C8/C10 Distillation Process

Study Notes

C8-C10 feed from T-410 bottom is routed to the middle of T-420 (C8 Tower).
T-420 separates the feed into three streams: overhead vapor (C8), side-draw (C10 product), and bottom liquid (C10+).
The overhead vapor stream from T-420 goes to the shell side of E-420 (C8 Tower Condenser) and is cooled by cooling water.
Liquid from E-420 is routed to the bottom of D-420 (C8 Tower Reflux Drum), while non-condensable vapor vents to D-531.
P-420A/B (C8 Tower Reflux & Product Pumps) direct liquid from D-420 back to T-420 as reflux or to E-422 (C8 Product Cooler) for cooling, before storage in TK-808/TK-1808 (C8 Product Tanks).
The C10 Product side-draw stream from T-420 is pumped by P-421A/B (C10 Product Pumps) to E-421 (C10 Product Cooler) for cooling, then sent to Unit 1791 for storage.
The bottom liquid stream from T-420 is routed to E-425 (C8 Tower Reboiler) and heated by 400 psig steam, with the resulting vapor returned to the bottom of T-420.
Steam condensate from E-425 goes to the Steam Condensate Header.
P-425A/B (C8 Tower Bottoms Pumps) send the liquid bottom stream to E-426 for cooling before it is routed to T-330 (TEA Tower).
The following equipment descriptions provide further details about the size, shape, internals, special features, etc. of each piece of equipment.

T-420 (3’6”D x 76’3”L) separates C8-C12 into a C8 overhead product and a C10 side-draw product.
The bottoms stream, a C10-C12 blend, is used as reflux for T-330.
Three key process control objectives: keep C10 concentration in the overhead at specification, keep C8 concentration in the side cut C10 product at specification, and produce bottoms at the proper flow rate for T-330 while keeping the C12 impurity of the side cut at specification.
C8-C10 feed enters the side, C8 exits the top, C10 exits the side, and C10-C12 exits the bottom.

E-420 is a shell and tube exchanger that cools and condenses overhead vapor from T-420 with cooling water.
It condenses the overhead to be used as reflux for T-411.

D-420 (4’D x 10’L) separates liquid for reflux and C8 product from non-condensable vapor.

E-422 is a shell and tube exchanger that cools C8 product with cooling water before storage.

E-425 is a kettle-type reboiler that heats T-420 bottoms with 400 psig steam.
It boils the bottoms into vapor, which exits the top, while remaining liquid exits the bottom.