A flue gas gas-liquid contact spraying method and system based on dynamic water balance

Abstract

This invention relates to a flue gas gas-liquid contact spraying method and system based on dynamic water balance, belonging to the field of flue gas purification spraying technology. The spraying unit establishes a circulating spray system through pipelines, a partitioned heat exchange unit, and a direct-heating unit for flue gas purification and heat exchange. The flash evaporation unit performs negative pressure flash evaporation on the desulfurization slurry after flue gas purification. The generated flash evaporation exhaust steam provides a heat source for the heat exchange unit. A vacuum pump unit performs vacuum treatment on the flash evaporation unit. The flash-evaporated desulfurization slurry enters the spraying unit after passing through the partitioned heat exchange unit. Water balance stability is significantly improved. Through dynamic prediction models and coordinated vacuum pressure adjustment, the system can complete adaptive water balance adjustment in a short time after coal type switching. Automation and intelligence levels are enhanced; the system achieves full-process automatic control through DCS integration, reducing manual intervention by more than 90%.

Description

Technical Field

[0001] This invention belongs to the field of flue gas purification spraying technology, and in particular relates to a flue gas gas-liquid contact spraying method and system based on dynamic water balance. Background Technology

[0002] Coal-fired power plants are one of the main energy supply facilities in the industrial sector, but their flue gas contains a large amount of sulfur oxides (SO₄). x ), nitrogen oxides (NO) x Pollutants such as particulate matter need to be purified using equipment such as spray towers. Simultaneously, direct contact spray heat exchange is required to reduce exhaust gas temperature and losses, thereby improving boiler efficiency. Traditional spray technology achieves cooling, desulfurization, dust removal, and heat exchange through gas-liquid contact, but it faces the following problems in actual operation:

[0003] Because the flue gas temperature decreases through spray heat exchange, when it drops to its equilibrium saturation temperature, water vapor in the flue gas begins to condense and fall into the spray tower pool, causing the spray tower's water level to rise continuously. In existing technologies, the water replenishment and drainage of the spray tower mainly rely on manual adjustment or fixed threshold control. However, coal-fired power plants often experience drastic changes in flue gas composition (such as water vapor content and ash content) due to coal type switching, which disrupts the system's water balance. For example, high-ash coal types increase the scaling rate of the demister unit, requiring a larger flushing water volume; while high-moisture coal types lead to an increase in water vapor content in the flue gas, requiring adjustments to the condensate flow rate to maintain the liquid level inside the tower. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a flue gas-liquid contact spraying method based on dynamic water balance.

[0005] The proposed solution is a flue gas-liquid contact spraying method based on dynamic water balance, the specific steps of which include:

[0006] S1. Flue gas enters the spray unit through the bottom of the spray unit and moves upward from the bottom of the spray unit to make gas-liquid contact with the spray medium to purify and exchange heat for the flue gas;

[0007] S2. The desulfurized slurry after purification and heat exchange enters the flash unit of the direct heat generator unit through the pipeline for flash evaporation. The exhaust steam generated by flash evaporation is used to provide a heat source for the heat exchange unit. The condensate generated after condensation in the flash evaporation unit is discharged, thereby maintaining the water balance of the spray tower.

[0008] S3. After changing the coal type, the elements of the flue gas change. Adjusting the vacuum pressure of the flash evaporation unit controls the water balance of the spray unit. Specifically,

[0009] S31. Real-time acquisition of furnace outlet temperature fluctuation time t ltck ;

[0010] S32, Based on the time t of the furnace outlet temperature fluctuation. ltck Calculate the time t when the new flue gas arrives at the inlet of the spray unit. ycpltrk ;

[0011] S33. Predict the change in inlet water of the spray unit within a unit per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type. Changes in flushing water volume of the demisting unit Changes in outlet water

[0012] S34. Based on the change in inlet water volume of the spray unit Changes in flushing water volume of the demisting unit Changes in outlet water Calculate the change in condensate water in a direct-heating unit

[0013] S35, Based on the time t of the furnace outlet temperature fluctuation. ltck Changes in condensate water in direct-heating unit Adjust the vacuum pressure of the direct-heating unit.

[0014] Furthermore, S31 acquires the real-time temperature fluctuation time t at the furnace outlet. ltck The method is,

[0015] S311. Collect furnace outlet temperature data through the boiler DCS system at a sampling frequency of not less than 1Hz, and perform 3-point moving average filtering on the data.

[0016] S312. When the furnace outlet temperature difference exceeds the set threshold T set This was determined to be a signal indicating the start of a coal type switch.

[0017] S313, Record the first trigger threshold T set The time is t ltck .

[0018] Furthermore, S32 adjusts the temperature fluctuation at the furnace outlet based on the time t. ltck Calculate the time t when the new flue gas arrives at the inlet of the spray unit. ycpltrk ,

[0019] S321. Obtain the geometric length L of the flue from the furnace outlet to the spray unit inlet. lt and real-time flue gas velocity v yq ;

[0020] S322, Calculate the theoretical transmission time t ys And introduce a flue resistance correction factor k, and the corrected transmission time t' ys ,

[0021]

[0022] S323. Calculate the time t when the fresh flue gas arrives at the inlet of the spray unit. ycpltrk ,

[0023] t ycpltrk =t ltck +t′ ys +Δt safe ;

[0024] Where, Δt safe This is for a safety margin.

[0025] Furthermore, S33 predicts the change in inlet water of the spray unit within a unit per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type. Changes in flushing water volume of the demisting unit Changes in outlet water The method is,

[0026] S331. Obtaining C6 from new coal types ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar The content, based on the carbon C content of the new coal type ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar Calculation of the content of the change in inlet water of the spray unit

[0027] S332. Obtain the contact area A of the demisting unit and the bulk density ρ of the scale on the new coal type. xash Ash content A in new coal types xar Bulk density ρ of scale on old coal types jash Ash content A in old coal types jar Calculate the change in flushing water volume of the demisting unit

[0028] S333, Obtain the flue gas flow rate Q of the old coal type jyq According to the flue gas flow rate Q of the old coal type jyq Calculate the change in outlet water of the spray unit

[0029] Furthermore, S331 obtains carbon C from new coal types. ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen Nar Water M ar The content, based on the carbon C content of the new coal type ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar Calculation of the content of the change in inlet water of the spray unit The method is,

[0030] S3311, Based on the carbon content (C) of the new coal type ar Hydrogen H ar Oxygen ar Sulfur S ar Theoretical air volume V calculated based on its content 0 ,

[0031] V 0 =0.0889C ar +0.265H ar -0.0333(O ar -S ar );

[0032] S3312, Based on the nitrogen (N) content in the new coal type ar Content, theoretical air volume V 0 Calculate the theoretical amount of nitrogen in the flue gas

[0033]

[0034] S3313, Based on the carbon content (C) of the new coal type ar and sulfur S ar Calculate the flow rate of triatomic gas based on its content.

[0035]

[0036] S3314, According to the new coal type with water content M ar Hydrogen H ar Theoretical air volume V 0 Calculation of water vapor content in flue gas

[0037]

[0038] S3315, Based on the flow rate of the triatomic gas Nitrogen quantity Water vapor content in flue gas Excess air coefficient V 0 Calculate the actual flue gas volume V y ,

[0039]

[0040] Where α is the excess air coefficient;

[0041] S3316, Based on the actual flue gas volume V y Water vapor content in flue gas Calculate the water vapor volume fraction φ of the new coal type x ,

[0042]

[0043] S3317, Based on the actual flue gas volume V y Coal consumption M xmz Calculate the flue gas flow rate Q of the new coal type yq ,

[0044] Q yq =M xmz *V y ;

[0045] Among them, coal consumption M xmz The hourly combustion mass of the new coal type;

[0046] S3318, Based on the water vapor volume fraction φ of the new coal type x Flue gas flow rate Q of old coal type jyq Water vapor volume fraction φ of old coal type j Calculate the change in inlet water of the sprinkler unit

[0047]

[0048] S332 obtains the contact area A of the demisting unit and the bulk density ρ of the scale on the new coal type. xash Ash content A in new coal types xar Bulk density ρ of scale on old coal types jash Ash content A in old coal types jar Calculate the change in flushing water volume of the demisting unit The method is,

[0049] S3321, Based on the contact area A of the demisting unit and the bulk density ρ of the scale on the old coal type. jash Ash content A in old coal types jar Flue gas flow rate Q of old coal type jyq Calculate the scale thickness δ of old coal types j ,

[0050]

[0051] Wherein, η is the deposition efficiency;

[0052] S3322, Obtain the average flow rate Q of the old coal type washing water. jp δ thickness of scale on old coal j ;

[0053] S3323, Based on the contact area A of the demisting unit and the bulk density ρ of the scale on the new coal type. xash Ash content A in new coal types xar Calculate the scale thickness δ of the new coal type x ,

[0054]

[0055] S3324, Based on the scaling thickness δ of the old coal type j Average flow rate Q of old coal washing water jp And the scaling thickness δ of new coal types x The average flow rate Q of the flushing water for the new coal type is calculated proportionally. xp ;

[0056]

[0057] S3325. Calculate the change in flushing water volume of the demisting unit.

[0058]

[0059] Furthermore, S333 obtains the flue gas flow rate Q of the old coal type. jyq According to the flue gas flow rate Q of the old coal type jyq Calculate the change in outlet water of the spray unit

[0060]

[0061] Where, φ c The volume fraction of water vapor at the outlet of the spray unit;

[0062] Furthermore, S34 adjusts the inlet water volume of the spray unit according to the change in water volume. Changes in flushing water volume of the demisting unit Changes in outlet water Calculate the change in condensate water in a direct-heating unit The method is,

[0063]

[0064] Furthermore, S35 adjusts the furnace outlet temperature fluctuation time t accordingly. ltck Changes in condensate water in direct-heating unit The method for adjusting the vacuum pressure of the direct-heating unit is as follows:

[0065] S351, Obtain the medium inlet flow rate Q of the old coal type direct heating unit.zrk The inlet temperature T of the medium in the direct-heating unit for old coal types jzrk The outlet temperature of the medium in the direct-heating unit of the old coal type is T. jzck Obtain the inlet temperature T of the medium in the direct-heating unit of the new coal type. xzrk ;

[0066] S352. When the inlet flow rate of the medium in the direct-heater unit remains constant for both new and old coal types, based on the change in the condensate flow rate of the direct-heater unit... Calculate the outlet temperature T of the medium in the direct-heater unit for the new coal type. xzck ,

[0067]

[0068] S353, Based on the new coal type direct-heater unit medium outlet temperature T xzck The outlet temperature of the medium in the direct-heating unit of the old coal type is T. jzck The vacuum pressure P corresponding to the temperature can be obtained from the table. xzck P jzck The change in vacuum pressure ΔP = P xzck -P jzck ;

[0069] S354, Based on the vacuum pressure change ΔP and the vacuum pump unit adjustment rate R P Calculate the start time t of the adjustment start ;

[0070]

[0071] S355, in t start Constantly send adjustment commands to the DCS system, setting the vacuum pressure to P. xzck When ΔP is positive, adjust the vacuum pump; when ΔP is negative, adjust the vacuum breaking valve.

[0072] A flue gas gas-liquid contact spraying system based on dynamic water balance, used to implement the flue gas gas-liquid contact spraying method based on dynamic water balance described in the above scheme, comprising:

[0073] The spray unit establishes a circulating spray system with the indirect heat exchange unit and the direct heat exchanger unit through pipelines, which is used for the purification and heat exchange of flue gas.

[0074] The direct heat exchanger unit includes: a flash evaporation unit, a heat exchange unit, and a vacuum pump unit. The flash evaporation unit is used to perform negative pressure flash evaporation on the desulfurization slurry after purifying the flue gas. The generated flash evaporation exhaust steam is used to provide a heat source for the heat exchange unit. The vacuum pump unit is used to perform vacuum treatment on the flash evaporation unit. The desulfurization slurry after flash evaporation enters the spray unit after passing through the partition wall heat exchange unit.

[0075] The acquisition unit is used to acquire the time t of the furnace outlet temperature fluctuation. ltck ,

[0076] The processing unit is used to calculate the time t when the fresh flue gas arrives at the inlet of the spray unit. ycpltrk This is used to predict the change in inlet water of the spray unit based on the flue gas inlet within a unit per unit time after the flue gas from the new coal type completely replaces the flue gas from the old coal type. Changes in flushing water volume of the demisting unit Changes in outlet water Used to calculate the change in condensate water in a direct-heating unit.

[0077] The control unit is used to adjust the furnace outlet temperature based on the time t. ltck Changes in condensate water in direct-heating unit Adjust the vacuum pressure of the direct-heating unit.

[0078] Beneficial effects:

[0079] The stability of the water balance is significantly improved. Through dynamic prediction model and vacuum pressure coordinated regulation, the system can complete the adaptive adjustment of water balance in a short time after coal type switching, reduce the fluctuation amplitude of liquid level, and reduce the probability of downtime and other events caused by liquid level fluctuation.

[0080] The system boasts enhanced automation and intelligence, achieving fully automated control through DCS integration and reducing manual intervention by over 90%. The furnace temperature fluctuation monitoring module can proactively identify coal type switching signals, allowing ample time for adjustments.

[0081] The equipment lifespan is extended, and precise water balance control reduces the scaling rate of the demisting unit, thus extending the equipment maintenance cycle. Attached Figure Description

[0082] Figure 1 This is a schematic diagram of the structure of the present invention;

[0083] Figure 2 This is a flowchart of the method of the present invention;

[0084] Figure 3 This is a system block diagram of the present invention. Detailed Implementation

[0085] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0086] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0087] The following describes the embodiments and appendices. Figure 1 and attached Figure 2 Further explanation of the present invention:

[0088] Example: A flue gas gas-liquid contact spraying method based on dynamic water balance, the specific steps of which include:

[0089] S1. Flue gas enters the spray unit through the bottom of the spray unit and moves upward from the bottom of the spray unit to make gas-liquid contact with the spray medium to purify and exchange heat for the flue gas;

[0090] This step involves introducing flue gas from the bottom of the spray unit, causing it to move upwards and form a counter-current contact with the spray medium (such as desulfurization slurry), thereby removing pollutants (such as SO2) from the flue gas. x NO x The process involves the purification of particulate matter and the exchange of heat. The spray medium is evenly distributed through atomizing nozzles, increasing the gas-liquid contact area and improving desulfurization efficiency and heat exchange. Through counter-current gas-liquid contact, pollutants are absorbed by the slurry and undergo chemical reactions (e.g., SO2 reacts with limestone slurry to form gypsum), lowering the flue gas temperature. Simultaneously, heat is transferred to the slurry, providing a basis for heat recovery in the subsequent flash evaporation unit. This step directly determines the purification efficiency and energy recovery potential.

[0091] S2. The desulfurized slurry after purification and heat exchange enters the flash unit of the direct heat generator unit through the pipeline for flash evaporation. The exhaust steam generated by flash evaporation is used to provide a heat source for the heat exchange unit. The condensate generated after condensation in the flash evaporation unit is discharged, thereby maintaining the water balance of the spray tower.

[0092] The purified desulfurization slurry is transported to the flash evaporation unit of the direct heat exchanger, where it undergoes flash evaporation under negative pressure. During flash evaporation, the moisture in the slurry rapidly vaporizes to generate exhaust steam, which is used as a heat source for the heat exchange unit, while the condensate is discharged from the system through pipelines. The flash evaporation process achieves efficient recovery of waste heat and reduces the consumption of fresh steam. The discharge of condensate dynamically regulates the liquid level in the spray tower, maintaining the system's water balance and preventing overflow due to excessively high liquid levels or pump cavitation problems caused by excessively low liquid levels.

[0093] S3. After changing the coal type, the elements of the flue gas change. Adjust the vacuum pressure of the flash evaporation unit to control the water balance of the spray unit.

[0094] In this system, when coal type switching causes changes in flue gas composition (such as water vapor and ash content), the vacuum pressure of the flash evaporation unit is adjusted to change the flash evaporation temperature and condensation rate, thereby controlling the water input and output balance of the spray unit. Dynamic vacuum pressure regulation can quickly respond to fluctuations in flue gas composition; for example, high-moisture coal types increase the demand for condensate, while high-ash coal types require increased flushing water volume. This step ensures that the system completes adaptive adjustments in a short time, effectively controlling the amplitude of liquid level fluctuations and significantly improving operational stability.

[0095] This application uses a direct-heating unit and a spray unit to purify and clean flue gas through gas-liquid contact. At the same time, it collects and reuses the heat in the flue gas, making energy use while ensuring that the flue gas meets environmental protection requirements. In addition, the flue gas changes in moisture content and element content due to the change of coal type, so the direct-heating unit needs to adjust the water balance in the spray unit to ensure the water balance of the entire system and thus achieve long-term system operation.

[0096] The method for controlling the water balance of the spray unit by adjusting the vacuum pressure of the flash evaporation unit after the element of the flue gas changes due to the change in coal type (S3) is as follows:

[0097] S31. Real-time acquisition of furnace outlet temperature fluctuation time t ltck ;

[0098] S32, Based on the time t of the furnace outlet temperature fluctuation. ltck Calculate the time t when the new flue gas arrives at the inlet of the spray unit. ycpltrk ;

[0099] S33. Predict the change in inlet water of the spray unit within a unit per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type. Changes in flushing water volume of the demisting unit Changes in outlet water

[0100] S34. Based on the change in inlet water volume of the spray unit Changes in flushing water volume of the demisting unit Changes in outlet water Calculate the change in condensate water in a direct-heating unit

[0101] S35, Based on the time t of the furnace outlet temperature fluctuation. ltck Changes in condensate water in direct-heating unit Adjust the vacuum pressure of the direct-heating unit.

[0102] Among them, the time t of the furnace outlet temperature fluctuation ltck This refers to the temperature at the boiler furnace outlet. After the flue gas from the new coal type completely replaces the flue gas from the old coal type, it refers to the time t when the new flue gas reaches the inlet of the spray unit. ycpltrk .

[0103] This application addresses the furnace outlet temperature fluctuation time t. ltck To determine the timing of coal type replacement, it is important to understand that the different elemental content of the new coal will alter its combustion degree, thus affecting the boiler furnace outlet temperature. Therefore, the timing of furnace outlet temperature fluctuations (t) is crucial. ltck This allows for more precise determination of when to switch coal types, eliminating the need for manual signaling.

[0104] The S31 acquires the furnace outlet temperature fluctuation time t in real time. ltck The method is,

[0105] S311. Collect furnace outlet temperature data through the boiler DCS system at a sampling frequency of not less than 1Hz, and perform 3-point moving average filtering on the data.

[0106] S312. When the furnace outlet temperature difference exceeds the set threshold T set This was determined to be a signal indicating the start of a coal type switch.

[0107] S313, Record the first trigger threshold T set The time is t ltck .

[0108] Wherein, threshold T set This was obtained by collecting, sorting, screening, and analyzing historical coal type change data;

[0109] S32 is based on the time t of the furnace outlet temperature fluctuation.ltck Calculate the time t when the new flue gas arrives at the inlet of the spray unit. ycpltrk ,

[0110] S321. Obtain the geometric length L of the flue from the furnace outlet to the spray unit inlet. lt and real-time flue gas velocity v yq ;

[0111] S322, Calculate the theoretical transmission time t ys And introduce a flue resistance correction factor k, and the corrected transmission time t' ys ,

[0112]

[0113] S323. Calculate the time t when the fresh flue gas arrives at the inlet of the spray unit. ycpltrk ,

[0114] t ycpltrk =t ltck +t′ ys +Δt safe ;

[0115] Where, Δt safe To allow for a safety margin, the geometric length L of the flue is... lt The flue resistance correction coefficient k can be obtained from the boiler equipment drawings and can be estimated by the equivalent length of local resistance sections such as elbows and baffles in the flue. This application will not describe it in detail.

[0116] The S33 prediction states that after the flue gas from the new coal type completely replaces the flue gas from the old coal type, the change in inlet water of the spray unit within the unit based on the flue gas inlet will occur per unit time. Changes in flushing water volume of the demisting unit Changes in outlet water The method is,

[0117] The acquisition of carbon C in new coal types ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar The content, based on the carbon C content of the new coal type ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar Calculation of the content of the change in inlet water of the spray unit

[0118] S332. Obtain the contact area A of the demisting unit and the bulk density ρ of the scale on the new coal type. xashAsh content A in new coal types xar Bulk density ρ of scale on old coal types jash Ash content A in old coal types jar Calculate the change in flushing water volume of the demisting unit

[0119] S333, Obtain the flue gas flow rate Q of the old coal type jyq According to the flue gas flow rate Q of the old coal type jyq Calculate the change in outlet water of the spray unit

[0120] The ash content can be obtained through elemental analysis of the coal.

[0121] S331 obtains carbon C from the new coal type. ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar The content, based on the carbon C content of the new coal type ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar Calculation of the content of the change in inlet water of the spray unit The method is,

[0122] S3311, Based on the carbon content (C) of the new coal type ar Hydrogen H ar Oxygen ar Sulfur S ar Theoretical air volume V calculated based on its content 0 ,

[0123] V 0 =0.0889C ar +0.265H ar -0.0333(O ar -S ar );

[0124] S3312, Based on the nitrogen (N) content in the new coal type ar Content, theoretical air volume V 0 Calculate the theoretical amount of nitrogen in the flue gas

[0125]

[0126] S3313, Based on the carbon content (C) of the new coal type ar and sulfur S ar Calculate the flow rate of triatomic gas based on its content.

[0127]

[0128] S3314, According to the new coal type with water content M ar Hydrogen H ar Theoretical air volume V 0 Calculation of water vapor content in flue gas

[0129]

[0130] S3315, Based on the flow rate of the triatomic gas Nitrogen quantity Water vapor content in flue gas Excess air coefficient V 0 Calculate the actual flue gas volume V y ,

[0131]

[0132] Where α is the excess air coefficient;

[0133] S3316, Based on the actual flue gas volume V y Water vapor content in flue gas Calculate the water vapor volume fraction φ of the new coal type x ,

[0134]

[0135] S3317, Based on the actual flue gas volume V y Coal consumption M xmz Calculate the flue gas flow rate Q of the new coal type yq ,

[0136] Q yq =M xmz *V y ;

[0137] The amount of coal burned M xmz The hourly combustion mass of the new coal type;

[0138] S3318, Based on the water vapor volume fraction φ of the new coal type x Flue gas flow rate Q of old coal type jyq Water vapor volume fraction φ of old coal type j Calculate the change in inlet water of the sprinkler unit

[0139]

[0140] Among them, the flue gas flow rate Q of old coal type jyq Can be used with Q yqThe calculation method is the same, and the water vapor volume fraction φ of old coal types is... j It can be compared with the water vapor volume fraction φ of new coal types x The calculation method is the same, coal consumption M xmz Data can be obtained through the boiler system.

[0141] S332 obtains the contact area A of the demisting unit and the bulk density ρ of the scale on the new coal type. xash Ash content A in new coal types xar Bulk density ρ of scale on old coal types jash Ash content A in old coal types jar Calculate the change in flushing water volume of the demisting unit The method is,

[0142] S3321, Based on the contact area A of the demisting unit and the bulk density ρ of the scale on the old coal type. jash Ash content Aj in old coal types ar Flue gas flow rate Q of old coal type jyq Calculate the scale thickness δ of old coal types j ,

[0143]

[0144] Wherein, η is the deposition efficiency;

[0145] S3322, Obtain the average flow rate Q of the old coal type washing water. jp δ thickness of scale on old coal j ;

[0146] S3323, Based on the contact area A of the demisting unit and the bulk density ρ of the scale on the new coal type. xash Ash content A in new coal types xar Calculate the scale thickness δ of the new coal type x ,

[0147]

[0148] S3324, Based on the scaling thickness δ of the old coal type j Average flow rate Q of old coal washing water jp And the scaling thickness δ of new coal types x The average flow rate Q of the flushing water for the new coal type is calculated proportionally. xp ;

[0149]

[0150] S3325. Calculate the change in flushing water volume of the demisting unit.

[0151]

[0152] Among them, the average flow rate Q of the old coal washing water jp δ thickness of scale on old coal j δ thickness of scale on old coal j The data acquisition or calculation method is the same as that for the new coal type.

[0153] This application takes into account that the ash content in the coal after changing the coal type will affect the degree of scaling on the surface of the demisting unit, which in turn affects the rinsing frequency of the self-cleaning rinsing water of the demisting unit, and ultimately affects the change in the rinsing water volume of the demisting unit, thus causing errors in water balance adjustment. This application incorporates the factor of the change in the rinsing water volume of the demisting unit, making the overall water balance control more accurate and the liquid level fluctuation in the spray unit smaller.

[0154] S333 obtains the flue gas flow rate Q of the old coal type. jyq According to the flue gas flow rate Q of the old coal type jyq Calculate the change in outlet water of the spray unit

[0155]

[0156] Where, φ c The volume fraction of water vapor at the outlet of the spray unit;

[0157] S34 is based on the change in inlet water volume of the spray unit. Changes in flushing water volume of the demisting unit Changes in outlet water Calculate the change in condensate water in a direct-heating unit The method is,

[0158]

[0159] The S35 is based on the time t of the furnace outlet temperature fluctuation. ltck Changes in condensate water in direct-heating unit The method for adjusting the vacuum pressure of the direct-heating unit is as follows:

[0160] S351, Obtain the medium inlet flow rate Q of the old coal type direct heating unit. zrk The inlet temperature T of the medium in the direct-heating unit for old coal types jzrk The outlet temperature of the medium in the direct-heating unit of the old coal type is T. jzck Obtain the inlet temperature T of the medium in the direct-heating unit of the new coal type. xzrk ;

[0161] S352. When the inlet flow rate of the medium in the direct-heater unit remains constant for both new and old coal types, based on the change in the condensate flow rate of the direct-heater unit... Calculate the outlet temperature T of the medium in the direct-heater unit for the new coal type. xzck ,

[0162]

[0163] S353, Based on the new coal type direct-heater unit medium outlet temperature T xzck The outlet temperature of the medium in the direct-heating unit of the old coal type is T. jzck The vacuum pressure P corresponding to the temperature can be obtained from the table. xzck P jzck The change in vacuum pressure ΔP = P xzck -P jzck ;

[0164] S354, Based on the vacuum pressure change ΔP and the vacuum pump unit adjustment rate R P Calculate the start time t of the adjustment start ;

[0165]

[0166] S355, in t start Constantly send adjustment commands to the DCS system, setting the vacuum pressure to P. xzck When ΔP is positive, adjust the vacuum pump; when ΔP is negative, adjust the vacuum breaking valve.

[0167] Among them, the vacuum pump unit adjustment rate R P Based on the parameters of the vacuum pump unit, the inlet flow rate Q of the medium in the old coal type direct-heater unit is obtained. zrk The inlet temperature T of the medium in the direct-heating unit for old coal types jzrk The outlet temperature of the medium in the direct-heating unit of the old coal type is T. jzck Data is obtained from the thermometers and flow meters within the system.

[0168] This application adjusts the flash temperature by regulating the vacuum pressure of the true heat engine unit, and ultimately adjusts the condensation rate of the condensate, thereby achieving dynamic adjustment of the system's water balance. At the same time, it predicts the start time of adjustment to ensure that the adjustment is completed when the flue gas generated by the new coal type enters the spray unit. Compared with the case of adjustment when changing coal type, this application minimizes the fluctuation of condensate.

[0169] The core of this invention lies in dynamically predicting the changes in the required flushing water volume of the demisting unit after coal type switching, and achieving adaptive adjustment through closed-loop control. The specific technical path is as follows:

[0170] Coal type switching signal identification

[0171] Temperature fluctuations are monitored in real time by acquiring furnace outlet temperature data at high frequency (sampling frequency ≥ 1Hz) and combining it with a moving average filtering algorithm. When the temperature range exceeds a preset threshold, it is determined as a coal type switching start signal, triggering the subsequent prediction process.

[0172] Calculation of flue gas transmission time for new coal types

[0173] By combining the geometric length of the flue, the real-time flue gas velocity, and the resistance correction coefficient, the transmission time of the flue gas of the new coal type from the furnace to the spray unit is accurately calculated, so as to reserve a time window for adjustment.

[0174] Dynamic prediction of flushing water volume changes

[0175] Ash content and scaling prediction: Based on the ash content of the new coal type, the bulk density of scale and the flue gas flow rate, the change in the scale thickness on the surface of the demisting unit is calculated, and the increase or decrease ratio of the required flushing water volume is derived.

[0176] Water vapor content correlation: By analyzing the elements of coal (carbon, hydrogen, sulfur, etc.), the volume fraction of water vapor in the flue gas is calculated. Combined with the difference in flue gas flow rate between new and old coal types, the dynamic changes in the inlet water volume of the spray unit are predicted.

[0177] Multi-factor coupling model: Taking into account the changes in inlet water, outlet water and flushing water of the spray unit, a water balance equation is constructed to correct the condensate discharge of the flash evaporation unit in real time.

[0178] Vacuum pressure coordinated regulation

[0179] Based on the predicted changes in condensate volume, the vacuum pressure of the flash evaporation unit is dynamically adjusted to change the flash evaporation temperature and condensation rate, thereby precisely controlling the liquid level in the spray tower. The adjustment process is automatically executed by the DCS system, ensuring that the water balance self-adaptive adjustment is completed within a short time after coal type switching.

[0180] Technical advantages and effects

[0181] Significantly improves water balance stability

[0182] Reduced level fluctuations: Through a dynamic prediction model, the system can anticipate the flushing water demand in advance, avoiding drastic level fluctuations caused by sudden changes in ash or water vapor content.

[0183] Extend equipment lifespan

[0184] Reduced scaling rate: By adaptively adjusting the flushing water volume, ash deposits on the surface of the demisting unit are effectively removed, avoiding increased pressure drop and decreased efficiency caused by thickened scale layer.

[0185] Extended maintenance cycle: Reduces the number of forced shutdowns for cleaning due to scaling, significantly increases equipment uptime, and lowers operation and maintenance costs.

[0186] Energy conservation and resource optimization

[0187] Reduced flushing water consumption: Traditional fixed threshold control often uses excessive flushing water to cope with the worst operating conditions, while dynamic adjustment supplies water only according to actual needs, significantly saving water resources.

[0188] Full-process automation and intelligence

[0189] Human intervention reduced by 90%: The system integrates a DCS control module to automate the entire process from coal type identification and water volume prediction to vacuum pressure regulation, reducing human error.

[0190] Rapid response and high-precision control: Based on real-time data feedback, the adjustment delay is reduced to the second level, ensuring the robustness of the system under complex working conditions.

[0191] Adaptable to flexible operation of multiple coal types

[0192] Compatible with different coal properties: Whether it is high-ash lignite or low-sulfur anthracite, the system can quickly adapt through dynamic model to avoid performance degradation caused by coal type switching.

[0193] Supports mixed coal combustion scenarios: Even under conditions where the proportion of coal blending changes frequently, the system can still maintain a stable water balance, expanding the flexibility of power plant fuel selection.

[0194] A flue gas gas-liquid contact spraying system based on dynamic water balance, used to implement the flue gas gas-liquid contact spraying method based on dynamic water balance described in the above scheme, comprising:

[0195] The spray unit establishes a circulating spray system with the indirect heat exchange unit and the direct heat exchanger unit through pipelines, which is used for the purification and heat exchange of flue gas.

[0196] The direct heat exchanger unit includes: a flash evaporation unit, a heat exchange unit, and a vacuum pump unit. The flash evaporation unit is used to perform negative pressure flash evaporation on the desulfurization slurry after purifying the flue gas. The generated flash evaporation exhaust steam is used to provide a heat source for the heat exchange unit. The vacuum pump unit is used to perform vacuum treatment on the flash evaporation unit. The desulfurization slurry after flash evaporation enters the spray unit after passing through the partition wall heat exchange unit.

[0197] The acquisition unit is used to acquire the time t of the furnace outlet temperature fluctuation. ltck ,

[0198] The processing unit is used to calculate the time t when the fresh flue gas arrives at the inlet of the spray unit. ycpltrk This is used to predict the change in inlet water of the spray unit based on the flue gas inlet within a unit per unit time after the flue gas from the new coal type completely replaces the flue gas from the old coal type. Changes in flushing water volume of the demisting unit Changes in outlet water Used to calculate the change in condensate water in a direct-heating unit.

[0199] The control unit is used to adjust the furnace outlet temperature based on the time t. ltck Changes in condensate water in direct-heating unit Adjust the vacuum pressure of the direct-heating unit.

[0200] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A flue gas gas-liquid contact spraying method based on dynamic water balance, characterized in that, The specific steps include, S1. Flue gas enters the spray unit through the bottom of the spray unit and moves upward from the bottom of the spray unit to make gas-liquid contact with the spray medium to purify and exchange heat for the flue gas; S2. The desulfurized slurry after purification and heat exchange enters the flash unit of the direct heat generator unit through the pipeline for flash evaporation. The exhaust steam generated by flash evaporation is used to provide a heat source for the heat exchange unit. The condensate generated after condensation in the flash evaporation unit is discharged, thereby maintaining the water balance of the spray tower. S3. After changing the coal type, the elements of the flue gas change. Adjusting the vacuum pressure of the flash evaporation unit controls the water balance of the spray unit. Specifically, S31. Real-time acquisition of furnace outlet temperature fluctuation time t ltck ; S32, Based on the time t of the furnace outlet temperature fluctuation. ltck Calculate the time t when the new flue gas arrives at the inlet of the spray unit. ycpltrk ; S33. Predict the change in inlet water of the spray unit within a unit per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type. Changes in flushing water volume of the demisting unit Changes in outlet water S34. Based on the change in inlet water volume of the spray unit Changes in flushing water volume of the demisting unit Changes in outlet water Calculate the change in condensate water in a direct-heating unit S35, Based on the time t of the furnace outlet temperature fluctuation. ltck Changes in condensate water in direct-heating unit Adjust the vacuum pressure of the direct-heating unit.

2. The flue gas gas-liquid contact spraying method based on dynamic water balance according to claim 1, characterized in that, S31 acquires real-time furnace outlet temperature fluctuation time t ltck The method is, S311. Collect furnace outlet temperature data through the boiler DCS system at a sampling frequency of not less than 1Hz, and perform 3-point moving average filtering on the data. S312. When the furnace outlet temperature difference exceeds the set threshold T set This is determined to be a signal indicating the start of a coal type switch. S313, Record the first trigger threshold T set The time is t ltck .

3. The flue gas gas-liquid contact spraying method based on dynamic water balance according to claim 1, characterized in that, S32 calculates the time t of the furnace outlet temperature fluctuation. ltck Calculate the time t when the new flue gas arrives at the inlet of the spray unit. ycpltrk , S321. Obtain the geometric length L of the flue from the furnace outlet to the spray unit inlet. lt and real-time flue gas velocity v yq ; S322, Calculate the theoretical transmission time t ys And introduce a flue resistance correction factor k, and the corrected transmission time t' ys , S323. Calculate the time t when the fresh flue gas arrives at the inlet of the spray unit. ycpltrk , t ycpltrk =t ltck +t' ys +Δt safe Where, Δt safe This is for safety margin.

4. The flue gas gas-liquid contact spraying method based on dynamic water balance according to claim 1, characterized in that, S33 predicts the change in inlet water of the spray unit within a unit per unit time after the flue gas from the new coal type completely replaces the flue gas from the old coal type. Changes in flushing water volume of the demisting unit Changes in outlet water The method is, S331. Obtaining C6 from new coal types ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar The content, based on the carbon C content of the new coal type ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar Calculation of the content of the change in inlet water of the spray unit S332. Obtain the contact area A of the demisting unit and the bulk density ρ of the scale on the new coal type. xash Ash content A in new coal types xar Bulk density ρ of scale on old coal jash Ash content A in old coal types jar Calculate the change in flushing water volume of the demisting unit S333, Obtain the flue gas flow rate Q of the old coal type jyq According to the flue gas flow rate Q of the old coal type jyq Calculate the change in outlet water of the spray unit 5. The flue gas gas-liquid contact spraying method based on dynamic water balance according to claim 4, characterized in that, S331 obtains carbon C from new coal types. ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar The content, based on the carbon C content of the new coal type ar Hydrogen H ar Oxygen ar Sulfur S ar Nitrogen N ar Water M ar Calculation of the content of the change in inlet water of the spray unit The method is, S3311, Based on the carbon content (C) of the new coal type ar Hydrogen H ar Oxygen ar Sulfur S ar Theoretical air volume V calculated based on its content 0 , V 0 =0.0889C ar +0.265H ar -0.0333(O ar -S ar ); S3312, Based on the nitrogen (N) content in the new coal type ar Content, theoretical air volume V 0 Calculate the theoretical amount of nitrogen in the flue gas S3313, Based on the carbon content (C) of the new coal type ar and sulfur S ar Calculate the flow rate of triatomic gas based on its content. S3314, According to the new coal type with water content M ar Hydrogen H ar Theoretical air volume V 0 Calculation of water vapor content in flue gas S3315, Based on the flow rate of the triatomic gas Nitrogen quantity Water vapor content in flue gas Excess air coefficient V 0 Calculate the actual flue gas volume V y , Where α is the excess air coefficient; S3316, Based on the actual flue gas volume V y Water vapor content in flue gas Calculate the water vapor volume fraction φ of the new coal type x , S3317, Based on the actual flue gas volume V y Coal consumption M xmz Calculate the flue gas flow rate Q of the new coal type yq , Q yq =M xmz *V y ; Among them, coal consumption M xmz The hourly combustion mass of the new coal type; S3318, Based on the water vapor volume fraction φ of the new coal type x Flue gas flow rate Q of old coal type jyq Water vapor volume fraction φ of old coal type j Calculate the change in inlet water of the sprinkler unit 6. The flue gas gas-liquid contact spraying method based on dynamic water balance according to claim 4, characterized in that, S332 obtains the contact area A of the demisting unit and the bulk density ρ of the scale on the new coal type. xash Ash content A in new coal types xar Bulk density ρ of scale on old coal jash Ash content A in old coal types jar Calculate the change in flushing water volume of the demisting unit The method is, S3321, Based on the contact area A of the demisting unit and the bulk density ρ of the scale on the old coal type. jash Ash content A in old coal types jar Flue gas flow rate Q of old coal type jyq Calculate the scale thickness δ of old coal types j , Wherein, η is the deposition efficiency; S3322, Obtain the average flow rate Q of the old coal type washing water. jp δ thickness of scale on old coal j ; S3323, Based on the contact area A of the demisting unit and the bulk density ρ of the scale on the new coal type. xash Ash content A in new coal types xar Calculate the scale thickness δ of the new coal type x , S3324, Based on the scaling thickness δ of the old coal type j Average flow rate Q of old coal washing water jp And the scaling thickness δ of new coal types x The average flow rate Q of the flushing water for the new coal type is calculated proportionally. xp ; S3325. Calculate the change in flushing water volume of the demisting unit.

7. The flue gas gas-liquid contact spraying method based on dynamic water balance according to claim 4, characterized in that, S333 obtains the flue gas flow rate Q of the old coal type. jyq According to the flue gas flow rate Q of the old coal type jyq Calculate the change in outlet water of the spray unit Where, φ c This represents the volume fraction of water vapor at the outlet of the spray unit.

8. The flue gas gas-liquid contact spraying method based on dynamic water balance according to claim 2, characterized in that, S34 based on the change in inlet water volume of the spray unit Changes in flushing water volume of the demisting unit Changes in outlet water Calculate the change in condensate water in a direct-heating unit The method is, 9. The flue gas gas-liquid contact spraying method based on dynamic water balance according to claim 2, characterized in that, S35 calculates the time t based on the furnace outlet temperature fluctuation. ltck Changes in condensate water in direct-heating unit The method for adjusting the vacuum pressure of the direct-heating unit is as follows: S351, Obtain the medium inlet flow rate Q of the old coal type direct heating unit. zrk The inlet temperature T of the medium in the direct-heating unit for old coal types jzrk The outlet temperature of the medium in the direct-heating unit of the old coal type is T. jzck Obtain the inlet temperature T of the medium in the direct-heating unit of the new coal type. xzrk ; S352. When the inlet flow rate of the medium in the direct-heater unit remains constant for both new and old coal types, based on the change in the condensate flow rate of the direct-heater unit... Calculate the outlet temperature T of the medium in the direct-heater unit for the new coal type. xzck , S353, Based on the new coal type direct-heater unit medium outlet temperature T xzck The outlet temperature of the medium in the direct-heating unit of the old coal type is T. jzck The vacuum pressure P corresponding to the temperature can be obtained from the table. xzck P jzck The change in vacuum pressure ΔP = P xzck -P jzck ; S354, Based on the vacuum pressure change ΔP and the vacuum pump unit adjustment rate R P Calculate the start time t of the adjustment start ; S355, in t start Constantly send adjustment commands to the DCS system, setting the vacuum pressure to P. xzck When ΔP is positive, adjust the vacuum pump; when ΔP is negative, adjust the vacuum breaking valve.

10. A flue gas gas-liquid contact spraying system based on dynamic water balance, used to implement the flue gas gas-liquid contact spraying method based on dynamic water balance as described in any one of claims 1-9, characterized in that, include: The spray unit establishes a circulating spray system with the indirect heat exchange unit and the direct heat exchanger unit through pipelines, which is used for the purification and heat exchange of flue gas. The direct heat exchanger unit includes: a flash evaporation unit, a heat exchange unit, and a vacuum pump unit. The flash evaporation unit is used to perform negative pressure flash evaporation on the desulfurization slurry after purifying the flue gas. The generated flash evaporation exhaust steam is used to provide a heat source for the heat exchange unit. The vacuum pump unit is used to perform vacuum treatment on the flash evaporation unit. The desulfurization slurry after flash evaporation enters the spray unit after passing through the partition wall heat exchange unit. The acquisition unit is used to acquire the time t of the furnace outlet temperature fluctuation. ltck , The processing unit is used to calculate the time t when the fresh flue gas arrives at the inlet of the spray unit. ycpltrk This is used to predict the change in inlet water of the spray unit based on the flue gas inlet within a unit per unit time after the flue gas from the new coal type completely replaces the flue gas from the old coal type. Changes in flushing water volume of the demisting unit Changes in outlet water Used to calculate the change in condensate water in a direct-heating unit. The control unit is used to adjust the furnace outlet temperature based on the time t. ltck Changes in condensate water in direct-heating unit Adjust the vacuum pressure of the direct-heating unit.

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