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A synthetic organic compound produced by the reaction of
ammonia with carbon dioxide, urea is the solid nitrogenous fertilizer
with the highest nitrogen content (46%). It is white, granular or
prilled material, which is easily stored and transported.
RAW MATERIALS:
- Liquid Ammonia.
- Carbon Dioxide.
MANUFACTURING STEPS:
1. Compression of Ammonia and Carbon Dioxide
Liquid ammonia and carbon dioxide gas are compressed to
140 kg/cm2 and fed to the high pressure mixer.
2. Synthesis
Most of the ammonia and carbon dioxide react
spontaneously to form ammonia carbamate in the high pressure of
condenser according to the following equation:
2NH3+ CO2 --> NH2-CO2-
NH4+ Heat
The mixture of carbamate, unreacted carbon dioxide and
ammonia is fed to the reactor, where the carbamate is partially
converted into urea according to the following equation:
NH2-CO2 --> NH2 -CO-NH2 + H2O
urea
3. Recirculation
Unreacted carbamate is separated and decomposed into
ammonia and carbon dioxide by heating and reducing pressure. Off-gases
are condensed and recycled to the high pressure condenser.
UREA I
1.Evaporation
The urea solution is concentrated to 96% by heating and
applying vacuum.
2. Granulation
The concentrated urea solution is sprayed with
atomization air into the granulator containing seed material (Urea) in a
fluidized state. The granular urea is formed by accretion of particle
build up inside the granulator. Urea from the granulator is cooled in
the fluid bed cooler and then fed to a vibration screen to separate the
desired product size. The product is further cooled in the second fluid
bed cooler and sent to storage.
UREA II & III
1. Evaporation and Crystallization
Urea solution is concentrated to urea melt by heating
and applying vacuum.
2. Melting and Prilling
Melted urea is directed to a rotating perforated bucket
(prilling device), where it is spilled out to form spheres called
prills. These prills are dried by air stream through fans located at the
top of the prilling tower. The dry prills are collected from the floor
of the prilling tower up to a vibrating screen to be separated to the
desired size. Urea prills are conveyed from the bottom of the tower to
the warehouse by a conveyer belt.
3.Granulation
Installation of a granulation unit similar to urea I is
in progress and expected to be completed in October 2002 . This unit
will replace the existing crystallizing, melting and prilling system. |
The Urea Plant
Urea |
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