ULTRA LOW SULFUR FUEL VALIDATION
European Union Directives for sulfur in Diesel will be reduced to 50mg/kg by 2005.
The directives also require Diesel with maximum sulfur concentration of 10 mg/kg to be available on market by 2005 and this lower concentration will become mandatory by 2009.
In USA the sulfur rules mandated by the EPA require Diesel with less than 15 ppm by 2006.
It will be responsibility of the oil industry to ensure that standards are met.
Directly after the choice of on line analyser in a market where suppliers claim for improvements monthly comes the questionable technology available for preparation, storage and handling of sample standards to validate reliable analytical procedures for measuring Ultra-Low Sulfur Diesel (ULSD).
How do you store Ultra-Low Sulfur Validation Diesel so you can get benefits of in line certification?
Those presuming that a simple storage tank (even with Nitrogen blanketing) just like for the past can suit with ULSD measurement are not going to see the light.
Of course Diesel is a stable product not subjected to weathering but the complex chemical sulfur compound to be analysed breaks with this stability:
a- Volatile Sulfur Compounds ( VSC’S) as methyl mercaptan with a 5.9 °C Boiling Point (BP) or dimethyl sulfide with a 47.2°C BP for the most common will evaporate with this type of storage and this standard integrity phenomen, negligible at 500 ppmS measurement will affect greatly the ULSD analytical system performances.
.b- at the outlet of the hydrotreating, aliphatic and alicyclic sulfur compounds are usually elliminated (if efficient) however dibenzothiophenes (DBT) and especially 4,6 alkyl sustituted DBTs are difficult to convert into H2S due to their adsorption to the catalyst surface, migration of these these compounds and residual sulfur adering to tank walls as well as their accumulation in the tank botom without velocity of flow or continuous mixing is a phenomen wellknown by the pipe-line transportation experts.
c- Today ASTM D-6708-01 covers the mathematical procedure for establishing “Equivalence with instruments that are part of existing ASTM method” and at the chapter of validation ASTM D 2885-99 describes how to use proto-fuels for very accurate comparative measurements. The statistical principes described for round-robin as well as the annexes describing preparation, storage and handling of proto-fuels used to validate analysers readings are invaluable and applicable to any certification of blends using on line analysers not just octanes.
Further to the succes of calibration piston floating cylinders, OPTA-PERIPH recently extended the range to bigger capacity cylinders (up to 1.000 dm3) and their application to ULSD measurements involves the following benefits:
Simplifies the Prototype Fuel Calibration procedure of ASTM D2885 applicable to analysers blend certification
Patented double piston barrier prevents VSC’s losses
No chilling procedure required before filling or during storage
Continuous mixing device to prevent residual sulfur accumulation on bottom and walls adhering
Features a patented Nitrogen inter-seal to prevent sulfur species oxydation
Contamination from surface accumulation between successive ULSD standards prevented by piston scraper wall cleaner.
All wetted parts in 316L S. S.polished to 0.2 µm Ra and PTFE, no soldered seams assembly or other contaminant agent.
Unopened ULS Diesel Fuel portable cylinder sytem for sample standard calibration supplied as option.