There are an estimated 40,000 distillation columns in the United States, which have a combined capital value in excess of $8 billion. These columns are estimated to have at least a 30-year life, and they are used in more than 95% of all chemical processes. The total energy use of these columns is approximately 3% of total U.S. energy consumption (Humphrey and Keller, 1987). Thus, estimating and, if possible, reducing capital and operating costs of distillation are important. Because they are a major energy user, saving energy in distillation systems is particularly important in a time of high and uncertain energy costs.