Flue gas water-saving and multi-pollutant removal device and working method thereof

Abstract

The application discloses a flue gas water-saving and multi-pollutant removal device and a working method thereof, and belongs to the technical field of flue gas water-saving. The device comprises a flue gas inlet pipe, a cylinder and a dehydrated flue gas passage which are sequentially connected. The outer wall of the cylinder is provided with a reinforced radiation cooling coating. A plurality of rows of high-voltage electrode columns and ground electrode columns are alternately arranged in the front section of the flue gas inlet pipe. The dehydrated flue gas passage is externally nested with a condensed water collecting device, and the condensed water collecting device is connected with the cylinder. A plurality of condensed water collecting openings are arranged in the outlet transition section, and the condensed water collecting openings are communicated with the condensed water collecting device. A vibrating string grid is arranged in the dehydrated flue gas passage, and a plurality of drainage holes are arranged on the dehydrated flue gas passage below the vibrating string grid. The device has the advantages of compact structure, small volume and low energy consumption, and can realize low-temperature and high-efficiency recovery of water in flue gas and simultaneous removal of multi-pollutants.

Description

Technical Field

[0001] This invention belongs to the field of flue gas water-saving technology, specifically relating to a flue gas water-saving and multi-pollutant removal device and its working method. Background Technology

[0002] Currently, wet flue gas desulfurization (FGD) devices are widely used in coal-fired power plants to achieve ultra-low emissions of pollutants. However, the slurry carried by the flue gas after passing through the wet FGD system can lead to the generation of new particulate matter and saturate the water vapor concentration in the flue gas at the FGD tower outlet. If the water cannot be recovered and the various pollutants carried by the flue gas, especially fine particulate matter, cannot be removed, on the one hand, a "white plume" will appear at the chimney outlet, causing visual obstruction and exacerbating the waste of water resources in coal-fired power plants; on the other hand, direct emission of desulfurized flue gas through the chimney will result in a high concentration of particulate matter, failing to meet increasingly stringent particulate matter emission standards and causing serious air pollution. Therefore, water recovery and utilization from dust-laden wet flue gas, as well as the removal of multiple pollutants, not only helps to significantly reduce water consumption in power plants, especially beneficial for water resource protection in water-scarce areas, but also reduces the concentration of pollutants in the flue gas emitted from the chimney, which is of great significance for environmental protection.

[0003] In terms of water conservation in dust-laden wet flue gas, current methods mainly involve condensation, solution absorption, and membrane methods. Among these, condensation is simple, economical, and stable in operation, and is widely used in industry. Based on heat exchangers, cold air / cooling water is used to achieve water vapor phase change condensation and recovery. The water collection device is connected to pipelines, and the recovered condensate is used to supplement wet flue gas desulfurization, reducing the total water demand. Based on existing heat exchangers, some water recovery devices couple additional field forces (electric, magnetic, or acoustic fields) to improve the water collection efficiency. The main problems with publicly available flue gas water recovery devices include: the cooling medium entering and exiting the device requires additional energy for driving force; the cooling medium and additional field forces increase the corrosion factor of the device, affecting its service life; and the temperature of the flue gas entering the device is limited by the temperature of the cooling medium itself, affecting the water collection efficiency.

[0004] The removal of multiple pollutants carried by flue gas is currently mainly achieved by enhancing the dust removal function of the desulfurization system itself and adding deep particulate matter removal equipment after the desulfurization system. The former technical approach mainly revolves around enhancing gas-liquid mass transfer and improving the scrubbing effect of the desulfurization slurry on the flue gas. The latter mainly revolves around adding specific dust removal equipment, such as electrostatic precipitators. The main problems include: optimizing the structure of the desulfurization system will lead to a significant increase in system resistance and a window for fine particulate matter, which can account for more than 90% of the total; currently, the downstream dust removal equipment of desulfurization systems generally has high investment and operating costs, complex systems, is prone to clogging, and has poor stability. It has a high removal efficiency for particles larger than 10 μm, but a very low removal efficiency for particles smaller than 10 μm, especially fine particles smaller than 2.5 μm. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a flue gas water-saving and multi-pollutant removal device and its operating method, which is compact in structure, small in size, and low in energy consumption, and can achieve low-temperature and high-efficiency recovery of moisture and simultaneous removal of multiple pollutants in flue gas.

[0006] This invention is achieved through the following technical solution:

[0007] This invention discloses a water-saving and multi-pollutant removal device for flue gas, comprising a flue gas inlet pipe, a cylinder, and a dehydrated flue gas channel connected in sequence. The cross-sectional area of ​​the inlet transition section between the outlet of the flue gas inlet pipe and the cylinder gradually expands, while the cross-sectional area of ​​the outlet transition section between the cylinder and the inlet of the dehydrated flue gas channel gradually decreases. The outer wall of the cylinder is provided with a reinforced radiation cooling coating. Several rows of high-voltage electrode columns and grounding electrode columns are alternately arranged in the front section of the flue gas inlet pipe. A condensate collection device is nested outside the dehydrated flue gas channel and is connected to the cylinder. Several condensate collection ports are provided in the outlet transition section and are connected to the condensate collection device. A vibrating wire grid is provided inside the dehydrated flue gas channel, and several drainage holes are opened on the dehydrated flue gas channel below the vibrating wire grid.

[0008] Preferably, the enhanced radiation cooling coating comprises, from the inside out, an adhesive, a silver plating layer, and a superpolymer hybrid film; the adhesive is bonded to the outer wall of the cylinder; and the thickness of the superpolymer hybrid film is ≥20μm.

[0009] Preferably, the outer wall of the cylinder is corrugated, and the inner wall is provided with a hydrophobic layer.

[0010] Preferably, the condensate collection device has an outlet at the bottom, and a condensate collection tank is provided below the outlet and the drain hole.

[0011] Preferably, the distance between the end of the front section of the flue gas inlet pipe and the beginning of the inlet transition section is 1 / 4 to 1 / 3 of the length of the front section of the flue gas inlet pipe.

[0012] Preferably, the surface roughness grade of the high-voltage electrode post and the grounding electrode post is higher than Ra12.5; the diameter D of the high-voltage electrode post and the grounding electrode post satisfies:

[0013] 2D≤L≤4D

[0014] Where L is the distance between the centers of adjacent high-voltage electrode posts and grounding electrode posts along the flue gas flow direction.

[0015] Preferably, the connection between the dehydrated flue gas passage and the condensate collection device is lower than the inlet of the dehydrated flue gas passage.

[0016] Preferably, the flue gas inlet pipe is arranged perpendicularly to the cylinder, the cylinder is arranged perpendicularly to the dehydration flue gas channel, and the inner wall of the connection between the cylinder and the flue gas inlet pipe and the dehydration flue gas channel is smoothly transitioned.

[0017] The working method of the above-mentioned flue gas water-saving and multi-pollutant removal device disclosed in this invention includes:

[0018] After the dust-laden wet flue gas from the desulfurization tower outlet enters the front section of the flue gas inlet pipe, under the combined action of electrocoagulation and turbulent coagulation by the high-voltage electrode column and the grounding electrode column, the particulate matter in the flue gas agglomerates and increases in size, with some particles being intercepted and captured by the high-voltage electrode column and the grounding electrode column. Subsequently, it enters the rear section of the flue gas inlet pipe, where the remaining strong turbulent coagulation further enhances the coagulation effect. After entering the cylinder, the enhanced radiation cooling coating cools and exchanges heat with the inner wall surface of the cylinder. The cooled inner wall surface of the cylinder and the dust-laden interior of the cylinder... The thermophoretic force generated by the temperature difference between the wet flue gas and the dry flue gas causes the particles to diffuse toward the boundary layer of the cylinder wall, and causes the water vapor in the flue gas to condense on the inner wall of the cylinder, separating it from the dehydrated flue gas. The particles in the flue gas that have condensed and increased in size, as well as water-soluble pollutants, dissolve in the condensate. Under the action of gravity, the condensate carrying multiple pollutants flows into the condensate collection device through the condensate collection port and is collected. The flue gas carrying some residual condensate and a small amount of particulate matter is intercepted by the vibrating wire grid in the dehydrated flue gas channel. The flue gas that has undergone dust removal and dehydration is finally discharged from the device.

[0019] Preferably, the thermophoretic force F T We obtain it from the following formula:

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026] In the formula, Kn is the Knudsen number, and R g The gas constant for air is 287 J / (kg·K), d m The average diameter of the nitrogen and carbon dioxide mixture particles is 0.161 nm, d p The particle size after the collision. Let be the mean free path of the gas molecules, γ be the specific heat capacity of the gas (taken as 1.4 in the calculation), and c be the mean free path of the gas molecules. v For constant volume specific heat capacity, S n With S t These are the momentum adjustment coefficients in the vertical and tangential directions, respectively, both taken as 1.0 in the calculation. T is the flue gas temperature, and p is the absolute pressure; a, π1 is a calculation parameter introduced to simplify the calculation;

[0027] By controlling the voltage of the high-voltage electrode post and the ground electrode post, the particle size d after the collision can be controlled. p , making the thermophoretic force F T The particle size d after the collision p The derivative of the thermophoretic force F is equal to 0, even if the thermophoretic force F T To achieve the maximum value, the optimal efficiency of pollutant particle removal is reached.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] This invention discloses a water-saving and multi-pollutant removal device for flue gas, capable of modularly treating dust-laden wet flue gas from the desulfurization tower outlet, achieving efficient moisture recovery and synergistic removal of multiple pollutants. On one hand, high-voltage electrode columns and grounding electrode columns are alternately arranged along the flue gas flow direction in the front section of the flue gas inlet pipe to enhance turbulent coagulation of the flue gas passing through this area. In this region, electrocoagulation and turbulent coagulation mechanisms are combined to achieve the coagulation of fine particulate matter in the flue gas. Then, in the rear section of the flue gas inlet pipe, turbulent coagulation is fully utilized to increase the size of particulate matter entering the enhanced radiation condensation zone, facilitating their dissolution and removal in the condensate. On the other hand, an enhanced radiation cooling coating replaces the cooling medium by enhancing the radiation heat exchange cooling wall surface. This coating cools the cylinder wall, creating a temperature difference between the wet flue gas entering this area and the inner wall surface, enhancing heat exchange between the wet flue gas and the inner wall surface, and achieving the condensation of saturated water vapor in the flue gas. During the condensation process, the particulate matter that has already condensed in the original dust-laden wet flue gas, as well as other water-soluble pollutants (such as NH4), are condensed.+ (Inorganic pollutants such as SO2 and Hg) dissolve in the condensate. Under the influence of gravity, the condensate carrying multiple pollutants condenses on the inner wall surface, flowing downwards along the wall and being collected through the condensate collection port, thus achieving water conservation and multi-pollutant removal. To prevent excessive residual condensate from adhering to the inner wall surface of the cylinder and being carried directly into the chimney by the flue gas continuously flowing into this area, reducing water collection efficiency, a vibrating wire grid is installed in the dehydrated flue gas collection channel downstream of the enhanced radiation condensation zone. This grid intercepts residual droplets carried in the flue gas, causing them to condense into larger droplets upon collision with the grid, adhering to the vibrating wires of the grid, and then flowing downwards under gravity for collection. Simultaneously, a small portion of particles that have already condensed and increased in size in the electro / turbulent synergistic condensation zone but have not dissolved in water for removal in the enhanced radiation condensation zone are also intercepted by the vibrating wire grid and collected with the droplets. Finally, the flue gas, after removing the condensate and multiple pollutants it carries, enters the chimney through the dehydrated flue gas channel after the vibrating wire grid and is discharged, achieving efficient removal of multiple pollutants in the flue gas while saving a significant amount of water.

[0030] Furthermore, the enhanced radiation cooling coating comprises, from the inside out, an adhesive, a silver plating layer, and a superpolymer hybrid film. The superpolymer hybrid film can emit heat from the cylinder wall outward in the form of infrared radiation, and the silver plating layer can effectively reflect solar irradiance, enabling the enhanced radiation cooling coating to reflect more than 96% of solar irradiance.

[0031] Furthermore, the outer wall of the cylinder is corrugated, which increases the area for radiative heat transfer.

[0032] Furthermore, the distance between the end of the front section of the flue gas inlet pipe and the beginning of the inlet transition section is 1 / 4 to 1 / 3 of the length of the front section of the flue gas inlet pipe. This distance can make full use of the turbulence effect in the front section to further increase the size of the particles in the flue gas, making it easier to remove them after dissolving in water.

[0033] Furthermore, the condensate collection device is equipped with an outlet at the bottom, and a condensate collection tank is located below the outlet and the drain hole, which can collect condensate from various locations and then treat it uniformly.

[0034] Furthermore, the surface roughness grade of the high-voltage electrode post and the grounding electrode post is higher than Ra12.5. The smooth surface makes it difficult for pollutants in the flue gas to deposit on the electrode post, reducing the cleaning frequency and avoiding the back corona phenomenon between the high-voltage electrode post and the grounding electrode post.

[0035] Furthermore, the connection between the dehydrated flue gas passage and the condensate collection device is lower than the inlet of the dehydrated flue gas passage, which allows the condensate in the condensate collection device to exchange heat with the flue gas in the dehydrated flue gas passage in this section, thereby increasing the amount of condensate.

[0036] Furthermore, the flue gas inlet pipe is set perpendicular to the cylinder, and the cylinder is set perpendicular to the dehydration flue gas channel, which can improve the compactness of the device and save space; the inner wall of the connection between the cylinder and the flue gas inlet pipe and the dehydration flue gas channel is smoothly transitioned, so that the flue gas flows smoothly and avoids stagnation.

[0037] The operating method of the above-mentioned flue gas water-saving and multi-pollutant removal device disclosed in this invention features low energy consumption, simple structure, and low cost. In particular, it enhances the radiative condensation zone to achieve energy-free condensation of moisture in the flue gas without introducing any new corrosion-causing devices. Overall, this invention achieves efficient recovery of moisture and removal of multiple pollutants from dust-laden wet flue gas in a regional and modular manner, demonstrating promising application prospects. Attached Figure Description

[0038] Figure 1 This is a front view of the overall structure of the present invention;

[0039] Figure 2 A transverse cross-sectional view of the electric / turbulent co-coagulation region;

[0040] Figure 3 A cross-sectional view of the coating used to enhance radiative heat transfer.

[0041] In the figure: 1 is the electro / turbulent synergistic condensation zone, 2 is the tail turbulent zone, 3 is the enhanced radiation condensation zone, 4 is the enhanced radiation cooling coating, 5 is the condensate collection port, 6 is the dehydrated flue gas outlet, 7 is the condensate collection device, 8 is the dehydrated flue gas channel, 9 is the vibrating wire grid, 10 is the drain hole, 11 is the condensate collection tank, 12 is the high-voltage electrode post, 13 is the grounding electrode post, 14 is the superpolymer hybrid film, 15 is the silver plating layer, and 16 is the adhesive. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This description is intended to explain the invention and not limit it.

[0043] like Figure 1 This invention discloses a flue gas water-saving and multi-pollutant removal device, comprising a flue gas inlet pipe, a cylinder, and a dehydrated flue gas channel 8 connected in sequence. The cross-sectional area of ​​the inlet transition section between the outlet of the flue gas inlet pipe and the cylinder gradually expands, while the cross-sectional area of ​​the outlet transition section between the cylinder and the inlet of the dehydrated flue gas channel 8 gradually decreases. Functionally, it includes an electro / turbulent flow synergistic condensation zone 1 within the flue gas inlet pipe, where a high-voltage electrode post 12 and a grounding electrode post 13 are installed; a tail turbulent flow zone 2 following the electro / turbulent flow synergistic condensation zone 1; and an enhanced radiation condensation zone 3 within the cylinder. No electrodes are arranged within the tail turbulent flow zone 2.

[0044] The outer wall of the cylinder is provided with a reinforced radiation cooling coating 4; several rows of high-voltage electrode columns 12 and grounding electrode columns 13 are alternately arranged in the front section of the flue gas inlet pipe; a condensate collection device 7 is nested outside the dehydrated flue gas channel 8 and is connected to the cylinder; several condensate collection ports 5 are provided in the outlet transition section and are connected to the condensate collection device 7; a vibrating wire grid 9 is provided in the dehydrated flue gas channel 8 and several drainage holes 10 are opened on the dehydrated flue gas channel 8 below the vibrating wire grid 9.

[0045] In a preferred embodiment of the present invention, the enhanced radiation cooling coating 4 comprises, from the inside out, an adhesive 16, a silver plating layer 15, and a superpolymer hybrid film 14; the adhesive 16 is bonded to the outer wall of the cylinder; the thickness of the superpolymer hybrid film 14 is ≥20μm.

[0046] In a preferred embodiment of the present invention, the condensate collection port 5 includes a plurality of annularly symmetrically arranged through holes, and each condensate collection port 5 is funnel-shaped.

[0047] In a preferred embodiment of the present invention, the outer wall of the cylinder is corrugated.

[0048] In a preferred embodiment of the present invention, the cylindrical body is made of silicon carbide ceramic, carbon steel, fluoroplastic or borosilicate glass, and the inner wall is provided with a hydrophobic layer.

[0049] In a preferred embodiment of the present invention, the condensate collection device 7 is provided with an outlet at the bottom, and a condensate collection tank 11 is provided below the outlet and the drain hole 10.

[0050] In a preferred embodiment of the present invention, the distance between the end of the front section of the flue gas inlet pipe and the beginning of the inlet transition section is 1 / 4 to 1 / 3 of the length of the front section of the flue gas inlet pipe.

[0051] In a preferred embodiment of the present invention, the surface roughness grade of the high-voltage electrode post 12 and the ground electrode post 13 is higher than Ra12.5; the diameter D of the high-voltage electrode post 12 and the ground electrode post 13 satisfies:

[0052] 2D≤L≤4D

[0053] Where L is the distance between the centers of adjacent high-voltage electrode post 12 and grounding electrode post 13 along the flue gas flow direction.

[0054] In a preferred embodiment of the present invention, the connection between the dehydrated flue gas channel 8 and the condensate collection device 7 is lower than the inlet of the dehydrated flue gas channel 8.

[0055] In a preferred embodiment of the present invention, the flue gas inlet pipe is arranged perpendicularly to the cylinder, the cylinder is arranged perpendicularly to the dehydration flue gas channel 8, and the inner wall of the connection between the cylinder and the flue gas inlet pipe and the dehydration flue gas channel 8 is smoothly transitioned.

[0056] The working method of the above-mentioned flue gas water-saving and multi-pollutant removal device includes:

[0057] After the dust-laden wet flue gas from the desulfurization tower outlet enters the front section of the flue gas inlet pipe, under the synergistic effect of electrocoagulation and turbulent coagulation of the high-voltage electrode column 12 and the grounding electrode column 13, the particulate matter in the flue gas agglomerates and increases in size. Some of the particulate matter is intercepted and captured by the high-voltage electrode column 12 and the grounding electrode column 13. Subsequently, it enters the rear section of the flue gas inlet pipe, where the remaining strong turbulent coagulation effect further enhances the coagulation effect. After entering the cylinder, the enhanced radiation cooling coating 4 cools and exchanges heat on the inner wall surface of the cylinder. The temperature difference between the cooled inner wall surface of the cylinder and the dust-laden wet flue gas inside the cylinder causes water vapor in the flue gas to condense on the inner wall of the cylinder and separate from the dehydrated flue gas. The agglomerated and enlarged particulate matter in the flue gas, as well as other water-soluble pollutants (NH4+), are removed. + (e.g., SO2, Hg, etc.) dissolve in the condensate. Under the action of gravity, the condensate carrying multiple pollutants flows into the condensate collection device 7 through the condensate collection port 5 and is collected. The flue gas carrying some residual condensate and a small amount of particulate matter is intercepted by the vibrating wire grid 9 in the dehydrated flue gas channel 8. After dust removal and dehydration, the flue gas is finally discharged into the chimney.

[0058] The main principles involved in this invention are as follows:

[0059] Within the channel of the electro / turbulent co-coagulation zone 1, high-voltage electrode columns 12 and grounding electrode columns 13 are alternately arranged along the flow direction of the dust-laden wet flue gas. This zone requires only a single high-voltage power supply to create a negative corona charging region between the high-voltage corona wire and the grounding electrode, and a positive corona charging region between the grounding corona wire and the high-voltage electrode. Simultaneously, the metal electrode serves not only as an electrode but also as a turbulence column, enhancing the turbulent disturbance of the dust-laden wet flue gas within the electro / turbulent co-coagulation zone 1, thus achieving both turbulent coagulation and electro-coagulation loads.

[0060] Consider the force conditions of particulate matter in the dust-laden wet flue gas within the channel of the electro / turbulent co-coagulation zone 1:

[0061] ①Use a spherical model to assume particulate matter in dust-laden wet flue gas and analyze the Coulomb force received by the particulate matter.

[0062] For ultrafine particles with a diameter of less than 0.1 μm, diffusion charging plays a dominant role:

[0063]

[0064] Where q is the diffusion charge on the particulate matter, and ε0 is the vacuum permittivity, with a value of 8.85 × 10⁻⁶. -12 F / m, d is the particle diameter, and k is the Boltzmann constant, which has a value of 1.38 × 10⁻⁶. -23 J / K, where T is the absolute temperature of the dust-laden wet flue gas, and e is the charge of a single electron, with a value of 1.6 × 10⁻⁶. -19 C, N io U represents the spatial ion concentration. i denoted as ρ, where ρ is the diffusion rate of the dust-laden wet flue gas, and t is the charging time.

[0065] For fine particles with a diameter greater than 1 μm, electric field charging plays a dominant role:

[0066]

[0067] Where E is the electric field strength of the particulate matter, ε r τ is the dielectric constant of the particulate matter, and τ is the time constant.

[0068] For submicron particles with a diameter between 0.1 and 1 μm, both of the above-mentioned charging mechanisms occur simultaneously:

[0069]

[0070] Therefore, the Coulomb force F experienced by the charged particle e for:

[0071] F e =qE

[0072] ② Since the electrodes in the electro / turbulent synergistic co-coagulation region 1 of this invention are set as smooth cylindrical electrodes, the turbulent co-coagulation effect in the region is enhanced. Therefore, it is necessary to analyze the viscous resistance F experienced by the particles. d :

[0073]

[0074] Among them, C d The viscous drag coefficient is given by an empirical formula, where ρ is the air density in the flow field, and u is the viscous drag coefficient. f Let be the airflow velocity in the flow field.

[0075] ③ After the flow of dust-laden wet flue gas in the channel of the electro / turbulent co-coagulation zone 1 stabilizes, when there is a significant velocity gradient in the flow field, there is a lift force perpendicular to the flow direction of the dust-laden wet flue gas, namely the Saffman force F. s :

[0076]

[0077] Where μ is the kinematic viscosity coefficient of the airflow in the flow field.

[0078] Taking into account the Coulomb force F acting on particulate matter e Viscous resistance F d and Saffman force F s The equations of motion for particulate matter in the flue gas within the channel of the electric / turbulent co-coagulation region 1 were obtained as follows:

[0079]

[0080] The above analysis neglects the gravity of the particles themselves, as well as the Magnus force that causes uncertainty in the particle trajectory due to fluid vorticity.

[0081] When the voltage of the external high-voltage power supply is stable, the agglomeration efficiency of particles in each particle size range can exceed 95%.

[0082] Specifically, since strong turbulent coagulation still exists a certain distance after leaving the electric / turbulent synergistic coagulation zone 1, this invention sets up a tail turbulent zone 2 after the electric / turbulent synergistic coagulation zone 1, the channel length of which is 1 / 4 to 1 / 3 of the channel length of the electric / turbulent synergistic coagulation zone 1. This design can further improve the coagulation efficiency of particulate matter in the dust-laden wet flue gas before entering the enhanced radiation condensation zone 2.

[0083] The enhanced radiation cooling coating 4 is used to enhance radiation heat transfer and achieve cooling of the cylindrical sidewall of the enhanced radiation condensation zone 3. The coating includes a superpolymer hybrid film 14 and a silver-plated layer 15 disposed beneath it, and is bonded to the outer wall of the cylinder with an adhesive 16. Specifically, the superpolymer hybrid film 14 is a random glass-polymer hybrid metamaterial, the structure of which includes micron-sized silica spheres randomly distributed in a matrix material, polymethyl methacrylate (TPX). Other transparent polymers, including polymethyl methacrylate and polyethylene, can also be used as the matrix material; the diameter of a single silica sphere is between 4 and 8 μm. Using TPX as the matrix material and randomly distributing micron-sized silica spheres therein, the superpolymer hybrid film 14, with a thickness of 50 μm, exhibits an average emissivity in the zenith direction for wavelengths in the range of 8 < λ < 13 μm. The reflectance can reach 0.93. To meet the heat dissipation requirements of the enhanced radiation cooling coating 4 on the cylinder, the thickness of the superpolymer hybrid film 14 should be greater than or equal to 20 μm. Since the superpolymer hybrid film 14 ultimately dissipates heat in the form of infrared radiation into the low-temperature space background of 3K, obstacles should be minimized between the superpolymer hybrid film 14 and the zenith direction. Considering practical application scenarios, to prevent solar radiation from penetrating the superpolymer hybrid film 14 and being absorbed by the cylinder, thus affecting the radiation cooling effect, this invention sets a silver-plated layer 15 under the superpolymer hybrid film 14, which can reflect up to about 96% of solar irradiance. Since the superpolymer hybrid film 14 is transparent, the average emissivity of the enhanced radiation cooling coating 4 in the atmospheric window (within the wavelength range of 8 < λ < 13 μm) can be considered to be 0.93, while the reflectance of solar irradiance is 96%. This indicates that the enhanced radiation cooling coating 4 efficiently emits infrared radiation to cool the cylindrical sidewall of the enhanced radiation condensation zone 3 while absorbing almost no solar irradiance, achieving the best cooling effect.

[0084] The radiative heat transfer of the coating satisfies the energy conservation equation:

[0085] c shell m shell ΔT=Q rad -Q atm -Q solar -Q conv+cond

[0086] In the left side of the equation, c shell For the heat capacity of the cylinder material, m shell For the mass of the cylinder, these two terms are property parameters of the cylinder; ΔT represents the temperature change of the cylinder caused by radiative heat transfer, neglecting heat conduction through the coating; the four terms on the right side of the equation: Q rad Q represents the thermal radiation emitted from the coating surface. atm Q represents the amount of heat absorbed by the coating from atmospheric radiation. solar Q represents the amount of heat absorbed by the coating from solar radiation. conv+cond This indicates the convective heat transfer to the coating from the fluid surrounding it.

[0087] Q rad -Q atm The following formula can be used to calculate:

[0088]

[0089] In the formula, σ is the Stefan-Boltzmann constant, with a value of 5.67 × 10⁻⁶. -8 W / (m 2 ·K 4 A represents the effective radiation area, i.e., the surface area of ​​the coating; T represents the effective radiation area. suf Indicates the surface temperature of the coating; T skyThe effective sky temperature, expressed as the average emissivity using the continuous spectrum assumption, is represented by this equation. and the local average temperature T set by the device a Functions:

[0090]

[0091] Average clear sky emissivity It can be calculated using the models of MARTIN and BERDAH:

[0092]

[0093] In the formula Δε h +Δε e For the location and time correction terms, T dew Here, RH is the dew point, and RH is the relative humidity.

[0094]

[0095]

[0096] Considering practical applications, since it's impossible to achieve clear skies throughout the entire process, the cloud cover impact factor Ca needs to be used. Make corrections:

[0097]

[0098] The cloud cover factor Ca is a function of the opaque cloud cover n. n represents the amount of sky covered by clouds, and its value ranges from 1 to 10. For example, when clouds cover 1 / 10 of the sky, the opaque cloud cover n is 1.

[0099] Ca = 1 + 0.0224n - 0.0035n 2 +0.00028n 3

[0100] The heat absorbed by the coating from solar radiation can be expressed as a function of the incident solar irradiance G and the effective radiant area A:

[0101]

[0102] In the formula The average solar absorptivity of the coating is 0.05. The incident solar irradiance G is a function of the angle θ between the incident solar ray and the normal to the coating surface.

[0103] G s,o =S c fcosθ

[0104] In the formula S c The solar constant has a value of (1370±6) W / m 2It is independent of geographical location or time of day. f is the Earth-Sun distance correction factor, which is generally taken as 0.97 to 1.03.

[0105] The convective heat transfer from the fluid surrounding the coating to it is a function of the local wind speed ω and the temperature difference between the coating surface and the ambient temperature.

[0106] Q conv+cond =(2.5+2ω)A(T) suf -T a )

[0107] After the device is operating stably, the obtained ΔT is the heat transfer driving force for water vapor condensation in the flue gas. Under static conditions, the enhanced radiation cooling coating 4 can cool the flue gas entering the enhanced radiation condensation zone 3 by 10.6°C.

[0108] Considering the actual application scenarios of the device of this invention, the biggest factors affecting the cooling effect of the enhanced radiation cooling coating 4 used in this invention are the cloud conditions and solar irradiance at the location where the device is applied. The above principle takes into account the quantitative parameter of cloud conditions—the amount of opaque cloud n—as well as weather conditions. Assuming that the invention is operating under a relatively extreme condition, namely from 11:00 AM to 1:00 PM (the temperature is relatively high, and the sun is directly overhead, with the solar irradiance of the enhanced radiation cooling coating 4 reaching its peak for the day), and that the clouds in the sky are scattered and occupy more than 40% of the sky area (the amount of opaque cloud n is 4 to 6), the temperature of the dust-laden wet flue gas decreases by 6°C after passing through the enhanced radiation condensation zone 3 of this invention.

[0109] Driven by this temperature difference, the dust-laden wet flue gas from the desulfurization tower outlet can be cooled without additional energy consumption. As the flue gas temperature decreases, water vapor condenses on the inner surface of the cylindrical sidewall of the enhanced radiation condensation zone 3. Under the action of gravity, the condensate flows downward along the inner wall and into the condensate collection device 7 through the condensate collection port 5.

[0110] Limited by gravity, the downward flow of condensate along the wall results in a small portion of the continuously condensing condensate not being discharged in time. When the liquid film on the wall is thick, the flue gas continuously flowing into this area may carry some residual condensate. If this condensate is directly discharged into the chimney, it will not only cause a "white plume" phenomenon at the chimney outlet but also reduce the actual water collection efficiency. Therefore, this invention sets a vibrating wire grid 9 in the dehydrated flue gas channel 8 downstream of the enhanced radiant condensation zone 3. This causes the residual condensate carried in the flue gas to collide and condense into large-diameter droplets, which adhere to the vibrating wire and flow into the condensate collection tank 11 under gravity. In addition, a small portion of undissolved particles that have condensed and increased in size within the enhanced radiant condensation zone 3 will be intercepted by the vibrating wire grid 9 and carried by the downward-flowing condensate into the condensate collection tank 11. The dust-removed and dehydrated flue gas finally enters the chimney for discharge.

[0111] Based on the above principle, condensate has two main generation areas: the inner wall of the cylindrical portion of the enhanced radiation condensation zone 3 and the vibrating wire grid 9. Considering the condensate volume in both areas, this invention arranges condensate collection ports 5 at the bottom non-cylindrical portion of the enhanced radiation condensation zone 3, specifically through holes arranged symmetrically in a ring, each through hole being funnel-shaped; additionally, in the portion of the dehydrated flue gas channel 8 where the vibrating wire grid 9 is located, funnel-shaped drainage holes 10 are evenly distributed on the bottom surface. The two generation areas contain water-soluble particulate matter, especially fine particulate matter that has already agglomerated and increased in size, as well as other pollutants, including NH4+. + Elements such as SO2 and Hg will dissolve in the condensate. The condensate collected in condensate collection tank 11 will be used to replenish the water supply for the desulfurization system.

[0112] Specifically, the collision efficiency between condensed droplets and already coagulated particles is influenced by particle size; the smaller the particle size, the more dominant the Brownian diffusion effect; the larger the particle size, the greater the role of inertial collision. As mentioned earlier, when the voltage of the applied high-voltage power supply is stable, considering the electro-turbulent synergistic coagulation zone 1, the coagulation efficiency of particles in each size range can exceed 95%. Therefore, it can be considered that the collision efficiency between condensed droplets and particles in the enhanced radiation condensation zone 3 is entirely affected by inertial collision and droplet interception effects. Therefore, the dimensionless semi-empirical formula for evaluating the collision efficiency E(d,D) is expressed as follows:

[0113]

[0114] In the formula, Re is the Reynolds number with a characteristic length equal to the droplet radius, Sc is the Schmidt number of the particulate matter, St is the Stokes number of the dust particle, and S... * Here, μ is a dimensionless number, D is the diameter of the droplet. a With μ w ρ represents the dynamic viscosity of the flue gas and the liquid droplets, respectively.w With ρ p These represent the densities of the smoke and the droplets, respectively. The subscripts Interception and Inertial impaction indicate the interception effect and inertial impaction of the droplets, respectively.

[0115] Due to the temperature difference ΔT between the inner wall of the cylinder before and after heat exchange, particles diffuse towards the boundary layer of the cylinder wall under the action of thermophoretic force F. T The calculation formula is

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122] In the formula, Kn is the Knudsen number, and R g The gas constant for air is 287 J / (kg·K), d m The average diameter of the nitrogen and carbon dioxide mixture particles is 0.161 nm, d p The particle size after the collision. Let be the mean free path of the gas molecules, γ be the specific heat capacity of the gas (taken as 1.4 in the calculation), and c be the mean free path of the gas molecules. v For constant volume specific heat capacity, S n With S t Here, are the momentum adjustment coefficients in the vertical and tangential directions, respectively, both taken as 1.0 in the calculation. T is the flue gas temperature, and p is the absolute pressure. a, π1 is a calculation parameter introduced to simplify the calculation.

[0123] By controlling the voltage of the high-voltage electrode post 12 and the ground electrode post 13, the particle size d after the collision can be controlled. p , making the thermophoretic force F T The particle size d after the collision p The derivative of the thermophoretic force F is equal to 0, even if the thermophoretic force F T To achieve the maximum value, the optimal efficiency of pollutant particle removal is reached.

[0124] 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 conceived by those skilled in the art within the scope of the technology disclosed in the present invention, or equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, should all be covered within the scope of protection of the present invention.

Claims

1. A flue gas water conservation synergistic multi-pollutant removal device characterized in that, The system includes a flue gas inlet pipe, a cylinder, and a dehydrated flue gas channel (8) connected in sequence. The cross-sectional area of ​​the inlet transition section between the outlet of the flue gas inlet pipe and the cylinder gradually expands, while the cross-sectional area of ​​the outlet transition section between the cylinder and the inlet of the dehydrated flue gas channel (8) gradually shrinks. The outer wall of the cylinder is provided with a reinforced radiation cooling coating (4). Several rows of high-voltage electrode columns (12) and grounding electrode columns (13) are alternately arranged in the front section of the flue gas inlet pipe. A condensate collection device (7) is nested outside the dehydrated flue gas channel (8), and the condensate collection device (7) is connected to the cylinder. Several condensate collection ports (5) are provided in the outlet transition section, and the condensate collection ports (5) are connected to the condensate collection device (7). A vibrating wire grid (9) is provided inside the dehydrated flue gas channel (8), and several drainage holes (10) are opened on the dehydrated flue gas channel (8) below the vibrating wire grid (9). The enhanced radiation cooling coating (4) consists of an adhesive (16), a silver plating layer (15), and a superpolymer hybrid film (14) from the inside out; the adhesive (16) is bonded to the outer wall of the cylinder; the thickness of the superpolymer hybrid film (14) is ≥20μm; The outer wall of the cylinder is corrugated, and the inner wall is provided with a hydrophobic layer; The flue gas inlet pipe is set perpendicular to the cylinder body, the cylinder body is set perpendicular to the dehydration flue gas channel (8), and the inner wall of the connection between the cylinder body and the flue gas inlet pipe and the dehydration flue gas channel (8) is smoothly transitioned. The distance between the end of the front section of the flue gas inlet pipe and the beginning of the inlet transition section is 1 / 4 to 1 / 3 of the length of the front section of the flue gas inlet pipe. The surface roughness grade of the high-voltage electrode post (12) and the grounding electrode post (13) is higher than Ra12.5; the diameter D of the high-voltage electrode post (12) and the grounding electrode post (13) satisfies: 2D≤L≤4D Where L is the distance between the centers of adjacent high-voltage electrode posts (12) and grounding electrode posts (13) along the flue gas flow direction; The connection between the dehydrated flue gas passage (8) and the condensate collection device (7) is lower than the inlet of the dehydrated flue gas passage (8).

2. The flue gas water conservation synergistic multi-pollutant removal device according to claim 1, characterized in that, The condensate collection device (7) has an outlet at the bottom, and a condensate collection tank (11) is provided below the outlet and the drain hole (10).

3. A method of operating a flue gas water conservation synergistic multi-pollutant removal device as defined in claim 1 or 2, wherein, include: After the dust-laden wet flue gas from the desulfurization tower outlet enters the front section of the flue gas inlet pipe, under the synergistic effect of electrocoagulation and turbulent coagulation of the high-voltage electrode column (12) and the ground electrode column (13), the particulate matter in the flue gas agglomerates and increases in size, and some particulate matter is intercepted and captured by the high-voltage electrode column (12) and the ground electrode column (13); then it enters the rear section of the flue gas inlet pipe, and the remaining strong turbulent coagulation effect is used to further enhance the coagulation effect; After entering the cylinder, the enhanced radiation cooling coating (4) cools and heats the inner wall of the cylinder. The temperature difference between the cooled inner wall of the cylinder and the dust-laden wet flue gas inside the cylinder causes the particles to diffuse toward the boundary layer of the cylinder wall and causes the water vapor in the flue gas to condense on the inner wall of the cylinder and separate from the dehydrated flue gas. The particles that have condensed and increased in size in the flue gas, as well as the pollutants that are soluble in water, dissolve in the condensate. Under the action of gravity, the condensate carrying multiple pollutants flows into the condensate collection device (7) through the condensate collection port (5) and is collected. The flue gas carrying some residual condensate and a small amount of particles is intercepted by the vibrating wire grid (9) in the dehydrated flue gas channel (8). The flue gas that has been dusted and dehydrated is finally discharged from the device.

4. The working method of the flue gas water-saving and multi-pollutant removal device according to claim 3, characterized in that, The thermophoretic force F T We obtain it from the following formula: In the formula, Kn For Knudsen numbers, R g Let J be the gas constant of air, with a value of 287 J / (kg·K). d m The average diameter of the nitrogen and carbon dioxide mixture particles is 0.161 nm. d p The particle size after the collision. λ_ The mean free path of gas molecules, γ Let be the specific heat capacity of the gas, which is taken as 1.4 in the calculation. c v For constant volume specific heat capacity, S n and S t These are the momentum adjustment coefficients in the vertical and tangential directions, respectively, both taken as 1.0 in the calculation. T For flue gas temperature, p Absolute pressure; a、 、π 1. Calculation parameters introduced to simplify calculations; By controlling the voltage of the high-voltage electrode post (12) and the ground electrode post (13), the particle size after collision can be controlled. d p make thermophoretic force F T Particle size after collision d p The derivative is equal to 0, even if the thermophoretic force F T To achieve the maximum value, the optimal efficiency of pollutant particle removal is reached.

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