What type of granulator is used in NPK fertilizer production lines?

The granulator is the core equipment of the NPK compound fertilizer production line, directly determining the shape, strength, nutrient uniformity, and production efficiency of the fertilizer granules. Based on production capacity, material characteristics, and product positioning, the mainstream granulators currently fall into three main categories: disc type, drum type, and extrusion type, each suited to different production scenarios.

Disc granulators are the preferred equipment for small and medium-sized production lines. Their core component is an inclined rotating disc; the material spirals upwards under the combined action of centrifugal force, gravity, and friction, gradually agglomerating into granules after being sprayed with a binder. This equipment has a simple structure and is easy to operate; even beginners can learn to use it after short-term training, and the initial purchase cost is low. The resulting granules are highly uniform and commercially attractive, suitable for processing loose materials and ideal for the production of high-end fertilizers for fruits, vegetables, and flowers, meeting the needs of startups or small-batch trial production.

Rotary drum granulators are the main type of machine for large-scale production. They use a horizontal rotating cylinder as the core, with baffles that cause the material to tumble axially, forming granules through collision and friction after being sprayed with a binder. They offer significant capacity advantages, can handle highly viscous materials, and are compatible with various NPK formulations, allowing for the flexible addition of trace elements. Although the unit energy consumption is slightly higher, the large capacity can offset labor and depreciation costs, making them suitable for large-scale production by large manufacturers. However, the equipment requires professional operation and an automated control system, resulting in higher initial investment.

Double roller press granulators focus on high-concentration, binder-free production. They use high-pressure extrusion with double rollers to shape dry powder raw materials, employing a cold process. The granules have excellent compressive strength and no nutrient loss, making them suitable for heat-sensitive raw materials such as humic acid and biological bacteria, and ideal for specialized fertilizers for tobacco and fruits and vegetables. However, the capacity is lower, and the granules are irregularly shaped and have poor flowability, which can easily clog fertilizer application equipment. They are more suitable for small and medium-sized specialized fertilizer production lines.

In addition, derivative processes such as high-tower granulation and ammoniation granulation are also used. The former produces smooth, easily soluble granules, suitable for top dressing; the latter offers strong nutrient stability and lower energy consumption. The key to selecting the right equipment lies in matching production capacity, material characteristics, and product requirements.  Disk-type equipment is suitable for small-scale, high-end production, rotary drum type for large-scale mass production, and extrusion type for specialized high-concentration fertilizers, in order to achieve a balance between production efficiency and product quality.