Patent Application
20130011316
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, through the application of heat, the subsequent release of gaseous ammonia for use in the selective catalytic reduction of NOx.
Compression ignition engines provide advantages in fuel economy, but produce both NOx 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. 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).
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.
In order to release the ammonia gas from its adsorptive or absorptive solid storage material, sufficient heat needs to be applied. In addition, the heat transfer needs to be efficient enough to reach the solid storage material through the containers or cartridge holding the material. Therefore, the present device and method relate to providing ammonia in solids for the purpose of ammonia storage and transport, and the effective delivery of heat to release the ammonia gas through thermal desorption for use in stationary and mobile applications, such as catalytic removal of NOx through 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, an ammonia storage material assembly comprises a cartridge and a plurality of nestable disks comprised of a heat conductive layer and an ammonia-containing material layer.
In an embodiment there is an assembly for storing solid ammonia, the assembly comprising a cartridge having sidewalls, a plurality of nestable disks comprised of a heat conductive layer and a compacted ammonia-containing material layer, wherein the plurality of nestable disks are inserted into the cartridge such that the heat conductive layer of each disk contacts the sidewalls.
In another embodiment, a solid material disk for storing solid ammonia and releasing it as a gas in an exhaust treatment system, is set forth. The disk comprises a solid ammonia-containing material layer having an upper section formed from a substantially parallel outer wall and a top surface with a recess, and a lower section formed from a substantially angular wall and a bottom surface, and a heat conductive layer.
In yet another embodiment, the lower section of a first disk is adapted for engaging the recess of a second disk forming a stacked plurality of nested disks having a heat conductive layer alternating between each disk.
In the disclosed method for storage and delivery of ammonia, the method comprises the steps of providing a cartridge having sidewalls, providing at least a first disk and a second disk comprised of a compacted ammonia-containing material, each disk having an upper section formed from a substantially parallel outer opposing wall and a top surface having a recess, and a lower section formed from substantially angular wall and a bottom surface, providing a heat conductive layer between each disk, engaging the lower section of the first disk with the recess of the second disk, creating a stack of nested disks and heat conductive layers, and inserting the stack into the cartridge.
In another embodiment, the method further comprises the step of applying a compression force to the stack after insertion into the cartridge, and contacting the heat conductive layer to the sidewall of the cartridge. Heat is provided from a heat source to the cartridge and heat conductive layer, which affects the release of ammonia gas from the ammonia-containing material.
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.
Referring to
As shown in
The disk 14 is made of an ammonia-containing material, generally in a solid form, such as a powder or granules. The disks 14 may be formed using existing powder metal press technology. Regardless of the technology used to prepare the disks, it is important to prevent the dissipation of ammonia during the formation of the disk. Suitable material for use in the disk 14 of the present assembly 10 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 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 creating the disk 14 of the present assembly 10.
As further shown in
The present assembly 10, including the combination disk 14 comprised of a compacted ammonia-containing material and heat conductive layer or plate 34, can be constructed by any suitable method.
In order to use the ammonia of the present device assembly 10 in, for example, the treatment of NOx in a vehicle exhaust system, it is necessary to apply a sufficient amount of heat in order to sublimate the solid ammonia into its useful gaseous form. It is contemplated that sufficient heat transfer can occur between the cartridge 12 and the ammonia-containing material disks 14, and the surrounding heat conductive layers 34 through the expansion of the disks and heat conductive layer, which when stacked together, are compressed through the application of sufficient compression pressure.
As noted, heat is required to release the ammonia gas from the solid ammonia-containing material. Heat may be applied to the cartridge 12 from a variety of sources, including but not limited to, an electrical resistive device, or hot exhaust gases from a combustion process. The heat would then transfer through the cartridge 12 to the nested disks 14 through the heat conductive layers 34 within the cartridge 12, releasing the ammonia gas within the cartridge. Although not shown, the ammonia gas may be delivered to an exhaust system through use of a controllable dosing valve to control the release of ammonia within the cartridge 12 to be used in the catalytic reduction of NOx in a vehicle exhaust system (not shown).
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 61317142 | Mar 2010 | US | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US11/29631 | 3/23/2011 | WO | 00 | 9/22/2012 |
