Combustion engine exhaust after-treatment system incorporating syngas generator

Abstract

A combustion engine exhaust after-treatment system includes a syngas generator for producing a syngas stream. The syngas stream is supplied to one or more parts of the engine system resulting in reduced emissions and/or reduced fuel consumption. The syngas generator produces a syngas stream via chemical reaction of the engine exhaust stream with a fuel stream.

1 . A method of operating an engine system comprising an exhaust after-treatment system and a syngas generator, the method comprising: 
 (a) directing a fuel stream from a fuel supply to said engine, and directing an air stream to said engine via an air intake line, and operating said engine to produce an engine exhaust stream;    (b) operating said syngas generator to produce a syngas stream;    (c) at least periodically directing at least a portion of said engine exhaust stream to at least one exhaust after-treatment device in said exhaust after-treatment system, for reducing regulated emissions from said engine system;    (d) at least periodically directing at least a portion of said syngas stream to said at least one exhaust after-treatment device for heating or regenerating said device, thereby producing a depleted syngas stream;    (e) directing a surplus syngas stream to said engine via said air intake line.    
   
   
       2 . The method of  claim 1  wherein said surplus syngas stream comprises said depleted syngas stream.  
   
   
       3 . The method of  claim 1  wherein said surplus syngas stream comprises the portion of said syngas stream that is not directed to said at least one exhaust after-treatment device.  
   
   
       4 . The method of  claim 1  wherein said surplus syngas stream is directed to said engine via a venturi or ejector in said air intake line.  
   
   
       5 . The method of  claim 1  wherein said surplus syngas stream is directed to said engine via a particulate filter.  
   
   
       6 . The method of  claim 1  wherein said surplus syngas stream is directed to said engine via a sulfur trapping bed.  
   
   
       7 . The method of  claim 1  wherein said surplus syngas stream is introduced into said air intake line upstream of an engine intake air compressor.  
   
   
       8 . The method of  claim 1  wherein at least a portion of said engine exhaust stream is recirculated to said engine via an exhaust gas recirculation line.  
   
   
       9 . The method of  claim 1  wherein the quantity of surplus syngas directed to said engine via said air intake line is adjusted in accordance with an operating parameter indicative of the engine power output demand.  
   
   
       10 . The method of  claim 9  wherein the operating parameter is the accelerator position, or air intake mass flow or the engine speed.  
   
   
       11 . The method of  claim 9  wherein the rate of production of syngas is adjusted in accordance with an operating parameter indicative of at least one of: the level of regulated emissions in said engine exhaust stream, oxygen content in the engine exhaust stream, air intake mass flow, engine speed and engine power output demand.  
   
   
       12 . The method of  claim 11  wherein the rate of production of syngas, and the quantity of surplus syngas directed to said engine via said air intake line, are both increased in response to an increase in at least one of the level of regulated emissions in said engine exhaust stream and the engine power output demand.  
   
   
       13 . The method of  claim 1  wherein fuel from said fuel supply and at least a portion of said engine exhaust stream are directed to said syngas generator and reacted therein to produce said syngas.  
   
   
       14 . The method of  claim 13  wherein the flow rate of said engine exhaust stream to said syngas generator is passively controlled.  
   
   
       15 . The method of  claim 1  wherein said syngas generator is operated whenever said engine is operated.  
   
   
       16 . The method of  claim 1  wherein said regulated emissions comprise NOx, particulate matter and hydrocarbons.  
   
   
       17 . The method of  claim 1  wherein said exhaust after-treatment system comprises at least one lean NOx trap.  
   
   
       18 . The method of  claim 1  wherein said exhaust after-treatment system comprises a pair of lean NOx traps.  
   
   
       19 . The method of  claim 18  wherein an engine exhaust gas flow diverter, located upstream of said pair of lean NOx traps, alternates between directing at least a portion of said engine exhaust stream to a first and then a second one of said pair of traps at the same time as a syngas gas flow diverter, located upstream of said pair of lean NOx traps, alternates between directing at least a portion of said syngas stream to the second and first of said pair of traps respectively, for regenerating said traps.  
   
   
       20 . The method of  claim 19  wherein at least one downstream flow diverter located downstream of said pair of lean NOx traps alternately directs said depleted syngas stream from whichever one of said pair of traps is being regenerated to said engine via said air intake line.  
   
   
       21 . The method of  claim 18  wherein a combined upstream flow diverter located upstream of said pair of lean NOx traps directs at least a portion of said engine exhaust stream to a first one of said pair of traps and at the same time directs at least a portion of said syngas stream to the second of said pair of traps for regenerating said second trap, alternately with directing at least a portion of said engine exhaust stream to the second one of said pair of traps at the same time as directing at least a portion of said syngas stream to the first of said pair of traps for regenerating said first trap.  
   
   
       22 . The method of  claim 20  wherein at least one downstream flow diverter located downstream of said pair of lean NOx traps alternately directs said depleted syngas stream from whichever one of said pair of traps is being regenerated to said engine via said air intake line.  
   
   
       23 . The method of  claim 18  wherein each of said pair of lean NOx traps is switched between operating in a regenerating mode and in a trapping mode, so that when one is in a regenerating mode the other is in a trapping mode.  
   
   
       24 . The method of  claim 23  wherein said switching of said traps between a regenerating mode and a trapping mode is performed based on a fixed cycle time or algorithm.  
   
   
       25 . The method of  claim 22  wherein said switching of said traps between a regenerating mode and a trapping mode is performed and adjusted based on a monitored operating parameter.  
   
   
       26 . The method of  claim 25  wherein said operating parameter is an operating parameter determined by at least one of a NOx sensor, a temperature sensor, and oxygen sensor, a hydrocarbon sensor.  
   
   
       27 . The method of  claim 23  wherein the duration of each said trapping mode less than about 20 seconds.  
   
   
       28 . The method of  claim 27  wherein the duration of each said regeneration mode is about the same as the duration of each said trapping mode.  
   
   
       29 . The method of  claim 28  wherein the duration of each said regeneration mode and of each said trapping mode is about 10 seconds.  
   
   
       30 . The method of  claim 1  wherein the syngas generator is a non-catalytic reactor.  
   
   
       31 . A combustion engine and after-treatment system comprising: 
 (a) a fuel tank and fuel supply subsystem for directing fuel to said engine;    (b) an air supply subsystem for directing air to said engine stream via an air intake line;    (c) an engine exhaust stream line connected to receive an exhaust stream from said engine;    (d) at least one exhaust after-treatment device actuatably fluidly connected to said engine exhaust stream line;    (e) a syngas generator comprising a syngas output line actuatably fluidly connected to said at least one exhaust after-treatment device;    wherein said air intake line is fluidly connected receive surplus syngas from at least one of said exhaust after-treatment device and said syngas output line.    
   
   
       32 . The combustion engine and after-treatment system of  claim 31  wherein said air intake line is fluidly connected receive surplus syngas from said exhaust after-treatment device and from said syngas output line.  
   
   
       33 . The combustion engine and after-treatment system of  claim 31  wherein said air intake line is fluidly connected receive said surplus syngas via a venturi or ejector located in said air intake line.  
   
   
       34 . The combustion engine and after-treatment system of  claim 31  wherein said air intake line is fluidly connected receive said surplus syngas via a particulate filter.  
   
   
       35 . The combustion engine and after-treatment system of  claim 31  wherein said air intake line is fluidly connected receive said surplus syngas via a sulfur trapping bed.  
   
   
       36 . The combustion engine and after-treatment system of  claim 31  wherein said air supply subsystem comprises a compressor and wherein said air intake line is fluidly connected to receive said surplus syngas upstream of said compressor.  
   
   
       37 . The combustion engine and after-treatment system of  claim 31  further comprising a controller for adjusting the quantity of surplus syngas directed to said engine via said air intake line in accordance with an operating parameter indicative of the engine power output demand.  
   
   
       38 . The combustion engine and after-treatment system of  claim 31  wherein said controller is also for adjusting the rate of production of syngas in accordance with an operating parameter indicative of at least one of: the level of regulated emissions in said engine exhaust stream, oxygen content in the engine exhaust stream, air intake mass flow, engine speed and engine power output.  
   
   
       39 . The combustion engine and after-treatment system of  claim 31  wherein said syngas generator is fluidly connected to said engine exhaust stream line for receiving at least a portion of said engine exhaust stream.  
   
   
       40 . The combustion engine and after-treatment system of  claim 31  wherein said syngas generator is fluidly connected to said fuel tank and fuel supply subsystem for receiving said fuel.  
   
   
       41 . The combustion engine and after-treatment system of  claim 31  wherein said exhaust after-treatment system comprises at least one lean NOx trap.  
   
   
       42 . The combustion engine and after-treatment system of  claim 31  wherein said exhaust after-treatment system comprises a pair of lean NOx traps.  
   
   
       43 . The combustion engine and after-treatment system of  claim 42  wherein each one of said pair of lean NOx traps is alternatingly fluidly connected to said engine exhaust stream line and to said a syngas generator via a flow diverter located upstream of said pair of traps.  
   
   
       44 . The combustion engine and after-treatment system of  claim 42  wherein said air intake line is fluidly connected receive depleted syngas alternately from each one of said pair of lean NOx traps via a flow diverter located downstream of said pair of traps.  
   
   
       45 . The combustion engine and after-treatment system of  claim 31  wherein said syngas generator is a non-catalytic reactor.  
   
   
       46 . The combustion engine and after-treatment system  claim 31  further comprising an exhaust gas recirculation line fluidly connecting said engine exhaust stream line to said air intake line.  
   
   
       47 . A method of mitigating a combustion engine exhaust stream comprising nitrogen oxides, the method comprising: 
 (a) operating a reducing agent generator to produce a reducing agent stream;    (b) in a trapping mode, introducing at least a portion of said engine exhaust stream into at least one catalytic lean NOx trap;    (e) in a regeneration mode, introducing at least a portion of said reducing agent stream said at least one lean NOx trap,    wherein the duration of each said trapping mode is less than about 20 seconds.    
   
   
       48 . The method of  claim 47  wherein the duration of each said regeneration mode is about the same as the duration of each said trapping mode.  
   
   
       49 . The method of  claim 48  wherein the duration of each said regeneration mode and of each said trapping mode is about 10 seconds.  
   
   
       50 . The method of  claim 47  wherein said reducing agent generator is a syngas generator and said reducing agent is syngas.  
   
   
       51 . The method of  claim 50  wherein a fuel stream and at least a portion of said engine exhaust stream are directed to said syngas generator to produce said syngas stream.  
   
   
       52 . The method of  claim 47  wherein in said trapping mode said engine exhaust stream flows through said catalytic lean NOx trap in a direction substantially opposite to the direction that said reducing agent stream flows through said catalytic lean NOx trap in said regeneration mode.  
   
   
       53 . The method of  claim 47  wherein said after-treatment module comprises a first lean NOx trap and a second lean NOx trap, said method further comprising alternatingly directing said engine exhaust stream and said reducing agent stream via said upstream flow diverter such that when said first lean NOx trap is in said trapping mode, said second lean NOx trap is in said regeneration mode, and when said first lean NOx trap is in said regeneration mode, said second lean NOx trap is in said trapping mode.  
   
   
       54 . A method of operating an engine system with improved fuel economy, the engine system comprising an exhaust after-treatment system and a syngas generator, the method comprising: 
 (a) injecting a fuel stream from a fuel supply to said engine, and directing an air stream to said engine via an air intake line, and operating said engine to produce an engine exhaust stream, wherein the timing of the fuel injection is selected for improved fuel economy but so that the level of regulated emissions in said engine exhaust stream, upstream of said exhaust after-treatment system, at least periodically exceeds regulation levels;    (b) operating said syngas generator to produce a syngas stream;    (c) at least periodically directing at least a portion of said engine exhaust stream to at least one exhaust after-treatment device in said exhaust after-treatment system, for reducing regulated emissions from said engine system below said regulated levels;    (d) at least periodically directing at least a portion of said syngas stream to said at least one exhaust after-treatment device for heating or regenerating said device;    
   
   
       55 . The method of  claim 54  wherein engine exhaust gas is not recirculated to the engine.