Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Solid component
Reexamination Certificate
1997-05-29
2002-04-02
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Solid component
C055S307000, C055S351000, C055S354000, C055S400000, C055S428000, C055S430000, C055SDIG008, C095S273000, C095S277000, C095S278000, C095S279000, C095S280000
Reexamination Certificate
active
06365119
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a method of operating a catalytic converter of one-part or multipart configuration, in particular for use in flue gas cleaning processes; a mechanical barrier, in particular a screen, whose mesh size depends on the particle size, is disposed on the inflow side of the catalytic converter configuration. The invention also relates to a catalytic converter configuration for carrying out the method.
When catalytic converters are employed in dust-containing flue gases or waste air streams (for example SCR DeNOx catalytic converters in a high-dust circuit), the operation repeatedly causes relatively large blockages of the catalytic converter ducts as a result of flue dust, in particular coarse flue ash particles or flue dust agglomerates. These particles remain stuck on the inflow side of the catalytic converters, they block the catalytic converter ducts and they form the seeds for large-area blockages, even with relatively fine flue dust. This results in a drastic reduction in the efficiency of the catalytic converters. Under unfavorable conditions, blockages of up to 70% of the overall catalytic converter surface have already been observed. In order to alleviate this problem, attempts have been made to install firmly fixed wire screens on the catalytic converters. The screens thereby have a mesh width which corresponds to the channel width of the catalytic converter ducts. Although these wire screens catch the relatively large ash particles, the larger particles or flue dust deposits remaining on the screens form seed cells for large-area dust deposits on the screens. This, in turn, leads to the catalytic converters to have no flow through them or themselves becoming blocked once more by flow dead zones on the leeward side (in the flow shadow) of the dust deposits.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method of operating a catalytic converter of one-part or multipart design, in particular for use in flue gas cleaning processes, and a catalytic converter configuration for carrying out the method, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which avoids the disadvantageous dust deposits and thus maintains proper efficiency of the system.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of operating a catalytic converter assembly exposed to a gas flow with particulate matter, the method which comprises:
providing a mechanical barrier having a mesh size adapted to a particle size of particulate matter contained in a gas flow to be cleaned, and placing the mechanical barrier on an inflow side of a catalytic converter configuration;
exposing the mechanical barrier to the gas flow and collecting the particulate matter with the mechanical barrier; and
moving the barrier relative to the catalytic converter assembly and removing the particulate matter from the barrier.
In accordance with an added feature of the invention, the method is applied in a flue gas cleaning process in which the barrier is exposed to flue dust and flue ashes. A preferred barrier is a screen or a net.
Deposits of flue dust are thus carried away with the screen as the transport device. Accordingly, the catalytic converter configuration can be operated at constant efficiency, even during operation, because deposits can be carried away as required at any time, without the operation being disadvantageously impaired. Furthermore, it is possible for the screen to have a mesh width which is distinctly smaller in comparison to the openings of the catalytic converter passages.
The movement of the screen can expediently be performed continuously or discontinuously, in particular during operation—depending on the actual circumstances.
The screen, as transport means, moves the collected accumulations of flue dust to one side of the catalytic converter configuration. There, the flue dust is removed from the screen, while the screen ensures optimum removal of the dust particles during operation.
According to a particular embodiment, the separation of flue dust takes place on both sides of the catalytic converter configuration, the screen moving firstly in one direction and then in the opposite direction.
With the above and other objects in view there is also provided, in accordance with another mode of the invention, a method of operating a catalytic converter assembly exposed to a flue gas containing flue dust, the method which comprises:
providing a mechanical barrier having a mesh size adapted to a particle size of a flue dust, and placing the mechanical barrier on an inflow side of a catalytic converter configuration; and
moving a cleaning system, such as a movable vacuum system, along the mechanical barrier and removing the flue dust collected by the barrier with the cleaning system.
The vacuum system may thereby move across the mechanical barrier continuously or discontinuously.
It is particularly effective if the use of the cleaning system is combined with the movement of the screen, which additionally transports flue ash particles as a transport device. Flue ash particles which are not carried away by the cleaning system are then removed on the side of the catalytic converter installation by the moving screen.
The speed of travel of the cleaning or suction system is 0.005-1.0 m/s, preferably 0.01-0.5 m/s.
In accordance with an additional feature of the invention, the cleaning efficiency may be increased when the suction device is also employed as a dust-blowing device. In this case, flue dust which can no longer be removed by the suction system can be blown out of the meshes of the screen.
With the above-noted and other objects in view there is also provided, in accordance with the invention, a catalytic converter assembly, comprising:
a catalytic converter configuration having an inflow side exposed to a flue gas containing flue dust;
a screen disposed on the inflow side of the catalytic converter configuration for collecting deposits of flue dust from the flue gas, the mechanical barrier having a mesh size adapted to a particle size of the flue dust in the flue gas, the screen being movably disposed relative to the catalytic converter configuration for removing the deposits of flue dust collected thereon. In addition, there is provided a roller system movably supporting the screen. As noted above, the significant feature of assembly is found in the provision that the screen can be moved relative to the catalytic converter configuration and it serves as a transport device for transporting off the deposits of flue dust.
The movement of the screen is ensured by a roller system, the guidance of the wire screen on the roller system being most expediently effected by specifically shaped (e.g. serrated) rolls.
In accordance with again an added feature of the invention, the screen is an endless roll.
A collecting container is located laterally of the catalytic converter configuration where the flue dust is removed from the screen (after it has been transported there by the movement of the screen), through a chute and to a transport system, such as a suction device or a corkscrew conveyor.
In the second embodiment of the invention, the suction system has at least one, preferably a plurality of, vacuum rakes, which communicate with a vacuum source.
When the catalytic converter configuration includes a plurality of catalytic converter modules spaced apart from one another, then the vacuum rakes—when not in use—are expediently placed in between the catalytic converter modules. In this case, the rake members serve as flow baffles which protect the gaps between the catalytic converter modules and they ensure that no flue gas can escape in the gaps without being exposed to and treated in the catalytic converter modules.
In accordance with a concomitant feature of the invention, the screen has a mesh width which is smaller than the openings of the catalytic converter passages. P
Hüttenhofer Klaus
Spitznagel Günther
Greenberg Laurence A.
Griffin Steven P.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
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