Yo5 VOFZ L0

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HEAT BALANCE EQUATIONS Q*=AQ'fz-(Qidi + Q vodi) Q.lvsiĀ«! IvsiMcHtDi-toi+i) q'R- (HtDl-htD -n)

HYDROCARBON PARTIAL PRESSURE ABOVE TRAY PI P'hc- (PrD>)[(Loi+i)/(LDl+> + VoDl-D2)]

Figure 2.19. Heat and material balance quantities at first sidestream product draw tray-type U tower.

2. The hydrocarbon which is to be revaporized in the 3. product stripper falls to the draw tray as part of the internal reflux from Tray (Dl + 1) rather than rising to 4. the tray as part of the product vapors. In passing across the draw tray, this liquid absorbs a small amount of the reflux heat. This heat absorption is calculated as 5. ^LSVl' Note from the example calculations that this heat quantity is quite small when compared to the reflux heat and could be neglected with no discernible loss of accuracy. It is included here for the sake of total definition of tower flows and heat quantities.

Calculate the heat removal capability of the reflux available to the tray as q^.

Calculate the internal reflux required to absorb the ex- j cess heat at Tray Dl as L[)j + j convert it to moles per hour. *

Calculate the mole fraction of hydrocarbon product vapor in the total vapor leaving the draw tray, neglecting the presence of the product to be removed on the next draw tray up in the tower. The reasoning behind this is that the product vapors which are to be withdrawn from draw trays above the next draw tray are

'VSN

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