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Phosphate Fertilizer Production Guide

This document discusses phosphoric acid and phosphate fertilizers. It provides details on: 1) The production of phosphoric acid through furnace and wet processes, with the wet process being most common for fertilizer use. 2) The wet process involves reacting phosphate rock with sulfuric acid to produce phosphoric acid and calcium sulfate. 3) Two common types of the wet process are the dihydrate and hemihydrate processes, which differ in the precipitation conditions for calcium sulfate. 4) Phosphate fertilizers produced include triple super phosphate and ammonium phosphates like DAP and MAP.

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515 views24 pages

Phosphate Fertilizer Production Guide

This document discusses phosphoric acid and phosphate fertilizers. It provides details on: 1) The production of phosphoric acid through furnace and wet processes, with the wet process being most common for fertilizer use. 2) The wet process involves reacting phosphate rock with sulfuric acid to produce phosphoric acid and calcium sulfate. 3) Two common types of the wet process are the dihydrate and hemihydrate processes, which differ in the precipitation conditions for calcium sulfate. 4) Phosphate fertilizers produced include triple super phosphate and ammonium phosphates like DAP and MAP.

Uploaded by

abderrahimn
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Phosphoric Acid

&
Phosphate Fertilizer

Phosphoric acid
Mineral acid
Also known as orthophosphoric acid or
phosphoric(V) acid
Chemical formula H3PO4
White solid or colorless, viscous liquid (>42 C)
World production: 33.5 million tonnes of P2O5
in 1993

Phosphoric Acid Production


Furnace Process
Blast-furnace process
Electric-furnace process

Wet Process
Most common means for producing phosphoric
acid for fertilizer use

Wet Process
Flourapatite

Wet Process (Contd.)

Types of Wet Processes

Dependence of CaSO4
Operating Conditions
Dihydrate
26-32% P2O5 , 70-80OC
Hemihydrate
40-52% P2O5 , 90-110OC

Dihydrate Process

Grinding
Some grades of commercial rock do not need
grinding, their particle size distribution being
acceptable for a dihydrate reaction section
(60-70% less then 150m). Most other
phosphate rocks need particle size reduction,
generally by ball or rod mills. Both mills can
operate with wet or dry rock.

Reaction
The tricalcium phosphate is converted by
reaction with concentrated sulphuric acid into
phosphoric acid and insoluble calcium sulphate.
The reactor maintains an agitated reaction
volume in circulation.
The operating conditions for dihydrate
precipitation are 26-32% P2O5 and 70-80C .
This temperature is controlled by passing the
slurry through a flash cooler, which also degasses the slurry and makes it easier to pump.

Filtration
Vacuum/pressure filtration
The filter medium must move in sequence
through the various stages for continuous
operation.
The initial separation must be followed by at
least two stages of washing, to ensure a
satisfactory recovery of soluble P2O5.

Concentration

The forced circulation evaporator consists of a heat exchanger, vapor or


flash chamber, condenser, vacuum pump, acid circulating pump and
circulation piping.

Advantages & Disadvantages

Hemihydrate Process

Advantages & Disadvantages

Gypsum Disposal
Around 5 tonnes of gypsum are generated per tonne of P2O5
produced as phosphoric acid. This represents a serious disposal
problem with the individual phosphoric acid production units of
over 1,000t.d-1 capacity now being built.
Two methods can be used to dispose of gypsum: Disposal to land
Disposal into water
By-product gypsum contains four types of impurity that are
considered to be potentially harmful: Residual acidity (P2O5)
Fluorine compounds (These are only harmful if disposal is into
fresh water because disposal into sea water results in the formation
of insoluble calcium fluoride.)
Undesirable trace elements
Radioactivity

Triple Super Phosphate


This fertilizer is produced by the action of concentrated
phosphoric acid on ground phosphate rock.

Triple Super Phosphate


The production of TSP involves:
Reaction
Denning
Storage and Curing
Granulation

Manufacturing Process of TSP

Advantages of TSP

Disadvantages of TSP

Ammonium Phosphates

DAP, MAP
Both contain N, P
Both have good physical Properties
Ease of storage & granulation depends on the
impurity content

MAP Block Diagram

DAP Block Diagram

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