Emulsified fuels are a type of emulsion that combines water with a combustible liquid, such as oil or fuel. An emulsion is a specialized form of dispersion that contains both a continuous phase and a dispersed phase. The most commonly utilized emulsified fuel is a water-in-diesel emulsion (also known as hydrodiesel). [1] In these emulsions, the two phases are immiscible liquids—water and oil. Emulsified fuels can be categorized as either microemulsions or conventional emulsions (sometimes called macroemulsions to distinguish them from microemulsions). The main differences between these types are related to stability and particle size. Microemulsions are thermodynamically stable, forming spontaneously with particle sizes of 10 to 200 nm. In contrast, macroemulsions are kinetically stabilized, created through a shearing process, with particle sizes ranging from 100 nm to over 1 micrometer. While microemulsions are isotropic, macroemulsions may undergo settling (or creaming) over time and experience changes in particle size. Both types use surfactants (also known as emulsifiers) and can be water-in-oil (inverted emulsions), oil-in-water (regular emulsions), or bicontinuous (also called multiple or complex emulsions).
Oil-in-water emulsified fuels, such as the Orimulsion system and bitumen emulsions, are examples of water-continuous systems. These emulsions are often considered high internal phase emulsions (HIPE) because the continuous phase makes up about 30% of the fuel composition, whereas the dispersed phase is usually the minor component. Emulsions of heavy crude oils and bitumen are easier to pump than their original forms, which typically require heating or dilution with light oils like kerosene to facilitate handling. Emulsions of residual fuels, including heavy fuel oils used in industrial applications, can also be created to reduce the reliance on cutter fluids and improve combustion emissions from lower-quality fuels.
Water-in-oil emulsified fuels, such as diesel and biodiesel-water emulsions, are widely used in Europe, with standards established by the CEN workshop (CWA 15145:2004). These emulsions usually contain between 5% and 30% water by mass. Water-in-diesel emulsions can serve as alternative fuels, offering lower emissions and improved brake thermal efficiency. [2]
Since 2006, Nonox Ltd. has offered on-demand water-in-fuel emulsions for heavy fuel oil (HFO) and diesel, used in shipping and stationary boilers. This approach, known as Emulsion to Combustion (E2C), allows for mixing without chemical surfactants, the adjustment of the water-to-fuel ratio based on load, and prevents separation during storage. This system has demonstrated reductions in soot emissions of up to 90% and NOx emissions by 40%, while also delivering fuel savings depending on baseline efficiency.
Microemulsions of fuels have been prepared using specific types of surfactants, which differentiate them from other commercial emulsion fuels. These microemulsions are often utilized in contexts where safety (e.g., fire prevention; [3] ) or enhanced commercial returns (e.g., improved oil recovery using surfactant flooding; [4] ) justify the additional costs.
The main benefits of using emulsified fuels instead of conventional fuels include environmental and economic advantages. Introducing water into the combustion process reduces temperatures and NOx emissions. [5] Research comparing water injection and emulsified fuels in diesel engines (both marine and stationary) has shown that emulsified fuels are particularly effective at simultaneously decreasing NOx and particulate matter emissions. [6] Additional studies have investigated the impact of exhaust gas recirculation (EGR) and emulsion fuels on diesel engines. [7]
An emulsion is a mixture of two or more liquids that are normally immiscible owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid is dispersed in the other. Examples of emulsions include vinaigrettes, homogenized milk, liquid biomolecular condensates, and some cutting fluids for metal working.
In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. The exhaust gas displaces atmospheric air and reduces O2 in the combustion chamber. Reducing the amount of oxygen reduces the amount of fuel that can burn in the cylinder thereby reducing peak in-cylinder temperatures. The actual amount of recirculated exhaust gas varies with the engine operating parameters.
Biodiesel is a renewable biofuel, a form of diesel fuel, derived from biological sources like vegetable oils, animal fats, or recycled greases, and consisting of long-chain fatty acid esters. It is typically made from fats.
A catalytic converter is an exhaust emission control device which converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually used with internal combustion engines fueled by gasoline or diesel, including lean-burn engines, and sometimes on kerosene heaters and stoves.
Lipophilicity is the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such compounds are called lipophilic. Such non-polar solvents are themselves lipophilic, and the adage "like dissolves like" generally holds true. Thus lipophilic substances tend to dissolve in other lipophilic substances, whereas hydrophilic ("water-loving") substances tend to dissolve in water and other hydrophilic substances.
Alternative fuels, also known as non-conventional and advanced fuels, are fuels derived from sources other than petroleum. Alternative fuels include gaseous fossil fuels like propane, natural gas, methane, and ammonia; biofuels like biodiesel, bioalcohol, and refuse-derived fuel; and other renewable fuels like hydrogen and electricity.
Vehicle emissions control is the study of reducing the emissions produced by motor vehicles, especially internal combustion engines. The primary emissions studied include hydrocarbons, volatile organic compounds, carbon monoxide, carbon dioxide, nitrogen oxides, particulate matter, and sulfur oxides. Starting in the 1950s and 1960s, various regulatory agencies were formed with a primary focus on studying the vehicle emissions and their effects on human health and the environment. As the worlds understanding of vehicle emissions improved, so did the devices used to mitigate their impacts. The regulatory requirements of the Clean Air Act, which was amended many times, greatly restricted acceptable vehicle emissions. With the restrictions, vehicles started being designed more efficiently by utilizing various emission control systems and devices which became more common in vehicles over time.
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack, or propelling nozzle. It often disperses downwind in a pattern called an exhaust plume.
Diesel exhaust is the exhaust gas produced by a diesel engine, plus any contained particulates. Its composition may vary with the fuel type or rate of consumption, or speed of engine operation, and whether the engine is in an on-road vehicle, farm vehicle, locomotive, marine vessel, or stationary generator or other application.
Microemulsions are clear, thermodynamically stable, isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. The aqueous phase may contain salt(s) and/or other ingredients, and the "oil" may actually be a complex mixture of different hydrocarbons. In contrast to ordinary emulsions, microemulsions form upon simple mixing of the components and do not require the high shear conditions generally used in the formation of ordinary emulsions. The three basic types of microemulsions are direct, reversed and bicontinuous.
In atmospheric chemistry, NOx is shorthand for nitric oxide and nitrogen dioxide, the nitrogen oxides that are most relevant for air pollution. These gases contribute to the formation of smog and acid rain, as well as affecting tropospheric ozone.
A NOx adsorber or NOx trap (also called Lean NOx trap, abbr. LNT) is a device that is used to reduce oxides of nitrogen (NO and NO2) emissions from a lean burn internal combustion engine by means of adsorption.
The Bancroft rule in colloidal chemistry states: "The phase in which an emulsifier is more soluble constitutes the continuous phase." This means that water-soluble surfactants tend to give oil-in-water emulsions and oil-soluble surfactants give water-in-oil emulsions. It is a general rule of thumb, still used, but regarded as inferior to HLD theory, which takes many more factors into consideration.
A miniemulsion is a particular type of emulsion. A miniemulsion is obtained by ultrasonicating a mixture comprising two immiscible liquid phases, one or more surfactants and, possibly, one or more co-surfactants. They usually have nanodroplets with uniform size distribution (20–500 nm) and are also known as sub-micron, mini-, and ultra-fine grain emulsions.
A dispersant or a dispersing agent is a substance, typically a surfactant, that is added to a suspension of solid or liquid particles in a liquid to improve the separation of the particles and to prevent their settling or clumping.
A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. Strictly speaking, defoamers eliminate existing foam and anti-foamers prevent the formation of further foam. Commonly used agents are insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols. The additive is used to prevent formation of foam or is added to break a foam already formed.
A hydrogen internal combustion engine vehicle (HICEV) is a type of hydrogen vehicle using an internal combustion engine. Hydrogen internal combustion engine vehicles are different from hydrogen fuel cell vehicles. Instead, the hydrogen internal combustion engine is simply a modified version of the traditional gasoline-powered internal combustion engine. The absence of carbon means that no CO2 is produced, which eliminates the main greenhouse gas emission of a conventional petroleum engine.
The Cummins X-series engine is an Inline (Straight)-6 diesel engine produced by Cummins for heavy duty trucks and motorcoaches, replacing the N14 in 2001 when emissions regulations passed by the EPA made the engine obsolete. Originally called the "Signature" series engine, the ISX uses the "Intellect System" to further improve the engine. This engine is widely used in on highway and vocational trucks and is available in power ranging from 430 hp all the way to 620 hp 2050 lb-ft. The QSX is the off-highway version of the ISX with the Q standing for Quantum. The QSX is used for industrial, marine, oil & gas and other off-highway applications. Cummins also produced a 650 hp and 1950 lb-ft version for the RV market.
Macroemulsions are dispersed liquid-liquid, thermodynamically unstable systems with particle sizes ranging from 1 to 100 μm, which, most often, do not form spontaneously. Macroemulsions scatter light effectively and therefore appear milky, because their droplets are greater than a wavelength of light. They are part of a larger family of emulsions along with miniemulsions. As with all emulsions, one phase serves as the dispersing agent. It is often called the continuous or outer phase. The remaining phase(s) are disperse or inner phase(s), because the liquid droplets are finely distributed amongst the larger continuous phase droplets. This type of emulsion is thermodynamically unstable, but can be stabilized for a period of time with applications of kinetic energy. Surfactants are used to reduce the interfacial tension between the two phases, and induce macroemulsion stability for a useful amount of time. Emulsions can be stabilized otherwise with polymers, solid particles or proteins.
Heavy fuel oil (HFO) is a category of fuel oils of a tar-like consistency. Also known as bunker fuel, or residual fuel oil, HFO is the result or remnant from the distillation and cracking process of petroleum. For this reason, HFO is contaminated with several different compounds including aromatics, sulfur, and nitrogen, making emissions upon combustion more polluting compared to other fuel oils. HFO is predominantly used as a fuel source for marine vessel propulsion using marine diesel engines due to its relatively low cost compared to cleaner fuel sources such as distillates. The use and carriage of HFO on-board vessels presents several environmental concerns, namely the risk of oil spill and the emission of toxic compounds and particulates including black carbon. The use of HFOs is banned as a fuel source for ships travelling in the Antarctic as part of the International Maritime Organization's (IMO) International Code for Ships Operating in Polar Waters (Polar Code). For similar reasons, an HFO ban in Arctic waters is currently being considered.