New York City schools are running a pilot project in which decades-old burners are being fueled with ultra-low sulfur (ULS) Number 2 fuel oil, said John Batey, technical director for the Oilheat Manufacturers Association (OMA).
Batey last year completed a study of fuel switching for the New York City School Construction Authority (SCA), which is responsible for maintenance of the city’s public schools. The goal of the study was to evaluate options for converting the schools from Number 6 residual fuel oil to Number 2 distillate oil or natural gas.
In a report to OMA, Batey listed his key findings:
· Switching from Number 6 to Number 2 oil is technically and economically feasible
· Efficiency advantages include lower smoke and higher combustion efficiency
· Reduced air emissions including particulate matter (PM) and sulfur oxide with ULS comparable to natural gas
· Number 2 ULS has environmental impact that is equal to or better than natural gas without the high cost of conversion
Batey concluded in his report that ULS heating oil ‘is a better option than natural gas,” a finding that he said ‘was unexpected by SCA.”
When asked whether his finding was surprising to others, Batey responded, ‘Not to me.” He continued, ‘When you go to ULS, you drop from 2,000 or 1,500 parts per million of sulfur down to 15 parts per million ‘ approaching zero.” A sulfur level of 15 ppm is ‘very close to the amount of sulfur that is in natural gas as an odorant,” Batey said. Sulfur-containing odorant is added to odorless natural gas as a safety measure, so that it can be detected in the event of a leak, Batey noted.
‘ULS and natural gas are virtually the same” in terms of particulate matter and sulfur oxide emissions, Batey said.
Work at Brookhaven National Laboratory, Upton, N.Y., has shown that particulate matter is related to sulfur content, Batey said. ‘When you take the sulfur content out, the particulate level also drops proportionately,” which means the PM level in ULS fuel oil approaches zero, making it ‘extremely clean,” Batey said.
Batey also mentioned that a study by the New York State Energy & Research Development Authority (NYSERDA), Albany, N.Y., ongoing for a number of years, is finding that heat exchangers are clean after a year of operation with ULS. ‘You still have to be sure to adjust the burner properly,” he warned.
In the pilot program of the New York City schools, Batey said, ‘They’re using existing rotary cup burners. Instead of tearing them out and putting in other equipment, they can just change the fuel grade because those burners are rated ‘all-grade’ for fuel.” The burners are running on Number 2 heating oil ‘with minor modifications ‘ replacing pulleys and belts,” Batey said.
Rotary cup burners feature a brass cup, into which the heating oil drips. The cup spins at approximately 5,400 rpms, atomizing the oil, Batey said. ‘It’s really trouble-free,” he said of the burners’ design. Such units have been operating in New York City schools for decades, he said.
Keeping the existing equipment and fueling it with ULS Number 2 would be ‘a lot more cost effective than switching to natural gas,” Batey said. ‘Just the pipe to bring [natural gas] into a building, and the hookup, costs on the order of half a million dollars per building,” he said.
Preferred Utilities, Danbury, Conn., is a manufacturer of rotary cup burners, Batey said.
A challenge for New York City will be dealing with the existing storage tanks stocked with Number 6 oil. Clean Fuels Associates hopes to offer a solution if the city decides to go ahead with a conversion to Number 2 ULS fuel oil. ‘We’re trying to become part of the project,” said Ron Philbrick, senior sales and marketing director of Clean Fuels Associates.
‘Number six oil is very, very heavy,” Philbrick said. ‘It’s thicker and gooier than molasses, and at room temperature it does not move. It has to be heated to 124 degrees just so it can be liquefied and moved.”
Clean Fuels is able to switch over existing tanks from Number 6 to Number 2 without manned entry, Philbrick said.
In the manned entry method, fuel is pumped out and a person enters the tank and squeegees out the sludge on the bottom and on the side walls. Then the tank is flushed out with either high pressure water, diesel fuel, or a chemical that breaks down oil. Once the tank is clean, it is pressure tested and refilled.
The Number 6 fuel oil is stored, in some cases, under the school buildings in New York City, more or less prohibiting manned entry, Philbrick said. Another factor working against manned entry is that it is very expensive, Philbrick said, because of Occupational Safety and Health Administration (OSHA) regulations and Environmental Protection Agency (EPA) requirements that apply and because of the need for vacuum truck services.
One way of cleaning Number 6 fuel oil from storage containers has been described by Daniel Karpen, a professional engineer and consultant based in Huntington, N.Y. It calls for burning the Number 6 fuel oil in a tank until it is almost empty, pumping out the remainder, and reselling it. Then clean the tank, and fill it up with Number 2 fuel oil. Then disconnect the heater for the Number 6 fuel oil, set up the fuel pump to run only when the burner is running, and change the burner nozzle and replace the fuel filter.
Another approach is a ‘filter flush,” Philbrick said. The Number 6 fuel oil is pumped out as much as possible, and then a solvent like Number 2 is added. Number 2 fuel oil is an effective solvent for Number 6 fuel oil, Philbrick said. The tank is continually flushed and filtered with Number 2, breaking down the Number 6. The tank is then pumped out and refilled, Philbrick said.
Clean Fuels’ customers include St. Paul’s School, a prep school in Concord, N.H., Philbrick said. ‘They have 7,000 gallons of Number six oil,” he said of the school. ‘We’re going to sell that for them,” Philbrick said. Proceeds from the sale will go to purchase Number 2 fuel oil for the school and to pay for Clean Fuels’ service, Philbrick said.