Gas storage improvements

Abstract

To ensure that oxygen or air delivered using activated carbon is substantially free of carbon monoxide.SOLUTION: A device (10) comprises a canister (12) filled with activated carbon (14) and oxygen (30) at a pressure between 4 and 20 barg, when measured at room temperature. The canister is sealed with a valve assembly (18) allowing release of oxygen from the canister on actuation of the valve assembly. To ensure that the activated carbon does not react with the oxygen generating carbon monoxide, the device further comprises a catalyst (16) that prevents or significantly reduces the presence of carbon monoxide. In a particularly favored embodiment, the device is filled with carbon dioxide and includes a high-volume discharge valve so as to be useful as a pet behavior correction device.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001]

[0001] The present invention relates to improvements in gas storage devices, more particularly to devices filed with, for example, oxygen or carbon dioxide. The invention also relates to improved methods of storing gas, particularly oxygen, carbon dioxide, nitrogen, or air, in the devices, and to the storage devices themselves. [Background technology]

[0002]

[0002] Traditionally, gas-filled canisters are either filled with compressed gas or use a propellant such as HFA-134a to facilitate delivery. Such systems have several disadvantages.

[0003]

[0003] For example, British Patent No. 2411812 discloses a pet behavior correction device comprising a canister filled with pressurized inert condensed gas in the form of a hydrofluorocarbon (HFC). In use, the gas is expelled towards, for example, the dog's head, producing a hissing sound. However, such devices have several limitations, including the undesirable properties of HFCs (environmental hazards) that have led to their legislative phase-out, the fact that their liquid nature limits their orientation in use (they do not work effectively upside down), and the fact that they undergo rapid cooling upon decompression, which can be painful (and possibly harmful) to pets if operated too close to the animal, and can cause freezer burns if accidentally operated, for example in the user's pocket.

[0004]

[0004] Alternative propellants may be used in place of HFCs, but for example, hydrocarbon gases such as butane are highly flammable and volatile, subject to potential abuse. Many of the propellants also leave behind residual deposits that can damage sensitive electronics in applications such as gas dusters, which are devices used to clean difficult-to-reach surfaces, such as grooves and crevices within equipment, and electronic or sensitive equipment that cannot be accessed or cleaned using conventional solvents.

[0005] However, air and its components, including oxygen, nitrogen and carbon dioxide, are not easily liquefied, so only small quantities of the gas can be stored without the need for backup against extremely high pressures.

[0006]

[0006] WO 2005 / 054742 discloses a storage vessel for gas comprising a sealed vessel having a quantity of activated carbon and a gas adsorbed on its surface.

[0007]

[0007] One such gas is oxygen.

[0008]

[0008] Containers filled with compressed oxygen may be used in a range of applications, such as for therapeutic or sports enhancement purposes.

[0009]

[0009] The use of activated carbon as a storage means makes it possible to store much larger quantities of gas in a given volume: in the case of oxygen, this is about two to three times that obtainable by compression alone at the same pressure, depending on the grade of activated carbon.

[0010] Typically, gas is stored at pressures of 4 to 17 barg (measured at room temperature) and the containers typically contain at least 40% by volume of activated carbon, although some canisters can withstand pressures of 20 barg.

[0011]

[0011] The device may be adapted to accommodate a mask, mouthpiece, and / or nosepiece, and typically includes a valve assembly to allow for filling and dispensing. The device may also contain a filter between the activated carbon and the valve of the valve assembly.

[0012]

[0012] The device may be connected to a mask, mouthpiece, and / or nosepiece via connectors, such as tubing, and these components may be sold separately or as a kit of parts.

[0013]

[0013] When the system is charged with oxygen at pressures above about 8 barg, it is desirable to use high activity carbon (activated carbon having an activity above 60% CTC (carbon tetrachloride)), although lower activity carbons can be used, especially at lower charge pressures.

[0014] Applicant has concluded that devices containing activated charcoal filed with oxygen or air under pressure will contain significant amounts of carbon monoxide (concentrations above 100 ppmv) as a result of the reaction between the activated charcoal and oxygen. While not inherently dangerous at such levels, carbon monoxide has 250 times the binding affinity for hemoglobin as oxygen. As a result, even relatively low levels of carbon monoxide can negate the benefits gained from inhaling pure oxygen. Indeed, at concentrations of 200 ppmv, carbon monoxide can cause headaches and nausea.

[0015] It is an object of the present invention to ensure that the oxygen or air delivered using activated carbon is substantially free of carbon monoxide.

[0016] A second independent aspect is managing the thermal effects associated with filling the canister with a gas, and this aspect is not limited to oxygen. In fact, this second aspect can be even more problematic when the gas is carbon dioxide, since the volume that can be adsorbed in a canister filled with activated carbon is much larger (as much as 25 times that of compressed carbon dioxide) and the adsorption is exothermic.

[0017]

[0017] Indeed, when the gas is carbon dioxide, WO 2005 / 054742 teaches filling the device with solid carbon dioxide or dry ice to counteract any exothermic reaction.

[0018] However, accurate distribution of dry ice has proven difficult; a deviation of just 3 g in a 1 L canister can result in a deviation of as much as 1.6 L of carbon dioxide, which can overpressure the system when equilibrated at room temperature.

[0019]

[0019] Alternatively, WO 2008 / 064293 teaches a method of filling by placing dry ice in a canister and then crimping a valve assembly onto the canister, without the need to perform a step-by-step filling process involving multiple cooling and recharging steps.

[0020]

[0020] The reason for this method is that devices are typically made using an aluminum canister and the valve assembly is crimped to the canister over a plastic seal such as PET or silicone rubber. Due to the high thermal conductivity of aluminum, in small devices (1 L or less), the applicant concluded that the rapid transfer of heat to the canister would distort the seal and cause failure of the device, i.e., leakage around the crimp, and therefore using the method taught in WO2008 / 064293.

[0021]

[0021] WO 2005 / 070788 teaches the filling of a canister, which is filled with the liquid product to be dispensed via a needle inserted into a hollow tube, and in operation a valve opens against the action of a biasing means, allowing liquid to pass through a passage and a dip tube, filling the canister to the product level.

[0022]

[0022] WO 2014 / 037086 teaches that the filling of the canister needs to be compatible with existing commercially available canister manufacturing / filling techniques and equipment to facilitate introduction and acceptance in the aerosol industry. The disclosed configuration is a bag-on-valve configuration, in which the bag-on-valve configuration is inserted through an opening, where gas is supplied through the opening around a loosely positioned valve block that is loosely held during the gas filling operation. Gas filling is ideally accomplished quickly, for example in about 1 second, and then the valve block is immediately and firmly fixed in the opening and sealed therein by a crimp / gasket. Thus, carbon is introduced into the canister 1 coupled with the bag-on-valve configuration and hermetically held in the canister without the need to manage or monitor its condition.

[0023]

[0023] Indeed, in terms of heat management, WO 2014 / 037086 teaches the use of a blanket gas and keeping carbon granules / pellets / toroids in contact with a source of carbon dioxide or other adsorbed gas, particularly a cryogenic gas, liquid or snow, before being placed in the canister.

[0024]

[0024] A further independent object of the present invention is to find an alternative method of managing heat or improving the manufacturing process in the manufacture of activated carbon loading equipment to reduce equipment failures and ensure simpler and, importantly, more accurate loading.

[0025]

[0025] In contrast to the above, applicant has concluded that by selecting a steel canister as opposed to the more common aluminium, it is possible, at least for small volume devices, i.e. canisters having a volume of 1 L or less, to fill the canister through the valve assembly of the device in a single or two step process using commercially available gas treatment equipment at room temperature and at pressures of at least up to 17 barg, and even up to 20 barg, thereby eliminating the need to either fill a partially assembled device and then crimp the valve assembly onto the canister, or to fill the device in steps with multiple cooling between each partial fill.

[0026]

[0026] This is i) Speeding up the filling process, and ii) reducing failure due to either canister failure around the crimp or canister overpressurization; This has the important advantage that

[0027]

[0027] In contrast to the teachings of WO 2008 / 064293, the method of a second independent aspect comprises or consists essentially of gassing an apparatus comprising a steel canister filled with activated carbon in a single-step or two-step process via a valve assembly.

[0028]

[0028] The gas is in particular carbon dioxide, but may also be oxygen, nitrogen or air.

[0029]

[0029] It is preferable that the device has a canister volume of 1L or less. Summary of the Invention [Means for solving the problem]

[0030]

[0030] According to a first aspect of the present invention there is provided an apparatus for dispensing oxygen under pressure comprising a canister filled with activated carbon and oxygen at a pressure of between 4 and 20 barg when measured at room temperature, the canister being sealed with a valve assembly which upon actuation of the valve assembly allows release of oxygen from the canister, and the apparatus further comprising a catalyst to prevent or significantly reduce the presence of carbon monoxide.

[0031] The preferred catalyst converts carbon monoxide to carbon dioxide at ambient temperatures.

[0032] The preferred catalyst is hopcalite, a mixture of copper oxide and manganese oxide. A variety of compositions are available, including the applicant's proprietary formulation SB100™.

[0033] As an example only, hopcalite I is 50% MnO, 30% CuO, 15% Co 2 O 3 , and 5% Ag 2 O, and "hopcalite II" is approximately a 3:1 mixture of manganese dioxide:copper oxide.

[0033]

[0034] Preferably, hopcalite is used at a concentration of greater than 0.4% (w / w).

[0034]

[0035] Hopcalite is available in several forms, the preferred form being pellets.

[0035]

[0036] The activated carbon may be any carbon that has been specially treated to develop a wide range of capabilities for adsorbing the gas being adsorbed.

[0036]

[0037] Suitable carbons include, for example, carbon sources such as peat, wood, coal, nut shells, petroleum, coke, and bone, or synthetic sources such as poly(acrylonitrile) or phenol formaldehyde.

[0037]

[0038] As disclosed in WO 2005 / 054742 (incorporated by reference), there are numerous methods for activating carbon, and the activation process develops a complex network of pores of various sizes ranging from macroporous (large pore diameters greater than 50 nm) to submicroporous (pore diameters less than 2 nm). The larger pores are known as transport pores and serve to provide access to the smaller pores where most of the adsorption of gas species takes place.

[0038]

[0039] Activated carbon may be provided in powder, granule, or pellet form and in a variety of sizes, both of which affect the adsorption kinetics. One skilled in the art will select the appropriate combination depending on the desired material adsorption performance required.

[0039]

[0040] Suitable activated carbons for use with oxygen include those of various origins, densities, activities and mesh sizes, selected to maximize adsorption, as outlined in Example 1 of WO 2005 / 054742. A preferred form is the applicant's proprietary activated carbon SBC™.

[0040]

[0041] High microporosity (<2 nm) and high surface area (500 m 2 / g, more preferably 1000m 2 It is clearly desirable to select an activated carbon having a molecular weight of greater than 10000 / g. One such material is shown in Table 3 of WO 2005 / 054742, the disclosure of which is incorporated by reference and which table is reproduced below as Table 1.

[0041]

[0042] [Table 1]

[0042]

[0043] For gas-filled devices, WO 2005 / 054742 teaches, for example, that carbon dioxide uptake can vary with the degree of activation (measured as the ability to adsorb carbon tetrachloride (CTC) vapour). WO 2005 / 054742 illustrates this for activated carbons with CTC values ​​ranging from 27% CTC to 111% CTC at a pressure range of 0 to 20 barg.

[0043]

[0044] At lower pressures, below about 8 barg (Figure 2 of the reference), it is reported that lower activity carbons may exhibit higher uptake, and it is further taught that the bulk density of the activated carbon appears to be one of the most important factors in maximizing adsorption. This teaching is based on a 0.35 to 0.55 g / cm 3 The bulk densities shown are in the range of 0.01 to 0.01.

[0044]

[0045] It will be apparent from this teaching that selecting an appropriate activated carbon for a given application is a routine task for those of skill in the art.

[0045]

[0046] Once the appropriate activated carbon is selected, the canister is filled with activated carbon, which for most applications is typically greater than 40%, through 50%, 60%, 70% or more (by volume), however, there are applications in which much smaller amounts of activated carbon may be used.

[0046]

[0047] Preferably, the device is also fitted with a filter located between the activated charcoal and the valve of the valve assembly, more preferably the filter is a HEPA filter.

[0047]

[0048] If the device is filled with oxygen or air, it is preferably provided with a mouth and / or nosepiece, face mask, etc., and a connector, e.g., flexible tubing, for connecting to the device. An actuator allows the release of adsorbed gas from the canister via a valve and optionally a regulator.

[0048]

[0049] Preferably, the device is charged through a valve assembly and care is taken to manage the exothermic nature of the filling process. This can be effectively achieved by using a steel canister of about 1 L or less in volume.

[0049]

[0050] According to a second independent aspect of the present invention there is provided an improved method of charging an apparatus for dispensing gas under pressure, the apparatus comprising a canister of volume 1 L or less filled with activated carbon for adsorbing gas under a pressure of between 4 and 20 barg when measured at room temperature, the canister being sealed with a valve assembly crimped onto the canister on a seal to allow release of gas from the canister upon actuation of the valve assembly, the gas being carbon dioxide, oxygen or air, the canister comprising steel, and the canister being filed in a single step or two step operation via the valve assembly.

[0050]

[0051] Preferably, the canisters have a volume of 1 L or less, including, for example, canisters of about 370 mL, 640 mL, and 980 mL.

[0051]

[0052] Canisters of such size, when filled, can typically accommodate approximately 10 L, 20 L, 30 L of oxygen, or 40 L, 70 L, or 100 L of carbon dioxide, respectively.

[0052]

[0053] According to a third aspect of the present invention there is provided an apparatus for dispensing gas under pressure, the apparatus comprising a canister of volume not exceeding 1 L filled with activated carbon for adsorbing gas under a pressure of between 4 and 20 barg when measured at room temperature, the canister being sealed with a valve assembly crimped onto the canister on a seal to allow release of gas from the canister upon actuation of the valve assembly, the gas being carbon dioxide, oxygen or air, and the canister comprising steel.

[0053]

[0054] The device is preferably filled with oxygen or carbon dioxide.

[0054]

[0055] Preferably, the canisters have a volume of 1 L or less, including, for example, 370 mL, 640 mL, and 980 mL canisters.

[0055]

[0056] A preferred carbon dioxide filled device is a pet behavior correction device, which is equipped with a large volume delivery valve.

[0056]

[0057] The large volume dispensing valve has a stem with an orifice diameter of at least 0.3 mm, more preferably at least 0.4 mm, and even about 0.6 mm.

[0057]

[0058] Another preferred device filled with carbon dioxide is a gas duster device, which includes a tube connectable to a valve assembly to allow the gas to be directed at a target surface upon exhalation.

[0058]

[0059] Preferably, the canister is filled with activated carbon to at least 85% by volume, more preferably at least 90%, and most preferably at least 95%. If the device is filled with dry ice, the dry ice should not be used to maximize efficient filling. Enough space must be left for chairs.

[0059]

[0060] If the gas is oxygen or air, the device may be provided with one or more of a mask, a mouthpiece, and / or a nosepiece, and connectors, e.g., tubing, which components may be sold separately or as a kit of parts.

[0060]

[0061] The device or kit may be provided with instructions for use.

[0061]

[0062] In further embodiments, the device may include a regulator and / or counter or other means for determining usage. The counter may be built into the device or may communicate usage to a device carried or worn by the user, such as, for example, a smartphone or a wearable device, such as the Fit Bit®. This allows the user or a third party to monitor the effect of oxygen intake on performance and recovery.

[0062]

[0063] Embodiments of the invention are further described below with reference to the accompanying drawings. [Brief description of the drawings]

[0063] [Figure 1] 1 is an apparatus according to a first aspect of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0064]

[0064] Figure 1 shows an apparatus (10) according to a first embodiment of the invention. The apparatus comprises a canister (12), preferably made of steel, filled with activated carbon (14) and a catalyst (16), which is sealed with a valve assembly (18) comprising a valve (20) and an actuator (22). A filter (24) prevents the activated carbon from clogging the valve stem (26).

[0065]

[0065] According to a second aspect of the invention, the device is filled with a gas (30), for example oxygen, which can be adsorbed in activated carbon and then released from the device by actuation of the actuator (22).

[0066] To fill the device (10), a unique gas handling system is used to force gas (30) under pressure through valve (20) into the canister (12).

[0067] The invention is further illustrated by reference to the test data generated in Examples 1 and 2.

[0068] Example 1 Effect of catalyst on carbon monoxide levels

[0069]

[0068] Canisters (12) of various sizes less than 1 L were assembled as follows. a) One or two pellets of hopcalite (16) were added to an empty (steel) canister (12) such that the net concentration of hopcalite was greater than about 0.5% w / w. b) The canister (12) was filled with granular activated carbon (14), preferably using vibration to maximize filling. c) The filter (24) was attached to the valve stem (26) of the valve assembly (18) and the protected valve stem (24, 26) was inserted into the activated carbon (14). d) The valve assembly (18) was crimped onto the canister (12). e) The apparatus (10) was gassed with oxygen (30) in a proprietary gassing apparatus.

[0070]

[0069] Analysis after charging confirmed that at high pressures, small amounts of carbon monoxide appear to be formed due to the interaction of oxygen with the highly activated carbon surface. Tests have shown that after one month of storage at room temperature, the carbon monoxide concentration in the gas exhaled from the device is approximately 300 ppmv and can be as high as 600 ppmv.

[0071]

[0070] This concentration, although not a direct health hazard, is highly undesirable in this type of product, so the applicant carried out some further tests to see if the problem could be alleviated by the addition of a catalyst (e.g. hopcalite).

[0072] As shown in Table 2, the type of activated carbon precursor was varied as was the amount of hopcalite, and the amount of carbon monoxide was determined approximately 200 days after filing. [Table 2]

[0073] As can be seen from Table 2, the addition of hopcalite significantly reduced carbon monoxide concentrations, and the data showed that concentrations greater than 0.4% were effective enough to ensure carbon monoxide concentrations were zero.

[0074] Gassing of the canisters with oxygen was carried out using a commercially available gassing equipment typically operating at 10 barg.

[0075] Example 2 Effect of canister type on heat transfer and equipment failure

[0076] When a conventional canister of aluminum construction was gassed with carbon dioxide, the exothermic adsorption of carbon dioxide onto the activated carbon was observed to cause a temperature rise of 46.5° C. This rapid temperature increase caused the seal (usually rubber) between the canister and the valve assembly to deform, resulting in leaks and premature depressurization of the system.

[0077] As a result, to avoid the risk of overheating and overpressure, it was necessary to introduce the gas in steps, allowing the apparatus to cool between steps.

[0078]

[0076] However, when a similar sized steel canister was gassed with carbon dioxide, it was determined that the temperature rise of the canister was only 3.7°C, thereby enabling the Applicant to fill the device in a single step procedure without risking stressing the rubber seals or overpressuring the container.

[0079]

[0077] The test results are as follows:

[0080] Gas used: Carbon dioxide

[0081]

[0079] Steel canister size: diameter 65 mm, height 195 mm, volume = πr2h = 646 mL

[0082]

[0080] Size of aluminum canister: diameter 66 mm, height 218 mm, volume = πr2h = 745 mL

[0083] Steel canister at room temperature: 14.5°C

[0084] Aluminum canister at room temperature: 14.5°C

[0085]

[0083] Carbon content of steel canister: 265 grams

[0086]

[0084] Carbon content of aluminum canister: 282 grams

[0087]

[0085] Both canisters were gassed at a pressure of 10 barg.

[0088] Temperature of steel canister after pressurization to 10 barg: 18.2°C

[0089] Temperature of aluminum canister after pressurization to 10 barg: 61° C.

[0090]

[0088] Thermal management is an important consideration in this process because too much heat can cause the device to fail due to deformation of the typically rubber seal located between the canister and the valve assembly where the two components are crimped together.

[0091]

[0089] Previously, thermal management was addressed by either using solid carbon dioxide or a filling process that required multiple gassing steps under pressure followed by cooling.

[0092] Preferred Source of Activated Carbon

[0093]

[0090] Although all of these forms and derivatives of activated carbon may be suitable for oxygen storage applications, it is preferred to use granular activated carbon derived from coconut shells, also known as HDS activated carbon, because it is a sustainable material with low ash content, offers excellent physical properties, and has environmentally friendly credentials.

[0094]

[0091] The precise particle size distribution must be such that the canisters can be filled to their maximum weight without causing handling problems.

[0092] Suitable mesh ranges are, for example, 30 x 70 or 12 x 20 US mesh for CTC activity >85% and moisture <5%.

[0095] A suitable, but non-limiting, density range is 0.4 to 0.5 gcm -3 It is.

Claims

1. An apparatus (10) for dispensing oxygen (30) under pressure, said apparatus comprising a canister (12) filled with at least 70% by volume of activated carbon (14) as a gas storage means and oxygen (30) at a pressure between 4 and 20 barg when measured at room temperature, said canister being sealed with a valve assembly (18) which allows release of oxygen from said canister upon actuation of said valve assembly, said activated carbon having high microporosity of less than 2 nm, high surface area of ​​more than 500 m2 / g, and a surface area of ​​0.35 to 0.55 g / cm3. and an activity of greater than 60% carbon tetrachloride (CTC), the apparatus further comprising a catalyst (16) added to the activated carbon that prevents or reduces the presence of carbon monoxide to less than 5 ppm, the catalyst (16) being either a mixture of copper oxide and manganese oxide, or a mixture of copper oxide, manganese oxide, cobalt oxide, and silver oxide, having a weight percent concentration of greater than 0.4% relative to the activated carbon (14), the canister (12) having a volume of 1 L or less, the catalyst being either a mixture of manganese dioxide and copper oxide in a 3:1 ratio, or 50% manganese oxide (MnO), 30% copper oxide (CuO), 15% cobalt oxide (Co2O3), and 5% silver oxide (Ag2O).

2. 10. The apparatus of claim 1, wherein the catalyst is a catalyst that converts carbon monoxide to carbon dioxide at ambient temperature.

3. The activated carbon has a density of 0.4 to 0.5 g cm －３ 3. The device according to claim 1 or 2, having a density of

4. 4. Apparatus according to any one of claims 1 to 3, further comprising a regulator and / or a counter for monitoring gas usage from the apparatus.

5. A kit comprising a device according to any one of claims 1 to 4 together with a mask, a mouthpiece and / or a nosepiece.

6. The kit of claim 5 further comprising a connector.

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