Ammonium molybdate (mainly including ammonium dimolybdate, ammonium tetramolybdate, and ammonium heptamolybdate) is an important intermediate in molybdenum deep processing. It is widely used in the production of molybdenum powder, molybdenum trioxide, catalysts, molybdenum metal products, and agricultural molybdenum fertilizers.
During ammonium molybdate production, agglomeration has long been a persistent challenge for the industry. This problem is particularly evident during evaporation crystallization, drying, and the subsequent hydrogen reduction process used to produce molybdenum powder.
Agglomeration mainly manifests in several ways. During crystallization, particles tend to adhere to each other, resulting in a broad and uneven dimensione delle particelle distribution. After drying, the material easily forms hard lumps or cakes. In addition, ammonium molybdate is highly hygroscopic and readily absorbs moisture, which further promotes agglomeration.
These issues significantly affect product performance. They reduce flowability and particle size uniformity and may also influence purity. In downstream applications, such as molybdenum powder production, agglomeration can lead to uneven hydrogen reduction and oversized particles. As a result, key properties of molybdenum powder—such as Fisher particle size, apparent density, and catalytic performance—are negatively impacted.
Traditional solutions include sieving, ball milling, or the addition of anti-caking agents. However, these methods often provide limited improvement. They may also introduce impurities or increase process complexity.
Principles and Advantages of Fresatura a getto
Jet milling (also known as fresatura a getto d'aria or fluidized-bed jet milling) is a dry ultrafine grinding technology that uses high-pressure compressed air or superheated steam to generate supersonic airflow (300–500 m/s). Within the grinding chamber, particles collide, rub, and shear at high speed, achieving both size reduction and deagglomeration.
This technology is particularly suitable for heat-sensitive, hygroscopic, or easily agglomerated materials. Its key advantages include:
- Highly effective deagglomeration: High-energy particle–particle collisions can efficiently break both soft and hard agglomerates, restoring the original particle size distribution, with deagglomeration efficiency approaching 100%.
- Low-temperature processing: Minimal heat generation makes it ideal for low-melting-point or heat-sensitive materials, preventing further agglomeration or thermal decomposition.
- Controllo preciso delle dimensioni delle particelle: Produces uniform particles with a narrow size distribution, smooth surfaces, and excellent dispersibility.
- Pulito e privo di contaminazioni: Enclosed operation with minimal metal wear, suitable for sterile or high-purity processing.
- Well suited for hygroscopic materials: Many highly hygroscopic compounds (including certain molybdenum compounds) are routinely processed by jet milling for deagglomeration and micronization.
In the powder processing industry, jet milling has been widely proven effective in solving agglomeration problems for materials such as nano zinc oxide, titanium dioxide, and aluminum hydroxide, significantly improving dispersion and application performance.
Application Potential of Fresatura a getto in Ammonium Molybdate Production
Traditionally, ammonium molybdate processing often relies on ball mills (such as horizontal stirred ball mills) to reduce oversize agglomerates. However, ball milling may introduce metal contamination, generate heat, and is generally less effective than jet milling in breaking soft agglomerates. Research and industrial practice indicate that:
- Molybdenum compounds (including certain molybdate salts) tend to agglomerate after spray drying or wet processing, and jet milling can effectively restore them to a single-dispersed state, even down to the submicron range.
- In upstream processing for molybdenum powder production, ammonium molybdate requires controlled particle size (e.g., Fisher size of 6–22 μm). Jet milling can accurately meet these specifications while breaking agglomerates and improving hydrogen reduction efficiency downstream.
- For hygroscopic ammonium molybdate, the low-temperature and dry environment of jet milling reduces moisture-induced agglomeration. When combined with inert gas protection, product stability can be further enhanced.
Practical industrial cases show that similar hygroscopic molybdenum compounds are frequently micronized using jet milling. This results in significantly improved flowability, particle uniformity, and catalytic performance. When applied to ammonium molybdate production lines, jet milling can be installed after crystallization and drying or before the reduction step. In this role, it functions as a dedicated deagglomeration stage. It can partially replace traditional sieving and ball milling processes, thereby simplifying the overall process while improving product quality.
Conclusione: Jet Milling as an Effective Solution
Jet milling is an effective solution to the persistent agglomeration problem in ammonium molybdate production. It efficiently breaks agglomerates and improves particle size distribution and powder dispersibility. At the same time, it preserves material purity and thermal stability. This makes it particularly suitable for the hygroscopic and heat-sensitive nature of ammonium molybdate.
With continued advancements in powder processing technology, the integration of jet milling into ammonium molybdate production is expected to increase. When combined with processes such as continuous evaporation crystallization and surface modification, jet milling will promote higher product quality and greater uniformity. This will enhance competitiveness in applications such as catalysts, molybdenum powder, and deep-processed molybdenum products.
In the future, further optimization of operating parameters—such as air pressure and feeding methods—may allow jet milling to become a standardized solution in ammonium molybdate production.
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— Pubblicato da Emily Chen