Catalytic Fines (Catfines – Al & Si)
Catalytic fines (also known as catfines) are aluminum and silicon oxides used in the refinery catalytic cracking process. Catfines are very hard abrasive particles which can cause excessive wear of the components in the combustion chamber such as piston grooves, piston rings, cylinder liners and the fuel injection equipment.
The ISO 8217:2005 Table 2 Fuel specification has a maximum limit of 80 mg/kg (or ppm) for catalytic fines based on the sample collected at the point of custody transfer during the bunkering. The catfines limit was reduced to 50 ppm in the ISO 8217:2010, ISO 8217:2012 and ISO 8217:2017 fuel specification for the RME 180 fuel grade and 60 ppm respectively for the rest of the RMG and RMK fuel grades.
It is expected that the vessel will have adequate fuel pre-treatment and optimal fuel cleaning system onboard which includes the settling and service tanks, centrifuges and filters thus allowing for the further reduction of the catalytic fines. Engine breakdown may occur from catalytic fines accumulated in the tanks. This can happen during rough weather when catfines which had settled in the settling and service tank are mixed back into the fuel system.
Engine builders recommend that after the onboard treatment, the fuel entering the engine should contain less than 10-15 ppm catalytic fines.
Fuel System Check
Operators should be more concerned with the level of catalytic fines entering the engine than the level of catfines in the bunkering sample.
Fuel System Efficiency Check testing to evaluate the separation efficiency is recommended when the vessel received fuels with more than 30 ppm catfines. This will help the Engineers ascertain the capability of the fuel treatment onboard to handle the catfines.
Catalytic fines are hydrophilic hence regular draining of the service and settling tank can reduce catfines which are drained with the water.
Using 10-micron final hot filters instead of 50micron filters will also reduce the levels of catfines reaching the engine.
Vessels should check the fuel separation and treatment by periodically sending onboard samples from the following location or when they receive fuels with catalytic fines of more than 30 ppm.
A. Vessel’s manifold
B. Bunker Tank
C. Settling Tank
D. Before Centrifuge/Purifier
E. After Centrifuge/Purifier
F. Service Tank
G. After final hot filter before the main engine