FLEXICOKING™ technology is a commercially proven, cost-effective, fluidized bed process that thermally converts heavy oils to lighter products and flexigas – “Coking without the Coke.” Low-cost feeds such as deep-cut vacuum resid, atmospheric resid, oil sands bitumen, heavy whole crudes and DAU, FCC and ebullated-bed bottoms are converted to high-value products. FLEXICOKING technology with integrated steam/air gasification offers greater flexibility than conventional Delayed Coking, and does it economically. The FLEXICOKING technology not only produces clean liquids of equivalent quantities and similar quality to Delayed Coking, but also gasifies the low-value coke to produce a clean, highvalue flexigas that can be used in place of natural gas and conventional fuel gas in refinery processes. Flexigas can also be used to generate electric power and to produce H2, N2, and CO2.
- Proven: Commercially proven for more than 38 years in ExxonMobil and in licensed third-party units. All FLEXICOKING units are operating today at capacities greater than original design. Current combined operating capacity is 227 kBd/12 MTA.
- FLEXible: A robust process, capable of handling a variety of feeds with a wide range of high Conradson Carbon Residue (CCR), sulfur and heavy metals, without the need for a feed furnace.
- Multi-Purpose: The high-sulfur, low-value coke is converted to a clean, economical multi-purpose flexigas which can be used in refinery furnaces, boilers and gas turbines or processed to recover H2, N2, and CO2. ExxonMobil’s FLEXSORB™ process is incorporated to reduce H2S in flexigas to 10 wppm, or as needed.
- Optimizable: Coke gasification can be optimized on the run, to debottleneck the unit or to satisfy operational requirements such as changes in feed formulations and variations in flexigas consumption.
- Economic: Integrated “simple” steam/air gasification, carbon steel construction throughout, and the absence of feed furnaces are key factors resulting in significantly lower capital investment when compared to Delayed Coking with “complex” oxygen gasification. Expect greater comparative savings in electric power-generation applications (steam or combined cycle).
- Environmental: Continuous, non-batch operation and closed coke handling system results in low-particulate and fugitive hydrocarbon emissions. Much lower SOx and NOx emissions are realized by burning the clean flexigas, when compared to burning high sulfur coke.
- Reliable: Continuous, steady state operation in combination with cold-wall carbon steel construction contributes to high reliability and service factors that routinely exceed 92 percent.
These benefits come to you in a compact package. The layout of modern FLEXICOKING units offers reduced plot space – about 20 percent less than that of a basic Delayed Coking unit of similar capacity.
How FLEXICOKING technology works
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 a gas. The gasifier products, consisting of a gas and coke mixture, return to the heater to heat up the coke. The gas 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.
Approximately 95 percent of the coke generated in the reactor is converted in the process. Only a small amount of product coke is collected as fines from the flexigas and purged from the heater to extract feed metals.
Full-Range Products Slate
FLEXICOKING technology produces a full range of products, from a C4- reactor gas to C5/975°F (525°C) liquid products, the multi-purpose flexigas, and lastly a small stream of low-sulfur coke that is purged to extract
The first FLEXICOKING unit began operation in 1976, and since then five others have come online, the most recent one in 2012. Since 2010, we have also licensed three new units with a combined capacity of 114kbd/6.3 MTA. These
are currently in different stages of construction.
ExxonMobil has licensed fluidized bed coking technology since the 1950s, including the largest fluid coker, which is located in Syncrude, Fort McMurray, Canada. Our experience ranges from 5 to 105 kbd (60 to 750 mtons/hr) unit capacities and a variety of difficult feeds with CCR values ranging between 17 and 37.
ExxonMobil has equally extensive experience supporting its licensees, and this is particularly true of the FLEXICOKING technology, because ExxonMobil owns and operates FLEXICOKING units in two of its largest refineries: Rotterdam in the Netherlands and Baytown, Texas, in the United States.
We see an increasing market interest in FLEXICOKING technology worldwide. We expect the trend to continue well into the future, particularly in parts of the world where natural gas is limited and/or expensive, and in environmentally sensitive areas.