Comparison of Hollow Structure Microgranule (Spray Dried Powder) and Flakes Products
1. Drying principle
- Hollow Structure Microgranule (Spray Dried Powder): The concentrated mineral sources potassium fulvate solution (or suspension liquid) is pumped under high pressure to the atomization device (centrifugal, pressure or air flow) at the top of the drying tower, where it is atomized into extremely fine droplets. These droplets are exposed to high-temperature hot air in the drying tower. The surface area of the droplets is huge, and the water evaporates instantly, forming dry hollow structure microgranule. This appearance looks like powder at first glance, but in fact, this spray drying technology polymerizes fulvic acid concentrate to hollow structure microgranule. Each small particle has a distinctive small pinhole, with uniform particle size, good fluidity and solubility, high product purity, and more stable product quality compared to flake products.
- Flakes: Evenly coat the concentrated mineral sources potassium fulvate liquid on the surface of a slowly rotating metal drum heated by steam (or heat transfer oil) inside. The material liquid forms a thin liquid film on the surface of the drum. During the rotation of the drum, the liquid film is heated and dried by the drum. When the drum rotates to a certain position (usually close to one full circle), the dry solid flakes are continuously scraped off by the sharp scraper installed on the drum and fall into the collection device below. The thin slices scraped off are usually brittle thin sheet-like solids. Some manufacturers' flakes products, in an effort to achieve low-cost competition, especially for the cheaper potassium humate products, often have excessive moisture content.
2. Product Features
- Hollow Structure Microgranule (Spray Dried Powder)
· Form: Hollow spherical microgranule (caused by the instantaneous evaporation and expansion of water), with relatively uniform particle distribution, similar to powder, and good fluidity, not prone to caking, and less dust than traditional milled powder.
· Solubility: It dissolves extremely fast, almost instantly, and is especially suitable for making instant and water-soluble fertilizers.
- Flakes
· Form: Irregular and brittle thin flake. To improve fluidity, some large-sized flakes usually need to be further milled into powder or small flakes.
· Solubility: The dissolution rate is relatively slow. Flakes require time to disintegrate and dissolve, and the solubility is worse than hollow structure microgranule (spray dried powder).
3. Product Composition and Purity
- Hollow Structure Microgranule (Spray Dried Powder): The intake air temperature is high and the evaporation of water droplets will take away a large amount of latent heat. However, the temperature of the material itself usually does not exceed the wet bulb temperature of the outlet air (generally between 70 and 90°C), and the heating time is extremely short. Therefore, the damage to the heat-sensitive active substances (such as small molecule fulvic acid) of potassium fulvate is relatively small, and its biological activity can be better maintained. Moreover, during the drying process, the material only comes into contact with hot air, so the product purity is relatively high and the introduction of impurities is less.
- Flakes: The materials come into direct contact with the high-temperature metal surface for a relatively long time. Although the surface temperature of the drum may be lower than the inlet air temperature in spray drying, the continuous heat conduction and the longer contact time make it more likely to cause local overheating, posing a higher risk of damage to heat-sensitive active substances and potentially reducing the biological activity of the product. Moreover, long-term operation may lead to slight wear on the drum surface, posing a risk of metal ion (such as iron ion) contamination of the product, which could affect the purity and stability of the product.
4. Production and Application
- Hollow Structure Microgranule (Spray Dried Powder): The equipment investment is huge and the production threshold is high. It is suitable for large-scale and continuous production, and is particularly suitable for the production of high-end and high-quality mineral source potassium fulvate products. In China, only some of the humic acid factories have advanced technologies and sufficient scale capabilities and have installed high-tower spray drying production lines. Spray powder is suitable for applications with high requirements for dissolution speed, active substance retention, fluidity, and purity, such as high-end water-soluble fertilizers, foliar fertilizers, biological stimulants, pharmaceuticals and health products, etc. It is the preferred choice for large-scale industrial production.
- Flakes: The equipment investment is not high, the production threshold is low, it is suitable for small-scale, intermittent or continuous production, and has high flexibility. Therefore, there are many manufacturers, and the quality varies. The sheet form is more suitable for applications where the requirement for dissolution speed is not high and the cost sensitivity is high.
Conclusion: The flakes products entered the market earlier and currently have a high market share. The spray powder entered the market later, but it has high quality and stability, a beautiful appearance, clear color, and a distinctive appearance, and is gradually being accepted by users in the market.