Abstract:
A port rodder assembly for a recovery boiler includes a duct affixed to and in fluid communication with an air port of the boiler, having a hollow interior, and an air inlet opening. A cutting head is slidably mounted within the duct adjacent to the air port and is adapted to clean the air port. An actuator selectively advances the cutting head though the air port to clean the air port. A wing is pivotally mounted within the duct. The wing interacts with the air inlet opening to control the flow of air through the duct and into the air port and is shaped such that incoming air flows smoothly through the duct to the air port.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
   This patent application claims the benefit of U.S. provisional patent application 60/575,633, filed May 28, 2004. 

   FIELD OF THE INVENTION 
   The present invention relates to a device for cleaning an air port arranged in the wall of a furnace and for regulating the flow of air through the air port which may be used, for example, in a recovery boiler or furnace. 
   BACKGROUND OF THE INVENTION 
   Within the cellulose production industry, the spent liquors from paper wood boiling (sulfate spent liquor and, in some cases, sulfite spent liquor) are combusted in a recovery boiler. The nature of the fuel and the process conditions result in a tendency of plugging of the air ports, which are openings through which combustion air is supplied. This clogging occurs through an accumulation of dust particles and flowing cinder products within the boiler. These pluggings are more accentuated in the lower regions of the air port and especially at the bottom. There are numerous known arrangements of cleaning devices which reciprocate through the air port for cleaning which are activated periodically as needed. It is important from environmental and process control points of view to achieve as complete a combustion as possible of the spent liquor within the recovery boiler. The supplemental supply of air through the air ports is an important parameter to achieve this goal. In addition to cleaning the air port, it is desirable to provide a regulating device which allows modulation of the air flow rate through the air port to achieve desired boiler operating parameters. 
   There are numerous examples of so-called port rodder devices for cleaning air ports which include damper assemblies for regulating air flow. In many examples of the prior art, the air regulating device provides a sharp edge orifice of variable area through which the air flows. Such an orifice configuration produces highly turbulent air flow into the combustion device. Due to its turbulence, this air flow is not able to penetrate deeply into the boiler interior, and thus produces a stratification of the air flow and available oxygen within the boiler interior. An ideal device of this type would produce an air stream into the boiler which has a velocity which enables it to penetrate into the interior of the boiler to provide a more homogeneous supply of combustion oxygen within the boiler interior. Additional examples of prior art rodder devices incorporate damper assemblies which must be retracted to a fully opened position before a cleaning cycle for the air port may be achieved. Thus, in such systems, the precisely adjusted damper position set for providing desirable furnace operating parameters is upset during the cleaning cycle. This can produce undesirable transient operating conditions within the boiler. 
   SUMMARY OF THE INVENTION 
   A port rodder assembly in accordance with the present invention is positioned adjacent to an air port of a boiler and incorporates a reciprocating cutting head for periodically cleaning the air port to ensure that it is opened to permit air flow. A damper in the form of a pivoting wing is provided within the cassette assembly of the device which can be rotated between a fully opened configuration which maximizes air flow to a closed position which reduces the effective air flow area. The wing provides a streamline shape for interaction with the air flow to provide a penetrating, smooth air flow jet into the boiler through the air port. The assembly includes features which enable the cutting head to be reciprocated for cleaning without interference with the wing or requiring its position to be changed. In this way, cleaning operations produce a minimal change in air flow through the port rodder assembly. 
   Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side cut-away view of the port rodder assembly in accordance with this invention; 
       FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 ; 
       FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 1 ; 
       FIG. 4  is an end view taken in the direction of lines  4  of  FIG. 1 ; 
       FIG. 5  is an end view taken in the direction of lines  5  of  FIG. 1 ; 
       FIG. 6  is a side cut-away view of the port rodder assembly in accordance with a second embodiment of this invention illustrating a modified wing configuration; 
       FIG. 7  is a side cut-away view of a port rodder assembly in accordance with a second embodiment of the this invention showing a mechanized actuation mechanism for adjusting the position of the wing; and 
       FIG. 8  is an end view of an array of port rodder assemblies in accordance with this invention. 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1-5 , a port rodder assembly in accordance with the teachings herein is shown generally at  10 . The port rodder assembly  10  is shown mounted to the exterior surface of a boiler outer wall  12 . The outer wall incorporates boiler tubes  14  to conduct water or steam for removing heat from the combustion process occurring within the boiler. An air port  16  is formed within the boiler outer wall  12 . The air port  16  defines a narrow rectangular slot which penetrates boiler wall  12  for the admission of combustion air, as previously described. A typical boiler will have a multiplicity of air ports  16 , strategically arranged around the perimeter of the boiler to admit supplemental atmospheric air in desired quantities. 
   The port rodder assembly  10  is used with wind box  18  mounted to the exterior surface of the boiler outer wall  12 . The wind box  18  is a sheet metal structure that is fastened to boiler wall  12  and provides support for the remaining components of the assembly  10 . The wind box  18  encloses the air ports  16  and includes an opening to allow air to enter the wind box  18 . 
   A cassette assembly  20  is mounted within the wind box  18  via a mounting flange  22 . The cassette assembly  20  is inserted into an elongated duct  24 . The duct  24  is formed of sheet metal and has a generally rectangular, hollow cross-section. One end of the duct  24  is connected to an adapter  26 . The adapter  26  connects the end of the duct  24  to the air port  16 . The duct  24  has an air inlet opening  28  to allow air to flow into the duct  24  from the interior of the wind box  18 . 
   A cutting head  30  is mounted within the duct  24  and includes a pair of cutting plates  32  and  34 , best shown in  FIG. 4 , which are shaped to closely approximate the inside surface shape of the air port  16 . The cutting plates  32  and  34  form elongated attachment legs  36  and  38 , as shown in  FIGS. 1 and 3 , which are connected to an actuator rod  40 . The actuator rod  40  is connected to an actuator  42 . The actuator  42  can be a fluid cylinder which may be operated pneumatically or by hydraulic fluid, or by other means. The actuator  42  causes the cutting head  30  to selectively move between a retracted position, as shown in solid lines in  FIG. 1 , and an extended position, as shown by the phantom lines in  FIG. 1 . In the retracted position, the cutting head  30  is positioned within the duct  24  and wind box  18 . In the extended position, the cutting head  30  projects through the air port  16  in the boiler wall  12  into the interior of the recovery boiler. When the actuator  42  extends the cutting head  30  to the extended position, the cutting plates  32  and  34  pass through the air port  16  and clean fouling deposits which may collect and obstruct air flow through the air port  16 . The cutting plates  32  and  34 , along with their associated legs  36  and  38 , provide a minimal obstruction to air flow through duct  24 . 
   A wing  44  is pivotally mounted within the duct  24 . The wing  44  is an elongated paddle-shaped member, preferably made of sheet metal. The wing  44  is mounted for pivotal rotation about a pivot pin  46  and acts as a damper. The wing  44  is capable of being moved through an angular range of motion between a fully opened position and a closed position. The fully opened position is shown in  FIG. 1  in solid lines, and the closed position is shown in phantom lines. In the fully opened position, the wing  44  is pressed against an upper surface of the duct  24 . Air is admitted into the duct  24  through the air inlet opening  28  and interacts with the inside surfaces of duct  24  and the wing  44 . The gap “G” designated in  FIG. 1  formed between a distal end  48  of the wing  44  and the bottom surface of the duct  24 , determines an adjustable flow area for air flow through the duct  24  and into the air port  16  and thereby into the boiler. Dimension G is shown for the wing  44  in the closed position (providing a minimal flow area) shown in phantom lines. As can be seen, the gap “G” between the distal end  48  of the wing  44  and the bottom surface of the duct is much larger when the wing  44  is in the fully opened position, thereby providing a larger cross-sectional flow area thereby allowing greater air flow through the duct  24 . 
   The wing  44  is pivotally mounted onto the pivot pin  46  and the pivot pin  46  is positioned outside the wind box  18 . This allows the wing  44  to be longer. The longer the wing  44  is, the more laminar the flow of air through the duct  24  will be. Also, by placing the pivot pin  46  outside the wind box  18 , the pivot pin  46  is easily accessible for maintenance and is positioned outside the high temperature interior of the wind box  18 . 
   The sliding movement of the cutting head  30  is independent of the pivotal movement of the wing  44 , and the wing  44  is shaped such that the cutting head  30  can be extended and retracted when the wing  44  is in any position without interference. 
   The adjustment of the angular position of the wing  44  is achieved through an actuator  50 . As shown in  FIG. 1 , the actuator  50  is a manually operated lever. A set screw  52  within an arcuate slot  54  enables the position of the operating lever  50 , and consequently the wing  44 , to be set as desired and locked into position by clamping the set screw  52 . Numerous other actuating or operating mechanisms for adjusting the position of the wing  44  are within the scope of this invention, including remotely controlled, hydraulic, electrical, pneumatic, and other forms of actuators which could set the angular position of the wing  44  to the desired point. An example of such a remotely controllable actuator for wing  44  is provided later in this description. 
   As illustrated in  FIG. 1 , air flowing in through the air inlet opening  28 , as designated by arrow  55 , encounters the wing  44  and accelerates as the cross-sectional flow area smoothly decreases in moving from the air inlet opening  28  to the distal end  48  of the wing  44 . The cooperation between the inside surfaces of the duct  24  and the wing  44  provides a streamlined flow path which produces a jet of air through the air port  16  which is able to penetrate deeply within the boiler. 
   It has been found that the shape of the wing  44  can influence the performance of the air flow. Specifically, it has been found that having some bend in the shape of the wing  44  is beneficial in some applications. As illustrated in  FIG. 1 , the wing  44  is generally arcuate along its length. Other configurations are within the scope of this invention. For example, the wing  44  could feature a paraboloid configuration. 
   Referring to  FIG. 6 , another embodiment of the present invention is shown generally at  110 . Elements of this embodiment (and later described embodiments) which are equivalent to those previously described are identified by like reference numbers. Reference to the prior description of these elements will describe them as used in this embodiment. The port rodder assembly  110  differs from the previously described port rodder assembly  10  with regard to the shape of the wing  144 . In this case, the wing  144  features a first arcuate bend  158  which extends from the pivot pin  46  to a position adjacent to, but short of the distal end  148  of the wing  144 . The arcuate bend  158  ends at a break line  160  and transitions to two planar segments  162  and  164  separated by another break line  166 . The modified configuration of the wing  144  in this embodiment may provide advantages in the control of air flowing into the boiler for certain applications. 
   Referring to  FIG. 7 , yet another embodiment of the present invention is shown generally at  210 . This embodiment  210  differs in two principal respects from the prior embodiments  10  and  110 . First, in this instance, the wing  244  is substantial planar in shape, and includes a lip formed by a planar segment  268  at the distal end  248  of the wing  244 . As in the case of the prior embodiments  10 ,  110 , this embodiment  210  is configured for particular applications and to provide a desired interaction with the interior surfaces of the duct  24  to provide the desired air flow characteristics. Additionally, the port rodder assembly  210  shown in  FIG. 7  includes a powered actuator  270  which may be electrically or fluid operated or by other means to provide remote adjustment of the angle of the wing  244  (or the other wings  44  and  144 ). 
     FIG. 8  illustrates a multi-port rodder assembly  310  that is made up of a plurality of port rodder assemblies of any of the previously described embodiments that work cooperatively to clean and control the air flow to a plurality of air ports  16 . The pivot pins  346  of the wings (not shown) are connected to one another such that a single actuator  370  can simultaneously adjust all of the wings (not shown) in unison. 
   While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.