Flue gas dust removal desulfurization tower and flue gas dust removal, desulfurization and wastewater treatment method
Technical Field
The invention belongs to the field of industrial waste gas purification, and relates to a flue gas dust removal and desulfurization tower and a flue gas dust removal, desulfurization and wastewater treatment method.
Background
The boiler flue gas and the flue gas discharged by a factory contain sulfur dioxide and dust, the sulfur dioxide and the dust are main component dust of atmospheric pollutants, the sulfur dioxide is a main reason for forming acid rain, and the dust with small particle size is one of the chief causes of haze formation.
Environmental pollution is increasingly serious, haze events are frequent, the national degree of attention on environmental protection is also higher and higher, and a series of laws and regulations, national standards and management methods for environmental protection are provided in recent years. GB 13223 Specification of 2011 emission Standard of atmospheric pollutants for thermal power plants: flue gas dust of coal-fired boiler not more than 30mg/Nm3SO of flue gas of newly-built coal-fired boiler2≯100mg/Nm3(ii) a The fume dust of coal-fired boiler in key areas is not more than 20mg/Nm3, SO2≯50mg/Nm3. Complete implementation of working schemes for ultralow emission and energy conservation modification of coal-fired power plants (environmental protection [2015 ]]164) the ultra-low emission indexes of the flue gas of the coal-fired power plant are as follows: flue gas dust not more than 10mg/Nm3, SO2≯35mg/Nm3. GB 31570 2015 emission Standard for Industrial pollutants for Petroleum refining stipulates: regenerated flue gas particulate matters of the catalytic cracking catalyst are not more than 50mg/Nm3,SO2≯100mg/Nm3(ii) a Particulate matter in key areas is not more than 30mg/Nm3, SO2≯50mg/Nm3。
The wet desulphurization has the advantages of high desulphurization rate, reliable device operation, simple operation and the like, so the existing flue gas desulphurization technology of various countries in the world mainly takes wet desulphurization as the main technology. The traditional wet desulphurization technology mainly comprises a limestone-gypsum method, a double alkali desulphurization method, a sodium alkali desulphurization method, an ammonia desulphurization method and the like. The flue gas desulfurization technology mainly adopts countercurrent spray, alkaline slurry is sprayed from the upper part of a desulfurization tower, and is free to settle under the action of gravity to be in countercurrent contact with flue gas to realize desulfurization reaction, but the diameter of sprayed liquid drops is relatively large, the contact area of single liquid drop and the flue gas is small, so that in order to improve the desulfurization efficiency, the number of times of circulating spray of the slurry needs to be increased, the liquid drops are in contact with the flue gas for many times to improve the absorption effect of the liquid drops on sulfur dioxide, the flow of a slurry circulating pump at the bottom of the tower is very large, the power of a motor is also very large, the power consumption of the slurry circulating pump is very large, and the operation cost is high.
The particle size of dust in the flue gas is small, most of the dust is 0.1-200 mu m, and the existing flue gas dust removal technology mainly comprises a cloth bag type dust removal technology, an electrostatic dust removal technology and a wet dust removal technology. Because the flue gas contains moisture, dust absorbs moisture and is bonded on a filter bag of the cloth bag type dust collector to block the pores of the filter bag, so that the filter bag needs to be cleaned or replaced frequently, and the application of the cloth bag type dust collector is greatly limited; the main disadvantages of the electrostatic dust collector are that the manufacturing cost is high, the requirements of installation, maintenance and management are strict, high-voltage power transformation and rectification control equipment is required, the power consumption is high, and the occupied area is large; the wet dust removal technology mainly removes dust carried in flue gas through spray water, and liquid drops with smaller particle sizes are still discharged out of a chimney along with the flue gas after being combined with the dust.
The desulfurization wastewater treatment processes disclosed in CN201110153423.3, CN201310338193.7 and CN201310421183.X are all provided with a flocculation tank and an oxidation tank, the flocculation tank and the oxidation tank are both provided with a stirrer, and slurry is conveyed by a pump. The dust removal and desulfurization wastewater treatment process disclosed by CN201310338193.7 and CN201310421183.X adopts a hydrocyclone to carry out solid-liquid separation. The desulfurization wastewater treatment process has the advantages of longer flow, more equipment and higher energy consumption.
Because the pollution emission index established by the state is more and more strict, enterprises with boilers and factories with flue gas emission need to modify newly-added flue gas dust removal and desulfurization devices or old devices so as to meet the standard emission of flue gas. Because most boilers and flue gas discharging devices are built according to old standards before, and the flue gas needs further deep dedusting and desulfurization when in construction, enough construction land is not reserved for flue gas dedusting and desulfurization modification during construction, and the flue gas dedusting and desulfurization devices or the old devices need to be newly built in the existing limited area. The wet desulphurization technology comprises flue gas desulphurization, desulphurization waste water oxidation treatment or regeneration units, the flow is long, the equipment is more, the occupied area is larger, the construction and upgrading reconstruction of the dust removal desulphurization device are seriously restricted, and partial devices and boilers cannot be upgraded and reconstructed due to the lack of enough space, so that the flue gas emission index cannot meet the current national standard and is forced to be shut down or destroyed and reconstructed. Therefore, the development of flue gas desulfurization technology with short flow, less equipment and less floor space is urgently needed.
With the large-scale popularization and application of the wet desulfurization technology in China, an obvious and difficult-to-overcome defect of the wet desulfurization technology gradually appears, and the defect is that the discharged flue gas can generate 'white smoke' at the opening of a chimney, even forms 'long white smoke' of kilometers, brings strong visual impact to people, and sometimes generates 'dust rain' on the ground. Therefore, how to eliminate the phenomenon of "white smoke" is a problem to be solved urgently.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the flue gas dust removal desulfurization tower and the flue gas dust removal, desulfurization and wastewater treatment method.
The flue gas dedusting and desulfurizing tower comprises a flue gas discharge area, a demisting area, a tower tray area, a spraying area and a wastewater treatment area from top to bottom in sequence; the center of the wastewater treatment area is divided into an oxidation flocculation area and a circulating clear liquid area through a vertical partition plate I, wherein the oxidation flocculation area is communicated with the spraying area, and the top of the circulating clear liquid area completely separates the circulating clear liquid area from the oxidation flocculation area and the spraying area through a partition plate II; the partition plate I is provided with at least one opening, preferably 1-20 openings, more preferably 1-4 openings, and the area of the opening is 10% -90% of that of the partition plate I, preferably 50% -70%; the opening of the clapboard I is fixed with a filter medium.
The filter medium is a net structure made of natural fibers, synthetic fibers, glass fibers and metal wires, and the mesh size is 0.1-1000 mu m, preferably 5-100 mu m.
The two ends of the baffle plate II are respectively connected with the baffle plate I and the tower wall of the circulating clear liquid area, and the included angle of the joint of the baffle plate I and the baffle plate II is generally 45-165 degrees, preferably 120-150 degrees. The partition plates I and II are sealed with the tower wall, so that gas and liquid short circuits at two sides of the partition plates are avoided.
The flue gas discharge area and the demisting area are preferably connected through conical reducing, and the tower diameter ratio of the demisting area to the flue gas discharge area is 1.2-5; the tower disc area and the spraying area are preferably connected through an inverted cone-shaped reducing area, and a wastewater treatment area is arranged below the spraying area; the tower diameter ratio of the tower tray area to the spraying area is 1.2-3.
The flue gas discharge area is generally a chimney structure in the conventional wet flue gas desulfurization process, the bottom of the chimney is connected with the tower body of the demisting area, preferably, the chimney is connected with the tower body of the demisting area through a cone-shaped reducing pipe, and the top of the chimney is provided with a flue gas outlet; preferably, an outer sleeve is arranged at the top of the chimney, the outer sleeve is of a cylindrical structure with an upper opening and a lower opening, and can be cylindrical or conical, the upper edge of the outer sleeve is higher than the top of the chimney by a certain distance, generally 0.2-10 m, preferably 0.5-5 m, the lower edge of the outer sleeve is lower than the upper edge of the chimney, preferably 0.5-5 m; an annular space is formed between the outer sleeve and the chimney, and the diameter of the bottom opening is preferably 1.01-1.2 times of that of the top opening of the chimney. The smoke enters the outer sleeve from the top of the chimney and is discharged from the top of the outer sleeve, the gas velocity of the smoke is high, negative pressure is generated between the chimney and the outer sleeve when the smoke flows through the outer sleeve, air flows through an annular space between the chimney and the outer sleeve under the action of suction of the negative pressure and enters the upper part of the outer sleeve, the air is mixed with the smoke in the outer sleeve and then is discharged from the top of the outer sleeve, the smoke is fully mixed with the air before leaving the top of the outer sleeve and being discharged, and the generation amount of 'white smoke' is greatly reduced.
The demisting zone is provided with demisting equipment for removing liquid drops carried by the flue gas, and the demisting equipment can be one or more of a cyclone demister, a wet electrostatic demister, a wire mesh demister or a baffling demister.
The tower tray area can be provided with one or more layers of tower trays, and the number of the tower trays is preferably 2-6; the tower tray can be one type of tower tray or various types of combined tower trays, comprises a float valve tower tray, a sieve tray, a guide sieve tray, a tongue fixing tower tray, a tongue floating tower tray or a three-dimensional mass transfer tower tray and the like, is used for gas-liquid full contact reinforced mass transfer to realize deep desulfurization of flue gas, captures micro dust particles between 0.1 mu m and 5 mu m in the flue gas to realize deep dust removal of the flue gas, and captures a large amount of micro fog drops carried by the flue gas to reduce the separation load of a demisting area.
And a liquid distributor is arranged between the tower tray area and the demisting area, and is connected with a circulating clear liquid pipeline I and used for uniformly distributing circulating clear liquid on the tower tray.
One or more layers of spraying pipelines are arranged at the upper part of the spraying area, and when the plurality of layers of spraying pipelines are arranged, the distance between the spraying pipelines is 0.5-5 m, and the preferable distance is 1-2.5 m; the spraying pipeline is connected with a circulating clear liquid pipeline II and is provided with a plurality of atomizing nozzles; the spraying area is used for atomizing the circulating clear liquid, and the atomized small liquid drops are in countercurrent contact with the flue gas to remove dust and sulfur dioxide carried in the flue gas; and the lower part of the spraying area is provided with a flue gas inlet I for connecting a flue gas pipeline I.
One side of the oxidation flocculation area, which is close to the tower wall, is respectively connected with an alkaline solution pipeline I, a flocculating agent pipeline and a liquid level meter I; the alkaline solution pipeline I is provided with a flow regulating valve for adding an alkaline solution into the desulfurization wastewater to regulate the pH value of the desulfurization wastewater; the flocculant pipeline is used for injecting a flocculant into the desulfurization wastewater, so that small-particle dust in the desulfurization wastewater is coagulated into large particles.
The bottom of the oxidation flocculation area is connected with a flue gas pipeline II and an outer discharging slurry pipeline; the flue gas pipeline II extends into the oxidation flocculation zone and is parallel to the partition plate I, a plurality of groups of flue gas branch pipes, preferably 2-4 groups of flue gas branch pipes, are horizontally distributed in sequence from bottom to top on the flue gas pipeline II in the oxidation flocculation zone, and the flue gas branch pipes are communicated with the flue gas pipeline II; each group of flue gas branch pipes consists of 2-8 flue gas branch pipes, each flue gas branch pipe is arc-shaped, and each group of flue gas branch pipes are uniformly distributed in the horizontal direction and have the same rotating direction; the spraying direction of the flue gas from the flue gas branch pipe is the tangential direction of an arc, the flue gas is sprayed at a high speed to push the slurry to rotate, the slurry in the oxidation flocculation area is stirred, the materials in the oxidation flocculation area are uniformly mixed, and dust particles on the filter medium are washed off; the external slurry discharge pipeline is used for discharging the slurry after oxidation and flocculation to a subsequent treatment unit, and a flow regulating valve and a pH meter are arranged on the external slurry discharge pipeline; the flow regulating valve regulates the flow of the discharged slurry according to a signal fed back by the liquid level meter I and is used for controlling the liquid level of the liquefaction flocculation area; the pH meter is used for measuring the pH value of the discharged slurry and feeding back a signal to the flow regulating valve on the alkaline solution pipeline I through the controller.
One side of the circulating clear liquid zone, which is close to the tower wall, is connected with a fresh water pipeline, an alkaline solution pipeline II, an oxidizing gas pipeline and a liquid level meter II; the fresh water pipeline is provided with a flow regulating valve which is used for regulating the flow of fresh water according to a signal fed back by the liquid level meter II and controlling the liquid level of the circulating clear liquid area; the alkaline solution pipeline II is provided with a flow regulating valve for regulating the flow of the alkaline solution filled into the circulating clear liquid area; the oxidizing gas pipeline is connected with the fan, extends to one side of the partition plate I of the circulating clear liquid zone and is connected with the oxidizing gas distribution pipe; the oxidizing gas distribution pipe is provided with a plurality of nozzles, the nozzles are opposite to the filter medium on the partition plate I, the oxidizing gas is sprayed out from the nozzles and penetrates through the filter medium to blow up dust particles on the filter medium in the oxidation flocculation area, the blown-up dust and the oxidizing gas are taken away by the rotating slurry, the dust and the flocculating agent are coagulated into large particles to be deposited at the bottom of the oxidation flocculation area under the action of gravity, and the oxidizing gas entering the oxidation flocculation area oxidizes sulfite in the slurry into sulfate so that the COD of the desulfurization wastewater reaches the standard.
The tower wall at the top of the circulating clear liquid area is provided with an air vent for ensuring the stable pressure of the circulating clear liquid area and avoiding the damage to the filter medium caused by overlarge pressure fluctuation.
The bottom of the circulating clear liquid zone is connected with a clear liquid leading-out pipeline, the leading-out pipeline is divided into two paths, one path of pipeline is connected with an external clear liquid discharging pipeline, the other path of pipeline is connected with a circulating clear liquid pump, a pH meter is arranged on the pipeline, and the circulating clear liquid pump is connected with a circulating clear liquid pipeline I and a circulating clear liquid pipeline II through a cooler; the pH meter is used for measuring the pH value of the circulating clear liquid and feeding back a measurement signal to the regulating valve of the alkaline solution pipeline II through the controller.
The method for dedusting and desulfurizing flue gas and treating wastewater comprises the following steps:
(1) the flue gas enters the flue gas dust removal desulfurization tower in two ways, one way enters from the lower part of a spray zone of the flue gas dust removal desulfurization tower through a flue gas pipeline I, the other way enters from the bottom of an oxidation flocculation zone of the flue gas dust removal desulfurization tower through a flue gas pipeline II and passes through slurry in the oxidation flocculation zone, the two ways of flue gas are converged and then are in countercurrent contact with circulating clear liquid in the spray zone to remove most of dust and sulfur dioxide carried in the flue gas, the flue gas passing through the spray zone enters a tower panel zone, deep dust removal and desulfurization are carried out on the tower panel zone and the circulating clear liquid, the purified flue gas enters a flue gas discharge zone after being demisted in a demisting zone, the purified flue gas enters an outer sleeve from the top of a chimney and is fully mixed with air and then is discharged from the top of the flue gas discharge zone;
(2) the desulfurization slurry absorbing the dust and the sulfur dioxide enters an oxidation flocculation area, and is fully mixed with oxidizing gas, a flocculating agent and an alkaline solution under the stirring action of the flue gas entering through a flue gas pipeline II, sulfite in the desulfurization slurry is oxidized into sulfate, small particle dust in the desulfurization slurry is flocculated into large particles, and meanwhile, the flue gas with a certain temperature enables the moisture in the desulfurization slurry to be continuously volatilized, and the salt concentration is gradually increased;
(3) the desulfurization slurry flows through a filter medium on a partition plate I to realize solid-liquid separation under the action of liquid level difference on two sides of the partition plate I, dust particles in the desulfurization slurry are filtered and left in an oxidation flocculation area, clear liquid enters a circulating clear liquid area, and the slurry after oxidation flocculation is led out from the bottom of the oxidation flocculation area and enters a subsequent treatment unit through an external discharge pipeline;
(4) oxidizing gas enters from the circulating clear liquid zone, is sprayed out from a nozzle of the oxidizing gas distribution pipe and penetrates through the filter medium, dust particles on the filter medium of the oxidation flocculation zone are blown up, the blown-up dust and the oxidizing gas are taken away by the rotating slurry, the dust and a flocculating agent are aggregated into large particles under the action of gravity and are deposited at the bottom of the oxidation flocculation zone, and sulfite in the slurry is oxidized into sulfate by the oxidizing gas entering the oxidation flocculation zone, so that the COD of the desulfurization wastewater reaches the standard;
(5) the clear liquid entering the circulating clear liquid zone after being filtered by the filter medium is mixed with fresh water and alkaline solution in the circulating clear liquid zone and then is led out from the bottom of the circulating clear liquid zone, a small amount of clear liquid is directly discharged to reduce the salt concentration of the circulating clear liquid, the rest clear liquid enters the cooler after being pressurized by the circulating clear liquid pump, one part of the clear liquid cooled by the cooler enters the spraying area, is atomized by the atomizing nozzle and then is in countercurrent contact with the flue gas to remove dust and sulfur, the other part of the clear liquid flows through the liquid distributor and enters the tower disc area, the deep desulfurization of flue gas is realized with the abundant contact of flue gas intensive mass transfer effect on the tray to catch the small dust particle between 0.1 mu m ~5 mu m in the flue gas, realize the degree of depth dust removal of flue gas, a large amount of small fog drops that the flue gas carried through the spray area also are caught by the clear liquid on the tray, have reduced the separation load that removes the fog district.
In the method, the flue gas in the step (1) is coal-fired boiler flue gas, coal-fired power plant flue gas, catalytic cracking catalyst regeneration flue gas, process heating furnace flue gas, coking flue gas or steel sintering flue gas and the like. The ratio of the amount of the flue gas entering the flue gas pipeline I to the amount of the flue gas entering the flue gas pipeline II is 20-500; the ratio of the circulating clear liquid to the flue gas in the spraying area is 5-50L/Nm3The preferred proportion is 8-25L/Nm3And the ratio of the circulating clear liquid to the flue gas in the tower tray area is 3-15L/Nm3。
In the method, the alkaline solution in the steps (2) and (5) is selected from one or more of sodium hydroxide solution, calcium hydroxide solution, magnesium hydroxide solution, sodium carbonate solution, sodium sulfite solution, sodium citrate solution, limestone slurry, ammonia water or seawater and the like.
In the method of the present invention, the oxidizing gas in the steps (2) and (4) is one or more of air, oxygen, ozone, etc., and preferably the oxidizing gas is air.
In the method, the oxidizing gas flow in the steps (2) and (4) is adjusted according to the Chemical Oxygen Demand (COD) of the slurry after flocculation concentration, and the COD control index is not more than 60 mg/L.
In the method, the flocculating agent in the steps (2) and (4) is aluminum sulfate, alum, sodium aluminate, ferric trichloride, ferrous sulfate, ferric sulfate, polyaluminum chloride, polyaluminum sulfate, polyaluminum phosphate, polyferric chloride, polyferric sulfate, polyferric phosphate, polyferric chloride, and polyphosphazeneOne or more of aluminum chloride, ferric polysilicate sulfate, aluminum ferric polysulfate sulfate, polymeric ferric polysilicate flocculant, aluminum-iron copolymerization composite flocculant, polymeric polysilicate flocculant, polyacrylamide flocculant and the like, wherein the addition amount of the flocculant is 0.05-2 kg/m3。
In the method, the pH value of the slurry after the oxidative flocculation in the step (3) is controlled to be 7-9, a pH online detector is positioned on a slurry external discharge pipeline, and the pH value of the desulfurized slurry is controlled by adjusting an adjusting valve on an alkaline solution pipeline I.
In the method, the liquid level difference between two sides of the partition plate I in the step (3) is 0.5-6 m, and the liquid level of the oxidation flocculation area is higher than that of the circulating clear liquid area.
In the method, the liquid level height of the oxidation flocculation area in the step (3) is controlled by an adjusting valve on an external slurry discharge pipeline.
In the method, the liquid level height of the circulating clear liquid area in the step (3) is controlled by a regulating valve on a fresh water pipeline.
In the method, the pH value of the circulating clear liquid area in the steps (3) to (5) is controlled to be 6-11, the preferable control range of the pH value is 7-8, the pH online detector is positioned on an inlet pipeline of a tower bottom circulating pump, and the pH value of the circulating clear liquid is controlled by adjusting an adjusting valve on an alkaline solution pipeline II.
In the method, the discharged slurry in the step (3) and the discharged clear liquid in the step (5) enter a subsequent treatment unit, can be used for preparing or producing products such as gypsum, sodium sulfite, sodium bisulfite, magnesium sulfite, magnesium sulfate, magnesium oxide, sodium sulfate, ammonium bisulfate and the like, and can also be discharged after being filtered to reach the standard.
Compared with the prior art, the invention has the advantages that:
1. the lower part of the flue gas dedusting and desulfurizing tower is provided with a wastewater treatment area which is divided into an oxidation flocculation area and a circulating clear liquid area by two clapboards, and the oxidation flocculation area realizes the oxidation, flocculation and concentration of the desulfurization wastewater; the vertical clapboard in the center of the wastewater treatment area is provided with a filter medium, and the filtration operation of the desulfurization slurry is realized by using the liquid level difference at the two sides of the vertical clapboard as a driving force. The circulating clear liquid obtained by filtering is used as a circulating medium for dust removal and desulfurization, and because the circulating clear liquid does not contain dust or has low dust content, compared with the prior art that slurry containing dust is used as the circulating medium for dust removal and desulfurization, the method has high dust removal efficiency. The invention divides the inlet flue gas into two paths, wherein the high-temperature flue gas entering from the bottom of the oxidation flocculation area is sprayed out from the arc-shaped flue gas branch pipe along the tangential direction to push the dust removal desulfurization waste liquid to rotate, so that the materials in the oxidation flocculation area are fully mixed and contacted, the oxidation flocculation reaction is facilitated, the dust and sulfur-containing oxides in the flue gas are absorbed to a certain extent, meanwhile, the waste heat of the high-temperature flue gas is fully utilized, the moisture in the dust removal desulfurization waste water is greatly vaporized, the primary concentration of the desulfurization waste water is realized in the oxidation flocculation area, and the energy consumption of subsequent units is reduced. Meanwhile, the oxidizing gas is introduced from the circulating clear liquid zone instead of directly entering the oxidation flocculation zone, and the oxidizing gas is used for washing the filter medium, so that washing equipment is omitted. The invention saves conventional stirring equipment and filtering equipment, does not need to consume additional energy in the wastewater treatment process, and greatly reduces the device investment and the operation cost.
2. According to the invention, the inverted cone-shaped reducing is arranged between the tray area and the spraying area, so that the gas velocity of the tray area is favorably reduced, the gas-liquid mass transfer effect is enhanced, the dust removal efficiency and the desulfurization efficiency of flue gas in the tray area are improved, and entrainment is reduced, so that the load of the demisting area is reduced; the smoke discharging area and the demisting area are provided with the cone-shaped reducing areas, so that the flow speed of smoke is improved, the higher the gas speed of the smoke is, the higher the lifting height of the smoke after the smoke leaves the smoke discharging area is, the more the smoke is favorably diffused, and smoke plumes are shorter.
3. The smoke discharging area of the smoke desulfurizing and dedusting tower adopts a structure of a chimney and an outer sleeve, after smoke is accelerated by a demisting area and a cone-shaped reducing area, negative pressure is generated when the smoke flows through the outer sleeve to suck outside air, the smoke and the air are fully mixed in the outer sleeve and then are discharged from the top of the outer sleeve, and the generation amount of white smoke is greatly reduced.
4. The invention completes flue gas dust removal, flue gas desulfurization and wastewater treatment in one tower, realizes triple functions of deep flue gas dust removal, desulfurization and standard-reaching wastewater COD discharge, has short process flow and remarkably reduces the cost required by device construction and transformation due to the cooperative cooperation of all functional areas.
Drawings
FIG. 1 is a schematic structural diagram of a flue gas dedusting and desulfurizing tower of the present invention.
FIG. 2 is a schematic view of the structure of the separator in the direction of A.
FIG. 3 is a schematic view of a direction B of a wastewater treatment zone according to the present invention.
FIG. 4 is a schematic view of the process of the present invention.
In the figure: 1-a flue gas discharge zone; 2-conical reducing; 3-a demisting area; 4-tower disc area; 5-inverted cone-shaped reducing; 6-spraying area; 6-1-circulating clear liquid line II; 6-2-flue gas pipeline I; 7-a wastewater treatment zone; 8-an oxidative flocculation zone; 8-1-level gauge I; 8-2-alkaline solution line I; 8-3-flocculant line; 8-4-an efflux slurry line; 8-5-flue gas pipeline II; 9-circulating clear liquid area; 9-1-level gauge II; 9-2-fresh water line; 9-3-alkaline solution line II; 9-4-oxidizing gas line; 9-5-clear liquid outlet line; 9-6-an efflux supernatant line; 10-a flue gas inlet; 11-a demister; 12-a liquid distributor; 12-1-recycle serum line I; 13-trays; 14-a spray line; 15-an atomizing nozzle; 16-a vent; 17-flue gas branch pipe; an 18-oxidizing gas distribution pipe; 19-separator II; 20-a separator I; 21-a filter medium; 22-a sealing strip; 23-a fastening screw; 24-a fan; 25-a cooler; 26-circulating clear liquid pump, 27-chimney and 28-outer sleeve.
Detailed Description
The present invention will be described in detail below with reference to the drawings and examples.
The flue gas dedusting and desulfurizing tower comprises a flue gas discharge area 1, a demisting area 3, a tower tray area 4, a spraying area 6 and a wastewater treatment area 7 from top to bottom in sequence; the flue gas emission area 1 is connected with the demisting area 3 through the cone-shaped reducing area 2, the tray area 4 is arranged below the demisting area 3, the tray area 4 is connected with the spraying area 6 through the inverted cone-shaped reducing area 5, and the wastewater treatment area 7 is arranged below the spraying area 6; waste water treatment district 7 central authorities divide into oxidation flocculation district 8 and circulation clear solution district 9 through a vertical baffle I20, wherein oxidation flocculation district 8 and spraying district 6 intercommunication, circulation clear solution district 9 top is separated circulation clear solution district 9 and oxidation flocculation district 8 and spraying district 6 completely through baffle II 19.
The partition plate I20 is provided with at least one opening, preferably 1-20 openings, more preferably 1-4 openings, and the area of the opening is 10% -90% of the area of the partition plate I20, preferably 50% -70%; a filter medium 21 is fixed on the opening of the clapboard I20; the filtering medium 21 is a net structure made of natural fibers, synthetic fibers, glass fibers and metal wires, preferably a metal net, and the mesh size is 0.1-1000 mu m, preferably 5-100 mu m; the filter medium 21 is fixed to the opening of the partition 20 by a seal strip 22 and a fastening screw 23.
Two ends of the partition plate II 19 are respectively connected with the partition plate I20 and the tower wall of the circulating clear liquid zone 9, and the included angle of the joint of the partition plate I20 and the partition plate II 19 is generally 45-165 degrees, preferably 120-150 degrees. The partition plates I20 and II 19 are sealed with the tower wall, so that gas and liquid short circuits at two sides of the partition plates are avoided.
The tower diameter ratio of the demisting area 3 to the flue gas discharge area 1 is 1.2-5; the tower tray area 4 and the spray area 6 have the tower diameter ratio of 1.2-3.
The flue gas discharge area 1 is generally a chimney 27 structure in the conventional wet flue gas desulfurization process, the bottom of the chimney 27 is connected with the tower body of the demisting area 3, preferably connected with the tower body of the demisting area 3 through the cone-shaped reducing area 2, and the top of the chimney 27 is provided with a flue gas outlet; preferably, an outer sleeve 28 is arranged at the top of the chimney 27, the outer sleeve 28 is a cylindrical structure with an upper opening and a lower opening, and can be cylindrical or conical, the upper edge of the outer sleeve 28 is higher than the top of the chimney 27 by a certain distance, generally 0.2-10 m, preferably 0.5-5 m, the lower edge of the outer sleeve 28 is lower than the upper edge of the chimney 27, preferably 0.5-5 m; the diameter of the bottom opening of the outer sleeve 28 is larger than that of the top opening of the chimney 27, and preferably 1.01-1.2 times of that of the top opening of the chimney 27; the smoke enters the outer sleeve 28 from the top of the chimney 27 and is discharged from the top of the outer sleeve 28, the smoke is high in gas velocity, negative pressure is generated between the chimney 27 and the outer sleeve 28 when the smoke flows through the outer sleeve 28, air flows through an annular space between the chimney 27 and the outer sleeve 28 under the suction effect of the negative pressure and enters the upper part of the outer sleeve 28, the air is mixed with the smoke in the outer sleeve 28 and then is discharged from the top of the outer sleeve 28, the smoke is fully mixed with the air before being discharged from the top of the outer sleeve 28, and the generation amount of 'white smoke' is greatly reduced.
Demisting zone 3 set up demisting equipment for detach the liquid drop that the flue gas carried, demisting equipment can be for one or several kinds among whirl defroster, wet-type electrostatic defroster, silk screen defroster or baffling formula defroster etc..
One or more layers of tower trays 13 can be arranged in the tower tray area 4, and the number of the tower tray layers is preferably 2-6; the tower tray can be one type of tower tray or various types of combined tower trays, comprises a float valve tower tray, a sieve tray, a guide sieve tray, a tongue fixing tower tray, a tongue floating tower tray or a three-dimensional mass transfer tower tray and the like, is used for gas-liquid full contact reinforced mass transfer to realize deep desulfurization of flue gas, captures micro dust particles between 0.1 mu m and 5 mu m in the flue gas to realize deep dust removal of the flue gas, and captures a large amount of micro fog drops carried by the flue gas to reduce the separation load of a demisting area 3.
And a liquid distributor 12 is arranged between the tray area 4 and the demisting area 3, and the liquid distributor 12 is connected with a circulating clear liquid pipeline I12-1 and is used for uniformly distributing circulating clear liquid on a tray 13.
One or more layers of spraying pipelines 14 are arranged at the upper part of the spraying area 6, and when the plurality of layers of spraying pipelines 14 are arranged, the distance between the spraying pipelines 14 is 0.5-5 m, and the preferable distance is 1-2.5 m; the spraying pipeline 14 is connected with the circulating clear liquid pipeline II 6-1, and a plurality of atomizing nozzles 15 are arranged on the spraying pipeline 14; the spraying area 6 is used for atomizing the circulating clear liquid, and the atomized small liquid drops are in countercurrent contact with the flue gas to remove dust and sulfur dioxide carried in the flue gas; the lower part of the spraying area 6 is provided with a flue gas inlet 10 which is used for connecting a flue gas pipeline I6-2.
One side of the oxidation flocculation area 8, which is close to the tower wall, is respectively connected with an alkaline solution pipeline I8-2, a flocculant pipeline 8-3 and a liquid level meter I8-1; the alkaline solution pipeline I8-2 is provided with a flow regulating valve for adding an alkaline solution into the desulfurization wastewater to regulate the pH value of the desulfurization wastewater; and the flocculant pipeline 8-3 is used for injecting a flocculant into the desulfurization wastewater so as to coagulate small-particle dust in the desulfurization wastewater into large particles.
The bottom of the oxidation flocculation area 8 is connected with a flue gas pipeline II 8-5 and an outer discharge slurry pipeline 8-4; the flue gas pipeline II 8-5 extends to the inside of the oxidation flocculation zone 8 and is parallel to the partition plate I20, the flue gas pipeline II 8-5 in the oxidation flocculation zone 8 is sequentially and horizontally distributed with a plurality of groups of flue gas branch pipes 17 from bottom to top, preferably 2-4 groups, and the flue gas branch pipes 17 are communicated with the flue gas pipeline II 8-5; each group of flue gas branch pipes 17 consists of 2-8 flue gas branch pipes 17, each flue gas branch pipe 17 is arc-shaped, and each group of flue gas branch pipes 17 are uniformly distributed in the horizontal direction and have the same rotating direction; the spraying direction of the flue gas from the flue gas branch pipe 17 is the tangential direction of an arc, the flue gas is sprayed at a high speed to push the slurry to rotate, the slurry in the oxidation flocculation area 8 is stirred, the materials in the oxidation flocculation area are uniformly mixed, and dust particles on the filter medium 21 are washed off; the external slurry discharge pipeline 8-4 is used for discharging oxidized and flocculated slurry to a subsequent treatment unit, and a flow regulating valve and a pH meter are arranged on the external slurry discharge pipeline 8-4; the flow regulating valve regulates the flow of the discharged slurry according to a signal fed back by the liquid level meter I8-1 and is used for controlling the liquid level of the liquefaction flocculation area; the pH meter is used for measuring the pH value of the discharged slurry and feeding back a signal to the flow regulating valve on the alkaline solution pipeline I8-2 through the controller.
One side of the circulating clear liquid zone 9, which is close to the tower wall, is connected with a fresh water pipeline 9-2, an alkaline solution pipeline II9-3, an oxidizing gas pipeline 9-4 and a liquid level meter II 9-1; a flow regulating valve is arranged on the fresh water pipeline 9-2, and the flow of the fresh water is regulated according to a signal fed back by the liquid level meter II9-1, so as to control the liquid level of the circulating clear water area 9; the alkaline solution pipeline II9-3 is provided with a flow regulating valve for regulating the flow of the alkaline solution filled into the circulating clear liquid zone 9; the oxidizing gas pipeline 9-4 is connected with a fan 24, extends to one side of the partition plate I20 of the circulating clear liquid zone 9 and is connected with an oxidizing gas distribution pipe 18; the oxidizing gas distribution pipe 18 is provided with a plurality of nozzles, the nozzles are opposite to the filter medium 21 on the partition plate I20, the oxidizing gas is sprayed out from the nozzles and penetrates through the filter medium 21, dust particles on the filter medium 21 of the oxidation flocculation area 8 are blown up, the blown-up dust and the oxidizing gas are taken away by the rotating slurry, the dust and a flocculating agent are coagulated into large particles under the action of gravity and are deposited at the bottom of the oxidation flocculation area 8, and the oxidizing gas entering the oxidation flocculation area 8 oxidizes sulfite in the slurry into sulfate so as to ensure that the COD of the desulfurization wastewater reaches the standard.
And the tower wall at the top of the circulating clear liquid area 9 is provided with an air vent 16 for ensuring the stable pressure of the circulating clear liquid area 9 and avoiding the damage to the filter medium 21 caused by overlarge pressure fluctuation.
The bottom of the circulating clear liquid zone 9 is connected with a clear liquid outlet pipeline 9-5, the outlet pipeline is divided into two paths, one path of pipeline is connected with an externally-discharged clear liquid pipeline 9-6, the other path of pipeline is connected with a circulating clear liquid pump 26, a pH meter is arranged on the pipeline, and the circulating clear liquid pump 26 is connected with a circulating clear liquid pipeline I12-1 and a circulating clear liquid pipeline II 6-1 through a cooler 25; the pH meter is used for measuring the pH value of the circulating clear liquid and feeding back a measurement signal to the regulating valve of the alkaline solution pipeline II9-3 through the controller.
Example 1
The utility model provides a flue gas dust removal desulfurizing tower, is flue gas discharge district 1, defogging district 3, tower tray district 4, spray district 6 and waste water treatment district 7 from top to bottom in proper order, and flue gas discharge district 1 links to each other through the conical reducing 2 with defogging district 3, and 3 below in defogging district are tower tray district 4, and tower tray district 4 links to each other through the inverted cone reducing 5 with spray district 6, and 6 below in spray district are waste water treatment district 7.
The flue gas emission area 1 is provided with a chimney 27 structure in a conventional flue gas wet desulphurization process, the bottom of the chimney 27 is connected with a demisting area 3 tower body through a cone-shaped reducing pipe 2, the top of the chimney 27 is provided with an outer sleeve 28, the outer sleeve 28 is of a cylindrical structure with an upper opening and a lower opening, the upper edge of the outer sleeve 28 is 5m higher than the top of the chimney 27, and the lower edge of the outer sleeve 28 is 1m lower than the upper edge of the chimney 27.
A wet-type electrostatic demister 11 is arranged in the demisting area 3, a liquid distributor 12 is arranged below the wet-type electrostatic demister 11, a tower tray area 4 is arranged below the liquid distributor 12, the tower tray area 4 is provided with 4 layers of tower trays, and sieve tray trays are selected; the spraying area 6 is provided with 3 layers of spraying pipelines 14, the distance between the spraying pipelines 14 is 2m, and the atomizing nozzles 15 are uniformly arranged on the spraying pipelines 14.
Waste water treatment district 7 central authorities divide into oxidation flocculation district 8 and circulation clear solution district 9 through a vertical baffle I20, and wherein oxidation flocculation district 8 and spraying district 6 intercommunication, circulation clear solution district 9 top is separated circulation clear solution district 9 and oxidation flocculation district 8 and spraying district 6 completely through baffle II 19, and baffle I20 links to each other through welding mode with baffle II 19, and baffle I20, baffle II 19 link to each other through welding mode between with the tower wall. An opening is formed in the partition plate I20, a metal net 21 with the aperture of 100 mu m is fixed in the opening area on one side of the oxidation flocculation area 8, and the metal net 21 is fixed on the partition plate I20 through a sealing strip 22 and a fastening screw 23; a flue gas pipeline II 8-5 is arranged at the bottom of the oxidation flocculation area 8, 5 groups of flue gas branch pipes 17 are arranged on the part of the flue gas pipeline II 8-5 extending to the oxidation flocculation area 8, each group of flue gas branch pipes 17 are uniformly distributed in the horizontal direction and have the same rotating direction, each group of flue gas branch pipes 17 consists of 4 flue gas branch pipes 17, and each flue gas branch pipe 17 is arc-shaped; an oxidizing gas pipeline 9-4 is arranged at one side of the circulating clear liquid zone 9 close to the tower wall, and the oxidizing gas pipeline 9-4 extends to one side of a partition plate I20 of the circulating clear liquid zone 9 and is connected with an oxidizing gas distribution pipe 18; the oxidizing gas distribution pipe 18 is provided with a plurality of nozzles which are opposite to the filter medium 21 on the partition plate I20; the tower wall at the upper part of the circulating clear liquid zone 9 is provided with an air vent 16.
The method for dedusting, desulfurizing and treating waste water of flue gas is that the flue gas treated by the method is regenerated flue gas of a catalytic cracking catalyst containing dust and sulfur dioxide, but the method is not limited to the flue gas. The method for flue gas dust removal, desulfurization and wastewater treatment specifically comprises the following steps:
(1) the flue gas enters the flue gas dust removal and desulfurization tower in two paths, one path enters from the lower part of a spraying area 6 of the flue gas dust removal and desulfurization tower through a flue gas pipeline I6-2, the other path enters from the bottom of an oxidation flocculation area 8 of the flue gas dust removal and desulfurization tower through a flue gas pipeline II 8-5 and passes through the slurry in the oxidation flocculation area 8, wherein the flow ratio of the flue gas in the flue gas pipeline I6-2 to the flue gas pipeline II 8-5 is 20, the two paths of flue gas are converged and then are in countercurrent contact with circulating clear liquid in the spraying area 6 to remove most of dust and sulfur dioxide carried in the flue gas, the flue gas passing through the spraying area 6 enters the tower disc area 4, deep dedusting and desulfurization are carried out on the tower tray area 4 and the circulating clear liquid, the purified flue gas enters the flue gas discharge area 1 after being demisted in the demisting area 3, enters the outer sleeve 28 from the top of the chimney 27 and is fully mixed with air, and then is discharged from the top of the flue gas discharge area 1;
(2) enabling the desulfurization slurry absorbing dust and sulfur dioxide to enter an oxidation flocculation area 8, controlling the pH value of desulfurization wastewater in the oxidation flocculation area 8 to be 7.5-8 by adjusting the flow of a sodium hydroxide solution (32 w%), fully mixing the desulfurization slurry with air, a polysilicic acid flocculant and a sodium hydroxide solution under the stirring action of flue gas entering through a flue gas pipeline II 8-5, oxidizing sulfite in the desulfurization slurry into sulfate, flocculating small particle dust in the desulfurization slurry into large particles, and enabling the moisture in the desulfurization slurry to be volatilized continuously by the flue gas with a certain temperature and gradually increasing the salt concentration;
(3) controlling the liquid level height of an oxidation flocculation area 8 by adjusting the flow of discharged slurry 8-6, and controlling the liquid level height of a circulating clear liquid area 9 by adjusting the flow of fresh water 9-2, so that the liquid level difference between the liquid level of the oxidation flocculation area 8 and the liquid level difference between the circulating clear liquid area 9 is kept at 1.0-2.0 m, the desulfurization slurry flows through a metal net 21 on a partition plate I20 under the action of the liquid level difference between two sides of a partition plate I20 to realize solid-liquid separation, dust particles in the desulfurization slurry are filtered and left in the oxidation flocculation area 8, clear liquid enters the circulating clear liquid area 9, and the slurry after oxidation flocculation is led out from the bottom of the oxidation flocculation area 8 and enters a subsequent treatment unit through a discharge pipeline;
(4) air from a fan 24 enters from the circulating clear liquid zone 9, is sprayed out from a nozzle of the oxidizing gas distribution pipe 18 and penetrates through the metal mesh 21, dust particles on the metal mesh 21 of the oxidation flocculation zone 8 are blown up, the blown-up dust and the oxidizing gas are taken away by the rotating slurry, the dust and the flocculating agent are aggregated into large particles under the action of gravity and deposited at the bottom of the oxidation flocculation zone, and the oxidizing gas entering the oxidation flocculation zone 8 oxidizes sulfite in the slurry into sulfate so as to ensure that the COD of the desulfurization wastewater reaches the standard;
(5) controlling the pH value of the desulfurization wastewater in the circulating clear liquid zone 9 to be 7.0-7.5 by adjusting the flow of a sodium hydroxide solution (32 wt%) entering the circulating clear liquid zone 9, filtering the mixture by a metal mesh 21, mixing the clear liquid entering the circulating clear liquid zone 9 with fresh water and a sodium hydroxide solution in the circulating clear liquid zone 9, leading out the mixture from the bottom of the circulating clear liquid zone 9, directly discharging a small amount of clear liquid to reduce the sodium sulfate content of the circulating clear liquid, pressurizing the rest clear liquid by a circulating clear liquid pump 26, then feeding the pressurized clear liquid into a cooler 25 to cool to 40 ℃, feeding a part of the clear liquid cooled by the cooler 25 into a spray zone 6, atomizing the atomized clear liquid by an atomizing nozzle 15 to be in countercurrent contact with the flue gas to remove dust and desulfurize, feeding the other part of the clear liquid into a tray tower tray 4 by a liquid distributor 12, fully contacting with the flue gas on a tower tray 13 to strengthen the mass transfer effect to realize deep desulfurization of the flue gas, and catching micro dust particles between 0.1 mu m and 5 mu m in the flue gas, the deep dust removal of the flue gas is realized, a large amount of micro fog drops carried by the flue gas through the spraying area 6 are also captured by clear liquid on the tower tray 13, and the separation load of the demisting area 3 is reduced. A
Example 2
The catalytic cracking flue gas temperature of a petrochemical enterprise is 120 ℃, wherein SO2The concentration is 1250mg/Nm3The dust concentration was 320mg/Nm3By adopting the flue gas dedusting and desulfurizing tower, the diameter of a chimney 27 is 5m, the diameter of an outer sleeve is 6m, the diameters of tower bodies of a demisting area 3 and a tower tray area 4 are 12m, and the diameters of tower bodies of a spraying area 6 and a wastewater treatment area 7 are 8 m. The temperature of the flue gas discharged from the flue gas discharge section 1 was 52 ℃ and the dust content was 7.5mg/Nm3,SO2The content is 12mg/Nm3Is superior to the regulation of GB 31570-2015 emission Standard of pollutants for Petroleum refining industry (the regenerated flue gas particulate matters of the catalytic cracking catalyst are not more than 50mg/Nm3,SO2≯100mg/Nm3(ii) a Particulate matter in key areas is not more than 30mg/Nm3,SO2≯50mg/Nm3) (ii) a Under the conditions that the ambient temperature is 20 ℃, the ambient wind speed is 4m/s and the ambient humidity is 70 percent, the length of the white smoke at the opening of the chimney is 65 m.
Example 3
In contrast, the flue gas dust removal desulfurization tower was not provided with the outer sleeve 28, and the length of "white smoke" at the chimney port was 90m as in example 1.