This application is a U.S. national phase application based on International Application No. PCT/SE2008/050297, filed 17 Mar. 2008.
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.
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:
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:
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.
Reference will be made in the following description of some putative embodiments to the attached drawings, of which:
The equipment according to the invention comprises, for example, a spreader unit, which has been given the general reference number 2 in
To return now to
Reference is now made to
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
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
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.
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
A first fixed pivot support has been given the reference number 60 in the embodiment according to
An alternative embodiment is shown in
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:
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.
Number | Date | Country | Kind |
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0700763 | Mar 2007 | SE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/SE2008/050297 | 3/17/2008 | WO | 00 | 11/13/2009 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2008/118071 | 10/2/2008 | WO | A |
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527676 | Nov 2005 | SE |
Number | Date | Country | |
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