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Ssac 353 lecture no. 18 19 p fertilizers_ classification_manufacturing_fate in soil
1. Dr.AB Jadhav, SSAC, AC, Pune’
18-19 Phosphatic fertilizers,
Classification
Manufacturing process and Properties
Fate of P-fertilizers and their reactions in soils.
5 Marks
Dr.AB. Jadhav,
Assistant Professor
Soil Sci. and Agril. Chemistry,
Agriculture College, Pune
6. Dr.AB Jadhav, SSAC, AC, Pune’
In the early days P-fertilizers were
manufactured from bones.
P-fertilizers are now manufactured
from rock-phosphate mineral source
found in igneous, sedimentary and
metamorphic
Minerals bearing P are apatite
(Major), quartz, silicates,
carbonates, sulphates,
sesquioxides, etc.
Two imp. Material required for
P-fertilizer production are rock
phosphate (32% P2O5) and H2SO4
Commercial rock phosphates types
1) Fluorapatite [Ca10(PO4)6F2)]
2) Hydroxyapatite [Ca10(PO4)6 (OH2)]
3) Chloroapatite [Ca10(PO4)6 (Cl2)]
Now SSP is being replaced by DAP
as high analysis fertilizers
Phosphatic Fertilizers
7. Dr.AB Jadhav, SSAC, AC, Pune’
Rock Phosphate
Direct application
Single Super phosphate
Triple super phosphate
Nitrophosphate
Dicalcium phosphate
8. Dr.AB Jadhav, SSAC, AC, Pune’
Furnace (Thermal) Process
Apatite is heated to above 14000C in presence of Si and C and reduced
to elemental P in a furnace. It is then oxidized to P2O5 and dissolved n
water to form H3PO3
Haeting
Ca10(PO4)6F2)] + 6 SiO2 + 15 C ===== 3 (3CaO.2SiO2) + 1.5 P4 + CaF2 + 15 CO
Apatite 14000C
P4 + 5 O2 ====2 P2O5
P2O5 + 3 H2O ==== 2 H3PO4 (Phosphoric acid)
Phosphoric acid is an important product to produce P fertilizers.
H3PO3 is produced by two processes
9. Dr.AB Jadhav, SSAC, AC, Pune’
Wet Process (Acidulation route)
Mineral acids like HNO3 or H2SO4 or HCl are rwacted with apatite to
produce phosphoric acid.902 % of H3PO4 comes from this processes.
Cost f production is very less as against furnace processes.
Ca10(PO4)6F2)] + 10 H2SO4 + 20 H2O ====6 H3PO4 + 10 CaSO4.2H2O + 2HF
10. Dr.AB Jadhav, SSAC, AC, Pune’
Manufacturing of superphosphates
In 1842, John Benet Lawes first time produced fertilizer called
“Superphosphate” in England and took a patent in 1843 by treating
Coprolit (Fossiized dung) + H2SO4
The name “Superphosphate” applies to fertilizer obtained by
treating finely ground rock phosphate with H2SO4 or H3PO4
“Superphosphate” CONTAINS 16 % P2O5 and referred as normal
single super phosphate (SSP).
The product made through H3PO4 contains 46 % P2O5 called as triple
super phosphate (TSP)
11. Dr.AB Jadhav, SSAC, AC, Pune’
In India first time SSP was
produced by EID Parry
(India) Ltd. At Ranipet (Near
chennai)
They started with bones +
H2SO4 to produce SSP and
then used rock phosphate
Production tech.simple,
supplied P @ 13% and Ca @
23%
Low analysis fertilizer , high
cost of transportation, and
application per unit of the
nutrient
Market share is only < 20% due
to low P content. Now a day
DAP is more used.
SSP in India
12. Dr.AB Jadhav, SSAC, AC, Pune’
Finely ground rock phosphate is treated with H2SO4 in the
manufacturing of SSAP and TSP
SSP
Ca10(PO4)6F2)] + 7 H2SO4 + 17 H2O ==== 3 Ca (H2PO4)2.H2O) + 7 CaSO4.2H2O + 2 HF
Monocalium phosphate
TSP
Ca10(PO4)6F2)] + 14 H3PO4 + 10 H2O ==== 10 Ca (H2PO4)2.H2O) + 2 HF
13. Dr.AB Jadhav, SSAC, AC, Pune’
Specifications of SSP and TSP
Specifications SSP TSP
Moisture content (maximum) 12 % 12%
Free phosphoric acid (Maximum) 4% H3PO4 (P2O5) 3 % H3PO4 (as P2O5 )
Water soluble P (Minimum) 16 % P2O5 42.5 % P2O5
Citrate soluble P (Minimum) - 3.5 % P2O5
Total P (Minimum) 16% P2O5 46 % P2O5
14. Dr.AB Jadhav, SSAC, AC, Pune’
These fertilizers are produced by reacting
NH3 and H3PO4
Cost of production, transportation and
application per unit nutrient is much less
Most important complex
fertilizers are MAP and
DAP
In india, DAP was
produced in 1967 by
Gujarat State Fertilizer
Corporation (GSFC)
MAP is acidic pH is 4.0
and while DAP is
neutral pH 7.0
Grades are 11:52:0 and
18:46:0
Water soluble, good
physical properties
Complex fertilizer- Ammonium Phosphate (MAP/DAP)
