Abstract: For the product drying system (RED) of a 300 kt/a propane/isobutane mixed dehydrogenation unit, several core problems emerged during long-term operation, including excessive H2S and water content, desiccant pulverization and deactivation, and cold box freezing and blockage. In response to these issues and in accordance with the unit's production planning requirement of "three-year turnaround interval", a systematic analysis of the key influencing factors during the adsorption and regeneration stages was conducted. A comprehensive optimization and retrofitting scheme for the RED unit was implemented, including the optimization of the sequential control program parameters of the dryer regeneration control system, technical transformation of the product cooling system, addition of a reforming hydrogen drying unit, replacement of high boiling point aromatic hydrocarbon washing solvents, and capacity expansion of the RED unit. Remarkable improvements were achieved. Industrial application results demonstrate that after optimization, no H2S or water was detected at the dryer outlet, effectively resolving the breakthrough issue ofH2S and water. The service life of the RED unit was extended to over 4 years, aligning with the "three-year turnaround" maintenance schedule and enabling long-term continuous operation of the plant. This optimization scheme successfully avoids unscheduled shutdowns caused by desiccant replacement, yielding a direct economic benefit of 6.275 6 million yuan and an annual cost saving of approximately 4.3 million yuan. This work provides a valuable reference for achieving long-term safe operation of RED units in similar dehydrogenation facilities.

Key words: propane/isobutane mixed dehydrogenation, product drying system, H?S penetration