Water quality calculation and control method for wet deacidification tower

Abstract

The invention discloses a water quality calculation and control method for a wet deacidification tower, and belongs to the technical field of environmental protection. A deacidification tower is included, a deacidification solution is recycled, a deacidification system is provided with a water replenishing port, an alkali liquor replenishing port, a flue gas inlet, a spraying pipe, a flue gas outlet, a drain outlet and a slurry circulating outlet, material balance of the deacidification system is analyzed, algorithm simplification is carried out on the material balance, a water balance calculation formula is established, the concept of slurry concentration multiple is introduced, and the algorithm formula is determined. The deacidification system is guided to control and adjust the pollution discharge flow by calculating the slurry discharge amount per unit time, and the deacidification system is guided to control and adjust the tap water supplement amount by interlocking the tap water supplement amount and the circulating water liquid level, so that the whole deacidification system is kept balanced, and the pollution discharge concentration of the deacidification system is kept at a constant target set value; the slurry concentration multiple can be used for assisting and guiding operation analysis of a deacidification system.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection, and in particular to a method for calculating and controlling water quality of a wet deacidification tower. Background Art

[0002] Wet deacidification is the most common flue gas purification method, with the advantages of high deacidification efficiency, mature technology and good stability. It has been widely used in coal-fired power plants, solid waste disposal and other industries. Its reaction principle is to dissolve alkaline reagents in water as deacidification solution, spray the deacidification solution with the flue gas in a certain gas-liquid ratio range to fully contact and react, thereby removing acidic gases such as sulfur dioxide and hydrogen chloride in the flue gas.

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

[0004] In order 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 deacidification tower, by establishing a simplified water balance calculation formula for the deacidification tower, introducing the concept of slurry concentration multiples, establishing an algorithm formula based on water balance parameters, rationally designing the algorithm logic and steps of each balance parameter, and selecting the tap water replenishment flow rate and slurry sewage discharge flow rate as the two main variables for the interlocking control of the deacidification system, so as to maintain the water balance and slurry sewage discharge concentration stability during the operation of the deacidification system. Specifically including the following contents:

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

[0006] 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:

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

[0008] Among them, Q b is the amount of water replenished per unit time, in m 3 / h,

[0009] Q y is the amount of droplets carried by smoke per unit time, in m 3 / h,

[0010] Q p The waste liquid discharge per unit time, in m 3 / h,

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

[0012] 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 after the deacidification solution reacts with the flue gas to generate a salt solution, and the salt solution circulates in the deacidification system and concentrates into slurry until it is discharged from the deacidification system. The algorithm formula for establishing the slurry concentration multiple is:

[0013]

[0014] Where N is the concentration multiple of the slurry, which has no unit dimension.

[0015] Q y is the amount of droplets carried by smoke per unit time, in m 3 / h,

[0016] Q p The waste liquid discharge per unit time, in m 3 / h;

[0017] Step three, according to the acid gas component content at the flue gas inlet and the deacidification efficiency, calculate the salt generation per unit time M of the deacidification. The deacidification efficiency is taken according to the design value of the deacidification system. The acid gas component content can be read in real time by setting a gas component concentration online monitoring device at the flue gas inlet of the deacidification tower. The acid gas generation can also be calculated by the elemental components before the material is burned, and the acid gas content entering the deacidification system is calculated after considering the processing efficiency of the deacidification front-end process.

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

[0019]

[0020] Where N is the concentration multiple of the slurry, which has no unit dimension.

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

[0022] M is the amount of salt generated per unit time during deacidification, in kg / h.

[0023] Q b is the amount of water replenished per unit time, in 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 amount of water replenished per unit time, in m 3 / h,

[0039] Q b1 The amount of tap water replenishment per unit time, unit m 3 / h,

[0040] Q b2 is the amount of flue gas condensate per unit time, in m 3 / h,

[0041] Q b3 is the amount of alkali solution replenished per unit time, in m 3 / h,

[0042] Q b1 Read through the flow meter installed on the water pipe; Q b2 It can be 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;

[0043] The formula in step 2 and step 3 is used to calculate the slurry concentration multiple N, which is used as one of the monitoring indicators of the deacidification system to assist in operation analysis and guide long-term operation.

[0044] As a further improvement of the present invention, the deacidification water of the deacidification tower is recycled, and the deacidification system is provided 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, and the material inlet and outlet conditions are as follows:

[0045] Material in = tap water replenishment + alkali solution supplement + imported flue gas + slurry circulation in,

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

[0047] Slurry drainage,

[0048] Under the premise of material balance in the deacidification tower, the input and output materials are equal.

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

[0050] Water replenishment + deacidification to generate salt = flue gas droplets + evaporated water + slurry sewage discharge.

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

[0052]

[0053] Wherein, M is the salt generation per unit time of deacidification, in kg / h,

[0054] is the amount of sodium sulfate generated per unit time, in kg / h,

[0055] M NaCl is the amount of sodium chloride salt produced per unit time, in kg / h,

[0056] M NaBr is the amount of sodium bromide salt produced per unit time, in kg / h,

[0057] In the above relationship,

[0058]

[0059] in, is the mass flow rate of SO2 in the flue gas at the inlet of the deacidification tower, in kg / h,

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

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

[0062] α SO2 , 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 %,

[0063] 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.

[0064] As a further improvement of the present invention, the deacidification circulating slurry concentration C of the deacidification system is set, which is the slurry discharge concentration of the deacidification system. The upper limit of the concentration 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 concentration 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.

[0065] As a further improvement of the present invention, the deacidification system is based on the calculated waste liquid discharge volume Q per unit time.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 can use manual adjustment or automatic interlocking of sewage discharge volume, and the deacidification system can use continuous sewage discharge or intermittent sewage discharge.

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

[0067]

[0068] Among them, Q b2 is the amount of flue gas condensate per unit time, in m 3 / h,

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

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

[0071] The humidity can be read in real time by setting up an online humidity monitoring device at the flue gas inlet of the deacidification tower, or it can be calculated based on 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.

[0072] As a further improvement of the present invention, only one parameter, the concentration C of the deacidification circulating slurry, needs to be set, and the deacidification system can automatically adjust the tap water replenishment volume Q per unit time. b1 And the waste liquid discharge per unit time Q p The two variables are adjusted to maintain the water balance during operation and the slurry discharge concentration stable at the C value.

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

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

[0075] (2) In terms of water quality control, based on the target set deacidification tower discharge concentration, the two parameters of deacidification system slurry discharge and tap water replenishment are selected as variables for control and adjustment to ensure that the water volume and water quality of the deacidification system are stable.

[0076] (3) Compared with the previous empirical control and fuzzy judgment, this method provides a detailed model analysis and calculation of water quality control in the wet deacidification system, which is more convincing in guiding engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0078] Figure 1 The invention discloses a method for calculating and controlling the water quality of a wet deacidification tower and a material inlet and outlet balance of the deacidification tower.

[0079] Figure 2 A simplified method for material balance of a deacidification tower is disclosed in an embodiment of the present invention, which is a method for calculating and controlling water quality of a wet deacidification tower.

[0080] Figure 3 The present invention is a flowchart of a method for calculating and controlling water quality in a wet deacidification tower according to an embodiment of the present invention.

[0081] Figure 4 This is a structural diagram of a deacidification tower deacidification system of a method for calculating and controlling water quality of a wet deacidification tower according to an embodiment of the present invention.

[0082] In the figure, 1 is a deacidification tower, 2 is a flue gas inlet, 3 is a flue gas outlet, 4 is a water inlet flow meter, 5 is a water inlet regulating valve, 6 is an alkali solution flow meter, 7 is a circulating pump, 8 is a spray device, 9 is a sewage regulating valve, 10 is a sewage flow meter, and 11 is a liquid level meter.

[0083] Figure 5 This is a relationship curve between the inlet and outlet temperature of a deacidification tower and the amount of water in flue gas in a water quality calculation and control method for a wet deacidification tower described in an embodiment of the present invention.

[0084] Figure 6 This is a curve of water temperature and saturation content in a water quality calculation and control method for a wet deacidification tower described in an embodiment of the present invention. DETAILED DESCRIPTION

[0085] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0087] In addition, in the description of the present invention, the terms used are for illustrative purposes only and are not intended to limit the scope of the present invention. The terms "include" and / or "comprise" are used to specify the presence of the elements, steps, operations and / or components, but do not exclude the presence or addition of one or more other elements, steps, operations and / or components. The terms "first", "second" and the like may be used to describe various elements, do not represent the order, and do not limit these elements. In addition, in the description of the present invention, unless otherwise specified, "multiple" means two or more. These terms are only used to distinguish one element from another. In conjunction with the following drawings, these and / or other aspects become apparent, and it is easier for a person of ordinary skill in the art to understand the description of the embodiments of the present invention. The accompanying drawings are used to depict the embodiments of the present invention for illustrative purposes only. Those skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods shown in the present invention may be adopted without departing from the principles of the present invention. A method for calculating and controlling the water quality of a wet deacidification tower described in an embodiment of the present invention, the material inlet and outlet balance of the deacidification tower is as follows Figure 1 As described above, a simplified method for balancing the inflow and outflow of materials in the deacidification tower is as follows: Figure 2 As shown,

[0088] Taking the deacidification tower as the analysis object, the interfaces of the deacidification system include water replenishment port, alkali liquid replenishment port, flue gas inlet, spray pipe, flue gas outlet, sewage outlet and slurry circulation outlet.

[0089] Tap water replenishment enters the deacidification system through the water replenishment port, alkali solution replenishment enters the deacidification system through the alkali solution replenishment port, flue gas before deacidification enters the deacidification system through the flue gas inlet, and the circulating slurry enters the deacidification system through the spray pipe;

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

[0091] The material balance in and out of the deacidification system during operation is:

[0092] Tap water replenishment + alkali solution supplement + imported flue gas + slurry circulation in = exported flue gas +

[0093] Flue gas carries droplets + evaporates water + slurry circulation discharge + slurry sewage discharge,

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

[0095] Water replenishment + desalination generation = flue gas carrying droplets + evaporation of water + continuous slurry discharge,

[0096] Among them, deacidification generates solid, water replenishment, evaporation of water, and continuous slurry discharge are liquid, and the salt generated by the deacidification reaction dissolves in water. The water balance formula based on volume units is established:

[0097] Water replenishment = flue gas droplets + evaporated water + continuous slurry discharge,

[0098] The water replenishment volume consists of three parts, namely, the tap water replenishment entering through the water replenishment port, the alkali replenishment entering through the alkali replenishment port, and the moisture in the flue gas entering through the flue gas inlet;

[0099] Smoke-carried droplets are small droplets of salt in liquid form that are carried by smoke;

[0100] Evaporated water is characterized by pure water loss, which contains no salt;

[0101] Continuous slurry discharge is to continuously discharge the deacidified slurry from the deacidification system, and the concentration of the slurry discharge 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 in the deacidification tower remains constant. Figure 3 As shown, an embodiment method includes the following steps:

[0103] Step 1: Analyze the material balance of the deacidification system, simplify the 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 b is the amount of water replenished per unit time, in m 3 / h,

[0106] Q y is the amount of droplets carried by smoke per unit time, in m 3 / h,

[0107] Q p The waste liquid discharge per unit time, in m 3 / h,

[0108] Qh is the amount of water evaporation per unit time, in m 3 / h.

[0109] Step 2: Define the concept of slurry concentration multiple N, where 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 due to the increase in the concentration of the salt solution caused by the loss of pure water in the deacidification system, the algorithm formula for establishing the slurry concentration multiple is:

[0110]

[0111] Where N is the concentration multiple of the slurry, which has no unit dimension.

[0112] Q y is the amount of droplets carried by smoke per unit time, in m 3 / h,

[0113] Q p The waste liquid discharge per unit time, in m 3 / h.

[0114] Step 3: Calculate the amount of salt generated per unit time M during deacidification based on the content of acidic gas components at the flue gas inlet and the deacidification efficiency.

[0115] It is known that the volume of the flue gas inlet of the deacidification system is 15200Nm 3 / h, SO2 volume flow rate in flue gas 549mg / Nm 3 , HCl volume flow rate is 137 mg / Nm 3 , HBr volume flow rate is 0mg / Nm 3 ,but

[0116] SO2 mass flow

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

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

[0119] The acid gas removal efficiency of each component of the deacidification 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 =58.5g / mol, Mr HBr =81 g / mol and Mr NaBr =103g / mol

[0123] The salt production per unit time of the deacidification system M is the mass of sodium sulfate produced per unit time by the deacidification reaction. Sodium chloride mass M NaCl 、Mass of sodium bromide M NaBr sum:

[0124]

[0125] The sewage concentration of the deacidification system is set to 2%, that is, the slurry circulation concentration C = 20kg / m3.

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

[0127]

[0128] Where N is the concentration multiple of the slurry, which has no unit dimension.

[0129] C is the concentration of deacidification circulating slurry, unit: kg / m 3 ,

[0130] M is the amount of salt generated per unit time during deacidification, in kg / h.

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

[0132] 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 .

[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 water pipe 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 water temperature and saturation content curve (such as Figure 6 The saturated water vapor content at 45°C of the flue gas outlet of the deacidification tower is 65g / m 3 , then calculate

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

[0148]

[0149] Q b3The value is Q, which is read by the flow meter installed on the alkali solution pipeline. b3 =0.005m3 / h;

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

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

[0152] Use the formula in step 3 to calculate the slurry concentration multiple N:

[0153]

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

[0155] It should be noted that the setting of the deacidification circulating slurry concentration C needs to take into account the maximum solubility of salt in the slurry and the treatment capacity of the downstream sewage treatment facilities for the maximum saline wastewater concentration after the deacidification system is discharged. If the upper limit of the wastewater concentration allowed by the sewage treatment facility is exceeded, the wastewater needs to be diluted, resulting in poor economic efficiency, 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] A method for calculating and controlling water quality in a wet deacidification tower according to an embodiment of the present invention, a typical embodiment and application scenario as follows Figure 4 As shown, a deacidification tower deacidification system of a wet deacidification tower water quality calculation and control method includes the following contents:

[0157] Deacidification tower 1 uses alkali solution to deacidify the flue gas.

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

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

[0160] One interface of the deacidification tower 1 is connected to the alkali liquid pipeline, on which an alkali liquid flow meter 6 is arranged.

[0161] A slurry circulation pipeline at an interface of the deacidification tower 1 is provided with a circulation pump 7.

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

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

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

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

[0166] Water replenishment = flue gas droplets + evaporated water + continuous slurry discharge

[0167] When the deacidification system is in operation, the circulating solution is first injected into the deacidification tower 1 through the water inlet pipe and the alkali solution pipe, and the circulating solution is transported to the spray device 8 under the action of the circulating pump 7. The spray device 8 allows the circulating solution to re-enter the deacidification tower 1 and fall into the water outlet space at the bottom. The acid-containing flue gas enters from the flue gas inlet 2 to contact and react with the alkaline spray liquid, and is discharged from the flue gas outlet 3.

[0168] Using two methods to express and calculate 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 takes into account its formation factors, that is, the concentration of the slurry is mainly due to the increase in the concentration of the salt solution caused by the loss of pure water in the deacidification system, and the following relationship is derived:

[0169]

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

[0171] According to the above-calculated slurry discharge volume per unit time, the opening of the discharge regulating valve 9 and the flow reading of the discharge flow meter 10 are interlocked to stabilize the discharge flow meter 10 at the calculated value of the slurry discharge volume.

[0172] When the flue gas undergoes acid-base neutralization reaction in the deacidification tower 1, the flue gas temperature decreases, and the flue gas changes from an unsaturated state of water vapor to a saturated state and an oversaturated state. Part of the flue gas condenses into liquid water and falls into the deacidification tower 1, becoming part of the water replenishment for the deacidification system.

[0173] The amount of alkali solution injected depends on the acid gas content in the flue gas. The water in the alkali solution is the second part of the water replenishment of the deacidification system.

[0174] The replenishment of the tap water pipeline is the third part of the deacidification system replenishment. The deacidification system also relies on adjusting the tap water replenishment amount to maintain the stability of the deacidification system liquid level. The liquid level indication of the liquid level meter 11 is interlocked with the water inlet regulating valve 5 on the tap water pipeline to keep the indication of the liquid level meter 11 stable.

[0175] The deacidification system completes the control of the sewage discharge flow and the tap water replenishment flow, achieving the water balance and constant sewage concentration of the deacidification system.

[0176] Further calculation shows that the first part of the water replenishment of the deacidification system is obtained by difference calculation of the water content in the inlet and outlet flue gas of the deacidification tower 1, the second part of the water replenishment is read by the alkali solution flowmeter 6, and the third part of the water replenishment is read by the water inlet flowmeter 4. The total water replenishment of the deacidification system is obtained by adding the three together, and its value is determined by any calculation method of the slurry concentration multiple. This value includes the relationship between the acid removal capacity and the water replenishment amount, which 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 description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0178] In addition, it will be understood by those skilled in the art that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

[0179] It will be appreciated by those skilled in the art that, although the present invention has been described with reference to exemplary embodiments, various changes may be made and equivalents may be substituted for its elements without departing from the scope of the present invention. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from the essential 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 after the deacidification solution reacts with the flue gas to generate a salt solution, and the salt solution circulates in the deacidification system and concentrates 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. 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; 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 taken according to the design value of the deacidification system. The acid gas component content is read in real time by setting a gas component concentration online 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 slurry concentration multiple N, the relationship between the salt generation per unit time M of deacidification and the slurry concentration multiple N is: Where N is the concentration multiple of the slurry, which has no unit dimension. 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. Q b is the amount of water replenished per unit time, in m 3 / h, 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; 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; Step 5: Combine the calculation formulas for the slurry concentration multiple N in step 2 and step 3, Derived waste liquid discharge per unit time Q p The calculation formula is: Among them, Q p The waste liquid discharge per unit time, in m 3 / h, M is the amount of salt generated per unit time during deacidification, in kg / h. C is the concentration of deacidification circulating slurry, unit: kg / m 3 , Q y is the amount of droplets carried by smoke per unit time, in m 3 / h, 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; 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 the water replenishment volume per unit time Q b , which includes tap water replenishment, flue gas condensate water and alkali solution replenishment, namely: Q b =Q b1 +Q b2 +Q b3 Among them, Q b is the amount of water replenished per unit time, in m 3 / h, Q b1 The amount of tap water replenishment per unit time, unit m 3 / h, Q b2 is the amount of flue gas condensate 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 can be 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 It can be read by the flow meter installed on the alkali solution pipeline; The formula in step 2 and step 3 is used to calculate the slurry concentration multiple N, which is used 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 + flue gas droplets + evaporated water + slurry circulation discharge + Slurry drainage, 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 can be simplified as follows: 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: The salt generation per unit time M of the deacidification system includes sodium sulfate, sodium chloride and sodium bromide generated by the deacidification reaction, and its calculation method is: Wherein, M is the salt generation per unit time of deacidification, in kg / h, M Na2SO4 is the amount of sodium sulfate generated per unit time, in kg / h, M NaC1 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 deacidification circulating slurry concentration 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 waste liquid discharge volume per unit time 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: Flue gas condensation per unit time Q b2 The calculation method when the flue gas at the outlet of the deacidification tower reaches the water vapor saturation state is: Among them, Q b2 is the amount of flue gas condensate per unit time, in m3 / h. is the water vapor content in the flue gas at the deacidification tower inlet, in m3 / h. is the water vapor content in the flue gas at the outlet of the deacidification tower, in m3 / h. The humidity can be read in real time by setting up an online humidity monitoring device at the flue gas inlet of the deacidification tower, or it can be calculated based on 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, is needed to set the concentration of deacidification circulating slurry. The deacidification system can automatically adjust the tap water replenishment volume per unit time Q. b1 And the waste liquid discharge per unit time 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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