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Seaford, Delaware | Refiners don’t talk about it, but LCO (Light Cycle Oil) in diesel fuel is increasing as refiners shift production from gasoline to diesel. And that means more coking, varnish and sludge to the end user. Demand for gasoline has fallen with the deepening recession, driving prices down to $1.50 per gallon. According to the Wall Street Journal, the price for diesel is holding steady at $2.50 per gallon thanks to the continuing demand for diesel exports overseas. The ratio of gasoline to diesel is the so-called 3-2-1 ratio that reflects the typical output of gasoline (two barrels) and diesel (one barrel) from three barrels of oil. U.S. refiners are going where the money is and switching as much of their pro-duction from gasoline to diesel, but without major refinery changes, only 2-3% of their production can be switched into diesel. As refiners stretch this capacity to the limit, ULSD (Ultra Low Sulfur Diesel) is experiencing an increase in sludge, coking and varnish at the end user level. One manifestation comes from tank bottoms. As the fuel mixes with moisture, black or brownish sludge collects at the bot-tom of bulk tanks. When the tank is filled, sludge is stirred up and makes its way into the equipment, plugging filters with a dark brown or black sludge and coking the injectors with varnish. A second way this manifests itself is when fuel is heated as it is circulated through the engine block and returns to the tank 20-30 degrees hotter. This heating of the fuel leads to asphaltenes cooking out of the fuel, also leading to a brown or black residue causing filter plugging and injector coking. A third manifestation is in the presence of unstable biodiesel. Many biodiesel fuels do not meet the National Biodiesel Specs, especially if it is “backyard bio” made by local blenders to a low spec. This fuel is also unstable in the presence of moisture, leading to coking, varnish and sludge. What is causing all these problems with filters and injectors? A little thing called LCOs (Light Cycle Oils). A refinery is just a big distillery. Crude goes in, is distilled under heat and pressure, and the main product, Gas Oil is used to make gasoline and diesel. Gas Oil is fed to the catalytic cracker where it is cracked in the presence of a catalyst to make gasoline. In the U.S., the ratio of gasoline to diesel production is 55% gasoline to 12% diesel. LCO (Light Cycle Oil) makes up about 10% of the catalytic cracker yields. Because it doesn’t crack well, LCO is sent back to the reactor feed where it is re-cracked and eventually recycled to extinction. And therein lies the problem. Even small amounts of LCO in diesel fuel will increase gum and varnish that typically plugs injector spray tips, resulting in uneven fuel burn, loss of power and fuel economy. Excessive amounts of LCO hurt thermal and storage stability and cause sludge buildup in the lines and can even plug filters, especially when it mixes with moisture in the fuel tank. LCO also reduces cetane. Use this knowledge to prepare your customers. Fuel Dr. and Diesel Treat are the best prescriptions for fuel performance.
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Diesel Fuel Quality Suffers As Refiners Cut Back On Gasoline
