Technical Field

The present invention relates generally to catalytic conversion devices used in combination with internal combustion engines, stationary turbines and steam boilers. The invention relates specifically to a device in which a stack of catalyst support tiles is used to enhance catalyst activity and catalyst handling. Background of the Invention The use of precious metal catalysts such as platinum, palladium and rhodium to convert N0 _χ and CO in effluent gases has generated an industry focussed on emission controls. Prior art emission control devices are typically configured to be inserted within the exhaust stream from internal combustion engines, turbines and steam boilers. Ceramic catalyst supports upon which the precious metals are deposited, are provided in bulk. The bulk catalyst support is used to introduce the active catalyst to the gaseous stream which flows through the catalyst support. Due to the varying temperature range experienced under engine operating conditions, there is cyclic expansion and contraction of the ceramic supports. This thermal cycling eventually leads to degradation of the ceramic support, which in turn reduces catalyst activity, and also leads to loose or broken ceramic pieces falling into the engine manifold, with obvious deleterious effects.

The present invention provides a modular approach to catalyst support. Rather than providing a single bulk cata¬ lyst, the instant device utilizes a series of catalyst support tiles which are individually structurally supported and which can be individually replaced. According to the present

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invention, the ceramic catalyst support tiles are provided in preassembled steel frames and the tile faces are encased in steel mesh. This modular approach provides for easy main¬ tenance, increased performance, lower replacement cost, interchangeability and easy adjustments.

Catalytic converters need periodic cleaning to maintai catalyst activity and to minimize any backpressure on the engine resulting from reduced flow capacities in the converter device. The cleaning process consists of removing the ceramic catalyst support and immersing the catalyst support in an aci solution. The present invention, which provides individuall contained and structurally sound catalyst support tiles, has significant advantages over bulk catalysts. Since the instan catalyst support tiles are protected by a wire mesh and steel frame, no special holding tools are required to remove th catalyst support for cleaning. Further, the containment syste of the present invention permits reuse of ceramic catalys support tiles which may be broken or cracked. Bulk catalys supports, on the other hand, must be specially handled, and an broken catalyst support tiles must be replaced.

Individually framing catalyst support tiles als permits the use of a greater range of tile thicknesses. Observed experience demonstrates that most catalytic reaction occur on the catalyst support tile surface. Therefore, catalyst performance is improved by stacking several thinne catalyst support tiles over the same total thickness as woul be used in bulk catalyst support systems. The use of stee frames for edge structural support permits use of generall thinner catalyst tiles, at greatly improved overall catalys ef iciency.

During routine maintenance, the present invention als provides for lower replacement cost. Experience has shown tha the most permanent contamination is accumulated on the face o the first catalyst tile facing the inlet stream. After certain period of use, the catalyst support tile has to b replaced due to clogged pores and reduced catalyst activity. The ability to use thinner catalyst support tiles permit

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replacement of the front catalyst support tile only, at reduce expense compared to the replacement of an unsupported thicke tile, as in the prior art devices.

Further, the modular approach of the instant inventio permits interchangeability of the catalyst support tiles. Th total quantity of catalyst required to effect conversion i proportional to the volume of exhaust flow from the emissio source. Due to the modular approach of the present invention, individually supported tiles can be easily mixed and exchange from one catalytic conversion unit to another. If it is desired to use the same catalytic converter for a higher flo engine or boiler, capacity can be easily increased by th addition of catalyst support tiles without sacrificing perfor¬ mance. Similarly, catalyst support tiles can be removed t provide for reduced capacities. Summary of the Invention

It is an object of the present invention to provide catalytic converter device containing modular catalyst suppor tiles. It is an object of the present invention to provide modular catalyst support system and catalytic converter which will protect the engine by preventing loose ceramic pieces fro falling into the engine manifold.

It is another object of the present invention to provide a catalytic converter which protects against undesir¬ able catalyst loss in the engine exhaust by retaining the catalyst support tiles in a mesh enclosure.

It is a still further object of this invention to provide a catalytic converter which is easy to maintain since the catalyst support tiles which are contained within a structural support are easily handled without need for special tools.

Another object of the present invention is to provide increased catalyst performance by effectively increasing the available surface area of the catalyst presented to the incoming stream.

It is an object of this invention to provide a modular

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catalyst support tiles to permit replacement of thinner singl catalyst support tiles thereby reducing replacement costs.

It is an object of the invention to enhance flexibilit of the catalytic converter by enabling the simple addition o reduction of the number of individually supported catalys support tiles depending upon the volume requirements of th application.

These and further objects of the invention will becom apparent to those of ordinary skill in the art by reference t the detailed description and figures which follow. Brief Description of the Figures

Figure 1 is a partially exploded perspective view o the catalytic converter of the instant invention.

Figure 2 is an elevational section of the catalys support tile and frame taken along line 2-2 in Figure 1. Figure 3 is an elevational view of a series of catalyst support tiles, taken along the line 3-3 in Figure 2.

Figure 4 is a side elevation of the catalytic converte device of the instant invention. Figure 5 is an end elevational view of the catalyti converter device from the emission outlet side.

Figure 6 is a graph of the catalyst activity versu catalyst tile thickness. Detailed Description of the Invention Referring to Figure 1, a catalytic converter device 1 is shown in a partially exploded view. An emission inlet 12 i flanged to be connected to an emission source not shown. A previously noted, the present catalytic converter device i adapted to be connected directly to internal combustio engines, stationary turbines and steam boilers. The emissio inlet 12 is found at the apex of a quadrilateral-based pyrami which forms an inlet member 13. An emission outlet 14 is fou on the other side of the device 10, also at the apex of quadrilateral-based pyramid which forms an outlet member 15 Catalyst support tile holding basket 16 is received within t rectangular mid-section of inlet member 13. Thus, the cataly is positioned directly in the flow of the incoming exhau

stream. Typically, the catalyst support is provided as honeycomb structure. The precious metal is deposited on th internal cell walls, and the exhaust gas is permitted to flo through the honeycomb structure. A variety of honeycom catalyst supports are commercially available. The selection o the correct ceramic structure, and the precious metal catalys to be deposited thereon, is a function of the application including the composition of the exhaust stream to be exhaust as well as to provide for compositional measurements of th various streams.

Once the holding basket 16 is inserted into the inle member 13, bolts 50 are used to secure and to seal the outle member 15 to the inlet member 13.

Another view of the converter, from the emission outle end, is shown in Figure 5. The catalyst support tiles 30 ca be seen inside the converter 10. The emission outlet flange 1 has bolt holes 60 disposed about its circumference. Th triangular faces of the outlet member 15 have sample prob access ports 20 disposed about the emission outlet 14. EXAMPLE

In measuring catalyst activity as shown in Figure 6, a internal combustion engine was connected to a catalyti converter containing CORDIERITE catalyst support, having honeycomb structure at 200 cells/sq. in. An emission of know composition was fed to the catalytic converter and measurement were made of the influent and influent temperature, pressure carbon monoxide, total hydrocarbon and N0 _χ levels. Catalyti activity across the catalyst support was measured by placin thermocouples in the support to detect temperature variations. Referring now to the performance data represented i

Figure 6, performance efficiency is plotted against catalys support tile thickness. This graph shows that most of th catalytic reaction occurs on the surface of the catalys support tile, thus indicating that three one inch titles ar more efficient than one three inch tile.

While the invention has been described with referenc to a specific embodiment, there are other embodiments an

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features which are intended to be within the scope of the claimed invention.

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