Dual-alkali flue gas desulfurization synergistic interaction process and system

Abstract

The invention relates to an efficient flue gas desulfurization synergistic interaction process and system based on a dual-alkali method, the process adopts the synergistic effect of a sodium-based desulfurizer and a calcium-based regenerant, sulfur dioxide in flue gas is efficiently absorbed by sodium alkali liquor in an absorption tower, and the absorption liquid is cyclically regenerated by calcium hydroxide in a regeneration pool. And efficient utilization and scaling inhibition of the desulfurizer are realized. The system comprises a multi-stage dust removal device, an absorption tower, a regeneration reaction tank and a gypsum generation module, and through cooperation of a spraying layer, a demister and a pH value regulation and control device, the sulfur dioxide removal efficiency is larger than or equal to 95%, and the dust particulate matter removal rate is larger than or equal to 98%. The method solves the problem of scaling and blocking of a traditional calcium-based method, and has the characteristics of low operation cost and long service life of equipment.

Description

Technical Field

[0001] The present invention relates to the field of industrial waste gas purification, and particularly to a double-alkali flue gas desulfurization synergistic enhancement process and system. Background Art

[0002] The traditional limestone-gypsum method has the following defects: (1) The calcium-based absorbent has low solubility and is prone to scale and blockage in the tower; (2) The forced oxidation system increases the energy consumption by 20-30%; (3) The desulfurization efficiency is significantly affected by the pH fluctuation of the slurry. Although the existing double-alkali method technology can alleviate the scaling problem, it has deficiencies such as large consumption of sodium alkali, low regeneration efficiency (usually <85%), and poor synergistic performance of dust removal and desulfurization.

[0003] It can be seen that the above-mentioned existing double-alkali flue gas desulfurization synergistic enhancement process and system are obviously still inconvenient and defective in terms of methods and use, and urgently need to be further improved. In order to solve the problems existing in the double-alkali flue gas desulfurization synergistic enhancement process and system, relevant manufacturers have tried their best to seek solutions, but no applicable design has been developed for a long time. Moreover, the general methods and the double-alkali flue gas desulfurization synergistic enhancement process and system do not have appropriate methods, manufacturing methods, processing methods, and structures to solve the above problems, which are obviously problems that relevant industries are eager to solve.

[0004] In view of the above defects of the existing double-alkali flue gas desulfurization synergistic enhancement process and system, the inventor, based on rich practical experience and professional knowledge in the design and manufacture of such products for many years, and in cooperation with the application of theory, actively conducts research and innovation, aiming to create a new double-alkali flue gas desulfurization synergistic enhancement process and system that can improve the general existing double-alkali flue gas desulfurization synergistic enhancement process and system and make it more practical. After continuous research, design, repeated trial production, and improvement, the present invention with practical value has finally been created. Summary of the Invention

[0005] The core innovation of the present invention lies in:

[0006] Process synergistic enhancement: Through the closed-loop system of "sodium alkali absorption - calcium alkali regeneration", through the coordination of dynamic regulation of pH in the absorption tower (pH = 8.5 - 10.5) and optimization of pH in the regeneration tank (pH = 6.5 - 7.5), efficient absorption and regeneration are achieved, and the sodium alkali recycling rate reaches more than 92%.

[0007] System integration optimization: A double-stage pretreatment of cyclone dust removal + electrostatic dust removal is set in front of the absorption tower, and an efficient demister is configured in the rear section to achieve the synergistic removal of dust and SO2.

[0008] Anti-crystallization design: An electric tracing system is set in the outlet pipeline of the regeneration tank to maintain the pipeline temperature at 45 - 50 °C to prevent the crystallization and blockage of sodium sulfite.

[0009] The main objective of the present invention is to provide a double-alkali flue gas desulfurization synergistic efficiency improvement process and system. The technical problem to be solved is to overcome the defects of large consumption of sodium alkali, poor synergy between dust removal and desulfurization, and high crystallization risk in the regeneration system in the existing double-alkali method. Through process parameter optimization and system integration design, the sodium alkali recycling utilization rate is ≥92%, the synergistic removal efficiency of dust and SO2 is ≥98%, and the continuous operation period of the system is ≥6 months without crystallization blockage, thereby reducing the operation cost and enhancing the industrial utilization value.

[0010] Another objective of the present invention is to provide a highly efficient crystallization-preventing sodium-calcium double-alkali regeneration system. The technical problem to be solved is to inhibit the crystallization and precipitation of sodium sulfite through the synergistic effect of pH grading control and electric tracing temperature, ensure that the temperature of the regeneration liquid pipeline is stable at 45 - 50 °C (higher than the crystallization critical temperature of 40 °C), reduce the scale inhibitor addition amount to 0.1 - 0.5%, and the annual scale thickness ≤0.5 mm.

[0011] Another objective of the present invention is to provide a multi-stage synergistic purification device. The technical problem to be solved is to achieve the integrated removal of dust and SO2. Through the double-stage pretreatment of pre-stage cyclone dust removal (efficiency ≥85%) + electrostatic dust removal (efficiency ≥95%), and the combined use of atomized spraying (particle size 50 - 150 μm) in the absorption tower and two-stage demisters, the outlet dust concentration ≤30 mg / Nm 3 and the SO2 concentration ≤35 mg / Nm 3 .

[0012] Another objective of the present invention is to provide a low-cost gypsum dehydration process. The technical problem to be solved is to improve the gypsum purity and reduce the energy consumption through the synergistic effect of hydrocyclone separation and vacuum dehydration, control the gypsum moisture content ≤10%, the content of calcium sulfate dihydrate ≥90%, and the power consumption of the dehydration system ≤15 kWh / ton of gypsum.

[0013] The objective of the present invention and the solution to its technical problem are achieved by adopting the following technical solutions. The present invention has obvious advantages and beneficial effects compared with the prior art. From the above technical solutions, in order to achieve the aforementioned invention objective, the main technical content of the present invention is as follows:

[0014] The present invention provides a double-alkali flue gas desulfurization synergistic efficiency improvement process and system, including:

[0015] A multi-stage dust removal device for removing particulate matter with a particle size greater than or equal to 1 micron in the flue gas;

[0016] An absorption tower, which is internally provided with a sodium alkali liquid spraying layer and a demister, the sodium alkali liquid concentration is 5% to 15%, and the spraying density is 3 cubic meters per square meter per hour to 8 cubic meters per square meter per hour;

[0017] A regeneration reaction tank is configured with calcium hydroxide slurry and a stirring device. The concentration of the calcium hydroxide slurry is 10% to 25%, and the stirring speed is 20 revolutions per minute to 60 revolutions per minute;

[0018] A gypsum generation module, including a hydrocyclone and a vacuum dewatering machine, is used to recover gypsum with a moisture content less than or equal to 10%;

[0019] A pH regulation device is used to adjust the pH value of the regeneration reaction tank to 6.5 to 7.5 in real time.

[0020] Preferably, the multi-stage dust removal device includes a cyclone dust collector and an electrostatic precipitator. The dust removal efficiency of the cyclone dust collector is greater than or equal to 85%, and the dust removal efficiency of the electrostatic precipitator is greater than or equal to 92%.

[0021] Preferably, the spray layer spacing of the absorption tower is 0.8 meters to 1.5 meters, and the nozzle atomization particle size is 50 microns to 150 microns.

[0022] Preferably, the sodium-based alkali solution is a mixed solution of sodium hydroxide and sodium sulfite, and the molar ratio of sodium hydroxide to sodium sulfite is 1:0.5 to 1:2.

[0023] Preferably, a polyacrylic acid scale inhibitor is added to the regeneration reaction tank, and the addition amount is 0.1% to 0.5% of the mass of the calcium hydroxide slurry.

[0024] Preferably, in the gypsum generation module, the separation efficiency of the hydrocyclone is greater than or equal to 95%, and the content of calcium sulfate dihydrate in the obtained gypsum is greater than or equal to 90%.

[0025] Furthermore, a high-efficiency flue gas desulfurization synergistic enhancement process based on the double-alkali method includes the following steps:

[0026] Treat the flue gas through a multi-stage dust removal device to make the dust concentration less than or equal to 30 milligrams per standard cubic meter;

[0027] In the absorption tower, the sodium-based alkali solution contacts the flue gas countercurrently, and the sulfur dioxide removal efficiency is greater than or equal to 95%;

[0028] Transport the absorption liquid enriched with sodium bisulfite to the regeneration reaction tank to react with calcium hydroxide to generate sodium sulfite and calcium sulfite;

[0029] Oxidize calcium sulfite to calcium sulfate, and obtain gypsum with a moisture content less than or equal to 10% after dehydration;

[0030] Reuse the regenerated sodium-based alkali solution to the absorption tower, and the fresh sodium-based alkali solution supplement amount is less than or equal to 5%.

[0031] Preferably, the reaction time of the regeneration reaction tank is 30 minutes to 90 minutes, and the temperature is controlled at 40 degrees Celsius to 60 degrees Celsius.

[0032] Preferably, the pH value of the sodium-based alkali solution in the absorption tower is 8.5 to 10.5, and the addition amount of calcium hydroxide is dynamically adjusted by a pH control device.

[0033] Preferably, the molecular weight of the polyacrylic acid scale inhibitor is 2,000 to 5,000, which is used to inhibit the growth of calcium sulfite crystals.

[0034] As can be seen from the above, the process of the present invention adopts the synergistic effect of a sodium-based desulfurizer and a calcium-based regenerant. Through the efficient absorption of sulfur dioxide in flue gas by the sodium-based alkali solution in the absorption tower and the cyclic regeneration of the absorption liquid by calcium hydroxide in the regeneration tank, the efficient utilization of the desulfurizer and the inhibition of fouling are realized. The system includes a multi-stage dust removal device, an absorption tower, a regeneration reaction tank, and a gypsum generation module. Through the coordinated cooperation of the spray layer, the demister, and the pH control device, the sulfur dioxide removal efficiency is ≥95%, and the dust particle removal rate is ≥98%. The present invention solves the problem of fouling and blockage in the traditional calcium-based method, and has the characteristics of low operating cost and long equipment life.

[0035] By means of the above technical solution, the double-alkali flue gas desulfurization synergistic enhancement process and system of the present invention at least have the following advantages:

[0036] Significantly improved sodium alkali utilization rate: Through the closed-loop regeneration system, the sodium alkali recycling utilization rate is increased from ≤85% in the traditional process to ≥92%, and the annual supplement amount is reduced by 40%;

[0037] High synergistic removal efficiency: Integrated removal of dust and SO2, with the outlet concentrations being ≤30mg / Nm 3 and ≤35mg / Nm 3 (better than the national standard GB13223-2011 limit value of 50mg / Nm 3 );

[0038] Strong anti-crystallization stability: The design of electric tracing + PTFE coating enables the continuous operation period of the regeneration system to be ≥6 months (≤3 months in the traditional process);

[0039] Double excellence in gypsum quality and energy consumption: The moisture content of gypsum is ≤10% (≥15% in the traditional process), and the dehydration power consumption is reduced by 30%.

[0040] The present invention solves the technical problems of low efficiency, unstable operation, and high cost in the existing double-alkali process through the innovative design of "sodium alkali absorption - calcium alkali regeneration" hierarchical pH control, multi-stage collaborative purification device, and anti-crystallization electric tracing system. Verified by examples:

[0041] The sodium alkali recycling utilization rate reaches 92 - 94%, and the annual operating cost is reduced by 25%;

[0042] The system resistance loss is ≤1200Pa (≥2000Pa in the traditional process);

[0043] The purity of gypsum is ≥90%, which can be directly sold as building materials raw materials to create additional income.

[0044] This invention realizes the collaborative optimization of the whole process of dust removal - desulfurization - regeneration - dehydration for the first time among similar technologies. No similar solutions have been publicly reported, and it has significant technological progress and industrial promotion value.

[0045] In summary, the special double-alkali flue gas desulfurization collaborative efficiency enhancement process and system of the present invention solve the problem of scaling and blockage in the traditional calcium-based method, and have the characteristics of low operating cost and long equipment life. It has the above-mentioned many advantages and practical values, and no similar designs have been publicly reported or used in similar methods and processes, so it is indeed innovative. It has made great improvements both in terms of method, process and function, has made great progress in technology, and has produced good and practical effects. Moreover, it has multiple enhanced effects compared with the existing double-alkali flue gas desulfurization collaborative efficiency enhancement process and system, so it is more suitable for practical use and has wide industrial utilization value. It is truly a novel, progressive and practical new design.

[0046] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following will be described in detail with the preferred embodiments of the present invention in conjunction with the accompanying drawings.

[0047] The specific process, system and implementation method of the present invention are given in detail by the following embodiments and their accompanying drawings. Description of the Drawings

[0048] Figure 1 : An example of the process flow diagram of the double-alkali flue gas desulfurization collaborative efficiency enhancement process. Detailed Embodiment

[0049] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following will describe in detail the specific implementation methods, methods, steps, features and their effects of a double-alkali flue gas desulfurization collaborative efficiency enhancement process and system according to the present invention in conjunction with the accompanying drawings and preferred embodiments.

[0050] Please refer to Figure 1 As shown, the double-alkali flue gas desulfurization collaborative efficiency enhancement process and system of the preferred embodiment of the present invention mainly include the following steps:

[0051] After the flue gas enters the inlet, first, flue gas pretreatment is carried out, and multi-stage dust removal is carried out. The flue gas first passes through a cyclone dust collector (efficiency ≥85%) to remove large particle dust (particle size ≥1μm); then passes through an electrostatic precipitator (efficiency ≥92%) to make the outlet dust concentration ≤30mg / Nm 3; It should be noted that the multi-stage dust removal device can select a combination of cyclone dust removal and electrostatic dust removal or bag dust removal according to the flue gas characteristics. The preferred implementation method is cyclone + electrostatic dust removal, where the plate spacing of the electrostatic precipitator is 200 - 400 mm and the operating voltage is 40 - 60 kV. The pretreated flue gas enters the absorption tower for desulfurization by sodium alkali spray absorption. In the first step, sodium alkali solution is prepared (concentration 5% - 15%, molar ratio of NaOH:Na2SO3 1:0.5 - 1:2); in the second step, it is sprayed countercurrently through the spray layer (spacing 0.8 - 1.5 m, atomization particle size 50 - 150 μm), and the spray density is 3 - 8 m 3 / (m 2 ·h); in the third step, the pH of the absorption liquid is dynamically adjusted to 8.5 - 10.5 to achieve a SO2 removal efficiency of ≥95%. Then, a regeneration reaction is carried out to achieve calcium alkali regeneration and scale inhibition. The absorption liquid enriched with sodium bisulfite is transported to the regeneration pool and reacts with 10% - 25% Ca(OH)2 slurry (stirring speed 20 - 60 rpm); a polyacrylic acid scale inhibitor (molecular weight 2000 - 5000, addition amount 0.1% - 0.5%) is added, and the reaction time is controlled for 30 - 90 minutes and the temperature is 40 - 60 °C; the pH of the regeneration pool is adjusted to 6.5 - 7.5 to generate sodium sulfite (for reuse) and calcium sulfite. It should be noted that the pH value in the absorption tower is adjusted in real time by the sodium hydroxide supplementary solution. When the pH is lower than 8.5, sodium hydroxide solution is automatically added, and when it is higher than 10.5, the addition amount is reduced. After passing through the regeneration reaction pool, gypsum is generated through a hydrocyclone and a vacuum dewatering machine. Air is introduced into the regeneration liquid to oxidize calcium sulfite to calcium sulfate; after being concentrated by the hydrocyclone (efficiency ≥95%), it is dehydrated by the vacuum dewatering machine (vacuum degree -0.08 to -0.1 MPa) to produce gypsum (water content ≤10%, calcium sulfate dihydrate content ≥90%). The regenerated sodium alkali liquid is recycled to the absorption tower, and the amount of fresh sodium alkali supplemented is ≤5%; the pipeline temperature is maintained at 45 - 50 °C by electric tracing throughout the process to prevent sodium sulfite crystallization from blocking.

[0052] The implementation method of the double-alkali flue gas desulfurization synergistic enhancement process and system provided by the present invention has key technical points in collaborative control, hierarchical pH regulation, and anti-crystallization design. The multi-stage dust removal (cyclone + electrostatic) and the absorption tower spray are coordinated to achieve synchronous and efficient removal of dust and SO2. During the hierarchical pH regulation process, the pH in the absorption section is 8.5 - 10.5 (efficient absorption of SO2); the pH in the regeneration section is 6.5 - 7.5 (optimize calcium alkali regeneration). The dual measures of scale inhibitor + electric tracing ensure that the system operates continuously for ≥180 days without blockage.

[0053] Example 1:

[0054] First, carry out system configuration:

[0055] Multi-stage dust removal device

[0056] Cyclone dust collector: inlet air velocity 18 m / s, dust removal efficiency 85%;

[0057] Electrostatic precipitator: plate spacing 300 mm, voltage 50 kV, dust removal efficiency 92%.

[0058] Absorption tower

[0059] Spray layer: spacing 1.5 m, nozzle atomization particle size 150 μm;

[0060] Sodium alkali solution: concentration 5%, molar ratio NaOH:Na2SO3 = 1:0.5;

[0061] pH regulation: pH in the absorption tower = 8.5.

[0062] Regeneration reaction tank

[0063] Calcium hydroxide slurry: concentration 10%, stirring speed 20 rpm;

[0064] Scale inhibitor: polyacrylic acid (molecular weight 2000,), dosage 0.1%;

[0065] Reaction conditions: time 30 minutes, temperature 40 °C.

[0066] Gypsum generation module

[0067] Cyclone separator: separation efficiency 95%;

[0068] Vacuum dewatering machine: vacuum degree -0.08 MPa, gypsum moisture content 9.5%.

[0069] Process Steps

[0070] Flue gas pretreatment:

[0071] Flue gas (initial dust 2000 mg / Nm 3 ) is reduced to 300 mg / Nm after cyclone dust removal 3 , and then reduced to 24 mg / Nm after electrostatic precipitator 3 .

[0072] Flue gas desulfurization in the absorption tower:

[0073] Spray density 3 m 3 / (m 2 ·h), liquid-gas ratio 8 L / m 3 , SO2 inlet concentration 2000 mg / Nm 3 ;

[0074] pH is adjusted to 8.5 - 9.0 in real time, and SO2 removal efficiency is 95.3%.

[0075] Regeneration reaction:

[0076] The absorption liquid reacts with calcium hydroxide for 30 minutes to produce sodium sulfite and calcium sulfite;

[0077] The pH of the regeneration pool is 6.5, and the sodium alkali regeneration rate is 92.1%.

[0078] Gypsum formation:

[0079] Calcium sulfite is oxidized (by introducing air, gas-liquid ratio 3m 3 / m 3 ) to produce calcium sulfate;

[0080] The underflow concentration of the hydrocyclone separator is 35%, and the calcium sulfate dihydrate content in the dehydrated gypsum is 90.5%.

[0081] Sodium alkali reuse:

[0082] The regenerated liquid is reused to the absorption tower, and the fresh sodium alkali supplement amount is 4.9% (meeting ≤ 5% of claim 7).

[0083] Verification Results

[0084] Indicators Measured Values Outlet Dust Concentration <![CDATA[24mg / Nm 3 > <![CDATA[SO2 removal efficiency]]> 95.3％ Sodium Alkali Supplement Amount 4.9％ Gypsum Moisture Content 9.5％ Scale Inhibitor Molecular Weight 2000

[0085] Example 2:

[0086] First, perform system configuration:

[0087] Multi-stage dust removal device

[0088] Cyclone dust collector: Dust removal efficiency is 87%;

[0089] Electrostatic precipitator: Dust removal efficiency is 95%.

[0090] Absorption tower

[0091] Spray layer: Spacing is 0.8m, and the nozzle atomization particle size is 50μm;

[0092] Sodium alkali solution: Concentration is 15%, and the molar ratio of NaOH:Na2SO3 is 1:2;

[0093] pH regulation: The pH of the absorption tower is 10.5.

[0094] Regeneration reaction pool

[0095] Calcium hydroxide slurry: Concentration is 25%, and the stirring speed is 60rpm;

[0096] Scale inhibitor: Polyacrylic acid (molecular weight 5000,), addition amount is 0.5%;

[0097] Reaction conditions: Time is 90 minutes, and temperature is 60°C.

[0098] Gypsum formation module

[0099] Cyclone separator: Separation efficiency 97%;

[0100] Vacuum dewatering machine: Vacuum degree -0.1 MPa, moisture content of gypsum 8.2%.

[0101] Process steps

[0102] Flue gas pretreatment

[0103] Flue gas (initial dust 2500 mg / Nm 3 ) is reduced to 325 mg / Nm after cyclone dust removal 3 , and then reduced to 14 mg / Nm after electrostatic precipitator 3 .

[0104] Flue gas desulfurization in the absorption tower

[0105] Spray density 8 m 3 / (m 2 ·h), liquid-gas ratio 12 L / m 3 , SO2 inlet concentration 3000 mg / Nm 3 ;

[0106] Dynamically adjust pH to 10.5, SO2 removal efficiency 98.6%.

[0107] Regeneration reaction

[0108] The absorption liquid reacts with calcium hydroxide for 90 minutes, and the pH of the regeneration pool = 7.5;

[0109] Sodium alkali regeneration rate 94.3%.

[0110] Gypsum formation

[0111] Oxidation temperature 60 °C, calcium sulfite oxidation rate 99%;

[0112] The underflow concentration of the cyclone separator is 45%, and the content of calcium sulfate dihydrate in gypsum is 93.8%.

[0113] Sodium alkali reuse

[0114] The regenerated liquid is reused to the absorption tower, and the fresh sodium alkali supplement amount is 4.1%.

[0115] Verification results

[0116] Indicators Measured Values Spray Layer Spacing 0.8m Cyclone Separation Efficiency 97％ Reaction Temperature 60℃ Scale Inhibitor Dosage 0.5％ Calcium Sulfate Dihydrate Content 93.8％

[0117] Example 3:

[0118] First, perform system configuration:

[0119] Multi-stage dust removal device

[0120] Cyclone dust collector: Dust removal efficiency 86%;

[0121] Electrostatic precipitator: Dust removal efficiency 93%.

[0122] Absorption tower

[0123] Spray layer: Spacing 1.2 m, nozzle atomization particle size 100 μm;

[0124] Sodium alkali solution: Concentration 10%, molar ratio NaOH:Na2SO3 = 1:1;

[0125] pH regulation: Absorption tower pH = 9.5.

[0126] Regeneration reaction tank

[0127] Calcium hydroxide slurry: Concentration 18%, stirring speed 40 rpm;

[0128] Scale inhibitor: Polyacrylic acid (molecular weight 3500), addition amount 0.3%;

[0129] Reaction conditions: Time 60 minutes, temperature 50 °C.

[0130] Gypsum generation module

[0131] Cyclone separator: Separation efficiency 96%;

[0132] Vacuum dewatering machine: Vacuum degree -0.09 MPa, gypsum moisture content 8.5%.

[0133] Process steps

[0134] Flue gas pretreatment

[0135] Flue gas (initial dust 1800 mg / Nm 3 ) is reduced to 252 mg / Nm after cyclone dust removal 3 , and then reduced to 21 mg / Nm after electrostatic precipitator 3 .

[0136] Flue gas desulfurization in the absorption tower

[0137] Spray density 5.5 m 3 / (m 2 ·h), liquid-gas ratio 10 L / m 3 , SO2 inlet concentration 2500 mg / Nm 3 ;

[0138] Dynamically adjust pH to 9.5, SO2 removal efficiency 97.2%.

[0139] Regeneration reaction

[0140] Regeneration tank pH = 7.0, sodium alkali regeneration rate 93.5%;

[0141] The scale inhibitor inhibits crystal growth to an average particle size of 8 μm.

[0142] Gypsum formation

[0143] The temperature in the oxidation stage is 50 °C, and the conversion rate of calcium sulfite is 98.5%;

[0144] The content of calcium sulfate dihydrate in gypsum is 92.4%.

[0145] Sodium alkali recycling

[0146] The regenerated liquid is recycled to the absorption tower, and the fresh sodium alkali supplement amount is 3.8%.

[0147] Verification results

[0148]

[0149] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications within the scope of the technical solution of the present invention to equivalent embodiments with equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An efficient flue gas desulfurization synergistic enhancement system based on the double-alkali method, characterized in that, Comprising: A multi-stage dust removal device for removing particulate matter with a particle size greater than or equal to 1 μm in flue gas; An absorption tower with a sodium alkali solution spraying layer and a demister inside, the concentration of the sodium alkali solution being 5% to 15%, and the spraying density being 3 m³ / (m²·h) to 8 m³ / (m²·h); A regeneration reaction tank equipped with calcium hydroxide slurry and a stirring device, the concentration of the calcium hydroxide slurry being 10% to 25%, and the stirring speed being 20 r / min to 60 r / min; A gypsum generation module including a hydrocyclone and a vacuum dewatering machine for recovering gypsum with a moisture content less than or equal to 10%; A pH regulation device for adjusting the pH value of the regeneration reaction tank to 6.5 to 7.5 in real time.

2. The system according to claim 1, wherein The multi-stage dust removal device includes a cyclone dust collector and an electrostatic precipitator. The dust removal efficiency of the cyclone dust collector is greater than or equal to 85%, and the dust removal efficiency of the electrostatic precipitator is greater than or equal to 92%.

3. The system according to claim 1, wherein The spacing between the spraying layers of the absorption tower is 0.8 m to 1.5 m, and the atomization particle size of the nozzles is 50 μm to 150 μm.

4. The system according to claim 1, wherein The sodium alkali solution is a mixed solution of sodium hydroxide and sodium sulfite, and the molar ratio of sodium hydroxide to sodium sulfite is 1:0.5 to 1:

2.

5. The system according to claim 1, characterized in that, A polyacrylic acid scale inhibitor is added to the regeneration reaction tank, and the addition amount is 0.1% to 0.5% of the mass of the calcium hydroxide slurry.

6. The system according to claim 1, wherein In the gypsum generation module, the separation efficiency of the hydrocyclone is greater than or equal to 95%, and the content of calcium sulfate dihydrate in the obtained gypsum is greater than or equal to 90%.

7. An efficient flue gas desulfurization synergistic process based on the double-alkali method, characterized in that, Including the following steps: Treating the flue gas through the multi-stage dust removal device to make the dust concentration less than or equal to 30 mg / Nm³; In the absorption tower, the sodium alkali solution is in countercurrent contact with the flue gas, and the sulfur dioxide removal efficiency is greater than or equal to 95%; Transporting the absorption liquid enriched with sodium bisulfite to the regeneration reaction tank to react with calcium hydroxide to generate sodium sulfite and calcium sulfite; Oxidizing calcium sulfite to calcium sulfate and obtaining gypsum with a moisture content less than or equal to 10% after dehydration; Recycling the regenerated sodium alkali solution to the absorption tower, and the fresh sodium alkali solution supplement amount is less than or equal to 5%.

8. The process according to claim 7, characterized in that, The reaction time of the regeneration reaction tank is 30 minutes to 90 minutes, and the temperature is controlled at 40 °C to 60 °C.

9. The process according to claim 7, characterized in that, The pH value of the sodium alkali solution in the absorption tower is 8.5 to 10.5, and the addition amount of calcium hydroxide is dynamically adjusted through the pH regulation device.

10. The process according to claim 7, characterized in that, The molecular weight of the polyacrylic acid scale inhibitor is 2000 to 5000, which is used to inhibit the growth of calcium sulfite crystals.

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