Method for preparing iron phosphate from yellow phosphorus by-product

Abstract

The invention discloses a method for preparing iron phosphate from yellow phosphorus by-products, which comprises the following steps: (1) placing 0.074 mm phosphorite powder accounting for 70% or more in a suspension roaster, and roasting at 300-600 DEG C in the presence of air to obtain roasted sand and P2O5 gas; (2) spraying and stirring P2O5 furnace gas to obtain a phosphoric acid solution; (3) mixing the roasted product with a leaching aid and the prepared phosphoric acid, heating, stirring and leaching, and carrying out solid-liquid separation 8-12 hours later to obtain a leaching solution containing iron and phosphorus; (4) adjusting the pH value of the leachate to obtain hydrated iron phosphate precipitate; and (5) calcining the precipitate at high temperature to obtain finished iron phosphate. Phosphate is used as a leaching aid, introduction of impurity elements is reduced, the suspension roaster is used for roasting, the roasting efficiency is high, and the roasting temperature is lower than that of conventional roasting; the technological process is simple, the yellow phosphorus by-product ferrophosphorus can be efficiently utilized, and the purposes of saving resources, saving energy and reducing emission can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of resource utilization of phosphorus chemical byproducts, and specifically relates to a method for preparing ferric phosphate from yellow phosphorus byproducts. Background Art

[0002] In recent years, due to the rapid development of the new energy vehicle industry, the demand for raw materials for the production of lithium iron phosphate has continued to increase. It is necessary to develop a new idea for the preparation of iron phosphate. Iron phosphate is mainly prepared by adding a phosphorus source to an iron-containing solution. Therefore, finding a suitable raw material can optimize the preparation process of iron phosphate. Ferrophosphorus is a by-product of the yellow phosphorus industry. For every ton of yellow phosphorus produced, 0.1-0.2 tons of ferrophosphorus are produced. my country's annual output of ferrophosphorus is about 300,000 tons. The main components of ferrophosphorus are FeP and Fe 2 The Fe content of ferrophosphorus is above 60%, and the P content is above 20%. It is cheap, non-toxic and harmless, and is a high-quality raw material for preparing ferrophosphate. Using ferrophosphorus slag as raw material can solve the problem of ferrophosphorus storage in yellow phosphorus plants and improve the utilization rate of phosphate rock resources.

[0003] Some people have done relevant work on the use of ferrophosphorus to prepare ferric phosphate. For example, CN108101014 discloses a method for preparing ferric phosphate using ferrophosphorus slag produced as a byproduct of yellow phosphorus. The method comprises crushing the ferrophosphorus slag and adding phosphoric acid to react with it to generate Fe(HzPO4)2, then adding an oxidant to oxidize it to generate ferric phosphate precipitate, filtering, drying, and calcining to obtain the finished ferric phosphate. This method has the problems of directly using phosphoric acid to dissolve ferrophosphorus, slow dissolution speed, and low dissolution rate. CN107792840B uses potassium chlorate acid solution to oxidize and leach ferrophosphorus to obtain an aqueous solution containing iron and phosphate. The leached and separated aqueous solution is purified to remove impurity elements, and the pH is adjusted to neutral with an alkaline solution to obtain a solid precipitate. The solid precipitate is slurried with water and the pH is reversely adjusted to 1-2 with a phosphoric acid solution to obtain a solid precipitate. After washing, drying and calcining, ferrophosphate is obtained. The method has a complex process of adjusting the solution pH twice. CN114620697A uses nitric acid to dissolve ferrophosphorus to obtain a ferrophosphorus solution, and then adds ferric nitrate, phosphoric acid and ammonia water to adjust the pH to 1-1.5 to obtain a dihydrate ferrophosphate slurry. The slurry is washed to obtain a dihydrate ferrophosphate residue, and the residue is dehydrated and then calcined at high temperature to obtain a finished ferrophosphate. This method uses nitric acid to dissolve, which will produce toxic nitrogen dioxide gas and introduce nitrogen into the solution system.

[0004] The invention directly uses ferrophosphorus as raw material and performs suspended oxidation roasting, with fast roasting speed and low roasting temperature. Phosphoric acid solution is prepared by furnace gas, and roasted sand is dissolved by the prepared phosphoric acid solution, and only a small amount of additional acid solution needs to be added. In addition, the pH value of the solution only needs to be adjusted once during the preparation process, the process flow is simple, and the utilization rate of ferrophosphorus is high. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing ferric phosphate from yellow phosphorus byproduct, so as to solve the problem of utilization of iron and phosphorus elements in ferrophosphorus.

[0006] The present invention provides a process route, which converts ferrophosphorus into iron oxide and phosphorus oxide by roasting, and transfers iron and phosphorus elements to the liquid phase by acid leaching with the addition of a leaching aid to achieve iron and phosphorus recovery. The process has the advantages of low cost, simple process, environmental protection, and easy to scale up.

[0007] To achieve the above object, the present invention provides a method for preparing ferric phosphate from yellow phosphorus byproduct, characterized in that it comprises the following steps: Step 1, crushing and grinding the yellow phosphorus by-product to obtain yellow phosphorus by-product phosphotyrite powder; Step 2: roasting the phosphate ore powder to obtain roasted sand and P 2 O 5 furnace gas; Step 3: P 2 O 5 The furnace gas is sprayed and stirred to obtain a phosphoric acid solution; Step 4: Mix the roasted sand and the leaching aid and add them to the phosphoric acid solution prepared in step 3, heat and stir, and separate the solid and liquid to obtain an iron-phosphorus leaching solution; Step 5: Add an alkaline solution to the iron-phosphorus leaching solution in step 3 to adjust the pH to obtain FePO 4 ∙2H 2 O precipitation; take the precipitate, dry and calcine to obtain the finished product FePO 4 .

[0008] Preferably, the ferrophosphorus is crushed and ground to -0.074 mm, accounting for more than 70%, to obtain ferrophosphorus ore powder.

[0009] Preferably, the phosphate ore powder is added into the suspension roasting furnace from the side. During the roasting process, hot air is blown into the bottom of the furnace to oxidize and roast the phosphate ore powder in the furnace. The temperature of the hot air is 150-200°C and the flow rate of the hot air is 3-10m 3 / h, roasting temperature 300℃-600℃. After the air is blown in, the mineral powder is in a turbulent state in the furnace.

[0010] Preferably, the leaching aid is one of sodium tripolyphosphate and sodium hexametaphosphate, and the amount used is 5wt% to 15wt% of the total amount of the leached mineral.

[0011] Preferably, the mass concentration of the phosphoric acid solution in step 4 is 40%-60%.

[0012] Further preferably, in the step 4, the leaching temperature is 85-95°C, the leaching time is 4-8h, the stirring speed is 300-450 r / min, and in the step 5, the pH of the iron-phosphorus leaching solution is 1-4 and the calcination temperature is 450°C-650°C.

[0013] Positive effects of the present invention: The invention uses ferrophosphorus as a raw material to prepare ferric phosphate, effectively utilizes waste resources generated in the production process of yellow phosphorus, has a simple process flow and low production cost.

[0014] The recovery of iron and phosphorus in ferrophosphorus is achieved by oxidation roasting and leaching in a suspension roasting furnace. The inner wall of the suspension roasting furnace is set to a smooth surface, such as a graphite surface. The smooth graphite surface can achieve a turbulent state of micropowder particles during the suspension calcination process. The addition of a phosphate leaching aid during the leaching process improves the leaching rate of ferrophosphorus. DETAILED DESCRIPTION

[0015] The specific embodiments further explain the technical solution of the present invention. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The protection scope of the present invention shall be subject to the contents recorded in the claims. Any modification or replacement of the technical solution of the present invention made by those skilled in the art without creative work shall fall within the protection scope of the present invention.

[0016] Example 1 Step 1: crush and grind the ferrophosphorus to -0.074mm, accounting for 78%, to obtain ferrophosphorus ore powder, weigh 50g.

[0017] Step 2: Add the mineral powder into the suspension roasting furnace from the side and add 10m from the bottom of the furnace. 3 / h, blow hot air preheated to 150℃ to make the mineral powder in a turbulent state, and roast it at 350℃ to obtain roasted sand and P 2 O 5 Furnace gas.

[0018] Step 3: P 2 O 5 The phosphoric acid solution is obtained by spraying with furnace gas and stirring.

[0019] Step 4: Take 10g of roasted sand and mix it with 0.5g of sodium tripolyphosphate, then add it to the phosphoric acid prepared in step 3, where the mass of phosphoric acid is 100g, the temperature is 85°C, the stirring speed is 350rpm, and the stirring is carried out for 2h, and the solid-liquid separation is performed to obtain the iron-phosphorus leaching solution.

[0020] Step 5: Add sodium hydroxide solution to the iron-phosphorus leaching solution in step 3 to adjust the pH to 1.1 to obtain FePO 4 ∙2H 2O precipitation; the precipitate was dried and calcined at 500°C in a muffle furnace to obtain the finished product FePO 4 .

[0021] In this embodiment, the ferrophosphorus dissolution rate is 88.5%, the iron leaching rate is 92.1%, and the phosphorus leaching rate is 89.2%.

[0022] Example 2 Step 1: crush and grind the ferrophosphorus to -0.074mm, accounting for 78%, to obtain ferrophosphorus ore powder, weigh 50g.

[0023] Step 2: Add the mineral powder into the suspension roasting furnace from the side and add 8m from the bottom of the furnace. 3 / h, hot air preheated to 200℃ is blown into the ore powder to make it in a turbulent state, and roasted at 400℃ to obtain roasted sand and P 2 O 5 Furnace gas.

[0024] Step 3: P 2 O 5 The phosphoric acid solution is obtained by spraying with furnace gas and stirring.

[0025] Step 4: Take 10g of roasted sand and 1g of sodium tripolyphosphate, mix them and add them to the phosphoric acid prepared in step 3, where the mass of phosphoric acid is 200g, the temperature is 85°C, the stirring speed is 350rpm, and the stirring is carried out for 3h, and the solid-liquid separation is performed to obtain the iron-phosphorus leaching solution.

[0026] Step 5: Add sodium hydroxide solution to the iron-phosphorus leaching solution in step 3 to adjust the pH to 1.2 to obtain FePO 4 ∙2H 2 O precipitation; the precipitate was dried and calcined at 500°C in a muffle furnace to obtain the finished product FePO 4 .

[0027] In this embodiment, the ferrophosphorus dissolution rate is 95.3%, the iron leaching rate is 90.8%, and the phosphorus leaching rate is 92.7%.

[0028] Example 3 Step 1: crush and grind the ferrophosphorus to -0.074mm, accounting for 78%, to obtain ferrophosphorus ore powder, weigh 50g.

[0029] Step 2: Add the mineral powder into the suspension roasting furnace from the side and add 8m from the bottom of the furnace. 3 / h, hot air preheated to 120℃ is blown into the ore powder to make it in a turbulent state, and roasted at 400℃ to obtain roasted sand and P 2 O 5 Furnace gas.

[0030] Step 3: P 2 O 5 The phosphoric acid solution is obtained by spraying with furnace gas and stirring.

[0031] Step 4: Take 10g of roasted sand and 1g of sodium hexametaphosphate, mix them and add them to the phosphoric acid prepared in step 3, where the mass of phosphoric acid is 100g, the temperature is 85°C, the stirring speed is 400rpm, and the stirring is carried out for 3h, and the solid-liquid separation is performed to obtain the iron-phosphorus leaching solution.

[0032] Step 5: Add sodium hydroxide solution to the iron-phosphorus leaching solution in step 3 to adjust the pH to 1.1 to obtain FePO 4 ∙2H 2 O precipitation; the precipitate was dried and calcined at 500°C in a muffle furnace to obtain the finished product FePO 4 .

[0033] In this embodiment, the ferrophosphorus dissolution rate is 94.2%, the iron leaching rate is 89.3%, and the phosphorus leaching rate is 90.1%.

[0034] Example 4 Step 1: crush and grind the ferrophosphorus to -0.074mm, accounting for 78%, to obtain ferrophosphorus ore powder, weigh 50g.

[0035] Step 2: Add the mineral powder into the suspension roasting furnace from the side and add 5m from the bottom of the furnace. 3 / h, hot air preheated to 200℃ is blown into the ore powder to make it in a turbulent state, and roasted at 400℃ to obtain roasted sand and P 2 O 5 Furnace gas.

[0036] Step 3: P 2 O 5 The phosphoric acid solution is obtained by spraying with furnace gas and stirring.

[0037] Step 4: Take 10g of roasted sand and 1.5g of sodium tripolyphosphate, mix them and add them to the phosphoric acid solution prepared in step 3, where the mass of phosphoric acid is 400g, the temperature is 95°C, the stirring speed is 400rpm, and the stirring is carried out for 4h, and the solid-liquid separation is performed to obtain the iron-phosphorus leaching solution.

[0038] Step 5: Add sodium hydroxide solution to the iron-phosphorus leaching solution in step 3 to adjust the pH to 1.0 to obtain FePO 4 ∙2H 2 O precipitation; the precipitate was dried and calcined at 500°C in a muffle furnace to obtain the finished product FePO 4 .

[0039] In this embodiment, the ferrophosphorus dissolution rate is 98.8%, the iron leaching rate is 95.7%, and the phosphorus leaching rate is 92.4%.

[0040] Comparative Example 1 Step 1: crush and grind the ferrophosphorus to -0.074mm, accounting for 78%, to obtain ferrophosphorus ore powder, weigh 10g.

[0041] Step 2: Take 10g of phosphite powder and add it to 400g of 6mol / L phosphoric acid, stir at 95°C, 400rpm, and stir for 4h to obtain iron-phosphorus leaching solution by solid-liquid separation.

[0042] Step 3: Add sodium hydroxide solution to the iron-phosphorus leaching solution in step 3 to adjust the pH to 1.0 to obtain FePO4 ∙2H2O precipitate; take the precipitate, dry it, and calcine it at 500° C. in a muffle furnace to obtain the finished product FePO4.

[0043] In this comparative example, the phosphorus-iron dissolution rate was 27.8%, the iron leaching rate was 13.4%, and the phosphorus leaching rate was 9.2%.

[0044] Comparative Example 2 Step 1: crush and grind the ferrophosphorus to -0.074mm, accounting for 78%, to obtain ferrophosphorus ore powder, weigh 10g.

[0045] Step 2: Take 10g of phosphogysate powder and 1g of sodium tripolyphosphate, mix them and add them to 400g of 6mol / L phosphoric acid, stir at 95°C, 400rpm, stir for 4h, and separate the solid and liquid to obtain the iron-phosphorus leaching solution.

[0046] Step 3: Add sodium hydroxide solution to the iron-phosphorus leaching solution in step 2 to adjust the pH to 1.2 to obtain FePO 4 ∙2H 2 O precipitation; the precipitate was dried and calcined at 500°C in a muffle furnace to obtain the finished product FePO 4 .

[0047] In this comparative example, the phosphorus-iron dissolution rate was 42.1%, the iron leaching rate was 31.7%, and the phosphorus leaching rate was 24.6%.

[0048] Comparative Example 3 Step 1: crush and grind the ferrophosphorus to -0.074mm, accounting for 78%, to obtain ferrophosphorus ore powder, weigh 10g.

[0049] Step 2: Take 10g of mineral powder and 1g of sodium hexametaphosphate, mix them and place them in 400g of 6mol / L phosphoric acid, stir at 95°C, 400rpm, stir for 4h, and separate the solid and liquid to obtain iron-phosphorus leaching solution.

[0050] Step 3: Add sodium hydroxide solution to the iron-phosphorus leaching solution in step 2 to adjust the pH to 1.1 to obtain FePO 4 ∙2H 2 O precipitation; the precipitate was dried and calcined at 500°C in a muffle furnace to obtain the finished product FePO 4 .

[0051] In this comparative example, the phosphorus-iron dissolution rate was 45.1%, the iron leaching rate was 35.4%, and the phosphorus leaching rate was 27.7%.

[0052] Comparative Example 4 Step 1: crush and grind the ferrophosphorus to -0.074mm, accounting for 78%, to obtain ferrophosphorus ore powder, weigh 50g.

[0053] Step 2: Place the mineral powder in an electric heating roasting furnace, open one end to allow air to flow in normally, and roast at 400°C for 2 hours to obtain roasted sand and P 2 O 5 Furnace gas.

[0054] Step 3: P 2 O 5 The phosphoric acid solution is obtained by spraying with furnace gas and stirring.

[0055] Step 4: Take 10g of roasted sand and 1.5g of sodium tripolyphosphate, mix them and add them to the phosphoric acid solution prepared in step 3, where the mass of phosphoric acid is 400g, the temperature is 95°C, the stirring speed is 400rpm, and the stirring is carried out for 4h, and the solid-liquid separation is performed to obtain the iron-phosphorus leaching solution.

[0056] Step 5: Add sodium hydroxide solution to the iron-phosphorus leaching solution in step 3 to adjust the pH to 1 to obtain FePO 4 ∙2H 2 O precipitation; the precipitate was dried and calcined at 500°C in a muffle furnace to obtain the finished product FePO 4 .

[0057] In this example, the phosphorus-iron dissolution rate is 85.7%, the iron leaching rate is 76.6%, and the phosphorus leaching rate is 69.5%. Combined with the comparative examples and embodiments, the direct use of phosphoric acid to acid-leach powdered ferrophosphorus has a low ferrophosphorus dissolution rate, and the iron and phosphorus leaching rates are also relatively low. Comparative Examples 1, 2 and 3 show that the addition of a leaching aid can effectively improve the dissolution rate and leaching rate. The technical solution of the present application can basically complete the ferrophosphorus acid leaching by adding an leaching agent after oxidative roasting of the ferrophosphorus. In Example 4, the ferrophosphorus dissolution rate reaches 98.8%, the iron leaching rate is 95.7%, and the phosphorus leaching rate is 92.4%. The mass fraction of Fe in the finished ferrophosphate prepared in the embodiment is 36.48%, the mass fraction of P is 20.22%, the iron-phosphorus ratio is 1:1, and the appearance is white.

Claims

1. A method for preparing ferric phosphate from yellow phosphorus byproduct, characterized in that: The steps include: Step 1, crushing and grinding the yellow phosphorus by-product to obtain yellow phosphorus by-product phosphotyrite powder; Step 2, roasting the phosphorus iron ore powder to obtain roasted sand and P2O5 furnace gas; Step 3, spraying and stirring the P2O5 furnace gas to obtain a phosphoric acid solution; Step 4: Mix the roasted sand and the leaching aid and add them to the phosphoric acid solution prepared in step 3, heat and stir, and separate the solid and liquid to obtain an iron-phosphorus leaching solution; Step 5: add alkaline solution to the iron-phosphorus leaching solution in step 3 to adjust the pH to obtain FePO4 ∙2H2O precipitate; take the precipitate, dry and calcine to obtain the finished product FePO4.

2. The method for preparing ferric phosphate from yellow phosphorus byproduct according to claim 1, characterized in that: The yellow phosphorus by-product in step 1 has an iron content greater than 60% and a phosphorus content greater than 20%.

3. The method for preparing ferric phosphate from yellow phosphorus byproduct according to claim 1, characterized in that: In step 1, the yellow phosphorus by-product is crushed and ground to -0.074 mm, accounting for more than 70%.

4. The method for preparing ferric phosphate from yellow phosphorus byproduct according to claim 1, characterized in that: The calcination in step 2 is carried out in a suspension calcination furnace at a calcination temperature of 300-600°C.

5. The method for preparing ferric phosphate from yellow phosphorus byproduct according to claim 4, characterized in that: During the roasting process, when the temperature in the suspension roasting furnace reaches 300-600℃, hot air at 150-200℃ is blown into the bottom of the suspension roasting furnace with a flow rate of 3-10m 3 / h.

6. The method for preparing ferric phosphate from yellow phosphorus byproduct according to claim 1, characterized in that: The soaking aid in step 3 is one of phosphates or metaphosphates, preferably one of sodium tripolyphosphate and sodium hexametaphosphate; the amount of the soaking aid is 5wt% to 15wt% of the total amount of roasted sand.

7. The method for preparing ferric phosphate from yellow phosphorus byproduct according to claim 1, characterized in that: In the step 3, the leaching temperature is 85-95° C., the leaching time is 4-8 hours, and the stirring speed is 300-450 r / min.

8. The method for preparing ferric phosphate from yellow phosphorus byproduct according to claim 1, characterized in that: In step 3, the iron concentration of the iron-phosphorus leaching solution is 35-50 g / L, and the phosphorus concentration is 10-25 g / L; the pH of the leaching solution is adjusted to obtain FePO4 ∙2H2O precipitation.

9. The method for preparing ferric phosphate from yellow phosphorus byproduct according to claim 1, characterized in that: Step 4: The solution pH is 1-4, and the calcination temperature is 450°C-650°C.