Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/12—Radiant burners
  • F23D14/18—Radiant burners using catalysis for flameless combustion
  • F23D14/181—Radiant burners using catalysis for flameless combustion with carbon containing radiating surface
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C13/00—Apparatus in which combustion takes place in the presence of catalytic material
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2203/00—Gaseous fuel burners
  • F23D2203/10—Flame diffusing means
  • F23D2203/101—Flame diffusing means characterised by surface shape
  • F23D2203/1012—Flame diffusing means characterised by surface shape tubular
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2212/00—Burner material specifications
  • F23D2212/10—Burner material specifications ceramic
  • F23D2212/105—Particles

Definitions

• the present disclosure relates to catalytic burners and catalytic media used in them.
• gaseous hydrocarbon fuel sources are converted to thermal energy inside a heat exchanger contained within the boiler.
• the space inside the heat exchanger is kept small to minimize the size of the boiler.
• the fuel is efficiently converted to thermal energy and the amount of deleterious byproducts (e.g., NO x , CO) is minimized.
• the present disclosure overcomes the foregoing problems by creating a high void fraction packed catalyst media particle bed disposed between the distributor and diffuser plates.
• the catalyst media particles lower the effective combustion temperature, and thus reduces the amount of thermal NO x generated.
• a packed catalyst media particle bed is desirable to achieve adequate residence time of the fuel in the presence of the catalyst.
• the thickness (or depth) and void fraction ( ⁇ ) of the catalyst media particle bed greatly affect the rate of heat transfer of the combusted fuel in the catalyst media particle bed.
• the heat from the combustion reaction is ineffectively removed from the catalyst media particle bed, causing the temperature of the bed to increase rapidly and potentially exceed the stability limit temperature of the catalyst, thus making it inactive.
• the bed temperature may exceed 800 °C.
• void fraction refers to the ratio of the volume of void space between particles to the total container volume (V conlamer , expressed in cubic centimeters (cm3 ⁇ 4 in a container packed full with the particles and is defined by the following expression:
• V container where V ex ⁇ er j or is the exterior volume in cubic centimeters (cm ⁇ ), including all solid material, open pores, and impervious portions.
• the exterior volume is defined as
• V W - S (2) exterior
• W is the saturated weight in grams
• S is the suspended weight in grams
• test liquid is water having a density of 1 gram per cubic centimeter (g/cm ⁇ ).
• High bed temperatures can cause the catalyst to become deactivated and/or volatilize off the surface and be carried away from the system with the exhaust stream. While the catalyst media particles can achieve low NO x emissions, the high catalyst bed temperatures progressively reduce the effectiveness of the catalyst.
• the bed temperature falls with increasing void fraction, accompanied by increasing catalyst media particles life, until at void fractions greater than 0.6, the bed temperature typically does not exceed 800 °C, and the palladium catalyst exhibits long life while still achieving low NO x emissions.
• the catalyst media particles are substantially free of, or even free of, internal void space.
• the present disclosure provides a catalytic burner comprising:
• catalyst media particles for catalyzing an oxidation reaction of a fuel stream to produce heat and an exhaust stream, wherein the catalyst media particles is disposed within the oxidation chamber, wherein the catalyst media particles comprise carrier particles, each carrier particle comprising refractory material, wherein at least some of the carrier particles have thereon an outer coating comprising an oxidation catalyst, and wherein the catalyst media particles have a void fraction of at least 0.6.
• the porous diffuser member and the porous distributor member comprise substantially parallel porous plates.
• the porous diffuser member comprises a first open end
• the porous distributor member is disposed at least partially inside the porous diffuser member
• the porous distributor member comprises a second open end.
• FIG. 1 is a schematic perspective view of an exemplary catalytic burner 100 according to the present disclosure.
• FIG. 1A is an enlarged detail of region 1A in FIG. 1.
• FIG. 2 is a schematic cross-sectional view of exemplary catalytic burner 200.
• FIG. 3 is an enlarged schematic cross-sectional view of an exemplary catalyst media particle 270.
• FIG. 4 is a schematic cross-sectional view of exemplary catalytic burner 400.
• FIG. 5 is a photomicrograph of an exemplary saddle-shaped carrier particle prepared in the PREPARATION OF CATALYST MEDIA PARTICLES E.
• FIG. 6 is a schematic cross-sectional view of an exemplary boiler including a catalytic burner according to the present disclosure.
• exemplary catalytic burner 100 has inlet opening 1 10, adjacent seal 160, for a fuel stream (not shown) that passes through holes 1 13 (see FIG. 1A) in porous distributor member 1 15, is oxidized internally within the burner, and then released as an exhaust stream (not shown) through holes 129 in porous diffuser member 120.
• Components of the catalytic burner, other than the catalyst media particles, may comprise any material capable of withstanding the heat (e.g., up to at least 800 °C) and corrosion due the oxidation of the fuel stream.
• Stainless steels e.g., in grade 304 or 316 are exemplary such materials.
• the catalytic burner may have any suitable design, for example, as known in the art, including ones not exemplified herein.
• suitable design for example, as known in the art, including ones not exemplified herein.
• various designs include cylindrical (e.g., as shown in FIGS. 1- 3), frustoconical (e.g., as described in PCT Publ. Appl. No. WO 201 1/076220 Al (Moller)), parallel plate, and spheroidal configurations (e.g., as described in U.S. Patent No. 5,474,443 (Viessmann et al.))
• the porous distributor member typically comprises a wall with a plurality of holes extending therethrough may be shaped, for example, as a cylindrical tube, conical tube, hollow spheroid, or a combination thereof, although this is not a requirement.
• the holes may be of any shape (e.g., slits and/or round holes) and pattern, but are preferably sufficiently sized that the catalyst media particles do not pass through them.
• the plurality of holes in the wall of the porous distributor member comprises from 1 to 30 area percent, preferably from 5 to 25 area percent, and more preferably 5 to 15 area percent, based on the total surface area of the wall, although this is not a requirement.
• the holes should be sufficiently small that flash back ignition is prevented.
• the selection of hole shape and size may depend on the composition of the fuel stream and its pressure, and will be known to those of ordinary skill in the art.
• the porous distributor member comprises a sintered porous metal frit.
• the porous diffuser member typically comprises a wall with a plurality of holes extending therethrough may be shaped, for example, as a cylindrical tube, conical tube, hollow spheroid, or a combination thereof, although this is not a requirement.
• the holes may be of any shape and pattern, but are preferably sufficiently sized that the catalyst media particles do not pass through them.
• the plurality of holes in the wall of the porous distributor member comprises from 10 to 90 area percent, preferably from 15 to 45 are percent, based on the total surface area of the wall, although this is not a requirement.
• the porous diffuser member comprises a wire mesh.
• the porous diffuser member is adapted to at least partially enclose the porous distributor member while creating an oxidation chamber (e.g., at least partially filled with catalyst media particles) that has a substantially constant gap between the porous diffuser member and the porous distributor member.
• an oxidation chamber e.g., at least partially filled with catalyst media particles
• the gap is typically from 0.5 millimeter to 3 millimeters, while higher gaps are typical with larger burners intended for use with commercial and industrial boilers.
• the porous distributor member and/or the porous diffuser member is/are hollow.
• catalytic burner 200 having the same exterior general appearance of catalytic burner 100 (shown in FIG. 1), comprises porous diffuser member 220, which comprises a cylindrical conduit 221 having a wall 222 with a plurality of holes (not shown) therethrough, and which comprises first and second open ends 225, 227.
• Porous distributor member 230 which comprises a cylindrical conduit 231 having a wall 232 with a plurality of holes 233 therethrough, is disposed inside porous diffuser member 220 and comprises third and fourth open ends 235,237.
• First open end 225 is covered by first end cap 240 and comprises an alignment pin 245 inwardly extending along longitudinal axis 250 of porous diffuser member 220.
• Second end cap 244 covers fourth open end 237, except for central opening 239 adapted to receive alignment pin 245.
• Annular seal 260 extends between porous diffuser member 220 and porous distributor member 230, thereby defining (in combination with first end cap 240) oxidation chamber 270.
• Catalyst media particles 280 are disposed within oxidation chamber 270, and catalyze an oxidation reaction in the fuel stream to produce heat and an exhaust stream.
• Catalyst media particles 280 comprise carrier particles 284 that comprise refractory material.
• the catalyst media particles pack with a void fraction of at least 0.6.
• a tubular screen may be disposed inside the porous distributor member to prevent any fragments of catalyst media particles that may form from passing inwardly through holes in porous diffuser member.
• carrier particle 184 has an outer coating 186 comprising an oxidation catalyst 182.
• Outer coating 186 comprises inner layer 188 comprising cerium oxide in contact with carrier particle 184 and supports outer layer 189 comprising the oxidation catalyst.
• cylindrically-shaped catalytic burner 400 having the same exterior general appearance of catalytic burner 100 (shown in FIG. 1), comprises porous diffuser member 420, which comprises a cylindrical conduit 421 having a wall 422 with a plurality of holes (not shown) therethrough, and which comprises first and second open ends 425, 427.
• Cylindrically-shaped porous distributor member 430 which comprises a cylindrical conduit 431 having a wall 432 with a plurality of holes 433 therethrough, is disposed inside porous diffuser member 420 and comprises third and fourth open ends 435,437.
• First open end 425 is covered by end cap 440.
• Third open end 435 engages groove 446 in end cap 440 thereby forming a seal.
• Annular seal 460 extends between porous diffuser member 420 and porous distributor member 430, thereby defining (in combination with end cap 440) oxidation chamber 470.
• Catalyst media particles 480 are disposed within oxidation chamber 470.
• the catalyst media particles catalyze an oxidation reaction of fuel stream to produce heat and an exhaust stream.
• the catalyst media particles comprise a plurality of carrier particles, at least some of which have an outer coating on at least a portion of their respective outer surface.
• the carrier particles are typically intentionally shaped (i.e., not randomly shaped as, for example, with crushed particles or powders) due to the process used to make them (e.g., by extruding or molding), although this is not a requirement.
• the selection of dimensions of the catalyst media particles is typically controlled, at least in part, by the size of the burner and the spacing between the porous distributor member and the porous diffuser member.
• the catalyst media particles have an average particle diameter
• the shape and size of the catalyst media particles is typically substantially the same as that of the carrier particles.
• the average spacing between the diffuser member and the distributor member is generally larger than the average particle diameter of the catalyst media particles. In some embodiments, the average spacing between the diffuser member and the distributor member is from 0.5 to 20 millimeters, from 0.5 to 10 millimeters, or from 1 to 6 millimeters, although this is not a requirement.
• the shape of the carrier particles is predetermined, for example, such as would result from a molding process.
• the carrier particles comprise, and may be composed of refractory material (i.e., one or more refractory materials).
• suitable refractory materials include aluminas (e.g., alpha alumina, beta alumina, gamma alumina, eta alumina, and/or theta alumina), mullite, aluminum titanate, zirconia, zircon, silica, fireclay (an impure kaolinite), cordierite, silicon carbide, and mixtures thereof.
• suitable refractory materials include oxides of metals selected from the group consisting of magnesium, aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, cerium, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, silver, samarium, indium, iron, tin, antimony, barium, lanthanum, hafnium, tungsten, rhenium, iridium, platinum, and combinations thereof.
• Preferred refractory materials comprise inorganic metal oxides (e.g., aluminas and mullite).
• the refractory material has relatively low thermal coefficient of expansion and/or are capable of enduring many thermal cycles without fracture and fragmentation.
• alumina carrier particles may be obtained from commercial sources or prepared, for example, according to known methods.
• alumina carrier particles can be made by extruding and optionally shaping (e.g., curling) a slurry or sol-gel comprising an alumina precursor (e.g., colloidal boehmite), cutting the extrudate to the desired length, drying the extrudate particles, optionally calcining them, and then sintering them generally as described in U.S. Patent Nos. 4,314,827 (Leitheiser et al.);
• Suitable saddle-shaped carrier particles can be prepared by extruding a boehmite sol-gel through a hollow needle with a bent tip as described in the PREPARATION OF CATALYST MEDIA PARTICLES E in the examples section hereinbelow, and shown in FIG. 5.
• the carrier particles have a substantially constant cross-sectional profile along their length. This is especially the case for carrier particles that are formed by an extrusion process.
• the catalyst media particles pack with substantial space between them (e.g., they pack with a void fraction of at least 0.6).
• the void fraction is at least 0.63, at least 0.65, at least 0.68, at least 0.70, at least 0.72, at least 0.75, at least 0.78, or even at least 0.80.
• the catalyst media particles do not pack in an ordered array.
• Any shape or combination of shapes that packs with the desired void fraction can be used.
• the catalyst media particles may have any suitable theoretical density. For example, they may have an theoretical density of at least 1.5 g/cm ⁇ , at least 1.7 g/cm ⁇ , at least 1.9 g/cm ⁇ , at least 2.1 g/cm ⁇ , at least 2.3 g/cm ⁇ , at least 2.5 g/cm ⁇ , at least 2.7 g/cm ⁇ , at least 2.9 g/cm ⁇ , at least 3.0 g/cm ⁇ , at least 3.1 g/cn , at least 3.3 g/cn , at least3.5 g/cn , at least 3.6 g/cn , at least 3.7 g/cn , at least 3.8 g/cn , or even at least 3.9 g/cn
• At least some of the carrier particles preferably at least a majority or even all of the carrier particles, have an outer coating on at least a portion of their outer surface.
• the degree of coverage by the outer coating will typically depend on the process used to deposit it on the carrier particles. For example, a solvent coating process may be effective to coat the entire surface, while physical vapor deposition may result in partial coverage of the surface of individual carrier particles.
• the outer coating may comprise one or more layers (e.g., one, two, or three layers).
• the outer layer may have any thickness, but is typically relatively thin. For example, it may have a thickness of from 1 nanometer (nm) to 10 microns, preferably from 1 nanometer to 1 micron.
• the outer coating comprises an oxidation catalyst for oxidizing the oxidizable gas in the fuel stream.
• an oxidation catalyst for oxidizing the oxidizable gas in the fuel stream.
• Such materials are well known in the art and include, for example, materials comprising platinum, iridium, osmium, palladium, ruthenium, rhodium, alloys thereof, oxides thereof, and combinations thereof. Of these palladium and its oxides are preferred.
• Palladium-based catalysts are known to possess high catalytic activity for methane oxidation.
• the most active phases in these catalysts are believed to be in the oxide form which is typically stable between 300 to 600 °C.
• PdO palladium oxide
• the metallic form also has a higher volatility than the oxide, and therefore poses a greater risk for catalyst material loss through vaporization processes during burner operation.
• the outer coating comprises an inner layer and an outer layer, which layers may comprise different materials.
• the inner layer i.e., the layer in contact with the carrier particle
• the inner layer comprises cerium oxide.
• the inner layer supports the outer layer comprising the oxidation catalyst.
• catalytically-active palladium is deposited onto the carrier particles using physical vapor deposition.
• Physical vapor deposition refers to the physical transfer of palladium from a palladium-containing source or target to the carrier particles. Physical vapor deposition may be viewed as involving atom-by-atom deposition, although in actual practice, the palladium may be transferred as extremely fine bodies constituting more than one atom per body. Once at the surface of the carrier particles, the palladium may interact with the surface physically, chemically, ionically, and/or otherwise.
• PVD physical vapor deposition
• Representative approaches include sputter deposition, evaporation, and cathodic arc deposition.
• PVD approaches may be used, although the nature of the PVD technique used can impact catalytic activity.
• the energy of the physical vapor deposition technique used can impact the mobility, and hence tendency of the deposited palladium atoms and clusters to agglomerate into larger bodies on the surface of the support. Higher energy tends to correspond to an increased tendency of the palladium to agglomerate. Increased agglomeration, in turn, tends to reduce catalytic activity.
• the energy of the depositing species is lowest for evaporation, higher for sputter deposition (which may include some ion content in which a small fraction of the impinging metal species are ionized), and highest for cathodic arc (which may be several tens of percents of ion content). Accordingly, if a particular PVD technique yields deposited palladium that is more mobile than might be desired, it may be useful to use a PVD technique of lesser energy instead.
• Physical vapor deposition generally is a line of sight/surface coating technique between the palladium source and the carrier particles. This means that only the exposed, outer surfaces of the carrier particles, but not inner pores (if any) that are well within the substrate, are directly coated. While the inner surfaces not in a direct line of sight with the source will also tend not to be directly coated with palladium, on some substrates, the atoms and small clusters of the deposited palladium can penetrate by diffusion a small distance into porous carrier particles.
• the active palladium species is collected essentially completely on the outermost portion of the carrier particles. This can be desirable since this is the surface of the catalyst system that interacts most readily with an oxidizable gas, for instance in a burner system.
• the palladium metal may be in the form of metal, an oxide, or some other oxidized form, and may have an oxidation state of, for instance, 0, +2, or +4. In general, it is preferable that at least a portion of the palladium be present in an oxidized form during the periods where the catalytic burner is promoting combustion.
• the palladium metal that is physically vapor deposited on the carrier particles may, in some embodiments, have a thickness of from 0.1 nm to 500 nm, from 1 nm to 400 nm, or even from 5 nm to 250 nm.
• the catalytic burner is typically coupled to an inlet member having an inlet port in fluid communication with the inlet opening for supplying a fuel stream from a source, and mounted within the boiler.
• exemplary boiler 600 comprises catalytic burner 605 coupled to inlet member 610 and disposed within cavity 615 in housing 630.
• Inlet member 610 comprises inlet port 620 in fluid communication with the inlet opening 625 of catalytic burner 605 for supplying fuel stream 670 from a source.
• Housing 630 has exhaust port 640 and heat exchanger coils 650 for circulating a heat exchange fluid (e.g., water).
• a heat exchange fluid e.g., water
• the boiler may further include one or more additional components such as, for example, a drain for condensate.
• Typical fuel streams are gaseous and typically comprise an oxidizable component and an oxidizing component (i.e. an oxidizer).
• suitable oxidizable components include acetylene, methane, ethane, propane, butane, pentane, and combinations thereof although other oxidizable gaseous materials may also be used.
• suitable oxidizing components include air, oxygen (pure or in combination with other gas(es) such as nitrogen, carbon dioxide, and/or noble gases, for example, as in air), or another oxidizing gas (e.g., nitrous oxide).
• Catalytic burners according to the present disclosure are useful, for example, in residential, commercial, and/or industrial boilers.
• the present disclosure provides a catalytic burner comprising:
• catalyst media particles for catalyzing an oxidation reaction of a fuel stream to produce heat and an exhaust stream, wherein the catalyst media particles is disposed within the oxidation chamber, wherein the catalyst media particles comprise carrier particles, each carrier particle comprising refractory material, wherein at least some of the carrier particles have thereon an outer coating comprising an oxidation catalyst, and wherein the catalyst media particles have a void fraction of at least 0.6.
• the present disclosure provides a catalytic burner according to the first embodiment, wherein the porous diffuser member comprises a first open end, wherein the porous distributor member is disposed at least partially inside the porous diffuser member, wherein the porous distributor member comprises a second open end.
• the present disclosure provides a catalytic burner according to the first or second embodiment, further comprising a first end cap, wherein the porous diffuser member further comprises a third open end, and wherein the first end cap covers the first open end.
• the present disclosure provides a catalytic burner according to the third embodiment, further comprising a second end cap, wherein: the first end cap comprises an alignment pin inwardly extending therefrom along a longitudinal axis of the porous distributor member;
• the porous distributor member further comprises a fourth open end
• the second end cap covers the fourth open end, except for a central opening in the second end cap adapted to receive the alignment pin.
• the present disclosure provides a catalytic burner according to the third or fourth embodiment, wherein the porous diffuser member comprises at least one of a cylindrical conduit or a frustoconical conduit.
• the present disclosure provides a catalytic burner according to any one of the first to fifth embodiments, wherein the porous diffuser member comprises a spheroidal portion.
• the present disclosure provides a catalytic burner according to any one of the first to sixth embodiments, wherein the outer coating is discontinuous.
• the present disclosure provides a catalytic burner according to any one of the first to seventh embodiments, wherein the void fraction is at least 0.65.
• the present disclosure provides a catalytic burner according to any one of the first to eighth embodiments, wherein the porous distributor member and the porous diffuser member are separated from each other by an average distance of from 1 to 6 millimeters.
• the present disclosure provides a catalytic burner according to any one of the first to ninth embodiments, wherein the catalyst media particles have an average particle diameter of from 0.5 millimeter to 3 millimeters.
• the present disclosure provides a catalytic burner according to any one of the first to tenth embodiments, wherein the carrier particles are saddle-shaped.
• the present disclosure provides a catalytic burner according to any one of the first to eleventh embodiments, wherein the carrier particles have a substantially constant cross- sectional profile along their length.
• the present disclosure provides a catalytic burner according to the twelfth embodiment, wherein the oxidation catalyst comprises palladium.
• the present disclosure provides a catalytic burner according to the thirteenth embodiment, wherein the palladium is deposited by physical vapor deposition.
• the present disclosure provides a catalytic burner according to any one of the first to fourteenth embodiments, wherein the outer coating comprises an inner layer comprising cerium oxide in contact with the carrier particle and supporting an outer layer comprising the oxidation catalyst.
• the present disclosure provides a catalytic burner according to any one of the second embodiment, further comprising a gas inlet member covering the first open end of the porous distributor member, wherein the gas inlet member comprises a gas inlet port.
• the present disclosure further comprises a screen disposed at least partially inside the porous distributor member.
• the present disclosure provides a boiler comprising:
• a catalytic burner disposed within a cavity in a housing, wherein the catalytic burner is coupled to an inlet member comprising an inlet port for supplying a fuel stream;
• a heat exchanger for circulating a heat exchange fluid disposed within the housing, and in fluid communication with the catalytic burner, wherein the housing further comprises an exhaust port in fluid communication with the inlet port through the catalytic burner.
• Palladium content for catalyst media particles was determined using inductively coupled plasma- optical emission spectroscopy (ICP-OES) equipment (obtained under the trade designation OPTIMA
• the catalyst media particles was analyzed against external calibration curves generated using acid-matched solution standards containing 0, 0.5, 1, and 2 parts per million (ppm) of palladium.
• a 0.5 ppm quality-control standard was used to monitor the accuracy of the calibration curves during the analysis.
• a 0.5 ppm solution of scandium was run in-line with the catalyst media particles and standards to serve as an internal standard.
• Catalyst media particles were measured as duplicate samples. About 100 mg of each duplicate sample were weighed into respective acid-washed quartz beakers. About 2 mL of concentrated sulfuric acid were added to the sample beakers and to two empty control beakers. The beakers were covered with acid-washed quartz watch glasses and heated at reflux (approximately 337 °C) for two hours. Next, the beakers were partially uncovered to allow the excess acid to evaporate until a solution volume of approximately 0.5 mL was obtained. About 1 mL of 30% hydrogen peroxide followed by 4 mL of aqua regia (3: 1 HC1:HN03) were added to each beaker, and the solutions were heated to approximately 90-100
• CARRIER PARTICLES A The void fraction of CARRIER PARTICLES A is 0.38 as calculated using Equations 1 and 2, and ASTM C20-00 (each described hereinabove).
• CARRIER PARTICLES A were wet (to near incipient wetness) with an acidic aqueous sol containing boehmite and cerium nitrate, and the solvent removed to produce partially dried, coated spheres, which were then calcined at 600°C for 4 hours to form a metal oxide (hereinafter referred to as a "Ce/Al oxide”) coating. Based on weight gain, the typical weight percentage of the Ce/Al oxide was about 5 weight percent of the resultant coated carrier particles.
• Palladium was then deposited by physical vapor deposition (PVD) onto the Ce/Al oxide coated carrier particles to various loading levels using magnetron sputtering and a particle agitator system.
• PVD physical vapor deposition
• Each sample of the Ce/Al oxide coated carrier particles was placed in the PVD apparatus described in FIGS. 1 and 2, and especially in paragraphs [0074]-[0076] of U.S. Patent Appl. Publ. No. 2009/054230 Al (Veeraraghavan et al.), except that blades 42 did not contain holes 44.
• the particle agitator 16 had a blade gap of 6.3 mm.
• the vacuum chamber 14 was then evacuated to a background pressure of about 5x10 " ⁇ Torr (6.6 mPa) or less, and argon sputtering gas was admitted to the chamber at a pressure of about 10 mTorr (133.3 mPa).
• a mass flow controller with read out (obtained from MKS Instruments, Inc., Wilmington, Massachusetts) was used to control the flow rate of argon in the chamber, and the argon flow rate was kept at 47 standard cubic centimeters per minute (seem).
• the palladium deposition process was then carried out by applying power to the palladium sputter target 32 for a pre-set period of time of 2 hours, with the particle agitator shaft 40 and blades 42 being rotated at 6 rpm. The duration of the palladium deposition process was 2 hours.
• the applied palladium sputter target power was 1 10 watts.
• the vacuum chamber was vented with air to ambient conditions, and the resultant coated particles (CATALYST MEDIA PARTICLES A) were removed from the PVD apparatus.
• the palladium content was determined according to the PALLADIUM CONTENT DETERMINATION METHOD (hereinabove) to be 0.19 weight percent Pd.
• CATALYST MEDIA PARTICLES C does not contain a Ce/Al oxide coating.
• the palladium content was determined according to the PALLADIUM CONTENT DETERMINATION METHOD (hereinabove) to be 0.18 weight percent Pd.
• Saddle-shaped carrier particles were created using a needle extrusion process with a 40 weight percent solids boehmite gel as follows.
• Boehmite alumina powder 4824 parts, available as "DISPERAL” from Sasol North America Inc. Houston Texas
• DISPERAL aqueous nitric acid
• the aged sol-gel was extruded through a 10-gauge needle crimped along the long axis with the end cut to about 45° to induce curling of the extruded parts.
• saddle-shaped sol-gel particles were sheared off, dried, and fired.
• the firing profile was a 20 °C/min ramp to 750 °C, 18 min soak, 20 °C/min ramp to 1200 °C, 48 min soak, and a 20 °C/min cooling to 25 °C.
• FIG. 5 is a representative optical microscopy image of a fired saddle-shaped alpha- alumina carrier particle.
• the fired saddle-shaped alpha-alumina carrier particles had an average longest dimension of about 2 millimeters.
• the void fraction of these particles is 0.61 as calculated using Equations 1 and 2, and ASTM C20-00 (each described hereinabove).
• This media is henceforth referred to as CARRIER PARTICLES B.
• Palladium was deposited on CARRIER PARTICLES B as in the preparation of CATALYST MEDIA PARTICLES A, resulting in a Pd content of 0.21 weight percent, resulting in CATALYST MEDIA PARTICLES E.
• CATALYST MEDIA PARTICLES E does not contain the Ce/Al oxide coating.
• CATALYST MEDIA PARTICLES F was a mixture of 50% (by volume) CARRIER
• FeCrAl metal fiber mesh available under the trade designation BEKAERT BEKINIT 100 from Bekaert, Kortrijk, Belgium, having a thickness of approximately 1.5 mm and an areal density of 1,500 g/m was heat treated to 900 °C for 4 hours resulting in CARRIER MESH A.
• Ce/Al oxide was applied using a method analogous to those described in CATALYST MEDIA PARTICLES A resulting in a Ce/Al oxide content of 3.56 weight percent.
• Physical vapor deposition was used to then vapor coat CARRIER MESH A with Pd at 250 watts for 5 min to give a Pd content of 0.06 weight percent (relative to the total substrate mass).
• Boiler testing was conducted in a residential sized boiler (NTI Trinity Til 50, commercially available from NY Thermal - St. John, New Brunswick, California). The burner is commercially available with a FeCrAl metal fiber mesh. This mesh was removed and replaced with various media for testing. Experiments were run at 30% excess air (EA) and firing rates of 15.8- 158 MJ/hr (15- 150 kBtu/hr)
• Boiler inlet water temperature was held constant at 60 °C, with a temperature rise through the boiler (outlet minus inlet temperature) of 1 1 °C.
• Gas emissions were sampled off the exhaust flue of the boiler and passed through a chiller to remove any water vapor before being sent to a series of gas analyzers.
• Carbon dioxide, carbon monoxide, and methane concentrations in the sampled gas were determined by infrared absorption methods using a Horiba VIA-510 gas analyzer, Irvine, California.
• Nitrogen oxide (NO x ) concentrations were measured by chemiluminescence using a Teledyne T200m NO x analyzer from Teladyne Advanced
• the first two sets of data compare CARRIER MESH A to CATALYST MEDIA PARTICLES G. Throughout the firing range, CATALYST MEDIA PARTICLES G show no significant deviation from the CARRIER MESH A. This is due to the line of sight limitation of physical vapor deposition, resulting in a surface coating with limited penetration through the mesh thickness. This surface concentrated coverage provides inadequate contact between the fuel and the catalyst and limits its effectiveness.
• the second two sets of data are for CATALYST MEDIA PARTICLES B and CATALYST MEDIA
• Burner testing was conducted in a custom open air burner. Methane and dry air were metered using mass flow controllers (available as AALBORG GFCS-010066 from Aalborg, Orangeburg, New York) and sent through a mixing chamber containing a series of perforated discs. The premixed gas was then combusted in a half cylindrical burner head that mimics the geometry of the boiler burner in Example 1 and is mounted on a flat face. The temperature of the packed bed was monitored using K-type thermocouples (Omega Engineering, Stamford, Connecticut) while the emissions were measured using methods described in Example 1.
• Table 4, 5 summarizes the NO x emissions and packed bed temperature data for CARRIER B, CARRIER A, CATALYST MEDIA PARTICLES D, and CATALYST MEDIA PARTICLES F. Comparing first the effect of the catalyst on NO x emissions, there is a significant drop in emissions for both CARRIER B and CARRIER A when the media is catalyzed.

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• 2013
  • 2013-11-21 JP JP2015547379A patent/JP2016503875A/ja not_active Ceased
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  • 2013-11-21 KR KR1020157018151A patent/KR20150096450A/ko not_active Withdrawn
  • 2013-11-21 WO PCT/US2013/071258 patent/WO2014092965A1/en active Application Filing
  • 2013-11-21 CN CN201380064469.5A patent/CN104870897B/zh not_active Expired - Fee Related
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