of air products in a liquid or gaseous state by low-temperature air separation in air separation plants is known and, for example, at H.-W. Häring (ed.), Industrial Gases Processing, Wiley-VCH, 2006 , in particular Section 2.2.5, "Cryogenic Rectification".

Air separation plants have distillation column systems which can be designed, for example, as two-column systems, in particular as classic Linde double-column systems, but also as three- or multi-column systems. In addition to the distillation columns for the production of nitrogen and / or oxygen in liquid and / or in the gaseous state, that is to say the distillation columns for nitrogen-oxygen separation, distillation columns can be provided for obtaining further air components, in particular the noble gases krypton, xenon and / or argon.

The distillation columns of the distillation column systems mentioned are operated at different pressure levels. Known double column systems have a so-called high pressure column (also referred to as a pressure column, medium pressure column or lower column, in the language used here the "first rectification column") and a so-called low pressure column (also referred to as upper column, in the language used here the "second rectification column"). The pressure level of the high-pressure column is, for example, 4 to 6 bar, in particular approximately 5 bar. The low pressure column is operated at a pressure level of, for example, 1.3 to 1.7 bar, in particular approximately 1.5 bar. In certain cases, for example for combined processes with integrated gasification (Integrated Gasification Combined Cycle, IGCC), pressures of 3 to 4 bar can also be used in the low pressure column.

In a particularly preferred variant of the method according to the invention, the first fluid or at least one of the first fluids and the third fluid or at least one of the third fluids each comprise compressed air which, after being guided through the heat exchange region in the first operating mode, has a low-temperature rectification in a rectification unit subjected and used after heating through the heat exchange area in the second operating mode for heating the rectification unit.

By means of a corresponding variant, in particular the apparatuses connected downstream of the heat exchanger can be slowly warmed up. This makes it possible to smooth or flatten temperature gradients occurring at the second end of the heat exchange area when a corresponding system is restarted, ie at the beginning of the first operating mode or when switching between the second and first operating modes. In this way, the cold end of a corresponding heat exchanger can also be protected during load changes without it having to be temperature-controlled in a second operating mode with cold fluid, which could possibly be mis-distributed. The tempering and the Prevention of thermal stresses is effected exclusively through the use of the third fluid or fluids.

In the method just explained, in a particularly preferred embodiment, a rectification unit with a first rectification column (“high pressure column”) operated at a first pressure level, a second rectification column (“low pressure column”) operated at a second pressure level below the first pressure level and a subcooler are used, wherein in the second operating mode the air is fed into the first rectification column after passing through the heat exchange area or the heat exchanger, and wherein fluid is removed from the first rectification column via a sump vent, passed through the subcooler, fed into the second rectification column and via a top draw the second rectification column is discharged.

A corresponding variant is particularly with reference to the attached Figure 3 explained. In this case, however, in deviation from the specific embodiment illustrated there, another fluid guide for temperature control can also be provided. A subcooler or supercooling counterflow (the terms are used synonymously here) is a heat exchanger in which at least fluids from the high and low pressure column or the first rectification column and the second rectification column are subjected to a heat exchange with one another.

Within the scope of the present invention, as previously explained, it can be provided that only the first end of the heat exchange area is tempered in the second operating mode. In this case, no fluids are supplied to the heat exchange area in the second operating mode and guided through the heat exchange area. There is therefore no specific temperature control at the cold end of the heat exchanger. However, a certain temperature influence can be brought about by the fluid fed in at the first end of the heat exchanger if it reaches the second end of the heat exchanger.

In the context of the present invention, however, it can alternatively be provided that in the second operating mode the second end of the heat exchange area is acted upon by one or more fourth fluids Heat exchange area is supplied at the second end and is or are guided in the direction of the first end through at least part of the heat exchange area, to the second temperature level or to a fourth temperature level which differs by no more than 80 Kelvin from the second temperature level. The fourth temperature level can in particular also differ from the second temperature level by less than 60, 40 or 20 Kelvin. In this connection, the above explanations apply mutatis mutandis with regard to the temperature control of the first end with the third fluid or fluids.

In particular, reference is made here to the explanations above regarding the meaning of the statement “in one or more partial periods”. The temperature of the second end of the heat exchange area can also be carried out intermittently, periodically, in accordance with a time specification and / or on the basis of a temperature measurement. The temperature of the second end of the heat exchange area can be initiated, in particular in preparation for the first operating mode, at a predetermined time interval before the first operating mode is to be initiated again, so that the first operating mode can then be resumed in a planned manner. It is also possible, for example, whenever a determined temperature at the second end of the heat exchange area rises above a predetermined value, to start the temperature control of the second end of the heat exchange area and to end it again when the determined temperature at the second end of the heat exchange area subsequently drops again decreases a predetermined value.

By intermittent temperature control of the second end of the heat exchange area or, more generally, temperature control only during one or more partial periods during the second operating period, an amount of the fourth fluid or fluids that are used for temperature control of the second end of the heat exchange area can be within the scope of the present invention , save on. In this way, the use of the invention results in an even more resource-efficient method.

If it is said here that the fourth fluid or fluids supplied to the heat exchange region at the second end are guided "in the direction" of the first end "through at least part of the heat exchange region", as in the case below of the third fluid or fluids, in particular also to be understood that the heat exchange region has one or more first sections adjoining the first end of the heat exchange region and one or more second sections adjoining the second end, the or the fourth fluids through the second section or sections, but not through the first section or sections. For further explanations, reference is expressly made to the explanations above.

Preferably, the fourth fluid or fluids in the second operating mode is or are supplied to the second end of the heat exchange region at the second or fourth temperature level. However, it can also be provided here that different temperatures are used, provided that this means that the second end of the heat exchange area is supplied by the application of the fourth fluid or fluids or that to the heat exchange area at the second end and in the direction of the first Is at least passed through at least part of the heat exchange area, is tempered to the second temperature level or the fourth temperature level.

In the case of temperature control at the warm (first) and cold (second) end of the heat exchange area, provision can in particular also be made to maintain a temperature profile in the heat exchanger or the heat exchange area. or to keep essentially. Such an embodiment of the present invention can include, in particular, that in the first operating mode, a first temperature profile from the first temperature level at the first end to the second temperature level at the second end is formed over the heat exchange region, and that in the second operating mode a second temperature profile from the first temperature level via the heat exchange region the first end to the second temperature level at the second end, which does not deviate from the first temperature profile by more than 80 Kelvin at any point. Within the scope of the present invention, a deviation can also be kept below 60, 40 or 20 Kelvin. A corresponding temperature profile, that is to say a temperature profile, can be determined, for example, by simulations which are based on one or more measuring points or temperature measurements at different positions of the heat exchanger.

The variant of the present invention which has just been explained can also be used in the context of a method for low-temperature air separation, as explained below. In particular, it is provided that the first fluid or at least one of the first fluids comprises or comprise compressed air which, after cooling in the heat exchanger, undergoes low-temperature rectification using a first rectification column operated at a first pressure level and one operated at a second pressure level below the first pressure level second rectification column is subjected.

In this embodiment of the present invention, the third fluid or at least one of the third fluids can be formed using an oxygen-enriched fraction formed in the first rectification column and / or using an oxygen-enriched fraction and / or the fourth fluid or at least one of the fourth fluids may be formed using a fraction formed in the first rectification column. In other words, the first end of the heat exchange region can be tempered with liquid that collects in the first and / or second rectification column. The second end of the heat exchange region can be tempered in particular with gas from the first rectification column. Both variants are below with reference to the Figure 7 explained in more detail.

The third fluid or at least one of the third fluids can or can be formed in particular by taking part of the oxygen-enriched fraction formed in the first rectification column and / or the second rectification column from the first and / or the second rectification column intermittently, increasing the pressure , heated to the first temperature level or the third temperature level and supplied to the heat exchange area at the first end. Alternatively or additionally, the fourth fluid or at least one of the fourth fluids can be formed in that part of the nitrogen-rich fraction formed in the second rectification column is removed from the second rectification column and fed to the heat exchange region at the second end at the second temperature level or the fourth temperature level.

In this case, in particular in the second operating period, for example after a predetermined time interval has elapsed or at a determined temperature at the first end and / or at the second end of the heat exchange section of the heat exchanger, sump liquid accumulating in a sump of the first and / or second rectification column at least partially used to fill a container. In a second step, the container can be pressurized, for example by pressure build-up evaporation. In a third step, fluid can be removed from the container and heated in a heat exchanger to the first or third temperature level and used as the or at least one of the first fluids for tempering the first end of the heat exchange region of the heat exchanger. In parallel, gaseous fluid can be removed from the first rectification column and, as mentioned, can be used at the second or fourth temperature level as the or at least one of the fourth fluids for temperature control of the second end.

The present invention makes it possible, in particular in a further embodiment, to achieve a comparatively high flow rate in the heat exchanger with an extremely small amount of gas, as a result of which corresponding incorrect distributions can also be ruled out when the second end of the heat exchange area is tempered.

For this purpose, this embodiment of the invention provides in the second operating mode for a suitable fluid, for example cold gas, which is provided for example from a tank by pressure build-up evaporation or from a rectification column system by evaporation, to be fed in at the cold end of the heat exchanger and through passages specifically dedicated to this To lead heat exchanger to its warm end. There, the correspondingly heated fluid can be heated further, for example with an additional air-heated heat exchanger, and is then guided through the heat exchanger from the warm end to the cold end by other passages specifically dedicated to this. Appropriate fluid can then be blown off into the atmosphere, for example. The fluid led from the cold to the warm end of the heat exchanger is thus a "fourth" fluid in the sense explained above and the heated fluid and subsequently led from the warm to the cold end of the heat exchanger is a "third" fluid this sense. In the following, we speak of "one" fluid. However, it goes without saying that a plurality of corresponding fluids can also be used in each case.

It is particularly advantageous if the number of passages for cold (fourth) and warm (third) fluid, that is to say for the fluid led from the cold to the warm end on the one hand and for the fluid subsequently leading from the warm to the cold end on the other hand, in terms of their fluidic properties are similar, so that comparable speeds and pressure drops can be achieved. The number of passages is preferably approximately the same or differs only slightly from one another.

In principle, three different approaches are possible within the scope of this embodiment of the present invention. In certain heat exchangers, for example comparatively large heat exchangers in which one or more fluids to be cooled are cooled by a number of first passages, for example 100 passages, and one or more fluids to be heated by a correspondingly large number of second passages, for example 100 passages can be heated, can be provided within the scope of the embodiment of the present invention to dedicate a defined smaller portion of the first passages and / or the second passages for the flow through the fourth or third and its heating and cooling.

For example, of the 100 first passages mentioned by way of example, which are used in the first operating mode for cooling the first fluid or fluids, five passages for heating and five passages, in particular each equally distributed in the stacking sequence, for cooling the fourth or third fluid be used in the second operating mode. Alternatively, it is also possible, of the 100 second passages mentioned as examples, which are used in the first operating mode for heating the second fluid or the second fluids to be heated, five passages for heating and five passages for cooling the fourth or third in the second operating mode. In a further alternative, for example, of the 100 first passages mentioned as examples, which are used in the first operating mode for cooling the first or second fluids to be heated, five passages for heating the fourth fluid and of the 100 mentioned as examples second passages used in the first operating mode for heating the fluid or fluids to be heated, five passages used for cooling the third fluid in the second operating mode or vice versa. It is understood that the numbers mentioned here are only example values.

If the first and second passages are each divided into groups, in each of which a fluid is guided, corresponding groups, individually or in combination, can be used in the second operating mode for heating and cooling the fourth or third fluid, if there is one fluidic design corresponds to the amount of fourth or third fluid to be cooled or heated. Further groups are then not flowed through in the second operating mode.

In alternative configurations, it is also possible to equip a heat exchanger with additional passage groups which are provided specifically for heating and cooling in the second operating mode using the fourth or third fluid and which are not used in the first operating mode. In this way, a particularly good adaptation to the quantities of the fourth or third fluid is possible, in particular if it is not possible to dedicate part of the "regular" heat exchanger passages.

An essential aspect of the embodiment of the present invention that has just been explained includes intermittent operation, which means that the heat exchanger or the corresponding passages in the second operating mode are only flowed through by the fourth or third fluid at certain times, but not in others , In this way, additional fluid can be saved, since this is only used when appropriate temperature control is required. As also explained below, a corresponding intermittent operation can include a fixed time specification, or it can be detected, for example using temperature sensors, when temperature control is required, for example when the heat exchanger has warmed up above a predetermined threshold value.

Overall, the embodiment of the present invention just explained proposes a method in which the heat exchange area of the heat exchanger is combined with a Number of heat exchanger passages is formed, and in which in the first operating mode, the first fluid or fluids is or are passed through a first subset of the number of heat exchanger passages and the second fluid or fluids are guided through a second subset of the number of heat exchanger passages, the first and the second subset is in particular disjoint subsets of the number of heat exchanger passages. As mentioned, the present invention extends, for example, to air separation plants or to plants for providing nitrogen-rich fluids, which can be provided in particular in liquid form. Thus, the fluid or fluids to be cooled can comprise, in particular, gaseous nitrogen, which is provided in the first operating mode, for example using an air separation unit, and liquefied by the cooling in the heat exchanger passages. The same also applies to other air processing systems, for example the systems mentioned for storing and recovering energy using liquid air, in which, for example, compressed air is liquefied to liquid air.

According to this embodiment of the present invention, it is now provided that in the second operating mode, in particular temporarily, ie intermittently in the sense explained above, one or more material flows as the or at least one of the fourth fluids are led and heated through a third subset of the number of heat exchanger passages and then as the or at least one of the third fluids is passed through a fourth subset of the heat exchanger passages and cooled, the third and fourth subset individually being smaller than the first and smaller than the second subset. A number of heat exchanger passages is therefore used, which is smaller than that used in the first operating mode for regular operation. In this way, the advantages already explained above can be achieved, in particular also with reference to the attached ones Figures 10 to 12 be explained again. As also explained in detail below, the third and fourth subsets can be subsets of the first and / or second subsets. In this case, a subset of the first and / or the second subset that are used in regular operation, i.e. the first operating mode for the fluid or fluids to be cooled or heated, i.e. in the second operating mode, for tempering the first and second ends of the heat exchange area of the Dedicated heat exchanger for the fourth fluid (s) and the third third fluid (s). The first, the second, the third and the fourth However, partial quantities can also be disjoint quantities in pairs, ie the heat exchanger passages used for the temperature control fluid in the second operating mode can be provided separately.

In particular, the disadvantages explained at the outset, which arise as a result of very low fluid flows or flow velocities and a resulting incorrect distribution, can be avoided. A suitable selection or provision of appropriate heat exchanger passages for the second operating mode can ensure that the number and the flow properties of the passages used in each case are at least largely similar.

In the context of the present invention, the temperature profile in a heat exchanger can be controlled and calculated very well during the downtime of a corresponding system, and thus the number of possible load changes (switching on and switching off) can be determined. Alternatively, if a required number of starts and stops and the respective downtime are known, the amount of feed gas (temperature control fluid) required and how, for example, optimal time or sensor-based control (see below) can be carried out.

The present invention enables a reliable construction. All fittings involved can be automated and, if necessary, controlled centrally and under safety monitoring. The system proposed in the embodiment of the invention which has just been explained is simple and easy to understand even for operating personnel and is therefore particularly reliable.

Because the temperature curve during operation and standstill are very similar to one another in the method proposed according to the invention, there are reduced thermal stresses on the heat exchanger, completely independent of the standstill time and largely independent of the start-up scenario. (Start-up scenario and downtimes are sometimes problematic or unknown with previously known solutions, since the start-up of a corresponding system depends on the operating personnel.) If, according to the prior art, heat is introduced into a corresponding system, for example by heating or a warm gas, one is such a system, however, is susceptible to restarting because it may be cold Gas hits a warm heat exchanger or vice versa. This disadvantage can be avoided within the scope of the present invention.

In the context of the method according to the invention, the third and fourth subsets can be disjoint subsets of the first subset, or the third and fourth subsets can be disjoint subsets of the second subset. The second case is particularly also with reference to the attached one Figure 9 explained. The passages denoted by Y are a second subset of the total heat exchanger passages through which low-pressure nitrogen is led in normal operation, that is to say the first operating mode. Further heat exchanger passages are used for other fluids in the first operating mode. In the second operating mode, a subset of the second subset, the third subset, is used for the fourth fluid or fluids and the fourth subset for the third fluid or fluids. In this embodiment, a heat exchanger can be tempered accordingly without additional passages having to be provided.

This is also the case if the third subset is a subset of the first subset and the fourth subset is a subset of the second subset, or if the third subset is a subset of the second subset and the fourth subset is a subset of the first Is subset. In this case, part of the fluid used in normal operation for heating the first fluid to be heated there is used in the second operating mode for a fourth fluid and part of the fluid used in normal operation for cooling the second fluid to be cooled there for a third fluid.

In particular, if a corresponding use is not possible or sensible, for example if it is not possible to equip it with appropriate headers, a corresponding method can be carried out in another alternative embodiment such that the first subset, the second subset, the third subset and the fourth subset are pairs of disjoint subsets of the number of heat exchanger passages. The passages intended for use with third and fourth fluids are therefore additionally provided. In this way, a particularly good adaptation to the required fluidic properties can also be achieved.

According to a particularly preferred embodiment of the present invention, which has already been mentioned above, the fourth fluid or fluids in the second operating mode can after heating in the third subset of the number of heat exchanger passages and before use as the or at least one of the fourth fluids, that is be subjected to further heating before cooling in the fourth subset of the number of heat exchanger passages. This allows a further targeted adaptation of the temperatures to the respective specific requirements. In particular, the further heating can be carried out using an air-heated heat exchanger, which can be produced and operated particularly simply and inexpensively in the present application scenario.

Although the present invention is described primarily with reference to air separation plants, the one or more of the fluids to be cooled in the first operating mode can generally be a fluid produced by means of a production plant as previously explained, the production plant in the first operating mode in Operation and in the second operating mode is out of order. In particular, as mentioned, use in a system for storing and recovering energy in different operating modes is also possible. The present invention permits temperature control or, if necessary, maintenance of a corresponding temperature profile in a heat exchanger in any production system, but in particular in the air processing systems explained. As also mentioned, the present invention is particularly suitable for use with a plant for liquefying a gaseous air product such as nitrogen.

As already mentioned, the fourth fluid or fluids used in the second operating mode can, in particular, be taken from a tank in the embodiment just explained. This tank can in particular be equipped with a pressure build-up evaporation device so that a fourth fluid can be provided under suitable pressure conditions. A corresponding tank can in particular also be filled in the first operating mode by a corresponding production system, so that the or at least one of the first or second fluids and the or at least one of the fourth fluids can have the same composition.

In particular, the first or second fluid or at least one of the first or second fluids and the fourth fluid can be air gases, in particular nitrogen-rich fluids. The one or more first or second fluids can be liquefied in the first operating mode by cooling in the heat exchanger passages and can be provided as a product in the liquefied state. These can also be liquefied in particular as part of a method for storing and recovering energy, which particularly benefits from the method according to the invention.

As mentioned, the present invention in the embodiment just explained enables maintenance of a temperature profile in a heat exchanger with small amounts of gas. In particular, a larger amount of fluid can flow through the first subset and the second subset of the number of heat exchanger passages than the third and fourth subset of the number of heat exchanger passages. For example, the amount of the fluids to be cooled, which are led through the first and the second subset of the heat exchanger passages in the first operating mode, can be twice as high or more than twice as high as the amount of the fluids passed through the third and fourth subset of the heat exchanger passages in the second operating mode Be fluid. Specific examples are explained with reference to the figures.

As mentioned, the fourth fluid and thus also the third fluid or fluids in the second mode of operation in the context of the present invention will be passed intermittently through the third and fourth subset of the heat exchanger passages. This is particularly advantageous because the amount of fluid used can be further saved in this way. Since temperature compensation processes take place comparatively slowly in the scenarios considered here, it can be advantageous, for example, to switch the supply of the second fluid on or off according to a specific time pattern. For example, in the second operating mode, the first and second portions of the heat exchanger passages can be flowed through for 30 minutes each, followed by a pause of, for example, 2 hours. The number of possible periods or their length in time is a function of the amount of gas used. Depending on the requirements, any flexibility can be achieved at the cost of the amount of gas used.

As an alternative or in addition to using a fixed time schedule, an intermittent operation can also be carried out using sensors which are attached to one or more locations of a corresponding heat exchanger. If, for example, a temperature at one or more points exceeds a target value by more than a predefined threshold value, flow through with the fourth or third fluid can be initiated.

According to a particularly preferred embodiment of the embodiment of the present invention which has just been explained, it is provided that a cold gas, in particular a gas which inevitably evaporates from the cryogenic liquid in a storage tank for a cryogenic liquid, is passed through the heat exchanger in the first and the second operating mode. In this way, the "cold" contained in a corresponding gas can be recovered, so that the method, even in the first operating mode, can be operated in a more energetically advantageous manner, or the operating costs can be reduced on average over both operating modes. A corresponding storage tank can in particular be a storage tank for liquid nitrogen. The illustrated embodiment of the present invention includes, in particular, leading a corresponding cold gas in the first and second operating modes through the same heat exchanger passages that are used in the second operating mode for third and fourth fluids, i.e. the third and fourth subsets of the heat exchanger passages ,

The present invention also extends to an arrangement having a heat exchanger having a heat exchange area extending between a first end and a second end, the arrangement comprising means adapted to switch the heat exchange area in a first mode of operation supplying a plurality of first fluids to be cooled at the first end at a first temperature level and passing them from the first end to the second end through the heat exchange area and supplying one or more second fluids to be heated at the second end at a second temperature level below the first temperature level and from the second end to the first end through the heat exchange area. According to the invention, means are provided which are set up to carry out the first operating mode in a first operating period, which is carried out by a second operating mode is interrupted, and to carry out a second operating mode in one or more partial periods of the second operating period, these means in the second operating mode supplying the first end of the heat exchange area to the heat exchange area at the first end by applying one or more third fluids and in the direction of the second end through at least a part of the heat exchange area or are tempered to the first temperature level or a third temperature level which does not differ from the first temperature level by more than 80 Kelvin.

For features and advantages of a corresponding arrangement, which is set up in particular to carry out a method as explained above, reference is expressly made to the above statements. In particular, such a system has a control device which is designed to switch between the first and the second operating mode when required, for example according to a fixed switching pattern, on the basis of a sensor signal or on request.

As mentioned, the present invention also extends to a system of the type explained above. According to the invention, this is distinguished by the fact that it comprises an arrangement as has just been explained. In particular, the system is designed to provide the or at least one of the fluids to be cooled in the first operating mode, which, as mentioned, can also be temporarily stored in a tank for use as the second fluid in the second operating mode. A corresponding system can in particular also be designed as a system for storing and recovering energy using liquid air, as an air separation system or as a system for liquefying a gaseous air product. Regarding features and advantages, reference is made to the above explanations regarding the method according to the invention.

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 decommissioning without the use of measures according to an embodiment of the present invention.
• Figure 2 illustrates temperature profiles in a heat exchanger after decommissioning during temperature control according to an embodiment of the present invention.
• Figure 3 illustrates an air separation plant with a heat exchanger that can be operated using a method according to an embodiment of the present invention.
• Figure 4 illustrates temperature profiles in an air separation plant according to Figure 3 , which is operated using a method according to an embodiment of the present invention.
• Figure 5 illustrates an arrangement of heat exchangers used in an air separation plant Figure 3 can be used according to an embodiment of the present invention.
• The Figures 6A to 6C illustrate different views of a heat exchanger used in an air separation plant Figure 3 or according to an order Figure 5 can be used.
• Figure 7 illustrates an air separation plant with a heat exchanger that can be operated using a method according to an embodiment of the present invention.
• The Figures 8A and 8B show an arrangement with a heat exchanger according to an embodiment of the invention in a first operating mode and in a second operating mode in a schematic representation.
• Figure 9 shows a layer arrangement of a heat exchanger operable according to an embodiment of the invention in a schematic representation.
• Figure 10 FIG. 12 shows a heat exchange diagram that results during operation of a heat exchanger according to an embodiment of the invention.
• Figure 11 FIG. 12 shows a heat exchange diagram that results during operation of a heat exchanger according to an embodiment of the invention.
• Figure 12 FIG. 12 shows a heat exchange diagram that results during operation of a heat exchanger according to an embodiment of the invention.

In the figures, elements that are identical or correspond to one another functionally or in terms of meaning are given identical reference numerals and are not explained repeatedly for the sake of clarity.

Detailed description of the drawings

Figure 1 illustrates temperature curves in a heat exchanger after decommissioning without the use of measures according to advantageous embodiments of the present invention in the form of a temperature diagram.

In the in Figure 1 The diagrams shown are a temperature denoted by H at the warm end of a corresponding heat exchanger or its corresponding heat exchange region (previously and hereinafter also referred to as "first end") and a temperature denoted by C at the cold end (previously and subsequently also as "second end" ) in each case in ° C on the ordinate versus a time in hours on the abscissa.

How out Figure 1 can be seen, the temperature H at the first (warm) end of the heat exchange area at the start of decommissioning, and thus the temperature in regular operation of the heat exchanger, is approx. 20 ° C and the temperature C at the second (cold) end is approx. -175 ° C. These temperatures become increasingly similar over time. The high thermal conductivity of the materials installed in the heat exchanger is responsible for this. In other words, heat flows from the first (warm) end towards the second (cold) end. Together with the heat input from the environment, this results in a medium one Temperature of approx. -90 ° C. The significant temperature increase at the second (cold) end of the heat exchange area is largely due to the internal temperature compensation in the heat exchanger and only to a lesser extent through external heat input.

As mentioned several times, strong thermal stresses can arise in the case shown if the first (warm) end of the heat exchanger is subjected to a warm fluid of approximately 20 ° C. in the example shown again after some time of regeneration without further measures.

Figure 2 illustrates temperature profiles in a heat exchanger after decommissioning during temperature control according to an advantageous embodiment of the present invention (internally designated IC2074 by the applicant) in the form of a temperature diagram.

This in Figure 2 The illustrated temperature diagram covers a longer time range and was created assuming different heat exchanger properties. However, the underlying principles of warming are the same as previously discussed. For comparison, the temperature denoted by H at the first (warm) end of the heat exchange region and the temperature denoted by C at the second (cold) are also shown, which result without the use of a temperature control according to an advantageous embodiment of the present invention.

In addition, a temperature denoted by H 'at the first (warm) end of the heat exchange area and a temperature denoted by C' at the second (cold) end are shown, which result when the first (warm) end of the heat exchange area is acted upon by an or a plurality of fluids, which is or are fed to the heat exchange area at the first (warm) end and is directed towards the second (cold) end through the heat exchange area or a section considered here, to a temperature level at which the first (warm) end at the beginning of the decommissioning or in the regular operating mode, or is tempered to a temperature level close to this temperature level. A corresponding fluid was previously and is also referred to below as "third fluid" or "warm fluid".

As can be seen, this measure allows the first (warm) end to be kept close to the temperature level at which the first (warm) end is at the beginning of the decommissioning or in the regular operating mode. This makes it possible to apply warm fluid to the first (warm) end again after a subsequent restart without causing excessive thermal stress at the first (warm) end. Since at the second (cold) end at a corresponding point in time there is typically no cold fluid available due to the intermittent decommissioning or a corresponding temperature gradient can be smoothed here, as with reference to FIG Figure 3 in combination with Figure 4 explained, temperature control of the second (cold) end to a correspondingly low temperature level can be omitted. This heats up accordingly.

As an alternative to the one shown in the diagram Figure 2 Measures illustrated, however, can also be provided within the scope of the present invention, as explained several times, when the heat exchanger is decommissioned, the second end of the heat exchange area by applying one or more fluids, which or the supplied to the heat exchange area at the second end and towards the first Is at least passed through at least part of the heat exchange area, to a correspondingly low temperature level. A corresponding fluid was previously and is also referred to below as "second fluid" or "warm fluid".

Figure 3 illustrates an air separation plant with a heat exchanger that can be operated using a method according to an advantageous embodiment of the present invention (namely, the designation internally designated IC2074 by the applicant).

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 corresponding specialist literature. An air separation plant for the use of the present invention can be designed in a wide variety of ways Figure 3 limited.

In the Figure 3 The illustrated air separation plant comprises a main heat exchanger unit 310, a relaxation / compression unit 320, a rectification unit 330 and an optional liquid storage unit 340, which are shown separately for the sake of clarity. Regular operation of a corresponding system is described first, that is to say the "first operating mode" mentioned several times before.

If the term "high pressure column" is used below, this means the rectification column (or part of a corresponding double column) otherwise referred to as "first rectification column" in the context of this application. If the term "high pressure column" is used below, this means the rectification column (or part of a corresponding double column) otherwise referred to as "first rectification column" in the context of this application. The "main heat exchanger" is the heat exchanger operated according to the embodiment of the present invention.

The (main) heat exchanger 1 is illustrated here with a heat exchange region 10 which extends between a first end 11 and a second end 12. As explained in detail below, in the first operating mode, a plurality of first fluids to be cooled are supplied to the heat exchange region 10 at the first end 11 at a first temperature level and are guided from the first end 11 to the second end 12 through the heat exchange region 10 and the heat exchange region 10 are in the first operating mode a plurality of second fluids to be heated are supplied at the second end 12 at a second temperature level below the first temperature level and guided from the second end 12 to the first end 11 through the heat exchange region 10.

The first operating mode is carried out in a first operating period, which is interrupted by a second operating period, the supply of the first fluids and the second fluids to the heat exchange region 10 being prevented in the second operating period, and wherein in one or more partial periods of the second operating period in In a second operating mode, the first end 11 of the heat exchange region 10 is acted upon by a third fluid which is supplied to the heat exchange region 10 at the first end 11 and in Is guided in the direction of the second end 12 through the heat exchange region 10 to the first or a third temperature level, which differs from the first temperature level by no more than 80 Kelvin. Here, in the second operating mode in the Figure 3 shown configuration no further fluid used for tempering.

The main heat exchanger unit 310 comprises as a central component the (main) heat exchanger 1, which can be designed in the form of one or more structural units. In the example shown here, the expansion / compression unit 320 comprises a first booster turbine 321 and a second booster turbine 322. However, one or more booster turbines can be replaced by one or more generator turbines or combinations of corresponding units can be used. The booster stage (s) of one or more booster turbines or the like can be designed as a conventional booster stage (s) or also as a so-called "cold" booster stage (s), the inlet temperature of which is lower than the ambient temperature. However, the expansion / compression unit 320 is always thermally coupled to the main heat exchanger unit 310 with the (main) heat exchanger 1, because fluid is exchanged with the expansion / compression unit 320 or its apparatuses from the latter.

In the example shown, the rectification unit 330 has a double column formed from a high-pressure column 21 and a low-pressure column 22 as well as a supercooling counterflow (subcooler) 23. The high-pressure column 21 and the low-pressure column 22 are in heat-exchanging connection via a main condenser 24. Furthermore, for example, a generator turbine 25 and a plurality of valves and pumps, not specifically identified, are provided.

The optional liquid storage unit 340 comprises, for example, a liquid nitrogen storage 41, a liquid air storage 42 and a liquid oxygen storage 43, which can each be designed as one or more, in particular insulated, tanks. A further liquid air storage functionally assigned to the liquid storage unit 40 can be provided. As mentioned, the liquid storage unit 340 is purely optional.

Operating air (AIR) is in the Figure 3 Air separation plant shown in the form of a feed air flow 301 sucked in via a simplified main air compressor 302, cooled in a pre-cooling unit 303 and cleaned in a cleaning unit 304. In the example shown, the air separation plant is set up to carry out a high air pressure process. The main air compressor 302 therefore compresses the air of the feed air stream 301 to a correspondingly high pressure level, which is clearly above the highest separation pressure used in the rectification unit 330. A corresponding compression can also be carried out using a main air compressor 301 and one or more secondary compressors. The invention can also be used in processes in which only part of a corresponding feed air flow 301 is compressed to a pressure above the highest separation pressure used in the rectification unit 330.

The compressed, cooled and cleaned air of the feed air stream 301 (MPAIR) is fed to the main heat exchanger unit 310 and the expansion / compression unit 320. In the main heat exchanger unit 310 and in the expansion and compression unit 320, a plurality of compressed air flows at different pressure and / or temperature levels are generated from the air of the feed air flow 301. In the Figure 3 A compressed air flow 305 (FEED) for direct feeding into the rectification unit 330 or its high-pressure column 21 and further compressed air flows 306 and 307 (JT1-AIR, JT2-AIR) are illustrated. The respective provision of the compressed air streams 305, 306 and 307 is shown in a highly schematic manner and can be done in different ways.

In the context of the present invention, all of these compressed air streams need not necessarily be formed. However, further compressed air flows can also be formed. For example, in the context of the present invention, a further compressed air flow can be provided at a pressure level of, for example, approximately 1.4 bar, which can then be directed into the low-pressure column 22 as so-called injection air.

The compressed air flow 305 (FEED) is provided at a pressure level of approximately 5.6 bar, for example, and is fed into the high-pressure column 21 of the rectification unit 330. Compressed air flow 306 (JT1-AIR) is provided at a pressure level that is above that of compressed air flow 305 (FEED). The Compressed air flow 307 (JT2-AIR) is optionally provided; its pressure level is also above that of compressed air flow 305 (FEED).

As mentioned, the compressed air flow 305 (FEED) is fed into the high pressure column 21 of the rectification unit 330. The compressed air stream 306 (JT1-AIR) is expanded into the high pressure column 21 of the rectification unit 330. In this case, for example, the generator turbine 25 shown and optionally one or more valves not specifically designated can be used. The optionally provided compressed air stream 307 (JT2-AIR) is also expanded into the high-pressure column 21 of the rectification unit 330 via a valve that is not specifically designated.

In the high-pressure column 21 of the rectification unit 330, an oxygen-enriched liquid bottoms product is generated, which is drawn off in the form of a fluid stream 331, passed through the supercooling counterflow 23 and expanded into the low-pressure column 22 via a valve, which is not specifically identified. In the high-pressure column 21, a nitrogen-enriched gaseous overhead product is also generated, which is drawn off in the form of a fluid stream 332. Part of the fluid stream 332 can be carried out as a gaseous, nitrogen-rich air product (PGAN) from the air separation plant. The rest is liquefied in the main condenser 24 in the example shown.

A part of the liquid formed can be carried out as a liquid nitrogen-rich air product (PLIN) from the air separation plant. A portion is returned to the high-pressure column 21 as a return. Another part of the can be led in the form of a fluid flow 333 through the supercooling counterflow 23 and can be expanded into the low-pressure column 22 via a valve (not specifically designated). Another part can be increased in the form of a fluid stream 334 by means of pumps not specifically designated, possibly combined with an increased nitrogen-rich liquid from the liquid nitrogen storage 41 of the liquid storage unit 340 and / or from the head of the low-pressure column 22, and as an internally compressed, liquid nitrogen-rich fluid stream (ICLIN ), in particular in the form of two partial streams, evaporated or pseudo-evaporated in the (main) heat exchanger 1 and subsequently provided as an internally compressed nitrogen-rich printed product, in particular at different pressure levels (ICGAN1, ICGAN2).

When the compressed air stream 306 (JT1-AIR) and optionally the compressed air stream 307 (JT2-AIR) expand into the high-pressure column 21, air liquefying can be drawn off in the form of a fluid stream 335 directly below the feed point of the streams mentioned, passed through the supercooling counterflow 23 and over a valve, not designated separately, can be expanded into the low-pressure column 22. A portion may be stored in the liquid air reservoir 42 or 45 of the liquid storage unit 40, if any. A fluid stream 336 is drawn off from the high-pressure column 21, passed through the supercooling counterflow 23 and expanded into the low-pressure column 22 via a valve, which is not specifically designated.

In the low-pressure column 32, a liquid, oxygen-rich bottom product is formed, which is drawn off in the form of a fluid stream 337 and, if present, possibly fed into the liquid oxygen reservoir 43 and / or increased in pressure by means of one of the pumps not specifically designated and as an internally compressed, liquid nitrogen-rich fluid stream ( ICLOX) evaporated or pseudo-evaporated in the (main) heat exchanger 1 and also provided as an internally compressed oxygen-rich printed product at two pressure levels (MP-GOX, HP-GOX). Depending on the operating mode and, if present, the liquid nitrogen-rich fluid stream (ICLOX) can also be formed using an oxygen-rich liquid removed from the liquid oxygen storage 43 of the liquid storage unit 40. A corresponding oxygen-rich liquid can also be taken from the liquid oxygen storage 43 of the liquid storage unit 40 and fed into the low-pressure column 22 via a pump.

A nitrogen-rich liquid in the form of a fluid stream 338 is removed from an upper region of the low-pressure column 22 and can be transferred in part to the liquid nitrogen reservoir 41, if present. Here too, an infeed or outfeed can take place. Part of the fluid stream 338 or all of the fluid stream 338 may, as mentioned, be treated as the fluid stream 334. Nitrogen-rich liquid can also be fed back from the liquid nitrogen storage 41, if present, into an upper region of the low-pressure column 32.

A nitrogen-rich fluid stream 339 drawn off from the top of the low-pressure column 32 can be led through the supercooling counterflow 23, heated in the (main) heat exchanger 1 and provided as a nitrogen product (GAN). On Another, not separately specified material flow, so-called impure nitrogen (UN2) is treated in a comparable way and used as so-called residual gas (rest).

If the system is in accordance with Figure 3 put out of operation, the (main) heat exchanger 1 heats up, as shown in the diagram Figure 1 illustrated unless further action is taken. One embodiment of the present invention therefore provides for temperature control of the (main) heat exchanger 1, as is shown in the diagram in FIG Figure 2 is illustrated.
For this, as in Figure 3 illustrated with increasingly illustrated flow paths, in a period in which the system is otherwise out of operation, that is to say in the "second operating mode" explained several times, a significantly smaller amount of air compared to the feed air flow 301 is used and by the (main) heat exchanger 1 in the heat exchange unit 310 and the relaxation / compression unit 320 performed. A small amount of fluid is sufficient.

So is in Figure 2 a diagram illustrates that was obtained with a heat exchanger that is part of a corresponding air separation plant and through which 300,000 standard cubic meters per hour are routed during normal operation. For temperature control when decommissioning the system can to the results of Figure 2 to deliver, on the other hand, work with only 300 standard cubic meters per hour that flow through the heat exchanger. The risk of incorrect distribution in the (main) heat exchanger 1 is significantly lower in the case of a warm current than in the case of cold currents, in which incorrect distributions can reinforce themselves. As in Figure 2 illustrates, the feeding of a corresponding warm current can be ended after about 50 hours, which can then already have reached a sufficient average temperature.

As illustrated, the second operating mode, which is illustrated by the reinforced flow paths, includes that fluid, such as material flow 331 in the first operating mode, is withdrawn from the high-pressure column via a sump vent, passed through the supercooling counterflow 23 and fed into the low-pressure column 22. In this way, slow heating of the above-mentioned apparatuses in the second operating mode can be achieved, which ensures that when the system is subsequently restarted, ie from the transition from the second to the first operating mode, correspondingly large ones are also achieved Temperature differences at the cold end of the (main) heat exchanger can be avoided. Other lines which may connect the high-pressure column 21 and the low-pressure column 22 via the supercooling countercurrent can also be used accordingly. In all cases, corresponding fluid can be blown out of the low-pressure column via pressure maintenance.

Due to the heat capacities of the apparatus in the rectification unit 330, the temperature gradient at the warm end of the (main) heat exchanger can be smoothed, as in Figure 4 illustrates, which also relates to a corresponding embodiment of the invention (namely the embodiment internally designated IC2074 by the applicant).

Figure 4 shows a diagram in which a temperature of a feed stream such as the feed air flow 301 into the (main) heat exchanger 1 of a corresponding air separation plant with FEED (cf. Figure 3 ), and temperatures of a low-pressure nitrogen stream and an impure nitrogen stream designated GAN and UN2. The temperatures are given in ° C on the ordinate versus a time in hours on the abscissa. Please refer to the explanations regarding the origin of the relevant material flows Figure 3 directed. How out Figure 4 can be seen, a temperature jump can be mitigated by the measures explained.

Another possibility to reduce the temperature jump when restarting is one of the illustration in the main heat exchanger 1 Figure 3 to develop a comparable cycle, in which, however, the feed air is not expanded in a turbine. Instead, a corresponding cycle can also be carried out via the Joule-Thomson relaxed streams 306 and 307, but otherwise comparable to that in Figure 3 , be formed. In this way, temperature gradients can be reduced, especially at the cold (second) end, provided the rest of the system is not as in Figure 4 was clearly warmed up.

By dispensing with a cold countercurrent (that is to say a fluid referred to as "fourth fluid" in the context of this application), the risk of mal-distribution in a corresponding heat exchanger can be reduced in the embodiments just explained. In the case of arrangements comprising parallel heat exchangers, in particular fin-plate heat exchangers or so-called multi-modules, That is, arrangements in which a plurality of heat exchanger modules with corresponding heat exchangers are used, the incorrect distribution is measured by means of temperature sensors or temperature sensors and the gas quantity is thus adjusted.

Figure 5 illustrates a corresponding arrangement of eight heat exchangers used in an air separation plant Figure 3 according to a corresponding embodiment of the present invention (namely the embodiment internally designated IC2074 by the applicant) can be used.

In the in Figure 5 illustrated arrangement, the eight heat exchangers are labeled 1 and 1 ', respectively, the heat exchangers labeled 1' are each equipped with one or more temperature sensors TI. The heat exchangers with 1 or 1 ′ are connected via a line system 501, which is illustrated in a highly simplified manner. in each case a pair of corresponding heat exchangers 1 or 1 'is located opposite one another. As part of the Figure 5 illustrated embodiment of the invention, a heat exchanger 1 'of the heat exchanger pairs provided at the outermost ends of the arrangement is equipped with the temperature sensor (s) TI in order to be able to detect extreme values in a corresponding arrangement. A comparable temperature distribution is to be expected with respect to the heat exchangers 1, 1 'corresponding to each other in pairs, so that it is not necessary to equip the two heat exchangers 1, 1' corresponding heat exchangers with temperature transmitters TI within the scope of the present invention.

The Figures 6A to 6C illustrate different views of a heat exchanger used in an air separation plant Figure 3 or according to an order Figure 5 (ie in the designation internally designated IC2074 by the applicant) can be used.

In Figure 6A is a corresponding heat exchanger designed as a fin-plate heat exchanger, which is equipped with several temperature sensors TI, as in Figure 5 designated 1 'and shown in a view in which the heat exchanger plates are in the paper plane or parallel to it. Headers of the heat exchanger 1 'are in Figure 6A each illustrated in a semicircle and illustrated at 601 to 618. They are used to feed or withdraw fluid flows are illustrated here with corresponding arrows. In the Figures 6B and 6C is the same heat exchanger 1 'in a view of the in Figure 1A left and right side shown with L and R respectively.

As can be seen, a corresponding heat exchanger 1 'has, for example, four blocks, which are not specifically identified and are arranged one behind the other. A heat exchanger 1 according to Figure 5 differs from that in Figure 6A to 6C illustrated heat exchanger 1 'essentially by the lack of the temperature sensor Tl. An example of an arrangement of the temperature sensor TI results from the overview of the Figures 1A to 1C ,

In the context of with reference to the Figures 2 to 5 6A to 6C illustrated embodiment of the invention (that is, in the embodiment internally designated IC2074 by the applicant), slow warming up with a small amount of gas and possibly the formation of a circuit via Joule-Thomson-relaxed operating air can explain the service life consumption when restarting Temperature compensation can be significantly reduced. The procedure is easy to implement and requires only minor design adjustments, for example the supply of purge gas, and possibly the provision of temperature sensors for monitoring. It enables a gentle restart after longer downtimes, after the temperature equalization would take place in the block without the above-described procedure, that is after about 20 to 40 hours, for example. (The temperature compensation is influenced by the warm current. The compensation temperature is increased by the addition of heat.) Restarting after a relatively short downtime can also be reduced. For example, with a block length of 7 meters after a standstill of approx. 6 hours without heating current at the warm end without using the present invention, there is already a temperature difference of approx. 40 Kelvin when restarting.

Figure 7 illustrates an air separation plant with a heat exchanger that can be operated using a method according to an advantageous embodiment of the present invention (namely, the designation internally designated IC2115 by the applicant). The air separation plant is illustrated in a very simplified manner. In particular, the illustration was based on a Numerous other fluid flows and apparatuses, such as compressors, pumps, valves, as well as column internals and the like, are dispensed with.

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 corresponding specialist literature. An air separation plant for the use of the present invention can be designed in a wide variety of ways Figure 7 limited.

The (main) heat exchanger 1 is illustrated with a heat exchange area 10 which extends between a first end 11 and a second end 12. As explained in detail below, in a first operating mode, a plurality of first fluids to be cooled (only one fluid is illustrated here) are fed to the heat exchange region 10 at a first temperature level and guided from the first end 11 to the second end 12 through the heat exchange region 10 and the heat exchange area 10 in the first operating mode, a plurality of second fluids to be heated (again only one fluid is illustrated) are supplied at the second end 12 at a second temperature level below the first temperature level and are guided from the second end 12 to the first end 12 through the heat exchange area 10 ,

The first operating mode is carried out in a first operating period, which is interrupted by a second operating period, the supply of the first fluids and the second fluids to the heat exchange region 10 being prevented in the second operating period, and wherein in one or more partial periods of the second operating period in a second mode of operation, the first end 11 of the heat exchange region 10 by applying a third fluid, which is supplied to the heat exchange region 10 at the first end 11 and guided in the direction of the second end 12 through the heat exchange region 10, to the first or a third temperature level, which differs from the first temperature level by no more than 80 Kelvin.

Furthermore, in the second operating mode, the second end 11 of the heat exchange region 10, as explained in detail below, is supplied with a fourth fluid which is supplied to the heat exchange region 10 at the second end 12 and in the direction of the first end 11 through at least part of the Heat exchange region 10 is performed, tempered to the second temperature level or to a fourth temperature level that does not differ from the second temperature level by more than 80 Kelvin.

In the in Figure 7 Air separation plant illustrated in the first operating mode, the (main) heat exchanger 1 is supplied with a compressed and purified feed air stream 601 via a valve V4. As is generally known, a plurality of feed air streams at different pressure and, if appropriate, temperature levels and, if appropriate, in different amounts can also be supplied in a corresponding air separation plant.

The aforementioned first fluid or at least one of the first fluids comprises or comprise compressed air. After cooling in the heat exchanger 1, this is subjected to low-temperature rectification using a first rectification column 21 (“high pressure column”) operated at a first pressure level and a second rectification column 22 (“low pressure column”) operated at a second pressure level below the first pressure level.

Any air products are formed, possibly heated in the (main) heat exchanger 1, and carried out from the system. This is illustrated here using the example of a nitrogen-rich stream 602 from the first rectification column 21, which is led to a consumer via a valve V5. The fluid can also, in particular, from the first rectification column 21, possibly via an in Figure 7 Hypothermia counterflow, not illustrated, are transferred to the second rectification column 22. The first rectification column 21 and the second rectification column 22 can be in heat-exchanging connection, in particular via a main condenser 24.

Will the regular operation of the in Figure 7 illustrated air separation plant, that is, the first operating mode, is interrupted and thus the supply of the first or the first and the second fluids to the heat exchanger and also a corresponding one If fluid exchange with the first rectification column 21 and the second rectification column 22 is prevented, the liquid present in each case in the first rectification column 21 and the second rectification column 22 and in any further rectification columns which may be present rains off and collects in the sump of these respective rectification columns.

After switching off the in Figure 7 Air separation plant shown, ie shortly after the first operating mode was interrupted, are all in Figure 7 illustrated valves V1 to V8 closed. Insulation losses introduce heat and the pressure in the first rectification column 21 increases. The valve V8 is used to maintain the pressure or to release excess pressure by blowing off fluid from the first rectification column 21 to the atmosphere (ATM).

After a certain time (for example a fixed time or based on a temperature measurement at the first end 11 and at the second end 12 of the heat exchange section 10 of the heat exchanger 1), the bottom liquid is used to periodically hold a container B1 with it in the sump of the first rectification column 21 and / or to fill the second rectification column 22 collecting liquid via the valve V1 and / or the valve. In a second step, the pressure in container B1 is then increased by closing valve V1 and opening valve V2 by means of evaporation of the liquid in a heat exchanger W1. In this context, valve V8 is also closed.

In a next step, the valve V3 is opened in order to supply a certain volume flow to a heat exchanger W2, which is completely evaporated by this heat exchanger W2 and is fed to the (main) heat exchanger 1 at almost ambient temperature. The valve V6 now serves to maintain the pressure in the first rectification column 21. In this way it is achieved that equally large amounts of warm and cold gas flow into the (main) heat exchanger 1 and the (main) heat exchanger 1 at the first end 11 of the heat exchange path almost heated to ambient temperature and cooled at the second end 12 to a temperature close to the boiling point in the first rectification column 21.

The (main) heat exchanger 1 is flowed through until the liquid level in the container B1 has fallen below a certain level. The design of the container B1 must be carried out in such a way that the amount of liquid stored is sufficient to restore the temperature profile in the (main) heat exchanger 1.

In other words, in the embodiment of the present invention illustrated here, the third fluid or at least one of the third fluids is or are formed using an oxygen-enriched fraction formed in the first rectification column 21 and / or using a second rectification column 22 and / or the fourth fluid or at least one of the fourth fluids is or are formed using a fraction formed in the first rectification column 21.

In the Figures 8A and 8B An arrangement 100 with a heat exchanger 1 according to a particularly preferred embodiment of the invention (referred to internally as IC2021) is shown schematically. The Figures 8A and 8B show two operating modes, one operating mode referred to throughout here as the "first" operating mode in Figure 8A and an operating mode referred to here as "second" operating mode throughout Figure 8B is shown. The arrangement 100 is, for example, part of a plant for the provision of liquid nitrogen or liquefaction of gaseous nitrogen, which for example comprises an air separation plant and further components, such as the air separation plant, not shown. As explained several times before, the present invention is particularly suitable for use in connection with plants for the liquefaction of gaseous air products, since no further rectification system is connected to them themselves and, if necessary, they can therefore be simplified and put out of operation more frequently.

The heat exchanger 1 is illustrated with a heat exchange area 10 which extends between a first end 11 and a second end 12. As explained in detail below, in a first operating mode, a plurality of first fluids to be cooled are supplied to the heat exchange region 10 at the first end 11 at a first temperature level and are guided from the first end 11 to the second end 12 through the heat exchange region 10 and the heat exchange region 10 are in the first operating mode a plurality of second fluids to be heated at the second end 12 at a second temperature level fed below the first temperature level and guided from the second end 12 to the first end 12 through the heat exchange region 10.

The first operating mode is carried out in a first operating period, which is interrupted by a second operating period, the supply of the first fluids and the second fluids to the heat exchange region 10 being prevented in the second operating period, and wherein in one or more partial periods of the second operating period in a second mode of operation, the first end 11 of the heat exchange region 10 by applying a third fluid, which is supplied to the heat exchange region 10 at the first end 11 and guided in the direction of the second end 12 through the heat exchange region 10, to the first or a third temperature level, which differs from the first temperature level by no more than 80 Kelvin. Furthermore, in the second operating mode, the second end 11 of the heat exchange region 10 is supplied with one or more fourth fluids, which is fed to the heat exchange region 10 at the second end 12 and is guided in the direction of the first end 11 through at least part of the heat exchange region 10 or are tempered to the second temperature level or to a fourth temperature level that does not differ from the second temperature level by more than 80 Kelvin.

The heat exchange region 10 here has a number of heat exchanger passages WZ, wherein in the first operating mode (the one in FIG Figure 8A is shown) the or at least one of the first fluids is or will be guided by a first subset of the number of heat exchanger passages WZ and the or at least one of the second fluids will be guided by a second subset of the number of heat exchanger passages WZ which is disjoint from the first subset and wherein in the second Operation mode ( Figure 8B ) one or more material flows as the or at least one of the fourth fluids are passed through a third subset of the number of heat exchanger passages WZ and heated and then as the or at least one of the third fluids through a fourth subset of the heat exchanger passages WZ and is cooled, wherein the third and fourth subsets are individually smaller than the first and smaller than the second subset.

In the first operating mode, which in Figure 8A is illustrated, and which corresponds to normal operation of the arrangement 100, ie operation of the arrangement 100, in which an associated plant, for example an air separation plant, is in production operation, a gaseous nitrogen stream a together with a nitrogen stream b in a multi-stage compressor arrangement 2, which is fed an additional nitrogen stream c at an intermediate stage, compressed to a condensing pressure level. The correspondingly compressed nitrogen is divided into two partial flows d and e, of which the partial flow d is fed to the heat exchanger 1 or its heat exchange region 10 at the warm (first) end 11. The partial flow e is further compressed in two turbine boosters 3 and 4 and then likewise fed to the heat exchanger 1 or the heat exchange area 10 at its warm (first) end 11.

Liquefied nitrogen removed from the heat exchanger 1 or its heat exchange region 10 at the cold (second) end, which is part of the partial flow e, is flashed into a container 6 via a valve 5. Liquid nitrogen drawn off from the bottom of the container 6 can be fed in the form of a liquid nitrogen stream f to the warm end of a subcooler 7, which is cooled using a partial stream g of the liquid nitrogen stream f, the amount of which is adjusted via a valve 8. After evaporation in the subcooler 7, the partial stream g is further heated in the heat exchanger 1 and is returned for compression in the form of the nitrogen stream b already mentioned. The remaining remainder of the liquid nitrogen stream f, illustrated here in the form of a liquid nitrogen stream h, can, for example, be dispensed as a product or stored in a tank (not shown).

The turbine boosters 3 and 4 are driven using the partial flow d and a further partial flow of the partial flow e, which is designated here by i. The partial flows d and i are each taken from the heat exchanger 1 at suitable intermediate temperatures. The correspondingly relaxed partial stream d is fed to the heat exchanger 1 at an intermediate temperature, in the heat exchanger 1 with nitrogen, which is drawn off in gaseous form from the head of the container 6 and is fed to the heat exchanger 1 at the cold end, heated and in the form of the nitrogen stream c already mentioned returned for compression. The partial stream i is fed into the container 6 after a corresponding expansion.

The heat exchanger passages of the heat exchanger 1 are designated W to Z for the following referencing.

In a second operating mode, which in Figure 8B is illustrated, and corresponds to an operation of the arrangement 100, which takes place when an associated plant, for example an air separation plant, is not in production operation, the components explained above, apart from the heat exchanger 1, are typically not in operation, as they are several times explained. Therefore, like the corresponding nitrogen flows a to i, these are not shown here. This also applies in reverse, ie in Figure 8A the components and material flows used in the second operating mode are not shown.

In the second operating mode, a gaseous, cold nitrogen stream k is taken from a tank 10 provided, for example, with a pressure build-up evaporation device 9 and fed to the cold (second) end of the heat exchanger 1 or its heat exchange region 10. This is a fluid that is referred to throughout the scope of the present application as the "fourth fluid".

The nitrogen stream k removed from the heat exchanger 1 at the warm end can in particular be passed through an air-heated heat exchanger 11 and then fed back into the heat exchanger 1 at the warm end. This is a fluid that is referred to throughout the scope of the present application as "third fluid". The nitrogen stream d is then carried out from the arrangement 100, for example blown off to the atmosphere.

In the second operating mode in the example shown here, the nitrogen stream k is passed through the heat exchanger passages Y, some of which are used for heating and some for the subsequent cooling, as explained below.

Figure 9 shows a layer arrangement 200 of a heat exchanger operable according to an embodiment of the invention, for example that in FIG Figures 8A and 8B shown heat exchanger 1 or its heat exchange area 10, in a schematic representation.

W, X, Y and Z illustrate passages for different fluids through the heat exchanger, the five passages Y highlighted in bold type being those for low-pressure nitrogen, in which, for example, the material flows g and k correspond Figure 8A and 8B can be performed in the manner described above.

The five passages labeled Y are divided, for example, into two headers, each with 2 or 3 passages. In normal operation, ie in Figure 8A illustrated first operating mode, all five passages are flowed through in parallel with nitrogen, for example the nitrogen stream g. If the associated system is at a standstill, ie the is in Figure 8B illustrated second mode of operation before, two passages with cold and three passages with warm gas, ie for example the material flow k according to Figure 8B is conducted in two passages from the cold to the warm end and in three passages from the warm to the cold end of the heat exchanger 1.

In the in Figure 8A Illustrated first operating mode, the nitrogen stream g is fed to the heat exchanger 1, for example in an amount of 3,030 standard cubic meters per hour, at a pressure level of 1.2 bar and at a temperature level of 94 K. The pressure loss in the heat exchanger 1 is, for example, 130 mbar. For example, the nitrogen stream g can also be distributed over several headers. In the in Figure 8B Illustrated second operating mode, the nitrogen flow is provided, for example, in a quantity of 1,200 standard cubic meters per hour, at a pressure level of 1.2 bar and at a temperature level of 80 to 95 K. The pressure loss under these conditions is, for example, 80 mbar. This allows the heat exchanger passages used in the first operating mode to be divided for the second operating mode in the manner explained, in which approximately half is used for heating and approximately half for cooling the nitrogen stream k, because comparable flow conditions can be achieved.

An influence on the temperature profile at standstill, that is to say Figure 8B explained second operating mode, in particular has the insulation loss. If possible, this should be reduced. For this purpose, the in the Figures 10 to 12 shown heat exchange diagrams, in each of which a block length of a corresponding heat exchanger in centimeters is plotted on the abscissa and a metal temperature in ° C on the ordinate.

The in the heat exchange diagrams of the Figures 10 to 12 Graphs 901 and 902 shown each represent temperatures in a heat exchanger over the length of the heat exchanger. This is the heat exchanger that is to be Figure 8A or 8B was explained. The graphs 901 represent the temperature in the second operating mode, in which three passages of warm and two passages of cold gas flow through. The graphs 902 accordingly represent the temperature in the first operating mode.

Figure 10 refers to a case in which an insulation loss of 22.14 kW was assumed. In this case, the inlet and outlet temperatures of the hot and cold flows into and from the heat exchanger largely correspond to one another, so that the problem explained at the outset that occurs due to different mass flows in the prior art is solved within the scope of the illustrated embodiment of the invention , A maximum temperature difference between the warm and cold currents is according to the in Figure 10 heat exchange diagram shown approx. 60 K.

In the in Figure 11 illustrated case, an insulation loss of only 12 kW was assumed. With largely identical inlet and outlet temperatures as in that in the heat exchange diagram of FIG Figure 10 illustrated case, there is only a temperature difference of 35 K.

This in Figure 12 The heat exchange diagram illustrated relates to a case in which the nitrogen flow has been increased to 3500 standard cubic meters per hour. The insulation losses are 22.14 kW. Here, too, are reduced compared to the in Figure 3 illustrated the temperature differences clearly.

Claims (15)

Method for operating a heat exchanger (1) with a heat exchange area (10) which extends between a first end (11) and a second end (12), wherein in a first operating mode the heat exchange area (10) has one or more first fluids to be cooled first end (11) is fed at a first temperature level and is or are guided from the first end (11) to the second end (12) through the heat exchange region (10) and the heat exchange region (10) has one or more second fluids to be heated at the second end ( 12) is fed at a second temperature level below the first temperature level and is or are led from the second end (12) to the first end (12) through the heat exchange area (10), characterized in that the first operating mode is carried out in a first operating period which is interrupted by a second operating period that in the second operating period the supply of the first fluid or fluids and de s or the second fluid to the heat exchange area (10), and that in one or more partial periods of the second operating period in a second operating mode, the first end (11) of the heat exchange area (10) by applying one or more third fluids, the or which are fed to the heat exchange area (10) at the first end (11) and are guided in the direction of the second end (12) through at least part of the heat exchange area (10), to the first temperature level or a third temperature level, which is no longer than 80 Kelvin from the first temperature level, is tempered. A method according to claim 1, in which in the first operating mode only the first fluid or fluids is or are passed from the first end (11) to the second end (12) through the heat exchange area (10), in the second operating mode only the second fluid or fluids from the first end (11) to the second end (12) through the heat exchange area (10), and in which a total of the or in the first operating mode from the first end (11) to the second end (12) through the heat exchange area ( 10) guided first fluids greater than a total of the one or more in the second Operating mode from the first end (11) to the second end (12) through the heat exchanger (1) second fluids. Method according to Claim 1 or 2, in which, in the second operating mode, the second end (11) of the heat exchange region (10) is tempered by applying the third fluid or fluids. The method of claim 3, wherein the first fluid or at least one of the first fluids and the third fluid or at least one of the third fluids each comprise compressed air which, after passing through the heat exchange region (10) in the first operating mode, undergoes low temperature rectification in a Rectification unit (20) and after passing through the heat exchange area (10) is used in the second operating mode for heating the rectification unit (20). Method according to Claim 4, in which a rectification unit (20) with a first rectification column (21), a second rectification column (22) and a subcooler (23) is used, wherein in the second operating mode the air after passing through the heat exchange area (10 ) fed into the first rectification column (21), fluid removed via a bottom draw from the first rectification column (21), passed through the subcooler (23), fed into the second rectification column (22) and via a top draw from the second rectification column (22) is diverted. Method according to one of the preceding claims, in which, in the second operating mode, the second end (11) of the heat exchange region (10) is supplied by one or more fourth fluids and which is supplied to the heat exchange region (10) at the second end (12) and towards of the first end (11) is or are passed through at least part of the heat exchange region (10), to the second temperature level or to a fourth temperature level which differs from the second temperature level by no more than 80 Kelvin. Method according to Claim 6, in which, in the first operating mode, a first temperature profile from the first over the heat exchange region (10) Temperature level at the first end (11) is formed to the second temperature level at the second end (12), and in which in the second operating mode via the heat exchange area (10) a second temperature profile from the first temperature level at the first end (11) to the second temperature level at the second End (12) is formed, which at no point deviates by more than 80 Kelvin from the first temperature profile. The method of claim 7, wherein the first fluid or at least one of the first fluids comprises compressed air which, after cooling in the heat exchanger (1), undergoes low temperature rectification using a first rectification column (21) operated at a first pressure level and one on one is subjected to a second pressure level below the first pressure level operated second rectification column (22), wherein the third fluid or at least one of the third fluids using an oxygen-enriched formed in the first rectification column (21) and / or using an in the second rectification column (22) Fraction is or are formed and / or wherein the fourth fluid or at least one of the fourth fluids is or are formed using a fraction formed in the first rectification column (21). Method according to Claim 6 or 7, in which the third fluid or at least one of the third fluids is formed in that a part of the oxygen-enriched fraction from the first and / / formed in the first rectification column (21) and / or the second rectification column (22) or intermittently removed from the second rectification column (22), increased in pressure, heated to the first temperature level or the third temperature level and fed to the heat exchange region (10) at the first end (11) and / or in which the fourth fluid or at least one of the fourth fluids thereby it is formed that a part of the nitrogen-rich fraction formed in the second rectification column (22) is taken from the second rectification column (22) and fed to the heat exchange region (10) at the second end (12) at the second temperature level or the fourth temperature level. A method according to claim 6 or 7, wherein the heat exchange area (10) comprises a number of heat exchanger passages (WZ), the first Operating mode the or at least one of the first fluids is or will be guided through a first subset of the number of heat exchanger passages (WZ) and the or at least one of the second fluids through a second subset of the number of heat exchanger passages (WZ) which is disjoint from the first subset and where in the second operating mode, one or more material flows as the or at least one of the fourth fluids are led and heated through a third subset of the number of heat exchanger passages (WZ) and thereafter as the or at least one of the third fluids through a fourth subset of the heat exchanger passages (WZ) and is or are cooled, the third and fourth subset individually being smaller than the first and smaller than the second subset. The method of claim 10, wherein the third and fourth subsets are disjoint subsets of the first subset, or wherein the third and fourth subsets are disjoint subsets of the second subset, or wherein the third subset is a subset of the first subset and the fourth Subset is a subset of the second subset, or in which the third subset is a subset of the second subset and the fourth subset is a subset of the first subset. Method according to one of claims 10 or 11, wherein the or the fourth fluid in the second operating mode after the heating and before use as the or at least one of the fourth fluids is subjected to further heating, in particular using an air-heated heat exchanger. Arrangement (100) with a heat exchanger (1), which has a heat exchange region (10), which extends between a first end (11) and a second end (12), the arrangement having means which are arranged for this purpose in in a first operating mode, supplying one or more first fluids to be cooled to the heat exchange region (10) at the first end (11) at a first temperature level and to guide them from the first end (11) to the second end (12) through the heat exchange region (10) and to the heat exchange region ( 10) one or more second fluids to be heated at the second end (12) at a second temperature level supply below the first temperature level and from the second end (12) to the first end (12) through the heat exchange area (10), characterized by means which are adapted to carry out the first operating mode in a first operating period, that by a second operating mode is interrupted, and in one or more partial periods of the second operating period, to carry out a second operating mode in which the first end (11) of the heat exchange region (10) is acted upon by one or more third fluids, or the heat exchange region (10) on the first End fed and in the direction of the second end (12) through at least a portion of the heat exchange region (10) or are tempered to the first temperature level or a third temperature level which differs by no more than 80 Kelvin from the first temperature level. System, characterized by an arrangement (100) according to claim 13, wherein the system is further configured to provide the or at least one of the fluids to be cooled in the first operating mode. Plant according to claim 14, characterized in that it is designed as a plant for storing and recovering energy using liquid air or as an air separation plant or comprises a device for liquefying a gaseous air product.

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