C12 Tower Operation

• C12-C24 feed from T-430 overhead is sent to F-444, the C12 Tower Feed Strainer.
• From F-444, feed goes to the shell side of E-443, the C12 Tower Feed Preheater.
• E-443 heats the feed, using 400 psig steam on the tube side.
• Steam condensate from E-443 is routed to the Steam Condensate Header.
• The heated feed goes to T-440, entering between the top and bottom beds onto a chimney tray.
• The chimney tray has down comers that deliver liquid to the feed distributor tray.
• The distributor tray evenly spaces liquid onto the bottom bed for proper vapor/liquid contact.
• In T-440, the feed separates into C12 overhead vapor (C12 Product) and C14-C24 bottom liquid.

C12 Product (Overhead Vapor)

• The T-440 overhead vapor stream flows to the shell side of E-440, the C12 Tower Condenser.
• E-440 is cooled by untreated boiler feed water on the tube side, producing steam routed to the 15 psig Steam Header.
• Condensed vapor from E-440 is routed to the top of D-440, the C12 Tower Reflux Drum.
• Non-condensable vapor from E-440 goes to the shell side of E-441, the C12 Tower Vent Condenser, and is cooled by cooling water on the tube side.
• A slip stream of condensed vapor from E-441 is routed back to D-440, while the rest of the condensate is routed to D-433.
• Cooled overhead gas from D-440 combines with non-condensables from E-480 for pressure control and goes to Z-440 (C12 Tower 1st Stage Ejector).
• Z-440 uses 100 psig steam to pull a vacuum and route the cooled overhead gas to the shell side of E-449 (C12 Tower Ejector Interstage Condenser), which is cooled with cooling water on the tube side.
• Condensate from E-449 goes to D-433, and the gas is then routed to Z-441 (C12 Tower 2nd Stage Ejector).
• Z-441 also uses 100 psig steam to pull a vacuum, routing the gas to E-480.

Reflux and Product Routing

• Liquid from the bottom of D-440 flows to F-440 (C12 Tower Reflux Strainer) via P-440A/B (C12 Reflux & Product Pumps).
• P-440A/B routes liquid back to T-440 as reflux.
• P-440A/B also routes liquid to the shell side of E-442 (C12 Product Cooler) and it is cooled by cooling water on the tube side.
• Cooled C12 product is routed to TK-812 (C12 Product Tank).
• Off-spec C12 is routed to Unit 1791 Heavy Rerun.

C14-C24 (Bottom Liquid)

• The T-440 bottom liquid stream flows to the shell side of E-445 (C12 Tower Reboiler).
• E-445 is heated by Dowtherm on the tube side.
• Overhead vapor from E-445 flows back to T-440 for temperature control.
• Liquid from the bottom of E-445 is routed by P-445A/B (C12 Tower Bottom Pumps) to T-450 (C14 Tower) as feed.

Equipment List

• F-444 (C12 Tower Feed Strainer)
• E-443 (C12 Tower Feed Preheater)
• T-440 (C12 Tower)
• E-440 (C12 Tower Condenser)
• D-440 (C12 Tower Reflux Drum)
• E-441 (C12 Tower Vent Condenser)
• Z-440 (C12 Tower 1st Stage Ejector)
• E-449 (C12 Tower Ejector Interstage Condenser)
• Z-441 (C12 Tower 2nd Stage Ejector)
• P-440A/B (C12 Reflux & Product Pumps)
• F-440 (C12 Tower Reflux Strainer)
• E-442 (C12 Product Cooler)
• E-445 (C12 Tower Reboiler)
• P-445A/B (C12 Tower Bottoms Pump)

F-444 (C12 Tower Feed Strainer)

• Removes particulate matter from the T-440 feed.

E-443 (C12 Tower Feed Preheater)

• Shell and tube exchanger
• Heats C12 feed on the shell side using 400 psig steam on the tube side.
• Preheat the C12 feed to T-440.

T-440 (C12 Tower)

• 4’6”D x 81’4”L
• Separates C12-C24 into a C12 overhead product.
• Bottoms stream is a C14-C24 blend, feed to T-450.
• Key process control objectives:
  • Keep the C14 concentration in the overhead at specification
  • Keep the C12 concentration in the bottoms at specification
• C12-C24 feed enters the side of the tower.
• C12 exits the top.
• C14-C24 exits the bottom.

E-440 (C12 Tower Condenser)

• Shell and tube exchanger
• Cools and condenses the overhead vapor from T-440 (shell side) using boiler feed water (tube side).
• Condenses overhead for reflux to T-440 and C12 product to storage.

D-440 (C12 Tower Reflux Drum)

• 3’6”D x 8’L
• Separates liquid for reflux to T-440 and C12 product from non-condensable vapor.

E-441 (C12 Tower Vent Condenser)

• Shell and tube exchanger
• Cools and condenses the overhead vapor from D-440 (shell side) using cooling water (tube side).

Z-440 (C12 Tower 1st Stage Ejector)

• Lowers the pressure of T-440 overhead, 1st stage.

E-449 (C12 Tower Ejector Interstage Condenser)

• Shell and tube exchanger
• Cools and condenses the steam from Z-440 (shell side) using cooling water (tube side).

Z-441 (C12 Tower 2nd Stage Ejector)

• Lowers the pressure of T-440 overhead, 2nd stage.

P-440A/B (C12 Reflux & Product Pumps)

• Single-stage centrifugal pumps
• Driven by 15 HP 3550 RPM horizontally-mounted induction electric motors.
• Circulate reflux to T-440 and route C12 product to TK-812.

F-440 (C12 Tower Reflux Strainer)

• Removes particulate matter from the T-440 feed.

E-442 (C12 Product Cooler)

• Shell and tube exchanger
• Cools the C12 product (shell side) using cooling water (tube side).
• Cools C12 product before routing to storage.

E-445 (C12 Tower Reboiler)

• Kettle-type reboiler
• Heats T-440 bottoms (shell side) using Dowtherm (tube side).
• Kettle shape provides space for vapor expansion.
• Boils the bottoms into a vapor.
• Vapor exits the top nozzle, remaining liquid exits the bottom nozzle.

P-445A/B (C12 Tower Bottoms Pumps)

• Single-stage centrifugal pumps
• Driven by 7.5 HP 3500 RPM horizontally-mounted induction electric motors.
• Routes the liquid bottoms from T-440 to T-450.