The effluent from the last reactor flows to high-pressure hot separator V-105, which makes the necessary separation between the desulfur-ized liquid product and recycled gas. Vapor from HP hot separator is cooled to 500°F by heat exchange with recycled gas. The cooled, partially condensed HP hot separator vapors are fed to HP warm separator V-106. The function of the HP warm separator is to remove asphaltenes that may be entrained in the vapor leaving the HP hot separator. If the asphaltenes are not removed, an oil/water emulsion may form when water and oil condense in the high pressure loop. The HP warm separator operates at 500°F, which is well above the dew point of water, 330°F.
Liquid from the HP warm separator is combined with liquid from the HP hot separator and let down in pressure through a power recovery turbine. Vapor from the HP warm separator is cooled to 105°F by heat exchange with recycled gas, by air cooler E-106, and finally by water cooler E-107. The partially condensed HP warm separator vapor at 105°F feeds HP cold separator V-107. The final separation between the liquid and recycled gas is made in this vessel. The condensed water is also removed in this vessel. Water and oil are separated here, although both the streams are sent to the low-pressure (LP) cold separator. The separation of oil and water in the HP cold separator is necessary to avoid emulsification of an oil/water mixture across the pressure let-down valve in the line to the low-pressure cold separator.
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