Hydrocracker Reactor Temperature Controls for Greater Safety, Reliability and Profitability

Today’s hydrocarbon pricing means that hydrocracking units, already one of industry’s most demanding process control challenges, are being pushed to greater limits.  Hydrocracking reactors operate at elevated temperatures and pressures, making safety a constant concern.  Recovering from temperature upsets can take hours and recovering from a complete depressurization takes days, with heavy cost and operational impact.  Reactions are exothermic, so that even minor disturbances in feed, heater, or quench controls can rapidly escalate to an urgent situation.  For these reasons, hydrocrackers have always demanded vigilant attention to design detail, management of change, and operability.  Any oversights can result in, or fail to prevent, depressurization events.  Key improvements, on the other hand, can bring large gains in refinery reliability and profitability.

Hydrocracker process control strategy for the past two decades has focused on installing automatic depressurization systems and multivariable controllers (MPC).  While these have brought important gains, experience now shows this leaves many gaps in excursion control and depressure prevention.  This article presents an updated hydrocracker control model that robustly addresses traditional hydrocracker control challenges, overcomes outdated hydrocracker control paradigms, and allows hydrocrackers to operate safely, reliably, and profitably, under today’s and tomorrow’s ever more demanding conditions.