Treatment of organofluorine compounds

Abstract

An apparatus for treating a fluid including an organofluorine compound, the apparatus including: a vessel that contains a liquid with a fluoride bonding agent; a combustion chamber in fluid communication with the vessel via an outlet submerged in the liquid; an inlet configured to introduce the fluid into the combustion chamber; and a flame source configured to produce a flame in the combustion chamber to at least partially break down the organofluorine compound to form a gaseous combustion product bearing fluoride, wherein the gaseous combustion product passes from the outlet of the combustion chamber through the liquid so that the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent.

Description

TREATMENT OF ORG ANOFLUORINE COMPOUNDSBackground

[0001] The present disclosure relates to the treatment of organofluorine compounds, including an apparatus and process for treating a fluid including an organofluorine compound and a burner assembly for use in an apparatus for treating a fluid including an organofluorine compound.Description of the Prior Art

[0002] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgement or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this disclosure relates.

[0003] It is known that the carbon-fluorine (C-F) bond is one of the strongest single chemical bonds, and one which strengthens and shortens as more fluorine is added to a carbon on a chemical compound. As a result, substances such as per- and polyfluoroalkyl substances (PF AS) possess high stability, tolerance to high temperatures and low surface energies.

[0004] These PF AS, by design, are thereby difficult to degrade due to the strength of multiple C-F chemical bonds in the chemical species, with thousands of such chemical species in existence categorised according to the carbon chain length and the polar functional groups attached, with shorter chain compounds that may be volatile. The widespread use of PF AS chemical species, leading to the ubiquitous presence of PFAS in the environment and waste streams, together with evidence of their adverse impact on human health and the environment, has given rise to a growing concern over PFAS in the environment, driving the need to develop effective treatment technologies.

[0005] In this context, commercial technologies are known for separating PFAS from certain media, in particular solutions, such as using ion exchange, nanofiltration, reverse osmosis, or foam fractionation. Although these technologies may act to separate out PFAS, the result is aconcentrated waste stream in which the PFAS remains unaltered. By example, rinsate from washing PFAS contaminated soils has become a problematic waste stream.

[0006] Technologies are thereby also known for the destruction of the PFAS chemical species, including thermal decomposition processes such as electric arc processes, electro-oxidation processes and incineration with kilns or hazardous waste incinerators. These technologies however come with several disadvantages, including being limited by the volume capacity for treatment and having destruction and removal efficiencies (DRE) that are unacceptably low, by example because of their inability to remove PFAS daughter and / or by products or attenuate volatile PFAS (vPFAS) chemical species and / or hydrogen fluoride (HF) that either exist in the feed or arise during thermal decomposition.

[0007] A further problem with the currently known technologies, particularly destruction technologies, is that they are also often fixed at a particular location by virtue of their nature. Therewith, PFAS sources must be transported to these locations, often over long distances, which presents extraordinary challenges due to the requirements for hazardous material transport.

[0008] Consequently, there are large stockpiles of PFAS based products, such as aqueous film firefighting foam (AFFF), in storage awaiting options for satisfactory treatment.Summary

[0009] According to an aspect, an apparatus for treating a fluid including an organofluorine compound is provided, the apparatus including: a vessel that contains a liquid with a fluoride bonding agent; a combustion chamber in fluid communication with the vessel via an outlet submerged in the liquid; an inlet configured to introduce the fluid into the combustion chamber; and a flame source configured to produce a flame in the combustion chamber to at least partially break down the organofluorine compound to form a gaseous combustion product bearing fluoride, wherein the gaseous combustion product passes from the outlet of the combustion chamber through the liquid so that the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent.

[0010] In an embodiment, the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent by forming a fluoride precipitate. The liquid contained in the vessel may be water with the fluoride bonding agent as a solute comprising one or more dissolved metal salts. At least one of the one or more dissolved metal salts may comprise aluminium, magnesium and / or calcium ions that act to form the fluoride precipitate as an aluminium, magnesium and calcium fluoride precipitate respectively. At least one of the one or more metal salts may comprise chloride ions. The one or more dissolved metal salts may comprise at least 20wt% aluminium, calcium or magnesium chloride.

[0011] In an embodiment, the solute at least partially suppresses evaporation of the liquid and / or the release of aerosols from the liquid.

[0012] In an embodiment, the temperature of the flame in the combustion chamber is in a range of 800°C to 1500°C.

[0013] In an embodiment, the flame source is a burner assembly including: a burner oxidant inlet that receives a source of pressurised oxidant; a fuel inlet that receives a source of fuel; and a burner outlet in fluid communication with the combustion chamber allowing an oxidant / fuel mixture to burn and thereby produce the flame in the combustion chamber. The source of pressurised oxidant may be pressurised air supplied by a high-pressure fan or blower. The source of fuel may include one or any combination of biogas, biofuel, natural gas, propane, fuel oil, kerosene, waste oil and diesel.

[0014] In an embodiment, the inlet includes a fluid line extending within the combustion chamber to a distal end proximate the burner outlet through which the fluid is introduced into the combustion chamber in a region of the flame. The fluid line may include a tube, the tube including a stainless steel, tungsten carbide, a titanium-based alloy and / or a nickel-based alloy.

[0015] In an embodiment, the fluid is introduced into the combustion chamber in the region of the flame at a flow rate in a range of 0.5 L / min to 3 L / min.

[0016] In an embodiment, the fluid is introduced into the combustion chamber at a pressure in a range of 500 kPa to 1050 kPa.

[0017] In an embodiment, a treated fluid passes from the liquid to an exit of the vessel. An organofluorine destruction and removal efficiency (DRE) at the exit in relation to the fluid introduced into the combustion chamber may be greater than 99%.

[0018] In an embodiment, a residence time of the fluid in the apparatus from the inlet to the exit is in a range of 0.5 s to 3 s.

[0019] In an embodiment, a treatment facility is provided downstream of the exit of the vessel to at least partially extract organofluorine from the treated fluid, the treatment facility including one or any combination of facilities selected from the group including: a filter; a scrubber; a mist eliminator; and a condenser. The filter may include filter media as fabric, granular activated carbon and / or resin beads. An organofluorine destruction and removal efficiency (DRE) downstream of the treatment facility in relation to the fluid introduced into the combustion chamber may be greater than 99.9%.

[0020] In an embodiment, the combustion chamber extends downwards in the vessel.

[0021] In an embodiment, the combustion chamber extends downwards in the vessel from a substantially conical section proximate the flame source to a substantially cylindrical section including the outlet submerged in the liquid.

[0022] In an embodiment, the outlet includes a plurality of ports placed circumferentially proximate a bottom of the cylindrical section.

[0023] In an embodiment, the combustion chamber is provided inside the vessel and coaxial with the vessel.

[0024] In an embodiment, the liquid is dosed with a base to at least partially neutralise hydrogen fluoride dissolved in the liquid. Dosing of the base may be performed so as to control the pH of the liquid in a range of 6.5 to 8.2.

[0025] In an embodiment, the apparatus includes a liquid level measuring device for measuring a parameter indicative of a liquid level in the vessel and / or a concentration measuring device for measuring a concentration of the fluoride bonding agent in the liquid. The liquid level measuring device may be operatively coupled with a liquid level controller configured tocontrol the liquid level in the vessel so as to at least one of replenish liquid in the vessel and control a fluid differential pressure in the apparatus. The liquid in the vessel may be replenished with a feed water including a base solution so as to adjust a pH of the feed water.

[0026] According to an aspect, a burner assembly for use in an apparatus for treating a fluid including an organofluorine compound is provided, the burner assembly including: a burner mount plate for mounting the burner assembly to a combustion chamber of the apparatus in a substantially downwards direction; a burner oxidant inlet that receives a source of pressurised oxidant; a fuel inlet that receives a source of fuel; a burner discharge sleeve extending substantially downwards to a burner outlet operatively in fluid communication with the combustion chamber to allow an oxidant / fuel mixture to bum and thereby produce a flame in the combustion chamber; and a fluid line extending through the burner mount plate and burner discharge sleeve to a distal end proximate the burner outlet and through which the fluid is introduced into the combustion chamber in a region of the flame.

[0027] In an embodiment, the fluid line extends through the burner discharge sleeve to the distal end so as to operatively introduce the fluid into the combustion chamber at approximately 20 mm or more beyond the burner outlet.

[0028] In an embodiment, the fluid line is adjustably mounted in the burner assembly so as to allow a position of the distal end of the fluid line to be adjusted relative the burner outlet. The fluid line may be adjustably mounted via a compression fitting proximate the burner mount plate.

[0029] In an embodiment, the fluid line includes a nozzle at the distal end for introducing the fluid into the combustion chamber as a spray.

[0030] According to an aspect, a process for treating a fluid including an organofluorine compound is provided, the process including: providing a liquid with a fluoride bonding agent in a vessel; producing a flame in a combustion chamber, the combustion chamber in fluid communication with the vessel via an outlet submerged in the liquid; introducing the fluid into the combustion chamber via an inlet to at least partially break down the organofluorine compound by means of the flame to form a gaseous combustion product bearing fluoride; passing the gaseous combustion product from the outlet of the combustion chamber throughthe liquid so that the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent.

[0031] It will be appreciated by those skilled in the art that the process according to this aspect may be performed as a batch, semi-batch and / or continuous process.

[0032] It will further be appreciated that the aspects of this disclosure, their respective features and examples as provided herein can be used in conjunction and / or independently, and reference to separate aspects is not intended to be limiting. Furthermore, it will be appreciated that features of the process can be performed using the apparatus and that features of the apparatus can be implemented using the process.Brief Description of the Drawings

[0033] Various examples and embodiments will now be described with reference to the accompanying drawings, in which: -

[0034] Figure l is a schematic representation of an apparatus for treating a fluid including an organofluorine compound in accordance with an aspect of the disclosure;

[0035] Figure 2 is a schematic representation of a burner assembly for use in an apparatus for treating a fluid including an organofluorine compound in accordance with an aspect of the disclosure; and

[0036] Figure 3 is a flow diagram of a process for treating a fluid including an organofluorine compound in accordance with an aspect of the disclosure.Detailed Description of Preferred Embodiments

[0037] An example of an apparatus 10 for treating a fluid including an organofluorine compound will now be described with reference to Figure 1.

[0038] The term “organofluorine compound” in the present context refers to any chemical compound that contains a carbon-fluorine bond, non-limiting examples of which include per- and polyfluoroalkyl compounds characterised as having carbon atoms linked to each other and bonded to fluorine atoms at some or all of the available carbon bonding sites. Therewith, theterm “fluid” will be understood to refer to any liquid, gas or other material that can be caused to flow and includes reference to particulate matter. A fluid including an organofluorine compound may therefore at least partially comprise the organofluorine compound, may entrain the organofluorine compound in its flow or include the organofluorine compound in any manner as will be appreciated from this disclosure by those skilled in the art.

[0039] Furthermore, the term “fluoride bonding agent” will be understood to refer to any agent that has the ability to chemically bond with fluoride ions towards forming a stable species.

[0040] In this example, the apparatus 10 includes a vessel 12 that contains a liquid 14 with a fluoride bonding agent and a combustion chamber 16 in fluid communication with the vessel 12 via an outlet 18 submerged in the liquid 14. The apparatus 10 further includes an inlet 20 configured to introduce the fluid into the combustion chamber 16 and a flame source 22 configured to produce a flame in the combustion chamber 16 to at least partially break down the organofluorine compound in the fluid to form a gaseous combustion product bearing fluoride. This gaseous combustion product passes from the outlet 18 of the combustion chamber 16 through the liquid 14 so that the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent.

[0041] It will be appreciated that the apparatus 10 thereby allows for providing a heat of combustion sufficient for carbon-fluorine (C-F) chemical bonds within the organofluorine compound to be broken down while further enabling the remaining organic compound to be at least partially reduced, by example to form carbon dioxide (CO2). The fluoride in the resultant gaseous combustion product, by example including inorganic solutes such as fluoride anions and hydrogen fluoride (HF), are subsequently bound, such as through chemical bonding or chelation, by the fluoride bonding agent to form stable species as the gaseous combustion product passes through the liquid 14.

[0042] Therewith and in an example, the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent by forming a fluoride precipitate, such as by chemical reaction with a molecular entity of the fluoride bonding agent. Formation of a fluoride precipitate in this manner facilitates separation thereof from the liquid 14, such as by settling under gravity, in the vessel 12 and subsequent removal from the vessel 12 as exemplified further herein.

[0043] In an example, the liquid 14 contained in the vessel 12 is water with the fluoride bonding agent as a solute comprising one or more dissolved metal salts, by example comprising aluminium, magnesium and / or calcium ions having a strong affinity for fluoride precipitation, and which act to form the fluoride precipitate as an aluminium, magnesium and calcium fluoride precipitate respectively. Therewith, the fluid introduced into the combustion chamber 16 may comprise water that is at least partially vaporised by the heat of combustion in the combustion chamber 16 and with the resultant water vapour introduced into the water-salt solution contained in the vessel 12 along with the gaseous combustion product. Formation of hydrofluoric acid from fluoride anions and / or HF in the gaseous combustion product may therewith also be mitigated against by the fluoride bonding agent through the formation of the stable species as described above.

[0044] Where the one or more dissolved metal salts comprise magnesium and / or calcium ions, it will be appreciated that calcium fluoride and magnesium fluoride precipitates may thereby form and which are both very stable, weakly soluble in water and have a negligible or neutral pH effect on the water-salt solution contained in the vessel 12.

[0045] In the example where the liquid 14 contained in the vessel 12 is a water-salt solution as described above, it will therewith be appreciated that at least one of the one or more metal salts can comprise chloride ions, in a preferred example at least 20 wt% aluminium, calcium or magnesium chloride, so that these metal chlorides can react with HF in the gaseous combustion to form weakly soluble metal fluoride precipitates and highly soluble hydrogen chloride.

[0046] It will further be appreciated that one of the one or more metal salts dissolved in the water can alter the colligative properties of the resultant water-salt solution, such as to lower vapour pressure, the solute thereby at least partially suppressing evaporation of the water from the water-salt solution and / or the release of aerosols from the water-salt solution. The extent to which the one or more metal salts dissolved in the water may reduce the amount of water vapour released can, by example, be influenced by adjusting its concentration, noting that in certain applications 200g / L or even lower may be suitable while in other applications up to 800g / L or more may be required.

[0047] In an example, the temperature of the flame in the combustion chamber 16 is in a range of 800°C to 1500°C. It will be appreciated that factors such as the requisite chemical kinetics,the nature of the organofluorine compound and the manner in which the fluid including the organofluorine compound is introduced into the combustion chamber 16 impact on the flame temperature necessary in order for the C-F chemical bonds in the organofluorine compound to be suitably broken down. By non-limiting examples, perfluorooctanesulfonic acid (PFOS), perfluoroheptanesulfonic acid (PFHpS), perfluorohexanesulfonic acid (PFHxS) and perfluorobutane sulfonate (PFBS) may substantially be broken down at a flame temperature as low as 810°C, while perfluorobutanoic acid (PFBA) may only substantially be broken down at a flame temperature of 970°C or greater.

[0048] In an example, the flame source 22 is a burner assembly including a burner oxidant inlet 24 that receives a source of pressurised oxidant, a fuel inlet 26 that receives a source of fuel and a burner outlet 28, shown in accordance with a preferred example as a distal end of a discharge sleeve, in fluid communication with the combustion chamber 16 so as to allow an oxidant / fuel mixture to burn and thereby produce the flame in the combustion chamber 16. In an example, the source of pressurised oxidant is pressurised air supplied by a high-pressure fan or blower, by non-limiting example a regenerative blower. In an example, the source of fuel includes one or any combination of biogas, biofuel, natural gas, propane, fuel oil, kerosene, waste oil and diesel. It will therewith be appreciated that the apparatus 10 may be operable at a wide range of locations where, by example, any one or more of biogas, biofuel, natural gas, propane, fuel oil, kerosene, waste oil and diesel is available. Furthermore, the apparatus 10 can provide for the sustainable treatment of organofluorine compound, at least through enabling the use of sources of fuel such as biogas, biofuel and waste oil.

[0049] In an example, the inlet 20 of the apparatus 10 includes a fluid line 30 extending within the combustion chamber 16 to a distal end proximate the burner outlet 28 and through which the fluid is introduced into the combustion chamber 16 in a region of the flame. The fluid line 30 may therewith include a tube, such as a stainless steel, tungsten carbide, a titanium -based alloy and / or a nickel-based alloy tube, so as to mitigate against its deformation during exposure to the heat of combustion.

[0050] In an example, the fluid is introduced into the combustion chamber 16 in the region of the flame at a flow rate in a range of 0.5 L / min to 3 L / min and / or at a pressure in a range of 500 kPa to 1050 kPa. It will be appreciated that introducing the fluid into the combustionchamber 16 in this manner can mitigate against the suppression of the flame in the combustion chamber 16 by the fluid as further described herein.

[0051] In an example, a treated fluid passes from the liquid 14 to an exit 32 of the vessel 12. In a preferred example, this treated fluid is formed as the gaseous combustion product bearing fluoride is bubbled via the outlet 18 through the fluid 14 so that the fluoride therein is at least partially bound by the fluoride bonding agent to form the treated fluid substantially free of fluoride when it is released at the surface of the liquid 14. It will be appreciated that the treated fluid may however still include fluoride from the gaseous combustion product not bound by the fluoride bonding agent. A residence time of the fluid in the apparatus 10 from the inlet 20 to the exit 32 may be in a range of 0.5 s to 3 s. By non-limiting example, this residence time may at least in part be influenced by a length of the combustion chamber 16 extending between the inlet 20 and the outlet 18. An organofluorine destruction and removal efficiency (DRE) at the exit 32 in relation to the fluid introduced into the combustion chamber 16 may be greater than 99%. In this context, the DRE may be calculated as follows:

[0052] In this Equation 1, Win is the mass feed rate of the organofluorine compound(s), which in the context of PF AS may also be referred to as the principle organic hazardous constituent s), in the fluid as introduced into the combustion chamber 16 at the inlet 20 and Wout is the mass emission rate of the organofluorine compound(s) or principle organic hazardous constituent s) at the exit 32.

[0053] As noted above, some of the organofluorine compound in the fluid may remain in the gaseous combustion product and therewith in the treated fluid, while daughter organofluorine products and organofluorine by-products may also be formed in the combustion chamber 16. Accordingly, in an example, a treatment facility 34 is provided downstream of the exit 32 of the vessel 12 to at least partially extract organofluorine from the treated fluid. The treatment facility 34 is shown in Figure 1 as a stack of the apparatus 10 including a mist eliminator 34.1 and a filter 34.2, such as including filter media as fabric, granular activated carbon and / or resin beads. The treatment facility 34 need however not be in the form of a stack nor needs to form part of the apparatus 10 and can include, by example, one or any combination of facilitiesselected from the group including a filter, a scrubber, a mist eliminator, and a condenser, whether as part of or separate from the apparatus 10.

[0054] Consequently, a DRE of greater than 99.9% may be achieved downstream of the treatment facility 34 in relation to the fluid introduced into the combustion chamber 16, by example as calculated in accordance with Equation 1 above with Win being the mass feed rate of the organofluorine compound(s) in the fluid as introduced into the combustion chamber 16 at the inlet 20 and Wout is the mass emission rate of the organofluorine compound(s) from the treatment facility 34.

[0055] In an example, the combustion chamber 16 extends downwards in the vessel 12. The combustion chamber 16 may therewith extend downwards in the vessel 12 from a substantially conical section 16.1 proximate the flame source 22 to a substantially cylindrical section 16.2 including the outlet 18 submerged in the liquid 14. In such an example, the flame source 22 may be in the form of a substantially downwards firing burner assembly as shown in Figure 1. In a preferred example, the outlet 18 comprises a plurality of ports 18.1 placed circumferentially proximate a bottom of the cylindrical section 16.2 and the combustion chamber 16 may be provided inside the vessel 12 and coaxial with the vessel 12. It will be appreciated that this configuration of the apparatus 10 may allow for passing the gaseous combustion product from the outlet 18 of the combustion chamber 16 through the liquid 14 in a distributed manner towards advancing the binding of the fluoride in the gaseous combustion product by the fluoride bonding agent.

[0056] In an example, the liquid 14 is dosed with a base to at least partially neutralise HF dissolved in the liquid, by non-limiting examples dosing with sodium hydroxide, potassium hydroxide and / or calcium hydroxide, such as to control the pH of the liquid 14 in a range of 6.5 to 8.2. It will be appreciated that this can mitigate corrosion within the vessel 12. By example, a particular dosage requirement may be established empirically, as dependent upon the organofluorine compound(s) being treated and the flow rate of the fluid at the inlet 20, or by means of an indicator solution provided in the fluid 14. A dosing pump, such as a chemical injection pump, can be configured to accordingly deliver the dose at a predetermined rate or otherwise. It will however be appreciated that this dosing need not necessarily be performed continuously or in an automated manner and can be performed in accordance with manualtesting performed on the liquid 14 in a batch or semi-batch manner, by non-limiting example on cooled liquid extracted from the liquid 14 in the vessel 12, by example on a daily basis and such as by means of a sample port 62.

[0057] In an example, the apparatus 10 includes a device 36, such as liquid level measuring device for measuring a parameter indicative of a liquid 14 level in the vessel 12 and / or a concentration measuring device for measuring a concentration of the fluoride bonding agent in the liquid 14. In an example where the device 36 is a liquid level measuring device, such as a level sensor or float switch, the device 36 can be operatively coupled with a liquid level controller 38 configured to control the liquid 14 level in the vessel 12 so as to at least one of replenish liquid 14 in the vessel 12, such as to account for liquid 14 lost to evaporation in the vessel 12, and control a fluid differential pressure in the apparatus 10, such as by means of controlling an influent stream 58. It will therewith be appreciated that the liquid level measuring device need not be limited to the above examples and may, by non-limiting example, include a pressure transducer or the like wherein the parameter indicative of the liquid 14 level is a measured fluid pressure.

[0058] It will be appreciated that, in an example where the liquid 14 is dosed with a base, such dosing may be performed by means of including the base in a liquid used to replenish the liquid 14 in the vessel 12, such as a liquid introduced by influent stream 58. Accordingly, and in a further example as alternative to or in addition to a liquid level measuring device as described above, replenishing the liquid 14 in the vessel 12 can be done by measuring a specific gravity of a replenishing fluid outside the vessel 12, equating that with desired head / fluid pressure, and then replenishing the liquid 14 in the vessel 12 with a relatively pure source of the liquid or with a liquid as a base solution wherein the pH has been adjusted by means of the addition of the base.

[0059] An example of a burner assembly 100 for use in an apparatus for treating a fluid including an organofluorine compound will now be described with reference to Figure 2.

[0060] The burner assembly 100 includes a burner mount plate 102 for mounting the burner assembly 100 to a combustion chamber 104 of the apparatus, such as the combustion chamber 16 described above with reference to the apparatus 10 as shown in Figure 1, in a substantially downwards direction. The burner assembly 100 further includes a burner oxidant inlet 106 thatreceives a source of pressurised oxidant and a fuel inlet 108 that receives a source of fuel. In this regard, it will be appreciated that the burner assembly 100 may further include directional vanes 124 placed in an oxidant supply line 126 of the burner oxidant inlet 106 as further described herein with reference to directional vanes 46 of Figure 1.

[0061] The burner assembly 100 also includes a burner discharge sleeve 110 extending substantially downwards to a burner outlet 112 operatively in fluid communication with the combustion chamber 104 to allow an oxidant / fuel mixture to bum and thereby produce a flame in the combustion chamber 104. The burner assembly 100 still further includes a fluid line 114 extending through the burner mount plate 102 and the burner discharge sleeve 110 to a distal end 116 proximate the burner outlet 112 and through which the fluid is introduced into the combustion chamber 104 in a region of the flame.

[0062] In an example, the fluid line 114 extends through the burner discharge sleeve 110 to the distal end 116 so as to operatively introduce the fluid into the combustion chamber 104 at approximately 20 mm or more beyond the burner outlet 112. The fluid line 114 may be adjustably mounted in the burner assembly 100 so as to allow a position of the distal end 116 of the fluid line 114 to be adjusted relative the burner outlet 112. The fluid line may be so adjustably mounted via a compression fitting 118 proximate the burner mount plate 102.

[0063] In this regard, the burner assembly 100 may include a flame detector 120, such as an ultraviolet flame detector. It will be appreciated that if the distal end 116 through which the fluid is introduced into the combustion chamber 104 is too close to the burner outlet 112, it may cause a fog to develop, and which can blind the flame detector 120. Blinding of the flame detector 120 can accordingly be mitigated against by operatively introducing the fluid into the combustion chamber 104 at approximately 20 mm or more beyond the burner outlet 112, in a preferred example at about 25 mm beyond the burner outlet 112.

[0064] In an example, the fluid line 114 comprises a nozzle 122 at the distal end 116 for introducing the fluid into the combustion chamber 104 as a spray, by non-limiting example in a hollow cone spray pattern.

[0065] In a non-limiting example, the nozzle 122 can be a hydraulic or atomizing nozzle to produce the spray at a suitably small droplet size and pressure so as to not upset the flame inthe combustion chamber 104 while also facilitating the breaking of C-F chemical bonds in the organofluorine compound contained in the spray. By example, a spray of droplets with a mean diameter of less than 500 pm, preferably around 250 pm, at 550 kPa can be provided. It will however be appreciated that selection of a nozzle 122, the pressure, the pattern of the spray and the spray droplet size is subject to various factors, such as the viscosity of the fluid to be introduced into the combustion chamber 104.

[0066] It will further be appreciated that various different spray systems and / or injectors may be suitable for use in accordance with aspects of the present disclosure for introducing fluid into a combustion chamber, including but not limited to full cone nozzles, flat spray nozzles, solid stream nozzles, hollow cone nozzles, fine spray nozzles, air atomizing spray nozzles, variable spray nozzles, electrically-actuated and air-actuated atomizing nozzles, hydraulic atomizing spray nozzles.

[0067] Furthermore, where a combustion chamber includes a substantially conical section 16.1 and a substantially cylindrical section 16.2 is provided, as described above with reference to Figure 1, the fluid may be introduced within the substantially conical section 16.1 and / or the substantially cylindrical section 16.2, by example through adjusting the distal end 116 of the fluid line 114 relative the burner outlet 112 and / or by means of a nozzle or nozzles disposed in the substantially conical section 16.1 and / or the substantially cylindrical section 16.2.

[0068] An example of a process 1000 for treating a fluid including an organofluorine compound will now be described with reference to Figure 3.

[0069] The process 1000 includes providing 1100 a liquid with a fluoride bonding agent in a vessel, producing 1200 a flame in a combustion chamber, the combustion chamber in fluid communication with the vessel via an outlet submerged in the liquid, introducing 1300 the fluid into the combustion chamber via an inlet to at least partially break down the organofluorine compound by means of the flame to form a gaseous combustion product bearing fluoride and passing 1400 the gaseous combustion product from the outlet of the combustion chamber through the liquid so that the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent.

[0070] It will be appreciated by those skilled in the art that this process 1000 can be performed in a batch, semi-batch or continuous manner and therewith the process 1000 need not necessarily be performed in the sequence as described above and various steps of the process may be performed in any series and / or simultaneously.

[0071] A number of further features will now be described with reference to a non-limiting example process, hereafter referred to as a submerged combustion process. The submerged combustion process is provided for treating a fluid including an organofluorine compound as a PF AS chemical species, such as any number of PFAS chemical species from firefighting foam, wastewater effluent, landfill leachate, biosolids, extracted with methanol from granulated activated carbon, ion exchange beads and other PFAS removal media, by means of the apparatus as shown in Figure 1 wherein like features are designated by the same reference numerals. It will be appreciated that designation is this regard in reference to the submerged combustion process is not intended to be limiting.

[0072] It will further be appreciated that various further compounds may also be present in the fluid including the PFAS chemical species, including microplastics, printed circuit board (PCB) waste, pharmaceuticals, and other compounds, by example where the process is used for treating a foamate from landfill leachate.

[0073] The submerged combustion process employs a flame source 22 as a downward firing burner and a combustion chamber 16 that forces hot gaseous products of combustion into a liquid 14 confined inside a vessel 12. The combustion chamber 16 is first purged of liquid by forcing air into the liquid 14, and thereafter a source of fuel is introduced and then the flame is lighted. Hot gases exit the bottom of the combustion chamber 16 at the outlet 18 and form bubbles which transfer heat into the liquid 14, as a water and dissolved metal salt solution. Vapour is formed as water diffuses along a partial pressure gradient into the bubble. The greater pool of solution 14 would however not reach boiling point, but vapour can be released from the solution’s 14 surface as further described herein below. This vapour is typically vented upward through exhaust stack(s) 34.

[0074] The flame temperature inside the combustion chamber 16 typically exceeds 1000°C and can reach as high as 1500°C depending on the source of fuel, with PFAS chemical species readily destroyed at these temperatures. Fluid including these PFAS chemical species can besprayed into the combustion chamber as a fine mist 40 with very little suppression of flame temperature. Addition of fluid in this manner at 1.5 litre per minute (L / min) may therewith suppress combustion chamber 16 temperature by only about 30°C, with addition of the fluid at greater than 3 L / min possibly overwhelming the flame.

[0075] It will be appreciated that the point of introducing the fluid may be selected so as to enhance contact between PFAS chemical species in the fluid and the flame. In this context, the fluid is atomized directly into the flame at a point just below the burner discharge sleeve 42 and at the top of the combustion chamber 16. While air and fuel are mixed within a burner mixing cone 44, further mixing occurs as the flame expands into the substantially conical section 16.1 of the combustion chamber 16 and eddy currents occur where this substantially conical section 16.1 meets a straight cylindrical section 16.2 of the combustion chamber 16. The PFAS chemical species are accordingly broken down and destroyed in the flame.

[0076] A flame shape in the combustion chamber 16 and / or an air / fuel mix efficiency can be manipulated by adjusting an air swirl with directional vanes 46 placed in a combustion air supply line 48 proximate where it meets the burner 22. Maximising flame temperature and mixing fluid droplets at the top of the combustion chamber 16 may consequently enhance PFAS destruction efficiency and minimise the need for longer fluid retention times in the combustion chamber 16. A 2 s retention time in the combustion chamber 16 at a temperature greater than 1000°C may accordingly be sufficient to break down and destroy the PFAS chemical species. However, and as noted above, it will be appreciated that the point at which the fluid including the PFAS chemical species is introduced into the combustion chamber 16 can influence the required retention time and, by example, as the fluid is introduced closer to the burner 22, retention times may be reduced, even down to 0.8 s such as where a combustion chamber 16 with a length of around 1.625 m is provided, subject to further factors such as the cross sectional area of the combustion chamber 16 and fluid flow rates to and / or within the combustion chamber 16.

[0077] Therewith, extending the length of the combustion chamber 16 and increasing the fluid travel distance through the combustion chamber 16, such as to around 2.03 m can add another 0.2 s retention time.

[0078] The solution 14 in the vessel 12, also referred to hereafter as the “catch” solution, is highly concentrated with dissolved salt(s), including by example combinations of different salts, resulting in colligative properties that resist evaporation and produce little water vapour. By example, evaporation of the solution 14 may be reduced by up to 75% compared to evaporation of the water absent the dissolved salt(s), even in instances where the catch solution 14 reaches temperatures of up to 100°C. It will however be appreciated that in operation the catch solution 14 can reach a bulk temperature of over 100°C, even up to 120°C. The effect is that water vapour in the treated fluid and thereby the amount of water vapour passing through the exhaust stack 34 is minimised. This enables, by example, utilising downstream treatment facilities such as granular activated carbon (GAC) filters as described herein, which would otherwise not be suitable as a result of excessive vapours preventing passage through the filter.

[0079] The catch solution 14 temperature may be monitored, such as by means of a temperature sensor 56, but it will be appreciated that in certain applications there may be limited direct control over the temperature of the catch solution 14 in the vessel 12, with this temperature to some extent rather being controlled as a function of the dissolved salt concentration in the catch solution 14, the flame temperature in the combustion chamber 16 and an evaporation rate of the catch solution 14. The flame temperature may in turn be increased or decreased by manipulating the feed rate of the fuel, the type of fuel as a function of its calorific value, and the air to fuel ratio.

[0080] As some water from the catch solution 14 is likely to be lost to evaporation it can be replenished, such as through the stream 58, with water, such as municipal water or a source of water that is very low in salinity and PF AS free. The liquid 14 level in the vessel 12 and the concentration of the dissolved metal salt(s) can be automatically controlled by a device 36 and controller 38, such as a programmable logic controller (PLC) and a pressure transducer attached to the vessel 12. A target “head” of the catch solution 14, expressed as millimetres of water column (mmWC), can thereby be maintained. It will be appreciated that this also enables controlling backpressure on the air and fuel supply to the flame.

[0081] The exhaust stack(s) 34 can be outfitted with a mist eliminator 34.1 to further suppress aerosol emissions from the process. That would be followed with a filter 34.2 composed of granular activated carbon (GAC), resin beads and / or other media to catch any fugitive PFASin a treated fluid released from the catch solution 14, such as PF AS that escaped thermal destruction in the combustion chamber 16.

[0082] Alternatively, the treated fluid could be directed to a condenser where the evaporated water could be collected and recycled through the process. This would produce a low-moisture exhaust gas that could be passed through a filter to catch vPFAS.

[0083] The catch solution 14 contains the dissolved salt(s) as the fluoride bonding agent and which have a strong affinity for fluoride precipitation. In an example, calcium and / or magnesium chloride can be added as the salt(s) in a range of 200g / L to 600g / L.

[0084] The catch solution 14 pH may be controlled to neutralise acidity from the process and to prevent scaling or corrosion of the combustion chamber 16, the vessel 12 and stack(s) 34. In this regard, hydrofluoric acid produced by the breaking of C-F chemical bonds can be captured by calcium chloride in the catch solution 14.

[0085] It will be appreciated that controlling the concentration of the dissolved metal salt(s) in the catch solution need not necessarily be performed in an automated or even continuous manner as described above. By example, where the submerged combustion process is operated in a batch fashion, the catch solution 14 may only require changing weekly or monthly as the amount of HF derived from C-F bond breaking will likely be quite low compared to the associated dissolved metal salt(s) concentration.

[0086] It will therewith be appreciated that the catch solution 14 can be configured to have a very high capacity to capture HF that is released during the destruction of PFAS by the thermal decomposition of its C-F chemical bonds. By non-limiting example and in particular applications, the catch solution 14 can be a mixture of salts having a gross concentration of 4.5 mol / L with at least 25% being calcium chloride for reaction with HF. Therewith, the fluoride compounds formed by the dissolved metal salt(s) would fall to the bottom 50 of the vessel 12 as precipitates along with other salts that may form in the catch solution 14. These can accordingly be easily discharged, such as along with any spent catch solution, through a discharge port 52. To still further facilitate discharging of precipitates and spent catch solution, the bottom 50 of the vessel 12 may be provided to slope towards the discharge port 52.

[0087] Spent catch solution from the submerged combustion process could be filtered and introduced to the flame in the combustion chamber 16 as part of the fluid including the PF AS chemical species. Similarly, bound PF AS that escaped from the solution 14 can be extracted from exhaust stack 34 filter(s) 34.1 and passed through the process again.

[0088] Turning now to the burner 22, the burner 22 design can allow for insertion of a stainless steel tube through the middle of the burner 22 so as to define the inlet 20. This tube is supplied by a flexible high-pressure hose with a stainless steel nozzle attached to a distal end thereof and through which the fluid including the PF AS chemical species is introduced into the combustion chamber 16. The nozzle is positioned about 20 mm below the end of the burner discharge sleeve 42. In this configuration, the tube may be protected from overheating by the fluid passing through it.

[0089] The tube is held in position by a compression fitting which can be retracted when not in use. The nozzle at the distal end of the tube is provided as an atomizing nozzle that creates a hollow cone pattern of mist. At the end of the burner discharge sleeve 42, where the nozzle is set, the flame undergoes rapid expansion. The PF AS laden aerosols formed by the nozzle are mixed with the flame inside the substantially conical section 16.1 of the combustion chamber 16. Further mixing may also occur near the intersection where the substantially conical section 16.1 meets the straight substantially cylindrical section 16.2 of the combustion chamber 16.

[0090] The upper third of the combustion chamber 16 can be lined internally with a refractory coating for protection against overheating, such as where the combustion chamber 16 is fabricated with stainless steel, such as 316L stainless steel. Lower portions of the combustion chamber 16 may in turn be cooled by splashing and vapour from the catch solution 14. It will be appreciated that the catch solution 14 can be corrosive due to the high chloride content and the presence of HF and accordingly components that come into contact with the catch solution 14 or vapours thereof, such as the combustion chamber 16 and the vessel 12, may also be fabricated from corrosion resistant materials such as Inconel, a titanium alloy or tungsten carbide.

[0091] Furthermore, ports 54 can also be provided at the top of the vessel 12 for nozzles that spray water to cool the top of the combustion chamber 16. It will be appreciated that thiscooling water could also act, at least in part, to replenish the catch solution 14 as described above by means of the stream 58. In an example, the ports 54 may therewith be in fluid flow communication with the stream 58 so as to selectively replenish the catch solution 14 via the ports 54 by means of a valve 60 operated by the PLC 38.

[0092] As mentioned, the flame temperature and flame shape in the combustion chamber 16 can also be manipulated with the directional vanes 46 that cause combustion air to mix in various patterns. A broader flame with higher temperatures near the top of the combustion chamber 16 may, by example, promote a more complete mix of the fluid being introduced into the combustion chamber 16. Furthermore, and as indicated above, the flame temperature can be increased or decreased by manipulating the fuel rate and the air to fuel ratio. The flame temperature can also be affected by the calorific value of the fuel source. By non-limiting example, using landfill biogas (roughly 50 / 50 methane / CCh) as the source of fuel, it may be possible to achieve a 1000°C flame temperature. The biogas may therewith be supplemented with a source of fuel having a higher calorific value, such as diesel fuel, which can achieve flame temperature such as 1200°C. It will be appreciated that higher flame temperatures may be used to increase PF AS chemical species destruction efficiency, by example in offsetting reduced retention times of the PF AS chemical species within a region of the flame.

[0093] The combustion air can, by example, be supplied by a high-pressure radial flow fan. It will be appreciated that backpressure on the combustion chamber 16 can affect flame shape, mixing of air and fuel and possibly PF AS exposure time in the combustion chamber. This backpressure can accordingly be manipulated by changing the liquid 14 level or head in the vessel 12, as measured from the top of the combustion chamber 16 ports 18.1, by non-limiting example to an average head level of 572 mmWC, in the manner as described above.

[0094] From the above description it will be understood by those skilled in the art that the treatment of organofluorine compound is provided that can achieve high DRE percentages with flame temperatures as low as 1000°C while enabling retention times below two seconds.

[0095] Furthermore, as is apparent from the aforegoing disclosure, by the nature of the apparatus 10, burner assembly 100 and process 1000, a mobile apparatus 10 can provided and which allows for the utilization of a wide range of sources of fuel for the thermal decomposition of organofluorine compounds such that it can be readily transported and operated atcontaminated sites such as air bases, landfills and the like. This provides a fundamental advance over the existing technologies, including that of the submerged combustion apparatus disclosed in the Applicant’s prior WO2017 / 197454, the contents of which are incorporated herein by reference.

[0096] Throughout this specification and claims which follow, unless the context requires otherwise, the words “comprise” and “include”, and variations such as “comprises”, “includes”, “comprising” and “including”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

[0097] While the foregoing description describes several examples, it will be understood by those skilled in the art that variations and modifications to these examples may be made without departing from the spirit and scope of the present disclosure. The present disclosure encompasses all combinations of various aspects and examples described herein. It is understood that any and all examples may be taken in conjunction with any other example to describe additional examples.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An apparatus for treating a fluid including an organofluorine compound, the apparatus including: a vessel that contains a liquid with a fluoride bonding agent; a combustion chamber in fluid communication with the vessel via an outlet submerged in the liquid; an inlet configured to introduce the fluid into the combustion chamber; and a flame source configured to produce a flame in the combustion chamber to at least partially break down the organofluorine compound to form a gaseous combustion product bearing fluoride, wherein the gaseous combustion product passes from the outlet of the combustion chamber through the liquid so that the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent.

2. The apparatus of claim 1, wherein the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent by forming a fluoride precipitate.

3. The apparatus of claim 2, wherein the liquid contained in the vessel is water with the fluoride bonding agent as a solute comprising one or more dissolved metal salts.

4. The apparatus of claim 3, wherein at least one of the one or more dissolved metal salts comprises aluminium, magnesium and / or calcium ions that act to form the fluoride precipitate as an aluminium, magnesium and calcium fluoride precipitate respectively.

5. The apparatus of claim 3 or 4, wherein at least one of the one or more metal salts comprises chloride ions.

6. The apparatus of claim 5, wherein the one or more dissolved metal salts comprises at least 20wt% aluminium, calcium or magnesium chloride.

7. The apparatus of any one of claims 3 to 6, wherein the solute at least partially suppresses evaporation of the liquid and / or the release of aerosols from the liquid.

8. The apparatus of any one of the preceding claims, wherein the temperature of the flame in the combustion chamber is in a range of 800°C to 1500°C.

9. The apparatus of claim 8, wherein the flame source is a burner assembly including: a burner oxidant inlet that receives a source of pressurised oxidant; a fuel inlet that receives a source of fuel; and a burner outlet in fluid communication with the combustion chamber allowing an oxidant / fuel mixture to burn and thereby produce the flame in the combustion chamber.

10. The apparatus of claim 9, wherein the inlet includes a fluid line extending within the combustion chamber to a distal end proximate the burner outlet through which the fluid is introduced into the combustion chamber in a region of the flame.

11. The apparatus of claim 10, wherein the fluid line includes a tube, the tube including a stainless steel, tungsten carbide, a titanium-based alloy and / or a nickel-based alloy.

12. The apparatus of claim 10 or 11, wherein the fluid is introduced into the combustion chamber in the region of the flame at a flow rate in a range of 0.5 L / min to 3 L / min.

13. The apparatus of any one of claims 10 to 12, wherein the fluid is introduced into the combustion chamber at a pressure in a range of 500 kPa to 1050 kPa.

14. The apparatus of any one of claims 9 to 13, wherein the source of pressurised oxidant is pressurised air supplied by a high-pressure fan or blower.

15. The apparatus of any one of claims 9 to 14, wherein the source of fuel includes one or any combination of biogas, biofuel, natural gas, propane, fuel oil, kerosene, waste oil and diesel.

16. The apparatus of any one of the preceding claims, wherein a treated fluid passes from the liquid to an exit of the vessel.

17. The apparatus of claim 16, wherein a residence time of the fluid in the apparatus from the inlet to the exit is in a range of 0.5 s to 3 s.

18. The apparatus of claim 16 or 17 with an organofluorine destruction and removal efficiency (DRE) at the exit in relation to the fluid introduced into the combustion chamber being greater than 99%.

19. The apparatus of any one of claims 16 to 18, wherein a treatment facility is provided downstream of the exit of the vessel to at least partially extract organofluorine from the treated fluid, the treatment facility including one or any combination of facilities selected from the group including: a filter; a scrubber; a mist eliminator; and a condenser.

20. The apparatus of claim 19, wherein the filter includes filter media as fabric, granular activated carbon and / or resin beads.

21. The apparatus of claim 19 or 20 with an organofluorine destruction and removal efficiency (DRE) downstream of the treatment facility in relation to the fluid introduced into the combustion chamber being greater than 99.9%.

22. The apparatus of any one of the preceding claims including the combustion chamber extending downwards in the vessel.

23. The apparatus of claim 22, wherein the combustion chamber extends downwards in the vessel from a substantially conical section proximate the flame source to a substantially cylindrical section including the outlet submerged in the liquid.

24. The apparatus of claim 23, wherein the outlet includes a plurality of ports placed circumferentially proximate a bottom of the cylindrical section.

25. The apparatus of any one of claims 22 to 24, wherein the combustion chamber is provided inside the vessel and coaxial with the vessel.

26. The apparatus of any one of the preceding claims, wherein the liquid is dosed with a base to at least partially neutralise hydrogen fluoride dissolved in the liquid.

27. The apparatus of claims 26, wherein dosing of the base is performed so as to control the pH of the liquid in a range of 6.5 to 8.2.

28. The apparatus of any one of the preceding claims including a liquid level measuring device for measuring a parameter indicative of a liquid level in the vessel and / or a concentration measuring device for measuring a concentration of the fluoride bonding agent in the liquid.

29. The apparatus of claim 28, wherein the liquid level measuring device is operatively coupled with a liquid level controller configured to control the liquid level in the vessel so as to at least one of replenish liquid in the vessel and control a fluid differential pressure in the apparatus.

30. The apparatus of claim 29, wherein the liquid in the vessel is replenished with a feed water including a base solution so as to adjust a pH of the feed water.

31. A burner assembly for use in an apparatus for treating a fluid including an organofluorine compound, the burner assembly including: a burner mount plate for mounting the burner assembly to a combustion chamber of the apparatus in a substantially downwards direction; a burner oxidant inlet that receives a source of pressurised oxidant; a fuel inlet that receives a source of fuel;a burner discharge sleeve extending substantially downwards to a burner outlet operatively in fluid communication with the combustion chamber to allow an oxidant / fuel mixture to burn and thereby produce a flame in the combustion chamber; and a fluid line extending through the burner mount plate and burner discharge sleeve to a distal end proximate the burner outlet and through which the fluid is introduced into the combustion chamber in a region of the flame.

32. The burner assembly of claim 31, wherein the fluid line extends through the burner discharge sleeve to the distal end so as to operatively introduce the fluid into the combustion chamber at approximately 20 mm or more beyond the burner outlet.

33. The burner assembly of claim 31 or 32, wherein the fluid line is adjustably mounted in the burner assembly so as to allow a position of the distal end of the fluid line to be adjusted relative the burner outlet.

34. The burner assembly of claim 33, wherein the fluid line is adjustably mounted via a compression fitting proximate the burner mount plate.

35. The burner assembly of any one of claims 31 to 34, wherein the fluid line includes a nozzle at the distal end for introducing the fluid into the combustion chamber as a spray.

36. A process for treating a fluid including an organofluorine compound, the process including: providing a liquid with a fluoride bonding agent in a vessel; producing a flame in a combustion chamber, the combustion chamber in fluid communication with the vessel via an outlet submerged in the liquid; introducing the fluid into the combustion chamber via an inlet to at least partially break down the organofluorine compound by means of the flame to form a gaseous combustion product bearing fluoride;passing the gaseous combustion product from the outlet of the combustion chamber through the liquid so that the fluoride in the gaseous combustion product is at least partially bound by the fluoride bonding agent.

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