Refiner Cetane Prediction Program Unveiled

Diesel Fuel News, April 30, 2001 by Jack Peckham

New Orleans -- An "Ethyl Distillate Optimizer" (EDO) computer program could help more refiners predict the best future blend recipes for on- and off-road diesel, plus avoid excessive cetane additization, according to a presentation at National Petrochemical & Refiners Association (NPRA) annual meeting here.

"EDO" builds on Ethyl's earlier "System for Predicting Efficient Cetane" (SPEC) computer program, and can be combined with PetroSpec's near-real-time (1-2 minute analysis) "Cetane 2000 Diesel Fuel Analyzer" to verify that the end-product indeed matches the predicted results, Ethyl says.

The system should allow refiners to employ more cost-efficient strategies for upgrading light-cycle oil (LCO), minimize giveaway on fuel quality specifications, minimize hydrogen, optimize cetane addition and boost profitability, Ethyl says.

In evaluation programs with current Ethyl customers, EDO has shown ability to save refiners from $3 million to $10 million per year through optimized distillate blending, Ethyl reports. "It might even show you that you don't need cetane additization" with certain blend schemes, Ethyl representative Tom Stocky said here.

While EDO to date is only being offered to current Ethyl customers, the company is considering possible ways to offer the program to a wider group of refiners, he said.

"In some cases, the cetane of the distillate pool is so low that a portion of the refinery's LCO production has become surplus and is now blended into resid fuel and/or sold into the distillate blendstock market," where margins are chronically thin, Ethyl points out.

On the other hand, EDO can analyze LCO process unit limitations, hydrogen availability/cost, and calculate market and specification limitations on kerosene, diesel, heating oil and resid, Ethyl says. Using EDO, "the optimized operation can produce benefits via improved deployment of processing units, more accurate blending recipes and in some cases the use of 2-EHN cetane additive," Ethyl reported in its NPRA paper.

With EPA 2006 regulations demanding a 15 ppm sulfur limit for ultra-low-sulfur diesel (ULSD), and possible sulfur limits (perhaps 500 ppm) coming for off-road diesel, "we envision a case where some refiners will employ a strategy of processing virgin distillate from the crude unit in their new ULSD hydrodesulfurization units, while diverting the coke and cracked distillates into their existing (and probably revamped) conventional HDS [hydrodesulfurization] unit for the 500 ppm off-road market," Ethyl says.

Problem: Diversion of LCO to off-road pool will reduce cetane and API gravity. Example: In one case Ethyl examined, such LCO diversion could create a 35 cetane off-road fuel with only 28 API gravity. "Analysis with the EDO model showed the most economical solution to be blending kerosene to meet the gravity specification, and using 2-EHN [cetane improver] to meet the cetane specification. The refiner will then have the option to construct a smaller hydrotreater to meet ULSD demands, continue to enjoy the benefits of the prior investment in the existing hydrotreater and have an overall more robust and economical operation," Ethyl found.