Halocarbon capture and recycling methods and systems

Abstract

A process for recovery of at least one gas bound to a material from the material, wherein the process comprises exposing the material to heat, reduced pressure and a purge flow in a chamber, to separate the gas bound to a material into a mixture of recovered gases and a degassed residual material.

Description

[0001] HALOCARBON CAPTURE AND RECYCLING METHODS AND SYSTEMS

[0002] Technical Field

[0003] The present invention relates to methods and systems for capturing and recycling halocarbons. In particular, the present invention relates to methods and systems for capturing and recycling halocarbons when used as volatile anaesthetic agents in medical environments.

[0004] A halocarbon is an organic chemical molecule composed of at least one carbon atom bound covalently with one or more halocarbon atoms. Halocarbons have many uses and are used in several industries as solvents, pesticides, refrigerants, fire-resistant oils, ingredients of elastomers, adhesives and sealants, electrically insulating coatings, plastics and anaesthetics. An alternative term for halocarbons is “halogenated fluorocarbons”.

[0005] Examples of halocarbons which are used as anaesthetic agents typically include desflurane, isoflurane, sevoflurane, halothane and enflurane. These anaesthetics may be referred to as volatile anaesthetic agents because they are liquid at room temperature but evaporate easily to produce a vapour for inhalation by a patient to induce anaesthesia. These agents are administered to patients using the breathing circuit of an anaesthetic machine, also known as a Boyle’s machine. Such anaesthetic machines are well known and will not be described further here. Our earlier application, WO 2016 / 027097, incorporated herein by reference in its entirety and to which further reference should be made, discusses an exemplary anaesthetic machine in detail.

[0006] As discussed in WO 2016 / 027097, gases exhaled by an anaesthetised patient include a portion of the anaesthetic agent that has not been absorbed by the patient. Excess waste gas is vented from the apparatus. The vented waste gas will contain at least trace amounts of unused anaesthetic agent vapour. Even trace amounts of anaesthetic in the air in a medical environment will have an effect on medical staff, continued exposure to which will cause adverse health conditions, such as headache, increased incidence of spontaneous abortion, congenital anomalies in babies and haematological malignancy. Accordingly, governmental agencies have set limits on the level of volatile anaesthetic agent that hospital staff may be exposed to. In the USA the level of volatile anaesthetic agent in the air of an operating theatre should not exceed 2 parts per million (ppm), and the level of N2O should not exceed 25ppm. The limit set for volatile agent in the UK is 50ppm, and for N2O the limit is set at 10Oppm.

[0007] In order to ensure that the environment within operating theatres and other medical environments stay within the above limits, the waste gas containing volatile anaesthetic agent vapour is prevented from entering the atmosphere of medical environments. To prevent the release of anaesthetic gases into the atmosphere of an operating theatre, in most developed countries, the waste anaesthetic gas is “scavenged” from the exhaust gas, typically by passing the waste gases through a canister containing activated charcoal. Such charcoal canisters are typically able to absorb twelve hours of waste gas. However, activated charcoal canisters, once used, have not been able to be recycled. Disposal is costly and volatile anaesthetic agent captured by the activated charcoal canisters may be slowly released after disposal.

[0008] In WO 2016 / 027097, we propose an alternative method and system for batch recovery of halocarbons from a gas. The method involves capturing halocarbons from the halocarbon-containing gas with an aerogel material and recovering the halocarbons from the aerogel material under supercritical CO2 conditions such that captured halocarbons are dissolved into the supercritical fluid to form a supercritical solution. The dissolved halocarbon may then be readily separated from the supercritical solution.

[0009] The system and method of WO 2016 / 027097 provides an advantageous procedure for recovery of halocarbons. However, the step of recovering the halocarbons from the aerogel material operates on a batch basis. A continuous or semi-continuous process, and associated systems, would be advantageous. It is with this objective in mind that the present invention has been devised.

[0010] Accordingly, in its broadest sense, in a first aspect, the present invention provides a process for recovery of at least one gas bound to a material from the material, wherein the process comprises exposing the material to heat, reduced pressure and a purge flow in a chamber, to separate the gas bound to a material into a mixture of recovered gases and a degassed residual material.

[0011] In some embodiments, the chamber is an elongate chamber and has a material inlet for introduction of material to the chamber and a material outlet for egress of processed material from the chamber, the inlet and outlet defining a material flow-path therebetween.

[0012] In certain embodiments, the material flow path includes a conveyor for transporting material along the material flow-path, optionally a belt conveyor or a screw conveyor. In some examples, the conveyor is a screw conveyor and the step of exposing the material to heat comprises providing an actively heated screw flight.

[0013] In some embodiments, the chamber includes a purge inlet operatively coupled to a source of humidified air or humidified nitrogen providing a purge flow; and a purge outlet attached to a source of reduced pressure, wherein the purge inlet and purge outlet define a purge flow flow-path therebetween; and wherein the purge flow acquires gases released from the material.

[0014] Advantageously, the purge flow flow-path has an opposite flow direction to a flow direction of the material flow path. Advantageously, the purge flow has a pressure of 100mbar or lower or a pressure of from 50 mbar to 100 mbar.

[0015] Advantageously, the material is exposed to heat at a temperature of from 100°C to 200°C, from 120° to 160°C or about 150 °C.

[0016] In some examples, the chamber has a substantially constant temperature along the material flow path.

[0017] In other examples, the chamber is heated to provide a temperature gradient along the material flow path.

[0018] In some embodiments, the purge flow is flowed from the purge outlet to a heat exchanger to condense the mixture of recovered gases.

[0019] In some embodiments, the chamber includes a housing, wherein the housing is manufactured from a non-magnetic material and the step of heating is provided by an induction heating step.

[0020] In a second aspect, the present invention provides a process for the purification and / or separation of a mixture of gases, the process comprising the steps of: alkaline extraction; membrane separation; and distillation. Optionally, the mixture of gases is obtained by a process as defined above for the first aspect of the invention.

[0021] In one embodiment, the steps are carried out in the sequence of alkaline extraction; membrane separation; and distillation.

[0022] In a further embodiment, the steps are carried out in the sequence of distillation; alkaline extraction; and membrane separation.

[0023] In some examples, the alkaline extraction step uses an aqueous alkaline solution, optionally an aqueous hydroxide solution, optionally comprising a solution of at least one of potassium hydroxide and sodium hydroxide.

[0024] In certain examples, the aqueous hydroxide solution has a concentration of 0.2 M or lower; or between 0.01 M and 0.1 M.

[0025] In some embodiments, the aqueous alkaline solution and mixture of gases are mixed within a mixing vessel for a period of 5 minutes or less prior to the step of membrane separation. In certain examples, a plurality of mixing vessels are arranged in series, wherein the mixture of gases is caused to flow from one mixing vessel to an adjacent mixing vessel in a gas flow direction; and wherein an aqueous alkaline solution is caused to flow from one mixing vessel to an adjacent mixing vessel in a direction opposite to the gas flow direction.

[0026] In some embodiments, the aqueous alkaline solution and mixture of gases are mixed using inline mixing elements fitted within flexible hosing arranged as coils and having a length sufficient to provide a predetermined residence time.

[0027] In some examples, a plurality of inline mixing elements are arranged in series, wherein an aqueous alkaline solution is caused to flow in a direction opposite a direction of gas flow through the series of inline mixing elements.

[0028] The membrane separation uses, in some examples, a hydrophobic separation membrane.

[0029] In some embodiments, the distillation is carried out using a distillation column containing adsorption materials selected to have a binding preference for the highest boiling material component of the mixture of gases.

[0030] The adsorption material, in some examples, is at least one material selected from activated carbon, modified activated carbons, silica gels, zeolites, zeolitic-imidazolate frameworks, structured covalent organic frameworks and functionalised polymers.

[0031] In a third aspect, the present invention provides an apparatus for recovery of at least one gas bound to a material from the material, the apparatus comprising a recovery chamber for exposing the material to heat and reduced pressure and for providing a purge flow in a chamber, to separate the gas bound to a material into a mixture of recovered gases and a degassed residual material.

[0032] In some embodiments, the chamber is an elongate chamber and has an material inlet for introduction of material to the chamber and a material outlet for egress of processed material from the chamber, the inlet and outlet defining a material flow-path therebetween.

[0033] In certain examples, the material flow path includes a conveyor for transporting material along the material flow-path.

[0034] Optionally, the conveyor is a belt conveyor or a screw conveyor. In one example, the conveyor is a screw conveyor and the step of exposing the material to heat comprises providing an actively-heated screw flight. In some embodiments, the chamber includes a purge inlet operatively coupled to a source of humidified air or humidified nitrogen providing a purge flow; and a purge outlet attached to a source of reduced pressure, wherein the purge inlet and purge outlet define a purge flow flow-path therebetween; and wherein the purge flow acquires gases released from the material.

[0035] Optionally, the purge flow flow-path is configured to have an opposite flow direction to a flow direction of the material flow path.

[0036] In certain examples, the purge flow has a pressure of 50 mbar to 100 mbar

[0037] In certain examples, the apparatus applies heat to the material at a temperature of from 100°C to 200°C, from 120° to 160°C or about 150 °C.

[0038] In some embodiments, the chamber provides a substantially constant temperature along the material flow path.

[0039] In other embodiments, the chamber is heated to provide a temperature gradient along the material flow path.

[0040] In certain embodiments, the purge flow is flowed from the purge outlet to a heat exchanger to condense the mixture of recovered gases.

[0041] In some embodiments, the chamber includes a housing, wherein the housing is manufactured from a non-magnetic material and heating is provided by an induction heating step.

[0042] In a fourth aspect, the present invention also provides a process for the separation of a mixture of gases, the process comprising the steps of: i) providing a mixture of gases; ii) cooling the mixture of gases by means of a first condensing unit to a first temperature, wherein the first temperature is a temperature at which a first gas of the mixture of gases condenses in a first vessel; iii) collecting the condensed first gas; iv) passing uncondensed gases to a second condensing unit and cooling the uncondensed gases to a second temperature, lower than the first temperature, at which a second gas of the mixture of gases condenses; and v) collecting the condensed second gas in a second vessel.

[0043] In some embodiments, the mixture of gases is obtained by a process as defined above in respect of the first aspect of the present invention.

[0044] In some embodiments, the process further comprising a step of passing uncondensed gases from the second vessel to a third condensing unit and cooling the gases to a third temperature, lower than the second temperature, at which a third gas of the mixture of gases condenses, and a step of collecting condensed third gas in a third vessel.

[0045] In some examples, the mixture of gases is a mixture comprising at least two of sevoflurane, isoflurane and desflurane; the first temperature is a temperature in the range of 0 to 5 °C, the second temperature is in the range of 0 to -10 °C; and the third temperature is in the range of -10 to 20 °C.

[0046] In some examples, a process of the fourth aspect of the present invention is followed by a process of the second aspect of the present invention. .

[0047] In a fifth aspect, the present invention provides an apparatus for the separation of a mixture of gases by the process of the fourth aspect of the present invention, wherein the apparatus comprises a first condensing unit in fluid communication with a first vessel; a second condensing unit in fluid communication with the first vessel and with a second vessel; and a third condensing unit in fluid communication with the second vessel and with a third vessel, wherein the second condensing unit operates at a second temperature that is lower than a first temperature at which the first condensing unit operates and wherein the third condensing unit operates at a third temperature that is lower than the second temperature.

[0048] In some embodiments, the first temperature is a temperature in the range of 0 to 5 °C, the second temperature is in the range of 0 to -10 °C; and the third temperature is in the range of -10 to 20 °C.

[0049] In certain embodiments, each vessel includes an upper float switch or sensor and a lower float switch or sensor, and wherein each vessel further includes a pump or valve for removal of condensed fluid within the vessel; wherein the pump is operated or the valve is opened in response to the upper float switch or sensor detecting an upper level for the condensed fluid and wherein the pump is stopped or the valve is closed in response to the lower float switch or sensor detecting a lower level for the condensed fluid in the vessel.

[0050] Further aspects of the invention are discussed further below.

[0051] The combination of the aspects of the invention enables halocarbon to be continuously recycled. In a medical environment, the halocarbon may be anaesthetic agent, which may be a volatile anaesthetic agent, and the invention enables the anaesthetic agent to be recycled and reused.

[0052] The methods and systems of the present invention take, as their starting material, a material comprising a substrate, typically a filter material, onto or into which one or more halocarbons have been adsorbed or absorbed. For example, in preferred examples, the starting material will be activated carbon or a material as described in WO 2016 / 027097. The material may be or comprise aerogel. The most common aerogel is made of silicon dioxide (SiC>2), but aerogels may be made from or comprise other materials, for example, resourcinol formaldehyde, carbon, calcium carbonate and zeolite (aluminosilicate). Zeolites are micro-porous alumina silicate minerals found naturally but may also be made artificially. Carbon may be exposed to high temperatures to expand its surface area for absorption. The filter material may be doped with a metal. The aerogel may be functionalised by the addition of one or more of halocarbon, metal oxide, cellulose, carbon nanotubes, or internally supported by polymers to improve their chemical or mechanical properties. These changes may improve the binding of halocarbons and / orthe stability of the aerogel. For example, functionalisation with halocarbon improves the binding of halocarbon to the material. The material may comprise granular particles.

[0053] Furthermore, the material may comprise or be a metal or metal oxide which may be formed by forming metal-oxygen-metal bridges. Examples include nickel oxide, molybdenum oxide, alumina, titania, zirconia, iron oxide, chromia, vanadia, platinum, rhodium, palladium and tungsten. The material may comprise or be a precious metal. A metal and / or a metal oxide may be added by deposition to the material, for example by physical or chemical vapour phase deposition.

[0054] The materials onto or into which the halocarbon is captured will not be described in further detail.

[0055] In the aspects described above, the one or more halocarbons may be one or more anaesthetic agents. The one or more anaesthetic agents may be one or more volatile anaesthetic agents. The one or more halocarbons may also be industrial halocarbons used or produced by industrial processes.

[0056] The separating system may comprise monitoring means for monitoring the product produced by the separating means. The monitoring means may comprise an infrared spectroscopy sensor. The infrared spectroscopy sensor may be a Fourier transform infrared spectroscopy device. Alternative monitoring means and methods include mass spectroscopy, UV detection, Raman spectroscopy, Acoustic resonance spectroscopy and piezoelectric crystal resonance.

[0057] Preferably, the system may comprise a controller for controlling the output of the separating means, wherein the controller may direct the output of the separating means to a collection module if the product contains halocarbon. The collection module may be arranged to separate one or more of the halocarbon types. The system may comprise a collection module control means for controlling the input of product into the collection module. The system may comprise a collection module monitoring means for monitoring the halocarbon type entering the collection module. The collection module monitoring means may comprise an infrared spectroscopy sensor. The infrared spectroscopy sensor may be a Fourier transform infrared spectroscopy device. The collection module may comprise at least one cyclonic collector. The aspects of the invention are interrelated to provide apparatus and methods which improve the reuse of halocarbons in the medical and industrial sectors.

[0058] Further aspects and embodiments are listed in the following numbered paragraphs.

[0059] 1. A process for the extraction of mixed anaesthetic gasses bound to a filter material by exposing the filter material to heat, vacuum and intermittent purge flow.

[0060] 2. A method as described by claim 1 whereby vacuum is provided to the system utilising a dry sealed pump such as scroll or roots blower type pumps.

[0061] 3. A method as described by claim 1 whereby the vacuum chamber contains a horizontal conveyor such as a belt or screw conveyor.

[0062] 4. A method as described by claim 1 whereby the normal operating temperature of the vacuum chamber is 150C.

[0063] 5. A method as described by claim 1 where a purge flow of humidified air is provided counter- currently to the material's horizontal movement within the chamber.

[0064] 6. A method as described by claim 1 where the purge flow is provided at a pressure no higher than lOOmbar.

[0065] 7. A method as described by claim 1 where the feed hopper and the outlet of the system have an airlock installed to allow material to be continuously fed and removed from the system during operation.

[0066] 1 A. A process for the extraction of mixed anaesthetic gasses bound to a filter material by exposing the filter material to heat, vacuum and intermittent purge flow.

[0067] 2A. A method as described in claim 1 A where the feed hopper is designed to provide material feed to multiple extraction chambers.

[0068] 1B. A method whereby the extracted gasses are passed through a heat exchanger to recover the extracted anaesthetic gasses.

[0069] 2B. A method as described in claim 1 B where the conveyor type is a screw conveyor with an actively heated screw flight. 3B. A method as described by claim 1 B where the conveyor housing is manufactured from non magnetic materials allowing the direct heating of the capture material by induction rather than conduction.

[0070] IC. A process for the purification of mixed anaesthetic gasses extracted a filter material by combining the mixed anaesthetic agents with hydroxide solutions to target selected contaminants before separating the biphasic mixture by membrane separator and performing a hybrid adsorption distillation to separate the anaesthetic agents.

[0071] 2C. A method as described in claim 1C where the hydroxides mixed with the anaesthetic agents is specified to be either sodium hydroxide or potassium hydroxide.

[0072] 3C. A method as described in claim 1C where the concentration of the hydroxide treatment solution is between 0.01-0.1 M but not exceeding 0.2M.

[0073] 4C. A method as described in claim 1C where the aqueous hydroxide solution and the anaesthetic agent are mixed within a mixing tank for a fixed time of no more than 5 minutes per stage before passing the mixture across a membrane separator.

[0074] 5C. A method as described in claim 1C where there are a multiplicity of mixing tanks and separators arranged in series with wash solution being cycled counter-currently to the anaesthetic flow within the system.

[0075] 6C. A method as described in claim 1C where the aqueous hydroxide solution and the anaesthetic agent mixture are mixed using inline mixing elements fitted within flexible hosing arranged as coils whose length is sufficient to provide the required mixing residence time.

[0076] ID. A process for the purification of mixed anaesthetic gasses extracted a filter material by combining the mixed anaesthetic agents with hydroxide solutions to target selected contaminants before separating the biphasic mixture by membrane separator and performing a hybrid adsorption distillation to separate the anaesthetic agents.

[0077] 2D. A method as described in claim 1 D where there are a multiplicity of inline mixing coils and separators arranged in series; with the hydroxide wash solution flowing counter-currently through the system to the anaesthetic agent

[0078] 3D. A method as described in claim 1 D where the separation membrane installed within the unit is hydrophobic. 4D. A method as described in claim 1 D where the distillation column contains an adsorption materials whose binding preference is for the highest boiling point component of the mixture.

[0079] 5D. A method as described in claim 1 D where the adsorption material is one of the following; activated carbon, modified activated carbons, silica gels, zeolites, zeolitic-imidazolate frameworks, structured covalent organic frameworks, functionalised polymers such as styrenes etc.

[0080] It is to be appreciated that one or more of the aspects, embodiments and features of any of the above aspects or embodiments of the invention may be readily combined, as will be readily apparent to the skilled person. Furthermore, the forgoing advantages may relate to more than one aspect of the present invention.

[0081] Brief Description of the Drawings

[0082] The above and other aspects of the invention will now be described in further detail, by way of example only, with reference to the accompanying drawings, in which:

[0083] Figure 1 is a flow diagram illustrating a first embodiment of a recovery process in accordance with the present invention;

[0084] Figure 2 is a flow diagram illustration a second embodiment of a recovery process in accordance with the present invention;

[0085] Figure 3 is a schematic view of a first embodiment of a desorption apparatus in accordance with the present invention;

[0086] Figure 4 is a schematic view of a second first embodiment of a desorption apparatus in accordance with the present invention;

[0087] Figure 5 is a graph comparing distillation recovery rates using active distillation column packing with recovery rates using inert distillation column packing;

[0088] Figure 6 shows bar charts comparing adsorption performance for a range of active column packing materials;

[0089] Figure 7 is a bar chart showing the results for methanol extraction for a range of hydroxide concentrations in an embodiment of the alkaline wash process of the present invention; Figure 8 is a bar chart showing the results for acetone extraction for a range of hydroxide concentrations in an embodiment of the alkaline wash process of the present invention;

[0090] Figure 9 is a bar chart showing the results for HFIP extraction for a range of hydroxide concentrations in an embodiment of the alkaline wash process of the present invention;

[0091] Figure 10 is a schematic view of an embodiment of a distillation configuration in accordance with the present invention;

[0092] Figure 11 is a schematic view of an embodiment of a multi-stage condensation process in accordance with the present invention; and

[0093] Figure 12 is a schematic side view showing details of a vessel of the embodiment of Figure 11.

[0094] Detailed Description

[0095] In the drawings like or equivalent components are assigned the same numerals.

[0096] The methods and systems of the present invention take, as their starting material, a material comprising a capture substrate, typically a filter material, onto or into which one or more halocarbons have been adsorbed or absorbed. For example, in preferred examples, the capture substrate will be activated carbon or a material as described in WO 2016 / 027097. The substrate may be or comprise an aerogel. The most common aerogel is made of silicon dioxide (SiC>2), but aerogels may be made from or comprise other materials, for example, resourcinol formaldehyde, carbon, calcium carbonate and zeolite (aluminosilicate). Zeolites are micro-porous alumina silicate minerals found naturally but may also be made artificially. Carbon may be exposed to high temperatures to expand its surface area for absorption. The capture substrate may be doped with a metal. The aerogel may be functionalised by the addition of one or more of halocarbon, metal oxide, cellulose, carbon nanotubes, or internally supported by polymers to improve their chemical or mechanical properties. These changes may improve the binding of halocarbons and / or the stability of the aerogel. For example, functionalisation with halocarbon improves the binding of halocarbon to the capture substrate. The capture substrate may be in the form of granular particles.

[0097] Furthermore, the capture substrate may comprise or be a metal or metal oxide which may be formed by forming metal-oxygen-metal bridges. Examples include nickel oxide, molybdenum oxide, alumina, titania, zirconia, iron oxide, chromia, vanadia, platinum, rhodium, palladium and tungsten. The capture substrate may comprise or be a precious metal. A metal and / or a metal oxide may be added by deposition to the substrate, for example by physical or chemical vapour phase deposition. The substrate materials onto or into which the halocarbon is captured will not be described in further detail.

[0098] Example processes of the present invention and associated apparatus will now be described in further detail.

[0099] A first example of a process in accordance with the present invention is set out in Figure 1. A second example is illustrated in Figure 1. In a first step, capture step 100, the desired recovery gas, typically a halocarbon or mixture of halocarbons, is captured onto a capture substrate. Suitable processes for capture of the gas are set out in WO 2016 / 027097 and will not be described here in further detail.

[0100] As discussed in WO 2016 / 027097, the gas is captured, on site, such as in an operating theatre or within the premises in which the gas is being used, in a canister which houses a quantity of the capture substrate. Following use of the canisters to capture the gases, a plurality of canisters are emptied to provide a bulk material 101 which is fed to an desorption apparatus, in the form of a conveyor extractor 102 to cause desorption of materials bound to the capture substrate 104, under heating and reduced pressure conditions. The desorbed materials comprise a mixture of polar materials 103, including the target halocarbon gas.

[0101] The mixture of polar materials, includes the target halocarbon or halocarbons, such as Isoflurane and Sevoflurane, together with other contaminating chemicals having similar boiling points, such as methanol, ethanol, acetone and hexafluoro-2-propanol.

[0102] The mixture of polar materials is subjected to a processing routine 110 comprising steps of alkaline extraction 105, membrane separation 106 and distillation 107 to isolate the desired target halocarbon or mixture of halocarbons 108. Contaminants separated at the membrane separation 106 and distillation 107 steps are removed 111 , suitably by combination with the separated capture carrier substrate 104 and subjected to an incineration or disposal step 109.

[0103] In the first process (Figure 1 ), the processing routine 110 comprises the steps, in sequence, of alkaline extraction 105, membrane separation 106 and distillation 107. In the second process (Figure 2), the processing routine 110 comprises the steps, in sequence, of distillation 107, alkaline extractions and membrane separation 106.

[0104] Individual steps of the process will now be described in further detail before continuing with the discussion of the processes of the present invention.

[0105] Desorption apparatus The desorption apparatus is configured to provide a generally horizontal pathway along which the accumulated bulk material passes whilst being subjected to heating in the presence of a counter- currently flowing humidified purge flow under vacuum.

[0106] A first embodiment of a desorption apparatus in accordance with the present invention is illustrated in Figure 3, in the form of a belt conveyor system 120. Belt conveyor system 120 includes an desorption chamber 121 having an inlet 122 for receipt of the bulk material and an outlet 123 for removal of processed bulk material, defining a material flow path therebetween. Bulk material flows between the inlet 122 and the outlet 123 by means of a motor-driven belt conveyor 124. Accordingly, it will be understood that the bulk material flows from right to left, as viewed in Figure 3.

[0107] Material inlet 122 is provided with bulk material in a conventional manner, which may include a hopper 125 and a material inlet valve arrangement 126 of material inlet valves (MIV) and inlet breather valves (IBV) to regulate and maintain an appropriate flow of material to be processed into the desorption chamber 121.

[0108] Material outlet 123 is similarly fitted with a material outlet valve arrangement 127 of material outlet valves (MOV) and outlet breather valves (OBV) to regulate and maintain an appropriate flow of material from the desorption chamber 121 for recovery and disposal or recycling.

[0109] Material inlet valve arrangement 126 and material outlet valve arrangement 127 are operable to provide an airlock to allow material to be fed continuously into and removed continuously out from the system during operation.

[0110] As discussed above, a humidified purge flow is provided within the desorption chamber 121, flowing with an opposite direction to the flow of bulk material. In the embodiment shown, this is provided by means of a purge flow inlet 130 from a purge inlet valve (PIV) 131 at the bulk material outlet 123 end of the extraction chamber and a purge flow outlet 132 upstream (with respect to the flow of the bulk material) from the bulk material inlet 122.

[0111] Purge flow outlet 132 is in fluid communication with a vacuum pump 133, to generate the counterflow of the humidified purge flow in the desorption chamber 121. Vacuum pump 133 outflows the purge flow to an extraction condenser unit 134 to condense the purge flow material and entrained polar materials recovered from the bulk material as it passes along the material flow path.

[0112] The vacuum pump typically operates within the range of 0.05 to 10 mbar and is suitably a dry-sealed pump, such as scroll or roots blower type pump. Chamber 121 includes a heating arrangement to enhance separation of the polar materials from the carrier substrate. In some examples, the heating arrangement is a conductive heating system, which may include a heating mat within the chamber. In other examples, the heating arrangement is a direct inductive heating arrangement.

[0113] The chamber is typically heated to a temperature of between 100°C and 200°C, more specifically, between about 120°C and about 150 °C.

[0114] Chamber 121 also includes appropriate sensors, such as a thermocouple 135 and pressure transducer 136 to provide data to a control system for the apparatus (not shown). The control system uses the data to control the rates of flow of bulk material and humidified purge flow through the extraction chamber 121.

[0115] A second embodiment of a desorption apparatus in accordance with the present invention is illustrated in Figure 4. Where components are the same as with the first embodiment of Figure 3, those components have the same reference numbers or are omitted for clarity.

[0116] The desorption apparatus 140 includes a desorption chamber 141 in the form of an Archimedian screw conveyor arrangement, having a motor-driven, elongate screw body 142 closely fitted within a desorption chamber housing 143 and including an inlet 122 through which bulk material is introduced into the desorption chamber 141 and an outlet 123 from which processed material is removed from the extraction chamber 141.

[0117] Desorption chamber housing 143 is provided with a humidified purge flow inlet 130 and a purge flow outlet 132 coupled to a vacuum pump and extraction condenser unit (omitted for clarity) as described above with respect to the embodiment of Figure 3.

[0118] Purification

[0119] In the first example process, shown in Figure 1 , The raw extracted product 103 from desorption condenser unit 134 is mixed with an aqueous alkaline solution. The contaminants partition into the aqueous phase. Mixing of the two phases may take place in any suitable environment, such as a static mixing tank or, in certain preferred embodiments, in one or more mixing coils comprising tubing housing inline mixing elements.

[0120] In preferred embodiments, mixing is carried out by a multiplicity of mixing coils and separators in which the hydroxide wash solution is fed counter-currently through the system to the direction of flow of the halocarbon mixture. The resultant biphasic mixture of washed mixed halocarbons and the aqueous phase containing the extracted contaminants are subjected to the membrane separation step 106 by being passed across a hydrophobic membrane separator. The organic phase is passed directly to the distillation stage 107 or to an intermediate holding vessel.

[0121] In the second example process, shown in Figure 2, the raw extracted product 103 from the desorption condenser unit 134 is subjected to the distillation process 107 prior to the alkaline extraction step 105, followed by membrane separation.

[0122] In each process, at the end of the distillation process, the distillation column was brought under vacuum, with heating, to regenerate the column and drive off any remaining halocarbons remaining in the system, for recovery and return to a subsequent distillation process.

[0123] Intermediate purification

[0124] In certain embodiments, desorption condenser unit 134 is formed, as shown in Figure 11 , as a multistage condensing unit comprising a plurality 150 of condensing units arranged in a series configuration in which each condensing unit in the series is set at a lower temperature to the immediately preceding condensing unit. In the embodiment shown, a first condensing unit 151 is downstream of vacuum pump 133 and is set at a temperature of 1 °C, selected for condensing sevoflurane. Non-condensed gases pass to second condensing unit 152, set at a temperature of -6 °C, for condensing isoflurane, and noncondensed gases from second condensing unit 152 pass to third condensing unit 153, at a temperature of -20 °C, for condensing desflurane.

[0125] This initial separation of anaesthetic agents from each other, increases efficiency and reduces downstream energy input from the purification processes.

[0126] Each of the plurality of condensing units 151 , 152, 153, includes an associated storage vessel 160 (Figure 12) held at 30 °C. Each storage vessel 160 includes a feed inlet line 161 extending to a position adjacent a bottom of the vessel and having an opening at its lower end, and a gas outlet line 162 having an opening located higher up the in the container.

[0127] An outflow from first condensing unit 151 is passed to associated vessel 160. Condensed product 163 accumulates in the vessel. Uncondensed product passes out of gas outlet line 162 to the second condensing unit. As the volume of condensed product increases, uncondensed components of the outflow from the first condensing unit are bubbled through the accumulated condensed product 163. Bubbling gas at the controlled temperature points selectively revapourises the lighter components of the mixture (isoflurane and desflurane) which passes from the vessel associated with the first condensing unit 151 to the second condensing unit 152, where the procedure is repeated, with collection of isoflurane and revapourisation of desflurane to the third condensing unit 153. The liquid level within each vessel can be controlled by providing a lower float switch 164 to maintain a minimum volume of liquid within the vessel, and positioned at a location above the opening of the feed inlet line 161. An upper float switch 165 is provided below the opening of the gas outlet line 162, which triggers operation of a valve and / or pump arrangement (not shown) for removal of accumulated condensed product 163 from the vessel.

[0128] By introducing a series of temperature controlled, semi-flooded product vessels and forcing the gas stream to bubble through liquid within the vessels, the lighter components of the mixture (principally Desflurane and Isoflurane) can be revapourised passed along the system to the next series of cooled vessel for the same bubble vaporisation fractionation process. This yields three separate vessels containing product, each vessel being enriched in the target component for that vessel.

[0129] Aqueous alkaline solution

[0130] Suitably, the alkaline solution is an aqueous solution containing a low concentration of hydroxide salts (suitably sodium hydroxide or potassium hydroxide, or a mixture of the two hydroxides). The aqueous hydroxide solution suitably has a concentration of 0.2 M or lower. Advantageously, the aqueous hydroxide solution has a concentration of between 0.01 M and 0.1 M.

[0131] We have determined that favourable results can be obtained if this stage of the process is carried out at a temperature of from 1°C to 10°C, optimally at about 5°C. Within this temperature range, efficient extraction of the aqueous-based contaminants is achieved whilst minimising the volume of Sevoflurane which partitions into the aqueous layer, thereby optimising yield.

[0132] A series of trials were carried out based a standardised mixture of 98.57% of sevoflurane spiked with ethanol, acetone and hexafluoro-2-propanol (HFIP) in an amount of between 1 ,500 to 2,000 ppm of sevoflurane. Sodium hydroxide was used as the alkaline solution at concentrations of 0.0M, 0.01 M, 0.02M, 0.05M, 0.1 M, 0.2M, 0.5M and 1 M and the spiked sevoflurane samples were mixed with the alkaline solution in a 1 : 1 ratio in a mixing tube with a residence time of 3 minutes. The treatment stream was then separated using a SEP-10 separator (Zaiput Flow Technologies). Each sample was passed through the process three times, with samples taken of each step in the process. Samples were analysed by GC-FID to monitor how the peak areas of the contaminants changes throughout the treatment process. The results are shown in Figures 7 to 9 and in Table 1 below.

[0133] TABLE 1 The results can be summarised as follows:

[0134] Methanol extraction (Figure 7)

[0135] Across the range of treatment concentrations, methanol was removed effectively, with only the 0.05M treatment concentration showing any methanol remaining post-treatment. Concentrations in the range of 0.2M to 1 M appear to be the most effective for removal of methanol.

[0136] Acetone extraction (Figure 8)

[0137] Across the range of treatment concentrations, acetone extraction was demonstrated, but at lower levels than for methanol. A concentration of 0.01 M showed enhanced acetone extraction.

[0138] For comparison, a sample was also subjected to the same process using 1 M NaHCOs. The NaHCOs- treated sample demonstrated a 62% reduction in acetone concentration, compared with 0.1 M NaOH, which demonstrated a total 43% reduction in acetone concentration.

[0139] HFIP extraction (Figure 9)

[0140] Across the range of treatment concentrations, HFIP was removed from the spiked samples effectively. 0M NaOH (deionised water) performed the least favourably of the tested concentrations; and concentrations in the range of 0.05M - 0.1 M appear to be most effective for removal of HFIP from spiked hospital samples.

[0141] Distillation

[0142] In preferred examples, distillation of the polar mixture from which the object halocarbons are to be separated is carried out in a distillation column provided with a structured packing material to increase mass transfer within the column by increasing surface area. Whilst inert packing materials such as inert steel or ceramic structures are suitable, an active packing material, such as a molecular sieve material, is preferable. The benefit is two-fold. Molecular sieves have a significantly higher surface area per unit volume than inert structured packing and the molecular sieve can be specifically selected to target the highest boiling component of the solution, thereby increasing the separation efficiency of the distillation process.

[0143] In laboratory trials, a distillation column having an active packing material of an active packing material was compared with an inert packing material of inert glass. The results for sevoflurane purity are shown in Figure 5 and in T ables 2 and 3 below, together with values for desflurane and isoflurane, from which it can be seen that complete recovery of the target halocarbon was achieved much more quickly with an active packing material.

[0144] TABLE 2

[0145] Inert glassware distillation

[0146] TABLE 3

[0147] Active packed distillation Several active packing materials were assessed, including Activated Carbon A (a 1150 mm column), Activated Carbon B (1450 mm), Activated Carbon B (300 mm), Ion Exchange Resin (1150 mm), Type X Zeolite (1150 mm) and activated carbon (500 mm), against Type A Zeolite (1150 mm) and an inert column. The results are shown in Figure 6 showing maximum percentage purity (left hand graph) and average percentage purity over repeated runs (right hand graph).

[0148] An example distillation system is illustrated in Figure 10 and forms another aspect of the present invention. The system 200 includes a distillation column 201 which, in certain embodiments, is a multisection distillation column. In the illustrated embodiment, the column has four sections 202, 203, 204, 205. This allows each section to be packed with different functionalised materials, to optimise the separation process. Each section may include a heater to aid regeneration of the column material between purification cycles, as is discussed further, below.

[0149] The column 201 has an inlet manifold 210 fluidly coupled to a boiler 211 in which the mixture to be separated is heated and vapourised. At the top of the column assembly, an outlet manifold 212 couples, via a still head valve 213, outflow from the distillation column to a heat exchanger 220, suitably cooled by glycol, to remove heat from vapours received from the column. The collected fractions are then collected from the heat exchanger in one of a series of receiving vessels 221, each isolatable by means of a respective product flow valve 222. In the illustrated embodiment, three receiving vessels 22T, 221”, 22T” are provided, for receipt of the impure fraction, the pure isoflurane fraction and the pure sevoflurane fraction, for example. A line 223 to which each receiving vessel is fluidly coupled from the heat exchanger 220 is coupled to a guarded vent 224 for scrubbing any uncollected gases from the outlet gas flow, prior to discharge from the system.

[0150] Intermediate still head valve 213 and heat exchanger 220, a reflux line 214 is coupled to the inlet manifold 210 intermediate the boiler 211 and column 201. Reflux line 214 includes a reflux line inlet valve 215 at its upper end and a reflux line outlet valve 216 at its lower end and includes a circulating reflux pump 217 therebetween.

[0151] Outlet manifold 212 is also fluidly coupled to a bypass line 223, bypassing still head valve 213, and including a vacuum inlet valve 224 to a regeneration vacuum pump 225. Outlet manifold 212 and valves 213, 224 allows flow to be directed either to the regeneration vacuum pump 225 or across the still head.

[0152] A plurality of thermocouples are provided along the length of the column 201 to provide temperature monitoring for the column.

[0153] Operation of the system is as follows:

[0154] Stage 1 : System Charging - The boiler 21 is filled with raw anaesthetic agent to the required fill level. The boiler is then secured to the distillation apparatus and the system valves are sealed prior to the start. The chiller attached to the Heat Exchanger 220 is initiated and the condenser system allowed to cool.

[0155] Stage 2: System Heating - The boiler is initiated and boiler outlet valve 230 is opened. Still head valve 213 is opened and both reflux line valves 215, 216 are opened.

[0156] Stage 3: System Reflux - When a thermocouple associated with the head of the column registers a temperature above 35°C, the reflux pump 217 on full flow to initiate full reflux within the column. Stage 4: High Reflux Low Boiling Fraction - When the column head thermocouple registers a stable temperature after a period of full reflux, the reflux pump is slowed to allow the low boiling fraction to pass through to the heat exchanger. First product flow valve 222’ is opened to allow the low boiling fraction to be collected within first receiving vessel 221’.

[0157] Stage 5: High Reflux Isoflurane Fraction - When the column head thermocouple registers that the temperature is stable at 48.5°C following the low boiling fraction pull off, the reflux pump remains engaged at a slowed rate to allow the Isoflurane fraction to pass to the heat exchanger. First product flow valve 221’ is closed and second product flow valve 222” is opened to direct the product to second receiving vessel 221”.

[0158] Stage 6: Medium Reflux Isoflurane Fraction - After about 10 minutes with the column head thermocouple remaining stable at 48.5°C during the Isoflurane fraction pull off, the pump is slowed further still to increase the fraction of product sent across the still head.

[0159] Stage 7: High Reflux Sevoflurane / lsoflurane Slop Fraction - When the temperature at the column head thermocouple begins to rise above 48.5°C, the reflux pump 217 is raised to high reflux and the second product flow valve 222” is closed. First product flow valve 222’ is reopened opened to direct the Sevoflurane / lsoflurane slop fraction to the first receiving vessel 221’.

[0160] Stage 8: High Reflux Sevoflurane Fraction - When the temperature at the column head thermocouple begins to stabilise at 58.5°C following the slop cut fraction pull off, first product flow valve 222’ is closed and third product flow valve 222’” is opened to direct the pure Sevoflurane fraction into third receiving vessel 221’”.

[0161] Stage 9: Low Reflux Sevoflurane Boil Up - Following 10 minutes of high reflux Sevoflurane fraction pull off, the pump rate is slowed to reduce the reflux and complete the boil up of the Sevoflurane within the system.

[0162] Stage 10: Column Heating - Once the boiler column has reached a state of infinite reflux, where there is insufficient anaesthetic volume within the system for further product to pass across the still head, whilst active reflux remains within the column and boil pot, the heater within the boiler 211 is disengaged and the liquid holdup within the system is allowed to drain for 10 minutes.

[0163] The reflux line valves 215, 216 are closed, together with still head valve 213. The regeneration vacuum valve 224 is opened and the pump 225 is engaged to bring the column down to vacuum pressure. Once a suitable level of vacuum pressure has been obtained, the column heaters, where provided, are engaged.

[0164] Stage 11 : Column Regeneration - Heaters in the column sections are allowed to reach 150°C and the system is held under vacuum for 12-24 hours in order to regenerate the adsorbent bed. Should the boiler be vacuum-tolerant, the boiler outlet valve 230 may also be opened and the boiler heating element briefly engaged to drive the liquid hold up volume, which was drained earlier, across the column and to the product vessels.

[0165] Stage 12: Column Repressurisation - Following the regeneration phase, the column regeneration vacuum pump 225 is disengaged along with the column heaters and boiler heater where present. Third product flow valve 222”’ is closed along with the vacuum inlet valve 224 and the still head valve 213 is opened to allow pressure to re-enter the column.

[0166] In preferred embodiments, operation of the components of the distillation apparatus is automated by means of a control system taking inputs from the thermocouples and operating the valves and pumps as required.

[0167] The combination of the aspects of the invention enables halocarbon to be continuously recycled. In a medical environment, the halocarbon may be anaesthetic agent, which may be a volatile anaesthetic agent, and the invention enables the anaesthetic agent to be recycled and reused.

[0168] In the aspects described above, the one or more halocarbons may be one or more anaesthetic agents. The one or more anaesthetic agents may be one or more volatile anaesthetic agents. The one or more halocarbons may also be industrial halocarbons used or produced by industrial processes.

[0169] The separating system may comprise monitoring means for monitoring the product produced by the separating means. The monitoring means may comprise an infrared spectroscopy sensor. The infrared spectroscopy sensor may be a Fourier transform infrared spectroscopy device. Alternative monitoring means and methods include mass spectroscopy, UV detection, Raman spectroscopy, Acoustic resonance spectroscopy and piezoelectric crystal resonance.

[0170] The system may comprise a controller for controlling the output of the separating means, wherein the controller may direct the output of the separating means to a collection module if the product contains halocarbon. The collection module may be arranged to separate one or more of the halocarbon types. The system may comprise a collection module control means for controlling the input of product into the collection module. The system may comprise a collection module monitoring means for monitoring the halocarbon type entering the collection module. The collection module monitoring means may comprise an infrared spectroscopy sensor. The infrared spectroscopy sensor may be a Fourier transform infrared spectroscopy device. The collection module may comprise at least one cyclonic collector.

[0171] The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims, which follow. Furthermore, features of one or more of the above embodiments may be readily combined with one or more features of another embodiment. It is also contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the scope of the invention as defined by the claims.

Claims

CLAIMS1. A process for recovery of at least one gas bound to a material from the material, wherein the process comprises exposing the material to heat, reduced pressure and a purge flow in a chamber, to separate the gas bound to a material into a mixture of recovered gases and a degassed residual material.

2. A process as claimed in claim 1 wherein the chamber is an elongate chamber and has an material inlet for introduction of material to the chamber and a material outlet for egress of processed material from the chamber, the inlet and outlet defining a material flow-path therebetween.

3. A process as claimed in claim 2 wherein the material flow path includes a conveyor for transporting material along the material flow-path; optionally wherein the conveyor is a belt conveyor or a screw conveyor, further optionally wherein the conveyor is a screw conveyor and the step of exposing the material to heat comprises providing an actively heated screw flight.

4. A process as claimed in any preceding claim wherein the chamber includes a purge inlet operatively coupled to a source of humidified air or humidified nitrogen providing a purge flow; and a purge outlet attached to a source of reduced pressure, wherein the purge inlet and purge outlet define a purge flow flow-path therebetween; and wherein the purge flow acquires gases released from the material.

5. A process as claimed in claim 5 wherein the purge flow flow-path has an opposite flow direction to a flow direction of the material flow path.

6. A process as claimed in claim 4 or claim 5 wherein the purge flow has a pressure of 100mbar or lower or a pressure of from 50 mbar to 100 mbar.

7. A process as claimed in any preceding claim wherein the material is exposed to heat at a temperature of from 100°C to 200°C, from 120° to 160°C or about 150°C; optionally wherein the chamber has a substantially constant temperature along the material flow path, or wherein the chamber is heated to provide a temperature gradient along the material flow path.

8. A process as claimed in any preceding claim wherein the purge flow is flowed from the purge outlet to a heat exchanger to condense the mixture of recovered gases.

9. A process as claimed in any preceding claim wherein the chamber includes a housing, wherein the housing is manufactured from a non-magnetic material and the step of heating is provided by an induction heating step.

10. A process for the purification and / or separation of a mixture of gases, the process comprising the steps of: i) alkaline extraction; ii) membrane separation; and iii) distillation.

11. A process as claimed in claim 10 wherein the mixture of gases is obtained by a process as claimed in any one of claims 1 to 19.

12. A process as claimed in claim 10 or claim 11 wherein the steps are carried out in the sequence of i) alkaline extraction; membrane separation; and distillation; or ii) distillation; alkaline extraction; and membrane separation.

13. A process as claimed in any one of claims 10 to 12 wherein the alkaline extraction step uses an aqueous alkaline solution, optionally an aqueous hydroxide solution, optionally comprising a solution of at least one of potassium hydroxide and sodium hydroxide; optionally wherein the aqueous hydroxide solution has a concentration of 0.2 M or lower or a concentration of between 0.01 M and 0.1 M.

14. A process as claimed in claim 13 wherein the aqueous alkaline solution and mixture of gases are mixed within a mixing vessel for a period of 5 minutes or less prior to the step of membrane separation.

15. A process as claimed in claim 14 comprising a plurality of mixing vessels arranged in series, wherein the mixture of gases is caused to flow from one mixing vessel to an adjacent mixing vessel in a gas flow direction; and wherein an aqueous alkaline solution is caused to flow from one mixing vessel to an adjacent mixing vessel in a direction opposite to the gas flow direction.

16. A process as claimed in any one of claims 10 to 15 wherein the aqueous alkaline solution and mixture of gases are mixed using inline mixing elements fitted within flexible hosing arranged as coils and having a length sufficient to provide a predetermined residence time; optionally comprising providing a plurality of inline mixing elements arranged in series, wherein an aqueous alkaline solution is caused to flow in a direction opposite a direction of gas flow through the series of inline mixing elements.

17. A process as claimed in any one of claims 10 to 16 wherein the membrane separation uses a hydrophobic separation membrane.

18. A process as claimed in any one of claims 10 to 17 wherein the distillation is carried out using a distillation column containing adsorption materials selected to have a binding preference for the highest boiling material component of the mixture of gases; optionally wherein the adsorption materialis at least one material selected from activated carbon, modified activated carbons, silica gels, zeolites, zeolitic-imidazolate frameworks, structured covalent organic frameworks and functionalised polymers.

19. An apparatus for recovery of at least one gas bound to a material from the material, the apparatus comprising a recovery chamber for exposing the material to heat and reduced pressure and for providing a purge flow in a chamber, to separate the gas bound to a material into a mixture of recovered gases and a degassed residual material.

20. An apparatus as claimed in claim 19 wherein the chamber is an elongate chamber and has an material inlet for introduction of material to the chamber and a material outlet for egress of processed material from the chamber, the inlet and outlet defining a material flow-path therebetween.

21. An apparatus as claimed in claim 20 wherein the material flow path includes a conveyor for transporting material along the material flow-path; optionally wherein the conveyor is a belt conveyor or a screw conveyor; further optionally wherein the conveyor is a screw conveyor and the step of exposing the material to heat comprises providing an actively heated screw flight.

22. An apparatus as claimed in any one of claims 19 to 21 wherein the chamber includes a purge inlet operatively coupled to a source of humidified air or humidified nitrogen providing a purge flow; and a purge outlet attached to a source of reduced pressure, wherein the purge inlet and purge outlet define a purge flow flow-path therebetween; and wherein the purge flow acquires gases released from the material.

23. An apparatus as claimed in claim 22 wherein the purge flow flow-path is configured to have an opposite flow direction to a flow direction of the material flow path; optionally wherein the purge flow has a pressure of 50mbar to 100mbar24. An apparatus as claimed in any one of claims 20 to 23 wherein the apparatus applies heat to the material at a temperature of from 100°C to 200°C, from 120° to 160°C or about 150°C; optionally wherein the chamber provides a substantially constant temperature along the material flow path, or wherein the chamber is heated to provide a temperature gradient along the material flow path.

25. An apparatus as claimed in any one of claims 20 to 24 wherein the purge flow is flowed from the purge outlet to a heat exchanger to condense the mixture of recovered gases.

26. An apparatus as claimed in any one of claims 20 to 25 wherein the chamber includes a housing, wherein the housing is manufactured from a non-magnetic material and heating is provided by an induction heating step.

27. A process for the separation of a mixture of gases, the process comprising the steps of:i) providing a mixture of gases; ii) cooling the mixture of gases by means of a first condensing unit to a first temperature, wherein the first temperature is a temperature at which a first gas of the mixture of gases condenses in a first vessel;Hi) collecting the condensed first gas; iv) passing uncondensed gases to a second condensing unit and cooling the uncondensed gases to a second temperature, lower than the first temperature, at which a second gas of the mixture of gases condenses; and v) collecting the condensed second gas in a second vessel.

28. A process as claimed in claim 27 wherein the mixture of gases is obtained by a process as claimed in any one of claims 1 to 10.

29. A process as claimed in claim 27 or claim 28 further comprising a step of passing uncondensed gases from the second vessel to a third condensing unit and cooling the gases to a third temperature, lower than the second temperature, at which a third gas of the mixture of gases condenses, and a step of collecting condensed third gas in a third vessel.

30. A process as claimed in any one of claims 27 to 29 wherein the mixture of gases is a mixture comprising at least two of sevoflurane, isoflurane and desflurane; and wherein the first temperature is a temperature in the range of 0 to 5°C, the second temperature is in the range of 0 to -10°C; and the third temperature is in the range of -10 to 20°C.

31. A process as claimed in any one of claims 27 to 30 followed by a process as claimed in any one of claims 11 to 20.

32. An apparatus for the separation of a mixture of gases by the process of any one of claims 27 to 31 wherein the apparatus comprises a first condensing unit in fluid communication with a first vessel; a second condensing unit in fluid communication with the first vessel and with a second vessel; and a third condensing unit in fluid communication with the second vessel and with a third vessel, wherein the second condensing unit operates at a second temperature that is lower than a first temperature at which the first condensing unit operates and wherein the third condensing unit operates at a third temperature that is lower than the second temperature.

33. An apparatus as claimed in claim 32 wherein the first temperature is a temperature in the range of 0 to 5 °C, the second temperature is in the range of 0 to -10°C; and the third temperature is in the range of -10 to 20°C.

34. An apparatus as claimed in claim 32 or claim 33 wherein each vessel includes an upper float switch or sensor and a lower float switch or sensor, and wherein each vessel further includes a pumpor valve for removal of condensed fluid within the vessel; wherein the pump is operated or the valve is opened in response to the upper float switch or sensor detecting an upper level for the condensed fluid and wherein the pump is stopped or the valve is closed in response to the lower float switch or sensor detecting a lower level for the condensed fluid in the vessel.

Images