Method and System for Precluding Air Pollution in Industrial Facilities

Abstract

A holistic system for sustained capture, confinement and depuration of acid mist generated in nonferrous metal electrodeposition processes utilizing lead anodes, for precluding zero release of gaseous fluid pollutants in the atmospheric air surrounding electrodeposition processes, providing an assured solution to acid mist control and total abatement in an effective, efficient manner and sustainable in time by immediate recovery and recycling back in the source generating the contaminant effluents as there are produced, according to a “cell by cell” strategy, and directly connecting each cell to a system for depuration, recovery and recycling the contaminants gaseous fluid flow extracted from each cell reducing them to innocuous levels in the discharge to the open atmosphere; complying the condition of “100% Null escape of acid mist” from each individual cell to the working environment, simultaneously with minimum power usage, and substantial global gaseous fluid contaminant reduction, far exceeding present minimum sustainability standards, in terms of human health, energy usage and environmental protection.

Description

FIELD OF THE INVENTION[0001]The invention relates to a method and system for precluding release of gaseous fluid pollutants in the atmospheric air surrounding industrial processes, more specifically, the invention is a method and system for capturing and eliminating acid mist generated by the process of electrodeposition of non-ferrous metals with insoluble anodes and impeding polluted gaseous fluids and / or air from the process to escape to the working ambient air.BACKGROUND OF THE INVENTION[0002]Many industrial processes release gaseous fluids with contents of chemicals / pollutants to the air, which require drastic measures for carrying out these processes to avoid harm to the workers in the facilities where these industrial processes take place. For example, in electrowinning, an electrolysis process used to obtain several types of non-ferrous metals (e.g. copper and zinc, etc.), involves using caustic acids, e.g. sulfuric acid. In facilities where electrowinning is carried out, a ...

AI Technical Summary

Benefits of technology

[0019]A second goal of eliminating acid mist in electrowinning tankhouses is achieved, according to the invention, with a substantial decrease of electric energy requirements for the capture, confinement, extraction, transport and treatment of the acid mist generated in each cell. The latter goal is achieved by implementing a “cell by cell” strategy instead of the “centralized” acid mist treatment strategy” common in all of the present art systems up to the present day.

[0020]Other goals of the invention are achieved by a substantial decrease of thermal energy losses, compared to prior art, by decreasing to an absolute minimum the air intake volume of colder working ambient air from the tankhouse into each cell, needed to replace the volume of acid mist and air being continuously extracted from the confinement volume; the small mass of colder air intake avoids cooling the electrolyte, and in fact, simultaneously takes advantages of atmospheric pressure to assist in minimizing the suction energy required for the extraction of the confined acid mist in each cell, while also eliminating all electrolyte exposure to direct contact, at all times, with the work ambient while the cell is in operation.

[0021]A “cell-by-cell” implementation, according to the invention, compared to prior art: (a) eliminates the ducting maze, (b) any travel distance of substantially increased volume diluted acid mist (c) and the need for a remote centralized acid mist depurator treatment installation altogether. In fact, “cell-by-cell” implementation immediately recycles all the useful components of the acid mist generated by each cell, both “in situ” right inside each cell where they originate, and also immediately upon the extraction of acid mist from each cell. In particular, the invention utilizes a functional removable anodic cover that is designed to promote coalescence of the liquid electrolyte particles dispersed as fine airborne drops in the acid mist. The latter cover actually enhances coalescence and growth of fine droplets of liquid until they fall back by gravity into the electrolyte without leaving the container. The remainder de acidified confined acid mist generated in each cell is individually extracted from each cell and carried to at least one or more successive depurators devices for further substantial cleaning of the gaseous fluid and returning immediately the resulting condensate back to the cells.

[0022]“Cell-by-cell” strategy provides immediate double or multi treatment of the gaseous fluid from each cell, with at least a primary acid mist depurator device installed on one external front wall in each cell; from the acid depurator device, the acid condensate is recovered and recycled immediately back to the process, while the partially or totally de-acidified gaseous fluid goes through a secondary multistage acid mist condenser / depurator device provided for similar primary acid mist depurator treatment of several gaseous flows from adjacent cells. Said second multistage condenser / depurator device is equipped with means for positively enhanced effectiveness in reducing the H2SO4 vapors to innocuous levels in the treated gaseous fluid finally discharged to the open atmosphere.

[0023]“Cell-by-cell” preferred execution in this invention not only eliminates all causes for the secondary operational problems and harvesting shortcomings of the prior art, and facilitates harvesting and other tankhouse tasks effectively and in an operator, friendly manner.

[0024]To simultaneously achieve the sustainability goals stably in time, it is essential to provide a reliable programmable automatic controller system including a continuous instantaneous monitoring of process variables in real time, for their precise measurement and instantaneous control and self-regulation of the extraction flow of acid mist at each individual cell, and simultaneously, at the global acid mist flow level of the plurality of cells in the tankhouse. The programmable monitoring and automatic controller system of the invention is comprised of two (2) separate control systems that operate concatenated. At each cell, a first control subsystem is provided for individual monitoring in real-time, measurement and instantaneous self-regulation control of its actual acid mist extraction flow rate setting. A second control subsystem for global monitoring in real time, measurement, control and instantaneous regulation for the minimum suction requirement for the total extraction of acid mist demanded instantaneously by the sum of each suction demand by each cell of the plurality of cells.

Problems solved by technology

In copper electrowinning facilities, for example, presence of acid mist in ambient air is known to cause multiple operational encumbrances, such as corrosion of installations, equipment and structural concrete structures, etc.

; and other hazards and process inefficiencies associated with electric usage, such as electric current leaks by the crystallites and buildup of CuSO4, copper node formations on the cathode plates and electrode short circuits, with attendant production losses and hazards.

Whichever cover system for the capture and confinement of acid mist is used in the cells, the volume of gases, vapors and gaseous fluids generated by the electrolytic process inevitably lead to a rise in the pressure inside the volume for confinement above the electrolyte; and eventually, when the confinement volume pressure rises above the ambient pressure of the tankhouse, the higher pressure will inevitably initiate a leak flow of acid mist from each of the cells to the tank house working atmosphere.

However, prior art systems using nonporous rigid covers, such as hoods placed on top of the cells, present a number of well-established short comings and inconveniences.

(1) Inevitable crystallization of the very fine CuSO4 airborne droplets in curve dead spots inside the maze of ducts, which need systematic cleaning at all times to prevent obstruction and crystallization buildups, that not only decrease the effectiveness of the centralized depurator treatment installation, but provide paths for high amperage current leaks that decrease overall electrodeposition current efficiencies;

(2) Aggressive high corrosion caused by acid mist of all equipment and Tankhouse installations;

(3) Maintenance of the expensive and fragile acid mist confining and / or extraction devices, such as the acid mist hoods current art in industry.

Prior art systems for capturing acid mist suffer from thermal losses caused by the large volume of air infiltrated from the tankhouse into each cell, which is generally at a lower temperature than that of the process electrolyte; the large volumes of colder air intake into the cells further imparts not only uncontrolled thermal losses in the circulating electrolyte, but more importantly, also enhances electrolyte evaporation; in fact, creating substantially more acid mist and exacerbating pollution much more than the electrolytic process itself generates!.

Moreover, prior art hood type systems suffer from yet another serious operational and environmental shortcoming: hood covers require removal from each cell in order to access the cathodes for harvest; with consequences: (1) wasted crane time and (2) no available floor space to retrieve / store hoods in most existing installations (built without considering acid mist hazards); and / or more recently, (3) complex automatic cranes that retrieve hoods while lifting the cathodes, and replacing the hoods before moving the cathodes, to minimize the time the cell electrolyte is exposed in direct contact with the working atmosphere.

So while cells are being harvested, the maximum allowed concentration of hazardous substances in the work ambient in the vicinity of cells far exceeds the limits of applicable Health and Work Safety Protocols and Regulations, an unacceptable shortcoming to the health and occupational hygiene of workers plus decreased plant productivity.

More importantly prior art systems for controlling acid mist cannot assure sustained and full compliance of the mandatory maximum content limits of contaminants continuously at all times in all the working areas in the tankhouse.

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