System for electrocoagulation fluid treatment

A system for electrocoagulation fluid treatment having a tubular member with a plurality of electrocoagulation assemblies disposed therein. The assemblies having a first and second conductive plate that are angularly oriented in relation to one another. A non-conductive block is positioned between the plates to stabilize and orient them within the tubular member. The conductive plates may be provided with alternating negative and positive charges to combat corrosion.

FIELD OF THE INVENTION

The present invention relates generally to fluid filtration systems and, more particularly, to a system and process for electrocoagulation fluid treatment.

BACKGROUND

Coagulation is a physiochemical operation used in water treatment. The process causes the destabilization and aggregation of smaller particles into larger particles. Generally, water contaminants such as ions (heavy metal) and colloids (organics and inorganics) are suspended in solution by electrical charges. Colloidal contaminants can be destabilized by the addition of ions having a charge opposite to that of the colloidal contaminant. The destabilized colloids can be aggregated and subsequently removed by sedimentation and/or filtration.

Coagulation can be achieved by chemical or electrical means. Electrocoagulation is an electro-chemical process that simultaneously removes heavy metals, suspended solids, emulsified organics and many other contaminants from water by passing electric current through the water. The process uses DC current, consumable anodes and cathodes to combine with contaminants in a waste stream, thus producing insoluble oxides and hydroxides, called floc, that are easily separated from the clear water. A variety of anode and cathode geometries, including plates, balls, fluidized bed spheres, wire mesh, rods and tubes have been utilized for the process.

In a common prior art system, contaminated water passes in a layer between metal plates charged with a direct electrical current. The plate material is discharged, as molecules, into the stream, where ionic and non-ionic contaminants are subjected to the electrical charge, electrolysis products, and the plate elements. The process produces a number of effects depending on the species present, but generally contaminants are reacted to their most stable state as floc, and then are removed from the wastewater by physical means—typical solids separation methods like clarification, settling tanks or weir plates may be employed.

It is known in the art that EC suffers from several shortcomings that limit the utility of the method. In a typical EC system, the spacing between the plates is commonly small (less than 1 inch) with many plates inside a unit. This limits the volumetric flow rate and requires very large units or a large number of smaller units. The buildup of corrosion byproducts will often create a bridge or “short” in the system and therefore these systems require constant maintenance and cleaning. Lastly, the pathway through the EC unit does not always provide adequate contact with the water being treated because of lack of mixing.

Accordingly, in view of the foregoing shortcomings, there is a need in the art for a system and process that overcomes the current limitations by providing excellent contact with the charged plates, thorough mixing, and no cleaning requirement, as well as possessing the ability to be taken out of service for extended periods and put back into service without protracted time limitations.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

With reference toFIGS. 1A & 1B, an electrocoagulation water clarification system10is illustrated according to an exemplary embodiment of the present invention. Water clarification system10includes an elongated tubular member12having a wall extending between a first end14and a second end16and defined along an axis17. A fluid port18is located adjacent each end14,16. Each end14,16is enclosed with an endplate20to form an enclosed chamber for electrocoagulation.

Disposed within tubular member12are one or more electrocoagulation assemblies22. Each assembly22comprises a first electrically conductive plate24a, a second electrically conductive plate24band a non-conductive block28. System10also includes a power source26, which may be a DC or AC current source. Those of ordinary skill in the art having the benefit of this disclosure will appreciate that tubular member12functions as the reaction chamber in which the electrocoagulation process of the present invention is carried out.

With reference toFIG. 2, plates24are preferably semi-circular or semi-elliptical in shape to correspond to the shape of elongated tubular member12. As such, plates24have an arcuate edge23and a flat edge25. However, those of ordinary skill in the art will appreciate that in other embodiments, tubular member12, as well as plates24, may be of other shapes without departing from the invention. For example, tubular member12may be square in shape, and plate24may be rectangular in shape. In any event, plates24may further include one or more apertures29therethrough for securing plates24within tubular member12. Again, those of ordinary skill in the art will having the benefit of this disclosure appreciate that other configurations for securing plates24may be used without departing from the invention. In this exemplary embodiment, plates24are formed of conductive material such as conductive metals, which may include, but is not limited to iron, steel, or aluminum.

Those of ordinary skill in the art will appreciate that plates24a,24bof an electrocoagulation assembly22function as the anode and cathode in the electrocoagulation process. One metal plate functions as the consumable or sacrificial structure, i.e., the anode, which will be the sacrificial electrode because it will corrode to become cations that will bind together the contaminants (i.e., the coagulation process). The other metal plate will function as the cathode. In another exemplary embodiment, the function of the plates24a,24bas either an anode or cathode may alternate.

With reference toFIGS. 3A & 3B, a non-conductive block28is illustrated according to an exemplary embodiment of the present invention. Block28includes a first slot30aand a second slot30b. In one embodiment, block28is characterized by a thickness so as to have a first face32aand a second face32b. First slot30ais formed along an axis31ain one face of block28and second slot30bis formed along an axis31bin the other face of block28. In certain embodiments, slots30aand30bare oriented in their respective faces so that the axis of the slots form an angle between 1 and 179 degrees. In one exemplary embodiment, the slots30a,30bof a block28are angled at 90 degrees relative to one another, as shown inFIG. 3B.

Furthermore, in certain exemplary embodiments of the invention, a length B of block28may be 1.341 inches, width A may be 0.75 inches, and a height C may be 0.987 inches. The preferred embodiment uses 6″ CPVC industrial pipe. The elements inside are elliptical and come in 2 halves. Each half is designed to be 7.579″×2.617″ and then fit into the insulation block to form an “X” as illustrated inFIGS. 1A and 1B. However, those ordinarily skilled in the art having the benefit of this disclosure realize that other dimensions may be utilized as desired.

With further reference toFIGS. 1A,1B, &2, and ongoing reference toFIGS. 3A & 3B, each plate24is mounted in a slot30formed in non-conductive block28so that plates24aand24bare spaced apart from one another (as shown inFIG. 1B), thereby preventing electrical contact between plates24aand24bof a block28. Specifically, edge25of each plate24seats in a slot30. While block28is illustrated as rectangular, those of ordinary skill in the art having the benefit of this disclosure will appreciate that block28may take any shape so long as block28-secures plates24aand24bin a spaced apart arrangement from one another. In those exemplary embodiments where slots30a,30bare angled at 90 degrees relative to one another, plates24aand24b, when mounted in slots30a,30b, are angled at 90 degrees to one another. As previously described, block28is formed of non-conducting material. Such non-conducting material may include, for example, polyvinyl chloride, chlorinated polyvinyl chloride, polytetrafluoroethylene, or elastomers.

With reference back toFIGS. 1A & 1B, electrocoagulation assemblies22are oriented in elongated tubular member12so that plates24are angled relative to axis17of tubular member12. In the exemplary embodiment where plates24a,24bare angled at 90 degrees relative to one another, plates24a,24bare preferably angled at 45 degrees relative to axis17.

According to an exemplary embodiment of the present invention, electrocoagulation assemblies22are secured within tubular member12by elongated rods34. More specifically, assemblies are alternatingly arranged so that plates24aof every other assembly22are parallel to one another. Likewise, plates24bof every other assembly22are parallel to one another. In such an orientation, a first aperture29in each of the parallel plates24ais aligned along an axis passing through the apertures29. Similarly, a first aperture29in each of the parallel plates24bis aligned along an axis passing through the apertures. An elongated rod34may be passed through each set of aligned apertures to secure the alternating assemblies22in tubular member12. Moreover, rods34may be threaded on the ends to permit rods34to be secured to end plates20.

In an alternate exemplary embodiment, block28may be eliminated and rods34may instead be utilized to orient and secure the plates. In another exemplary embodiment, rods34are conductive such that as a rod34passes through the aperture28of a plate24, electrical contact between the plate24and rod34is established. In such an embodiment, as will be described below, rod34can be utilized to form a conductive path from power source26to plates24.

Further referring toFIG. 1A, in some preferred embodiments, end plates20are non-conductive and rods34are secured to end plates20with internally threaded fasteners (not shown) disposed to engage the threaded ends of rods34. In other embodiments, rods34may be secured against end plates20by other non-conductive support structures. Those of ordinary skill in the art having the benefit of this disclosure will appreciate that rather than threaded ends and threaded fasteners, other types of fasteners may be utilized to secure rods34. Furthermore, in the alternative, non-conductive bushings, washers, sleeves or similar insulating structure may be utilized to support rods34carried by end plates20in which case, end plats20may be metal.

In other exemplary embodiments, rods34may be used to secure end plates20over the open ends of elongated tubular member12. Engaging fasteners to the threaded ends of rods34can be used to cause plates20to compress against the open ends14,16of tubular member12. A sealing gasket may also be provided to ensure sealing between plate20and the ends14,16of tubular member12.

Further referring toFIG. 1A, a fitting36is provided on each end of elongated tubular member12. In certain embodiments, as illustrated, fitting36is a T-fitting defining port18. In certain embodiments, power source26is a direct current power source, operating at 10-200 amps, preferably 70-90 amps, and supplies a voltage of 1-15 volts DC, preferably 4-6 volts. During testing of the present invention, it was discovered that a system10with a tubular member12that is approximately 90 inches long and 6 inches in diameter and operating with these preferred voltage and current ranges can treat fluid flowing at approximately 350-400 gallons per minute, although flow rates as high as 500 gallons per minute have been achieved. As previously described, power source26is in electrical contact with rods34. As such, rods34function as an electrical conduit to provide positive and negative charges to the plates24to facilitate the electrocoagulation process.

An exemplary operation of the present invention will now be described. In a hydrocarbon context, fluids are recovered from a wellbore and treated with the electrocoagulation system described herein. The recovered fluids are fracturing fluids pumped down a wellbore in order to fracture the formation to stimulate hydrocarbon flow. The recovered fracturing fluid is directed into the first port18aand caused to pass around plates24. The angular orientation of plates24aand24brelative to one another, as well as the alternating orientation of plates24abetween adjacent electrocoagulation assemblies22, inhibit laminar flow through tubular member12, and create turbulence along axis17, thereby enhancing the electrochemical reactions in member12.

Moreover, but significantly, this turbulence inhibits corrosion and build-up on plates24that could interfere with the efficiency of system10. Referring toFIG. 1A, as the fluid flows across a plate24functioning as an anode, the plate will be subjected to oxidation, releasing free ions that will combine with the contaminants to form precipitates or floc in the fluid. The treated fluid and floc exit the reaction chamber, i.e., tubular member12, via the second port18b, at which point the floc can then be removed from the fluid by various means known in the art, including sedimentation or filtration. The treated fluid may then be mixed with proppant and/or other components and subsequently reinjected into the formation.

In ongoing operations, a first portion of the plates (e.g.,24a) are provided with a positive charge (the anode plates) and a second portion of the plates (e.g.,24b) are provided with a negative charge (the cathode plates). In an alternative exemplary embodiment, the charges may be alternated over a given time period to minimize corrosion and build up. Typically, a cathode will be subjected to formation of deposits on its surface, known as passivation, which can affect process optimization. Alternating the charges in this way, particularly when combined with the turbulent flow through the member12, will minimize passivation. In one non-limiting example, the charges on the plates of any given electrocoagulation assembly22may be reversed every 24 hours, such that the anodes become the cathodes, and vice-versa.

An exemplary embodiment of the present invention provides an electrocoagulation fluid treatment system comprising a tubular member having a wall extending between a first end and a second end and defined along an axis, and an electrocoagulation assembly disposed along the axis of the tubular member. The electrocoagulation assembly comprises a first electrically conductive plate and a second electrically conductive plate, wherein the first and second electrically conductive plates are secured adjacent one another so as to form an angle between one another. The fluid treatment system further comprises a power source electrically coupled to the first and second electrically conductive plates.

An exemplary methodology of the present invention provides an electrocoagulation fluid treatment process comprising the steps of providing a tubular member having a wall extending between a first end and a second end and defined along an axis, and providing an electrocoagulation assembly disposed along the axis of the tubular member. The electrocoagulation assembly comprises a first electrically conductive plate and a second electrically conductive plate, wherein the first and second electrically conductive plates are secured adjacent one another so as to form an angle between one another. The method also comprises the steps of providing a positive electrical charge to the first electrically conductive plate, providing a negative charge to the second electrically conductive plate, passing the fluid across the first and second electrically conductive plates, thereby creating floc within the fluid, and removing the floc from the tubular member, thereby treating the fluid.

Yet another exemplary methodology of the present invention provides a process for treating fluid received from a downhole fracturing operation, the method comprising the steps of pumping a fracturing fluid down a wellbore, recovering the fracturing fluid from the wellbore, and directing the recovered fluid into a first port of a chamber, the chamber comprising at least one electrocoagulation assembly disposed therein. The electrocoagulation assembly comprises a first electrically conductive plate and a second electrically conductive plate, wherein the first and second electrically conductive plates are secured adjacent one another so as to form an angle between one another. The process also comprises the steps of providing a positive electrical charge to the first electrically conductive plate, providing a negative charge to the second electrically conductive plate, passing the recovered fluid across the first and second electrically conductive plates, thereby creating floc within the recovered fluid, removing the floc from the tubular member, thereby producing a treated fluid, and reusing the treated fluid as fracturing fluid for the wellbore.

Although various embodiments and methodologies have been shown and described, the invention is not limited to such embodiments and methodologies and will be understood to include all modifications and variations as would be apparent to one skilled in the art. For example, although described herein in conjunction with the treatment of fracturing fluid, the present invention may be utilized to filter a variety of other fluids. Therefore, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.