@ urea fertilizer

HABIBUR RAHMAN20121107042

Department of Applied Chemistry and Chemical Engineering.

BSMRSTU

Course Title: Chemical TechnologyCourse No: ACCE 410

Urea Fertilizer

• 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

• Granular Urea Specifications• Prilled Urea Specifications

Physical forms of urea

Total nitrogen 46% min

Biuret content 1% max

Moisture 0.5% maxParticle 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

Prilled form Granular form

• 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

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

Urea Synthesis Process

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

Figure: Flow diagram of urea synthesis process

• 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.

• 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.

• 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

• 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

• 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

• 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

• 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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