Unstripped jet fuel

The pressure at point A in Fig. 10.4 was 13 psig. This means that the pressure drop in the vapor line from the stripper, back to the fractionator, was 3 psig. In order for the unstripped jet fuel, to flow out of the lower-pressure fractionator, and into the higher-pressure stripper, it had to overcome this 3-psig pressure difference. The 16-ft elevation difference between the draw-off nozzle on the fractionator and the stripper inlet provided the necessary liquid head driving force. 

Let us assume that the specific gravity of the unstripped jet fuel was 0.59. Also, note that for water, which has a specific gravity of 1.0 ... 

This means that the pressure head of a column of water 2.31 ft high, equals 1 psig. The height of a column of unstripped jet fuel, equal to a pressure head of one psig, is then... 

The pressure head of the column of unstripped jet fuel 16 ft high, shown in Fig. 10.4, is... 

Raising the steam flow to the stripper increased the pressure drop in the overhead vapor line from 3 to 5 psi. The pressure at point A in Fig. 10.4 then increased from 13 to 15 psig. The 4-psi pressure head driving force was not sufficient to overcome the 5-psi pressure drop of the stripper s overhead vapor line. The unstripped jet fuel could no longer flow out of the fractionator and into the stripper, and the liquid level in the stripper was lost. 

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