EP0125157A1 - Chemical oxygen generator for breathing equipment - Google Patents

Abstract

Cartridge with chemical generation of oxygen of the cartridge type intended to receive an absorbent mass in the form of lozenges, such as potassium superoxide. The cartridge is provided with a central inlet nozzle (5) for the gases to be purified, extended vertically in the inlet duct (5 ') until the bottom of the housing (9) is released at the perforated lower wall ( 7) supporting the regenerative charge, this conduit emerging at the center of this wall to which it is fixed; the upper part of the cartridge case (6) on the side of the outlet for the gases to be treated, is provided with a series of radiators (11) parallel to the direction of flow of the gas flows in the regenerative charge, fixed to the walls of the case (12) and whose length is less than the spacing between the two walls (7) and (8). Application to regenerations of prolonged duration at a high kinetic level, and almost total use of the reactive potential of the cartridge.

Description

The present invention relates to a breathing apparatus with chemical generation of oxygen, of the cartridge type intended to receive an absorbent mass in the form of pellets, such as potassium superoxide possibly supplemented with an oxide or hydroxide of alkaline earth metal or potassium. , in particular cartridges working at a high kinetic level.

Various types of cartridges are already known, British Patent 671,107 describes a filter for a breathing apparatus comprising several layers of peroxide compound. The peroxide layers are separated by a metal grid, springs holding them in place at the bottom and the gases being introduced via a central tube.

U.S. Patent 3,767,367 provides an expired gas regeneration cartridge which can be incorporated into an individual breathing apparatus, which has a self-supporting vault at the bottom consisting of a filter maintaining the regeneration charge.

A device is generally designed to meet the respiratory needs of a man performing a given level of effort for a specific period of time.

We are therefore led, for each device, to seek the minimum weight of superoxide corresponding to a maximum utilization rate, which implies correlating at best various parameters, such as the reactivity of the superoxide, its behavior at temperature, the size and forms superoxide pellets and in particular the structure of the regenerative charge.

Respirators with chemical oxygen generation are sometimes subjected to intensive regeneration conditions when the respiratory level reaches a flow rate higher than 35 liters per minute (and even 70 liters / minute, for a few minutes for carbon dioxide contents included between 4 and 5%).

Under these conditions, the particles of solid reagents based on potassium superoxide are the seat of the reactions of the superoxide with carbon dioxide and with water vapor. These oxygen-releasing reactions are very exothermic, subjecting the reagent particles to very high temperatures of up to 200 to 300 ° C.

We know that the superoxide reacts more quickly with carbon dioxide than with water vapor, which corresponds to a more accelerated fixation of C0 _{2 '} whereas the pure potassium oxide superoxide generates oxygen from water vapor to form relatively fusible potassium hydrates.

And, when a bed of particles of regeneration of breathable atmospheres is subjected to the action of a gas corresponding to a high respiratory level, it is found that the layer of regeneration product located at the leading edge of the gas to be regenerated is carbonate quickly and the particles retain their shape and mechanical properties, while downstream of this layer, the regeneration particles receive a large amount of water and are quickly deformed and made deliquescent.

If the operation is continued, this degradation progresses until the particles melt, thus causing a partial collapse of the regenerative charge, with the formation on the one hand of a compact molten mass offering the gas a very reduced reactive surface and d on the other hand, empty reagent caves which probably constitute preferential channels taken by the gas to be regenerated and in which the carbon dioxide is retained in a very imperfect manner. Although there is still a significant proportion of reactive product in the bed of regenerative particles, a rapid increase in the carbon dioxide content of the effluent gas is observed, corresponding to a sharp decrease in the overall reactivity of the bed; this reduction in the gas purification rate is often accompanied by a large increase in the pressure drop in the particle bed. This results in improper use of the reactive potential initially used.

We sought to overcome this drawback by giving the cartridge a structure such that the gas passes at low speed only a small thickness of the superoxide, or by dividing the charge into small fractions by numerous metal partitions which come into contact with the wall; this leads to complex structures in which the weight of non-reactive material is relatively large; they are of a high cost price and their filling is quite difficult and does not lend itself to automation.

Recently, a means has been proposed for suppressing the excessive increase in pressure losses of potassium superoxide during intensive regeneration conditions. According to patent application 2,521,034 a certain proportion of alkaline earth oxide in the pulverulent state is incorporated into the potassium superoxide, before granulation or tabletting; the degradation of particles caused by water vapor is slowed down. Calcium oxide is particularly effective in achieving this effect. However, this addition of lime has an impact on the amount of general potential oxygen, this being limited by the dilution of the superoxide.

This means is not entirely satisfactory when it is desired to produce beds of relatively thick reactive mixtures, up to around twenty centimeters, which work at a high kinetic level, with an extended regeneration time and an almost total use of the reactive potential of the solid. .

We have looked for devices allowing the treatment of gas mixtures corresponding to high respiratory levels, for a so-called high duration, that is to say greater than 90 minutes, and with a practically complete use of the reactive potential of the charge. generator.

- According to the invention, a metallic cartridge has been found for breathing apparatuses with chemical generation of oxygen, working at high respiratory levels, provided with internal arrangements which, by promoting the partial elimination towards the outside of the heat generated, leads to optimal use of thick beds of pure potassium superoxide or mixtures based on potassium superoxide possibly containing calcium oxide.

According to an internal arrangement of a cartridge in which the circulation of the gases to be regenerated takes place from bottom to top, the upper part of the cartridge housing is furnished with a series of radiators parallel to the direction of circulation of the gas flows in the regenerative load, fixed to the walls of the housing and whose LON _'LATIONS is less than the height of said load.

It has been found that the length of the radiators is advantageously between half and a third of the spacing between the two perforated walls supporting and maintaining the regenerative charge.

These internal arrangements placed in the upper part of the regenerative charge, on the side of the outlet of the gas to be treated, are made of materials which are good conductors of heat, such as copper and brass, for example from 0. 5 to 1 mm thick.

Although simple, economical and easily achievable solutions, such as straight tubes, smooth sheets, give excellent results, we can also use more elaborate solutions such as fins, corrugated sheets, etc.

In some cases, endothermic transformation materials such as alloys whose melting temperatures are within the operating range of the regenerative charge can be used for the production of radiators.

When the internal arrangement of the cartridge housing is limited to the radiators, the latter may include two open bottoms, with a coaxial intake nozzle formed on the lower bottom of the housing and a coaxial evacuation nozzle formed on the upper bottom of the housing.

An advantageous embodiment consists of two internal arrangements of the cartridge, namely the vertical central conduit for the introduction of the gases to be purified which opens into the clearance at the bottom of the housing and the arrangement of a series of radiators parallel to the direction of circulation of the gas flows. in the regenerative charge, fixed to the walls of the housing and whose length is less than the height thereof, preferably between half and a third of the spacing between the two perforated walls delimiting the height of the regenerative charge. In this type of device, the cartridge case has an open upper bottom in which the coaxial nozzles for gas inlet and outlet are fitted.

According to one of the internal arrangements of this breathing apparatus with vertical gas circulation consisting of a box having an open bottom and a closed bottom, the coaxial gas inlet and outlet nozzles are concentrically formed on the upper bottom of the box, l central nozzle for admitting the gases to be exhausted being extended in a vertical duct, open at its base, until the bottom of the housing is released at the level of the lower perforated wall supporting the regenerative charge, this intake duct opening to the center of this perforated wall to which it is fixed, by welding, stamping ...

The gases to be purified circulate from bottom to top in the intake duct, then they are distributed in the clearance at the bottom of the housing before passing through the perforated wall supporting the regenerative charge and circulating in it from bottom to top, the gas re generated through the upper perforated wall maintaining the regenerative charge, then escaping through the discharge nozzle.

The internal arrangement constituted by the central tube for admitting the gases to be purified is advantageously chosen from heat-conducting materials, such as metals such as copper and brass.

• La figure I représente un dispositif à fonds ouverts sans aménagement interne selon une vue en coupe.
• La figure II représente une vue en coupe d'un appareil de régénération avec tube central d'admission des gaz à épurer, et fond supérieur ouvert.
• Les figures III et III' montrent selon l'invention des vues en coupe d'un boîtier de cartouche à fonds ouverts, aménagé avec des radiateurs.
• Les figures IV et IV' sont des vues en coupe de l'association des deux aménagements internes ; tube central d'admission et radiateurs ; et la figure V est une vue en perspective cavalière dans le cas où les radiateurs sont des ailettes.

The invention will be illustrated with the aid of figures and examples described below.

• Figure I shows an open bottom device without internal arrangement in a sectional view.
• Figure II shows a sectional view of a regeneration device with central gas inlet tube to be purified, and open upper bottom.
• Figures III and III 'show according to the invention sectional views of an open bottom cartridge housing, fitted with radiators.
• Figures IV and IV 'are sectional views of the association of the two internal arrangements; central intake tube and radiators; and Figure V is a perspective view in the case where the radiators are fins.

Figure I shows a metal housing body (1) on which is welded, at its upper end, a bottom (2) with a central perforation (2 '). On it is welded, on the outside and in its center, a pierced end piece (3) which can be connected to a tubing of regenerated gases, not shown. At the lower end of the housing, the bottom (4) is welded with a central perforation (¢ '). On it is welded on the outside and in its center, a pierced intake nozzle (5) or inlet pipe of the gas to be regenerated.

Inside the housing body is the regeneration cartridge (6) which has a lower perforated side wall (7), and an upper perforated side wall (8), between which is housed the regenerative charge. Between the bottom bottom (4) and the perforated wall (7) is a clearance from the bottom of the housing (9).

In this regeneration device, the gas to be regenerated is introduced through the lower manifold, passes from bottom to top the regenerative charge and after regeneration is discharged through the upper manifold.

Figure II shows a housing body (1) to which are welded, at its upper end, a bottom (2) with a central perforation (2 ') and at its lower end a closed bottom (4).

On the bottom (2) are welded the coaxial ends of the gas inlet to be purified (5) and of the regenerated gas outlet (3); the open central endpiece extends into an intake duct (5 ') opening into the center of the perforated lower wall (7).

As before, inside the housing body, is the regeneration cartridge (6) with the two walls (7) and (8) and there is a lower clearance bottom (9).

• Les figures III et III' montrent un boîtier du type de la figure I, comportant comme aménagement interne une série de radiateurs parallèles (11) fixés par les soudures (12) sur les parois latérales du boîtier. La coupe selon la ligne AB montre sur la figure III' la disposition des radiateurs et leurs points d'insertion sur les parois du boîtier (12) et de contact entre-eux (13), notamment pour des radiateurs en forme d'ailettes.
• La figure IV montre un boîtier du type de la figure II comportant, en plus, le second aménagement interne constitué par une série de radiateurs parallèles (11) fixés comme précédemment. Et, sur la figure IV', selon la coupe AB, on peut voir la distribution des radiateurs, leurs points de fixation sur les parois du boîtier (12) et de contact entre-eux (13), ainsi que leurs points de fixation (14) sur le conduit central d'admission des gaz à épurer (5').
• La figure V montre une vue en perspective cavalière du boîtier, avec la figuration des sens des gaz à épurer et après régénération, dans le cas de l'association du conduit central d'admission et des radiateurs à ailettes, avec sortie du gaz à la partie supérieure de la cartouche placée dans le boîtier.

In this regeneration device, the gases to be purified are introduced into the upper part by the intake nozzle (5) and circulate vertically from top to bottom in the intake duct (5 '), are distributed in the clearance of the bottom of housing (9) and attack the potassium superoxide bed from bottom to top, escape through the upper perforated wall (8), circulate in the upper clearance bottom (10) then the coaxial evacuation nozzle ( 3). towards the regenerated gas tubing, not shown.

• Figures III and III 'show a housing of the type of Figure I, comprising as internal arrangement a series of parallel radiators (11) fixed by the welds (12) on the side walls of the housing. The section along line AB shows in FIG. III 'the arrangement of the radiators and their points of insertion on the walls of the housing (12) and of contact between them (13), in particular for radiators in the form of fins.
• Figure IV shows a housing of the type of Figure II comprising, in addition, the second internal arrangement constituted by a series of parallel radiators (11) fixed as above. And, in Figure IV ', according to section AB, we can see the distribution of the radiators, their fixing points on the walls of the housing (12) and of contact between them (13), as well as their fixing points ( 14) on the central duct for admitting the gases to be purified (5 ').
• Figure V shows a perspective view of the housing, with the representation of the directions of the gases to be purified and after regeneration, in the case of the association of the central intake duct and finned radiators, with gas outlet at the upper part of the cartridge placed in the housing.

• Il comprend un générateur de gaz pulsé à vingt pulsations par minute et à un débit moyen de 35 litres par minute à 20°C. Ce générateur reçoit à chaque pulsation un volume constant d'anhydride carbonique correspondant à un débit moyen de 1,57 litre/minute (4,5% de 35 1/mn). Ce gaz porté à 37°C, saturé d'eau à cette température est envoyé sur un lit de superoxyde de potassium, puis recueilli dans un sac respiratoire et aspiré dans le générateur où il est remis au titre en anhydride carbonique et vapeur d'eau. L'ensemble fonctionne ainsi en circuit semi-fermé ; le générateur de gaz rejette à l'atmosphère un volume de gaz épuré équivalent au volume d'anhydride carbonique introduit ; une soupape tarée sur le sac respiratoire élimine l'excès d'oxygène éventuellement fourni par la charge respiratoire de superoxyde de potassium. Des analyseurs d'oxygène et d'anhydride carbonique donnent en continu la composition du gaz épuré ; on mesure aussi la variation de perte de charge de l'ensemble : lit de superoxyde-sac respiratoire, à l'expiration et à l'inspiration.

To evaluate the improvement in the performance of breathing apparatuses with chemical oxygen generation, the experimental device briefly described below is used:

• It includes a pulsed gas generator with twenty pulses per minute and an average flow rate of 35 liters per minute at 20 ° C. This generator receives at each pulse a constant volume of carbon dioxide corresponding to an average flow rate of 1.57 liters / minute (4.5% of 35 l / min). This gas brought to 37 ° C, saturated with water at this temperature is sent to a bed of potassium superoxide, then collected in a respiratory bag and sucked in the generator where it is given again as carbon dioxide and water vapor. . The whole thus operates in a semi-closed circuit; the gas generator rejects to the atmosphere a volume of purified gas equivalent to the volume of carbon dioxide introduced; a calibrated valve on the respiratory bag eliminates the excess oxygen possibly supplied by the respiratory load of potassium superoxide. Oxygen and carbon dioxide analyzers continuously give the composition of the purified gas; we also measure the pressure drop variation of the whole: respiratory superoxide-bag bed, at expiration and inspiration.

The time at the end of which one of the following limits is reached is called autonomy of the cartridge, namely: the C0 ₂ content of the purified gas is greater than 1.5%; the increase in pressure drop at expiration is greater than 5 millibars (this measures the increase in pressure drop in the superoxide bed due to partial clogging); the variation in pressure drop on inspiration suddenly increases and the respiratory bag is flat (this translates to a zero or greatly reduced generation of oxygen which no longer compensates for the respiratory need).

Under the experimental conditions described above, we find below the description of some of the tests carried out

Examples 1 to 4:

A 162 cm2 section of potassium superoxide with a rectangular section is used, crossed from bottom to top on exhalation by the gas to be purified. The charge used, weighing 1,600 g, consists of biconcave pellets 9 mm in diameter and 4.5 mm thick made from a mixture based on superoxide containing 70% KO ₂ , 10% of CaO, 15% KOH and 0.135% Cu ⁺⁺ in the form of oxychloride.

With the device in FIG. I, without internal arrangement, the CO ₂ content of the purified gas exceeds 1.5% after 78 minutes of operation.

With that of FIG. II with a central intake tube, this limit is reached in 68 minutes.

With the radiators shown diagrammatically in FIG. III, this C0 ₂ content of the effluent is reached only after 97 minutes of operation.

With the device, according to FIG. IV, combining the central intake tube and the radiators, the measured autonomy with respect to CO ₂ is then 102 minutes.

In all cases, the increase in pressure drop remains far below the fixed limit.

Example 5:

1,800 g of potassium superoxide 73.3% KO ₂ , 8% CaO and 10 ppm Cu ^{++ are} placed in a 162 cm 2 section cartridge, shown in FIG. I. The operation is carried out under the same experimental conditions as for the previous examples, but in addition, the cartridge is placed in a case similar to that used in the commercial type respiratory system.

It can be seen that the pressure drop at expiration remains practically constant, after stabilization in a few minutes at the start of the operation. The carbon dioxide content of the effluent gas goes through a maximum of 0.8% in the 72nd minute, then decreases rapidly and is only 0.2% in the 97th minute.

The generation of oxygen stops after 97 minutes of operation, the respiratory bag is then flat and the pressure drop on inspiration suddenly increases.

Claims (7)

1. Respirator with chemical generation of oxygen and vertical circulation from bottom to top of the gases to be regenerated, of the cartridge type intended to receive an absorbent regenerative charge in the form of pellets, characterized in that the upper part of the cartridge housing (6) on the outlet side of the gases to be treated is lined with a series of radiators (11) parallel to the direction of circulation of the gas flows under the regenerative charge, fixed to the walls of the housing (12) and whose length is shorter at the height of the load. 2. Breathing apparatus with chemical generation of oxygen, and vertical circulation from bottom to top of the gases to be regenerated, according to claim 1, characterized in that the length of the radiators (11) is between one third and one half of the spacing between the two perforated walls (7 and 8) supporting and maintaining the regenerative charge (6). 3. Breathing apparatus according to claim 1, characterized in that the radiators (11) are made of a material which is a good conductor of heat. 4. Breathing apparatus according to claim 3, characterized in that the radiators (11) are in the form of fins. 5. Breathing apparatus for chemical generation of oxygen, and vertical circulation from bottom to top of the gases to be regenerated, of the cartridge type intended to receive an absorbent regeneration charge in the form of pellets according to claim 1, characterized by the combination of two internal fittings, consisting of a central inlet nozzle (5) for the gases to be purified, extended vertically into the inlet duct (5 ') until the bottom of the housing (9) is cleared at the level of the perforated lower wall (7 ) supporting the regenerative charge, this intake duct (5 ′) opening at the center of this perforated wall (7) to which it is fixed; and the upper part of the cartridge case (6), on the side of the outlet for the gases to be treated, is provided with a series of radiators (11) parallel to the direction of circulation of the gas flows in the regenerative charge, fixed to the walls of the housing (12) and whose length is less than the spacing between the two perforated walls (7) and (8). 6. Breathing apparatus according to claim 1, characterized in that the radiators contain an endothermic transformation material. 7. Breathing apparatus for chemical generation of oxygen and vertical circulation of gases, of the cartridge type according to claim 5, characterized in that the central tube for admitting the gases to be purified (5 and 5 ′) is made of a conductive material. the heat.

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