f e r t i l i z e r i n d u s t r y l e c t u r e 1
Post on 25-May-2015
231 Views
Preview:
TRANSCRIPT
FERTILIZER INDUSTRY LECTURE 1
INTRODUCTION• Fertilizers are composed of nitrogen, phosphorus, and potassium compounds.
They also contain trace elements that improve the growth of plants.
• Plants use nitrogen in the synthesis of proteins, nucleic acids, and hormones.
• Plants also need phosphorus, a component of nucleic acids, phospholipids, and
several proteins.
• Potassium is another major substance that plants get from the soil. It is used in
protein synthesis and other key plant processes.
• Early scientists such as Francis Bacon and Johann Glauber describe the
beneficial effects of the addition of saltpeter to soil.
• Glauber developed the first complete mineral fertilizer, which was a mixture of
saltpeter, lime, phosphoric acid, nitrogen, and potash.
• A patent issued to Sir John Lawes, first outlined a method for producing a form of
phosphate that was an effective fertilizer.
The Manufacturing Process
Nitrogen fertilizers
1) Ammonia can be synthesized from in-expensive raw materials.
Natural gas and steam are pumped into a large vessel.
Next, air is pumped into the system, and oxygen is removed by the burning of natural gas and steam.
This leaves primarily nitrogen, hydrogen, and carbon dioxide.
The carbon dioxide is removed and ammonia is produced by introducing an electric current into the system.
Catalysts such as magnetite (Fe3O4 ) have been used to improve the speed and efficiency of ammonia synthesis.
The NPK Manufacturing Process
Nitrogen fertilizers (contd.)
2) Nitric acid:
Produced by first mixing ammonia and air in a tank.
In the presence of a catalyst, a reaction occurs which converts the ammonia
to nitric oxide.
The nitric oxide is further reacted in the presence of water to produce nitric
acid.
3) Ammonium nitrate:
Nitric acid and ammonia are used to make ammonium nitrate.
It is a good fertilizer component because it has a high concentration of nitrogen.
The two materials are mixed together in a tank and a neutralization reaction
occurs, producing ammonium nitrate.
This can be granulated and blended with the other fertilizer components.
The NPK Manufacturing ProcessPhosphatic fertilizer:
To isolate phosphorus from phosphate rock, it is treated with sulfuric acid,
producing phosphoric acid.
Some of this material is reacted further with sulfuric acid and nitric acid to
produce a triple superphosphate, an excellent source of phosphorous in solid
form.
2) Ammonium phosphate:
Some of the phosphoric acid is also reacted with ammonia in a separate tank.
This reaction results in ammonium phosphate, another good primary fertilizer.
1) Superphosphate:
The NPK Manufacturing Process
Granulating and Blending:
To produce fertilizer in the most usable form, each of the different compounds,
ammonium nitrate, potassium chloride, ammonium phosphate, and triple
superphosphate are granulated and blended together.
The solid materials are placed into a rotating drum which has an inclined axis. As
the drum rotates, pieces of the solid fertilizer take on small spherical shapes.
They are passed through a screen that separates out adequately sized particles.
A coating of inert dust is then applied to the particles, keeping each one discrete
and inhibiting moisture retention.
Finally, the particles are dried, completing the granulation process.
The blending is done in a large mixing drum that rotates a specific number of turns
to produce the best mixture possible.
After mixing, the fertilizer is emptied onto a conveyor belt, which transports it to
the bagging machine.
Composite fertilizer manufacture:
The NPK Manufacturing ProcessBagging:
Fertilizers are typically supplied to farmers in large bags. To fill these bags the fertilizer is first delivered into a large hopper. An appropriate amount is released from the hopper into a bag that is held open by a clamping device. The bag is on a vibrating surface, which allows better packing. When filling is complete, the bag is transported upright to a machine that seals it closed. The bag is then conveyored to a palletizer, which stacks multiple bags, readying them for shipment to distributors and eventually to farmers.
AMMONIA
Uses:
85% of ammonia production is used for nitrogen fertilizers
40% of ammonia produced is used in urea production
Other solid nitrogen fertilizers are ammonium nitrate, ammonium sulfate and
ammonium phosphates.
Synthesis:
Difficult to synthesize using Nitrogen from air due to the high BDE, IE&EA of
Nitrogen molecule is very high.
N2 +3H2 ↔ 2NH3 ∆H = -91.444 kJ/mol
Temperature is crucial parameter
Ammonia (mol%) in equilibrium synthesis gas; H2/N2 =3mol/mol
AMMONIA SYNTHESIS REACTORS
Reactor design in ammonia synthesis is critical since temperature control is
crucial. Methods applied to achieve this are:
1)Quench reactors- Cold feed gas is added at different heights in the
reactor.
2)The heat produced is removed between the catalyst beds by heat
exchangers. Hence, heat is removed at the highest possible temperature.
ICI quench reactor Temperature-Concentration profile
Kellogg a) Vertical (left fig.) b) Horizontal (right fig.) quench reactors
Haldor Topsoe radial flow reactors
Multi-bed converter with indirect cooling; (a) catalyst, (b) feed-effluent heat exchanger, (c) cold bypass, (f) product.
Integrated Ammonia Plant
Specific energy requirements of various ammonia processes
Process GJ (LHV)*/t ammonia
Classical Haber-Bosch (coke) 80-90
Reformer pressure 5-10 bar (1953-1955)
47-53
Reformer pressure 30-35 bar(1965-1975)
33-42
Low-energy concepts (1975-1984)
27-33
State of the art (since 1991) 24-26
*Lower heating value
top related