Electrochemical Treatment Methods
20180009681 · 2018-01-11
Inventors
- David Victor CAM (Brisbane, AU)
- John Frederick ELLERS (Brisbane, AU)
- Brook Douglas HILL (Brisbane, AU)
Cpc classification
B01D17/06
PERFORMING OPERATIONS; TRANSPORTING
B03C11/00
PERFORMING OPERATIONS; TRANSPORTING
Y02W10/37
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
C02F2301/08
CHEMISTRY; METALLURGY
C02F2303/24
CHEMISTRY; METALLURGY
B03C2201/02
PERFORMING OPERATIONS; TRANSPORTING
C02F9/00
CHEMISTRY; METALLURGY
C02F1/283
CHEMISTRY; METALLURGY
International classification
B01D17/06
PERFORMING OPERATIONS; TRANSPORTING
C02F1/467
CHEMISTRY; METALLURGY
Abstract
Methods of treating a fluid mixture include performing a first treatment on the mixture with electrochemically produced ions to separate an aqueous phase and a hydrophobic phase and performing a second electrochemical treatment on the separated aqueous phase to thereby remove aqueous contaminants from the aqueous phase wherein substantially laminar flow of fluid occurs between electrodes in the second electrochemical treatment.
Claims
1. A method of treating a fluid mixture, the fluid mixture including an aqueous phase, a hydrophobic phase and aqueous contaminants, the method including the steps of: (i) Performing a first treatment on the mixture with electrochemically produced ions to at least partially separate the aqueous phase and the hydrophobic phase; and (ii) Performing a second electrochemical treatment on the at least partially separated aqueous phase to thereby remove aqueous contaminants from the aqueous phase; wherein substantially laminar flow of fluid occurs between electrodes in the second electrochemical treatment.
2. The method of claim 1, wherein the first treatment is a first electrochemical treatment and substantially laminar flow of fluid occurs between electrodes in both the first and second electrochemical treatments.
3. The method of claim 1, wherein the residence time of fluid in the second electrochemical treatment is less than 10 minutes.
4. The method of claim 1, wherein said electrodes are from 1 to 8 mm apart in the second electrochemical treatment.
5. The method of claim 1, wherein the fluid mixture is or is derived from fluid from an oil or gas well.
6. The method of claim 5, wherein the fluid mixture is produced water or flow-back water.
7. The method of claim 2, wherein the first electrochemical treatment is performed at a resistance of greater than 5Ω.
8. The method of claim 1, wherein the first treatment substantially separates the aqueous phase and the hydrophobic phase.
9. The method of claim 1, wherein the first treatment is performed at a pH of less than 6.5.
10. The method of claim 1, wherein the second electrochemical treatment is performed at a resistance of less than 5Ω.
11. The method of claim 1, wherein the aqueous contaminants include one or more of: a gelling agent, a cross-linker for cross-linking the gelling agent, a boiling point modifier, a salt, a surfactant, an antiscaling agent, a breaking agent, a pH modifier, an anti-clay swelling or suspension agent, an iron chelant, an iron chelate, a microorganism, a de-emulsification agent and an agent to control microorganism content.
12. The method of claim 1, wherein the second electrochemical treatment reduces the concentration of boron in the aqueous phase by at least 40%.
13. The method of claim 1, wherein the second electrochemical treatment reduces the chemical oxygen demand of the aqueous phase by at least 30%.
14. The method of claim 1, wherein the second electrochemical treatment is performed in the presence of at least one treatment agent.
15. The method of claim 14, wherein the at least one treatment agent is an oxidant.
16. The method of claim 15, wherein the oxidant is a persulfate.
17. The method of claim 1, wherein a treatment enhancer is applied to the aqueous phase during or after the second electrochemical treatment.
18. The method of claim 17, wherein the treatment enhancer is ultraviolet light or ultrasonic waves.
19. A method of electrochemically treating an aqueous solution including a source of chloride ions, the method including the steps of: (i) adding a source of sulfate radicals to the solution; and (ii) electrochemically treating the solution of step (i); wherein substantially laminar flow of the solution occurs between electrodes in step (ii).
Description
BRIEF DESCRIPTION OF DRAWINGS
[0237] Examples of the invention will now be described by way of example with reference to the accompanying figures, in which:
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[0276] Preferred features, embodiments and variations of the invention may be discerned from the following Description which provides sufficient information for those skilled in the art to perform the invention. The following Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way.
DESCRIPTION OF EMBODIMENTS
[0277] Embodiments of the invention will now be described with reference to
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[0279] After the first electrochemical treatment step is complete, the fluid flows to a first clarifier 410. Solid residue from the first clarifier 410 then flows to a dewatering apparatus 424. Hydrophobic matter from the first clarifier 410 may be removed (not shown in
[0280] After the second electrochemical treatment step, the aqueous solution flows to a second clarifier 416. Solid residue from the second clarifier 416 flows to the dewatering apparatus 424, whereas supernatant is filtered at filters 418. If desired, the supernatant from the first clarifier 410 may flow directly to the filters 418. Further treatment agents or additives may be added to the retentate and permeate from the filters 420, and permeate from the filters 418 may flow to a further fluid storage 422 for disposal, and retentate from the filters 418 may flow to dewatering apparatus 424. The solid residue is dewatered at the dewatering apparatus 424, after which the dewatered solid residue is transported away for disposal 426.
[0281] If desired, the plant or system 400 may be configured to allow the two electrochemical treatment apparatuses 408 and 414 to operate in parallel rather than in series. If these apparatuses 408 and 414 operate in parallel (which may be advantageous for produced water, for example), then both apparatuses 408 and 414 may be for performing the first electrochemical treatment step or the second electrochemical treatment step. Similarly, various steps in the method or components of the plant or system 400 may be omitted, including first clarifier 410, second clarifier 416, filters 418 and fluid storages 404 and 422.
[0282] A further process is illustrated in
[0283] Exemplary electrochemical apparatuses and systems which may be used in any of the electrochemical treatment steps as described above are now discussed with reference to
[0284]
[0285] In an electrochemical (especially electrocoagulation) process, a fluid being treated flows past an electric field generated between an anode 44 and a cathode 42. Metal ions may be generated at the anode 44, along with production of hydroxyl ions (or radicals) and possibly sulfate ions (or radicals) at the cathode 42. Gases may also be formed, such as hydrogen gas. These ionic species (and gases) may result in chemical modification of contaminants in the liquid (such as through oxidation), as well as destabilisation of electrical charges holding contaminants in the liquid (i.e. reduction of the net surface charge of the contaminants, which thereby reduces repulsive charges). This latter effect may allow the contaminant particles to move closer together and allow aggregation (through, for example, van der Waals forces), and aggregation may also be aided by the presence of gelatinous polymeric metal hydroxides in the solution.
[0286] The apparatus 1 of the present disclosure may be used (or be configured) to remove, immobilise, oxidise or reduce contaminants in or from a liquid. Contaminants may be selected from one or more of the group consisting of: metals (including transition and heavy metals), salts, solids, pathogens (including bacteria, protozoa, viruses and other organisms including algae), amphoteric species, colloids (organic and inorganic), suspended solids, organic chemicals, oils (such as in droplet and emulsified forms), refractory organics and various other undesirable substances. The contaminants are typically removed from the liquid in the floc. The contaminants may also include an aqueous contaminant, as described above.
[0287] As used herein, the term “floc” relates to any coagulated, precipitated matter or sludge (which, for example, may be solid or gelatinous in form, or may be or include oils) produced during the electrochemical treatment. The process of electrochemical treatment to form the floc causes impurities in the liquid (especially water) to be easily removable or separable from the floc.
[0288] The application of an electrical field between the electrodes 40 (between the at least one cathode 42 and the at least one anode 44) in the treatment chamber 10 may result in the creation of highly charged polymeric metal hydroxide species (these are typically created at the at least one anode 44). These species typically neutralise the electrostatic charges on contaminants in the liquid (such as suspended solids or oil droplets) and facilitate their coagulation or agglomeration and resultant separation from the liquid. In prior art apparatuses, electrochemical treatment typically results in the precipitation of certain metals, salts and amphoteric species as coagulated particles within the apparatus and especially on the surface of the electrodes 40. This surface fouling or passivation of the electrodes 40 is a significant disadvantage of prior art apparatuses.
[0289] In one embodiment, the liquid rises (or ascends) as it travels through the treatment chamber 10. In a further embodiment, the liquid obliquely rises as it travels through the treatment chamber 10.
[0290] The treatment chamber 10 may be of any suitable shape. In
[0291] The base 12 of the treatment chamber 10 illustrated in
[0292] The treatment chamber 10 may be of any suitable size. In one embodiment, the treatment chamber 10 accommodates from 125 kL to 500 kL of liquid, especially about 250 kL. The apparatus 1 may be configured for a liquid flow rate of at least 10 L/s, especially about 23 L/s. The residence time of the liquid in the treatment chamber 10 may be less than 2 minutes, especially about 30 seconds.
[0293] An exemplary disperser 22 is illustrated in
[0294] The disperser 22 may further include a diffuser, for evenly distributing the liquid exiting the disperser 22. A diffuser may further improve the movement of the liquid to be treated into the treatment chamber 10. For example, when a liquid enters the disperser the pressure may be higher at the liquid entry point 24 than at a position on the disperser 22 furthest from the liquid entry point 24. To counter this, one solution may be to vary the size of the inlet 20 openings, so that the inlet 20 openings are larger at the liquid entry point 24 end of the disperser 22, and the inlet 20 openings are smaller at the position on the disperser 22 furthest from the liquid entry point 24.
[0295] The at least one inlet 20 and/or disperser 22 may be positioned at any suitable point or points in the treatment chamber 10. In
[0296] At least one treatment agent may be used to assist in the treatment of the liquid. The at least one treatment agent may be a fluid (including a gas or a liquid) or a solid. The at least one treatment agent may be an oxidant or reductant.
[0297] The at least one treatment agent may be for reaction with certain contaminants in the liquid to be treated, may be used to adjust the properties of the liquid being treated (for example to adjust the pH of the liquid), or may be for adjusting the properties of the floc (for example the agglomeration, viscosity or flowability of the floc).
[0298] The at least one treatment agent may be a gas (which may be inert, an oxidant or a reductant, for example). The gas may be advantageously used to improve or increase the liquid flow velocity between the electrodes and/or to increase or improve the reaction of components within the liquid. The gas may, in particular, create favourable conditions at the face of the electrodes 40 wherein reduction or oxidation processes can be better controlled by the presence of gaseous reactants, which can include either reactive or inert gaseous reactants.
[0299] Increasing the liquid flow velocity between the electrodes 40 may be advantageous for several reasons. First, increased liquid flow velocity between the electrodes 40 may reduce the accumulation of dangerous gases, such as hydrogen, chlorine and hydrogen sulfide at the electrodes 40. Although such gases are typically formed in the electrocoagulation process, in the absence of high current densities the formation rate of such gases is usually so low that poor clearance of these gases occurs. The addition of a buoyant gas to the treatment chamber 10 improves the clearance of such dangerous gases.
[0300] A second and related advantage of increasing the liquid flow velocity between the electrodes 40 is that passivation of the at least one cathode 42 may be reduced, as higher liquid flow rates decreases the potential for material build-up (such as floc) on the at least one cathode 42.
[0301] A third advantage of increasing the liquid flow velocity between the electrodes 40 is that the liquid is more likely to push any floc (including, for example, coalescing oil droplets) being formed to the top 14 of the treatment chamber 10, where the floc may be efficiently removed or recovered for further processing or sale. This prevents the floc from settling on the base 12 of the treatment chamber 10.
[0302] The gas introduced to the treatment chamber 10 may also be used to contribute to chemical reactions occurring within the treatment chamber 10, allowing for the formation of additional compounds to assist in treatment or purification of the liquid. For example, and as discussed above, the gas selected may be used as an oxidant or a reductant. Specific types of gases may be selected for removal of targeted ionic species.
[0303] Examples of gases that may be used in the apparatus 1 include one or more of the group consisting of: air, hydrogen, oxygen, ozone, carbon monoxide, carbon dioxide, sulphur dioxide, hydrogen sulfide, nitrogen, chlorine, fluorine, chlorine dioxide, ammonia, or a combination thereof; especially hydrogen, hydrogen sulfide, ozone, chlorine, carbon monoxide, air, carbon dioxide, or a combination thereof; more especially air, carbon dioxide, hydrogen sulfide, ozone, hydrogen, carbon monoxide, or a combination thereof. The gas may be especially known for its ability to display enhanced reactivity in an electric field with ionic species present in such water and wastewater systems. The gas may be a buoyant gas.
[0304] A plurality of treatment agents may enter the treatment chamber 10, such as an inert gas and an oxidant or reductant.
[0305] The at least one treatment agent may be introduced into the treatment chamber 10 in any suitable way. For example, if the treatment agent is a solid, the solid may be added directly to the treatment chamber 10, such as by dropping the solid into the treatment chamber 10 at the top 14 of the treatment chamber 10. In another example, the at least one treatment agent (which may be a solid, liquid or gas) may be mixed with the liquid to be treated before the liquid enters the treatment chamber. If the at least one treatment agent is a solid, the solid treatment agent may be dissolved in the liquid to be treated, or a suspension or colloid may be formed. If the at least one treatment agent is a gas, the gas treatment agent may be added to, or dissolved within, the liquid to be treated (for example this may be achieved under pressure). The added gas may form microbubbles in the treatment chamber 10 (for example in suspension as the pressure is progressively reduced), and these microbubbles may rise through the treatment chamber 10. As the microbubbles contact the electrodes 40, turbulent mixing conditions may be provided, along with a reducing or oxidative environment as required. The microbubbles may entrain materials forming at the electrodes 40 so as to keep the electrodes 40 clear of reaction products or may for example provide gases for reductive or oxidative processes at the face or reactive surface of the electrodes 40. In one embodiment, the apparatus 1 includes a mixer in fluid communication with the at least one inlet for a liquid to be treated 20, wherein the mixer is for mixing at least one treatment agent (which may be a liquid, gas or solid) with the liquid to be treated, before the liquid to be treated passes through the at least one inlet 20.
[0306] If the at least one treatment agent is a solid or a fluid, the at least one treatment agent may enter the treatment chamber 10 through at least one treatment inlet for entry to the treatment chamber 10 of the at least one treatment agent. Therefore, the treatment chamber 10 may further include at least one treatment inlet for entry of a treatment agent for assisting in the treatment of the liquid. The treatment chamber 10 may include at least one treatment inlet (or a plurality of treatment inlets in fluid communication with each other) for each or each mixture of treatment agents. Advantageously, the at least one treatment inlet may allow for further control over the rate of addition or concentration of the at least one treatment agent within the treatment chamber 10 (and if the at least one treatment agent is an oxidant or reductant, for example, the at least one treatment inlet may allow control over the rate at which electrochemical oxidation or reduction reactions may occur). The at least one treatment agent may, for example, be mixed with a liquid (such as a portion of the liquid to be treated) before it passes through the at least one treatment inlet. The at least one treatment agent may be mixed with the liquid as discussed in the previous paragraph before it passes through the at least one treatment inlet.
[0307] In one embodiment, the at least one treatment inlet is a plurality of treatment inlets for dispersing the treatment agent into the treatment chamber 10, especially for evenly dispersing the treatment agent throughout the treatment chamber 10. The treatment chamber 10 may include at least 10 treatment inlets, especially at least 15 inlets, more especially at least 20 inlets, and most especially at least 30 inlets.
[0308] Advantageously, by using a plurality of inlets for entry of a treatment agent, the treatment agent may evenly enter the treatment chamber 10. This may permit a consistent concentration and/or distribution of the treatment agent in the liquid below the electrodes 40 or in the liquid before the treatment agent is proximate to the electrodes 40, which in turn may allow for improved reaction of the liquid to be treated. When the treatment agent is a gas, a plurality of inlets for a gas treatment agent may improve even fluid flow throughout the treatment chamber 10 and may maximise efficient contact between the electrodes 40 positioned within the treatment chamber 10 and the liquid being treated. A plurality of inlets for a gas treatment agent may also improve the distribution of the gas within the liquid being treated, which in turn may improve the effect of the gas in chemical/electrochemical reactions within the treatment chamber 10 (for example, when the gas is an oxidant or reductant, the performance of the apparatus 1 in treatment, separation or recovery of contaminants may be improved).
[0309] The at least one treatment inlet may be at least one fluid treatment inlet (the fluid may include gases and liquids, and for example, the liquids may include suspended solids). For avoidance of doubt, the term “fluid treatment inlet” does not mean that the treatment agent is in fluid form (although it may be), only that a fluid at least including the treatment agent passes through the fluid treatment inlet. The at least one fluid treatment inlet may be in the form of a fluid treatment disperser. The at least one fluid treatment inlet may be at least one liquid treatment inlet (again, the term “liquid treatment inlet” means that a liquid at least including the treatment agent passes through the liquid treatment inlet). The at least one liquid treatment inlet may be in the form of a liquid treatment disperser. The liquid treatment disperser may be as described above for the liquid disperser.
[0310] The at least one treatment inlet may be an inlet for a gas treatment agent (i.e. a gas inlet 60). The treatment chamber 10 may include a gas disperser 62, especially in the form of a gas manifold, the gas disperser 62 having a plurality of gas inlets 60 to the treatment chamber 10.
[0311] An exemplary gas disperser 62 is illustrated in
[0312] The at least one treatment inlet may be positioned at any suitable point or points in the treatment chamber 10. In one embodiment, the at least one treatment inlet is positioned beneath the electrodes 40 (especially so that the treatment agent substantially rises as it travels through the treatment chamber 10).
[0313] In further embodiments, the apparatus 1 may include a liquid pump for pumping liquid to be treated through the at least one liquid inlet 20, and/or at least one treatment agent pump (which may be a liquid pump and/or a gas pump) for pumping the treatment agent through the at least one treatment inlet.
[0314] The at least one outlet 30 may be positioned above the electrodes 40 (especially at the top 14 of the treatment chamber 10), especially so that the liquid substantially rises as it travels through the treatment chamber 10. In one embodiment, the at least one outlet 30 includes a floc outlet 32 for exit of floc, and/or a liquid outlet 34 for exit of electrochemically treated liquid. The floc outlet 32 may be positioned above the liquid outlet 34. For the avoidance of doubt, some liquid may exit the treatment chamber 10 at the floc outlet 32 with the floc, and some floc may exit the treatment chamber 10 through the liquid outlet 34 (although substantially all floc especially exits the treatment chamber 10 through the floc outlet 32).
[0315] The liquid outlet 34 may be positioned in any suitable way within the treatment chamber 10, provided that substantially no floc is able to exit the treatment chamber 10 through the liquid outlet 34. In the embodiment illustrated in
[0316] The liquid outlet 34 may be in the form of an aperture or passageway extending from the side wall of the treatment chamber 10 (as illustrated in
[0317] In the embodiment illustrated in
[0318] Advantageously, the apparatus 1 of the present disclosure may allow substantially all coagulated floc to rise to the surface of the liquid, where the floc can be separated after passing through the floc outlet 32. This is in marked difference to many existing electrochemical liquid treatment apparatuses, in which floc often settles at the bottom of the apparatus, where it needs to be removed via a drain.
[0319] In one example, the apparatus 1 includes at least one floc outlet 32, especially in the form of a weir or spillway. In other examples, the apparatus 1 includes two, three or four floce outlets 32, especially in the form of a weir or spillway. In a further example, there may be a floc outlet 32 on each side of the treatment chamber 10 (again, especially in the form or a weir or spillway). The floc outlet 32 may include an adjustable baffle, which may be in the form of a plate. The adjustable baffle may form the lower lip of a weir or spillway, and the baffle may be raised or lowered to adjust the separation of the floc from the electrochemically treated liquid. For example, by raising the baffle typically less electrochemically treated liquid would pass through the floc outlet 32.
[0320] The apparatus 1 may also include a floc mover 80 (especially in the form of a floc skimmer as illustrated in
[0321] The floc outlet 32 may be especially at the top 14 of the treatment chamber 10, and may be especially positioned substantially at the intended height of the liquid within the treatment chamber 10.
[0322] A separator 70 may be positioned in fluid communication with the floc outlet 32 to separate floc from the liquid. The separated floc may be disposed of, further treated, or otherwise used. The separated liquid may be combined with the liquid exiting the treatment chamber 10 via the liquid outlet 34; returned to the treatment chamber 10 for further treatment; or diverted elsewhere (for example by the use of a float or sensor actuated submersible sludge pump) for further treatment or release to the environment.
[0323] The separator 70 may be in the form of a filter. In one embodiment, the filter may be a filtration bag, especially a filtration bag made of a polymeric material, more especially a filtration bag having woven polymeric fibres which trap the solids and permit the free flow of separated liquid.
[0324] The plurality of electrodes 40 may be selected from the group consisting of an anode 44, a cathode 42 and an electrical conductor 46; especially at least one anode 44, at least one cathode 42 and at least one electrical conductor 46, wherein said at least one electrical conductor 46 is positioned intermediate said at least one cathode 42 and said at least one anode 44.
[0325] In use, the apparatus includes at least one anode 44 and at least one cathode 42. However, the electrodes 40 may all be of similar structure and only become an anode 44, a cathode 42 or an electrical conductor 46 by virtue of the power connected to the electrode 40 (or lack thereof in the case of an electrical conductor 46; the electrical conductor 46 is not intended to accept power from a power source external to the treatment chamber 10. However, due to the electrical current resulting from the application of power to the anode 44 and cathode 42 and the movement of ions in the liquid, when the apparatus 1 is in use the at least one electrical conductor 46 will carry charge). The at least one electrical conductor 46 is especially positioned between at least one anode 44 and at least one cathode 42.
[0326] In one embodiment, from 2 to 12 electrodes 40 in the apparatus 1 are connected to a power source; especially from 2 to 10 or from 2 to 8 electrodes 40 in the apparatus 1 are connected to a power source; more especially from 2 to 6 or from 2 to 4 electrodes 40 in the apparatus 1 are connected to a power source; most especially three electrodes 40 in the apparatus 1 are connected to a power source. If three electrodes 40 in the apparatus 1 are connected to a power source, the two terminal electrodes (i.e. at each end of the plurality of electrodes 40) will have the same polarity (i.e. either an anode 44 or a cathode 42) and an electrode 40 intermediate the terminal electrodes 40 (especially substantially equidistant between the terminal electrodes 40) will have the opposite polarity (i.e. either an anode 44 or a cathode 42). The remaining electrodes 40 in the plurality of electrodes 40 will be electrical conductors 46. The apparatus 1 may include from 10 to 1000 electrodes 40; especially from 20 to 500 electrodes 40; more especially from 30 to 250 electrodes 40; most especially from 40 to 100 electrodes 40.
[0327] The electrodes 40 may be replaceable and/or removable. For example, the electrodes 40 may be removable from the treatment chamber 10 by means of an overhead gantry. The electrodes 40 may be removed for temporary storage as a set (for example in horizontal racks above the unit), or can be replaced individually such as when an electrode 40 loses its anodic potential through corrosion.
[0328] Each electrode 40 may be of any suitable shape, although certain shapes facilitate easy removal from the treatment chamber 10. For example, each electrode 40 may be curved or planar, especially planar (as in the embodiment exemplified in
[0329] Each electrode 40 may be made of any suitable material. Exemplary materials include aluminium, iron, steel, stainless steel, steel alloy (including mild carbon steel), magnesium, titanium and carbon. In another embodiment, each electrode may be made of an alloy of or containing a material selected from the group consisting of: aluminium, iron, steel, magnesium, titanium and carbon. Each electrode 40 may be selected depending upon the liquid to be treated, the contaminants in the liquid, the floc to be created and the relative cost of the various metallic electrodes at the time. Each said electrode 40 within the apparatus 1 may be the same or different, and may include the same metal or different metals (for example depending on the desired performance).
[0330] The electrodes 40 may be positionable above or below the level of the liquid in the treatment chamber 10. However, the electrodes 40 are especially positionable below the level of the liquid in the treatment chamber 10 so as not to impede any liquid or floc horizontal flow at the surface of the liquid.
[0331] The electrodes 40 may be positionable within the reaction chamber at any suitable angle. For example, the plurality of electrodes 40 positioned within the treatment chamber 10 may be angled from a vertical plane. In another example, the electrodes 40 or a portion of the electrodes 40 (such as an upper portion) may be angled from a vertical plane (obliquely configured). In the example illustrated in
[0332] Positioning the electrodes 40 within the treatment chamber 10 at an angle may result in a number of advantages. First, positioning the electrodes 40 at an angle may mean that the liquid flows against the electrodes 40 as it rises through the treatment chamber 10 (also gases may travel against the electrode 40 as the gas rises through the treatment chamber 10). This assists in preventing build-up of material (such as floc) on the electrodes 40.
[0333] Secondly, positioning the electrodes 40 at an angle results in a horizontal movement being applied to the liquid as it travels through the treatment chamber 10. This can assist in directing the liquid through the at least one outlet 30, and especially floc through the floc outlet 32. In one example, the horizontal movement applied to the liquid forces any coagulated sediment or floc away from the treatment chamber 10 thereby providing a clear disposal path for the floc from the treatment chamber 10.
[0334] Thirdly, positioning the electrodes 40 at an angle may assist in agglomerating floc. For example, as liquid rises through the treatment chamber 10, the floc may flow against the electrodes 40. This means that floc is more concentrated against the electrodes 40 which assist in agglomeration. In an exemplary embodiment, if the floc includes oil particles, the rising oil particles may be coalesced into larger droplets as a result of entrainment beneath the electrodes 40. This does not generally occur when the plates are in a vertical configuration, and in this exemplary embodiment the dissolved or emulsified oil particles in the liquid may contact the underside of the electrodes 40 where they accumulate and combine with other forming oil particles at the charged interface until such time as a larger (coalesced) droplet forms which then floats to the surface aided by the predominantly diagonal and vertical liquid flow.
[0335] In one embodiment of the present disclosure, the floc is or includes hydrocarbon (or oil) particles. In one example, during electrochemical treatment the coalesced hydrocarbons (or oils) rise to the surface of the liquid and is evacuated from the treatment chamber 10 by means of a horizontal flow imparted by a combination of the natural buoyancy of the oil droplet, the lower density or specific gravity of the entrained oil droplet and the angled electrodes 40. In a further example, during electrochemical treatment the coalescing oil droplets forming beneath the electrodes 40 are forced to the surface with an additional flow of gas and, combined with the horizontal flow imparted by the angled electrodes 40, are cleared from the treatment chamber 10. In another example, during electrochemical treatment the coalesced hydrocarbon droplets are forced to the surface of the liquid via the forced, circulating flow of liquid and a horizontal moment imparted on the liquid via the angle of the electrodes 40.
[0336] Each electrode 40 may also be of any suitable thickness, for example from 1 mm to 20 mm thick, especially from 1 mm to 10 mm thick, more especially from 1 mm to 5 mm thick, most especially about 3 mm thick. In some embodiments, each electrode 40 is less than 20 mm thick, especially less than 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3 or 2 mm thick. In other embodiments, each electrode 40 is greater than 0.5 mm thick, especially greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19 mm thick. In a further embodiment, the thickness of the electrode 40 may be a range in which the upper and lower limits are as previously described.
[0337] The electrodes 40 may be spaced at any suitable distance. For example, the electrodes 40 may be from 1 mm to 150 mm apart, especially from 1 mm to 100 mm apart or from 1 mm to 50 mm apart, more especially from 1 mm to 10 mm apart. The electrodes 40 may be from 1 mm to 5 mm apart, more especially about 3 mm apart. In some embodiments, the electrodes 40 are less than 150 mm apart, especially less than 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4 or 3 mm apart. In other embodiments, the electrodes 40 are greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130 or 150 mm apart. The electrodes 40 may also be a range apart in which the upper and lower limits are as previously described. When the treatment chamber includes more than 2 electrodes, each electrode 40 may be the same distance apart or different distances apart. The electrodes 40 may be held apart in any suitable way. For example, the treatment chamber 10 may include guides for holding the electrodes 40 in position. In one embodiment, the guides may be grooves or slots positioned in opposite walls of the treatment chamber 10. The guides may be made from a high-density, electrically insulating polymeric material, such as HDPE or PVC, or a material as discussed below for the electrode holder 100.
[0338] In one embodiment, the electrodes 40 are from 1 mm to 10 mm thick, more especially from 1 mm to 5 mm thick; and the electrodes 40 are from 1 mm to 10 mm apart, more especially from 1 mm to 5 mm apart. Using thinner electrodes 40 positioned close together enables a greater number of electrodes 40 to be positioned within the treatment chamber 10. This increases the surface area of the electrodes 40 in contact with the liquid, which may enhance the electrochemical treatment of the liquid.
[0339] To improve fluid flow, the electrodes 40 may have a tapered lower edge 41. The lower edge 41 of the electrodes 40 may be tapered to an angle of about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 degrees relative to the longitudinal axis of the electrode. The taper may extend less than 40%, 30%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4% or 3% of the length of the electrode 40. The lower edge 41 of the electrode 40 may be tapered on one or more sides, such as two opposed longitudinal sides, more especially one longitudinal side. If the lower edge 41 of the electrode 40 is tapered on more than one side, then the taper on each side may be the same or different.
[0340] Any suitable electrical current may be applied to the plurality of electrodes 40. However, the current applied to the plurality of electrodes 40 may especially be a direct current of adjustable frequency of alternation. This means that the electrodes 40 functioning as the at least one cathode 42 and the at least one anode 44 may switch during the electrochemical treatment. This enables the electrodes 40 to create a reversible electrical field within the treatment chamber 10, which may assist the electrodes 40 in remaining clear of debris or reaction products that might otherwise inhibit the electrochemical treatment by electro passivation. The polarity switching of the electrodes 40 may allow specific chemical reactions to be delayed or accelerated as required. Therefore, in one embodiment the polarity of the electrodes 40 is reversed during the electrochemical treatment.
[0341] In a further embodiment, the voltage and amperage of the electrical field within the treatment chamber 10 may be adjusted as necessary by placing selected electrodes 40 in electrical contact with a voltage source. The voltage source may be a separate, proprietary manufactured transformer.
[0342] The apparatus 1 may also include at least one non-conductive element positioned within the treatment chamber 10. This non-conductive element may be used to alter the electrical field (amperage and voltage) within the treatment chamber 10. The position, shape and configuration of the non-conductive element may be as described above for the electrodes 40. However, the non-conductive element is made of a material that does not conduct electricity, such as, for example, a material selected from the group consisting of: a polymer plastic (such as polyvinyl chloride (PVC), high density polyethylene (HDPE), low density polyethylene (LDPE), acrylonitrile butadiene styrene (ABS), polypropylene (PP)); a composite material made with a non-conducting fibre or panel (such as fibreglass) mixed with a resin or resin solution (such as a polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, polypropylene or polyether ether ketone (PEEK)) to produce a polymer matrix, or a combination of the aforementioned materials. In one embodiment the apparatus 1 does not include any non-conductive elements.
[0343] The apparatus 1 may further include a flow aligner 90 for aligning the flow of the liquid between the electrodes 40, the flow aligner being positioned or positionable within the treatment chamber 10. A flow aligner 90 may be advantageous as the liquid beneath the electrodes 40 in the treatment chamber may especially be turbulent. The flow aligner 90 may assist the liquid in moving substantially along the same longitudinal axis as the plurality of electrodes 40, which in turn may improve the reaction between the liquid to be treated and the electrodes 40.
[0344] The flow aligner 90 may be in the form of at least one (especially a plurality of) baffles or baffle walls 92 extending beneath the electrodes 40. The at least one baffle or baffle wall 92 may extend substantially vertically beneath the electrodes 40. The at least one baffle or baffle wall 92 may extend along substantially the same longitudinal axis as the electrodes 40. The at least one baffle or baffle wall 92 may be positioned transversely or substantially perpendicularly to the electrodes 40. The flow aligner 90 may integrally formed with the treatment chamber 10, or may be removable and/or replaceable. Each baffle or baffle wall 92 may be in the form of a plate. Each baffle or baffle wall 92 may be from 20 mm to 500 mm long, especially from 50 mm to 250 mm long or from 60 mm to 150 mm long, more especially from 80 mm to 120 mm long, most especially about 100 mm long.
[0345] The flow aligner 90 may be made of any suitable material, but especially may be made of a non-conductive material. The flow aligner 90 may be made of the materials discussed above for the treatment chamber 10. The flow aligner 90 may be especially made from a composite material made with a non-conducting fibre or panel (such as fibreglass) mixed with a resin or resin solution (such as a polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, polypropylene or polyether ether ketone (PEEK)) to produce a polymer matrix; a polymer plastic such as high density polyethylene (HDPE), polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC); a phenolic polymer plastic; or be fabricated from a number of composite materials including carbon fibre (for example a carbon fibre insulated using a polymer plastic or a composite material) and variations thereof.
[0346] The treatment chamber 10 may be configured to releasably engage with at least one electrode holder 100 holding a plurality of electrodes 40 for electrochemical treatment of the liquid. The treatment chamber 10 may include at least one guide for guiding the electrode holder 100 into position. The treatment chamber 10 may include at least one (or a plurality of) grooves for slidable engagement of the electrode holder 100 in the treatment chamber. The treatment chamber 10 may include at least one power connector for connecting power to the electrode holder, to thereby power at least one of the electrodes 40 held by the electrode holder. The treatment chamber 10 may include a plurality of power connectors (for example of different polarity) for connecting power to each electrode holder. For example, if the apparatus 1 includes one electrode holder 100, then the treatment chamber 10 may include at least one power connector for connecting power to at least one anode 44 (especially one or two power connectors) and at least one power connector for connecting power to at least one cathode 46 (especially one or two power connectors). The at least one power connector may be located on a wall of the treatment chamber, especially in a groove in which the electrode holder 100 may be slideably engaged. In one embodiment, only one wall of the treatment chamber 10 includes a power connector for each electrode holder 100.
[0347] The treatment chamber may be configured to releasably engage with from 1 to 100 electrode holders 100, especially from 2 to 50 electrode holders 100, more especially from 2 to 40, from 2 to 30, from 2 to 20, or from 2 to 10 electrode holders 100.
[0348] The apparatus 1 may further include an electrode holder 100 (an exemplary electrode holder 100 is illustrated in
[0349] The electrode holder 100, especially the at least two side walls 104 of the electrode holder 104, may be configured to releasably engage with the treatment chamber 10. The electrode holder 100 (especially the at least two side walls 104) may be slidably engageable with the treatment chamber 10. The electrode holder 100 (especially the at least two side walls 104) may be releasably engageable in the treatment chamber 10 by friction, by a clamp, or by another suitable fastener. In one example, the treatment chamber 10 or the electrode holder 100 may include a clamp for releasably clamping the electrode holder 100 in position. The electrode holder 100 (especially at least one of the at least two side walls 104) may be configured to accept power, especially from the wall of the treatment chamber 10, more especially by way of a power connector located in the electrode holder 100 (especially a side wall 104 of the electrode holder 100). The electrode holder 100 (especially at least one of the at least two side walls 104) may be configured to supply power along a longitudinal edge of at least one electrode 40 held by the electrode holder. Providing power along a longitudinal edge of at least one electrode 40 may provide superior flow of power than if power was only supplied to the at least one electrode 40 at a single point.
[0350] Power connectors in the electrode holder 100 and the treatment chamber 10 may connect in any suitable way. For example, the two power connectors may connect by way of abutting surfaces or projections, or by way of a male-female connection.
[0351] The electrode holder 100 may hold a plurality of electrodes 40. The electrodes 40 within the electrode holder 100 may be replaceable and/or removable. In one embodiment, the electrodes 40 within the electrode holder 100 may not be replaceable and/or removable. The electrode holder 100 may include slots machined to enable the electrodes 40 to slide in and out of the electrode holder 100 as required. This may enable replacement of the electrodes 40 within the electrode holder 100 whilst the machine continues to operate with a prior electrode holder 100. The electrodes 40 may be as described above. Furthermore, the spacings between the electrodes in the electrode holder 100 may be as described above for the spacings for the electrodes 40 in the treatment chamber 10.
[0352] The electrode holder 100 may include a flow aligner 90, as described above. The flow aligner 90 may be positioned opposite to the handle 102, beneath the electrodes 40.
[0353] Any suitable number of electrodes 40 may be held by the electrode holder 100. In one embodiment, the electrode holder may hold from 3 to 100 electrodes 40; especially from 3 to 50 electrodes 40; more especially from 3 to 25 electrodes 40; most especially from 5 to 15 electrodes 40 or about 10 electrodes 40. In one embodiment, the electrode holder 100 holds at least 3, 4, 5, 6, 7, 8, 9 or 10 electrodes 40. In another embodiment, the electrode holder 100 holds less than 100, 90, 80, 70, 80, 70, 60, 50, 40, 30, 20 or 15 electrodes 40.
[0354] The electrode holder 100 or the electrodes 40 within the electrode holder 100 may be positionable within the treatment chamber 10 at any suitable angle. In one embodiment, the electrode holder 100 is positionable substantially vertically within the treatment chamber 10. In this embodiment, the electrodes 40 may be held substantially vertically by the electrode holder 100, or the electrodes 40 may be held at an angle from the vertical by the electrode holder 100. In another embodiment, the electrode holder is positionable at an angle within the treatment chamber 10. In this embodiment, the electrodes 40 may be held substantially vertically by the electrode holder 100 (i.e. the longitudinal axis of the electrodes 40 held by the electrode holder 100 may be substantially the same as the longitudinal axis of the electrode holder 100). Alternatively in this embodiment, the electrodes 40 may be held at angle within the electrode holder 100. The angle of the electrode holder 100, or the angle of the electrodes 40 within the electrode holder 100 may be as described above for the angle of the electrodes 40 within the treatment chamber 10. For example, the electrodes 40 within the electrode holder 100 may be held at an angle of from 10 to 30 degrees from the vertical, especially at an angle of 10 to 15 degrees or about 15 degrees from the vertical. In another example, the electrode holder 100 may be held at an angle of from 10 to 30 degrees from the vertical, especially at an angle of 10 to 15 degrees or about 15 degrees from the vertical. The electrodes 40 within the electrode holder 100 may be from 1 mm to 10 mm apart, especially about 3 mm apart. The electrodes 40 within the electrode holder 100 may be replaceable and/or removable.
[0355] The electrode holder 100 advantageously may allow for the easy and rapid exchange of electrodes 40 in the apparatus 1. The electrode holder 100 may overcome the delays inherent in changing individual electrodes 40 within the reaction chamber and may be particularly advantageous in areas of low head height.
[0356] The frame of the electrode holder 100 may be made of any suitable material, but especially may be made of a non-conductive material. The frame of the electrode holder 100 may be made of the materials discussed above for the treatment chamber 10. The frame of the electrode holder 100 may be especially made from a composite material made with a non-conducting fibre or panel (such as fibreglass) mixed with a resin or resin solution (such as a polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, polypropylene or polyether ether ketone (PEEK)) to produce a polymer matrix; or a polymer plastic such as high density polyethylene (HDPE), polyethylene (PE), polyethylene terephthalate (PET) or polyvinyl chloride (PVC); a phenolic polymer plastic; or a carbon fibre insulated using a polymer plastic or a composite material.
[0357] The electrode holder 100 may be removable by way of a lifting device which lifts the electrode holder 100 substantially vertically before allowing for horizontal movement of the electrode holder 100 above the apparatus 1. The lifting device may be slideably mounted on at least one (especially two) rails. In one embodiment, the electrode holder 100 may be removable using an overhead gantry.
[0358] In a further embodiment, the apparatus 1 may include a current controller for controlling the amperage and voltage applied to the at least one anode 44 and the at least one cathode 42.
[0359] In a further embodiment, the apparatus 1 may include a plurality of treatment chambers 10. Each said treatment chamber 10 may include at least one inlet 20 for entry of a liquid to be treated, and at least one outlet 30 for exit of electrochemically treated liquid; and a plurality of electrodes 40 positioned within the treatment chamber 10 for electrochemical treatment of the liquid. In one example, the apparatus 1 may include at least a first and a second treatment chamber 10a, 10b, and the apparatus 1 may be configured so that liquid from said at least one outlet 34a of the first treatment chamber 10a flows into said at least one inlet 20b of the second treatment chamber 10b. The apparatus 1 of
[0360] In another embodiment, the floc exiting a first treatment chamber 10a through a floc outlet 32a is diverted so that this floc does not travel to the second treatment chamber 10b, and similarly the floc exiting the second treatment chamber 10b through a floc outlet 32b is diverted so that this floc does not travel to the third treatment chamber 10c. However, in this embodiment the liquid from the liquid outlet 34a of a first treatment chamber 10a flows into the inlet 20b of a second treatment chamber 10b, and the liquid from the liquid outlet 34b of the second treatment chamber 10b flows into the inlet 20c of a third treatment chamber 10c.
[0361] The apparatus 1 may include a pretreater positioned prior to, and in fluid communication with the liquid inlet 20. The pretreater may be, for example, a filter to remove larger particulate solids from the fluid stream that could lodge between the electrodes and disrupt liquid flows or otherwise impede with the functioning of the device. However, such pretreatment is typically not necessary.
[0362] When the apparatus 1 is used, the liquid to be treated enters the treatment chamber 10 through the at least one inlet 20 and a voltage is applied to the plurality of electrodes 40 (especially to provide at least one anode 44 and at least one cathode 42), to thereby electrochemically treat the liquid. Floc may be generated as the liquid is electrochemically treated, and the floc may rise to the surface of the liquid. The floc may exit the treatment chamber 10 at the floc outlet 32 (for subsequent separation of the floc from liquid, such as by filtering) and the electrochemically treated liquid may exit the treatment chamber 10 at the liquid outlet 34. A treatment agent may be introduced into the treatment chamber 10 during the electrochemical treatment. A treatment enhancer may be applied to the treatment chamber 10 during the electrochemical treatment.
[0363] The apparatus 1 may be operable at any suitable temperature and pressure. However, the apparatus 1 is especially operable at atmospheric temperature and pressure. In another embodiment, the apparatus 1 is operable at greater than atmospheric pressure, or less than atmospheric pressure, as defined elsewhere in the specification.
[0364] The apparatus 1 of the present disclosure may also form one component of a larger water treatment system.
[0365]
[0366] As shown in
[0367] The fluid then flows through ball valves (the first of which is an 80 mm valve) to the treatment chamber 210 where electrochemical treatment occurs. The pH of the fluid during the electrochemical treatment may be controlled by the introduction of an acid from acid tank 305. The electrochemically treated fluid then flows to the defoaming chamber 250. The electrochemical process may be controlled via a system for regulating the electrochemical treatment (which includes a controller (PLC) 307). Electrochemically treated fluid then flows to clarifiers 306 (which have a level switch) through a 65 mm conduit and 50 mm electric ball valves.
[0368] Clarified fluid (and floc) may exit the clarifiers 306 via 50 mm ball valves before passing through a positive displacement pump and then to successive 50 mm ball valves to a drain connection. Alternatively, the clarified fluid (and floc) from the clarifiers 306 may pass to a screw press 308 having a float valve. Pressed floc exits the screw press through a 25 mm ball valve to a waste bin. Fluid exiting the screw press 306 passes through a 25 mm ball valve to centrifugal pump, and then through a 25 mm check valve before passing back to clarifiers 306.
[0369] Clarified fluid may be passed from clarifiers 306 via a 100 mm conduit to a drop tank 310 (in which the tank has a level transmitter and a level switch). Fluid exiting drop tank 310 passes through a centrifugal pump and then to sand filters 312 (for separation of floc from the fluid) or optionally back through clarifiers 306 by way of 50 mm ball vales and 65 mm check valve. After sand filtration the fluid may be passed to a storage tank 314 (where is it optionally treated by a treatment agent (stored in a dosing tank 304, in which the treatment agent may be pumped into the storage tank 314 by way of a positive displacement pump)), passing through 50 mm ball valves and a 65 mm conduit. From storage tank 314 the treated fluid may pass through 80 mm ball valves and centrifugal pump before being released. Alternatively, fluid from the storage tank 314 may pass through ball valves (80 mm and 25 mm), through centrifugal pump and then to: (i) further components of a filtration system, including a carbon filter 316, nanofilter 318, and reverse osmosis system 320; (ii) screw press 308; or (iii) treatment chamber 210 and defoaming chamber 250. The filtered fluid may pass to a storage tank 322 before re-electrochemical treatment or disposal. In
[0370] The system 200 illustrated in
[0371] Three example treatment chambers 210, electrode holders 280, and defoaming chambers 250 are illustrated in
[0372] The treatment chamber 210 in the apparatus 201 of
[0373] The treatment chamber 210 in
[0374] The treatment chamber 210 in
[0375] The apparatuses 201 illustrated in
[0376] In the examples of
[0377] In
[0378] The treatment chambers 210 in
[0379] The treatment chambers 210 include a disperser 222, and the disperser 222 includes a tube with one fluid entry point 224 and a plurality of inlets 220. The disperser 222 illustrated in the apparatuses 201 of
[0380] The apparatuses 201 further include a flow aligner 290. The flow aligner 290 is connected to the electrode holders 280 (see
[0381] The flow aligner 290 in the apparatuses 201 of
[0382] The flow aligner 290 in
[0383] The apparatus 201 may be configured to electrochemically treat the fluid in the presence of at least one treatment enhancer or at least one treatment agent. The at least one treatment enhancer is capable of penetrating a solid wall of the treatment chamber, and consequently the at least one treatment enhancer (such as ultraviolet radiation, microwave radiation or ultrasonic waves) may be applied to a side wall 216 of the treatment chamber 210. The at least one treatment agent may enter the treatment chamber 210 through at least one treatment inlet, such as through a gas inlet 260 (see
[0384] The treatment chamber 210 also includes at least one outlet 230 for exit of electrochemically treated fluid. In the apparatuses 201 of
[0385] In the apparatuses 201 of
[0386] In the apparatus 201 of
[0387] In the apparatus 201 of
[0388] In the apparatus 201 of
[0389] In
[0390] In the apparatuses of
[0391] Within each electrode holder 280 only two or three electrodes 240 may be connected to power (and thereby become anodes and cathodes). The remaining electrodes may all be electrical conductors. In each electrode holder 280 each electrode 240 is substantially planar and is of solid construction. The electrodes 240 may have a tapered lower edge, as previously described. The apparatuses 201 of
[0392] As illustrated in
[0393] The treatment chamber 210 of
[0394] A different mechanism for connecting power to the electrodes 240 is illustrated in the treatment chamber 210 of
[0395] A similar mechanism for connecting power to the electrodes 240 is illustrated in the treatment chamber 210 of
[0396] In
[0397] In the apparatus 201 of
[0398] In the apparatus 201 of
[0399] The treatment chamber 210 in
[0400] As illustrated in
[0401] The apparatus 201 of
[0402] Any suitable current may be applied to the electrodes 240 during the electrochemical treatment, however the voltage applied to each electrode holder 280 in the treatment chamber 210 in
[0403] In use, fluid is pumped into the treatment chamber 210 via the at least one inlet 220, and fluid pressure builds beneath flow aligner 290. Fluid passes through the flow aligner 290 and between the electrodes 240 where the fluid is electrochemically treated and floc is generated. The floc and electrochemically treated fluid then flow to the upper portion of the treatment chamber 210, and gas bubbles (from gas inlets 260, for example) may assist in driving the floc and electrochemically treated fluid vertically. The floc and electrochemically treated fluid then pass through the at least one outlet 230 and into the defoaming chamber 250, over/around flow diverter(s) 232 and optionally past defoamers 252. This process leads to defoaming of the floc/electrochemically treated liquid. The floc/electrochemically treated fluid then flows out the outlet 254 in the defoaming chamber 250 and then to a vessel for separation of the floc (e.g. clarifier 306).
[0404] A further apparatus 201 is illustrated in
[0405] The apparatus 201 of
EXAMPLES
[0406] In examples 1-8, unless otherwise described the following test conditions outlined in Table 1 were used for the electrochemical treatment steps.
TABLE-US-00001 TABLE 1 Test Conditions Used for Electrochemical Treatment Steps Value Units Contact Time 0.5 to 1.0 min Flow Rate 1.15 L/m Initial Voltage 37.9 V Number of Electrodes 13 Number of Active Electrodes 12 Surface Area of One Electrode Face 150 cm.sup.2 Total Exposed Electrode Area 3,600 cm.sup.2 Polarity Reversal Period 30 s
[0407] For the first electrochemical treatment step, a low current was typically used (1-5 A), and mild steel electrodes. For the second electrochemical treatment step a high current was typically used (8-15 A) and aluminium electrodes. The electrodes in the electrochemical treatment steps were configured to reverse their polarity about every 30 seconds.
[0408] Experiments were performed on frac return water (Example 1, Table 2), flowback water (Example 2, Table 3), frac flowback water (Example 3, Table 4), and produced water (Example 4, Table 5). An exemplary landfill waste characterisation is also provided in Example 5 (Table 6). The experiments may be generally performed in accordance with the process flow diagram illustrated in
Example 1: Frac Return Water
[0409]
TABLE-US-00002 TABLE 2 Purification of Frac Return Water Cooper Basin Australia After first After second Diluted electrochemical electrochemical After Targets Landfill 2:1 Raw treatment step treatment step filtration (mg/L) Waste Element (mg/L) (mg/L) (mg/L) (mg/L) (P) = Preferred (mg/kg) Boron 55 40 15 0.1 <5 (P) 1,800 Hydrocarbons 405 5 0.1 0.01 <10 (P) <500 Bacteria NR 1 0.01 0.01 <100,000 0 pH 7.5 8 9 8 6-8 N/A Temp NR Ambient Ambient Ambient 40° F.-100° F. N/A Chloride 10,000 10,200 10,050 150 <15,000 <50,000 Calcium 75 6 2 0.1 <500 2,500 Magnesium 25 3 1 0.1 25-500 830 Iron 1 2.5 1 0.1 <2 (P) 30 Fluoride 10 8 6.4 1 <10 300 Phosphate 1 0.8 0.65 0.1 <5 30 Red. agents NR 0 2 0 0 0 Sulfates 100 80 64 1 <500 (P) 3,300 TDS 50,000 50,000 50,000 5 <50,000 N/A COD 3,000 1730 732 1 <10 N/A BOD 630 363 154 0.2 <10 N/A
Example 2: Flowback Water
[0410]
TABLE-US-00003 TABLE 3 Purification of Flowback Water Cooper Basin After first After second Flowback electrochemical electrochemical After Targets Landfill Raw treatment step treatment step filtration (mg/L) Waste Element (mg/L) (mg/L) (mg/L) (mg/L) (P) = Preferred (mg/kg) Boron 56.3 38.9 14.7 0.1 <5 (P) 1,850 Hydrocarbons NR 6 0.1 0.1 <10 (P) <500 Bacteria NR 1 0.01 0 <100,000/mL 0 pH 8.1 8.5 9.1 8 6-8 N/A Temp NR Ambient Ambient Ambient 40° F.-100° F. N/A Chloride 13,560 13,720 13,400 172 <15,000 <50,000 Calcium 199.4 18 6 0.1 <500 (P) 6,462 Magnesium 66.8 9 3 0.3 25-500 2,011 Iron 2.4 6 2.5 0.1 <2 (P) 75 Fluoride 10 9 6.5 1.5 <10 291 Phosphate 1 0.9 0.7 0.1 <5 29 Red. agents NR 0 2 0.5 0 0 Sulfates 53.1 41.1 32.8 0.1 <500 (P) 2,100 TDS 24,303 24,303 24,303 2.4 <50,000 N/A COD 2820 1613 698 0.1 <10 N/A BOD 604 361 155 0 <10 N/A
Example 3: Frac Flowback Water
[0411]
TABLE-US-00004 TABLE 4 Purification of Frac Flowback Water Cooper Basin After first After second Australia electrochemical electrochemical After Targets Landfill Raw treatment step treatment step filtration (mg/L) Waste Element (mg/L) (mg/L) (mg/L) (mg/L) (P) = Preferred (mg/kg) Boron 23.9 17 6 0 <5 (P) 794 Hydrocarbons NR 7 0.2 0.1 <10 (P) <500 Bacteria NR 1 0.01 0 <100,000/mL 0 pH 7 8.5 9.1 8 6-8 N/A Temp NR Ambient Ambient Ambient 400 F.-1000 F. N/A Chloride 8,784 8,555 8,415 120 <15,000 <50,000 Calcium 518 48 15 0.3 <500 (P) 15,242 Magnesium 53 7 3 0.2 25-500 1,756 Iron 17 42 17 1.1 <2 (P) 545 Fluoride 10 9 6 1.3 <10 279 Phosphate 1 0.8 0.7 0.1 <5 28 Red. agents NR 0 2 0.5 0 0 Sulfates 18 14 11 0 <500 (P) 1,009 TDS 11,694 11,694 11,694 120 <50,000 N/A COD 2,480 1412 622 5 <10 N/A BOD 1090 612 256 2 <10 N/A
Example 4: Produced Water
[0412]
TABLE-US-00005 TABLE 5 Purification of Produced Water Produced Water Cooper After first After second Basin electrochemical electrochemical After Targets Landfill (Raw) treatment step treatment step filtration (mg/L) Waste Element (mg/L) (mg/L) (mg/L) (mg/L) (P) = Preferred (mg/kg) Boron 5.7 4 0.1 0 <5 (P) 190 Hydrocarbons NR 8 0.1 0.1 <10 (P) <500 Bacteria NR 1 0 0 <100,000/mL 0 pH 8.02 8.5 8 8 6-8 N/A Temp NR Ambient Ambient Ambient 400 F.-1000 F. N/A Chloride 7,867 7,546 7,189 105 <15,000 <50,000 Calcium 417 30 3 0.5 <500 (P) 13,567 Magnesium 261 29 11 1 25-500 8,624 Iron 2.9 7 <1 0.1 <2 (P) 82 Fluoride 10 9 6.5 1.5 <10 288 Phosphate 1 0.8 0.7 0.1 <5 26 Red. agents NR 0 0.5 0.5 0 0 Sulfates 4455 3573 121 12 <500 (P) 98,211 TDS 10,680 10,680 10,680 155 <50,000 N/A COD 50 33 0.1 0 <10 N/A BOD 2 1 0 0 <10 N/A
Example 5: Landfill Waste Characterisation
[0413]
TABLE-US-00006 TABLE 6 Characterisation of Landfill Waste Exemplary EPA Landfill (S.A.) Exemplary AS4439 waste TCLP Parameter Target Landfill waste Target Leachate Test Barium 300 300 100 21 Benzo(a)pyrene 1 <0.1 0.001 — Cadmium 3 2 0.5 — Cobalt 170 <20 — — Copper 60 <40 10 — Lead 300 <10 — — Manganese 500 <300 — — Mercury 1 <1 — — Nickel 60 <20 — — TPH (C6-C9) 65 <1.0 — <0.01 TPH (C10-C36) 1000 978 — <0.02 Total BTEX n/r <2.0 — <0.1 Total PAH 5 <2.5 — <0.1 Zinc 200 — <1.0
Example 6: Composition of Formation Water
[0414] The concentration of components in formation water influences the strategy selected for treatment. Therefore the concentration of various components (analytes) in formation water was determined, and the results are provided below.
TABLE-US-00007 TABLE 7 Composition of Formation Water Analyte Test 1 Test 2 pH 7.84 8.1 Temperature 21.9 Conductivity (as μS/cm) 11,370 10,700 Heterotrophic Plate Count (22° C.) CFU/mL 1,500 1,700 Heterotrophic Plate Count (36° C.) CFU/mL 2,000 Total Organic Carbon (TOC) (mg/L) <1 2 Dissolved Organic Carbon (DOC) (mg/L) <1 1 Turbidity 1.18 0.3 True colour (Pt—Co) 1.7 4 Apparent Colour (Pt—Co) 22.2 5 Total Dissolved Solids (mg/L) 6145 6330 Total Suspended Solids (TSS) mg/L 28 <25 Silica as Si (mg/L) (Total) 6.4 7 Silica (Colloidal) 0.4 0.42 Silica (Dissolved) 6.0 6.58 Sodium as Na (mg/L) 2,468 2,240 Potassium as K (mg/L) 14 15 Total Hardness (mg/L as CaCO.sub.3) 340 343 Calcium as Ca (mg/L) 71.4 78 Magnesium as Mg (mg/L) 35.6 36 Barium as Ba (mg/L) 14.0 14.2 Strontium as Sr (mg/L) 17.0 17.4 Alkalinity (mg/L as CaCO.sub.3) 420 389 Bicarbonate (mg/L as CaCO.sub.3) 420 389 Carbonate (mg/L as CaCO.sub.3) 0 <1 Aluminium as Al (mg/L) 0.021 <0.01 Iron (Total) 2.0 2.1 Iron as Fe (mg/L) 0.008 Manganese 0.144 0.14 Sulfate (Sulfate) <1 <1 Chloride 3,546 3,740 Nitrate (as nitrate) nd nd Boron (as mg/L) 0.8 0.62 Fluoride 2.58 1.5 Carbon Dioxide 350 342 Ammonia (as NH.sub.3) 3.6 3.49 Total Phosphorus as P (mg/L) 0.055 0.02 Phosphate, dissolved as PO.sub.4 (mg/l) nd 0.04 Total Nitrogen as N (mg/L) 3.9 3.7 UV 254 nm Absorbance 0.0071
Example 7: Electrochemical Treatment of Formation Water—Aluminium Electrodes
[0415] The formation water outlined in example 6 was subjected to electrochemical treatment. Unless otherwise defined, the conditions for the electrochemical treatment were as outlined above for examples 1-5.
[0416] In the present example, aluminium electrodes (including aluminium sacrificial anodes) were used, and the effect of various contact (residence) times was analysed. The results are provided in Table 8.
TABLE-US-00008 TABLE 8 Purification of Formation Water using Aluminium Electrodes Aluminium electrodes Contact Time (s) 60 30 10 5 Calcium Removal Efficiency (%) 45.0 31.3 28.7 11.8 Magnesium Removal Efficiency 90.9 49.3 56.2 42.9 (%) Barium Removal Efficiency (%) 35.7 44.3 46.1 33.1 Strontium Removal Efficiency (%) 36.6 34.6 24.2 17.4 Silica Removal Efficiency (%) 98.1 96.6 95.8 93.2 Iron Removal Efficiency (%) nd nd 9.1 10.0 Aluminium 3.6 3.1 3.0 0.846 Iron 0.01 0.01 0.01 0.018 Initial CSG Formation Water pH 7.74 7.74 8.01 n.d. Treated Effluent pH 8.52 8.43 8.49 n.d. Utility and Material Consumption Contact time 60 30 10 5 Average Voltage (V) 28.2 32.6 30.8 30.0 Average Current (A) 8.95 8.73 10.7 10.7 Flow Rate (L/min) 1.15 1.15 4.05 8.1 Litres of Water Treated in Single 0.575 0.575 0.575 0.575 Pass
Example 8: Electrochemical Treatment of Formation Water—Mild Steel Electrodes
[0417] The formation water outlined in example 6 was subjected to electrochemical treatment. Unless otherwise defined, the conditions for the electrochemical treatment were as outlined above for examples 1-5.
[0418] In the present example, mild steel electrodes (including mild steel sacrificial anodes) were used, and the effect of various contact (residence) times was analysed. The results are provided in Table 9.
TABLE-US-00009 TABLE 9 Purification of Formation Water using Mild Steel Electrodes Electrodes - Mild Steel Contact Time (s) 60 30 10 5 Settled Floc volume after 60 minutes (ml) 1420 1300 490 250 Calcium Removal Efficiency (%) 84.8 74.0 40.9 32.7 Magnesium Removal Efficiency (%) 89.7 59.8 29.9 23.3 Barium Removal Efficiency (%) 69.9 54.9 25.8 25.2 Strontium Removal Efficiency (%) 52.8 36.6 11.1 10.1 Silica Removal Efficiency (%) 94.3 94.2 83.2 78.6 Residual Iron or Aluminium in Treated CSG Water (mg/L) Aluminium 0.002 0.003 0.07 0 Iron 0.006 0.006 0.0 0.021 Bulk Solution pH Initial CSG Water 8.16 8.16 n.d. n.d. Treated Effluent 9.69 9.2 n.d. n.d. Utility and Material Consumption Average Voltage (V) 31.61 33.07 30 36.5 Average Current (A) 10.08 10.59 10.92 9.3 Flow Rate (L/min) 1.05 1.05 4.05 8.1 Power Consumption (kWh/kL) 10.12 5.56 1.35 0.70 Power Cost (A$/kL) 1.01 0.55 0.13 0.07 Total Volume of Water Treated (L) 0.0 0.0 64.7 23.7 Total Test time (min) n.d. n.d. 15.98 2.92
Example 9: Purification of Frac Return Water
[0419] The results from the treatment of Frac return water is provided in Tables 10A, 10B and 10C. In this treatment the apparatus 201 illustrated in
[0420] In the method, frac return water is obtained as raw untreated water. This water typically smells strongly of hydrocarbons and other additives which may have become putrescent from anerobic storage and use.
[0421] The frac return water is subjected to a first electrochemical treatment step. This step typically involves a 5 A treatment at 40 V with mild steel (iron) electrodes. This step achieves emulsion breaking and phase separation with recovery of some hydrocarbon content as a floating froth and film. Ferrous sludge typically settles.
[0422] The electrochemically treated water is then subjected to a second electrochemical treatment step. This step typically involves a current of 10-15 A at 30-40V using aluminium electrodes and an oxidant to achieve reduction in COD through oxidation of refractory organics. Exemplary oxidants include peroxide, persulfate, permanganate and ozone. The selection of oxidant depends upon the concentration of chloride in the solution. If the concentration of chloride exceeds 10,000 mg/L then a persulfate oxidant is used. Otherwise, any of the above oxidants may be used.
[0423] The twice-electrochemically treated liquid is then carbon-filtered to remove low-level residual colouring organics and membrane foulants such as tannins and lignins which colour the water. If water clarity is not critical (such as when the treated water is for re-use in oilfield operations), this step may be omitted.
[0424] Following carbon filtering or the second electrochemical treatment step, the solution may be filtered through sand or other media. This achieves final polishing of the water prior to re-use or for membrane filtration.
[0425] Nanofiltration may be performed on the sand or media filtered water. However, nano-filtration is only needed when there are stringent discharge standards for Chemical Oxygen Demand (COD). Similarly, nano-filtered water may be passed through a reverse osmosis membrane, but this is only necessary when the total dissolved solids (TDS) and chloride require removal so that the water can be re-used in agriculture or other high-value end uses.
TABLE-US-00010 TABLE 10A Purification of Frac Return Water Boron Boron (aluminium C.sub.6-C.sub.36 (iron plates) plates) Hydrocarbons Element mg/L mg/L mg/L Bacteria pH Typical frac return 55-80 55-80 200-900 — 7.5-8.0 Following first EC 35-40 15-20 2-5 — 8.0-9.0 treatment Following second EC 20-25 5-10 <1 — 7.5-8.0 treatment After carbon 15-18 5-10 <0.5 — 2.0-3.0 filtration After media/ 10-15 5-7 0.1 1 CFU/ 8.0 sand filtration 100 ml After nano filtration 15 5 0.01 0 8.0 After reverse osmosis 2 0.5 0.01 0 8.0 (RO) Maximum Target <10 mg/l <10 mg/l <30 mg/l <10.sup.5/mL 6-8 Preferred Targets <5 mg/l <5 mg/l <10 mg/l 1 CFU/ end-use 100 ml dependent
TABLE-US-00011 TABLE 10B Purification of Frac Return Water Iron (iron Chloride Calcium Magnesium plates) Element Temp mg/L (mg/L) mg/L mg/L Typical frac return Ambient 10-20,000 75 25 1 Following first EC Ambient — <5 <5 2-3 treatment Following second EC Ambient 10-20,000 <10 <5 <5.0 treatment After carbon Ambient 10-20,000 <2 <2 <1.0 filtration After media/ Ambient 10-20,000 <2 <2 1-2 sand filtration After nano filtration Ambient 10-20,000 <1 <1 0.75-1.0 After reverse osmosis Ambient 150 0.1 0.1 0.1 (RO) Maximum Target 40° F.-100° F. <15,000 <2,000 25-500 <10 Preferred Targets — end-use <500 — <2 dependent
TABLE-US-00012 TABLE 10C Purification of Frac Return Water Total Chemical Iron Dissolved Oxygen (aluminium Solids Demand plates) Fluoride Phosphate (TDS) (COD) Element mg/L mg/L mg/L mg/L mg/L Typical frac return 1 10-30 5-10 <50,000 3,500-8,000 Following first EC <1 5-10 <5 <50,000 1,700-2,500 treatment Following second EC <1 <5 <1 <50,000 600-800 treatment After carbon <0.5 <10 <0.1 <50,000 400-500 filtration After media/ <1 <10 <1 <50,000 <400 sand filtration After nano filtration 0.5 <10 <1 <35,000 <40 After reverse osmosis 0.1 <2 0.1 <5 1-2 (RO) Maximum Target — <10 <5 <50,000 <10 Preferred Targets — end-use end-use end-use end-use dependent dependent dependent dependent
[0426] The methods described above in preferred embodiments of the present disclosure (as for example illustrated in
[0435] The apparatus 1, 201 defined in preferred embodiments of the present disclosure (as for example illustrated in
[0452] The above advantages when considered individually or collectively provide an apparatus with improved efficiency for electrochemical processes (especially electrocoagulation processes), in particular for oil and gas wastewater treatments. This may include one or more of: improved removal of contaminants, enhanced oxidation or reduction processes, reduced down-time for maintenance, reduced power consumption and higher through-put of a fluid being treated compared to prior art processes. For the avoidance of doubt, this does not mean that other features of the present disclosure do not also provide improved efficiency of electrochemical processes.
[0453] In the present specification and claims, the word ‘comprising’ and its derivatives including ‘comprises’ and ‘comprise’ include each of the stated integers but does not exclude the inclusion of one or more further integers.
[0454] Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.
[0455] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described includes preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.