US20030200742A1 - Apparatus and method for regenerating a particulate filter of an exhaust system of an internal combustion engine - Google Patents

Abstract

An apparatus for removing particulate soot from an exhaust gas of an internal combustion engine includes a particulate filter assembly having a catalyst and a soot filter positioned downstream of the catalyst for trapping soot particles therein. Hydrogen gas is introduced into the exhaust gas at a location upstream of the catalyst. The catalyst catalyzes an exothermic oxidation reaction between the hydrogen gas and oxygen in the exhaust gas. Heat from this exothermic oxidation reaction is transferred to the soot filter thereby igniting the soot particles trapped therein. A method for regenerating a particulate filter assembly is also disclosed.

Description

• This application claims priority to U.S. Provisional Patent Application No. 60/375,134 entitled “Apparatus and Method for Regenerating a Particulate Filter of an Exhaust System of an Internal Combustion Engine” filed on Apr. 24, 2002 by Rudolf M. Smaling, the disclosure of which is hereby incorporated by reference.[0001]
FIELD OF THE DISCLOSURE
• The present disclosure relates generally to an emission abatement device, and more particularly to a particulate filter assembly for reducing soot emissions.[0002]
BACKGROUND
• Untreated internal combustion engine emissions include various effluents such as NO[0003]_X(oxides of nitrogen), hydrocarbons, and carbon monoxide, for example. Moreover, the untreated emissions from certain types of internal combustion engines, such as diesel engines, also include particulate carbon-based soot. Federal regulations relating to soot emission standards are becoming more and more rigid thereby furthering the need for devices and/or methods which remove soot from engine emissions. For example, the amount of soot produced and/or released by an engine system can be reduced by fuel injection rate shaping and/or by the use of an emission abatement device such as a filter or trap. Such a filter or trap is periodically regenerated in order to remove the soot therefrom. The filter or trap may be regenerated by use of a burner or electric heater to burn the soot off of the filter.
SUMMARY
• According to the present disclosure, an apparatus is provided for removing particulate soot from an exhaust gas of an internal combustion engine. The apparatus includes a particulate filter assembly having a catalyst and a soot filter positioned downstream of the catalyst for trapping soot particles therein. Hydrogen gas is introduced into the exhaust gas at a location upstream of the catalyst. The catalyst catalyzes an exothermic reaction between the hydrogen gas and a gas containing oxygen. Heat from this exothermic reaction is transferred to the filter thereby igniting the soot particles trapped therein.[0004]
• In one exemplary embodiment, the source of hydrogen gas is embodied as a hydrogen generator for generating hydrogen to be introduced into the exhaust gas prior to entering the particulate filter assembly.[0005]
• In one implementation of this exemplary embodiment, the hydrogen generator is embodied as a fuel reformer which reforms a hydrocarbon fuel into a hydrogen-rich gas.[0006]
• In another implementation of this exemplary embodiment, the fuel reformer is embodied as a plasmatron fuel reformer.[0007]
• Further according to the present disclosure, a method for regenerating a soot filter is provided. The method includes generating a reformate gas and introducing the reformate gas into an exhaust gas from an internal combustion engine. The exhaust gas and the reformats gas are advanced into contact with a catalyst that catalyzes an exothermic reaction between the reformate gas and the exhaust gas. Heat generated from the reaction of the reformate gas and exhaust gas with the catalyst ignites the soot present in the soot filter.[0008]
BRIEF DESCRIPTION OF THE DRAWINGS
• The detailed description particularly refers to the accompanying figures in which:[0009]
• FIG. 1 is a block diagram which demonstrates the concepts of the present disclosure for treating exhaust gases from an internal combustion engine;[0010]
• FIG. 2 is a block diagram of a specific exemplary implementation of the concepts of FIG. 1;[0011]
• FIG. 3 is a diagrammatic cross sectional view of a particulate filter assembly for use with the concepts disclosed herein;[0012]
• FIG. 4 is a block diagram similar to FIG. 2, but showing the particulate filter assembly positioned downstream of a supplemental emission abatement device that partially treats exhaust gases prior to advancement of the gases through the particulate filter assembly; and[0013]
• FIG. 5 is a block diagram similar to FIG. 2, but showing a pair of particulate filter assemblies arranged in a parallel arrangement.[0014]
DETAILED DESCRIPTION OF THE DRAWINGS
• Referring now to FIG. 1, there is shown an[0015]emission abatement device10 for removing soot particles from the exhaust gases of aninternal combustion engine12. Theemission abatement device10 includes acatalyst14 and asoot filter16. Theoxidation catalyst14 is positioned upstream of thesoot filter16. Theoxidation catalyst14 may be spaced apart from thesoot filter16 by a predetermined distance, may be positioned in contact with thesoot filter16, or may even be fabricated as a common structure with the soot filter16 (e.g., a common structure having a catalyst portion positioned upstream of a filter portion).
• The[0016]oxidation catalyst14 is configured to catalyze an oxidation reaction between a gaseous component containing oxygen and hydrogen gas. Specifically, when hydrogen gas is advanced into contact with theoxidation catalyst14 in the presence of a gaseous component containing oxygen, the oxidation catalyst catalyzes an oxidation reaction which converts the hydrogen gas and a portion of the oxygen into, amongst other things, water.
• This oxidation reaction is highly exothermic, and, as a result, produces heat that is transferred to the downstream-positioned[0017]soot filter16. The heat, which may illustratively be in the range of 600-650 degrees Celsius, raises the temperature of the soot particles trapped in thefilter16 to a temperature sufficient to ignite the particles thereby regenerating thefilter16. It should be appreciated that such regeneration of thesoot filter16 may be self-sustaining once initiated by heat from the exothermic reaction catalyzed by theoxidation catalyst14. Specifically, once thesoot filter16 is heated to a temperature at which the soot particles trapped therein begin to ignite, the ignition of an initial portion of soot particles trapped therein can cause the ignition of the remaining soot particles much in the same way a cigar slowly burns from one end to the other. In essence, as the soot particles “burn,” an amount of heat is released in the “burn zone.” Locally, the soot layer (in the burn zone) is now much hotter than the immediate surroundings. As such, heat is transferred to the as yet un-ignited soot layer downstream of the burn zone. The energy transferred may be sufficient to initiate oxidation reactions that raise the un-ignited soot to a temperature above its ignition temperature. As a result of this, heat from theoxidation catalyst14 may only be required to commence the regeneration process of the soot filter16 (i.e., begin the ignition process of the soot particles trapped therein).
• In an illustrative embodiment, the[0018]soot filter16 may have a catalytic material such as, for example, a precious metal catalytic material, disposed on the surfaces thereof. The amount of catalytic material disposed on thefilter16 may be varied to fit the needs of a given system design. In one illustrative implementation, thesoot filter16 may only use about 3% of the amount of catalytic material (e.g., precious metals) that is present on a typical oxidation catalyst. In such a configuration (i.e., use of a catalyzed filter16), the ignition temperature of the soot particles trapped in thefilter16 is reduced. Indeed, depending on, amongst other things, the amount of catalytic material disposed on thefilter16 and the amount of accumulated soot particles, the ignition temperature of the soot particles may be lowered to an ignition temperature of between 300-600 degrees Celsius. In other exemplary implementations, the soot ignition temperature may be lowered to a temperature in the range of 300-550 degrees Celsius, more particularly in the range of 300-450 degrees Celsius, and even more particularly in the range of 300-350 degrees Celsius.
• It should be appreciated that in addition to the aforedescribed use of the[0019]oxidation catalyst14 to regenerate thesoot filter16, theoxidation catalyst14 may also function as an oxidation catalyst for removing certain compounds from the exhaust gases of theengine12. In particular, theoxidation catalyst14 may be configured to catalyze, in the presence of heat supplied by the exhaust gasses (e.g., 250 degrees Celsius), an oxidation reaction which converts, for example, hydrocarbons (HC) and carbon monoxide (CO) into water vapor, carbon dioxide, and other less toxic gases. Hence, theemission abatement device10 may be used to not only remove soot from the engine's exhaust gases, but also other compounds as well (e.g., HC, CO).
• As with conventional aftertreatment configurations, such functionality of an[0020]oxidation catalyst14 is generally not achieved until the exhaust gases produced by theengine12 become hot enough to heat theoxidation catalyst14 to its light off temperature (e.g., approximately 250 degrees Celsius). Hence, during startup, emissions of such compounds can reach undesirable levels since compounds can pass untreated through theoxidation catalyst14 prior to thecatalyst14 reaching its light off temperature. However, hydrogen gas may be supplied to theoxidation catalyst14 during startup to instantaneously, or near instantaneously, light off theoxidation catalyst14. Specifically, during startup of theengine12, hydrogen gas may be advanced to the face of theoxidation catalyst14 thereby quickly lighting off thecatalyst14 in a much shorter period of time than if thecatalyst14 had to be lighted off by heat from the engine's exhaust gases passing therethrough. Such instantaneous, or near instantaneous, light off of thecatalyst14 prevents the release of untreated compounds during engine startup that thecatalyst14 is otherwise designed to treat.
• As described above, the[0021]oxidation catalyst14 catalyzes an exothermic reaction between a gaseous component containing oxygen and hydrogen. Generally, exhaust gases from theinternal combustion engine12 may function as the source of oxygen. In particular, suitable amounts of oxygen for sustaining such an oxidation reaction exist in the exhaust gases of an internal combustion engine without the introduction of additional oxygen. However, to fit the needs of a given design or implementation, supplemental oxygen may be introduced into the engine's exhaust gases prior to advancement thereof into theemission abatement device10. One way to do this is by use of an air inlet (not shown) positioned upstream of theoxidation catalyst14 for introducing a desired amount of air into the engine's exhaust gases prior to advancement thereof into contact with theoxidation catalyst14.
• As shown in FIG. 1, hydrogen gas is supplied from a source of[0022]hydrogen gas18. The source ofhydrogen gas18 may be embodied as a number of different types of devices. For example, the source of hydrogen gas may be embodied as tank of hydrogen gas (i.e., “bottled” hydrogen gas). Alternatively, the source ofhydrogen gas18 may be embodied as a hydrogen generator that generates hydrogen from other compounds. One example of a hydrogen generator is a device that produces hydrogen gas via electrolysis. Other examples of a hydrogen generator include fuel reformers that reform (i.e., convert) hydrocarbon fuels into a reformate gas that includes, amongst other things, hydrogen gas. Examples of such fuel reformers include, amongst other types, catalytic fuel reformers and thermal fuel reformers.
• One additional type of fuel reformer, which is particularly useful as the source of[0023]hydrogen gas18, is a plasma-fuel reformer, or “plasmatron”. A plasmatron uses plasma to convert hydrocarbon fuel into a reformate gas which is rich in, amongst other things, hydrogen gas and carbon monoxide. Systems including plasmatrons are disclosed in U.S. Pat. No. 5,425,332 issued to Rabinovich et al.; U.S. Pat. No. 5,437,250 issued to Rabinovich et al.; U.S. Pat. No. 5,409,784 issued to Bromberg et al.; and U.S. Pat. No. 5,887,554 issued to Cohn, et al., the disclosures of each of which is hereby incorporated by reference. Additional examples of systems including plasmatrons are disclosed in copending U.S. patent application Ser. No. 10/158,615 entitled “Low Current Plasmatron Fuel Converter Having Enlarged Volume Discharges” which was filed on May 30, 2002 by A. Rabinovich, N. Alexeev, L. Bromberg, D. Cohn, and A. Samokhin, along with copending U.S. patent application Ser. No. ______ entitled “Plasmatron Fuel Converter Having Decoupled Air Flow Control” which was filed on Apr. 11, 2003 by A. Rabinovich, N. Alexeev, L. Bromberg, D. Cohn, and A. Samokhin, the disclosures of both of which are hereby incorporated by reference.
• In such an exemplary implementation, a plasmatron may be operated to reform the same hydrocarbon fuel being combusted by the engine[0024]12 (such as gasoline or diesel fuel, for example). Alternatively, a plasmatron may be operated to reform a type of hydrocarbon fuel that is distinct from the engine's fuel. In either case, a plasmatron may be operated to produce only the amount of hydrogen-rich reformate gas that is needed by theemission abatement device10 thereby eliminating the need to store additional quantities of hydrogen gas. As such, a plasmatron may be operated to produce hydrogen-rich reformate gas “on demand”.
• More specific exemplary embodiments of the concepts of the present disclosure will now be described in regard to FIGS.[0025]2-5. The exemplary embodiments hereinafter described in regard to FIGS.2-5 relate to the use of a specific fuel reformer, a plasmatron, along with a specific type of internal combustion engine, a diesel engine. It should be appreciated that while the specific exemplary embodiments described in regard FIGS.2-5 have significant advantages, such embodiments are merely descriptive in nature, and should not be construed as limiting to the claims in any way absent specific language in the claims to the contrary.
• Referring now to FIG. 2, there is shown an emission abatement system for use in conjunction with a[0026]diesel engine50. The system includes anemission abatement device52 and aplasmatron54. Theplasmatron54 convertshydrocarbon fuel60 into areformate gas58 that is rich in, amongst other things, hydrogen and carbon monoxide. Thehydrocarbon fuel60 is supplied by afuel tank62 to both theengine50 and theplasmatron54. As shown in FIGS. 2 and 3,air64 is also input into theplasmatron54. A fuel input mechanism, such as a fuel injector, injectshydrocarbon fuel60 andair64 into a plasma arc created by theplasmatron54. The fuel injector may be any type of fuel injection mechanism that produces a desired mixture offuel60 andair64 and thereafter injects such a mixture into the plasma-generating portion of theplasmatron54. In certain configurations, it may be desirable to atomize the fuel-air mixture prior to, or during, injection of the mixture into the plasma-generating portion of theplasmatron54. Such fuel injector assemblies (i.e., injectors which atomize the fuel mixture) are commercially available. Moreover, additional amounts ofair64 may also be input into theplasmatron54 by use of, for example, an air inlet valve (not shown) to allow for the creation of a desired air-to-fuel ratio within theplasmatron54.
• As shown in FIG. 2, the[0027]hydrocarbon fuel60 supplied to theplasmatron54 is generally the same hydrocarbon fuel being combusted by the diesel engine50 (i.e., diesel fuel). Alternatively, thehydrocarbon fuel60 supplied to theplasmatron54 may be a type of hydrocarbon fuel that is distinct from the engine's fuel.
• The hydrogen-[0028]rich reformate gas58 generated by theplasmatron54 is supplied to theemission abatement device52 to regenerate thedevice52. Specifically, as shown in FIG. 3, theemission abatement device52 may be configured as aparticulate filter assembly72 having acatalyst74 and asoot particulate filter76 positioned downstream fromcatalyst74. Thecatalyst74 may be spaced apart from thesoot filter16 by a predetermined distance (as shown in FIG. 3), may be positioned in contact with thesoot particulate filter76, or may even be fabricated as a common structure with the soot particulate filter76 (e.g., a common structure having a catalyst portion positioned upstream of a filter portion).
• The[0029]catalyst74 may be embodied as any type of catalyst that is configured to catalyze the herein described reactions. In one exemplary embodiment, thecatalyst74 is embodied as substrate having a precious metal or other type of catalytic material disposed thereon. Such a substrate may be constructed of ceramic, metal, or other suitable material. The catalytic material may be, for example, embodied as platinum, rhodium, palladium, including combinations thereof, along with any other similar catalytic materials.
• The[0030]soot particulate filter76, on the other hand, traps soot or other particulates present in the untreatedexhaust gases66 from thediesel engine50. Thesoot particulate filter76 may be embodied as any known exhaust particulate filter such as a “deep bed” or “wall flow” filter. Deep bed filters may be embodied as metallic mesh filters, metallic or ceramic foam filters, ceramic fiber mesh filters, and the like. Wall flow filters, on the other hand, may be embodied as a cordierite or silicon carbide ceramic filter with alternating channels plugged at the front and rear of the filter thereby forcing the gas advancing therethrough into one channel, through the walls, and out another channel.
• Similarly to as described above in regard to the[0031]soot filter16, thesoot particulate filter76 may also be impregnated with a catalytic material such as, for example, a precious metal catalytic material. In such a configuration, the ignition temperature of the soot trapped in thefilter76 may be significantly lowered thereby lowering the amount of heat that is required from the exothermic reactions at the face of thecatalyst74. The amount of catalytic material disposed on thesoot particulate filter76 may be varied to fit the needs of a given system design. For example, in one illustrative implementation, thesoot particulate filter76 may only use about 3% of the amount of catalytic material (e.g., precious metals) that is present on a typical oxidation catalyst. In such a configuration (i.e., use of a catalyzed filter76), the ignition temperature of the soot particles trapped in thefilter76 is reduced. Indeed, depending on, amongst other things, the amount of catalytic material disposed on thefilter76 and the amount of accumulated soot particles, the ignition temperature of the soot particles may be lowered to an ignition temperature of between 300-600 degrees Celsius. In other exemplary implementations, the soot ignition temperature may be lowered to a temperature in the range of 300-550 degrees Celsius, more particularly in the range of 300-450 degrees Celsius, and even more particularly in the range of 300-350 degrees Celsius.
• [0032]Reformate gas58 from theplasmatron54 is advanced into contact with thecatalyst74 to catalyze an oxidation reaction between the oxygen in theexhaust gas66 of theengine50 and thereformate gas58. Specifically, when thereformate gas58 is advanced into contact with thecatalyst74 in the presence ofexhaust gas66, thecatalyst74 catalyzes an oxidation reaction which converts the hydrogen gas present in thereformate gas58 and the oxygen present in theexhaust gases66 into, amongst other things, water. Moreover, thecatalyst74 catalyzes an oxidation reaction which converts the carbon monoxide present in thereformate gas58 and the oxygen present in theexhaust gases66 into carbon dioxide. Both of these oxidation reactions are highly exothermic, and, as a result, produce heat that is transferred to the downstream-positionedsoot particulate filter76. The heat, which may illustratively be in the range of 600-650 degrees Celsius, ignites soot particles trapped in theparticulate filter76 thereby regenerating thefilter76.
• It should be appreciated that in the case of lowering the ignition temperature of the soot particles by use of a catalyzed[0033]soot filter76, the amount of heat required from the exothermic reactions catalyzed by thecatalyst74 is reduced. In particular, if the ignition temperature of the soot particles trapped in thefilter76 is reduced by use of a catalytic filter design, the amount of heat required from the upstream oxidation reactions at thecatalyst74 is likewise reduced. As such, the design of thecatalyst74 may be varied (e.g., use of different, perhaps less expensive, catalyst materials) to produce only the amount of heat needed to ignite the soot particles trapped in the catalyzedfilter76. Alternatively, the amount or type of reformate gas may also be varied to produce only the amount of heat needed to ignite the soot particles trapped in the catalyzedfiler76.
• It should be appreciated that such regeneration of the[0034]soot filter76 may be self-sustaining once initiated by heat from the exothermic reaction catalyzed by thecatalyst74. Specifically, once thesoot particulate filter76 is heated to a temperature at which the soot particles trapped therein begin to ignite, the ignition of an initial portion of soot particles trapped therein can sustain the ignition of the remaining soot particles much in the same way a cigar slowly burns from one end to the other. In particular, similarly to as described herein in regard to thesoot filter16 of FIG. 1, as the soot particles trapped in thefilter76 “burn,” an amount of heat is released in the “burn zone.” Locally, the soot layer (in the burn zone) is now much hotter than the immediate surroundings. As such, heat is transferred to the as yet un-ignited soot layer downstream of the burn zone. The energy transferred may be sufficient to initiate oxidation reactions that raise the un-ignited soot to a temperature above its ignition temperature. As a result of this, heat from thecatalyst74 may only be required to commence the regeneration process of the soot particulate filter76 (i.e., begin the ignition process of the soot particles trapped therein). Hence, during regeneration of thefilter76, theplasmatron74 may be operated to supply a predetermined amount ofreformate gas58 to thecatalyst74 to ignite an initial portion of the soot particulate trapped in thesoot particulate filter76, and thereafter cease generation of thereformate gas58 once the regeneration process within thesoot particulate filter76 becomes self-sustaining.
• It should be appreciated that in addition to the aforedescribed use of the[0035]catalyst74 to regenerate thesoot particulate filter76, thecatalyst74 may also function as an oxidation catalyst for removing certain compounds from theexhaust gases66 of thediesel engine50. In particular, thecatalyst74 may be configured to catalyze, in the presence of heat supplied by the exhaust gasses (e.g., approximately 250 degrees Celsius), an oxidation reaction which converts, for example, hydrocarbons (HC) and carbon monoxide (CO) into water vapor, carbon dioxide, and other less toxic gases.
• As with conventional aftertreatment configurations, such functionality of an oxidation catalyst is generally not achieved until the exhaust gases produced by the[0036]engine50 become hot enough to heat the catalyst to its light off temperature (e.g., approximately 250 degrees Celsius). Hence, during engine startup, emissions of such compounds can reach undesirable levels since such compounds can pass untreated through the catalyst prior to the catalyst reaching its light off temperature. However, theplasmatron54 may be operated during engine startup to instantaneously, or near instantaneously, light off thecatalyst74. Specifically, during startup of theengine50, theplasmatron54 may be operated to providereformate gas58 to thecatalyst74 thereby quickly lighting off thecatalyst74 in a much shorter period of time than if thecatalyst74 had to be lighted off by heat from theexhaust gases66 passing therethrough. Such instantaneous, or near instantaneous, light off of the catalyst prevents the release of untreated compounds during engine startup that the catalyst is otherwise designed to treat.
• Referring now to FIG. 3, the[0037]particulate filter assembly72 is shown in greater detail. Thecatalyst74 and thefilter76 of theparticulate filter assembly72 are housed in aninterior chamber96 of ahousing78. Thehousing78 has afirst end80 coupled to anexhaust pipe82, and asecond end84 coupled to either anotherexhaust pipe86 that is open to the atmosphere or coupled to an additional exhaust system component (not shown) positioned downstream of theparticulate filter assembly72. Thefirst end80 of thehousing78 defines anexhaust gas inlet90, whereas thesecond end84 of thehousing78 defines anexhaust gas outlet92. Hence,exhaust gases66 from thediesel engine50 enter thehousing78 through theexhaust gas inlet90, are advanced through thecatalyst74 and thesoot particulate filter76, and then are exhausted from thehousing78 via theexhaust gas outlet92.
• The[0038]particulate filter assembly72 has aninlet88 for receivingreformate gas58 from theplasmatron14. The inlet may be configured as an orifice that is defined in the walls of thehousing78, or, alternatively, may include a tube, coupling assembly, or other structure which extends through the wall of thehousing78. In addition, if thereformate gas58 is introduced upstream of thefirst end80 of thehousing78, theexhaust gas inlet90 of thehousing78 functions as the reformate gas inlet of theparticulate filter assembly72.
• The[0039]plasmatron54 is fluidly coupled to the reformate gas inlet associated with theparticulate filter assembly72. In particular, a first end of afluid line94 is coupled to the outlet of theplasmatron54, whereas a second end of thefluid line94 extends through, or is coupled to, thegas inlet88 such thatreformate gas58 may be advanced into thechamber96 of thehousing78. In such a manner,reformate gas58 from theplasmatron54 may be introduced into the exhaust gases of theengine50 prior to advancement thereof into contact with thecatalyst74.
• A[0040]control valve98 is utilized to control the flow ofreformate gas58 from theplasmatron54 to theparticulate filter assembly72. Thecontrol valve98 is under the control of acontroller100. Thecontroller100 also controls the operation of theplasmatron54. Specifically, thecontroller100 is coupled to theplasmatron54 via asignal line102 to selectively actuate and deactuate theplasmatron54 thereby selectively controlling the production ofreformate gas58.
• It should be appreciated that in certain design configurations, the[0041]controller100 may control the flow ofreformate gas58 to theparticulate filter assembly72 without the use of thecontrol valve98. Specifically, one particularly useful feature of theplasmatron54 is its relatively rapid response to requests for changes in the production of reformate gas. Indeed, unlike other types of fuel reformers (e.g., catalytic fuel reformers or thermal fuel reformers), the amount of reformate gas produced by theplasmatron54 may be quickly increased or decreased to fit the needs of a given situation. As such, in lieu of thecontrol valve98, the algorithms executed by thecontroller100 may provide for relatively fast actuation and deactuation of theplasmatron54 thereby eliminating the need for thecontrol valve98.
• As shown in FIG. 3, the[0042]controller100 is also electrically coupled to a pair ofpressure sensors104 via asignal line106. Thepressure sensors106 may be utilized to sense the pressure difference across theparticulate filter assembly72 in order to determine when thefilter assembly72 requires regeneration. Specifically, when the pressure drop across theparticulate filter assembly72 increases to a predetermined value, thecontroller100 commences the filter regeneration process. It should be appreciated that while shown in FIG. 3 as utilizing two pressure sensors, a single pressure sensor on either side offilter assembly72 may be utilized, if desired. In such a configuration, thecontroller100 would monitor when the pressure sensed by the single pressure sensor exceeded a predetermined upper threshold or was below a predetermined lower threshold, as opposed to monitoring the pressure drop across thefilter assembly72.
• As shown in FIGS. 2 and 3,[0043]reformate gas58 from theplasmatron14 is introduced into theexhaust gases66 from thediesel engine50 at a location upstream of thecatalyst74. In this way, the gaseous compound containing hydrogen and carbon monoxide (e.g., reformate gas from the plasmatron14) is introduced into the gaseous compound containing oxygen (e.g., exhaust gas) prior to advancement thereof into contact with thecatalyst74. As such, when the gases contact the catalytic substrate, an exothermic reaction hot enough to light off thesoot particulate filter76 is initiated.
• In operation,[0044]exhaust gases66 from thediesel engine50 are advanced through theparticulate filter assembly72. As described above, during such advancement ofexhaust gases66 through theparticulate filter assembly72, thecatalyst74 catalyzes a reaction which removes the hydrocarbons and carbon monoxide from theexhaust gases66 by converting such hydrocarbons and carbon monoxide into water vapor, carbon dioxide, and other less toxic gases. During startup of theengine50, thecontroller100 may actuate the plasmatron54 (and open theflow valve98, if such a valve is used) to generate and deliverreformats gas58 to thecatalyst74 so as to light off thecatalyst74 contemporaneously with startup of theengine50 thereby preventing the escape of certain untreated emissions through thecatalyst74 prior to light off of thecatalyst74 by the heat from theexhaust gases66. However, once thecatalyst74 has achieved its light off temperature (e.g., 250 degrees Celsius), thecontroller100 deactuates the plasmatron54 (and closes theflow valve98, if such a valve is used) such that no additionalreformate gas58 is produced and delivered to thecatalyst74.
• During advancement of the[0045]exhaust gases66 from theengine50 through theparticulate filter assembly72, soot particles present in theexhaust gases66 are trapped by thesoot particulate filter76. Thecontroller100 maintains theplasmatron54 in its deactuated mode of operation (i.e., such that noreformate gas58 is produced) until thecontroller100 determines that theparticulate filter assembly72 needs to be regenerated. Specifically, thecontroller100 monitors the output signals from thepressure sensors104 on thesignal line106 to determine if the buildup of soot in thesoot particulate filter76 has reached a predetermined level. Once thecontroller100 determines that thesoot particulate filter76 is in need of regeneration, the controller actuates the plasmatron54 (and opens theflow valve98, if such a valve is used) so as to generate and deliverreformate gas58 into contact with thecatalyst74 to catalyze oxidation reactions between the oxygen in theexhaust gas66 and the hydrogen and carbon monoxide in thereformate gas58. These highly exothermic oxidation reactions produce heat that is transferred to the downstream-positionedsoot particulate filter76. This heat, which may be illustratively in the range of 600-650 degrees Celsius (or less in the case of use of a catalyzed soot particulate filter76), ignites soot particles trapped in theparticulate filter76 thereby regenerating thefilter76.
• As described herein, regeneration of the[0046]soot filter76 may be self-sustaining once initiated by heat from the exothermic reaction catalyzed by thecatalyst74. Hence, once thesoot particulate filter76 is heated to its a temperature at which the soot particles trapped therein begin to ignite, and the soot ignition process is self-sustained in thefilter76, thecontroller100 deactuates the plasmatron54 (and closes theflow valve98, if such a valve is used) such that no additionalreformate gas58 is produced and delivered to thecatalyst74. Thecontroller100 then monitors the output from thepressure sensors104 to determine when theparticulate filter assembly72 is again in need of regeneration.
• As described herein, the[0047]catalyst74 ofparticulate filter assembly72 may be configured to burn (i.e., convert) hydrocarbons and carbon monoxide and thus operates as a catalytic converter to remove such effluents from exhaust gases66 (in addition to functioning as a trap to trap soot particles in filter76). However, it should be appreciated thatparticulate filter assembly72 may be used in, for example, a series arrangement with anotheremission abatement device108, as shown in FIG. 4. In such a manner,exhaust gases66 from theengine50 may be passed through theemission abatement device108 to remove, for example, hydrocarbons (HC), oxides of nitrogen (NO_X), oxides of sulfur (SO_X), and/or carbon monoxide (CO) from theexhaust gases66. To do so, theemission abatement device108 may be embodied as a catalytic converter or a trap or other similar device which removes desired compounds from the engine'sexhaust gases66.
• Soot particles in the partially treated[0048]exhaust gases110 which exit theemission abatement device108 are then trapped by thefilter76 of theparticulate filter assembly72 as described above. When thefilter76 needs to be regenerated, theplasmatron54 may be actuated to producereformate gas58 in the manner described above.
• It should be appreciated that when the[0049]particulate filter assembly72 is used in conjunction with an additionalemission abatement device108, thecatalyst74 may still be configured to remove certain compounds from the engine'sexhaust gases66. In particular, theemission abatement device108 may be used to remove a first number of compounds from the engine'sexhaust gases66, whereas thecatalyst74 is configured to remove a second number of compounds from theexhaust gases66. Alternatively, thecatalyst74 may be configured to perform only the function of catalyzing the reactions necessary to regenerate thesoot filter76 with all other emission abatement functions being performed by theemission abatement device108 or other devices.
• It should be appreciated that reformate gas from the[0050]plasmatron54 may also be used to light off the catalysts (not shown) associated with theemission abatement device108 during startup in a similar manner to as described herein in regard to thecatalyst74. In such a case, theplasmatron54 would be fluidly coupled to an inlet (not shown) associated withemission abatement device108 via a fluid line (not shown) to provide for the advancement ofreformate gas58 from theplasmatron54 to thedevice108.
• As shown in FIG. 5, it is also within the scope of this disclosure for a pair of[0051]particulate filter assemblies72 to be used in a parallel arrangement. Adiverter valve112, which is under the control of thecontroller100, selectively diverts the flow ofexhaust gases66 between the twoparticulate filter assemblies72. For example,exhaust gases66 from theengine50 may be routed through one of theparticulate filter assemblies72 while theother assembly72 is maintained “offline.” The offlineparticulate filter assembly72 may then be regenerated by use of theplasmatron54 as described above. Once thesoot filter76 of the offlineparticulate filter assembly72 has been regenerated, the position of thediverter valve112 may be switched such thatexhaust gases66 from theengine50 are routed through the newly regeneratedparticulate filter assembly72, while the otherparticulate filter assembly72 is offline for soot filter regeneration.
• While the disclosure is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and has herein be described in detail. It should be understood, however, that there is no intent to limit the disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.[0052]
• There are a plurality of advantages of the present disclosure arising from the various features of the apparatus and methods described herein. It will be noted that alternative embodiments of the apparatus and methods of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of an apparatus and method that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the present disclosure.[0053]

Claims (45)

1. An apparatus for removing particulate soot from an exhaust gas of an internal combustion engine, comprising:

a source of hydrogen gas,

a catalyst configured to catalyze an exothermic oxidation reaction between the hydrogen gas and a gaseous component comprising oxygen, and

a soot filter positioned proximate to the catalyst, wherein heat generated by the exothermic oxidation reaction is transferred to the soot filter.

2. The apparatus ofclaim 1, further comprising a housing, wherein the catalyst and the soot filter are housed in the housing.

3. The apparatus ofclaim 1, wherein the heat generated by the exothermic reaction obtains a temperature of between approximately 600 degrees Celsius and approximately 650 degrees Celsius.

4. The apparatus ofclaim 1, wherein the catalyst is disposed on a ceramic or metallic substrate.

5. The apparatus ofclaim 1, wherein the source of hydrogen gas comprises a fuel reformer.

6. The apparatus ofclaim 5, wherein the fuel reformer comprises a plasma fuel reformer.

7. The apparatus ofclaim 1, wherein the soot filter has a catalytic material disposed thereon.

8. The apparatus ofclaim 7, wherein the heat generated by the exothermic reaction obtains a temperature of between approximately 300 degrees Celsius and approximately 600 degrees Celsius.

9. The apparatus ofclaim 7, wherein the heat generated by the exothermic reaction obtains a temperature of between approximately 300 degrees Celsius and approximately 350 degrees Celsius.

10. An apparatus for removing particulate from an exhaust gas of an internal combustion engine, comprising:

a hydrogen generator configured to produce hydrogen gas, and

a particulate filter assembly having a catalyst and a soot filter, the particulate filter assembly configured to receive (i) hydrogen gas from the hydrogen generator, and (ii) the exhaust gas from the internal combustion engine.

11. The filter apparatus ofclaim 10, wherein the soot filter is positioned downstream of the catalyst.

12. An apparatus for removing particulate soot from an exhaust gas, comprising:

a housing having a chamber and a hydrogen gas inlet,

a catalyst positioned in the chamber at a position downstream of the hydrogen gas inlet, the catalyst being configured to catalyze an exothermic oxidation reaction between hydrogen gas and a gaseous component comprising oxygen, and

a filter positioned in the chamber at a position downstream of the catalyst, the filter being configured to trap soot from the exhaust gas.

13. The apparatus ofclaim 12, further comprising a source of hydrogen gas fluidly coupled to the hydrogen gas inlet.

14. The apparatus ofclaim 13, wherein the source of hydrogen gas comprises a fuel reformer.

15. The apparatus ofclaim 14, wherein the fuel reformer comprises a plasma fuel reformer.

16. The apparatus ofclaim 12, wherein:

the chamber further has an exhaust gas inlet and an exhaust gas outlet,

the catalyst being positioned between the filter and the exhaust gas inlet, and

the filter being positioned between the catalyst and the exhaust gas outlet.

17. A method of regenerating a particulate filter comprising the steps of:

advancing hydrogen gas into contact with a catalyst,

generating heat from an exothermic oxidation reaction between the hydrogen gas and a gaseous component containing oxygen in the presence of the catalyst, and

igniting particulate trapped in the particulate filter with the heat.

18. The method ofclaim 17, further comprising the step of reforming a hydrocarbon fuel to produce the hydrogen gas.

19. The method ofclaim 17, wherein the igniting step comprises heating the particulate trapped in the particulate filter to a temperature of between approximately 600 degrees Celsius and approximately 650 degrees Celsius.

20. The method ofclaim 17, wherein:

the particulate filter has a catalytic material disposed thereon, and

the igniting step comprises heating particulate trapped in the particulate filter to a temperature of between approximately 300 degrees Celsius and approximately 600 degrees Celsius.

21. The method ofclaim 17, wherein:

the particulate filter has a catalytic material disposed thereon, and

the igniting step comprises heating the particulate trapped in the particulate filter to a temperature of between approximately 300 degrees Celsius and approximately 350 degrees Celsius.

22. A method of regenerating a soot filter comprising the steps of:

introducing hydrogen gas into an exhaust gas of an internal combustion engine,

advancing the hydrogen gas and the exhaust gas into contact with a catalyst,

generating heat from a reaction between the hydrogen gas and the exhaust gas in the presence of the catalyst, and

igniting soot trapped in the soot filter with the heat.

23. The method ofclaim 22, further comprising the step of reforming a hydrocarbon fuel to produce the hydrogen gas.

24. The method ofclaim 22, wherein the igniting step comprises heating the soot trapped in the soot filter to a temperature of between approximately 600 degrees Celsius and approximately 650 degrees Celsius.

25. The method ofclaim 22, wherein:

the soot filter has a catalytic material disposed thereon, and

the igniting step comprises heating the soot trapped in the soot filter to a temperature of between approximately 300 degrees Celsius and approximately 600 degrees Celsius.

26. The method ofclaim 22, wherein:

the soot filter has a catalytic material disposed thereon, and

the igniting step comprises heating the soot trapped in the soot filter to a temperature of between approximately 300 degrees Celsius and approximately 350 degrees Celsius.

27. A method of regenerating a particulate carbon-based soot filter of a diesel engine, the method comprising the steps of:

operating a fuel reformer to produce a reformate gas,

introducing the reformate gas into an exhaust gas from the diesel engine,

advancing the reformate gas and the exhaust gas through an oxidation catalyst to generate an exothermic reaction, and

heating the soot filter with heat from the exothermic reaction to a sufficient temperature to ignite soot particulates trapped in the soot filter.

28. The method ofclaim 27, wherein the operating step comprises operating a plasmatron fuel reformer.

29. The method ofclaim 27, wherein the operating step comprises operating the fuel reformer to produce a hydrogen-rich reformate gas.

30. An apparatus for removing particulate soot from an exhaust gas of an internal combustion engine, comprising:

a source of an oxidizable gas,

a catalyst configured to catalyze an exothermic oxidation reaction between the oxidizable gas and a gaseous component comprising oxygen, and

a soot filter positioned proximate to the catalyst, wherein heat generated by the exothermic oxidation reaction is transferred to the soot filter.

31. The apparatus ofclaim 30, further comprising a housing, wherein the catalyst and the soot filter are housed in the housing.

32. The apparatus ofclaim 30, wherein the heat generated by the exothermic reaction obtains a temperature of between approximately 600 degrees Celsius and approximately 650 degrees Celsius.

33. The apparatus ofclaim 30, wherein the catalyst is disposed on a ceramic or metallic substrate.

34. The apparatus ofclaim 30, wherein the source of oxidizable gas comprises a fuel reformer.

35. The apparatus ofclaim 34, wherein the fuel reformer comprises a plasma fuel reformer.

36. The apparatus ofclaim 30, wherein the soot filter has a catalytic material disposed thereon.

37. The apparatus ofclaim 36, wherein the heat generated by the exothermic reaction obtains a temperature of between approximately 300 degrees Celsius and approximately 600 degrees Celsius.

38. The apparatus ofclaim 36, wherein the heat generated by the exothermic reaction obtains a temperature of between approximately 300 degrees Celsius and approximately 350 degrees Celsius.

39. The apparatus ofclaim 30, wherein the oxidizable gas comprises hydrogen.

40. The apparatus ofclaim 30, wherein the oxidizable gas comprises carbon monoxide.

41. An emission abatement assembly, comprising:

a fuel reformer configured to reform hydrocarbon fuel into a reformate gas,

a catalyst configured to catalyze an exothermic oxidation reaction between the reformate gas and a gaseous component comprising oxygen, and

a soot filter positioned downstream of the catalyst, wherein heat generated by the exothermic oxidation reaction is transferred to the soot filter.

42. The assembly ofclaim 41, further comprising a housing having a reformate gas inlet, wherein:

the fuel reformer is fluidly coupled to the reformate gas inlet, and

the catalyst and the soot filter are housed in the housing.

43. The assembly ofclaim 41, wherein the catalyst is disposed on a ceramic or metallic substrate.

44. The assembly ofclaim 41, wherein the soot filter has a catalytic material disposed thereon.

45. The assembly ofclaim 41, wherein the fuel reformer comprises a plasma fuel reformer.

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