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Category: Process Control
Question: How is a multiple effect evaporation system usually controlled?
Keywords: v1i7,evaporation,station,multiple,effect,evaporator,control
Answer: It's common to use an online density transmitter or a online viscometer measuring the product stream leaving the station. The instrument will first measure the density (or viscosity) at the process temperature and then compute the density (or viscosity) at a reference temperature. This value may then be used to compute the outlet concentration. This can be output as a 4-20mA for input to the controller. The control variable is often time the steam flow to the sytem, but can also be the feed liquor rate or other variables (such as the vacuum source).