Patent Application
20060048502
The present invention relates to the field of internal combustion engines, including diesel-fueled and gasoline-fueled internal combustion engines.
The present integrated system is capable of reducing fuel consumption and regulated emissions of internal combustion engines. This capability is achieved by integrating a fuel processing device with the engine system and other devices that assist in reducing regulated emissions. The present integrated fuel processing system supplies 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 cost of fuel, operators of internal combustion engines are always searching for methods to reduce fuel costs. Also, engine manufactures are always searching for cost effective methods to reduce emissions so that new engine designs can be certified to emission regulations that are continually being made more stringent.
To date, reducing fuel consumption has usually meant increasing emissions. Conversely, methods that reduce emissions typically increase fuel consumption. Neither of these outcomes is desirable to engine operators or engine manufacturers. The trade-off between emissions and fuel consumption is therefore a significant problem facing engine operators and manufacturers.
The present integrated system reduces both fuel consumption and regulated emissions simultaneously, without significant adverse effect on capital costs and with the potential for improved operating costs as a result of better fuel efficiency. Capital cost can be potentially reduced by eliminating certain parts, such as exhaust gas recirculation system components, and/or enabling certain parts, such as diesel particulate filters and engine displacement/total cylinder volume, to be reduced in size.
In the past, NOx emissions have been reduced primarily by increasing and/or cooling the exhaust gas recycle stream (EGR). Another technique employed to reduce NOx (nitrogen oxide) emissions has been to retard fuel injection timing. In this regard, the timing of fuel injection into the engine's combustion chamber(s) can be advanced in relation to fuel injection timing that is retarded to reduce NOx emissions. Advancing fuel injection timing increases fuel economy and engine exhaust NOx emissions, which are in turn reduced downstream in the after-treatment portion of the present system.
Although each of the foregoing techniques is capable of reducing NOx emissions, they each also increase the engine's fuel consumption. To date, there have been no established techniques for reducing both NOx emissions and fuel consumption simultaneously.
The above-described and/or other shortcomings of prior techniques for reducing NOx emissions are overcome by an integrated NOx after-treatment system for an internal combustion engine. The system comprises:
In a preferred system embodiment, conversion of the fuel stream directed to the fuel processor to an outlet stream comprising H2 and CO can be promoted by thermal means. In a preferred system embodiment, conversion of the fuel stream directed to the fuel processor to an outlet stream comprising H2 and CO can also be promoted by a catalyst material. A preferred catalyst material adsorbs CO, and preferably comprises platinum. The platinum-containing catalyst material can be disposed on a supporting substrate. A preferred supporting substrate is ceramic, preferably selected from the group consisting of zirconia and alumina.
In a preferred system embodiment, the fuel processor outlet stream molar concentration of each of H2 and CO is in the range of 5-30 percent.
In a preferred system embodiment, the fuel processor outlet stream comprising H2 and CO is passed periodically through the catalyst/adsorbent bed to evolve adsorbed NOx at a temperature lower than the NOx desorption temperature of stream compositions other than that of the fuel processor outlet stream. In a preferred system embodiment, the fuel processor outlet comprising H2 and CO is passed periodically through the catalyst/adsorbent bed to evolve adsorbed SOx at a temperature lower than the SOx desorption temperature of stream compositions other than that of the fuel processor outlet stream.
A method for reducing NOx emissions and fuel consumption in an internal combustion engine comprises:
In a preferred method embodiment, fuel injection timing is advanced in relation to fuel injection timing that is retarded to reduce NOx emissions.
In a preferred method embodiment, conversion of the fuel stream directed to the fuel processor to an outlet stream comprising H2 and CO can promoted by thermal means. In a preferred method embodiment, conversion of the fuel stream directed to the fuel processor to an outlet stream comprising H2 and CO can also be promoted by a catalyst material. A preferred catalyst material adsorbs CO, and preferably comprises platinum. The platinum-containing catalyst material can be disposed on a supporting substrate. A preferred supporting substrate is ceramic, preferably selected from the group consisting of zirconia and alumina.
In a preferred method embodiment, the fuel processor outlet stream molar concentration of each of H2 and CO is in the range of 5-30 percent.
In a preferred method embodiment, the fuel processor outlet stream comprising H2 and CO is passed periodically through the catalyst/adsorbent bed to evolve adsorbed NOx at a temperature lower than the NOx desorption temperature of stream compositions other than that of the fuel processor outlet stream. In a preferred method embodiment, the fuel processor outlet comprising H2 and CO is passed periodically through the catalyst/adsorbent bed to evolve adsorbed SOx at a temperature lower than the SOx desorption temperature of stream compositions other than that of the fuel processor outlet stream.
A fuel and an engine exhaust stream are employed in the present system and method to produce a stream containing hydrogen and carbon monoxide. This stream is produced substantially continually in a fuel processing device and supplied to a catalyst and adsorbent bed, which has trapped oxides of nitrogen (NOx) adsorbed to the adsorbent and/or the adsorbent/catalyst. The stream promotes NOx desorption and reacts with the NOx and regenerates the NOx adsorption material so that it can be made available to another cycle of trapping NOx from the engine's exhaust stream. The catalyst and adsorbent bed can be contained within a number of beds, including a rotating bed, that is controlled in a manner that decreases or minimizes the reducing agent required to achieve a desired reduction in NOx emissions, and/or decreases or minimizes the size and cost of the equipment involved, and/or provides some trade-off between the amount of reducing agent required and the size/cost of the equipment. The adsorbent material can also be contained in a plurality of beds that are made to undergo a cycle of adsorption and regeneration. The cycle length and frequency is controlled or set so as to decrease or minimize the quantity of reducing agent required or desirable to achieve a desired reduction in NOx emissions.
A single material could potentially act as both a catalyst and an adsorbent. Such a material would include platinum, which in hydrocarbon catalytic reactors (reformers) can act as a catalyst for the decomposition of the hydrocarbon feed material to hydrogen, carbon dioxide and carbon monoxide, and also acts as an adsorbent of carbon monoxide, which preferentially adsorbs on catalytic materials containing platinum. Other such adsorbent/catalyst materials are carbon nanohorns, which adsorb ethanol and, in the presence of oxygen, catalyze the oxidation reaction between ethanol and oxygen (see Nisha et al., “Adsorption and catalytic properties of single-walled carbon nanohorns”, Chemical Physics Letters 328 (2000), pp. 381-386).
In
Fuel stream 2 is supplied to the internal combustion engine 3. Typically the supply of fuel stream 2 is via fuel injectors that could have various fuel spray patterns and injection schemes controlled by the engine's control unit 14. The spray patterns and injection schemes are employed to improve or optimize the fuel consumption and exhaust emission operating parameters. Fuel supply equipment is continuously being improved and thus the fuel supply equipment employed in the embodiment should be those that are deemed to be available and well-or best-suited for the desired end use.
Internal combustion engine 3 could be a diesel, gasoline, natural gas, liquid propane gas (LPG) or similarly fueled engine of either compression ignition of spark ignition type. The engine mostly likely will have an EGR system but this is not required for the present embodiment. Also, the engine can optionally have various after-treatment devices (not shown in
The engine exhaust stream 4a exits engine 3 and an exhaust gas recycle stream 4b is drawn from stream 4a as controlled by the engine control unit 14 via the EGR valve 4c. A stream 5 that is a portion of the engine's full exhaust stream is also taken from the full exhaust stream. This can be taken at various locations in streams 4, 4b, 4d and 4e. Stream 5 is directed to a fuel processing device 7. The quantity of exhaust supplied via stream 5 can optionally be controlled with a valve or other similar flow control device. Preferably, there should be no active control device and a wide range of flows that result from the passive nature of the device are acceptable for the fuel processor's requirements. An example of such a passive device is an orifice that relies on the concept of sonic flow to limit the flow or flow range through the orifice. The fuel processor is designed to operate as desired within the range resulting from the passive nature. A fuel stream 6 is also supplied at a rate controlled by the engine control unit, 14. The fuel stream 6 is preferably composed of the same type of fuel as in stream 2 and, preferably, is supplied from the same storage device (not shown in
The fuel processing device 7 employs the oxygen and the water in the engine's exhaust stream to convert the fuel stream 6 into 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 employed in the downstream after-treatment portion of the present system. The exact composition will depend on a number of parameters such as the amount of exhaust stream supplied and the exhaust stream's composition. The composition is a result of the internal design of the fuel processor. Preferably, there is no catalyst employed to promote the desired reactions. Important design considerations are reactant mixing rates, temperature profiles, catalysts employed (if any) and their position in the fuel processing device 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 mechanically integrated with the exhaust stream 11 to assist with desired temperature profiles in the device and reduce equipment costs. This is envisioned to have the reactor tube be positioned within the full exhaust stream tubing but this is not required.
Not requiring the use of reactants other than the fuel stream and engine exhaust stream greatly simplifies the system and thus reduces costs and increases system reliability.
The fuel processor's product stream 8 can optionally be supplied, in part or in whole, to the engine's air intake stream 1. If a portion of stream 8 is to be supplied to the engine's intake it can be done directly or via the EGR stream 4d, as shown in
Another very beneficial reason for supplying some or all of stream 8 to the engines air intake is that it allows the fuel processor 7 to operate in a completely or rather steady state manner rather than continually going through various transients. Operation at steady state will place less stress on the device and thus extend its lifetime.
All or a portion of the fuel processor's product stream 9 is supplied to a NOx trapping device 12 that can trap NOx from the exhaust stream 11 when it is passed through the bed material made up of catalyst and/or adsorbent type materials. When the material in the bed is properly exposed to the stream from the fuel processor 9, the NOx desorbs and reacts to form harmless emissions such as N2 and H2O. The fuel processor product stream 9 is also employed to remove sulfur oxide (SOx) compositions that may have adsorbed onto the adsorbent material in the same way that NOx may have adsorbed.
All or a portion of stream 8 or other syngas stream can also be directed to a diesel particulate filter to assist in regeneration of that device. (Syngas, also referred to as synthesis gas, is a generic term that refers to a fluid stream that contains hydrogen and carbon monoxide, such as that formed, for example, in industrial processes utilizing coal-derived mixtures of carbon monoxide and hydrogen.) This regeneration assistance could be either passive or active or a combination depending on equipment design and the application's duty cycle.
Other practitioners of the technology involved here employ agents such as diesel fuel to remove NOx and SOx adsorbed to the bed. The use of H2 and/or CO allows the removal of these materials in a more effective manner and at lower temperatures that allow a simpler, less expensive system with a longer life time.
The core's structure 21 onto which the active materials are placed can be made from various materials such as cordierite, metal meshes, wire meshes and/or fiberglass.
The materials can be deposited in a non-uniform way so as to more optimally meet the desired requirements of low product cost and minimal reducing agent requirements.
With the use of appropriate mechanical design, stream 11 is directed through a trapping segment 22 of the bed while the reducing agent stream 9 is directed through the regenerating segment 23 of the bed. The relative sizes of the two segments depend on the specific characteristics of the application and the desired results. The bed can be rotated in either a clockwise or counter clockwise direction so that all parts of the bed are alternately exposed to the exhaust stream 11 and the fuel processor's product stream 9. The speed at which the bed rotates can be controlled if desired. Adjusting the rotational speed of the bed can reduce or minimize the bed size and reduce or minimize the amount of stream 9 that is required. It may be desirable to rotate the bed at a rate between 2 and 120 revolutions per minute (1 cycle every 0.5 sec to 30 seconds). Due to the very fast adsorption, desorption and reaction rates a fast cycle rate would reduce or minimize the size of the bed.
The bed can also be rotated at such a rate as to keep the NOx loading at a level that is a good trade-off between the efficiency of the adsorption steps and the efficiency of the desorption/reduction steps that result in low NOx emissions.
In
In
Some groups have proposed the use of a single-leg configuration where the full engine exhaust stream is passing through the adsorbent bed during the regeneration step. This configuration requires large amounts of oxygen to be consumed by combusting with fuel every time the adsorbent bed is to be regenerated. The benefits of the configurations shown in
The exhaust stream with reduced regulated emissions is then sent to the atmosphere via stream 13a. Exhaust stream 13a can optionally be passed through other after-treatment devices before being exhausted to the atmosphere.
The engine's fuel consumption can also be reduced by advancing the fuel injection timing and using the above-described after-treatment portion of the present system to reduce to acceptable levels engine exhaust stream NOx levels that result from the advanced fuel injection timing. Fuel injection timing advance has the additional benefit of reducing the diesel particulate matter in the exhaust and thus reducing the size and cost of equipment required to remove diesel particulate matter.
While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.
This application is related to and claims priority benefits from U.S. Provisional Patent Application Ser. No. 60/592,050 filed Jul. 29, 2004, and U.S. Provisional Patent Application Ser. No. 60/640,936 filed Dec. 30, 2004, each of which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60592050 | Jul 2004 | US | |
| 60640936 | Dec 2004 | US |
