Analysis of DPF Incombustible Materials from Volvo Trucks Using DPF-SCR-Urea With API CJ-4 and API CI-4 PLUS Oils

This paper reports on a field test with 23 Volvo D12C non-exhaust gas recirculation diesel engines using the Diesel Particulate Filter (DPF), Selective Catalytic Reduction (SCR), and urea system with Ultra-Low-Sulfur-Diesel (ULSD). This combination will be used to meet the on-highway emission standards for U.S. 2010, Japan 2010, and Europe 2013. Because of future widespread use of DPF-SCR, this study reports on our field experience with this system, and focuses on enhancing our understanding of the incombustible materials which are collected in the DPF with API CJ-4 and API CI-4 PLUS oils. The average weight of incombustibles was lower in the trucks using API CJ-4 oils at 1.0% sulfated ash, than in those using API CI-4 PLUS oils at 1.4% sulfated ash. The difference in weight between the two groups was highly significant. Further, the weight of the incombustibles per kilometer substantially decreased with each subsequent cleaning within a truck. The gray powder of incombustible materials recovered from the DPF is dominated by inorganic lubricant additives—Ca, Mg, P, S, Zn, and Mo. Calcium sulfate, zinc magnesium phosphate and zinc pyrophosphate were iden-tified. These materials accounted for more than 90% of the materials from the DPF. Wear metals and a small amount of carbon were also identified, and made up the material unaccounted for by the lube oil inorganics. The particle size distribution of the incombustibles is bimodal, with a large number of particles at 0.4 microns and the remaining at 10 microns. Particles at 0.4 microns present inhalation and irritation health risk, and so exposure to incombustible trap ash should be minimized. The DPF-SCR system provided excellent durability and reliability during this five year field test. Both API CJ-4 and API CI-4 PLUS oils demonstrated equal wear, viscosity control, and oil drain capability based on used oil analysis.