Patent Application
20150047992
The present device and method relate to the storage and delivery of ammonia. Particularly, the device and method relate to storage of ammonia in a solid form and subsequent release of gaseous ammonia for use on a vehicle in the selective catalytic reduction of NOx.
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 NOx reducing exhaust treatment schemes are being employed in a growing number of systems.
One such system is the direct addition of ammonia gas to the exhaust stream. 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. Previous designs for delivery of solid ammonia, such as ammonia saturated strontium chloride, included wrapping the material into aluminum foil balls. The balls are then placed in a canister where they are pressed under a load of up to 300 tons to reach a density of approximately 1.2 g/cc. However, the machines typically required to fill and wrap the foil balls needs to be at very high speed (6 parts per second) in order to achieve the necessary rate for high volume. In addition, such machines tend to be expensive and difficult to maintain. Finally, it can be difficult to load the balls into the machine without damaging them, in that the wrapping can become unsealed, loose and subject to leakage. Therefore, conveying the foil balls at the speed required to meet the desired volume would likely be difficult to do without damaging them.
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 (an CO2).
Therefore, the present device and method relate to providing ammonia in solid form for the purpose of ammonia storage, transport and delivery for use in stationary and mobile applications, such as catalytic removal of NOx, i.e., selective catalytic reduction using ammonia.
There is disclosed herein a device and method, each of which avoids the disadvantages of prior devices and methods while affording additional structural and operating advantages.
Generally speaking, a device and method for storage and delivery of ammonia for use in connection with NOx reduction in the exhaust system of a vehicle, is disclosed. In one embodiment of the device for storage and delivery of ammonia, the device includes a pre-formed, sealable container and a predetermined amount of solid ammonia-containing material, wherein the container is filled with the ammonia-containing material prior to sealing.
In another embodiment, the device includes a pre-formed, sealable container, a predetermined amount of ammonia-containing material, wherein the container is filled with the ammonia-containing material prior to sealing, and a canister for receiving the filled, sealed containers. The container comprises a compactable material, for stacking and compressing the filled, sealed containers within the canister for a desired amount of the ammonia-containing material.
In the disclosed method, an embodiment for the method of storage and delivery of ammonia includes the steps of providing a pre-formed container having a top edge and a flat bottom, and a cover for sealing the top edge of the container. The method also includes providing a predetermined amount of ammonia-containing material, filling the container with the predetermined amount of the ammonia-containing material, and sealing the top edge of the container after filling with the ammonia-delivery material, thereby forming a stackable container.
In another embodiment, the method further comprises the steps of compressing the stacked containers within the canister, and subsequently crushing the filled containers within the canister for subsequent release of the ammonia.
These and other aspects of the invention may be understood more readily from the following description and the appended drawings.
For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated.
While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to embodiments illustrated.
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The container 12 is easily sealable using known methods. A cover 18 is provided for engaging the top edge 14 of the container 12. In one embodiment, the cover 18 can be crimped to the top edge 14 of the container in such a manner that it forms a flat surface, either flush with or slightly below, the top of the container. The flat surface created by the cover 18 facilitates later stacking the filled containers one of top of the other. Filling the container 12 and attaching the cover 18 can be accomplished by methods that are known in the art, for instance, by using automated fill and seal packaging methods used in the food industry. The cover 18 should also be made of a material that is compressible, crushable and easily transfers heat. In one embodiment, the cover 18 may be made from a foil sheet having a suitable thickness.
Ammonia-delivery material 20 useful in the present device 10 can include many types of storage materials capable of releasing ammonia through thermal desorption. Suitable ammonia-delivery material 20 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 of 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 invention 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 in the container 12 of the present device 10. The container 12 is filled with an appropriate ammonia-delivery material 20 having a density of between about 0.4-0.6 g/cc.
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The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants' contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US11/29698 | 3/24/2011 | WO | 00 | 9/24/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61318657 | Mar 2010 | US | |
| 61355397 | Jun 2010 | US |
