Sieve plate distillation dynamics

This dissertation is a study of the composition dynamics of a bench size sieve-plate distillation column. The column was 2-3/4 inches in diameter, 30 inches in length, and contained 10 sieve-plates spaced 2-1/4 inches apart. A benzene-toluene mixture was used as the feed to the column.

The pulse testing method for obtaining dynamic information was used. The column was upset by introducing a rectangular pulse increase in benzene composition in the feed stream. The response of each plate was measured in the form of temperature and was converted to a composition response. Frequency response curves were determined for each plate from the pulse response. For the frequency response analysis, the forcing function of a plate was considered to be a weighted sum of the compositions of the liquid and vapor streams entering the stage, while the output function was considered to be the liquid composition on the plate near the exit downcomer.

The resulting frequency response was relatively flat in the frequency region of primary interest. The flatness of the frequency response was attributed to poor liquid mixing on tha plates. Based on the experimental observations, a plate in the column may be mathematically represented by a dead time and a steady-state gain.