No abstract

No abstract

No abstract

No abstract

A new model for predicting the hydrodynamics, flow distribution, and mass transfer efficiency of multipass distillation trays is presented. Separate submodels apply to two-, three-, and four-pass trays, which may be any type of cross flow tray with downcomers: sieve, valve, or bubble cap.It was found that the liquidhapor flow ratio in one pass of a poorly designed multipass tray can be several times that in adjacent passes, and that the mean tray efficiency of such a tray is substantially less than the optimum possible. It is shown that multipass trays can be designed with essentially perfect flow distribution and optimum (maximum) overall tray efficiency. WILLIAM L. BOLLESMonsonto Company 800 N. Lindbergh Blvd. St. Louis, Missouri 631 66 SCOPEThe simplest type of cross flow tray for vapor liquid contacting with mass transfer as used for distillation is the one-pass configuration. However, when the liquid load is proportionately high (compared to the vapor), or where the tower diameter is large, it is necessary to employ multipass trays of two, three, four, and sometimes more passes in order to accommodate the hydrodynamic flow characteristics.The objectives of this study were to determine the effect of tray geometry on the liquid and vapor flow distribution among the various passes, to determine the effect of liquidhapor flow distribution on mean plate efficiency, and to determine how to design a multipass tray with optimum flow distribution and plate efficiency.These objectives were met by deriving a mathematical model for multipass flow distribution and mean Murphree plate efficiency. This model was then programmed for digital computer solution so that any multipass tray could be rated on its hydrodynamic and efficiency characteristics. The model was then executed on over 150 multipass tray geometry configurations to find the basic principles of optimum multipass tray design.The scope of the present work included two-, three-, and four-pass trays. However, trays of any number of passes may be analyzed by following the same principles.The multipass model requires hydrodynamic and mass transfer efficiency submodels for single passes where the liquid and vapor flow rates are known. These single-pass submodels were taken from the prior literature.However, prior to this work there were no publications of any studies of overall mass transfer efficiency in multipass trays.This study is theoretical and is not backed up by experimental data. However, the models employed are theoretically sound, and it is believed that the conclusions are valid and sound.