Abstract: A mathematical model for discribing the start-up period of a plate distillation column operating undertotal reflux is presented.Based on the differential-difference equation expressing the material balance onthe trays in a complete column with holdups in the reboiler,trays and condenser,the present model isderived and an analytical solution is obtained.The existence of a constant concentration point during thestart-up period is proved mathematically.Experimental work on start-up period is carried out in a seven sieve tray distillation column of 0.17meter in diameter with a water-acetic acid system.Good agreement is found between the experimentaldata and the calculated results.The experimental results also show the evidence of a constant concentra-tion point in the column during start-up period.

摘要： A mathematical model for discribing the start-up period of a plate distillation column operating undertotal reflux is presented.Based on the differential-difference equation expressing the material balance onthe trays in a complete column with holdups in the reboiler,trays and condenser,the present model isderived and an analytical solution is obtained.The existence of a constant concentration point during thestart-up period is proved mathematically.Experimental work on start-up period is carried out in a seven sieve tray distillation column of 0.17meter in diameter with a water-acetic acid system.Good agreement is found between the experimentaldata and the calculated results.The experimental results also show the evidence of a constant concentra-tion point in the column during start-up period.