AMMONIA PLANT

Ammonia is used as the main raw material and additive in many areas, from household cleaning agents to explosives, from the pharmaceutical industry to cooling system, especially in production of chemical fertilizers and various chemicals.

Eti Gübre A.S. has been engineered and built ammonia plant with total production capacity of 100.000 metric ton per year based on technology by Haldor Topsoe for about 80 years and is a leading supplier in this field.

Raw Materials

The main raw materials of ammonia production are natural gas, water and air. The required energy is 8 MW and it is supplied by Eti Bakir A.S. steam turbine which generates the 32 MW.

Feed Purification

The plant is designed for operation with natural gas feedstock. Natural gas contains contaminants, the main contaminant being sulfur, which deactivates the reforming and CO conversion catalysts. The contaminants are removed in the feed purification section. Since the natural gas contains both hydrogen sulfide and organic sulfur compounds, the desulphurization takes place in two stages. First, the organic sulfur compounds are converted to hydrogen sulfide in the hydrogenator, and then the hydrogen sulfide is absorbed in the sulfur absorbers.

Hydrogenation

In the hydrogenator, organic sulfur compounds are converted to hydrogen sulfide.

Sulfur Absorption

Hydrogenated process gas is sent to the sulfur absorbers where sulfur from hydrogen sulfide is absorbed. Two identical sulfur absorbers are located in series. The second absorber acts as a guard in case of sulfur breakthrough from the first reactor or when the first reactor is taken out of service for catalyst replacement. Process gas leaving the feed purification is considered free of sulfur.

Reforming

In the reforming section, the desulfurized hydrocarbon feed is converted into synthesis gas by catalytic reforming of the hydrocarbon mixture with steam. The reforming of the hydrocarbon feed takes place in three stages. The reforming of higher hydrocarbons in natural gas feed to methane takes place in adiabatic prereformer. Most of the methane reforming takes place in the primary reformer. The remaining unconverted methane is converted in the secondary reformer.

CO Conversion

Carbon monoxide and steam are converted into carbon dioxide and hydrogen by the exothermic water gas shift reaction in two adiabatic reactors: the HT CO converter operating at high temperaturE and the LT CO converter operating at low temperature.

CO2 Removal

The CO2 removal system is based on the OASE process. The carbon dioxide is removed from the gas by reactive absorption in the OASE solution, which is based on amines and contains an activator which increases the mass transfer rate of carbon dioxide from the gas phase to the liquid phase.

Methanation

In the methanation section, the residual carbon oxides are converted into methane and water. As the amount of carbon dioxide is negligible. The methane acts as an inert gas in the ammonia synthesis loop, whereas oxygen-containing compounds such as carbon oxides are severe poisons to the ammonia synthesis catalyst.

Ammonia Loop

The ammonia synthesis from hydrogen and nitrogen proceeds according to following reaction 3H₂+N₂↔2NH₃+heat The ammonia synthesis takes place in the ammonia converter. Only part of the hydrogen and nitrogen is converted when the gas passes through the catalyst bed. The unconverted remainder is recycled to the converter after cooling and separation of the liquid ammonia product.

Ammonia Refrigeration

Ammonia is used as a cooling medium in a refrigeration circuit. The primary scope of the refrigeration circuit is to condense the ammonia contained in the effluent of the ammonia converter, but it is also used for cooling of purge gas and inert vent gas to recover the ammonia present in them.

Ammonia Recovery Unit

In the ammonia recovery section ammonia is recovered from the purge gas from the ammonia loop and from various other low pressure off-gases, and delivered as liquid ammonia meeting the product purity specifications.

Hydrogen Recovery Unit

Hydrogen is recovered from the purge gas after removal of ammonia. Gas from the purge gas absorber is sent to the hydrogen recovery unit, where hydrogen is recovered from the purge gas and is mixed with the make-up gas in the ammonia loop section. The off-gas is used as fuel for the burners in the primary reformer in the reforming section.