WO2020019854A1 - Method for producing zinc oxide by means of double leaching - Google Patents

Abstract

A method for producing zinc oxide by means of double leaching, comprising a primary leaching step, an optional purification step, a first precipitation step, a second precipitation step, a primary calcination step, a secondary leaching step, a crystallization step under increased pressure, a decomposition step under reduced pressure, an optional rinsing step, and a secondary calcination step.

Description

Method for producing zinc oxide by double extraction Technical field

The invention belongs to the technical field of inorganic chemical technology, relates to the resource utilization of low-grade zinc-containing raw ore, and particularly relates to a method for producing zinc oxide by a double-leaching method, and particularly relates to starting from a low-grade zinc oxide raw ore through two extraction processes Method for producing zinc oxide.

Background technique

It is a problem faced by mining enterprises in many countries and regions that low-grade zinc ore is difficult to be effectively used in production. China's total zinc ore reserves are relatively abundant, but overall the zinc grade is low. At present, dead or poor ore that cannot be economically used occupy a large part of the reserves, especially hundreds of millions of tons of zinc oxide containing 3% to 5% of mining Tailings and ore dressing tailings are stored for a long time and cannot be effectively used, causing great pressure. The supply of available zinc raw materials is inadequate, and at the same time a large number of mineral sources cannot be used, and the contradiction between the two is outstanding. In this context, the development of efficient use of low-grade zinc oxide ore resources is of great significance to alleviate the contradiction between supply and demand of zinc raw materials.

For the direct utilization of low-grade zinc oxide ore in the prior art, the main process is to produce zinc oxide by the fire method. However, this process has high energy consumption and high pollution, and is a process that should be eliminated. Therefore, it is strictly restricted by national industrial policies.

Low-grade zinc ore is difficult to use directly as a raw material in industrial processes. Generally, zinc components need to be enriched in a beneficiation process to meet the needs of subsequent industrial production. However, the problems of low beneficiation recovery rate and low concentrate grade are common problems in zinc oxide beneficiation at home and abroad. And the current beneficiation mainly uses flotation, which requires adding a large amount of sodium sulfide for vulcanization treatment. The vulcanized and wrapped zinc needs to be treated by the fire method or pressure oxidation secondary treatment before it can be directly used as the raw material for producing zinc metal or zinc oxide. It is cumbersome and causes serious pollution. It can be seen that the existing beneficiation process has many disadvantages, and it is difficult to effectively utilize low-grade zinc ore through the existing beneficiation method.

At present, there are also processes for extracting zinc ore by wet method and then recovering the zinc component. Existing representative wet processes include sulfuric acid leaching, calcium chloride, and ammonium chloride. The sulfuric acid leaching method has low selectivity, it will leaching a large amount of soluble silicon in the ore, the generated colloidal silicon is difficult to filter, and the acid leaching method generates a large number of sulfate residues, causing great environmental protection treatment pressure; the calcium chloride method cannot be effective The leaching of zinc silicate, zinc ferrite and other components in the raw ore is processed, and the leaching rate is not ideal. High temperature leaching is required, and the comprehensive economic benefit is not good. In the ammonium chloride method, the process of recovering the zinc component from the leaching solution after leaching the raw ore is very difficult. When the zinc ore grade is low, the disadvantages of the existing wet process are more prominent.

Therefore, the use of low-grade zinc-containing raw ore by the existing process is not yet satisfactory.

Summary of the Invention

Problems to be solved by invention

The current low-grade zinc oxide ore utilization process has problems such as high energy consumption, low yield, severe environmental pollution, and low comprehensive economic value. The present invention solves the above-mentioned problems in the utilization of low-grade zinc ore by improving the zinc ore processing technology.

Solution to Problem

In order to solve the problems existing in the prior art, the present disclosure provides a method for producing zinc oxide by a two-leaching method, which includes the following steps:

One extraction step: mixing the ground zinc-containing raw ore with a first extractant and then filtering to obtain a first extract, wherein the first extractant is a mixed aqueous solution of ammonia and ammonium bicarbonate, or A mixed aqueous solution of ammonia and ammonium carbonate, or a mixed aqueous solution of ammonia, ammonium bicarbonate and ammonium carbonate;

Optionally, purifying the first leachate obtained in the one extraction step;

First precipitation step: adding calcium oxide and / or calcium hydroxide to the first leach solution, stirring, and then filtering to obtain a first solid and a first filtrate;

The second precipitation step: adding calcium hydroxide and / or calcium oxide to the first filtrate, stirring, and then filtering to obtain a second solid and a second filtrate;

One calcination step: take the second solid for calcination, and the calcination temperature is 150 to 1050 ° C, preferably 150 to 350 ° C;

Second extraction step: adding a second extractant to the calcined product obtained in the first calcination step, stirring, and then filtering to obtain a second extractant, wherein the second extractant is a mixture of ammonia and ammonium bicarbonate An aqueous solution, or a mixed aqueous solution of ammonia and ammonium carbonate, or a mixed aqueous solution of ammonia, ammonium bicarbonate, and ammonium carbonate;

Pressure crystallization step: passing pressurized carbon dioxide into the second leaching solution to obtain a slurry containing crystals;

Decompression step under reduced pressure: the slurry obtained in the pressure crystallization step is filtered in a sealed environment to obtain a third solid and a third filtrate, and the third filtrate is decompressed to normal pressure, so that the first Part of the ammonium carbonate in the three filtrates is decomposed into ammonia and carbon dioxide;

Optionally, rinsing the third solid with water;

The second calcination step: drying the third solid and calcining at a temperature of 450 to 900 ° C. to obtain a zinc oxide product.

In the method for producing zinc oxide by the two-leaching method provided by a further embodiment of the present disclosure, the mass concentration of total ammonia in the first extractant is 5% to 15%, and The molar concentration of effective carbonate is:

C _{first extractant carbonate} = (n _{raw ore total zinc-} n _{raw ore zinc carbonate} ) × a / V _{first extractant}

among them,

C the _{first extractant} carbonate is the molar concentration of effective carbonate in the first extractant,

n _{raw ore total zinc} is the amount of zinc element in the zinc-containing raw ore,

n _{raw ore zinc carbonate} is the amount of zinc _carbonate in the zinc-containing raw ore,

V _{leaching agent} is the _first volume of the first extraction agent,

The value of a ranges from 100% to 600%, preferably from 150% to 250%;

The mass concentration of total ammonia in the second extractant is 6% to 12%, and the mass concentration of effective carbonate is 8% to 15%.

In the method for producing zinc oxide by the two-leaching method provided by a further embodiment of the present disclosure, the concentration of zinc ammine complex ion (based on the mass of zinc element) in the first leachate is 10 g / L or more, preferably 10 to 50 g / L, more preferably 10 to 25 g / L.

In the method for producing zinc oxide by the two-leaching method provided in a further embodiment of the present disclosure, the amount of the calcium oxide and / or calcium hydroxide substance added in the first precipitation step is in the first leachate The amount of effective carbonate substance is 100% to 130%, preferably 100% to 110%.

In the method for producing zinc oxide by the two-leaching method provided by a further embodiment of the present disclosure, the amount of the calcium oxide and / or calcium hydroxide substance added in the first precipitation step is:

n _pretreatment = (n _{first leachate carbonate-} n _{zinc ammonia complex ion} ) × b

Among them, n _pretreatment is the amount of calcium hydroxide and / or calcium oxide substances added in the first precipitation step, n _{first leachate carbonate} is the amount of effective carbonate substances in the first leachate, n _{zinc ammonia complex The ion} is the amount of the zinc ammine _ion in the first leaching solution, and the range of b is 90% ≦ b ≦ 110%.

In the method for producing zinc oxide by the two-leaching method provided in a further embodiment of the present disclosure, in the second precipitation step, an amount of a calcium hydroxide and / or a calcium oxide substance is added to the first filtrate. The ratio to the amount of the zinc ammonia complex ion in the first filtrate is 1 to 1.2: 2, and preferably 1 to 1.1.2.

In the method for producing zinc oxide by the two-leaching method provided by a further embodiment of the present disclosure, in the second precipitation step, calcium hydroxide and / or calcium oxide is added to the first filtrate until a precipitate is formed. No more increase.

In the method for producing zinc oxide by the two-leaching method provided by a further embodiment of the present disclosure, in the pressure crystallization step, the crystallization pressure is 0.3 to 0.6 MPa.

In the method for producing zinc oxide by the two-leaching method provided by a further embodiment of the present disclosure, in the reduced-pressure decomposition step, a reaction of decomposing part of the ammonium carbonate in the third filtrate into ammonia and carbon dioxide is performed at 70 Performed at a temperature of ~ 90 ° C.

In the method for producing zinc oxide by the two-leaching method provided in a further embodiment of the present disclosure, carbon dioxide is passed into the second filtrate obtained in the second precipitation step, and the second filtrate passed with carbon dioxide is used as the first filtrate. An leaching agent, which is recycled for a single leaching of zinc-containing raw ore.

In the method for producing zinc oxide by the two-leaching method provided in a further embodiment of the present disclosure, in the reduced-pressure decomposition step, after the third filtrate is decompressed to normal pressure:

Collect the carbon dioxide released by the decomposition of ammonium carbonate and recycle it for pressure crystallization;

The third filtrate after decompression to normal pressure was collected and recycled for secondary extraction.

In the method for producing zinc oxide by the two-leaching method provided by a further embodiment of the present disclosure, in the pressurized crystallization step, before pressurized carbon dioxide is passed into the second leachate, An active agent is added to the second leachate.

In the method for producing zinc oxide by the two-leaching method provided in a further embodiment of the present disclosure, the active agent is one or more selected from the group consisting of sodium hexametaphosphate and sodium dodecylbenzenesulfonate.

Effect of the invention

The present disclosure achieves advantageous technical effects in one or more of the following aspects:

1) The present disclosure for the first time realizes the synthesis of calcium zincate in a zinc ammonia environment, combining wet leaching with a synthetic process, achieving high selectivity, high yield, and simple and convenient recovery of zinc components from low-grade zinc ore leachate, and High-purity zinc oxide products are obtained through two extraction and recovery processes.

2) Break the traditional method of zinc ion crystallization separation by heating and evaporating ammonia in the traditional ammonia-carbon ammonium zinc complex leaching process. This application creatively utilizes the zinc ammonia present in the carbon ammonium-zinc ammonia complex system. The balance of complex ion-zinc ion-calcium zincate realizes the selective crystallization and separation of zinc element by promoting equilibrium movement and movement, and realizes the selective recovery of zinc component without destroying the ammonia environment of the solution, thereby avoiding heating The ammonia steaming process has many disadvantages such as high energy consumption, high temperature and pressure safety hazards, equipment corrosion, large amount of co-precipitation of impurities, and pollution caused by volatilization of ammonia.

3) In the secondary extraction and recovery process, the decomposition conditions of ammonium carbonate are creatively used, and the recycling of carbon dioxide is realized through the pressure difference.

4) The method of the present disclosure has a wide range of applications. The ammonia-ammonium carbonate secondary leaching and recovery process can effectively extract and utilize various forms of zinc-containing raw ore to obtain high-quality zinc oxide products.

5) The method disclosed in the present disclosure has less pollution and the auxiliary materials can be recycled, which solves the problem of environmental pollution caused by the auxiliary materials of the existing zinc oxide treatment process.

detailed description

Various exemplary embodiments, features, and aspects of the disclosure will be described in detail below. The word "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

In addition, in order to better illustrate the present disclosure, numerous specific details are given in the detailed description below. In some examples, methods, means, reagents, and equipment that are well known to those skilled in the art are not described in detail, but those skilled in the art can implement the technical solutions of the present disclosure according to general knowledge in the art.

The scope of application of the method of the present disclosure is not particularly limited, and it can be widely applied to the utilization of various zinc-containing raw ores. The advantages of the method disclosed herein are particularly prominent when using low-grade zinc oxide raw ore as a production raw material. For example, a low-grade zinc-containing raw ore may be a zinc-containing raw ore having a zinc content of 3% to 15%; in particular, prior to the present disclosure, a zinc-containing raw ore (lean, dressing tailings having a zinc content of 3% to 6%) There are a large number of ore deposits, and the existing various processes cannot use them economically, resulting in great processing pressure, and the method disclosed in the present disclosure not only technically achieves the low-grade zinc-containing raw ore. Effective utilization, simple and easy process, low cost, and high economic value.

In the present disclosure, the existence form of the zinc component in the zinc-containing raw ore is not particularly limited, and for example, the zinc component may exist in one or more forms including, but not limited to, zinc oxide, zinc carbonate, zinc silicate, and the like. Glossary

In this document, unless otherwise stated, "zinc ammonium carbonate" is a general term for compounds formed by zinc ammonium ions and carbonate, including [Zn (NH ₃ ) ₄ ] CO ₃ (tetraammonium zinc carbonate), [Zn (NH ₃ ) ₃ ] CO ₃ (zinc ammonium carbonate), [Zn (NH ₃ ) ₂ ] CO ₃ (zinc ammonium carbonate), [Zn (NH ₃ )] CO ₃ (zinc ammonium carbonate) Wait.

In this document, unless otherwise stated, "zinc ammonia complex ions" is a collective term for all levels of ammonia zinc complex ions, including [Zn (NH ₃ ) ₄ ] ²⁺ (tetraammine zinc ion), [Zn (NH ₃ ) ₃ ] ²⁺ (triammonium zinc ion), [Zn (NH ₃ ) ₂ ] ²⁺ (diammonium zinc ion), [Zn (NH ₃ )] ²⁺ (monoammonium zinc ion), and the like.

In this document, unless otherwise stated, "effective carbonate" in a solution (including but not limited to various liquids such as a first extractant, a first extractant, a second extractant, etc.) means that the carbonate and Sum of bicarbonate.

"Optional" or "optionally" means that a step described later may or may not be performed, and the expression includes a case where the step described later is performed and a case where the step described later is not performed.

Chemical reaction

One-time extraction

a. Zinc oxide extraction

Ammonia and ammonium bicarbonate as leaching agents

ZnO + (i-1) NH ₃ + NH ₄ HCO ₃ = [Zn (NH ₃ ) _i ] CO ₃ + H ₂ O (i is an integer from 1 to 4)

Ammonia and ammonium carbonate as leaching agents

ZnO + (i-2) NH ₃ + (NH ₄ ) ₂ CO ₃ = [Zn (NH ₃ ) _i ] CO ₃ + H ₂ O (i is an integer from 2 to 4)

b. Zinc hydroxide extraction

Ammonia and ammonium bicarbonate as leaching agents

Zn (OH) ₂ + (i-1) NH ₃ + NH ₄ HCO ₃ = [Zn (NH ₃ ) _i ] CO ₃ + 2H ₂ O

(i is an integer from 1 to 4)

Ammonia and ammonium carbonate as leaching agents

Zn (OH) ₂ + (i-2) NH ₃ + (NH ₄ ) ₂ CO ₃ = [Zn (NH ₃ ) _i ] CO ₃ + 2H ₂ O

(i is an integer from 2 to 4)

c. Zinc carbonate (magnesite) leaching

ZnCO ₃ + iNH ₃ = [Zn (NH ₃ ) _i ] CO ₃ (i is an integer from 1 to 4)

d. Zinc silicate extraction

Ammonia and ammonium bicarbonate as leaching agents

ZnSiO ₃ + (i-1) NH ₃ + NH ₄ HCO ₃ = [Zn (NH ₃ ) _i ] CO ₃ + H ₂ O + SiO ₂

(i is an integer from 1 to 4)

Ammonia and ammonium carbonate as leaching agents

ZnSiO ₃ + (i-2) NH ₃ + (NH ₄ ) ₂ CO ₃ = [Zn (NH ₃ ) _i ] CO ₃ + H ₂ O + SiO ₂

(i is an integer from 2 to 4)

2. First precipitation

Lime reacts with water

CaO + H ₂ O = Ca (OH) ₂

precipitation

Ca (OH) ₂ + (NH ₄ ) ₂ CO ₃ = CaCO ₃ ↓ + 2NH ₃ · H ₂ O

Ca (OH) ₂ + NH ₄ HCO ₃ = CaCO ₃ ↓ + NH ₃ + 2H ₂ O

[Zn (NH ₃ ) _i ] CO ₃ + Ca (OH) ₂ = [Zn (NH ₃ ) _i ] (OH) ₂ + CaCO ₃ ↓

(i is an integer from 1 to 4)

Possible reactions:

Ca (OH) ₂ + [Zn (NH ₃ ) _i ] CO ₃ = CaCO ₃ ↓ + Zn (OH) ₂ ↓ + iNH ₃

(i is an integer from 1 to 4)

3. Second precipitation

Synthesis of calcium zincate:

2 [Zn (NH ₃ ) _i ] (OH) ₂ + Ca (OH) ₂ + 2H ₂ O = Ca (OH) ₂ · 2Zn (OH) ₂ · 2H ₂ O + 2iNH ₃

(i is an integer from 1 to 4)

Total precipitation:

Ca (OH) ₂ + [Zn (NH ₃ ) _i ] CO ₃ = CaCO ₃ ↓ + Zn (OH) ₂ ↓ + iNH ₃

(i is an integer from 1 to 4)

4. One-time calcination

Ca (OH) ₂ · 2Zn (OH) ₂ · 2H ₂ O = Ca (OH) ₂ + 2ZnO + 4H ₂ O

or

Ca (OH) ₂ · 2Zn (OH) ₂ · 2H ₂ O = CaO + 2ZnO + 5H ₂ O;

CaCO ₃ = CaO + CO ₂

Ca (OH) ₂ = CaO + H ₂ O

5. Secondary extraction

ZnO + (i-2) NH ₃ + (NH ₄ ) ₂ CO ₃ = [Zn (NH ₃ ) _i ] CO ₃ + H ₂ O (i is an integer from 2 to 4)

6. Pressurized crystallization

2NH ₃ · H ₂ O + CO ₂ = (NH ₄ ) ₂ CO ₃ + H ₂ O

3 [Zn (NH ₃ ) _i ] CO ₃ + 3H ₂ O = ZnCO ₃ · 2Zn (OH) ₂ · H ₂ O + 2 (NH ₄ ) ₂ CO ₃ + (3i-4) NH ₃ (i is 2 to Integer of 4)

7. Decompression under reduced pressure

(NH ₄ ) ₂ CO ₃ + H ₂ O = 2NH ₃ · H ₂ O + CO ₂

8. Secondary Calcination

ZnCO ₃ · 2Zn (OH) ₂ · H ₂ O = 3ZnO + CO ₂ + 3H ₂ O

Specific process steps

Step 1 once extraction

The ground low-grade zinc-containing raw ore is mixed with the prepared first extractant in a certain ratio and stirred for leaching. The first leaching agent may be selected from: a mixed aqueous solution of ammonia and ammonium bicarbonate; a mixed aqueous solution of ammonia and ammonium carbonate; a mixed aqueous solution of ammonia, ammonium bicarbonate and ammonium carbonate.

The total ammonia concentration and the effective carbonate concentration in the first leaching agent are not particularly limited, and those skilled in the art may select according to factors such as raw ore composition, grade and the like according to actual needs.

In a preferred solution, the mass concentration of total ammonia in the first extractant is 5% to 15%, and more preferably 6% to 8%. This concentration range can achieve a sufficient extraction effect and avoid excessive ammonia. Waste and environmental issues.

In a preferred solution, the effective amount of carbonate in the first extractant is increased by 0 to 500 based on the difference between the theoretical consumption of carbonate complexed with zinc minus the amount of carbonate carried by zinc carbonate in the raw material. %, More preferably the amount of effective carbonate in the extractant is increased by 50% -150% based on the difference between the theoretical consumption of carbonate complexed with zinc minus the amount of carbonate carried by zinc carbonate in the raw material. The theory of complex zinc carbonate consumption refers to the amount of carbonate used to completely convert the zinc element in the raw ore to ammonium zinc carbonate. Therefore, the molar concentration of effective carbonate in the first extractant can be calculated as follows:

C _{first extractant carbonate} = (n _{raw ore total zinc-} n _{raw ore zinc carbonate} ) × a / V _{first extractant}

Among them, C _{first leaching agent carbonate} is the molar concentration of effective carbonate in the first leaching agent, n _{raw ore total zinc} is the amount of zinc element in the zinc containing raw ore, and n _{raw ore zinc carbonate} is in the zinc containing raw ore The amount of the substance of zinc carbonate, V the _{first extractant is the} volume of the first extractant, a is a coefficient, and the value of a is 100% to 600%, preferably 150% to 250%. The mass concentration of carbonate in the first extractant can be converted based on the molar concentration.

The preferred effective carbonic acid concentration of the first leaching agent can complete the leaching of zinc in the raw ore, and can realize the circulation of carbonic acid in the process, while avoiding excessive carbonic acid pressure on subsequent processing.

The weight ratio of the first leaching agent to the zinc-containing raw ore powder is not particularly limited as long as the zinc component can be leached. Preferably, the weight ratio of the first leaching agent to the zinc-containing raw ore powder is 3: 1 to 5: 1, which can obtain a satisfactory leaching effect and avoid waste of the first leaching agent.

The leaching temperature is not particularly limited as long as the zinc component in the raw ore is leached. The extraction is preferably performed at normal temperature, for example, at 15-30 ° C; the extraction can also be performed at a slightly higher temperature (such as 30-55 ° C). You can also choose the appropriate temperature according to the actual conditions.

The zinc oxide raw ore is mixed with the first leaching agent and stirred. The stirring time is not particularly limited as long as the zinc component in the raw ore is leached. The stirring time is preferably 1 to 4 hours, and more preferably 1 to 2 hours.

In one leaching process, the zinc element in the raw ore is converted into zinc ammonia complex ions (the zinc ammonia complex ions formed during the leaching process are mainly zinc ammonia complex ions at various levels) and enter the liquid phase. After leaching, filtering is performed to obtain a first leaching solution containing zinc ammonia complex ions. The first leaching solution can be used in the decarburization process.

In the first leaching solution obtained in the leaching process, the zinc ammonia complex ion concentration is not particularly limited, but the zinc ammonia complex ion concentration (based on the mass of zinc element) in the leaching solution is preferably 10 g / L or more, preferably 10 to 50 g / L, more It is preferably 10 to 25 g / L, which can optimize the processing efficiency of the process, obtain good yield and purity in the subsequent calcium zincate synthesis step, and have the best comprehensive economic benefits. If the concentration of zinc ammonia ion in the original leaching liquid is not within the preferred range, the leaching liquid may optionally be concentrated or diluted to adjust the concentration of zinc ammonia ion in the leaching liquid to a preferred range of 10 to 25 g / L.

Step 2 purification

Step 2 is optional. If necessary, choose Step 2. The first leaching solution is purified by a known method to remove impurities such as iron, manganese, lead, and copper. An exemplary purification method is to add zinc powder for replacement and then filter to remove heavy metal contaminants, but various other known purification methods can also be used. The purification step helps to improve the purity of the final product.

Step 3 First precipitation step

In the first precipitation step, calcium hydroxide and / or calcium oxide are added to the first leachate, and the reaction is stirred to obtain a precipitate (first solid), and then filtered to obtain a first solid and a first filtrate. The first precipitation step is mainly to remove a part or all of the effective carbonate in the first leachate, while most of the zinc ammonium ions remain in the first filtrate. The first filtrate obtained by filtering in this step is used for the next step, and the calcium carbonate contained in the first solid can be calcined into calcium oxide and carbon dioxide to realize recycling. The stirring reaction time in this step is preferably 1 to 2 hours, which can make the reaction sufficient and control the energy consumption within a reasonable range. The temperature of the stirring reaction is preferably, for example, a normal temperature of 15 to 25 ° C.

The amount of calcium hydroxide and / or calcium oxide added in the first precipitation step can be specifically selected according to the actual situation. Here are two options to choose from:

The first solution is to perform substantially complete decarburization of the first leachate, that is, match the amount of calcium oxide and / or calcium hydroxide added in the first precipitation step according to the amount of all effective carbonates in the first leachate, so that the first The effective carbonate in an leaching solution is converted to calcium carbonate precipitation. For example, it is preferable that the amount of the calcium hydroxide and / or calcium oxide substance added in the first precipitation step is 100% to 130%, and more preferably 100% to 110% of the amount of the effective carbonate group substance in the first leachate. After adding calcium oxide and / or calcium hydroxide, the mixture is stirred and filtered. The first solid component obtained by the filtration is calcium carbonate. If the concentration of zinc ammonium ions in the first leachate is too high, part of the zinc components may be co-precipitated with calcium carbonate in the form of zinc hydroxide, so that the first solid may also contain a small amount of zinc hydroxide. If the first solid contains a large amount of zinc, the technician can consider switching to the second solution.

The second solution is to pretreat the first leachate, and only convert the remaining effective carbonate in the first leachate into calcium carbonate precipitation (the first solid) and remove it by filtration, instead of all the effective carbonate in the first leachate. Root removed. Therefore, in the second solution, the amount of calcium hydroxide and / or calcium oxide added in the first precipitation step can be determined according to the amount of remaining effective carbonate in the first leachate. For example, the total effective carbonate concentration in the first leachate is detected, and the total effective carbonate volume in the first leachate other than the carbonates involved in the formation of zinc ammonium carbonate is calculated in combination with the total volume of the first leachate (for ammonia carbonate). For zinc, the amount of zinc ammonium ions and carbonate ions is roughly 1: 1), and then the amount of calcium hydroxide and / or calcium oxide needed to remove some or all of the remaining effective carbonate ions in the leachate ( Slight excess is allowed). For example, according to the second scheme, the amount of the calcium hydroxide and / or calcium oxide substance added in the first precipitation step can be calculated as follows:

n _pretreatment = (n _{first leachate carbonate-} n _{zinc ammonia complex ion} ) × b

Wherein n _pretreatment is the amount of calcium hydroxide and / or calcium oxide substances added in the first precipitation step (pretreatment step), and n _{first leachate carbonate} is the amount of effective carbonate substances in the first leachate. , N _{zinc ammine ion} is the amount of the zinc ammine _ion in the first leaching solution, and b is a coefficient. The value range of b is preferably 90% ≦ b ≦ 110%.

Step 4 second precipitation step

The purpose of the second precipitation step is to convert zinc ammine ions in the first filtrate into a solid form and precipitate them, thereby recovering the zinc component.

In the second precipitation step, calcium hydroxide and / or calcium oxide are added to the first filtrate obtained in step 3, and the reaction is carried out by stirring. During the reaction, a shift in the balance of zinc ammonium ion-zinc ion-zinc hydroxide / calcium zincate occurs. Zinc ammonia complex ions are decomposed, and most of the zinc components in the first filtrate are converted into precipitates. If the first leachate is completely decarburized in step 3, the zinc component is mainly precipitated in the form of calcium zincate during the stirring reaction in this step; if only a part of the effective carbonate in the first leachate is removed in step 3, then During the stirring reaction in the step, part of the zinc component is co-precipitated with calcium carbonate in the form of zinc hydroxide, and the other part is converted into calcium zincate and precipitated.

The reaction temperature is not particularly limited, and may be, for example, 15 to 90 ° C, preferably 20 to 90 ° C, and more preferably 30 to 60 ° C; or a reaction temperature of 15 to 25 ° C. This temperature range has no heating, energy saving, and reduced ammonia volatilization. The advantages. After reaction for 0.5 to 2 hours (preferably 0.5 to 1 hour), filtration can be performed without long reaction and aging processes. After the reaction, filtration is performed to obtain a second solid and a second filtrate. Carbon dioxide may be passed to the second filtrate, and then used as a first extractant for recycling the zinc-containing raw ore. The component of the second solid is mainly calcium zincate, and may also contain a certain amount of calcium carbonate and zinc hydroxide.

The ratio of the amount of the calcium hydroxide and / or calcium oxide substance added to the amount of the zinc ammonia complex ion substance in the first filtrate is preferably 1 to 1.2: 2, and more preferably 1 to 1.1.2. Alternatively, this step can also be performed by gradually adding materials and observing, and gradually adding calcium hydroxide and / or calcium oxide until the precipitate no longer increases.

Step 5 one-time calcination

In this step, the second solid obtained in step 4 is calcined to decompose the calcium zincate in the second solid; if the second solid contains zinc hydroxide, the calcination process will also convert zinc hydroxide to zinc oxide . The calcination temperature is 150 to 1050 ° C, preferably 150 to 350 ° C. The calcined product is a mixture. If the calcination temperature is 150-350 ° C, the main components of the calcined product are zinc oxide and calcium hydroxide, and there may be a small amount of calcium carbonate; if a higher calcination temperature is used, calcium hydroxide and carbonic acid are used. Calcium may be further converted into calcium oxide, so the calcined product mainly contains zinc oxide and calcium oxide.

Step 6 secondary extraction

The prepared second leaching agent is added to the mixture obtained in a single calcination step and stirred for leaching, preferably for 1 to 4 hours. The second extractant may be a mixed aqueous solution of ammonia and ammonium bicarbonate, or a mixed aqueous solution of ammonia and ammonium carbonate, or a mixed aqueous solution of ammonia, ammonium bicarbonate, and ammonium carbonate, preferably an aqueous ammonia-ammonium carbonate solution, in which the total ammonia mass The concentration is 6-12%, and the effective carbonate mass concentration is 8-15%.

In this step, the calcium hydroxide (or calcium oxide) in the primary calcined product reacts with water and effective carbonate in the second extractant to form a calcium carbonate precipitate, and the zinc oxide in the mixture is converted into zinc ammonium carbonate ( [Zn (NH ₃ ) _i ] CO ₃ , where i is an integer of 1 to 4). After the reaction is completed, the calcium carbonate precipitate is removed by filtration. The filtrate obtained by the filtration is a second leaching solution containing zinc ammonia complex ions, which is used in the subsequent pressure crystallization step.

Step 7 pressure crystallization

Carbon dioxide gas is pressed into the second leaching solution, so that the free ammonia in the second leaching solution is converted into ammonium carbonate, and the zinc component loses the complexation condition, and crystallizes and precipitates in the form of basic zinc carbonate. The crystallization pressure is controlled from 0.3 to 0.6 MPa, and the reaction temperature in this process is lower than the high temperature. Since the ammonium carbonate in the aqueous solution can decompose by itself at 70 ° C under normal pressure, the pressure difference can be effectively used in the industry to realize the recycling of carbon dioxide and reduce the process carbon dioxide consumption. Therefore, the preferred reaction temperature in this step is controlled at 70-90 ° . In this step, a slurry containing basic zinc carbonate crystals is obtained and sent to the next step.

In addition, if it is desired to control the crystal grain size so as to obtain a nano-zinc oxide product, in this step, an active agent is first added to the second leachate, and then carbon dioxide gas is pressed into the second leachate. The active agent is preferably sodium hexametaphosphate or sodium dodecylbenzenesulfonate, and the amount is preferably 0.01 to 0.05% of the estimated final product mass.

Step 8 decompression

The crystallized slurry was filtered in a sealed environment (an environment in which a pressurized state was maintained) to obtain a third solid and a third filtrate. The main component of the third solid is basic zinc carbonate, and ammonium carbonate is dissolved in the third filtrate. The third filtrate was decompressed to normal pressure to decompose part of the ammonium carbonate in the third filtrate into ammonia and carbon dioxide. The released carbon dioxide gas can be used for cyclic pressure crystallization, and ammonia is mainly present in the solution in the form of free ammonia. The preferred decomposition reaction temperature is 70-90 ° C. The reaction is carried out in a normal pressure environment at this temperature for 1 to 2 hours. The ammonium carbonate in the aqueous solution can decompose about 60-70%. The liquid after the decomposition reaction has complexing conditions again, and can be recycled for secondary extraction.

Step 9 rinse

Step 9 is optional. If necessary, choose Step 9. The third solid whose main component obtained in step 8 is basic zinc carbonate is rinsed with water, the liquid-solid ratio is 5 to 10: 1, and the number of rinses is 1 to 2 times.

Step 10 secondary calcination

The third solid whose main component is basic zinc carbonate is dried and then calcined, and the calcination temperature is 450-900 ° C. The basic zinc carbonate is decomposed to obtain the final product zinc oxide solid. If an active agent is added in step 7, a nano-zinc oxide solid can be obtained after the decomposition of the basic zinc carbonate in this step, and the average particle diameter is 10-100 nm.

The embodiments of the present disclosure will be described in detail below with reference to examples, but those skilled in the art will understand that the following examples are only used to illustrate the present disclosure and should not be considered as limiting the scope of the present disclosure. If the specific conditions are not indicated in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that are commercially available.

Example 1

A zinc mine in Yunnan, with a zinc content of 5.6% and an original ore oxidation rate of 96.3%. The zinc component of this mine is mainly zinc carbonate.

Take 2000 g of zinc oxide raw ore and put it into 6000 ml of ammonia-ammonium carbonate mixed solution (total ammonia concentration 10%, carbonate concentration 3%) for stirring and leaching. The leaching temperature is normal temperature and the stirring time is 2 hours. Then filtering is performed. The filtered liquid contains zinc component (calculated as zinc oxide equivalent) of 1.632%, the mass concentration of carbonate in the liquid is 4.23%, and the increase is brought in by zinc carbonate in the raw ore. According to the inspection data, the recovery rate of soluble zinc in the raw ore was 90.79%, and the total zinc recovery rate was 87.43%.

The leaching solution containing the zinc ammonia complex ions obtained by the filtration is subjected to purification treatment.

145 g of calcium oxide was added to the purified leachate to precipitate carbonate, and the reaction was filtered after 1 hour.

Take 5000 ml of the filtered liquid, add 24.5 g of calcium hydroxide for the synthesis of calcium zincate, stir the reaction, and filter after 1 hour of reaction. After filtration, a solid with calcium zincate as the main component is obtained.

The calcium zincate solid was dried at 105 ° C for 2 hours, and then calcined at 300 ° C.

Take 80 g of the calcined solid, add 800 ml of ammonia-ammonium carbonate mixed solution (ammonia concentration 10%, carbonate concentration 12%) for stirring and leaching, the stirring time is 2 hours, and then filter.

The filtered filtrate is heated to 70 ° C and placed in the reaction kettle. Compressed carbon dioxide gas is passed into the reaction kettle for reaction. The pressure is controlled at 0.3MPa. Samples are tested. When the zinc concentration in the liquid is less than 0.5%, the carbon dioxide is stopped. , Pump into the positive pressure filter for filtration.

The basic zinc carbonate obtained by filtration was rinsed twice with a liquid-solid ratio of 10: 1 and water. The rinsed basic zinc carbonate was dried at 105 ° C for 2 hours, and then calcined at 800 ° C for 2 hours. The obtained zinc oxide product was tested and analyzed. , Where the zinc oxide content is 99.76%.

Example 2

A zinc mine in Chongqing, with a zinc content of 4.7% and an original ore oxidation rate of 95.52%. The zinc component in this mine is mainly zinc silicate.

Take 2000 g of zinc oxide raw ore and put it into 6000 ml of ammonia-ammonium carbonate mixed solution (mass concentration of ammonia water is 10%, carbonate concentration is 3%) for stirring and leaching. The leaching temperature is normal temperature, and the stirring time is 2 hours. After filtering, the filtered liquid contains zinc component (calculated as zinc oxide equivalent) of 1.367%, the mass concentration of carbonate in the liquid is 3.54%, and the increase is brought in by zinc carbonate in the raw ore. According to the inspection data, the recovery rate of soluble zinc in the raw ore was 91.35% and the total zinc recovery rate was 87.26%.

The leaching solution containing the zinc ammonia complex ions obtained by the filtration is subjected to purification treatment.

145 g of calcium oxide was added to the purified leachate to precipitate carbonate, and the reaction was filtered after 1 hour.

Take 5,000 ml of the filtered liquid, add 20 g of calcium hydroxide for the synthesis of calcium zincate, stir for reaction, filter after 1 hour of reaction, and obtain a solid with calcium zincate as the main component after filtering.

The calcium zincate solid was dried at 105 ° C for 2 hours, and then calcined at 300 ° C.

Take 80 g of the calcined solid and put it into 800 ml of ammonia-ammonium carbonate mixed solution (ammonia concentration 10%, carbonate concentration 12%) for stirring and leaching, the stirring time is 2 hours, and then filtering.

The filtered filtrate is heated to 70 ° C and placed in a reaction kettle. Compressed carbon dioxide gas is passed into the reaction kettle for reaction. The pressure is controlled at 0.3 MPa. Samples are tested. When the zinc concentration in the liquid is less than 0.5%, the carbon dioxide is stopped. Pump in a positive pressure filter for filtration.

The filtered basic zinc carbonate was rinsed twice with a liquid-solid ratio of 10: 1 and water. The rinsed basic zinc carbonate was dried at 105 ° C for 2 hours, and then calcined at 800 ° C for 2 hours. The obtained zinc oxide product was tested and analyzed. Of which the zinc oxide content is 99.8%.

Example 3

A zinc mine in Yunnan, with a zinc content of 5.6% and an original ore oxidation rate of 96.3%. The zinc component of this mine is mainly zinc carbonate.

Take 2000 g of zinc oxide raw ore and put it into 6000 ml of ammonia-ammonium carbonate mixed solution (total ammonia concentration 10%, carbonate concentration 3%) for stirring and leaching. The leaching temperature is normal temperature and the stirring time is 2 hours. Then filtering is performed. The filtered liquid contains zinc component (calculated as zinc oxide equivalent) of 1.632%, the mass concentration of carbonate in the liquid is 4.23%, and the increase is brought in by zinc carbonate in the raw ore. According to the inspection data, the recovery rate of soluble zinc in the raw ore was 90.79%, and the total zinc recovery rate was 87.43%.

The leaching solution containing the zinc ammonia complex ions obtained by the filtration is subjected to purification treatment.

145 g of calcium oxide was added to the purified leachate to precipitate carbonate, and the reaction was filtered after 1 hour.

Take 5000 ml of the filtered liquid, add 24.5 g of calcium hydroxide for the synthesis of calcium zincate, stir the reaction, and filter after 1 hour of reaction. After filtration, a solid with calcium zincate as the main component is obtained.

The calcium zincate solid was dried at 105 ° C for 2 hours, and then calcined at 300 ° C.

Take 80 g of the calcined solid, and add 800 ml of ammonia-ammonium carbonate mixed solution (ammonia concentration 10%, carbonate concentration 12%) for stirring and leaching, the stirring time is 2 hours, and then filtering.

5 mg of sodium dodecylbenzenesulfonate was added to the filtered filtrate, and the filtrate was heated to 70 ° C. and placed in a reaction kettle. The compressed carbon dioxide gas was passed into the reaction kettle for reaction. The pressure was controlled at 0.3 MPa. When the concentration of zinc in the liquid is less than 0.5%, the addition of carbon dioxide is stopped, and a positive pressure filter is drawn for filtration.

The basic zinc carbonate obtained by filtration was rinsed twice with a liquid-solid ratio of 10: 1 and water. The rinsed basic zinc carbonate was dried at 105 ° C for 2 hours, and then calcined at 800 ° C for 2 hours. The obtained nano zinc oxide product was tested. According to the analysis, the zinc oxide content was 99.76%, and the average particle size was 32.1 nm.

Example 4

A zinc mine in Chongqing, with a zinc content of 4.7% and an original ore oxidation rate of 95.52%. The zinc component in this mine is mainly zinc silicate.

Take 2000 g of zinc oxide raw ore and put it into 6000 ml of ammonia-ammonium carbonate mixed solution (mass concentration of ammonia water is 10%, carbonate concentration is 3%) for stirring and leaching, the leaching temperature is normal temperature, and the stirring time is 2 hours, then After filtering, the filtered liquid contains zinc component (calculated as zinc oxide equivalent) of 1.367%, the mass concentration of carbonate in the liquid is 3.54%, and the increase is brought in by zinc carbonate in the raw ore. According to the inspection data, the recovery rate of soluble zinc in the raw ore was 91.35% and the total zinc recovery rate was 87.26%.

The leaching solution containing the zinc ammonia complex ions obtained by the filtration is subjected to purification treatment.

145 g of calcium oxide was added to the purified leachate to precipitate carbonate, and the reaction was filtered after 1 hour.

Take 5,000 ml of the filtered liquid, add 20 g of calcium hydroxide for the synthesis of calcium zincate, stir for reaction, filter after 1 hour of reaction, and obtain a solid with calcium zincate as the main component after filtering.

The calcium zincate solid was dried at 105 ° C for 2 hours, and then calcined at 300 ° C.

80 g of the calcined solid was taken and placed in 800 ml of an ammonia-ammonium carbonate mixed solution (ammonia concentration 10%, carbonate concentration 12%) for stirring and leaching. The stirring time was 2 hours, and then filtered.

5 mg of sodium dodecylbenzenesulfonate was added to the filtered filtrate, and the filtrate was heated to 70 ° C. and placed in a reaction kettle. Compressed carbon dioxide gas was passed into the reaction kettle for reaction. The pressure was controlled at 0.3 MPa. When the concentration of zinc in the liquid is less than 0.5%, the addition of carbon dioxide is stopped, and a positive pressure filter is drawn for filtration.

The filtered basic zinc carbonate was rinsed twice with a liquid-solid ratio of 10: 1 and water. The rinsed basic zinc carbonate was dried at 105 ° C for 2 hours, and then calcined at 800 ° C for 2 hours. The obtained nano zinc oxide product was tested. According to the analysis, the zinc oxide content was 99.8%, and the average particle size was 36.2 nm.

Example 5

A zinc mine in Yunnan, with a zinc content of 11.67% and an original ore oxidation rate of 95.2%. The zinc component of this mine is mainly zinc carbonate.

Take 2000 g of zinc oxide raw ore and put it into 6000 ml of ammonia-ammonium carbonate mixed solution (total ammonia concentration 10%, carbonate concentration 5%) for stirring and leaching. The leaching temperature is normal temperature and the stirring time is 2 hours. After filtering, the filtered liquid contains 3.374% of zinc (calculated as zinc oxide equivalent), and the mass concentration of carbonate in the liquid is 6.21%. The increase is brought in by zinc carbonate in the raw ore. According to the test data, the recovery rate of soluble zinc in the raw ore was 91.11%, and the total zinc recovery rate was 86.74%.

The leaching solution containing the zinc ammonia complex ions obtained by the filtration is subjected to purification treatment.

Take 5,000 ml of the purified leachate and add 195 g of calcium oxide to remove excess carbonates other than the carbonates involved in the formation of ammonium zinc carbonate. The reaction was stirred for 1 hour and then filtered.

To the filtered liquid, 115 g of calcium oxide was added to precipitate the zinc component. The reaction was carried out with stirring, and after 1 hour of reaction, filtration was performed.

The filtered mixture of zinc hydroxide, calcium carbonate and zinc zincate was dried and then calcined at 300 ° C for 2 hours. After sampling analysis, the content of zinc oxide in the calcined product was 52.36%.

Take 200 g of the calcined product, add 1600 ml of ammonia-ammonium carbonate mixed solution (total ammonia mass concentration 10%, carbonate mass concentration 12%) for stirring and extraction, the stirring time is 2 hours, and then filter. The concentration of zinc component (calculated as zinc oxide equivalent) in the filtrate after filtration was 6.52%.

The filtered filtrate is heated to 70 ° C and placed in the reaction kettle. Compressed carbon dioxide gas is passed into the reaction kettle for reaction. The pressure is controlled at 0.3MPa. Samples are tested. When the zinc concentration in the liquid is less than 0.5%, the carbon dioxide is stopped. , Pump into the positive pressure filter for filtration.

The basic zinc carbonate obtained by filtration was rinsed twice with a liquid-solid ratio of 10: 1 and water. The rinsed basic zinc carbonate was dried at 105 ° C for 2 hours, and then calcined at 800 ° C for 2 hours. The obtained zinc oxide product was tested and analyzed. , Where the zinc oxide content is 99.76%.

Example 6

A zinc mine in Chongqing, with a zinc content of 12.93% and an original ore oxidation rate of 94.82%. The zinc component in this mine is mainly zinc silicate.

Take 2000 g of zinc oxide raw ore and put it into 6000 ml of ammonia-ammonium carbonate mixed solution (total ammonia concentration 10%, carbonate concentration 6%) for stirring and leaching, the leaching temperature is 50 ° C, and the stirring time is 2 hours Then, it is filtered. The filtered liquid contains zinc component (based on zinc oxide equivalent) of 3.681%, and the mass concentration of carbonate in the liquid is 6.34%. The increase is brought by the zinc carbonate in the raw ore. According to the inspection data, the recovery rate of soluble zinc in the raw ore during the leaching process was 90.07%, and the total zinc recovery rate was 85.41%.

The leaching solution containing the zinc ammonia complex ions obtained by the filtration is subjected to purification treatment.

Take 5000 milliliters of purified leachate and add 190 grams of calcium oxide to remove excess carbonates other than carbonates involved in the formation of ammonium zinc carbonate. The reaction was stirred for 1 hour and then filtered.

130 g of calcium hydroxide was added to the filtered liquid for precipitating the zinc component, and the reaction was carried out with stirring. After 1 hour of reaction, filtration was performed.

The filtered mixture of zinc hydroxide, calcium carbonate and zinc zincate was dried and then calcined at 300 ° C for 2 hours. After sampling analysis, the content of zinc oxide in the calcined product was 52.51%.

200 g of the calcined product was taken and placed in 1600 ml of an ammonia-ammonium carbonate mixed solution (total ammonia concentration 10%, carbonate concentration 12%) for stirring and extraction, the stirring time was 2 hours, and then filtration was performed. The concentration of zinc component (calculated as zinc oxide equivalent) in the filtered filtrate was 6.53%.

The filtered filtrate is heated to 70 ° C and placed in a reaction kettle. Compressed carbon dioxide gas is passed into the reaction kettle for reaction. The pressure is controlled at 0.3 MPa. Samples are tested. When the zinc concentration in the liquid is less than 0.5%, the carbon dioxide is stopped. Pump in a positive pressure filter for filtration.

The filtered basic zinc carbonate was rinsed twice with a liquid-solid ratio of 10: 1 and water. The rinsed basic zinc carbonate was dried at 105 ° C for 2 hours, and then calcined at 800 ° C for 2 hours. The obtained zinc oxide product was tested and analyzed. Of which the zinc oxide content is 99.8%.

Example 7

A zinc mine in Yunnan, with a zinc content of 11.67% and an original ore oxidation rate of 95.2%. The zinc component of this mine is mainly zinc carbonate.

Take 2000 g of zinc oxide raw ore and put it into 6000 ml of ammonia-ammonium carbonate mixed solution (total ammonia concentration 10%, carbonate concentration 5%) for stirring and leaching. The leaching temperature is normal temperature and the stirring time is 2 hours. After filtering, the filtered liquid contains 3.374% of zinc (calculated as zinc oxide equivalent), and the mass concentration of carbonate in the liquid is 6.21%. The increase is brought in by zinc carbonate in the raw ore. According to the test data, the recovery rate of soluble zinc in the raw ore was 91.11%, and the total zinc recovery rate was 86.74%.

The leaching solution containing the zinc ammonia complex ions obtained by the filtration is subjected to purification treatment.

Take 5,000 ml of the purified leachate and add 195 g of calcium oxide to remove excess carbonates other than the carbonates involved in the formation of ammonium zinc carbonate. The reaction was stirred for 1 hour and then filtered.

To the filtered liquid, 115 g of calcium oxide was added to precipitate the zinc component. The reaction was carried out with stirring, and after 1 hour of reaction, filtration was performed.

The filtered mixture of zinc hydroxide, calcium carbonate and zinc zincate was dried and then calcined at 300 ° C for 2 hours. After sampling analysis, the content of zinc oxide in the calcined product was 52.36%.

Take 200 g of the calcined product, add 1600 ml of ammonia-ammonium carbonate mixed solution (total ammonia mass concentration 10%, carbonate mass concentration 12%) for stirring and extraction, the stirring time is 2 hours, and then filter. The concentration of zinc component (calculated as zinc oxide equivalent) in the filtrate after filtration was 6.52%.

30 mg of sodium dodecylbenzenesulfonate was added to the filtered filtrate, and the filtrate was heated to 70 ° C. and placed in a reaction kettle. Compressed carbon dioxide gas was passed into the reaction kettle for reaction. The pressure was controlled at 0.3 MPa. When the concentration of zinc in the liquid is less than 0.5%, the addition of carbon dioxide is stopped, and a positive pressure filter is drawn for filtration.

The basic zinc carbonate obtained by filtration was rinsed twice with a liquid-solid ratio of 10: 1 and water. The rinsed basic zinc carbonate was dried at 105 ° C for 2 hours, and then calcined at 800 ° C for 2 hours. The obtained nano zinc oxide product was tested. According to the analysis, the zinc oxide content was 99.76%, and the average particle diameter was 21.6 nm.

Example 8

A zinc mine in Chongqing, with a zinc content of 12.93% and an original ore oxidation rate of 94.82%. The zinc component in this mine is mainly zinc silicate.

Take 2000 g of zinc oxide raw ore and put it into 6000 ml of ammonia-ammonium carbonate mixed solution (total ammonia concentration 10%, carbonate concentration 6%) for stirring and leaching, the leaching temperature is 50 ° C, and the stirring time is 2 hours Then, it is filtered. The filtered liquid contains zinc component (based on zinc oxide equivalent) of 3.681%, and the mass concentration of carbonate in the liquid is 6.34%. The increase is brought by the zinc carbonate in the raw ore. According to the inspection data, the recovery rate of soluble zinc in the raw ore during the leaching process was 90.07%, and the total zinc recovery rate was 85.41%.

The leaching solution containing the zinc ammonia complex ions obtained by the filtration is subjected to purification treatment.

Take 5000 milliliters of purified leachate and add 190 grams of calcium oxide to remove excess carbonates other than carbonates involved in the formation of ammonium zinc carbonate. The reaction was stirred for 1 hour and then filtered.

130 g of calcium hydroxide was added to the filtered liquid for precipitating the zinc component, and the reaction was carried out with stirring. After 1 hour of reaction, filtration was performed.

The filtered mixture of zinc hydroxide, calcium carbonate and zinc zincate was dried and then calcined at 300 ° C for 2 hours. After sampling analysis, the content of zinc oxide in the calcined product was 52.51%.

Take 200 g of the calcined product, put it into 1600 ml of ammonia-ammonium carbonate mixed solution (total ammonia mass concentration 10%, carbonate mass concentration 12%) for stirring and extraction, the stirring time is 2 hours, and then filter. The concentration of zinc component (calculated as zinc oxide equivalent) in the filtered filtrate was 6.53%.

30 mg of sodium dodecylbenzenesulfonate was added to the filtered filtrate, and the filtrate was heated to 70 ° C. and placed in a reaction kettle. Compressed carbon dioxide gas was passed into the reaction kettle for reaction. The pressure was controlled at 0.3 MPa. When the concentration of zinc in the liquid is less than 0.5%, the addition of carbon dioxide is stopped, and a positive pressure filter is drawn for filtration.

The filtered basic zinc carbonate was rinsed twice with a liquid-solid ratio of 10: 1 and water. The rinsed basic zinc carbonate was dried at 105 ° C for 2 hours, and then calcined at 800 ° C for 2 hours. The obtained zinc oxide product was tested and analyzed. Among them, the zinc oxide content is 99.8%, and the average particle size is 17.6nm.

The embodiments of the present disclosure have been described above, the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the embodiments described. The terminology used herein is chosen to best explain the principles of the embodiments, practical applications or technical improvements in the market, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims (14)

1. A method for producing zinc oxide by two-leaching method, characterized in that the method for producing zinc oxide by two-leaching method includes the following steps:

   One extraction step: mixing the ground zinc-containing raw ore with a first extractant and then filtering to obtain a first extract, wherein the first extractant is a mixed aqueous solution of ammonia and ammonium bicarbonate, or A mixed aqueous solution of ammonia and ammonium carbonate, or a mixed aqueous solution of ammonia, ammonium bicarbonate and ammonium carbonate;

   Optionally, purifying the first leachate obtained in the one extraction step;

   First precipitation step: adding calcium oxide and / or calcium hydroxide to the first leach solution, stirring, and then filtering to obtain a first solid and a first filtrate;

   The second precipitation step: adding calcium hydroxide and / or calcium oxide to the first filtrate, stirring, and then filtering to obtain a second solid and a second filtrate;

   One calcination step: take the second solid for calcination, and the calcination temperature is 150 to 1050 ° C, preferably 150 to 350 ° C;

   Second extraction step: adding a second extractant to the calcined product obtained in the first calcination step, stirring, and then filtering to obtain a second extractant, wherein the second extractant is a mixture of ammonia and ammonium bicarbonate An aqueous solution, or a mixed aqueous solution of ammonia and ammonium carbonate, or a mixed aqueous solution of ammonia, ammonium bicarbonate, and ammonium carbonate;

   Pressure crystallization step: passing pressurized carbon dioxide into the second leaching solution to obtain a slurry containing crystals;

   Decompression step under reduced pressure: the slurry obtained in the pressure crystallization step is filtered in a sealed environment to obtain a third solid and a third filtrate, and the third filtrate is decompressed to normal pressure, so that the first Part of the ammonium carbonate in the three filtrates is decomposed into ammonia and carbon dioxide;

   Optionally, rinsing the third solid with water;

   The second calcination step: drying the third solid and calcining at a temperature of 450 to 900 ° C. to obtain a zinc oxide product.
2. The method for producing zinc oxide by a two-leaching method according to claim 1, wherein the mass concentration of the total ammonia in the first extractant is 5% to 15%, and the first extractant The molar concentration of effective carbonate in:

   C _{first extractant carbonate} = (n _{raw ore total zinc-} n _{raw ore zinc carbonate} ) × a / V _{first extractant}

   among them,

   C the _{first extractant} carbonate is the molar concentration of effective carbonate in the first extractant,

   n _{raw ore total zinc} is the amount of zinc element in the zinc-containing raw ore,

   n _{raw ore zinc carbonate} is the amount of zinc _carbonate in the zinc-containing raw ore,

   V _{leaching agent} is the _first volume of the first extraction agent,

   The value of a ranges from 100% to 600%, preferably from 150% to 250%;

   The mass concentration of total ammonia in the second extractant is 6% to 12%, and the mass concentration of effective carbonate is 8% to 15%.
3. The method for producing zinc oxide by the two-leaching method according to claim 1 or 2, characterized in that the concentration of zinc ammonia complex ion (based on the mass of zinc element) in the first leach solution is 10 g / L or more, It is preferably 10 to 50 g / L, and more preferably 10 to 25 g / L.
4. The method for producing zinc oxide by the two-leaching method according to claim 1 or 2, characterized in that, in the one-time leaching step, the concentration of zinc ammonia complex ions in the first leaching solution obtained by filtration is (Calculated based on the mass of zinc element) to 10 to 25 g / L.
5. The method for producing zinc oxide by the two-leaching method according to any one of claims 1 to 4, characterized in that the amount of the calcium oxide and / or calcium hydroxide substance added in the first precipitation step is The amount of the carbonate-effective substance in the first leachate is 100% to 130%, preferably 100% to 110%.
6. The method for producing zinc oxide by the two-leaching method according to any one of claims 1 to 4, characterized in that the amount of the calcium oxide and / or calcium hydroxide substance added in the first precipitation step is :

   n _pretreatment = (n _{first leachate carbonate-} n _{zinc ammonia complex ion} ) × b

   Wherein, n _pretreatment is the amount of calcium hydroxide and / or calcium oxide substances added in the first precipitation step, n _{first leachate carbonate} is the amount of effective carbonate substances in the first leachate, n _{zinc ammonia complex The ion} is the amount of the zinc ammine _ion in the first leaching solution, and the range of b is 90% ≦ b ≦ 110%.
7. The method for producing zinc oxide by the two-leaching method according to claim 5, characterized in that, in the second precipitation step, a calcium hydroxide and / or calcium oxide substance is added to the first filtrate. The ratio of the amount to the amount of the zinc ammonia complex ion in the first filtrate is 1 to 1.2: 2, and preferably 1 to 1.1.2.
8. The method for producing zinc oxide by the two-leaching method according to claim 6, characterized in that in the second precipitation step, calcium hydroxide and / or calcium oxide are added to the first filtrate until precipitation Things no longer increase.
9. The method for producing zinc oxide by the two-leaching method according to any one of claims 1 to 8, characterized in that in the pressure crystallization step, the crystallization pressure is 0.3 to 0.6 MPa.
10. The method for producing zinc oxide by the two-leaching method according to any one of claims 1 to 9, characterized in that in the reduced-pressure decomposition step, a part of the ammonium carbonate in the third filtrate is decomposed into ammonia The reaction with carbon dioxide is performed at a temperature of 70 to 90 ° C.
11. The method for producing zinc oxide by the two-leaching method according to any one of claims 1 to 10, wherein carbon dioxide is passed into the second filtrate obtained in the second precipitation step, and carbon dioxide is passed through The second filtrate is used as the first leaching agent, and is recycled for the primary leaching of the zinc-containing raw ore.
12. The method for producing zinc oxide by the two-leaching method according to any one of claims 1 to 11, characterized in that, in the decompression step, the third filtrate is decompressed to normal pressure:

    Collect the carbon dioxide released by the decomposition of ammonium carbonate and recycle it for pressure crystallization;

    The third filtrate after decompression to normal pressure was collected and recycled for secondary extraction.
13. The method for producing zinc oxide by the two-leaching method according to any one of claims 1 to 12, characterized in that, in the pressure crystallization step, pressurized carbon dioxide is passed into the second leaching solution. Previously, an active agent was added to the second leachate.
14. The method for producing zinc oxide by the two-leaching method according to claim 13, wherein the active agent is one or more selected from the group consisting of sodium hexametaphosphate and sodium dodecylbenzenesulfonate.