🏭 Manufacturing of Ammonium Sulphate, Ammonium Chloride, and Ammonium Nitrate

This lesson summarizes manufacturing routes, specifications, and handling aspects of ammonium sulphate, ammonium chloride, and ammonium nitrate fertilizers.

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Manufacturing of ammonium sulphate, ammonium nitrate and ammonium

chloride

A mmoinum sulphate

(NH4)2 SO4 is one of the important fertilizers produced in India. It contains about

21% N and 24% S and has been traditionally been very popular in various parts of the

country. It is a white crystaline salt having good keeping quality in dry conditions.

Production capacity

The total installed capacity in the country is about one million tones of (NH4)2 SO4

Raw materials / sources

The raw materials required to produce (NH4)2SO4 are:

• H2SO4 for its recovery from coke oven plants.
• NH3 and H2SO4 for neutralization process.
• Gypsum (natural or by product from H3PO4 plants) and NH3 for process using gypsum route.

Method of manufacture

The following methods are used for producing (NH4)2 SO4.

(i) Recovery from coke-ovens

The coke-oven gas (obtained when coal is heated to make coke) contains about

1% NH3 by volume. The gas is cooled and passed into saturators containing weak

H2SO4 so as to form (NH4)2SO4 crystals which is then recovered, centrifuged, washed

and dried. This process is used in the steel plants where large coke- oven batteries are

in operation.

(ii) Direct neutralization

Gaseous ammonia is directly neutralized with H2SO4 to produce (NH4)2SO4.

2NH3 + H2SO4  (NH4)2SO4

The neutralizer reactor and the crystallizer are interconnected so that the heat

released during neutralization is used to evaporate water in the slurry. The crystallizer is

designed to produce uniformly sized crystals.

Amorphous (NH4)2 SO4 is prepared by reacting gaseous NH3 and H2SO4 in spray

towers. The heat of reaction removes all the water present and the dry, fine product is

continuously removed from the base of the tower. This product is suitable for making

dry-mixed and granular fertilizers, FCI (Sindri), FACT (Alwaye) use the direct

neutralization process.

In the manufacture of some granular NPK fertilizers, (NH4)2SO4 is formed directly

with other ammonium salts. E.g. in the 16 – 20 – 0 grade product made by FACT, a

mixture of H3PO4 and H2SO4 is neutralized with NH3 to form a slurry of (NH4) PO4 and

(NH4)2 SO4, which is then granulated.

(iii) Gypsum process

NH3 gas is absorbed in water and then converted to (NH4)2CO3 by absorbing

CO2. The (NH4)2CO3 is reacted with gypsum (CaSO4. 6 H2O) to produce (NH4)2SO4 and

CaCO3.

CaCO3 is removed by filtration (NH4)2SO4 solution is evaporated, crystallized,

centrifuged and dried. Naturally occurring gypsum, or by product gypsum from

H3PO4 plants can be used for this process. CaCO3 produced can be used for cement

manufacture FCI (Sindri), FACT (Alwaye), EID-parry (Ennore), and GSFC (Baroda),

produce (NH4)2 SO4 from Ca SO4.

(iv) Byproduct

(NH4)2SO4 from caprolactum plants (NH4)2SO4 solution is formed during the

manufacture of caprolactum (the starting material for Nylon- 6). The solution is

concentrated and (NH4)2SO4 is recovered by crystallization, centrifuging and drying.

GSFC (Baroda) has commissioned a 20,000 t p a caprolactum plant which will produce

about 80,000 tonnes of (NH4)2 SO4 per year.

Specification as per FCO

- Moisture % by weight. Max 1.0

- NH4 – N % by weight Min 20.6

- Free acidity as H2SO4 % by weight max 0.025

- Arsenic (As As2 O3) % by weight max 0.01

Handling storage and packing

Crystalline (NH4)2 SO4 is free flowing and does not normally pose any problem in

handling and storage. However, it generally contains some powdered material which

causes caking especially under high humidity.

Due to its susceptibility to caking and slight acidity (NH4)2SO4 is normally bagged

in polyethylene lined gunny bags or high density polyethylene (HDPE) woven sacks.

Properties

• It is a white crystalline salt and to some extent hygroscopic

• It has good storage quality

• It is very soluble in water and so called as quick acting fertiliser

• It should not be used along with alkaline materials

• It is physiologically acidic in nature

Reactions in soil

• +CaSO4 (soluble)

Col1	Soil colloid N

Ammonia gas is evolved when ammonium sulphate reacts with alkaline materials

When lime and ammonium sulphate is used together in the soil, ammonia gas is

produced

A mmonium chloride (NH4 Cl) 26% N

This is sometimes called nitrate of ammonia. It is commercially prepared by

combining ammonia with HCl and the resultant product, NH4Cl is found to have very

good physical condition. Though this fertilizer has not been used extensively as straight

fertilizer, it is preferred in preparing many fertilizer mixtures because of its good physical

properties. This fertilizer is also obtained as a by product of the Solvay process of

making (Na)2 CO3.

The commercial sample is a white, crystalline salt containing 26% N in the NH4 form.

The fertilizer is suitable for many crops except for those, which are sensitive to high

chlorine content. This is physiologically acidic fertilizer.

Manufacture

Sodium chloride is treated with ammonia and carbon dioxide to form ammonium

chloride and sodium bicarbonate. The resulting ammonium chloride is then separated

Ammonium chloride is also obtained as a byproduct of soda ash (Na2CO3) and

manufactured as Solvays process. It is prepared by reacting calcium chloride with

ammonium carbonate. Ammonium chloride is obtained by double decomposition

between ammonium sulphate and sodium chloride at 1300 [0] C

A mmonium nitrate (NH4 NO3) – 33% N

This is mainly manufactured by passing NH3 gas into HNO3 and then isolating

the product in a solid form suitable for use as fertilizer. The equipment should be

stainless steel or other special alloys.

NH4 NO3 is continuously produced with the aid of a neutralization tower. NH3 gas

is introduced near the bottom of the tower, while air is added at a higher point to cool the

solution and carry off the water vapor. The solution containing about 80% of NH4 NO3 is

with drawn and converted to crystals or pellets as the case may be.

Pure NH4 NO3 is a white crystalline salt having 33% of N, one half of which is in

the NH4 form and the other half in the NO3 form. It is readily soluble in water and

completely utilized by crops and hence no residues are left in the soil. It is highly

hygroscopic and cakes up very soon. But, when the crystal is coated with about 5% of a

conditioning agent like clay etc, it is found to have good physical properties. It is an

excellent fertilizer both for direct application to the soil and for use in mixtures. It is an

economical source of fertilizer N, suited to a wide range of crops, soils and climatic

conditions. Its NO3 content contributes to rapid crop response while the NH4- N makes it

more resistant to leaching losses than other materials carrying their entire N in the NO3

form.

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Summary Cheat Sheet

Topic	Key exam point
Main lesson topic	Industrial manufacture of ammonium sulphate and related ammonium fertilizers
Raw material idea	Ammonia and acid/sulphate-bearing sources are central raw materials
Major methods	Recovery from coke ovens, direct neutralization, gypsum process, and by-product routes
Product class	Nitrogenous fertilizer containing ammoniacal nitrogen
Production logic	Manufacturing route depends on source of ammonia and sulphate radical
Specification point	FCO specifications and quality standards are important for manufactured fertilizers
Handling point	Storage and packing matter because some ammonium fertilizers are sensitive to moisture/caking
Exam distinction	Manufacturing method names are commonly asked separately from fertilizer properties
Agronomic note	Ammonium sulphate also contributes sulphur in addition to nitrogen
Trap	Do not confuse manufacturing route with nutrient content classification

References

3 sources • [1] [2] [3]

[1]

Indian Council of Agricultural Research (ICAR)

Official

[2]

Principles of Soil Science and Agricultural Chemistry — Standard BSc Agriculture Textbook

Book

[3]

Department of Agriculture & Farmers Welfare

Website