Inprocess at Beyond Optimize 2021: Offline Digital Twin Benefits for a Steam Cracker


A steam Cracker unit is one of the most technically complex plants in the chemical industry, as it operates in a wide range of pressure and temperature conditions, which need to be controlled in order to avoid the appearance of undesired by-products or reaching trip conditions.

ORLEN Unipetrol, the largest refining and petrochemical company in the Czech Republic, requested Inprocess to provide an operator training simulator for its steam cracker unit at Litvinov.  The objective was to improve the operator’s competence, achieve a better process and control understanding, increase plant’s safety, improve operating procedures and reduce shutdown and trip conditions.

Inprocess Solution

An Operator Training Simulator (OTS) based on 1st principle dynamic model can enable operators to be trained in a virtual environment on normal, abnormal and relevant safety-critical scenarios. This approach:

  • Increases the plant’s safety
  • Allows a faster and smoother start-up
  • Reduces trips occurrences and flaring
  • Improves the operator’s understanding of the process, control logic and safety logic.

Inprocess developed a 1st principle dynamic model, which included the cracking furnaces, hot section, charge gas compressor, cold section, refrigerant compressors, separation, selective hydrogenation of pyrolysis gasoline and Pyrotol unit.

The dynamic model was validated against real plant data, concluding that the dynamic model was able to replicate the plant’s operating conditions and transient dynamics, which was critically important as the OTS needs to feel as the real plant to provide a realistic training. 

In addition, the steam cracker pyrolysis furnaces were modelled using a yield shift approach in order to take into account the multiple feedstocks as well as its behavior in transient conditions.

Operating procedures used in the OTS were drafted between Inprocess and Unipetrol with the intention of compiling Unipetrol’s know-how and best practices as well as including the main transient dynamics expected at each step. 


  • Estimated savings of $2.6 million per year from the steam cracker unit by deploying an Operator Training Simulator (OTS)
  • Improved operator competence by performing extensive virtual training without risk for the process units, resulting in:
    • A significant reduction of their startup and shutdown time
    • A relevant decrease of human error incidents and flaring
    • More benefits from their Advanced Process Control (APC) systems

Such a contribution is already available for downloading from our website here. For more information, please do not hesitate to get in contact with us.