Method for stably controlling pH value of desulfurization slurry based on theoretical slurry supply amount

Abstract

The invention relates to a method for stably controlling the pH value of desulfurization slurry based on theoretical slurry supply amount, which belongs to the field of desulfurization and comprises the following steps: (1) calculating the mass and the amount of substance of SO2; (2) calculating the mass of CaCO3 required for absorbing SO2; (3) calculating the basic slurry supply flow for keeping the pH value of the absorption tower unchanged during SO2 absorption, obtaining the CaCO3 mass required for SO2 absorption through the step (2), obtaining the limestone slurry density through a limestone slurry densimeter, and obtaining the required limestone slurry supply amount; (4) calculating the pH deviation limestone slurry flow compensation amount; and (5) obtaining a theoretical slurry supply amount. The method has the advantages that the problem that the slurry supply amount cannot rapidly track the change of boiler load and the sulfur content of fire coal during normal operation of a normal thermal power generating unit is solved, the fluctuation range of slurry supply is reduced, and the pH value of slurry in an absorption tower is kept within a proper change range.

Description

Technical Field

[0001] The invention relates to a method for stably controlling the pH value of desulfurization slurry based on theoretical slurry supply amount, and belongs to the field of desulfurization. Background Art

[0002] During the operation of thermal power plants, the sulfur content and flow rate in flue gas will fluctuate dramatically due to the rapid changes in unit load and the uncertainty of coal quality. These fluctuations are a huge challenge to the desulfurization system, especially the pH control in the absorption tower. The pH value in the absorption tower is a key factor affecting the desulfurization efficiency and the quality of by-product gypsum. When the pH value fluctuates too much, it will not only reduce the desulfurization efficiency and cause the outlet SO2 concentration to exceed the standard, but also may cause corrosion and scaling problems of the equipment in the tower, increasing the maintenance cost and operation risk of the system.

[0003] The challenges faced by power plant desulfurization systems, especially the difficulty in pH control in the absorber, reveal several drawbacks of existing technologies:

[0004] Slow response speed: Traditional control systems may not be able to respond quickly to rapid changes in unit load, resulting in delayed adjustment of slurry supply and additives when the load suddenly increases or decreases, and inability to maintain pH stability in time.

[0005] Insufficient control accuracy: Fixed control parameters and simple control strategies may not be able to adapt to fluctuations in coal quality, resulting in insufficient pH control accuracy and inability to guarantee desulfurization efficiency and gypsum quality.

[0006] Reliance on experience: Many desulfurization systems rely too much on the operator’s experience for manual adjustments, which is not only inefficient but also prone to misjudgment and operational errors when faced with complex and rapidly changing operating conditions.

[0007] Equipment corrosion and scaling: Large fluctuations in pH value will accelerate the corrosion rate of equipment in the tower and promote the formation of scale, which not only shortens the service life of the equipment, but also increases the difficulty and cost of cleaning and maintenance.

[0008] Environmental risks: Excessive SO2 concentration at outlets not only violates environmental regulations, but may also have serious impacts on the surrounding environment and human health, increasing the company's environmental responsibilities and legal risks.

[0009] Increased energy consumption: In order to cope with pH fluctuations, operators may have to increase the amount of slurry supplied or the amount of additives added, which not only increases the consumption of raw materials but also increases the energy consumption of the system. Summary of the invention

[0010] In order to overcome the defects of the prior art, the present invention provides a method for stabilizing the pH value of desulfurization slurry based on the theoretical slurry supply amount. The technical solution of the present invention is:

[0011] A method for stabilizing the pH value of desulfurization slurry based on theoretical slurry supply, comprising the following steps:

[0012] (1) Calculate the mass and amount of SO2;

[0013] (2) Calculate the mass of CaCO3 required to absorb SO2;

[0014] (3) Calculate the basic slurry flow rate for absorbing SO2 and maintaining the pH of the absorption tower unchanged, obtain the mass of CaCO3 required for absorbing SO2 through step (2), and obtain the density of limestone slurry through a limestone slurry densitometer, and calculate the required limestone slurry supply amount;

[0015] (4) Calculate the pH deviation limestone slurry flow compensation;

[0016] (5) Determine the theoretical slurry supply.

[0017] The step (1) is specifically as follows:

[0018] The inlet flue gas CEMS device was used to measure the SO2 concentration of the inlet flue gas, and the flue gas flow meter was used to measure the inlet flue gas flow of the absorber. The SO2 mass entering the absorber per unit time was calculated:

[0019] Then the amount of SO2 entering the absorption tower is obtained:

[0020] The step (2) is specifically as follows: according to the calcium-sulfur ratio Ga / S designed for the absorption tower, the calcium-sulfur ratio is a constant, that is, to maintain the absorption tower reaction, the amount of CaCO3 required to absorb 1 mole of SO2 is obtained as follows:

[0021]

[0022] Then the mass of CaCO3 required to absorb SO2 is obtained:

[0023]

[0024] The step (3) is specifically as follows:

[0025] The basic slurry supply of the limestone is:

[0026]

[0027] The step (4) is specifically as follows:

[0028] Calculate the amount deviation of H+ in the absorption tower based on the measured pH value and the expected pH value

[0029] According to H + In the reaction formula with CaCO3, the molar ratio is 2:1, and the amount of CaCO3 that needs to be increased or decreased is:

[0030]

[0031] Then the mass of CaCO3 that needs to be increased or decreased is:

[0032]

[0033] The pH deviation limestone slurry flow compensation is obtained as follows:

[0034]

[0035] The step (5) is specifically as follows:

[0036] Q 理论供浆 =k1*Q 基本供浆 +k2+k3*Q 供浆补偿 ;

[0037] Right now:

[0038]

[0039] Also includes the steps for correction:

[0040] When water flushing causes the pH value indication to be inaccurate, Q 供浆补偿 Calculation error, at this time Q 供浆补偿 Set to 0, then:

[0041]

[0042] When the inlet flue gas CEMS measuring device is back-flushed and calibrated, resulting in inaccurate indication of the inlet SO2 concentration, the slurry supply mode is switched to a mode in which the actual pH value of the absorption tower is used as feedback and the expected pH value of the absorption tower is used as the set value.

[0043] The invention has the advantages of solving the problem that the slurry supply cannot quickly track the changes of boiler load and coal sulfur content during normal operation of a normal thermal power unit, reducing the fluctuation amplitude of the slurry supply, and keeping the pH value of the absorber slurry within a suitable variation range.

[0044] Precise control: Through real-time monitoring and data collection, this method can accurately calculate the required theoretical slurry supply, thereby achieving precise control of pH value.

[0045] High degree of automation: The integration of automatic feedback adjustment mechanism reduces human intervention and improves the degree of automation and response speed of operations.

[0046] Improve desulfurization efficiency: By maintaining a suitable pH value, optimize the desulfurization reaction conditions, improve the SO2 removal efficiency, and reduce the risk of excessive SO2 concentration at the outlet. DETAILED DESCRIPTION

[0047] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0048] The present invention relates to a method for stabilizing the pH value of a desulfurization slurry based on a theoretical slurry supply amount, comprising the following steps:

[0049] (1) Calculate the mass and amount of SO2;

[0050] (2) Calculate the mass of CaCO3 required to absorb SO2;

[0051] (3) Calculate the basic slurry flow rate for absorbing SO2 and maintaining the pH of the absorption tower unchanged, obtain the mass of CaCO3 required for absorbing SO2 through step (2), and obtain the density of limestone slurry through a limestone slurry densitometer, and calculate the required limestone slurry supply amount;

[0052] (4) Calculate the pH deviation limestone slurry flow compensation;

[0053] (5) Determine the theoretical slurry supply.

[0054] The above steps achieve the following:

[0055] Precise control: By accurately calculating the required CaCO3 mass, the efficiency of the desulfurization reaction can be ensured and unnecessary chemical waste can be reduced.

[0056] pH stability: By maintaining the stability of the pH value in the absorption tower, the desulfurization efficiency can be improved, SO2 emissions can be reduced, and environmental protection requirements can be met.

[0057] Dynamic adjustment: According to the real-time monitoring and deviation of pH value, the slurry supply is dynamically adjusted to achieve real-time control of the desulfurization process.

[0058] The step (1) is specifically as follows:

[0059] The inlet flue gas CEMS device was used to measure the SO2 concentration of the inlet flue gas, and the flue gas flow meter was used to measure the inlet flue gas flow of the absorber. The SO2 mass entering the absorber per unit time was calculated:

[0060] Then the amount of material entering the absorption tower S02 is obtained:

[0061] The step (2) is specifically as follows: according to the calcium-sulfur ratio Ga / S designed for the absorption tower, the calcium-sulfur ratio is a constant, that is, to maintain the absorption tower reaction, the amount of CaCO3 required to absorb 1 mole of SO2 is obtained as follows:

[0062]

[0063] Then the mass of CaCO3 required to absorb SO2 is obtained:

[0064]

[0065] The step (3) is specifically as follows:

[0066] The basic slurry supply of the limestone is:

[0067]

[0068] The step (4) is specifically as follows:

[0069] According to the measured pH value and the expected pH value, calculate the H + The amount of substance deviation:

[0070] According to H + In the reaction formula with CaCO3, the molar ratio is 2:1, and the amount of CaCO3 that needs to be increased or decreased is:

[0071]

[0072] Then the mass of CaCO3 that needs to be increased or decreased is:

[0073]

[0074] The pH deviation limestone slurry flow compensation is obtained as follows:

[0075]

[0076] The step (5) is specifically as follows:

[0077] Q 理论供浆 =k1*Q 基本供浆 +k2+k3*Q 供浆补偿 ;

[0078] Right now:

[0079]

[0080] Also includes the steps for correction:

[0081] When water flushing causes the pH value indication to be inaccurate, Q 供浆补偿 Calculation error, at this time Q 供浆补偿 Set to 0, then:

[0082]

[0083] When the inlet flue gas CEMS measuring device is back-flushed and calibrated, resulting in inaccurate indication of the inlet SO2 concentration, the slurry supply mode is switched to a mode in which the actual pH value of the absorption tower is used as feedback and the expected pH value of the absorption tower is used as the set value.

[0084] In the above formula, the letters have the following meanings:

[0085] (1) is the SO2 concentration at the absorption tower entrance, in kg / m 3 .

[0086] (2)Q 入口烟气 is the flue gas flow rate at the absorption tower inlet, in m 3 / h.

[0087] (3) It is the mass of SO2 entering the absorption tower, in kg.

[0088] (4) It is the amount of SO2 substance entering the absorption tower, in mol.

[0089] (5) The amount of CaCO3 required to absorb the SO2 entering the absorption tower, in mol.

[0090] (6) The mass of CaCO3 required to absorb the SO2 entering the absorption tower, in kg.

[0091] (7)Q 基本供浆 The slurry flow rate of CaCO3 required to absorb SO2 entering the absorption tower is m 3 / h.

[0092] (8) 64 and 100 are the molar masses of SO2 and CaCO3, respectively, in g / mol.

[0093] (9)Ga / S is the absorption tower design parameter, calcium-sulfur ratio, the amount of CaCO3 required to absorb 1 mole of SO2.

[0094] (10)ρ 供浆 It is the slurry density, that is, the density of limestone powder mixed with water.

[0095] (11) 2700 and 1000 are the densities of CaCO3 and water, respectively, in kg / m 3 .

[0096] (12)h 吸收塔 is the liquid level of the absorption tower, unit is m.

[0097] (13)r 吸收塔 is the radius of the absorption tower, in m.

[0098] (14)Q 供浆补偿 In order to adjust the current pH value of the absorption tower to the desired value, the amount of slurry supply required or reduced.

[0099] (15) k1 is the basic slurry supply correction coefficient.

[0100] (16) k2 is the correction deviation of basic slurry supply.

[0101] (17) K3 is the pH deviation compensation adjustment coefficient, which adjusts the pH change response speed.

[0102] In the present invention, the theoretical slurry supply is calculated according to the inlet SO2 concentration, the inlet flue gas volume, the calcium-sulfur ratio and the slurry supply concentration, and then the theoretical slurry supply is compensated up and down according to the pH value deviation. The theoretical slurry supply is used as the set value, and the actual slurry supply and pH value are used as feedback to overcome the problem of large pH value fluctuations when a single pH feedback regulation loop is used.

[0103] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for stabilizing the pH value of desulfurization slurry based on theoretical slurry supply, characterized in that: The steps include: (1) Calculate the mass and amount of SO2; (2) Calculate the mass of CaCO3 required to absorb SO2; (3) Calculate the basic slurry flow rate for absorbing SO2 and maintaining the pH of the absorption tower unchanged, obtain the mass of CaCO3 required for absorbing SO2 through step (2), and obtain the density of limestone slurry through a limestone slurry densitometer, and calculate the required limestone slurry supply amount; (4) Calculate the pH deviation limestone slurry flow compensation; (5) Determine the theoretical slurry supply.

2. The method for stabilizing the pH value of desulfurization slurry based on theoretical slurry supply according to claim 1, characterized in that: The step (1) is specifically as follows: The inlet flue gas CEMS device was used to measure the SO2 concentration of the inlet flue gas, and the flue gas flow meter was used to measure the inlet flue gas flow of the absorber. The SO2 mass entering the absorber per unit time was calculated: Then the amount of SO2 entering the absorption tower is obtained:

3. The method for stabilizing the pH value of desulfurization slurry based on theoretical slurry supply according to claim 2, characterized in that: The step (2) is specifically as follows: according to the calcium-sulfur ratio Ga / S designed for the absorption tower, the calcium-sulfur ratio is a constant, that is, to maintain the absorption tower reaction, the amount of CaCO3 required to absorb 1 mole of SO2 is obtained as follows: Then the mass of CaCO3 required to absorb SO2 is obtained:

4. The method for stabilizing the pH value of desulfurization slurry based on theoretical slurry supply according to claim 3, characterized in that: The step (3) is specifically as follows: The basic slurry supply of the limestone is:

5. The method for stabilizing the pH value of desulfurization slurry based on theoretical slurry supply according to claim 4, characterized in that: The step (4) is specifically as follows: According to the measured pH value and the expected pH value, calculate the H + The amount of substance deviation According to H + In the reaction formula with CaCO3, the molar ratio is 2:1, and the amount of CaCO3 that needs to be increased or decreased is: Then the mass of CaCO3 that needs to be increased or decreased is: The pH deviation limestone slurry flow compensation is obtained as follows:

6. The method for stabilizing the pH value of desulfurization slurry based on theoretical slurry supply according to claim 5, characterized in that: The step (5) is specifically as follows: Q 理论供浆 =k1*Q 基本供浆 +k2+k3*Q 供浆补偿 ; Right now:

7. The method for stabilizing the pH value of desulfurization slurry based on theoretical slurry supply according to claim 6, characterized in that: Also includes the steps for correction: When water flushing causes the pH value indication to be inaccurate, Q 供浆补偿 Calculation error, at this time Q 供浆补偿 Set to 0, then: When the inlet flue gas CEMS measuring device is back-flushed and calibrated, resulting in inaccurate indication of the inlet SO2 concentration, the slurry supply mode is switched to a mode in which the actual pH value of the absorption tower is used as feedback and the expected pH value of the absorption tower is used as the set value.

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