Flue gas comprehensive treatment system in cement industry

Abstract

The invention discloses a comprehensive flue gas treatment system in the cement industry, which relates to the technical field of cement production, has the advantages of reducing SOemission in tail flue gas of a cement kiln, absorbing ammonia gas in the flue gas and reducing ammonia escape, and is characterized by comprising a staged combustion denitration device utilizing ammonia water and a wet desulphurization device; the wet desulphurization device comprises an SOabsorption system and a lime slurry preparation system; the SOabsorption system comprises an absorption tower, a plurality of spraying layers and a plurality of demisters, the spraying layers and the demisters are sequentially arranged in the absorption tower from bottom to top, circulating pipelines communicated with the spraying layers are arranged on the outer wall of the absorption tower, and the ends, away from the absorption tower, of the circulating pipelines are communicated with the lower-layer space in the absorption tower. A slurry circulating pump is arranged on each circulating pipeline, an inlet pipe for flue gas to enter is arranged on one side wall of the absorption tower, the spraying layer is positioned above the inlet pipe, and a stirrer and an oxidation system which are positioned below the inlet pipe are arranged on the side wall of the absorption tower.

Description

Technical Field

[0001] The invention relates to the technical field of cement production, in particular to a comprehensive smoke treatment system for the cement industry. Background Art

[0002] There are a large number of cement kilns in operation in my country, which produce a large amount of flue gas at the kiln tail during operation. The main components of the flue gas are NOx, SO2, etc.

[0003] A Chinese patent with application number CN201720210300.1 discloses an ERD+ coal-fired saturated steam catalytic combustion denitrification device, comprising: a decomposition furnace, a secondary air inlet is arranged at the bottom, and is connected to a cement rotary kiln; the decomposition furnace comprises a reduction zone, a main combustion zone, a reburning zone, and a burnout zone from bottom to top, and a reduction zone saturated steam catalytic burner and a reburning zone saturated steam catalytic burner are installed in the reduction zone and the reburning zone respectively; the reduction zone saturated steam catalytic burner and the reburning zone saturated steam catalytic burner are connected to a steam flow metering device, the steam flow metering device is connected to a steam pressure regulating tank, the steam pressure regulating tank is connected to a steam main pipeline, the main combustion zone and the burnout zone are respectively connected to tertiary air and burnout air, which are oxygen-enriched combustion zones to ensure that the system coal powder is burned out. C5 is connected at the connection between the decomposition furnace and the cement rotary kiln. The C5 is the fifth-stage preheating separator. SNCR spray guns are arranged at the outlet of C5. The SNCR spray guns are evenly arranged on the circumferential wall surface of the outlet of C5. Ammonia water is sprayed on the SNCR spray guns. In conjunction with the SNCR spray guns arranged at the outlet flue of the decomposition furnace at the top of the decomposition furnace in the ERD high-efficiency reburning denitrification system, the residual nitrogen oxides are further removed, reaching an ammonia-free denitrification standard of more than 80%, and a comprehensive denitrification efficiency of more than 95%.

[0004] However, the above-mentioned denitrification process utilizes ammonia water, and the flue gas will contain ammonia after being discharged, causing ammonia escape. The emission concentration of ammonia in the flue gas is also standardized, and the SO2 in the flue gas cannot be treated after the above-mentioned flue gas denitrification. Therefore, the applicant has developed a new technical solution in the actual production process to solve the above-mentioned technical problems. Summary of the invention

[0005] In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a comprehensive flue gas treatment system for the cement industry, which has the advantages of reducing SO2 emissions in the flue gas at the tail of the cement kiln, absorbing ammonia in the flue gas, and reducing ammonia escape.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: The present invention provides a comprehensive flue gas treatment system for the cement industry, including a staged combustion denitrification device using ammonia water and a wet desulfurization device; The wet desulfurization device includes a SO2 absorption system and a lime slurry preparation system; The SO2 absorption system comprises an absorption tower and multiple spray layers and multiple demisters arranged in sequence from bottom to top inside the absorption tower. The outer wall of the absorption tower is provided with a circulation pipeline connected to each spray layer. One end of each circulation pipeline away from the absorption tower is connected to the lower space inside the absorption tower. Each circulation pipeline is provided with a slurry circulation pump. An inlet pipe for flue gas is provided on one side wall of the absorption tower. The spray layer is located above the inlet pipe. An agitator and an oxidation system located below the inlet pipe are provided on the side wall of the absorption tower. The lime slurry preparation system provides lime slurry to the absorption tower; The outer wall of the absorption tower is provided with a slurry discharge pipe which is communicated with the lower space inside the absorption tower, and the slurry discharge pipe is provided with a gypsum slurry pump.

[0007] By adopting the above technical scheme, the staged combustion denitrification device and the wet desulfurization device are respectively used to reduce the NOx and SO2 emissions in the flue gas. The flue gas to be treated enters the absorption tower and contacts with the sprayed lime slurry to remove the SO2 in the flue gas. A demister is arranged on the upper part of the absorption tower to remove the droplets in the flue gas. The slurry circulation pump in the absorption tower provides a large flow of lime slurry to the absorption tower, which is beneficial to the full contact between the flue gas and the lime slurry and improves the absorption efficiency of SO2. An oxidation fan is set to oxidize the calcium sulfite in the slurry into calcium sulfate. An agitator is arranged in the absorption tower to ensure uniform mixing and prevent the precipitation of the slurry in the lower layer of the absorption tower. The gypsum generated after oxidation is discharged through the gypsum slurry pump.

[0008] Preferably, a pH sensor is provided on the inner wall of the absorption tower, and the pH sensor detects the pH value of the slurry in the lower space inside the absorption tower.

[0009] Preferably, the lime slurry preparation system includes a lime slurry tank and a stirring paddle located in the lime slurry tank, a motor for driving the stirring paddle to rotate is provided at the top of the lime slurry tank, a drain pipe is provided at the bottom of the lime slurry tank, a lime slurry pump is provided on the drain pipe, and one end of the drain pipe away from the lime slurry tank is connected to the interior of the absorption tower, and the connection position is located below the spray layer.

[0010] Preferably, the oxidation system comprises a plurality of ventilation pipes arranged in the lower layer inside the absorption tower and distributed horizontally, each of the ventilation pipes is distributed along the same horizontal plane, and one end is connected through a main pipe, a vertical pipe is provided on the outer wall of the main pipe, an oxygen pipe extending out of the outer wall of the absorption tower is provided at the upper end of the vertical pipe, the oxygen pipe is connected to an oxidation blower, and a plurality of blowing holes are provided on the outer wall of each of the ventilation pipes to discharge oxygen out of the ventilation pipe.

[0011] Preferably, the agitator includes a stirring rod obliquely inserted into the side wall of the absorption tower, the stirring rod is rotatably connected to the inner wall of the absorption tower, the outer wall of the absorption tower is provided with a first motor for driving the stirring rod to rotate, the outer wall of the stirring rod located in the absorption tower is provided with a plurality of main blades, the main blades make the stirring rod an axial flow agitator when it rotates, the angle between the axis of the stirring rod and the horizontal line is 8°±2°, the stirring rod is located in the lower slurry of the absorption tower and above each ventilation pipe.

[0012] Preferably, the agitator includes a rotating shaft located above the liquid level of the slurry in the lower layer of the absorption tower, the rotating shaft is rotatably connected to the side wall of the absorption tower and is coaxially driven by a second motor arranged on the outer wall of the absorption tower, the end of the rotating shaft away from the inner wall of the absorption tower is coaxially fixedly connected to a driving bevel gear, the inner wall of the absorption tower is provided with connecting plates on both sides of the rotating shaft, one end of the two connecting plates is rotatably connected to an intermediate rod, the intermediate rod is located on the side of the driving bevel gear away from the rotating shaft, the outer wall of the intermediate rod is coaxially fixedly connected to an intermediate bevel gear, the intermediate bevel gear is meshed with the driving bevel gear, a U-shaped swing arm is fixedly connected to the two connecting plates, a stirring shaft is rotatably connected to the swing arm, one end of the stirring shaft passes through the swing arm and is coaxially fixedly provided with a driven bevel gear meshing with the intermediate bevel gear, and the other end obliquely penetrates into the liquid in the lower layer of the absorption tower, and a plurality of stirring blades are provided on the outer wall of the stirring shaft.

[0013] Preferably, when the pH sensor detects that the pH value of the slurry in the lower space inside the absorption tower is less than 5, the pH sensor controls the gypsum slurry pump to start working to extract part of the slurry, and then controls the lime slurry pump to start working to extract the lime slurry into the absorption tower, and the amount of the lime slurry extracted is the amount of the extracted slurry; When the pH sensor detects that the pH value of the slurry in the lower space inside the absorption tower is greater than 8, the pH sensor controls the gypsum slurry pump to start working to extract part of the slurry, and then controls the lime slurry pump to start working to extract the lime slurry into the absorption tower. The amount of lime slurry extracted is the amount of slurry extracted.

[0014] Preferably, the two ends of the swing arm are rotatably connected to the two connecting plates through a rotating rod, and the ends of the two rotating rods away from the swing arm are rotatably connected to the inner wall of the absorption tower, and one end of one of the rotating rods extends out of the absorption tower and is coaxially driven to rotate by a third motor fixed to the outer wall of the absorption tower, the lower end of the stirring shaft extends to the lower end of each ventilation pipe, the stirring blade is located above each ventilation pipe, and a plurality of stirring plates are provided at the lower end of the stirring shaft.

[0015] Preferably, the slurry discharge pipe discharges the slurry to the gypsum cyclone and the vacuum dehydrator in sequence.

[0016] Preferably, the absorption tower is provided with an enhanced absorption layer below the spray layer, and the enhanced absorption layer includes an air distribution plate covering the cross-section of the absorption tower, and the air distribution plate is provided with a long through groove, and the through groove runs through the upper and lower ends of the air distribution plate, and the air distribution plate is located above the inlet pipe, and the size of each of the through grooves gradually increases in the direction away from the inlet pipe.

[0017] The beneficial effects of the present invention are as follows: a staged combustion denitrification device and a wet desulfurization device are respectively used to reduce the NOx and SO2 emissions in the flue gas; the flue gas to be treated enters the absorption tower and contacts with the sprayed lime slurry to remove the SO2 in the flue gas; a demister is arranged on the upper part of the absorption tower to remove the mist droplets in the flue gas; a slurry circulation pump in the absorption tower provides a large flow of lime slurry for the absorption tower, which is beneficial to the full contact between the flue gas and the lime slurry and improves the absorption efficiency of SO2; an oxidation fan is arranged to oxidize the calcium sulfite in the slurry into calcium sulfate; an agitator is arranged in the absorption tower to ensure uniform mixing and prevent the precipitation of the slurry in the lower layer of the absorption tower; the gypsum generated after oxidation is discharged through the gypsum slurry pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is a schematic diagram of the structure of Embodiment 1; Figure 2 This is a schematic diagram of the structure of the absorption tower in Example 1; Figure 3 This is a schematic diagram of the structure of the stirring shaft according to Embodiment 2; Figure 4 This is a schematic diagram of the structure of the active bevel gear according to the second embodiment.

[0020] Description of reference numerals: In the figure: 1. staged combustion denitrification device; 2. SO2 absorption system; 21. absorption tower; 22. spray layer; 221. circulation pipeline; 222. slurry circulation pump; 223. inlet pipe; 23. demister; 24. slurry discharge pipe; 241. gypsum slurry pump; 25. ventilation pipe; 251. vertical pipe; 252. oxygen pipe; 253. oxidation fan; 254. stirring rod; 255. first motor; 256. main blade; 26. rotating shaft; 261. Two electric motors; 262, driving bevel gear; 263, connecting plate; 264, intermediate rod; 265, intermediate bevel gear; 266, rocker arm; 267, stirring shaft; 268, driven bevel gear; 269, stirring blade; 27, rotating rod; 271, stirring plate; 28, air distribution plate; 281, through groove; 29, flushing pipe; 3, lime slurry preparation system; 31, lime slurry tank; 32, stirring paddle; 33, motor; 34, discharge pipe; 35, lime slurry pump. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1: A comprehensive flue gas treatment system for cement industry, such as Figure 1 and Figure 2 , including a staged combustion denitrification device 1 using ammonia water and a wet desulfurization device; the staged combustion denitrification device 1 can be the ERD+ coal-fired saturated steam catalytic combustion denitrification device in application number CN201720210300.1, so that the emission of NOx meets the standard, and the flue gas coming out of the staged combustion denitrification device 1 enters the wet desulfurization device for the final step of treatment.

[0023] The wet desulfurization device includes a SO2 absorption system 2 and a lime slurry preparation system 3; The SO2 absorption system 2 includes an absorption tower 21 and a plurality of spray layers 22 and a plurality of demisters 23 sequentially arranged inside the absorption tower 21 from bottom to top. A circulation pipe 221 communicating with each spray layer 22 is arranged on the outer wall of the absorption tower 21. One end of each circulation pipe 221 away from the absorption tower 21 is communicated with the lower space inside the absorption tower 21. A slurry circulation pump 222 is arranged on each circulation pipe 221. An inlet pipe 223 for flue gas to enter is arranged on one side wall of the absorption tower 21. The spray layer 22 is located above the inlet pipe 223. An agitator and an oxidation system located below the inlet pipe 223 are arranged on the side wall of the absorption tower 21. like Figure 1 and Figure 2The lime slurry preparation system 3 provides lime slurry to the absorption tower 21. After the lime slurry enters the absorption tower 21, it is sucked into each spray layer 22 by the slurry circulation pump 222 on each circulation pipe 221 for spraying. The sprayed lime slurry accumulates in the lower space of the absorption tower 21, so that each circulation pipe 221 can suck the lime slurry into each spray layer 22 again; the spray layer 22 includes a plurality of mother pipes arranged on the inner wall of the absorption tower 21, the mother pipes of each spray layer 22 are arranged on the same horizontal plane and one side of each mother pipe is connected by a connecting pipe, which is arranged on the inner wall of the absorption tower 21, one end of the circulation pipe 221 enters the absorption tower 21 and is connected with the connecting pipe. At this time, the lime slurry in the circulation pipe 221 is transported to each mother pipe through the connecting pipe. In addition, the mother pipes of adjacent spray layers 22 are staggered, and each mother pipe is provided with a plurality of nozzles spraying downward. In addition, a flushing pipe 29 for flushing the demister 23 may be provided in the absorption tower 21. The flushing pipe 29 is provided with a plurality of nozzles for spraying water toward the demister 23. The flushed water flows to the lower space of the absorption tower 21. One end of the flushing pipe 29 extends out of the absorption tower 21 and connects to the water pool.

[0024] like Figure 1 and Figure 2 The outer wall of the absorption tower 21 is provided with a slurry discharge pipe 24 which is connected with the lower space inside the absorption tower 21 , and the slurry discharge pipe 24 is provided with a gypsum slurry pump 241 .

[0025] like Figure 1 and Figure 2 The staged combustion denitrification device 1 and the wet desulfurization device are respectively used to reduce the NOx and SO2 emissions in the flue gas. The flue gas to be treated enters the absorption tower 21 and contacts with the sprayed lime slurry to remove the SO2 in the flue gas. The demister 23 is arranged on the upper part of the absorption tower 21 to remove the droplets in the flue gas; the slurry circulation pump 222 in the absorption tower 21 provides a large flow of lime slurry for the absorption tower 21, which is beneficial to the full contact between the flue gas and the lime slurry and improves the absorption efficiency of SO2. An oxidation fan 253 is set to oxidize the calcium sulfite in the slurry into calcium sulfate; an agitator is arranged in the absorption tower 21 to ensure uniform mixing and prevent the precipitation of the slurry in the lower layer of the absorption tower 21. The gypsum generated after oxidation is discharged through the gypsum slurry pump 241.

[0026] When the flue gas and the lime slurry flow in the absorption tower 21 in the reverse direction, the flue gas and the lime slurry react with the lime in the suspension to form calcium sulfite, etc. The calcium sulfite is oxidized into calcium sulfate by the oxidizing air in the lower space of the absorption tower 21 and crystallized into gypsum.

[0027] The main reaction equation is as follows:

[0028] like Figure 1 and Figure 2The lime slurry preparation system 3 includes a lime slurry tank 31 and a stirring paddle 32 located in the lime slurry tank 31. A motor 33 for driving the stirring paddle 32 to rotate is provided on the top of the lime slurry tank 31. A drain pipe 34 is provided at the bottom of the lime slurry tank 31. A lime slurry pump 35 is provided on the drain pipe 34. Two lime slurry pumps 35 are provided in parallel, one for use and the other for standby. The end of the drain pipe 34 away from the lime slurry tank 31 is connected to the inside of the absorption tower 21, and the connection position is located below the spray layer 22. The lime slurry tank 31 is provided with a pipeline for facilitating the entry of calcium oxide powder and water. The function of the stirring paddle 32 is to facilitate the formation of lime slurry and reduce precipitation. The lime slurry pump 35 is used to send the lime slurry in the lime slurry tank 31 to the absorption tower 21.

[0029] like Figure 1 and Figure 2 , a pH sensor is provided on the inner wall of the absorption tower 21, and the pH sensor detects the pH value of the slurry in the lower space inside the absorption tower 21. The staged combustion denitrification device 1 can be the ERD+ coal-fired saturated steam catalytic combustion denitrification device in the application number CN201720210300.1. In this process, in addition to reducing the emission of NOx, ammonia will also be contained in the flue gas. The flue gas containing ammonia enters the absorption tower 21, and the lime slurry absorbs ammonia to reduce ammonia escape, but the pH value of the lime slurry will increase. Since the lime slurry absorbs sulfur dioxide, the increase in the pH value of the lime slurry is not conducive to the absorption of sulfur dioxide. Therefore, a pH sensor is required to continuously monitor the pH value of the lime slurry in the absorption tower 21.

[0030] Specifically: when the pH sensor detects that the pH value of the slurry in the lower space inside the absorption tower 21 is less than 5, it means that too much sulfur dioxide is absorbed. Therefore, the pH sensor controls the gypsum slurry pump 241 to start working to extract part of the slurry, so that part of the lime slurry in the absorption tower 21 is discharged, and then controls the lime slurry pump 35 to start working to extract new lime slurry into the absorption tower 21. The amount of lime slurry extracted is the amount of extracted slurry. At this time, the new lime slurry replenished re-neutralizes the lime slurry previously retained in the absorption tower 21, so that the pH value of the lime slurry increases, which is convenient for the absorption of sulfur dioxide.

[0031] When the pH sensor detects that the pH value of the slurry in the lower space inside the absorption tower 21 is greater than 8, due to the continuous absorption of ammonia, it indicates that the efficiency of lime slurry in absorbing sulfur dioxide is low. The pH sensor controls the gypsum slurry pump 241 to start working to extract part of the slurry, and then controls the lime slurry pump 35 to start working to extract the lime slurry into the absorption tower 21. The amount of lime slurry extracted is the same as the amount of extracted slurry. The newly added lime slurry reduces the pH value of the overall lime slurry in the absorption tower 21, and the gypsum in the extracted lime slurry is also extracted, which is convenient for the absorption of sulfur dioxide.

[0032] Therefore, when the lime slurry is injected into the absorption tower 21 and then circulated and sprayed to absorb sulfur dioxide, it is necessary to continuously observe the pH value of the slurry in the lower layer of the absorption tower 21 to facilitate better absorption of sulfur dioxide. A large number of tests have shown that when the pH value is 5.9, the absorption and reduction reaction efficiency of sulfur dioxide is the highest.

[0033] like Figure 1 and Figure 2 The oxidation system includes a plurality of ventilation pipes 25 which are arranged in the lower layer inside the absorption tower 21 and are horizontally distributed. Each ventilation pipe 25 is distributed along the same horizontal plane and one end is connected through a main pipe. Both ends of the main pipe are arranged on the inner wall of the absorption tower 21. A vertical pipe 251 is arranged on the outer wall of the main pipe. An oxygen pipe 252 extending out of the outer wall of the absorption tower 21 is arranged on the upper end of the vertical pipe 251. The oxygen pipe 252 is connected to an oxidation fan 253. The oxidation fan 253 can also be arranged in two in parallel, one for use and the other for standby. The main pipe, the vertical pipe 251 and the oxygen pipe 252 are connected to each other, so that the oxidation fan 253 can transport oxygen to each ventilation pipe 25. A plurality of blowing holes for discharging oxygen from the ventilation pipe 25 are arranged on the outer wall of each ventilation pipe 25. Each of the blowing holes is distributed circumferentially along the ventilation pipe 25, so as to ventilate the surrounding space of the ventilation pipe 25.

[0034] like Figure 1 and Figure 2 The agitator includes a stirring rod 254 obliquely inserted into the side wall of the absorption tower 21, the stirring rod 254 is rotatably connected to the inner wall of the absorption tower 21, and the outer wall of the absorption tower 21 is provided with a first motor 255 for driving the stirring rod 254 to rotate. The outer wall of the stirring rod 254 located in the absorption tower 21 is provided with a plurality of main blades 256, and the main blades 256 make the stirring rod 254 an axial flow agitator when rotating. The angle between the axis of the stirring rod 254 and the horizontal line is 8°±2°, and the stirring rod 254 is located in the lower slurry of the absorption tower 21 and above each ventilation pipe 25. The first motor 255 drives the stirring rod 254 to rotate. The agitator configured in this way is characterized by large circulation capacity, low power consumption, and a certain shear force, so that the liquid in the absorption tower 21 is well mixed and the precipitation of the material in the absorption tower 21 can be reduced.

[0035] like Figure 1 The absorption tower 21 is provided with an enhanced absorption layer below the spray layer 22. The enhanced absorption layer includes an air distribution plate 28 covering the cross section of the absorption tower 21. The air distribution plate 28 is provided with a long through groove 281. The through groove 281 runs through the upper and lower ends of the air distribution plate 28, and the air distribution plate 28 is located above the inlet pipe 223. The size of each through groove 281 gradually increases in the direction away from the inlet pipe 223, so as to improve the uniformity of the smoke entering the spray layer 22.

[0036] Example 2: A comprehensive flue gas treatment system for cement industry, such as Figure 3 and Figure 4 , which is different from Example 1, is that the agitator includes a rotating shaft 26 located above the slurry level in the lower layer of the absorption tower 21, the rotating shaft 26 is rotatably connected to the side wall of the absorption tower 21, and is coaxially driven by a second motor 261 arranged on the outer wall of the absorption tower 21. At this time, the rotating shaft 26 is horizontally distributed, and one end of the rotating shaft 26 away from the inner wall of the absorption tower 21 is coaxially fixedly connected to a driving bevel gear 262, and the inner wall of the absorption tower 21 is provided with connecting plates 263 on both sides of the rotating shaft 26, and one end of the two connecting plates 263 is rotatably connected to an intermediate rod 264, and the intermediate rod 264 is located at the driving bevel gear 262. On the side of the gear 262 facing away from the rotating shaft 26, the outer wall of the intermediate rod 264 is coaxially fixedly connected with an intermediate bevel gear 265, and the intermediate bevel gear 265 is meshed with the active bevel gear 262. A U-shaped swing rod 266 is fixedly connected to the two connecting plates 263, and a stirring shaft 267 is rotatably connected to the swing rod 266. One end of the stirring shaft 267 passes through the swing rod 266 and is coaxially fixed with a driven bevel gear 268 meshing with the intermediate bevel gear 265, and the other end obliquely penetrates into the lower layer of the absorption tower 21. A plurality of stirring blades 269 are provided on the outer wall of the stirring shaft 267.

[0037] like Figure 3 and Figure 4 At this time, the second motor 261 drives the rotating shaft 26 to rotate, and the rotating shaft 26 drives the intermediate bevel gear 265 to rotate through the active bevel gear 262, and at this time also drives the driven bevel gear 268 to rotate, so that the stirring shaft 267 rotates, so that the stirring blades 269 on the stirring shaft 267 stir the lower layer of the absorption tower 21, so that oxygen can oxidize calcium sulfite into calcium sulfate and reduce precipitation.

[0038] like Figure 3 and Figure 4 The above agitator has the following advantages over the agitator in Example 1: The agitator in Example 1 also needs to replace the mechanical seal regularly. The rotating shaft 26 is above the slurry level in the lower layer of the absorption tower 21, thereby reducing the possibility of leakage.

[0039] like Figure 3 and Figure 4 The two ends of the swing rod 266 are rotatably connected to the two connecting plates 263 through the rotating rod 27 respectively. The two rotating rods 27 are coaxially distributed with the middle rod 264. The ends of the two rotating rods 27 away from the swing rod 266 are rotatably connected to the inner wall of the absorption tower 21, and one end of one of the rotating rods 27 extends out of the absorption tower 21 and is coaxially driven to rotate by a third motor fixed on the outer wall of the absorption tower 21. The lower end of the stirring shaft 267 extends to the lower end of each ventilation pipe 25, and the stirring blade 269 is located above each ventilation pipe 25. A plurality of stirring plates 271 are provided at the lower end of the stirring shaft 267.

[0040] like Figure 3 and Figure 4The third motor drives the rotating rod 27 to rotate, so that the rotating rod 27 drives the swing rod 266 to rotate, and then the swing rod 266 drives the stirring shaft 267 to rotate. The purpose is that when the gypsum slurry pump 241 starts to work to extract the slurry, the stirring shaft 267 can still rotate and move, reducing the gypsum precipitation at the bottom of the absorption tower 21, which is convenient for the gypsum slurry pump 241 to extract. The slurry discharge pipe 24 discharges the slurry to the gypsum cyclone and the vacuum dehydrator in turn. When the slurry in the absorption tower 21 reaches a certain concentration, it needs to be discharged regularly for gypsum dehydration and extraction. The gypsum cyclone and the vacuum dehydrator facilitate the dehydration and reuse of gypsum.

[0041] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A comprehensive flue gas treatment system for the cement industry, characterized in that: It includes a staged combustion denitrification device (1) using aqueous ammonia and a wet desulfurization device; The wet desulfurization device comprises a SO2 absorption system (2) and a lime slurry preparation system (3); The SO2 absorption system (2) comprises an absorption tower (21) and a plurality of spray layers (22) and a plurality of demisters (23) arranged in sequence from bottom to top inside the absorption tower (21); a circulation pipe (221) communicating with each spray layer (22) is provided on the outer wall of the absorption tower (21); one end of each circulation pipe (221) away from the absorption tower (21) is communicated with the lower space inside the absorption tower (21); each circulation pipe (221) is provided with a slurry circulation pump (222); an inlet pipe (223) for flue gas to enter is provided on one side wall of the absorption tower (21); the spray layer (22) is located above the inlet pipe (223); and a stirrer and an oxidation system located below the inlet pipe (223) are provided on the side wall of the absorption tower (21); The lime slurry preparation system (3) provides lime slurry to the absorption tower (21); The outer wall of the absorption tower (21) is provided with a slurry discharge pipe (24) which is in communication with the lower space inside the absorption tower (21), and the slurry discharge pipe (24) is provided with a gypsum slurry pump (241).

2. A comprehensive flue gas treatment system for cement industry as claimed in claim 1, characterized in that: A pH sensor is provided on the inner wall of the absorption tower (21), and the pH sensor detects the pH value of the slurry in the lower space inside the absorption tower (21).

3. A comprehensive flue gas treatment system for cement industry as claimed in claim 1, characterized in that: The lime slurry preparation system (3) comprises a lime slurry tank (31) and a stirring paddle (32) located in the lime slurry tank (31); a motor (33) for driving the stirring paddle (32) to rotate is provided at the top of the lime slurry tank (31); a drainage pipe (34) is provided at the bottom of the lime slurry tank (31); a lime slurry pump (35) is provided on the drainage pipe (34); an end of the drainage pipe (34) away from the lime slurry tank (31) is connected to the inside of the absorption tower (21), and the connection position is located below the spray layer (22).

4. A comprehensive flue gas treatment system for cement industry as claimed in claim 3, characterized in that: The oxidation system comprises a plurality of ventilation pipes (25) arranged in the lower layer of the absorption tower (21) and distributed horizontally, each of the ventilation pipes (25) being distributed along the same horizontal plane and connected at one end through a main pipe, a vertical pipe (251) being provided on the outer wall of the main pipe, an oxygen pipe (252) extending out of the outer wall of the absorption tower (21) being provided at the upper end of the vertical pipe (251), the oxygen pipe (252) being connected to an oxidation blower (253), and a plurality of blowing holes for discharging oxygen from the ventilation pipe (25) being provided on the outer wall of each of the ventilation pipes (25).

5. A comprehensive flue gas treatment system for cement industry as claimed in claim 4, characterized in that: The stirrer comprises a stirring rod (254) obliquely inserted into the side wall of the absorption tower (21); the stirring rod (254) is rotatably connected to the inner wall of the absorption tower (21); the outer wall of the absorption tower (21) is provided with a first motor (255) for driving the stirring rod (254) to rotate; the outer wall of the stirring rod (254) located in the absorption tower (21) is provided with a plurality of main blades (256); the main blades (256) enable the stirring rod (254) to be an axial flow stirrer when rotating; the angle between the axis of the stirring rod (254) and the horizontal line is 8°±2°; the stirring rod (254) is located in the lower layer slurry of the absorption tower (21) and is located above each ventilation pipe (25).

6. A comprehensive flue gas treatment system for cement industry as claimed in claim 4, characterized in that: The agitator comprises a rotating shaft (26) located above the slurry liquid level in the lower layer of the absorption tower (21); the rotating shaft (26) is rotatably connected to the side wall of the absorption tower (21) and is coaxially driven by a second motor (261) arranged on the outer wall of the absorption tower (21); one end of the rotating shaft (26) away from the inner wall of the absorption tower (21) is coaxially fixedly connected to a driving bevel gear (262); connecting plates (263) are provided on both sides of the rotating shaft (26) on the inner wall of the absorption tower (21); one end of the two connecting plates (263) is rotatably connected to an intermediate rod (264); the intermediate rod (264) is located at the end of the driving bevel gear (262) away from the rotating shaft ( On one side of the absorption tower (26), an intermediate bevel gear (265) is coaxially fixedly connected to the outer wall of the intermediate rod (264), and the intermediate bevel gear (265) is meshed with the driving bevel gear (262). A U-shaped swing rod (266) is fixedly connected to the two connecting plates (263), and a stirring shaft (267) is rotatably connected to the swing rod (266). One end of the stirring shaft (267) passes through the swing rod (266) and is coaxially fixed with a driven bevel gear (268) meshed with the intermediate bevel gear (265), and the other end obliquely penetrates into the lower layer liquid of the absorption tower (21). The outer wall of the stirring shaft (267) is provided with a plurality of stirring blades (269).

7. A comprehensive flue gas treatment system for cement industry as claimed in claim 6, characterized in that: When the pH sensor detects that the pH value of the slurry in the lower space inside the absorption tower (21) is less than 5, the pH sensor controls the gypsum slurry pump (241) to start working to extract part of the slurry, and then controls the lime slurry pump (35) to start working to extract the lime slurry into the absorption tower (21), and the amount of the lime slurry extracted is the amount of the extracted slurry; When the pH sensor detects that the pH value of the slurry in the lower space inside the absorption tower (21) is greater than 8, the pH sensor controls the gypsum slurry pump (241) to start working to extract part of the slurry, and then controls the lime slurry pump (35) to start working to extract the lime slurry into the absorption tower (21). The amount of lime slurry extracted is the amount of slurry extracted.

8. A cement industry flue gas comprehensive treatment system as claimed in claim 6, characterized in that: The two ends of the swing rod (266) are rotatably connected to the two connecting plates (263) via a rotating rod (27), respectively; the ends of the two rotating rods (27) away from the swing rod (266) are both rotatably connected to the inner wall of the absorption tower (21); one end of one of the rotating rods (27) extends out of the absorption tower (21) and is coaxially driven to rotate by a third motor fixed to the outer wall of the absorption tower (21); the lower end of the stirring shaft (267) extends to the lower end of each ventilation pipe (25); the stirring blade (269) is located above each ventilation pipe (25); and a plurality of stirring plates (271) are provided at the lower end of the stirring shaft (267).

9. A comprehensive flue gas treatment system for cement industry as claimed in claim 1, characterized in that: The slurry discharge pipe (24) discharges the slurry to the gypsum cyclone and the vacuum dehydrator in sequence.

10. A comprehensive flue gas treatment system for cement industry as claimed in claim 1, characterized in that: The absorption tower (21) is provided with an enhanced absorption layer below the spray layer (22), the enhanced absorption layer comprising an air distribution plate (28) covering the cross section of the absorption tower (21), the air distribution plate (28) being provided with long strip-shaped through grooves (281), the through grooves (281) penetrating the upper and lower ends of the air distribution plate (28), and the air distribution plate (28) is located above the inlet pipe (223), and the size of each through groove (281) gradually increases in a direction away from the inlet pipe (223).

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