Lessons Learned on Binary Distillation Column Control Scheme Design

There are over 40,000 distillation towers in operation in the United States. Distillation is a low thermal efficiency unit operation that currently consumes 4.8 quadrillion BTUs of energy—40% of the processing energy used in refining and continuous chemical processes. The multiphase gas/liquid flow patterns in distillation columns are complex, making them difficult to predict and control.

The control scheme for the column has 3 objectives as follows.

1. Produce product streams that meet their respective quality specifications
2. Perform the component separation at the lowest energy consumption
3. Operate with the least amount of operator intervention

For the basic binary distillation column with a constant feed, there are 24 combinations of the regulatory control schemes. Which do you choose to achieve the objectives of the column listed above? If you implement Advanced Multivariable Control, which underlying regulatory control scheme and manipulated variables are the best?

This presentation will explore these topics and provide some insight into what has worked well and what has not! Plant examples will be used to demonstrate the concepts.