Abstract: Multi-effect evaporation is a commonly used energy-saving process in industrial production. However, in actual engineering design, few people have proposed the exact design method for the effective heat transfer temperature difference distribution of each effect. In practice, the temperature difference of each effect is generally realized through self balance. Accordingly, the operation controllability in production is poor, and problems such as pressure fluctuation, liquid flooding or mist entrainment are easy to occur. This paper takes the problems occurred during the start-up of an ethylene oxide plant as an example, analyzes the reasons and effect of the operating pressure deviation from design value from two aspects of process design and control operation, gives solutions to the problems and optimizes the design, greatly improving the operation stability of the plant.

Key words: multiple effect evaporation, ethylene glycol, ethylene oxide, COD exceeds the standard