WO2017035680A1 - System for ventilation by means of low-energy crossed airflow for electrowinning tankhouses and method for ventilation by means of low-energy crossed airflow - Google Patents

Abstract

The present invention relates to a system for ventilation by means of low-energy crossed airflow for electrowinning tankhouses, which comprises: a plurality of flat air injectors located above electrowinning cells to generate a homogeneous crossed airflow; at least one extraction chamber located on a wall downstream of the flat injectors to generate a homogeneous extraction front; at least one wet air-scrubber device connected to the respective extraction chamber; a plurality of extractor fans located downstream of the at least one scrubber device; at least one duct for extracting the clean air discharged by the at least one scrubber device; and a plurality of secondary injectors or louvres for the inlet of clean air from outside the tankhouse, located downstream of the flat injectors at a height that promotes separation between the air above the cells and the rest of the air in the electrowinning tankhouse. The invention also relates to the associated method.

Description

 Low energy cross air flow ventilation system for electro-collection ships and low energy cross air flow ventilation method

SCOPE

The present invention relates to a ventilation system by applying a cross flow of low energy air, which allows the removal of pollutants generated by the electro-obtaining process of copper or other metals.

BACKGROUND

The electro-obtaining process of copper or other metals is based on the application of an electric potential difference on two conductive metal plates submerged in a solution called electrolyte, where the metal to be obtained is in solution.

In the case of the electro-obtaining of copper, the solution of cupric sulfate (CuSO4) from leaching is introduced into an electrolytic cell, which is composed of lead anodes and stainless steel cathodes. The cell described is schematized in Figure 1. A power source (101) generates the difference in electrical potential between the electrochemical anode (102) and the electrochemical cathode (103). When applying the electric potential, the deposition of the metal ions in the electrochemical cathode occurs.

The global reaction that governs the process is given by:

Cu ⁺² + H ₂ O → Cu ⁰ + ½ O ₂ + 2H ⁺ E ° = -0.89 VENH

As a result of the electro-obtaining process, copper is reduced in the cathode where it is deposited, while gaseous oxygen is generated in the electrochemical anode in an oxidation reaction.

The oxygen in the form of bubbles (104) rises to the free surface of the electrolyte, where the bubble bursts producing microscopic aerosols (105), which are subsequently transported by the movement of air into the spacecraft. This phenomenon is known as "acid mist", since in i In our case, the small droplets in suspension have the same electrolyte composition, mostly containing sulfuric acid and copper sulfate in solution.

The acid mist is very harmful, since aerosols travel through the air to the operator, causing irritation of the skin, eyes, mucous membranes, teeth and respiratory tract, since the smallest drops of mist (of the order of 20 pm) they are difficult to eliminate, reaching the lungs of the operators without modification, being able to produce a great damage in the health, besides producing high levels of corrosion in the environment damaging the structure of the buildings, also affecting the machinery of the plant; Therefore, these emissions are heavily regulated by health and environmental control entities (Electro Obtainment Plant Operation Training, ENAMI - Vallenar Plant, Dr. Cristian Vargas R., Department of Chemical Engineering University of Santiago de Chile).

The current state of the art to mitigate acid mist emissions resulting from the electro-obtaining process of copper or other metals, presents the following solutions: i) mitigation of emissions from the emitting source (electro-obtaining cells) by use of surfactants (FC-1 100®, quillay, etc.) and use of mechanical barriers (polypropylene pellets), among others; I) use of extractor hoods on the cells (SAME® High Energy Hoods, Outotec® System); i¡¡) local ventilation over each of the cells (LateralVex® system, SELE® system); iv) Ventilation by cross air flow over the cells (DESOM® system).

The article "Recommendations for the design of push-pull ventilation systems for open suríace tanks" (M. Robinson and DB Ingham) published in 1996, refers to the ventilation of open industrial surfaces through the push-pull system, which it is related to the generation of air flow from the side of the surface to be ventilated, and where said flow carries emissions from said surface. However, the same article indicates that the implementation of this solution is not recommended for large surfaces.

A solution based on the same principles of the previous article is that described in US462351 1 (A). This document discloses a system of ventilation for nuclear installations comprising a plurality of air nozzles located above the surface of the water and directed through said surface; a conduit connected to said nozzles, at least one collection bell having a plurality of openings therein positioned above said surface and separated from said nozzles. The system further comprises means to extract the air through the openings of the hood to collect the air above said surface. The described solution is rather related to the ventilation of a channel and not of a more extensive surface, such as an electro-obtaining ship.

With regard to ventilation in electro-obtaining ships, the state of the art describes some solutions for this application. The article "Modeling the flow pattern of acid mist in a tank house" (A. Steiner and R. Kühn) published in 2005, describes the modeling of a cross-flow ventilation system where air is conducted from the outside through lateral lattices, from the space on the cells by a line of fans and removed from the building. High-speed air injectors induce a flow from the upper surface of the cells and take it to the fans to be removed from the top of the building. This configuration allows the extraction of gas, however, there are areas where there is a high concentration of said gas that cannot be taken from the ship.

US5855749 (A) describes a ventilation system for an electrolytic cell comprising a first conduit that extends along one side of said cell, perpendicular to a plurality of parallel electrode plates when said electrode plates are present; a fan to force air into said first duct; a plurality of spaced openings formed in said conduit, wherein said openings adapted to face said electrolytic solution when said electrolytic solution is presented, and positioned adjacent to arrange an electrode plate. The openings are positioned to direct a stream of air along each surface of said electrode plates. A second conduit extends along one side of the cell, parallel to said first conduit, with an elongate groove extending along said second conduit, said groove in front of said openings and are in parallel alignment with said openings; and an air extractor to create a suction in said second duct to extract air through said slot. In this case, the gas extraction is local and there is no cross flow that allows said extraction to be extensible to all cells, requiring that this system be installed in each cell individually. On the other hand, this system is not able to remove the emissions that escape from the electro-obtaining cells.

The DESOM® system solves the injection of clean air through round injectors located on the side of an electro-procurement vessel. These injectors generate a cross air flow over the cells, which is extracted through exhaust fans located on the opposite wall of the ship. The flow of extracted air is conducted through a pipeline to a washing equipment that is responsible for removing the acid mist from the air flow before being released into the atmosphere. A lattice arrangement is responsible for providing the external air flow required to maintain the mass balance between the total incoming air and the air drawn by the fans.

TECHNICAL PROBLEM

The state of the art in cross flow ventilation systems for electro-obtaining ships presents the following technical difficulties: i) the air injectors that produce the cross flow are separated from each other, which generates recirculation of the air flow and / or dead zones (areas with poor ventilation); I) The air injectors are symmetrical, which leads to the incorporation of ambient air in a symmetrical way, which makes the separation process between the flow of contaminated air (just above the cells) and the rest of the air inside of the ship; i¡¡) The extraction of air through the extractor fans is not homogeneous, since the fans generate a point of precise, non-homogeneous extraction (the speed field decays rapidly with the distance from the fans), generating places with ventilation deficient; iv) the fans are directly exposed to the flow of contaminated air, which due to its corrosive content, reduces the useful life of the fans These problems lead to a more disorderly and less vertically confined cross flow, which results in a greater mix between dirty air (just above the cell) and ambient air.

TECHNICAL SOLUTION

To solve the problems described above, a low energy cross-air ventilation system is proposed for copper electro-obtaining ships and low-energy cross-air ventilation method. The present invention relates to the system described above and the associated method.

The system comprises a plurality of primary injectors distributed in an arrangement for high-speed air supply, which are arranged on electro-obtaining cells inside electro-obtaining ships. Said injectors generate a cross horizontal velocity field over the cells. An arrangement of secondary injectors or lattices that supply air at low speed, is responsible for providing a supply of clean air, from the outside, to reduce the incorporation of contaminated air into the flow of air carried by the primary injectors. The cross-flow of air obtained allows pollutants to be transported to the side of the electro-procurement warehouse, where they are extracted through a washing wall, which has two main objectives: i) to impose a homogeneous extraction of pollutants by generating a constant load loss over its entire length, without a specific suction that generates dead zones; ¡I) system of washing by means of the humid way integrated to the wall, that allows the removal of the pollutants from the air flow, for its later discharge towards the atmosphere.

DESCRIPTION OF THE FIGURES

Figure 1 represents a scheme of the process of electro-obtaining copper and the formation of acid mist through the breaking of oxygen bubbles on the free surface of the electrolyte in the electro-obtaining cell.

Figure 2 depicts a scheme of a cross-flow ventilation system of the state of the art. Figure 3 represents a detail of the gas collection system by means of fans of the state of the art cross flow ventilation system.

Figure 4 represents a scheme of the cross flow ventilation system according to an embodiment of the invention.

Figure 5 represents a detail of the gas collection system of the cross flow ventilation system according to an embodiment of the invention.

Figure 6 represents a view of a flat injector cross flow ventilation system according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 2 depicts a cross flow ventilation system currently used. The system comprises the injection of clean air through round injectors (201) located on the side of the ship. These injectors generate a cross-air flow over electrolytic cells (202) inside an electro-obtaining ship. This cross air flow is extracted through a plurality of exhaust fans (203) located on the opposite wall of the ship. The flow of extracted air is conducted through a duct (204) to a washing equipment (205) that is responsible for removing the acid mist from the air flow before being released into the atmosphere. A lattice arrangement (206) is responsible for providing the external air flow (207) required to maintain the mass balance between the total incoming air and the air drawn by the fans. This type of system presents the following technical difficulties: i) the air injectors (201) that produce the cross flow are separated from each other, which generates recirculation of the air flow and / or dead zones (areas with poor ventilation); I) The air injectors are symmetrical, which leads to the incorporation of ambient air in a symmetrical way, which makes the separation process between the flow of contaminated air (just above the cells) and the rest of the air inside of the ship; i¡¡) The extraction of air through the extractor fans (203) is not homogeneous, since the fans generate a non-homogeneous point extraction front (208), as shown in Figure 3 (speed field decays quickly with the distance from the fans), generating places with poor ventilation. These problems lead to a more disorderly and less vertically confined cross flow (209), which leads to a greater mix between dirty air (just above the cell) and ambient air.

Referring to the problem presented by this type of system, the present invention relates to a cross flow system that presents differences with the system described above, as can be seen in Figures 4 and 5.

The system of the present invention comprises: a plurality of injectors (401) arranged in an arrangement, wherein said injectors correspond to the type flat jets. Said injectors (401) are located on electrolytic cells (402), generating a more homogeneous ventilation front than round injectors. The injectors (401) have been modified in such a way that they comprise a plenum before discharge and in their respective upper part they have an extension (601) in the direction of ejection of the air flow (Figure 6). This extension makes it possible to channel the flow in the horizontal direction and decrease the supply of the air that is above the position of the injectors (401), favoring the drag of air with acid mist from the bottom of said injectors, decreasing the mixture with the Cleaner air located above the injectors.

On the other hand, the arrangement of modified injectors (401) incorporates injectors at intermediate points of the ship (403, 404, 405) that provide greater energy to the cross flow in order to counteract the vertical thrust generated by the natural convection of the cells (402 ).

The extraction of the contaminated air is carried out through at least one extractor chamber (406) that covers the entire extension of the wall opposite the direction of the generating flow by the injectors (401), which allows a more homogeneous extraction (407) compared with systems that use direct extraction using discrete fans or extractors. Each of the extraction chambers (406) comprises at least one grid (406a), located at the entrance of each chamber (406) and whose function is to decrease the kinetic energy of the flow that reaches the chamber (406) and decrease the components of air flow velocity that are not parallel to the main inlet flow of the chamber. The contaminated air is treated by at least one wet washing device (408) of air, attached to the rear wall of the extractor chamber (406), forming an integral part thereof. The washing device (408) is located downstream of a plurality of exhaust fans (409). Each of said fans (409) is mounted in its respective extraction duct (410). In this way, the fans (409) are prevented from being directly exposed to a contaminated environment, where they would be exposed to corrosion, and consequently, to a shorter life.

Finally, the clean air is discharged into the environment through the extraction ducts or chimneys (410). From the washing device (408) washing water with diluted contaminant is extracted, which is sent to a recirculation tank (41 1), allowing its reuse in the electro-obtaining process or other process that requires it. Upstream the location of the flat injectors (401) a plurality of secondary or lattice injectors (412) are arranged, which allow to maintain the balance of mass air flow between the total flow drawn and the fresh air injected into the ship. These secondary injectors or lattices (412) are located at a height such that they favor the separation between the contaminated air, just above the cell (402), and the air from the rest of the ship.

Claims

one . Low energy cross flow ventilation system for electro-obtaining ships, CHARACTERIZED because it comprises:  a) a plurality of flat air injectors located on electro-obtaining cells to generate a homogeneous cross air flow; b) at least one extractor chamber located in a wall downstream of the flat injectors to generate a homogeneous extraction front;  c) at least one wet air washing device, attached to the respective extraction chamber;  d) a plurality of exhaust fans located downstream of the at least one washing device;  e) at least one duct for extracting the clean air discharged by the at least one washing device; Y  f) a plurality of secondary injectors or clean air inlet lattices from outside the ship, located downstream of the flat injectors, at a height that favors the separation between the air over the cells and the rest of the air in the ship of electro-obtaining. 2. The ventilation system according to claim 1, CHARACTERIZED in that the plurality of injectors are distributed in several points of the electro-obtaining ship, downstream of the cell, in order to counteract the vertical thrust generated by natural convection in the cells. 3. The ventilation system according to any of the preceding claims, CHARACTERIZED in that each of the flat air injectors comprises a plenum before discharge and a solid surface or extension attached to the top of the jet discharge point flat. 4. The ventilation system according to claim 1, CHARACTERIZED because at least one air extractor chamber is arranged along the entire length of the wall downstream, in such a way that a homogeneous air extraction front is generated in the entire area of the electro-obtaining cells. 5. The ventilation system according to claim 1, CHARACTERIZED, comprises at least one grid located at the entrance of each chamber and whose function is to decrease the kinetic energy of the air flow that reaches the chamber. 6. The ventilation system according to claim 1, CHARACTERIZED in that the wet scrubber air washers are integrated into the chambers at their rear and in turn located downstream of the exhaust fans, which allows these Last operate in a clean environment. 7. Method of ventilation of electro-obtaining ships by means of a low energy cross flow ventilation system, CHARACTERIZED because it comprises the steps of:  a) Inject ambient air from the outside through a plurality of secondary injectors or lattices located on a wall of the ship; g) Injecting air at high speed through a plurality of flat air injectors located on electro-obtaining cells to generate a homogeneous cross air flow, to collect the contaminant and gases that leave said cells;  h) Collect the contaminated gas through at least one extraction chamber located in a wall downstream of the flat injectors to generate a homogeneous extraction front;  i) Wash the gas by at least one wet air washing device, attached to the respective extraction chamber; j) Boost the washed air by means of a plurality of exhaust fans located downstream of the at least one washing device; Y Send the air outwards through at least one exhaust duct of the clean air discharged by the at least one washing device.