Method and arrangement for collecting and removal of acid mist from an electrolytic cell

A method and an arrangement for collecting and removal of acid mist from an electrolytic cell. The arrangement includes a cover for covering an open top of a container of the electrolytic cell so that a space is formed between a surface of electrolyte contained in the container and the cover, a decontamination system provided with an acid mist suction channel terminating in an upwards facing inlet opening in the space, and a cleaning arrangement for spraying the upwards facing inlet opening with washing fluid. The cleaning arrangement has a fluid nozzle. The fluid nozzle is in the acid mist suction channel. The fluid nozzle is arranged to spray washing fluid at least downwards into the acid mist suction channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Entry under 35 USC §371 of PCT Patent Application Serial No. PCT/FI2015/050274 filed Apr. 22, 2015, which claims the benefit under 35 USC §119(e) to Finnish Patent Application No. 20145376, filed Apr. 23, 2014, the disclosure of each of these applications are expressly incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The invention relates to a method for collecting and removal of acid mist from an electrolytic cell in a metal electrowinning process or in a metal electrorefining process, where an electric current is passed between a plurality of electrodes, from anodes to cathodes alternately arranged and submerged in electrolyte contained in a container having an open top, wherein the method comprising covering the open top of the container with a cover so that a space is formed between a surface of the electrolyte contained in the container and the cover, providing a decontamination system provided with an acid mist suction channel terminating in an upwards facing inlet opening in the space between the surface of the electrolyte contained in the container and the cover, and provided with suction means for sucking acid mist from the space between the surface of the electrolyte contained in the container and the cover, sucking acid mist from the space between the surface of the electrolyte contained in the container and the cover by means of the suction means of the decontamination system, providing a cleaning arrangement for spraying the upwards facing inlet opening of the acid mist suction channel with washing fluid to prevent the upwards facing inlet opening of the acid mist suction channel from being blocked, and spraying the upwards facing inlet opening of the acid mist suction channel with washing fluid by means of the cleaning arrangement to prevent the upwards facing inlet opening of the acid mist suction channel from being blocked, as defined in the preamble of independent claim1.

The invention also relates to an arrangement for collecting and removal of acid mist from an electrolytic cell in a metal electrowinning process or in a metal electrorefining process, where an electric current is passed between a plurality of electrodes, from anodes to cathodes alternately arranged and submerged in electrolyte contained in a container having an open top, wherein the arrangement comprising a cover for covering the open top of the container so that a space is formed between a surface of the electrolyte contained in the container and the cover, a decontamination system provided with an acid mist suction channel terminating in an upwards facing inlet opening in the space between the surface of the electrolyte contained in the container and the cover, and provided with suction means for sucking acid mist from the space between the surface of the electrolyte contained in the container and the cover, and a cleaning arrangement for spraying the upwards facing inlet opening of the acid mist suction channel with washing fluid to prevent the upwards facing inlet opening of the acid mist suction channel from being blocked, as defined in the preamble of independent claim10.

BACKGROUND INFORMATION

Blocking of the vertical acid mist suction channel due to scaling such as copper sulfate scaling at the upwards facing inlet opening is a problem. This can hinder the acid mist flow, which results in increased acid mist in the tankhouse space atmosphere causing increased worker health risk and also equipment corrosion.

Various methods and arrangements for collecting and removal of acid mist from an electrolytic cell in metal electrowinning process or a metal electrorefining process are known in the art.

Publication US 2011/0108414 presents a multi-element cover system for controlling acid mist in metal electrowinning or electrorefining cells is made of an electrolyte resistant material and is applied above the surface of the electrolyte and below the electrical connections of the electrodes in order to provide a continuous and substantially airtight seal above the electrolyte. The cover system comprises a plurality of flexible longitudinally concave caps arranged between the cathode and the anode that help to shift the acid mist towards the sides of the cell using the same energy that disengages it from the electrolyte; lids between the electrodes and the wall of the corresponding end of the cell; and lateral enclosures located at both sides of the cell in the space between the electrodes and the lateral walls of the cell, the lateral enclosures having at least a top side, end walls at each end and an inner side projecting towards the electrolyte, thus forming a chamber inside the lateral enclosure, with the lower side of the enclosure or the electrolyte itself acting as the bottom boundary of the chamber, the chamber being connected to external acid mist suction means and its inner side provided with bores above the electrolyte level so as to in this fashion, in collaboration with the flexible caps, uniformly suck and remove the acid mist confined under the caps throughout the entire cell with a gentle suction and without the risk of crystal formation due to oversaturation of the droplets contained in the mist.

SUMMARY

An object of the invention is to provide a method and an arrangement for collecting and removal of acid mist from an electrolytic cell in a metal electrowinning process or in a metal electrorefining process, which has an effective arrangement for preventing blocking of the vertical acid mist suction channel.

The method of the invention is characterized by the definitions of independent claim1.

Preferred embodiments of the method are defined in the dependent claims2to9.

The arrangement of the invention is correspondingly characterized by the definitions of independent claim10.

Preferred embodiments of the arrangement are defined in the dependent claims11to18.

The invention is based on arranging the cleaning arrangement for spraying the upwards facing inlet opening of the acid mist suction channel at least partly in the acid mist suction channel. The cleaning arrangement has a fluid nozzle and a pipe for feeding washing fluid to the fluid nozzle. The pipe and the fluid nozzle are arranged so that the pipe is at least partly located in the acid mist suction channel and so that the fluid nozzle is located at the upwards facing inlet opening of the acid mist suction channel. Washing fluid is sprayed at least downwards into the acid mist suction channel by means of the fluid nozzle of the cleaning arrangement.

An advantage with the method and the arrangement is that this requires no openings or holes in the cover covering the open top of the container. Additionally, when the cover is lowered, only a small part of the fluid nozzle will be visible, because the fluid nozzle is protected by the acid mist suction channel, and this reduces considerably the risk that the cover hits the fluid nozzle and/or the piping, and thus the fluid nozzle will keep its position better.

DETAILED DESCRIPTION

The invention relates to a method and to an arrangement for collecting and removal of acid mist (not shown in the drawings) from an electrolytic cell1in a metal electrowinning process or in a metal electrorefining process, where an electric current is passed between a plurality of electrodes, from anodes4to cathodes5alternately arranged and submerged in electrolyte6contained in a container2having an open top (not marked with a reference numeral). The metal may be copper.

First the method and some preferred embodiments and variants of the method will be described in greater detail.

The method comprises covering the open top of the container2with a cover3so that a space9is formed between a surface10of the electrolyte6contained in the container2and the cover3.

The method comprises providing a decontamination system7provided with an acid mist suction channel8terminating in an upwards facing inlet opening13in the space9between the surface10of the electrolyte6contained in the container2and the cover3, and provided with suction means11for sucking acid mist from the space9between the surface10of the electrolyte6contained in the container2and the cover3. The decontamination system7provided in the method may have a scrubber12for scrubbing acid mist originating from at least one electrolytic cell1. Several electrolytic cells1may be connected to one and the same decontamination system7. For clarity reasons is only one electrolytic cell1shown inFIG. 1.

The method comprises sucking acid mist from the space9between the surface10of the electrolyte6contained in the container2and the cover3by means of the suction means11of the decontamination system7.

The method comprises providing a cleaning arrangement14for spraying the upwards facing inlet opening13of the acid mist suction channel8with washing fluid15to prevent the upwards facing inlet opening13of the acid mist suction channel8from being blocked.

The method comprises spraying the upwards facing inlet opening13of the acid mist suction channel8with washing fluid15by means of the cleaning arrangement14to prevent the upwards facing inlet opening13of the acid mist suction channel8from being blocked.

The method comprises providing a cleaning arrangement14having a fluid nozzle16and a pipe17for feeding washing fluid15to the fluid nozzle16.

The method comprises arranging the pipe17and the fluid nozzle16so that the pipe17is at least partly located in the acid mist suction channel8and so that the fluid nozzle16is located at the upwards facing inlet opening13of the acid mist suction channel8.

The method comprises spraying washing fluid15at least downwards into the acid mist suction channel8by means of the fluid nozzle16of the cleaning arrangement14. The definition “to spray washing fluid15downwards” does not necessarily mean “to spray washing fluid15in a direction vertically downwards”, but includes also “to spray washing fluid15in an inclined direction downwards”. It is possible that in addition to spraying washing fluid15downwards into the acid mist suction channel8by means of the fluid nozzle16, washing fluid15is additionally sprayed vertically and/or upwards into the acid mist suction channel8by means of the fluid nozzle16.

The method may include arranging the fluid nozzle16in the middle of the acid mist suction channel8and by spraying washing fluid15360 degrees around the fluid nozzle16.

The method may include providing a fluid nozzle16that has a spring loaded cap18that protects the fluid nozzle16when the fluid nozzle16is inactive and that is adapted to open for allowing washing fluid15to be sprayed from the fluid nozzle16when washing fluid15is sprayed by means of the fluid nozzle16.

The method may include spraying washing fluid15at least downwards into the acid mist suction channel8by means of the fluid nozzle16of the cleaning arrangement14in predetermined time intervals and/or when needed.

Washing fluid15containing water, preferably washing fluid15being water, may be used in the method.

The method may include providing a decontamination system7having an acid mist suction channel8having a vertical channel section19terminating at the upwards facing inlet opening13.

The method may include arranging the pipe17of the cleaning arrangement14to penetrate a wall structure20of the acid mist suction channel8of the decontamination system7at an opening21located a level below the fluid nozzle16to that the pipe17of the cleaning arrangement14have pipe17section located in the acid mist suction channel8of the decontamination system7between the opening21and the fluid nozzle16.

In the method, the container2of the electrolytic cell1may have an upper peripheral surface22surrounding the open top of the container2, and the upwards facing inlet opening13of the acid mist suction channel8may be arranged vertically at the level of the upper peripheral surface22surrounding the open top of the container2.

The method may include providing an acid mist removal box23at the outer surface of the container2so that the acid mist removal box23having an upper surface located vertically at an upper peripheral surface22surrounding the open top of the container2, providing the acid mist removal box23with a channel forming a part of the acid mist suction channel8of the decontamination system7, wherein the channel in the acid mist removal box23having an opening at the upper surface forming the upwards facing inlet opening13of the acid mist suction channel8of the decontamination system7, and covering the open top of the container2so that the cover3covers at least the opening of the acid mist removal box23. The acid mist removal box23may be provided as an integral part of the container2or as a part that is fastened to the container2.

Next the arrangement and some preferred embodiments and variants of the arrangement will be described in greater detail.

The arrangement comprises a cover3for covering the open top of the container2so that a space9is formed between a surface10of the electrolyte6contained in the container2and the cover3.

The arrangement comprises a decontamination system7provided with an acid mist suction channel8terminating in an upwards facing inlet opening13in the space9between the surface10of the electrolyte6contained in the container2and the cover3, and provided with suction means11for sucking acid mist from the space9between the surface10of the electrolyte6contained in the container2and the cover3. The decontamination system7may have a scrubber12for scrubbing acid mist originating from at least one electrolytic cell1. Several electrolytic cells1may be connected to one and the same decontamination system7. For clarity reasons is only one electrolytic cell1shown inFIG. 1.

The arrangement comprises a cleaning arrangement14for spraying the upwards facing inlet opening13of the acid mist suction channel8with washing fluid15to prevent the upwards facing inlet opening13of the acid mist suction channel8from being blocked.

The cleaning arrangement14has a fluid nozzle16and a pipe17for feeding washing fluid15to the fluid nozzle16.

The pipe17and the fluid nozzle16are arranged so that the pipe17is at least partly located in the acid mist suction channel8and so that the fluid nozzle16is located at the upwards facing inlet opening13of the acid mist suction channel8.

The fluid nozzle16of the cleaning arrangement14are arranged to spray washing fluid15at least downwards into the acid mist suction channel8. The definition “to spray washing fluid15downwards” does not necessarily mean “to spray washing fluid15in a direction vertically downwards”, but includes also “to spray washing fluid15in an inclined direction downwards”. It is possible that the fluid nozzle16of the cleaning arrangement14in addition to being arranged to spray washing fluid15downwards into the acid mist suction channel8, is additionally arranged to spray washing fluid15vertically and/or upwards into the acid mist suction channel8.

The fluid nozzle16may be arranged in the middle of the acid mist suction channel8, and the fluid nozzle16may be arranged to spray washing fluid15360 degrees around the fluid nozzle16.

The fluid nozzle16may have a spring loaded cap18that protects the fluid nozzle16when the fluid nozzle16is inactive and that is adapted to open for allowing washing fluid15to be sprayed from the fluid nozzle16when washing fluid15is sprayed by means of the fluid nozzle16.

The cleaning arrangement14may be configured for spraying washing fluid15at least downwards into the acid mist suction channel8by means of the fluid nozzle16of the cleaning arrangement14in predetermined time intervals and/or when needed.

The washing fluid15may contain water, or preferably contain solely water.

The acid mist suction channel8of the decontamination system7may have a vertical channel section19terminating at the upwards facing inlet opening13.

The pipe17of the cleaning arrangement14may penetrate a wall structure20of the acid mist suction channel8of the decontamination system7at an opening21located a level below the fluid nozzle16so that the pipe17of the cleaning arrangement14have pipe17section located in the acid mist suction channel8of the decontamination system7between the opening and the fluid nozzle16.

The container2may have an upper peripheral surface22surrounding the open top of the container2, and the upwards facing inlet opening13of the acid mist suction channel8may be arranging vertically at the level of the upper peripheral surface22surrounding the open top of the container2.

The arrangement may comprise an acid mist removal box23provided at the outer surface of the container2so that the acid mist removal box23have an upper surface located vertically at an upper peripheral surface22surrounding the open top of the container2, and so that the acid mist removal box23have a channel forming a part of the acid mist suction channel8of the decontamination system7, wherein the channel in the acid mist removal box23having an opening at the upper surface forming the upwards facing inlet opening13of the acid mist suction channel8of the decontamination system7, and so that the cover3for covering the open top of the container2covering at least the opening of the acid mist removal box23. The acid mist removal box23may be an integral part of the container2or a part that is fastened to the container2.

It is apparent to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.