JP2009541705A - Steam generation method for gas pipe steam boiler and gas pipe steam boiler for implementing the above method - Google Patents

Abstract

  The heat exchange chamber (2) filled with water forming the water surface (2A), the above-mentioned water surface, the axis (10) being defined by the substantially vertical cylindrical wall (1) and the top plate (4) Steam head space (8), a steam outlet (6) connected to the steam head space, a gas pipe extending through the heat exchange chamber (2) and the steam head space (8), and the gas Means for supplying heated gas to the gas pipe to generate a steam flow from the water surface by heat exchange between the pipe and the water; and the water surface (2A) to the steam outlet (6) A steam flow conduit (7 ′, 7 ″) disposed in the steam headspace (8) for directing a steam flow, wherein the steam flow conduit comprises at least one of the gas pipes (3). The steam flow is transverse to the gas pipe (3), preferably substantially perpendicular to the gas pipe (3). Extending across the steam flow path, the configuration of the steam flow path is such that more than half, preferably substantially all, of the steam in the steam flow is projected onto the horizontal plane and the first point of the wall and the second point. And is constrained to flow along a flow path having a length at least equal to a minimum distance between one point and a second point on the wall opposite the horizontal direction, wherein the minimum distance is If the wall is cylindrical, a gas pipe steam boiler that has a diameter D of this cylindrical wall.

Description

  The present invention relates to a steam generation method for a gas pipe steam boiler and a gas pipe steam boiler for carrying out the above method.

  In connection with such methods and apparatus, it is important to optimize the energy transfer from the gas pipe to the water and steam in order to reduce the overall boiler size for a given energy output. Typically, key design parameters include input gas temperature, exhaust gas temperature, desired maximum energy output, ie feed water temperature, steam pressure, temperature and mass flow rate. Preferably, the steam should be dry and more preferably superheated.

  From U.S. Pat. No. 1,546,665 it is known to provide a gas pipe steam boiler with a baffle plate that provides an annular opening along the boiler wall, so that the steam flow from the water surface is from the water surface. Flow is restricted to the annular opening and from there to a steam outlet located in the center. In this structure, most of the generated steam passes only through the gas pipe by a distance corresponding to about half the diameter of the gas pipe boiler, and the gas pipe and the generated steam are insufficient. Will lead to a good heat exchange.

  In particular, but not exclusively, marine boilers are very important because the size of the boiler is limited due to the limited space available, and thus the above-described methods and methods that reduce boiler space requirements It is an object of the present invention to provide an apparatus.

According to the invention, this object is achieved by a method comprising the following steps.
Providing a gas pipe steam boiler,
The gas pipe steam boiler is
A heat exchange chamber filled with water forming the water surface;
A steam head space defined by a cylindrical wall and a top plate on the water surface, the axis of which is substantially vertical;
A steam outlet connected to the steam head space;
One or more gas pipes extending through the heat exchange chamber and the steam headspace;
With
And supplying a heated gas to the gas pipe to generate a steam flow from the water surface by heat exchange between the gas pipe and the water in the heat exchange chamber,
More than half, preferably substantially all, of the vapor in the flow in the headspace when projected onto a horizontal plane, the first point of the wall and the second of the wall opposite the first point in the horizontal direction. The steam flow is constrained to flow along a flow path having a length at least equal to a minimum distance between the points and transversely to the gas pipe, preferably substantially orthogonal. Flowing through the steam headspace from the water surface to the steam outlet,
The minimum distance is the diameter of the cylindrical wall, if the wall is cylindrical,
Residual heat in the gas pipe is transferred to the steam flow.

  This greatly improves the heat transfer from the gas pipe to the steam in the steam headspace, increasing the efficiency of the boiler, and at the same time, the generated steam is dried and possibly overheated. The quality becomes even higher.

  In a presently preferred embodiment of the method according to the invention, the horizontal projection of the flow path is at least twice the minimum distance. In this way, the contact between the gas pipe and the steam flow from the water surface to the steam outlet is increased and the heat transfer in the steam head space is increased.

  In a presently preferred embodiment of the method according to the invention, the steam outlet is located away from the axis of the wall, preferably near the wall of the headspace, so that the steam flow is from the steam outlet. It is restricted to flow laterally along all gas lines before exiting.

  In a presently preferred embodiment of the method according to the invention, the horizontal projection of the flow path passes through the axis from or near the first point of the wall and is opposite the first point. It extends to the vicinity of the second point of the wall on the side or to the second point, and preferably returns from the second point and at least halfway back to the first point. Thus, the steam stream is moved through all the gas lines, preferably at least twice before leaving the steam outlet.

  In a presently preferred embodiment of the method according to the invention, the flow rate of the steam flow from the second point to the first point is higher than when the vapor flow flows from the vicinity of the first point to the second point. The flow rate is lower and provides a relatively high speed, preferably about 15-30 m / s, more preferably about 15-25 m / s in the portion between the water surface and the steam outlet, and slowed down. In the subsequent part of the path from the water surface to the steam outlet for passing through the gas pipe at a speed, it is preferably about 10-15 m / s. Thus, the high speed provides turbulent flow around the gas pipe to ensure highly efficient heat transfer and ensures the possibility of water droplets in the steam colliding with the pipe and evaporating.

  In a presently preferred embodiment of the method according to the invention, the hot gas for the gas pipe is provided from a combustion chamber, burns oil, charcoal, natural gas, etc., and from a gas turbine or an internal combustion motor. Exhaust gas heat can also be used. When using hot gas from a combustion chamber, the combustion chamber will be provided in contact with water in the heat exchange chamber to further transfer heat directly from the combustion chamber to water.

In a second aspect, the present invention relates to a gas pipe steam boiler comprising:
The above boiler is
A heat exchange chamber filled with water forming the water surface;
A steam headspace defined by a cylindrical wall and a top plate on the water surface, the axis of which is substantially vertical;
A steam outlet connected to the steam head space;
One or more gas pipes extending into the heat exchange chamber and the steam head space; and for generating a steam flow from the water surface by heat exchange between the gas pipe and the water in the heat exchange chamber; Means for supplying heated gas to the gas pipe;
A steam flow conduit disposed in the steam head space for directing the steam flow from the water surface to the steam outlet;
The vapor flow path, at least one of the gas pipes extends across the vapor flow path so that the vapor flow flows transversely, preferably substantially perpendicular to the gas pipe,
The configuration of the steam flow path is such that more than half of the steam in the steam flow, preferably substantially all of the first and second points of the wall are horizontally opposite when projected onto a horizontal plane. Being constrained to flow along a flow path having a length at least equal to a minimum distance between the second point of the wall;
The minimum distance is the diameter of the cylindrical wall if the wall is cylindrical.

  This gas pipe steam boiler is particularly suitable for carrying out the method described above.

In a third aspect, the present invention relates to a gas pipe steam boiler comprising:
The above boiler is
A heat exchange chamber filled with water forming the water surface;
A steam headspace defined by a cylindrical wall and a top plate on the water surface and having a substantially vertical axis;
A steam outlet connected to the steam head space;
One or more gas pipes extending through the heat exchange chamber and the steam headspace;
Means for supplying heated gas to the gas pipe to generate a steam flow from the water surface by heat exchange between the gas pipe and the water in the heat exchange chamber;
A steam flow conduit disposed in the steam head space for directing the steam flow from the water surface to the steam outlet;
The steam flow conduit is
The first plate disposed at a distance in the vertically downward direction h1 of the top plate and spaced apart from the wall to provide a first vapor flow gap between the first plate and the wall. A substantially horizontal first plate having a gap forming edge is provided.

  Preferred embodiments of the gas pipe steam boiler according to the second and third aspects of the present invention (the advantages of which will become apparent from the following detailed description) are defined in the dependent claims 11 to 21 and 23. Revealed at ~ 31.

In the following, the invention will be described in more detail with reference to embodiments which are shown by way of example only in the drawings. here,
1 schematically shows an AA longitudinal sectional view of a boiler according to a preferred embodiment of the present invention. 1 schematically shows the boiler as viewed from above in FIG. 1, and also shows a section line in the cross-sectional views of FIGS. FIG. 2 schematically shows a BB longitudinal section perpendicular to the section of FIG. 1. The perspective view of the composition of a baffle board is shown roughly. A possible configuration for the steam headspace of the boiler according to the invention is shown. A possible configuration for the steam headspace of the boiler according to the invention is shown. A possible configuration for the steam headspace of the boiler according to the invention is shown. A possible configuration for the steam headspace of the boiler according to the invention is shown.

  The gas pipe steam boiler shown in FIG. 1 includes a heat exchange chamber 2 filled with water forming a water surface 2a, the water forming the water surface 2a, a substantially vertical shaft 10, a top plate 4, and a diameter D. And a steam headspace 8 on the water surface defined by a cylindrical wall 1 having The steam outlet 6 is connected to the steam head space 8, and some gas pipes 3 pass through the heat exchange chamber 2 and the steam head space 8. The heated gas flows through the gas pipe 3 in order to generate a steam flow from the water surface by heat exchange between the gas pipe 3 and the heat exchange chamber 2.

  In the embodiment shown in FIGS. 1-3 and 5, the steam flow from the water surface flows along a flow path defined by the baffle plates 7 ′, 7 ″. The steam traverses the gas pipe 3. All the steam in the steam flow flows in the horizontal direction between the two baffle plates 7 ′, 7 ″ and horizontally in the opposite direction between the upper baffle plate 7 ″ and the top plate 4. And is constrained to discharge from the steam outlet 6.

  As shown in FIGS. 2 and 3, the two baffle plates 7 ′ and 7 ″ each cover an area smaller than the transverse area of the steam head space 5, and the ends of the two baffle plates are Connected to the vertical plate 9 extending between the respective positions in the cylindrical wall of the steam head space 5 in the vertical and horizontal directions down from the top plate 4 to the lower baffle plate 7 ′.

  The gas pipe 3 extends from the bottom of the boiler, if possible, from the combustion chamber 14 shown in FIG. 2 through the heat exchange chamber 2 filled with water and the steam headspace 5, and the gas pipe 3 The gas extends through the holes of the top plate 4 through the plates 7 ′ and 7 ″, and the gas is discharged from the gas discharge port 11.

  The heat exchange between the gas pipe and the water produces steam entering the steam headspace 5 at the water surface, and the plate 7 'moves the steam to the left around the gap forming edge 12 as shown in FIG. As shown in FIG. 1, the gap between the two plates 7 ′ and 7 ″ is moved to the right around the gap forming edge 13, and the gap between the plate 7 ′ and the top plate 4 is moved to the steam outlet 6. As a result, the steam is moved in a direction transverse to the gas pipe 3 by a distance approximately twice the diameter of the boiler 1. A slight gap between the opening of the plates 7 'and 7 "and the gas pipe 3 is provided. Steam leakage would not be a problem because the steam in these small gaps is very close to the tube wall and is heated here. In order to provide sufficient heat exchange between the gas pipe and the steam flow, preferably more than half of the total steam in the flow in the headspace is along the flow path and across the gas pipe, preferably It is constrained to flow in a substantially orthogonal direction. The channel has a length at least equal to the diameter of the cylindrical wall when projected onto a horizontal plane. This feature distinguishes the present invention from the aforementioned US Pat. No. 1,546,665 where less than half of the steam flows at a distance equivalent to less than 3/4 of the diameter of the cylindrical wall.

  When the vapor leaves the water surface, it usually contains small water droplets, but due to the forced flow across the gas tube 3 at a relatively high flow velocity, the water droplets will collide with the gas tube 3 and evaporate. Furthermore, the relative high flow rate of the steam will provide heat exchange between the steam and the gas pipe in the steam headspace 5. Compared to the conventional boiler structure in which the steam in the open steam head space, without the plates 7 'and 7 ", mainly moves slowly in parallel with the gas pipe 3 from the water surface to the steam outlet. In addition, the heat exchange can be increased, and the distance between the water level and the top plate can be reduced, and usually the distance is used to avoid high concentration of water droplets in the steam exiting the steam outlet 6. Relatively large.

  When the water in the boiler 1 is not boiling, the water level in the boiler coincides with a level measured by a different conventional device, for example, a differential pressure between two known levels, a water level gauge or the like. However, the presence of a large amount of vapor bubbles in the water area will increase the actual water level seen in the boiler. And the water level will fluctuate more or less depending on the heat load and vapor pressure. The highest water level will be near the gas pipe 3. Therefore, the gas pipe is moistened to this level by water, and generally the water level is about 250 mm above the measured water level, hereinafter referred to as the water surface in the cooled state.

  The total height h of the steam head space 5 is the distance h1 between the top plate 4 and the first plate 7 "and the distance h2 between the first plate 7" and the second plate 7 '. Finally, it is subdivided into a distance h3 between the second plate 7 'and the water surface in the cooled state.

  In a preferred embodiment, the steam flow rate between the top plate 4 and the first plate 7 ″ is about 10-15 m / s and the steam flow rate between the two plates 7 ′ and 7 ″ is The distances h1 and h2 are dimensioned in such a way that about 20-30 m / s, ie the distance h1 is about twice the distance h2. Under all circumstances, the distance h3 should be sufficient to ensure that the actual water level should be about 200 mm below the second plate 7 'during boiling at full load.

  In the steam head space, as described above, the steam flow perpendicular to the gas pipe 3 is relatively fast between the two plates 7 ′ and 7 ″ and slightly between the top plate 4 and the plate 7 ″. slow. And even between the water surface and the plate 7 ′ there will be some intersecting flow with respect to the gas pipe 3. The steam flow rate provides high heat exchange efficiency from the gas pipe 3 to the steam as compared to the conventional situation where the steam headspace 5 delivers steam at a low speed and is substantially parallel to the pipe. . In practice, the heat exchange is close to a similar heat exchange present in the heat exchange chamber 2 filled with water in which water is in direct contact with the gas pipe 3.

  The generated steam is not only free of water droplets upon exiting the boiler from the steam outlet 6, but is actually superheated. This overheating results in no salt in the boiler and no deposits in the steam pipe from the boiler to the user. Furthermore, the available steam outlet valve after the steam outlet can be dimensioned to a higher steam flow rate, which can reduce the size of the valve, i.e. reduce the space, weight and cost of the steam outlet valve. Means that. Furthermore, the total heat transfer surface can be reduced due to increased heat transfer, which means that the tube length, number of tubes, boiler height and the weight and cost of the boiler can be reduced.

The following table shows the process data of the gas pipe steam boiler according to the present invention.

The following table compares the conventional sized gas tube steam boiler shown as standard with the gas tube steam boiler according to the present invention shown as new. The two boilers were designed to have similar steam capacity, thermal efficiency (ie similar fuel gas outlet temperature) and similar pressure drop.

  The direct result from the use of the present invention shows that about 40% (about 240 kg) of the tube can be saved in the standard boiler design. Furthermore, the tube length and the corresponding boiler height are shortened by 520 mm, and accordingly the boiler diameter is 1300 mm and the plate thickness is 12 mm, providing a difference in plate weight of about 200 kg.

  Although the present invention has been described above with reference to preferred embodiments, many improvements can be envisaged without departing from the following claims. In such a modification, the omission of the second plate 7 ′ results in a simpler structure, but the majority of the steam in the steam flow in the steam head space 5 has the same length as the diameter of the boiler 1. It still provides a steam flow from the water surface through the steam headspace 5 to the steam outlet 6 in such a way that it is constrained to flow in a direction across the gas pipe along the path. This possibility is illustrated in FIG. 4 and the preferred embodiment described above is schematically illustrated in FIG. Another possibility as shown in FIGS. 6 and 7 is the above, restrained by a first plate having a hole in the center for vapor passage and a second plate above the first plate. Provide a steam flow from the water surface to the steam outlet. The second plate then provides an annular opening along the boiler wall, the steam flow first abruptly outward and then suddenly towards the steam outlet 6 installed in the center. Limited to flow across the gas line.

  In the embodiment of FIG. 7, the steam flow is limited to a spiral flow path by a spirally shaped plate placed between a central tube and the boiler outer wall, and the steam flow path Also has a length that matches at least the distance between the two opposite sides of the wall of the boiler 1.

Claims (31)

Providing a gas pipe steam boiler,
The gas pipe steam boiler is
A heat exchange chamber filled with water forming the water surface;
A steam headspace defined by a cylindrical wall and a top plate on the water surface, the axis of which is substantially vertical;
A steam outlet connected to the steam head space;
One or more gas pipes extending through the heat exchange chamber and the steam headspace;
With
And supplying a heated gas to the gas pipe to generate a steam flow from the water surface by heat exchange between the gas pipe and the water in the heat exchange chamber,
More than half, preferably substantially all, of the vapor in the flow in the headspace when projected onto a horizontal plane, the first point of the wall and the second of the wall opposite the first point in the horizontal direction. The steam flow is constrained to flow along a flow path having a length at least equal to a minimum distance between the points and transversely to the gas pipe, preferably substantially orthogonal. Flowing through the steam headspace from the water surface to the steam outlet,
The minimum distance is the diameter of the cylindrical wall, if the wall is cylindrical,
A steam generation method characterized in that residual heat in the gas pipe is transmitted to the steam flow. The steam generation method according to claim 1,
The steam generation method, wherein the residual heat in the gas pipe is transmitted to the steam flow to the extent that all steam flowing out from the steam space through the steam outlet is superheated. The steam generation method according to claim 1 or 2,
A steam generation method, wherein the horizontal projection length of the flow path is at least twice the minimum distance. In the steam production method according to any one of claims 1 to 3,
Steam generating method, characterized in that the steam outlet is located away from the axis of the wall, preferably near or in the wall. In the steam production method according to any one of claims 1 to 4,
The horizontal projection of the flow path passes through the axis from the first point of the wall or from the first point, and near the second point of the wall or the second point on the opposite side of the first point. A steam generation method characterized by extending to a point. The steam generation method according to claim 5,
The steam generation method according to claim 1, wherein the horizontal projection of the flow path returns from the second point or at least halfway back to the first point. The steam generation method according to claim 6,
Steam generation characterized in that the flow velocity of the steam flow is lower when flowing from the second point to the first point than when flowing from the vicinity of the first point to the second point. Method. The steam generation method according to claim 7,
The steam flow velocity is about 10-15 m / s when flowing from the second point to the first point, and preferably about when the flow from the vicinity of the first point to the second point. 15-30 m / s, More preferably, it is 15-25 m / s, The steam generation method characterized by the above-mentioned. In the steam production method according to any one of claims 1 to 8,
The heated gas is
a) Combustion chamber
b) Gas turbine or
c) an internal combustion motor,
d) For example, an engine fueled with gas or oil for ship propulsion, power production, heating process, industrial and power plant,
A steam generation method characterized by being supplied from any of the above. A heat exchange chamber filled with water forming the water surface;
A steam headspace defined by a cylindrical wall and a top plate on the water surface, the axis of which is substantially vertical;
A steam outlet connected to the steam head space;
One or more gas pipes extending into the heat exchange chamber and the steam head space; and for generating a steam flow from the water surface by heat exchange between the gas pipe and the water in the heat exchange chamber; Means for supplying heated gas to the gas pipe;
A steam flow conduit disposed in the steam head space for directing the steam flow from the water surface to the steam outlet;
The vapor flow path, at least one of the gas pipes extends across the vapor flow path so that the vapor flow flows transversely, preferably substantially perpendicular to the gas pipe,
The configuration of the steam flow path is such that more than half of the steam in the steam flow, preferably substantially all of the first and second points of the wall are horizontally opposite when projected onto a horizontal plane. Being constrained to flow along a flow path having a length at least equal to a minimum distance between the second point of the wall;
The gas pipe steam boiler according to claim 1, wherein, when the wall is cylindrical, the minimum distance is a diameter of the cylindrical wall. The gas pipe steam boiler according to claim 10,
A gas pipe steam boiler, characterized in that the steam outlet is located in the top plate near the wall, away from the axis of the wall. The gas pipe steam boiler according to claim 10 or 11,
The steam flow path includes a substantially horizontal first plate, and the first plate is disposed at a distance in a vertically downward direction h1 of the top plate, and a first plate between the first plate and the wall. A gas pipe steam boiler having a first gap forming edge disposed away from said wall to provide a single steam flow gap. The gas pipe steam boiler according to claim 12,
The steam flow path includes a substantially horizontal second plate, and the second plate is disposed at a distance in the first vertical downward direction h2, and between the second plate and the wall. A gas tube steam boiler having a second gap forming edge disposed away from said wall to provide a second steam flow gap. The gas pipe steam boiler according to claim 13,
The gas pipe steam boiler according to claim 1, wherein the first gap and the second gap are disposed opposite to each other with respect to the axis. The gas pipe steam boiler according to any one of claims 12 to 14,
The gas pipe steam boiler according to claim 1, wherein the steam outlet is disposed in the vicinity of or in the wall opposite to the first gap with respect to the shaft. In the gas pipe steam boiler according to any one of claims 13 to 15,
The flow velocity of the steam flow is higher than the flow velocity in the portion of the conduit installed between the first and second plates, the flow velocity in the portion of the conduit installed between the top plate and the first plate. The gas pipe steam boiler is characterized in that the distance h1 is larger than the distance h2 so as to be lower. The gas pipe steam boiler according to claim 16,
A gas pipe steam boiler, wherein all of the gas pipes extend through the first and second plates. In the gas pipe steam boiler according to any one of claims 13 to 17,
The water surface when the water is in a cooled state is installed at a distance in the vertical downward direction h of the top plate,
The distance h1 is about 15 to 25%, preferably 18 to 22% of the distance h, and the distance h2 is about 7 to 13%, preferably 8 to 12% of the distance h. Gas pipe steam boiler to do. The gas pipe steam boiler according to any one of claims 12 to 18,
The first and second plates have an area smaller than the cross-sectional area of the steam head space;
Gas pipe steam characterized in that the ends of the first and second plates extending from the first and second gap forming edges respectively are interconnected with a top plate by vertical plates to form a tube. boiler. The gas pipe steam boiler according to any one of claims 12 to 19,
The first plate has an area smaller than the cross-sectional area of the steam head space;
A gas pipe steam boiler characterized in that ends of the first plates extending from the first gap forming edge are interconnected by vertical plates to form a tube. In the gas pipe steam boiler according to any one of claims 12 to 20,
A gas pipe steam boiler, wherein the first and second plates are substantially rectangular. A heat exchange chamber filled with water forming the water surface;
A steam headspace defined by a cylindrical wall and a top plate on the water surface and having a substantially vertical axis;
A steam outlet connected to the steam head space;
One or more gas pipes extending through the heat exchange chamber and the steam headspace;
Means for supplying heated gas to the gas pipe to generate a steam flow from the water surface by heat exchange between the gas pipe and the water in the heat exchange chamber;
A steam flow conduit disposed in the steam head space for directing the steam flow from the water surface to the steam outlet;
The steam flow conduit is
The first plate is disposed at a distance in the vertically downward direction h1 of the top plate and spaced apart from the wall to provide a first vapor flow gap between the first plate and the wall. A gas pipe steam boiler comprising a substantially horizontal first plate having a gap forming edge. The gas pipe steam boiler according to claim 22,
The steam flow guide path includes a substantially horizontal second plate, and the second plate is disposed at a distance in the vertical downward direction h2 of the first plate, and the second plate and the wall A gas pipe steam boiler having a second gap forming edge disposed away from said wall to provide a second steam flow gap therebetween. The gas pipe steam boiler according to claim 23,
The gas pipe steam boiler, wherein the first gap and the second gap are disposed opposite to each other with respect to the axis. 25. A gas pipe steam boiler according to any one of claims 22 to 24,
The gas pipe steam boiler according to claim 1, wherein the steam outlet is disposed in the vicinity of or in the wall opposite to the first gap with respect to the shaft. In the gas pipe steam boiler according to any one of claims 23 to 25,
A distance such that the flow velocity of the steam flow is lower in the portion of the conduit between the top plate and the first plate than the flow velocity of the portion of the conduit between the first and second plates. A gas pipe steam boiler characterized in that h1 is larger than the distance h2. A gas pipe steam boiler according to any one of claims 23 to 26,
A gas pipe steam boiler, wherein all of the gas pipes extend through the first and second plates. 28. A gas pipe steam boiler according to any one of claims 23 to 27,
The water surface when the water is in a cooled state is installed at a distance in the vertical downward direction h below the top plate,
The distance h1 is about 15 to 25%, preferably 18 to 22% of the distance h, and the distance h2 is about 7 to 13%, preferably 8 to 12% of the distance h. Gas pipe steam boiler to do. A gas pipe steam boiler according to any one of claims 22 to 28,
The first and second plates have an area smaller than the cross-sectional area of the steam head space;
A gas pipe steam boiler characterized in that ends of the first and second plates extending from the first and second gap forming edges are interconnected by vertical plates to form a tube. A gas pipe steam boiler according to any one of claims 22 to 29,
The first plate has an area smaller than the cross-sectional area of the steam head space;
A gas pipe steam boiler, characterized in that the ends of the first plate extending from the first gap forming edge are interconnected by vertical plates to form a tube. The gas pipe steam boiler according to any one of claims 22 to 30,
A gas pipe steam boiler, wherein the first and second plates are substantially rectangular.

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