Vanadium is present in the main magnet of vanadium and titanium ore, coal, aluminum, alumina or the like, the content is very low. The traditional vanadium slag vanadium extraction process is vanadium slag sodium sulphide roasting-water immersion-purification-ammonium salt vanadium-vanadate ammonium pyrolysis. The traditional stone coal vanadium extraction process is sodium salt roasting-water immersion-acid precipitation-alkali The solution-ammonium salt precipitation-ammonium metavanadate pyrolysis finally yields a vanadium pentoxide product in which vanadium is precipitated from the solution using an ammonium salt as a precipitant. The ammonium salt is vanadium, the acidic ammonium salt is vanadium, the weakly acidic ammonium salt is vanadium and the basic ammonium salt is vanadium. The most widely used is the acidic ammonium salt vanadium. The acidic ammonium salt vanadium is characterized by simple operation, fast crystallization of vanadium, low consumption of ammonium salt, high purity of products, high energy consumption, large discharge of wastewater, and the purity of V 2 O 5 cannot be further improved. To this end, the vanadium precipitation was studied by solvent extraction method, and the three phases of oil phase, water phase and sediment were coexisted in the back extraction process, and the ammonium vanadate precipitate was directly separated. First, the test materials The vanadium-containing leaching solution used in the test is a vanadium-containing solution after the vanadium slag is subjected to sodium oxide roasting, sulfuric acid leaching and purification, and its composition is: Ï(V)=17.3g/L, Ï(Na + )=12.8～16.7g /L, Ï(P) = 0.01 to 0.016 g/L, Ï(∑Cr) = 0.076 to 0.058 g/L, p(SO 4 2- ) = 2.35 g/L, Ï(Cl - ) = 9.33 to 10.96 g/L, pH = 7.75 to 8.74. Chemical reagents used in the test: primary carbon primary amine (N1923), octanol, sulfonated kerosene, TPB, concentrated sulfuric acid (98%), sodium hydroxide (solid), ammonium carbonate, ammonia. Second, the test process and principle (1) Test methods and principles Before the test, the prepared extractant is transformed with sulfuric acid solution; the purified vanadium-containing solution is added in proportion, stirred, and sulfuric acid is added dropwise to ensure the pH value of the aqueous phase solution is 2±0.5; after stirring for a specified time, the sample is allowed to stand. Phase, the oil phase is a vanadium-containing organic phase; the raffinate aqueous phase entrained in the vanadium-containing organic phase is washed, and a stripping agent is added as needed to perform back extraction; after stirring for a predetermined time, water, oil and precipitate are mixed. The slurry liquid is filtered; the slurry liquid is filtered to obtain a filter cake; the filter cake is washed and placed in a muffle furnace to deamination at 400 to 500 ° C to obtain a powdery vanadium pentoxide product. (2) Main chemical reactions during the test The vanadium in the vanadium solution is selectively extracted by the secondary oxycarbamide (N1923) with an oxyanate anion under certain conditions, and separated from the cations such as sodium and chromium . The vanadium in the supported organic phase is back-extracted with ammonium carbonate solution, converted into ammonium vanadate precipitate, filtered and washed, and then thermally decomposed (melted) to obtain a powder (tablet) vanadium pentoxide product. (3) Analytical methods Vanadium and iron were determined by volumetric method; silicon and phosphorus were determined by colorimetry; other elements were determined by atomic absorption spectrometry. Third, the results and discussion (1) Extraction 1. Selection of extraction system The main ion in the solution is the oxyacid anion and sodium ion of vanadium. The selective extraction of the oxo-acid anion of vanadium by an amine extraction system can achieve separation from sodium ions. Extraction best primary amine, amine species in the water in a small solubility of metal ions with high selectivity, and easily back-extracted, select a primary amine N1923 Test as an extractant, kerosene as diluent, with the phase modulator . The volume of the extracted stock solution was 100 mL, Ï(V) = 17.3 g/L, the temperature was room temperature (28 ° C), the mixing time was 4 min, and the V a :V o =2:1 of the first and third groups, the second and fourth groups of V a : V o =1. During the test, 2.2 mL of sulfuric acid solution (1+1) was added. The extraction test results of different extraction systems are shown in Table 1. Table 1 Extraction test results of vanadium solution by different extraction systems It can be seen from Table 1 that the equilibrium pH of the raffinate aqueous phase is between 1 and 2, and vanadium can be effectively extracted, and the single extraction rate is 86.9% to 99.9%. Among the components of the extractant, alcohols and lipids can effectively improve the handling properties and increase the solubility of the extract of the primary amine N19 23 after vanadium extraction in kerosene. When the extraction system is N1923+ octanol + kerosene, the extraction process is fast, the interface is clear, and the extraction rate can reach about 90%. After removing the octanol, the extraction rate decreases, the organic phase is viscous, and the interface is not clear, which is not conducive to the separation of the two phases of water and oil. When TPB is used instead of octanol, it has the best extraction effect, and the extraction rate can reach 99.9%. However, TPB contains P, P and V elements. The chemical properties are similar, which will affect the extraction and precipitation of V. Used in. 2. Determination of the saturation capacity of the extractant The cross-flow extraction of 1 transitional organic phase and multiple stock solutions was carried out, and the saturated capacity of vanadium extracted by 10% N1923+10% octanol + 80% kerosene extraction system was determined. In the extract solution, Ï(V)=17.3g/L, the temperature is room temperature (28°C), V a :V o =1, and the mixing time is 5 min. During the extraction process, 2 mL of sulfuric acid solution (1+1) was added per 100 mL of stock solution. During the cross-flow extraction test, the two-phase mixture is fast, clear, and clear. The vanadium-containing organic phase obtained by cross-flow extraction at each stage was back-extracted with V a :V o =1 for 10 min with 100 g/L NaOH solution, and the vanadium mass concentration was determined. The test results are shown in Table 2. Table 2 Determination of the saturation capacity of vanadium extracted from 10% N1923+10% octanol +80% kerosene system It can be seen from Table 2 that after three cross-flow extractions, the mass concentration of vanadium in the raffinate aqueous phase is consistent with that of the stock solution, indicating that the organic phase is saturated. Under the test conditions, the saturated capacity of vanadium extracted by 10% N1923+10% octanol + 80% kerosene extraction system was 29.5g/L. 3. Extraction kinetics test The extractant is directly extracted with the original solution, and a certain amount of sulfuric acid solution is added during the extraction process to ensure the pH of the raffinate aqueous phase is between 1.5 and 2.0. As vanadium undergoes hydrolysis under acidic conditions to form hydrated vanadium pentoxide: Therefore, the extraction of vanadium is different from the extraction of other non-ferrous metals such as molybdenum . It is not possible to adjust the pH of the raw solution with acid, but only add acid during the extraction process, first extract a part of vanadium into the organic phase, and reduce the water phase. The mass concentration of vanadium ensures smooth operation. The extract solution Ï (V) = 17.3 g / L, pH = 1.75, temperature is room temperature (28 ° C), V a : V o = 1:1, 4 mL (1 + 1) of sulfuric acid solution per 100 mL of stock solution. The effect of mixing time on vanadium extraction rate was investigated. The results are shown in Figure 1. Figure 1 Relationship between mixing time and vanadium extraction rate During the extraction process, it was observed that the water and oil phases were fast, clear, and the interface was clear. The vanadium concentration in the aqueous phase is the result of filtration after precipitation of ammonium vanadate. It can be seen from Figure 1 that as the mixing time is prolonged, the mass concentration of vanadium in the equilibrium aqueous phase is reduced from 1.01 g/L to 0.95 g/L, and then rises back to 1.05 g/L. At the mixing time of 4 min, the concentration of vanadium in the equilibrium aqueous phase was the lowest, while the extraction rate of vanadium was the highest, 95.4%. It can be seen that the primary amine N1923 system extracts vanadium faster, and the extraction equilibrium is reached in about 4 minutes. (2) Back extraction 1, the choice of stripping agent After the amine is extracted from vanadium, it is generally back extracted with an alkali. As the stripping agent, there are NaOH, Na 2 CO 3 , ammonia water and ammonium salts. In order not to introduce additional metal cations, ammonia water, (NH 4 ) 2 CO 3 was used for the back extraction test. The Ï(V)=17.0g/L in the supported organic phase, the back extraction test results under different stripping agents and different back extraction conditions are shown in Table 3. Table 3 Back-extraction test results for vanadium with different composition stripping agents It can be seen from Table 3 that the ammonia solution, the ammonium carbonate solution and the mixed solution of the two can effectively back-extract vanadium, and the single-stage back extraction rate of vanadium is more than 99%, and the anti-extraction process simultaneously obtains the ammonium salt of vanadate which is insoluble in water. Appropriately increase the stripping temperature, the obtained vanadium ammonium salt crystal particles are coarse and easy to precipitate, and the filtration and washing are fast, and the product quality is good. From the operating environment, 170 g / L (NH 4 ) 2 CO 3 solution was selected as the stripping agent. 2. Back extraction kinetics test The supported organic phase Ï (V) = 16.0 g / L, the stripping agent was 170 g / L ammonium carbonate solution, compared to V a : V o = 1:1, temperature 40 ° C. The effect of mixing time on vanadium back extraction rate is shown in Figure 2. During the test, it was observed that when mixed for 5 min, flocculation appeared at the interface of water and oil phase, and there was less sediment in the water phase; when the mixing time was extended to 10 min, the interface became clear and the sediment in the aqueous phase became more; continue to extend the mixing time. The interface is clear and there are many precipitates in the water phase. Figure 2 Relationship between mixing time and vanadium back extraction It can be seen from Fig. 2 that vanadium is back-extracted with 170 g/L ammonium carbonate solution, and the vanadium back extraction rate is over 99% after mixing the two phases for 10 min. From the perspective of saving energy and increasing equipment capacity, the back extraction mixing time is determined to be 10 to 15 minutes. Single-stage countercurrent back extraction is sufficient. (3) Preparation of vanadium pentoxide products The slurry obtained in the stripping process is filtered, the oil phase entrained in the filter cake is washed with water, and then decomposed in a muffle furnace at 400-500 ° C to obtain a brown or orange-red powdery pentoxide. Two vanadium products. Product quality analysis is shown in Table 4, reaching the GB3283-1987 metallurgical class 99 standard. Table 4 Quality analysis results of vanadium pentoxide product % Fourth, the conclusion (1) Precipitating vanadium by solvent extraction on vanadium slag leachate. The primary amine N1923 is selected as the extracting agent, and the ammonium carbonate solution is the stripping agent, and the ammonium vanadate precipitate can be directly obtained in the stripping process. (2) The vanadium solution is subjected to single-stage extraction in N1923 extraction system for 4 minutes, the extraction rate can reach 95%; after 10 minutes of back extraction in ammonium carbonate solution, the stripping rate is over 99%; the quality of vanadium pentoxide product obtained It has reached the GB3283-1987 metallurgical class 99 standard. Industrial large fans often have diameters of several meters, weights of tens or even hundreds of kilograms, and are suspended for installation and rotation. It is necessary to consider various aspects such as speed, material, noise, and energy consumption. The safety of industrial large fans is closely related to the material of their blades and the structure of the entire machine, and there are strict requirements for material strength and toughness. Warehouse large fan, workshop large fan, Installation of large fan in workshop Julai (Chongqing) ventilation equipment Co.,Ltd , https://www.julaifans.com