WO2008082464A1

WO2008082464A1 - Filter regeneration using ultrasonic energy

Info

Publication number: WO2008082464A1
Application number: PCT/US2007/025142
Authority: WO
Inventors: Herbert F. M. Dacosta; Mohamed I. Daoud
Original assignee: Caterpillar Inc.
Priority date: 2006-12-28
Filing date: 2007-12-06
Publication date: 2008-07-10
Also published as: US20080155969A1

Abstract

An exhaust treatment system (10) of a power source system includes a filter (20) having an inlet (23) and an outlet (25) and a first exhaust line (14) located between the filter and a power source (12) of the power source system. The exhaust treatment system further includes an ultrasonic energy generating device (32) coupled to the filter. In addition, the exhaust treatment system includes a second exhaust line (28) coupled downstream of the filter.

Description

FILTER REGENERATION USING ULTRASONIC ENERGY

Technical Field

This disclosure relates generally to a regeneration system and, more particularly, to regeneration of particulate filters in a low temperature environment.

Background

Internal combustion engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of gaseous emissions. The gaseous emissions may be composed of gaseous compounds, which may include nitrous oxides (NOx), and solid particulate matter, which may include unburned carbon particulates called soot.

Due to increased attention on the environment, exhaust emission standards have become more stringent, and the amount of gaseous compounds emitted to the atmosphere from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine. One method that has been implemented by engine manufacturers to comply with the regulation of these engine emissions includes recirculating the exhaust gas. Such systems recirculate the exhaust gas byproducts into the intake air supply of the internal combustion engine. The exhaust gas directed to the engine cylinder reduces the concentration of oxygen within the cylinder and increases the specific heat of the air/fuel mixture, thereby lowering the maximum combustion temperature within the cylinder. The lowered maximum combustion temperature and reduced oxygen concentration can slow the chemical reaction of the combustion process and decrease the formation of NOx. In many exhaust recirculation applications, the exhaust gas is passed through a particulate filter and, in some cases, a catalyst containing precious metals. The particulate filter may capture a portion of the solid particulate matter carried by the exhaust. After a period of use, the particulate filter may become sufficiently loaded to require cleaning through a regeneration process wherein the particulate matter is purged from the filter. In addition, the catalyst may oxidize a portion of the unburned carbon particulates contained within the exhaust gas and may convert sulfur present in the exhaust to sulfate (SO₃). U.S. Patent No. 6,793,716 to Rigaudeau et al. (the '716 patent") discloses cleaning a particulate filter using, inter alia, ultrasonic agitation. In particular, the filter cleaning method of the '716 patent requires removal of the filter from the exhaust system and submerging the filter in a cleaning solution. Once in the cleaning solution, the filter is cleaned by agitating the cleaning solution with, for example, ultrasonic agitation. A major drawback of the filter cleaning system of the '716 patent relates to the time and expense associated with the required removal of the filter from the exhaust system and the soaking of the filter in the cleaning solution. The present disclosure is directed towards overcoming one or more of these shortcomings.

Summary of the Invention

In accordance with one disclosed exemplary embodiment, an exhaust treatment system of a power source system includes a filter having an inlet and an outlet and a first exhaust line located between the filter and a power source of the power source system. The exhaust treatment system further includes an ultrasonic energy generating device coupled to the filter. In addition, the exhaust treatment system includes a second exhaust line coupled downstream of the filter.

In accordance with another disclosed exemplary embodiment, a method of regenerating a filter of a combustion engine system includes directing a portion of engine exhaust flow through the filter to collect particulate matter in the filter and exposing at least a portion of the filter to ultrasonic energy to burn particulate matter in the filter.

According to another exemplary disclosed embodiment, an exhaust treatment system of a diesel combustion engine system includes a diesel particulate filter having an inlet and an outlet and a first exhaust line located between the filter and a diesel combustion engine of the engine system. The exhaust treatment system further includes an ultrasonic energy generating device coupled to the exhaust treatment system and a controller coupled to the ultrasonic energy generating device and configured to actuate the ultrasonic energy generating device when conditions indicate that liquid is present in the filter. In addition, the exhaust treatment system includes a second exhaust line located downstream of the filter.

Brief Description of the Drawings FIG. l is a diagrammatic illustration of an engine having an exhaust treatment system according to an exemplary disclosed embodiment; and FIG. 2 provides a diagrammatic view of a particulate filter of the exhaust treatment system of Fig. 1.

Detailed Description Fig. 1 illustrates a power source 12 having an exemplary exhaust treatment system 10. The power source 12 may include an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fluid driven engine, or any other engine apparent to one skilled in the art. The power source 12 may, alternately, include another source of power such as a furnace or any other source of power known in the art.

The exhaust treatment system 10 may be configured to direct exhaust gases out of the power source 12, treat the gases, and introduce a portion of the treated gases into an intake 26 of the power source 12. The exhaust treatment system 10 may include an energy extraction assembly 16, a regeneration device 18, a filter 20, and a recirculation line 24 fluidly connected downstream of the filter 20.

A flow of exhaust produced by the power source 12 may be directed from the power source 12 to components of the exhaust treatment system 10 by flow lines 14. The flow lines 14 may include pipes, tubing, and/or other exhaust flow carrying means known in the art. The flow lines 14 may be made of alloys of steel, aluminum, and/or other materials known in the art. The flow lines 14 may be rigid or flexible, and may be capable of safely carrying high temperature exhaust flows, such as flows having temperatures in excess of 700⁰C (approximately 1,292°F).

The energy extraction assembly 16 may be configured to extract energy from, and reduce the pressure of, the exhaust gases produced by the power source 12. The energy extraction assembly 16 may be fluidly connected to the power source 12 by one or more flow lines 14 and may reduce the pressure of the exhaust gases to any desired pressure. The energy extraction assembly 16 may include one or more turbines of a turbocharger, diffusers, or other energy extraction devices known in the art. It is also understood that in another embodiment of the present disclosure, the energy extraction assembly 16 may, alternately, be omitted. In such an embodiment, the power source 12 may include, for example, a naturally aspirated engine.

In an exemplary embodiment, the regeneration device 18 may be fluidly connected downstream from the energy extraction assembly 16 via flow line 14, and may be configured to raise the temperature of the exhaust flowing from the power source 12. The regeneration device 18 may be controlled to raise the exhaust temperature to an active regeneration temperature of the filter 20. Accordingly, the regeneration device 18 may be configured to assist in regenerating the filter 20. The regeneration device 18 may include, for example, a fuel-driven burner including a fuel injector (as shown). Alternatively, the regeneration device may include an electric heater having heat coils (not shown), combustion chambers of the power source 12, and/or other heat sources known in the art. Such regeneration devices 18 and may be configured to assist in increasing the temperature of the flow of exhaust through convection, combustion, and/or other methods. In an exemplary embodiment in which the regeneration device 18 includes a fuel-driven burner, it is understood that the regeneration device 18 may receive a supply of a combustible substance and a supply of oxygen to facilitate combustion within the regeneration device 18. The combustible substance may be, for example, gasoline, diesel fuel, reformate, and/or any other combustible substance known in the art. The supply of oxygen may be provided in addition to the relatively low pressure flow of exhaust gas directed to the regeneration device 18 through flow line 14. In an exemplary embodiment, the supply of oxygen may be delivered with a supply of recirculated exhaust gas and ambient air to the regeneration device 18 separately from the flow of exhaust gas.

As shown in FIG. 1 , the filter 20 may be connected downstream of the regeneration device 18. The filter 20 may have a housing 21 including an inlet 23 and an outlet 25. In an exemplary embodiment, the regeneration device 18 may be disposed outside of the housing 21 and may be fluidly connected to the inlet 23 of the housing 21. In another exemplary embodiment, the regeneration device 18 may be disposed within the housing 21 of the filter 20. The filter 20 may be any type of filter known in the art capable of extracting matter from a flow of gas. It is also understood that in another embodiment of the present disclosure, the regeneration device 18 may, alternatively, be omitted. In an embodiment of the present disclosure, the filter 20 may be, for example, a diesel particulate matter filter positioned to extract particulates from an exhaust flow of the power source 12. The filter 20 may include, for example, a ceramic substrate, a metallic mesh, foam, or any other porous material known in the art. These materials may form, for example, a honeycomb structure within the housing 21 of the filter 20 to facilitate the removal of particulates. The particulates may be, for example, soot contained in the exhaust flow.

As illustrated in FIG. 2, the filter 20 of the exhaust treatment system 10 may include catalyst materials useful in collecting, absorbing, adsorbing, and/or storing hydrocarbons, oxides of sulfur, and/or oxides of nitrogen contained in the exhaust flow. Such catalyst materials may include, for example, aluminum, platinum, palladium, rhodium, barium, cerium, and/or alkali metals, alkaline-earth metals, rare-earth metals, or combinations thereof. The catalyst materials may be situated within the filter 20 so as to maximize the surface area available for collection, adsorption, and or storage of, for example, hydrocarbons. The catalyst materials may be located on a substrate of the filter 20. The catalyst materials may be added to the filter 20 by any conventional means such as, for example, coating or spraying, and the substrate of the filter 20 may be partially or completely coated with the materials. It is understood that the presence of catalyst materials, such as, for example, platinum and/or palladium, upstream of the recirculation line 24 may result in the formation of sulfate in the exhaust treatment system 10. Accordingly, to minimize the amount of sulfate formed in the exemplary embodiment of FIG. 2, only minimal amounts of catalyst materials may be incorporated into the filter 20. As illustrated in FIG. 2, an ultrasonic energy generating device 32 may be coupled to the filter 20 in order to produce a plurality of ultrasound waves 34 within at least a portion of the main body 40 of the filter 20. The ultrasonic energy generating device 32 may include any device, for example, a plurality of ultrasound transducers, capable of producing ultrasound waves within the filter 20. The ultrasonic energy generating device 32 may be configured to produce the ultrasound waves 34 manually or automatically such as during a prescribed event, including, for example, during or after an engine idling period. The ultrasonic energy generating devices 32 may be controlled by an electronic controller 19 or similar device based on measured conditions of the power source or exhaust system. For example, the ultrasonic energy generating device 32 may be triggered by the controller in response to system conditions indicating that the power source 12 is operating, or has operated, in an idle condition, that the exhaust temperature is approximately 100° C or below, and/or conditions indicating that liquid, such as water, is present in the filter 20. Alternatively, controller 19 may trigger the ultrasonic energy generating device 32 at predetermined and/or periodic intervals.

Referring again to FIG. 1, the exhaust treatment system 10 may further include the recirculation line 24 fluidly connected downstream of the filter 20 and upstream of an exhaust system outlet 28. The recirculation line 24 may be configured to controllably direct a portion of the exhaust flow from the filter 20 to the inlet 26 of the power source 12. The recirculation line 24 may include a recirculation control valve 27 activated by electronic controller 19 to meter the amount of exhaust flow directed back to the inlet 26 of the power source 12. The recirculation line 24 may include piping, tubing, and/or other exhaust flow carrying means known in the art and may be structurally similar to the flow lines 14 described above.

Industrial Applicability

The exhaust treatment systems 10 of the present disclosure may be used with any combustion-type device such as, for example, an engine, a furnace, or any other power source device known in the art. The exhaust treatment systems 10 may be useful in reducing the amount of harmful exhaust emissions discharged to the environment and reducing or substantially eliminating the amount of sulfate produced during treatment of the exhaust gas. The exhaust treatment systems 10 may also be capable of purging a portion of the captured particulate matter of the exhaust gas through a regeneration process.

As discussed above, the combustion process may produce a complex mixture of gaseous emissions. These chemical species may exist in solid, liquid, and/or gaseous form. In general, the solid and liquid species may fall into four categories of ash, soot, soluble organic fraction (SOF), and sulfates. The organic particulate matter produced during combustion may include carbonaceous materials and soluble organic fraction which may include unburned hydrocarbons that are deposited on or otherwise chemically combined with the soot. The sulfates produced in the combustion process may be formed from sulfur molecules contained within the fuel and may be released in the form of SO₂. This SO₂ may react with oxygen molecules contained within the exhaust flow to form SO₃. The SO₂ may also be converted into SO₃ in the presence of, for example, platinum, palladium, and/or other rare earth metals used as catalyst materials in conventional catalysts. It is understood that the combustion process may also produce small amounts of SO₃.

In a conventional exhaust treatment system, a portion of the SO₃ produced may be released to the atmosphere through an outlet of the exhaust system. The exhaust treatment systems 10 of the present disclosure, however, may substantially reduce the formation of sulfates by minimizing the amount of platinum, palladium, and/or other precious earth metals used. The operation of the exhaust treatment systems 10 will now be explained in detail. Unless otherwise noted, the exhaust treatment system 10 of FIG. 1 will be referred to for the duration of the disclosure. The power source 12 may combust a mixture of fuel, recirculated exhaust gas, and ambient air to produce mechanical work and an exhaust flow containing the gaseous compounds discussed above. The exhaust flow may be directed, via flow line 14, from the power source 12 through the energy extraction assembly 16. The exhaust flow may pass through the regeneration device 18 to the filter 20. The regeneration device 18 may be deactivated during the normal operation of the power source 12. As the exhaust flow passes through the filter 20, a portion of the particulate matter 30 (Fig. 2) entrained with the exhaust flow may be captured by the substrate, mesh, and/or other structures within the filter 20. Any catalyst materials, such as those disposed within the filter 20, may assist in oxidizing the hydrocarbons and soluble organic fraction carried by the exhaust flow.

A portion of the filtered exhaust flow may be controllably extracted downstream of the filter 20. The extracted portion of the exhaust flow may enter the recirculation line 24 and may be recirculated back to the power source 12. After passing through the filter 20, a portion of the exhaust flow may also exit the exhaust treatment system 10 through an exhaust system outlet 28.

Over time, particulate matter/soot 30 produced by the combustion process may collect in the filter 20 and may begin to impair the exhaust treatment system. Sensors (not shown) may be configured to sense parameters of the power source 12 and/or the exhaust treatment system 10 to determine the loading of the filter 20. Such parameters may include, for example, engine speed, engine temperature, exhaust flow temperature, exhaust flow pressure, and particulate matter content. Controller 19 may use the information sent from the sensors in conjunction with an algorithm or other pre-set criteria to determine whether the filter 20 is in need of regeneration. Once this saturation point has been reached, the controller may send appropriate signals to components of the exhaust treatment system 10 to begin the regeneration process. A preset algorithm stored in the controller 19 may assist in this determination and may use the sensed parameters as inputs. Alternatively, regeneration may commence according to a set schedule based on fuel consumption, hours of operation, and/or other variables.

During prolonged engine idling events, the exhaust flow and filter 20 may obtain a reduced temperature, for example, approximately 100° C or below. As a result, moisture, such as condensation of liquid water, may develop within the filter 20. Thus, as the exhaust flow travels in a first flow direction 36 into the inlet 23 of the filter 20, an amount of soot, such as particulate matter 30, entrained within the exhaust flow may become saturated with moisture contained within the filter 20. When such moisture is contained within the filter 20, the ultrasonic energy generating device 32 may be configured to receive signals from controller 19 to begin a regeneration process. The regeneration process may include enabling the ultrasonic energy generating device 32 to produce ultrasound waves 34 within at least a portion of the filter 20. The moisture surrounding an amount of particulate matter soot 30, may be exposed to the ultrasound waves 34 to form microbubbles in the moisture layer. The microbubbles may begin to oscillate as a result of exposure to the ultrasound waves 34. This may produce hot spots as the oscillating microbubbles generate heat and increased temperatures around the encapsulated soot particles. Additional processes, such as cavitation, may also occur as the microbubbles oscillate under high heat and increased temperature. Regeneration of the soot may occur as the microbubbles combust under cavitation and the heat generated by the hot spots is received by the particulate matter 30. The heat generated under the regeneration process of the disclosed embodiment may be sufficient such that soot contained within the filter 20 may be burned away to restore the storage some or all of the capability of the filter 20. This indirect method of filter regeneration does not require significant fuel consumption to provide the heat sufficient for filter regeneration. Regeneration device 18 may be initiated concurrently with the initiation of the ultrasonic energy generating device 32, or under may be initiated based on different sensed or predetermined conditions.

Other embodiments of the disclosed exhaust treatment system 10 will be apparent to those skilled in the art from consideration of the specification. For example, the system 10 may include additional devices including, for example, a liquid injection device configured to supply moisture to the filter 20 in order to facilitate saturation of the soot within the filter 20. Other devices may include equipment to artificially cool down the filter and/or exhaust flow received therein to change saturation of the particulate matter in the filter. It is intended that the specification and examples be considered as exemplary only, with the true scope of the invention being indicated by the following claims. -l i¬

lt will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed apparatus and method without departing from the scope of the disclosure. Additionally, other embodiments of the apparatus and method will be apparent to those skilled in the art from consideration of the specification. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.

Claims

1. An exhaust treatment system ( 10) of a power source system, comprising: a filter (20) having an inlet (23) and an outlet (25); a first exhaust line (14) located between the filter and a power source (12) of the power source system; an ultrasonic energy generating device (32) coupled to the filter; and a second exhaust line (28) coupled downstream of the filter.

2. The system of claim 1, wherein the ultrasonic energy generating device is coupled to the inlet of the filter.

3. The system of claim 1, wherein the ultrasonic energy generating device includes a plurality of ultrasound transducers (32) coupled to the filter.

4. The system of claim 1, further including a regeneration device (18) disposed upstream of the filter.

5. The system of claim 4, wherein the regeneration device is a fuel-driving burner coupled to the first exhaust line.

6. The system of claim 1, wherein the filter is a diesel particulate filter.

7. The system of claim 6, wherein the filter includes catalyst materials.

8. The system of claim 1, further including an exhaust recirculation line (24) located downstream of the filter.

9. A method of regenerating a filter (20) of a combustion engine system, comprising: directing a portion of engine exhaust flow through the filter to collect particulate matter (30) in the filter; and exposing at least a portion of the filter to ultrasonic energy to burn particulate matter in the filter.

10. The method of claim 9, further including actively heating the exhaust gas upstream of the filter to further regenerate the filter.