For preliminary process synthesis, the flowsheet is prepared including the reactors (ATR), separators, heat exchangers and compressors. Material and energy balances are done by using ASPEN plus process simulator.
Autothermal Reforming ASPEN PLUS simulation process flowsheet analysis:
Basis: Natural gas with a 1 kmol/sec is taken as basis of the study,
The process is simulated with initial value, i.e feed temperature is set 500oC, feed pressure is 2 atm, oxygen flow rate 0.5 kmol/sec, reactor pressure drop 0.5 atm, length of the reactor 8 m, to establish the process with no error warning and the initial trial run results for the reactor profile are shown below.
Simulation is performed to obtain the hydrogen production by varying the following variables
- Oxygen flow rate
- Autothermal Reactor feed temperature
- Autothermal Reactor feed pressure
Oxygen is varied from 0.1 to 2 kmol/sec while keeping all the other parameters unchanged the variation in reactor profile is shown below. At 0.7 kmol/Sec oxygen flow rate methane is consumed out and Hydrogen is produced with upper limit composition, along with it CO, CO2 and water also produced. This component mixture called as synthesis gas in process industries. On further purification and separation, hydrogen recovered with fewer impurities.
Autothermal Reactor feed temperature
By fixing the oxygen flow rate to 0.7kmol/sec the temperature of the reactor feed is varied and simulated. At 800K CO2 formation is less, lower CO2 concentration gas is cost lesser in purification section. H2 gas composition is above the 800K show less increment and so 800 K (526.85oC) is selected for further simulation.
Autothermal Reactor feed pressure
For fixed 800 K (526.85oC) temperature and 0.7 kmol/sec, flow rate of oxygen, as the pressure increases the methane conversion decreases and so rate of hydrogen formation decreases however carbon dioxide and carbon monoxide formation increases. Less operation pressure are favorable to the autothermal reaction because the reaction precedes the volume of the product increase and so the less pressure is advantages to the forward reactions.