US20100077733A1

US20100077733A1 - Emission system, apparatus, and method

Info

Publication number: US20100077733A1
Application number: US12/238,973
Authority: US
Inventors: Benjamin Hale Winkler; Dan Hancu; Ke Liu; Gregg Deluga; Daniel Norton; Ashish Balkrishna Mhadeshwar
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2008-09-26
Filing date: 2008-09-26
Publication date: 2010-04-01

Abstract

An emission reduction apparatus is provided that includes a fuel conversion unit configured to convert a first portion of fuel from a fuel tank into a set of reducing agents that includes hydrogen, an exhaust path configured to convey an exhaust stream containing nitrogen oxides away from an engine, a transport system configured to transport each of a second portion of fuel from the fuel tank, the set of reducing agents, and the hydrogen into the exhaust path such that a mixture is formed, and the catalytic material configured to aid in a conversion of at least a portion of the nitrogen oxides in the exhaust stream of the mixture into nitrogen.

Description

BACKGROUND

1. Technical Field
The invention includes embodiments that relate to an engine exhaust emission reduction system. Embodiments of the invention relate to vehicles, locomotives, generators, and the like. Embodiments of the invention relate to a method of controlling engine exhaust system emissions.
2. Discussion of Art
Production of emissions from mobile and stationary combustion sources such as locomotives, vehicles, power plants, and the like, contribute to environmental pollution. One particular source of such emissions are nitric oxides (NO_x), such as NO or NO₂, emissions from vehicles, locomotives, generators, and the like. Environmental legislation restricts the amount of NO_xthat can be emitted by vehicles. In order to comply with this legislation, efforts have been directed at reducing the amount of NO_xemissions.
As such, it may be desirable to have a system that has aspects and features that differ from those that are currently available. Further, it may be desirable to have a method that differs from those methods that are currently available.

BRIEF DESCRIPTION OF THE INVENTION

Aspects of the invention provide an apparatus including a fuel conversion unit, an exhaust path configured to convey an exhaust stream that contains nitrogen oxides away from an engine, a transport system, and a catalytic material positioned within the exhaust path. The fuel conversion unit is configured to convert a first portion of fuel from a fuel tank into a set of reducing agents that includes hydrogen. The transport system is configured to transport each of a second portion of fuel from the fuel tank and the set of reducing agents into the exhaust path such that a mixture is formed. The mixture comprises the second portion of fuel, the set of reducing agents, and the exhaust stream. The catalytic material is positioned within the exhaust path and configured to aid in a conversion of at least a portion of the nitrogen oxides in the mixture into nitrogen. The conversion reduces a quantity of the nitrogen oxides in the exhaust stream.
Aspects of the invention also provide a method that includes converting a first portion of fuel from a fuel supply to a plurality of first reductants, and passing the plurality of first reductants into an exhaust stream. The exhaust stream includes a plurality of nitrogen oxides. The method further includes transforming a second portion of liquid fuel from the fuel supply into a gaseous fuel and passing the first reductants, the exhaust stream, and the gaseous fuel over a selective catalytic reduction (SCR) component such that a portion of the plurality of nitrogen oxides is converted into nitrogen.
Aspects of the invention also provide a method that includes acquiring a first portion of fuel from an engine supply fuel tank, converting the first portion of fuel into at least a plurality of reductants, mixing the plurality of reductants and a quantity of gaseous fuel from a second portion of fuel from the engine supply fuel tank with an engine exhaust containing nitrogen oxides to create a first mixture including the plurality of reductants, the quantity of gaseous fuel, and the engine exhaust. The method further includes catalyzing a chemical reaction in the first mixture over a selective catalytic reduction (SCR) unit. The catalyzed chemical reaction reduces at least a portion of the nitrogen oxides in the first mixture to nitrogen.
Various other features may be apparent from the following detailed description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate at least one preferred embodiment presently contemplated for carrying out the invention.

In the drawings:

FIG. 1 is a flowchart depicting an exemplary technique according to an embodiment of the invention.

FIG. 2 is a schematic diagram of an emission reduction scheme according to an embodiment of the invention.

FIG. 3 is another schematic diagram of an emission reduction scheme according to an embodiment of the invention.

DETAILED DESCRIPTION

The invention includes embodiments that relate to engine emission reduction systems. The invention includes embodiments that relate to an apparatus for controlling the emissions of an engine. The invention includes embodiments that relate to a method of controlling the emissions of an engine.
Embodiments of the invention provide an apparatus including a fuel conversion unit, an exhaust path configured to convey an exhaust stream that contains nitrogen oxides away from an engine, a transport system, and a catalytic material positioned within the exhaust path. The fuel conversion unit is configured to convert a first portion of fuel from a fuel tank into a set of reducing agents that includes hydrogen. The transport system is configured to transport each of a second portion of fuel from the fuel tank and the set of reducing agents into the exhaust path such that a mixture is formed. The mixture comprises the second portion of fuel, the set of reducing agents, and the exhaust stream. The catalytic material is positioned within the exhaust path and configured to aid in a conversion of at least a portion of the nitrogen oxides in the mixture into nitrogen. The conversion reduces a quantity of the nitrogen oxides in the exhaust stream.
Embodiments of the invention provide a method that includes converting a first portion of fuel from a fuel supply to a plurality of first reductants, and passing the plurality of first reductants into an exhaust stream. The exhaust stream includes a plurality of nitrogen oxides. The method further includes transforming a second portion of liquid fuel from the fuel supply into a gaseous fuel and passing the first reductants, the exhaust stream, and the gaseous fuel over a selective catalytic reduction (SCR) component such that a portion of the plurality of nitrogen oxides is converted into nitrogen.
Embodiments of the invention provide a method that includes acquiring a first portion of fuel from an engine supply fuel tank, converting the first portion of fuel into at least a plurality of reductants, mixing the plurality of reductants and a quantity of gaseous fuel from a second portion of fuel from the engine supply fuel tank with an engine exhaust containing nitrogen oxides to create a first mixture including the plurality of reductants, the quantity of gaseous fuel, and the engine exhaust. The method further includes catalyzing a chemical reaction in the first mixture over a selective catalytic reduction (SCR) unit. The catalyzed chemical reaction reduces at least a portion of the nitrogen oxides in the first mixture to nitrogen.
Embodiments of the invention provide a method that includes acquiring a first portion of fuel from an engine supply fuel tank, converting the first portion of fuel into at least a plurality of reductants, mixing the plurality of reductants and a gaseous second portion of fuel from the engine supply fuel tank with an engine exhaust containing nitrogen oxides to create a first mixture including the plurality of reductants, the second portion of gaseous fuel, and the engine exhaust. The method further includes catalyzing a chemical reaction in the first mixture over a selective catalytic reduction (SCR) unit. The catalyzed chemical reaction reduces at least a portion of the nitrogen oxides in the first mixture to nitrogen.
Referring to FIG. 1, a technique 100 for reducing noxious emissions from an engine is depicted according to an embodiment of the invention. According to the embodiment of FIG. 1, a technique 100 for reducing nitrogen oxide (NO_x) emissions from an engine is shown. At BLOCK 102, a first portion of fuel from an engine (e.g., an internal combustion engine such as a spark or compression ignition engine) fuel supply is converted into at least a set of first reductants. A second portion of fuel from the same engine fuel supply is transformed into a gaseous fuel at BLOCK 104. The set of first reductants of BLOCK 102 and the gaseous fuel of BLOCK 104 are allowed to mix with an exhaust stream of the engine to create a mixture at BLOCK 106. At BLOCK 108, the mixture is allowed to pass over or through a selective catalytic reduction (SCR) unit to reduce NO_xemissions. That is, as the mixture passes over the SCR unit, a chemical reaction takes place that reduces the quantity of NO_xin the exhaust stream. As such, NO_xemissions are reduced. An exemplary chemical reaction of a NO_xemission reduction may be represented by:
NO_x+O₂+organic reductant
N₂+CO₂+H₂O (Eqn. 1).
Technique 100 can be employed using a wide variety of engines, not just combustion engines. For example, embodiments of the invention effectively reduce engine NO_xemissions of vehicles, locomotives, generators, gas turbines of power plants, or the like. That is, embodiments of the invention are effective for reducing emissions from any exhaust source containing NO_x. As shown in the flowchart of FIG. 1, two separate fuel sources are not required to reduce NO_xemissions. That is, NO_xemissions may be reduced using fuel from the same supply that powers the engine.
SCR catalysts are those catalyst materials that enable the chemical reduction of NO_xspecies to less harmful constituents such as nitrogen (i.e., N₂). Many of the SCR catalyst materials that promote reduction of NO_xspecies via reaction with an exhaust stream and reductants may be suitable for use in embodiments of the invention described herein. For example, silver on an Alumina support that is coated on a monolith support structure may be used. In particular, 3.0% silver on Mesoporous Alumina that is coated on a monolith core has been found to be particularly effective in embodiments described herein.
A schematic block diagram embodying technique 100 of FIG. 1 is depicted in FIG. 2. Although fuel described in embodiments herein may comprise diesel fuels, it is contemplated that embodiments of the invention may, in the alternative, use other fuels such as jet-fuel, fuel oil, and bio-fuels such as bio-diesel. In one embodiment, the fuel composition can be bio-diesel or another bio-fuel. In other embodiments, the fuel composition includes synthetic fuels with compositions similar to conventional fuels. Further non-limiting examples include gasoline and other fuels obtained by petroleum refining. In some embodiments, this includes fuels from distillate fuels, diesel fuel oil, light fuel oil and the like. As shown in FIG. 2, a first portion of diesel fuel 120 from an engine diesel fuel supply 122 is allowed to pass through a fuel conversion unit (e.g., a diesel conversion unit (DCU)) 124 where it is converted into a set or plurality of reductants such as hydrogen. The DCU 124 may contain an auto thermal cracking material, a catalytic partial oxidation material, or the like to enable such a conversion. With regard to auto thermal cracking materials, a cracking catalyst is employed. The term “cracking catalyst” refers to those catalysts that enable reactions that convert a hydrocarbon material having a comparatively high molecular weight (e.g., diesel or ultra low sulfur diesel) into one or more hydrocarbon species having lower molecular weights. With regard to the DCU 124, the cracking catalyst material enables conversion of the primary hydrocarbon into at least one secondary hydrocarbon having a lower molecular weight than the primary hydrocarbon. In addition, the cracking component conveniently allows for the production of reductant species from the very fuel 122 powering the engine 123. The cracking catalyst can also convert the fuel from the diesel fuel supply 122 into carbon monoxide, carbon dioxide, and reductants or co-reductants such as hydrogen. In one embodiment, the cracking catalyst material comprises a zeolite. Zeolites may be favored for their effectiveness in enabling cracking of heavy hydrocarbons. Zeolite crystals, found in such cracking catalysts, have a regular network of very small diameter pores, the size and nature of which can be controlled by controlling the chemistry and processing of the zeolite. Zeolites include silicon or aluminum atoms tetrahedrally surrounded by four oxygen atoms. A tetrahedron containing silicon is neutral in charge, while each tetrahedron containing aluminum has a net charge of −1, which must be balanced by a positive ion such as a proton. Protons that balance the negative charge of aluminum tetrahedral have strong acidity, which is known to catalyze cracking reactions. Thus, the catalyzing properties of the zeolite, in addition to being controlled by controlling pore size, may be further controlled by proper selection of a “silicon to aluminum ratio” of the zeolite, (i.e., the relative amounts of aluminum and silicon in the zeolite).
In embodiments of the invention, the DCU 124 may include a catalytic partial oxidation (CPO) material. CPO materials are capable of enabling the conversion of hydrocarbon species, such as the primary hydrocarbon (e.g., the first portion of diesel fuel 120), into a syngas (a mixture of hydrogen and carbon monoxide). This syngas, as will be described in greater detail below, can be used to further increase the rate of NO_xreduction. CPO materials have catalyst-endowed functional capabilities. Further, CPO materials also help to minimize the degradation of cracking catalysts resulting from coke build-up. Coke build-up occurs during a variety of processes, such as fluidized catalytic cracking (FCC). As such, during the cracking of hydrocarbons, coke often builds up on the surface of the cracking catalysts. By employing a CPO material, coke build-up on the surface of the cracking catalyst material may be removed, thereby retaining active sites for cracking appreciably longer than would be available if the CPO material were not present. Further, since a catalytic partial oxidation reaction is an exothermic reaction while cracking is an endothermic reaction, the heat generated at a catalytic partial oxidation site facilitates the endothermic cracking reaction in a neighboring cracking site while also facilitating the oxidation of coke that may be present in the DCU 124.
The CPO material generally comprises one or more noble metals that perform the catalytic partial oxidation function. In particular embodiments, the CPO material comprises one or more “platinum group” metal components. As used herein, the term “platinum group” metal means rhodium, platinum, iridium, palladium, osmium, ruthenium, or mixtures of any of these. Exemplary platinum group metal components are rhodium, platinum, and optionally, iridium. The platinum-group metal is present in the multifunctional catalyst in an amount greater than about 0.1 weight percent, such as in a range from about 0.1 weight percent to about 5 weight percent. A particular exemplary composition for the CPO material is 0.5% Pt-0.5% Rh-0.25% Ir (percentages based on total loading by weight of multi-functional catalyst). In alternative embodiments, the platinum-group metal is present in the multi-functional catalyst in an amount of about 1 weight percent. The platinum group metal components optionally may be supplemented with one or more base metals and oxides of the metals, including, for example, base metals of Group VIIIB, Group IB, Group VB and Group VIB of the Periodic Table of Elements. Exemplary base metals include cerium, iron, cobalt, nickel, copper, vanadium, and chromium. In some embodiments, the CPO material is disposed on the cracking catalyst.
Still referring to the embodiment of FIG. 2, once created by the DCU 124, the reductants, including any hydrogen, in the DCU output 126 are allowed to pass into an engine exhaust path 128. As a result, the DCU output 126 mixes with the engine exhaust stream 130, which contains a plurality of nitrogen oxides (NO_x). A second portion of diesel fuel 132 passes into the engine exhaust path 128 by, for example, an atomization or spray method. Upon entering the exhaust path 128, the heat from the exhaust stream 130 transforms the second portion of diesel fuel 132 into gaseous diesel fuel. The constituents described above, that is, the DCU output 126 and the second portion of diesel fuel 132, may be conveyed into the exhaust path 128 via a transport system 134 comprising containment tubes, hoses, or the like.
As a consequence of passing the set of reductants in the DCU output 126, which may include hydrogen, along with the second portion of diesel fuel 132 from the diesel fuel supply 122 into the exhaust stream 130, a mixture 136 is created. This mixture 136 is allowed to pass over or into the SCR unit 138 located within the exhaust path 128. The SCR unit 138 enables a chemical reaction to take place, where the hydrocarbons present in the second portion of diesel fuel 132 and the hydrocarbons present (if any) in the DCU output 126 reduce at least a portion of the NO_xin the exhaust stream 130 to at least nitrogen (N₂). As such, the amount of NO_xin the engine emissions 140 is reduced. Further, any H₂present in the DCU output 126 will increase the rate of NO_xreduction over the SCR unit 138 at given temperatures. In one embodiment, which will be more fully described through example with respect to FIG. 3, the quantity of H₂produced by the DCU 124 may be manipulated by allowing oxygen 142 into the DCU 124 environment. The intake of such oxygen may be controlled by a control component 144, which will also be more fully described with respect to FIG. 3.
The second portion of fuel 132 and the set of reducing agents, which includes the hydrogen, in the DCU output 126 all act as reducing agents over the catalytic material for the conversion of nitrogen oxides. The proportions of each of these reducing agents can be adjusted to optimize the conversion of nitrogen oxides. Examples of the manner in which such optimizations may occur will be more fully described below with respect to FIG. 3
Referring now to FIG. 3, a schematic diagram according to an embodiment of the invention is shown, which illustrates NO_xreduction in engine emission in a “cool” environment. Due to the nature of the chemical reaction that occurs that reduces the amount of NO_xin the exhaust stream 130, the rate at which the reaction occurs is often slowed as the temperature of the exhaust stream 130 is reduced. However, this rate can be increased if the mixture 136 also contains hydrogen (H₂). To exploit the effects of H₂as a reductant or co-reductant, oxygen 142 and the first portion of fuel 120 is allowed to pass through the fuel conversion unit 124 having a CPO material (not shown) therein. The oxygen could, for example, come from an air intake on the fuel conversion unit 124. That is, in one embodiment, ambient air may be brought into the fuel conversion unit 124 to provide an “oxygen rich” environment. Due to the “oxygen rich” fuel conversion unit 124 environment (i.e., an environment that includes the first portion of fuel 120 and oxygen 142), a chemical reaction occurs that results in a quantity of hydrogen (H₂), a reductant, being present among the set of reductants in the fuel conversion unit output 126. As such, by manipulating the amount of oxygen allowed to pass into the fuel conversion unit 124, the production of H₂can be controlled. In addition to manipulating the amount of oxygen that enters the fuel conversion unit 124 to control H₂production, the temperature of the fuel conversion unit 124 may also be manipulated to increase or decrease the amount of hydrogen that will be present among the set of reductants in the fuel conversion unit output 126. Once created, the reductants, along with the H₂, are then allowed to pass into the exhaust stream 130 with the second portion of fuel 132. As a consequence, the mixture 136 now includes H₂, which can increase the rate of NO_xreduction over the SCR unit 138. Though described above in terms of increasing the rate of NO_xreduction in a “cool” exhaust stream 130, it will be appreciated by one skilled in the art that the H₂may also increase the reduction rate in a “warm” environment.
Further, it is contemplated that a water gas shift (WGS) catalyst 150 could be employed to further increase the quantity of H₂entering into the mixture 136. For example, still referring to FIG. 3, the system can be configured such that the fuel conversion unit output 126 is allowed to pass over or through a sulfur tolerate water gas shift catalyst 150 (shown in phantom). The reductants found in the fuel conversion unit output 126 generally include H₂, CO, and light hydrocarbons. The CO found in the fuel conversion unit output 126 can be converted into additional H₂by passing it and the other output reductants 126 over the WGS catalyst 150. Steam in the catalyst, either brought in with the reductants or injected from another steam source 153 (shown in phantom), reacts with the CO to produce H₂as represented by the following equation:
CO+H2O
H2+CO2 (Eqn. 2).
As such, the WGS output 152 will have a greater quantity of H₂than the fuel conversion unit output 126. That is, the WGS output 152 will include H₂from the fuel conversion unit output 126 and H₂produced during the WGS reaction over the WGS catalyst 150. Consequently, the NO_xreduction of the SCR unit 138 will increase. As discussed above, it is contemplated that the steam brought in for the reaction over the WGS catalyst 150 may come from an outside steam source 153. Since a typical WGS reaction occurs within a given temperature range (e.g., 250-450° C.), the steam brought in from the outside steam source 153 can also cool the fuel conversion unit output 126 to within the WGS reaction temperature range. For fuels containing sulfur, it is preferable that the WGS catalysts 150 is commercially available sulfur tolerate WGS catalyst. For bio-fuels that do not contain sulfur, an active noble metal WGS catalysts can be used to reduce the size of the WGS catalyst bed.
As shown in FIG. 3, it is contemplated that a control component 144 such as a switch or other control circuit can provide control capabilities to the system. Such control capabilities can include the manipulation of the reducing agent ratios relative to one another and/or the manipulation of the rate the reducing and/or co-reducing agents are created. For example, a control component 144 may be employed to allow or not allow quantities of oxygen 142 to pass into the fuel conversion unit 124. If the exhaust stream 130 were cool, whether due to environmental reasons or other conditions, the control component 144 could be “turned on” to create an “oxygen rich” environment in the fuel conversion unit 124, thus enabling a CPO material in the fuel conversion unit 124 to create at least hydrogen. As such, the rate of NO_xreduction over the SCR unit 138 can be increased. On the other hand, if the exhaust stream 130 were “warm,” the control component 144 could be turned off, thus not allowing oxygen 142, or extra oxygen, to enter the fuel conversion unit 124 environment. As a result, the cracking material of the fuel conversion unit 124 converts the first portion of fuel 120 into a set of reductants rich with hydrocarbons. In such an embodiment, the mixture 136 is a combination of the set of reductants rich with hydrocarbons that comprises the fuel conversion unit output 126, the exhaust stream 130, and the hydrocarbons of the gaseous fuel (i.e., the second portion of fuel 132). Using the plurality of hydrocarbons, the SCR unit 138 aids in the reduction of the quantity of NO_xin the emissions 140.
It is further contemplated that the control component 144 of FIG. 3 could be controlled in such a manner to fine tune the amount of oxygen 142 allowed to pass into the fuel conversion unit 124 environment, thus maximizing the NO_xreduction rates in a variety of environments. That is, for example, by repetitively switching the control component 144 at different rates, the quantity of H₂and hydrocarbons in the fuel conversion unit output 126 can be manipulated. As such, the rate at which the hydrogen and reducing agents are created can also be manipulated. The activation or deactivation of the control component 144 could also be employed to by-pass the fuel conversion unit 124. Accordingly, hydrocarbon reducing agents or H₂would not be created by the fuel conversion unit 124. For example, if it is determined that H₂is not needed to increase the rate of NO_xreduction because the exhaust stream 130 is “warm,” and/or it is determined that excess hydrocarbons created with the cracking material are not needed, the control component 144 could be activated (e.g., “turned off”) such that the fuel conversion unit 124 is by-passed or not used.
Still referring to FIG. 3, it is also contemplated that a “state conversion unit” 154 could be employed to transform the second portion of fuel 132 from the fuel supply 122 into gaseous fuel. For example, rather than relying on an atomizer, or the like, and the heat of an exhaust stream 130, as described with respect to FIG. 2, a heating element 154 could be employed to transform the second portion of fuel 132 into gaseous fuel. As such, the gaseous fuel output 156 and the fuel conversion unit output 126 could then be allowed to pass into the exhaust stream 130 via the transport system 134. Further control may be enabled through the utilization of the contemplated controller 158 or the like. Such a controller could be used to manipulate the quantity of fuel allowed to enter the exhaust path 128 and the fuel conversion unit 124. As such, the degree of NO_xreduction may be controlled.
A technical contribution for the disclosed method and apparatus is that it provides for a controller implemented control of NO_xemissions.
The invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.

Claims

1. An apparatus comprising:

a fuel conversion unit configured to convert a first portion of fuel from a fuel tank into a set of reducing agents, wherein the set of reducing agents comprise hydrogen;

an exhaust path configured to convey an exhaust stream away from an engine, wherein the exhaust stream comprises nitrogen oxides;

a transport system configured to transport each of a second portion of fuel from the fuel tank and the set of reducing agents into the exhaust path such that a mixture is formed, wherein the mixture comprises the second portion of fuel, the set of reducing agents, and the exhaust stream; and

a catalytic material positioned within the exhaust path and configured to aid in a conversion of at least a portion of the nitrogen oxides in the mixture into nitrogen, wherein the conversion reduces a quantity of the nitrogen oxides in the exhaust stream.

2. The emission reduction apparatus of claim 1 further comprising a control component configured to adjust a rate at which the fuel conversion unit converts the first portion of fuel into the set of reducing agents such that a quantity of the hydrogen produced is manipulated.

3. The emission reduction apparatus of claim 1 wherein the first and second portion of fuel is a first and second portion of diesel fuel, respectively.

4. The emission reduction apparatus of claim 1 further comprising a state conversion unit configured to transform the second portion of fuel into a gas before the second portion of fuel enters into the exhaust stream.

5. The emission reduction apparatus of claim 1 further comprising an oxygen intake configured to transport oxygen into the fuel conversion unit to initiate catalytic partial oxidation to convert the first portion of fuel from the fuel tank into the set of reducing agents, wherein the hydrogen in the mixture increases a rate of the conversion of the mixture over the catalytic material within the exhaust path.

6. The emission reduction apparatus of claim 1 wherein the fuel conversion unit is configured to initiate auto-thermal cracking to convert the first portion of fuel from the fuel tank into the set of reducing agents, wherein the set of reducing agents further comprises secondary hydrocarbons and carbon monoxide.

7. The emission reduction apparatus of claim 6 wherein the fuel conversion unit is further configured to convert at least a portion of the secondary hydrocarbons into hydrogen such that a rate of the conversion of the mixture is increased, wherein the conversion of the mixture is aided by the catalytic material.

8. The emission reduction apparatus of claim 1 further comprising a water gas shift catalyst to convert a portion of the reducing agents from the fuel conversion unit into additional hydrogen.

9. A method comprising:

converting a first portion of fuel from a fuel supply to a plurality of first reductants;

passing the plurality of first reductants into an exhaust stream, wherein the exhaust stream comprises a plurality of nitrogen oxides;

transforming a second portion of liquid fuel from the fuel supply into a gaseous fuel; and

passing the plurality of first reductants, the exhaust stream, and the gaseous fuel over a selective catalytic reduction (SCR) component such that a portion of the plurality of nitrogen oxides is converted into nitrogen.

10. The method of claim 9 wherein the first portion of fuel from the fuel supply is converted to the plurality of first reductants by passing the first portion from the fuel supply over a fuel conversion unit.

11. The method of claim 10 further comprising:

passing a quantity of oxygen over the fuel conversion unit such that hydrogen is produced;

regulating the quantity of oxygen passing over the fuel conversion unit such that the production of the hydrogen is regulated; and

regulating the first portion of fuel from the fuel supply passing through the fuel conversion unit such that the production of the hydrogen is regulated.

12. The method of claim 9 further comprising regulating the transformation of the second portion of liquid fuel from the fuel supply into the gaseous fuel such that the conversion of the plurality of nitrogen oxides into nitrogen is regulated.

13. The method of claim 9 further comprising ceasing the conversion of the first portion of fuel to the plurality of first reductants based on one of an exhaust stream temperature and a nitrogen oxide concentration in the exhaust stream.

14. The method of claim 9 wherein converting the first portion of fuel from the fuel supply to the plurality of first reductants comprises implementing at least one of auto thermal cracking and catalytic partial oxidation.

15. The method of claim 9 wherein the first and second portion of fuel is diesel fuel.

16. The method of claim 9 further comprising:

converting a portion of the first portion of fuel into hydrogen; and

passing the hydrogen over the SCR component to increase a reaction rate at which the portion of the plurality of nitrogen oxides is converted into the nitrogen.

17. The method of claim 16 further comprising increasing a temperature of a catalyst in a fuel conversion unit to increase production of the hydrogen.

18. A method comprising:

acquiring a first portion of fuel from an engine supply fuel tank;

converting the first portion of fuel into at least a plurality of reductants;

mixing the plurality of reductants and a quantity of gaseous fuel from a second portion of fuel from the engine supply fuel tank with an engine exhaust containing nitrogen oxides to create a first mixture comprising the plurality of reductants, the quantity of gaseous fuel, and the engine exhaust; and

catalyzing a chemical reaction in the first mixture over a selective catalytic reduction (SCR) unit, wherein the chemical reaction reduces at least a portion of the nitrogen oxides in the first mixture to nitrogen.

19. The method of claim 18 wherein the at least a plurality of reductants comprises a quantity of hydrogen, and wherein the quantity of hydrogen increases a rate at which the nitrogen oxides reduce over the SCR unit.

20. The method of claim 19 further comprising at least one of:

adjusting the quantity of hydrogen produced during the conversion of the first portion of the fuel such that a rate of the reduction of the at least a portion of the nitrogen oxides in the first mixture to the nitrogen is regulated; and

adjusting the quantity of gaseous fuel mixed with the plurality of reductants and the exhaust stream such that the rate of the reduction of the at least a portion of the nitrogen oxides in the first mixture to the nitrogen is regulated.

21. The method of claim 18 wherein the engine supply fuel tank holds fuel that contains diesel.

22. The method of claim 18 wherein the plurality of reductants comprises secondary hydrocarbons.

23. The method of claim 22 further comprising:

converting the secondary hydrocarbons to hydrogen; and

mixing the hydrogen with the first mixture to increase a rate at which the nitrogen oxides reduce over the SCR unit.