THERMAL STUDY OF COOLANT CIRCUITS OF BUILT-IN DEPHLEGMATORS OF DIABATIC DISTILLATION COLUMN

Abstract

Diabatic distillation by using additional heat exchangers in the stages can significantly increase the energy efficiency of the column compared to adiabatic distillation. The paper proposes a calculation method for the condensation of ascending vapors on the tube surface of dephlegmators that are internally integrated on the trays of a multistage distillation column. The influence of parallel and series circuits of the coolant water supply to the dephlegmators on the technological parameters of the diabatic distillation unit is evaluated. For three types of coolant circuits, the following parameters are determined: thermal power, coolant temperature at the outlet of the tube dephlegmator, wall temperature on the condensate side, convective heat transfer coefficients, overall heat transfer coefficients, and thermal resistances on each tray of the distillation column. The results show that the parallel circuit to supply coolant water to the internal dephlegmators is the most suitable, providing the control of water flow rate on each tray and obtaining of the required temperature profile for height of the column to achieve the maximum efficiency of the separation process. For the parallel circuit, the heat transfer resistance can be concentrated in the heat transfer from both the coolant water to the wall of the dephlegmator tubes and the liquid condensed on the outer surface of these tubes.