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

Abstract

The invention relates to a flue gas gas-liquid contact spraying method and system based on dynamic water balance, and belongs to the technical field of flue gas purification spraying. A spraying unit builds circulating spraying with a dividing wall type heat exchange unit and a direct heating machine unit through pipelines and is used for carrying out purification and heat exchange on flue gas; the flash evaporation unit is used for carrying out negative pressure flash evaporation on desulfurization slurry obtained after flue gas purification, generated flash evaporation dead steam is used for providing a heat source for the heat exchange unit, the vacuum pump unit is used for carrying out vacuum treatment on the flash evaporation unit, and the desulfurization slurry obtained after flash evaporation passes through the dividing wall type heat exchange unit and then enters the spraying unit; the water balance stability is remarkably improved, and the system can complete water balance self-adaptive adjustment within a short time after coal type switching through cooperative adjustment of a dynamic prediction model and vacuum pressure. The automation and intelligence level is improved, the system achieves full-process automatic control through DCS integration, and manual intervention is reduced by 90% or above.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas purification spraying, and particularly relates to a flue gas gas-liquid contact spraying method and system based on dynamic water balance. Background Art

[0002] Coal-fired power plants are one of the main energy supply facilities in the industrial field. However, the flue gas emitted by them contains a large amount of pollutants such as sulfur oxides (SO x ), nitrogen oxides (NO x ) and particulate matters, etc., which need to be purified through equipment such as spray towers. At the same time, it is necessary to reduce the flue gas discharge temperature and its heat loss through the way of direct contact spray heat transfer to improve the boiler efficiency. Traditional spray technologies realize functions such as cooling, desulfurization, dust removal and heat transfer through gas-liquid contact. However, the following problems are faced in actual operation:

[0003] Due to spray heat transfer, the flue gas temperature decreases. When it drops to its equilibrium saturation temperature, the water vapor in the flue gas begins to have condensed water falling into the spray tower pool, causing the liquid level in the spray tower to rise continuously. In the prior art, the makeup water and drainage of the spray tower mainly rely on manual adjustment or fixed threshold control. However, coal-fired power plants often cause drastic changes in flue gas components (such as water vapor content, ash content, etc.) due to coal type switching, thereby breaking the system water balance. For example, high-ash coal types will increase the scaling rate of the demisting unit and require an increase in the flushing water volume; while high-moisture coal types will cause an increase in the water vapor content in the flue gas, and it is necessary to adjust the condensed water volume to maintain the liquid level in the tower. Summary of the Invention

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

[0005] The solution is a flue gas gas-liquid contact spraying method based on dynamic water balance. The specific steps include,

[0006] S1. The flue gas enters the inside of the spray unit from the bottom of the spray unit and moves upward from the bottom of the spray unit to conduct gas-liquid contact with the spray medium to purify and heat exchange the flue gas;

[0007] S2. The desulfurized slurry after purification and heat exchange enters the flash evaporation unit of the direct heat engine unit through a pipeline for flash evaporation. The steam exhausted from the flash evaporation is used as a heat source for the heat exchange unit, and the condensed water generated after condensation in the flash evaporation unit is discharged, thereby maintaining the water balance of the spray tower;

[0008] S3. After the coal type is changed, the elements of the flue gas change, and the vacuum pressure of the flash evaporation unit is adjusted to control the water balance of the spray unit. Specifically,

[0009] S31. Obtain the moment t of the temperature fluctuation at the furnace outlet in real time ltck ;

[0010] S32. Calculate the arrival time t of the new flue gas at the inlet of the spray unit according to the furnace outlet temperature fluctuation time t ltck ; ycpltrk ;

[0011] S33. Predict the change in the water volume at the inlet of the spray unit based on the flue gas inlet per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type Change in the washing water volume of the demisting unit Change in the outlet water volume

[0012] S34. Calculate the change in the condensate water volume of the direct heating unit according to the change in the water volume at the inlet of the spray unit Change in the washing water volume of the demisting unit Change in the outlet water volume ;

[0013] S35. Adjust the vacuum pressure of the direct heating unit according to the furnace outlet temperature fluctuation time t ltck and the change in the condensate water volume of the direct heating unit .

[0014] Furthermore, the method for S31 to obtain the furnace outlet temperature fluctuation time t ltck in real time is as follows

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

[0016] S312. When the range of the furnace outlet temperature exceeds the set threshold T set it is determined as the starting signal for coal type switching;

[0017] S313. Record the time when the threshold T set is first triggered as t ltck .

[0018] Furthermore, S32 calculates the arrival time t of the new flue gas at the inlet of the spray unit according to the furnace outlet temperature fluctuation time t ltck ; ycpltrk

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

[0020] S322. Calculate the theoretical transmission time t ys , and introduce the flue resistance correction coefficient k, and the corrected transmission time t' ys , ​

[0021]

[0022] S323. Calculate the moment t when the new flue gas reaches the inlet of the spray unit ycpltrk ,

[0023] t ycpltrk =t ltck +t' ys +Δt safe ;

[0024] Among them, Δt safe is the safety margin.

[0025] Furthermore, S33 predicts the change amount of the water at the inlet of the spray unit based on the flue gas inlet per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type The change amount of the washing water of the demisting unit The change amount of the outlet water The method is as follows

[0026] S331. Obtain the contents of carbon C ar , hydrogen H ar , oxygen O ar , sulfur S ar , nitrogen N ar , water M ar in the new coal type, and calculate the change amount of the water at the inlet of the spray unit according to the contents of carbon C ar , hydrogen H ar , oxygen O ar , sulfur S ar , nitrogen N ar , water M ar in the new coal type

[0027] S332. Obtain the contact area A of the demisting unit, the bulk density ρ of the fouling substances of the new coal type xash , the ash content A in the new coal type xar , the bulk density ρ of the fouling substances of the old coal type jash , the ash content A in the old coal type jar and calculate the change amount of the washing water of the demisting unit

[0028] S333. Obtain the flue gas flow rate Q of the old coal type jyq , and calculate the change amount of the outlet water of the spray unit according to the flue gas flow rate Q of the old coal type jyq

[0029] Furthermore, S331 obtains the carbon C ar , hydrogen H ar , oxygen O ar , sulfur S ar , nitrogen N​ar , the content of water M ar , based on the carbon C in the new coal type ar , hydrogen H ar , oxygen O ar , sulfur S ar , nitrogen N ar , the content of water M ar , calculate the change in the water volume at the inlet of the spray unit The method is as follows

[0030] S3311. Calculate the theoretical air volume V ar , based on the carbon C in the new coal type ar , hydrogen H ar , oxygen O ar , sulfur S 0 ,

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

[0032] S3312. Calculate the nitrogen volume in the theoretical flue gas based on the content of nitrogen N ar in the new coal type and the theoretical air volume V 0

[0033]

[0034] S3313. Calculate the flow rate of triatomic gases based on the content of carbon C ar and sulfur S ar in the new coal type

[0035]

[0036] S3314. Calculate the water vapor volume in the flue gas based on the content of water M ar , hydrogen H ar , and the theoretical air volume V 0 in the new coal type

[0037]

[0038] S3315. Calculate the actual flue gas volume V based on the flow rate of triatomic gases the nitrogen volume the water vapor volume in the flue gas 0 and the excess air coefficient V y ,

[0039] ​

[0040] where α is the excess air coefficient;

[0041] S3316. Calculate the volume fraction φ of water vapor in the new coal type according to the actual flue gas volume V y , the water vapor amount in the flue gas , x ,

[0042]

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

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

[0045] where the coal consumption M xmz is the combustion mass per hour of the new coal type;

[0046] S3318. Calculate the change amount of the water inlet of the spray unit according to the volume fraction φ of water vapor in the new coal type x , the flue gas flow rate Q of the old coal type jyq , the volume fraction φ of water vapor in the old coal type j ,

[0047]

[0048] The method for S332 to obtain the contact area A of the demisting unit, the bulk density ρ of the scaling substances of the new coal type xash , the ash content A in the new coal type xar , the bulk density ρ of the scaling substances of the old coal type jash , the ash content A in the old coal type jar to calculate the change amount of the flushing water of the demisting unit is as follows:

[0049] S3321. Calculate the scaling thickness δ of the old coal type according to the contact area A of the demisting unit, the bulk density ρ of the scaling substances of the old coal type jash , the ash content A in the old coal type jar , the flue gas flow rate Q of the old coal type jyq , j ,

[0050]

[0051] where η is the deposition efficiency;

[0052] S3322. Obtain the average flow rate Q of the flushing water for the old coal type jp , and the scaling thickness δ of the old coal type j ;

[0053] S3323. Calculate the scaling thickness δ of the new coal type based on the contact area A of the demisting unit, the bulk density ρ of the scaling substances of the new coal type xash , and the ash content A in the new coal type xar ; x ,

[0054]

[0055] S3324. Calculate the average flow rate Q of the flushing water for the new coal type according to the scaling thickness δ of the old coal type j , the average flow rate Q of the flushing water for the old coal type jp , and the scaling thickness δ of the new coal type x by proportion; xp ;

[0056]

[0057] S3325. Calculate the change amount of the flushing water for the demisting unit

[0058]

[0059] Furthermore, S333 obtains the flue gas flow rate Q of the old coal type jyq , and calculates the change amount of the water at the outlet of the spraying unit according to the flue gas flow rate Q of the old coal type jyq ;

[0060]

[0061] wherein, φ c is the volume fraction of the water vapor at the outlet of the spraying unit;

[0062] Furthermore, S34 calculates the change amount of the condensate water of the direct heat engine unit according to the change amount of the water at the inlet of the spraying unit , the change amount of the flushing water for the demisting unit , and the change amount of the water at the outlet ; the method is as follows ;

[0063]

[0064] Furthermore, S35 adjusts the vacuum pressure of the direct heat engine unit according to the furnace outlet temperature fluctuation time t ltck , and the change amount of the condensate water of the direct heat engine unit ; the method is as follows

[0065] S351. Obtain the medium inlet flow rate Q of the direct heat engine unit for the old coal typezrk 、The inlet temperature T of the medium of the old coal type direct heat engine unit jzrk 、The outlet temperature T of the medium of the old coal type direct heat engine unit jzck to obtain the inlet temperature T of the medium of the new coal type direct heat engine unit xzrk ;

[0066] S352. When the inlet flow rate of the medium of the direct heat engine unit for the new and old coal types remains unchanged, calculate the outlet temperature T of the medium of the new coal type direct heat engine unit according to the change amount of condensate water in the direct heat engine unit xzck ,

[0067]

[0068] S353. Look up the vacuum pressure P corresponding to the temperature according to the outlet temperature T of the medium of the new coal type direct heat engine unit xzck and the outlet temperature T of the medium of the old coal type direct heat engine unit jzck to obtain the change amount of vacuum pressure ΔP = P xzck 、P jzck , and obtain the change amount of vacuum pressure ΔP = P xzck -P jzck ;

[0069] S354. Calculate the adjustment start time t according to the change amount of vacuum pressure ΔP and the adjustment rate R of the vacuum pump unit P start ;

[0070]

[0071] S355. Send an adjustment instruction to the DCS system at time t start to set 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 is used to implement the flue gas gas-liquid contact spraying method based on dynamic water balance described in the above solution, including:

[0073] A spraying unit, which establishes a circulating spray through pipelines with a shell-and-tube heat exchange unit and a direct heat engine unit, and is used for purifying and heat exchanging the flue gas

[0074] A direct heat engine unit, including a flash evaporation unit, a heat exchange unit, and a vacuum pump unit. The flash evaporation unit is used for negative pressure flash evaporation of the desulfurized slurry after purifying the flue gas. The generated flash evaporation exhaust steam is used as a heat source for the heat exchange unit. The vacuum pump unit is used for vacuum treatment of the flash evaporation unit. The desulfurized slurry after flash evaporation enters the spraying unit through the shell-and-tube heat exchange unit

[0075] ​​An acquisition unit for acquiring the furnace outlet temperature fluctuation moment t ltck ,

[0076] A processing unit for calculating the moment t when the new flue gas reaches the inlet of the spray unit ycpltrk , for predicting the change amount of the water at the inlet of the spray unit based on the flue gas inlet per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type The change amount of the flushing water of the demisting unit The change amount of the outlet water For calculating the change amount of the condensate water of the direct-heat engine unit

[0077] A control unit for adjusting the vacuum pressure of the direct-heat engine unit according to the furnace outlet temperature fluctuation moment t ltck and the change amount of the condensate water of the direct-heat engine unit Adjust the vacuum pressure of the direct-heat engine unit.

[0078] Beneficial effects:

[0079] The stability of the water balance is significantly improved. Through the coordinated adjustment of the dynamic prediction model and the vacuum pressure, the system can complete the self-adaptive adjustment of the water balance in a short time after the coal type is switched, the amplitude of the liquid level fluctuation is reduced, and the probability of events such as shutdown caused by the liquid level fluctuation is reduced.

[0080] The level of automation and intelligence is improved. The system realizes full-process automatic control through DCS integration, reducing manual intervention by more than 90%. The furnace temperature fluctuation monitoring module can identify the coal type switching signal in advance, leaving sufficient time for adjustment.

[0081] The service life of the equipment is extended. Precise water balance control reduces the scaling rate of the demisting unit, and the equipment overhaul period is extended. Description of the drawings

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

[0083] Figure 2 is a flow chart of the method of the present invention;

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

[0085] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0086] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0087] The following further describes the present invention in conjunction with embodiments and Figure 1 and Figure 2 the drawings:

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

[0089] S1. The flue gas enters the inside of the spraying unit from the bottom of the spraying unit and moves upward from the bottom of the spraying unit to conduct gas-liquid contact with the spraying medium to purify and exchange heat with the flue gas;

[0090] Among them, in this step, by introducing the flue gas from the bottom of the spraying unit, making it move upward and form a countercurrent contact with the spraying medium (such as desulfurization slurry), the purification of pollutants (such as SO x , NO x , particulate matter) in the flue gas and the exchange of heat are realized. The spraying medium is evenly distributed through atomizing nozzles, increasing the gas-liquid contact area, improving the desulfurization efficiency and heat exchange effect. Through the gas-liquid countercurrent contact, the pollutants are absorbed by the slurry and chemical reactions occur (such as the reaction of SO2 with limestone slurry to form gypsum), and the temperature of the flue gas decreases. At the same time, the heat is transferred to the slurry, providing a basis for the heat energy recovery of 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 evaporation unit of the direct heat engine unit through a pipeline for flash evaporation. The steam exhausted from the flash evaporation is used as the heat source provided by the heat exchange unit, and the condensed water generated after condensation in the flash evaporation unit is discharged, thereby maintaining the water balance of the spray tower.

[0092] Among them, the purified desulfurized slurry is transported to the flash evaporation unit of the direct heat engine unit for flash evaporation under negative pressure conditions. During the flash evaporation process, the moisture in the slurry quickly vaporizes to generate steam exhausted, which is used as the heat source for the heat exchange unit, while the condensed water is discharged from the system through a pipeline. The flash evaporation process realizes the efficient recovery of waste heat and reduces the consumption of fresh steam. The discharge of the condensed water dynamically adjusts the liquid level of the spray tower, maintains the system water balance, and avoids problems such as overflow caused by too high a liquid level or pump cavitation caused by too low a liquid level.

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

[0094] Among them, when the change of coal type causes changes in the flue gas components (such as water vapor, ash content, etc.), by adjusting the vacuum pressure of the flash evaporation unit, the flash evaporation temperature and the condensation rate are changed, so as to control the balance between the water input and output of the spray unit. The dynamic vacuum pressure adjustment can quickly respond to the fluctuations of the flue gas components. For example, a coal type with high moisture content will increase the demand for condensed water, while a coal type with high ash content requires an increase in the flushing water volume. This step ensures that the system completes the adaptive adjustment in a short time, effectively controls the amplitude of the liquid level fluctuation, and significantly improves the operation stability.

[0095] In this application, the flue gas is purified and cleaned by using a gas-liquid contact method through the direct heat engine unit and the spray unit, and at the same time, the heat existing in the flue gas is collected and reused. On the premise of ensuring that the flue gas meets the environmental protection requirements, the energy is utilized. At the same time, due to the change of the coal type, the water content and element content of the flue gas change, and then it is necessary to adjust the water balance in the spray unit through the direct heat engine unit to ensure the water balance of the entire system, so as to achieve long-term system operation.

[0096] The method in S3 for controlling the water balance of the spray unit by adjusting the vacuum pressure of the flash evaporation unit after the elements of the flue gas change after changing the coal type is as follows:

[0097] S31. Obtain the moment t of the temperature fluctuation at the furnace outlet in real time ltck ;

[0098] S32. Calculate the moment t when the new flue gas reaches the inlet of the spray unit according to the moment t of the temperature fluctuation at the furnace outlet ltck ycpltrk ;

[0099] S33. Predict the change in the amount of water at the inlet of the spray unit inside the spray unit per unit time based on the flue gas inlet after the flue gas of the new coal type completely replaces the flue gas of the old coal type. Change in the amount of water for flue gas demisting unit flushing Change in the amount of water at the outlet

[0100] S34. Based on the change in the amount of water at the inlet of the spray unit Change in the amount of water for flue gas demisting unit flushing Change in the amount of water at the outlet Calculate the change in the amount of condensate water in the direct heating unit.

[0101] S35. According to the moment t of the furnace outlet temperature fluctuation ltck and the change in the amount of condensate water in the direct heating unit Adjust the vacuum pressure of the direct heating unit.

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

[0103] This application determines the moment of coal type change through the moment t of the furnace outlet temperature fluctuation ltck . Since the combustion degree will change due to the different elemental contents of the new coal type after the coal type is changed, which will in turn affect the furnace outlet temperature of the boiler, and then the moment of coal type change is determined more accurately through the moment t of the furnace outlet temperature fluctuation ltck , without the need for manual initiation of a change signal.

[0104] The method for the said S31 to obtain the moment t of the furnace outlet temperature fluctuation in real time ltck is as follows:

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

[0106] S312. When the range of the furnace outlet temperature exceeds the set threshold T set it is determined as the starting signal for coal type switching;

[0107] S313. Record the moment when the threshold T set is first triggered as t ltck .

[0108] Among them, the threshold T set is obtained through sorting, screening, and analysis of historical coal type change data;

[0109] The said S32 is based on the moment t of the furnace outlet temperature fluctuationltck Calculate the moment t when the new flue gas reaches the inlet of the spray unit ycpltrk ,

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

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

[0112]

[0113] S323. Calculate the moment t when the new flue gas reaches the inlet of the spray unit ycpltrk ,

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

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

[0116] The S33 predicts the change amount of the water at the inlet of the spray unit based on the flue gas inlet per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type The change amount of the washing water of the demisting unit The change amount of the outlet water The method is as follows

[0117] The method for obtaining the contents of carbon C ar , hydrogen H ar , oxygen O ar , sulfur S ar , nitrogen N ar , water M ar in the new coal type, and calculate the change amount of the water at the inlet of the spray unit according to the contents of carbon C ar , hydrogen H ar , oxygen O ar , sulfur S ar , nitrogen N ar , water M ar in the new coal type

[0118] S332. Obtain the contact area A of the demisting unit and the accumulation density ρ of the scaling substances of the new coal type xash、Amount of ash in new coal xar , the accumulation density of scale deposits in old coal jash 、Amount of ash in old coal jar Calculate the change in flushing water for the demisting unit

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

[0120] Among them, the ash content can be obtained through elemental analysis of coal types.

[0121] S331 obtains carbon C in new coal ar 、H ar , oxygen ar , Sulfur ar 、N ar , Water ar The content of carbon C in new coal ar 、H ar , oxygen ar , Sulfur ar 、N ar , Water ar Calculate the change in water inlet of the spray unit The method is,

[0122] S3311, according to the new coal carbon C ar 、H ar , oxygen ar , Sulfur ar Calculate the theoretical air volume V 0 ,

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

[0124] S3312, according to the new coal nitrogen N ar Content, theoretical air volume V 0 Calculate the amount of nitrogen in the theoretical flue gas

[0125]

[0126] S3313, according to the new coal carbon C ar and sulfur ar Calculate the flow rate of triatomic gas

[0127]

[0128] S3314. Calculate the amount of water vapor in the flue gas according to the content of water M, hydrogen H, and theoretical air volume V in the new coal type. ar , hydrogen H ar , theoretical air volume V 0 in the new coal type.

[0129]

[0130] S3315. Calculate the actual flue gas volume V according to the flow rate of triatomic gases, nitrogen volume, water vapor volume in the flue gas, and excess air coefficient α, where α is the excess air coefficient. nitrogen volume water vapor volume in the flue gas excess air coefficient V 0 in the flue gas. y ,

[0131]

[0132] Among them, α is the excess air coefficient;

[0133] S3316. Calculate the volume fraction φ of water vapor in the new coal type according to the actual flue gas volume V and the water vapor volume in the flue gas. y , water vapor volume in the flue gas in the new coal type. x ,

[0134]

[0135] S3317. Calculate the flue gas flow rate Q of the new coal type according to the actual flue gas volume V and the coal combustion amount M, where Q = M * V; the coal combustion amount M is the mass of the new coal type burned per hour. y , coal combustion amount M xmz in the new coal type. yq ,

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

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

[0138] S3318. Calculate the change amount of water at the inlet of the spray unit according to the volume fraction φ of water vapor in the new coal type, the flue gas flow rate Q of the old coal type, and the volume fraction φ of water vapor in the old coal type. Among them, the flue gas flow rate Q of the old coal type x of the old coal type, the volume fraction φ of water vapor in the old coal type jyq in the old coal type. j can be the same as Q

[0139]

[0140] of the old coal type. jyq can be the same as Q yqThe calculation method is the same for the volume fraction φ of water vapor in the old coal type j as that for the volume fraction φ of water vapor in the new coal type x The calculation method is the same for the coal consumption M xmz and the data can be obtained through the boiler system.

[0141] The above-mentioned S332 obtains the contact area A of the demisting unit, the bulk density ρ of the scaling substance in the new coal type xash , the ash content A in the new coal type xar , the bulk density ρ of the scaling substance in the old coal type jash , and the ash content A in the old coal type jar The method for calculating the change in the flushing water volume of the demisting unit is as follows

[0142] S3321. Calculate the scaling thickness δ of the old coal type based on the contact area A of the demisting unit, the bulk density ρ of the scaling substance in the old coal type jash , the ash content Aj in the old coal type ar , and the flue gas flow rate Q of the old coal type jyq , where η is the deposition efficiency j ,

[0143]

[0144]

[0145] S3322. Obtain the average flushing water flow rate Q of the old coal type jp and the scaling thickness δ of the old coal type j ;

[0146] S3323. Calculate the scaling thickness δ of the new coal type based on the contact area A of the demisting unit, the bulk density ρ of the scaling substance in the new coal type xash , and the ash content A in the new coal type xar , x ,

[0147]

[0148] S3324. Calculate the average flushing water flow rate Q of the new coal type by proportional calculation based on the scaling thickness δ of the old coal type j , the average flushing water flow rate Q of the old coal type jp , and the scaling thickness δ of the new coal type x ; xp

[0149]

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

[0151]

[0152] ​​Among them, the average flow rate Q of the flushing water for the old coal type jp , the scaling thickness δ of the old coal type j , the scaling thickness δ of the old coal type j are the same as the data acquisition or calculation methods for the new coal type.

[0153] In this application, considering that the ash content in the coal type will affect the scaling degree on the surface of the demisting unit after changing the coal type, thereby affecting the flushing frequency of the self-cleaning flushing water of the demisting unit, ultimately affecting the change in the flushing water volume of the demisting unit, and then causing an error in the horizontal balance adjustment. After adding the factor of the change in the flushing water volume of the demisting unit in this application, the overall horizontal balance control becomes more accurate, and the liquid level fluctuation in the spraying unit is smaller.

[0154] S333 obtains the flue gas flow rate Q of the old coal type jyq , and calculates the change in the outlet water volume of the spraying unit according to the flue gas flow rate Q of the old coal type jyq

[0155]

[0156] Among them, φ c is the volume fraction of water vapor at the outlet of the spraying unit;

[0157] S34 calculates the change in the condensate volume of the direct heat engine unit according to the change in the inlet water volume of the spraying unit the change in the flushing water volume of the demisting unit the change in the outlet water volume The method is as follows

[0158]

[0159] S35 adjusts the vacuum pressure of the direct heat engine unit according to the furnace outlet temperature fluctuation time t ltck , the change in the condensate volume of the direct heat engine unit The method is as follows

[0160] S351. Obtain the medium inlet flow rate Q of the direct heat engine unit of the old coal type zrk , the medium inlet temperature T of the direct heat engine unit of the old coal type jzrk , the medium outlet temperature T of the direct heat engine unit of the old coal type jzck , and obtain the medium inlet temperature T of the direct heat engine unit of the new coal type xzrk ;

[0161] S352. When the medium inlet flow rates of the direct heat engine units for the old and new coal types are unchanged, calculate the medium outlet temperature T of the direct heat engine unit of the new coal type according to the change in the condensate volume of the direct heat engine unit xzck ​​​​

[0162]

[0163] S353. According to the medium outlet temperature T of the direct heat engine unit for the new coal type xzck and the medium outlet temperature T of the direct heat engine unit for the old coal type jzck look up the corresponding vacuum pressure P from the table xzck and P jzck to obtain the change in vacuum pressure ΔP = P xzck - P jzck ;

[0164] S354. Calculate the start time t of the regulation according to the change in vacuum pressure ΔP and the regulation rate R of the vacuum pump unit P start ;

[0165]

[0166] S355. Send a regulation instruction to the DCS system at time t start to set the vacuum pressure to P xzck . When ΔP is positive, regulate the vacuum pump; when ΔP is negative, regulate the vacuum-breaking valve.

[0167] Among them, the regulation rate R of the vacuum pump unit P is obtained according to the equipment parameters of the vacuum pump unit, and the medium inlet flow rate Q of the direct heat engine unit for the old coal type zrk , the medium inlet temperature T of the direct heat engine unit for the old coal type jzrk , and the medium outlet temperature T of the direct heat engine unit for the old coal type jzck are obtained according to the thermometers and flow meters in the system.

[0168] In this application, the vacuum pressure of the direct heat engine unit is regulated to regulate the flash evaporation temperature, and finally the condensation amount of the condensed water is regulated, so as to realize the dynamic regulation of the system water balance. At the same time, the time node of the start of regulation is predicted to ensure that the regulation is completed when the flue gas generated by the new coal type enters the spray unit. Compared with the situation of regulating when the coal type is changed, this application minimizes the fluctuation of the condensed water.

[0169] The core of the present invention lies in dynamically predicting the change in the demand for the flushing water volume of the demisting unit after the coal type is switched, and realizing adaptive regulation through closed-loop control. The specific technical path is as follows:

[0170] Identification of coal type switching signal

[0171] By high-frequency collecting the furnace outlet temperature data (sampling frequency ≥ 1 Hz) and combining with the moving average filtering algorithm, the temperature fluctuation is monitored in real time. When the temperature range exceeds the preset threshold, it is determined as the starting signal of coal type switching, and the subsequent prediction process is triggered.

[0172] Calculation of Flue Gas Transmission Time for New Coal Types

[0173] Combined with the geometric length of the flue, real-time flue gas flow velocity, and resistance correction coefficient, accurately calculate the transmission time of flue gas from the furnace to the spray unit for new coal types, and reserve a time window for adjustment.

[0174] Dynamic Prediction of Flushing Water Volume Change

[0175] Ash and Fouling Prediction: Based on the ash content of the new coal type, the bulk density of the fouling deposit, and the flue gas flow rate, calculate the change in the fouling thickness on the surface of the demisting unit, and deduce the increase or decrease ratio of the required flushing water volume.

[0176] Water Vapor Content Correlation: Through the elemental analysis of coal types (carbon, hydrogen, sulfur, etc.), calculate the volume fraction of water vapor in the flue gas, and combine the difference in flue gas flow rates between the new and old coal types to predict the dynamic change in the water volume at the inlet of the spray unit.

[0177] Multi-Factor Coupling Model: Considering the changes in the inlet water volume, outlet water volume of the spray unit, and the change in the flushing water volume of the demisting unit, construct a water balance equation and real-time correct the condensate discharge volume of the flash unit.

[0178] Vacuum Pressure Synergistic Regulation

[0179] According to the predicted change in condensate, dynamically adjust the vacuum pressure of the flash unit, change the flash temperature and condensation rate, thereby accurately controlling the liquid level of the spray tower. The adjustment process is automatically executed through the DCS system to ensure the adaptive adjustment of the water balance is completed within a short time after the coal type is switched.

[0180] Technical Advantages and Effects

[0181] Significantly Improve the Stability of Water Balance

[0182] Reduce the Liquid Level Fluctuation Range: Through the dynamic prediction model, the system can anticipate the flushing water volume requirement in advance, avoiding drastic liquid level fluctuations caused by sudden changes in ash content or water vapor content.

[0183] Extend the Service Life of Equipment

[0184] Reduce the Fouling Rate: By adaptively adjusting the flushing water volume, effectively remove the ash deposit on the surface of the demisting unit, avoiding the increase in pressure drop and efficiency decline caused by the thickening of the fouling layer.

[0185] Prolong the Maintenance Cycle: Reduce the number of forced shutdowns for cleaning caused by fouling, significantly increase the equipment operation time, and reduce the operation and maintenance costs.

[0186] Energy Saving and Resource Optimization

[0187] Reduced flushing water consumption: Traditional fixed-threshold control often overuses flushing water to cope with the worst-case scenarios, while dynamic adjustment only supplies water according to actual needs, significantly saving water resources.

[0188] Full-process automation and intelligence

[0189] 90% reduction in manual intervention: The system integrates a DCS control module to achieve full-process automation from coal type identification, water volume prediction to vacuum pressure regulation, reducing human operation errors.

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

[0191] Flexible operation adaptable to multiple coal types

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

[0193] Supports the scenario of blended coal combustion: Under the condition of frequent changes in the blending ratio of coal for combustion, the system can still maintain a stable water balance, expanding the flexibility of fuel selection in power plants.

[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 solution, including:

[0195] A spraying unit, which establishes a circulating spray through pipelines with a shell-and-tube heat exchange unit and a direct heat engine unit, and is used for purifying and heat-exchanging the flue gas;

[0196] The direct heat engine unit includes: a flash evaporation unit, a heat exchange unit, and a vacuum pump unit. The flash evaporation unit is used for negative-pressure flash evaporation of the desulfurized slurry after purifying the flue gas, and the generated flash steam is used to provide heat source for the heat exchange unit. The vacuum pump unit is used for vacuum treatment of the flash evaporation unit. The desulfurized slurry after flash evaporation enters the spraying unit through the shell-and-tube heat exchange unit;

[0197] An acquisition unit, used to acquire the moment t of the temperature fluctuation at the furnace outlet ltck ,

[0198] A processing unit, used to calculate the moment t when the new flue gas reaches the inlet of the spraying unit ycpltrk , used to predict the change amount of the water at the inlet of the spraying unit based on the flue gas inlet per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type The change amount of the flushing water for the demisting unit The change amount of the outlet water Used to calculate the change amount of the condensate water in the direct heat engine unit

[0199] A control unit for adjusting the vacuum pressure of the direct heating unit according to the furnace outlet temperature fluctuation moment t ltck and the change amount of the condensate water of the direct heating unit Adjust the vacuum pressure of the direct heating unit.

[0200] The above has described the embodiments of the present invention in detail, but the content described is only the preferred embodiments of the present invention and cannot be considered as limiting the implementation scope of the present invention. All equivalent changes and improvements made according to the scope of the present invention application shall still fall within the scope covered by the patent 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. The flue gas enters the inside of the spray unit from the bottom of the spray unit, and moves upward from the bottom of the spray unit to conduct gas-liquid contact with the spray medium to purify and heat-exchange the flue gas; S2. The desulfurized slurry after purification and heat exchange enters the flash unit of the direct heat engine unit through a pipeline for flashing. The flashed steam exhaust is used to provide heat source for the heat exchange unit, and the condensed water generated after condensation in the flash 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, and the vacuum pressure of the flash unit is adjusted to control the water balance of the spray unit. Specifically: S31. Obtain the moment t of the furnace outlet temperature fluctuation in real time ltck ; S32. According to the moment t when the furnace outlet temperature fluctuates ltck Calculate the moment t when the new flue gas reaches the inlet of the spray unit ycpltrk ; S33. Predict the change in the amount of water at the inlet of the spray unit based on the flue gas inlet inside the spray unit per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type Change in the amount of flushing water for the demisting unit Change in the amount of water at the outlet S34. According to the change in the inlet water volume of the spray unit The change in the flushing water volume of the demisting unit The change in the outlet water volume Calculate the change in the condensate water volume of the direct heat engine unit S35. Adjust the vacuum pressure of the direct-heating machine unit according to the moment t of the furnace outlet temperature fluctuation ltck and the change amount of the condensate water in the direct-heating machine unit ​ 2. The method for flue gas-gas liquid contact spraying based on dynamic water balance according to claim 1, wherein The method for S31 to obtain the moment t of the furnace outlet temperature fluctuation in real time ltck is as follows S311. Collect the furnace outlet temperature data through the boiler DCS system at a sampling frequency not lower than 1 Hz, and perform 3-point moving average filtering on the data; S312. When the temperature difference at the furnace outlet exceeds the set threshold T set It is determined as the starting signal for coal type switching; S313. Record the moment t when the first trigger threshold T is triggered. set ltck .

3. The method for flue gas-gas liquid contact spraying based on dynamic water balance according to claim 1, wherein S32 calculates the arrival time t of the fresh flue gas at the inlet of the spray unit according to the furnace outlet temperature fluctuation time t ltck ycpltrk ,​ S321. Obtain the flue geometric length L from the furnace outlet to the inlet of the spray unit lt and the real-time flue gas flow velocity v yq ; S322. Calculate the theoretical transmission time t ys , and introduce the flue resistance correction coefficient k. After correction, the transmission time is t' ys , S323. Calculate the arrival time t of the fresh flue gas at the inlet of the spray unit ycpltrk , t ycpltrk = t ltck + t' ys + Δt safe where Δt safe is the safety margin.

4. The method for flue gas-gas-liquid contact spraying based on dynamic water balance according to claim 1, wherein S33 predicts the change in the amount of water at the inlet of the spray unit based on the flue gas inlet inside the spray unit per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type Change in the amount of water for flushing the demisting unit Change in the amount of outlet water The method is as follows S331. Obtain the contents of carbon C, hydrogen H, oxygen O, sulfur S, nitrogen N, and water M in the new coal type, and calculate the change in the inlet water volume of the spraying unit according to the contents of carbon C, hydrogen H, oxygen O, sulfur S, nitrogen N, and water M in the new coal type. ar Hydrogen H ar Oxygen O ar Sulfur S ar Nitrogen N ar Water M ar in the new coal type, and calculate the change in the inlet water volume of the spraying unit according to the contents of carbon C ar Hydrogen H ar Oxygen O ar Sulfur S ar Nitrogen N ar Water M ar in the new coal type. S332. Obtain the contact area A of the demisting unit, the bulk density ρ of the scale deposits of the new coal type, xash the ash content A in the new coal type, xar the bulk density ρ of the scale deposits of the old coal type, jash the ash content A in the old coal type, jar Calculate the change amount of the flushing water for the demisting unit. S333. Obtain the flue gas flow rate Q of the old coal type jyq , and calculate the change in the outlet water volume of the spray unit based on the flue gas flow rate Q of the old coal type jyq ​ 5. The method for flue gas-gas liquid contact spraying based on dynamic water balance according to claim 4, wherein, S331 Obtain the carbon C ar , hydrogen H ar , oxygen O ar , sulfur S ar , nitrogen N ar , water M ar content in the new coal type. According to the carbon C ar , hydrogen H ar , oxygen O ar , sulfur S ar , nitrogen N ar , water M ar content in the new coal type, the method for calculating the change amount of the water at the inlet of the spraying unit is as follows S3311. Calculate the theoretical air volume V according to the contents of carbon C ar , hydrogen H ar , oxygen O ar , sulfur S ar in the new coal type, 0 , V 0 = 0.0889C ar + 0.265H ar - 0.0333(O ar - S ar ); S3312. Calculate the nitrogen content in the theoretical flue gas based on the nitrogen N content and the theoretical air volume V in the new coal type ar in the new coal type, and the theoretical air volume V 0 in the new coal type S3313. Calculate the flow rate of triatomic gas based on the carbon C ar and sulfur S ar contents in the new coal type S3314. Calculate the amount of water vapor in the flue gas based on the content of water M ar , hydrogen H ar , and theoretical air volume V 0 in the new coal type S3315. According to the flow rate of the triatomic gas Amount of nitrogen Amount of water vapor in the flue gas Excess air coefficient V 0 Calculate the actual flue gas volume V y , where α is the excess air coefficient; S3316. Calculate the volume fraction φ of water vapor in the new coal type according to the actual flue gas volume V y and the water vapor amount in the flue gas . x , S3317. Calculate the flue gas flow rate Q of the new coal type based on the actual flue gas volume V y and the coal consumption M xmz . yq , Q yq = M xmz * V y ; Among them, the coal consumption M xmz is the hourly combustion mass of the new coal type; S3318. Calculate the change in the water volume at the inlet of the spray unit according to the volume fraction φ of water vapor in the new coal type x , the flue gas flow rate Q of the old coal type jyq , and the volume fraction φ of water vapor in the old coal type j ​ 6. The method for flue gas-gas-liquid contact spraying based on dynamic water balance according to claim 4, characterized in that S332 Obtain the contact area A of the demisting unit, the bulk density ρ of the scale deposits of the new coal type xash , the ash content A in the new coal type xar , the bulk density ρ of the scale deposits of the old coal type jash , the ash content A in the old coal type jar Calculate the change amount of the flushing water of the demisting unit The method is as follows S3321. Calculate the fouling thickness δ of the old coal type based on the contact area A of the demisting unit, the bulk density ρ of the fouling deposit of the old coal type jash , the ash content A in the old coal type jar , the flue gas flow rate Q of the old coal type jyq j ,​ where η is the deposition efficiency; S3322. Obtain the average flow rate Q of the old coal type during flushing jp , and the fouling thickness δ of the old coal type j ; S3323. Calculate the fouling thickness δ of the new coal type based on the contact area A of the demisting unit, the bulk density ρ of the fouling substances of the new coal type xash , and the ash content A in the new coal type xar x , S3324. Calculate the average flow rate Q of the new coal type for flushing according to the scaling thickness δ of the old coal type j and the average flow rate Q of flushing of the old coal type jp and the scaling thickness δ of the new coal type x , and calculate the average flow rate Q of flushing of the new coal type by proportion xp ; S3325. Calculate the change amount of the flushing water for the demisting unit 7. The method for gas-liquid contact spraying of flue gas based on dynamic water balance according to claim 4, characterized in that 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 the water volume at the outlet of the spray unit Among them, φ c is the volume fraction of water vapor at the outlet of the spraying unit.

8. The method for flue gas-gas-liquid contact spraying based on dynamic water balance according to claim 2, wherein S34 According to the change in the water volume at the inlet of the spray unit The change in the flushing water volume of the demisting unit The change in the water volume at the outlet The method for calculating the change in the condensate water volume of the direct heat engine unit is as follows 9. The method for flue gas-gas liquid contact spraying based on dynamic water balance according to claim 2, wherein S35 According to the moment t when the furnace outlet temperature fluctuates ltck and the change amount of the condensate water in the direct heating unit The method for adjusting the vacuum pressure of the direct heating unit is as follows S351. Obtain the inlet flow rate Q of the medium of the direct heating machine unit for the old coal type zrk , the inlet temperature T of the medium of the direct heating machine unit for the old coal type jzrk , the outlet temperature T of the medium of the direct heating machine unit for the old coal type jzck , and obtain the inlet temperature T of the medium of the direct heating machine unit for the new coal type xzrk ; S352. When the inlet flow rate of the direct heating unit medium for the new and old coal types remains unchanged, calculate the outlet temperature T of the direct heating unit medium for the new coal type based on the change in condensate water of the direct heating unit xzck ,​ S353. According to the medium outlet temperature T of the direct heating machine unit for the new coal type xzck and the medium outlet temperature T of the direct heating machine unit for the old coal type jzck look up the table to obtain the vacuum pressure P corresponding to the temperature xzck and P jzck to obtain the change in vacuum pressure ΔP = P xzck - P jzck ; S354. Calculate the adjustment start time t based on the change in vacuum pressure ΔP and the adjustment rate R of the vacuum pump unit P start ;​ S355. At time t start send an adjustment instruction to the DCS system to set 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, which is used to implement the flue gas gas-liquid contact spraying method based on dynamic water balance according to any one of claims 1-9, and is characterized in that, including: The spray unit is connected in a circulating spray through a pipeline with the shell-and-tube heat exchange unit and the direct heat engine unit, and is used to purify and heat-exchange the flue gas; The direct heat engine unit includes: a flash unit, a heat exchange unit, and a vacuum pump unit. The flash unit is used to perform negative pressure flashing on the desulfurized slurry after purifying the flue gas. The flashed steam exhaust is used to provide heat source for the heat exchange unit. The vacuum pump unit is used to perform vacuum treatment on the flash unit. The desulfurized slurry after flashing enters the spray unit after passing through the shell-and-tube heat exchange unit; An acquisition unit for acquiring the moment t of the furnace outlet temperature fluctuation ltck , A processing unit for calculating the time t when the new flue gas reaches the inlet of the spraying unit ycpltrk , for predicting the change amount of the water at the inlet of the spraying unit based on the flue gas inlet inside the spraying unit per unit time after the flue gas of the new coal type completely replaces the flue gas of the old coal type The change amount of the washing water of the demisting unit The change amount of the outlet water For calculating the change amount of the condensate water of the direct heat engine unit A control unit for adjusting the vacuum pressure of the direct heat engine unit according to the furnace outlet temperature fluctuation time t ltck and the change amount of condensate water in the direct heat engine unit ​

Images