This is a precise presentation on NPK fertilizers or complex fertilizers. It has detailed flowsheets with descriptions about all manufacturing processes of NPK fertilizers as well

1. PL.Sriram , G.Sudarshan
Recent Developments
in Fertilizer industry

2. History of Fertilizers

3. • Nitrogen fertilizers
• Crushed animal bones (P-rich)
• Leibig – Crushed bones with dilute
sulphuric acid - Ph0sphate fertilizers
• Invention of Ammonia by Haber and
Bosch
History of Fertilizers

4. • Phosphate rock (RP) is the main source of phosphorus
in fertilizers.
• First deposits of phosphate rock were discovered in the
early 19th century and its mining started in 1867 in South
Carolina, USA.
• Rock phosphate was first used for direct application for
more than 150 years
• Research on rock phosphate for direct application as a
fertilizer started over 100 years ago
Phosphate Rock : The natural
Non – Renewable Source of Phosphate

5. Classification of
Fertilizers

6. •The main nitrogen-based straight fertilizer is ammonia
or its solutions
•Ammonium nitrate (NH4NO3) is also widely used
•Urea is another popular source of nitrogen, having the
advantage of being a solid and non-explosive
Single Nutrient Fertilizers

7.  These fertilizers are the most common ones.
They consist of two or more nutrient components
 Major two-component fertilizers provide both nitrogen
and phosphorus to the plants.
 These are called NP fertilizers. The main NP fertilizers are
monoammonium phosphate (MAP) and diammonium
phosphate (DAP).
 The active ingredient in MAP is NH4H2PO4. The active
ingredient in DAP is (NH4)2HPO4. About 85% of MAP
and DAP fertilizers are soluble in water.
Multi Nutrient Fertilizers

8.  NPK fertilizer is usually thought of as a chemical
fertilizer, but NPK applies to any soil amendment that
supplies Nitrogen, Phosphorous, and Potassium,
including organic fertilizers
 Plants need nitrogen for leaf growth, phosphorus for
root formation, stem growth, and fruiting, and
potassium for flowering and plant immunity
 Organic NPK fertilizers can be slow-releasing or fast-
releasing.
NPK Fertilizers

9. • Granulation with a pipe reactor system
 Mixed Acid Route
 Nitrophosphate Route
Methods of NPK Fertilizer
Manufacture

10. Granulation with a pipe
reactor system

11. Granulation

12. • Classical
Granulation loop
• Two pipe reactors
• Phosphoric +
Sulphuric acid –
Neutralized by
ammonia

13. Solid raw materials -
potassium chloride,
potassium sulphate,
superphosphate,
secondary nutrients,
micronutrients
Granulation
and
Drying section

14. Granulation
and
Drying section
• Concentrated
ammonium nitrate
solution may be
added directly into
the granulator –
Ammoniation
• A pipe reactor
fitted in the dryer is
fed with phosphoric
acid and ammonia
• N/P
mol ratio is 1.00 -
MAP

15. • MAP produced
consists of very
fine particles,
passes via the
cyclones , screens
back to the
granulation
drum
• The granules
obtained are dried
in a drying section
using a heated air
stream
Granulation
and
Drying section

16. Screening,
Crushing,
Cooling,
Coating
• Oversize
• Undersize
• On-spec fraction

17. • Gases from the
granulator and
dryer are scrubbed
in venturi scrubbers
with recirculating
ammonium
phosphate or
ammonium sulpho-
phosphate solution
• The scrubber
liquor which
is being recycled is
fed to the pipe
reactor in the
granulator.
Gas scrubbing,
Dust removal

18. • The gases coming
from the dryer are
de-dusted in high
efficiency cyclones
to remove the
majority of the dust
before scrubbing.
• The air coming
from the cooling
equipment is
generally
recycled as
secondary air to the
dryer after de-
dusting
Gas scrubbing,
Dust removal

19. Mixed Acid Route

20. •Cheap raw materials
such as phosphate rock
•Digestion of phosphate
rock with nitric acid
resulting
in a solution of
phosphoric acid and
calcium nitrate
•Gases such as oxides of
nitrogen
and fluorine compounds
are formed during the
digestion, depending on
the type of phosphate
rock.
Digestion reactors

21. • Raw materials such as
phosphoric, sulphuric
and nitric acids are
added after the digestion
(Exothermic)
•The slurry is
ammoniated
with gaseous ammonia
and after neutralization,
other components such as
ammonium
phosphates,
superphosphates,
ammonium sulphate,
compounds containing
potassium
and magnesium are
added
Digestion reactors

22. Ammoniation
reactors
• The design of the reactor
battery can vary from a few
large reactors to many,
smaller
reactors
• Common for all the
designs of the reactor
battery is that the row of
reactors ends
with a buffer tank.

23. Mixed
acid route

24. Storage and
Transfer
Equipments

25. Solid raw materials
• The main solid raw materials are potash and phosphate rock
• These raw materials are transported to the production site by
ships, trains or lorries.
• Grab cranes are traditionally used for the unloading of ships
and with this method there is
the risk that some fine material may spread to the
environment in the harbor area.
•It is recommended that closed unloading methods
Ship unloading

26. Unloading of rail waggons or
lorries
Waggons/
Lorries
Hoppers
Conveyors

27. • Raw materials are stored in closed buildings or silos
• Materials in storage are handled by payloader, scraper or crane
•Bulk storage is in closed buildings with
walls to separate different grades of product
• Fertilizers are hygroscopic and thus it is recommended that
the storage atmosphere be air-conditioned
Storage

28. Nitrophosphate process

29. • The nitrophosphate process was a method for the industrial
production of nitrogen fertilizers invented by Erling Johnson in the
municipality of Odda, Norway around 1927.
• Although Johnson created the process while working for the Odda
Smelteverk, his company never employed it.
Instead, it licensed the process to Norsk Hydro, BASF, Hoechst, and
DSM.
• Each of these companies used the process, introduced variations, and
licensed it to other companies.
Due to the alterations of the process by the various companies who
employed it, the process is now generally referred to as the
nitrophosphate process.
The Odda process - Introduction

30.  Phosphate sources must be converted into a form which can be
taken up by plants
 This can be achieved by using the integrated “Nitrophosphate”
process which produces compound fertilizers containing
ammonium nitrate, phosphate and potassium
 This process aims to produce nitrate-containing straight and
compound fertilizers starting from rock phosphate and using all the
nutrient components in an integrated process without solid wastes
and with minimal gaseous and liquid emissions.
Goals of the process

31. Process block diagram

32. The Main Steps of NP process is as under
• Rock Phosphate Storage and Handling
• Dissolution of rock phosphate with nitric acid
• Crystallization of Dissolving solution and separation of calcium
nitrate crystals from nitrophosphate acid
• Ammoniation (i.e. neutralization of nitrophosphate acid)
• Prilling of the slurry and conditioning of the product
Summary of processes involved

33.  Rock phosphate is weighed and added into the first dissolving
reactorwhere it is mixed with the proper amount of Nitric acid plus
wash acid. In order to avoid foaming during the reactions, required
quantities of antifoaming agent is sent to the first dissolving reactor
 The phosphate solution is cooled to about 400C by means of
cooling water and fed to the crystallization lines A, B, C, D, E and F.
In the crystallizers calcium nitrate is crystallized out as calcium
nitrate tetra hydrate crystals
 The mother liquor from filter drum is pumped to the neutralizers.
To obtain the proper NP ratio in the end product, a certain amount
of ammonium nitrate solution from the calcium nitrate conversion
plant is recycled to this tank
Process description

34.  The neutralizer is also fed with a proper amount of ammonia in order
to effect adequate neutralization. The amount of ammonia is
controlled by an automatic pH control
 Gases leaving the neutralizer are washed in scrubber. After
neutralization, the NP solution is concentrated in evaporators
 The Melt from the evaporator is fed to a prilling tower
 The prills are removed from the bottom of the tower by means of a
scraper at about 950C
 Prills are conveyed by means of a belt conveyor to a cooling unit,
cooling is done by air induced by a blower
 Cooled Product is sent to Handling plant for Bagging and storage.
Process description

35. Reactions involved

36.  This process on the core is still being by almost all
industries till date
 The basic underlying acidulation of Phosphate rock is a
fixed constant
 But process conditions are optimized
 At the same time recovery of byproducts is made more
efficient
 Let us look at some of the developments….
Developments in process

37. Morocco phosphate rock is preferred over Egyptian Rock
Phosphate and Algerian Rock Phosphate due to following
reasons-
 High P2O5 due to which low rock consumption / ton of NP
production
 Low silica contents increases plant on- stream hours and less
erosion
 Ideal particle size distribution
 No adverse affect observed while testing this rock phosphate
Choice of Phosphate rock

39.  CN centrifuges were used for separation of CN crystals from
mother liquor solution
 Very high failure rate due to which they have high maintenance
and operational cost
 The common maintenance problems were damaging of the
separation screens, damaging of solution pusher ring and oil
leakages due to vibrations
 These screens were replaced with slow moving rotary filter
drums. Double filtration technique was adopted successfully in
the year 1996 with Komline Sanderson filter drum of USA.
CN Centrifuge design
improvements

40.  Urea solution is added in first dissolving reactor to
control NOx in off –gases
 Urea solution addition started in the year 2005 in
dissolving reactors
 Now, Nox emission in stack < 10 ppm before urea
addition it was 200 ~ 300 ppm.
Urea Control system

41. Prilling
Fluidized bed dryer

42. nptel.ac.in/courses/103107086/module5/lecture5/lecture5.pdf
http://www.fertilizerseurope.com/fileadmin/user_upload/user_uploa
d_prodstew/documents/Booklet_nr_8_Production_of_NPK_Compou
nd_Fertilizers_by_Mixed_Acid_route.pdf
www.tandontech.net/fertilisers.html
www.newworldencyclopedia.org/entry/Fertilizer
nptel.ac.in/courses/103107086/module5/lecture6/lecture6.pdf
faidelhi.org/FAI%20Seminar%202015/Presentations-
PDF/Abir%20Banerjee.pdf
https://books.google.co.in/books?isbn=0824791886
References

43. Questions ?