Flue gas desulfurization system

Abstract

The present application provides a flue gas desulfurization system, which is provided with a dust collector, a first desulfurization tower and a second desulfurization tower, and the flue gas discharged from the boiler is subjected to two-stage desulfurization treatment after being dedusted by the dust collector, and then sequentially passes through the first desulfurization tower and the second desulfurization tower, thereby improving the desulfurization efficiency, and transferring the slurry absorbed by the second desulfurization tower to the first desulfurization tower for utilization, thereby improving the utilization rate of the absorbed slurry and reducing the output of absorbed solid waste. The system of the present application overcomes the adverse consequences of incomplete desulfurization in the traditional single tower, which easily causes sulfur escape and leads to excessive flue gas emissions, through the coordinated use of the above-mentioned equipment.

Description

Technical Field

[0001] The present application relates to the technical field of boiler flue gas desulfurization, and in particular to a flue gas desulfurization system. Background Art

[0002] The sulfur contained in coal will be oxidized by oxygen in the air during the combustion of coal and exist in the flue gas in the form of sulfur dioxide. As one of the air pollutants, sulfur dioxide is the culprit of the greenhouse effect and acid rain. Acid rain not only changes the chemical and physical properties of the soil, making most plants unable to grow normally, but also acidifies the water, corrodes buildings, causes biological mutations, and causes respiratory diseases and even death to people themselves. In my country, the economic losses caused by acid rain can exceed 100 billion yuan each year. Therefore, controlling the emission of sulfur dioxide is particularly important for the environment, economy and human health.

[0003] At present, in order to deal with the sulfur dioxide produced by coal combustion, three major types of technologies that can control and reduce sulfur dioxide emissions have been developed, mainly including 1) pre-combustion desulfurization technology: including biological methods, physical methods and chemical methods; 2) desulfurization technology during combustion: taking fluidized bed combustion and furnace calcium injection method as examples; 3) flue gas desulfurization technology after combustion: including semi-dry method and wet flue gas desulfurization. Based on the considerations of equipment investment, processing cost and desulfurization effect, wet flue gas desulfurization is currently the most widely used desulfurization method. Its main desulfurization process is to use alkaline slurry such as lime slurry as an absorbent, which contacts with boiler flue gas in countercurrent in the desulfurization tower, and absorbs and removes sulfur dioxide and other acidic substances in the flue gas. The existing wet desulfurization method mostly uses a single tower for desulfurization, but this desulfurization method is prone to sulfur escape, resulting in the adverse consequences of excessive flue gas emissions. Utility Model Content

[0004] The present application provides a flue gas desulfurization system to solve the problem that the single-tower desulfurization in the existing wet desulfurization method is prone to sulfur escape, resulting in excessive flue gas emissions.

[0005] The present application provides a flue gas desulfurization system, comprising a boiler, a dust collector, a first desulfurization tower, a second desulfurization tower and a chimney connected in series in sequence;

[0006] The gas output end of the first desulfurization tower is connected to the gas input end of the second desulfurization tower; the absorption liquid output end of the second desulfurization tower is connected to the absorption liquid input end of the first desulfurization tower;

[0007] The absorption liquid output end of the first desulfurization tower is connected to the wastewater treatment system.

[0008] Optionally, the first desulfurization tower includes a tower body;

[0009] The interior of the tower body is divided into an upper oxidation zone and a lower absorption zone by a partition. A first slurry pool is arranged at the bottom of the absorption zone, and a first demister and a first slurry spray layer are arranged in sequence from top to bottom in the absorption zone; a first air inlet located between the first slurry spray layer and the first slurry pool is arranged on one side of the tower body of the absorption zone; the first slurry pool is connected to the first slurry spray layer through a first circulation pump; a first agitator is arranged in the first slurry pool; and the first slurry pool is also connected to a wastewater treatment system;

[0010] A hood is provided on the partition to connect the oxidation zone and the absorption zone; an oxidant outlet is provided on one side of the bottom of the tower body in the oxidation zone, and a second demister, an oxidant spray layer and a first packing layer are provided in the oxidation zone from top to bottom; a first gas outlet is provided on the top of the tower body;

[0011] The oxidant outlet is communicated with the oxidant storage tank, and the oxidant storage tank is connected to the oxidant spraying layer through a second circulation pump.

[0012] Optionally, the wastewater treatment system comprises a filter press, a wastewater storage tank, an evaporation tower and a cyclone separator connected in series in sequence;

[0013] The wastewater storage tank is connected to the evaporation tower through a liquid transfer pump, and the evaporation tower is also connected in series with an air heater and a second induced draft fan.

[0014] Optionally, a gas distributor and a liquid atomizer are sequentially arranged in the evaporation tower from top to bottom; an exhaust port is opened at the bottom of the tower;

[0015] The gas distributor is connected to the air heater; the liquid atomizer is connected to the output end of the liquid transfer pump; and the exhaust port is connected to the input end of the cyclone separator.

[0016] Optionally, the wastewater treatment system further comprises: a first induced draft fan and a heat exchanger connected to the cyclone separator in sequence, and the heat exchanger is arranged between the second desulfurization tower and the chimney.

[0017] Optionally, a wet dust collector is also provided between the second desulfurization tower and the heat exchanger.

[0018] Optionally, a third demister, a second slurry spraying layer and a second packing layer are sequentially arranged in the second desulfurization tower from top to bottom; a second gas outlet is arranged at the top of the second desulfurization tower and a second slurry pool is arranged at the bottom;

[0019] A second air inlet is provided on one side wall of the second desulfurization tower between the second slurry pool and the second filler layer;

[0020] The second slurry pool is connected to the second slurry spraying layer through a third circulation pump; a second agitator is arranged in the second slurry pool;

[0021] The first gas outlet is communicated with the second gas inlet.

[0022] The flue gas desulfurization system provided by the present application is provided with a dust collector, a first desulfurization tower and a second desulfurization tower. After the flue gas discharged from the boiler passes through the dust collector for dust removal, it passes through the first desulfurization tower and the second desulfurization tower in sequence for two-stage desulfurization treatment, thereby improving the desulfurization efficiency. Moreover, the slurry absorbed by the second desulfurization tower is transferred to the first desulfurization tower for utilization, thereby improving the utilization rate of the absorption slurry and reducing the output of absorption solid waste. The system of the present application overcomes the adverse consequences of incomplete desulfurization in the traditional single tower, which easily causes sulfur escape and leads to excessive flue gas emissions, through the coordinated use of the above-mentioned equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 A schematic diagram of a flue gas desulfurization system provided in one embodiment of the present application;

[0025] Figure 2 A schematic diagram of the structure of a first desulfurization tower provided in one embodiment of the present application;

[0026] Figure 3 A schematic diagram of a wastewater treatment system provided in one embodiment of the present application;

[0027] Figure 4 A schematic diagram of the structure of an evaporation tower provided in one embodiment of the present application;

[0028] Figure 5 A schematic diagram of a flue gas desulfurization system provided in another embodiment of the present application;

[0029] Figure 6 A schematic diagram of the structure of a second desulfurization tower provided in one embodiment of the present application.

[0030] Description of reference numerals:

[0031] 1. Boiler; 2. Dust collector; 3. First desulfurization tower; 4. Second desulfurization tower; 5. Chimney; 6. Wastewater treatment system; 7. Wet dust collector; 31. Tower body; 32. Baffle; 33. First slurry pool; 34. First demister; 35. First slurry spray layer; 36. Second demister; 37. Oxidant spray layer; 38. First packing layer; 39. Oxidant storage tank; 41. Third demister; 42. Second slurry spray layer; 43. Second packing layer; 44. Second slurry pool; 60. Filter press; 61. Wastewater storage tank; 62. Evaporation tower; 6 3. Cyclone separator; 64. First induced draft fan; 65. Heat exchanger; 66. Air heater; 67. Second induced draft fan; 301. First air inlet; 302. Oxidant outlet; 303. First gas outlet; 321. Upper hood; 331. First circulation pump; 332. First agitator; 391. Second circulation pump; 401. Second gas outlet; 402. Second air inlet; 441. Third circulation pump; 442. Second agitator; 601. Exhaust port; 611. Liquid transfer pump; 621. Gas distributor; 622. Liquid atomizer. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work also fall within the scope of protection of the present application.

[0033] like Figure 1 As shown, the present application provides a flue gas desulfurization system, comprising a boiler 1, a dust collector 2, a first desulfurization tower 3, a second desulfurization tower 4 and a chimney 5 connected in series in sequence;

[0034] The gas output end of the first desulfurization tower 3 is connected to the gas input end of the second desulfurization tower 4; the absorption liquid output end of the second desulfurization tower 4 is connected to the absorption liquid input end of the first desulfurization tower 3;

[0035] The absorption liquid output end of the first desulfurization tower 3 is connected to the wastewater treatment system 6 .

[0036] The flue gas desulfurization system provided in the present application has the following working process: when in use, the flue gas output by the boiler 1 is denitrified in the flue and then enters the dust collector 2 for dust removal. The flue gas after dust removal first enters the first desulfurization tower 3 for preliminary desulfurization and further treatment, and then enters the second desulfurization tower 4 for further desulfurization to improve the desulfurization efficiency. The desulfurized flue gas is input into the chimney 5 for discharge.

[0037] When the absorption liquid in the second desulfurization tower 4 is circulated and absorbed to a certain extent, it is transferred to the first desulfurization tower 3 for full utilization; when the absorption slurry in the first desulfurization tower 3 is saturated, the absorption slurry in the first desulfurization tower 3 is transferred to the wastewater treatment system 6 for treatment.

[0038] The system of the present application is provided with a dust collector 2, a first desulfurization tower 3 and a second desulfurization tower 4. After the flue gas discharged from the boiler 1 passes through the dust collector 2 for dust removal, it passes through the first desulfurization tower 3 and the second desulfurization tower 4 in sequence for two-stage desulfurization treatment, thereby improving the desulfurization efficiency. Moreover, the slurry absorbed by the second desulfurization tower 4 is transferred to the first desulfurization tower 3 for utilization, thereby improving the utilization rate of the absorption slurry and reducing the output of the absorption solid waste. The system of the present application overcomes the adverse consequences of the traditional single-tower desulfurization that is not thorough, easily causing sulfur escape and resulting in excessive flue gas emissions, through the coordinated use of the above-mentioned equipment.

[0039] like Figure 2 As shown, optionally, the first desulfurization tower 3 includes a tower body 31;

[0040] The interior of the tower body 31 is divided into an upper oxidation zone and a lower absorption zone by a partition 32. A first slurry pool 33 is provided at the bottom of the absorption zone, and a first demister 34 and a first slurry spray layer 35 are provided in the absorption zone from top to bottom. A first air inlet 301 located between the first slurry spray layer 35 and the first slurry pool 33 is provided on one side of the tower body 31 of the absorption zone. The first slurry pool 33 is connected to the first slurry spray layer 35 through a first circulation pump 331. A first agitator 332 is provided in the first slurry pool 33. The first slurry pool 33 is also connected to the wastewater treatment system 6.

[0041] A hood 321 is provided on the partition 32 to connect the oxidation zone and the absorption zone; an oxidant outlet 302 is provided on one side of the bottom of the tower body 31 of the oxidation zone, and a second demister 36, an oxidant spray layer 37 and a first packing layer 38 are provided in the oxidation zone from top to bottom; a first gas outlet 303 is provided on the top of the tower body 31;

[0042] The oxidant outlet 302 is communicated with the oxidant storage tank 39 , and the oxidant storage tank 39 is connected to the oxidant spraying layer 37 via a second circulation pump 391 .

[0043] In the present application, when in use, the flue gas output by the boiler 1 is denitrated in the flue and then enters the dust collector 2 for dust removal. The dust-removed flue gas enters the absorption zone in the tower body 31 of the first desulfurization tower 3 from the first air inlet 301 of the first desulfurization tower 3, and moves from bottom to top. The first slurry spraying layer 35 sprays the absorption liquid (lime slurry in the present application) downward to contact and mix with the flue gas in countercurrent. The sulfur dioxide in the flue gas contacts and reacts with the alkaline calcium salt of the calcium hydroxide agent in the slurry to generate calcium sulfite, which is then oxidized into calcium sulfate (also The sulfide (mainly sulfur dioxide) in the flue gas is removed again, and the slurry after the flue gas washing falls into the first slurry pool 33 at the bottom of the tower body 31, and is sucked and supplied to the first slurry spray layer 35 by the first circulation pump 331 for circulating spray washing; the flue gas after the slurry is sprayed by the first slurry spray layer 35 to absorb and desulfurize the flue gas goes up, and after the first demister 34 defogs to reduce the moisture carried by the flue gas, the flue gas passes through the wind hood 321 set on the partition 32 and enters the oxidation zone in the tower body.

[0044] Due to the slow gas-liquid mass transfer and the relatively small solubility of sulfur dioxide in water, sulfur dioxide will inevitably remain in the flue gas after absorption and washing in the absorption zone. Therefore, in order to further remove the residual sulfur dioxide in the flue gas, the washed flue gas is passed into the oxidation zone for oxidation treatment (mainly to oxidize sulfur dioxide into sulfur trioxide that is more soluble in water). In the oxidation zone, the second circulation pump 391 sprays the oxidant in the oxidant storage tank 39 (aqueous hydrogen peroxide solution with a concentration of 8 to 10%wt is used in this application) and contacts the flue gas entering the oxidation zone in the first packing layer 38, where mass transfer and heat transfer occur to oxidize the sulfur dioxide in the flue gas. The flue gas entering the oxidation zone is oxidized. Since the flue gas entering the oxidation zone is sprayed and washed, the moisture content therein will increase, making it easier to transfer mass and react with the sprayed oxidant. The oxidant sprayed through the oxidant spray layer 37 contacts and reacts with the residual sulfur dioxide in the flue gas, oxidizing the sulfur dioxide into sulfur trioxide that is more soluble in water for absorption. The sulfur trioxide generated after the flue gas is oxidized in the oxidation zone is partially dissolved in the oxidant, and another part will be defogged along with the flue gas through the second demister 36 to reduce the moisture carried by the flue gas and then enter the second desulfurization tower 4. In a feasible manner, the first slurry pool 33 is also connected to an air supply pipeline for introducing air into the first slurry pool 33 to promote the oxidation of sulfite in the slurry into sulfate, thereby fixing the sulfur in the flue gas in the form of sulfate.

[0045] In the present application, dilute sulfuric acid can be obtained as a product output in the oxidation zone, which can also avoid the situation where the traditional desulfurization tower outputs a single product and affects the profit.

[0046] like Figure 3As shown, optionally, the wastewater treatment system 6 includes a filter press 60, a wastewater storage tank 61, an evaporation tower 62, and a cyclone separator 63 connected in series in sequence;

[0047] The wastewater storage tank 61 is connected to the evaporation tower 62 via a liquid transfer pump 611 , and the evaporation tower 62 is also connected in series with an air heater 66 and a second induced draft fan 67 in sequence.

[0048] In the present application, the purpose of the second induced draft fan 67 is to transfer the outside air into the air heater 66 to generate hot air; the filter press 60 is used to filter the absorption slurry to achieve solid-liquid separation, and the filter cake obtained by separation is gypsum. The filtrate can be transferred to the wastewater storage tank 61 and transferred to the evaporation tower 62 by the liquid transfer pump 611, and contacted with the hot air generated by the air heater 66 to dry the wastewater.

[0049] The hot air flow (containing some particulate matter) after the wastewater is dried is discharged from the evaporation tower 62 and enters the cyclone separator 63 to achieve solid-gas separation. The separated solid is output from the bottom of the cyclone separator 63 and enters the corresponding processing section for treatment.

[0050] like Figure 4 As shown, optionally, a gas distributor 621 and a liquid atomizer 622 are sequentially arranged in the evaporation tower 62 from top to bottom; an exhaust port 601 is opened at the bottom of the tower;

[0051] The gas distributor 621 is connected to the air heater 66 ; the liquid atomizer 622 is connected to the output end of the liquid transfer pump 611 ; and the exhaust port 601 is connected to the input end of the cyclone separator 63 .

[0052] In the present application, when the evaporation tower 62 is in use, the liquid transfer pump 611 pumps the desulfurization wastewater into the liquid atomizer 622 at the top of the evaporation tower 62, and atomizes it into fine droplets and sprays it down. At the same time, the second induced draft fan 67 draws the outside air into the air heater 66 for heating (temperature is 120-150°C) to form hot air, which is blown into the evaporation tower 62 from the gas distributor 621 at the top of the liquid atomizer 622 in the evaporation tower 62, and contacts with the misted desulfurization wastewater entering the tower to carry out a mass transfer and heat transfer drying process. After drying, the droplets of the desulfurization wastewater will form particulate matter (the desulfurization wastewater contains a large amount of heavy metal inorganic salts. After the water is evaporated, these inorganic salts will crystallize to form particulate matter). These particulate matter is discharged from the exhaust port 601 at the bottom of the evaporation tower 62 along with the hot air flow.

[0053] like Figure 5 As shown, optionally, the wastewater treatment system 6 also includes a first induced draft fan 64 and a heat exchanger 65 which are sequentially connected to the cyclone separator 63 , and the heat exchanger 65 is also arranged between the second desulfurization tower 4 and the chimney 5 .

[0054] In the present application, during the solid-gas separation process of the cyclone separator 63, the separated solid is output from the bottom of the cyclone separator 63 and enters the corresponding processing section for processing; the separated gas carries high temperature (100-120°C), and these high-temperature gases enter the shell side of the heat exchanger 65, and transfer heat with the desulfurized flue gas from the second desulfurization tower 4 in the tube side, raising the flue gas temperature, and then discharged into the chimney 5 to avoid the occurrence of chimney rain. Among them, the high-temperature flue gas after heat exchange can be transferred to the chimney 5 for discharge or further treated before discharge.

[0055] Therefore, a heat exchanger 65 is arranged between the second desulfurization tower 4 and the chimney 5 to heat exchange and heat up the flue gas discharged from the second desulfurization tower 4, thereby reducing the phenomenon of chimney rain caused by the desulfurization flue gas emission. Moreover, since the heat exchange medium of the heat exchanger 65 is the high-temperature airflow formed after the evaporation tower 62 uses hot air to dry the desulfurization wastewater, which contains water vapor evaporated from the wastewater, part of the water vapor in the airflow can be condensed through heat exchange and recovered.

[0056] It should be noted that, during use, since the high-temperature airflow for heat exchange has a high moisture content, if the high-temperature airflow with high moisture content is directly mixed with the desulfurized flue gas, although the flue gas can be heated, the large amount of water vapor introduced will more easily cause chimney rain and white smoke phenomenon at the top of the chimney 5, so the two cannot be directly mixed and discharged.

[0057] like Figure 5 As shown, optionally, a wet dust collector 7 is also provided between the second desulfurization tower 4 and the heat exchanger 65 .

[0058] In the present application, since the moisture content in the desulfurized flue gas discharged from the second desulfurization tower 4 is relatively high, and the flue gas temperature drops after multiple washings, it is easy to reach the dew point of water vapor, which leads to the phenomenon of chimney rain when the flue gas is discharged through the chimney 5. A wet dust collector 7 is provided to remove moisture and dust in the desulfurized flue gas and reduce the water vapor content in the discharged flue gas.

[0059] like Figure 6 As shown, optionally, a third demister 41, a second slurry spraying layer 42 and a second packing layer 43 are sequentially arranged in the second desulfurization tower 4 from top to bottom; a second gas outlet 401 is arranged at the top of the second desulfurization tower 4, and a second slurry pool 44 is arranged at the bottom;

[0060] A second air inlet 402 is provided on one side wall of the second desulfurization tower 4 between the second slurry pool 44 and the second filler layer 43;

[0061] The second slurry pool 44 is connected to the second slurry spraying layer 42 via a third circulation pump 441; a second agitator 442 is provided in the second slurry pool 44;

[0062] The first gas outlet 303 is in communication with the second gas inlet 402 .

[0063] In the present application, during the use of the second desulfurization tower 4, the flue gas enters from the second air inlet 402 of the second desulfurization tower 4, contacts with the alkaline slurry (the same as the absorption slurry in the first desulfurization tower 3) sprayed down from the second slurry spray layer 42 in the second packing layer 43, absorbs the acidic gas in the flue gas (mainly sulfur trioxide generated after the oxidation of sulfur dioxide), and mainly generates calcium sulfate to further remove the sulfur-containing gas in the flue gas. The desulfurized flue gas is defogged by the third demister 41 and discharged from the second gas outlet 401 at the top of the tower. After passing through the wet dust collector 7 to remove moisture and dust carried in the flue gas, it is passed through the heat exchanger 65 for heat exchange and temperature increase, and then is discharged into the chimney 5.

[0064] In order to make full use of the absorption slurry at the bottom of the second desulfurization tower 4, the absorption slurry at the bottom of the second desulfurization tower 4 should be regularly transferred to the first desulfurization tower 3 for use, and the second agitator 442 stirs the second slurry pool 44 to prevent the slurry from agglomerating and clogging the pipeline.

[0065] A flue gas desulfurization system, the working process of which is as follows:

[0066] When in use, the flue gas output by the boiler 1 enters the dust collector 2 for dust removal after denitrification in the flue. The dust-removed flue gas enters the absorption zone in the tower body 31 of the first desulfurization tower 3 from the first air inlet 301 of the first desulfurization tower 3, and moves from bottom to top. The first slurry spraying layer 35 sprays the absorption liquid (lime slurry in this application) downward to contact and mix with the flue gas in countercurrent. The sulfur dioxide in the flue gas contacts and reacts with the alkaline calcium salt of the calcium hydroxide agent in the slurry to generate calcium sulfite, which is then oxidized into calcium sulfate (i.e. Gypsum), the sulfide (mainly sulfur dioxide) in the flue gas is removed again, and the slurry after the flue gas washing falls into the first slurry pool 33 at the bottom of the tower body 31, and is sucked and supplied to the first slurry pool 33 by the first circulation pump 331 for circulating spray washing; the slurry is sprayed on the flue gas through the first slurry spray layer 35 to absorb and desulfurize the flue gas, and the flue gas goes up after defogger 34 to reduce the moisture carried by the flue gas, and then the flue gas passes through the hood 321 set on the partition 32 and enters the oxidation zone in the tower body.

[0067] Due to the slow gas-liquid mass transfer and the relatively small solubility of sulfur dioxide in water, sulfur dioxide will inevitably remain in the flue gas after absorption and washing in the absorption zone. Therefore, in order to further remove the residual sulfur dioxide in the flue gas, the washed flue gas is passed into the oxidation zone for oxidation treatment (mainly to oxidize sulfur dioxide into sulfur trioxide that is more soluble in water). In the oxidation zone, the second circulation pump 391 sprays the oxidant in the oxidant storage tank 39 (aqueous hydrogen peroxide solution with a concentration of 8 to 10%wt is used in this application) and contacts the flue gas entering the oxidation zone in the first packing layer 38, where mass transfer and heat transfer occur to oxidize the sulfur dioxide in the flue gas. Since the flue gas entering the oxidation zone is spray-washed, the moisture content therein will increase, making it easier to transfer mass and react with the sprayed oxidant. The oxidant sprayed through the oxidant spray layer 37 contacts and reacts with the residual sulfur dioxide in the flue gas, oxidizing the sulfur dioxide into sulfur trioxide which is more soluble in water for absorption. The sulfur trioxide generated after the flue gas is oxidized in the oxidation zone is partially dissolved in the oxidant, and another part will enter the second desulfurization tower 4 after the flue gas passes through the second demister 36 for defogger to reduce the moisture carried by the flue gas.

[0068] The flue gas enters from the second air inlet 402 of the second desulfurization tower 4, contacts with the alkaline slurry (the same as the absorption slurry in the first desulfurization tower 3) sprayed from the second slurry spray layer 42 in the second packing layer 43, absorbs the acidic gas in the flue gas (mainly sulfur trioxide generated after the oxidation of sulfur dioxide), and mainly generates calcium sulfate to further remove the sulfur-containing gas in the flue gas. The desulfurized flue gas is defogged by the third demister 41 and discharged from the second gas outlet 401 at the top of the tower. After passing through the wet dust collector 7 to remove the moisture and dust carried in the flue gas, it is heated by the heat exchanger 65 and then discharged into the chimney 5.

[0069] The absorption slurry at the bottom of the second desulfurization tower 4 will be regularly transferred to the first desulfurization tower 3 for use. The second agitator 442 stirs the second slurry pool 44 to prevent the slurry from agglomerating and clogging the pipeline; similarly, the first agitator 332 stirs the absorption slurry in the first slurry pool 33 to prevent the slurry from agglomerating and clogging the pipeline.

[0070] When the gypsum content in the first slurry pool 33 at the bottom of the tower body 31 of the first desulfurization tower 3 reaches a certain value (the pH value of the slurry is between 6.5 and 7.5), the slurry in the first slurry pool 33 is transferred to the filter press 60 for filtration. The filter cake obtained by filtration is crude gypsum, which can be sent to the corresponding gypsum treatment section for purification and drying operations to easily produce pure gypsum. The filtrate obtained by filtration is also the desulfurization wastewater, which is transferred to the wastewater storage tank 61 for temporary storage.

[0071] The liquid transfer pump 611 pumps the desulfurized wastewater into the liquid atomizer 622 at the top of the evaporation tower 62, where it is atomized into fine droplets and sprayed down. At the same time, the second induced draft fan 67 draws the outside air into the air heater 66 for heating (temperature is 120-150°C) to form hot air, which is blown into the evaporation tower 62 from the gas distributor 621 at the top of the liquid atomizer 622 in the evaporation tower 62, and contacts with the misted desulfurized wastewater entering the tower to carry out a mass transfer and heat transfer drying process. After drying, the droplets of the desulfurized wastewater will form particles (the desulfurized wastewater contains a large amount of heavy metal inorganic Salt, after evaporating the water, these inorganic salts will crystallize to form particles), these particles are discharged from the exhaust port 601 at the bottom of the evaporation tower 62 along with the hot air flow into the cyclone separator 63 to achieve solid-gas separation, the separated solid is output from the bottom of the cyclone separator 63 and enters the corresponding processing section for processing; the separated gas also carries high temperature (100-120°C), these high-temperature gases enter the shell side of the heat exchanger 65, transfer heat with the desulfurized flue gas in the tube side, increase the flue gas temperature, and then discharge into the chimney 5 to avoid the occurrence of chimney rain. The high-temperature gas after heat exchange can be transferred to the chimney 5 for discharge or further treatment before discharge.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A flue gas desulfurization system, characterized in that: It comprises a boiler (1), a dust collector (2), a first desulfurization tower (3), a second desulfurization tower (4) and a chimney (5) which are connected in series in sequence; The gas output end of the first desulfurization tower (3) is connected to the gas input end of the second desulfurization tower (4); the absorption liquid output end of the second desulfurization tower (4) is connected to the absorption liquid input end of the first desulfurization tower (3); The absorption liquid output end of the first desulfurization tower (3) is connected to the wastewater treatment system (6).

2. The flue gas desulfurization system according to claim 1, characterized in that: The first desulfurization tower (3) comprises a tower body (31); The interior of the tower body (31) is divided into an upper oxidation zone and a lower absorption zone by a partition (32); a first slurry pool (33) is provided at the bottom of the absorption zone, and a first demister (34) and a first slurry spray layer (35) are provided in the absorption zone from top to bottom; a first air inlet (301) located between the first slurry spray layer (35) and the first slurry pool (33) is provided on one side of the tower body (31) of the absorption zone; the first slurry pool (33) is connected to the first slurry spray layer (35) via a first circulation pump (331); a first agitator (332) is provided in the first slurry pool (33); and the first slurry pool (33) is also connected to a wastewater treatment system (6); The partition plate (32) is provided with a hood (321) to connect the oxidation zone and the absorption zone; an oxidant outlet (302) is provided on one side of the bottom of the tower body (31) of the oxidation zone; the oxidation zone is provided with a second demister (36), an oxidant spray layer (37) and a first packing layer (38) in sequence from the top to the bottom; and a first gas outlet (303) is provided on the top of the tower body (31); The oxidant outlet (302) is in communication with an oxidant storage tank (39), and the oxidant storage tank (39) is connected to the oxidant spray layer (37) via a second circulation pump (391).

3. The flue gas desulfurization system according to claim 1 or 2, characterized in that: The wastewater treatment system (6) comprises a filter press (60), a wastewater storage tank (61), an evaporation tower (62), and a cyclone separator (63) which are sequentially connected in series; The wastewater storage tank (61) is connected to the evaporation tower (62) via a liquid transfer pump (611), and the evaporation tower (62) is also connected in series with an air heater (66) and a second induced draft fan (67).

4. The flue gas desulfurization system according to claim 3, characterized in that: The evaporation tower (62) is provided with a gas distributor (621) and a liquid atomizer (622) in order from top to bottom; an exhaust port (601) is provided at the bottom of the tower; The gas distributor (621) is connected to the air heater (66); the liquid atomizer (622) is connected to the output end of the liquid transfer pump (611); and the exhaust port (601) is connected to the input end of the cyclone separator (63).

5. The flue gas desulfurization system according to claim 3, characterized in that: The wastewater treatment system (6) further comprises: a first induced draft fan (64) and a heat exchanger (65) which are sequentially connected to the cyclone separator (63); the heat exchanger (65) is arranged between the second desulfurization tower (4) and the chimney (5).

6. The flue gas desulfurization system according to claim 5, characterized in that: A wet dust collector (7) is also provided between the second desulfurization tower (4) and the heat exchanger (65).

7. The flue gas desulfurization system according to claim 2, characterized in that: The second desulfurization tower (4) is provided with a third demister (41), a second slurry spraying layer (42) and a second packing layer (43) in order from top to bottom; the second desulfurization tower (4) is provided with a second gas outlet (401) at the top and a second slurry pool (44) at the bottom; A second air inlet (402) is provided on one side wall of the second desulfurization tower (4) between the second slurry pool (44) and the second filler layer (43); The second slurry pool (44) is connected to the second slurry spraying layer (42) via a third circulation pump (441); a second agitator (442) is provided in the second slurry pool (44); The first gas outlet (303) is in communication with the second gas inlet (402).

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