(87e) Quench Pass Plugging

In 2020, several of the gas furnaces in the OL-5 unit at Norco suffered quench pass plugging events that caused short runlengths and reduced operational availability. The production team made several operational adjustments, including increasing the minimum quench oil flow rates, that remedied this issue. However, in 2021 during the start-up after Hurricane Ida, the first two liquid furnaces that were brought online ran for less than a day before their quench passes were plugged. The quench oil flow was substantially increased, and the next furnaces brought online ran smoothly.

Following these events, Norco requested a formula that could predict the minimum amount of quench oil flow and the resulting quench temperature setpoint given certain operating conditions such as furnace feed rate, dilution steam to feed ratio, and quench oil quality. A review of recent quench oil sample data demonstrated that the heavy end of the quench oil had become significantly lighter compared to the premise used for the tangential quench nozzle (TQN) redesign proposed for the OL-5 gas furnaces in 2014. Pro/II simulation and multiple linear regression were used to generate formulas with inputs of ethane feed flow, dilution steam flow, and quench oil 90% cut point.