TECHNICAL FIELD

[0001] The present system and method relate to the storage and delivery of ammonia. Particularly, the system and method relate to an ammonia dosing system incorporating a modular housing having at least one canister containing a solid ammonia-containing material, the canisters connected to a common manifold for use in the release of gaseous ammonia for selective catalytic reduction of NO _x in the exhaust stream of a vehicle.

BACKGROUND

[0002] Compression ignition engines provide advantages in fuel economy, but produce both Οχ and particulates during normal operation. New and existing regulations continually challenge manufacturers to achieve good fuel economy and reduce the particulates and NO _x 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 NO _x as well. Accordingly, the use of NO _x reducing exhaust treatment schemes is being employed in a growing number of systems.

[0003] One such system is the direct addition of ammonia gas to the exhaust stream. It is an advantage to deliver ammonia directly in the form of a gas, both for simplicity of the flow control system and for efficient mixing of reducing agent, ammonia, with the exhaust gas. The direct use of ammonia also eliminates potential difficulties related to blocking of the dosing system, which are cause 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 CO ₂ ).

[0004] Transporting ammonia as a pressurized liquid, however, can be hazardous if the container bursts caused by an accident or if a valve or tube breaks. In the case of using a solid storage medium, the safety issues are much less critical since a small amount of heat is required to release the ammonia and the equilibrium pressure at room temperature can be— if a proper solid material is chosen— well below 1 bar. Solid ammonia can be provided in the form of disks or balls loaded into the cartridge or canister. The canisters are then loaded into a mantle or other storage device and secured to the vehicle for use. Appropriate heat is applied to the canisters, which then causes the ammonia-containing solid storage material to release its ammonia gas into the exhaust system of a vehicle, for example.

[0005] However, it can be a challenge to dose a consistent amount of ammonia into the after-treatment device for a continuous reduction of NO _x . Therefore, the present system and method incorporates a modular housing having at least one solid ammonia storage canister, wherein the canisters are connected together by a common manifold into a common flow path. In this manner, when one canister is emptied of its ammonia, that canister is closed, while another opens, maintaining a consistent flow of ammonia into the common flow path to the after-treatment device. Thus, the present system and method provides for a continuous flow of ammonia gas into the after-treatment device for continuous reduction of NO _x in the exhaust stream. In addition, because it is not practical to design a unique packaging system for each application, the present system offers a modular housing, such that the

orientation/configuration of the housing can be varied, as well as the number of canisters within the housing, depending on requirements of the particular application.

SUMMARY

[0006] There is disclosed herein a system and method, each of which avoids the disadvantages of prior systems and methods while affording additional structural and operating advantages.

[0007] Generally speaking, the system and method relate to an ammonia dosing system incorporating a modular housing containing at least one solid ammonia canister therein and a common manifold having a plurality of inlets feeding into a common manifold.

[0008] In one embodiment, an ammonia canister system for providing ammonia to a vehicle after-treatment device, is disclosed. The system comprises a housing having an interior, at least one solid ammonia canister having a supply of solid ammonia stored therein, positioned within the housing, a connector associated with each canisters, an ammonia flow module having a built-in valve for controlling the flow of ammonia from each of the at least one solid ammonia canisters, and a manifold having a plurality of inlets feeding into a common flow path, wherein each inlet is coupled to each connector, and a single outlet coupled to the flow module.

[0009] In another embodiment, each of the plurality of inlets and the outlet of the manifold comprises a check valve.

[0010] In yet another embodiment, a modular canister housing system is disclosed. The system comprises a housing having an interior, the housing adapted for receiving at least one canister containing a solid ammonia-containing material, and a guide for loading and removing the canister within the interior of the housing, wherein the guide corresponds with the number of canisters contained within the housing, and wherein the housing is positionable in a variety of orientations.

[0011] A method for the selected delivery of ammonia to a vehicle exhaust gas after- treatment device, is disclosed. In one embodiment, the method comprises the steps of seating at least one ammonia canister having a supply of solid ammonia-containing material into a housing, coupling each of the at least one ammonia canisters to one of a plurality of connectors, wherein each of the plurality of connectors is connected to a separate feed line, heating the at least one ammonia canister to start a flow of ammonia, opening a valve in an ammonia flow control module to create a flow of ammonia, directing the ammonia flow from the at least one ammonia canister, through the first connector to the corresponding feed line, into a common manifold and through the ammonia flow control module, metering the ammonia flow from the ammonia flow control module to an ammonia injector coupled to an exhaust gas after-treatment device, and injecting the ammonia into the exhaust gas after- treatment device.

[0012] In another embodiment, the method further comprises the step of turning off the heating to the at least one ammonia canister when the supply of ammonia in the canister reaches a predetermined volume and closing the canister. In yet another embodiment, the method further comprises the step of heating a second canister to create a second ammonia flow after the first canister is closed, and directing the second ammonia flow from the second canister into the common manifold.

[0013] These and other embodiments and their advantages can be more readily understood from a review of the following detailed description and the corresponding appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a schematic view of an exhaust gas NO _x reduction (EGNR) system;

[0015] FIG. 2 is one embodiment of the modular canister housing arrangement of the present system;

[0016] FIG. 3 is another embodiment of the modular canister housing arrangement of the present system;

[0017] FIG. 4 is another embodiment of the modular canister housing arrangement of the present system;

[0018] FIG. 5 is another embodiment of the modular canister arrangement of the present system;

[0019] FIG. 6 is another embodiment of the modular canister housing arrangement of the present system;

[0020] FIG. 7 is a perspective view of the housing containing the main canisters;

[0021] FIG. 8 is a right side view of the housing showing the common manifold;

[0022] FIG. 9 is a left side view of the housing common manifold; and,

[0023] FIG. 10 is a schematic view of the ammonia flow control module; and,

[0024] Appendix.

DETAILED DESCRIPTION

[0025] Referring to FIGS. 1-10 and the Appendix, there is illustrated a system and method for storage of ammonia, specifically in a solid form, and delivery of gaseous ammonia for use in the reduction of NO _x in an exhaust stream. FIG. 1 illustrates an exhaust gas Οχ reduction system (EGNR), including the ammonia delivery system schematic, in which the present modular canister housing system 10 is used, specifically for supplying ammonia gas to an after-treatment device for use in the exhaust system of a compression ignition engine (not shown). The components of the EGNR will not be discussed in further detail with the exception of how it relates to the present system. As the exhaust system of a vehicle, including that of a diesel engine, is well known, it will not be described in detail.

[0026] As shown in FIGS. 2-6, the modular canister housing 10 of the present system, typically comprises a housing 12 having a closed, rectangular shape. The housing 12 can be sealed with a door 14, pivotally attached by known means. The housing can be constructed from any durable material, such as steel, aluminum or plastics, and can be secured, using known attachment means, to the frame of a vehicle (not shown), for retention on the vehicle during use. The housing 12 is a modular unit, constructed with standardized dimensions for use in a variety of applications, yet providing flexibility in the number of canisters that can be installed therein. Ideally, the housing 12 is constructed base on industry standards such that it would fit within any vehicle, yet the number of canisters, be it one or more, can be loaded into the standard housing. As shown in FIGS. 2-6, the housing 12 can be positioned in a number of ways, and contain a variety of canisters, making it a cost-effective, semi- customizable unit.

[0027] Seated within the interior of the housing 12 is at least one canister (cartridge or container) containing a solid ammonia-containing material. The canisters 16 contained within the housing 12 are referred to as the main canister units. The EGNR system may also include a start-up canister 18. The start-up canister 18 is typically attached to the outside of the housing 12. As shown in FIGS. 2-6, the start-up canister may be positioned anywhere on the outside of the housing 12. The canisters, whether the start-up or main canisters can have any useable shape, including a cylindrical shape. The canisters can be constructed from any suitable material that is durable for loading and transporting the ammonia-containing material (not shown). In addition, the material for constructing the canisters should ideally conduct heat, because the solid ammonia-containing material used in the present system and method, require heat to release the ammonia from the solid as a gas for a gradual release based on ammonia dosing demands. Aluminum sheets are a suitable material for use in constructing the canisters in a known manner. Aluminum has a low mass density and excellent thermal conductivity.

[0028] Positioning and securing the canisters 16 within the housing may be accomplished using a guide or securing means, such as a track or rail. As shown in FIGS. 2-6, a rail 20 may be placed in the interior of the housing 12. The canister 16 may include a plurality of grooves 22, which permit the canister to be slid along the track or rail and secured within the housing 12. In this manner, no matter what position the housing is in, or how many canisters are added to the housing, the canisters remain in place within the housing. The number of rails 20 provided within the housing 12 may vary depending on the number of canisters 16 to be loaded within the housing.

[0029] Heating of the main canisters 16 may be accomplished through a heating device (not shown), such as a resistive element which generates heat when an electrical current is passed through the element, or is a conduit for a liquid, such as engine coolant. The heating device may optionally be installed within the interior of the canister, or outside the canister. Although not shown, it should be understood that the heating device is connected to a power source (not shown) to control the amount of heat generated by the heating device. Similarly, the canisters 16 include temperature sensors and pressure sensors for sending appropriate signals to an electronic control module (not shown) for monitoring and control of the heating device.

[0030] The ammonia-containing material loaded into the canisters 16 is generally in a solid form, such as a compressed powder or granules, and may include any suitable shape for packing into the canisters 16, including disks, balls, granules, or a tightly -packed powder. The material may be formed using existing powder metal press technology. Regardless of the technology used to prepare the material, it is important to prevent the dissipation of ammonia during the formation of the material. Therefore, materials that are suitable for storage at ambient conditions on a vehicle at substantially atmospheric pressure, are desirable. Suitable material for use in the EGNR 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 700°C, and preferably to a temperature of from 100° to 500°C. Generally speaking, metal ammine salts useful in the present device include the general formula M( H ₃ ) _n X _z , 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, CI, Br, I, S0 ₄ , Mo0 ₄ , P0 ₄ , etc. Preferably, ammonia saturated strontium chloride, Sr(NH ₃ )Cl _2, is used.

[0031] Each canister 16 includes a connector 24. The connector 24 may be quick-release connector, which permits the transfer of ammonia gas from the canister 16 to for use in the EGNR system. In addition, the connector 24 should be self-sealing through the use of an integrated check valve, such that when the canister is removed from the housing 12 for replacement or recharging, any residual ammonia gas in the canister does not leak out into the environment. Optionally, the canisters 16 can be re-charged with ammonia in situ or onboard by connecting to a source of ammonia, for example, a tank containing liquid ammonia.

[0032] Control of and metering the flow of ammonia from the canister 16 when the appropriate amount of heat is applied to the ammonia-containing material within the canister, is accomplished through the use of an ammonia flow control module 28 (FIG. 10). As shown in FIG. 10, the ammonia flow control module contains a plurality of temperature and pressure sensors and valves for use in controlling the ammonia flow through the system, from the canisters to the after-treatment device. The ammonia flow control module 28 controls the flow of ammonia from the canisters through the opening and closing of its control valve 40, the operation of which is based on the ammonia dosing demands of the overall system. The ammonia demand is substantially that amount of ammonia that is able to remove all of the Οχ in the exhaust system. Therefore, various sensors for measuring the level of NO _x within the ammonia flow module, may be used to determine the ammonia demand. Alternatively, information from an engine control module (not shown) or combustion process controller (not shown) may also be used to estimate the operating state of the engine, and the level of Οχ in the exhaust system, and thus, the amount of ammonia required for treatment. Regardless of the manner of detecting the level of NO _x in the system, the desired result is the opening and closing operation of the control valve 40 within the ammonia control module 28 for releasing the appropriate amount of ammonia into the after-treatment device and exhaust stream.

[0033] Supplying the after-treatment device and exhaust stream with ammonia released from the canisters 16 18 is accomplished through the use of a common manifold 30. The manifold 30 includes a plurality of inlets 32 and one common outlet 34. Each canister 16 through its respective connector valve 24 is fluidly connected to a corresponding feed line 36. Each feed line 36 is then connected to one of the plurality of inlets 32 for the common manifold 30. The inlets 32 are typically a check valve. Any suitable check valve will work in the present system, including a butterfly valve or a ball valve. The inlet check valve 32 directs the flow of ammonia gas in one direction from the canister 16 through the feed line 36, into the common manifold 30, while preventing backflow of ammonia from the manifold to the feed line and back into the canister. By using the common manifold 30, the ammonia is separately released from each canister 16 based on the signals from the ammonia control module, and into a single flow path. From the common manifold 30, the ammonia flows through the outlet 34 of the manifold, and eventually to the after-treatment device 26 and the exhaust stream. The outlet 34 is also a check valve, which again maintains the flow in one direction outwardly toward the after-treatment device, and prevents backflow of the ammonia gas back into the manifold.

[0034] The present method provides delivering ammonia gas to a vehicle exhaust gas after-treatment device for reduction of NOx in the exhaust stream. The method is designed to provide a consistent flow of ammonia into the after-treatment device and exhaust stream. The method includes seating at least one ammonia canister 16 having a supply of solid ammonia-containing material into housing 12 secured on a vehicle (not shown), each canister including a connector 24, wherein each connector is connected to a separate feed line 36. The method further includes heating the at least one ammonia canister 16 to start a flow of ammonia, opening the control valve 40 within the ammonia flow control module 28 to create a flow of ammonia, directing the ammonia flow from the at least one ammonia canister, through the first connector to the corresponding feed line, into a common manifold 30. The ammonia flow is directed from the common manifold 30 through a single outlet 34 to an ammonia flow module, and ultimately to the after-treatment device.

[0035] The present system and method provides for sequential and continuous flow of ammonia. For example, if the system includes three separate canisters 16a, 16b, 16c, such as shown in FIGS. 7-9 within housing 12, a heating device is turned on and heat is applied to the first of the three canisters 16a, activating it to release its ammonia gas into the feed line and the common manifold. Once the level of ammonia in the first canister 16a reaches a predetermined level, the heating device is turned off, which then stops the flow of ammonia gas, if any is left in the canister. In the next step, the heating device is turned on and heat is applied to a second canister 16b in the series, which will then start releasing its ammonia gas into the common manifold, until it too reaches a predetermined level, and the heating device is turned off. Following in the series, the heating device is turned one and heat is applied to a third canister 16c, releasing ammonia gas from the third canister into the common manifold, until it reaches a predetermined level, and so on. In this manner, empty canisters can either be recharged on-line with ammonia or replaced, to maintain the cycle of providing ammonia gas to the system on a consistent basis.

[0036] Regardless of the number of canisters used in the system, the ammonia flows through the common manifold 30 through a single outlet to an ammonia flow module 28. The ammonia flow module meters the ammonia flow to an ammonia injector 26a coupled to the exhaust gas after-treatment device 26, injecting the ammonia into the exhaust gas after- treatment device for the reduction of NO _x in the exhaust stream. The method provides for a continuous flow of ammonia into the after-treatment device and thus, continuous reduction of Οχ in the exhaust stream.