Plant 16 Fractionation Section
The primary process objective of Plant 16 is to separate the hydrocarbon liquids from the condensate stripper and the deethanizer into three salable liquid products: propane, butane, and NGL.
Plant 16 consists of a debutanizer, C-1600, and a depropanizer, C-1610. The debutanizer separates the hydrocarbon liquids into an overhead C3/C4 stream and a NGL product stream. The depropanizer, C-1610, splits the C3/C4 stream into propane and butane products.
This section provides a detailed process description of Plant 16.
The debutanizer, C-1600, splits liquids from the condensate stripper, C-1020, and the deethanizer, C-1220, into a C3/C4 stream and a NGL product. Feed from the condensate stripper enters the column at Tray 16, at a design rate of 3600 BPOD. The feed from the deethanizer enters the column at Tray 28 at a design rate of 3600 BPOD.
C-1600 contains 40 valve trays to separate the C3/C4 from the heavier components. The liquid flows down and across the trays in the column. The hot vapors stripped out in the column go overhead to the debutanizer overhead condenser, E-1601.
The debutanizer overhead gases are totally condensed as they are cooled from 144oF to 120oF. The condensed hydrocarbon from C-1601 flows by gravity into the debutanizer reflux drum, V-1601. A portion of the liquid in V-1601 is returned to the top tray (Tray 40) of the column as reflux by P-1601A and B. Net hydrocarbon liquid from the reflux drum is also pumped by P-1601A and B to C3/C4 treating in Plant 17.
The bottom of the debutanizer is maintained at 284oF and 145 psig. The column bottom is divided in two sections, with a separation baffle. This causes all of the liquids from the bottom tray to enter the debutanizer reboiler, E-1600. This is required to minimize light components in the bottom product stream.
E-1600 partially vaporizes the liquid to remove light ends and provide stripping vapors. These enter the column below the bottom tray. Net liquids from the reboiler compartment overflow into the column net bottoms compartment. The net bottoms NGL stream is cooled to 110¢ªF in the NGL cooler, E-1603, and sent to C5+ sweetening in Plant 17. After Merox treating, the NGL is stored in the NGL product tankage.
Heat is supplied to E-1600 by condensing 80-PSIG stream on the tubeside of the reboiler. Steam condensate is collected in the condensate pot, V-1600, located directly beneath E-1600, and routed to the condensate collection drum, V-1620.
Depropanizer
The depropanizer, C-1610, splits treated C3/C4 from Plant 17 into propane and butane. The liquid feed is heated to 157oF in the depropanizer feed/bottoms exchanger, E-1612, and then fed to Tray 24 of C-1610. The design feed rate is 3640 BPOD.
C-1610 contains 40 valve trays to separate the propane from the butane in the feed. As liquid flows down and across the trays in the column, hot vapors rising up through the valves on the trays strip out the propane. The hot vapors at 113oF are routed overhead to the depropanizer overhead condenser, E-1611. Hot regeneration gas from the propane dryers is also sent to E-1611.
The hot gases are totally condensed as they are cooled to 110oF. The condensed propane flows to the depropanizer reflux drum, V-1611. The reflux pump, P-1611A and B, returns a portion of the liquid in V-1611 to the top tray of the depropanizer as reflux. The rest of the liquids from P-1611A and B are routed to the propane dryers using the propane booster pumps, P-1612A and B.
The depropanizer bottoms are maintained at 208oF and 215 psig. Liquid from the bottom tray goes to the depropanizer reboiler, E-1610. E-1610 partially vaporizes the liquid to remove light ends and to provide stripping in the column. Net liquid from the reboiler compartment overflows into the column net bottom compartment. The bottoms product from C-1610 is cooled in the depropanizer feed/bottoms exchanger, E-1612, then sent to butane storage.
Heat is supplied to E-1610 by condensing 80 psig steam on the tubeside of the reboiler. Condensate is collected in the condensate pot, V-1610, located directly beneath E-1610, and pumped to the condensate collection drum, V-1620, using the condensate booster pumps, P-1610A and B.
Propane Drying
Liquid propane from the depropanizer is dried in the propane dryers, V-1630A and B, to pass the GPA dryness test (cobalt bromide).
The propane dryers are molecular sieve packed beds. The molecular sieves selectively retain water allowing propane to pass through. Each bed can handle 100% of the design propane flow. The dryers operate on alternating 24-hour cycles: one is on-line for 24 hours, while the other is off-line for regeneration. This arrangement provides continuous propane drying capability.
During the drying cycle, wet propane from P-1612 flows up through the on-line dryer at a rate of 1825 BPOD. As the propane flows up through the dryer, the water is adsorbed on to the molecular sieve. The dried propane flows out the top and is sent to storage.
During the regeneration cycle, water is desorbed from the off-line propane dryer. A slip stream of dried propane is vaporized and heated to 450oF in the regeneration vaporizer, E-1630. The hot propane passes down through the off-line molecular sieve bed, vaporizing the adsorbed water and carrying it out of the dryer. The wet propane vapor is then recycled to the depropanizer overhead condenser, E-1611, where it is condensed. The desorbed water accumulates in the boot section of V-1611 and is removed from the drum periodically.
Steam Condensate Collection
Steam condensate from the reboiler condensate pots (V-1020, V-1220, V-1600 and V-1610), the glycol regenerator, E-1260, and Plant 17 is routed to the condensate collection drum, V-1620. Due to the pressure letdown, some of the condensate is vaporized as it enters V-1620. The vapors flow to the overhead condenser, E-1620, where they are condensed and sent back to V-1620. Condensate is pumped out of V-1620 by P-1620A and B and sent to the boiler plant for reuse in steam production.