Patent Publication Number: US-6988468-B2

Title: Automatic combustion air port cleaner with air/oil indexing mechanism

Description:
This application claims benefit of U.S. Provisional Application Ser. No. 60/478,314 filed Jun. 12, 2003. 

   BACKGROUND OF THE INVENTION 
   Automatic cleaning of combustion air ports in chemical recovery boilers is well established since Anthony-Ross Company pioneered the industry in the early 1980s. Refer to U.S. Pat. Nos. 4,423,533 and 4,822,428, held by Anthony-Ross Company. The disclosures of these patents are incorporated herein by reference. Since the introduction of these mechanisms in the 1980s, the worldwide pulp and paper industry has adopted automatic port cleaning in large scale and Anthony-Ross Company enjoys over 70% market share. During the intervening period, Anthony-Ross Company has worked continuously to refine and perfect the “index cleaning” mechanism first described in U.S. Pat. No. 4,822,428. This method of automatic port cleaning has proven to be very effective and robust and the current refined mechanism contains essentially all of the elements of the original “indexing APC”. The current mechanism contains a single linear actuator (typically a pneumatic cylinder) that drives multiple cleaning rods (up to eight rods), each rod fitted with a cleaning tip, and each cleaning a single port. Therefore there is a cleaning rod and tip for every port on the boiler. Typically there may be upwards of one hundred primary air ports on a recovery boiler. In the current embodiment, each rod/tip is positioned in front of a corresponding air port, and each rod extends out of the windbox where it engages the automatic port cleaner (APC) mechanism. This arrangement has several advantages: Each rod has its own support bearings therefore the bearing loads are reduced; each rod can be adjusted relative to the port opening from outside the furnace; in the event a tip becomes stuck in the port opening, the individual rod can be loosened from the mechanism simplifying the retrieval process; there is very little obstruction of the ports inside the windbox; and the number of expensive actuators is reduced. All of these features have proven advantageous by the reliability and effectiveness of the mechanism. While the worldwide market overwhelmingly considers the Anthony-Ross APC as the “gold standard”, there is still room for improvement. 
   SUMMARY OF THE INVENTION 
   Major improvements embodied in the new version APC described herein are to improve the appearance of the APC system when it is installed on a recovery boiler. This has been achieved by reducing the number of cleaning rods that project from the windbox, and by simplifying the indexing mechanism. 
   The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  is a top view of an apparatus according to the invention; 
       FIG. 2  is a side view thereof; 
       FIG. 3  is view of the hydraulic pump that attaches to the rear of the air cylinder linear actuator; 
       FIG. 4  is a view of the linear actuator; and 
       FIG. 5  is a view of an adjustment mechanism to enable adjusting of the cleaning tips from outside the wind box. 
   

   DETAILED DESCRIPTION 
   To reduce the size of the equipment as installed on a recovery boiler, the new version APC terminates the cleaning rods inside the windbox. Each rod is attached to a single horizontal bar  12  (the “extension bar”) also residing inside the windbox. The extension bar is in turn attached to the external drive mechanism  13  via two bearing rods  14  (the “fulcrum rods”). The fulcrum rods are slideably engaged in fulcrum tubes  16  that extend into and out of the windbox via a spherical fulcrum housing  18  supporting each fulcrum tube. The fulcrum housings are bolted to a faceplate  20  that removeably attaches the APC to the boiler via a mounting frame. The spherical fulcrum housings engage semi-spherical balls  21  through which the fulcrum tubes are mounted. This arrangement seals the windbox against air leakage and provides a means to pivot the fulcrum tubes and subsequently the cleaning rods and tips. The two fulcrum rods are sized to withstand the forces of the unit in operation that previously were absorbed by the individual cleaning rods and engage the fulcrum tubes via generously sized replaceable bushings. With the cleaning rods and extension bar now located inside the windbox, the width of the APC outside the windbox is reduced and constant regardless of the number of ports cleaned by each unit. For example, a current version APC cleaning five ports with 12 inch port spacing will be about 50 inches wide. The new version APC, also cleaning five ports will be less than 15 inches wide outside the windbox. 
   A second benefit of the new design is that the linear cleaning motion is completely contained within the fulcrum tubes; therefore the external motion of the APC is reduced to the periodic angular displacement of the unit about the spherical fulcrum housings. The angular displacement occurs as the unit indexes the cleaning tip to a new location after each cleaning stroke. 
   A third benefit of the new design is the replacement of the mechanical indexing drive with an air/oil mechanism. The new mechanism greatly increases the indexing force available; creates a consistent indexing force in all tip positions; indexes the tips when they are well clear of the port; and eliminates all of the external mechanism required to drive the indexing. The new indexing mechanism consists of two main parts: A hydraulic pump attached to the rear of the air cylinder (the linear actuator used to translate the cleaning rods), and a hydraulic manifold incorporating a hydraulic cylinder and valves. The pump consists of a housing with a cylindrical bore containing a spring-loaded piston. The housing is sized to match the dimensions of the attached air cylinder. A portion of the material surrounding the perimeter of the housing is removed and this portion is covered by a piece of stainless steel tubing to form a fluid reservoir. The tubing is the same material used for the air cylinder barrels. The assembled pump is attached to the tail end (opposite the rod end) of the air cylinder with the pump piston extending through a hole in the tail of the air cylinder, such that when the air cylinder retracts (tips withdrawn from the air ports) the air cylinder piston contacts and depresses the pump piston forcing a charge of hydraulic fluid to the manifold. When the air cylinder extends (tips into the ports), the air cylinder piston disengages the pump piston, allowing the pump piston to retract by the force of the internal spring. As the pump piston retracts, a charge of hydraulic fluid is drawn into the pump cylinder from the reservoir via a check valve. The pump is then ready to send a next charge of fluid to the manifold. With each stroke of the air cylinder and pump piston, a charge of fluid is sent to the hydraulic cylinder housed in the manifold. Each shot of fluid causes the piston in the hydraulic cylinder to be displaced incrementally. As the hydraulic piston is incrementally displaced, the hydraulic cylinder rod extends (or retracts) incrementally which causes the APC to index. A series of valves incorporated into the manifold reverses the indexing direction and otherwise controls the indexing motion. As the hydraulic piston moves, fluid is displaced from the low-pressure side and forced back to the reservoir surrounding the pump. In this manner the fluid is constantly circulated between the pump and the manifold. The pump is connected to the manifold by two high-pressure flexible hoses. The two previously described fulcrum tubes are held in rigid alignment by a cross brace. The manifold is suspended between the cross brace and the APC faceplate, with the hydraulic cylinder rod pivotally attached to the faceplate, and the manifold pivotally attached to the cross brace. 
   While the above illustrated embodiment employs an interaction of the air cylinder to depress an indexing pump, an alternate manner of accomplishing the desired result for indexing is to employ a hydraulic rotary actuator, wherein, for example, a vane type pump or rotary piston pump is employed. Further, electrically operated indexing mechanisms may be employed. 
     FIG. 5  illustrates components to enable adjustment of the cleaning rods, wherein a single cleaning rod  20  is shown as an example. The tip  22  end of the rod extends into the interior of the port, while the distal end  24  of the rod is threaded to receive a nut thereon. A tube  28  is positioned between the nut and the mounting bar outer wall  30 . Spaced inwardly from the outer wall is an inner wall  32 , which has a beveled opening  34  to receive the cleaning rod therethrough. Corresponding wedge members  36  are mounted on sides of the rod, and the wedges receive bolt members  38  therethrough, via threaded apertures  40  so that the wedges act also as nuts on the bolts. The bolts extend through to the outer wall where the bolt head  42  is accessible. In operation, an opening  44  is provided for access to the various above-described bolt heads and nuts, and the wedges may be loosened by turning the bolt head. In operation, to adjust the position of the cleaning rod (and therefore, the rod tip) to the left or right, the bolt for the wedge on the side to which movement is desired is loosened. The bolt may be tapped upon to free up the wedge member. Then, the bolt for the wedge on the opposite side is turned to tighten up the wedge (that is, to draw the wedge closer to the bolt head) which causes movement of the cleaning rod toward the direction of the loosened wedge. Then, when the rod is moved to the desired position, the loosened wedge bolt is retightened, securing the rod in the new adjusted position. This is desirable to accommodate for thermal expansion, for example. 
   The cleaning rod positions relative to the actuators can be adjusted horizontally somewhat by providing a slotted engagement. Then, to adjust the positioning of the rods, the mounting may be loosened, and slid within the slots. 
   In the embodiment of  FIG. 1 , for example, the cleaning rods are configured with one rod, the 4 th  rod from the left  46  in the view of  FIG. 1 . This rod is not provided with the wedge adjustment mechanism. However, the remaining rods are provided with the mechanism. In use, the system is mounted so that the fixed rod  46  is positioned relative to the port it corresponds to, and the remaining rods can then be adjusted via the wedge mechanism to accommodate differences. 
   While a preferred embodiment of the present invention has been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects. The appended claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.