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

Abstract

The application discloses a white smoke eliminating method and device for wet desulfurization flue gas, and one of the methods comprises the following steps: A, collecting the atmospheric temperature T e and the atmospheric relative humidity data at the corresponding height of the wet desulfurization chimney exhaust outlet; B, collecting the flue gas temperature T0 after wet desulfurization or after wet desulfurization and condensation in real time, and calculating the white smoke eliminating critical heating temperature T e by combining the atmospheric temperature T HCT and the atmospheric relative humidity; C, adjusting the heat medium amount of the heat exchanger in the white smoke eliminating device in real time until the exhaust flue gas temperature T OUT is equal to the white smoke eliminating critical heating temperature T HCT , and then performing flue gas exhaust. The application can realize the automatic control of the heat medium (or refrigerant) amount of the white smoke eliminating device, so that the white smoke is eliminated, and unnecessary energy consumption of the device caused by the lack of theoretical basis for adjusting the exhaust flue gas temperature by the 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 smoke from flue gas: direct flue gas heating, direct flue gas condensation, and pre-condensation followed by heating. For "direct heating for white smoke elimination" and "pre-condensation followed by heating for white smoke elimination" devices, the critical heating temperature for eliminating white smoke from wet desulfurization flue gas is closely related to environmental conditions. The lower the ambient temperature and the higher the ambient humidity, the higher the heating temperature required to achieve white smoke elimination from wet desulfurization flue gas, and vice versa. In actual operation, wet desulfurization white smoke elimination devices generally operate at the design temperature. Although the flue gas emission temperature can be appropriately reduced under favorable weather conditions (high ambient temperature, low humidity), operators often lack theoretical basis for adjusting the exhaust gas temperature, leading to blind adjustments. This results in white smoke appearing when the exhaust gas temperature is too low, and high energy consumption when the exhaust gas temperature is too high. For "direct condensation for white smoke elimination" devices, white smoke appears when the exhaust gas condensation temperature is too high, and high energy consumption occurs when the exhaust gas condensation temperature is too low.

[0004] Therefore, there is an urgent need for a wet desulfurization flue gas whitening method and device that can calculate the critical flue gas temperature of white smoke in real time according to different atmospheric ambient temperature and humidity conditions, and adjust the amount of heat medium (or cold medium) in real time to control the temperature of the exhaust flue gas, so as to realize the automatic control of the amount of heat medium (or cold medium) used in the white smoke elimination device, thereby eliminating white smoke while avoiding unnecessary energy consumption of the device due to the lack of theoretical basis for operators to adjust the exhaust flue gas temperature.

[0005] 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

[0006] The purpose of this invention is to provide a method and apparatus for eliminating white smoke in wet desulfurization flue gas. It can calculate the critical flue gas temperature of white smoke in real time according to different atmospheric ambient temperature and humidity conditions, and adjust the amount of heat medium (or cold medium) in real time to control the temperature of the exhaust flue gas, so as to realize the automatic control of the amount of heat medium (or cold medium) used in the white smoke elimination device. In this way, while eliminating white smoke, unnecessary energy consumption of the device caused by the lack of theoretical basis for operators to adjust the exhaust flue gas temperature is avoided.

[0007] To achieve the above objectives, according to a first aspect of the present invention, the present invention provides a method for eliminating whitening in wet desulfurization flue gas, comprising the following steps: A. Collecting the atmospheric temperature T at a corresponding height at the external discharge outlet of the wet desulfurization chimney. e and atmospheric relative humidity B. Real-time acquisition of flue gas temperature T0 after wet desulfurization or after wet desulfurization and condensation, combined with atmospheric temperature T e and atmospheric relative humidity The critical heating temperature T for whitening was calculated. HCT C. In the whitening elimination device that uses direct heating or condensation followed by heating, adjust the heat exchanger's heat transfer medium usage in real time until the exhaust gas temperature T is reached. OUT With the critical heating temperature T for whitening HCT When the values ​​are equal, the flue gas is discharged.

[0008] Furthermore, in the above technical solution, the critical heating temperature T for whitening in step B is... HCT The calculation is performed in the following way:

[0009]

[0010]

[0011]

[0012]

[0013] Where Ps is the partial pressure of saturated water vapor, that is, the partial pressure of water vapor when the relative humidity of the gas is 100%, and the unit is Pa; the tangent point (T) tan ω tan ) is the state point passing through the environment (T) e ω e The point of tangency of the tangent line drawn to the saturated humid air curve is T. tan The tangent temperature is expressed in Kelvin (K). The relative humidity is expressed as a percentage. The flue gas after wet desulfurization is saturated wet flue gas. ω tan =f(T) tan ), where is the saturated moisture content at the tangent point.

[0014] Furthermore, in the above technical solution, when the flue gas contains droplets in a supersaturated state, the critical heating temperature T for whitening is determined by the droplet content A. HCT The calculation formula (1) is modified as follows:

[0015]

[0016] Where A is the droplet content in the flue gas after wet desulfurization, in g / kg dry flue gas.

[0017] 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.

[0018] Furthermore, in the above technical solution, when there is a certain distance between the temperature measuring point of the heated flue gas and the chimney outlet, the critical heating temperature T for whitening can be determined by the temperature deviation σ. HCT The calculation formula (5) is modified as follows:

[0019]

[0020] Where σ is the temperature deviation, specifically defined as -5℃ to 5℃.

[0021] Furthermore, in the above technical solution, the temperature deviation σ can be 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.

[0022] To achieve the above objectives, according to a second aspect of the present invention, the present invention provides a method for eliminating whitening in wet desulfurization flue gas, comprising the following steps: A. Collecting the atmospheric temperature T at a corresponding height at the external discharge outlet of the wet desulfurization chimney. e and atmospheric relative humidity Data; B, combined with atmospheric temperature T e and atmospheric relative humidity The tangent temperature T for flue gas whitening was calculated. tan C. The refrigerant flow rate of the heat exchanger in the direct condensation whitening device is adjusted in real time until the exhaust gas temperature T is reached. OUT With the critical condensation temperature T of flue gas tan When the values ​​are equal, the flue gas is discharged.

[0023] Furthermore, in the above technical solution, the critical condensation temperature T of the flue gas in step B... tan The calculation is performed in the following way:

[0024]

[0025]

[0026]

[0027] Where Ps is the partial pressure of saturated water vapor, that is, the partial pressure of water vapor when the relative humidity of the gas is 100%, and the unit is Pa; the tangent point (T) tan ω tan ) is the state point passing through the environment (T) e ω e The point of tangency of the tangent line drawn to the saturated humid air curve is T. tan The tangent temperature is expressed in Kelvin (K). The relative humidity is expressed as a percentage. The flue gas after wet desulfurization is saturated wet flue gas. ω tan =f(T) tan ), where is the saturated moisture content at the tangent point.

[0028] Furthermore, in the above technical solution, when the temperature measuring point after flue gas condensation is at a certain distance from the chimney outlet, the critical condensation temperature T of the flue gas is determined by the temperature deviation β. tan The calculation formula (2) is modified as follows:

[0029]

[0030] Wherein, β is the temperature deviation, specifically defined as -5℃ to 5℃.

[0031] Furthermore, in the above technical solution, the temperature deviation β can be 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.

[0032] To achieve the above objectives, according to a third aspect of the present invention, a wet desulfurization flue gas whitening device is provided, which employs a direct heating whitening method and separates the wet desulfurization tower from the chimney. The device includes an atmospheric monitoring unit installed at a corresponding height outside the exhaust outlet of the wet desulfurization chimney, for collecting the atmospheric temperature T at said height. e and atmospheric relative humidity The data includes: a desulfurization flue gas temperature detection unit, located at the rear end of the demister in the wet desulfurization tower, used to collect the real-time flue gas temperature T0 after wet desulfurization; and a whitening critical heating temperature calculation unit, which calculates the flue gas temperature T0 and the atmospheric temperature T... e and atmospheric relative humidity The critical heating temperature T for whitening was calculated. HCT The exhaust control unit is used to adjust the heat transfer medium flow rate of the heat exchanger in real time during direct heating whitening methods, up to the exhaust gas temperature T. OUT The critical heating temperature T for whitening HCT When the values ​​are equal, the flue gas is discharged.

[0033] To achieve the above objectives, according to a fourth aspect of the present invention, a wet desulfurization flue gas whitening device is provided, which employs a direct condensation whitening method and separates the wet desulfurization tower and the chimney. The device includes an atmospheric monitoring unit installed at a corresponding height outside the exhaust outlet of the wet desulfurization chimney, for collecting the atmospheric temperature T at said height. e and atmospheric relative humidity Data; the critical condensation temperature calculation unit for whitening, which uses atmospheric temperature T e and atmospheric relative humidity The tangent temperature T for flue gas whitening was calculated. tan The critical condensation temperature of the flue gas is used as the external exhaust control unit, which is used to adjust the refrigerant dosage of the heat exchanger in real time in the direct condensation whitening method until the external exhaust gas temperature T is reached. OUT With the critical condensation temperature T of flue gas tan When the values ​​are equal, the flue gas is discharged.

[0034] To achieve the above objectives, according to a fifth aspect of the present invention, a wet desulfurization flue gas whitening device is provided, which employs a whitening method of condensation followed by heating, and the wet desulfurization tower and chimney are integrated into one unit. The device includes: an atmospheric monitoring unit, which is installed at a corresponding height at the external exhaust outlet of the integrated desulfurization tower and chimney, for collecting the atmospheric temperature T at said height. e and atmospheric relative humidity The data includes: a desulfurization condensate flue gas temperature detection unit, located at the rear end of the condensation and demisting section, used to collect the real-time flue gas temperature T0 after wet desulfurization and condensation; and a whitening critical heating temperature calculation unit, which calculates the flue gas temperature T0 and atmospheric temperature T... e and atmospheric relative humidity The critical heating temperature T for whitening was calculated. HCT The exhaust control unit is used to adjust the amount of heat transfer medium used in the heating section in real time during the whitening method of condensation followed by heating, until the exhaust gas temperature T is reached. OUT With the critical heating temperature T for whitening HCT When the values ​​are equal, the flue gas is discharged.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) Based on external weather conditions such as temperature and humidity, as well as the flue gas temperature after wet desulfurization and condensation, this invention automatically calculates the critical heating (or condensation) temperature required to eliminate white smoke in the flue gas. By adjusting the amount of heat medium (or cold medium) in the device, the temperature of the exhaust flue gas is made equal to the critical heating (or condensation) temperature. This effectively achieves automatic control of the amount of heat medium (or cold medium) in the device, avoiding blind adjustments by operators that could lead to white smoke due to excessively low exhaust flue gas heating temperature, excessively high device energy consumption due to excessively high exhaust flue gas heating temperature, excessively high exhaust flue gas condensation temperature leading to white smoke, and excessively low exhaust flue gas condensation temperature leading to excessive device energy consumption.

[0037] 2) 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 in calculating the critical heating temperature for whitening. This invention uses the droplet content A to correct the calculation formula for the critical heating temperature for whitening, so that the calculation result is more accurate and the whitening method of this invention is more consistent with the actual situation, thus improving the accuracy and reliability of whitening.

[0038] 3) Due to the large measuring range of the measuring instruments themselves, and imperfections in their mechanical performance or electrical structure, there are often certain measurement errors. Improper instrument installation or significant interference in the operating environment can also cause errors, and may even lead to instrument malfunction or failure. Furthermore, there is a certain distance between the temperature measuring point after flue gas heating or condensation and the chimney outlet; the flue gas temperature decreases after passing through this distance, resulting in a certain 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 a temperature deviation σ (or β) to correct the calculation formula for the critical heating (or condensation) temperature for whitening. The value of the temperature deviation σ (or β) is determined after adjustments based on actual field conditions, thereby making the calculation formula for the critical heating (or condensation) temperature for whitening more accurate. This makes the whitening smoke elimination method of this invention more consistent with actual conditions, improving the accuracy and reliability of the invention.

[0039] 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

[0040] Figure 1 This is a schematic diagram illustrating the principle of the wet desulfurization flue gas whitening method of the present invention.

[0041] Figure 2 This is a schematic flowchart of one embodiment of the wet desulfurization flue gas whitening method of the present invention.

[0042] Figure 3This is a schematic flowchart of another embodiment of the wet desulfurization flue gas whitening method of the present invention.

[0043] Figure 4 This is a schematic diagram of one embodiment of the wet desulfurization flue gas whitening device of the present invention.

[0044] Figure 5 This is a schematic diagram of another embodiment of the wet desulfurization flue gas whitening device of the present invention.

[0045] Explanation of key figure labels:

[0046] 100-Wet desulfurization tower, 101-Demister, 102-Desulfurization flue gas temperature detection unit; 200-Chimney, 201-First atmospheric monitoring unit; 300-Heat exchanger, 301-Heating medium or cooling medium, 302-First exhaust flue gas temperature detector; 400-Exhaust fan;

[0047] 500 - Integrated desulfurization chimney tower, 501 - Desulfurization section, 502 - Condensation and cooling section, 503 - Demisting section, 504 - Heating section, 505 - Chimney section, 506 - Second atmospheric monitoring unit, 507 - Second exhaust gas temperature detector, 508 - Desulfurization condensate flue gas temperature detection unit, 509 - Heat medium inlet, 510 - Heat medium outlet. Detailed Implementation

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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".

[0053] The inventors discovered through research that the critical heating temperature for eliminating white smoke in wet desulfurization flue gas is closely related to environmental conditions for both the "direct heating to eliminate white smoke" and "condensation followed by heating to eliminate white smoke" methods. Lower ambient temperatures and higher humidity require higher heating temperatures to achieve white smoke elimination in wet desulfurization flue gas, and vice versa. In actual operation, wet desulfurization generally operates at the design temperature for white smoke elimination. However, under favorable weather conditions (high ambient temperature and low humidity), the flue gas emission temperature can be appropriately reduced; that is, it is not always necessary to operate at the design temperature. This effectively saves energy while avoiding the "white smoke" phenomenon.

[0054] like Figure 2As shown, based on the above research, this invention provides a wet desulfurization flue gas whitening method (i.e., direct heating method or condensation followed by heating method), comprising the following steps:

[0055] 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 The data refers to the location of the chimney exhaust outlet, which is near or at the same height as the chimney exhaust outlet. The chimney heights for wet desulfurization flue gas vents vary across different industries, generally exceeding 50m, with some cement chimneys even surpassing 200m. Temperature and humidity at high altitudes differ from those at ground level. For every 100m increase in altitude, the temperature decreases by 0.5–1.5℃, and humidity also varies. This invention adds an atmospheric monitoring unit (i.e., [missing information]) near or at the same height as the wet desulfurization chimney exhaust outlet. Figure 4 The first atmospheric monitoring unit 201 and Figure 5 The second atmospheric monitoring unit (in the system) detects the atmospheric temperature T at the location where the wet desulfurization flue gas is emitted. e and atmospheric relative humidity Therefore, compared with ground-based testing, the critical heating (or condensation) temperature calculated by this invention will be more accurate and have less error.

[0056] Step S102: Real-time acquisition of flue gas temperature T0 after wet desulfurization or after wet desulfurization and condensation, combined with the atmospheric temperature T in step S101. e and atmospheric relative humidity The critical heating temperature T for whitening was calculated. HCT .

[0057] Specifically, when using direct heating for whitening, and using Figure 4 When using the whitening device shown, the flue gas temperature T0 after wet desulfurization is collected in real time by the desulfurization flue gas temperature detection unit 102, and then the critical heating temperature T for whitening is determined by the following formula. HCT Calculation:

[0058]

[0059] Furthermore,

[0060]

[0061]

[0062]

[0063] Where Ps is the partial pressure of saturated water vapor, that is, the partial pressure of water vapor when the relative humidity of the gas is 100%, and the unit is Pa; the tangent point (T)tan ω tan ) is the state point passing through the environment (T) e ω e The point of tangency of the tangent line drawn to the saturated humid air curve is T. tan The tangent temperature is expressed in Kelvin (K). The relative humidity is expressed as a percentage. The flue gas after wet desulfurization is saturated wet flue gas. ω tan =f(T) tan ), where is the saturated moisture content at the tangent point.

[0064] Furthermore, Ps in formula (3) can be calculated as follows:

[0065]

[0066] In the formula, C1 = -7.90298, C2 = 5.028081, C3 = 1.3816 × 10 -7 C4 = 8.1328 × 10 -3 C5 = lg1013.246, a = 373.16; (i.e., the Goff-Gratch formula).

[0067] Furthermore, in formula (4) It can be calculated in the following way:

[0068]

[0069] Further research by the inventors revealed that existing demisters used in wet desulfurization processes have high removal efficiency for larger droplets (≥30μm), but lower efficiency for smaller droplets. Therefore, droplets are inevitably present in the flue gas after wet desulfurization. When calculating the critical heating temperature for eliminating white smoke, if the influence of droplets is not considered, and the flue gas after wet desulfurization is treated as saturated wet flue gas with its state point considered to be on the saturated humid air line, the critical heating temperature for eliminating white smoke T... HCT The calculation results will have some deviation. Since the flue gas contains droplets, the flue gas is in a supersaturated state at this time, and the flue gas state point should be located above the saturated humid air line. Therefore, the critical heating temperature T for whitening can only be calculated by the aforementioned formula (1). 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 for whitening. HCT The calculation formula was modified to make the calculation results more accurate.

[0070] 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.

[0071] Considering the four influencing factors highly correlated with droplet content A, a specific value for droplet content A can be defined based on the actual on-site conditions. That is, when the flue gas contains droplets in a supersaturated state, the defined droplet content A is used to determine the critical heating temperature T for whitening elimination. HCT The calculation formula (1) is modified as follows:

[0072]

[0073] Where A is the droplet content in the flue gas after wet desulfurization, in g / kg dry flue gas.

[0074] Further research by the inventors revealed that measuring instruments with large ranges, imperfect mechanical performance, or flawed electrical structures often exhibit errors. Improper instrument installation or significant interference in the operating environment can also cause errors, even leading to instrument malfunction or failure. Furthermore, the temperature measuring point after flue gas heating is some distance from the chimney outlet; 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 for whitening. HCT The calculation formula was further revised, and the value of the temperature deviation σ was determined after debugging based on the actual site conditions, so as to make the calculation formula for the critical heating temperature of whitening more accurate.

[0075] Temperature deviation σ is related to many factors. The inventors have found that a comprehensive definition of temperature deviation σ using factors such as 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 is more scientific and effective. Specifically, 1) Regarding the heat transfer area factor, the exhaust gas temperature (T...) out The heat transfer area between the measuring point and the chimney outlet, and between the flue and / or the chimney and the atmosphere, and its relationship with the shape and size of the flue and / or chimney, as well as the exhaust gas temperature (T). out The temperature deviation is related to factors such as the distance between the measuring point and the chimney exhaust outlet; the larger the heat transfer area, the greater the temperature deviation. 2) Regarding chimney structural factors, the exhaust gas temperature (T...) out 1) The material, wall thickness, and material and / or thickness of the duct and / or chimney lining and / or insulation layer (thermal insulation layer) between the measuring point and the chimney outlet. A higher thermal conductivity of the duct and / or chimney material, and the material of the lining and / or insulation layer (thermal insulation layer) requires a larger temperature deviation; a larger wall thickness and a thicker lining and / or insulation layer (thermal insulation layer) require a smaller temperature deviation. 2) Regarding the temperature difference factor between flue gas and the atmosphere, a larger temperature difference (in winter) requires a larger temperature deviation; a smaller temperature difference (in summer) requires a smaller temperature deviation. 3) Regarding the wind force factor in the ambient air, stronger winds are more conducive to heat dissipation from the flue gas, resulting in a larger temperature deviation. 4) Regarding the flue gas velocity factor, higher flue gas velocity is more conducive to heat dissipation from the flue gas, resulting in a larger temperature deviation.

[0076] 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 the temperature measuring point after flue gas heating is a certain distance from the chimney emission outlet, the temperature deviation σ can be used to determine the critical heating temperature T for whitening elimination. HCT The calculation formula (5) is modified as follows:

[0077]

[0078] Where σ is the temperature deviation, which can be defined as -5℃ to 5℃ depending on the site conditions.

[0079] In step S102, when the whitening is removed by condensation followed by heating, and using... Figure 5 When the whitening device is shown, the temperature T0 of the flue gas after wet desulfurization and condensation is collected in real time by the desulfurization condensation flue gas temperature detection unit 508, and then the critical heating temperature T for whitening is determined by the aforementioned formulas (1) to (4). HCT The calculation, namely the T value for whitening using the method of condensation followed by heating. HCT Calculate T compared to the aforementioned direct heating method HCTThe calculation method is exactly the same and will not be repeated here. Since the process of condensation followed by heating requires the flue gas to first exchange heat with a refrigerant to cool down, and then exchange heat with a heating medium to heat the flue gas, this invention uses... Figure 5 The desulfurization chimney integrated tower 500 shown performs flue gas whitening. From bottom to top, the desulfurization chimney integrated tower 500 includes a desulfurization section 501, a condensation and cooling section 502, a demisting section 503, a heating section 504, and a chimney section 505. A desulfurization condensate flue gas temperature detection unit 508 is located between the demisting section 503 and the heating section 504 to collect the flue gas temperature T0 after wet desulfurization and condensation. In the heating section 504, the heat transfer medium enters through the heat transfer medium inlet 509 and flows out through the heat transfer medium outlet 510, heating the flue gas.

[0080] When using the pre-condensation followed by heating method for de-bleaching, the critical heating temperature T for de-bleaching can also be determined using the aforementioned droplet content A and / or temperature deviation σ. HCT The calculation formula is modified, and the specific modification method is the same as the aforementioned formula (5) and formula (6), which will not be repeated here.

[0081] Step S103: In the whitening device using direct heating or condensation followed by heating, adjust the heat exchanger's heat transfer medium usage in real time until the exhaust gas temperature T... OUT Compared with the critical heating temperature T for whitening in step S102 HCT When the values ​​are equal, the flue gas is discharged.

[0082] Specifically, when using direct heating to remove blemishes, one can... Figure 4 The whitening process is carried out in the illustrated desulfurization device, which includes a wet desulfurization tower 100, a heat exchanger 300, an induced draft fan 400, and a chimney 200 connected in sequence. The chimney 200 and the wet desulfurization tower 100 are separate units. A demister 101 is installed in the wet desulfurization tower 100, and a desulfurization flue gas temperature detection unit 102 is located at the rear end of the demister 101. The whitening critical heating temperature T is used to determine the temperature. HCT The calculation results are used to heat the flue gas through the heat medium 301 in the heat exchanger 300 until it is heated to the same temperature as T. HCT After the calculation results are equal, the flue gas is discharged through the induced draft fan 400. During this period, the temperature of the discharged flue gas is detected by the first discharged flue gas temperature detector 302.

[0083] When using the method of first condensing and then heating to remove whitening, it is possible to... Figure 5 The whitening process is carried out in the whitening device shown, based on the critical whitening heating temperature T. HCT The calculation results are used to heat the flue gas through the heat medium in heating section 504 until it is heated to the same temperature as T. HCT After the calculation results are equal, the flue gas is discharged from the chimney section 505. During this period, the temperature of the discharged flue gas is detected by the second discharged flue gas temperature detector 507.

[0084] like Figure 3 As shown, this invention provides another method for eliminating whitening in wet desulfurization flue gas (i.e., direct condensation method), comprising the following steps:

[0085] Step S201: Collect the atmospheric temperature T at the corresponding height of the exhaust outlet of the wet desulfurization chimney. e and atmospheric relative humidity The data. This step is the same as step S101 above, and will not be repeated here.

[0086] Step S202, combined with atmospheric temperature T e and atmospheric relative humidity The tangent temperature T for flue gas whitening was calculated. tan , which serves as the critical condensation temperature of the flue gas.

[0087] Specifically, the critical condensation temperature T of the flue gas tan The calculation is performed in the following manner (i.e., using formulas (2) to (4) in the aforementioned step S102):

[0088]

[0089]

[0090]

[0091] Where Ps is the partial pressure of saturated water vapor, that is, the partial pressure of water vapor when the relative humidity of the gas is 100%, and the unit is Pa; the tangent point (T) tan ω tan ) is the state point passing through the environment (T) e ω e The point of tangency of the tangent line drawn to the saturated humid air curve is T. tan The tangent temperature is expressed in Kelvin (K). The relative humidity is expressed as a percentage. The flue gas after wet desulfurization is saturated wet flue gas. ω tan =f(T) tan ), where is the saturated moisture content at the tangent point.

[0092] Furthermore, the critical condensation temperature T of the flue gas can be determined by the temperature deviation β. tan The calculation is corrected, that is, when the temperature measuring point after flue gas condensation is a certain distance from the chimney outlet, the critical condensation temperature T of the flue gas is corrected by the temperature deviation β. tan The calculation formula (2) is modified as follows:

[0093]

[0094] Here, β represents the temperature deviation, specifically defined as -5℃ to 5℃. The temperature deviation β can also be comprehensively defined by factors such as 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.

[0095] Step S203: In the direct condensation whitening device, adjust the refrigerant usage of the heat exchanger in real time until the exhaust gas temperature T OUT With respect to the critical condensation temperature T of the flue gas tan When the values ​​are equal, the flue gas is discharged.

[0096] The whitening method can be achieved by direct condensation, or by using... Figure 4 The whitening device shown is used in this step, where refrigerant is introduced into the heat exchanger of the whitening device.

[0097] Example 1

[0098] like Figure 4 As shown, the whitening device consists of a wet desulfurization tower 100, a chimney 200, a heat exchanger 300, and an induced draft fan 400. The wet desulfurization tower 100 is equipped with a demister 101, and a desulfurization flue gas temperature detection unit 102 is installed above the demister 101. A first atmospheric monitoring unit 201 is installed below the exhaust outlet of the chimney 200 to detect the atmospheric temperature and relative humidity in real time. A first exhaust flue gas temperature detector 302 is installed on the flue gas outlet pipeline of the heat exchanger 300.

[0099] A wet desulfurization process uses direct condensation to eliminate white smoke in the flue gas. The volume of the desulfurized flue gas is 100,000 Nm³. 3 The design requires the elimination of white smoke under ambient conditions of 15℃ and 50% relative humidity. The design value for flue gas exhaust temperature is 22.9℃. Heat exchanger 300 adopts a series connection of circulating water cooler and chilled water cooler. Refrigerant 301 uses circulating water and 7℃ chilled water prepared by lithium bromide refrigerator. To meet the design requirements, 180t / h of circulating water and 375t / h of chilled water are required.

[0100] This wet desulfurization and white smoke elimination device employs the wet desulfurization flue gas white smoke elimination method of this invention. Based on external weather conditions such as temperature and humidity, it automatically calculates the critical condensation temperature required for white smoke elimination. By adjusting the refrigerant dosage, the exhaust gas temperature is made equal to the critical condensation temperature, effectively achieving automatic control of the refrigerant dosage. For example, firstly, the first atmospheric monitoring unit 201 located below the exhaust outlet of the chimney 200 obtains real-time atmospheric temperature of 26.5℃ and relative humidity of 58%; secondly, the control system converts the obtained atmospheric temperature (T... e =26.5℃) and relative humidity Substituting into formula (2), the tangent temperature (T) for flue gas whitening is calculated. tan =33.8℃), which is the critical condensation temperature of the flue gas; finally, the control system adjusts the refrigerant usage of the heat exchanger 300 in real time so that the flue gas temperature (T) displayed by the first exhaust flue gas temperature detector 302 installed on the outlet pipeline of the heat exchanger 300 is 33.8℃. OUT ) and the calculated critical condensation temperature for flue gas whitening (T) tan =33.8℃) is equal. At this time, the circulating water consumption is 180t / h, the chilled water consumption is 165t / h, the chilled water consumption is 210t / h lower than the design value, the refrigerant consumption is greatly reduced, and the energy consumption is reduced accordingly.

[0101] Example 2

[0102] like Figure 4 As shown, the white smoke elimination device in this embodiment is the same as that in embodiment 1. Since the flue gas enters the chimney after passing through the heat exchanger 300, there will be a certain temperature drop during the process of the flue gas flowing through the flue after the heat exchanger 300 and the chimney 200. Therefore, the flue gas temperature detected by the first exhaust flue gas temperature detector 302 installed on the flue gas outlet pipeline of the heat exchanger 300 is somewhat different from the flue gas temperature discharged from the top of the chimney 200. Formula (2) is corrected by using the temperature deviation β to obtain formula (7). The temperature deviation β is set to 1.5℃. At this time, no white smoke appears in the exhaust flue gas. The circulating water consumption is 180t / h, the chilled water consumption is 130t / h, the chilled water consumption is 35t / h lower than that in embodiment 1, and 245t / h lower than the design value. The refrigerant consumption is greatly reduced, and the energy consumption is reduced accordingly.

[0103] Example 3

[0104] like Figure 4 As shown, the whitening device in this embodiment differs from that in embodiment 1 in that the heat exchanger 300 is a steam heater and the heat source 301 is steam; otherwise, they are the same.

[0105] A wet desulfurization process uses direct heating to eliminate white smoke in the flue gas. The flue gas volume before the desulfurization tower is 150,000 Nm³. 3 / h, the temperature of the flue gas after desulfurization is 50℃. The design requires the elimination of white smoke under the conditions of atmospheric ambient temperature of 10℃ and atmospheric relative humidity of 45%. The design value of the flue gas exhaust temperature is 102℃. The heat medium 301 of heat exchanger 300 adopts steam at 1.0MPa and 250℃. To meet the design requirements, 4.9t / h of steam is required.

[0106] This wet desulfurization smoke elimination device employs the wet desulfurization flue gas smoke elimination method of this invention. Based on external weather conditions such as temperature and humidity, and the temperature of the flue gas after wet desulfurization, it automatically calculates the critical heating temperature required for smoke elimination. By adjusting the amount of heat medium (steam) used in the device, the flue gas exhaust temperature is made equal to the critical heating temperature, thus effectively achieving automatic control of the heat medium usage. For example, firstly, the first atmospheric monitoring unit 201 located below the exhaust port of the chimney 200 obtains real-time atmospheric temperature of 16.0℃ and relative humidity of 52%; secondly, the control system collects real-time flue gas temperature (T0 = 50℃) after wet desulfurization and combines the flue gas temperature (T0 = 50℃) with the obtained atmospheric temperature (T... e =16.0℃) and atmospheric relative humidity Substituting into formula (1), the critical heating temperature (T) for flue gas whitening is calculated. HCT =81.4℃); Finally, the control system adjusts the heat medium usage of heat exchanger 300 in real time so that the flue gas temperature (T) displayed by the first exhaust gas temperature detector 302 on the outlet pipeline of heat exchanger 300 is 81.4℃; OUT ) and the calculated critical heating temperature for flue gas whitening (T) HCT =81.4℃) is equal. At this time, the steam consumption at 1.0MPa and 250℃ is 2.9t / h, which is 2t / h lower than the design target. The steam consumption is reduced significantly, and the energy consumption is reduced accordingly.

[0107] Example 4

[0108] The whitening device and method in this embodiment are the same as those in Embodiment 3. 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 200. After diagnosing the relevant influencing factors of the device, it was found that the demisting efficiency of the demister 101 installed in the wet desulfurization tower 100 was reduced, and the flue gas after desulfurization contained a large number of mist droplets. After sampling and testing, the mist droplet content was as high as 1.5 g / kg dry flue gas. The mist droplet content A was used to correct formula (1), and formula (1) was corrected to formula (5). After the correction, the white smoke in the flue gas discharged from the chimney 200 disappeared, making the whitening method of the present invention more consistent with the actual situation and improving the accuracy and reliability of the present invention.

[0109] Example 5

[0110] like Figure 5As shown, the wet desulfurization flue gas whitening device in this embodiment is a desulfurization chimney integrated tower 500, which includes, from bottom to top, a desulfurization section 501, a condensation and cooling section 502, a demisting section 503, a heating section 504, and a chimney section 505. A second atmospheric monitoring unit 506 is installed near the exhaust port of the chimney section 505 of the desulfurization chimney integrated tower 500, a second exhaust flue gas temperature detector 507 is installed on the upper part of the heating section 504, and a desulfurization condensed flue gas temperature detection unit 508 is installed between the demisting section 503 and the heating section 504.

[0111] The wet desulfurization flue gas whitening device in this embodiment adopts a condensation-then-heating process to eliminate white smoke. According to the design conditions, the flue gas volume at the desulfurization tower inlet is 200,000 Nm³. 3 The flue gas is first condensed to 45℃ and then heated to 80℃ to eliminate white smoke. The steam consumption at 1.0MPa and 250℃ is 4.2t / h.

[0112] The wet desulfurization flue gas whitening method of this invention can automatically and rapidly calculate the critical heating temperature required for whitening flue gas based on external weather conditions such as temperature and humidity, as well as the temperature of the flue gas after wet desulfurization condensation. By adjusting the amount of heat medium (steam) used in the device, the flue gas exhaust temperature is made equal to the critical heating temperature, thereby effectively achieving automatic control of the heat medium usage. For example, firstly, the second atmospheric monitoring unit 506 installed below the exhaust port of chimney 505 obtains the atmospheric temperature as 21.5℃ and the relative humidity as 45% in real time; secondly, the control system collects the flue gas temperature (T0 = 45℃) after wet desulfurization condensation in real time, and combines the flue gas temperature (T0 = 45℃) with the obtained atmospheric temperature (T... e =21.5℃) and atmospheric relative humidity Substituting into formula (1), the critical heating temperature (T) for eliminating white smoke in flue gas is calculated. HCT =52℃); Finally, the control system adjusts the steam consumption of the heating section 504 in real time so that the flue gas temperature (T) displayed by the second exhaust gas temperature detector 507 installed above the heating section 504 is 52℃; OUT ) and the calculated critical heating temperature for flue gas whitening (T) HCT =52℃) is equal. At this time, the steam consumption at 1.0MPa and 250℃ is 0.8t / h, which is 3.4t / h lower than the design target. The steam consumption is greatly reduced, and the energy consumption is reduced accordingly.

[0113] Example 6

[0114] The whitening device and whitening method in this embodiment are the same as those in embodiment 5. After one and a half years of operation, a small amount of white smoke was found in the flue gas discharged from the top exhaust port of chimney section 505. The flue gas after demister 503 was sampled and analyzed. The droplet content A = 0.08 g / kg dry flue gas. Formula (1) was modified by using droplet content A and temperature deviation σ, and modified into formula (6). According to the relevant influencing factors, the temperature deviation σ was set to 2℃. At this time, no white smoke appeared in the exhaust gas.

[0115] 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, Includes 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 Data; B. Real-time monitoring of flue gas temperature after wet desulfurization or after wet desulfurization and condensation. T 0 And in combination with the atmospheric temperature T e and atmospheric relative humidity Calculation of the critical heating temperature for whitening T HCT The critical heating temperature for whitening in step B. T HCT The calculation is performed in the following way: ； ； ； ； Where Ps is the partial pressure of saturated water vapor, that is, the partial pressure of water vapor when the relative humidity of the gas is 100%, and the unit is Pa; tangent point For passing the environmental state point Find the point of tangency of the tangent line to the saturated humid air curve. The relative humidity is expressed as a percentage. The flue gas after wet desulfurization is saturated wet flue gas. ; , where is the saturated moisture content at the tangent point; When the flue gas contains droplets and is in a supersaturated state, the critical heating temperature for whitening is determined by the droplet content A. T HCT The calculation formula (1) 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. C. In the whitening device, whether it is a direct heating or condensation-then-heating process, adjust the heat exchanger's heat transfer medium usage in real time until the exhaust gas temperature reaches the specified level. T OUT The critical heating temperature for whitening T HCT When the values ​​are equal, the flue gas is discharged.

2. The wet desulfurization flue gas whitening method according to claim 1, characterized in that, When the temperature measuring point of the heated flue gas is a certain distance from the chimney outlet, the temperature deviation is used to measure the temperature difference. The critical heating temperature for whitening 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, 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. A method for eliminating whitening in wet desulfurization flue gas, characterized in that, Includes 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 Data; B. In conjunction with the aforementioned atmospheric temperature T e and atmospheric relative humidity Calculate the tangent temperature for flue gas whitening The critical condensation temperature of the flue gas in step B is used as the critical condensation temperature of the flue gas. The calculation is performed in the following way: ； ； ； Where Ps is the partial pressure of saturated water vapor, that is, the partial pressure of water vapor when the relative humidity of the gas is 100%, and the unit is Pa; tangent point For passing the environmental state point Find the point of tangency of the tangent line to the saturated humid air curve. The relative humidity is expressed as a percentage. The flue gas after wet desulfurization is saturated wet flue gas. ; , where is the saturated moisture content at the tangent point; When the temperature measuring point of the condensed flue gas is a certain distance from the chimney outlet, the temperature deviation is used to measure the temperature difference. The critical condensation temperature of the flue gas The calculation formula (2) is modified as follows: ； in, The temperature deviation is specifically defined as -5℃ to 5℃; 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. C. In the direct condensation whitening device, adjust the refrigerant usage of the heat exchanger in real time until the exhaust gas temperature reaches the specified level. T OUT With respect to the critical condensation temperature of the flue gas When the values ​​are equal, the flue gas is discharged.

5. A wet desulfurization flue gas whitening device, characterized in that, The method for eliminating whitening as described in any one of claims 1 to 3, wherein the whitening method is a direct heating method and the wet desulfurization tower and the chimney are separately or integrated, includes: An atmospheric monitoring unit is installed at a corresponding height outside the exhaust outlet of the wet desulfurization chimney to collect atmospheric temperature data at that height. T e and atmospheric relative humidity Data; The desulfurization flue gas temperature detection unit, located downstream of the demister in the wet desulfurization tower, is used to collect the temperature of the flue gas after wet desulfurization in real time. T 0 ; The critical heating temperature calculation unit for whitening is based on the flue gas temperature. T 0 The atmospheric temperature T e and atmospheric relative humidity Calculation of the critical heating temperature for whitening T HCT ; The exhaust control unit is used to adjust the heat transfer medium flow rate of the heat exchanger in real time during the direct heating elimination method, up to the exhaust gas temperature. T OUT The critical heating temperature for whitening T HCT When the values ​​are equal, the flue gas is discharged.

6. A wet desulfurization flue gas whitening device, characterized in that, The whitening method described in claim 4, wherein the whitening method is a direct condensation whitening method and the wet desulfurization tower and the chimney are separately installed or integrated, includes: An atmospheric monitoring unit is installed at a corresponding height outside the exhaust outlet of the wet desulfurization chimney to collect atmospheric temperature data at that height. T e and atmospheric relative humidity Data; The critical condensation temperature calculation unit for whitening is based on the atmospheric temperature. T e and atmospheric relative humidity Calculate the tangent temperature for flue gas whitening , which serves as the critical condensation temperature of the flue gas; The exhaust control unit is used to adjust the refrigerant flow rate of the heat exchanger in real time during the whitening process of direct condensation, up to the exhaust gas temperature. T OUT With respect to the critical condensation temperature of the flue gas When the values ​​are equal, the flue gas is discharged.

7. A wet desulfurization flue gas whitening device, characterized in that, The whitening method described in any one of claims 1 to 3, wherein the whitening method is a method of whitening by first condensing and then heating, and the wet desulfurization tower and the chimney are integrated or separate units, includes: An atmospheric monitoring unit is installed at a corresponding height at the external exhaust outlet of the integrated desulfurization chimney tower to collect atmospheric temperature data at that height. T e and atmospheric relative humidity Data; The desulfurization condensate flue gas temperature detection unit, located at the rear end of the condensation and demisting sections, is used to collect the temperature of the flue gas after wet desulfurization and condensation in real time. T 0 ; The critical heating temperature calculation unit for whitening is based on the flue gas temperature. T 0 The atmospheric temperature T e and atmospheric relative humidity Calculation of the critical heating temperature for whitening T HCT ; The exhaust control unit is used to adjust the amount of heat transfer medium used in the heating section in real time during the whitening method of condensation followed by heating, until the exhaust gas temperature reaches the specified level. T OUT The critical heating temperature for whitening T HCT When the values ​​are equal, the flue gas is discharged.

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