US20080173007A1

US20080173007A1 - System for reducing emissions generated from diesel engines used in low temperature exhaust applications

Info

Publication number: US20080173007A1
Application number: US11/753,747
Authority: US
Inventors: Julian A. Imes
Original assignee: Donaldson Co Inc
Current assignee: Donaldson Co Inc
Priority date: 2007-01-22
Filing date: 2007-05-25
Publication date: 2008-07-24

Abstract

Systems and methods for using off-board regeneration technology are disclosed herein. According to one method, off-board regeneration technology is used to allow a diesel particulate filter to be effectively used for an engine application having an operating temperature less than the operating temperature at which the diesel particulate filter would normally be capable of passively regenerating.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/881,853, filed Jan. 22, 2007, which application is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally to engine exhaust treatment systems and methods.

BACKGROUND

Vehicles equipped with diesel engines may include exhaust systems that have diesel particulate filters for removing particulate matter from the exhaust stream. With use, soot or other carbon-based particulate matter accumulates on the diesel particulate filters. As particulate matter accumulates on the diesel particulate filters, the restriction of the filters increases causing the buildup of undesirable back pressure in the exhaust systems. High back pressures decrease engine efficiency. Therefore, to prevent diesel particulate filters from becoming excessively loaded, diesel particulate filters should be regularly regenerated by burning off (i.e., oxidizing) the particulates that accumulate on the filters. Since the particulate matter captured by diesel particulate filters is mainly carbon and hydrocarbons, its chemical energy is high. Once ignited, the particulate matter burns and releases a relatively large amount of heat.
Systems have been proposed for regenerating diesel particulate filters. Some systems use a fuel fed burner positioned upstream of a diesel particulate filter to cause regeneration (see U.S. Pat. No. 4,167,852). Other systems use an electric heater to regenerate a diesel particulate filter (see U.S. Pat. Nos. 4,270,936; 4,276,066; 4,319,896; 4,851,015; 4,899,540; 5,388,400 and British Published Application No. 2,134,407). Detuning techniques are also used to regenerate diesel particulate filters by raising the temperature of exhaust gas at selected times (see U.S. Pat. Nos. 4,211,075 and 3,499,260). Self regeneration systems have also been proposed. Self regeneration systems can use a catalyst on the substrate of the diesel particulate filter to lower the ignition temperature of the particulate matter captured on the filter. An example of a self regeneration system is disclosed in U.S. Pat. No. 4,902,487.
Air quality/emissions regulations at the state and federal level have driven manufacturers to develop improved diesel engine emission control technologies that are effective over a wide range of operating conditions and engine types. The state of California is a leader in the implementation of diesel engine emission regulations. The California Air Resources Board (CARB) has set forth a verification procedure for exhaust treatment strategies used in the treatment of diesel engine emissions. For the removal of particulate material from diesel engine exhaust, the CARB verification procedure defines three levels of classification which include level 1, level 2 and level 3. An emissions control device can be verified as a level 1 device for a specified application of a specified category of diesel engine if it is shown to reduce particulate material emissions by at least 25 percent. An emissions control device can be verified as a level 2 device for a specified application of a specified category of diesel engine if it is shown to reduce particulate material emissions by at least 50 percent. An emissions control device can be verified as a level 3 device for a specified application of a specified category of diesel engine if it is shown to reduce particulate material emissions by at least 85 percent or provides total particulate material emissions that are less than 0.01 grams per brake horsepower-hour (g/bhp-hr).
Best Available Control Technology (BACT) regulations have been implemented to complement emissions regulations. BACT regulations generally require diesel engine emissions to be treated with the best available technology that reasonably can be used for the particular category of diesel engine. Thus, if a first technology is verified as a level 2 device for treating a first category of diesel engine, and a second technology is verified as a level 3 device of treating the first category of diesel engine, BACT dictates that the level 3 device be used.
Best Available Control Technology (BACT) regulations have encouraged manufacturers to develop DPF's for the full operating temperature range, making them the only alternative for 1994 and newer engines. Passively regenerated DPF's are effective for diesel engines that operate at relatively high temperatures. For diesel engines that operate at relatively low temperatures, actively regenerated DPF's using on-board electric heaters have been developed. The difference between passively regenerated DPF's and actively regenerated DPF's having on-board regeneration equipment is significant. In contrast to passively regenerated DPF's, electrically regenerated DPF's with on-board heaters require a costly infrastructure. The market is much more interested to apply passive DPF's due to the lower maintenance and infrastructure costs.

SUMMARY

One aspect of the present disclosure relates to systems and methods for using off-board regeneration technology to allow a diesel particulate filter to be effectively used for an engine application having an operating temperature less than the operating temperature at which the diesel particulate filter would normally be capable of passively regenerating.
Examples representative of a variety of inventive aspects are set forth in the description that follows. The inventive aspects relate to individual features as well as combinations of features. It is to be understood that both the forgoing general description and the following detailed description merely provide examples of how the inventive aspects may be put into practice, and are not intended to limit the broad spirit and scope of the inventive aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example method in accordance with the principles of the present disclosure;

FIG. 2 shows another example method in accordance with the principles of the present disclosure;

FIG. 3 shows an example diesel particulate filter that can be used in accordance with aspects of the present disclosure;

FIG. 4 is a perspective view of an aftertreatment device pulse regenerator that can be used in practicing methods in accordance with the principles of the present disclosure;

FIG. 5 is a perspective view of the pulse regenerator of FIG. 4 with the walls of the cabinet removed to show the interior components;

FIG. 6 is a front view of the pulse regenerator of FIG. 4 with the two front doors removed;

FIG. 7 is a right side view of the pulse regenerator of FIG. 4 with the side wall removed;

FIG. 8 is a rear view of the pulse regenerator of FIG. 4;

FIG. 9 is a top view of the pulse regenerator of FIG. 4 with the top wall removed;

FIG. 10 is a front view of an aftertreatment device thermal regenerator that can be used in practicing methods in accordance with the principles of the present disclosure;

FIG. 11 is a side view of the thermal regenerator of FIG. 10;

FIG. 12 is a perspective view of a vent and hood assembly of the thermal regenerator of FIG. 10;

FIG. 13 is a perspective view of a heating element and collection container of the thermal regenerator of FIG. 10;

FIG. 14 is a cross-sectional view taken along section line 14-14 of FIG. 13;

FIG. 15 is a perspective view of a base assembly of the thermal regenerator of FIG. 10;

FIG. 16 is an end view of the base assembly of FIG. 15;

FIG. 17 shows an insulation layer for insulating an aftertreatment device during the thermal regeneration process;

FIG. 18 is a flow chart explaining a further method in accordance with the principles of the present disclosure;

FIG. 19 is an end view an exhaust treatment system having active on-board regeneration;

FIG. 20 is a cross-sectional view taken along section line 20-20 of FIG. 19;

FIG. 21 is an end view of an on-board heating element used in the exhaust treatment system of FIGS. 19 and 20;

FIG. 22 is a perspective view of a shore station used to control regeneration of exhaust treatment devices such as the exhaust treatment device shown in FIGS. 19 and 20; and

FIG. 23 is a schematic diagram of the shore station of FIG. 22.

While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail below. It is to be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.

DETAILED DESCRIPTION

For 1994 and later diesel engines, standard passively regenerated DPF systems have been verified as level 3 devices for applications having duty cycles with average temperature profiles greater than 240 degrees Celsius for at least 40 percent of the operating cycles. Specialized DPF systems capable of regenerating at lower operating temperatures have been developed for lower temperature applications. Such systems have been verified as level 3 devices for diesel engines used in applications having duty cycles with average temperature profiles greater than 200 degrees Celsius for at least 40 percent of the operating cycles. An example of this type of specialized system is disclosed at U.S. Patent Application Ser. No. 60/784,621, entitled Low Temperature Diesel Particulate Matter Reduction System, and filed on Mar. 21, 2006, that is hereby incorporated by reference in its entirety.
Passively regenerated DPF systems typically have DPF's with relatively high catalyst loadings that assist in causing particulate material on the DPF's to be combusted using heat generated from the engine. However, lower temperature applications do not provide sufficient engine heat to reliably passively regenerate a DPF. Therefore, at present, standard DPF's are level 3 verified only for applications having high exhaust temperatures (e.g., duty cycles with average temperature profiles greater than 240 degrees Celsius for at least 40 percent of the operating cycles). Specialized low-temperature DPF systems of the type identified in the previous paragraph have a wider range of use and are level 3 verified for applications having duty cycles with average temperature profiles greater than 200 degrees Celsius for at least 40 percent of the operating cycles. To date, the only verified level 3 technology that does not have operating temperature use limitations includes active regeneration DPF systems with on-board heating technology (e.g., electric heaters, fuel burners, etc.) for generating the higher temperatures needed to regenerate the DPF's.
The present disclosure relates to a strategy for using off-board regeneration technology to economically extend the use of a DPF system to an application having a duty cycle with an average temperature profile lower than the average temperature profile for which the DPF system would normally be able to passively self regenerate in use. The average exhaust temperature profile can be established or defined by measuring and recording engine exhaust temperatures over repeated operating cycles (e.g., in the field or in a test lab) using a data-logging process. The strategy proposes allowing the application of DPF's below their normal temperature cut-off to allow a customer to avoid using costly on-board heating technology. There are significant capital cost and maintenance advantages with this approach.
As shown at FIG. 1, the exhaust treatment strategy involves the intentional application of a DPF system that does not include active, on-board regeneration technology for applications having normal engine operating temperatures (as determined by initial measurement and data-logging) below the temperature cut-off for in situ passive regeneration the DPF system (see block 2 of FIG. 1), and then using off-board regeneration technology to regenerate the DPF system when necessary (see block 4 of FIG. 1). To implement the exhaust treatment strategy, the DPF system would preferably be verified (e.g., verified under CARB, verified under the United States Environmental Protection Agency or verified under any other governmental exhaust emissions regulatory body) for use in treating exhaust gas emitted from a diesel engine applications having an average temperature profile below the temperature cut-off for passive in situ regeneration of the DPF system being verified. In one embodiment, the DPF system can be verified as a CARB level 3 device for applications having duty cycles with average temperature profiles greater than 240 degrees Celsius for less than 40 percent of the operating cycle. In another embodiment, the DPF system can be verified as a CARB level 3 device for applications having duty cycles with average temperature profiles greater than 220 degrees Celsius for less than 40 percent of the operating cycle. In still another embodiment, the DPF system can be verified as a CARB level 3 device for applications having duty cycles with average temperature profiles greater than 200 degrees Celsius for less than 40 percent of the operating cycle.
As shown at FIG. 2, the verification process can include submitting an application for verification of the diesel emission control strategy to a regulating agency such as CARB, EPA, or other regulatory body (see block 5 of FIG. 2). The verification application can include data showing that the diesel emission control strategy satisfies predetermined emission reduction targets (e.g., 85 percent reduction as defined by level 3 CARB verification) (see block 6 of FIG. 2) when used to treat exhaust generated from diesel engines used in applications having duty cycles with average temperature profiles greater than a predetermined temperature (e.g., 240, 220 or 200 degrees Celsius) for less than a certain percentage (e.g., 40 percent) of the operating cycle. The diesel emission control strategy provided in the application can specify a particular DPF system in combination with an off-board DPF regeneration technology. The DPF system can have a passive regeneration temperature requirement that will not be met by the average exhaust temperature profile for which verification is being sought (see block 7 of FIG. 2). Data-logging of measured exhaust temperature values can be used to show or verify that the engine operating temperature profile of the exhaust generated by the engine during the given application is insufficient to cause passive regeneration of the DPF. Data showing compliance with a certain level of emissions reduction (e.g., CARB level 2 or level 3 emissions reduction) can be generated using the specified DPF system in combination with the specified off-board DPF regeneration technology (see block 8 of FIG. 2). Regeneration frequencies or criteria for determining when regeneration is necessary can also be specified in the application.
After verification, the DPF system can be sold as a verified system (e.g., a CARB level 2 or 3 verified system) for use in treating exhaust gas emitted from diesel engines used in applications that exceed a predetermined temperature (e.g., 240, 220 or 200 degrees Celsius) for less than a certain percentage of their normal operating cycles (e.g., 40 percent). Literature (e.g., advertising, brochures, instructions, etc.) can be provided to customers explaining that when the DPF system is used for diesel engine applications that exceed the predetermined temperature for less than the predetermined percentage of their normal operating cycles, the DPF system should be periodically regenerated using off-board DPF regeneration technology. The customer can then use the DPF system to treat exhaust generated from diesel engine applications that exceed the predetermined temperature for less than the predetermined percentage of their normal operating cycles, and can periodically have the DPF system regenerated using off-board DPF regeneration technology. To reduce the customer's upfront capital expenditure, the off-board regeneration services can be provided by a party other than the customer (e.g., a service dealer that owns and operates off-board regeneration equipment). Thus, the customer need not purchase the off-board regeneration technology.
A. Low Temperature Exhaust Applications
The most likely customers for this type of application (e.g., diesel engine applications having duty cycles with average temperature profiles greater than 240 degrees Celsius for less than 40 percent of the operating cycles) at present include refuse and municipal fleet operators whose vehicles do not generate enough heat for consistent or reliable filter regeneration. These fleets are both currently regulated in California and other places, and they need a way to retrofit their fleet with DPF's. For example, municipal fleets generally put on only 5,000 to 10,000 miles per year, and even when operating, they do a lot of idling and do not generate a lot of heat. Due to cost issues, it is difficult to justify an on-board active regeneration DPF system for this type of vehicles with such limited operation.
B. DPF System
Diesel particulate filter substrates can have a variety of known configurations. An exemplary configuration includes a monolith ceramic substrate having a “honey-comb” configuration of plugged passages as described in U.S. Pat. No. 4,851,015 that is hereby incorporated by reference in its entirety. This type of filter can be referred to as a wall-flow trap or filter. Common materials used for wall-flow filters include cordierite, mullite, alumina, SiC, refractory metal oxides or other materials. Wire mesh, corrugated metal foil and other flow-through type filter configurations can also be used. In certain embodiments, the filter substrate can include a catalyst. Exemplary catalysts include precious metals such as platinum, palladium and rhodium, and other types of components such as base metals or zeolites.
As shown at FIG. 3, an example DPF 10 suitable for use in treating exhaust generated from diesel engines for applications that exceed a predetermined temperature (e.g., 240, 220 or 200 degrees Celsius) for less than 40 percent of their normal operating cycles is depicted. The DPF 10 is a wall-flow filter having a substrate 11 housed within an outer casing 12. In certain embodiments, the substrate 11 can have a silicon carbide (SiC) construction. A mat layer 13 can be mounted between the substrate 11 and the casing 12. Ends 14 of the casing can be bent radially inwardly to assist in retaining the substrate 11 within the casing 12. End gaskets 15 can be used to seal the ends of the DPF 10 to prevent flow from passing through the mat layer 13 to bypass the substrate 11.
Still referring to FIG. 3, the substrate includes walls 16 defining a honeycomb arrangement of longitudinal passages 17 (i.e., channels) that extend from a downstream end 18 to an upstream end 19 of the substrate 11. The passages 17 are selectively plugged adjacent the upstream and downstream ends 18, 19 such that exhaust flow is forced to flow radially through the walls 16 between the passages 17 in order to pass through the DPF 10. As shown at FIG. 3, this radial wall flow is represented by arrows A.
In one embodiment, the DPF can be lightly catalyzed or not be catalyzed at all. For example, the DPF embodiment can have a precious metal loading that is less than 50 grams per cubic foot of substrate, or less than 30 grams per cubic foot of substrate or less than 10 grams per cubic foot of substrate or less than 5 grams per cubic foot of substrate. By minimizing the precious metal loading on the DPF, the production of NO₂during treatment of exhaust is minimized, and cost is reduced as well. In other embodiments, the DPF can be more heavily catalyzed to reduce the frequency at which the DPF will need to be regenerated by the off-board regeneration equipment.
The DPF 10 preferably has a particulate mass reduction efficiency greater than 85% so as to comply with CARB level 3 verification. Most preferably, the DPF 10 has a particulate mass reduction efficiency equal to or greater than 90%. For the purposes of this specification, particulate mass reduction efficiency is determined by subtracting the particulate mass that enters the DPF from the particulate mass that exits the DPF, and by dividing the difference by the particulate mass that enters the DPF. The test duration and engine cycling during testing are preferably determined by the federal test procedure (FTP) heavy-duty transient cycle that is currently used for emission testing of heavy-duty on-road engines in the United States (see C.F.R. Tile 40, Part 86.1333).
Another DPF system suitable for use in treating exhaust generated from diesel engines that exceed a predetermined temperature (e.g., 240, 220 or 200 degrees Celsius) for less than 40 percent of their normal operating cycles is disclosed at U.S. Patent Application Ser. No. 60/784,621, entitled Low Temperature Diesel Particulate Matter Reduction System, and filed on Mar. 21, 2006, that is hereby incorporated by reference in its entirety. For systems having multiple filters, selected filters of the system may be regenerated more often than other filters of the system. Also, in a multi-filter system, some filters may be designed to require regular off-board regeneration while other filters may regenerate passively on-board the vehicle.
C. Off-Board Regeneration Technology
For the purpose of this disclosure, off-board DPF regeneration systems are DPF regeneration systems that include off-board DPF regeneration equipment such as an off-board heating device (e.g., a resistive heating element, a burner or other heating devices) and/or an off-board air movement device (e.g., a fan, a blower, a pulse generator, etc.). Off-board equipment is defined as equipment that is not carried by the vehicle or vehicle exhaust system during normal operation of the vehicle. In certain embodiments, the off-board DPF regeneration equipment can be used to regenerate a DPF of a vehicle by temporarily connecting the off-board DPF regeneration equipment to the vehicle exhaust system while the vehicle is stationary/parked. In such embodiments, the DPF can be regenerated without removing the DPF from the vehicle exhaust system. In other embodiments, the DPF is removed from the vehicle exhaust system and regenerated by the off-board DPF regeneration equipment at a location off-board from the vehicle. In such embodiments, a replacement DPF can optionally be used in the vehicle exhaust system while the removed DPF is being regenerated.
A passive regeneration DPF system traditionally is used for engine applications having temperatures high enough to cause self regeneration of the DPF at fairly regular intervals without the aid of supplemental regeneration equipment. Over an extended period of time and many passive regeneration events, the DPF can become plugged with ash. In the prior art, off-board cleaning technology has been used to removed such ash. In contrast to the prior art, one aspect of the present invention involves intentionally using a DPF system for engine applications having temperatures too low for the DPF system to regularly/reliably passively regenerate itself in situ. Rather than rely on passive regeneration, off-board regeneration equipment is used periodically to regenerate the DPF system. The off-board regeneration equipment is not merely being used to remove ash. Instead, a majority of the material being removed from the DPF by the off-board regeneration equipment is typically soot rather than ash. The off-board regeneration equipment is used more regularly than would be necessary for mere ash removal with respect to a passive regeneration system because self/passive regeneration of the DPF does not regularly occur between uses of the off-board regeneration equipment.
FIGS. 4-9 illustrate an off-board regeneration device 20 that can be used in accordance with the principles of the present disclosure to regenerate DPF's used to treat exhaust gas emitted from diesel engines having duty cycles with average temperature profiles greater than 200 degrees Celsius for less than 40 percent of the operating cycle. The regeneration device 20 includes a cabinet 21 having a top side 22, a bottom side 24, a left side 26, a right side 28, a front side 30 and a back side 32. The cabinet 21 includes an upper region 34, an intermediate region 36 and a lower region 38. The front side 30 of the cabinet 21 includes a front wall 40 positioned at the upper region 34. A pressure gage 42 and a control panel 44 are mounted to the front wall 40. The front side of the cabinet 21 also includes a first door 46 for providing access to the interior of the intermediate region 36 of the cabinet 21, and a second door 48 for providing access to the interior of the lower region 38 of the cabinet 21. An electrical connection opening 45 and an air inlet opening 47 are provided at the top side 22 of the cabinet 21. Adjustable feet 50 are provided at the bottom side 24 of the cabinet 21 for leveling the cabinet 21. A crank handle 52 is provided at the side 28 of the cabinet 21. An air outlet 54 (see FIGS. 5 and 8) is provided at the back side 32 of the cabinet 21.
Referring to FIGS. 5-9, an air pressure tank 60 is provided at the upper region 34 of the cabinet 21, a DPF mount 62 is provided at the intermediate region 36 of the cabinet 21 and a primary filter mount 64 is located at the lower region 38 of the cabinet 21. The air pressure tank 60 and its corresponding flow control arrangement function as a pulse generator that generates pulses of air for regenerating a DPF 70 positioned at the DPF mount 62. A primary filter 72 positioned at the primary filter mount 64 functions to capture material flushed from the DPF 70. A safety filter 66 is provided for re-filtering the air that passes through the primary filter 72 before the air exits the cabinet 21 through the air outlet 54. Further details regarding the regeneration device 20 are provided in U.S. application Ser. No. 11/335,163, filed Jan. 18, 2006 and entitled Apparatus for Cleaning Exhaust Aftertreatment Devices and Methods, which is hereby incorporated herein by reference in its entirety.
In use of the system, the DPF 10 is removed from a vehicle having a diesel engine having exhaust that exceeds 200 degrees Celsius for less than 40 percent of the normal operating cycle of the vehicle. The DPF 10 is loaded at the DPF mount 62 and the primary filter 72 is positioned at the primary filter mount 64. With the filters 70, 72 mounted within the cabinet 21, the cabinet doors 46, 48 are closed and the air pressure tank 60 is pressurized with air. When the air pressure tank 60 is filled to a predetermined air pressure, the air pressure tank 60 is opened causing a pulse of air to flush or dump downwardly from the pressure tank 60 through the DPF 10. As the pulse of air moves downwardly through the DPF 10, material (e.g., soot, ash, oil, soluble organic fraction or other material) accumulated on the DPF 10 during use is dislodged/flushed from the DPF 10 and re-captured at the primary filter 72. After passing through the primary filter 72, the air can exit the cabinet 21 through the air outlet 54 and its corresponding safety filter 66. A blower 74 is provided within the cabinet 21 for providing continuous positive pressure to the top side of the DPF 10 between air pulses. The movement of air from the blower 74 assists in causing material loosened by the air pulses to migrate downwardly to the primary filter 72. In other embodiments, a vacuum may be placed downstream of the DPF and the primary filter 72 for continuously drawing air through the DPF 10 and the primary filter 72.
It is typically preferred to mount the DPF 10 in the DPF mount 62 with the outlet side of the filter facing upwardly toward the pressure tank 60. In this configuration, the pulses of compressed air back-flush collected material from the DPF. However, in other embodiments, a filter may be regenerated by alternating between a first orientation where the outlet side faces upwardly toward the pressure tank 60 and a second orientation where the outlet side faces downwardly away from the pressure tank 60. By selectively reversing the orientation of a given filter during regeneration, material accumulated on the filter will alternately be exposed to pulses from opposite directions thereby assisting in dislodging accumulated material from the filter.
Typical DPF's are 10.5 or 11.25 inches in diameter and 14 inches in length. Another common DPF size is 12 inches in diameter and 15 inches in length. To accommodate these sizes of filter, in one non-limiting embodiment, the air pressure tank can have a volume of about 22 gallons, and the air pressure tank is pressurized to about 8-10 pounds per square inch (psi) before dumping its volume of air to generate an air pulse. In other embodiments, the air pressure tank can have a volume in the range 5-50 gallons, or a volume of at least 5 gallons. In one non-limiting embodiment, the air tank is pressurized to a pressure less than 15 psi in the range of 3-15 psi. In certain embodiments, it is desirable for the air flow through the DPF during an air pulse to have an approach velocity of in the range of 20-100 feet per second, or in the range of 50-70 feet per second. Approach velocity is defined as the average speed of the air during a pulse measured at a position immediately upstream of the DPF being regenerated. Example pulse durations are in the range of 1/50 of a second to 1 second or in the range of 1/30 of a second to 0.5 second. A preferred pulse duration is about 1/20 of a second. It will be appreciated that the above numerical information is provided for illustration purposes only, and is not intended to limit the broad inventive aspects of the present disclosure.
In one embodiment, the entire pulse regeneration process can be completed in 15 minutes or less. However, certain filters may take longer than 15 minutes to regenerate. Therefore, the broad aspects of the invention need not be limited to a particular time frame.
It has been determined that the initial pulse is the most effective at flushing material from an aftertreatment device. Thereafter, the pulses progressively flush less and less material from the device being regenerated as the device becomes regenerated. In view of the particular effectiveness of the initial pulses, certain aftertreatment devices may be regenerated by using only a few pulses or even a single pulse. In practicing one method, 1-100 pulses may be used. In practicing another method, 20-70 pulses may be used. In practicing a further method, 40-60 pulses may be used. Other numbers of pulses than those specified can also be used without departing from the broad concept of the present disclosure.
At times, merely pulsing air through a given filter or other aftertreatment device may not provide adequate regeneration. For these types of circumstances, the pulse regeneration process can be used in combination with a heating process. For example, a DPF or other aftertreatment device can be initially pulse regenerated as described above. If the pulse regeneration does not result in the adequate removal of material from the aftertreatment device, the aftertreatment can be heated to combust soot or other combustible materials from the filter. After combusting the combustible material from the aftertreatment device, the aftertreatment device can again be air pulsed to flush other remaining material from the device.
An example off-board regeneration device 120 for combusting soot or other materials from an aftertreatment device such as DPF 10 is disclosed at FIGS. 10-17. The device 120 includes a cabinet 121 having a rectangular housing 122 supported on legs 133 that elevate the housing 122 above the ground. The legs 133 and a bottom wall 124 of the housing 122 cooperate to form a base assembly 125 (see FIGS. 13 and 14) of the cabinet 121. The front of the cabinet 121 includes a door 140 that can be opened to provide access to the interior of the housing 122. A collection container 142 is mounted under the housing 122 for collecting material that drops from the DPF's as the DPF's are regenerated. A vent stack 144 is mounted at the top of the housing 122 for venting the products of combustion from the housing 122.
Referring to FIG. 12, the vent stack 144 is in fluid communication with a fume and heat containment chamber 123 within the interior of the housing 122. The vent stack 144 is part of an assembly including a hood 146. The hood 146 is mounted beneath the vent stack 142 within the chamber 123.
Referring to FIGS. 13 and 14, a heating element 150 (e.g., an electric heating element (e.g., a coil, grid or other structure) or other heating structure) is mounted in the chamber 123 adjacent the bottom wall 124 of the housing 122. A heat reflector 152 (e.g., a porous ceramic disc/plate) is mounted beneath the heating element 150. Preferably, the reflector 152 is sufficiently porous to readily allow air and ash to pass therethrough. In one embodiment, the reflector 152 includes 5-25 pores per inch and has a thickness in the range of 0.5-2 inches. The reflector 152 prevents radiant heat loss into the container since air flow through the reflector 152 carries heat from the reflector upwardly to the diesel particulate filter being serviced.
The heating element 150 and the reflector 152 are mounted within a cylindrical first pipe section 200 having flanged upper and lower ends. The flanged upper end allows an aftertreatment device to be clamped in place (e.g., with v-band clamp 202) over the heating element 150. The lower flanged end of the first pipe section 200 is clamped to the upper flanged end of a second pipe section 204 (e.g., with v-band clamp 206). The second pipe section 204 includes an enlarged diameter portion 208 connected to a reduced diameter portion 210 by a conical diameter transition portion 212. The second pipe section 204 is secured (e.g., welded or fastened) to a rim 214 secured to the bottom wall 124 of the cabinet 121. The reduced diameter portion 210 of the second pipe section 204 projects downwardly below the bottom wall 124 and has a flanged lower end.
The collection container 142 is clamped (e.g., with v-band clamp 216) to the lower flanged end of the second pipe section 204. The collection container 142 includes a main bin 143 having an open top end covered by a lid 145. A pipe section 147 is mounted at the center of the lid 145. The pipe section 147 extends though the lid 145 and has a flanged upper end that can be clamped to the lower flanged end of the second pipe section 204. The lid 145 is removable from the bin 143 to allow collected material to be emptied from the bin 143.
A compressed air outlet 145 (e.g., a nozzle, hose, pipe, of other structure) is positioned between the reflector 152 and the container 142. For example, in FIG. 12, the outlet 45 is shown connected to a compressed air line 122 that extends through an opening 220 in the second pipe section 204. In the depicted embodiment, the outlet 145 is configured to direct air in a downward direction toward the container 142. In other embodiments, the outlet may direct air upwardly toward the heating element or laterally toward the side wall of the second pipe section 204.
It is preferred of the outlet 145 to be in fluid communication with a source of compressed air 224 via the line 222. A controller 226 controls the amount of air provided to the outlet 145. The flow can be controlled/metered to control the rate of combustion at the aftertreatment device being serviced. In one embodiment, the controller interfaces with a solenoid 228 that opens and closes to provide pulses of air to the outlet 145. In one embodiment, the source of compressed air has a pressure of at least 60 pounds per square inch (psi), or in the range of 60-100 psi, or preferably about 90 psi. In another embodiment, flow rates preferably in the range of 0.5-2.0 standard cubic feet per minute (SCFM) are provided beneath the heating element during regeneration. In still another embodiment, pulses having durations in the range of 0.25-1 s, a pulse frequency of about 2-15 or 2-8 pulses per minute, and a flow rate in the range of 0.5-2.5 SCFM or 0.75-1.25 SCFM are provided beneath the heating element. It will be appreciated that the above numerical information is provided for illustration purposes only, and is not intended to limit the broad inventive aspects of the present disclosure.
The pulses of air provide a number of functions. For example, the air pulses impinge on the aftertreatment device causing soot and ash packed on the device to be dislodged and to fall into the container 42. The upward flow of air also carries and distributes heat evenly through the aftertreatment device. By controlling the air flow rate, the amount of oxygen supplied to the aftertreatment device can also be controlled to control the core temperature and combustion rate. In a preferred embodiment, the high pressure air pulse can penetrate soot built-up on the diesel particulate filter.
A blower 170 or fan is also mounted in the housing 122. A wall 152 (see FIG. 11) separates the blower 150 from the chamber 123. A hose 154 provides fluid communication between the blower 150 and the interior of the main chamber. The blower 170 forces air into the main chamber to facilitate venting the products of combustion from the chamber. Further details regarding the device 120 are provided in PCT App. No. US 06/01850, filed Jan. 18, 2006 and entitled Apparatus for Combusting Collected Diesel Exhaust Material from Aftertreatment Devices and Methods, which is hereby incorporated by reference in its entirety.
In use of the system, the DPF 10 is removed from its corresponding vehicle, and the front door 140 of the cabinet is opened to provide access to the chamber 123. With the door 140 open, the DPF 10 can be mounted (e.g., clamped or otherwise secured) on top of the heating element. Preferably, the DPF is mounted with the inlet side facing downwardly and the outlet side facing upwardly. Once the DPF is in place, the door 140 is closed and the heating element is activated to heat the core of the DPF to a temperature suitable for combusting soot and ash on the DPF (e.g., 900-1500 F). During an initial warm-up period (e.g., about 20 minutes), the heating element is activated. During this warm up period, it is preferred to not provide air pulses to the system so that more uniform radiant heating is provided across the entire face of the core being serviced. Uniform heating prevents preferential air flow paths from developing in the DPF that may interfere with the ability to uniformly regenerate the entire DPF. After the warm-up period, the air outlet 45 begins to direct pulses of air downwardly into the container 42 (e.g., at a pulse rate of 0.5 seconds on and 15 seconds off). The pulses of air reflect off the container 142 and migrate upwardly through the heat reflector 152, the heating element 150 and the DPF mounted on the heating element 150. The pulses of air assist in providing uniform combustion temperatures across the entire volume of the DPF while maintaining a controlled combustion. The pulses of air also assist is dislodging soot and ash from the DPF during the combustion process. The dislodged material falls downwardly from the DPF through the heating element 150 and the heat reflector 152 and is collected in the container 142. The container 142 is preferably periodically disconnected from the cabinet to be emptied.
After the combustion process has been completed (e.g., about 3-5 hours), the heating element 150 turned off and the air flow is increased during the cool-down. In one embodiment, the flow rate is increased to at least 1.5 times the regeneration air flow rate. For example, the pulse rate can be increased to 0.5 second on and 4-10 s or 7.5 to 10 seconds off). The cool-down period can often extend for 2-3 hours. After the heating element and cabinet interior cool to a predetermined temperature (e.g., 140 F), the front door 40 can be opened to remove the regenerated DPF. Thereafter, another DPF can be mounted on the heating element 150 and the process can be repeated.
During heating, if the heating element fails (e.g., a heating controller does not modulate), the solenoid fails (e.g., sticks open or closed), or the cabinet temperature exceeds a predetermined temperature, the system can be programmed to abort the regeneration cycle.
To make the process more efficient, the DPF 10, the pipe sections 200, 204 and the container 142 can be covered with insulating layers (e.g., heat shields, blankets, sheaths, etc.) For example, FIG. 15 schematically shows an insulation sheath/blanket 250 wrapped around the DPF and the pipe sections 200, 204.
D. Implementation Method
FIG. 18 is a flow chart outlining certain aspects of the present disclosure. At block 320 of FIG. 18, a customer is sold a DPF for use on a low operating temperature vehicle. At the time of the sale, the customer can be offered a service plan and service schedule (i.e., a service contract) that details costs associated with regenerating the DPF and also provides a regeneration schedule. The service plan can be carried out by dealers or other third parties. At the time of the sale, the customer can also be provided with an option to upgrade the DPF to an on-board active regeneration system in the event that the regeneration frequency exceeds the amount set forth in the initial service plan.
At block 340 of FIG. 18, the regeneration service is implemented to maintain the DPF. Off-board regeneration systems such as a pulse regenerator, a thermal regenerator or other systems can be used. Dealers affiliated with the DPF manufacturer can be used to implement the service schedule.
At block 360 of FIG. 18, the regeneration frequency for the DPF is monitored. If the frequency exceeds a predetermined amount, or if the customer is otherwise dissatisfied with the DPF or the regeneration schedule, the DPF can be converted to an active system.
E. On-Board Active Regeneration System
FIGS. 19-21 illustrate a diesel engine exhaust treatment device 420 equipped with on-board active regeneration equipment. The device 420 can be used to treat exhaust from engines emitted from diesel engines having duty cycles with average temperature profiles greater than 200 degrees Celsius for less than 40 percent of the operating cycle in the event that a system without on-board active regeneration fails to meet customer needs. The exhaust treatment device 420 includes an outer body 422 (e.g., a housing or conduit) having an inlet end 424 and an outlet end 426. The exhaust treatment device 420 also includes a diesel oxidation catalyst 428 (i.e., a catalytic converter/DOC) and a diesel particulate filter 430 (i.e., a DPF) positioned within the outer body 422. The DOC 428 is positioned upstream from the DPF 430. An on-board heater 432 is positioned within the outer body 422 between the DOC 428 and the DPF 430. The heater 432 is adapted to selectively provide heat for regenerating the DPF 430. The exhaust treatment device 420 also includes a power line 434 for providing electricity to the heater 432, a thermocouple 436 for measuring the temperature of the heater 432, a back pressure sensor 438 for sensing the back pressure generated behind the DPF 430, and an air inlet 440 for providing combustion air within the outer body 422 during regeneration of the DPF 430. The exhaust treatment device 420 also includes a heat shield 442 that surrounds the outer body 422 along a region coinciding with the DOC 428, the heater 432 and the DPF 430. A controller (e.g., a controller 406 provided at a shore station 440 as shown at FIGS. 22 and 23) can be used to control the regeneration process. For example, the controller can be programmed with a regeneration recipe (e.g., regeneration protocol) that sets parameters such as regeneration heating temperatures, heating durations, cool-down durations, and air flow rates during heating and cool-down. The shore station 440 can also provide power to the heater. Further details regarding the device 420 are provided at PCT Publication No. WO06/96244, filed Jan. 18, 2006, which application is hereby incorporated by reference in its entirety.
F. Verification Process
The process for verifying emissions control technology with CARB is set forth at Title 13, California Code of Regulations, sections 2700 to 2710 (see attached as Exhibit 1). The verification application includes information such as a definition of the technology desired to be verified, a definition of the applicable diesel engine characteristics, a definition of the type of application, an indication the type of verification being sought (e.g., level 1, 2 or 3), a description of the principles of operation of the technology, a listing of emission reduction test results, a listing of durability test results, and a field demonstration.
In the present case, the technology desired to be verified includes a DPF device in combination with the off-board regeneration equipment such as an off-board heating device for combustion soot on the DPF and/or an off-board air movement device for blowing soot from the DPF. By way of example, the DPF device can have the same structure as the DPF 10 previously described herein. Also by way of example, the off-board regeneration technology can include the off-board regeneration device 20 and/or the off-board regeneration device 120. Of course, other configurations of DPF's and off-board regenerating systems can also be used.
It will be appreciated that a number of parameters can be used to define the category/type of diesel engine being verified. For example, the verification could apply to diesel engines originally manufactured from model year 1994 through the present.
The aspects of the present disclosure relate to obtaining verification (e.g., level 2 or level 3 verification) for a DPF system that does not include active, on-board regeneration equipment used in an application having a duty cycle with an average temperature profile greater than a predetermined temperature (e.g., 240, 220 or 200 degrees Celsius) for less than a certain percentage (e.g., 40 percent) of the engine operating cycle.
To generate emissions production test results, durability test results and a field demonstration, the DPF device will be tested in accordance with the requirements specified by Title 13 of the California Code of Regulations, Sections 2703, 2704 and 2705. During the testing protocol, the DPF device will periodically be regenerated using an off-board regeneration system. The preferred duration between off-board regeneration events can be set forth in the verification application. For example, off-board regeneration can be conducted at set intervals (e.g., bimonthly), when a back pressure sensor detects that a predetermined level of back pressure is behind the DPF, or when the engine has operated a predetermined number of hours since the last regeneration.

Claims

1. A method for obtaining verification for a diesel particulate filter for use in applications having duty cycles with average temperature profiles greater than 240 degrees Celsius for less than 40 percent of the duty cycles, the method comprising:

submitting a verification application that includes data showing that the diesel particulate filter satisfies predetermined emission reduction targets when used to treat exhaust generated from diesel engines used in applications having duty cycles with average temperature profiles greater than 240 degrees Celsius for less than 40 percent of the duty cycles, the diesel particulate filter being used in combination with off-board regeneration equipment including at least one of an off-board heating device for combusting soot on the diesel particulate filter and an off-board air moving device adapted for blowing soot from the diesel particulate filter.

2. The method of claim 1, wherein the verification application is an application for CARB level 2 verification, and wherein the data shows that the diesel particulate filter satisfies an emission reduction target required for the diesel particulate to be verified as a CARB level 2 device.

3. The method of claim 1, wherein the verification application is an application for CARB level 3 verification, and wherein the data shows that the diesel particulate filter satisfies an emission reduction target required for the diesel particulate to be verified as a CARB level 3 device.

4. The method of claim 1, wherein the verification application includes data showing that the diesel particulate filter satisfies predetermined emission reduction targets when used to treat exhaust generated from diesel engines used in applications having duty cycles with average temperature profiles greater than 220 degrees Celsius for less than 40 percent of the duty cycles.

5. The method of claim 1, wherein the verification application includes data showing that the diesel particulate filter satisfies predetermined emission reduction targets when used to treat exhaust generated from diesel engines used in applications having duty cycles with average temperature profiles greater than 200 degrees Celsius for less than 40 percent of the duty cycles.

6. The method of claim 1, wherein the diesel particulate filter is not catalyzed with a precious metal catalyst.

7. The method of claim 1, wherein the diesel particulate filter has a precious metal catalyst loading of less than 50 grams per cubic foot of filter substrate.

8. The method of claim 1, wherein the diesel particulate filter is required to be removed from an exhaust system of the diesel engine during regeneration.

9. A method for obtaining governmental verification for a diesel particulate filter, the method comprising:

verifying the diesel particulate filter in combination with off-board regeneration equipment, the off-board regeneration equipment including at least one of an off-board heating device for combusting soot on the diesel particulate filter and an off-board air moving device adapted for blowing soot from the diesel particulate filter.

10. The method of claim 9, wherein the diesel particulate filter is not catalyzed with a precious metal catalyst.

11. The method of claim 9, wherein the diesel particulate filter has a precious metal catalyst loading of less than 50 grams per cubic foot of filter substrate.

12. The method of claim 9, wherein the diesel particulate filter is required to be removed from an exhaust system of the diesel engine during regeneration.

13. A method of providing technology for use in treating exhaust gas emitted from diesel engines for low temperature applications, the method comprising:

providing a diesel particulate filter system that does not include active, on-board regeneration, the diesel particulate filter system being verified by a governmental agency in combination with off-board regeneration equipment, the off-board regeneration equipment including at least one of an off-board heating device for combusting soot on the diesel particulate filter and an off-board air moving device adapted for blowing soot from the diesel particulate filter.

14. The method of claim 13, wherein the diesel particulate filter is not catalyzed with a precious metal catalyst.

15. The method of claim 13, wherein the diesel particulate filter has a precious metal catalyst loading of less than 50 grams per cubic foot of filter substrate.

16. The method of claim 13, wherein the diesel particulate filter is required to be removed from an exhaust system of the diesel engine during regeneration.

17. A method for treating exhaust from a diesel engine used for an application having an initially measured temperature profile, the method comprising:

treating diesel engine exhaust with a diesel particulate filter intentionally designed to not be capable of being regularly passively regenerated at the initially measured temperature profile; and

regenerating the diesel particulate filter with off-board regeneration equipment, the off-board regeneration equipment including at least one of an off-board heating device for combusting soot on the diesel particulate filter and an off-board air moving device adapted for blowing soot from the diesel particulate filter.

18. The method of claim 17, wherein the diesel particulate filter is not catalyzed with a precious metal catalyst.

19. The method of claim 17, wherein the diesel particulate filter has a precious metal catalyst loading of less than 50 grams per cubic foot of filter substrate.

20. The method of claim 17, wherein the diesel particulate filter is required to be removed from an exhaust system of the diesel engine during regeneration.