SE533545C2 - A boiler fitted with a cooled screen wall in the flue - Google Patents

Description

20 25 30 533 545 áL In this way you can absorb the heat in the boiler's flue in an improved way, and also reach a higher practically usable overheating temperature.

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

Another purpose is to use the screen walls to build up separate spaces in the boiler's 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, the fate of which can be driven only by self-circulation, or where pumps can be present to facilitate and facilitate the fate. The circulation system comprises water pipes or steam pipes arranged to be able to circulate boiler water through the pipes in a cycle where water flows from the steam in the outer downcomer to the fireplace and convection parts and where 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 intermediate superheaters to heat-absorbing partition walls according to the invention.

The boiler comprises a thin-walled screen wall in the flue gas passage arranged protruding from the walls of the flue passage and intended to direct the flue gases in the flue passage past these screen walls without passing through these screen walls. The screen wall is cooled and comprises a number of outer tube tubes integrated in the screen wall 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 one of the boiler water pipes and a closed lower end. The inner tube has an upper open end connected to a boiler water supply and a lower open end at the closed lower end of the outer tube. In some embodiments, the upper open end of the inner tube is located at the upper end of the outer tube and they are connected to the same water line or fl desert for boiler water.

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

In a towed embodiment, the axial length of the outer pipe tubes constitutes at least 70% of the protruding length of the cutting wall from the walls of the flue.

Suitably, the adjacent outer tubular tube wall is also connected to heat-conducting dry pipe connectors over at least 70% of the axial length of the outer tubular tubes.

These connecting piece can suitably consist of a plate or plate iron which is preferably welded to the outer pipe tubes. Alternatively, other anchoring can take place without welding being 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 partition wall.

In cases where the screen walls are to function as cooking surfaces, the liquid circulating through the pipes for cooling the outer tube tubes is used as heat-absorbing media, which liquid is led from a steam either directly or via other cooking surfaces or consists of newly added liquid which replaces that driven by the steam. In cases where the screen walls are to act as superheaters for steam, the steam circulating through the pipes for cooling the outer tube tubes is used as heat-absorbing media, which steam is led from a steam either directly or via other superheaters.

In cases where you want access to the flue gas passage in the flue gas passage in the current position of the screen wall, an internally arranged concentric lead-through pipe is suitably arranged in the inner pipe, which leads through the entire inner pipe and protrudes into the other closed end of the outer pipe. Through this lead-through pipe one can connect to a source for adding additive to flue gas via the screen wall, or connect to a control unit for connection to a thermocouple arranged at the other closed end of the outer pipe and which thermocouple is exposed to the flue gases.

According to another embodiment, a flue gas duct formed by the walls of the boiler may comprise a separating partition wall which separates two parts of the flue gas duct from each other. The partition wall can then be at least partially built up of a cooled screen wall according to the invention, i.e. a cooled screen wall which comprises a number of integrated outer tube tubes with an inner tube placed inside 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 wherein the inner tube has an upper open end at the upper end of the outer tube and a lower open end at the closed lower end of the outer tube and wherein the cooled device extends at least partially in the vertical direction downwards from the point where the outer pipe is connected to the water pipe or steam pipe.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 seematically 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; Figure 3a shows a cooled screen 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 the fate of cooling water through a pipe tube used in the screen wall; Figure 5 shows a cooled screen wall in a third embodiment of the invention; Figure 6 shows a cooled screen wall in a fourth embodiment of the invention; Figure 7 shows a cooled screen 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 screen wall in a seventh embodiment of the invention curved in a cylindrical shape; Figure 10 shows a cooled partition wall in an eighth embodiment of the invention with a curved cylindrical shape.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1, a boiler 1 is shown which includes a fireplace 6 where combustion takes place. The boiler 1 can, as shown in the figure, be a recovery boiler where black liquor BL is injected into the bottom of the fireplace while the combustion hatch is supplied at different levels. The air is normally added in a recovery boiler with primary air PMR at the bottom, and then with secondary lu fi SMR a little higher up, but still below the addition point for black liquor, and finally with tertiary lu fi in one or more levels, TAIRJ and TAIRQ, above the black liquor additive. Critical for the incineration of the recovery boiler in the fireplace is that the upward flow of flue gases does not go too fast towards the outlet, so the different air additions can take place crosswise to affect the residence time in the different zones and with increasing air content (towards and above stoichiometric ratio) during passage in the flue.

However, the boiler can be any other boiler where a production of hot water and / or steam takes place, for example FB boilers (fluidizing bed), power boilers, cogeneration 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 be able to circulate boiler water through the pipes 3, 4 in a circuit where operation of steam boiler 1 in a heated liquid HL goes from the different heat-absorbing surfaces 12a-12d of the fireplace 6 and up to a steam 5 where steam is separated from the circuit and water CL flows again in the direction of the fireplace 6 and its heat-absorbing surfaces for passage thereof again. Steam ST can then be led from the steam to other heat-absorbing surfaces to obtain superheated steam.

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

In addition to the boiler water circulation circuit, a circulation of steam ST (steam) from the steam dome 5 is also included, which is led to heat-absorbing surfaces, here 12a, 12b and l2e, in which the steam is heated to superheated steam SST (superheated steam). This superheated steam is often led to the steam turbine for the production of electrical energy or to other use of the steam. Figure 1 shows a separate burner superheater with its own burner EB with superheating surfaces in the form of screen walls 12a for steam. 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 down and out of this space via passage over the inner edges of the screen walls and are mixed with flue gases from the boiler's main combustion. Figure 1 also shows a number of cooled screen walls l2b which form deflection walls for the flue gas in the flue gas duct. The även clock also shows that screen walls l2e and 12d can be arranged as heat-absorbing partitions in a turning shaft 7 for the flue gases, which there divide the flue gas fl fate into parallel lanes. The figure shows a superheater 12e for steam hanging from the roof of the turning shaft and then cooking surfaces 12d projecting from the walls of the turning shaft. All these partition walls 12a, 12b, 12e and 12d are suitably formed by cooled screen walls 12 according to the invention and here have an increased service life due to their ability to withstand heat.

A cooled screen wall 12 before walling in refractory material will now be explained with reference to Figures 2a and 2b. The cooled screen 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 an 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 steam line 3 incoming steam 3 for steam ST and a lower open end 18 at the closed lower end 16 of the outer tube tubes. In the embodiment of 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 screen wall 12 may extend either vertically or horizontally from the point where the outer tube 13 is connected to an incoming steam line 3. The axial length of the outer tube tubes 13 suitably constitutes at least 70% of the extension length of the partition wall from the walls of the flue. In order to form a cohesive screen wall, adjacent outer tube tubes 13 in the screen wall are interconnected with heat conductive connectors 40 over at least 70% of the axial length of the outer tube tubes. These can be welded to the outer tubes or otherwise anchored to these, which are also shown in Figure 2a. These connecting rods 40 suitably consist of a plate or plate iron which is preferably welded to the outer pipe tubes. In this way a simple thin-walled screen wall is obtained with optimal cooling on the most exposed portions of the screen wall, i.e. at the outer end of the screen wall, corresponding to the lower end in figure 2. Figures 3a and 3b show the same screen wall 12 but where the outer tube tubes 13 are walled in a refractory material 41 which forms the outer surface of the screen wall. The application takes place in the applications where the partition wall is exposed to highly corrosive environments at high temperature.

The function of the outer tube tubes of the cooled cutting wall 12 in a suitable embodiment where these are 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 conduit 3 which flows through boiler water, and where self-circulation is used in each outer tube 13. When the cooled tube 13 extends downwardly into a hot flue gas zone, water located in the gap between the outer tube 13 and the inner tube 14 will have a lower density steam-water mixture than the water present. inside the inner pipe 14. The meadow-water mixture therefore rises upwards in the gap between the outer pipe tube 13 and the inner pipe 14. The water which is inside the inner pipe 14 has a higher density and will instead sink downwards. Some of the boiler water passing in the line 3 will then be sucked down into the inner pipe 14 and then return upwards and then absorb heat energy from the area around the cooled device 12. It will be appreciated that the boiler water in the water line 3 flows from left to right in the figure that appears from the arrows. Normal water velocity in water line 3 is in the range 0.3 to 1.5 rn / s.

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

Another embodiment of the screen wall is shown in Figure 5, where the incoming steam line 3 for steam ST is located coaxially in a collection chamber for outgoing line 3 for superheated steam SST. In this way one can get a compact construction of the connections to the inner pipes 14 and the outer pipe tubes 13. Another embodiment of the partition wall 12 is shown in figure 6 where the screen wall is built with a connection corresponding to shown in Figure 4, and which is preferably used if boiler water with natural circulation is used as cooling medium for the pipe tubes 13. Another embodiment of the screen wall 12 is shown in Figure 7, and which corresponds to that shown in Figures 3a and 3b. The difference here is that adjacent outer tube tubes 13 in the screen wall are connected to a plurality of thermally conductive connectors 40a in the form of shorter struts or clamps. These struts can be welded to the outer tube tubes or otherwise anchored to them. The mummification with refractory material 41 results in a simple thin-walled cutting wall with protection against hot gas corrosion and with optimal cooling on the most exposed parts of 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 where at least some of the pipe tubes are provided with a through pipe 21 which is passed through the outer wall of the water pipe 3 and through some of the inner pipes 14 of the cooled cutting wall 12. In the second pipe from the right in the figure connects the through pipe 21 with its lower end to the outer pipe tube 13 of the cooled cutting wall 12. The through pipe 21 in this case constitutes an element which can be used to introduce additives into the steam boiler from a source Ch or to suck out flue gases for sampling.

Without the cooled screen wall 12, the hot flue gases would act unhindered on this element. The cooled screen wall 12 can now cool the continuous pipe and help increase its service life. In the first tube from the right in the figure, contact lines from a control unit CU to a thermocouple 20 are passed 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 screen 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 screen wall corresponding to Figures 2a and 2b, and Figure 10 corresponds to Figures 3a and 3b.

It should be understood that the embodiments shown in the figures can be used in boilers of different types and in principle 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 flow into lanes and where the screen wall requires cooling. The thin-walled screen walls can also be bent into shapes other than a strictly flat-shaped structure or circular structure, and can, for example, be bent into an L-shaped structure on the screen wall.

Claims (9)

A boiler (1) with a fireplace (6) and a circulation system for heat-absorbing media arranged in the flue from the boiler, which circulation system (2) comprises lines (3, 4) arranged that in operation of the boiler (1) be able to circulate heat-absorbing media through the conduits (3, 4) in a circuit and which parma (1) comprises thin-walled screen walls in the flue which screen walls are arranged projecting from the flue walls for controlling the flue gases through the flue past these screen walls without passing through these screen walls is characterized in that the screen wall forms a deflection wall (12a, 12b) for the flue gas in the flue gas duct so that the flue gases are forced over the inner edges of the screen walls and comprises a plurality of outer tube tubes (13) integrated in the screen wall. the outer tube tubes (13) are walled in a refractory material (41) which forms the outer surface of the screen wall, each outer tube tube (13) at 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) placed in the outer tube (13) and the inner tube (14) have a first open end (17) connected to a second conduit (3) for heat-absorbing media and a second open end (18) at the closed second end (16) of the outer tube (13), and where circulation of heat-absorbing media takes place between the first and second pipe for cooling the pipe tube arranged inside the screen wall. A boiler (1) according to claim 1, k a 'n n e t e c k n a d in that the axial length of the outer pipe tubes (13) constitutes at least 70% of the projection length of the screen wall from the walls of the flue. A parma (1) according to claim 2, characterized in that adjacent outer tube tubes (13) in the screen wall are interconnected with thermally conductive connectors (40) over at least 70% of the axial length of the outer tube tubes. A boiler (1) according to claim 3, characterized in that the connecting piece (40) consists of a plate or flat 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 pipes (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. 10 533 545 “i A boiler (1) according to any one of the preceding claims, characterized in that the inner tube (14) comprises an internally arranged concentric lead-through tube (21), which leads through the entire inner tube and protrudes into the outer tube (13). other closed end. A boiler (1) according to claim 7, characterized in that the concentric bushing (21) is connected to a source (Ch) for adding additives to the flue gases via the screen wall. A boiler (1) according to claim 7, characterized in that the concentric feed-through tube (21) is connected to a control unit (CU) for connection to a tin element (20) arranged at the second closed end of the outer tube (13) and which thermocouple is exposed to the flue gases.