WO1994021351A1 - Filtres actifs pour le nettoyage integre de flux de gaz de combustion - Google Patents

Filtres actifs pour le nettoyage integre de flux de gaz de combustion Download PDF

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Publication number
WO1994021351A1
WO1994021351A1 PCT/US1994/002922 US9402922W WO9421351A1 WO 1994021351 A1 WO1994021351 A1 WO 1994021351A1 US 9402922 W US9402922 W US 9402922W WO 9421351 A1 WO9421351 A1 WO 9421351A1
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Prior art keywords
filter
active
chemically
filter wall
oxides
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PCT/US1994/002922
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English (en)
Inventor
Maria Flytzani-Stephanopoulos
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Massachusetts Institute Of Technology
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Publication of WO1994021351A1 publication Critical patent/WO1994021351A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/24491—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2068—Other inorganic materials, e.g. ceramics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/2429—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material of the honeycomb walls or cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/24492—Pore diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2455—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the whole honeycomb or segments
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2474—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the walls along the length of the honeycomb
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2476—Monolithic structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2482—Thickness, height, width, length or diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2484—Cell density, area or aspect ratio
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/54—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms
    • B01D46/543—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms using membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/508—Sulfur oxides by treating the gases with solids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8631—Processes characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2267/00—Multiple filter elements specially adapted for separating dispersed particles from gases or vapours
    • B01D2267/40—Different types of filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2275/00—Filter media structures for filters specially adapted for separating dispersed particles from gases or vapours
    • B01D2275/10—Multiple layers

Definitions

  • This invention relates to filters in general, and more specifically to using chemically-active and regenerable filter wall composites for the simultaneous removal of entrained particulate matter and gaseous pollutants from flue gases, fuel gases and other industrial gas streams.
  • FIG. 1 shows an example of a prior art power-plant, wir ooiler 10, and economizer 11, producing flue gas 12 which is treated in seriatim to achieve removal of NO , particulates, and S0 2 using, respectively, selective catalytic reduction of NO X in vessel 13 with injected ammonia gas 14 to produce nitrogen and water vapor, a filter house 15 to remove particulate matter (fly ash) 16 and wet (or dry) scrubbers 17 for S0 2 removal.
  • the S0 classroom is typically in the form of a waste 18, e.g. calcium sulfate, and needs further disposal.
  • scrubber off-gas is reheated and sent to stack 19 from which treated gases 20 are released. Removal efficiencies are typically about 80% of NO X, 98% of particulate ⁇ , and 90% of S0 9 ⁇ . Each of these units is operated at different temperature for peak efficiency, which fixes their respective installation at different locations along the flue gas ductwork.
  • U.S. Patent 4,220,633 to Pirsh teaches baghouses for fly ash removal with simultaneous catalytic reduction of nitric oxides with injected ammonia gas on a catalyst phase coated on or lodged within the fiber structure of the baghouse.
  • the S0 2 in the flue gas is removed downstream of the baghouse by scrubbing to produce a waste as explained above.
  • U.S. Patent 4,728,503 to Iida describes a filter medium for treating exhaust gases, especially those emitted by municipal waste incinerators.
  • the filter described consists of several layers of different materials performing several functions in a prescribed direction, and is limited to a filter having a free outer surface. More specifically, this filter consists of a porous ceramic filter medium to capture fly ash.
  • a denitration catalyst is applied as a coating to remove nitric oxides by selective catalytic reduction with ammonia, while on the other side (outer) of the filter medium a composite layer is applied to remove hydrogen chloride by slaked iir-e (as CaCl 2 waste).
  • M shown here to be of valence 2
  • M can be of any valence and is a transition metal, rare earth element, alkali or alkaline earth or other element or oxide which is not poisoned by S0 2 for catalyzing reaction (2), or the sulfate of which is also a catalyst for reaction (2), as shown above. Additionally, the sulfate should be regenerable by thermal or chemical treatment.
  • metal oxides that meet these criteria, for example, CuO, Fe 2 0_, NiO, CeO .
  • mixed metal oxides each possessing a different activity for reactions (1) and (2) may be used.
  • U.S. Patent, 4,977,123 to Flytzani-Stephanopoulos et al teaches a method for preparation of extrusions of bulk mixed oxide compounds with both high macroporosity and mechanical strength.
  • compositions are described as regenerable absorbents of hydrogen sulfide for application to desulfurization of gasifier exit fuel gas streams at high temperatures.
  • a similar extrusion process could be used for extruding compositions for various applications, such as for combined SO X/NOX removal from flue gases, waste incinerator exhausts, or other industrial gases.
  • the reference generally discloses the possibility of combining the active phase functions with particulate filtration.
  • Ceramic filters including layered or gradiated porosity have been described.
  • U.S. Patent 4,629,483 to Stanton describes a method for forming a monolithic, layered, tubular ceramic filter structure with clearly defined layers of different porosities and permeabilities.
  • U.S. Patent 4,810,273 to Komoda describes how to make a ceramic filtering layer of gradually increasing porosity on a planar ceramic support of larger porosity.
  • Neither reference discloses "active" filters, i.e. filter bodies comprising chemically-active phases useful for combined pollutant removal in the absence of interaction from fly ash which is effectively retained on the surface of the barrier filter.
  • These references utilize refractory ceramic materials to form the filter body, including: alumina, silica, zirconia, cordierite, mullite, or silicon carbide.
  • an active phase composition e.g. of single or mixed metal oxides
  • certain active phase compositions are limited to low-temperature preparations, so that they retain certain phases in uncombined form or high dispersion. With lower firing temperatures the strength of the filters described by the above references would be greatly compromised.
  • compositions and methods are disclosed for active filter/sorbent/catalyst media aimed at simultaneous fly ash/gaseous pollutant removal applications, not limited by the choice of the specific active phase composition.
  • a filter for multiphase cleanup of gas streams, in particular flue gas streams includes filter wall composites comprising a bulk macroporous support having a microporous membrane on one side and a chemically-active deposit on the opposite side.
  • the bul. ⁇ ⁇ acropcrous support has a surface
  • the microporous membrane on the bulk macroporous support has a thickness of less than about 100.0 microns.
  • the chemically-active deposit has a thickness of between about 0.0 millimeter to about 10.0 millimeter.
  • the process of multiphase clean-up of gas streams comprises passing a gas stream, comprising particulate and gaseous pollutants (such as nitrogen oxides, sulfur oxides, volatile organic compounds (VOC's), hydrogen sulfide, organosulfur compounds, etc.) through a filter having walls formed of a microporous membrane, a bulk macroporous support, and a chemically-active deposit.
  • the gas is forced to pass through the microporous membrane, which acts as a barrier filter, blocking passage of the particulates entrained in the gas.
  • the non-particulate pollutants in the flue gas are then passed through the bulk macroporous support and the chemically-active deposit, where they react so that a clean effluent gas is discharged from the filter.
  • the chemically-active deposit may be a denitration catalyst, an ammonia decomposition catalyst, a VOC oxidation catalyst, a regenerable sulfur dioxide or hydrogen sulfide absorbent, or possess a compatible combination of such functions.
  • the bulk macroporous support may be coated with a high-activity catalyst, e.g. a denitration catalyst, followed by a chemically-active deposit that functions primarily as a regenerable SOpole-sorben .
  • a certain catalyst may be poisoned by SO_ , whereupon the SO_-sorbent may be deposited upstream of a layer of the sensitive catalyst.
  • Regeneration of the saturated sorbent would be accomplished thermally or chemically to recover the sulfur value in concentrated form and the solid in the original active form.
  • Backflushing with air, jet pulsing or other similar method can be used periodically to remove the particulates collected on the membrane side of the filter
  • FIG. 1 illustrates a prior art process flow diagram for removing particulate pollutants, sulfur oxides and nitrogen oxides from a flue gas stream
  • FIGS. 2A, 2B, and 2C are schematic, sectional views of various embodiments of the filter wall composite of the present invention.
  • FIGS. 3A and 3B are schematic views of a candle filter utilizing various embodiments of the filter wall composite of the present invention.
  • FIG. 4 is a schematic sectional view of an alternately plugged-cell, honeycomb-monolith active filter geometry
  • FIGS. 5A and 5B are detailed views of various embodiments of the filter shown in FIG. 4;
  • FIG. 6 illustrates the process flow diagram of FIG. 1 utilizing active filters incorporating the filter wall composites of the present invention
  • FIG. 6A is a special case of FIG. 6 wherein sulfur recovery is performed in a single stage with the regeneration of the active filters;
  • FIG. 7 is a graph of combined SOoppo/NO removal by sorbent/catalyst composition C (Table 1) at 500°C, wherein conversion of sorbent is based on CuSO and Ce flick(SO. )_ ormation,
  • FIG. 8 is a graph of cyclic sulfation performance of composition A (Table 1) at 400 "> C, having an inlet gas composition (mol%) 0.15 S0 2 , 3 0 2 , balance N , wherein conversion is based on CuSO 4. formation;
  • FIG. 9 is a graph of cyclic sulfation performance of composition F (Table 1) at 500°C and regeneration at 600°C; conversion of sorbent is based on CuSO. and Ce 2 (S0.)., formation;
  • FIG. 10 is a graph of sulfur products distribution in regeneration of sorbent composition C (Table 1) with 10%CO, 10%CO 2 , balance N 2 ;
  • the present invention provides active, multifunctional filter media composition and methods for multiphase clean up of gas streams.
  • a filter wall composite 30 for multiphase clean up of gas streams includes a bulk macroporous support 40 having a microporous membrane 42 on one side, and a chemically-active deposit 50 on the opposite side.
  • Bulk macroporous support 40 may be made from a wide variety of materials, depending on the operating conditions of a particular application. Preferred materials are those which are able to withstand high temperatures and long-term exposure to pollutants, such as sulfur and nitrogen oxides, alkali metals, etc. For example, these materials include ceramics, metal alloys, cermet composites, and certain polymers. More preferably, bulk macroporous support 40 is constructed of refractory ceramic materials having good mechanical strength, thermal shock resistance, chemical resistance, etc. required for a long service of the filter. Such materials include oxides of aluminum, silicon, magnesium, zirconium, titanium, nitrides and carbides of silicon, binary and ternary oxide compounds, such as mullite and cordierite, and several others.
  • the macroporous support 40 may be constructed from a mixture of compounds, at least one of which is chemically-active, while another serves as a dispersant or structural or textural promoter.
  • Active compounds include elements and oxides of the groups of the transition metals, alkali, alkaline earths, copper, zinc, rare earths, either single or combined in mixed oxide form, alloy form, oxide compound or oxide solid solution form, etc.
  • the structural promoter can be alumina, chromia, titania, silica, magnesia and other such oxides added to improve dispersion or structural stability, resistance to chemical attack, mechanical strength, etc. of the active phase.
  • the bulk, macroporous support 40 may be extruded in planar, tubular or other form as a single element or a multi-element filter body.
  • the filter may, thus, be of cross-flow configuration, such as the one described by Westinghouse in EP 0,057,251; or a through-flow honeycomb monolith with alternatively plugged inlet and exit passages, such as that described by Fukutani in U.S. Patent 4,632,683; or it may be in the form of ceramic candles, hollow tubes, etc. prepared by techniques well-known in the art.
  • the bulk, macroporous support 40 typically has a surface
  • macroporous support 40 has a surface area between about 1.0 m 2/g to about 15.0 m2/g, and a compressive crush strength between about 2.0 lbs/mm to about 10.0 lbs/mm.
  • the macroporous support 40 is between about 1.0 millimeter to about 3.0 millimeters thick possessing sufficient mechanical strength to withstand stresses that occur in the filter during operation and regeneration.
  • Macroporous support 40 has at least 60% of its porosity in large pores with diameters of between about 2.0 microns to about 50.0 microns, which allows for low pressure drop as gas streams are passed through the macroporous support 40.
  • macroporous support 40 may possess adequate activity for certain reactions with gaseous pollutants, often its reactivity is limited due to the high-temperature heat-treatment used to strengthen the filter body during preparation. High temperature firing decreases the surface area and enhances solid oxide compound formation which may not be the desired chemically-active phases. Also, often, the support 40 may contain a large fraction of inert phases to improve the structural stability and/or mechanical strength of the active phase. In such situations, it will be necessary to incorporate a higher-activity phase in the filter wall. Several methods may be used for this step, depending on the specific application of the active filter. For example, a thin coating of the active composition may be deposited on the discharge side of the macroporous support by wet or dry application techniques, such as washcoati g from
  • the active compositions can be applied to the macroporous support 40 in quantities ranging from about 5.0 to about 50.0 percent by weight.
  • Chemically active deposit 50 may be in the form of a film or a foam, which is coated onto macroporous support 40 on the gas-discharge side (opposite microporous membrane 42) .
  • the chemically-active film deposit typically has a thickness less than 2.0 millimeters; a foam deposit is typically between about 2.0 millimeters and about 10.0 millimeters thick. It is noted, however, that variously sized deposits may be utilized, depending upon the chemical composition of deposit 50, pressure drop through the filter wall, and system design.
  • the chemically-active film deposit 50 is prepared as described above and is applied to macroporous support 40 prior to construction of a filter monolith, or slip-coated within an existing monolith's channels.
  • a macroporous solid foam, chemically-active deposit is typically prepared from a slurry, consisting of the metal oxide composition, water, a foaming agent, and a binder. Any suitable binder material can oe used, including inorganic binders, such as aluminum phosphate, or organic binders, such as methyl cellulose, ethyl cellulose, polyvinyl alcohol, or a mixture, thereof.
  • the slurry is charged into a monolith s channels where it is dried and foamed, thereby expanding within the passage.
  • a similar foam preparation is described in U.S. Patent No. 4,363,644 to Sato et al. , which is incorporated herein by reference.
  • deposit 50 may occasionally consist of two zones, 50' and 50", of distinct chemical composition, either of which is disposed next to support 40, depending, on the application.
  • zone 50' may be an active SCR catalyst that precedes the sorbent zone 50" (lower activity) to improve the NO removal efficiency.
  • zone 50' may be a denitration catalyst sensitive to S0 2 which should, therefore, be disposed downstream of the S0 2 -sorbent zone 50" to preserve its activity.
  • Microporous membrane 42 may be made from the same variety of materials used to form macroporous support 40. Similar to macroporous support 40, microporous membrane 42 may be an inert, ceramic phase or a mixture of inert- and active-phase compositions. Extruded microporous membrane 42 compositions are fused with macroporous supports 40 by techniques known in the art. It is noted that at least one component material of the microporous membrane is desirable to be present in the macroporous support 40 to prevent spalling, or delamination.
  • microporous membrane 42 is less than about 100.0 microns thick and has an average pore diameter less than about 2.0 micron. Preferably, the average pore diameter of microporous membrane 42 is less than about 0.5 micron.
  • Microporous membrane 42 serves as a barrier filter of particulate pollutants, such as fly ash, typically present in fuel gas or combustion gas streams, thereby reducing filter contamination.
  • microporous membrane 42 is unitary with macroporous support 40.
  • they may be produced together from the "green state' according to a technique described in U.S. Patent 4,629,483 to Stanton, which is incorporated herein by reference.
  • a technique described in U.S. Patent 4,810,273 to Komoda which teaches how to make a ceramic filtering layer of gradually increasing porosity on a planar ceramic support of larger porosity may be used, and is incorporated herein by reference.
  • filter wall 30 is part of a candle filter or a multi-element, cross-flow or through-flow monolith (not shown), which is disposed in the flow path of a multiphase pollutant gas stream 12.
  • Gas stream 12 is typically a flue gas, fuel gas, or other industrial gas stream comprising particulate pollutants 16, and gaseous pollutants, such as sulfur and nitrogen oxides, hydrogen sulfide, organosulfur compounds, ammonia, VOC'S, etc. While passing through filter wall 30, the particulate pollutants 16, such as fly ash, are blocked by and collected on the microporous membrane 42.
  • the non-particulate pollutants such as sulfur and nitrogen oxides and the like, are reacted with chemically-active compositions) disposed in the macroporous support 40 and/or chemically-active deposit 50.
  • the non-particulate pollutants are absorbed or converted into innocuous species by the sorbent or catalyst phases of the deposit, respectively. For example, for SO_/NO removal, such processes occur according to reactions (1) and (2).
  • clean gas stream 25 exits filter wall 30.
  • Filter bodies are constructed from filter wall composites 30 (FIGS. 2A, 2B and 2C) , by techniques known in the art, to form overall structures of various configurations.
  • cross-flow filters with orthogonally displaced inlet and discharge channels can be formed as described in EP 0,057,251 to Westinghouse.
  • Chemically-active deposit 50 in either film or foam composition, can be deposited into discharge channels as described above.
  • cylindrical candle filters may be used. Schematic, sectional views of such filters are shown in FIGS. 3A and 3B. These can be extruded in various sizes and wall thicknesses to meet required ranges of mechanical strength and pressure drop.
  • FIG. 4 a schematic, sectional view of a through-flow filter 70 is shown. In this embodiment gas flows in and out of filter 70 along the same axis.
  • the through-flow filter 70 can be extruded in a variety of configurations, sizes and cell densities, such as a honeycomb monolith design.
  • the filter 70 is modified by plugging the entrance of every other channel 71 with a ceramic plug 72 on each end of the monolith.
  • the alternate channel plugging limits the entrance of flue gases into every other channel 71, and subsequently blocks the exit of the flue gases though the channel 71 it entered.
  • the flue gas 12 is then forced to cross through the wall composites 30, and exits through a parallel channel 71.
  • Particulate pollutants 16 are blocked by microporous membrane 42 (FIGS. 2A, 2B and 2C), while the non-particulate pollutants are removed in macroporous support 40 and/or chemically-active deposit 50, which is deposited into alternate (clean side) channels 71 where clean exhaust gas 25 is discharged.
  • FIGS. 5A and 5B are detailed views of the elements of through-flow filter 70 shown in FIG. 4.
  • FIG. 5A shows flue gas 12 entering channel 71 of filter 70.
  • the gas 12 is forced to cross through filter wall composite 30.
  • Particulate pollutants 16 are filtered by the microporous membrane 42, while non-particulate pollutants are removed in the macroporous support 40 and/or chemically-active deposit 50.
  • a film 51 deposit is coated onto clean side channel 71 where clean exhaust gas 25 is discharged.
  • FIG. 5B is similar to FIG. 5A, except chemically-active deposit 50 is a foam 52 deposited in clean-side channel 71.
  • active filters of the present invention are included in the process flow diagram shown in FIG. 1. It can be seen that the active filters 21 replace traditional in seriatim units, including a filter house to remove particulate matter, a separate vessel for NO reduction, and wet (or dry) scrubbers for S0 2 removal.
  • boiler 10 and economizer 11 produce flue gas 12, which is passed through filters 21.
  • the filters 21 remove particulate pollutants, and react with S0 2 to form sulfated metal oxides which, together with the original oxides, catalyze the conversion of NO X to molecular nitrogen by reaction with ammonia, fed by ammonia stream 14.
  • Clean gas 28 is taken to stack 19, from which treated gas stream 20' is discharged into the atmosphere without reheating.
  • one active filter 21 is cleaned by backflushing, while a second filter 21 is utilized as described above. Fly ash, or other particles 16, blocked by the microporous membrane, are removed and collected for disposal.
  • the chemically-active compositions can be regenerated with a reducing gas, such as natural gas, carbon monoxide, hydrogen, or mixtures thereof, produced from a gasifier 22 or another source.
  • the reducing gas is typically diluted with nitrogen, steam, or other suitable diluent gas.
  • an off-gas is produced, containing primarily S0 2 in variable concentration, depending on the conditions of regeneration. This stream is then taken to a catalytic sulfur recovery unit 23, where SO ?
  • any unconverted SO ? and reduced sulfur compound products e.g. COS, H 2 S
  • the concentrated SO -containing off-gas stream may be taken to a catalytic oxidation unit to produce oleum, SO , or to produce sulfuric acid, H_S0 .
  • the sulfur value of the flue gas is recovered in the form of salable products, and no waste by-product is generate .
  • the sulfur recovery catalyst material is compatible with the sorbents and conditions used in active filters 21.
  • the catalyst can be mixed with the active composition in filters 21.
  • the catalyst is also an active composition for S0 /N0 removal.
  • sulfur recovery reactor 23 is not needed.
  • provision is taken to recycle stream 27 to the active filters 21.
  • Figure 6A shows a schematic of such a single-stage, regeneration-sulfur recovery process, where the sulfur value is recovered in the form of elemental sulfur. Accordingly, the regeneration off-gas is recycled (stream 27) to the regenerator vessel of active filters 21 to increase conversion of SO- to elemental sulfur, which is separated out by condensation 25. Any unconverted SO and reduced sulfur compounds in the tail gas 26 are recycled to boiler 10 or to absorption vessel of active filters 21.
  • Removal efficiencies, utilizing the active filters of the present invention, are about 99.9% particulates, and greater than 98% and 80% for S0 and NOX, respectively.
  • the active compositions used in this invention for combined removal of SO-/NO were bulk mixed oxides of copper and aluminum, copper and cerium, or copper, cerium, and aluminum.
  • Various compositions of the mixed oxides can be used, depending on the flue gas type and clean-up temperature.
  • transition metal oxides such as iron, nickel, etc.; other rare earth or alkaline earth oxides as catalyst/ ⁇ orbent promoters; or it may be beneficial to replace aluminum oxide by other oxides typically used as dispersants, or structural or textural promoters of the active composition, as discussed above. Such cases are considered to fall within the scope of the present invention.
  • An alternative is to disperse the active phase, in an inert or low-activity phase, such as oxides of aluminum, chromium, titanium in bulk.
  • an inert or low-activity phase such as oxides of aluminum, chromium, titanium in bulk.
  • Active metal oxide compositions were prepared according to a slightly modified complexation technique, namely, the amorphous-citrate technique.
  • a slightly modified complexation technique namely, the amorphous-citrate technique.
  • Marcilly, C, Courty, P., Delmon, B. "Preparation of Highly Dispersed Mixed Oxides and Oxide Solid Solutions by Pyrolysis of Amorphous Organic Precursors " , . Ame . Ceram. Soc. , Vol. 53(1), 56-57 (1970).
  • the technique involves rapid dehydration (under vacuum at 70°C) of an aqueous solution containing metal salts (e.g.
  • compositions A-E were prepared by the amorphous citrate technique. In some cases, a coprecipitation technique is employed to prepare binary or ternary oxides.
  • Active composition F comprising copper, cerium, and aluminum oxides, was prepared by coprecipitating the carbonates, or hydroxycarbonates, of the metals from an aqueous solution of the respective nitrate salts by addition of sodium carbonate. The precipitate was filtered, washed of sodium several times, dried at 110°C overnight, and then calcined in air at 550°C for 3 hours. Active metal oxide compositions A-F are presented in Table 1.
  • composition B Two-zone system with gas flowing first through composition B, then comDosition A.
  • the bulk oxide compositions (in 20-35 mesh particle size) were tested in a fixed-bed, quartz reactor assembly under isothermal conditions. Simplified, simulated flue cases were used in these tests with composition (mol%) : 30 , 0.15SO 2 , 0.06NO, balance N .
  • gaseous NH_ in 1 : 1 molar ratio with NO, was added in the inlet gas stream after it was preheated. After some time on stream, different for each sorbent type, S0 2 would break through. The time at which 150 ppm SO_ would be measured into the exit gas streams was recorded as the breakthrough-time-at-90%-SO 2 removal efficiency.
  • Regeneration of the sulfated sorbent would then follow, using, carbon monoxide diluted in nitrogen, or in nitrogen and C0 2 gas mixtures, at temperatures of 400-600°C.
  • Gases were analyzed by on-line NO/NO gas analyzers and gas chromatographs equipped with sulfur compound detectors. Gas flowrates were set to give corresponding gas hourly space velocities (G.H.S.V.) of 2,000-25,000 h _1 (STP).
  • Table 2 shows the combined SO-/NO removal performance of various active compositions.
  • cerium oxide alone is an excellent SCR catalyst, better than CuO-containing compositions, at temperatures exceeding 400°C.
  • copper oxide has a higher sulfation activity, so that it can be fully sulfated (100%) at 400°C, either when it is combined with aluminum oxide, as in composition A, or when it is combined with cerium oxide, as in composition C. Note that 26% sulfation conversion of composition C at 400°C is equivalent to fully ⁇ ulfating, the CuO-component of that material.
  • a new finding in this work was the promotion of the cerium oxide sulfation by copper.
  • composition D which was not an admixture of B and A, but a two-layered B/A bed with B first in the gas stream flow and A following, achieved 98% NO removal at 500°C, identical to the performance of composition B, while its sulfation conversion was similar to that of composition A.
  • the NO X conversion shown in Table 2 is attained after partial sulfation of the oxide compositions.
  • the initial activity (for fresh or regenerated composition) is typically lower.
  • the sulfates are better SCR catalysts than the corresponding oxides.
  • FIG. 7 shows an example of the combined removal performance of composition C at 500°C.
  • FIG. 8 There is a small loss of sulfation conversion after the first cycle, which corresponds to loss of surface area.
  • Composition F is an example of a ternary oxide mixture of copper, cerium, and aluminum, prepared by coprecipitation, containing 33 percent by weight of each oxide, i.e. 66 percent by weight active phase.
  • FIG. 9 shows the sulfation performance of composition F (sulfation at 500°C, regeneration at 600°C) . After initial loss of conversion, the second and third cycle performances were identical, a definite improvement over composition C.
  • the use of an inert alumina framework suppressed the structural degradation of the active phases caused by volume expansion, or grain growth, and the like. Large porosity also helps to moderate similar structural problems in mixed metal oxides. Such guidelines will help to optimize the compositional structure of these and similar sorbent/catalyst materials which have to show performance regenerability over multi-cycle operation at high temperatures.
  • Sulfated cerium oxide supported on alumina, has been reported to produce a mixture of S0 2 and reduced sulfur compounds (H 2 S) during regeneration with hydrogen.
  • H 2 S reduced sulfur compounds
  • FIG. 10 shows the sulfur products distribution during regeneration of composition C at various temperatures. Elemental sulfur produced was collected in an ice bath and is not indicated in the figure.
  • cerium oxide for the production of elemental sulfur during regeneration offers the possibility of recycling the off-gas back to the regenerator to continue reduction of SO- with CO over the now-regenerated cerium oxide catalyzing the formation of elemental sulfur.
  • the need for downstream processing of regenerator off-gases is eliminated.
  • the only product is elemental sulfur condensed out of the off-gas and a tail gas carrying any unconverted SO- and product COS back to the boiler or the oxidative absorption unit.
  • composition E Table 1
  • To prepare the foam we ground the material into a fine powder
  • a slurry of the powder was made by mixing, under continuous stirring, 3.77 grams of composition E with 11 milliliters of de-ionized water and
  • Active filter J exhibited overall performance characteristics similar to powder composition E used to make the foam. Also, the pressure drop through the foamed filter, while higher than that of the bare one, was below 4" H-0 for a gas flowrate of 1 SLM. All of the powder and active filter tests were conducted at the same ratio of sorbent mass to gas flowrate (0.5 gram sorbent per liter/min of gas). Because of the different geometry of the two systems (packed powder in a tube versus a honeycomb filter with foam-containing channels), the two systems had different space velocities: 25,000 h ⁇ for the powder and 2,500 h for the active filter.
  • FIG. 11 shows the stabilized sulfur dioxide removal performance of the active filter, compared to the sorbent powder composition E at 400°C. Both systems achieved 100% SO--removal efficiency prior to breakthrough. Similarly high (80-90%) sorbent conversion at breakthrough was measured for the powder and the active filter. Since these similarities were obtained at very different space velocities, design flexibility is indicated for the active filters, namely, that they can be operated at relatively high space velocities (>20,000 h ⁇ ).
  • FIG. 12 shows the catalytic activity of the two systems in fresh (unsulfated) form for NO reduction by NH_ as a function of reaction temperature. Both tests were conducted with a gas mixture containing (moll): 0.06NO, 0.06NH-, 30 2# and N 2 balance. The results show that the SCR characteristics of active filter J are very similar to those of powder composition E.

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Abstract

Un filtre de nettoyage à phases multiples de flux de gaz, en particulier de flux de gaz de combustion, est constitué de matériaux composites de paroi de filtre comprenant un support macroporeux massif (40) présentant une membrane microporeuse (42) d'un côté, et un dépôt chimiquement actif (50) de l'autre. Ledit support macroporeux massif présente une surface de moins de 5,0 m2/g, une cohésion à la compression d'environ 1,0 lb/mm à 10,0 lb/mm, et une épaisseur d'environ 1,0 mm à 3,0 mm. La membrane microporeuse et le dépôt chimiquement actif présentent respectivement des épaisseurs de moins de 100,0 microns et de moins de 10,0 mm. Le procédé de nettoyage à phases multiples de flux de gaz consiste à faire passer un flux de gaz comprenant des polluants particulaires (16) et gazeux dans un filtre doté de parois composites constituées d'un support macroporeux massif à membrane microporeuse d'un côté et à dépôt chimiquement actif de l'autre.
PCT/US1994/002922 1993-03-17 1994-03-17 Filtres actifs pour le nettoyage integre de flux de gaz de combustion WO1994021351A1 (fr)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996023134A1 (fr) * 1995-01-24 1996-08-01 Axel Hartenstein Dispositif pour elimination de substances sous forme de gaz et de vapeur dans un courant d'air evacue
US7056487B2 (en) 2003-06-06 2006-06-06 Siemens Power Generation, Inc. Gas cleaning system and method
WO2008052838A1 (fr) * 2006-11-03 2008-05-08 Robert Bosch Gmbh Élément de filtrage notamment destiné à filtrer des gaz d'échappement d'un moteur à combustion interne
JP2015073959A (ja) * 2013-10-10 2015-04-20 トヨタ自動車株式会社 排ガス浄化用助触媒及びその製造方法
WO2016067236A1 (fr) * 2014-10-29 2016-05-06 Ecospray Technologies S.R.L. Réacteur à granulés pour le traitement d'agents polluants présents dans des gaz industriels contenant des matières particulaires, appareil de traitement comportant ledit réacteur et procédé de traitement mis en œuvre par ledit appareil

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4728502A (en) * 1984-05-02 1988-03-01 Hamill Brendan J Apparatus for the chemical synthesis of oligonucleotides
US4729889A (en) * 1985-03-29 1988-03-08 California Institute Of Technology High temperature regenerative H2 S sorbents
US4810273A (en) * 1985-04-17 1989-03-07 Ngk Insulators, Ltd. Porous ceramic filter
WO1989003720A1 (fr) * 1987-10-23 1989-05-05 Massachusetts Institute Of Technology Procedes et dispositifs de nettoyage de gaz
US4973459A (en) * 1989-05-09 1990-11-27 Westinghouse Electric Corp. Apparatus and method for removing gaseous contaminants and particulate contaminants from a hot gas stream
US4977123A (en) * 1988-06-17 1990-12-11 Massachusetts Institute Of Technology Preparation of extrusions of bulk mixed oxide compounds with high macroporosity and mechanical strength

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4728502A (en) * 1984-05-02 1988-03-01 Hamill Brendan J Apparatus for the chemical synthesis of oligonucleotides
US4729889A (en) * 1985-03-29 1988-03-08 California Institute Of Technology High temperature regenerative H2 S sorbents
US4810273A (en) * 1985-04-17 1989-03-07 Ngk Insulators, Ltd. Porous ceramic filter
WO1989003720A1 (fr) * 1987-10-23 1989-05-05 Massachusetts Institute Of Technology Procedes et dispositifs de nettoyage de gaz
US4977123A (en) * 1988-06-17 1990-12-11 Massachusetts Institute Of Technology Preparation of extrusions of bulk mixed oxide compounds with high macroporosity and mechanical strength
US4973459A (en) * 1989-05-09 1990-11-27 Westinghouse Electric Corp. Apparatus and method for removing gaseous contaminants and particulate contaminants from a hot gas stream

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
M. SATRIANA, ed; "New Developments on Flue Gas Desulfurization Technology", published 1981, NOYES DATA CORPORATION (NEW JERSEY), page 267-268 and 270-272. *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996023134A1 (fr) * 1995-01-24 1996-08-01 Axel Hartenstein Dispositif pour elimination de substances sous forme de gaz et de vapeur dans un courant d'air evacue
US7056487B2 (en) 2003-06-06 2006-06-06 Siemens Power Generation, Inc. Gas cleaning system and method
WO2008052838A1 (fr) * 2006-11-03 2008-05-08 Robert Bosch Gmbh Élément de filtrage notamment destiné à filtrer des gaz d'échappement d'un moteur à combustion interne
JP2015073959A (ja) * 2013-10-10 2015-04-20 トヨタ自動車株式会社 排ガス浄化用助触媒及びその製造方法
WO2016067236A1 (fr) * 2014-10-29 2016-05-06 Ecospray Technologies S.R.L. Réacteur à granulés pour le traitement d'agents polluants présents dans des gaz industriels contenant des matières particulaires, appareil de traitement comportant ledit réacteur et procédé de traitement mis en œuvre par ledit appareil
US10040027B2 (en) 2014-10-29 2018-08-07 Ecospray Technologies S.R.L. Granule reactor for treating polluting agents present in particulate-containing industrial gases, treatment apparatus comprising said reactor and method of treatment implemented by said apparatus

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