CN113912125A - Calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia - Google Patents
Calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia Download PDFInfo
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Abstract
The invention discloses a calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia, which relates to the technical field of tungsten oxide preparation. According to the invention, ammonium paratungstate is calcined at three stages of temperatures, water molecules and ammonia molecules on the surface of ammonium paratungstate are volatilized and dissociated at first temperature, calcination is carried out at second temperature for cracking, and a complex intermediate product is generated, and calcination is continued at third temperature for generating tungsten oxide.
Description
Technical Field
The invention relates to the technical field of tungsten oxide preparation, in particular to a calcining process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia.
Background
Tungsten is an important strategic resource and is widely used due to its excellent properties of high melting point, high hardness, high ductility, wear resistance, corrosion resistance, etc.
Tungsten oxide is an extremely important intermediate product in the field of tungsten industry, and in industry, tungsten oxide products with high specific surface area are generally produced by a physical crushing method, such as airflow crushing, ball milling and the like, by using the tungsten oxide products as raw materials. However, the method for processing the produced tungsten oxide is high in cost, and the crushing means usually greatly destroys the crystal form and crystal appearance of the tungsten oxide product, thereby causing great negative effects on subsequent deep processing of the tungsten product. Therefore, the field of application is extremely small by means of physical crushing, and the application is rarely applied industrially.
The yellow tungsten oxide is a finely divided yellow crystalline powder. It is to strictly control the temperature and separate the bound water or water and ammonia during the calcination of ammonium paratungstate. The precise control of time and temperature greatly affects the physical properties of tungsten oxide. In the production process of the yellow tungsten oxide, the production conditions are contradictory to the influences of the specific surface area and the residual ammonia, and generally, the high specific surface area and the low residual ammonia are difficult to be considered at the same time, but with the improvement of the environmental protection requirement, the supervision of the pollution factor ammonia is increasingly intensified, and the residual ammonia in the tungsten oxide is increasingly required to be as low as possible.
Disclosure of Invention
The invention aims to at least solve one of the technical problems in the prior art and provide a calcining process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia.
The technical solution of the invention is as follows:
a calcining process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia comprises the steps of dissociating ammonium paratungstate at a first temperature lower than 300 ℃ in an oxidizing atmosphere to obtain an ammonium tungsten compound, calcining the ammonium tungsten compound at a second temperature lower than 300 ℃ in the oxidizing atmosphere, and continuously heating to a third temperature lower than 500 ℃ in the oxidizing atmosphere to calcine the ammonium tungsten compound to obtain the yellow tungsten oxide.
Preferably, the first temperature is 200-.
Preferably, the second temperature is 350-.
Preferably, the third temperature is 550-.
Preferably, the calcination is carried out while simultaneously withdrawing the ammonia and water vapor generated during the calcination.
Preferably, the rate of withdrawal is 2-3.5m3/min。
Preferably, the ammonium paratungstate is pretreated before calcination, and is uniformly mixed in the polymer solution.
Preferably, the polymer solution is: dissolving polyvinyl alcohol or polyvinylpyrrolidone in distilled water to obtain a polymer solution with the mass concentration of 10-20%.
The invention has the beneficial effects that:
(1) according to the calcination process for preparing the yellow tungsten oxide with high specific surface area and low residual ammonia, ammonium paratungstate is calcined at three stages of temperatures, water molecules and ammonia molecules on the surface of the ammonium paratungstate are volatilized and dissociated at the first temperature, calcination is carried out at the second temperature for cracking, a complex intermediate product is generated, and calcination is continued at the third temperature to generate tungsten oxide.
(2) According to the calcining process for preparing the yellow tungsten oxide with high specific surface area and low residual ammonia, air extraction is started during calcining, the influence of the reducing atmosphere of ammonia gas on the tungsten oxide can be reduced, and the residual ammonia rate can be reduced.
(3) According to the calcination process for preparing the yellow tungsten oxide with high specific surface area and low residual ammonia, the ammonium paratungstate is mixed with the polymer solution to obtain the mixed gelled solution with the network-shaped template, and the probability of coarsening of the particle size of the ammonium paratungstate can be reduced in the low-temperature calcination process of the ammonium paratungstate, so that the calcination process has an improvement effect on the particle size refinement of the ammonium paratungstate.
Detailed Description
A calcining process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia comprises the steps of dissociating ammonium paratungstate at a first temperature lower than 300 ℃ in an oxidizing atmosphere to obtain an ammonium tungsten compound, calcining the ammonium tungsten compound at a second temperature lower than 300 ℃ in the oxidizing atmosphere, and continuously heating to a third temperature lower than 500 ℃ in the oxidizing atmosphere to calcine the ammonium tungsten compound to obtain the yellow tungsten oxide.
Preferably, the first temperature is 200-.
Preferably, the second temperature is 350-.
Preferably, the third temperature is 550-.
Preferably, the calcination is carried out while simultaneously withdrawing the ammonia and water vapor generated during the calcination.
Preferably, the rate of withdrawal is 2-3.5m3/min。
Preferably, the ammonium paratungstate is pretreated before calcination, and is uniformly mixed in the polymer solution.
Preferably, the polymer solution is: dissolving polyvinyl alcohol or polyvinylpyrrolidone in distilled water to obtain a polymer solution with the mass concentration of 10-20%.
The present invention is further illustrated by the following examples. But is not limited thereto.
Example 1
Putting APT into a feeding bin, feeding the APT into a rotary furnace with the relative vacuum degree of-200 Pa by a screw feeder at the speed of 180kg/h, opening a furnace tail observation mirror to form an open system, and controlling the temperature to be as follows: the first temperature control area is 200 ℃ and oxygen atmosphere, and the second temperature control area is 320 ℃ and oxygen atmosphere; the third temperature control area is 550 ℃, the temperature is controlled, the oxygen atmosphere is kept, the rotating speed of the furnace tube is 2.5r/min, ammonia gas and water vapor generated in the calcining process are extracted, and the extracting rate is 2.5m3And/min, calcining by a rotary furnace, cooling and sieving to obtain the yellow tungsten oxide.
Example 2
Putting APT into a feeding bin, feeding the APT into a rotary furnace with the relative vacuum degree of-200 Pa by a screw feeder at the speed of 180kg/h, opening a furnace tail observation mirror to form an open system, and controlling the temperature to be as follows: the temperature of the first temperature control area is 180 ℃, the oxygen atmosphere is realized, the temperature of the second temperature control area is 350 ℃, the oxygen atmosphere is realized, the temperature of the third temperature control area is 600 ℃, the rotating speed of the furnace tube is 2.5r/min, ammonia gas and water vapor generated in the period are extracted while calcining is carried out, and the extraction speed is 3.5m3And/min, calcining by a rotary furnace, cooling and sieving to obtain the yellow tungsten oxide.
Example 3
Putting APT into a feeding bin, feeding the APT into a rotary furnace with the relative vacuum degree of-200 Pa by a screw feeder at the speed of 180kg/h, opening a furnace tail observation mirror to form an open system, and controlling the temperature to be as follows: the temperature of the first temperature control area is 190 ℃, the oxygen atmosphere, the temperature of the second temperature control area is 380 ℃, the oxygen atmosphere, the temperature of the third temperature control area is 650 ℃, the oxygen atmosphere and the rotating speed of the furnace tube is 2.5r/min, and ammonia gas and water vapor generated in the period of calcination are pumped out at the same timeThe rate of extraction was 3.5m3And/min, calcining by a rotary furnace, cooling and sieving to obtain the yellow tungsten oxide.
Example 4
Pretreating ammonium paratungstate before calcining, uniformly mixing the ammonium paratungstate and a high polymer solution in a mass ratio of 1:12 in the high polymer solution, uniformly stirring, standing until bubbles disappear completely, and obtaining a sol-gel substance containing APT, wherein the high polymer solution is: polyvinyl alcohol was dissolved in distilled water to obtain a polymer solution having a mass concentration of 10%.
Putting the sol-gel substance containing APT into a feeding bin, feeding the sol-gel substance into a rotary furnace with the relative vacuum degree of-200 Pa by a screw feeder at the speed of 180kg/h, opening a furnace tail observation mirror to form an open system, and controlling the temperature to be as follows: the temperature of the first temperature control area is 190 ℃, the oxygen atmosphere is realized, the temperature of the second temperature control area is 380 ℃, the oxygen atmosphere is realized, the temperature of the third temperature control area is 650 ℃, the rotating speed of the furnace tube is 2.5r/min, ammonia gas and water vapor generated in the period are extracted while calcination is carried out, and the extraction speed is 3.5m3And/min, calcining by a rotary furnace, cooling and sieving to obtain the yellow tungsten oxide.
Example 5
Pretreating ammonium paratungstate before calcining, uniformly mixing the ammonium paratungstate and a high polymer solution in a mass ratio of 1:15 in the high polymer solution, uniformly stirring, standing until bubbles disappear completely, and obtaining a sol-gel substance containing APT, wherein the high polymer solution is: polyvinylpyrrolidone was dissolved in distilled water to obtain a polymer solution with a mass concentration of 15%.
Putting the sol-gel substance containing APT into a feeding bin, feeding the sol-gel substance into a rotary furnace with the relative vacuum degree of-200 Pa by a screw feeder at the speed of 180kg/h, opening a furnace tail observation mirror to form an open system, and controlling the temperature to be as follows: the temperature of the first temperature control area is 190 ℃, the oxygen atmosphere is realized, the temperature of the second temperature control area is 380 ℃, the oxygen atmosphere is realized, the temperature of the third temperature control area is 650 ℃, the rotating speed of the furnace tube is 2.5r/min, ammonia gas and water vapor generated in the period are extracted while calcination is carried out, and the extraction speed is 3.5m3And/min, calcining by a rotary furnace, cooling and sieving to obtain the yellow tungsten oxide.
Comparative example 1 (one stage calcination)
Putting APT into a feeding bin, feeding the APT into a rotary furnace with the relative vacuum degree of-200 Pa by a screw feeder at the speed of 180kg/h, opening a furnace tail observation mirror to form an open system, and controlling the temperature to be as follows: the temperature control area is 650 ℃, the oxygen atmosphere is adopted, the rotating speed of the furnace tube is 2.5r/min, ammonia gas and water vapor generated in the period are extracted while calcining is carried out, and the extraction rate is 3.5m3And/min, calcining by a rotary furnace, cooling and sieving to obtain the yellow tungsten oxide.
Comparative example 2 (two-stage calcination)
Putting APT into a feeding bin, feeding the APT into a rotary furnace with the relative vacuum degree of-200 Pa by a screw feeder at the speed of 180kg/h, opening a furnace tail observation mirror to form an open system, and controlling the temperature to be as follows: the temperature of the first temperature control area is 380 ℃, the oxygen atmosphere is realized, the temperature of the second temperature control area is 650 ℃, the oxygen atmosphere is realized, the rotating speed of the furnace tube is 2.5r/min, ammonia gas and water vapor generated in the period are extracted while calcination is carried out, and the extraction rate is 3.5m3And/min, calcining by a rotary furnace, cooling and sieving to obtain the yellow tungsten oxide.
Comparative example 3
Putting APT into a feeding bin, feeding the APT into a rotary furnace with the relative vacuum degree of-200 Pa by a screw feeder at the speed of 180kg/h, opening a furnace tail observation mirror to form an open system, and controlling the temperature to be as follows: the temperature of the first temperature control area is 190 ℃, the oxygen atmosphere is realized, the temperature of the second temperature control area is 380 ℃, the oxygen atmosphere is realized, the temperature of the third temperature control area is 800 ℃, the rotating speed of a furnace tube is 2.5r/min, ammonia gas and water vapor generated in the period are extracted while calcination is carried out, and the extraction rate is 3.5m3And/min, calcining by a rotary furnace, cooling and sieving to obtain the yellow tungsten oxide.
COMPARATIVE EXAMPLE 4 (No bleed)
Putting APT into a feeding bin, feeding the APT into a rotary furnace with the relative vacuum degree of-200 Pa by a screw feeder at the speed of 180kg/h, opening a furnace tail observation mirror to form an open system, and controlling the temperature to be as follows: the first temperature control area is 190 ℃ in oxygen atmosphere, the second temperature control area is 380 ℃ in oxygen atmosphere, the third temperature control area is 650 ℃ in oxygen atmosphere, the rotating speed of a furnace tube is 2.5r/min, and after calcination by a rotary furnace, the yellow tungsten oxide is obtained by cooling and sieving.
The above examples and comparative examples were subjected to a performance particle size test (laser particle size detector) and an amount of residual ammonia (spectrophotometry);
the test results are shown in Table 1.
| Test specimen | Particle size (. mu.m) | Residual ammonia amount (%) |
| Example 1 | 11 | ＜0.01 |
| Example 2 | 10 | ＜0.01 |
| Example 3 | 9 | ＜0.01 |
| Example 4 | 6 | ＜0.01 |
| Example 5 | 5 | ＜0.01 |
| Comparative example 1 | 25 | 0.04 |
| Comparative example 2 | 18 | 0.04 |
| Comparative example 3 | 16 | 0.05 |
| Comparative example 4 | 14 | 0.08 |
As can be seen from the above table, the particle size of the examples is small, the residual ammonia rate is low, and the main reasons may be as follows, as can be seen from the analysis of comparative example 1 and comparative example 2, the ammonium paratungstate is calcined at three stages in the examples, the water molecules and ammonia molecules on the surface of the ammonium paratungstate are volatilized and dissociated first at the first temperature, the calcination is carried out at the second temperature for cracking, and a complex intermediate product is generated, and the calcination is continued at the third temperature for generating tungsten oxide. It is understood from the analysis of comparative example 3 that the particle size of tungsten oxide after calcination tends to be coarser at temperatures higher than 700 deg.C, which may be the cause of the growth of the particles at higher temperatures. From the analysis of comparative example 4, it is understood that in the examples, the effect of the reducing atmosphere of nitrogen and hydrogen on tungsten oxide at the decomposition of ammonia gas can be reduced and the residual ammonia rate can be reduced by starting the evacuation at the time of calcination. In addition, the particle sizes of examples 4 and 5 are smaller, mainly because the ammonium paratungstate is mixed with the polymer solution to obtain the mixed gelled solution with the network-shaped template, and the probability of coarsening of the particle size is reduced due to the limitation of the network-shaped template framework in the process of calcining the ammonium paratungstate at the low temperature section, so that the particle size refinement effect is improved.
The above additional technical features can be freely combined and used in superposition by those skilled in the art without conflict.
The above description is only a preferred embodiment of the present invention, and the technical solutions that achieve the objects of the present invention by substantially the same means are within the protection scope of the present invention.
Claims (8)
1. A calcining process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia is characterized in that ammonium paratungstate is dissociated at a first temperature lower than 300 ℃ in an oxidizing atmosphere to obtain an ammonium tungsten compound, the ammonium tungsten compound is calcined at a second temperature lower than 300 ℃ in an oxidizing atmosphere, and the temperature is continuously increased to a third temperature lower than 500 ℃ in an oxidizing atmosphere to obtain the yellow tungsten oxide.
2. The calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia according to claim 1, wherein the first temperature is 200-285 ℃.
3. The calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia as claimed in claim 1, wherein the second temperature is 350-460 ℃.
4. The calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia as claimed in claim 1, wherein the third temperature is 550-680 ℃.
5. The calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia according to claim 1, wherein the calcination process is carried out while extracting ammonia gas and water vapor generated in the calcination process.
6. The calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia according to claim 4, wherein the extraction rate is 2-3.5m3/min。
7. The calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia according to claim 1, wherein the ammonium paratungstate is pretreated before calcination and is uniformly mixed in a polymer solution.
8. The calcination process for preparing yellow tungsten oxide with high specific surface area and low residual ammonia according to claim 7, wherein the polymer solution is: dissolving polyvinyl alcohol or polyvinylpyrrolidone in distilled water to obtain a polymer solution with the mass concentration of 10-20%.
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