(17d) The Butterfly Effect: How a Column Revamp Improved the Performance of an Ethylene Oxide Plant.

Located in Al-Jubail, the Saudi Kayan petrochemical complex produces chemicals, polymers, and specialty products. The complex includes a world-scale ethylene oxide / ethylene glycol (EO/EG) plant.

EO is produced by the catalytic oxidation of ethylene with oxygen in the EO Reactor. This reactor gas product is sent to the EO Absorber, where EO is absorbed into an aqueous liquid product, resulting in a gas stream comprising ethylene, oxygen, carbon dioxide (CO₂) and other components. This gas stream is sent to the CO₂ Absorber, and subsequently recycled back to the EO Reactor, hence is also called the “cycle gas”. In the CO₂ Absorber, a major portion of the CO₂ is removed from the cycle gas stream, using reactive absorption with a hot potassium carbonate solution.

Reducing the CO₂ and water content in the cycle gas to the EO Reactor brings several benefits to the EO catalyst. Both the selectivity and activity of the catalyst are enhanced. Improved catalyst activity allows lower operating temperatures and extends catalyst life. These improvements were realized via a relatively simple revamp of the CO₂ Absorber.

The CO₂ content in the cycle gas to the EO Reactor ranged between 0.55 to 0.60 vol% historically during start-of-run conditions. In April 2023, the mass transfer equipment in the CO₂ Absorber was upgraded from Sulzer I‑Ring^TM random packing to Sulzer MellapakPlus^TM structured packing. After the revamp, the CO₂ content is lowered to between 0.30 to 0.35 vol% due to improved CO₂ absorption efficiency. Additionally, a small portion of the cycle gas typically bypasses the CO₂ Absorber and the improved absorption performance provided flexibility to increase the bypass flowrate as needed, thereby reducing the water content in the overall cycle gas. The improved activity, selectivity, and lifespan of the catalyst resulted in cost savings of 1.6 to 1.9 million USD per catalyst cycle.