2026/06/26
What is the Rotary Drum Steam Granulation Process?
The rotary drum steam granulation process (also known as steam spray rotary drum granulation) is one of the most classic and mature granulation processes in the production of large-scale compound fertilizers and general-purpose compound fertilizers (NPK). Its core principle is: saturated steam is sprayed into a layer of powdery material inside an inclined rotating drum. The latent heat released by the steam and the condensate cause the material to agglomerate into spheres under the dual action of heat and liquid phase.
Steam plays a dual role: firstly, as a heat source, saturated steam at 0.2–0.6 MPa and a temperature of 130–160℃ is introduced, causing thermoplastic nitrogen fertilizer particles such as urea to slightly melt; secondly, as a wetting agent, the small amount of water formed after steam condensation forms a liquid film on the surface of the material particles, providing the liquid phase required for granulation. Inside the drum, the material is subjected to friction and centrifugal force, resulting in rolling, agglomeration, and densification, ultimately forming spherical particles with a diameter of Φ2–Φ4 mm.
Compared to conventional water-based granulation, steam granulation offers a more uniform liquid phase distribution, effectively preventing problems such as soft, mushy granules and uneven clumping caused by excessive water addition. This process typically achieves a pelletizing rate of 70%–85%, increases granule compactness by 30%, and significantly reduces the heat load of subsequent drying processes.
Steps of Rotary Drum Steam Granulation Process:
Step 1: Raw Material Pretreatment and Batching. Nitrogen, phosphorus, and potassium fertilizers, along with fillers, are crushed, sieved, and precisely mixed according to the formula to ensure uniform nutrient distribution.
Step 2: Steam Preheating and Granulation. The mixed raw materials are fed into a rotary drum granulator, where high-temperature steam at 100–120℃ is introduced to rapidly increase the material's temperature and humidity. The drum rotates at a uniform speed, causing the material to tumble and collide fully within the drum, agglomerating into uniform granules.
Step 3: Drying and Cooling. The formed granules are sent to a rotary dryer for low-temperature drying (inlet temperature ≤200℃ to protect nitrogen), followed by cooling in a cooler.
Step 4: Sieving and Returning Material. Screening removes substandard particles—fine particles are directly returned to the granulator to continue participating in pelletizing, while large particles are crushed and returned.
Step 5: Coating and Packaging. Qualified products are coated with a film by a coating machine to prevent clumping, then weighed and packaged by an automatic packaging scale and stored.
Drum Granulator: The Core of the Process
The drum granulator is a key piece of equipment in the compound fertilizer industry. Its main body is a cylindrical structure, driven by a motor through a reducer, which drives a large gear ring to rotate the drum. The inside of the drum is lined with a special rubber plate or acid-resistant stainless steel plate, enabling automatic removal of scabs and nodules.
In the steam granulation process, the core design of the drum granulator includes: a steam injection system—steam pipes are embedded in the material layer, and spray pipes are installed above to ensure uniform steam distribution; an anti-sticking lining design—the lining rotates with the drum, and adhering materials automatically fall off due to gravity; and high capacity flexibility—a Φ2.2×8m drum can achieve 8-12 t/h, while large lines can reach 20-30 t/h or more.
Core Advantages and Applicable Scenarios The core advantages of rotary drum steam granulation technology are: high granulation efficiency, with a throughput of 10-50 tons per hour, and the ability to operate continuously for 24 hours; excellent granule quality, round and full, with high compressive strength (≥12-18N/granule), and less prone to clumping; energy saving and environmental protection, reducing energy consumption by more than 20% compared to traditional processes.
This technology is particularly suitable for the low-cost manufacturing of high-nitrogen urea-based compound fertilizers (total nutrients ≥45%, nitrogen content ≥20%), and is widely applicable to large-scale, standardized compound fertilizer plants with an annual output of 50,000-300,000 tons. If you are planning a high-concentration NPK compound fertilizer production line, please contact us—we provide complete rotary drum steam granulation equipment and full-process solutions, from raw material pretreatment and steam injection systems to drying, cooling, screening, and coating integrated design. A professional team is on-site for commissioning, helping you achieve high-quality continuous production of 10-50 tons per hour with granule strength ≥12N.
The rotary drum steam granulation process stands as the cornerstone of modern high‑concentration NPK production, offering unmatched efficiency, product quality, and operational stability. At its heart, the rotary drum granulator – paired with a precise steam injection system – transforms powdered npk fertilizer raw materials processing into dense, spherical granules with compressive strength ≥12N and a granulation rate of 70‑85%. This npk fertilizer granulator machine equipment is the core of the entire npk fertilizer manufacturing process, where steam acts as both a heat source and a liquid binder, eliminating the need for excessive water and significantly reducing downstream drying load. The integrated downstream system, including a fertilizer drying and cooling machine, ensures final moisture content below 2% and particle stability, while screening and coating units deliver a premium, anti‑caking product ready for packaging. Whether for urea‑based or other high‑nitrogen formulations, the entire train – from batching to granulation, drying, cooling, and screening – is orchestrated as a seamless npk compound fertilizer machine system, capable of continuous operation at 10‑50 t/h with minimal energy consumption. In short, the rotary drum steam route remains the most reliable and cost‑effective npk fertilizer granulator machine solution for large‑scale producers seeking consistent quality, low operating costs, and rapid return on investment – making it the undisputed workhorse of the compound fertilizer industry.