Patent Publication Number: US-2011067388-A1

Title: Diesel particulate filtration (dpf) system

Description:
TECHNICAL FIELD 
     This disclosure relates generally to exhaust gas treatment systems and more particularly to diesel particulate filtration (DPF) systems. 
     BACKGROUND 
     As is known in the art, most current diesel exhaust gas treatment systems today include a DOC (Diesel Oxidation Catalyst) followed by a DPF (Diesel Particulate Filter). The DPF includes a substrate (sometimes referred to as a substrate brick or brick) with the outlet end closed on the inlet channel and the inlet end closed on the outlet channel. Exhaust gas flows through the inlet channel, crosses the wall of cells, and then exits through the outlet channel. The particles are filtrated in the inlet channel. 
     As is also known in the art, particulate filters are used in the exhaust systems of internal combustion engines, especially diesel engines to trap and remove particulate material (soot), which is primarily formed of carbon, based material. As the engine exhaust passes through the DPF, the particulates are trapped in the filter and accumulate over time. This leads to an increase in the resistance of the exhaust gas flow through the DPF, and therefore, to an increase in the backpressure on the engine. This increase in backpressure has an adverse effect on engine operation, and especially on fuel consumption. In order to reduce backpressure to acceptable levels, the DPF is periodically regenerated by burning off the accumulated particulates, most of which are combustible. 
     As is also known in the art, a traditional cordierite or SiC DPF system needs to under going a regeneration process to burn out soot (i.e., diesel particulate) collected on the DPF wall surface. A few problems are associated with this procedure: 1. A fuel penalty because diesel fuel is injected either through post injection or down pipe injection to generate high exhaust temperature. Usually fuel penalty is in the range of 3 to 5%; 2. Unevenly distributed soot resulted from poor flow uniformity will lead to high temperature gradient inside DPF substrate, and cause durability issue such as ring-off-crack failure; and 3. Very low or even negative NOx conversion efficiency is found during DPF regeneration, usually takes more than 10 minutes. This is becoming an issue for meeting level III emission requirements. 
     SUMMARY 
     In accordance with the present disclosure, a Diesel Particulate Filtration (DPF) system is provided having a supply of diesel particulate filtering material, a first portion of the material being disposed in a path of exhaust gasses passing through the system to collect diesel particulate in the exhaust gasses, and a motor for moving the first portion of the material out of the path while drawing a second portion of the material from the supply into the path. 
     In one embodiment, the supply of material is paper. 
     In one embodiment the material is in a continuous roll. 
     In one embodiment, the system includes a control system for operating the motor to move the material as a function of measured backpressure. 
     In one embodiment, the motor operates to move the material when the measured backpressure exceeds a predetermined limit. 
     In one embodiment, a Diesel Particulate Filtration (DPF) system is provided comprising: a supply of material disposed in a supply region; a collection region; and an electromechanical system for conveying the material in the supply region to collection region with portions of the material between the supply region and the collection region being conveyed through a region separating the inlet section from the outlet section 
     In one embodiment, a method is provided removing soot from exhaust gases of an internal combustion engine comprising: introducing a first portion of a soot filtering material from a supply of the material into a path of exhaust gasses to collect the soot on the soot filtering material; and subsequently moving the first portion of the material out of the path while moving a second portion of the material from the supply into the path. 
     In one embodiment, a Diesel Particulate Filtration (DPF) system is provided having a supply roller and a take-up roller; a filter disposed on the supply roller and having an end connected to the supply roller; portions of the filter between the supply roller and the take-up roller passing through exhaust gasses passing through the system; and a motor for moving the portions of the filter between the supply roller and the take-up roller. 
     In one embodiment, the filter is a fiber paper having a high porosity of about 80% and a high filtration efficiency of about 99%. As the exhaust gas passes through the DPF system, the soot gets collected on an upstream side of the fiber paper. 
     In one embodiment, a fiber-paper based Diesel particulate Filtration (DPF) apparatus possessing high filtration efficiency and a high porosity, the apparatus comprising at least two rollers capable of rotating over rotors with the help of a controlled motor and capable of supplying fiber paper at the exhaust gas inlet. As the exhaust gas moves over the fiber paper supplied from one of the rollers, the soot gets gradually collected on the fiber paper and keeps on increasing the backpressure thereon. The moment when the backpressure increases beyond a limit, the loaded section of the fiber paper is replaced by fresh fiber paper from the other roller. The loaded fiber is sent to an off-board regeneration facility for regeneration. 
     With such system and method, as the exhaust gas passes through the DPF system, the soot gets collected on the top of the filter paper. As the mass of soot collected in the filter paper increases, the backpressure across its surface increases gradually. At this point, loaded section of the filter paper is rolled through a controlled motor, and is replaced by fresh fiber paper for soot collection. The loaded filter may be taken to a regeneration facility for burning out the collected soot. 
     The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram of an internal combustion engine, here a diesel engine, coupled to an exhaust treatment system, here including a diesel particulate filtration system according to the disclosure; 
         FIG. 2  is a top view diagrammatical sketch of an internal portion of the diesel particulate filtration system shown in  FIG. 1  according to the disclosure, such sketch showing covers for a supply roller and a take-up roller, small guiding rollers, and side guides for the material; 
         FIG. 3  is a side view showing side guides for the filter material used in the diesel particulate filtration system shown in  FIG. 1  according to the disclosure; 
         FIG. 4  is sketch of one of a pair of guide rollers used in the diesel particulate filtration system shown in  FIG. 1  according to the disclosure; and 
         FIG. 5  is a diagram showing a supply of filter material according to another embodiment of the disclosure. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , an internal combustion engine  10 , here a diesel engine, is coupled to an exhaust treatment system, here including a diesel particulate filtration system  12 . The diesel particulate filtration system  12  has housing  13  having an inlet section  14  separated from an outlet section  16  by a portion  18   a  of a filter material  18  of length L as shown, for removing soot from exhaust gases of  19  the internal combustion engine  10 . The filter material  18  is here, for example, a fiber paper having a porosity of fiber paper that may be, for example, larger than 80%, and filtration efficiency as high as 99.9 Due to the elimination of active DPF regeneration, exhaust temperature is below 650 C under all operation conditions. The fiber material can be glass fibers or ceramic fibers which can stand temperature up to 700 C. 
     The fiber-paper based Diesel particulate Filtration (DPF) system  12  possessing a high filtration efficiency and a high porosity and includes at least two rollers; a supply roller  20  and a take-up roller  22  capable of supplying the portion  18   a  of the fiber paper  18  in the path of the exhaust gas with the help of an electromechanical system, here an electric motor  24 , controlled by a motor controller  26  in response to a measured backpressure in the inlet section  14  sensed by a pressure sensor  28  disposed in the inlet section  14 . As the exhaust gas moves over the portion  18   a  of the fiber paper  18  supplied from the supply roller  20 , soot in the exhaust gases  19  gets gradually collected on the portion  18   a  of the fiber paper  18  resulting in increasing backpressure in the inlet section  14 . The moment when the backpressure increases beyond a limit, the motor  24  drives the take-up roller  22 , here contraclockwise as shown by the arrow  30  and the portion  18   a  of the paper  18  is advanced, here to the right one length, L, and the portion of paper between the inlet section  14  and the outlet section  16  is replaced by a new portion  18   a  of fresh fiber paper  18  from the supply roller  20 . Once all the paper is used, the take-up roller  22  with the used paper  18  is sent to an off-board regeneration facility for regeneration. 
     More particularly, referring also to  FIGS. 2 and 3 , the housing  13  has a pair of side guides  31 , a forward guide  32  and a rear guide  34  for receiving the paper  18  as the paper passes through the housing  13 . The filter paper  18  is disposed on the supply roller  20  and has an end feed through the forward guide  32 , the sides of the feed paper then pass through the pair of side guides  31  and then through the rear guide  34  and the end is then connected to the take-up roller  22 . There is a pair of small guiding rotors  36   a ,  36   b  as shown in  FIG. 4  for rotor  36   a . Also shown are covers  32  for the supply roller  20  and the take-up roller  22 . 
     As noted above, portions  18   a  of the paper  18  between the supply roller  20  and the take-up roller  22  removes soot or diesel particulate in the exhaust gasses  19  passing through the system (passing from the inlet section  14  to the outlet section  16 ). The motor  24  moves the portion  18   a  of the paper  18  between the supply roller  20  and the take-up roller  22  under the control of a motor controller  26 . The pressure sensor  28  is provided in the inlet section  14  to measure backpressure in the inlet section  14 , such backpressure increasing as the amount of soot on the portion  18   a  of the filter paper increases. The motor controller  26  operates the motor  24  to move the portion  18   a  of the paper  18  between the supply roller  20  and the take-up roller  22  as a function of backpressure in the system, here measured by the pressure sensor  28 . More particularly, the motor controller  26  operates to move the portion  18   a  of the paper  18  between the supply roller  20  and the take-up roller  22  when the measured back pressure in the system exceeds a predetermined limit as set by a predetermined pressure threshold level. Thus, the portion  18   a  of the paper between the supply roller  20  and the take-up roller  22  is supplied with fresh paper  18  from the supply roller  20 . 
     The process of advancing the filter paper portion  18   a  from the supply roller  20  to the take-up roller  22  continues until all the fiber paper  18  on supply roller  20  is used up. Then, the take-up roller  22  is removed for stationery-regeneration facility for burn out the soot and the supply roller  20  is replaced. Additional procedure may be used to clean ash by re-rolling roller  22  to roller  20  with wind power to blow ash away. Roller  20  can be reused. The limitation of backpressure can be easily adjusted by the selection of the threshold pressure level to assure lower backpressure for higher fuel economy. 
     A number of embodiments of the disclosure have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, other types of filter material may be used. Still further, the supply of material need not be on a roller but may be stacked in sheets as shown in  FIG. 5 . Further, the supply and take-up may be included within the housing. Accordingly, other embodiments are within the scope of the following claims.