阅读说明：本技术 一种钨酸一步氨溶脱磷除钼制取仲钨酸铵的方法 (Method for preparing ammonium paratungstate by removing molybdenum through one-step ammonia solution dephosphorization of tungstic acid ) 是由 徐国钻 羊求民 何光浪 傅雨 王红云 林丽萍 张龙辉 于 2021-08-18 设计创作，主要内容包括：本发明提供一种钨酸一步氨溶脱磷除钼制取仲钨酸铵的方法,具体是将球磨得到的白钨矿细粉用盐酸浸出得到粗制钨酸,再将钨酸转至氨溶釜内,同时加入一定体积的氨水和一定质量的镁盐、硫化铵、硫酸铜,反应一段时间后,过滤得到钨酸铵溶液,经蒸发结晶即可得到合格的仲钨酸铵产品。本发明将钨酸氨溶和脱磷除砷过程结合在一起,化三步为一步,不仅缩短了工艺流程,还提高了生产效率；充分利用了氨溶渣的促进形核和吸附特性,使除磷渣、除钼渣与氨溶渣共沉淀,大大提高了反应效率和除杂效果,降低了试剂的消耗,节约了生产成本,适用于大规模工业化生产。(The invention provides a method for preparing ammonium paratungstate by removing phosphorus and molybdenum from tungstic acid through one-step ammonia dissolution, which comprises the steps of leaching fine scheelite powder obtained through ball milling with hydrochloric acid to obtain rough tungstic acid, transferring the tungstic acid into an ammonia dissolution kettle, simultaneously adding a certain volume of ammonia water and certain mass of magnesium salt, ammonium sulfide and copper sulfate, reacting for a period of time, filtering to obtain an ammonium tungstate solution, and evaporating and crystallizing to obtain a qualified ammonium paratungstate product. The invention combines the processes of ammonia tungstate dissolution and dephosphorization and dearsenification, and the three steps are combined into one step, thereby not only shortening the process flow, but also improving the production efficiency; the method makes full use of the characteristics of promoting nucleation and adsorption of the ammonia slag, so that the phosphorus-removing slag, the molybdenum-removing slag and the ammonia slag are subjected to coprecipitation, the reaction efficiency and the impurity removal effect are greatly improved, the consumption of reagents is reduced, the production cost is saved, and the method is suitable for large-scale industrial production.)

1. A method for preparing ammonium paratungstate by removing molybdenum from tungstic acid through one-step ammonia solution dephosphorization is characterized by comprising the following steps:

step 1: hydrochloric acid leaching of scheelite

Throwing the scheelite fine powder subjected to ball milling into an acid decomposition kettle, adding a certain volume of hydrochloric acid, reacting for a period of time, cooling, filtering, allowing the filtrate to enter an acid filtrate tank, and allowing the tungstic acid to stay in a plate frame;

step 2: dissolving tungstic acid in ammonia and removing impurities

Transferring a certain amount of tungstic acid into an ammonia dissolving kettle, adding a certain volume of ammonia water, a certain mass of magnesium salt and a molybdenum removing reagent, reacting for a period of time, and filtering to obtain an ammonium tungstate solution;

and step 3: evaporative crystallization

And (3) evaporating and crystallizing the ammonium tungstate solution obtained in the step (2) to obtain a qualified ammonium paratungstate product.

2. The method for preparing ammonium paratungstate by one-step ammonia-dissolving, dephosphorizing and molybdenum-removing tungstic acid according to claim 1, which is characterized in that: the molybdenum removing reagent in the step 3 is ammonium sulfate and copper sulfate.

3. The method for preparing ammonium paratungstate by one-step ammonia solution dephosphorization and molybdenum removal of tungstic acid according to claim 1 or 2, which is characterized in that: in the step 2, the mass ratio of the magnesium salt to the ammonium sulfide to the copper sulfate to the tungstic acid is 0.5-5: 0.096-0.12: 1.6-2: 100.

4. The method for preparing ammonium paratungstate by one-step ammonia-dissolving, dephosphorizing and molybdenum-removing tungstic acid according to claim 1, which is characterized in that: the method comprises the step 1 of ball milling of scheelite, wherein a certain amount of scheelite is added into a ball mill for ball milling, the ball-material ratio is 1.5-4: 1, the diameter of a milling ball is 5-40 mm, the ball milling medium is water, the adding amount of the ball milling medium is 1-3: 1, the ball milling time is 1-15 h, and the average particle size of scheelite fine powder obtained after the ball milling is 10-40 mu m.

5. The method for preparing ammonium paratungstate by one-step ammonia-solution dephosphorization and molybdenum removal of tungstic acid according to any one of claims 1 or 3, characterized in that: the average particle size of the scheelite fine powder is 5-40 mu m.

6. The method for preparing ammonium paratungstate by one-step ammonia-dissolving, dephosphorizing and molybdenum-removing tungstic acid according to claim 1, which is characterized in that: in the step 1, the volume of hydrochloric acid/weight of ore is 1.5-4.0 mL:1g, the concentration of hydrochloric acid is 10-31%, the reaction temperature is 60-100 ℃, and the reaction time is 1-5 h.

7. The method for preparing ammonium paratungstate by one-step ammonia-dissolving, dephosphorizing and molybdenum-removing tungstic acid according to claim 1, which is characterized in that: the volume mass ratio of ammonia to tungstic acid in the step 2 is 1.5-3.0 mL:1 g.

8. The method for preparing ammonium paratungstate by one-step ammonia-dissolving, dephosphorizing and molybdenum-removing tungstic acid according to claim 1, which is characterized in that: the ammonia water concentration in the step 2 is more than 100g/L, preferably more than 210g/L, and more preferably 270 g/L.

9. The method for preparing ammonium paratungstate by one-step ammonia-dissolving, dephosphorizing and molybdenum-removing tungstic acid according to claim 1, which is characterized in that: the magnesium salt in the step 2 is one or more of magnesium sulfate, magnesium nitrate and magnesium chloride, and preferably magnesium sulfate.

10. The method for preparing ammonium paratungstate by one-step ammonia-dissolving, dephosphorizing and molybdenum-removing tungstic acid according to claim 1, which is characterized in that: in the step 2, the reaction temperature is normal temperature to 100 ℃, preferably 50 to 100 ℃, and the reaction time is 0.5 to 4 hours.

Technical Field

The invention belongs to the technical field of tungsten smelting, and particularly relates to a method for preparing ammonium paratungstate by one-step ammonia-soluble purification of tungstic acid, in particular to a method for removing phosphorus and molybdenum by one-step ammonia-soluble purification.

Background

In the tungsten smelting production process, along with the gradual decrease of the black tungsten concentrate, the white tungsten concentrate resource plays an increasingly important role in the tungsten industry, and the search for an efficient, clean and simple white tungsten smelting process is more important. The scheelite decomposition mainly comprises two methods, namely acid decomposition and alkali decomposition, tungsten ore alkali cooking slag is regarded as dangerous waste in 2016, so that the cost for decomposing the scheelite by the alkali method is obviously increased, many enterprises treat the scheelite by using the acid decomposition process, firstly, tungstic acid is prepared, then, an ammonium tungstate solution is prepared by an ammonia solution process, and finally, impurity removal, purification, evaporation and crystallization are preferably carried out to prepare ammonium paratungstate. Although the process has the advantages of short process flow, low production cost and the like, the impurity elements such as potassium, sodium, phosphorus, molybdenum and the like in the scheelite concentrate can be circulated to subsequent products along with the production process, and finally the impurity elements of ammonium paratungstate exceed the standard.

In order to remove impurity ions such as phosphorus, molybdenum and the like in an ammonium tungstate solution, magnesium salt is usually added into the ammonium tungstate solution to remove phosphorus, and then molybdenum is removed by using a traditional ammonium sulfide-copper sulfate process. Funan university of China (deep removal of magnesium ions in ammonium tungstate solution, rare metals and hard alloy, volume 46, phase 4, pages 1-5) adopts D850 chelating resin to adsorb Mg in ammonium tungstate solution²⁺The method can produce APT products which reach the national standard GB/T10116-88 APT-0, but the process is complex in process, generates more waste water in the adsorption and desorption processes, is high in cost and is not beneficial to being applied to large-scale industrial production. In the prior art, molybdenum removal methods comprise ion exchange, liquid phase precipitation, APT evaporative crystallization and the like, are generally carried out step by step with a phosphorus removal process, and not only is the flow long, but also the impurity removal effect of each step is not good.

Therefore, it is very urgent for those skilled in the art how to realize the removal of molybdenum by dephosphorization in one step in the ammonia dissolving process without introducing excessive impurities such as magnesium ions.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a method for preparing ammonium paratungstate by one-step ammonia-soluble dephosphorization and molybdenum removal of tungstic acid, which is characterized in that scheelite is decomposed by hydrochloric acid to prepare crude tungstic acid, then magnesium salt and a molybdenum removal reagent are added when the tungstic acid is dissolved in ammonia, and the dissolution of impurities such as phosphorus, arsenic, silicon, molybdenum and the like can be effectively inhibited by controlling the technological parameters of ammonia dissolution, so that the ammonia dissolution of the tungstic acid is realized, the impurities such as phosphorus, arsenic, silicon, molybdenum and the like are effectively removed, the generated precipitate stays in slag, and the ammonium tungstate solution is evaporated and crystallized to obtain qualified ammonium paratungstate. The specific technical scheme is as follows:

a method for preparing ammonium paratungstate by removing molybdenum from tungstic acid through one-step ammonia solution dephosphorization comprises the following steps:

step 1: hydrochloric acid leaching of scheelite

And (3) pumping the ball-milled scheelite fine powder into an acid decomposition kettle, adding a certain volume of hydrochloric acid, reacting for a period of time, cooling, filtering, feeding the filtrate into an acid filtrate tank, and stopping the tungstic acid in a plate frame.

Step 2: dissolving tungstic acid in ammonia and removing molybdenum by dephosphorization

Transferring a certain amount of tungstic acid into an ammonia dissolving kettle, adding a certain volume of ammonia water and certain mass of magnesium salt, ammonium sulfide and copper sulfate reagents, reacting for a period of time, and filtering to obtain an ammonium tungstate solution.

And step 3: evaporative crystallization

And (3) evaporating and crystallizing the ammonium tungstate solution obtained in the step (2) to obtain a qualified ammonium paratungstate product.

Further, the molybdenum removing reagent in the step 3 is ammonium sulfate and copper sulfate.

Further, the mass ratio of the magnesium salt, the ammonium sulfide, the copper sulfate and the tungstic acid in the step 2 is 0.5-5: 0.096-0.12: 1.6-2: 100.

Further, a step of ball milling the scheelite is also included before the step 1, a certain amount of scheelite is added into a ball mill for ball milling, and the ball-to-material ratio is 1.5-4: 1, the diameter of a grinding ball is 5-40 mm, the ball milling medium is water, and the adding amount of the ball milling medium is 1-3: 1, ball milling time is 1-15 h, and the average particle size of the scheelite fine powder obtained after final ball milling is 10-40 μm.

Further, the volume of hydrochloric acid/weight of ore in the step 1 is 1.5-4.0 mL:1g, the concentration of hydrochloric acid is 10-31%, the reaction temperature is 60-100 ℃, and the reaction time is 1-5 h.

Further, the volume-mass ratio of ammonia to tungstic acid in the step 2 is 1.5-3.0 mL:1 g.

Furthermore, the ammonia water concentration in the step 2 is more than 100g/L, preferably more than 210g/L, and more preferably 270 g/L.

Further, the magnesium salt in the step 2 is one or more of magnesium sulfate, magnesium nitrate and magnesium chloride, and the mass ratio of the magnesium salt to the tungstic acid is 0.5-5: 100.

Further, the reaction temperature in the step 2 is normal temperature to 100 ℃, preferably 50 to 100 ℃, and the reaction time is 0.5 to 4 hours.

The inventor proposes that the rough tungstic acid is prepared when hydrochloric acid decomposes scheelite, then magnesium salt and molybdenum removing reagent are added when ammonia tungstate is dissolved, and ammonia dissolving process parameters are controlled, so that the dissolution of impurities such as phosphorus, arsenic, silicon, molybdenum and the like can be effectively inhibited when the ammonia tungstate is dissolved, the impurities such as phosphorus, arsenic, silicon, molybdenum and the like can be effectively removed while the ammonia tungstate is dissolved, the phosphorus, arsenic, silicon and molybdenum are generated and precipitated and stay in slag, and the qualified ammonium tungstate can be obtained by evaporating and crystallizing the ammonium tungstate solution obtained by filtering, wherein the process flow is shown in the attached drawing. The process can realize the short-process preparation of ammonium paratungstate, reduces the dosage of a magnesium salt reagent and residual magnesium ions while efficiently removing impurities, and greatly shortens the process flow by changing three processes into one process. The specific process principle is as follows:

Mg²⁺+NH₄ ⁺+PO₄ ^3-→MgNH₄PO₄↓

Mg²⁺+NH₄ ⁺+AsO₄ ^3-→MgNH₄AsO₄↓

MoO₄ ^2-+2S^2-+Cu²⁺→CuMoS₄↓

from the analysis of the chemical reaction mechanism, it can be found that: the reaction for increasing the ammonia concentration proceeds rightwards, which is favorable for forming magnesium ammonium phosphate precipitate, the dephosphorization efficiency is improved, the molybdenum removal reagent ammonium sulfide and magnesium salt are added simultaneously, the addition of ammonium sulfate can also increase the ammonia ion concentration in the solution, and the removal of phosphorus and arsenic is further promoted; according to thermodynamic calculation analysis, the temperature is increased, so that the reaction is favorably carried out rightwards, the formation of magnesium ammonium phosphate sediment is favorably realized, and the removal of phosphorus is favorably realized; on one hand, the micro ammonia dissolving slag generated by ammonia dissolving can release seed crystals to promote nucleation in the ion precipitation process, and on the other hand, the main component of the residue after ammonia dissolving in the tungstic acid is SiO₂When removing molybdenum by dephosphorization, these fine SiO₂The slag can adsorb MgNH₄PO₄And CuMoS₄And the coprecipitation is formed, so that the reaction is promoted, and the dephosphorization and molybdenum removal efficiency is improved.

According to the method, in the step 1, scheelite is added into a ball mill for ball milling, so that the scheelite is crushed into scheelite fine powder, calcium tungstate and other associated silicate minerals can be separated to a certain degree, and calcium tungstate wrapped by other compounds insoluble in hydrochloric acid is prevented from being dissolved out, so that the recovery rate of tungsten is reduced; in addition, the ball-material ratio is controlled to be 1.5-4 by controlling the process and parameters in the ball milling process: 1. the diameter of the grinding ball is 5-40 mm, the ball milling medium is water, and the addition amount is 1-3L: 1kg, ball milling time of 1-15 h and the like, and finally obtaining the scheelite fine powder with the particle size of 10-40 mu m. Experiments show that the scheelite fine powder obtained by the ball milling process is leached by hydrochloric acid to generate rough tungstic acid, then the ammonia dissolving slag generated in the ammonia dissolving process is in a micro suspension state, and the fine scheelite fine powder has good nucleation promoting and adsorption effects on the phosphorus removal slag and the molybdenum removal slag during the ammonia dissolving process.

In the acid decomposition process, the material ratio and the reaction parameters are controlled, the volume-to-mass ratio of the added hydrochloric acid to the scheelite concentrate fine powder is controlled to be 1.5-4.0L: 1kg, the concentration of the hydrochloric acid is 10-31%, the reaction temperature is 60-100 ℃, and the reaction time is 1-5 hours. In the reaction process, part of calcium impurities in the scheelite fine powder are dissolved by hydrochloric acid and can be removed along with filtration; and part of the silicon dioxide and silicate fine powder particles can not be dissolved by hydrochloric acid, the hydrochloric acid reacts with the scheelite fine powder to generate tungstic acid precipitate which is in a gel state in the solution and is aggregated with the silicon dioxide and silicate particles, unreacted calcium tungstate, phosphorus, arsenic and other impurities, and the mixture stays in the plate frame after being cooled and filtered.

The method is vital to the ammonia dissolving process of rough tungstic acid, is a key link for preparing national standard zero-level ammonium paratungstate by one-step ammonia dissolving of tungstic acid, adding a tungstic acid crude product obtained by filtering after acid decomposition into an ammonia dissolving kettle, then adding a certain volume of ammonia water and a certain mass of magnesium salt, controlling the adding amount and concentration of the ammonia water, wherein the adding amount of the ammonia water ensures that the tungstic acid can be fully dissolved to generate ammonium tungstate, and is not particularly limited, and the volume-mass ratio of the ammonia water to the tungstic acid is 1.5-3.0 mL:1 g; the concentration of ammonia water can influence the rate of the ammonia dissolving process of the tungstic acid, in the ammonia dissolving process of a crude product of the tungstic acid, insoluble substance fine particles gathered in the tungstic acid in the acid decomposition process can be released, and the formed micro-suspension-shaped ammonia dissolving residue can be used as a seed crystal to accelerate nucleation and crystallization of other precipitation processes, such as magnesium ammonium phosphate, magnesium ammonium arsenate and copper thiomolybdate, wherein mixed crystals can be generated to be separated out together due to the fact that the magnesium ammonium phosphate and the magnesium ammonium arsenate have similar crystal lattices, and enrichment precipitation of phosphorus and arsenic is accelerated and promoted. Meanwhile, because the molybdenum removal is carried out by adopting the process of firstly carrying out vulcanization and then adding copper sulfate for precipitation, stirring is stopped during precipitation, sulfo-molybdate ions slowly generated in the solution by the vulcanization are combined with copper ions to form copper thiomolybdate precipitate, at the moment, the micro-fine suspended ammonia slag generated in the ammonia dissolving process can adsorb and remove phosphorus slag, and the suspended state can more easily adsorb and precipitate the copper thiomolybdate, so that the molybdenum removal efficiency is greatly improved, therefore, the ammonia slag can better inhibit the dissolution of impurities such as phosphorus, arsenic, silicon, molybdenum and the like, and further promote the removal of the impurity elements such as phosphorus, arsenic, silicon, molybdenum and the like. According to the invention, the concentration of the ammonia water is controlled to be more than 100g/L, the ammonia water concentration is too low, the ammonia dissolution rate is influenced, the micro ammonia dissolution slag cannot timely generate coprecipitation with magnesium ammonium phosphate, magnesium ammonium arsenate, copper molybdenum sulfide and the like, the adsorption effect is weak, the concentration of the ammonia water is preferably controlled to be more than 210g/L, and a better effect can be achieved; when the concentration of the ammonia water exceeds 270g/L, the generated coprecipitation and adsorption effects are not obviously increased, so that the concentration of the ammonia water is preferably controlled to be 210-270g/L in order to save raw materials and cost.

The impurity removing agent added in the ammonia dissolving process is magnesium salt, the type of the magnesium salt is not particularly limited, the impurity removing agent can be one or more of magnesium sulfate, magnesium nitrate and magnesium chloride, and the magnesium sulfate is preferably used. The invention limits the addition of magnesium salt to fully precipitate impurities such as phosphorus, silicon, arsenic and the like in the ammonia dissolving process, and does not cause the excessive residual in the solution to cause the magnesium content in the ammonium paratungstate product prepared by evaporation crystallization to exceed the standard. According to the indexes, the impurity content in the raw materials and the purity requirement of the final product are comprehensively considered, and the mass ratio of the added magnesium salt to the added tungstic acid is controlled to be 0.5-5: 100.

The reaction temperature and time in the ammonia dissolving process are not particularly limited, but the temperature in the ammonia dissolving process can also certainly affect the removal of impurities in the coprecipitation process, the ammonia dissolving temperature can affect the ammonia dissolving rate, and further affect the formation rate and the coprecipitation effect of the fine ammonia dissolving slag. Finally, adding magnesium salt while dissolving ammonia to remove impurities, optimizing process parameters, and filtering after the ammonia dissolution is finished to obtain WO₃150-300 g/L ammonium tungstate solution, wherein the concentrations of phosphorus, arsenic, silicon and magnesium ions are less than 0.01g/L, and the total weight of the ammonia slag is 3-10% of the weight of the raw ore.

In the technical scheme provided by the invention, the preparation of the ammonium paratungstate by evaporating and crystallizing the ammonium tungstate solution after impurity removal is not particularly limited, and the conventional operation in the field can be applied in the technical scheme of the invention.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention skillfully combines ammonium tungstate dissolution and dephosphorization and molybdenum removal together, and combines three steps into one step, thereby not only shortening the process flow, but also improving the production efficiency.

2. The invention fully utilizes the characteristics of the ammonia dissolving process, greatly promotes the efficiency of removing phosphorus and molybdenum, reduces the consumption of reagents and saves the production cost.

3. The invention utilizes the adsorption characteristic of the ammonia soluble slag to ensure that the phosphorus-removing slag, the ammonia soluble slag and the molybdenum-removing slag are coprecipitated, thereby greatly improving the reaction efficiency and the impurity removal effect, reducing the concentration of magnesium ions in the ammonium tungstate solution after impurity removal to 10mg/L, and respectively reducing phosphorus, arsenic, silicon and molybdenum to 7mg/L, 8mg/L and 10 mg/L.

Drawings

FIG. 1 is a schematic diagram of a process for preparing ammonium paratungstate by removing molybdenum through one-step ammonia stripping.

Detailed Description

In order to better explain the present invention and to facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is defined by the claims.

The invention takes the process of producing tungstic acid by a certain scheelite in China as a research object, and the main components of the scheelite are shown in Table 1.

TABLE 1 composition and content of scheelite

Name (R)	WO3	Mo	SiO2	P	Ca	Others
							Content/wt%	85	0.67	10	0.38	1.7	2.25

According to one embodiment of the invention, scheelite with the components shown in table 1 is added into a ball mill for ball milling, wherein the ball-to-material ratio is 1.5-4: 1, the diameter of a grinding ball is 5-40 mm, the ball milling medium is water, and the adding amount of the ball milling medium is 1-3: 1, ball milling time is 1-15 h, and the average particle size of the scheelite fine powder obtained after final ball milling is 10-40 μm.

In one technical scheme of the invention, the preferable ball-to-material ratio is 2-3: 1, the diameter of a grinding ball is 5-40 mm, the ball milling medium is water, and the addition amount of the ball milling medium is 1.5-2.5: 1, ball milling for 5-8 h to obtain scheelite fine powder with the average particle size of 10-30 mu m.

Example 1

Adding 100g of scheelite which is not subjected to ball milling and has the particle size of 75 mu m into an acid decomposition kettle, adding 150mL of hydrochloric acid, wherein the concentration of the hydrochloric acid is 31%, the reaction temperature is 100 ℃, the reaction time is 4 hours, cooling, filtering and washing, enabling filtrate to enter an acid filtrate tank, enabling tungstic acid to stay in a plate frame, and repeating the steps for several times to prepare a certain amount of tungstic acid. Adding 100g of tungstic acid into a reaction kettle, adding 150mL of 6mol/L ammonia water, heating to 50 ℃, reacting for 0.5 hour, washing and filtering to obtain 9g of ammonia dissolving residue and 220mL of ammonium tungstate solution. At a timeFiltering the filtrate: WO₃The concentration was 238g/L, the phosphorus concentration was 146mg/L and the molybdenum concentration was 205 mg/L. 6g of magnesium sulfate is added into the filtrate, the mixture is stirred for 2 hours, the phosphorus concentration in the secondary filtering solution is 36mg/L, the magnesium ion concentration is 59mg/L, the molybdenum concentration is 205mg/L, 1.5mL of 80g/L ammonium sulfide solution is added into the filtrate, 2g of copper sulfate is added after stirring for 2 hours, the phosphorus concentration in the filtering solution is 36mg/L after 3 hours of sedimentation, the magnesium ion concentration is 59mg/L, the molybdenum concentration is 45mg/L, and the ammonium tungstate solution is subjected to impurity removal, evaporative crystallization and other steps to prepare an ammonium paratungstate product, wherein the impurity content is shown in the following table.

TABLE 2 example 1 ammonium paratungstate product impurity content (mg/kg)

Element(s)

Mg

P

As

Si

Mo

Others

EXAMPLE 1 product

33

15

12

14

18

National standard zero-grade product

10

7

8

8

20

Results

Out of limits

Out of limits

Out of limits

Out of limits

Reach the standard

Qualified

Example 2

Placing 100g of scheelite in a ball milling tank, setting the ball-material ratio to be 2:1, the diameters of grinding balls are respectively 25% of 5 mm, 15 mm, 25 mm and 40mm, the ball milling medium is water, and the addition amount of the ball milling medium is 2:1, ball milling for 8 hours to obtain scheelite fine powder with the average grain diameter of 18 mu m. Adding 100g of scheelite fine powder into an acid decomposition kettle, adding 250mL of hydrochloric acid, wherein the concentration of the hydrochloric acid is 25%, the reaction temperature is 90 ℃, the reaction time is 3 hours, cooling, filtering and washing, enabling filtrate to enter an acid filtrate tank, enabling tungstic acid to stay in a plate frame for several times, and preparing a certain amount of tungstic acid. Adding 100g of tungstic acid into a reaction kettle, adding 150mL of 7.7mol/L ammonia water, adding 1.5g of magnesium sulfate, heating to 100 ℃, reacting for 0.5 hour, washing and filtering to obtain 11g of ammonia dissolving residue and 220mL of ammonium tungstate solution. In the filtrate: WO₃340g/L of concentration, 5mg/L of phosphorus concentration, 205mg/L of molybdenum concentration and 10mg/L of magnesium ion concentration, adding 1.5mL of 80g/L of ammonium sulfide solution into the filtrate, stirring for 2 hours, adding 2g of copper sulfate, precipitating for 3 hours, filtering to obtain a solution with 36mg/L of phosphorus concentration, 44mg/L of molybdenum concentration and 11mg/L of magnesium ion concentration, removing impurities from the ammonium tungstate solutionAnd evaporating and crystallizing to prepare the ammonium paratungstate product, wherein the impurity content is shown in the table.

TABLE 3 example 2 ammonium paratungstate product impurity content (mg/kg)

Element(s)

Mg

P

As

Si

Mo

Others

EXAMPLE 2 product

<3

5

<3

<3

17

National standard zero-grade product

10

7

8

8

20

Results

Reach the standard

Reach the standard

Reach the standard

Reach the standard

Reach the standard

Qualified

Example 3

Placing 100g of scheelite in a ball milling tank, setting the ball-material ratio to be 3: the grinding ball diameter is respectively 33.3% of 15 mm, 25 mm and 40mm, the ball milling medium is water, and the adding amount of the ball milling medium is 2.5: 1, ball milling for 5 hours to obtain scheelite fine powder with the average grain diameter of 30 mu m. Adding 100g of scheelite fine powder into an acid decomposition kettle, adding 300mL of hydrochloric acid, wherein the concentration of the hydrochloric acid is 20%, the reaction temperature is 85 ℃, the reaction time is 3 hours, cooling, filtering and washing, enabling filtrate to enter an acid filtrate tank, enabling tungstic acid to stay in a plate frame for several times, and preparing a certain amount of tungstic acid. Adding 100g of tungstic acid into a reaction kettle, adding 250mL of 6.5mol/L ammonia water, heating to 80 ℃, reacting for 2 hours, filtering and washing to obtain 11g of ammonia dissolving residue and 260mL of ammonium tungstate solution. Adding 11g of magnesium sulfate into the ammonium tungstate solution, reacting for 2 hours, and filtering: WO₃The concentration is 260g/L, the phosphorus concentration is 5mg/L, the magnesium ion concentration is 75mg/L, 1.5mL of 80g/L ammonium sulfide solution is added into the filtrate, after stirring for 0.5 hour, 2g of copper sulfate is added, after 3 hours of sedimentation, the phosphorus concentration in the filtrate is 36mg/L, the molybdenum concentration is 45mg/L, the magnesium ion concentration is 75mg/L, and the ammonium tungstate solution is subjected to impurity removal, evaporative crystallization and other steps to prepare an ammonium paratungstate product, wherein the impurity content is shown in the following table.

TABLE 4 example 3 ammonium paratungstate product impurity content (mg/kg)

Element(s)

Mg

P

As

Si

Mo

Others

EXAMPLE 3 product

50

5

<3

<3

18

National standard zero-grade product

10

7

8

8

20

Results

Out of limits

Reach the standard

Reach the standard

Reach the standard

Reach the standard

Qualified

Example 4

Placing 100g of scheelite in a ball milling tank, setting the ball-material ratio to be 2.5: 1, the diameters of grinding balls are respectively 25% of 5 mm, 15 mm, 25 mm and 40mm, the ball milling medium is water, and the addition amount of the ball milling medium is 1.5: 1, ball milling for 6.5 hours to obtain scheelite fine powder with the average grain diameter of 16 mu m. Adding 100g of scheelite fine powder into an acid decomposition kettle, adding 300mL of hydrochloric acid, wherein the concentration of the hydrochloric acid is 31%, the reaction temperature is 90 ℃, the reaction time is 4 hours, cooling, filtering and washing, enabling filtrate to enter an acid filtrate tank, enabling tungstic acid to stay in a plate frame for several times, and preparing a certain amount of tungstic acid. Adding 100g of tungstic acid into a reaction kettle, adding 200mL of 7mol/L ammonia water, adding 2g of magnesium sulfate, heating to 60 ℃, reacting for 2 hours, washing and filtering to obtain 11g of ammonia dissolving residue and 270mL of ammonium tungstate solution. In the filtrate: WO₃The concentration was 302g/L and the phosphorus concentration was 7 mg/L. The concentration of magnesium ions is 22mg/L, 1.5mL of 80g/L ammonium sulfide solution is added into the filtrate, after stirring for 2 hours, 2g of copper sulfate is added, after precipitation for 3 hours, the phosphorus concentration in the filtered solution is 36mg/L, the molybdenum concentration is 44mg/L, the concentration of magnesium ions is 21mg/L, and the ammonium tungstate solution is subjected to impurity removal, evaporative crystallization and other steps to prepare an ammonium paratungstate product, wherein the impurity content is shown in the following table.

TABLE 5 example 4 ammonium paratungstate product impurity content (mg/kg)

Element(s)

Mg

P

As

Si

Mo

Others

EXAMPLE 4 product

<3

7

8

<3

17

National standard zero-grade product

10

7

8

8

20

Results

Reach the standard

Reach the standard

Reach the standard

Reach the standard

Reach the standard

Qualified

Example 5

Placing 100g of scheelite in a ball milling tank, setting the ball-material ratio to be 2:1, the diameters of grinding balls are respectively 25% of 5 mm, 15 mm, 25 mm and 40mm, the ball milling medium is water, and the addition amount of the ball milling medium is 2:1, ball milling for 7 hours to obtain scheelite fine powder with the average grain diameter of 28 mu m.Adding 100g of scheelite fine powder into an acid decomposition kettle, adding 300mL of hydrochloric acid, wherein the concentration of the hydrochloric acid is 20%, the reaction temperature is 85 ℃, the reaction time is 3 hours, cooling, filtering and washing, enabling filtrate to enter an acid filtrate tank, enabling tungstic acid to stay in a plate frame for several times, and preparing a certain amount of tungstic acid. Adding 100g of tungstic acid into a reaction kettle, adding 250mL of 6mol/L ammonia water, adding 1.5g of magnesium sulfate and 1.5mL of 80g/L ammonium sulfide solution, heating to 50 ℃, reacting for 4 hours, adding 2g of copper sulfate, washing and filtering to obtain 13g of slag and 300mL of ammonium tungstate solution. In the filtrate: WO₃The concentration is 250g/L, the phosphorus concentration is 16mg/L, and the molybdenum concentration is 9 mg/L. The concentration of magnesium ions is 10mg/L, and the ammonium tungstate solution is subjected to impurity removal, evaporative crystallization and other steps to prepare an ammonium paratungstate product, wherein the impurity content is shown in the following table.

TABLE 6 example 5 ammonium paratungstate product impurity content (mg/kg)

Element(s)

Mg

P

As

Si

Mo

Others

EXAMPLE 5 product

<3

6

<3

<3

8

National standard zero-grade product

10

7

8

8

20

Results

Reach the standard

Reach the standard

Reach the standard

Reach the standard

Reach the standard

Qualified

Example 6

100g of scheelite is placed in a ball milling tank, the ball material ratio is set to be 3:1, the diameters of grinding balls are respectively 33.3% of 15 mm, 25 mm and 40mm, the ball milling medium is water, and the addition amount of the ball milling medium is 2:1, ball milling for 6 hours to obtain scheelite fine powder with the average grain diameter of 25 mu m. Adding 100g of scheelite fine powder into an acid decomposition kettle, adding 300mL of hydrochloric acid, wherein the concentration of the hydrochloric acid is 25%, the reaction temperature is 80 ℃, the reaction time is 2 hours, cooling, filtering and washing, enabling the filtrate to enter an acid filtrate tank, enabling the tungstic acid to stay in a plate frame for several times, and preparing a certain amount of tungstic acid. Adding 100g of tungstic acid into a reaction kettle, adding 300mL of 6mol/L ammonia water, adding 1.5g of magnesium sulfate and 1.2mL of 80g/L ammonium sulfide solution, heating to 50 ℃, reacting for 1.5 hours, adding 1.6g of copper sulfate, reacting for 3 hours, washing and filtering to obtain 12g of ammonia soluble residue and 305mL of ammonium tungstate solution. In the filtrate: WO₃The concentration was 230g/L and the phosphorus concentration was 18 mg/L.The concentration of magnesium ions is 10mg/L, the concentration of molybdenum is 25mg/L, and the national standard zero-order ammonium paratungstate product can be prepared by the steps of impurity removal, evaporative crystallization and the like of the ammonium tungstate solution.

TABLE 7 example 6 ammonium paratungstate product impurity content (mg/kg)

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.