JPH0729014B2 - Apparatus for separating granular material from hot gases - Google Patents

Description

This invention relates to systems for separating particulate material from hot gases. More particularly, this invention relates to a hot gas filtration system including a gas-permeable filter element and means for periodically cleaning the filter element.

BACKGROUND OF THE INVENTION Modern combustion and gasification processes have created a demand for particulate separators capable of efficiently and reliably separating particulate material from hot combustion or product gases. In circulating fluidized bed combustion or gasification processes, large amounts of dust, such as solid bed materials, ash, unburned fuel, and even reactive sorbents for sulfur capture, are continuously mixed with the hot gases discharged from the combustion chamber, separated from the hot gases, and then recycled back to the combustion chamber. The separators used must be able to withstand the high temperatures and corrosive conditions of the solids circuit without compromising separation efficiency and stability. In addition to enhancing the efficiency of the circulating fluidized bed process itself, an effective separator also minimizes fouling of heat exchange surfaces in the subsequent gas path by removing particulate material.

In modern combined cycle power plants, where hot combustion gases expand in gas turbines, efficient cleaning systems for the hot gases greatly extend the life and operating time of the gas turbines. Particulate material in the hot gases significantly increases erosion and fouling of the turbine blades.

On the other hand, current concerns about air pollution have created a demand for efficient dust collectors that can handle high temperature gases and have increased capacity.

Various types of granular separators for gas purification processes have been proposed and constructed to meet the requirements for stable separation of solid particles from gases at high temperatures and often high pressures. Recently, gas-permeable high-temperature filters have become an attractive alternative to conventional vertical cyclones for separating such granular materials. Conventional vertical cyclones require significant space for both the cyclone itself and the cyclone support structure. Filter separators, on the other hand, are significantly more compact and can be incorporated into simpler systems. Filters made from porous superalloys or ceramics can withstand high temperatures and do not require the protection of cooling surfaces or refractory linings that conventional cyclones do. In pressurized processes, filter separators can be very easily integrated into the pressurized system.

In a filter separator, dust gradually accumulates on the surface of the porous material, so the filter needs to be cleaned periodically. If a large amount of dust can accumulate on the filter surface, a large pressure difference will occur between the two sides of the filter,
A large amount of pressure, or energy, is required to force the gas through.

Filters such as low-temperature gas bag filters have been cleaned by shaking, agitating, vibrating, or brushing or scraping to loosen the dust that has accumulated on the filter media. High-temperature rigid ceramic filters, such as long, thin tube filters, are quite fragile and can therefore be damaged by rough handling as described above.

Cleaning of rigid ceramic filters is typically accomplished by backwashing by forcing clean gas back through the filter media. During backwashing, the primary separation process in the filter separator must be stopped in order to allow clean gas to flow back through the filter. This disrupts the continuous process and of course expels large amounts of gas.

It has also been proposed to clean filter tubes by periodically injecting compressed air pulses into the tubes. The compressed air acts in pulses to loosen dust from the surfaces of the filter tubes. Each filter tube must have its own compressed air injector to ensure that all filter tubes are cleaned, or there must be a common, movable injector for several tubes. U.S. Pat. No. 4,468,240 shows a filter separator with a filter cleaning device according to the aforementioned technique.
The separator has a housing divided into a dust-laden gas space and a clean gas space, and a filter tube is disposed in the dust-laden gas space.
Clean gas flows into the filter tube from the outside and passes through the filter tube wall into the clean gas space.
The filter tube is cleaned by an injector in a reciprocating chamber located in the clean gas space.
This is achieved by supplying compressed air to the filter tubes to be cleaned, a construction that is quite complex and space-consuming.

U.S. Pat. No. 4,584,003 discloses a filter separator including a filter housing divided into several compartments with vertically arranged filter tubes and horizontally arranged filter tube supports. Dust-containing gas is introduced into the filter tube at the upper end, and separated particles are discharged from the lower end. Clean gas flows through the porous tube walls into clean gas spaces surrounding the tubes. Each clean gas space has a clean gas outlet. The filter separator is compact and simple in structure. A cleaning method for the aforementioned filter separator is disclosed in Japanese Patent Application No. 61-268330. A diffuser is disposed on each clean gas outlet pipe outside the filter housing. Gas from a high-pressure compressor is introduced into the clean gas spaces through the diffuser throat and the clean gas outlet pipe. Also, a high pressure gas jet is generated in the circumferential direction of the clean gas from the gas outlet conduit due to the injector effect of the throat, generating a large backwash gas flow.
During the backwash step, the primary separation process does not need to be stopped.

When filtering high-temperature, high-pressure gases, the diffuser in the clean gas outlet pipe is very space-consuming. The diffuser itself is relatively large and forms a large protrusion on one side of the filter separator. Because the backwash gas needs to be at roughly the same temperature as the hot gas in the filter to eliminate thermal shock to the filter, both the diffuser and the clean gas outlet pipe need to be very well insulated, which significantly adds to the size of the elements protruding from the filter housing. This makes the otherwise compact filter housing less attractive from a construction standpoint.

OBJECTS OF THE INVENTION It is an object of the present invention to minimize the disadvantages of known filter face cleaning systems. Another object of the present invention is to provide a filter cleaning system which can be used without disrupting the separation operation. A still further object of the present invention is to provide a compact and simple filter separator for hot gas cleaning. A still further object of the present invention is to provide an easily adjustable apparatus for separating particulate material from hot gases.

SUMMARY OF THE INVENTION In accordance with the present invention, a filter housing is provided containing a plurality of open-ended, parallel, hollow, gas-permeable filter elements for separating particulate material from hot gas. The filter housing includes at least one pair of cross-sectional support plates having openings therethrough, dividing the filter housing into at least three sections and supporting the filter elements. The support plates divide the filter housing into an upper end section having an inlet for contaminated gas, a lower end section associated with an outlet for separated particulate material, and an intermediate filtration chamber therebetween. The filter elements are disposed in the intermediate filtration chamber, which extends from the upper support plate to the lower support plate. End portions of the hollow, gas-permeable filter elements are secured in the openings in the support plates. The gas-permeable filter elements allow clean gas to flow from the hollow space within the filter element through the gas-permeable side sections to the clean gas space within the intermediate filtration chamber. The inlet openings of the filter elements are positioned in communication with the upper end section of the filter housing to direct contaminated gas to the filter elements. An outlet opening in the filter element communicates with the lower end section to discharge separated particulate material from the filter element. A clean gas outlet conduit communicates with the clean gas space in the intermediate filtration chamber to discharge clean gas from the filter housing. An important feature of the present invention is the provision within the filter housing of means for supplying a countercurrent high-pressure pulse of high-energy gas to the filtration chamber to clean the porous filter media. The countercurrent high-pressure pulse may be supplied through a relatively small pipe connected to a compressor.

The present invention is particularly suitable for filter separators in pressurized systems. The cleaning system is a vertical cylinder,
It can be advantageously integrated into a pressure-resistant filter housing.

The cleaning gas pulse injector is preferably disposed in communication with the clean gas outlet conduit at its inlet end. The cleaning gas may be delivered through a gas nozzle disposed in coaxial alignment with the inlet end of the clean gas outlet conduit. Ejector means is disposed within the inlet means of the clean gas outlet conduit to prevent the high-pressure cleaning gas pulse from entering the clean gas outlet conduit. As the cleaning gas pulse is blown into the ejector throat, a gas plug is formed in the throat to prevent the clean gas from escaping. The gas pulse is extremely short and does not disrupt the overall separation process.

The inlet end of the clean gas outlet conduit containing the ejector may be positioned to extend into the clean gas space of the filtration chamber. According to one embodiment of the invention, the clean gas outlet is positioned parallel to the longitudinal direction of the filter element. The clean gas outlet may be positioned to exit the filtration chamber through either the upper end section or the lower end section and then through the end wall to exit the filter housing.

According to the invention, the filtering chamber may be provided with a further intermediate cross-sectional support plate for dividing the filtering chamber into two or more clean gas compartments, each of which may have its own clean gas outlet conduit and sweep gas nozzle.

The clean gas outlet conduits from the individual compartments preferably have individual outlet ports through the filter housing wall or are combined so that the gas is discharged through a common gas outlet port. In pressurized systems, it is advantageous to have as few and as small ports through the pressure vessel wall as possible. In another embodiment of the invention, the clean gas outlet conduits may be arranged to conduct clean gas from one clean gas compartment to the next adjacent clean gas compartment and ultimately out either end section and corresponding end wall.

According to yet another embodiment of the present invention, separate clean gas discharge chambers are provided adjacent to the filtration chambers. Clean gas outlet conduits are arranged to connect each clean gas compartment to the common clean gas discharge chamber. In this case, only one clean gas outlet port is required on the surrounding filter housing. The clean gas discharge chambers may be arranged in a vertical, cylindrical pressure vessel, parallel to the upright filtration chambers and extending from the upper filter tube support plate to the lower support plate. In this case, only one clean gas outlet port is required on the cylindrical side wall of the pressure vessel.

The filter elements used in the device according to the present invention may be any filter tube or element which defines filtration channels therebetween, and may be made from a porous ceramic material or a superalloy.

The present invention provides a smaller, more compact particle separation system that does not require large, protruding (bulky) isolated outlet ports or diffuser devices. Therefore, the space required for such protruding elements and support structures does not need to be taken up externally of the filter vessel. While the filter housing itself is slightly larger, this is easily accommodated when constructing the filter system, and the filter system can be easily adjusted and more easily pre-sized and pre-designed.

Thus, the present invention provides an improved filter module design. Previous designs had multiple outlets for the pressure vessel, exiting from the side of the vessel. With the present invention, the filter module can be designed with only one gas outlet from the bottom, top, or side of the vessel. Particularly in pressurized and high temperature systems, any expansion joint between the main filter housing and any outlet port is a weak point in the system, and therefore the number of outlet or inlet ports should be minimized.

A single outlet at the bottom of the vessel can be achieved by arranging filter tubes in a ring in the filter chamber and locating the clean gas outlet conduit containing the sweeping ejector in the center of the filter chamber. A central outlet from multiple compartments can be achieved by dividing the clean gas outlet conduit into as many branches as there are compartments, with all branches passing through the lowest compartment or lower end section at the bottom of the filter housing. In that case, all branches except one clean gas outlet conduit branch lead upward to the next compartment, and so on. Fly ash can be collected in multiple hoppers in the bottom end section and discharged through a pipe at the bottom of each hopper.

In this way, a more compact device and a single connection to the clean hot flue gas outlet can be achieved, and assembly and inspection of the filter housing is also much easier.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic vertical cross-sectional view of a filter separator according to the present invention; Figure 2 is a cross-sectional view taken along line A-A; Figures 3, 5, 7 and 9 are schematic vertical cross-sectional views similar to Figure 1 showing other embodiments of the present invention; Figures 4, 6, 8 and 10 are cross-sectional views taken along line A-A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, like elements are designated by like reference numerals in all embodiments.

In Figure 1, there is shown a filter separator 1 consisting of a generally vertical cylindrical filter housing 2. The filter housing has an insulated side wall 3 and upper and lower end walls 4 and 5. The filter housing is divided into three sections by two support plates or tube sheets 6 and 7.
That is, it is divided into an upper end section 8, a lower end section 9 and an intermediate section or filtering chamber 10.

An open-ended hollow filter tube 11 is disposed in the filtration chamber 10 and extends from the upper support plate to the lower support plate. The filter tube is fixed in an opening 12 in the upper and lower support plates, connecting the space in the upper end section with the space in the lower end section. An inlet 13 for particulate-laden gas is arranged in the upper end section, through which particulate-laden gas can be introduced into the filter separator. Clean gas flows from the inside of the hollow filter tube 11 through the tube wall into the filtration chamber.
The gas flows into the clean gas space at 10. The particulate matter is trapped inside the filter tubes. A hopper 14 in the lower end section has an opening below it that is connected to the filter tube. The hopper collects the particulate material that has been separated from the particulate-laden gas in the filter tube. The hopper has a discharge pipe 15 connected to its bottom, which discharges the collected particulate matter out of the filter through a small opening 16 in the lower end wall 5.

In the center of the lower support plate 7 is an outlet conduit for clean gas.
17 is disposed in the filter chamber 10. A clean gas outlet conduit is further arranged through the lower end section 9 and an opening 18 in the lower end wall 5.

The inlet end 19 of the clean gas outlet conduit 17 is configured as an ejector 20 having a throat 21. A relatively small pipe 22 is disposed in the clean gas outlet conduit and delivers pulses of high pressure gas through the ejector 20 and into the filtration chamber. The jet of high pressure gas forces gas back through the walls of the filter tube, loosening dust that has accumulated on the inner walls of the filter tube.

2 shows a cross-section of the separator as described above taken along line A--A. An outlet conduit 17 for clean gas is located in the middle of the housing 2 and a filter tube 11 is arranged annularly around said conduit.

Figures 3 and 4 show another embodiment of the present invention. An intermediate support plate 23 is positioned in the filtration chamber 10 to support the filter tubes. The support plate divides the filtration chamber 10 into two separate clean gas compartments 24, 25. Each compartment has a separate clean gas outlet conduit 26, 27 that extends downwardly to the lower end section 9 of the filter housing. The conduits 26, 27 are combined into a common outlet conduit 28. By combining the clean gas outlet conduits, only one clean gas outlet opening is required in the filter housing wall, thereby significantly simplifying construction.

5 and 6 show yet another embodiment of the present invention.
The filter chamber is divided by two intermediate support plates into three separate compartments 29, 30, 31, each having a clean gas outlet conduit 32, 33, 34. Clean gas conduit 34 from compartment 31 conducts gas to adjacent compartment 30, and clean gas conduit 33 conducts gas from compartment 30 to compartment 29. Clean gas leaves the filter chamber via conduit 32,
It passes through the upper end wall 4 via an opening 35 .

7 and 8 show a filter chamber 10 divided into compartments by support plates, each compartment having a separate outlet conduit for clean gas.
3 shows a filter housing having nozzles 37 and 38. In this embodiment, the outlet conduits leave the filter housing through separate openings in the upper end wall, which makes it easier to locate the outlet ports than in the cylindrical side wall 3.

9 and 10 show an embodiment of the invention in which the clean gas chamber 39 is arranged vertically parallel to the filtering chamber 10. The filtering chamber is divided into separate compartments 41 and 42 by a support plate 40. Both compartments pass gas through the clean gas chamber 39.
a clean gas outlet conduit 43,4 arranged to discharge into
4. A clean gas outlet port 45 is provided in the cylindrical side wall 3. This embodiment is advantageous when there is little or no space around the top and bottom of the filter housing for providing a clean gas outlet. There is still only one clean gas outlet and no space-consuming diffuser is used.

Claims (6)

[Claims] 1. An apparatus for separating particulate material from hot gas, comprising: a vertical filter housing (2) having a plurality of openings (12), said filter housing having an upper end section (8), a lower end section (9), and
a pair of support plates (6, 7) extending in the cross-section of the filter housing to divide the filtering chamber into at least two clean gas compartments (24, 25, 29, 30, 31, 41, 42) in which the particulate material is separated; a pair of support plates (6, 7) extending in the cross-section of the filter housing to divide the filtering chamber into at least two clean gas compartments (24, 25, 29, 30, 31, 41, 42) in which the particulate material is separated; an inlet (13) for a particulate material-containing gas in the upper end section; and a discharge port (16) in the lower end section for discharging the separated particulate material. a plurality of hollow, elongated filter elements (11) secured at opposite end portions to the plurality of openings (12) in the support plate (6, 7), the filter elements (11) having end inlets communicating with the upper end section (8), end outlets communicating with particulate material discharge elements (14, 15) communicating with the discharge ports (16) in the lower end section (9), and gas permeable sides located in the filtration chamber to allow gas to flow into the filtration chamber from the internal hollow space through the gas permeable sides; and at least two clean gas outlet conduits (17, 26, 27, 32, 33, 34, 37, 38, 43, 44) located within the filtration chamber and communicating with each of the at least two clean gas compartments, the at least two clean gas outlet conduits (17, 26, 27, 32, 33, 34, 37, 38, 43, 44) having venturi devices (20, 22) at their inlets (19).
1. An apparatus for separating granular material from hot gas, comprising at least two cleaning gas outlet conduits (22) each having a respective inlet (1) for cleaning gas, and at least two nozzles (22) arranged coaxially with the inlets of the at least two cleaning gas outlet conduits, for injecting cleaning gas in pulses into the filtering chamber, characterized in that a clean gas discharge chamber (39) is provided within the filter housing (2), the at least two clean gas outlet conduits are arranged to direct the clean gas into the clean gas discharge chamber (39), and a common clean gas outlet conduit (45) is connected to the clean gas discharge chamber (39) for discharging the clean gas from the filter housing. 2. Claim 1, characterized in that the filter housing (2) is a pressure-resistant upright cylindrical container.
Item 10. An apparatus for separating granular material according to item 10. 3. Apparatus for separating particulate material according to claim 1, characterized in that said nozzle (22) is arranged to inject sweeping gas into the throat portion (21) of said venturi device. 4. The outlet conduit for clean gas (17, 26, 27, 32, 3
4. Apparatus for separating granular material according to claim 3, characterized in that a plurality of filter elements (3, 34, 37, 38) are arranged in parallel with the filter element (11) in the filtering chamber. 5. Apparatus for separating granular material according to claim 1, characterized in that said filter elements are tubes (11) extending between said support plates. 6. A vertical cylindrical pressure vessel (2), an inlet port (1) for introducing particulate-containing gas into said pressure vessel.
3) and a clean gas outlet port (28) in said pressure vessel.
a pair of cross-sectional tube sheets (6, 7) dividing the pressure vessel into an upper gas inlet chamber (8), a lower end chamber (9), and a filtration chamber (10) between the upper and lower chambers; a plurality of filter tubes (11) disposed between the pair of cross-sectional tube sheets and arranged to connect the gas inlet chamber to the lower end chamber; at least one intermediate cross-sectional tube sheet (23) disposed between the pair of cross-sectional tube sheets, supporting the filter tubes and dividing the filtration chamber into at least two clean gas compartments (24, 25) adapted to receive clean gas through the filter tubes; and at least two clean gas outlet conduits (26, 27) projecting into each of the clean gas compartments (24, 25), all of which direct clean gas from each compartment to a common clean gas outlet port (28) on the pressure vessel. a venturi (19, 20) disposed at the inlet end of each of the clean gas outlet conduits; and a nozzle (22) disposed at the inlet end of the clean gas outlet conduits and arranged to direct pulses of high-pressure gas into a throat portion (21) of the venturi.