EP0745180B1 - Procede et structure catalytiques ameliores assurant un echange thermique integral avec eventuellement une flamme entretenue en aval - Google Patents

Procede et structure catalytiques ameliores assurant un echange thermique integral avec eventuellement une flamme entretenue en aval Download PDF

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Publication number
EP0745180B1
EP0745180B1 EP95911772A EP95911772A EP0745180B1 EP 0745180 B1 EP0745180 B1 EP 0745180B1 EP 95911772 A EP95911772 A EP 95911772A EP 95911772 A EP95911772 A EP 95911772A EP 0745180 B1 EP0745180 B1 EP 0745180B1
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European Patent Office
Prior art keywords
catalyst
channels
coated
mixture
catalytic
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German (de)
English (en)
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EP0745180A4 (fr
EP0745180A1 (fr
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Ralph A. Dalla Betta
Toru Shoji
David K. Yee
Scott A. Magno
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Catalytica Inc
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Tanaka Kikinzoku Kogyo KK
Catalytica Inc
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    • 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
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2807—Metal other than sintered metal
    • F01N3/281—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2807—Metal other than sintered metal
    • F01N3/281—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates
    • F01N3/2814—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates all sheets, plates or foils being corrugated
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2807—Metal other than sintered metal
    • F01N3/281—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates
    • F01N3/2821—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates the support being provided with means to enhance the mixing process inside the converter, e.g. sheets, plates or foils with protrusions or projections to create turbulence
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2882—Catalytic reactors combined or associated with other devices, e.g. exhaust silencers or other exhaust purification devices
    • 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 
    • F23C6/00—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion
    • F23C6/04—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection
    • F23C6/045—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with staged combustion in a single enclosure
    • 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 
    • F23C9/00—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
    • F23C9/006—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber the recirculation taking place in the combustion chamber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/02—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being a heat exchanger
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/30—Honeycomb supports characterised by their structural details
    • F01N2330/32—Honeycomb supports characterised by their structural details characterised by the shape, form or number of corrugations of plates, sheets or foils
    • F01N2330/321—Honeycomb supports characterised by their structural details characterised by the shape, form or number of corrugations of plates, sheets or foils with two or more different kinds of corrugations in the same substrate
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/30—Honeycomb supports characterised by their structural details
    • F01N2330/32—Honeycomb supports characterised by their structural details characterised by the shape, form or number of corrugations of plates, sheets or foils
    • F01N2330/323—Corrugations of saw-tooth or triangular form
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/30—Honeycomb supports characterised by their structural details
    • F01N2330/42—Honeycomb supports characterised by their structural details made of three or more different sheets, foils or plates stacked one on the other
    • 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 
    • F23C2900/00—Special features of, or arrangements for combustion apparatus using fluid fuels or solid fuels suspended in air; Combustion processes therefor
    • F23C2900/13002—Catalytic combustion followed by a homogeneous combustion phase or stabilizing a homogeneous combustion phase

Definitions

  • This invention relates to a catalyst structure employing integral heat exchange in an array of longitudinally disposed, adjacent reaction passageways or channels which are either catalyst-coated or catalyst-free, as well as a method for using the catalyst structure in highly exothermic processes, such as combustion or partial combustion processes. More particularly, this invention is directed to such a catalyst structure employing integral heat exchange wherein the catalytic and non-catalytic channels differ from each other in certain critical respects whereby the exothermic reaction in the catalytic channels and heat exchange between the catalytic and non-catalytic channels are optimized while undesired exothermic reaction in the non-catalytic channels is suppressed.
  • the combustor must operate over a range of air and fuel flows. If the combustor system uses a catalyst to combust the fuel and limit emissions, then this catalyst system must be able to operate over a wide range of air flows, fuel/air ratios (F/A) and pressures.
  • F/A fuel/air ratios
  • the air flow over the load range of 0% to 100% will be approximately constant.
  • the fuel flow will vary to match the load required so the F/A will vary.
  • the pressure will increase somewhat as the power output is increased.
  • the catalytic combustor must operate over a wide range of F/A and a range of pressures but at relatively constant mass flow.
  • a variable portion of the air flow can be bypassed around the combustor or bled from the gas turbine to decrease the air flow and maintain a more constant F/A. This will result in a narrower range of F/A over the catalyst but a wider range of mass flows.
  • the air flow and pressure can vary widely over the operating range. This results in a wide variation of total mass flow and pressure in the combustor. Similar to the situation described above for the electric power generation turbine, the air can be bypassed or bled to control the F/A range resulting in a combustor that must operate over a range of mass flows.
  • One particular application that could benefit from catalytic combustion is a gas turbine applied to a vehicle to achieve very low emissions. Once started, this engine must operate from idle to full load and achieve low emissions over this entire range. Even if the gas turbine is used in a hybrid vehicle design combined with a storage component such as a battery, flywheel, etc., the engine must still operate at idle and full load and must transit between these two operating points. This requires operation at mass flows and pressures of both of these conditions.
  • the present invention employs a catalyst structure made up of a series of adjacently disposed catalyst-coated and catalyst-free channels for passage of a flowing reaction mixture, wherein the catalytic and non-catalytic channels share a common wall such that integral heat exchange can be used to dissipate the reaction heat generated on the catalyst and thereby control or limit the temperature of the catalyst. That is, the heat produced on the catalyst in any given catalyst-coated channel flows through the common wall to the opposite non-catalytic surface to be dissipated into the flowing reaction mixture in the adjacent catalyst-free channel.
  • the configuration of the catalytic channels differs from the non-catalytic channels in one or more critical respects, in particular the tortuosity of the flow channel, such that, when applied to catalytic combustion, catalytic and homogeneous combustion is promoted within the catalytic channels and not promoted or substantially limited in the non-catalytic channels while heat exchange is otherwise optimized.
  • These uniquely configured catalyst structures substantially widen the window of operating parameters for catalytic combustion and/or partial combustion processes.
  • the design of the catalyst structure disclosed is such that the configuration of the catalyst-coated channels and catalyst-free channels is the same with the catalytic and non-catalytic flow channels in each case being essentially straight and of the same cross-sectional area throughout their lengths.
  • US 5,202,303 discloses a multiple-stage combustion apparatus which can be used in a high-temperature environment, such as with a gas turbine.
  • a first stage which is an ignition stage, is a reactor formed of a metal strip which is coated with a catalyst on only one side. The strip is also corrugated with a herringbone pattern. The strip is then folded back and forth upon itself to form a reactor of a desired cross-section.
  • the reactor has rows of channels that are formed between the layers of the metal.
  • the single coated side of the metal defines the walls of the channels in every other row.
  • the fuel-air mixture that flows through the coated channels is combusted.
  • the one or more stages subsequent to the ignition stage can employ a catalyst capable of operating at the very high temperatures present in gas turbines.
  • the subsequent stages can also be non-catalytic. Thus, the first stage provides catalytic ignition, and the subsequent stages complete the combustion.
  • DE 4202018 C1 discloses a method for stabilising a catalytically supported combustion.
  • a flame holder is located downstreams a catalyst. Thereby a recirculation zone is established which results in a stable after-burning in a consecutive homogeneous combustion zone.
  • combustible gas passageways or channels are formed by alternating broad or narrow corrugations of a corrugated metal foil such that the size of the alternating catalytic and non-catalytic channels are varied to allow 80% of the gas flow to pass through the catalytic channels and 20% through the non-catalytic channels in one case (FIG. 6A), or 20% of the gas flow to pass through the catalytic channels and 80% through the non-catalytic channels in the other case (FIG. 6B).
  • this patent teaches that any level of combustible gas conversion to combustion products between 5% and 95% can be achieved while incorporating integral heat exchange.
  • the integral heat exchange structure In cases where the integral heat exchange structure is used to carry out catalytic partial combustion of a fuel followed by complete combustion after the catalyst, the catalyst must burn a portion of the fuel and produce an outlet gas sufficiently hot to induce homogeneous combustion after the catalyst. In addition, it is desirable that the catalyst not become too hot since this would shorten the life of the catalyst and limit the advantages to be gained from this approach. As the operating condition of the catalyst is changed, it is noted with the integral heat exchange structures of the prior art, discussed above, that operating window of such catalysts are limited. That is, that the gas velocity or mass flow rate must be within a certain range to prevent catalyst overheating.
  • a catalyst structure comprised of a series of adjacently disposed catalyst-coated and catalyst-free channels for passage of a flowing reaction mixture wherein the channels at least partially coated with catalyst are in heat exchange relationship with adjacent catalyst-free channels and wherein the catalyst-coated channels have a configuration which forms a more tortuous flow passage for the reaction mixture than the flow passage formed by the catalyst-free channels.
  • catalyst-coated channels or “catalytic channels” in the catalyst structures of the invention may refer to single channels or groupings of adjacent channels which are all coated with catalyst on at least a portion of their surface, in effect a larger catalytic channel subdivided into a series of smaller channels by catalyst support walls or pervious or impervious barriers which may or may not be coated with catalyst.
  • the "catalyst-free channels” or “non-catalytic channels” may be a single channel or grouping of adjacent channels which are all not coated with catalyst, that is, a larger catalyst-free channel subdivided into a series of smaller channels by catalyst support walls or pervious or impervious barriers which are not coated with catalyst.
  • increased tortuosity of the flow passages formed by the catalyst-coated channels means that the catalyst-coated channels are designed such that at least a portion of the reaction mixture entering the catalyst-coated channels will undergo more changes in direction of flow as it traverses the length of the channel than will any similar portion of reaction mixture entering the catalyst-free channels.
  • the longitudinal axes of the catalyst-coated channels is a straight line leading from the inlet of the channel to the outlet of the channel
  • increasing the tortuosity of the channel would result in a reaction mixture flow pathway which shows increasing directional deviations from the axis such that the path traveled by tracing the deviations becomes increasing longer than the path drawn by the axis.
  • the increased tortuosity of the flow passage in the catalyst-coated channels can be accomplished by a variety of structural modifications to the channels including periodically altering their direction and/or changing their cross-sectional area along their longitudinal axis while the catalyst-free channels remain substantially straight and unaltered in cross-sectional area.
  • the tortuosity of the catalyst-coated channels is increased by varying their cross-sectional area though repeated inward and outward bending of channels walls along the longitudinal axis of the channels or through the insertion of flaps, baffles or other obstructions at a plurality of points along the longitudinal axes of the channels to partially obstruct and/or divert the direction of reaction mixture flow in the channels.
  • the catalyst structure can be further characterized by catalyst-coated channels that differ from the catalyst-free channels in one or more critical structural defining elements which, in turn, take advantage of, and expand upon, the concept of the increased tortuosity of the catalyst-coated channels.
  • the preferred catalyst structure of the invention typically employs a plurality of longitudinally disposed channels coated on at least a portion of their interior surface with catalyst, that is, catalyst-coated channels, in heat exchange relationship with adjacent channels not coated with catalyst or catalyst-free channels wherein:
  • the average hydraulic diameter or D h which is defined as four times the average cross-sectional area of ail of the channels of a particular type, e.g., catalyst-coated channels, in the catalyst structure divided by the average wetted perimeter of all of the channels of that type in the catalyst structure, is reflective of the finding that the catalyst-free channels are most advantageously designed to have a larger hydraulic diameter and to be less effected by changes in configuration than the catalyst-coated channels.
  • the film heat transfer coefficient or h is an experimentally determined value which correlates with, and expands upon the tortuosity of the average catalyst-coated channel versus that of the average catalyst-free channel in the catalyst structure.
  • the catalyst structure is particularly useful when equipped with appropriate catalytic materials for use in a combustion or partial combustion process wherein a fuel, in gaseous or vaporous form, is typically partially combusted in the catalyst structure followed by complete homogeneous conibustion downstream of the catalyst
  • a fuel in gaseous or vaporous form
  • the catalyst structure it is possible to obtain more complete combustion of fuel in the catalytic channels with minimum combustion in the non-catalytic channels over a wider range of linear velocities, gas inlet temperatures and pressures than has here-to-for been possible with catalyst structures of the prior art, including those employing integral heat exchange.
  • the invention also encompasses a catalyst structure for use in the combustion or partial combustion of a combustible fuel, as well as a process for combusting a mixture of a combustible fuel and air or oxygen-containing gas, using the catalyst structure.
  • a flameholder or other means for inducing recirculation into the partially combustible gas mixture flowing into a homogeneous combustion zone immediately downstream from the outlet end of the catalyst structure involves the addition of a flameholder or other means for inducing gas recirculation downstream of the outlet end of the catalyst structure.
  • the addition of a flameholder or other means for inducing gas recirculation downstream of the outlet end of the catalyst structure provides additional flexibility in the range of suitable operating parameters for catalytic combustion and/or partial combustion processes, including reduced catalyst operating temperatures which could have an overall favorable effect on catalyst lifetimes.
  • the catalyst structures of the invention are typically monolithic-type structures comprising a heat resistant support material composed of a plurality of common walls which form a multitude of adjacently disposed longitudinal channels for passage of a gaseous reaction mixture wherein at least a portion of the channels are coated on at least a part of their interior surface with a catalyst for the reaction mixture (catalyst-coated channels) and the remaining channels are not coated with catalyst on their interior surface (catalyst-free channels) such that the interior surface of the catalyst-coated channels are in heat exchange relationship with the interior surface of adjacent catalyst-free channels and wherein the catalyst-coated channels differ in configuration from the catalyst-free channels such that the desired reaction is promoted in the catalytic channels and suppressed in the non-catalytic channels.
  • the critical difference in the design of the catalytic versus non-catalytic channels will insure more complete combustion of the fuel in the catalytic channels and minimum combustion in the non-catalytic channels over a wider range of linear velocity, inlet gas temperature and pressure.
  • tortuosity is defined as the difference between the length of the path which a given portion of reaction mixture will travel through the passage formed by the channel as a result of changes in direction of the channel and/or changes in channel cross-sectional area versus the length of the path traveled by a similar portion of the reaction mixture in a channel of the same overall length without changes in direction or cross-sectional area, in other words, a straight channel of unaltered cross-sectional area.
  • the deviations from a straight or linear path result in a longer or more tortuous path and the greater the deviations from a linear path the longer the traveled path will be.
  • differences in tortuosity between catalytic and non-catalytic channels is determined by comparing the average tortuosity of all of the catalytic channels in the structure to the average tortuosity of all of the non-catalytic channels in the structures.
  • the tortuosity of the catalytic channels can be increased by periodically changing their direction, for example, by using channels having a zig-zag or wavy configuration or by repeatedly changing their cross-sectional area through periodic inward and outward bending of channel walls along their longitudinal axis or through the insertion of flaps, baffles or other obstructions to partially obstruct or divert the direction of reaction mixture flow at a plurality of points along the longitudinal axis of the channel.
  • the tortuosity of the catalytic channels is increased by changing their cross-sectional area at a multiplicity of points along their longitudinal axes.
  • One preferred way of accomplishing this change in tortuosity for the catalytic channels involves the use of a stacked arrangement of non-nesting corrugated sheets of catalyst support material which are corrugated in a herringbone pattern with at least a portion of one side of a given corrugated sheet facing and stacked against another corrugated sheet being coated with catalyst such that the stacked sheets in question form a plurality of catalytic channels.
  • the channels formed by the stacked sheets alternately expand and contract in cross-sectional area along their longitudinal axis due to the inwardly and outwardly bending peaks and valleys formed by the herringbone pattern of the corrugated sheets.
  • Other preferred ways of changing the cross-sectional area of the catalyst-coated channels include the periodic placement of flaps or baffles on alternate sides of the channels along their longitudinal axis or the use of screens or other partial obstructions in the flow path formed by the catalytic channels. To avoid undue pressure drops across the channel the cross-sectional area of the channel should not be reduced by more than about 40% of its total cross-sectional area by any obstruction placed in the flow path formed by the channel.
  • the channels coated with catalyst differ from the catalyst-free channels by having an average hydraulic diameter (D h ) which is lower than the average hydraulic diameter of the catalyst-free channels and/or by having a higher film heat transfer coefficient (h) than the catalyst-free channels. More preferably, the catalyst-coated channels have both a lower D h and a higher h than the catalyst-free channels.
  • the average hydraulic diameter is defined in Whitaker, Fundamental Principles of Heat Transfer, Krieger Publishing Company (1983) at page 296 by the following formula:
  • the average D h can be determined by first finding the D h for all of the catalyst-coated channels in the structure by calculating the average D h for any given channel over its entire length and then determining the average D h for the catalyst-coated channels by totalling up all of the calculated D h s for the individual channels, multiplied by a weighing factor representing the fractional open frontal area for that channel.
  • the average D h for the catalyst-free channels in the structure can also be determined.
  • the finding that the catalyst-coated channels most advantageously have a lower average D h than the catalyst-free channels can be explained, in part, by the fact that the catalyst-coated channels desirably have a surface to volume ratio which is higher than that of the catalyst-free channels, since hydraulic diameter bears an inverse relationship to surface to volume ratio.
  • the difference in average D h of the catalyst-coated channels and catalyst-free channels gives an indication that the catalyst-free channels, on average, must be more open channeled and therefore, the gas flow through these channels is less effected by changes in the channel diameter than the catalyst-coated channels, again, in part, because of the higher surface to volume ratios in the catalyst-coated channels.
  • the numeric ratio of the average D h of the catalyst-coated channels to the average D h of the catalyst-free channels is between about 0.15 and about 0.9 and, most preferably, the ratio of average D h of catalyst-coated channels to catalyst-free channels is between about 0.3 and 0.8.
  • the film heat transfer coefficient provides useful means of characterizing the different flow geometries provided by the various flow channel configurations which distinguish the catalyst-coated channels from the catalyst-free channels of the catalyst structure according to the invention.
  • the film heat transfer coefficient provides some measure of tortuosity as it is employed in the catalyst structures of the invention. While one skilled in the art could conceive of a variety of methods to measure or otherwise determine h in the catalyst structures of the invention, one convenient method would involve constructing an experimental test structure, for example, a solid thick metal structure, with internal space machined to simulate the desired channel shape; and then to test it in environments where the wall temperature is essentially constant from inlet to outlet or varies from inlet to outlet and is measured at several points along the channel length in the structure. For monoliths such as the straight channel structure depicted in FIG.
  • test structure can be a single channel or a linear array of channels.
  • test structure would be a section of the linear region containing channels of non-nesting herringbone configuration between two metal sheets sufficiently wide to minimize side effects.
  • each of the channel configurations can be tested separately and the numeric ratio for h(cat)/h(non-cat) can be determined by summing up the h's for each channel type (multiplied by a weighing factor representing the fractional open frontal area) in the catalyst structure and then dividing the sum of the h's for the catalytic channels by the sum of the h's for the non-catalytic channels.
  • the h(cat)/h(non-cat) ratios which characterize the difference in the configuration of the catalyst-coated and catalyst-free channels in the catalyst structure of the invention are further defined by the principle that in cases where h(cat)/h(non-cat) is greater than 1, the numeric ratio of the average hydraulic diameter (D h ) for the catalyst-coated channels divided by the average D h for the catalyst-free channels is smaller than the numeric ratio of the open frontal area of the catalyst-coated channels divided by the open frontal area of the catalyst-free channels.
  • open frontal area refers to the cross-sectional area of channels of a given type, i.e., catalytic or non-catalytic, averaged over the catalyst structure in question; the cross-sectional area being the area open to reaction mixture flow in a channel, measured perpendicular to the reaction mixture flow direction.
  • This numeric ratio based on open frontal area is reflective of the fact that the catalyst-coated channels of the present invention have a sufficient increase in tortuosity over the catalyst-free channels to be clearly distinguishable from prior art structures employing integral heat exchange where the flow ratio through catalytic and non-catalytic channels is controlled by the use of different sized channels of the same basic configuration.
  • the catalytic channels have a smaller average D h than the non-catalytic channels and the ratio of h(cat)/h(non-cat) can exceed 1.
  • the catalyst structures of the present invention can be distinguished by the use of higher film heat transfer coefficients (h) for the catalytic channels verses non-catalytic channels than is characteristic of the prior art structures employing catalytic and non-catalytic channels which are of different size but the same basic configuration.
  • the heat transfer coefficient of the catalytic channels would be approximately 1.5 times the heat transfer coefficient of the non-catalytic channels.
  • the structures of this invention would have heat transfer coefficients in the catalytic channels substantially larger than 1.5 times the heat transfer coefficient of the non-catalytic channels.
  • catalyst structures of the invention have h(cat)/h(non-cat) ratios in the range of about 1.1 and about 7, and most preferably the ratio is between about 1.3 and about 4.
  • the performance of the catalyst structures of the invention can be further optimized if the catalyst-coated and catalyst-free channels are configured such that the heat transfer surface area between the catalyst-coated and the catalyst-free channels divided by the total channel volume in the catalyst structure is greater than about 0.5 mm -1 .
  • the ratio of heat transfer area between the catalyst-coated and the catalyst-free channels divided by the total channel volume in the catalyst structure or R is between about 0.5 mm -1 and 2 mm -1 with Rs in the range of about 0.5 mm -1 to about 1.5 mm -1 being most preferred.
  • the catalyst structures of the invention can be designed to operate over a wide reaction mixture flow distribution between the catalytic and non-catalytic channels.
  • the ratio of reaction mixture flow through the catalyst structure is controlled so that between about 35% to about 70% of the flow is through the catalytic channels with most preferred catalyst structures having about 50% of the flow through the catalytic channels.
  • the reaction mixture flow distribution is controlled such that the open frontal area of the catalytic channels represents from about 20% to about 80% of the total open frontal area, while the catalytic and non-catalytic channels are configured such that the ratio of the average D h of the catalytic channels to the average D h of the non-catalytic channels is smaller than the ratio of open frontal area of the catalytic channels to the open frontal area of the non-catalytic channels.
  • open frontal area refers to the cross-sectional area of channels of a given type, i.e., catalytic or non-catalytic averaged over the catalyst structure in question; the cross-sectional area being the area open to reaction mixture flow in a channel measured perpendicular to the reaction mixture flow.
  • the ratio h(cat)/h(non-cat) is desirably greater than about 1.5 when the catalytic channels represent from about 20% to about 80% of the total open frontal area in the catalyst structure.
  • Preferred catalytic structures of this type have h(cat)/h(non-cat) ratios in the range of about 1.5 to about 7.
  • the present invention is directed to catalyst structures which are uniquely useful in the catalytic combustion or partial combustion of a fuel.
  • These catalyst structures are typically monolithic in nature and comprise a heat resistant support material composed of a plurality of common walls which form a multitude of adjacently disposed longitudinal channels for passage of a combustible mixture, e.g., a fuel in gaseous or vaporous form mixed with an oxygen-containing gas such as air.
  • the adjacently disposed channels are designed so that at least a portion of the channels are coated on at least a part of their interior surface with a catalyst suitable for oxidizing the combustible mixture, that is, catalyst-coated channels, and the remaining channels are not coated with catalyst on their interior surface, that is, catalyst-free channels, such that the interior surface of the catalyst-coated channels are in heat exchange relationship with the interior surface of adjacent catalyst-free channels.
  • the above-described catalyst structures are characterized by the presence of catalyst-coated channels or catalytic channels which differ in configuration from the catalyst-free channels or non-catalytic channels in one or more of the critical respects described above such that the desired combustion or oxidation reaction is promoted in the catalytic channels while it is substantially suppressed in the non-catalytic channels.
  • This extra element of control of the reaction coupled with the enhanced heat transfer which is obtained allows the catalytic combustion process to be operated over a wider range of operating parameters, such as linear velocity, inlet gas temperature and pressure.
  • the catalyst structure is suitably a platinum group metal-based catalyst on a ceramic or metal monolith.
  • the monolithic support is assembled such that the catalytic and non-catalytic channels extend in a longitudinal direction from one end of the support to the other, thus enabling the combustible gas to flow from end to end through the length of the channels.
  • the catalytic channels which have catalyst coated on at least a portion of their interior surfaces, need not be coated along their entire length. Further, the channels not coated with catalyst or non-catalytic channels have no catalyst on their interior walls or an inactive or very low activity coating on their walls.
  • the support materials suitably employed in the catalyst structures may be any conventional heat resistant, inert material such as a ceramic, heat resistant inorganic oxides, intermetallic materials, carbides, nitrides or metallic materials.
  • the preferred supports are high temperature resistant intermetallic or metallic materials. These materials are strong yet malleable, may be mounted and attached to surrounding structures more readily and offer more flow capacity, per unit of cross-sectional area, due to walls which are thinner than can be readily obtained in ceramic supports.
  • Preferred intermetallic materials include metal aluminides, such as nickel aluminide and titanium aluminide, while suitable metallic support materials include aluminum, high temperature alloys, stainless steels, aluminum-containing steels and aluminum-containing alloys.
  • the high temperature alloy may be a nickel or cobalt alloy or other alloy rated for the required temperature service. If heat resistant inorganic oxides are employed as the support material they are suitably selected from silica, alumina, magnesia, zirconia and mixtures of these materials.
  • the preferred materials are aluminum-containing steels such as those found in U.S. Patent Nos. 4,414,023 to Aggen et al., 4,331,631 to Chapman et al., and 3, 969,082 to Cairns et al.
  • the support material preferably metallic or intermetallic
  • the support material may be fabricated using conventional techniques to form a honeycomb structure, spiral rolls or stacked patterns of corrugated sheet, -sometimes inter-layered with sheets which may be flat or of other configuration, or columnar or other configuration which allow for the presence of adjacent longitudinal channels which are designed to present flow channels in accordance with the design criteria set forth above. If intermetallic or metallic foil or corrugated sheet is employed, the catalyst will be applied to only one side of the sheet or foil or in some cases the foil or sheet will remain uncoated depending on the catalyst structure design chosen.
  • the catalyst takes advantage of the integral heat exchange concept, allowing heat produced on the catalyst to flow through the structure wall into contact with the flowing gas at the opposite non-catalytic wall thereby facilitating heat removal from the catalyst and maintaining the catalyst temperature below the temperature for complete adiabatic reaction.
  • the adiabatic combustion temperature is the temperature of the gas mixture if the reaction mixture reacts completely and no heat is lost from the gas mixture.
  • washcoat may be applied using an approach such as is described in the art, e.g., the application of gamma-alumina, zirconia, silica, or titania materials (preferably sols) or mixed sols of at least two oxides containing aluminum, silicon, titanium, zirconium, and additives such as barium, cerium; lanthanum, chromium, or a variety of other components.
  • a primer layer can be applied containing hydrous oxides, such as a dilute suspension of pseudo-boehmite alumina, as described in U.S. Patent No. 4,279,782 to Chapman et al.
  • the primed surface may be coated with a gamma-alumina suspension, dried, and calcined to form a high surface area adherent oxide layer on the metal surface.
  • a zirconia sol or suspension is the washcoat.
  • Other refractory oxides such as silica and titania, are also suitable.
  • platinum group metals notably palladium, is a mixed zirconia/silica sol where the two have been mixed prior to application to the support.
  • the washcoat may be applied in the same fashion one would apply paint to a surface, e.g., by spraying, direct application, dipping the support into the washcoat material, etc.
  • Aluminum structures are also suitable for use in this invention and may be treated or coated in essentially the same manner.
  • Aluminum alloys are somewhat more ductile and likely to deform or even to melt in the temperature operating envelope of the process. Consequently, they are less desirable supports but may be used if the temperature criteria can be met.
  • the sheet may be heat treated in air to grow whiskers at the surface that increase adhesion of subsequent layers or provide increased surface area for direct application of a catalyst.
  • a silica, alumina, zirconia, titania, or refractory metal oxide washcoat may then be applied by spraying onto the metal foil a solution suspension, or other mixture of one or more materials selected from alumina, silica, zirconia, titania and a refractory metal oxide, and drying and calcining to form a high surface area washcoat.
  • the catalyst can then be applied, again such as by spraying, dripping or coating a solution, suspension, or mixture of the catalytic components onto the washcoats on the metal strip.
  • the catalytic material may also or alternatively be included in the washcoat material and coated onto the support thereby partially eliminating the separate catalyst inclusion step.
  • the catalyst structure may be sized to achieve a gas temperature exiting the catalyst no more than 1000°C, preferably in the range of 700°C and 950°C.
  • the preferred temperature is dependent on the fuel, the pressure and on the specific combustor design.
  • the catalyst can incorporate a non-catalytic diffusion barrier layer on the catalytic material such as that described in U.S. Patent No. 5,232,357.
  • the catalytic metal content of the composite i.e., the catalyst structure, is typically quite small, e.g., from 0.01% to about 15% by weight, and preferably from 0.01% to about 10% by weight.
  • Group VIII noble metals or platinum group metals palladium, ruthenium, rhodium, platinum, osmium, and iridium are preferred. More preferred are palladium (because of its ability to self-limit combustion temperatures) and platinum.
  • the metals may be used singly or in mixtures. Mixtures of palladium and platinum, are desirable since they produce a catalyst having the temperature limiting capabilities of palladium, although at a different limiting temperature, and the mixture is less susceptible to deactivation by reaction with impurities in the fuel or by reaction with the catalyst support
  • the platinum group metals or elements may be incorporated onto the support employed in the catalyst structure of the invention by a variety of different methods using noble metal complexes, compounds, or dispersions of the metal.
  • the compounds or complexes may be water of hydrocarbon soluble.
  • the metal may be precipitated from solution.
  • the liquid carrier generally needs only to be removable from the catalyst carrier by volatilization or decomposition while leaving the metal in a dispersed form on the support.
  • Suitable platinum group metal compounds are, for example, chloroplatinic acid, potassium platinum chloride, ammonium platinum thiocyanate, platinum tetrammine hydroxide, platinum group metal chlorides, oxides, sulfides, and nitrates, platinum tetrammine chloride, platinum ammonium nitrite, palladium tetrammine chloride, palladium ammonium nitrite, rhodium chloride, and hexamine iridium chloride. If a mixture of metals is desired, they may be in water soluble form, for example, as amine hydroxides or they may be present in such forms as chloroplatinic acid and palladium nitrate when used in preparing the catalyst of the present invention.
  • the platinum group metal may be present in the catalyst composition in elemental or combined forms, e.g., as an oxide or sulfide. During subsequent treatment such by calcining or upon use, essentially all of the platinum group metal is converted to the elemental form.
  • the catalyst will "light off' more easily and yet not cause "hot spots" in the latter regions of the structure.
  • the leading portion may be more active because of higher catalyst loadings, higher surface area, or the like.
  • the catalyst structure of the invention should be made in such a size and configuration that the average linear velocity of the gas through the longitudinal channels in the catalyst structure is greater than about .02 m/second throughout the catalytic structure and no more than about 80 m/second.
  • the lower limit is larger than the flame front speed for methane in air at 350°C and the upper limit is a practical one for the type of supports currently commercially available. These average velocities may be somewhat different for fuels other than methane. Slower burning fuels may permit use of a lower minimum and maximum space velocity.
  • the average size of the channels employed in the catalyst structure can vary widely dependent on the nature of the reaction mixture.
  • suitable catalyst structures contain about 50 to about 600 channels per square inch.
  • the catalyst structure will contain from about 150 to about 450 channels per square inch.
  • the catalytic combustion process of the invention employing the catalyst structure of the invention may be used with a variety of fuels and at a broad range of process conditions.
  • normally gaseous hydrocarbons e.g., methane, ethane, and propane
  • methane ethane
  • propane propane
  • the fuels may be liquid or gaseous at-room temperature and pressure.
  • Examples include the low molecular weight hydrocarbons mentioned above, as well as butane, pentane, hexene, heptene, octane, gasoline, aromatic hydrocarbons, such as benzene, toluene, ethylbenzene, xylene, naphthas, diesel fuel, kerosene, jet fuels, other middle distillates, heavy distillate fuels (preferably hydrotreated to remove nitrogenous and sulfurous compounds), oxygen-containing fuels, such as alcohols including methanol, ethanol, isopropanol, butanol, or the like; ethers, such as diethylether, ethyl phenyl ether, MTBE, etc.
  • Low-BTU gases such as town gas or syngas, may also be used as fuels.
  • the fuel is typically mixed into the combustion air in an amount to produce a mixture having a theoretical adiabatic combustion temperature or Tad greater than the catalyst or gas phase temperatures present in the catalysts employed in the process of the invention.
  • the adiabatic combustion temperature is above 900°C, and most preferably above 1000°C.
  • Non-gaseous fuels should be vaporized prior to their contacting the initial catalyst zone.
  • the combustion air may be compressed to a pressure of 500 psig. or more. Stationary gas turbines often operate at pressures in the vicinity of 150 psig.
  • the process of the invention can be carried out in a single catalytic reaction zone employing the catalyst structure of the invention or in multiple catalytic reaction zones, usually 2 or 3, using catalyst structures designed specifically for each catalytic stage.
  • the catalytic reaction zone will be followed by a homogeneous combustion zone in which the gas exiting from the earlier catalytic combustion zone is combusted under non-catalytic, non-flame conditions to afford the higher gas temperature, e.g., temperatures in the range of 1000-1500°C, required by gas turbines.
  • the homogeneous combustion zone is sized to achieve substantially complete combustion and to reduce the carbon monoxide level to the desired concentration.
  • the gas residence time in the post-catalyst reaction zone is 2 to 100 ms, preferably 10 to 50 ms.
  • An additional aspect of the invention which is particularly suited to the catalytic combustion or partial combustion of a fuel, relates to improved catalytic reaction systems and/or processes for catalytic combustion wherein a flameholder or other means for inducing gas recirculation into the homogeneous combustion zone downstream of a catalytic structure employing integral heat exchange, preferably the improved catalyst structures of the present invention, is used to further broaden the range of operating conditions at which the combustion can take place with little or no concomitant formation of NO x .
  • flameholders have generally been applied to rich F/A mixtures at low temperatures, in many cases with the use of an additional ignition device to initiate combustion.
  • equipping the homogeneous combustion zone downstream of a catalyst structure employing integral heat exchange with a flameholder or similar gas recirculation inducing means allows the flameholder to act in a passive fashion to stabilize the homogeneous combustion in the region of recirculation downstream from the flameholder, with the result being that stabilized homogeneous combustion can be obtained at lower catalyst structure outlet temperatures and/or leaner F/A ratios.
  • the ability to operate at lower catalyst structure outlet temperatures has practical benefits to the system in that enhanced catalyst lifetimes can be obtained and/or the size of the catalytic structure can be reduced while still obtaining essentially complete combustion (minimal unburned hydrocarbons and CO being present in the combustion gases) with little or no NO x formation.
  • this aspect of the invention employs any means for inducing gas recirculation in the homogeneous combustion zone including conventional flameholders and the use of homogeneous combustion zones where the cross-sectional area defined by the containment wall or walls of the homogeneous combustion zone is changed or varied over the length of the combustion zone in the direction of partially-combusted gas flow such that turbulence and recirculation are induced into the gas flow by the restrictions and/or expansions in areas the gas flow encounters as it moves through the zone.
  • the flameholder device is a physical object or a flow pattern that results in gas recirculation that causes an increase in the residence time for some portion of the fuel/air mixture. If the longer residence time is in the range of the ignition delay time for that specific gas mixture and gas temperature, then the gas mixture will ignite and combustion will be stabilized in the recirculation region. The combustion heat and radicals will spread into the main flow path and the combustion wave will spread until the entire flowing fuel/air mixture is combusted.
  • Conventional flameholder devices which are suitable for use in the present invention include a bluff body, a V-gutter, a cone, a perforated plate and a swirler, each of which may be inserted into the homogeneous combustion zone immediately downstream from the outlet end of the catalyst structure.
  • the flameholder or combination of flameholders employed suitably provide a geometric flow blockage in the homogeneous combustion zone of from about 5 to about 90 percent, with geometric flow blockages in the range of about 20 to about 70 percent being preferred.
  • the positioning of the flameholder in the homogeneous combustion zone will depend on. a variety of factors including the temperature of the partially-combusted gas at the catalyst structure outlet, -the F/A ratio of the fuel mixture, the gas flow rate, the type of fuel being combusted, the percent combustion occurring in the catalyst structure and the intensity of mixing or extent of gas recirculation obtained using the flameholder.
  • the flameholder will be positioned at a point in the homogeneous combustion zone downstream of the catalyst structure outlet such that the average residence time of the partially-combusted fuel in the region of recirculation created by the flameholder approximates the ignition delay time for the specific gas mixture and gas temperature present in the homogeneous combustion zone.
  • the flameholder will be positioned from about 0.1 to about 50 cm downstream from the outlet end of the catalyst structure and preferably from about 0.5 to about 20 cm downstream from the catalyst structure outlet.
  • the theoretical adiabatic combustion temperature or Tad of the fuel/air mixture fed to the catalyst structure is typically between about 900 to 1000°C and, preferably, in the low end of that range, for example, 900 to 1300°C.
  • the advantage achieved by the flameholder in stabilizing combustion in the homogeneous combustion zone is most apparent when between about 20 and 70 percent of the fuel in the combustible mixture is combusted in the catalyst structure to afford an outlet temperature for the partially-combusted, gaseous mixture flowing out of the outlet end of the catalyst structure of between about 700 and about 1000°C.
  • FIGS. 1 and 2 depict end views of repeating units of two conventional catalyst structures employing integral heat exchange.
  • the repeating units shown would appear in a stacked or layered pattern in the complete catalyst structure.
  • the support is made up of two metallic sheets or strips one (10) having an undulating or wavy corrugation pattern and the other (12) being flat.
  • the crests and valleys formed by the corrugation extend in a longitudinal direction over the width of the sheet and nest against the flat sheets both above and below the corrugated sheet to form straight longitudinal channels (14 and 16) which extend over the width of the stacked or nesting sheets.
  • the undulating or sinusoidal corrugation pattern shown here is only representative.
  • the corrugation can be sinusoidal, triangular, or any other conventional structure.
  • the bottom side of the undulating sheet (10) and the top side of the flat sheet (12) are coated with catalyst or washcoat plus catalyst (18) such that when the sheets are stacked together as shown, channels coated with catalyst (14) are in integral heat exchange with channels not coated with catalyst (16).
  • the catalytic channels (14) and non-catalytic channels (16) formed are essentially straight and of unaltered cross-sectional area.
  • This structure provides catalytic and non-catalytic channels wherein the ratio of the average D h of the catalytic channels to average D h of the non-catalytic channels is 1 and the h(cat)/h(non-cat) ratio is also 1.
  • the repeating unit shown in FIG. 2 is comprised of two corrugated metallic sheets (20 and 22) having a herringbone corrugation pattern extending in a longitudinal direction over the length of the sheets.
  • One of the corrugated sheets (22) is coated with catalyst (24) on its top side while the other corrugated sheet is coated with catalyst on its bottom side such that when the sheets are stacked together in non-nesting fashion a catalyst-coated channel (26) is formed in integral heat exchange with a catalyst-free channel (28).
  • FIG. 3 shows further detail of the metallic sheets having herringbone corrugation pattern which are suitably employed in the structure shown in FIG. 2 above or in structures of the invention when herringbone corrugations are used to induce tortuosity into the catalytic channels.
  • the sheet is corrugated to form peaks (30) and valleys (32) which in turn form the herringbone pattern along the width of the sheet.
  • the triangular corrugation pattern shown in FIGS. 2 and 3 is only for representation.
  • the corrugation can be triangular, sinusoidal or any other corrugated structure envisioned in the art.
  • FIGS. 3A, 3B and 3C show cross-sectional views of the repeating unit taken from the end view (FIG. 3A - which is the same as FIG. 2) and at incremental points on the longitudinal axis of the channels (FIGS. 3B and 3C) where the different directional orientations of the stacked herringbone corrugations cause the peaks and valleys formed by the corrugations in each sheet to change position relative to the position of the peaks and valleys of the corrugated sheet directly above and below it in the repeating unit.
  • FIG. 3A - which is the same as FIG. 2
  • FIGS. 3B and 3C show cross-sectional views of the repeating unit taken from the end view (FIG. 3A - which is the same as FIG. 2) and at incremental points on the longitudinal axis of the channels (FIGS. 3B and 3C) where the different directional orientations of the stacked herringbone corrugations cause the peaks and valleys formed by the corrugations in each sheet to change position relative to the position of the
  • the channels, both catalytic (26) and non-catalytic (28) have a repeating V-shaped cross-section wherein FIG. 3B the change in channel wall orientation caused by different directional orientations in the peaks and valleys of adjacent herringbone patterned corrugations results in channels (26 and 28) which are rectangular in cross-sectional area.
  • the catalytic channels (26) and non-catalytic channels (28) have a diamond shaped cross-sectional area.
  • this pattern of changing cross-sectional shape of the channels will repeat itself over and over along the entire length of the channel defined by the non-nesting herringbone corrugations.
  • the structure shown in FIG. 2 provides catalytic and non-catalytic channels wherein the average D h of the catalytic channels is equal to the average D h of the non-catalytic channels and where the h(cat)/h(non-cat) ratio is equal to 1.
  • FIG. 4 represents an end view of a repeating unit of a catalyst structure of the invention wherein a series of metallic sheets of various configurations are employed in a stacked pattern to afford catalytic channels which differ in configuration from the non-catalytic channels in accordance with the invention.
  • This repeating unit is made up of a combination of two flat sheets (40), one corrugated sheet (42) a straight corrugation pattern forming straight channels, and two corrugated sheets (44) having herringbone corrugation pattern.
  • Catalytic channels (46) and non-catalytic channels (48) are formed by selectively coating one side of the two flat sheets and one side of one of the corrugated sheets with catalyst (50).
  • non-catalytic channels are formed from the stacking of the flat sheets with the straight channel sheet to provide large opened channels.
  • the catalytic channels are formed from herringbone corrugation foils or sheets stacked in non-nesting fashion between two flat sheets such that channels having tortuous flow paths and smaller D h are provided by the structure.
  • This structure having the dimensions given in Example 2, below, provides catalytic and non-catalytic channels wherein the ratio of average D h of the catalytic channels to the average D h of the non-catalytic channels is 0.66 and the h(cat)/h(non-cat) ratio is 2.53. In that case, the ratio of heat transfer area between catalyst-coated and catalyst-free channels divided by the total channel volume in the structure is 0.30 mm -1 .
  • FIG. 5 depicts a preferred catalyst structure according to the invention by means of an end view of the repeating unit which is stacked to form the catalyst structure.
  • This repeating unit is made up of three different types of corrugated metallic sheet (52, 54a and 54b).
  • the first type of corrugated sheet (52) is essentially a flat sheet in which the extended flat regions are separated periodically by sharp peaked corrugations with the peaked corrugations extending straight across the foil forming a straight corrugation pattern.
  • the second type of corrugated sheet (54a and 54b) is made up of a series of corrugations in the herringbone pattern.
  • two of the herringbone corrugated sheets are stacked in non-nesting fashion on top of the sheet having wide regions of flat sheet separated by sharp peaked corrugations.
  • a second flat sheet with sharp peaked corrugations is stacked on top of the top corrugated sheet in the non-nesting corrugated herringbone pattern stack.
  • Catalyst (56) is coated on the bottom of each of the flat sheets with sharp peaked corrugations and on the top of the bottom corrugated herringbone pattern sheet thereby forming catalytic channels (58a and 58b) having small hydraulic diameters and tortuous flow channels and non-catalytic channel (60) which is a larger more open channel of substantially straight configuration.
  • the ratio of the average D h of the catalytic channels to the average D h of the non-catalytic channels is 0.41 while the h(cat)/h(non-cat) ratio is 1.36. Further, the ratio of heat transfer area between catalytic and non-catalytic channels, divided by the total channel volume in this preferred structure having the dimensions given in Example 3, is 0.74.
  • the preferred structure depicted in FIG. 5 can be readily modified to increase the number and tortuosity of the catalytic channels by inserting additional corrugated sheets having a herringbone corrugation pattern between the two flat sheets with sharp peaked corrugations. If additional corrugated sheets are inserted in the repeat unit (stacked in non-nesting fashion with the two sheets shown in the Figure) they can be coated on one side of the other or remain uncoated depending on the catalyst structure desired.
  • FIG. 6 illustrates the repeat unit of another catalyst structure of the invention viewed from its inlet end.
  • the support is made up of two essentially flat metallic sheets (62) wherein the horizontal flat regions are periodically divided by vertical strips to form large open regions and three corrugated metallic sheets having a herringbone corrugation pattern (64, 66 and 68) which are stacked in non-nesting fashion between the two essentially flat sheets.
  • These three corrugated sheets differ in the severity of the corrugations, that is, the number of corrugations per unit of width, with the top and middle corrugated sheets (64 and 66) having a more severe corrugation pattern than the bottom corrugated sheet (68).
  • the catalyst (70) is coated on the bottom of the two essentially flat sheets (62) and on the bottom of the top corrugated sheet (64) and top of the bottom corrugated sheet (68) with the result being as large open non-catalytic channel (72) which is essentially straight in configuration and three catalytic channels (74, 76 and 78) which have very small average D h 's and configurations which create tortuous flow paths.
  • sheet (62) has a height of 1.6 mm and a flat region of 3.3 mm; sheet (68) has a height of 0.41 mm and a peak-to-peak period of 0.66 mm; sheet (66) has a height of 1.1 mm and a peak-to-peak period of 0.33 mm; and sheet (64) has a height of 0.69 mm and a peak-to-peak period of 0.31 mm, the ratio of average D h of the catalytic channels to average D h of the non-catalytic channels is 0.15 and the h(cat)/h(non-cat) ratio is 2.72. In this case the ratio of heat transfer area between the catalyst-coated and catalyst-free channels divided by the total channel volume in the structure is 0.91 mm -1 .
  • FIGS. 7 and 8 show end views of repeat units for the structures which are depicted.
  • corrugated metal sheets (80 and 82) having a herringbone corrugation pattern are stacked in non-nesting fashion between a corrugated metal sheet (84) having crests and valleys extending in a longitudinal straight direction over the length of the sheet.
  • Catalyst (86) is coated on the bottom of the top corrugated sheet (80) and the top of the bottom corrugated sheet (82) such that catalytic channels (88) of small average D h and significant tortuosity are formed in integral heat exchange with larger more open catalyst-free channels (90) which present essentially straight flow channels.
  • FIG. 8 three corrugated metallic sheets (92, 94 and 96), having a herringbone corrugation pattern are stacked in non-nesting fashion between a straight channel corrugated metal sheet (98) of similar configuration to the corrugated sheet used in the structures of FIG. 7.
  • Catalyst (100) is coated on the bottom of the top corrugated sheet (92) and the top of the bottom corrugated sheet (96) to form catalyst-coated channels (102) having a small average D h and tortuous flow paths in heat exchange relationship with larger, open catalyst-free channels (104) which have essentially straight flow paths.
  • FIGS. 9 and 10 depict schematic representations of the reaction system according to the invention wherein the homogeneous combustion zone downstream of the catalyst structure is equipped with a flameholder to stabilize combustion of a partially-combusted fuel/air mixture within the homogeneous combustion zone.
  • FIG. 9 depict schematic representations of the reaction system according to the invention wherein the homogeneous combustion zone downstream of the catalyst structure is equipped with a flameholder to stabilize combustion of a partially-combusted fuel/air mixture within the homogeneous combustion zone.
  • the reaction system is made up of a combustor (110) containing a catalytic section or zone (112) and a homogeneous combustion zone (114) with the fuel/air mixture (116) being fed to the inlet end of the catalytic section where partial combustion of the fuel occurs in the presence of the catalyst to afford a heated, partially-combusted, gaseous mixture which flows from the outlet end of the catalytic-section through the homogeneous combustion zone where the residual fuel is completely combusted under non-catalytic conditions.
  • a hemispherical disk flameholder (118) is positioned in the homogeneous combustion zone immediately downstream of the catalytic section outlet such that some portion of the heated, partially-combusted, gaseous mixture flowing past the hemispherical disk flameholder is recirculated in the region of the homogeneous combustion zone just downstream of the flameholder and non-catalytic combustion is stabilized in the region of recirculation.
  • FIG. 10 similarly shows combustor (120) comprised of a catalytic section (122) and a homogeneous combustion zone (124) downstream of the catalytic section with the fuel/air mixture (126) being introduced into the inlet end of the-catalytic section.
  • the flameholder (128) positioned immediately downstream of the catalytic section is a V-gutter flameholder which effects recirculation of the heated, partially-combusted, gaseous mixture leaving the catalytic section in a manner similar to that obtained with the hemispherical disk flameholder described above.
  • the catalytic section can be any catalytic structure employing integral heat exchange including the structures described in U.S. Patent No. 5,250,489 but preferably is one of the improved catalyst structures of the present invention which are described in detail above.
  • temperature sensors can be positioned at various points downstream of the flameholder to monitor the temperature profile of the hot gases in the homogeneous combustion zone.
  • FIGS. 11A through 14B show a cone-type flameholder (130) affixed to the sidewall of the homogeneous combustion zone (132) via support struts or bars (134).
  • FIGS 14A and 14B show a swirler-type flameholder having a series of swirl vanes (160), which are secured inside the sidewall of the homogeneous combustion zone (162) via support plates or bars (164) and bluff body (166) which may be solid or a hollow shell.
  • a SiO 2 /ZrO 2 powder was prepared by first mixing 20.8 g of tetraethylorthosilicate with 4.57 cc of 2 mM nitric acid and 12.7 g of ethanol. The mixture was added to 100 g of zirconia powder having a specific surface are of 100 m 2 /gm. The resulting solid was aged in a sealed glass container for about a day and dried. One portion was calcined in air at 500°C and another portion was calcined in air at 1000°C.
  • a sol was prepared by mixing 152 g of the SiO 2 /ZrO 2 powder calcined at 1000°C and 15.2 g of the SiO 2 /ZrO 2 powder calcined at 500°C with 3.93 g of 98% H 2 SO 4 and 310 cc of distilled water. This mixture was milled using ZrO 2 grinding media for eight hours to product a SiO 2 /ZrO 2 sol.
  • a Fe/Cr/Al alloy (Fe/20%Cr/5%Al) foil strip 76 mm wide was corrugated in a herringbone pattern to a corrugation height of 1.20 mm and a peak to peak period of 2 mm and the herringbone pattern had channel lengths of 20 mm and a channel angle of 6° and forms a monolithic structure with about 185 cells per square inch.
  • This foil was heat treated in air at 900°C to form a rough oxide coated surface.
  • the SiO 2 /ZrO 2 sol was sprayed onto one side of the herringbone corrugated foil to a thickness of about 40 micrometers and the coated foil calcined in air at 950°C.
  • Pd(NH 3 ) 2 (NO 2 ) 2 and Pt(NH 3 ) 2 (NO 2 ) 2 was dissolved in water and an excess of nitric acid to form a solution containing about 0.1 g Pd/ml and a Pd/Pt ratio of 6; this solution was sprayed onto the SiO 2 /ZrO 2 coated corrugated to form a final Pd loading of about 0.25 g Pd/g of SiO 2 /ZrO 2 and calcined in air at 950°C.
  • a strip of the above foil was folded against itself to place the catalyzed side of the foil facing itself and the structure rolled to form a spiral monolithic structure of 50 mm diameter.
  • This catalyst (rolled into a spiral wound structure with 50 mm diameter) was installed in the test rig described above. Thermocouples were installed to measure the substrate temperature and to measure temperatures of the gas downstream of the catalyst. In addition, a water-cooled gas sampling probe was installed in the reactor to measure the composition of the gas stream at the position 25 cm downstream of the catalyst.
  • the test sequence was as follows:
  • indolene clear gasoline was used as the fuel. This is a standard unleaded regular gasoline used for emissions qualification.
  • the fuel was injected into the main flow stream of heated air through a spray nozzle and vaporized prior to passing through the static mixer to form a uniform fuel/air mixture at the catalyst inlet. Fuel and air flow was continuously measured in real time and controlled through automatic feedback control.
  • this catalyst At idle conditions, this catalyst will operate at a F/A ratio equivalent to an adiabatic combustion temperature of 1150°C over an inlet temperature range of 230 to 400°C. At 1200°C Tad, this inlet temperature range has narrowed to 220-260°C and at 1250°C the catalyst will not operate without overheating.
  • this catalyst system operates reasonably well with an operating range of 540 to >620°C at 1200°C Tad, and 420 to 570°C at 1300°C.
  • This catalyst system does not have a wide operating range at idle and cannot be used in a turbine that must operate from idle to full load, unless the fuel/air ratio is controlled to a very narrow range.
  • the catalyst structure shown in FIG. 4 was evaluated using the same fuel as employed in Example 1.
  • the straight channel corrugation had a corrugation height of 1.65 mm and was approximately triangular with a peak-to-peak period of 3.90 mm.
  • the herringbone corrugation foils were similar to that described in Example 1, except the foils had height of 0.76 mm and 0.91 mm and peak-to-peak period of 1.84 and 2.45 for the two foils.
  • the catalytic coating (Pd-Pt/SiO 2 /ZrO 2 ) was prepared and applied as described in Example 1. The performance of this catalyst structure using the same procedure described in Example 1 is shown in Table 2.
  • This unit has substantially better performance at idle than the catalyst of Example 1. At these very low air flow rates, the catalyst substrate does not overheat so readily. However, the operating window at full load has decreased and the unit does not provide the inlet temperature operating range at 1200 and 1300°C Tad required for optimum performance. Clearly, the use of open and large non-catalytic channels allows the catalyst to operate better at very low mass velocities but this particular design appears to have limited heat exchange between the catalytic channels and the non-catalytic channels. This results in a low outlet gas temperature from the catalyst at high mass flows and less than optimum performance at full load conditions.
  • the catalyst structure of FIG. 5 was prepared and tested according to the procedures described in Example 1.
  • the herringbone corrugation foils were similar to that described in Example 1, except the foils had heights of 0.76 mm and 1.2 mm and pitches of 1.84 and 2.90 and a chevron angle of 6° for the two herringbone foils and the straight corrugation peaked foil had a height of 1.63 mm, a peak-to-peak period of 4.52 mm and a flat region length of 3.7 mm.
  • the catalyst was Pd-Pt/SiO 2 /ZrO 2 prepared in accordance with Example 1, and it was applied as shown in FIG. 5. The operating window conditions and test results are shown below using the Indolene Clear gasoline in Table 3.
  • the catalyst structure has very wide operating windows at both idle and full load condition. At idle, this catalyst can operate over an inlet temperature range of 160°C at 1200°C Tad and over a range of 210°C at 1300°C Tad. At full load the range is >50°C at 1200°C. These operating windows are sufficient Tad and is >50°C at 1200°C Tad and >150°C at 1300°C. These operating windows are sufficient to make this catalyst system viable for use in a practical gas turbine.
  • Example 3 can operate from 1200 to 1300°C Tad range at both idle and full load while the conventional catalyst of Example 1 could only operate from 1150°C to 1200°C Tad and only over very narrow catalyst inlet temperatures at idle.
  • the conventional technology of Example 1 would require very narrow control of fuel/air ratio which may be very difficult and costly.
  • the technology of Example 3 has much broader operating windows and would permit more easy practical application. The operating. range at full load was nearly as wide for the catalyst of Example 3 compared to Example 1.
  • a reaction system as illustrated in FIGS. 9 and 10 was set up using a hemispherical disk flameholder (FIG. 9) or a V-gutter flameholder (FIG. 10) and using the general procedure set forth in Example 1 (including catalyst preparation) the flameholder equipped reaction systems were compared to the same reaction system minus a flameholder in the catalytic combustion of indolene gasoline.
  • the catalyst structure employed was the improved catalyst structure of the invention as depicted in FIG. 5 hereto and temperature sensors were placed downstream of the flameholders or in a similar location in the case where no flameholder was used.
  • the reaction system minus the flameholder will be referred to as Configuration 1
  • the system equipped with the hemispherical disk flameholder and the V-gutter flameholder will be designated as Configurations 2 and 3, respectively.
  • FIGS. 15 and 6 show the temperature of the gas at a position just downstream of the catalyst or flameholder, as measured by the temperature sensor.
  • the temperature profile for these tests show the following:
  • FIG. 15 For the catalyst only, Configuration 1, the gas temperature is relatively low and increased linearly as the fuel/air mixture (adiabatic combustion temperature) is increased. There is no homogeneous combustion of the fuel/air mixture up to the 7 cm post-catalyst position for this catalyst design and gas velocity. Homogeneous combustion is occurring at some position downstream of the 7 cm temperature sensor.
  • FIG. 16 compares the catalyst only, Configuration 1, with the catalyst plus V-gutter flameholder, Configuration 3. Again, the flameholder makes the combustion wave appear at much lower Tad values, in the case of the V-gutter flameholder, it appears at 100°C to 1150°C Tad at a 500°C inlet temperature.

Claims (24)

  1. Système de réaction pour combustion d'un mélange combustible de carburant et d'un gaz contenant de l'oxygène, dans lequel un flux d'écoulement du mélange combustible, sous forme de vapeur ou de gaz, est soumis initialement à une combustion partielle en présence d'un catalyseur, suivie par une combustion complète dans des conditions non-catalytiques dans une zone de combustion homogène située en aval du catalyseur, comportant :
    (a) une structure de catalyseur réalisée en un matériau de support résistant à la chaleur, constituée d'une pluralité de parois communes qui forment une multitude de canaux longitudinaux disposés de manière adjacente pour le passage du mélange combustible, dans laquelle au moins une partie de la surface intérieure d'une partie des canaux est revêtue de catalyseur pour le mélange combustible, et la surface intérieure des canaux restants n'est pas revêtue de catalyseur, de telle sorte que la surface intérieure des canaux revêtus de catalyseur est dans une relation d'échange thermique avec la surface intérieure des canaux sans catalyseur adjacents, et dans laquelle les canaux revêtus de catalyseur ont une configuration qui forme un passage d'écoulement plus tortueux pour le mélange réactionnel que le passage d'écoulement formé par les canaux sans catalyseur, de telle sorte que seule une partie du mélange combustible subit une combustion pour permettre à un mélange gazeux partiellement brûlé de s'écouler à température élevée à partir de l'extrémité de sortie de la structure de catalyseur,
    (b) une zone de combustion homogène comportant un espace clos en communication de fluide avec la structure de catalyseur, et positionnée immédiatement en aval de l'extrémité de sortie de la structure de catalyseur, et
    (c) des moyens pour provoquer une remise en circulation dans le mélange partiellement brûlé s'écoulant à travers la zone de combustion homogène, de sorte qu'une combustion homogène du mélange partiellement brûlé est stabilisée dans la zone de remise en circulation, et une combustion complète du mélange partiellement brûlé est favorisée dans la zone de combustion homogène.
  2. Système de réaction selon la revendication 1, dans lequel les canaux revêtus de catalyseur de la structure de catalyseur sont modifiés périodiquement par l'intermédiaire d'un changement de surface en coupe, d'un changement de direction le long de l'axe longitudinal des canaux, ou d'une combinaison des deux changements de surface en coupe et de direction le long de leur axe longitudinal, de telle sorte que la direction d'écoulement d'au moins une partie du mélange réactionnel gazeux dans les canaux revêtus d'un catalyseur est modifiée au moins partiellement au niveau d'une pluralité de points lorsque le mélange réactionnel gazeux passe à travers les canaux revêtus de catalyseur, tandis que les canaux sans catalyseur sont pratiquement rectilignes et ont une surface en coupe non modifiée le long de leur axe longitudinal, de telle sorte que la direction d'écoulement du mélange réactionnel gazeux à travers les canaux sans catalyseur est pratiquement inchangée.
  3. Système de réaction selon la revendication 2, dans lequel les canaux revêtus de catalyseur ont une surface en coupe modifiée par l'intermédiaire d'une incurvation répétée vers l'intérieur et vers l'extérieur des parois de canaux le long de l'axe longitudinal des canaux, ou par l'intermédiaire de l'utilisation de volets, de déflecteurs ou d'autres obstacles positionnés au niveau d'une pluralité de points le long de l'axe longitudinal des canaux, pour obstruer partiellement la direction d'écoulement de mélange réactionnel gazeux.
  4. Système de réaction selon la revendication 3, dans lequel les canaux revêtus de catalyseur ont une surface en coupe modifiée par l'intermédiaire de l'incurvation répétée vers l'intérieur et vers l'extérieur des parois des canaux revêtus de catalyseur, qui est accomplie à l'aide de canaux revêtus d'un catalyseur qui sont ondulés selon un motif de chevrons en utilisant des feuilles ondulées empilées d'une manière sans emboítement.
  5. Système de réaction selon la revendication 4, dans lequel les canaux revêtus de catalyseur et les canaux sans catalyseur sont formés par l'intermédiaire d'une structure à trois couches se répétant, constituée d'une première couche en feuille ondulée munie de pics longitudinaux séparés par des zones plates, empilées, sur une deuxième couche constituée de feuille ondulée dans laquelle les ondulations ont la forme de crêtes et de vallées longitudinales adjacentes, ces crêtes et vallées formant un motif en chevrons le long de la longueur de la feuille constituant la deuxième couche, la deuxième couche étant empilée d'une manière sans emboítement sur une troisième couche constituée de feuille métallique ondulée dans laquelle les ondulations ont la forme de crêtes et de vallées longitudinales adjacentes, les crêtes et les vallées formant un motif en chevrons le long de la longueur de la feuille constituant la troisième couche, et le catalyseur pour le mélange réactionnel étant sous forme de revêtement sur le côté inférieur de la première couche et sur le côté supérieur de la troisième couche, de telle sorte que des canaux sans catalyseur sont formés lorsque la première couche de la structure se répétant est établie en dessous de la troisième couche de la structure à trois couches se répétant adjacente suivante selon un motif empilé, et des canaux revêtus de catalyseur sont formés entre la partie inférieure de la première couche et la partie supérieure de la deuxième couche, et entre la partie inférieure de la deuxième couche et la partie supérieure de la troisième couche de la structure à trois couches se répétant.
  6. Système de réaction selon la revendication 1, dans lequel :
    (i) les canaux revêtus de catalyseur ont un diamètre hydraulique moyen (Dh) plus petit que les canaux sans catalyseur, et
    (ii) les canaux revêtus de catalyseur ont un coefficient de transfert thermique de film (h) plus élevé que les canaux sans catalyseur.
  7. Système de réaction selon la revendication 6, dans lequel les canaux revêtus de catalyseur ont un coefficient de transfert thermique de film (h) qui est plus de 1,5 fois plus grand que le h des canaux sans catalyseur, et les canaux revêtus de catalyseur représentent d'environ 20 % à environ 80 % de la surface frontale ouverte totale de la structure de catalyseur.
  8. Système de réaction pour combustion d'un mélange combustible de carburant et d'un gaz contenant de l'oxygène, dans lequel un flux d'écoulement du mélange combustible, sous forme de vapeur ou de gaz, est soumis initialement à une combustion partielle en présence d'un catalyseur, suivie par une combustion complète dans des conditions non-catalytiques dans une zone de combustion homogène située en aval du catalyseur, comportant :
    (a) une structure de catalyseur réalisée en matériau de support résistant à la chaleur, constituée d'une pluralité de parois communes qui forment une multitude de canaux longitudinaux disposés de manière adjacente pour le passage du mélange combustible, dans laquelle au moins une partie de la surface intérieure d'une partie des canaux est revêtue de catalyseur pour le mélange combustible, et la surface intérieure des canaux restants n'est pas revêtue de catalyseur, de telle sorte que la surface intérieure des canaux revêtus de catalyseur est dans une relation d'échange thermique avec la surface intérieure des canaux sans catalyseur adjacents, et dans laquelle les canaux revêtus d'un catalyseur ont un diamètre hydraulique moyen (Dh) plus petit que les canaux sans catalyseur, et le rapport numérique de Dh moyen des canaux revêtus de catalyseur divisé par le Dh moyen des canaux sans catalyseur est inférieur au rapport numérique de la surface frontale ouverte des canaux revêtus de catalyseur divisée par la surface frontale ouverte des canaux sans catalyseur, de telle sorte que seule une partie du mélange combustible subit une combustion pour permettre à un mélange gazeux partiellement brûlé de s'écouler à une température élevée à partir de l'extrémité de sortie de la structure de catalyseur,
    (b) une zone de combustion homogène comportant un espace clos en communication de fluide avec la structure de catalyseur, et positionnée immédiatement en aval de l'extrémité de sortie de la structure de catalyseur, et
    (c) des moyens pour provoquer une remise en circulation dans le mélange partiellement brûlé s'écoulant à travers la zone de combustion homogène, de sorte qu'une combustion complète du mélange partiellement brûlé est stabilisée dans la zone de remise en circulation, et une combustion complète du mélange partiellement brûlé est favorisée dans la zone de combustion homogène.
  9. Système de réaction selon la revendication 8, dans lequel les canaux revêtus de catalyseur ont un coefficient de transfert thermique de film (h) plus élevé que les canaux sans catalyseur.
  10. Système de réaction selon l'une quelconque des revendications 1 à 9, dans lequel les moyens pour provoquer une remise en circulation dans l'écoulement de mélange partiellement brûlé sont constitués d'un porte-flamme positionné en aval de l'extrémité de sortie de la structure de catalyseur.
  11. Système de réaction selon la revendication10, dans lequel le porte-flamme est sélectionné parmi un corps non-profilé, une gouttière en forme de V, un cône, une plaque perforée, un dispositif de tourbillonnement ou des moyens pour modifier la surface en coupe de la zone de combustion homogène dans la direction d'écoulement de gaz partiellement brûlé, ou une combinaison quelconque de ceux-ci.
  12. Système de réaction selon la revendication 11, dans lequel le porte-flamme est positionné entre environ 0,2 et environ 20 cm en aval de l'extrémité de sortie de la structure de catalyseur.
  13. Système de réaction selon la revendication 12, dans lequel le porte-flamme fournit un blocage d'écoulement géométrique dans la zone de combustion homogène d'environ 10 à environ 70 %.
  14. Système de réaction selon la revendication 12, dans lequel entre environ 10 et environ 70 % du carburant du mélange combustible est brûlé dans la structure de catalyseur.
  15. Système de réaction selon la revendication 12, dans lequel entre environ 20 et environ 70 % du carburant du mélange de combustible est brûlé dans la structure de catalyseur.
  16. Système de réaction selon la revendication 14 ou 15, dans lequel la température du mélange gazeux partiellement brûlé s'écoulant vers l'extérieur de l'extrémité de sortie de la structure de catalyseur est comprise entre environ 700 et 1000°C.
  17. Procédé pour la combustion d'un mélange combustible comportant les étapes consistant à :
    (a) mélanger un carburant et un gaz contenant de l'oxygène pour former un mélange combustible,
    (b) mettre en contact le mélange avec un support de catalyseur résistant à la chaleur constitué d'une pluralité de parois communes qui forment une multitude de canaux longitudinaux disposés de manière adjacente pour le passage du mélange combustible, dans lesquels au moins une partie de la surface intérieure d'une partie des canaux est revêtue d'un catalyseur pour le mélange combustible, et la surface intérieure des canaux restants n'est pas revêtue de catalyseur, de telle sorte que la surface intérieure des canaux revêtus de catalyseur est dans une relation d'échange thermique avec la surface intérieure de canaux sans catalyseur adjacents, et dans lesquels les canaux revêtus de catalyseur ont un coefficient de transfert de chaleur de film (h) plus élevé que les canaux sans catalyseur, les canaux revêtus de catalyseur ont un diamètre hydraulique moyen Dh plus petit que les canaux sans catalyseur, et les canaux revêtus de catalyseur forment un passage d'écoulement plus tortueux pour le mélange combustible que le passage d'écoulement formé par les canaux sans catalyseur, en brûlant ainsi une partie du mélange combustible pour donner un mélange gazeux partiellement brûlé, et
    (c) faire passer le mélange gazeux partiellement brûlé vers une zone de combustion homogène munie d'un porte-flamme pour effectuer une remise en circulation d'au moins une partie du mélange partiellement brûlé, de telle sorte qu'une combustion homogène est stabilisée dans la zone de remise en circulation, et qu'une combustion sensiblement complète du mélange partiellement brûlé est obtenue.
  18. Procédé pour la combustion d'un mélange combustible, comportant les étapes consistant à :
    (a) mélanger un carburant et un gaz contenant de l'oxygène pour former un mélange combustible,
    (b) mettre en contact le mélange avec un support de catalyseur résistant à la chaleur constitué d'une pluralité de parois communes qui forment une multitude de canaux longitudinaux disposés de manière adjacente pour le passage du mélange combustible, dans lesquels au moins une partie de la surface intérieure d'une partie des canaux est revêtue de catalyseur pour le mélange combustible, et la surface intérieure des canaux restants n'est pas revêtue de catalyseur, de telle sorte que la surface intérieure des canaux revêtus de catalyseur est dans une relation d'échange thermique avec la surface intérieure de canaux sans catalyseur adjacents, et dans lesquels les canaux revêtus de catalyseur ont un coefficient de transfert de chaleur de film (h) plus élevé que les canaux sans catalyseur, les canaux revêtus de catalyseur ont un diamètre hydraulique moyen Dh plus petit que les canaux sans catalyseur, et le rapport numérique de Dh moyen des canaux revêtus de catalyseur divisé par le Dh moyen des canaux sans catalyseur est inférieur au rapport numérique de la surface frontale ouverte des canaux revêtus de catalyseur divisée par la surface frontale ouverte des canaux sans catalyseur, de sorte qu'une partie du mélange combustible est brûlée pour donner un mélange gazeux partiellement brûlé, et
    (c) faire passer le mélange gazeux partiellement brûlé vers une zone de combustion homogène munie d'un porte-flamme pour effectuer une remise en circulation d'au moins une partie du mélange partiellement brûlé, de telle sorte qu'une combustion homogène est partiellement stabilisée dans la zone de remise en circulation, et qu'une combustion pratiquement complète du mélange partiellement brûlé est obtenue.
  19. Procédé selon la revendication 17 ou 18, dans lequel la surface superficielle de transfert thermique entre les canaux revêtus de catalyseur et les canaux sans catalyseur divisée par le volume de canal total dans la structure est supérieure à environ 0,5 mm-1.
  20. Procédé selon la revendication 17 ou 18, dans lequel le porte-flamme est sélectionné parmi un corps non-profilé, une gouttière en forme de V, un cône, une plaque perforée, un dispositif de tourbillonnement ou des moyens pour modifier la surface en coupe de la zone de combustion homogène dans la direction de l'écoulement de gaz partiellement brûlé, ou une combinaison quelconque de ceux-ci.
  21. Procédé selon la revendication 20, dans lequel le porte-flamme est positionné entre environ 0,2 et environ 20 cm en aval de l'extrémité de sortie de la structure de catalyseur.
  22. Procédé selon la revendication 21, dans lequel le support de flamme fournit un blocage d'écoulement géométrique dans la zone de combustion homogène d'environ 10 à environ 70 %.
  23. Procédé selon la revendication 22, dans lequel entre environ 10 et environ 70 % du carburant du mélange combustible est brûlé dans la structure de catalyseur.
  24. Procédé selon la revendication 23, dans lequel la température du mélange gazeux partiellement brûlé s'écoulant vers l'extérieur de l'extrémité de sortie de la structure de catalyseur est comprise entre environ 700 et 1000°C.
EP95911772A 1994-03-02 1995-02-28 Procede et structure catalytiques ameliores assurant un echange thermique integral avec eventuellement une flamme entretenue en aval Expired - Lifetime EP0745180B1 (fr)

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US08/205,279 US5512250A (en) 1994-03-02 1994-03-02 Catalyst structure employing integral heat exchange
US205279 1994-03-02
US08/378,206 US5518697A (en) 1994-03-02 1995-01-25 Process and catalyst structure employing intergal heat exchange with optional downstream flameholder
US378206 1995-01-25
PCT/US1995/001989 WO1995023915A1 (fr) 1994-03-02 1995-02-28 Procede et structure catalytiques ameliores assurant un echange thermique integral avec eventuellement une flamme entretenue en aval

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AU1921495A (en) 1995-09-18
EP0745180A4 (fr) 1998-02-18
EP0745180A1 (fr) 1996-12-04
ATE215669T1 (de) 2002-04-15
CN1147288A (zh) 1997-04-09
CA2184752A1 (fr) 1995-09-08
WO1995023915A1 (fr) 1995-09-08
DE69526212T2 (de) 2004-03-25
JPH10501052A (ja) 1998-01-27
JP3705299B2 (ja) 2005-10-12
DE69526212D1 (de) 2002-05-08

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