Raising the Tower Pressure Target

Ambient pressure in Denver is about 13 psia (Ib/in absolute) (vs. 14.7 psia at sea level). Higher pressures reduce the volumetric flow of vapor. In other words, volume is inversely proportional to pressure  

The pressure we are concerned with is the absolute pressure Initial pressure = 24 psig + 13 psi = 37 psia Final pressure = 30 psig + 13 psi = 43 psia 

The absolute tower pressure (in psia) increased by 17 percent, and hence the volume (as well as the velocity of vapor through the valve 

Another reason to raise tower pressure is to permit higher reflux rates. If the pressure controller in Fig. 6.1 is set too low, then during hot weather, when condenser capacity becomes marginal, the level in the reflux drum will be lost. If we then raise the pressure set point, the drum will refill— but why  

Raising the tower pressure also increases the reflux drum pressure, raising, in turn, the temperature at which the vapors condense. The rate of condensation is then calculated from the following  

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