Patent Publication Number: US-2015082563-A1

Title: Beater for dust-affected tube walls

Description:
The invention is directed to an apparatus for introducing beating or pulsed movements into tube walls within a pressure vessel, wherein a first ram imparting the beating pulse to the tube wall presses through the pressure vessel wall, guided into a pressurized first annular space which is acted upon by a second ram guided in a further tubular chamber. 
     There are a number of applications of beaters of this type, in particular for heat exchangers in chemical processes, which are used inside or outside pressure vessels, e.g. in the case of tube walls of the pressure vessel for coal gasification, in which it is attempted to maintain the operation also of the transfer of heat into the tube walls at a high level. Devices of this type for introducing striking pulses into the tube walls in order that the dust can flow off are described, for example, in WO 2010/0637552 A1 or WO 2010/063755 A1. 
     A pneumatic beater is disclosed in DE 196 52 707 C2, and a beating or striking apparatus on heating boilers is also disclosed in DE 10 2010 007 197 A1, to name just a few examples. 
     Since, for example, comparatively high pressures arise in the pressure vessels used for the coal gasification and as a result, inter alia, the rams or hammers used for transferring pulses are subjected to wear, not only is it necessary to provide for special sealing of the inner space of the pressure vessel with respect to the surroundings, but rather it is also necessary to make it possible to compensate for the shortening of the hammers or rams caused by the wear. In this respect, the solution according to WO 2010/063755 A1, for example, provides a compression spring acting on the ram in a chamber, this chamber being at a pressure that is slightly higher than the internal pressure of the coal gasifier owing to gas being fed in from outside. 
     In practice, it has been found that it is entirely possible for springs of this type to fracture. It is also the case that the escape of dust-afflicted synthesis gas is not ensured with absolute certainty. 
     A slightly different solution with merely one pressure chamber is disclosed by WO 2010/063752 A1, as already mentioned above, in which the striking ram is fastened to the end face of a chamber subjected to pressurized gas. 
     It is an object of the invention to provide a solution which both compensates for the wear of the hammer or ram acting upon the tube wall over the longest possible time and also ensures effective sealing with respect to the surroundings. 
     With an apparatus of the type mentioned in the introduction, this object is achieved according to the invention in that the second ram is provided with at least one first guide, acting upon the inner wall of the tubular chamber, in the region of the end thereof which makes contact with the first ram, and is provided with a second guide equipped with a sealing element in the region of the end thereof which protrudes from the tubular chamber, and in that the second ram is enclosed between the two guides by a compensator fixed in a gas-tight manner. 
     The compensator or bellows ensures that no gas can escape from the pressure vessel into the surroundings without the mobility of the ram which transfers the beating or pulsed movements to the tube wall being influenced. 
     One possible configuration of the invention consists in the fact that the second ram with the compensator is surrounded in the tubular chamber by a compression spring, but a preferred configuration of the invention consists in the fact that the guide of the second ram is provided with seals to form an annular space sealed off with respect to the surroundings, the outwardly facing ram being surrounded by a static seal. 
     The latter configuration has the advantage that, by way of example, a static seal can have different physical and chemical properties to, for instance, a dynamic seal, which is subjected to abrasion as it moves, for example. 
     One configuration consists according to the invention in the fact that the seals are formed by O ring seals, which are positioned in the annular disks surrounding the second ram, at least one annular disk being provided with an annular flange facing into the annular space to fix one end of the compensator. 
     A modified embodiment of the seal consists in the fact that the static seal is positioned between an annular disk surrounding the second ram and the end face of the annular space, the annular disk being provided with an annular flange facing into the annular space to fix one end of the compensator. 
     In order to prevent dust-laden gas from getting into the surroundings or into the region of seals of the second annular space, it is provided according to the invention that a filter element surrounding the first ram and preventing the passage of dust is provided in the annular space. 
     One configuration of such an element preventing the passage of dust consists in the fact that the filter element is formed by a sintered metal tube portion positioned between two annular disks, the annular disks tightly enclosing the first ram, whereas the sintered metal tube portion surrounds the first ram at a distance. 
     One configuration of the filter element consists in the fact that the annular disk facing toward the annular space is provided with recesses on the marginal edge thereof which bears against the first ram, and the second annular disk is provided with recesses on the marginal edge thereof which makes contact with the inner wall of the annular space, it also being possible to provide for the fact that the respective other marginal edge of the annular disks has an O ring seal. This makes it possible to achieve flow through the sintered metal tube portion. 
     It is expedient to visually identify the change in length of the hammer or of said ram. In this respect, the invention provides that the end of the second ram protruding from the chamber is equipped with an electronic or mechanical device which identifies changes in length, in particular the abrasion of the first ram. 
     A robust, simple and less interference-prone design of such an element can consist in the fact that the ram end protruding from the chamber is equipped with an indicator, to which an immovable scale is assigned. 
    
    
     
       The invention is explained in more detail by way of example hereinbelow with reference to the drawing, in which: 
         FIG. 1  shows a simplified sectional illustration through an overall view of the apparatus according to the invention, 
         FIGS. 2 to 4  show, in an enlarged sectional illustration, a partial region of three exemplary embodiments, and 
         FIG. 5  shows an enlarged illustration of a filter element surrounding the ram or hammer. 
     
    
    
     The apparatus which is shown in  FIG. 1  in a simplified sectional illustration and is denoted in general by  1  serves for applying beating pulses to a tube wall  2 , shown in part, in a pressure vessel  3 , as is used for example in coal gasification plants. 
     The apparatus  1  is formed substantially by a beating pulse generator  4  or actuator, which triggers the beating pulses and the for example pneumatically operated impact piston  5  of which transfers pulses via a piston rod  6 , referred to hereinbelow as second ram  6 , to a hammer, referred to hereinbelow as first ram  7 , which presses through the pressure vessel wall  3  and introduces the pulse into the tube wall via, for example, a baffle plate  18 , which is fastened to the tube wall. Since the inner space of the pressure vessel  3  is both at a high temperature of approximately 500° C. and also at a high pressure of e.g. 50 bar, the passage of the first ram  7  is guided into the pressure vessel in a substantially gas-tight manner, for which purpose a casing tube  8  is screwed to a tube connection piece  9  welded to the pressure vessel  3 . 
     At the side facing toward the tube wall, the first ram  7  is guided in a guide  10 , and with the end thereof which is remote from the tube wall protrudes, already outside the pressure vessel, into the end face of a tubular chamber denoted by  11 , in which a piston rod, referred to hereinbelow as second ram  6 , is also guided. 
     A filter element denoted in general by  12  is provided inside the casing tube  8  and is intended to ensure that no fine dust and therefore also the gas transporting the fine material passes to the outside. In addition, provision is made here of a pressurized gas line  13  in the blocking flange  14  of the casing tube  8 , in order to build up a pressure which is slightly higher than the internal pressure in the pressure vessel  3  in the annular space  15  between the casing tube  8  and the first ram  7 . The blocking flange  14  serves to fasten the casing tube  8  to the tube connection piece  9  and therefore to the pressure vessel  3 . In the example shown in  FIG. 1 , the tubular chamber  11  surrounding the piston rod or the second ram  6  is equipped with two fastening flanges  16  and  17 , the fastening flange  16  serving to fasten the tubular chamber  11  to the blocking flange  14 , while the fastening flange  17  serves to fasten the beating pulse generator  4  to the tubular chamber  11 . 
     At its end facing toward the first ram  7 , the second ram  6 , which is guided in the tubular chamber  11 , has a guide  6   a,  which in the example shown in  FIG. 1  is formed as a disk in one piece with the second ram  6  and at its end has an O ring seal, with other designs being evident from the following figures. The guide  6   a  can also be formed by a separate annular disk. 
     The ram  6  is also held in a guide  6   b,  the end  6   c  of the ram protruding from the tubular chamber  11 . This second guide  6   b  is part of a flange element  21  formed as an annular disk, a static seal  19  being provided between the flange element  12  and the fastening flange  17  in the example shown in  FIG. 1 . 
     It can also be seen from  FIG. 1  that a compensator  20  is fixed between the two guides  6   a  and  6   b  in such a manner that the annular space denoted by  22  between the tubular chamber  11  and the second ram is closed off in a gas-tight manner with respect to the surroundings, in the example shown in  FIG. 1  in conjunction with the seal  19 , by virtue of the compensator being fixed in a pressure-tight manner to the guides  6   a  and  6   b.    
     In the example shown in  FIG. 1 , the annular space  22  can be exposed to a pressurized gas by way of a gas feed line  23  in such a manner that the pressure in the annular space  22  acts on the guide  6   a  and therefore, since the latter is freely movable and sealed off by way of a seal  24  in the tubular chamber  11 , presses the second ram  6  onto the first ram  7  in such a manner as to always ensure that the first ram  6  fixedly rests on the second ram  7  upon wear to the ram  7 . 
     An enlarged illustration of the region of the second guide  6   b  of the second ram  6  in the tubular chamber  11 , in particular the region where the ram  6  emerges outward from the chamber, is shown on an enlarged scale in  FIG. 2 . Part of a rod system, e.g. made up of a plurality of threaded rods  25   a,  is also clearly shown in said figure, these being used to fix the beating pulse generator  4  to the fastening flange  17 . It is shown here that it is possible to arrange a device  26  on one of the threaded rods  25  which makes it possible to visually identify the penetration of the piston rod  6  into the tubular chamber  11  in the event of wear to the first ram  7 , e.g. by means of an indicator in combination with a scale  27 . A device  26  of this type can also have an electronic configuration or can identify the change in position of the second ram  6  in a different way. 
       FIG. 3  shows a modified exemplary embodiment. Here, the second guide  6   b  is part of an annular disk with an outer O ring seal  24   a  designed as a static seal, the second guide  6   b  being held by a fixing flange  28  that is screwed to the tubular chamber  11 . 
       FIG. 4  shows, as a modification to the embodiment shown in  FIG. 1 , that the compensator  20  is surrounded by a compression spring  29 , which is positioned inside the annular space  22  and is supported in a pressure-tight manner on the first guide  6   a  and the second guide  6   b.  Since the first guide  6   a  is mounted displaceably with the second ram  6 , the compression spring  29  ensures that the second ram  6  rests permanently on the first ram  7 , as can also be seen from  FIG. 4 . 
       FIG. 5  shows an enlarged illustration of, inter alia, the filter element  12 , which is formed substantially from two annular disks  30  and  31 , a sintered metal tube portion  32  being positioned between the two annular disks  30  and  31  at a distance from the first ram  7  and from the casing tube  8 . As illustrated by dashed lines, the annular disk  30  has a ring seal  33  bearing against the outside of the casing tube  8 , channels or grooves  34  being provided in the end face of the annular disk  30  which bears against the first ram  7 . 
     By contrast, the annular disk  31  has a ring seal, e.g. an O ring  35 , to be precise on the end face which bears against the first ram, whereas the end face which faces toward the tube connection piece  8  is equipped with passage grooves  36 . It is thereby ensured that gas which is introduced via the line  13  into the annular space  15  at a pressure which is slightly elevated compared to the pressure in the pressure vessel  3  has the possibility can pass through the grooves  36  the sintered metal tube portion  32  and then via the grooves  34  into the annular space  15   a  between the casing tube  8  and the first ram  7 , and therefore is able to prevent a possible flow of gas in the reverse direction from the pressure vessel  3 . In the event of a reverse flow, dust particles are deposited on the outer surface of the sintered metal tube portion, and therefore any gas which escapes is free of dust particles. 
     The described exemplary embodiment of the invention can of course also be modified in a variety of ways without departing from the basic concepts. Thus, the design of a compression spring  29  which may be provided can be different to that shown, the design of the compensator  20  can also differ from the variant shown, and so on. 
     LIST OF REFERENCE SIGNS 
       1  Apparatus 
       2  Tube wall 
       3  Pressure vessel 
       4  Beating pulse generator 
       5  Impact piston 
       6  Piston rod, second ram 
       6   a  First guide 
       6   b  Second guide 
       6   c  End 
       7  First ram, hammer 
       8  Casing tube 
       9  Tube connection piece 
       10  Guide 
       11  Tubular chamber 
       12  Filter element 
       13  Pressurized gas line 
       14  Blocking flange 
       15 ,  15   a,    22  Annular space 
       16 ,  17  Fastening flange 
       18  Baffle plate 
       19 ,  24  Seal 
       20  Compensator 
       21  Flange element+annular disk 
       23  Gas feed line 
       25  Threaded rods 
       26  Device 
       27  Scale 
       28  Flange 
       29  Compression spring 
       30 ,  31  Annular disk 
       32  Sintered metal tube portion 
       33 ,  35  O ring seal 
       34 ,  36  Grooves