Method and device for eliminating white smoke from flue gas of wet desulfurization

Abstract

The application discloses a method and device for eliminating white smoke of wet desulfurization flue gas, which mixes hot air with flue gas to eliminate white smoke, collects various temperature and humidity data and carries out corresponding calculation, and finally calculates the critical heating temperature T of hot air required by flue gas white smoke elimination HCT , then adjusts the amount of heat medium of the heater in real time until the temperature T of hot air is equal to the critical heating temperature T ah of hot air HCT , and then the flue gas is discharged. The application is suitable for mixed heating and white smoke elimination of saturated wet flue gas of hot air and wet desulfurization, and is also suitable for mixed heating and white smoke elimination of wet desulfurization flue gas after cooling and condensation. The critical heating temperature of hot air for realizing white smoke elimination of flue gas can be determined in real time, the amount of heat medium is adjusted in real time to control the temperature of hot air, the automatic control of the amount of heat medium for mixed heating and white smoke elimination is realized, white smoke is eliminated, and unnecessary energy consumption of the device caused by lack of theoretical basis for adjusting the temperature of discharged flue gas by an operator is avoided.

Description

Technical Field

[0001] This invention relates to the field of flue gas emission control technology, and in particular to a method and apparatus for eliminating white spots in wet desulfurization flue gas. Background Technology

[0002] Currently, the environmental protection field generally adopts wet desulfurization process in flue gas desulfurization. This process involves spraying alkaline solution in the desulfurization absorption tower to wash away or absorb SO2 in the flue gas. The saturated wet flue gas after wet desulfurization is discharged from the chimney and comes into contact with the cooler ambient air. During the cooling process, water vapor in the flue gas condenses and precipitates out. The condensed water droplets refract and scatter light, forming a white plume.

[0003] Currently, there are three main methods for eliminating white spots in flue gas: direct flue gas heating, direct flue gas condensation, and flue gas condensation followed by heating. Flue gas heating primarily employs two methods: First, indirect heating, where the flue gas and heating medium are separated by a solid wall, preventing mixing, and heat exchange occurs through the wall. Examples include GGH (flue gas-to-flue gas reheater) and MGGH (heat medium-type flue gas-to-flue gas reheater). However, due to the presence of dust, aerosols, and SO3 droplets in the flue gas, the resistance of indirect heaters gradually increases during operation, leading to scaling, corrosion, and blockage, causing downtime for maintenance and affecting long-term operation. Second, mixed heating, where hot clean gas is mixed with the desulfurized purified flue gas before being discharged into the atmosphere, heating the flue gas to the required temperature. Hot clean gas includes hot air, hot secondary air, and hot flue gas. The mixing location between the hot clean gas and the flue gas is between the flue gas desulfurization unit and the chimney, thus avoiding the problems of indirect heating and leading to its widespread application.

[0004] For "hybrid heating to eliminate white smoke" devices, the critical heating temperature of the hot cleaning gas is closely related to environmental conditions. Lower ambient temperatures and higher humidity result in a higher critical heating temperature of the hot cleaning gas required to eliminate white smoke from wet desulfurization flue gas, and vice versa. In actual operation, the critical heating temperature of the hot cleaning gas is generally set according to the design temperature. Although the critical heating temperature can be appropriately lowered under favorable weather conditions (high ambient temperature, low humidity), operators often lack a theoretical basis for adjusting this temperature, leading to haphazard adjustments. This can result in white smoke appearing when the heating temperature is too low, or excessive energy consumption when the heating temperature is too high.

[0005] Therefore, there is an urgent need for a wet desulfurization flue gas whitening method and device that can determine the critical heating temperature of the hot air to achieve flue gas whitening in real time and adjust the amount of heat medium to control the hot air temperature in real time, so as to realize the automatic control of the amount of heat medium used for mixed heating whitening, and achieve the elimination of white plumes with minimal energy consumption, thereby reducing the energy consumption of the device.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a method and apparatus for eliminating white smoke from wet desulfurization flue gas. This method is applicable to both hot air and saturated wet flue gas from wet desulfurization, and also to hot air and cooled / condensed wet desulfurization flue gas. It can determine the critical heating temperature of the hot air required to eliminate white smoke in real time and adjust the amount of heat transfer medium to control the hot air temperature, thereby achieving automatic control of the heat transfer medium usage for mixed heating and white smoke elimination. This eliminates white smoke while avoiding unnecessary energy consumption caused by operators lacking theoretical basis for adjusting the exhaust gas temperature.

[0008] To achieve the above objectives, according to a first aspect of the present invention, the present invention provides a method for eliminating whitening of flue gas in wet desulfurization, which eliminates whitening of flue gas by mixing hot air with flue gas, comprising the following steps: A. Collecting the atmospheric temperature T at the corresponding height of the exhaust outlet of the wet desulfurization chimney. e and atmospheric relative humidity Data; collecting air temperature T at the fan inlet. a and relative humidity of air Data; B, via atmospheric temperature T e and atmospheric relative humidity air temperature T a and relative humidity of air Atmospheric moisture content ω was calculated. e and air humidity ω a C. Collect the flue gas temperature T of the saturated wet flue gas after wet desulfurization. G And the moisture content ω of the flue gas was calculated. G D. Collect the dry air flow rate F at the fan outlet. a and the dry flue gas flow rate F after wet desulfurization G Combined with air humidity ω a and the moisture content of flue gas ω G Calculate the moisture content ω of the flue gas and air mixture. mix E. Utilizing the moisture content ω of the mixed gas mix Calculate the temperature at the intersection T mix According to the temperature T at the intersection pointmix Moisture content ω of mixed gas mix Flue gas temperature T G Moisture content in flue gas ω G and atmospheric moisture content ω e Calculate the critical heating temperature T of hot air required for flue gas whitening HCT F. Adjust the amount of heat transfer medium used in the heater in real time until the hot air temperature T is reached. ah Critical heating temperature T of hot air HCT When the values ​​are equal, the flue gas is discharged.

[0009] Furthermore, in the above technical solution, the atmospheric moisture content ω in step B... e air humidity ω a And the moisture content ω of the flue gas in step C G The calculation can be performed in the following way:

[0010]

[0011] Among them, P s The partial pressure of water vapor in saturated air is the pressure of water vapor when the relative humidity of the gas is 100%, and the unit is Pa; the unit of moisture content is g / kg dry air.

[0012] The moisture content ω of the mixed gas in step D mix The calculation can be performed in the following way:

[0013]

[0014] The intersection temperature T in step E mix The calculation can be performed in the following way:

[0015]

[0016] The critical heating temperature T of the hot air in step E HCT The calculation can be performed in the following way:

[0017]

[0018] Furthermore, in the above technical solution, when the flue gas contains droplets in a supersaturated state, the critical heating temperature T of the hot air is controlled by the droplet content A. HCT The calculation formula (4) is modified as follows:

[0019]

[0020] Where A is the droplet content in the flue gas after wet desulfurization, in g / kg dry flue gas.

[0021] Furthermore, in the above technical solution, the droplet content A can be comprehensively defined by the demister structure factor, flue gas velocity factor, demister pressure drop factor, and demister flushing factor.

[0022] Furthermore, in the above technical solution, when the temperature measuring point of the hot air is at a certain distance from the mixing point of the flue gas and hot air, and / or when the mixing point of the flue gas and hot air is at a certain distance from the chimney outlet, the critical heating temperature T of the hot air is determined by the temperature deviation σ. HCT The calculation formula (5) is modified as follows:

[0023]

[0024] Where σ is the temperature deviation, specifically defined as -5℃ to 5℃.

[0025] Furthermore, in the above technical solution, when there is a certain distance between the mixing point of flue gas and hot air and the chimney outlet, the temperature deviation σ is comprehensively defined by the heat transfer area factor, the chimney structure factor, the temperature difference factor between flue gas and the atmosphere, the flue gas flow rate factor, and the environmental wind force level factor.

[0026] Furthermore, in the above technical solution, when the critical heating temperature T of the hot air... HCT ≤Air temperature at the fan inlet T a When this happens, the heat transfer medium consumption of the heater should be adjusted to 0 t / h.

[0027] Furthermore, in the above technical solution, the flue gas whitening method pressurizes the air by a fan, heats the pressurized air by a heater, mixes it with the flue gas after wet desulfurization, and then discharges the heated flue gas into the atmosphere through a chimney.

[0028] Furthermore, in the above technical solution, the flue gas whitening method is applicable to the mixed heating of hot air and saturated wet flue gas after wet desulfurization, or to the mixed heating of hot air and cooled and condensed wet desulfurization flue gas.

[0029] To achieve the above objectives, according to a second aspect of the present invention, a wet desulfurization flue gas whitening device is provided, wherein the wet desulfurization tower and the chimney are integrated or separate, and flue gas whitening is achieved by mixing hot air with flue gas. The device includes: an atmospheric and air data acquisition unit, which is used to acquire the atmospheric temperature T at a corresponding height at the exhaust outlet of the wet desulfurization chimney. e and atmospheric relative humidity Data; collecting air temperature T at the fan inlet. a and relative humidity of air Data; atmospheric and air humidity calculation unit, which is used to calculate atmospheric temperature T e and atmospheric relative humidity air temperature Ta and relative humidity of air Atmospheric moisture content ω was calculated. e and air humidity ω a The flue gas temperature acquisition and moisture content calculation unit is used to acquire the flue gas temperature T of the saturated wet flue gas after wet desulfurization. G And the moisture content ω of the flue gas was calculated. G ; Flow acquisition and mixed gas moisture content calculation unit, which is used to collect the dry air flow rate F at the fan outlet. a and the dry flue gas flow rate F after wet desulfurization G Combined with air humidity ω a and the moisture content of flue gas ω G Calculate the moisture content ω of the flue gas and air mixture. mix The hot air critical heating temperature calculation unit utilizes the moisture content ω of the mixed gas. mix Calculate the temperature at the intersection T mix According to the temperature T at the intersection point mix Moisture content ω of mixed gas mix Flue gas temperature T G Moisture content in flue gas ω G and atmospheric moisture content ω e Calculate the critical heating temperature T of hot air required for flue gas whitening HCT The flue gas exhaust control unit is used to adjust the amount of heat medium used in the heater in real time until the hot air temperature T is reached. ah Critical heating temperature T of hot air HCT When the values ​​are equal, the flue gas is discharged.

[0030] Furthermore, in the above technical solution, when a condenser or condensation section is installed between the wet desulfurization tower and the chimney, the flue gas temperature T G and dry flue gas flow rate F G This is the data for the condensed flue gas.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1) The flue gas whitening method and apparatus of the present invention adopts a mixed heating method of hot clean gas (air) and desulfurized purified flue gas to eliminate white smoke, which effectively avoids the problems of increased heater resistance, scaling, corrosion and blockage that exist in the whitening of flue gas by indirect wall heaters.

[0033] 2) Based on external weather conditions such as temperature and humidity, as well as the flue gas temperature after wet desulfurization or after desulfurization and condensation, this invention automatically calculates the critical heating temperature T of hot air required for mixed heating to eliminate white smoke. HCT The temperature T of the hot air is adjusted by regulating the amount of heat transfer medium used in the device. ahEqual to the calculated critical heating temperature of hot air, it can effectively realize the automatic control of the heat medium usage of the device, avoid blind adjustment by operators, avoid situations where white smoke appears in the exhaust gas due to excessively low hot air heating temperature, or excessive energy consumption of the device due to excessively high hot air heating temperature, and can also effectively reduce the workload of operators.

[0034] 3) Since the flue gas contains droplets, it is in a supersaturated state. The flue gas state point should be located above the saturated humid air line. Therefore, there will be some error when calculating the critical heating temperature for whitening. This invention uses the droplet content A to correct the calculation formula for the critical heating temperature of hot air, so that the calculation results are more accurate and the whitening method of this invention is more consistent with the actual situation, thus improving the accuracy and reliability of whitening.

[0035] 4) Due to the large measuring range of the measuring instruments themselves, and imperfections in their mechanical performance or electrical structure, there is often a certain measurement error. Improper instrument installation or significant interference in the operating environment can also cause errors, and may even lead to instrument malfunction or failure. Furthermore, because there is a certain distance between the temperature measuring point of the hot air and the mixing point of the flue gas and hot air, especially between the mixing point and the chimney outlet (and this distance cannot be adjusted), the temperature of the flue gas decreases after passing through this distance. Therefore, there is a certain deviation between the actual temperature of the hot air required for eliminating white smoke and the temperature at the measuring point. To address these issues, this invention uses a temperature deviation σ to correct the calculation formula for the critical heating temperature of the hot air. The value of the temperature deviation σ is determined after adjustments based on actual field conditions, thereby making the calculation formula for the critical heating temperature of the hot air more accurate. This makes the white smoke elimination method of this invention more consistent with actual conditions, improving the accuracy and reliability of the invention.

[0036] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0037] Figure 1 This is a schematic diagram illustrating the principle of the wet desulfurization flue gas whitening method of the present invention.

[0038] Figure 2 This is a schematic diagram illustrating the principle of the flue gas mixing and heating method for eliminating white spots according to the present invention.

[0039] Figure 3 This is a schematic flowchart of the wet desulfurization flue gas whitening method of the present invention.

[0040] Figure 4This is a schematic diagram of one embodiment of the wet desulfurization flue gas whitening device of the present invention.

[0041] Figure 5 This is a schematic diagram of another embodiment of the wet desulfurization flue gas whitening device of the present invention.

[0042] Explanation of key figure labels:

[0043] 100-Wet desulfurization tower; 101-Demister; 200-Chimney; 201-Second ambient temperature and humidity detector; 300-Heater; 301-Hot air temperature detector; 302-Heating medium; 303-Flow regulating valve; 400-Fan; 401-Air monitoring unit; 402-Air flow detector; 500-Integrated desulfurization and chimney tower; 501-Dust removal and desulfurization section; 502-Demister section; 503-First flue gas temperature detector; 504-First flue gas flow detector; 505-Chimney section; 506-First ambient temperature and humidity detector; 600-Condenser; 601-Refrigerant; 602-Second flue gas temperature detector; 603-Second flue gas flow detector. Detailed Implementation

[0044] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0045] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0046] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0047] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0048] refer to Figure 1 There are three main methods for eliminating white smoke in flue gas: direct heating of flue gas, direct condensation of flue gas, and condensation followed by heating of flue gas. Figure 1 The saturation curve diagram shows that after the flue gas passes through the wet desulfurization tower, it forms low-temperature saturated wet flue gas, and its state is as follows: Figure 1 Point A is shown above, and the ambient atmospheric conditions are shown at point C. The intersection of the straight line between points A and C with the saturation curve will produce white smoke. Further, as shown... Figure 1 As shown, the direct flue gas heating method (ABC) involves heating the desulfurized and purified flue gas, changing its state point from A to B, and reducing its relative humidity. The line segment BC is tangent to the saturation curve at point F. This means that the flue gas will not become saturated during the process of changing from state point B to ambient air state point C, thus preventing the formation of "white smoke." Further details are provided below. Figure 1 As shown, the flue gas condensation followed by heating (ADEC) method involves: cooling the exhaust gas, changing it from state point A to state point D, during which condensate water is released, reducing the absolute humidity and water vapor content; then heating the condensed flue gas, changing it from state point D to state point E, further reducing the relative humidity and eliminating the white plume; the line segment EC is tangent to the saturation curve at point F, meaning that the flue gas will not reach saturation or form "white smoke" during the transition from state point E to ambient air state point C. Further details are provided... Figure 1 As shown, Direct Flue Gas Condensation (ADFC) cools the clean flue gas, changing it from state point A to state point F, with the temperature approaching the ambient temperature. This advances the condensation process of the wet flue gas outside the chimney to occur before the chimney, allowing the flue gas to directly merge with the environment after entering the atmosphere, thus preventing the formation of "white smoke".

[0049] This invention employs a hybrid heating method for eliminating white smoke, suitable for mixing flue gas from wet desulfurization with hot air, or mixing flue gas from wet desulfurization and condensation with hot air. The principle of hybrid heating for eliminating white smoke is as follows: (Refer to...) Figure 2 As shown, the state point A of the flue gas after wet desulfurization is located on the water vapor saturation curve (saturated moist air line) (when the flue gas contains mist droplets, the state point of the flue gas becomes A', and A' is located above the water vapor saturation curve); the moisture content of the gas after mixing with hot air decreases to ω = ω mix Draw a tangent line from the environmental state point E to the water vapor saturation curve (the point of tangency is T). The extension of ET intersects ω = ω mix They intersect at point B, and the temperature at point B is (T). mix The temperature at which the mixed gas can eliminate white smoke is the critical mixing temperature. EC is the isohyet heating line for air; after passing through the heater, the air's moisture content remains constant while its temperature increases. EC intersects the extension of AB at point C. The temperature at point C (T) is...HCT This is the critical heating temperature of hot air, which is the temperature of the air after passing through the heater that is greater than or equal to T. HCT This can eliminate white smoke from wet desulfurization (when the flue gas contains droplets, the extensions of EC and A'B intersect at point C', then the temperature at point C' is the critical heating temperature T of the hot air). HCT ).

[0050] The wet desulfurization flue gas whitening method of the present invention eliminates flue gas whitening by mixing hot air with flue gas, and includes the following steps:

[0051] Step S101: Collect the atmospheric temperature T at the corresponding height of the exhaust outlet of the wet desulfurization chimney. e and atmospheric relative humidity Data; collecting air temperature T at the fan inlet. a and relative humidity of air data.

[0052] Specifically, the present invention can be achieved through... Figure 4 The first large temperature and humidity detector 506 shown is... Figure 5 The second large temperature and humidity detector 201 shown collects the atmospheric temperature T at the corresponding height of the chimney exhaust outlet. e and atmospheric relative humidity Data. The height of the chimneys used for wet desulfurization flue gas discharge varies across different industries, generally exceeding 50m, with some cement chimneys even surpassing 200m in height. Temperature and humidity at high altitudes differ from those at ground level. For every 100m increase in altitude, the air temperature decreases by 0.5–1.5℃, and humidity also varies. This invention installs temperature and humidity detectors near the chimney discharge outlet or on structures at the same height to measure the atmospheric temperature T at the location where the flue gas is emitted. e and atmospheric relative humidity Therefore, compared with ground-based testing, the critical heating temperature of hot air obtained by this invention is more accurate and has less error.

[0053] Furthermore, the present invention can be achieved through... Figure 4 or Figure 5 The air monitoring unit 401 shown collects the air temperature T at the fan inlet. a and relative humidity of air data.

[0054] Step S102, using the atmospheric temperature T collected in step S101 e and atmospheric relative humidity air temperature T a and relative humidity of air Atmospheric moisture content ω was calculated. e and air humidity ωa .

[0055] Specifically, atmospheric moisture content ω e and air humidity ω a (Unit: g / kg dry air) can be calculated as follows:

[0056]

[0057] Among them, P s P represents the partial pressure of saturated water vapor, which is the partial pressure of water vapor when the relative humidity of the gas is 100%, and is expressed in Pa. s The calculation can be performed using the Goff-Gratch formula (see the formula below); T is the temperature, in K.

[0058]

[0059] In this formula,

[0060] C1=-7.90298, C2=5.028081, C3=1.3816×10 -7 C4 = 8.1328 × 10 -3 C S =lg1013.246, a=373.16.

[0061] Step S103: Collect the flue gas temperature T of the saturated wet flue gas after wet desulfurization. G And the moisture content ω of the flue gas was calculated. G .

[0062] Specifically, through Figure 4 The first flue gas temperature detector 503 shown in the figure collects the flue gas temperature T after wet desulfurization in the "integrated tower". G Or through Figure 5 The second flue gas temperature detector 602 shown collects the temperature T of the flue gas after wet desulfurization and condensation in the "split tower". G Further analysis was conducted using the collected flue gas temperature T. G and (The flue gas after wet desulfurization is saturated wet flue gas) Substitute into the aforementioned formula (1) and still calculate the flue gas moisture content ω using the aforementioned Goff-Grech formula. G .

[0063] Step S104: Collect the dry air flow rate F at the outlet of the fan. a and the dry flue gas flow rate F after wet desulfurization G Combined with the aforementioned air humidity ω a and the moisture content ω of the flue gas GCalculate the moisture content ω of the flue gas and air mixture. mix .

[0064] Specifically, the present invention through Figure 4 or Figure 5 The air flow meter 402 shown collects the dry air flow F at the outlet of the fan 400. a ;pass Figure 4 The first flue gas flow meter 504 shown collects the dry flue gas flow rate F after wet desulfurization in the "integrated tower". G ,pass Figure 5 The second flue gas flow meter 603 shown collects the flow rate F of the dry flue gas after wet desulfurization and condensation in the "split tower". G .

[0065] Combined with the air humidity ω calculated in step S102 above a and the moisture content ω of the flue gas calculated in step S103 G The moisture content ω of the flue gas-air mixture is calculated using the following method. mix :

[0066]

[0067] Step S105, passing the atmospheric environment state point (T) e ω e Draw a tangent to the water vapor saturation curve (reference) Figure 2 ), the tangent point is (T) tan ω tan ),

[0068]

[0069]

[0070] in,

[0071] Step S106, using the moisture content ω of the mixed gas obtained in step S104 mix Calculate the temperature at the intersection T mix According to the temperature T at the intersection point mix Moisture content ω of mixed gas mix and the aforementioned flue gas temperature T G The aforementioned moisture content ω in flue gas G Atmospheric moisture content ω e Calculate the critical heating temperature T of hot air required for flue gas whitening HCT .

[0072] Specifically, the intersection temperature T mix The calculation is performed in the following way:

[0073]

[0074] Hot air critical heating temperature T HCT The calculation is performed in the following way:

[0075]

[0076] Further research by the inventors revealed that existing wet desulfurization demisters are highly efficient at removing larger droplets (≥30μm), but less efficient at removing smaller droplets. Therefore, droplets are inevitably present in the flue gas after wet desulfurization. When calculating the critical heating temperature of hot air, if the influence of droplets is not considered, and the flue gas after wet desulfurization is treated as saturated wet flue gas, its state point (reference) is assumed to be... Figure 2 Point A in the diagram is located on the saturated humid air line, and the critical heating temperature T of the hot air is... HCT The calculation results may have some deviation. Because the flue gas contains droplets, it is in a supersaturated state, and the flue gas state point should be located above the saturated moist air line (reference). Figure 2 Point A' in the equation (4) is used to calculate the critical heating temperature T of the hot air using only the aforementioned formula (4). HCT There will be some error in the calculation. Therefore, this invention further uses the droplet content A to determine the critical heating temperature T of the hot air. HCT The calculation formula was modified to make the calculation results more accurate.

[0077] The droplet content A is related to many factors. The inventors have found that a more scientific and effective approach is to comprehensively define the droplet content A using factors such as demister structure, flue gas velocity, demister pressure drop, and demister flushing. Specifically: 1) Regarding the demister's structural type, different types such as flat-plate demisters, ridge demisters, cyclone demisters, electrostatic demisters, and tubular demisters result in different demisting efficiencies and droplet contents in the flue gas. 2) Regarding the flue gas velocity, excessively high velocities cause previously removed droplets to be carried away again, leading to secondary carryover, reduced demisting efficiency, and increased droplet content in the flue gas. Conversely, insufficient centrifugal force results in inadequate droplet removal, also increasing droplet content. 3) Regarding the demister pressure drop (i.e., the degree of fouling), severe fouling reduces the flue gas flow area, increases the pressure drop, lowers demisting efficiency, and increases droplet content in the flue gas. 4) Regarding the pressure, frequency, volume, and coverage of the demister flushing water, reducing these factors will lead to a decrease in demister efficiency and an increase in the mist droplet content in the flue gas.

[0078] Considering the four influencing factors highly correlated with droplet content A, the specific value of droplet content A can be defined based on the actual on-site conditions. That is, in step S105, preferably but not limitingly, when the flue gas contains droplets in a supersaturated state, the droplet content A is used to determine the critical heating temperature T of the hot air. HCT The calculation formula (4) is modified as follows:

[0079]

[0080] Where A is the droplet content in the flue gas after wet desulfurization, in g / kg dry flue gas.

[0081] Further research by the inventors revealed that the measuring instruments themselves often exhibit errors due to their large range, imperfect mechanical performance, or flawed electrical structure. Improper instrument installation or significant interference in the operating environment can also cause errors, even leading to instrument malfunction or failure. More importantly, there is a certain distance between the temperature measuring point of the hot air and the mixing point of the flue gas and hot air, and also a certain distance between the mixed flue gas and hot air and the chimney outlet. This distance between the mixing point and the chimney outlet cannot be eliminated by adjusting the equipment structure. The flue gas temperature decreases after passing through this distance, resulting in a deviation between the actual temperature of the flue gas emitted into the atmosphere and the temperature at the measuring point. To address these issues, this invention uses the temperature deviation σ to determine the critical heating temperature T of the hot air required for eliminating white smoke. HCT The calculation formula was further revised, and the value of the temperature deviation σ was determined after adjustments based on the actual site conditions, thereby determining the critical heating temperature T of the hot air. HCT The calculations are more accurate.

[0082] To address the calculation errors caused by the distance between the flue gas and hot air mixing point and the chimney outlet, this invention addresses the temperature deviation σ, which is related to many factors. The inventors have found that a comprehensive definition of the temperature deviation σ using factors such as the heat transfer area factor, chimney structure factor, flue gas-atmosphere temperature difference factor, flue gas velocity factor, and environmental wind force level factor is more scientific and effective. Specifically, 1) Regarding the heat transfer area factor, the heat transfer area between the measuring point at the flue gas and hot air mixing point and the chimney outlet, and / or between the chimney and the atmosphere, is related to factors such as the shape and size of the flue and / or chimney, as well as the distance between the measuring point and the chimney outlet. The larger the heat transfer area, the greater the temperature deviation. 2) Regarding chimney construction factors, the material, wall thickness, and material and thickness of the duct and / or chimney between the measuring point at the flue gas and hot air mixing point and the chimney outlet are crucial. A higher thermal conductivity of the duct and / or chimney material, and the material of the lining and / or insulation layer, results in a larger required temperature deviation; a larger wall thickness and a thicker lining and / or insulation layer result in a smaller required temperature deviation. 3) Regarding the temperature difference factor between flue gas and the atmosphere, a larger temperature difference (in winter) results in a larger required temperature deviation; a smaller temperature difference (in summer) results in a smaller required temperature deviation. 4) Regarding the wind force factor in the ambient air, stronger winds facilitate heat dissipation from the flue gas, resulting in a larger required temperature deviation. 5) Regarding the flue gas velocity factor, higher flue gas velocity facilitates heat dissipation from the flue gas, resulting in a larger required temperature deviation.

[0083] Considering the five influencing factors highly correlated with temperature deviation σ, the specific value of temperature deviation σ can be defined based on the actual site conditions. That is, when there is a certain distance between the flue gas and hot air mixing point and the chimney exhaust outlet, the temperature deviation σ is used to determine the critical heating temperature T of the hot air. HCT The calculation formula (5) is modified as follows:

[0084]

[0085] Where σ is the temperature deviation, specifically defined as -5℃ to 5℃.

[0086] Step S107: Adjust the amount of heat medium 302 used in heater 300 in real time until the heated air temperature T is reached. ah The critical heating temperature T of the hot air calculated in step S106 HCT When the values ​​are equal, the flue gas is discharged.

[0087] Specifically, such as Figure 4 , 5As shown, this invention introduces pressurized air through a fan 400. After the air enters the heater 300, the flow regulating valve 303 adjusts the amount of heat medium 302 to heat the air. When the hot air temperature detector 301 detects the hot air temperature T... ah The critical heating temperature T of the hot air calculated in step S106 HCT When they are equal, hot air and wet desulfurization (reference) Figure 4 (or wet desulfurization followed by condensation) (refer to) Figure 5 The flue gas is mixed with the exhaust gas to avoid white smoke in the exhaust. Furthermore, if the critical heating temperature T of the hot air... HCT ≤Air temperature T a If so, the heat transfer medium consumption of the heater is adjusted to 0t / h (i.e., no air heating is required).

[0088] This invention eliminates whitening of flue gas by mixing hot air with flue gas. The flue gas can be flue gas from wet desulfurization, for example... Figure 4 The desulfurization and desulfurization integrated tower 500 shown includes, from bottom to top, a dust removal and desulfurization section 501, a demisting section 502, and a chimney section 505. The desulfurized and demisted flue gas mixes with heated air at the base of the chimney section 505, and the mixed flue gas is then discharged to eliminate white smoke. The flue gas can also be the flue gas from wet desulfurization and condensation, for example... Figure 5 The "split tower" shown includes a wet desulfurization tower 100 and a chimney 200. The wet desulfurization tower 100 is equipped with a demister 101. Before entering the chimney 200, the flue gas after wet desulfurization is condensed by refrigerant 601 in the condenser 600. The cooled flue gas is then mixed with hot air at the base of the chimney 200, and the mixed flue gas is discharged to eliminate white smoke. It should be noted that... Figure 4 The "integrated tower" can also have a condensation section added between the desulfurization section 501 and the demisting section 502, so that the flue gas to be mixed becomes the flue gas after wet desulfurization and condensation; similarly, Figure 5 The "split tower" in the process can also eliminate the condenser, so that the flue gas to be mixed becomes the flue gas after wet desulfurization.

[0089] Example 1

[0090] like Figure 4As shown, the whitening device in this embodiment consists of a wet desulfurization tower, a heater 300, and a fan 400. The wet desulfurization tower is an integrated desulfurization and chimney tower 500, which includes a desulfurization section 501, a demisting section 502, and a chimney section 505 from bottom to top. A first flue gas temperature detector 503 and a first flue gas flow detector 504 are installed above the demisting section 502. A first atmospheric temperature and humidity detector 506 is installed near the exhaust port of the chimney section 505 of the integrated desulfurization and chimney tower 500. A hot air temperature detector 301 is installed on the hot air outlet pipeline of the heater 300, an air monitoring unit 401 is installed at the inlet of the fan 400, and an air flow detector 402 is installed at the outlet of the fan 400.

[0091] A wet desulfurization process uses hot air mixing to heat and eliminate white smoke in the flue gas. The relevant design parameters are as follows: the volume of the desulfurized flue gas is 200,000 Nm³. 3 / h (wet basis), flue gas temperature after desulfurization is 50℃, and the design requires the elimination of white smoke under the conditions of ambient temperature of 10℃ and relative humidity of 50%, with a fan air volume of 100,000 Nm³ / h. 3 / h (wet basis), the design value of the hot air temperature after heating is 113.4℃. The heater 300 adopts a series connection of low temperature water heater and steam heater. The heat medium 302 is low temperature hot water at 80℃ and steam at 1.0MPa and 250℃. To meet the design requirements, it is necessary to consume 100t / h of low temperature hot water and 3.1t / h of steam.

[0092] The automatic control process for the amount of heat transfer medium 302 used in the wet desulfurization flue gas whitening method and apparatus of the present invention is as follows:

[0093] First, the atmospheric temperature T is obtained in real time by the first atmospheric temperature and humidity detector 506 installed below the exhaust outlet of chimney section 505. e 19℃, atmospheric relative humidity The air temperature T is 55%, and the air temperature T is obtained in real time through the air monitoring unit 401 installed at the inlet of the fan 400. a 20℃, relative humidity The dry air flow rate F is 58%, and the dry air flow rate F is obtained in real time through the air flow detector 402 installed at the outlet of the fan 400. a 98673 Nm 3 / h, a first flue gas temperature detector 503 and a first flue gas flow detector 504 are installed above the demisting section 502 to obtain the flue gas temperature T respectively. G For 50℃ and dry flue gas flow rate F G 175794 Nm 3 / h;

[0094] Secondly, the obtained atmospheric temperature T e and atmospheric relative humidity air temperature T a and relative humidity Substituting into formula (1), the atmospheric moisture content ω is calculated. e =7.501 g / kg dry air, and air moisture content ω a =8.431 g / kg dry air, the obtained flue gas temperature T G and Substituting into formula (1) and the Goff-Grech formula, we obtain the moisture content ω of the flue gas. G = 81.216 g / kg dry flue gas;

[0095] Then, the obtained dry air flow rate F a and dry flue gas flow rate F G The calculated air humidity ω a and the moisture content of flue gas ω G Substituting into formula (2), we obtain the moisture content ω of the mixed gas. mix = 58.252 g / kg dry flue gas;

[0096] Then, passing the atmospheric environmental state point (T) e ω e Draw a tangent line to the water vapor saturation curve, with the point of tangency at (T). tan ω tan );

[0097] Next, the tangent line and the line ω=ω are calculated using formula (3). mix The intersection temperature T mix =56.4℃;

[0098] Next, the critical heating temperature T of the hot air required for the elimination of white smoke in the flue gas is calculated using formula (4). HCT =67.9℃;

[0099] Finally, the control system adjusts the steam consumption of the heater 300 in real time through the flow regulating valve 303 to maintain the hot air temperature T. ah The calculated critical heating temperature T of hot air HCT equal.

[0100] At this time, the consumption of low-temperature hot water is 100t / h, and the consumption of steam is 0.46t / h. The steam consumption is 2.64t / h lower than the design value. The steam consumption is significantly reduced, and the energy consumption is reduced accordingly.

[0101] Example 2

[0102] like Figure 4As shown, the white smoke elimination method and device in this embodiment are the same as those in Embodiment 1. After running for a period of time, it was found that a small amount of white smoke appeared in the flue gas discharged from the top outlet of the chimney section 505. After diagnosing the device, it was found that the demisting efficiency of the demister 501 installed in the desulfurization chimney integrated tower 500 was reduced, and the flue gas after desulfurization contained a large number of mist droplets. Taking into account the influence factor of the mist droplet content A, and after sampling and testing, the mist droplet content was as high as 1.0 g / kg dry flue gas. The mist droplet content A was used to modify formula (4) to obtain formula (5). After the modification, the white smoke in the flue gas discharged from the chimney section 505 disappeared, making the white smoke elimination method of the present invention more consistent with the actual situation and improving the accuracy and reliability of the present invention.

[0103] Example 3

[0104] like Figure 5 As shown, the whitening elimination device consists of a wet desulfurization tower 100, a chimney 200, a heater 300, a fan 400, and a condenser 600. The wet desulfurization tower 100 is equipped with a demister 101. A second atmospheric temperature and humidity detector 201 is installed below the exhaust outlet of the chimney 200 to monitor atmospheric temperature and relative humidity in real time. A hot air temperature detector 301 is installed on the flue gas outlet pipeline of the heater 300. An air monitoring unit 401 is installed at the inlet of the fan 400, and an air flow detector 402 is installed at the outlet of the fan 400. A second flue gas temperature detector 602 and a second flue gas flow detector 603 are installed on the flue gas exhaust pipeline of the condenser 600.

[0105] A wet desulfurization flue gas system uses a hot air mixing heating method to eliminate white smoke. The relevant design parameters are as follows: First, a 600 condenser is used to condense and cool the saturated wet flue gas from the wet desulfurization process. The volume of the flue gas after condensation and cooling is 150,000 Nm³. 3 The design requires eliminating white smoke under the following conditions: a wet basis (h), flue gas temperature of 45℃, ambient temperature of 5℃, and relative humidity of 60%. The fan air volume is 50,000 Nm³ / h. 3 / h (wet basis), the design value of the hot air temperature after heating is 173.7℃, the heat medium 302 of heat exchanger 300 adopts 1.0MPa, 250℃ steam, and it requires 4.9t / h of steam to meet the design requirements.

[0106] The automatic control process for the amount of heat transfer medium 302 used in the wet desulfurization flue gas whitening method and apparatus of the present invention is as follows:

[0107] First, the atmospheric temperature T is obtained in real time through the second large temperature and humidity detector 201 installed below the exhaust outlet of chimney 200. e 25℃, atmospheric relative humidity The air temperature T is 65% and is obtained in real time through the air monitoring unit 401 installed at the inlet of the fan 400.a 27℃, relative humidity The dry air flow rate F is 67%, and the dry air flow rate F is obtained in real time through the air flow detector 402 installed at the outlet of the fan 400. a 48832 Nm 3 / h, the temperature T of the flue gas after condensation and cooling is obtained by the second flue gas temperature detector 602 and the second flue gas flow detector 603 installed on the flue gas exhaust pipeline of the condenser 600. G For 45℃ and dry flue gas flow rate F G 135911 Nm 3 / h;

[0108] Secondly, the obtained atmospheric temperature T e and atmospheric relative humidity air temperature T a and relative humidity Substituting into formula (1), the atmospheric moisture content ω is calculated. e =12.893 g / kg dry air, and air moisture content ω a =15.009 g / kg dry air, the obtained flue gas temperature T G and Substituting into formula (1) and the Goff-Grech formula, we obtain the moisture content ω of the flue gas. G = 64.963 g / kg dry flue gas;

[0109] Then, the obtained dry air flow rate F a and dry flue gas flow rate F G The calculated air humidity ω a and the moisture content of flue gas (ω) G Substituting into formula (2), we obtain the moisture content ω of the mixed gas. mix = 51.759 g / kg dry flue gas;

[0110] Then, passing the atmospheric environmental state point (T) e ω e Draw a tangent line to the water vapor saturation curve, with the point of tangency at (T). tan ω tan );

[0111] Next, the tangent line and the line ω=ω are calculated using formula (3). mix The intersection temperature T mix =47.3℃;

[0112] Next, the critical heating temperature T of the hot air required for the elimination of white smoke in the flue gas is calculated using formula (4). HCT =54.2℃.

[0113] Finally, the control system adjusts the steam consumption of the heater 300 in real time through the flow regulating valve 303 to maintain the hot air temperature T. ah The calculated critical heating temperature of hot air (T) HCT )equal.

[0114] At this point, the steam consumption is 0.8 t / h, which is 4.1 t / h lower than the design value. The steam consumption is significantly reduced, and the energy consumption is reduced accordingly.

[0115] Example 4

[0116] The whitening device and whitening method in this embodiment are the same as those in embodiment 3. After one year of operation, it was found that a small amount of white smoke appeared in the flue gas discharged from the top exhaust port of chimney 200. By comprehensively considering the influence factor of droplet content A, the flue gas after condenser 600 was sampled and analyzed, and the droplet content A was defined as 0.2 g / kg dry flue gas. By comprehensively considering the influence factor of temperature deviation σ, the temperature deviation σ was defined as 2℃. The formula (5) was modified by using droplet content A and temperature deviation σ, and modified into formula (6). At this time, the exhaust flue gas no longer showed white smoke.

[0117] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A method for eliminating whitening in wet desulfurization flue gas, characterized in that, Smoke whitening is achieved by mixing hot air with flue gas, including the following steps: A. Collect the atmospheric temperature at the corresponding height of the exhaust outlet of the wet desulfurization chimney. T e and atmospheric relative humidity φ e Data; collecting air temperature at the fan inlet. T a and relative humidity of air φ a data; B. Based on the atmospheric temperature T e and atmospheric relative humidity φ e The air temperature T a and relative humidity of air φ a Calculate atmospheric moisture content and air humidity ; C. Collect the flue gas temperature of the saturated wet flue gas after wet desulfurization. T G And calculate the moisture content of the flue gas. ; D. Collect the dry air flow rate at the outlet of the fan. F a and dry flue gas flow rate after wet desulfurization F G Combined with the aforementioned air humidity content and the moisture content of the flue gas Calculate the moisture content of the mixture of flue gas and air. ; E. Utilizing the moisture content of the mixed gas Calculate the temperature at the intersection point T mix According to the temperature at the intersection point T mix The moisture content of the mixed gas The flue gas temperature T G The moisture content of the flue gas and the atmospheric moisture content Calculate the critical heating temperature of hot air required for flue gas whitening T HCT ; F. Adjust the heat transfer medium usage of the heater in real time until the hot air temperature reaches the target level. T ah Critical heating temperature of the hot air T HCT When the values ​​are equal, the flue gas is discharged. The atmospheric humidity in step B air humidity and the moisture content of the flue gas in step C The calculation is performed in the following way: ； in, P s The partial pressure of water vapor in saturated air is the pressure of water vapor when the relative humidity of the gas is 100%, and the unit is Pa; the unit of moisture content is g / kg dry air. The moisture content of the mixed gas in step D The calculation is performed in the following way: ； The intersection temperature in step E T mix The calculation is performed in the following way: ； The critical heating temperature of hot air in step E T HCT The calculation is performed in the following way: ； When the flue gas contains droplets and is in a supersaturated state, the critical heating temperature of the hot air is determined by the droplet content A. T HCT The calculation formula (4) is modified as follows: ； Wherein, A is the droplet content in the flue gas after wet desulfurization, in g / kg dry flue gas; the droplet content A is comprehensively defined by the demister structure factor, flue gas velocity factor, demister pressure drop factor, and demister flushing factor.

2. The wet desulfurization flue gas whitening method according to claim 1, characterized in that, When the temperature measuring point of the hot air is at a certain distance from the mixing point of the flue gas and hot air, and / or when the mixing point of the flue gas and hot air is at a certain distance from the chimney outlet, the temperature deviation is used to measure the temperature. The critical heating temperature of the hot air T HCT The calculation formula (5) is modified as follows: ； in, This refers to the temperature deviation, specifically defined as -5℃ to 5℃.

3. The wet desulfurization flue gas whitening method according to claim 2, characterized in that, When there is a certain distance between the mixing point of flue gas and hot air and the chimney outlet, the temperature deviation... The factors are comprehensively defined by heat transfer area factor, chimney structure factor, temperature difference factor between flue gas and atmosphere, flue gas velocity factor, and environmental wind force level factor.

4. The wet desulfurization flue gas whitening method according to claim 1, characterized in that, When the hot air reaches its critical heating temperature T HCT ≤Air temperature at the inlet of the fan T a When this happens, the heat transfer medium consumption of the heater is adjusted to 0 t / h.

5. The wet desulfurization flue gas whitening method according to claim 1, characterized in that, The flue gas whitening method involves pressurizing the air using the fan, heating the pressurized air with the heater, and then mixing it with the flue gas after wet desulfurization. The heated flue gas is then discharged into the atmosphere through a chimney.

6. The wet desulfurization flue gas whitening method according to claim 5, characterized in that, The flue gas whitening method is applicable to mixed heating of hot air and saturated wet flue gas after wet desulfurization, or to mixed heating of hot air and cooled and condensed wet desulfurization flue gas.

7. A wet desulfurization flue gas whitening device, characterized in that, The method described in any one of claims 1 to 6, wherein the wet desulfurization tower and the chimney are integrated or separate, and flue gas whitening is achieved by mixing hot air with flue gas, includes: The atmospheric and air data acquisition unit is used to collect the atmospheric temperature at the corresponding height of the exhaust outlet of the wet desulfurization chimney. T e and atmospheric relative humidity φ e Data; collecting air temperature at the fan inlet. T a and relative humidity of air φ a data; Atmospheric and air humidity calculation unit, which is used to calculate the atmospheric temperature T e and atmospheric relative humidity The air temperature T a and relative humidity of air Calculate atmospheric moisture content and air humidity ; The flue gas temperature acquisition and moisture content calculation unit is used to collect the flue gas temperature of the saturated wet flue gas after wet desulfurization. T G And calculate the moisture content of the flue gas. ; The flow rate acquisition and mixed gas moisture content calculation unit is used to acquire the dry air flow rate at the fan outlet. F a and dry flue gas flow rate after wet desulfurization F G Combined with the aforementioned air humidity content and the moisture content of the flue gas Calculate the moisture content of the mixture of flue gas and air. ; The hot air critical heating temperature calculation unit utilizes the moisture content of the mixed gas. Calculate the temperature at the intersection point T mix According to the temperature at the intersection point T mix The moisture content of the mixed gas The flue gas temperature T G The moisture content of the flue gas and the atmospheric moisture content Calculate the critical heating temperature of hot air required for flue gas whitening T HCT ; The flue gas exhaust control unit is used to adjust the amount of heat medium used in the heater in real time, up to the temperature of the hot air. T ah Critical heating temperature of the hot air T HCT When the values ​​are equal, the flue gas is discharged.

8. The wet desulfurization flue gas whitening device according to claim 7, characterized in that, When a condenser or condensation section is provided between the wet desulfurization tower and the chimney, the flue gas temperature T G and dry flue gas flow rate F G This is the data for the condensed flue gas.

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