Fuel

This invention relates to fuel, in particular, liquid fuel such as can be burned in boilers or other heaters, and in combustion engines, such as internal combustion engines.

Conventional liquid fuels petrol (gasoline), diesel, kerosene (paraffin) are all essentially hydrocarbon fuels produced by distillation of crude mineral oil. In recent times, in view of the finite reserves of mineral oils and a desire for carbon-neutral fuels to combat global warming, biodiesel has, to a small extent, supplemented or replaced fossil fuels.

While all fossil fuels contribute to increasing atmospheric carbon dioxide levels, unless carbon dioxide is removed from flue or exhaust gases for sequestration, judicious refining and additives, together with burner and engine management systems, can reduce the emissions of other pollutants, principally NOx and, in the case of diesel engines, carbon particulates.

Cleaner burning biodiesel is disclosed in US2003/0126790 by adding a minor proportion of an alcohol-based fuel such as ethanol. WO95/27021 discloses water and carbonaceous engine fuel emulsions, of which the carbonaceous fuel is gasoline, straight run gasoline, kerosene or diesel, with added alcohol and a non-ionic emulsifier, which reduces atmospheric pollution, but is stable, storable and non-inflammable outside the engine.

GB2285227 notes that the use of water in oil emulsions reduces pollutant emissions, with better carbon burnout and reduced NOx emissions, and gives cleaner combustion of cheaper, heavier fuels, but discloses the use of oil in water dispersions as giving advantages over water in oil emulsions, and teaches forming the dispersion, which is relatively unstable, close to the point of burn.

It is now found, surprisingly, that even heavy fuel oils, and even residues and mineral hydrocarbons previously considered unsuitable as fuel, such, for example, as bitumen from the Orinoco basin or Athabasca tar sands, can be used directly as fuels, without the step of forming an emulsion, by forming a dispersion in the feed to a burner.

Likewise, unrefined biofuels, such as untreated palm oil, can be used, either alone or in a mixture with heavy mineral oils.

The invention, in one aspect, comprises treating a heavy or unrefined oil between a reservoir and a burner to make a dispersion in water, the dispersion comprising a minor proportion by weight of water and the water comprising the continuous phase

The invention, in another aspect, comprises a method for making a liquid fuel from a combustible oil such as a heavy or unrefined oil, comprising feeding the oil from a reservoir to a burner through a mixing device to make a dispersion of the oil in an aqueous host liquid, the dispersion comprising a minor proportion by weight of the host liquid, and the host liquid comprising the continuous phase, and controlling the mixing

device to produce a uniform, predetermined quality of the dispersion. This can, of course, be used for any combustible oil, not just heavy or unrefined oils.

The oil may comprise a heavy unrefined mineral oil or a residue mineral oil after fractions have been refined off, or it may comprise a bitumen or an unprocessed or incompletely processed biofuel such as a vegetable oil.

The oil may comprise a mixture of a mineral oil and a biofuel oil such as bio-diesel. A mineral oil component of such a mixture may comprise less than 75% by weight of the whole, and may preferably comprise between 40% and 75%.

A dispersion stabiliser may be added, and may comprise a surfactant, such as nonyl phenyl ethoxylate, and may be present in an amount between 0.1% and 5% by weight. In amounts, insufficient to form a stable emulsion, the surfactant will act as a lubricity enhancer.

The dispersion may comprise a minor proportion by weight of an organic compound having a detachable OH group. Such compound may comprise an alcohol or an oxydol, which may be a bio-alcohol or bio-oxydol. The host liquid may comprise a water solution of the organic compound, which may preferably be present in an amount between 5% and 25% by weight of the host liquid.

The liquid fuel is prepared close to the point of combustion, the mixing device being in line between the reservoir to a burner such as the combustion chamber of a CI engine. Long term stability of the liquid is thus not a requirement and because no provision need be made for it, other aspects of the fuel need not be compromised.

The quality control measures may comprise a measurement of the electrical conductivity of the dispersion, and may comprise a feedback arrangement, which may act on the mixing device or the supply of one or other fluid to it to maintain the electrical conductivity constant or within an acceptable range.

The invention also comprises apparatus for making a liquid fuel from a combustible oil such as a heavy or unrefined oil, comprising: a supply for an aqueous host liquid; a mixing device adapted to be continuously fed with the oil and the host liquid in predetermined proportion and to form a dispersion of the oil in the host liquid, so that the dispersion comprises a minor proportion by weight of the host liquid, and the host liquid comprises the continuous phase; and a quality control arrangement checking the quality of the dispersion; the mixing device being adapted for installation in a fuel supply line to a burner in which the fuel is burned.

The burner may be a combustion chamber of an IC engine such as a CI engine or a liquid fuel fired gas turbine engine, e.g. for power generation or for marine propulsion. The burner may also be a burner for a furnace or boiler.

The apparatus may comprise a mixing arrangement for a surfactant and the host liquid, and may comprise a mixing arrangement for making an aqueous phase host liquid from an organic compound and water.

The quality control arrangement may comprise an electrical conductivity meter. The quality control arrangement may comprise a feedback arrangement that may act on the mixing device or the supply of one or other fluid to it to maintain the electrical conductivity constant or within an predetermined range.

The apparatus may be supplied as a kit for converting a burner from burning fuel oil alone to burning a liquid fuel comprising a heavy or unrefined oil as a dispersion in an aqueous host liquid. The liquid fuel of the invention has considerable advantages over fuel oil alone. Nitrogen oxide production can be reduced by around 50%, and almost complete carbon burn out ensures low particulate emissions. In large common rail diesel engines, there can be a significant reduction in fuel supply line pressures. Methods and apparatus for making liquid fuels according to the invention will now be described with reference to the accompanying drawing, in which the single Figure is a diagrammatic illustration of apparatus for making a liquid fuel according to the invention;

The drawing illustrates apparatus 11 for making a liquid fuel from a combustible oil such as a heavy or unrefined oil, comprising: a supply 14 for an aqueous host liquid 15; a mixing device 16 adapted to be fed with the oil 13 from a reservoir and the host liquid 15 in predetermined proportion and to form a dispersion of the oil in the host liquid, so that the dispersion comprises a minor proportion by weight of the host liquid, and the host liquid comprises the continuous phase; and a quality control arrangement 24 checking the quality of the dispersion; the mixing device 16 being adapted for installation in a fuel supply line to a burner 17 in which the fuel is burned.

The burner 17 may be a combustion chamber of an IC engine such as a CI engine or liquid-fuelled gas turbine engine, or a burner for a furnace or boiler.

The apparatus 11 comprises a mixing arrangement 18 for a surfactant 19 and the host liquid 15, and comprises a mixing arrangement 21 for making an aqueous phase host liquid 15 from the organic compound 22 and water 23. The apparatus comprises a quality control arrangement 24 checking the quality of a mixture of the combustible oil 13 and the host liquid 14. The quality control arrangement 24 comprises a electrical conductivity meter 25.

Electrical conductivity of fuel oils is measured in pico Siemens/metre (pS/m) and usually amounts to some hundreds of pS/m, depending on the oil and additives used and conductivity meters able to measure such quantities are commercially available. It may also be desirable to control the conductivity as an end in itself, where static electricity hazards need to be countered. The quality control arrangement 24 comprises a feedback arrangement, signals from the conductivity meter 25 being fed to a controller 26 that controls the flow of host liquid 14 and the mixing arrangement 18 so as to keep the conductivity constant or within predetermined limits. The apparatus may be supplied as a kit, as indicated by the broken line box in Figure 1, for converting a burner 17 from burning fuel oil alone to burning a liquid fuel comprising a combustible oil as a dispersion in a host liquid comprising an organic compound having a detachable OH group. The burner itself may require some adaptation, especially if it is a combustion chamber of an IC engine, in terms, at least, of air/fuel ratio.

The burner may be arranged to operate on fuel oil alone or on a mixture according to the invention, being interconnected to the mixing device 16 so that when the latter is operating to generate a liquid fuel according to the invention the burner 17 is arranged to operate efficiently on such fuel, but if the host liquid is not being used, the burner 17 is automatically adjusted to operate on fuel oil alone. When burning the oil alone, of course, the advantages of the invention will not be obtained, but it may be desirable to provide the facility for doing so in case a suitable aqueous host is not available.

The term 'dispersion' as used herein refers to an unstable suspension of droplets. The droplets are droplets of fuel oil in the host liquid. The host liquid itself will usually comprise an aqueous carrier which may have a dissolved alcohol or oxydol, which have detachable OH groups that assist combustion of the fuel. By 'unstable' is meant that, after a relatively short time, the dispersion would begin to separate out into its constituent parts.

Usually, where water is used in fuel, the water is suspended as droplets in the fuel. The effect of the water in that instance is to vaporise rapidly when the fuel is ignited and increase the expanded volume, or pressure, when confined, as well as to act as a coolant. The water is suspended as an emulsion, which is stable, stability being imparted or enhanced by the presence of a surfactant. A fuel tank can thus be filled with such an emulsion, and the fuel can be designed to remain stable during normal usage. By

contrast, the liquid fuel of the present invention need only be made just shortly before it is burned, and, indeed, is usually made just while the combustible oil is en route to the burner. The combustible oil 13 may comprise a mineral oil and/or a bio-fuel such as bio-diesel. The invention is of particular use in connection with bio-diesel, which can be made in a variety of ways, some of which result in a product that is more or less equivalent to diesel fuel cracked from mineral oil, but some of which produce something more akin to a vegetable oil, and, indeed, CI engines can run on vegetable oil such as palm or soya oil without any processing.

The organic compound that has the detachable OH group can be, for example, an alcohol or an oxydol, which may be a bio-alcohol or bio-oxydol. A bio-alcohol may comprise ethanol derived for example from fermentation of corn. Ethanol, of course, can be used as a fuel in its own right, but it has combustion characteristics that are different from those of diesel and other mineral-based oil fuels. It use in the present invention is not as a Rxύper se, but as a fuel extended or enhancer, aiding combustion and reducing harmful emissions. A mineral oil or bio-fuel component of a fuel blend according to one embodiment of the invention comprises less than 75% by weight of the whole, and may comprise between 40% and 75%.

The surfactant 19, in one embodiment of the invention, comprises nonyl phenyl ethoxylate, which is present in an amount between 0.1% and 1.0% by weight. It acts as a dispersal stabiliser, ensuring that the dispersion does not break down in the time between making and burning the liquid fuel. Such a small amount of surfactant is much less than would be required to stabilise an emulsion. The organic compound having a detachable OH group need not be highly purified, and indeed a mixture of such compounds can be used. Some impurities can be tolerated, including varying amounts of water. The cost can be substantially less than the cost of gasoline extenders, where high purity and dryness are required. The dispersions typically produced by the method and apparatus as described are characterised by a very small and uniform droplet size, smaller than is customarily obtained from conventional atomisers. This leads to substantially complete combustion and conversion into carbon dioxide and water with substantially no carbon particulates in the emission, and also suppresses the generation of nitrogen oxides. The improvement in emissions quality is often so marked that cruise ships powered by large marine diesel engines can operate on low-grade heavy or unrefined fuels oils yet be so 'clean' as to be permitted to access ports usually denied them.