Highs and Lows of Ultra-Low

While the introduction timetable for ultra-low sulfur heating oil remains uncertain in some markets, it has been introduced in others, enabling additive makers to gain valuable experience in working with it. What lessons have they learned? Fuel Oil News interviewed a number of additive suppliers about their experiences with both ultra-low sulfur heating oil and ultra-low sulfur diesel. Here’s what they had to say.

When a different fuel is suddenly put into a storage system that has held the same fuel for years, some repercussions can be expected, and that is so with the transition to ultra-low sulfur heating oil and diesel, said Ed Kitchen of Fuel Management Services, Jeffersonton, Va., which markets additives, including dispersants, cold flow improvers and stabilizers.

‘Unfortunately, ultra-low is going to be less stable” than low-sulfur fuel in storage, Kitchen said. ‘We’ve learned that already.” There is also a slight loss of density and heating value, he noted. However, ‘solvency is the greatest single problem that we have,” Kitchen said. Introduction of ultra-low sulfur fuel to storage systems that have been regularly fed a different fuel can exacerbate that problem, he said. The solvency issue requires that tanks are clean ‘or ULSD will clean them out for us,” Kitchen wrote in a paper he composed as a reference for his oil dealer customers. He noted other matters that require dealers’ attention.

The hydroprocessing of feedstocks to produce ultra-low sulfur fuel makes it less lubricating and less conductive, Kitchen stated. While these characteristics are corrected at the end of the pipeline terminal or at the receiving marine terminal, he said, some of the lubricity additives themselves can cause complications.

Kitchen said the troublesome additives are oil derivatives of a certain type of tree that, in the presence of water, can form insoluble salts or soaps. These can combine with other insoluble gums during the transition from LSD to ULSD and foul filters, he said. Kitchen advised checking with terminals to find out whether they are using a synthetic or organic lubricity improver. ‘This is a case where the synthetic should be the product of choice,” he said.

The ultra-low sulfur fuel has more wax content than its low-sulfur cousin, Kitchen also noted. ‘When ultra-low reaches its cloud point, it has been generating more wax in a shorter temperature range than LSD,” Kitchen wrote in his paper. ‘It has also been more difficult to move the CFPP of ULSD.” He recommended increased batch testing ‘to minimize any performance surprises.”

‘That first winter that the ultra-low was being used there were a lot of unknowns about the product,” Jerry Sava, president and co-owner of C&S Scientific Corp, Hightstown, N.J., said. ‘One of the things we observed in our lab, when we got samples before the heating season began, was that in cold weather, once that separation takes place in ultra-low the wax would build up at the bottom of the diesel tank or even at the bottom of a heating oil tank. And when it warmed up, that wax was very resistant to re-dissolving back into a fluid.”

Sava said, ‘It was almost like candle wax. It had to become much warmer than the typical point where separation occurred before it would begin to re-dissolve.”

Having discovered this, Sava said, C&S adjusted the ingredients somewhat in its additives ‘ Antigel for heating oil and Diesel-Add for diesel fuel ‘ aiming to make both more effective in addressing cold flow. The added ingredients included heavy wax modifiers and wax anti-settling agents, he said.

A common method for addressing cold flow has been to put in 20 percent, 30 percent or more kerosene to thin the fuel, Sava noted. An advantage of using an additive is that the treatment rate is much less ‘ more like one-tenth of one percent of the fuel ‘ and it reduces the gelling point equally as well or better than blending large proportions of kerosene, Sava said. The additives often are injected at oil dealers’ own terminals or they can be added at the customers’ locations.

While the cold flow problems are similar in ultra-low sulfur heating oil and in ultra-low sulfur diesel, ‘some of the problems might show up a little quicker” in diesel systems, Sava pointed out, because those systems feature ‘much closer tolerances, orifices, where the oil is being injected.”

In general, except for the cold flow, Sava said, ‘the problems you would run into with ultra-low, whether heating oil or diesel fuel, would be pretty similar to what you run into with the higher sulfur fuels.” These include the chance for soot and carbon buildup, and the development of sludge, he noted. ‘Ultra-low sulfur diesel maybe maintains its quality a little longer,” Sava said, ‘but it will form sludge eventually.”

Ultra-low sulfur heating oil ‘has the same set of problems that high sulfur heating oil has,” said Bob Tatnall of Fairville Products, Wilmington, Del., which markets Fuel Right additives for preventing sludge and corrosion of tanks. ‘It still grows great sludge.”

As for lubricity, Tatnall said it is a concern in diesel systems because wear of injector pumps can be an issue. ‘The gear pumps we use in heating oil are not as sensitive to that,” he commented.

Overall, he said of ultra-low sulfur fuel, ‘I don’t think it’s going to be any worse than the product we have now. But of course, everybody, I think, pretty much agrees that the product we have now is very often quite unacceptable. The stability and quality of the fuel is really bad.”

Newer home heating systems that feature very small nozzles ‘are the ones that are going to have severe problems because of black particles that pretty much form right at the nozzle adaptor cavity,” Tatnall said. ‘They plug up the pre-filter on the back of the nozzle and you get a no-heat call.”

A spec for stability would go a long way toward easing the maintenance and use of ultra-low sulfur heating oil and diesel, Tatnall suggested.

‘Wholesalers are now wise to the fact that they can blend light cycle oils with ultra-low sulfur products, just as they have with high-sulfur products,” Tatnall said. If such blending becomes a widespread practice, ultra-low will ‘become as problematic as the high-sulfur product we’ve been dealing with up until now,” Tatnall said. ‘That’s my biggest concern.”

The issue could be resolved if the industry were to establish ‘a meaningful stability spec,” Tatnall said. Asked who should write it, he suggested any state association, the National Oilheat Research Alliance (NORA) and the American Petroleum Institute (API) as possibilities.

‘Any of them has the power to write a spec,” Tatnall said. ‘Whether they could enforce it is up to oil dealers.” If oil dealers declare they want fuel oil that meets a particular stability spec ‘they can always get it,” Tatnall said, though they may have to pay a premium for it.

Tatnall also advocated for grades of stability specs: Grade A and Grade B, for example. Industrial users could burn Grade B, he said. Ship operators, who need not be concerned about stability and small nozzles susceptible to plugging, could use Grade B, he suggested.

The use of ULSD will offer emissions benefits, and the reduced sulfur will result in cleaner fire boxes and heat exchangers, said Duane McLevedge, premium fuels manager for Global Companies LLC, Waltham, Mass., ‘but you’re still going to have to treat that fuel in the storage tank with stabilizers, corrosion inhibitors, metal deactivators” and so on.

McLevedge said cold flow is more of an issue with ultra-low sulfur heating oil than with the diesel fuel.

‘With the introduction of the ULSD and the processes at the refineries to produce that product, the drawback is that you’re left with some high-wax ends on the fuel molecules, whereas with the 500 ppm, or the higher sulfur fuels, you don’t have that issue,” he said.

McLevedge said Global made chemical adjustments to its additive to address the cold flow of ultra-low sulfur fuel. The vendor’s Heating Oil Plus is designed to resolve fuel-quality issues and help eliminate callbacks due to clogged filters, screens and nozzles. It is rack-injected at many Global terminals and is also available in five-gallon pails and 55-gallon drums. Global also offers truck-mount and bulk plant injection systems.

Generally, the need to address fuel stability, corrosion and other issues will remain, McLevedge said. Further, there is the coming introduction of biofuels in Massachusetts, he noted. ‘That’s going to be an issue,” he said. ‘We’re going to have to take care of or stabilize that product too.”