Fuel and related compositions – Liquid fuels – Emulsion fuel
Reexamination Certificate
1998-05-20
2001-02-13
Medley, Margaret (Department: 1721)
Fuel and related compositions
Liquid fuels
Emulsion fuel
C044S302000, C044S403000, C044S399000, C044S434000, C044S443000
Reexamination Certificate
active
06187063
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to liquid fuels known variously as bunker fuels and residual fuels, and to substitutes for these fuels that offer the advantages of lower viscosity and cleaner burning.
2. Background of the Invention
Bunker fuels are heavy residual oils used as fuel by ships and industry, and in large-scale heating installations. The fuel oil known as No. 6 fuel oil, which is also known as “Bunker C” fuel oil, is used in oil-fired power plants as the major fuel and is also used as a main propulsion fuel by deep draft vessels in the shipping industry. The fuel oils known as No. 4 and No. 5 fuel oils are used in commercial applications such as schools, apartment buildings, and other large buildings, and for large stationary and marine engines. The heaviest fuel oil is the vacuum residuum from the fractional distillation, commonly referred to as “vacuum resid,” with a boiling point of 565° C. and above. Vacuum resid is primarily used as asphalt and coker feed.
The viscosity of the numbered fuel oils increases with the numerical designation. Fuel oil Nos. 4, 5, and 6 thus have higher viscosities and specific gravities than Nos. 1, 2 and 3, and vacuum resid has the highest. Because of their high viscosity, both vacuum resid and the higher numbered fuel oils generally require heating before they can be pumped. Of the numbered fuel oils, No. 6 fuel oil has the highest specific gravity (typically 0.9861 at 15/15° C.) and the highest viscosity (typically 36,000 cSt at 37.8° C.). Pumping of No. 6 fuel oil requires preheating heating to about 165° F. (74° C.), which adds considerably to the cost of its use and to the capital cost of the installation. Fuel oil Nos. 4 and 5 have a similar problem, although the heating requirement is less. In addition, both the vacuum resid and the numbered fuel oils have high sulfur contents (among the numbered fuel oils, No. 6 fuel oil having the highest sulfur content) and, like many petroleum fuels, their use entails a risk of high NO
x
emissions and high particle emissions.
SUMMARY OF THE INVENTION
It has now been discovered that residuum-based fuel oils such as vacuum resid, visbroken vacuum resid, liquefied coke, and fuel oil Nos. 4, 5, and 6 can be converted into low-viscosity, clean-burning liquid fuels by combining the oil with an aqueous liquid to form a macroemulsion, and incorporating sufficient emulsion stabilizer(s) to stabilize the emulsion. The resulting fuel emulsion is useful as a substitute for the non-emulsified fuel oil. For example, the emulsion prepared from No. 6 fuel oil can be used in any furnace, boiler, engine, combustion turbine or power plant where No. 6 fuel oil has heretofore been known for use. Also, the emulsion prepared from vacuum resid, visbroken vacuum resid, or liquefied coke can be used as a substitute for No. 6 fuel oil or lower-numbered fuel oils. For any of the numbered fuel oils, the viscosity of the resulting emulsion is low enough to permit pumping of the emulsion at ambient temperature, which is particularly valuable for emulsions formed with No. 6 fuel oil. Furthermore, the burning of the emulsion offers significant reductions in NO
x
and particulates relative to the non-emulsified fuel oil. This reduces the need and cost of exhaust gas treatment. There is also a significant reduction in the amount of soot generated, which reduces maintenance and, in boilers, improves heat transfer efficiency. In diesel engines and combustion engines, the emulsion prolongs the useful life of the lubricating oil. In general, the fuel component of the emulsion undergoes a more complete combustion which leads to improvements in fuel efficiency and thermal efficiency. In addition, the ability of the oil to be pumped at ambient temperatures lowers maintenance costs and capital costs since it eliminates the need for heated or lined transport vessels and pipelines. Emulsions prepared from vacuum resid or visbroken vacuum resid offer the further advantage of having the characteristics of the numbered fuel oils without requiring blending of the resid with a cutter stock (i.e., a distillate fraction). This provides a cheaper alternative to the numbered fuel oils.
Further features, options, advantages and embodiments of the invention will be apparent from the description that follows.
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Medley Margaret
Townsend and Townsend / and Crew LLP
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