DE112005001835B4 - Integrated system for reducing fuel consumption and emissions of an internal combustion engine - Google Patents

Abstract

An internal combustion engine and aftertreatment system, comprising: (a) a fuel tank and a fuel delivery subsystem for supplying fuel to the engine, (b) an air delivery subsystem for routing air to the engine via an air intake conduit, (c) an engine exhaust streamline adapted to receive an exhaust stream from the engine (d) at least one exhaust aftertreatment device operably fluidly connected to the engine exhaust stream line; (e) a fuel processor for generating a syngas stream, the fuel processor having a syngas discharge line operably fluidly connected to the at least one exhaust aftertreatment device therethrough characterized in that the air inlet conduit is fluidly connected to receive excess syngas from the exhaust aftertreatment means and from the syngas discharge conduit.

Description

Field of the invention

The present invention relates to the field of internal combustion engines including diesel powered and gasoline powered internal combustion engines, and more particularly to an internal combustion engine having an exhaust aftertreatment system and a method of operating such an engine system.

Background of the invention

The present integrated system is capable of reducing fuel consumption and controlled emissions of internal combustion engines. This capability is achieved by incorporating a fuel processor into the engine system and other devices that help reduce regulated emissions. The present integrated fuel processing system delivers a hydrogen-containing stream to one or more parts of the engine system, resulting in reduced fuel consumption and reduced emissions. The present system is integrated such that components of the engine provide benefits in addition to reducing fuel consumption and reduced regulated emissions.

Due to the ever increasing fuel price, operators of internal combustion engines are always looking for ways to reduce fuel costs. Furthermore, engine manufacturers are always looking for cost-effective methods for reducing emissions so that new engine designs can be certified to ever-stricter emissions regulations.

So far, reducing fuel consumption has usually been associated with increased emissions. Conversely, processes that reduce emissions typically increase fuel economy. None of these results is desirable for engine operators or engine manufacturers. The trade-off between emissions and fuel consumption is therefore a significant problem faced by engine operators and manufacturers.

In the past, NO _x emissions have been reduced mainly by increasing and / or cooling the exhaust gas recirculation (EGR) flow. Another approach used to reduce NO _x emissions was to retard fuel injection timing. In this regard, the timing of fuel injection into the combustion chamber (s) of the engine may take place earlier than a fuel injection timing delayed to reduce NO _x emissions. Advancing the fuel injection timing reduces fuel consumption and increases NO _x emissions in the engine exhaust, which in turn are reduced downstream in the aftertreatment section of the present system.

Although each of the above approaches is capable of reducing NO _x emissions, they also increase the fuel consumption of the engine. So far, there are no established approaches to simultaneously reduce both NO _x emissions and fuel consumption.

From the DE 102 11 122 A1 a generic engine system and a method for operating the same is known.

From the EP 1 421 987 A2 For example, a method and system for regenerating NO _x adsorbers and / or particulate filters is known. For regenerating the NO _x adsorber, H ₂ and CO are fed from a reformer into the exhaust gas stream which enters the NO _x adsorber.

Summary of the invention

The present integrated system reduces both fuel consumption and concurrently regulated emissions without a significant adverse effect on capital costs and with the potential for improved operating costs as a result of better fuel economy. Capital costs can potentially be reduced by eliminating certain parts, such as components of an exhaust gas recirculation system, and / or by making it possible to make certain parts, such as diesel particulate filters and engine displacement / volume, smaller.

The above and / or other disadvantages of known NO _x emission reduction techniques are overcome by an internal combustion engine and an aftertreatment system according to claim 1.

In a preferred system embodiment, the conversion of the fuel flow directed to the fuel processor into an output stream containing H ₂ and CO may be assisted by a thermal means. In a preferred system embodiment, the conversion of the fuel flow directed to the fuel processor into an output stream containing H ₂ and CO may also be assisted by a catalyst material. A preferred catalyst material absorbs CO and preferably comprises platinum. The platinum-containing catalyst material can be arranged on a carrier substrate. A preferred carrier substrate is ceramic, preferably selected from the group consisting of zirconia and alumina.

In a preferred system embodiment, the molar concentration of the fuel processor output stream of H ₂ and CO is each in the range of 5 to 30%.

In a preferred system embodiment, the H ₂ and CO containing fuel processor output stream is periodically passed through the catalyst / adsorbent bed to release adsorbed NO _x at a temperature lower than the NO _x desorption temperature of current compositions other than the fuel processor output stream. In a preferred system embodiment, the H ₂ and CO containing fuel processor output stream is periodically passed through the catalyst / adsorbent bed to release adsorbed SO _x at a temperature lower than the SO _x desorption temperature of stream compositions other than the fuel processor output stream.

Methods according to the invention for reducing NO _x emissions and / or fuel consumption of an internal combustion engine are specified in claims 13 and 31.

In a preferred embodiment of the method, the fuel injection timing is advanced over a fuel injection timing that is retarded to reduce NO _x emissions.

In a preferred embodiment of the method, the conversion of the fuel flow directed to the fuel processor into an output stream containing H ₂ and CO may be assisted by a thermal means. In a preferred embodiment of the method, the conversion of the fuel flow directed to the fuel processor into an output stream containing H ₂ and CO may also be assisted by a catalyst material. A preferred catalyst material adsorbs CO and preferably comprises platinum. The platinum-containing catalyst material can be arranged on a carrier substrate. A preferred carrier substrate is ceramic, preferably selected from the group consisting of zirconia and alumina.

In a preferred embodiment of experience, the molar concentration of fuel processor output current to H ₂ and CO is each in the range of 5 to 30%.

In a preferred embodiment of the process, the H ₂ and CO containing fuel processor output stream is periodically passed through the catalyst / adsorbent bed to release adsorbed NO _x at a temperature lower than the NO _x desorption temperature of current compositions other than the fuel processor output stream. In a preferred embodiment of the process, the H ₂ and CO containing fuel processor output stream is periodically passed through the catalyst / adsorbent bed to release SO _x at a temperature lower than the SO _x desorption temperature of current compositions other than the fuel processor output stream.

In the present system and method, a fuel and an engine exhaust stream are used to generate a hydrogen and carbon monoxide containing stream. This stream is generated substantially continuously in a fuel processor and fed to a catalyst and adsorbent bed which contains adsorbed nitrogen oxides (NO _x ) adsorbed on the adsorbent and / or the adsorbent / catalyst. The stream promotes NO _x desorption and reacts with the NO _x and regenerates the NO _x adsorbent material so that it can be made available from the engine exhaust stream for another cycle of capturing NO _x . The catalyst and adsorbent bed may be contained in various beds including a rotating bed which is controlled in a manner which minimizes the amount of reductant required to achieve a desired reduction in NO _x emissions and / or the size and cost of the catalyst reduced or minimized and / or offers some compromise between the amount of reductant required and the size / cost of the equipment involved. The adsorbent may also be included in a number of beds undergoing a cycle of adsorption and regeneration. The cycle length and frequency are controlled or adjusted to minimize the amount of reductant required or desirable to achieve a desired reduction in NO _x emissions.

Potentially, a single material can serve as both a catalyst and adsorbent. Such a material would include platinum, which acts as a catalyst for decomposing the hydrocarbon feedstock into hydrogen, carbon dioxide and carbon monoxide in catalytic hydrocarbon reactors (reformers) and also acts as a carbon monoxide adsorbent which preferentially adsorbs to platinum-containing catalyst materials. Other such adsorbent / catalyst materials are carbon nanohorns that adsorb ethanol and catalyze the oxidation reaction between ethanol and oxygen in the presence of oxygen (see Nisha et al., "Adsorption and catalytic properties of single-walled carbon nanohorns", Chemical Physics Letters 328 (US Pat. 2000), pp. 381-386).

Brief description of the figure (s)

1 FIG. 12 is a schematic process flow diagram illustrating a preferred embodiment of the present system for reducing emissions and fuel consumption of an internal combustion engine system. FIG.

2 FIG. 12 is a schematic plan view of the rotating adsorbent bed of FIG 1 illustrated system for reducing emissions and fuel consumption.

3 Figure 3 is a schematic cross-sectional view of the rotating adsorbent bed of the illustrated system for reducing emissions and fuel consumption.

4 shows an alternative catalyst and adsorbent bed assembly in which two or more beds are toggled between an adsorption and a regeneration step.

Detailed Description of the Preferred Embodiment (s)

In 1 becomes an input airflow 1 an internal combustion engine 3 fed. The air intake system typically includes filters and flow control devices such as a throttle valve or a compressor of some type. When a compressor such as a turbocharger or a compressor is employed, an intercooler may be part of the air intake system. Sensors such as temperature and flow meters are typically included to aid in optimizing engine operation. Most engines will also supply the input air exhaust as part of an exhaust gas recirculation (EGR) system used to reduce engine emissions.

A fuel flow 2 becomes the internal combustion engine 3 fed. Typically, the delivery of fuel flow takes place 2 by means of fuel injectors, which may have different fuel spray patterns and injection schemes provided by the engine control unit 14 to be controlled. The spray patterns and injection schemes are used to improve or optimize fuel economy and exhaust emission operating parameters. Fuel supply devices are constantly being improved, and therefore the fuel supply device used in the embodiment should be the one that is considered to be available and good or most suitable for the desired end use.

The internal combustion engine 3 may be a compression ignition or spark ignition type diesel, gasoline, natural gas, liquid propane gas (LPG) or similar fuel driven engine. The engine will most likely have an exhaust gas recirculation system, but this is not required for the present embodiment. Also, the engine may optionally include various aftertreatment devices (in 1 not shown), which are arranged in the exhaust system. Such aftertreatment devices would typically be oxidation catalysts and particulate filters that help the engine system to meet various emissions regulations.

The engine exhaust stream 4a leaves the engine 3 and an exhaust gas recirculation stream 4b gets from the stream 4a subtracted, controlled by the engine control unit 14 by means of the exhaust gas recirculation valve 4c , A stream 5 , which is a part of the total exhaust gas flow of the engine, is also subtracted from the total exhaust stream. This can be done in different places of the streams 4 . 4b . 4d and 4e occur. The current 5 becomes a fuel processing device 7 fed. The by means of the current 5 supplied amount of exhaust gas can optionally be controlled by a valve or similar flow control device. Preferably, there should be no active controller, but a wide range of flow rates is acceptable to the requirements of the fuel processor resulting from the passive nature of the device. An example of such a passive device is an opening based on the concept of sonic velocity flow to limit the flow rate or range of flow through the aperture. The fuel processor is designed to function as desired in the region resulting from the passive nature. Further, a fuel flow 6 in one of the engine control unit 14 supplied controlled amount. The fuel flow 6 is preferably of the same fuel type as in the stream 2 is preferably composed of the same storage device (in 1 not shown). However, it is possible that the fuel in the stream 6 different from the fuel type of the stream 2 is.

The fuel processing device 7 uses the oxygen and water in the engine exhaust stream to convert the fuel flow 6 in components such as hydrogen and carbon monoxide. The presence of carbon dioxide in the engine exhaust stream also has beneficial effects on the reactions that produce the desired hydrogen and carbon monoxide components used in the downstream aftertreatment section of the present system. The exact composition depends on a number of parameters, such as the amount of exhaust gas flow supplied and the exhaust flow composition. The composition is a result of the internal construction of the Fuel processor. Preferably, no catalyst is used to assist the desired reactions. Important design considerations include reactant mixture rates, temperature profiles, catalysts used (if any) and their location in the fuel processing facility, as well as other considerations. The design of the fuel processor and its operating parameters will be different for each different application. The fuel processor 7 is preferably mechanical in the exhaust stream 11 integrated to support desired temperature profiles in the facility and reduce equipment costs. In this regard, it is intended to arrange the reactor tube in the overall exhaust gas flow line, but this is not necessary.

Not requiring reactants other than fuel flow and engine exhaust stream greatly simplifies the system, thereby reducing costs and increasing system reliability.

The product stream 8th of the fuel processor may optionally be wholly or partially the air inlet stream 1 be supplied to the motor. If a part of the stream 8th the engine inlet to be supplied, this can be directly or by means of the exhaust gas recirculation flow 4d happen, as in 1 shown. In some engine designs, the supply of H ₂ and CO to the air intake stream affects the combustion characteristics in a favorable manner that can be used to reduce emissions and fuel consumption. For example, in a gasoline engine, the addition of H ₂ and CO or such compounds will extend the lean burn limit of the combustion mixture. This allows more air to be burned, thus reducing emissions and increasing efficiency. Such performance improvements have also been reported by diesel compression ignition engines. Another advantage is that the engine power is increased when H ₂ and CO or such compounds are supplied to the engine's input air from the fuel processor.

Another very advantageous reason for supplying part or all of the electricity 8th to the air intake of the engine is that this is the fuel processor 7 allows you to work in a completely or fairly stationary way rather than constantly going through different transient states. Stationary operation leads to less stress on the device and thus increases its service life.

Part or all of the product stream 9 the fuel processor is a NO _x -Aufangeinrichtung 12 fed, the NO _x from the exhaust stream 11 when it passes through the bedding material consisting of catalyst and / or adsorbent. When the material of the bed meets the current 9 is properly exposed from the fuel processor, desorbs and reacts the NO _x to form harmless emissions such as N ₂ and H ₂ O. The product stream 9 The fuel processor is also used to remove sulfur oxide (SO _x ) compounds which may have been adsorbed to the adsorbent in the same manner as NO _x which may have been adsorbed.

Part or all of the electricity 8th or another syngas stream may also be directed to a diesel particulate filter to aid in the regeneration of that device (syngas, also referred to as syngas, is a generic term that refers to a fluid stream containing hydrogen and carbon monoxide, such as, for example formed in industrial processes using coal-derived mixtures of carbon monoxide and hydrogen). This regeneration support may be either passive or active or a combination, depending on the device design and the work cycle of the application.

Other users of the technology involved here use substances such as diesel fuel to remove NO _x and SO _x adsorbed on the bed. The use of H ₂ and / or CO allows the removal of these materials in a more efficient manner and at lower temperatures, enabling a simpler, cheaper system with longer life.

2 shows some details of the adsorbent bed 12 , The core 21 of the bed 12 is a structure which is covered with materials that supplement the capacity to absorb NO _x and NO _x TYPES in species such as N _2, H ₂ O and convert CO _2. The adsorbent typically contains platinum, barium oxide and rhodium. Other suitable adsorbents may also be used. The exact materials used and their quantities depend on the specific properties of the application and the desired results.

The structure of the nucleus 21 on which the active materials are placed can be made of different materials such as cordierite, metal mesh, wire mesh and / or fiberglass.

The materials can be deposited in a non-uniform manner to better meet the desired requirements of low product cost and minimal reductant requirements.

Using a suitable mechanical design, the current 11 through a collection segment 22 led the bed while the reducing agent flow 9 through the regeneration segment 23 of the bed. The relative sizes of the two segments depend on the particular characteristics of the application and the desired results. The bed can be rotated either clockwise or counterclockwise so that all parts of the bed alternate with the exhaust flow 11 and the product stream 9 are exposed to the fuel processor. The speed at which the bed turns can be controlled if desired. Adjusting the rotational speed of the bed can reduce or minimize bed size and the required amount of flow 9 reduce or minimize. It may be desirable to rotate the bed at a rate between 2 and 120 revolutions per minute (one cycle every 0.5 seconds to 30 seconds). Due to the very rapid adsorption, desorption and reaction rates, a fast cycle rate would reduce or minimize bed size.

The bed can also be rotated at a rate to maintain NO _x loading at a level that is a good compromise between the efficiency of the adsorption steps and the efficiency of the desorption / reduction steps resulting in low NO _x emissions.

In 3 become the exhaust gas flow 11 and the stream 9 supplied to a valve which is capable of controlling the flow of both the flow 9 as well as the current 11 to lead to the desired beds. It is possible to have any number of beds larger than 1, with the electricity 9 only in each case to a small number, including only one bed is passed. The most practical embodiment would comprise 2 to 5 beds, with the electricity 9 each to a bed, while the other beds the electricity 11 receive.

In 4 becomes a valve 31a used to the flow of streams 9 and 11 alternately to beds 32 and 33 to lead. The valve 31a is adjusted at such a speed that the size of the two beds 32 and 33 minimized and at the same time a desired regeneration of the beds is possible. As with the rotating bed, the valve can be switched back and forth at a rate that keeps the bed's NO _x loading substantially constant. The valve 31a can also be toggled at a speed that helps reduce the overall size and mass of the system. A valve 31b will be simultaneously with the valve 31a switched back and forth. A stream 13b from the bed that is being regenerated may then be directed into the air inlet stream to avoid wasting fuel energy. A stream 13a is analogous to the current 10 out 1 however, has the advantage that the recirculated stream flows over / through the catalyst and adsorbent beds to provide a cleaning effect on the beds. As stated above, this can also increase engine performance due to increased fuel supply or lead to advantageous combustion conditions.

Some groups have suggested the use of a single-stranded design in which the entire engine exhaust stream passes the adsorbent bed during the regeneration step. This construction requires large amounts of oxygen, which must be consumed by burning with fuel each time the adsorbent bed is to be regenerated. The benefits of in the 2 to 4 Arrangements shown are that the amount of oxygen that must be consumed so that regeneration can take place, is significantly reduced, thereby significantly reducing the additional fuel consumption associated with a regeneration.

The exhaust flow with reduced regulated emissions then becomes by means of the flow 13a released into the atmosphere. The exhaust gas flow 13a may optionally be passed through other aftertreatment devices before being expelled to the atmosphere.

The fuel consumption of the engine can also be reduced by advancing the fuel injection timing, and using the above-mentioned post-treatment portion of the present system in order to reduce NO _x levels in the engine exhaust gas flow, resulting from the early fuel injection timing to acceptable levels. Advancing the fuel injection timing has the further advantage of reducing particulate diesel in the exhaust and thus reducing the size and cost of equipment required to remove diesel soot.

Claims (32)

An internal combustion engine and aftertreatment system, comprising: (a) a fuel tank and a fuel delivery subsystem for supplying fuel to the engine, (b) an air delivery subsystem for routing air to the engine via an air intake conduit, (c) an engine exhaust streamline adapted to receive an exhaust stream from the engine (d) at least one exhaust aftertreatment device operably fluidly connected to the engine exhaust streamline; (e) a fuel processor for generating a syngas stream, the fuel processor having a syngas discharge line operable fluidly connected to the at least one exhaust aftertreatment device, characterized in that the air inlet line is fluidly connected to receive excess syngas from the exhaust aftertreatment device and from the syngas discharge line. The internal combustion engine and aftertreatment system of claim 1 wherein the fuel processor is fluidly connected to the engine exhaust streamline to obtain at least a portion of the engine exhaust stream. The internal combustion engine and aftertreatment system of claim 2, wherein the fuel processor is fluidly connected to the engine exhaust streamline to receive at least a portion of the engine exhaust stream via a passive flow control device. The internal combustion engine and aftertreatment system of claim 1, wherein the fuel processor is fluidly connected to the fuel tank and the fuel delivery subsystem to receive the fuel. The internal combustion engine and aftertreatment system of claim 1, wherein the exhaust aftertreatment system comprises at least one lean NO _x trap. The internal combustion engine and aftertreatment system of claim 1, wherein the exhaust aftertreatment system comprises a pair of lean NO _x traps. Combustion engine and the post-treatment system according to claim 6, wherein each of the pair of lean NO _x traps is alternately fluidly connected with the engine exhaust gas flow line and with the fuel processor is arranged by a pair upstream of the case flow switch. The internal combustion engine and aftertreatment system of claim 6, wherein the air inlet conduit is fluidly connected to receive spent syngas alternately from each of the pair of lean NO _x traps through a flow diverter located downstream of the trap pair. The internal combustion engine and aftertreatment system of claim 1, wherein the fuel processor is a non-catalytic reactor. The internal combustion engine and aftertreatment system of claim 1, wherein the fuel processor is a catalytic reactor. The internal combustion engine and after-treatment system according to claim 1, wherein the molar concentration of H ₂ and CO in the syngas stream is in the range of 5 to 30%, respectively. The internal combustion engine and aftertreatment system of claim 1, wherein the system does not include an exhaust gas recirculation line for guiding at least a portion of the engine exhaust stream to the air inlet. A method of operating an engine system having an exhaust aftertreatment system and a fuel processor, the method comprising: (a) passing a fuel flow from a fuel supply to the engine and passing an airflow to the engine via an air intake conduit and operating the engine to produce an engine exhaust stream; (b) operating the fuel processor to generate a syngas stream, (c) at least periodically directing at least a portion of the engine exhaust stream to at least one exhaust aftertreatment device in the exhaust aftertreatment system to reduce regulated emissions from the engine system, (d) at least periodically guiding at least a portion of the syngas stream to the at least one exhaust aftertreatment device to heat or regenerate the device, thereby producing a depleted syngas stream; (e) passing an excess syngas stream containing the depleted syngas stream from the at least one exhaust aftertreatment device and syngas from the fuel processor to the engine via the air inlet line. The method of claim 13, wherein at least a portion of the engine exhaust stream is recirculated to the engine via an exhaust gas recirculation line. The method of claim 13, wherein the excess syngas and at least a portion of the engine exhaust stream are recirculated to the engine via an exhaust gas recirculation line. The method of claim 13, wherein fuel is supplied from the fuel supply and at least a portion of the engine exhaust stream to the fuel processor and reacted therein to produce the syngas. The method of claim 16, wherein the flow rate of engine exhaust stream to the fuel processor is passively controlled. The method of claim 13, wherein the controlled emissions comprise NO _x , particulate matter and hydrocarbons. The method of claim 13, wherein the exhaust aftertreatment system comprises at least one lean NO _x trap. The method of claim 13, wherein the exhaust aftertreatment system comprises a pair of lean NO _x traps. The method of claim 20, wherein an engine exhaust flow diverter located upstream of the lean NO _x trap pair switches between passing at least a portion of the engine exhaust flow to a first and then a second of the pair of traps at the same time as an upstream of the lean NO _x- pair of trapped syngas gas flow switch between passing at least a portion of the syngas stream to the second and the first trap of the pair of traps to regenerate the traps. The method of claim 20, wherein a combined flow diverter located upstream of the lean NO _x trap pair carries at least a portion of the engine exhaust flow to a first trap of the trap pair and simultaneously delivers at least a portion of the syngas flow to the second trap trap trap for regeneration of the second trap alternating with passing at least a portion of the engine exhaust stream to the second trap of the trap pair simultaneously with passing at least a portion of the syngas stream to the first trap of the trap pair to regenerate the first trap. The method of claim 21 or 22, wherein at least one downstream flow diverter located downstream of the lean NO _x trap pair alternately directs the discharged syngas flow from the trap of the trap pair being regenerated to the engine via the air inlet duct. The method of claim 20, wherein each trap of the lean NO _x trap pair is toggled between operation in a regeneration mode and a trap mode, such that when one is in a regeneration mode, the other is in a trap mode , The method of claim 13, wherein the fuel processor is operated substantially continuously to generate syngas while the engine is running. The method of claim 13, wherein the fuel injection timing of the engine is advanced over a fuel injection timing that is retarded to reduce NO _x emissions. The method of claim 13, wherein the engine exhaust stream is not recycled to the engine via an exhaust gas recirculation line. The method of claim 13, wherein a conversion of fuel flow to the fuel processor into a syngas stream is assisted by a thermal device. The method of claim 13, wherein the conversion of fuel flow to the fuel processor into a syngas stream is assisted by a catalyst material. The method of claim 13, wherein the molar concentration of H ₂ and CO in the syngas stream is in the range of 5 to 30%, respectively. A method of operating an engine system with improved fuel economy, the engine system including an exhaust aftertreatment system and a fuel processor, the method comprising: (a) injecting a fuel flow from a fuel supply to the engine and directing air flow to the engine through an air intake conduit and operating the engine to produce an engine exhaust stream, wherein the timing of fuel injection is selected for improved fuel economy, but such that the value regulated emissions in the engine exhaust stream upstream of the exhaust aftertreatment system exceed at least periodically regulatory values, (b) operating the fuel processor to generate a syngas stream, (c) at least periodically routing at least a portion of the engine exhaust stream to the at least one exhaust aftertreatment device in the exhaust aftertreatment system to reduce regulated emissions from the engine system below the regulated values, (D) at least periodically guiding at least a portion of the syngas stream to the at least one exhaust aftertreatment device for heating or regenerating the device. The method of claim 31, wherein engine exhaust is not returned to the engine.

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