A Complete Refinery Modeled in Symmetry
VMG presents an atomically balanced simulation of a refinery that includes rigorous reactive unit operations. This refinery model has been created from publicly available data and designed as a starting point that can be adapted to create a specific, predictive model of a particular site. The complete refinery uses a constant component slate that has the resolution and range to capture process indicators from asphaltene precipitation and coke formation in heavy oil units all the way to specific lighter range molecule tracking and reactions in naphtha and gas processes. The refinery is modeled in connected functional sections that can be easily arranged to pass material including production and consumption of utilities such as hydrogen and steam. The effect of changes to feed blends, impurities or operating conditions can be tracked system-wide within this one simulation.
Refinery Model Highlights:
A unique characterization method allows a component slate with a molecular mixture representing the crude feed to be populated from commonly measured properties. The model uses an optimal refinery component slate that can be selected pre-configured which is suitable for the full range of reactive and thermodynamic refinery processes. Different feeds can be characterized and blended. The component slate allows the effect of different feeds to be tracked throughout the refinery. Sulfur, nitrogen and metallic compounds are included as heteroatomic molecules and can be tracked throughout the refinery as they are reacted and separated. The catalyst poisoning effect of trace components is predicted and accounted for within reactive units.
The atmospheric and vacuum towers are modeled with heat integration. The vapour breakout caused by thermal cracking during pre-heating is predicted using Symmetry's reactive furnace along with service time coke build-up considerations within the coils.
Vacuum fractions and slurry oil are reacted in Symmetry's Fluidized Catalytic Cracker that maintains an energy and pressure loop balance throughout the catalyst riser and regeneration process to predict coke deposition, catalyst recirculation rates and utility requirements.
Gas oil is hydrocracked in the HCC unit. The sintering, poisoning and coke deposition effect on the catalyst can be seen with service time, feed and process changes. Kinetic pathways affected by the de-activation will result in effluent changes that will have downstream consequences. Mitigating strategies can be tested, understood, and optimized in the model.
A delayed coking model is included with access to a rigorous cracking furnace to thermally crack the vacuum residue. The agglomeration and dehydrogenation of heavy aromatics releases hydrogen for the production of valuable lighter components. Symmetry’s batch Delayed Coker calculates the change in equilibrium with time as vapour is released from the liquid to accurately predict product composition.
Distillated and cracked material for low sulfur applications are reacted with hydrogen in the hydrotreater. Reactive hydrogen dependent units like the hydrotreater are sensitive to the hydrogen partial pressure and the hydrogen balance through the reactor or across the refinery can be predicted or optimized.
High octane aromatic components and hydrogen are created in the moving or fixed semi-gen bed catalytic reformer. RON calculations take into account the contribution of every component in the slate as well as the interactions between components leading to a rigorous prediction. The component slate has increased resolution in the naphtha range required to capture the different properties of high and low branched molecules.
The refinery model extends into paraxylene production. An isomerization reactor maximises the paraxylene yield and a transalkylation unit increases the available C8 aromatics. The equilibrium between the reactive loops and the xylene column is captured and the effect of changes to the refinery operation or feedstock can be seen in the product yields.
Continuing to Petrochemicals and Other Detailed Plant Sections
The additional cracking furnace models, amines package, Claus package, and Flare simulation tools included within Symmetry allows for further expanded modeling. This allows optimization of both individual plant sections or an overall plant wide effort.
Please contact your local VMG office for more information.
Chris Arthur, P.Eng., VMG Calgary