Abstract:
An apparatus for use in a furnace system to facilitate efficient and complete combustion of coal streams in a carrier gas. The apparatus, capable of being positioned horizontally or vertically in the coal pipes between the grinding mills and the furnace burner, contains a plurality of adjustable blades that are movable between an open and closed position. The position of the adjustable blades and the differing geometric shapes of the apparatus housing manipulate the amount and direction of coal streams in a carrier gas. This design reduces the amount of turbulent eddies in the pipe system, which helps to achieve a more homogenous flow of coal in a carrier gas and the efficient and complete combustion of coal in a carrier gas within the furnace burner.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is related to the copending U.S. patent application entitled “Tower Distributor,” filed on Feb. 7, 2003 to Joel Vatsky.  
         BACKGROUND OF THE INVENTION  
         [0002]    Many industrial processes require the equal distribution of heterogeneous flows to multiple receptors. For example in the electric utility industry, pulverized coal (“PC”) is transported through a pipe (duct) system that connects a grinding mill to one, or more, burners of a furnace. The PC is transported within the pipe system by a carrier gas, e.g., air. Thus, the heterogeneous flow, or stream, is made up of the PC and air (i.e., a two-phase flow or multi-phase flow). Ideally, one grinding mill is capable of supplying one or more such streams to multiple burners (receptors) of the furnace.  
           [0003]    Unfortunately, as a stream moves through a long length of pipe, the solid particles in the stream tend to concentrate together in a pattern generally characterized as being in the shape of a rope strand. This phenomenon is commonly referred to as roping, or laning. As such, any attempt to further distribute, or split, a stream into multiple streams for transport to respective receptors seldom, if ever, yields equal amounts of PC going to each of the receptors. In other words, when roping occurs in a stream, splitting that stream into multiple streams results in a flow imbalance between the multiple streams. This flow imbalance is also compounded by unequal pressure drops across the coal pipes caused by non-identified pipe length and configurations. Resulting flow imbalances could be on the order of ±30% between the multiple streams.  
           [0004]    Likewise, with respect to receptors fed by multiple sources, roping makes it difficult to combine the flows from these multiple sources such that each of the receptors are supplied with equal flows.  
           [0005]    Various methods and devices have been utilized to obtain more uniform and homogenous two-phase flow through a fuel pipe system, as the flow travels from the coal mill to the furnace. Such methods and devices are implemented at different points downstream of the coal mill. One such method and device is a conventional adjustable orifice, as illustrated in FIG. 1. The conventional adjustable orifice can be implemented at any point along the furnace pipe system. Such an adjustable orifice comprises opposed gate boxes  120  and  121  located along a pipe or between pipes. The gate boxes include slidable gates  123  and  124 , which can be adjusted to regulate the resistance to the flow of coal and a carrier gas flowing into the pipe  111  from pipe  110  by altering the opening between gates  123  and  124 .  
           [0006]    To increase the amount of coal and a carrier gas into the pipe  111 , the gates can be retracted into the gate boxes  120  and  121 . Conversely, to reduce the amount of flow through the pipe  111 , the gates  123  and  124  can be positioned closer together.  
           [0007]    The use of such an adjustable orifice has disadvantages. The adjustable orifice was initially designed for use in a single-phase flow. As shown in FIG. 1, if used in a two-phase system, once the flow passes through the gateway opening, coal eddies  125  are created from streams of coal, which are interrupted as they travel over the top edges  123 - 1  and  124 - 1  of the gates  123  and  124 . Such eddies not only wear down the interior walls of the pipe, but leave piles of coal immediately outside the gates  123  and  124 . Additionally, coal piles up within the gate boxes  120  and  121 , unless a complicated sealing system is used, eventually making it difficult to retract the gates into the gate boxes. As a result such orifices are most effective when used in a vertical direction, in order to minimize coal pile-up downstream of the gates.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention relates to an improved furnace system that supplies a uniform flow of fuel and a carrier gas such as through a pipe system to a furnace. Specifically, the present invention is directed to a furnace system having a balancing damper assembly that contains a plurality of adjustable blades. The adjustable blades are constructed and arranged so as to facilitate an efficient and uniform flow of fuel and a carrier gas in a burner assembly.  
           [0009]    In one embodiment of the invention, a balancing damper comprises a housing, with an inlet end and an outlet end, that contains a plurality of blades disposed within the center of the housing. Furthermore, there are at least two blades that are capable of being moved between an open and closed position. This particular arrangement and construction of the blades allows streams of pulverized coal and a carrier gas that enter the balancing damper housing, to travel between the two blades, as well as between the outer edges of the blades and the inner edges of the housing walls.  
           [0010]    In another embodiment, the balancing damper further comprises at least one blade that has at least one turning baffle.  
           [0011]    In accordance with another aspect of this invention, an assembly for use in a furnace system comprises three sections: a burner assembly, a pipe arranged upstream of the burner assembly, and a balancing damper located within the pipe. The balancing damper comprises a housing having an inner and outer wall, at least two blades located within the housing that are capable of being moved between an open and closed position.  
           [0012]    In another embodiment, the assembly for use in a furnace system further comprises a tower distributor. In yet another embodiment, the assembly comprises a fuel injector. In another embodiment, the assembly comprises an air register assembly.  
           [0013]    In accordance with another aspect of this invention, a furnace system is comprised of four components: a furnace, a burner assembly, which delivers pulverized fuel in a carrier gas, a pipe that is arranged upstream of the burner assembly, and a balancing damper located downstream of a fuel source.  
           [0014]    A balancing damper according to the present invention will overcome the shortcomings in the prior art. A balancing damper according to the present invention will allow optimum flow of coal and a carrier gas, while prolonging the life of the pipe system. The design of the present invention reduces the amount of turbulent eddies present in a pipe system by directing any turbulent eddies towards the center of the pipe. This reduces the amount of wear and tear on the interior walls of the pipe. The present design is also advantageous because unlike prior art orifices, it may be positioned in the horizontal or vertical direction without coal piling up downstream of the balancing damper.  
           [0015]    It is therefore, an object of the present invention to provide an assembly for use in a furnace system that will produce a more homogeneous flow of coal in a carrier gas and the efficient and complete combustion of coal in a carrier gas within the furnace burner.  
           [0016]    It is also an object of the present invention to provide a balancing damper for use in a furnace system that will produce a single, laminar, and homogeneous stream.  
           [0017]    It is also an object of the present invention to provide a balancing damper for use in a furnace system that will prolong the life of the pipes carrying a two-phase flow of pulverized coal and a carrier gas.  
           [0018]    Another object of this invention is to provide a balancing damper for use in a furnace system that is capable of being oriented in either the vertical or horizontal position along a furnace pipe assembly.  
           [0019]    Another object of this invention is to provide a balancing damper for use in a furnace assembly that will eliminate the buildup of coal that collects along the pipe. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 shows a prior art adjustable orifice.  
         [0021]    [0021]FIG. 2 is an illustrative block diagram of a furnace system&#39;s fuel and primary air circuit according to the present invention.  
         [0022]    [0022]FIG. 3 is a cross-sectional view of a balancing damper assembly in accordance with one principal of the invention.  
         [0023]    [0023]FIG. 4 is a second cross sectional view of a two-phase flow traveling through the balancing damper assembly.  
         [0024]    [0024]FIG. 5 is a top view of the balancing damper assembly of FIG. 3.  
         [0025]    [0025]FIG. 6 is a perspective top view of the balancing damper assembly of FIG. 3.  
         [0026]    [0026]FIG. 7 is another perspective top view of the balancing damper assembly according to the present invention.  
         [0027]    [0027]FIG. 8 is a side view of an adjustment means for the balancing damper assembly of FIG. 3.  
         [0028]    [0028]FIG. 9 is a second, enlarged, side view of an adjustment means for the balancing damper assembly.  
         [0029]    [0029]FIG. 10 is a cross-sectional view of a two-phase flow traveling through the balancing damper assembly referenced in FIG. 6.  
         [0030]    [0030]FIG. 11 is a top view of a blade of the balancing damper assembly according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0031]    A preferred furnace assembly according to the present invention is illustrated in FIG. 2. The furnace assembly comprises a coal mill  20 , coal pipes  24 ,  24 - 1 ,  24 - 2  and  25 , a balancing damper assembly  26 , a tower distributor  22 , a fuel injector  28 , an air register assembly  30 , and a burner zone  32 . Streams of fuel, such as pulverized coal, and a carrier gas (e.g., air) originate at the coal mill  20 . The flow passes through a tower distributor  22  that helps to provide a balanced two-phase flow of fuel and a carrier gas prior to their entry into a coal pipe  24 . Tower distributor  22 , such as that disclosed in a related U.S. application entitled “Tower Distributor” to Vatksy, which is incorporated by reference herein, has an elongated passageway to provide an area for turbulent eddies to settle down and form a more laminar and homogenous flow of fuel and air. Once the flow of pulverized coal and primary air travel through the tower distributor  22 , it is distributed among one or more coal pipes, such as represented by pipes  24 ,  24 - 1 ,  24 - 2  and  25 . The coal pipes eventually lead the flow of coal and carrier air into a burner zone  32 , where the fuel stream is consumed. For simplicity, the second stream with respect to coal pipe  24  is only described herein.  
         [0032]    During its travel through coal pipes  24  and  25 , the fuel flow is typically exposed to turbulence. To reduce the amount of turbulence created downstream of the coal mill or tower distributor, the fuel flow is further directed in accordance with the principal of the invention through a balancing damper assembly  26 , which can be located a predetermined distance downstream from the coal mill  20 . The balancing damper assembly  26  permits on-line adjustment of resistance in the pipe circuits to optimize pipe-to-pipe coal balance. In doing so, it prolongs the life of the pipes  24  and  25  by reducing the occurrences of turbulent streams of pulverized coal and air that impinge upon the coal pipes and directing turbulent streams towards the center of the pipe. The balancing damper assembly  26  is described in greater detail below.  
         [0033]    Once the flow of fuel and air passes through the balancing damper assembly  26 , the flow will pass through coal pipe  25  that feeds directly into fuel injector  28 . Air register assemblies  30  provide a swirl of air that surrounds the fuel injector. This permits adjustment of the flame that results when the fuel and carrier air are injected into the burner zone  32 .  
         [0034]    The overall effect of the furnace assembly of the present invention is to achieve improved balance of coal and carrier air between coal pipes leaving a mill, while prolonging the life of the furnace assembly components. This ultimately allows a greater percentage of fuel to be burned in the burner zone, thereby reducing the amount of harmful pollutants emitted into the atmosphere and increasing the efficiency of the furnace system.  
         [0035]    It should be noted that in alternative embodiments, the furnace assembly may comprise different variations of the aforementioned system. Certain components of the assembly, such as the tower distributor and air register assembly need not be present for the furnace assembly to function properly. Thus, an alternative furnace assembly may consist of a coal mill, a balancing damper assembly (i.e., an adjustable damper assembly) and fuel injector. Similarly, another furnace assembly may consist of a coal mill, a balancing damper assembly, a fuel injector and an air register assembly.  
         [0036]    In the description that follows, references will be made to FIGS. 3-11, all of which illustrate various aspects of the invention. A balancing damper assembly  26  according to the present invention is illustrated in FIG. 3. The balancing damper assembly  26  preferably has a housing  42  and two blades  40  and  41  disposed within the center of the housing  42 . The blades respectively have outer edges  40 - 1  and  41 - 1  and interior edges  40 - 2  and  41 - 2 . The balancing damper assembly  26  may be constructed using steel with various wear-resistant materials, such as metals, certain polymers, ceramic, etc.  
         [0037]    The two-phase flow of fuel and air enters the balancing damper assembly  26  at its inlet end  80 . The fuel flow travels between the inner edges  40 - 2  and  41 - 2 , as well as between the inner walls  42 - 2  of the housing  42  and the outer edges  40 - 1  and  41 - 1  of the blades  40  and  41 . Once the flow has passed around the blades  40  and  41 , the flow continues through the outlet end  82  into coal pipe  25  (FIG. 2). The illustration of the directions and flow of air are also shown in FIGS. 4 and 6.  
         [0038]    In order to regulate or alter the flow of air and fuel passing through the balancing damper assembly  26 , the blades  40  and  41  can be adjusted. This is accomplished through use of an adjustment means  84 , as illustrated in FIGS. 7, 8 and  9  and described further below.  
         [0039]    A preferred adjustment means comprises a system wherein the blades  40  and  41  are simultaneously adjustable. In the present invention, the blades  40  and  41  are connected to rotatable shafts  122 - 1  and  122 - 2 , as illustrated in FIGS. 3 and 5. The rotatable shafts  122 - 1  and  122 - 2  extend through the housing  42  of the balancing damper assembly  26 .  
         [0040]    As shown in FIGS. 8 and 9, a control knob  90  is provided to adjust rotatable shafts  122 - 1  and  122 - 2 , such that the blades  40  and  41  can be placed in an open or closed position. Control knob  90  turns control stem  92 , which is in turn connected to rotatable shafts  122 - 1  and  122 - 2 . Control knob  90  can be rotated in either a clockwise or counter-clockwise direction. This manipulation forces movement of the control stem  92  to shift upwards or downwards (depending on the direction the control knob is turned), thereby causing movement of the rotatable shafts  122 - 1  and  122 - 2 . In a preferred embodiment, clockwise rotation of control knob  90  will cause movement of the rotatable shafts  122 - 1  and  122 - 2 , such that blades  40  and  41  move towards each other into a closed position. Similarly, rotation of the control knob  90  in a counter-clockwise direction will cause movement of the rotatable shafts  122 - 1  and  122 - 2 , such that blades  40  and  41  move apart from each other into an open position. In a preferred embodiment, control knob  90  is capable of adjusting both blades  40  and  41  at the same time.  
         [0041]    In an alternative embodiment, the adjustment means may be electronically controlled, either by remote control, a control panel implemented on the balancing damper itself or another part of the furnace assembly. Additionally, the adjustment means may be constructed and arranged so that the blades are individually controlled. In such an embodiment, separate controls may be implemented to independently adjust each blade. Further, the counter-clockwise movement of the control knob  90  may move the blades into a closed position and a clockwise movement of the control knob  90  will move the blades into an open position.  
         [0042]    The direction and amount of two-phase flow through the balancing damper assembly  26  is further manipulated by the geometric configuration of the balancing damper assembly. As illustrated in FIG. 7, both the inlet end  80  and outlet end  82  may have circular cross-sections. The central portion  48  of the housing  42  preferably has a rectangular cross-section. The rectangular shape of the central portion  48  provides additional room for the two-phase flow to pass between the outer edges  40 - 1  and  41 - 2  of the blades  40  and  41 , and the inner walls of the housing  42 - 2 . Additionally, the balancing damper assembly  26  has a transition region  49 , wherein the balancing damper assembly  26  transitions from a circular to square cross-section at its inlet end  80 , and then back to a circular cross-section at its outlet end  82 . It should be appreciated that the components of the balancing damper assembly  26  are not limited to any particular geometric configuration.  
         [0043]    The shape and construction of the blades further manipulates the direction and amount of two-phase flow through the balancing damper assembly. As illustrated in FIGS. 3 and 6, the blades  40  and  41 , are preferably rectangular in shape, but the blades can have various geometric configurations in alternate embodiments.  
         [0044]    The blades  40  and  41  can be attached to the housing in a variety of ways. Preferably, the blades  40  and  41  are welded to rotatable shafts  122 - 1  and  122 - 2 . Alternatively, the blades  40  and  41  can be screwed or nailed to the rotating shafts  122 - 1  and  122 - 2 .  
         [0045]    To connect the balancing damper assembly  26  to the pipes  24  and  25 , as illustrated in FIG. 7, an inlet plate  96  and outlet plate  86  connect the balancing damper assembly  26  to the coal pipes  24  and  25 . The balancing damper assembly may be circular in shape and can be secured to the coal pipes  24  and  25  in a variety of ways. According to one preferred embodiment, inlet plate  96  and outlet plate  86  can be screwed to the coal pipes  24  and  25  through screw holes  86 - 1  to  86 - 18  and  96 - 1  to  96 - 18  (not all shown) located on the inlet and outlet plates  86  and  96 . It should be appreciated that the number of screw holes will depend on the size and strength of the screws utilized. The inlet plate  86  and outlet plate  96  can also be attached by rivets, clamps, friction, adhesives, etc. Additionally the balancing damper housing  42  may be directly welded to coal pipes  24  and  25  without the inlet circular plate  96  and outlet circular plate  86 .  
         [0046]    In another preferred embodiment, as illustrated in FIGS. 10 and 11, a set of turning baffles  130  and  132  are disposed on each of the blades  40  and  41 . The turning baffles  130  and  132  provide yet another feature of the present invention. The turning baffles  130  and  132  further eliminate the occurrences of turbulent eddies in the coal pipe that result in long-term damage to the coal pipes. As illustrated in FIG. 10, the location of the turning baffles  130  and  132  on the blades  40  and  41  distributes the flow of pulverized fuel and the carrier gas towards the center of the blades  40  and  41  and the center of the balancing damper assembly  26 . This ultimately directs the two-phase flow through the center of the coal pipe  25 . Thus, any turbulent eddies that may develop are therefore concentrated at the center of pipe and are harmless to the inner walls of the furnace pipe system. FIG. 11 shows a top view of a blade  40  having a set of turning baffles  130  and  132 .  
         [0047]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.