ExxonMobil’s Wet Gas Scrubbing (WGS) technology allows refiners to reliably meet tough FCC emission regulations with well-proven technology.
In 2002 and 2003, ExxonMobil Research and Engineering Company (EMRE) and Hamon Research-Cottrell (HR-C), entered into licensing and sublicensing agreements to provide ExxonMobil’s Wet Gas Scrubbing technology to sublicensees of HR-C.
Hamon Research-Cottrell / ExxonMobil wet gas scrubber (WGS) technology removes particulates and SO2 by intimate mixing with an aqueous scrubbing liquid. The technology can be enhanced to meet tighter restrictions on NOx (WGS Plus) or particulate with the addition of integrated WESP polishing.
WGS technology can be retrofitted into full-burn or partial-burn FCC units, even those with first generation CO boilers and very low flue gas pressure.
In partial-burn units, where the available flue gas pressure is low the WGS Jet Ejector Venturi design is used. The JEV creates suction pressure at the venturi throat from the action of the recirculated scrubber liquid. The application of WGS JEV scrubbing may avoid the need to upgrade older CO boiler. This JEV design offers the lowest pressure drop of any commercial scrubber.
For full-burn units, where higher gas pressures are available, the WGS High Energy Venturi is used. The HEV design uses the available energy in the flue gas to create the small droplets needed to scrub particulate and SO2 at high efficiency.
The typical scope for a WGS project includes the scrubber vessel from the flue gas inlets to the stack, the recirculation pumps and piping, scrubber instrumentation and control, caustic and water make up systems, scrubber purge, and the purge treatment unit to produce solids for disposal and benign waste water.
Since introduction of the technology in the 1970s, more than 30 FCC units have been fitted with ExxonMobil WGS systems worldwide. Hamon Research-Cottrell has been providing these systems for major refiners since 2005.
The robustness of the design means that even the earliest units continue to reliably perform today. At the same time the combined experience of ExxonMobil and Hamon Research-Cottrell has brought improvements in performance and capital cost, while maintaining the integrity and reliability of the system.
With run lengths in excess of four years and matching the longest FCCU up-time in the industry, WGS units operate until the FCC is ready for its turnaround. In fact, no FCCU has ever shut down due to a problem in an ExxonMobil WGS.
Two scrubber designs to meet all needs:
Uses gas pressure to push gas through venturi
Gas kinetic energy breaks liquid into drops
Preferred choice when flue gas pressure is high
Liquid flow in the venturi creates suction pressure (Bernoulli’s Principle)
Has lower back pressure than any other scrubber on the market
Liquid kinetic energy breaks liquid into drops
Preferred choice when flue gas pressure is low
Ideal for retrofits with older CO boilers that cannot take high back pressure