what is a Urea melt granulation production line？

what is a Urea melt granulation production line？

Urea melt granulation production line Core principle: urea melting (molten urea solution) → granulation → cooling → screening → finished product packaging. The mainstream is divided into tower spray granulation (traditional high tower granulation) and drum/disc melting granulation (compound fertilizer melting granulation, also known as melt granulation, slurry granulation). The most classic urea monomer is urea high tower melting granulation.

Process flow (urea tower melting granulation, most commonly used)

The solid urea particles of the raw material melting unit enter the melting tank (melting tank), which is generally heated by steam jacket, with a temperature controlled at 132-138 ℃ (the melting point of urea is about 132.7 ℃), completely melted into uniform molten urea, and kept warm to prevent recrystallization. At the same time, a small amount of defoaming and degassing can be carried out.

Key point: The temperature should not be too high for a long time (>145 ℃), as urea will decompose and produce biuret, which will affect product quality.

The molten urea pump of the lifting and distribution spray unit transports the melt to the granulation nozzle (rotating nozzle/fixed nozzle) at the top of the tower, where the melt is dispersed into small droplets that fall freely.
Cold air is introduced from bottom to top into the tower for counter current cooling and solidification. During the falling process, the droplets exchange heat with the cold air in counter current, gradually cooling and solidifying into spherical urea particles, which fall to the bottom of the tower.
After the bottom of the cooling and screening tower is discharged, it enters the fluidized bed cooling machine/rotary drum cooling machine for further cooling, followed by vibration screening, crushing of large particles, and returning of fine particles to the system for circulation.
Finished product transportation, measuring and packaging qualified particles are transported to the silo, automatically weighed and sewn to obtain finished large particle urea.

Main equipment list

Melting system: molten urine tank, steam heat exchanger, molten urea pump, insulation pipeline, filter
Granulation system: Granulation tower, rotating granulation nozzle, transmission mechanism
Wind system: induced draft fan, cooling tower, air filter, dust removal system
Post processing: fluidized bed cooler, vibrating screen, crusher, belt conveyor
Auxiliary: DCS automatic control system, steam system, circulating water, tail gas washing (urea dust+ammonia washing, essential for environmental protection)

Core control points

1. Melting temperature: 132-138 ℃, strictly control the increase of biuret
2. Nozzle speed and aperture: directly determine the particle size
3. Cooling air volume and air temperature: determine particle solidification, strength, and pulverization rate
4. Environmental Protection: Urea dust and ammonia emissions must be washed with water to meet emission standards

Frequently Asked Questions

Excessive biuret: melting temperature too high, residence time too long
Uneven and trailing particles: nozzle wear, unstable rotational speed, and molten material with bubbles
Tower wall adhesive: high wind temperature, low melt temperature, nozzle bias