A Block Diagram of Ammonia Production from Natural Gas

Block diagram of ammonia production using natural gas

Ammonia production from natural gas

Natural gas consists of high concentrations of Hydrogen than any other fossil fuel gases. Due to its availability and hydrogen fraction, it is selected as the raw material for the production of Ammonia past many years. Nitrogen for ammonia is taken from the 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 causes harm to the catalyst in the reformers and reactors. The process is designed to remove sulphur as an impurity in the form of hydrogen sulphide or absorb it on the packed bed. By means of the endothermic reaction of steam and natural gas maximum percentage of methane will be converted into hydrogen and oxide compounds of carbon in primary reformer. The secondary reformer is an exothermic autothermal reactor model it assures the nitrogen addition from the 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 of ammonia plant block diagram
BlocksUnit process/operations Description
DesulphurizationHydrogenation and AbsorptionsSulphur is reacted with hydrogen to form hydrogen sulphide and then absorbed on packed bed absorber
Primary reformerCatalytic reformingMethane converted to CO,H2,CO2
Secondary reformerCatalytic autothermal reactionResidual methane conversion to CO2 and H2
High temperature shit conversionWater-gas shift reaction at high temperatureCO converted to CO2
Low temperature shift conversionWater-gas shift reaction at low temperatureResidual CO converted to CO2
Carbon dioxide absorptionChemical AbsorptionCO2 absorbed by G.V solution
Carbon dioxide strippingStrippingCO2 stripped from G.V
MethanatorMethanationCO2 and CO traces in process gas are converted to methane
Synthesis gas compressorCentrifugal compressionTo develop operating pressure for synthesis reactor
Ammonia synthesis reactorDouble Packed bed ReactorAmmonia formation
ChillingHeat exchangerAmmonia vapor cooling
Refrigeration and compressionScrew compressionTo liquefy ammonia for storage
Purge gas and recoveryAbsorption, separationTo separate traces of nitrogen, argon, methane and hydrogen in the process
World’s top ammonia production plants; the year 2012

Capacity, Million Tonnes

Yara≈ 7.1
CF industries≈ 7.0