WO2024208267A1 - Process method and device for reducing tin dioxide to metal tin - Google Patents

Abstract

Disclosed in the present invention are a process method and a device for reducing tin dioxide to metal tin. The process method comprises: establishing at least one electrolytic cell, wherein an anode and a cathode are arranged in the electrolytic cell, the anode is connected to a positive electrode of an electrolytic power supply, and the cathode is connected to a negative electrode of the electrolytic power supply; adding tin dioxide and an electrolyte solution into the electrolytic cell to bring the tin dioxide into direct contact with the cathode or metal tin on the cathode; turning on the electrolytic power supply to perform an electrolysis operation, wherein an electrochemical oxidation reaction is performed on the anode so as to dissolve a soluble anode metal or electrically generate chlorine and/or oxygen at an insoluble anode, and the cathode makes the tin dioxide which is in direct contact with the cathode and/or the tin dioxide which is in direct contact with the metal tin on the cathode undergo an electrochemical reduction reaction so as to electrically generate metal tin; and collecting for use the electrically generated metal tin and/or a solid product and/or a solution product of a tin compound obtained by means of the reaction of metal tin and an electrolyte. In the present invention, by utilizing the conductivity of a tin dioxide solid, the tin dioxide solid is converted into metal tin by means of an electrochemical reduction reaction, and/or the obtained metal tin is further converted into a solid product and/or a solution product of a tin compound by using the electrolyte.

Description

A process and device for reducing tin dioxide to metallic tin Technical Field

The invention belongs to the technical field of reduction treatment of metal oxides, and specifically relates to a process method and a device for reducing tin dioxide into metallic tin.

Background Art

Tin dioxide is an inorganic substance, which is divided into tetragonal, hexagonal or orthorhombic crystal powders, insoluble in water, and also difficult to dissolve in acid or alkaline solutions. It exists in nature in the form of reddish-brown cassiterite. In addition, tin-containing waste mud is produced from the industrial production process of modern tin plating technology and tin stripping technology, and its amount is also quite large and needs to be collected for environmental protection treatment. The main component of the hazardous waste tin mud is tin dioxide. The prior art reduces tin dioxide to metallic tin, respectively, in two ways: sodium hydroxide melting method and high-temperature reduction method. Among them, the high-temperature reduction method is to react tin dioxide with reducing agent carbon, carbon monoxide, and hydrogen under high temperature conditions to generate metallic tin and carbon dioxide or metallic tin and water. Another sodium hydroxide melting method is also to melt sodium hydroxide under high temperature conditions and react with tin dioxide to generate sodium stannate and water, and then use other methods to generate metallic tin by reaction with sodium stannate.

Both of the above methods are operated under high temperature conditions, and it is difficult for small-scale production enterprises to popularize their processes in treating tin-containing waste mud. In order to overcome the problems of high-temperature processes and meet the requirements that enterprises that produce tin mud pollution can convert their own hazardous waste tin mud into divalent tin salts or metallic tin and recycle them into production, so that production enterprises can reduce environmental pollution and production costs. It is urgent to study a new process for reducing tin dioxide to metallic tin.

Summary of the invention

Although tin dioxide is an inorganic powder, it has unique conductive properties. The present invention utilizes the conductivity of solid tin dioxide to convert it into metallic tin through an electrochemical reduction reaction, and/or utilizes an electrolyte to further convert the obtained metallic tin into a solid product and/or a solution product of a tin compound.

The first object of the present invention is to provide a process for reducing tin dioxide to metallic tin, and the second object is to use a device for reducing tin dioxide to metallic tin to achieve the first object.

A process for reducing tin dioxide to metallic tin can be achieved through the following operating steps.

Step 1: Establish at least one electrolytic cell, wherein an anode and a cathode are provided in the electrolytic cell, wherein the anode is connected to the positive electrode of an electrolytic power source, and the cathode is connected to the negative electrode of an electrolytic power source, and tin dioxide and an electrolyte solution are put into the electrolytic cell, so that the tin dioxide is in direct contact with the cathode or with the metal tin on the cathode during the electrolysis process;

Step 2: Turn on the electrolysis power supply to perform electrolysis operation, the anode undergoes an electrochemical oxidation reaction to dissolve the soluble anode metal or to electrolyze chlorine and/or oxygen at the insoluble anode, and the cathode undergoes an electrochemical reduction reaction to electrolyze metallic tin by causing the tin dioxide in direct contact with the cathode and/or the tin dioxide in direct contact with the metallic tin on the cathode;

Step 3: Collect and utilize the solid product and/or solution product of the metallic tin obtained by electrolysis and/or the tin compound obtained by the reaction between the metallic tin and the electrolyte.

The electrolyte solution described in step 1 is an aqueous solution containing a soluble electrolyte, and the soluble electrolyte is at least one of an organic and/or inorganic soluble salt, acid, and base. Preferably, the salt is one or more combinations of sodium salts, potassium salts, and ammonium salts, the acid is one or more combinations of hydrochloric acid, sulfuric acid, and nitric acid, and the base is one or more combinations of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, ammonium hydroxide, ammonium carbonate, and ammonium bicarbonate. When the electrolyte solution contains more than one soluble electrolyte, the concentration and ratio of various soluble electrolytes are not limited.

Since the electrolyzed metallic tin is an amphoteric metal, it reacts with alkaline solutions and also forms salts with acids. For example:

The reaction formula of tin and sodium hydroxide is: Sn+2NaOH+2H ₂ O→Na ₂ [Sn(OH) ₄ ]+H ₂ ↑.

At the same time, a chemical reaction occurs: Na ₂ [Sn(OH) ₄ ]→SnO+H ₂ O+2NaOH.

The reaction formula of tin and hydrochloric acid is: Sn+2HCl→SnCl ₂ +H ₂ ↑.

In order to obtain a higher yield of metallic tin, the electrolyte solution is preferably a salt solution, and more preferably a soluble sulfate solution is used.

In the electrolytic cell in step 1, the process of the present invention can select an electrolytic cell without a separator alone, or select an electrolytic cell with a separator to separate the electrolytic cell into an anode tank area and a cathode tank area, or select the above two electrolytic cells at the same time. Among them, the separator of the electrolytic cell is a material that can effectively block electrolytic bubbles and tin dioxide, so as to prevent the oxidizing gas in the anode tank area from mixing and migrating to the cathode tank area to corrode the electrolytic metal tin, thereby improving the yield of the electrolytic metal tin. The separator is preferably a cation exchange membrane, an anion exchange membrane, a bipolar membrane, a reverse osmosis membrane, an ion-free selective filter membrane, a proton membrane and a filter cloth. One or more of them are used in combination. The above-mentioned reverse osmosis membrane is a reverse osmosis membrane. When an electrolytic cell with a separator is selected, tin dioxide needs to be put into the cathode tank area and directly contact with the cathode or the metal tin on the cathode to be energized to achieve the purpose of the process of the present invention.

The advantage of using an electrolytic cell with a separator is that it can separate the gas electrolyzed in the anode tank area from the hydrogen electrolyzed in the cathode tank area, which is convenient for their collection and utilization, reducing the safety problem of explosion caused by the mixture of oxidizing gas and hydrogen, and at the same time, it can reduce the migration of oxidizing substances in the anode tank area to the cathode electrolyte to corrode the metal tin electrolyzed in the cathode. However, the electrolytic cell with a separator has a complex structure, high power consumption in production, and high equipment cost.

In step 2, a variety of reaction conditions using different anode materials and different electrolyte compositions are used to generate Different electrochemical reactions will produce a variety of different reaction results.

When a soluble metal anode is used as the anode material, the electrochemical reaction that mainly occurs on the anode is the conversion of metal into metal ions. For example:

(1) When using zinc metal anode, Zn- ^2e- →Zn ^2- .

(2) When using iron metal anode, Fe-2e ^- →Fe ²⁺ .

When the anode material is an insoluble anode and the anode electrolyte is a solution without chloride ions, at least one of the following electrochemical reactions occurs on the anode to generate oxygen:
4[OH] ^- -4e ^- →2H ₂ O+O ₂ ↑.
2H ₂ O-4e ^- →4H ⁺ +O ₂ ↑.

When an insoluble anode is used as the anode material and the anode electrolyte contains chloride ions, the following electrochemical reactions occur on the anode to generate chlorine gas:
2Cl ^- -2e ^- →Cl ₂ ↑.

Tin dioxide in direct contact with the cathode and/or tin dioxide in direct contact with metallic tin on the cathode is reduced to metallic tin, usually accompanied by the electrolysis of hydrogen. During the electrolysis process, the first tin dioxide in direct contact with the cathode is reduced to metallic tin. Because metallic tin is conductive, the metallic tin on the cathode surface can be regarded as part of the cathode, and the tin dioxide in contact with it is also reduced to metallic tin. At least one of the following electrochemical reactions occurs on the cathode:
SnO ₂ +4e ^- +2H ₂ O→Sn+4[OH] ^- .
SnO ₂ +4e ^- +4H ⁺ →Sn+2H ₂ O.
2H ⁺ +2e ^- →H ₂ ↑.

Preferably, the anode is an insoluble anode.

The inventors have found that increasing the chance of tin dioxide contacting the cathode surface can effectively improve the electrochemical reduction reaction of tin dioxide. Therefore, any one or more of the following preferred solutions can be adopted to make tin dioxide contact with the cathode more fully.

Preferred solution 1: using an inclined electrolytic cell, and placing the cathode at a low position inside the inclined electrolytic cell, and using gravity to make the tin dioxide powder accumulate around the cathode.

Preferred solution 2: The cathode is structurally improved to a cathode conductive carrier, which has a flat or spoon-shaped or grooved cathode structure capable of loading tin dioxide powder. Part or all of the contact surface of the cathode conductive carrier with the loaded tin dioxide is a conductive material electrically connected to the negative electrode of the electrolytic power source. When the cathode conductive carrier has a groove, the higher the groove wall is, the more effectively it can limit the tin dioxide from leaving the cathode conductive carrier.

Preferred solution three: Use filter bags and/or filter plates to surround the cathode to trap at least most of the tin dioxide. The contact rate between the tin dioxide and the cathode is increased by limiting the area near the cathode. Preferably, a filter bag made of filter cloth is used to facilitate cleaning and reuse, thereby reducing the cost of use.

The present invention can be improved as follows: a vertical electrolytic cell is used, that is, the cathode is arranged below at least one anode. The vertical electrolytic cell can be an electrolytic cell without a separator or an electrolytic cell with a separator. When the vertical electrolytic cell is combined with the cathode conductive carrier of the above-mentioned preferred embodiment 2, a better effect of saving electric energy can be achieved. This is because when the cathode conductive carrier is used to load tin dioxide, the electric field lines between the anode and the cathode conductive carrier reaction surface are long, resulting in low current efficiency. The use of a vertical electrolytic cell can shorten the electric field lines between the anode and the cathode conductive carrier reaction surface so that the problem is solved.

Preferably, when a vertical electrolytic cell with a separator is used, the side of the cathode tank area facing the anode is a separator and a slanted cover plate separator fixing frame composed of a movable slanted cover plate separator, the holes of the slanted cover plate separator fixing frame are sealed with a separator, and an outlet for exhausting gas or gas and liquid is also provided in the upper part of the cathode tank area. It can not only prevent the rising hydrogen gas from being electrolyzed from mixing with the oxidizing gas electrolyzed from the anode and make the hydrogen gas easy to collect, but also prevent the conductive tin dioxide particles from adhering to the ion diaphragm to become a secondary electrode and damage it, so as to reduce the maintenance cost of the production equipment. The cathode tank area with a slanted cover plate separator can also be regarded as a cathode conductive carrier, and the movable structural design of the slanted cover plate separator facilitates the addition of tin dioxide to the cathode tank area.

Preferably, when a vertical electrolytic cell without a partition and a cathode conductive carrier are used at the same time, the cathode conductive carrier has a groove and the bottom of the groove is set to a funnel-shaped structure with a liquid outlet pipe, and a filter medium is installed in the liquid outlet pipe. The bottom funnel structure is used to use external force to suck away the hydrogen-containing electrolyte during electrolysis and then discharge it to the outside to avoid mixing with the oxidizing gas electrolyzed by the anode at the top of the electrolytic cell. The filter medium in the liquid outlet pipe at the bottom of the funnel is used to prevent the tin dioxide particles from being sucked away. The inner wall of the funnel at the bottom of the groove is preferably provided with a pit for dredging the hydrogen-containing electrolyte that is sucked.

The present invention can also be improved as follows: tin dioxide and electrolyte are mixed to form slurry, which is then added to the electrolytic cell, so that the tin dioxide is more evenly distributed in the electrolyte, so that the slurry can serve as an ion exchange channel and facilitate more tin dioxide powder to be in close contact with the cathode for direct electricity.

The present invention can also be improved as follows: the electrolyte is used to react in the electrolysis process to generate soluble tetravalent tin salts and/or divalent tin compounds to directly or through conventional chemical reactions to produce at least one of divalent tin salts, stannous hydroxide and metallic tin as production raw materials for recycling. The tetravalent tin salt solution can be further reduced by a reduction method to produce a recycled production raw material that meets the production process requirements.

The present invention can also be improved as follows: the collected contaminated tin mud is first pre-treated by high-temperature heating to decompose organic matter in the tin mud by high temperature, and a relatively pure tin dioxide powder is obtained after the treatment.

The second object of the present invention is to achieve the first object of the invention by using a device for reducing tin dioxide to metallic tin according to the above operation.

A device for reducing tin dioxide to metallic tin comprises at least one electrolytic cell, in which an anode and a cathode are arranged, the anode is connected to the positive electrode of an electrolytic power source, the cathode is connected to the negative electrode of the electrolytic power source, and during the electrolysis process, the cathode or the metallic tin on the cathode is in direct contact with the tin dioxide.

As a preferred solution, an inclined electrolytic cell is used to electrochemically reduce tin dioxide. The cathode is set at a low position inside the inclined electrolytic cell. Gravity is used to make the tin dioxide powder gather around the cathode and directly contact the cathode or the metal tin on the cathode to conduct electrochemical reaction.

As a more preferred embodiment, the present invention structurally improves the cathode to a cathode conductive carrier to load tin dioxide, so that tin dioxide and the cathode conductive carrier are in direct large-area contact to increase the reaction rate. The cathode conductive carrier is a conductive material or a combination of a conductive material and an electrical insulator material, forming a spoon-shaped or grooved cathode structure capable of loading tin dioxide powder. The cathode conductive carrier is electrically connected to the negative electrode of the electrolytic power source at one or more negative electrode connection points; the more negative electrode connection points the more conducive to the uniformity of current distribution at the contact portion with the loaded tin dioxide.

When the cathode conductive carrier is a combination of a conductive material and an electrical insulator material, the inner bottom and/or inner side of the cathode conductive carrier is a conductive material electrically connected to the negative electrode of the electrolytic power source, and/or its groove is provided with a conductive material electrically connected to the negative electrode of the electrolytic power source, and the remaining parts are electrical insulator materials and/or conductive materials coated with electrical insulator materials, so that the tin dioxide powder loaded on it can directly contact the conductive material in its inner bottom and/or inner side and/or groove to produce an electrochemical reduction reaction. The use of electrical insulator materials or coated electrical insulator materials in the parts of the cathode conductive carrier that cannot contact the loaded tin dioxide can effectively improve the electrical efficiency of the reaction, reduce hydrogen generation, and save electricity.

As a preferred embodiment, the present invention adopts a vertical electrolytic cell, and the cathode is arranged below at least one anode. The vertical electrolytic cell can be an electrolytic cell without a separator or an electrolytic cell with a separator. When the vertical electrolytic cell is an electrolytic cell with a separator, the separator is preferably a filter cloth, which is more cost-effective than an ion diaphragm. In the vertical electrolytic cell with a separator, a separator is provided on the side of the cathode cell area facing the anode, and separators and/or plates are used on the other sides.

More preferably, when a vertical electrolytic cell with a separator is used, the separator on the side of the cathode tank area facing the anode and the inclined cover plate separator fixing frame form a movable inclined cover plate separator arranged on the top of the cathode tank area, and the holes of the fixing frame inclined cover plate separator fixing frame are sealed with separators, and an outlet for exhausting gas or gas and liquid is also provided in the upper part of the cathode tank area. The inclined cover plate separator fixing frame is preferably made of polymer resin. The inclined cover plate is temporarily fixed to the top of the cathode tank area by a fixing device, or connected to the groove by a movable part. The movable part is preferably a hinge.

More preferably, when a vertical electrolytic cell without a partition and a cathode conductive carrier are used at the same time, the cathode conductive carrier has a groove and the bottom of the groove is configured as a funnel-shaped structure with a liquid outlet pipe, and a filter medium is installed in the liquid outlet pipe. The filter medium is selected from a filter screen and/or a filter cloth, preferably a filter screen. The inner wall of the funnel at the bottom of the groove is preferably provided with a pit.

The insoluble anode material in the electrolytic cell is gold, platinum or its alloy or titanium-based coating insoluble anode or conductive graphite. Preferably, titanium-based coating insoluble electrode or platinum metal electrode is used.

The conductive material of the cathode or cathode conductive carrier in the electrolytic cell can be selected from gold, platinum, tin, titanium, alloys containing at least one of the above metals, stainless steel, and conductive graphite. When the electrolyte contains chloride ions, the cathode material is preferably titanium; when the electrolyte contains sulfate ions, stainless steel is preferably used as the cathode material. More preferably, tin is used as the cathode.

The present invention can be improved as follows: an electrode filter bag is added, and the electrode filter bag is used to wrap the tin dioxide and the cathode together to make the tin dioxide in close contact with the cathode, while reducing the force of the tin dioxide powder flowing with the electrolyte or the floating of hydrogen bubbles during electrolysis to separate from the cathode.

The present invention can also be improved as follows: additional sensors and automatic program controllers are provided. The sensors are respectively acidity meter, pH meter, hydrometer, oxidation-reduction potentiometer (ORP meter), photoelectric colorimeter, liquid level meter, thermometer, weight meter, chlorine gas detector, and hydrogen gas detector. The equipment is automatically operated according to the designed program.

The present invention can also be improved as follows: a temporary storage tank is added, which is connected to the electrolytic tank through a pipeline and is used for storing chemicals and/or used as a chemical reaction tank.

The present invention can also be improved as follows: an overflow buffer tank is added, which is connected to at least one electrolytic tank and/or tank body in the device through a pipeline, so that the solution can flow smoothly between the tanks.

The present invention can also be improved as follows: a gas-liquid separation tank is added, which is connected to at least one electrolytic tank and/or tank body in the device through a pipeline, so that bubbles can escape from the bubble-containing solution during gentle flow.

The present invention can also be improved as follows: an exhaust gas processor is added, which is connected to at least one electrolytic cell and/or cell body in the device through a gas pipeline to collect or recycle the escaped gas. The gas guider is a spray tower or a vacuum ejector.

The present invention can also be improved as follows: a solid-liquid separator is added, which separates the solid-liquid mixture into solid and liquid through a pipeline and at least one electrolytic cell and/or cell body in the device. The solid-liquid separator can be divided into filter press, centrifuge and filter according to the structure.

The present invention can also be improved as follows: a stirrer is added to at least one electrolytic cell and/or cell body in the device to make the concentration and temperature of the solution uniform. The stirrer includes an impeller stirrer and a liquid flow pump pipe stirrer.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention solves the process problem of only using high temperature operation to reduce tin in the prior art, and can use a room temperature reduction method to reduce tin oxide to obtain metallic tin. The process conditions are simple and the application market is broad. The obtained metallic tin can be directly used according to demand or further chemically reacted to obtain tin salt for further use.

2. The process of the present invention is safe, easy to operate, requires little equipment and occupies little capital.

3. The reduction treatment process of the present invention not only produces metallic tin, stannous hydroxide and divalent tin salt products, but also does not add new pollution sources.

4. The present invention can help enterprises that produce polluted tin mud to carry out environmentally friendly treatment to turn waste into treasure, thereby improving the economic benefits of the enterprise.

5. Compared with the prior art, the present invention consumes less energy and is pollution-free, meeting the new process requirements of energy conservation and emission reduction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a tilted electrolytic cell of the present invention;

FIG2 is a top view of an A-type cathode conductive carrier of the present invention;

FIG3 is a cross-sectional view of the cathode conductive carrier of the A-type structure in FIG2 from MM;

FIG4 is a top view of a cathode conductive carrier of a B-type structure according to the present invention;

FIG5 is a cross-sectional view of a cathode conductive carrier of type B structure in FIG4;

FIG6 is a cross-sectional view of a C-shaped cathode conductive carrier of the present invention;

FIG7 is a cross-sectional view of a D-shaped cathode conductive carrier of the present invention;

FIG8 is a vertical electrolytic cell using the C-shaped cathode conductive carrier in FIG6;

FIG9 is a vertical electrolytic cell using the D-type cathode conductive carrier in FIG7;

FIG10 is a device for reducing tin dioxide to metallic tin according to Example 1 of the present invention;

FIG11 is a device for reducing tin dioxide to metallic tin according to Example 2 of the present invention;

FIG12 is a device for reducing tin dioxide to metallic tin according to Example 3 of the present invention;

FIG13 is a device for reducing tin dioxide to metallic tin according to Example 4 of the present invention;

FIG14 is a device for reducing tin dioxide to metallic tin according to Example 5 of the present invention;

FIG15 is a device for reducing tin dioxide to metallic tin according to Example 6 of the present invention;

FIG16 is a device for reducing tin dioxide to metallic tin according to Example 7 of the present invention;

FIG. 17 is a device for reducing tin dioxide to metallic tin according to Example 8 of the present invention.

Description of reference numerals:
1-electrolytic cell, 2-separator, 3-anode, 4-cathode, 5-cathode conductive carrier, 6-cathode insulating layer, 7-slope
Cover plate partition, 8-electrolytic power supply, 9-temporary storage tank, 10-sensor, 11-automatic program controller, 12-overflow buffer tank, 13-impeller agitator, 14-liquid flow pump tube agitator, 15-spray tower, 16-vacuum ejector, 17-acidic solution, 18-acidic saline solution, 20-alkaline saline solution, 21-neutral saline solution, 22-zinc metal, 24-metallic tin, 25-stannous hydroxide, 26-tetravalent tin salt solution, 27-divalent tin salt solution, 29-tin dioxide, 30 -contaminated tin mud, 32-hydrochloric acid, 34-sodium hydroxide, 39-hydrogen high-altitude discharge pipe, 40-exhaust processor, 41-solid-liquid separator, 42-salt-containing waste liquid, 43-stannous oxide, 44-valve, 45-pump, 47-high-temperature heating furnace, 49-filter bag, 50-filter screen, 51-hinge, 52-slanted cover partition fixing frame, 53-funnel with pits, 54-bubble baffle, 55-electrolysis power supply negative electrode connecting line, 56-liquid inlet pipe, 57-liquid outlet pipe, 58-gas-liquid separation tank.

DETAILED DESCRIPTION

In order to make the purpose, technical scheme and advantages of the present invention more obvious, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described in the present invention, all other embodiments obtained by those skilled in the art without paying creative work should fall within the protection scope of the present invention.

In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

It should be understood that the present invention can be implemented in different forms and should not be interpreted as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

In order to fully understand the present invention, a detailed structure will be proposed in the following description to illustrate the technical solution proposed by the present invention. The optional embodiments of the present invention are described in detail as follows, but in addition to these detailed descriptions, the present invention may also have other implementations.

The electrolytic cell, electrolytic anode, electrolytic cathode, cathode conductive carrier, temporary storage tank, overflow buffer tank, agitator, spray tower, vacuum ejector, and tail gas processor used in the embodiments of the present invention are all products produced by Foshan Yegao Environmental Protection Equipment Manufacturing Co., Ltd., Guangdong Province, China. The electrolytic power supply, sensor, automatic program controller, solid-liquid separator, electrolytic cell separator, valve, pump, and chemical raw materials are all commercially available products. In addition to the above-mentioned products, those skilled in the art can also select other products with similar performance to the above-mentioned products listed in the present invention according to conventional selection, and all of them can achieve the purpose of the present invention.

Example 1

As shown in FIG10 , a device for reducing tin dioxide to metallic tin according to this embodiment is shown, which mainly comprises an electrolytic cell 1 .

The electrolytic cell 1 is an inclined electrolytic cell without a partition as shown in Figure 1, and the electrolytic anode 3 and the cathode 4 are both placed in the electrolytic cell, wherein the electrolytic anode 3 is connected to the positive electrode of the electrolytic power supply 8, and the electrolytic cathode 4 is connected to the negative electrode of the electrolytic power supply 8, wherein the anode material is an insoluble anode with a gold-plated surface, and the cathode material is conductive graphite and the cathode 4 is arranged at a low position inside the inclined electrolytic cell.

The electrolyte solution 21 in the electrolytic cell 1 is a slurry of a mixture of a sodium sulfate solution and tin dioxide powder.

The process of reducing tin dioxide to metallic tin in this embodiment has the following operating steps:

1. The electrolyte slurry is poured into an inclined electrolytic cell so that both the anode 3 and the cathode 4 are immersed in the electrolyte slurry, wherein the electrolytic cathode 4 is placed at the lowest point in the inclined electrolytic cell and is in close contact with the tin dioxide 29 in the slurry.

2. Turn on the electrolysis power supply 8 to perform the electrolysis operation. The anode 3 undergoes an electrochemical reaction of electrolyzing oxygen, and the cathode 4 mainly undergoes an electrochemical reaction of reducing the tin dioxide 29 to metallic tin, accompanied by the electrolysis of hydrogen.

3. Collect the metallic tin electrolyzed on the cathode 4.

The above is a process according to the present invention to obtain metallic tin by reducing tin dioxide at normal temperature and pressure.

Example 2

As shown in FIG. 11 , a device for reducing tin dioxide to metallic tin in this embodiment is shown, which mainly comprises an electrolytic cell 1 and a filter bag 49 .

The electrolytic cell 1 is an electrolytic cell without a separator, wherein the electrolytic anode 3 and the cathode 4 are both placed in the electrolytic cell 1, wherein the anode 3 is connected to the positive electrode of the electrolytic power source 8, and the cathode 4 is connected to the negative electrode of the electrolytic power source 8, wherein the anode material is a soluble anode of zinc metal 22, and the cathode material is conductive graphite and is wrapped together with tin dioxide 29 by an electrode filter bag 49. The filter bag 49 can surround the cathode with a filter plate having the same function, and at least most of the tin dioxide is confined to the range near the cathode to increase the contact rate between SnO ₂ and the cathode.

The electrolyte in the electrolytic cell 1 is an acidic salt solution 18 of sulfuric acid, hydrochloric acid, nitric acid, formic acid, citric acid, ammonium chloride, sodium sulfate, potassium chloride, and sodium citrate.

The process of reducing tin dioxide to metallic tin in this embodiment has the following operating steps:

1. Pour an acidic salt electrolyte into an electrolytic cell 1, so that the anode 3 and the filter bag 49 wrapped with the cathode 4 and the tin dioxide 29 are immersed in the electrolyte.

2. Turn on the electrolysis power supply 8 to perform electrolysis. The anode 3 undergoes an electrochemical reaction to dissolve the zinc metal 22 and generate zinc salt in the electrolyte. The cathode 4 undergoes an electrochemical reduction reaction to reduce tin dioxide to metallic tin 24. Hydrogen is electrolyzed during the process, and the process is accompanied by a chemical reaction between the acid and the metallic tin.

3. Collect the metal tin 24 electrolyzed on the cathode 4.

The above is a process according to the present invention in which tin dioxide is subjected to a reduction reaction at normal temperature and pressure to obtain metallic tin.

Example 3

As shown in FIG12 , a device for reducing tin dioxide to metallic tin in this embodiment is shown. The device mainly comprises an electrolytic cell 1 and a cathode conductive carrier 5. The cathode conductive carrier 5 serves as the cathode 4 of the electrolytic cell 1 and is a spoon-shaped improved cathode structure capable of loading _SnO2 powder.

The electrolytic cell 1 is an electrolytic cell without a separator, and the electrolytic anode 3 and the cathode conductive carrier 5 are both placed in the electrolytic cell 1, wherein the anode 3 is connected to the positive electrode of the electrolytic power supply 8, and the cathode conductive carrier 5 is connected to the negative electrode of the electrolytic power supply 8, and the cathode conductive carrier 5 is electrically connected to the negative electrode of the electrolytic power supply 8 at one negative electrode connection point, wherein the anode 3 material is a platinum metal insoluble anode, the cathode material is platinum metal and the A-type structure cathode shown in Figures 2 and 3 is selected, and the cathode conductive carrier 5 is a conductive material electrically connected to the negative electrode of the electrolytic power supply.

The electrolyte in the electrolytic cell 1 is a neutral salt solution 21 of sodium sulfate. The tin dioxide 29 is placed in the groove of the cathode conductive carrier 5 and immersed in the electrolyte.

The process of reducing tin dioxide to metallic tin in this embodiment has the following operating steps:

1. Put a neutral salt-containing electrolyte into the electrolytic cell 1, so that the anode 3 and the cathode conductive carrier 5 are immersed in the electrolyte.

2. Turn on the electrolysis power supply 8 to perform electrolysis operation. An electrochemical reaction occurs at the anode 3 to electrolyze oxygen. An electrochemical reaction mainly occurs on the cathode 4, i.e., the cathode conductive carrier 5, to reduce tin dioxide to metallic tin 24 and electrolyze hydrogen.

3. Collect the metal tin 24 electrolyzed on the cathode 4.

The above is a process according to the present invention in which tin dioxide is subjected to a reduction reaction at normal temperature and pressure to obtain metallic tin.

Example 4

As shown in FIG13 , a device for reducing tin dioxide to metallic tin in this embodiment mainly comprises an electrolytic cell 1, a cathode conductive carrier 5 as a cathode 4 of the electrolytic cell 1, and a cathode conductive carrier 5 as a cathode structure capable of loading SnO ₂ powder.

The electrolytic cell 1 is an electrolytic cell without a separator, wherein the electrolytic anode 3 and the cathode 4 are both placed in the electrolytic cell 1, wherein the anode 3 is connected to the positive electrode of the electrolytic power source 8, and the cathode 4 is connected to the negative electrode of the electrolytic power source 8, wherein the anode material is an insoluble anode with a gold-plated surface, and the cathode material is stainless steel, and a B-type cathode structure as shown in FIGS. 4 and 5 is adopted, and the inner bottom and/or inner side of the cathode conductive carrier 5 is a conductive material electrically connected to the negative electrode of the electrolytic power source, and the cathode conductive carrier 5 is electrically connected to the negative electrode of the electrolytic power source 8 at two or more negative electrode connection points; and The more connection points the negative pole of the power source has, the more conducive it is to the uniformity of current distribution at the contact point with the loaded tin dioxide. The higher the groove wall of the cathode conductive carrier 5 is, the more effectively it can limit the tin dioxide from leaving the cathode conductive carrier.

The electrolyte of the electrolytic cell 1 is an alkaline salt solution 20 of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, ammonium hydroxide, ammonium bicarbonate, and sodium sulfate. Tin dioxide 29 is put into the groove of the B-type structure cathode conductive carrier 5, and the cathode conductive carrier 5 is immersed in the alkaline electrolyte.

The process of reducing tin dioxide to metallic tin in this embodiment has the following operating steps:

1. Pour the alkaline salt electrolyte 20 into the electrolytic cell 1, so that the anode 3 and the cathode conductive carrier 5 are immersed in the electrolyte.

2. Turn on the electrolysis power supply 8 to perform the electrolysis operation. The anode 3 undergoes an electrochemical reaction to electrolyze oxygen. The cathode 4, i.e., the cathode conductive carrier 5, undergoes a major electrochemical reaction to reduce the tin dioxide 29 to metallic tin 24 and electrolyze hydrogen.

3. Collect the metal tin 24 electrolyzed from the cathode conductive carrier 5 and the stannous oxide 43 generated during the reaction.

The above is a process of reducing tin dioxide at room temperature and pressure to obtain metallic tin according to the process of the present invention. In the process, metallic tin 24 reacts with an alkaline substance such as sodium hydroxide to produce stannous oxide 43. Due to the use of a strong alkaline electrolyte, the yield of metallic tin is reduced.

Example 5

As shown in FIG. 14 , a device for reducing tin dioxide to metallic tin in this embodiment mainly comprises an electrolytic cell 1 , a cathode conductive carrier 5 , an exhaust gas treatment 40 , and a gas-liquid separation tank 58 .

The electrolytic cell 1 is a vertical electrolytic cell with a separator as shown in Figure 8, wherein the cathode conductive carrier 5 adopts the C-type structure shown in Figure 6 to improve the cathode, the cathode conductive carrier 5 is a cathode structure that can load _SnO2 powder, the cathode conductive carrier 5 constitutes a cathode slot area, the cathode conductive carrier 5 is a conductive material, and a conductive material electrically connected to the negative pole of the electrolytic power supply is arranged in the groove of the cathode conductive carrier 5, that is, a conductive cathode 4 is arranged to increase the contact area between the _SnO2 powder and the cathode, and at the same time, a movable inclined cover plate separator 7 is arranged on the top of the groove, and the separator on the side of the cathode slot area facing the anode and the inclined cover plate separator fixing frame constitute the inclined cover plate separator 7. The inclined cover plate partition fixing frame 52 of the inclined cover plate partition 7 is rotatably mounted on the cathode tank area through a hinge 51, and the partition thereon is a filter cloth to separate and prevent the mixing of electrolytic chlorine and hydrogen. As shown in FIG8 , the cathode tank area can be filled with electrolyte through a pump 45 and a liquid inlet pipe 56, and then the electrolyte in the cathode tank area flows through a liquid outlet pipe 57 to the separation area formed by the bubble baffle 54 and the electrolytic cell 1, and hydrogen is electrolytically precipitated in the separation area to prevent the precipitated hydrogen from mixing with chlorine and/or oxygen. The electrolytic anode 3 is placed in a vertical anode tank area; the anode 3 is connected to the positive pole of the electrolytic power supply 8, and the cathode conductive carrier 5 and the cathode 4 are connected to the negative pole of the electrolytic power supply 8 through the negative pole connecting line 55 of the electrolytic power supply, and the cathode 4 is arranged below the anode 3. Anode The material is a titanium-based coated insoluble anode, and the cathode conductive material is titanium.

As a replaceable improved cathode structure of the present embodiment, a cathode structure with grooves that can be composed of a conductive material and an electrical insulating material and that can be loaded with _SnO2 powder, as shown in FIG8 , the cathode conductive carrier 5 is also a C-shaped structure with grooves, but the cathode conductive carrier is entirely or partially wrapped with a cathode insulating layer 6, and a conductive material electrically connected to the negative pole of the electrolytic power source is provided at the bottom of the groove of the cathode conductive carrier 5, and the conductive material serves as the cathode 4 that is in direct contact with the _SnO2 powder.

The electrolyte of the electrolytic cell 1 is an acidic solution 17, and hydrochloric acid is used in this embodiment.

The tail gas processor 40 with a spray tower 15 on the top uses a solution of sodium hydroxide 34 to absorb chlorine gas to produce a sodium hypochlorite solution.

Tin dioxide 29 is put into the groove of the cathode conductive carrier 5.

The gas-liquid separation tank 58 is connected to the cathode tank area and is used to separate hydrogen bubbles in the cathode electrolyte through pump circulation, so that the hydrogen bubbles escape in a gentle flow.

The process of reducing tin dioxide to metallic tin in Example 5 has the following operating steps:

1. The electrolyte is put into the vertical electrolytic cell 1 and the gas-liquid separation cell 58, the tin dioxide 29 is put into the groove of the C-shaped cathode, and the anode 3 and the cathode conductive carrier 5 are immersed in the hydrochloric acid electrolyte.

2. Start pumps 45-1 and 45-2 and turn on electrolysis power supply 8 to perform electrolysis operation. Electrochemical reaction occurs on anode 3 to electrolyze chlorine gas, and electrochemical reaction mainly occurs on cathode conductive carrier 5 to reduce tin dioxide 29 to metallic tin and electrolyze hydrogen gas.

3. The electroprecipitated metallic tin reacts with hydrochloric acid to generate stannous chloride to form a divalent tin salt solution 27 which is collected as a product.

4. During the process, the sodium hypochlorite solution in the exhaust gas treatment device is collected for other uses.

The above is a process according to the present invention in which tin dioxide is subjected to a reduction reaction at room temperature and pressure to obtain metallic tin, during which tin reacts with hydrochloric acid to obtain a stannous chloride solution product. In addition, the electrolytically precipitated chlorine is treated for environmental protection to obtain a sodium hypochlorite solution for other uses.

Example 6

As shown in FIG15 , a device for reducing tin dioxide to metallic tin in this embodiment is shown, which mainly comprises an electrolytic cell 1, a high-temperature heating furnace 47, a cathode conductive carrier 5 of a D-shaped structure as shown in FIG7 , a gas-liquid separation tank 58, and a hydrogen high-altitude discharge pipe 39.

The electrolytic cell 1 is a vertical electrolytic cell without partitions as shown in FIG9 . The electrolytic anode 3 is placed on the upper part of the electrolytic cell 3 , and the electrolytic cathode 4 is installed in a cathode conductive carrier 5 of a D-shaped structure. The anode 3 is connected to the positive pole of the electrolytic power source 8 , The cathode conductive carrier 5 is connected to the negative electrode of the electrolytic power source 8, the anode material is conductive graphite, and the cathode material in the D-type structure cathode conductive carrier 5 is titanium. In this embodiment, the D-type structure cathode conductive carrier 5 has a groove and the bottom of the groove is set to a funnel-shaped structure with a liquid outlet pipe 57. A filter medium is installed in the liquid outlet pipe, and the hydrogen-containing electrolyte can be sucked away by an external force such as a pump to discharge the electrolyzed hydrogen to avoid mixing with the oxidizing gas electrolyzed from the anode at the top of the electrolytic cell. The inner wall of the funnel-shaped structure at the bottom of the groove of the D-type structure cathode conductive carrier 5 is provided with a pit for guiding the sucked hydrogen-containing electrolyte, and a filter screen 50 is installed in the liquid outlet pipe 57 at the bottom of the funnel as a filter medium to prevent the tin dioxide particles from being sucked away. The filter screen 50 can be replaced with other filter structures such as filter cloth.

The electrolyte in the electrolytic cell 1 is a sodium sulfate solution.

The high temperature heating furnace 47 is used to perform high temperature treatment on the recovered contaminated tin mud 30 to remove organic impurities, so that the organic matter is decomposed at high temperature to obtain clean tin dioxide material.

The decontaminated tin dioxide 29 is placed into the D-shaped cathode conductive carrier 5 .

In this embodiment, the inner bottom and/or inner side of the cathode conductive carrier 5 is a conductive material electrically connected to the negative electrode of the electrolytic power source. The cathode conductive carrier 5 can also adopt a structure combining a conductive material and an electrical insulator material. A conductive material electrically connected to the negative electrode of the electrolytic power source is provided in the groove, and the remaining parts are electrical insulator materials and/or conductive materials coated with electrical insulator materials, so that the _SnO2 powder loaded thereon can directly contact the conductive material in the inner bottom and/or inner side and/or the groove to produce an electrochemical reduction reaction.

The process of reducing tin dioxide to metallic tin in Example 6 has the following operating steps:

1. Pour the electrolyte into a vertical non-separator electrolytic cell, so that the anode 3 and the cathode conductive carrier 5 are immersed in the electrolyte.

2. Start pumps 45-1 and 45-2 to circulate the electrolyte, turn on the electrolysis power supply 8 to perform electrolysis, an electrochemical reaction occurs on the anode 3 to electrolyze oxygen and escape out of the electrolytic cell 1, and an electrochemical reduction reaction mainly occurs on the cathode 4 to reduce the tin dioxide 29 to metallic tin and electrolyze hydrogen.

3. Most of the hydrogen electrolyzed during the process is sucked from the bottom of the electrolytic cell 1 by the flowing electrolyte and brought to the gas-liquid separation tank 58 for separation and discharged from the hydrogen high-altitude discharge pipe 39.

4. Collect the metal tin electrolytically deposited in the groove of the cathode conductive carrier 5.

The above is a process according to the present invention in which tin dioxide is subjected to a reduction reaction at normal temperature and pressure to obtain metallic tin.

Example 7

As shown in FIG16 , a device for reducing tin dioxide to metallic tin is shown in this embodiment. The device mainly comprises an electrolytic cell 1, a solid-liquid separator 41, four temporary storage tanks 9, and three sensors 10. The cathode conductive carrier 5 of the electrolytic cell 1 adopts the B-type structure shown in FIGS. 3 and 4 .

The electrolytic cell 1 is an electrolytic cell with a separator, and the separator is a bipolar membrane. The electrolytic anode 3 is placed in the anode tank area, and the tin dioxide 29 is put into the cathode conductive carrier 5 of the B-type structure, and the cathode conductive carrier 5 is placed in the cathode tank area. The anode 3 is connected to the positive pole of the electrolytic power supply 8, and the cathode conductive carrier 5 is connected to the negative pole of the electrolytic power supply 8. The anode material is a titanium-based coating insoluble anode, and the cathode material is stainless steel.

The electrolyte in the anode tank area is an alkaline salt solution 20 containing a mixture of ammonium carbonate and sodium hydroxide. The starting solution of the electrolyte in the cathode tank area is hydrochloric acid 32. The hydrochloric acid 32 is fed from the temporary storage tank 9-4 to the cathode tank area via the pump 45-3. The sensor 10-1 in the cathode tank area is an acidity meter to control the pump 45-3 to add hydrochloric acid 32. The sensor 10-2 is a specific gravity meter, which detects the concentration of stannous chloride in the cathode electrolyte to control the opening and closing of the pump 45-1. The pump 45-1 extracts the cathode electrolyte to the temporary storage tank 9-1. The sensor 10-3 in the temporary storage tank 9-1 is a pH meter, which controls the addition of sodium hydroxide 34 to react stannous chloride with sodium hydroxide to produce stannous hydroxide. An impeller stirrer 13 is provided in the temporary storage tank 9-1.

The solid-liquid mixture of stannous hydroxide in the temporary storage tank 9-1 can be pumped by pump 45-2 to the solid-liquid separator 41. The solid-liquid separator 41 is a filter press, which is specially used for solid-liquid separation in the solid-liquid mixture of stannous hydroxide. The obtained stannous hydroxide 25 is placed in the temporary storage tank 9-2, and the obtained salt-containing waste liquid 42 is discharged to the temporary storage tank 9-3.

The process of reducing tin dioxide to metallic tin in Example 7 has the following operating steps:

1. Two electrolytes are respectively put into the anode tank area and the cathode tank area, and tin dioxide is put into the cathode conductive carrier 5 of the B-type structure. The anode 3 and the cathode conductive carrier 5 are immersed in their respective electrolytes.

2. Turn on the electrolysis power supply 8 to perform electrolysis operation. The anode 3 undergoes an electrochemical reaction to electrolyze oxygen and produce carbon dioxide gas. The cathode 4 undergoes a main electrochemical reaction to reduce the tin dioxide 29 to metallic tin 24 and electrolyze hydrogen.

3. During the process, the sensor 10-1, i.e., the acidity meter, controls the pump 45-3 to add hydrochloric acid so that the hydrochloric acid reacts with the electrolyzed metal tin 24 to generate a stannous chloride solution and the concentration continues to increase. When the sensor 10-2, i.e., the hydrometer, reaches the set value, the electrolysis power supply 8 is turned off and the pump 45-1 is started to pump the cathode electrolyte into the temporary storage tank 9-1.

4. According to the sensor 10-3, i.e., the pH meter, sodium hydroxide 34 is added to the temporary storage tank 9-1 for neutralization reaction, so that stannous hydroxide precipitate is precipitated from the reaction liquid.

5. The solid-liquid mixture in the temporary storage tank 9-1 is subjected to solid-liquid separation to obtain stannous hydroxide 25.

6. Collect the stannous hydroxide 25 product obtained by the reaction in the temporary storage tank 9-2.

The above is a process according to the present invention that reduces tin dioxide at room temperature and pressure to obtain metallic tin, and obtains stannous hydroxide product through chemical reaction for recycling.

Example 8

As shown in FIG17 , a device for reducing tin dioxide to metallic tin is shown in this embodiment. It mainly includes two electrodes. The electrolytic cell 1 is respectively denoted as the electrolytic cell 1-1 and the electrolytic cell 1-2, an exhaust gas processor 40, two overflow buffer tanks 12 are respectively denoted as the overflow buffer tank 12-1 and the overflow buffer tank 12-2, three temporary storage tanks 9 are respectively denoted as the temporary storage tank 9-1, the temporary storage tank 9-2 and the temporary storage tank 9-3, two hydrogen high altitude discharge pipes 39 are respectively denoted as the hydrogen high altitude discharge pipe 39-1 and the hydrogen high altitude discharge pipe 39-2, two liquid flow pump tube agitators 14 are respectively denoted as the liquid flow pump tube agitator 14-1 and the liquid flow pump tube agitator 14-2, four sensors 10 are respectively denoted as the sensor 10-1, the sensor 10-2, the sensor 10-3 and the sensor 10-4, and an automatic program controller 11, and pumps 45 and valves 44 are provided to control the flow transfer of liquid and gas.

Both the electrolytic cell 1 - 1 and the electrolytic cell 1 - 2 are electrolytic cells with separators, wherein the separator 2 - 1 of the electrolytic cell 1 - 1 is an anion exchange membrane, and the separator 2 - 2 of the electrolytic cell 1 - 2 is a cation exchange membrane. Two electrolytic anodes 3 are placed in their respective anode slot areas, the cathode conductive carrier 5-1 in the electrolytic cell 1-1 is of A-type structure, and the cathode conductive carrier 5-2 in the electrolytic cell 1-2 is of B-type structure, and are placed in their respective cathode slot areas, respectively. Tin dioxide 29 is put into the grooves of the cathode conductive carrier 5-1 and the cathode conductive carrier 5-2, respectively. The cathode slot area of the electrolytic cell 1-1 is connected to the hydrogen high-altitude discharge pipe 39-1, and the cathode slot area of the electrolytic cell 1-2 is connected to the hydrogen high-altitude discharge pipe 39-2; the anode 3-1 of the electrolytic cell 1-1 and the anode 3-2 of the electrolytic cell 1-2 are respectively connected to the positive electrodes of the corresponding electrolytic power sources 8-1 and 8-2, the cathode conductive carrier 5-1 is connected to the negative electrode of the corresponding electrolytic power source 8-1 as the cathode 4-1, and the cathode conductive carrier 5-2 is connected to the negative electrode of the corresponding electrolytic power source 8-2 as the cathode 4-2. The material of the anode 3-1 is conductive graphite, the material of the anode 3-2 is a titanium-based coated insoluble anode, and the cathode conductive materials of the cathode conductive carrier 5-1 and the cathode conductive carrier 5-2 are both titanium.

The electrolyte of the two electrolytic cells is hydrochloric acid 32, and the electrolytic cell 1-1 is provided with a liquid flow pump tube agitator 14-1, and the electrolytic cell 1-2 is provided with a liquid flow pump tube agitator 14-2.

The tail gas processor 40 is connected to a pump 45-1 and a vacuum ejector 16, and is used to absorb the chlorine gas overflowing from the electrolytic cell and react with a mixed solution of hydrochloric acid and ferrous chloride in an acidic saline solution 18 to produce a ferric chloride solution.

Among them, sensor 10-1 is a hydrometer, sensor 10-2 is an acidity meter, and sensor 10-3 is a hydrometer, which respectively control pumps 45-6, 45-5, and 45-4 to add hydrochloric acid 32 in temporary storage tank 9-1. Sensor 10-4 is a chlorine concentration detector to prevent chlorine leakage and ensure safe production.

The process of reducing tin dioxide to metallic tin in Example 8 has the following operating steps:

1. The electrolyte is respectively put into each tank area of the two electrolytic cells, and the tin dioxide 29 is respectively put into the grooves of the cathode conductive carrier 5-1 and the cathode conductive carrier 5-2, and the two anodes and the two cathode conductive carriers are immersed in their respective electrolytes.

2. Two electrolytic power supplies are turned on respectively to carry out electrolytic operation. Electrochemical reactions occur at both anodes to electrolyze chlorine, and main electrochemical reactions occur at both cathodes to reduce tin dioxide to metallic tin and electrolyze hydrogen.

3. During the process, sensor 10-1 hydrometer, sensor 10-2 acidity meter, sensor 10-3 hydrometer and sensor 10-4 The chlorine concentration detector transmits the detection data to the automatic program controller 11 for processing, and controls the pumps 45-4, 45-5 and 45-6 to add hydrochloric acid respectively, so that the electrolysis operation of each tank proceeds normally.

4. The cathode electrolytes of the electrolytic cells 1-1 and 1-2 also react with metallic tin to generate stannous chloride solution during the electrolytic reaction. The formed divalent tin salt solution 27 passes through the overflow buffer tank 12-1 and the overflow buffer tank 12-2 respectively, and is finally collected in the temporary storage tank 9-2.

5. The anode electrolyte of the electrolytic cell 1-2 is oxidized to Sn ⁴⁺ due to the migration of some Sn ²⁺ ions from the cathode cell area to the anode cell area, and then reacts to generate SnCl ₄ . The formed tetravalent tin salt solution 26 is collected and pumped to the cell 9-3 for temporary storage.

6. After the reaction is completed, the remaining metal tin on the two cathode conductive carriers is collected.

7. Collect the ferric chloride solution in the tail gas processor for other uses.

According to the process of the present invention, tin dioxide is subjected to a reduction reaction at room temperature and pressure to obtain metallic tin, and stannous chloride and stannic chloride solution are obtained in the process and used as other production raw materials. In addition, the chlorine gas produced by electrolysis is treated for environmental protection to obtain ferric chloride solution for reuse.

As other feasible embodiments of the present invention, in order to increase the chance of tin dioxide contacting the cathode surface, the cathode is structurally improved to be a cathode conductive carrier with a flat or spoon-shaped or grooved cathode structure that can load tin dioxide powder. This can also achieve the purpose of the present invention.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims (18)

A process for reducing tin dioxide to metallic tin, characterized in that it comprises the following steps: Step 1: Establish at least one electrolytic cell, wherein an anode and a cathode are provided in the electrolytic cell, wherein the anode is connected to the positive electrode of an electrolytic power source, and the cathode is connected to the negative electrode of an electrolytic power source, and tin dioxide and an electrolyte solution are put into the electrolytic cell, so that the tin dioxide is in direct contact with the cathode or with the metal tin on the cathode during the electrolysis process; Step 2: Turn on the electrolysis power supply to perform electrolysis operation, the anode undergoes an electrochemical oxidation reaction to dissolve the soluble anode metal or to electrolyze chlorine and/or oxygen at the insoluble anode, and the cathode undergoes an electrochemical reduction reaction to electrolyze metallic tin by causing the tin dioxide in direct contact with the cathode and/or the tin dioxide in direct contact with the metallic tin on the cathode; Step 3: Collect and utilize the solid product and/or solution product of the metallic tin obtained by electrolysis and/or the tin compound obtained by the reaction between the metallic tin and the electrolyte. The process for reducing tin dioxide to metallic tin according to claim 1 is characterized in that the electrolyte solution in step 1 is an aqueous solution comprising an organic and/or inorganic soluble electrolyte, and the soluble electrolyte is at least one of a soluble salt, an acid, and an alkali. The process for reducing tin dioxide to metallic tin according to claim 2 is characterized in that: the soluble salt of the soluble electrolyte is one or a combination of sodium salt, potassium salt, and ammonium salt, the soluble acid of the soluble electrolyte is one or a combination of hydrochloric acid, sulfuric acid, and nitric acid, and the soluble base of the soluble electrolyte is one or a combination of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, ammonium hydroxide, ammonium carbonate, and ammonium bicarbonate. The process for reducing tin dioxide to metallic tin according to claim 1 is characterized in that: the electrolytic cell in step 1 is a single electrolytic cell without a separator, or an electrolytic cell with a separator that separates the electrolytic cell into an anode cell area and a cathode cell area, or two electrolytic cells without a separator and with a separator are selected at the same time; wherein the separator of the electrolytic cell is a material that can effectively block electrolytic bubbles and tin dioxide; when an electrolytic cell with a separator is selected, tin dioxide needs to be put into the cathode cell area and be in direct contact with the cathode or the metallic tin on the cathode to be energized. The process for reducing tin dioxide to metallic tin according to claim 4 is characterized in that the separator is one or more of a cation exchange membrane, an anion exchange membrane, a bipolar membrane, a reverse osmosis membrane, a non-ion selective filter membrane, a proton membrane and a filter cloth. The process for reducing tin dioxide to metallic tin according to claim 1, characterized in that the anode of the electrolytic cell in step 1 is an insoluble anode. The process for reducing tin dioxide to metallic tin according to claim 1, characterized in that: in step 1, the tin dioxide and the electrolyte are mixed to form a slurry and then put into the electrolytic cell to make the tin dioxide more evenly distributed. The mixed slurry is distributed in the electrolyte so that it can not only serve as an ion exchange channel but also facilitate more tin dioxide powder to be in close contact with the cathode of the electrolytic cell to obtain direct contact and electricity. The process for reducing tin dioxide to metallic tin according to claim 1 is characterized in that it also includes the step of using the electrolyte to react during the electrolysis process to generate a soluble tetravalent tin salt and/or a divalent tin compound to directly or through a conventional chemical reaction to produce at least one of a divalent tin salt, stannous hydroxide and metallic tin as a production raw material for recycling. A device for reducing tin dioxide to metallic tin according to any one of claims 1 to 8, characterized in that it comprises at least one electrolytic cell, wherein an anode and a cathode are arranged in the electrolytic cell, wherein the anode is connected to the positive electrode of an electrolytic power supply, and the cathode is connected to the negative electrode of the electrolytic power supply, and during the electrolysis process, the cathode or the metallic tin on the cathode is in direct contact with the tin dioxide. The device for reducing tin dioxide to metallic tin according to claim 9 is characterized in that: the electrolytic cell adopts an inclined electrolytic cell, and the cathode of the electrolytic cell is arranged at a low position inside the inclined electrolytic cell, and the tin dioxide powder is piled around the cathode by gravity and directly contacts the cathode or the metallic tin on the cathode to conduct electrochemical reaction by electricity. According to the device for reducing tin dioxide to metallic tin as described in claim 9, it is characterized in that: the cathode of the electrolytic cell is a cathode conductive carrier, the cathode conductive carrier is a flat or spoon-shaped or grooved cathode structure capable of loading tin dioxide powder, the cathode conductive carrier is a conductive material or a combination of a conductive material and an electrical insulator material, part or all of the contact surface of the cathode conductive carrier with the loaded tin dioxide is a conductive material electrically connected to the negative electrode of the electrolytic power supply, and the cathode conductive carrier is electrically connected to the negative electrode of the electrolytic power supply at one or more negative electrode connection points. According to the device for reducing tin dioxide to metallic tin as described in claim 11, it is characterized in that: when the cathode conductive carrier is a combination of a conductive material and an electrical insulating material, the inner bottom and/or inner side of the cathode conductive carrier is a conductive material electrically connected to the negative pole of the electrolytic power supply, and/or the groove of the cathode conductive carrier is provided with a conductive material electrically connected to the negative pole of the electrolytic power supply, and the remaining parts are electrical insulating materials and/or conductive materials coated with electrical insulating materials, so that the tin dioxide powder loaded therein can directly contact the conductive materials in the inner bottom and/or inner side and/or groove of the cathode conductive carrier to produce an electrochemical reduction reaction. The device for reducing tin dioxide to metallic tin according to claim 9 is characterized in that: a filter bag and/or a filter plate is used to surround the cathode to confine the tin dioxide to a range near the cathode to increase the contact rate between the tin dioxide and the cathode. The device for reducing tin dioxide to metallic tin according to claim 9, characterized in that: the electrolytic cell The electrolytic cell is a vertical electrolytic cell, that is, the cathode in the electrolytic cell is arranged below at least one anode, and the electrolytic cell is an electrolytic cell without a separator and/or an electrolytic cell with a separator. The device for reducing tin dioxide to metallic tin according to claim 14 is characterized in that: when a vertical electrolytic cell with a separator is used, the side of the cathode cell area facing the anode is a movable inclined cover separator composed of a separator and an inclined cover separator fixing frame, the holes of the inclined cover separator fixing frame are closed with a separator, and an outlet for exhausting gas or gas and liquid is also provided in the upper part of the cathode cell area. The device for reducing tin dioxide to metallic tin according to claim 15, characterized in that the separator is a filter cloth. The device for reducing tin dioxide to metallic tin according to claim 14 is characterized in that when a vertical electrolytic cell without a partition and a cathode conductive carrier are used at the same time, the cathode conductive carrier has a groove and the bottom of the groove is configured as a funnel-shaped structure with a liquid outlet pipe, and a filter medium is installed in the liquid outlet pipe. The device for reducing tin dioxide to metallic tin according to claim 17 is characterized in that: the inner wall of the funnel-shaped structure at the bottom of the groove of the cathode conductive carrier is provided with a pit for draining the sucked hydrogen-containing electrolyte.