Abstract:
The arrangement is for positioning equipment in association with an opening in a boiler wall and has a rotation mechanism that rotates the equipment around a virtual rotation axis that lies within the outer wall of the boiler. During the use of a liquor spreader for the introduction of combustible material, the opening of the liquor spreader is arranged in the virtual center of rotation so that the point at which the combustible material is introduced is retained independently of the angle of rotation. The liquor spreader is united either with a glide device or the guide in the rotation mechanism.

Description:
PRIOR APPLICATION 
     This application is a U.S. national phase application based on International Application No. PCT/SE2008/050297, filed 17 Mar. 2008. 
     TECHNICAL AREA 
     The invention relates generally to equipment for boilers with combustion arrangements for liquid fuel, and it has primarily been developed to be used for the combustion of black liquor in soda boilers or in other furnaces for the processing of spent liquor. The invention thus hereby concerns an arrangement for the adjustment of equipment that is associated with the boiler, which equipment can be introduced through a boiler wall. 
     It is preferable that this arrangement comprises an adjustment of a spreader unit with a nozzle at the forward end of the unit for the distribution of a liquid fuel into a furnace in a boiler. The concept of “boiler” is hereby to include combustion ovens in general. The equipment may also relate to rodding arrangements, soot blowers, cameras or other protective equipment that is to be positioned in the boiler or in the vicinity of its opening. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     In a soda boiler, combustion liquor, normally black liquor, is supplied to the furnace through spreaders into the boiler (the reactor). Air is added at the same time, at several levels. Drying, evaporation, vaporisation, combustion, pyrolysis and several other processes that the liquor undergoes take place not only in the liquor and in the volume of gas formed, but also in and above the roasting bed. Since it is ideally the case that these processes take place in local trajectories, comprising different processes in different local volumes, rather than a mixture of processes in a global volume, with as similar processes as possible in all local volumes, careful control of each input control variable is of the utmost importance. Of the three main variables relating to operation that can be influenced—the supply of combustion air, the distribution of liquor (i.e. the location in the reactor at which liquor is supplied), and the spread of the liquor (i.e. the manner in which the liquor is supplied and distributed inside the reactor), the present invention relates to the spread of the liquor. 
     The atmosphere within the furnace is heavily corrosive for all equipment in the furnace environment, in particular given that the atmosphere also is rapidly changing. Thus, alternation between an oxidising atmosphere and a reducing atmosphere takes place in a soda boiler, combined with a high-temperature environment with attack by an alkali smelt. The lifetime for such items as liquor spreaders, therefore, is normally counted in weeks, rather than months. A well-defined and unchanging localisation of critical components of the spreader is necessary in order to obtain a controlled and longer lifetime. Arrangements and measures in order to protect these critical components are effective only for very small, well-defined volumes, mainly as a result of the chaotic nature of the flow patterns in the furnace and the severe aggression of the thermochemical attack. The difficulties of protecting the said critical components of the spreader are not made any less by the fact that the shortest distance between the inner surface of the furnace and the mechanical equipment outside of the boiler cannot be made shorter than approximately 0.5 m due to the wall of a modern soda boiler (reactor) consisting of high-pressure tubes on the inside, protective walls, insulation and external cladding, which all together give the significant thickness of wall. 
     These conditions—the aggressive atmosphere and the geometrical limitations—apply also for other equipment in a soda boiler, such as mechanical cleaning equipment, soot blowers, and other flow-based cleaning equipment, together with furnace cameras and other sensors. The present invention can be used also for such equipment. 
     Similar conditions are present also in other combustion equipment, even if the severe chemical attack is lacking in such combustion equipment. The invention can therefore be used in such other combustion equipment such as, for example, equipment for the combustion of biofuels, bubble bed furnaces, circulating fluidising bed furnaces, and in certain other reactors, such as that used to roast iron pyrites. 
     The spreader according to prior art technology, which is described in, for example, SE 527676, can be rotated in the vertical direction around horizontal axes, centres of rotation, or pivots outside of the reactor wall. When rotating the spreader unit around such axes, centres of rotation or pivots outside of the reactor wall, the angular position of the spreader nozzle inside the furnace changes at the same time, as does its height and its distance from the wall. Due to the thickness of the wall, this means also that the region, or the volume, within which the spreader nozzle moves is large, and this in turn means that deviations from the ideal positioning of the spreader nozzle and the ideal pattern of spread will be significant, while at the same time the possibility of efficiently protecting the spreader is significantly made more difficult, or made impossible. 
     It may be desirable during operation of the boiler also to introduce other equipment into the boiler through openings in the boiler wall. 
     It may be desired to introduce, for example:
         rodding arrangements, which are used to mechanically remove by poking deposits in association with openings or located on surfaces inside the boiler in association with the opening, or   soot blowers, which are introduced into the interior of the boiler in order to force with the aid of pressurised air, steam or explosive charges deposits to be released either from walls of the boiler or from tubes inside the boiler, or from both, and   camera equipment, which is introduced for inspection, and   various protective arrangements such as screens or cooling equipment.       

     The introduction of such equipment requires a hole to be made in the boiler wall, where the construction of the boiler wall must be altered around the hole, and in those cases in which tubes are integrated into the wall it is necessary to reroute these, giving high costs. It is therefore desirable that the opening in the wall be made as small as possible, such that as few tubes as possible in the boiler wall need to be rerouted. 
     The aim of the invention is to deal with the set of problems described above. This aim can be achieved through the equipment that is to be introduced into the boiler through an opening in the boiler wall, preferably a nozzle for the distribution of liquor, being such that it can be directed into different angular positions through rotation around a virtual centre of rotation located within the outer surface of the boiler wall. 
     Since the equipment that is to be introduced or positioned is a nozzle for the distribution of black liquor, this virtual centre of rotation is arranged to coincide with the position from which the fuel is spread adjacent to the opening of the nozzle into the furnace, or in an opening into the boiler. It is preferable that the said virtual centre of rotation is constituted by an imaginary horizontal line, which remains stationary during rotation of the nozzle. It is characteristic of the invention that also the said virtual centre of rotation lacks an axis in its physical meaning in the region of the said centre of rotation in the form of a machinery component that is arranged to be stationary or to rotate and that is supported by bearings. 
     The particular equipment that is to be positioned in the opening of the boiler is, in the embodiments that are described below, a spreader nozzle for black liquor or fuel. This spreader nozzle is arranged at the outlet of a pipe, denoted a “spreader pipe” below, that extends through an opening in a boiler wall. 
     The invention has its principal application in soda boilers, where facilitation of protective measures for the critical components of the equipment supplements the process technical advantages of being able to orient the equipment, preferably the nozzle, in different angular positions by rotating it around a centre of rotation inside the reactor or at the level of the boiler wall. The process technical advantages of having better control dominate in other combustion equipment and reactors. Among a number of clear advantages that can be achieved with the location of the centre of rotation at a well-defined and essentially unchanged position within the wall of the reactor offered by the present invention, the following can be mentioned:
         The distance of the spreader nozzle to the closest boiler wall does not change when the spreader unit is rotated, and this reduces the risk of the splashing of combustion liquid (liquor) onto the wall, during large changes of angle. This provides not only a gain in efficiency, but also an increase in safety. Liquor or other combustion liquid that runs down the wall may under disadvantageous conditions give rise to an explosion in the boiler.   A fixed position of the nozzle that is independent of the angle of rotation makes it also possible to limit the protection of critical components of the spreader from mechanical, thermal and chemical attack to a smaller area, and thus makes this simpler or more efficient, or both.   The spreader nozzle and the pattern of spread from the nozzle remain stationary relative to fixed supply points for combustion air and relative to the fixed position of the bed at the bottom of the furnace.   If it is necessary to adjust the height of the spreader nozzle, this can be carried out as a separate measure that does not affect the angular setting of the spreader nozzle.   It becomes easier to calculate the combustion process in the reactor if the position of spread is fixed. Nearly all currently used calculation procedures assume in practice that this condition is true, and this is thus a false assumption when using currently available technology.   The opening that is required in the boiler wall for the front part of the spreader unit, comprising at least the actual spreader nozzle itself, to reach inside of the reactor can be made smaller, and this leads to, among other results, considerably lower costs for the rerouting of tubes in the wall of the boiler.   A well-defined positioning of the spreader nozzle in the furnace gives also the possibility for the use of remote monitoring of the distribution, of flame-watch type used in burners. Such remote monitoring may be of major significance for preventing, for example, water-smelt explosions due to a failure of the combustion liquid (the liquor) to be distributed and thus meeting the bed in a collected stream, as a result of erroneous function.   It is not necessary to decrease the angular setting of the spreader nozzle from a large angle before it is possible to withdraw the unit from its operating position to its maintenance position, such as may be necessary according to prior art technology, in order to prevent a component of the equipment colliding with the boiler wall.   A smaller amount of cooling agent is required to cool, and thus protect, critical components of the spreader equipment, than that required with prior art technology, and this means that disturbance to the combustion process as a result of the supply of large quantities of cooling agent can be avoided.   Displacement of the equipment between its operating position (within the furnace) and its maintenance position (fully or partially withdrawn) is facilitated in that it is not necessary to check whether the spreader unit is located at a position that is approved for its withdrawal or introduction. Not only manual methods but also remotely controlled equipment can be used while retaining safety. The same functional advantages are achieved, independently of whether the displacement takes place to and from the operation position along a straight line using wheeled transport or along rails, or through any form of curved movement based on linkage arms, shafts or other machinery components.       

     Other characteristics and aspects of the invention and its advantages are made clear by the non-independent claims, and by the following description of some embodiments. 
    
    
     
       DETAILED DESCRIPTION 
       Reference will be made in the following description of some putative embodiments to the attached drawings, of which: 
         FIG. 1  illustrates schematically the fundamental principle of the invention, 
         FIG. 2  illustrates how the principle according to  FIG. 1  can be realised, whereby the drawing shows a view in perspective of equipment according to a first embodiment of the invention, comprising a spreader unit in its operating position in a soda boiler, of which a part of the boiler wall is shown, 
         FIG. 3  shows the equipment according to  FIG. 2  in a view seen obliquely from below, 
         FIG. 4  illustrates how a spreader unit can be rotated through a certain angle of rotation relative to a fixed member of the equipment according to the embodiment according to  FIGS. 2 and 3  around a centre of rotation in the region of the opening of a spreader nozzle in the forward end of the spreader unit, 
         FIG. 5  illustrates schematically the equipment and the function of the first embodiment of the invention according to  FIGS. 2-4 , 
         FIG. 6  illustrates how the spreader unit can be rotated according to a second embodiment around the same centre of rotation as that according to the first embodiment, and 
         FIG. 7  illustrates how the rotation of the spreader unit can be carried out according to a third embodiment, 
         FIG. 8  illustrates how the rotation of the spreader unit can be carried out according to a fourth embodiment, partially freed, 
         FIG. 9  illustrates a lower position of the rotation in the fourth embodiment, 
         FIG. 10  illustrates an upper position of the rotation in the fourth embodiment. 
     
    
    
     DESCRIPTION OF SOME PREFERRED EMBODIMENTS 
     The equipment according to the invention comprises, for example, a spreader unit, which has been given the general reference number  2  in  FIG. 1 , for the distribution of combustion liquor to a soda boiler. A part of the tubular wall  3  of the soda boiler is shown, this part being a unit of high-pressure tubes, together with a thick protective wall and insulation, given the general reference number  4 , outside of the tubular wall, and an external cladding  8 . An opening  5  extends through the boiler wall; this opening is surrounded by a protective cladding  9  of non-combustible material. A furnace on the inner surface of the tubular wall  3 , i.e. to the right in  FIG. 1 , has been given the reference numeral  7 .  FIG. 4  shows in more detail how the spreader unit illustrated schematically in  FIG. 1  is constructed. This consists, according to the embodiment, of a tubular injector body  10 , a connecting pipe  11  connected to the injector body  10 , the forward end part  37  of which pipe  11  is angled obliquely downwards, a spreader nozzle  12  arranged at the end of this angled part  37  and a spreader plate  13  arranged under the spreader nozzle  12 , which is, actually, of previously known type. The injector body  10  and the connecting pipe  11  will be denoted in this text jointly as a “spreader pipe”  14 . A flexible steel tube  15  for the supply of combustion liquor is connected to the rear end of the injector body  10 , i.e. to the end of the spreader pipe  14 . 
     To return now to  FIG. 1 , the spreader unit  2  in its operating position has been introduced through the opening  5  to such an extent that the spreader nozzle  12  is located in the furnace  7  inside of the tubular wall  3 , or possibly, at the same level as the wall. What is particularly characteristic for the invention is that the spreader unit  2  can be rotated in a vertical plane around a centre of rotation  27  in the furnace  7 , which centre of rotation has the form of an imaginary horizontal line that extends through a point in the region of the opening of the spreader nozzle  12 . 
     Reference is now made to  FIGS. 2 and 3 , which show equipment according to the invention generally denoted by reference number  1 . This includes the spreader unit  2 , which has been described above with reference to  FIG. 4 , and which comprises a spreader pipe  14 . A pneumatic cylinder  17  is arranged under the spreader pipe  14 . The cylinder  17  is united with the spreader pipe  14  through a coupling  18  in a manner that allows its removal. A cleaning device is present at the end of the piston rod  19  of the pneumatic cylinder  17 , in the form of a poker (not shown in the drawings) used to hack away slag and other deposits from the spreader unit in association with at least one of the nozzle  12  and the spreader plate  13 . Other equipment with operative functions within the boiler, such as a furnace camera and other sensors, can be attached in a similar manner to the spreader pipe  14 . 
     A support for the spreader unit  2  has the form of a bracket  20 , which supports two horizontal guides. The bracket  20  with the guides  21  is attached to and extends from the boiler wall under the opening  5 . A carriage  24  is arranged on the guides  21  such that it can be displaced. Two parallel, vertical guide plates  25  are united with the carriage by welding or by another permanent manner, and extend from approximately the level of the pneumatic cylinder  17  towards the plane of the floor. A guide track  26  with the form of an arc of a circle is present in each guide plate  25 —such a guide plate  25  is shown also in  FIG. 4 . The radial centre of a guide track is located at the said point in the centre of the opening of the spreader nozzle  12 , which point is also the centre of rotation  27  for the spreader unit  2 . 
     A steel construction  30  is located under the pneumatic cylinder  17  in the form of a box arranged between the guide plates  25 . The box  30  is united with the spreader unit  2  through the pneumatic cylinder  17 . A pair of horizontal shafts  32 ,  33  extend through the box  30 . The shafts  32 ,  33  are so mounted in the box  30  that they are coaxial with a pair of double-flanged wheels  34 ,  35 , which have been introduced into the guide track  26  that is present in each of the guide plates  25 . 
     The mechanical arrangements that have been described function in the manner that will now be described with reference to  FIGS. 1-5 , when the spreader unit  2  has been introduced into its operating position. When the spreader unit  2  is in its operating position,  FIGS. 1 and 2 , the spreader nozzle  12  is located inside the furnace chamber  7  a short distance inside of the tubular wall  3 , or possible at the same level as this wall. The spreader plate  13  is essentially horizontal in this position, and a forward part  37  of the connecting pipe  11  is directed downwards towards the spreader plate  13  at a fixed angle to it in a manner that is known. If it is desired to direct the forward part  37  of the spreader pipe in a more downwards direction and to angle at the same time the spreader plate  13  also downwards, the spreader pipe  14  is moved upwards, which it would be possible in principle to carry out manually with the aid of the handle  39  on the upper surface of the spreader pipe  14 . A displacement means  48 , however, is available, in the form of a screw arranged between the fixed and rotating parts of the equipment  1  when in its operating position. According to the embodiment, the screw extends between a horizontal rod  36  located at a lower rear corner of the box  30  and a horizontal rod  38 ,  FIG. 3 , that extends between a pair of brackets on the carriage  24 . The lower end of the screw  48  may be attached to the box  30  in a manner that allows displacement, and introduced into the rod  38  through a hole with a corresponding thread for a nut. Alternatively, the screw  48  can be constituted by a stretching screw that is united with matching left and right-threaded holes in the rod  38 , and with the rod  36  in the box  30 . A knob  42  is located at the rear upper end of the screw  48 . 
     The lower rear corner of the box is drawn, through rotating the knob  42  in a certain direction, backwards and upwards, taking with it the shafts  32 ,  33 , and thus also the wheels  34 ,  35 , which are compelled to follow the guide tracks  26  in the plates  25 , which are fixed relative to the carriage  24 . The compels the wheels  34 ,  35  and the shafts  32 ,  33  to move along the arc of a circle that has its centre in the said centre of rotation  27  in the region in which the opening of the spreader nozzle  12  is located, and this in turn compels the complete spreader unit  2 , and any arrangements that may be connected to the spreader unit, such as the pneumatically operated cleaning device, to rotate around this centre of rotation  27 . When the desired angle of rotation has been reached—the maximum angle of rotation according to the embodiment is α°, FIG.  4 ,—the spreader unit  2  can be fixed in its new position by locking the screw  48  with a conventional lock device, such as a locking nut. 
       FIG. 5  illustrates in schematic form the principle of the embodiment according to  FIGS. 2-4 . The drawing illustrates that the displacement means  48 , which in the detailed embodiment is constituted by a screw, can be arranged at a freely chosen location between the fixed units, which are represented by the plates  25  and the tubular injector body  10 . 
     The mechanical arrangements described are basically so simple that a precision can be achieved that is sufficient to ensure that the location of a horizontal central line in the opening of the spreader nozzle  12  moves to an insignificant degree as a result of the rotational movement of the spreader unit  2  that has been described. The maximum deviation from the theoretical centre of rotation  27  can lie within the area of a circle with its centre at the said theoretical centre of rotation and having a maximum radius of 2 cm, and preferably a maximum radius of 1 cm. 
     In one variant of the embodiment that has been described with reference to the drawings  2 - 5 , a pair of segments of toothed wheels can be used instead of a pair of guide tracks having the form of an arc of a circle. These segments may be united with the spreader pipe  14 . A box or another rigid construction can be arranged between a pair of such segments of toothed wheels, which construction is attached to the carriage  24 . A horizontal shaft can in this case extend through the box, mounted in bearings in the box, and which supports on each side of the box a securely wedged toothed wheel that interacts with the relevant segment of toothed wheel. The relevant segments of toothed wheel form, in the same manner as the guide tracks in the preceding embodiment, a pair of arcs of a circle, the radial centre of which coincides with the said centre of rotation  27 , which is constituted by a putative horizontal line in the region of the opening of the spreader nozzle  12 . By rotating the said toothed wheels, which can be carried out with the aid of a hand crank or with the aid of an electric motor through a suitable transmission, the complete spreader unit  2  is rotated in a manner that is equivalent to the function of the preceding embodiment. 
     There are two centres of rotation in the embodiment according to  FIG. 6 : not only the said centre of rotation  27  in the region of the opening of the spreader nozzle  12  (which centre of rotation constitutes a first centre of rotation in the movement system), but also a second centre of rotation  50 , which is parallel with the said first centre of rotation  27  and which is located at one member  51 , under and united with the spreader pipe  14 . The said member  51  can have the form of two parallel plates, united with the spreader pipe  14 . A pair of lower plates  52  is united with the spreader pipe  14  through the member  51  through a horizontal shaft  53 . The shaft  53  has its centre of rotation coincident with the said second centre of rotation  50 . The plates  52 , which are mounted in bearings around the shaft  53 , can be displaced vertically with the aid of a first displacement means  54 , a screw, for example, as it was in the preceding embodiment, and the spreader pipe  14 , and with it the complete spreader unit  2 , can be rotated around the said second centre of rotation  50  with the aid of a second displacement means  55 , which also may be constituted by a screw, arranged between the spreader pipe  14  and the plates  52 . A resultant rotation of the spreader unit  2  around the said first centre of rotation  27  can also in this case be achieved by control of the displacement means  54 ,  55 , i.e. the same final result as in the preceding embodiments. 
     A first fixed pivot support has been given the reference number  60  in the embodiment according to  FIG. 7 . This has at its upper end a contact means, that may be constituted by a pair of wheels  61 . A member under the spreader unit  2 , for example a box  62  united with the spreader unit  2 , makes contact at its forward surface  63  with the wheels  61  on the support  60 . A base link  65  makes contact at its lower end  66  with the lower end  60  of the support, in a manner that allows rotation. A pair of links  67 ,  68 , which are not parallel with each other, are united not only with the base link  65 , but also with the box  62 , in a manner that allows rotation. The manner of this uniting is illustrated in  FIG. 7 . The link  66  is united at the positions  68  and  69  with the base link  65  and with the box  62  in a manner that allows rotation, and in an equivalent manner the link  67  is united at positions  70 ,  71  with the base link  65  and the box  62 , in a manner that allows rotation. The centres of rotation  68 ,  69 ,  70 ,  71  for the said pivot positions form the corners of a quadrilateral that is not constituted by a parallelogram. The displacement means for lifting or lowering the base link  65  is symbolically represented in the drawing by the double arrow  73 . Through selection of the lengths of the links and the relative distances between the pivot points  68 - 71 , it is possible to achieve a pattern of movement in which the wheels  61  roll against the side  63  of the box  62 , and this gives the same final result with respect to the rotation of the spreader unit  2  around the said centre of rotation  27  as in the preceding embodiments. 
     An alternative embodiment is shown in  FIG. 8  that differs from the embodiments shown in  FIGS. 2-5  in that the circular guidance is constituted by a bent guide beam  26   b  instead of a guide track. The guide beam  26   b  is an integral part of a fixture  20   b  that is rigidly fixed to the bracket or to the carriage that slides along the bracket. The liquor spreader is attached in a suitable manner to the upper parts of two rails  25   b , which rails are arranged one on each side of the guide beam  26   b  (only one of the rails  25   b  is shown in  FIG. 8 ). Guide rollers  34   a  (two rollers) and  35   b  are arranged between these rails, where two of the guide rollers  34   a  are located on the convex side of the guide beam  26   b , while one guide roller is located on the concave side of the guide beam  26   b . The guide beam has been provided in a similar manner with a curvature such that it has a centre of curvature that coincides with the virtual centre of rotation. 
       FIG. 9  shows the lower position, equivalent to that shown in  FIG. 8 , but in this case with the second rail  25   b  mounted in place, such that the axles of the guide rollers are held in position between these rails  25   b.    
       FIG. 10  shows a position at which the rails, and thus also the equipment that is to be positioned and that is united with these rails, displaced upwards on the guide beam. 
     Characteristic for all of these embodiments is that the rotation mechanism is constituted by simple physical guiding of the liquor spreader during its rotation in the vertical plane, i.e. an adjustment of one degree of freedom using the rotation mechanism. These rotation mechanisms can subsequently be combined as necessary with other simple adjustment mechanisms that control other degrees of freedom such as, for example:
         the height of the complete equipment, i.e. a degree of freedom that entails a parallel displacement in the vertical direction, or   a simple regulatory mechanism that can rotate the equipment, the liquor spreader, along its longitudinal direction.
 
It is appropriate that the rotation mechanism be located on a carriage that can be displaced towards and away from the opening of the boiler, on a bracket that is attached to the boiler.
       

     While the present invention has been described in accordance with preferred compositions and embodiments, it is to be understood that certain substitutions and alterations may be made thereto without departing from the spirit and scope of the following claims.