Gas separation – With nonliquid cleaning means for separating media – With heating or cooling means
Reexamination Certificate
1999-09-10
2001-08-14
Simmons, David A. (Department: 1724)
Gas separation
With nonliquid cleaning means for separating media
With heating or cooling means
C055S502000, C055S508000, C055S523000
Reexamination Certificate
active
06273925
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to hot-gas cleanup systems and more particularly to a filter assembly that includes an all metal fail-safe/regenerator device, a metal filter housing and a metallic type filter element, that requires only a single particulate barrier seal and allows ease of attachment of the fail-safe/regenerator device to the filter housing.
BACKGROUND INFORMATION
Modern industrial methods have resulted in a need for an apparatus that is capable of efficiently filtering high temperature combustion gases containing particulate material. In combustion turbine applications, for example, a combustion turbine uses energy generated from hot pressurized combustion gases produced by burning natural or propane gas, petroleum distillates or low ash fuel oil. When coal and other solid fuels are burned, particulates carried over from the combustion of such solid fuels can cause turbine blade erosion and fouling. An efficient system for filtering of such hot combustion gases would permit the use of such solid fuels. As another example, in conventional boiler operations, the boilers undergo routine shutdown for cleaning the fireside surfaces and for inspection. An efficient hot gas filtering system would greatly extend the life and operational time for a boiler to operate between inspections. Fouling of the fireside surface due to ash deposition and corrosion would be eliminated or minimized.
Also, as a key component in advanced coal-or biomass-based power applications, hot gas filtration systems protect the downstream heat exchanger and gas turbine components from particle fouling and erosion, cleaning the process gas to meet emission requirements. When installed in either pressurized fluidized-bed combustion plants, pressurized circulating fluidized-bed combustion plants, or integrated gasification combined cycle plants, lower downstream component costs are projected, in addition to improved energy efficiency, lower maintenance, and elimination of additional expensive fuel or flue gas treatment systems. As a critical component, long-term performance, durability, and life of the filter elements and associated high temperature gasket seals are essential to the successful operation of hot gas filtration systems in advanced combustion and gasification applications.
U.S. Pat. Nos. 5,185,019 and 5,433,771 (Haldipur et al. and Bachovchin et al., respectively) disclose a thick walled hot gas candle filter mounting assembly. U.S. Pat. No. 5,474,586 (Eaton et al.) discloses a thin walled hot gas candle filter mounting assembly, and discusses gasket assemblies generally. U.S. Pat. No. 5,876,471 (Lippet et al.), provides a filtering apparatus that can filter aggressive, high temperature, high pressure gases, having an improved, double gasket assembly that can be employed with a conventional ceramic candle filter and a thin walled filament wound ceramic composite. There, both the topmost and bottom gaskets consist of a two component system, made of an interior ceramic fibrous mat filler in compliant annular form covered by a short sheet of a woven or braided sleeving surrounding or encasing the mat filler, which sleeving is stitched together on the outside diameter of the gasket. This system, however, uses a complicated series of sleeving and gaskets. Additionally, U.S. Ser. No. 09/263,436 filed on Mar. 4, 1999 (99P7487US, Alvin et al.) provided an improved gasketing assembly, with an optional fail-safe/regenerator, and described possible use of metallic filter elements having the same connection and configuration as standard ceramic candle filers.
Experience has shown that oxidation of non-oxide-based, ceramic, monolithic, continuous fiber reinforced ceramic composites (“CFCC”), and reticulated foam ceramic matrices, has resulted when these materials are used in the construction of porous candle filter elements which experienced long-term field operation of 500-3000 hours of pressurized fluidized-bed combustion or pressurized circulating fluidized-bed combustion. Similarly, oxide-based monoliths were shown to be susceptible to thermal fatigue and/or shock during process operation. Oxide-based, ceramic CFCC and ceramic filament wound matrices were also shown to have low strength semi-densified flanges; have low strength and load bearing filter bodies; have the potential for embrittlement of the contained CFCC fibers; and to debond along inverted plugs, seams, applied membranes, component layers, and the like.
As a result, there is a need to develop use of other filter element materials and better and simpler connections within the filter assembly for advanced coal-fired and other higher temperature operation applications, that would be resistant to combinations of sulfur and steam contact at high temperatures. There is also a need for improved heat transfer from incoming cold gas flowing into the filter elements during back pressure cleaning operations. Finally, it would be desirable that any improved filter assembly be able to substitute into existing systems in the field.
SUMMARY OF THE INVENTION
Therefore, it is a main object of this invention to provide an improved filter assembly and fail-safe/regenerator device having strengthened, non-brittle, toughened filter elements that are resistant to sulfur, alkali, chlorides, and other contaminants found in steam laden coal gas.
It is a further object to improve heat transfer efficiency of the filter assembly during cleaning operations and provide a design that can easily substitute into existing units.
These and other objects are accomplished by providing a filter assembly for holding a filter element within a hot gas cleanup system pressure vessel, the filter element including a porous metallic type body having two opposing ends, one defining a weldable open end and the other defining a closed end; the filter element body having a uniform diameter, said filter assembly comprising:
(a) a filter housing, said filter housing having a certain axial length and having a peripheral sidewall, said sidewall defining an interior chamber;
(b) a one piece, all metal, fail-safe/regenerator device, having a top and bottom end, disposed within the interior chamber of the filter housing, extending beyond the axial length of the filter housing, said device containing an outward extending radial flange near the top of the device within the filter housing, for seating an essential sealing means, the device also having heat transfer media disposed between a screening means at the top of the device within the filter housing and a screening means at the bottom of the device;
(c) one essential sealing means consisting of one compliant gasket separate and apart from the filter housing, said compliant gasket positioned next to and above the outward extending radial flange of the fail-safe/regenerator device said gasket effective to provide a seal between the filter housing and the fail-safe/regenerator device; and
(d) a porous metallic corrosion resistant superalloy type filter element body welded at the bottom of the metal fail-safe/regenerator device outside of the filter housing.
The invention also resides in a metal fail-safe/regenerator device with a welded metallic-type filter element as set forth in b. and d. above. A metal adapter ring may be used to mate and form a better weld between the porous filter element and the fail-safe/regenerator device. Such a design provides increased volume within the fail-safe/regenerator device for heat transfer during cleaning, utilizes a very strong essentially all metal type design with a metal type porous filter made of a superalloy which is corrosion resistant in porous form in the presence of steam, alkalis, chlorides, and allows quick and easy repairs in the field, being compatible with most prior art units. These filter assemblies have no ceramic components and so have less problems associated with coefficient of thermal expansion between metal and ceramic components.
REFERENCES:
patent: 4758272 (1988-07-01), Pierotti et al.
patent: 5185019 (1993-02-01),
Alvin Mary Anne
Bruck Gerald J.
Lippert Thomas E.
Smeltzer Eugene E.
Hopkins Robert A.
Simmons David A.
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