Method for recovering magnesium and phosphorus resources in phosphate rock

Abstract

This invention discloses a method for recovering magnesium and phosphorus resources from phosphate rock, belonging to the field of phosphate rock resource utilization technology. The invention involves grinding phosphate rock, zinc sulfate, and disodium ethylenediaminetetraacetate to obtain a phosphate slurry. This slurry is then used as an absorbent in a spray absorption tower to absorb sulfur-containing flue gas from a single-stage process for desulfurization and magnesium removal, yielding a reacted phosphate slurry. The reacted slurry is then dehydrated, and the dehydrated residue can be used as raw material for a wet-process phosphoric acid production process. Calcium hydroxide is added to the dehydrated liquid for a two-stage precipitation process, yielding magnesium hydroxide as the precipitate. This invention improves the leaching rate of magnesium and phosphorus from the phosphate slurry by adding zinc sulfate and EDTA-2Na to the phosphate rock without affecting desulfurization efficiency, thus improving the overall economic efficiency of the subsequent magnesium extraction process and achieving SO2 emission standards. It achieves significant advantages such as cleaner production, environmental protection, energy conservation, cost reduction, efficiency improvement, and reduced investment, resulting in substantial economic and social benefits for producers.

Description

Technical Field

[0001] This invention belongs to the field of phosphate rock resource utilization technology, specifically relating to a method for recovering magnesium and phosphorus resources from phosphate rock. Background Technology

[0002] Phosphate rock is a non-renewable and irreplaceable important non-metallic mineral resource, widely used in agriculture, medicine, food, defense, sugar refining, new energy, and many other fields. Especially in agriculture, phosphate fertilizer, as one of the three major agricultural fertilizers, has a significant effect on increasing the yield of most crops, and many countries have included phosphate rock in their strategic mineral resource lists.

[0003] Extracting metallic elements from phosphate rock is an economically valuable and sustainable development approach for phosphate resources. Patent CN100392124C discloses a method for demagnesizing high-magnesium phosphate rock using a composite demagnesizing agent containing sulfuric acid and at least one component selected from disodium ethylenediaminetetraacetate and nitric acid. This process dissolves magnesium from the phosphate rock, followed by precipitation and solid-liquid separation to obtain magnesium hydroxide. However, this patent uses only 98% sulfuric acid for demagnesification, and the amount of disodium ethylenediaminetetraacetate added is excessively high, resulting in high costs. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this invention proposes a method for recovering magnesium and phosphorus resources from phosphate rock.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for recovering magnesium phosphorus resources from phosphate rock, comprising the following steps:

[0006] (1) Phosphate ore, zinc sulfate and disodium ethylenediaminetetraacetate were ground to prepare phosphate ore slurry;

[0007] (2) Phosphate slurry is used as an absorbent to enter the spray absorption tower to absorb sulfur-containing flue gas that has undergone one-turn-one-absorption to carry out desulfurization and demagnesification reactions, and the reacted phosphate slurry is obtained.

[0008] (3) Dehydrate the reacted phosphate rock slurry. The dehydrated residue can be used as raw material for wet phosphoric acid process.

[0009] (4) Add calcium hydroxide to the dehydrated liquid to make the pH of the supernatant 8.0-8.5, centrifuge and take the supernatant, add calcium hydroxide to the supernatant to obtain the precipitate as magnesium hydroxide product.

[0010] In a preferred embodiment of the present invention, the total mass percentage of zinc sulfate in the phosphate rock, zinc sulfate, and disodium ethylenediaminetetraacetate is 0.1-0.3%, and the mass percentage of disodium ethylenediaminetetraacetate is 0.2-0.5%.

[0011] In a preferred embodiment of the present invention, in step (1), the solid-liquid mass ratio of the phosphate rock slurry is 25-40%.

[0012] As a preferred embodiment of the present invention, in step (2), the phosphate rock slurry in the spray absorption tower absorbs sulfur-containing flue gas in a countercurrent manner, and the spray layer of the spray absorption tower is set with 3 layers and the layer spacing is 1.5m.

[0013] In a preferred embodiment of the present invention, in step (2), the temperature of the spray absorption tower is 25-45℃; the gas flow rate is 0.5-3m / s; the gas includes sulfur-containing flue gas and oxygen, with an oxygen content of 5-20%; and the liquid-to-gas ratio is 9-10L / m³. 3 .

[0014] In a preferred embodiment of the present invention, in step (2), the SO2 concentration in the sulfur-containing flue gas is 1000-5000 mg / m³. 3 The flue gas volume is 10,000-30,000 m³. 3 / h.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) This method uses a counter-current spray absorption tower. Phosphate ore is prepared into phosphate slurry in a slurry tank and then sprayed into the top of the absorption tower. The tail gas of the "one-turn-one-absorption" process is introduced into the bottom of the absorption tower, absorbed, and discharged from the top. The slurry after reaction is collected at the bottom and sent to a dewatering device. The supernatant after dewatering enters the magnesium recovery workshop to extract magnesium. In this process, the SO2 removal rate can reach more than 98%, and can be close to 100% at its highest, which is lower than the SO2 removal rate specified in the flue gas emission standard GB18485-2014. x Emission concentration 80 mg / Nm 3 .

[0017] (2) In this invention, the addition of zinc sulfate and EDTA-2Na to the phosphate rock slurry does not affect the desulfurization efficiency, but effectively increases the PO4 content in the phosphate rock. 3- The leaching rate can reach about 110%, and the leaching rate of magnesium can reach more than 96%. Moreover, the liquid produced in this process can also be used as a raw material for magnesium production.

[0018] (3) This invention organically combines the desulfurization of sulfur-containing flue gas and the resource utilization of phosphate rock through the "one-turn-one-absorption" process. It can achieve SO2 emission standards and make phosphate rock a resource, while the by-product Mg(OH)2 can also increase economic benefits. The process of this invention is simple and can be easily upgraded and transformed without changing or with minimal changes to the existing wet flue gas purification equipment, thus saving costs. This invention uses phosphate rock for desulfurization and resource utilization, realizing the resource utilization of sulfur dioxide and phosphate rock. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for recovering magnesium and phosphorus resources from phosphate rock. Detailed Implementation

[0020] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0021] Example 1

[0022] like Figure 1 As shown, a method for recovering magnesium and phosphorus resources from phosphate rock includes the following steps:

[0023] (1) Phosphate rock with a mass percentage of 99.6%, zinc sulfate with a mass percentage of 0.1%, and disodium ethylenediaminetetraacetate with a mass percentage of 0.3% were ground to prepare a phosphate rock slurry with a solid-liquid mass ratio of 25%.

[0024] (2) Phosphate rock slurry, used as an absorbent, is pumped into a counter-current spray absorption tower via a circulating pump pipeline for desulfurization and demagnesification reactions. Three spray layers are set up with a spacing of 1.5m between layers. The treated flue gas is sulfur-containing flue gas that undergoes a single-stage rotation and absorption process. The oxygen concentration in the sulfur-containing flue gas is 5%, and the SO2 concentration is 1000 mg / m³. 3 The flue gas volume is 10000m³ 3 / h; the empty tower gas velocity is 2m / s, and the liquid-to-gas ratio is 9L / m 3 The reaction temperature was 25℃, and the measured SO2 removal rate was 97.9%.

[0025] (3) The reacted phosphate rock slurry is dewatered, and the dewatered residue is used as raw material for the wet phosphoric acid process. The magnesium leaching rate can reach 96.8%, and PO4... 3- The leaching rate was 95.6%.

[0026] (4) The dehydrated liquid is sent to the magnesium recovery workshop, and calcium hydroxide is added to make the pH of the supernatant 8.0-8.5. The supernatant and solid are separated, and the solid is further processed.

[0027] (5) Add excess calcium hydroxide to the supernatant, then remove impurities from the precipitate, purify it, dehydrate and dry it to obtain a solid with a magnesium hydroxide content of 96.4%.

[0028] Example 2

[0029] A method for recovering magnesium phosphorus resources from phosphate rock includes the following steps:

[0030] (1) Phosphate rock with a mass percentage of 99.4%, zinc sulfate with a mass percentage of 0.2%, and disodium ethylenediaminetetraacetate with a mass percentage of 0.4% were ground to prepare a phosphate rock slurry with a solid-liquid mass ratio of 30%.

[0031] (2) Phosphate rock slurry, used as an absorbent, is pumped into a counter-current spray absorption tower via a circulating pump pipeline for desulfurization and demagnesification reactions. Three spray layers are set up with a spacing of 1.5m between layers. The treated flue gas is sulfur-containing flue gas that undergoes a single-stage rotation and absorption process. The oxygen concentration in the sulfur-containing flue gas is 20%, and the SO2 concentration is 2000 mg / m³. 3 The flue gas volume is 15000m³ 3 / h; the empty tower gas velocity is 3m / s, and the liquid-to-gas ratio is 9.5L / m 3 The reaction temperature was 35℃, and the measured SO2 removal rate was 98.4%.

[0032] (3) The reacted phosphate rock slurry is dewatered, and the dewatered residue is used as raw material for the wet phosphoric acid process. The magnesium leaching rate can reach 96.9%, and PO4... 3- The leaching rate was 97.8%.

[0033] (4) The dehydrated liquid is sent to the magnesium recovery workshop, and calcium hydroxide is added to make the pH of the supernatant 8.0-8.5. The supernatant and solid are separated, and the solid is further processed.

[0034] (5) Add excess calcium hydroxide to the supernatant, then remove impurities from the precipitate, purify it, dehydrate and dry it to obtain a solid with a magnesium hydroxide content of 95.8%.

[0035] Example 3

[0036] A method for recovering magnesium phosphorus resources from phosphate rock includes the following steps:

[0037] (1) Phosphate rock with a mass percentage of 99.2%, zinc sulfate with a mass percentage of 0.3%, and disodium ethylenediaminetetraacetate with a mass percentage of 0.5% were ground to prepare a phosphate rock slurry with a solid-liquid mass ratio of 30%.

[0038] (2) Phosphate rock slurry is used as an absorbent and is fed into a counter-current spray absorption tower via a circulating pump pipeline for desulfurization and demagnesification reactions. Three spray layers are set up with a layer spacing of 1.5m. The treated flue gas is sulfur-containing flue gas that undergoes a single-stage rotation and absorption process. The oxygen concentration in the sulfur-containing flue gas is 15%, and the SO2 concentration is 5000 mg / m³. 3 The flue gas volume is 30,000 m³. 3 / h; the empty tower gas velocity is 0.5m / s, and the liquid-to-gas ratio is 10L / m 3 The reaction temperature was 45℃, and the measured SO2 removal rate was 98.7%.

[0039] (3) The reacted phosphate rock slurry is dewatered, and the dewatered residue is used as raw material for the wet phosphoric acid process. The magnesium leaching rate can reach 98.4%, and PO4... 3- The leaching rate was 97.3%.

[0040] (4) The dehydrated liquid is sent to the magnesium recovery workshop, and calcium hydroxide is added to make the pH of the supernatant 8.0-8.5. The supernatant and solid are separated, and the solid is further processed.

[0041] (5) Add excess calcium hydroxide to the supernatant, then remove impurities from the precipitate, purify it, dehydrate and dry it to obtain a solid with a magnesium hydroxide content of 94.3%.

[0042] Comparative Example 1

[0043] A method for recovering magnesium phosphorus resources from phosphate rock includes the following steps:

[0044] (1) Phosphate rock with a mass percentage of 99.7% and disodium ethylenediaminetetraacetate with a mass percentage of 0.3% were ground to prepare a phosphate rock slurry with a solid-liquid mass ratio of 25%.

[0045] (2) Phosphate rock slurry, used as an absorbent, is pumped into a counter-current spray absorption tower via a circulating pump pipeline for desulfurization and demagnesification reactions. Three spray layers are set up with a spacing of 1.5m between layers. The treated flue gas is sulfur-containing flue gas that undergoes a single-stage rotation and absorption process. The oxygen concentration in the sulfur-containing flue gas is 5%, and the SO2 concentration is 1500 mg / m³. 3 The flue gas volume is 10000m³ 3 / h; the empty tower gas velocity is 2m / s, and the liquid-to-gas ratio is 9L / m 3 The reaction temperature was 25℃, and the measured SO2 removal rate was 98.7%.

[0046] (3) The reacted phosphate rock slurry is dewatered, and the dewatered residue is used as raw material for the wet phosphoric acid process. The magnesium leaching rate can reach 87.8%, and PO4... 3- The leaching rate was 84.9%.

[0047] (4) The dehydrated liquid is sent to the magnesium recovery workshop, and calcium hydroxide is added to make the pH of the supernatant 8.0-8.5. The supernatant and solid are separated, and the solid is further processed.

[0048] (5) Add excess calcium hydroxide to the supernatant, then remove impurities from the precipitate, purify it, dehydrate and dry it to obtain a solid with a magnesium hydroxide content of 89.6%.

[0049] Comparative Example 2

[0050] A method for recovering magnesium phosphorus resources from phosphate rock includes the following steps:

[0051] (1) Phosphate rock with a mass percentage of 99.7% and zinc sulfate with a mass percentage of 0.3% were ground to prepare a phosphate rock slurry with a solid-liquid mass ratio of 25%.

[0052] (2) Phosphate rock slurry, used as an absorbent, is pumped into a counter-current spray absorption tower via a circulating pump pipeline for desulfurization and demagnesification reactions. Three spray layers are set up with a spacing of 1.5m between layers. The treated flue gas is sulfur-containing flue gas that undergoes a single-stage rotation and absorption process. The oxygen concentration in the sulfur-containing flue gas is 5%, and the SO2 concentration is 1500 mg / m³. 3 The flue gas volume is 10000m³ 3 / h; the empty tower gas velocity is 2m / s, and the liquid-to-gas ratio is 9L / m 3 The reaction temperature was 25℃, and the measured SO2 removal rate was 99.4%.

[0053] (3) The reacted phosphate rock slurry is dewatered, and the dewatered residue is used as raw material for the wet phosphoric acid process. The magnesium leaching rate can reach 91.4%, and PO4... 3- The leaching rate was 87.4%.

[0054] (4) The dehydrated liquid is sent to the magnesium recovery workshop, and calcium hydroxide is added to make the pH of the supernatant 8.0-8.5. The supernatant and solid are separated, and the solid is further processed.

[0055] (5) Add excess calcium hydroxide to the supernatant, then remove impurities from the precipitate, purify it, dehydrate and dry it to obtain a solid with a magnesium hydroxide content of 91.6%.

[0056] Comparative Example 3

[0057] A method for recovering magnesium phosphorus resources from phosphate rock includes the following steps:

[0058] (1) The phosphate rock with a mass percentage of phosphate rock was ground to prepare a phosphate rock slurry with a solid-liquid mass ratio of 25%.

[0059] (2) Phosphate rock slurry, used as an absorbent, is pumped into a counter-current spray absorption tower via a circulating pump pipeline for desulfurization and demagnesification reactions. Three spray layers are set up with a spacing of 1.5m between layers. The treated flue gas is sulfur-containing flue gas that undergoes a single-stage rotation and absorption process. The oxygen concentration in the sulfur-containing flue gas is 5%, and the SO2 concentration is 1500 mg / m³. 3 The flue gas volume is 10000m³ 3 / h; the empty tower gas velocity is 2m / s, and the liquid-to-gas ratio is 9L / m 3 The reaction temperature was 25℃, and the measured SO2 removal rate was 99.2%.

[0060] (3) The reacted phosphate rock slurry is dewatered, and the dewatered residue is used as the wet phosphoric acid process. Based on this principle, the magnesium leaching rate can reach 75.3%, and the PO4 leaching rate can also be increased. 3- The leaching rate was 73.9%.

[0061] (4) The dehydrated liquid is sent to the magnesium recovery workshop, and calcium hydroxide is added to make the pH of the supernatant 8.0-8.5. The supernatant and solid are separated, and the solid is further processed.

[0062] (5) Add excess calcium hydroxide to the supernatant, then remove impurities from the precipitate, purify it, dehydrate and dry it to obtain a solid with a magnesium hydroxide content of 84.5%.

[0063] A comparison of Examples 1 and 1-3 shows that zinc sulfate and disodium ethylenediaminetetraacetate (EDTA) work synergistically to increase the leaching of magnesium and phosphorus and the content of magnesium hydroxide in the solid. Zinc sulfate can separate calcium fluorophosphate (Ca5(PO4)3F) and magnesium calcium carbonate (CaMg(CO3)2) from phosphate rock. However, the sulfate ions generated from sulfur dioxide react with these two substances to produce calcium sulfate (CaSO4·2H2O), which adheres to the particle surface, thereby inhibiting the leaching of magnesium and phosphorus. The addition of disodium ethylenediaminetetraacetate can occupy the active sites for calcium sulfate formation, thereby enhancing the leaching of magnesium and phosphorus.

[0064] Comparative Example 4

[0065] A method for recovering magnesium phosphorus resources from phosphate rock includes the following steps:

[0066] (1) Phosphate rock with a mass percentage of 99.6%, zinc sulfate with a mass percentage of 0.1%, and disodium ethylenediaminetetraacetate with a mass percentage of 0.3% were ground to prepare a phosphate rock slurry with a solid-liquid mass ratio of 25%.

[0067] (2) Phosphate rock slurry, used as an absorbent, is pumped into a counter-current spray absorption tower via a circulating pump pipeline for desulfurization and demagnesification reactions. Three spray layers are set up with a spacing of 1.5m between layers. The treated flue gas is sulfur-containing flue gas that undergoes a single-stage rotation and absorption process. The oxygen concentration in the sulfur-containing flue gas is 5%, and the SO2 concentration is 1000 mg / m³. 3 The flue gas volume is 10000m³ 3 / h; the empty tower gas velocity is 2m / s, and the liquid-to-gas ratio is 9L / m 3 The reaction temperature was 25℃, and the measured SO2 removal rate was 97.9%.

[0068] (3) The reacted phosphate rock slurry is dewatered, and the dewatered residue is used as raw material for the wet phosphoric acid process. The magnesium leaching rate can reach 95.5%, and PO4... 3- The leaching rate was 96.1%.

[0069] (4) The liquid obtained by dehydration is sent to the magnesium recovery workshop, excess calcium hydroxide is added, and then the precipitate is purified, dehydrated and dried to obtain a solid with a magnesium hydroxide content of 85.0%.

[0070] Compared with Comparative Example 4 and Example 1, the present invention uses a two-stage neutralization method, which can overcome the situation where the precipitate obtained by single-stage neutralization contains a large number of impurities, resulting in a low magnesium hydroxide content.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for recovering magnesium and phosphorus resources from phosphate rock, characterized in that, Includes the following steps: (1) Phosphate ore, zinc sulfate and disodium ethylenediaminetetraacetate are ground to prepare phosphate slurry; (2) The phosphate rock slurry is used as an absorbent to enter the spray absorption tower to absorb the sulfur-containing flue gas in a one-turn-one-absorption process for desulfurization and demagnesification reaction, and the reacted phosphate rock slurry is obtained; wherein, the phosphate rock slurry in the spray absorption tower absorbs the sulfur-containing flue gas in a countercurrent absorption manner. (3) Dewater the reacted phosphate rock slurry, and the resulting residue is obtained from the dewatered residue. (4) Add calcium hydroxide to the dehydrated liquid to make the pH of the supernatant 8.0-8.5, centrifuge and take the supernatant, add calcium hydroxide to the supernatant to obtain the precipitate as magnesium hydroxide product.

2. The method for recovering magnesium and phosphorus resources from phosphate rock as described in claim 1, characterized in that, The total mass of the phosphate rock, zinc sulfate, and disodium ethylenediaminetetraacetate contains 0.1-0.3% zinc sulfate and 0.2-0.5% disodium ethylenediaminetetraacetate.

3. The method for recovering magnesium and phosphorus resources from phosphate rock as described in claim 1, characterized in that, In step (1), the solid-liquid ratio of the phosphate rock slurry is 25-40%.

4. The method for recovering magnesium and phosphorus resources from phosphate rock as described in claim 1, characterized in that, In step (2), the spray layer of the spray absorption tower is set with 3 layers and the layer spacing is 1.5m.

5. The method for recovering magnesium and phosphorus resources from phosphate rock as described in claim 1, characterized in that, In step (2), the temperature of the spray absorption tower is 25-45℃; the gas flow rate is 0.5-3m / s; the gas includes sulfur-containing flue gas and oxygen, with an oxygen content of 5-20%; and the liquid-to-gas ratio is 9-10L / m³. 3 .

6. The method for recovering magnesium and phosphorus resources from phosphate rock as described in claim 1, characterized in that, In step (2), the SO2 concentration in the sulfur-containing flue gas is 1000-5000 mg / m³. 3 The flue gas volume is 10,000-30,000 m³. 3 / h.

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