Abstract:
A nozzle tip [ 100 ] for a pulverized solid fuel pipe nozzle [ 200 ] of a pulverized solid fuel-fired furnace includes: a primary air shroud [ 120 ] having an inlet [ 102 ] and an outlet [ 104 ], wherein the inlet [ 102 ] receives a fuel flow [ 230 ]; and a flow splitter [ 180 ] disposed within the primary air shroud [ 120 ], wherein the flow splitter disperses particles in the fuel flow [ 230 ] to the outlet [ 104 ] to provide a fuel flow jet which reduces NOx in the pulverized solid fuel-fired furnace. In alternative embodiments, the flow splitter [ 180 ] may be wedge shaped and extend partially or entirely across the outlet [ 104 ]. In another alternative embodiment, flow splitter [ 180 ] may be moved forward toward the inlet [ 102 ] to create a recessed design.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present invention claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 61/034,780, entitled “LOW NOx NOZZLE TIP”, and co-pending U.S. Provisional Patent Application 61/034,796, entitled “LOW NO X  NOZZLE TIP FOR A PULVERIZED SOLID FUEL FURNACE” both of which are hereby incorporated by reference as if set forth in there entirety herein. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    The U.S. Government has rights in this invention pursuant to Contract No. DE-FC26-04NT42300 awarded by the U.S. Department of Energy. 
     
    
     TECHNICAL FIELD 
       [0003]    The present disclosure relates generally to firing systems for use with pulverized solid fuel-fired furnaces, and more specifically, to a low NOx pulverized solid fuel nozzle tip providing separate and discrete air/pulverized fuel jets for use in such firing systems. 
       BACKGROUND 
       [0004]    Pulverized solid fuel has been successfully burned in suspension in furnaces by tangential firing methods for a long time. The tangential firing method has many advantages, among them being good mixing of the pulverized solid fuel and air, stable flame conditions, and long residence time of combustion gases in the furnaces. 
         [0005]    Systems for delivering the pulverized solid fuel (e.g., coal) to a steam generator typically include a plurality of nozzle assemblies through which the pulverized coal is delivered, using air, into a combustion chamber of the steam generator. The nozzle assemblies are typically disposed within windboxes, which may be located proximate to the corners of the steam generator. Each nozzle assembly includes a nozzle tip, which protrudes into the combustion chamber. Each nozzle tip delivers a single stream, or jet, of the pulverized coal and air into the combustion chamber. After leaving the nozzle tip, the single pulverized coal/air jet disperses in the combustion chamber. 
         [0006]    Typically, the nozzle tips are arranged to tilt up and down to adjust the location of the flame within the combustion chamber. The flames produced at each pulverized solid fuel nozzle are stabilized through global heat- and mass-transfer processes. Thus, a single rotating flame envelope (e.g., a “fireball”), centrally located in the furnace, provides gradual but thorough and uniform pulverized solid fuel-air mixing throughout the entire furnace. 
         [0007]    Recently, more and more emphasis has been placed on minimization of air pollution. In connection with this, with reference in particular to the matter of NO X  control, it is known that oxides of nitrogen are created during fossil fuel combustion primarily by two separate mechanisms which have been identified to be thermal NO X  and fuel NO X . Thermal NO X  results from the thermal fixation of molecular nitrogen and oxygen in the combustion air. The rate of formation of thermal NO X  is extremely sensitive to local flame temperature and somewhat less sensitive to local concentration of oxygen. Virtually all thermal NO X  is formed at a region of the flame which is at the highest temperature. The thermal NO X  concentration is subsequently “frozen” at a level prevailing in the high temperature region by the thermal quenching of the combustion gases. The flue gas thermal NO X  concentrations are, therefore, between the equilibrium level characteristic of the peak flame temperature and the equilibrium level at the flue gas temperature. 
         [0008]    On the other hand, fuel NO X  derives from the oxidation of organically bound nitrogen in certain fossil fuels such as coal and heavy oil. The formation rate of fuel NO X  is highly affected by the rate of mixing of the fossil fuel and air stream in general, and by the local oxygen concentration in particular. However, the flue gas NO X  concentration due to fuel nitrogen is typically only a fraction, e.g., approximately 20 to 60 percent, of the level which would result from complete oxidation of all nitrogen in the fossil fuel. From the preceding, it should thus now be readily apparent that overall NO X  formation is a function both of local oxygen levels and of peak flame temperatures. 
         [0009]    Although the pulverized solid fuel nozzle tips of the prior art are operative for their intended purposes, there has nevertheless been evidenced in the prior art a need for such pulverized solid fuel nozzle tips to be further improved, specifically in the pursuit of reduced air pollution, e.g., NO X  emissions. More specifically, a need has been evidenced in the prior art for a new and improved low NO X  pulverized solid fuel nozzle tip for use in a tangential firing system that would enable more flexibility in the control of undesirable emissions such as nitric oxides. 
       SUMMARY 
       [0010]    According to the aspects illustrated herein, there is provided a nozzle tip for a pulverized solid fuel pipe nozzle of a pulverized solid fuel-fired furnace. The nozzle tip includes: a primary air shroud having an inlet and an outlet, wherein the inlet receives a fuel flow; and a flow separator disposed within the primary air shroud, wherein the flow separator disperses the fuel flow from the outlet to provide a fuel flow jet which reduces NO X  in the pulverized solid fuel-fired furnace 
         [0011]    The above described and other features are exemplified by the following figures and detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike: 
           [0013]      FIG. 1  is a cutaway front perspective view of a nozzle tip according to an exemplary embodiment of the present invention. 
           [0014]      FIG. 2  is a cutaway rear perspective view of the nozzle tip of  FIG. 1 . 
           [0015]      FIG. 3  is a partial cross-sectional side view showing the nozzle tip of  FIGS. 1 and 2  connected to a pulverized solid fuel pipe of a pulverized solid fuel-fired furnace. 
           [0016]      FIG. 4  is a photograph of a water table test which illustrates separate air-fuel jets exiting the nozzle tip of  FIGS. 1-3 . 
           [0017]      FIG. 5  is a partial cross-sectional side view showing a nozzle tip according to an alternative exemplary embodiment of the present invention. 
           [0018]      FIG. 6  is a plan view from the outlet side of an alternative embodiment of the nozzle tip of the present invention employing air deflectors. 
           [0019]      FIG. 7  is a rear perspective view of the nozzle tip of  FIG. 6 . 
           [0020]      FIG. 8  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 6 and 7 . 
           [0021]      FIG. 9  is a plan view from the outlet side of an alternative embodiment of the nozzle tip of the present invention employing a center bluff. 
           [0022]      FIG. 10  is a rear perspective view of the nozzle tip of  FIG. 9 . 
           [0023]      FIG. 11  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 9 and 10 . 
           [0024]      FIG. 12  is a plan view from the outlet side of an alternative embodiment of the nozzle tip of the present invention employing a recessed center bluff. 
           [0025]      FIG. 13  is a rear perspective view of the nozzle tip of  FIG. 12 . 
           [0026]      FIG. 14  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 12 and 13 . 
           [0027]      FIG. 15  is a plan view from the outlet side of an “X”-shaped nozzle tip being an alternative embodiment of and of the present invention. 
           [0028]      FIG. 16  is a rear perspective view of the nozzle tip of  FIG. 15 . 
           [0029]      FIG. 17  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 15 and 16 . 
           [0030]      FIG. 18  is a plan view from the outlet side of a nozzle tip employing a flow splitter with diffuser blocks according to another embodiment of the present invention. 
           [0031]      FIG. 19  is a rear perspective view of the nozzle tip of  FIG. 18 . 
           [0032]      FIG. 20  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 18 and 19 . 
           [0033]      FIG. 21  is a plan view from the outlet side of a round coal nozzle tip according to another embodiment of the present invention. 
           [0034]      FIG. 22  is a rear perspective view of the nozzle tip of  FIG. 21 . 
           [0035]      FIG. 23  is a computer-generated simulation showing the predicted particle concentration for the nozzle tip of  FIGS. 21 and 22 . 
           [0036]      FIG. 24  is a plan view from the outlet side of a round coal nozzle tip with a recessed swirler in accordance with another embodiment of the present invention. 
           [0037]      FIG. 25  is a rear perspective view of the nozzle tip of  FIG. 24 . 
           [0038]      FIG. 26  is a computer-generated simulation showing the predicted particle concentration for the nozzle tip of  FIGS. 24 and 25 . 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    As with all of the figures, elements with the same reference numbers perform the same or very similar function with the same or very similar structure. Therefore, a description in connection with one figure will apply to the element having the same reference number in all other figures. 
         [0040]    Disclosed herein is a low NO X  pulverized solid fuel nozzle tip, and more specifically, a pulverized solid fuel nozzle tip that provides separate and discrete air/pulverized fuel jets for use in a firing system of a pulverized solid fuel-fired furnace. As compared to a nozzle providing a single air/pulverized fuel jet, penetration of the separate and discrete air/pulverized fuel jets is decreased, and a surface area thereof is increased. As a result, NO x  emissions of the pulverized solid fuel-fired furnace are substantially reduced and/or effectively minimized, as will hereinafter be described in further detail with reference to the accompanying drawings. 
         [0041]    Referring to  FIGS. 1 and 2 , a nozzle tip  100  having an inlet end  102  and an outlet end  104  includes a secondary air (SA) shroud  110  and a primary air (PA) shroud  120  enclosed therein. The PA shroud  120  includes PA shroud side plates  122 , a PA shroud top plate  124  and a PA shroud bottom plate  126 . 
         [0042]    The SA shroud  110  is supported by supports  130  located between the SA shroud  110  and the PA shroud  120 . Further, an SA duct  135  substantially surrounds the PA shroud  110 . Specifically, the SA duct  135  includes spaces created between the supports  130  and the PA shroud top plate  124 , the supports  130  and the PA shroud bottom plate  126 , and spaces created between the supports  130  and the PA shroud side plates  122 . 
         [0043]    A primary air-pulverized solid fuel (PA-PSF) duct  150  is formed in a space created within the PA shroud side plates  122 , the PA shroud top plate  124  and the PA shroud bottom plate  126 . Splitter plates  160  are formed in the PA-PSF duct  150 . As shown in  FIG. 1 , the splitter plates  160  are disposed in the PA-PSF duct  150 , and extend substantially parallel to corresponding surfaces defining the PA shroud top plate  124  and the PA shroud bottom plate  126 , respectively. 
         [0044]    In an exemplary embodiment, such as illustrated in  FIG. 1 , the splitter plates  160  are formed to have a curve. Specifically, portions of the splitter plates  160  closest to the nozzle tip outlet end  104  curve outward, e.g., away from a central inner area of the PA-PSF duct  150 . More specifically, a portion of an upper splitter plate  160  curves toward the PA shroud top plate  124 , while a portion of a lower splitter plate  160  curves toward the PA shroud bottom plate  126 , as shown in  FIG. 1 . However, alternative exemplary embodiments are not limited thereto. For example, each of the splitter plates  160  may be formed to be substantially straight, e.g., rectilinear, or, alternatively, the splitter plates  160  may be formed to have a series of discrete angular, e.g., not smoothly curved, bends. 
         [0045]    Still referring to  FIG. 1 , the splitter plates  160  include shear bars  170 . In an exemplary embodiment, the upper splitter plate  160  includes a first shear bar  170  disposed proximate to the outlet  104  and on the portion of the upper splitter plate  160  which curves toward the PA shroud top plate  124 , while the lower splitter plate  160  includes a second shear bar  170  disposed proximate to the outlet  104  and on the portion of the lower splitter plate  160  which curves toward the PA shroud bottom plate  126 . Further, the first shear bar  170  is disposed on a surface of the upper splitter plate  160  which faces the PA shroud top plate  124 , while the second shear bar  170  is disposed on a surface of the lower splitter plate  160  which faces the PA shroud bottom plate  126 . It will be noted that alternative exemplary embodiments are not limited to the above-mentioned description, e.g., the shear bars  170  may be located at different locations on the splitter plates  160  than as shown in  FIG. 1 . For example, in an alternative exemplary embodiment, the shear bars  170  may be located on different, e.g., opposite, surfaces of the upper splitter plate  160  and/or the lower splitter plate  160 . 
         [0046]    A flow splitter  180  is disposed in the PA-PSF duct  150  between the splitter plates  160 . In an exemplary embodiment, the flow splitter  180  is disposed approximately midway between ends of the curved portions of the splitter plates  160  (described in greater detail above). Further, the flow splitter  180  extends between the PA shroud side plates  122 , as shown in  FIG. 1 , but alternative exemplary embodiments are not limited thereto. For example, the flow splitter  180  may not extend fully between the PA shroud side plates  122 , e.g., may have length less than a distance measured between the PA shroud side plates  122 . In addition, the flow splitter  180  may be located in a different area of the PA-PSF duct  150 , e.g., not approximately midway between the ends of the curved portions of the splitter plates  160  in alternative exemplary embodiments. For instance, in one embodiment the flow splitter  180  may extend from one PA shroud side plate  122  to approximately the mid point of the PA shroud. Furthermore, a location of the flow splitter  180  between the edges of the splitter plates  160  may be adjusted based upon predetermined requirements of PA-PSF jets, discussed in greater detail below. For example, in an alternative exemplary embodiment, the flow splitter  180  may be disposed closer to one splitter plate  160  than another. 
         [0047]    In an exemplary embodiment, the flow splitter  180  has a substantially triangular wedge shape in cross section, as shown in  FIG. 1 , but alternative exemplary embodiments are not limited thereto. Rather, the flow splitter  180  may be other shapes, such as rectangular, trapezoidal, pentagonal and other polygonal shapes, for example, or any other shape suitable for operative purposes thereof, e.g., to assist separation of an air/pulverized fuel jet into separate and discrete jets which do not recombine until after traveling a predetermined distance into a furnace, as will be described in further detail below with reference to  FIG. 3 . In addition, the flow splitter  180  according to an exemplary embodiment may include one or more shear bars  170  disposed thereon. Likewise, shear bars  170  may be disposed on additional surfaces such as the PA shroud side plates  122 , the PA shroud top plate  124  and/or the PA shroud bottom plate  126 , for example, but alternative exemplary embodiments are not limited thereto. 
         [0048]    Referring now to  FIG. 2 , the sides of the SA shroud  110  and the PA shroud side plates  122  each have an aperture  190  therethrough. The apertures  190  are aligned along a common axis which serves as a pivot point  191  (best shown in  FIG. 3 ) to allow the nozzle tip  100  to tilt up and down during operation. 
         [0049]    Referring now to  FIG. 3 , the nozzle tip  100  is mounted on a pulverized solid fuel pipe nozzle  200  of a pulverized solid fuel pipe  210  mounted within a pulverized solid fuel-air delivery conduit  220 . More specifically, the pulverized solid fuel pipe nozzle  200  is attached to the aperture  190  at the nozzle tip inlet end  102  ( FIG. 1 ) of the nozzle tip  100 . The pulverized solid fuel pipe  210  delivers a fuel flow  230 , e.g., a PSF-PA inlet jet  230 , to the PS-PSF duct  150  through the nozzle tip inlet end  102 , while secondary air  240  is delivered to the SA duct  135  of the nozzle tip  100 , as shown in  FIG. 3 . Seal plates  250  attached to the pulverized solid fuel pipe nozzle  200  form an annular sealing shroud (not shown) which prevents the PA-PSF inlet jet  230  from entering the SA duct  135  and/or the SA  240  from entering the PA-PSF duct  150 . The seal plates  250  may be omitted in an alternative exemplary embodiment. 
         [0050]    The PA-PSF duct  150  of the nozzle tip  100  according to an exemplary embodiment is divided into three (3) chambers. Specifically, the PA-PSF duct  150  is divided into an upper PA-PSF chamber  260 , a middle PA-PSF chamber  270  and a lower PA-PSF chamber  280 . More specifically, the upper PA-PSF chamber  260  is defined by the PA shroud top plate  124  and an upper (with respect to  FIG. 3 ) splitter plate  160 , the middle PA-PSF chamber  270  is defined by the upper splitter plate  160  and a lower (with respect to  FIG. 3 ) splitter plate  160 , and the lower PA-PSF chamber  280  is defined by the lower splitter plate  160  and the PA shroud bottom plate  126 . As described above in greater detail and illustrated in  FIG. 3 , the flow splitter  180  is thus disposed within the middle PA-PSF jet chamber  270 , while the shear bars  170  are disposed on respective splitter plates  160  within the upper PA-PSF jet chamber  260  and the lower PA-PSF jet chamber  280 , but alternative exemplary embodiments are not limited thereto. For example, the shear bars  170 , or an additional shear bar  170 , may be disposed within the middle PA-PSF jet chamber  270 , while the flow splitter, or additional flow splitters  180 , may be disposed in any or all of the upper PA-PSF jet chamber  260 , the middle PA-PSF jet chamber  270  and/or the lower PA-PSF jet chamber  280 . 
         [0051]    Operation of the nozzle tip  100  will now be described in further detail with reference to  FIG. 3 . During operation of a pulverized solid fuel-fired furnace (not shown) having the nozzle tip  100 , the PA-PSF inlet jet  230  is supplied to the PA-PSF duct  150  of the nozzle tip  100  through the pulverized solid fuel pipe  210  via the pulverized solid fuel pipe nozzle  200 . 
         [0052]    Once inside the nozzle tip  100  and, more specifically, once inside the PA-PSF duct  150  of the nozzle tip  100 , the PA-PSF inlet jet  230  is divided into three (3) separate jets, e.g., an upper PA-PSF jet  290 , a middle PA-PSF jet  300  and a lower PA-PSF jet  310 , as shown in  FIG. 3 . The three (3) separate jets are formed based on the geometry, described above in greater detail, of the nozzle tip  100 . More specifically, division of the PA-PSF inlet jet  230  into the three (3) separate jets is based upon physical dimensions of each of the upper PA-PSF chamber  260 , the middle PA-PSF chamber  270  and the lower PA-PSF chamber  280 . These physical dimensions are based on a predetermined shape and placement of the splitter plates  160  and the flow splitter  180  within the PA-PSF duct  150 , for example, but are not limited thereto. As a result, an optimum division of the PA-PSF inlet jet  230  into the three (3) separate jets, e.g., the upper PA-PSF jet  290 , the middle PA-PSF jet  300  and the lower PA-PSF jet  310 , is obtained, based upon desired and/or actual operating conditions and characteristics of the pulverized solid fuel-fired furnace (not shown), as will be described in further detail below. 
         [0053]    After traversing the PA-PSF duct  150 , the upper PA-PSF jet  290 , the middle PA-PSF jet  300  and the lower PA-PSF jet  310  exit the nozzle tip  100  at the nozzle tip outlet end  104  into the pulverized solid fuel-fired furnace (not shown). When exiting the nozzle tip  100 , the upper PA-PSF jet  290 , the middle PA-PSF jet  300  and the lower PA-PSF jet  310  exit the nozzle tip  100  form two (2) separate, e.g., discrete, jets, namely an upper PA-PSF outlet jet  320  and a lower PA-PSF outlet jet  330 , as shown in  FIG. 3 . Components within the PA-PSF duct  150 , e.g., the splitter plates  160 , the shear bars  170  and the flow splitter  180 , as well as the arrangement of the abovementioned components, described in greater detail above, determine formation of the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330 . In particular, the flow splitter  180  causes the upper PA-PSF jet  290 , the middle PA-PSF jet  300  and the lower PA-PSF jet  310  to combine such that the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  exit the nozzle tip  100  as separate, discrete jets, e.g., such that the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  do not mix with each other after exiting the nozzle tip  100  and entering the pulverized solid fuel-fired furnace (not shown). More specifically, the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  remain separate and discrete for a predetermined distance after leaving the nozzle tip  100 , as shown in  FIG. 4 . In an exemplary embodiment, the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  remain separate and discrete for a distance from the nozzle tip equal to approximately 2 to approximately 8 jet diameters of the upper PA-PSF outlet jet  320  and/or the lower PA-PSF outlet jet  330 , after which the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  begin to disburse and mix with gases in the furnace, but alternative exemplary embodiments are not limited thereto. Further, after partial disbursement of the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330 , portions thereof, e.g., on a periphery of the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330 , may recirculate back towards the center flow splitter  180 , thereby enhancing ignition and flame stability of the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330 . As a result, NO x  emissions from a pulverized solid fuel-fired furnace utilizing the nozzle tip  100  according to an exemplary embodiment are substantially reduced as compared to NO x  emissions from a pulverized solid fuel-fired furnace utilizing a nozzle tip of the prior art. Specifically, test results have shown that, according to one exemplary embodiment, improvements, e.g., reductions, in NO x  emissions of approximately 20 percent to approximately 30 percent are obtained, due to implementation of the nozzle tip  100  (with other parameters affecting NO x  emissions at equivalent levels). Depending upon the type of coal burned, further testing shows that the nozzle tip according to an exemplary embodiment reduces NO x  emissions by approximately 36 percent to approximately 50 percent as compared to other known nozzle tips of the prior art. 
         [0054]    Thus, as can be seen in  FIG. 3 , the flow splitter  180  divides the middle PA-PSF jet  300 , into an upper portion  350  and a lower portion  360 . Thus, upon exiting the nozzle tip  100 , the upper portion  350  of the PA-PSF jet  300  combines with the upper PA-PSF jet  290  to form the upper PA-PSF outlet jet  320 . In a similar manner, the lower portion  360  of the PA-PSF jet  300  combines with the lower PA-PSF jet  310  to form the lower PA-PSF outlet jet  330 . 
         [0055]    The physical dimensions, shape, and placement of the splitter plates  160  and the flow splitter  180  within the PA-PSF duct  150 , which result in the optimum division of the PA-PSF inlet jet  230  into the three (3) separate jets (as described above), further result in optimum formation of each of the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  according to desired and/or actual operating conditions and characteristics of the pulverized solid fuel-fired furnace (not shown). For example, an initial separation distance between the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330 , dimensions thereof (e.g., diameters), and a distance which the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  travel after exiting the nozzle tip  100  before disbursing is determined base on the physical dimensions, shape, and placement of the splitter plates  160  and the flow splitter  180  within the PA-PSF duct  150 . 
         [0056]    Bent portions  340  on the PA shroud top plate  124  and the PA shroud bottom plate  126  near the nozzle tip outlet end  104  further prevent mixing of the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  after leaving the nozzle tip  100 . In an exemplary embodiment, the bent portions  340  bend outward, e.g., away from the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  exiting the nozzle tip  100 . 
         [0057]    In an exemplary embodiment, the PA-PSF inlet jet  230  is evenly divided by the splitter plates  160  in the PA-PSF duct  150  such that the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330  each include approximately 50 percent of a total flow through the nozzle tip  100 , e.g., each include approximately 50 percent of the PA-PSF inlet jet  230 , but alternative exemplary embodiments are not limited thereto. Further, proportions of jet flow in the upper PA-PSF chamber  260 , the middle PA-PSF chamber  270  and the lower PA-PSF chamber  280  may be substantially equally divided, e.g., each having approximately ⅓ of the total flow through the nozzle tip  100 . However, alternative exemplary embodiments are not limited thereto; for example, proportions of jet flow in the upper PA-PSF chamber  260 , the middle PA-PSF chamber  270  and the lower PA-PSF chamber  280  may be approximately 30 percent, approximately 40 percent and approximately 30 percent, respectively. 
         [0058]    As described above in greater detail, the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  are separate and discrete, and enter a combustion chamber of the pulverized solid fuel-fired furnace (not shown) through the nozzle tip outlet end  104  of the nozzle tip  100  as separate and discrete jets. Further, the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  remain separate and discrete in the combustion chamber. Specifically, the upper PA-PSF outlet jet  320  and the lower PA-PSF outlet jet  330  do not mix until traveling a predetermined distance after leaving the nozzle tip  100  according to an exemplary embodiment, as best shown in  FIG. 4  and described above in greater detail with reference to  FIG. 3 . 
         [0059]    In an alternative exemplary embodiment, the flow splitter  180  is omitted, as shown in  FIG. 5 . It will be noted that the same reference numerals in  FIG. 5  denote the same or like components as shown in  FIG. 3 , and any repetitive detailed description thereof of has been omitted. Referring to  FIG. 5 , the middle PA-PSF jet  300  is dispersed whereby an upper portion  350  thereof combines with the upper PA-PSF jet  290  to form the upper PA-PSF outlet jet  320 , and the lower portion  360  thereof combines with the lower PA-PSF jet  310  to form the lower PA-PSF outlet jet  330 . 
         [0060]    As a result of dividing the PA-PSF inlet jet  230  into separate jets, e.g., into the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330 , a low pressure area is formed in a region substantially between the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330 , relative to pressures of other areas substantially adjacent to (or even within) each of the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330 . Thus, the low pressure area substantially between the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330  provides a low resistance path to permit a combustion flame to ignite the fuel (e.g., coal particles) disposed within the inner portion of the outlet fuel jet, thereby consuming oxygen therein. As a result, oxygen in the low pressure region is effectively depleted, resulting in less oxygen available for NO x  formation, thereby substantially decreasing NO x  emissions from a pulverized solid fuel-fired boiler having the nozzle tip according to an exemplary embodiment. Specifically, computational fluid dynamics modeling and combustion testing of a nozzle tip according to an exemplary embodiment suggest that concentrating the coal particles towards the outside of the coal stream is advantageous for reducing NO X  emissions while minimizing unburned carbon levels. One will appreciate that this embodiment shown and described hereinbefore in  FIGS. 1-3  having a flow splitter  180  provides a similar low pressure area disposed at the an outer surface of the flow splitter. 
         [0061]    Dividing the PA-PSF inlet jet  230  into separate and discrete jets, e.g., into the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330 , results in a low pressure area in a region substantially between the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330 , relative to pressures of other areas substantially adjacent to (or even within) each of the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330 . Thus, the low pressure area substantially between the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330  results in a combustion flame being drawn to the low pressure area, thereby consuming oxygen therein. As a result, oxygen in the low pressure region is effectively depleted, resulting in less oxygen available for NO x  formation, thereby substantially decreasing NO x  emissions from a pulverized solid fuel-fired boiler having the nozzle tip according to an exemplary embodiment. 
         [0062]    In addition, dividing the PA-P SF inlet jet  230  into the separate and discrete jets, e.g., into the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330 , further results in each of the separate and discrete jets having a decreased diameter relative to a diameter of the upper PA-PSF outlet jet  320 . More specifically, assuming a cross-sectional surface area A of the PA-PSF inlet jet  230  having a diameter a diameter D, the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330  each have a diameter D 1 =D/√{square root over (2)} (given that a summed cross-sectional surface area of an area of the upper PA-PSF outlet jet  320  and an area of the lower PS-PSF outlet jet  330  is equal to A). Thus, jet penetration for the separate and discrete jets (compared to a single jet of equivalent area) decreases while jet dispersion thereof increases, since jet penetration is directly proportional to jet diameter and jet dispersion is indirectly proportional to jet diameter. 
         [0063]    Furthermore, a total wetted perimeter P T  of the two separate and discrete jets having the diameter D 1  is substantially increased or effectively improved as compared to a wetted perimeter P of a single jet, e.g., the PA-PSF inlet jet  230  having the cross-sectional area A. Specifically, the upper PA-PSF outlet jet  320  and the lower PS-PSF outlet jet  330 , each having the diameter D 1 =D/√{square root over (2)} combine to yield a resultant total wetted perimeter P T =2(2*π*(D 1 /2))=√{square root over (2)}*P. As a result, jet dispersion, e.g., jet breakdown, is further increased. The increased total wetted perimeter of the separate and distinct jets allows for controlled amounts of air available at a near field of combustion in the combustion chamber to mix with pulverized solid fuel, thereby improving early flame stabilization and devolatilization. The increased total wetted perimeter also allows for improved mixing and recirculation of hot products of combustion over a greater area of the fuel jet, also resulting in improved early flame stabilization and early devolatilization of the fuel and/or fuel-bound nitrogen in an oxygen-limited, fuel-rich substoichiometric region of a near field of a region downstream of the nozzle tip  100 . 
         [0064]    Thus, the nozzle tip  100  according to exemplary embodiments described herein provides at least the advantages of decreased primary air/pulverized fuel jet penetration and increased primary air/pulverized fuel jet surface area, wetted area and dispersion, thereby enhancing early ignition, early flame stabilization, fuel devolatilization and early fuel bound nitrogen release. As a result, NO X  emissions from a pulverized solid fuel-fired boiler having the nozzle tip in accordance with an exemplary embodiment of the present invention are substantially decreased or effectively reduced. The aforementioned advantages are apparent when implementing the nozzle tip according to an exemplary embodiment in a boiler designed to have reduced main burner zone (“MBZ”) stoichiometry, e.g., in a staged combustion environment in which it is desirable to initiate combustion closer to the nozzle tip (as compared to boilers having a high MBZ stoichiometry), but alternative exemplary embodiments are not limited thereto. 
         [0065]      FIG. 6  is a plan view from the outlet side of an alternative embodiment of the nozzle tip of the present invention employing air deflectors. This embodiment is similar to that of  FIG. 5 , with the exceptions that splitter plates  160  do not diverge, shear bars  170  are not employed and air deflectors  175  are added as shown. 
         [0066]      FIG. 7  is a rear perspective view of the nozzle tip of  FIG. 6 . Here splitter plates  160  are shown as well as the air deflectors  175 . 
         [0067]      FIG. 8  is a computer-generated simulation showing the predicted particle concentration for the nozzle tip of  FIGS. 6 and 7 . In this, and all following simulations, a computer model was generates using applicable conditions to predict how the particles were concentrated after they had passed through the nozzle. These simulations are important in designing a low NOx nozzle. 
         [0068]    No simulation data was generated for the areas in white. In this case, it was the air passing through the secondary air nozzle  135 . 
         [0069]      FIG. 9  is a plan view from the outlet side of an alternative embodiment of the nozzle tip of the present invention employing a center bluff.  FIG. 10  is a rear perspective view of the nozzle tip of  FIG. 9 . This embodiment will be described with reference to both  FIGS. 9 and 10 . 
         [0070]    A splitter plate  160  is positioned through the center of outlet  104  in both a vertical direction and a horizontal direction. Here the flow splitter  180  having a wedge shape having a base  483  and an apex edge  481 . Flow splitter  180  is positioned at the center relative to the vertical and horizontal directions. It is also placed at the rear of the nozzle  100 , flush with the outlet  104 . This embodiment also includes air deflectors  175 . 
         [0071]      FIG. 11  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 9 and 10 . There is a pattern of particle distribution to downstream from the nozzle. Since flow splitter  180  has a hollow base  181 , particles are allowed to recirculate into flow splitter  180 . 
         [0072]      FIG. 12  is a plan view from the outlet side of an alternative embodiment of the nozzle tip of the present invention employing a recessed center bluff.  FIG. 13  is a rear perspective view of the nozzle tip of  FIG. 12 . The elements of this embodiment will be described in connection with both  FIGS. 12 and 13 . 
         [0073]    This embodiment includes multiple splitter plates  160  oriented in both the vertical and horizontal directions. Flow splitter  180  is enclosed with a flat base  481 . The flow splitter  180   0  is offset, or recessed inward away from the outlet  104  edge as compared with the flow splitter of  FIGS. 9 and 10 . 
         [0074]      FIG. 14  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 12 and 13 . The apex edge  483  of the flow splitter cuts through the oncoming flow of particles and splits the flow into a flow above and below the flow splitter  180 . There is a turbulent zone immediately downstream from the base  481  of flow splitter  180 . 
         [0075]      FIG. 15  is a plan view from the outlet side of an “X”-shaped nozzle tip being an alternative embodiment of and of the present invention.  FIG. 16  is a rear perspective view of the nozzle tip of  FIG. 15 . This embodiment will be described in connection with both  FIGS. 15 and 16 . 
         [0076]    Outlet  104  has a general “X” shape, with the outlet  104  extending outward into 4 outlet lobes  106  of outlet  104 . 
         [0077]    A flow splitter  180  is positioned on a splitter plate  160  oriented horizontal across the nozzle  100  approximately evenly bisecting outlet  104  into an upper half and a lower half. 
         [0078]    The flow splitter  180  has a leading section  181  and a trailing section  182  both inclines toward a center of the flow splitter both along its length and width. The leading section  181  has a 4-sided pyramid shape with a leading apex  183  and a base (not shown). 
         [0079]    The trailing section [ 182 ] also is shaped like a 4-sided pyramid having an apex  184  and a base (not shown). In this embodiment, the bases of the pyramids are together with the apices pointing away from each other. 
         [0080]    Each side of the leading section  181  of the flow splitter  180  are positioned, sized and angled to deflect incident flow toward its nearest outlet lobe  105 . This effectively splits the flow into 4 components, one for each outlet lobe  106 . 
         [0081]      FIG. 17  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 15 and 16 . The cross sectional shape of flow splitter  180  can be seen in this figure. Leading section  181  here appears having a triangular cross-sectional shape. Trailing section  182  also has a cross sectional shape. The apex  183  of leading section  181  is visible as is apex  184  of the trailing section  182 . 
         [0082]    In an alternative embodiment, only a leading section  181  is used for the flow splitter  180 . This may have a flat base, or be hollow. 
         [0083]      FIG. 18  is a plan view from the outlet side of a nozzle tip employing a flow splitter with diffuser blocks.  FIG. 19  is a rear perspective view of the nozzle tip of  FIG. 18 . These embodiments are the subject of U.S. Pat. No. 6,439,136 B1 issued Aug. 27, 2002 to Jeffrey S. Mann and Ronald H. Nowak, hereby incorporated by reference as if set forth in its entirety herein. A full description of this embodiment is presented in this application. 
         [0084]    Here the flow splitter  180  employs several diffusion blocks adjacent to each other on alternating sides of splitter plate  160 . 
         [0085]      FIG. 20  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 18 and 19 . This shows the cross-sectional shape of the nozzle. The diffusion blocks  186  attached to the splitter plates  160  can be seen in cross section. 
         [0086]      FIG. 21  is a plan view from the outlet side of a round coal nozzle tip.  FIG. 22  is a rear perspective view of the nozzle tip of  FIG. 21 . This, and related embodiments are the subject of pending U.S. patent Ser. No. 11/279,123 filed Apr. 10, 2006 entitled “Pulverized Solid Fuel Nozzle” by Oliver G. Biggs, Jr., Kevin E. Connolly, Kevin A. Greco, Philip H Lafave and Galen H. Richards (the “Round Nozzle Tip Application”) hereby incorporated by reference as if set forth in its entirety herein. A full description of this embodiment is presented in this application. 
         [0087]    A circular outlet  408  houses a rotor  470  on a rotor hub  480 . An annular air duct  435  encircles the circular outlet  408 . 
         [0088]      FIG. 23  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 21 and 22 . This shows it&#39;s cross sectional structure. Rotor hub  480  mixes the particles as they pass through the rotor and out of outlet  404 . 
         [0089]      FIG. 24  is a plan view from the outlet side of a round coal nozzle tip with a recessed swirler.  FIG. 25  is a rear perspective view of the nozzle tip of  FIG. 24 . This is similar to the Round Nozzle Tip Application above. 
         [0090]    These figures show a similar structure to that  FIGS. 21-22 , except that the rotor  470  is recessed within the nozzle. 
         [0091]      FIG. 26  is a computer-generated simulation showing the predicted particle flow concentration for the nozzle tip of  FIGS. 24 and 25 . This shows it&#39;s cross sectional structure. Rotor hub  480  and outlet  408  are visible in this view. 
         [0092]    While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.