EP2204219A1 - Inertisation method to prevent and/or extinguish fires and inertisation system to implement the method - Google Patents

Abstract

The method involves separating a part of oxygen from a gas mixture in gas separation systems (3, 4). A gas mixture enriched with nitrogen is guided at room temperature of enclosed rooms (2), and is provided at an outlet of the gas mixture. A control unit (5) controls the gas separation systems in such a manner that an oxygen residual content of the gas mixture enriched with the nitrogen is changed as a function of the oxygen content in the room atmosphere of another enclosed room (10). An independent claim is also included for an inerting system for setting and holding predetermined oxygen content in a room atmosphere, comprising a gas separating system.

Description

The present invention relates to an inerting method according to the preamble of claim 1. Accordingly, the invention relates to an inerting method for fire prevention and / or fire extinguishing, in which in the room atmosphere of an enclosed space a predeterminable and compared to the normal ambient air reduced oxygen content is set and maintained. For this purpose, an initial gas mixture is provided, which comprises oxygen, nitrogen and optionally other components, wherein from this provided initial gas mixture in a gas separation system at least part of the oxygen separated and provided in this way at the outlet of the gas separation system, a nitrogen-enriched gas mixture , and wherein this nitrogen-enriched gas mixture is conducted into the room atmosphere of the enclosed space.

The invention further relates to an inerting system for setting and / or holding a predeterminable and compared to the normal ambient air reduced oxygen content in the room atmosphere of an enclosed space, wherein the inerting has a gas separation system, with which of a nitrogen and oxygen-containing initial gas mixture at least a portion the oxygen is separated and thus provided at the output of the gas separation system, a nitrogen-enriched gas mixture, and wherein the inerting system comprises a supply line system for supplying the nitrogen-enriched gas mixture to the enclosed space.

An inerting installation of the aforementioned type is, in particular, a facility for reducing the risk and extinguishing fires in a protected area to be monitored, with the protection space being permanently inertised for fire prevention or fire fighting. The mode of operation of such an inerting system is based on the knowledge that in enclosed spaces the risk of fire can be counteracted by the fact that in the affected area the oxygen concentration is normally lowered permanently to a value of, for example, about 12 to 15% by volume. At this oxygen concentration, most flammable materials can no longer burn. The main areas of use are in particular IT areas, electrical switch and distribution rooms, enclosed facilities as well as storage areas with high-quality assets.

The prevention or extinguishing effect resulting from the inertization process is based on the principle of oxygen displacement. Normal ambient air is known to be about 21 vol .-% of oxygen, about 78 vol .-% of nitrogen and about 1 vol .-% of other gases. In order to be able to effectively reduce the risk of the formation of a fire in a shelter, the oxygen concentration in the relevant space is reduced by introducing inert gas, such as nitrogen. With regard to the fire extinction of most solids, it is known that a extinguishing effect already starts when the oxygen content drops below 15% by volume. Depending on the combustible materials present in the shelter, further lowering of the oxygen content to, for example, 12 vol.% May be required. Thus, by permanently inerting the shelter, the risk of a fire developing in the shelter can be effectively reduced.

The present invention is based on the problem, an inerting of the type mentioned in such a way that can be set and maintained in the most economical manner in the enclosed space a predetermined inerting level. In particular, a solution is to be specified with which the costs incurred in the inerting of an enclosed space operating costs can be reduced. Furthermore, a corresponding inerting method should be specified, which ensures cost-effective inerting and in particular permanent inerting of an enclosed space.

With regard to the method, this object is achieved with an inerting process of the type mentioned in the present invention, that the oxygen radical content of the nitrogen gas-enriched gas mixture provided at the outlet of the gas separation system is changed as a function of the oxygen content currently prevailing in the room atmosphere of the enclosed space.

With regard to the device, the object underlying the invention with an inerting of the type mentioned is achieved in that a control device is provided which is designed to control the gas separation system such that the oxygen radical content of the nitrogen-enriched gas mixture in dependence on the currently in the room atmosphere of the enclosed space prevailing oxygen content is changed.

The invention is based on the finding that the nitrogen purity of the gas mixture provided at the outlet of the gas separation system and enriched with nitrogen or the oxygen radical content of the nitrogen-enriched gas mixture provided at the outlet of the gas separation system has an influence on the so-called "settling time". The term "lowering time" is to be understood as the time duration which is necessary in order to set a given inerting level in the room atmosphere of the enclosed space.

Specifically, it has been found in the present case that with increasing nitrogen purity, the air factor of the gas separation system increases exponentially.

The term "air factor" means the ratio of the amount of initial gas mixture provided per unit time to the gas separation system to the amount of nitrogen-enriched gas provided per unit time at the outlet of the gas separation system. In a nitrogen generator usually the nitrogen purity at the outlet of the gas separation system is freely selectable and can be adjusted on the nitrogen generator. It basically applies that the operating costs of the nitrogen generator are the more favorable, the lower the set nitrogen purity precipitates. For then, with a comparatively short run time of the compressor at the outlet of the gas separation system, a nitrogen-enriched gas mixture with the set nitrogen purity can be provided.

However, with regard to the inerting of the room, the operating costs of the inerting system must take into account other factors. These include in particular rinsing factors in order to use the provided at the output of the gas separation system and nitrogen-enriched gas mixture, the oxygen in The space atmosphere of the enclosed space to displace so far that the predetermined inerting level is reached or can be maintained. These rinsing factors include, in particular, the amount of nitrogen-enriched gas which can be supplied per unit time by the gas separation system, the volume of space of the enclosed space and the difference between the oxygen content currently prevailing in the room atmosphere of the enclosed space and the oxygen content corresponding to the given inerting level. It should be noted that, with regard to the lowering time, the nitrogen purity of the gas mixture provided at the outlet of the gas separation system or the oxygen radical content of the nitrogen-enriched gas mixture also plays a decisive role, since the purging process proceeds faster, the lower the residual oxygen content the nitrogen-enriched gas mixture.

The term "gas separation system" used here is to be understood as a system with which an initial gas mixture which has at least the components "oxygen" and "nitrogen" can be split into oxygen-enriched gas and nitrogen-enriched gas , Usually, the operation of such a gas separation system is based on the action of gas separation membranes. The gas separation system used in the present invention is designed in the first line for the separation of oxygen from the initial gas mixture. Such a gas separation system is often referred to as a "nitrogen generator".

In such a gas separation system, for example, a membrane module or the like is used, in which the various components contained in the initial gas mixture (such as oxygen, nitrogen, noble gases, etc.) diffuse at different rates through the membrane according to their molecular structure. As a membrane, a hollow fiber membrane can be used. Oxygen, carbon dioxide and hydrogen have a high degree of diffusion and, due to this, leave the initial gas mixture relatively quickly when the membrane module flows through it. Nitrogen with a low degree of diffusion penetrates the hollow-fiber membrane of the membrane module very slowly and accumulates in this way as it flows through the hollow fiber or the membrane module. The nitrogen purity or the oxygen radical content in the gas mixture leaving the gas separation system is determined by the flow rate. By varying the pressure and flow rate, the gas separation system can be adjusted to the required nitrogen purity and the required amount of nitrogen. Specifically, the purity of the Nitrogen is controlled by the rate at which the gas flows through the membrane (residence time).

The separated, oxygen-enriched gas mixture is usually collected and blown into the atmosphere under atmospheric pressure. The compressed, nitrogen-enriched gas mixture is provided at the exit of the gas separation system. In the analysis of the product gas composition, the measurement is made on the oxygen radical content in Vol .-%. The nitrogen content is calculated by subtracting the measured residual oxygen content from 100%. It should be noted that this value is indeed referred to as nitrogen content or nitrogen purity, but it is in fact the inert content, since this partial stream not only from nitrogen, but also from other gas components, such as noble gases, composed.

Usually, the gas separation system or the nitrogen generator is supplied with compressed air, which is cleaned by upstream filter units. In principle, it is possible to use nitrogen pressure enriched gas (PSA) technology employing two molecular sieve beds, both screens being alternately switched from a filter mode to a regeneration mode, thereby allowing the flow of nitrogen-enriched gas ,

For example, when a membrane technique is used in the nitrogen generator, the general discovery is that different gases diffuse through materials at different rates. In the case of the nitrogen generator, in this case the different diffusion rates of the main components of the air, namely nitrogen, oxygen and water vapor, are used technically to produce a nitrogen stream or a nitrogen-enriched air. In particular, for the technical realization of a membrane-based nitrogen generator, a separation material is applied to the outer surfaces of hollow-fiber membranes, through which water vapor and oxygen diffuse very well. The nitrogen, however, has only a low diffusion rate for this separation material. If the thus prepared hollow fiber is traversed inside by air, water vapor and oxygen quickly diffuse through the hollow fiber wall to the outside, while the nitrogen is largely maintained in the fiber interior, so that during the passage through the hollow fiber, a strong concentration of nitrogen takes place. The effectiveness of this separation process is essentially dependent on the flow rate in the fiber and the pressure difference across the Hohlfaserwandung away. With decreasing flow velocity and / or higher pressure difference between the inside and outside of the hollow fiber membrane increases the purity of the resulting nitrogen flow. Thus, generally speaking, with a membrane-based nitrogen generator, the degree of nitrogen enrichment in the nitrogen-enriched air provided by the nitrogen generator may be controlled in response to the residence time of the compressed air provided by the compressed air source in the nitrogen separator air separation system.

If, on the other hand, the PSA technology is used, for example, in the nitrogen generator, different binding rates of the atmospheric oxygen and atmospheric nitrogen on specially treated activated carbon are utilized. In this case, the structure of the activated carbon used is changed so that an extremely large surface with a large number of micro and submicropores (d <1 nm) is present. At this pore size, the oxygen molecules of the air diffuse into the pores much faster than the nitrogen molecules, so that the air in the vicinity of the activated carbon enriches with nitrogen. Therefore, in a nitrogen generator based on PSA technology, as with a membrane-based generator, the degree of nitrogen enrichment in the nitrogen-enriched air provided by the nitrogen generator may be controlled as a function of the residence time of the compressed air in the nitrogen generator provided by the compressed air source become.

As already indicated, the solution according to the invention is based on the recognition, on the one hand, that with increasing nitrogen purity, the air factor of the gas separation system increases exponentially, and on the other hand, that the compressor of the inerting system must run the longer the lower the difference between in the room atmosphere of the enclosed space currently prevailing oxygen content and the oxygen radical content in the nitrogen-enriched gas mixture. It should be noted that the duration of the lowering of a space to be inerted, be it for the holding control of the room at a fixed residual oxygen content or while lowering to a new lowering level, the energy consumption of the inerting is almost directly proportional, as the gas separation system upstream compressor is driven digitally at its operating point with optimal efficiency.

Accordingly, it should be noted that - if a low value of, for example, only 90 vol .-% is selected for the nitrogen purity - the inert gas system for setting a Inertization levels must be operated relatively long. If, for example, the value of the nitrogen purity is increased to 95% by volume, the difference between the oxygen content of the inertization level to be set and the residual oxygen content of the gas mixture provided at the outlet of the gas separation system also increases, which in itself reduces the transit time of the gas mixture required for setting an inertization level Compressor and thus reduces the energy consumption of the inerting system. However, the fact that the nitrogen purity is increased at the outlet of the gas separation system inevitably also increases the air factor. With regard to the running time of the compressor required for setting an inertization level or the energy consumption of the inerting system, this circumstance has a negative effect. This negative influence predominates when the increase in the air factor caused by increasing the nitrogen purity becomes noticeable.

Contrary to the usual known from the prior art systems in which a fixed value is selected for the nitrogen purity, it was recognized in the inventive solution that in the inerting of the enclosed space of the oxygen radical content in the provided at the exit of the gas separation system and with nitrogen enriched gas mixture at the currently prevailing in the room atmosphere of the enclosed space oxygen content is preferably automatically or optionally automatically adjusted to adjust in this way the nitrogen purity of the gas separation system to a time-optimized value.

The term "time-optimized value of the nitrogen purity" as used herein means the nitrogen purity of the gas separation system or the residual oxygen content in the nitrogen-enriched gas mixture provided at the outlet of the gas separation system, with which the per Constant amount of nitrogen-enriched gas mixture which can be provided for a given period of time, the time duration for the lowering process assumes a minimum from a current oxygen content to an oxygen content corresponding to a predetermined and inerting level.

Advantageous developments of the solution according to the invention are specified in the subclaims.

In a preferred embodiment of the inertization process according to the invention, it is provided that the oxygen radical content of the nitrogen-enriched gas mixture or the nitrogen purity of the gas separation system is preferably set automatically according to a previously determined characteristic curve. This characteristic indicates the time-optimized course of the oxygen radical content in the nitrogen-enriched gas mixture compared to the oxygen content in the room atmosphere of the enclosed space. The expression "time-optimized course of the oxygen radical content" is understood to mean the time-optimized values of the oxygen radical content which are dependent on the oxygen content in the room atmosphere of the enclosed space. As already indicated, the time-optimized value of the oxygen radical content corresponds to the value of the residual oxygen content to be selected in the gas separation system, so that a predeterminable and in comparison to the normal ambient air reduced oxygen content can be set with the aid of the inerting process in the room atmosphere of the enclosed space within a very short time.

The characteristic curve according to which, in the preferred embodiment of the inertization process according to the invention, the oxygen radical content is set as a function of the oxygen content currently prevailing in the room atmosphere of the enclosed space, has been previously determined (measured or calculated) for the gas separation system or the inerting system.

Since, in the solution according to the invention, the nitrogen purity of the gas separation system or the oxygen radical content in the nitrogen-enriched gas mixture is preferably set automatically depending on the oxygen content currently prevailing in the room atmosphere of the enclosed space, in order to inertize the room with the lowest possible operating costs To be able to make it, it is preferred if the current oxygen content in the room atmosphere of the enclosed space is measured either directly or indirectly at predetermined times and / or events. Furthermore, it is preferred if the oxygen radical content in the nitrogen-enriched gas mixture is adjusted to a predetermined, time-optimized value continuously or at given times and / or events. This predetermined, time-optimized value should correspond to an oxygen residual content at which the inerting method allows the oxygen content in the room atmosphere of the enclosed space to be lowered within a very short time by a predefined reduction amount to the respective current oxygen content.

In a preferred further development of the solution according to the invention, it is provided that not only the nitrogen purity of the gas separation system depends on the currently prevailing oxygen content in the room atmosphere of the enclosed space is changed, but also that the oxygen content in the initial gas mixture is changed depending on the currently prevailing in the room atmosphere of the enclosed space oxygen content. Here, the knowledge is exploited that the air factor of the gas separation system can be reduced if the initial gas mixture, with which the gas separation system is supplied, has a reduced oxygen content.

Accordingly, in a preferred realization of the solution according to the invention, provision is made for provision of the initial gas mixture to remove part of the room air contained in the enclosed space in a controlled manner from the room and to supply fresh air to the extracted part of the room air in a regulated manner. In order to prevent the pressure inside the enclosed space from being changed by the supply of nitrogen-enriched gas or by the discharge of a part of the room air, the amount of fresh air mixed in the room air taken from the room is prevented chosen that the amount of air taken from the room per unit time is identical to the amount of the nitrogen-enriched gas mixture, which is provided at the exit of the gas separation system and per unit time in the space atmosphere of the enclosed space.

In the following, a preferred realization of the inerting plant according to the invention will be described with reference to the attached drawings.

Fig. 1

eine schematische Ansicht einer Inertisierungsanlage gemäß einer ersten Ausführungsform der vorliegenden Erfindung;

Fig. 2

eine schematische Ansicht einer Inertisierungsanlage gemäß einer zweiten Ausführungsform der vorliegenden Erfindung;

Fig. 3

eine graphische Darstellung des Luftfaktors gegenüber der Stickstoff-Reinheit bei der Inertisierungsanlage gemäß Fig. 1 oder Fig. 2, sowie eine graphische Darstellung der Absenkzeit gegenüber der Stickstoff-Reinheit, und zwar bei der Absenkung des Sauerstoffgehaltes von ursprünglich 17,4 Vol.-% auf 17,0 Vol.-% sowie bei einer Absenkung des Sauerstoffgehaltes von ursprünglich 13, 4 Vol.-% auf 13,0 Vol.-%;

Fig. 4

eine graphische Darstellung der zeitoptimierten Stickstoff-Reinheit gegenüber dem aktuellen Sauerstoffgehalt in der Raumatmosphäre des umschlossenen Raumes bei der Inertisierungsanlage gemäß Fig. 1 oder Fig. 2;

Fig. 5

eine graphische Darstellung des Luftfaktors des Gasseparationssystems bei der Inertisierungsanlage gemäß Fig. 1 oder Fig. 2 gegenüber dem Sauerstoffgehalt des Anfangs-Gasgemisches, welches dem Gasseparationssystem zugeführt wird, um zumindest ein Teil des Sauerstoffes aus dem AnfangsGasgemisch abzutrennen und auf diese Weise am Ausgang des Gasseparationssystems ein mit Stickstoff angereichertes Gasgemisch bereitzustellen;
und

Fig. 6

eine graphische Darstellung der erzielbaren Energieeinsparungen, wenn mit der erfindungsgemäßen Lösung in der Raumatmosphäre des umschlossenen Raumes der Sauerstoffgehalt abgesenkt wird.

Show it:

Fig. 1

a schematic view of an inerting according to a first embodiment of the present invention;

Fig. 2

a schematic view of an inerting according to a second embodiment of the present invention;

Fig. 3

a graphical representation of the air factor against the nitrogen purity in the inerting according to Fig. 1 or Fig. 2 , and a graph of the reduction time compared to the nitrogen purity, namely in the reduction of the oxygen content of originally 17.4 vol .-% to 17.0 vol .-% and at a reduction in the oxygen content of originally 13, 4 vol. -% to 13.0% by volume;

Fig. 4

a graphical representation of the time-optimized nitrogen purity compared to the current oxygen content in the room atmosphere of the enclosed space in the inerting according to Fig. 1 or Fig. 2 ;

Fig. 5

a graphical representation of the air factor of the gas separation system in the inerting according to Fig. 1 or Fig. 2 to the oxygen content of the initial gas mixture fed to the gas separation system to separate at least a portion of the oxygen from the initial gas mixture and thus to provide a nitrogen-enriched gas mixture at the exit of the gas separation system;
and

Fig. 6

a graphical representation of the achievable energy savings when the solution according to the invention in the room atmosphere of the enclosed space, the oxygen content is lowered.

Fig. 1 shows in a schematic representation of a first exemplary embodiment of an inerting system 1 according to the present invention. The illustrated inerting system 1 serves for setting and maintaining a predeterminable inerting level in the room atmosphere of an enclosed space 2. The enclosed space 2 can be, for example, a storage hall in which the oxygen content in the room air as a preventive fire protection measure is reduced to a certain inerting level of, for example, 12 vol. % or 13 vol .-% oxygen content is lowered and maintained.

The inerting of the enclosed space 2 is optionally carried out automatically with the aid of a control device 5. For this purpose, the inerting system 1 according to the in Fig. 1 illustrated embodiment, a gas separation system consisting of a compressor 3 and a nitrogen generator 4. The compressor 3 is used to provide the nitrogen generator 4 in a compressed manner, an initial gas mixture having at least the components of oxygen and nitrogen. For this purpose, the output of the compressor 3 is connected via a line system 17 to the inlet of the nitrogen generator 4 in order to supply the nitrogen generator 4 with the compressed initial gas mixture. It is conceivable that at the outlet of the compressor 3, the initial gas mixture is compressed to a pressure of for example 7.5 to 9.5 bar and preferably 8.8 bar.

The nitrogen generator 4 has at least one membrane module 19, for example a hollow-fiber membrane module, through which the initial gas mixture provided by the compressor 3 is pressed after it has passed through a suitable filter 18. In the membrane module 19, the various components (in particular oxygen and nitrogen) contained in the initial gas mixture diffuse at different rates through the hollow-fiber membrane of the membrane module 19 in accordance with their molecular structure. The gas separation is based on the known principle of action, according to which nitrogen with a low degree of diffusion the hollow fiber membrane penetrates very slowly and accumulates in this way when flowing through the hollow fibers of the membrane module 19. At the output 4a of the nitrogen generator 4, a nitrogen-enriched gas mixture is provided in this way. This enriched with nitrogen gas mixture is - as well as the input of the nitrogen generator 4 fed initial gas mixture - in compressed form, although the flow through the at least one membrane module 19 of the nitrogen generator 4 to a pressure drop of, for example, 1.5 to 2.5 bar leads.

Although in Fig. 1 is not explicitly shown, the nitrogen generator 4 deposited and enriched with oxygen gas mixture is collected and blown off under atmospheric pressure in the environment.

The nitrogen-enriched gas mixture provided at the outlet 4a of the nitrogen generator 4 is supplied via a supply line 7 to the enclosed space 2 in order to reduce the oxygen content in the room atmosphere of the enclosed space 2 or by a lowering level already set in the space 2 by tracking with Maintain nitrogen-enriched gas.

In order that the pressure inside the enclosed space 2 does not change when it is supplied from the nitrogen-enriched gas mixture, a suitable pressure relief is to be provided. This can, for example, in the form of self-opening or closing pressure relief valves (in Fig. 1 not shown) executed. On the other hand, it is also conceivable that the volume of room air to be discharged during the inerting of the room 2 for the purpose of depressurization is fed via a return line system 9 to a mixing chamber 6.

The discharged from the enclosed space 2 room air is supplied via a first input 9a of the return line 9 of the mixing chamber 6. The mixing chamber 6 also has a second input 8a, in which a supply line system 8 for supplying Fresh air to the mixing chamber 6 opens. In the mixing chamber 6, the initial gas mixture is provided, which is compressed by means of the compressor 3, and from which in the gas separation system (nitrogen generator 4) at least a part of the oxygen is separated. For this reason, the output of the mixing chamber 6 is connected to the input of the compressor 3 via a suitable conduit system 15.

Specifically, in the return line 9 a first controllable with the control device 5 valve 11, which is designed in particular as a shut-off valve, and in the fresh air supply line 8, a second controllable also with the control device 5 valve 10, in particular in the form of a shut-off valve provided. In this way it can be ensured by a suitable control of the corresponding valves 10, 11, that the amount of fresh air, which is mixed with the room air taken from the room 2, is selected so that the amount of room air taken from the room 2 per unit time is identical with the amount of nitrogen gas-enriched gas mixture provided at the outlet 4a of the nitrogen generator 4, which is conducted per unit time into the room atmosphere of the enclosed space 2.

The inerting system 1 according to the in Fig. 1 schematically illustrated embodiment of the present invention is characterized in that the aforementioned control device 5 is connected to the corresponding controllable components of the inerting 1 and designed to automatically control the nitrogen generator 4 and the gas separation system 3, 4 such that the output 4a of Gasseparationssystems 3, 4 provided and enriched with nitrogen gas mixture has a residual oxygen content, which depends on the currently prevailing in the room atmosphere of the enclosed space 2 oxygen content. In particular, in the illustrated preferred embodiment of the inerting system 1 according to the invention with the aid of the control device 5, the nitrogen generator 4 is controlled such that, depending on the oxygen content measured in the room atmosphere of the enclosed space 2 with the aid of an oxygen measuring system 16, the nitrogen-enriched gas mixture has an oxygen radical content between 10, 00 vol .-% to 0.01 vol .-%, wherein the oxygen radical content of the nitrogen-enriched gas mixture decreases with decreasing oxygen content in the room atmosphere of the enclosed space.

For this purpose, the inerting system 1 according to the invention, in addition to the already mentioned oxygen measuring system 16 for measuring or determining the actual oxygen content in the room atmosphere of the enclosed space 2, further comprises an oxygen radical content measuring system 21 for measuring the oxygen radical content in the outlet 4a of the nitrogen generator 4 provided and enriched with nitrogen gas mixture or for determining the nitrogen purity of the provided at the output 4a of the nitrogen generator 4 gas mixture. Both measuring systems 16, 21 are connected to the control device 5 accordingly.

In Fig. 2 is shown in a schematic view of an inerting system 1 according to a second embodiment of the present invention. The inerting system 1 according to the second embodiment is particularly suitable for setting and maintaining a predetermined inerting level in the most economical manner in an air-conditioned space, such as in a cold room or in a cold storage warehouse. The structure and operation of the inerting system 1 according to the in Fig. 2 illustrated embodiment substantially correspond to the structure and operation of the previously with reference to Fig. 1 described inertization, so that to avoid repetition below, only the differences should be discussed.

As in Fig. 2 shown, it is preferred for the most economical inertization of an air-conditioned space 2, when in the return line 9 between the chamber 2 and the mixing chamber 6, a heat exchanger system 13 is provided. Furthermore, it is advantageous if - as in Fig. 2 indicated - the return line system 9 with a corresponding thermal insulation 20 at least partially shrouded so icing of the return line system 9 can be avoided if the discharged from the enclosed space 2, cooled room air is supplied via the return line 9 to the heat exchanger system 13 before the room air then is passed into the mixing chamber 6. If required, the heat exchanger system 13 can have a support fan 14, so that the room air can be removed from the room atmosphere of the enclosed space 2 without loss of pressure.

The heat exchanger system 13 is used to exploit at least a portion of the heat generated during operation of the compressor 3 waste heat to heat up the discharged and cooled room air accordingly. For the heat exchanger system 13 different systems are used, such as a finned heat exchanger, via which at least a portion of the thermal energy of the exhaust air of the compressor 3 via a heat exchange medium, such as water, is transferred to the discharged room air, so that the temperature of the discharged room air to warm to a moderate temperature, for example, 20 ° C, which is for the operation and efficiency of the nitrogen generator 4 is advantageous.

After the room air discharged from the enclosed space 2 has passed the heat exchanger system 13, it is supplied to the mixing chamber 6 via a first input 9a of the return line 9. The mixing chamber 6 also has a second input 8a, in which a supply line system 8 for supplying fresh air to the mixing chamber 6 opens. In the mixing chamber 6, the initial gas mixture is provided, which is compressed by means of the compressor 3, and from which in the gas separation system (nitrogen generator 4) at least a part of the oxygen is separated. For this reason, the output of the mixing chamber 6 is connected to the input of the compressor 3 via a suitable conduit system 15.

As described below with reference to the graphs according to the FIGS. 3 to 5 Specifically, by appropriately adjusting the nitrogen purity of the nitrogen generator 4, or by appropriately setting the oxygen radical content in the nitrogen-enriched gas mixture provided at the outlet 4a of the gas separation system 4, a predetermined lowering level in the atmosphere of the room can be achieved in a time-optimized manner enclosed space 2 are set. Accordingly, it is provided in the solution according to the invention that the nitrogen purity of the nitrogen generator 4 is set and adjusted during the inerting of the enclosed space 2 as a function of the current oxygen content in the room atmosphere of the enclosed space.

The nitrogen purity can be changed by varying the residence time of the initial gas mixture in the at least one membrane module 19 of the nitrogen generator 4. For this purpose, it is conceivable, for example, that the flow through the membrane module 19 and a back pressure are controlled at the outlet of the membrane module 19 with a suitable control valve 24. A high pressure on the membrane and a long residence time (low flow) lead to a high nitrogen purity at the output 4a of the nitrogen generator.

Preferably, a time-optimized value is selected for the respective nitrogen purity, which enables the inerting system to set and maintain a predefined inerting level in the enclosed space 2 in the shortest possible time. By using appropriate time-optimized nitrogen purity values, it is possible to set and maintain a given inertization level in the room atmosphere of the enclosed space, the duration of the settling process (be it for holding at a fixed residual oxygen level or during the lowering to a new lowering level) and thus also to reduce the energy consumption of the inerting system, since the compressor 3 is driven on its operating point with optimum efficiency digitally (on / off).

Furthermore, the inerting system 1 is characterized according to the in Fig. 1 or in Fig. 2 illustrated embodiment in that the gas separation system consisting of the compressor 3 and the nitrogen generator 4 from the mixing chamber 6, an initial gas mixture is provided which has an oxygen content lower than the oxygen content of normal ambient air (ie about 21 vol .-%) can be. Specifically, for this purpose, the already mentioned return line 9 is provided, with which at least a part of the room air of the enclosed space 2 of the mixing chamber 6 can be supplied in a controlled by the control device 5 via the valve 11 way. Accordingly, if the oxygen content is already reduced in the enclosed space 2, a gas mixture enriched with nitrogen in comparison with the normal ambient air is supplied to the mixing chamber 6 via the return line 9. This part of the room air is mixed in the mixing chamber 6 with supply air to provide for the compressor 3 and the nitrogen generator 4, the required amount of the initial gas mixture. Since the oxygen content of the initial gas mixture has an influence on the air factor of the gas separation system or the nitrogen generator 4, and thus also has an influence on the time-optimized value of the nitrogen purity of the nitrogen generator 4, in the Fig. 1 illustrated embodiment of the inerting system 1 according to the invention in the conduit system 15 between the output of the mixing chamber 6 and the input of the compressor 3, an oxygen measuring system 22 for measuring the oxygen content in the output gas mixture provided. Optionally, it is also conceivable to provide corresponding oxygen measuring systems 23, 24 in the return line 9 or in the fresh air supply line 8 in order to detect the oxygen content in the supply air and in the room air enriched with nitrogen continuously or at predetermined times or events. Based on the measurement results, the composition of the initial gas mixture (in particular with regard to the oxygen content) can be suitably influenced by suitably activating the valves 10 and 11.

Hereinafter, referring to the graphs of FIGS FIGS. 3 to 5 the mode of action of the solution according to the invention with reference to the in Fig. 1 or in Fig. 2 described inerting system 1 described. It is assumed that the in Fig. 1 or Fig. 2 schematically illustrated inerting 1 of the enclosed space 2 has a volume of 1,000 m ³ . Further It should be assumed that the inerting system 1 is designed to provide a maximum of 48 m ³ nitrogen-enriched gas per hour at the outlet 4 a of the nitrogen generator 4.

In Fig. 3 is a graph of the air factor at the in Fig. 1 or Fig. 2 schematically illustrated inerting system 1 for use coming nitrogen generator 4 shown at different nitrogen purities. Accordingly, it should be noted that the air factor increases exponentially with decreasing residual oxygen content in the nitrogen-enriched gas mixture provided at the exit 4a of the nitrogen generator 4. In detail, the air factor at an oxygen radical content of 10% by volume (nitrogen purity: 90%) is about 1.5, which means that per m ^{3 of} initial gas mixture at the outlet 4 a of the nitrogen generator 4 an amount of 0.67 m ³ can be provided to nitrogen-enriched gas mixture. This ratio deteriorates with increasing nitrogen purity, as shown in the graph in FIG Fig. 3 can be removed.

In Fig. 3 is shown in addition to the evolution of the air factor, how the Regelabsenkzeit at different nitrogen purities with increasing nitrogen purity behaves. Specifically, on the one hand it is shown how long the compressor 3 has to run in order to reduce the oxygen content in the room atmosphere of the enclosed space 2 from originally 17.4% by volume to 17.0% by volume. In addition to this, on the other hand it is shown how long the compressor 3 has to run in order according to the inerting system 1 Fig. 1 or Fig. 2 in the room air atmosphere of the enclosed space 2 to lower the oxygen content from originally 13.4 vol .-% to 13.0 vol .-%.

The comparison of the two lowering times (lowering time with regulation 17.4% by volume → 17.0% by volume and lowering time with regulation 13.4% by volume → 13.0% by volume) shows that for adjusting and Maintaining an inerting level of 17.0 vol .-%, the running time of the compressor 3 can be minimized when the nitrogen generator 4, a nitrogen purity of about 93.3 vol .-% is set. For adjusting and maintaining an inerting level at 13% by volume oxygen content, on the other hand, the time-optimized purity is about 94.1% by volume of nitrogen. Accordingly, the lowering time of the compressor 3 for setting a predetermined inertization level in the room air atmosphere of the enclosed space 2 is dependent on the set at the nitrogen generator 4 nitrogen purity or depending on the set on the nitrogen generator 4 oxygen radical content in that at the output 4a of the nitrogen generator 4th provided and enriched with nitrogen gas mixture.

The respective minima of the lowering time compared to the nitrogen purity is referred to below as "time-optimized nitrogen purity". In the illustration according to Fig. 4 is the time-optimized nitrogen purity in the inerting 1 according to Fig. 1 or Fig. 2 shown. Specifically, the time-optimized purity is given for different oxygen concentrations in the room atmosphere of the enclosed space 2, which for the gas separation system 3, 4 of the inerting system 1 according to Fig. 1 or Fig. 2 applies.

The in Fig. 4 is shown directly that the nitrogen generator 4 is set so that decreases with decreasing oxygen content in the room atmosphere of the enclosed space 2 of the oxygen radical content in the provided at the output 4a of the gas separation system 3, 4 gas mixture. Accordingly, when the nitrogen purity of the nitrogen generator when inerting the enclosed space 2 according to the in Fig. 4 is operated, it is possible to set the lowest possible running time of the compressor 3 and thus with the least possible expenditure of energy, the predetermined inerting in the room atmosphere of the enclosed space 2 and hold.

In Fig. 5 is shown in a graph of the influence of the oxygen content in the initial gas mixture on the air factor of the gas separation system 3, 4. Thus, the air factor at a fixed nitrogen purity of the gas separation system 3, 4 decreases with reduction of the oxygen content in the initial gas mixture. As already indicated, in the inerting system 1 according to the schematic representation in FIG Fig. 1 the return line 9 is provided, via which part of the (possibly already enriched with nitrogen) room air is supplied in a controlled manner to the mixing chamber 6, in order in this way the oxygen content in the initial gas mixture of the original 21 vol .-% (oxygen content of normal ambient air). As a result of this recirculation of the room air already enriched with nitrogen, the air factor of the gas separation system 3, 4 can thus be further reduced, so that the efficiency of the gas separation system 3, 4 increases and the energy to be set and maintained for setting a given inertization level can be further reduced.

Preferably, the in Fig. 5 illustrated characteristic with the previously with reference to the graphs in the FIGS. 3 and 4 thus combined, that for each oxygen concentration in the initial gas mixture and in the space 2, an optimized delivery unit of the nitrogen is found.

In Fig. 6 are - for a calculated application - achievable energy savings (in%) over the set in the room atmosphere of an enclosed space oxygen content shown when the solution according to the invention, the oxygen concentration in the room atmosphere of the enclosed space is lowered. In this case, a case was considered in which on the one hand during the inerting of the space for the nitrogen purity of the nitrogen generator, the time-optimized nitrogen purity was selected, and on the other hand, a recirculation of the already enriched with nitrogen room air was carried out to in this way the air factor of the Nitrogen generator continues to reduce and increase its efficiency.

The invention is not limited to the embodiments shown with reference to the drawings of the attached drawings.

Claims (16)

Inertization method for fire prevention and / or fire extinguishing, wherein in the room atmosphere of an enclosed space (2) a predetermined and compared to the normal ambient air reduced oxygen content is set and maintained, the method comprising the following steps: - It is provided an initial gas mixture having oxygen, nitrogen and optionally other components; - It is separated in a gas separation system (3, 4) at least a portion of the oxygen from the provided initial gas mixture and in this way at the output (4a) of the gas separation system (3, 4) provided with a nitrogen-enriched gas mixture; and the nitrogen-enriched gas mixture is passed into the room atmosphere of the enclosed space (2), characterized in that
the oxygen radical content of the nitrogen-enriched gas mixture is changed as a function of the oxygen content currently prevailing in the room atmosphere of the enclosed space (10). Inertization process according to claim 1,
wherein the oxygen radical content of the nitrogen-enriched gas mixture is reduced with decreasing oxygen content in the space atmosphere of the enclosed space (2). Inertization process according to claim 1 or 2,
wherein the oxygen radical content of the nitrogen-enriched gas mixture is set according to a predetermined characteristic, the characteristic indicating the time-optimized value of the oxygen radical content of the nitrogen-enriched gas mixture over the oxygen content in the room atmosphere of the enclosed space (2) according to which within the shortest possible time by the inerting process Time in the room atmosphere of the enclosed space (2) a predetermined and compared to the normal ambient air reduced oxygen content is adjustable. Inertization process according to claim 1 or 2,
wherein continuously or at predetermined times and / or events of the currently in the room atmosphere of the enclosed space (2) prevailing oxygen content is measured directly or indirectly, and
wherein continuously or at predetermined times and / or events, the oxygen radical content of the nitrogen-enriched gas mixture is set to a predetermined value, wherein in the inerting process, the oxygen content in the room atmosphere of the enclosed space within a very short time by a predetermined reduction amount to the current oxygen content is lowerable. Inertization process according to one of claims 1 to 4,
wherein the oxygen radical content of the nitrogen-enriched gas mixture, depending on the current oxygen content in the room atmosphere of the enclosed space to a value between 0.01 vol .-% and 10.00 vol .-%, and preferably to a value between 5, 5 vol. -% and 7.5 vol .-% is set. Inertization process according to one of claims 1 to 5,
wherein the oxygen content of the initial gas mixture, from which at least a portion of the oxygen is separated, is changed in dependence on the currently in the room atmosphere of the enclosed space (2) prevailing oxygen content. Inertisation method according to one of claims 1 to 6,
wherein, for providing the initial gas mixture, part of the room air contained in the enclosed space (2) is taken out of the space (2) in a controlled manner is, and wherein the extracted part of the room air in a controlled manner fresh air is added. Inertisierungsverfahren according to claim 7,
wherein the amount of fresh air admixed with the room air taken from the room (2) per unit time is selected so that the amount of room air taken from the room (2) per unit time is identical to the amount of the nitrogen-enriched gas mixture per Time unit in the room atmosphere of the enclosed space (2) is passed. Inertisation method according to one of claims 1 to 8,
wherein the oxygen radical content of the nitrogen-enriched gas mixture is automatically adjusted in dependence on the currently in the room atmosphere of the enclosed space (2) prevailing oxygen content. Inertizing plant for adjusting and / or maintaining a predeterminable and reduced compared to the normal ambient air oxygen content in the room atmosphere of an enclosed space (2), said inerting system (1) having a gas separation system (3, 4), with which of a nitrogen and oxygen contained At least a portion of the oxygen is separated from the initial gas mixture and in this way at the output (4a) of the gas separation system (3, 4) a nitrogen-enriched gas mixture is provided, and wherein the inerting system (1) comprises a feed line system (7) for supplying the Nitrogen-enriched gas mixture to the enclosed space (2), characterized by,
a control device (5) which is designed to control the gas separation system (3, 4) such that the oxygen radical content of the nitrogen-enriched gas mixture is changed as a function of the oxygen content currently prevailing in the room atmosphere of the enclosed space (10). Inertizing plant according to claim 10,
wherein the control device (5) is further designed to control the gas separation system (3, 4) in dependence on the oxygen content currently prevailing in the room atmosphere of the enclosed space such that the oxygen radical content of the oxygen at the outlet (4a) of the gas separation system (3, 4) is provided and automatically reduced with nitrogen-enriched gas mixture, when the oxygen content in the room atmosphere of the enclosed space (2) decreases; and or
wherein the control device (5) is further designed to control the gas separation system (3, 4) in such a way that the nitrogen-enriched gas mixture provided at the outlet (4a) of the gas separation system (3, 4) has an oxygen radical content of between 10.00% by volume. to 0.01% by volume. Inertizing plant according to one of claims 10 or 11,
which further comprises an oxygen measuring system (16) which is designed to detect the oxygen content in the room atmosphere continuously or at predetermined times and / or events and to supply the value of the detected oxygen content to the control device (5) as the current oxygen content. Inertizing plant according to one of claims 10 to 12,
wherein a mixing chamber (6) is provided for providing the initial gas mixture, wherein in the mixing chamber (6) a first conduit system (9) opens, via which in a manner controlled by the control device (5) a part of the enclosed space (2) contained in the room (2) and the mixing chamber (6) is supplied, and wherein in the mixing chamber (6), a second conduit system (8) opens, via which in a controlled by the control device (5) way fresh air Mixing chamber (6) is supplied. Inertizing plant according to claim 13,
which further comprises in the first line system (9) a first controllable with the control device (5) valve (11), in particular shut-off valve, and in the second line system (8) a second with the control device (5) controllable valve (10), in particular shut-off valve , wherein the control device (5) is designed to control the first and / or second valve (11, 10) such that the amount of room air taken from the space (2) per unit of time is identical to the amount of the nitrogen-enriched gas mixture , which per unit time of the room atmosphere of the enclosed space (2) is supplied. Inertisierungsanlage according to claim 13 or 14,
wherein the gas separation system (3, 4) comprises a nitrogen generator (4) and a compressor (3), wherein via the control device (5) the nitrogen purity or the oxygen radical content of the nitrogen-enriched gas mixture provided at the outlet (4a) of the nitrogen generator (4) is adjustable, and wherein the compressor (3) is arranged between the mixing chamber (6) and the nitrogen generator (4). Inertizing plant according to one of claims 13 to 15,
wherein in the first conduit system (9), a heat exchanger system (13) is provided for transmitting thermal energy between the extracted from the enclosed space (2) room air and the waste heat of the compressor (3).

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