• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    In a combustion installation for burning a fuel, which installation includes a hearth operating as a circulating fluidized bed, and in which installation at least a fraction of the flow of solid particles resulting from the combustion of the fuel in the hearth is returned to the hearth via a heat exchanger operating as a fluidized bed, the method of decreasing nitrogen oxide emissions consisting in the heat exchanger being fed with a fluidization gas which is considerably poorer in oxygen than air.
    公开号:US20010004516A1
    申请号:US09/739,105
    申请日:2000-12-19
    公开日:2001-06-21
    发明作者:Francois Malaubier；Eugene Guilleux
    申请人:Alstom Power Boiler SA；ABB Alstom Power Combustion；
    IPC主号:F23C10-04
    专利说明:
    [0001] The invention relates to a combustion installation for burning a fuel, which installation includes a hearth operating as a circulating fluidized bed, and in which installation at least a fraction of the flow of solid particles resulting from the combustion of the fuel in the hearth is returned to the hearth via a heat exchanger operating as a fluidized bed. [0001] BACKGROUND OF THE INVENTION
    [0002] In a circulating fluidized bed installation, the fuel, which may be crushed coal, is usually injected into the bottom portion of the hearth, where a reducing atmosphere prevails. [0002]
    [0003] In that zone, the fuel is subjected to pyrolysis, with the combustible matter being separated firstly into volatile matter containing a fraction of the nitrogen from the original fuel (volatile-N), and secondly into solid matter containing the remaining nitrogen from the original fuel (coke-N). The coke grains can remain for various lengths of time in the bottom portion of the hearth, where a reducing atmosphere prevails. Under those conditions, the reaction products of the coke-N contain molecular nitrogen rather than the pollutant NOx. The time for which the coke grains remain in the reducing zone depends essentially on the size of each grain. The finest particles leave the zone rapidly and then pass through the top portion of the hearth, where the reactions continue. [0003]
    [0004] More particularly in FIG. 1, the flow of solid particles coming from the hearth [0004] 1 and collected by a suitable device such as a cyclone 3 is made up not only of inorganic ash but also of coke resulting from the fuel burning incompletely in the hearth. That coke contains the original elements of the fuel, and in particular carbon, sulfur, and nitrogen.
    [0005] Those solid particles are sent back to the hearth via a suitable device such as a recycling loop [0005] 4 equipped with a siphon 5. In FIG. 1, a fraction of the flow of solid particles recycled to the hearth 1 goes through a heat exchanger 7 operating as a fluidized bed. In FIG. 2, a heat exchanger 7 operating as a fluidized bed is constituted by a casing 71 containing packets of zigzag tubes 72 through which water or steam flows. The flow of solid particles enters via an inlet duct 73 and passes through the heat exchanger by means of a fluidization system and then exits via an outlet duct 74. The top level of the bed of solid particles in the heat exchanger is indicated by the line L. In this example, the heat exchanger 7 is outside the hearth 1 and only a fraction of the flow of solid particles being recycled to the hearth 1 passes through it. It is to be understood that the following description also applies when the heat exchanger 7 is part of the hearth 1 and receives the entire flow of solid particles.
    [0006] In FIG. 2, the inside of the casing [0006] 71 of the heat exchanger 7 is subdivided into a plurality of chambers 75A, 75B, 75C, 75D, separated by walls 76. The chambers 75B and 75C receive the packets of tubes 72B, 72C through which water or steam passes internally. The floor 77 of the heat exchanger is equipped with nozzles 78 making it possible to inject gas for fluidizing the solids. Below the floor 77, a wind box 79 is placed that contains the fluidization gas. The wind box 79 may optionally be subdivided into at least as many compartments 79A, 79B, 79C, 79D as there are chambers inside the casing.
    [0007] After passing through the solids from the bottom at floor level to above the top level L of the bed of solid particles, the fluidization gases are removed via the outlet duct [0007] 74 to the hearth 1. As the solids pass through the heat exchanger 7, their temperature is lowered from the temperature they have at the outlet of the cyclone (about 850° C. to 900° C.) to a temperature of about 500° C. to 700° C. depending on the number and the surface area of the tubes 72 inside the casing 71.
    [0008] In the state of the art, the fluidization gas used in the heat exchanger [0008] 7 is atmospheric air that is usually at a temperature of in the range 20° C. to 300° C. and at a compression level that is sufficient to enable the solids to flow from the inlet chamber 75A to the outlet chamber 75D, for example. An atmosphere that is strongly oxidizing, or, in other words, an atmosphere that has a very high oxygen partial pressure, prevails in each chamber. That technique suffers from the drawback that nitrogen oxides form by reaction between the above-mentioned coke-N and the fluidization air of the heat exchanger 7. The production of nitrogen oxide is much higher in the inlet chambers 75A, 75B than in the outlet chambers 75C, 75D because of the amount of coke-N consumed in the inlet chambers and, above all, because the temperature of the solids is much higher in the inlet chambers than in the outlet chambers. By way of example, for a heat exchanger having four chambers as shown in FIG. 2, the temperature of the solids is typically about 850° C. to 800° C. in chamber 75A, about 650° C. to 800° C. in chamber 75B, and about 500° C. to 650° C. in chamber 75C. The nitrogen oxides that are formed in the chambers by reaction between the coke-N and the fluidization air are thus conveyed to the hearth, where they mix with the flue gases produced, thereby participating in the overall emission of pollutant. OBJECTS AND SUMMARY OF THE INVENTION
    [0009] An object of the invention is to decrease the emission of nitrogen oxides in such an installation. [0009]
    [0010] To this end, the invention provides a method of decreasing nitrogen oxide emissions in a combustion installation for burning a fuel, which installation includes a hearth operating as a circulating fluidized bed, and in which installation at least a fraction of the flow of solid particles resulting from the combustion of the fuel in the hearth is returned to the hearth via a heat exchanger operating as a fluidized bed, wherein the heat exchanger is fed with a fluidization gas which is considerably poorer in oxygen than air. [0010]
    [0011] The idea behind the invention is thus to control the oxygen partial pressure inside the chambers of the heat exchanger so as to minimize any formation of nitrogen oxides. The oxygen partial pressure is controlled to lie in the range 1% to 4%. The oxygen-poor fluidization gas, typically containing less than 12% (molar) of oxygen, is preferably constituted by flue gases preferably taken downstream from a dust filter for removing dust from the flue gases. Dust is thus removed from the flue gases, which dust could otherwise damage, by abrasion or clogging, the fans used to send the fluidization gas under pressure into the heat exchanger. [0011]
    [0012] Each heat-exchange chamber of the heat exchanger is fed separately with the oxygen-poor fluidization gas used on its own or as mixed with air. By adjusting the proportion of air in the mixture, it is thus possible to obtain combustion of the carbon in the heat exchanger in the presence of an atmosphere having a low oxygen content, and thus with minimized nitrogen oxide emissions. [0012]
    [0013] To avoid recycling too much flue gas into the heat exchanger, it is advantageous to feed the coldest chambers of the heat exchanger with air not mixed with the flue gases because nitrogen oxide formation is low in those chambers. [0013] BRIEF DESCRIPTION OF THE DRAWINGS
    [0014] FIG. 1 shows a combustion installation for implementing the method of the invention. [0014]
    [0015] FIG. 2 is a more detailed view of a fluidized bed heat exchanger. [0015] MORE DETAILED DESCRIPTION
    [0016] The combustion installation shown in FIG. 1 is described in part above. The flue gases that exit from the top of the cyclone [0016] 3 go through an electrostatic or bag dust filter for removing the dust from them before they are removed via a chimney. Downstream from the dust filter 6, a fraction of the flue gases is taken to serve as fluidization gas for the heat exchanger 7 after being blown by a fan 9. Air blown by a fan 10 may also be used to fluidize the flow of solid particles in the heat exchanger 7 as shown in FIG. 2.
    [0017] In FIG. 2, the flue gases on their own or as mixed with air feed the hottest chambers [0017] 75A and 75B of the heat exchanger 7 so as to fluidize the flow of solid particles. The coldest chambers 75C and 75D are preferably fed with air only. Whether the fluidization gas is constituted by air on its own, by flue gases on their own, or by a mixture of flue gases and of air, the flow rate of the fluidization gas into each chamber through the wind boxes 79 and the nozzles 78 is adjusted by valves 80. The quantity of air in the air/flue gas mixture is also adjusted by a valve 81. It is to be understood that oxygen-poor flue gases could also be injected into all of the chambers of the heat exchanger.
    权利要求:
    Claims (4)
    [1" id="US-20010004516-A1-CLM-00001] 1. A method of decreasing nitrogen oxide emissions in a combustion installation for burning a fuel, which installation includes a hearth operating as a circulating fluidized bed, and in which installation at least a fraction of the flow of solid particles resulting from the combustion of the fuel in the hearth is returned to the hearth via a heat exchanger operating as a fluidized bed, wherein the heat exchanger is fed with a fluidization gas which is considerably poorer in oxygen than air.
    [2" id="US-20010004516-A1-CLM-00002] 2. A method according to
    claim 1 , in which the combustion installation includes a dust filter for removing the dust from the flue gases, and in which the oxygen-poor fluidization gas is constituted by the flue gases taken downstream from the dust filter.
    [3" id="US-20010004516-A1-CLM-00003] 3. The method according to
    claim 1 , in which the heat exchanger is subdivided into a plurality of heat-exchange chambers through which the flow of solid particles passes, and each chamber is fed separately with the oxygen-poor fluidization gas used on its own or as mixed with air.
    [4" id="US-20010004516-A1-CLM-00004] 4. A method according to
    claim 3 , in which one or more of the heat-exchanger chambers are fed with the oxygen-poor fluidization gas used on its own or as mixed with air, and the other heat-exchanger chamber(s) is/are fed with air.
    类似技术:
    公开号 | 公开日 | 专利标题
    US4196676A|1980-04-08|Fluid bed combustion method and apparatus
    FI69694B|1985-11-29|NOX REDUCTION I MULTISOLIDA SVAEVBAEDDSFOERBRAENNINGSANORDNINGAR
    CA1271326A|1990-07-10|Fluid bed hog fuel dryer
    US4981111A|1991-01-01|Circulating fluidized bed combustion reactor with fly ash recycle
    AU1616999A|1999-06-16|Control of cement clinker production by analysis of sulfur content in the end product
    US5269263A|1993-12-14|Fluidized bed reactor system and method of operating same
    CA1281239C|1991-03-12|Method for improving solids distribution in a circulating fluidized bed system
    US5237963A|1993-08-24|System and method for two-stage combustion in a fluidized bed reactor
    HU213482B|1997-07-28|Method and apparatus for decreasing the emission of n2o in the flue gases of fuel having nitrogen burnt in fluidization reactor
    US6415743B2|2002-07-09|Method of decreasing nitrogen oxide emissions in a circulating fluidized bed combustion system
    US4681065A|1987-07-21|Multibed fluidized bed boiler
    US4477251A|1984-10-16|Process and apparatus for calcining pulverulent material
    EP0571234B1|1998-07-15|Process for decreasing N2O emissions from a fluidized bed reactor
    US7004089B2|2006-02-28|Combined fluidized bed and pulverized coal combustion method
    US5396849A|1995-03-14|Combustion method producing low levels of pollutants and apparatus for same
    CN102483231A|2012-05-30|Method and arrangement for optimising combustion conditions in a fluidised-bed boiler
    EP0237712B1|1990-05-09|Method of combustion for fluidized bed incinerators
    EP0685688B1|2000-11-15|Combustion method and apparatus
    EP0667832A1|1995-08-23|Method and apparatus for transporting solid particles from one chamber to another chamber.
    WO2008077462A2|2008-07-03|Process and plant for the thermal treatment of particulate solids, in particular for producing metal oxide from metal hydroxide
    HU199966B|1990-03-28|Equipment for hybrid firing of fluidized-pulverized coal
    HU188819B|1986-05-28|Device for securing the heat flow and/or material flow between various materials,carrying out chemical and physical processes,first for burning or gasifying solid fuel
    HU227832B1|2012-05-02|Method and apparatus for biomass firing in furnace with vertical burner heated by pulverised coal
    同族专利:
    公开号 | 公开日
    ES2232398T3|2005-06-01|
    US6415743B2|2002-07-09|
    FR2803020A1|2001-06-29|
    FR2803020B1|2002-04-12|
    DE60015908D1|2004-12-23|
    CN1145755C|2004-04-14|
    EP1111301A1|2001-06-27|
    DE60015908T2|2005-11-03|
    CN1300917A|2001-06-27|
    EP1111301B1|2004-11-17|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20090120379A1|2007-11-14|2009-05-14|Alstom Technology Ltd.|Boiler having an integrated oxygen producing device|US4257478A|1979-06-27|1981-03-24|Stal-Laval Apparat Ab|Gaseous media heat exchanger|
    DE3922765A1|1989-07-11|1991-01-17|Babcock Werke Ag|BURNING, ESPECIALLY FLUIDIZED BURNING|
    US5218932A|1992-03-02|1993-06-15|Foster Wheeler Energy Corporation|Fluidized bed reactor utilizing a baffle system and method of operating same|
    US5341766A|1992-11-10|1994-08-30|A. Ahlstrom Corporation|Method and apparatus for operating a circulating fluidized bed system|
    US5406914A|1992-11-10|1995-04-18|A. Ahlstrom Corporation|Method and apparatus for operating a circulating fluidized bed reactor system|
    US5339774A|1993-07-06|1994-08-23|Foster Wheeler Energy Corporation|Fluidized bed steam generation system and method of using recycled flue gases to assist in passing loopseal solids|
    FI102316B|1996-06-05|1998-11-13|Foster Wheeler Energia Oy|Method and apparatus for reducing corrosion caused by harmful components of solid state suspensions on heat transfer surfaces|
    FR2775061B1|1998-02-16|2000-03-10|Gec Alsthom Stein Ind|CIRCULATING FLUIDIZED BED BOILER WITH IMPROVED NITROGEN OXIDE REDUCTION|FR2848641B1|2002-12-11|2005-12-16|Alstom Switzerland Ltd|INDIRECT HEATING SYSTEM WITH VALORIZATION OF ULTRA FINE FUEL PARTICLES|
    DE102007062390B3|2007-12-22|2009-04-02|Michael Kaden|Fluidized-bed furnace for combustion of fuel, has fluid bed, where heat is received from fluid bed such that surplus bed material overflows from fluid bed and cooled bed material in fluid bed is recycled to fluid bed|
    FI123853B|2009-03-06|2013-11-15|Metso Power Oy|A method for reducing nitrogen oxide emissions from oxygen combustion|
    FR2975094B1|2011-05-12|2013-05-03|Lafarge Sa|DECARBONATION PROCESS|
    CN105180159B|2015-08-26|2018-10-09|中国科学院工程热物理研究所|Mend the circulating fluidized bed combustion method of air cooling|
    法律状态:
    2000-12-19| AS| Assignment|Owner name: ABB ALSTOM POWER COMBUSTION, FRANCE Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MALAUBIER, FRANCOIS;GUILLEUX, EUGENE;REEL/FRAME:011384/0863 Effective date: 20001206 |
    2002-06-20| STCF| Information on status: patent grant|Free format text: PATENTED CASE |
    2005-12-16| FPAY| Fee payment|Year of fee payment: 4 |
    2009-12-22| FPAY| Fee payment|Year of fee payment: 8 |
    2011-10-06| AS| Assignment|Owner name: ALSTOM POWER SYSTEMS SA, FRANCE Free format text: MERGER & NAME CHANGE;ASSIGNORS:ALSTOM POWER BOILERS;ALSTOM POWER CENTRALES;REEL/FRAME:027026/0383 Effective date: 20090331 |
    2012-01-24| AS| Assignment|Owner name: ALSTOM TECHNOLOGY LTD, SWITZERLAND Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ALSTOM POWER SYSTEMS SA;REEL/FRAME:027585/0254 Effective date: 20111223 |
    2013-12-30| FPAY| Fee payment|Year of fee payment: 12 |
    2016-08-17| AS| Assignment|Owner name: GENERAL ELECTRIC TECHNOLOGY GMBH, SWITZERLAND Free format text: CHANGE OF NAME;ASSIGNOR:ALSTOM TECHNOLOGY LTD;REEL/FRAME:039714/0578 Effective date: 20151102 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR9916244A|FR2803020B1|1999-12-22|1999-12-22|PROCESS FOR REDUCING NITROGEN OXIDE EMISSIONS IN A FLUIDIZED BED COMBUSTION PLANT|
    FR9916244||1999-12-22||
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