Butane liquid level, increase

As the butane liquid level in the condenser increased, the area of the exchanger exposed to the condensing vapors would decrease. Let s assume that the tower s reboiler duty was constant. The vapor flow rate to the condenser would then be constant. To condense the same flow rate of vapor, with a shrinking exchanger surface area, the pressure of condensation must increase. The tower pressure would also go up, as the condenser pressure rose. 

But, let s assume that the first microsecond after the introduction of the rat, that the liquid did vaporize. The vapor so generated, would be trapped in the reflux drum. The pressure in the drum would increase. Not by 20 psig, but just a little. The small increase in pressure in the reflux drum would push up the liquid level in the condenser. The surface area of the condenser, available to subcool the liquid, would increase. The liquid temperature would be reduced. As the subcooled liquid flowed across the dead rat, its pressure would drop. The liquid s pressure would fall, to exactly that pressure that corresponds to the vapor pressure of the butane, at the temperature in the reflux drum. 

Crude oil or condensate stabilization is the removal of light components from a hydrocarbon liquid to lower its vapor pressure to a desired level. Stabilization may be used to meet a required pipeline sales contract specification or to minimize the vaporization of the hydrocarbon liquid stored in an atmospheric stock-tank. The stabilization process also results in reducing the amount of intermediate hydrocarbon components (propane and butane) that flash to the vapor state, increasing the liquid volume. Thus, it results in both increasing the liquid sales and decreasing the vapor pressure of the liquid. 

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