CA2880227A1 - System and method for oil sands tailings treatment - Google Patents

Abstract

A system and method for treating tailings is described. The method includes: pre-treating the tailings; electrolytically treating the pre-treated tailings; in the electrolytically treated tailings, separating solids from liquids; and filtering the liquid to result in a filtrand and a filtrate comprising the treated tailings. The system includes: a pre-treatment system for pre-treating the tailings; an electrolytic treatment system for electrolytically treating the pre-treated tailings; a separation system for separating, in the electrolytically treated tailings, separating solids from liquids; and a filtering system for filtering the liquid to result in a filtrand and a filtrate comprising the treated tailings.

Description

SYSTEM AND METHOD FOR OIL SANDS TAILINGS TREATMENT
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of U.S.
Provisional Patent Application No. 61/513,040 filed July 29, 2011, which is incorporated herein by reference in its entirety.
FIELD

[0002] The present disclosure relates generally to treatment of oil and gas tailings and in particular, oil sands tailings.
BACKGROUND

[0003] Extraction and refining of oil, for example oil obtained from oil sands, may result in tailings that include, for example, solid, dissolved or suspended pollutants. The pollutants may be, for example, organic pollutants, such as hydrocarbon mixtures.
Examples of hydrocarbon mixtures include bitumen, naptha, organic compounds like naphthenic acids (NAs); phenols; benzene, ethylbenzene, toluene, xylenes (BETX);
polycyclic aromatic hydrocarbons (PAHs); oil & grease; and inorganic compounds, for example C1, S042-, Al, As, Cr, Ca, Pb, Ni, Zn, and other metals. Usual loads of organic and inorganic compounds confer to tailings alkalinity (600-800 mg CaCO3/L), hardness (90-120 mg CaCO3/L), TDS (1900-2300 mg/L), TSS (<7000 mg/L), NAs (50-120 mg/L), BOD (10-70 mg02/L), COD (-350 mg 02/4 oil & grease (9-92 mg/L), Cu (0.002-0.9 mg/L), and Ni (0.006-2.8 mg/L).

[0004] A discussion of oil sands tailings can be found in: FTFC (Fine Tailings Fundamentals Consortium), 1995, "Advances in Oil Sands Tailings Research", Alberta Department of Energy, Oil Sands and Research Division, Publisher; and Devenny, D. W., "A Screening Study of Oil Sands Tailings Technologies and Practices", March 2010, Alberta Energy Research Institute. The noted documents are incorporated herein by reference.

[0005] These broad range of harmful pollutants found in tailings streams pose a significant risk to the environment and/or human health if left untreated.
Government regulations often mandate that various organic, inorganic, chemical, and microbial components of a tailing stream must be treated before the tailing stream can be discharged to the environment.

[0006] It is desirable to provide a method and system for treating the tailings to attempt to remove, destroy, or both remove and destroy, as much of the pollutants as possible. Electrochemical methods and systems for treating sewage wastewater are discussed in PCT Applications: PCT/1699/01276, PCT/CA2003/001780, and PCT/CA2007/002037; and in U.S. Patent Application 12/905,350. The content of the noted applications are incorporated herein by reference.
SUMMARY

[0007] According to one aspect of the present disclosure, there is provided amethod of treating tailings, the method includes: pre-treating the tailings;
electrolytically treating the pre-treated tailings; in the electrolytically treated tailings, separating solids from liquids; and filtering the separated liquids to result in a filtrand and a filtrate comprising the treated tailings.

[0008] The method may additionally include electrolytically treating the filtrate comprising the treated tailings, or the separated liquids.

[0009] Pre-treating the tailings may include: screening the tailings to remove substantially all particles greater than 1 mm; removing floating oils from the tailings to result in less than about 2 mg of floating oil per L of tailings; or both.

[0010] Electrolytically treating the pre-treated tailings may include:
applying a continuously pulsed electrical signal to at least one of a pair of electrodes submersed in an aqueous liquid to generate bubbles of an oxyhydrogen-rich gas; and contacting the pre-treated tailings with the oxyhydrogen-rich gas bubbles.

[0011] The pulsed electrical signal may have a mark-space ratio of between approximately 1:1 and 10:1 and a pulse frequency of approximately 10Hz-250 kHz.

[0012] The aqueous liquid may be the pre-treated tailings.

[0013] The method may further include: separating the oxyhydrogen-rich gas from the electrolytically treated tailings; and transporting the oxyhydrogen-rich gas to a secondary process. The secondary process includes production of energy in a fuel cell or combustion device.

[0014] Separating solids from liquids in the electrolytically treated tailings may include: coagulating the solids, coalescing the solids, precipitating the solids, settling the solids, flocculating the solids, or any combination thereof; and separating the coagulated solids, the coalesced solids, precipitated solids, settled solids, or flocculated solids from the liquids.

[0015] According to another aspect of the present disclosure, there is provided a system for treating tailings. The system includes: a pre-treatment system for pre-treating the tailings; an electrolytic treatment system for electrolytically treating the pre-treated tailings; a separation system for separating, in the electrolytically treated tailings, separating solids from liquids; and a filtering system for filtering the separated liquids to result in a filtrand and a filtrate comprising the treated tailings.

[0016] The system may further include: a recycling system to return the treated tailings filtrate or the separated liquids to the electrolytic treatment system.

[0017] The pre-treatment system may include: a screening system to remove substantially all particles greater than 1 mm from the tailings; a skimmer to remove floating oils from the tailings to result in less than about 2 mg of floating oil per L of tailings; or both.

[0018] The electrolytic treatment system may include: at least one pair of electrodes submersed in an aqueous liquid; and a source of a continuously pulsed electrical signal connected to least one of the electrodes to generate bubbles of an mryhydrogen-rich gas.

[0019] The pulsed electrical signal may have a mark-space ratio of between approximately 1:1 and 10:1 and a pulse frequency of approximately 10Hz-250 kHz.

[0020] The aqueous liquid may be the pre-treated tailings.

[0021] The system may further include: a separator for separating the mryhydrogen-rich gas from the electrolytically treated tailings; and a transporter for transporting the mryhydrogen-rich gas to a secondary system. The secondary system may be a fuel cell or a combustion device.

[0022] The separation system may include: one or more systems for coagulating the solids, for coalescing the solids, for precipitating the solids, for settling the solids, for flocculating the solids, or for any combination thereof.
BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures.

[0024] Fig. 1 is a schematic of a method for treating oil and gas tailings.

[0025] Fig. 2 is an illustration of the chemical oxygen demand (COD) concentration in a liquid as a function of the number of electrolytic treatments.

[0026] Fig. 3 is an illustration of reactions that may occur during electrolysis.

DETAILED DESCRIPTION

[0027] Generally, the present disclosure provides a method and system for electrochemically processing tailings using electrolysis to attempt to remove, destroy, or both remove and destroy, pollutants. The tailings may be, for example, tailings from oil sands operations or tailings from other similar operations.

[0028] Embodiments herein are intended to allow pollutants to be removed, destroyed, or both removed and destroyed, at lower Hydraulic Retention Times than in conventional biological or physical-chemical systems. The process may reduce the amount of residual bio-solids, thereby reducing additional treatment or disposal. Off gas may be produced during treatment, and may be separated and purified. The separated and purified off gas may be, for example: sold, used to produce energy in a fuel cell or combustion device, used to produce energy to be sold back to a utility company or another user of electricity, consumed in the process, or any combination thereof.

[0029] The tailings may comprise an influent tailing stream.
Alternatively, the tailings may comprise an intermediate waste or wastewater stream such as supernatant or biosolids, for example, in the context of a larger wastewater treatment system. In still other examples, the tailings may include chemical processing effluent from an oil cracking process. Tailings may be subjected to preliminary processing steps, such as oil skimming, screening, grit removal, or any combination thereof. Oil skimming, screening, and/or grit removal may be particularly important when tailings comprises raw wastewater influent from oil sands operations.

[0030] Pre-treated tailings may be pumped between a set of electrodes where highly oxidative species, for example ozone, hydrogen peroxide, hydroxyl radicals, or any combination thereof, are generated. Alternatively, the set of electrodes may be used to generate the highly oxidative species separately from the pre-treated tailings and then subsequently mixed with at least a portion of the pre-treated tailings. The mixture of oxidative species produced may be controlled by modulating the input signal.
The mixture of oxidative species may be selected in order to target specific pollutants.

[0031] Water molecules and other constituents in the liquid may be split by the electrodes into a mixture of hydrogen, oxygen, nitrogen, and traces of CO2.
Fig. 1 illustrates reactions that may occur during electrolysis. Chemicals, for example phosphorous, and suspended solids may be coagulated, coalesced, precipitated, settled, flocculated, or any combination thereof. The oxidative species may oxidize organic matter. In such a manner, the method and system may reduce the amount of organics in the tailings, reduce toxicity, convert ammonia to nitrogen gas, reduce the level of pathogens in the tailings, or any combination thereof. A small fraction of the original solids in the raw tailings may remain after treatment and may be directly disposed.

[0032] The system may be designed as a continuous-flow, a batch-flow, or a recycling-flow system.

[0033] It is desirable for the tailings entering the system to be substantially free of floating oil, for example it is desirable for the tailings to have less than 2 mg of floating oil per L of tailings. It is desirable for the tailings entering the system to be substantially free of particles larger than about 1 mm in size. The system and method may include a pretreatment to reduce the amount of floating oil, reduce the number of particles larger than about 1 mm in size, or both, before electrolytic treatment of the tailings.

[0034] The system may include one or more blowers to dilute and vent gas produced by the system, for example H202, to the atmosphere. The system may include stainless steel components for gas exhaust, hydrogen gas sensors (for example located downstream from a gas-liquid separator), building fans, or any combination thereof in order to protect against any risk of hydrogen combustion. Because of the non-biological character of the solids, there is generally no need for digesters, therefore eliminating the production of CH4 or mercaptans.

[0035] The system and method may include multiple electrolytic treatments, where each electrolytic treatment is followed by settling and removing the resulting solids.
Further, each electrolytic treatment may include multiple passes, for example two passes, through the electrodes before settling and removing the resulting solids.

[0036] In view of the above, the method of treating tailings includes:
pre-treating the tailings; electrolytically treating the pre-treated tailings; in the electrolytically treated tailings, separating solids from liquids; and filtering the separated liquids to result in a filtrand and a filtrate comprising the treated tailings.

[0037] The method may additionally include electrolytically treating the filtrate comprising the treated tailings, or the separated liquids.

[0038] Pre-treating the tailings may include: screening the tailings to remove substantially all particles greater than 1 mm; removing floating oils from the tailings to result in less than about 2 mg of floating oil per L of tailings; or both.

[0039] Electrolytically treating the pre-treated tailings may include:
applying a continuously pulsed electrical signal to at least one of a pair of electrodes submersed in an aqueous liquid to generate bubbles of an mryhydrogen-rich gas; and contacting the pre-treated tailings with the mryhydrogen-rich gas bubbles. The pair of electrodes may be spaced less than 5 mm apart.

[0040] The pulsed electrical signal may have a mark-space ratio of between approximately 1:1 and 10:1 and a pulse frequency of approximately 10Hz-250 kHz.

[0041] The aqueous liquid may be the pre-treated tailings.

[0042] The method may further include: separating the oxyhydrogen-rich gas from the electrolytically treated tailings; and transporting the oxyhydrogen-rich gas to a secondary process. The secondary process includes production of energy in a fuel cell or combustion device.

[0043] Separating solids from liquids in the electrolytically treated tailings may include: coagulating the solids, coalescing the solids, precipitating the solids, settling the solids, flocculating the solids, or any combination thereof; and separating the coagulated solids, the coalesced solids, precipitated solids, settled solids, or flocculated solids from the liquids.

[0044] Similarly, the system for treating tailings includes: a pre-treatment system for pre-treating the tailings; an electrolytic treatment system for electrolytically treating the pre-treated tailings; a separation system for separating, in the electrolytically treated tailings, separating solids from liquids; and a filtering system for filtering the separated liquids to result in a filtrand and a filtrate comprising the treated tailings.

[0045] The system may further include: a recycling system to return the treated tailings filtrate or the separated liquids to the electrolytic treatment system.

[0046] The pre-treatment system may include: a screening system to remove substantially all particles greater than 1 mm from the tailings; a skimmer to remove floating oils from the tailings to result in less than about 2 mg of floating oil per L of tailings; or both.

[0047] The electrolytic treatment system may include: at least one pair of electrodes submersed in an aqueous liquid; and a source of a continuously pulsed electrical signal connected to least one of the electrodes to generate bubbles of an mryhydrogen-rich gas. The pair of electrodes may be spaced less than 5 mm apart.

[0048] The pulsed electrical signal may have a mark-space ratio of between approximately 1:1 and 10:1 and a pulse frequency of approximately 10Hz-250 kHz.

[0049] The aqueous liquid may be the pre-treated tailings.

[0050] The system may further include: a separator for separating the mryhydrogen-rich gas from the electrolytically treated tailings; and a transporter for transporting the mryhydrogen-rich gas to a secondary system. The secondary system may be a fuel cell or a combustion device.

[0051] The separation system may include: one or more systems for coagulating the solids, for coalescing the solids, for precipitating the solids, for settling the solids, for flocculating the solids, or for any combination thereof.

[0052] One specific example of a method according to the present disclosure is illustrated in Fig. 2. Tailings (10) from oil and gas production are screened and de-gritted (12) to generate screenings (14). Oil (16) that floats is removed from the screened and de-gritted tailings at (18). The de-oiled tailings are again screened, using a 1-2 mm fine screen (20), to generate fine screenings (22). The resulting de-oiled and screened tailings are electrolytically treated (24). In the particular method illustrated in Fig. 2, the electrolytic treatment uses an mryhydrogen gas generator and implements a water dissociation technology, as discussed in greater detail below, generating mryhydrogen-rich gas (26). Electrolytic treatment oxidizes organic matter present in the de-oiled and screened tailings.

[0053] The mryhydrogen-rich gas (26) may optionally be separated and purified.
The separated and purified off gas may be used for a secondary use (28). For example, it may be sold, used to produce energy in a fuel cell or combustion device, used to produce energy to be sold back to a utility company or another user of electricity, consumed in the process, or any combination thereof.

[0054] The electrolytic treatment (24) coagulates, coalesces, precipitates and/or flocculates chemicals and suspended solids, which are separated (30) from the treated tailings to generate solids (32). The solids (32) may be treated, for example by thermophilic aerobic digestion, to reduce the biological demand before disposal.
Thermophilic digestion of biological agents may be effected at, for example: a temperature of about 55 C to about 60 C for a period of about 10 days; or a temperature of about 50 for a period of about 5 days. In particular examples, the thermophilic digestion may be effected at about 25 C for about 4 to about 6 hours. This reduced time and temperature may be due to the electrolytic treatment reducing the biological demand of the tailings before the solids (32) are collected.

[0055] The effluent from the solids separation is filtered (34), using for example sand or granular activated carbon (GAC) to generate treated filtrate (36) and filtrand (38).
The filtrand (38) may be additionally treated (40), for example by being regenerated and reused, or disposed through environmentally safe and cost effective processes.

Regeneration may be achieved, for example, by incineration of the filtrand (38). Disposal of the filtrand (38) may include, for example, washing and dewatering. The screenings (14), fine screenings (12) and/or the solids (32) may also be treated (step(s) not shown) and disposed through environmentally safe and cost effective processes. The additional treatment of the screenings (14), fine screenings (12) and/or the solids (32) may include washing and dewatering. The screenings (14), fine screenings (12) and/or the solids (32) may be treated together.

[0056] The treated effluent (36) and/or the effluent from the solids separation may be electrolytically treated more than once. For example, the tailings may be electrolytically treated 2, 3, 4, 5, 6, 7, 8, 9, or more than 9 times by recycling the treated effluent and/or the effluent from the solids separation to the electrolytic treatment system, as illustrated in Fig. 2. The COD concentration in mg/L of the treated effluent is illustrated in Fig. 3 for untreated effluent (that is, where the electrolytic treatment step = 0), as well as for effluent that has been eletrolytically treated 1, 2, 3, 4, 5, 6, 7 and 8 times by recycling the effluent from the solids separation system to the electrolytic treatment system.

[0057] The method and system are intended and expected to remove in the range of 80 to 98% of the pollutants in the tailings. The method and system are intended and expected to have a hydraulic retention time from 3 to 60 minutes. The method and system are intended and expected to have power requirements around 0.5 to 40 kWh/m3.

[0058] The method and system may destabilize colloidal particles and increase the settling velocity of the resulting particles. In some examples, the electrolytically treated tailings may be settled in 5 to 20 minutes, resulting in a clear supernatant and settled solids. The method and system can be controlled to generate a mixture of oxidative species suitably targeted to destabilize tailings having varying compositions.
The settled solids may include 50 to 70% v/v of the water from added tailings.
The settled solids may have water capillary suction times of less than 10 seconds and may be dewatered using, for example, sloped banks. Dried settled solids are typically easier to dewater and compact than solids produced by chemical or biological treatment.
The quantity of water continuously released (i.e. not needing to be dewatered from the solids) is intended to be in the range of 30 to 50% in volume. Overall, the system and method are designed to remove organic contaminants and reduce toxicity of the tailings input at the same time that fine tailings are being precipitated.

[0059] The tailings are expected to have a chemical oxygen demand (COD: an indirect measurement of the amount of organic compounds) in the range of 40,000 mg/L.
After electrochemical (electrolytic) treatment, the COD is intended to be in the range of 200 mg/L. After filtering, for example using granular activated carbon, the COD is intended to be in the range of 50 mg/L.

[0060] Table 1 provides a list of exemplary pollutants found in tailings from oil sands, and their resulting levels after electrolytic treatment. BOD
(biological oxygen demand) is an indirect measurement of organic compounds that can be oxidized biologically.
Pollutant in mg/L Sample 1 Sample 2 Sample 3 Raw Treated Raw Treated Raw Treated Benzene 92.9 <0.0005 0.014 <0.0005 <0.0005 <0.0005 Toluene 263 <0.0005 0.119 <0.0005 0.0013 <0.0005 Ethyl Benzene 39.3 <0.0005 0.111 <0.0005 <0.0005 <0.0005 Xylenes 360 <0.00015 0.7 <0.00015 0.0034 <0.00015 Methanol 16.8 27800 28.7 130 4-methyl-2-pentanone - <0.002 117 <0.0002 - <0.0002 COD 1750000 25 40000 19.4 260 132 BOD 12.5 11 122 Calcium 432 22.7 107 8.41 86.6 15.8 Chloride 10600 29.5 2590 29.3 841 182 Magnesium 81.4 16.7 14.5 12.6 18.3 13.5 Table 1

[0061] Electrolysis may be performed using an oxyhydrogen gas generator and may implement a water dissociation technology, such as the kind disclosed in U.S. Pat.
Nos. 6,419,815 and 6,126,794 of Chambers, both issued to Xogen Technologies Inc. and incorporated herein by reference (hereinafter "the Xogen patents"). As described in the Xogen patents at columns 3-5, gas generation apparatuses in accordance with embodiments include electrode "cells" each including two or more spaced-apart electrodes adapted to be immersed in a working fluid including water. In the embodiments described herein, the working fluid comprises tailings or a tailings stream.
The electrodes are preferably made of the same material. One electrode material is stainless steel for its low cost and durability, but it may be possible to use other conductive metals. An equal spacing between the electrodes is maintained and it is preferable to minimize the spacing between the electrodes. However, the spacing between the electrodes cannot be positioned excessively close because arcing between the electrodes would occur. It has been determined that a spacing of 1 mm or less is optimal spacing for producing oxyhydrogen-rich gas, but an increased spacing of up to approximately 5 mm may work effectively while being less subject to fouling due to accumulation of solids between the electrodes. A spacing above 5 mm may also be feasible, but tends to reduce the output of oxyhydrogen gas and increases power requirements.

[0062] It is preferable to include many pairs of electrodes (e.g.
dozens or hundreds) within each cell. The electrodes can be almost any shape, but preferably comprise flat plates closely spaced and parallel to each other. Alternative embodiments may include coaxially aligned cylinders. Insulating spacers can be interposed between adjacent electrodes to maintain equal spacing between the electrodes and to prevent current leakage therebetween.

[0063] As further described in the Xogen patents, a high- frequency pulsed direct current (DC) electrical signal is applied to the electrodes. The pulsed signal can be almost any waveform and have a variable current level, voltage level, frequency and mark-space ratio (i.e., a ratio of the duration of a single pulse to the interval between two successive pulses). The source of power for the power supply may include a mains 110 volts or batteries, such as 12-volt car batteries. For example, the power supply may comprise two 12-volt batteries arranged in series to provide a 24-volt supply. For powering a large-scale gas generator (GG1) in a large tailings treatment system, a more complex power supply may be required for generating 24-volt pulsed DC signal having sufficient power to drive the large cells required. Alternatively, multiple smaller electrode cells may be provided for redundancy and spaced apart in a reaction vessel or other reaction zone, in which case the cells may be driven by simpler independent power supplies.

[0064] A controller is used in conjunction with the batteries or other power source to generate one of a variety of pulsed output waveforms, such as a square wave, a saw tooth wave, or a triangular wave, which can be applied to the electrodes. The pair of electrodes may be spaced less than 5 mm apart. At present, the best results for producing oxyhydrogen-rich gas have been obtained using a square wave. In one embodiment a pulsed signal has a mark-space ratio of between approximately 1:1 and 10:1 and a pulse frequency of approximately 10Hz-250 kHz.

[0065] After initiation of the pulsed signal from the power supply, the electrodes continuously and almost instantaneously generate bubbles of oxyhydrogen-rich gas from water molecules in an interaction zone that extends between the electrodes and slightly beyond the edges of the electrodes. The generated bubbles are not bunched around or on the electrodes and thus readily float to the surface of the fluid in the reactor vessel or other reaction zone. Therefore, there is no need to add a chemical catalyst to assist the conduction of the solution or inhibit bubbles from bunching around or on the electrodes.

Thus, many different kinds of tailing streams can be used as the working fluid, as can other sources of water, such as surface water and ordinary tap water.

[0066] Oxyhydrogen gas generator GG3 may be submerged in tailings contained in a reaction vessel and operated for an interval of from approximately 60 seconds to up to approximately 10 minutes, then power to the gas generator GG3 may be shut off. In particular examples, the oxyhydrogen gas generator is operated for an interval between about 3 minutes and about 10 minutes. After an interval of operation of gas generator GG3, a substantial amount of solids may collect on the surface of the tailings. While a modest amount of solids may collect on the surface of the tailings during operation of gas generator GG3, a surprisingly large increase in floating solids occurs nearly immediately after de-energizing of gas generator GG3 and stopping of a recycle flow through the reaction vessel. De-energizing of gas generator GG3 and stopping of the recycle flow results in quiescent conditions within the reaction vessel, which allow for unhindered floatation of solids. An extracted gas floatation unit process includes one or more cycles each including the following steps: (1) operating the gas generator GG3 (typically by applying a high-frequency pulsed electrical signal) for between approximately 60 seconds and approximately 10 minutes, (2) de-energizing gas generator GG3, (3) waiting until solids collect on the surface of the fluid (typically between approximately 30 seconds and 2 minutes), and (4) removing the solids from the surface (by skimming the surface, for example). The cycles can be repeated continually until a desired amount of solids has been removed from the tailings.

[0067] Oxyhydrogen gas generator may be mounted on a frame that is hung from a set of floats so that the submergence of the oxyhydrogen gas generator is maintained at a desired level below the surface of the fluid. Alternatively, the oxyhydrogen gas generator may be mounted to a fixed lid or other fixed support for positioning at a fixed height in reaction vessel. Floats may also serve to seal the top of reaction vessel. The frame may be adjustable so that the submergence level of the gas generator can be adjusted independent of the depth of fluid in the reaction vessel.

[0068] Alternatively, the oxyhydrogen gas generator may be placed on a pedestal or other support so that it is positioned below the middle of the depth of fluid in the reaction vessel. Placement of gas generator low in the reaction vessel (or other reaction zone) increases the distance that bubbles of oxyhydrogen-rich gas must rise through fluid, thus increasing their residence time and probability of contacting a solid particle or other treatable molecule. Preferably, the oxyhydrogen gas generator may be positioned at least slightly above the floor of the reaction vessel to avoid buildup of sediment and sludge between the electrodes of the gas generator.

[0069] The oxyhydrogen gas generator may include a series of closely-spaced electrode plates that are oriented generally vertically and arranged such that the spaces between adjacent plates are open to the reactor contents at both the top and bottom edges of the plates. A pulsed electrical signal from a power source may be provided to the electrode plates via power transmission wires. The application of the pulsed electrical signal may cause water molecules in the fluid suspension to be dissociated in an interaction zone extending between the plates and slightly beyond the openings between the plates, to thereby form an oxyhydrogen-rich gas including hydrogen and oxygen. The oxyhydrogen-rich gas may collect in the interaction zone to form bubbles that rise through the fluid suspension between the plates and can then be collected at the surface of the fluid suspension under a gas containment lid. Because the aggregate density (specific gravity) of flocs in the fluid suspension is only marginally greater than 1.0, the rising bubbles may transport the flocs upward and into contact with the oxygen and hydrogen in the liberated gas bubbles and/or the atmosphere collected under the containment lid.

[0070] In the process of generating oxyhydrogen-rich gas, heat is generated around the oxyhydrogen gas generator and the temperature of the fluid suspension in the reaction vessel may increase. A portion of the contents of the reaction vessel may be withdrawn on a continual and variable basis and recirculated through a heat exchanger via a feed/recirculation pump to maintain the temperature of the fluid suspension at a desired level for the specific application in question. In addition to providing temperature control, the recirculation loop may also provide a degree of positive mixing in the reaction vessel to help keep the solids in suspension and thus in a position to be transported upwards toward the surface of the fluid suspension or another contact zone where the solids are more likely to contact oxyhydrogen-rich gas. Sample ports may be provided in the recirculation line to allow samples of the solids to be collected and analyzed for various parameters in order to determine the degree of treatment that has been achieved at any point in time.

[0071] In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the examples.
However, it will be apparent to one skilled in the art that these specific details are not required. The above-described examples are intended to be exemplary only. Alterations, modifications and variations can be effected to the particular examples by those of skill in the art without departing from the scope, which is defined solely by the claims appended hereto.

Claims (18)

WHAT IS CLAIMED IS:

1. A method of treating tailings, the method comprising:
pre-treating the tailings;
electrolytically treating the pre-treated tailings;
in the electrolytically treated tailings, separating solids from liquids; and filtering the separated liquids to result in a filtrand and a filtrate comprising the treated tailings.

2. The method according to claim 1 further comprising:
electrolytically treating the treated tailings filtrate or the separated liquids.

3. The method according to claim 1 or 2, wherein pre-treating the tailings comprises:
screening the tailings to remove substantially all particles greater than 1 mm;
removing floating oils from the tailings to result in less than about 2 mg of floating oil per L of tailings; or both.

4. The method according to any one of claims 1-3 wherein electrolytically treating the pre-treated tailings comprises:
applying a continuously pulsed electrical signal to at least one of a pair of electrodes submersed in an aqueous liquid to generate bubbles of an oxyhydrogen-rich gas; and contacting the pre-treated tailings with the oxyhydrogen-rich gas bubbles.

5. The method according to claim 4 wherein the pulsed electrical signal has a mark-space ratio of between approximately 1:1 and 10:1 and a pulse frequency of approximately 10Hz-250 kHz.

6. The method according to claim 4 or 5 wherein the aqueous liquid is the pre-treated tailings.

7. The method according to any one of claims 4-6 further comprising:
separating the oxyhydrogen-rich gas from the electrolytically treated tailings; and transporting the oxyhydrogen-rich gas to a secondary process.

8. The method according to claim 7 wherein the secondary process is production of energy in a fuel cell or combustion device.

9. The method according to any one of claims 1-8 wherein separating solids from liquids in the electrolytically treated tailings comprises:
coagulating the solids, coalescing the solids, precipitating the solids, settling the solids, flocculating the solids, or any combination thereof; and separating the coagulated solids, the coalesced solids, precipitated solids, settled solids, or flocculated solids from the liquids.

10. A system for treating tailings, the system comprising:
a pre-treatment system for pre-treating the tailings;
an electrolytic treatment system for electrolytically treating the pre-treated tailings;
a separation system for separating, in the electrolytically treated tailings, separating solids from liquids; and a filtering system for filtering the separated liquid to result in a filtrand and a filtrate comprising the treated tailings.

11. The system according to claim 10 further comprising:
a recycling system to return the treated tailings filtrate or the separated liquid to the electrolytic treatment system.

12. The system according to claim 10 or 11, wherein the pre-treatment system comprises:
a screening system to remove substantially all particles greater than 1 mm from the tailings;
a skimmer to remove floating oils from the tailings to result in less than about 2 mg of floating oil per L of tailings; or both.

13. The system according to any one of claims 10-12 wherein the electrolytic treatment system comprises:
at least one pair of electrodes submersed in an aqueous liquid; and a source of a continuously pulsed electrical signal connected to least one of the electrodes to generate bubbles of an oxyhydrogen-rich gas.

14. The system according to claim 13 wherein the pulsed electrical signal has a mark-space ratio of between approximately 1:1 and 10:1 and a pulse frequency of approximately 10Hz-250 kHz.

15. The system according to claim 13 or 14 wherein the aqueous liquid is the pre-treated tailings.

16. The system according to any one of claims 13-15 further comprising:
a separator for separating the oxyhydrogen-rich gas from the electrolytically treated tailings; and a transporter for transporting the oxyhydrogen-rich gas to a secondary system.

17. The system according to claim 16 wherein the secondary system a fuel cell or a combustion device.

18. The system according to any one of claims 10-17 wherein the separation system comprises:
one or more systems for coagulating the solids, for coalescing the solids, for precipitating the solids, for settling the solids, for flocculating the solids, or for any combination thereof.