CN102120637B - Method for controlling and treating alumina alkaline waste water from aluminum factory by using acidic smoker waste gas - Google Patents

Abstract

The invention relates to a method for controlling and treating alumina alkaline waste water from an aluminum factory by using acidic smoker waste gas. The method comprises the following steps: introducing the acidic smoker waste gas into a smoker waste gas filtration device, and spraying the alumina alkaline waste water by a spray system in the smoker waste gas filtration device so that acidic waste gas particles fully react with spray particles of alkaline waste water in the air, wherein the spray system comprises multiple nozzles which are used for repeatedly spraying descending smoker waste gas many times so as to gradually reduce the alkaline of the alumina alkaline waste water. Tests prove that the method has practicable application value, can effectively neutralize the alumina alkaline waste water, responds national laws and regulations related to environment protection, saves a large amount of funds and energy source, reduces the emission of waste water and waste gas and has the advantages of small investment and high resource utilization rate; in addition, sulfides and nitric oxides in the smoker waste gas are absorbed by the alumina alkaline waste water, thereby achieving the technical effects of smoke abatement, desulfuration and dust removal.

Description

A method for treating alumina alkaline wastewater in an aluminum plant by using smoke and dust acid waste gas

technical field

The invention relates to a method for alumina alkaline wastewater in an aluminum plant, in particular to a method for treating alumina alkaline wastewater by using soot acid waste gas.

Background technique

At present, the popularized and applied scheme to reduce alumina alkaline wastewater from aluminum plants is to carry out alumina alkaline industrial wastewater and domestic sewage treatment for the specific situation that alumina alkaline wastewater contains certain flocculation components and the requirements for alumina reuse water are not high. Two kinds of waste water with different properties interact with each other to purify sewage technical scheme. According to the pH value of alkaline wastewater, different mixing ratios are selected, and a sewage treatment method is developed. The treated water quality meets the requirements of alumina production and reuse. In this scheme, the flocculation components in alkaline industrial wastewater promote the settlement of suspended solids, and the pollutants are purified through flocculation settlement, separation and dilution. The mixing ratio of sewage (alkaline industrial wastewater/domestic sewage) has a great relationship with the pH value and alkalinity of alkaline industrial wastewater. Through industrial application tests, according to the difference in pH value of alkaline industrial wastewater, the mixing ratio is selected at 3: In the range of 1 to 1:3, at present, two optimal mixing ratios have been found. When the pH value of alkaline industrial sewage is less than 10, the mixing ratio is 3:1; when the pH value is 10-11, the mixing ratio is 1 : 1; when the pH value is greater than 11, the mixing ratio of domestic sewage can be increased appropriately, and the maximum should not exceed 1: 3. The water quality after mixed and purified sewage can meet the requirements of alumina production and reuse. The operation shows that after mixing domestic sewage and alkaline industrial wastewater, the existing industrial wastewater treatment station facilities are used for treatment. In addition, some large-scale production enterprises have also formulated a treatment plan for "zero discharge" of alumina wastewater. The specific measures are to choose a reasonable sewage treatment process (sedimentation-filtration) according to the different water quality requirements of reclaimed water users, and adopt dual water sources for water points such as important equipment and key processes, that is, reclaimed water and industrial fresh water are used as backups for each other.

There are many small-scale aluminum plants launched by local methods in our country. The discharge of alumina alkaline wastewater exceeds the standard and is difficult to treat, causing great harm to the water environment. And because alkali is one of the main materials for producing alumina, the discharge process of waste water is also a process of material and alkali loss. However, the cost of the various existing solutions for treating alumina alkaline wastewater is too high, that is, it needs to consume a lot of water resources, and it needs to invest a lot of money, which hinders the use of many small aluminum plants.

Contents of the invention

The invention provides a method for treating alumina alkaline wastewater by using smoke and dust acid waste gas. The method has been proved to have practical application value, can effectively neutralize alumina alkaline wastewater, and responds to the relevant national environmental protection requirements. Regulations, save a lot of money and energy, less investment, high resource utilization, and reduce the discharge of waste water and waste gas.

At the same time, the present invention can also use alumina alkaline wastewater to absorb sulfide and nitrogen oxides in the smoke and dust waste gas, achieving the technical effect of smoke elimination, desulfurization and dust removal.

The present invention provides a method for treating alumina alkaline waste water in an aluminum plant by adopting soot acid waste gas. The soot waste gas containing acidic oxides, sulfides and nitrogen oxides is passed into the soot waste gas filtering device 18, and the alumina alkaline waste water is collected by the soot The spraying system 9 in the waste gas filter device 18 sprays, so that the spray particles of acidic waste gas and alkaline waste water fully react in the air.

Spraying system 9 comprises filter screen 12, booster pump 13, electromagnetic valve 14, nozzle 16 and spray pipeline, booster pump 13 pressurization, alumina alkaline waste water passes through filter screen 12, booster pump 13, solenoid valve along spray pipeline 14, sprayed from the nozzle 16.

Preferably, the spray system 9 includes a three-layer nozzle structure, and each layer includes three rows of nozzles, and each row has two nozzles 16, repeatedly spraying the falling smoke and dust waste gas repeatedly, so that the alkalinity of the alumina alkaline wastewater Decrease gradually.

The soot and acid waste gas enters the soot and waste gas treatment chamber 3 of the soot and dust filter device 18 from the soot and waste gas inlet 1, and is sprayed by the spray system 9. The descending channel 4 falls into the circulating water pool 6, and the volatilized smoke and dust exhaust gas is discharged from the smoke and dust exhaust gas outlet 1 along the smoke and dust exhaust gas ascending channel 5.

Preferably, the end of the soot and exhaust gas inlet 10 adopts an upper elbow structure, so that the acid exhaust gas is sprayed toward the nozzle 16 sideways.

The equipment used in the method includes an alumina alkaline waste water collection tank 11 , a spray system 9 , a soot filtering device 18 and a circulating water pool 6 .

The soot and waste gas filtering device 18 includes a soot and waste gas treatment chamber 3, the soot and waste gas inlet 10 and the soot and waste gas descending passage 4 are placed in the center of the soot and waste gas treatment chamber 3, and the soot and waste gas ascending passage 5 is placed on the periphery of the soot and waste gas descending passage 4. The lower part of the smoke and dust waste gas filtering device 18 is the circulation pool 6 of alumina alkaline waste water.

Alkaline wastewater collection box 11, filter screen 12, and nozzle 16 are all made of high-temperature-resistant and corrosion-resistant materials.

Description of drawings

Fig. 1 is the schematic diagram of the working principle of adopting soot acid waste gas to control alumina alkaline wastewater in the present invention;

Fig. 2 is the schematic diagram of soot exhaust gas filtering device, wherein,

1. Smoke and dust exhaust gas outlet; 2. Inspection hole; 3. Smoke and dust waste gas treatment chamber; 4. Smoke and dust waste gas descending channel; 5. Smoke and dust waste gas ascending channel; 6. Circulating pool; 7. Overflow pipe; , Spray system; 10, smoke and dust exhaust gas inlet; 11, alumina alkaline wastewater collection box; 12, filter screen; 13, booster pump; 14, solenoid valve; 16, nozzle; 18, smoke and dust filter device

Detailed ways

The equipment for treating alumina alkaline wastewater by using acidic oxides in flue gas includes an alumina alkaline wastewater collection box 11 , a spraying system 9 and a flue dust filtering device 18 .

The aluminum oxide alkaline waste water collection box 11 is made of stainless steel, with a volume of 15 cubic meters and a thickness of 5 millimeters.

The spray system 9 includes a filter screen 12, a booster pump 13, a solenoid valve 14, a nozzle 16 and a spray pipeline. The working process of the spray system 9 is as follows. After the booster pump 13 works, the alumina alkaline wastewater enters the booster pump 13 through the filter screen 12, and the booster pump 13 increases the pressure to about 1 MPa, and the spray pipeline passes through the solenoid valve 14, Finally, it is sprayed out by the nozzle 16.

The smoke and dust exhaust gas filtering device 18 includes a smoke and dust exhaust gas inlet 10, a smoke and dust exhaust gas outlet 1, and a maintenance hole 2 for maintenance. The smoke and dust exhaust gas outlet 1, the maintenance hole 2, the nozzle 16 and the smoke and dust exhaust gas descending channel 4 are arranged in sequence from top to bottom. And the smoke and dust exhaust gas treatment chamber 3 of the smoke and dust exhaust gas ascending passage 5. The soot and waste gas inlet 10 and the soot and waste gas descending passage 4 are placed in the center of the soot and waste gas treatment chamber 3, the soot and waste gas ascending passage 5 is placed on the periphery of the soot and waste gas descending passage 4, and the lower part of the soot and waste gas filtering device 18 is the circulation of alumina alkaline wastewater pool6. After adopting such a structure, the working process of the soot and waste gas treatment of this filtering device 18 is: soot and waste gas inlet 10-smoke and dust waste gas treatment chamber 3-spray system 9 spraying-smoke and dust waste gas descending channel 4-alumina alkalinity at the bottom of the chimney Waste water circulation pool 6-smoke and dust exhaust gas ascending channel 5-smoke and dust exhaust gas outlet 1.

The sulfides and nitrogen oxides in the alumina alkaline wastewater and soot have chemical effects, and the moisture is still the dominant component, and the water also plays a big role. The moisture here refers to the sulfide in the alumina alkaline wastewater. Moisture, no need to add water. The sulfur dioxide and nitrogen dioxide contained in the flue gas enter the flue gas treatment device 18, and the high-temperature gas meets water to form sulfuric acid, sulfurous acid, nitric acid, and nitrous acid, which fall into the circulating pool 6 together with water.

The smoke and dust exhaust gas filtering device 18, as shown in Figure 2, adopts a screen cylinder structure, and the filter screen has 15 layers. During the working process, a layer of water film will be formed on the screen, and the water film plays the role of dust filtration and desulfurization, forming a screen The screens on the sides and bottom of the net cylinder can be made of any high-temperature-resistant and corrosion-resistant materials (such as stainless steel). Their apertures can be the same or different, generally 3.6mm respectively. If the aperture is too small, the dust in the soot and exhaust gas will block the mesh, if the aperture is too large, the speed of the soot and exhaust gas passing through the screen cylinder will be accelerated, and the desulfurization effect will decrease. The screens constituting the sides and bottom of the screen cylinder can be made of stainless steel wires with diameters of 0.5 mm and 1.0 mm, respectively. The selection of stainless steel wire diameter mainly considers manufacturing cost and corrosion resistance factors. Because the bottom is more corroded than the surroundings, it is made of thicker stainless steel wire. Spraying systems 9 are respectively arranged at the top, middle and bottom of the smoke and dust waste gas filtering device 18, and each layer of spraying systems has three rows, and each row is composed of two nozzles 16, as shown in the A-A sectional view in Fig. 1 . The nozzle 16 is made of stainless steel, with an aperture of 1.5mm.

The spraying system 9 comprises a filter screen 12, a booster pump 13, a solenoid valve 14, and a nozzle 16. The filter screen 12 uses a 100-purpose stainless steel mesh as the main filter element to filter impurities in the alumina alkaline wastewater. The booster pump 13 adopts a pipeline booster pump BLC70/037 horizontal corrosion-resistant water pump, which is a horizontal booster pump with a closed single-suction impeller structure, a flow rate of 1-7m ³ /h, the number of impellers is 1, and the lift is 17- 10m, shaft power 0.37kW. Solenoid valve 14 adopts anti-corrosion solenoid valve M324969 of Beijing Zhongxi Yuanda Technology Co., Ltd.

A suction motor with a power of 4 kilowatts is installed at 10 places of the smoke and dust exhaust gas inlet. The soot and exhaust gas collide with the spray to make the contact more thorough, which not only reduces the alkalinity of alumina, but also makes the treatment effect of soot and exhaust gas significantly better than that of the straight pipe structure.

The average concentration of sulfur dioxide in the flue gas is 150 mg/m ³ . Since the size of the acidic oxides in the flue dust is only 0.8 μm to 5 μm, these particles are suspended in the hot air of the chimney to form smoke, and the aluminum oxide sprayed by the nozzle 16 The particle size of alkaline wastewater is 3 μm to 5 μm. When the acid oxide particles in the soot are smaller than the alumina alkaline wastewater spray particles, the acid oxide particles in the soot are surrounded by the alumina alkaline wastewater spray particles. When the acidic oxides in the soot are equal to the particle size of alumina alkaline wastewater, the soot particles and the alumina alkaline wastewater particles undergo an acid-base chemical reaction one-to-one. When the acidic oxide particles in the soot are larger than the size of the alumina alkaline wastewater particles, The alkaline wastewater spray particles surround the acidic oxides in the soot, so that the alumina alkaline wastewater droplets attached to the acidic oxide particles in the soot are not completely neutralized and sink to the circulating pool at the same time6 In the middle, since the acid-base chemical action only occurs on the outer layer of each droplet in the first sprayed alumina alkaline wastewater, the particles of smoke and dust do not have acid-base chemical action phenomenon inside, thus falling into the circulating pool. Alumina alkaline wastewater still has a strong alkaline chemical effect. In our design, this phenomenon is taken into consideration, so multiple cycle injections are carried out, so that the acidic oxide particles contained in the alumina alkaline wastewater gradually decrease, while the alkalinity decreases gradually, and finally the acidic oxides in the smoke are the least, and the cycle injection Five times, the alumina content contained in the alumina alkaline wastewater can be gradually reduced, and the soot acid oxides in the soot exhaust gas can be removed. The results are shown in Table 1.

Table 1

According to the test results of the laboratory, the alkalinity of alumina has dropped from about 10 to 7, and the acidic oxides in the smoke and exhaust gas have been significantly reduced, and the effect of meeting the national testing standards is obvious. It is also pointed out here that the alumina alkaline wastewater from the aluminum plant is a strong alkaline oxide, which can neutralize all the acidic oxides in the flue gas. It has been tested that the PH value of the wastewater from the aluminum factory is reduced from about 10 to 7 after being neutralized by the acidic oxides of the soot. Alumina for basic purposes.

In addition, it should be noted that the salt compounds produced by the neutralization reaction of all the acidic oxides in the alumina alkaline wastewater and flue gas of the aluminum plant that are finally discharged into the circulation pool are also a type of industrial wastewater. Its reuse or processing is made a special statement by another patented technology. The central technology of the patent of the present invention is only for the purpose of utilizing soot and acidic waste gas to control aluminum oxide alkalinity in aluminum plant wastewater. As for the equipment used, it is also possible to adopt the structure design idea of the equipment including almost all equipments for eliminating the acidic oxides in the smoke in the prior art. More include: filtration equipment, spray, water film generation equipment, sedimentation or recovery equipment.

Claims (7)

1. A method of adopting soot acid waste gas to control alumina alkaline waste water in aluminum plants, characterized in that, the soot waste gas containing acidic oxides, sulfides and nitrogen oxides is passed into the soot waste gas filtering device (18), and the alumina Alkaline waste water is sprayed by the spray system (9) extending into the soot waste gas filter device (18), so that the spray particles of acid waste gas particles and alkaline waste water fully react in the air, The spray system (9) includes a three-layer nozzle structure, and each layer includes three rows of nozzles, and each row has two nozzles (16), which repeatedly spray the falling smoke and dust exhaust gas, so that the aluminum oxide alkaline wastewater The alkalinity gradually decreases, The smoke and dust waste gas filtering device (18) comprises a smoke and dust waste gas treatment chamber (3), the smoke and dust waste gas inlet (10) and the smoke and dust waste gas descending passage (4) are placed in the center of the smoke and dust waste gas treatment chamber (3), and the smoke and dust waste gas ascending passage (5) is placed On the periphery of the smoke and dust waste gas descending channel (4), the lower part of the smoke and dust waste gas filtering device (18) is a circulating pool (6) for alumina alkaline waste water. 2. method as claimed in claim 1, is characterized in that, spraying system (9) comprises filter screen (12), booster pump (13), solenoid valve (14), nozzle (16) and spray pipeline, pressurization The pump (13) is pressurized, and the alumina alkaline waste water is sprayed out from the nozzle (16) through the filter screen (12), the booster pump (13), and the electromagnetic valve (14) along the spray pipe. 3. The method according to claim 2, characterized in that, the soot acid waste gas enters the soot waste gas treatment chamber (3) of the soot waste gas filtering device (18) from the soot waste gas inlet (10), and is sprayed through the spray system (9) Spraying, the acidic waste gas particles and the spray particles of alkaline wastewater fully react, the sprayed soot and waste gas falls into the circulating pool (6) along the soot and waste gas descending channel (4), and the volatilized soot and waste gas goes along the soot and waste gas ascending channel (5) Discharge from the smoke and dust exhaust outlet (1). 4. The method according to claim 3, characterized in that the end of the smoke and dust exhaust gas inlet (10) adopts an upper elbow structure, so that the acid exhaust gas is sprayed laterally toward the nozzle (16). 5. as the arbitrary described method of claim 1-4, it is characterized in that, used equipment comprises aluminum oxide alkaline waste water collection box (11), spraying system (9), flue dust waste gas filtering device (18) and circulation Pool (6). 6. The method according to claim 5, characterized in that the smoke and dust exhaust gas filtering device (18) adopts a screen cylinder structure with 15 layers of filter screens. 7. The method according to claim 6, characterized in that, the alkaline waste water collecting tank (11), the filter screen (12), and the nozzles (16) are all made of high-temperature-resistant and corrosion-resistant materials.

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