A process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater

Abstract

A process for obtaining low-arsenic yellow phosphorus from phosphorus-containing sewage, relating to the field of water pollution control and resource regeneration technology. It includes the following steps: step S1 filtration: filter the phosphorus-containing sewage to obtain dried filter residue and filtrate; step S2 detection: detect the content of P element in the filtrate; step S3 precipitation: add magnesium salt to the filtrate, mix evenly, let stand, filter to obtain residue and clear liquid; step S4 drying; step S5 granulation: add lime, coke powder and binder to the dried residue, mix and granulate to obtain mixed balls; step S6 sintering: sinter the mixed balls at 200-300°C to obtain pellets; step S7 decomposition: decompose the pellets at 1200-1350°C to obtain low-arsenic yellow phosphorus. This process for obtaining low-arsenic yellow phosphorus from phosphorus-containing sewage is energy-saving, environmentally friendly, and has high yellow phosphorus quality and conversion rate.

Description

Technical Field

[0001] The invention relates to the technical field of water pollution control and resource recycling, and in particular to a process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater. Background Art

[0002] Phosphorus is an important element of life and one of the main causes of eutrophication of water bodies. Although the global phosphate reserves are relatively abundant, it is undeniable that phosphate is a non-renewable resource and the distribution of phosphate resources is extremely uneven around the world, resulting in a shortage of phosphorus resources in many countries and regions.

[0003] With the increase of human activities, a large amount of phosphorus-containing domestic sewage and industrial wastewater are discharged into lakes, rivers and other water bodies, which increases the nutrients in the water bodies, causes abnormal reproduction of algae and aquatic plants in the water bodies, and causes eutrophication of the water bodies. Compared with industrial wastewater with clear composition, domestic wastewater and agricultural wastewater have complex compositions, containing organic matter, sulfate, phosphate, bicarbonate, sodium, potassium, calcium, aluminum, magnesium, etc. Reasonable disposal of such wastewater not only protects the environment, but also increases the access to resources.

[0004] Industrial yellow phosphorus products contain high arsenic content, generally 100ppm~300ppm, which is the most difficult impurity to remove in yellow phosphorus production. Arsenic is a toxic and harmful substance, and high arsenic content greatly reduces the value of yellow phosphorus products. Low arsenic yellow phosphorus: P4≥99.95%, As≤10ppm, mainly used as raw materials in food, medicine, electronics and other industrial sectors. In the food industry, it is used to produce various food additives; in the pharmaceutical industry, it is used as raw materials for drugs such as immunosuppressants, vasodilators, and brain metabolism-improving drugs; in the electronics industry, it is used as a raw material for electronic equipment and semiconductors; it is also used as a raw material for the manufacture of phosphides. Summary of the invention

[0005] The present invention aims to provide a method for recovering low-arsenic yellow phosphorus from phosphorus-containing wastewater. The method is energy-saving, environmentally friendly, and has high yellow phosphorus quality and conversion rate.

[0006] The present invention solves the technical problem by adopting the following technical solutions.

[0007] The present invention provides a process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater, characterized in that it comprises the following steps:

[0008] Step S1: filtration pressing: filtering the phosphorus-containing wastewater to obtain a dried filter residue and a filtrate;

[0009] Preferably, the filter pressing is carried out at a pressure difference of 0.6-1.0 MPa.

[0010] Step S2: Detection: Detect the content of P element in the filtrate; use a traditional or independently developed method to detect the content of P element, and calculate the content of P element in the filtrate in mol / L.

[0011] Step S3 precipitation: adding magnesium salt to the filtrate, wherein the molar ratio of the P element in the filtrate to the magnesium element in the magnesium salt is 1:(0.9-1.1), mixing evenly, standing, and filtering to obtain a slag and a clear liquid; adding magnesium salt to the filtrate can cause a precipitation reaction to generate a slag and a clear liquid, thereby precipitating the P element.

[0012] Preferably, after mixing, add ferric oxide and stir.Adding ferric oxide after the reaction can not only reduce the acidity of acidic sewage, affect the balance of reaction, increase the precipitation amount of P element, and accelerate the formation of struvite crystals.And, after adjusting pH, it is also possible to make the solution system slowly generate iron phosphate, and iron phosphate further induces struvite crystals to become larger.Finally, the struvite crystals heavy in the solution are grown large enough to facilitate subsequent filtration.If ferric oxide is not added, struvite crystals are relatively small, flocculent, difficult to filter, time-consuming, and energy-consuming.

[0013] Preferably, the amount of ferric oxide used is 0.5‰ to 2‰ of the total mass of the sewage. When the amount added is within this range, the size and amount of struvite crystals are good, and the amount of ferric oxide used is small.

[0014] Preferably, the stirring is for 20-40 minutes, and the standing is for 30-60 minutes. During the stirring and standing process, the struvite crystals further grow.

[0015] Step S4: drying: drying the struvite;

[0016] Preferably, the struvite is dried to a moisture content of less than 5%. Drying the struvite to a moisture content of less than 5% facilitates the subsequent granulation step, while too much moisture makes it inconvenient to form spheres.

[0017] Step S5: Granulation: Add lime, coke powder and binder to the dried struvite and mix them to make mixed balls; mix the above raw materials to make mixed balls, and the mixed balls undergo chemical changes in the subsequent decomposition reaction. The spherical design can better facilitate the removal of phosphorus vapor during the decomposition process, and can accelerate the reaction rate and reaction conversion rate.

[0018] Preferably, in parts by weight, the dried struvite is 1 part, the lime is 0.04-0.15 parts, the coke powder is 0.1-0.3 parts, and the binder is 0.015-0.040 parts. Granulation according to the above raw material ratio can ensure full reaction without wasting raw materials.

[0019] Preferably, the adhesive is one or more of humic acid, starch or lignin. The above adhesive is easy to decompose and has good adhesion to struvite, lime and coke powder.

[0020] Step S6: sintering: sintering the mixed balls at 200-300° C. to obtain balls;

[0021] Step S7: Decomposition: Decomposing the pellets at 1200-1350° C. to obtain low-arsenic yellow phosphorus. At this temperature, phosphorus vapor fully overflows.

[0022] Preferably, the sintering in step S6 and the decomposition in step S7 are both performed for 1-2 hours. Phosphorus vapor fully overflows during the above time.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Protect the environment. Utilizing wastewater as a resource can reduce environmental pollution and contribute to green, circular and sustainable development.

[0025] (2) Protect resources. Recycle phosphorus in wastewater, reduce the exploitation of non-renewable phosphate resources, and protect phosphate resources.

[0026] (3) High primary phosphorus recovery rate and high conversion rate. When the technical solution of the present invention produces low-arsenic yellow phosphorus, there is less mud phosphorus, and the primary recovery rate of yellow phosphorus (i.e., excluding phosphorus recovered from mud phosphorus) is as high as more than 90%, which is higher than the recovery rate of more than 80% of phosphorus in traditional electric furnaces.

[0027] (4) Low power consumption, reducing the production cost of yellow phosphorus. The melting point of the incineration ash obtained by the technical solution of the present invention is relatively low - about 1200~1350℃, while the reduction temperature of the traditional electric furnace method for producing yellow phosphorus is 1350℃~1450℃, which can reduce the reaction temperature of the yellow phosphorus electric furnace and thus reduce power consumption. In addition, since the coke powder is granulated together, it is evenly dispersed, the reduction speed is accelerated, the reaction conversion rate is high, and the power consumption per ton of yellow phosphorus is low.

[0028] (5) The quality of yellow phosphorus products is high. High value-added low-arsenic yellow phosphorus can be directly obtained, and its As content is less than 10ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 This is a schematic diagram of the process flow of Example 1 of the present invention. DETAILED DESCRIPTION

[0031] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. If no specific conditions are specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer shall be followed.

[0032] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The embodiments of the present invention include but are not limited to the following embodiments. Example

[0033] This embodiment provides a process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater, which specifically includes the following steps:

[0034] Step S1: filter pressing: filter the phosphorus-containing wastewater under a pressure difference of 0.8 MPa to obtain a dried filter residue and a filtrate;

[0035] Step S2: Detection: The content of P element in the filtrate of the filter press in step S1 is detected by a conventional method, and the content of P element in the filtrate is calculated in mol / L.

[0036] Step S3 precipitation: adding magnesium salt to the above filtrate, wherein the molar ratio of the P element in the filtrate to the magnesium element in the magnesium salt is 1:1, after mixing evenly, adding 1.2‰ of the total mass of the sewage, and stirring for 30 minutes, standing for 45 minutes, filtering to obtain struvite and clear liquid;

[0037] Step S4: Drying: Dry the struvite obtained by precipitation in step S3 to a moisture content of 3%.

[0038] Step S5: Granulation: 0.1 ton of lime, 0.2 ton of coke powder and 30 kg of binder are added to 1 ton of dried struvite and then granulated to obtain mixed balls. In this embodiment, the binder is 10 kg each of humic acid, starch or lignin.

[0039] Step S6: sintering: sintering the mixed balls at 250°C for 1.5 hours to obtain pellets;

[0040] Step S7: Decomposition: Decompose the pellets at 1300°C for 1.5 hours to obtain low-arsenic yellow phosphorus. In this embodiment, an electric furnace is used for decomposition. Example

[0041] This embodiment provides a process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater, which specifically includes the following steps:

[0042] Step S1: filter pressing: filter the phosphorus-containing wastewater under a pressure difference of 0.8 MPa to obtain a dried filter residue and a filtrate;

[0043] Step S2: Detection: The content of P element in the filtrate of the filter press in step S1 is detected by a conventional method, and the content of P element in the filtrate is calculated in mol / L.

[0044] Step S3 precipitation: adding magnesium salt to the above filtrate, wherein the molar ratio of the P element in the filtrate to the magnesium element in the magnesium salt is 1:1, mixing evenly, standing for 45 minutes, and filtering to obtain struvite and a clear liquid;

[0045] Step S4: Drying: Dry the struvite obtained by precipitation in step S3 to a moisture content of 3%.

[0046] Step S5: Granulation: 0.1 ton of lime, 0.2 ton of coke powder and 30 kg of binder are added to 1 ton of dried struvite and mixed and then granulated to obtain mixed balls. In this embodiment, the binder is 10 kg each of humic acid, starch or lignin. In other embodiments, the binder can also be one or two of humic acid, starch or lignin, and the three can be in other proportions.

[0047] Step S6: sintering: sintering the mixed balls at 250°C for 1.5 hours to obtain pellets;

[0048] Step S7: decomposition: decompose the pellets at 1300°C for 1.5h to obtain low-arsenic yellow phosphorus. Example

[0049] This embodiment provides a process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater, which specifically includes the following steps:

[0050] Step S1: filter pressing: filter the phosphorus-containing wastewater under a pressure difference of 0.6 MPa to obtain a dried filter residue and a filtrate;

[0051] Step S2: Detection: The content of P element in the filtrate of the filter press in step S1 is detected by a conventional method, and the content of P element in the filtrate is calculated in mol / L.

[0052] Step S3 precipitation: adding magnesium salt to the above filtrate, wherein the molar ratio of the P element in the filtrate to the magnesium element in the magnesium salt is 1:0.9, after mixing evenly, adding 0.5‰ of the total mass of the sewage ferric oxide, stirring for 40 minutes, standing for 30 minutes, filtering to obtain struvite and clear liquid;

[0053] Step S4: Drying: Dry the struvite obtained by precipitation in step S3 to a moisture content of 4%.

[0054] Step S5: Granulation: 0.04 tons of lime, 0.3 tons of coke powder and 15 kg of binder are added to 1 ton of dried struvite and then granulated to obtain mixed balls. It should be noted that the binder in this embodiment is humic acid, and in other embodiments, it can also be starch or lignin.

[0055] Step S6: sintering: sintering the mixed balls at 200°C for 2 hours to obtain pellets;

[0056] Step S7: Decomposition: Decompose the pellets at 1350° C. for 1 h to obtain low-arsenic yellow phosphorus. Example

[0057] This embodiment provides a process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater, which specifically includes the following steps:

[0058] Step S1: filtration: filtering the phosphorus-containing wastewater under a pressure difference of 1 MPa to obtain a dried filter residue and a filtrate;

[0059] Step S2: Detection: The content of P element in the filtrate of the filter press in step S1 is detected by a conventional method, and the content of P element in the filtrate is calculated in mol / L.

[0060] Step S3 precipitation: adding magnesium salt to the above filtrate, wherein the molar ratio of the P element in the filtrate to the magnesium element in the magnesium salt is 1:1.1, after mixing evenly, adding ferric oxide of 2‰ of the total mass of the sewage, stirring for 20 minutes, standing for 60 minutes, and filtering to obtain struvite and clear liquid;

[0061] Step S4: Drying: Dry the struvite obtained by precipitation in step S3 to a moisture content of 2%.

[0062] Step S5: Granulation: 0.15 tons of lime, 0.1 tons of coke powder and 40 kg of binder are added to 1 ton of dried struvite and then granulated to obtain mixed balls. In this embodiment, the binder is starch.

[0063] Step S6: sintering: sintering the mixed balls at 300°C for 1 hour to obtain balls;

[0064] Step S7: decomposition: decompose the pellets at 1200°C for 2 hours to obtain low-arsenic yellow phosphorus.

[0065] In summary, the process of obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater according to the embodiment of the present invention can utilize wastewater resources, reduce environmental pollution, and contribute to the sustainable development of green circulation. And the phosphorus in the wastewater is recycled, the exploitation of non-renewable phosphate resources is reduced, and the phosphate resources are protected. The process of the present invention has a high phosphorus recovery rate and a high conversion rate. When producing low-arsenic yellow phosphorus, there is less mud phosphorus, and the yellow phosphorus recovery rate is as high as more than 90%, which is higher than the traditional yellow phosphorus synthesis method. Compared with the traditional yellow phosphorus synthesis process, the reaction temperature of the yellow phosphorus electric furnace can be reduced, thereby reducing power consumption. In addition, since the coke powder is granulated together, it is evenly dispersed, the reduction speed is accelerated, the reaction conversion rate is high, and the power consumption per ton of yellow phosphorus is low. High value-added low-arsenic yellow phosphorus can be directly obtained, and its As content is less than 10ppm.

[0066] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater, characterized in that: It includes the following steps: step S1 filtration: filtration of phosphorus-containing wastewater to obtain dried filter residue and filtrate; Step S2: detecting the content of P element in the filtrate; Step S3 precipitation: adding magnesium salt to the filtrate, wherein the molar ratio of the P element in the filtrate to the magnesium element in the magnesium salt is 1:(0.9-1.1), mixing evenly, standing, and filtering to obtain a slag and a clear liquid; Step S4: drying: drying the slag; Step S5: Granulation: adding lime, coke powder and binder to the dried slag, mixing and granulating to obtain mixed balls; Step S6: sintering: sintering the mixed balls at 200-300° C. to obtain balls; Step S7: decomposing the pellets at 1200-1350° C. to obtain low-arsenic yellow phosphorus; In step S3, after mixing evenly, add ferric oxide and stir; In step S3, the amount of ferric oxide used is 0.5‰~2‰ of the total mass of the sewage; In the step S5, the dried slag is 1 part, the lime is 0.04-0.15 parts, the coke powder is 0.1-0.3 parts, and the binder is 0.015-0.040 parts by weight.

2. The process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater according to claim 1, characterized in that: In the step S3, the stirring is for 20-40 min, and the standing is for 30-60 min.

3. The process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater according to claim 1, characterized in that: In the step S5, the adhesive is one or more of humic acid, starch or lignin.

4. The process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater according to claim 1, characterized in that: In the step S1, the filter pressing is performed under a pressure difference of 0.6-1.0 MPa.

5. The process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater according to claim 1, characterized in that: In the step S4, the slag is dried until the moisture content is less than 5%.

6. The process for obtaining low-arsenic yellow phosphorus from phosphorus-containing wastewater according to claim 1, characterized in that: The sintering in step S6 and the decomposition in step S7 both take 1-2 hours.

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