US20070125282A1 - METHODS AND SYSTEMS FOR REDUCED NOx COMBUSTION OF COAL WITH INJECTION OF HEATED NITROGEN-CONTAINING GAS - Google Patents

METHODS AND SYSTEMS FOR REDUCED NOx COMBUSTION OF COAL WITH INJECTION OF HEATED NITROGEN-CONTAINING GAS Download PDF

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US20070125282A1
US20070125282A1 US11/563,374 US56337406A US2007125282A1 US 20070125282 A1 US20070125282 A1 US 20070125282A1 US 56337406 A US56337406 A US 56337406A US 2007125282 A1 US2007125282 A1 US 2007125282A1
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containing gas
nitrogen
oxygen
gas
coal
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US11/563,374
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Rajani Varagani
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Priority to US11/563,374 priority Critical patent/US20070125282A1/en
Priority to JP2008542852A priority patent/JP2009517626A/ja
Priority to AU2006321344A priority patent/AU2006321344A1/en
Priority to EP06831594A priority patent/EP1957868A1/fr
Priority to CA002631898A priority patent/CA2631898A1/fr
Priority to KR1020087016098A priority patent/KR20080084998A/ko
Priority to PCT/IB2006/003366 priority patent/WO2007063386A1/fr
Publication of US20070125282A1 publication Critical patent/US20070125282A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D1/00—Burners for combustion of pulverulent fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L7/00—Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam
    • F23L7/007—Supplying oxygen or oxygen-enriched air
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Definitions

  • NOx generally refers to nitrogen monoxide NO and nitrogen dioxide NO2. Both are major contributors to acid rain and smog (ground level ozone) issues.
  • the NOx partition in the flue gases of pulverized coal boilers is typically more than 95% NO and the remainder NO2 (Mitchell S. C., NOx in Pulverized Coal Combustion, IEA Clean Coal Center Report CCC/05, 1998).
  • the NOx production originates from three different mechanisms:
  • NOx In pulverized coal boilers, 70% to 80% of NOx is formed from the fuel-bound nitrogen species (ftiel-N) via the fuel-NOx mechanism, and the remaining NOx is formed from atmospheric nitrogen (N2), via the thermal-NOx mechanism (5-25%) and via the prompt-NOx mechanism (less than 5%) (Wu Z., NOx controlfor pulverized coal-fired power stations, IEA Clean Coal Center Report CCC/69, 2002). Understanding and limiting the NOx formation in pulverized coal combustion is therefore strongly related to the fuel-N conversion mechanism. A complex series of reactions explains the transformation of coal bound fuel-nitrogen into NOx or N2, including more than 50 intermediate species and hundreds of reactions.
  • Coal nitrogen content (bound nitrogen only), also strongly impacts NOx emission levels.
  • Coal typically contains 0.5% to 3% nitrogen by weight on a dry basis.
  • natural gas also contains some nitrogen (0.5 to 20%); however it is molecular nitrogen N2, and thus is not affected by the fuel-NOx mechanism.
  • FIG. 1 summarizes the main reactions affecting fuel-nitrogen in the combustion process (Zevenhoven R., Kilpinen P., Control of pollutants in flue gases and fuel gases, Picaset Oy, Espoo, ISBN 951-22-5527-8, 2001). Four main steps can be identified:
  • Both volatile-N and char-N can be evolved as NO or as N2.
  • Fuel-NOx formation is minimized by implementing specific conditions leading to N2 rather than NO (see Van Der Lans R. P., Glarborg P. and Dam-Johansen K., Influence of process parameters on nitrogen oxide formation in pulverized coal burners, Prog. Energy Combust. Sci. Vol. 23, p. 349-377, 1997; Bowman C. T., Kinetics of Pollutant Formation and Destruction on Combustion, Prog Energy Combust Sci 1 33-45, 1975; and Proceedings of the 6th International Conference on Technologies and Combustion for a Cleaner Environment, Oporto, Portugal, 2001).
  • Fuel rich (reducing) conditions at the burner level by arranging fuel-rich “zones” in the furnace during the devolatilization stage, the nitrogen species in gas phase (volatiles) are more likely to be reduced to molecular nitrogen (N2) rather than oxidized to NO.
  • a method is provided and a system for performing the method.
  • a stream of nitrogen-containing gas is heated and injected into a stream of coal and conveying gas to produce a stream of mixed nitrogen-containing gas, coal, and conveying gas.
  • the mixed nitrogen-containing gas, coal, and conveying gas are combusted with oxygen in a combustion chamber.
  • FIG. 1 is a schematic summarizing the main reactions affecting fuel-nitrogen in the combustion process; 100221
  • FIG. 2 is a schematic view of the system with oxygen injection upstream of the burner;
  • FIG. 3 is a schematic view of the system with oxygen injection at the burner
  • FIG. 4 is a perspective view of a tubular injection element having rectangular apertures
  • FIG. 5A is a schematic of a circular aperture for use in a tubular injection element
  • FIG. 5B is a schematic of a rectangular aperture for use in a tubular injection element
  • FIG. 5C is a schematic of a triangular aperture for use in a tubular injection element
  • FIG. 5D is a schematic of an elliptical aperture for use in a tubular injection element
  • FIG. 6 is a perspective view of a tubular injection element having three sets of rectangular apertures
  • FIG. 7 is a perspective view of a tubular injection element having three sets of decreasingly shorter rectangular apertures
  • FIG. 8 is a perspective view of a tubular injection element having rectangular apertures arranged in a staggered pattern
  • FIG. 9 is a perspective view of a tubular injection element having a vertically non-uniform distribution of rectangular apertures
  • FIG. 10 is a perspective view of a tubular injection element having an aerodynamic pointed tip with rectangular apertures
  • FIG. 11 is a perspective view of a tubular injection element having an aerodynamic rounded tip with rectangular apertures
  • FIG. 12 is a perspective view of a tubular injection element having an aerodynamic rounded tip with elliptical apertures
  • FIG. 13 is a perspective view of a tubular injection element having an aerodynamic pointed tip with elliptical apertures
  • FIG. 14 is a cross-sectional view of two concentric injections with swirler-type injection elements
  • FIG. 15A is a perspective view of two injections with a swirler disposed on the nitrogen lance and a tangentially injecting injection element disposed on an inner wall of the fuel duct wherein the swirl and tangential injections are generally in the same direction;
  • FIG. 15B is a perspective view of two injections with a swirler disposed on the nitrogen lance and a tangentially injecting injection element disposed on an inner wall of the fuel duct wherein the swirl and tangential injections are generally in the opposite direction;
  • FIG. 16 is a side elevation view of a swirler showing opening and wall widths
  • FIG. 17 is a perspective view (with the aerodynamic tip not illustrated) of four injection elements radially spaced from one another having a leg with at least one aperture at an end thereof;
  • FIG. 18 is a side elevation view (with the aerodynamic tip illustrated) of the injection element configuration of FIG. 17 ;
  • FIG. 19 is a front elevation view (with the aerodynamic tip illustrated) of the injection element configuration of FIG. 17 ;
  • FIG. 20 is a front elevation view of a two-injection element configuration having a fin configuration
  • FIG. 21 is a side elevation view of the two-injection element configuration of FIG. 20 ;
  • FIG. 22A is a side elevation view of an axial injection element with a vertically oriented, elliptical cross-sectional shape
  • FIG. 22B is a side elevation view of an axial injection element with a horizontally oriented, elliptical cross-sectional shape
  • FIG. 23 is a perspective view of a tubular injection element having three radially spaced apertures at an end, thereof for injecting oxygen at an angle to the axis;
  • FIG. 24A is a side elevation view of a tubular injection element with apertures configured as circles arranged in a circle with one aperture in the middle;
  • FIG. 24B is a side elevation view of a tubular injection element with a saw tooth-shape pattern of apertures at a peripheral portion thereof;
  • FIG. 24C is a side elevation view of a tubular injection element with a four-wedge type pattern of apertures
  • FIG. 24D is a side elevation view of a tubular injection element with a star-shaped aperture
  • FIG. 24E is a side elevation view of a tubular injection element with a curved, cross-shaped aperture disposed at a center thereof;
  • FIG. 24F is a side elevation view of a tubular injection element with a curved, cross-shaped aperture similar to that of FIG. 24E but having a greater thickness and extending to a peripheral portion thereof.
  • the system for burning coal with reduced NOx emissions includes the following: a source of a mixture of coal and conveying gas; a source of oxygen-containing gas; a source of nitrogen-containing gas; a heating device adapted and configured to heat nitrogen from the nitrogen source; a combustion chamber; a burner disposed at a wall of the combustion chamber; a burner operatively associated with a combustion chamber; a fuel duct in fluid communication with the source of a mixture of coal and conveying gas, the fuel duct extending towards the burner; and a nitrogen-containing gas injection element in fluid communication with the heating device and the fuel duct, the nitrogen injection element being adapted and configured to inject heated nitrogen-containing gas from the heating device into a stream of a mixture of coal and conveying gas and mix therewith inside the fuel duct.
  • a method of combusting coal with reduced NOx emissions includes the following steps.
  • a stream of nitrogen-containing gas is heated.
  • the heated stream of nitrogen-containing gas is injected into a stream of coal and conveying gas to produce a stream of mixed nitrogen-containing gas, coal, and conveying gas.
  • the mixed nitrogen-containing gas, coal, and conveying gas are introduced at a burner disposed at a wall of a combustion chamber.
  • the coal is combusted with oxygen in the combustion chamber.
  • the system or method can include any one or more of the following aspects:
  • an oxygen-containing gas injection element is in fluid communication with the source of oxygen and the fuel duct, the oxygen-containing gas injection element fluidly communicating with the fuel duct downstream of where the nitrogen-containing gas injection element fluidly communicates with the fuel duct and upstream of or at the burner, the oxygen-containing gas injection element being adapted and configured to inject oxygen-containing gas from the oxygen-containing gas source into the stream of mixed heated nitrogen-containing gas, coal, and conveying gas;
  • the source of oxygen-containing gas and the source of nitrogen-containing gas comprise an Air Separation Unit (ASU);
  • ASU Air Separation Unit
  • the conveying gas comprises flue gas from the combustion chamber mixed with oxygen-containing gas from the oxygen-containing gas source;
  • the heating device is adapted and configured to directly impart heat to nitrogen from the nitrogen-containing gas source from a flame;
  • the heating device is a heat exchanger adapted and configured to exchange heat between nitrogen-containing gas from the nitrogen-containing gas source and heat from combustion of the coal and oxygen in the combustion chamber;
  • the conveying gas is flue gas from the combustion chamber mixed with oxygen
  • the heating device is a heat exchanger adapted and configured to exchange heat between nitrogen-containing gas from the nitrogen-containing gas source and heat from combustion of the coal and oxygen in the combustion chamber;
  • the heating device is a heat exchanger adapted and configured to exchange heat between nitrogen-containing gas from the nitrogen-containing gas source and heat from combustion of the coal and oxygen in the combustion chamber;
  • the conveying gas is air
  • the oxygen-containing gas injection element fluidly communicates with the fuel duct at the burner
  • the nitrogen-containing gas injection element fluidly communicates with the fuel duct at a peripheral portion of the fuel duct;
  • the nitrogen-containing gas injection element fluidly communicates with the fuel duct along a central axis of the fuel duct;
  • the oxygen-containing gas injection element fluidly communicates with the fuel duct at a peripheral portion of the fuel duct;
  • the oxygen-containing gas injection element fluidly communicates with the fuel duct along a central axis of the fuel duct;
  • the nitrogen-containing gas and oxygen are obtained from an ASU;
  • the step of heating a nitrogen-containing gas stream comprises directly imparting heat from a flame to the nitrogen stream;
  • the step of heating a nitrogen-,containing gas stream comprises indirectly imparting heat from a flame to the nitrogen stream via a heat exchanger;
  • the step of heating a nitrogen-containing gas stream comprises indirectly imparting heat from the step of combusting to the nitrogen stream via a heat exchanger;
  • the stream of nitrogen-containing gas is heated to a temperature such that a desired level of devolatilization occurs
  • the stream of nitrogen-containing gas is heated to a temperature in the range of from about 1,000° F. to about 1,800° F.;
  • injection of the heated stream of nitrogen-containing gas causes devolatilization of most of a volatile species content in the coal
  • oxygen-containing gas is injected into the collected flue gas in an amount such that an oxygen concentration in the mixed oxygen-containing gas and flue gas is from about 3% to about 20%.
  • the step of heating a nitrogen-containing gas stream comprises indirectly imparting heat from the step of combusting to the nitrogen stream via a heat exchanger.
  • the proposed method and system also reduces the fuel-NOx formation in a coal combustion process.
  • the fuel bound N can be transformed into either molecular N (N2) or NO depending on the local conditions where the devolatilization took place.
  • N2 molecular N
  • NO nitrogen-containing gas
  • Injecting hot nitrogen-containing gas into the coal stream releases volatiles and fuel-bound N compounds in a reducing environment.
  • the reducing environment drives the coal derived N compounds to convert to N2.
  • the temperature and quantity of nitrogen-containing gas to be injected depends on the type of coal and the NOx reduction targets.
  • the temperature of the nitrogen-containing gas is chosen to be above the devolatilization temperature of the volatile species in the coal.
  • the volatilization characteristics of various general types of coals are well known. In the case of a specific type of coal, the volatilization characteristics may be determined experimentally in a known manner. Generally speaking, the temperature should be selected such that a desired degree of devolatilization occurs for the particular type of coal being combusted.
  • a suitable temperature is in the range of from about 1,000° F. to about 1,800° F.
  • the location of nitrogen-containing gas injection should be strategically placed so that just enough residence time is available for the devolatilization and the conversion to nitrogen-containing gas to occur. Injecting hot nitrogen-containing gas more than this distance can pose safety issues as volatiles are very flammable and unfavorable combustion could occur.
  • the nitrogen-containing gas need not be pure nitrogen. Indeed, gaseous mixtures having a majority of nitrogen with minor amounts of other gases are suitable for use with the process and system. Such minor constituents include O2 and inert gases such as Ar and CO2.
  • a preferred source for both the nitrogen-containing gas to be heated and the O2 is from an air separation unit (ASU). Suitable ASU's include those operated via pressure swing adsorption (PSA), vacuum swing adsorption (VSA), cryogenic distillation, and membrane permeation. Typical N2 and O2 concentrations in nitrogen-enriched and oxygen-enriched streams from these types of ASU's are well known and need not be repeated here.
  • Other sources of the nitrogen can include a gaseous mixture comprising nitrogen and flue gas.
  • the oxygen-containing gas to be optionally injected into the mixed nitrogen-containing gas, conveying gas, and coal also need not be pure.
  • Suitable gases include those having an oxygen concentration greater than that of air up to 100% pure oxygen.
  • the nitrogen-containing gas can be heated in “direct fired mode” or “indirect fired mode”.
  • direct fired mode the incoming nitrogen-containing gas is heated by direct contact with a small flame.
  • indirect fired mode the nitrogen-containing gas is heated at a heat exchanger taking heat from a small flame or from a combustion process.
  • the oxygen-containing gas is injected at a location which achieves both safety goals and good mixing with the stream of coal/conveying gas/nitrogen-containing gas.
  • the location is desirably upstream of the burner throat in order to reduce the risk of incurring partial combustion of coal particles in local pockets that are oxygen-enriched. At the same time, the location is not so close to the burner that little mixing of the oxygen-containing gas and coal/conveying gas/nitrogen-containing gas is achieved.
  • the conveying gas comprises any gas to convey fuel particles from a particle storage or generation location, e.g., mills, to the burner level and the combustion chamber.
  • this gas can comprise the primary air used to convey pulverized or micronized coal in a coal-fired boiler.
  • Preferred conveying gases are air and mixtures of recirculated flue gas and oxygen.
  • these mixtures of recirculated flue gas and oxygen include about 60-90% CO2, 5-20% N2, and 3-20% O2.
  • An especially preferred mixture of recirculated flue gas and oxygen contains about 80% CO2 and about 20% O2.
  • injection elements may be employed. It should be noted that each of the nitrogen-containing gas and oxygen-containing gas injection elements may be the same as one another or different. Several examples of injection elements follow.
  • FIGS. 2-9 A system for performing the method is best illustrated in FIGS. 2-9 .
  • a stream of coal and conveying gas 1 enters fuel duct 8 .
  • a heated stream of nitrogen-containing gas from first injection element 3 is mixed with the coal and conveying gas downstream of element 3 .
  • Oxygen-containing gas is optionally injected into the mixed coal, conveying gas, and nitrogen-containing gas by injection element 4 upstream of burner 9 .
  • the mixed nitrogen-containing gas, oxygen-containing gas (if optionally injected), coal, and conveying gas is introduced to combustion chamber 6 via a burner where combustion 7 takes place.
  • a stream of coal and conveying gas 1 enters fuel duct 8 .
  • a heated stream of nitrogen-containing gas from first injection element 3 is mixed with the coal and conveying gas downstream of element 3 .
  • Oxygen-containing gases optionally injected into the mixed coal, conveying gas, and nitrogen-containing gas by injection element 5 at burner 9 .
  • the mixed nitrogen-containing gas, oxygen-containing gas (if optionally injected), coal, and conveying gas is introduced to combustion chamber 6 via burner 9 where combustion 7 takes place.
  • injection elements 3 , 5 need not be disposed centrally along an axis of the fuel duct 8 . Rather, they may be disposed along a peripheral portion of the fuel duct 8 . Some of these various configurations are best illustrated in some of the following injection element designs.
  • one injection element 10 is a tube having a closed end 16 and plurality of rectangular apertures 13 . This design provides radial injection from the circumferential face of the injection element 10 .
  • the length, D 1 , and width, D 2 , of these apertures, as well as the circumferential arc distance, D 0 , between two adjacent apertures may be varied to control the momentum ratio J (ratio of the oxygen-containing gas or nitrogen-containing gas jet momentum to the momentum of the stream of non-gaseous fuel/conveying gas).
  • D 1 , D 2 , and D 0 also control the penetration of the injection gas into the primary stream or primary stream mixed with nitrogen-containing gas as appropriate.
  • a small D 2 /D 1 ratio (streamlined rectangular apertures) will minimize the perturbation to solid fuel particles, such as coal.
  • a big D 2 /D 1 ratio (bluff-body slots) will have a greater influence on the solid phase and will push solid fuel particles, such as pulverized coal, away from the centerline of the burner primary air duct. Those two different aspect ratios will lead to different distribution of particles and nitrogen or oxygen at the duct outlet.
  • Those three parameters, S 1 , D 1 , and D 2 control the penetration of the injection gas into the primary stream or primary stream mixed with nitrogen-containing gas as appropriate.
  • a small D 2 /D 1 ratio (streamlined slots) will minimize the perturbation to the solid phase.
  • a big D 2 /D 1 ratio (bluff-body slots) will have a greater influence on the solid phase and will push the coal particles away from the centerline of the burner primary air duct.
  • Those two different aspect ratios will lead to different distribution of particles and nitrogen or oxygen at the duct outlet.
  • the slot shape itself could be circular, rectangular, triangular, or elliptical, respectively.
  • the injection element 20 includes apertures 23 arranged in axially extending rows along the axis of the injection element 20 . This pattern performs a better mixing if the axial distance D 3 between two adjacent apertures 23 in a same row is sufficiently large.
  • the dimension D 3 between the apertures 23 could be the same or could vary in the axial direction towards the closed end 26 .
  • the length dimensions D 1 , D 4 , and D 5 of the apertures 33 in injection element 30 may vary from short to long going in the direction of the closed end 36 .
  • these length dimensions could vary in any order from short to long, long to short, long to short and then back to long, short to long and then back to short, and other permutations.
  • the dimensions D 1 or D 2 could also vary in the azimuthal (radial) direction. This offers more precise control over the penetration of the injection gas into the primary stream.
  • D 3 can be tailored to the conditions of each process to optimize mixing and minimal redistributions of particles.
  • the apertures 43 in injection element 40 need not extend in the axial direction. Rather, they may be staggeredly disposed at different angles ⁇ with respect to one another. ⁇ can vary from less than 180° (streamlined slots/axial slots) to 90° (bluff-body slots/radial slots).
  • the injection element 50 need not have a uniform distribution of apertures 53 in the azimuthal direction.
  • the coal particle loading is not always uniform throughout the cross-section (sometimes due to the so-called “roping phenomenon”).
  • the particle concentration in the stream of coal/conveying gas 56 (or coal/conveying gas/nitrogen-containing gas) at the bottom of the injection element 50 may be higher than the same in the stream of coal/conveying gas (or coal/conveying gas/nitrogen-containing gas) 57 at the top of the injection element 50 .
  • the thickness of arrows represents the loading of particles in the gas stream.
  • the advantage offered by this is that more nitrogen-containing gas or oxygen-containing gas could be introduced in the locations where particle loading is higher 58 than locations where particle loading is lower 59 . This will reduce the likelihood of creating local pockets with less devolatilization potential (in the case of nitrogen-containing gas injection) or local pockets that are fuel-lean (in the case of oxygen-containing gas injection) each of which could lead to higher levels of NOx. With respect to this problem and solution, the particle loading distribution could easily be determined by experimental or modeling studies.
  • the apertures 53 may be staggered and vary in size in the axial and azimuthal directions. The distance between apertures 53 , the number of rows of apertures 53 , or the surface area of apertures 53 could also be varied.
  • This injection element 50 has a particularly beneficial application to coal-fired boilers whose burner geometry include coal concentrators or splitters (identified technique in the prior art for reducing NOx emissions from pulverized coal burners). Varying levels of nitrogen-containing gas or oxygen-containing gas injection may be located to achieve higher concentration of N2 or O2 in coal richer zones. As a result, the equivalence ratio between coal and N2 (in the case of nitrogen-containing gas injection) coal and O2 (in the case of oxygen-containing gas injection) can be controlled in the coal richer zone (concentrated zone) as well as in the coal leaner zones.
  • the injection element 100 , 110 , 120 , 130 , 140 may have an aerodynamic closed end 106 , 116 , 126 , 136 , 146 .
  • An aerodynamic shape tends to reduce re-circulation of the stream of coal/conveying gas (in the case of nitrogen-containing gas injection) or of the stream of coal/conveying gas/nitrogen-containing gas (in the case of oxygen-containing gas injection), and creation of a particle deficient and low/reverse velocity zone in the wake of the injection element 100 , 110 , 120 , 130 , 140 .
  • rectangular apertures 103 could be added to closed end 106 in all the permutations described in FIGS. 1-7 .
  • the closed end 106 could be pointed, and terminate at point P 1 .
  • the distances D 8 and D 9 and the angle ⁇ defined by lines L 1 and L 2 could be varied in order to optimize the mixing in a shortest distance and to cause least disturbance to the non-gaseous fuel.
  • rectangular apertures 113 could be added to closed end 116 in all the permutations described in FIGS. 1-7 .
  • the closed end 116 could be rounded, instead of extending to point P 2 at the intersection of lines L 4 and L 5 .
  • the distances D 10 and D 11 , and the angle 6 defined by lines L 4 and L 6 could be varied in order to optimize the mixing in a shortest distance and to cause least disturbance to the non-gaseous fuel.
  • apertures 123 A, 123 B, 123 C may be present on injection element 120 .
  • the injection element 120 extends to a rounded tip 126 .
  • Each of apertures 123 A, 123 B, and 123 C is configured to inject streams of nitrogen-containing gas or oxygen-containing gas PA, PB, PC into the mixed stream of coal/conveying gas (in the case of nitrogen-containing gas injection) or coal/conveying gas/nitrogen-containing gas (in the case of oxygen-containing gas injection) at an angle to the axis of the lance.
  • apertures 133 A, 133 B, 133 C may be present on injection element 130 .
  • the injection element 130 extends to a pointed tip 136 .
  • Each of apertures 133 A, 133 B, and 133 C is configured to inject a stream of nitrogen-containing gas or oxygen-containing gas PD, PE, PF into the mixed stream of coal/conveying gas (in the case of nitrogen-containing gas injection) or coal/conveying gas/nitrogen-containing gas (in the case of oxygen-containing gas injection) at an angle to the axis of the oxygen lance.
  • the arrangement of the fuel duct 231 with respect to the conduit 239 defined by walls 232 A, 232 B is a tube within a tube.
  • Nitrogen-containing gas is fed to the central injection element 235 from oxygen lance 236 . It is injected with a swirl S 2 .
  • Oxygen-containing gases fed from conduit 239 to the single peripheral injection element 234 , which is disposed flush with the inner wall of fuel duct 231 .
  • the directions of swirls S 1 , S 2 may the same or different.
  • the flow passage leading to and from the peripheral injection element 234 could be aerodynamically (like a venturi) designed to cause minimum disturbance to the flow. In other words, shoulders before and after the injection element 234 could be used. It should also be understood that fuel duct 238 need not extend beyond injection element 231 A, 231 B.
  • the conduit 239 may actually be a plurality of conduits surrounding the fuel duct 231 , any or all of which feeds injection element 234 .
  • another Oxynator®-based design includes fuel duct 241 surrounded by a conduit 249 (known by those ordinarily skilled in the art as a secondary or transition stream zone) defined by walls 242 A, 242 B. Disposed in a central axis of fuel duct 241 is nitrogen-containing gas lance 244 at the end of which is an injection element 244 (based upon Oxynator®. Disposed along the inner wall of the fuel duct 241 is a plurality of tangentially injecting injection elements 245 A, 245 B, 245 C, 245 D. In operation, nitrogen-containing gas fed by lance 244 to injection element 244 is injected into fuel duct 241 with a swirl S 3 .
  • Oxygen-containing gas fed by conduit 249 to injection elements 245 A, 245 B, 245 C, 245 D is tangentially injected with respect to fuel duct 241 into fuel duct 241 with a swirl S 4 that is in the same direction as swirl S 3 .
  • another Oxynator®-based design includes fuel duct 251 surrounded by a conduit 259 (known by those ordinarily skilled in the art as a secondary or transition stream zone) defined by walls 252 A, 252 B. Disposed in a central axis of fuel duct 251 is nitrogen-containing gas lance 254 at the end of which is an injection element 254 (based upon Oxynator®. Disposed along the inner wall of the fuel duct 251 is a plurality of tangentially injecting injection elements 255 A, 255 B, 255 C, 255 D. In operation, nitrogen-containing gas fed by lance 254 to injection element 254 is injected into fuel duct 251 with a swirl S 5 .
  • Oxygen-containing gas fed by conduit 259 to injection elements 255 A, 255 B, 255 C, 255 D is tangentially injected with respect to fuel duct 251 into fuel duct 251 with a swirl S 6 whose direction is opposite that of swirl S 5 .
  • All of the Oxynator®-based designs of FIGS. 14, 15A , and 15 B may be varied as follows.
  • injection element Arc 222 along the circumferential border of open space 221 between two adjacent vanes 223 has a dimension A 1 .
  • the circumferential edge of vane 223 has a dimension A 2 .
  • the number of vanes 223 and the dimensions A 1 , and A 1 may be varied in order to optimize the mixing and particle loading.
  • the ratio of dimensions A 1 , A 2 may be chosen to optimize the injection velocity and thus the penetration of the jet.
  • a small ratio A 2 /A 1 is preferred to minimize the disturbance to the solid phase.
  • Oxygen-containing gas may be injected at several locations at roughly a single axial position by several different injection elements.
  • an injection element comprising a leg member having first and second portions 302 A, 303 A and at least one aperture 304 A at the end of second portion 303 A.
  • Other injection elements similarly comprise a leg member having first and second portions ( 302 B, 303 B; 302 C, 303 C, 302 D, 303 D) and at least one aperture 304 B, 304 C, 304 D at the end of the second portions 303 B, 303 C, 303 D.
  • an aerodynamic tip 306 is included at the end of lance portion 301 just after the junction between lance portion 301 and the first portions 302 A, 302 B, 302 C, 302 D.
  • each injection element has height and length dimensions D 13 , D 14 .
  • the injection elements inject nitrogen-containing gas or oxygen-containing gas into the fuel duct at an angle P with respect to an axis of the fuel duct and defined by lines L 10 , and L 11 .
  • the cumulative projection area of all these injection elements perpendicular to the flow area is much smaller than the flow area of the primary stream.
  • these injection elements do not offer any significant obstruction to the flow of the particle-laden stream.
  • the dimensions D 13 , and D 14 , injection angle A, and a diameter of each aperture could be independently adjusted to precisely control the nitrogen-containing gas penetration or oxygen-containing gas penetration and local mixing.
  • the first and second portions are replaced with shapes that are more streamlined.
  • Extending from a lance portion 401 are radially spaced fins 402 .
  • the side elevation of FIG. 19 depicts a plurality of apertures 403 on surfaces of at least two fins that face in a direction perpendicular to that of the flow of the coal/conveying gas.
  • this type of surface, an opposed surface on the other side of the fin or a surface of the fin facing downstream could have apertures 403 to introduce injection gas with precise control over the jet momentum and local penetration of the injection gas.
  • the lance 402 portion terminates in an aerodynamic body 405 having an aerodynamic tip 406 .
  • Each of the fins 402 is aerodynamically streamlined in shape.
  • the apertures 403 are configured as circular holes, slots, slits, and other shaped openings such as those depicted in FIGS. 3A-3D .
  • the shape of any tip at the end of the lance has an aerodynamic design with or without one or more openings.
  • the openings on the tip could be of any design previously described above.
  • Another type of injection element is configured to inject nitrogen-containing gas or oxygen-containing gas axially into the flow of coal/conveying gas from a surface that faces downstream. This surface could have any number of apertures of any shape. Some exemplary shapes 701 A-F are best shown in FIGS. 24 A-F. The number of apertures, size, shape and angle of injection could be adjusted in order to optimize mixing and solid fuel loading.
  • Baffles arranged near the outlet end can facilitate a uniform mixing of nitrogen-containing gas and/or oxygen-containing gas (the use of baffles is an improvement over prior art designs as it accomplishes more efficient mixing by increasing the turbulence at the outlet end).
  • Various baffles number, shape and size may be utilized. As the velocity control of the jet outgoing from the pipe is a crucial parameter governing burner aerodynamics, the cross-sectional area of those baffles will be chosen carefully.
  • Similar types of axially injecting injection elements have a modified cross-section.
  • a vertical elliptical cross-section for example, will cause fewer disturbances to the particle trajectories and at the same time could provide improved mixing.
  • Modifications of the cross-section of the pipe allow decreasing or increasing the velocity of the axial nitrogen-containing gas or oxygen-containing gas jet.
  • nitrogen or oxygen lance 503 terminates in a horizontally oriented elliptical end 502 .
  • FIG. 22B depicts a vertically oriented elliptical end 505 .
  • another axial injecting-type of injection element includes member 601 having radially spaced apertures 602 A, 602 B, 602 C on a downstream surface.
  • Each of apertures 602 A, 602 B, 602 C is configured to inject flows of nitrogen-containing gas or oxygen-containing gas F 4 , F 5 , F 6 at an angle with respect to an axis of the fuel duct.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
US11/563,374 2005-12-02 2006-11-27 METHODS AND SYSTEMS FOR REDUCED NOx COMBUSTION OF COAL WITH INJECTION OF HEATED NITROGEN-CONTAINING GAS Abandoned US20070125282A1 (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
US11/563,374 US20070125282A1 (en) 2005-12-02 2006-11-27 METHODS AND SYSTEMS FOR REDUCED NOx COMBUSTION OF COAL WITH INJECTION OF HEATED NITROGEN-CONTAINING GAS
JP2008542852A JP2009517626A (ja) 2005-12-02 2006-11-27 加熱した窒素含有ガスの注入を用いる、ＮＯｘが低減された石炭燃焼方法及びシステム
AU2006321344A AU2006321344A1 (en) 2005-12-02 2006-11-27 Methods and systems for reduced NOx combustion of coal with injection of heated nitrogen-containing gas
EP06831594A EP1957868A1 (fr) 2005-12-02 2006-11-27 Procedes et systemes d'obtention d'une combustion de charbon a nox reduit par injection d'un gaz a l'azote chauffe
CA002631898A CA2631898A1 (fr) 2005-12-02 2006-11-27 Procedes et systemes d'obtention d'une combustion de charbon a nox reduit par injection d'un gaz a l'azote chauffe
KR1020087016098A KR20080084998A (ko) 2005-12-02 2006-11-27 가열된 질소-함유 기체를 주입시켜 석탄의 ＮＯｘ 연소물을감소시키기 위한 방법 및 시스템
PCT/IB2006/003366 WO2007063386A1 (fr) 2005-12-02 2006-11-27 Procedes et systemes d'obtention d'une combustion de charbon a nox reduit par injection d'un gaz a l'azote chauffe

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US74211905P 2005-12-02 2005-12-02
US11/563,374 US20070125282A1 (en) 2005-12-02 2006-11-27 METHODS AND SYSTEMS FOR REDUCED NOx COMBUSTION OF COAL WITH INJECTION OF HEATED NITROGEN-CONTAINING GAS

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US20100126491A1 (en) * 2008-11-25 2010-05-27 Harold Angus Swanson Burner for combustion of fuel in pellet or granular form
US20100282185A1 (en) * 2008-01-17 2010-11-11 L'air Liquide Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Burner and method for implementing an oxycombustion
US20120104055A1 (en) * 2010-10-27 2012-05-03 Alstom Technology Ltd Flow deflectors for fuel nozzles
US20150167971A1 (en) * 2011-11-23 2015-06-18 Honeywell International Inc. Burner with oxygen and fuel mixing apparatus

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US20120104055A1 (en) * 2010-10-27 2012-05-03 Alstom Technology Ltd Flow deflectors for fuel nozzles
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JP2009517626A (ja) 2009-04-30
KR20080084998A (ko) 2008-09-22
EP1957868A1 (fr) 2008-08-20
WO2007063386A1 (fr) 2007-06-07
AU2006321344A1 (en) 2007-06-07
CA2631898A1 (fr) 2007-06-07

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