Abstract:
Internal combustion engine exhaust filter devices and the like are regenerated by placement in a reclamation or burn-off furnace, raising the temperature to at least about 800° F. to 900° F. and conducting relatively low volumes of low pressure air through the filter media to combust entrapped particulates and other materials residing on the filter media. The reclamation furnace includes an afterburner for combusting materials discharged from the filter devices into the furnace chamber so that complete combustion of materials is accomplished before discharge from the furnace. The flow of combustion air for the filter devices is controlled by manifolding and valving connected to a source and the oxygen content of combustion air may be enhanced by a separate source of oxygen injected into the combustion air flow stream.

Description:
BACKGROUND OF THE INVENTION 
   Regulatory authorities around the world have established that emissions from internal combustion engines, including gasoline and diesel engines, will be regulated. Diesel and gasoline engine exhaust streams present unique filtration problems. The only solution to these problems is the development of a particulate (soot) filter to extract particulate material from the exhaust stream. However, filters which include fluid and particulate filtration media, typically ceramic honeycomb type structures, eventually become clogged with matter trapped by the media and such filters must either be discarded or subjected to a time consuming and expensive regeneration or cleaning process. The capital cost of such filters is not inconsequential, as compared with conventional engine intake air filters and the like, for example. Accordingly, discarding engine exhaust filters is expensive and regeneration of the filter media is desirable. The present invention provides an improved method and apparatus for regenerating or cleaning filters, including ceramic filters for gasoline and diesel engines, in particular. 
   SUMMARY OF THE INVENTION 
   The present invention provides an apparatus for cleaning or regenerating fluid filters, particularly internal combustion engine exhaust filters constructed of metal or ceramic housings and typically including ceramic porous filter media disposed therein. 
   The present invention also provides an improved method for regenerating or cleaning filters, particularly exhaust filters which are subject to accumulations of soot and other particulates generated during the combustion of hydrocarbon fuels in reciprocating piston and turbine engines. 
   In accordance with one aspect of the present invention, a furnace is provided for producing substantial heat to be transmitted to engine exhaust filter devices and the like which are placed within the furnace, the filter devices being subjected to a substantial temperature rise over the exterior thereof and substantial heating of the filter media. Material trapped by the filter media is removed by incineration from the heat generated by the furnace and from pumping a quantity of combustion air to the interior of the filter device to incinerate accumulated soot, and other particulate matter which has been trapped by the filter media. Combustion products from incinerating material accumulated on the filter media are conducted through a suitable treatment process as part of the furnace operation, which process includes flow of filter combustion products and other material through an afterburner for further incineration of material removed from the filter media. 
   In accordance with another aspect of the present invention, a somewhat conventional reclamation or “burn-off” type furnace is provided which is modified to support one or more engine exhaust filter devices therewithin and to be connected to a source of low pressure air from exterior of the furnace to provide for combusting or incinerating, within the furnace, material accumulated on the media of the filter devices. 
   In accordance with still another aspect of the present invention, a reclamation or burn-off type furnace is provided which includes plural conduits for supplying combustion air in relatively low volumes and at low pressures directly to plural engine exhaust filters disposed in the furnace. The source of combustion air is external to the burn-off furnace and such air is conducted to the filter devices to be treated by suitable conduits which extend through the furnace wall, preferably, from a manifold connected to the source. During operation, as the reclamation or burn-off furnace heats the filter devices to a suitable temperature, air flowing directly through the filter devices supplies oxygen so that carbon soot and any other trapped material within the filter&#39;s ceramic honeycomb structure will be incinerated and removed as combustion products in gaseous form. The speed and completeness of reclamation, regeneration or cleaning of the filter media may be enhanced by increasing the concentration of oxygen in the combustion air supplied to the interiors of the filter devices. 
   Those skilled in the art will further appreciate the above-mentioned advantages and superior features of the invention together with other important aspects upon reading the detailed description which follows in conjunction with the drawing. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The drawing FIGURE is a somewhat schematic diagram of an apparatus for regenerating engine exhaust filters and the like in accordance with the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the description which follows, like parts are marked throughout the specification and drawing with the same reference numerals, respectively. The drawing FIGURE is not intended to be to scale and certain features may be shown in somewhat schematic or generalized form in the interest of clarity and conciseness. 
   Referring to the drawing FIGURE, there is illustrated in somewhat schematic form, a so-called reclamation or burn-off furnace  10  comprising an insulated, rectangular box-like structure  12  having a top wall  14 , a bottom wall  16 , opposed sidewalls  18  and  20  and opposite opposed sidewalls, not shown. One of the sidewalls not shown may include a suitable door for access to the furnace interior. The drawing FIGURE may be considered to be a vertical central section view through a typical rectangular or square box-like structure comprising the housing  12 . Furnace  10  includes a primary heating element or burner  22  for generating a flame  23  and connected to a source of fuel, not shown, by way of a suitable controller  24 . Typical sources of fuel for burner  22  would be liquid hydrocarbon or gaseous hydrocarbon fuels, for example. Combustion takes place in a burner housing  26  and combustion products, primarily heated air, carbon dioxide and water vapor are emitted into a chamber  28  via one or more ports  27 . Airflow into burner housing  26  and air flow out of the burner housing into the chamber  28  takes place in a conventional manner. In fact, the reclamation or burn-off furnace illustrated may be similar in some respects to that described in U.S. Pat. No. 4,270,898 to Kelly, issued Jun. 2, 1981 to the assignee of the present invention. 
   Burn-off furnace  10  includes a secondary burner  30  also operably connected to the controller  24  for generating a flame  31  in a secondary or afterburner housing  32 . Heated air and combustion products generated in and existing in the chamber  28  flow through an opening or port  33 , and are preferably subjected to secondary combustion prior to being vented through a stack  34  so that emissions from stack  34  comprise, essentially, inert gasses and water vapor. Temperature sensor  38  monitors the temperature in the chamber  28  so that controller  24  may adjust the intensity of heating being carried out by the burners  22  and  30 . Temperature conditions in chamber  28  and stack  34  may also be controlled by a water spray controller  40  operably connected to the temperature sensor  36  and operable to provide a fine spray of water  42  by way of a nozzle  44  extending within the chamber  28 . 
   Referring further to the drawing FIGURE, a suitable rack or similar support structure  50  is disposed within the chamber  28  for supporting one or more engine exhaust filters, each designated by the numeral  52 . The exhaust filters  52  are each characterized by a substantially cylindrical metal outer housing  53 , an inlet port  54 , an exhaust port  55  and a ceramic honeycomb filter media  56  disposed within the housing  53  for trapping particulate material emitted by internal combustion engines, such as gasoline and diesel engines of both piston and turbine types, for example. The exhaust filters  52  may be one of several types commercially available. The filters  52  are disposed for exposure to heated gasses circulating within the chamber  28  between burner outlet port  27  and burner inlet port  33 . The filters  52  may be mounted horizontally, as shown, vertically or inclined. Vertical orientation with the exhaust ports facing upward may be preferred. 
   It has been determined in accordance with the invention that particulates and other materials formed by or including unburned or partially combusted hydrocarbon fuels, and trapped by the filter media  56  of the filters  52 , may be removed from the media by raising the temperature of the media to about 800° F. to 900° F., or possibly higher temperatures, for predetermined periods of time. However, it has also been determined that thorough regeneration or cleaning of the filter media  56  is enhanced and the time for cleaning is shortened by circulating relatively low volumes of low pressure gas, such as ambient air, through the filter devices  52 . In accordance with the invention, the apparatus  10  is preferably provided with a relatively low pressure blower or air pump  60  operable to intake ambient air and discharge pressure air to a manifold  62 . Respective conduits  64 , operably connected to manifold  62 , extend through furnace wall  12  and are suitably sealed to prevent escape of combustion gasses from chamber  28 . Conduits  64  may be connected to suitable sections of flexible conduits  66  which are releasably connected directly to the inlet ports  54  of the filter units  52  by way of suitable fittings  67 , as generally shown in the drawing FIGURE. Other arrangements of manifolding and connecting the filter units  52  to a source of low pressure air may be provided without departing from the invention. For example, the conduits  64  and  66  may be of sufficient length, or connected to respective heat exchanger means, not shown, so as to preheat the air flowing through the filters  52 , preferably using heat generated in chamber  28 . 
   In instances when the oxygen content of ambient air supplied by manifold  62  is not sufficient to burn off or incinerate all of the material or residue trapped by the filter elements or media  56 , the air conducted through the filter elements by way of the manifold  62  and the respective conduits  64 ,  66  may be enriched by a source of oxygen  70  connected to the manifold  62  by way of a suitable control valve  72 . In like manner each of the conduits  64  is also provided with a suitable control valve  74  so that the volume of air being conducted to each one of the filter devices  52  may be appropriately adjusted. A suitable check valve  76  may be interposed the manifold  62  and the blower or air pump  60 . 
   Accordingly, in operation, the filter devices  52  may be placed in the chamber  28  and connected to the manifold  62  by way of the respective conduits  64 ,  66  and fittings  67 . A source of combustion air containing ambient concentrations of oxygen or enhanced concentrations of oxygen may be conducted through the filter devices  52  while the temperature in the chamber  28  is raised to a suitable value, such as at least about 800° F. to 900° F. in order to oxidize or combust carbonaceous material in the filters  52 . The overall method of cleaning the filter devices  52  in accordance with the invention is believed to be more efficient in that the temperature in the chamber  28  is not required to be raised as high and for as long a period of time as with prior art reclamation processes, since a suitable flow of combustion air is being supplied to the interior of the filter devices  52  in a forced manner. Of course, as combustion air flowing through the filter devices  52  exits the respective filter devices into the chamber  28  and flows to the afterburner  32 , any material removed from the filter devices  52  will normally be further oxidized, if possible, since operating temperatures within the secondary or afterburner  32  may, typically, be in the range of 1200° F. to 1400° F. Typical volumes for combustion air to be conducted through the filter devices  52  range from about fifty cubic feet per hour to one hundred fifty cubic feet per hour for filters of sizes used in applications for over-the-road motor truck diesel propulsion engines, for example. Of course, the size of the filter devices  52  and the treatment time desired will dictate, to some extent, the volume of combustion air supplied by the blower or pump  60  and the pressurized oxygen source  70 , if used, for example. 
   The construction and operation of the reclamation or burn-off furnace  10  and the method of the present invention are believed to be readily understandable to one of ordinary skill in the art based on the foregoing description. Although preferred embodiments of the invention have been described in detail sufficient to enable one skilled in the art to practice the invention, it will be appreciated that various substitutions and modifications may be made without departing from the scope and spirit of the appended claims.