WO2024032804A1 - Method for extracting zinc and enriching iron in cooperation with consumption of co2 by means of hot alkali dissolution of metallurgical dust - Google Patents

Abstract

The present invention belongs to the technical field of solid waste resource utilization, and provides a method for extracting zinc and enriching iron in cooperation with the consumption of CO₂ by means of the hot alkali dissolution of metallurgical dust. In the present invention, metallurgical dust and an alkali liquor are mixed and then subjected to a dissolved-out reaction, and reaction products are filtered to obtain an iron-rich powder and a dissolved-out solution; the iron-rich powder is subjected to secondary washing by using production circulating water to obtain a fine iron powder, the dissolved-out solution is diluted with a washing solution, and the diluted solution is subjected to settling separation to obtain a sodium salt dissolved-out solution and sediment impurities; and the precipitated impurities are subjected to solid-liquid separation to obtain a dissolved-out solution and impurities, a flue gas is introduced into the dissolved-out solution, and CO₂ in the flue gas reacts with the dissolved-out solution. The method of the present invention has relatively mild reaction conditions and a high impurity removal efficiency, and recycles a high-concentration alkali medium, such that the production cost is reduced; and the present invention can not only greatly improve the iron-rich grade of same, but can achieve resource utilization of elements such as silicon, aluminum, zinc in the metallurgical dust, and can also effectively consume the CO₂ generated by iron and steel enterprises.

Description

A method for extracting zinc and rich iron from metallurgical dust by hot alkali dissolution and synergistically absorbing CO2

This application is required to be submitted to the China Patent Office on September 30, 2022. The application number is CN202211213398.8 and the invention name is "A method for extracting zinc and rich iron from hot alkali dissolution of metallurgical dust and synergistically absorbing CO ₂ " priority, the entire contents of which are incorporated herein by reference.

Technical field

The present invention relates to the technical field of solid waste resource utilization, and in particular to a method for hot alkali dissolution of metallurgical dust to extract zinc and rich iron to synergistically absorb CO ₂ .

Background technique

Metallurgical dust generally refers to kiln smoke produced during metal smelting or heating. It comes from various processes of iron and steel smelting, including sintering, blast furnace, converter, electric furnace and steel rolling. Therefore, metallurgical dust has a large number, various types and compositions. Characteristics such as large fluctuations. Under the dual tasks of comprehensive utilization of solid waste resources and energy conservation and carbon reduction, the resource utilization and clean treatment of multi-source metallurgical dust have attracted widespread social attention.

The mainstream domestic process technologies for the resource utilization of multi-source metallurgical dust are the rotary kiln process and the rotary hearth furnace process. Among them, the rotary kiln process for resource utilization of metallurgical dust consumes a lot of energy. The current technology level generally requires the addition of 20 to 25% coal coke powder, which reduces fuel consumption. The amount is large, the amount of auxiliary materials added is large, and the cost is high; after the metallurgical dust is treated with zinc extraction, the Zn content in the slag is unstable and the iron content is low. The load of harmful elements caused by returning to the blast furnace is high, making it difficult to utilize the kiln slag and reducing the added value. ; During the recycling process of metallurgical dust, especially high-speed rail low-zinc dust, the rotary kiln is prone to ring formation, frequent furnace cleaning, and high costs; the recycling process of metallurgical dust involves long-term high-temperature smelting, serious loss of refractory bricks in the rotary kiln, frequent brick replacement, and short furnace life. The metallurgical dust resource utilization process of the rotary hearth furnace process requires a large amount of gas and reducing agent, and the applicability of the raw materials is poor. It is mainly used to process metallurgical dust with a zinc content of less than 2% and an iron content of more than 45%; the metallurgical dust resource recovery process The pulverization rate of medium pellets is high, and it is easy to stick to the furnace bottom and cause corrosion; a large amount of heat will be taken away by the flue gas and the volatile smoke dust can easily stick to and block the heat exchanger, seriously affecting the flue gas waste heat recovery efficiency and equipment The failure rate is high; the performance of metallized pellets is unstable, and the metallization rate and residual zinc rate fluctuate greatly due to differences in raw materials.

In summary, no matter what treatment technology is used in the current metallurgical dust resource utilization process, it is carried out around carbothermal reduction. However, high-temperature resource utilization using coal, coke, etc. as energy carriers has high energy consumption, large carbon emissions, and serious pollution. It is a common problem that is difficult to avoid. In the context of dual carbon, choosing a technically reliable and economically reasonable green resource recycling technology for metallurgical dust is a thorny issue faced by most steel companies.

Contents of the invention

The purpose of the present invention is to provide a method for hot alkali dissolution of metallurgical dust to extract zinc, rich iron, and synergistically absorb CO ₂ to achieve green high-value resource utilization of multi-source metallurgical dust and recycling of CO ₂ .

In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

The invention provides a method for extracting zinc and rich iron from metallurgical dust by hot alkali dissolving and synergistically absorbing CO ₂ , which includes the following steps:

1) Mix metallurgical dust and alkali liquid to perform a dissolution reaction, and filter the reaction product to obtain iron-rich powder and dissolution liquid;

2) Use production circulating water to wash the iron-rich powder twice until the Cl ^- content in the iron-rich powder is ≤ 3.0% to obtain iron concentrate powder; use the washing liquid obtained from the second washing to dilute the eluate of step 1), The diluted liquid is subjected to sedimentation separation to obtain sodium salt eluate and precipitated impurities;

The sodium salt dissolution solution includes sodium silicate, sodium zincate and sodium aluminate;

3) Perform solid-liquid separation on the precipitated impurities to obtain eluate and impurities. The impurities are returned to step 1) for dissolution reaction, and the eluate enters the purification tank;

4) Pass the flue gas into the dissolution solution in step 3), and the CO ₂ in the flue gas reacts with the dissolution solution to obtain a solution and a precipitate containing silicon, zinc, and aluminum.

In the present invention, the eluate in step 3) is specifically a mixed solution of the sodium salt eluate obtained by sedimentation separation and the filtrate obtained by solid-liquid separation of precipitated impurities.

Unless otherwise specified, the percentages in the present invention are mass percentages.

Preferably, the mass-to-volume ratio of the metallurgical dust and alkali solution in step 1) is 1g:2-4mL, and the mass of the metallurgical dust is calculated on a dry basis.

Preferably, the temperature of the dissolution reaction in step 1) is 130-200°C, the time of the dissolution reaction is 30-60 min, and the pressure of the dissolution reaction is 0.6-1.0MPa.

Preferably, in the metallurgical dust in step 1), 70 to 90% of the metallurgical dust has a particle size ≥ 100 mesh; in the alkali solution, the concentration of Na ₂ O is 220 to 250 g/L.

Preferably, a vacuum filter is used for filtration in step 1), and the vacuum degree of the vacuum filter is -0.03~-0.06MPa.

Preferably, the concentration of Na ₂ O in the diluent in step 2) is 100-120g/L, and the temperature of the sedimentation separation is 60-80°C.

Preferably, in step 2), the diluent and the flocculant solution are mixed before sedimentation separation is performed, Among them, the mass ratio of flocculant and dry metallurgical dust is 20-100g:1t; the mass concentration of the flocculant solution is 0.08-0.12%.

Preferably, the flocculant solution is obtained by mixing a flocculant and a dilute alkali solution, and the concentration of Na ₂ O in the dilute alkali solution is 8 to 12 g/L.

Preferably, the flocculant is polyacrylamide.

Preferably, the pressure of solid-liquid separation in step 3) is 0.3-0.6MPa.

Preferably, the solid-liquid separation in step 3) is performed in a plate and frame filter press.

Preferably, it also includes: filtering the precipitate containing silicon, zinc, and aluminum described in step 4) to obtain a filter cake, and returning the solution to step 1) for use as alkali solution after adjusting the concentration and alkalinity.

The beneficial effects of the present invention include the following points:

1) The present invention provides a method for hot alkali dissolution of metallurgical dust to extract zinc, rich iron, and synergistically absorb CO ₂ , realizing the green high-value resource utilization of multi-source metallurgical dust and the recycling of CO ₂ , and solving the problems in the existing technology. The resource utilization of metallurgical dust has problems such as high energy consumption, large _CO2 emissions, and serious environmental pollution.

2) The present invention uses hot alkali solution to extract and remove impurities from metallurgical dust. The reaction conditions are relatively mild, the process is simple, the impurity removal efficiency is high, and the industrial operability is strong. The high-concentration alkali medium is recycled, which greatly reduces the cost of extracting and removing impurities. The raw material consumption in the process reduces the production cost, the comprehensive cost is low, the environmental and economic benefits are outstanding, and it is conducive to industrial promotion.

3) The present invention can not only greatly improve the rich iron grade, but also can resourcefully utilize silicon, aluminum, zinc and other elements in metallurgical dust, and can also effectively absorb CO ₂ generated by steel enterprises; the method of the present invention is used to produce High-purity iron powder has low overall cost and significant economic benefits.

Description of drawings

Figure 1 is a process flow chart of the method of extracting zinc and rich iron from metallurgical dust by hot alkali dissolution and synergistically absorbing CO ₂ according to the present invention.

Detailed ways

The invention provides a method for extracting zinc and rich iron from metallurgical dust by hot alkali dissolving and synergistically absorbing CO ₂ , which includes the following steps:

1) Mix metallurgical dust and alkali liquid to perform a dissolution reaction, and filter the reaction product to obtain iron-rich powder and dissolution liquid;

2) Use production circulating water to wash the iron-rich powder twice until the Cl ^- content in the iron-rich powder is ≤ 3.0% to obtain iron concentrate powder; use the washing liquid obtained from the second washing to dilute the eluate of step 1), The diluted liquid is subjected to sedimentation separation to obtain sodium salt eluate and precipitated impurities;

The sodium salt dissolution solution includes sodium silicate, sodium zincate and sodium aluminate;

3) Perform solid-liquid separation on the precipitated impurities to obtain eluate and impurities. The impurities are returned to step 1) for dissolution reaction, and the eluate enters the purification tank;

4) Pass the flue gas into the dissolution solution in step 3), and the CO ₂ in the flue gas reacts with the dissolution solution to obtain a solution and a precipitate containing silicon, zinc, and aluminum.

In the present invention, the mass-to-volume ratio of the metallurgical dust and alkali solution in step 1) is preferably 1g:2-4mL, more preferably 1g:2.5-3.5mL, and more preferably 1g:3mL.

In the present invention, the temperature of the dissolution reaction in step 1) is preferably 130-200°C, further preferably 150-190°C, more preferably 160-180°C; the time of the dissolution reaction is preferably 30-60 min, further preferably 30 ~50min, more preferably 35~45min, the dissolution reaction time is determined according to the physical and chemical properties of the metallurgical dust to be treated and the target grade; the dissolution reaction pressure is preferably 0.6~1.0MPa, further preferably 0.7~0.9MPa, more preferably 0.75~0.8MPa. The pressure of the dissolution reaction is determined according to the physical and chemical properties of the metallurgical dust to be treated and the target grade.

The dissolution reaction device of the present invention is preferably a pressure cooking stirring tank or a bauxite piped dissolution device commonly used in the alumina industry, and the material of the dissolution reaction device is preferably stainless steel.

Among the metallurgical dust described in step 1) of the present invention, it is preferable that 70 to 90% of the metallurgical dust have a particle size ≥ 100 mesh, and it is also preferred that the particle size of the metallurgical dust is ≥ 100 mesh.

In the present invention, the alkali solution is a sodium hydroxide solution, and the concentration of the alkali solution is calculated based on the Na ₂ O content in the solution; in the alkali solution, the concentration of Na ₂ O is preferably 220 to 250 g/L. , further preferably 230 to 240g/L. The concentration of Na ₂ O in the alkali solution is determined according to the physical and chemical properties and target grade of the metallurgical dust to be treated. The metallurgical dust is preferably metallurgical dust produced in multiple processes of the steel manufacturing process.

The filtration in step 1) of the present invention preferably uses a vacuum filter. The vacuum degree of the vacuum filter is preferably -0.03~-0.06MPa, further preferably -0.04~-0.06MPa, and more preferably -0.05~-0.06MPa.

Since the main impurities in metallurgical dust are CaO, SiO ₂ , Al ₂ O ₃ and ZnO, and the harmful components are FeS, FeS ₂ and CaS, etc., they can all be dissolved in hot alkali solution (Na ₂ O <30%). Inventor will Metallurgical dust and alkali are mixed to carry out product extraction and impurity removal reaction (i.e. dissolution reaction). The main chemical reactions that occur are as follows:
CaO+H ₂ O→Ca(OH) ₂ (l)
ZnO(s)+2NaOH→NaZnO ₂ (l)+H ₂ O
SiO ₂ (s)+2NaOH→Na ₂ SiO ₃ (l)+H ₂ O
Al ₂ O ₃ (s)+2NaOH→2NaAlO ₂ (l)+H ₂ O
2FeS(FeS ₂ )(s)+4NaOH+2.5O ₂ →Na ₂ SO ₄ (l)+Na ₂ S(l)+Fe ₂ O ₃ (s)+2H ₂ O
CaS+2NaOH→Na ₂ S(l)+Ca(OH) ₂ (s).

The concentration of Na ₂ O in the diluent in step 2) of the present invention is preferably 100-120g/L, further preferably 105-115g/L, and more preferably 110g/L; the temperature of the sedimentation separation is preferably 60-80 °C, more preferably 65 to 75°C, more preferably 70°C.

In step 2) of the present invention, the diluent is preferably mixed with the flocculant solution and then subjected to sedimentation separation, wherein the mass ratio of the flocculant and the dry basis of metallurgical dust is preferably 20-100g:1t, and further preferably 30-80g:1t. More preferably, it is 50-70g:1t; the mass concentration of the flocculant solution is preferably 0.08-0.12%, further preferably 0.09-0.11%, and more preferably 0.1%; the flocculant solution is obtained by mixing the flocculant and dilute alkali liquid , in the dilute alkali solution, the concentration of Na ₂ O is preferably 8 to 12 g/L, more preferably 9 to 11 g/L, and more preferably 10 g/L; the flocculant is preferably polyacrylamide.

The flocculant of the present invention can accelerate the settling rate of solid particles, thereby greatly improving the solid-liquid separation efficiency; the impurities are returned to the raw material bin to repeat the dissolution reaction of step 1), and the dissolution liquid enters the pressurized purification tank.

In the present invention, the pressure for solid-liquid separation in step 3) is preferably 0.3 to 0.6 MPa, and more preferably 0.4 to 0.5 MPa.

The solid-liquid separation in step 3) of the present invention is preferably carried out in a plate and frame filter press, and a ground pump is used to drive the precipitated impurities into the plate and frame filter press for solid-liquid separation.

The flue gas in step 4) of the present invention is the flue gas produced by the steel enterprise. The CO ₂ in the flue gas reacts with the sodium silicate, sodium zincate and sodium aluminate in the dissolution solution to obtain a solution containing silicon, zinc, For the precipitation of aluminum, the eluate in step 3) is specifically a mixed solution of the sodium salt eluate obtained by sedimentation and separation and the filtrate obtained by solid-liquid separation of precipitated impurities.

In step 4) of the present invention, the precipitate containing silicon, zinc, and aluminum is preferably obtained by press filtration to obtain a filter cake. The filter press preferably uses a plate and frame filter press. It is further preferred that the precipitate is driven into the plate and frame filter press through a ground pump. The plate and frame press The pressure of the filter is preferably 0.3~0.6MPa, and further preferably 0.4~0.5MPa; the filter cake is sold; the solution is preferably returned to step 1) after adjusting the concentration and alkalinity to be used as alkali liquid to achieve efficient circulation of the alkali liquid medium and save money cost.

The process flow of the method of extracting zinc and enriching iron from metallurgical dust by hot alkali dissolution and synergistically absorbing _CO2 is shown in Figure 1.

The technical solutions provided by the present invention will be described in detail below with reference to the examples, but they should not be understood as limiting the protection scope of the present invention.

Example 1

The electric furnace metallurgical dust produced by a steel enterprise in Hebei was used as raw material to extract and remove impurities. The composition of the electric furnace metallurgical dust is: TFe 42.88wt%, SiO ₂ 2.62wt%, Al ₂ O ₃ 0.55wt%, CaO 12.95wt% , MgO 1.25wt%, ZnO 9.85wt%.

Pass 70 to 90% of the electric furnace metallurgical dust through a 100-mesh sieve and mix it with an alkali solution with a Na ₂ O concentration of 240g/L. The volume mass ratio of the alkali solution and the electric furnace metallurgical dust is 3mL:1g. The pressure is 0.8MPa and the temperature is 160°C. The dissolution reaction is carried out under the conditions, and the dissolution reaction time is 30 minutes. The reaction product is filtered through a vacuum filter (the vacuum degree of the vacuum filter is -0.03MPa) to obtain iron-rich powder and eluate. Use production circulating water to wash the iron-rich powder twice until the Cl ^- content in the iron-rich powder is ≤ 3.0% to obtain iron concentrate powder. The composition of iron fine powder is: TFe 64.43%, SiO ₂ 0.83%, Al ₂ O ₃ 0.21%, MgO 1.82%, and ZnO 0.22%.

The above-mentioned dissolution liquid is diluted with the washing liquid from the secondary washing of iron-rich powder. The concentration of Na ₂ O in the obtained diluted liquid is 100g/L. A flocculant (polyacrylamide) is added to the diluted liquid. The amount of flocculant added is 40g/t dry-based electric furnace metallurgical dust, the flocculant is added in the form of a solution. The flocculant solution is obtained by dissolving polyacrylamide in dilute alkali solution. The Na ₂ O concentration in the dilute alkali solution is 10g/L. The mass of the obtained flocculant solution The concentration is 0.1%), and sedimentation separation is performed at 65°C to obtain sodium salt eluate (including sodium silicate, sodium zincate and sodium aluminate) and precipitated impurities. The sedimentation speed of impurities in 35 minutes is 1.24m/h, the content of floating matter in the supernatant in 35 minutes is 0.98g/L, and the underflow compression liquid-to-solid ratio is 4.15 (the lower part of the reactor settles as the underflow and the upper part is the supernatant), which can meet the needs of production. Require.

Use a ground pump to drive the precipitated impurities into the plate and frame filter press, perform solid-liquid separation at 0.4MPa, and obtain the eluate and impurities. The impurities are returned to the raw material bin as electric furnace metallurgical dust to repeat the dissolution reaction, and the eluate (sodium salt obtained from sedimentation is dissolved out The mixed liquid and the filtrate obtained by plate and frame press filtration) enters the pressure purification tank, The flue gas generated by the steel enterprise is introduced, and the CO ₂ in the flue gas reacts with sodium silicate, sodium zincate, and sodium aluminate in the dissolution solution to obtain a solution and a precipitate containing silicon, zinc, and aluminum. The precipitate containing silicon, zinc and aluminum is driven into the plate and frame filter press through a ground pump, and filtered at 0.4MPa to obtain a filter cake. The filter cake is sold, and the solution is returned to the raw material after adjusting the concentration and alkalinity for use as alkali liquid.

Example 2

Converter dust from a steel enterprise in Shandong was used as raw material for product extraction and impurity removal. The composition of the converter dust is: TFe 54.77wt%, SiO ₂ 2.58wt%, Al ₂ O ₃ 1.78wt%, CaO 13.53wt%, MgO 1.65wt %, ZnO 5.41wt%.

Pass 70 to 90% of the converter dust through a 100-mesh sieve and mix it with an alkali solution with a Na ₂ O concentration of 250 g/L. The volume-to-mass ratio of the alkali solution and the converter dust is 2.8 mL: 1 g. Under the conditions of pressure 0.85 MPa and temperature 170°C The dissolution reaction is carried out under the condition of 35 min. The reaction product is filtered by a vacuum filter (the vacuum degree of the vacuum filter is -0.05MPa) to obtain iron-rich powder and eluate. Use production circulating water to wash the iron-rich powder twice until the Cl ^- content in the iron-rich powder is ≤ 3.0% to obtain iron concentrate powder. The composition of iron fine powder is: TFe 66.85%, SiO ₂ 0.81%, Al ₂ O ₃ 0.55%, MgO 2.01%, ZnO 0.37%.

The above-mentioned eluate was diluted with the washing liquid from the secondary washing of the iron-rich powder. The concentration of Na ₂ O in the obtained diluted liquid was 110g/L. A flocculant (polyacrylamide) was added to the diluted liquid. The added amount of the flocculant was 45g/t dry base converter dust, the flocculant is added in the form of a solution. The flocculant solution is obtained by dissolving polyacrylamide in dilute alkali solution. The Na ₂ O concentration in the dilute alkali solution is 10g/L. The mass concentration of the obtained flocculant solution (0.1%), carry out sedimentation separation at 75°C to obtain sodium salt eluate (including sodium silicate, sodium zincate and sodium aluminate) and precipitated impurities. The sedimentation speed of impurities in 40 minutes is 1.22m/h, the floating matter content in the supernatant in 40 minutes is 0.99g/L, and the underflow compression liquid-to-solid ratio is 4.0, which can meet production requirements.

Use a ground pump to drive the precipitated impurities into the plate and frame filter press, perform solid-liquid separation at 0.5MPa, and obtain the eluate and impurities. The impurities are returned to the raw material bin as converter dust to repeat the dissolution reaction, and the eluate (sodium salt eluate obtained from sedimentation) and the filtrate obtained by plate and frame press filtration) enters the pressurized purification tank, and the flue gas generated by the steel enterprise is introduced. The CO ₂ in the flue gas reacts with sodium silicate, sodium zincate, and sodium aluminate in the dissolution solution. A solution and a precipitate containing silicon, zinc, and aluminum are obtained. The precipitate containing silicon, zinc and aluminum is driven into the plate and frame filter press through a ground pump, and filtered at 0.5MPa to obtain a filter cake. The filter cake is sold, and the solution is returned to the raw material after adjusting the concentration and alkalinity for use as alkali solution.

Example 3

The blast furnace bag ash from a steel enterprise in Liaoning Province was used as raw material to extract and remove impurities. The composition of the blast furnace bag ash is: TFe 34.03wt%, SiO ₂ 7.65wt%, Al ₂ O ₃ 3.23wt%, CaO 8.21wt% , MgO 2.1wt%, ZnO 6.79wt%.

Pass 70 to 90% of the blast furnace bag ash through a 100-mesh sieve and mix it with an alkali solution with a Na ₂ O concentration of 230g/L. The volume-to-mass ratio of the alkali solution and blast furnace bag ash is 3.5mL:1g. The pressure is 0.9MPa and the temperature is 180 The dissolution reaction is carried out under ℃ conditions. The dissolution reaction time is 40 minutes. The reaction product is filtered by a vacuum filter (the vacuum degree of the vacuum filter is -0.04MPa) to obtain iron-rich powder and eluate. Use production circulating water to wash the iron-rich powder twice until the Cl ^- content in the iron-rich powder is ≤ 3.0% to obtain iron concentrate powder. The composition of iron fine powder is: TFe 55.26%, SiO ₂ 1.35%, Al ₂ O ₃ 0.47%, MgO 3.12%, and ZnO 0.25%.

The above-mentioned eluate was diluted with the washing liquid from the secondary washing of the iron-rich powder. The concentration of Na ₂ O in the obtained diluted liquid was 120g/L. A flocculant (polyacrylamide) was added to the diluted liquid. The amount of flocculant added was 50g/t dry basis blast furnace bag ash, the flocculant is added in the form of a solution. The flocculant solution is obtained by dissolving polyacrylamide in dilute alkali solution. The Na ₂ O concentration in the dilute alkali solution is 10g/L. The mass of the obtained flocculant solution The concentration is 0.9%, and sedimentation separation is performed at 70°C to obtain sodium salt eluate (including sodium silicate, sodium zincate and sodium aluminate) and precipitated impurities. The sedimentation speed of impurities in 45 minutes is 1.20m/h, the floating matter content in the supernatant in 45 minutes is 0.97g/L, and the underflow compression liquid-to-solid ratio is 4.02, which can meet production requirements.

Use a ground pump to drive the precipitated impurities into the plate and frame filter press, perform solid-liquid separation at 0.45MPa, and obtain the eluate and impurities. The impurities are returned to the raw material bin as blast furnace bag ash to repeat the dissolution reaction, and the eluate (sodium salt obtained by sedimentation is dissolved out The mixed liquid and the filtrate obtained by plate and frame press filtration) enters the pressurized purification tank, and the flue gas generated by the steel enterprise is introduced. The CO ₂ in the flue gas reacts with the sodium silicate, sodium zincate, and sodium aluminate in the dissolution solution. , to obtain a solution and a precipitate containing silicon, zinc, and aluminum. The precipitate containing silicon, zinc and aluminum is driven into the plate and frame filter press through a ground pump, and filtered at 0.45MPa to obtain a filter cake. The filter cake is sold, and the solution is returned to the raw material after adjusting the concentration and alkalinity for use as alkali solution.

The above are only preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims (12)

1. A method for extracting zinc, rich iron, and synergistically consuming CO ₂ from metallurgical dust by hot alkali dissolution, which is characterized in that it includes the following steps:

   1) Mix metallurgical dust and alkali liquid to perform a dissolution reaction, and filter the reaction product to obtain iron-rich powder and dissolution liquid;

   2) Use the production circulating water to wash the iron-rich powder twice until the Cl ^- content in the iron-rich powder is ≤ 3.0% to obtain iron fine powder; use the washing liquid obtained from the second washing to wash the eluate of step 1) Dilute, and the diluted liquid is subjected to sedimentation separation to obtain sodium salt eluate and precipitated impurities;

   The sodium salt dissolution solution includes sodium silicate, sodium zincate and sodium aluminate;

   3) Perform solid-liquid separation on the precipitated impurities to obtain eluate and impurities. The impurities are returned to step 1) for dissolution reaction, and the eluate enters the purification tank;

   4) Pass the flue gas into the dissolution solution in step 3), and the CO ₂ in the flue gas reacts with the dissolution solution to obtain a solution and a precipitate containing silicon, zinc, and aluminum.
2. The method according to claim 1, characterized in that the mass volume ratio of the metallurgical dust and alkali solution in step 1) is 1g:2-4mL.
3. The method according to claim 1 or 2, characterized in that the temperature of the dissolution reaction in step 1) is 130-200°C, the time of the dissolution reaction is 30-60 min, and the pressure of the dissolution reaction is 0.6-1.0MPa.
4. The method according to claim 3, characterized in that, in the metallurgical dust in step 1), 70 to 90% of the metallurgical dust has a particle size ≥ 100 mesh; in the alkali solution, the concentration of Na ₂ O is 220 to 250g/L.
5. The method according to claim 1, characterized in that the filtration in step 1) adopts a vacuum filter, and the vacuum degree of the vacuum filter is -0.03~-0.06MPa.
6. The method according to claim 1 or 4, characterized in that the concentration of Na ₂ O in the diluent in step 2) is 100-120g/L, and the temperature of the sedimentation separation is 60-80°C.
7. The method according to claim 6, characterized in that in step 2), the diluent and the flocculant solution are mixed before sedimentation separation, wherein the mass ratio of the flocculant and metallurgical dust dry basis is 20-100g:1t; The mass concentration of the flocculant solution is 0.08-0.12%.
8. The method according to claim 7, characterized in that the flocculant solution is obtained by mixing a flocculant and a dilute alkali liquid, and the concentration of Na ₂ O in the dilute alkali liquid is 8 to 12 g/L.
9. The method according to claim 7, characterized in that the flocculant is polyacrylamide.
10. The method according to claim 1, characterized in that the pressure of solid-liquid separation in step 3) is 0.3~0.6MPa.
11. The method according to claim 1, characterized in that the solid-liquid separation in step 3) is performed in a plate and frame filter press.
12. The method according to claim 1, further comprising: filtering the precipitate containing silicon, zinc and aluminum in step 4) to obtain a filter cake, and returning the solution to step 1) after adjusting the concentration and alkalinity. Use as lye.