Patent Application
20070036695
The invention relates to a method for improving the operation safety of the smelt spout area of a recovery boiler and the smelt spout area of a recovery boiler.
The spent lye, i.e. the so-called black liquor created in pulp manufacture is burnt in a recovery boiler, on one hand, in order to recover the energy it includes, and on the other hand, in order to recover the chemicals in it and to recycle them back to circulation. A char bed is created on the bottom of the recovery boiler when burning black liquor, which in a high temperature forms into smelt, which is removed from the boiler as a continuous flow via smelt spouts to a dissolving tank.
Below the furnace is located the cover area of the dissolving tank of the recovery boiler, i.e. the smelt spout area, where the smelt from the lower part of the furnace is directed along the so-called smelt spout to the dissolving tank.
It is necessary to work in the vicinity of the smelt spouts relatively often, because the operation of the smelt spouts must be monitored at regular intervals. When necessary, pluggings must be removed from the smelt spouts in order for the smelt to be able to travel to the dissolving tank. In addition, the primary air nozzles 5 are often located in the vicinity of the smelt spout area (on the so-called primary register level), in which case checking and adjusting the nozzles requires working in the smelt spout area.
Typically, the smelt is very hot (for example 750 to 820° C.). The possible splashes of smelt cause danger to the personnel working and moving in the vicinity. Because of this, there is typically a protection area near the smelt spouts, moving on which area should be avoided and working on which area requires using special protection equipment.
The main purpose of the present invention is to disclose a new solution for increasing work safety.
To attain this purpose, the method according to the invention is primarily characterized in that in the method the smelt spouts are separated from the working area by a shielding wall arranged movable in relation to the smelt spouts. The smelt spout area of a recovery boiler according to the invention, in turn, is primarily characterized in that the smelt spout area comprises one or more shielding walls arranged movable in relation to the smelt spout in order to separate the smelt spouts from the working area. The dependent claims will present some preferred embodiments of the invention.
The basic idea of the invention is to arrange a shielding wall in front of the smelt spouts, which can be moved, for example closed and opened. According to the basic idea the closed shielding wall settles between the person working in the working area and the smelt spout. The shielding wall prevents the possible smelt splashes from falling on the person. In an advantageous embodiment the shielding wall also muffles the noise from the smelt spouts towards the working area. In an embodiment the heat radiation radiated from the smelt spouts to the working area is dampened by the shielding wall.
The method according to the invention discloses a solution for improving the operation safety of the smelt spout area of a recovery boiler, which smelt spout area comprises a working area, as well as smelt spouts connected to the lower part of the boiler to direct the smelt from the boiler to a dissolving tank. In the method, the smelt spouts are separated from the working area by a shielding wall that is arranged movable in relation to the smelt spouts. Correspondingly, in a power plant according to the invention, the smelt spout area comprises one or more shielding walls arranged movable in relation to the smelt spout in order to separate the smelt spouts from the working area.
In an embodiment the shielding wall is formed of one or more shielding units arranged movable. The shielding units can move in different directions application-specifically, such as, for example horizontally or vertically.
The movable shielding wall enables different usage, service and maintenance operations requiring a great deal of moving space. In an advantageous embodiment the shielding wall can be opened for a large uniform length.
The shielding wall can be implemented in a variety of ways. Advantageously the wall is formed of several units, in which case handling it is easier than handling large units. For example, the wall may be composed of sliding doors, lattice doors, shutters and/or folding doors. The direction of motion of individual units of the wall depends on the application. For example, the direction of motion can be horizontal or vertical. The wall can also move parallel or perpendicularly in relation to the bank of smelt spouts of the boiler.
In an embodiment the smelt spout area also comprises a service platform arranged movable in relation to the smelt spouts, which platform comprises a shielding wall. The service platform is meant for the usage, service and maintenance operations of targets located higher, such as the primary register level.
The shielding wall advantageously comprises inspection openings, such as, for example, windows and/or hatches that can be opened, through which it is possible to perform, inter alia, visual monitoring, rodding the spouts, as well as other usage, service and maintenance operation. There can be different kinds and shapes of hatches and windows, which provide as optimal as possible user interfaces for different tasks.
By the solution according to the invention, many significant advantages are achieved when compared with the solutions of prior art. The safety of the smelt spout area of a recovery boiler is improved, when the shielding structure separates the smelt spouts from the personnel. The shielding structure can application-specifically prevent different splashes, steams and/or pressure shocks from reaching the working area.
In an application the noise level of the smelt spout area is decreased. Muffling the noise is affected by the design and materials of the shielding structure. Decreased noise level improves work conditions and increases work safety for its part.
In one case the invention, in turn, enables the efficient utilization of the smelt spout area, because the shielding area can be decreased due to the shielding solution and the area that is thus freed can be used efficiently.
In the following, the invention will be described in more detail with reference to the appended principle drawings, in which
For the sake of clarity, the figures only show the details necessary for understanding the invention. The structures and details that are not necessary for understanding the invention, but are obvious for anyone skilled in the art, have been omitted from the figures in order to emphasize the characteristics of the invention.
By opening the shielding wall 8 partly or entirely is created a large and as clear as possible passage to the area behind the line formed by the shielding wall 8, such as, for example, to the smelt spouts 2. Thus, it is easier to perform more extensive usage, service and maintenance operation. As can be seen in
In an application the attachment of the shielding unit 9 of the shielding wall 8 is arranged with a quick clamping, which enables the easy and fast detachment, and if necessary, the removal and/or changing of the shielding unit.
The shielding wall 8 may application-specifically be located on different sides of the boiler (on one or more sides). In a power plant application the shielding wall 8 is on those sides of the boiler where the smelt spouts 2 are located. In another power plant application the shielding wall 8 is placed around the boiler.
The structure of the shielding wall 8 and the individual shielding units 9 may vary application-specifically. Some possible solutions include different kinds of sliding doors, lattice doors, folding doors, roller shutters, etc. In addition, the direction of motion of the shielding units 9 may vary application-specifically. In the previous example the direction of motion of the shielding units 9 is horizontal and in the direction of the boiler wall. In another application the direction of motion of the shielding unit 9 is substantially perpendicular to the boiler wall. In an application the direction of motion of the shielding unit 9 is substantially vertical. In an application the direction of motion of the movement taking place vertically is, in turn, slanted. Especially different curtain-type shielding walls 8 are advantageous to be arranged to move upwards, preferably vertically if possible, in which case the structure does not necessarily have to be rigid in order to control the movement of the shielding wall 8. The movement of the shielding wall 8 can also be controlled by different solutions, such as, for example, rolls, glides, guide bars, hinges and junction structures.
In selecting the material for the shielding wall 8 it is advantageous to pay attention to, inter alia, thermal resistance and the resistance of the occurring chemicals. The shielding wall 8 should be incombustible and preferably sound-insulating. Because of ease of processing the shielding units 9 of the shielding wall 8 should be light, which, in addition to the materials, is affected by the size and shape of the shielding unit. In some tests a shielding wall 8 manufactured of stainless steel has been detected to be useful. Its sound-insulation can be improved with different sound-insulating materials. There are also other alternatives, such as, for example structures manufacture entirely or partly of metal, composite or ceramic.
The shielding wall 8 must also endure great temperature fluctuations, which occur, inter alia, in connection with the start-up and shutdown of the boiler. Thermal radiation of the boiler causes the dimensions of the shielding wall 8 to change. In addition, a change in the temperature of the shielding wall 8 causes the dimensions to change in its structure. For easy handling the shielding wall 8 must enable the thermal expansion of both the shielding wall and other structures. The changes caused by thermal expansion affecting the shielding wall 8 may be several tens of centimeters in size. The shielding wall 8 can, for example, be implemented in such a manner that its structure is flexible or its structure increases and decreases according to need. It is also possible that the attachment solution enables thermal radiation.
The space around the boiler defined by the shielding wall can be substantially solid or breathing. A breathing structure can be implemented in a variety of ways. The shielding wall 8 can, for example, be formed in such a manner that air can flow between the shielding units 9 of the shielding wall. It is also possible to use different breather and valve structures for pressure balancing. The flow of air and other gases can also be controlled with various types of channel structures. For example, a pipe can be lead to the outside from the space defined around the boiler by the shielding wall 8. Different pressure shocks may occur in the space in question, for example, when a malfunction is created in the smelt spout 2, such as, for example, a smelt flush.
The shielding wall 8 described above protects the person 1 on the service platform 7. It is also possible to arrange a shielding wall 10 in connection with the service platform 7. Thus, the shielding wall 10 moves along with the service platform 7 always being between the working area of the service platform and the smelt spouts 2, thus protecting the working area. The shielding wall 10 of this service platform 7 can also be equipped with different hatches and windows, for example, as has been described above. The size and appearance of the shielding wall 10 of the service platform may vary depending on the target of use.
The shielding effect of the shielding wall 8, as well as work safety can be improved by arranging the devices in the smelt spout area in advantageous positions. By designing the primary air nozzles 5 for example smaller, the working position is made safer and more ergonomic. As can be seen in
By combining, in various ways, the modes and structures disclosed in connection with the different embodiments of the invention presented above, it is possible to produce various embodiments of the invention in accordance with the spirit of the invention. Therefore, the above-presented examples must not be interpreted as restrictive to the invention, but the embodiments of the invention may be freely varied within the scope of the inventive features presented in the claims hereinbelow.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20055432 | Aug 2005 | FI | national |
