Pressure control is the most important parameter that is used in distillation optimization. Engineers realize that there are three important parameters in distillation optimization: temperature, pressure, and composition. When two of these are controlled, the other parameter is fixed. When pressure and temperature are controlled and/or optimized, the composition is known. Effective column pressure control is critical to controlling product quality targets.
This article will illustrate that even when a design configuration has been installed many times; it can be the source of problems, unexpected consequences, and even possibly result in unit shutdowns. This article will present a common vapor bypass design that is prone to operating instabilities and will suggest a better design configuration. Good designs are those that avoid failure even when they are operating outside of their intended operation range.