New correlation for sieve‐tray point efficiency, entrainmnt, and section efficiency

Abstract

A comprehensive composite database for distillation sieve-tray eficiency is used to develop point eficiency and entrainment correlations based on a model that considers the fluid on the distillation tray to be contained in a liquid-continuom region near the tray deck and a vapor-continuous region on top of the liquid-continuous region. This model allows estimates of the portion of the mass transfer that occurs in each region and the mass-transfer resistance that occurs on the liquid side and vapor side of the interface. For most cases, most of the mass transfer occurs within the liquid-continuous region. The liquid side resistance is often significant.The entrainment correlation is consistent with the work of Bennett et al., which relates entrainment to the ratios of the liquid to vapor density and the froth height to the tray spacing. A simple liquid continuous-only mass-transfer model containing only four empirical parameters correlates the point eficiency data to within 6.4%. Despite a twofold change in vapor Schmidt number, no dependency on vapor Schmidt number is seen. Important dimensionless groupings are the Reynolds number based on the hole velocity, effective froth density, ratio of the liquid inventoiy to the perforation diameter, and fraction of the tray area perforated. Mathematically simple and accurate methods allow the prediction of the section eficiency for trays operating in cross or parallel flow. They address vapor and liquid mixing, entrainment and a criterion to avoid significant degradation of the tray eficiency due to weeping.

A Hybrid Discrete/Continuous Dynamic Model of Trayed Tower Hydraulics

“…Liquid flow over the downcomer weir (L T ) follows the correlation of Bennett et al (1997). Stream L D is derived from the conventional correlation for head loss under the downcomer apron.…”

“…Entrainment is generally negligible in the froth regime. However, L E has been modeled using the Bennett et al (1997) correlation. Separate mass balances are derived for the tray and the downcomer:…”

Efficiency of non‐reactive isothermal bubble column based on mass transfer

“…is a function of dispersion number of liquid, gas to liquid flow ratio and the axial equilibrium distribution; (4) if both gas and liquid are only partially mixed, as per Bennet's [22] concept of gas dispersion in liquid, the mass transfer efficiency of the entire column may be a function of mixing characteristic which depends on geometric, dynamic and physical variables of the system. A correlation has been developed by dimensional analysis to analyze the efficiency of mass transfer for the entire column in terms of physical, dynamic and geometric variables of the system.…”

Unstable Operation in an Acetaldehyde Purification Tower

“…When simulation agrees with the data for the normal operation of the tower [7], then the results of the simulation can be trusted. The efficiency of trays and the height equivalent to a theoretical plate (HETP) for the packed part were calculated from the correlation of Bennett et al [8] and by Norton Chemicals method [9], respectively. Comparing the reflux ratio, purity of the distillate, percent of the crotonaldehyde in the side draw, and the temperature profile of simulation and normal operation in the plant (see Tab. 2), no considerable differences were found so an operational fault was not included as a possible reason.…”