JPH0452291A - Method for refining zinc - Google Patents

Abstract

PURPOSE:To increase the efficiency of refining of zinc, to reduce the cost and to improve the working environment by recovering oxygen generated on the anode in a process for electrolyzing zinc and effectively utilizing the oxygen in various processes for refining zinc. CONSTITUTION:An electrolytic cell is divided with a diaphragm to form a cathode chamber and an airtight anode chamber and the cathode is rotated. Zinc is electrolyzed in the cell and zinc deposited on the surface of the rotating cathode is separated and recovered. An anolyte-gaseous oxygen mixture discharged from the anode chamber is subjected to vapor-liq. separation and the gaseous oxygen is recovered and used in at least one of a process for producing oxygen enriched air for roasting a zinc sulfide concentrate, a process for oxidizing and removing manganese in a zinc electrolytic soln., a process for oxidizing a soln. prepd. by releaching zinc from residue obtd. by leaching zinc and a process for leaching zinc from a zinc sulfide concentrate under pressure. Almost all of the pure oxygen is relatively simply recovered without a loss and can effectively be utilized. Maintenance work necessary for the anode is relieved and the pollution of the working environment by mist of an electrolytic soln. contg. free sulfuric acid is remarkably reduced.

Description

Detailed Description of the Invention (a) Technical field The present invention relates to a method for electrolytic smelting of zinc, and more specifically, a method for recovering oxygen generated at an anode in the electrolytic process of zinc electrolytic smelting,
The present invention relates to a zinc smelting method that effectively utilizes the oxygen in various steps of zinc smelting.

(b) Prior Art Electrolytic smelting has been practiced as the main method for smelting zinc, and the outline of the method is as follows.

The raw material, zinc sulfide concentrate with a zinc content of around 50%, is oxidized and roasted in a roasting furnace by blowing air into it, and the sulfur content, which becomes sulfur dioxide gas, is recovered as sulfuric acid.

On the other hand, zinc and other metals that have become oxides in the roasting process are leached out in the electrolytic tailing liquid containing free sulfuric acid that is repeated from the zinc electrolytic process. , cobalt, nickel, cadmium, germanium, antimony, etc. are cleaned with zinc dust, etc.

After that, use this clean zinc sulfate solution as the electrolyte stock solution.
Electrowinning of zinc is carried out in the electrolytic process.

In addition, the leaching residue generated in the above leaching process contains about 10% of the zinc in the raw material, as well as about half of the copper and all of the gold, silver, lead, etc., as undissolved components. The leaching residue is treated in an appropriate manner to recover these valuable metals.

Now, in this zinc electrolysis process, generally, as shown in FIG.
A lead-based alloy plate is vertically immersed in the electrolytic solution 36 as an anode plate 37 alternately with the cathode plate 35, and a current density of 400 to 600 A/m'' is applied. Electrolysis is carried out, and zinc is electrolytically deposited in the form of a plate on the surface of the cathode plate 35 for about 48 hours.

At this time, the main reaction on the cathode plate 35 is the electrodeposition reaction of zinc, but hydrogen is generated as a side reaction, reducing the cathode current efficiency. In addition, in the anode plate 37, as a main reaction, 0.5 mol of oxygen is generated per 1 mol of zinc electrolytically deposited.
Further, as a side reaction, an anodic oxidation reaction of divalent manganese ions present in the electrolytic solution from 1 to 5 g/l to difeminated manganese occurs.

In addition, as the electrolytic cycle progresses, undesirable whisker-like or bump-like deposits that grow from the cathode side, and the manganese dioxide scale mentioned above that grows from the anode side, can cause the yin-fist-anode bipolar plate to deteriorate. If the gap is bridged, the electrolytic current will be short-circuited, reducing the cathode current efficiency.

In the zinc electrolytic method, the electric power required to produce one ton of electrolytic zinc, that is, the basic unit of electrolytic power, is expressed by the following equation (1).

w = (820XVt) / η ---" (1) W: Electrolysis power unit (kwh / t) vt: Electrolytic sliding voltage (malt) η: Cathode current efficiency (0 < η < 1) Therefore, the electrolysis power To reduce the basic unit, electrolytic sliding voltage (
It is sufficient to reduce vB and increase cathode current efficiency (η).

In actual operation, electrolysis conditions such as the distance between electrodes, zinc concentration, electrolyte composition such as free sulfuric acid concentration, and electrolyte temperature are required to minimize the electrolysis power consumption rate.

Various conditions such as current density and additives are selected appropriately, but the basic unit of electrolysis power is usually 3000 to 3800 k.
wh/ is the degree.

Now, the cathode plates 35, which have been electrolyzed for about 48 hours and have had zinc electrodeposited in the form of plates, are lifted from the electrolytic bath 34 in appropriate numbers using a transport device such as a hoist crane, and then peeled off using an automatic peeling machine or the like. transport to the extraction facility. Here, the zinc plate electrolytically deposited on the cathode plate 35 is peeled off and recovered, and the cathode plate 35 is returned to the electrolytic cell 34 again.

On the other hand, the anode plate 37 is periodically (about 20 days)
4 in the same manner as the cathode plate 35, and the anode plate 3
At 71, the manganese dioxide scale deposited and grown by the anodic oxidation reaction is removed from the electrolytic solution 36 using an anode cleaning machine, and then the electrolytic solution is returned to the electrolytic cell 34 again.

In addition, a part of the manganese dioxide scale mentioned above peels off and falls from the anode plate 37 due to its own weight, etc., and the electrolytic #ll
34, so that the electrolytic cell 34 is periodically vacuum-suctioned from the bottom to avoid contact with the bottoms of the cathode plates 35 and anode plates 37, which are suspended alternately in the electrolytic cell 34. Remove.

In the conventional technology mentioned above, with the successive progress of zinc electrolysis technology, efforts have been made to increase the size of electrode plates, enlarge the size of electrolytic cells, and automate material handling.
It has achieved considerable results in improving efficiency and saving labor.

For example, when increasing the size of electrode plates, those commonly known as ``super jumbo'' with an effective area of 3 m2 per plate can be used without any problems, and when increasing the size of electrolytic cells,
Approximately 100 super jumbo-sized cathode plates and anode plates each have been put into practical use per tank, and these have been combined with automation such as material handling machines, stripping machines, and 7-node cleaning machines to improve production efficiency. It has brought about great effects in improving space efficiency, reducing various capital investments, and saving labor.

However, in order to further increase the size of the electrode plate, in the case of damage to the electrode plate due to problems with each of the S devices mentioned above, the size or weight is approaching the limit when it becomes necessary to dispose of it manually. Increasing the size of the electrolytic cell is also close to its limit because it becomes difficult to make the flow state of the electrolytic solution uniform within the electrolytic cell, resulting in non-uniform electrolytic reaction and non-uniform electrodeposition.

For the reasons described above, the current situation is that dramatic progress cannot be expected as an extension of the progress that has been made in the prior art.

Furthermore, in consideration of the above-mentioned situations, the prior art has some problems.

The first is that a large amount of oxygen generated at the anode is not recovered and is released into the atmosphere. The reason for this is that when recovering oxygen, it is basically necessary to change the structure of the electrolytic cell itself from an open-top type to a closed type, which makes the structure of the electrolytic cell complicated and increases the capital investment accordingly. In addition, there are complicated issues such as how to deal with tasks such as the periodic lifting of the cathode and anode plates and the discharge of manganese dioxide scale from the bottom of the electrolytic cell.

I couldn't find an easy solution.

Furthermore, if oxygen is recovered, it would be economically advantageous if it were to be utilized in a zinc smelting system, but no suitable utilization site commensurate with the amount of oxygen generated has been found.

Next, the second is that with the release of oxygen gas into the atmosphere,
The mist of zinc electrolyte containing free sulfuric acid floats and diffuses into the atmosphere, contaminating the working environment. In order to suppress the pollution of the working environment due to this acid mist, a common method is to add a foaming agent such as soybean meal to the electrolyte to form a layer of foam on the surface of the electrolyte in the electrolytic cell. There are, but not enough.

In addition, an air curtain method has been proposed in which a fan sucks in floating acid mist from one side above the liquid surface of an electrolytic cell, and fresh air is sent in from the other side. This is not an adequate method as it requires a large amount of power to cover a large space.

The third problem is that there is a limit to the nighttime power usage rate, that is, the ratio of nighttime power usage to total power usage.

Recently, the demand for electricity has been increasing due to the increase in air conditioners, air conditioners, and electronic devices in society, and the peak demand has become prominent during the day, so the gap between maximum electricity consumption and average electricity consumption is widening. As a result, the overall utilization rate of electric power facilities is deteriorating. For this reason, electric power companies are implementing a time-of-day rate system in which nighttime electricity rates are set lower than daytime rates in order to improve energy use efficiency, that is, to suppress power peaks.

Therefore, zinc smelters whose electricity is purchased from electric power companies try to reduce production costs by using cheap electricity at night as much as possible.

By the way, in the electrolysis of zinc, an aluminum plate is used for the cathode and a dissimilar metal plate of a lead-based alloy is used for the anode, as described above. As a battery is formed and a back electromotive force is generated, the zinc deposited on the aluminum plate is redissolved at the cathode.

Cathode current efficiency decreases.

Furthermore, at the anode, a stable layer of lead dioxide formed on the surface by the anodic oxidation reaction of lead is reduced to lead sulfate, followed by a dissolution reaction of lead sulfate into the electrolyte.
The lead concentration in the electrolyte increases, resulting in an increase in the lead content in the electrodeposition on the cathode plate, which reduces the purity of the product.
This causes problems such as shortening the life of the anode plate.

As a measure to reduce production costs, the electrolytic current is stopped during the day when the unit price of electricity is high, so the electrolytic solution must be quickly drained from the electrolytic cell after the electricity is stopped to prevent the above-mentioned disadvantages. It is extremely difficult to carry out this process, as it takes a considerable amount of time to drain the electrolyte, and the capacity of the storage tank that temporarily stores the drained electrolyte becomes extremely large when combined with the electrolyte from all the electrolytic tanks. Ta.

Therefore, in the conventional technology, during the daytime when the electricity unit price is high, the operation is carried out at the lowest technically possible current that does not cause the re-dissolution reaction of zinc from the cathode, for example, around 50 A/m2 in terms of current density. There is a tendency to operate at full capacity at the full rated capacity of the rectifier, for example around 500 A/m'', at night when the unit price of electricity is low, aiming to increase the nighttime power utilization rate as much as possible and reduce production costs.

However, there are naturally limits to improving the nighttime power utilization rate using the above method.

The fourth problem is that in the conventional technology, undesirable whisker-like or lump-like deposits that grow as the electrolysis time progresses, as well as manganese scale with double resistivity generated from the anode side, can cause negative and positive images. If the electrode gap is bridged, the electrolytic current is short-circuited and the cathode current efficiency is reduced, so the distance between the anode II intestine electrodes can only be shortened to the extent that the above-mentioned disadvantages are tolerated.

There is a limit to the reduction of the resistance of the electrolytic solution related to the distance between the electrodes, that is, the electrolytic voltage and the basic unit of electrolytic power.

(C) Disclosure of the Invention The present invention has been made to solve the above-mentioned problems, and is to recover oxygen generated at the anode during the electrolytic process, and to use the oxygen effectively in various processes of zinc smelting. This is a zinc smelting method characterized by the use of a diaphragm to separate the electrolyte layer to form a cathode chamber and an airtight anode chamber, and a rotating cathode that collects the zinc deposited on the surface of the cathode. The mixture of anolyte and oxygen gas discharged from the airtight anode chamber is separated and recovered, and the mixture of anolyte and oxygen gas is separated into gas and liquid to recover oxygen gas, and the oxygen gas is used to produce oxygen-enriched air for roasting zinc sulfide concentrate. , a zinc smelting method characterized in that it is used in at least one of the steps of removing manganese oxidation in a zinc electrolyte, the oxidation treatment step of a re-leaching test solution of zinc leaching residue, and the pressure leaching step of zinc sulfide concentrate. It provides law.

Next, the present invention will be explained in detail.

The reaction in the electrolytic cell during the zinc electrolysis process is as follows (2)
), (3), (4), (5), and (6).

Anodic reaction H, 0=2H” +1/2 0. +2e * 11
@(2)(Mn2” +2H20=MnO,+4H”
+2e)・Conflict・Φ(3) Cathode reaction znZ+2e=Zn11111+ 11 e * e
*(4) (2H+2e=H2) e a *
* e * * (5) Equations (2) and (3) above are anodic reactions, equations (4) and (5) are cathodic reactions, and (2)
) and (4) are the main reactions at each pole, and (3) and (5
) formula indicates a side reaction.

Therefore, the whole is expressed by equation (6).

Z n2” +H20= 2H” +Z n+1/20
．． *...(6) That is, when 1 mol of zinc is electrolytically deposited on the cathode, 0.5 mol of oxygen is simultaneously generated on the anode.

Here, in the case of a zinc smelter that produces 150,000 tons of electrolytic zinc per year, the amount of oxygen generated is specifically calculated as follows from the above equation (6).

15XlO' ()7/year) X [(05!/2
) / 2! +]=37×108 (tons/year)...
(7) Next, when the above-mentioned generated oxygen is recovered, no suitable use suitable for the amount of generated oxygen has been found so far in the zinc smelting system.

For example, in a zinc smelting system, iron in the raw material dissolved in a solution is processed into a pressurized reaction vessel (called the hematite method) in the leaching residue treatment process.
There is a process to remove iron oxide as iron oxide using an autoclave).

In this process, in order to produce 150,000 tons of electrolytic zinc per year, 300,000 tons of raw material concentrate is required, and since the raw material contains 8% iron, the total amount of iron in the raw material is The amount of iron is 24×10” tons/year. In the hematite method, the amount of oxygen used to remove this total amount of iron is calculated by the following equation (8).

2FeSO4+1/202 +2H20=Fe2 o3
+ 2H2SO411” ” ” (8) 24X1
0” (tons/year) XlB/112=3.4X10
s (tons/year)... (theoretical amount)・Fist・
・ (9) 3.4X10” (tons/year) Xl, 35 (factor)
=ts X 10” (door/year) 1111@
(Actual amount)...Φ・(lO) In other words, the amount of oxygen used in the hematite method is 4.6×1O
2I tons/year, and the amount of oxygen generated above is 37X10B.
) This is only 12% of the 1977 figure.

In recent years, in the field of nonferrous metal smelting, particularly in copper smelting, a method has been proposed and has been effective in improving the throughput of a furnace by using so-called oxygen-enriched air, which is air enriched with oxygen.

Zinc smelting involves roasting and sulfuric acid processes, as well as leaching and purification processes.

The process is broadly divided into the electrolytic process and the leaching residue treatment process, and if the torrefaction and sulfuric acid processes are a bottleneck due to production capacity, the raw materials in the torrefaction furnace can be reduced by using oxygen-enriched air as described above. Processing capacity can be improved, and thus overall production capacity can be improved.

Although this method is not yet common in zinc smelting,
It requires a relatively small amount of capital investment, and if the demand for zinc increases due to social conditions and the price increases, there can be sufficient economic benefits to purchase expensive liquid oxygen or install an oxygen plant. .

In zinc smelting, the reaction in the roasting furnace is expressed by the following equation (11).

Z ns+3/202 =ZnO+SO1* *(11
) In other words, the raw material (zinc sulfide concentrate) is processed in an appropriate amount of oxygen, but this oxygen is supplied from the air blown into the furnace. , the reaction of the above equation (11) is allowed to proceed to the right while flowing the raw materials in the furnace.

Since the reaction of equation (11) is an exothermic reaction, no fuel is required once the reaction has started, and the raw materials are continuously charged into the furnace from the feed nozzle at the middle level of the furnace.
After the reaction, the burnt ore is continuously discharged from the furnace at an appropriate level. The temperature inside the furnace is controlled to be maintained at about 950° C. by a method such as arranging a cooling coil inside the furnace.

By the way, when using oxygen-enriched air, the amount of heat generated increases, so it is necessary to increase cooling (heat exchange).
This is necessary because the temperature of the exhaust gas containing sulfur dioxide discharged from the top of the furnace increases, increasing the heat load on the exhaust heat recovery boiler installed next to the furnace in the exhaust gas system.

Therefore, there is naturally a limit to the degree of oxygen enrichment in #element-enriched air, and the oxygen concentration in oxidized-enriched air is 23%.
is preferred.

In other words, when oxygen-enriched air with an oxygen concentration of 23% is used, the amount of oxygen in the same volume is 23/21 = 1.1 times that of air with an oxygen concentration of 21%, and the above formula (11) is As can be seen from the reaction equation, based on a zinc smelter that uses 1.1 times the amount of raw material, 10% per year, or 15X10")
The amount of oxygen used in this case is as follows:

15X10” (door/year) X3/202/Z
n=1IX10” (tons/year) --(theoretical amount)
・ φ ・ (12) 11XIO” ()7/year)
...(13) That is, the amount of oxygen used as oxygen-enriched air in the roasting process of zinc concentrate is 13 x 103) 77 years, and the amount of oxygen required to produce 150,000 tons of electrolytic zinc per year is Generated amount 37
x10m) 35% of 1977.

Furthermore, in recent years, a composite zinc smelting system that combines a direct pressure leaching method in the raw material treatment process in addition to the conventional roasting and sulfuric acid processes has been attracting attention.

The outline of this method is to use a pressurized reaction vessel (autoclave) to directly produce zinc sulfide concentrate under oxygen pressure without going through the roasting process by subjecting the raw material zinc sulfide concentrate to the basic reaction shown in equation (14) below. The zinc content in the concentrate is leached into the solution as zinc sulfate.

Z n S + Ht S OJL + 1/20 t
=ZnSO4+H@o+s' 11 * 115
(14) As can be seen from equation (14), sulfur in the raw material is separated and recovered from the solution as elemental sulfur.

Therefore, when trying to increase the production capacity of an existing zinc smelting system, this method can be used to connect new large equipment such as a torrefaction furnace or sulfuric acid plant when there is a limit to increasing the existing torrefaction and sulfuric acid processes. This has the advantage that there is no need to install it, and the amount of capital investment is small.

However, the ratio of introduction of the direct pressure leaching method to the total production of electrolytic zinc is limited by the following points.

In other words, zinc sulfide concentrate, which is the raw material, contains various elements in addition to zinc, and among these, so-called halogen elements such as fluorine and chlorine are volatilized into gas in the conventional roasting process and are removed from the roasting furnace. migrates into exhaust gas containing sulfur dioxide gas,
Thereafter, it is absorbed into the cleaning liquid in the exhaust gas cleaning process of a spray tower or the like, and by bleeding off this cleaning liquid to a wastewater treatment plant, the accumulation of halogen elements in the system liquid is prevented.

However, in the direct pressure leaching method, the halogen element dissolves into the leachate along with zinc, so the concentration level of the halogen element in the system solution increases. For example, when the fluorine concentration becomes 1O g/1 or more, During the electrolytic process, it becomes difficult to peel off the zinc plate electrolytically deposited on the cathode plate, causing problems in operation.

Furthermore, when the chlorine concentration reaches a high concentration of 100 g/fL or more, the lead alloy anode plate is corroded, causing problems such as shortening the life of the anode plate.

Therefore, unless a new process for removing halogen elements by electrodialysis or other methods is added from the system solution, the proportion of direct pressure leaching is limited to such an extent that these adverse effects do not become noticeable.

Specifically, the proportion of the direct pressure leaching process to the total electrolytic zinc production is normally operated at about 20%.

As mentioned above, based on a zinc smelter that produces 150,000 tons of electrolytic zinc per year, by introducing the direct pressure leaching method, the annual production rate can be reduced by 20%, or 3%, with a relatively small capital investment. A production capacity of 10,000 tons of electrolytic zinc will be built.

The amount of oxygen used in this case is calculated as follows.

30X10” C ton/year) X 1/20t/
Z n =? , 4X10” (door/year)---(J
! Theoretical quantity-・・(15)? , 4 XIO" () 7/'F) The amount of oxygen used is 15X10” tons/year, and the amount of oxygen generated when producing 150,000 tons of electrolytic zinc in one year is 37XIO.
1) It will be 40% of 2027.

Next, one of the uses of the generated oxygen is the removal of manganese from the solution in the zinc smelting system.

In other words, the zinc sulfate concentrate used as a raw material contains around 0.15% manganese, and this manganese is processed through the roasting process, leaching, and
It exists as divalent manganese ions in the electrolyte stock solution (also called a neutral solution due to the properties of the solution) after the solution purification process. These manganese ions become manganese dioxide through anodic oxidation during the electrolytic process, and as the electrolysis time progresses, this manganese dioxide scale grows from the anode plate and reaches the opposing cathode, or it peels off from the anode plate and cross-links with the cathode. However, the electrolytic current is short-circuited, reducing the cathode current efficiency, and the anode plate is melted, shortening the life of the anode plate, and some of the dissolved lead ions are deposited on the cathode.

This results in a decrease in product quality, such as an increase in the lead content in the electrolytic submersible.

Further, as the scale of manganese dioxide on the surface of the anode plate becomes thicker, the electrical resistance increases, the electrolytic sliding voltage increases, and as a result, the electrolytic power consumption rate increases.

Therefore, it is preferable to remove manganese from the electrolytic stock solution prior to the electrolysis process to reduce such adverse effects to an acceptable level. This is achieved by oxidizing manganese dioxide and separating and removing it. The reaction is expressed by the following formula (17): Ozone used in the above reaction is usually produced by the silent discharge method, and the ozone concentration produced is generally 4-5% for air raw material and 6-8% for oxygen raw material. %, but by increasing the cooling effect of the ozone generator, it can be reduced to 14% in the case of oxygen raw material.
ozone can also be produced.

In any case, by recovering and using the oxygen generated in the above electrolysis process (producing ozone using the silent discharge method), ozone can be produced efficiently without building a new oxygen plant. Costs can be reduced.

The amount of oxygen used to remove manganese from the liquid in a zinc smelting system using the method described above is 15% per year.
Based on a zinc smelter that produces 10,000 tons of electrolytic zinc, it is calculated as follows.

The amount of zinc sulfide concentrate used as raw material is 300,000 tons per year, and the manganese content is 0. On the other hand, the ozone concentration produced by the silent discharge method using oxygen as a raw material is 10%, and the oxidation reaction rate of divalent manganese ions to manganese dioxide by ozone is 100%.

30XIO' ()77)Xl, 5 Xl0-"
X021/Nn=0.39X10” (
) 77) --(18) The amount of ozone used is 0.39
X 102I tons/year, and the amount of oxygen used to produce ozone is 0.39X103X C110,10>
= 3.9
7X10” () 1977).

The main uses in the zinc smelting system when oxygen generated in the electrolytic process is recovered have been described above, using a zinc smelter that produces 150,000 tons of electrolytic zinc per year as a specific example. Namely, ・ Oxygen-enriched air production process for roasting zinc sulfide concentrate (35%) ・ Manganese oxidation removal process in zinc electrolyte (11%) ・ Oxidation treatment process for re-leaching test solution of zinc leaching residue (12%) %) - Pressurized acid leaching process of zinc sulfide concentrate (40%) More than 98% of the recovered oxygen is effectively utilized in the four usage processes.

As listed above, with the recent technological progress in zinc smelting, composite zinc smelting systems that combine several types of processes are attracting attention. It can be seen that there is enough oxygen and the potential for oxygen recovery is great.

Next, in order to recover the large amount of oxygen generated from the anode, the structure of the electrolytic cell is basically complicated, which increases the equipment cost per electrolytic cell, so it is necessary to increase the current density as much as possible to improve production efficiency. Reducing the number of electrolytic cells by increasing the number of electrolytic cells is advantageous not only in terms of equipment investment but also in terms of maintenance and space savings.

Several methods have generally been adopted to cope with high current density electrolysis, including the use of pulsed or periodic reversal currents, or increasing the concentration of target metal ions to be electrolytically deposited on the cathode in the electrolyte. be.

Although these methods can of course increase the current density in industrial zinc electrolytic refining methods, the conventional 4
There is a limit to increasing the current density from 00 to 600 A/m2 to a high current density of 100 OA/mz or more.

As a countermeasure to this problem, the inventors have repeatedly conducted tests and research, and found that by rotating the Wk electrode plate or forcibly circulating the electrolyte in the electrolytic cell, the relative movement speed between the electrolyte and the cathode plate was reduced by 0.5.
m/sec or more, preferably 1 m/sec or more, the mass transfer of zinc ions in the electrolyte to the cathode is promoted, and the current density is 400 to 600 A/m, which is the conventional current density.
'L with much higher current density than 1000 A/m
We discovered a method for obtaining electrodeposited zinc with a preferable electrodeposition form of 2 or more, and were able to establish the basic conditions for recovering oxygen generated in industrial zinc electrolytic smelting methods.

By the way, although high current density electrolysis increases production efficiency and is advantageous in terms of equipment investment, maintenance savings, and space savings, on the other hand, the electrolytic sliding voltage increases in proportion to the current density, and the electrolytic power consumption rate decreases. It is disadvantageous for

Here, the electrolytic power consumption unit W (kwh/l) is the electrolytic sliding voltage Vt (maoft) and the cathode current efficiency η (0<η×1)
is expressed by the above equation (1), and furthermore, this electrolytic sliding voltage Vt
can be decomposed as shown in equation (18) below.

Vt=α+β・imiα+(βI+β2+β3)・i (19) α: Theoretical resolution voltage passing voltage MA01t) β: Total ohmic resistance (Ω・cm”) β word: Ohmic resistance of electrolyte βg!Near node Ohmic resistance of the scale β8: Ohmic resistance of the contact part and conductor part i2 Current density (A / c ■2
) From the above relational expression, there are several methods for suppressing the increase in electrolysis power unit as much as possible in high current density electrolysis.

The first is to remove manganese from the electrolyte stock solution using the method described above prior to the electrolytic process, to suppress the formation and growth of manganese dioxide scale on the TeWA electrode plate to a negligible level during the electrolytic process, and to reduce the The objective is to reduce such resistance, that is, the ohmic resistance of the anode scale (manganese dioxide scale).

Furthermore, this may cause negative effects such as a decrease in cathode current efficiency due to cross-linking of manganese dioxide, melting of the anode plate, and an increase in lead content in the deposited zinc, and periodic (20 days) removal of manganese dioxide from the anode plate. It is possible to eliminate the work of lifting manganese dioxide scale for scale cleaning and discharging manganese dioxide scale from the bottom of the electrolytic cell.

In addition, instead of a lead-based alloy plate as an anode material, a so-called DSE anode in which a titanium substrate with a low oxygen overvoltage is coated with an oxide of a platinum metal element can be used.
The overvoltage associated with this can be reduced by around 0.5 volts. This is because when manganese dioxide scale forms and covers the DSE anode plate, the original function of lowering the oxygen overvoltage is lost, so it could not be used.

The second purpose is to reduce the resistance related to βS, that is, the ohmic resistance of the electrolyte. Examples of this method include shortening the distance between the electrodes and changing the electrolyte composition such as zinc concentration and free sulfuric acid concentration.

First, in order to shorten the distance between the electrodes, the distance between the cathode and anode can be reduced by combining the removal of manganese from the electrolytic stock solution mentioned above and the removal of the dendritic deposits that have grown by rotating the cathode plate with a scraper. Short circuits can be prevented, and the distance between the electrodes can be significantly shortened compared to conventional methods.

As a specific example, as shown in Example 1 below, an appropriate amount of additives such as glue is added to the electrolytic solution, electrolysis is performed for the purpose of electrodepositing zinc in a plate shape, and the electrolysis time elapses. Undesirable whisker-like or lump-like deposits that occasionally grow from one electrode side due to the electrolysis can be removed by rotating the cathode plate using a simple bar-type scraper fixed in the cathode chamber in the electrolytic cell. Alternatively, as shown in Example 2 below, zinc can be electrolyzed in a dendritic form without using glue or other additives, and zinc can be deposited sequentially from a single pole to a dendritic form. The extending deposits are removed by rotating the cathode plate using a scraper similar to the above, and the deposits continuously dropped from the bottom of the cathode chamber are discharged and collected. Electrodeposited zinc can be obtained in any of the preferred electrodeposited forms.

As mentioned above, high current density electrolysis and shortening the distance between the electrodes can reduce the number of electrolytic cells and the volume of the electrolytic cell! ! 2.In addition to reducing capital investment, the capacity of the electrolytic solution in the electrolytic cell is compressed and reduced, so the electrolytic current can be stopped during the day when the electricity unit price is high, and 1.The electrolytic solution can be removed from the electrolytic cell as quickly as possible after the electricity is stopped. can be drained, further improving the nighttime power utilization rate and reducing production costs.

Next, the electrolyte composition can be changed by partitioning the anode and cathode with a diaphragm and changing the compositions of the anolyte and catholyte.

That is, by combining the first method (removal of manganese from the electrolyte) and the second method (reducing the ohmic resistance of the electrolyte) described above, it is possible to prevent the generation of lano manganese dioxide scale on the anode side in the electrolytic cell.・Since it is possible to prevent the growth and fall-off of dendritic deposits from the cathode side, it is possible to prevent clogging of the diaphragm due to scale and damage due to dendritic deposits, and it is possible to use the diaphragm for a long time. It can be done.

Here, the conductivity of the electrolytic solution is expressed by the following equation (20).

K = -o, ootso* [Z nl +o, 001
43 [Ht Soa] +0.00489
[T] +0.08780...(20) K: Conductivity (S/c■) [Zn]: Zinc concentration (g/view) [Hz S Oa]: 1N sulfuric acid concentration (g/J
L) [T]: Electrolyte temperature ("C) That is, the lower the zinc concentration and the higher the free sulfuric acid concentration and the electrolyte temperature, the better the electrical conductivity.

Therefore, for the anolyte in the anolyte chamber separated by a diaphragm, which is not directly related to the zinc electrodeposition reaction, a good electrolyte composition with a zinc-free free sulfuric acid concentration of 200 to 400 g/AC is required. preferable.

Regarding the catholyte in the cathode chamber, which is related to the zinc electrodeposition reaction, the zinc concentration is preferably 60 to 90 g/l from the viewpoint of cathode current efficiency and conductivity, and the free sulfuric acid concentration is the electrolyte stock solution (neutral solution). ) Calculating backward from the zinc concentration of 160 g/l, it becomes 100 to 150 g/l.

Furthermore, regarding the electrolyte temperature, it is preferable for both the anolyte and catholyte to be higher in high current density electrolysis due to the relationship between conductivity, but from the viewpoint of heat resistance of the electrolytic cell and piping materials, etc.
A temperature of 0 to 70°C is preferable.

The type of diaphragm used in the present invention may be any of cation exchange membranes, neutral membranes, anion exchange membranes, etc., and may be selected as appropriate. Neutral membranes are advantageous in that they are relatively inexpensive. However, it is determined by comprehensively considering physical properties such as electrical resistance and mechanical strength, function, life, running cost, etc.

Next, regarding an example of an electrolytic cell for implementing the present invention,
The outline will be explained below.

Fig. 1 is an explanatory diagram showing the overall flow mainly of the electrolytic cell according to the present invention, and Figs. 2 to 4 are principle explanatory diagrams showing the side, plane, and front sides of the electrolytic cell according to the present invention, respectively. .

In Figs. 1 to 4, 1 is a rectangular box-shaped electrolytic cell;
The electrolytic cell 1 is partitioned by a partition 115 into a cathode chamber 6 at the center and an anode chamber 4 at the outside, and the anode chamber 4 has an anolyte supply port for supplying the anolyte 8 from the bottom. 24
and an anolyte discharge port 25 for discharging the gas-liquid mixture of the anolyte 8 and generated oxygen 9 from the upper part. 25 is connected to an anolyte tank 21 which has the function of separating the discharged gas-liquid mixture into oxygen 9 and anolyte 8.

The oxygen 9 separated in the anolyte tank 21 is sent to each usage process, and the anolyte 8 is sent to the anolyte head tank 20 via the anolyte circulation pump 22 and strainer 23, and then to the anolyte supply port 24. is supplied to the anode chamber 4 from

On the other hand, the catholyte chamber 6 at the center of the electrolytic cell l, which is partitioned by a distance H5, has a catholyte supply port 26 at its bottom that continuously supplies the catholyte 7, and a catholyte 7 at the upper wall of the chamber 6. A catholyte discharge port 27 is provided for continuously discharging the catholyte, and a disk ffi eyelid electrode is provided in the center of the cathode chamber 6 and rotates in a direction perpendicular to the surface of the catholyte 7 while approximately half of it is immersed in the catholyte 7. 2 is installed.

The center portion of the disc-shaped cathode 2 is fixed by a rotating shaft lO,
The rotating shaft lO is supported by a bearing 29 provided on the electrolytic cell wall 28, and is connected to a speed reduction device 30 via a pulley at one end.

The disk-shaped cathode 2 is made of an aluminum plate, and the outer circumferential portion of the disk and the central liquid-contacted portion attached to the rotating shaft 10 are covered with an insulating sheet (12).
is masked by. Furthermore, a scraper 11 is provided close to both sides of the disc-shaped cathode 2, and the eyelid plate 2
The zinc deposited on both sides is peeled off and recovered.

A contact ring 33 is pivotally attached to the other end of the rotating shaft 10, and the contact ring 33 is connected to the rectifier 1 through an energized brush 32.
On the other hand, the anode 3 provided on the side of the electrolytic cell 1 is connected to the rectifier 1 via the anode terminal 31.
It is electrically connected to the positive side of 9.

The catholyte 7 is transferred from the electrolyte stock solution tank 18 to the catholyte tank! After the liquid is sent to supply pump 14.5 and the liquid composition, temperature, etc. are adjusted. The catholyte is supplied to the catholyte chamber 6 from the catholyte supply port 26 through the strainer 13, and after electrolysis is discharged from the catholyte discharge port 27 and sent to the catholyte tank 15.

5 and 6 are diagrams explaining the principle of another electrolytic cell for carrying out the present invention, in which the cathode 2 is a rotating vertical drum cathode 40, and the catholyte 7 in the cathode chamber 6 partitioned by a diaphragm 5 is While the entire drum 40 is immersed and horizontally rotated, zinc is deposited in the shape of a dendritic structure on the surface of the cathode plate on the surface of the drum, and this is scraped off with a scraper 11. The precipitated zinc is continuously discharged and collected.

In this case, as shown in Example 2, the surface of the cathode 40 is masked with an insulating Teflon tape or the like, and the Teflon tape is perforated to appropriately select the effective area as a cathode.
Dendritic zinc may be made easier to electrodeposit.

Moreover, in the case of the electrolytic cell shown in FIGS. 5 and 6, the cathode chamber can also be made airtight, so that the hydrogen generated can also be recovered.

The present invention is constructed as described above, and the compositions of the anolyte 8 and the catholyte 7 are completely different, and the anolyte 8 is connected to a circuit centered on the anode chamber 4 separated by a distance j15 (see FIG. 1). The Wk electrolyte 7 is circulated in a circuit centered around the cathode chamber 6, and the electrolytic solution is mixed with the electrolytic stock solution, electrolytic test solution, electrolytic tail solution, etc. to completely recover the oxygen 9 generated in the anode chamber 4. The composition is adjusted and electrolyzed in the #1 electrode chamber 6, deposited on a rotating cathode plate having the shape described above, and electrolytically extracted as plate-like or dendritic zinc.

Next, the present invention will be explained by examples.

(d) Examples Example 1 The electrolytic cell shown in Figs. 2 to 4 was used as the main body, and the apparatus for carrying out the present invention shown in Fig. An electrolytic test was conducted for 2 hours under the electrolytic conditions shown below.

Electrolysis conditions: Anode material = 1% Ag-containing Pb plate Cathode material = A vertical plate Pole effective area: 130cm fat 2 Cathode plate rotation speed: 100 rpm・Relative movement speed between catholyte and cathode plate: 0. 4 to 0.8 m/sec Distance between anode and diaphragm: 5 Peng Distance between cathode and diaphragm: 5 mm Type of diaphragm: Neutral 5 (manufactured by Grace, Daramic
250) Electrolyte temperature = 60℃ Amount of catholyte: 1-7i/min Anolyte circulation amount: 20.4 g/min Electrolysis time = 2 hours Amount of glue added (catholyte additive): 60g/ l-Cathode zinc strontium carbonate addition amount (anolyte additive): IKg/
One cathode zinc current density (Dk): 5000 A/m"The electrolyte was prepared by pre-electrolyzing the electrolytic stock solution from the actual operation of electrolytic factory A as the catholyte, and the electrolyte was 5 g/d of zinc, free sulfuric acid: 125 g/m,
A composition solution with manganese = 3g/diluted was used, and as the anolyte, commercially available first grade concentrated sulfuric acid was diluted with water to obtain free sulfuric acid: 300g/
A pure sulfuric acid solution of i was used.

As a result, the surface condition of the cathode zinc electrodeposited in the form of a plate on the cathode plate was good, and the impurity content in the electrodeposited cathode zinc was as follows: lead: 3pp layer, cadmium: 3pp layer, iron: 2pp layer, copper:
lpp layer and tin: 1 pp or less, and were of high quality.

In addition, the electrolysis power consumption rate is 3570 kwh/l, and a lead-based alloy plate is used as an anode, and the power consumption is approximately 10 kWh/l compared to the conventional method.
Even though electrolysis was performed at twice as high current density (5000 A/m2), it was comparable to the conventional method and was satisfactory.

This is thought to be due to the fact that the electrolytic sliding voltage was kept relatively low at 4.14 malt and the cathode current efficiency (95%) was improved.

Furthermore, there is no loss of pure oxygen from the anode chamber;
It was possible to recover approximately 1OO%.

Example 2 An electrolytic cell different from that of Example 1 as shown in Figures 5 and 6 was used, and for the purpose of electrodepositing zinc in a dendritic form on a drum-shaped cathode, no glue was added to the catholyte and no glue was added to the anolyte. without adding strontium carbonate as a lead ion remover.
A test was conducted using the same method and electrolytic conditions as in Example 1.

However, for the cathode, after masking the entire surface of the catholyte immersion area with insulating Teflon tape, holes with a diameter of 41φ are made in the Teflon tape uniformly over the entire cathode immersion area, and the hole occupied area ratio is 22%. Only the perforated portion effectively acted as a cathode, facilitating the electrodeposition of the target dendritic zinc. In addition, the current density is 5000 in terms of anode (D^)
Tested at A/m2.

As a result, the cathode zinc grew in a dendritic shape and was continuously scraped off by a bar-type scraper provided in the cathode chamber, and was continuously discharged and collected from the bottom of the electrolytic cell.

The impurity content in the dendritic deposited zinc is the lead:Bpp layer.
, cadmium: 3 pp layer, iron: 3 P pH, copper: 2 pp layer, and tin: 1 pp layer or less, and dendritic deposited zinc with a low lead content was obtained despite no addition of strontium carbonate.

In addition, the electrolytic power consumption rate is 3770 kwh/l,
Electrolytic sliding voltage: 4.23 maof, cathode current efficiency: 9
At 2%, the results were satisfactory as in Example 1.

Furthermore, we were able to completely recover almost 100% of pure oxygen from the anode chamber, and the small amount of hydrogen generated from the cathode chamber was also airtight! It was possible to recover it because it was a toothed electrode chamber.

(E) Effects of the Invention Since the present invention is constructed as described above, it has the following advantages.

a) Since the anode chamber and cathode chamber of the electrolytic cell are separated by a diaphragm and the upper part of the anode chamber is sealed, pure oxygen can be almost completely recovered relatively easily and without loss.

b) Since the manganese in the electrolytic stock solution can be removed in advance using the recovered oxygen, there is no need to periodically lift up the anode plate for cleaning the manganese dioxide scale or to discharge the scale from the bottom of the electrolytic cell. Maintenance work related to the anode is reduced.

C) Since the oxygen generated in the anode chamber is almost completely recovered, there is no emission of electrolyte mist containing free sulfuric acid into the atmosphere, thus significantly reducing the pollution of the working environment.

d) Since the positive and negative electrode chambers are separated by a diaphragm, dissolved oxygen dissolved in the anolyte reaches the cathode and is reduced.
There are no adverse effects such as re-dissolution of zinc deposited on the cathode, and the cathode current efficiency is significantly improved.

e) Since the positive and negative picture electrode chambers are separated by a diaphragm, even if a lead-based alloy is used as the anode plate, the trace amounts of lead ions eluted into the anolyte due to the solubility product can be minimized from reaching the cathode. Since the amount of strontium carbonate is suppressed, the quality of the deposited zinc is improved, and the amount of strontium carbonate added to deposit lead ions in the anolyte is reduced, resulting in lower costs.

f) It is extremely significant that the oxygen recovered by the method of the present invention can be effectively utilized almost completely within the composite zinc smelting system, and the present invention is an innovative zinc smelting method.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the overall flow mainly of the electrolytic cell according to the present invention, FIG. 2 is a side explanatory diagram of the electrolytic cell according to the present invention, and FIG. 3 is a plan explanatory diagram of the electrolytic cell according to the present invention. , FIG. 4 is a front cross-sectional explanatory diagram of an electrolytic cell according to the present invention, FIG. 5 is a plan explanatory diagram of another electrolytic cell according to the present invention, and FIG. 6 is a front cross-sectional explanatory diagram of another electrolytic cell according to the present invention. FIG. 7 is a perspective view of a conventional L-face open type electrolytic cell. Symbol explanation 1 - Electrolytic cell 2 - Rotating circle m-type cathode 3 - WA electrode - i electrode chamber 5 - Separation 11 6 - Cathode chamber 7 - [1 liquid 8 - Anolyte
9-Generated oxygen 10-Rotating shaft 11-Scraper 12-
Insulating sheet 13 - strainer 14 - catholyte supply pump 15 - catholyte tank 16 - electrolytic tailing liquid 17 - electrolytic stock solution addition pump 18 - electrolytic stock tank 19 - rectifier 20 - anolyte head tank 21 - anolyte tank 22 -
QI polar fluid circulation pump 23-Strainer 24-Anolyte supply port 25-Anolyte discharge port 26-#I polar fluid supply port 27
- Cathode liquid outlet 28 - Electrolytic cell wall (insulator) 29 - Bearing 30 - Reduction drive device 31 - Anode terminal 32 - Current-carrying brush 33 - Contact ring 34 - 9 rice-type electrolytic cell 35 - Conventional cathode plate 36 - Electrolyte 37 - Conventional anode plate 38 - Electrode beam 39 - Insulator 4 - Vertical drum cathode 41 - Electrodeposit outlet 43 - Sealed bearing device 42 - Hydrogen gas outlet Akita Smelting Co., Ltd. Figure 5 Figure 4

Claims (2)

[Claims] (1) Collecting oxygen generated at the anode during the electrolysis process,
A zinc smelting method characterized in that the oxygen is effectively utilized in various steps of zinc smelting. (2) The electrolytic cell is partitioned with a diaphragm to form a cathode chamber and an airtight anode chamber, and the zinc electrolytically deposited on the cathode surface is separated and recovered from the rotationally driven cathode and discharged from the airtight anode chamber. A process for producing oxygen-enriched air for roasting zinc sulfide concentrate, a process for removing manganese oxidation from a zinc electrolyte,
A zinc smelting method characterized in that it is used in at least one of the steps of oxidizing the liquid after re-leaching of zinc leaching residue and pressurizing leaching of zinc sulfide concentrate.