EP0611584B1 - Apparatus for the generation of air in a closed container - Google Patents

Description

The present invention relates to a device for air regeneration in a closed or almost closed enclosure with autonomous operating energy whose production requires the use of a material stored in cryogenic form.

Maintaining air quality in a closed enclosure such that the interior of a submarine is a complex operation since it requires producing the oxygen needed for men's breathing crew, reduce the amount of carbon dioxide in the air which tends to increase significantly due to human respiration and eliminate pollutants air organic matter produced by human activity.

Until now, air regeneration in the cabin of the submarines is carried out by means of processes chemical or electrochemical performing the functions of oxygen production and carbon dioxide removal and pollutants. Oxygen is also generated, either by electrolysis of water, either from liquid oxygen or by chemical reaction using a metal chlorate alkali or an alkali metal superoxide. Elimination carbon dioxide is usually done using molecular sieves or by absorption, for example with amines. Finally, the removal of pollutants is carried out at using activated carbon absorbers or beds catalytic.

However, the regeneration facilities of the air remains often bulky, complex materials, consuming a large amount of energy. In addition, electrochemical oxygen generators also produce, as a result of electrolysis reactions, large quantities of hydrogen which must then be treated.

Finally, it should be noted that the elimination of certain organic pollutants by active carbon although very effective, poses some problems related to the fact that the lighter pollutants are desorbed by pollutants the heaviest. This property makes it extremely

Difficult to determine a precise material balance of the atmospheric system, especially as decomposition or synthesis reactions are always possible between the various pollutants.

For the air treatment installations in service, we have known accommodate these various disadvantages.

However, most of the systems currently developed are not usable for submarines using an anaerobic source of energy chemical origin; these systems are usually too big energy consumers in relation to the amount of energy on board.

US Patent 3,775,976 uses for the operation of a motor to combustion a cryogenic source which, by heating, allows the solidification of carbon dioxide from combustion gases.

Patent EP 0041702 used for aerobic culture of microorganisms liquid oxygen which, when contacted with carbon dioxide produced during the fermentation of microorganisms, allows the solidification of it.

The object of the invention is therefore to apply this principle to regeneration air from a space confined in breathing air, in order to have a reduced energy consumption, especially for an anaerobic system such than a submarine that has limited energy.

The object of the invention is therefore the application to the regeneration of air polluted in breathing air in a closed or almost closed enclosure, device with autonomous operating energy, comprising conventionally a tank (12) containing a cryogenic material used for the production of operating energy and an exchanger main thermal (10) operating at atmospheric pressure for exchanging heat between a gaseous medium containing carbon dioxide carbon, on the one hand, and the cryogenic material, on the other hand, characterized in that the gaseous medium consists of air at regenerate and in that the heating of the cryogenic material until its operating temperature in energy production allows lower the temperature of the air to be regenerated to a value below the solidification temperature of carbon dioxide.

The device according to the invention as defined above can thus be used in a submarine, the cold source being constituted by all or part of the mass of liquid oxygen on board which has a sufficient cooling capacity to cool the air to regenerate and condense carbon dioxide.

la figure 1 représente schématiquement le principe utilisé dans le dispositif selon l'invention, et

la figure 2 représente un schéma synoptique d'un mode de réalisation de l'invention.

The objects, objects and characteristics of the invention will appear better on reading the following description made with reference to the drawings in which

FIG. 1 schematically represents the principle used in the device according to the invention, and

FIG. 2 represents a block diagram of an embodiment of the invention.

In a submarine using a chemical source anaerobic energy, the oxidizer used for combustion is oxygen stored in cryogenic form in a tank, intended for use in batteries with fuels, internal combustion engines such as diesel engines, internal combustion engines external combustion such as Stirling engines or others systems implementing oxidation reactions of a fuel. This oxygen which is at a temperature of about -170 ° C, must therefore be reheated before it can be used. The temperature of the gaseous oxygen is thus raised to -20 ° C at the entry of the submarine engine.

Referring to Figure 1, the principle of the invention consists in using a heat exchanger 10 which receives cryogenic oxygen from of the storage tank 12, and on the other hand the air to regenerate by air inlet 14 at pressure atmospheric.

In the exchanger 10, the liquid oxygen loses its frigories (or acquires calories) and therefore heats up to reach a temperature of around -20 ° C at the outlet oxygen 16. During the same time, the air to be regenerated cools in exchanger 10 to a temperature about -135 ° C and is evacuated by the outlet of regenerated air 18. The temperature reached by the air being lower than the solidification temperature (-78.5 ° C) of the dioxide carbon gas at atmospheric pressure, carbon dioxide carbon solidifies with the passage of air in the exchanger and can therefore be easily retrieved from this latest. The air at outlet 18 is therefore rid of the excess carbon dioxide due mainly to the human respiration in the closed enclosure.

Although carbon dioxide solidifies (at atmospheric pressure) at a temperature of -78.5 ° C, it is necessary to lower the air temperature to a value much lower than -78.5 ° C, for example at -135 ° C As we have just seen. This lower temperature is indeed necessary, at atmospheric pressure, to obtain a vapor pressure of CO ₂ in the treated air such that the CO ₂ concentration becomes lower than the maximum admissible concentration for the duration of exposure selected.

Figure 2 shows schematically the mode of preferred embodiment of the invention. Air to regenerate powered by a fan 20 is first sent to a Annex heat exchanger or cold recuperator 22 before reaching the heat exchanger 10. The air which enter the latter by entrance 14 is therefore an air pre-cooled. On the other hand, the cooled air at outlet 18 of the exchanger 10 is therefore heated in contact with the air at room temperature in the cold recuperator 22.

As before, solid carbon dioxide is recovered at the outlet of the heat exchanger 10. By against the air propelled by the fan 20 in the cold recuperator 22, cools sufficiently to that the excess water vapor contained in the air at regenerate either liquefied. Liquid water is collected at the outlet 24 of recuperator 22 and part of this water is then recycled in the humidifier 26 to restore the humidity level of the regenerated air at the outlet, while excess water is collected at outlet 30.

In addition to carbon dioxide, the air to be regenerated contains various pollutants which are either dissolved in the recovered water, either condensed at the same time as the carbon dioxide at low temperature. These pollutants are pentane, molecular weight hydrocarbons benzene and benzene derivatives, the carbon tetrachloride, certain nitrogen oxides, certain freons ...

The air regenerated at outlet 28 may still be too cold to be sent into the passenger compartment. A solution consists in reheating it with a hot source such as Seawater.

Although not shown in Figures 1 and 2, the heat transfer in the exchanger 10 can take place, for safety reasons, by means of a fluid heat transfer intermediate so as to avoid convey liquid oxygen near the air circuits.

In the heat exchanger 10, the mass of carbon dioxide and various pollutants gradually increases. In the long run, this mass can become troublesome. This is why it is useful to plan for the elimination of this mass of CO ₂ and of pollutants. Various solutions exist which are linked to the shape of the CO ₂ phase balance diagram and the presence of a triple point.

A first solution consists in evacuating to carbon dioxide outside: we isolate the exchanger thermal and we stop the oxygen supply. Temperature increases and the pressure rises until reaching a sufficient pressure to eject the carbon dioxide at outside or store it in a compressed form.

A second solution consists in reheating the isolated exchanger until the CO2 is liquefied, for example at 5 bars and -52 ° C. Liquid CO ₂ can be pumped out.

In a third solution, the exchanger is heated to a temperature between -105 ° C and -75 ° C. At this time the CO ₂ is gaseous at a pressure between 0.1 and 1 bar. It can then be compressed outwards by means of a compressor.

Finally, the fourth solution consists in heating the exchanger to a temperature such that the vapor pressure is sufficient to supply a primary vacuum pump. For example at -120 ° C, the CO ₂ vapor pressure is of the order of 0.01 bar. CO ₂ can therefore be compressed to atmospheric pressure and then discharged to the outside by a compressor. This solution is preferably used.

consommation 0₂ du moteur: 100kg/heure

température de 0₂ à l'entrée du moteur : -20°C

nombre de personnes: 30

consommation humaine de O₂: 25 l/homme/ heure

production humaine de CO₂: 20 l/homme/heure

teneur en CO₂ dans l'habitacle: <0,7%

température moyenne: 20°C

The implementation of the invention in a submarine powered by a Bertin Mesma type chemical engine is based on the following values:

motor consumption 0 ₂ : 100kg / hour

0 ₂ temperature at the motor inlet: -20 ° C

number of people: 30

human consumption of O ₂ : 25 l / man / hour

human CO _{2 production} : 20 l / man / hour

CO ₂ content in the passenger compartment: <0.7%

average temperature: 20 ° C

débit de CO₂ à éliminer: 600 l/heure soit 1178g/h

débit de 0₂ au moteur: 100kg/heure

débit d'air à traiter: 600/0,007.10/9(coefficient de sécurité)soit 114 Kg/h

débit d'eau à éliminer:1809 g/h

In steady state, the flow rates to be observed are therefore as follows:

CO ₂ flow rate to be eliminated: 600 l / hour or 1178 g / h

0 ₂ flow to the motor: 100kg / hour

air flow to be treated: 600 / 0.007.10 / 9 (safety coefficient) or 114 Kg / h

water flow rate to be eliminated: 1809 g / h

1) refroidissement de l'air à régénérer d'une température de +20°C à une température de 0°C.

air: 570 kcal/h

eau: 36 kcal/h

CO₂: négligeable

Total → 600 kcal/h

2) condensation de H₂O et élimination à 0°C

eau: 1128 kcal/h

3) refroidissement de l'air de 0°C à -135°C

air: 3848 kcal/h

4) congélation du CO₂

CO₂: 160,5 kcal/h

Taking into account the specific heats of the different products involved in regeneration, the quantities of heat involved are as follows:

1) cooling the air to be regenerated from a temperature of + 20 ° C to a temperature of 0 ° C.

air: 570 kcal / h

water: 36 kcal / h

CO ₂ : negligible

Total → 600 kcal / h

2) condensation of H ₂ O and elimination at 0 ° C

water: 1128 kcal / h

3) air cooling from 0 ° C to -135 ° C

air: 3848 kcal / h

4) freezing of CO ₂

CO ₂ : 160.5 kcal / h

réchauffage à -20°C= 3821 kcal/h

donc un total de 8281 kcal/h

This corresponds to a total of 5743 kcal / h . This value is much lower than the quantity of frigories available to pass the cryogenic oxygen (-70 ° C) to the temperature of - 20 ° C, or vaporization = 5000 kcal / h.

reheating to -20 ° C = 3821 kcal / h

so a total of 8281 kcal / h

Although the device of the invention has been described in conjunction with a submarine it can be obviously used for any system with a closed or almost closed enclosure with a source autonomous energy using a material stored at very low temperature, the energy source being used for propulsion or something else. For example, it is possible to use the device of the invention in a aircraft for which we are trying to reduce the cabin air renewal for reasons fuel economy. In this case the source of cold that constitutes the atmosphere (at around -50 ° C) can be sufficient for pollutants and water vapor.

Another application of the device of the invention is its use in an aircraft or shuttle spatial. In this type of machine, it is planned to take a large quantity (several tens of tonnes) liquid hydrogen and sometimes liquid oxygen. Through Therefore, it is easy to use the the invention to obtain a regeneration of the atmosphere of the closed cabin, thanks to the frigories recovered by warming of cryogenic materials.

Claims (9)

1. The use of apparatus for the purpose of regenerating polluted air so as to transform it into breathable air in a closed or almost closed enclosure, said apparatus being provided with a stand-alone source of operating energy, said apparatus comprising, conventionally, a tank (12) containing a cryogenic material used to produce operating energy and a main heat exchanger (10) operating at atmospheric pressure for exchanging heat between the cryogenic material and a gaseous medium containing carbon dioxide, said use being characterized in that the gaseous medium is constituted by the air to be regenerated, and in that, by heating the cryogenic material to its energy-production operating temperature, it is possible to lower the temperature of the air to be regenerated to a value lower than the solidification temperature of carbon dioxide.
2. The use according to claim 1, characterized in that the temperature of the air to be regenerated is lowered to a temperature of -135°C.
3. The use according to claim 1 or 2, characterized in that it further implements an accessory heat exchanger (22) through which the air to be regenerated passes and through which the regenerated air passes, so that heat is exchanged between the air to be regenerated and the regenerated air (18) coming from the main heat exchanger (10), so that the air to be regenerated is pre-cooled prior to entering the main heat exchanger, and the regenerated air is pre-heated prior to being released into the enclosure.
4. The use according to claim 3, characterized in that the excess water vapor in the air to be regenerated is liquefied by passing the regenerated air through the accessory heat exchanger (22), and in that a portion of the water recovered in this way is sent to a humidifier (26) at the outlet of the accessory heat exchanger so as to restore suitable humidity to the regenerated air.
5. The use according to any one of claims 1 to 4, characterized in that it further implements means for removing the solid carbon dioxide recovered in the main heat exchanger (10), which means are made up of means for heating the heat exchanger that is not operating, of a vacuum pump, and of a compressor, the heating making it possible to obtain a carbon dioxide vapor pressure that is sufficient for feeding the pump, and the compressor serving to compress the carbon dioxide so as to expel it to the outside.
6. The use according to any preceding claim, characterized in that the main heat exchanger (10) also serves to condense the pollutants contained in the regenerated air.
7. The use according to any one of claims 1 to 6, characterized in that the cryogenic material is liquid oxygen.
8. The use according to any one of claims 1 to 7, characterized in that the closed enclosure is constituted by the manned quarters of a submarine propelled by an energy source whose oxidant is oxygen stored in cryogenic form in the tank (2).
9. The use according to any one of claims 1 to 8, characterized in that the closed enclosure is constituted by the cockpit and/or cabin of an aircraft.

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