Process for producing urea granules

Abstract

Urea granules having a desired size are produced in a fluidized bed formed in a vertical cylindrical vessel which is partitioned into an upper compartment and a lower compartment by means of a funnel shaped partition having numerous holes through which the lower compartment is connected to the upper compartment, by: (A) feeding urea solid seed particles into the upper compartment; (B) atomizing and injecting upward a liquid containing a material to be incorporated onto the urea seed particles into the upper compartment through a nozzle having a top thereof located just above a center of the bottom of the funnel-shaped partition; (C)-(1) upwardly blowing a number of streams of an inert gas having a temperature of from 50.degree. to 98.degree. C. into the upper compartment through the holes of the funnel-shaped partition; (C)-(2) blowing upward a stream of an inert gas having a temperature of from 30.degree. to 120.degree. C. into the upper compartment through an annular opening formed in the bottom of the funnel-shaped partition and surrounding the atomizing nozzle, whereby the atomized liquid droplets can adhere to the urea seed particles and be dried or solidified while the particles are circulated in a fluidized bed in the upper compartment; (D) discharging the resultant urea granules from the upper compartment through the annular opening and; (E) discharging exhaust gas from the top end of the upper compartment.