To produce ethylene glycols (EGs) and ethylene oxide (EO) from ethylene using oxygen as the oxidizing agent.
Modern EO/EG plants are highly integrated units where EO produced in the EO reaction system can be recovered as glycols (MEG, DEG and TEG) with a co-product of purified EO, if desired. Process integration allows for a significant utilities savings as well as the recovery of all bleed streams as high-grade product, which would otherwise have been recovered as a lesser grade product. The integrated plant recovers all MEG as fiber-grade product and EO product as low-aldehyde product. The total recovery of the EO from the reaction system is 99.7% with only a small loss as heavy glycol residue.
Ethylene and oxygen in a diluent gas made up of a mixture of mainly methane or nitrogen along with carbon dioxide (CO2) and argon are fed to a tubular catalytic reactor (1). The temperature of reaction is controlled by adjusting the pressure of the steam which is generated in the shell side of the reactor and removes the heat of reaction. The EO produced is removed from the reaction gas by scrubbing with water (2) after heat exchange with the circulating reactor feed gas.
Byproduct CO2 is removed from the scrubbed reaction gas (3, 4) before it is recompressed and returned to the reaction system where ethylene and oxygen concentrations are restored before returning to the EO reactor.
The EO is steam stripped (5) from the scrubbing solution and recovered as a more concentrated water solution (6) that is suitable for use as feed to a glycol plant (8) or to an EO purification system (7). The stripped water solution is cooled and returned to the scrubber. The glycol plant feed along with any high aldehyde EO bleeds from the EO purification section are sent to the glycol reactor (9) and then to a multi-effect evaporation train (10, 11, 12) for removal of the bulk of the water from the glycols. The glycols are then dried (13) and sent to the glycol distillation train (14, 15, 16) where the MEG, DEG and TEG products are recovered and purified.
Product quality: The SD process has set the industry standard for fibergrade MEG quality. When EO is produced as a co-product it meets the low aldehyde specification requirement of 10-ppm aldehyde maximum, which is required for EO derivative units.
Yield: The ethylene yield to glycols is 1.81 kg of total glycols per kg of ethylene. The ethylene yield for that portion of the production going to purified EO is 1.31 kg of EO product / kg of ethylene.
Licensor: Scientific Design Company, Inc.