A water quality calculation and control method for a wet desulfurization tower

Abstract

A method for calculating and controlling the water quality of a wet desulfurization tower belongs to the technical field of environmental protection. It includes a desulfurization tower with the desulfurization solution recycled. The desulfurization system is provided with a water replenishment port, an alkali liquor replenishment port, a flue gas inlet, a spray pipe, a flue gas outlet, a sewage discharge port and a slurry circulation outlet. By analyzing the material balance of the desulfurization system and simplifying its algorithm, a water balance calculation formula is established. The concept of slurry concentration multiple is introduced and its algorithm formula is determined. By calculating the slurry discharge amount per unit time, the desulfurization system is guided to control and adjust the sewage discharge flow. By interlocking the tap water replenishment amount and the circulating water level, the desulfurization system is guided to control and adjust the tap water replenishment amount, so that the entire desulfurization system maintains balance, and the sewage discharge concentration of the desulfurization system maintains a constant target set value. The slurry concentration multiple can be used to assist and guide the operation analysis of the desulfurization system.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection, and more specifically, to a method for calculating and controlling the water quality of a wet desulfurization tower. Background Art

[0002] Wet desulfurization is one of the most common flue gas purification methods, which has the advantages of high desulfurization efficiency, mature process and good stability, and is widely used in industries such as coal-fired power plants and solid waste disposal. Its reaction principle is to dissolve alkaline agents in water as the desulfurization solution, and spray the desulfurization solution to fully contact and mix with the flue gas within a certain gas-liquid ratio range, so as to remove acidic gases such as sulfur dioxide and hydrogen chloride in the flue gas.

[0003] The main equipment for wet desulfurization is the wet desulfurization tower. In order to maintain a suitable reaction gas-liquid ratio range, the desulfurization solution needs to be recycled, otherwise it will result in huge water consumption and a large amount of salt-containing wastewater. Recycling the desulfurization solution will increase the concentration of the circulating liquid. The circulating liquid can be stored in an independent circulating water tank, or the lower space of the desulfurization tower can be used as a storage water tank. Since it contains multiple inlets and multiple outlets, it is difficult to control the water volume balance and water quality stability of the circulating liquid during the operation of the desulfurization tower. Summary of the Invention

[0004] To solve the above problems, the purpose of the present invention is to provide a method for calculating and controlling the water quality of a wet desulfurization tower. By establishing a simplified water balance calculation formula for the desulfurization tower, introducing the concept of slurry concentration multiple, establishing its algorithm formula based on water balance parameters, reasonably designing the algorithm logic and steps of each balance parameter, and selecting the tap water makeup flow rate and slurry drainage flow rate as the two main variables for interlocking control of the desulfurization system, the water volume balance and slurry drainage concentration stability during the operation of the desulfurization system are maintained. The specific contents are as follows:

[0005] A method for calculating and controlling the water quality of a wet desulfurization tower, the method comprising the following contents:

[0006] Step 1, analyze the material balance relationship of the desulfurization system, simplify its algorithm, and establish a water balance calculation formula according to the simplification result:

[0007] Q b = Q y + Q p + Q h

[0008] wherein, Q b is the makeup water volume per unit time, with the unit of m 3 / h,

[0009] Q y is the droplet amount carried by the flue gas per unit time, with the unit of m 3 / h,

[0010] Q p is the waste liquid discharge volume per unit time, with the unit of m 3 / h,

[0011] Q h is the water evaporation volume per unit time, with the unit of m 3 / h;

[0012] Step 2: Define the concept of the slurry concentration multiple N. N represents the ratio of the concentration of the slurry discharged from the deacidification system to the concentration of the salt solution generated by the deacidification reaction when the deacidification solution reacts with the flue gas to form a salt solution and then the salt solution is circulated and concentrated into a slurry in the deacidification system until it is discharged from the deacidification system. The algorithm formula for determining the slurry concentration multiple is as follows:

[0013]

[0014] where N is the slurry concentration multiple, dimensionless,

[0015] Q y is the droplet amount carried by the flue gas per unit time, with the unit of m 3 / h,

[0016] Q p is the waste liquid discharge volume per unit time, with the unit of m 3 / h;

[0017] Step 3: Calculate the salt generation amount M per unit time of deacidification according to the acidic gas component content at the flue gas inlet and the deacidification efficiency. The deacidification efficiency is taken according to the design value of the deacidification system. The acidic gas component content can be read in real time by setting an on-line monitoring device for gas component concentration at the flue gas inlet of the deacidification tower, or the acidic gas generation amount can be calculated through the elemental components before material combustion, and the acidic gas content entering the deacidification system can be calculated after considering the treatment efficiency of the process before deacidification.

[0018] According to the definition of the slurry concentration multiple N, the relationship between the salt generation amount M per unit time of deacidification and the slurry concentration multiple N is:

[0019]

[0020] where N is the slurry concentration multiple, dimensionless,

[0021] C is the concentration of the deacidification circulating slurry, with the unit of kg / m 3 ,

[0022] M is the salt generation amount per unit time of deacidification, with the unit of kg / h,

[0023] Q b is the makeup water volume per unit time, with the unit of m 3 / h,

[0024] Set the target value of the deacidification circulating slurry concentration C. The effective range of C takes into account the water consumption saving of the deacidification system, while ensuring the deacidification efficiency of the deacidification system and the downstream treatment capacity of saline wastewater;

[0025] Step 4: Calculate the amount of droplets Q carried by the flue gas per unit time at the deacidification tower flue gas outlet according to the relationship curve between the inlet and outlet temperature of the deacidification tower and the amount of water carried by the flue gas. y The relationship curve between the inlet and outlet temperature of the deacidification tower and the water content of the flue gas can be obtained through experiments, and the curve can be input into the deacidification system for comparison reading or fitted into a correlation formula for calculation;

[0026] Step 5: Combine the calculation formulas for the slurry concentration multiple N in step 2 and step 3,

[0027]

[0028] Derived waste liquid discharge per unit time Q p The calculation formula is:

[0029]

[0030] Among them, Q p The waste liquid discharge per unit time, in m 3 / h,

[0031] M is the amount of salt generated per unit time during deacidification, in kg / h.

[0032] C is the concentration of deacidification circulating slurry, unit: kg / m 3 ,

[0033] Q y is the amount of droplets carried by smoke per unit time, in m 3 / h,

[0034] According to the calculated waste liquid discharge volume per unit time Q p Value, the deacidification system issues a control instruction on the sewage flow rate;

[0035] Step 6: Maintain the water balance in the deacidification system, interlock the tap water replenishment flow rate regulating device and the deacidification circulating water level, so that the deacidification circulating water level remains unchanged, and the deacidification system issues a control instruction for the tap water replenishment flow rate based on the liquid level control;

[0036] Step 7: Calculate the water replenishment volume per unit time Q b , which includes tap water replenishment, flue gas condensate water and alkali solution replenishment, namely:

[0037] Q b =Q b1 +Q b2+Q b3

[0038] Among them, Q b is the water make-up volume per unit time, with the unit of m 3 / h,

[0039] Q b1 is the tap water make-up volume per unit time, with the unit of m 3 / h,

[0040] Q b2 is the flue gas condensation water volume per unit time, with the unit of m 3 / h,

[0041] Q b3 is the lye make-up volume per unit time, with the unit of m 3 / h,

[0042] Q b1 is read through the flowmeter set on the tap water pipeline; Q b2 can be calculated through the inlet and outlet temperatures and moisture content of the flue gas. When the outlet flue gas does not reach the water vapor saturation state, Q b2 is equal to 0; Q b3 is read through the flowmeter set on the lye pipeline;

[0043] Calculate the slurry concentration multiple N using the formulas in Step 2 and Step 3. As one of the monitoring indicators of the deacidification system, it assists in operation analysis and guides long-term operation.

[0044] As a further improvement of the present invention, the deacidification water of the deacidification tower is recycled. The deacidification system is provided with a water make-up port, a lye make-up port, a flue gas inlet, a spray pipe, a flue gas outlet, a sewage discharge port, and a slurry circulation outlet. The material inlet and outlet conditions are as follows:

[0045] Material inlet = tap water make-up + lye supplement + inlet flue gas + slurry circulation inlet,

[0046] Material outlet = outlet flue gas + flue gas carried droplets + evaporated water + slurry circulation discharge +

[0047] slurry sewage discharge,

[0048] On the premise of the material balance of the deacidification tower, the inlet and outlet materials are equal.

[0049] As a further improvement of the present invention, the material balance relationship of the deacidification tower can be simplified as:

[0050] Water make-up + salts generated by deacidification = flue gas carried droplets + evaporated water + slurry sewage discharge.

[0051] As a further improvement of the present invention, the salt generation amount M per unit time of deacidification includes sodium sulfate, sodium chloride, and sodium bromide generated by the deacidification reaction. Its calculation method is:

[0052]

[0053] Among them, M is the salt production amount per unit time of deacidification, with the unit of kg / h.

[0054] is the production amount of sodium sulfate per unit time, with the unit of kg / h.

[0055] M NaCl is the production amount of sodium chloride salt per unit time, with the unit of kg / h.

[0056] M NaBr is the production amount of sodium bromide salt per unit time, with the unit of kg / h.

[0057] In the above relational expressions,

[0058]

[0059] Among them, is the mass flow rate of SO 2 in the flue gas at the inlet of the deacidification tower, with the unit of kg / h.

[0060] M HCl is the mass flow rate of HCl in the flue gas at the inlet of the deacidification tower, with the unit of kg / h.

[0061] M HBr is the mass flow rate of HBr in the flue gas at the inlet of the deacidification tower, with the unit of kg / h.

[0062] α SO2 and α HCl and α HBr are the sulfur dioxide removal efficiency, hydrogen chloride removal efficiency, and hydrogen bromide removal efficiency of the designed deacidification system in sequence, with the unit of %.

[0063] Mr HCl and Mr NaCl and Mr HBr and Mr NaBr are the molar masses of sulfur dioxide, sodium sulfate, hydrogen chloride, sodium chloride, hydrogen bromide, and sodium bromide in sequence, with the unit of g / mol.

[0064] As a further improvement of the present invention, the concentration C of the deacidification circulating slurry set in the deacidification system is the slurry discharge concentration of the deacidification system. The upper limit of the C value depends on the salt solubility in the circulating liquid, the designed deacidification efficiency, and the downstream's ability to treat the concentration of the salt-containing wastewater. The lower limit of the C value depends on the water consumption limit of the deacidification system and the downstream's ability to treat the total amount of the salt-containing wastewater.

[0065] As a further improvement of the present invention, the deacidification system issues a control instruction for the sewage discharge flow rate according to the calculated sewage discharge amount Q of the waste liquid per unit time p Specifically, by controlling the opening degree of the pipeline valve connected to the sewage discharge port of the deacidification tower or the operating speed of the transfer pump, the sewage discharge flow rate is maintained at Q p , the deacidification system can adopt manual adjustment or automatic interlocking of the sewage discharge amount, and the deacidification system can adopt continuous sewage discharge or intermittent sewage discharge.

[0066] As a further improvement of the present invention, the calculation method of the flue gas condensation water volume Q per unit time b2 when the flue gas at the outlet of the deacidification tower reaches the water vapor saturation state is as follows:

[0067]

[0068] Among them, Q b2 is the flue gas condensation water volume per unit time, with the unit of m 3 / h,

[0069] is the water vapor content in the flue gas at the inlet of the deacidification tower, with the unit of m 3 / h,

[0070] is the water vapor content in the flue gas at the outlet of the deacidification tower, with the unit of m 3 / h,

[0071] can be read in real time by setting a humidity on-line monitoring device at the flue gas inlet of the deacidification tower, or can be obtained by calculating the elemental composition before the material combustion; Affected by the flue gas temperature at the outlet of the deacidification tower, according to the curve of water temperature and saturation content, its value is equal to the water vapor content in the flue gas at the outlet of the deacidification tower.

[0072] As a further improvement of the present invention, only by setting one parameter of the deacidification circulating slurry concentration C, the deacidification system can automatically adjust the two variables of the tap water make-up amount Q per unit time b1 and the waste liquid sewage discharge amount Q per unit time p to maintain the water volume balance during operation and the slurry sewage discharge concentration stable at the C value.

[0073] The beneficial effects of the present invention are as follows:

[0074] (1) In terms of water quality calculation, a simplified water balance formula for the deacidification system is established, the concept of slurry concentration multiple is introduced and its algorithm formula based on water balance parameters is established, which simplifies the calculation and assists the operation monitoring of the deacidification system.

[0075] (2) In terms of water quality control, based on the set sewage concentration of the deacidification tower, two parameters, namely the slurry sewage discharge and tap water make-up of the deacidification system, are selected as variables for control and adjustment to keep the water volume and quality of the deacidification system stable.

[0076] (3) Compared with the previous empirical control and fuzzy judgment, this method provides a detailed model analysis and calculation for the water quality control of the wet deacidification system, which is more persuasive for guiding engineering practice. Description of the Drawings

[0077] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0078] Figure 1 The material input and output balance of the deacidification tower for the water quality calculation and control method of a wet deacidification tower according to the embodiment of the present invention.

[0079] Figure 2 The simplified method of the material balance of the deacidification tower for the water quality calculation and control method of a wet deacidification tower according to the embodiment of the present invention.

[0080] Figure 3 The flow chart of the water quality calculation and control method of a wet deacidification tower according to the embodiment of the present invention.

[0081] Figure 4 The structure diagram of the deacidification system of the deacidification tower for the water quality calculation and control method of a wet deacidification tower according to the embodiment of the present invention,

[0082] In the figure, 1 is the deacidification tower, 2 is the flue gas inlet, 3 is the flue gas outlet, 4 is the influent flowmeter, 5 is the influent regulating valve, 6 is the alkali liquid flowmeter, 7 is the circulation pump, 8 is the spraying device, 9 is the sewage regulating valve, 10 is the sewage flowmeter, and 11 is the liquid level gauge.

[0083] Figure 5 The relationship curve between the inlet and outlet temperatures of the deacidification tower and the water volume carried by the flue gas in the water quality calculation and control method of a wet deacidification tower according to the embodiment of the present invention.

[0084] Figure 6 The curve of the water temperature and saturation content in the water quality calculation and control method of a wet deacidification tower according to the embodiment of the present invention. Detailed Embodiments

[0085] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0086] It should be noted that if there are directional indications (such as up, down, left, right, front, back,...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative position relationship, movement conditions, etc. between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0087] In addition, in the description of the present invention, the terms used are only for the purpose of illustration and are not intended to limit the scope of the present invention. The terms "include" and / or "comprise" are used to specify the existence of the described elements, steps, operations, and / or components, but do not exclude the existence or addition of one or more other elements, steps, operations, and / or components. The terms "first", "second", etc. may be used to describe various elements, do not represent an order, and do not limit these elements. In addition, in the description of the present invention, unless otherwise specified, "a plurality of" means two or more. These terms are only used to distinguish one element from another. With reference to the following drawings, these and / or other aspects become obvious, and it is easier for those of ordinary skill in the art to understand the description of the embodiments of the present invention. The drawings are only used to depict the embodiments of the present invention for the purpose of illustration. Those skilled in the art will easily recognize from the following description that alternative embodiments of the structure and method shown in the present invention can be adopted without departing from the principles of the present invention. A method for calculating and controlling the water quality of a wet desulfurization tower described in the embodiments of the present invention, the material input and output balance of the desulfurization tower is as Figure 1 described, and the simplified method for the material input and output balance of the desulfurization tower is as Figure 2 shown.

[0088] Taking the desulfurization tower as the analysis object, the interfaces included in the desulfurization system are a water replenishment port, an alkali liquor replenishment port, a flue gas inlet, a spray pipe, a flue gas outlet, a sewage discharge port, and a slurry circulation outlet.

[0089] Tap water is replenished into the desulfurization system through the water replenishment port, alkali liquor is replenished into the desulfurization system through the alkali liquor replenishment port, the flue gas before desulfurization enters the desulfurization system through the flue gas inlet, and the circulation of the slurry enters the desulfurization system through the spray pipe.

[0090] The deacidified flue gas, the liquid droplets carried by the flue gas, and the evaporated water characterized by pure water loss are discharged from the deacidification system through the flue gas outlet. The continuous blowdown of the slurry is discharged from the deacidification system through the blowdown port, and the circulating blowdown of the slurry is discharged from the deacidification system through the slurry circulation outlet.

[0091] During operation, the material balance of the deacidification system is as follows:

[0092] Make-up water from tap water + make-up of lye + inlet flue gas + slurry circulation in = outlet flue gas +

[0093] liquid droplets carried by the flue gas + evaporated water + slurry circulation out + slurry blowdown,

[0094] After analysis, the material balance of the deacidification system is simplified to:

[0095] Make-up water + formation of deacidified salts = liquid droplets carried by the flue gas + evaporated water + continuous slurry blowdown,

[0096] Among them, the formation of deacidified salts is solid, the make-up water, the evaporated water, and the continuous slurry blowdown are liquid, and the salts generated by the deacidification reaction are dissolved in water. A water balance formula based on volume units is established:

[0097] Make-up water = liquid droplets carried by the flue gas + evaporated water + continuous slurry blowdown,

[0098] The make-up water volume includes three parts, namely, the make-up water from tap water entering through the make-up water port, the make-up of lye entering through the lye make-up port, and the water in the flue gas entering through the flue gas inlet;

[0099] The liquid droplets carried by the flue gas are small liquid droplets containing salt in liquid state carried by the flue gas;

[0100] The evaporated water is characterized by pure water loss and contains no salt inside;

[0101] The continuous slurry blowdown is to continuously discharge the deacidified slurry from the deacidification system, and the slurry blowdown concentration is the same as the concentration of the circulating slurry in the deacidification system.

[0102] Based on the above water balance, the total amount of water inside the deacidification tower remains constant. The water quality calculation and control method of a wet deacidification tower described in the embodiments of the present invention, as Figure 3 shown, an embodiment method includes the following steps:

[0103] Step 1, analyze the material balance of the deacidification system, simplify its algorithm, and establish a water balance formula based on the simplified algorithm:

[0104] Q b =Q y +Q p +Q h

[0105] Among them, Q bThe water make-up volume per unit time, unit: m 3 / h,

[0106] Q y is the droplet volume carried by the flue gas per unit time, unit: m 3 / h,

[0107] Q p is the waste liquid discharge volume per unit time, unit: m 3 / h,

[0108] Q h is the water evaporation volume per unit time, unit: m 3 / h.

[0109] Step 2: Define the concept of the slurry concentration multiple N. N represents the ratio of the slurry discharge concentration to the concentration of the salt solution generated by the deacidification reaction. Since the concentration of the slurry is mainly increased due to the loss of pure water in the deacidification system, the algorithm formula for the slurry concentration multiple is established as:

[0110]

[0111] where N is the slurry concentration multiple, dimensionless quantity,

[0112] Q y is the droplet volume carried by the flue gas per unit time, unit: m 3 / h,

[0113] Q p is the waste liquid discharge volume per unit time, unit: m 3 / h.

[0114] Step 3: Calculate the salt generation amount M per unit time of deacidification according to the acidic gas component content at the flue gas inlet and the deacidification efficiency.

[0115] It is known that the volume of the flue gas at the inlet of the deacidification system is 15200 Nm 3 / h, the volume flow rate of SO 2 in the flue gas is 549 mg / Nm 3 , the volume flow rate of HCl is 137 mg / Nm 3 , the volume flow rate of HBr is 0 mg / Nm 3 , then

[0116] SO 2 mass flow rate

[0117] HCl mass flow rate M HCl = 15200×137×10 -6 kg / h = 2.082 kg / h,

[0118] HBr mass flow rate MHBr = 0 kg / h,

[0119] The acid gas removal efficiency of each component of the acid removal system is designed to be 100%, that is

[0120] The molar masses of sulfur dioxide, sodium sulfate, hydrogen chloride, sodium chloride, hydrogen bromide, and sodium bromide are as follows:

[0121] Mr HCl = 36.5 g / mol,

[0122] Mr NaCl = 58.5 g / mol, Mr HBr = 81 g / mol and Mr NaBr = 103 g / mol

[0123] The salt generation amount M per unit time of the acid removal system is the sum of the mass of sodium sulfate generated per unit time in the acid removal reaction the mass of sodium chloride M NaCl and the mass of sodium bromide M NaBr :

[0124]

[0125] Set the blowdown concentration of the acid removal system to 2%, that is, the slurry circulation concentration C = 20 kg / m3.

[0126] According to the definition of the slurry concentration multiple N, the relationship between the salt generation amount M per unit time of acid removal and the slurry concentration multiple N is:

[0127]

[0128] where N is the slurry concentration multiple, dimensionless,

[0129] C is the acid removal circulating slurry concentration, unit kg / m 3 ,

[0130] M is the salt generation amount per unit time of acid removal, unit kg / h,

[0131] Q b is the makeup water amount per unit time, unit m 3 / h.

[0132] Step 4, according to the relationship curve between the inlet and outlet temperatures of the acid removal tower and the water carried by the flue gas, calculate the droplet amount Q carried by the flue gas at the outlet of the acid removal tower per unit time y .

[0133] It is known that the inlet flue gas temperature of the deacidification tower is 134℃ and the outlet flue gas temperature is 45℃. The relationship curve between the inlet and outlet temperature of the deacidification tower and the water content of the flue gas is obtained through experiments (such as Figure 5 As shown), the horizontal axis is the flue gas inlet temperature t1, the vertical axis is the water content of the flue gas, and from top to bottom in the quadrant are the water content curves of different flue gas outlet temperatures t0.

[0134] From the curve, the water carrying capacity Q of the deacidification system when the flue gas inlet temperature t1 = 134 ° C and the flue gas outlet temperature t0 = 45 ° C y =0.17×10 -3 m3 / h.

[0135] Step 5: Combine the calculation formulas for the slurry concentration multiple N in step 2 and step 3,

[0136]

[0137] Derived waste liquid discharge per unit time Q p The calculation formula is:

[0138]

[0139] Substitute the parameter results obtained in step 3 and step 4, then:

[0140]

[0141] According to the calculated waste liquid discharge volume per unit time Q p The deacidification system issues a control instruction for the sewage discharge flow, which adjusts the valve opening of the pipeline connected to the sewage outlet of the deacidification tower and the waste liquid discharge volume per unit time Q p Interlocking is performed.

[0142] Step six, maintain the water balance in the deacidification system, interlock the tap water replenishment flow regulating device and the deacidification circulating water level to keep the deacidification circulating water level unchanged, and the deacidification system issues a control instruction for the tap water replenishment flow based on the liquid level control.

[0143] Step 7: Calculate the water replenishment volume per unit time Q b , which includes the tap water replenishment volume per unit time Q b1 , Flue gas condensation per unit time Q b2 And the amount of alkali solution replenishment per unit time Q b3 Three parts.

[0144] Read Q through the flow meter installed on the tap water pipeline b1 =2.80m3 / h;

[0145] By setting up an online humidity monitoring device at the flue gas inlet of the deacidification tower, the water vapor content in the flue gas inlet of the deacidification tower can be read

[0146] According to the curve of water temperature and saturation content (as Figure 6 shown), the saturated water vapor content at the flue gas outlet of the deacidification tower at 45 °C is 65 g / m 3 , then calculate

[0147] Then calculate the condensate water volume of the flue gas per unit time in the deacidification tower:

[0148]

[0149] Q b3 Read through the flowmeter set on the alkali liquid pipeline, and the value is Q b3 = 0.005 m3 / h;

[0150] Calculate the makeup water volume Q per unit time of the deacidification system b :

[0151] Q b = Q b1 + Q b2 + Q b3 = 2.80 + 2.94 + 0.005 = 5.75 m3 / h.

[0152] Use the formula in step three to calculate the slurry concentration multiple N:

[0153]

[0154] The above calculation and control method of the deacidification system only needs to set one parameter of the deacidification circulating slurry concentration C, and the deacidification system can automatically adjust the makeup water volume Q of tap water per unit time b1 and the waste liquid discharge volume Q per unit time p for two variables, and maintain the water volume balance during operation and the slurry discharge concentration stable at the C value.

[0155] It should be noted that when setting the deacidification circulating slurry concentration C, the maximum solubility of salts in the slurry needs to be considered, and the treatment capacity of the downstream sewage treatment facility for the maximum salt-containing wastewater concentration after the deacidification system discharges sewage should be considered. If it exceeds the upper limit of the wastewater concentration allowed by the sewage treatment facility, the wastewater needs to be diluted, resulting in poor economy, because the high concentration multiple of the deacidification system is obtained at the risk of reduced deacidification efficiency and increased corrosion of equipment and pipelines.

[0156] The water quality calculation and control method of a wet deacidification tower described in the embodiments of the present invention, a typical embodiment and application scenario are as Figure 4 shown. The deacidification system of the water quality calculation and control method of a wet deacidification tower includes the following contents:

[0157] The deacidification tower 1 uses lye to deacidify the flue gas.

[0158] The flue gas inlet 2 and the flue gas outlet 3 are located on the side wall and the top of the deacidification tower 1 respectively.

[0159] An interface of the deacidification tower 1 is connected to the tap water pipeline, on which a water inlet flowmeter 4 and a water inlet regulating valve 5 are arranged.

[0160] An interface of the deacidification tower 1 is connected to the lye pipeline, on which a lye flowmeter 6 is arranged.

[0161] An interface of the deacidification tower 1 is connected to the slurry circulation pipeline, on which a circulation pump 7 is arranged.

[0162] An interface of the deacidification tower 1 is connected to the spraying device 8, and the inlet of the spraying device 8 is connected to the outlet of the circulation pump 7.

[0163] The outlet pipeline of the circulation pump 7 is also connected to the sewage pipeline, on which a sewage regulating valve 9 and a sewage flowmeter 10 are arranged.

[0164] A liquid level gauge 11 is arranged at the lower part of the deacidification tower 1.

[0165] Establish the water balance of the deacidification system:

[0166] Make-up water = liquid droplets carried by flue gas + evaporated water + continuous slurry sewage discharge

[0167] When the deacidification system is running, the circulating solution is first injected into the deacidification tower 1 through the water inlet pipeline and the lye pipeline, and under the action of the circulation pump 7, the circulating solution is transported to the spraying device 8. The spraying device 8 makes the circulating solution re-enter the deacidification tower 1 and fall into the lower water outlet space. The acid-containing flue gas enters from the flue gas inlet 2, contacts and reacts with the alkaline spraying liquid, and is discharged from the flue gas outlet 3.

[0168] Using two expressions and calculation methods of the slurry concentration multiple, one is based on its conceptual definition, that is, the ratio of the slurry discharge concentration to the concentration of the salt solution generated by the deacidification reaction, and the other considers its formation factors, that is, the concentration of the slurry is mainly increased due to the loss of pure water in the deacidification system, the following relational expressions are derived:

[0169]

[0170] Among them, the target concentration of the slurry sewage is considered set, the amount of deacidification salts generated per unit time is calculated through the content of acidic components in the flue gas, and the amount of liquid droplets carried by the flue gas can be obtained through the demisting performance experiment of the deacidification tower, then the slurry sewage discharge amount per unit time of the deacidification system can be calculated.

[0171] Based on the calculated slurry sewage discharge per unit time, the opening degree of the interlocked sewage regulating valve 9 and the flow indication of the sewage flowmeter 10 are adjusted to stabilize the sewage flowmeter 10 at the calculated value of the slurry sewage discharge.

[0172] While the acid-base neutralization reaction occurs in the deacidification tower 1, the flue gas temperature decreases. The flue gas changes from an unsaturated state of water vapor to a saturated state and then to a supersaturated state, and part of it will condense into liquid water and fall into the interior of the deacidification tower 1, becoming part of the makeup water for the deacidification system.

[0173] The injection amount of the lye is based on the content of acidic gases in the flue gas, and the water in the lye is the second part of the makeup water for the deacidification system.

[0174] The makeup water from the tap water pipeline is the third part of the makeup water for the deacidification system. The deacidification system also relies on adjusting the makeup water volume of the tap water to maintain the stable liquid level of the deacidification system. The liquid level indication of the liquid level gauge 11 is interlocked with the inlet regulating valve 5 on the tap water pipeline to keep the indication of the liquid level gauge 11 stable.

[0175] Then, the deacidification system completes the control of the sewage flow and the tap water makeup water flow, achieving the water volume balance and constant sewage concentration of the deacidification system.

[0176] Through further calculation, the first part of the makeup water of the deacidification system is obtained by calculating the difference in the water content of the flue gas at the inlet and outlet of the deacidification tower 1. The second part of the makeup water is read through the lye flowmeter 6, and the third part of the makeup water is read through the inlet flowmeter 4. The sum of these three parts is calculated to obtain the total makeup water volume of the deacidification system. Its value is determined using any of the calculation methods for the slurry concentration multiple, which reflects the relationship between the acid removal ability and the makeup water volume and is of great significance for guiding the long-term stable operation of the deacidification system and measuring the water-saving index of the deacidification system.

[0177] In the specification provided here, a large number of specific details are described. However, it can be understood that the embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures, and technologies are not shown in detail so as not to obscure the understanding of this specification.

[0178] In addition, those of ordinary skill in the art can understand that although some of the embodiments described herein include certain features included in other embodiments rather than other features, the combination of the features of different embodiments means that it is within the scope of the present invention and forms different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0179] Those skilled in the art should understand that although the present invention has been described with reference to exemplary embodiments, various changes can be made and its elements can be replaced with equivalents without departing from the scope of the present invention. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the present invention without departing from the substantial scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed, but the present invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for calculating and controlling water quality in a wet deacidification tower, characterized in that: The method comprises the following contents: Step 1: Analyze the material balance relationship of the deacidification system, simplify the algorithm, and establish the water balance calculation formula based on the simplified results: Q b =Q y +Q p +Q h Among them, Q b is the amount of water replenished per unit time, in m 3 / h, Q y is the amount of droplets carried by smoke per unit time, in m 3 / h, Q p The waste liquid discharge per unit time, in m 3 / h, Q h is the amount of water evaporation per unit time, in m 3 / h; Step 2: Define the concept of slurry concentration multiple N. N represents the ratio of the slurry discharge concentration to the concentration of the salt solution generated by the deacidification reaction when the deacidification solution reacts with the flue gas to generate a salt solution, and the salt solution circulates in the deacidification system and is concentrated into slurry until it is discharged from the deacidification system. The algorithm formula for establishing the slurry concentration multiple is: Where N is the concentration multiple of the slurry, which has no unit dimension. Step 3: Calculate the salt generation per unit time M of deacidification according to the acid gas component content at the flue gas inlet and the deacidification efficiency. The deacidification efficiency is determined according to the design value of the deacidification system. The acid gas component content is read in real time by setting an online gas component concentration monitoring device at the flue gas inlet of the deacidification tower, or by calculating the acid gas generation by the elemental components before material combustion, and the acid gas content entering the deacidification system is calculated after considering the processing efficiency of the deacidification front-end process. According to the definition of N, the relationship between M and N is: in, C is the concentration of deacidification circulating slurry, unit: kg / m 3 , M is the amount of salt generated per unit time during deacidification, in kg / h. Set the target value of C. The effective range of C takes into account the water consumption saving of the deacidification system, while ensuring the deacidification efficiency of the deacidification system and the downstream treatment capacity of saline wastewater; Step 4: Calculate the Q of the flue gas outlet of the deacidification tower according to the relationship curve between the inlet and outlet temperature of the deacidification tower and the water content of the flue gas. y The relationship curve between the inlet and outlet temperature of the deacidification tower and the water content of the flue gas is obtained through experiments. The curve is entered into the deacidification system for comparison and reading or fitted into a correlation formula to calculate Q y ; Step 5: Combine the calculation formulas of N in step 2 and step 3. Derived Q p The calculation formula is: According to the calculated Q p Value, the deacidification system issues a control instruction on the sewage flow rate; Step 6: Maintain the water balance in the deacidification system, interlock the tap water replenishment flow rate regulating device and the deacidification circulating water level, so that the deacidification circulating water level remains unchanged, and the deacidification system issues a control instruction for the tap water replenishment flow rate based on the liquid level control; Step 7: Calculate Q b , which includes tap water replenishment, flue gas condensate water and alkali solution replenishment, namely: Q b =Q b1 +Q b2 +Q b3 in, Q b1 The tap water replenishment volume per unit time, unit m 3 / h, Q b2 is the amount of flue gas condensation per unit time, in m 3 / h, Q b3 is the amount of alkali solution replenished per unit time, in m 3 / h, Q b1 Read through the flow meter installed on the water pipe; Q b2 It is calculated by the inlet and outlet temperature and moisture content of the flue gas. When the outlet flue gas does not reach the water vapor saturation state, Q b2 =0; Q b3 Read through the flow meter installed on the alkali solution pipeline; Use the formula in steps 2 and 3 to calculate N as one of the monitoring indicators of the deacidification system to assist in operation analysis and guide long-term operation.

2. The method for calculating and controlling water quality of a wet deacidification tower according to claim 1, characterized in that: The deacidification water of the deacidification tower is recycled. The deacidification system is equipped with a water replenishment port, an alkali liquid replenishment port, a flue gas inlet, a spray pipe, a flue gas outlet, a sewage outlet and a slurry circulation outlet. The material inlet and outlet conditions are as follows: Material in = tap water replenishment + alkali solution supplement + imported flue gas + slurry circulation in, Material out = outlet flue gas + liquid droplets carried by flue gas + evaporated water + slurry circulation discharge + slurry sewage discharge, Under the premise of material balance in the deacidification tower, the input and output materials are equal.

3. A method for calculating and controlling water quality of a wet deacidification tower according to claim 1 or 2, characterized in that: The material balance relationship of the deacidification tower is simplified to: Water replenishment + deacidification to generate salt = flue gas droplets + evaporated water + slurry sewage discharge.

4. The method for calculating and controlling water quality of a wet deacidification tower according to claim 1, characterized in that: M includes sodium sulfate, sodium chloride and sodium bromide generated by the deacidification reaction, and its calculation method is: in, M Na2SO4 is the amount of sodium sulfate generated per unit time, in kg / h, M NaCl is the amount of sodium chloride salt produced per unit time, in kg / h, M NaBr is the amount of sodium bromide salt produced per unit time, in kg / h, In the above relationship, in, is the mass flow rate of SO2 in the flue gas at the inlet of the deacidification tower, in kg / h, M HCl is the mass flow rate of HCl in the flue gas at the inlet of the deacidification tower, in kg / h, M HBr is the mass flow rate of HBr in the flue gas at the inlet of the deacidification tower, in kg / h, α HCl , α HBr They are the sulfur dioxide removal efficiency, hydrogen chloride removal efficiency and hydrogen bromide removal efficiency of the designed deacidification system, in %, Mr HCl Mr. NaCl Mr. HBr and Mr. NaBr They are the molar masses of sulfur dioxide, sodium sulfate, hydrogen chloride, sodium chloride, hydrogen bromide and sodium bromide, respectively, in g / mol.

5. The method for calculating and controlling water quality of a wet deacidification tower according to claim 1, characterized in that: The C of the deacidification system is the slurry discharge concentration of the deacidification system. The upper limit of the C value depends on the salt solubility in the circulating liquid, the designed deacidification efficiency and the downstream concentration treatment capacity for saline wastewater. The lower limit of the C value depends on the water consumption limit of the deacidification system and the downstream treatment capacity for the total amount of saline wastewater.

6. The method for calculating and controlling water quality of a wet deacidification tower according to claim 1, characterized in that: The deacidification system is based on the calculated Q p Issue a control instruction for the sewage flow rate, specifically by controlling the opening of the pipeline valve connected to the sewage outlet of the deacidification tower or the operating speed of the delivery pump to maintain the sewage flow rate at Q p The deacidification system adopts manual adjustment or automatic interlocking of sewage discharge volume, or adopts continuous sewage discharge or intermittent sewage discharge.

7. The method for calculating and controlling water quality of a wet deacidification tower according to claim 1, characterized in that: Q b2 The calculation method when the flue gas at the outlet of the deacidification tower reaches the water vapor saturation state is: in, is the water vapor content in the flue gas at the deacidification tower inlet, unit: m 3 / h, is the water vapor content in the flue gas at the outlet of the deacidification tower, unit: m 3 / h, The humidity can be obtained by setting an online humidity monitoring device at the flue gas inlet of the deacidification tower for real-time reading or by calculating the elemental composition of the material before combustion. Affected by the flue gas temperature at the outlet of the deacidification tower, according to the water temperature and saturation content curve, its value is equal to the water vapor content in the flue gas at the outlet of the deacidification tower.

8. The method for calculating and controlling water quality of a wet deacidification tower according to claim 1, characterized in that: Only one parameter C needs to be set, and the deacidification system will automatically b1 and Q p The two variables are adjusted to maintain the water balance during operation and the slurry discharge concentration stable at the C value.

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