Optimum regeneration of diesel particulate filters and NOx traps using fuel reformers

Abstract

Pollution control apparatus. An exhaust aftertreatment unit is fitted to the exhaust of an internal combustion engine and a fuel reformer provides hydrogen rich gas in an optimal way to the aftertreatment unit to regenerate the aftertreatment unit. It is preferred that the hydrogen rich gas be provided only to a portion of the aftertreatment unit at any time to regenerate that portion. Stored hydrogen may be used.

1 . Pollution control apparatus comprising: 
 an exhaust aftertreatment unit fitted to the exhaust of an internal combustion engine;    a fuel reformer providing hydrogen rich gas to the aftertreatment unit to regenerate the aftertreatment unit;    and wherein the fuel flow rate and/or the oxygen-to-carbon ratio of reagents entering the reformer varies during regeneration.    
   
   
       2 . The pollution control apparatus of  claim 1  wherein the fuel reformer is a plasmatron fuel reformer.  
   
   
       3 . The pollution control apparatus of  claim 1  wherein the aftertreatment unit is a particulate filter.  
   
   
       4 . The pollution control apparatus of  claim 1  wherein the aftertreatment unit is a NOx trap.  
   
   
       5 . The pollution control apparatus of  claim 1  wherein the aftertreatment unit comprises a particulate filter and an NOx trap.  
   
   
       6 . The pollution control apparatus of  claim 1  wherein the internal combustion engine is a diesel engine.  
   
   
       7 . The pollution control apparatus of  claim 1  wherein the fuel reformer operates at a higher oxygen-to-carbon ratio for particulate filter regeneration than for NOx trap regeneration.  
   
   
       8 . The pollution control apparatus of  claim 1  wherein the fuel reformer operates at one O/C ratio during start of regeneration and subsequently changes the O/C ratio and/or the fuel flow rate.  
   
   
       9 . The pollution control apparatus of  claim 8  wherein the fuel reformer operates at a high O/C ratio during start of regeneration and subsequently lowers the O/C ratio.  
   
   
       10 . The pollution control apparatus of  claim 1  wherein exhaust gas is introduced into the fuel reformer to provide a source of oxygen.  
   
   
       11 . The pollution control apparatus of  claim 1  wherein the fuel reformer is operated at an oxygen-to-carbon ratio between 0.5 and 1, or higher than for full combustion (lean combustion).  
   
   
       12 . Pollution control apparatus comprising: 
 an exhaust aftertreatment unit fitted to the exhaust of an internal combustion engine;    a fuel reformer providing hydrogen rich gas to the aftertreatment unit to regenerate the aftertreatment unit;    wherein hydrogen rich gas is provided only to a portion of the aftertreatment unit at any time.    
   
   
       13 . The pollution control apparatus of  claim 12  further including movable vanes to localize the hydrogen rich gas to the portion of the aftertreatment unit.  
   
   
       14 . The pollution control apparatus of  claim 13  wherein the vanes are located upstream of the aftertreatment unit.  
   
   
       15 . The pollution control apparatus of  claim 1  wherein the vanes are located downstream of the aftertreatment unit.  
   
   
       16 . The pollution control apparatus of  claim 12  further including multiple injection ports for introducing the hydrogen rich gas so that the hydrogen rich gas be localized to the portion being regenerated.  
   
   
       17 . The pollution control apparatus of  claim 12  further including monitoring apparatus to determine timing and/or duration of regeneration at a given portion of the aftertreatment unit.  
   
   
       18 . The pollution control apparatus of  claim 17  wherein the monitoring apparatus comprises at least one flow meter.  
   
   
       19 . The pollution control apparatus of  claim 17  wherein the monitoring apparatus comprises at least one pressure transducer.  
   
   
       20 . The pollution control apparatus of  claim 17  wherein a sensor to monitor the composition of the gas exiting the aftertreatment device is used to optimize the performance of the aftertreatment device.  
   
   
       21 . The pollution control apparatus of  claim 20  wherein the sensor measures NO x .  
   
   
       22 . The pollution control apparatus of  claim 20  wherein the sensor measures H 2 .  
   
   
       23 . The pollution control apparatus of  claim 20  wherein the sensor measures CO.  
   
   
       24 . The pollution control apparatus of  claim 12  further including valves to control timing and/or duration of regeneration at a given portion of the aftertreatment unit.  
   
   
       25 . The pollution control apparatus of  claim 12  wherein the aftertreatment unit comprises a carousel containing a plurality of particulate filter cartridges.  
   
   
       26 . The pollution control apparatus of  claim 12  wherein the aftertreatment unit comprises a carousel containing a plurality of NO x  trap cartridges.  
   
   
       27 . The pollution control apparatus of  claim 25  wherein at least one of the particulate filter cartridges receives the hydrogen rich gas for regeneration and at the same time at least another cartridge receives the engine exhaust.  
   
   
       28 . The pollution control apparatus of  claim 26  wherein at least one of the NO x  trap cartridges receives the hydrogen rich gas for regeneration and at the same time at least another cartridge receives the engine exhaust.  
   
   
       29 . The pollution control apparatus of  claim 3  wherein the hydrogen rich gas mixes with exhaust gas upstream of the particulate filter whereby particulates combust with free oxygen in the exhaust gas.  
   
   
       30 . The pollution control apparatus of  claim 4  wherein hydrogen rich gas does not mix with the exhaust gas upstream of the NO x  trap whereby a reducing environment required for regeneration is provided with a minimum of fuel penalty.  
   
   
       31 . The pollution control apparatus of  claim 12  wherein exhaust gas is introduced into the fuel reformer to provide a source of oxygen.  
   
   
       32 . The pollution control apparatus of  claim 12  further including a heat exchanger to transfer heat from the exhaust gas to the reformates entering the fuel reformer.  
   
   
       33 . The pollution control apparatus of  claim 1  wherein the aftertreatment unit is partitioned axially into different partitions.  
   
   
       34 . The pollution control apparatus of  claim 33  wherein the hydrogen rich gas mixes with products of regeneration from one filter section before entering another section.  
   
   
       35 . The pollution control apparatus of  claim 34  wherein downstream partitions are generated separately from upstream partitions.  
   
   
       36 . The pollution control apparatus of  claim 33  wherein materials and construction of different partitions are different from each other.  
   
   
       37 . The pollution control apparatus of  claim 33  wherein the aftertreatment unit is a diesel particulate filter and the material and composition of the different partitions are such that large particles are trapped in upstream partitions while smaller particles are trapped in downstream partitions.  
   
   
       38 . The pollution control apparatus of  claim 36  wherein regeneration of a given partition is optimized for the particulate size trapped in said partition.  
   
   
       39 . Pollution control apparatus comprising: 
 an exhaust aftertreatment unit fitted to the exhaust of an internal combustion engine;    a source of hydrogen gas providing the hydrogen gas to the aftertreatment unit to regenerate the aftertreatment unit, wherein the fuel flow rate and/or the oxygen-to-carbon ration of reagents entering the reformer varies during regeneration.    
   
   
       40 . The pollution control apparatus of  claim 39  wherein the hydrogen gas is stored on a vehicle.  
   
   
       41 . Pollution control apparatus comprising: 
 an exhaust aftertreatment unit fitted to the exhaust of an internal combustion engine;    a source for providing hydrogen gas to the aftertreatment unit to regenerate the aftertreatment unit;    wherein the hydrogen gas is provided only to a portion of the aftertreatment unit at any time.