Abstract:
A compact, light, and continuous-process apparatus for filtering impurities and separating organics contained in an electrolyte stream feeding an electrowinning cell, the apparatus includes an outer body having an octagonal tubular piece, a rear cover and rims or flanges, and an inner body having support housing, a common cover, at least one perforated or slotted tube and at least one high-contract surface filler. The apparatus also includes a rich electrolyte input, a rich electrolyte output, a contaminated electrolyte output, a lower flow input chamber, a mid-chamber for filtered electrolyte output, an upper chamber, and a lower distribution chamber.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application claims priority from Chilean Patent Application No. 0928-2014 filed Apr. 11, 2014, which is hereby incorporated by reference herein in its entirety. 
       FIELD 
       [0002]    The invention is related to the field of metal electrowinning and refers specifically to an apparatus for recovering organics from the solvent extraction process before going to the electrolytic cells. 
       BACKGROUND 
       [0003]    Preferably, the solvent extraction (SX) process is used for recovering copper from leaching solutions, which consists of concentrating the copper content present in these solutions using organic solvents for such purpose. Once the copper content from the leaching solutions is captured using these solvents, the copper is discharged obtaining a new solution with a much higher concentration than the initial solution, in a process commonly known as “stripping”. 
         [0004]    All electrowinning (EW) plants, with an SX-EW configuration, have some degree of permanent organic dragging to cells, coming from SX. Similarly, many of them have had specific and severe organic dragging incidents, due to uncontrolled operations or operational contingencies, from the SX solvent extraction stage to the electrowinning building. The presence of organics in the cell feeding causes many problems, the main one being the loss of physical and chemical quality of electro-deposited copper cathodes. This results in losses, because such cathodes have to be marketed at lower prices, due to quality punishment. In some plants, this situation, which is permanent, has not allowed quality certification in bags such as LME, affecting the ability to qualify for better prices and preferential contracts. The presence of organics also creates other problems, such as fouling and rapid deterioration of equipment or components within the cell, such as spheres used for the mitigation of Acid Mist. 
         [0005]    Also, the organics foul the electrodes, capping boards and contact bars, causing conduction problems, because, when evaporating light phases of the organics, a thick paste that retains fine solids starts to generate. This paste is very difficult to remove and clean. 
         [0006]    In relation to safety, the presence of organics (hydrocarbons), which are flammable by nature, creates a permanent risk of ignition and fire, a situation that is not unique, since it is common to find hot contact points due to shorts or sparks usually generated on the cells during sowing or arrangement of electrodes. Additionally, the organics reaching the cell normally accumulate between electrodes and low surface flow points, such as corners and edges. This happens with a wider impact when the cell has a baffle plate before the sump (to prevent dragging of spheres), because the floating organics begin to cover the cell&#39;s entire free surface, unable to drain to the poor electrolyte (PE) manifold. 
         [0007]    In specific cases, where for some reason there has been passing or “dragging” of organics from SX in large amounts, the result has been a complete loss of plant production and its inability to remove and clean the organics. 
         [0008]    The processes for separating organics from the electrolyte are well documented, since such separation is a key element in the solvent extraction stage, for which there are different equipment types and combinations. Those common in the art are demayters, which, by means of a low-speed passing and high residence times, allow the mixed organics and electrolyte flow to separate by density differences, and to be selectively retrieved. Since this process usually let organics pass in the electrolyte stream, it happens that before the rich or “charged” electrolyte is sent to the electrowinning building, this flow normally passes through a filter bank, which typically have a porous filler formed by anthracite, clay or other fillers, which have the disadvantage of getting saturated. Therefore, they operate on batteries and, depending on their level of saturation, they enter into washing cycles. Since it is difficult to determine the saturation level, the operation is normally sequential, with a time control for the washing process. 
         [0009]    Chilean application 3044-2012 entitled “Process for capturing undesired organic solids from the solvent extraction processes by using a filter, provided with plastic, continuous and extruded monofilaments; and a filter”, describes a process to capture and retain, in a filtering bed of continuous and extruded monofilaments, all kinds of undesired organic solids from the solvent extraction processes; also, due to the characteristics of the material comprising the filtering bed, it allows capturing pieces of organics present in the electrolyte. The disadvantage of this process is that the recovery of the captured organics is performed by subjecting the filter to a flow in favor or against such filter, and it is not in a continuous process, as in the case of the proposed invention, which saves time in the filter cleaning operations, as it involves removing same from the feeding line. Another difference is that filtering in application 3044-2012 is mechanical, whereas in the proposed invention it promotes coalescence to capture the organics by means of a high-contact surface filler. 
         [0010]    There is also a big difference in that the apparatus described in application 3022-2012 is introduced as an apparatus to filter the total flow coming from SX, usually located outside the building, since this is a large piece of equipment, while the apparatus of the proposed invention is modular, and it is located inside the building, in front of each cell. This characteristic of the proposed invention is valuable because it solves problems of space and opportunity to install the apparatus in a plant that is in operation. 
         [0011]    The proposed apparatus operates at pressures higher than atmospheric pressure and is unique in that it may be used in any process where the need is to separate two phases, one aqueous and one organic. 
         [0012]    Regarding shape, this apparatus is designed in a very compact fashion, which allows the apparatus, in the case of electrowinning cells for typical feeding flow ranges in the industry, to have a size such as to be installed on one end of the cell, usually at the lateral passageway, where the ER manifold is found. Still more, in many electrowinning buildings, the apparatus may be placed under the cell. 
       SUMMARY 
       [0013]    In an embodiment, the present invention provides for a compact, light, and continuous-process apparatus for filtering impurities and separating organics contained in an electrolyte stream feeding an electrowinning cell, the apparatus including an outer body having an octagonal tubular piece, a rear cover and rims or flanges, and an inner body having support housing, a common cover, at least one perforated or slotted tube, and at least one high-contract surface filler. The apparatus also includes a rich electrolyte input, a rich electrolyte output, a contaminated electrolyte output, a lower flow input chamber, a mid-chamber for filtered electrolyte output, an upper chamber, and a lower distribution chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
           [0015]      FIG. 1  shows an isometric view of the inner body of the apparatus viewed from the front. 
           [0016]      FIG. 2  shows an isometric view of the inner body of the apparatus viewed from behind. 
           [0017]      FIG. 3  shows an isometric view of the outer body of the apparatus viewed from the front. 
           [0018]      FIG. 4  shows an isometric view of the outer body of the apparatus viewed from behind. 
           [0019]      FIG. 5  shows a longitudinal section of the entire apparatus. 
           [0020]      FIG. 6  shows the installation of the apparatus in an electrolyte circuit for electrowinning cell. 
           [0021]      FIG. 7  shows an electrolyte circuit for electrowinning cell without the invention. 
           [0022]      FIG. 8  shows an A-A sectional view according to  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The apparatus ( 50 ), designed for use in electrowinning facilities, comprises a body built from composite materials, mainly fiberglass with resins that are resistant to the environment and to typical operating conditions of the process, where normally pressures are higher than atmospheric pressure, but low (less than 5 bars), and temperatures usually are between 25° C. and 65° C. The high-contact surface filler ( 15 ) may be comprised of composite materials, PVC or plastics, with a resistance to the environment and to temperature and pressure conditions. For typical industrial operating conditions, this apparatus ( 50 ), in a dry fashion, that is, without any liquid inside, usually has a weight no greater than  25  kilograms, which allows it to be carried by a person inside the building, to be installed in places to which it typically has no easy access. 
         [0024]    The apparatus consists essentially of an inner body ( 51 ) or support-housing and an outer body ( 52 ) or housing. The outer body ( 52 ) consists of an octagonal tubular piece, with a size greater than the inner body ( 51 ) to contain it. This outer body ( 52 ) allows the inner body ( 51 ) to be inserted inside the outer body ( 52 ) and, by means of rims or flanges ( 53 ), to close against a common cover ( 54 ), holding the inner body ( 51 ) supported in its bottom against the bottom wall ( 20 ) of the outer body ( 50 ). 
         [0025]    The apparatus ( 50 ) operates between the rich electrolyte manifold ( 31 ) and the electrowinning cells ( 44 ) and may be installed in front or under each cell ( 44 ); the electrolyte flow received by the apparatus ( 50 ) is equivalent to that received by each cell ( 44 ) where it is installed. The apparatus ( 50 ) has a flow input ( 1 ), which allows connection by means of a flexible junction or pipe ( 41 ) to the electrolyte output of the rich electrolyte manifold ( 31 ); the rich electrolyte manifold output includes a shutoff valve ( 32 ) to interrupt feeding to the apparatus, if necessary; impurities in the electrolyte entering through the flow input ( 1 ) are retained in an input chamber ( 2 ) by a mesh ( 55 ) made of stainless steel or other environment-resistant material. 
         [0026]    The apparatus has a first flow output ( 9 ), which delivers more than 95% of the inflow and connects directly to the electrowinning cell ( 44 ) through a flexible junction or pipe ( 42 ), providing an impurity-free filtering at the output ( 36 ). The apparatus ( 50 ) has a second flow output ( 8 ) which delivers up to 5% of the input flow and connects directly to the poor electrolyte manifold ( 35 ) by means of a flexible junction or pipe ( 49 ), or to the poor electrolyte output of the electrowinning cell ( 44 ), said flow output ( 8 ) delivers a mixture of electrolyte with organics separated by the apparatus ( 50 ). Inside the apparatus ( 50 ), between the upper chamber of the apparatus ( 7 ) and the lower chamber of the apparatus ( 4 ), there is a high-contact surface filler ( 15 ) comprised by a plurality of flat or slotted plates separated by a distance of about 20 mm from each other, thus, channels or spaces are generated through which electrolyte may flow from the bottom to the top. Under the high-contact surface filler ( 15 ) and in the lower chamber ( 4 ), there is one or more slotted or perforated tubes ( 3 ) for distribution of the electrolyte from the bottom of the high-contact surface filler ( 15 ) to the top. The organic separated inside the high-contact surface filler ( 15 ) floats and accumulates against the upper chamber of the apparatus ( 7 ), leaves the apparatus through the output chamber ( 13 ) and then through the output ( 8 ) towards the poor electrolyte manifold through the flexible junction or pipe ( 49 ). 
         [0027]    The high-contact surface filler ( 15 ) and the distribution tubes ( 3 ) are contained inside a longitudinally symmetrical conduit in its vertical plane, which has, at its upper edges, an inward curvature ( 18 ) to contain the high-contact surface filler ( 15 ). 
         [0028]    The filtered and separated electrolyte flow, after exiting at the top of the high-contact surface filler ( 15 ), turns towards the sides of the filler and through a space ( 23 ) formed between the vertical walls of the conduit and the apparatus housing ( 50 ), enters through the openings ( 29 ) connecting the side channels with the output mid-chamber ( 10 ), and moves towards the filtered and separated electrolyte output ( 9 ) of the apparatus ( 50 ). 
         [0029]    The lower chamber for flow input ( 2 ) is separated from the mid-chamber for filtered electrolyte output ( 10 ) through a plate ( 27 ), while the mid-chamber for filtered electrolyte output ( 10 ) is separated from the apparatus upper chamber ( 7 ) by means of another plate ( 30 ). 
         [0030]    The operation of the apparatus ( 50 ) is based on the fact that the electrolyte contaminated by the organics and eventually by suspended solids enters the input chamber ( 2 ) through the hole ( 1 ) of the common cover ( 54 ). Once inside the input chamber, this moves towards the distribution tubes ( 3 ), where the electrolyte is distributed along a channel under the high-contact surface filler ( 15 ). The electrolyte, when passing through the high-contact surface filler ( 15 ), gets to separate the organic phase, which, due to surface tension and Stokes&#39; law, is grouped in increasingly larger drops, which in turn adhere to the filler ( 15 ) and slowly climb the filler ( 15 ) up to the top, where they become detached and float to the upper chamber ( 7 ) of the apparatus ( 50 ). Meanwhile, the electrolyte, climbing the filler regularly ( 15 ), exits at the top of the filler ( 15 ) and moves towards the sides of the channel, down the sides ( 23 ) of the inner body ( 51 ), between this and the outer body ( 52 ), and then moves through that section to the output mid-chamber ( 10 ), entering through the openings ( 29 ) of the output mid-chamber ( 10 ). Moreover, the organics separated by gravity will float against the top of the apparatus, inside the outer body ( 52 ), so that, when in contact with the organic output perforation ( 8 ) of the common cover, this may exit the apparatus ( 50 ) continuously due to the internal pressure of the apparatus ( 50 ). 
         [0031]    The apparatus opens at one end for cleaning the high-contact surface filler ( 15 ) and removing solids that have been retained in the mesh ( 55 ) of the input chamber ( 2 ). 
         [0032]    In relation to installation, the apparatus ( 50 ) has to be installed at an angle of at least 0.5° with regard to its length, making the highest point with respect to the horizontal position to be that of the separated organics output chamber ( 8 ). 
         [0033]    A process for the use of the apparatus is described below: the rich electrolyte enters the apparatus from a pressure rich electrolyte manifold ( 31 ) through the input ( 1 ); the rich electrolyte enters the lower distribution chamber ( 4 ); the mesh ( 55 ) inside the lower distribution chamber ( 4 ) retains impurities; the electrolyte is distributed in the perforated or slotted tubes ( 3 ); the perforated or slotted tubes ( 3 ) push the electrolyte upwards; the electrolyte enters the filler ( 15 ) from below; the electrolyte goes through the filler ( 15 ) reaching the upper chamber ( 7 ) being separated; the treated electrolyte overflows the filler, falling down its sides into the space ( 23 ) for the liquid to move; the treated electrolyte enters through the openings ( 29 ) and enters the mid-chamber ( 10 ); the treated electrolyte exits through the filtered liquid output ( 9 ); the treated electrolyte is introduced in the electrowinning cell ( 44 ); the organics recovered in the filler ( 5 ) in step g) float on the liquid surface in the upper chamber; the recovered organics exit through the organic phase output ( 8 ) with some amounts of electrolyte; the recovered organics are introduced into the poor electrolyte manifold. 
         [0034]    While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. 
         [0035]    The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.