WO1993003262A1

WO1993003262A1 - Particulate trap regeneration apparatus and method

Info

Publication number: WO1993003262A1
Application number: PCT/US1991/005449
Authority: WO
Inventors: John Maxwell Bailey
Original assignee: Caterpillar Inc.
Priority date: 1991-08-01
Filing date: 1991-08-01
Publication date: 1993-02-18

Abstract

An apparatus (10) and method for regenerating a trap (18) which removes particulates from an exhaust stream, and more particularly, an apparatus (10) and method for cleaning a particulate trap core (24) by directing a gas at high temperature through the trap core (24) in a direction opposite to the flow of exhaust at a constant high flow rate or a pulsed high flow rate so as to blow a significant portion of the particulate matter collected in the trap core (24) out of the trap core (24) prior to being burned in the trap core (24).

Description

P.ARTICULATE TRAP REGENERATION APPARATUS AND METHOD

Technical Field

This invention relates to an apparatus and method for regenerating a trap which removes particulates from an exhaust stream, and more particularly, to an apparatus and method for cleaning a particulate trap by directing a gas at high temperature through the trap in a direction opposite to the flow of exhaust at a constant high flow rate or a pulsed high flow rate.

Background Art

Particulate traps are one means of trapping exhaust particles from exhaust streams so as to prevent the dispersal of particles into the atmosphere. However, after awhile, the traps fill with particulate matter and must be cleaned or regenerated in order to continue to remove particles from the exhaust stream and so as not to cause undesirable back pressure on the engine, or other power unit. In typical earlier apparatuses and methods for regeneration, the regeneration gas was directed at the inlet end of the trap in the same direction as the exhaust, where it was heated by some means and a hot burning zone would then pass across the trap toward the outlet end thereof, so as to burn out the particulates and cleanse the trap. Faults of such systems were the hot products of combustion were forced directly into the porous trap material, thus heating the materials to such a high temperature that the service life of the trap was adversely affected, and also, the ash resulting from the combustion of the particulates was forced directly into the porous material of the trap, eventually plugging the pores of the trap material. This reduced the efficiency of the trap and forced more and more frequent regeneration until finally the trap was completely plugged.

Eventually, it was theorized that if the regeneration gas was introduced at the outlet end of the trap in a direction opposite to the flow of exhaust gas, the above mentioned faults of the earlier systems would be reduced, if not eliminated. However, tests showed the above was true only at relatively high flow rates. At relatively low flow rates, reverse flow regeneration caused traps to attain a somewhat higher temperature than forward flow regeneration. This correlation between high and low flow rates was unexpected.

Analytically, it was expected that because more oxygen is fed to the hot burning zone at high flow rates, the hot burning zone would burn hotter thus heating the trap to higher temperatures.

However, bench tests showed otherwise. Subsequently, it was theorized that in the case of reverse flow, at high flow rates, a large amount of the particulates in the trap were blown out of the trap and were partially or completely burned outside of the trap during the regeneration process. This was confirmed by photographic evidence of particulates being blown out of the trap at high flow rates but not at low flow rates. This lead to the conclusion that the trap temperature attained during regeneration, whether forward or reverse flow, is directly related to the amount of particulates which are actually burned in the trap. The higher temperature expected from the increased oxygen is more than offset by blowing a significant amount of particulate out of the trap, resulting in a lower trap temperature.

With the above background information, it was apparent that it was advantageous to dislodge a significant portion of the particulates and remove them from the trap prior to burning. A high flow rate of regeneration gas could dislodge and carry away a significant amount of particulates while low flow rates could not. However, in many systems such as on some on-highway trucks, a constant high flow rate is undesirable, if not impractical, because the electrical heaters necessary to heat the regeneration gas require more energy than is usually available on the truck. Similarly, very high constant air flow would require a compressor much larger than is normally used on a vehicle for brakes and other accessories.

Basically, one aspect of the subject invention uses a reverse flow of oxygen-containing gas pulsed between short bursts at high flow rates and longer periods of low or no flow rates, for example, one second and five seconds, respectively. This permits a high peak flow rate for blowing much of the particulates accumulated in the trap while requiring much lower average flow rates (about one-sixth for the example given) . Consequently, the electrical heating and air supply capacities required are much lower than would be required if a constant high flow rate of regeneration gas was used for regeneration. However, blowing particulates out of the trap prior to burning led to one other concern; what to do with the particulates blown out. Because the particulates are blown out in relatively large "cakes" of agglomerated particulates, a secondary filter was added upstream of the trap core through which the particulates in the exhaust gas could pass but through which the relatively large "cakes" blown out of the trap could not.

Disclosure of the Invention

In one aspect of the present invention, a method of regenerating a particulate trap core through which exhaust flows from a first end and egresses as filtered exhaust gas at a second end is disclosed. The method includes the steps of:

(a) using a device coaxially aligned with the second end of the core to periodically pulse hot, oxygen-containing gas towards the second end of the core at a rate independent of the exhaust gas rate sufficient to blow a significant portion of particulate out of the core prior to being burned in the core;

(b) catching the particulates blown out of the core on a secondary filter; (c) causing the hot, oxygen-containing gas to travel through the core and egress at the first end thereof;

(d) burning the particulate matter remaining in the core; and (e) burning the particulate on the secondary filter.

In another aspect of the present invention, an apparatus for practicing the above method is disclosed. The apparatus includes: a device coaxially aligned with the second end of the core for directing oxygen-containing gas through a heater element toward the second end of the core at a first rate independent of the exhaust gas rate and sufficient to blow a significant portion of particulate out of the core prior to being burned in the core, and burning the particulate matter remaining within the core in a reverse flow manner; a means for pulsing the hot, oxygen-containing gas between the first rate and a lesser second rate; and a secondary filter upstream from the core, the secondary filter allowing substantially all of the exhaust particulates to pass through while catching a substantial portion of the particulates blown out of the core during regeneration, whereon the particulates are burned.

Brief Description of the Drawings

Fig. 1 is a diagrammatic elevational view of a particulate trap regeneration apparatus of the present invention, with a repetitive centered portion of the vertical stack broken away for illustrative convenience; and

Fig. 2 is a horizontal cross-section of a representative trap assembly taken along line 2-2 of Fig. 1.

Best Mode for Carrying Out the Invention

Looking at Fig. 1, a particulate trap regeneration apparatus 10 is shown as it might be installed on a heavy duty, on-highway truck in the location of the usual muffler. It is contemplated that the regeneration apparatus 10 could be serially connected to a conventional muffler, although it inherently has noise-muffling capability. The apparatus 10 includes a vertically arranged exhaust housing or stack 12 connected at the bottom to an engine exhaust inlet pipe 14 and at the top to an outlet pipe 16 and a number of trap assemblies 18, in this case seven, mounted within the housing 12. The housing 12 and the trap assemblies 18 are particularly set forth and more fully described in U.S. Patent Application Serial No. 07/531,264, entitled "Particulate Trap Regeneration Apparatus and Method", which was allowed on June 18, 1991, and which is incorporated in its entirety herein by reference.

In normal operation, exhaust gases enter the housing 12 through the inlet pipe 14 and eventually enter a trap assembly 18 at a first end 20, pass through and exit at a second end 22, whereupon the exhaust gases are vented through the outlet pipe 16. A cross section of a representative one of the trap assemblies 18 is illustrated in Fig. 2. Each trap assembly includes a cylindrical particulate trap core 24 made of a high temperature resistant ceramic material and having a first end 26 for normally receiving the exhaust gases and a second end 28 for discharging the filtered exhaust gases. Preferably, the trap core defines a first plurality of passages 30 in open communication with the interior of the duct

32, and a second plurality of passages 34 in generally open communication with the interior of the duct 36 during normal operation. The elongate and juxtaposed passages 30 and 34 are exaggerated in size within the broken open sectionalized window in Fig. 2 in order to view them. The opposite^" ends of adjacent passages 30 and 34 are blocked or plugged in order to force the exhaust gases to travel radially through a plurality of relatively thin porous walls identified by the reference number 38. Porous walls 38 are typically in the range of 0.5 millimeters thick, or less. Since these wall flow trap cores are known in the art, they need not be further described.

Each of the trap cores 24 is sealingly secured within the respective sleeve 40 by a cylindrical band or mat 42 of an insulating material having resistance to high temperature. The sleeve flange 44 is releasably secured to the second partition 46 at the opening 48, and an annular retainer 50 is connected to the flange 44 through an electrically insulating washer pad 52 by any suitable electrically insulated fastening device, not shown. Each trap assembly 18 includes a ceramic disc 54 which is secured radially within an inboard annular collar 56 of the retainer 50, and which has formed therein one or more spiral grooves 58 that open inwardly toward the trap core 24 to receive a corresponding number of electrical heating elements 60, only one of which is shown. A plurality of holes 62 extend through the disc 54 at preselected relatively uniform distances along the spiral grooves 58. One end of each heating element 60 is electrically connected to the sleeve 40 (which is grounded to the vehicle) as at 62, and at the other end to a bus 64, which is electrically connected to the positive side of a battery. The retainer 50 also has an outwardly facing annular seat 64 of a generally conical configuration.

Each trap assembly 18 further includes a secondary filter 66. The secondary filter 66 is located upstream of the particulate trap core 24 such that the exhaust gas will flow through the secondary filter 66 before encountering the trap core 24. The secondary filter 66 has passages large enough to allow substantially all of the exhaust gas particulates to pass through yet small enough to catch most of the relatively large cakes of agglomerated particulates which are blown out of the trap core 24 during reverse flow regeneration, as later explained. The soot cakes will be burned on the secondary filter 66 during regeneration, therefore, the secondary filter 66 must be made of material having high temperature capability, such as porous silicon carbide, and, preferably, the material should have a reasonably high heat capacity to be able to absorb heat so as to reduce the maximum temperature of the material when the soot cakes are being burned. The secondary filter 66 is preferably conically shaped and has a uniform cross-section.

Each trap assembly 18 further includes a reverse flow device 68 oriented substantially along the central axis 70 of the trap core 24. A cylindrical opening 72 is formed in each cover 74 along the respective axis 70, and a tubular guide member 76 is releasably secured to the cover 74. A cap 78 having an internal cylindrical chamber 80 is connected to the guide member 76 to receive a reciprocating piston element 82 therein. The piston element 82 includes a piston head 84 and a hollow rod portion 86 having a cylindrical flow director 88 connected thereto which is serially connected to an internal chamber 90 in the hollow rod portion 86, which in turn is serially connected to a relief valve 92. The internal chamber 90 opens radially outwardly via a plurality of ports 94. A compression spring 96 is seated within the cap 78 so as to continually bias the piston head 84 and the piston element 82 outwardly or to the right when viewing Fig. 2.

During normal operation the piston element 82 is located to the right of the position illustrated in Fig. 2, and at that position a conical seat 98 formed on the inboard end of the guide member 76 is sealingly engaged by a corresponding conical seat 100 formed* on the inboard end of the rod portion 86. A funnel-shaped shield or conical diffuser member 102 extends axially inwardly from the inboard end of the rod portion 86 and defines an inwardly facing annular seat 104. In the normal mode the conical seat 104 is axially displaced from the corresponding conical seat 64 on the retainer 50. A suitably perforated flow-distribution plate 106 is optionally rigidly connected to the inboard end of the flow director 88 so as to define a generally conical chamber 108 within the diffuser member 102 and immediately around the flow director 88 to assure an even flow of an oxygen-containing gas to the ceramic disc 54 and to the trap core 24.

Connected to the cap 78 through a flow choking orifice 110 is a 3-way valve 112. The valve 112 is of the electrically actuated solenoid type. Each of the 3-way valves 112 is connected to a common header 114 which in turn is connected to an accumulator 116 which in turn is connected to a source 118 of pressurized gas, preferably oxygen-containing gas. The 3-way valve 112 has three openings: a first opening 119 at the header 114; a second opening 121 at the flow choking orifice 110; and a third opening 123 to a vent 117. The valve can operate to close all three openings or only one of the three openings, leaving an open passage between the other two openings. Optionally, two 2-way valves can be used in place of the 3-way valve.

Oxygen-containing gas, in this case air, in the accumulator 116 and header 114 is under constant pressure, preferably at least 40 to 100 psig. The source 118 of pressurized air may be a compressor or it may be an air brake reservoir of a vehicle connected to the accumulator 116 through a relief valve, such that when the engine is started the air brake reservoir will pressurize and at a certain pressure a relief valve will open, thus pressurizing the air in the accumulator and header.

As shown representatively in Fig. 1, the regeneration apparatus 10 includes control means or a control device 120 for sequentially controlling the operation of the 3-way valves, as later explained. Electrical leads 122 extend from the control device 120 to each 3-way valve 112.

Industrial Applicability

As the trap cores 24 become loaded with particulate matter, the pressure drop across the cores 24 increases and at some point regeneration is required. Various means for sensing the time at which the trap cores 24 are loaded can be utilized. A signal is then sent to the control device 120, which is preferably of the solid state type. The control device 120 will then begin the timed regeneration event for each trap assembly 18, in sequence. As one trap assembly 18 is being regenerated, the other trap assemblies 18 will remain in normal operation trapping particulate matter from the exhaust gas.

The control device 120 sends electrical current through the leads 122 to the solenoid of the 3-way valve 112 to open the first 119 and second 121 openings in the valve 1Ϊ2 thus creating a passage for the pressurized air to travel from the header 114 to the flow choking orifice 110.

The pressurized air travels from the header 114, through the valve 112, and through the orifice 110 into the chamber 124. The choking orifice 110 controls the air flow rate to a preselected substantially constant range so that the flow of the air will be nearly constant and relatively insensitive o external factors. The pressurized air fills the chamber 124, forcing the piston element 82 to the left to the position illustrated, whereupon the conical diffuser member 102 abuts the retainer 50 and the conical seats 64 and 104 are forced together. As pressure builds up in the chamber 124, a relatively significant force is generated on the piston head 84 sufficient to offset the exhaust pressure acting on the conical diffuser member 102 and to provide a relatively tightly closed seal joint at the seats 64 and 104. The contacting of the seats 64 and 104 completes the electrical circuit of the heater element 60 which then begins to heat up.

As pressure further builds up in the chamber 124 the pressurized air will overcome the relief valve 92 and travel through hollow rod portion 86, into chamber 90, and out the radially oriented ports 94 into the conical chamber 108. From the conical chamber 108 pressurized air will travel through the variably spaced distribution holes in the perforated plate 106, the holes 62 in the ceramic disc 54 around the heating element 60, and will enter the passages 34 in the trap core 24.

As stated previously, it is necessary that the air flow through the trap core 24 at a high rate to blow a substantial portion of the particulates accumulated in the core 24 out of the core 24. A flow rate of at least 5 standard cubic feet per minute per liter (scfm/1) is required, however, rates of about 15 scfm/1 are preferred. If a means is available that can provide constant high flow rate, then the passage between the header 114 and orifice 110 can be left open throughout regeneration.

However, trying to provide a constant high flow rate may be disadvantageous for at least two reasons. First, at constant high flow rates, there ust exist a source to provide continuous high pressure. In many applications, such a source is not readily available. Second, at constant high flow rates, the air has a cooling effect on the heater element 60, thus, greater electrical energy is required to keep the heater at a sufficiently high temperature to heat the regeneration air to a temperature which will ignite and burn the particulates in the trap core 24. In many applications, for instance on-highway trucks, the electrical energy necessary to heat the heating element 60 to such temperatures and to continuously run a compressor to provide the relatively high pressure gas is not readily available. However, it is not necessary that the high flow rate be constant. A series of short periods, or bursts, of high flow rate followed by periods of low or no flow rate, are adequate. This pulsing of the pressurized gas is a viable and functional alternative to constant high flow rate air.

In a preferred system of this type, the passage in the valve 112 from the header 114 to the orifice 110 will be opened for about 1 second, then closed for about 5 seconds, then opened for 1 second, then closed for 5 seconds, etc. This pulsed series of opening and closing will continue for a preselected period of time sufficient to completely regenerate the trap.

In such a system, the average electrical energy and pressurized gas requirements are only about one-sixth of that required for constant flow at the same maximum flow rate, consequently, there is less of a cooling effect by the gas and there is less pressurized gas required. Yet, the short burst provides enough force to blow an amount of -13-

particulates out of the trap 24 during the regeneration event comparable to constant high flow rate, much like how a comparable number of leaves will be blown off a tree during repeated gusts of high wind as will be blown off during the same period from a sustained wind at the same magnitude. Preferably, at least about 15% of the particulates are blown out of the core prior to being burned in the core.

Considering le above chain of events during pulsed regeneration mc -a closely, when the first 119 and second 121 openings in the valve 112 are opened by the control device 120, oxygen-containing gas will flow from the header 114 through the valve 112 at a relatively high rate (as determined by orifice 110 and the system gas pressure and temperature) and into the chamber 124, until the valve 112 is closed. The accumulator 116 and header 114 are sized such that the short bursts of gas through the valve 112 will not appreciably decrease the pressure in the system, until it can be repressurized. More than one burst of gas may be required to pressurize the chamber 124. The build-up of pressure in the chamber 124 will force the piston element 82 to the left to the position illustrated, whereupon the conical diffuser member 102 abuts the retainer 50 and the conical seats 64 and 104 are forced together. This action will provide a ground connection to the heater element 60, thus energizing it. When the diffuser assembly stops moving, the short bursts of pressurized gas will build up pressure in the chamber 124 until the pressure overcomes the relief valve 92, which is set at about 30 pounds per square inch. Pressurized air will blow through the valve 92 for a short period of time until the pressure in the chamber 124 has dissipated to a level at which it cannot overcome the relief valve 92 and the relief valve 92 reseats. The next burst of air through the valve 112 will again pressurize the chamber 124 enough to overcome the relief valve 92 for a short period of time until the pressure dissipates and the relief valve 92 reseats. When the relief valve 92 is open, gas is permitted to pass through the heater element 60, through the core 24, and through the secondary filter 66, until it enters duct 32. Pressurized gas trapped in the chamber 124 by the seated relief valve 92 will prevent the diffuser assembly from retracting when the pulse of flow is cut-off, thus maintaining the heater ground connection and preventing leakage of exhaust through the trap 24 in the forward direction, which would cool the trap 24 and heater element 60.

Following energization of the heater element 60, the element 60 will continue to increase in temperature until the short pulse of gas which passes through it will be heated to about 600 degrees Celsius and will accordingly carry the heat emitted by the heater element 60 into the trap material. After the heater element 60 reaches about 600 degrees Celsius, an equilibrium condition will exist in which the average flow of oxygen-containing gas will be sufficient to remove the energy supplied to the element 60. Consequently, the air temperature and element 60 temperature will remain essentially constant. Heated gas enters the trap core 24 by way of the second end 28 and travels from the second plurality of passages 34 to the first plurality of passages 30 through the walls 38. The porous material of the walls 38 subsequently becomes heated until it reaches a temperature of approximately 500 degrees Celsius, or slightly above that value, at which time the particulates remaining in the trap core 24 will ignite and primarily burn progressively toward the first end 26 of the trap core 24.

The particulates blown out of the trap 24 by the repeated short pulses of air are primarily in the form of relatively large "cakes" of agglomerated particulates which are able to be collected on the secondary filter 66. After the air exiting the trap 24 has reached about 500 degrees Celsius, the particulates on the secondary filter 66 will ignite and be burned completely by the continuing short bursts of heated air. Also any ash which was collected in the trap core 24 will be blown out of the core 24, pass through the relatively open secondary filter 66, and eventually settle in the ash trap (not shown) located at the bottom of the inlet pipe 14.

After the trap core 24 and secondary filter 66 are regenerated, which can be signaled by the end of a predetermined period or by the measurement of an acceptable pressure drop across the trap core 24, the control device 120 will send a current of reverse polarity to the valve 112, closing the first opening 119 at the header 114 and opening the second 121 and third 123 openings at the orifice 110 and vent 117, thus creating a passage through which the pressurized gas in the chamber 124 can be vented. As the pressure in the chamber 124 dissipates, the spring 96 overcomes the pressure and moves the diffuser assembly to the right to its original position, thus de-energizing the heater element 60 and permitting exhaust to again flow through the trap assembly 18. At this time, the control device 120 will terminate electrical energy to the valve 112 permitting it to return to its neutral position with all passages closed. The next trap assembly 18 is then regenerated by the same process. Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.

Claims

1. A method of regenerating a particulate trap core (24) wherein said core (24) has a first end (26) exposed to exhaust gas having particulate matter therein and wherein said exhaust gas flows from said first end (26) of said core (24) through said core and egresses as filtered exhaust gas at a second end (28) of said core (24), comprising the steps of: (a) directing gas towards said second end

(28) of said core (24) at a first rate independent of said exhaust gas rate sufficient to blow a significant portion of particulate matter out of said core (24) prior to being burned in said core (24); (b) means (60) for heating said gas for burning a substantial portion of the particulate matter remaining in said core (24) , and

(c) causing said heated gas to travel through said core (24) and egress at said first end (26) thereof.

2. The method of claim 1, wherein said gas is directed toward said second end (28) of said core (24) by a device (68) substantially coaxially aligned with said second end (28) of said core (24) .

3. The method of claim 1, wherein after said gas has been directed towards said second end (28) of said core (24) at said first rate, said first rate is decreased to a second rate.

4. The method of claim 3, wherein said gas is pulsed periodically between said first rate and said second rate.

5. The method of claim 3, wherein said first rate is at least five standard cubic feet per minute per liter of core.

6. The method of claim 1, wherein at least

15% of the particulate matter trapped in said core (24) is blown out of said core (24) prior to being burned in said core (24) .

7. The method of claim 1, further comprising the steps of:

(d) catching a significant portion of the particulate matter blown out of said core (24) on a secondary filter (66) ; and (e) burning the particulate matter on said secondary filter (66) .

8. The method of claim 7, wherein said first rate is at least five standard cubic feet per minute per liter of core.

9. The method of claim 7, wherein at least 15% of the particulate matter trapped in said core (24) is blown out of said core (24) prior to being burned in said core (24) .

10. A particulate trap regeneration apparatus (10) of the type including a particulate trap core (24) having a first end (26) opening into an exhaust gas having particulate matter therein and allowing said exhaust gas to flow through said core (24) and egress as filtered exhaust gas from a second end (28) of said core (24) , the improvement comprising: regeneration means (68) for directing gas toward said second end (28) of said core (24) at a first rate independent of said exhaust gas rate and sufficient to blow a significant portion of the particulate matter out of said core (24) prior to being burned in said core (24), and a means for heating said gas for burning a substantial portion of the particulate matter remaining within said core (24) in a reverse flow manner.

11. The apparatus of claim 10, including a means (112) for decreasing said rate at which said gas is directed toward said second end (28) of said core (24) from said first rate to a lesser second rate.

12. The apparatus of claim 11, including a means (112) for pulsing said gas between said first rate and said second rate.

13. The apparatus of claim 10 wherein the regeneration means (68) includes a reverse flow device (68) substantially coaxially aligned with said core (24) and an electrical heating element (60) adjacent said second end (28) of said core (24) .

14. A particulate trap regeneration apparatus (10) of the type including a particulate trap core (24) having a first end (26) opening into an exhaust gas having particulate matter therein and allowing said exhaust gas to flow through said core

(24) and egress as filtered exhaust gas from a second end (28) of said core (24) , said core (24) including a plurality of porous walls (38) defining a first plurality of axial passages (30) in open communication with said first end (26) of said core (24) and a second plurality of axial passages (34) in open communication with said second end (28) of said core (24) , the improvement comprising: a source (18) of pressurized gas; regeneration means (68) for directing said pressurized gas toward said second end (28) of said core (24) , into said second plurality of passages (34) , through said porous walls (38) into said first plurality of passages (30) and out said first end (26) in a reverse flow direction at a rate sufficient to blow a significant portion of particulate matter out of said core (24) ; and means (60) for heating said pressurized gas for burning a substantial portion of the particulate matter remaining in said core (24) .

15. The apparatus of claim 14, including a means (112) for decreasing said rate at which said gas is directed toward said second end (28) of said core (24) from said first rate to a lesser second rate.

16. The apparatus of claim 15, including a means (112) for pulsing said gas between said first rate and said second rate.

17. The apparatus of claim 14 wherein the regeneration means (68) includes a reverse flow device (68) substantially coaxially aligned with said core (24) and an electrical heating element (60) adjacent said second end (28) of said core (24) .

18. A particulate trap regeneration apparatus (10) of the type including a particulate trap core (24) having a first end (26) opening into an exhaust gas stream having particulate matter therein and allowing the egress of filtered exhaust gases from a second end (28) thereof, the improvement comprising: regeneration means (68) for directing a gas toward said second end (28) of said core (24) at a first rate sufficient to blow a significant portion of particulate matter out of said core (24) ; and a secondary filter (66) upstream from said core (24) , said secondary filter (66) allowing substantially all of said exhaust particulates to pass through said secondary filter (66) while catching a substantial portion of the particulates matter blown out of said core (24) during regeneration.

19. The apparatus of claim 18, including a means (112) for decreasing said rate at which said gas is directed toward said second end (28) of said core (24) from said first rate to a lesser second rate.

20. The apparatus of claim 19, including a means (112) for pulsing said gas between said first rate and said second rate.

21. The apparatus of claim 18, wherein the regeneration means (68) includes a reverse flow device (68) substantially coaxially aligned with said core (24) and an electrical heating element (60) adjacent said second end (28) of said core (24) .

22. The apparatus of claim 19, wherein said gas travels through said trap core (24) and egresses at said first end (26) thereof and wherein said gas is made hot prior to exiting said trap core (24) for igniting and burning the particulate matter remaining within said trap core (24) .

23. The apparatus of claim 20, wherein the gas egressing from said core (24) ignites and burns the particulate matter on said secondary filter (66) .

24. The apparatus of claim 22, including a means (112) for decreasing said rate at which said gas is directed toward said second end (28) of said core (24) from said first rate to a lesser second rate.

25. The apparatus of claim 22, wherein the regeneration means (68) includes a reverse flow device (68) substantially coaxially aligned with said core (24) and an electrical heating element (60) adjacent said second end (28) of said core (24) .