JP2015194281A - waste heat recovery boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste heat recovery boiler which effectively prevents deformation and cracks caused by a difference of thermal expansion coefficients even when a hopper disposed at a lower part of a boiler body is formed by an anticorrosive material and a water supply header fixed to an upper part of the hopper is formed by a material different from that of the hopper.SOLUTION: In a waste heat recovery boiler 10, a water supply header 20 is disposed at the lower part side of a boiler body 11 and a hopper 13 is disposed at the lower part side. The waste heat recovery boiler 10 recovers waste heat from a high temperature exhaust gas introduced into the boiler body 11 through a water pipe 21 connected to the water supply header 20 and disposed along an inner surface of the boiler body 11. A hopper casing 13a forming the hopper 13 is formed by an anticorrosive stainless material. Further, the water supply header 20 formed by a material different from that of the hopper casing 13a is movably attached to the hopper casing 13a so as to absorb expansion and contraction caused by a difference of thermal expansion coefficients.

Description

  The present invention relates to a waste heat recovery boiler, and more particularly, to a waste heat recovery boiler provided as an accessory to a smelting furnace used for copper smelting, for example.

In a smelting furnace used for copper smelting, for example, a flash smelting furnace, a waste heat recovery boiler is attached to the flash smelting furnace in order to recover waste heat from waste gas. An example of the waste heat recovery boiler is disclosed in Patent Document 1. In the flash smelting furnace, copper concentrate and oxygen are reacted to produce mat and slag. At that time, waste gas containing sulfur oxides is generated, so the waste gas is introduced into a waste heat recovery boiler for heat recovery and then sent to a sulfuric acid factory. The waste heat recovery boiler has a radiant part into which waste gas is introduced and a convection part arranged continuously to the radiant part. A water pipe is arranged along the inner wall of the radiant part and at the lower part thereof. A hopper for collecting dust contained in the waste gas is provided. A large number of water pipes are arranged in the convection section so that the waste heat is recovered from the waste gas using the water passing through the water pipes as a heat medium. In such a waste heat recovery boiler, as shown in Patent Document 2, the thinning of the water pipe is likely to proceed due to corrosion mainly due to the SO ₂ gas component in the waste gas. In particular, since the corrosion of the casing of the hopper and the casing of the discharge conveyor disposed at the lower part of the boiler main body of the radiating portion progresses quickly, it is necessary to frequently repair the corroded portion.

In order to repair the corroded part, the waste heat recovery boiler has to be cooled once, so that it is forced to stop the operation for a long time. Further, with the hopper casing corrosion free air intrusion proceeds SO ₂ SO ₃ of the gas into the boiler body is promoted, if the internal temperature by a reduction in the gas temperature due to free air reaches the dew point In this case, sulfuric acid corrosion of the water pipe and the hopper casing of the radiant portion is more likely to proceed. Therefore, a composite pipe using austenitic stainless steel having high corrosion resistance as the surface layer may be used as the water pipe.

JP-A-53-82901 Japanese Patent Laid-Open No. 03-62961

  However, the water supply header that is welded and fixed to the lower part of the boiler body and to the upper part of the hopper is usually formed of a carbon steel pipe. Even if a composite pipe is used as the water pipe, the water supply header is a carbon steel pipe. It is usually used as it is.

  In addition, as mentioned above, stainless steel is also used as a corrosion countermeasure for waste heat recovery boiler hoppers used in copper smelting, such as using a composite pipe with a surface layer of austenitic stainless steel with high corrosion resistance as the water pipe. It is desirable to use steel, but welding and fixing the carbon steel used as the feed header material to the stainless steel used as the hopper material is the difference in thermal expansion coefficient between the stainless steel and carbon steel when receiving heat. Implementation has been postponed until now because of concerns about deformation and cracking. This is because in the unlikely event that a crack occurs in the water supply header due to the difference in thermal expansion coefficient, it is forced to suspend operation for a long period of time for repair.

  In the present invention, as described above, the feed header disposed at the lower part of the boiler body is made of carbon steel, and the hopper material located therebelow is made of a stainless steel material having excellent corrosion resistance. It was made as a result of earnest examination to solve the problem that it could not be carried out because of fear of deformation and cracking due to, improved the joint structure between the water header made of carbon steel and the stainless steel hopper, It aims at providing the waste heat recovery boiler which can eliminate the influence of a thermal expansion coefficient.

  Moreover, even if the water pipe disposed on the inner wall of the boiler body is, for example, a composite pipe coated with a stainless steel material on the outside, the tip of the water pipe that becomes a connection portion with a water supply header formed of carbon steel material The present invention provides a waste heat recovery boiler having a joint structure of a water supply header and a hopper that simultaneously solves the corrosion countermeasures of the carbon steel material portion on the tip side of the water pipe. For the purpose.

  In order to solve the above-mentioned problem, the present invention according to claim 1 is characterized in that a water supply header is arranged on the lower side of the boiler body, a hopper is arranged on the lower side thereof, and is connected to the water supply header to be connected to the inner surface of the boiler body. In a waste heat recovery boiler that recovers waste heat from high-temperature waste gas introduced into the boiler body through a water pipe disposed along the hopper, a hopper casing that forms the hopper is formed of a corrosion-resistant stainless steel material. The water supply header formed of a material different from that of the hopper casing is movably attached to the hopper casing so as to absorb a difference in expansion and contraction due to a difference in coefficient of thermal expansion.

  In order to solve the above-mentioned problem, the present invention according to claim 2 is the waste heat recovery boiler according to claim 1, wherein the feed water header is made of carbon steel pipe, and is attached for bolting the feed water header to the hopper casing. The bolt hole provided in the member is made larger than the diameter size of the bolt using the bolt hole to absorb expansion and contraction due to a difference in thermal expansion coefficient.

  In order to solve the above-mentioned problem, the present invention according to claim 3 is the waste heat recovery boiler according to claim 1 or 2, wherein the temperature inside the boiler body is the end side of the water pipe connected to the feed header. The point which faces the inner side of the boiler main body of the water pipe arrange | positioned in the position which may reach an acid dew point is covered with the refractory.

  In order to solve the above-mentioned problem, the present invention according to claim 4 is the waste heat recovery boiler according to claim 3, wherein the water pipe is formed of an inner pipe formed of a carbon steel pipe on the inner side and corrosion resistance on the outermost side. The end of the water pipe connected to the feed header is made of carbon steel to facilitate welding with the feed header, formed by a multi-layer composite pipe with an outer pipe formed of a stainless steel material having The inner pipe formed is exposed, and the portion facing the inner side of the boiler body on the end side of the water pipe where the inner pipe made of carbon steel is exposed is covered with a refractory.

  In order to solve the above-mentioned problem, the present invention according to claim 5 is the waste heat recovery boiler according to claim 4, wherein free air is prevented from entering between the refractory and the hopper casing and the coefficient of thermal expansion is reduced. A friction reducing member for reducing friction between the irregular refractory and the hopper member during expansion and contraction due to the difference is arranged.

  According to the waste heat recovery boiler according to the present invention, the hopper casing forming the hopper is made of a stainless steel material, and a water supply header formed of a different material, for example, a carbon steel material, absorbs expansion and contraction due to a difference in thermal expansion coefficient. As described above, the hopper casing and the water supply header are attached so as to be relatively movable, so that the water supply header and the hopper formed of different materials can be connected without causing deformation or cracking. effective.

  Moreover, according to the waste heat recovery boiler according to the present invention, even when carbon steel is used for the water pipe, even when a composite pipe is used for the water pipe, the carbon steel pipe is used for the portion connected to the feed header, Cover the end of the water pipe made of carbon steel pipe, which is used as a carbon steel feed header, with refractory and cover the water pipe part where there is a risk of acid dew point due to temperature drop in the boiler body. As a result, the corrosion of the water pipe and the water supply header can be suppressed.

  Furthermore, according to the waste heat recovery boiler according to the present invention, at least the hopper can be made of a highly corrosion-resistant stainless steel material, and further, corrosion of the water pipe and the feed water header can be suppressed. There is an effect that long-term shutdown due to corrosion can be eliminated.

It is a side view which shows the outline | summary of the waste-heat recovery boiler connected with the flash smelting furnace. It is AA sectional drawing of the waste heat recovery boiler which concerns on this invention. It is an expanded sectional view of the connection part of a boiler main body and a hopper. It is an expanded sectional view of a water pipe.

  Hereinafter, a preferred embodiment of a waste heat recovery boiler according to the present invention will be described with reference to the drawings. 1 is a side view showing an outline of a waste heat recovery boiler connected to a flash furnace, FIG. 2 is a cross-sectional view taken along line AA of the waste heat recovery boiler according to the present invention, and FIG. 3 is a connection between a boiler body and a hopper. It is an expanded sectional view of a part.

[Configuration of waste heat recovery boiler]
First, the waste heat recovery boiler 10 shown in FIG. 1 is provided so as to be attached to the uptake 3 of the flash smelting furnace 1 that generates mats and slag by reacting concentrate and separates them by specific gravity. And arranged so as to extend to the rear side of the uptake 3 (right side in FIG. 1). The waste heat recovery boiler 10 includes a boiler main body 11, and the boiler main body 11 is configured by a radiant portion 11a into which waste gas is first introduced and a convection portion 11b in which a large number of water pipes (not shown) are arranged to recover waste heat. Has been. In the convection section, partition walls 12 and 12 each having a gap formed on the upper side or the lower side are arranged back and forth, and waste gas is guided vertically through the gap.

[Boiler body]
As shown in FIG. 2, a supply header 20 is disposed on the lower side of both side surfaces of the boiler body 11 on the side of the radiating portion 11 a, and a hopper 13 is disposed on the lower side of the supply header 20. Further, a discharge conveyor 15 for collecting dust that has fallen in the boiler body 11 is disposed on the lower side of the hopper 13. And while the water pipe 21 is arrange | positioned along the inner wall of the boiler main body 11 by the side of the radiation part 11a, the water pipe 21 is attached so that the supply header 20 may be connected.

[Water supply header]
The supply header 20 is a pipe that is connected to the water pipe 21 and distributes water serving as a heat medium, and is arranged on both sides of the lower portion along the longitudinal direction of the boiler body 11. Further, the lower side of the boiler body 11 is formed so as to have a substantially inverted truncated pyramid shape in which the width size is gradually narrowed from the upper side to the lower side, and the supply header 20 is slightly lower than the lower position of the boiler body 11. It is arranged at a position spaced outside. The supply header 20 is formed of a carbon steel pipe.

[Water pipe]
The water pipe 21 is disposed along the inner wall surface of the boiler body 11, and a portion connected to the supply header 20 is formed to bend toward the supply header 20 side. The water pipe 21 communicates with a pipe (not shown) arranged at the upper part of the boiler body 11 and further communicates with a water pipe (not shown) arranged in the convection section 11b, and the high-temperature waste introduced into the boiler body 11 Heat is recovered from the gas.

  The water pipe 21 may be a carbon steel pipe formed entirely of carbon steel, or may be the same material as the outer pipe 21a formed of an austenitic stainless steel material on the outer side and the supply header 20 on the inner side as shown in FIG. A composite pipe provided with an inner pipe 21b formed of carbon steel can also be used. When a composite pipe is used for the water pipe 21, an outer pipe 21a formed of a material having corrosion resistance and an inner pipe 21b formed of carbon steel which is the same material as the supply header 20 are provided. Therefore, the composite pipe is not limited to a composite pipe having a double structure. For example, a composite pipe having a triple or higher structure in which a pipe (not shown) formed of another material is further provided inside the inner pipe 21b. Good.

Here, the pressure of the recovered steam of the waste heat recovery boiler 10 in copper smelting is 4 to 6 MPa, and the saturated steam temperature is 250 to 270 ° C. The exhaust gas introduced from the flash furnace 1 to the waste heat recovery boiler 10 contains 50 to 60 vol% of SO ₂ gas, but 1 to 3% of SO ₂ is SO ₃ in the boiler. The acid dew point temperature may rise to the saturation temperature of circulating water due to the amount of SO ₃ and moisture in the gas. At that time, high-concentration sulfuric acid is condensed on the outside of the water pipe to promote corrosion. In particular, the lower part of the boiler body, that is, the connecting part side between the supply header 20 and the water pipe 21 is likely to condense. When a composite pipe is used as the water pipe 21, the outer pipe 21a is formed of a stainless steel material having corrosion resistance, so that corrosion due to waste gas containing SO ₂ is effectively prevented. Even if a carbon steel pipe is used for the water pipe 21, the upper side away from the supply header 20 is unlikely to be below the acid dew point, so corrosion does not proceed rapidly.

  On the other hand, when a carbon steel pipe is used for the water pipe 21 or when a composite pipe is used, the inner pipe 21b is provided with a carbon steel pipe of the same quality as the supply header 20, so that even if both are joined by welding, thermal expansion occurs. Since there is no difference in rate, there is no worry of deformation or cracking of the connecting part. However, even when the water pipe 21 is a carbon steel pipe or a composite pipe, the lower side portion connected to the supply header 20 by welding is in a state where the carbon steel pipe is exposed, and this exposed portion is inside the boiler body 11. Because it will be exposed to the waste gas. As described above, corrosion tends to proceed. Therefore, as will be described later, the carbon steel pipe portion exposed on the lower side of the boiler body 11, that is, the water pipe 21 arranged at a position where there is a possibility of reaching the acid dew point is covered with a refractory 30 to protect it from corrosion. ing.

[Hopper]
A hopper 13 is disposed below the boiler body 11 and collects dust contained in the waste gas introduced into the boiler body 11. The waste gas contains dust components that are in a molten state at a high temperature, and the dust components in the molten body solidify and fall as dust as the temperature of the waste gas decreases in the boiler body 11. To do. The fallen dust is collected by the discharge conveyor 15 arranged at the lower part of the hopper 13. A plurality of hoppers 13 are arranged along the longitudinal direction. The hopper casing 13a constituting the hopper 13 is made of a stainless steel material having corrosion resistance.

[Connecting structure of boiler body and hopper top]
Next, the connection structure of the upper part of the boiler main body 11 and the hopper 13 is demonstrated. FIG. 3 is an enlarged cross-sectional view of a connecting portion between the boiler body 11 and the hopper 13. The water pipes 21 arranged along the inner wall surface of the boiler body 11 are bent outward toward the water supply header 20 in the vicinity of the connecting portion with the hopper 13 and are arranged on both side surfaces on the lower side of the boiler body 11. Each of the water supply headers 20 is welded. And the plate-shaped attachment fin 20a is attached to the lower part side of the water supply header 20 toward the downward direction, and the attachment fin 40a and the upper surface of the hopper 13 via the attachment member 40 whose side surface shape is substantially L-shaped. Are connected. The mounting fin 20a and the mounting member 40 are fixed by welding, and the mounting member 40 and the upper part of the hopper 13 are fastened and fixed by bolts 41. Note that the mounting fins 20 a, the mounting members 40, and the bolts 41 are formed of a carbon steel material as with the water supply header 20. Here, a bolt hole (not shown) drilled in the upper surface of the mounting member 40 and the hopper 13 for mounting the bolt 41 has a diameter larger than the diameter of the bolt 41. Note that the bolt hole can be formed in a circular shape or an elliptical shape. Thereby, even if there is a difference in expansion and contraction due to a difference in thermal expansion coefficient between the hopper casing 13a of the hopper 13 formed of stainless steel material and the mounting member 40 formed of carbon steel material or the water supply header 20, the water supply header 20 can be Since it is movably attached to 13a, the difference is absorbed and deformation and cracking are effectively prevented.

[Refractories]
On the other hand, the front end side of the water pipe 21 welded to the water supply header 20 is in a state where an inner pipe 21b made of carbon steel, which is the same material as the water supply header 20, is exposed. Thereby, the welding connection between the water supply header 20 and the inner pipe 21b of the water pipe 21 is easily performed and the influence due to the difference in thermal expansion is prevented. However, since the exposed portion of the water pipe 21 is exposed to the waste gas in the boiler body 11 and is easily affected by corrosion, the inner pipe 21b exposed in the boiler body 11 is refractory as shown in FIG. It is covered with the object 30. As the refractory, an irregular refractory, for example, a castable refractory C130 manufactured by Yotai Co., Ltd. can be used, and the inner tube 21b exposed by the irregular refractory is completely covered. Of course, the refractory is not limited to an irregular refractory, and may be arranged so as to cover the inner pipe 21b exposed in the boiler body 11 by molding a regular refractory into a predetermined shape.

  Further, friction for preventing free air from entering between the refractory 30 and the hopper casing 13a of the hopper 13 and reducing friction between the irregular refractory and the hopper member during expansion and contraction due to a difference in thermal expansion coefficient. A mitigating member 35 is arranged. As the friction reducing member 35, a fireproof heat insulating material in which fibers are laminated to form a blanket can be used. For example, an isowool blanket manufactured by Isolite Kogyo Co., Ltd. can be used. Thereby, even when the inner pipe 21b exposed in the boiler body 11 is covered with the refractory 30, the friction reducing member 35 is interposed between the hopper 13 and the refractory 30, so that the difference in thermal expansion coefficient. The refractory 30 is prevented from cracking or peeling off even if expansion and contraction occurs due to. If the friction reducing member 35 to be arranged is too thin, it contracts when an irregular refractory is poured as the refractory 30 so that the frictional force cannot be sufficiently reduced, and if it is too thick, free air enters. Therefore, the thickness is preferably about 10 to 30 mm.

  As described above, the preferred embodiment of the present invention has been described in detail. However, the present invention is not limited to the specific embodiment, and within the scope of the gist of the present invention described in the claims, Needless to say, various modifications and changes are possible. In the above embodiment, the water supply header 20 is a carbon steel pipe, and the hopper casing of the hopper 13 is made of a stainless steel material. However, the present invention is not limited to this, and it is a case where different materials are used. It can also be applied to cases where deformation or cracking is a concern.

DESCRIPTION OF SYMBOLS 1 Flash furnace 3 Uptake 10 Waste heat recovery boiler 11 Boiler main body 11a Radiation part 11b Convection part 12 Partition 13 Hopper 13a Hopper casing 15 Discharge conveyor 20 Water supply header 20a Mounting fin 21 Water pipe 21a Inner pipe 21b Inner pipe 30 Refractory 35 Friction Reduction member 40 Mounting member 41 Bolt

Claims (5)

A water supply header is disposed on the lower side of the boiler body, a hopper is further disposed on the lower side thereof, and is connected to the water supply header and disposed in the boiler body via a water pipe disposed along the inner surface of the boiler body. In the waste heat recovery boiler that recovers waste heat from the introduced high-temperature waste gas,
The hopper casing forming the hopper is formed of a corrosion-resistant stainless steel material, and the hopper casing is formed of a material different from the hopper casing so as to absorb a difference in expansion and contraction due to a difference in coefficient of thermal expansion. A waste heat recovery boiler that is movably attached to a casing. In the waste heat recovery boiler according to claim 1,
The water supply header is made of carbon steel pipe,
The expansion and contraction due to the difference in thermal expansion coefficient is absorbed by making the bolt hole provided in the mounting member for bolting the water supply header to the hopper casing larger than the diameter of the bolt. Waste heat recovery boiler. In the waste heat recovery boiler according to claim 1 or 2,
A portion facing the inner side of the boiler body of the water pipe that is disposed at a position where the temperature inside the boiler body is likely to reach the acid dew point on the end side of the water pipe connected to the water supply header by a refractory A waste heat recovery boiler characterized by being coated. In the waste heat recovery boiler according to claim 3,
The water pipe is formed by a composite pipe having a plurality of layers including an inner pipe formed of a carbon steel pipe on the inner side and an outer pipe formed of a stainless steel material having corrosion resistance on the outermost side. The end side of the connected water pipe is formed by exposing the inner pipe made of carbon steel in order to facilitate welding with the water supply header,
A waste heat recovery boiler, characterized in that a portion facing the inner side of the boiler body, which is the end side of the water pipe exposed from an inner pipe made of carbon steel, is covered with a refractory. In the waste heat recovery boiler according to claim 4,
A friction reducing member is disposed between the refractory and the hopper casing to prevent intrusion of free air and reduce friction between the irregular refractory and the hopper member during expansion / contraction due to a difference in thermal expansion coefficient. A featured waste heat recovery boiler.

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