Patent Publication Number: US-2003223920-A1

Title: Method for repairing catalytic heaters

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to a method for repairing catalytic heaters and a replacement catalyst cartridge used therein.  
       [0002] Catalytic heaters are used in many industrial applications. Typical catalytic heaters have a housing or heater frame, a fuel gas supply system for supplying fuel gas or vapors into the housing, a catalyst material within the housing, and a system for distributing the fuel gas over the cross sectional area of the catalyst. The catalyst typically comprises a thermally-resistant cloth having a plurality of gas passage openings. A catalytically active material such as platinum, rhodium, or palladium is deposited on the thermally-resistant cloth. Some sort of retention device secures the supported catalyst in the housing.  
       [0003] While the catalyst in the catalytic heater is not consumed over time, it can become clogged with inert materials that reduce its efficiency and heat output. While catalytic heaters in this condition can be repaired, many companies are reluctant to service the heaters due to the downtime normally involved. The only options available to these companies were to (1) send back entire catalytic heaters to manufacturers for refurbishment, (2) purchase spare catalytic heaters to substitute for those being repaired or (3) rebuild the catalytic heaters on-site. In the past, these options have not been desirable because of the expense and lost production time involved.  
       SUMMARY OF THE INVENTION  
       [0004] Accordingly, it is an object of the present invention to provide a method for repairing and refurbishing catalytic heaters on site.  
       [0005] It is a further object of the present invention to provide a method as above which is economically beneficial and does not result in undue lost production time.  
       [0006] It is yet a further object of the present invention to provide a replacement catalyst cartridge for use in the repair method.  
       [0007] The foregoing objects are attained by the repair method and the replacement (and replaceable) catalyst cartridge of the present invention.  
       [0008] In accordance with the present invention, a method for repairing and refurbishing catalytic heaters broadly comprises the steps of removing a face frame and a face screen from a heater frame of a heater to be refurbished, removing catalyst material from an interior portion of the heater, providing a catalyst cartridge having a layer of catalyst material, and securing the cartridge to the heater frame.  
       [0009] A replacement catalyst cartridge used in the method of the present invention comprises a frame, an upper screen joined to the frame, a lower screen joined to the frame, and a layer of catalyst material positioned between the upper and lower screens.  
       [0010] Other details of the repair method and the replacement catalyst cartridge of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 is a sectional view of a typical catalytic heater to be refurbished;  
     [0012]FIG. 2 is a top view of the catalytic heater of FIG. 1 stripped and ready for refurbishment;  
     [0013]FIG. 3 is a side view of the catalytic heater of FIG. 1;  
     [0014]FIG. 4 illustrates a face frame secured to a heater body;  
     [0015]FIG. 5 illustrates one embodiment of a replacement catalyst cartridge in accordance with the present invention; and  
     [0016]FIG. 6 is a sectional view of an alternative embodiment of a replacement catalyst cartridge in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)  
     [0017] As previously mentioned, it becomes necessary to periodically replace the active catalyst layer in a catalytic heater to improve the performance of the heater. In accordance with the refurbishment method of the present invention, a catalytic heater  10 , such as that shown in FIGS.  1 - 4 , is preferably first removed from an oven (not shown) for initial retro-fit. While it is preferred to remove the heater  10  from the oven, this may not be necessary for all retro-fit repairs and refurbishments. Before removing the heater  10  from its oven, heater locations and plumbing connections should be mapped and marked. Lack of attention to this may delay re-installation of the refurbished heater. After removal from the oven, the heater  10  should be stripped of any wiring and plumbing connections.  
     [0018] After removing all wiring and jumpers from the electrical junction box, the pre-heat elements  12  in the heater  10  should be checked for continuity and ohms. Any suitable testing device known in the art may be used to check the continuity and ohms. Following this, the orifice  14  for supplying gas to the heater  10  is removed from the heater by tipping the catalytic heater  10  on the side and removing it. The orifice  14  may be removed using any suitable tool known in the art, such as a ¼″ socket driver. Compressed air is then blown in the orifice  14  to make sure the orifice is free of any debris. Preferably, a wand (not shown) is used to blow the compressed air into the orifice  14 . When a wand is used, it should be waved back and forth across the orifice  14 . The orifice  14  may be confirmed as being clean by holding it up to the light. After cleaning has been completed, the orifice  14  is replaced using any suitable tool known in the art.  
     [0019] As can be seen from FIG. 2, a typical catalytic heater  10  has a face frame  16  and a face screen  18  surrounded by the face frame  16 . A plurality of fastening elements  20 , such as rivets, are typically used to secure the face frame  16  to a lip  36  of a heater frame or housing  22  as shown in FIG. 4. The fastening elements  20  are removed, such as by drilling the fastening elements  20  out using a ⅛″ steel drill bit, so that the face frame  16  and the face screen  18  may be removed from the heater frame  22 . After the fastening elements  20  have been removed, the face frame  16  and the face screen  18  may be removed, if not easily lifted away from the heater body, using a suitable tool, such as a putty knife.  
     [0020] After the face frame  16  and the screen  18  have been removed, the catalyst material  24  within the heater  10  is exposed. The catalyst material  24  is peeled back, preferably rolling the material  24  from one end, and removed, thus exposing pre-heat elements  12  sitting on top of an insulating layer  28 . The catalyst material  24 , if desired, may be set aside for potential use later. Depending upon the thickness, or settling of existing insulating material with respect to its depth from the heater lip, just the catalyst can be removed, leaving behind supporting insulating layer.  
     [0021] Every hole  26  in the heater lip  36  is then cleaned and any fastening element fragments caused by the fastening element removal are cleaned out. A cutting wheel/grinder and hole punch may be used to perform this step. If necessary, fastening element bodies may be pulled from the underside of the lip  36  using a pair of pliers. Air is then gently blown across the heater face to remove all dust and debris.  
     [0022] The heater  10  should have a first piece  30  of heat insulation lying over the point where the pre-heat elements  12  terminate in the heater and a second piece  32  of heat insulation over the thermoswitch  34  to protect the insulation piece above it. If these insulation pieces are missing, new ones may be cut from the backing of the old catalyst layer by removing or peeling off the outer layer of used catalyst material to create a relatively clean piece of insulating material.  
     [0023] The heater  10  should then be inspected to determine whether it is necessary to build up the insulating layer in the heater  10  to be even with the lip  36  of the heater frame  22 . If this is necessary, an additional layer of insulating material may be placed within the interior of the heater frame  22 .  
     [0024] Referring now to FIG. 5, a catalyst cartridge  38  is then used to replace the catalytic material. The cartridge  38  comprises a frame  40  having a shape which corresponds to the shape of the heater frame or housing  22 . The cartridge  38  has a bottom screen  42  and an upper screen  44  joined to the frame  40 . A layer of catalytic material  46  is positioned between the upper and bottom screens  44  and  42  respectively. The catalytic material  46  may comprise a layer of any suitable catalytic material known in the art such as a layer of platinum, rhodium, or palladium. The upper screen  44  may be planar as shown in FIG. 5 or have a three dimensional corrugated configuration as shown in FIG. 6. The use of a three dimensional corrugated screen is extremely beneficial in that it allows an increase in the amount of catalyst surface area relative to the dimensional size of the heater, thus allowing an increase in the heat output.  
     [0025] The replacement cartridge  38  also has a layer of high temperature insulating material  50  which is split at locations  52  to accommodate a plurality of flat head screw barrels  54 . The barrels  54  receive screws  56  to secure the insulating material  50  to the cartridge  38 . By using such an arrangement, the insulating material  50  is pulled up, thus allowing the lower portion of the insulating material  50  to rest on heater lip  36  to form a gastight seal. The replacement cartridge  38  may be attached to the heater  10  by any suitable joining means resulting in a consistent downward force on the cartridge  38 . The joining means may be spring clips, carriage bolts, flexible hose clamps, screw, rivets, or the like.  
     [0026] Prior to re-installation, the refurbished catalytic heater  10  may be flame tested to determine whether there is an even gas flow exiting the heater. Further, a source of flame, such as a torch, may be passed directly over each fastening element and along the outside edge of the heater  10  to make sure there are no leaks. Any leaking fastening elements should be replaced.  
     [0027] The wiring and plumbing may then be reinstalled and the heater  10  may be replaced within the oven.  
     [0028] One of the advantages of the present invention is that the replacement catalyst cartridge  38  itself can be easily replaced when the catalyst has outlived its useful life without removing the heater  10  from its oven. This can be done by unscrewing or unhooking the fastener arrangement, removing the old catalyst cartridge  38 , and inserting a new catalyst cartridge  38 .  
     [0029] The use of the replaceable catalytic cartridge  38  in the repair method of the present invention allows companies to simply replace the active catalyst layer on existing heaters with a pre-fabricated catalytic face cartridge and make the heaters like new. In some cases, the catalytic heaters do not have to be unwired, or un-plumbed, or even removed from the oven. The catalyst cartridge forms a gas tight seal over existing flanges and can easily be secured to the heater.  
     [0030] It is apparent that there has been provided in accordance with the present invention a method for repairing catalytic heaters and a replacement cartridge therefore which fully satisfies the objects, means and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations which fall within the broad scope of the appended claims.