Study On Entrainment Model Of DJ Tray And Enhancement The Vapor Flow Capacity

After years of continuous development,DJ trays have been widely used in the industrial field.In the production practice,the requirements for gas phase load are getting higher and higher.How to increase the gas phase upper limit is a problem faced by the DJ tray;the upper limit of the gas phase can be reflected by the entrainment of the tray.At present,there are not many researches on the entrainment of DJ trays,and the existing correlation formulas for predicting the amount of entrainment are mostly based on ordinary sieve tray.Therefore,in order to reduce the entrainment,the DJ-5 tray is taken as the research object.The formation mechanism of the entrainment is analyzed through experiments.and the model of the entrainment applied to the DJ tray is calculated.According to the spacing packing-combined tray technology,the DJ-5 tray is improved to adapt to the special conditions of high gas phase loading and higher liquid phase loading.The elongated standing-valve tray and the round standing-valve tray were tested with an air-water system in the transparent plexiglass experimental column with an inner diameter of 600 mm and a tray spacing of 600 mm.The entrainments of elongated fixed valve tray were measured and compaired with those of the round standing-valve tray in condition of different empty column kinetic energy factors and spray densities.The experimental results showed that the entrainment rates of DJ-5 elongated standing-valve tray was lower than the round standing-valve valve tray by 10~40%.The elongated standing-valve with guiding function performs better than the round standing-valve on entrainment.At the same time,the variation of the entrainment of the DJ-5 tray conforms to the double transition point theory of the two-phase contact state,that is,the transition of the spray state-mixed foam state-foam state.Based on the entrainment mechanism and combined with the existing model,the correlation of the entrainment suitable for DJ-5 tray is derived,which provides a theoretical reference for future engineering practice.The new correlation can well predict the entrainment of DJ-5 valve tray in mixed foam state.In order to improve the limit of vapor phase load of DJ tray and optimize the anti-entrainment performance,a new type of tray(DJ-5 Plus tray)was proposed which combined structured packings with DJ-5 tray based on the spacing packing-combined tray technology.The dry plate pressure drop,wet plate pressure drop,entrainment and leakage of DJ-5 tray,DJ-5 Plus tray and F1 valve tray were compared under different spray densities and vapor phase loads.The experimental results showed that the entrainment rates of DJ-5 Plus tray were lower than those of the common DJ-5 and F1 valve tray;the dry pressure drop of DJ-5 Plus tray is higher than that of DJ-5 tray and lower than that of F1 valve;the wet pressure drop of DJ-5 Plus tray is similar to that of DJ-5 tray and much smaller than that of F1 valve;the leakage rate of DJ-5 Plus tray is higher than that of F1 valve and smaller than that of DJ-5 tray.In addition,the mathematical correlation was obtained by fitting the dry / wet pressure drop of DJ-5 Plus,which provides theoretical guidance for industrial practice.DJ-5 Plus tray performanced well in hydrodynamics and was especially suitable for applications with high vapor phase loads.The tray has been successfully implemented in a certain industrial revamping case for enhancing capacity and increasing economic benefit with good outputs.