FI125463B - Arrangement and method of recovery boiler - Google Patents

Description

Arrangement and method of recovery boiler

Background

The invention relates to an arrangement in a recovery boiler having a curtain piping fitted in the furnace of the recovery boiler comprising a second draw, at least one superheater being fitted to the second draw, and the second draw arranged to be cooled by on one side wall. The invention further relates to a method in a recovery boiler, the recovery boiler comprising a second draw, a curtain tube fitted to the furnace, and at least one superheater fitted to a second draw, the method cooling the second draw with cooling medium from the curtain piping.

In the pulp production process, black liquor is burned in a recovery boiler. The tasks of the recovery boiler include the recovery of chemicals and the recovery of thermal energy from combustion.

The soda boiler has a furnace to supply black liquor and the air needed for combustion. There are superheaters at the top of the boiler and after the superheater area there is a flue gas duct. The flue gas duct has a cooking surface and economizers. The thermal energy generated by combustion produces superheated superheated steam, which can be used, inter alia, in power generation.

When it is desired to raise the temperature of the superheated steam, part of the superheaters may be fitted to a second draft, i.e. to the first channel section of the flue gas duct after the boiler. As a result, the temperature of the surfaces of the second draw may increase too much.

Short description

The arrangement and method according to the invention are characterized by what is disclosed in the characterizing parts of the independent claims. Other embodiments of the invention are characterized by what is set forth in the other claims.

Inventive embodiments are also disclosed in the specification and drawings of this application. The inventive content contained in the application may also be defined otherwise than as set forth in the claims below. The inventive content may also consist of several separate inventions, particularly if the invention is considered in the light of the express or implied subtasks or the benefits or classes of benefits achieved. In this case, some of the attributes contained in the claims below may be redundant for individual inventive ideas. Aspects of various embodiments of the invention may be applied in conjunction with other embodiments within the scope of the inventive concept.

The arrangement according to the invention is characterized in that the arrangement comprises a second draw ashtray comprising front wall cooling pipes and / or rear wall cooling pipes, and that said cooling pipes are connected to receive a cooling medium from the curtain pipe system.

The advantage is that the second draft in the hot area can be effectively cooled. A further advantage is that the cooling circuit of the curtain piping can be secured.

The method according to the invention is characterized in that the second draw comprises a second draft ash hopper and that a cooling medium from the curtain piping is introduced into the front and / or rear wall of the second draw ash hopper.

The advantage is that the temperature of the second draw can be controlled efficiently and simply.

The following is a list of features of some embodiments of the invention in random order:

The idea of one embodiment is that the ash hopper of the second draw comprises an annular chamber which is fitted to the lower part of the ashtray and connected via a connecting tube to the curtain tube to receive the cooling medium and distribute the coolant to the cooling pipes and The advantage is that the cooling medium can be distributed evenly across the various cooling tubes.

The idea of one embodiment is that the ashtray cooling tubes form the gas-tight front and rear walls of the ashtray, and that above, the cooling tubes are arranged as a grid conduit for the passage of flue gases. The advantage is that the ash hopper can be cooled very efficiently and that the thermal energy of the flue gases can be collected above.

The idea of one embodiment is that the front and / or rear wall cooling pipes form a sealed roof of the second draft and are connected to the second upper chamber and thereby to the cylinder. The advantage is that the heat energy of the flue gases can also be collected from the ceiling of the second draw.

The idea of one embodiment is that the side walls of the second draw are coupled to a vapor circulation to cool the side walls. The advantage is that said sidewalls can be used as a superheater.

The idea of one embodiment is that the cooling cycle of the recovery boiler is implemented as a natural cycle, and that the cooling tubes of the front wall and the rear wall of the second draft ash hopper are all arranged above the curtain piping. The advantage is that the implementation of the cooling circuit is simple and reliable.

The idea of one embodiment is that at least one side wall of the second draw is connected to the cylinder by a downer to receive cooling water. The advantage is that the cooling of the second draw and the recovery of thermal energy are enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates schematically a side and partially open section of one recovery boiler, Figure 2a schematically shows a side and partially open ash section of the ash hopper and a second draft ashtray, Figure 2b shows a sectional view of the other and section Fig. 3a schematically shows a side view of a second draft ash side and partially sectioned, Fig. 3b shows first cross sections of the ash hopper according to Fig. 3a, Fig. 3c shows a second cross sectional view schematically illustrates another construction of the second draft of the second recovery boiler, seen from the side and partially in section, Fig. 6 schematically shows a and Fig. 7 schematically shows a fourth lateral and partially open view of a second draft of the recovery boiler.

For the sake of clarity, the figures are simplified. Like parts are denoted by like reference numerals in the figures.

Detailed description

Fig. 1 schematically shows a recovery boiler from the side and partly in section. The soda boiler includes a furnace 1 for supplying black liquor for combustion through the nozzles 2. The combustion air is supplied to the furnace 1 via the air nozzles 3.

On the upper part of the furnace 1 of the soda boiler are provided heating surfaces 4 which are superheaters. The superheaters 4 are elements formed by a plurality of parallel vertical tubes which are arranged in parallel in the transverse direction of the recovery boiler. Steam in the superheaters, which heats up as hot flue gases heat the pipes from the outside.

The sump boiler comprises a flue gas flow control nozzle 6. At the nose 6 and below the superheaters 4 there is a curtain pipe 7. The curtain pipe 7 has relatively few curtain pipes and circulates water which is partially evaporated by the flue gases flowing past the curtain pipes. Correspondingly, this causes the temperature of the flue gases to drop before reaching the superheaters 4. In addition, the ducting 7 protects the superheaters 4 from direct radiation from the furnace.

The curtain tubes 7 are generally a vapor-proof surface and operate in a natural cycle. The curtain tubes are arranged at a non-horizontal angle so that the ends closest to their nose 6 are higher than the distal ends.

The walls 5, superheaters 4 and curtain piping 7 of the soda boiler are so-called. heat transfer surfaces. The thermal surfaces represented by reference numeral 4 'may be, for example, superheaters or curtain piping. These heat surfaces either have separate pipes or are formed by welding gas-tight walls such as boiler walls 5. Within these heat surfaces, water or steam or a mixture of these flows, which is heated by combustion or hot gases outside.

After the upper part of the furnace 1, the flue gases flow to the convection heat surfaces 8, which comprise successive end-to-end duct portions. The first of these duct sections is the second draw 9.

The second draw 9 is provided with superheaters 4 '. These superheaters 4 'increase the temperature of superheated steam compared to the solution where only superheaters are located at the top of the recovery boiler. This makes it possible, for example, to produce steam at 515 ° C.

The second draw 9 comprises an ash hopper 14 for collecting ash and through which the ash can be removed from the second draw 9.

The ash hopper 14 comprises a cooled front wall 15 and a cooled rear wall 16 for lowering the temperature of the surfaces of the ash hopper 14. The structure and function of the cooled front and rear walls 15, 16 will be discussed in more detail below. The cooled front and back walls can lower the temperature of the ash hopper surfaces to reduce their risk of damage.

Convection heat surfaces 8 after the second draw 9 typically have additional heat surfaces, for example known cooking surfaces 10 and economizers 11.

The recovery boiler further comprises a water and steam system. This includes a cylinder 12, from which hot water is supplied, inter alia, to the curtain pipe 7 via the drain pipe 13. The figure shows only one downpipe 13, but of course the number may be larger.

The curtain piping 7 is connected by one or more interconnecting pipes 17 to the front draft cooling pipes 15 and the rear wall cooling pipes 16 of the second draft ash hopper 14. .

Cooling pipes 15, 16 of the ash hopper 14 are connected via a front wall hollow section 18 and a rear wall lattice section 19 to a circulating pipe 20 and further to a cylinder 12. The lattice section 19, 20 comprises pipes spaced apart and at least substantially upright. Only one rotary tube 20 is shown, but the number may be greater. In the curtain piping 7, cooling conduits 15, 16 and lattice conduits 18, 19, the heated refrigerant medium, which is steam or a mixture of water and steam, is thus returned to cylinder 12 or to the subsequent superheating step.

If the cooling cycle of the recovery boiler has been carried out in a so-called. preferably, the front wall cooling tubes 15 and the rear wall cooling tubes 16 of the second draft ash hopper 14 are preferably arranged entirely above the curtain piping 7, whereby the connecting tube 17 is ascending downstream of the cooling medium and the natural circulation is effected efficiently.

It should also be noted that, for the sake of simplicity, not all of the water and steam system pipes connected to the heating surfaces are shown in the attached figures. However, in practice, several downpipes may be led to each heating surface and multiple circuits may be led from the thermal surface to the cylinder.

Fig. 2a schematically shows a curtain tube system of a recovery boiler and a second draft ash hopper connected thereto and a partially open cut-out in Fig. 2b, viewed from above and partly in section.

The curtain piping 7 comprises a plurality of heating surface tubes 21 grouped in tube elements 26. In the embodiment shown in the figure, each put tube element 26 comprises five thermal surface tubes 21; however, it is clear that this number as well as the number of tube elements 26 may be different.

The curtain piping 7 comprises a distribution chamber 23 which distributes the incoming cooling medium to the element distribution chambers 22. The elementary distribution chamber 22 distributes the cooling medium to the thermal surface tubes 21. The cooling medium leaving the thermal surface tubes 21 is led to the interconnecting tube 17.

The cooling system of the second draw ash hopper 14 comprises an ash hopper manifold, for example an annular chamber 25, to which each pipe element 26 is connected by its own connecting pipe 17. According to another idea, two or more pipe elements 26 are connected to a common connecting pipe 17.

The annular chamber 25 is disposed in the lower part of the ash hopper 14 and divides the cooling medium 15 from the curtain piping 7 into the cooling tubes 15 and the rear wall cooling tubes 16. According to another idea, the

The ash hopper 14 is thus cooled by a relatively low temperature cooling medium. Thus, the ash hopper 14 is subjected to an effective cooling effect.

After the ash hopper 14, the cooling medium flows from the ash hopper front wall cooling tubes 15 to the front wall gutter piping 18 and, respectively, from the ash hopper wall cooling tubing 16 to the rear wall gutter piping 19.

Figure 3a schematically shows a side view of a second draft ashtray and a partially sectioned view, Figure 3b shows the first cross sections A to A and Figure 3c the second cross sections B to B.

The cooling tubes 15, 16 interconnected by fins 38 form gas-tight front and rear walls of the ash hopper 14 as shown in Figure 3b. Such a structure can be manufactured, for example, by welding. Of course, the gas-tight structure can also be formed in other ways, for example by directly connecting adjacent cooling tubes 30. On its sides, the ash hopper 14 is limited to the side walls of the second draw 8.

Above the ash funnel 14, the cooling tubes are grouped into a lattice shape as a front wall lattice pipe 18 and a rear wall lattice pipe 19. One cross-section of the lattice shape is shown in Figure 3c. The grid shape may, of course, be different, provided that the cooling tubes 30 are loosely arranged to allow the flue gases to flow through.

The ash hopper cooling tubes 15, 16 may be connected via the front wall gate tube 18 and the rear wall gate tube 19 to one or more manifold chambers 28, 29 and further to the circulation tube 20 and cylinder 12.

The front and / or rear wall lattice conduits 18, 19 may form a second draft gas-tight roof 27 having a cross-sectional view as shown in Figure 3b. In this case, the ceiling 27 also acts as a heating surface. Figure 3a shows an embodiment in which the rear wall gate conduit 19 forms a second draft gas-tight roof 27.

According to one idea, the cooling tubes of the roof 27 are connected via a sizing chamber 28, 29 and a circulating tube 20 to a cylinder 12.

However, it should be noted that the above roof solution and / or manifold chamber 28, 29 may be omitted from the arrangement.

Fig. 4 schematically shows a side elevation and a partially cut-away structure of a second draw side wall of a recovery boiler.

According to one idea, the sidewalls of the second draw 9 are coupled to a steam cycle to cool the sidewalls while serving as superheaters.

In the solution shown in Fig. 4, steam is introduced from the cylinder through a steam supply tube 31 and discharged to superheaters via a steam outlet tube 32.

Steam in the direction of travel indicated by arrows S flows from the first upper chamber 33 disposed on the upper portion of the second draft 9 to the lower chamber 34 disposed on the lower portion of the second draft 9 and further upwards to the second upper chamber 35 disposed on the upper portion of the second draft 9.

Between the first upper chamber and the lower chamber 33, 34 there is provided a first side wall press 36a and a lower side wall 36b between the lower chamber and the second upper chamber 34, 35.

According to one idea, the side wall superheater 36a, 36b has a cross-sectional view as shown in Figure 3b.

It should be noted, however, that according to another idea, the sidewalls of the second draw 9 are cooled by the circulation of the coolant in tubes arranged in the sidewalls according to the principle of natural circulation.

Fig. 5 is a schematic side and partially sectional view of another embodiment of a second draw of the recovery boiler.

The connecting pipe 17 leads from the curtain piping, not shown in the figure, to a cooling medium for the second draft of the ash hopper 14 to the front and rear walls 15, 16, from where it rises to the front wall gutter 18 and rear wall gutter 19 and so on.

At least one of the side drawings 37a, 37b of the second draw comprises cooling tubes by means of which the other draw can be cooled. It should be noted that Figure 5 shows only the first side tongue 37a of the second tension: the second side wall 37b is disposed on the opposite side of the second tension.

The cooling pipes of the side wall 37a, 37b are connected via cylinder at least one side wall drain pipe 39 to the cylinder 12. The side wall drain pipe 39 leads the cooling medium, in this case water, to the cooling pipes of the side wall 37a, 37b.

By cooling the side wall 37a, 37b, the cooling of the second draw and the recovery of thermal energy are enhanced.

Fig. 6 schematically shows a third side view of a second drawstroke of a recovery boiler, partly in section.

Here, at least one of the second draw side walls 37a, 37b comprises cooling tubes connected by at least one side wall connecting tube 41 to the curtain piping. Thus, the cooling medium from the curtain piping can be passed not only to the front and rear walls 15, 16 of the ash hopper 14, but also to at least one of the side drains 37a, 37b of the second draw.

One advantage of the solution is that it is possible to increase the capacity of the second draw cooling tubes to receive the cooling medium from the curtain tubes. In this way, the volume of the cooling medium through the curtain tubes can be increased.

Fig. 7 schematically shows a fourth side view of a second draft of the recovery boiler, partially and partially cut away.

As in the solution shown in Fig. 6, here at least one of the second draw side walls 37a, 37b comprises cooling tubes which are connected to the curtain piping by at least one side wall connecting tube 41. The curtain piping is further connected by a connecting pipe 17 to the cooling pipes of the rear wall 16 of the ash funnel 14, but not to the cooling pipes of the front wall 15. Instead, the cooling tubes of the front wall 15 are connected by at least one ash hopper drainage tube 42 to cylinder 12. That is, the ash hopper 15 is cooled by cooling medium from cylinder 12, e.g.

One of the advantages of the solution is the further increase in the cooling capacity of the second stroke.

It should be noted in this connection that, according to one idea, the cylinder 12 is connected via the ash hopper drain pipe 42 only to the ashtray rear wall 16 cooling pipes. In this case, the cooling tubes of the front wall 15 can be cooled by cooling medium from the curtain piping.

According to another idea, the cylinder 12 is connected via the ash hopper drain pipe 42 to both the cooling pipes of the front wall 15 and the cooling pipes of the rear wall 16. Thus, at least one of the second draw from the side walls 37a, 37b comprises cooling tubes connected by at least one side wall connecting tube 41 to receive cooling media from the curtain piping.

According to a third idea, the front wall 15 or rear wall 16 of the ash hopper is provided without cooling, and cooling of the second stroke is effected by cooling the opposite wall 15, 16 and / or at least one of the second stroke side walls 37a, 37b.

In some cases, the features set forth in this application may be used as such, despite other features. On the other hand, the features disclosed in this application may be combined, if necessary, to form different combinations.

The drawings and the description related thereto are intended only to illustrate the idea of the invention. It will be apparent to one skilled in the art that the invention is not limited to the embodiments described above, in which the invention is illustrated by some examples, but that many modifications and various embodiments of the invention are possible within the inventive concept defined in the claims below.

Reference Numbers 1 firebox 2 black liquor nozzle 3 air nozzle 4,4 'heating surface 5 wall 6 beak 7 curtain piping 8 convection heat sink 9 second draft 10 cooking surface 11 economizer 12 cylinder 13 downpipe 14 second draft ashtray 15 ashtray rear wall 16 ashtray rear wall 19 ashtray circulating tube 21 heating surface tube 22 element manifold 23 manifold 24 element manifold chamber 25 annular chamber 26 tube element 27 second draft ceiling 28 first manifold chamber 29 second manifold 30 cooling manifold 31 steam inlet pipe 32 second manifold 34 second manifold 34 second manifold 34 fin 39 side wall down pipe 40 coolant outlet pipe 41 side wall connecting pipe 42 ash hopper down steam

Claims (10)

An arrangement in a soda boiler, in which the fireplace (1) of the soda boiler is provided with a screen tube system (7) and the soda boiler comprises a second drawer (9), in which the second drawer (9) is arranged at least one superheater (4 '), and which second feature (9) is arranged to be cooled by a coolant coming from the screen tube system (7), the coolant coming from the screen tube system (7) is arranged to be directed to at least one side wall (37a, 37b) of the second feature (9), characterized in that the arrangement comprises an ash funnel (14) for the second feature, which ash comprises a front wall cooling pipe (15) and / or a rear wall cooling pipe (16), and said cooling pipe (15, 16) being coupled to receive the cooling medium from the screen tube system (7). 2. Arrangement according to claim 1, characterized in that the second funnel ash funnel (14) comprises an ashtray distribution chamber, which is arranged in the lower part of the ash funnel (14) and connected with a connecting tube (17) to the screen tube system (7). the cooling medium and distributing the cooling medium in said cooling pipe on the front wall (15) and / or cooling pipe on the rear wall (16). Arrangement according to claim 1 or 2, characterized in that the cooling tube (15, 16) of the ash funnel (8) forms a gas-tight front and / or rear wall for the ash funnel (8), and that higher up they are arranged as grid tube systems (18, 19). ) to pass through flue gases. 4. Arrangement according to claim 3, characterized in that the cooling pipes (15, 16) form a gas-tight roof (27) for the second draft (9), and that they are connected via a collection chamber (28, 29) to a cylinder (12). Arrangement according to one of the preceding claims, characterized in that at least one side wall (37a, 37b) of the second drawbar (9) is coupled with an outlet tube (39) to a cylinder (12) for receiving cooling water. Arrangement according to one of the preceding claims, characterized in that at least one side wall (37a, 37b) of the second draw (9) is coupled to steam circulation to cool the side walls. Arrangement according to one of the preceding claims, characterized in that the screen tube system (7) comprises pipe elements (26), which have heating surface pipes (21) arranged on each other, each of which a pipe element (26) is connected with a separate connecting pipe (17). to the second pull (9). A method in a soda boiler, the soda boiler comprising a second draw (9), a screen tube system (7) arranged in a fireplace (1), and at least one superheater (4 ') arranged in the second draw (9), in which method the second draw (9) is cooled with a cooling medium conducted from the screen tube system (7) by passing it to at least one side wall (37a, 37b) of the second draw (9), characterized in that the second draw (9) comprises the second the funnel ash funnel (14), and to the front wall and / or rear wall (15, 16) of the second draw ash funnel (14), cooling medium is led from the screen tube system (7). 9. A method according to claim 8, characterized in that cooling water is led from the cylinder (12) to at least one side wall (37a, 37b) of the second draw (9). Method according to one of Claims 8-9, characterized in that the side walls (37a, 37b) of the second drawbar (9) are coupled to steam circulation.