Application: ExxonMobil’s Research & Engineering’s (EMRE’s) can reduce fluid catalytic cracking unit (FCCU) particulate (catalyst) and sulfur oxides (SOx) and nitrogen oxide (NOx) emissions to achieve compliance with environmental regulations—generally NSPS (New Source Performance Standards) and consent decrees (in the US). The technology can also be adapted for other refinery applications, e.g., coke calciners when flue gases must be treated to reduce SOx and particulate emissions.
Description: The WGS process takes dirty gas from FCCUs and simultaneously removes particulate matter and SOx via direct contact with a buffered liquid. Particulate removal is accomplished via inertial impaction of the particulate with the scrubbing liquid. SO2 removal is accomplished ia absorption into and reaction with the buffered scrubbing liquid. SO3 removal is accomplished via a combination of nucleate condensation, absorption and inertial impaction. All of this can be accomplished with low-pressure (3-in. of water column) or no pressure drop. This is important when aged heat recovery systems are involved.
The liquid purge from the WGS system is further treated in either the refinery wastewater system or in a segregated system, either of which will remove solids for landfill disposal and will reduce the chemical oxygen demand (COD) of the stream to meet local discharge requirements.
NOx can be removed by adding an additional
Operation of WGS systems demonstrates:
• Flexible/”forgiving” performance under a wide range of FCCU operations/upsets
• Service factors equal to or better than FCCUs with runs exceeding 12 years
• Low/zero pressure drop
• Ability to meet stringent emission regulations, e.g., consent decree requirements.
Performance: All WGS facilities are in compliance with their permitted values. Compliance has been achieved for the current consent decree particulate limits that can require emission of less than ¼ -lb of particulates 1,000 lb of coke burned. They are also in compliance with consent decree SO2 requirements of 25 vppmd @ 0% O2 and SO3 consent decree emission requirements of less than 10 vppmd. In addition, the WGS has recorded run lengths in excess of 12 years without affecting FCCU throughput.
Licensor: Hamon Research-Cottrell, GN-Hamon, LLC.
