A Block Diagram of Ammonia Production from Natural Gas

Natural gas consists of high concentrations of Hydrogen than any other fossil fuel gases. Due its availability and hydrogen fraction, it is selected as raw material for production of Ammonia past many years. Nitrogen for ammonia is taken from air. Both hydrogen and nitrogen are reacted on catalyst like iron. Most of the well-engineered industries today produce hydrogen by steam reforming followed by autothermal oxidation. To understand such scientifically researched and approved process a block diagram is needed. It shows every unit operation involved in the process train, for example, Desulphurization.  Natural gas contains ppm level of sulphur that cause harm to the catalyst in the reformers and reactors. Process is designed to remove sulphur as impurity in the form of hydrogen sulphide or absorb it on the packed bed. By means of endothermic reaction of steam and natural gas maximum percentage of methane will be converted into hydrogen and oxide compounds of carbon in primary reformer. Secondary reformer is a exothermic autothermal reactor model it assure the nitrogen addition from air and complete conversion of methane to carbon dioxide or carbon monoxide and hydrogen. The whole system is well-established engineering model obtained by rigorous simulations and analysis.  Recovery of carbon dioxide and carbon monoxide is done by absorption and stripping block. Nitrogen and Hydrogen mole fractions are maintained after the absorption and reforming operations, in the presence of iron catalyst ammonia is formed and then liquefied for storage and transportation. 

Short description on ammonia plant block diagram

Blocks	Unit process/operations	Description
Desulphurization	Hydrogenation and Absorptions	Sulphur is reacted with hydrogen to form hydrogen sulphide and then absorbed on packed bed absorber
Primary reformer	Catalytic reforming	Methane converted to CO,H2,CO2
Secondary reformer	Catalytic autothermal reaction	Residual methane conversion to CO2 and H2
High temperature shit conversion	Water-gas shift reaction at high temperature	CO converted to CO2
Low temperature shift conversion	Water-gas shift reaction at low temperature	Residual CO converted to CO2
Carbon dioxide absorption	Chemical Absorption	CO2 absorbed by G.V solution
Carbon dioxide stripping	Stripping	CO2 stripped from G.V
Methanator	Methanation	CO2 and CO traces in process gas are converted to methane
Synthesis gas compressor	Centrifugal compression	To develop operating pressure for synthesis reactor
Ammonia synthesis reactor	Double Packed bed Reactor	Ammonia formation
Chilling	Heat exchanger	Ammonia vapor cooling
Refrigeration and compression	Screw compression	To liquefy ammonia for storage
Purge gas and recovery	Absorption, separation	To separate traces of nitrogen, argon, methane and hydrogen in the process