Multi-pollutant flue gas purification device and control method

Abstract

The invention discloses a multi-pollutant flue gas purification device and a control method, and relates to the technical field of flue gas purification. The multi-pollutant flue gas purification device includes an SNCR denitration system, an SDA semi-dry deacidification tower and a dust and nitrate integrated device, wherein: the SNCR denitration system is arranged at a suitable temperature window of the incinerator; the SDA semi-dry deacidification tower and the dust and nitrate integrated device are sequentially connected to the rear of the incinerator through a flue, the top of the SDA semi-dry deacidification tower is provided with a rotary atomizer for atomizing slaked lime slurry, and the upper part of the tower body of the SDA semi-dry deacidification tower is provided with a NaOH solution atomizing nozzle group along the circumferential direction; an SGH steam heat exchanger is provided on the flue between the SDA semi-dry deacidification tower and the dust and nitrate integrated device; the flue gas outlet of the dust and nitrate integrated device is connected to an external economizer, and the outlet of the external economizer is connected to the chimney through an induced draft fan. The present invention has a short process, small footprint, low water consumption, no wastewater generation, small flue gas resistance, and is convenient for transformation and implementation of existing projects.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas purification, and in particular to a multi-pollutant flue gas purification device and a control method. Background Art

[0002] The usual flue gas purification technology is to simply stack and connect various flue gas treatment technologies, resulting in a lengthy overall process flow, high raw material and energy consumption, and large investment. In terms of deacidification technology, the SDA semi-dry deacidification process plus dry deacidification process is generally used in the early stage. In some places, the "SDA semi-dry + dry + wet" three-stage deacidification combination process is mainly used. In terms of denitrification technology, the use of in-furnace SNCR denitrification in the early stage can meet the emission requirements. With the increase of NO x The emission indicators are improved mainly by adding SCR denitrification technology on the basis of SNCR.

[0003] In order to meet the emission requirements, the current relatively complete waste incineration flue gas treatment process route is "SNCR + SDA semi-dry deacidification + dry deacidification + activated carbon injection adsorption of dioxins + bag dust removal + wet deacidification + SCR". The above process has the following disadvantages: (1) When the three-stage deacidification combined process is adopted, the water consumption is large and a large amount of wastewater needs to be treated; the system process is long, the flue gas flow resistance is large, the equipment cost and energy consumption are high; the device occupies a large area, and it is difficult to transform and implement existing projects. (2) When the SDA semi-dry method plus dry deacidification process is used, it is difficult to achieve high deacidification requirements by relying solely on the traditional SDA semi-dry deacidification method. It is necessary to use the dry deacidification process for supplementary deacidification. Usually, baking soda, which is highly active but expensive, is used as a deacidification agent and is sprayed into the flue in front of the bag filter. However, the low flue gas temperature is not conducive to baking soda deacidification, and the flue gas residence time is short and the gas-solid mixing is uneven. Excessive baking soda needs to be sprayed, resulting in excessive operating costs; (3) A separate SCR denitrification reactor needs to be set up, which is generally arranged after the wet deacidification tower. The flue gas temperature deviates from the active temperature window of the SCR by a large amount, and heat exchange equipment with a large heat exchange capacity needs to be configured. The system cost is high and the operation is not economical. Summary of the invention

[0004] In view of this, the embodiments of the present invention provide a multi-pollutant flue gas purification device and control method with a short process, small footprint, low water consumption, no wastewater generation, small flue gas resistance, and easy implementation in the transformation of existing projects.

[0005] On the one hand, the present invention provides a multi-pollutant flue gas purification device, including a SNCR denitration system, an SDA semi-dry deacidification tower and a dust and nitrate integrated device, wherein:

[0006] The SNCR denitration system is arranged at a suitable temperature window of the incinerator. The SNCR denitration system comprises a reducing agent storage tank, a reducing agent delivery pump and a reducing agent atomizing spray gun group A which are connected in sequence. The reducing agent atomizing spray gun group A is used to spray the reducing agent required by the SNCR to a suitable temperature window of the incinerator;

[0007] The SDA semi-dry deacidification tower and the dust and saltpeter integrated device are sequentially connected to the rear of the incinerator through a flue. The top of the SDA semi-dry deacidification tower is provided with a rotary atomizer for atomizing slaked lime slurry, and the rotary atomizer is connected to a slaked lime slurry preparation system and a cooling water supply system. The upper part of the tower body of the SDA semi-dry deacidification tower is provided with a NaOH solution atomization nozzle group along the circumferential direction, and the NaOH solution atomization nozzle group is connected to a NaOH solution preparation system.

[0008] The flue between the SDA semi-dry deacidification tower and the dust and saltpeter integrated device is provided with an SGH steam heat exchanger for heating the flue gas temperature from 150-160°C to 180-250°C by utilizing the heat of steam;

[0009] A catalytic filter element is arranged in the dust and saltpeter integrated device, and the flue gas outlet of the dust and saltpeter integrated device is connected to an external economizer, and the outlet of the external economizer is connected to the chimney through an induced draft fan.

[0010] In another aspect, the present invention provides a control method for the above-mentioned multi-pollutant flue gas purification device, comprising:

[0011] Step 1: Set the control target values ​​of HCl concentration and SO2 concentration in the flue gas at the induced draft fan outlet: SV_HCl and SV_SO2, and proceed to step 2;

[0012] Step 2: Determine whether the set value of SV_HCl or SV_SO2 is less than the respective critical values ​​Crit_HCl, Crit_SO2. When any of the set values ​​is less than the corresponding critical value, execute step 3, otherwise execute step 8;

[0013] Step 3: Control the opening of the NaOH solution flow regulating valve according to the preset sodium acid molar ratio SV_NSR_Na, that is, calculate the theoretical mass flow value CV_F_Na of the NaOH solution to be added according to the measured values ​​PV_HCl_in and PV_SO2_in of HCl and SO2 monitored by CEMS at the inlet of the SDA semi-dry deacidification tower, the set value SV_HCl, the set value SV_SO2, the measured value PV_F_Gas of the flue gas flow monitored by CEMS at the outlet of the induced draft fan, and the mass concentration C_Na of the NaOH solution, respectively. The theoretical mass flow value CV_F_Na of the NaOH solution and the measured value PV_F_Na of the NaOH solution flow monitored by the NaOH solution flowmeter are used as the input values ​​of the PID function module, and the calculated output value controls the opening of the NaOH solution flow regulating valve, and execute step 4;

[0014] Step 4: Continue to spray slaked lime slurry into the SDA semi-dry deacidification tower to provide the required deacidification agent. The control loop of the slaked lime slurry injection amount uses the PID function blocks of HCl and SO2 to perform differential adjustment according to their respective set values ​​SV_HCl, SV_SO2 and the HCl and SO2 measurement values ​​PV_HCl_out, PV_SO2_out of the outlet CEMS. The value after the output superposition is used as the set value of the slaked lime slurry flow adjustment PID, which is compared with the monitoring value PV_F_Ca of the slaked lime slurry flow meter to perform differential adjustment on the deviation. The output signal adjusts the opening of the slaked lime slurry flow control valve to ensure that the PV_HCl_out and PV_SO2_out of the induced draft fan outlet CEMS are not greater than the target value, and then execute step 5;

[0015] Step 5: Calculate the actual calcium acid molar ratio NSR_Ca at this time, and compare it with the preset first calcium acid molar ratio SV1_NSR_Ca. When NSR_Ca≥SV1_NSR_Ca, execute step 6, otherwise execute step 4;

[0016] Step 6: Control the opening of the slaked lime slurry flow regulating valve according to the preset first calcium-acid molar ratio SV1_NSR_Ca, that is, calculate the theoretical mass flow rate CV_F_Ca of slaked lime slurry to be added according to the measured values ​​PV_HCl_in and PV_SO2_in of HCl and SO2 monitored by the inlet CEMS of the SDA semi-dry deacidification tower, the set value SV_HCl, the set value SV_SO2, the measured value PV_F_Gas of the flue gas flow monitored by the CEMS at the outlet of the induced draft fan, and the mass concentration C_Ca of the slaked lime slurry, respectively. The theoretical mass flow rate CV_F_Ca of the slaked lime slurry and the measured value PV_F_Ca of the slaked lime slurry flow monitored by the slaked lime slurry flowmeter are used as input values ​​of the PID function module, and the output value after PID calculation controls the opening of the slaked lime slurry flow regulating valve, and execute step 7;

[0017] Step 7: Continue to spray NaOH solution into the SDA semi-dry deacidification tower. The control loop of the NaOH solution injection amount uses the PID function blocks of HCl and SO2 to perform differential adjustment according to their respective set values ​​SV_HCl, SV_SO2 and measured values ​​PV_HCl_out, PV_SO2_out. The calculated value after the output superposition is used as the set value of the NaOH solution flow adjustment PID, which is compared with the monitoring value PV_F_Na of the NaOH solution flow meter to perform differential adjustment on the deviation. The output signal adjusts the opening of the NaOH solution flow control valve to ensure that the PV_HCl_out and PV_SO2_out of the induced draft fan outlet CEMS are not greater than the target value, and then execute step 1;

[0018] Step 8: Calculate the actual calcium acid molar ratio NSR_Ca and compare it with the preset second calcium acid molar ratio SV2_NSR_Ca. When NSR_Ca≤SV2_NSR_Ca, execute step 9, otherwise execute step 10;

[0019] Step 9: spray slaked lime slurry into the SDA semi-dry deacidification tower. The control loop of the slaked lime slurry injection amount uses the PID function blocks of HCl and SO2 to perform differential adjustment according to their respective set values ​​SV_HCl, SV_SO2 and measured values ​​PV_HCl_out, PV_SO2_out. The value after the output superposition is used as the set value of the slaked lime slurry flow adjustment PID, which is compared with the monitoring value PV_F_Ca of the slaked lime slurry flow meter to perform differential adjustment on the deviation. The output signal adjusts the opening of the slaked lime slurry flow control valve to ensure that the PV_HCl_out and PV_SO2_out of the induced draft fan outlet CEMS are not greater than the target value, and execute step 8;

[0020] Step 10: Control the opening of the slaked lime slurry flow regulating valve according to the preset second calcium acid molar ratio SV2_NSR_Ca, that is, calculate the theoretical mass flow rate CV_F_Ca of slaked lime slurry to be added according to the measured values ​​PV_HCl_in and PV_SO2_in of HCl and SO2 monitored by CEMS at the inlet of the SDA semi-dry deacidification tower, the set value SV_HCl, the set value SV_SO2, the measured value PV_F_Gas of the flue gas flow monitored by CEMS at the outlet of the induced draft fan, and the mass concentration C_Ca of the slaked lime slurry, respectively. The theoretical mass flow rate of the slaked lime slurry and the measured value PV_F_Ca of the slaked lime slurry flow monitored by the slaked lime slurry flowmeter are used as input values ​​of the PID function module, and the calculated output value controls the opening of the slaked lime slurry flow regulating valve, and execute step 11;

[0021] Step 11: Continue to spray NaOH solution into the SDA deacidification tower. The control loop of the NaOH solution injection amount uses the PID function blocks of HCl and SO2 to perform differential adjustment according to their respective set values ​​SV_HCl, SV_SO2 and measured values ​​PV_HCl_out, PV_SO2_out. The value after the output superposition is used as the set value of the NaOH solution flow adjustment PID, which is compared with the monitoring value PV_F_Na of the NaOH solution flow meter to perform differential adjustment on the deviation. The output signal adjusts the opening of the NaOH solution flow control valve to ensure that the PV_HCl_out and PV_SO2_out of the induced draft fan outlet CEMS are not greater than the target value, and then execute step 12;

[0022] Step 12: Calculate the actual sodium acid molar ratio NSR_Na at this time, and compare it with the preset sodium acid molar ratio SV_NSR_Na. When NSR_Na≤SV_NSR_Na, execute step 11, otherwise execute step 3.

[0023] The present invention has the following beneficial effects:

[0024] The multi-pollutant flue gas purification device and control method of the present invention achieve coupled deacidification of slaked lime slurry and NaOH solution on the SDA semi-dry deacidification tower, and simultaneously utilize the dust and nitrate integrated device to achieve coordinated removal of multiple pollutants, thereby solving the problems existing in the prior art. On the premise of ensuring that the overall deacidification and denitrification effects meet the emission requirements, it is possible to provide a flue gas purification device and control method with a short process, small footprint, low water consumption, no wastewater generation, small flue gas resistance, and easy implementation in the transformation of existing projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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 description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a structural schematic diagram of the multi-pollutant flue gas purification device of the present invention;

[0027] Figure 2 It is a schematic flow chart of a control method of a multi-pollutant flue gas purification device of the present invention;

[0028] Figure 3 This is a schematic diagram of the effect of NSR_Ca on deacidification efficiency in a certain plant in the present invention;

[0029] Figure 4 This is a schematic diagram of the curve showing the effect of NSR_Na on the cost of the deacidifying agent in a certain factory in the present invention.

[0030] In the figure: 1-incinerator, 2-SDA deacidification tower, 3-SGH steam heat exchanger, 4-dust and saltpeter integrated device, 5-external economizer, 6-induced draft fan, 7-chimney, 8-NaOH solution storage tank, 9-NaOH solution delivery pump, 10-NaOH solution flow control valve, 11-NaOH solution flow meter, 12-NaOH solution atomizing nozzle group, 13-slaked lime slurry tank, 14-slaked lime slurry delivery pump, 15-slaked lime slurry flow control valve, 16-slaked lime slurry flow meter, 17-cooling water tank, 18-cooling water delivery pump, 19-cooling water flow regulating valve, 20-cooling water flow meter, 21-reducing agent storage tank, 22-reducing agent delivery pump, 23-reducing agent atomizing nozzle group A, 24-inlet CEMS, 25-SDA deacidification tower outlet temperature measuring element, 26-SGH steam heat exchanger outlet temperature measuring original, 27-low-temperature economizer outlet temperature measuring element, 28-outlet CEMS, 29-rotary atomizer, 30-reducing agent atomizing nozzle group B. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0032] It should be clear that the described embodiments are only some embodiments of the present invention, not all 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.

[0033] In one aspect, the present invention provides a multi-pollutant flue gas purification device, such as Figure 1As shown, it includes a SNCR denitration system, an SDA semi-dry deacidification tower 2 and a dust and salt integrated device 4, wherein:

[0034] The SNCR denitration system is used to be arranged at a suitable temperature window of the incinerator 1. The SNCR denitration system includes a reducing agent storage tank 21, a reducing agent delivery pump 22 and a reducing agent atomizing spray gun group A23 which are connected in sequence. The reducing agent atomizing spray gun group A23 is used to spray the reducing agent (such as ammonia water) required by the SNCR to a suitable temperature window (850-950°C) of the incinerator to complete preliminary denitration control;

[0035] The SDA semi-dry deacidification tower 2 and the dust and saltpeter integrated device 4 are sequentially connected to the rear of the incinerator 1 (specifically, they can be behind the economizer of the incinerator 1) through a flue. The top of the SDA semi-dry deacidification tower 2 is provided with a rotary atomizer 29 for atomizing slaked lime slurry, and the rotary atomizer 29 is connected to a slaked lime slurry preparation system and a cooling water supply system. The upper part of the tower body of the SDA semi-dry deacidification tower 2 is arranged with a NaOH solution atomizing nozzle group 12 along the circumferential direction, and the NaOH solution atomizing nozzle group 12 is connected to a NaOH solution preparation system;

[0036] An SGH steam heat exchanger 3 is provided on the flue between the SDA semi-dry deacidification tower 2 and the dust and saltpeter integrated device 4 for heating the flue gas temperature from 150 to 160°C to 180 to 250°C by utilizing the heat of steam, so as to meet the flue gas temperature requirement during denitration of the dust and saltpeter integrated device; specifically, the denitration temperature window of the dust and saltpeter integrated device 4 is 180 to 250°C, while the outlet temperature of the SDA semi-dry deacidification tower 2 is between 150 and 160°C, so the SGH steam heat exchanger 3 is required to heat the flue gas temperature to within the temperature window (180 to 250°C) of the dust and saltpeter integrated device 4;

[0037] A catalytic filtering element is arranged in the dust and saltpeter integrated device 4, and the flue gas outlet of the dust and saltpeter integrated device 4 is connected to the external economizer 5, which reduces the flue gas temperature from 230-250°C to 140-150°C to utilize the waste heat of the flue gas; the outlet of the external economizer 5 is connected to the chimney 7 through the induced draft fan 6.

[0038] Preferably, the slaked lime slurry preparation system may include a slaked lime slurry tank 13, a slaked lime slurry delivery pump 14, a slaked lime slurry flow regulating valve 15 and a slaked lime slurry flow meter 16 connected in sequence. The slaked lime slurry in the slaked lime slurry tank 13 is delivered to the rotary atomizer 29 by the slaked lime slurry delivery pump 14. The rotary atomizer 29 is used to atomize the slaked lime slurry droplets into fine slaked lime slurry droplets, which are fully mixed with the flue gas containing acidic gas, that is, the gas-liquid is fully mixed and contacted with the flue gas entering the SDA semi-dry deacidification tower body to complete the absorption and removal of acidic gases such as SO2, HCl, SO3, HF in the flue gas; as the flue gas moves forward, on the one hand, the acidic gas enters the slurry droplets and reacts with the slaked lime to achieve the purpose of removing the acidic gas and purifying the flue gas, and on the other hand, the moisture in the slurry droplets is also continuously evaporated, thereby producing a dry by-product mainly composed of CaCl2, CaSO3, CaSO4 and unreacted Ca(OH)2.

[0039] Preferably, the cooling water supply system may include a cooling water tank 17, a cooling water pump 18, a cooling water flow regulating valve 19 and a cooling water flow meter 20 connected in sequence. In order to obtain a higher deacidification efficiency, it is necessary to ensure that the flue gas temperature at the flue gas outlet of the SDA deacidification tower 2 is close to and slightly higher than the adiabatic saturation temperature of the flue gas. Usually, the flue gas temperature at the inlet of the SDA semi-dry deacidification tower 2 is between 200 and 230°C, and the flue gas temperature at the outlet needs to be controlled between 150 and 160°C. Therefore, while spraying slaked lime slurry and NaOH solution, cooling water is sprayed, and the flue gas temperature at the outlet of the SDA semi-dry deacidification tower 2 is controlled by adjusting the amount of cooling water.

[0040] Preferably, the NaOH solution preparation system may include a NaOH solution storage tank 8, a NaOH solution delivery pump 9, a NaOH solution flow regulating valve 10 and a NaOH solution flow meter 11 connected in sequence. When a higher deacidification efficiency is required, the NaOH solution preparation system is started, and the NaOH solution in the NaOH solution storage tank 8 is delivered to the NaOH solution atomizing nozzle group 12 via the NaOH solution delivery pump 9, and the NaOH solution is physicalized into droplets of a specified particle size, and the highly reactive NaOH droplets are used to complete the auxiliary absorption and removal of acidic gases such as SO2, HCl, SO3, and HF.

[0041] Preferably, the inlet of the SDA semi-dry deacidification tower 2 is provided with an inlet CEMS (continuous flue gas pollutant monitoring system) 24, and the monitoring items include at least SO2 concentration, HCl concentration, NO concentration, NO2 concentration, NH3 concentration, O2 content and H2O content;

[0042] The outlet of the induced draft fan 6 may be provided with an outlet CEMS 28, and the monitoring items include at least SO2 concentration, HCl concentration, NO concentration, NO2 concentration, O2 content, H2O content, NH3 concentration, dust concentration and flue gas flow;

[0043] Temperature monitoring elements 25, 26, 27 may be provided at the outlet of the SDA semi-dry deacidification tower 2, the outlet of the SGH steam heat exchanger 3, and the outlet of the external economizer 5, respectively.

[0044] Preferably, the catalytic filter element is a catalytic filter bag or a catalytic ceramic filter cartridge, and the catalytic filter bag loaded with an SCR catalyst can realize the coordinated treatment of secondary deacidification, heavy metal adsorption and removal, dust removal, denitrification and dioxin decomposition.

[0045] Preferably, the inlet flue gas temperature of the integrated dust and saltpeter device 4 is between 180 and 250°C. In order to improve the overall thermal efficiency of the system, an external economizer 5 is used for heat recovery, and the flue gas temperature at the outlet of the external economizer 5 is between 140 and 150°C.

[0046] It can be understood that the reducing agent required for dust and saltpeter integration can be sprayed only through the reducing agent atomizing spray gun group A 23 (the reducing agent atomizing spray gun group B is not provided), that is, the reducing agent required for denitration of the dust and saltpeter integrated device 4 is the unreacted ammonia sprayed by the SNCR system, and the ammonia spraying grid is no longer provided separately. The reducing agent can be ammonia water or urea solution. Different from the conventional SNCR system, the SNCR system needs to consider the reducing agent consumption required by the dust and saltpeter integrated device 4 in addition to the reducing agent consumption required by the SNCR process itself. At this time, the injection amount of the reducing agent can be controlled by the NO concentration measurement value, NO2 concentration measurement value, and NH3 concentration measurement value of the outlet CEMS;

[0047] Alternatively, the reducing agent delivery pump 22 is also connected to a reducing agent atomizing spray gun group B 30 arranged on the inlet flue of the dust and saltpeter integrated device 4, and the reducing agent required by the dust and saltpeter integrated device 4 is sprayed at the inlet of the dust and saltpeter integrated device 4 through a separate reducing agent atomizing spray gun group B 30. At this time, the reducing agent flow rate of the reducing agent atomizing spray gun group A23 can be controlled by the NO concentration measurement value, NO2 concentration measurement value and NH3 concentration measurement value of the inlet CEMS24, and the reducing agent flow rate of the reducing agent atomizing spray gun group B 30 can be controlled by the NO concentration measurement value, NO2 concentration measurement value and NH3 concentration measurement value of the outlet CEMS28.

[0048] On the other hand, the present invention also provides a control method for the above-mentioned multi-pollutant flue gas purification device, such as Figure 2 As shown, including:

[0049] Step 1( Figure 2 (not shown in the figure): set the control target values ​​of HCl concentration and SO2 concentration in the flue gas at the outlet of the induced draft fan: SV_HCl and SV_SO2, and execute step 2;

[0050] Step 2: Determine whether the set value of SV_HCl or SV_SO2 is less than the respective critical values ​​Crit_HCl, Crit_SO2. When any of the set values ​​is less than the corresponding critical value, execute step 3, otherwise execute step 8;

[0051] As an optional embodiment, the Crit_HCl and Crit_SO2 can be obtained through field tests, that is, when the NaOH solution semi-dry deacidification system is not put into operation and only the slaked lime slurry semi-dry system is put into operation, the value of the calcium-acid ratio is gradually increased until the HCl and SO2 readings detected by the CEMS at the induced draft fan outlet basically no longer change with the increase of the calcium-acid molar ratio. At this time, the main limiting factor of the deacidification reaction is no longer the injection amount of slaked lime slurry, but the diffusion rate and reaction rate of the slaked lime slurry with HCl and SO2. The HCl and SO2 readings detected by the outlet CEMS at this time are taken as Crit_HCl and Crit_SO2, and the corresponding calcium-acid molar ratio at this time is taken as SV1_NSR_Ca. According to the test data, the following is made: Figure 3 The relationship curve shown in FIG. 1 is used to find the point where the first-order derivative (slope) of the deacidification efficiency curve tends to be flat with the increase of NSR_Ca, and the calcium-acid molar ratio at this point is taken as SV2_NSR_Ca (specifically, in Figure 3 When NSR_Ca≥1.6, the first-order derivative (slope) of the deacidification efficiency curve tends to be flat with the increase of NSR_Ca, and SV2 NSR_Ca=1.6 can usually be selected; when NSR_Ca≥2.0, the deacidification efficiency no longer increases significantly with the increase of NSR_Ca, and SV1_NSR_Ca=2.0 can usually be selected); you can also directly select the values ​​determined by multiple tests: Crit_HCl=20, Crit_SO2=50, SV1_NSR_Ca=2.0, SV2 NSR_Ca=1.6 (see Figure 3 );

[0052] Step 3: Control the opening of the NaOH solution flow regulating valve according to the preset sodium-acid molar ratio SV_NSR_Na (specifically, it can be less than 1), that is, according to the actual measured values ​​PV_HCl_in (mg / m 3 , standard state, dry basis, converted oxygen), PV_SO2_in(mg / m 3 , standard state, dry basis, converted oxygen), set value SV_HCl (mg / m 3 , standard state, dry basis, converted oxygen), set value SV_SO2 (mg / m 3 , standard state, dry basis, converted oxygen) and the actual measured value of flue gas flow PV_F_Gas (Nm 3 / h, standard state, dry basis, converted oxygen), mass concentration C_Na (%) of NaOH solution, calculate the theoretical mass flow value CV_F_Na (kg / h) of NaOH solution to be added, the theoretical mass flow value CV_F_Na (kg / h) of NaOH solution and the actual measured value PV_F_Na (kg / h) of NaOH solution flow monitored by the NaOH solution flow meter are used as input values ​​of the PID function module, and the calculated output value controls the opening of the NaOH solution flow regulating valve, and executes step 4;

[0053] As an optional embodiment, the theoretical mass flow rate CV_F_Na (kg / h) of the NaOH solution to be added is calculated as follows:

[0054]

[0055] Wherein, the value of SV_NSR_Na can be determined on site through a set of tests, that is, under the conditions of fixed SV_HCl and SV_SO2 set values, the injection amount of NaOH solution is determined according to NSR_Na = 0.1, 0.2, 0.3, 0.4, 0.5 respectively, and the injection amount of slaked lime slurry is automatically adjusted by PID. The consumption of NaOH and slaked lime is obtained by statistics of DCS record data, and the total cost of deacidification agent under various working conditions is calculated. According to the test data, the following is made: Figure 4 The relationship curve shown in the figure selects the NSR_Na corresponding to the lowest deacidification agent cost as SV_NSR_Na (i.e. Figure 4 The lowest point of the middle curve); the value determined based on multiple tests can also be used: SV_NSR_Na=0.3.

[0056] Step 4: Since NSR_Na is less than 1 at this time, it is necessary to continue to spray slaked lime slurry into the SDA deacidification tower to provide the required deacidification agent. The control loop of the slaked lime slurry injection amount first uses the PID function blocks of HCl and SO2 to perform differential adjustment according to their respective set values ​​SV_HCl, SV_SO2 and the HCl and SO2 measurement values ​​PV_HCl_out, PV_SO2_out of the outlet CEMS. The value after the output superposition is used as the set value of the slaked lime slurry flow adjustment PID, which is compared with the monitoring value PV_F_Ca of the slaked lime slurry flow meter to perform differential adjustment on the deviation. The output signal adjusts the opening of the slaked lime slurry flow control valve to ensure that the PV_HCl_out, PV_SO2_out of the induced draft fan outlet CEMS are not greater than the target value, and then execute step 5;

[0057] Step 5: Calculate the actual calcium acid molar ratio NSR_Ca at this time, and compare it with the preset first calcium acid molar ratio SV1_NSR_Ca. When NSR_Ca≥SV1_NSR_Ca, execute step 6, otherwise execute step 4;

[0058] As an optional embodiment, the actual calcium acid molar ratio NSR_Ca is calculated as follows:

[0059]

[0060] Step 6: Control the opening of the slaked lime slurry flow regulating valve according to the preset first calcium-acid molar ratio SV1_NSR_Ca, that is, according to the measured values ​​PV_HCl_in (mg / m 3 , standard state, dry basis, converted oxygen), PV_SO2_in(mg / m 3 , standard state, dry basis, converted oxygen), set value SV_HCl (mg / m 3 , standard state, dry basis, converted oxygen), set value SV_SO2 (mg / m 3 , standard state, dry basis, converted oxygen) and the actual measured value of flue gas flow PV_F_Gas (Nm 3 / h), mass concentration C_Ca (%) of slaked lime slurry, calculate the theoretical mass flow rate CV_F_Ca (kg / h) of slaked lime slurry to be added, the theoretical mass flow rate value CV_F_Ca of slaked lime slurry and the measured value PV_F_Ca of slaked lime slurry flow monitored by the slaked lime slurry flow meter are used as input values ​​of the PID function module, and the output value after PID calculation controls the opening of the slaked lime slurry flow regulating valve, and executes step 7;

[0061] As an optional embodiment, the theoretical mass flow rate CV_F_Ca (kg / h) of the slaked lime slurry to be added is calculated according to the following formula:

[0062]

[0063] Step 7: Continue to spray NaOH solution into the SDA semi-dry deacidification tower. The control loop of the NaOH solution injection amount first uses the PID function blocks of HCl and SO2 to control the injection amount according to their respective set values ​​SV_HCl, SV_SO2 and measured values ​​PV_HCl_out, PV_SO 2_out is regulated without difference, and the calculated value after output superposition is used as the set value of NaOH solution flow regulation PID, which is compared with the monitoring value PV_F_Na of NaOH solution flow meter, and the deviation is regulated without difference. The output signal adjusts the opening of NaOH solution flow control valve to ensure PV_HCl_out and PV_SO 2_ If out is not greater than the target value, execute step 1;

[0064] Step 8: Calculate the actual calcium acid molar ratio NSR_Ca, and compare it with the preset second calcium acid molar ratio SV2_NSR_Ca. When NSR_Ca≤SV2_NSR_Ca, execute step 9, otherwise execute step 10;

[0065] In this step, SV2_NSR_Ca can be selected using the field test data from step 2, or it can be directly selected based on multiple tests to determine SV2_NSR_Ca = 1.6 (see Figure 3 );

[0066] As an optional embodiment, the actual calcium acid molar ratio NSR_Ca is calculated as follows:

[0067]

[0068] Step 9: spray slaked lime slurry into the SDA semi-dry deacidification tower. The control loop of the slaked lime slurry injection amount first uses the PID function blocks of HCl and SO2 to perform differential adjustment according to their respective set values ​​SV_HCl, SV_SO2 and measured values ​​PV_HCl_out, PV_SO2_out. The value after the output superposition is used as the set value of the slaked lime slurry flow adjustment PID, which is compared with the monitoring value PV_F_Ca of the slaked lime slurry flow meter to perform differential adjustment on the deviation. The output signal adjusts the opening of the slaked lime slurry flow control valve to ensure that the PV_HCl_out and PV_SO2_out of the induced draft fan outlet CEMS are not greater than the target value, and then execute step 8;

[0069] Step 10: Control the opening of the slaked lime slurry flow regulating valve according to the preset second calcium-acid molar ratio SV2_NSR_Ca (specifically, 1.6), that is, according to the measured values ​​PV_HCl_in (mg / m3, standard state, dry basis, converted oxygen) and PV_SO2_in (mg / m3, standard state, dry basis, converted oxygen) of HCl and SO2 monitored by CEMS at the inlet of the SDA semi-dry deacidification tower, and the set value SV_HCl (mg / m 3 , standard state, dry basis, converted oxygen), set value SV_SO2 (mg / m 3 , standard state, dry basis, converted oxygen), PV_F_Gas (Nm3 / h, standard state, dry basis, converted oxygen), and the actual measured value of flue gas flow PV_F_Gas (Nm 3 / h, standard state, dry basis, converted oxygen), mass concentration C_Ca (%) of slaked lime slurry, calculate the theoretical mass flow rate CV_F_Ca (kg / h) of slaked lime slurry to be added, the theoretical mass flow rate value CV_F_Ca of slaked lime slurry and the measured value PV_F_Ca of slaked lime slurry flow monitored by the slaked lime slurry flowmeter are used as input values ​​of the PID function module, and the calculated output value controls the opening of the slaked lime slurry flow regulating valve, and executes step 11;

[0070] As an optional embodiment, the theoretical mass flow rate CV_F_Ca (kg / h) of the slaked lime slurry to be added is calculated according to the following formula:

[0071]

[0072] Step 11: Continue to spray NaOH solution into the SDA semi-dry deacidification tower. The control loop of the NaOH solution injection amount first uses the PID function blocks of HCl and SO2 to perform differential adjustment according to their respective set values ​​SV_HCl, SV_SO2 and measured values ​​PV_HCl_out, PV_SO2_out. The value after the output superposition is used as the set value of the NaOH solution flow adjustment PID, which is compared with the monitoring value PV_F_Na of the NaOH solution flow meter to perform differential adjustment on the deviation. The output signal adjusts the opening of the NaOH solution flow control valve to ensure that the PV_HCl_out and PV_SO2_out of the induced draft fan outlet CEMS are not greater than the target value, and then execute step 12;

[0073] Step 12: Calculate the actual sodium acid molar ratio NSR_Na at this time, and compare it with the preset sodium acid molar ratio SV_NSR_Na (specifically, it can be 0.3). When NSR_Na≤SV_NSR_Na, execute step 11, otherwise execute step 3;

[0074] As an optional embodiment, the actual sodium acid molar ratio NSR_Na is calculated as follows:

[0075]

[0076] Where: a is the utilization rate of slaked lime.

[0077] The utilization rate a of slaked lime can be calculated based on the content of each calcium-based compound in the deacidified ash generated when the typical calcium-acid molar ratio (for example, 1.2, 1.4, 1.6, etc.) is used on site. The utilization rates of slaked lime corresponding to other calcium-acid molar ratios can be obtained by interpolation calculation. The specific method is to analyze the mass content of each calcium-based compound CaSO3, CaSO4, CaCO3, CaCl2, CaF2, and Ca(OH)2 in the deacidified ash, and convert them into the molar content of each calcium-based compound in the deacidified ash Mole_CaSO3, Mole_CaSO4, Mole_CaCO3, Mole_CaCl2, Mole_CaF2, and Mole_Ca(OH)2, and then calculate the utilization rate of slaked lime.

[0078] In the embodiment of the present invention, the mass content of each calcium-based compound CaSO3, CaSO4, CaCO3, CaCl2, CaF2, and Ca(OH)2 in the deacidified ash when the calcium-acid molar ratio is 1.6 is analyzed and then converted into the molar content of each calcium-based compound in the deacidified ash Mole_CaSO3, Mole_CaSO4, Mole_CaCO3, Mole_CaCl2, Mole_CaF2, and Mole_Ca(OH)2. The results are listed in Table 1:

[0079] Table 1

[0080] Serial number Calcium-based compounds Mass content (%) Molar content 1 <![CDATA[CaSO3]]> 5.25 0.0438 2 <![CDATA[CaSO4]]> 7.92 0.0582 3 <![CDATA[CaCO3]]> 8.07 0.0807 4 <![CDATA[CaCl2]]> 31.4 0.2831 5 <![CDATA[CaF2]]> 0.23 0.0029 6 <![CDATA[Ca(OH)2]]> 18 0.2432

[0081] The utilization rate of slaked lime is calculated using the following formula, and we obtain a=0.55.

[0082]

[0083] In summary, the present invention has achieved the following beneficial effects compared with the prior art:

[0084] 1. The multi-pollutant flue gas purification device and control method of the present invention can be used for flue gas purification in biomass power plants, waste incineration power plants, hazardous waste incineration treatment plants, etc. It solves the problem that only using slaked lime SDA semi-dry deacidification cannot meet the ultra-low emission requirements. By adding a NaOH solution atomizing nozzle group to the SDA deacidification tower, coupling slaked lime slurry semi-dry deacidification and NaOH solution semi-dry deacidification, it can ensure that the overall deacidification efficiency meets the ultra-low emission requirements, without the need to add additional dry deacidification or wet deacidification facilities, with a short process, small footprint, low water consumption, no wastewater generation, and easy on-site transformation and implementation.

[0085] 2. The integrated dust and NOx device can remove dust and NOx synergistically. x, dioxins and other pollutants, and has the effect of secondary deacidification. When the catalytic filter element is a catalytic filter bag, it is only necessary to replace the filter bag in the original bag dust collector with a catalytic filter bag, which can make full use of the original bag dust collector shell, steel structure, and auxiliary system. The transformation cost is low, the land occupation is small, and it is easy to implement on-site transformation.

[0086] 3. The control method of the semi-dry multi-pollutant flue gas purification of the present invention can coordinate the coordinated operation of the slaked lime slurry semi-dry deacidification facilities and the NaOH solution semi-dry deacidification facilities to ensure that the ultra-low emission requirements are met while saving absorbent consumption.

[0087] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A control method for a multi-pollutant flue gas purification device, characterized in that: The multi-pollutant flue gas purification device includes a SNCR denitration system, an SDA semi-dry deacidification tower and a dust and nitrate integrated device, wherein: The SNCR denitrification system is arranged at a suitable temperature window of the incinerator. The SDA semi-dry deacidification tower and the dust and saltpeter integrated device are sequentially connected to the rear of the incinerator through a flue, a rotary atomizer for atomizing slaked lime slurry is arranged on the top of the SDA semi-dry deacidification tower, and a NaOH solution atomizing nozzle group is arranged along the circumferential direction on the upper part of the tower body of the SDA semi-dry deacidification tower; The flue gas outlet of the dust and saltpeter integrated device is connected to an external economizer, and the outlet of the external economizer is connected to the chimney through an induced draft fan; The control method of the multi-pollutant flue gas purification device comprises: Step 1: Set the control target values ​​of HCl concentration and SO2 concentration in the flue gas at the induced draft fan outlet: SV_HCl and SV_SO2, and proceed to step 2; Step 2: Determine whether the set value of SV_HCl or SV_SO2 is less than the respective critical values ​​Crit_HCl, Crit_SO2. When any of the set values ​​is less than the corresponding critical value, execute step 3, otherwise execute step 8; Step 3: Control the opening of the NaOH solution flow regulating valve according to the preset sodium acid molar ratio SV_NSR_Na, and execute step 4; Step 4: Continue to spray slaked lime slurry into the SDA semi-dry deacidification tower to provide the required deacidification agent, adjust the opening of the slaked lime slurry flow control valve, ensure that the measured values ​​PV_HCl_out and PV_SO2_out of the induced draft fan outlet CEMS are not greater than the target values, and execute step 5; Step 5: Calculate the actual calcium acid molar ratio NSR_Ca at this time, and compare it with the preset first calcium acid molar ratio SV1_NSR_Ca. When NSR_Ca≥SV1_NSR_Ca, execute step 6, otherwise execute step 4; Step 6: Control the opening of the slaked lime slurry flow regulating valve according to the preset first calcium acid molar ratio SV1_NSR_Ca, and execute step 7; Step 7: Continue to spray NaOH solution into the SDA semi-dry deacidification tower, adjust the opening of the NaOH solution flow control valve, ensure that the PV_HCl_out and PV_SO2_out of the CEMS at the outlet of the induced draft fan are not greater than the target value, and execute step 1; Step 8: Calculate the actual calcium acid molar ratio NSR_Ca and compare it with the preset second calcium acid molar ratio SV2_NSR_Ca. When NSR_Ca≤SV2_NSR_Ca, execute step 9, otherwise execute step 10; Step 9: Spray slaked lime slurry into the SDA semi-dry deacidification tower, adjust the opening of the slaked lime slurry flow control valve, ensure that the PV_HCl_out and PV_SO2_out of the CEMS at the outlet of the induced draft fan are not greater than the target values, and execute step 8; Step 10: Control the opening of the slaked lime slurry flow regulating valve according to the preset second calcium acid molar ratio SV2_NSR_Ca, and execute step 11; Step 11: Continue to spray NaOH solution into the SDA deacidification tower, adjust the opening of the NaOH solution flow control valve, ensure that PV_HCl_out and PV_SO2_out of the CEMS at the outlet of the induced draft fan are not greater than the target value, and execute step 12; Step 12: Calculate the actual sodium acid molar ratio NSR_Na at this time, and compare it with the preset sodium acid molar ratio SV_NSR_Na. When NSR_Na≤SV_NSR_Na, execute step 11, otherwise execute step 3; The Crit_HCl and Crit_SO2 are obtained through field tests, that is, when the NaOH solution semi-dry deacidification system is not put into operation and only the slaked lime slurry semi-dry system is put into operation, the value of the calcium-acid ratio is gradually increased until the HCl and SO2 readings detected by the CEMS at the induced draft fan outlet no longer change with the increase of the calcium-acid molar ratio. The HCl and SO2 readings detected by the outlet CEMS at this time are taken as Crit_HCl and Crit_SO2, the corresponding calcium-acid molar ratio at this time is taken as SV1_NSR_Ca, and the calcium-acid molar ratio corresponding to the point where the deacidification efficiency tends to be flat with the increase of NSR_Ca is taken as SV2_NSR_Ca.

2. The control method of the multi-pollutant flue gas purification device according to claim 1, characterized in that: The SNCR denitration system comprises a reducing agent storage tank, a reducing agent delivery pump and a reducing agent atomizing spray gun group A connected in sequence, wherein the reducing agent atomizing spray gun group A is used to spray the reducing agent required by the SNCR to a suitable temperature window of the incinerator; The rotary atomizer is connected to a slaked lime slurry preparation system and a cooling water supply system, and the NaOH solution atomizing nozzle group is connected to a NaOH solution preparation system; The flue between the SDA semi-dry deacidification tower and the dust and saltpeter integrated device is provided with an SGH steam heat exchanger for heating the flue gas temperature from 150-160°C to 180-250°C by utilizing the heat of steam; A catalytic filtering element is arranged in the dust and saltpeter integrated device.

3. The control method of the multi-pollutant flue gas purification device according to claim 2, characterized in that: The slaked lime slurry preparation system comprises a slaked lime slurry tank, a slaked lime slurry delivery pump, a slaked lime slurry flow regulating valve and a slaked lime slurry flow meter which are connected in sequence; And / or, the desuperheating water supply system comprises a desuperheating water tank, a desuperheating water pump, a desuperheating water flow regulating valve and a desuperheating water flow meter which are connected in sequence; And / or, the NaOH solution preparation system comprises a NaOH solution storage tank, a NaOH solution delivery pump, a NaOH solution flow regulating valve and a NaOH solution flow meter which are connected in sequence.

4. The control method of the multi-pollutant flue gas purification device according to claim 2, characterized in that: The inlet of the SDA semi-dry deacidification tower is provided with an inlet CEMS, and the monitoring items include at least SO2 concentration, HCl concentration, NO concentration, NO2 concentration, NH3 concentration, O2 content and H2O content; And / or, the outlet of the induced draft fan is provided with an outlet CEMS, and the monitoring items include at least SO2 concentration, HCl concentration, NO concentration, NO2 concentration, O2 content, H2O content, NH3 concentration, dust concentration and flue gas flow; And / or, temperature monitoring elements are respectively provided at the outlet of the SDA semi-dry deacidification tower, the outlet of the SGH steam heat exchanger and the outlet of the external economizer.

5. The control method of the multi-pollutant flue gas purification device according to claim 2, characterized in that: The catalytic filter element is a catalytic filter bag or a catalytic ceramic filter cartridge.

6. The control method of the multi-pollutant flue gas purification device according to claim 2, characterized in that: The inlet flue gas temperature of the integrated dust and saltpeter device is between 180 and 250°C, and the outlet flue gas temperature of the external economizer is between 140 and 150°C.

7. The control method of the multi-pollutant flue gas purification device according to claim 4, characterized in that: The reducing agent required by the dust and saltpeter integrated device is only sprayed through the reducing agent atomizing spray gun group A, and the injection amount of the reducing agent is controlled by the NO concentration measurement value, NO2 concentration measurement value, and NH3 concentration measurement value of the outlet CEMS.

8. The control method of the multi-pollutant flue gas purification device according to claim 4, characterized in that: The reducing agent delivery pump is also connected to a reducing agent atomizing spray gun group B arranged on the inlet flue of the dust and saltpeter integrated device. The reducing agent required by the dust and saltpeter integrated device is sprayed through the reducing agent atomizing spray gun group B. The reducing agent flow rate of the reducing agent atomizing spray gun group A is controlled by the NO concentration measurement value, NO2 concentration measurement value and NH3 concentration measurement value of the inlet CEMS, and the reducing agent flow rate of the reducing agent atomizing spray gun group B is controlled by the NO concentration measurement value, NO2 concentration measurement value and NH3 concentration measurement value of the outlet CEMS.

9. The control method of a multi-pollutant flue gas purification device according to claim 1, characterized in that: The specific operation of adjusting the opening in step 3 is: according to the measured values ​​PV_HCl_in and PV_SO2_in of HCl and SO2 monitored by CEMS at the inlet of the SDA semi-dry deacidification tower, the set value SV_HCl, the set value SV_SO2, and the measured value PV_F_Gas of the flue gas flow monitored by CEMS at the outlet of the induced draft fan, and the mass concentration C_Na of the NaOH solution, the theoretical mass flow value CV_F_Na of the NaOH solution to be added is calculated, and the theoretical mass flow value CV_F_Na of the NaOH solution and the measured value PV_F_Na of the NaOH solution flow monitored by the NaOH solution flowmeter are used as the input values ​​of the PID function module, and the calculated output value controls the opening of the NaOH solution flow regulating valve. The theoretical mass flow value CV_F_Na of the NaOH solution to be added is calculated as follows: ； Wherein, the value of SV_NSR_Na is determined on site through a set of tests, that is, under the conditions of fixed SV_HCl and SV_SO2 set values, the injection amount of NaOH solution is determined according to NSR_Na=0.1, 0.2, 0.3, 0.4, and 0.5, respectively, and the injection amount of slaked lime slurry is automatically adjusted by PID, and the consumption of NaOH and slaked lime is obtained by statistics of DCS record data, and the total cost of deacidification agent under each working condition is calculated. A relationship curve is drawn based on the test data, and the NSR_Na corresponding to the working condition with the lowest deacidification agent cost is selected as SV_NSR_Na, or a value determined based on multiple tests is selected; And / or, in step 5, the actual calcium acid molar ratio NSR_Ca is calculated as follows: ； Wherein, PV_F_Ca is the measured value of slaked lime slurry flow rate monitored by the slaked lime slurry flowmeter, C_Ca is the mass concentration of slaked lime slurry, PV_HCl_in and PV_SO2_in are the measured values ​​of HCl and SO2 respectively monitored by the inlet CEMS of the SDA semi-dry deacidification tower, and PV_F_Gas is the measured value of flue gas flow rate monitored by the CEMS at the outlet of the induced draft fan; And / or, the specific operation of adjusting the opening in step 6 is: according to the measured values ​​PV_HCl_in and PV_SO2_in of HCl and SO2 monitored by the inlet CEMS of the SDA semi-dry deacidification tower, the set value SV_HCl, the set value SV_SO2, and the measured value PV_F_Gas of the flue gas flow monitored by the CEMS at the outlet of the induced draft fan, and the mass concentration C_Ca of the slaked lime slurry, the theoretical mass flow rate CV_F_Ca of the slaked lime slurry to be added is calculated, and the theoretical mass flow rate CV_F_Ca of the slaked lime slurry and the measured value PV_F_Ca of the slaked lime slurry flow monitored by the slaked lime slurry flowmeter are used as input values ​​of the PID function module, and the output value after PID calculation controls the opening of the slaked lime slurry flow regulating valve, The theoretical mass flow rate CV_F_Ca of the slaked lime slurry to be added is calculated as follows: ； And / or, in step 8, the actual calcium acid molar ratio NSR_Ca is calculated as follows: ； Wherein, PV_F_Ca is the measured value of slaked lime slurry flow rate monitored by the slaked lime slurry flowmeter, C_Ca is the mass concentration of slaked lime slurry, PV_HCl_in and PV_SO2_in are the measured values ​​of HCl and SO2 respectively monitored by the inlet CEMS of the SDA semi-dry deacidification tower, and PV_F_Gas is the measured value of flue gas flow rate monitored by the CEMS at the outlet of the induced draft fan; And / or, the specific operation of adjusting the opening in step 10 is: according to the measured values ​​PV_HCl_in and PV_SO2_in of HCl and SO2 monitored by CEMS at the inlet of the SDA semi-dry deacidification tower, the set value SV_HCl, the set value SV_SO2, and the measured value PV_F_Gas of the flue gas flow monitored by CEMS at the outlet of the induced draft fan, and the mass concentration C_Ca of the slaked lime slurry, the theoretical mass flow rate CV_F_Ca of the slaked lime slurry to be added is calculated, and the theoretical mass flow rate of the slaked lime slurry and the measured value PV_F_Ca of the slaked lime slurry flow monitored by the slaked lime slurry flowmeter are used as input values ​​of the PID function module, and the calculated output value controls the opening of the slaked lime slurry flow regulating valve, The theoretical mass flow rate CV_F_Ca of the slaked lime slurry to be added is calculated as follows: ； And / or, in step 12, the actual sodium acid molar ratio NSR_Na is calculated as follows: ； In the formula, PV_F_Na is the measured value of the NaOH solution flow rate monitored by the NaOH solution flowmeter, C_Na is the mass concentration of the NaOH solution, PV_HCl_in and PV_SO2_in are the measured values ​​of HCl and SO2 respectively monitored by the inlet CEMS of the SDA semi-dry deacidification tower, PV_F_Gas is the measured value of the flue gas flow rate monitored by the CEMS at the outlet of the induced draft fan, and a is the utilization rate of slaked lime.

10. The control method of a multi-pollutant flue gas purification device according to claim 1, characterized in that: The preset sodium acid molar ratio SV_NSR_Na has a value range of 0.2 to 0.5; And / or, the value range of the first calcium acid molar ratio SV1_NSR_Ca is 1.8 to 2.2; And / or, the value range of the second calcium acid molar ratio SV2_NSR_Ca is 1.2 to 1.8.

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