CN115159573B - Method for purifying ammonium metavanadate and method for preparing vanadium pentoxide - Google Patents
Method for purifying ammonium metavanadate and method for preparing vanadium pentoxide Download PDFInfo
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- CN115159573B CN115159573B CN202210884015.3A CN202210884015A CN115159573B CN 115159573 B CN115159573 B CN 115159573B CN 202210884015 A CN202210884015 A CN 202210884015A CN 115159573 B CN115159573 B CN 115159573B
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Abstract
The invention discloses a method for purifying ammonium metavanadate or a method for preparing vanadium pentoxide from ammonium metavanadate, which comprises the following steps: (1) removing impurities by an impurity removing agent: adding an oxidant and a pH regulator into the aqueous solution of the crude ammonium metavanadate, regulating the pH value to 9-11, adding an impurity removing agent for reaction, and filtering to obtain a filtrate; (2) vanadium precipitation: adding ammonium chloride into the filtrate obtained in the step (1) to carry out vanadium precipitation reaction; (3) circularly washing and removing impurities: and (3) separating the ammonium metavanadate precipitate in the material subjected to vanadium precipitation reaction in the step (2), circularly washing the ammonium metavanadate precipitate, and dehydrating to obtain purified ammonium metavanadate, wherein the circularly washing comprises at least 10 times of washing, and the liquid used for washing for the 2 nd time and the later batches is an ammonium chloride solution obtained by evaporating and condensing all or part of washing water generated by the previous washing and evaporated washing raw water optionally supplemented with water. The method of the invention can reduce the generation amount of ammonia nitrogen wastewater and the generation amount of salt slag in the evaporation process, the quality of the high-purity vanadium pentoxide product is ensured.
Description
Technical Field
The invention belongs to the field of vanadium pentoxide preparation, and relates to a method for purifying ammonium metavanadate and a method for preparing vanadium pentoxide.
Background
In the conventional process for preparing vanadium pentoxide by taking ammonium metavanadate as a raw material, one process is to dissolve ammonium chloride into deionized water, and carry out fractional centrifugal dehydration washing on the ammonium metavanadate by using 2% ammonium chloride deionized water solution with the mass of 8 times of that of the ammonium metavanadate so as to remove soluble impurities such as potassium and sodium in the ammonium metavanadate and ensure the quality of a high-purity vanadium pentoxide product. The method has the following defects: about 12 tons of ammonia nitrogen wastewater is mostly generated in the preparation of each ton of high-purity vanadium pentoxide, 240kg of ammonium chloride is added, the treatment capacity of the ammonia nitrogen wastewater is increased, the amount of the added ammonium chloride is converted into salt slag, the production and operation cost is high, the wastewater circulation rate is low, and the like.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a method for preparing high-purity vanadium pentoxide by taking ammonium metavanadate as a raw material, which utilizes the principle that ammonium chloride is volatile, obtains a high-purity ammonium chloride solution in an evaporation and condensation mode, realizes the evaporation and self-circulation washing of ammonium metavanadate washing water, and removes soluble impurities such as potassium, sodium and the like in a product. The method for preparing the high-purity vanadium pentoxide has the advantages of no increase of ammonia nitrogen wastewater production, relatively low energy consumption, low raw material consumption, the production amount of ammonia nitrogen wastewater and the production amount of salt slag in the evaporation process are reduced, and meanwhile, the problem of high impurity content of the product can be solved in the full washing process, so that the quality of the high-purity vanadium pentoxide product is ensured.
Specifically, the invention provides a method for purifying ammonium metavanadate or a method for preparing vanadium pentoxide from ammonium metavanadate, which comprises the following steps:
(1) Removing impurities with an impurity removing agent: adding an oxidant and a pH regulator into the aqueous solution of the crude ammonium metavanadate, regulating the pH value to 9-11, adding an impurity removing agent for reaction, and filtering to obtain a filtrate;
(2) And (3) vanadium precipitation: adding ammonium chloride into the filtrate obtained in the step (1) to carry out vanadium precipitation reaction;
(3) Circularly washing and removing impurities: and (3) separating the ammonium metavanadate precipitate in the material subjected to vanadium precipitation reaction in the step (2), circularly washing the ammonium metavanadate precipitate, and dehydrating to obtain purified ammonium metavanadate, wherein the circularly washing comprises at least 10 times of washing, and the liquid used for washing for the 2 nd time and the later batches is an ammonium chloride solution obtained by evaporating and condensing all or part of washing water generated by the previous washing and evaporated washing raw water optionally supplemented with water.
In one or more embodiments, in step (1), the oxidizing agent is sodium chlorate.
In one or more embodiments, in step (1), the pH adjusting agent is one or more selected from the group consisting of sodium hydroxide, sodium carbonate, and sodium bicarbonate.
In one or more embodiments, in step (1), the scavenger comprises a chelating agent and a flocculating agent.
In one or more embodiments, the chelating agent is ethylenediaminetetraacetic acid.
In one or more embodiments, the flocculant is one or more selected from the group consisting of aluminum sulfate, magnesium chloride, and aluminum chloride.
In one or more embodiments, the mass ratio of the chelating agent to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is (2-10): 10000.
in one or more embodiments of the present invention, the mass ratio of the usage amount of the flocculating agent to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is (5-50): 100.
in one or more embodiments, in the step (1), after the impurity removing agent is added, the heat-preservation standing reaction is performed.
In one or more embodiments, in the step (1), the temperature for the heat-preservation standing reaction by adding the impurity removing agent is 60-80 ℃, and/or the time for the heat-preservation standing reaction is 4-6h.
In one or more embodiments, in step (2), the mass ratio of the amount of ammonium chloride to the theoretical amount of vanadium pentoxide in the filtrate is 1: (0.5-1.0).
In one or more embodiments, in step (2), the vanadium precipitation reaction time is 8 to 16 hours.
In one or more embodiments, in step (3), the number of washes of the cyclic wash is 10 to 15.
In one or more embodiments, in the step (3), after each washing, the washing water is introduced into an evaporation device by means of siphonage, and the liquid in the evaporation device is evaporated and condensed to obtain the ammonium chloride solution.
In one or more embodiments, in the step (3), the vapor formed by evaporating the evaporated raw washing water is introduced into a washing device for washing the ammonium metavanadate precipitate, a condensing device is arranged at the top of the washing device, and the vapor is condensed by the condensing device to obtain the ammonium chloride solution.
In one or more embodiments, in the step (3), the concentration of ammonium chloride of the evaporation washing raw water is controlled to be 1wt% to 45wt%.
In one or more embodiments, in the step (3), after each washing, when the concentration of ammonium chloride in the evaporation washing raw water does not reach 35wt% to 45wt%, the evaporation washing raw water is directly heated without supplementing water to form steam, the steam is condensed to obtain the ammonium chloride solution, when the concentration of the evaporation washing raw water reaches 35wt% to 45wt%, after optionally discharging part of the evaporation washing raw water, preferably 75 wt% to 85 wt%, the water is supplemented, and then the evaporation washing raw water is heated to form steam, and the steam is condensed to obtain the ammonium chloride solution.
In one or more embodiments, the method for producing vanadium pentoxide from ammonium metavanadate further comprises the steps of:
(4) And (3) calcining: and (4) calcining the purified ammonium metavanadate obtained in the step (3) to obtain vanadium pentoxide.
In one or more embodiments, in step (4), the calcination temperature is from 500 to 550 ℃, and/or the calcination time is from 3 to 5 hours.
Drawings
FIG. 1 is a schematic diagram of the configuration of a depuration reactor and a vanadium precipitation reactor used in some embodiments of the present invention. In fig. 1, 101 is a steam inlet, 102 is a stirrer, 103 is a water inlet, 104 is a steam coil, 105 is a manhole, 106 is an impurity removal reactor, 107 is a discharge valve, 108 is a plate-and-frame filter press, 109 is a filtrate pipe, 110 is a feed inlet, 111 is a stirrer, 112 is a manhole, 113 is a vanadium precipitation reactor, 114 is a discharge valve, and 115 is a water pump.
FIG. 2 is a schematic diagram of the construction of a recirculation washing apparatus used in some embodiments of the present invention. In fig. 2, 116 is a filter screen, 117 is a filter screen, 118 is a water inlet, 119 is a cooling water outlet, 120 is a condenser pipe, 121 is a water seal tank, 122 is a cooling water inlet, 123 is a seal valve, 124 is a feed pipe, 125 is a liquid level pipe, 126 is a manhole, 127 is a siphon pipe, 128 is a washing tank, 129 is a filter plate, 130 is a siphon valve, 131 is a drain valve, 132 is a vanadium precipitation tail water collecting tank, 133 is a discharge valve, 134 is a centrifuge, 135 is a filter valve, 136 is a communicating pipe, 137 is a steam coil, 138 is a manhole, 139 is a heat preservation jacket, 140 is an evaporation tank, and 141 is a blowdown valve.
Detailed Description
To make the features and effects of the invention comprehensible to those skilled in the art, general description and definitions shall be provided below with respect to terms and words mentioned in the specification and claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The theory or mechanism described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
The terms "comprising," including, "" containing, "and the like, herein, encompass the meanings of" consisting essentially of … … "and" consisting of … …, "e.g., when" a comprises B and C, "a consists essentially of B and C," and "a consists of B and C" are to be considered disclosed herein.
All features defined herein as numerical ranges or percentage ranges, such as values, amounts, levels and concentrations, are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to cover and specifically disclose all possible subranges and individual numerical values (including integers and fractions) within the range.
Herein, unless otherwise specified, the percentage means mass percentage, and the proportion means mass ratio.
Herein, when embodiments or examples are described, it is to be understood that they are not intended to limit the invention to these embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described herein are intended to be included within the scope of the invention as defined by the appended claims.
In this context, for the sake of brevity, not all possible combinations of features in the various embodiments or examples are described. Therefore, the respective features in the respective embodiments or examples may be arbitrarily combined as long as there is no contradiction between the combinations of the features, and all the possible combinations should be considered as the scope of the present specification.
The method for purifying ammonium metavanadate and the method for preparing vanadium pentoxide from ammonium metavanadate comprise an impurity removing step of an impurity removing agent, a vanadium precipitation step and a circulating washing impurity removing step.
In the impurity removing step of the impurity removing agent, the impurity removing agent is used for removing impurities from the ammonium metavanadate crude product. The purity of the crude ammonium metavanadate suitable for the present invention may be 95% to 99%, preferably 96% to 98.5%, e.g. 96.5%, 97%, 97.8%, 98.1%. The impurity elements possibly contained in the crude ammonium metavanadate are mainly silicon, phosphorus, iron, manganese, potassium, sodium and the like. In some embodiments, the crude ammonium metavanadate used in the present invention contains the following impurity elements: (A) One or more or all selected from silicon, phosphorus, iron and manganese; and (B) one or two selected from potassium and sodium. In the invention, the impurity removal function of the impurity removing agent is to remove impurity elements such as silicon, phosphorus, iron, manganese and the like in the crude ammonium metavanadate. Generally, preparing an aqueous solution of a crude ammonium metavanadate product, adding an oxidant and a pH regulator into the aqueous solution of the crude ammonium metavanadate product, regulating the pH value to 9-11, and adding an impurity removing agent for reaction. The impurity removing reaction of the impurity removing agent can be carried out in an impurity removing reactor (such as an impurity removing reaction kettle). The concentration of the crude ammonium metavanadate in the crude ammonium metavanadate aqueous solution can be 20wt% -25wt%.
The crude ammonium metavanadate and water can be mixed, heated and stirred to completely dissolve the crude ammonium metavanadate in the water, so as to obtain the aqueous solution of the crude ammonium metavanadate. Heating may be performed using steam coils. The heating temperature may be 60-100 ℃.
Useful oxidizing agents include sodium chlorate. The oxidizing agent (e.g., sodium chlorate) can be used in an amount of 0.1 wt.% to 1 wt.%, e.g., 0.2 wt.%, 0.25 wt.%, 0.5 wt.%, based on the mass of the crude ammonium metavanadate. Useful pH adjusters include sodium hydroxide, sodium carbonate and sodium bicarbonate. After the pH value is adjusted, stirring and preserving heat for a period of time (the preserving temperature can be 60-100 ℃, and the preserving time can be 0.5-2 h), and then adding an impurity removing agent.
In the present invention, the impurity removing agent preferably comprises a chelating agent and a flocculating agent. Useful chelating agents include ethylenediaminetetraacetic acid. Useful flocculants include one or more selected from the group consisting of magnesium chloride, aluminum chloride and aluminum sulfate. In the invention, the mass ratio of the using amount of the chelating agent to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is preferably (2-10): 10000. for example, 3: 100. for example, 10.
In the invention, an impurity removing agent is added into the solution after the pH value is adjusted, and the solution is subjected to heat preservation and standing reaction, so that the impurities are flocculated and/or complexed, and the impurities are removed by filtering. The temperature of the heat preservation can be 60-80 ℃. The standing time can be 4-6h. In some embodiments, the ethylene diamine tetraacetic acid is added into the solution after the pH value is adjusted, after the solution is stirred and dissolved, the magnesium chloride and/or the aluminum chloride are added, after the solution is stirred and dissolved, the heat preservation and the standing reaction are carried out. After the heat preservation and standing reaction, the mixture can be cooled and then filtered. The cooling may be to 35-45 ℃. The filtration may be pressure filtration, for example using a plate and frame filter press.
And after the impurity removing agent removes impurities, filtering to obtain filtrate, and performing the next vanadium precipitation reaction. The vanadium precipitation reaction can be carried out in a vanadium precipitation reactor (such as a vanadium precipitation reaction kettle).
In some embodiments, the impurity removal is performed in an impurity removal reactor 106 shown in fig. 1, the crude ammonium metavanadate and water in the impurity removal reactor 106 are heated to 60-100 ℃ by a steam coil 104, and stirred by a stirrer 102, so that the crude ammonium metavanadate is completely dissolved in the water, an aqueous solution of the crude ammonium metavanadate is obtained, an oxidant and a pH regulator are added, the pH value is adjusted to 9-11, the impurity removal agent is added, after uniform mixing, stirring is stopped, a heat preservation standing reaction is performed, heat preservation standing is performed at 60-80 ℃ for 4-6 hours, then cooling is performed to 35-45 ℃, the feed liquid is discharged through a discharge valve 107, and the feed liquid enters a plate and frame filter press 108 through a filter press valve for filtration, and the filtrate obtained through filtration enters a vanadium precipitation reactor 113 through a filtrate pipe 109.
In the step of vanadium precipitation, ammonium chloride is added into the filtrate to carry out vanadium precipitation reaction. The mass ratio of the using amount of the ammonium chloride to the theoretical amount of the vanadium pentoxide in the solution can be 1 to (0.5-1.0). The vanadium precipitation reaction time can be 8-16h. The vanadium precipitation reaction is carried out under stirring. And feeding the material liquid obtained by the vanadium precipitation reaction into the next step for cyclic washing and impurity removal. The cyclic washing for impurity removal can be carried out in a cyclic washing apparatus as shown in FIG. 2.
In some embodiments, the vanadium precipitation reaction is performed in the vanadium precipitation reactor 113 shown in fig. 1, ammonium chloride is added into the filtrate in the vanadium precipitation reactor 113, the mass ratio of the ammonium chloride to the theoretical amount of vanadium pentoxide in the solution is 1 to (0.5-1.0), and the mixture is stirred by using a stirrer 111 and reacted for 8-16h; after the reaction is complete, the feed solution is discharged through discharge valve 114 and then may enter wash tank 128 via feed line 124 shown in FIG. 2 by water pump 115.
In some embodiments, as shown in fig. 1, the impurity removal reactor 106 comprises a stirrer 102, a steam coil 104 (having a steam inlet 101), a water inlet 103, a manhole 105 and a discharge valve 107, the impurity removal reactor 106 is connected with a plate-and-frame filter press 108 via the discharge valve 107 through a pipe provided with a pump, the plate-and-frame filter press 108 is connected with a vanadium precipitation reactor 113 through a filtrate pipe 109, and the vanadium precipitation reactor 113 comprises a feeding port 110, a stirrer 111, a manhole 112 and a discharge valve 114. The vanadium precipitation reactor 113 may be connected to a feed pipe 124 of a wash tank 128 of the circulation wash apparatus shown in fig. 2 through a pipe provided with a water pump 115 via a discharge valve 114.
In the invention, the step of circularly washing and removing impurities comprises separating ammonium metavanadate precipitate in materials after vanadium precipitation reaction, and then circularly washing the ammonium metavanadate precipitate, wherein the circularly washing comprises 10 times or more than 10 times, preferably 10-15 times of washing, and liquid used for washing for the 2 nd time and the later batches is ammonium chloride solution obtained by evaporating and condensing all or part of washing water generated in the previous washing and evaporated washing raw water optionally supplemented with water. The function of circularly washing and removing impurities is to remove soluble impurity elements such as potassium, sodium and the like in the ammonium metavanadate. In the invention, the step of circularly washing and removing impurities is carried out in a circularly washing device comprising a washing device, an evaporation device and a condensation device.
The material after vanadium precipitation reaction can be separated into ammonium metavanadate precipitate and vanadium precipitation tail water by adopting a filtration mode. In the present invention, the washing device preferably comprises a filtration device. After the material after vanadium precipitation reaction enters a washing device, ammonium metavanadate precipitate in the material is retained in the washing device by a filtering device to be washed. In some embodiments, as shown in fig. 2, the circulation washing apparatus includes a washing tank 128, and a filter valve 135 and a filter plate 129 disposed below the washing tank 128, and the material resulting from the vanadium precipitation reaction is separated into ammonium metavanadate precipitate and vanadium precipitation tail water using the filter plate 129. In some embodiments, as shown in fig. 2, the circulation washing apparatus further comprises a drain valve 131 and a vanadium precipitation tail water collecting tank 132, and the vanadium precipitation tail water is drained into the vanadium precipitation tail water collecting tank 132 through the drain valve 131.
In the present invention, the ammonium metavanadate precipitate may be subjected to a first washing with clean water. The clear water is preferably triple effect evaporation condensed water, which has the advantage of less impurities and is beneficial to obtaining better circular washing and impurity removing effects. The ammonium metavanadate precipitate contains a lot of entrained water with a large amount of ammonium chloride, which is dissolved in water as a detergent in the first washing process, and thus the washing water obtained after washing contains ammonium chloride. Before the next washing, the washing water is heated and evaporated, and because the ammonium chloride is volatile, the ammonium chloride is evaporated into steam along with water, and then the high-purity ammonium chloride solution is formed through condensation and is used as a detergent for the next washing. The concentration of ammonium chloride in the raw water for evaporation washing may be adjusted by adding water to the washing water or by adding water after discarding a part of the washing water. The washing raw water can be heated and evaporated by the steam coil. The mass of the washing agent (condensed water or condensed ammonium chloride solution) is preferably 3 to 5 times, for example 2.5 times, 4 times, 4.5 times, the mass of the ammonium metavanadate precipitate in each washing, which is advantageous for increasing the washing efficiency and for achieving higher purity and yield.
In some embodiments, as shown in fig. 2, the circulation washing apparatus includes a water-sealed barrel 121 (having a water inlet 118), a sealing valve 123, a communication pipe 136, an evaporation tank 140 and a washing tank 128, the water-sealed barrel 121 and the communication pipe 136 are connected by a pipeline, the sealing valve 123 is disposed on the pipeline connecting the water-sealed barrel 121 and the communication pipe 136, the evaporation tank 140 includes a steam coil 137, a manhole 138, a heat-insulating jacket 139 and a blowdown valve 141, a condensation pipe 120 (having a cooling water inlet 122 and a cooling water outlet 119) is disposed on the top of the washing tank 128, and the condensation pipe 120 and the water-sealed barrel 121 are connected by a pipeline having a filter screen 116 and a filter screen 117. Before the first washing, water is added into a water sealing barrel 121 in the circulating washing device, the water in the water sealing barrel 121 enters an evaporation tank 140 through a sealing valve 123 and a communication pipe 136, a steam coil 137 arranged in the evaporation tank 140 heats and evaporates the water to form water vapor, the water vapor enters a washing tank 128 through the communication pipe 136, and the water vapor is condensed by a condensation pipe 120 to form condensed water which falls into the washing tank 128 to wash ammonium metavanadate precipitate. In some embodiments, as shown in fig. 2, the evaporation tank 140 includes a feed pipe 124, a level pipe 125, and a manhole 126. The condenser tube may be a serpentine condenser tube.
In the present invention, it is preferable to suck the washing water after washing from the washing system by siphoning. After absorbing the washing water by adopting a siphon mode, directly taking the absorbed washing water as the raw water for evaporating and washing, or optionally or preferably mixing the absorbed washing water with the possibly remained raw water for evaporating and washing, omitting partial raw water for evaporating and washing and/or supplementing water according to requirements, and then evaporating and condensing the raw water for evaporating and washing to obtain an ammonium chloride solution as the detergent for washing next time. In some embodiments, as shown in fig. 2, the circulation washing device comprises a washing tank 128, an evaporation tank 140, a siphon valve 130 and a siphon 127 arranged between the washing tank 128 and the evaporation tank 140, a communicating pipe 128 and a condensation pipe 120 arranged at the top of the washing tank 128, after washing is completed, washing water enters the evaporation tank 128 through the siphon valve 130 and the siphon 127, liquid in the evaporation tank 128 is heated, and the obtained vapor containing ammonium chloride volatile enters the washing tank 128 through the communicating pipe 136, is condensed by the condensation pipe 120 to form ammonium chloride solution, and falls into the washing tank 128 to circularly wash ammonium metavanadate precipitate.
In a preferred embodiment, in the step of circularly washing and removing impurities, materials after vanadium precipitation reaction are added into a washing device (for example, the washing tank 128), ammonium metavanadate precipitate in the materials is separated by using a filtering device, then the ammonium metavanadate precipitate is circularly washed, clear water is added into an evaporation device before the ammonium metavanadate precipitate is washed for the first time, then the clear water in the evaporation device is heated, the mass of a washing agent entering the washing device after evaporation and condensation is controlled to be 3-5 times, for example, about 4 times, of the mass of the ammonium metavanadate precipitate in the washing device, after each washing, the washing water is sucked into the evaporation device in a siphoning mode, the washing water and liquid possibly remaining in the evaporation device are mixed into evaporated washing raw water, the evaporated washing raw water in the evaporation device is heated, and the mass of the washing agent entering the washing device after each evaporation and condensation is controlled to be 3-5 times of the mass of the ammonium metavanadate precipitate in the washing device. In the present invention, the volume of the evaporation device (e.g., the evaporation tank 140) is preferably 1.5-2.5 times, more preferably about 2 times, the volume of the washing device (e.g., the washing tank 128), and at this time, before the first washing, clean water with a volume of 1/2 to 3/4, e.g., about 2/3, of the volume of the evaporation device can be added to the evaporation device, and the clean water in the evaporation device is heated during each washing, so that the washing device is substantially filled with the detergent evaporated and condensed into the washing device, and the mass of the detergent is maintained to be about 3-5 times, e.g., about 4 times, of the mass of the ammonium metavanadate precipitate in the washing device, so as to improve the washing efficiency, and to facilitate obtaining high purity and yield.
In the present invention, the number of washing cycles in the cyclic washing process is preferably 10 to 15, which is advantageous in obtaining high purity and yield. The washing times are too few, which is not beneficial to ensuring the purity of the product; too many washing times are not favorable for ensuring the yield of the product.
In the present invention, it is preferable to control the ammonium chloride concentration of the evaporation washing raw water to be between 1wt% and 45wt%, preferably between 1wt% and 40wt%, for example, 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%. The ammonium chloride concentration of the evaporated washing raw water can be adjusted by diluting with water and optionally discarding part of the evaporated washing raw water. In some embodiments, when the ammonium chloride content of the raw evaporation wash water (e.g., liquid in the evaporation tank 128) reaches a certain concentration (e.g., 45wt%, 40wt%, 35 wt%), water is added after an amount (preferably 75% to 85%, e.g., 80%) of the raw evaporation wash water is optionally or preferably drained to control the concentration of the raw evaporation wash water within the aforementioned range. According to the invention, the concentration of ammonium chloride in the evaporation washing raw water is controlled, so that the evaporation washing raw water enters an evaporation condensation washing cycle as far as possible, and the detergent obtained by evaporation condensation is kept to have a proper ammonium chloride concentration, so that the ammonium chloride contained in the ammonium metavanadate precipitate can be dissolved and washed away, and the ammonium metavanadate precipitate cannot be dissolved to cause loss. In some embodiments, when the concentration of ammonium chloride in the raw water in the evaporation tank 128 is enriched to 40wt%, 80% of the raw water is discharged through the blowdown valve 141 of the evaporation tank 128, and the fresh water (e.g., triple effect evaporation condensed water) is supplemented into the evaporation tank 128 from the water seal bucket 121 through the sealing valve 123 and the communicating pipe 136. The volume of the additional water may be substantially equal to the volume of the discharged raw water for evaporation washing. The discharged evaporation washing raw water can enter an ammonia nitrogen wastewater collection tank.
And dehydrating the ammonium metavanadate precipitate after the cyclic washing to obtain a purified ammonium metavanadate product, wherein the purified ammonium metavanadate product can be used for preparing vanadium pentoxide by calcining. The dehydration can be performed by centrifugation. In some embodiments, a discharge valve 133 is disposed below the washing tank 128, and the circulation washing device may include a centrifuge 134, and the ammonium metavanadate precipitate after washing is discharged through the discharge valve 133 and enters the centrifuge 134 for centrifugal dehydration to obtain a purified ammonium metavanadate product.
The method for preparing vanadium pentoxide from ammonium metavanadate further comprises a calcining step. And the calcining step comprises calcining the purified ammonium metavanadate after the cyclic washing and impurity removal to obtain the high-purity vanadium pentoxide. The calcination temperature may be 500-550 ℃. The calcination time may be 3-5h. The calcination may be carried out in a rotary kiln. In the present invention, the high-purity vanadium pentoxide refers to a vanadium pentoxide product with a vanadium pentoxide content of 99.5wt% or more, preferably 99.7wt% or more.
In some embodiments, the method for preparing vanadium pentoxide from ammonium metavanadate according to the present invention comprises the steps of:
(a) Dissolving: heating deionized water in an impurity removal reactor to 60-100 ℃ through a steam coil, adding an ammonium metavanadate crude product, and uniformly stirring until the ammonium metavanadate crude product is completely dissolved to obtain an aqueous solution of the ammonium metavanadate crude product;
(b) Adjusting the pH value: adding an oxidant such as sodium chlorate into the aqueous solution of the crude ammonium metavanadate obtained in the step (a) for oxidation, and adjusting the pH value of the aqueous solution to 9-11 by using a pH regulator such as sodium carbonate solution;
(c) Removing impurities with an impurity removing agent: adding an impurity removing agent into the solution treated in the step (b), wherein the impurity removing agent comprises a chelating agent and a flocculating agent, the chelating agent is ethylenediamine tetraacetic acid, and the mass ratio of the consumption of the ethylenediamine tetraacetic acid to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is (2-10): 10000; the flocculant is one or more selected from magnesium chloride, aluminum chloride and aluminum sulfate, and the mass ratio of the usage amount of the flocculant to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is (5-50): 100; keeping the temperature at 60-80 ℃, standing for 4-6h, stopping heating, cooling the solution to about 40 ℃, and performing filter pressing to obtain a filtrate;
(d) And (3) vanadium precipitation: sending the filtrate obtained in the step (c) into a vanadium precipitation reactor, and adding ammonium chloride into the filtrate in the vanadium precipitation reactor, wherein the mass ratio of the use amount of the ammonium chloride to the theoretical amount of vanadium pentoxide in the solution is 1: 0.5-1.0; the vanadium precipitation time is 8-16h;
(e) Circularly washing and removing impurities: using the circulating washing device shown in fig. 2 to carry out circulating washing and impurity removal, pumping the materials in the vanadium precipitation reactor to a washing tank 128 in the circulating washing device, filtering the materials by a filter plate 129, discharging the vanadium precipitation tail water into a vanadium precipitation tail water collecting tank 132 through a liquid discharge valve 131, and closing the liquid discharge valve 131 after the liquid discharge is finished;
adding clear water, such as triple-effect evaporation condensed water, into the water-sealed barrel 121, and supplementing water to an evaporation tank 140 in the circulating washing device through a sealing valve 123;
the siphon valve 130 is opened, the steam coil 137 heats the water in the evaporation tank 140 to form water vapor, the water vapor enters the washing tank 128 through the communication pipe 136, is condensed in the condensation pipe 120 and then falls into the washing tank 128;
the ammonium metavanadate precipitate in the wash tank 128 carries a large amount of ammonium chloride, and water is contacted with the ammonium chloride during the washing process to form an ammonium chloride solution, which is sucked into the evaporation tank 140 via the siphon valve 130 and the siphon 127;
the steam coil 137 heats the raw water for evaporation and washing in the evaporation tank 140, the water vapor communicating pipe 136 containing ammonium chloride volatile matter enters the washing tank 128 and is condensed in the condensation pipe 120 to form high-purity ammonium chloride solution, the high-purity ammonium chloride solution falls into the washing tank 128 to wash the ammonium metavanadate precipitate, the washing solution is sucked into the evaporation tank 140 again through the siphon valve 130 and the siphon 127, the evaporation, condensation and washing are circularly carried out in the way, the washing frequency is more than 10 times, preferably 10-15 times, and the washing process is finished; when the concentration of ammonium chloride in the evaporation washing raw water in the evaporation tank 140 is enriched to 35wt% -45wt%, for example, 40wt%, 75 wt% -85 wt% and 80% of the evaporation washing raw water is discharged through the blowdown valve 141, and clear water, for example triple effect evaporation condensed water, is supplemented through the sealing valve 123 to continue to operate;
discharging the washed ammonium metavanadate through a discharge valve 133, and sending the ammonium metavanadate into a centrifuge 134 for dehydration to obtain purified ammonium metavanadate;
(f) And (3) calcining: calcining the purified ammonium metavanadate obtained in the step (e) in a rotary kiln at 500-550 ℃ for 3-5h to obtain the high-purity vanadium pentoxide.
The method has the advantages of simple process control and stable product quality, reduces the generation amount of the ammonia nitrogen wastewater at the source, saves raw materials, reduces energy consumption, meets the requirement of clean production, and is suitable for large-scale production. Through detection, the content of the high-purity vanadium pentoxide prepared by the process can reach over 99.7 percent; the impurity content is less than 100ppm, especially the content of soluble impurities such as potassium, sodium and the like is extremely low, and the vanadium pentoxide can be used as the special high-purity vanadium pentoxide for the vanadium electrolyte.
The invention has the following beneficial effects:
the method has the advantages of simple process control and stable product quality, reduces the generation amount of the ammonia nitrogen wastewater from the source, saves raw materials, reduces energy consumption, meets the requirement of clean production, and is suitable for large-scale production. Through detection, the content of the high-purity vanadium pentoxide prepared by the process can reach over 99.7 percent; the impurity content of potassium and sodium can reach below 100ppm, the content of soluble impurities such as potassium, sodium and the like is extremely low, and the vanadium pentoxide can be used as special high-purity vanadium pentoxide for vanadium electrolyte.
The present invention will be further described with reference to specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the present invention. The methods and reagents used in the examples are, unless otherwise indicated, conventional in the art.
Example 1
In this example, the following steps were used to prepare high-purity vanadium pentoxide by using the impurity removal reactor and the vanadium precipitation reactor shown in fig. 1 and the circulating washing apparatus shown in fig. 2:
1. removing impurities with an impurity removing agent: 4000kg of crude ammonium metavanadate (with the purity of 98.1 percent and impurity elements including silicon, phosphorus, iron, manganese, potassium and sodium) and 14000kg of deionized water are mixed in an impurity removal reactor 107, heated to 85 ℃, and stirred until the ammonium metavanadate is completely dissolved, so as to obtain an aqueous solution of the crude ammonium metavanadate; adding 10kg of sodium chlorate, adding sodium carbonate to adjust the pH value of the solution to 10.5, stirring, and keeping the temperature at 85 ℃ for 1h; firstly, adding Ethylene Diamine Tetraacetic Acid (EDTA), wherein the mass ratio of the dosage of the EDTA to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is 5:10000, stirring for 20 minutes, and then adding magnesium chloride, wherein the mass ratio of the using amount of the magnesium chloride to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is 20:100, stirring and dissolving, and then keeping the temperature at 70 ℃ and standing for 4 hours; cooling the materials to 40 ℃, performing pressure filtration by using a plate-and-frame filter press 108, and putting the obtained filtrate into a vanadium precipitation reactor 113;
2. and (3) vanadium precipitation: adding ammonium chloride with the mass 1 time of the theoretical mass of vanadium pentoxide in the filtrate into a vanadium precipitation reactor 113, and carrying out vanadium precipitation reaction for 12h, wherein the ammonium metavanadate is completely precipitated; the material in the vanadium precipitation reactor 113 is pumped to a wash tank 128 in a circulating wash unit;
3. circularly washing and removing impurities: the bottom of the washing tank 128 is provided with a filter valve 135, a filter plate 129 is arranged below the filter valve 135, a pipeline below the filter plate 129 is provided with three connectors which are respectively connected with a drain valve 131, a siphon valve 130 and a discharge valve 133, the filter valve 135 and the drain valve 131 are opened, ammonium metavanadate precipitate in the material is intercepted by the filter plate 129, vanadium precipitation tail water is discharged into a vanadium precipitation tail water collecting tank 132 through the drain valve 131, and the drain valve 131 is closed after liquid discharge is completed. Supplementing triple-effect evaporation condensate water in a water seal barrel 121 in the circulating washing device, supplementing water to two thirds of the liquid level of an evaporation tank 140 in the circulating washing device through a sealing valve 123, wherein the volume of the evaporation tank 140 is 2 times of that of the washing tank 128, and closing the sealing valve 123 after the water is supplemented. The siphon valve 130 is opened, water in the evaporation tank 140 is heated by a steam coil 137 arranged in the evaporation tank 140 to form water vapor, the water vapor enters the washing tank 128 through a communicating pipe 136, a condensing pipe 120 is arranged at the top of the washing tank 128, the condensing pipe 120 is connected with a water sealing barrel 121 through a pipeline provided with a filter screen 116 and a filter screen 117, the water vapor is condensed in the condensing pipe 120 to form condensed water which falls into the washing tank 128, the washing tank 128 is basically filled with the detergent obtained by condensation during each washing, and the mass of the detergent is 4 times of the mass of ammonium metavanadate precipitate in the washing tank 128. Ammonium metavanadate precipitate in the washing tank 128 carries a large amount of ammonium chloride, evaporated condensed water is contacted with the ammonium chloride to form a high-purity ammonium chloride solution in the washing process, washing water after washing is sucked into the evaporation tank 140 through a siphon valve 130 and a siphon 127, then liquid in the evaporation tank 140 (namely, evaporated washing raw water) is heated, steam enters the washing tank 128 through a communicating pipe 136 and is condensed through a condensing pipe 120 to form an ammonium chloride solution, the ammonium metavanadate precipitate is washed, evaporation, condensation, washing and siphon are circularly performed in the above way, the siphon frequency is 12 times, the washing process is finished, the ammonium metavanadate is discharged through a discharge valve 133, and centrifugal dehydration is performed by using a centrifugal machine 134 to obtain purified ammonium metavanadate; in the washing process, when the concentration of ammonium chloride in the evaporation washing raw water in the evaporation tank 140 is enriched to 40wt%, 80% of the evaporation washing raw water is discharged through a drain valve 141 at the bottom of the evaporation tank 140 and enters an ammonia nitrogen wastewater collection pool, a sealing valve 123 is opened to supplement triple-effect evaporation condensed water with the same volume as the discharged evaporation washing raw water to the evaporation tank 140, and the operation is continued;
4. and (3) calcining: the purified ammonium metavanadate is calcined in a rotary kiln for 4 hours at 550 ℃, the calcined solid powder is brick red, namely a vanadium pentoxide product, the purity of the vanadium pentoxide product is 99.82% by analysis, wherein the impurity content of potassium and sodium is less than 30ppm, the quality requirement of the high-purity vanadium pentoxide of the electrolyte is met, and the yield of the vanadium pentoxide is 97.2%.
Example 2
In this example, the impurity removal reactor and the vanadium precipitation reactor shown in fig. 1 and the circulating washing device shown in fig. 2 were used to prepare high-purity vanadium pentoxide by the following steps:
1. removing impurities by an impurity removing agent: mixing 4000kg of crude ammonium metavanadate (the purity is 97.8 percent, and the impurity elements comprise silicon, phosphorus, iron, manganese, potassium and sodium) and 14000kg of deionized water in an impurity removal reactor 107, heating to 85 ℃, and stirring until the ammonium metavanadate is completely dissolved to obtain an aqueous solution of the crude ammonium metavanadate; adding 10kg of sodium chlorate, adding sodium carbonate to adjust the pH value of the solution to 10.5, stirring, and keeping the temperature at 85 ℃ for 1h; firstly, adding Ethylene Diamine Tetraacetic Acid (EDTA), wherein the mass ratio of the dosage of the EDTA to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is 5:10000, stirring for 20 minutes, and then adding magnesium chloride, wherein the mass ratio of the using amount of the magnesium chloride to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is 20:100, stirring and dissolving, and then keeping the temperature at 70 ℃ and standing for 4 hours; cooling the materials to 40 ℃, performing pressure filtration by using a plate-and-frame filter press 108, and putting the obtained filtrate into a vanadium precipitation reactor 113;
2. and (3) vanadium precipitation: adding ammonium chloride with the mass 1 time of the theoretical mass of vanadium pentoxide in the filtrate into a vanadium precipitation reactor 113, and carrying out vanadium precipitation reaction for 12h, wherein the ammonium metavanadate is completely precipitated; the material in the vanadium precipitation reactor 113 is pumped to a wash tank 128 in a circulating wash unit;
3. circularly washing and removing impurities: the bottom of the washing tank 128 is provided with a filter valve 135, a filter plate 129 is arranged below the filter valve 135, a pipeline below the filter plate 129 is provided with three connectors which are respectively connected with a drain valve 131, a siphon valve 130 and a discharge valve 133, the filter valve 135 and the drain valve 131 are opened, ammonium metavanadate precipitate in the material is intercepted by the filter plate 129, vanadium precipitation tail water is discharged into a vanadium precipitation tail water collecting pool 132 through the drain valve 131, and the drain valve 131 is closed after liquid drainage is completed. Supplementing triple-effect evaporation condensate water in a water seal barrel 121 in the circulating washing device, supplementing water to two thirds of the liquid level of an evaporation tank 140 in the circulating washing device through a sealing valve 123, wherein the volume of the evaporation tank 140 is 2 times of that of the washing tank 128, and closing the sealing valve 123 after the water is supplemented. The siphon valve 130 is opened, water in the evaporation tank 140 is heated by using a steam coil 137 arranged in the evaporation tank 140 to form water vapor, the water vapor enters the washing tank 128 through a communicating pipe 136, a condensing pipe 120 is arranged at the top of the washing tank 128, the condensing pipe 120 is connected with a water seal barrel 121 through a pipeline provided with a filter screen 116 and a filter screen 117, the water vapor is condensed in the condensing pipe 120 to form condensed water which falls into the washing tank 128, the washing tank 128 is basically filled with the detergent obtained by condensation during each washing, and the mass of the detergent is 4 times of that of ammonium metavanadate precipitate in the washing tank 128. Ammonium metavanadate precipitates in the washing tank 128 carry a large amount of ammonium chloride, evaporated condensed water is contacted with the ammonium chloride to form a high-purity ammonium chloride solution in the washing process, the washed washing water is sucked into the evaporating tank 140 through the siphon valve 130 and the siphon 127, then liquid in the evaporating tank 140 (namely evaporated washing raw water) is heated, steam enters the washing tank 128 through the communicating pipe 136 and is condensed into an ammonium chloride solution through the condensing pipe 120 to wash the ammonium metavanadate precipitates, the evaporation, the condensation, the washing and the siphon are circularly carried out, the siphon frequency is 10 times, the washing process is finished, the ammonium metavanadate is discharged through the discharge valve 133, and the centrifugal dehydration is carried out by utilizing the centrifugal machine 134 to obtain purified ammonium metavanadate; in the washing process, when the concentration of ammonium chloride in the evaporation washing raw water in the evaporation tank 140 is enriched to 40wt%, 80% of the evaporation washing raw water is discharged through a drain valve 141 at the bottom of the evaporation tank 140 and enters an ammonia nitrogen wastewater collection pool, a sealing valve 123 is opened to supplement triple-effect evaporation condensed water with the same volume as the discharged evaporation washing raw water to the evaporation tank 140, and the operation is continued;
4. and (3) calcining: the purified ammonium metavanadate is calcined in a rotary kiln for 4 hours at 550 ℃, the calcined solid powder is brick red, namely a vanadium pentoxide product, the purity of the vanadium pentoxide product is 99.78% by analysis, wherein the impurity content of potassium and sodium is less than 30ppm, the quality requirement of the high-purity vanadium pentoxide of the electrolyte is met, and the yield of the vanadium pentoxide is 97.4%.
Example 3
In this example, the impurity removal reactor and the vanadium precipitation reactor shown in fig. 1 and the circulating washing device shown in fig. 2 were used to prepare high-purity vanadium pentoxide by the following steps:
1. removing impurities with an impurity removing agent: mixing 4000kg of crude ammonium metavanadate (the purity is 97.8 percent, and the impurity elements comprise silicon, phosphorus, iron, manganese, potassium and sodium) and 14000kg of deionized water in an impurity removal reactor 107, heating to 85 ℃, and stirring until the ammonium metavanadate is completely dissolved to obtain an aqueous solution of the crude ammonium metavanadate; adding 10kg of sodium chlorate, adding sodium carbonate to adjust the pH value of the solution to 10.5, stirring, and keeping the temperature at 85 ℃ for 1h; firstly, adding Ethylene Diamine Tetraacetic Acid (EDTA), wherein the mass ratio of the dosage of the EDTA to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is 5:10000, stirring for 20 minutes, and then adding magnesium chloride, wherein the mass ratio of the using amount of the magnesium chloride to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is 20:100, stirring and dissolving, and then keeping the temperature at 70 ℃ and standing for 4 hours; cooling the materials to 40 ℃, performing pressure filtration by using a plate-and-frame filter press 108, and putting the obtained filtrate into a vanadium precipitation reactor 113;
2. and (3) vanadium precipitation: adding ammonium chloride with the mass 1 time of the theoretical mass of vanadium pentoxide in the filtrate into a vanadium precipitation reactor 113, and carrying out vanadium precipitation reaction for 12h, wherein the ammonium metavanadate is completely precipitated; the material in the vanadium precipitation reactor 113 is pumped to a wash tank 128 in a circulating wash unit;
3. circularly washing and removing impurities: the bottom of the washing tank 128 is provided with a filter valve 135, a filter plate 129 is arranged below the filter valve 135, a pipeline below the filter plate 129 is provided with three connectors which are respectively connected with a drain valve 131, a siphon valve 130 and a discharge valve 133, the filter valve 135 and the drain valve 131 are opened, ammonium metavanadate precipitate in the material is intercepted by the filter plate 129, vanadium precipitation tail water is discharged into a vanadium precipitation tail water collecting pool 132 through the drain valve 131, and the drain valve 131 is closed after liquid drainage is completed. Supplementing triple-effect evaporation condensate water in a water seal barrel 121 in the circulating washing device, supplementing water to two thirds of the liquid level of an evaporation tank 140 in the circulating washing device through a sealing valve 123, wherein the volume of the evaporation tank 140 is 2 times of that of the washing tank 128, and closing the sealing valve 123 after the water is supplemented. The siphon valve 130 is opened, water in the evaporation tank 140 is heated by a steam coil 137 arranged in the evaporation tank 140 to form water vapor, the water vapor enters the washing tank 128 through a communicating pipe 136, a condensing pipe 120 is arranged at the top of the washing tank 128, the condensing pipe 120 is connected with a water sealing barrel 121 through a pipeline provided with a filter screen 116 and a filter screen 117, the water vapor is condensed in the condensing pipe 120 to form condensed water which falls into the washing tank 128, the washing tank 128 is basically filled with the detergent obtained by condensation during each washing, and the mass of the detergent is 4 times of the mass of ammonium metavanadate precipitate in the washing tank 128. Ammonium metavanadate precipitates in the washing tank 128 carry a large amount of ammonium chloride, evaporated condensed water is contacted with the ammonium chloride to form a high-purity ammonium chloride solution in the washing process, the washed washing water is sucked into the evaporating tank 140 through the siphon valve 130 and the siphon 127, then liquid in the evaporating tank 140 (namely evaporated washing raw water) is heated, steam enters the washing tank 128 through the communicating pipe 136 and is condensed into an ammonium chloride solution through the condensing pipe 120 to wash the ammonium metavanadate precipitates, the evaporation, the condensation, the washing and the siphon are circularly carried out, the siphon frequency is 15 times, the washing process is finished, the ammonium metavanadate is discharged through the discharge valve 133, and the centrifugal dehydration is carried out by utilizing the centrifuge 134 to obtain purified ammonium metavanadate; in the washing process, when the concentration of ammonium chloride in the evaporation washing raw water in the evaporation tank 140 is enriched to 40wt%, 80% of the evaporation washing raw water is discharged through a drain valve 141 at the bottom of the evaporation tank 140 and enters an ammonia nitrogen wastewater collection pool, a sealing valve 123 is opened to supplement triple-effect evaporation condensed water with the same volume as the discharged evaporation washing raw water to the evaporation tank 140, and the operation is continued;
4. and (3) calcining: the purified ammonium metavanadate is calcined in a rotary kiln for 4 hours at 550 ℃, the calcined solid powder is brick red, namely a vanadium pentoxide product, the purity of the vanadium pentoxide product is 99.83% by analysis, wherein the impurity content of potassium and sodium is less than 30ppm, the quality requirement of the high-purity vanadium pentoxide of the electrolyte is met, and the yield of the vanadium pentoxide is 97.2%.
Example 4
In this example, the following steps were used to prepare high-purity vanadium pentoxide by using the impurity removal reactor and the vanadium precipitation reactor shown in fig. 1 and the circulating washing apparatus shown in fig. 2:
1. removing impurities with an impurity removing agent: 4000kg of crude ammonium metavanadate (the purity is 98.1%, and impurity elements comprise silicon, phosphorus, iron, manganese, potassium and sodium) and 14000kg of deionized water are mixed in an impurity removal reactor 107, heated to 85 ℃, and stirred until the ammonium metavanadate is completely dissolved, so as to obtain an aqueous solution of the crude ammonium metavanadate; adding 10kg of sodium chlorate, adding sodium carbonate to adjust the pH value of the solution to 10.5, stirring, and keeping the temperature at 85 ℃ for 1h; firstly, adding Ethylene Diamine Tetraacetic Acid (EDTA), wherein the mass ratio of the dosage of the EDTA to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is 5:10000, stirring for 20 minutes, and then adding magnesium chloride, wherein the mass ratio of the using amount of the magnesium chloride to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is 20:100, stirring and dissolving, and then keeping the temperature at 70 ℃ and standing for 4 hours; cooling the materials to 40 ℃, performing pressure filtration by using a plate-and-frame filter press 108, and putting the obtained filtrate into a vanadium precipitation reactor 113;
2. and (3) vanadium precipitation: adding ammonium chloride with the mass 1 time of the theoretical mass of vanadium pentoxide in the filtrate into a vanadium precipitation reactor 113, and carrying out vanadium precipitation reaction for 12h, wherein the ammonium metavanadate is completely precipitated; the material in the vanadium precipitation reactor 113 is pumped to a wash tank 128 in a circulating wash unit;
3. circularly washing and removing impurities: the bottom of the washing tank 128 is provided with a filter valve 135, a filter plate 129 is arranged below the filter valve 135, a pipeline below the filter plate 129 is provided with three connectors which are respectively connected with a drain valve 131, a siphon valve 130 and a discharge valve 133, the filter valve 135 and the drain valve 131 are opened, ammonium metavanadate precipitate in the material is intercepted by the filter plate 129, vanadium precipitation tail water is discharged into a vanadium precipitation tail water collecting pool 132 through the drain valve 131, and the drain valve 131 is closed after liquid drainage is completed. Supplementing triple-effect evaporation condensate water in a water seal barrel 121 in the circulating washing device, supplementing water to two thirds of the liquid level of an evaporation tank 140 in the circulating washing device through a sealing valve 123, wherein the volume of the evaporation tank 140 is 2 times of that of the washing tank 128, and closing the sealing valve 123 after the water is supplemented. The siphon valve 130 is opened, water in the evaporation tank 140 is heated by using a steam coil 137 arranged in the evaporation tank 140 to form water vapor, the water vapor enters the washing tank 128 through a communicating pipe 136, a condensing pipe 120 is arranged at the top of the washing tank 128, the condensing pipe 120 is connected with a water seal barrel 121 through a pipeline provided with a filter screen 116 and a filter screen 117, the water vapor is condensed in the condensing pipe 120 to form condensed water which falls into the washing tank 128, the washing tank 128 is basically filled with the detergent obtained by condensation during each washing, and the mass of the detergent is 4 times of that of ammonium metavanadate precipitate in the washing tank 128. Ammonium metavanadate precipitate in the washing tank 128 carries a large amount of ammonium chloride, evaporated condensed water is contacted with the ammonium chloride to form a high-purity ammonium chloride solution in the washing process, washing water after washing is sucked into the evaporation tank 140 through a siphon valve 130 and a siphon 127, then liquid in the evaporation tank 140 (namely, evaporated washing raw water) is heated, steam enters the washing tank 128 through a communicating pipe 136 and is condensed through a condensing pipe 120 to form an ammonium chloride solution, the ammonium metavanadate precipitate is washed, evaporation, condensation, washing and siphon are circularly performed in the above way, the siphon frequency is 8 times, the washing process is finished, the ammonium metavanadate is discharged through a discharge valve 133, and centrifugal dehydration is performed by using a centrifugal machine 134 to obtain purified ammonium metavanadate; in the washing process, when the concentration of ammonium chloride in the evaporation washing raw water in the evaporation tank 140 is enriched to 40wt%, 80% of the evaporation washing raw water is discharged through a drain valve 141 at the bottom of the evaporation tank 140 and enters an ammonia nitrogen wastewater collection pool, a sealing valve 123 is opened to supplement triple-effect evaporation condensed water with the same volume as the discharged evaporation washing raw water to the evaporation tank 140, and the operation is continued;
4. and (3) calcining: the purified ammonium metavanadate is calcined in a rotary kiln for 4 hours at 550 ℃, the calcined solid powder is brick red, namely a vanadium pentoxide product, the purity of the vanadium pentoxide product is 99.6% by analysis, the impurity content of potassium and sodium is less than 30ppm, the quality requirement of the high-purity vanadium pentoxide of the electrolyte is met, and the yield of the vanadium pentoxide is 97.4%.
Claims (12)
1. A method for purifying ammonium metavanadate, comprising the steps of:
(1) Removing impurities with an impurity removing agent: adding an oxidant and a pH regulator into the aqueous solution of the crude ammonium metavanadate, regulating the pH value to 9-11, adding an impurity removing agent for reaction, and filtering to obtain a filtrate;
(2) And (3) vanadium precipitation: adding ammonium chloride into the filtrate obtained in the step (1) to carry out vanadium precipitation reaction;
(3) Circularly washing and removing impurities: separating ammonium metavanadate precipitate in the material subjected to vanadium precipitation reaction in the step (2), circularly washing the ammonium metavanadate precipitate, and dehydrating to obtain purified ammonium metavanadate, wherein the circularly washing comprises at least 10 times of washing, wherein the ammonium metavanadate precipitate is washed for the first time by using clear water, and the liquid used for washing for the 2 nd time and later batches is an ammonium chloride solution obtained by evaporating and condensing all or part of washing water generated by the previous washing and optionally evaporated washing raw water for replenishing water;
the oxidizing agent is sodium chlorate, the pH regulator is one or more selected from sodium hydroxide, sodium carbonate and sodium bicarbonate, the impurity removing agent comprises a chelating agent and a flocculating agent, the chelating agent is ethylenediamine tetraacetic acid, and the flocculating agent is one or more selected from aluminum sulfate, magnesium chloride and aluminum chloride;
in the step (1), after an impurity removing agent is added, carrying out heat preservation and standing reaction;
in the step (3), the concentration of ammonium chloride in the evaporation washing raw water is controlled to be 1wt% -45wt%, after each washing, when the concentration of ammonium chloride in the evaporation washing raw water does not reach 35wt% -45wt%, water is not supplemented, the evaporation washing raw water is directly heated to form steam, the steam is condensed to obtain the ammonium chloride solution, when the concentration of the evaporation washing raw water reaches 35wt% -45wt%, water is supplemented after the evaporation washing raw water is discharged partially, then the evaporation washing raw water is heated to form steam, and the steam is condensed to obtain the ammonium chloride solution.
2. The method for purifying ammonium metavanadate according to claim 1, wherein the mass ratio of the dosage of the chelating agent to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is (2-10): 10000.
3. the method for purifying ammonium metavanadate according to claim 1, wherein the mass ratio of the dosage of the flocculating agent to the theoretical amount of vanadium pentoxide in the aqueous solution of the crude ammonium metavanadate is (5-50): 100.
4. the method for purifying ammonium metavanadate according to claim 1, wherein in the step (1), the temperature for the heat-preserving standing reaction by adding the impurity removing agent is 60-80 ℃, and/or the time for the heat-preserving standing is 4-6h.
5. The method for purifying ammonium metavanadate according to claim 1, wherein in the step (2), the mass ratio of the using amount of ammonium chloride to the theoretical amount of vanadium pentoxide in the filtrate is 1: (0.5-1.0).
6. The method for purifying ammonium metavanadate according to claim 1, wherein in the step (2), the vanadium precipitation reaction time is 8-16h.
7. The method for purifying ammonium metavanadate according to claim 1, wherein the number of washing times of the cyclic washing in the step (3) is 10 to 15.
8. The method for purifying ammonium metavanadate according to claim 1, wherein in the step (3), after each washing, washing water is introduced into an evaporation device in a siphonic manner, and liquid in the evaporation device is evaporated and condensed to obtain the ammonium chloride solution.
9. The method for purifying ammonium metavanadate according to claim 1, wherein in the step (3), vapor formed by evaporating the evaporated raw washing water is introduced into a washing device for washing ammonium metavanadate precipitate, a condensing device is arranged at the top of the washing device, and the vapor is condensed into the ammonium chloride solution by the condensing device.
10. The method for purifying ammonium metavanadate according to claim 1, wherein in the step (3), when the concentration of the evaporation washing raw water reaches 35wt% to 45wt% after each washing, after discharging 75% to 85% of the evaporation washing raw water, replenishing water, and then heating the evaporation washing raw water to form vapor, and the vapor is condensed to obtain the ammonium chloride solution.
11. A method for producing vanadium pentoxide from ammonium metavanadate, characterized in that the method comprises step (1), step (2) and step (3) in the method according to any one of claims 1 to 10, and the method further comprises the steps of:
(4) And (3) calcining: and (4) calcining the purified ammonium metavanadate obtained in the step (3) to obtain vanadium pentoxide.
12. The method of claim 11, wherein in step (4), the calcination temperature is 500-550 ℃ and/or the calcination time is 3-5h.
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