WO2015001666A1

WO2015001666A1 - Waste-heat boiler

Info

Publication number: WO2015001666A1
Application number: PCT/JP2013/068528
Authority: WO
Inventors: 朝彦白石; 祐太横山; 泉西本; 大橋　俊樹; 優史種村
Original assignee: 川崎重工業株式会社
Priority date: 2013-07-05
Filing date: 2013-07-05
Publication date: 2015-01-08
Also published as: CN204084298U; CN104279541A

Abstract

[Problem] To provide a waste-heat boiler which comprises a vertical water-tube boiler capable of being used in a large-scale production plant which generates a high-temperature, high-pressure process gas. [Solution] A waste-heat boiler (10) is configured as a double structure which uses: a vertically extending casing (20) having a circular transverse cross-section; and a vertically extending heat-resistant wall (30) disposed within the casing (20). Also, the waste-heat boiler (10) is provided with an inlet duct (11) which penetrates through the casing (20), is connected to the heat-resistant wall (30), and supplies a process gas to a space surrounded by the heat-resistant wall (30). Heat-transfer tubes (60) are arranged in the space surrounded by the heat-resistant wall (30).

Description

Waste heat boiler

The present invention relates to a waste heat boiler that recovers heat from process gas in a plant.

A facility (plant) is known in which a raw material is burned in a combustion furnace to generate a process gas, and then a desired product is manufactured from the process gas. Further, in order to effectively use the thermal energy of the process gas, it has been conventionally performed to provide a waste heat boiler for recovering heat from the process gas and using it for power generation or the like on the downstream side of the combustion furnace.

As an example, a sulfuric acid production facility (sulfuric acid plant) that produces sulfuric acid using sulfur as a raw material will be described. Sulfuric acid production facility generally includes a converter for generating a combustion furnace to generate a process gas comprising SO ₂ gas by burning sulfur, which was oxidized SO ₂ gas using a V ₂ O ₅ catalyst SO ₃ gas An absorption tower that reacts SO ₃ gas with H ₂ O to produce H ₂ SO ₄ (sulfuric acid). In such a sulfuric acid production facility, in order to effectively use the thermal energy of the process gas including SO ₂ gas, heat is recovered from the process gas between the combustion furnace and the converter to generate high-pressure steam from the boiler water. A waste heat boiler to be generated is provided.

The waste heat boiler is provided with a casing such as a shell and a heat transfer tube arranged inside the casing. Conventionally, boilers used as waste heat boilers for sulfuric acid production facilities include natural-circulation water pipe boilers (hereinafter referred to as heat exchangers such as boiler water) that flow through heat transfer tubes and process gases flow around the heat transfer tubes Generally, there are two types of tube-type smoke tube boilers (hereinafter also simply referred to as smoke tube boilers), in which process gas flows inside the heat transfer tubes and boiler water flows around the heat transfer tubes. It was adopted.

The smoke tube boiler has the advantage of a simple structure compared to the water tube boiler. However, in the smoke tube boiler, a high-pressure heat medium such as boiler water flows inside the shell. For this reason, if the capacity of the manufacturing equipment increases, the capacity of the waste heat boiler increases due to an increase in process gas and the shell of the smoke tube boiler becomes large, the thickness of the shell of the smoke tube boiler increases to withstand the pressure from the heat medium. There is a need to. Therefore, if a smoke tube boiler is employed in a large-capacity manufacturing facility, the cost of the waste heat boiler may increase. On the other hand, in a water tube boiler, high-pressure water / steam flows inside a heat transfer tube with a small diameter, so that the thickness of the heat transfer tube can be reduced to a realistic one. Can be easily accommodated. For this reason, a smoke tube boiler is generally adopted in a small manufacturing facility, and a water tube boiler is advantageous in a large manufacturing facility. For example, since a conventional sulfuric acid production facility is relatively small, a smoke tube boiler is usually employed. On the other hand, in recent years, the size of sulfuric acid production facilities is increasing. For this reason, it is necessary to employ a water pipe boiler in the sulfuric acid production facility.

As a water tube boiler, a horizontal water tube boiler in which a process gas flows in a horizontal direction and a vertical water tube boiler in which a process gas flows in a vertical direction are known. When a large water tube boiler is required, a vertical water tube boiler is usually adopted in consideration of the safety of the entire boiler and the ease of manufacturing and installing the boiler. For example, Patent Document 1 proposes to use a waste heat boiler composed of a vertical water tube boiler in order to recover the heat of process gas generated in an ammonia production facility.

Incidentally, in a sulfuric acid production facility, an ammonia production facility, or the like, a very high temperature process gas, for example, about 1000 ° C. can be supplied to the waste heat boiler. For this reason, high heat resistance is required for the casing of the waste heat boiler. Considering such problems, for example, in the waste heat boiler described in Patent Document 1, a fireproof heat insulating layer having heat resistance is provided on the inner surface of the casing.

JP-A-8-42806

The process gas supplied to the waste heat boiler may be not only high temperature but also high pressure. For example, in a sulfuric acid production facility, in order to prevent SO ₃ rich gas from reaching the converter, at a predetermined pressure from the waste heat boiler toward the converter, for example, a positive pressure of about 0.5 atm (about 5000 mmH 2 O). Process gas needs to be fed. In this case, not only heat resistance but also pressure resistance is required for the casing of the waste heat boiler. Further, in the sulfuric acid production facility, since the process gas contains SO ₂ gas and some water vapor, the casing is required to have not only the above heat resistance and pressure resistance but also the corrosion resistance.

The present invention has been made in consideration of such points, and provides a waste heat boiler composed of a vertical water tube boiler that can be used in a large-scale manufacturing facility where high-temperature and high-pressure process gas is generated. With the goal.

The present invention is a waste heat boiler for recovering heat from process gas in a plant,
A casing having a circular cross section extending in the vertical direction, a heat-resistant wall disposed inside the casing and extending in the vertical direction, penetrating through the casing and connected to the heat-resistant wall and surrounded by the heat-resistant wall. An inlet duct for supplying a process gas to the space, and a plurality of heat transfer tubes disposed in the space surrounded by the heat-resistant wall and through which a heat medium is passed, wherein the heat transfer tube heats the process gas. The waste heat boiler is configured such that the vapor of the heat medium generated by absorbing the heat can flow upward due to the difference in specific gravity between the heat medium and the liquid heat medium.

In the waste heat boiler according to the present invention, a space surrounded by the heat-resistant wall has a first flue extending in the vertical direction and a second smoke extending in the vertical direction and passing through the process gas after passing through the first flue. It may be divided into roads.

In the waste heat boiler according to the present invention, the heat-resistant wall includes a plurality of cooling pipes through which a cooling medium passes and fins attached to the cooling pipes so as to fill gaps between the two adjacent cooling pipes. And may have.

The waste heat boiler according to the present invention is connected to the lower ends of the plurality of heat transfer tubes, and is connected to the distribution header that distributes the liquid heat medium to the heat transfer tubes, and to the upper ends of the plurality of heat transfer tubes, and heat of the process gas And an assembly header that collects the heat medium evaporated by each heat transfer tube. In this case, preferably, each of the distribution header and the assembly header is disposed in a space surrounded by the heat-resistant wall.

In the waste heat boiler according to the present invention, an intermediate pipe penetrating the casing and the heat-resistant wall may be connected to the distribution header and the collective header. In this case, a portion of the casing through which the intermediate pipe passes may be covered from the outside by a gas sealing member. Moreover, the part which the said intermediate piping penetrates among the said heat-resistant walls may have a curved shape corresponding to the outline of the said intermediate piping, and may be comprised by the cooling pipe which lets a cooling medium pass inside.

The waste heat boiler according to the present invention may further include a support mechanism for supporting the heat transfer tube. The support mechanism may include a support tube suspended from above and a support member connected to the support tube and supporting the heat transfer tube from below.

In the waste heat boiler according to the present invention, a heat medium may be passed through the support tube of the support mechanism.

In the waste heat boiler according to the present invention, the heat-resistant wall includes a plurality of cooling pipes through which a cooling medium passes and fins attached to the cooling pipes so as to fill gaps between the two adjacent cooling pipes. And may have. In this case, the waste heat boiler is connected to lower ends of the plurality of cooling pipes, and is connected to a lower header that distributes a cooling medium in a liquid state to the respective cooling pipes, and upper ends of the plurality of cooling pipes. An upper header that collects the cooling medium evaporated by heat from each cooling pipe may be further provided. In this case, preferably, the support pipe of the support mechanism is supported by the upper header.

In the waste heat boiler according to the present invention, the heat-resistant wall may have a rectangular cross section.

In the waste heat boiler according to the present invention, a reinforcing plate may be attached to the inner surface of the casing, and the reinforcing plate may be disposed at a certain interval from the outer surface of the heat-resistant wall.

In the waste heat boiler according to the present invention, a baffle plate extending in a horizontal direction may be provided in a space between the inner surface of the casing and the outer surface of the heat-resistant wall.

According to the present invention, the waste heat boiler includes a casing that extends in the vertical direction and has a circular cross section, and a heat-resistant wall that is disposed inside the casing and extends in the vertical direction. Further, the high temperature process gas is supplied to the space surrounded by the heat resistant wall. For this reason, it is possible to suppress the heat of the process gas from being transmitted to the casing by the heat resistant wall. Therefore, it is not necessary for the casing to have high heat resistance, which can increase the degree of freedom in designing the casing. Further, according to the present invention, the differential pressure between the process gas and the atmospheric pressure acts on the casing, but does not act on the heat resistant wall. Therefore, it is not necessary for the heat-resistant wall to have a high pressure resistance, which can increase the degree of freedom in designing the heat-resistant wall. For example, according to the present invention, it is possible to adopt a design method in which a casing is designed mainly considering pressure resistance and a heat resistant wall is designed mainly considering heat resistance. That is, the pressure resistance and heat resistance required for the waste heat boiler can be ensured by two different components. For this reason, the upper limit of the pressure resistance and heat resistance which a waste heat boiler can achieve can be raised. This makes it possible to provide a large vertical water tube boiler that can be used under severe conditions. For example, a large vertical water tube boiler can be employed under conditions where high pressure resistance, heat resistance and corrosion resistance are required for a waste heat boiler such as a large sulfuric acid production facility. Therefore, the safety of the entire waste heat boiler and the ease of manufacturing and installing the waste heat boiler can be improved.

FIG. 1 is a longitudinal sectional view showing a waste heat boiler according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a casing and a heat-resistant wall of the waste heat boiler shown in FIG. FIG. 3 is a longitudinal sectional view showing a reinforcing plate provided between the casing and the heat-resistant wall. FIG. 4 is a longitudinal sectional view showing a baffle plate provided between the casing and the heat-resistant wall. FIG. 5 is a side view showing a heat transfer tube arranged in a space surrounded by a heat-resistant wall. FIG. 6 is a view showing a support tube and a support member for supporting the heat transfer tube shown in FIG. 5. FIG. 7 is a plan view showing a case where an upper header provided on the upper portion of the waste heat boiler is viewed from above. FIG. 8 is a diagram illustrating an example of a method of connecting the distribution header and the assembly header to a branch pipe outside the casing. FIG. 9 is a diagram illustrating a state in which the intermediate pipe passes through the heat-resistant wall and is connected to the distribution header and the assembly header.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 9. In the drawings, elements that represent the same function may be denoted by the same reference numerals and description thereof may be omitted.

First, the entire waste heat boiler 10 that recovers the heat of the process gas will be described with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal sectional view showing a waste heat boiler 10 installed in a production facility where a high-temperature and high-pressure process gas is generated, such as a sulfuric acid production facility or an ammonia production facility. FIG. 2 is a cross-sectional view showing the casing 20 and the heat-resistant wall 30 of the waste heat boiler 10 shown in FIG. Here, the case where the waste heat boiler 10 is installed in the sulfuric acid production facility will be described.

Waste heat boiler Waste heat boiler 10 is introduced with a high-temperature and high-pressure process gas containing SO ₂ gas generated by burning sulfur using a combustion furnace. In FIG. 1, arrows with reference numerals f 1 to f 5 represent the flow direction of the process gas introduced into the waste heat boiler 10. In the waste heat boiler 10 according to the present embodiment, heat is recovered from the process gas flowing in the vertical direction. That is, the waste heat boiler 10 is a vertical type. However, the present invention is not limited to this, and the technical idea of the present invention may be applied to a horizontal waste heat boiler that recovers heat from a process gas flowing in a horizontal direction.

As shown in FIGS. 1 and 2, the waste heat boiler 10 extends in a vertical direction (vertical direction), has a casing 20 having a circular cross section, and a heat-resistant wall that is disposed inside the casing 10 and extends in the vertical direction. 30 and an inlet duct 11 for supplying process gas to the inside of the waste heat boiler 10, and an outlet duct 12 for sending the process gas after heat recovery from the inside of the waste heat boiler 10 to the converter. ing. The casing 20 is configured to be able to stand on its own. In addition, in FIG. 2, although the example in which the casing 20 has a perfect circular cross section is shown, it is not restricted to this. Various shapes can be adopted as the cross-sectional shape of the casing 20 as long as the pressure difference between the process gas and the atmospheric pressure can be withstood. For example, the casing 20 may have an elliptical cross section.

As shown in FIGS. 1 and 2, the heat-resistant wall 30 is disposed on the inlet duct 11 side and extends in the longitudinal direction, the front wall 31 is disposed on the outlet duct 12 side, and the rear wall 32 extends in the longitudinal direction. The first side wall 33 and the second side wall 34 are disposed between the wall 31 and the rear wall 32 and extend in the vertical direction. The front wall 31, the rear wall 32, the first side wall 33, and the second side wall 34 each have a planar shape. As a result, as shown in FIG. 2, the heat-resistant wall 30 has a rectangular cross section, for example, a square cross section. The term “planar” means that elements constituting the walls 31 to 34, for example, a cooling pipe 35 and fins 36, which will be described later, are arranged on the same plane.

The heat-resistant wall 30 can be easily manufactured and installed by combining the walls 31 to 34. In addition, by making the cross section of the heat resistant wall 30 rectangular, the space surrounded by the heat resistant wall 30 can be utilized without waste.

As shown in FIG. 1, the inlet duct 11 penetrates the casing 20 and is connected to the front wall 31 of the heat-resistant wall 30. As shown in FIG. 1, the outlet duct 12 also penetrates the casing 20 and is connected to the rear wall 32 of the heat-resistant wall 30 in the same manner as the inlet duct 11. As shown in FIG. 1, the heat transfer tube 60 for recovering the heat of the process gas is disposed in a space surrounded by the heat-resistant wall 30 from the side. In this case, the process gas supplied to the waste heat boiler 10 exchanges heat with the heat medium passed through the heat transfer tube 60 while mainly flowing in the space surrounded by the heat-resistant wall 30. Then, it is sent toward the converter from the outlet duct 12. That is, it is mainly the inner surface of the heat-resistant wall 30 that is affected by the heat of the process gas, and the heat of the process gas is not transmitted to the inner surface of the casing 20 so much. Therefore, the casing 20 does not need to have high heat resistance. For this reason, the structure of the casing 20 can be simplified compared with the case where high heat resistance is required for the casing. For example, in a conventional waste heat boiler, a refractory material and a heat insulating material are provided on the inner surface of the casing in order to impart heat resistance and fire resistance to the casing. On the other hand, according to this Embodiment, such a refractory material and a heat insulating material can be made unnecessary. As a result, the cost required for production and maintenance of the casing 20 can be reduced. Moreover, the weight of the casing 20 can be reduced, and thereby the self-supporting property and the earthquake resistance of the casing 20 can be improved.

In the present embodiment, the heat-resistant wall 30 does not have to be completely airtight. That is, the space between the casing 20 and the heat-resistant wall 30 and the space surrounded by the heat-resistant wall 30 may partially communicate with each other. For example, the process gas may leak from the inside of the heat-resistant wall 30 to the outside in a portion where an intermediate pipe described later passes through the heat-resistant wall 30. Even in this case, since the flow path resistance of the space surrounded by the heat resistant wall 30 is significantly lower than the flow path resistance in the portion where the intermediate pipe passes through the heat resistant wall 30, the process gas mainly contains the heat resistant wall 30. Will flow through the space surrounded by. In addition, when the space between the casing 20 and the heat-resistant wall 30 and the space surrounded by the heat-resistant wall 30 are partially communicated, the pressures in the two spaces are substantially the same. In this case, since there is almost no differential pressure acting on the heat resistant wall 30, it is not necessary for the heat resistant wall 30 to have high pressure resistance. For this reason, compared with the case where high pressure resistance is required for the heat-resistant wall 30, the structure of the heat-resistant wall 30 can be simplified, or the degree of freedom in designing the heat-resistant wall 30 can be increased. For example, as the shape of the cross section of the heat-resistant wall 30, a rectangular shape can be adopted as described above.

(Heat-resistant wall)
Next, the structure of the heat-resistant wall 30 will be described in detail with reference to FIG. In the present embodiment, the front wall 31, the rear wall 32, the first side wall 33, and the second side wall 34 of the heat-resistant wall 30 respectively extend in the vertical direction and have a plurality of cooling pipes 35 through which a cooling medium passes. And fins 36 attached to the respective cooling pipes 35 so as to fill a gap between the two adjacent cooling pipes 35. The fin 36 is attached to each cooling pipe 35 by welding, for example. As the cooling medium passed through the cooling pipe 35, for example, boiler water, that is, saturated water or air-water mixed water is used. Thus, in the present embodiment, the walls 31 to 34 of the heat-resistant wall 30 are configured as so-called water walls. In this case, since the heat of the process gas can be recovered by the boiler water passing through the cooling pipes 35 of the walls 31 to 34, the heat of the process gas flowing through the space surrounded by the heat resistant wall 30 is transmitted to the casing 20. Can be further suppressed. Moreover, since the heat of process gas can be collect | recovered using a cooling medium simultaneously with suppressing that the heat of process gas is transmitted to the casing 20, the energy efficiency of the waste heat boiler 10 can be improved.

The configuration for passing the cooling medium through each cooling pipe 35 of the heat-resistant wall 30 is not particularly limited, and various configurations can be adopted. For example, as shown in FIG. 1, a lower header 46 for distributing a cooling medium in a liquid state to each cooling pipe 35 is connected to the lower end of each cooling pipe 35 constituting the front wall 31 and the rear wall 32, and An upper header 47 that collects the cooling medium evaporated by the heat of the process gas from each cooling pipe 35 may be connected to the upper end of each cooling pipe 35. By adopting such a configuration, the cooling medium can be efficiently supplied to the plurality of cooling pipes 35 and the cooling medium can be efficiently recovered from the plurality of cooling pipes 35. Although not shown in FIG. 1, the lower header and the upper header are also connected to the lower end and the upper end of each cooling pipe 35 constituting the first side wall 33 and the second side wall 34, respectively.

(Flues)
Next, a flow path that is formed in a space surrounded by the heat-resistant wall 30 and through which process gas passes, that is, a so-called flue will be described. In the present embodiment, as shown in FIGS. 1 and 2, the space surrounded by the heat-resistant wall 30 communicates with the inlet duct 11 and communicates with the first flue P1 extending in the vertical direction and the outlet duct 12. However, it may be partitioned into a second flue P2 that extends in the vertical direction and through which the process gas passes through the first flue P1. In this case, the process gas supplied to the waste heat boiler 10 along the arrow f1 first flows upward along the first flue P1, as indicated by the arrow f2. The process gas discharged from the first flue P1 reverses its traveling direction at the upper part of the casing 20, as indicated by an arrow f3. Thereafter, the process gas flows downward along the second flue P2 as indicated by an arrow f4. The process gas that has reached the lower portion of the waste heat boiler 10 is discharged by the outlet duct 12 as indicated by an arrow f5. As described above, in the present embodiment, two flues extending in the vertical direction are formed inside one trunk (casing). Such a form is also referred to as one-body two-time flow. In the single cylinder double flow, the length of the flue formed inside one casing 20 can be doubled in the case of the single cylinder single flow, so that the heat transfer tubes 60 arranged in the flue can be provided. It is possible to recover the heat of the process gas sufficiently. For this reason, the energy efficiency of the waste heat boiler 10 can be improved.

Hereinafter, other advantages of adopting a one-body two-time flow will be described. First, for comparison, consider the case where the flue of the process gas is not folded inside the waste heat boiler, that is, the case of a single cylinder and one flow. In this case, in order to obtain a flue having the same length as in the present embodiment, the height of the casing and the heat-resistant wall needs to be about twice that in the present embodiment. For this reason, it is possible that the independence of a casing falls and manufacture and installation of a casing and a heat-resistant wall become difficult. On the other hand, according to the present embodiment, the length of the flue of the process gas can be reduced while suppressing the height of the casing 20 and the heat-resistant wall 30 from becoming too large by adopting a one-cylinder and two-turn flow. It can be secured sufficiently. Thereby, the self-supporting property of the casing 20 and the ease of manufacturing and installing the casing 20 and the heat-resistant wall 30 can be ensured.
Further, for comparison, a case where one waste heat boiler 10 includes two casings, that is, a case of two-cylinder two-way flow will be considered. In this case, the length of the flue of the process gas can be sufficiently secured by using a casing having almost the same height as that in the present embodiment. However, since two casings are required, it is considered that the cost required for manufacturing the waste heat boiler increases. On the other hand, according to the present embodiment, the length of the flue of the process gas is sufficiently secured while the cost required for the production of the waste heat boiler 10 is kept low by adopting the double flow of one cylinder. Can do.

Next, a specific structure for realizing the above-described one-body two-way flow will be described. For example, as shown in FIGS. 1 and 2, an intermediate wall 38 is provided between the front wall 31 and the rear wall 32. The intermediate wall 38 is configured to shield the flow of process gas in the horizontal direction. For example, the intermediate wall 38 includes a vertical portion 38a extending in the vertical direction. As in the case of the walls 31 to 34 of the heat-resistant wall 30, the vertical portion 38a extends in the vertical direction and includes a plurality of cooling pipes 35 through which a cooling medium passes, and two adjacent cooling pipes 35. And fins 36 attached to the respective cooling pipes 35 so as to fill the gaps therebetween.
As shown in FIG. 1, the lower end of each cooling pipe 35 constituting the intermediate wall 38 is connected to the lower header 46 at a place where the lower end of each cooling pipe 35 constituting the front wall 31 is connected to the lower header 46. May be. Accordingly, as shown in FIG. 1, the intermediate wall 38 can have a lower surface portion 38c extending from the vertical portion 38a toward the front wall 31 in the lower portion of the first flue P1. In this case, by providing the fins 36 between the cooling pipes 35 constituting the lower surface portion 38c, the process gas supplied from the inlet duct 11 to the first flue P1 passes through the lower part of the waste heat boiler 10 to the second. Reaching the flue P2 or the outlet duct 12 can be prevented. The lower header 46 to which the lower end of each cooling pipe 35 constituting the intermediate wall 38 is connected may be the same as the lower header 46 to which the lower end of each cooling pipe 35 constituting the front wall 31 is connected, Or they may be different.
As shown in FIG. 1, the upper end of each cooling pipe 35 constituting the intermediate wall 38 is connected to the upper header 47 at a place where the upper end of each cooling pipe 35 constituting the rear wall 32 is connected to the upper header 47. It may be connected. Thereby, the place where the cooling medium is collected from each cooling pipe 35 constituting the rear wall 32 and the place where the cooling medium is collected from each cooling pipe 35 constituting the intermediate wall 38 can be brought close to each other. Thus, the structure for taking out the vapor of the cooling medium can be simplified. In this case, as shown in FIG. 1, the intermediate wall 38 has an upper surface portion 38b extending from the vertical portion 38a toward the rear wall 32 in the upper portion of the first flue P1. On the other hand, as described above, the process gas discharged from the first flue P1 must be reversed and flow into the second flue P2. Accordingly, the upper surface portion 38b is configured to allow the process gas to pass therethrough. For example, the fins 36 described above are not provided between the cooling pipes 35 constituting the upper surface portion 38b. As a result, the process gas can pass through the upper surface portion 38b of the intermediate wall 38 and flow into the second flue P2.

By the way, when the process gas is turned up in the upper part of the waste heat boiler 10 as described above, the process gas discharged from the first flue P1 comes into direct contact with the inner surface of the upper part of the casing 20. In this case, in order to prevent the upper part of the casing 20 from being damaged by the heat of the process gas, the upper part of the casing 20 may have high heat resistance. For example, as shown in FIG. 1, the casing 20 is positioned below the upper end of the heat-resistant wall 30, and the vertical portion 21 extending in the vertical direction is in contact with the process gas that is folded after being discharged from the first flue P <b> 1. It may be configured by combining the folded portion 22. In this case, the folded portion 22 may be provided with a refractory material and a heat insulating material on the inner surface for imparting heat resistance and fire resistance. On the other hand, since the vertical portion 21 does not need to have high heat resistance, the structure of the vertical portion 21 is simpler than the folded portion 22. As a result, the cost and weight of the entire casing 20 can be reduced as compared with the case where the entire casing 20 has heat resistance and fire resistance. Although the specific structure for giving heat resistance to the folding | returning part 22 is not specifically limited, For example, a castable anchor, a heat insulation caster, a fireproof caster etc. can be used.
Moreover, since the structure of the vertical part 21 is simplified, the manhole for implementing the maintenance of the waste heat boiler 10 can be easily provided in the vertical part 21. For this reason, the access to the inside of the waste heat boiler 10 becomes easy, and this makes it possible to simplify the maintenance work of the waste heat boiler 10. As will be described below, a maintenance manhole may be provided in the folded portion 22.
The heat of the process gas is recovered to some extent in the first flue P <b> 1 until reaching the turn-up portion 22. For example, when the temperature of the process gas supplied from the inlet duct 11 is about 1000 ° C., the temperature of the process gas that has reached the folded portion 22 is about 600 ° C. Therefore, the structure of the folded portion 22 is simple. For this reason, the above-described manhole for maintenance can be easily provided in the folded-back portion 22 as compared with the conventional case.

Incidentally, as described above, the process gas leaking from the heat-resistant wall 30 may slightly reach the inner surface of the vertical portion 21 of the casing 20. The process gas contains SO ₂ gas as described above, and the process gas may contain a small amount of water vapor. In this case, if the atmospheric temperature outside the casing 20 is significantly lower than the temperature of the process gas, the temperature of the inner surface of the vertical portion 21 is below the acid dew point, and as a result, the sulfuric acid gas is condensed and the vertical portion 21 A drop of sulfuric acid may appear on the inner surface. In order to prevent such condensation, a heat insulating member 23 may be provided in the vertical portion 21 as shown in FIG. Thereby, it can suppress that the temperature of the inner surface of the vertical part 21 falls below an acid dew point. Thereby, it can suppress that the inner surface of the vertical part 21 is damaged by corrosion.

(Heat transfer tube)
Next, the structure of the heat transfer tube 60 disposed in the space surrounded by the heat resistant wall 30 will be described with reference to FIGS. 1 and 5. FIG. 5 is an enlarged side view showing the heat transfer tube 60 shown in FIG.

The heat transfer tube 60 allows the heat medium vapor generated by absorbing the heat of the process gas to flow upward due to the specific gravity difference between the heat transfer tube 60 and the liquid heat medium existing inside the heat transfer tube 60. It is configured. As shown in FIG. 1, the heat transfer tube 60 meanders in a plane parallel to the flow direction of the process gas, that is, in a plane extending in the vertical direction in order to realize efficient heat exchange with the process gas. It may extend in a shape. In this case, the overall shape of the heat transfer tube 60 can also be expressed as a panel shape. For example, in FIG. 2 mentioned above and FIG. 8 shown later, the heat transfer tube 60 is drawn in a panel shape. Hereinafter, a comprehensive shape formed by the heat transfer tubes extending in a serpentine shape is sometimes referred to as a “heat transfer tube panel”, and a plane formed by the heat transfer tube panels is sometimes referred to as a “heat transfer tube panel surface”.

As shown in FIG. 5, the heat transfer tube 60 has a plurality of straight tube portions 61 extending linearly and a plurality of folded portions that connect two adjacent straight tube portions 61. The folded portion is connected to the end of the two adjacent straight pipe portions 61 on the inlet duct 11 side (front wall 31 side), and has a first folded portion 62 having a substantially U-shape and two adjacent two The straight pipe portion 61 is connected to an end portion on the outlet duct 12 side (rear wall 32 side) and includes a second folded portion 63 having a substantially U-shape. The heat transfer tube panel surface described above is formed by alternately arranging the plurality of straight tube portions 61 and the plurality of folded

portions

62 and 63 in a plane extending in the vertical direction.

As shown in FIG. 5, each straight pipe portion 61 of the heat transfer tube 60 extends in a direction inclined with respect to the horizontal direction. For this reason, the vapor of the heat medium can flow upward along the heat transfer tube 60 based on the difference between the specific gravity of the heat medium in the gas state and the specific gravity of the heat medium in the liquid state. This makes it possible to circulate the heat medium naturally without using a pump or the like. That is, a natural circulation water tube boiler can be realized. As the heat medium passed through the heat transfer tube 60, for example, boiler water is used as in the case of the cooling medium passed through the cooling tube 35 of the heat-resistant wall 30. In this case, the vapor of the heat medium, that is, water vapor flows upward along the heat transfer tube 60 due to the specific gravity difference between water and water vapor.

The configuration for passing the heat medium through the heat transfer tube 60 is not particularly limited, and various configurations can be adopted. For example, as shown in FIGS. 1 and 5, a distribution header 41 for supplying a liquid heat medium to the heat transfer tube 60 is connected to the lower end of the heat transfer tube 60, and a process header is connected to the upper end of the heat transfer tube 60. A collective header 42 that collects the heat medium evaporated by the heat of the gas from the heat transfer tube 60 may be connected.

As shown in FIG. 5, a plurality of, for example, three heat transfer tubes 60 are provided in the surface of one heat transfer tube panel, and the distribution header 41 and the assembly header having the same lower end and upper end of each heat transfer tube 60 are provided. 42 may be connected. By adopting such a configuration, heat can be efficiently recovered from the process gas. Each heat transfer tube 60 may be connected to the distribution header 41 and the assembly header 42 via the short tube 41a and the short tube 42a. The short pipe 41a and the short pipe 42a are connected to the distribution header 41, the assembly header 42, and the heat transfer pipe 60 by welding, for example.

As shown in FIG. 2, a plurality of heat transfer tubes 60 (heat transfer tube panels) are arranged along the normal direction of the heat transfer tube panel surface, and the lower ends of the heat transfer tubes 60 constituting each heat transfer tube panel and The upper end may be connected to the same distribution header 41 and collective header 42. That is, the heat transfer tube panel group which consists of a some heat transfer tube panel may be arrange | positioned in the place of the same height. By adopting such a configuration, the heat medium can be efficiently supplied to the plurality of heat transfer tubes 60, and the heat medium can be efficiently recovered from the plurality of heat transfer tubes 60.

As shown in FIG. 1, a plurality of heat transfer tube panel groups may be arranged along the flow direction of the process gas, that is, along the vertical direction. For example, in FIG. 1, three heat transfer tube panel groups are arranged in the vertical direction in the first flue P1, and two heat transfer tube panel groups are arranged in the vertical direction in the second flue P2. The number of straight pipe portions 61 of the heat transfer tubes 60 constituting each heat transfer tube panel is determined according to the temperature of the process gas at the position where the heat transfer tubes 60 are arranged.
For example, the high-temperature process gas generated in the combustion furnace is supplied to the first flue P1. For this reason, each heat transfer tube 60 can generate | occur | produce the heat | fever of a heat medium fully recovering the heat | fever of process gas by using the three-stage straight pipe part 61 arranged along the up-down direction.
On the other hand, the process gas after a certain amount of heat is recovered while passing through the first flue P1 is supplied to the second flue P2. For this reason, it is preferable that each heat transfer tube 60 has more straight tube portions 61 than three stages. For example, the heat transfer tube 60 located on the upper side of the second flue P2 has a four-stage straight pipe portion 61, and the heat transfer tube 60 located on the lower side of the second flue P2 has six stages. A straight pipe portion 61 is provided.

(Boiler water circulation system)
Next, a system for circulating a cooling medium used in the cooling pipe 35 constituting the heat resistant wall 30 will be described. Here, the case where boiler water is used as a cooling medium is demonstrated. In FIG. 1, a boiler water circulation system that circulates boiler water is denoted by reference numeral 15. The boiler water circulation system 15 includes an air water cylinder 16 that houses boiler water 19 and high-pressure steam of the boiler water, and a downcomer pipe 17 for sending the boiler water 19 in the air water cylinder 16 toward the cooling pipe 35 and the heat transfer pipe 60. And a return pipe 18 for returning the steam of boiler water generated in the cooling pipe 35 and the heat transfer pipe 60 to the air / water cylinder 16. Although not shown in the figure, the air / water cylinder 16 is further connected to a pipe for extracting the generated high-pressure steam and a pipe for replenishing the boiler water 19 to the air / water cylinder 16.

The downpipe 17 and the return pipe 18 each extend in the vertical direction. A plurality of branch pipes 17 a extending toward the lower header 46 and the distribution header 41 are connected to the downcomer pipe 17 in order to supply the boiler water 19 to the lower header 46 and the distribution header 41 described above. Similarly, a plurality of branch pipes 18 a extending toward the upper header 47 and the collective header 42 are connected to the return pipe 18 in order to collect steam of boiler water from the above-described upper header 47 and collective header 42. In FIG. 1, boiler water 19 from each branch pipe 17a toward the lower header 46 and the distribution header 41 is indicated by a one-dot chain line arrow. Moreover, the steam of the boiler water which goes to each branch pipe 18a from the top header 47 and the assembly header 42 is also shown with the dashed-dotted arrow.

(Structure for connecting the branch pipe to the distribution header and the assembly header)
Next, a structure for connecting the branch pipe 17a and the distribution header 41 and a structure for connecting the branch pipe 18a and the assembly header 42 will be described in detail with reference to FIG. FIG. 8 is a cross-sectional view showing a case where the waste heat boiler 10 is cut by a horizontal plane passing through the distribution header 41 and the assembly header 42.

As shown in FIG. 8, the distribution header 41 and the assembly header 42 are each disposed in a space surrounded by the heat-resistant wall 30. Thereby, as will be described later, a heat transfer tube module can be manufactured by combining the distribution header 41, the assembly header 42 and the heat transfer tube 60 in advance in a factory or the like. Thereby, the work at the installation site of the waste heat boiler 10 can be facilitated.

As shown in FIG. 8, one end of an intermediate pipe 43 that penetrates the casing 20 and the heat-resistant wall 30 is connected to the end of the distribution header 41 by, for example, welding. In addition, outside the casing 20, a branch pipe 17a is connected to the other end of the intermediate pipe 43 by, for example, welding. As a result, the branch pipe 17 a and the distribution header 41 are communicated with each other, and boiler water can be supplied to the distribution header 41. Similarly, one end of an intermediate pipe 44 that penetrates the casing 20 and the heat-resistant wall 30 is connected to the end of the collective header 42 by, for example, welding. In addition, outside the casing 20, a branch pipe 18a is connected to the other end of the intermediate pipe 44 by, for example, welding. Thereby, the branch pipe 18a and the collective header 42 are communicated with each other, and the steam of the boiler water can be recovered from the collective header 42.

As shown in FIG. 8, a portion of the casing 20 through which the

intermediate pipes

43 and 44 penetrate may be covered with a gas sealing member 45 from the outside. Thereby, it is possible to prevent the process gas from leaking out of the casing 20 from the portion of the casing 20 through which the

intermediate pipes

43 and 44 penetrate. As the gas sealing member 45, for example, a metal for gas sealing made of a general steel material such as SS400 can be used.

Further, as shown in FIG. 8, a portion of the heat-resistant wall 30 through which the

intermediate pipes

43 and 44 penetrate has a curved shape corresponding to the outline of the

intermediate pipes

43 and 44, and a cooling pipe through which a cooling medium is passed. 35 may be comprised. That is, as shown in FIG. 9, the

intermediate pipes

43 and 44 penetrate by partially bending the cooling pipe 35 to form a curved portion 35 a having a curved shape corresponding to the contour of the

intermediate pipes

43 and 44. A hole that can be formed may be formed in the heat-resistant wall 30. By adopting such a structure, the

intermediate pipes

43 and 44 can be passed through the heat-resistant wall 30 while maintaining the cooling function and the heat recovery function based on the cooling pipe 35.

Although not shown, the structure for connecting the branch pipe 17a and the lower header 46 and the structure for connecting the branch pipe 18a and the upper header 47 are the same as those in the case of the distribution header 41 and the assembly header 42 described above. Similarly, a structure using the

intermediate pipes

43 and 44 may be employed.

8 shows an example in which the end on the first side wall 33 side of the distribution header 41 and the assembly header 42 is connected to the branch pipe 17a and the branch pipe 18a, but is not limited thereto. Although not shown, the end of the distribution header 41 and the assembly header 42 on the second side wall 34 side is also connected to a branch pipe 17a and a branch pipe 18a different from those connected to the end of the first side wall 33 side. It may be connected. That is, boiler water may be supplied from both ends of the distribution header 41, and steam of boiler water may be recovered from both ends of the assembly header 42.

(Configuration to support the heat transfer tube)
Next, a configuration for supporting the heat transfer tube 60 will be described in detail with reference to FIGS. 1, 5, and 6. In FIG. 1 and FIG. 5, a support mechanism that supports the heat transfer tube 60 is denoted by reference numeral 50. FIG. 6 is an enlarged view of the support mechanism 50 shown in FIGS. 1 and 5. In FIG. 1, the support tube 51 of the support mechanism 50 is represented by a dotted line in order to prevent the drawing from becoming complicated.

The support mechanism 50 includes a support tube 51 suspended from above, and a support member 52 connected to the support tube 51 and supporting the straight tube portion 61 of the heat transfer tube 60 from below. By supporting the heat transfer tube 60 using the support tube 51 and the support member 52, the heat transfer tube 60 can be stably supported over the entire region in the vertical direction. As shown in FIG. 6, support members 52 may be connected to both sides of the support tube 51. Thereby, the support tube 51 can support the heat transfer tube panels on both sides thereof (see FIG. 2). Hereinafter, the background of using such a support mechanism 50 will be described.

First, a configuration for supporting the heat transfer tube 60, which has been employed in a conventional waste heat boiler, will be described. In the conventional waste heat boiler, generally, the support of the heat transfer tube 60 is realized by connecting the folded

portions

62 and 63 of the heat transfer tube 60 to the inner surface of the container of the waste heat boiler. For example, hooks configured to be connectable to each other are attached to both the folded

portions

62 and 63 and the inner surface of the container. In such a conventional waste heat boiler, when the heat transfer tube 60 is carried into the container at the installation site, in order to prevent the hook on the container side and the hook on the heat transfer tube 60 side from interfering with each other, It is necessary to carry it into the container in an inclined state with respect to the final installation posture. However, in this case, since it is difficult to incline the plurality of heat transfer tubes 60 together, the heat transfer tubes 60 are carried into the container one by one. For this reason, it is impossible to connect the distribution header 41 and the assembly header 42 to the heat transfer tube 60 in advance. Therefore, after the heat transfer tube 60 is carried into the container, the heat transfer tube 60 is connected to the distribution header 41 and The assembly header 42 will be welded. For this reason, the work at the installation site becomes complicated, and as a result, the production cost of the waste heat boiler becomes high.

On the other hand, according to the present embodiment, the heat transfer tube 60 can be supported by using the support tube 51 suspended from above. For this reason, the heat transfer tube 60 maintained in the final installation posture can be carried into the heat resistant wall 30 from above. This makes it possible to carry a plurality of heat transfer tubes 60 together into the heat resistant wall 30. Therefore, after connecting the distribution header 41 and the assembly header 42 to the heat transfer tube 60 in advance in a factory or the like, these can be brought together into the heat-resistant wall 30. Thereby, the work at the installation site of the waste heat boiler 10 can be facilitated.

(Configuration to support the support tube)
Next, a configuration for suspending the support tube 51 from above will be described in detail with reference to FIG.

As shown in FIG. 1, the support mechanism 50 includes a support beam 53 disposed on the upper portion of the waste heat boiler 10, a suspension bar 54 coupled to the support beam 53 and hanging from the support beam 53, and a lower end of the suspension bar 54. And attached hanging metal fittings 55. In this case, the support pipe 51 can be suspended from above by connecting the suspension fitting 55 to the support pipe 51.

Next, an example of a method for arranging the support beam 53 on the upper portion of the waste heat boiler 10 will be described with reference to FIG. FIG. 7 is a plan view showing the upper header 47 provided above the heat-resistant wall 30 as viewed from above. In FIG. 7, the cooling pipe 35 and the support pipe 51 are indicated by dotted lines in order to show the positional relationship between the upper header 47 and the support beam 53 and the cooling pipe 35 and the support pipe 51.

As shown in FIG. 7, an upper header 47 assembled in a well shape is disposed on the upper portion of the waste heat boiler 10. The upper header 47 assembled in a well shape is disposed so as to intersect the upper header 47a connected to the cooling pipe 35 constituting the front wall 31 and the rear wall 32, and to intersect the upper header 47a. And an upper header 47 b connected to the cooling pipe 35 constituting the two side walls 34. And the support beam 53 of the support mechanism 50 is arrange | positioned on the upper header 47 assembled in the well shape. That is, the support beam 53 is supported by the upper header 47. In addition, a fixture 56 to which the support tube 51 is connected is attached to the support beam 53. By adopting such a configuration, it is possible to easily realize suspension of the support tube 51 from above.

Although not shown, a fixture for fixing the support beam 53 to the upper header 47, such as a bolt and a nut, may be provided. Further, as shown in FIG. 7, a pair of support beams 53 arranged at a predetermined interval is used for a plurality of support tubes 51 arranged in a line from the first side wall 33 toward the second side wall 34. May be.

Although not shown, similarly to the cooling pipe 35 and the heat transfer pipe 60, a cooling medium or a heat medium that can recover heat from the process gas, such as boiler water, is passed through the support pipe 51. May be. Although not shown, a lower header and an upper header for supplying boiler water to the support pipe 51 and recovering steam of the boiler water from the support pipe 51 may be connected to the support pipe 51. For example, as shown in FIG. 1, the lower end of the support pipe 51 is the same as the lower header 46 connected to the lower end of the cooling pipe 35 of the heat-resistant wall 30, or the lower header disposed in the vicinity of the lower header 46. It may be connected to. Similarly, the upper end of the support pipe 51 is connected to the same upper header 47 as the upper header 47 connected to the upper end of the cooling pipe 35 of the heat-resistant wall 30 or an upper header disposed in the vicinity of the upper header 47. Also good.

By the way, the load caused by the load of the heat transfer tube 60 and the load of the support tube 51 is applied to the support beam 53. For this reason, as the material constituting the support beam 53, a material having sufficient load resistance is used. On the other hand, the support beam 53 is disposed on the upper portion of the waste heat boiler 10, and a certain amount of heat is recovered in the upper portion of the waste heat boiler 10 while passing through the first flue P1 as described above. Later process gas arrives. For example, a process gas of about 600 ° C. arrives. For this reason, the material which comprises the support beam 53 does not use the material which has especially high heat resistance, but can use the material which has normal heat resistance. For example, general heat resistant steel such as SUS304 can be used. As described above, according to the present embodiment, the heat transfer tube 60 can be suspended with a simple configuration.

(Configuration of the space between the casing and the heat-resistant wall)
Next, an example of components disposed in the space between the casing 20 and the heat resistant wall 30 will be described. First, the reinforcing mechanism 24 that suppresses fluctuation of the heat-resistant wall 30 in the horizontal direction will be described. FIG. 2 shows a cross-sectional view when the waste heat boiler 10 is cut by a horizontal plane passing through the reinforcing mechanism 24.

As described above, the casing 20 has a circular cross section, and the heat-resistant wall 30 has a rectangular cross section. That is, the shape of the cross section of the casing 20 and the shape of the cross section of the heat-resistant wall 30 are different from each other. Accordingly, the distance between the inner surface of the casing 20 and the outer surface of the heat-resistant wall 30 is large at a specific location. As a result, it is considered that the heat-resistant wall 30 greatly fluctuates in the horizontal direction at a specific place. In order to prevent such fluctuation, a reinforcing mechanism 24 for suppressing fluctuation of the heat-resistant wall 30 may be attached to the inner surface of the casing 20 as shown in FIG.

FIG. 3 is a longitudinal sectional view showing the reinforcing mechanism 24 in an enlarged manner. The reinforcing mechanism 24 includes a reinforcing plate 24 a that is disposed at a certain distance from the outer surface of the heat-resistant wall 30. The reinforcing mechanism 24 further includes a reinforcing member 24b having one end fixed to the inner surface of the casing 20 and the other end fixed to the reinforcing plate 24a. In this case, the reinforcing plate 24 a functions as a stopper against fluctuation of the heat resistant wall 30. Therefore, the heat resistant wall 30 can be prevented from greatly fluctuating in the horizontal direction. That is, the rigidity of the entire waste heat boiler 10 can be increased.

2 and 3, a reinforcing mechanism 37 for suppressing fluctuation of the heat-resistant wall 30 may also be provided on the heat-resistant wall 30 side. The reinforcing mechanism 37 includes, for example, a reinforcing plate 37a disposed at a predetermined interval from the reinforcing plate 24a, and a reinforcing member 37b fixed to the reinforcing plate 37a and the cooling pipe 35. Thereby, the fluctuation | variation of the heat-resistant wall 30 can be suppressed more stably. The distance between the reinforcing plate 24a and the reinforcing plate 37a is, for example, in the range of 10 to 15 mm.

As described above, since the high-temperature process gas mainly flows in the space surrounded by the heat resistant wall 30, the reinforcing mechanism 24 and the reinforcing mechanism 37 disposed between the casing 20 and the heat resistant wall 30 have high heat resistance. Is not required. For this reason, a general material can be used as a material which comprises the reinforcement mechanism 24 and the reinforcement mechanism 37, for example, common steel materials, such as SS400, can be used.

Next, the baffle plate 26 that extends in the horizontal direction and is disposed in the space between the casing 20 and the heat-resistant wall 30 will be described.

As described above, the

intermediate pipes

43 and 44 are penetrated through the heat-resistant wall 30. For this reason, it is not possible to completely prevent the process gas from leaking from the heat-resistant wall 30. Therefore, it is considered that a certain amount of process gas leaks from the heat resistant wall 30 in the space between the casing 20 and the heat resistant wall 30. The baffle plate 26 described above is provided to prevent such process gas from flowing in the vertical direction.

Although a specific configuration for providing the baffle plate 26 is not particularly limited, for example, as shown in FIG. 4, a mounting plate 26 a and a mounting plate 26 b are respectively provided on the inner surface of the casing 20 and the cooling pipe 35 of the heat-resistant wall 30. The baffle plate 26 may be provided on the mounting plate 26a and the mounting plate 26b.

In the space between the casing 20 and the heat-resistant wall 30, condensation of gas containing sulfuric acid occurs, and as a result, condensed water containing sulfuric acid may be generated. If such condensed water remains on the baffle plate 26 when the operation of the waste heat boiler 10 is stopped, the baffle plate 26 may be corroded by sulfuric acid. In order to prevent such corrosion from occurring, each baffle plate 26 may be connected to a drain pipe (not shown) for discharging condensed water on the baffle plate 26. Thereby, it is possible to prevent the condensed water from accumulating on the baffle plate 26.

Next, the operation and effect of the present embodiment having such a configuration will be described. First, a method for manufacturing the waste heat boiler 10 will be described.

(Waste heat boiler manufacturing method)
First, work performed in the factory will be described. In the factory, a module is manufactured by combining a plurality of components constituting the waste heat boiler 10. For example, first, the plurality of heat transfer tubes 60 are connected to the distribution header 41 and the assembly header 42 using a welding method or the like. Thus, a heat transfer tube group in which the distribution header 41 and the assembly header 42 are combined can be manufactured. Next, each heat transfer tube 60 of the heat transfer tube group is attached to the support tube 51 via the support member 52. In this manner, a heat transfer tube module in which the heat transfer tube 60, the distribution header 41, the assembly header 42, and the support mechanism 50 are combined can be manufactured.

In the factory, the heat-resistant wall 30 may be manufactured by connecting the cooling pipe 35 and the fin 36 by welding. Further, the cooling pipe 35 and the lower header 46 and the upper header 47 may be connected to manufacture a heat resistant wall module.

Next, the work performed at the installation site will be described. First, the vertical portion 21 of the casing 20 is self-supported. Next, the above-mentioned heat resistant wall module is carried into the space inside the vertical portion 21. Thereafter, the above-described heat transfer tube module is carried into the space surrounded by the heat resistant wall 30 from above, and the heat transfer tube module is attached to the heat resistant wall 30. For example, the support beam 53 of the support mechanism 50 of the heat transfer tube module is fixed on the upper header 47 assembled in a well shape. In this way, the plurality of heat transfer tubes 60 can be easily installed in the space surrounded by the heat resistant wall 30.

Thereafter, the

intermediate pipes

43 and 44 are passed through the casing 20, and the

intermediate pipes

43 and 44 are welded to the distribution header 41, the assembly header 42, the lower header 46, and the upper header 47. Further, the folded portion 22 is disposed on the vertical portion 21. In this way, the waste heat boiler 10 configured as a vertical water tube boiler can be obtained.

Next, an example of a method for using the waste heat boiler 10 in the sulfuric acid production facility will be described. The operating conditions of the sulfuric acid production facility and the waste heat boiler 10 are as follows.
Process gas flow rate: 130000 Nm ³ / h
Process gas pressure: 5000 mmH2O
Process gas composition: SO ₂ 11%, O ₂ 10%, N ₂ 79%, H ₂ O 0.01%
-Process gas temperature in the inlet duct: 1000 ° C
-Process gas temperature at the folded part: 600 ° C
-Process gas temperature at outlet duct: 410 ° C
・ Operating pressure of waste heat boiler: 6 MPag
-Steam temperature of boiler water: 400 ° C
・ Boiler water evaporation: 80t / h
・ Power generation: 16MW

First, in a combustion furnace, sulfur is burned using air dried with concentrated sulfuric acid. Thereby, a process gas including SO ₂ gas is generated. The generated process gas is supplied to the waste heat boiler 10 at 1000 ° C. The process gas supplied to the waste heat boiler 10 first flows upward along the first flue P1. At this time, the heat of the process gas is recovered by the heat transfer pipe 60 and the cooling pipe 35 arranged in the first flue P1. The recovered heat is used for power generation using a steam turbine.

The process gas at 600 ° C. discharged upward from the first flue P1 is folded back by the folded portion 22 of the casing 20, flows into the second flue P2, and flows downward along the second flue P2. . At this time, the heat of the process gas is recovered by the heat transfer pipe 60 and the cooling pipe 35 disposed in the second flue P2. The recovered heat is used for power generation using a steam turbine.

The 410 degreeC process gas which reached | attained the lower part of the waste heat boiler 10 is discharged | emitted from the waste heat boiler 10 by the exit duct 12, and goes to a converter. In the converter, the SO ₂ gas is oxidized using a V ₂ O ₅ catalyst to generate SO ₃ gas. When the temperature of the process gas that has reached the converter is expected to be lower than the desired temperature, the process gas is sent to the converter without passing through the second flue P2 of the waste heat boiler 10. May be. For example, as shown in FIG. 1, a bypass duct 13 that sends out process gas toward the converter may be provided in the folded portion 22 of the waste heat boiler 10 as indicated by an arrow f <b> 6. Thereby, the temperature of the process gas supplied to the converter can be maintained at a desired temperature. In order to adjust the amount of process gas sent out from the outlet duct 12 toward the converter and the amount of process gas sent out from the bypass duct 13 toward the converter, the outlet duct 12 and the bypass duct 13 respectively The damper 12a and the damper 13a which can adjust a flow volume may be provided.

Here, the effect obtained by the bypass duct 13 will be further described by comparing with the case of a smoke tube boiler. Assuming that a smoke tube boiler is adopted as the type of waste heat boiler, the bypass method is a mode in which a high-temperature (about 1000 ° C.) process gas is taken out from the smoke tube boiler and sent to the converter. Will be adopted. In this case, since a high-temperature process gas must be handled, it is difficult to design a damper for adjusting the flow rate. On the other hand, when a water tube boiler is employed as in the present embodiment, the process gas can be taken out from the middle of the water tube boiler and sent out to the converter. For example, as described above, it is possible to take out the process gas at about 600 ° C. that has reached the folded portion 22. For this reason, compared with the case of a smoke tube boiler, the design of the damper 13a for adjusting a flow volume becomes easy.

Thereafter, in an absorption tower disposed downstream of the converter, SO ₃ gas and H ₂ O are reacted to generate H ₂ SO ₄ (sulfuric acid). In this manner, sulfuric acid can be produced while effectively using the heat of the process gas using the waste heat boiler 10. Note that a gas cooler for cooling the SO ₃ gas may be provided between the converter and the absorption tower.

Here, according to the present embodiment, the waste heat boiler 10 is formed in a double structure using a heat-resistant wall 30 that defines a space through which the process gas passes and a casing 20 that is disposed around the heat-resistant wall 30. Has been. In this case, a thermal load caused by the temperature of the process gas is applied to the heat-resistant wall 30, while a pressure load caused by the difference between the pressure of the process gas and the atmospheric pressure is applied to the casing 20. In other words, the heat resistance requirement and the pressure resistance requirement can be shared by the heat resistant wall 30 and the casing 20, respectively. For this reason, simplification of each structure of the heat-resistant wall 30 and the casing 20 is realizable. As a result, for example, the weight of the waste heat boiler 10 as a whole can be reduced. Thereby, the durability and safety of the waste heat boiler 10 as a whole can be improved. For this reason, the enlargement of the waste heat boiler 10 can be realized, and this makes it possible to cope with an increase in capacity of the sulfuric acid production facility.

Further, according to the present embodiment, since the durability and safety of the waste heat boiler 10 as a whole can be improved, the waste heat boiler 10 can be configured using a vertical water tube boiler. For this reason, a heat medium such as boiler water can be circulated naturally without using a pump or the like. Therefore, even if the sulfuric acid production facility is installed in an area where power supply is unstable, the waste heat boiler 10 can be stably operated. Further, the waste heat boiler 10 capable of natural circulation has an advantage that its operation work and maintenance work are easier than a waste heat boiler using forced circulation. Moreover, in areas where power supply is unstable, such as emerging countries, generally, the skill level of the operator who operates the sulfuric acid production facility and the waste heat boiler 10 is low. Considering these points, the waste heat boiler 10 according to the present embodiment has a high demand for sulfuric acid, and therefore, the waste heat boiler is required to be enlarged, and the operation work and the maintenance work are also required to be simplified. It is especially suitable for emerging countries.

DESCRIPTION OF SYMBOLS 10 Waste heat boiler 11 Inlet duct 12 Outlet duct 13 Bypass duct 15 Boiler water circulation system 16 Air cylinder 17 Precipitation pipe 18 Return pipe 20 Casing 23 Thermal insulation member 24 Reinforcement mechanism 26 Baffle plate 30 Heat-resistant wall 35 Cooling pipe 37 Reinforcement mechanism 38 Intermediate wall 41 Distribution header 42 Collective header 45 Gas sealing member 46 Lower header 47 Upper header 50 Support mechanism 51 Support tube 60 Heat transfer tube P1 1st flue P2 2nd flue

Claims

A waste heat boiler that recovers heat from process gas in a plant,
A casing extending in the longitudinal direction and having a circular cross section;
A heat-resistant wall disposed inside the casing and extending in the longitudinal direction;
An inlet duct that passes through the casing and is connected to the heat-resistant wall and supplies process gas to a space surrounded by the heat-resistant wall;
A plurality of heat transfer tubes arranged in a space surrounded by the heat-resistant wall and through which a heat medium passes;
The heat transfer tube is configured so that the vapor of the heat medium generated by absorbing the heat of the process gas can flow upward due to a specific gravity difference with the heat medium in a liquid state. .
A space surrounded by the heat-resistant wall is partitioned into a first flue extending in the vertical direction and a second flue extending in the vertical direction and through which the process gas passes through the first flue. The waste heat boiler according to claim 1.
The heat-resistant wall includes a plurality of cooling pipes through which a cooling medium is passed, and fins attached to the cooling pipes so as to fill a gap between the two adjacent cooling pipes. Or the waste heat boiler of 2.
The waste heat boiler is
A distribution header connected to the lower ends of the plurality of heat transfer tubes and distributing a heat medium in a liquid state to each heat transfer tube;
An assembly header connected to the upper ends of the plurality of heat transfer tubes, and collecting the heat medium evaporated by the heat of the process gas from each heat transfer tube,
The waste heat boiler according to any one of claims 1 to 3, wherein each of the distribution header and the collective header is disposed in a space surrounded by the heat-resistant wall.
Intermediate pipes that pass through the casing and the heat-resistant wall are connected to the distribution header and the assembly header, respectively.
The portion of the casing through which the intermediate pipe passes is covered from the outside by a gas sealing member,
The portion of the heat-resistant wall through which the intermediate pipe passes has a curved shape corresponding to the contour of the intermediate pipe, and is configured by a cooling pipe through which a cooling medium passes. Waste heat boiler.
The waste heat boiler further includes a support mechanism for supporting the heat transfer tube,
6. The support mechanism according to claim 1, comprising: a support pipe suspended from above; and a support member connected to the support pipe and supporting the heat transfer pipe from below. Waste heat boiler.
The waste heat boiler according to claim 6, wherein a heat medium is passed through the support tube of the support mechanism.
The heat-resistant wall has a plurality of cooling pipes through which a cooling medium is passed, and fins attached to the cooling pipes so as to fill a gap between the two adjacent cooling pipes,
The waste heat boiler is
A lower header connected to the lower ends of the plurality of cooling pipes and distributing a liquid cooling medium to the cooling pipes;
An upper header connected to the upper ends of the plurality of cooling pipes and collecting the cooling medium evaporated by the heat of the process gas from each cooling pipe;
The waste heat boiler according to claim 6 or 7, wherein the support pipe of the support mechanism is supported by the upper header.
The waste heat boiler according to any one of claims 1 to 8, wherein the heat-resistant wall has a rectangular cross section.
A reinforcing plate is attached to the inner surface of the casing,
The waste heat boiler according to claim 9, wherein the reinforcing plate is disposed at a predetermined interval from an outer surface of the heat-resistant wall.
The waste heat boiler according to any one of claims 1 to 10, wherein a baffle plate extending in a horizontal direction is provided in a space between an inner surface of the casing and an outer surface of the heat-resistant wall.