NL8102587A - ELECTROLYTIC CELL, PARTICULARLY FOR THE PRODUCTION OF ZINC. - Google Patents

Description

ï ï 813119 / Ke / cd _u

Short indication; Electrolytic cell, in particular for zinc production *

Drill Applicants are named as inventors Renato Guerriero and Itato Yittadini

The invention relates to industrial electrolytic cells, and more particularly to electrolytic cells used for zinc production. The invention improves these electrolytic cells which can be used in a number of electrolytic processes in which gases are generated. but particularly suitable for the processes of electrolytic zinc production *

Although, in the following, reference will often be made specifically to the production of zinc, it is to be understood that the invention is also advantageously applicable to other industrial electrolytic processes *.

It is known that the primary zinc production process consists of a number of steps in which an acidic solution of a zinc salt, generally zinc sulfate, is obtained in high purity, which in the last step is reduced to metal zinc by electrolysis .

These electrolytic cells consist of vessels containing a number of opposing anodes and cathodes »

As a rule, the anodes are made of lead and the cathodes are made of aluminum * 20 33r zinc is deposited in metal form on the cathode to form a thin layer, which is removed from time to time by scraping, which generally involves personnel Required * The spacing between the electrodes placed apart should be reduced as far as practicable to limit the voltage drop through the solution, which is proportional to the spacing between the electrodes; moreover, the electrodes must be parallel to each other with great precision to obtain an even deposition over the entire cathode surface and thus a well-formed layer.

The primary and secondary reactions that take place in such an electrochemical reactor are the following; 81 02 5 87 * -2-

F V

t

ZnSO ^ + 12 -) Zn + H2S04 + 1/2 02 (1)

HgO —-> H2 + 1/2 02 (2)

Zn + H2S04 - »ZnS04 + H2 (5)

The first two reactions take place simultaneously and the clear predominance of reaction (1), d »w0z. the primary reaction, relative to reaction (2), determines the electrical yield of the reactor *

The action (5), according to which the zinc redissolves »can unintentionally take place when the power supply to electricity 10 is interrupted * Reactions (2) and (3) take place everywhere ophthemical reasons, such as insufficient purity of the electrolyte, and / or for physical reasons, such as temperature *

One effect of the evolution of gas, whether considered "normal" production of gaseous oxygen by IS reaction (1), or an "abnormal" production of hydrogen by reactions (2) and (3), is the formation of acidic mist *

The phenomenon is due to the formation of small drops of acidic solution, which, especially under "abnormal" electrolysis conditions, are taken from the surface of the bath and carried with the air to the environment.

Another undesirable effect is experienced when the working conditions are "abnormal", which is the formation of topical explosive mixtures »

Under "normal" working conditions, the haze content in a chamber with electrolytic cells is about a few mg 3 per normal m of air, in terms of sulfur acidity * Under "abnormal" conditions, this rises to much higher values »

The removal of the zinc from the cathodes takes place at predetermined time intervals, generally between 24 and 48 hours, and it is done mechanically. * This operation requires the presence of personnel near the cells so that these personnel are exposed to the aggressive environment.

In the long run, this causes changes in the nasal septum, oral cavity, teeth and generally the respiratory tract. »

However, such an environment is also aggressive for the machinery, equipment and construction of the cell rooms, so that they must be built with special precautions »81 0 2 5 8 7 ψ · ** -3-

An attempt has been made to overcome these drawbacks by cleaning the working environment with forced ventilation $ with a total replacement of Thought bags 5 and 10 times per ear. However, this treatment shows a number of drawbacks such as the development of strong luchi-5 flows, the difficulty of air treatment especially for installations located in cold areas, and a significant consumption of energy.

The present invention aims to overcome these drawbacks and thus prevent the pollution of the environment in the chamber with 100 electrolytic cells.

Another object of the invention is to pollute the gaseous pollutants as soon as they are formed.

The electrolytic cells of the invention consist of a vessel fitted with suction manifolds formed in the top edges of the vessel at a height immediately above the free surface of the electrolyte. * These manifolds have suction ports emerging from the air chamber above the free mirror of the electrolyte immediately extract the gases that are generated there ·

The invention will be explained below with reference to the appended drawing of an exemplary embodiment

Fig. 1A schematically shows a section through the vessel;

Fig. 1B shows the vessel partly in top view;

Fig. 2 shows a mounted set of electrodes;

Fig. 3 shows a perspective view of the whole 25 with disassembled parts ·

Fig. 1A shows the sprout branches 1 together with gates 2, formed by an extension 3 in the upper part of the side wall 4

The electrolyte level is indicated by 5 «Alternatively, the manifold may also be arranged in only one side wall of the vessel · 6 indicates an overflow.

The sets of anodes and cathodes are alternately immersed in the vessel and rest on support members mounted on the top edge of the cell · The cell is covered by a set of 33 baffles attached along the entire length of the anodes and cut along the centerline of the spacing of the anodes, according to the working positions of the cathodes

The space thus created not only makes it possible to remove and replace the cathodes for removal 81 02 58 7 1 C1 '-¾

Aran the deposited zinc layer, but also forms a reference that of. is useful for correct placement and an instant check of the correct position of the electrodes0

The configuration of the assembled set of electrodes is shown in FIG. 2, in which the anodes are indicated by and the connections resting on the supports are indicated by 8, while the methods and the corresponding connections are indicated by 10 and 10 respectively.

The shielding plates or partitions are indicated by 11; they are attached to the connections 8 by spring members 12 and / or 10 with screws.

The partitions preferably consist of a resilient material so that they are sufficiently tight, while they do not interfere with the displacement of the cathode. The partitions concerned can also be attached in another way, such as because the horizontal top surfaces of the the connections 8 are provided with a set of grooves, while the partitions 11 are provided with protrusions that fit in those grooves · By placing all partitions, a space is insulated above the electrolyte and thus it is possible to remove the developed gas from the space, together with the 20 acidic mist that simultaneously forms above the electrolyte

The exhaust manifolds are connected to a main suction line, which in turn is connected to a conventional extraction system, equipped with electrolytic extraction fans and / or blowers.

The electrolytic cells according to the invention make it possible to overcome the above drawbacks because the removal of the acid mist is carried out with a small volume of air extracted, and thus with a low energy consumption, so that the air treatment in the room as a whole does not problem.

The cells according to the invention also make it possible, if desired, to create an atmosphere enriched in oxygen. The extracted gases and mist can be distributed in the atmosphere through a chimney in a diluted state, so that it is * conducted gases are harmless; As an alternative, a gas decomposition system may be used, which should be used at least when "abnormal" reaction conditions prevail ·

When electric extractors are used, those types deserve the preference in which the moving parts have anti-explosion bearings. · 81 02 5 8 7 i. Τ '· -5-

The negative pressure used for aspirating the air above the electrolyte is up to about 150 Pa *. This value is related to the sealing provided by the partitions, because too low absolute values of the underpressure do not allow suitable extraction, while too high values create an useless airflow through the extraction openings, whereby the extracted gases are diluted without use while a higher energy consumption is required · Whenever a system is used to break off the extracted gases, the extraction system will drop under the influence of extra pressure *

To better understand the meaning and advantages of the invention, the table below lists some data obtained from a test cell *

Working conditions Composition of the atmosphere in the cell 15 Coename ° 2 H2 content HgSQ. Content vol * J ^ mg / nor.mr mg / nör * sr normal + 1.0 300 1.0 «+ 2.0 250 0, 8 irregular + 2.0 550 3> 0 20 "+ 1.2 700 7.0 M + 2.0 1000 15.0" + 3.0 400 5.0 2

By maintaining a suction of 150 nor * m / h in the device located in the inner rim of the vessel, no discernible changes have occurred in the composition of the air in the room in which the cell was placed *

The cells of the invention can be built with conventional materials, such as coated or protective cement, acid-resistant oxygen materials such as reinforced polyvinyl chloride, or glass-reinforced synthetic resin * Air ports, manifolds, and suction connections can enter the cell applied during construction or they can be manufactured separately and then attached to the cell

In the former case, however, the ribs resulting from the insertion of such members into the structure of those elements will cooperate to improve the strength and stiffness of the structure itself *

Suction manifolds can also form the support structure for the electrodes * 81 02 5 8 7. * «R •" 5 Μ

A possible alternative to the negative pressure suction system is to pressurize the entire chamber in which the cell is located to a value slightly higher than atmospheric pressure, thereby preventing gases from entering the space above the electrolyte level flow around the environment, but in such a way that reverse flow from the space in the chamber to the space above the electrolyte is prevented and thus flow in the direction of the manifolds is prevented »

This approach, which is undoubtedly a bit more complicated, 1 (5 may show greater caution and thus may be preferable for special electrochemical processes in the galvanic industry »-Conclusions- 81 02 5 8 7

Claims (3)

Device according to claim 1 or 2, characterized in that the partitions are attached to the anodes, so that the cathodes can be removed without removing the partitions · Device according to any one of the preceding claims, characterized in that the suction tips and the respective row of suction ports are arranged along a longitudinal axis Device according to any one of the preceding claims, characterized in that the extraction of the gases present in the space above the electrolyte is carried out by pressurizing the environment in the cell chamber to a pressure slightly above atmospheric pressure is 81 81 587