JP6712872B2 - Furnace bottom evaporation pipe, boiler having the same, furnace bottom protection method and furnace bottom repair method - Google Patents

Description

The present invention relates to a bottom evaporation tube, a boiler having the same, a bottom protection method, and a bottom repair method.

The boiler has a furnace that has a hollow shape and is installed in the vertical direction, and a plurality of combustion burners are arranged on the furnace wall along the circumferential direction. The wall surface of the furnace is formed by an evaporation pipe through which cooling steam and feed water pass, and fins that close the space between the evaporation pipes, so that the wall surface is not overheated. Of the wall surfaces of the furnace, the bottom of the furnace wall, which is the bottom of the furnace wall, is also composed of a furnace bottom evaporation pipe through which cooling steam and feed water pass, and fins that close the space between the evaporation pipes so that the wall surface does not overheat. ..

Here, in a coal-fired boiler or the like, since pulverized coal as a fuel is burned in a furnace, coal ash and the like in the combustion gas aggregate, so-called clinker (lump of ash) is generated, and adheres to the side wall of the furnace. It solidifies and grows. A clinker, which has grown to become large on the furnace wall, may fall on the bottom of the boiler. When the clinker falls and collides with the furnace bottom evaporation pipe, the furnace bottom evaporation pipe may be damaged and may need to be repaired. On the other hand, Patent Document 1 describes a structure in which a reinforcing portion is provided on the outer surface of the inner wall of the furnace wall water pipe (furnace bottom evaporation pipe). It is described that the reinforcing portion has a fin shape or a thick portion that becomes a protrusion shape. Patent Document 2 describes a structure in which a fin for crushing a clinker is arranged above a cooling pipe (furnace bottom evaporation pipe).

Japanese Utility Model Publication No. 05-008201 Japanese Utility Model Publication No. 59-009162

In the structures described in Patent Document 1 and Patent Document 2, the strength against the clinker falling from the upper side in the vertical direction is insufficient, and the water pipes in the furnace wall may be damaged. Specifically, in the structure described in Patent Document 1, the thickness of the uppermost surface in the vertical direction, which is estimated to be likely to collide with the clinker, is the same as the thickness of the cylinder. Therefore, there is a possibility that the strength against the clinker collision cannot be secured, and the shape of the upper convolution surface does not have a further convex portion, so that the effect of crushing the clinker and reducing the collision force cannot be obtained so much. Since the structure described in Patent Document 2 has a shape in which fins for crushing the clinker are provided only in part, if the clinker falls to a position where the fins are not provided, the cooling pipe may be damaged. ..

The present invention is to solve the above-mentioned problems, and in particular, even if a clinker falls from vertically above, it is possible to suppress damage to the evaporation pipe of the furnace bottom, a bottom evaporation tube having the same, and a bottom protection. It is intended to provide a method and a hearth bottom repair method.

In order to achieve the above object, the furnace bottom evaporation pipe is a plurality of furnace bottom evaporation pipes that are connected to each other via fins to close at least a part of the furnace bottom of the boiler, and are cylindrical heat transfer tubes. Part, and a coating portion provided on the surface of the heat transfer tube portion on the furnace inner side of the boiler, of the coating portion, of the coating portion provided vertically above the heat transfer tube portion. The outer diameter is at least smaller than the outer diameter of the heat transfer tube portion.

The furnace bottom evaporation pipe is provided with a coating portion, and in the coating portion, the outer peripheral diameter of the coating portion provided vertically above the heat transfer tube portion is at least smaller than the outer peripheral diameter of the heat transfer tube portion. By doing so, the clinker that has dropped toward the furnace bottom can be easily crushed by the covering portion. Further, by providing the coating portion in the area where the falling clinker may come into contact, the wall thickness of the furnace bottom evaporation pipe at the position where the falling clinker may come into contact can be increased. As a result, it is possible to reduce the collision force of the clinker that falls by crushing the clinker, and increase the strength by increasing the wall thickness. From the above, damage to the furnace bottom can be suppressed even if the clinker falls.

Here, in a cross section orthogonal to the longitudinal axis of the heat transfer tube section, with the center of the heat transfer tube section as a fulcrum, an outer peripheral surface of the covering section and an end surface where the outer peripheral surface of the heat transfer tube section intersects, and a horizontal plane is formed. The angle is preferably 50° or less. By arranging the covering portion in the above range, it is possible to more surely cover the position where the clinker may come into contact with the covering portion. As a result, the covering portion can be more surely arranged at the position where the clinker falls, the clinker can be crushed by the covering portion, and the strength can be increased.

Further, in a cross section orthogonal to the longitudinal axis of the heat transfer tube portion, with the center of the heat transfer tube portion as a fulcrum, the uppermost position in the vertical direction of the covering portion and the upper end in the vertical direction of the heat transfer tube portion are formed. The angle is preferably 10° or less. To make it easier to crush the falling clinker by arranging the uppermost position in the vertical direction of the covering part, that is, arranging the protruding tip at a position of 10° or less with respect to the vertical upper end of the heat transfer tube. You can

Further, it is preferable that the outer surface of the coating portion has an arc shape in a cross section orthogonal to the longitudinal axis of the heat transfer tube portion. By forming the covering portion into an arc shape, manufacturing can be simplified.

In addition, it is preferable that at least a part of the outer surface of the covering portion is formed by a straight line in a cross section orthogonal to the longitudinal axis of the heat transfer tube portion, and the covering portion has a vertex at which an intersection of the straight line and a straight line is a corner portion. With the shape having the apex, the destructive force that is the force for crushing the clinker can be made higher than that in the case where the cross section has a curved line, the clinker can be easily crushed, and damage to the furnace bottom evaporation pipe 70b can be suppressed.

In addition, it is preferable that the covering section has a plurality of vertices in a cross section orthogonal to a longitudinal axis of the heat transfer tube section. By providing a plurality of vertices, the destructive force, which is a force for crushing the clinker, can be made higher than that in the case where there is one apex, the clinker can be easily crushed, and damage to the furnace bottom evaporation pipe 70b can be suppressed.

In addition, it is preferable that a recess be formed between the apexes of the coating section in a cross section orthogonal to a longitudinal axis of the heat transfer tube section. By forming the uneven shape, the apex can be formed into a more acute shape, the destructive force that is the force for crushing the clinker can be increased, the clinker can be easily crushed, and damage to the furnace bottom evaporation pipe 70b can be prevented. Can be suppressed.

Further, in the cross section orthogonal to the longitudinal axis of the heat transfer tube section, the covering section has a diameter r, a diameter R of the heat transfer tube, and an angle θ1 between the horizontal and the end is 0, It is preferable that 0.3≦r/R≦0.9 and 20°≦θ≦50 are satisfied. Since the destructive force of the clinker can be improved, the crusher can be easily crushed, the wall thickness can be increased to improve the strength, and the position where the clinker may collide with the covering portion 102 can be wide in a wide range. Can be covered.

In order to achieve the above object, the furnace bottom evaporation pipe is a plurality of furnace bottom evaporation pipes that are connected to each other via fins to close at least a part of the furnace bottom of the boiler, and are cylindrical heat transfer tubes. Part, including a thick coating portion provided in the furnace of the boiler of the heat transfer tube portion, the outer diameter of the one direction side of the coating portion, the outer diameter of the heat transfer tube portion is larger than the outer diameter. In a cross section that is small and is orthogonal to the axis of the heat transfer tube, where r is the diameter, R is the diameter of the heat transfer tube, and θ1 is the angle between the horizontal and the end, 0.3≦r/R≦ It is characterized by satisfying 0.9 and 20°≦θ≦50.

In the furnace bottom evaporation pipe, the coating portion having the above-described shape is provided in a portion of the heat transfer tube portion exposed in the furnace of the boiler, so that the coating portion is provided in a region vertically above the heat transfer tube portion in the furnace bottom. be able to. Accordingly, the clinker that has dropped toward the furnace bottom can be easily crushed by the covering portion. Further, by providing the coating portion in the area where the falling clinker may come into contact, the wall thickness of the furnace bottom evaporation pipe at the position where the falling clinker may come into contact can be increased. As a result, it is possible to reduce the collision force of the clinker that falls by crushing the clinker, and increase the strength by increasing the wall thickness. From the above, damage to the furnace bottom can be suppressed even if the clinker falls. Further, by setting the covering portion in the above range, the destructive force of the clinker can be improved, so that the clinker can be easily crushed, the wall thickness can be increased to improve the strength, and the clinker can collide. The covering portion 102 can cover a wide range of positions having a certain property.

In order to achieve the above object, a boiler has a plurality of furnace bottom evaporation pipes according to any of the above, and a burner that is inserted into a furnace and injects fuel, the furnace bottom evaporation pipes. Is arranged vertically below the burner.

By arranging the furnace bottom evaporation pipe having the coating portion vertically below the burner, it is possible to prevent the coating portion from being disposed in a region where the burner is disposed and the temperature becomes high. Since the burner is arranged and the furnace bottom evaporation pipe is not arranged in the area where the clinker is unlikely to drop, the furnace bottom evaporation pipe can be arranged at a necessary position.

Further, a cylindrical first evaporation pipe connected to one end of the furnace bottom evaporation pipe and a cylindrical second evaporation pipe connected to the other end of the furnace bottom evaporation pipe are further provided. Is preferred. As a result, the furnace bottom evaporation pipe can be arranged at a required position, and the conventional cylindrical evaporation pipe can be arranged at an unnecessary position. By using the conventional cylindrical evaporation tube, the unnecessary position is different from the bottom evaporation tube whose thickness varies depending on the position, and since the cylindrical evaporation tube can be used, there is no restriction on the orientation at the time of installation. It is possible to use an evaporation tube having a simpler structure.

Further, it is preferable that the plurality of furnace bottom evaporation pipes are adjacent to each other in the horizontal direction. As a result, manufacturing can be simplified, and a structure in which the coating portion is arranged on the upper side in the vertical direction of the heat transfer tube can be facilitated.

In order to achieve the above object, there is provided a furnace bottom protection method for protecting at least a part of a bottom surface of a furnace of a boiler, wherein a heat transfer tube portion and a coating disposed on a surface inside the furnace of the boiler of the heat transfer tube portion. A furnace bottom evaporation pipe having a portion is arranged at a position of the coating portion where the outer peripheral diameter of the coating portion provided vertically above the heat transfer tube portion is at least smaller than the outer circumferential diameter of the heat transfer tube portion. However, it is characterized in that the covering portion suppresses damage due to a clinker that has dropped from the furnace wall.

By crushing the clinker that has fallen in the coating portion of the furnace bottom evaporation pipe with the coating portion, the collision force of the clinker that falls by crushing the clinker can be reduced, and the wall thickness can be reduced by providing the coating portion. The strength can be increased by increasing the thickness. From the above, damage to the furnace bottom can be suppressed even if the clinker falls.

In order to achieve the above object, a method for repairing a bottom of a furnace of a boiler is a method for repairing a bottom of a furnace, a step of removing a bottom evaporation pipe in a region to be repaired, a cylindrical heat transfer tube portion, and the heat transfer tube. Part of the coating portion provided on the surface of the boiler inside the furnace, the outer diameter of the coating portion, which is provided vertically above the heat transfer tube portion, of the coating portion is at least the above. Arranging a furnace bottom evaporation pipe smaller than the outer diameter of the heat transfer pipe portion.

The furnace bottom evaporation pipe is provided with a covering portion, and the portion of the covering portion whose upper side in the vertical direction is exposed in the furnace of the boiler and which is arranged in a portion inclined with respect to the vertical direction is in the upper side in the vertical direction. The clinker that has dropped toward the furnace bottom can be easily crushed by the coating portion by directing the clinker toward the furnace. Further, by providing the coating portion in the area where the falling clinker may come into contact, the wall thickness of the furnace bottom evaporation pipe at the position where the falling clinker may come into contact can be increased. As a result, it is possible to reduce the collision force of the clinker that falls by crushing the clinker, and increase the strength by increasing the wall thickness. From the above, damage to the furnace bottom can be suppressed even if the clinker falls.

According to the present invention, by providing the coating portion projecting upward in the vertical direction and covering the surface of the heat transfer tube as the wall thickness of the heat transfer tube, it is easy to crush the clinker that has dropped and the wall thickness is increased. As a result, the damage to the heat transfer tube on the furnace bottom can be suppressed even if the clinker falls.

FIG. 1 is a schematic configuration diagram showing a coal-fired boiler of the present embodiment. FIG. 2 is a perspective view schematically showing the furnace bottom evaporation pipe. FIG. 3 is a sectional view of the furnace bottom evaporation pipe. FIG. 4 is a diagram showing an example of the influence of the size of the coating of the furnace bottom evaporation pipe. FIG. 5 is a diagram showing an example of the influence of the coating size of the furnace bottom evaporation pipe. FIG. 6 is a cross-sectional view of another example of the furnace bottom evaporation pipe. FIG. 7 is a cross-sectional view of another example of the furnace bottom evaporation pipe. FIG. 8 is a cross-sectional view of another example of the furnace bottom evaporation pipe. FIG. 9 is a sectional view of another example of the furnace bottom evaporation pipe. FIG. 10 is a flowchart showing an example of a method of installing the furnace bottom evaporation pipe.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to this embodiment, and when there are a plurality of embodiments, the present invention also includes those configured by combining the embodiments.

FIG. 1 is a schematic configuration diagram showing a coal-fired boiler of the present embodiment.

The boiler of the present embodiment uses pulverized coal obtained by pulverizing coal as pulverized fuel (solid fuel) for burning solid fuel, burns the pulverized coal with a combustion burner, and supplies heat generated by this combustion to water supply or It is a coal-fired boiler that can exchange heat with steam to generate superheated steam.

In the present embodiment, as shown in FIG. 1, a coal-fired boiler (boiler) 10 has a furnace 11, a combustion device 12, and a flue 13. The furnace 11 has a hollow rectangular tube shape and is installed along the vertical direction. The wall surface of the furnace 11 is composed of an evaporation pipe (heat transfer pipe) and fins that connect the evaporation pipe, and suppresses an increase in temperature of the furnace wall by exchanging heat with water supply or steam. Specifically, on the side wall surface of the furnace 11, a plurality of evaporation pipes are arranged, for example, in the vertical direction, and arranged side by side in the horizontal direction. The fin closes the gap between the evaporation tubes. The furnace 11 has an inclined surface on the bottom of the furnace, and the inclined surface serves as the bottom surface. This point will be described later.

The combustion device 12 is provided on the vertically lower side of the furnace wall forming the furnace 11. In the present embodiment, the combustion device 12 has a plurality of combustion burners (for example, 21, 22, 23, 24, 25) mounted on the furnace wall. For example, a plurality of combustion burners (burners) 21, 22, 23, 24, 25 are arranged at equal intervals along the circumferential direction of the furnace 11. However, the shape of the furnace, the number of combustion burners in one stage, and the number of stages are not limited to this embodiment.

The combustion burners 21, 22, 23, 24, 25 are connected to pulverizers (pulverized coal machines/mills) 31, 32, 33, 34, 35 via pulverized coal supply pipes 26, 27, 28, 29, 30. It is connected. When coal is transferred by a transfer system (not shown) and introduced into the crushers 31, 32, 33, 34, 35, it is crushed into a predetermined fine powder size here, and pulverized coal supply pipe 26 is supplied by the transfer air. , 27, 28, 29, 30 can supply pulverized coal (pulverized coal) to the combustion burners 21, 22, 23, 24, 25.

Further, in the furnace 11, a wind box 36 is provided at a mounting position of each combustion burner 21, 22, 23, 24, 25, and one end portion of an air duct 37 is connected to the wind box 36. A blower 38 is attached to the other end of the duct 37.

In addition, a flue 13 is connected vertically above the furnace 11, and a plurality of heat exchangers (41, 42, 43, 44, 45, 46, 47) for producing steam in the flue 13 are connected. Are arranged. Therefore, the combustion burner injects a mixture of fuel and air into the furnace 11 to form a flame, and combustion gas is generated and flows into the flue 13. Then, the combustion gas heats feed water and steam flowing through the furnace wall and the plurality of heat exchangers (41 to 47) to generate superheated steam, and supplies the generated superheated steam to rotationally drive a steam turbine (not shown). , A power generator (not shown) connected to the rotary shaft of the steam turbine can be rotationally driven to generate power. An exhaust gas passage 48 is connected to the flue 13, and an air heater 49 for exchanging heat between the air sent from the blower 38 to the air duct 37 and the exhaust gas sent through the exhaust gas passage 48, and purification of combustion gas. A denitration device 50, a soot and dust treatment device 51, an induced air blower 52, and the like for performing the above are provided, and a chimney 53 is provided at the downstream end.

The structure of the bottom surface of the furnace 11 of this embodiment will be described below with reference to FIGS. 2 to 10 in addition to FIG. 1. FIG. 2 is a perspective view schematically showing the furnace bottom evaporation pipe. FIG. 3 is a sectional view of the furnace bottom evaporation pipe. 4 and 5 are diagrams showing an example of the influence of the size of the coating portion of the furnace bottom evaporation pipe. 6 to 9 are sectional views of other examples of the furnace bottom evaporation pipe. FIG. 10 is a flowchart showing an example of a method of installing the furnace bottom evaporation pipe.

As shown in FIG. 1, the furnace 11 has a vertical surface 60, an inclined surface 62 provided below the vertical surface 60, a horizontal plane 64 arranged vertically below the inclined surface 62, and a curved surface 66. , 68 and. The vertical surface 60 and the inclined surface 62 are connected by a curved surface 66, and the inclined surface 62 and the horizontal surface 64 are connected by a curved surface 68. In the furnace 11, the vertical surface 60, the inclined surface 62, and the horizontal surface 64 are each linear, and the curved surfaces 66 and 68 are curved in a cross section along the vertical direction. The furnace 11 is inclined in such a direction that the inner width of the furnace 11 (the left-right direction in the drawing) becomes narrower as the inclined surface 62 goes downward in the vertical direction. The horizontal portion 64 is connected to an end portion of the inclined surface 62 on the lower side in the vertical direction, and extends in a direction in which the width of the inside of the furnace 11 widens. In the furnace 11, the inclined surface 62 serves as the bottom of the furnace 11, adheres to the inner wall surface of the furnace 11, etc., and becomes a part that easily collides when there is a clinker that has fallen from the adhered position. Further, the inclined surface 62 makes the inclination angle formed by the inclined surface 62 and the horizontal plane equal to or more than the reclined angle (45°) of the clinker, and prevents the fallen clinker from accumulating on the inclined surface 62.

As shown in FIGS. 1 and 2, the furnace 11 includes a vertical surface 60, a curved surface 66, an inclined surface 62, a curved surface 68, a horizontal surface 64, and an evaporation pipe, and the evaporation pipes arranged in each part are connected to each other. There is. In the furnace 11, a furnace bottom evaporation pipe 70 is arranged in at least a part of the entire area where the heat transfer pipes of the vertical surface 60, the curved surface 66, the inclined surface 62, the curved surface 68, and the horizontal surface 64 are used. There is. In the furnace 11, the first evaporation pipe 72 is arranged in a region of the vertical surface 60 where the furnace bottom evaporation pipe 70 is not arranged, and the second evaporation pipe 74 is arranged in a region of the horizontal surface 64 where the furnace bottom evaporation pipe 70 is not arranged. It is arranged. One end of the furnace bottom evaporation pipe 70 is connected to the first evaporation pipe 72, and the other end thereof is connected to the second evaporation pipe 74. Further, in the present embodiment, in the furnace 11, the longitudinal direction of the first evaporation pipe 72 extends in the vertical direction, and the furnace bottom evaporation pipe 70, the first evaporation pipe 72, and the second evaporation pipe 74 are arranged side by side in the horizontal direction. The furnace bottom evaporation pipe 70 is installed on the vertical surface 60, the curved surface 66, and the inclined surface 62, and the fins 76 close the space between the adjacent evaporation pipes. The first evaporation pipe 72 and the second evaporation pipe 74 have a conventional cylindrical shape with a constant wall thickness, and steam or feed water flows inside. As shown in FIG. 2, the furnace bottom evaporation pipe 70 on the inclined surface 62 is arranged by providing a thick portion (a covering portion 102 described later) on the vertical upper side in the cross section of the furnace bottom evaporation pipe 70.

Next, the furnace bottom evaporation pipe 70 will be described. As shown in FIG. 3, the furnace bottom evaporation pipe 70 has a circular inner diameter in the cross section of the furnace bottom evaporation pipe 70, and is provided with a thick portion on one side (Z direction, upper side of the drawing). It has a heat pipe portion 100, a covering portion 102, and a reinforcing portion 104, and has a line-symmetrical shape with a line passing through the center in the Z direction as a symmetry axis. The heat transfer tube portion 100 has a cylindrical shape with a constant thickness, and steam or feed water flows inside. As an example, in the furnace bottom evaporation pipe 70, the Z direction of the portion arranged on the inclined surface 62 serving as the furnace bottom may be the upper side in the vertical direction. In this case, the inclined surface 62 is a portion whose upper surface in the vertical direction is exposed in the furnace of the boiler and is arranged in a portion inclined with respect to the vertical direction. In the furnace bottom evaporation pipe 70, the Z direction of the portion arranged on the vertical surface 60 is horizontal.

The coating portion 102 is provided so as to protrude toward the outer surface side of the heat transfer tube portion 100 in the Z direction and have a large wall thickness. The covering portion 102 is arranged in a region including an end portion of the heat transfer tube portion 100 on the side farthest from each other in the Z direction. The covering portion 102 is a curved surface having an arcuate outer surface in a cross section orthogonal to the axial direction of the heat transfer tube portion 100. The covering portion 102 is the thickest portion at a position where it overlaps with the end portion of the heat transfer tube portion 100 on the apex side in the Z direction, and is a position protruding to the farthest side in the Z direction. On the outer surface of the furnace bottom evaporation tube 70, the radius r of the Z direction apex of the coating portion 102 is smaller than the heat transfer tube radius R of the heat transfer tube portion 100. The coating portion 102 is a surface of the heat transfer tube portion 100 on the inner side of the furnace of the boiler 10, and the outer peripheral diameter of the coating portion 102 provided vertically above the heat transfer tube portion 100 is at least the outer circumference of the heat transfer tube portion 100. The shape is smaller than the diameter.

The reinforcing portion 104 is provided by increasing the wall thickness so that no concave groove portion is formed between the outer surface of the heat transfer tube portion 100 and the covering portion 102 in the region including the end portion of the covering portion 102. The reinforcing portion 104 is smoothly and continuously connected to the covering portion 102, the heat transfer tube portion 100, and the outer surface thereof. In the furnace bottom evaporation pipe 70, the surface provided with the covering portion 102, that is, the surface exposed to the inside of the furnace 11 is a curved surface having no refraction point by the reinforcing portion 104.

The boiler 10 having the furnace bottom evaporation pipe 70 has a clinker (lump of ash) that is aggregated and adhered and grown on the inner wall surface of the furnace 11 when the clinker is peeled off from the inner wall surface due to a thermal expansion difference caused by a temperature difference or the like. It drops inside 11 vertically downward, reaches the bottom of the furnace where the bottom evaporation pipe 70 is arranged, and collides with it. The furnace bottom evaporation pipe 70 installed on the furnace bottom such as the inclined surface 62 is arranged with the thickest covering portion 102 provided on the vertically upper side. The furnace bottom evaporation pipe 70 has a vertically upper surface exposed inside the furnace of the boiler 10, and a covering portion 102 of a portion arranged in a portion inclined with respect to the vertical direction is provided on the vertically upper side. There is. Specifically, the side of the coating portion 102 that protrudes to the outer surface side of the furnace bottom evaporation pipe 70 and that has the largest wall thickness and that is most distant in the Z direction is arranged vertically upward. Therefore, when the clinker falls, the surface provided with the covering portion 102 collides with the clinker. The radius of the Z-direction apex portion of the covering portion 102 is a curved surface having a smaller diameter than the heat transfer tube portion 100, and therefore has a shape more convex than the heat transfer tube portion 100, and the most protruding portion is the upper end in the vertical direction. It is provided in the section. Since the force for crushing the clinker is roughly proportional to the falling mass of the clinker and inversely proportional to the collision area with the clinker, the smaller the radius of the Z direction apex of the covering section 102 is, the smaller the clinker is. Make it easier to crush. If the clinker is crushed, a part of the energy held when the clinker is dropped is converted into crushed energy, so the collision force due to the clinker falling is reduced, and the damage to the furnace bottom evaporation pipe 70 due to the collision is reduced. Significantly reduced.

In the present embodiment, in the furnace bottom evaporation pipe 70 installed on the inclined surface 62, the portion where the covering portion 102 is provided first collides with the clinker, so that the covering portion 102 can easily crush the clinker. This can reduce the impact force of the clinker. Further, in the furnace bottom evaporation pipe 70, the covering portion 102 covers the base material 100, so that the portion that collides with the clinker can be made thicker than the heat transfer pipe portion 100. As a result, the strength of the portion that collides with the clinker can be increased, and damage to the furnace bottom evaporation pipe 70 can be suppressed.

As described above, in the furnace bottom evaporation pipe 70, the coating portion 102 having a diameter smaller than that of the heat transfer pipe portion 100 is provided in the region including the end portion of the heat transfer pipe portion 100 in the Z direction so that the Z direction is vertically upward. By installing the clinker on the bottom surface (inclined surface 62) of the furnace 11, the clinker that has fallen can be easily crushed by the covering portion 102. Further, by providing the covering portion 102 in the area where the falling clinker may collide, the wall thickness of the furnace bottom evaporation pipe 70 at the position where the falling clinker may collide is increased to improve the strength. be able to. As a result, the furnace bottom evaporation pipe 70 can reduce the collision force of the falling clinker by crushing the clinker, and can also increase the strength by increasing the wall thickness. From the above, even if the clinker falls, damage to the furnace bottom evaporation pipe 70 at the furnace bottom can be suppressed.

Further, the boiler 10 can have a structure in which the coating portion 102 is continuous in the direction in which the plurality of furnace bottom evaporation pipes are arranged by horizontally adjoining the plurality of furnace bottom evaporation pipes 70, and the clinker is the furnace. When it is larger than the arrangement interval of the bottom evaporation tubes 70, it is possible to make the plurality of covering portions 102 collide with the clinker. Thereby, the clinker can be more easily crushed by the plurality of coating portions 102, the collision force of the clinker with respect to one coating portion 102 can be reduced, and damage to the furnace bottom evaporation pipe 70 can be suppressed more reliably. it can. Further, the furnace bottom evaporation pipe 70 is formed by forming the covering portion 102 by thickening only the Z direction side, and the thickness of the joint portion with the fin 76 is the same as that of the conventional evaporation pipe. Further, the vertical upper side of the covering portion 102 becomes the space of the furnace, and the addition of the covering portion 102 does not interfere with other structures. That is, installing the furnace bottom evaporation pipe 70 in the furnace 11 of the boiler 10 is no different from the conventional evaporation pipe. Therefore, even if the function of the coating portion 102 is added to the furnace bottom evaporation pipe 70, the manufacturing of the furnace bottom of the furnace 11 can be simplified as before, and the coating portion 102 of the heat transfer tube portion 100 can be manufactured. The structure can be easily arranged vertically above.

Here, as shown in FIGS. 4 and 5, in order to effectively suppress damage to the clinker of the furnace bottom evaporation pipe 70, the shape and size of the covering portion 102 are optimized with respect to the size of the heat transfer pipe portion 100. Preferably. The destructive force F by the furnace bottom evaporation pipe 70 when the clinker falls into the furnace bottom evaporation pipe 70 is set as follows using the Hertz's equation. By using Hertz's contact surface pressure formula, we assume the destructive force of the clinker that allows for instantaneous deformation of the contact surface due to collision of the clinker.

The general formula for the Hertz contact surface pressure is:
P=0.388 [fE ² ((1/R) ² ] ^1/3 ...Equation (1)
Here, when P: contact surface pressure, f: load, E: Young's modulus, R: radius of contact portion r=R is used as a reference surface pressure and is normalized to P=1.0,
F=((1/r) ² ) ^1/3 /((1/R) ² ) ^1/3 ...Equation (2)
Here, F: destructive force of clinker (normalized to F=1.0 when r=R)
r is the radius of the Z direction apex of the coating, and R is the radius of the heat transfer tube of the heat transfer tube.
Further, the thickness t at the thickest position of the covering portion 102 (thickness at the position 120 in the present embodiment) is assumed to be, for example, about 4 mm to 5 mm.

As shown in FIG. 4, consider a condition in which the clinker has a destructive force F of more than 1.0 and a destructive force F of 2.0 to 2.5 can be obtained by providing the covering portion 102. Then, in the furnace bottom evaporation tube 70, it is preferable that the relationship between the coating portion radius r of the coating portion 102 and the heat transfer tube radius R of the heat transfer tube portion 100 is 0.3≦r/R≦0.9. When r/R is less than 0.3, the destructive force of the clinker is improved, which is preferable, but since the protection ratio of the heat transfer tube portion 100 described later decreases to about 60% or less, r/R is 0.3. Is the lower limit. Further, when r/R is larger than 0.9, the destructive force of the clinker is about the same as when the covering portion 102 is not provided (F=1.0), so r/R is set to 0.9 as the upper limit. By setting the radius of the covering portion in the above range, the destructive force of the clinker can be improved, so that the clinker can be easily crushed and the wall thickness can be increased to improve the strength.

The coating portion 102 has an angle (end portion angle) between the end surface where the outer peripheral surface of the coating portion 102 and the outer peripheral surface of the heat transfer tube portion 100 intersect with the horizontal plane with the center of the heat transfer tube portion 100 as a fulcrum (end portion angle). Further, the angle θ1 formed is calculated from the configuration shape.
θ1=sin ⁻¹ [(R−r)/(R−r+t)]...Equation (3)

As shown in FIG. 4, assuming that the thickness t is, for example, about 4 mm to 5 mm, when the breaking force F of the clinker exceeds 1.0 to obtain 2.0 to 2.5, 0.3≦r The end angle θ1 corresponding to /R≦0.9 is more preferably 20° or more and 50° or less.

Since the clinker falls from a height of several meters from the bottom of the furnace, the clinker often falls almost vertically. When the furnace bottom evaporation tube 70 is viewed from above in the vertical direction (Z direction), the rate of covering the surface of the heat transfer tube section 100 is evaluated as the protection rate C.
C=[Rcos θ1]/[R]=cos θ1 (4)

The end angle θ1 corresponding to 0.3≦r/R≦0.9 shown in FIG. 4 is more preferably 20° or more and 50° or less in the present embodiment, and accordingly, FIG. As shown in, the protection ratio C is 60%≦C≦95%. That is, by setting the angle θ1 forming the covering portion 102 in the above range, the covering portion 102 can cover a wide range of positions where the clinker may collide.

Here, the installation of the furnace bottom evaporation pipe 70 of the present embodiment at the furnace bottom of the furnace 11 is performed by covering the cross section of the heat transfer tube portion 100 in the Z direction in the circumferential direction with the center of the heat transfer tube portion 100 as the fulcrum. The uppermost position in the vertical direction of the portion 102, that is, the protruding tip 120 and the upper end 130 of the heat transfer tube portion 100 in the vertical direction are aligned. That is, the vertex angle θ2 at the uppermost position in the vertical direction of the covering portion 102 with respect to the upper end in the vertical direction when the heat transfer tube part 100 is installed on the furnace bottom is set to 0°. As a result, the protruding portion of the covering portion 102 can be arranged on the upper side in the vertical direction, and the clinker can be easily crushed.
Here, the vertex angle θ2 is most preferably 0°, but the vertex angle θ2 corresponds to the fact that the angle θ1 formed is replaced by θ1±θ2 in the above formula (4). In order to be within 10%, it is preferable that θ2 is approximately ±10° or less, that is, −10°≦θ2≦10°. By setting the apex angle θ2 to ±10° or less, the covering portion 102 can be more surely arranged at the position where the clinker falls, the covering portion 102 facilitates crushing of the clinker, and the thick thickness of the covering portion 102 is increased. It can be protected by covering with.

In the furnace bottom evaporation pipe 70, the thickness of the heat transfer pipe part 100 is T, and the thickness of the cover part 102 at the thickest position (thickness at the position 120 in this embodiment) is t in the circumferential direction of the heat transfer pipe part 100. In this case, t/T≦1.5 is preferable, and 0.5≦t/T≦1.5 is more preferable. By setting t/T≦1.5, the coating portion 102 in the Z direction becomes too thick, which lowers the heat transfer property of the furnace bottom evaporation pipe 70, lowers the cooling performance, and reduces the surface of the coating portion 102. It is possible to prevent the temperature from increasing and exceeding the design allowable temperature. On the other hand, by setting 0.5≦t/T, even if the radius r of the covering portion is r/R=0.3 and the covering portion radius r is small, the effect of protecting by covering with the covering portion 102 with the protection ratio C being 50% or more. Can be demonstrated. Further, the thickness t is preferably 3.0 mm or more and 8.0 mm or less, and is preferably 4.0 mm to 5.0 mm as an example. When the thickness is in the above range, the durability is increased, the heat transfer property of the furnace bottom evaporation pipe 70 is lowered, the cooling performance is lowered, and the temperature of the surface of the coating portion 102 is too high, so that the material is It is possible to prevent the strength from decreasing. More specifically, by setting the above range, the outer surface temperature of the furnace bottom evaporation pipe 70 can be made equal to or lower than the design allowable temperature of the material, the creep life of the pipe can satisfy the use requirement, and the furnace bottom The outlet temperature can satisfy the usage requirement by suppressing an increase in the temperature of steam or feed water flowing through the evaporation pipe 70, and the connection between the furnace bottom evaporation pipe 70 and the first evaporation pipe 72 and the second evaporation pipe 72 can be suppressed. High durability can be maintained.

Further, the furnace bottom evaporation pipe 70 is preferably arranged vertically below the combustion burner 25. By disposing the furnace bottom evaporation pipe 70 having the covering portion 102 vertically below the combustion burner 25, the covering portion 102 is arranged in the region where the combustion burner 25 is arranged and the temperature becomes high, and It is possible to prevent the material strength from decreasing due to the surface temperature becoming too high. Further, since the combustion burner 25 is arranged and the furnace bottom evaporation pipe 70 is not arranged in a region where the clinker is unlikely to drop, the furnace bottom evaporation pipe 70 can be arranged at a necessary position.

Further, the boiler 10 has a cylindrical first evaporation pipe 72 connected to one end of the furnace bottom evaporation pipe 70 and a second evaporation pipe 74 connected to the other end of the furnace bottom evaporation pipe 70. By providing, the furnace bottom evaporation pipe 70 can be arranged at a required position, and a conventional cylindrical evaporation pipe having the same wall thickness in the circumferential direction can be arranged at an unnecessary position to reduce the cost. ..

The boiler 10 of the present embodiment has a structure in which the furnace bottom evaporation pipe 70 is arranged from the vertical surface 60 to the curved surface 66, the inclined surface 62, and the curved surface 68, and one end of the furnace bottom evaporation pipe 70 is The first evaporation pipe 72 is connected, and the other end is connected to the second evaporation pipe 74. With this structure, welding work is not performed on the curved surface 66 and the curved surface 68, thereby improving workability and reliability. However, it is not limited to this. The arrangement area of the furnace bottom evaporation pipe 70 may include at least a part of the inclined surface 62. Here, the furnace bottom evaporation pipe 70 is an end portion, that is, the first evaporation pipe 72 or the second evaporation pipe, at a portion other than the curved portions 66 and 68, that is, any of the vertical surface 60, the inclined surface 62, and the horizontal surface 64. It is preferable that the connection part with 74 is arranged. By providing the connecting portion of the evaporation pipe in the linear portion, the welding workability is good, and it is possible to suppress the concentration of heat and stress loads on the connecting portion, thereby increasing the durability of the furnace 11 and making it reliable. It is possible to improve the property. Further, both ends of the furnace bottom evaporation pipe 70, which are connection parts, may be arranged in the inclined surface 62. Further, in the boiler 10, among the evaporation pipes on the bottom of the furnace arranged on the inclined surface 62, a part of the evaporation pipes on the bottom of the furnace is provided with the covering portion 102 of the present embodiment for an area where the clinker easily falls. The furnace bottom vaporizing tube 70 may be used, and the other furnace bottom evaporation tubes may be conventional evaporation tubes that are cylindrical and have the same circumferential wall thickness and are not provided with the coating portion 102.

The furnace bottom evaporation pipe 70 is preferably manufactured by integrally forming the heat transfer pipe portion 100, the covering portion 102, and the reinforcing portion 104. For example, you may manufacture by a die extrusion manufacturing method. Further, in the case of manufacturing by the die extrusion manufacturing method, after manufacturing the straight bottom furnace bottom evaporation pipe, by bending the position corresponding to the curved portion, it is possible to manufacture the furnace bottom evaporation pipe of the present embodiment. .. The method of manufacturing the furnace bottom evaporation pipe 70 is not limited to this, and the covering portion 102 and the reinforcing portion 104 may be separately manufactured and joined onto the heat transfer pipe portion 100. Specifically, the covering portion 102 and the reinforcing portion 104 may be manufactured by overlay welding.

Further, it is preferable that the outer surface of the covering portion 102 is arcuate in a cross section orthogonal to the axial direction of the heat transfer tube portion 100. By forming the covering portion 102 into a smooth arc shape, manufacturing can be simplified.

Next, a modified example of this embodiment will be described. The furnace bottom evaporation pipe 70 a shown in FIG. 6 has a heat transfer pipe portion 100 and a coating portion 102. The furnace bottom evaporation pipe 70 a has the same structure as the furnace bottom evaporation pipe 70 except that the reinforcing portion 104 is not provided. Even if the structure is not provided with the reinforcing portion 104 like the furnace bottom evaporation pipe 70a, a part of the thickened portion of the heat transfer tube portion 100 is thinner than the furnace bottom evaporation pipe 70, It is possible to increase the wall thickness of the area contacting with the clinker at the covering portion 102, and to facilitate the crushing of the clinker at the covering portion 102. Accordingly, the furnace bottom evaporation pipe 70 a can obtain the same effect as that of the furnace bottom evaporation pipe 70. Moreover, since the reinforcing portion 104 is not provided, the cost can be reduced.

The furnace bottom evaporation pipe 70b shown in FIG. 7 has a heat transfer pipe portion 100 and a coating portion 102b. The coating part 102b is provided on the outer surface side of the heat transfer tube part 100, extends two tangents of the heat transfer tube part 100, and has a convex shape in which an intersection is provided on the side of the heat transfer tube part 100 which is separated in the Z direction. The shape is line-symmetrical with the line passing through the center of the direction as the axis of symmetry. That is, the covering portion 102b has a straight cross section and has a shape in which the apex is arranged in the Z direction of the heat transfer tube portion 100. When the covering portion 102b is provided as a straight line, the intersection of the straight portion and the outer surface of the cylinder becomes the end portion of the covering portion 102b, and the angle between this point and the horizontal plane is θ1. Further, the diameter r of the covering portion 102b is an arc connecting the apex and the end. In the furnace bottom evaporation pipe 70b, the breaking line, which is a force for crushing the clinker, is further improved by making the line of the cross section a straight line rather than a curve so that the end on the side separating the coating part 102b in the Z direction becomes a corner. The height can be increased, the clinker can be easily crushed, and damage to the furnace bottom evaporation pipe 70b can be suppressed.

The furnace bottom evaporation pipe 70c shown in FIG. 8 has a heat transfer pipe portion 100 and a coating portion 102c. The coating portion 102c is provided on the outer surface side of the heat transfer tube portion 100, and the outer shape line is formed by four straight lines. The covering portion 102c has a line-symmetrical shape with a line extending through the vertical direction and passing through the center of the heat transfer tube portion 100 in the Z direction as an axis of symmetry. The covering portion 102c has a vertex 140 and two vertices 142. The apex 140 is the end of the covering portion 102c on the most distant side in the vertical direction. The apex 142 is formed between the apex 140 and the end of the covering portion 102c, and has a shape that is convex in a direction away from the heat transfer tube portion 100. When the covering portion 102c is provided as a straight line, the intersection of the straight line portion and the outer surface of the cylinder becomes the end portion of the covering portion 102c, and the angle between this point and the horizontal plane is θ1. Further, the diameter r of the covering portion 102c is an arc connecting the apex 140 and the end portion. The furnace bottom evaporation pipe 70c has a straight line instead of a curved line so that the end on the side separating the covering part 102c in the Z direction is a corner, and by providing a plurality of vertices, the force for crushing the clinker can be obtained. A certain destructive force can be increased, the clinker can be easily crushed, and damage to the furnace bottom evaporation pipe 70c can be suppressed.

The furnace bottom evaporation pipe 70d shown in FIG. 9 includes a heat transfer pipe portion 100 and a coating portion 102d. The covering portion 102d is provided on the outer surface side of the heat transfer tube portion 100, and the outer shape line is formed by a plurality of straight lines. The covering portion 102d has a line-symmetrical shape with a line extending through the Z direction and passing through the center of the heat transfer tube portion 100 in the Z direction as the axis of symmetry. The covering portion 102d has a vertex 150, two vertices 152, and two vertices 154. The apex 150 is the end of the covering portion 102d on the side most separated in the Z direction. The apex 152 is formed between the apex 150 and the end of the covering portion 102d, and has a shape that is convex in the direction away from the heat transfer tube portion 100. Further, a recess 156 is formed between the apex 150 and the apex 152.

The apex 154 is formed between the apex 152 and the end of the covering portion 102d and has a shape that is convex in a direction away from the heat transfer tube portion 100. Further, a recess 158 is formed between the apex 152 and the apex 154. When the covering portion 102d is provided as a straight line, the intersection of the straight line portion and the outer surface of the cylinder becomes the end portion of the covering portion 102d, and the angle between this point and the horizontal plane is θ1. The diameter r of the covering portion 102d is an arc connecting the apex 150 and the end. The vertices 152 and 154 are included in the arc. In the furnace bottom evaporation pipe 70d, the line of the cross section is not a curved line but a straight line, and a plurality of apexes are formed, and concave portions 156 and 158 which are valleys are formed so that the end portion on the upper side in the vertical direction of the covering portion 102d becomes a corner. By doing so, the vertices 152, 154 can be made to have a more acute angle, the destructive force that is the force for crushing the clinker can be increased, the clinker can be easily crushed, and damage to the furnace bottom evaporation pipe 70d can be suppressed. it can.

Next, with reference to FIG. 10, an example of a method of installing the furnace bottom evaporation pipe will be described. FIG. 10 shows a method of replacing a part of the furnace bottom evaporation pipe with the furnace bottom evaporation pipe of this embodiment. The process shown in FIG. 10 can be applied, for example, when replacing a furnace bottom evaporation pipe that has a shape that is not the present embodiment and that needs to be replaced. The process shown in FIG. 10 can be implemented by an operator using a cutting device or a fusing device.

The operator identifies the furnace bottom evaporation pipe to be replaced (step S12). For example, it is specified as a furnace bottom evaporation pipe in which the clinker drops and is damaged, or a furnace bottom evaporation pipe that replaces the furnace bottom evaporation pipe at a position where the clinker may drop frequently. In the present embodiment, the furnace bottom evaporation pipe 70 is such that, in the furnace bottom of the furnace 11, the covering portion 102 is formed by thickening only the vertically upward direction, and the vertically upper side of the furnace bottom evaporation pipe 70 is the space of the furnace. Since there is no obstructing structure, it is possible to easily visually inspect whether or not the furnace bottom evaporation pipe 70 is damaged. Therefore, it is easy to specify the furnace bottom evaporation pipe as the replacement of the furnace bottom evaporation pipe.

After identifying the furnace bottom evaporation pipe, the worker cuts and removes the specified furnace bottom evaporation pipe (step S14). The worker then fixes the furnace bottom evaporation pipe 70 having the coating portion 102 at the position where the furnace bottom evaporation pipe is removed (step S16). Specifically, the furnace bottom evaporation pipe 70 to be replaced is arranged at the removed position and is welded to the evaporation pipe facing the end of the heat transfer pipe portion 100 to connect the pipe lines. Further, fins 76 are arranged between the newly installed furnace bottom evaporation pipe and the adjacent furnace bottom evaporation pipe, and fixed by welding or the like.

As described above, by exchanging the furnace bottom evaporation pipe arranged at the furnace bottom of the boiler 10 with the furnace bottom evaporation pipe 70 having the coating portion 102, the durability of the boiler 10 against falling of the clinker can be increased.

Further, in the process shown in FIG. 10, the repair method has been described as an example of the installation method, but the furnace bottom evaporation pipe 70 having the coating portion 102 of the present embodiment may be installed in the furnace 11 of the newly manufactured boiler.

Further, in the above-described embodiment, the boiler of the present invention is a coal-fired boiler, but the solid fuel may be a boiler that uses biomass, petroleum coke, petroleum residue, or the like. Further, the fuel is not limited to the solid fuel, and can be used for an oil-fired boiler such as heavy oil, and further, gas (byproduct gas) can be used as the fuel. And, it can be applied to mixed combustion of these fuels.

10 coal-fired boiler (boiler)
11 furnace 12 combustion device 13 flue 21, 22, 23, 24, 25 combustion burner 41, 42, 43, 44, 45, 46, 47 heat exchanger 60 vertical surface 62 inclined surface 64 horizontal surface 66, 68 curved surface 70, 70a, 70b, 70c, 70d Furnace bottom evaporation tube 72 First evaporation tube 74 Second evaporation tube 100 Heat transfer tube section 102, 102a, 102b, 102c, 102d Cover section 104 Reinforcement section θ1 End angle θ2 Vertex angle angle
t thickness

Claims (18)

At least a part of the furnace bottom of the boiler, a plurality of furnace bottom evaporation pipes interconnected and closed through fins,
A cylindrical heat transfer tube section,
A coating portion provided on a surface of the heat transfer tube portion inside the furnace of the boiler;
Wherein one of the cover portion, the outside diameter of the covering portion provided in the vertically upward direction with respect to the heat transfer tube portion is rather smaller than the outer peripheral diameter of at least the heat transfer tube portion,
The coating portion, in a cross section orthogonal to the longitudinal axis of the heat transfer tube portion, at least a portion of the outer surface is configured by a straight line, the intersection of the straight line and the straight line has an apex that is a corner,
The furnace bottom evaporation pipe , wherein the coating portion is integrated with the heat transfer pipe portion . In a cross section orthogonal to the longitudinal axis of the heat transfer tube section, an angle formed by a horizontal plane and an end surface where the outer peripheral surface of the coating section and the outer peripheral surface of the heat transfer tube section intersect with each other with the center of the heat transfer tube section as a fulcrum is 50. The furnace bottom evaporation pipe according to claim 1, wherein the evaporation temperature is not more than °. In a cross section orthogonal to the longitudinal axis of the heat transfer tube section, with the center of the heat transfer tube section as a fulcrum, the angle between the uppermost position in the vertical direction of the coating section and the upper end in the vertical direction of the heat transfer tube section is The furnace bottom evaporation pipe according to claim 1, wherein the evaporation angle is 10° or less. The furnace bottom evaporation pipe according to any one of claims 1 to 3, wherein the covering portion has a plurality of the apexes in a cross section orthogonal to a longitudinal axis of the heat transfer pipe portion. The furnace bottom evaporator tube according to claim 4 , wherein the coating portion has a recess formed between the apexes in a cross section orthogonal to a longitudinal axis of the heat transfer tube portion. In the cross section orthogonal to the longitudinal axis of the heat transfer tube section, the covering section has a diameter r, a diameter R of the heat transfer tube section, and an angle θ1 between the horizontal and the end is 0. 3 ≦ r / R ≦ 0.9 and furnace bottom evaporator tube according to any one of claims 1 5, characterized in that satisfy 20 ° ≦ θ ≦ 50. At least a part of the furnace bottom of the boiler, a plurality of furnace bottom evaporation pipes interconnected and closed through fins,
A cylindrical heat transfer tube section,
A thick coating portion provided in the furnace of the boiler of the heat transfer tube portion,
The outer peripheral diameter on one side of the coating portion is smaller than the outer peripheral diameter of the heat transfer tube portion,
In a cross section orthogonal to the axis of the heat transfer tube, when the diameter is r, the diameter of the heat transfer tube is R, and the angle between the horizontal and the end is θ1, 0.3≦r/R≦0 .9 and meet the 20 ° ≦ θ ≦ 50,
The coating portion, in a cross section orthogonal to the longitudinal axis of the heat transfer tube portion, at least a portion of the outer surface is configured by a straight line, the intersection of the straight line and the straight line has an apex that is a corner,
The furnace bottom evaporation pipe , wherein the coating portion is integrated with the heat transfer pipe portion . When the thickness of the thickest portion of the covering portion is t and the thickness of the heat transfer tube portion is T, 0.5≦t/T≦1.5, and the thickness t is 3.0 mm or more and 8.0 mm or less. furnace bottom evaporator tube according to any one of claims 1 to 7, characterized in that it. A furnace bottom evaporation pipe according to any one of claims 1 to 8 ,
A burner that is inserted into the furnace and injects fuel,
The boiler, wherein the furnace bottom evaporation pipe is arranged vertically below the burner. A cylindrical first evaporation pipe connected to one end of the furnace bottom evaporation pipe;
The boiler according to claim 9 , further comprising a cylindrical second evaporation pipe connected to the other end of the furnace bottom evaporation pipe. The boiler according to claim 9 or 10, wherein the plurality of furnace bottom evaporation tubes are horizontally adjacent to each other. The furnace bottom evaporation pipe is arranged vertically below the burner, a part of the vertical surface of the furnace, an inclined surface provided on the lower side of the vertical surface, and a vertical direction lower than the inclined surface. The boiler according to any one of claims 9 to 11, wherein the boiler is disposed on a horizontal plane disposed on the side . A furnace bottom protection method for protecting at least a part of a bottom surface of a furnace of a boiler,
A furnace bottom evaporation pipe having a heat transfer tube section and a coating section arranged on the furnace inner surface of the boiler of the heat transfer tube section is provided in the coating section in a vertically upward direction with respect to the heat transfer tube section. The outer peripheral diameter of the coating portion is arranged at a position smaller than the outer peripheral diameter of at least the heat transfer tube portion, and in the coating portion, damage due to a clinker dropped from the furnace wall is suppressed ,
The coating portion, in a cross section orthogonal to the longitudinal axis of the heat transfer tube portion, at least a portion of the outer surface is configured by a straight line, the intersection of the straight line and the straight line has an apex that is a corner,
The furnace bottom protection method , wherein the coating portion is manufactured integrally with the heat transfer tube portion . When the thickness of the thickest portion of the covering portion is t and the thickness of the heat transfer tube portion is T, 0.5≦t/T≦1.5, and the thickness t is 3.0 mm or more and 8.0 mm or less. furnace bottom protection method according to claim 13, characterized in that. The boiler is
At least a part of the furnace bottom of the boiler, a plurality of furnace bottom evaporation pipes that are interconnected and closed by fins,
A burner that is inserted into the furnace and injects fuel,
A cylindrical first evaporation pipe connected to one end of the furnace bottom evaporation pipe;
A cylindrical second evaporation pipe connected to the other end of the furnace bottom evaporation pipe,
The furnace bottom evaporation pipe is arranged vertically below the burner, a part of the vertical surface of the furnace, an inclined surface provided on the lower side of the vertical surface, and a vertical direction lower than the inclined surface. The bottom protection method according to claim 13 or 14, wherein the bottom surface and the horizontal surface are arranged on the side . A method for repairing the bottom of a furnace of a boiler,
Removing the bottom evaporation tube in the area to be refurbished,
A cylindrical heat transfer tube section, and a coating section provided on the surface of the heat transfer tube section inside the furnace of the boiler, and of the coating section, the coating section is provided vertically above the heat transfer tube section. and the outside diameter of the covering portion, possess placing a small furnace bottom evaporator tube than the outer peripheral diameter of at least the heat transfer tube portion,
The coating portion, in a cross section orthogonal to the longitudinal axis of the heat transfer tube portion, at least a portion of the outer surface is configured by a straight line, the intersection of the straight line and the straight line has an apex that is a corner,
The furnace bottom repair method, wherein the coating portion is manufactured integrally with the heat transfer tube portion. When the thickness of the thickest portion of the covering portion is t and the thickness of the heat transfer tube portion is T, 0.5≦t/T≦1.5, and the thickness t is 3.0 mm or more and 8.0 mm or less. The method for repairing a hearth bottom according to claim 16, wherein: The boiler is
At least a part of the furnace bottom of the boiler, a plurality of furnace bottom evaporation pipes that are interconnected and closed by fins,
A burner that is inserted into the furnace and injects fuel,
A cylindrical first evaporation pipe connected to one end of the furnace bottom evaporation pipe;
A cylindrical second evaporation pipe connected to the other end of the furnace bottom evaporation pipe,
The furnace bottom evaporation pipe is arranged vertically below the burner, a part of the vertical surface of the furnace, an inclined surface provided on the lower side of the vertical surface, and a vertical direction lower than the inclined surface. The method for repairing a bottom of a furnace according to claim 16 or 17, wherein the bottom surface is arranged on the side .

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