Ethylene oxide
| 원료 | Ethylene | ||||||||||||
| 생산물 | ethylene | ||||||||||||
| 적용 | To produce ethylene oxide (EO) from ethylene using either air or oxygen as the oxidizing agent. | ||||||||||||
| 설명 | Description: The flowsheet for an oxygen-based unit is only one of the many possible process schemes. Compressed oxygen or air, ethylene and recycle gas are mixed and fed to a myltitubular catalytic reactor (1). The temperature of oxidation is controlled by boiling water in the shell side of the reactor. From the reactor the effluent gases, which contain ethylene oxide, are cooled and compressed. The cooling is accomplished by recuperative exchange with the recycle gases. The gases then pass to a scrubber (2) where the ethylene oxide is absorbed as a dilute aqueous solution. Most of the unabsorbed gases are returned to the reactor via the recuperative exchanger, thus completing a closed circuit. A portion of the recycle gas is diverted through a CO2 removal system (3,4) before being returned to the reaction system. When air is used as the oxidant, a portion of these gases is diverted to a secondary (or purge) reactor, to purge accumulated inert gases. In large plants, three stages of reaction are used to improve the ethylene yield. The secondary and/or purge reactors convert most of the remaining ethylene using a flow scheme similar to the main reactor. The final stage purge gas is sent to treatment (to reduce hydrocarbons) and then to power recovery. EO recovery and refining systems are the same for both processes. Ethylene oxide is steam-stripped (5) from the EO-rich absorber bottoms and recovered as refined or purified product in a fraction train (6,7). Air-based plants can be converted to use oxygen at increased production and higher yields, with minimum downtime. Yields: The weight yield of purified EO (kg per kg ethylene feed) is in excess of 110 and 120% for the air and O2-based processes respectively. In addtion, a significant amount of technical-grade glycol is recovered by processing the waste streams. Air vs. oxygen: For "normal" raw material and utility prices and with high-purity ethylene, oxygen will be more economical unless the plant is very small and there is no other large requirement of oxygen or nitrogen. |
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