Fertilizer Granule Formation with Recovered Phosphorus by PHOS4green

Transfer of the finished suspension directly into a dry, dust-free granulate with defined properties

Using continuous spray granulation to produce phosphate-containing fertilizer

Spray granulation in the fluid bed refines the digested phosphate into a marketable product. This enables you to produce round pellets with a compact, homogeneous particle structure. The process allows the drying of liquids – like suspensions from sewage sludge ash – while at the same time producing dust-free, flowable, easy-to-dose granules with high bulk density and narrow particle size distribution.

Fluidized bed processes are used for thermal treatment and drying to form granules from powders or liquids and to coat particles. A fluidized bed is formed when process air lifts and fluidizes a layer of solid particles. The process air simultaneously provides the thermal energy required for particle production. The process time varies depending on the raw materials and the end product, for example, if substances in the formulation tend to stick together. Once the target size of the fertilizer granules is reached, the product is discharged. It is immediately ready for use and can be directly packaged, marketed and dosed.

The phosphate suspension is sprayed into the fluidized bed in the process chamber and dries on its surface, initiating layer-by-layer particle growth. The small solid particles required to maintain the granular structure are generated in the process itself. These serve as carrier nuclei for the formation of new fertilizer granules. Only the suspension as a liquid raw material is required.

Watch the video on Continuous Spray Granulation in the Fluid Bed on the Glatt Youtube Channel here.

Principle of spray granulation in the fluidized bed: solid particles from the suspension are wetted with spray liquid, which evaporates and forms a solid shell consisting of several layers.

Exceptional fertilizer quality due to the special type of granulation

The granules produced have a dense surface with high abrasion resistance. Advantages for the practice are improved product properties as well as the reduced occurrence of undesirable drift phenomena when spreading the fertilizers. In addition, the solubility of such granules can be very well adapted to soil-, plant- and weather-specific application conditions. Parameters such as particle size, residual moisture and solids content can be specifically influenced to achieve different product properties.

compact and
particle structure







grain size

Here are some examples of different phosphate fertilizers and phosphate-containing multi-nutrient fertilizers:

Optional: Further options for functionalization with subsequent fluidized bed coating.

If required, the particles can then be coated with a functional protective layer to adjust further active substance combinations. Such a coating protects active substances, for example, from storage, transport or application-related influences, masks unwanted odor and enables colored branding as well as the targeted release of active ingredients.

Watch the video on continuous particle coating in the fluid bed on the Glatt Youtube channel here.

The application of the cladding material by spraying the solids-containing liquid onto the fluidized particles, as well as the drying and solidification of the film, take place in one process step.

Glatt uses its many years of experience in the production of special fertilizers to meet customer requirements, e.g.:

  • long-term fertilization
  • multi-component fertilization
  • functionalities such as controlled release or slow release through defined coating of the fertilizer granules

The application of various coating materials with the aid of fluid bed coating makes it possible to fulfill such functions.
The coating/enveloping of the fertilizer granules is carried out in compliance with the currently valid regulations of the Fertilizer Ordinance – German Düngemittelverordnung (DüMV) and Regulation EG No. 2019/1009. Conformity to some of these requirements is often only achieved through the use of such auxiliary materials.

Coating materials that are used in the process of fertilizer coating in the fluid bed, among others:

  • customized materials
  • hydrophobic materials
  • nitrification inhibitors
  • urease inhibitors
  • dyes
  • polyolefins
  • magnesium
  • polymers, sulfur-coated
  • biopolymers
Here are some examples of fertilizer granules that have been additionally coated with a coating layer: