Methods for heating the heat exchange medium in a fluidized bed boiler, fluidized bed boiler and loop-sealed heat exchanger

Abstract

A method for heating a heat exchange medium in a fluidized bed boiler includes: burning a first fuel in a first furnace of the fluidized bed boiler to generate a first flue gas; recovering heat from the first flue gas to the heat exchange medium using a first heat exchanger; conveying the heat exchange medium from the first heat exchanger to a second heat exchanger, at least a portion of the second heat exchanger being configured to contact the fluidized bed of the fluidized bed boiler; burning a second fuel in the second furnace to generate a second flue gas; conveying the heat exchange medium from the second heat exchanger to a third heat exchanger; and recovering heat from the second flue gas to the heat exchange medium using the third heat exchanger. The fluidized bed boiler performing this method is also described. When a loop-sealed heat exchanger is installed in the loop seal of a circulating fluidized bed boiler, it is configured to burn a second fuel in the second furnace to generate a second flue gas; convey the heat exchange medium from the second heat exchanger to the third heat exchanger; and recover heat from the second flue gas to the heat exchange medium using the third heat exchanger.

Description

Technical Field

[0001] This invention relates to fluidized bed boilers. Specifically, it relates to circulating bed type fluidized bed boilers. It relates to loopseal heat exchangers for circulating fluidized bed boilers. It relates to generating steam by boiling water. It relates to producing steam hot enough for power generation in a steam turbine. It relates to methods for reducing corrosion on heat transfer surfaces. It relates to generating steam by burning low-quality fuels. It relates to operating fluidized bed boilers at low loads. Background Technology

[0002] To efficiently generate mechanical energy from heat, such as for producing electricity, superheated steam is required. Saturated steam can be generated by boiling water, and the steam can be further heated (i.e., superheated) in a superheater (i.e., the first heat exchanger) that recovers heat from flue gas. However, when burning low-quality fuels, the flue gas contains significant amounts of alkali metals and / or halogens, which can corrode these heat transfer surfaces at certain temperatures, for example, when gaseous alkali metal halides condense on heat transfer surfaces that are cooler than the flue gas. Therefore, this imposes an upper limit on the temperature of the superheated steam. But for efficiency reasons, hotter steam is needed.

[0003] In fluidized bed boilers, this limitation can be overcome by using a second superheater (i.e., a second heat exchanger) downstream of the first heat exchanger, which is located inside the fluidized bed composed of solid particulate bed material. Within the fluidized bed, the content of corrosive components in the flue gas is much lower, and heat transfer from the fluidized bed to the second heat exchanger is much better. Therefore, fewer compounds condense on the heat transfer surfaces, and the surface temperatures on these surfaces are higher, thus reducing corrosion. When designed in this way, under normal operating conditions, high-temperature steam can be generated by subsequently heating the heat transfer medium in both the first and second heat exchangers.

[0004] However, when the load on a fluidized bed boiler decreases, less fuel is burned. As a result, the temperature of the bed material and / or the amount of bed material after circulation may become so low that the second heat exchanger cannot adequately superheat the steam for the purposes of the steam turbine. In this case, the steam turbine must be shut down to prevent turbine failure. Therefore, no electricity can be generated, even though this is the original purpose of power generation equipment including fluidized bed boilers. Operating the boiler with excess fuel at low loads, even if feasible, would significantly reduce efficiency.

[0005] In this field, document WO 2019 / 086752 discloses a method and system for maintaining steam temperature and thus power generation efficiency through load reduction in a steam turbine power generation device, which includes a fluidized bed boiler and a fluidized bed superheater suitable for superheating steam supplied to the steam turbine. The steam temperature can be maintained by providing additional heating to the fluidized bed material in an external circulation outside the boiler, thereby increasing the available thermal energy in the fluidized bed material. Furthermore, document WO 2019 / 122509 discloses a fluidized bed boiler with a loop-sealed heat exchanger. The loop-sealed heat exchanger includes at least an inlet chamber, a bypass chamber, a first heat exchange chamber, and heat exchanger tubes disposed in the first heat exchange chamber. Summary of the Invention

[0006] It has been found that steam from the second superheater (i.e., from the second heat exchanger) is further heated in a third heat exchanger. The heat required by the third heat exchanger can be provided by burning a second fuel. Preferably, the second fuel is a high-quality fuel to avoid the corrosion problems detailed in the background art in the first heat exchanger. This method is disclosed more specifically in claim 1. The fluidized bed boiler is disclosed more specifically in claim 11. The fluidized bed boiler may be part of the power generation equipment disclosed in claim 15. The second fuel may be burned in a loop-sealed heat exchanger. The loop-sealed heat exchanger is disclosed more specifically in claim 16. The loop-sealed heat exchanger is suitable for use in a circulating fluidized bed boiler. The dependent claims specifically disclose some preferred embodiments. These and other embodiments are disclosed in the description and drawings. Attached Figure Description

[0007] Figure 1a A circulating fluidized bed boiler is shown for performing a method of heating a heat exchange medium in a fluidized bed boiler;

[0008] Figure 1b A bubble fluidized bed boiler is shown as a method for performing a method of heating a heat exchange medium in a fluidized bed boiler.

[0009] Figure 2a This illustrates the operation of a fluidized bed boiler at low load.

[0010] Figure 2b This illustrates the operation of a fluidized bed boiler under high load.

[0011] Figure 2c This shows the operation of a damper.

[0012] Figure 3 Showing the loop-sealed heat exchanger along Figure 1a The cross-sectional view of Ill-Ill shown in the figure;

[0013] Figure 4 Showing the loop-sealed heat exchanger along Figure 3 The cross-sectional view of section IV-IV shown in the figure;

[0014] Figure 5 Showing the loop-sealed heat exchanger along Figure 3 The cross-sectional view of VV shown in the figure;

[0015] Figure 6 Showing the loop-sealed heat exchanger along Figure 3 The cross-sectional view of section VI-VI shown in the figure;

[0016] Figure 7 Showing the loop-sealed heat exchanger along Figure 3 The cross-sectional view of section VII-VII shown in the figure;

[0017] Figure 8a This illustrates the method of using a second flue gas recirculation system for fluidizing gases;

[0018] Figure 8b This illustrates the method of using a second flue gas recirculation system for fluidizing gases;

[0019] Figure 9a A cross-sectional view of a loop-sealed heat exchanger is shown.

[0020] Figure 9b Showing the loop-sealed heat exchanger along Figure 9a The cross-sectional view of IXb-IXb shown in the figure;

[0021] Figure 10a A cross-sectional view of a loop-sealed heat exchanger is shown.

[0022] Figure 10b Showing the loop-sealed heat exchanger along Figure 10b The image shows a cross-sectional view taken from Xb-Xb;

[0023] Figure 10c Show Figure 10b A cross-sectional view of a loop-sealed heat exchanger, some of which have walls formed by baffles; and the baffles are in a first position;

[0024] Figure 10d Show Figure 10c A cross-sectional view of a loop-sealed heat exchanger, wherein the baffle is in the second position;

[0025] Figure 10e This illustrates the recovery of heat from excess second flue gas to heat fluidizing gas for a chamber with a second heat exchanger;

[0026] Figure 10f This illustrates the use of an excess of second flue gas as a fluidizing gas in the first furnace.

[0027] Figure 11 A horizontal cross-sectional view of a loop-sealed heat exchanger is shown, which has a higher specific efficiency than... Figure 3 The loop-sealed heat exchanger has fewer chambers;

[0028] Figure 12 A vertical cross-sectional view of a loop-sealed heat exchanger is shown, which has a higher specific efficiency than... Figure 9b The loop-sealed heat exchanger has fewer chambers;

[0029] Figure 13 A vertical cross-sectional view of a loop-sealed heat exchanger is shown, which has a higher specific efficiency than... Figure 10b A loop-sealed heat exchanger with fewer chambers;

[0030] Figure 14 A cross-sectional view of a one-loop sealed heat exchanger is shown; and

[0031] Figure 15 The integrated headers of the second and third heat exchangers are shown.

[0032] In the accompanying diagram, Sx, Sy, and Sz represent three mutually perpendicular directions oriented according to the right-hand rule, meaning that the vector product (i.e., cross product) of Sx and Sy in this order equals Sz. In practice, the direction Sz is vertically upward, that is, opposite to gravity. Detailed Implementation

[0033] Figure 1a and Figure 1b An embodiment of a fluidized bed boiler 100 is shown. Figure 1a The fluidized bed boiler is a circulating fluidized bed boiler 100. Figure 1b The fluidized bed boiler in this article is a bubble fluidized bed boiler 100.

[0034] refer to Figure 1a and Figure 1bThe fluidized bed boiler 100 includes a first furnace 162 for burning a first fuel 165 to produce a first flue gas 163. The first fuel may be of low quality. Typically, the first fuel 165 comprises solid materials, such as biomass and / or residue-derived fuels. To recover heat from the first flue gas 163, the fluidized bed boiler 100 includes a first heat exchanger 310 for recovering heat from the first flue gas 163 to a heat exchange medium. The first heat exchanger 310 may be a superheater, i.e., a heat exchanger configured to receive and heat steam. The heat exchange medium includes at least one of water and steam. For example, saturated steam comprises H2O in both gaseous and liquid (i.e., steam and water) forms. However, superheated steam does not contain liquid water. As detailed in the background art, the purpose of a fluidized bed boiler is to produce superheated steam from water.

[0035] For reasons noted in the background art, the steam from the first heat exchanger 310 needs to be further heated. Therefore, the fluidized bed boiler 100 includes a second heat exchanger 320 and a first line 312 for conveying the heat exchange medium from the first heat exchanger 310 to the second heat exchanger 320. Preferably, the first line 312 does not include a heat exchanger configured to heat or cool the heat exchange medium between the first heat exchanger 310 and the second heat exchanger 320. In this way, preferably, in the direction of steam flow within the steam cycle of the fluidized bed boiler 100, the first heat exchanger 310 is such a final heat exchanger that no other heat exchanger downstream of the first heat exchanger 310 is configured to contact the first flue gas 163. Therefore, in this case, the first heat exchanger 310 is also such a final heat exchanger that other heat exchangers in which the steam is at least as hot as the steam in the first heat exchanger 310 are not configured to contact only the first flue gas 163 (see...). Figure 1a and Figure 1b Naturally, downstream of the steam turbine 152, the steam can be condensed and recirculated to the heat exchanger 122, which comes into contact with the first flue gas 163. Furthermore, the second heat exchanger 320 is not configured to contact only the first flue gas because it is in contact with the bed material. Additionally, the third heat exchanger 330 is preferably not in contact with the first flue gas 163 at all, as detailed below.

[0036] The second heat exchanger 320 is positioned such that, during use, a fluidized bed of bed material is configured to contact the second heat exchanger 320. The bed material comprises solid and heat-resistant particulate materials. Therefore, the bed material in contact with the second heat exchanger 320 can be fluidized by blowing in a sufficient amount of fluidizing gas. The bed material is heat-resistant and therefore will not burn in the first furnace 162. The benefits of contacting the second heat exchanger with the fluidized bed have been discussed in the background section.

[0037] For example, the second heat exchanger 320 may be disposed in the first chamber (412, 162) of the fluidized bed boiler 100 or may be disposed in the wall of the first chamber (412, 162), wherein the fluidized bed is configured to be formed in use within the first chamber (412, 162). In this sense, the first furnace 162 may be considered a chamber.

[0038] refer to Figure 1a In a circulating fluidized bed boiler, the first chamber 412 may be a chamber of a loop-sealed heat exchanger 400. The heat exchange surface (such as heat exchange tubes) of the second heat exchanger 320 may be disposed within the first chamber 412. Alternatively or additionally, the heat exchange surface (such as heat exchange tubes) of the second heat exchanger 320 may be disposed within the wall of the first chamber 412.

[0039] refer to Figure 1b In a bubble fluidized bed boiler, the first furnace 162 can be used as a first chamber. The heat exchange surface (such as heat exchange tubes) of the second heat exchanger 320 can be disposed in the lower part of the first furnace 162, such that the bubble fluidized bed is configured to be formed in the lower part of the first furnace 162.

[0040] refer to Figure 1a and Figure 1b In order to further heat the heat exchange medium, the fluidized bed boiler 100 includes a second furnace 172 and a third heat exchanger 330. The second furnace is used to burn a second fuel 175 to produce a second flue gas 173, and the third heat exchanger is used to recover heat from the second flue gas 173 to the heat exchange medium received from the second heat exchanger 320. Figure 2a The second furnace 172, the second fuel 175, the second flue gas 173, the third heat exchanger 330 disposed in the second chamber 422, and the passage 178 for conveying the second flue gas 173 to the second chamber 422 are shown in more detail. Figure 2aAs shown, burner 176 is disposed in a second furnace 172. Burner 176 is configured to burn a second fuel 175. This applies to at least one of a fluidized bed boiler 100 and a loop-sealed heat exchanger 400 for a circulating fluidized bed boiler. In this way, the fluidized bed boiler 100 or the loop-sealed heat exchanger 400 includes burner 176 disposed in a second furnace 172. Burner 176 can be configured to burn a gaseous or liquid second fuel 175. It is apparent that burner 176 can also be disposed in a second furnace 172 in other figures, although not explicitly shown.

[0041] refer to Figure 1a The second heat exchanger 320 and the third heat exchanger 330 can be arranged close to each other. Therefore, the heat exchange medium can flow directly from the second heat exchanger 320 to the third heat exchanger 330, for example, through a short pipe, which can be considered as part of one of the heat exchangers 320 and 330, or as part of the second pipeline 322.

[0042] refer to Figure 1b The fluidized bed boiler 100 may include a second pipeline 322 for conveying a heat exchange medium from a second heat exchanger 320 to a third heat exchanger 330. Preferably, the second pipeline 322 does not include a heat exchanger configured to heat or cool the heat exchange medium between the second heat exchanger 320 and the third heat exchanger 330.

[0043] refer to Figure 2a and Figure 2b The fluidized bed boiler 100 and / or the loop-sealed heat exchanger 400 for a circulating fluidized bed boiler can operate in two modes. (Reference) Figure 2a In the first mode (i.e., in the first time period), the second furnace 172 is used to burn the second fuel 175, and in this way the heat exchange medium is further heated by the second flue gas 173. In the first mode, the second heat exchanger 320 does not need to heat the heat exchange medium. (Reference) Figure 2b In the second mode (i.e., in the second time period), the second furnace 172 is not used (i.e., the second fuel 175 is not burned), or a very small amount of the second fuel 175 is burned. Therefore, the third heat exchanger 330 is actually not used.

[0044] More specifically, see reference Figure 1a and Figure 1bIn both the first and second modes, the method for heating the heat exchange medium in the fluidized bed boiler 100 includes: burning a first fuel 165 in a first furnace 162 of the fluidized bed boiler 100 to generate a first flue gas 163; and recovering heat from the first flue gas 163 to the heat exchange medium using a first heat exchanger 310. The heat exchange medium is conveyed from the first heat exchanger 310 to a second heat exchanger 320. As described above, at least a portion of the second heat exchanger 320 is configured to contact the fluidized bed of the fluidized bed boiler 100. More preferably, all heat transfer surfaces of the second heat exchanger 320 are configured to contact the fluidized bed of the fluidized bed boiler 100. The fluidized bed may be disposed in a loop-sealed heat exchanger 400. Figure 1a ) or in the first furnace 162 ( Figure 1b The method also includes conveying the heat exchange medium through the second heat exchanger 320 and from the second heat exchanger 320 to the third heat exchanger 330.

[0045] refer to Figure 2a In a first mode, i.e., during a first time period, the method includes: burning a second fuel 175 in a second furnace 172 of a fluidized bed boiler 100 to produce a second flue gas 173; and recovering heat from the second flue gas 173 to a heat exchange medium using a third heat exchanger 330. The first mode may correspond to operating conditions where the fluidized bed boiler 100 has a low load. Therefore, in one embodiment, during the first time period, the load of the fluidized bed boiler 100 is less than a threshold. Furthermore, because the fluidized bed (at least a portion of the second heat exchanger 320 is disposed in the fluidized bed) does not need to be hot during the first time period, the heat exchange medium does not need to be heated in the second heat exchanger 320. However, the heat exchange medium is heated in the third heat exchanger 330. Additionally, the fluidized bed is typically slightly hotter than the heat exchange medium flowing through the second heat exchanger 320. Therefore, preferably, the method further includes: during a first time period, using a second heat exchanger 320 to recover heat from the fluidized bed of the fluidized bed boiler 100 to the heat exchange medium, at least a portion of the second heat exchanger being configured to contact the fluidized bed of the fluidized bed boiler 100.

[0046] Regarding the arrangement of at least a portion of the second heat exchanger 320 in contact with the fluidized bed of the fluidized bed boiler 100, for Figure 1a and Figure 1b For reference. In the case of a circulating fluidized bed boiler 100 ( Figure 1aA circulating fluidized bed is disposed in a first furnace 162. The heat exchange medium heating the circulating fluidized bed boiler includes circulating bed material from the first furnace 162 to a cyclone separator 132, from the cyclone separator 132 to a loop seal 140, and from the loop seal 140 back to the first furnace 162 (e.g., via a return passage 136). However, the loop seal 140 may be configured to contact the wall of the first furnace 162, thereby allowing the return passage 136 to be shorter, for example, through a hole in the wall. In use, another fluidized bed is disposed in the loop seal 140 of the circulating fluidized bed boiler 100 to facilitate the circulation of bed material through the loop seal. Figure 1a In this embodiment, the second heat exchanger 320 is disposed in the loop seal 140 of the fluidized bed boiler 100. This is also the preferred location for the second heat exchanger 320 for several reasons:

[0047] -Because the particle velocity is lower, the erosion is less than that in the first furnace.

[0048] -Because the cyclone separator 132 separates the corrosive first flue gas 163 into the flue gas passage 120, the corrosion is less than that in the first furnace.

[0049] - Easier to integrate with the second furnace 172 and the third heat exchanger 330.

[0050] Bed material can be conveyed from the bottom of the cyclone separator 132 via a dipple (material seal tube) passage 134 to a loop-sealed heat exchanger 400 disposed in the loop seal section 140. The term "dipple" refers to a passage in which the bed material is configured to flow primarily downwards. The bed material is configured to return from the loop-sealed heat exchanger 400 to the first furnace 162 via a return passage 136.

[0051] (Circulating or bubble-type) fluidized bed boiler 100 and / or loop-sealed heat exchanger 400 for circulating fluidized bed boiler 100 may include baffles, i.e., a third baffle 475, such as Figure 2c As shown. If the third baffle 475 is used in the first mode (i.e., during the first time period), the third baffle 475 is in the open position so that the second flue gas 173 can be circulated.

[0052] refer to Figure 2b In the second mode (i.e., during the second time period), the method includes recovering heat from a fluidized bed configured to contact at least a portion of the second heat exchanger 320 to a heat exchange medium via the second heat exchanger 320.

[0053] Preferably, the fluidized bed boiler 100 is designed such that the circulation of the heat exchange medium does not need to be controlled when switching from a first mode to a second mode. Therefore, in one embodiment, also in the second mode, the method includes: conveying the heat exchange medium from a second heat exchanger 320 to a third heat exchanger 330; and conveying the heat exchange medium through the third heat exchanger 330. Thus, in the second mode, the heat exchange medium can be circulated in a manner similar to that in the first mode. While this may eliminate the need to heat the heat transfer medium, it reduces investment costs and increases the robustness of the fluidized bed boiler 100.

[0054] However, in the second mode, during the second time period, the heat exchange medium is delivered through the third heat exchanger 330 without burning the second fuel 175 in the second furnace 172. This reduces the use of the second fuel 175. Alternatively, a smaller amount of the second fuel 175 can be burned during the second time period (in terms of average mass per unit time) compared to the first time period. For example, the consumption of the second fuel 175 during the second time period (in terms of average mass per unit time) can be less than half, less than one-quarter, or less than one-tenth of the consumption of the second fuel 175 during the first time period (in terms of mass per batch).

[0055] Because the heat exchange medium also circulates through the third heat exchanger 330 in the second mode (i.e., during the second time period), the fluidized bed boiler 100 and / or the loop-sealed heat exchanger 400 for the fluidized bed boiler 100 may include a third baffle 475. The purpose of the third baffle is to prevent air circulation through the third heat exchanger 330 in the second mode. Therefore, in the second time period, the third baffle 475 may be in the closed position, such as... Figure 2c As shown. In this way, the heat loss of the circulating air is minimized in the second period. However, depending on the design details, the natural convection of air through the third heat exchanger 330 may be so small that a third baffle 475 is unnecessary. The third baffle 475 may, for example, be sliding. The third baffle 475 may, for example, be about axis 476 (see... Figure 2c Pivotable. Further or other baffles may be used for the purposes detailed below. Figure 2cIn this configuration, the third baffle 475 is positioned downstream of the third heat exchanger 330 (downstream of the flow direction of the second flue gas 173 during the first time period). Although not shown, the third baffle 475 may be positioned upstream of the burner 176. Although not shown, the third baffle 475 may be positioned both downstream of the burner 176 and upstream of the third heat exchanger 330. Note that during the second time period, even with the baffle, the steam is slightly cooled as it propagates through the third heat exchanger 330.

[0056] The second mode may correspond to operating conditions where the fluidized bed boiler 100 is under high load. Therefore, in one embodiment, the load of the fluidized bed boiler 100 during the second time period is greater than the load during the first time period. For example, the load of the fluidized bed boiler 100 during the second time period may be at least equal to a threshold. Refer to the load threshold discussed in conjunction with the first mode. The precise value of the threshold depends on the details of the situation, but in a typical circulating fluidized bed boiler, the threshold may be, for example, 30% to 70% of the maximum load of the fluidized bed boiler, such as 50% of the maximum load of the fluidized bed boiler.

[0057] In a preferred embodiment, the third heat exchanger 330 does not come into contact with the first flue gas 163. This has the effect that even if a low-quality fuel is used as the first fuel 165 to generate the first flue gas 163, the corrosive compounds of the first flue gas 163 will not corrode the third heat exchanger 330.

[0058] In a preferred embodiment, the third heat exchanger 330 does not contact the fluidized bed of the fluidized bed boiler 100. Specifically, in one embodiment, the third heat exchanger 330 does not contact the same fluidized bed that contacts the second heat exchanger 320. Preferably, the third heat exchanger 330 does not contact any fluidized bed composed of fluidized solids, heat-resistant materials, or particulate materials. This has the effect that the heat from the second fuel 175 can be directly utilized at the third heat exchanger 330. Therefore, the heat from the second flue gas 173 is not consumed to heat the bed material of the fluidized bed. Furthermore, process control becomes more rapid because the bed material does not need to be heated when changing from the second mode to the first mode, and does not need to be cooled when changing from the first mode to the second mode. Additionally, when the third heat exchanger 330 does not contact the fluidized bed of the fluidized bed boiler 100, problems related to agglomeration and / or sintering of the bed material are avoided, at least near the third heat exchanger 330. Furthermore, when the third heat exchanger 330 is not in contact with the fluidized bed of the fluidized bed boiler 100, problems related to the erosion of the heat exchanger surface by the bed material are avoided at the surface of the third heat exchanger 330.

[0059] The method and fluidized bed boiler allow the use of fluidized bed boiler 100 at low loads (by operating in the first mode), and also when low-quality fuel is used as the first fuel 165. Here, the term "fuel quality" refers at least to the total content of alkalis and halogens in the fuel (applicable to both first fuel 165 and second fuel 175). The term "alkali metal" refers to elements in Group 1 of the IUPAC periodic table, excluding hydrogen, while the term "halogen" refers to elements in Group 17 of the IUPAC periodic table. Alkali metals and halogens typically constitute the compounds in the fuel. When burned, at least some of the alkali metals and halogens eventually enter the flue gas (applicable to both first and second flue gas 163; however, the second fuel may be substantially free of alkali metals and halogens). In the flue gas, these elements typically form alkali metal halides, i.e., compounds containing alkali metal elements and halogen elements, examples of which include NaCl, NaF, NaBr, KCl, KF, and KBr. Some of the alkali metals and halogens remain in the ash. By using high-quality fuel as the second fuel 175, corrosion problems associated with low-quality fuels are avoided.

[0060] Therefore, in one embodiment, the second flue gas 173 contains less alkali metals and halogens than the first flue gas 163. Alkali metals and / or halogens may be contained in the alkali metal halides of the flue gases (163, 173). These compounds originate from the quality of the fuel. Therefore, in the same or another embodiment, the second fuel 175 contains less alkali metals and halogens than the first fuel 165. More specifically, the second fuel 175 contains a less content of compounds containing at least one of alkali metals and halogens than the first fuel 173.

[0061] In a preferred embodiment, the second fuel 175 contains less than 500 ppm or less than 100 ppm of alkali metal atoms and halogen atoms by weight. Naturally, these atoms are not free, but rather part of the chemical composition(s) of the second fuel 175. Furthermore, in one embodiment, the second flue gas 173 contains less than 500 ppm, preferably less than 100 ppm, of alkali metal halides by weight.

[0062] Typically, high-quality fuels are gases or liquids, such as natural gas or light oil. Therefore, in one embodiment, at a temperature of 20°C and a pressure of 1 atm, the second fuel 175 is a liquid or gas, such as a gas comprising natural gas or a liquid comprising oil (e.g., light fuel oil). More preferably, to ensure smooth feeding of the second fuel 175, the second fuel is free of solid particles at the aforementioned temperature and pressure.

[0063] However, as stated above, the first fuel 165 does not need to be of high quality. Furthermore, to save operating costs, the first fuel 165 is preferably of low quality. Therefore, in one embodiment, at a temperature of 20°C and a pressure of 1 atm, the first fuel 165 comprises solid materials, such as biomass and / or residue-derived fuels. Even more preferably, at the aforementioned temperature and pressure, [A] the second fuel 175 is a gas or liquid, and [B] the first fuel 165 comprises solid materials.

[0064] As described above, preferably, the second furnace 172 is disposed in the loop seal section 142 of the circulating fluidized bed boiler. More preferably, the second furnace 172 and the third heat exchanger 330 are disposed as part of the loop seal heat exchanger 400. Figures 3 to 7 Details of the loop-sealed heat exchanger 400 are shown. When installed in the loop seal section of the circulating fluidized bed boiler 100, the loop-sealed heat exchanger 400 is configured as follows:

[0065] - The second fuel 175 is burned in the second furnace 172 of the loop-sealed heat exchanger 400 to produce the second flue gas 173;

[0066] - The heat exchange medium is conveyed from the second heat exchanger 320 to the third heat exchanger 330 of the loop-sealed heat exchanger 400; and

[0067] - Using a third heat exchanger 330, heat is recovered from the second flue gas 173 to the heat exchange medium.

[0068] Other components of the fluidized bed boiler 100 (in) Figure 1a The image (shown for understanding the context of the embodiment) includes: a feeder 164 configured to feed first fuel 165 into a first furnace 162; and an air passage 104 for feeding combustion air 106 into the first furnace 162. The combustion air 106 functions as an oxygen source for combustion and as a fluidizing gas (at least a portion of it). As detailed below, the term "combustion air" may refer to a mixture of air with certain other gases, particularly a mixture of air and second flue gas 173a. As detailed below, other gases (particularly the second flue gas) may also be used to further fluidize the material within the first furnace 162.

[0069] Between the air passages 104, ash passages 112 are provided for removing bottom ash from the first furnace 162. Bottom ash coolers 114 are configured to receive hot bottom ash and recover heat therefrom. A first heat exchanger 310 is disposed in the flue gas duct 120. The fluidized bed boiler may include further heat exchangers, such as a heat exchanger 122 configured to recover heat from the first flue gas 163. Typically, the heat exchanger is a heat exchanger that receives a liquid heat exchange medium (particularly water). Typically, water will not boil even when heated in the heat exchanger. The heat exchanger 122 is disposed upstream of the first heat exchanger 310 in the flow direction of the heat exchange medium. A drum 124 may be provided between the first heat exchanger 310 and the heat exchanger 122 to separate the liquid portion (e.g., water) from the gaseous portion (e.g., steam) of the heat exchange medium. In addition, other heat exchangers (not shown) may be connected to drum 124 to boil the water and generate saturated steam.

[0070] The heated heat exchange medium is preferably used to generate mechanical energy in the steam turbine 152. Therefore, in an embodiment of the method, the heat exchange medium comprises steam, and the method includes conveying steam from a third heat exchanger 330 to the steam turbine 152. Preferably, steam is conveyed from the third heat exchanger 330 to the steam turbine 152 such that no heat exchanger is provided between the third heat exchanger 330 and the steam turbine 152. Therefore, preferably, the third heat exchanger 330 is the last heat exchanger before the steam turbine 152. Correspondingly, the power generation equipment includes a fluidized bed boiler 100 and a steam turbine 152, such as... Figure 1a and Figure 1b As shown. The power generation equipment also includes a third pipeline 332 configured to deliver a heat exchange medium from a third heat exchanger 330 to a steam turbine 152. Preferably, the third pipeline 332 does not include a heat exchanger configured to heat or cool the heat exchange medium between the third heat exchanger 330 and the steam turbine 152.

[0071] Preferably, the method further includes using a steam turbine 152 to operate a generator 155 and generate electricity in this manner. The corresponding power generation device includes a generator 155, which is mechanically connected to the steam turbine 152. For example, a shaft may be configured to be rotated by the steam turbine 152 and to operate the generator, i.e., to rotate multiple components of the generator 155.

[0072] Figure 3 A cross-section of an embodiment of the loop-sealed heat exchanger 400, viewed from top, is shown (see...). Figure 1a(See section line III-III in the diagram). In use, the loop-sealed heat exchanger 400 is installed in the loop seal section 140 of the circulating fluidized bed boiler 100. Therefore, the loop-sealed heat exchanger 400 is suitable for this purpose, even though it is not part of the boiler. The first chamber 412 of the fluidized bed boiler 100 is, in this embodiment, the first chamber 412 of the loop-sealed heat exchanger 400. Furthermore, in this embodiment, the third heat exchanger 330 is installed in the second chamber 422 of the loop-sealed heat exchanger 400.

[0073] The walls of the loop-sealed heat exchanger 400 define (i.e., the loop-sealed heat exchanger 400 includes) a first chamber 412, a second chamber 422, and a second furnace 172, the functions of which have been detailed above. A second heat exchanger 320 is disposed in the first chamber 412, a third heat exchanger 330 is disposed in the second chamber 422, and a second conduit 322 connects the second heat exchanger 320 and the third heat exchanger 330. The second conduit 322 may extend only within the chambers 412, 422, such as... Figure 3 As shown, or a portion of the second pipeline may extend to the outside of chambers 412, 422, such as Figure 9b As shown.

[0074] The loop-sealed heat exchanger includes an inlet chamber 431, through which the circulating bed material flows from an immersion tube channel 134 (see...). Figure 1a The bed material flows from the entrance chamber 431 to at least one of the entrance chamber 433 and the bypass chamber 432 (see [link to relevant documentation]). Figure 3 ).

[0075] The bypass chamber 432 has two functions. First, heat recovery through the second heat exchanger 320 can be controlled by controlling the amount of bed material flowing through the bypass chamber 432. The bypass chamber 432 does not have a heat exchanger surface for heating the heat exchange medium. Therefore, by guiding the bed material to flow only or primarily through the bypass chamber and not through the first chamber 412, the heat exchange medium is heated to a lesser extent in the second heat exchanger 320. Second, the bypass chamber 432 acts as a gaslock. The bypass chamber 432 is an upleg, meaning that the bed material flows primarily upwards in the bypass chamber 432. This, in conjunction with the immersion tube passage 134, provides a gaslock that prevents the bed material from flowing in the wrong direction (i.e., from the first furnace 162 to the loop-sealed heat exchanger 400).

[0076] The inlet chamber 433 is also designed as an upper branch. Therefore, the inlet chamber 433 primarily functions as an airlock connected to the infiltration tube channel 134. Additionally, another function of the inlet chamber 433 is to feed bed material to the first chamber 412. The bed material flows from the first chamber 412, which is formed as an infiltration tube, to the outlet chamber 435, which is designed as an upper branch.

[0077] exist Figure 3 In one embodiment, the second heat exchanger 320 is disposed within the first chamber 412 of the loop-sealed heat exchanger 400, while the third heat exchanger 330 is disposed within the second chamber 422 of the loop-sealed heat exchanger 400. Disposing the heat exchangers within chambers is preferred because it increases the area of ​​the heat transfer surface and facilitates maintenance. However, the second heat exchanger 320 may be disposed within the wall of the first chamber 412. Similarly, the third heat exchanger 330 may be disposed within the wall of the second chamber 422.

[0078] The bed material flows from the exit chamber 435 and / or from the bypass chamber 432 to the return passage 136. The flow direction of the bed material is from... Figure 3 Arrows 451, 452, 453, 454, 455, and 457 are shown in the diagram. The geometric details of the loop-sealed heat exchanger 400 can vary. For example, as... Figure 14 As shown, a portion of the return channel 136 may be disposed between the parallel walls of the bypass chamber 432 and the outlet chamber 435, and the bed material is configured to flow through the perforations in these parallel walls to the return channel 136. Other types of loop-sealed heat exchangers will be described in detail below.

[0079] In this way, the present invention also relates to a novel fluidized bed heat exchanger 400. As described above, and as... Figures 3 to 10b and Figure 14 As shown, an embodiment of the fluidized bed heat exchanger 400 includes a first chamber 412 and a second chamber 422. A second heat exchanger 320 is disposed within the first chamber 412 (i.e., in the first chamber) or disposed within the wall defining the first chamber 412 (i.e., as part of the wall). A third heat exchanger 330 is disposed within the second chamber 422 (i.e., in the second chamber) or disposed within the wall defining the second chamber 422 (i.e., as part of the wall). The loop-sealed heat exchanger 400 may include a second line 322 for conveying the heat exchange medium from the second heat exchanger 320 to the third heat exchanger 330; and includes a first nozzle 462 (see...). Figure 7The system is configured to fluidize the bed material in the first chamber 412. To further heat the heat exchange medium already within the loop-sealed heat exchanger 400, the loop-sealed heat exchanger 400 includes: a second furnace 172 for burning a second fuel 175 to generate a second flue gas 173; and a passage 178 for conveying the second flue gas 173 to the second chamber 422.

[0080] exist Figure 3 , Figure 11 and Figure 14 In this configuration, the second chamber 422 is located adjacent to the first chamber 412. Furthermore, in... Figure 3 , Figure 11 and Figure 14 In the middle, the second furnace 172 is located next to the inlet chamber 433. Figure 3 and Figure 14 ) or next to the dental room 431 ( Figure 11 These two features, whether individually or in combination, are beneficial from an energy recovery perspective. Because of this arrangement, the second furnace 172 is heated via the first wall 441. Therefore, the second furnace 172 is heated not only by burning the second fuel but also by means of a heated bed material disposed in the adjacent chamber. Similarly, the second chamber 422 is heated via the first wall 441. Therefore, the second chamber is heated not only by burning the second fuel but also by means of a heated bed material. In this way, in one embodiment, a first side of one wall of the loop-sealed heat exchanger 400 (i.e., the first side of the first wall 441) defines the first chamber 412, and the opposite second side of that wall (i.e., the first wall 441) of the loop-sealed heat exchanger defines the second chamber 422. Additionally, preferably, the first wall 441 includes heat transfer tubes for recovering heat to the heat exchange medium. This applies to both the circulating fluidized bed boiler 100 and the loop-sealed heat exchanger 400. Furthermore, when the second heat exchanger 320 and the third heat exchanger 330 are disposed on opposite sides of the first wall 441 such that the normal N of the first wall 441 (see...) Figure 3 When extending through both the second heat exchanger 320 and the third heat exchanger 330, the second heat exchanger 320 and the third heat exchanger 330 can be easily integrated. In other words, the connecting second pipeline 322 can be made very short. This simplifies the structure of the loop-sealed heat exchanger and reduces manufacturing costs.

[0081] Furthermore, the second chamber 422 and the first chamber 412 share a common wall. (See reference) Figure 3 The second chamber 422 and the first chamber 412 typically share the second wall 443 of the loop-sealed heat exchanger 400. (Reference) Figure 3The second chamber 422 and the first chamber 412 typically share a third wall 445 of the loop-sealed heat exchanger 400. Additionally, preferably, the second wall 443 includes heat transfer tubes for recovering heat to the heat exchange medium. Also preferably, the third wall 445 includes heat transfer tubes for recovering heat to the heat exchange medium.

[0082] Regarding the term "wall" used here, it refers to a planar object that defines a chamber. Therefore, the first wall 441 defines chambers 433, 172, 422, and 412 (see...). Figure 3 ).like Figure 3 As shown, the second wall 443 defines chambers 422, 412, and 435; while the third wall 445 defines... Figure 3 All chambers of the loop-sealed heat exchanger.

[0083] Therefore, in one embodiment, a first side of one wall (i.e., the second wall 443) of the loop-sealed heat exchanger defines a first chamber 412, and the first side of the same wall (i.e., the second wall 443) defines a second chamber 422. This is also advantageous from the perspective of keeping the loop-sealed heat exchanger 400 simple in shape for easy installation.

[0084] Although the location of the third wall 445 is not critical, for manufacturing reasons, this wall preferably defines both the first chamber 412 and the second chamber 422. Therefore, in Figure 3 In the loop-sealed heat exchanger, a first side of one wall (i.e., the third wall 445) defines a first chamber 412, and the first side of the same wall (i.e., the third wall 445) defines a second chamber 422. As shown, the second wall and the third wall (443, 445) are spaced apart from each other; that is, they are not different parts of the same wall.

[0085] In the above structure, the second conduit 322 can be made very short or omitted. For example, see reference... Figure 15 The second heat exchanger 320 may include an inlet manifold 320a and an outlet manifold 320b, through which steam from the first superheater 310 may be distributed to the tubes of the second superheater 320 via the inlet manifold 320a, and the steam flowing through the tubes of the second superheater 320 may be collected in the outlet manifold 320b of the second heat exchanger 320. Similarly, the third heat exchanger 330 may include an inlet manifold 330a for distributing steam to the tubes of the third heat exchanger 330, and an outlet manifold 330b for collecting the steam that has flowed through the tubes of the third heat exchanger 330.

[0086] refer to Figure 15The outlet manifold 320b of the second heat exchanger 320 and the inlet manifold 330a of the third heat exchanger can be configured as part of the steam chamber 335. A portion of the steam chamber 335 can be considered as forming the second pipeline 322. This arrangement, where the steam chamber 335 serves as both the outlet manifold 320b of the second heat exchanger 320 and the inlet manifold 330a of the third heat exchanger 330, further simplifies the structure of the loop-sealed heat exchanger 400, thereby reducing manufacturing costs. Additionally, this structure is mechanically robust. As shown, this structure is easily implemented when the second heat exchanger 320 and the third heat exchanger 330 are arranged in adjacent chambers 412, 422. This also relates to the issue of the normal N of the first wall 441 of the loop-sealed superheater extending through both the second heat exchanger 320 and the third heat exchanger 330; this issue will be further detailed below.

[0087] refer to Figure 15 The inlet manifold 320a of the second heat exchanger 320 can be mechanically connected to the outlet manifold 330b of the third heat exchanger 330. However, in this case, for example if the connection between manifold 320a and manifold 330b is a pipeline, a plug 325 can be used to prevent steam from flowing directly from the inlet manifold 320a of the second heat exchanger 320 to the outlet manifold 330b of the third heat exchanger 330. The inlet manifold 320a of the second heat exchanger 320 and the outlet manifold 330b of the third heat exchanger 330 can be components of the same tubular structure equipped with the plug 325.

[0088] Regarding the circulation of bed material within the loop-sealed heat exchanger 400 and through the first chamber 412, a first opening 451' is provided in the lower part of the inlet chamber 431 to allow bed material to flow into the inlet chamber 433, as indicated by arrow 451 (see...). Figure 3 and Figure 4 The second opening 453' is located in the upper part of the inlet chamber 433 to allow bed material to flow into the first chamber 412, as indicated by arrow 453 (see...). Figure 4 and Figure 7 A third opening 455' is provided in the lower part of the first chamber 412 to allow bed material to flow to the outlet chamber 435, as indicated by arrow 455 (see...). Figure 7 Finally, a fourth opening 457' is provided in the upper part of the outlet chamber 435 to allow bed material to exit the loop-sealed heat exchanger 400, as indicated by arrow 457.

[0089] Regarding the circulation of bed material within the loop-sealed heat exchanger 400 and through the bypass chamber 432, a fifth opening 452' is provided in the lower part of the inlet chamber 431 to allow bed material to flow into the bypass chamber 432, as indicated by arrow 452 (see...). Figure 3 and Figure 4 A sixth opening 454' is provided in the upper part of the bypass chamber 432 to allow bed material to exit the loop-sealed heat exchanger 400, as indicated by arrow 454.

[0090] The bed material is fluidized in the chambers of the loop-sealed heat exchanger 400 (except for those chambers without bed material (i.e., at least the first furnace 172 and the second chamber 422)). However, the bed material does not need to be fluidized simultaneously in all chambers. For example, fluidization of the material in the bypass chamber 432 can be stopped to control the flow through other chambers. For fluidization purposes, the loop-sealed heat exchanger 400 includes nozzles 460 (see...). Figure 4 and Figure 5 These nozzles are positioned at the bottom of those chambers in which the material is fluidized. For more detailed functionality of nozzle 460, the loop-sealed heat exchanger 400 includes a first nozzle 462 (see...). Figure 5 and Figure 7 The first nozzle is configured to fluidize the bed material in the first chamber 412. In this way, a fluidized bed is formed in the first chamber 412 so that the second heat exchanger 320 comes into contact with the fluidized bed of the fluidized bed boiler.

[0091] The loop-sealed heat exchanger 400 includes a second nozzle 464 (see...) Figure 4 The second nozzle is configured to fluidize the bed material in the fluidized bypass chamber 432. The loop-sealed heat exchanger 400 includes a third nozzle 466 (see...). Figure 4 The third nozzle is configured to fluidize the bed material in the inlet oral cavity 433. By controlling the amount of fluidizing air in the bypass chamber 432 and the inlet oral cavity 433, the amount of bed material directed to the bypass chamber 432 and the amount of bed material directed to the inlet oral cavity 433 can be controlled. Typically, the more fluidizing gas is fed, the easier the bed material flows, and in this way the bed material flow increases; and vice versa.

[0092] Since the purpose of the third heat exchanger 330 is to superheat the steam to the final temperature during the first period (see...) Figure 2a Therefore, the temperature of the heat exchange medium within the third heat exchanger 330 is at its highest during the first time period. Consequently, the second flue gas 173 also has such a high temperature downstream of the third heat exchanger 330 that the second flue gas 173 can be used at least in the following ways:

[0093] - The heat exchange medium used to heat the upstream of the third heat exchanger 330, for example by using the second heat exchanger 320 and / or the first heat exchanger 310; and / or

[0094] - As the fluidizing gas or part of the fluidized bed boiler 100.

[0095] Regarding the former, the second flue gas 173 may, for example, be mixed with the first flue gas 163 upstream of the first heat exchanger 310. However, for the purpose of heat recovery, it would be beneficial to feed the second flue gas 173 further upstream of the first heat exchanger, whereby the second flue gas may be used as a fluidizing gas, for example.

[0096] Regarding the latter, since the temperature of the second flue gas 173 is very high, using it as a fluidizing gas or as part of a fluidizing gas means that the residual heat energy of the second flue gas 173 is transferred to the bed material of the fluidized bed, and therefore can be utilized in the process and recovered by conventional methods. Examples of fluidized beds in which the second flue gas 173 can be used as a fluidizing gas include the first furnace 162 (see...). Figure 1a and Figure 1b ) and first chamber 412 (see Figure 1a ).

[0097] The fluidizing gas may also include gases other than the second flue gas 173. Not all of the second flue gas needs to be used as at least a portion of the fluidizing gas. Therefore, a preferred embodiment includes using a fluidizing gas containing at least some of the second flue gas 173 to fluidize the fluidized bed located within the fluidized bed boiler 100. For process simplification, it is preferable that all of the second flue gas 173 is used in the same manner. Therefore, a more preferred embodiment includes using at least 75% (by volume) of the second flue gas 173 to fluidize one or more fluidized beds of the fluidized bed boiler 100. Here, the fluidized bed may be a fluidized bed in the first furnace 162 or a fluidized bed in the first chamber 412; and the second flue gas 173 may be used as at least a portion of the fluidizing gas in either of the aforementioned fluidized beds.

[0098] Accordingly, the fluidized bed boiler 100 preferably includes a passage 179 for conveying at least some of the second flue gas 173 to a chamber in the fluidized bed boiler in which a fluidized bed is configured to form in use. As an example, the fluidized bed boiler 100 may include a second flue gas passage 179 for conveying at least some of the second flue gas 173 to a portion of a first furnace 162 in which a fluidized bed is configured to form. Reference Figure 1a In use, in a circulating fluidized bed boiler, almost the entire material within the first furnace chamber 162 is fluidized. (Reference) Figure 1b In use, in a bubble fluidized bed boiler, the material in the lower part of the first furnace 162 is fluidized.

[0099] For example, in Figure 1a as well as Figures 3 to 7 In the context of an embodiment, such as Figure 8aAs shown, the second flue gas 173 can be conveyed to the return channel 136 through the second flue gas passage 179. At some point within the second flue gas passage 179, the second flue gas 173 mixes with the bed material in the return channel 136. Subsequently, both the bed material and the second flue gas 173 are conveyed into the first furnace 162 via the combined second flue gas passage 179 and return channel 136. In the first furnace, the second flue gas 173 becomes mixed with other fluidizing gases (i.e., combustion air) and is thus used as part of the fluidizing gas in the first furnace. Therefore, the second flue gas 173 does not need to be fed through the combustion air passage 104 of the fluidized bed boiler. However, as... Figure 8b As shown, the second flue gas 173 can be mixed with combustion air to be fed into the first furnace through combustion air passage 104. When the combustion air is preheated (as is typically the case), the second flue gas is preferably mixed with the preheated combustion air (i.e., downstream of the combustion air preheater) to improve preheating efficiency. In this way, a portion of the combustion air duct forms part of the second flue gas passage 179.

[0100] As described above, the third heat exchanger 330 may be arranged side by side with respect to the second heat exchanger 320 (in the horizontal direction Sx). In other words, the first wall 441 may be a vertical wall.

[0101] refer to Figure 9a and Figure 9b The third heat exchanger 330 can be positioned on top of the second heat exchanger 320. In this case, the first wall 441 is substantially horizontal, as... Figure 9b As shown. As described above, the second heat exchanger 320 is disposed on a first side of the first wall 441, while the third heat exchanger is disposed on the opposite second side of the first wall 441. Furthermore, the first wall 441 defines a first chamber 412 (in which the second heat exchanger 320 is disposed), and the first wall 441 also defines a second chamber 422 (in which the third heat exchanger 330 is disposed). Finally, the second heat exchanger 320 and the third heat exchanger 330 are arranged such that the normal N of the first wall 441 extends through both the second heat exchanger 320 and the third heat exchanger 330. The technical effects are described above. The outlet manifold 320b of the second heat exchanger 320 can be connected to the inlet manifold of the third heat exchanger 330. Figure 15 For reference only. However, in this case, the steam chamber 335 can be vertical.

[0102] The second wall 443 and the third wall 445 are in Figure 9aAs shown, a second heat exchanger 320 is disposed on a first side of a second wall 443, and a third heat exchanger 330 is disposed on a first side of a second wall 443. Furthermore, the second wall 443 defines a first chamber 412 (in which the second heat exchanger 320 is disposed) and a second chamber 422 (in which the third heat exchanger 330 is disposed). As shown, a second heat exchanger 320 is disposed on a first side of a third wall 445, and a third heat exchanger 330 is disposed on a first side of a third wall 445. Furthermore, the third wall 445 defines a first chamber 412 (in which the second heat exchanger 320 is disposed) and a second chamber 422 (in which the third heat exchanger 330 is disposed).

[0103] exist Figure 9a and Figure 9b In one embodiment, for example, by providing a flue gas passage at the top of the outlet chamber 435, the second flue gas 173 can be used as a fluidizing gas in the first furnace 162. Figures 3 to 7 , Figure 9a and Figure 9b It is known that, Figures 3 to 7 as well as Figure 9a and Figure 9b The loop-sealed heat exchanger 400 is similar in that the bed material is configured to flow through those chambers (i.e., chambers 431, 433, 412, 435, and 432). Therefore, in Figure 9a and Figure 9b In one embodiment, the second flue gas can flow through a flue gas passage disposed on top of the outlet chamber 435, through the outlet chamber 435 to the return passage 136, and finally through the return passage 136 to the first furnace 162. Therefore, the outlet chamber 435 forms part of the passage 179 for conveying at least some of the second flue gas 173 to a chamber of a fluidized bed boiler in which the fluidized bed is configured to be formed in use. For other portions of the passage 179, see [reference needed]. Figure 9b .

[0104] refer to Figure 9a and Figure 9b The above applies to both the loop-sealed heat exchanger 400 and the fluidized bed boiler 100.

[0105] refer to Figures 10a to 10f The third heat exchanger 330 can be positioned below the second heat exchanger 320. In this case, the first wall 441 is essentially horizontal, as... Figure 10bAs shown. As described above, the second heat exchanger 320 is disposed on a first side of the first wall 441, while the third heat exchanger 330 is disposed on the opposite second side of the first wall 441. Furthermore, the first wall 441 defines a second chamber 422 in which the third heat exchanger 330 is disposed. Finally, the second heat exchanger 320 and the third heat exchanger 330 are arranged such that the normal N of the first wall extends through both the second heat exchanger 320 and the third heat exchanger 330. See above for technical effects. The outlet manifold 320b of the second heat exchanger 320 can be connected to the inlet manifold of the third heat exchanger 330. Figure 15 For reference only. However, in this case, the steam chamber 335 can be vertical.

[0106] The second wall 443 and the third wall 445 are in Figure 10a As shown, a second heat exchanger 320 is disposed on a first side of a second wall 443, and a third heat exchanger 330 is disposed on a first side of a second wall 443. Furthermore, the second wall 443 defines a first chamber 412 in which the second heat exchanger 320 is disposed, and the second wall 443 also defines a second chamber 422 in which the third heat exchanger 330 is disposed. As shown, a second heat exchanger 320 is disposed on a first side of a third wall 445, and a third heat exchanger 330 is disposed on a first side of a third wall 445. Furthermore, the third wall 445 defines a first chamber 412 in which the second heat exchanger 320 is disposed, and the third wall 445 also defines a second chamber 422 in which the third heat exchanger 330 is disposed.

[0107] exist Figures 10a to 10d In one embodiment, the second flue gas 173 can be used as a fluidizing gas in the first chamber 412. The principle is... Figure 10b As shown, the second flue gas 173 flows through the heat exchanger tubing of the third heat exchanger 330 and from there flows through the first nozzle 462 to the first chamber 412. In this embodiment, air ( Figure 10b The "air" in the text is used both as the oxidizing medium for the second fuel 175 (i.e., the combustion air in the second furnace) and as the fluidizing gas for the first chamber 412. Therefore, in the second operating mode, i.e., during the second time period (see...), Figure 2b Air can cool the heat exchange medium flowing through the third heat exchanger 330.

[0108] The solution to this problem has been found Figure 10c and Figure 10d As shown in the image. Figure 10c and Figure 10dThe loop-sealed heat exchanger includes a first baffle 471 and optionally a first pivot 472. The first baffle 471 is pivotable about the first pivot 472. However, the baffle 471 can be understood as using two sliding baffles (corresponding to the position of the first baffle 471, one horizontal and the other vertical) without a pivot. Reference Figure 10c During the first time period, the first baffle 471 is positioned such that it is configured to direct the second flue gas 173 to the third heat exchanger 330. (Reference) Figure 10d During the second time period, the first baffle 471 is positioned such that it is configured to guide fluidized air or second flue gas 173 (as appropriate) to bypass the third heat exchanger 330. In this embodiment, during the second time period, there is no need to burn even a small amount of second fuel 175. Therefore, typically in this embodiment, no second flue gas is generated, and only air is guided by the first baffle [A] to bypass the third heat exchanger 330 and [B] to reach the first nozzle 462.

[0109] To further ensure that air does not cool the third heat exchanger 330 during the second period, the loop-sealed heat exchanger 400 may include a second baffle 473 and optionally a second pivot 474, such as Figure 10c and Figure 10d As shown. Figure 10c and Figure 10d Two second baffles 473 and a second pivot 474 for each second baffle 473 are shown.

[0110] The second baffle 473 is pivotable about the second pivot 474. As described above, a sliding baffle may be used alternatively or additionally. (See reference) Figure 10c During the first time period, the second baffle 473 is positioned such that it is configured to guide the second flue gas 173 from the third heat exchanger 330 to the first nozzle 462. (Reference) Figure 10d During the second time period, the second baffle 473 is positioned such that it is configured to prevent fluidizing air or the second flue gas 173 (as applicable) from flowing to the third heat exchanger 330. The first baffle 471 and the second baffle 473 are used in combination with a reference... Figure 2c The third baffle 475 discussed serves the same purpose.

[0111] Therefore, embodiments of the fluidized bed boiler 100 or the loop-sealed heat exchanger for a circulating fluidized bed boiler include a baffle device comprising at least one baffle (471, 473, 475), wherein the baffle device is configured to:

[0112] -Enables the second flue gas 173 to circulate from the second furnace 172 to the third heat exchanger 330; and

[0113] - Prevent air circulation through the third heat exchanger 330.

[0114] The former applies to the first time period (see Figure 2a , Figure 2c ,as well as Figure 10c The latter applies to the second period (see...). Figure 2b , Figure 2c ,as well as Figure 10d Regarding the latter, if a small amount of second flue gas is also burned during the second period, the air in it may include the second flue gas.

[0115] It has been further discovered that, in the first mode, i.e., in the first time period, more combustion air is typically required to burn the second fuel 175 than is needed to fluidize the bed material in the first chamber 412. It has been found that the excess heat can be recovered to the combustion air, which is then used for combustion in the second furnace 172.

[0116] refer to Figure 10e In one embodiment, the loop-sealed heat exchanger 400 includes a fourth heat exchanger 340. The fourth heat exchanger is configured to recover heat from the second flue gas 173 to air, particularly to combustion air used in the second furnace 172. This embodiment also includes a fourth line 342 configured to deliver heated air from the fourth heat exchanger 340 to the second furnace 172 for use as an oxidizing medium therein. This embodiment also includes a valve 344 configured to restrict the flow of the second flue gas through the fourth heat exchanger 340. Therefore, valve 344 can be used to control the amount of second flue gas used as a fluidizing gas in the loop-sealed heat exchanger 400. The second flue gas can also be used to fluidize the bed material in another chamber (or other chambers) of the loop-sealed heat exchanger besides the first chamber 412.

[0117] To recover heat from the excess second flue gas 173, a portion of the second flue gas 173 can be fed into the first furnace 162, and only a portion of the second flue gas 173 can be used as the fluidizing medium in the loop-sealed heat exchanger 400. An example of this solution is shown in... Figure 10f As shown, a portion of the second flue gas 173 is drawn from upstream of the fluidizing nozzle 460 and conveyed through a portion of channel 179 to the return channel 136. The second flue gas 173 flows through the return channel 136 to the first furnace 162, as illustrated above, for example, in reference to [reference needed]. Figure 8a The second flue gas 173 can be divided into a portion supplied to nozzle 460 and a portion supplied to the first furnace 162 using a valve (not shown). Although not shown, excess second flue gas 173 can be mixed with combustion air in the first furnace 162, such as... Figure 8b As detailed above.

[0118] The heat from the portion of the second flue gas 173 used to fluidize the bed material in the second chamber 412 and thus conveyed through nozzle 460 can be recovered by using the gas as part of the fluidizing gas in the first furnace 162 or by other methods detailed above. Figure 8a , Figure 8b , Figure 9a ,as well as Figure 9b For reference. For example, an opening may be provided above the outlet chamber 435 to allow the used fluidizing gas to flow to the return channel 136, or even... Figure 10e or Figure 10f The diagram shows the use of another portion of the second flue gas.

[0119] Although not shown, excess second flue gas 173 (i.e., the portion of second flue gas not conveyed through nozzle 460) can be mixed with first flue gas 163 downstream of the fluidized bed located in the first furnace 162 (e.g., downstream of the cyclone separator 132 in a circulating fluidized bed boiler, as appropriate) in this case. In this scenario, mixing flue gas 173 and 163 upstream of the first heat exchanger 310 would be advantageous. However, from an energy recovery point of view, it is more advantageous to use excess second flue gas or all of the second flue gas as part of the fluidizing gas in the first furnace 162.

[0120] refer to Figures 10a to 10f The above applies to both the loop-sealed heat exchanger 400 and the fluidized bed boiler 100.

[0121] although Figures 3 to 10f The chambers (431, 432, 433, 412, 435) through which the bed material is configured to extend are arranged relative to each other in the same manner, but the second furnace 172 and the third heat exchanger 330 can also be arranged in a simpler loop-sealed heat exchanger 400, such as... Figures 11 to 13 As shown.

[0122] exist Figures 11 to 13 In the loop-sealed heat exchanger, the bed material enters the inlet chamber 431 through the immersion pipe channel 134, such as Figure 3 As shown. However, at least a portion of the bed material enters the first chamber 412 directly from the inlet chamber 431, as indicated by arrow 451. For this purpose, an opening may be provided in the lower part of the inlet chamber 431. The second heat exchanger 320 is disposed in the first chamber 412. In the first chamber 412, the bed material flows upward and also along... Figure 11 The material flows in the negative Sx direction. The bed material exits from the first chamber 412 and reaches the return channel 136, as indicated by arrow 457. For this purpose, an opening may be provided in the upper part of the first chamber 412. Figure 11The loop-sealed heat exchanger 400 also includes a bypass chamber 432. At least some of the bed material can bypass the second heat exchanger 320 by flowing through the bypass chamber 432, as indicated by arrows 452 and 454. Figure 3 In the illustrated embodiment, the description of the bed material circulation through the bypass chamber 432 also applies.

[0123] Figure 11 The loop-sealed heat exchanger 400 also includes a second chamber 422, in which a third heat exchanger 330 is disposed, and a burner 176 is provided in the second furnace 172. Although Figure 11 Not shown, but the second flue gas is configured to flow from the second furnace 172 to the second chamber 422, where a third heat exchanger 330 is already installed. See reference. Figure 6 Even in Figure 11 In this process, the second chamber 422 is positioned along the positive Sy direction from the second furnace 172.

[0124] Figure 11 The loop-sealed heat exchanger 400 includes a first wall 441. (Reference) Figures 3 to 7 The description of the first wall 441 and its normal N applies here. Figure 11 The loop-sealed heat exchanger 400 includes a second wall 443. (Reference) Figures 3 to 7 The description of the second wall 443 applies here. Figure 11 The loop-sealed heat exchanger 400 includes a third wall 445. (Reference) Figures 3 to 7 The description of the third wall 445 applies here. The outlet manifold 320b of the second heat exchanger 320 can be connected to the inlet manifold 330a of the third heat exchanger 330, as follows. Figure 15 As shown.

[0125] Although not shown, the loop-sealed heat exchanger 400 is provided with a nozzle 460 (see nozzle 462 above) for blowing fluidizing gas into the first chamber 412 and a nozzle 460 (see nozzle 464 above) for blowing fluidizing gas into the bypass chamber 432, so as to fluidize the bed material therein.

[0126] exist Figure 11 In this configuration, the first chamber 412 and the second chamber 422 are arranged side-by-side along a horizontal direction (Sx). However, the first and second chambers can be arranged such that the third heat exchanger 330 is positioned above the second heat exchanger, as shown below. Figure 12 As shown. In Figure 12 In one embodiment, the second flue gas 173 downstream of the third heat exchanger 330 can be transported through the first chamber 412 to the return channel 136 to serve as a fluidizing medium in both the first chamber 412 and the first furnace 162. Figure 12The loop-sealed heat exchanger 400 includes a first wall 441. (Reference) Figure 9a and Figure 9b The description of the first wall 441 and its normal N applies. Even if not in Figure 12 As shown in the figure, Figure 12 The loop-sealed heat exchanger 400 includes a second wall 443 and a third wall 445, the purpose of which is consistent with the reference. Figure 9a and Figure 9b The disclosed wall 443 and 445 are the same.

[0127] Furthermore, the first chamber 412 and the second chamber 422 can be configured such that the third heat exchanger 330 is located below the second heat exchanger 320, as shown below. Figure 13 As shown. The second flue gas 173 can be used to fluidize the bed material in the first chamber 412. When an excess of the second flue gas is available, a portion of the flue gas does not need to be conveyed through nozzle 460 (specifically nozzle 462). The excess second flue gas can be conveyed through the above-mentioned reference... Figure 10e and Figure 10f One of the methods discussed can be used. See the above references. Figure 10c and Figure 10d The proposed scheme is to prevent the combustion air used for the second fuel 175 from cooling the third heat exchanger 330.

[0128] Figure 13 The loop-sealed heat exchanger 400 includes a first wall 441. (Reference) Figures 10a to 10f The description of the first wall 441 and its normal N applies here. Although Figure 13 Not shown in the image, but Figure 13 The loop-sealed heat exchanger 400 includes a second wall 443 and a third wall 445, the purpose of which is consistent with the reference. Figures 10a to 10f The disclosed wall 443 and 445 are the same.

Claims

1. A method for heating a heat exchange medium in a fluidized bed boiler (100), the method comprising, in a first time period: The first fuel (165) is burned in the first furnace (162) of the fluidized bed boiler (100) to produce the first flue gas (163). Heat is recovered from the first flue gas (163) to the heat exchange medium using a first heat exchanger (310); The heat exchange medium is transported from the first heat exchanger (310) to the second heat exchanger (320), at least a portion of which is configured to contact the fluidized bed of the fluidized bed boiler (100). A second fuel (175) is burned in the second furnace (172) of the fluidized bed boiler (100) to produce a second flue gas (173). The heat exchange medium is transported from the second heat exchanger (320) to the third heat exchanger (330); and Heat is recovered from the second flue gas (173) to the heat exchange medium using the third heat exchanger (330), wherein: The third heat exchanger (330) does not contact the fluidized bed of the fluidized bed boiler (100), and The second flue gas (173) contains less alkali metals and halogens than the first flue gas (163); and / or The second fuel (175) contains less alkali metals and halogens than the first fuel (165).

2. The method according to claim 1, wherein: The third heat exchanger (330) does not come into contact with the first flue gas (163).

3. The method according to claim 1 or 2, wherein the second time period includes: Heat is recovered from the fluidized bed of the fluidized bed boiler (100) to the heat exchange medium using the second heat exchanger (320), and The heat exchange medium is transported from the second heat exchanger (320) to the third heat exchanger (330), and [A]： During the second time period, the second fuel (175) is not burned in the second furnace (172); or [B] During the second time period, less second fuel (175) is burned in the second furnace (172) compared to the first time period.

4. The method according to claim 3, wherein, The method during the second time period includes: The heat exchange medium is delivered through the third heat exchanger (330).

5. The method according to claim 3, wherein: The load of the fluidized bed boiler (100) during the second time period is greater than the load of the fluidized bed boiler (100) during the first time period.

6. The method according to claim 5, wherein: The fluidized bed boiler (100) experiences a load less than a threshold during the first time period, and The load of the fluidized bed boiler (100) during the second time period is at least equal to the threshold.

7. The method according to claim 1 or 2, wherein: The second fuel (175) is a liquid or a gas; and / or The first fuel (165) comprises a solid material.

8. The method according to claim 7, wherein: The second fuel (175) is a gas including natural gas or a liquid including oil, and the first fuel (165) includes biomass and / or residue-derived fuels.

9. The method according to claim 1 or 2, comprising: The bed material is circulated from the first furnace chamber (162) to the cyclone separator (132), from the cyclone separator (132) to the loop seal (140), and from the loop seal (140) to the first furnace chamber (162), wherein: The second heat exchanger (320) is disposed in the loop seal (140) of the fluidized bed boiler (100).

10. The method according to claim 9, wherein: The first side of the first wall (441), the first side of the second wall (443), and the first side of the third wall (445) of the loop-sealed heat exchanger (400) define a first chamber (412). The second chamber (422) is defined by the first side of the second wall (443) and the first side of the third wall (445) of the loop-sealed heat exchanger (400) and the opposite second side of the first wall (441). The second heat exchanger (320) is disposed in the first chamber (412) or in the wall defining the first chamber (412). The third heat exchanger (330) is disposed in the second chamber (422) or in the wall defining the second chamber (422).

11. The method according to claim 1 or 2, comprising: The fluidized bed within the fluidized bed boiler (100) is fluidized using a fluidizing gas containing at least some of the second flue gas (173).

12. A fluidized bed boiler (100), comprising: A first furnace (162) is used to burn a first fuel (165) comprising solid materials to produce a first flue gas (163). A first heat exchanger (310) is used to recover heat from the first flue gas (163) to the heat exchange medium; A second heat exchanger (320) is disposed in a location of the fluidized bed boiler (100) such that a fluidized bed containing bed material is configured to contact the second heat exchanger (320) during use. A first pipeline (312) is used to transport the heat exchange medium from the first heat exchanger (310) to the second heat exchanger (320). The second furnace (172) is used to burn the second fuel (175) to produce the second flue gas (173). The burner (176) is disposed in the second furnace chamber (172); as well as A third heat exchanger (330) is used to recover heat from the second flue gas (173) to the heat exchange medium received from the second heat exchanger (320), wherein The third heat exchanger (330) is configured not to contact the fluidized bed of the fluidized bed boiler (100); and The burner (176) is configured to burn the second fuel (175), which is a liquid or a gas.

13. The fluidized bed boiler (100) according to claim 12, comprising: cyclone separator (132); as well as Loop sealing part (140); wherein: The bed material is configured to circulate from the first furnace chamber (162) through the cyclone separator (132) to the loop seal (140) and from the loop seal (140) to the first furnace chamber (162).

14. The fluidized bed boiler (100) according to claim 13, wherein: The fluidized bed boiler (100) includes a loop-sealed heat exchanger (400) disposed in the loop seal (140). The loop-sealed heat exchanger (400) includes a first chamber (412) and a second chamber (422); The first side of the first wall (441), the first side of the second wall (443), and the first side of the third wall (445) of the loop-sealed heat exchanger (400) define the first chamber (412); and The second chamber (422) is defined by the first side of the second wall (443), the first side of the third wall (445), and the opposite second side of the first wall (441). The second heat exchanger (320) is disposed in the first chamber (412) or in the wall defining the first chamber (412); The third heat exchanger (330) is disposed in the second chamber (422) or in the wall defining the second chamber (422).

15. The fluidized bed boiler (100) according to any one of claims 12 to 14, comprising: Channel (179) for conveying at least some of the second flue gas (173) to a portion of the fluidized bed boiler (100), in which the fluidized bed is configured to be formed in use.

16. A power generation device, comprising: Fluidized bed boiler (100) according to any one of claims 12 to 15; Steam turbine (152); Pipeline (332) is configured to convey heat exchange medium from the third heat exchanger (330) to the steam turbine (152); and The generator (155) is configured to be mechanically connected to the steam turbine (152).

17. A loop-sealed heat exchanger (400), comprising: First chamber (412) and second chamber (422); The second heat exchanger (320) is disposed in the first chamber (412) or in the wall defining the first chamber (412); A third heat exchanger (330) is disposed in the second chamber (422) or in the wall defining the second chamber (422); A first nozzle (462) is used to fluidize the bed material in the first chamber (412); The second furnace (172) is used to burn the second fuel (175) to produce the second flue gas (173). The burner (176) is disposed in the second furnace chamber (172); and Passage (178) for conveying the second flue gas (173) to the second chamber (422), wherein The third heat exchanger (330) is configured not to contact the fluidized bed; and The burner (176) is configured to burn the second fuel (175), which is a liquid or a gas.

18. The loop-sealed heat exchanger (400) according to claim 17, comprising: The first wall (441) makes: The second heat exchanger (320) is disposed on a first side of the first wall (441), and the third heat exchanger (330) is disposed on a second side of the first wall (441); and The normal (N) of the first wall (441) extends through both the second heat exchanger (320) and the third heat exchanger (330).

19. The loop-sealed heat exchanger (400) according to claim 17 or 18, comprising: The second wall (443) makes: The first side of the second wall (443) defines the first chamber (412); and The first side of the second wall (443) defines the second chamber (422).

20. The loop-sealed heat exchanger (400) according to claim 19, wherein, The loop-sealed heat exchanger (400) also includes: The third wall (445) makes: The first side of the third wall (445) defines the first chamber (412); and The first side of the third wall (445) defines the second chamber (422).

21. The loop-sealed heat exchanger (400) according to claim 17 or 18, comprising a baffle device, the baffle device comprising at least one baffle, wherein, The baffle device is configured to: This allows the second flue gas (173) to circulate from the second furnace (172) to the third heat exchanger (330); and Prevent air from circulating through the third heat exchanger (330).

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