Injector Fouling Performance and Solubility of GTL Diesel Dosed with Zinc 2013-01-1697
The success of modern diesel passenger cars is, to some extent, attributable to the advent of common rail diesel injection technology. Today almost all new diesel engines use this technology which is characterised by high fuel injection pressure and very small diameter nozzle holes. The industry rapidly developed a new test procedure to assess a fuel's propensity to cause injector fouling and also to assess the ability of additives to clean and to keep such injectors clean. The CEC F-98-08 DW10 test procedure was approved in March 2008 by the CEC and is now considered an industry standard test method. The test method requires 1ppm zinc to be dosed into all test fuels in order to accelerate injector fouling.
This paper presents DW10 test results for gas-to-liquids (GTL) diesel. A similar test method, using a different engine, was developed in-house and showed good correlation with the DW10 test. The results confirm a significantly different response with GTL diesel compared to regular diesel when both have been dosed with zinc. A series of chemical laboratory test work investigated the solubility of zinc in GTL. The results reveal that, when compared to EN590 diesel, zinc more readily drops out of a GTL-zinc solution, prepared in a similar way to that used in the DW10 test. It was also found that zinc is less readily taken up into solution with GTL from solid zinc components than it is by EN590 diesel.
The lower solvency of GTL diesel results in greater injector deposit formation due to zinc drop-out in the DW10 test method. Zinc pick-up tests, however, demonstrate that GTL diesel is less likely to pick up zinc in the logistic chain in the market. It is shown that various deposit control additives are very effective in preventing deposit formation in a GTL-zinc solution and have the ability to clean up zinc-fouled injectors.