Method for leaching calcium from phosphate tailings and method for mineralizing and sealing carbon dioxide and co-producing light calcium carbonate

Abstract

The invention discloses a method for leaching calcium from phosphate tailings and a method for mineralizing and sealing carbon dioxide and co-producing light calcium carbonate, and relates to the technical field of utilization and sealing of CO2 mineralized phosphate tailings. The method for leaching calcium from phosphate tailings comprises the following steps that the phosphate tailings are subjected to ball milling and then calcined, and calcined phosphate tailings powder is obtained; organic amine is protonated and then diluted with water, and a leaching solution is obtained; and leaching the calcined phosphate tailing powder by adopting the leaching solution to obtain a calcium leaching solution. The invention also provides a method for mineralizing and sealing carbon dioxide and co-producing light calcium carbonate, which comprises the following steps: introducing a gas containing carbon dioxide into the calcium leachate for reaction, and then carrying out solid-liquid separation to obtain the light calcium carbonate. According to the method, calcium ions are cyclically leached by adopting organic amine and are used for carbon dioxide mineralization storage and co-production of light calcium carbonate, so that the method has relatively high application value and environmental protection significance.

Description

Technical Field

[0001] The invention relates to the technical field of utilization and storage of CO2 mineralized phosphate tailings, and in particular to a method for leaching calcium from phosphate tailings and a method for mineralizing and storing carbon dioxide and co-producing light calcium carbonate. Background Art

[0002] Excessive emissions of greenhouse gases (CO2, etc.) have seriously affected the global climate pattern. Responding to climate change and reducing CO2 emissions are currently one of the hot topics of greatest concern to the international community. The energy structure is gradually shifting from fossil energy-based to clean utilization of traditional energy, green energy complementarity, and coordinated expansion of low-carbon energy. The industrial sector is facing multiple challenges, such as strengthening multi-industry technology integration, improving resource utilization, and coordinating greenhouse gas emissions reduction.

[0003] Carbon capture, utilization and storage (CCUS) technology is considered to be the main way to reduce CO2 emissions from fossil energy. CO2 mineralization is an important development direction of CCUS technology. It uses calcium-magnesium-based minerals in nature or industrial processes to convert CO2 into carbonates. It is a thermodynamically favorable process and is expected to achieve low-energy consumption and large-scale CO2 solidification and storage. If phosphate tailings are fully utilized for mineralization and fixation of CO2, an annual fixed reduction of 1-2 million tons of CO2 can be achieved, which has significant economic and environmental benefits and market prospects.

[0004] The accumulation problem of large amounts of phosphate tailings not only occupies a large amount of land resources, but also causes a serious threat to the ecological environment by the infiltration of heavy metal elements into the land. It also wastes resources such as phosphorus, magnesium, and calcium in the tailings, which urgently need to be utilized as resources.

[0005] At present, the methods for recovering calcium, magnesium, phosphorus and other elements from phosphate tailings mainly include calcination-carbonization method, calcination-leaching method and acid leaching method. The carbonization method has the disadvantage of incomplete digestion, and the obtained calcium carbonate product has poor dispersibility, poor stability and irregular crystal form. At present, the calcination-leaching method generally uses ammonium salt as a leaching agent to leach the calcium and magnesium components in the phosphate tailings, but this method has the disadvantages of ammonia overflow and the need for repeated ammonia replenishment, which is not conducive to circulation. The acid leaching method also has the disadvantage of being difficult to recycle. Therefore, it is necessary to select a suitable leaching agent to achieve Ca 2+ It is of great significance for the efficient leaching of CO2 and the regeneration of leaching reagents after CO2 mineralization and storage. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a method for leaching calcium from phosphate tailings and a method for mineralizing and storing carbon dioxide to co-produce light calcium carbonate. The method uses organic amines to cyclically leach calcium ions and is used for mineralizing and storing carbon dioxide to co-produce light calcium carbonate, which has strong application value and environmental significance.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: a method for leaching calcium from phosphate tailings is provided, comprising the following steps:

[0008] (1) ball-milling the phosphate tailings and then calcining them to obtain calcined phosphate tailings powder;

[0009] (2) protonating the organic amine and diluting it with water to obtain an extract;

[0010] (3) using the leaching solution obtained in step (2) to leach the calcined phosphate tailings powder obtained in step (1) to obtain a calcium leaching solution.

[0011] The beneficial effects of adopting the scheme of the present invention are:

[0012] The main minerals in phosphate tailings are fluorapatite (Ca5(PO4)3F), dolomite (CaMg(CO3)2) and silicon dioxide (SiO2). After calcination, calcium is converted into calcium oxide. The specific reaction process is as follows:

[0013] CaMg(CO3)2→CaCO3+MgO+CO2↑

[0014] CaCO3→CaO+CO2↑

[0015] Protonated amines can leach calcium oxide to form calcium ions. Protonated amines release protons to form amine molecules, which are convenient for the subsequent mineralization process to absorb CO2. Taking monoethanolamine (MEA) as an example, the reaction process is as follows:

[0016] R1NH2+HCl→R1NH3 + +Cl -

[0017] 2R1NH3 + +CaO→2R1NH2+Ca 2+ +H2O

[0018] During the mineralization regeneration process, amine molecules absorb CO2 to form protonated amines, which promote the formation of calcium carbonate by the carbonate ions formed by the hydrolysis of CO2 and the calcium ions. The reaction process is as follows:

[0019] 2R1NH2+CO2→R1NHCOO - +R1NH3 +

[0020] R1NH2+CO2+H2O→HCO3 - +R1NH3 +

[0021] HCO3 - +H2O→CO3 2- +H3O +

[0022] CO3 2- +Ca 2+ →CaCO3↓

[0023] R1NHCOO - +Ca 2+ +H2O→CaCO3↓+R1NH3 +

[0024] Furthermore, in step (1), the powder is ball-milled to a particle size of less than 200 mesh.

[0025] Furthermore, in step (1), the temperature is raised to 800-1000° C. at a rate of 5-15° C. / min and calcined for 1-3 hours.

[0026] Furthermore, in step (2), the organic amine is at least one of monoethanolamine, diethanolamine and triethanolamine.

[0027] Furthermore, in step (2), the organic amine is protonated using hydrochloric acid.

[0028] Furthermore, in step (2), the molar ratio of hydrogen chloride to organic amine in hydrochloric acid is 0.3-0.7:1. During the protonation process, equimolar H + Combined with organic amines to form protonated amines, the degree of protonation is 30-70%.

[0029] Furthermore, in step (2), the concentration of the organic amine in the leaching solution is 1-3 mol / L.

[0030] Furthermore, in step (3), the mass ratio of the leaching solution to the calcined phosphate tailings powder is 6-11:1; and the leaching time is 10-40 min.

[0031] Furthermore, in step (3), the leaching is carried out at a temperature of 30-50° C. and a stirring speed of 200-400 r / min.

[0032] The present invention also provides a method for mineralizing and sealing carbon dioxide and co-producing light calcium carbonate, wherein a gas containing carbon dioxide is introduced into the calcium leaching solution obtained above to react, and then the solid and liquid are separated to obtain light calcium carbonate.

[0033] Further, the reaction is carried out at a temperature of 30-60° C. and a stirring speed of 200-400 r / min.

[0034] Furthermore, the concentration of carbon dioxide in the gas is 5-20%.

[0035] The present invention has the following beneficial effects:

[0036] 1. The method of the present invention firstly ball-mills the phosphate tailings to increase the specific surface area of ​​the powder, make the calcination more complete, and partially decompose the calcium into CaO, so that it can be leached by organic amine. The prior art uses acidic substances or ammonium salts to leach phosphate tailings, which will leach calcium and magnesium at the same time, which is not conducive to subsequent separation. The present invention uses organic amine as a leaching agent, and the titration results of the leaching solution show that more than 60% of calcium is leached and less than 1% of magnesium is leached. The ICP results show that Ca in the leaching solution is 1.5% and 2.5% respectively. 2+ The ion concentration is 23253.91 mg / L, Mg 2+ The ion concentration is 47.25 mg / L. It can be considered that the organic amine used in the present invention selectively leaches calcium but not magnesium, thereby improving the purity of subsequent products and eliminating the purification step.

[0037] 2. The organic amine leaching agent in the method of the present invention can be circulated to leach the phosphate tailings. Before leaching, the organic amine is protonated, and the organic amine combines with H in the acid to + Protonated amines are formed, which act as proton donors to promote the Ca 2+ Leaching from phosphate tailings and converting into free amine molecules. The calcium leachate uses CO2 gas bubbling method for CO2 mineralization. During the carbonation process, organic amines can promote the mass transfer of CO2 from gas phase to liquid phase, and release protons through CaCO3 precipitation reaction, and regenerate in situ to protonated amines. Organic amine leaching agents have little loss during the circulation process, and can still maintain a high leaching rate after multiple cycles. No fresh leaching agent needs to be added during the process.

[0038] 3. The leaching process of the method of the present invention can be carried out at room temperature, the reaction time is short, no waste gas and other substances are generated, and it has the advantages of mild conditions, equipment-friendly and environmentally friendly. The present invention can produce calcite, aragonite and vaterite calcium carbonate products with a particle size of 2-25μm, which have great application prospects and economic value in the fields of daily use, biomedicine and new materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0041] Example 1

[0042] A method for leaching calcium from phosphate tailings and mineralizing and storing carbon dioxide to produce light calcium carbonate, the process flow is as follows Figure 1 As shown, the following steps are included:

[0043] (1) ball-milling the phosphate tailings for 10 minutes, passing through a 200-mesh sieve, and then heating to 800° C. at a rate of 5° C. / min and calcining for 1 hour to obtain calcined phosphate tailings powder;

[0044] (2) protonating the organic amine with hydrochloric acid at a molar ratio of hydrogen chloride to monoethanolamine of 0.3:1, and then diluting with water to 1-3 mol / L to obtain an extract;

[0045] (3) the leaching solution obtained in step (2) and the calcined phosphate tailings powder obtained in step (1) are mixed in a mass ratio of 6:1, and leached for 10 minutes at a temperature of 30° C. and a stirring speed of 200 r / min to obtain a calcium leaching solution;

[0046] (4) introducing flue gas with a carbon dioxide concentration of 15% into the calcium leaching solution obtained in step (3), reacting at a temperature of 30° C. and a stirring speed of 200 r / min. When the outlet carbon dioxide concentration is 15%, the reaction is considered to be saturated, and the solid-liquid separation is performed to obtain light calcium carbonate.

[0047] Example 2

[0048] A method for leaching calcium from phosphate tailings and mineralizing and storing carbon dioxide to co-produce light calcium carbonate, comprising the following steps:

[0049] (1) ball-milling the phosphate tailings for 20 minutes, passing through a 200-mesh sieve, and then heating to 900° C. at a rate of 10° C. / min and calcining for 2 hours to obtain calcined phosphate tailings powder;

[0050] (2) protonating the organic amine with hydrochloric acid at a molar ratio of hydrogen chloride to diethanolamine of 0.5:1, and then diluting with water to 2 mol / L to obtain an extract;

[0051] (3) the leaching solution obtained in step (2) and the calcined phosphate tailings powder obtained in step (1) are mixed in a mass ratio of 9:1, and leached for 20 minutes at a temperature of 40° C. and a stirring speed of 300 r / min to obtain a calcium leaching solution;

[0052] (4) introducing flue gas with a carbon dioxide concentration of 15% into the calcium leaching solution obtained in step (3), reacting at a temperature of 40° C. and a stirring speed of 300 r / min. When the outlet carbon dioxide concentration is 15%, the reaction is considered to be saturated, and the solid-liquid separation is performed to obtain light calcium carbonate.

[0053] Example 3

[0054] A method for leaching calcium from phosphate tailings and mineralizing and storing carbon dioxide to co-produce light calcium carbonate, comprising the following steps:

[0055] (1) ball-milling the phosphate tailings for 30 minutes, passing through a 200-mesh sieve, and then heating to 1000° C. at a rate of 15° C. / min and calcining for 3 hours to obtain calcined phosphate tailings powder;

[0056] (2) protonating the organic amine with hydrochloric acid at a molar ratio of hydrogen chloride to triethanolamine of 0.7:1, and then diluting with water to 3 mol / L to obtain an extract;

[0057] (3) the leaching solution obtained in step (2) and the calcined phosphate tailings powder obtained in step (1) are mixed in a mass ratio of 11:1, and leached for 40 minutes at a temperature of 50° C. and a stirring speed of 400 r / min to obtain a calcium leaching solution;

[0058] (4) introducing flue gas with a carbon dioxide concentration of 15% into the calcium leaching solution obtained in step (3), reacting at a temperature of 60° C. and a stirring speed of 400 r / min. When the outlet carbon dioxide concentration is 15%, the reaction is considered to be saturated, and the solid-liquid separation is performed to obtain light calcium carbonate.

[0059] The calcium ion leaching rate and carbonization rate measured in Examples 1-3 are shown in Table 1.

[0060] Table 1 Calcium ion leaching rate and carbonization rate

[0061] Calcium ion leaching rate % Calcium ion carbonization rate % Example 1 66.76％ 99.93 Example 2 71.90％ 99.95 Example 3 74.62％ 99.64

[0062] As shown in Table 1, the method of the present invention has a high calcium ion leaching rate for phosphorus tailings, and the calcium leaching solution has a good effect in capturing carbon dioxide in flue gas, and the calcium ion carbonization rate is more than 99.95%. The method not only treats solid waste phosphorus tailings, improves the quality of phosphorus in phosphorus tailings, but also reduces the emission of industrial flue gas and co-produces light calcium carbonate products, which is a new type of clean production process.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for leaching calcium from phosphate tailings, characterized in that: The following steps are involved: (1) ball-milling the phosphate tailings and then calcining them to obtain calcined phosphate tailings powder; (2) protonating the organic amine and diluting it with water to obtain an extract; (3) using the leaching solution obtained in step (2) to leach the calcined phosphate tailings powder obtained in step (1) to obtain a calcium leaching solution.

2. The method for leaching calcium from phosphate tailings as claimed in claim 1, characterized in that In step (1), the temperature is raised to 800-1000° C. at a rate of 5-15° C. / min and calcined for 1-3 hours.

3. The method for leaching calcium from phosphate tailings as claimed in claim 1, characterized in that: In step (2), the organic amine is at least one of monoethanolamine, diethanolamine and triethanolamine.

4. The method for leaching calcium from phosphate tailings as claimed in claim 1, characterized in that: In step (2), the organic amine is protonated using hydrochloric acid.

5. The method for leaching calcium from phosphate tailings as claimed in claim 4, characterized in that: In step (2), the molar ratio of hydrogen chloride to organic amine in the hydrochloric acid is 0.3-0.7:

1.

6. The method for leaching calcium from phosphate tailings as claimed in claim 1, characterized in that: In step (2), the concentration of the organic amine in the leaching solution is 1-3 mol / L.

7. The method for leaching calcium from phosphate tailings as claimed in claim 1, characterized in that: In step (3), the mass ratio of the leaching solution to the calcined phosphate tailings powder is 6-11:1; and the leaching time is 10-40 min.

8. A method for mineralizing and storing carbon dioxide and producing light calcium carbonate, characterized in that: A gas containing carbon dioxide is introduced into the calcium leaching solution obtained in any one of claims 1 to 7 to react, and then the solid and liquid are separated to obtain light calcium carbonate.

9. The method for mineralizing and storing carbon dioxide and producing light calcium carbonate according to claim 8, characterized in that: The reaction is carried out at a temperature of 30-60°C and a stirring speed of 200-400 r / min.

10. The method for mineralizing and storing carbon dioxide and producing light calcium carbonate according to claim 8, characterized in that: The concentration of carbon dioxide in the gas is 5-20%.

Images