DE102011003391A1 - Plant has shut-off valve that is provided to prevent fluid communication between cryogenic temperature region and high temperatures region - Google Patents

Abstract

The plant has equipment components that are provided in region. The shut-off valve is provided to prevent fluid communication between cryogenic temperature region (10) and high temperatures region. The cryogenic temperature is range from 270[deg] C to 0[deg] C. The high temperature is range from 0[deg] C to 100[deg] C. The shut-off valve is controlled based on characteristics of casing. The casing is made of the helium, hydrogen and neon. An independent claim is included for method for removing cryogenic enriched contaminations in plant.

Description

The present invention relates to a plant for the cryogenic liquefaction of a feed gas stream and a cleaning method for such a plant.

State of the art

Cryogenic condenser, so plants for the liquefaction of gases such as helium, hydrogen, neon and the like, have long been known. Such systems are usually continuously exposed to more or less contaminated by foreign gases process gas. A cleaner upstream of the feed gas stream removes these foreign gases as far as possible. Remaining residues freeze in the plant in the liquefaction mode.

These foreign gases have a higher melting and / or boiling point than the gas to be liquefied, freeze or condense therefore at the temperatures used, and thus jeopardize in particular expansion stages of a corresponding system. Such contaminants, hereinafter referred to as "cryogenically enriched impurities", in extreme cases block lines in the condenser and thereby cause a plant shutdown. In any case, even in less severe cases, a condenser plant loses power over time due to increasing contamination and / or decreases in purity of the respective product over time.

Although reference is made in the following explanations essentially to plants or processes for the liquefaction of helium, it is to be understood that corresponding devices using comparable advantages in plants for the liquefaction of other gases, such as those mentioned above, are used can. Also be understood in the context of this application under the name "cryogenic enriched impurities" in addition to solid, so frozen, contaminants and condensed contaminants, which can reduce the performance of a plant in the same way.

Increasingly contaminated with cryogenically enriched contaminants condenser systems must be cleaned periodically. Larger systems often have parallel alternating bed adsorbers for this purpose. When Aufreicherung in one of the beds this can be locked and switched to the other bed. Through analysis, the remaining service life is monitored and a controlled regeneration is performed.

For smaller systems, however, is usually dispensed with such a change operation for cost reasons. Even simpler systems also have no adsorber for cleaning the process gas, so that residual impurities can freeze in the system. In addition, such smaller systems are usually operated discontinuously. If there is enough liquefied product, the system is turned off and warms up. The enriched impurities go back into gas phase and spread over the entire system. In order to minimize creeping accumulation and the associated power loss, we regularly blow off a large part of the process gas. A corresponding system is therefore maintenance-intensive and leads to product losses.

Against this background, there is therefore a need for simple and cost-effective possibilities for the cryogenic liquefaction of gases or gas mixtures which are suitable for overcoming the disadvantages mentioned.

Disclosure of the invention

Against this background, the present invention proposes a system for the cryogenic liquefaction of a feed gas stream with at least one held in a liquefaction operation of the system at cryogenic temperatures and at least one held in a liquefaction operation of the plant at higher temperatures range, and a method for removing cryogenically enriched impurities Such a system each with the features of the independent claims before.

Preferred embodiments are the subject of the respective subclaims and the following description.

Advantages of the invention

An inventively proposed system provides shut-off, which are adapted to prevent existing in the liquefaction fluid communication between at least one held in the liquefaction at cryogenic temperatures and at least one held in the liquefaction at higher temperatures range in standstill operation or plant shutdown.

The present invention is based on the finding that, when the liquefaction operation of a cryogenic condenser is interrupted, it naturally warms up and the warm-up in this case is particularly fast in the low-temperature range within the scope of the present invention Signed as "cryogenic temperatures" area called, going on. This is because the specific heat capacity of the materials used in this area is usually very low.

In systems which either have no adsorber or an adsorber without shut-off valves, enriched foreign gases are vaporized from time to time as part of a cleaning step over the operating period in this area. For this purpose, the entire system is usually heated. The impurities are unfavorably into the process gas, d. H. in the gas volume of the condenser, released. This results in a contamination of the entire system, because in all communicating, so in fluid communication, volumes of the system, the degree of contamination increases.

The warm process space, in the context of this application referred to as "held at higher temperatures range", usually determines the geometric volume of the corresponding system and includes about 6/7 of the total volume of all piping and components. At the same time, very clean process gas is usually present in the region held at higher temperatures. However, the gas content of this area is low due to the lower density of the gases contained and is only about one third of the total content of such a plant.

Conversely, the geometric volume of the cryogenic temperature range is significantly lower and is only about one-seventh of the total volume of the plant. However, due to the low temperatures and the much higher average density of the corresponding gases, the range kept at cryogenic temperatures contains up to 2/3 of the total gas content. However, all impurities are released here again. It thus reaches a relatively large amount of gas in a relatively small volume for release and contaminates the geometric volume defining, held at higher temperatures range considerably.

The contamination of the liquefied at higher temperatures held range or the process gas or end product present therein could be avoided in conventional systems in that all gas or liquefied components are blown off when heating the held at cryogenic temperatures range. However, the process gas is usually too valuable to take such a step.

As also explained in more detail below, the present invention in the form of shut-off means provides a simple, reliable solution to these contamination problems.

The present invention further contemplates that commonly used compressors that are regularly provided in the region held at higher temperatures in liquefaction operation typically require a defined restart pressure. If polluted process gas is largely blown off, it must be replaced by clean gas. This part of the condenser is lost.

When a corresponding condenser is restarted, expansion stages, for example expansion turbines, form the coldest point of the system over wide temperature ranges. Impurities freeze in this phase preferably here. Due to the enrichment of the foreign gases in the process gas, the expansion stages are acutely endangered. The system therefore loses power in ever shorter time; Under certain circumstances, a standstill threatens due to failure of an expansion stage.

These problems are solved safely and inexpensively by the present invention.

With particular advantage, the cryogenic temperatures of such a system include a temperature range of -270 ° C to 0 ° C, in particular from -200 ° C to -50 ° C. The higher temperatures preferably comprise a temperature range from 0 ° C to 100 ° C, especially from 10 ° C to 50 ° C. A corresponding system can therefore be used for liquefying the aforementioned gases.

With particular advantage, the shut-off means proposed according to the invention are designed as shut-off valves, in particular as automatic shut-off valves, or have such a shut-off valve. The provision of such a valve makes it possible in a particularly advantageous manner, automatically, so without additional user intervention would be required to prevent the fluid communication between the at least one held in the liquefaction at cryogenic temperatures range and the at least one held in the liquefaction at higher temperatures range , This can be done, for example, in the event of an intentional or unintentional warming up of the area held at cryogenic temperatures or in the case of an intended or unintentional pressure drop. For this purpose, corresponding sensors or measuring devices can be provided. An integration into a, for example, software-defined, cleaning routine can also be advantageous.

It may also be advantageous to equip the shut-off means with a control device which is set up for triggering the shut-off means on the basis of system characteristics, a defined sequence and / or user inputs. Such a control device may, for example, operate on the basis of a cleaning program requested by a user, which, for example, prescribes actuation of the shut-off means and defined heating of the area held in operation at cryogenic temperatures within the scope of a defined sequence of individual cleaning steps.

As mentioned, the system proposed according to the invention is particularly advantageously designed for the cryogenic liquefaction of an at least partially charged with gaseous impurities feed gas stream. A corresponding system does not have to be equipped with a system for pre-cleaning a feed gas stream, which significantly reduces the creation and / or maintenance costs. In particular, in smaller plants, which are used locally to service a need for liquefied gases, for example for use as a refrigerant, the proposed measures are therefore advantageous.

It is particularly advantageous if the region held at cryogenic temperatures has at least one cryogenically operating heat exchanger and in the region held at higher temperatures at least one compressor and / or at least one filter and / or at least one adsorber is provided. As mentioned, the proposed shut-off means can reliably avoid contamination of the region held at higher temperatures, which has a significantly larger geometric volume than the region which is kept at cryogenic temperatures.

In particular, the measures according to the invention can then develop their advantageous effect if the plant is a plant for helium, hydrogen or neon liquefaction. Corresponding systems are particularly often provided on site (in the form of so-called on-site systems), so that maintenance, for example of adsorbers, is not always guaranteed here.

For the method according to the invention also proposed for removing cryogenically enriched impurities from a corresponding system, reference is expressly made to the features and advantages explained above. A corresponding method includes, in particular, to prevent fluid communication between the at least one region held in the liquefaction operation at cryogenic temperatures and the at least one liquefaction operation at higher temperatures and then the previously held in cryogenic operation, cryogenic on a range to heat higher temperature. As mentioned, a corresponding method can be implemented with particular advantage in a control unit and, for. B. based on a user request, be processed automatically.

A corresponding method may also include reducing an operating pressure in the at least one cryogenically maintained range and maintaining the operating pressure in the range maintained at least at higher temperatures. This can be dispensed with particular advantage to a new pressure build-up in the held at higher temperatures range, thereby waiting times are avoided, which would otherwise be needed to set a form for one or more provided there compressors. Clean process gas remains with the product stream instead of flowing into the refrigeration cycle as a replacement.

As mentioned, the inventive method is particularly suitable for gases present as solids at cryogenic temperatures, but in the same way also for corresponding liquids. In systems known hitherto, for example for the liquefaction of helium, it has been possible to choose between a complete storage of the helium in the clean system with the consequence of a steady accumulation of gaseous impurities or a blow off of maximally 50 percent of the heated gas into the recovery. In the latter case, it was generally intended to then pass the warmed-up, blown into the recovery gas back through the entire cleaning process. As a result, only a dilution of impurities in the clean system to 50 percent could be achieved. By implementing the measures according to the invention, however, it is possible to get less than just about 10 percent of the gas content in the system in the recovery: The relatively clean process gas in the warm process chamber is maintained at high pressure. The cold process room can be unloaded immediately, for example, after switching off the system in a clean buffer, since a warming has not yet occurred. When the shut-off device is activated, this space can warm up and the contaminants are released. This now heavily contaminated process gas can be transferred to the gas recovery system.

In this case, it is particularly advantageous that the shut-off means provided, expediently in the region held at relatively high temperatures, are cost-effective and simple in corresponding ones Equipment can be retrofitted, resulting in a significant cost advantage over large systems with cryogenic Absperramaturen and Wechselbettadsorbern results. The invention can therefore be easily and practically implemented in existing plants.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described in detail below with reference to the drawing.

figure description

1 shows a plant for the cryogenic liquefaction of a gas or gas mixture according to a preferred embodiment of the invention.

A particularly preferred embodiment of the invention is in the single 1 presented a plant 100 for helium liquefaction, which operates essentially according to the Claude process. The system is shown greatly simplified, in particular, cross-connections between individual lines, buffer vessels, valves, measuring and control devices and the like are not shown.

The system has a cold-insulated area or a coldbox 10 within, within or whose components 22 to 26 . 51 to 54 . 71 and 72 be kept at cryogenic temperatures. Outside the cold box components are preferably exposed to higher temperatures, in particular ambient temperature.

A liquefied, corresponding pressurized feed gas stream E, preferably crude helium with gaseous impurities, the plant is 100 over a dryer 21 fed, in which moisture is separated from the feed gas stream.

Subsequently, the feed gas stream E enters the coldbox 10 where he has a for example four heat exchangers 22 to 25 freezing or condensation cleaning system 20 passes. After passing through the second heat exchanger 23 for example, in a separator 26 condensed nitrogen separated from the feed gas stream and serves in a heat exchanger explained below 51 as a refrigerant.

As refrigerant for the four heat exchangers 22 to 25 the freezing or condensation cleaning system 20 During the liquefaction process, cooled helium is produced by the freeze-out or condensation purification system 20 purified helium containing the four heat exchangers 22 to 25 in countercurrent, used.

After passing through the freezing or condensation cleaning system 20 becomes the purified feed gas stream E of a cooling unit 50 supplied, in this again four heat exchangers 51 to 54 passes.

In a first heat exchanger 51 the cooled stream is cooled against evaporating liquid nitrogen LIN, which is partially externally fed to the plant and to another part of the separator 26 the freezing or condensation cleaning system 20 comes. The vaporized nitrogen is released into the ATM atmosphere.

In a second heat exchanger 52 becomes a part of the stream to be cooled via a branch of an expansion turbine 71 fed, relaxed there and cooled. The thus cooled stream is used as refrigerant in a third heat exchanger 53 used and then again on an expansion turbine 72 relaxed.

Another part of the cooled stream is after the third heat exchanger via a branch the freezing or condensation cleaning system 20 supplied and used there as a refrigerant.

The rest of the stream to be cooled passes through all the heat exchangers 51 to 54 and is there successively cooled to a temperature at which helium begins to condense at the present pressures. The condensed helium is stored in an insulated liquid helium tank 60 outside the coldbox 10 collected and can be removed there.

A non-condensed, gaseous fraction of the stream to be cooled is passed countercurrently through the heat exchangers 54 to 51 guided and successively combined with the respective branched streams. The combined stream is then a compressor plant 30 For example, with a compressor 31 , in particular a screw compressor with oil injection, as well as two fine filters 32 . 33 and an adsorber 34 fed to the oil separation. Additionally or alternatively, further oil separation devices, for example gravity separators, can be provided.

According to the embodiment is a, preferably automatically switching, shut-off valve 40 provided, which allows a separation between the held on cryogenic temperatures area of the cold box 10 and the higher temperature area outside the coldbox 10 make. Through this shut-off valve 40 can, as explained above, relatively pure process gas in the held at higher temperatures outside the cold box 10 be kept at high pressure even if the previously held at cryogenic temperatures range of the cold box 10 depressurized and / or heated.

For cleaning, the area of the cold box which is kept at cryogenic temperatures is first of all 10 located process gas in a clean gas storage, not shown outside the coldbox 10 unloaded and kept there for later re-feed. Subsequently, the shut-off valve 40 closed and the previously held at cryogenic temperatures area of the cold box 10 is warmed and / or depressurized to remove cryogenically enriched contaminants, as previously discussed.

Claims (9)

Investment ( 100 ) for the cryogenic liquefaction of a feed gas stream (E), with at least one in a liquefaction operation of the plant ( 100 ) held at cryogenic temperatures ( 10 ) and at least one in a liquefaction plant of the plant ( 100 ) held at higher temperatures, said areas being in fluid communication 21 - 72 ), characterized by blocking means ( 40 ) arranged to effect fluid communication between the at least one cryogenic temperature range of liquefaction operation ( 10 ) and the at least one held in the liquefaction at higher temperatures range to prevent. Investment ( 100 ) according to claim 1, wherein the cryogenic temperatures comprise a temperature range from -270 ° C to 0 ° C, in particular from -200 ° C to -50 ° C, and wherein the higher temperatures have a temperature range from 0 ° C to 100 ° ° C, in particular from 10 ° C to 50 ° C include. Investment ( 100 ) according to claim 1 or 2, wherein the blocking means ( 40 ) have a shut-off valve, in particular an automatic shut-off valve. Investment ( 100 ) according to one of the preceding claims, in which the blocking means ( 40 ) have a control device which is suitable for controlling the shut-off means on the basis of parameters of the system ( 100 ), a defined process and / or user input is set up. Investment ( 100 ) according to one of the preceding claims, in which the at least one region held at cryogenic temperatures in the liquefaction operation ( 10 ) at least one cryogenic heat exchanger ( 22 - 25 . 51 - 54 ) and / or wherein the at least one held in the liquefaction at higher temperatures range at least one compressor ( 31 ), Filters ( 32 . 33 ) and / or oil separator ( 34 ) having. Investment ( 100 ) according to one of the preceding claims, which is used as an adsorberless system ( 100 ) for liquefying an at least partially acted upon with gaseous components feed gas stream (E) is formed. Investment ( 100 ) according to any one of the preceding claims, which is a helium, hydrogen or neon liquefaction plant ( 100 ) is trained. Method for removing cryogenically enriched impurities from a region kept at cryogenic temperatures in a liquefaction operation ( 10 ) of a plant ( 100 ) according to one of the preceding claims, comprising: a) Preventing fluid communication between the at least one region held at cryogenic temperatures in the liquefaction operation ( 10 ) and the at least one held in the liquefaction at higher temperatures range by operating the shut-off ( 40 ), and b) heating the area held at cryogenic temperatures in the liquefaction operation ( 10 ) to a higher temperature. The method of claim 8, further including maintaining an operating pressure in the at least one region maintained at cryogenic temperatures in the liquefaction operation. 10 ) and to maintain an operating pressure in the at least one region maintained at a higher temperature in the liquefaction operation.

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