The vacuum resid feed enters the scrubber for “direct-contact heat exchange” with the reactor overhead product vapors. The higher boiling-point hydrocarbons (~975°F+/525°C+) present in the reactor product vapors condense in the scrubber and return to the reactor, in mixture with the fresh feed. Lighter overhead product vapors in the scrubber go to conventional fractionation and light-ends recovery. The feed is thermally cracked in the reactor fluidized bed to a full range of gas and liquid products, and coke. Coke inventory is maintained by circulating the bed coke from the reactor to the heater via the cold coke transfer line.
In the heater, the coke is heated by the gasifier products and circulated back to the reactor via the hot coke transfer line to supply the heat that sustains the thermal cracking reaction. The excess coke in the heater is transferred to the gasifier, where it reacts with air and steam to produce flexigas. The gasifier products, consisting of flexigas and coke mixture, return to the heater to heat up the coke. The flexigas exits the heater overhead and goes to steam generation, to dry/wet particulate removal, and to desulfurization in the integrated FLEXSORB™ process. The clean flexigas is then ready for use as fuel in refinery boilers and furnaces and/or for steam and power generation.
Only a small amount of product (1% weight on Fresh Feed) is collected as fines from the flexigas and purged from the heater to extract feed metals.
