Method for preparing ammonium metavanadate from low-grade vanadium slag

Abstract

The invention provides a method for preparing ammonium metavanadate from low-grade vanadium slag, and belongs to the field of ammonium metavanadate production. The method comprises the following steps: roasting the low-grade vanadium slag to decompose sodium oxalate in the low-grade vanadium slag to obtain a roasted product; pulping the roasted material by using a dilute sodium carbonate solution to obtain first mixed slurry; the first mixed slurry is subjected to solid-liquid separation, and high-grade vanadium slag and a sodium carbonate solution are obtained; mixing the high-grade vanadium slag with a solvent to obtain second mixed slurry; adjusting the pH value of the second mixed slurry to carry out vanadate conversion reaction to obtain third mixed slurry; carrying out solid-liquid separation on the third mixed slurry to obtain vanadium-containing filtrate; adding soluble ammonium salt into the vanadium-containing filtrate to carry out ammonium metavanadate precipitation reaction to obtain fourth mixed slurry; and carrying out solid-liquid separation on the fourth mixed slurry to obtain ammonium metavanadate. Therefore, the impurity content of the ammonium metavanadate product is reduced while resource utilization of the low-grade vanadium slag is realized.

Description

Technical Field

[0001] The present application relates to the technical field of ammonium metavanadate production, and in particular to a method for preparing ammonium metavanadate from low-grade vanadium slag. Background Art

[0002] The Bayer process of alumina production produces a vanadium-containing complex salt, commonly known as "vanadium slag" in the industry. Ammonium metavanadate prepared from vanadium slag has high economic value. However, due to the complex composition of the mother liquor of the Bayer process of alumina, while the mother liquor is recycled, the sodium carbonate and oxalate in it will continue to be enriched. When the concentration reaches supersaturation, they will precipitate together with the vanadium slag, resulting in a decrease in the grade of the vanadium pentoxide content of the vanadium slag and an increase in impurity components.

[0003] The traditional process is to directly add water and acid to the vanadium slag for dissolution, and then add ammonium salt to prepare ammonium metavanadate after filtering. This process has the following problems: First, the alkali content is high, and direct acid dissolution not only consumes a large amount of acid, but also causes a waste of alkali resources; second, after the vanadium slag is dissolved with acid, the sodium sulfate and sodium oxalate content in the vanadium solution is extremely high, resulting in poor quality of ammonium metavanadate; third, the vanadium slag is of low grade, and the solution after acid dissolution has low vanadium content and high impurity content, which not only reduces production efficiency, but also produces high impurity content in the prepared ammonium metavanadate; fourth, the oxalate in the vanadium slag is not separated, resulting in a high oxalate content in the vanadium extraction wastewater, low wastewater evaporation efficiency, and difficulty in treatment. Therefore, how to reduce the impurity content of ammonium metavanadate products while utilizing low-grade vanadium slag as a resource is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a method for preparing ammonium metavanadate from low-grade vanadium slag to solve the following technical problem: how to reduce the impurity content of the ammonium metavanadate product while utilizing the low-grade vanadium slag as a resource.

[0005] The present application provides a method for preparing ammonium metavanadate from low-grade vanadium slag, the method comprising:

[0006] roasting the low-grade vanadium slag to decompose the sodium oxalate in the low-grade vanadium slag to obtain a roasted product;

[0007] The roasted material is pulped using a dilute sodium carbonate solution of a set concentration to obtain a first mixed slurry;

[0008] performing solid-liquid separation on the first mixed slurry to obtain high-grade vanadium slag and sodium carbonate solution;

[0009] Mixing high-grade vanadium slag with a solvent to obtain a second mixed slurry;

[0010] Adjusting the pH of the second mixed slurry to a set pH to perform a vanadate conversion reaction to obtain a third mixed slurry;

[0011] Performing solid-liquid separation on the third mixed slurry to obtain a vanadium-containing filtrate;

[0012] adding a soluble ammonium salt to the vanadium-containing filtrate having a first set temperature to perform an ammonium metavanadate precipitation reaction to obtain a fourth mixed slurry having a second set temperature; and

[0013] The fourth mixed slurry is subjected to solid-liquid separation to obtain ammonium metavanadate.

[0014] Optionally, the heating temperature of the calcination is 250° C. to 350° C., and the insulation time of the calcination is 30 min to 60 min.

[0015] Optionally, the set concentration is 1% to 5%.

[0016] Optionally, the pulping temperature is 30° C. to 50° C., and the pulping stirring time is 30 min to 60 min.

[0017] Optionally, the high-grade vanadium slag includes the following chemical components, measured by mass fraction: vanadium pentoxide: 20% to 35%, sodium carbonate: 3% to 5%, sodium oxalate: 1% to 3%, and sodium aluminate: 40% to 60%.

[0018] Optionally, after obtaining the high-grade vanadium slag and the sodium carbonate solution, the method further comprises:

[0019] The sodium carbonate solution is evaporated and crystallized to obtain by-product sodium carbonate and distilled water; the mass concentration of sodium carbonate in the sodium carbonate solution is 200 g / L to 250 g / L;

[0020] The distilled water is used as a solvent and circulated in the step of mixing the high-grade vanadium slag with the solvent.

[0021] Optionally, concentrated sulfuric acid is used to adjust the pH of the second mixed slurry, and the set pH is 7-10.

[0022] Optionally, the temperature of the vanadate conversion reaction is 50°C to 80°C, and the time of the vanadate conversion reaction is 60min to 90min.

[0023] Optionally, the first set temperature is 45°C to 60°C; and / or

[0024] The second set temperature is 30°C to 38°C.

[0025] Optionally, the soluble ammonium salt includes: one or more of ammonium sulfate, ammonium chloride and ammonium bicarbonate, and the mass ratio of the soluble ammonium salt to the vanadium pentoxide in the vanadium-containing filtrate is (2-4):1.

[0026] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0027] The present application provides a method for preparing ammonium metavanadate from low-grade vanadium slag, which comprises: roasting the low-grade vanadium slag to decompose sodium oxalate in the low-grade vanadium slag to obtain a roasted product; slurrying the roasted product using a dilute sodium carbonate solution of a set concentration to obtain a first mixed slurry; performing solid-liquid separation on the first mixed slurry to obtain high-grade vanadium slag and a sodium carbonate solution; mixing the high-grade vanadium slag with a solvent to obtain a second mixed slurry; adjusting the pH of the second mixed slurry to a set pH to perform a vanadate conversion reaction to obtain a third mixed slurry; performing solid-liquid separation on the third mixed slurry to obtain a vanadium-containing filtrate; adding a soluble ammonium salt to the vanadium-containing filtrate having a first set temperature to perform an ammonium metavanadate precipitation reaction to obtain a fourth mixed slurry having a second set temperature; and performing solid-liquid separation on the fourth mixed slurry to obtain ammonium metavanadate. First, by roasting low-grade vanadium slag, the sodium oxalate in the low-grade vanadium slag is decomposed into sodium carbonate, reducing the impact of sodium oxalate on the purity of the product and avoiding the high oxalate content in the vanadium extraction wastewater; secondly, by washing the low-grade vanadium slag with a dilute sodium carbonate solution, the sodium carbonate in the low-grade vanadium slag can be effectively separated, thereby converting the low-grade vanadium slag into high-grade vanadium slag, and sodium carbonate by-product can be obtained, greatly improving the production efficiency; secondly, in the vanadate conversion reaction, the aluminum in the slurry will be converted into colloidal aluminum hydroxide during the acid dissolution process, which can absorb the impurity elements of the vanadium-containing filtrate, thereby improving the purity of ammonium metavanadate; finally, through the ammonium metavanadate precipitation reaction, 99-grade ammonium metavanadate is obtained. In this way, the impurity content of the ammonium metavanadate product is reduced while the low-grade vanadium slag is utilized as a resource. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0030] Figure 1 A flow chart of a method for preparing ammonium metavanadate from low-grade vanadium slag provided in an embodiment of the present application;

[0031] Figure 2 A schematic diagram of a method for preparing ammonium metavanadate from low-grade vanadium slag provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0034] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0035] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0036] Figure 1 A schematic flow chart of a method for preparing ammonium metavanadate from low-grade vanadium slag provided in an embodiment of the present application; Figure 2 A schematic diagram of a method for preparing ammonium metavanadate from low-grade vanadium slag provided in an embodiment of the present application.

[0037] See also Figure 1 and Figure 2 The present application provides a method for preparing ammonium metavanadate from low-grade vanadium slag, the method comprising:

[0038] S1, roasting low-grade vanadium slag to decompose sodium oxalate in the low-grade vanadium slag to obtain a roasted product;

[0039] In some embodiments, the low-grade vanadium slag includes the following chemical components, measured by mass fraction: vanadium pentoxide: 3% to 10%, sodium carbonate: 20% to 50%, sodium oxalate: 10% to 30%, and sodium aluminate: 10% to 30%.

[0040] In some embodiments, the heating temperature of the calcination is 250° C. to 350° C., and the holding time of the calcination is 30 min to 60 min.

[0041] The heating temperature of roasting is limited to 250℃~350℃, and this temperature range is the temperature that needs to be controlled for the thermal decomposition of sodium oxalate into sodium carbonate. Sodium oxalate will undergo a decomposition reaction when heated to a certain temperature to generate carbon dioxide and sodium carbonate. Controlling within this temperature range can ensure that sodium oxalate can be fully decomposed while avoiding excessive reduction or oxidation of other components (such as vanadium pentoxide). The holding time of roasting is limited to 30min~60min, which can ensure that sodium oxalate is fully decomposed and improve the decomposition rate. Exemplarily, the heating temperature of roasting can be 250℃, 270℃, 290℃, 300℃, 320℃, 340℃, 350℃, etc., and the holding time of roasting can be 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc.

[0042] In some embodiments, the heating temperature of the calcination is 270° C. to 320° C., and the holding time of the calcination is 40 min to 60 min.

[0043] In some embodiments, the conversion rate of sodium oxalate to sodium carbonate is >99%.

[0044] S2, slurrying the roasted material using a dilute sodium carbonate solution of a set concentration to obtain a first mixed slurry;

[0045] In some embodiments, the washing tank used for pulping is a tank commonly used in industry, and the stirring is a stirring form commonly used in industry, preferably a frame stirring form.

[0046] It should be noted that slurrying is a process of mixing the roasted material with water or a dilute solution and forming a uniform slurry by stirring, grinding or other means.

[0047] The principle of washing low-grade vanadium slag with dilute sodium carbonate solution is mainly based on the solubility of sodium carbonate and its inhibitory effect on the dissolution of sodium vanadate. Specifically: sodium carbonate is easily soluble in water, so the use of dilute sodium carbonate solution can effectively dissolve the sodium carbonate impurities in low-grade vanadium slag. At the same time, direct washing with water may cause partial dissolution of sodium vanadate in the vanadium slag, thereby reducing the purity of the product. The use of dilute sodium carbonate solution can inhibit the dissolution of sodium vanadate through the interaction between carbonate ions and vanadate ions in the solution while dissolving sodium carbonate, thereby retaining the effective ingredients.

[0048] In some embodiments, the set concentration is 1% to 5%.

[0049] The percentage concentration of sodium carbonate in the dilute sodium carbonate solution is limited to 1% to 5%, so as to ensure that the sodium carbonate in the vanadium slag is fully dissolved and the dissolution of sodium vanadate can be inhibited. For example, the percentage concentration of sodium carbonate can be 1%, 2%, 3%, 4%, 5%, etc.

[0050] In some embodiments, the mass ratio of the dilute sodium carbonate solution to the calcined product is (1-5):1.

[0051] The mass ratio of the dilute sodium carbonate solution to the calcined product is limited to (1-5):1. Increasing the liquid-to-solid ratio can increase the contact area and contact time between the dilute sodium carbonate solution and the calcined product, thereby facilitating the full dissolution of sodium carbonate. However, a mass ratio higher than 5:1 will result in an increase in liquid volume, which is not conducive to improving production efficiency. Exemplarily, the mass ratio of the dilute sodium carbonate solution to the calcined product can be 1:1, 1:2, 1:3, 1:4, 1:5, etc.

[0052] In some embodiments, the temperature of the pulping is 30° C. to 50° C., and the stirring time of the pulping is 30 min to 60 min.

[0053] The temperature of pulping is limited to 30°C to 50°C, and the stirring time of pulping is 30min to 60min, which is conducive to the dissolution of sodium carbonate and the stability of sodium vanadate. At the same time, through a sufficiently long stirring time, it can be ensured that the dilute sodium carbonate solution and the roasted material are fully mixed to form a uniform slurry. Exemplarily, the temperature of pulping can be 30°C, 35°C, 40°C, 45°C, 50°C, etc., and the stirring time of pulping can be 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc.

[0054] S3, performing solid-liquid separation on the first mixed slurry to obtain high-grade vanadium slag and sodium carbonate solution;

[0055] In some embodiments, the filter press used for the solid-liquid separation is a commonly used industrial filter press, preferably a plate and frame filter press.

[0056] In some embodiments, the high-grade vanadium slag includes the following chemical components, measured by mass fraction: vanadium pentoxide: 20% to 35%, sodium carbonate: 3% to 5%, sodium oxalate: 1% to 3%, and sodium aluminate: 40% to 60%.

[0057] The present invention can effectively separate the sodium carbonate in the low-grade vanadium slag by decomposing the sodium oxalate in the low-grade vanadium slag into sodium carbonate, and washing with a dilute sodium carbonate solution. The vanadium pentoxide content is increased from 3% to 10% to 20% to 35%, the sodium carbonate content is reduced from 20% to 50% to 3% to 5%, and the sodium oxalate content is reduced from 10% to 30% to 1% to 3%. The low-grade vanadium slag is transformed into high-grade vanadium slag, which greatly improves production efficiency, greatly reduces production costs, and significantly improves product quality.

[0058] In some embodiments, after obtaining the high-grade vanadium slag and the sodium carbonate solution, the method further comprises:

[0059] The sodium carbonate solution is evaporated and crystallized to obtain by-product sodium carbonate and distilled water; the mass concentration of sodium carbonate in the sodium carbonate solution is 200 g / L to 250 g / L;

[0060] The distilled water is used as a solvent and circulated in the step of mixing the high-grade vanadium slag with the solvent.

[0061] In some embodiments, the evaporator used for the evaporative crystallization is an evaporator commonly used in industry, preferably a triple-effect forced circulation evaporator, and the evaporative crystallization is an evaporative crystallization method commonly used in industry.

[0062] S4, mixing the high-grade vanadium slag with a solvent to obtain a second mixed slurry;

[0063] In some embodiments, the mass ratio of the high-grade vanadium slag to the solvent is (1-3):1.

[0064] In some embodiments, the solvent is water or a water analog.

[0065] S5, adjusting the pH of the second mixed slurry to a set pH to perform a vanadate conversion reaction to obtain a third mixed slurry;

[0066] During the pH adjustment process, aluminum will be converted into colloidal aluminum hydroxide during the acid dissolution process, which will adsorb the impurity elements in the vanadium-containing filtrate and further improve the product quality.

[0067] In some embodiments, concentrated sulfuric acid is used to adjust the pH of the second mixed slurry, and the set pH is 7-10.

[0068] In the second mixed slurry, by adjusting the pH value to a set range (7 to 10), the conversion reaction of vanadate can be promoted to metavanadate without other adverse chemical reactions. At the same time, it is also beneficial to the generation and purification of ammonium metavanadate in subsequent steps. Exemplarily, the set pH can be 7, 7.5, 8, 8.5, 9, 9.5, 10, etc.

[0069] In some embodiments, the stirring is a stirring form commonly used in industry, preferably anchor stirring. The concentrated sulfuric acid is concentrated sulfuric acid commonly used in industry, with a concentration of 90% to 98%, preferably 93% to 98%.

[0070] In some embodiments, the temperature of the vanadate conversion reaction is 50° C. to 80° C., and the time of the vanadate conversion reaction is 60 min to 90 min.

[0071] After adjusting to the set pH value, the vanadate in the second mixed slurry will undergo a conversion reaction to generate metavanadate. This reaction is a chemical equilibrium process. The temperature of the vanadate conversion reaction is limited to 50°C to 80°C, and the time of the vanadate conversion reaction is 60min to 90min. The chemical reaction rate is moderate, which is conducive to the conversion of vanadate to metavanadate, and the reaction is fully carried out. Exemplarily, the temperature of the vanadate conversion reaction can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc., and the time of the vanadate conversion reaction can be 60min, 65min, 70min, 75min, 80min, 85min, 90min, etc.

[0072] S6, performing solid-liquid separation on the third mixed slurry to obtain a vanadium-containing filtrate;

[0073] In step S6, the main components of the obtained filter cake are aluminum hydroxide and sodium sulfate.

[0074] In some embodiments, the solid-liquid separation method is a commonly used industrial filtration method, preferably a plate and frame filter press.

[0075] S7, adding a soluble ammonium salt to the vanadium-containing filtrate having the first set temperature to perform an ammonium metavanadate precipitation reaction to obtain a fourth mixed slurry having a second set temperature; and

[0076] In some embodiments, the first set temperature is 45°C to 60°C; and / or

[0077] The second set temperature is 30°C to 38°C.

[0078] Adding soluble ammonium salts (such as ammonium chloride, ammonium sulfate, etc.) to the vanadium-containing filtrate can trigger the precipitation reaction of ammonium metavanadate. This reaction is based on the combination of vanadate ions and ammonium ions to generate water-insoluble ammonium metavanadate precipitates. The first set temperature is limited to 45°C to 60°C, which is the crystallization temperature that needs to be controlled in the production of ammonium metavanadate, and this temperature is conducive to crystal growth. The second set temperature is limited to 30°C to 38°C. The precipitation reaction of ammonium metavanadate is an exothermic reaction. Lowering the temperature is conducive to the reaction in the direction of the product and improving the recovery rate of vanadium. Exemplarily, the first set temperature can be 45°C, 48°C, 50°C, 52°C, 55°C, 58°C, 60°C, etc., and the second set temperature can be 30°C, 32°C, 34°C, 36°C, 38°C, etc.

[0079] S8. Perform solid-liquid separation on the fourth mixed slurry to obtain ammonium metavanadate.

[0080] In some embodiments, the soluble ammonium salt includes: one or more of ammonium sulfate, ammonium chloride and ammonium bicarbonate, and the mass ratio of the soluble ammonium salt to the vanadium pentoxide in the vanadium-containing filtrate is (2-4):1.

[0081] The mass ratio of the soluble ammonium salt to the vanadium pentoxide in the vanadium-containing filtrate is limited to (2-4):1. The reaction is a reversible reaction. Increasing the concentration of the reactants can easily promote the reaction to the product direction and improve the vanadium recovery rate. Exemplarily, the mass ratio of the soluble ammonium salt to the vanadium pentoxide in the vanadium-containing filtrate can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1, etc.

[0082] In summary, the beneficial effects of this application are as follows:

[0083] (1) The present invention decomposes sodium oxalate in low-grade vanadium slag into sodium carbonate, and can effectively separate sodium carbonate from low-grade vanadium slag by washing with a dilute sodium carbonate solution, increasing the vanadium pentoxide content from 3-10% to 20-35%, reducing the sodium carbonate content from 20%-50% to 3%-5%, and reducing the sodium oxalate content from 10%-30% to 1%-3%. Low-grade vanadium slag is converted into high-grade vanadium slag, which greatly improves production efficiency, greatly reduces production costs, and significantly improves product quality.

[0084] (2) The present application uses a simple and effective process to separate and recover the sodium carbonate from the low-grade vanadium slag, thereby obtaining sodium carbonate as a by-product. This not only avoids the waste of alkali resources, but also greatly reduces the acid consumption during the acid dissolution process. The content of sodium sulfate and organic matter in the vanadium-containing filtrate is significantly reduced, and the product quality is stable.

[0085] (3) The present application uses a roasting process to almost completely decompose sodium oxalate, and the vanadium extraction wastewater contains almost no organic matter. During the wastewater evaporation treatment process, the evaporation efficiency is improved, which solves the problem of the difficulty in treating vanadium extraction wastewater and realizes a closed process.

[0086] (4) The present application uses a dilute sodium carbonate solution to wash low-grade vanadium slag, which can not only effectively dissolve the sodium carbonate therein, but also avoid the dissolution of vanadium and aluminum. The vanadium loss rate is almost zero, and the aluminum therein will be converted into colloidal aluminum hydroxide during the acid dissolution process, which absorbs the impurity elements of the vanadium-containing filtrate, further improving the product quality.

[0087] (5) Low-grade vanadium slag is a process solid waste. This application can not only treat it harmlessly, but also recover the vanadium and sodium carbonate therein at high value, without generating any secondary wastewater, waste gas or solid waste, which is environmentally friendly and efficient.

[0088] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0089] The low-grade vanadium slag in this embodiment comes from an alumina plant under the China Aluminum Corporation, and has the following chemical composition: 4.22% vanadium pentoxide, 41.21% sodium carbonate, 27.54% sodium oxalate, and 27.31% sodium aluminate.

[0090] Example 1

[0091] (1) 10 tons of low-grade vanadium slag is fed into a rotary kiln for roasting, heated to 280° C., and kept warm for 40 minutes to decompose the sodium oxalate therein into sodium carbonate;

[0092] (2) 5 tons of low-grade vanadium slag roasted in (1) was put into a washing tank, and 5 tons of 2.1% dilute sodium carbonate solution was added to the slurry under stirring conditions, maintained at 35° C., and stirred for 35 minutes;

[0093] (3) pumping the solid-liquid mixture of the slurried low-grade vanadium slag into a filter press, and performing solid-liquid separation by filtration to obtain high-grade vanadium slag decarbonated with sodium carbonate and a sodium carbonate solution, wherein the vanadium pentoxide content of the high-grade vanadium slag decarbonated with sodium carbonate is 25.33%;

[0094] (4) feeding the sodium carbonate solution in step (3) into an evaporator to obtain by-product sodium carbonate and distilled water by evaporation and crystallization, wherein the content of the by-product sodium carbonate is 98.45% and the water content is 2.55%;

[0095] (5) Mix 3 tons of the sodium decarbonate high-grade vanadium slag in step (3) and 4.5 tons of distilled water in step (4), add 93% concentrated sulfuric acid under stirring, adjust the pH value of the solid-liquid mixture to 9, react at 55° C. for 60 minutes, filter, and obtain a vanadium-containing filtrate.

[0096] (6) The temperature of the vanadium-containing filtrate was controlled at 48° C., 800 kg of ammonium chloride was added under stirring, and the reaction was kept warm for 60 minutes. The temperature was slowly lowered to 37° C., and the solution was filtered to obtain ammonium metavanadate.

[0097] Example 2

[0098] (1) 10 tons of low-grade vanadium slag is fed into a rotary kiln for roasting, heated to 300°C, and kept at this temperature for 50 minutes to decompose the sodium oxalate therein into sodium carbonate;

[0099] (2) 5 tons of low-grade vanadium slag roasted in (1) was put into a washing tank, and 10 tons of 3% dilute sodium carbonate solution was added to make slurry under stirring, maintained at 40° C., and stirred for 45 minutes;

[0100] (3) pumping the solid-liquid mixture of the slurried low-grade vanadium slag into a filter press, and performing solid-liquid separation by filtration to obtain high-grade vanadium slag decarbonated with sodium carbonate and a sodium carbonate solution, wherein the vanadium pentoxide content of the high-grade vanadium slag decarbonated with sodium carbonate is 27.51%;

[0101] (4) feeding the sodium carbonate solution in step (3) into an evaporator to obtain by-product sodium carbonate and distilled water by evaporation and crystallization, wherein the content of the by-product sodium carbonate is 98.85% and the water content is 2.12%;

[0102] (5) Mix 3 tons of the sodium decarbonate high-grade vanadium slag in step (3) and 6 tons of distilled water in step (4), add 98% concentrated sulfuric acid under stirring, adjust the pH value of the solid-liquid mixture to 8, react at 50° C. for 70 minutes, filter, and obtain a vanadium-containing filtrate.

[0103] (6) The temperature of the vanadium-containing filtrate was controlled at 50° C., 1500 kg of ammonium sulfate was added under stirring, and the reaction was kept warm for 70 minutes. The temperature was slowly lowered to 35° C., and the solution was filtered to obtain ammonium metavanadate.

[0104] Example 3

[0105] (1) 10 tons of low-grade vanadium slag is fed into a rotary kiln for roasting, heated to 330° C., and kept at this temperature for 60 minutes to decompose the sodium oxalate therein into sodium carbonate;

[0106] (2) 5 tons of low-grade vanadium slag roasted in (1) was put into a washing tank, and 15 tons of 4.5% dilute sodium carbonate solution was added to make slurry under stirring conditions, maintained at 50° C., and stirred for 60 minutes;

[0107] (3) pumping the solid-liquid mixture of the slurried low-grade vanadium slag into a filter press, and performing solid-liquid separation by filtration to obtain high-grade vanadium slag decarbonated with sodium carbonate and a sodium carbonate solution, wherein the vanadium pentoxide content of the high-grade vanadium slag decarbonated with sodium carbonate is 21.42%;

[0108] (4) feeding the sodium carbonate solution in step (3) into an evaporator to obtain by-product sodium carbonate and distilled water by evaporation and crystallization, wherein the content of the by-product sodium carbonate is 98.21% and the water content is 2.85%;

[0109] (5) Mix 3 tons of the sodium decarbonate high-grade vanadium slag in step (3) and 7.5 tons of distilled water in step (4), add 95% concentrated sulfuric acid under stirring, adjust the pH value of the solid-liquid mixture to 7, react at 75° C. for 80 minutes, filter, and obtain a vanadium-containing filtrate.

[0110] (6) The temperature of the vanadium-containing filtrate was controlled at 55° C., 1800 kg of ammonium bicarbonate was added under stirring, the reaction was kept warm for 80 minutes, the temperature was slowly lowered to 33° C., and the solution was filtered to obtain ammonium metavanadate.

[0111] The ammonium metavanadate product and the sodium carbonate byproduct were subjected to purity determination, and the results are shown in Table 1 and Table 2.

[0112] Table 1 Quality indicators and measured results of ammonium metavanadate

[0113]

[0114]

[0115] Table 2 Quality indicators and measured results of by-product sodium carbonate

[0116] Ingredient content (%) Quality index (%) Example 1 Example 2 Example 3 <![CDATA[Na2CO3]]> ≥98.0 98.45 98.85 98.21 <![CDATA[H2O]]> ≤3 2.55 2.12 2.85

[0117] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0118] In the embodiment of the present invention, the purity of the ammonium metavanadate product is greater than 99.0%, and the purity of the sodium carbonate byproduct is greater than or equal to 98.0%.

[0119] In the embodiment of the present invention, by decomposing sodium oxalate in low-grade vanadium slag into sodium carbonate and effectively separating the sodium carbonate, the content of vanadium pentoxide is significantly increased from 3-10% to 20-35%, while the contents of sodium carbonate and sodium oxalate are reduced, thereby realizing the transformation of low-grade vanadium slag into high-grade vanadium slag, thereby greatly improving production efficiency, reducing production costs, and significantly improving product quality.

[0120] In the embodiment of the present invention, the separated sodium carbonate is effectively recovered and used as a by-product, thereby avoiding the waste of alkali resources. At the same time, in the acid dissolution process, due to the recovery of sodium carbonate, the acid consumption is significantly reduced, and the sodium sulfate and organic matter content in the vanadium-containing filtrate is also significantly reduced, further improving the product quality stability.

[0121] In the embodiment of the present invention, sodium oxalate is almost completely decomposed by the roasting process, and the vanadium extraction wastewater contains almost no organic matter, thereby improving the efficiency of wastewater evaporation treatment, realizing a closed process loop, and solving the problem that vanadium extraction wastewater is difficult to treat.

[0122] In the embodiment of the present invention, when a dilute sodium carbonate solution is used to wash low-grade vanadium slag, not only sodium carbonate is effectively dissolved, but also vanadium and aluminum are prevented from being dissolved, and the vanadium loss rate is almost zero. Aluminum is converted into colloidal aluminum hydroxide during the acid dissolution process, which has an adsorption effect and can adsorb impurity elements in the vanadium-containing filtrate, further improving the product quality.

[0123] In the embodiment of the present invention, not only the harmless treatment of low-grade vanadium slag is achieved, but also the maximization of resource utilization is achieved by recovering the vanadium and sodium carbonate therein at high value. No secondary wastewater, waste gas and solid waste are generated in the whole process, which embodies the concept of environmental protection and high efficiency.

[0124] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing ammonium metavanadate from low-grade vanadium slag, the method comprising: roasting the low-grade vanadium slag to decompose the sodium oxalate in the low-grade vanadium slag to obtain a roasted product; The roasted material is pulped using a dilute sodium carbonate solution of a set concentration to obtain a first mixed slurry; performing solid-liquid separation on the first mixed slurry to obtain high-grade vanadium slag and sodium carbonate solution; Mixing high-grade vanadium slag with a solvent to obtain a second mixed slurry; Adjusting the pH of the second mixed slurry to a set pH to perform a vanadate conversion reaction to obtain a third mixed slurry; Performing solid-liquid separation on the third mixed slurry to obtain a vanadium-containing filtrate; Adding a soluble ammonium salt to the vanadium-containing filtrate having a first set temperature to perform an ammonium metavanadate precipitation reaction to obtain a fourth mixed slurry having a second set temperature; as well as The fourth mixed slurry is subjected to solid-liquid separation to obtain ammonium metavanadate.

2. The method according to claim 1, characterized in that The heating temperature of the calcination is 250° C. to 350° C., and the heat preservation time of the calcination is 30 min to 60 min.

3. The method according to claim 1, characterized in that The set concentration is 1% to 5%.

4. The method according to claim 1, characterized in that The temperature of the pulping is 30° C. to 50° C., and the stirring time of the pulping is 30 min to 60 min.

5. The method according to claim 1, characterized in that Calculated by mass fraction, the high-grade vanadium slag includes the following chemical components: vanadium pentoxide: 20% to 35%, sodium carbonate: 3% to 5%, sodium oxalate: 1% to 3%, and sodium aluminate: 40% to 60%.

6. The method according to claim 1, characterized in that After obtaining the high-grade vanadium slag and sodium carbonate solution, the method further comprises: The sodium carbonate solution is evaporated and crystallized to obtain by-product sodium carbonate and distilled water; the mass concentration of sodium carbonate in the sodium carbonate solution is 200 g / L to 250 g / L; The distilled water is used as a solvent and circulated in the step of mixing the high-grade vanadium slag with the solvent.

7. The method according to claim 1, characterized in that The pH of the second mixed slurry is adjusted using concentrated sulfuric acid, and the set pH is 7-10.

8. The method according to claim 1, characterized in that The temperature of the vanadate conversion reaction is 50° C. to 80° C., and the time of the vanadate conversion reaction is 60 min to 90 min.

9. The method according to claim 1, characterized in that: The first set temperature is 45°C to 60°C; and / or The second set temperature is 30°C to 38°C.

10. The method according to claim 1, characterized in that The soluble ammonium salt includes one or more of ammonium sulfate, ammonium chloride and ammonium bicarbonate, and the mass ratio of the soluble ammonium salt to the vanadium pentoxide in the vanadium-containing filtrate is (2-4):1.

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