Based on the conversion and retrofitting project of a certain ethylene oxide/ ethylene glycol (EO/EG) unit, over 80% of the reactor's ethylene oxide equivalent (EOE) capacity was utilized to produce purified ethylene oxide (PEO) for the first time by adding an EO purification system operated in series, thereby converting ethylene glycol production to ethylene oxide production. The new EO purification tower employs novel composite sieve plates to meet the capacity expansion requirements. An optimized heating control system was used to accommodate broader feed compositions, while an integrated aldehyde removal system was developed to control the aldehyde content in the product of the new EO purification tower.