Abstract:
A landfill methane burner flare has a methane riser within a shroud. The methane riser terminates in a series of spuds that are bent to promote turbulence and mixing in methane passing through and out of the spuds. Louvers can be positioned in the riser to selectively establish a methane gas pressure within the riser, and/or louvers can be positioned between the methane riser and shroud to selectively establish combustion air flow in the flare.

Description:
I. FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to landfill gas extraction systems.  
       II. BACKGROUND OF THE INVENTION  
       [0002]     Landfills produce methane gas which must be extracted from the landfills. In some cases, this can be done passively, simply by placing open pipes in the landfill through which the methane can vent. For environmental reasons, however, many localities require that the methane be eliminated as much as possible by actively directing the methane through a flare, which burns the gas.  
         [0003]     Two types of flares are generally provided. The first type is referred to as a utility flare, which has a cylindrical shroud with an open top, above which a flame appears when the flare is burning gas. A methane riser extends from the ground into the shroud, with the bottom of the shroud generally being above the ground and supported on the riser. The methane is pumped up through the riser and out of an outlet into the shroud, where an ignition device ignites the gas to produce the flame and oxidize the methane.  
         [0004]     A second type of flare is referred to as an enclosed flare, which is essentially a utility flare with methane riser and shroud disposed inside a cylindrical flare housing that extends to the ground. Combustion air is provided through louvers in the flare housing wall.  
         [0005]     In either case, it is desired that the flare burn as much methane as possible, as well has have a large operating range, so that it can effectively burn methane at both low and high extraction rates. The “turndown ratio” of a flare refers to the operating range of the flare. Currently, most flares provide at best around a 5:1 turndown ratio (e.g., most flares can effectively burn methane at rates of, to give but one example, 100,000 BTU/minute to 500,000 BTU/minute. The reason that better turndown ratios have not been achieved are many, but include the fact that most flares cannot be optimized for any particular methane flow rate, but instead must be able to burn methane at what often are widely varying and unpredictable methane flow rates. Moreover, most localities require the exhaust constituents remain within nitrous oxide and carbon monoxide specifications, which can compete with the desire to burn as much methane as possible. Also, flares must typically achieve a desired amount of destruction of non-methane organic compounds, and this consideration can compete with methane oxidation optimization. Having recognized the above considerations, the present invention has been provided.  
       SUMMARY OF THE INVENTION  
       [0006]     A landfill gas flare includes a shroud and a methane riser in the shroud and defining a methane passageway. Plural non-straight pipes are mounted on the methane riser in communication with the methane passageway. Also, a flow alteration assembly is juxtaposed with the methane riser to selectively establish a fluid flow through the assembly.  
         [0007]     The flare can be an enclosed flare or a utility flare. The flow alteration assembly can surround the methane riser within the shroud, and can include movable louvers that are disposed between the shroud and the methane riser. The louvers are movable to establish a combustion air flow past the pipes. In a preferred embodiment, the louvers are coupled to an operating member that extends outside the shroud and that is manipulable by a person or computer to move the louvers.  
         [0008]     Alternatively the flow alteration assembly (or, in addition to the assembly discussed above, a second assembly) can be disposed in the top end of the riser. In this embodiment, the flow alteration assembly includes movable louvers disposed to at least partially block the top end of the riser. The louvers are movable to establish a methane gas pressure.  
         [0009]     In either flare type, each pipe, referred to herein as a “spud”, includes a radial segment lying along a radius of the methane riser and a distal segment establishing an angle with respect to the radial segment. The angle can be approximately fifty five degrees for some spuds and approximately sixty degrees for other spuds.  
         [0010]     If the flare is an enclosed flare having a housing surrounding the shroud and riser and extending to the ground, housing louvers can be formed near the bottom of the housing to establish a means for controlling combustion and quench air flow in the housing.  
         [0011]     In another aspect, a landfill flare includes a shroud defining an open top end, and a methane riser in the shroud. The methane riser terminates in at least two exhaust pipes that are configured for inducing turbulence in methane gas passing through the exhaust pipes. A movable louver assembly is disposed between the riser and shroud to establish a combustion air flow and/or in the top of the riser to establish a gas pressure.  
         [0012]     In still another aspect, a landfill flare includes a shroud, a housing enclosing the shroud and defining a wall, and a methane riser in the shroud. The methane riser terminates in at least two exhaust pipes that are configured for inducing turbulence in methane gas passing through the exhaust pipes. A louver assembly is disposed between the shroud and the methane riser, with the louver assembly being movable to establish a combustion air flow past the exhaust pipes, and/or a louver assembly is disposed in the riser to establish a gas pressure.  
         [0013]     The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is perspective view of a utility flare according to the present invention, schematically showing a landfill and a computerized louver control system;  
         [0015]      FIG. 2  is a top view of the methane riser and spud assembly of the flare shown in  FIG. 1 , with the louver assemblies removed for clarity, schematically showing radii of the methane riser along which the radial segments of the spuds lie;  
         [0016]      FIG. 3  is a top plan view of the open top end of the riser shown in  FIG. 1 , with the louvers in a mostly closed configuration;  
         [0017]      FIG. 4  is a top plan view of the open top end of the riser shown in  FIG. 1 , with the louvers in a mostly open configuration;  
         [0018]      FIG. 5  is an elevational view of the flare of the present invention, with portions cut away for clarity to show the louver assembly placed between the riser and shroud, showing an optional enclosed flare housing in phantom; and  
         [0019]      FIG. 6  is a top plan view of an alternate flare, showing three multi-spud assemblies.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]     Referring initially to  FIG. 1 , a flare is shown, generally designated  10 , that includes a methane riser  12  in fluid communication with a landfill  14  for removing methane gas from the landfill  14 . A methane pump or blower  15  can be provided to direct methane gas to the methane riser  12 .  
         [0021]     The flare  10  includes a shroud  16  surrounding the methane riser  12 , if desired in a coaxial relationship and radially spaced therefrom, with the shroud  16  being located above the ground. Brackets  18  can connect the shroud  16  and the methane riser  12 . The shroud  16  has an open top end  20 . An ignition device  21  can be provided near the open top end  20  to provide an ignition spark within the flare  10 . If desired, the shroud  16  can have an open bottom end  22 . When burning methane, a flame  24  appears inside and above the open top end  20 . Also, a louver actuator  26  is disposed in the shroud  16  and has an end that extends outside the shroud  16  for purposes to be shortly disclosed. It is to be understood that the louver actuator  26  can be manipulated by a person or a computerized control system  27  to move the below-disclosed louvers in accordance with the disclosure below. The control system  27  may receive input from various gas sensors/flow rate sensors/pressure sensors within the flare  10  and/or landfill  14  and move one or both sets of louvers described below in response thereto to establish desired riser  12  gas pressures and/or shroud  16  combustion air flow rates.  
         [0022]      FIG. 2  shows the preferred spud arrangement of the present invention. Plural spuds  28 , preferably four, six, or eight (six spuds  28  shown), can be provided on the methane riser  12  in fluid communication with a methane gas passageway  30  defined by the methane riser  12 . Each spud  28  is a non-straight short pipe that in the preferred embodiment includes at least a radial segment  32  and a distal segment  34  that is angled relative to the radial segment  32 . Each distal segment  34  has an open distal end  36  through which methane gas is exhausted.  
         [0023]     As shown, the preferred angular spacing a between adjacent spuds  28  can be sixty degrees (60°). Also, each radial segment  32  of each spud  28  can lie along a respective radius  38  that is defined by the methane riser  12 .  
         [0024]     As shown in the preferred embodiment of  FIG. 2 , a spud angle β, preferably an oblique angle or even a right angle, is defined between each radial segment  32  and its distal segment  34 . As indicated in  FIG. 2 , for every other spud  28 , the spud angle β is fifty five degrees (55°), with the intervening spuds having spud angles of sixty degrees (60°). With the arrangement shown, the distal segments  34  are oriented with their axial dimensions more or less tangent to the methane riser  12 . While  FIG. 2  shows each of the individual spud segments  32 ,  34  to be straight, the segments can also be curved.  
         [0025]     While  FIG. 2  shows a preferred non-limiting spud arrangement and configuration, it is to be understood that in general the spuds of the present invention are configured to induce turbulence and mixing of the methane as it exits the spuds  28  and is ignited. In part because of the tangential orientation of the distal segments  34 , the methane gas ignites while it is in somewhat of a vortex-type flow pattern. With this cooperation of structure, improved turndown ratios and lower emission levels can be achieved.  
         [0026]      FIGS. 3 and 4  show the preferred louver assembly for covering the top end of the riser  12  below the spuds  28  to establish pressure in the riser. Plural movable louvers (two louvers  40  shown in the exemplary non-limiting embodiment of  FIG. 3 ) are mounted on the riser  12  at or near the top end thereof. In one embodiment, each louver  40  is coupled to the riser  12  (or to supporting structure that can be on the riser  12 ) by being slidably mounted at or near their outer peripheries to a support  42 . The louvers  40  are connected at or near their inner edges to the louver actuator  26  by a linkage  46 , such that when the actuator  26  is moved, the inner edges move and up and down, the outer edges slide along the support  42 , and the louvers  40  are pivoted thereby between open and closed configurations.  
         [0027]     Accordingly, each louver  40  pivots between a closed configuration, shown in  FIG. 3 , wherein the top end of the riser  12  is mostly or completely blocked by the louvers  40 , and an open configuration, shown in  FIG. 4 , wherein the top end of the riser  12  is mostly unblocked and gas can flow (in the preferred non-limiting embodiment) around the outer edges of the louvers  40 . By establishing the configuration of the louvers  40 , the gas pressure within the riser  12  can be established as appropriate for maximizing the turndown rate in combination with the arrangement of the spuds  28  in  FIG. 2  while remaining within specifications for carbon monoxide, nitrous oxides, and non-methane organic compounds, i.e., the louvers  40  of the flare  10  can be adjusted to optimize the burning of methane.  
         [0028]     While  FIGS. 3 and 4  show a manually activated louver actuator  26 , as mentioned above if desired, the actuator  26  could be activated by the computerized control system  27  ( FIG. 1 ) in response to variables such as pressure, temperature, methane gas flow rate, methane gas concentration, etc. that can be sensed by sensors within the flare  10 .  
         [0029]     In addition to or as an alternative to the above-described louver assembly that can be positioned in the riser  12  to establish gas pressure in the riser  12 ,  FIG. 5  shows that a louver assembly can be disposed between the riser  12  and the wall of the shroud  16  near the bottom end of the shroud to establish a combustion air flow rate in the flare.  
         [0030]     This second louver assembly in all essential respects can be identical in operation to the louver assembly shown in  FIGS. 3 and 4 .  FIG. 5 , however, shows an alternative non-limiting exemplary louver mounting implementation that can be used if desired. Louvers  62  of the louver assembly  60  shown in  FIG. 5  can be pivotally mounted between the methane riser  12  and the wall of the shroud  16  to provide a means for establishing combustion air flow in the flare. More specifically, each louver  62  can be mounted by means of a respective pivot mount  64  to a stationary radial flange  66  in the shroud  16  (or to the wall of the shroud itself, if desired). A manually-activated or computer-activated actuator  68  can be attached through a linkage to the louvers  62  to move the louvers  62  in the directions indicated by the arrows  70 . Regardless of how the louvers are mounted, it may now be appreciated that by moving the louvers  62 , the amount of combustion air flowing to the spud assembly  58  around the outside of the methane riser  12  can be established to maximize/optimize the turndown ratio of the flare.  
         [0031]     If desired, the shroud  16  and riser  12  can be disposed inside of a cylindrical flare housing  72  that extends to the ground to establish an enclosed flare. The housing  72  can be formed with conventional housing louvers  74  near its bottom to establish another means for controlling combustion and quench air flow in the flare.  
         [0032]      FIG. 6  shows an enclosed or utility flare  80  that includes a shroud  82  with multiple (in the exemplary embodiment shown, three) spud assemblies  84  disposed in the shroud  82 . Each spud assembly  84  is substantially identical in configuration and operation to the spud assembly shown in  FIG. 2 .  
         [0033]     While the particular LANDFILL GAS EXTRACTION FLARE as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited as a “step” instead of an “act”. Absent express definitions herein, claim terms are to be given all ordinary and accustomed meanings that are not irreconciliable with the present specification and file history.