#2 Fluid Catalytic Cracking Unit (#2 FCCU)

The feedstock to the # 2 FCCU, Unit 12, consists of hot VLGO, AGO, some VTB from the #2 CDU and cold imported feed from storage. The maximum charge to the unit is approximately 13,000 BPSD, however this can vary with seasonal conditions and feedstock quality. The unit produces Full Range Gasoline, Light Cycle Stock, Decant oil, Propane / Propylene mix, Butane / Butylene mix, and Fuel gas.

The feed, after passing through a fired preheater, or provided as hot feed directly from the crude units, enters the unit at the base of the riser where it contacts hot, regenerated catalyst and is vaporized. The heavier gas oil hydrocarbons are cracked to form lighter components as they contact the catalyst in the riser, producing gas, unsaturated LPG, FCCU gasoline, light cycle oil and residual heavy cycle oils. The cracking reactions will continue for the very short time it takes for the oil vapors / catalyst mix to reach the top of the riser, where they are disengaged in the reactor. The cracked products in the vapor phase leave the reactor overhead and flow to the fractionation section. In the fractionation section / gas plant, the reactor vapors are cooled, compressed, condensed and split into the various product streams.

The cracking reactions are endothermic (absorb energy) and coke is deposited on the circulating catalyst during the reactions process suppressing catalyst activity. The spent catalyst flows from the reactor, through the steam stripping section to remove residual hydrocarbons, and into the regenerator. In the Regenerator air is contacted with the spent catalyst and the coke is burned off to provide regenerated catalyst.

The regenerated catalyst then exits the regenerator via the stand-pipe and circulates back to the base of the riser to restart the process. The heat of combustion raises the catalyst temperature to the 1200 to 1300 F range and thus supplies the heat of reaction, since most of this energy is transferred into cracking the feed in the riser. Cyclones internal to the regenerator vessel retain the catalyst in the circulating system. Hot flue gases exiting the regenerator cyclones are utilized to generate steam in a waste heat recovery system before exiting into the flue stack.

The FCCU main fractionator receives the superheated vapors from the overheads of the Reactor separator. The Reactor contains a riser termination device and cyclones which efficiently separate the catalyst from the hydrocarbon vapors, and minimize catalyst fines losses into the downstream oil separation systems. The main fractionator column quenches, cools, condenses and separates the heavy and light cycle oil products. The overheads vapors enter the FCCU Gas Recovery Plant (#2 GRP) which further recovers the FCCU gasolines and separates the olefinic LPG streams from the fuel gas produced by the cracking process. The Propane / Propylene mix LPG stream is fed to the Propylene splitter section for recovery as a saleable chemical feedstock. The Butane / Butylene mixture is routed into the Alkylation unit. FCCU gasolines are merox treated and routed into the gasoline blending systems.

In the #2 FCCU, modifications have been implemented to the reactor internals to allow

processing of approximately 3,000 BPD of sweet crude vacuum tower bottoms residues from the

#2 CDU. This included modifications to the riser catalyst disengager, stripper, and cyclones and

installation of a catalyst pre-stripper and a Light Cycle stock recycle to quench the riser. The

modifications allow increased upgrading of VTB to higher value products.

A new fired feed pre-heater has been installed to handle the increased volumes of cold imported

gas oils required to replace the LVGO and HVGO that has been diverted to Lube feed. Other

modifications have been made to the bottoms pumparound and overhead condensers to increase

heat removal capacity in the main fractionator. The LPG Merox Treater section was also

modified to process increased mercaptans levels from increased resid cracking operations.