Patent Publication Number: US-2015086427-A1

Title: Line break indicator (wire in ammonia lines)

Description:
TECHNICAL FIELD 
     The present device and methods relate to connection and ammonia feed status indicators for an ammonia delivery system. More specifically, the device and methods relate to detection of an ammonia feed line break and indication of the same to prevent excessive ammonia loss. 
     BACKGROUND 
     Compression ignition engines provide advantages in fuel economy, but produce both NO x  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. 
     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 the reducing agent, ammonia, with the exhaust gas. The direct use of ammonia also eliminates potential difficulties related to blocking of the dosing system, which difficulties are typically caused by, e.g., precipitation or impurities 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 ). 
     Due to its caustic nature, transporting ammonia as a pressurized liquid can be hazardous if the container bursts as the result of 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 a 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 storage material to release ammonia gas from the canister into a feed line where it is metered into the exhaust system of a vehicle, for example. 
     However, as the ammonia leaves the canister, it is in gas form and presents a potential hazard if released through an improper canister connection or through a broken feed line. Even a small leak could be problematic if only for the loss of ammonia, which may deplete the source earlier than scheduled replacement. 
     Further, as alluded to above, eventually the ammonia in a canister is depleted and must be recharged or replaced. Unfortunately, there are no systems in place which are capable of indicating the fill-status of a canister. This shortcoming requires a plurality of canisters to be used in a vehicle system in order to provide a level of redundancy. Further, the canisters are typically changed on a regular basis, regardless of the fill-level, to avoid the possibility of ammonia depletion during engine operation. The result is sometimes the carrying of too much ammonia to provide the desired redundancy, and sometimes the removal and replacement of partially-filled ammonia canisters with full canisters to avoid depletion. Such conditions and procedures may increase the possibility of an accidental ammonia release. 
     Thus, the present system and methods provide an on-board indication of a proper connection between the ammonia canister and the ammonia feed line. The system and methods facilitate proper scheduling of removal and replacement of ammonia canisters as well as provide real-time ammonia loads for canisters. These and other problems are addressed and resolved by the disclosed systems and method of the present application. 
     SUMMARY 
     Generally speaking, an ammonia delivery system includes at least one canister containing a supply of ammonia in solid form (powder or granular) coupled, via a delivery line, to an exhaust gas after-treatment system having an ammonia injector. The delivery line is connected at one end to the ammonia injector and at another end it is detachably coupled by a coupler to the at least one canister. A controller may be used for metering flow of ammonia through the delivery line to the injector. 
     In an embodiment of the disclosed ammonia delivery system, a line-break detector for detecting a disconnection, such as a break, within the delivery line is used. In an aspect of the invention, a line-break indicator coupled to the line-break detector may be used, wherein the indicator activates upon the detector detecting a disconnection in the delivery line. 
     In various embodiments of the system, the line-break indicator comprises an annunciator electronically connected to the line-break detector. The annunciator may emit a visual signal, such as a LED light or a reading from an analog or digital display, an audible signal, such as a click, beep, buzz, chime, etc., or both. 
     In a preferred embodiment of the system, the line-break detector comprises at least one wire extending a length of the delivery line, wherein a break in the wire activates an annunciator. The wire(s) may be positioned on an external surface of the delivery line, integrated into a sidewall of the delivery line, located within the delivery line, or some combination of these configurations. An electric signal being transmitted through the at least one wire terminates when the at least one wire experiences a break or disconnection. 
     In a method for determining a break in an ammonia feed line, an ammonia canister is positioned for connection to a coupler fixed to an ammonia feed line to allow feeding of ammonia from the canister through the feed line to an ammonia injector. An electronic signal is passed along a length of the feed line and a disruption in the signal may be detected to signify a line break. 
     It is a further aspect of the method to activate an annunciator upon detection of a disruption in the electronic signal. In an embodiment, at least one wire extending along a length of the feed line, either on an outer surface, an inner surface, within the sidewall, or some combination, is used for transmitting the electric signal. A break in the ammonia line results in a break in the at least one wire and, thus, a disruption in the electric signal. 
     In various embodiments, the annunciator may include initiating a visual signal, an audible signal, or both. A emergency stop may be triggered in the ammonia flow controller by the signal disruption as well. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic overview of an ammonia storage and delivery system working in conjunction with a vehicle engine system, exhaust gas after-treatment system and the vehicle electronics; 
         FIG. 2  is a schematic illustrating an embodiment of the present on-board fill-status indicator system; 
         FIG. 3  is a schematic illustrating a partial cross-section of an ammonia canister and an embodiment of the present canister fill-status indicator system; 
         FIG. 4  illustrates a particular embodiment of the indicator system used in a three cartridge array; 
         FIG. 5  is a schematic illustrating an embodiment of a feed line coupler/canister connection status indicator; 
         FIG. 6  is a schematic illustrating an embodiment of a line-break detection and indicator system; and 
         FIGS. 7A-7D  illustrate various embodiments of the placement of the line-break detection wire. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1-7 , the embodiments of the system and methods are described to one of skill in the relevant art. Ammonia storage and dosing systems (ASDS), which are part of the exhaust gas NO x  reduction (EGNR) system used in vehicles, may be comprised of several components, including a start-up canister, at least one main canister contained within a housing or storage compartment, wherein the canisters contain an ammonia adsorbing/desorbing material, an ammonia control module (AFM), a peripheral interface module (PIM), and possibly other components depending on vehicle specifications. Generally speaking, an ammonia delivery system, designated with the reference number  10  in the figures, typically works in conjunction with an internal combustion engine  12 , the exhaust gas after-treatment system  14 , and the vehicle electronics  16 . 
     In an embodiment of the ammonia delivery system  10 , at least one canister  20  containing a supply of ammonia in an ammonia adsorbing/desorbing material is loaded into a carrier and secured in place. The canister  20  is connected to a metering system  22  via special tubing  24  and a special connector  26  to prevent leakage of the ammonia. In most systems, a plurality of canisters will be used to provide greater travel distance between recharging. However, the current system works sufficiently with a single canister for some applications and as desired or necessary. A heating jacket (not shown) is typically used around the canister to bring the ammonia adsorbing/desorbing material to a sublimation temperature. 
     Suitable ammonia adsorbing/desorbing material useful in the treatment of NO x  in an exhaust stream includes 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 or desorbed 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. It has been found that the ammine salt is best having the general formula M(NH 3 ) n X z , where M is one or more metal ions selected from the group consisting of Li, Mg, Ca, Sr, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, n is the coordination number in the range of from 2 to 12, and X is one or more anions, depending on the valence of M, selected from the group consisting of F, Cl, Br, I, SO 4 , MoO 4 , and PO 4 . A saturated strontium chloride has been found to be preferable for the canister storage space. While embodiments using ammonia as the preferred reductant are disclosed, the invention is not limited to such embodiments, and other reductants may be utilized instead of, or in addition to, ammonia for carrying out the inventions disclosed and claimed herein. Examples of such other, or additional reductants include, but are not limited to, urea, ammonium carbamate, and hydrogen. 
     Once converted to a gas, the ammonia is metered at the ammonia flow module (AFM)  28  and is directed to an exhaust gas after-treatment system  14  having an ammonia injector  30 , as shown in  FIG. 1 . The AFM  28  includes a controller  34  for metering flow of ammonia to an injector located within the after-treatment system  14 . By “metering” it is meant that the controller  34  controls ammonia flow (rate and duration) and stores information about such details, possibly including for example: (1) the amount of ammonia required by the exhaust gas after-treatment system  14 ; (2) the amount of ammonia being delivered; (3) which of the multiple canisters provided ammonia; (4) the starting volume of deliverable ammonia in the canister; and (5) other such data which may be relevant to determining the amount of deliverable ammonia in each canister. The information may be monitored on a periodic or continuous basis. When the controller  34  determines that the amount of deliverable ammonia (i.e., approximately the amount of ammonia remaining in a particular canister) is below a predetermined level, a status indicator  40  electronically connected to the controller  34  is activated. The indicator  40  may be used to generally indicate a status of the canister  20 , such as, for example, “Full” or “Empty” (see  FIG. 4 , for example) or it may be a type of analog or digital gauge used to indicate a specific amount of remaining deliverable ammonia. 
     In an embodiment for indicating a general threshold level of ammonia, the status indicator is preferably a single LED or other such simple visual indicator capable of signifying two separate conditions (e.g., LED “on”=empty and “off”=not empty). The predetermined threshold level may be “empty” or it may be, for example, when only 10% of deliverable ammonia remains in a canister. In a similar embodiment, the status indicator may include a series of LEDs (or other such visual indicators) to indicate ranges or a decreasing series of different threshold levels of deliverable ammonia remaining—e.g., one light=80%, two lights=50%, three lights=20%, etc. For more acute concerns, the status indicator may use an analog or digital display of remaining ammonia, much like a fuel gauge on a vehicle operates. 
     The visual indicator  40  may be mounted in proximity to the canister storage area to better advise those individuals charged with recharging and replacing empty canisters, and/or the indicator  40  may be mounted within the vehicle cab as part of the vehicle instrument cluster  42 . When a first canister registers as “empty” or when it is removed from the canister mounting, the controller  34  automatically switches to a second supply of ammonia in a second canister. 
     In another feature of an embodiment of the present system, a method for tracking the ammonia level in the ammonia canister  20  may be used on each canister, as illustrated in  FIG. 3 . That is, after a canister is removed from the vehicle&#39;s ammonia storage and delivery system, the remaining ammonia in the subject canister can be readily determined. Generally speaking, the method comprises attaching a memory storage device to each ammonia canister, determining the volume of ammonia in the canister, storing information relevant to the determined volume in the memory storage device and periodically updating the information on the memory storage device as the ammonia is used. 
     As with the system  10  previously described, the method further comprises metering the use of the ammonia after the step of storing the information. The system controller  34  previously described is suitable for such metering and information storage. However, the controller  34  remains with the vehicle when the ammonia canisters are removed and, therefore, cannot suitably operate to make such information available for a removed canister. Instead, the memory storage device  50  affixed to the ammonia canister comprises an RFID tag  50  which can be read by a conventional RFID reader  52 . 
     When a canister  20  is connected to the vehicle&#39;s ammonia storage and delivery system  10 , an RFID reader/writer in the metering system  22  can frequently update the information stored on the RFID tag  50  as ammonia is depleted. As the controller  34  determines information about each coupled canister  20 , the RFID reader/writer can easily write such information to the individual RFID tag  50  on each canister. Periodically or continuously updating the information merely comprises the steps of calculating the amount of ammonia remaining in the canister based on the flow rate and duration metered by the controller  34  and then storing a value relevant to the calculated amount on the memory storage device, i.e., the RFID tag  50 . 
     In an embodiment of the canister ammonia volume tracking method, each ammonia canister  20  comprises a memory storage device (e.g., RFID tag)  50  affixed to the canister  20 , wherein the memory storage device contains information relevant to the volume of ammonia stored in the canister at a given time. The vehicle components include a metering device for tracking the amount of ammonia delivered from the canister over a period of time, and an input device (e.g., RFID reader/writer) for periodically updating the memory storage device based on the amount of ammonia delivered from the canister  20  as tracked by the metering device  22 . 
     Before the canister  20  is removed from the vehicle, the memory storage device  50  is updated with current ammonia load information. Then, a conventional handheld RFID reader  52  may be used at canister drop-off locations to determine the fill-status of each canister  20 . 
     Referring to  FIGS. 5-7 , another aspect of the present system can be more readily understood. There are two additional points for potential ammonia leaks in the present system. The first is as a result of an improper coupling at any point in the ammonia flow, while the second is as a result of a break in the feed line. 
     As to leaks due to improper couplings, an embodiment of the system includes a positive connection indicator  60  which signals when a proper connection is achieved between the ammonia supply and the feed/delivery line  24 . At least one canister  20  containing a supply of ammonia in an ammonia adsorbing/desorbing material is connected, via a coupler  26  attached to an end of an ammonia delivery line  24 , to an exhaust gas after-treatment system  14  having an ammonia injector  30 . As previously described, an AFM  28  having a controller  34  is used for metering flow of the ammonia through the delivery line  24  to the injector  30 . The connection status indicator  60  is used to provide a connection status of the coupler  26  to the canister  20  or a manifold (not shown) where multiple canisters are in use. 
     In an embodiment of the ammonia delivery system  10 , the status indicator  60  may provide a visual signal  62 , an audible signal  66 , or both when a proper connection is made. A preferred indicator is an LED or a series of LEDs. Alternatively, the visual signal  62  may be provided by an analog display/gauge  63  or a digital display  64 . The audible signal  66  may be provided by an electronic annunciator using any variety or combination of sounds, including a click, beep, buzzer, etc. The status indicator  60  can be used to indicate either proper or improper connection or disconnection of the coupler  26  to the canister  20 . 
     In use, the user is able to verify a proper connection between an ammonia canister  20  and a coupler attached to a feed line  24  for a delivery system  10 . First, at least one ammonia canister  20  must be positioned for connection to a coupler  26  fixed to an ammonia feed line  24 . Then, a mechanism such as the status indicator  60  must be set to activate upon a proper connection between the ammonia canister  20  and the coupler  26 . When the user connects the coupler  26  to the ammonia canister  20 , the user is able to determine whether the mechanism has been activated and, therefore, whether a proper connection has been made. 
     Where an activation of the status indicator  60  is not made—i.e., the connection is not proper—then the user may disconnect the coupler  26  from the ammonia canister  20  and then reconnect the coupler  26  to the ammonia canister  20 . This disconnect/reconnect pattern can be followed until the user has determined that that the status indicator  60  has been activated. 
     The other potential for an ammonia gas leak is as a result of a break or disconnection of some kind in the ammonia delivery line  24 . Accordingly, a feature of another embodiment of the ammonia delivery system  10  is the use of a line-break detector  70  and indicator  72 . The line-break indicator  72  is connected and responsive to the detector  70  and is useful for visually and/or audibly indicating a disconnection or break at any point in the ammonia delivery line  24 . 
     As with the connection indicator  60  described above, a preferred mechanism for use with the line-break indicator  72  is an electronic annunciator connected to the line break detector  70 . The annunciator may be a LED, a series of LEDs, or some other electronic visual signal, such as a analog or digital gauge. The annunciator may also emit an audible signal such as a beep, buzz, click, chime or the like. 
     The preferred line-break detector  70  for the ammonia delivery system  10  comprises at least one wire  74  extending a length of the feed line  24 , from the coupler  26  to the flow controller  28 . The wire(s)  74  would have an electric signal constantly running there through such that a break in any part of the wire  74  would prevent transmission of the signal. A break in the wire(s)  74  would coincide with a break in the physical ammonia feed line  24 . The termination of the electric signal would trigger the activation of the line-break indicator  72 . 
     The positioning of the line-break detector  70  is variable. As illustrated in  FIGS. 7A-7D , the wire(s)  74  may be positioned on an external surface of the feed line  24  ( 7 A), integrated into a sidewall of the feed line  24  ( 7 B), located within an interior of the feed line  24  ( 7 C), or a combination of these locations ( 7 D). 
     As still a further safety feature of the present ammonia delivery system  10 , the ammonia flow controller  28  may be signaled to automatically stop the ammonia flow from the canister  20  through the feed line  24  upon an event related to a line break, such as termination of the electric signal or activation of the line-break indicator  72 .