Patent Document

TECHNICAL FIELD 
     The present disclosure relates registers for furnaces that burn pulverized coal and more specifically to swirl registers for wall burners of furnaces that burn pulverized coal. 
     BACKGROUND 
     Current coal fired boilers employ burners located in the furnace wall (“wall burners”) to burn pulverized coal. These typically are used to make steam for generation of electricity. 
     Generally, pulverized coal is suspended in an air stream and blown into a boiler&#39;s furnace for burning. Air is introduced into the combustion chamber through registers along with the pulverized coal in a swirled fashion around a core of the pulverized coal stream. This provides more efficient burning and control over NO, emissions. 
     Combustion air is provided to the registers through an air conduit referred to as a ‘windbox’. The air passes from the windbox through the registers into the combustion chamber. 
     Some registers employ vanes that direct the incoming stream of air into a helical shape. The fuel stream passes longitudinally through the center of the burner and mixes with the swirling air from the register. The vanes may be moveable to adjust the swirl of air entering the register. The position of the vanes changes the ratio of axial airflow to tangential airflow. 
     These different flow patterns determine the shape and length of the flame produced and allow the proportion of the air&#39;s axial and tangential component to change the shape of the flame. The proper flame shape reduces flame quenching when it contacts the far boiler wall. 
     Therefore, it is important to be able to adjust the vanes to provide more efficient combustion. 
     In the prior art designs the linkage mechanism that controls the position of the vanes was located in the windbox. Typically, this is acceptable. However, when certain regenerative air heaters are used, exhaust gas impurities, such as flyash is transferred from the exiting flue gas into the windbox. Since the mechanism to rotate the vanes is also in the windbox, the accumulation of these impurities causes clogging and failure of the vane motion mechanism. 
     Prior art designs have the vanes on pivots between two parallel plates. The plate and vane closer to the combustion chamber experiences a higher temperature. The plate further from the combustion chamber experiences a lower temperature. The temperature differential causes differential expansion of the parts and structure. This variable expansion causes binding of the vanes between the plates. This binding prohibits the motion of the vanes, and leads to inefficient operation. 
     Since different vanes and different number of vanes may bind at different times, it introduces mechanical and reliability problems. 
     What further complicates the situation is that the mechanism that operates the motion of the vanes is typically located within the windbox. Its location is difficult to access for maintenance. It may require shutting down the boiler and may also require disassembly to access the windbox to adjust or repair the mechanism. 
     Currently, there is a need for an efficient burner for a furnace that is simple, inexpensive and more reliable than current designs. 
     SUMMARY 
     The present invention may be embodied as a swirl register [ 1000 ] for use in a furnace with a windbox comprising: 
     a first side plate [ 1110 ] being generally flat; 
     a second side plate [ 1120 ] being generally flat; 
     a plurality of swirl blocks [ 1150 ] spaced apart from each other connected between the side plates [ 1110 ,  1120 ] so as to cause the side plates [ 1110 ,  1120 ] to be fixed generally parallel to each other, and to create a plurality of air ducts [ 1155 ] between the swirl blocks [ 1150 ]; 
     a plurality of vane rods [ 1160 ] each having a first end and a second end, the vane rods [ 1160 ] extending generally perpendicularly through the second side plate [ 1120 ]; 
     a plurality of vanes [ 1130 ] each attached to the first end of each vane rod [ 1160 ] and positioned within the air ducts [ 1155 ], such that the vanes [ 1130 ] are allowed to move between a closed position in which the vanes [ 1130 ] close the air ducts [ 1155 ] and at least one open position in which the ducts [ 1155 ] are at least partially open when the vane rods [ 1160 ] are rotated. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a simple and economical wall burner swirl register. 
     It is another object of the present invention to provide a more reliable wall burner swirl register than current designs. 
     It is another object of the present invention to provide a wall burner swirl register that employs vanes that exhibit less binding than conventional swirl registers. 
     It is another object of the present invention to provide a wall burner swirl register that employs a more reliable vane movement mechanism. 
     It is an object of the present invention to provide a wall burner swirl register that withstands large temperature differentials without failure. 
     It is an object of the present invention to provide a wall burner swirl register that is more accessible and easier to maintain. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings, wherein like items are numbered alike in the various Figures: 
         FIG. 1  is a front perspective view of a swirl register for a pulverized solid fuel burner according to the present invention; 
         FIG. 2  is a rear perspective view of the swirl register of  FIG. 1 ; 
         FIG. 3  is a side elevational view of another embodiment of the swirl register; 
         FIG. 4  is a cross sectional view of swirl register of  FIG. 3  along lines “B-B”; 
         FIG. 5  is a cross sectional view of swirl register of  FIG. 3  along lines “A-A”. 
     
    
    
     DETAILED DESCRIPTION 
     A new swirl register design has been developed which provides for a reliable, rigid, yet lightweight device. 
     This swirl register includes pivoting vanes that, depending upon their position, provides a full range of swirl directions from full axial flow to full tangential flow. The swirl register also is adjustable to stop airflow, as required in a burner shut off position. 
       FIG. 1  is a front perspective view of a swirl register  1000  for a burner for pulverized solid fuel according to the present invention.  FIG. 2  is a rear perspective view of the swirl register  1000  of  FIG. 1 . This embodiment will be described with reference to  FIGS. 1 and 2 . 
     The swirl register  1000  consists of two parallel side plates  1110 ,  1120  separated and joined together by a series of swirl blocks  1150 . These swirl blocks  1150  are attached between the side plates  1110 ,  1120  to provide a lightweight and rigid structure. 
     This rigid structure resists twisting and flexing under variable heating conditions which have caused problems in prior art registers. 
     The swirl blocks  1150  each have an angled side, or are positioned to have angled sides to create angled air ducts  1155  between them. The angled air ducts  1155  direct air radially inward as well as tangentially around a circumferential path within the swirl register  1000 . The angled air ducts  1155  cause swirling of the secondary air prior to mixing it with the fuel stream. 
     A plurality of vanes  1130  is provided in each of the air ducts  1155 . These function to allow the air ducts  1155  to remain fully open, partially opened or fully closed. In the fully closed position, air is prevented from flowing though the air ducts  1155  of swirl register  1000 , shutting off the burner when it is not in service. 
     Each vane  1130  is attached to a vane rod  1160  that rotates its respective vane  1130  to adjust the opening of its respective air duct  1155 . The vane rods  1160  each extend through side plate  1120 , support tube  1170  located in the windbox and through a windbox front plate  1250 . A linkage assembly  1200  is located on the windbox front plate  1250 . 
     Linkage assembly  1200  links to and rotates vane rods  1160 . The vane rods  1160  are linked together with linkage assembly  1200  so that they can be operated in unison from the windbox front plate  1250 . Linkage assembly  1200  employs a gearbox  1230  that actuates a drive link  1201 . Drive link  1201  is pivotally connected to a tangential link  1203  that is pivotally connected to another drive link  1201  causing it to rotate the vane rod  1160  to which it is connected. 
     Since linkage assembly  1200  is mounted on the windbox front plate  1250  on the side facing away from the side plates  1110 ,  1120 , and outside of the windbox, it is readily accessible without the need to disassemble the windbox or shut down the furnace. All of the operating mechanisms are located external to the windbox. This provides easy access to a linkage assembly  1200  that pivots the vanes  1130 . 
       FIG. 3  is a side elevational view of another embodiment of the swirl register. This embodiment shares many of the same structures and functions of that of  FIGS. 1 and 2 , however this shows the embodiment employed in a functioning burner. The main difference is that the access holes are in different locations. 
     In this view it can be seen that windbox front plate  1250  secures to the outside of a windbox wall  20 . A plurality of support tubes hold side plate  1120  a fixed distance from windbox wall  20 . Rods  1160  pass through holes in windbox front plate  1250  through the windbox wall  20  through the support tubes  1170 , through side plate  1120  to attach to vanes  1130 . Vanes  1130  are positioned between side plates  1120  and  1110 . An extension lip  1500  extends out of the windbox and into a burner. 
     Fuel tube  10 , that typically carries pulverized coal particles suspended in airflow, passes through the length of the swirl register. Secondary air passes between the swirl blocks  1150  and into the center of swirl register  1000 . This swirling flow exits through secondary air annulus  1300 . 
     The linkage assembly  1200  shown here from the side is driven by a gearbox  1230 . Gearbox  1230  increases the mechanical advantage to provide a smooth motion of linkage assembly  1200 . There is a position indicator ( 1235  of  FIG. 5 ) that visually indicates the position of the vanes  1130  for operation and maintenance purposes. 
       FIG. 4  is a cross sectional view of swirl register of  FIG. 3  along lines “B-B” showing air duct assembly  1100 . In this view, swirl blocks  1150  are shown in phantom since they are on the other side of side plate  1120 . The construction using swirl blocks  1150  results in a rigid structure. 
     Here it can be seen that two adjacent swirl blocks  1150  each have a block wall  1151 ,  1153  that face each other. They are spaced apart to create an air duct  1155  between them. At least one of the block walls  1151 ,  1153  should be angled with respect to a radial direction from the center of side plate  1120  to create the rotation of the incoming airflow. In this case the block wall  1151  is angled. 
     The vanes  1130  are shown here in a partially opened position allowing secondary air to enter through ducts  1155  as indicated by the arrows marked “A”. The angle and geometry cause the air to spiral around fuel flow tube  10 . 
     As the vane rods  1160  are rotated (clockwise from this view) vanes  1130  move in the direction of arrow marked “B” to partially, or fully close air ducts  1155 . 
     When vane  1130  is rotated counter clockwise to touch swirl block  1150 , it is in the axial position. The position of vane  1130  shown here is its full tangential flow position. Rotating it clockwise closes off airflow. 
     When the vanes  1130  are fully open, they create the lowest ratio of swirling to axial flow. When the vanes  1130  are moved toward a closed position, they reduce the airflow. The swirl register of the present invention functions to adjust combustion and shape the flame produced by its associated burner. 
     When closed, the air ducts  1155  shut off air flowing to its associated burner. This is important when a furnace with multiple burners is using less than all burners. 
       FIG. 5  is a cross sectional view of swirl register of  FIG. 3  along lines “A-A” showing a vane control mechanism  1600 . In this view, the parts of the linkage assembly  1200  are visible. A gearbox  1230  drives the linkage assembly  1200 . These causes drive link  1201  to move. The drive links  1201  are also connected to tangential links  1203 . As the drive links  1201  pivot about the vane rod  1160 , they move the tangential links  1203  in a direction abound the perimeter of windbox plate  1250 . Since the other side of each tangential link  1203  is then connected to another drive link  1201 , making a circular linkage pattern. This linkage assembly  1200  insures that all vane rods  1160  rotate simultaneously by the same amount, and are in the same relative position with each of the air ducts  1155 . A visual position indicator  1235  shows the position of the vanes  1130 . This may also be supplemented with electronic sensors that monitor the position of the vanes  1130  and provide that information to a user control panel. 
     The vane rods  1160  pass through the windbox plate  1250  through a plurality of holes in windbox plate  1250 . Each of these have a seal in a small box structure called a rod box seal  1207 . These hold the vane rods  1160 , allow them to rotate and prevent significant leakage of hot gasses from the windbox. 
     Therefore, the swirl register  1000  according to the present invention is a rigid, lightweight design that keeps the operating mechanisms properly aligned, throughout the range of operation. 
     The present invention allows for the full tangential or full axial flow. In addition, the user may select other ratios of tangential to axial flow. The present invention can be placed in a closed position to stop airflow to a burner when it is not in use. 
     Unlike conventional registers, the swirl register of the present invention has the advantage of maintaining a consistent inlet opening for various vane positions thus keeping the air pressure drop through the register substantially constant. 
     Operating linkage and drive are located external to the windbox providing for easier inspection and maintenance. It also provides increased reliability. 
     The design allows for a full range of secondary air swirl control from full axial to tangential flow. It also incorporated a shutoff position of the vane within the air duct for burner airflow shut off or biasing. 
     Although the invention has been described and illustrated with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention. Accordingly, other embodiments are within the scope of the following claims.

Technology Category: 2