Patent Publication Number: US-2013227877-A1

Title: Three-phase emulsified fuel and methods of preparation and use

Description:
BACKGROUND 
     It is known that the combustion of liquid hydrocarbons, for example for feeding internal combustion engines or for producing heat, leads to the formation of numerous pollutants, in particular soot, particulates, carbon monoxide (CO), nitrogen oxides (NOx), sulphur oxides (SOx), and noncombusted hydrocarbons, which contribute significantly towards atmospheric pollution. 
     It is also known that the addition of controlled amounts of water to fuels including to viscous fuels like heavy petroleum, vacuum residuum and high numbered fuel oils can significantly reduce the production of pollutants. It is believed that this effect is the result of various phenomena arising from the presence of water in the combustion zone. For example, the lowering of the peak combustion temperature by water reduces the emission of nitrogen oxides (NOx), the formation of which is promoted by high temperatures. In addition, the instantaneous vaporization of the water promotes better dispersion of the fuel in the combustion chamber, thereby significantly reducing the formation of soot, particulates and CO. These phenomena take place without adversely affecting the yield for the combustion process. 
     Several proposals have therefore been made to add water to liquid fuel before or at the time of use, which is before the fuel is injected into the combustion chamber, or directly into the chamber itself. 
     SUMMARY 
     In accordance with one or more aspects, a micro-emulsion may comprise about 70 to 85% by volume of a hydrocarbon fuel, about 5 to 10% by volume of air, and about 10 to 25% by volume of an aqueous solution. The aqueous solution may comprise a first emulsifying agent in an amount effective to separate and disperse the hydrocarbon fuel, and a second emulsifying agent in an amount effective to stabilize the micro-emulsion. The aqueous solution may form a continuous phase, the air may form a first dispersed phase and the hydrocarbon fuel may form a second dispersed phase. 
     In some aspects, the hydrocarbon fuel may be selected from the group consisting of heavy petroleum and fuel oil Nos. 4, 5, and 6. In at least one aspect, the micro-emulsion may comprise about 85% by volume of the hydrocarbon fuel. In other aspects, the micro-emulsion may comprise about 80% by volume of the hydrocarbon fuel. In some nonlimiting aspects, the micro-emulsion may comprise a plurality of droplets each having a size in the range of about 10 to about 100 microns. In some aspects, at least one of the first and second emulsifying agents includes anionic agents, while in other aspects, at least one of the first and second emulsifying agents includes nonionic agents. 
     In some aspects, at least one of the first and second emulsifying agents includes one or more of a detergent, a wetting agent, a dispersing agent, a surfactant, an agent improving lubricity, a mixing aid, and a heat stabilization aid. In other aspects, at least one of the first and second emulsifying agents is present in an amount sufficient to stabilize the micro-emulsion for up to six months at room temperature. In still other aspects, the first emulsifying agent may include one or more of monoethanolamine, triethanol ammonium laurylsulphate, ethoxylate propoxylated fatty acid alcohol, coconut fatty betaine, and coconut alkylolamide. In yet other aspects, the second emulsifying agent includes one or more of D-limonene, 4-nonylphenol ethoxylate, triethanol amine, sulfonic acid, and ethylene glycol. In some aspects, at least some of the first dispersed phase substantially encapsulates at least some of the second dispersed phase. In at least certain aspects, the micro-emulsion may have a viscosity at room temperature of between about 80 and about 200 cSt. In other aspects, the micro-emulsion may have a viscosity at 80° C. of less than about 40 cSt. 
     In accordance with one or more aspects, a method of preparing a three-phase micro-emulsion may comprise combining a hydrocarbon fuel and an aqueous solution, agitating the combined hydrocarbon fuel and aqueous solution in the presence of a first emulsifying agent while introducing air at a first flow rate to form an intermediate mixture, and agitating the intermediate mixture in the presence of a second emulsifying agent while introducing air at a second flow rate to form the three-phase micro-emulsion in which the hydrocarbon fuel and air form dispersed phases and the aqueous solution forms a continuous phase. 
     In some aspects, the method may further comprise terminating agitation upon achieving a predetermined viscosity value for the micro-emulsion. In at least one aspect, the method may further comprise adding at least one of the first and second emulsifying agents in an amount of about 0.4 to about 0.8% by volume of the hydrocarbon fuel. In some nonlimiting aspects, at least one of the first and second emulsifying agents comprises one or more of D-limonene, 4-nonylphenol ethoxylate, triethanol amine, sulfonic acid, and ethylene glycol. In other nonlimiting aspects, at least one of the first and second emulsifying agents comprises one or more of monoethanolamine, triethanol ammonium laurylsulphate, ethoxylate propoxylated fatty acid alcohol, coconut fatty betaine, and coconut alkylolamide. 
     In some aspects, the method may further comprise proportioning the hydrocarbon fuel and the aqueous solution in a ratio between about 70%-30% and about 85%-15%. In other aspects, the method may further comprise proportioning the hydrocarbon fuel and the aqueous solution in a ratio of about 80%-20%. In at least some nonlimiting aspects, agitating comprises pneumatically agitating for between about 1 and 2 hours. In some aspects, the predetermined viscosity value comprises about 80 to 200 cSt at room temperature. In other aspects, the predetermined viscosity value comprises less than about 40 cSt at 80° C. In at least certain aspects, the method may further comprise pumping the micro-emulsion. 
     Aspects of embodiments of the present invention may relate to air-water-hydrocarbon three-phase emulsified fuel. Some aspects relate to air-water-hydrocarbon three-phase emulsified fuel prepared by adding water, air, and emulsifier compositions to liquid hydrocarbon fuels, and to methods of preparation and uses of the emulsions. 
     One aspect of an embodiment relates to an air-water-hydrocarbon three-phase emulsified fuel prepared by adding water, air, and emulsifier compositions to liquid hydrocarbon fuels, to the methods of preparation, and to the uses of the said emulsions. More specifically aspects of embodiments relate to a three-phase emulsion fuel prepared by emulsifying heavy hydrocarbons such as bunker fuel oil (numbers 4, 5 and 6) and heavy petroleum, with water or an aqueous solution, air, and emulsifier compositions to be used as an alternative energy fuel that offers the advantages of lower viscosity, higher performance and cleaner burning. By heavy hydrocarbons, it is understood to include all hydrocarbons with an API less than 16.0. Aspects of embodiments relate also to the methods of preparation of the above said fuel and its use in internal combustion engines, boilers, heaters, furnaces, combustion turbines or power plants. 
     An exemplary fuel is produced in a process plant or directly on a user&#39;s premises. It is a three-phase micro-emulsion, which is composed of hydrocarbon-air-water, which is stable and homogenous. Compared to the use of crude oil, refinery residues or fuel oil, emulsion fuels according to aspects of embodiments exhibit lower viscosity, greater efficiency, and fewer emissions. 
     According to some embodiments, a liquid fuel comprises: a three-phase micro-emulsion including in ratios relative to the whole: about 70 to 85% by volume of a hydrocarbon fuel; about 5 to 10% by volume of air; and about 10 to 25% by volume of an aqueous solution; in which the aqueous solution forms a continuous phase, the air forms a first dispersed phase and the hydrocarbon fuel forms a second dispersed phase. The hydrocarbon fuel can, in some variations, be selected from the group consisting of heavy petroleum and fuel oil Nos. 4, 5, and 6. In a more particular variation, the liquid fuel may be about 85% by volume of the hydrocarbon fuel. In another more particular variation, the liquid fuel may be about 80% by volume of the hydrocarbon fuel. In some variations, the aqueous solution comprises water and an emulsifier. In further variations, the emulsifier includes anionic agents or the emulsifier includes nonionic agents. In yet other variations, the emulsifier includes one or more of a detergent, a wetting agent, a dispersing agent, a surfactant, an agent improving lubricity, a mixing aid, and a heat stabilization aid. In even other variations, the emulsifier includes a first emulsifying additive in an amount effective in stabilizing said emulsion for up to six months at room temperature. In yet further variations, the first emulsifying additive includes one or more of monoethanolamine, triethanol ammonium laurylsulphate, ethoxylate propoxylated fatty acid alcohol, coconut fatty betaine, and coconut alkylolamide; and there may be a second emulsifying additive including one or more of D-limonene, 4-nonylphenol ethoxylate, triethanol amine, sulfonic acid, and ethylene glycol. 
     In accordance with one or more embodiments, the micro-emulsion of some embodiments has droplets of the first dispersed phase and the second dispersed phase that are small enough to give the emulsion an appearance of a homogeneous, single, liquid phase. The micro-emulsion of some nonlimiting embodiments has a viscosity at room temperature or ambient temperature (about 15° C. to about 27° C.) of substantially between 80-250 cSt (centistokes), for example, between 150-250 cSt. Some nonlimiting embodiments may further have a viscosity at 80° C., of lower than 40 cSt. Still other nonlimiting micro-emulsion embodiments have a viscosity at 50° C. of substantially between 40-80 cSt. 
     According to other embodiments, a method for the preparation of a liquid fuel comprises: combining a hydrocarbon fuel and an aqueous solution; and agitating said combined hydrocarbon fuel and aqueous solution in the presence of an emulsion stabilizing additive to form a three-phase micro-emulsion in which the hydrocarbon fuel and air form dispersed phases and the aqueous solution forms a continuous phase. The method may further comprise: terminating the agitating upon the liquid fuel having reached a predetermined low viscosity value to give the emulsion the appearance of a homogenous single liquid phase. The method may yet further comprise: adding the emulsion stabilizing additive in an amount of 0.4 to 0.6% by volume of the liquid fuel. The emulsion stabilizing additive of some methods may be a combination of D-limonene, 4-nonylphenol ethoxylate, triethanol amine, sulfonic acid, and ethylene glycol. The method may even yet further comprise: adding to the aqueous solution a quantity between 0.6 to 0.8% by volume of the liquid fuel of a combination of one or more of monoethanolamine, triethanol ammonium laurylsulphate, ethoxylate propoxylated fatty acid alcohol, coconut fatty betaine, and coconut alkylolamide. According to some variations, combining may further comprise: proportioning the hydrocarbon fuel and the aqueous solution in a ratio between 70%-30% and 85%-15%. According to other variations, combining further comprises: proportioning the hydrocarbon fuel and the aqueous solution in a ratio of about 80%-20%. According to some other variations, agitating further comprises: pneumatically agitating for between 1 and 2 hours. According to yet some other variations, the method further comprises: terminating agitating when the liquid fuel has a desired viscosity. According to some nonlimiting variations of the method, the desired viscosity is between 80-200 cSt (centistokes) at room temperature or ambient temperature (about 15° C. to about 27° C.), while according to others, the desired viscosity is between 40-80 cSt at 50° C., while according to still others, the desired viscosity is lower than 40 cSt at 80° C. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more fully understood from the following description, when read in conjunction with the accompanying drawings: 
         FIG. 1  represents the resulting emulsified fuel with a higher combustion efficiency after the viscosity of the heavy hydrocarbon has been lowered. 
         FIG. 2  shows the water in the emulsified fuel vaporizing, expanding, and entering the droplet of hydrocarbon and air once the temperature has been raised. 
         FIG. 3  shows the water inside the droplet bursting through the hydrocarbon droplet&#39;s skin, disintegrating the droplet. 
         FIG. 4  represents the increase in the fuel-effective contact area with oxygen. 
         FIG. 5  shows the increases in the combustion efficiency. 
         FIG. 6  shows a schematic of an emulsification process in accordance with one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     A three-phase micro-emulsion fuel according to aspects of embodiments has utility in connection to easier handling and transportation, and a cleaner and more efficient combustion of viscous fuels like heavy petroleum and fuel oils Nos. 4, 5, and 6. Such a fuel is useful since it has a significantly lower pour point and viscosity compared to the original fuel, reducing the need for heating before the fuel is pumped. Such a fuel solves long-standing problems of the formulation of fuel emulsions between liquid hydrocarbons and water in the presence of emulsifiers (surfactants) for the purpose of uniformly dispersing the water in the hydrocarbon phase and to stabilize the emulsion. 
     Aspects of embodiments include the production of an emulsified fuel by mixing of liquid hydrocarbons with active ingredients to develop a three-phase emulsified fuel comprising liquid hydrocarbons, air and water, the hydrocarbon and the air forming a dispersed phase and the aqueous solution forming a continuous phase. 
     In certain embodiments, the method for producing a micro-emulsion may be used to lower the viscosity of a product or component stream in a particular process. In certain exemplary and nonlimiting embodiments, the micro-emulsion compositions and methods disclosed herein may be used to facilitate pumping of a process stream from a first location to a second location by lowering the viscosity of the process stream. In some embodiments, the method for producing a micro-emulsion is a stand-alone process, and in others the method is capable of being inserted into a multi-step process. Exemplary methods and compositions may include, but are not limited to, the production or consumption of fuel, facilitating pumping in pipelines, remediation or cleaning efforts, or treatment of either incoming or waste streams from industry, such as in oil or gas production. In certain other embodiments, the micro-emulsion compositions and methods disclosed here may be used for cleaning purposes, for example in incremental cleaning of a furnace or engine. 
     In accordance with one or more embodiments, an air-water-hydrocarbon three-phase micro-emulsified fuel may be prepared by adding water, air, and one or more emulsifying agents to liquid hydrocarbon fuels. The three-phase micro-emulsion fuel may be prepared by emulsifying heavy hydrocarbons such as bunker fuel oil and heavy petroleum from the fraction distillation of petroleum, with water or an aqueous solution, air, and emulsifier composition. The hydrocarbon fuel and the air may form dispersed phases and the aqueous solution may form a continuous phase. 
     The exemplary three-phase emulsified fuel now described is easy to handle and is also easy to transport. Additionally, it yields a cleaner and more efficient combustion of viscous fuels like heavy petroleum, vacuum residuum, petroleum distillate fractions, such as oil Nos. 4, 5, and 6. The resulting emulsified fuel may be used as an alternative energy fuel in internal combustion engines, boilers, heaters, furnaces, combustion turbines or power plants offering the advantages of lower viscosity, higher performance and cleaner burning than the original fuel. 
     In certain exemplary and non-limiting embodiments, the micro-emulsion compositions and methods disclosed here may be used to pump a hydrocarbon fuel from one location to another with little or no requirement for additional heating of the fuel. For example, in a pipeline transport or industrial process setting, the target fuel can be used in any one of the exemplary methods described here to produce a three-phase micro-emulsion possessing a lower viscosity than the original hydrocarbon fuel. The micro-emulsion is not only lower in viscosity, but is also capable of remaining stable, making it easier to pump than the original fuel. The micro-emulsion can subsequently be pumped from one location to another, and unlike traditional methods for lowering the viscosity of hydrocarbon fuels, the methods disclosed here require little or no additional heating of either the fuel or the micro-emulsion. In certain embodiments, the micro-emulsion is pumped from one location to another for the purpose of being used as a component stream in a larger process. In other embodiments, the micro-emulsion is pumped from one location to another for the purpose of being used as an end-product, for example, as fuel for a furnace, boiler, or engine. 
     In certain exemplary and non-limiting embodiments, the methods and compositions disclosed here require a lower preheating temperature than a crude oil when pumped from one location to another. For example, in certain embodiments crude oil requires preheating to a temperature of 90° C. in order to lower the viscosity to a point where it can properly be fed into a boiler. In the same setting, the micro-emulsion needs to be preheated to a temperature of 50° C. to obtain the same result. 
     In certain exemplary embodiments, the required pressure for moving fuel through a feed line or pipeline is reduced when using the methods and compositions disclosed here. For example, in certain embodiments, a crude oil requires a pressure of 50 psi when moved through a feed line at a desired rate. This value drops to a value of 30 psi when a micro-emulsion of the fuel is used. 
     In certain exemplary and non-limiting embodiments, the methods disclosed here may be used to lower the viscosity of a target hydrocarbon fuel. For example, in certain embodiments, a crude oil with a viscosity at room temperature of 33,000 cSt can be reduced to 250 cSt. In certain other embodiments, a crude oil with a viscosity of 3090 cSt at 50° C. can be reduced to 56 cSt. 
     In certain exemplary and non-limiting embodiments, the micro-emulsion composition disclosed here may be used as a fuel. For example, the micro-emulsion can be used in place of heavy or residual hydrocarbons, including, but not limited to, crude oils with an API of less than 12°, or oil refining residues. In certain embodiments, the micro-emulsion fuel can be used in place of distilled hydrocarbons, for example, Diesel No. 2. In certain embodiments, the micro-emulsion fuel can be used in any number of applications or equipment, including, but not limited to, use in electrical generation, maritime engines, industrial boilers, construction equipment, trains, public transportation fleets, or trash collection fleets. When used as fuel, the micro-emulsion yields several beneficial results, including cost reductions from the corresponding decrease in fuel consumption and improved combustion efficiencies. In addition, use of the micro-emulsion as a fuel leads to reductions in harmful emissions to the environment. In certain exemplary applications, replacing the use of fuel oil Nos. 4 and 6 in a power generation setting with a micro-emulsion fuel could yield a 30-40% reduction in total costs. Consumers end up benefiting from these cost reductions by experiencing an estimated 3-5% decrease in fuel consumption. In certain applications, use of the micro-emulsion fuel can reduce both NOx and particulate emissions by up to 80%. 
     Exemplary methods and compositions disclosed here may include, but are not limited to, remediation or cleaning efforts, for example in incremental cleaning of a furnace or engine, or for use in treatment of either incoming or outgoing process streams in industrial settings, such as in oil or gas production. 
     Various desired base hydrocarbons may be used to prepare the disclosed micro-emulsions. In accordance with one or more nonlimiting embodiments, a base hydrocarbon such as heavy petroleum, or bunker fuel oil Nos. 4, 5, and 6 can be converted into low-viscosity, clean-burning liquid fuels by combining the oil with an aqueous solution and air to form a micro-emulsion, and incorporating effective quantities of emulsifier compositions to stabilize the emulsion. In certain other exemplary and non-limiting embodiments, the base hydrocarbon may include, but is not limited to, petroleum refining process wastes, crude or refined bitumen, diesel, kerosene, lubricating oils, paraffin waxes, tar, or any combination thereof. Additional and alternative suitable base hydrocarbons will be recognized by those skilled in the art given the benefit of this disclosure. The resulting three-phase fuel micro-emulsion is useful as a substitute for the non-emulsified fuels. For example, the micro-emulsion prepared from fuel oil No. 6 can be used in any furnace, boiler, engine, combustion turbine or power plant where fuel oil No. 6 or lower-numbered fuel oils have heretofore been known for use. Also, the micro-emulsion prepared from heavy crude oil can be used as a substitute for fuel oil No. 6 or lower-numbered fuel oils. For any of the above-numbered fuel oils, the viscosity of the resulting micro-emulsion is low enough to permit pumping of the emulsion at lower temperatures or even at ambient temperature, which is particularly valuable for micro-emulsions formed with heavy petroleum or bunker fuel oils No. 4, 5 and 6. Furthermore, the burning of the three-phase air-water-hydrocarbon micro-emulsion offers significant reductions in nitrogen oxides (NOx) and particulate emissions relative to the non-emulsified fuel oil. This reduces the need for 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 general, the fuel component of the micro-emulsion undergoes a more complete combustion, which leads to improvements in fuel efficiency and thermal efficiency. In addition, the ability of the micro-emulsion to be pumped at lower or ambient temperatures lowers maintenance costs and capital costs since it eliminates the need for heated or lined transport vessels and pipelines. Micro-emulsions prepared from heavy crude oil offer the further advantage of having the characteristics of the above-numbered fuel oils without requiring blending with a cutter stock or a distillated fraction. This provides a less expensive alternative to the above-numbered fuel oils. 
     In accordance with one or more embodiments, a micro-emulsion may generally include a continuous phase and at least one dispersed phase. In some embodiments, the micro-emulsion may include first and second dispersed phases. In some nonlimiting embodiments, air may be present in a first dispersed phase and a hydrocarbon fuel may be present in a second dispersed phase. The at least one dispersed phase may be dispersed in the continuous phase of the micro-emulsion. At least some of the first dispersed phase may at least partially encapsulate the second dispersed phase. In some embodiments, the first dispersed phase may substantially or entirely encapsulate the second dispersed phase. Encapsulation may result in a plurality of droplets present in the continuous phase. In some embodiments, this may be described as a continuous phase and a dispersed phase, where the dispersed phase comprises hydrocarbon fuel encapsulated in air. The size of the droplets may vary. 
     In accordance with one or more embodiments, the micro-emulsion may contain a plurality of droplets of the dispersed phase that are small enough to give the emulsion the appearance of a homogeneous single liquid phase. The micro-emulsion is one in which the continuous phase is the aqueous solution and the dispersed phase is the fuel oil either partially or completely encapsulated by air. The droplet size (of the dispersed phase) can be controlled to some extent by using a conventional pneumatic mixer (Ingersoll Rand Compressor, Dublin, Ireland or similar) and/or a high-shear in-line mixer with work heads (Silverson 450 LS, Ohio, USA or similar). The size of the droplet is also dependent on the density of the hydrocarbon fuel used. In general, the lighter the hydrocarbon (possessing a higher API), the smaller the droplet. Additionally, the asphaltene or paraffinic content of the hydrocarbon may affect droplet size. The droplet size can be reduced by decreasing the size of the hole in the work heads through which the micro-emulsion is forced. The droplet size can also be controlled by the selection and amount of additives. In certain nonlimiting and exemplary embodiments, the droplet size may vary from about 1 to about 200 microns. In other embodiments, the droplet size may range from about 10 to about 100 microns, depending on the desired application and the equipment used. In some nonlimiting embodiments, the droplet size may be between about 40 and 80 microns. 
     The relative amounts of dispersed and continuous phases can vary while still falling within the scope of the invention. The dispersed phase will generally constitute from about 70 to 80% by volume of the micro-emulsion and the continuous phase from about 10 to 25% by volume of the micro-emulsion. The percentage of the continuous phase may be directly dependent on the API and viscosity of the heavy petroleum or fuel oil used. The lower the API, the greater the percentage of the aqueous continuous phase. 
     As used here, the word “about” is used to account for variance in measurement due to inherent errors associated with measurement techniques. The word “about”, even if not explicitly used, is understood to modify all measurements disclosed, unless otherwise stated. 
     The continuous phase of the micro-emulsion may contain water as its major component. The continuous phase may also include one or more emulsifying additives or emulsifying agents. The micro-emulsions contain additives, some or all of which are miscible with or soluble in water, resulting in an aqueous solution of these additives. 
     The emulsifying additives can be a mixture of at least one or more of emulsifying agents, detergents, wetting agents, dispersing agents, surfactants, and other components that serve a variety of functions, including, but not limited to: increasing lubricity, serving as a mixing aid, and functioning as a heat stabilizer. The choice can include anionic and nonionic agents. 
     According to aspects of an exemplary embodiment, the formation of the emulsion may be performed in two steps: first adding to an oil and water mixture a first emulsifying additive that separates and disperses the hydrocarbon clusters, and second adding to the mixture a second emulsifying additive that forms and stabilizes the final three-phase micro-emulsion. Hydrocarbon molecules have the tendency to group together and form long molecular clusters or chains. The presence of these clusters or chains does not allow for oxygen molecules to come in contact with fuel molecules. Because of this, the hydrocarbon molecules, which make up the fuel, do not burn completely. The residue or byproduct composed of partially oxidized molecules is exhausted to the environment as gaseous emissions that add to pollution. Aspects of exemplary embodiments disclosed here reduce such pollution by reducing the undesired clustering. 
     In certain exemplary and non-limiting embodiments, the three-phase micro-emulsion may be prepared by mixing a volume of viscous fuels, such as heavy petroleum and petroleum distillate fractions (fuel oil Nos. 4, 5, and 6), with at least one emulsifying additive and water, each constituting between 10 and 25% by volume of the total volume followed by pneumatic agitation. Thus, a three-phase micro-emulsion is obtained, leaving the hydrocarbon and air components as the dispersed phase. The three-phase micro-emulsion alters the physical characteristics of the original hydrocarbon component used by significantly diminishing its viscosity, given the presence of water, emulsifying agents, and air that produce a reduction of viscosity and interlaminar friction. 
     In certain exemplary and non-limiting embodiments, the emulsifying additives may be mixed with water in separate preparation tanks before they are pumped into a larger batch tank. In certain embodiments, the mixing in the preparation tanks is performed by pneumatic agitation. In certain embodiments, the emulsifying additives are pumped into the larger batch tank at ambient temperature. 
     In certain exemplary and non-limiting embodiments, mixing between the hydrocarbon fuel and the aqueous solution is performed by pneumatic agitation. Pneumatic agitation may be achieved, for example, by introducing air at a rate capable of producing an emulsion with targeted physical or chemical characteristics. In some embodiments, air is introduced at a rate between 500-6000 cubic feet per minute. In other embodiments, air is introduced at a rate of between 600-1000 cubic feet per minute at a pressure between 100-150 psi. In other embodiments, air is introduced at a rate of between 2000-4000 cubic feet per minute at a pressure between 30-40 psi. In certain exemplary embodiments, the rate of air that is introduced may vary throughout the mixing process, or the air may be introduced at one rate at one stage of mixing, and at another rate during a different stage of mixing. For example, according to one aspect, the air may be introduced at a rate of between 3000-4000 cubic meters per hour when a first emulsifying agent is added to the hydrocarbon fuel mixture. According to another aspect, the air may be introduced at a rate of between 4000-5000 cubic meters per hour when a second emulsifying agent is added to the hydrocarbon fuel mixture. According to a further aspect, the air may be introduced at a rate that varies throughout the mixing cycle. 
     In accordance with one or more embodiments, a double emulsion process may result in a three-phase product. A first emulsion step may occur under a first set of conditions, such as at a first air flow rate and in the presence of a first emulsifying agent. A second emulsion step may occur under a second set of conditions, such as at a second air flow rate and in the presence of a second emulsifying agent. In order to develop the emulsified fuel using the double emulsion process to obtain a three-phase emulsion, one or more emulsifying agents may be used. In some nonlimiting embodiments, it is preferred to specifically use the additives referred to herein as Ox and Px, which may include biodegradable substances applied in the previously stated conditions. 
     In accordance with one or more embodiments, pumping air to a micro-emulsion may lower the viscosity of the micro-emulsion without needing to raise the temperature. This may reduce the cost of use as well as the capital cost of installation. The viscosity of the micro-emulsion may decrease dramatically with increasing pneumatic agitation as the micro-emulsion becomes prevalent in a fuel and aqueous solution combination. This may permit better handling of the resulting product. In some embodiments, oxygen molecules may be brought closer to the fuel in a three-phase emulsion. In at least some embodiments, this may be particularly true if the long fuel chains have been broken. The viscosity may be lowered by insertion of air molecules, the combustion efficiency increased, and pollutants reduced with the resulting more complete combustion. In accordance with one or more embodiments, pneumatic agitation for introducing air may be related to achieving a predetermined viscosity and homogenous appearance. The predetermined viscosity may vary depending on the intended application. 
     In accordance with one or more nonlimiting embodiments, the micro-emulsion may include droplets of about 40 to about 80 microns and a viscosity between about 150 and 250 cSt at room temperature. A droplet may be an air bubble that has fuel entrapped inside, surrounded by water. Upon combustion, the water may vaporize, expand and enter inside the fuel, bursting through the fuel skin and carrying part of the skin and disintegrating the fuel, thereby increasing the fuel-effective contact area with the oxygen. This micro-explosion may result in higher combustion efficiency. 
     In certain embodiments, Ox primarily functions as an agent that separates and disperses clusters of hydrocarbon molecules. Without being bound by any particular theory, it is believed that Ox may act to decrease the surface tension of the hydrocarbon molecules, allowing them to separate and disperse. The active ingredients for Ox may include, but are not limited to, D-limonene; 4-nonylphenol ethoxylate; triethanol amine; sulfonic acid; ethylene glycol, or a combination thereof. In certain non-limiting embodiments, Ox is chemically compatible with Px. Additional and alternative suitable Ox agents will be recognized by those skilled in the art given the benefit of this disclosure. 
     In certain embodiments, Px primarily functions as an agent that facilitates and stabilizes the generation of the three-phase micro-emulsion. Without being bound by any particular theory, it is believed that Px may act to allow the air molecules to either completely or partially encapsulate the hydrocarbon fuel droplets and to maintain the aqueous solution as the continuous phase. Stabilization may generally involve maintaining a dispersion of the micro-emulsion. The active ingredients for Px may include, but are not limited to, monoethanolamine; triethanol ammonium lauryl sulfate; ethoxylate propoxylated fatty acid alcohol as the one produced by Plurafac D-25, a product of Wyandotte Chemical Division of BASF Corporation, also described in U.S. Pat. No. 3,382,285; coconut fatty betaine; coconut alkylolamide, or a combination thereof. Additional and alternative suitable Px agents will be recognized by those skilled in the art given the benefit of this disclosure. 
     In certain exemplary and non-limiting embodiments disclosed here, the process to make the emulsified fuel comprises: 
     A) adding to the heavy hydrocarbon to be processed a mixture of water and additive Ox. The mixture of water and additives varies from 5 to 10% of the total amount of the final emulsified fuel amount. In the mixture of water and Ox, the amount of Ox used varies from 0.4 to 0.6% of the final amount of emulsified fuel; 
     B) pneumatically agitating the above for between 1 and 2 hours, depending on the heavy hydrocarbon&#39;s viscosity, API gravity, and the agitators&#39; capacity, to separate and disperse the hydrocarbon clusters; 
     C) adding to the mixture of the heavy hydrocarbon with water and Ox additive a mixture of water and Px additive in percentages that range from 5 to 15% of the final amount of emulsified fuel to be produced. In the mixture of water and Px, the amount of Px varies from 0.6 to 0.8% of the total final amount of emulsified fuel to be produced; 
     D) pneumatically agitating the above until the micro-emulsion has an appearance of a homogeneous single liquid phase, in which the hydrocarbon and the air form the dispersed phase and the aqueous solution forms the continuous phase with the viscosity of the micro-emulsion reaching a desired value. The desired value at room temperature or ambient temperature may be between about 80-200 cSt (centistokes) in some nonlimiting embodiments. At 80° C., the viscosity may be lower than 40 cSt. 
     In some nonlimiting embodiments, a method of preparing a three-phase micro-emulsion may involve combining a hydrocarbon fuel and an aqueous solution. The combined hydrocarbon fuel and aqueous solution may be agitated in the presence of a first emulsifying agent while introducing air at a first flow rate to form an intermediate mixture. The first agitation may be performed for a predetermined duration or until a predetermined viscosity is attained. The intermediate mixture may then be agitated in the presence of a second emulsifying agent while introducing air at a second flow rate to form the three-phase micro-emulsion. The hydrocarbon fuel and air may form dispersed phases and the aqueous solution may form a continuous phase. The second agitation may be performed for a predetermined duration or until a predetermined viscosity is attained. 
       FIG. 6  presents an exemplary process flow diagram for producing a three-phase micro-emulsion. In general terms, water is mixed with emulsification additives in separate preparation batch tanks. The emulsification additives are pumped separately into a larger batch tank containing crude oil and water. The emulsification additives are mixed with crude oil and water in the larger batch tank using pneumatic agitation to produce a micro-emulsion. When the desired viscosity is obtained, the micro-emulsion may be pumped to a separate holding tank. In a specific embodiment, Ox and water are mixed in a first preparation batch tank (capacity 27 m 3 ). The resulting Ox solution is pumped into a larger batch tank at a rate of 54 m 3 /hour and pneumatically agitated with crude oil and water in a larger batch tank (capacity 398 m 3 ). Air flow to the larger batch tank is supplied by a blower at a rate of 1000 cfm and further controlled by a process controller and an in-line emulsifier with a capacity of 75 m 3 /hour. Px and water are mixed in a second preparation batch tank (capacity 53 m 3 ). The resulting Px solution is pumped into the larger batch tank at a rate of 106 m 3 /hour and pneumatically agitated with the Ox solution, water, and crude oil until the desired viscosity is obtained. The resulting micro-emulsion is approximately 80% hydrocarbon fuel and 20% aqueous solution. Optionally, the micro-emulsion may be pumped to a secondary batch tank, where further processing, for example, additional pneumatic agitation, occurs. 
     Although one exemplary method to prepare a micro-emulsion is disclosed here, it is to be understood that other methods and processing techniques for preparing the micro-emulsion may also be used. Other methods of producing micro-emulsions are possible. Various factors, such as the type of hydrocarbon fuel used, may alter process conditions, for example, the time required for pneumatic agitation, or the type of pumps used to provide air to the process. The method used also varies depending on specific process needs in an industrial setting. The subject matter disclosed in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and methods described above are disclosed as example forms of implementing the claims. 
     EXAMPLES 
     One fuel&#39;s viscosity and aqueous combination was measured over time as a constant pneumatic agitation source was applied. In a tank holding 50,000 gallons, 38,000 gallons of fuel oil No. 4 (heavy hydrocarbon) was deposited and mixed with 2,500 gallons of the Ox additive and water mixture that had 200 gallons of Ox and 2,300 gallons of water. The mixture was pneumatically agitated for 2.0 hours, introducing air at the rate of 3,400 cubic meters per hour. 
     After the 2.0 hours, 7,500 gallons of a mixture of Px and water was added. The mixture of the Px additive and water consisted essentially of 400 gallons of Px additive and 7,100 gallons of water. The Px and water mixture was added through a mixing pump. Again, pneumatic agitation was applied, now at the rate of 5,100 cubic meters per hour for 3 hours. 
     The resulting micro-emulsion was with bubbles (hydrocarbon surrounded by air) of 40 to 80 microns in size and a viscosity of less than 40 cSt at 80° C. 
     In addition to lowering the viscosity of the heavy hydrocarbon, the resulting emulsified fuel has higher combustion efficiency. As shown in  FIG. 1 , the emulsified fuel is a three-phase emulsion,  100 , including a hydrocarbon or oil phase,  101 , an air phase,  102 , and a water phase,  103 .  FIG. 2  shows how, upon raising the temperature of the emulsion as happens for example on injection into an operating furnace, the water,  203 , in the emulsified fuel vaporizes, expands, and enters the droplets of hydrocarbon,  201 , and air,  202 . The water,  303 , inside the droplet,  304 , of hydrocarbon and air turns into steam, and the resulting pressure increase causes the steam to burst through the hydrocarbon and air droplet&#39;s skin, disintegrating the droplet into fragments,  305 , as shown in  FIG. 3 . Thereby, the contact area,  406 , between fuel and oxygen where ignition takes place is increased, as shown in  FIG. 4 . This increases the combustion efficiency, as the flame front,  507 , rapidly consumes the fragmented fuel droplets,  505 , as shown in  FIG. 5 . 
     When the emulsified fuel is exposed to oxygen present in air, it facilitates the combustion reaction. The emulsified fuel produces a fast and improved combustion of the hydrocarbon molecules and it is far more efficient and clean than heavy fuels and numbered fuel oils, with the added advantage of reduced pollutant emissions. 
     The characteristics of the emulsified fuel include that it is stable for periods greater than six months at room temperature. It has a high thermal efficiency and it is non-explosive. It is safe to produce, transport, handle and store. It has a low pour point and good combustion characteristics. It is an environmentally friendly fuel. It is a non-refined fuel, which looks, is handled, and burns like a fuel with a higher API gravity than the original product. When preparing the emulsion, no flammable solvents are added to the original hydrocarbon, yet the emulsion provides easy ignition and combustion characteristics. It has a density below one, which allows it to float in water. 
     The following analysis compares the viscosity and the burning performance of crude oil (12.3° API) and the emulsified fuel created from the same crude oil (12.3° API). The emulsified fuel is designed to fraction molecular clusters with the purpose of exposing the hydrocarbon chains to the oxygen molecules available, thus, increasing fuel oxidation and as a consequence, diminishing the total amount of pollutant emissions. Chart 1 shows a comparative analysis between crude oil and the exemplary emulsified fuel in tests carried out in actual operational conditions in a pyrotubular boiler that usually burns 12.3° API crude oil. 
     
       
         
           
               
               
               
             
               
                 CHART 1 
               
               
                   
               
               
                   
                   
                 Emulsified 
               
               
                 Parameter 
                 Crude Oil 
                 Fuel 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Pour Point 
                 10 
                 6 
               
               
                 Viscosity (Cst) 
                 367.8@ 
                 191@ 
               
               
                   
                 65 degrees C. 
                 50 degrees C. 
               
               
                 Sulphur content (% weight) 
                 1.42 
                 0.71 
               
               
                 Gross Combustion Heat (Mj/Kg) 
                 43.87 
                 34.31 
               
               
                 Fuel Injection Pressure @ 60° C. (psi) 
                 50 
                 20 
               
               
                 Required Fuel Preheating (° C.) 
                 90 
                 50 
               
               
                 Consumption (gal/hr) 
                 13.6-15* 
                 13 
               
               
                   
               
               
                 *Consumption oscillates since the crude oil doesn&#39;t burn homogeneously. 
               
            
           
         
       
     
     Although the exemplary emulsified fuel has a smaller gross caloric potential than crude oil because of its added fuel combustion efficiency, fuel consumption is diminished between 4% and 13%. This can be proven not only by fuel consumption figures but also by the reduction of pollutant particulate emissions (partially combusted carbon) and the absence of carbon monoxide in the resulting emissions, which translates into a complete or near total combustion, which reflects a far better usage of the available caloric potential. 
     The exemplary emulsified fuel has a lower pouring point, is less viscous, requires less pre-heating and less pressure for its injection, generates less polluting emissions and is far more efficient. 
     Chart 2 provides emission figure comparisons between crude oil and the exemplary emulsified fuel. 
     
       
         
           
               
               
               
               
             
               
                   
                 CHART 2 
               
               
                   
                   
               
               
                   
                 Emissions 
                 Crude oil 
                 Emulsified fuel 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Particulate Matter (mg/m 3 ) 
                 100 
                 29.1 
               
               
                   
                 SO x  (mg/m 3 ) 
                 2435 
                 1710 
               
               
                   
                 NO x  (mg/m 3 ) 
                 138.4 
                 8.02 
               
               
                   
                   
               
            
           
         
       
     
     The exemplary emulsified fuel emits substantially less volume of sulfur oxides emissions (SOx) and nitrogen oxides (NOx), compared to crude oil. 
     Chart 3 summarizes an analysis of the exemplary emulsified fuel combustion exhaust gas composition. 
     
       
         
           
               
             
               
                 CHART 3 
               
               
                   
               
               
                 Emulsified fuel exhaust gas composition 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Carbon Dioxide (% CO2) 
                 4.4 
               
               
                   
                 Oxygen (% O2) 
                 10.4 
               
               
                   
                 Carbon Monoxide (% CO) 
                 0 
               
               
                   
                 Nitrogen (% N2) 
                 85.2 
               
               
                   
                   
               
            
           
         
       
     
     The first experimental exemplary emulsified fuel can be combusted with substantially no carbon monoxide (CO) emissions. 
     The first exemplary emulsified fuel, when compared to conventional non-emulsified fuel, has greater combustion efficiency. This advantage translates into a considerable increase in the reduction of contaminant emissions to the environment and increased efficiency. In addition, the emulsified fuel is less viscous and easier to handle. 
     In sum, the first experimental emulsified fuel, when compared to the non-emulsified fuel, exhibits lower viscosity, lower pour point, requires less injection pressure, and less injection temperature, is easier to handle, has greater efficiency, has better performance, requires less consumption, and produces less CO emissions, less NOx emissions, less SOx emissions, and less particulate matter emissions. 
     A second experiment was carried out using two embodiments of the exemplary micro-emulsion disclosed here. The composition of the sample emulsions is summarized in Chart 4. 
     
       
         
           
               
               
               
               
               
             
               
                 CHART 4 
               
               
                   
               
               
                   
                 Fuel Oil No. 4 
                 P x   
                 O x   
                 Water 
               
               
                 Concentration 
                 (Gallons) 
                 (Gallons) 
                 (Gallons) 
                 (Gallons) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 85% Fuel Oil 
                 6274 
                 59 
                 30 
                 1019 
               
               
                 No. 4, 0.8% P x , 
               
               
                 0.4% O x , 
               
               
                 13.8% Water 
               
               
                 80% Fuel Oil 
                 13652 
                 137 
                 68 
                 3208 
               
               
                 No. 4, 0.8% P x , 
               
               
                 0.4% O x , 
               
               
                 18.8% Water 
               
               
                   
               
            
           
         
       
     
     The exemplary micro-emulsions were each burned and compared against the control Fuel Oil No. 4 in a steam boiler. The compared results are outlined in Chart 5. The results showed that the micro-emulsions produced 14.37% and 4.23% more steam using the 85/15 and 80/20 concentrations, respectively. 
     
       
         
           
               
               
               
               
             
               
                 CHART 5 
               
               
                   
               
               
                   
                 Total steam 
                 Total EFO 
                 Lbs of steam 
               
               
                   
                 generated by boiler 
                 burned 
                 produced per gallon 
               
               
                 Product 
                 (lbs/hr) 
                 (gallons/hr) 
                 of EFO burned 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Micro- 
                 31929.46 
                 281.07 
                 113.6 
               
               
                 emulsion 
               
               
                 85/15 
               
               
                 Micro- 
                 79828.43 
                 771.08 
                 103.53 
               
               
                 emulsion 
               
               
                 80/20 
               
               
                 Fuel Oil No. 4 
                 14343.48 
                 144.4 
                 99.33 
               
               
                   
               
            
           
         
       
     
     In addition, the micro-emulsions resulted in a 64% reduction in the emission of particulate matter and at least a 90% decrease in carbon monoxide emissions. 
     A third experiment was carried out using two embodiments of the micro-emulsion disclosed here. The composition and physical properties of the sample emulsions and the Napo Crude are summarized in Charts 6 and 7. 
     
       
         
           
               
               
               
               
               
             
               
                 CHART 6 
               
               
                   
               
               
                   
                 Napo Crude Oil 
                 P x   
                 O x   
                 Water 
               
               
                 Concentration 
                 (Gallons) 
                 (Gallons) 
                 (Gallons) 
                 (Gallons) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 75% Napo 
                 7125 
                 76 
                 38 
                 2261 
               
               
                 Crude Oil, 
               
               
                 0.8% P x , 0.4% 
               
               
                 O x , 23.8% 
               
               
                 Water 
               
               
                 75% Napo 
                 2850 
                 30.4 
                 15.2 
                 904.4 
               
               
                 Crude Oil, 
               
               
                 0.8% P x , 0.4% 
               
               
                 O x , 23.8% 
               
               
                 Water 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                 CHART 7 
               
               
                   
                   
               
               
                   
                   
                 Micro- 
                 Napo Crude 
               
               
                   
                 Parameter 
                 emulsion 
                 Oil 
               
               
                   
                   
               
             
            
               
                   
                 Cinematic Viscosity (cSt) 
                 191 (50° C.) 
                 367.8 (65° C.) 
               
               
                   
                 Fluidity Point (° C.) 
                 6 
                 10 
               
               
                   
                 Sulfur (%) 
                 0.72 
                 1.42 
               
               
                   
                 Brute Caloric Power 
                 34.31 
                 43.8 
               
               
                   
                 (Mj/Kg) 
               
               
                   
                   
               
            
           
         
       
     
     The exemplary micro-emulsions were each burned and compared against the control Napo Crude Oil. The results indicated that the atmospheric emission of carbon monoxide when burning the micro-emulsion was reduced to zero, indicating that complete and efficient combustion had occurred. In addition, crude consumption reduced from 15 gallons/hour to 13 gallons/hour. 
     Two additional experiments have been carried out using embodiments of the exemplary emulsified fuel, with the following results. The additional experiments included comparisons, under actual operating conditions of a 400 BHP steam furnace, between crude fuel conventionally used in the furnace, an exemplary fuel including 85% crude and 15% water+chemicals (the 85/15 mix), and another exemplary fuel including 80% crude and 20% water+chemicals (the 80/20 mix). The chemicals used were Ox and Px, as described above. The compositions of the exemplary fuels is outlined below in Chart 8. 
     
       
         
           
               
               
               
               
               
             
               
                 CHART 8 
               
               
                   
               
               
                   
                 Crude Oil 
                 P x   
                 O x   
                 Water 
               
               
                 Concentration 
                 (Gallons) 
                 (Gallons) 
                 (Gallons) 
                 (Gallons) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 85% Crude Oil, 
                 15120 
                 142 
                 71 
                 2455 
               
               
                 0.8% P x , 0.4% 
               
               
                 O x , 13.8% 
               
               
                 Water 
               
               
                 80% Crude Oil, 
                 15120 
                 151 
                 76 
                 3553 
               
               
                 0.8% P x , 0.4% 
               
               
                 O x , 18.8% 
               
               
                 Water 
               
               
                   
               
            
           
         
       
     
     A substantial savings in fuel consumption was realized by both the 85/15 mix and the 80/20 mix. The savings achieved by the exemplary embodiments was 13.70% when burning the 85/15 mix emulsion and 19.58% when burning the 80/20 mix emulsion. 
     Substantial positive environmental impact results were also obtained in the area of particulate emissions. The laboratory under contract to monitor emissions at the furnace used in these experiments found that crude combustion (conventional fuel) produced 282 mg/m3 of particle matter, while the exemplary embodiments of emulsion fuels reduced the measured particulate emissions to 96 mg/m3 and 84 mg/m3 when burning emulsions of the 85/15 mix and the 80/20 mix, respectively. 
     In this experiment, the values obtained for emission of sulfur dioxide and nitrous oxide do not show a clear or real tendency. 
     The sulfur dioxide should have reduced by at least the same percentages as that by which crude was substituted by water (i.e., 15% and 20% for the 85/15 mix and the 80/20 mix, respectively). Instead, over the course of the test, a control run produced 893 mg/m3 while burning crude; emissions of sulfur dioxide increased to 968 mg/m3 when subsequently burning the 85/15 mix; and then later the sulfur dioxide emissions fell to 863 mg/m3 when burning the 80/20 mix. The testing laboratory has concluded that the natural furnace cleaning process that occurs through the burning of cleaner fuel occurred more slowly than expected while burning the exemplary emulsions, to the degree that when the measurements were taken, distorted values resulted. Upon continuous consumption of exemplary emulsion fuel, the sulfur dioxide emissions reduced considerably once the furnace cleaning process finalized. 
     The nitrous oxide also did not demonstrate typical behavior during combustion of the exemplary embodiments. The emulsions tested during this experiment produced increased nitrous oxide emissions. While emissions from burning crude produced 76 mg/m3, the burning of the 85/15 mix produced 95 mg/m3 and the burning of the 80/20 mix produced 145 mg/m3. This result of the second and third tests is considered an unexplained anomaly because of contrary results obtained during other tests, including the first test described above. 
     In some embodiments, the emulsified fuel is in a liquid state and may be utilized to operate internal combustion engines, boilers, heaters, furnaces, combustion turbines or power plants. The exemplary emulsified fuel is an effective answer to three basic needs that the world faces today: the growing need for low cost energy, the preservation of a non-renewable resource and the preservation of the environment. 
     The benefits obtained from the use of the emulsified fuel have been evaluated both technically and environmentally in several laboratories, and in industrial tests under the supervision of qualified scientists. When compared to the usage of heavy fuels, the exemplary emulsified fuel presents the following advantages: it homogenizes and stabilizes the fuel, it separates out the molecular clusters or aggregates exposing the hydrocarbon molecules to the oxygen molecules, it facilitates the handling and transportation, it improves combustion, it improves fuel performance, it reduces particulate and contaminating gas emissions, and it reduces operational costs. 
     Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.