Ammonium Sulphate [(NH4)2SO4] is the first nitrogenous fertilizer, which is very important and is manufactured in India. It contains 21% nitrogen and 24% Sulphur. It is very famous in some parts of the country.
It is used at the time of sowing and can also be used as a top dressing during crop growth, as it hurts germination. Due to its external structure and physical properties, ammonium sulphate is very useful for making dry mixtures. And can be formulated with phosphate and phosphatic fertilizers, which contain lime, as a result of which nitrogen can be reduced.
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Pertinent Properties
| Chemical Formula | (NH4)2SO4 |
| Melting point | 512.2 °C |
| Boiling point | NA |
| Molecular weight | 132 mol/gram |
| Colour | White |
| Specific gravity | 1.769 |
| Block Density | 1040 kg/m3 |
| pH | 5.5 |
| Solubility in cold water | 70.6g/100 water |
| Index of refraction | 1.521, 1.523, 1.533 |
Methods of Manufacturing
Ammonium Sulphate Fertilizer is mainly manufactured through two types of processes which are as follows.
I. Direct Neutralization Process
II. Gypsum Process
I. Direct Neutralization Process
Ammonia, sulfuric acid, and coal gas are used as raw materials in this process.
Raw Materials
i. Ammonia (NH3)
ii. Sulphuric Acid (H2SO4)
iii. Coal Gas
Chemical Reaction
2NH3 + H2SO4 ⟶ (NH3)2SO4
Process Description
First of all, ammonia is taken to an ammonia evaporator. Then sulphuric acid and coal gas are taken to the reactor through the compressor. Compressed sulphuric acid and coal gas are taken to the reactor through the compressor.
As a result of the reaction in the reactor, a residue of ammonium sulphate is obtained. This precipitate is aerated by centrifugal process. As a result, ammonium sulphate (NH4)2SO4 is obtained.
II. Gypsum Process
In this process, ammonium sulphate is produced using gypsum.
Raw Materials
i. Gypsum (CaSO4.2H2O)
ii. Ammonia (NH3)
iii. Carbon dioxide (CO2)
Chemical Reaction
NH3 + H2O ⟶ NH4OH
2NH4OH + CO2 ⟶ (NH4)2CO3 + H2O
(NH4)2CO3+CaSO4.2H2O⟶(NH4)2SO4+CaCO3+ 2H2O
Process Description
To prepare ammonia sulphate by this method, NH3 is cooled and sent to the NH3 synthesis tower. This ammonium carbonate solution is sent to the reactor, where finely ground and dry gypsum is sent. They remain engaged in the reactor, heat the suspension with the help of coils and keep stirring the suspension continuously with the help of the agitator.
As a result of the reaction, ammonium Sulphate and calcium carbonate are obtained. This mixture is sent to the filter process where after filtration, the mixture of ammonium sulphate and calcium carbonate is separated. This mixture is sent to the settler, where the calcium carbonate settles at the bottom.
This solution is heated using hot steam, after which the excess water evaporates into vapour. Then this concentrated solution is sent to the evaporator in crystal form. This is a special type of evaporator. In this, the solution evaporates and crystals of the concentrated solution are obtained. These crystals are sent to the centrifugal, from where moist crystals are obtained. These crystals are sent to the rotary dryer and dried at 120 to 130 °C. In this way, the final product is obtained.
Handling, Storage, and Packing
Crystal ammonium sulphate is free-flowing. Hence there is no problem in its transfer. However, due to high humidity, the problem of encrustation arises. Hence it is packed in high-density polyethylene bags.
Ammonium sulphate Uses
1. As a regent in the laboratory.
2. It is used in making alum.
3. In making other ammonia products.
4. It not only provides fertilizer but also other nutrients like K, Na, Ca, etc. to the plants.
5. It contains 25% ammonia.