EP0125157B1 - Chemical oxygen generator for breathing equipment - Google Patents

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 added 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, GB-A-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.

US-A-3,767,367 proposes a cartridge for regenerating exhaled gases which can be incorporated into an individual breathing apparatus, which comprises at the bottom a self-supporting vault constituted by a filter maintaining the charge of regeneration.

FR-A-2 442 637 describes an air purification cartridge of complex structure, constituted by baskets, containing the regenerative charge, in which the gas circulates radially, said baskets being arranged on each side of a central tube which constitutes the exhaust pipe of the regenerated air. The central tube is perforated along its length in contact with the baskets.

According to this prior teaching, the entry of gases is through a non-central tube, representing the top of the cartridge. The gas circulation in the cartridge is first of all horizontal in a chamber above the load baskets, then the exhaled gas enters through an opening, circulates in chimneys formed between the external wall of the cartridge and the perforated walls of the baskets, then the gas flows radially through the regenerative charge and after purification rises through the central tube.

US-A-4,193,966, describes a cartridge with vertical gas circulation, filled with a layer of absorbent material; the cartridge is provided with disk-shaped moisture condensers fixed by lugs to the walls thereof.

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 solid reagent particles 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 superoxide reacts more quickly with carbon dioxide than with water vapor, which corresponds to a more accelerated fixation of CO ₂ , while pure potassium superoxide generates oxygen from water vapor forming 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 sharp 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 ill-suited to automation.

Recently, a way has been proposed to suppress the excessive increase in pressure losses of potassium superoxide during intensive regeneration conditions. According to FR-A-2 521 034 (published on 12.08.83) a certain proportion of alkaline earth oxide in the pulverulent state is incorporated into the potassium superoxide, before granulation or pelleting; 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 quantity 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. cleared, leads to optimal use of thick beds of pure potassium superoxide or mixtures based on potassium superoxide possibly containing calcium oxide.

This chemical oxygen generation breathing cartridge consists of a housing allowing vertical circulation from bottom to top of the gases to be regenerated, said housing being intended to receive an absorbent regenerative charge in the form of pellets, and said housing comprising in addition to a vertical central duct for the intake of the gases to be purified and the radiators.

According to the invention, this conduit is constituted by an end piece extended vertically through a perforated upper wall until the bottom of the housing is released at a perforated lower wall, said conduit opening at the center of this perforated lower wall to which it is fixed. And, a series of radiators parallel to the direction of flow of the gas flows in the regenerative charge is fixed to the walls of the housing and the length of the radiators is between one third and half the spacing between the two perforated upper and lower walls. These radiators are arranged at the upper part of the regenerative charge, said upper and lower walls holding the regenerative charge between them.

According to the internal arrangement of this respiratory cartridge 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 gas inlet nozzle to be purified 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 inlet duct opening out at the center of this perforated wall to which it is fixed, by welding, stamping ...

The gases to be purified flow 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 carrying the regenerative charge and circulating in it from bottom to top, the regenerated gases passing through the upper perforated wall maintaining the regenerative charge, then escaping through the discharge nozzle.

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 radiators placed in the upper part of the regenerative charge, on the outlet side 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.

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

• La figure 1 donnée à titre comparatif représente un dispositif à fonds ouverts sans aménagement interne selon une vue en coupe.
• La figure 2 donnée à titre comparatif 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 3 et 3a données à titre comparatif . montrent selon l'invention des vues en coupe d'un boîtier de cartouche à fonds ouverts, aménagé avec des radiateurs.
• Les figures 4 et 4a sont des vues en coupe de l'association des deux aménagements internes ; tube central d'admission et radiateurs ;
• et la figure 5 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 1 given for comparison represents an open bottom device without internal arrangement in a sectional view.
• FIG. 2 given by way of comparison represents a sectional view of a regeneration device with central tube for admitting the gases to be purified, and open upper bottom.
• Figures 3 and 3a are given for comparison. according to the invention show sectional views of a cartridge case with open bottoms, fitted with radiators.
• Figures 4 and 4a are sectional views of the association of the two internal arrangements; central intake tube and radiators;
• and Figure 5 is a perspective view in the case where the radiators are fins.

Comparative figure 1 shows a body of metal case (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 (4 '). On it, is welded on the outside and in its center, a pierced intake nozzle (5) or tubing d entry 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.

Comparative Figure 2 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 is extended 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).

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 case (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) in the direction of the regenerated gas tube, not shown.

Comparative Figures 3 and 3a 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 4 according to the invention shows a housing of the type of Figure II comprising, in addition, the second internal arrangement consisting of a series of parallel radiators (11) fixed as above. And, in FIG. 4 ′, 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 5 according to the invention 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 the finned radiators, with outlet gas at the top 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 minutes 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 I/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 I / min). This gas brought to 37 ° C, saturated with water at this temperature is sent over 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.

• Dans les conditions expérimentales ci-dessus décrites, on trouve, ci-dessous, la description de quelques uns des essais réalisés.

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 cm ² potassium superoxide bed with rectangular section is used, traversed from bottom to top on expiration by the gas to be purified. The charge used, weighing 1600 g, consists of biconcave pellets 9 mm in diameter and 4.5 mm thick made from a mixture based on superoxide containing 70% K0 ₂ , 10 % CaO, 15% KOH and 0.135% Cu ⁺⁺ in the form of oxychloride.

With the device of comparative figure 1, without internal arrangement, the C0 ₂ content of the purified gas exceeds 1.5% after 78 minutes of operation.

With that of comparative figure 2 with central intake tube, this limit is reached in 88 minutes.

With the radiators shown diagrammatically in comparative figure 3, this CO ₂ content of the effluent is reached only after 97 minutes of operation.

With the device, according to comparative figure 4, combining the central intake tube and the radiators, the measured autonomy with respect to C0 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% K0 ₂ , 8% CaO and 10 ppm Cu ^{++ are} placed in a 162 cm ² section cartridge, shown in FIG. 1. 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 passes through a maximum of 0.8% in the 72 ^th minute, then decreases rapidly and is only 0.2% in the 97 ⁸ 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 (5)

1. Respiratory cartridge (6) for chemical generation of oxygen, constituted of a housing (1) permitting a vertical circulation of gases to be regenerated upward from below, the said housing (1) being defined to receive an absorbing regenerating charge in form of pastilles, the said housing (1) comprising further a vertical central conduit of admission of gases to be purified (5) and radiators (11), characterized in that the conduit (5) is constituted by a connecting piece vertically prolongated across a perforated superior wall (8) to a distance from the bottom (9) of the housing (1) at the level of an inferior perforated wall (7), the said conduit (5) terminating in the center of this inferior perforated wall (7) to which it is fixed, and in that a series of radiators (11) parallel in the sense of circulation of gaseous flows in the regenerating charge is fixed to the walls of the housing (1) and the length of the radiators (11) being between the third and the half of the spacing between the two perforated superior and inferior walls (7, 8), these radiators (11) being positioned in the superior part of the regenerating charge, the said superior and inferior walls (7, 8) maintaining the regenerating charge between themselves.

2. Respiratory cartridge for the chemical generation of oxygen according to claim 1, characterized in that the radiators (11) are of well heat conducting material.

3. Respiratory cartridge for the chemical generation of oxygen according to claim 1, characterized in that the radiators (11) are in the form of vanes.

4. Respiratory cartridge for the chemical generation of oxygen, according to claim 1, characterized in that the radiators comprise a material for endothermic transformation.

5. Respiratory cartridge for chemical generation of oxygen according to claim 1, characterized in that the central tube admitting gases to be purified (5 and 5') is of a heat conducting material.

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