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1. 1
 Manufacturing process of fertilizers
(1) Ammonia (Haber-Bosch process): Uncombined N2 + H2
Steam
(CO + H2) 5000
C
Water gas
Producer gas Fe, Mo
Air (CO + N2) Compressor
250 Atm.
CO2 Liquid NH3
(i) Air and steam are passed over red hot coke to produce a mixture of water gas (Co + H2)
and producer gas (CO + N2) which are the main source of hydrogen and nitrogen,
respectively. Now a day Naptha and natural gas are also used as source of H2 and N2
from atmosphere ( Namrup, Assam).
Iron oxide
(ii) CO + H2 (CO2 + H2)
The carbon monoxide is removed by passing the mixture in to a saturation tower in the
presence of iron oxide catalyst to convert carbon monoxide to carbon dioxide.
(iii) The resultant CO2 is removed by raising the pressure up to 250 atmospheres and by
converting in solid form.
(iv) The gas mixture (N2 + H2) is adjusted to one volume of nitrogen to three volume of
hydrogen, compressed to 250 atmospheres and the last traces of CO2 are removed.
(v) By raising the temperature to 5000 C and in the presence of platinized asbestos or
powdered iron, the two gases united to form ammonia
5000
C
N2 + 3H2 2NH3 + 24400 cal.
Catalyst Fe, Mo
(vi) The ammonia is directly used as fertilizer or in manufacturing of other nitrogenous
fertilizers.
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Hot Coke
Saturation
Tower
(Iron oxide)
Catalyst
Catalyst
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Hot Coke
Saturation
Tower
(Iron oxide)
Catalyst
Catalyst
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Hot Coke
Saturation
Tower
(Iron oxide)
Catalyst
Catalyst
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2. 2
(2) Ammonium Sulphate (Gypsum process):
NH3 (25%)
Ammonium Removal
Of
Carbonate CaCO3
Al ring
CO2
Ammonium
Sulphate
(i) A 25% solution of ammonia is passed into a tower with full of aluminum rings through
which CO2 is bubbled and ammonium carbonate is formed.
2NH3 + CO2 + 2H2O (NH4)2CO3 + H2O
(ii) The ammonium Carbonate solution is mixed with a cream of calcium sulphate
(Gypsum) to obtain Ammonium Sulphate.
(NH4)2CO3 + CaSO4 (NH4)2SO4 + CaCO3
The Calcium Carbonate is removed
(iii) The ammonium sulphate solution is concentrated in vacuum evaporators, crystals are
removed by filtration, drier, cooled and sold as Ammonium Sulphate.
Mixing tank
Gypsum slurry
Vacuum
evaporator
Drier
Cooler

3. 3
(3) Urea:
CO2 Urea CO2 + NH3 Recycle
Liquid NH3
Urea tower
Prilled Urea
 Reaction:
160-2000 C
2NH3 + CO2 NH2COONH4
400 Atm. Ammonium carbamate
 Principle: Exo-thermic synthesis of ammonium carbamate with its subsequent
dehydration to urea
 Process:
(i) The carbon dioxide and liquid ammonia are allowed to react in the liquid phase
under greatly elevated pressure and temperature in convertor
(ii) The unreacted NH3 and CO2 are removed by means of evaporator still and are
then recycled
(iii) Urea solution is pumped to crystallizer where cooling and crystallization takes
placed.
(iv) The urea crystals are centrifuged and dried.
Compressor
High pressure
pump
Convertor
160-2000
C
400 Atm.
Evaporator
Still
Crystallizer
Centrifuge Conditioning
agent
Mixer
Drier

4. 4
(v) The solution evaporated to less than 1 % moisture, the molten urea is sprayed
down to tower against a counter current of dry air to get pellets or Prilled urea
(4) Diammonium Phosphate (DAP):
1
2
Neutralizing Tanks
3
Thickner
 Reaction: DAP
2NH3 + H3PO4 (NH4)2 HPO4
Ammonia OPA DAP
 Process:
(i) DAP is manufactured by mixing excess quantity of ammonia with phosphoric acid. The
phosphoric acid first synthesized from rock phosphate and the crud phosphoric acid is
used for the manufacturing of DAP
(ii) The reaction is carried out in a series of agitator (neutralizing tanks) lined with acid
proof bricks and lead.
Anhydrous
Ammonia
Evaporator
50%
H3PO4
Drier
Drier
Drier
Drier
Drier
Drier
Anhydrous
Ammonia
Evaporator
50%
H3PO4
50%
H3PO4
50%
H3PO4
50%
H3PO4
Anhydrous
Ammonia
Evaporator
50%
H3PO4
Anhydrous
Ammonia
Evaporator
50%
H3PO4
Anhydrous
Ammonia
Evaporator
50%
H3PO4
Anhydrous
Ammonia
Evaporator
50%
H3PO4
Drier

5. 5
(iii) The resultant slurry becomes pasty and crystallizes to an almost solid mass on cooling.
(iv) The product is dried, granulated and sold as Diammonium Phosphate (DAP)
(5) Single Super Phosphate (SSP):
Ground rock phosphate
Storage tank
H2SO4
Tank Dust
scale
Acid scale
Elevator
Pan mixer
Den or Pit
SSP Cutter
 Reaction:
3Ca3 (PO4)2CaF2 + 7H2SO4 3Ca (H2PO4)2 + 7CaSO4 + 2H4
 Principle: Rock phosphate is treated with sulphuric acid to convert the insoluble and
unavailable tricalcium phosphate to available monocalcium phosphate
 Process:
(i) The calculated quantity of sulphuric acid and 4 mesh ground rock phosphate are
introduce and mixed very thoroughly then dropped in den or pit
(ii) The mixture is allowed for 24 to 35 hours for reaction in pit. There is a loss of
volume by 10 % due to escape of water, CO2 and florin compounds.
Temperature is rise to 1000
C
(iii) The product is dried and ground to very fine powder and stored for sufficient
time for curing of material, then granulated and sold as single Super Phosphate
(SSP)

6. 6
(6) Muriate of Potash (KCl):
NaCl + KCl + Clay sylvinite
Brine
Slimes
Tailing
Tailing
NaCl slime to waste
Muriate of Potash
Grinding and
screening
Pulping and
scrubbing
Desliming
Conditioning
Rougher Cell
Cleaner Cell
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Centrifuge
Drying and
Screening
Leaching
Thickning Crystalizati
on
Grinding and
screening
Pulping and
scrubbing
Desliming
Conditioning
Rougher Cell
Cleaner Cell
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7. 7
 Principle: This process isbased on differences in specific gravity of KCl
(1,988) and NaCl (2.164). KCl having lesser specific gravity floats on top of NaCl.
 Process: This method of refining is the most widely practiced and the most economical
method of recovering Sylvite (KCl) from Sylvinite (Mixture of KCl, NaCl & clay). The
major steps in floatation process are as under.
(i) Crushing and screening.
(ii) Adding a saturated brine of NaCl and KCl to produce a pulp containing 50 to 70 %
solid.
(iii) Wet grinding and removal of slimes.
(iv) Introducing the Sylvite containing brine in to a series of rougher floatation cells,
providing agitation and introducing air which adheres in the form of bubbles to the
surface.
Floatation concentrate is harvested from the top of the rougher cells.
(v) It is introduced in to the cleaner floatation circuit for further refining the Sylvite.
(vi) The unfloated particles from the cleaner circuit recurred to the rougher cell.
(vii) Drying in rotary drier, screening and begging and sold as Muriate of Potash (MOP)