Compression and Water Knockout

The water content of both gaseous and liquefied acid gas was discussed in an earlier chapter. 

In the compression of the acid gas we try to take advantage of one of two observations (1) the minimum in the water content of acid gas or (2) liquefied acid gas can dissolve more water than the gas under pressure. 

In the design of a compressor for optimal water knock out, a water content diagram is constructed. 

In order to achieve optimal water knock out the discharge pressure from the next to last stage should be in the range of 3 to 7 MPa (435 to 1000 psia), again being careful to avoid liquefaction of the acid gas on the interstage. 

Also shown in figure 6.5 is the compression curve. The compressor suction is 0.150 MPa and 48.9°C (21.8 psia and 120°F) and at these conditions the water content is off scale for this plot, but it is 

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