FR2976260A1 - PROCESS FOR PACKAGING NO / N2 MIXTURES WITH PURGE STAGES AND PRIOR GAS RINSING - Google Patents

Abstract

The method of conditioning a gaseous mixture NO / N in at least one container, characterized in that, prior to the introduction of said NO / N mixture, said at least one container is subjected to at least one purge step during which the internal volume of the container is in fluid communication with the ambient atmosphere; a vacuuming step during which the internal volume of the container is depressed; and a gaseous rinsing step during which an inert gas is introduced into said at least one container. Preferably, the final gas mixture NO / N contains an NO content of less than or equal to 1200 ppm by volume for a pressure of between P1 and 800 bar.

Description

The invention relates to a method for conditioning a NO / N2 gas mixture in a container, in particular one or more gas cylinders, comprising several successive purge and gaseous rinsing steps. NO / N2 gas mixtures are commonly used to treat pulmonary vasoconstriction in adults or children, particularly in neonates with primary pulmonary hypertension or in patients undergoing cardiac surgery. These NO / N2 mixtures are conventionally packaged in steel gas cylinders. Typically, these bottles contain 100 to 1000 ppm by volume of NO and nitrogen (N2) for the rest. These bottles usually have a water capacity of 2 to 50 liters, which allows to introduce a total charge of up to 15 m3 NO / N2 mixture. The packaging, that is to say the bottling of these mixtures, is done in gas conditioning centers.

However, given the low content of NO in the mixture, typically of the order of a few hundred ppm by volume, the packaging of these mixtures is not always easy to achieve industrially. In particular, the gaseous mixture NO / N2 is sensitive to the presence of residual oxygen-type impurities that may be present in the bottles during their filling.

Indeed, it is essential to be able to ensure that the bottles were, before filling, properly cleaned of any gaseous impurities they may contain, in particular oxygen which can react with the NO to form toxic NO2. In other words, if the purging and cleaning of the internal volume of the bottles is not properly carried out, the NO / N2 mixtures produced will not comply with the specifications and must be discarded. The problem is therefore to propose an improved packaging method making it possible to eliminate all or almost all the impurities, in particular oxygen, which may be in one or more gas cylinders to receive an NO type gas mixture. / N2. The solution of the invention is then a method of conditioning a gaseous mixture NO / N2 in at least one container, in particular one or more gas cylinders, characterized in that, prior to the introduction of said NO / N2 mixture said at least one container, i.e. the at least one container, is subjected to at least: a) a purge step during which the internal volume of the container is in fluid communication with the ambient atmosphere, b ) a vacuuming step during which the internal volume of the container is depressurized, that is to say that the internal pressure of the container is decreased until a pressure below atmospheric pressure (<1 bar absolute) is reached ), and c) a gaseous rinsing step during which an inert gas is introduced into said at least one container. Depending on the case, the method of the invention may comprise one or more of the following technical characteristics: step b) of evacuation is carried out by drawing off gas by means of a vacuum pump. said at least one container is subjected, several times in succession, to steps a) and c), prior to introducing said NO / N2 mixture into said at least one container. two successive sequences of steps a) and c) are separated by a sequence of steps a), b) and c). sequence of steps a), b) and c) is immediately followed by a sequence of steps a) and c) or a sequence of steps a), c) and a). during steps c), the inert gas used to carry out the gaseous rinsing is nitrogen. several gas containers are simultaneously subjected to steps a) to c). - Subsequent to the implementation of at least two sequences of steps a) to c), is introduced into the vessel or containers a gaseous mixture of NO and N2. - Subsequent to the implementation of at least two sequences of steps a) and c), is introduced into the vessel or containers successively: i) a gaseous premix of NO and N2 containing an NO content less than 10 % by volume until reaching a first pressure P1 with P1> 1 bar absolute; ii) nitrogen gas to obtain, by mixing nitrogen with said premix NO / N2, a final gas mixture NO / N2 containing an NO content less than or equal to 1200 ppm by volume and a second pressure P2 between Pl and 800 bar. step g) of gaseous rinsing comprises the introduction of nitrogen gas into the container or receptacles until a rinsing pressure of between 2 and 20 bar is obtained within the receptacle or receptacles, preferably between 2 and 12 bar; . during the purging step a), the internal volume of the container is maintained in fluid communication with the atmosphere as long as the internal pressure of the container is greater than a minimum purge pressure (Pmin) such that: 3.5 bar> Pmin> 1 bar, preferably between 1.1 and 3 bar approximately. during at least one step b) of evacuation, the internal volume of the container is depressurized until a pressure level of less than 0.5 bar, preferably less than 0.2 bar, is reached. - It comprises, prior to step a), a step d) of evacuation and a step e) purge at least one hose connecting the filling ramp to a gas container. during gaseous rinsing step c, the introduction of inert gas into said at least one receptacle is stopped when the pressure in said at least one receptacle reaches a value of between 2 and 20 bar, preferably between 3 and 10, bar. the fluidic communication with the ambient atmosphere is stopped during the purging step a) when the pressure in the internal volume of the receptacle reaches a value of between 1 and 1.5 bar. the first pressure P1 is between 2 and 10 bar, preferably less than or equal to 5 bar. the second pressure is between 100 and 700 bar, preferably at least 200 bar. - The gaseous premix of NO and N2 contains an NO content of less than or equal to 8% by volume, preferably a NO content of less than or equal to 5% by volume. the gaseous premix consisting of NO and N2 contains an NO content of the order of 4% by volume and the first pressure P1 is of the order of 2 to 10 bar abs, for example of the order of 2 to 5 bar abs. the final gas mixture NO / N2 contains an NO content less than or equal to 1000 ppm by volume, preferably the final gas mixture NO / N2 contains an NO content of between 200 and 1000 ppm by volume, more preferably between 200 and 1000 ppm by volume; and 800 ppm by volume. - It is implemented through a gas containers packaging ramp comprising connecting means for filling several containers at a time. the container is a gas bottle, preferably a gas cylinder with a steel body, aluminum or an aluminum alloy. In the context of the present invention, the pressures given are absolute pressures. The invention will now be better understood thanks to the description given hereinafter with reference to the appended figures in which: FIG. 1 shows schematically an embodiment of a conditioning cycle according to the present invention and FIG. diagram of an installation for implementing the method of the invention. Figure 1 shows schematically an embodiment of a conditioning cycle applicable in the context of the NO / N2 gas mixture conditioning process of the present invention. As can be seen, this conditioning cycle comprises several successive steps, ranging over time from TO to T13, which are applied to each bottle and which are detailed below. The successive steps a) to c) of the process of the invention have been indicated in FIG.

Between TO and T1, the hoses of the installation are emptied in the open air, that is to say that the internal volume of the filling hoses is put in fluid communication with the ambient atmosphere to evacuate any residual overpressure . During this phase, the valve (s) of gas containers connected to the hoses are closed, therefore no gas exchange takes place with the container (s). This corresponds to step d) of the process.

Between T1 and T2, a vacuum pump is used to put the inside of the hoses into a branch depression, that is to say at a pressure below atmospheric pressure, for example of the order of 0.15 bar. , which allows to evacuate the residual gas and / or air therein. This phase is also realized closed tap. Vacuuming the hoses is a safety feature that makes it possible to check the correct connection of all hoses and the absence of leaks. Indeed, in case of leakage or incorrect connection of a hose vacuum will not be established stably. This corresponds to step e) of the process schematized in Figure 1. Between T2 and T3, the operator opens the valve of each bottle and the residual pressure present in each bottle then rises to the pressure sensor, which detects said ascent pressure. Typically, the residual pressure of the bottle is of the order of about 3 to 4 bar absolute. After T2, no gaseous flushing of the vessel with nitrogen has yet occurred. This corresponds to step f) of the process shown schematically in FIG. 1. Between T3 and T4, the actual processing of each bottle begins. More specifically, each bottle is vented, that is to say that is allowed to escape the gas contained in the bottle to the outside atmosphere simply by the effect of the pressure difference between inside and outside. outside of the bottle so as to bring the internal pressure of the bottle to atmospheric pressure. This corresponds to step a) of the process of the invention. At T4, the internal pressure of the gas cylinder is therefore substantially equal to the atmospheric pressure (1 atm = about 1 bar absolute), that is to say of the order of 1 to 1.5 bar abs. Between T4 and T5, the bottle is rinsed with nitrogen during which its internal pressure is increased to about 10 bar. The addition of nitrogen is via a gas pipeline and / or nitrogen storage under pressure so as to bring the internal pressure of the bottle to the desired pressure. This corresponds to step c) of the process of the invention. Between T5 and T6, the nitrogen contained in the bottle is again escaped to the atmosphere, which eliminates any impurities in the bottle. This corresponds to a new step a) of the process of the invention. Between T6 and T7, the bottle is purged by depressurizing its internal volume by withdrawing the residual gas therein by means of a vacuum pump until an internal negative pressure of less than 0.2 bar abs, preferably less than 0.1 bar, for example of the order of 0.05 bar. This corresponds to a new step b) of the process of the invention.

Between T7 and T8, the bottle is re-rinsed with nitrogen until its internal pressure is approximately 10 bar, as between T4 and T5. This corresponds to a new step c) of the process of the invention. Between T8 and T9, the bottle undergoes a new exhaust towards the ambient atmosphere as during times T5 and T6. The gaseous residual pressure is then maintained at approximately 1.35 bar to prevent untimely entry of atmospheric contaminants. This corresponds to a new step a) of the process of the invention. Between T9 and T10, the bottle is further rinsed with nitrogen until its internal pressure is about 10 bar, as before. This corresponds to a new step c) of the process of the invention.

Between T10 and T11, the nitrogen is escaped to the atmosphere, as between T8 and T9 and between T5 and T6, but this time maintaining an internal residual pressure of the order of 3 bar. This corresponds to a new step a) of the process of the invention. Between T11 and T12, is introduced into the bottle, a gaseous premix of NO and N2 containing an NO content of less than 10% by volume until reaching a first filling pressure P1 with Pl> 1 bar, typically a pressure Pl of the order of 2 to 10 bar abs, preferably from 3 to 5 bar abs about. Advantageously, the gaseous premix consisting of NO and N2 contains an NO content of about 4% by volume. Between T12 and T13, nitrogen containing gas is then introduced into the vessel containing the NO / N2 premix at the first pressure P1 until a final NO / N2 gas mixture is obtained containing an NO content of less than or equal to 1200 ppm. in volume, for example a final NO content of 200 to 800 ppm, and a second pressure P2 between P1 and 800 bar, for example here a pressure of 180 to 200 bar. This method can be implemented by means of a packaging installation such as that shown diagrammatically in FIG. 2 equipped with a ramp 14 for packaging gas containers, that is to say, gas cylinders, comprising means connection 15 to fill several containers 11 to 13 at a time, typically from 2 to 20 bottles concomitantly. The nitrogen is stored in the tank 1 in liquid form and then withdrawn in liquid form by a cryogenic pump 2 which compresses it to a pressure of the order of 100 to 300 bar, before sending it to an atmospheric heater 3 where it is vaporized to obtain nitrogen gas. As can be seen, it comprises a pipe or main line 20 for conveying nitrogen from a tank 1 to the ramp 14 of conditioning. In fact, the pressure in the line varies between about 100 bar immediately downstream of the collapse of the buffer capacity in the bottles and about 260 bar which corresponds to the stopping threshold of the pump. The nitrogen gas is then conveyed via line 20 to a purification device 6 making it possible to remove traces of O 2 and H 2 O, for example a suitable molecular sieve, for example of the zeolite, silica gel, alumina or the like type, or their mixtures. It should be noted that the line 20 is also fluidly connected to a buffer capacity 4 for storing a portion of the nitrogen gas, as well as backup frames 5 each comprising several bottles of nitrogen. Furthermore, the installation also comprises a cabinet 16 comprising a plurality of bottles 9 of a premix of NO / N2 containing here 4% by volume of NO, which bottles 9 are fluidly connected to the line 20 by a feed line 22. premix NO / N2. In fact, the lines NO / N2 22 and nitrogen 20 are not connected directly to one another but they are connected to the valve block 8 which is connected to it by the line 21 to the ramp (s) 14 The valves of the valve block 8 make it possible to choose the fluid with which the bottles 11 to 13 of the ramp 14 are filled. The nitrogen lines 20 and premix lines NO / N2 22 are thus fluidly connected firstly by the block valve 8, then a common section 21 to the filling ramp 14. The valve block 8 comprises valves, control elements controlled by the control device 10 ... flow meters 7 can measure the amount of N2 and of NO flowing in lines 20 and 22, and transmit the measured information to a control device 10, such as a computer or the like.

The installation also comprises a vent line 17 for evacuating the gases to the ambient atmosphere, especially during the purge step or stages during which the internal volume of the container is placed in fluid communication with the atmosphere room.

A vacuum pump (not shown) makes it possible to operate the evacuation (s) of the containers, that is to say to reduce their internal pressure until a pressure lower than atmospheric pressure is obtained, ie <1 bar absolute.

Claims (15)

REVENDICATIONS1. Process for conditioning a gaseous mixture NO / N2 in at least one container, characterized in that, prior to the introduction of said NO / N2 mixture, said at least one container is subjected to at least: a) a purge step during which the internal volume of the container is placed in fluid communication with the ambient atmosphere, b) a vacuuming step during which the internal volume of the container is depressed, and c) a gaseous rinsing step during which a gas inert material is introduced into the at least one container. 2. Method according to the preceding claim, characterized in that said at least one container is subjected, several times in succession to steps a) and c), prior to the introduction of said mixture NO / N2 in said at least one container. . 3. Method according to one of the preceding claims, characterized in that two sequences of steps a) and c) successive are separated by a sequence of steps a), b) and c). 4. Method according to one of the preceding claims, characterized in that a sequence of steps a), b) and c) is immediately followed by a sequence of steps a) and c) or a sequence of steps a), c) and a). 5. Method according to one of the preceding claims, characterized in that, in steps c), the inert gas for performing the gaseous rinsing is nitrogen. 6. Method according to one of the preceding claims, characterized in that several gas containers are subjected simultaneously to steps a) to c). 7. Method according to one of the preceding claims, characterized in that, subsequent to the implementation of at least two sequences of steps a) and c), is introduced into the container or containers a gas mixture of NO and N2. 8. Method according to one of the preceding claims, characterized in that, subsequent to the implementation of at least two sequences of steps a) and c), is introduced into the container or containers successively: i) a premix gaseous NO and N2 containing NO content less than 10% by volume to a first pressure P1 with P1> 1 bar absolute; ii) nitrogen gas to obtain, by mixing nitrogen with said premix NO / N2, a final gas mixture NO / N2 containing an NO content less than or equal to 1200 ppm by volume and a second pressure P2 between Pl and 800 bar. 9. Method according to one of the preceding claims, characterized in that the gaseous flushing step c) comprises the introduction of nitrogen gas into the container or containers until a flushing pressure of between 2 and 20 bar within said container or receptacles, preferably between 2 and 12 bar. 10. Method according to one of the preceding claims, characterized in that during the purging step a), the internal volume of the container is maintained in fluid communication with the atmosphere as the internal pressure of the container is greater than one. minimum purge pressure (Pmin) such that: 3.5 bar> Pmin> 1 bar, preferably between 1.1 and 3 bar approximately. 11. Method according to one of the preceding claims, characterized in that during at least one step b) of evacuation, the internal volume of the container is depressurized to reach a pressure level of less than 0.5 bar preferably less than 0.2 bar. 12. Method according to one of the preceding claims, characterized in that it comprises, prior to step a), a step d) of evacuation and a step e) purge at least one hose connecting the filling ramp to a gas container. 13. Method according to one of the preceding claims, characterized in that the final gas mixture NO / N2 contains an NO content less than or equal to 1000 ppm by volume, preferably the final gas mixture NO / N2 contains a content of NO between 200 and 1000 ppm by volume, more preferably between 200 and 800 ppm by volume. 14. Method according to one of the preceding claims, characterized in that during step c) gaseous rinsing, the introduction of inert gas into said at least one container when the pressure in said at least one container reaches a value between 2 and 20 bar, preferably between 3 and 10 bar. 15. Method according to one of the preceding claims, characterized in that it stops the setting in fluid communication with the ambient atmosphere during the purge step a) when the pressure in the internal volume of the container reaches a value of between 1 and 1.5 bar.