EP3111999A1 - Oxygen reducing installation and method for dimensioning out an oxygen reducing installation - Google Patents

Abstract

The invention relates to a system for reducing the oxygen content in the room atmosphere of an enclosed area and / or for keeping a reduced oxygen content in the room atmosphere of an enclosed area below a predetermined and reduced compared to the oxygen concentration of the normal ambient air operating concentration. For this purpose, the system has a gas separation system whose outlet is connected in terms of flow with the enclosed area for continuously supplying an oxygen-reduced gas mixture or oxygen-displacing gas. The gas separation system is designed such that in a continuous operation of the gas separation system, the oxygen concentration in the room atmosphere of the enclosed area is always in a range between the predetermined operating concentration and a predetermined or definable lower limit concentration.

Description

The present invention relates to a system for reducing the oxygen content in the space atmosphere of an enclosed area or for holding a reduced oxygen content in the room atmosphere of an enclosed area below a predetermined concentration and reduced concentration (operating concentration) compared to the oxygen concentration of the normal ambient air.

The plant according to the invention is in particular designed to prevent the formation or spread of fires by introducing an oxygen-reduced gas mixture or an oxygen-displacing gas into the room atmosphere of an enclosed area. In addition, the system according to the invention is basically also suitable for extinguishing fires in the enclosed area.

Accordingly, the system according to the invention serves, for example, to reduce the risk and to extinguish fires in an area to be monitored, wherein the enclosed area is also permanently inertized at different levels of reduction for fire prevention or fire fighting.

The basic principle of the inertization technique for fire prevention is based on the knowledge that in enclosed areas, their equipment is sensitive responds to the action of water, the risk of fire can be countered by the fact that the oxygen concentration in the affected area is lowered to a value of, for example, 15 vol .-%. With such a (reduced) oxygen concentration, most flammable materials can no longer ignite. Accordingly, the main area of application of this inertization technique for fire prevention is also computerized areas, electrical switching and distribution rooms, enclosed facilities such as storage areas with particularly high-value assets.

The fire prevention effect resulting from this inertization technique is based on the principle of oxygen displacement. Normal ambient air is known to be 21% by volume of oxygen, 78% by volume of nitrogen and 1% by volume of other gases. For fire prevention, by introducing an oxygen-reduced gas mixture or an oxygen-displacing gas, such as nitrogen, the oxygen content in the room atmosphere of the enclosed area is reduced.

Further, as an example of application for the system according to the invention, the storage of objects, in particular foods, preferably pome fruit, under a so-called "Controlled Atmosphere (CA)" called, among other things, the percentage of atmospheric oxygen is regulated in order to slow the aging process perishable goods.

Oxygen reduction systems, particularly those used as fire prevention systems, fire extinguishing systems, explosion suppression systems or explosion protection systems by an atmosphere is generated in an enclosed area, which has a lower continuous oxygen concentration than under ambient conditions, - compared to water extinguishing systems, such as sprinkler systems or Spray mist extinguishing systems - in particular the advantage that they are suitable for volume extinguishing. For this purpose, however, it is necessary to place in the enclosed area a pre-calculated (minimum) amount of the oxygen-reduced gas mixture or the oxygen-displacing gas in the enclosed area to meet the purpose of the oxygen reduction plant, such as fire prevention , explosion suppression, explosion protection or fire extinguishing. Calculated this (minimum) amount of the oxygen-reduced gas mixture or oxygen-displacing gas to be introduced into the area is determined by the effective volume and the airtightness of the space envelope of the enclosed area.

The airtightness of the envelope of an enclosed area, such as a building envelope, is typically determined by a blower door test. A ventilator let into a room envelope creates and maintains a constant overpressure and negative pressure of (for example) 50 Pa within the enclosed area. The amount of air leaking through leaks in the enclosure of the enclosed area must be forced in by the fan into the enclosed area and measured. The so-called n50 value (unit: 1 / h) indicates how often the interior volume is converted per hour.

The airtightness determined with a differential pressure test thus corresponds to an air exchange rate caused by leaks in a space envelope of the enclosed area, which is also referred to herein as a "charge-independent air exchange rate". In particular, however, the airtightness determined by a differential pressure test does not take into account an air exchange which is caused by openings, which can be formed in the space envelope, such as doors, gates or windows, as required for the purpose of loading and / or inspecting the enclosed area. This rate of air exchange is also referred to herein as a "feed-dependent air exchange rate".

In contrast to the feed-independent air exchange rate, the feed-dependent air exchange rate can generally not be determined beforehand, since the feed-dependent air exchange rate varies over time and depends on when and how often for the purpose of loading and / or inspection the space envelope of the enclosed area is opened, such as long is the opening formed for the purpose of loading and / or walking in the space envelope of the enclosed area, and how big this opening ultimately is.

As a rule, these parameters which determine the charge-dependent air exchange rate can not be determined in advance, so that, with regard to the charge-dependent air exchange rate of the enclosed area during the design an oxygen reduction system always assumes peak values by assuming maximum loading and / or commissioning. In this way, it is ensured that with the oxygen reduction system, a sufficient amount of oxygen-displacing gas can always be provided per unit time in order to be able to securely hold a reduced oxygen content in the room atmosphere of the enclosed area below the predetermined operating concentration even in extreme cases.

An object of the invention is to provide a method for designing an oxygen reduction system, with which the oxygen reduction system is optimally projected in terms of the actual conditions.

In particular, should be taken into account in the design of the oxygen reduction system actually occurring / present feed-dependent air exchange rate in order to avoid over-dimensioning of the oxygen reduction system in this way. At the same time it should be ensured that with the oxygen reduction system at any time the oxygen content in the room atmosphere of the enclosed area can be kept below a predetermined and reduced compared to the oxygen concentration of the normal ambient air operating concentration.

In addition, a corresponding oxygen reduction system is to be specified, which is better adapted to the actual conditions of the enclosed area compared to oxygen reduction systems, which are designed and projected according to the previous approach.

With regard to the oxygen reduction system, the object underlying the invention is achieved by the subject matter of independent claim 1, advantageous developments of which are given in the dependent claims 2 to 19.

With regard to the method for designing an oxygen reduction system for an enclosed area, the object underlying the invention is achieved by the subject matter of the independent patent claim 20. Accordingly, the invention particularly relates to an oxygen reduction system which is designed to reduce the oxygen content in the room atmosphere of an enclosed area to a concentration which is below a predetermined operating concentration and reduced compared to the oxygen concentration of the normal ambient air. Alternatively or additionally, the oxygen reduction system according to the invention is designed to keep a reduced oxygen content in the room atmosphere of an enclosed area below a predetermined and reduced operating concentration compared to the oxygen concentration of the normal ambient air.

For this purpose, the oxygen reduction system has a gas separation system whose outlet is fluidly connected to the enclosed area to continuously supply an oxygen-reduced gas mixture or an oxygen-displacing gas to the space atmosphere of the enclosed area. In other words, according to the invention it is provided that the gas separation system is operated continuously, so that continuously, i. in time, the room atmosphere of the enclosed area is supplied with an oxygen-reduced gas mixture or an oxygen-displacing gas.

The gas separation system is designed such that, in a continuous operation of the gas separation system in a first mode of operation, the oxygen concentration in the room atmosphere of the enclosed area is always in a range between the predetermined operating concentration and a predetermined or definable lower limit concentration. In this case, in the first operating mode of the gas separation system at the outlet of the gas separation system per unit time, a quantity of an oxygen-reduced gas mixture lying within a predefined or definable range is continuously provided.

The advantages that can be achieved with the solution according to the invention are obvious: since it is provided that the gas separation system is operated continuously, the oxygen-reduced gas mixture can be provided at the outlet of the gas separation system in an amount that corresponds to the quantity as if it were larger dimensioned gas separation system is operated discontinuously. Therefore, compared to off the stand The technology known approaches the gas separation system and the oxygen reduction system are dimensioned smaller overall, so that thereby the cost of the initial installation of the oxygen reduction system are reduced.

The continuous operation of the gas separation system also has the further advantage of minimizing wear on the gas separation system due to repeated on and off switching.

According to one aspect of the present invention, it is provided that the predetermined operating concentration, which is reduced in comparison to the oxygen concentration of the normal ambient air, corresponds to the design concentration of the enclosed area. The design concentration in accordance with VdS guideline 3527 (version: filing date) refers to the ignition limit minus a safe distance and is therefore dependent on the materials stored in the enclosed area.

However, the present invention is not limited to such embodiments in which, with the aid of the oxygen reduction system, a reduced oxygen content in the space atmosphere of an enclosed area is kept below the design concentration of the area. Rather, the invention also encompasses those embodiments in which generally a reduced oxygen content in the room atmosphere of the enclosed area is kept below a predetermined and reduced operating concentration compared to the oxygen concentration of normal ambient air, which predetermined operating concentration is also above the design concentration of the area can.

The solution according to the invention is particularly suitable for an oxygen reduction system, which is projected with regard to an enclosed area, wherein the air exchange rate of the enclosed area varies cyclically with respect to time. This is the case, for example, in rooms or warehouses, the envelope of which is temporarily opened for the purpose of inspection and / or loading, whereby the frequency of the inspection / loading is subject to a certain cycle, for example a day cycle or a week cycle, so that overall the air exchange rate of the enclosed area in terms of the time varies cyclically and each time cycle is divisible into several consecutive time periods. The mean air exchange rate of the enclosed area assumes a corresponding value for each time period.

So it is conceivable, for example, that in a three-shift operation a warehouse is used 6 days a week. In this example, it is thus envisaged that the total air exchange rate of the enclosed area (here: warehouse) varies cyclically at weekly intervals, the average total air exchange rate of the enclosed area (warehouse) during the 6 working days being a feed-dependent air exchange rate and a feed-independent air exchange rate composed. By contrast, during the (single) day of rest, the feed-dependent air exchange rate is negligible, so that the mean total air exchange rate essentially corresponds to the charge-independent air exchange rate of the enclosed area.

As stated at the beginning, in the charge-independent air exchange rate (unwanted or unavoidable) leaks in the enclosure of the enclosed area are taken into account, ie those leaks that are unrelated to a loading and / or inspection of the enclosed area. On the other hand, the feed-dependent air exchange rate takes into account an air exchange that takes place through openings in the space envelope of the enclosed area, which are (intentionally) formed as required for the purpose of loading and / or inspection. These openings are, in particular, doors, gates, locks or windows.

In the application example in which the air exchange rate of the enclosed area varies cyclically with respect to time, wherein each time cycle is divided into a plurality of consecutive time periods, according to one aspect of the present invention, it is provided in particular that the gas separation system takes into account the respective duration of the time periods Taking into account the respective mean total air exchange rates for each period of time is designed so that in a continuous operation of the gas separation system in a first mode of operation, the oxygen concentration in the room atmosphere of the enclosed area always in a range between the predetermined operating concentration (such as the design concentration the enclosed area) and the predetermined or definable lower limit concentration.

According to a preferred realization of the oxygen reduction system according to the invention, it is provided that the gas separation system can be operated in at least two and preferably three different operating modes. In these at least two modes of operation, the gas separation system continuously provides an oxygen-reduced gas mixture at the outlet. In contrast to the first operating mode, however, in the second operating mode of the gas separation system, the amount of an oxygen-reduced gas mixture continuously provided per unit time at the outlet is increased, relative to a reference value of a residual oxygen concentration.

On the other hand, it is conceivable in this context that the gas separation system is further operable in a third operating mode in which - compared to the first mode of operation - the continuously provided per unit time at the outlet amount of an oxygen-reduced gas mixture - based on a reference value of a residual oxygen concentration - is reduced.

• i) Aufteilen eines vorab festgelegten Zeitzyklus in mehrere aufeinander folgende Zeitperioden;
• ii) Ermitteln einer mittleren Luftwechselrate des umschlossenen Bereiches für jede Zeitperiode;
• iii) Wichten der ermittelten mittleren Luftwechselraten hinsichtlich der entsprechenden Zeitdauern der zugehörigen Zeitperioden; und
• iv) Anpassen bzw. Auswählen eines Gasseparationssystems der Sauerstoffreduzierungsanlage unter Berücksichtigung der gewichteten, mittleren Luftwechselraten des umschlossenen Bereiches derart, dass bei einem kontinuierlichen Betrieb des Gasseparationssystems in einem ersten Betriebsmodus, in welchem am Auslass des Gasseparationssystems pro Zeiteinheit eine innerhalb eines vorab festgelegten oder festlegbaren Bereiches liegende Menge eines sauerstoffreduzierten Gasgemisches oder sauerstoffverdrängenden Gases kontinuierlich bereitgestellt wird, die Sauerstoffkonzentration in der Raumatmosphäre des umschlossenen Bereiches stets in einem Bereich zwischen einer vorab festgelegten Betriebskonzentration, wie etwa der Auslegungskonzentration des umschlossenen Bereiches, und einer vorab festlegbaren unteren Grenzkonzentration liegt.

The invention is not limited only to an oxygen reduction system of the type described above, but also relates to a method for designing an oxygen reduction system for an enclosed area. For this purpose, the method according to the invention has in particular the following method steps:

• i) dividing a predetermined time cycle into a plurality of consecutive time periods;
• ii) determining an average air exchange rate of the enclosed area for each period of time;
• iii) weighting the determined mean air exchange rates with respect to the respective durations of the associated time periods; and
• iv) adjusting a gas separation system of the oxygen reduction plant taking into account the weighted mean air exchange rates of the enclosed area such that in a continuous flow Operation of the gas separation system in a first operating mode, in which at the outlet of the gas separation system per unit time an amount of an oxygen-reduced gas mixture or oxygen displacing gas within a predetermined or fixed range is continuously provided, the oxygen concentration in the room atmosphere of the enclosed area always in a range between a predetermined operating concentration, such as the design concentration of the enclosed area, and a pre-settable lower limit concentration.

Hereinafter, the invention will be described in detail with reference to the accompanying drawings.

FIG. 1

ein prinzipielles Zeitdiagramm zum Erläutern der Betriebsweise einer herkömmlichen Sauerstoffreduzierungsanlage;

FIG. 2

ein prinzipielles Zeitdiagramm zum Erläutern der Betriebsweise einer ersten exemplarischen Ausführungsform der erfindungsgemäßen Sauerstoffreduzierungsanlage; und

FIG. 3

ein prinzipielles Zeitdiagramm zum Erläutern der Betriebsweise einer zweiten exemplarischen Ausführungsform der erfindungsgemäßen Sauerstoffreduzierungsanlage.

Show it:

FIG. 1

a principle time chart for explaining the operation of a conventional oxygen reduction system;

FIG. 2

a principle time chart for explaining the operation of a first exemplary embodiment of the oxygen reduction system according to the invention; and

FIG. 3

a principle time chart for explaining the operation of a second exemplary embodiment of the invention oxygen reduction system.

FIG. 1 shows a principle timing diagram for explaining the operation of a conventional, known from the prior art oxygen reduction system. It is an oxygen reduction system that is used to maintain the oxygen concentration in the room atmosphere of an enclosed area below a predetermined concentration (= operating concentration) which is reduced compared to the oxygen concentration of the normal ambient air. The in the time diagram in FIG. 1 total period considered is one week (7 days).

In FIG. 1 In particular, the temporal evolution of the oxygen concentration in the room atmosphere of the enclosed area is shown. It can be seen in particular that the oxygen concentration is always in a range between about 15.0 vol .-% and 14.9 vol .-%. This is a classical control range defined by an upper threshold and a lower threshold oxygen concentration in the room atmosphere of the enclosed area.

The upper threshold oxygen concentration in the room atmosphere of the enclosed area represents the turn-on threshold at which a gas separation system associated with the oxygen reduction system is turned on to provide an oxygen depleted gas mixture at the outlet of the gas separation system. The provided oxygen-reduced gas mixture is then introduced into the room atmosphere of the enclosed area, so that subsequently the oxygen concentration in the room atmosphere decreases accordingly.

Upon reaching the lower threshold, which defines the turn-off threshold of the gas separation system, the operation of the gas separation system is discontinued. As a result, the supply of the oxygen-reduced gas mixture is interrupted in the room atmosphere of the enclosed area, as a result, in the space atmosphere of the enclosed area, the oxygen concentration increases again accordingly.

This is due to the fact that the space envelope of the enclosed area is not made airtight; Rather, in the space envelope (unwanted or unavoidable) leaks are present, which have a certain (charge-independent) air exchange rate. This charge-independent air exchange rate can be determined in advance in particular by means of a differential pressure measurement.

In addition to this charge-independent air exchange rate, however, there is also a charge-dependent air exchange rate, ie an air exchange through openings provided in the envelope of the enclosed area which are opened for the purpose of loading and / or inspecting the enclosed area.

In FIG. 1 is a situation in which the enclosed area is used 6 days a week (here: Monday to Saturday) in a three-shift operation. A "utilization in three-shift operation" is to be understood as meaning a semi-continuous all-round operation which takes place in the in FIG. 1 shown embodiment is interrupted only on Sunday.

Based on the time course of the oxygen concentration in the time chart according to FIG. 1 It can be seen that the envelope of the enclosed area on Sunday is more airtight compared to the other days of the week. This is particularly evident from the fact that on Sunday the falling flanks of the oxygen concentration are steeper compared to other days of the week, and that the rising flanks of the oxygen concentration on Sunday are flatter.

To use in the previous operating procedures, as in FIG. 1 Based on the basic time diagram shown there, to keep the oxygen concentration in the room atmosphere of the enclosed area in the control range between the upper and lower threshold, the gas separation system is required on and off, so operated discontinuously.

In contrast, it is provided in the inventive solution that the gas separation system of the oxygen reduction system is operated continuously in an operating mode in which at the outlet of the gas separation system per unit time a lying within a predetermined or definable range amount of an oxygen-reduced gas mixture is continuously provided, said per Time unit provided is greater than 0 liters per hour.

Hereinafter, referring to the principle time chart according to FIG. 2 the operation of an exemplary embodiment of the invention oxygen reduction system described in more detail.

In detail is in FIG. 2 the temporal evolution of the oxygen concentration in the room atmosphere of an enclosed area shown, for which the oxygen reduction plant according to the invention is designed and projected. It This is an enclosed area (for example, a warehouse) used in three shifts 6 days a week.

The oxygen reduction system has a gas separation system, which is designed and designed taking into account a feed-dependent air exchange rate and a feed-independent air exchange rate over the course of the week. The feed-dependent air exchange rate during the course of the week takes into account the fresh air intake by feeding and / or inspection of the enclosed area.

This feed or walk-dependent fresh air entry for the first case according to FIG. 2 is given by way of example in Table 1.

In the following Table 2, however, the total fresh air entry is indicated during the week, for the case example according to FIG. 2 , The total fresh air intake is composed of the feed-dependent air exchange rate on the one hand and the feed-independent air change rate at an average wind speed of 3 m / s.

In order to be able to keep the oxygen content in the room atmosphere of the enclosed area below a predetermined operating concentration and reduced compared to the oxygen concentration of the normal ambient air, it is necessary to supply an oxygen-reduced gas mixture or an oxygen-displacing gas in such a way that the total fresh air input at least partially equalized.

In the exemplary embodiment considered here, nitrogen (N ₂ ) having a residual oxygen concentration of, for example, 5% is used as the oxygen-reduced gas mixture or oxygen-displacing gas. The nitrogen required for leveling the total fresh air intake during the week is summarized in Table 3.

The time course of the nitrogen requirement is also in the time chart according to FIG. 2 located. It can be seen in particular that on Sunday (rest day) the nitrogen requirement drops to a relatively low value of 144 m ³ / h. This reduced nitrogen requirement results from the reduced air exchange rate on Sunday, as on Sunday the air exchange rate is determined by the feed-independent air exchange rate (the feed-dependent air exchange rate is negligible on the day of rest, since no loading and / or inspection of the enclosed area is provided).

From Monday, however, the feed-dependent air exchange rate is significantly increased, as at the beginning of a working week or in the working week increased pallet movement and thus loading takes place. Accordingly, the demand for nitrogen will increase accordingly from Monday.

In contrast to the conventional mode of operation known from the prior art, it is provided according to the present invention that the gas separation system belonging to the oxygen reduction system is operated continuously, in which context in particular also means operation on Sunday (rest day). In this case, the operating mode of the gas separation system is selected such that an amount of an oxygen-reduced gas mixture is continuously provided at the outlet of the gas separation system per unit time, so that the oxygen concentration in the room atmosphere of the enclosed area in the entire week cycle in a range between the predetermined, reduced operating concentration and a pre fixed or definable lower limit concentration. In other words, during idle times, the continuous operation of the gas separation system establishes a calculated nitrogen buffer in the enclosed area that is used for a subsequent period of time with increased nitrogen demand.

At the in FIG. 2 As shown in the timing chart, the preset, reduced operating concentration is 15% by volume and the preset or definable lower limit concentration is 14.6% by volume. Of course, other concentration values are also conceivable.

In detail and as per the timing diagram FIG. 2 can be taken, the gas separation system of the oxygen reduction plant is operated continuously so that at the outlet of the gas separation system continuously per hour 526 m ^{3 of} the oxygen-reduced gas mixture is provided. This operating mode of the gas separation system ensures that over the week cycle the oxygen concentration in the room atmosphere of the enclosed area is always below the predetermined, reduced operating concentration of 15% by volume.

In contrast to a conventionally designed or projected oxygen reduction system, however, can be significantly smaller dimensions with the solution according to the invention, the gas separation system. It should be noted that the in FIG. 1 In the case shown, the gas separation system is designed for a delivery capacity of more than 1,000 m ³ / h.

Hereinafter, referring to the principle time chart according to FIG. 3 another exemplary embodiment of the present invention is described. Specifically, here is shown the operation of an oxygen reduction plant which is designed and projected for an enclosed area (warehouse) used in two shifts 6 days a week. As with the in FIG. 2 shown case example is according to the timing diagram FIG. 3 Sunday is a rest day.

Because - in contrast to the in FIG. 2 shown situation - in the case example according to FIG. 3 the enclosed area (storage) is used in the two-shift operation, the feed-dependent air exchange rate of the enclosed area in the course of the week is different from the feed-dependent air exchange rate, which in the case according to FIG. 2 taken into consideration.

In detail, the feed and / or walk-dependent fresh air entry in the case example according to FIG. 3 summarized in Table 4 over the course of the week.

The total fresh air entry in the course of the week for the case study according to FIG. 3 is summarized in Table 5.

The resulting nitrogen requirement is summarized in Table 6.

The time course of the nitrogen requirement is also in the time chart according to FIG. 3 located.

Compared to the in FIG. 2 As shown in the situation shown in which a three-shift operation has been taken into account, it is expected according to the case study FIG. 3 the proportion of the feed and / or slip-dependent fresh air intake lower. This has the consequence that in the case of example FIG. 3 the amount of an oxygen-reduced gas mixture to be continuously provided per unit time by the gas separation system can be reduced.

Specifically, it is according to the case example FIG. 3 424 m ^{3 of} nitrogen per hour are provided by the gas separation system to ensure that during the week the oxygen concentration in the room atmosphere of the enclosed area is always below the pre-determined operating concentration of 15% by volume.

The timing diagrams of the case examples according to FIG. 2 and FIG. 3 show that in a continuous operation of the gas separation system of the oxygen reduction system per unit time such a sufficient amount of an oxygen-reduced gas mixture (continuously) is provided that the oxygen concentration in the room atmosphere of the enclosed area always below the predetermined, reduced operating concentration and a predetermined or definable lower Boundary concentration is.

In the case examples, the predetermined operating concentration is 15% by volume, while the predetermined or definable lower limit concentration is at most 1% by volume of oxygen and preferably at most 0.5% by volume of oxygen below that of the predetermined, reduced Operating concentration corresponding to the oxygen content.

Furthermore, according to the timing diagrams FIG. 2 and 3 it can be seen that the total air exchange rate of the enclosed area varies cyclically with respect to time (here: in the weekly cycle), each time cycle being divided into several consecutive time periods, and for each time period a mean total air exchange rate of the enclosed area assumes a corresponding value , In this context, reference is made to the entries in Table 2 for the case study FIG. 2 or to Table 5 for the case study according to FIG. 3 directed.

The respective duration of the time periods of the time cycle and the respective mean total air exchange rate for each time period then play a role in the design or planning of the gas separation system of the oxygen reduction system. As already stated, in the case example according to FIG. 2 due to the considered there three-shift operation, the feed-dependent air exchange rate, at least on the weekdays from Monday to Saturday higher in comparison to the situation in the case according to FIG. 3 , This has the consequence that in the case of example FIG. 2 the gas separation system needs to provide a larger amount of an oxygen displacing gas mixture (nitrogen) per unit of time as compared to the gas separation system described in the case study of FIG. 3 is used.

The invention is not with reference to the time charts according to FIG. 2 and FIG. 3 limited examples described. In particular, the solution according to the invention is generally suitable for an enclosed area whose total air exchange rate varies cyclically with time, each time cycle being divided into several consecutive time periods, and for each time period a mean total air exchange rate of the enclosed area assuming a corresponding value ,

For example, in this context, it is conceivable that within a first time period of the plurality of consecutive time periods of a time cycle, the average air exchange rate of the enclosed area is within a first value range, and within at least a second time period of the plurality of consecutive time periods of the time cycle, the average air exchange rate of enclosed area within at least a second range of values, wherein the mean value of the at least one second value range is greater than the average value of the first range of values. In this case, it is preferable that the gas separation system of the oxygen reduction system be designed to take into account the time duration of the first and the at least one second time periods and the average total air exchange rate of the enclosed area during the first and the at least one second time periods In a continuous operation of the gas separation system in the first operation mode, the oxygen concentration in the room atmosphere of the enclosed area is always in a range between the preset operation concentration and the predetermined or definable lower limit concentration.

With reference to the timing diagrams according to the FIGS. 2 and 3 described case examples, an average wind speed of 3.0 m / s is taken into account. This condition may not always exist in reality. In particular, it can not be ruled out that significantly higher wind speeds will be present at least temporarily. This would then have an influence in particular on the feed-independent air exchange rate, ie the air exchange rate, which are caused by unwanted or indispensable leaks in the enclosure of the enclosed area.

In order to achieve that with the oxygen reduction system according to the invention a reduced oxygen concentration in the room atmosphere of the enclosed area can be kept below a predetermined operating concentration even in such exceptional situations, it is provided in an advantageous development of the oxygen reduction system according to the invention that the gas separation system can be operated in at least two different operating modes is. In this case, the gas separation system is operated starting from its standard operating mode (first operating mode) in its second operating mode, when the average total air exchange rate of the enclosed area increases in particular in an unpredictable manner and in particular in an uncyclical manner.

In the second operating mode of the gas separation system, compared to the first operating mode, the amount of an oxygen-reduced gas mixture continuously provided per unit time at the outlet of the gas separation system is increased correspondingly to a reference value of a residual oxygen concentration. On the other hand, in the first operating mode of the gas separation system, the specific power of the gas separation system is lower than the specific power of the gas separation system in the second operation mode.

As used herein, "specific performance of the gas separation system" (at a reference temperature of, for example, 20 ° C) is the specific energy demand of the gas separation system to provide a volume unit of the oxygen-reduced gas mixture (relative to a reference level of residual oxygen concentration).

In this context, it is conceivable, for example, that the gas reduction system of the oxygen reduction system is designed to be operated either in a VPSA mode or in a PSA mode, wherein the first operating mode of the gas separation system corresponds to the VPSA mode and the second operating mode of the gas separation system PSA mode corresponds.

A gas separation system operated in a VPSA mode is generally a vacuum pressure swing adsorption (VPSA) system for providing nitrogen-impinged air. According to one aspect of the present invention, such a VPSA system is used in the oxygen reduction system as a gas separation system, which, however, if necessary, especially if the average total air exchange rate of the enclosed area increases in an unforeseeable manner and / or non-cyclically - in a PSA system. Mode is operated. The abbreviation "PSA" stands for "pressure swing adsorption", which is commonly referred to as "pressure swing adsorption".

In order to be able to switch the operating mode of the gas separation system used in this aspect of the present invention from VPSA to PSA, in a preferred implementation of the oxygen reduction system according to the invention, initially an initial gas mixture is provided which comprises oxygen, nitrogen and optionally further components , The initial gas mixture provided is suitably compressed and, in the gas separation system, at least part of the oxygen contained in the initial compressed gas mixture is separated so that a nitrogen-enriched gas mixture is provided at the outlet of the gas separation system. This nitrogen-enriched gas mixture at the outlet of the gas separation system corresponds to the oxygen-reduced gas mixture which is introduced continuously into the room atmosphere of the enclosed area.

According to a further aspect of the present invention, it is provided that the degree of compression of the initial gas mixture by the compressor system is increased when the gas separation system has to be switched from the first operating mode to the second operating mode due to increased air exchange. In an exemplary embodiment In this context, it is conceivable to increase the degree of compression performed from originally 1.5 to 2.0 bar to 7.0 to 9.0 bar. In other embodiments, an increase in compression to up to 25.0 bar is conceivable. In particular, the invention is not limited to the exemplary values given above.

According to one aspect of the present invention, it is provided that the gas separation system is operated in the second operating mode when the oxygen concentration in the enclosed area exceeds a predetermined or definable upper limit value, in particular due to an averaged air exchange rate the upper limit oxygen concentration preferably corresponds to an oxygen concentration which is at or above the oxygen concentration corresponding to the predetermined operating concentration. Preferably, the predetermined or definable upper limit oxygen concentration corresponds to an oxygen concentration which is at most 1.0 vol.% And preferably at most 0.2 Vol .-% above the oxygen concentration, which corresponds to the predetermined operating concentration.

In this context, it is also conceivable that the gas separation system in the second operating mode in at least two predetermined, different power levels is operable, wherein the at least two power levels differ in that - compared to a first power level - in a second power level the per unit of time of the gas separation system provideable amount of an oxygen-reduced gas mixture is higher, based on a predetermined reference value of a residual oxygen concentration. In this case, it is advantageous if, depending on the degree of exceeding of the predetermined or definable upper limit value of the oxygen concentration, the power stage of the gas separation system is preferably automatically selected in the second operating mode.

Alternatively or additionally, it is conceivable further to provide a further, independent of the gas separation system inert gas source, in particular in the form of a compressed gas storage in which an oxygen-reduced gas mixture or inert gas is stored in compressed form. The further inert gas source is fluidly connected to the enclosed area when the oxygen concentration in the enclosed area exceeds a predetermined or definable upper limit, in particular due to a mean time-increased rate of air change. Again, the predetermined or definable upper limit preferably corresponds to an oxygen concentration that is at or above the oxygen concentration that corresponds to the predetermined operating concentration. In this case, the predetermined or definable upper limit value preferably corresponds to an oxygen concentration which is at most 1% by volume and preferably at most 0.2% by volume above the oxygen concentration which corresponds to the operating concentration.

According to a further aspect of the invention there is further provided a means for reducing a feed-dependent air exchange rate of the enclosed area on demand, wherein the feed-dependent air exchange rate takes into account an air exchange caused by openings for the purpose of loading and / or commissioning in the space envelope of the enclosed area , This device is designed to preferably automatically reduce the charge-dependent air exchange rate of the enclosed area when the oxygen concentration in the enclosed area exceeds a predetermined or determinable upper limit. The predetermined or definable upper limit value preferably corresponds to an oxygen concentration which is at or above the oxygen concentration corresponding to the predetermined operating concentration.

Accordingly, it is conceivable, at least temporarily, to reduce the charge-dependent air exchange rate, and thus also the overall air exchange rate, via suitable charge management. It is conceivable, for example, that only a limited number of doors or gates can be opened as part of the feed management and / or the opening hours are limited.

According to a further aspect of the present invention, it is provided that the gas separation system is further operable in a third operating mode, in which - compared to the first operating mode - the continuously per unit time At the outlet provided amount of an oxygen-reduced gas mixture - based on a reference value of a residual oxygen concentration - is reduced. Here, in the first mode of operation, the specific power of the gas separation system should be higher than the specific power of the gas separation system in the third mode of operation.

In particular, it is conceivable in this context to operate the gas separation system in the third operating mode if the oxygen concentration in the enclosed region falls below a predefinable lower limit value, in particular due to an average mean air exchange rate which is reduced in the time average. In particular, this predetermined lower limit value corresponds to an oxygen concentration which is at or above the oxygen concentration which corresponds to the predefinable lower limit concentration or above the predefinable lower limit concentration.

However, for operating the gas separation system in the different operating modes, it is also conceivable for the gas separation system to have a large number of nitrogen generators operated in parallel, these nitrogen generators being switched on or off as required.

Briefly, the present invention particularly relates to a system for maintaining a reduced oxygen content in the room atmosphere of an enclosed area below a predetermined and reduced operating concentration compared to the oxygen concentration of the normal ambient air, the system comprising a continuously operated gas separation system designed such that in a continuous operation of the gas separation system, the oxygen concentration in the room atmosphere of the enclosed area is always in a range between the predetermined operating concentration and a predetermined or definable lower limit concentration.

Preferably, the oxygen reduction system is associated with an enclosed area whose total air exchange rate varies cyclically with time, each time cycle being divided into a plurality of consecutive time periods, and wherein for each time period a mean total air exchange rate of the enclosed one Range assumes a corresponding value. In this case, the gas separation system is designed taking into account the respective duration of the time periods and taking into account the respective average total air exchange rates such that in a continuous operation of the gas separation system, the oxygen concentration in the room atmosphere of the enclosed area always in a range between the predetermined operating concentration and the advance fixed or definable lower limit concentration.

In a particularly preferred implementation, the time cycle is a weekly cycle, wherein continuously during at least a first time period of preferably at least 4 to 48 hours, especially at least 4 to 24 hours, and more preferably at least 6 to 24 hours, the average total air exchange rate of and wherein during the remaining time of the week cycle the average total air exchange rate of the enclosed area corresponds to a sum, in particular a weighted sum of a feed-dependent air exchange rate and a feed-independent air exchange rate.

The gas separation system of the oxygen reduction system according to the invention is designed such that in a continuous operation of the gas separation system, the oxygen concentration in the room atmosphere of the enclosed area during the at least a first time period is reduced such that the oxygen concentration in the room atmosphere of the enclosed during the remaining time of the week cycle Range does not exceed the design concentration. Illustratively, the oxygen reduction system is designed so that a nitrogen buffer is built up in the enclosed area during a calculated rest period with low air exchange rate. This buffer then compensates for the higher air exchange rate during the operating times, so that this compensation does not have to be provided by the oxygen reduction system and this can be operated evenly.

The invention is not limited to the described case examples, but results from a synopsis of all features disclosed herein.

Claims (15)

An apparatus for reducing the oxygen content in the room atmosphere of an enclosed area and / or maintaining a reduced oxygen content in the room atmosphere of an enclosed area below a predetermined and reduced operating concentration compared to the oxygen concentration of the normal ambient air, the system having a gas separation system whose outlet is fluid is connected to the enclosed area for continuously supplying an oxygen-reduced gas mixture or oxygen displacing gas, wherein the gas separation system is designed so that in a continuous operation of the gas separation system in a first operating mode, in which at the outlet of the gas separation system per unit time within a predetermined or determinable Range of an oxygen-reduced gas mixture is continuously provided, the oxygen concentration in the room The atmosphere of the enclosed area shall always be in the range between the predetermined operating concentration and a predetermined or definable lower limit concentration. The plant of claim 1, wherein the total air exchange rate of the enclosed area varies cyclically with respect to time, each time cycle being divided into a plurality of consecutive time periods, and wherein for each time period a mean total air exchange rate of the enclosed one Range assumes a corresponding value, the gas separation system is designed taking into account the respective duration of the time periods and taking into account the respective mean total air exchange rates such that in a continuous operation of the gas separation system in the first operating mode, the oxygen concentration in the room atmosphere of the enclosed area always in range between the predetermined operating concentration and the predetermined or definable lower limit concentration. The system of claim 2, wherein within a first time period of the plurality of consecutive time periods of a time cycle, the average total air exchange rate of the enclosed area is within a first value range, and wherein within at least a second time period of the plurality of consecutive time periods of the time cycle, the average total air exchange rate of the enclosed one Range within at least a second range of values, wherein the mean of the at least one second range of values is greater than the average value of the first range of values, and wherein the gas separation system taking into account the duration of the first and the at least one second time period and taking into account the average total air exchange rate of enclosed area during the first and at least a second time period is designed such that in a continuous operation of the gas separation system in the first Betriebsmod the oxygen concentration in the room atmosphere of the enclosed area is always in a range between the predetermined operating concentration and the predetermined lower limit concentration. Installation according to one of claims 1 to 3, in particular according to claim 2 or 3, wherein in a continuous operation of the gas separation system in the first operating mode, the continuously provided at the outlet of the gas separation system per unit time amount of an oxygen-reduced gas mixture selected depending on at least one of the parameters listed below is: - the volume of the enclosed area; - a feed-independent air exchange rate due to leaks in the enclosure of the enclosed area; and or - A feed-dependent air exchange rate by for the purpose of loading and / or commissioning if necessary ausbildbare openings in the enclosure of the enclosed area. Plant according to one of claims 2 to 4, wherein the time cycle is a weekly cycle, and wherein continuously during at least a first time period of preferably at least 4 to 48 hours, in particular of at least 4 to 24 hours, and more preferably of at least 6 to 24 hours, the average total air exchange rate of the enclosed area corresponds to a feed-independent air exchange rate of the enclosed area, and wherein during the remaining time of the weekly cycle the average total air exchange rate of the enclosed area corresponds to a sum, in particular a weighted sum of a feed-dependent air exchange rate and a feed-independent air exchange rate the gas separation system is designed such that in a continuous operation of the gas separation system in the first operating mode, the oxygen concentration in the room atmosphere of the enclosed area during the at least one first time Ze is reduced so that even during the remaining time of the week cycle, the oxygen concentration in the room atmosphere of the enclosed area does not exceed the operating concentration. Installation according to one of claims 1 to 5, wherein the gas separation system is further operable in a second operating mode in which - compared to the first mode of operation - the continuously per unit time at the outlet provided amount of an oxygen-reduced gas mixture - relative to a reference value of a residual oxygen concentration - increased In particular, in the first operating mode, the specific power of the gas separation system is lower than the specific power of the gas separation system in the second operating mode. The system of claim 6, wherein the gas separation system is configured to operate in either a VPSA mode or in a PSA mode and wherein the first operating mode of the gas separation system corresponds to the VPSA mode and the second operating mode of the gas separation system corresponds to the PSA mode. Plant according to claim 6 or 7, wherein the plant comprises a compressor system connected to the gas separation system for compressing an initial gas mixture, wherein the gas separation system is adapted to separate at least a portion of the oxygen contained in the initial compressed gas mixture and at an exit of the gas separation system oxygen-reduced gas mixture to provide, and wherein the compression ratio of the compressor system is adjustable such that the initial gas mixture in the compressor system selectively to a first low pressure value or a second, high pressure value, in particular to a first pressure of 1.5 to 2.0 bar or a second pressure of 7.0 to 9.0 bar, and wherein in the first operating mode of the gas separation system, the initial gas mixture is compressed to the first pressure value and in the second operating mode, the initial gas mixture to the second pressure value. Plant according to one of claims 6 to 8, wherein the gas separation system is operated in the second operating mode, when the oxygen concentration in the enclosed area exceeds a predetermined or definable upper limit, in particular due to an averaged increase in the air exchange rate, the predetermined or specifiable upper limit of the oxygen concentration preferably corresponds to an oxygen concentration which is at or above the oxygen concentration which corresponds to the predetermined operating concentration, and wherein the predetermined or definable upper limit of the oxygen concentration preferably corresponds in particular to an oxygen concentration not exceeding 1% by volume and preferably at most 0.2% by volume above the oxygen concentration, which corresponds to the operating concentration. Plant according to claim 9, wherein in the second operating mode, the gas separation system is operable in at least two predetermined, different power levels, wherein the at least two power levels differing in that, in a second power stage, in a second power stage, the amount of an oxygen-reduced gas mixture available per unit time by the gas separation system is higher, based on a predetermined reference oxygen content, and depending on the degree of exceedance of the predetermined or definable upper limit value of the oxygen concentration, the power stage of the gas separation system in the second operating mode is preferably automatically selected. Installation according to one of claims 1 to 10, wherein there is further provided an inert gas source independent of the gas separation system, in particular in the form of a compressed gas reservoir in which an oxygen-reduced gas mixture or inert gas is stored in compressed form, the further inert gas source being in flow with the enclosed area is connected when the oxygen concentration in the enclosed area exceeds a predetermined or definable upper limit, in particular due to a mean time averaged air exchange rate, wherein the predetermined or definable upper limit oxygen concentration preferably corresponds to an oxygen concentration which is at or above the oxygen concentration which corresponds to the predetermined operating concentration, and wherein the predetermined or definable upper limit of the oxygen concentration is preferably in particular S corresponds to a maximum of 1 vol .-% and preferably by at most 0.2 vol .-% above the oxygen concentration, which corresponds to the operating concentration. An apparatus according to any one of claims 1 to 11, further comprising means for reducing a feed-dependent air exchange rate of the enclosed area on demand, the feed-dependent air exchange rate taking into account air changes necessitated by openings for forming and / or loading as required Space envelope of the enclosed area, wherein the device is designed to preferably automatically reduce the feed-dependent air exchange rate of the enclosed area, when the oxygen concentration in the enclosed area exceeds a predetermined or definable upper limit value, wherein the predetermined or definable upper limit value of the oxygen concentration preferably corresponds to an oxygen concentration which is at or above the oxygen concentration corresponding to the predetermined operating concentration, and wherein the above fixed or definable upper limit of the oxygen concentration preferably corresponds in particular to an oxygen concentration which is at most 1% by volume and preferably at most 0.2% by volume above the oxygen concentration which corresponds to the operating concentration. Installation according to one of claims 1 to 12, wherein the gas separation system is further operable in a third operating mode in which - compared to the first mode of operation - the continuously provided per unit time at the outlet amount of an oxygen-reduced gas mixture - based on a reference value of a residual oxygen concentration - is reduced wherein, in the first operating mode, the specific power of the gas separation system is in particular higher than the specific power of the gas separation system in the third operating mode, and / or wherein the gas separation system is operated in the third operating mode in particular when the oxygen concentration in the enclosed area - especially due to a mean total air exchange rate, which is reduced in the mean time over time, falls below a predefinable lower limit value, the lower limit value of the oxygen concentration, which can be defined in advance, being an oxygen concentration which is at or above the oxygen concentration corresponding to the predetermined or definable lower limit concentration. Installation according to one of claims 1 to 13,
wherein the predetermined operating concentration corresponds to the design concentration; and or
wherein the predetermined or definable lower limit concentration is at most 3% by volume of oxygen and more preferably at most 0.5% by volume of oxygen below the oxygen content corresponding to the predetermined operating concentration; and or wherein the gas separation system comprises a plurality of parallel-operated nitrogen generators. Method for laying out an oxygen-reduction plant for an enclosed area, the method comprising the following method steps: i) dividing a predetermined time cycle into a plurality of consecutive time periods; ii) determining a mean total air exchange rate of the enclosed area for each period of time; iii) weighting the determined average total air exchange rates with respect to the respective durations of the associated time periods; and iv) adjusting a gas separation system of the oxygen reduction system taking into account the weighted mean total air exchange rates of the enclosed area such that in a continuous operation of the gas separation system in a first operating mode in which at the outlet of the gas separation system per unit time one within a predetermined or The oxygen concentration in the room atmosphere of the enclosed area is always in a range between a predetermined operating concentration and a presettable lower limit concentration.

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