Fertilizers Manufacturing Process:
The ammonia process is one of the major achievements of industrial chemistry in this century. In Kuwait, it is based on natural gas.
Ammonia is produced from a mixture of hydrogen (H2) and nitrogen (N2) with a ratio of H2 to N2 of 3 to 1.
Ammonia is used as a raw material in the urea and ammonium sulfate process. |
The Ammonia Plant |
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RAW MATERIAL:
Kuwait natural gas
For the ammonia plant in Kuwait, the source of H2 is hydrocarbons in the form of natural gas & water in the form of steam. The source of N2 is, as in all ammonia plants, the atmospheric air. |
The Ammonia Plant |
MANUFACTURING STEPS:
1. Natural Gas Purification
Hydrocarbon feed is washed in the MEA section where the bulk of the sulphur content is removed. The content of hydrogen sulphide and organic sulphur in the natural gas is reduced to below 80 ppm by volume according to the following reactions:
2 HOCH2CH2NH2 |
+ |
H2S |
|
(HOCH2CH2NH3) 2S |
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|
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|
|
(HOCH2CH2NH3) 2S |
+ |
H2S |
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2 HOCH2CH2NH3HS |
2. Desulphurization
Hydrocarbon feed is completely desulphurized in the desulphurization section.
3. Reforming
The desulphurized hydrocarbon is reformed into raw synthesis gas by using steam and air. The synthesis gas contains hydrogen and nitrogen, and also carbon monoxide (CO) and carbon dioxide (CO2). The reforming takes place at about 30 Kg/cm2g. The steam reforming of hydrocarbons can be described by the following reactions:-
CnHm |
+ |
2n H2O |
|
n CO2 |
+ |
(2n + m/2) H2 |
(1) |
CH4 |
+ |
2H2O |
|
CO2 |
+ |
4H2 |
- |
heat |
(2) |
CO2 |
+ |
H2 |
|
CO |
+ |
H2O |
- |
heat shift conversion |
(3) |
4. Shift Conversion
In the gas purification section CO is first converted into CO2 and H2 by means of steam which increases the H2 yield. CO2 is then removed in the CO2 removal section and the remaining amount of CO and CO2 is afterwards removed in the methanator by converting it into CH4.
The following reaction takes place:
CO |
+ |
H2O |
|
CO2 |
+ |
H2 |
+ |
heat |
5. Ammonia Synthesis
In the ammonia synthesis section the purified synthesis gas is converted into ammonia by a catalytic reaction at a pressure of about 220 Kg/cm2g.
The ammonia synthesis takes place according to the following reaction scheme:
3H2 |
+ |
N2 |
|
2NH2 |
+ |
heat |
6. Ammonia absorption
In the ammonia absorption section, ammonia contained in purge and let-down gases coming from the 4th, and 2nd and the 3rd ammonia lines is recovered by absorption in water followed by a distillation of this ammonia water. The recovered ammonia is then sent to the storage tanks or to the Urea plants as feed.
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The Control Room |
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