Transients and Equilibration Time in Continuous Distillation

Control of Distillation Column for Producing High-Purity Overheads and Bottoms Streams

“…Figure 9 summarizes these data for the whole column; Figures 10 and 11 show corresponding data for differing sizes and directions of such upsets. Dead time is confined to the end trays of the column and is apparently larger for smaller upsets, in agreement with previous work on column equilibration time (8).…”

Nonlinear waves and asymmetric dynamics of countercurrent separation processes

“…found that the transition departing from the optimal steady state (in the sense of maximum separation) is always faster than the corresponding transition returning to it (De Lorenzo et al, 1972;Stathaki et al, 1985). The difference is usually drastic (Rose et al, 1956;Mizuno et al, 1972). This note aims at providing a cause-and-effect analysis of such behavior by using the concept of wave propagation.…”

“…A well-recognized difficulty in controlling such processes is the nonlinearity of their dynamic behavior. Stemming from nonlinearity, an intriguing phenomenon known as "asymmetric dynamics" was observed by several investigators (Rose et al, 1956;Moczek et al, 1965; Mizuno et al, 1972; De Lorenzo et al., 1972;Fuentes and Luyben, 1983;Stathaki et al, 1985) in their numerical simulation of distillation columns. This term refers to the difference in response times either for a steady state perturbed by a pair of step changes of the same magnitude but in opposite directions, or for the forward and reverse transitions between two steady states.…”

The transient startup behavior of a liquid-liquid extraction pulse column

“…Rose et al (31) calculated times to 99.9% of steady state in a dis tillation column on an IBM digital computer and a Reeves electronic ana log computer. The digital technique was similar to that described above.…”