FI126903B - Thermal device, its use and method for heating the heat carrier - Google Patents

Description

A thermal device, its use and a method for heating a heat transfer medium

Object of the invention

The invention relates to thermal devices, such as gasification reactors and combustion boilers, in particular fluidized bed boilers, such as fluidized bed boilers. The invention relates to thermal devices for heating a heat transfer medium. In particular, the invention relates to thermal devices for heating a heat transfer medium, such as steam, to very high temperatures.

Background of the Invention

Combustion boilers are used to burn combustible material and thus produce energy such as heat. The heat is recovered from the boiler surfaces to a heat transfer medium such as water and / or steam. Hot steam can be used to generate electricity, for example by steam turbines.

The efficiency of energy production is improved when the temperature of the heated heat transfer medium is raised. However, there are some challenges in raising the temperature. Raising the temperature will inevitably raise the temperature of the outer surfaces of the heat transfer pipes. Since corrosive substances such as salts are condensed on surfaces and temperature rise generally accelerates chemical reactions, corrosion is significantly accelerated due to temperature rise.

In addition, to produce a special hot heat transfer medium, the heat transfer tube for recovering heat should be in a very hot environment. The pressure inside the heat transfer tube is usually considerable (such as tens of bars, typically above 30 bar); for example, pressure and temperature may correspond to saturated vapor pressure, at least at low temperatures. At higher temperatures, the vapor is generally superheated, whereby its temperature is higher than that of the saturated vapor at the corresponding pressure, or the critical point of the heat transfer medium, the critical temperature, is exceeded (with water at 374 ° C). The heat transfer tube used in such a hot environment must withstand the pressure inside the tube and the stresses of the corrosive environment outside the tube. Heat transfer tubes that are resistant to corrosion in hot environments and high pressures are typically very expensive solutions.

WO 2006/070075 discloses corrosion protection for a heat exchanger tube and a method for reducing corrosion. US 4177765 discloses flagged bushings in a fluidized bed boiler. Heat exchanger tubes are provided inside the sleeves, and by flagging the sleeves, the heat transfer efficiency can be adjusted. JP 2001330207 discloses a heat exchanger tube passage to a gas duct. The lead-through is designed such that its structure receives thermal stresses. WO 2008/111885 discloses a heat exchanger tube shield. The cover consists of two interconnected parts.

Summary of the Invention Ivhvt

It is an object of the present invention to provide a thermal device, such as a gasification reactor or a combustion boiler, which makes it possible to heat the heat transfer medium to a high temperature while still using conventional materials.

In one embodiment, the thermal device comprises - at least a first wall defining a gas flow passage, and - a heat exchanger tube comprising at least an inner tube from which a first portion of at least a heat exchanger tube is disposed in said gas flow passage and extending from said first wall in said gas flow passage or to another wall defining a gas flow passage, and - said first portion of the heat exchanger tube comprises a second portion of the heat exchanger tube extending in said gas flow passage.

In the thermal device, the second portion of the heat exchanger tube comprises o at least a portion of an inner tube for transferring heat transfer medium from one end to the other end and recovering heat to the heat transfer medium, o an outer tube radially surrounding said portion of the inner tube and o and - said second portion of the heat exchanger tube extends directly or bends less than 90 degrees.

In addition, (A) - the inner tube of the first section of said heat exchanger tube is uninsulated from the gas flow passage in one or more uninsulated areas such that - all points in the uninsulated areas of the first section of the heat exchanger tube are not more than 15 cm apart; or (B) - the inner tube of the first portion of said heat exchanger tube is insulated along its entire path from the gas flow passage by said outer tube and / or insulation.

The thermal device can be used, for example, to heat steam. In one embodiment of the thermal device, the heat transfer medium is allowed to flow in said inner tube, - steam is used as the heat transfer medium, and - the temperature of the heat transfer medium flowing in the inner tube is at least 500 ° C, preferably at least 530 ° C.

The thermal device can be used to heat the heat transfer medium so that the surface temperature of one of the heat exchanger tubes during operation is remarkably high. In this way, the condensation of the corrosive substances on the pipe surface is prevented or at least reduced. In one embodiment, the temperature of the outer surface of the outer tube is greater than 600 ° C.

In addition, in the combustion boiler shown, the use of combustion additives is enhanced when the means for supplying the additive are located at a location where the operating temperature is typically good for feeding the additive.

Using a thermal device leads to a method. In a corresponding method for heating the heat transfer medium: - producing a gas heated by a thermal device, - introducing said gas into a gas flow passage, - introducing a heat transfer medium into a heat exchanger tube comprising at least a flow channel to the same wall or another wall, said first portion of the heat exchanger tube comprising a second portion of the heat exchanger tube extending in said gas flow channel, and - recovering heat to the heat transfer medium by means of the heat exchanger tube.

In the method, the second portion of the heat exchanger tube comprises o at least a portion of an inner tube for transferring heat transfer medium from a first end to a second end of a portion of the inner tube and recovering heat to the heat transfer medium, o an outer tube radially surrounding and - said second portion of the heat exchanger tube extends directly or bends less than 90 degrees.

In addition, (A) - the inner tube of the first portion of said heat exchanger tube is uninsulated from the gas flow passage in one or more uninsulated areas such that - all locations of all non-insulated regions of the first portion are not more than 15 cm apart; or (B) - the inner tube of the first portion of said heat exchanger tube is insulated along its entire path from the gas flow passage by said outer tube and / or insulation.

Description of the drawings

Figure 1a is a side view of a thermal device,

Figure 1b is a side view of a thermal device,

Figure 1c is a side view of a thermal device,

Figure 1d is a side view of a thermal device,

Figure 1e is a side view of a thermal device,

Fig. 1f is a side view of a thermal device, Figures 1g1-1g4 are cross-sectional views of a heat exchanger tube, at various points within the gas flow path of a thermal device, Figures 1h1-1h3 show a straight and curved second portion of a heat exchanger tube, Figure 1i in profile,

Figure 2 is a side view of a thermal device,

Figure 3a is a more detailed side view of the first region of a wall of a thermal device,

Figure 3b is a plan view of the wall area of Figure 3a, seen from above,

Figure 4a is a plan view of a wall area and a housing viewed from above,

Figure 4b is a plan view of a wall area and a housing viewed from above and

Figure 5 is a side view of a heat exchanger, i.e. a superheater tube arrangement or superheater.

Detailed Description of the Invention

Thermal devices are used to generate energy, such as electricity and / or heat, and / or fuel from combustible materials such as municipal waste and / or bio-based raw materials such as wood-based raw materials. For example, a thermal device may refer to a boiler in which combustible material is burned to produce energy. Combustion boilers can be classified according to the material to be burned. the following combustion boilers: recovery boiler (for black liquor burning), oil boiler, coal boiler, dust incinerator and waste boiler (in power plant). Combustion boilers can be classified according to the design of the boiler. combustion boilers such as a fluidized bed boiler such as a circulating fluidized bed boiler (CFB) and a bubbling fluidized bed boiler (BFB), a grate boiler, a water-tube boiler, and a fire tube boiler. For example, a thermal device may refer to a gasification reactor in which combustible material is oxidized to produce synthesis gas. Synthesis gas can be further processed into a fuel such as biofuel. For example, a thermal device may mean a pyrolysis reactor in which combustible material is pyrolysed to produce a pyrolysis oil. Pyrolysis oil can be further refined. Still further, a thermal device may mean a torrefaction reactor in which combustible material is heat treated to evaporate water and light hydrocarbons from the combustible material. The combustible material so treated can be used as fuel in subsequent processes. Similarly, a thermal process refers to a process in which energy and / or fuel is generated. Following the reactors described above, the thermal process may be, for example, a combustion, gasification, pyrolysis or torrefaction process. The combustible material referred to above may be, for example, a biological material of biological origin such as wood.

An example of thermal devices and their use is mentioned here. Combustion boilers are used to burn combustible material and thus produce energy such as heat. The heat is recovered from the boiler surfaces to a heat transfer medium such as water and / or steam. Hot steam can be used to generate electricity, for example by steam turbines.

Another example of thermal devices and their use is the gasification reactor. The gasification reactors are used to oxidize combustible material under low oxygen conditions to produce synthesis gas. Heat can be recovered from the synthesis gas. The heat is recovered from the thermal surfaces of the gasification reactor to a heat transfer medium such as water and / or steam. Hot steam can be used to generate electricity, for example by steam turbines.

A third example of thermal devices and their use is pyrolysis reactors. In these, pyrolysis vapor is formed and can be condensed. In condensation, heat can be recovered as described above.

The efficiency of energy production is improved when the temperature of the heated heat transfer medium is raised. The heat transfer medium is usually water and / or steam. In this specification, steam also refers to steam whose temperature exceeds the temperature of the critical point of water (373 ° C), such steam sometimes being referred to as gas because po. at temperature the steam cannot be liquefied to water by increasing the pressure.

Thermal devices such as combustion boilers comprise walls defining, for example, a furnace, a gasification reactor gasification stage and / or various gas channels such as flue gas channels, synthesis gas channels or pyrolysis-steam channels. For example, the term "wall" may refer to a reactor wall or ceiling. The thermal devices further comprise heat exchangers for recovering the heat generated in the reactions. The surface temperature of the heat exchanger during operation significantly affects the surface corrosion of the heat exchanger. Roughly speaking, if said surface temperature is low, the gases will condense the corrosive substances to solids. At low temperatures, solids do not significantly corrode surfaces. On the other hand, if said surface temperature is high, significant amounts of corrosive substances do not condense in the gases, whereby the corrosion is also quite slow. There is an area where corrosive substances are condensed from the gases into liquid substances on the heat surfaces, whereby corrosion is very rapid. The values of these temperatures will be described in more detail later. Raising the surface temperature of the heat exchanger pipe is very challenging because the pipe at its operating temperature must withstand the pressure inside.

The present invention is illustrated in the accompanying drawings. 1a and 1g1 show a thermal device comprising - at least a first wall 112 defining a gas flow passage 115 and - a heat exchanger tube 200 comprising at least an inner tube 210 of which heat exchanger tube at least a first portion 202 of the heat exchanger tube is disposed in said gas flow passage 115 and extending in said gas flow passage 115 from said first wall 112 to said first wall 112 or a second wall 114 (Figures 1a to 1e) defining a gas flow passage, and - said first heat exchanger tube portion 202 comprising a second heat exchanger tube portion 240 in the flow passage 115. Thus, here, the "heat exchanger tube" refers to a possibly long pipe, the (at least one) first portion 202 of which is located all along its path in the gas flow passage 115. Accordingly, the first portion 202 n a continuous piece of pipe as continuous as possible in the flow duct, i.e., a part extending from wall to wall (to one or another wall). The second portion 240 of the heat exchanger tube, said first portion 202, is a shielded solution in which the outer tube 220 protects the inner tube 210. The second portion 240 may be shorter than or equal to the first portion 202. Fig. 1g1 illustrates the construction of another portion 240 of such a heat exchanger tube.

Referring to Fig. 1g1, in the embodiments shown, the second portion 240 of the heat exchanger tube comprises o at least a portion of the inner tube 210 for transferring heat transfer medium from the first end to the second end of the inner tube and recovering heat to the heat transfer medium between said outer tube 220 and a portion of said inner tube 210. Such a structure has the advantage that, due to the medium layer 230, the surface temperature of the outer tube 220 is so high in operation of the thermal device that there is no significant condensation of corrosive substances on its surface. Such a layer-shaped tube is heavier than a single-layer tube. Further, it has been found that if the layered tube is bent, the outer tube will come into contact with the inner tube, causing the aforementioned media layer to be absent. the bent portion. In the absence of a medium layer, heat is too well drawn from the outer tube to the inner tube, which lowers the surface temperature of the outer tube to a critical area for corrosion, at least when the present solution is used under hot conditions and hot heat transfer medium. In addition, a relatively straight tube is more easily self-supporting than a highly curved tube. For these reasons - said second portion 240 of the heat exchanger tube extends directly or bends less than 90 degrees.

The function of the outer tube 220 is e.g. protecting the inner tube 210. It is possible that, in addition to the outer tube 220 (Figures 1c and 1g4) or alternatively to the outer tube 220 (Figures 1b and 1g2 and 1g3), at least at some points in the gas flow passage,

Furthermore, it is possible that at a point where the temperature in the flow channel 115 is otherwise low, the inner tube is not protected at all; neither with insulation nor with outside pipe. Such locations are typically located near thermal surfaces such as walls 112, 114. Here, too, the inner tube 210 is shielded almost the entire distance it is in the gas flow passage 115. Thus, in some embodiments (A), the inner tube 210 of the first portion 202 of said heat exchanger tube is partially insulated from the gas flow passage 115 by said outer tube 220 and / or the inner tube 210 of the first section 202 of said heat exchanger tube being uninsulated from the gas flow passage 115 in one or more uninsulated regions 270 (Fig. 1i) such that (A1) - the largest non-insulated region 270 of the first section 202 does not exceed 15 cm; preferably, the length of the largest non-insulated region 270 does not exceed 10 cm, where the length is measured in the longitudinal direction of the inner tube 210; or (A2) - all points in the non-insulated regions 270 of the first portion 202 are not more than 15 cm from other thermal surfaces (other than the heat exchanger tube 200 itself) of the thermal device; preferably up to 10 cm; or (B) - the first portion 202 of the said heat exchanger tube or the inner tube 210 of the first portion 202 is insulated over the entire distance from the gas flow passage 115 by said outer tube 220 and / or insulator 260 (Figures 1a - 1f).

Referring to (A, A1 and A2) and Figure 1i, preferably the first portion 202 comprises at most two such uninsulated areas 270 (one at each end) and all uninsulated regions 270 (either alone or both) extend from the wall (112, 114) of the thermal device 100. ) to the flow passage 115.

Point (A2) is also a possible solution, since typically the temperature of the gases in the flow passage 115 near the thermal surfaces is lower than the temperature of the gases far from other thermal surfaces. The heat exchanger tube may also extend in the flow passage 115 in the vicinity of the heat surface or parallel to the heat surface or substantially parallel to the heat surface. Typically, the heat exchanger tube extends substantially perpendicular to the wall (Figure 1 i).

Even more preferably, the first portion does not comprise any non-insulated region 270 (Figure 1a-1f), whereby the inner tube 210 is protected over the entire distance it is in the gas flow passage 115 (see paragraph B above).

An embodiment of the present invention is illustrated in Figure 1a. The thermal device 100 of Fig. 1, such as a combustion boiler, comprises: - a first wall 112 (wall illustrated) comprising a first region 122 of the boiler wall, - a second wall 114 (wall illustrated) comprising a second region 124 of the boiler wall; ; such as (a) burning the material of the furnace 110 and generating the flue gases, or (b) oxidizing the raw material of the gasification and synthesis gas, wherein - at least said first wall 112 of the thermal device delimits the gas flow passage 115 Between the second region 124 of the wall 100, a portion of the flue gas flow passage 115 remains.

In the device of Figure 1a, said gas flow passage 115 is rectangular in cross-section, wherein the thermal device 100 comprises four walls. The invention is also applicable to thermal devices in which the gas flow channel is of circular cross-section. Such a thermal device 100 comprises only a first wall 112. Further, if the heat exchanger tube 200 extends through the passage 115, the first wall 112 of the device further comprises a second wall region 124 into which the heat exchanger tube 200 (at least its inner tube 210) extends. Thus, generally, the thermal device only optionally comprises a second wall 114. Preferably, the thermal device comprises at least four walls defining a gas flow passage 115. In the embodiment of Figure 1a, the thermal device 100 comprises a second wall region 124 comprising said second wall 114.

Figure 1a further shows the feed gas supply passage 104. The combustion air can be supplied to the combustion boilers by the supply passage 104. For example, oxygenation and / or water vapor may be fed to the gasification plants to gasify the feedstock. For example, in an incinerator, combustion air is supplied through a duct 104 and through a grate 102 to a furnace 110. Preferably, the incinerator 100 is a fluidized bed boiler such as a fluidized bed boiler or a circulating fluidized bed boiler; preferably a fluidized bed boiler. In a fluidized bed boiler, such as a fluidized bed boiler, the combustion air causes the solid and combustible material in the fire chamber 110 to be fluidized, i.e. forming a fluidized bed.

Referring still to Fig. 1a, heat can be recovered in the boiler 100 by primary superheaters 152 in post-furnace smoke salt 160. Heat can be recovered by superheaters 156 in the top of the furnace 150, e.g. , for cleaning or finishing, is illustrated by arrow 175. The combustion boiler 100 may also comprise a cam 180 for controlling the flue gases and protecting the tertiary sprinklers 156, for example, from direct radiant heat. 1a, the beak 180 is drawn in dashed lines to illustrate that the boiler 100 does not necessarily comprise the beak 180. In FIG. flow (and during use) from the primary superheater 152 to the secondary superheater 154 and thereafter to the tertiary superheater 156.

The combustion boiler of Figure 1a further comprises a heat exchanger tube 200 specially adapted for this purpose as described above. The first part 202 of the heat exchanger tube is arranged in the gas flow passage 115. In the case of Fig. 1a, the first part 202 of the heat exchanger tube consists of the second part 240 of the heat exchanger tube illustrated in Fig. 1g1. In other words, the sandwich second section 240 also extends along the entire flue gas passage 115.

As stated above, in one embodiment, the second portion 240 of the heat exchanger tube extends directly or bends less than 90 degrees. Preferably, the second portion 240 curves less than 45 degrees, less than 30 degrees, or less than 15 degrees.

Referring to Figures 1h1 to 1h3, the phrase "less than a degree of curvature" means that - said heat exchanger tube 200 extends with the second portion 240 extending in the flow passage 115, and - said second heat exchanger tube portion 240 having a first longitudinal direction S1 at its first point p1. The second portion 240 of said heat exchanger tube has at all its points p2 a longitudinal direction S2 that is parallel to or forms an angle less than said a degree with a second portion of said heat exchanger tube with a first longitudinal direction S1. Here, the longitudinal direction of the heat exchanger tube refers to the longitudinal direction of flow of the heat transfer medium. For example, in Fig. 1h1, the direction S2 of the heat exchanger tube is parallel to the direction S1, regardless of how points p1 and p2 are selected. Thus, in Figure 1h1, the second portion 240 of the heat exchanger tube extends directly.

For example, in Fig. 1h2, the direction S2 of the heat exchanger tube deviates from the direction S1, with certain choices of points p1 and p2, but is parallel with some other choices. However, regardless of how points p1 and p2 are selected, the angle α between directions S2 and S1 is less than 90 degrees. Thus, in Figure 1h2, the second portion 240 of the heat exchanger tube curves less than 90 degrees.

For example, in Fig. 1h3, the direction S2 of the heat exchanger tube differs from the direction S1 by certain selection of points p1 and p2. With the selection shown in the figure, the directions S2 and S1 are opposite, so the angle α is 180 degrees. Thus, in Figure 1h3, the second portion 240 of the tube curves more than 90 degrees.

1a, said heat exchanger tube 200 extends such that a second portion 240 of said heat exchanger tube extends from said first region 122 of the device wall to a second region 124 of said device wall such that said second portion 240 of the heat exchanger tube has a center axis at each point a radius of curvature of at least 25 cm, at least 50 cm, at least 1 m, at least 5 m, and most preferably at least 10 m.

Also, the large radius of curvature results in the bending of the layered tube between the outer tube 220 and the inner tube 210 at each point by a layer of medium 230. In addition, such a relatively straight tube is more easily self-supporting.

In one embodiment, the first region 122 of the device wall (such as a wall) is located opposite the second region 124 of the device wall, on the opposite side of the flow passage 115. In one embodiment, the first wall 112 of the device is opposite the second wall 114 of the boiler.

In one embodiment, the first region 122 of the boiler wall and the second region 124 of the boiler wall are in the same direction, or the angle between the planes in the region is less than 45 degrees, such as less than 30 degrees or less than 15 degrees. The wall areas may also be perpendicular, for example, if the first part of the heat exchanger tube extends between two angled walls.

The continuation of the second section 240 of the tube in the flow passage 115 may be described by one or more of: - the curvature of the second section 240, in particular the angle of curvature (angle?), And

For example, the second portion 240 may curve up to 45 degrees so that the radius of curvature is at least 1 m.

1a and 2, the heat exchanger tube portion 240 extends directly from said first boiler wall region 122 to said second boiler wall region 124. In this embodiment, the heat exchanger tube portion 240 has a longitudinal direction parallel to said first heat exchanger at all points. As discussed above, the heat exchanger tube 200 may curve in the flow passage 215; for example, less than 90 degrees, or according to the radius of curvature, but from a manufacturing point of view, bending is not preferred. From an engineering point of view, it is preferred that the inner tube 220 be slidable through the outer tube 220 in the longitudinal direction thereof. This is achieved, for example, when the outer tube 220 is straight.

As shown above and in Figure 1a, the first portion 202 may consist of a second portion 240. Referring to Figure 1b, the first portion 202 of the heat exchanger tube may not necessarily consist of a second portion of the heat exchanger tube. In the embodiment of Fig. 1b - thermal device 100 comprises an insulator 255 adjacent to the first wall 112 extending from said first region 122 of the device wall to a gas flow passage 115, - said insulator 255 adjacent to the first wall 112 is arranged to insulate at least inner tube 210 of heat exchanger 200 - thermal device 100 comprising an insulator 257 adjacent to a second wall 114 extending from said second region 124 of the device wall to a gas flow passage 115, - said second wall adjacent dielectric 257 arranged to insulate at least the heat exchanger tube 210 from the gas flow passage 115; extending from said insulator adjacent to the first wall of the device 255 to said insulator 257 adjacent to the second wall of the device. Such an insulated structure is illustrated in FIG. the sheer 210 is insulated only by the insulator 255, 257 adjacent to the (first or second) wall.

It will be appreciated that the dielectric may alternatively only be used with either one, for example the first wall (not shown). In this case - thermal device 100 comprises a wall adjacent insulation 255 extending from said first wall area 122 of the device wall to a gas flow passage 115, - said wall adjacent dielectric 255 arranged to insulate at least the heat exchanger tube 210 from the gas flow passage 115, and - said second heat exchanger tube portion 240 an insulator 255 adjacent to the device wall and to said second region 124 of the device wall.

Alternatively, it is possible, for example, that: - the thermal device 100 comprises a wall adjacent dielectric 255 extending from said first wall region 122 of the device to a gas flow passage 115, - said wall adjacent dielectric 255 arranged to insulate at least the heat exchanger tube 210 from the gas flow duct 115, the inner tube of the first section being uninsulated from the gas flow passage in one uninsulated region 270 such that: - said uninsulated region 270 extends from a second region 124 of the wall of the device to a gas flow passage 115;

Preferably, the length of the uninsulated region 270 is short as described above.

Referring to Figure 1c, it is possible that the heat exchanger tube comprises a bend, or a bend, possibly a steeper bend. However, as discussed above, it is very difficult to ascertain the local thermal conductivity of the sandwich tube, since the thickness of the medium layer 230 (Figures 1g1 and 1g4) is difficult to control. 1c, the heat exchanger tube comprises a first second part 240 and a second second part 240b. These second sections 240 and 240b are illustrated by the above-described features regarding the second section, such as straightness and sandwich structure. In this case, the heat exchanger tube comprises a thermally insulated part 250, in which part the first part 202 of the tube may bend even steeply. In the thermally insulated section 250, the dielectric 260 (Figures 1g3 and 1g4) may insulate the inner tube 210 alone from the gas flow duct 115 as in Figure 1g3, or the thermal duct 260 may insulate the outer duct 220 from the gas flow duct 115 as shown in Fig. In these embodiments - said first part 202 of the heat exchanger tube comprises a heat insulated part 250 in said gas flow passage 115 where the inner tube 210 is not surrounded by an outer tube in the heat insulated part 250 o and the inner tube 210 is thermally insulated by a gas duct 260; 1g3; or o the inner tube 210 is surrounded by an outer tube 220, and in said thermally insulated part 250, the outer tube 220 is thermally insulated by means of a thermal insulator 260 from the gases of the flow passage 115; 1g4.

As an insulator 255,257 adjacent to the wall and / or as an insulator 260 of the thermal insulating area 250, for example, collector, mortar, or putty may be used. The thermal conductivity κ of the insulator (255, 257, 260) is preferably less than 75 W / mK (W / m and Kelvin), more preferably less than 50 W / mK, or even more preferably less than 10 W / mK; wherein the thermal conductivity is given at room temperature of 20 ° C. For example, mortar can be used as insulation. For example, in this case, the thermal conductivity of the insulator (255, 257, 260) may be less than 2.5 W / mK. For example, some ceramics have a thermal conductivity of a few dozen W / mK, such as 60 W / mK for silicon carbide (SiC) and 32 W / mK for alumina (Al2O3), and 20 W / mK for silicon nitride (S13N4). The thickness t of the insulator (255, 257, 260) is preferably at least 0.5 mm, more preferably at least 1 mm, and more preferably at least 2 mm. If necessary, the ceramic coating may be thin. Preferably, when using mortar or putty, the coating is thicker. In this case, the outer surface of the heat exchanger tube may be provided with projections, such as pins, to hold the insulation in place. This can be done especially when fixing the insulator 255, 257 adjacent to the wall. In this case, the thickness of the insulation may be, for example, 10 mm to 30 mm. In one embodiment, the insulator 255, 257 adjacent to the wall is secured to the heat exchanger tube (outer tube or inner tube) by means of projections.

The insulator 255, 257, 260, for example a mass or ceramic, can be selected so that the insulator 260 is heat resistant and achieves the desired heat transfer level from the flow passage 115 to the heat transfer tube 200. The desired heat transfer level may depend on e.g. For example, thickness and thermal conductivity may be selected such that the thermal conductivity (i.e., conductance) of the dielectric layer, determined by thermal conductivity κ and thickness t by the formula κ / t, is not more than 80,000 W / m2K, more preferably not more than 30,000 W / m2K; where the thermal conductivity κ is given at room temperature 20 ° C. In addition, the insulation (255, 257, 260) must withstand temperatures corresponding to the operating temperature. Preferably (255, 257, 260) can withstand, without melting, burning above 900 ° C, such as above 1000 ° C; optionally, the insulation need not withstand temperatures above 1500 ° C.

Referring to Figure 1d, in one embodiment comprising a heat insulating region 250, the heat exchanger tube is po. area insulated by both insulation material and shield 252. The insulating material may be mortar or putty as described above. In addition, the shield 252 may, for example, serve as a heat-resistant, at least partially open top, such as a tray or box. From above, at least a partially open piece may be, for example, a metal trough or a box. The curved portion of the heat exchanger tube 200 may be arranged po. Such a solution is easy to implement, and furthermore, a top open piece 252 protects the insulating material 260 between the heat exchanger tube 200 and the piece 252.

Preferably, in such a curved insulating region 250, the heat exchanger tube 200 does not comprise an outer tube 220. This is because the heat exchanger tube is generally made of a straight tube by bending. Damage during bending, such as micro fractures, occurs at a particularly bending point. If the outer tube 220 is not used at the bendable point, the condition of the bent point of the inner tube 210 after bending is easier to ascertain than the condition of the structure where the inner tube 210 would remain inside the outer tube 220.

1a to 1c, in these embodiments - at least inner tube 210 extends from said first wall region 122 outside the gas flow passage 115, and - at least inner tube 210 extends from said second wall region 124 outside the gas flow passage 115.

1a to 1f, at least part of the heat exchanger tube 200, in particular the second part 240, is arranged in the gas flow conduit 115 defined by the walls 112, 114 and thus at least part po. a distance from the heat exchanger tube, particularly its second part 240, is provided from walls 112, 114. Such a distance may be, for example, more than 15 cm, such as more than 50 cm or more than 1 m. Typically, the combustion boiler comprises a plurality of heat exchanger tubes as described and / or parts thereof forming a heat exchanger, such as a superheater. However, the heat exchanger is not necessarily a separate unit housed in the flow passage 115, since the inner tube 210 may also extend outside the flow passage 115 due to the passageways located in the areas 122 and 124 of the wall (or walls). If the areas 122 and 124 are opposed or angular to each other, the distance between the areas 122 and 124 can be, for example, at least 0.5 m, such as at least 1 m, typically at least 2 m or at least 3 m. The spacing between, for example, may be from 1 m to 10 m, preferably from 3 m to 6 m. The short distance ensures sufficient stability of the structure, on the other hand, the long distance ensures sufficient heat recovery capacity. In these embodiments, the length of the second section 240 may also be as described above, for example from 1 m to 10 m, preferably from 3 m to 6 m. In these embodiments, the first portion 202 of the heat exchanger tube is subjected to significant shear forces since the tubes are substantially perpendicular to gravity.

Still other embodiments are illustrated in Figures 1d and 1e. In these embodiments, the first portion 202 of the heat exchanger tube curves 180 degrees but the curve is shielded by insulator 260, i.e., the first portion 202 of the heat exchanger tube comprises a thermally insulated portion 250 in said gas flow passage 115. Said thermally insulated portion 250 divides said first portion 202 into two : first second part 240 and second second part 240b. 1d and 1e, the first wall of the device is the ceiling of the device.

In the embodiment of Figure 1d, - said first wall 112 comprises a first region 122 of the device wall, and - thermal device 100 comprises an insulator 255 adjacent to the wall extending from said first region 122 of the device wall to a gas flow passage 115, wall insulator 255 up to said heat insulated part 250, and - said wall insulator 255 is arranged to insulate at least the inner tube 210 of the heat exchanger tube from the flow passage 115.

In the embodiment of Figure 1e, in turn, - said first wall 112 comprises a first region 122 of the device wall, and - said second portion 240 of the heat exchanger tube extends from said first region 122 of the device wall to said insulated portion 250.

In Figure 1f, the heat exchanger tube 200 comprises the first two parts; a first first portion 202a and a second first portion 202b. Each first portion 202a, 202b comprises a second portion, for example, the first first portion 202a comprises a first second portion 240 and a second first portion 202b comprises a second second portion 240b. In Fig. 1f, the roof of the structure acts as a first wall 112. The thermal device comprises a beak, and each first portion 202a, 202b extends from wall 112 to beak 180. Each first portion 202a, 202b comprises insulator 255, 257 adjacent the wall at each end. The second portions 240 and 240b extend between the insulators. Insulator 257 extends from cam 180 to the gas flow passage. The cam 180 forms a second wall 114.

In the embodiments of Figures 1d to 1f, the length of the second section 240 may be significantly longer than that described above. For example, the second portion may have a length of 1m to 25m, preferably 3m to 15m. In these embodiments, the first portion 202, 202a, 202b of the heat exchanger tube is not subject to significant shear forces since the tubes are oriented at a slight angle to gravity.

Preferably, and as shown in Figures 1a, 1e and 2, said second part 240, 240b of the heat exchanger tube extends from said first region of the device wall to said gas flow passage. This provides the advantage that at least the part adjacent to the wall of the heat exchanger tube is insulated from the gas flow passage by at least an outer tube. Outer tube 220 has been found to be a more durable and easier to maintain (e.g., replaceable) solution for corrosion protection than using insulator 255. Furthermore, the structure can then be mechanically strengthened by attaching, for example, welding, the outer tube to the wall. Such a structure has certain technical advantages.

First, the medium layer 230 thermally insulates the inner tube 210 from the outer tube 220. Thus, heat transfer from the outside to the inner tube 210 and further to the heat transfer medium is poor. Therefore, heat loss in such a tube occurs to a greater extent in the medium layer 230 than in the inner tube 210. Thus, even though the heat transfer tube 200 is placed in a very high temperature environment, the surface temperature of the heat exchanger tube 200 becomes too high. in terms of the design rules for the material of the inner tube. Similarly, if the temperature of the inner surface of the inner tube 210 is to be increased due to the desire to form a hotter heat transfer medium, the layer structure of Figure 1g1, particularly by adjusting the thickness of the intermediate layer 230, can ensure that the outer surface of the inner tube 210 does not rise too high. Since, during use, the inner tube 210 contains a heat transfer medium under pressure, the inner tube 210 must withstand a corresponding pressure. It is known that at high temperatures materials resist pressure less than at low temperatures. The above-mentioned "too high" temperature refers to the temperature at which the inner tube 210 can no longer withstand the pressure inside. Similarly, the fluid layer 230 does not need to withstand pressure because the inner tube 210 carries pressure. Furthermore, the outer tube 220 does not need to withstand pressure. In the gas flow passage, the first portion 202 of said heat exchanger tube or the inner tube 210 of the first portion 202 of said heat exchanger tube is insulated throughout or almost the entire distance of the gas flow passage by said outer tube and / or insulation. This prevents locally, for example, an uninsulated site, from raising the temperature of the inner tube to the prevailing pressure level. In addition, corrosion is prevented from condensing on the outer surface of the inner tube. The solution may comprise uninsulated regions 270 as shown above (Figure 1i). Preferably, however, such areas are only in the vicinity of other thermal surfaces, such as wall 112, 114. This has been described in more detail earlier. Preferably, all locations of all non-insulated regions 270 are not more than 15 cm from the thermal surfaces of the thermal device (except heat exchanger tube 200 itself); more preferably not more than 10 cm. At this point, the temperature of the gases in the flow channel 115 is typically significantly lower than in the center of the flow channel.

Secondly, the outer tube 220 protects its internal structures, i.e. the media layer 230, and the inner tube 210 from corrosion and mechanical wear. The outer tube 220 is preferably integral, whereby the outer tube effectively protects the media layer 230 and the inner tube 210 from mechanical wear. Such a continuous outer tube 220 is, for example, seamless. Further or alternatively, such a continuous outer tube 220 is, for example, perforated. Furthermore, the outer tube 220 may protect the dielectric layer 230 and the inner tube 210 over at least the entire flue gas flow passage 115. Thus, the second portion 240 of the tube preferably comprises an outer tube 220 which is continuous and continuous throughout. Even more preferably, such a second portion extends throughout the first portion 202.

Third, because of the high surface temperature of the outer tube 220 as described above, no corrosion promoting agents such as salts are condensed on its surface.

The same applies to the insulated area 250. Salts condense from flue gases to heat surfaces when their partial vapor pressure in the flue gas exceeds the saturated vapor pressure. The pressure of the saturated steam, on the other hand, depends significantly on the temperature. In the combustion process, salts in the vapor phase are formed in the flue gases in such quantities that condensation occurs, typically, for example, when the temperature of the heating surface is below 500 ° C, below 550 ° C, or below 600 ° C. Similarly, condensation does not occur if the surface temperature of the heating surface is higher. Preferably, during use, the temperature of the outer surface 220 of the heat exchanger tube 200 is at least 550 ° C, at least 600 ° C, or at least 650 ° C, such as about 670 ° C or more. In one use of a thermal device, - the heat transfer medium is allowed to flow in said inner tube such that - the outer surface temperature of the outer tube is above 600 ° C.

In addition, steam is preferably used as the heat transfer medium.

For uninsulated areas 270 near other thermal surfaces, it is noted that at lower temperatures, the corrosion problem is reduced for the reasons described above.

Fourth, the structure allows the use of fuels with a higher heavy metal or chlorine content than usual. As stated above, the temperature of the outer surface of the outer tube 220 rises due to the insulating layer 230. Thus, the condensation of heavy metals and / or chlorides (e.g., NaCl, KCl) on the outer surface of the outer tube 220 is prevented, or at least significantly reduced. Thus, it is possible to operate the boiler 100 for long periods of time for air maintenance, even if the heavy metal and / or chloride concentrations of the flue gases are higher than those of the known boilers. This further allows the use of said fuels in a boiler.

Fifth, although the layered structure of the heat exchanger tube 200 increases the mass of the heat exchanger tube 200, the disclosed structure carries the mass of the heat exchanger tube 200, since the second portion 240 of the heat exchanger tube 200 extends substantially in the same direction If the second portion 240 of the tube would bend in the flue gas flow passage 215, the other portion 240 of the heat exchanger tube would apply its relatively high torque support structures, or separate support structures should be installed in the flow channel 115. Due to this support, the length of the second portion 240 is preferably shorter, at least when the second portion is horizontal, as will be described below.

Preferably, the tubes 210, 220 have a circular cross-section. Such tubes are easy to manufacture and more resistant to pressure than other shapes.

For example, the inner tube 210 may have an inner diameter of 30 mm to 60 mm, such as 40 mm to 50 mm, preferably about 45 mm, such as 42 mm to 46 mm. For example, the inner tube shell may have a thickness of 4.5 mm to 7.1 mm. Shell thickness refers to the thickness of the tube wall, i.e. half of the difference between the outer diameter and the inner diameter. The inner tube 210 may comprise, for example, steel. The inner tube 210 may comprise, for example, ferrite or austenitic steel. Preferably, the inner tube 210 comprises austenitic steel. The thickness of the medium layer 230 is preferably 0.5 mm to 4 mm, such as 1 mm to 2 mm. The medium layer may comprise a solid, liquid or gaseous medium. The media layer may comprise at least one of the following gas (such as flue gas, air, synthesis gas, pyrolysis vapor), putty, and ceramic. Preferably, the media layer comprises putty, and the putty layer has a thickness of 1 mm to 2 mm. The kit may be selected, for example, so that the kit can withstand (e.g., unburned and / or melted) temperatures of at least 700 ° C; however, possibly temperatures up to 1000 ° C.

The inner diameter of the outer tube 220 is dimensioned according to the outer diameter of the inner tube 210 and the thickness of the media layer 230. Since the medium layer 230 may comprise gas, increasing the inner diameter of the outer tube 220 will increase the thickness of the insulating layer 230 if the outer diameter of the inner tube 210 is not increased accordingly. The inner diameter of the outer tube 220 may be, for example, 35 mm to 70 mm. The casing thickness of the outer tube 220 may be, for example, 4.5 mm to 7.1 mm. The outer tube 220 may comprise, for example, steel. The outer tube 220 may comprise, for example, ferrite or austenitic steel. Preferably, the outer tube 220 comprises austenitic steel.

Typically, in a thermal device such as a combustion boiler, the temperature depends on the location, and in particular the height came from the body 110. 1a-1c and Fig. 2 - the first part 202 of the heat exchanger tube is horizontal, or the longitudinal direction of said first part 202 forms an angle less than 30 degrees with the horizontal at each of its points. The angle may also be, for example, less than 20 degrees, less than 10 degrees, or less than 5 degrees. The term "horizontal" means a horizontal line, such as a horizontally curved tube or a horizontal tube. The term "each point" specifies that the longitudinal direction of the tube depends on the viewing point if the tube is not straight. This provides the advantage that the outer tube 220 of the second part 240 of the entire heat exchanger tube is then substantially at the same temperature. The vertical positioning of the second portion 240 ensures that the entire outer tube is at the same, sufficiently high temperature for condensation to corrode. When the second portion 240 of the entire heat exchanger tube 200 is at substantially the same temperature, dimensioning the structure to allow for the production of a hot heat transfer medium on the one hand and not to exceed or under 1 e) or in another direction (Figure 1 f). It should be noted that even though one portion 240 (or other portions 240, 240b) is horizontal, the portion 200 of the conduit 200 outside the flow passage 115 may be in the other direction, such as vertical, as shown in Figure 2.

In a preferred embodiment, the first portion 202 of the heat exchanger tube 200 is, for example, less than 6 m in length, wherein the first portion 202 of the heat exchanger tube 200 is also self-supporting in the horizontal direction. Self-supporting means a structure which is supported only at its ends. Thus, separate support structures for the first pipe section 202 are not required in the flue gas flow passage 115. The heat exchanger tube 200, in particular the inner tube 210, is supported in the first and second regions (122, 124), from which the inner tube is passed through the wall or walls. Preferably, the first portion 202 has a length of up to 5 m, and more preferably up to 4.5 m. To provide sufficient heat transfer power, the first portion 240 is preferably at least 1 m, such as at least 2 m, and more preferably at least 3 m. 4 m. What is said here about the length of the first portion 202 also applies to the length of the second portion 240.

Also, in the self-supporting structure, the heat exchanger tubes 200 or portions thereof need not be supported with one another in the flue gas flow passage 115. In one embodiment, the first heat exchanger tube portion 202 extends freely in the flow conduit 115. In this case, the heat exchanger tube portion 202 the ceiling of the thermal device 100, the second heat exchanger tube 200, the second first portion 202b of the same heat exchanger tube 200, or the second second portion 240b of the same heat exchanger tube 200. Such a freely continuous structure is easier to manufacture in terms of manufacturing technology than the supported structure. In addition, the freestanding structure has no support structures that conduct heat to the heat exchanger tube. The presence of support structures would further complicate the design of the appropriate operating temperature and the maintenance of the thermal device.

With the disclosed solution, it is possible to raise the temperature of the outer surface of the heat exchanger tube 200 µl of the co-tube 220 so that no corrosive substances such as heavy metals and / or alkali salts, in particular sodium chloride (NaCl) or potassium chloride (KCl), condense thereon. During operation, the temperature of the outer surface of the tube 200 is preferably high, as described above. Similarly, during use, the temperature of the heat transfer medium, such as steam, flowing inside the inner tube 210 is, for example, at least 500 ° C, such as at least 530 ° C, and preferably at least 540 ° C. In one use of the thermal device: - the heat transfer medium is allowed to flow in said inner tube 210, - steam is used as the heat transfer medium, and - the heat transfer medium flowing in the inner tube 210 is at least 500 ° C, preferably at least 530 ° C. For such use, the temperature of the inner tube 210 is, for example, between 500 ° C and 700 ° C, and preferably between 500 ° C and 600 ° C. To achieve these values, some dimensions have been presented above. Further, in one embodiment of the thermal device 100, the heat exchanger tube of the invention is positioned relative to other heat transfer tubes and flow directions so that said temperature values are met. In some embodiments, the first portion of the heat transfer tube described is located in a desired temperature zone in the thermal device 100, selecting for said first tube portion 202 the desired elevation in the thermal device 100, such as a boiler.

Figure 2 illustrates an advantageous way of selecting said desired elevation and positioning the first portion 202 of the heat exchanger tube. In this embodiment, the thermal device 100 comprises a plurality of other heat transfer tubes, such as superheaters 154 and 156, to recover heat inside the walls of the gas flow passage 115, the other heat transfer tubes (154, 156) forming a continuous heat transfer fluid flow passage for heating the heat transfer fluid, and said heat transfer fluid flow passage comprising a heat exchanger element located in the first heat exchanger element 200b of said heat transfer element. Since the various first parts may be desirably named, said first part 202 (not shown) may serve as such a first part.

For example, the heat transfer medium flow passage mentioned in Figure 2 comprises superheaters 154 and 156 and a heat exchanger tube 200 mm. its other parts 240 and 240b. In Figure 2, second portions 240 are also first portions 202; the insulation (255, 257) adjacent to the wall is not shown. Hereby, a first part of the heat exchanger tube (part 202b in the figure) is the last heat transfer element, such as a heat exchanger tube or heat transfer tube, located in the gas flow passage 115 of the said circulation. From such a first section 202b comprising a second second section 240b in Fig. 2, the heated heat transfer medium is led through the return circuit 420, for example, to power generation.

After said first portion 202, the heated heat transfer medium is not conducted to a heat transfer element (such as a heat transfer tube or heat exchanger tube) in the gas flow passage.

Another preferred elevation is also realized in the embodiment of Figure 1d. In this embodiment - the thermal device 100 comprises a plurality of other heat transfer tubes 152, 156 within the walls of the gas flow passage 115 for heat recovery, - said heat exchanger tube 200 and said other heat transfer tubes 152, 156 forming a a first portion 202 of the last heat exchanger tube disposed in the gas flow passage and at least one heat transfer tube disposed therethrough in the downstream direction of the heat transfer medium (such as tube 152 in Fig. 1d); l heat transfer tubes (tube 152 in Figure 1d).

For example, the heat transfer medium flow passage mentioned in Figure 1d comprises superheaters 152 and 156 and a heat exchanger tube 200 mm. its other parts 240 and 240b. In Fig. 1d, the first portion 202 comprises second portions 240 and 240b. Then, the first portion 202 shown in Figure 1d is the last portion of the heat exchanger tube 202 disposed in the flow direction of the heat transfer medium. 202, is disposed in the direction of flow of the gas flowing outside the outer tube 220 before said heat transfer tubes 152 following it in the flow direction of the heat transfer medium. The gas flow direction is illustrated by arrows 175. Clearly, the tube 152 is downstream of the gas 200. In such use, an uninsulated heat transfer tube coming after the first portion 202 of the last heat exchanger tube may be located in the flue gas flow duct at a temperature below 500 ° C, for example. In addition, when said temperature of the heated medium in said last first heat exchanger tube portion 202 is preferably at least 500 ° C, no condensation occurs on the surface of the uninsulated tube. In one use - said heat transfer medium flow direction in a final first heat section 202 of a heat exchanger tube located in a gas flow passage is heated to a first temperature, - at least one of said first about. In this case, the sandwich heat exchanger tube 200, in particular the last first portion 202, 202b of the heat exchanger tube located in the gas flow passage, is arranged in a hotter location than the other heat transfer tubes. In such a solution, the heated heat transfer medium in the last portion of the heat exchanger tube 202, 202b located in the gas flow passage is typically so hot that no significant condensation on the surface of the subsequent heat transfer tubes occurs. If in the flow direction of the heat transfer medium the last heat transfer element disposed in the gas flow passage 115 is a shielded structure as described, there is no subsequent heat transfer tube on which the corrosive substances are condensed on the surface.

Preferably, the heat exchanger tube 200 is arranged close to the heat generation site. For example, in the combustion boiler, the first portion 202 of the sandwich heat exchanger tube closest to the grate 102 (in the flue gas flow direction) may be at least 5 m or at least 10 m away from the grate 102 to ensure a sufficiently large furnace 110. On the other hand, the first portion 202 of the sandwich heat exchanger tube 200 may have a distance from the grate 102 of, for example, up to 50 m, up to 40 m or up to 35 m to ensure ambient heat in the heat exchanger tube 200. Similarly, in the thermal device 100, the height of the first portion 202 of the heat exchanger tube 200 from the ground may be up to 50 m, up to 40 m or up to 35 m, respectively.

Referring to Figure 2, the thermal device according to one embodiment comprises: - an additive supply means 300 for feeding a process additive, such as an incineration process additive, e.g. to a furnace or process area, of which - a portion of the additive supply means 300 is located in the gas flow passage 115; after said or a first portion 202. This provides the advantage that the additive is only introduced into the flue gases cooled by the heat exchanger tube 200, whereby the effectiveness of the additives is improved.

The additive is preferably liquid, for example an aqueous solution of the reactant. The means 300 comprise a tube or the like for introducing a liquid additive into the gas flow passage 115 and one or more nozzles 310. Preferably, the supply means 300 extend through the flow passage 115 in one direction, substantially adding the additive throughout the flow passage.

The additive comprises, for example, at least one of ammonia (Nhh), ammonium ion (NhV), ferrous sulfate (Fe 2 (SO 4) s), ferrous sulfate (FeSCU), aluminum sulfate (A ^ SCUh), ammonium sulfate ((NFU ^ SCU), ammonium hydrogen sulfate (( NFU3HSCU), sulfuric acid (H2SO4), and sulfur (S), and aqueous solutions thereof, Preferably the additive comprises ammonia (NH3) or ammonium ions (NH4 +) One way of operating the combustion boiler 100 is to supply the additive comprising ammonia (NH3) ) or ammonium ions (NH4 +) In one application of a thermal device, - said additive supply means comprises feeding to the thermal device an additive comprising - at least one of ammonia (Nhh), ammonium ion (NH4 +), (Fe2 (SO4) 3), (FeSO4), ( Al 2 (SO 4) 3), ((NH 4) 2 SO 4), ((NH 4) HS 4 O), (H 2 SO 4), and sulfur (S), and aqueous solutions thereof. In one preferred embodiment, the additive comprises ammonia (Nhh) t ai ammonium ions (NH4 +).

Referring further to Figure 2, one embodiment comprises: - a first heat exchanger comprising said heat exchanger tube 200 and further a plurality of heat exchanger tubes 200 comprising an inner tube 210, at least one outer tube 220 and a media layer 230 between the outer tube and the inner tube portion; a heat exchanger comprising a plurality of heat transfer tubes which: - a first heat exchanger is arranged in the gas flow direction before said second heat exchanger, - a second heat exchanger is spaced from the first heat exchanger, leaving a space 350 between the second heat exchanger and the first heat exchanger in the flow passage 115 and - said part of the additive supply means 300 is arranged in said space 350.

For example, the second heat exchanger may be provided at the top of the process area 110 of the thermal device 100, as shown in Figure 2. The second heat exchanger may be, for example, a conventional tube package comprising a plurality of heat transfer tubes. The second heat exchanger is, in one embodiment, Figure 2, a secondary superheater 154.

Clearly, some of the additive feeder tubes are located outside the combustion boiler. Further, it is obvious that other additive supply means may be located in other parts of the combustion boiler.

Referring to Figure 2, an embodiment of the combustion boiler 100 comprises: - a first section 202 of said heat exchanger tube, i.e. a first first section 202 of a heat exchanger tube, - a second first section 202b extending in said gas flow passage from one wall (second wall 114, Fig. 2). or another wall (first wall 112, Fig. 2) which: - the second first portion 202b or the inner tube of said second first portion 202b is insulated from the gas flow passage by a second ui tube and / or insulation, and - said inner tube 210 connects said heat exchanger tube a first first portion to said second first portion of a heat exchanger tube outside said gas flow passage. In this case, the inner tube 210 is easily guided back into the conduit 115, and a separate insulated region 150 is not necessarily required, although the first portions extend directly into the flow conduit 115.

It is also possible that the second first portion 202b is only insulated almost entirely along the flow passage 115 as previously described (see alternatives A, A1, A2 and B above). The second first part comprises at least an inner tube which is isolated - at least largely - from the gas flow passage 115. As described above, the second first part may comprise, and preferably comprise, a second second part in which the outer tube surrounds the inner first tube.

In Figure 2, a first first portion 202 extends from a first region 122 of the device wall to a second region 124 of the device wall in the flow direction of the heat transfer medium and a second first portion 202b extends from said second region 124 of the device wall to a first region 122 of the device wall.

As described above, the first first portion 202 comprises a first second portion 240. Preferably, the second first portion 202b also comprises a second second portion 240b. Further, it would be possible for either of the first portions 202, 202b to comprise a plurality of second portions as shown in Figure 1c. Preferably, portions 240, 240b extend directly in the flue gas duct 115. In one embodiment, - said first second portion 240 of the heat exchanger tube extends directly in a gas flow conduit, wherein said first second portion 240 extends in a longitudinal direction Sx of the filing medium; directly in the gas flow passage, wherein said second portion 240b extends in a longitudinal direction -Sx of the fluid flowing in the second tube which - the second longitudinal direction -Sx is opposite to the first longitudinal direction Sx, and - said inner tube 210 connects said first 202b outside said flue gas flow passage 115.

Preferably, only the inner tube 210 connects a first first portion 202 of said heat exchanger tube to a second first portion 202b of said heat exchanger tube outside said flue gas flow passage 115, since this simplifies the construction. Naturally, it is also possible for the outer tube 220 to extend beyond the flow passage 115. This solution has the advantage that in this way the heat exchanger tube 200, or the corresponding heat exchanger, can be connected to the water circulation of the device 100 so that the flow and return circuits are on the same side of the boiler; 2 and 5b to the left. The same effect is also achieved by using an insulated and bent tube as shown in Figures 1d and 1e. In this embodiment, the thermal device comprises: - a heat transfer medium flow passage 410 for supplying a heat transfer medium to a heat exchanger tube 200;

Preferably, the heat exchanger tube 200 acts as the last superheater of the combustion boiler 100. In this case, the combustion boiler comprises: - means for supplying heat transfer medium from the tertiary supercharger 156 to said heat exchanger tube 200. At this stage, the heat transfer medium is typically superheated steam.

If the thermal device 100 comprises two or more insulated first portions 202 as described with a distance in the gas flow direction between at least two heat exchanger tube portions (202, 202b), the portions (202, 202b) are preferably located downstream in the gas flow path; both downstream of the medium and downstream of the gases. More specifically, in such a thermal device - said second first portion 202b of the heat exchanger tube is located downstream of the first first portion 202b of said heat exchanger tube in the inner tube 210, and - said second first portion 202b of the heat exchanger tube is located outside the heat exchanger tube.

For example, in Figure 2, the second first portion 202b is located above the first first portion 202. As superheated steam passes from the inside of the first first portion 202 to the inside of the second first portion 202b, at a corresponding time, the gases flow upward, i.e. from the outer surface of the first first portion 202 toward the outer surface of the second first portion 202b. In such an arrangement, the two parts 202 and 202b are heated more uniformly with each other than in the arrangement where the parts 202, 202b would be upstream of the flows. More even heating reduces heat stress and improves service life.

Preferably, the tertiary bulb 156 is also directed downstream, as shown in FIG. The flow direction of the heat transfer medium flowing out of the tertiary supercharger 156 is illustrated by arrow 405. The superheated steam from the return cycle of the tertiary supercharger 156 is further directed to the flow passage 410 of the layered heat exchanger tube 200.

During operation of the thermal device, the heat transfer medium and the flue gas hate as described above. At other times in the boiler 100, the heat transfer medium and the flue gas are arranged to flow as described above. The direction of flow from the thermal device is obvious to one skilled in the art. The heat transfer medium flows from the feed for use, such as power generation or heat use. Gases hate use in the process area, such as heat recovery or extraction.

In the embodiment shown in Fig. 2 - the wall of a thermal device, such as a boiler, comprises a cam 180 and - said first portion 202 of the heat exchanger tube extends from said cam 180.

In Figure 2, cam 180 comprises a second region 124 of the wall of said device. Areas and walls may be freely named, so that the cam could alternatively comprise first region 122 of said boiler wall. In addition, first boiler wall 112 may comprise cam 180, or .

When the cam 180 comprises the first area 122 or the second area 124 of the wall of said device, the span of the first portion 202 (or 202b) of the heat exchanger tube 200 is shortened as the cam 180 extends from the boiler wall toward the gas flow passage 115. The cam thus forms a projection on the wall which is directed to the gas flow passage. The beak narrows the gas flow path. The shorter span strengthens the structure of the heat exchanger tubes 200. Preferred lengths for the first portion 202 and the second portion 240 of the heat exchanger tube 200, which corresponds to said span, were shown above.

Fig. 3a shows one way of connecting the heat exchanger tube 200 to the first wall 112 of the thermal device 100 in a first region 122 of the wall. The connection can be similarly made in the second region 124 of the wall.

The boiler wall 112 shown in Figure 3a comprises heat transfer tubes 510 for recovering heat. Through the wall, the first region 122 is provided with inner tubes 210a to 21 Of which, on the flue gas flow passage 115 side, are arranged inside the outer tubes 220a, a to 220a, f and 220b, a to 220b, f as described above. Thus, the outer tubes are included in first second portions 240a, x and second second portions 240b, x, where x is a, b, c, d, e or f. Similarly, inner tube 21Ox is divided into first first portion 202a, x and second first portion 202b, x. At least a portion of the first portions 202a, x and 202b, x is surrounded by an outer tube 220a, x or 220b, x, respectively, as described above. Since the outer tubes are connected to areas 122, 124, and the temperature of said areas is lower than the temperature in the flow passage 115, the temperature of the co-tubes 220 increases as the area passes 122, 124 to the middle portions of the flow channel. This results in a temperature gradient in the outer tube, and said temperature gradient may reduce the life of the outer tube 220.

In the embodiment of Figures 3a and 3b, the first area 122 or second 124 of the wall of the thermal device 100 comprises a housing 450 which extends outwardly of said gas flow conduit 115 from the wall of the thermal device such as the first 112 or second 114, the housing 450 comprising a oe for discharging said inner tube 210, 210a to 21 Oe from a reaction area 110 of a thermal device, such as a furnace furnace furnace 110 or a gas flow passage 115, and o having an outer tube 220, 220a, 220e, and optionally an intermediate layer 230 for protection, o from the inner surface of the housing 450 extending from the wall 255, 257 to the reaction area 110 of the thermal device or to the gas flow passage 115; or o from said inner surface of the housing 450 extending said non-insulated region 470 (Fig. 1i) of the first portion 202 to the reaction region 110 of the thermal device or to the gas flow passage 115.

Preferably, the outer tube 220 is sealed to the inner surface of the housing 450 to prevent the flue gases of the flue gas duct 115 from contacting the insulating layer 230 or the inner tube 210. For example, the outer tube may be welded to the housing 450.

Also, in the embodiments of Figures 1b and 1c, a housing 450 may be used. In this case, an insulation 255 adjacent to the wall extends from the inner surface of the housing 450 to the gas flow passage 115 to protect the inner tube of the heat exchanger tube.

Further, according to Figures 1i and 3b, it is possible that the uninsulated region 270 of the inner tube 210 is housed in the housing 450.

When the housing 450 protrudes from the boiler wall as described above, the gas 450 in the housing 450 is extremely slow compared to the flow of the gas flow passage 115. In this case, the condensation causing the corrosion is noticeably low. First, because of the low flow rate, the amount of gas from which condensation can occur is reduced. The condensation itself is thereby reduced. Second, since heat is also recovered from the gases in the housing, the gas contained in the housing is cooler than the gas flowing in the flow passage 115. In such colder areas, corrosion is slow, as discussed above.

Further, the temperature in the housing 450 rises from the peripheral region towards the flow passage 115. In the casing solution, the temperature of the outer tube 220 rises significantly longer than in the absence of said protruding housing. Longer distance, in turn, means a smaller temperature gradient, which increases the service life compared to a solution without the enclosure. To reduce corrosion and sufficiently reduce the temperature gradient, the housing depth L (Fig. 3b) may be, for example, at least 10 cm, more preferably at least 15 cm or at least 20 cm.

Figure 3b is a plan view of the situation of Figure 3a seen from above. 3b, there is a distance d between the inner surface of said housing 450 and the outer surface of said outer tube 220, wherein said outer tube 220 (and thus also the inner tube 210) is thermally insulated from the boiler wall. For example, the distance d may be at least 1 mm, at least 5 mm or at least 10 mm. As discussed above, in the housing, the inner tube 210 may in one embodiment be insulated by an insulator 255, 257 adjacent to the wall (Figs. 1b, 1c). In this embodiment, there is preferably a distance d between the inner surface of the housing 450 and the outer surface of said insulator 255, 257, wherein said insulation is also thermally insulated from the housing. Again, the distance d can be, for example, at least 1 mm, at least 5 mm or at least 10 mm. In yet another embodiment, where part of the inner tube is uninsulated, a distance d is maintained between the inner surface of said housing 450 and the uninsulated region 470. The inner tube 210 is then thermally insulated from the wall of the thermal device. Such a distance further thermally insulates the heat exchanger tube 200 from the boiler wall (112, 114) and increases the life expectancy, or life expectancy, of the heat exchanger tube 200. As will be shown later, the distance d is not necessarily constant if, for example, the inside surface of the housing 450 is curved. Distance d refers to the shortest distance from the outer surface of the outer tube 220 or dielectric 260 from the segment formed by the housing 450 to the boiler wall from which the housing 450 protrudes (e.g., first wall 112, see Figures 4a and 4b). More specifically, the distance d is the distance of the outer surface from the wall 112 of the device 100 at the flow end 115 of the housing 450.

Preferably, at least one of the walls of the housing 450 does not comprise a heat transfer tube 510 to maintain the temperature of the housing high. This further reduces said temperature difference. For structural reasons, a single heat transfer tube 510 'which would continue in normal design in the wall 112 may be displaced aside from the housing 450 and heat exchanger tubes 200 (210, 220). Preferably, such a displaced heat transfer tube 510 'and the housing 450, as shown in Fig. 3b, remain at a distance to also insulate the housing from said heat transfer tube. This distance, di (Fig. 3b), can be, for example, at least 1 mm or at least 2 mm, such as at least 5 mm.

The enclosure 450 shown may also be used in connection with a heat exchanger tube which does not comprise an outer tube at all but only at least partially insulate the first portion. The enclosure 450 shown may also be used in connection with a heat exchanger tube which does not comprise a substantially straight outer tube. Such a thermal device comprises - at least a first wall defining a gas flow passage, and - a heat exchanger tube comprising at least an inner tube from which the first a second wall defining a gas flow passage such that (A) - the inner tube 210 of the first section 202 of said heat exchanger tube is partially insulated from the gas flow passage 115 by said outer tube 220 and / or insulator 260, and non-insulated from the gas flow passage 115 in one or more non-insulated regions 270 (Fig. 1i) such that (A1) - the largest non-insulated region 270 of the first portion 202 does not exceed 15 cm in length: ; preferably, the length of the largest non-insulated region 270 does not exceed 10 cm, where the length is measured in the longitudinal direction of the inner tube; or (A2) - all points in the non-insulated regions 270 of the first portion 202 are not more than 15 cm from other thermal surfaces (other than the heat exchanger tube 200 itself) of the thermal device; preferably up to 10 cm; or (B) - the first portion of said heat exchanger tube or the inner tube of the first portion of said heat exchanger tube is insulated from the gas flow passage by an outer tube and / or insulation.

Further, the wall of the thermal device comprises a housing which - the housing protrudes from the wall of the thermal device, outwardly of said gas flow passage, - the casing comprises a lead-through for venting said inner tube out of the process area or gas flow passage of the thermal device.

Said outer tube may be connected to the inner surface of the housing. Insulation may be provided from the inner surface of the housing adjacent the wall to the gas flow passage to protect the inner tube of the heat exchanger tube.

Figures 4a and 4b are top views of some embodiments of the housing 450. In the figures, the housing wall 452 forms a flexible structure within the housing 450, which is arranged to receive the thermal expansion of the thermal device 100 and the heat exchanger tube 200.

For example, Fig. 4a shows a top plan view of a housing 450. In the embodiment of Fig. 4a, - at least one wall 452 of said housing 450 forms at least two bends 455, wherein - said wall 452 of housing 450 provides a flexible structure such as boiler 100, and heat expansion tube 200.

Figure 4b further illustrates an embodiment that more efficiently receives thermal expansion. In the embodiment of Figure 4b, - at least one wall 452 of said housing 450 forms at least one fold 460 which diverges from the line of the wall 450 of housing 450, wherein said fold 460 forms a flexible structure in housing 450 arranged to receive a thermal device such as boiler 100 and heat exchanger tube 200. thermal expansion. Fold 460 forms a bellows 450 from the housing 450, i.e. a tubular structure which shortens when pressed and lengthens when pulled. The length of such a bellows casing 450 is arranged to change under the influence of thermal stresses.

The line of the wall of the housing 450 refers to the plane best suited to the shape of the (folded) wall of the housing. When the wall of the housing comprises a fold 460, it comprises at least three bends 455 (not shown by reference numerals in Figure 4b).

In Fig. 4b, the housing 450 protrudes (divides outward) from the first wall 112 of the thermal device 100. Fold 460 further protrudes from the line 452 of the wall 452 of the housing 450 so that the fold 460 extends parallel to said first wall 112. Instead of protruding, the fold could be detached from the line 452 of the wall into the housing 450 inwardly. Further, in the case of at least two folds, the first fold 460 may separate outwardly (extend) and the second fold apart inwardly. 4b, each wall of the housing 450 shown in Fig. 4b comprises two folds 460.

Above, receiving thermal expansion of thermal device 100 and heat exchanger tube 200 means that although heat exchanger tube 200 and thermal device 100 (such as a boiler, e.g., boiler wall) expand by different amounts due to different operating temperatures and / or different thermal expansion rates of thermal device 100 and significant thermal stresses because the structure is flexible, i.e., receives thermal expansion. In such a structure, at least a portion of the wall 452 of the housing 450 is arranged to bend as a result of thermal stresses. When the housing wall 452 comprises a bend, the expansion will cause the bend to become more straightened or curved, which requires considerably less stress than, for example, stretching or pressing the straight wall of housing 450 in the direction of the housing wall.

Figure 5 shows another preferred solution in the combustion boiler. Figure 5 is a side view of a heat exchanger comprising heat exchanger tubes 200 and parts thereof as shown. Part 5a of Figure 5 is shown earlier in connection with Figure 3a. The solution comprises a plurality of inner tubes 210a-210f. Each inner tube comprises a first first portion and a second first portion, e.g., the inner tube 21 Of comprises a first first portion 202a, f and a second first portion 202b, f. The first portions 202a, f and 202b, f consist of the described second portions 240a, f and 240b, f (respectively), i.e., po. the second portions extending directly and comprising outer tubes 220a, f and 220b, f respectively. The heat exchanger tube (such as tube 200) extends from the first boiler wall 112 to the opposite wall 114. In Figure 5, the heat exchanger tube extends from the first boiler wall 112 to the opposing wall 114 cam 180, as in Figure 2. The heat exchanger shown flow channel 115 and pivot outside flow channel 115, in this case inside cam 180 (cf. Figures 2 and 3a).

A first housing 450a is provided in the first region 122 for passing the inner tubes 220, such as the inner tube 21 Of, from the outside of the flue gas flow duct 115 to the flow duct 115. In addition, the flow duct side 115 is provided with inner tubes 220 such as outer ducts 220a, f, as described above. Similarly, a second housing 450b is provided in the second region 124 for projecting the inner tube 210 from the side of the flow passage 115 into the cam 180. The second housing 450b comprises two folds 460b for receiving thermal expansion.

In Figure 5, a plurality of inner tubes 220 are passed through the same housing. It is also possible to provide a single housing for each single passage of one pipe. Such a single housing may comprise at least two bends 455, such as a fold 460, as described above. This solution provides the advantage that, at uneven operating temperature, each heat exchanger tube 200 can expand differently since each individual housing receives thermal expansion of each single tube section 240, 240b.

The embodiment of Figure 5 can also be implemented in a more general thermal device. In general, the thermal apparatus shown in Figures 1-5 may be of the type, for example: - a pyrolysis reactor, - a gasification reactor, or - a combustion boiler such as a fluidized bed boiler, for example a fluidized bed boiler or a circulating fluidized bed boiler; preferably a fluidized bed boiler.

In addition to the thermal device, a method for heating the heat transfer medium is described above. The method comprises: - producing gas heated by the thermal device 100, - introducing said gas into a gas flow passage 115, - introducing a heat transfer medium into a heat exchanger tube 200, wherein at least a first portion 202 of the heat exchanger tube is located in a gas flow passage 115 ) on the same (112, 114) or another (114, 112) wall of said flow conduit 115, said first portion 202 of the heat exchanger tube comprising a second portion 240 of a heat exchanger conduit extending in said gas flow conduit 115, and - recovering heat to the heat transfer medium 200 .

The method utilizes a heat exchanger tube 200 for heat recovery such that said second portion 240 of heat exchanger tube 200 comprises o at least a portion of inner tube 210 for transferring heat transfer medium from first end to second end of inner tube portion and for heat recovery to heat transfer medium; and o a fluid layer 230 extending radially between said outer tube and said inner tube portion, and - said second heat exchanger tube portion 240 extending directly or curved less than 90 degrees, and (A) - the inner tube 210 of said first heat exchanger tube portion 202 being partially insulated from the gas flow path. 115 by means of said outer tube 220 and / or insulation 260, and - the inner tube 210 of the first part 202 of said heat exchanger tube being uninsulated by one or more non-insulated gas flow channels 115 -mällä area 270 (Figure 1i), so that (A1), - the maximum of 270 length of the uninsulated area does not exceed the 15-cm; preferably, the length of the largest non-insulated region 270 does not exceed 10 cm, where the length is measured in the longitudinal direction of the inner tube; or (A2) - all points in all non-insulated regions 270 are not more than 15 cm from other thermal surfaces of the thermal device (other than heat exchanger tube 200 itself); preferably up to 10 cm; or (B) - the first portion 202 of said heat exchanger tube 200 or the inner tube 210 of the first portion 202 of said heat exchanger tube 200 is insulated along its entire path from the gas flow passage 115 by said outer tube 240 and / or insulator 260.

The temperature characteristics of the process are described above in connection with the use of the device. Aspects related to the additive feed of the method are described above in connection with the use of the device. The technical features of the structures used in the method are described above as features of a thermal device.

Claims (19)

A thermal device (100) comprising: - at least a first wall (112) defining a gas flow passage (115); and - a heat exchanger tube (200) comprising at least an inner tube (210), of which heat exchanger tube (200) at least a first portion ( 202) is disposed in said gas flow passage (115) and extends in said gas flow passage (115) from said first wall (112) to said first wall (112) or a second wall (114) defining a gas flow passage (115), and the first portion (202) comprising a second portion (240) of the heat exchanger tube extending in said gas flow passage (115), wherein - said second portion (240) of the heat exchanger tube comprises o at least a portion of the inner tube (210) for transferring heat transfer medium from heat transfer interval o an outer tube (220) radially surrounding said portion of the inner tube (210); and o a fluid layer (230) extending radially between said outer tube (220) and a portion of said inner tube (210), wherein the thermal device (A) the inner tube (210) of the first part (202) of the heat exchanger tube being uninsulated from the gas flow passage (115) in one or more uninsulated areas (270) such that: - all points of all uninsulated areas (270) of the first part (202) not more than 15 cm; or (B) - a first portion (202) of said heat exchanger tube or an inner tube (210) of the first portion (202) of said heat exchanger tube insulated throughout the distance from the gas flow passage (115) of said outer tube (220) and / or insulation (230, 255, 257, 260). ), characterized in that - said second part (240) of the heat exchanger tube extends directly or bends less than 90 degrees, - the wall (112, 114) of the device (100) comprises a projection directed to the gas flow conduit (115); a portion (202) extending from said projection. The thermal device (100) of claim 1, wherein - said second portion (240) of the heat exchanger tube extends from said first wall (112) of said device to said gas flow passage (115); preferably, said second portion (240) of the heat exchanger tube comprises a first portion (202) of said heat exchanger tube. A thermal device (100) according to claim 1 or 2, wherein said heat exchanger tube (200) comprises - a first portion (202, 202a) of said heat exchanger tube, i.e., a first first portion (202a) of a heat exchanger tube, - said heat exchanger tube (200) comprising a second first portion (202b) extending in said gas flow passage (115) from one wall (112, 114) to one or another wall (112, 114) which (i, a) - the second first part (202b) or its inner tube (210) non-insulated from the flow passage (115) in one or more non-insulated regions (270) such that - all points of all non-insulated regions (270) of the second first portion (202b) are at most 15 cm apart from other thermal surfaces of the thermal device (100); or (ib) - a second first portion (202b) or an inner tube (210) of said second first portion (202b) isolated from the gas flow passage (115) by a second outer tube (240b) and / or insulation (230, 255, 257, 260). and (ii) - said inner tube (210) connects a first first portion (202a) of said heat exchanger tube to a second first portion (202b) of said heat exchanger tube outside said gas flow path (115). The thermal device (100) according to claim 3, wherein - said second first portion (202b) of the heat exchanger tube is located downstream of said first heat exchanger tube first portion (202a) in said inner tube (210), and - said second first portion (202b) of heat exchanger tube. ) is located outside the heat exchanger tube downstream of the first first portion (202a) of said heat exchanger tube. The thermal device (100) according to any one of claims 1 to 4, wherein - said first part (202, 202a, 202b) of the heat exchanger tube comprises a heat insulated part (250) in said gas flow passage (115), wherein the heat insulated part (250) ) is not surrounded by an outer tube (220), and in said thermally insulated part (250), the inner tube (210) is heat insulated (255, 257, 260) by gases of the flow passage (115) or the inner tube (210) is surrounded by an outer tube (220) in the part (250), the outer tube (220) is thermally insulated by means of a thermal insulator (255, 257, 260) from the gases of the flow passage (115). The thermal device (100) of claim 5, wherein (A) - said second portion (240) of the heat exchanger tube extends from said first wall (112) of the device to said thermally insulated portion (250), or (B) - the thermal device (100) comprises a wall adjacent insulation (255, 257) extending from said first wall (112) of the device to a gas flow passage (115), - said second portion (240) of the heat exchanger tube extending from said adjacent wall of the device (255, 257) to said heat insulated portion (250), and - said wall-adjacent insulator (255, 257) is arranged to insulate at least the inner tube (210) of the heat exchanger tube from the gas flow passage (115). The thermal device (100) according to any one of claims 1 to 6, wherein - said first portion (202, 202a, 202b) of the heat exchanger tube is horizontal, or the longitudinal direction of said first portion (202, 202a, 202b) of said heat exchanger tube forms an angle with the horizontal; which is less than 30 degrees. The thermal device (100) according to any one of claims 1 to 7, wherein - the thermal device (100) comprises a plurality of other heat transfer tubes (154, 156) inside the walls of the gas flow passage (115) for heat recovery, - said heat exchanger tube (200) and the heat transfer tubes (154, 156) forming a continuous heat transfer fluid flow passage for heating the heat transfer fluid, and (A) - said heat transfer fluid flow passage comprising a heat transfer fluid downstream of the gas transfer conduit (115) a first portion (202) of the heat exchanger tube disposed downstream of the heat transfer medium in the flow direction of the gas transfer conduit (115) and of the at least one gas transfer conduit thereafter in the flow direction of the heat transfer medium said first heat exchanger tube (154, 156) and - said last heat exchanger tube first portion (202) arranged in the direction of flow of the gas flowing outside the outer tube (220) before said heat transfer tubes (154, 156) located downstream of said heat transfer medium. The thermal device (100) according to any one of claims 1 to 8, comprising: - an additive supply means (300) for the process of feeding an additive, - a portion of the additive supply means (300) located in a gas flow passage (115); arranged downstream of said or a first portion (202, 202a, 202b) of said heat exchanger tube (200). The thermal device (100) of claim 9, comprising: - a first heat exchanger comprising said heat exchanger tube (200) and further a plurality of heat exchanger tubes (200) comprising an inner tube (210), at least one outer tube (220) and a media layer (200). 230) trapped between a portion of the outer tube (220) and the inner tube (210), - a second heat exchanger (154, 156) comprising a plurality of heat transfer tubes (154, 156), - a first heat exchanger arranged in the gas flow direction before said second heat exchanger, the second heat exchanger being at a distance from the first heat exchanger, leaving a space (350) between the second heat exchanger and the first heat exchanger, and - said portion of the additive supply means (300) being arranged in said space (350). The thermal device (100) according to any one of claims 1 to 10, wherein - the wall (112, 114) of the thermal device (100) comprises a housing (450) extending from the wall (115) of said thermal device, said gas flow path. (115) looking outward, which - the housing (450) comprises a lead-through for discharging said inner tube (210) out of the process area (110) or gas flow conduit (115) of the thermal device (100), and - (i) said outer tube (220), (ii) insulating (255, 257) an interior adjacent wall of the housing (450) to a gas flow passage, or (iii) said insulating region (470) of the first portion (202, 202a, 202b) extending from the inner surface of the housing (450). a gas flow passage (115) for protecting the inner tube (210) of the heat exchanger tube (200). The thermal device (100) of claim 11, wherein - a distance (d) is maintained between the inner surface of said housing (450) and the outer surface of said outer tube (220); - there is a distance (d) between the inner surface of said housing (450) and the insulation (255, 257) adjacent to said wall; or - a distance (d) between the inner surface of said housing (450) and said uninsulated region (270), wherein said inner tube (210) is thermally insulated from the wall of the thermal device (100), since such distance (d) insulates the heat exchanger tube (200) (100) from the wall (112, 114). The thermal device (100) according to claim 11 or 12, wherein - the wall (452) of said housing (450) forms a flexible structure within the housing (450) which is arranged to receive thermal expansion of the thermal device (100) and heat exchanger tube (200). A thermal device (100) according to any one of claims 1 to 13, wherein the thermal device is of the type: - a pyrolysis reactor, - a gasification reactor, or - a combustion boiler such as a fluidized bed boiler, for example a fluidized bed boiler or a circulating fluidized bed boiler; preferably a fluidized bed boiler. Use of a thermal device (100) according to one of Claims 1 to 14, characterized in that - the temperature of the outer surface of the outer tube (220) is above 600 ° C. Use of a thermal device (100) according to any one of claims 1 to 14, characterized in that - the heat transfer medium is allowed to flow in said inner tube (210), - steam is used as the heat transfer medium and - the temperature of the heat transfer medium flowing in the inner tube (210) 530 ° C. Use according to claim 16, characterized in that - the temperature of the outer surface of the outer tube (220) is above 600 ° C. Use of a thermal device (100) according to claim 9 or 10, characterized in that - said additive supply means (300) feeds to the thermal device (100) an additive comprising - at least one of ammonia (NH3), ammonium ion (NH4 +), ferrous sulphate (Fe 2 (SO 4) 3), ferrous sulphate (Fe SO 4), aluminum sulphate (Al 2 (SO 4) s), ammonium sulphate ((NH 4) 2 SO 4), ammonium hydrogen sulphate ((NH 4) HS 4), sulfuric acid (H 2 SO 4) aqueous solutions of these. A method of heating a heat transfer medium comprising: - producing gas heated by a thermal device (100), - introducing said gas into a gas flow passage (115), - introducing a heat transfer medium into a heat exchanger tube (200) comprising at least an inner tube (210) at least the first portion (202) of the heat exchanger tube is disposed in the gas flow duct (115) and extends in said gas flow duct (115) from the wall (112, 114) of said flow duct to the same or another wall (112, 114) of said flow duct a first portion (202) comprising a second portion (240) of the heat exchanger tube extending in said gas flow passage (115), and - recovering heat to the heat transfer medium by said heat exchanger tube (200), wherein - said second portion (240) of the heat exchanger tube (200) part an inner tube (210) for transferring heat transfer medium from a first end to one end of a portion of the inner tube (210) and for recovering heat into the heat transfer medium, o an outer tube (220) radially surrounding said portion of the inner tube (210); (220) and a portion of said inner tube (210); and (A) - the inner tube (210) of the first section (202) of said heat exchanger tube is uninsulated from the gas flow passage (115) in one or more uninsulated areas (270) such that - all points of the non-insulated regions (270) the other heating surfaces of the device shall not exceed 15 cm; or (B) - the first portion (202) of said heat exchanger tube or the inner tube (210) of the first portion (202) of said heat exchanger tube being insulated throughout the distance from the gas flow passage (115) of said outer tube (220) and / or insulation (230, 255, 257). , 260), characterized in that - said second part (240) of the heat exchanger tube extends directly or bends less than 90 degrees, - the wall (112, 114) of the device (100) comprises a projection directed to the gas flow passage (115); the first portion (202) of the heat exchanger tube extending from said projection. claim: