Nano calcium carbonate prepared by capturing carbon dioxide from steel slag and amine circulation method of nano calcium carbonate

Abstract

The invention belongs to the technical field of waste resource utilization, and discloses nano calcium carbonate prepared by capturing carbon dioxide from steel slag and an amine circulation method of the nano calcium carbonate. The amine circulation method for preparing nano calcium carbonate by capturing carbon dioxide through steel slag comprises the following steps: mixing steel slag powder with an ammonium acetate solution, and carrying out a leaching reaction to obtain a mixed solution; adding an ammonium hydroxide solution into the obtained mixed solution, and filtering to obtain filter residues and leachate; introducing the flue gas into an ammonia water absorption tower to obtain an ammonium bicarbonate solution; and carrying out carbonization reaction on the ammonium bicarbonate solution and the leachate to obtain the nano calcium carbonate. According to the method, the waste residues in the steel industry are recycled, waste is turned into wealth, and high-added-value utilization of the steel slag and the carbon dioxide can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of waste resource utilization, and in particular to nano calcium carbonate prepared by capturing carbon dioxide with steel slag and an amine circulation method thereof. Background Art

[0002] Climate change and industrial solid waste disposal are currently prominent global challenges. In recent years, with the continuous acceleration of industrialization, the proportion of industrial carbon emissions has increased year by year. The steel industry accounts for 25% of global industrial carbon emissions. At the same time, the increase in crude steel production has led to a large amount of idle accumulation of steel slag, causing certain pollution to the environment. Therefore, reducing carbon emissions in the steel industry and promoting the resource utilization of steel slag are issues that need to be urgently addressed.

[0003] Steel slag contains a large amount of calcium oxide. There are currently two research methods for fixing carbon dioxide through steel slag, direct method and indirect method. The direct method is that the steel slag directly reacts with carbon dioxide to form a carbonation product, which is a complex mixture with low value and can only be disposed of in landfills or used in construction in better cases. The indirect carbonation method is to first leach the calcium ions and magnesium ions in the steel slag, and then react with carbon dioxide to form carbonates. In contrast, the indirect method stands out for its ability to produce high-purity precipitated calcium carbonate.

[0004] The process of fixing CO2 by indirect method of steel slag currently focuses on the utilization of solid waste, but does not control the cost. For example, CN202310292657.9 discloses a circulation process for fixing CO2 and preparing nano calcium carbonate by industrial solid waste. The process uses a variety of mixed industrial solid waste as raw materials, extracts calcium ions by ammonium chloride solution, and introduces industrial tail gas containing carbon dioxide into the leaching solution to prepare nano calcium carbonate. The disadvantage of this process is that it fails to fully utilize steel slag waste as raw materials, and the reaction efficiency of flue gas and leaching solution is much lower than that of ammonia absorption method. It only recycles the leaching solution, and does not establish an amine circulation system between processes, which increases the cost and has low reaction efficiency.

[0005] Therefore, it is of great significance to study a method for preparing nano-calcium carbonate and its amine circulation by capturing carbon dioxide from steel slag with low cost and high reaction efficiency. Summary of the invention

[0006] In view of this, the present invention provides a nano calcium carbonate prepared by capturing carbon dioxide with steel slag and an amine circulation method thereof, the purpose of which is to solve the problem of large-scale emission of steel slag waste and carbon dioxide.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] The present invention provides an amine circulation method for preparing nano calcium carbonate by capturing carbon dioxide with steel slag, comprising the following steps:

[0009] 1) mixing steel slag powder and ammonium acetate solution and performing leaching reaction to obtain a mixed solution;

[0010] 2) adding ammonium hydroxide solution to the obtained mixed solution and filtering to obtain filter residue and leachate;

[0011] 3) passing the flue gas into an ammonia absorption tower to obtain an ammonium bicarbonate solution;

[0012] 4) Carrying out carbonization reaction between the ammonium bicarbonate solution and the leaching solution to obtain nano calcium carbonate.

[0013] Preferably, the particle size of the steel slag powder in step 1) is ≤75 μm;

[0014] The steel slag powder comprises the following components in mass fractions: 40-50% CaO, 5-15% MgO, 10-20% SiO2, 1-5% Al2O3, 10-20% FeO and 1-5% MnO.

[0015] Preferably, in step 1), the ammonium acetate solution is an aqueous solution of ammonium acetate, and the concentration of the aqueous solution of ammonium acetate is 2 to 3 mol / L;

[0016] The usage ratio of steel slag powder to ammonium acetate solution is 8-12g:300-400mL.

[0017] Preferably, the temperature of the leaching reaction in step 1) is 50-70° C., and the time of the leaching reaction is 30-60 min.

[0018] Preferably, in step 2), the ammonium hydroxide solution is an aqueous ammonium hydroxide solution, the concentration of the ammonium hydroxide solution is 1-1.5 mol / L, and the amount of the ammonium hydroxide solution added is such that the pH value of the mixed solution is 10.5-11.

[0019] Preferably, in step 3), the flue gas is industrial tail gas in which the carbon dioxide content after desulfurization and denitrification is 15-25%.

[0020] Preferably, in step 4), the ratio of the amount of the ammonium bicarbonate solution to the leachate is 0.5-1.5:0.5-1.5.

[0021] Preferably, in step 4), the carbonization reaction time is 45 to 90 minutes, and the carbonization reaction temperature is 60 to 70°C.

[0022] Preferably, ammonia is generated in both step 2) and step 4), and the generated ammonia enters an ammonia absorption tower to carry out the reaction in step 3).

[0023] The present invention also provides nano-calcium carbonate prepared by the amine circulation method for preparing nano-calcium carbonate by capturing carbon dioxide with steel slag. The purity of the nano-calcium carbonate is ≥98%, and the whiteness of the nano-calcium carbonate is ≥95%.

[0024] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0025] The invention uses ammonium acetate to leach steel slag, uses an ammonia method to absorb CO2 in flue gas, and reacts the obtained saturated ammonium bicarbonate solution with the leaching solution to prepare a high-purity nano calcium carbonate product. The ammonium acetate solution and ammonia generated in the leaching and mineralization processes are all recycled, and no waste water or waste gas is generated in the process.

[0026] The present invention can not only effectively improve the utilization rate of steel slag, but also improve the environmental problems caused by steel slag accumulation and carbon dioxide emissions, while also avoiding environmental pollution and waste of resources, solving the problems of low utilization rate of steel slag, high production cost, complex process, low product added value, generation of waste gas and waste slag, and secondary pollution in existing process technology. The nano calcium carbonate product prepared by the present invention has high purity and low cost, and is an effective means to solve the carbon reduction and solid waste utilization in the steel industry. The present invention makes the waste slag of the steel industry resource-utilized, turning waste into treasure, and can achieve high added value utilization of steel slag and carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 This is the SEM spectrum of the nano calcium carbonate obtained in Example 4;

[0029] Figure 2 is a process flow chart of the present invention;

[0030] Figure 3 is the slag mineralization rate of Examples 1 to 2 and Comparative Examples 1 to 3;

[0031] Figure 4 It is the steel slag mineralization rate of Example 1, Examples 3-4 and Comparative Examples 4-5. DETAILED DESCRIPTION

[0032] The present invention provides an amine circulation method for preparing nano calcium carbonate by capturing carbon dioxide with steel slag, comprising the following steps:

[0033] 1) mixing steel slag powder and ammonium acetate solution and performing leaching reaction to obtain a mixed solution;

[0034] 2) adding ammonium hydroxide solution to the obtained mixed solution and filtering to obtain filter residue and leachate;

[0035] 3) passing the flue gas into an ammonia absorption tower to obtain an ammonium bicarbonate solution;

[0036] 4) Carrying out carbonization reaction between the ammonium bicarbonate solution and the leaching solution to obtain nano calcium carbonate.

[0037] In the present invention, the particle size of the steel slag powder in step 1) is preferably ≤75 μm, more preferably ≤70 μm, and more preferably ≤65 μm;

[0038] The steel slag powder preferably includes the following components in mass fraction: 40-50% CaO, 5-15% MgO, 10-20% SiO2, 1-5% Al2O3, 10-20% FeO and 1-5% MnO; the mass fraction of CaO is preferably 42-48%, more preferably 44-47%, more preferably 45-46%, the mass fraction of MgO is preferably 7-13%, more preferably 8-12%, more preferably 9-10%, the mass fraction of SiO2 is preferably 12-18%, more preferably 14-17%, more preferably 15-16%, the mass fraction of Al2O3 is preferably 2-4%, more preferably 3%, the mass fraction of FeO is preferably 12-18%, more preferably 14-17%, more preferably 15-16%, and the mass fraction of MnO is preferably 2-4%, more preferably 3%.

[0039] In the present invention, the steel slag powder is obtained by ball milling the steel slag produced by converter steelmaking. The ball-to-material ratio of the ball mill is preferably 1:1, the rotation speed of the ball mill is preferably 200-400rpm, further preferably 250-350rpm, more preferably 300-320rpm, and the medium of the ball mill is preferably zirconia beads.

[0040] In the present invention, in the step 1), the ammonium acetate solution is preferably an aqueous solution of ammonium acetate, and the concentration of the aqueous solution of ammonium acetate is preferably 2 to 3 mol / L, more preferably 2.2 to 2.8 mol / L, and more preferably 2.5 to 2.6 mol / L;

[0041] The usage ratio of the steel slag powder to the ammonium acetate solution is preferably 8-12 g:300-400 mL, more preferably 9-11 g:320-380 mL, and more preferably 10 g:340-350 mL.

[0042] In the present invention, when the concentration of the ammonium acetate solution is lower than 2 mol / L, the silicon passivation layer covering the steel slag cannot be completely dissolved, resulting in a low mineralization rate; when the concentration of the ammonium acetate solution is greater than 3 mol / L, since a large amount of ammonium ions are contained in the high-concentration ammonium salt leaching agent, the ammonium ions are hydrolyzed into NH3H2O, and the high-concentration ammonia water will volatilize part of the ammonia gas, causing the pH value of the solution to continue to decrease, affecting the dissolution of CO2 in water to generate H2CO3, thereby resulting in a decrease in the mineralization rate.

[0043] In the present invention, the temperature of the leaching reaction in step 1) is preferably 50-70°C, more preferably 55-65°C, more preferably 60°C, and the leaching reaction time is preferably 30-60 min, more preferably 35-55 min, more preferably 40-50 min.

[0044] In the present invention, when the temperature of the leaching reaction is greater than 70° C., the leaching effect will be weakened due to the evaporation of the acid at high temperature.

[0045] In the present invention, in the step 2), the ammonium hydroxide solution is preferably an aqueous ammonium hydroxide solution, the concentration of the ammonium hydroxide solution is preferably 1-1.5 mol / L, more preferably 1.1-1.4 mol / L, more preferably 1.2-1.3 mol / L, and the amount of ammonium hydroxide solution added is preferably such that the pH value of the mixed solution is 10.5-11, more preferably 10.6-10.9, more preferably 10.7-10.8.

[0046] In the present invention, in step 3), the flue gas is preferably an industrial tail gas in which the carbon dioxide content after desulfurization and denitrification is 15-25%, more preferably 18-24%, and more preferably 20-22%.

[0047] In the present invention, in step 3), the ammonium bicarbonate solution is preferably a saturated ammonium bicarbonate solution.

[0048] In the present invention, the ratio of the amount of the ammonium bicarbonate solution to the leaching solution in step 4) is preferably 0.5-1.5:0.5-1.5, more preferably 0.8-1.2:0.8-1.2, and more preferably 1:1.

[0049] In the present invention, in the step 4), the carbonization reaction time is preferably 45 to 90 min, more preferably 50 to 80 min, more preferably 60 to 70 min, and the carbonization reaction temperature is preferably 60 to 70°C, more preferably 62 to 68°C, more preferably 65 to 66°C.

[0050] In the present invention, ammonia is generated in both step 2) and step 4), and the generated ammonia preferably enters an ammonia water absorption tower to carry out the reaction in step 3).

[0051] In the present invention, in the step 4), after the carbonization reaction, filter pressing dehydration, rinsing and drying are carried out in sequence; the number of times of filter pressing dehydration is preferably 2 to 4 times, and more preferably 3 times; the rinsing reagent is preferably anhydrous ethanol, the drying temperature is preferably 100 to 110°C, more preferably 102 to 108°C, and more preferably 105 to 106°C, and the drying time is preferably 10 to 15h, more preferably 11 to 14h, and more preferably 12 to 13h.

[0052] The present invention also provides nano calcium carbonate prepared by the amine circulation method for preparing nano calcium carbonate by capturing carbon dioxide with steel slag. The purity of the nano calcium carbonate is ≥98%, and the whiteness of the nano calcium carbonate is ≥95.

[0053] In the present invention, the purity of the nano-calcium carbonate is preferably ≥98.2%, more preferably ≥98.8%, more preferably ≥99%, and the whiteness of the nano-calcium carbonate is preferably ≥96%, more preferably ≥97%, more preferably ≥98%.

[0054] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0055] In the embodiment of the present invention, the steel slag is produced by converter steelmaking, and includes the following components by mass fraction: 45% CaO, 10% MgO, 15% SiO2, 5% Al2O3, 20% FeO and 5% MnO.

[0056] Example 1

[0057] The steel slag was ball-milled at a speed of 300 rpm in a ball mill with a ball-to-material ratio of 1:1 (the ball-milling medium was zirconia beads) to obtain steel slag powder with a particle size of 75 μm;

[0058] 10 g of steel slag powder was mixed with 300 mL of ammonium acetate aqueous solution (concentration: 2 mol / L) and subjected to leaching reaction at 60° C. for 45 min in a tank reactor to obtain a mixed solution;

[0059] Add 1 mol / L ammonium hydroxide aqueous solution to the obtained mixed solution until the pH value of the mixed solution reaches 10.5, and then filter to obtain filter residue and leachate. This process produces ammonia gas, which is passed into an ammonia absorption tower;

[0060] The flue gas (the proportion of carbon dioxide after desulfurization and denitrification is 15%) is passed into an ammonia absorption tower to obtain a saturated ammonium bicarbonate solution;

[0061] The saturated ammonium bicarbonate solution and the leaching solution were mixed in a mass ratio of 1:1, and a carbonization reaction was carried out at 65°C in a carbonization reactor for 60 minutes. The carbonization reaction produced ammonia gas, which was passed into an ammonia absorption tower. The product after the carbonization reaction was filtered and dehydrated three times, and then rinsed with anhydrous ethanol. The rinsed product was dried at 105°C for 12 hours to obtain nano calcium carbonate.

[0062] The purity of the nano calcium carbonate obtained in this embodiment is 98.2%, and the whiteness is 98%.

[0063] Example 2

[0064] The concentration of the ammonium acetate aqueous solution in Example 1 was replaced with 3 mol / L, and the other steps were the same as in Example 1.

[0065] Example 3

[0066] The temperature of the leaching reaction in Example 1 was replaced with 50° C., and the other steps were the same as in Example 1.

[0067] Example 4

[0068] The temperature of the leaching reaction in Example 1 was replaced with 70° C., and the other steps were the same as in Example 1.

[0069] Comparative Example 1

[0070] The concentration of the ammonium acetate aqueous solution in Example 1 was replaced with 0.5 mol / L, and the other steps were the same as in Example 1.

[0071] Comparative Example 2

[0072] The concentration of the ammonium acetate aqueous solution in Example 1 was replaced with 1 mol / L, and the other steps were the same as in Example 1.

[0073] Comparative Example 3

[0074] The concentration of the ammonium acetate aqueous solution in Example 1 was replaced with 4 mol / L, and the other steps were the same as in Example 1.

[0075] Comparative Example 4

[0076] The temperature of the leaching reaction in Example 1 was replaced with 40° C., and the other steps were the same as in Example 1.

[0077] Comparative Example 5

[0078] The temperature of the leaching reaction in Example 1 was replaced with 80° C., and the other steps were the same as in Example 1.

[0079] The mineralization rates in Examples 1 to 4 and Comparative Examples 1 to 5 were tested respectively, and the test results are shown in Table 1:

[0080] Table 1 Mineralization rate in Examples 1 to 4 and Comparative Examples 1 to 5

[0081]

[0082] As shown in Table 1, when the concentration of the ammonium acetate aqueous solution is lower than 2 mol / L, as the concentration of the ammonium acetate aqueous solution increases, the silicon passivation layer wrapped around the steel slag gradually dissolves, the calcium ions in the steel slag are gradually released into the solution, and the mineralization rate is significantly improved. However, when the concentration of the ammonium acetate aqueous solution is greater than 3 mol / L, the mineralization rate will decrease. When the leaching temperature is between 50 and 70 ° C, the internal diffusion of the leachate and the external diffusion of metal ions are enhanced, which improves the mass transfer efficiency and the reaction rate of the steel slag and ammonium acetate. However, when the leaching temperature exceeds 70 ° C, the leaching effect will weaken due to the evaporation of the acid at high temperature. Therefore, controlling the leaching temperature can greatly improve the mineralization rate.

[0083]

[0084] In formula I: η is the carbonation efficiency of steel slag;

[0085] Q CO2 is the amount of carbon dioxide adsorbed, mol;

[0086] m is the mass of converter slag, g;

[0087] θ is the mass fraction of the element in the slag, %.

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An amine circulation method for preparing nano calcium carbonate by capturing carbon dioxide with steel slag, characterized in that: The steps include: 1) mixing steel slag powder and ammonium acetate solution and performing leaching reaction to obtain a mixed solution; 2) adding ammonium hydroxide solution to the obtained mixed solution and filtering to obtain filter residue and leachate; 3) passing the flue gas into an ammonia absorption tower to obtain an ammonium bicarbonate solution; 4) Carrying out carbonization reaction between the ammonium bicarbonate solution and the leaching solution to obtain nano calcium carbonate.

2. The amine circulation method for preparing nano calcium carbonate by capturing carbon dioxide with steel slag according to claim 1, characterized in that: The particle size of the steel slag powder in step 1) is ≤75 μm; The steel slag powder comprises the following components in mass fractions: 40-50% CaO, 5-15% MgO, 10-20% SiO2, 1-5% Al2O3, 10-20% FeO and 1-5% MnO.

3. The amine circulation method for preparing nano calcium carbonate by capturing carbon dioxide with steel slag according to claim 2, characterized in that: In the step 1), the ammonium acetate solution is an aqueous solution of ammonium acetate, and the concentration of the aqueous solution of ammonium acetate is 2 to 3 mol / L; The usage ratio of steel slag powder to ammonium acetate solution is 8-12g:300-400mL.

4. The amine circulation method for preparing nano calcium carbonate by capturing carbon dioxide from steel slag according to claim 2 or 3, characterized in that: The leaching reaction temperature in step 1) is 50-70° C., and the leaching reaction time is 30-60 minutes.

5. The amine circulation method for preparing nano-calcium carbonate by capturing carbon dioxide with steel slag according to claim 4, characterized in that: In the step 2), the ammonium hydroxide solution is an aqueous solution of ammonium hydroxide, the concentration of the ammonium hydroxide solution is 1-1.5 mol / L, and the amount of the ammonium hydroxide solution added is such that the pH value of the mixed solution is 10.5-11.

6. The amine circulation method for preparing nano-calcium carbonate by capturing carbon dioxide with steel slag according to claim 5, characterized in that: In the step 3), the flue gas is industrial tail gas in which carbon dioxide accounts for 15-25% after desulfurization and denitrification.

7. The amine circulation method for preparing nano-calcium carbonate by capturing carbon dioxide with steel slag according to claim 6, characterized in that: In the step 4), the ratio of the amount of the ammonium bicarbonate solution to the amount of the leaching solution is 0.5-1.5:0.5-1.

5.

8. The amine circulation method for preparing nano-calcium carbonate by capturing carbon dioxide with steel slag according to claim 7, characterized in that: In the step 4), the carbonization reaction time is 45 to 90 minutes, and the carbonization reaction temperature is 60 to 70°C.

9. The amine circulation method for preparing nano-calcium carbonate by capturing carbon dioxide with steel slag according to claim 5 or 8, characterized in that: Ammonia gas is generated in both step 2) and step 4), and the generated ammonia gas enters an ammonia water absorption tower to carry out the reaction in step 3).

10. The nano-calcium carbonate prepared by the amine circulation method for preparing nano-calcium carbonate by capturing carbon dioxide with steel slag as claimed in any one of claims 1 to 9, characterized in that: The purity of the nano calcium carbonate is ≥98%, and the whiteness of the nano calcium carbonate is ≥95%.

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