Passive flue gas water heat recovery device and working method thereof

Abstract

The application discloses a passive type recovery flue gas water heat device and a working method thereof, and belongs to the technical field of flue gas water heat recovery. The device comprises a flue gas recovery pipe, a divergent cooling pipe section, a nozzle section and a phase separation modulation pipe section which are sequentially arranged in the flue gas flow direction in the flue gas recovery pipe, and a pressurized cold air channel is formed between the flue gas recovery pipe and the divergent cooling pipe section, the nozzle section and the phase separation modulation pipe section. The divergent cooling pipe section comprises a porous material pipe, and the inlet of the porous material pipe is communicated with a flue gas source. The through-flow surface inside the nozzle section is gradually expanded along the flue gas flow direction. The phase separation modulation pipe section comprises an outer pipe and a hollow reticular inner pipe arranged in the outer pipe, and the outer pipe is connected with the nozzle section. A dehydrated flue gas channel is formed between the outer pipe and the hollow reticular inner pipe in a ring shape. The front end of the hollow reticular inner pipe is closed, and the rear end is opened and connected with a water collecting system. The device has a simple structure, does not need to be greatly reconstructed on the basis of the existing system, can efficiently recover water in flue gas, and reduces the corrosion of equipment in the process.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas water heat recovery, and in particular relates to a passive flue gas water heat recovery device and a working method thereof. Background Art

[0002] Coal-fired power plants are highly dependent on water resources. However, due to the uneven spatial distribution of water and coal resources, most coal-based power plants are often located in areas with relatively scarce water resources. The flue gas at the tail of the desulfurization system contains a large amount of saturated or unsaturated water vapor. If this water is not recovered and directly discharged, it will further exacerbate the coal-fired power plant's waste of water resources. At the same time, the direct discharge of water-containing flue gas through the chimney will form a "white plume" at the chimney outlet, causing visual obstruction. Furthermore, the flue gas at the tail of the desulfurization system has a temperature of approximately 50°C, representing a waste heat resource with considerable recovery value. Exploring ways to rationally utilize this waste heat is a key focus of flue gas treatment at the tail of the desulfurization system.

[0003] The recovery of water from the flue gas at the tail end of the desulfurization system can be achieved through condensation, solution absorption, and membrane methods. The condensation method is widely used in industry due to its simplicity, ease of implementation, good economy, and high stability. Based on the rational design of the heat exchanger, a cooling medium is introduced to condense the saturated or unsaturated water vapor in the flue gas at the tail end of the desulfurization system on the surface of the heat exchange surface, and then the condensed water is collected by a water collection device. In addition, the subsequent treatment of the cooling medium used involves the utilization of the waste heat of the flue gas, that is, transferring the large amount of latent heat of vaporization released when the water vapor condenses to the cooling medium. Therefore, the condensation method can better achieve the combination of flue gas water and heat recovery.

[0004] The main problems with the devices that have been disclosed for recovering moisture from the flue gas at the tail of the desulfurization system and utilizing waste heat using the condensation method include: in the selection of the cooling medium, ambient air or water is generally used, and the amount of cooling obtained is limited. On the one hand, the temperature difference between the ambient temperature and the flue gas is limited. If the temperature difference between the two is increased, additional energy is required to pre-cool the air or water; on the other hand, due to the volume limit of the heat exchanger, the heat exchange area between the cooling medium and the flue gas is limited. Increasing the heat exchange area means an increase in the volume of the device. If an equivalent method is adopted, there will be greater difficulties in the specific implementation. In addition, most of the existing devices that achieve flue gas water saving based on the condensation method condense water vapor on the surface of the heat exchange surface and use gravity to make the condensed water flow along the heat exchange surface into the collection device. Considering that the heat exchange surface has a limited carrying capacity for condensed water, the dehydrated flue gas may carry the condensed water on the heat exchange surface again and enter the chimney for discharge, affecting the overall water collection rate of the device. Summary of the Invention

[0005] In order to solve the above-mentioned existing problems, the purpose of the present invention is to provide a passive flue gas hydrothermal recovery device and its working method, which has a simple structure, does not require large-scale modification of the existing system, can efficiently recover moisture in the flue gas, and reduces equipment corrosion during the process.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention discloses a passive flue gas recovery hydrothermal device, comprising a flue gas recovery pipe and a diverging cooling pipe section, a nozzle section, and a phase modulation pipe section sequentially arranged in the flue gas recovery pipe along the direction of flue gas flow; an annular pressurized cold air channel is formed between the flue gas recovery pipe, the diverging cooling pipe section, the nozzle section, and the phase modulation pipe section;

[0008] The diverging cooling pipe section includes a porous material tube, the inlet of which is connected to the flue gas source; the flow surface inside the nozzle section gradually expands along the direction of flue gas flow; the phase modulation pipe section includes an outer tube and a hollow mesh inner tube arranged in the outer tube, and the outer tube is connected to the nozzle section; an annular dehydrated flue gas channel is formed between the outer tube and the hollow mesh inner tube, and the dehydrated flue gas channel is connected to the flue gas treatment system; the front end of the hollow mesh inner tube is closed, and the rear end is open and connected to the water collection system; the inlet of the pressurized cold air channel is connected to the pressurized cold air source, and the outlet of the pressurized cold air channel is connected to the air preheater.

[0009] Preferably, the effective pore size d of the hollow mesh inner tube mesh is e Satisfy the following formula:

[0010]

[0011] Where σ is the surface tension, g is the acceleration due to gravity, and ρ is the surface tension. l and ρ g are the densities of the liquid and gas phase components in the mixture entering the phase modulation section, respectively.

[0012] Preferably, the structural parameters of the nozzle section satisfy the following formula:

[0013]

[0014] Wherein, σ is the surface tension, ΔP is the pressure difference between the dehydrated flue gas channel and the inside of the hollow mesh inner tube, and ω is the thickness of the hollow mesh inner tube surface.

[0015] Preferably, the front end of the hollow mesh inner tube is a conical mesh surface or a flat mesh surface.

[0016] Preferably, the outer diameter of the front end of the hollow mesh inner tube is 0.7 to 0.8 times the inner diameter of the end of the nozzle section.

[0017] Preferably, the outer diameter of the outer tube is 1.2 to 1.5 times the outer diameter of the hollow mesh inner tube.

[0018] Preferably, the outer tube and the hollow mesh inner tube are connected via a plurality of groups of fixing brackets, and each group of fixing brackets is evenly distributed on the cross section of the dehydrated flue gas channel.

[0019] Further preferably, a through hole is provided on the fixing bracket.

[0020] Preferably, the porous material tube is made of a ceramic-based composite porous material or a metal-based composite porous material.

[0021] Preferably, the inlet of the pressurized cold air channel is connected to the pressurized cold air source, and the outlet of the pressurized cold air channel is connected to the air preheater.

[0022] The working method of the passive flue gas hydrothermal recovery device disclosed in the present invention includes:

[0023] The pressurized cold air from the pressurized cold air source enters the pressurized cold air channel, and is divergently cooled through the porous material tube in the divergent cooling pipe section, and is converted into a mixture of liquid phase droplets and gaseous phase flue gas with the flue gas containing saturated water vapor inside the porous material tube. After the pressure is reduced in the nozzle section, passive gas-liquid phase separation is achieved in the phase modulation pipe section. The liquid phase droplets enter the hollow mesh inner tube under the action of capillary force, and then enter the water collection system. The gaseous phase flue gas enters the flue gas treatment system through the dehydration flue gas channel; the air in the pressurized cold air channel that has been heated by heat exchange enters the air preheater as the secondary air of the boiler.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] The present invention discloses a passive flue gas hydrothermal recovery device, which realizes the separation of the cooling and condensation process of saturated water vapor in the flue gas and the gas-liquid phase separation process based on the condensation method. In terms of cooling method, the divergent cooling pipe section of the present invention uses porous materials to realize divergent cooling, and pressurized cold air is selected as the cooling medium. The device can be arranged in a smaller volume, and the cooling amount required to condense the saturated water vapor in the flue gas can be achieved with a smaller temperature difference in a short time. After passing through the divergent cooling section, the pure gas phase wet flue gas containing saturated water vapor is transformed into a mixture containing liquid phase droplets and gas phase flue gas. In terms of the mechanism of gas-liquid phase separation, the phase modulation pipe section of the present invention uses a hollow mesh inner tube to divide this part into an internal area and a dehydrated flue gas channel between the hollow mesh inner tube and the outer tube to realize passive phase separation. On the one hand, the liquid phase component in the mixture is isolated in the internal area, which is convenient for collecting the discharged condensed water at the rear end of the hollow mesh inner tube. On the other hand, isolating the gaseous components in the mixture in the dehydrated flue gas channel effectively avoids the problem that the excessive condensed water attached to the wall or heat exchange surface cannot be discharged in time in the device that uses the wall or heat exchange surface to carry the condensed water, so as to increase the subsequent demisting device. The nozzle section between the divergent cooling pipe section and the phase modulation pipe section realizes the pressure reduction of the gas-liquid mixture in the channel, so that at the hollow mesh inner pipe surface of the phase modulation pipe section, the gaseous components in the mixture will not pass through the mesh surface due to the large pressure difference, but can only allow the liquid phase components in the mixture to enter its internal area under the action of capillary force, thereby realizing passive phase separation of gas and liquid. In addition, the tail of the present invention can not only collect the condensed water obtained by condensation and separation, but also recycle the pressurized cold air after heating and pass it into the air preheater as the secondary air of the boiler, thereby alleviating the susceptibility of the flue gas side to low-temperature corrosion caused by directly passing the air at ambient temperature into the air preheater. In practical application, the present invention does not require large-scale transformation of the existing system and has good adaptability.

[0026] The working method of the passive flue gas hydrothermal recovery device disclosed in the present invention has a simple process, low manufacturing and operating costs, and can efficiently realize the comprehensive recovery of water and heat from flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic axial cross-sectional view of the overall structure of the present invention;

[0028] Figure 2 It is a left side view of the cross section of the phase modulation pipe section including the fixing bracket of the present invention;

[0029] Figure 3 This is a schematic diagram of the principle of radiative cooling achieved by the porous material of the present invention.

[0030] In the figure: 1 is the divergent cooling pipe section, 2 is the nozzle section, 3 is the phase modulation pipe section, 4 is the pressurized cold air channel, 5 is the porous material tube, 6 is the hollow mesh inner tube, 7 is the fixed bracket, 8 is the flue gas recovery pipe, 9 is the outer tube, and 10 is the through hole. DETAILED DESCRIPTION

[0031] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it:

[0032] like Figure 1 The passive flue gas recovery hydrothermal device of the present invention comprises a flue gas recovery pipe 8 and a diverging cooling pipe section 1, a nozzle section 2, and a phase modulation pipe section 3 sequentially arranged in the flue gas recovery pipe 8 along the direction of flue gas flow; an annular pressurized cold air channel 4 is formed between the flue gas recovery pipe 8 and the diverging cooling pipe section 1, the nozzle section 2, and the phase modulation pipe section 3;

[0033] The diverging cooling pipe section 1 includes a porous material tube 5, the inlet of the porous material tube 5 is connected to the flue gas source; the flow surface inside the nozzle section 2 gradually expands along the flue gas flow direction; the phase modulation pipe section 3 includes an outer tube 9 and a hollow mesh inner tube 6 arranged in the outer tube 9, and the outer tube 9 is connected to the nozzle section 2; an annular dehydrated flue gas channel is formed between the outer tube 9 and the hollow mesh inner tube 6, and the dehydrated flue gas channel is connected to the flue gas treatment system; the front end of the hollow mesh inner tube 6 is closed, and the rear end is open and connected to the water collection system; the inlet of the pressurized cold air channel 4 is connected to the pressurized cold air source, and the outlet of the pressurized cold air channel 4 is connected to the air preheater.

[0034] In a preferred embodiment of the present invention, the effective aperture d of the mesh of the hollow mesh inner tube 6 is e Satisfy the following formula:

[0035]

[0036] Where σ is the surface tension, g is the acceleration due to gravity, and ρ is the surface tension. l and ρ g are the densities of the liquid phase component and the gas phase component in the mixture entering the phase-separation modulation pipe section 3 respectively.

[0037] In a preferred embodiment of the present invention, the structural parameters of the nozzle section 2 satisfy the following formula:

[0038]

[0039] Wherein, σ is the surface tension, ΔP is the pressure difference between the dehydrated flue gas channel and the inside of the hollow mesh inner tube 6, and ω is the thickness of the mesh surface of the hollow mesh inner tube 6.

[0040] In a preferred embodiment of the present invention, the front end of the hollow mesh inner tube 6 is a conical mesh surface or a flat mesh surface.

[0041] In a preferred embodiment of the present invention, the outer diameter of the front end of the hollow mesh inner tube 6 is 0.7 to 0.8 times the inner diameter of the end of the nozzle section 2 .

[0042] In a preferred embodiment of the present invention, the outer diameter of the outer tube 9 is 1.2 to 1.5 times the outer diameter of the hollow mesh inner tube 6 .

[0043] like Figure 2 In a preferred embodiment of the present invention, the outer tube 9 is connected to the hollow mesh inner tube 6 by a plurality of sets of fixing brackets 7, each set of fixing brackets 7 being evenly distributed across the cross section of the dehydrated flue gas passage. Preferably, the fixing brackets 7 are provided with through holes 10.

[0044] In a preferred embodiment of the present invention, the porous material tube 5 is made of a ceramic-based composite porous material or a metal-based composite porous material.

[0045] In a preferred embodiment of the present invention, the inlet of the pressurized cold air passage 4 is connected to a pressurized cold air source, and the outlet of the pressurized cold air passage 4 is connected to an air preheater.

[0046] The working method of the above-mentioned passive flue gas hydrothermal recovery device includes:

[0047] The pressurized cold air from the pressurized cold air source enters the pressurized cold air channel 4, and is subjected to divergent cooling in the divergent cooling pipe section 1 through the porous material tube 5. The flue gas containing saturated water vapor inside the porous material tube 5 is converted into a mixture of liquid phase droplets and gaseous phase flue gas. After the pressure is reduced in the nozzle section 2, passive gas-liquid phase separation is achieved in the phase modulation pipe section 3. The liquid phase droplets enter the hollow mesh inner tube 6 under the action of capillary force, and then enter the water collection system. The gaseous phase flue gas enters the flue gas treatment system through the dehydration flue gas channel; the air in the pressurized cold air channel 4 that has been heated by heat exchange enters the air preheater as the secondary air of the boiler.

[0048] The main principles of the present invention are as follows:

[0049] The divergent cooling pipe section 1 uses porous materials to achieve divergent cooling of the water-containing flue gas in the channel. In order to improve the dehydration efficiency, pressurized cold air is used as the cooling medium.

[0050] like Figure 3 As shown, the porous material, with a thickness of h, divides the device into a central cylindrical hot end, where wet flue gas circulates, and an annular region between the flue gas recovery pipe 8 and the porous material tube 5, representing the cold end, where pressurized cold air circulates. The model for stable heat exchange between the hot and cold ends is as follows.

[0051] The governing equations include:

[0052] (1) Continuity equation:

[0053]

[0054] Where, ρ f is the density of pressurized cold air, and u is the speed at which pressurized cold air is introduced.

[0055] (2) Momentum equation:

[0056]

[0057] Where p is the pressure of pressurized cold air, μ is the kinematic viscosity of pressurized cold air; K is the permeability of the porous material, and F is the inertia coefficient of the porous medium, which are calculated using the following formulas:

[0058]

[0059]

[0060] (3) Energy equation for pressurized cold air:

[0061]

[0062] Where h f is the enthalpy of pressurized cold air, T f is the temperature of the pressurized cold air in the pores of the porous material; f,eff is the effective thermal conductivity of the pores of the porous material, which is calculated using the following formula:

[0063] λ f,eff =ελ f

[0064] Q sf The heat exchange between the pressurized cold air and the porous material is calculated using the following formula:

[0065] Q sf =αh sf (T s -T f )

[0066] Where, T s is the temperature of the solid part of the porous material, α is the specific surface area of ​​the porous medium, and is calculated using the following formula:

[0067]

[0068] h sf is the heat transfer coefficient between the pressurized cold air and the solid part in the pores inside the porous material, calculated using the following formula:

[0069]

[0070] (4) Energy equation of the solid part of porous material:

[0071]

[0072] Where λ s,eff is the effective thermal conductivity of the solid part of the porous material, calculated using the following formula:

[0073] λ s,eff =(1-ε)λ s

[0074] Boundary conditions include:

[0075] (1) Cold end boundary condition (x=0).

[0076] For porous materials:

[0077]

[0078] For a mass flow rate of m, the initial temperature is T ∞ Pressurized cold air:

[0079]

[0080] Where c p is the specific heat capacity at constant pressure of pressurized cold air, h c is the heat transfer coefficient between the pressurized cold air at the cold end boundary and the solid part of the porous material, calculated using the following formula:

[0081] h c =0.664Re 1 / 2 Pr 1 / 3

[0082] Where Re and Pr represent the Reynolds number and Prandtl number of the pressurized cold air, respectively.

[0083] (2) Hot end boundary condition (x = h):

[0084] After entering the flue gas channel, the boundary condition is the wet flue gas condition of the present invention.

[0085] Compared to existing condensation-based cooling methods for recovering moisture from flue gas, this invention uses a divergent cooling mechanism to cool wet flue gas. This utilizes the expanded surface area of ​​porous materials to achieve high cooling capacity in a short period of time without increasing the device's volume. The flue gas temperature can be reduced by more than 6-8°C as it passes through the divergent cooling section.

[0086] Specifically, after the pressurized cold air flows through the porous tube 5 and into the flue gas main flow channel, it is influenced by the flue gas's main flow direction and moves along the porous material surface, forming a thin air film. This air film has a negligible effect on the heat exchange effect, but its presence can effectively isolate the flue gas from the porous tube 5, reducing corrosion to the porous tube 5.

[0087] After passing through the diverging cooling pipe section 1, the pure gas phase wet flue gas containing saturated water vapor is transformed into a mixture containing liquid phase droplets and gas phase flue gas.

[0088] The phase modulation tube section 3 uses a fixed bracket 7 with a through hole 10 to suspend a hollow mesh inner tube 6 in an outer tube 9, forming an annular area between the outer tube 9 and the hollow mesh inner tube 6, which is separated from the internal area in the center of the hollow mesh inner tube 6.

[0089] In particular, the fixed brackets 7 are symmetrically arranged in 2 to 3 cross sections along the main flow direction of the flue gas in the annular area, and a through hole 10 is opened in the middle of each fixed bracket 7 to ensure smooth flow of the dehydrated flue gas in the annular area.

[0090] Under the action of capillary forces, the liquid phase components of the mixture are drawn into the interior region through the tiny pores on the front end and sidewalls of the hollow mesh inner tube 6, while the gas phase components of the mixture are trapped within the annular region. Capillary force is the force acting within a capillary tube that causes liquids, whether wet or non-wetted with the tube wall, to naturally pass through the capillary tube. This force points in the direction of the liquid's concave surface, and its magnitude is proportional to the liquid's surface tension and inversely proportional to the radius of the capillary tube. In the present invention, capillary force acts on the liquid phase components of the mixture, causing them to pass through the pores on the mesh of the hollow mesh inner tube 6 and enter the interior region. The above process achieves passive phase separation of the water-containing flue gas after passing through the divergent cooling tube section 1.

[0091] Specifically, the hollow mesh inner tube 6 has meshed sides, a tapered or flat front end, and an opening on the rear end for discharging separated condensate. The mesh on the front end first separates the gas and liquid phases of the mixture flowing into the phase-separation modulation section 3. The liquid phase components that enter the inner region without passing through the front end of the hollow mesh inner tube 6 enter the inner region through the side of the hollow mesh inner tube 6 in the annular region.

[0092] The effective aperture d of each mesh surface e The following formula should be satisfied:

[0093]

[0094] Where σ is the surface tension, g is the acceleration due to gravity, and ρ is the surface tension. l and ρ g are the densities of the liquid and gas phase components, respectively.

[0095] The hollow mesh inner tube 6 utilizes capillary forces to allow only the liquid phase of the mixture to pass through the mesh surface and enter the inner region, while the gas phase is completely isolated in the annular region. To prevent the gas phase of the mixture from entering the inner region, the pressure difference ΔP between the annular region and the inner region should satisfy the following formula:

[0096]

[0097] Where ω is the mesh thickness and D is the inner diameter of the hollow mesh cylinder.

[0098] Since D is much larger than ω, the term after the minus sign can be ignored in practical applications. That is, the pressure difference ΔP in the practical application of the present invention should satisfy the following formula:

[0099]

[0100] In order to meet the above pressure difference requirements, the present invention arranges a nozzle section 2 between the outlet of the divergent cooling pipe section 1 and the inlet section of the phase modulation pipe section 3, specifically, a gradually diverging nozzle.

[0101] After the wet flue gas passes through the present invention, the condensed water flowing out of the rear end of the hollow mesh inner tube 6 passes through a water collector and can be used to replenish system water, for example. The dehydrated flue gas flowing out of the annular area between the hollow mesh inner tube 6 and the outer tube 9 is discharged into the chimney. In particular, the heated pressurized cold air flowing out of the annular area between the outer tube 9 and the flue gas recovery pipe 8 can be introduced into the air preheater as boiler secondary air. Typically, ambient air is introduced into the air preheater and heated to provide oxygen for the boiler secondary air. However, sulfur oxides produced by fuel combustion react with water vapor in the flue gas to form sulfuric acid vapor, which significantly raises the flue gas dew point. If the air temperature below the air preheater is low, sulfuric acid vapor can condense on the preheater heating surface, causing sulfuric acid corrosion. Passing heated pressurized cold air into the air preheater as boiler secondary air can effectively mitigate low-temperature corrosion on the flue gas side of the air preheater. Furthermore, the heated pressurized cold air reduces the heat demand on the air preheater, thereby utilizing waste heat from the flue gas at the tail end of the desulfurization system.

[0102] The above description is merely an embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention, or equivalent structures or equivalent process transformations made using the contents of the present invention's description and drawings, or direct or indirect applications in other related technical fields, should all be covered by the scope of protection of the present invention.

Claims

1. A passive flue gas hydrothermal recovery device, characterized in that: The invention comprises a smoke recovery pipe (8) and a diverging cooling pipe section (1), a nozzle section (2) and a phase modulation pipe section (3) arranged in sequence along the flow direction of the smoke in the smoke recovery pipe (8); an annular pressurized cold air channel (4) is formed between the smoke recovery pipe (8) and the diverging cooling pipe section (1), the nozzle section (2) and the phase modulation pipe section (3); The radiating cooling pipe section (1) includes a porous material pipe (5), the inlet of the porous material pipe (5) is connected to the flue gas source; the flow surface inside the nozzle section (2) gradually expands along the flue gas flow direction; the phase modulation pipe section (3) includes an outer pipe (9) and a hollow mesh inner pipe (6) arranged inside the outer pipe (9), and the outer pipe (9) is connected to the nozzle section (2); an annular dehydrated flue gas channel is formed between the outer pipe (9) and the hollow mesh inner pipe (6), and the dehydrated flue gas channel is connected to the flue gas treatment system; the front end of the hollow mesh inner pipe (6) is closed, and the rear end is open and connected to the water collection system; the inlet of the pressurized cold air channel (4) is connected to the pressurized cold air source, and the outlet of the pressurized cold air channel (4) is connected to the air preheater.

2. The passive flue gas hydrothermal recovery device according to claim 1, characterized in that: The effective aperture d of the mesh of the hollow mesh inner tube (6) e Satisfy the following formula: Where σ is the surface tension, g is the acceleration due to gravity, and ρ is the surface tension. l and ρ g are respectively the densities of the liquid phase component and the gas phase component in the mixture entering the phase separation modulation pipe section (3).

3. The passive flue gas hydrothermal recovery device according to claim 1, characterized in that: The structural parameters of the nozzle section (2) satisfy the following formula: Wherein, σ is the surface tension, ΔP is the pressure difference between the dehydrated flue gas channel and the inside of the hollow mesh inner tube (6), and ω is the thickness of the mesh surface of the hollow mesh inner tube (6).

4. The passive flue gas hydrothermal recovery device according to claim 1, characterized in that: The front end of the hollow mesh inner tube (6) is a conical mesh surface or a flat mesh surface.

5. The passive flue gas hydrothermal recovery device according to claim 1, characterized in that: The outer diameter of the front end of the hollow mesh inner tube (6) is 0.7 to 0.8 times the inner diameter of the end of the nozzle section (2).

6. The passive flue gas hydrothermal recovery device according to claim 1, characterized in that: The outer diameter of the outer tube (9) is 1.2 to 1.5 times the outer diameter of the hollow mesh inner tube (6).

7. The passive flue gas hydrothermal recovery device according to claim 1, characterized in that: The outer tube (9) and the hollow mesh inner tube (6) are connected via a plurality of groups of fixed brackets (7), and each group of fixed brackets (7) is evenly distributed on the cross section of the dehydrated flue gas channel.

8. The passive flue gas hydrothermal recovery device according to claim 7, characterized in that: A through hole (10) is provided on the fixing bracket (7).

9. The passive flue gas hydrothermal recovery device according to claim 1, characterized in that: The porous material tube (5) is made of a ceramic-based composite porous material or a metal-based composite porous material.

10. The operating method of the passive flue gas hydrothermal recovery device according to any one of claims 1 to 9, characterized in that: include: The pressurized cold air from the pressurized cold air source enters the pressurized cold air channel (4), and is subjected to divergent cooling in the divergent cooling pipe section (1) through the porous material pipe (5), and is converted into a mixture of liquid phase droplets and gas phase flue gas with the flue gas containing saturated water vapor inside the porous material pipe (5). After the pressure is reduced in the nozzle section (2), passive gas-liquid phase separation is achieved in the phase modulation pipe section (3). The liquid phase droplets enter the hollow mesh inner pipe (6) under the action of capillary force, and then enter the water collection system. The gas phase flue gas enters the flue gas treatment system through the dehydration flue gas channel; the air in the pressurized cold air channel (4) that has been heated by heat exchange enters the air preheater as the secondary air of the boiler.

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