Flue gas decarbonization and pollution reduction and calcium recycling system for iron and steel lime kiln

Abstract

The utility model relates to the technical field of flue gas purification and resource recycling of iron and steel lime kilns, in particular to a flue gas decarburization and pollution reduction and calcium recycling system of an iron and steel lime kiln. According to the method, the flue gas of the steel lime kiln is purified, standard emission of multiple pollutants can be achieved, meanwhile, CO2 in the flue gas of the lime kiln is captured, absorbed and recycled through high-hardness waste water, purification of the multiple pollutants, CO2 capturing and calcium recycling are achieved, and the pollution and carbon reduction effect is remarkable; according to the method, purification of multiple pollutants in the flue gas, capture of CO2 in the low-cost steel lime kiln flue gas and cyclic utilization of calcium are achieved, the emission of the discharged flue gas reaches the standard, the problems that high-hardness wastewater is high in treatment difficulty and difficult to recycle are solved, decarburization and pollution reduction of the steel lime kiln flue gas and cyclic utilization of calcium are achieved, and the method conforms to a green, low-carbon and high-quality development route.

Description

Technical Field

[0001] This utility model relates to the field of flue gas purification and resource recycling technology in steel lime kilns, specifically to a system for decarbonization and pollution reduction of flue gas and calcium recycling in steel lime kilns. Background Technology

[0002] Lime kilns are essential equipment in the steel industry. Their main function is to process limestone into calcium oxide, or lime, which has certain reactive properties and can be widely used as a flux and desulfurizing agent in steelmaking. However, lime production generates large amounts of dust, SO2, NOx, and other pollutants, causing air pollution. Simultaneously, the CO2 concentration in the flue gas is approximately 20%, resulting in significant carbon emissions. As the non-electricity industry with the largest carbon dioxide emissions, the steel industry is vigorously developing carbon capture and utilization technologies.

[0003] Currently, CO2 capture methods mainly include physical absorption, chemical absorption, adsorption, and separation. However, due to the complex composition of steel flue gas and relatively high treatment costs, there is a lack of effective demonstration applications. Simultaneously, the steel smelting process generates large amounts of high-hardness wastewater, such as wastewater from steel slag treatment, ore slag treatment, and desulfurization slag treatment. This wastewater contains large amounts of alkaline earth metal ions such as calcium, which easily form scale and cause corrosion and damage to equipment, making it difficult to treat and recycle. If high-hardness wastewater and flue gas treatment can be combined, utilizing the high-hardness wastewater to capture and absorb CO2 from lime kiln flue gas and then recycling it, it would be possible to achieve purification of multiple pollutants, CO2 capture, and calcium recycling, resulting in significant pollution reduction and carbon reduction effects. Utility Model Content

[0004] Technical problems to be solved

[0005] To address the aforementioned shortcomings of existing technologies, this utility model provides a system for decarbonization, pollution reduction, and calcium recycling of flue gas from steel lime kilns. This system effectively solves the problems of high treatment costs for lime kiln flue gas and the inability to utilize high-hardness wastewater to capture and treat CO2 from lime kiln flue gas in existing technologies.

[0006] Technical solution

[0007] To achieve the above objectives, this utility model provides the following technical solution:

[0008] A system for decarbonization, pollution reduction, and calcium recycling of flue gas from a steel lime kiln includes a lime kiln, a spray tower, an aeration tank, and a chimney connected in sequence. It also includes a primary sedimentation tank, a secondary sedimentation tank, and a plate filter press. The primary sedimentation tank is connected between the spray tower and the aeration tank. The secondary sedimentation tank is connected to the outlet end of the aeration tank. The inlet end of the plate filter press is connected to the primary sedimentation tank, the aeration tank, and the secondary sedimentation tank. The outlet end of the plate filter press is connected to the lime kiln and the primary sedimentation tank.

[0009] Furthermore, a first blower, a first electric valve, and an aeration pipe extending into the aeration tank are sequentially installed between the spray tower and the aeration tank.

[0010] Furthermore, a second electric valve, a second fan, and a fourth pollutant monitoring point are sequentially installed between the first fan and the chimney.

[0011] Furthermore, a first pollutant monitoring point is installed between the first fan and the first electric valve.

[0012] Furthermore, a second pollutant monitoring point is connected to the aeration tank.

[0013] Furthermore, a third pollutant monitoring point is connected to the discharge pipe of the secondary sedimentation tank.

[0014] Furthermore, the spray tower is an integrated dust removal, desulfurization, and denitrification spray tower, and the spraying method is circulating spraying.

[0015] Furthermore, the aeration tank is a sealed structure.

[0016] Furthermore, the aeration pipe is a perforated pipe.

[0017] Furthermore, the aeration pipe extends to the bottom of the aeration tank.

[0018] Beneficial effects

[0019] Compared with known public technologies, the technical solution provided by this utility model has the following beneficial effects:

[0020] This application purifies and treats flue gas from a lime kiln in the steel industry, achieving compliant emissions of multiple pollutants. Simultaneously, it utilizes high-hardness wastewater to capture and absorb CO2 from the lime kiln flue gas, enabling resource utilization. This achieves multi-pollutant purification, CO2 capture, and calcium recycling, resulting in significant pollution reduction and carbon reduction. First, high-hardness wastewater is used to capture CO2 from the lime kiln flue gas, and the actual CO2 emissions are reduced through the recycling of the precipitated CaCO3, achieving low-cost carbon capture and recycling. Second, calcium is recovered from the high-hardness wastewater, simultaneously addressing system scaling issues and enabling the reuse of high-hardness wastewater resources, thus reducing costs and increasing efficiency. Finally, the multiple pollutants in the lime kiln flue gas are purified, ensuring that the final exhaust gas dust concentration meets ultra-low emission requirements, and the concentrations of sulfur dioxide and nitrogen oxides meet relevant standards. In summary, this application not only achieves the purification of multiple pollutants in flue gas and low-cost CO2 capture and calcium recycling in flue gas from steel lime kilns, ensuring that the exhaust gas emissions meet standards, but also solves the problems of difficult treatment and recycling of high-hardness wastewater. It realizes decarbonization and pollution reduction of flue gas from steel lime kilns and calcium recycling, which is in line with the green, low-carbon and high-quality development path. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the flue gas treatment system for steel lime kilns according to this utility model.

[0023] The numbers in the diagram represent: 1-lime kiln; 2-spray tower; 3-first blower; 4-primary sedimentation tank; 5-aeration tank; 6-aeration pipe; 7-secondary sedimentation tank; 8-second blower; 9-chimney; 10-plate filter press; 11-first pollutant monitoring point; 12-second pollutant monitoring point; 13-third pollutant monitoring point; 14-fourth pollutant monitoring point; 15-first electric valve; 16-second electric valve. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0025] The present invention will be further described below with reference to the embodiments.

[0026] Example

[0027] This embodiment of a flue gas decarbonization and pollution reduction and calcium recycling system for steel lime kilns includes a lime kiln 1, a spray tower 2, an aeration tank 5, and a chimney 9 connected in sequence. It also includes a primary sedimentation tank 4 connected between the spray tower 2 and the aeration tank 5, a secondary sedimentation tank 7 connected to the aeration tank 5, and a plate filter press 10 connected to the lime kiln 1. The spray tower 2 is an integrated dust removal, desulfurization, and denitrification spray tower, and the spraying method is circulating spraying. The aeration tank 5 is a sealed structure, and the aeration pipe 6 is a perforated pipe.

[0028] The inlet end of the plate filter press 10 is connected to the primary sedimentation tank 4, the aeration tank 5, and the secondary sedimentation tank 7, and the outlet end of the plate filter press 10 is connected to the lime kiln 1 and the primary sedimentation tank 4.

[0029] A first blower 3, a first electric valve 15, and an aeration pipe 6 extending into the aeration tank 5 are installed sequentially between the spray tower 2 and the aeration tank 5. A second electric valve 16, a second blower 8, and a fourth pollutant monitoring point 14 are installed sequentially between the first blower 3 and the chimney 9.

[0030] The primary sedimentation tank 4, aeration tank 5 and secondary sedimentation tank 7 are all connected to the lime kiln 1 via a plate filter press 10. A first pollutant monitoring point 11 is installed between the first blower 3 and the first electric valve 15. A second pollutant monitoring point 12 is connected to the aeration tank 5. A third pollutant monitoring point 13 is connected to the discharge pipe of the secondary sedimentation tank 7.

[0031] The above-mentioned flue gas treatment system for steel lime kilns is used to treat the flue gas from steel lime kilns. The treatment method includes the following steps:

[0032] S1. When treating the flue gas from the steel lime kiln, the flue gas in the lime kiln 1 is introduced into the bottom of the spray tower 2 so that the flue gas comes into contact with the hydrogen peroxide solution sprayed down in the spray tower 2 to remove dust, sulfur dioxide and nitrogen oxides in the flue gas. After passing through the first fan 3, it enters the pipeline. After being detected by the first pollutant monitoring point 11, a portion of the flue gas is distributed into the aeration tank (5) through the aeration pipe (6) by controlling the first electric valve 15 and the second electric valve 16. The remaining flue gas is directly discharged into the atmosphere from the chimney 9 through the second fan 8. Here, the fourth pollutant monitoring point 14 after the second fan 8 detects the concentration of dust, sulfur dioxide, nitrogen oxides and carbon dioxide in the discharged flue gas to ensure that the flue gas emission meets the standards.

[0033] The spray tower 2 sprays a hydrogen peroxide solution with a volume concentration of 2-4%. The hydrogen peroxide solution oxidizes nitrogen oxides into nitric acid and sulfur dioxide into sulfuric acid. Calcium hydroxide in the flue gas reacts with nitric acid and sulfuric acid respectively, thereby removing sulfur dioxide and nitrogen oxides from the flue gas. At the same time, dust in the flue gas is also removed from the flue gas due to the spraying action. The first pollutant monitoring point (11) detects whether the concentration of pollutants in the flue gas discharged from the spray tower meets the standard, thereby adjusting the amount of hydrogen peroxide solution added to the spray tower (2). The second pollutant monitoring point (12) monitors the reaction in the aeration tank (5) and controls the opening of the first electric valve (15) and the second electric valve (16) to achieve a reasonable distribution of the amount of flue gas introduced into the aeration tank (5) and avoid excessive or insufficient carbon dioxide.

[0034] S2. Both the high-hardness wastewater and the wastewater in the spray tower 2 are fed into the primary sedimentation tank 4. The wastewater after sedimentation in the primary sedimentation tank 4 is fed into the aeration tank 5. The sediment after sedimentation is fed into the plate filter press 10.

[0035] S3. When the flue gas in S1 is introduced into the aeration tank 5, it reacts with the calcium hydroxide in the wastewater flowing into the primary sedimentation tank 4 in S2 to form calcium carbonate precipitate, which removes carbon dioxide from the flue gas and achieves decarbonation. The flue gas after the reaction is discharged into the atmosphere through the chimney 9 via the second blower 8. Here, the fourth pollutant monitoring point 14 after the second blower 8 detects the concentration of dust, sulfur dioxide, nitrogen oxides and carbon dioxide in the discharged flue gas to ensure that the flue gas emission meets the standards. At this time, the wastewater in the aeration tank 5 will be introduced into the secondary sedimentation tank 7 for further sedimentation. The water that passes the test of the third pollutant monitoring point 13 after sedimentation is returned to the plant as recycled water. The precipitates obtained in the aeration tank 5 and the secondary sedimentation tank 7 are introduced into the plate filter press 10.

[0036] During aeration, the aeration time is 8-12 minutes, the liquid level in aeration tank 5 is 1.5-2.5m, the pH value in aeration tank 5 is 8.5-10.5, and the temperature in aeration tank 5 is 55-65℃ to ensure the efficiency of the reaction between carbon dioxide and calcium hydroxide and to ensure the carbon dioxide removal effect. The third pollutant monitoring point 13 measures the TDS, conductivity, total hardness, suspended solids, and HCO3- in the effluent from the secondary sedimentation tank 7. - Content and CO3 2- content.

[0037] S4. After the sediment in the plate filter press 10 is filtered, the calcium carbonate solid obtained by filtration is sent back to the lime kiln 1 for recalcination, and the filtrate is passed into the primary sedimentation tank 4 for further sedimentation.

[0038] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A steel lime kiln flue gas decarburization and pollution reduction and calcium recycling system, comprising a lime kiln (1), a spray tower (2), an aeration tank (5) and a chimney (9) connected in sequence, characterized in that: It also includes a primary sedimentation tank (4), a secondary sedimentation tank (7), a plate filter press (10), the primary sedimentation tank (4) is connected between the spray tower (2) and the aeration tank (5), the secondary sedimentation tank (7) is connected to the outlet end of the aeration tank (5), the inlet end of the plate filter press (10) is connected to the primary sedimentation tank (4), the aeration tank (5) and the secondary sedimentation tank (7), and the outlet end of the plate filter press (10) is connected to the lime kiln (1) and the primary sedimentation tank (4).

2. The system for flue gas decarburization, pollution reduction and calcium recycling of a steel lime kiln according to claim 1, characterized in that, The first fan (3), the first electric valve (15) and the aeration pipe (6) extending into the aeration tank (5) are sequentially installed between the spray tower (2) and the aeration tank (5).

3. The system for flue gas decarburization, pollution reduction and calcium recycling of a steel lime kiln according to claim 2, characterized in that, The second electric valve (16), the second fan (8) and the fourth pollution monitoring point (14) are sequentially installed between the first fan (3) and the chimney (9).

4. The steel lime kiln flue gas decarburization, pollution reduction and calcium recycling system according to claim 3, characterized in that, The first pollution monitoring point (11) is installed between the first fan (3) and the first electric valve (15).

5. The steel lime kiln flue gas decarburization, pollution reduction and calcium recycling system according to claim 3, characterized in that, The second pollution monitoring point (12) is connected to the aeration tank (5).

6. The system for flue gas decarburization, pollution reduction and calcium recycling of a steel lime kiln according to claim 3, characterized in that, The third pollution monitoring point (13) is connected to the discharge pipe of the secondary sedimentation tank (7).

7. The system for flue gas decarburization, pollution reduction and calcium recycling of a steel lime kiln according to claim 1, characterized in that, The spray tower (2) is a dust removal, desulfurization and denitrification integrated spray tower, and the spraying mode is circulating spraying.

8. The system for flue gas decarburization, pollution reduction and calcium recycling of a steel lime kiln according to claim 1, characterized in that, The aeration tank (5) is a sealed structure.

9. The system for flue gas decarburization, pollution reduction and calcium recycling of a steel lime kiln according to claim 2, characterized in that, The aeration pipe (6) is a perforated pipe.

10. The system for flue gas decarburization, pollution reduction and calcium recycling of a steel lime kiln according to claim 2, characterized in that, The aeration pipe (6) extends to the bottom position in the aeration tank (5).

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