Method for green treatment and recycling of vanadium precipitation wastewater

Abstract

The application discloses a kind of green treatment recycling methods of vanadium precipitation wastewater, belong to chemical industry.Green treatment recycling methods of vanadium precipitation wastewater include the following steps: removing metal impurity ions from sodium vanadium extraction vanadium precipitation wastewater, then adding calcium oxide and passing compressed air to remove ammonia, ammonia gas generated by ammonia removal is absorbed to obtain ammonium sulfate solution, calcium sulfate is calcined to generate calcium oxide and sulfur dioxide, and further prepared sulfuric acid, after ammonia removal, the wastewater is passed into carbon dioxide to generate sodium bicarbonate, evaporation concentration is obtained sodium bicarbonate solid and condensate, and the residual concentrated slurry returns evaporation concentration process.In the process flow, the generated sodium bicarbonate returns the roasting process, the condensate returns the leaching process, the ammonium sulfate solution returns the vanadium precipitation process, and the calcium oxide returns the ammonia removal process.The green treatment recycling method of vanadium precipitation wastewater has the advantages of low cost, convenient operation, resource recycling, etc., and realizes the green treatment of vanadium precipitation wastewater.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of chemical industry and relates to a green treatment and recycling method for vanadium precipitation wastewater. BACKGROUND

[0002] Vanadium is widely used in the fields of steel, chemical industry, aerospace, energy storage, medicine and the like. Vanadium extraction by sodiumization roasting of vanadium slag is a mainstream process for producing vanadium products. Sodium carbonate is used as an additive to roast at 750-850 DEG C, and then ammonium sulfate is added after water immersion and impurity removal, and sulfuric acid is used to adjust the pH value and heat to precipitate vanadium to obtain ammonium polyvanadate and then produce a series of vanadium products. The vanadium precipitation wastewater from sodiumization vanadium extraction is usually treated by reduction of vanadium and chromium, neutralization, filtration and evaporation concentration to obtain condensed water which is returned to the leaching process for recycling. This process produces a large amount of sodium sulfate which is difficult to recycle, and has become a bottleneck of the sodiumization vanadium extraction process. Therefore, green treatment and recycling of vanadium precipitation wastewater from the sodiumization vanadium extraction process have become a hot spot in the industry.

[0003] There are many methods for treating vanadium precipitation wastewater in the prior art. For example, CN 105384293A discloses a method for treating vanadium precipitation wastewater after impurity removal and ammonia removal; CN 105967233A relates to a method for reducing vanadium precipitation; and CN 107089749A provides a method for treating vanadium precipitation wastewater. However, the existing methods for treating vanadium precipitation wastewater have high cost and complex process, and therefore there is an urgent need to develop a low-cost method for treating vanadium precipitation wastewater. SUMMARY

[0004] The application solves the problem of high cost of treating vanadium precipitation wastewater in the prior art.

[0005] The application solves the problem of high cost of treating vanadium precipitation wastewater in the prior art.

[0006] a. Impurity removal treatment is performed on the vanadium precipitation wastewater, then calcium oxide is added and compressed air is introduced to remove ammonia to obtain ammonia gas, and then filtration is performed to obtain ammonia removal wastewater and calcium sulfate;

[0007] b. Further treatment method of the product in step a:

[0008] The ammonia gas is absorbed by a dilute sulfuric acid solution to obtain an ammonium sulfate solution;

[0009] The calcium sulfate is calcined to obtain calcium oxide and sulfur dioxide;

[0010] The ammonia removal wastewater is carbonized and then evaporated and concentrated to obtain sodium bicarbonate crystals and residual concentrated slurry;

[0011] c. Further treatment method of the product in step b:

[0012] The ammonium sulfate solution is recycled back to the vanadium precipitation process in sodium roasting vanadium extraction.

[0013] Calcium oxide is returned to step a for recycling;

[0014] Sulfur dioxide can be recycled in the impurity removal process of step a, or it can be recycled in the acid production system after being generated into sulfuric acid and then returned to the deammoniation process of step a.

[0015] Sodium bicarbonate crystals are recycled back to the roasting process in sodium roasting for vanadium extraction.

[0016] The remaining concentrated slurry is returned to the evaporation and concentration process for secondary evaporation and crystallization.

[0017] In step a above, the vanadium precipitation wastewater is wastewater generated from sodium roasting for vanadium extraction, and its main chemical components are V 0.1-0.8 g / L, Cr 0.5-2.5 g / L, Na 20-65 g / L, and SO42-0.5 g / L. 2- 50-150g / L, NH 4+ 3-15 g / L, Si 0.1-1.0 g / L, Ca 2+ 0.05-0.5 g / L, Mg 2+ 0.05-0.5 g / L, pH 1.6-2.5.

[0018] In step a above, the method for removing impurities is as follows: Add a reducing agent at a molar ratio of 1.0-1.5 eq of vanadium and chromium in the vanadium-precipitated wastewater and stir to react, controlling the V in the vanadium-precipitated wastewater after reduction. 5+ and Cr 6+ The concentration is <0.01g / L. Then add alkali solution to adjust the pH to 6-9 and filter.

[0019] Furthermore, the above-mentioned impurity removal method shall at least satisfy one of the following:

[0020] The reducing agent is at least one of sodium sulfite, sodium metabisulfite, and sulfur dioxide;

[0021] The alkaline solution is at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, ammonia, and urea.

[0022] The stirring reaction time is 30-90 minutes.

[0023] In step a above, calcium oxide is added to the vanadium-precipitated wastewater after impurity removal to adjust the pH of the wastewater to 10-12, and compressed air at 0.6-1.0 MPa is introduced to remove ammonia.

[0024] In step b above, a dilute sulfuric acid solution with a concentration of 10-25% is used to spray and absorb ammonia gas.

[0025] In step b, the calcium sulfate is calcined at 1000-1400 DEG C for 60-180 min.

[0026] In step b, the carbonization method is that the deamination wastewater is carbonized by carbon dioxide, and the pH of the wastewater after carbonization is controlled to be 7-9.

[0027] In step b, the evaporation concentration method is that the evaporation concentration is performed at 0.04-0.08 MPa negative pressure and 80-100 DEG C until the concentration of sodium bicarbonate in the wastewater after carbonization is 12-18 g / L, then the wastewater is transferred into a crystallizer and cooled to 20-50 DEG C, and after being kept for 2-6 h, centrifugal separation is performed.

[0028] Further, the condensed water discharged from the crystallizer is recycled to the leaching process in the sodium roasting vanadium extraction.

[0029] The method provided by the application is a complete vanadium precipitation wastewater treatment system, no new waste is generated in the treatment process, and all by-products can be recycled. DETAILED DESCRIPTION

[0030] The technical scheme of the application can be implemented in the following manner.

[0031] The method for green treatment and recycling of vanadium precipitation wastewater comprises the following steps.

[0032] The vanadium precipitation wastewater generated in sodium roasting vanadium extraction is neutralized by a reducing agent and an alkali liquor to remove metal impurity ions such as vanadium and chromium, calcium oxide is added and compressed air is introduced to remove ammonia, the ammonia generated in the ammonia removal is absorbed by a dilute sulfuric acid solution to obtain an ammonium sulfate solution, the calcium sulfate is calcined to generate calcium oxide and sulfur dioxide and further prepared into sulfuric acid, the wastewater after ammonia removal is introduced into carbon dioxide to generate sodium bicarbonate, evaporation concentration is performed to obtain sodium bicarbonate solids and condensed water, and the residual concentrated slurry is returned to the evaporation concentration process.

[0033] The vanadium precipitation wastewater is wastewater generated in sodium roasting vanadium extraction, and the main chemical components are V 0.1-0.8 g / L, Cr 0.5-2.5 g / L, Na 20-65 g / L, SO4 2- 50-150 g / L, NH 4+ 3-15 g / L, Si 0.1-1.0 g / L, Ca 2+ 0.05-0.5 g / L, Mg 2+0.05-0.5g / L, pH 1.6-2.5.

[0034] The vanadium precipitation wastewater reduction refers to adding one or more of sodium sulfite, sodium metabisulfite, sulfur dioxide, etc. according to 1.0-1.5 eq of vanadium and chromium molar quantity, stirring for 30-90 min, and controlling the concentration of pentavalent vanadium and hexavalent chromium ions in the reduced vanadium precipitation wastewater to be <0.01 g / L.

[0035] The vanadium precipitation wastewater neutralization refers to adding one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, ammonia water, urea, etc. to the reduced vanadium precipitation wastewater, and adjusting pH = 6-9.

[0036] The vanadium precipitation wastewater deamination refers to adding calcium oxide to the reduced and neutralized vanadium precipitation wastewater, controlling pH = 10-12, blowing off ammonia in the wastewater by blowing in compressed air at 0.6-1.0 MPa, and absorbing the generated ammonia gas by spraying 10%-25% dilute sulfuric acid solution to obtain an ammonium sulfate solution. Filtering to obtain deamination wastewater and calcium sulfate, calcining the calcium sulfate at 1000°C-1400°C for 60-180 min to obtain calcium oxide and sulfur dioxide, and returning the sulfur dioxide to the reduction process or to the acid making system to generate sulfuric acid and then return to the deamination system to absorb ammonia gas.

[0037] The vanadium precipitation wastewater carbonization refers to blowing in carbon dioxide into the deamination wastewater, controlling the pH of the carbonized wastewater to be 7-9, and converting sodium into sodium bicarbonate.

[0038] The vanadium precipitation wastewater evaporation concentration refers to evaporating the carbonized wastewater at 0.04-0.08 MPa negative pressure and 80°C-100°C, controlling the concentration of sodium bicarbonate to reach 12-18 g / L, transferring to a crystallizer to cool to 20°C-50°C, and keeping warm for 2-6 h. Centrifugal separation of sodium bicarbonate crystals, returning the separated concentrated slurry to the evaporation concentration system for secondary evaporation crystallization, and returning the generated sodium bicarbonate to the calcination process and the condensed water to the leaching process for recycling.

[0039] The technical solutions and effects of the present application are further described below through actual examples.

[0040] Example

[0041] Example 1

[0042] A 2L chemical composition is V 0.5g / L, Cr 1.5g / L, Na 28g / L, SO4 2- 50g / L, NH4 + 5g / L, Si 0.6g / L, Ca 2+ 0.5g / L, Mg 2+0.4g / L, pH=1.6 vanadium precipitation wastewater, the proportion of the reducing agent: vanadium, chromium molar ratio = 2:1 of sodium sulfite was added, stirring for 30 min to obtain the reduced wastewater, then sodium hydroxide was added to adjust pH=7.5, filtration to obtain vanadium chromium sludge and purified wastewater, then lime milk was added to the wastewater, pH=10-11 was controlled, and 0.8 MPa compressed air was used for stirring deamination for 6h, the generated ammonia gas was passed into 15% sulfuric acid solution for absorption; calcium sulfate and sodium hydroxide solution were obtained by filtration, carbon dioxide gas was passed into the solution for 1h, then evaporation concentration was carried out at 85-90℃ under 0.06 MPa negative pressure, when the concentration of sodium bicarbonate reached 20g / L, the slurry was transferred into the crystallizer for 3h, sodium bicarbonate crystals and concentrated solution were obtained by centrifugal separation. After drying, the sodium bicarbonate content was 99.2%, and the other indicators met the requirements of GB / T 1606-2008 standard.

[0043] Example 2

[0044] 2L chemical composition of V 0.5g / L, Cr 2.5g / L, Na 38g / L, SO4 2- 65g / L, NH4 + 8g / L, Si 1.0g / L, Ca 2+ 0.5g / L, Mg 2+ 0.4g / L, pH=1.8 vanadium precipitation wastewater, the proportion of the reducing agent: vanadium, chromium molar ratio = 1.5:1 of sodium sulfite was added, stirring for 60 min to obtain the reduced wastewater, then sodium carbonate was added to adjust pH=8.5, filtration to obtain vanadium chromium sludge and purified wastewater, then lime milk was added to the wastewater, pH=11-12 was controlled, and 0.6 MPa compressed air was used for stirring deamination for 12h, the generated ammonia gas was passed into 25% sulfuric acid solution for absorption; calcium sulfate and sodium hydroxide solution were obtained by filtration, carbon dioxide gas was passed into the solution for 4h, then evaporation concentration was carried out at 75-80℃ under 0.08 MPa negative pressure, when the concentration of sodium bicarbonate reached 25g / L, the slurry was transferred into the crystallizer for 5h, sodium bicarbonate crystals and concentrated solution were obtained by centrifugal separation. After drying, the sodium bicarbonate content was 99.5%, and the other indicators met the requirements of GB / T 1606-2008 standard.

Claims

1. A method for green treatment and recycling of vanadium precipitation wastewater, characterized in that The method comprises the following steps: a. Vanadium precipitation wastewater is subjected to impurity removal treatment, a reducing agent is added in an amount of 1.0-1.5 eq based on the molar amount of vanadium and chromium in the vanadium precipitation wastewater, and stirring reaction is performed, the concentration of V 5+ and Cr 6+ after reduction in the vanadium precipitation wastewater is controlled to be <0.01 g / L, lye is further added to adjust the pH to 6-9 and filtration is performed; then calcium oxide is added and compressed air is introduced to remove ammonia to obtain ammonia gas, and filtration is performed to obtain deamination wastewater and calcium sulfate; b. Further treatment method of the product in step a: ammonia is absorbed by dilute sulfuric acid solution to obtain an ammonium sulfate solution; calcium sulfate is calcined to obtain calcium oxide and sulfur dioxide; carbonization of the deamination wastewater is followed by evaporation and concentration to obtain sodium bicarbonate crystals and residual concentrated slurry; c. Further treatment method of the product in step b: the ammonium sulfate solution is recycled to the vanadium precipitation process in the sodium roasting vanadium extraction process; the calcium oxide is recycled to step a; the sulfur dioxide is returned to the reduction process or is introduced into an acid production system to generate sulfuric acid which is then returned to the deamination system to absorb ammonia; the sodium bicarbonate crystals are recycled to the calcination process in the sodium roasting vanadium extraction process; the residual concentrated slurry is returned to the evaporation and concentration process for secondary evaporation and crystallization, and is evaporated and concentrated to a sodium bicarbonate concentration of 12-18 g / L in the carbonized wastewater under a negative pressure of 0.04-0.08 MPa and at a temperature of 80-100 ℃, and is then transferred to a crystallizer to be cooled to 20-50 ℃, and is centrifuged after being kept at the temperature for 2-6 h; condensed water discharged from the crystallizer is recycled to the leaching process in the sodium roasting vanadium extraction process.

2. The method for green treatment and recycling of vanadium precipitation wastewater according to claim 1, characterized in that: In step a, the vanadium precipitation wastewater is the wastewater produced in the sodium roasting for extracting vanadium, and the main chemical components are V 0.1-0.8 g / L, Cr 0.5-2.5 g / L, Na 20-65 g / L, SO4 2- 50-150 g / L, NH 4+ 3-15 g / L, Si 0.1-1.0 g / L, Ca 2+ 0.05-0.5 g / L, Mg 2+ 0.05-0.5 g / L, and pH is 1.6-2.

5.

3. The method for green treatment and recycling of vanadium precipitation wastewater according to claim 1, characterized in that: At least one of the following is satisfied: The reducing agent is at least one of sodium sulfite, sodium metabisulfite and sulfur dioxide; The alkali solution is at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, ammonia water and urea; The stirring reaction time is 30-90 min.

4. The method for green treatment and recycling of vanadium precipitation wastewater according to claim 1, characterized in that: In step a, calcium oxide is added to the vanadium precipitation wastewater after impurity removal to adjust the pH of the wastewater to 10-12, and 0.6-1.0 MPa compressed air is introduced to remove ammonia.

5. The method for green treatment and recycling of vanadium precipitation wastewater according to claim 1, characterized in that: In step b, ammonia is absorbed by spraying a dilute sulfuric acid solution with a concentration of 10-25%.

6. The method for green treatment and recycling of vanadium precipitation wastewater according to claim 1, characterized in that: In step b, the calcium sulfate is calcined at 1000-1400 ℃ for 60-180 min.

7. The method for green treatment and recycling of vanadium precipitation wastewater according to claim 1, characterized in that: In step b, the carbonization method is as follows: the deamination wastewater is carbonized by introducing carbon dioxide, and the pH of the carbonized wastewater is controlled to be 7-9.