Gasification Process by ExxonMobil

Application: ExxonMobil’s Reserach & Engineering’s (EMRE’s) continuous fluid-bed coking with integrated steam gasification technology to convert heavy hydrocarbons (vacuum residuum, extra heavy oil or bitumen) to lighter liquid products and a clean burning fuel gas, Flexigas, with minimum coke production. Attractive when coking for complete resid conversion with low or no fuel oil production is preferred and when outlets for fuel coke are limited or not economic, and especially when low-cost clean fuel gas is needed or where natural gas is high cost.

Products: Liquid product yields are similar to delayed coking and are upgraded to transportation fuels in the refinery by hydrotreating, hydrocracking, fluid catalytic cracker (FCC), or other processes. A large quantity of clean fuel gas is produced, which can be burned in a variety of grassroots or revamp furnaces and boilers in the refinery or in nearby power plants with low SOx and NOx emissions.

Description: FLEXICOKING has essentially the same feed system and fluid bed reactor (1) and scrubber (2) sections as FLUID COKING, and also has the same process flexibility to directly process vacuum tower bottoms without the need for a preheat furnace. It can also handle very heavy feeds, and can adjust recycle cut point depending upon gasoil product quality requirements. A steam /air gasification fluid bed reactor (4) is added to convert coke produced in the reactor to a CO and H2-rich fuel gas, diluted by N2.

pic1 15 - Gasification Process by ExxonMobil

The heater vessel (3) serves as a fluid solids heat exchanger to provide process heat for reactions in the heater and gasifier and to initially cool and clean Flexigas from the gasifier. Flexigas overhead from the heater (3) is cooled and cleaned in several steps (5) to remove fines and is then treated with FLEXSORB hindered amine to reduce H2S to as low 10 wppm if needed. Typically 95 wt%–97 wt% of the coke generated in the reactor is gasified to produce process heat and Flexigas, depending upon the amount of nickel (Ni) and vanadium (V) in the feed, A small amount of purge or net product coke is withdrawn from the heater (3) and fines removal system (5), which can be burned in cement kilns or used for recovery of V. Partial gasification with coke withdrawal can also be used to provide additional process flexibility for increased capacity or to make fuel grade coke if attractive markets are available.

Reactor yields: Typical 1,050°F+ cut point vacuum resid (~26 wt% Conradson
carbon, 4.6 wt% sulfur, 125 wppm Ni + V)
Component yield wt% wt%
Fuel gas (C2 –) 6.7
LPG, (C3 / C4) 4.4
Total C4– 11.1
Naphtha (C5-430°F) 15.3
Distillate (430°F – 650°F) 11.0
Gas oil (650°F – 975°F) 32.2
Total C5+ liquids 58.6
Net product coke 1.7
Gasified coke 28.6
Total reactor coke 30.3
Total: 100 100

Fuel gas production: Steam and air gasification of coke produced in the reactor generates a large fuel gas stream that is rich in CO / H2, which can be used as fuel. Fuel gas production consistent with the above yields for a 31,000 bpd FLEXICOKING Unit is:
Flexigas production: 1,580 MBtu / hr [460 MW (th)]
Flexigas heating value: 128 Btu / SCF
H2S content:

Competitive advantages:
• Integrated coking and gasification technology that yields the same valuable liquid products as other coking processes but produces clean fuel gas instead of high-sulfur coke.
• Fluid bed process with coke transferred pneumatically and contained within fluid solids reactors and product silos.
• Environmental advantages with lower SOx, NOx, and particulates emissions than conventional delayed coking processes
• Much lower investment and more reliable than delayed coking plus partial oxidation or direct gasification of solids or heavy feeds. Particularly attractive for SAGD tar sands upgrading with large fuel requirements.

Licensor: ExxonMobil Research and Engineering Co.


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