Experimental Study On The Liquid Equal Mean Residence Time Distributions Of A Large DJ Tray

In practical industrial production, there are some difference in liquid velocity distributions because of different tray constructs and gas-liquid loads. The liquid non-uniform flow influences plate efficiency severely. In thivS paper, the liquid equal mean residence time distributions of a large DJ tray were studied by tracing technique with hot-water as tracer. The main purpose was to study the extent of liquid non-uniform flow, to put forward effective measures in order to improve the non-uniform flow on the basis of experimental results, to provide available experimental data for the optimization design of large DJ trays and the prediction of plate efficiency.In the process of experiments, computerized multipass thermometer developed was used to detect the variance of liquid temperatures in the tray, the computerized multipass thermometer was debugged with air-water system in a Plexiglas rectangular column of 300mm X 200mm. The purposes of the debugging experiments were to measure the temperature measuring precision, dynamic errors, recurrence, resolving power, veracity and reliability of its measuring results. The experimental results show that: the measuring precision of this apparatus is 1.5 rate, its time constant is 4.0 ~ 4.8s and relative lagging time is 0.05 ~ 0.3s, it has good recurrence and resolving power. By comparing the liquid eddy diffusion coefficient from the AIChE correlation with that from the experiments, themeasuring results of computerized multipass thermometer are satisfactory.In this paper, the liquid equal mean residence time distributions of a newly DJ tray with anti-dumping unit were measured by using of computerized multipass thermometer, stimulus-response technology using hot water tracer was adopted. The experiments were carried out in a Φ 1200 DJ tray using air-water system. The main purposes were to study the effect of directed-plate on liquid flow, to optimize the location of directed-plate, to study the influence of liquid and gas rates on liquid distributions at the same time. The experimental results show that: the anti-dumping unit can not only decrease dumping and improve the column efficiency, but also the gas perforating the inclined perforation can impel the liquid to the tray. The directed-plate has a guiding role for the liquid and can improve liquid distributions. In the range of experiments, when the directed-plate was located at 1/3 length from the inner edge of the anti-dumping unit, the lines of equal mean residence time distributions were nearly parallel to the out weir, the equal mean residence time distributions were to uniform. With the increasing of air rate, liquid flow was improved slightly. With the increasing of gas rate, liquid flow was improved obviously. When the rate of liquid and gas all increased, the extent of liquid turbulence pricked up and the lines of equal mean residence time distributions were parallel to the out weir.