SE0950276A1 - A boiler fitted with a cooled screen wall in the flue - Google Patents

Description

10 15 20 25 30 In this way, you can absorb the heat in the boiler's flue in an improved way, and even reach one higher practically usable overheating temperature.

Another object is to obtain a partition wall which can be easily installed as an upgrade of a boiler, where the cutting wall can be installed in the flue to divert the flue gases to the desired one degree so that the combustion is optimal.

Another purpose is to use the cutting walls to build up separate spaces in the boiler flue where you can fire with a less corrosive fuel.

DESCRIPTION OF THE INVENTION The invention relates to a boiler with a circulation system for boiler water or steam, whose flow can be operated solely by self-circulation, or where pumps can be located to facilitate and facilitate fl fate. The circulation system includes water pipes or steam pipes arranged to be able to circulate boiler water through the pipes in one during operation of the steam boiler cycles where water flows from the steam in the outer downcomers to the fireplace and convection parts and there water and steam go from the fireplace and convection parts up to a steam where steam is separated from the cycle. The steam can then be led from the steam directly or via an intermediate superheater for heat-absorbing partitions according to the invention.

The boiler comprises a thin-walled cutting wall in the flue gas passage arranged projecting from the walls of the flue and intended to direct the flue gases in the flue past these screen walls without to pass through these partitions. The partition wall is cooled and comprises a plurality of i the screen wall integrated outer tube tubes arranged in the plane of the screen wall and an inner tube placed in the outer tube. The outer tube has an upper end with an open connection to it one of the boiler water pipes and a closed lower end. The inner tube has an upper open end connected to a water pipe for boiler water and a lower open end at the outside the closed lower end of the tube. In some embodiments, the upper open end of the inner tube is located at the upper end of the outer pipe and they are connected to the same water line or flow for boiler water.

The tube tubes in the screen wall can optionally extend in the vertical or horizontal direction downwards from the point where the outer pipe is connected to a water pipe.

In a preferred embodiment, the axial length of the outer tube tubes constitutes at least 70% of the protrusion length of the screen wall from the walls of the flue.

Suitably, nearby outer tube tubes in the partition wall are also connected to heat conductive connectors over at least 70% of the axial length of the outer tubes.

These connecting piece can suitably consist of a plate or plate iron, which is preferably 0906SE_Beskrivn.docx.doc 10 15 20 25 30 welded to the outer pipe tubes. Alternatively, other anchoring can be done without welding performed on the often pressure-rated pipe tubes.

To further protect the outer tube tubes, these can be walled in a refractory material that forms the outer surface of the cutting wall.

In those cases, the partition walls shall act as cooking surfaces used as heat-absorbing media the liquid circulating through the conduits for cooling the outer tubes, which liquid is led from a vapor either directly or via other cooking surfaces or consists of newly added liquid which replaces that which is driven by the steam.

In cases where the screen walls are to act as superheaters for steam was used as heat-absorbing media the steam circulating through the pipes for cooling the external the tube tubes, which steam is led from a steam either directly or via other superheaters.

In cases where you want access to the flue gas duct in the current position for the screen wall the flue gas passage is suitably arranged in the inner pipe an internally arranged concentrically lead-through pipe, which leads through the entire inner pipe and opens into the other of the outer pipe closed end. Through this bushing you can connect to a source for the addition of additives to the flue gases via the screen wall, or connect to a control unit for connection to a terrnoelement arranged at the other closed end of the outer tube and which terrnoelement is exposed to flue gases.

According to another embodiment, a flue gas duct formed by the walls of the boiler may comprise one separating partition that separates two parts of the flue gas duct from each other. The partition can then be at least partially built up of a cooled partition wall according to the invention, that is say a cooled core wall comprising a number of integrated outer tube tubes with an inner tube placed in the outer tube and which outer tube at an upper end has an open connection to one of the water pipes for boiler water and a closed lower end, the inner pipe having one upper open end at the upper end of the outer tube and a lower open end at the outer tube closed lower end and wherein the cooled device extends at least partially in vertical downward direction from the point where the outer pipe is connected to the water main or the steam line.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 schematically shows a cross-section of a boiler, here a recovery boiler; Figure 2a shows a cooled screen wall in a first embodiment of the invention; Figure 2b shows the screen wall in figure 2a seen in a view from below; 0906SE_Beskrivn.docx.doc 10 15 20 25 30 Figure 3a shows a cooled partition wall in a second embodiment of the invention; Figure 3b shows the cutting wall in figure 3a seen in a view from below; Figure 4 shows fl the fate of cooling water through a pipe tube used in the cutting wall; Figure 5 shows a cooled partition wall in a third embodiment of the invention; Figure 6 shows a cooled partition wall in a fourth embodiment of the invention; Figure 7 shows a cooled partition wall in a fifth embodiment of the invention; Figure 8 shows a cooled partition wall in a sixth embodiment of the invention; Figure 9 shows a cooled partition wall in a seventh embodiment of the invention curved in one cylindrical forrn; Figure 10 shows a cooled partition wall in an eighth embodiment of the invention with curved cylindrical forrn.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1, a boiler 1 is shown which includes a fireplace 6 where the combustion happens. Boiler 1 can, as shown in fi guren, be a recovery boiler where black liquor BL is injected into the bottom on the fireplace while the combustion flue is supplied in different levels. The air addition takes place normally in a recovery boiler with primary air P AIR at the bottom, and then with secondary air S AIR slightly higher up, but still below the point of addition of black liquor, and finally with tertiary air in one or fl your levels, TA1R_1 and T AIM, above the black liquor addition. Critical to the incineration of the recovery boiler in the fireplace is that upwards fl the fate of flue gases do not go out too quickly towards the outlet, so the various air additions can take place crosswise to influence the residence time in the different zones and with increasing air share (towards and over stoichiometric ratio) during the passage in the flue.

However, the boiler can be any other boiler where a production of hot water and / or steam occurs, for example FB (Fluidizing Bed) boilers, power boilers, power-heating boilers or ordinary steam boilers, which are either fired with fuels or waste.

Boiler 1 has a circulation system for boiler water, including any pumps.

The circulation system comprises water pipes 3, 4 which are arranged to, during operation of the boiler 1 can circulate boiler water through the pipes 3, 4 in a cycle where water and steam in a heated liquid HL goes from the fireplace 6 different heat-absorbing surfaces l2a-l2d and up to a steam 5 where steam is separated from the cycle and water CL flows back in direction 0906SE_Beskrivn.docx.doc 10 15 20 25 30 35 towards the fireplace 6 and its heat-absorbing surfaces for passage thereof again. Steam ST can then passed from the steam to other heat-absorbing surfaces to obtain superheated steam.

In Figure 1, the reference numeral indicates 3 water pipes where water and steam HL rise in the direction against the steam 5 while the reference numeral 4 denotes water pipes where water CL flows down from the steam room 5 in the direction of the area of the fireplace 6. The descending ones the water pipes 4 may suitably be arranged separately from the fireplace 6, for example on outside the boiler 1 so that water flowing from the steam is not supplied with heat the way down. Once down in the area of the fireplace 6, the water can then be used to absorb heat energy and transfer the heat energy to the steam. Boiler water circulation in The conduction usually takes place through a strong self-circulation which is driven by the strong heat which generated in the fireplace 6. Meadow mixed water with low density rises upwards in the pipes while water with higher density from the steam 5 flows downwards. If the pipeline network is extensive and has a higher pressure drop, pumps can also be installed to facilitate circulation if not self-circulation is sufficient.

In addition to the boiler circulation circuit, a steam ST circulation is also included (steam) from the vapor 5, which is led to heat-absorbing surfaces, here 12a, 12b and l2c, in which steam is heated to superheated steam SST (Superheated steam). This is often led superheated steam for steam turbine for the production of electricity or for other uses of the steam. Figure 1 shows a separate burner superheater with its own burner EB superheating surfaces in the form of steam partitions 12a. These partition walls 12a protrude from the walls of the flue and enclose a separate fireplace for the burner EB. The flue gases are forced here down and out of this space via passage over the inner edges of the partition walls and mixed with flue gases from the boiler's main combustion. Figure 1 also shows one tal ertal cooled partition walls 12b which form deflection walls for the flue gas in the flue gas duct. IN the figure also shows that partition walls l2c and 12d can be arranged as heat absorption partitions in a turning shaft 7 for the flue gases, which there divide the flue gas fl fate in parallel lanes. The visas clock shows a superheater 12c for steam hanging from the roof in the turning shaft and then cooking surfaces l2d projecting from the walls of the turning shaft. All these partitions 12a, 12b, 12c and 12d are suitably formed of cooled partition walls 12 according to the invention and here get one increased service life due to its ability to withstand heat.

A cooled screen wall 12 before immersion in refractory material will now be explained with reference to Figure 2a and 2b. The cooled partition wall 12 is shown in figure 2a connected to a line 3 for flowing steam ST. The cooled cutting wall 12 comprises a number of outer tube tubes 13 and one inner tube 14 placed in each of the outer tube tubes 13. The outer tube tube 13 has in an upper end 15 an open connection to the outgoing steam line 3 for superheated steam SST and a closed lower end 16. The inner tubes 14 have an upper open end 17 which is connected to a 0906SE_Beskrivn.docx.doc 10 15 20 25 30 35 incoming steam line 3 for steam ST and a lower open end 18 at the outer tube tubes closed lower end 16. In the embodiments according to Figure 2a, the lower end 18 of the inner tube 14 is located at the closed lower end 16 of the outer tube 13. The cooled cutting wall 12 can extend either vertically or horizontally from the point where the outer tubes 13 are connected to an incoming steam line 3. The axial length of the outer pipe tubes 13 suitably constitutes at least 70% of the protruding length of the cutting wall from the walls of the flue. In order to a cohesive partition wall to be formed is adjacent outer tube tubes 13 in the partition wall interconnected with heat-conducting connectors 40 over at least 70% of the outer ones axial length of the tube tubes. These can be welded to the outer tubes or otherwise anchored to these which are also shown in Figure 2a. These connectors 40 are suitably made of a plate or flat iron which is preferably welded to the outer tube tubes. In this way one is obtained simple thin-walled partition wall with optimal cooling on the most exposed parts the screen wall, i.e. at the outer end of the screen wall, corresponding to the lower end of Figure 2.

Figures 3a and 3b show the same cutting wall 12 but where the outer tube tubes 13 are walled in a refractory material 41 which forms the outer surface of the cutting wall. The walling takes place in the applications there the partition wall is exposed to highly corrosive environments at high temperatures.

The function of the outer tube tubes of the cooled partition wall 12 in a suitable embodiment where these cooled with boiler water is shown in Figure 4. Here the outer tube tubes 13 and the inner tube 14 are connected to the same line 3 which is flowed through by boiler water, and where one utilizes self-circulation in each outer tubular tube 13. When the cooled tubular tube 13 extends downwards into a hot flue gases come water that is in the gap between the outer tube 13 and the inner tube 14 to obtain a vapor-water mixture of lower density than the water which is located inside the inner tube 14. The meadow-water mixture therefore rises upwards in the gap between the outer tube 13 and the inner tube 14. The water contained within the inner tube the tube 14 has a higher density and will instead sink downwards. Part of the boiler water as passes in the line 3 will then be sucked down into the inner tube 14 and then return upwards and then absorb thermal energy from the area around the cooled device 12. It it is understood that the boiler water in the water pipe 3 flows from left to right in the figure as appears from the pilama. Normal water velocity in water line 3 is in the range 0.3 to 1.5 m / s.

The water velocity established in descending pipe 14 is 0.5 to 2.5 rn / s and in the outer gap between tubes 13 and 14 is 0.2 to 1.0 rn / s.

Another embodiment of the partition wall is shown in figure 5, where incoming steam line 3 leads steam ST is placed coaxially in a collection chamber for outgoing line 3 for overheated steam SST. In this way, a compact construction of the connections to the inner pipes can be obtained 14 and the outer tube tubes 13. 0906SE_Beskrivn.docx.doc 10 15 20 25 30 Another embodiment of the screen wall 12 is shown in figure 6 where the screen wall was built with a connection corresponding to that shown in Figure 4, which is preferably reused Boiler water with natural circulation was used as cooling medium for the pipe tubes 13. Yet another embodiment of the partition wall 12 is shown in Figure 7, and corresponding to that shown in FIG. Figures 3a and 3b. The difference here is that adjacent outer tube tubes 13 in the cutting wall are connected to a plurality of thermally conductive connectors 40a in the form of shorter struts or staples. These struts can be welded to the outer tube tubes or otherwise anchored to these. Through the mummification with refractory material 41, a simple thin-walled cutting wall is obtained with protection against hot gas corrosion and with optimal cooling on the most exposed parts the screen wall, i.e. at the outer end of the screen wall, corresponding to the lower end of Figure 7.

Figure 8 shows an embodiment in which at least some of the pipe tubes are provided with one continuous pipe 21 which is passed through the outer wall of the water pipe 3 and through some of the inner tubes 14 of the cooled cutting wall 12 in the second tube from the right in the connects the through pipe 21 with its lower end to the outside of the cooled cutting wall 12 tube tube 13. The through tube 21 in this case constitutes an element that can be used to insert additives into the boiler from a source Ch or to extract flue gases for sampling.

Without the cooled partition wall 12, the hot flue gases would act unhindered against this element. The cooled cutting wall 12 can now cool the continuous pipe and help to increase it its service life. In the first pipe tube from the right in the figure, overhead contact lines from one control unit CU to a thermocouple 20 through the through pipe 21. The thermocouple is then kept cooled by means of the cooled device 12.

Figures 9-10 show other alternatives according to the invention where the thin-walled partition wall 12 is curved into a cylindrical shape and can be placed, for example, in outlets on cyclones in the flue. Figure 9 shows a circular partition wall corresponding to fi gur 2a and 2b, and fi gur 10 corresponds to Figures 3a and 3b.

It is to be understood that the embodiments shown in the figures may be used in boilers of different sizes types and basically everywhere where you want to install a screen wall for diverting the flue gases in the flue or where you want to divide the flue gas fl fate in lanes and where the screen wall requires cooling. The thin-walled partitions can also be bent in other forms than a strict one platform structure or circular structure, and can for example be bent into an L-shaped structure on the screen wall. 0906SE_Beskrivn.docx.doc

Claims (9)

A patent (1) with a fireplace (6) and a circulation system for heat-absorbing media arranged in the flue of the steam boiler, which circulation system (2) comprises lines (3, 4) arranged that during operation of the boiler (1 ) be able to circulate heat-absorbing media through the conduits (3, 4) in a circuit and which boiler (1) comprises thin-walled screen walls in the flue which screen walls are arranged protruding from the flue walls for controlling the flue gases through the flue past these screen walls without passing through them screen walls characterized in that the screen wall comprises a plurality of outer tube tubes (13) integrated in the screen wall arranged in the plane of the screen wall and that the outer tube tubes (13) are walled in a refractory material (41) forming the outer surface of the screen wall, each outer tube tube (13 ) in a first end (15) has an open connection to a first conduit (3) for heat-absorbing media and a closed second end (16), and where an inner tube (14) located in the outer tube (13) and the inner tube (14) has a first open end (17) connected to a second conduit (3) for heat absorbing media and a second open end (18) at the outer tube (13) closed second end (16), and where circulation of friend-receiving media takes place between the first and second conduits for cooling the pipe tube arranged inside the cutting wall. A boiler (1) according to claim 1, characterized in that the axial length of the outer pipe tubes (13) constitutes at least 70% of the protruding length of the cutting wall from the walls of the flue. . A boiler (1) according to claim 2, characterized in that adjacent outer pipe tubes (13) in the screen wall are connected to heat-conducting connectors (40) over at least 70% of the axial length of the outer pipe tubes. A boiler (1) according to claim 3, characterized in that the connecting piece (40) consists of a plates or plate iron which is preferably welded to the outer pipe tubes. . A boiler (1) according to any one of the preceding claims, characterized in that the heat-absorbing medium circulated through the conduits (3, 4) for cooling the outer tube tubes (13) consists of liquid, and which is subjected to boiling in the tube. A boiler (1) according to any one of the preceding claims, characterized in that the heat-absorbing medium circulated through the conduits (3, 4) for cooling the outer tube tubes (13) consists of steam conducted in conduits from a steam unit (5), which in the tube is exposed to overheating. 0906SE_Krav.docx 10 A boiler (1) according to any one of the preceding claims, characterized in that the inner tube (14) comprises an internally arranged concentric regeneration tube (21), which leads through the entire inner tube and terminates in the outer tube (13). other closed end. A boiler (1) according to claim 7, characterized in that the concentric feedthrough tube (21) is connected to a source (Ch) for adding additives to the flue gases via the cutting wall. A boiler (1) according to claim 7, characterized in that the concentric regeneration tube (21) is connected to a control unit (CU) for connection to a thermocouple element (20) arranged at the second closed end of the outer tube (13) and which thermocouple element is exposed to the flue gases. 0906SE_Krav.docx