Recently published data indicate that the water vapor content of a gas, asdetermined by dew point measurement, is inaccurate when the gas has beendehydrated with diethylene glycol. Water vapor contents and dew pointmeasurements of gases dehydrated with triethylene glycol have been obtained inthis investigation in order to determine the magnitude of a similar error, ifone exists.
Experimental data show a very low concentration of triethylene glycol vaporin gases dehydrated at atmospheric temperatures and pressures ranging from 500to 2,500 psia, and that the accuracy of dew point measurements is not impairedby the presence of triethylene glycol vapor.
Nearly all natural gas transported by pipe line to northern and easternmarkets must be dehydrated to a low residual moisture content in order toassure maximum transmission efficiency and continuous delivery under peak loadconditions. Without dehydration, water vapor often condenses in pipe lines inquantities sufficient to restrict the flow and, under low atmospherictemperature conditions, gas hydrates may form and plug gathering, transmissionand distribution facilities.
Gas may be dehydrated to pipe line specifications by a number of methods.The most widely used methods are
adsorption of water vapor on a soliddessicant such as activated bauxite, alumina or silica gel,
by absorptionof water vapor by either diethylene or triethylene glycol-water solutions ofhigh glycol concentration, and
by simultaneous expansion-refrigeration ofvery high pressure gas in which gas hydrates are purposely formed and thenquickly decomposed.
Of these three fundamental methods, the adsorption andabsorption processes provide the bulk of the dehydrated gas moving to market atthe present time. The expansion-refrigeration process, a relatively newdevelopment, is gaining in favor because of its simplicity but is sharplylimited in its application by available differentials between source andgathering system pressures.