Advanced treatment process for sodium roasting vanadium extraction wastewater

Abstract

The invention relates to the technical field of sodium-method roasting vanadium extraction wastewater treatment, in particular to a deep treatment process of sodium-method roasting vanadium extraction wastewater, which comprises pretreatment, pH adjustment, ferrous sulfate addition, compressed air oxidation, flocculant addition and solid-liquid separation. According to the method, the content of TV and TCr (all vanadium and all chromium) in the wastewater can be effectively treated to be lower than 1 mg / L, the color of the wastewater becomes clear and transparent, colored solid components cannot be separated out even if the wastewater is continuously evaporated to be completely crystallized, the ferrous sulfate and aeration oxidation process is adopted, the treatment cost is reduced, the process feasibility is improved, and the method is suitable for industrial production. The wastewater can be deeply treated by most enterprises under the condition that the investment is not increased too much, and the method has generalization performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium roasting vanadium extraction wastewater treatment, and particularly relates to a deep treatment process for sodium roasting vanadium extraction wastewater. Background Art

[0002] Vanadium extraction wastewater treatment refers to the technology of removing pollution elements such as vanadium, chromium, and ammonia nitrogen from vanadium-containing wastewater generated in the industrial production process, and realizing the resource recovery and utilization of vanadium, chromium, nitrate, salt, etc. as much as possible. In industries such as steel, chemical engineering, and metallurgy, vanadium, as an important metal element, is widely used in the production of high-strength steel, alloys, and chemical catalysts. However, these industrial processes will produce a large amount of high-salt vanadium-containing wastewater, which may cause serious environmental pollution if not treated.

[0003] At present, vanadium extraction wastewater treatment technologies mainly include chemical precipitation method, ion exchange method, adsorption method, membrane separation technology, biological treatment method, etc. The chemical precipitation method adds a precipitant to the wastewater to form a precipitate of vanadium in the wastewater and then separates it, which is a widely used treatment method. The ion exchange method uses ion exchange resin to adsorb vanadium ions in the wastewater to achieve the recovery of vanadium and the purification of wastewater. The adsorption method usually uses porous materials such as activated carbon to adsorb vanadium in the wastewater, which has the advantages of simple operation and low cost. The membrane separation technology removes vanadium and other harmful substances in the wastewater through the selective permeability of the membrane. The biological treatment method uses the biochemical action of microorganisms to remove vanadium in the wastewater, which is an environmentally friendly treatment method.

[0004] Although the existing vanadium extraction wastewater treatment technologies have developed to a certain extent, they still face some challenges, such as treatment efficiency, cost control, secondary pollution and other problems. In addition, with the increasingly strict environmental protection regulations and the improvement of the awareness of resource recovery, developing more efficient, economical and environmentally friendly vanadium extraction wastewater treatment technologies has become an important direction for the development of the industry. Therefore, researching and developing new vanadium extraction wastewater treatment processes can not only meet the current environmental protection requirements, but also effectively recover vanadium resources, which has important social, economic and environmental benefits.

[0005] The main vanadium plants in China that adopt the "sodium roasting vanadium extraction process" (with an annual output of more than 10,000 tons of vanadium pentoxide), such as Pangang Vanadium, Chengyu Vanadium Titanium, and Hebei Chengde Steel, etc., the wastewater generated by their production lines is all high-salt and contains pollution elements such as vanadium, chromium, and ammonia nitrogen. To meet the "zero discharge" requirement of wastewater in the current environmental protection policy, the previous method of removing pollutants such as vanadium, chromium, and ammonia nitrogen from the wastewater and then transporting the high-salt wastewater to the factory for centralized treatment is no longer feasible. Each mainstream vanadium plant has added an evaporation crystallization system to further treat the high-salt wastewater. Through the evaporation concentration system, condensate recycled water that can be used for production, as well as industrial salts such as sodium sulfate and sodium chloride, are obtained for continued utilization as renewable resources.

[0006] However, when most evaporation and concentration systems are in operation and it is found that the concentration multiple of the wastewater is too high, "green salt" will crystallize out, resulting in a decrease in quality, not meeting the national standards for industrial salt, unable to be sold externally, piling up in the factory, and causing secondary pollution.

[0007] Through the full-process tracking and analysis of the treatment of vanadium-containing wastewater, it is found that the main reason for this phenomenon is that after removing pollution factors such as vanadium, chromium, and ammonia nitrogen from the vanadium extraction wastewater, that is, before entering the evaporation and concentration system, due to the limitations of the existing process, it is impossible to filter out extremely fine particles of chromium hydroxide completely, and the content of TV and TCr (total vanadium and total chromium) in the wastewater is very difficult to be treated to less than 1 mg / L. When the wastewater treatment of multiple production lines reaches this process, there is still a light blue residue. After the evaporation and concentration multiple increases, there will be obvious green adhesion when crystals precipitate, and the product cannot meet the chromaticity requirements in the national standards. In view of this practical problem commonly existing in the production site, a deep treatment process for sodium roasting vanadium extraction wastewater is proposed. Summary of the Invention

[0008] The purpose of the present invention is to solve the technical problems raised in the above background technology.

[0009] The present invention adopts the following technical solutions: A deep treatment process for sodium roasting vanadium extraction wastewater, comprising the following steps:

[0010] S1: After the wastewater is treated for vanadium removal, chromium removal, and ammonia nitrogen removal, it is uniformly collected into a reaction kettle;

[0011] S2: Detect the pH value of the wastewater. If it is lower than 10, slowly add liquid caustic soda and stir to adjust the pH value to about 10;

[0012] S3: Add ferrous sulfate with a concentration of 1 - 2 kg / m 3 and stir for 20 minutes;

[0013] S4: Introduce compressed air, keep stirring and ventilation, and stop ventilation after the color of the solution completely turns yellowish-red;

[0014] S5: Add a flocculant with a concentration of 3 g / m 3 and stir for 5 minutes, then stop stirring;

[0015] S6: Transport the solid-liquid mixture to a filter press to filter out the clear and transparent liquid.

[0016] Preferably, the liquid caustic soda in step S2 is a sodium hydroxide solution. Here, by using a sodium hydroxide solution to adjust the pH value, the pH value of the wastewater can be stably controlled within the target range, improving the efficiency and effect of the treatment process.

[0017] Preferably, the amount of ferrous sulfate added in step S3 is adjusted according to the free water content of ferrous sulfate. Here, the dosage of ferrous sulfate is precisely controlled to ensure the sufficiency and effectiveness of the reaction, avoid waste of the reagent, optimize the reaction conditions, improve the efficiency of vanadium and chromium removal, and reduce the risk of secondary pollution.

[0018] Preferably, the compressed air introduced in step S4 is introduced through the compressed air pipe at the bottom of the reaction kettle. Here, it is beneficial to the full oxidation and reaction of pollutants in the wastewater, ensures the uniformity of the reaction, improves the reaction efficiency and effect, thoroughly oxidizes pollutants such as vanadium and chromium in the wastewater, and improves the transparency and quality of the treated wastewater.

[0019] Preferably, the flocculant in step S5 is polyaluminum chloride. Here, polyaluminum chloride has strong adsorption and precipitation capabilities, can quickly and effectively remove suspended solids and pollutants in the wastewater, improve the clarity and treatment effect of the wastewater, and reduce the content of residual pollutants.

[0020] Preferably, the stirring speed in step S5 is 200 - 300 revolutions per minute. Here, it ensures the full mixing and reaction of the reactants, improves the treatment efficiency and effect, optimizes the reaction conditions, ensures the uniformity and stability of the reaction, and improves the quality of the treated wastewater.

[0021] Preferably, the filter press in step S6 is a plate and frame filter press. Here, using a plate and frame filter press for solid - liquid separation can efficiently remove suspended solids and pollutants in the wastewater, obtain treated wastewater that meets the standards, and reduce the risk of secondary pollution.

[0022] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0023] 1. In the present invention, pollutants such as vanadium, chromium, and ammonia nitrogen can be effectively removed, and the contents of total vanadium (TV) and total chromium (TCr) in the wastewater are treated to be less than 1 mg / L, ensuring that the treated wastewater meets the environmental protection standards. At the same time, valuable elements such as vanadium and chromium in the wastewater are effectively recovered and converted into recycled resources such as industrial salts, improving the utilization efficiency of resources and having significant economic benefits.

[0024] 2. In the present invention, through in - depth treatment, the problem of crystallization and precipitation of unqualified green salt during the evaporation and concentration process of the wastewater is avoided, ensuring the quality of industrial salts, meeting the requirements of national standards, avoiding secondary pollution, enabling the treated wastewater to be reused or safely discharged, meeting the requirements of current strict environmental protection policies, promoting the realization of "zero discharge" of wastewater, and reducing environmental pollution.

[0025] 3. In the present invention, the ferrous sulfate and aeration oxidation process is adopted, which reduces the treatment cost, improves the process feasibility, enables most enterprises to deeply treat wastewater without excessive investment, and has the promotion potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. is a flow chart of a deep treatment process for sodium roasting vanadium extraction wastewater proposed by the present invention;

[0027] Figure 2 FIG. is a process diagram of a deep treatment process for sodium roasting vanadium extraction wastewater proposed by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described below with reference to the drawings and embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0029] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed in the following specification.

[0030] Embodiment 1

[0031] Take 1 liter of wastewater after vanadium and chromium removal from Pangang Vanadium into a beaker. At this time, the solution is light green, with a pH value of 9. Add liquid caustic soda to adjust the pH to 10. Weigh 1 gram of analytical pure ferrous sulfate heptahydrate with a balance and add it to the solution, and stir for 20 minutes. At this time, the solution has become a dark green turbid liquid. Connect the compressed air pipe and aerate for 10 minutes until the solution completely turns yellowish-red. Take out the compressed air pipe, add 3 milliliters of flocculant, and stir quickly for 1 minute. Finally, filter to obtain a clear and colorless solution.

[0032] Embodiment 2

[0033] Take 1 liter of wastewater after vanadium and chromium removal from Pangang Vanadium into a beaker. At this time, the solution is light green. Weigh 1 gram of polyferric sulfate (Fe content 20%) with a balance and add it to the solution, and stir for 20 minutes. At this time, the solution has become a reddish-yellow turbid liquid. Add 3 milliliters of flocculant and stir quickly for 1 minute. Finally, filter to obtain a clear and transparent solution with a faint yellow residue.

[0034] Embodiment 3

[0035] Take 1 liter of wastewater after vanadium and chromium removal from Pangang Vanadium into a beaker. At this time, the solution is light green. Weigh 0.5 gram of wood activated carbon with a balance and add it to the solution, and stir for 20 minutes. Stop stirring and directly filter to obtain a clear and colorless solution.

[0036] Example 1 is the process solution used in the present invention, and Examples 2 and 3 are common water treatment processes.

[0037] Embodiment

[0038] Please refer to Figure 1-2 , the present invention provides a technical solution: a deep treatment process for the wastewater from sodium roasting vanadium extraction, including the following steps:

[0039] a. Pretreatment: The wastewater generated by the sodium roasting vanadium extraction process is subjected to preliminary vanadium removal, chromium removal, and ammonia nitrogen removal, and then uniformly collected in a reaction kettle for treatment.

[0040] b. pH adjustment: Start the stirrer of the reaction kettle, detect whether the pH value of the wastewater in the reaction kettle is lower than 10. If it is lower than 10, slowly add liquid caustic soda and stir to adjust the pH of the wastewater to about 10.

[0041] c. Add ferrous sulfate: Keep the stirrer of the reaction kettle running, add ferrous sulfate at a concentration of 1-2 kg / m 3 , and adjust the addition amount according to the free water content of ferrous sulfate, and stir for 20 minutes to make it react fully.

[0042] d. Compressed air oxidation: Open the compressed air pipe leading to the bottom of the reaction kettle, keep stirring and ventilation, draw the solution in the kettle into a glass beaker every 5 minutes to observe. After the color of the solution completely turns yellowish-red, stop ventilation.

[0043] e. Add flocculant: Add the prepared flocculant at a concentration of 3 g / m 3 , continue to stir for 5 minutes, and then stop stirring.

[0044] f. Solid-liquid separation: Open the bottom transfer pump of the kettle, transfer all the solid-liquid mixture in the reaction kettle to a filter press for solid-liquid separation, and the clarified and transparent liquid filtered out is the qualified liquid obtained by this process.

[0045] The above is only a preferred embodiment of the present invention, and it is not a limitation of the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A deep treatment process for vanadium extraction wastewater by sodium roasting, characterized in that: The following steps are involved: S1: After the wastewater is treated to remove vanadium, chromium and ammonia nitrogen, it is collected uniformly into the reactor; S2: Check the pH value of the wastewater. If it is lower than 10, slowly add liquid alkali and stir to adjust the pH value to about 10; S3: Add concentration of 1-2kg / m 3 of ferrous sulfate, stirring for 20 minutes; S4: Introduce compressed air, keep stirring and aerating, and stop aerating when the color of the solution completely changes to yellow-red; S5: Add concentration of 3g / m 3 flocculant, stirring for 5 minutes and then stop stirring; S6: The solid-liquid mixture is transported to a filter press to filter out a clear and transparent liquid.

2. The deep treatment process for vanadium extraction wastewater by sodium roasting according to claim 1, characterized in that: The liquid alkali in step S2 is a sodium hydroxide solution.

3. The deep treatment process for vanadium extraction wastewater by sodium roasting according to claim 1, characterized in that: The amount of ferrous sulfate added in step S3 is adjusted according to the free water content of the ferrous sulfate.

4. The deep treatment process for vanadium extraction wastewater by sodium roasting according to claim 1, characterized in that: The compressed air introduced in the step S4 is introduced through the compressed air pipe at the bottom of the reactor.

5. The deep treatment process for vanadium extraction wastewater by sodium roasting according to claim 1, characterized in that: The flocculant in step S5 is polyaluminium chloride.

6. The deep treatment process for vanadium extraction wastewater by sodium roasting according to claim 1, characterized in that: The stirring speed in step S5 is 200-300 rpm.

7. The deep treatment process for vanadium extraction wastewater by sodium roasting according to claim 1, characterized in that: The filter press in step S6 is a plate and frame filter press.

Images