Urea is a nitrogen-rich fertilizer produced from ammonia and carbon dioxide. It exists as white crystalline prills or granules and contains 46% nitrogen. Urea is synthesized through a two-stage reaction where ammonium carbamate is first formed and then dehydrated to melt urea. The process occurs in a tower reactor at high pressure and temperature. The molten urea is then prilled or granulated and dried. Urea fertilizer is widely used due to its high nitrogen content and low production cost, though it can decompose rapidly if not packaged properly.

2. RASHIDUL ISLAM
20121107007
Department of Applied Chemistry and
Chemical Engineering.
BSMRSTU

3. Course Title: Chemical Technology
Course No: ACCE 410

4. • Urea is a type of nitrogenous fertilizer which is white crystalline
substance with the chemical formula NH2CONH2.
• It is highly water soluble.
• It contains 46% nitrogen.
Urea Fertilizer

5. • Granular Urea Specifications• Prilled Urea Specifications
Physical forms of urea
Total nitrogen 46% min
Biuret content 1% max
Moisture 0.5% max
Particle size 1-2.8 mm
Total nitrogen 46% min
Biuret content < 1%
Moisture < 0.5%
Particle size 2-4 mm
Two forms of urea are available

6. Prilled form Granular form

7. • Raw Materials:
ammonia (NH3)
carbon dioxide (CO2)
• Reaction:
Urea is synthesized from NH3 and CO2 in two stage reaction.
1. Formation of ammonium carbamate
2NH3 + CO2 → NH2COONH4
Manufacture of Urea

8. 2. Dehydration of the carbamate to form a melt of urea
NH2COONH4 → NH2CONH2 + H2O
The reaction takes place at 130-135 0C and about 35 atm pressure.
The conversion is about 40%.
Reaction Ratio:
Ratio of NH3 and CO2 is 2:1

9. Urea Synthesis Process
Several parts
• Ammonia pumping
• Carbon dioxide compression
• Urea synthesis tower
• Distillation tower and Flash drum
• Vacuum Evaporator
• Prilling Tower

10. Figure: Flow diagram of urea synthesis process

11. • Ammonia pumping : Liquid ammonia is pumped from the
multistage pump which maintain the reaction pressure in the
vertical stainless steel vessel.
• Carbon dioxide compression: ammonia plant directly boost the
carbon dioxide from the compression section as it readily form
at the CO2 section of ammonia production plant.
• Urea synthesis tower: It is lined with film of oxides to protect
form corrosion. Catalyst bed is placed in the inner side of the
autoclave structure and 180- 200 atm pressure at temperature
about 180-200 deg centigrade is maintained. Plug flow operation
take places and molten urea is removed from the top of the
tower.

12. • Distillation tower and Flash drum: This high pressure slurry is
flashed to 1 atm pressure and distilled to remove excess
ammonia and decomposed ammonia carbamated salts are
removed and recycled
• Vacuum Evaporator: The solution is fed to vacuum evaporator
for concentrating the slurry
• Prilling Tower: It is dryer where the molten slurry is passed from
top of the tower into a bucket which rotates and sprinkles the
slurry and air is passed from the bottom. All the moisture is
removed as the urea form into granules during it journey to the
bottom of the tower. This granules are sent by conveyor to the
bagging section.

13. • CO2 should be free from oxygen and hydrogen.
• The ratio of NH3 and CO2 should be maintained.
• Preheating of ammonia is essential for good yield.
• Average reaction temperature (3800F) should be controlled.
• Average pressure (2700 psi) should be maintained for a good
yield of urea.
Condition for a good yield

14. • Widely used in the agricultural sector both as a fertilizer and
animal feed additive.
• Provides the plants with nitrogen to promote green leafy growth.
• Makes the plants look lush (fresh).
• Necessary for the photosynthesis of plants.
• Helps to develop stem and leaves at primary stage of plants.
Application of Urea Fertilizer

15. • Highest nitrogen content than other available nitrogenous
fertilizers in the market.
• The cost of production of urea is relatively low.
• Can be used for all types of crops and soils and has no harm to
the soil.
• easy to store and does not pose as a fire risk for long-term
storage.
• Urea manufacture releases few pollutants to the environment.
Advantages of Urea Fertilizer

16. • Highly soluble in water so requires better packaging quality.
• Not as stable as other solid nitrogenous fertilizers.
• Decomposes even at room temperatures that results in serious
loss.
• If urea contains impurities more than 2 percent, it cannot be
used as a fertilizer, since the impurities are toxic.
Disadvantages of Urea Fertilizer

17. • Sharma B.K. Industrial Chemistry including Chemical
Engineering.
• http://www.extension.umn.edu/agriculture/nutrient-
management/nitrogen/fertilizer-urea/
• https://www.sabic.com/corporate/en/productsandservices/agri-
nutrients/prilled-rea-granular-rea
• http://enggyd.blogspot.com/2010/09/flow-diagram-of-urea-
production-process.html
• http://fertilizer-machine.com/solution/urea-fertilizer.html
References

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