Flooded condenser design, reflux drum

The function of the reflux drum in a flooded condenser design is to... 

Sometimes we see tower pressure control based on feeding a small amount of inert or natural gas into the reflux drum. This is bad. The natural gas dissolves in the overhead liquid product and typically flashes out of the product storage tanks. The correct way to control tower pressure in the absence of noncondensable vapors is to employ flooded condenser pressure control. If, for some external reason, a variable level in the reflux drum is required, then the correct design for tower pressure control is a hot-vapor bypass. 

Conversion of any existing scheme to flooded condenser is more than just a change in control configuration. It requires a full process design check and is likely to result in changes to relief valves and other safety-related systems. There are also a number of ways in which it can be configured. For example the drum can also be flooded thus avoiding the need to install a valve on its inlet. The pressure controller can then either manipulate either the reflux flow or the distillate flow directly. 

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