Patent Application
20140325964
The present system and method relates to the delivery of a reducing agent or reductant into the exhaust stream of a vehicle for reduction of NOx in the exhaust stream. Particularly, the system and method relates to the addition of a pressure boosting device within the reductant supply line to increase the pressure of reductant and improve reductant distribution within the exhaust stream.
Compression ignition engines provide advantages in fuel economy, but produce both NO and particulates during normal operation. New and existing regulations continually challenge manufacturers to achieve good fuel economy and reduce the particulates and NOx emissions. Lean-burn engines achieve the fuel economy objective, but the high concentrations of oxygen in the exhaust of these engines yields significantly high concentrations of NOx as well. Accordingly, the use of NO reducing exhaust treatment schemes is being employed in a growing number of systems.
One such system is the direct addition of a reductant or reducing agent, such as ammonia gas, to the exhaust stream. It is an advantage to deliver ammonia directly into the exhaust stream in the form of a gas, both for simplicity of the flow control system and for efficient mixing of the reducing agent, ammonia, with the exhaust gases. The direct use of ammonia also eliminates potential difficulties related to blocking of the dosing system, which may be caused by precipitation or impurities, e.g., in a liquid-based urea solution. In addition, an aqueous urea solution cannot be dosed at a low engine load since the temperature of the exhaust line would be too low for complete conversion of urea to ammonia (and CO2).
A couple specific challenges with the direct injection of a gaseous reductant, such as ammonia, relate to dispersion and mixing of the reductant or reducing agent with the hot exhaust gases. Generally, the cartridge storing the reductant-containing material needs to be heated to a sufficient temperature level so that the released reductant has enough pressure to overcome the pressure of the exhaust stream upon injection. Thus, the dispersion issue considers how to deliver or spread ammonia to the greatest volume of flowing exhaust, while the mixing issue concerns how to create the most homogenous mixture of exhaust and ammonia to facilitate NOx reduction.
Thus, the present system and method provide for a reduction in the time required to inject the reductant into the exhaust stream, as well as, improving the distribution of the reductant into the exhaust stream. Additionally, the present system and method result in a reduction in energy requirements for heating the cartridges and reductant-containing material to the necessary level. These and other problems are addressed and resolved by the disclosed system and method.
There is disclosed herein a system and method which avoids the disadvantages of prior devices and methods while affording additional structural and operating advantages.
Generally, a system for delivering a reductant into an engine exhaust stream, is disclosed. The system comprises a canister having an interior space for storing the reductant containing material, a fluid supply line fluidly connected to the canister for receiving the reductant, a pressure boosting device for boosting the flow of reductant a flow management device, and, an injector for injecting the reductant into an after-treatment system for combining with the exhaust stream.
In an embodiment of the system, the pressure boosting device is a pump integrated within the fluid supply line.
In another embodiment of the system, the pump is integrated within the fluid supply line between the cartridge and the injector.
A method for reducing NOx in an exhaust gas stream of a diesel-engine vehicle, is disclosed. The method comprises the steps of fluidly coupling components of an exhaust gas treatment system package to an engine exhaust gas system, wherein the components comprise a cartridge having an interior space for storing a reductant containing material, a conduit fluidly connected to the cartridge for receiving the reductant upon release from the material, a pressure boosting device for boosting the pressure of the reductant, a flow management device; and, an injector for injecting the reductant into the exhaust stream. The method further comprises the steps of increasing the flow of reductant through the pump and the flow management device, injecting gaseous ammonia into the engine exhaust gas system through the injector, and, reacting the reductant with the engine exhaust gas stream reducing the level of NOx in the exhaust gas stream.
Referring to
In addition to the ASDS 50, the EGNR 10 includes vehicle engine components, including an electronic control module 32. The specific components of the ASDS 50 and EGNR will not be discussed in further detail with the exception of discussing, as necessary, how a component or system may relate to the present system and method. Further, as the vehicle ignition system and the vehicle exhaust system, including those used on a diesel engine vehicle, are well-known, these systems also will not be described in detail.
In the ASDS system, the components for storing a reductant or reducing agent, including an ammonia adsorbing/desorbing material (not shown), stored within a main canister or cartridge 20. The present system may include a start-up canister 24, generally useful for the initial release of reductant into the exhaust stream before the main canister 20 or canisters reach the required temperature level to release its reductant. As heat is necessary to release the reductant or reducing agent from the adsorbing/desorbing material within the cartridge, it is useful to have a heating source, such as through an electrical source or an engine coolant sourced heater. Alternatively, the cartridge 20 may be placed within a heating unit or jacket or other type of housing for storage, heating and transport (not shown).
The ammonia adsorbing/desorbing material loaded into the main and start-up cartridges 20 and 24, respectively, is generally in a solid form, such as a compressed powder or granules, and may include any suitable shape for packing into the cartridges, including balls, granules, or a tightly-packed powder formed as a disk. Suitable adsorbing/desorbing material for use with the present system include metal-ammine salts, which offer a solid storage medium for ammonia, and represent a safe, practical and compact option for storage and transportation of ammonia. Ammonia may be released from the metal ammine salt by heating the salt to temperatures in the range from 10° C. to the melting point to the metal ammine salt complex, for example, to a temperature from 30° to 150° C. Generally speaking, metal ammine salts useful in the present device include the general formula M(NH3)nXz, where M is one or more metal ions capable of binding ammonia, such as Li, Mg, Ca, Sr, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, etc., n is the coordination number usually 2-12, and X is one or more anions, depending on the valence of M, where representative examples of X are F, Cl, Br, I, SO4, MoO4, PO4, etc. Preferably, ammonia saturated strontium chloride, Sr(NH3)Cl2, is used. While embodiments using ammonia as the preferred reductant are disclosed, the disclosure is not limited to such embodiments, and other reductants may be utilized instead of, or in addition to, ammonia for carrying out the system and method disclosed and claimed herein. Examples of such other, or additional reductants include, but are not limited to, urea, and ammonium carbamate.
As noted above, in order to use ammonia gas in the treatment of NOx in an exhaust system, it is necessary to apply a sufficient amount of heat to the cartridges and the contained ammonia adsorbing/desorbing material, in order to release the ammonia into its useful gaseous form. Once released, the ammonia gas is delivered to the exhaust stream by way of a fluid tubing or conduit 34 connected at one end to the ammonia source (main or start-up canister) 20, 24 and at the other end to an injector 62 positioned within the after-treatment assembly 60 (
In the present system, in order to increase the pressure and reduce the time for injecting the reductant into the exhaust stream, a pressure boosting device 100 is added to the system. Specifically, a pressure boosting device 100 is integrated to the fluid supply line 34. As shown in
The present pressure boosting device 100 is useful in a method that reduces the amount of time need for the ASDS to be able to inject a reductant, such as ammonia, into the exhaust stream, while also improving the distribution of reductant in the exhaust stream. The present method includes the steps of fluidly coupling components of an exhaust gas NOx reduction (EGNR) system package to an engine exhaust gas system, wherein the components comprise a cartridge 20 having an interior space for storing a reductant containing material, a conduit 34 fluidly connected to the cartridge for receiving the reductant upon release from the material, a pressure boosting device 100 for boosting the flow of reductant, a flow management device 26, and, an injector 62 for injecting the reductant into the exhaust stream flowing through an after-treatment assembly 60. The method further includes increasing the pressure of reductant through the pressure boosting device and the flow management device, injecting gaseous ammonia into the engine exhaust gas system through the injector, and, reacting the reductant with the engine exhaust gas stream thereby reducing the level of NOx in the exhaust gas stream. In the present method, the pressure boosting device is a pump, which is integrated into the reductant supply line or conduit between the cartridge and the flow management device.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US12/21644 | 1/18/2012 | WO | 00 | 7/15/2014 |
