High-sulfur yellow phosphorus tail gas boiler flue gas purification treatment system and method

Abstract

The invention discloses a high-sulfur yellow phosphorus tail gas boiler flue gas purification treatment system and method, relates to the technical field of yellow phosphorus tail gas boiler flue gas treatment, and solves the problem of low removal efficiency of sulfur-containing impurities by unit slaked lime in the existing removal process of the sulfur-containing impurities in boiler flue gas after combustion of yellow phosphorus tail gas. The method comprises the following steps: step 1, carrying out staged combustion on yellow phosphorus tail gas, and carrying out preliminary desulfurization, denitration and dephosphorization while combusting to obtain high-temperature flue gas; step 2, cooling the high-temperature flue gas to 230 to 280 DEG C; 3, the flue gas in the step 2 is subjected to primary dust removal; step 4, mixing the flue gas subjected to primary dust removal in the step 3 with sprayed slaked lime powder for thorough desulfurization, and spraying cooling water for cooling in the desulfurization process; step 5, carrying out secondary dust removal on the thoroughly desulfurized flue gas obtained in the step 4; step 6, emptying the flue gas obtained after secondary dust removal in the step 5; the invention aims to create a proper temperature for continuous desulfurization through accurate control of the flue gas temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of yellow phosphorus tail gas boiler flue gas treatment, and in particular relates to a high-sulfur yellow phosphorus tail gas boiler flue gas purification treatment system and method. Background Art

[0002] Yellow phosphorus tail gas is a by-product produced by electric furnaces during the production of yellow phosphorus. Its main components include phosphine (PH3), hydrogen sulfide (H2S), sulfur dioxide (SO2), elemental phosphorus (P) and carbon monoxide (CO). In view of its high calorific value, production units often recycle it as boiler fuel gas to achieve energy recycling. The sulfur, nitrogen, phosphorus and other impurities in yellow phosphorus tail gas will be converted into harmful pollutants such as sulfates, nitrogen oxides and phosphates during the combustion process. These substances have potential hazards to the environment and human health. Therefore, countries have issued relevant regulations on the use of yellow phosphorus tail gas. Strict requirements are put forward for the emission standards of boiler flue gas, and yellow phosphorus tail gas needs to be deeply purified; traditional desulfurization technologies mainly include wet desulfurization, dry desulfurization and semi-dry desulfurization. Wet desulfurization usually uses limestone or slaked lime as absorbent to remove SO2 through a wet scrubber; denitrification technology is mainly divided into selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR) and adsorption; dephosphorization technology usually involves chemical precipitation, which uses certain chemicals to react with phosphorus to form insoluble precipitates, thereby achieving phosphorus removal.

[0003] However, in the existing process of removing sulfur-containing impurities in yellow phosphorus tail gas, the removal efficiency of sulfur-containing impurities per unit of slaked lime is prone to be low, and it cannot be adaptively adjusted according to the flow rate of yellow phosphorus tail gas; and the solid particles generated in the desulfurization process will cause scaling or blockage in the equipment, affecting the normal operation of the system; due to the different origins of phosphate rocks and the content of harmful elements, the sulfur content in yellow phosphorus tail gas has a wide range and large fluctuations, and in various provinces across the country, the operating time of yellow phosphorus electric furnaces is affected to varying degrees by electricity prices, which shows that the utilization of yellow phosphorus tail gas cannot achieve the goal of stable operation like traditional gas-fired power plants or chemical plants with stable raw material sources, and it is difficult for desulfurization equipment to achieve stable and effective operation. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a flue gas purification treatment system and method for a high-sulfur yellow phosphorus tail gas boiler. The present invention accurately controls the temperature of flue gas cooling, which is crucial to the desulfurization process. Too high or too low temperature may affect the rate and efficiency of the desulfurization reaction. The present invention can effectively reduce the temperature of the flue gas of the yellow phosphorus tail gas boiler by spraying cooling water, and by adjusting the spraying amount and temperature of the cooling water, the flue gas temperature can be accurately controlled to create suitable temperature conditions for continuous desulfurization reaction.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A flue gas purification treatment system for a high-sulfur and phosphorus tail gas boiler includes a desulfurization tower, a first air inlet is arranged on the desulfurization tower, and a plurality of first nozzles are arranged inside the desulfurization tower, wherein two of the first nozzles are arranged on the upper and lower sides of the first air inlet; the device also includes a power generation boiler, a buffer assembly, and a first dust removal assembly connected in sequence, and the air outlet of the first dust removal assembly is connected to the first air inlet of the desulfurization tower through a pipeline.

[0007] A method for purifying flue gas from a high sulfur and phosphorus tail gas boiler comprises the following steps:

[0008] Step 1: Burn the yellow phosphorus tail gas in stages, and perform preliminary desulfurization, denitrification and dephosphorization during combustion to obtain high-temperature flue gas;

[0009] Step 2: Cool the high-temperature flue gas to t1, where t1 ranges from 140 to 200°C;

[0010] Step 3: Perform the first dust removal on the flue gas in step 2;

[0011] Step 4: Mix the flue gas after the first dust removal in step 3 with the sprayed slaked lime powder for thorough desulfurization, and spray cooling water for cooling during the desulfurization process;

[0012] Step 5: performing a second dust removal on the completely desulfurized flue gas obtained in step 4;

[0013] Step 6: Exhaust the flue gas obtained after the second dust removal in step 5.

[0014] Preferably, in step 1, limestone is sprayed to perform preliminary desulfurization, urea is sprayed to perform denitrification, and coal gangue powder is sprayed to perform dephosphorization.

[0015] Preferably, the large-particle gangue after dephosphorization in step 1 is returned to the dephosphorization step in step 1 to continue dephosphorization.

[0016] Preferably, the first dust removal in step 3 is performed using an electrostatic dust collector, and the second dust removal in step 5 is performed using a bag dust collector.

[0017] Preferably, the complete desulfurization in step 4 comprises the following steps:

[0018] Step 401: Step 4 is performed in a desulfurization tower, flue gas is introduced into the desulfurization tower, and a thermometer monitors the temperature of the flue gas introduced into the desulfurization tower in real time;

[0019] Step 402: The control system receives feedback of the flue gas temperature in real time and sends a signal to the nozzle for spraying cooling water mist, thereby spraying cooling water mist to cool the flue gas to temperature t2;

[0020] Step 403: When the temperature detected by the thermometer drops to t2, slaked lime powder is sprayed in. At this time, the nozzle continues to spray cooling water mist so that the real-time temperature of the flue gas is maintained at t2. At the same time, air flow is introduced to suspend the slaked lime powder in the flue gas and the cooling water mist.

[0021] Step 404: The slaked lime powder is sprayed for a period of time T, and the slaked lime powder after the reaction is discharged, and then sprayed to replace the slaked lime powder.

[0022] Preferably, in step 402, the production status of the power generation boiler in different time periods is different, and the exhaust gas supply, that is, the load of the boiler is different. Therefore, according to the exhaust gas supply of the power generation boiler, the initial temperature entering the desulfurization tower will change, and the size of the cooling water mist is adjusted according to the initial temperature. When the real-time temperature is maintained at t2, the cooling water mist is maintained at this size.

[0023] Preferably, in step 404, T is 40 to 60 minutes.

[0024] Preferably, in step 402, t2 is 100-130°C.

[0025] Preferably, the temperature of the cooling water mist sprayed in step 402 is room temperature, the flow rate is 0 to 7.5 t / h, and the area of ​​the sprayed water mist covers the cross section of the desulfurization tower.

[0026] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0027] 1. Accurately controlling the temperature of flue gas cooling is crucial to the desulfurization process. Too high or too low a temperature may affect the rate and efficiency of the desulfurization reaction. The present invention can effectively reduce the temperature of the flue gas of the yellow phosphorus tail gas boiler by spraying cooling water, and can accurately control the flue gas temperature by adjusting the spraying amount and temperature of the cooling water, thereby creating suitable temperature conditions for continuous desulfurization reaction;

[0028] 2. The spraying of cooling water can not only reduce the flue gas temperature, but also react with the unreacted quicklime (CaO) in the slaked lime to produce more calcium hydroxide (Ca(OH) 2 ), which helps to improve the activity and reactivity of slaked lime, optimize the desulfurization reaction conditions, and increase SO 2 The removal rate of slaked lime can be improved, the utilization efficiency of slaked lime and the desulfurization efficiency can be improved, the amount of desulfurizer used can be reduced, the operating cost can be reduced, and the economy of the system can be improved; pollutant emissions can be reduced; and the unreacted quicklime in the slaked lime can be consumed, reducing its accumulation in the desulfurization system and avoiding blockage or wear on equipment and pipelines;

[0029] 3. Due to the improved desulfurization efficiency, the emission of secondary pollutants such as sulfate or sulfite that may be generated during the desulfurization process can be reduced;

[0030] 4. By precisely controlling the flue gas temperature and optimizing the use of desulfurizers, the reliability and stability of the entire desulfurization system can be improved, and downtime caused by equipment failure or operating errors can be reduced.

[0031] 5. By real-time monitoring of the flue gas temperature entering the desulfurization tower, it can be adjusted according to the actual production situation of the yellow phosphorus tail gas to achieve stable operation of the desulfurization device, so that the yellow phosphorus tail gas can be utilized as a resource, and the waste gas generated can also be treated in a more stable and effective way. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0033] Figure 1 It is a schematic structural diagram of the in-furnace desulfurization, denitrification and dephosphorization device for flue gas from a high sulfur and phosphorus tail gas boiler in the present invention;

[0034] Figure 2 It is a structural schematic diagram of the desulfurization tower in the present invention;

[0035] Figure 3 The present invention Figure 2 Schematic diagram of the enlarged structure of part A in the middle.

[0036] Reference numerals

[0037] 1-desulfurization tower, 2-first air inlet, 3-air outlet, 4-first nozzle, 5-first channel, 6-nozzle, 7-fixed plate, 8-second nozzle, 9-rotating shaft, 10-anti-sticking layer, 11-power generation boiler, 12-third nozzle, 13-fourth nozzle, 14-separator, 15-second channel, 16-second air inlet, 17-buffer assembly, 18-slag outlet, 19-first dust removal assembly, 20-second dust removal assembly, 21-emptying tower. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0039] Combine the following Figures 1 to 3 The present invention is described in detail.

[0040] Example 1

[0041] A high sulfur phosphorus tail gas boiler flue gas purification treatment system, see attached Figure 1, comprising a desulfurization tower 1, wherein a first air inlet 2 is arranged on the desulfurization tower 1, and a plurality of first nozzles 4 are arranged inside the desulfurization tower 1, wherein two of the first nozzles 4 are arranged on the upper and lower sides of the first air inlet 2; by arranging the first nozzles 4 on the upper and lower sides of the first air inlet 2 of the desulfurization tower 1, the first nozzles 4 spray water mist, thereby quickly reducing the temperature of the sulfur-containing flue gas sprayed from the first nozzle 4, and the mist sprayed from the first nozzle 4 can make the quicklime in the slaked lime react thoroughly, thereby improving the utilization efficiency of the slaked lime; the water mist sprayed from the first nozzle 4 can wash the slaked lime attached to the inside of the desulfurization tower 1.

[0042] The first air inlet 2 is used for introducing sulfur-containing flue gas.

[0043] The first nozzle 4 is connected to the water source through a pipeline, and a water pump is installed on the pipeline.

[0044] In this embodiment, the desulfurization tower 1 is connected with a first channel 5 for inputting slaked lime, and the end of the first channel 5 is connected to the interior of the desulfurization tower 1 through a nozzle 6; the first channel 5 is used to input slaked lime, and the nozzle 6 can spray the slaked lime out.

[0045] The head end of the first channel 5 is connected to the supply end of slaked lime powder, and the nozzle 6 is also connected to a booster pump.

[0046] In this embodiment, a fixed plate 7 is further provided inside the desulfurization tower 1, and a plurality of second nozzles 8 are provided on the fixed plate 7; the second nozzles 8 are provided on the fixed plate 7, and the second nozzles 8 are used to spray out gas flows, so as to fully disperse the slaked lime powder and mix it with the sulfur-containing flue gas for full reaction.

[0047] Among them, several second nozzles 8 are connected to the air pump through pipelines and universal heads.

[0048] In this embodiment, refer to the attached Figure 2 There are two fixed plates 7, which are respectively hinged to the inner wall of the desulfurization tower 1 through a rotating shaft 9; when the slaked lime and the sulfur-containing flue gas fully react, the waste slaked lime needs to be discharged. At this time, the fixed plate 7 is opened by rotating the rotating shaft 9, and the slaked lime is discharged through the bottom slag discharge port of the desulfurization tower 1.

[0049] In this embodiment, an anti-sticking layer 10 is provided on the inner wall of the desulfurization tower 1; the anti-sticking layer 10 further prevents the solid particles generated during the desulfurization process from causing scaling or clogging in the equipment.

[0050] In this embodiment, refer to the attached Figure 3The device also includes a power generation boiler 11, a buffer component 17, and a first dust removal component 19 which are connected in sequence through pipelines. The air outlet of the first dust removal component 19 is connected to the first air inlet 2 of the desulfurization tower 1 through a pipeline; the power generation boiler 11 discharges sulfur-containing flue gas after combustion and power generation, the buffer component 17 adjusts the temperature of the sulfur-containing flue gas to prevent the sulfur-containing flue gas from overheating, and the first dust removal component 19 removes dust from the sulfur-containing flue gas. The sulfur-containing flue gas after preliminary dust removal is passed into the desulfurization tower 1.

[0051] The buffer assembly 17 adopts a containing tower, and the containing tower contains a high-temperature superheater, a low-temperature superheater and several air preheaters from top to bottom;

[0052] The first dust removal assembly 19 adopts an electrostatic precipitator.

[0053] The upper part of the power generation boiler 11 is also connected to a feed port for introducing coal gangue.

[0054] In this embodiment, the gas outlet 3 of the desulfurization tower 1 is connected to the second dust removal component 20 and the emptying tower 21 in sequence through a pipeline; the second dust removal component 20 is used to thoroughly remove the dust from the flue gas discharged from the desulfurization tower 1, and finally pass it into the emptying tower 21 for emptying.

[0055] Wherein, the second dust removal component 20 adopts a bag dust collector.

[0056] In this embodiment, a slag outlet 18 is provided at the lower portion of the buffer assembly 17 ; the slag outlet 18 is used to discharge ash and slag dropped from the buffer assembly 17 .

[0057] In this embodiment, a third nozzle 12 and a fourth nozzle 13 are respectively provided on the side walls of the power generation boiler 11; a second air inlet 16 is also provided on the side wall at the bottom of the power generation boiler 11; the third nozzle 12 and the fourth nozzle 13 respectively spray limestone powder and urea to perform dephosphorization and desulfurization.

[0058] The third nozzle 12 is connected to the limestone powder through a pipeline, and a high-pressure pump is installed on the pipeline;

[0059] The fourth nozzle 13 is connected to a urea supply end pipeline, and a high-pressure pump is installed on the pipeline.

[0060] In this embodiment, a separator 14 is connected between the power generation boiler 11 and the buffer assembly 17 through a pipeline, and the bottom of the separator 14 is connected to the side wall of the power generation boiler 11 through a second channel 15; the separator 14 is used to separate the coal gangue introduced into the power generation boiler 11, and the coal gangue passes through the separator 14, and the particles with large particle size continue to enter the power generation boiler 11 through the second channel 15 for dephosphorization, and the particles with small particle size, i.e., fine particles, enter the back-end flue gas treatment system after pre-treatment by the dust collector, that is, the second stage of desulfurization is carried out in the desulfurization tower 1.

[0061] The separator 14 is a cyclone separator 14 .

[0062] Examples 2 to 8 and Comparative Examples 1 to 3

[0063] According to a flue gas purification method for a high sulfur and phosphorus tail gas boiler, flue gas purification is performed using the device described in Example 1, including the following steps:

[0064] Step 1: The yellow phosphorus tail gas is combusted in stages in the power generation boiler 11, and preliminary desulfurization (desulfurization is performed by limestone powder injected by the third nozzle 12), denitrification (denitrification is performed by urea injected by the fourth nozzle 13) and dephosphorization (dephosphorization is performed by coal gangue introduced into the boiler) are performed during the combustion to obtain high-temperature flue gas with a temperature of 360-390° C.;

[0065] Step 2: The high-temperature flue gas is cooled to t1 through the air preheater and economizer. The range of t1 is 140-200℃. The maximum and minimum temperatures of t1 are limited, which can save energy as much as possible while ensuring the best heat exchange effect of the high-temperature flue gas. And lowering the high-temperature flue gas to a suitable temperature will help reduce the subsequent flue gas temperature in the desulfurization tower, which will help balance the subsequent water spraying volume, so that the moisture in the flue gas reaches the most reasonable value, better control the acid dew point, and reduce corrosion to the equipment.

[0066] Step 3: The flue gas in step 2 is subjected to a first dust removal, and the first dust removal is performed in the first dust removal component 19;

[0067] Step 4: Mix the flue gas after the first dust removal in step 3 with the sprayed slaked lime powder for thorough desulfurization, and spray cooling water for cooling during the desulfurization process;

[0068] Step 5: The flue gas obtained in step 4 after thorough desulfurization is subjected to a second dust removal, and the second dust removal is performed in the second dust removal assembly 20;

[0069] Step 6: exhaust the flue gas obtained after the second dust removal in step 5, and the exhaust is carried out through an exhaust tower 21.

[0070] In this embodiment, in step 1, limestone is sprayed to perform preliminary desulfurization, urea is sprayed to perform denitrification, and coal gangue powder is sprayed to perform dephosphorization.

[0071] In this embodiment, the large-particle coal gangue after dephosphorization in step 1 is returned to the dephosphorization step in step 1 to continue to be dephosphorized.

[0072] In this embodiment, the first dust removal in step 3 is performed using an electrostatic dust collector, and the second dust removal in step 5 is performed using a bag dust collector.

[0073] In this embodiment, the complete desulfurization in step 4 includes the following steps:

[0074] Step 401: Step 4 is performed in the desulfurization tower 1, the flue gas is introduced into the desulfurization tower 1, and a thermometer monitors the temperature of the flue gas introduced into the desulfurization tower 1 in real time;

[0075] Step 402: The control system receives feedback of the flue gas temperature in real time and sends a signal to the nozzle 6 for spraying cooling water mist, thereby spraying cooling water mist to cool the flue gas to temperature t2;

[0076] Step 403: When the temperature detected by the thermometer drops to t2, slaked lime powder is sprayed in. At this time, the nozzle 6 continues to spray cooling water mist to keep the real-time temperature of the flue gas at t2. At the same time, air flow is introduced to suspend the slaked lime powder in the flue gas and the cooling water mist.

[0077] Step 404: The slaked lime powder is continuously sprayed and completely reacted for T time. The slaked lime powder contacts the boiler flue gas and is carried to the bag filter by the flue gas. During this period, the slaked lime powder reacts with the sulfur dioxide in the flue gas until it is discharged from the hopper below the bag filter. The slaked lime powder is thus renewed, and the slaked lime powder in the absorption tower can always maintain high activity.

[0078] In this embodiment, in step 402, the production status of the power generation boiler 11 in different time periods is different, and the exhaust gas supply, that is, the load of the boiler is different. Therefore, according to the exhaust gas supply of the power generation boiler 11, the initial temperature entering the desulfurization tower 1 will change, and the size of the cooling water mist is adjusted according to the initial temperature. When the real-time temperature is maintained at t2, the cooling water mist is maintained at this size.

[0079] In this embodiment, in step 404, T is 50 minutes.

[0080] In this embodiment, t2 in step 402 is 100-130°C.

[0081] In this embodiment, the temperature of the cooling water mist sprayed in step 402 is room temperature, the flow rate is 0 to 7.5 t / h, and the area of ​​the sprayed water mist covers the cross section of the desulfurization tower 1 .

[0082] Table 1: t1, t2, the amount of slaked lime required to remove sulfur impurities in flue gas and the time table of consumed sulfur impurities in Examples 2 to 8 and Comparative Examples 1 to 3.

[0083] The length of the absorption section of desulfurization tower 1 is about 32m. In actual operation, when the boiler load reaches more than 60t / h, the flue gas flow rate is about 3-5m 3 / s, the reaction time is about 6.5 to 10s; when the boiler load is 35 to 60t / h, the flue gas velocity is 1.5 to 3m 3 / s, the reaction time is about 10 to 21s, and the subsequent flue gas carries slaked lime into the bag filter. The main reaction takes place in the desulfurization tower 1.

[0084]

[0085]

[0086] In Comparative Examples 1 to 3, t1 and t2 are selected at temperatures lower than the range recorded in this application, and in Comparative Examples 4 to 6, t1 and t2 are selected at temperatures higher than the range recorded in this application. Under low temperature conditions, desulfurization and denitrification will be affected; and under ultra-high temperature conditions, although it will not affect the removal of nitrogen oxides, it will affect the removal of sulfur dioxide; therefore, only when t1 and t2 are in the most suitable temperature range can the optimal desulfurization and denitrification effects be guaranteed.

[0087] Among them, the ratio of slaked lime consumed to remove unit concentration of sulfur dioxide = [sulfur dioxide concentration under standard conditions before removal (monitoring value) - after removal (monitoring value)] / actual consumption of slaked lime.

[0088] From the data in Table 1 above, it can be seen that when the t1 temperature is controlled at 140-200°C and the t2 temperature is controlled at 100-130°C, the efficiency of removing sulfur dioxide is the highest and the actual amount of slaked lime consumed is the least.

[0089] It should be noted that:

[0090] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A flue gas purification system for a high sulfur and phosphorus tail gas boiler, characterized in that: The invention comprises a desulfurization tower (1), wherein the desulfurization tower (1) is provided with a first air inlet (2), and a plurality of first nozzles (4) are provided inside the desulfurization tower (1), wherein two of the first nozzles (4) are provided on the upper and lower sides of the first air inlet (2); the device also comprises a power generation boiler (11), a buffer component (17), and a first dust removal component (19) which are connected in sequence, and the air outlet of the first dust removal component (19) is connected to the first air inlet (2) of the desulfurization tower (1) through a pipeline.

2. A method for purifying flue gas from a high sulfur and phosphorus tail gas boiler, characterized in that: The following steps are involved: Step 1: Burn the yellow phosphorus tail gas in stages, and perform preliminary desulfurization, denitrification and dephosphorization during combustion to obtain high-temperature flue gas; Step 2: Cool the high-temperature flue gas to t1, where t1 ranges from 140 to 200°C; Step 3: Perform the first dust removal on the flue gas in step 2; Step 4: Mix the flue gas after the first dust removal in step 3 with the sprayed slaked lime powder for thorough desulfurization, and spray cooling water for cooling during the desulfurization process; Step 5: performing a second dust removal on the completely desulfurized flue gas obtained in step 4; Step 6: Exhaust the flue gas obtained after the second dust removal in step 5.

3. A method for purifying flue gas from a high sulfur phosphorus tail gas boiler according to claim 2, characterized in that: In step 1, limestone is sprayed to perform preliminary desulfurization, urea is sprayed to perform denitrification, and coal gangue powder is sprayed to perform dephosphorization.

4. The method for purifying flue gas from a high sulfur phosphorus tail gas boiler according to claim 3, characterized in that: The large-particle coal gangue after dephosphorization in step 1 is returned to the dephosphorization step in step 1 to continue dephosphorization.

5. The method for purifying flue gas from a high sulfur phosphorus tail gas boiler according to claim 2, characterized in that: The first dust removal in step 3 is performed by using an electrostatic dust collector, and the second dust removal in step 5 is performed by using a bag dust collector.

6. The method for purifying flue gas from a high sulfur phosphorus tail gas boiler according to claim 2, characterized in that: The complete desulfurization in step 4 includes the following steps: Step 401: Step 4 is performed in the desulfurization tower (1), the flue gas is introduced into the desulfurization tower (1), and a thermometer monitors the temperature of the flue gas introduced into the desulfurization tower (1) in real time; Step 402: The control system receives feedback of the flue gas temperature in real time and sends a signal to the nozzle (6) for spraying cooling water mist, thereby spraying cooling water mist to cool the flue gas to temperature t2; Step 403: When the temperature detected by the thermometer drops to t2, slaked lime powder is sprayed in. At this time, the nozzle (6) continues to spray cooling water mist so that the real-time temperature of the flue gas is maintained at t2. At the same time, air flow is introduced to suspend the slaked lime powder in the flue gas and the cooling water mist. Step 404: The slaked lime powder is sprayed for a period of time T, and the slaked lime powder after the reaction is discharged, and then sprayed to replace the slaked lime powder.

7. The method for purifying flue gas from a high sulfur and phosphorus tail gas boiler according to claim 6, characterized in that: In step 402, the production status of the power generation boiler (11) is different in different time periods, and the exhaust gas supply, that is, the load of the boiler, is different. Therefore, the exhaust gas supply of the power generation boiler (11) changes, and the initial temperature entering the desulfurization tower (1) will change. The size of the cooling water mist is adjusted according to the initial temperature. When the real-time temperature is maintained at t2, the cooling water mist is maintained at this size.

8. The method for purifying flue gas from a high sulfur and phosphorus tail gas boiler according to claim 6, characterized in that: In step 404, T is 40 to 60 minutes.

9. The method for purifying flue gas from a high sulfur and phosphorus tail gas boiler according to claim 7, characterized in that: In step 402, t2 is 100-130°C.

10. The method for purifying flue gas from a high sulfur and phosphorus tail gas boiler according to claim 7, characterized in that: The temperature of the cooling water mist sprayed in step 402 is room temperature, the flow rate is 0 to 7.5 t / h, and the area of ​​the sprayed water mist covers the cross section of the desulfurization tower (1).

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