These calculations showed that, with a vapor velocity in the tower amounting to about 80% of the maxi-
mum, the development of reflux in the upper part of the tower by the upper PTsO-1 makes it possible to
recover approximately 77% of the entire amount of heat withdrawn from the column, and the development of
reflux by the lower PtsO-2 can give 23% recovery. This gives a more favorable variation of load with respect
to tower height, and fewer trays are involved in the circulating reflux loop, so that it is possible to improve
the closeness of distillate separation.
Such a distribution of heat withdrawn by PTsO-1 and PTsO-2, with the tower capacity specified by
design, is in complete accord with the possibilities of its recovery in heating crude oil. Thus, the rational
redistribution in the heat exchange system of the heat in the distillate and residue streams, as well as the
replacement of cold water by hot spent water in washing out the salts, makes it possible to increase the heat
recovery and provide heating of the crude oil to 220~ ahead of the topping tower T-1 [9-11].
Experience in the operation of analogous crude oil distillation units indicates the desirability of maxi-
mum development of reflux in the upper part of the atmospheric tower, which will make it possible to improve
the closeness of distillate separation [2]. In combination with the supply of heat to the lower part of the tower
strippers through reboilers, this can give a substantial improvement in distillate separation in an atmospheric
crude oil distillation tower.
Inadequate distillate separation in the stripping section of the tower is related to the small amount of
steam supplied to the tower bottom (1.44% instead of the 1.75% specified by design). Owing to the low vapor
flux in the lower part of the tower, the contact between these vapors and the large volume of liquid is not as
efficient as it should be.
On the basis of the studies reported here, we have established the optimal operating indices for the T-2
tower in atmospheric distillation of crude oil. Depending on the composition of the feedstock being processed
and the required yields of light products, it is possible to select the most rational scheme for supplying and
recovering heat in a complex tower.
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