Urea Granulation Technology: Spout Fluid Bed Granulation Process


TOYO started the establishment of a urea granulation process based on a Spout Bed type urea granulator and expanded its own Technical range to provide a variety of urea fertilizer products since the late 1970s in addition to the conventional Urea Prill Product and Urea Solution Product. In the 1980s, TOYO further improved its design of the granulator by applying the Spout-Fluid Beds for the granulator, which is a combination of the spouted beds and fluidizing beds and reduces energy requirements and improves the quality of the product granules.


TOYO’s Spout Fluid Bed Granulation Process has the following features.

  • 1. High energy efficiency (low power consumption)

    • No requirement of compressed atomizing air for granulator
    • Seed circulation at optimized recycle temperature
    • Optimal fluidized bed height to minimize the required fluidizing air pressure
    • Uniquely designed low-pressure drop dust scrubber
  • 2. High product quality

    • Rapid cooling of the urea solution sprayed in the granulator to reduce biuret formation to negligibly small
    • Efficient drying in the granulator to achieve low moisture content in products and high product hardness
    • Optimal combination of spouted bed and fluidized bed to produce round and uniform products
  • 3. Low emission

    • Low dust formation in the granulator
    • Uniquely designed low-pressure drop dust scrubber
Conceptual drawing of TOYO’s Spout Fluid Bed granulator

Outline of TOYO’s granulation process

The urea solution or molten urea is fed on the spouting urea seeds through the multi-spray nozzles to enlarge the recycle particles (seeds) in the granulator. The water in the feed urea solution is evaporated by spouting air on the spouted beds in the granulator to produce the urea granules. The enlarged granules are cooled to a suitable temperature by fluidizing air on the internal fluidized beds in the granulator. Coarse urea granules produced in the granulator are screened to separate the product size granules from over and undersize granules through the double-deck screen.Undersized granules are recycled back to the granulator as the seed and oversized granules are crushed through the double roller type crusher and recycled back to the granulator together with the undersized granules as the seeds. The product size granules are cooled by the cooler and come out as a product.

Process flow diagram of TOYO’s granulation process

Product quality

Total Nitrogen
46.3 wt.%
0.8 wt.%
0.2 wt.%
0.45 wt.%
Size 2 - 4 mm
95 wt.%
3.5kg/granule for 3 mm

*Typical standard figure depending on the design conditions of each plant.

Consumption per unit of service

0.01 MT/MT *1
24 kWh/MT *2

*1 Typical standard figure depending on the atmospheric conditions of each plant, utility conditions, and concentration of feed urea solution
*2 Typical standard figure in case of fluidizing product cooler. In case of bulk flow cooler by cooling water, power consumption becomes 19kW/MT. Depend on production capacity, atmospheric condition, utility and concentration of urea solution

Clean emission

Air containing urea dust from the granulator is washed with circulating water in the uniquely designed low-pressure drop dust scrubber to reduce urea dust to less than 30 mg/Nm3-Air and discharged to the atmosphere. In case ammonia content discharged to the atmosphere also needs to be reduced, an acid scrubbing system where sulfuric acid or nitric acid is used can be applied.

Conceptual drawing of TOYO’s dust scrubber

Various product sizes and applications

TOYO’s granulation plant has the capability to produce various sizes of products to meet each application by changing the mesh size of the screen with the same plant.

Product size and application

※TOYO does not produce urea in-house. Please note that TOYO is unable to respond to requests for business negotiations for supply of urea or sample provision of urea product.

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