Industrial carbon dioxide capturing and utilizing and sodium-based recycling method based on cavitation air floatation

Abstract

The invention relates to the technical field of wastewater treatment, and discloses an industrial carbon dioxide capture and utilization and sodium-based recycling method based on cavitation air floatation, which comprises the following steps: S1, proportioning integrated wastewater of an iron and steel plant and waste ammonia water obtained by a coking plant to obtain a first target mixed solution, s2, carbon dioxide-containing gas in an iron and steel plant serves as a gas supply source of a first-stage cavitation air flotation fan blade, and carbon dioxide rapidly reacts with calcium and magnesium ions in the first target mixed solution to generate calcium carbonate, magnesium carbonate crystals and other solid impurities, and S3, the ammonia-containing treatment solution, the integrated wastewater and the waste ammonia water are matched to obtain a second target mixed solution; in a steel mill environment, carbon capture and waste water can be realized in the same device, waste ammonia which can be easily obtained by a steel mill is utilized, waste water and flue gas are integrated for coupling, and economic extraction of calcium and magnesium ions and sodium groups is realized. The extract can be used in steel mills or produce economic by-products, so that reasonable utilization of resources is realized, and meanwhile, the wastewater and waste gas treatment cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, specifically an industrial carbon dioxide capture and utilization and sodium-based resource utilization method based on vortex cavitation air flotation. Background Art

[0002] Although carbon capture technology has been applied to a certain extent in the steel industry, it still faces challenges in terms of technology maturity, energy efficiency, cost, etc. The stability and reliability of the technology need to be further verified and optimized in actual applications. The construction and operation costs of carbon capture technology are relatively high, which limits its promotion in large-scale commercial applications. Installing carbon capture facilities will lead to an increase in the cost of steel products, thus affecting the competitiveness of enterprises. The carbon capture process itself consumes a large amount of energy, which may reduce the energy efficiency of the entire steel production system. How to improve the energy efficiency of the carbon capture process, reduce energy consumption, and seek practical and effective new routes for carbon capture and utilization is an urgent problem to be solved currently.

[0003] A large amount of flue gas containing carbon dioxide is generated in steel mills, and integrated wastewater is also generated in steel mills. Due to the particularity of steel mills, the wastewater from steel mills mainly contains suspended solids, heavy metals, organic substances, acid-base substances, salts, etc. Under normal operations, the integrated wastewater from steel mills is treated through steps such as precipitation, filtration, and reverse osmosis, and the recycled desalinated water (reclaimed water) is used as the whole-plant engineering water (such as water cooling, washing, etc.), and the concentrated water is discharged after meeting the standards. Such wastewater and waste gas need to be purified and treated before harmless discharge, resulting in an increase in the environmental treatment economic cost. Co-disposing of wastewater and waste gas resources and bringing environmental and economic benefits is an urgent problem to be solved currently. Summary of the Invention

[0004] The purpose of the present invention is to provide an industrial carbon dioxide capture and utilization and sodium-based resource utilization method based on vortex cavitation air flotation to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution:

[0006] An industrial carbon dioxide capture and utilization and sodium-based resource utilization method based on vortex cavitation air flotation, comprising:

[0007] Step S1: Mix the integrated wastewater from the steel mill with the waste ammonia water obtained from the coking plant to obtain a first target mixed solution, and the first target mixed solution is pumped to the first-stage vortex cavitation air flotation tank through a water pump. The pH value of the first target mixed solution is 7.5 - 8.0;

[0008] Step S2: The carbon dioxide-containing gas from the steel mill is used as the air supply source for the first-stage vortex cavitation air flotation fan blade. Carbon dioxide quickly reacts with calcium and magnesium ions in the first target mixed solution to form calcium carbonate, magnesium carbonate crystals, and other solid impurities. After treatment, the first target mixed solution becomes an ammonia-containing treatment solution;

[0009] Step S3: The ammonia-containing treatment liquid, the integrated wastewater, and the waste ammonia water are proportioned to obtain a second target mixed liquid, and the second target mixed liquid is transported to the secondary vortex cavitation air flotation tank by a water pump. The pH value of the second target mixed liquid is 8.4 - 9.0;

[0010] Step S4: The gas containing carbon dioxide in the steel plant is used as the gas supply source for the secondary vortex cavitation air flotation fan blades, and excessive carbon dioxide gas is introduced to rapidly react with the sodium ions in the wastewater to form sodium bicarbonate crystals and other solid impurities.

[0011] As a further scheme of the present invention: it further includes: Step S5: The collected solid sodium bicarbonate is recycled to the steel plant, including but not limited to flue gas desulfurization process, pickling wastewater treatment process, surface rust prevention and passivation in the rolling and casting process.

[0012] As a further scheme of the present invention: In Steps S2 and S4, the gas containing carbon dioxide is directly utilized by the low-concentration carbon dioxide gas after desulfurization and denitrification of the hot blast stove flue gas, and the concentration is 20 - 28%.

[0013] As a further scheme of the present invention: In Steps S2 and S4, the gas containing carbon dioxide is utilized by the high-concentration carbon dioxide gas after carbon capture, and the concentration is 50 - 99.9%, which can further accelerate the reaction rate and improve the product production efficiency.

[0014] As a further scheme of the present invention: Remove Step S4, and replace Step S3 with Step S3A: Inject the remaining waste ammonia water in Step S1 into the primary vortex cavitation air flotation tank, adjust the pH value of the ammonia-containing treatment liquid in the primary vortex cavitation air flotation tank to 8.4 - 9.0, and carbon dioxide gas reacts with the sodium ions in the wastewater to form sodium bicarbonate crystals.

[0015] As a further scheme of the present invention: Replace Step S3 with Step S3B: Inject the remaining waste ammonia water in Step S1 and the integrated wastewater into the primary vortex cavitation air flotation tank, adjust the injection ratio of the waste ammonia water and the integrated wastewater, and the pH value of the liquid after mixing the ammonia-containing treatment liquid, the waste ammonia water, and the integrated wastewater is 8.4 - 9.0. Carbon dioxide gas reacts with the sodium ions in the wastewater to form sodium bicarbonate crystals and other impurities.

[0016] As a further scheme of the present invention: Replace Step 4 with Step 4B: Continuously introduce waste ammonia water and / or integrated wastewater and / or ammonia-containing treatment liquid into the primary vortex cavitation air flotation tank after being treated in Step S3B, adjust the pH value of the primary vortex cavitation air flotation tank to 7.5 - 8.0, and repeat Step S1 in a cycle.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] In the steel mill environment, carbon capture and wastewater resource utilization can be achieved in the same device, using waste ammonia that can be easily obtained by the steel mill, integrating wastewater and flue gas to achieve economic extraction of calcium, magnesium and sodium bases. The extract can be used in the steel mill or produce economic by-products, realizing the rational utilization of resources and reducing the cost of wastewater and waste gas treatment.

[0019] Compared with the traditional process of separate operation of carbon dioxide capture and utilization, it reduces the large-scale investment in equipment and the initial construction and operation costs, and significantly reduces the operating costs. It effectively avoids the cumbersome steps of material regeneration through temperature or pressure changes in traditional carbon capture technology, thereby greatly improving the overall timeliness. After the CO2 in the flue gas is captured, it does not need to go through the high-energy desorption process but directly reacts with the co-reactant and is converted into downstream products, which is expected to significantly reduce the cost of emission reduction. It is a new high-efficiency, low-energy consumption CO2 emission reduction technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 A schematic diagram of industrial carbon dioxide capture and utilization based on cavitation flotation and sodium-based resource recovery method; DETAILED DESCRIPTION

[0022] See also Figure 1 , Embodiment 1:

[0023] This embodiment includes the following steps:

[0024] Step S1: The integrated wastewater from the steel plant and the waste ammonia water obtained from the coking plant are mixed to obtain a first target mixed liquid, and the first target mixed liquid is transported to a primary vortex flotation tank through a water pump. The pH value of the first target mixed liquid is 7.5-8.0.

[0025] In step S1: the integrated wastewater mainly comes from the production water and domestic water of the whole plant. Due to the particularity of the steel plant, the wastewater of the steel plant mainly contains suspended matter, heavy metals, organic matter, acid and alkali substances caused by the chemicals used in the production process, such as chlorides and sulfates and other salts. Suspended matter such as iron ore and coal particles, heavy metals such as lead, zinc, copper and cadmium, organic matter such as oils and chemical plasticizers, these components will cause pollution to the environment, and effective wastewater treatment measures need to be taken to reduce the impact on the water body and reduce energy consumption to provide water reuse efficiency.

[0026] In step S1: The main use of the waste ammonia water is to provide an alkaline environment inside the cavitation flotation to promote the formation of crystals. Optionally, a small portion of the waste ammonia water is taken from the coking plant of the steel mill or ammonia water is purchased externally as an alternative solution. The alkaline environment of the first target mixture is mainly regulated by the amount of waste ammonia water introduced. The integrated wastewater of the whole plant is generally neutral, with a pH value of about 7.0. By introducing a part of the waste ammonia water from the coking plant or purchasing ammonia water externally, and adjusting the ratio of the integrated wastewater to the waste ammonia water, and the reference factors for ratio adjustment such as ammonia content, flow rate, and velocity, and comprehensively regulating with the ammonia content, flow rate, and velocity as reference factors, the pH value can be stabilized in the range of 7.5 - 8.0, which is conducive to the reaction of calcium and magnesium ions with carbon dioxide to precipitate.

[0027] Step S2: The gas containing carbon dioxide from the steel mill is used as the gas supply source for the impeller of the first-stage cavitation flotation. Carbon dioxide reacts rapidly with the calcium and magnesium ions in the first target mixture to form calcium carbonate, magnesium carbonate crystals, and other solid impurities. The first target mixture is processed into an ammonia-containing treated liquid after treatment.

[0028] In step S2: The carbon dioxide gas inhaled by the high-speed rotating impeller reacts with the first target mixture. At this time, due to the alkaline environment in the pH range of 7.5 - 8.0, carbon dioxide reacts rapidly with the calcium and magnesium ions in the first target mixture to form calcium carbonate and magnesium carbonate crystals. At the same time, a large number of microbubbles are generated inside by the high-speed rotating impeller, and the crystals adhere to the surface of the bubbles and float to the surface of the cavitation flotation, and are collected by the bristles on the conveyor belt. The collected carbonate solids are subjected to subsequent treatment, optionally including sorting or mixed use, and are sold as agricultural or building materials. The first target mixture after the extraction of calcium carbonate and magnesium carbonate is called the ammonia-containing treated liquid, and the ammonia-containing treated liquid is subjected to secondary treatment.

[0029] Step S3: The ammonia-containing treated liquid, the integrated wastewater, and the waste ammonia water are proportioned to obtain a second target mixture. The second target mixture is pumped to the second-stage cavitation flotation tank by a water pump, and the pH value of the second target mixture is 8.4 - 9.0.

[0030] In step S3: The pH value is adjusted again to the range of 8.4 - 9.0. Under normal temperature and pressure, it is beneficial for the precipitation and crystallization of sodium-based within this range. In this step, the integrated wastewater and waste ammonia water are introduced into the ammonia-containing treatment liquid again, and the ratio of the introduced integrated wastewater to waste ammonia water is adjusted, so that the pH value can be stabilized in the range of 8.4 - 9.0. Excessive carbon dioxide gas is introduced to react rapidly with the sodium ions in the wastewater to form sodium bicarbonate crystals. Here, "excessive" mainly refers to the excess of the carbonate concentration that can be combined with the sodium ions in the wastewater under this condition. When excessive carbon dioxide is introduced into the mixed solution of sodium chloride and ammonia water, "excessive" means that the added amount of carbon dioxide exceeds the theoretical stoichiometry required to completely convert all the ammonia in the system into ammonium bicarbonate and further react fully with sodium chloride to form sodium bicarbonate precipitate. Specifically, when both NH3 in the ammonia water and NaCl in the solution are completely consumed, at this time, NaHCO3 reaches saturation due to its low solubility and precipitates out. The continuously introduced CO2 no longer participates in the main reaction, only resulting in a further decrease in the solution pH, the formation of H2CO3 due to the dissolution of CO2 and the release of H + or part of the CO2 escapes in the form of gas. At this time, there is neither enough alkaline substance such as NH3 in the system to react with CO2, nor enough Na + to combine with HCO3 - to form a new precipitate, so it is determined that CO2 is excessive. The concentration range of directly discharged carbon dioxide from steel plants is generally 4 - 28%. Optionally, hot blast stove flue gas with a relatively high carbon dioxide concentration of about 20 - 28% is selected here, or high-concentration carbon dioxide of 50 - 99.9% after carbon capture can also be used, and it is introduced excessively into the cavitation flotation device.

[0031] Step S4: The carbon dioxide-containing gas from the steel plant is used as the gas supply source for the secondary cavitation flotation fan blade. Excessive carbon dioxide gas is introduced to react rapidly with the sodium ions in the wastewater to form sodium bicarbonate crystals and other solid impurities.

[0032] Step S5: The collected sodium bicarbonate solid is recycled to the steel plant, including but not limited to flue gas desulfurization process, pickling wastewater treatment process, surface anti-rust and passivation in the rolling and casting process.

[0033] In step S5: The flue gas desulfurization process includes: Application method of dry / semi-dry process: directly sprayed into the high-temperature flue, decomposed to generate active sodium carbonate, and highly efficient in removing SO2 generated in processes such as sintering and coking. Application method of pickling wastewater treatment process: gently neutralize the strongly acidic wastewater after hydrochloric acid pickling to avoid redissolution of metal ions caused by local over-alkalinity, which is superior to strong alkalis such as sodium hydroxide. Application method of surface anti-rust and passivation in the rolling and casting process: replace toxic chromates, prepare a passivation solution to form a dense oxide film to prevent rust return of precision steel such as cold-rolled sheets, etc., and reduce the cost of purchasing sodium bicarbonate externally.

[0034] Supplementary note: In steps S2 and S4, the carbon dioxide-containing gas is directly utilized as the low-concentration carbon dioxide gas after desulfurization and denitrification of the hot blast stove flue gas, with a concentration of 20-28%. In steel plant equipment, the carbon dioxide concentration in the hot blast stove flue gas is high and can be directly applied.

[0035] Supplementary note: In steps S2 and S4, the carbon dioxide-containing gas is selected as the high-concentration carbon dioxide gas after carbon capture for utilization, with a concentration of 50-99.9%, which can further accelerate the reaction rate and improve the product production efficiency. The low-concentration carbon dioxide gas generated in other processes is used after the concentration is increased by carbon capture, and the crystallization formation rate increases.

[0036] Example 2:

[0037] Step S1: Mix the integrated wastewater from the steel plant and the waste ammonia water obtained from the coking plant to obtain the first target mixed solution, which is pumped to the primary cavitation flotation cell through a water pump. The pH value of the first target mixed solution is 7.5-8.0;

[0038] Step S2: The carbon dioxide-containing gas from the steel plant is used as the gas supply source for the primary cavitation flotation impeller. Carbon dioxide quickly reacts with calcium and magnesium ions in the first target mixed solution to form calcium carbonate, magnesium carbonate crystals and other solid impurities. After treatment, the first target mixed solution becomes the ammonia-containing treatment solution;

[0039] Step S3A: Inject the remaining waste ammonia water from step S1 into the primary cavitation flotation cell, adjust the pH value of the ammonia-containing treatment solution in the primary cavitation flotation cell to 8.4-9.0, and carbon dioxide gas reacts with sodium ions in the wastewater to form sodium bicarbonate crystals.

[0040] In this example, the secondary cavitation flotation cell is cancelled, and the reuse operation is carried out in the primary cavitation flotation cell. After removing calcium and magnesium ions in the ammonia-containing treatment solution, the pH value of the ammonia-containing treatment solution is adjusted by adding waste ammonia water to precipitate sodium-based crystals in the ammonia-containing treatment solution.

[0041] This method has an impact on liquid retention for continuous wastewater treatment. Because under the condition of regulating the state by waste ammonia water in the primary cavitation flotation cell, it is impossible to inject the integrated wastewater. This method is applicable to the application in an environment where wastewater generation is non-continuous.

[0042] Example 3:

[0043] Step S1: Mix the integrated wastewater from the steel plant and the waste ammonia water obtained from the coking plant to obtain the first target mixed solution, which is pumped to the primary cavitation flotation cell through a water pump. The pH value of the first target mixed solution is 7.5-8.0;

[0044] Step S2: The gas containing carbon dioxide from the steel plant is used as the air supply source for the first-stage cavitation flotation fan blades. Carbon dioxide rapidly reacts with calcium and magnesium ions in the first target mixed liquid to form calcium carbonate, magnesium carbonate crystals, and other solid impurities. After treatment, the first target mixed liquid becomes the ammonia-containing treatment liquid;

[0045] Step S3B: Inject the remaining waste ammonia water and integrated wastewater from Step S1 into the first-stage cavitation flotation tank, and adjust the injection ratio of the waste ammonia water and the integrated wastewater. The pH value of the liquid mixture of the ammonia-containing treatment liquid, waste ammonia water, and integrated wastewater is 8.4 - 9.0. Carbon dioxide gas reacts with sodium ions in the wastewater to form sodium bicarbonate crystals and other impurities.

[0046] Step 4B: Continuously inject waste ammonia water and / or integrated wastewater and / or ammonia-containing treatment liquid into the first-stage cavitation flotation tank after being treated in Step S3B, adjust the pH value of the first-stage cavitation flotation tank to 7.5 - 8.0, and repeat Step S1 in a cycle.

[0047] In this embodiment, by changing the injection ratio of the waste ammonia water and the integrated wastewater into the first-stage cavitation flotation tank, the pH value of the first-stage cavitation flotation tank changes within two range intervals to achieve the mixed extraction of calcium and magnesium ions and sodium-based substances. The specific principle is as follows:

[0048] In Step S1, the first target mixed liquid generally extracts particulate matter on the liquid surface in the form of overflow or brushing. The volume of the first target mixed liquid is fixed, and the overflowing liquid is the ammonia-containing treatment liquid. The sodium-based substances in the ammonia-containing treatment liquid are not extracted, so the ammonia-containing treatment liquid flows back into the first-stage cavitation flotation tank.

[0049] In Step S3B, after the extraction of calcium carbonate and magnesium carbonate in the first-stage cavitation flotation tank, most of the liquid in the flotation tank is the ammonia-containing treatment liquid. At this time, adjust the injection ratio of the waste ammonia water and the integrated wastewater into the first-stage cavitation flotation tank to regulate the ammonia-containing treatment liquid into a mixed waste liquid with a pH value of 8.4 - 9.0. In this process, a small amount of calcium and magnesium ions in the added integrated wastewater crystallize out during the increase of the pH value, and the crystallization rate decreases with the increase of the pH value. As the pH reaches 8.4 - 9.0, the extraction rate of the sodium-based substances increases. After Step S3B lasts for a period of time, the ratio of the calcium and magnesium content to the sodium-based content in the wastewater increases. Enter the stage of Step S4B.

[0050] In Step S4B, inject the overflowing ammonia-containing treatment liquid combined with waste ammonia water and integrated wastewater into the first-stage cavitation flotation tank. Readjust the pH value of the wastewater in the first-stage cavitation flotation tank to 7.5 - 8.0 to continue the calcium and magnesium extraction step.

[0051] This method is applicable to continuous wastewater treatment, and cancels the application of the secondary cavitation flotation tank, reducing the equipment volume and increasing the applicability.

[0052] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. An industrial carbon dioxide capture, utilization and sodium-based resource utilization method based on cavitation air flotation, characterized in that: Including: Step S1: Mix the integrated wastewater from the steel plant and the waste ammonia water obtained from the coking plant in a certain ratio to obtain a first target mixed liquid. The first target mixed liquid is pumped to a primary cavitation flotation tank through a water pump, and the pH value of the first target mixed liquid is 7.5 - 8.0; Step S2: The gas containing carbon dioxide from the steel plant is used as the gas supply source for the primary cavitation flotation fan blade. Carbon dioxide rapidly reacts with calcium and magnesium ions in the first target mixed liquid to form calcium carbonate, magnesium carbonate crystals and other solid impurities. After treatment, the first target mixed liquid becomes an ammonia-containing treatment liquid; Step S3: The ammonia-containing treatment liquid, integrated wastewater and waste ammonia water are mixed in a certain ratio to obtain a second target mixed liquid. The second target mixed liquid is pumped to a secondary cavitation flotation tank through a water pump, and the pH value of the second target mixed liquid is 8.4 - 9.0; Step S4: The gas containing carbon dioxide from the steel plant is used as the gas supply source for the secondary cavitation flotation fan blade. Excessive carbon dioxide gas is introduced and rapidly reacts with sodium ions in the wastewater to form sodium bicarbonate crystals and other solid impurities.

2. The method for industrial carbon dioxide capture, utilization and sodium-based resource recovery based on cavitation air flotation according to claim 1, wherein: It also includes: Step S5: The collected sodium bicarbonate solid is recycled to the steel plant, including but not limited to flue gas desulfurization process, pickling wastewater treatment process, surface rust prevention and passivation of rolling and casting processes.

3. The method for industrial carbon dioxide capture, utilization and sodium-based resource utilization based on cavitation air flotation according to claim 1, wherein: In Step S2 and Step S4, the gas containing carbon dioxide is selected from hot blast stove flue gas or high-concentration carbon dioxide gas after carbon capture.

4. The method for industrial carbon dioxide capture, utilization and sodium-based resource recovery based on cavitation air flotation according to claim 1, wherein: Remove Step S4, and replace Step S3 with Step S3A: Inject the remaining waste ammonia water in Step S1 into the primary cavitation flotation tank, adjust the pH value of the ammonia-containing treatment liquid in the primary cavitation flotation tank to 8.4 - 9.0, and carbon dioxide gas reacts with sodium ions in the wastewater to form sodium bicarbonate crystals.

5. The method for industrial carbon dioxide capture, utilization and sodium-based resource recovery based on cavitation air flotation according to claim 1, characterized in that: Replace Step S3 with Step S3B: Inject the remaining waste ammonia water in Step S1 and the integrated wastewater into the primary cavitation flotation tank, adjust the injection ratio of the waste ammonia water and the integrated wastewater. The pH value of the liquid mixture of the ammonia-containing treatment liquid, waste ammonia water and integrated wastewater is 8.4 - 9.0, and carbon dioxide gas reacts with sodium ions in the wastewater to form sodium bicarbonate crystals and other impurities.

6. The method for industrial carbon dioxide capture and utilization and sodium-based resource utilization based on cavitation air flotation according to claim 5, characterized in that: Replace Step 4 with Step 4B: Continuously inject waste ammonia water and / or integrated wastewater and / or ammonia-containing treatment liquid into the primary cavitation flotation tank after being treated in Step S3B, adjust the pH value of the primary cavitation flotation tank to 7.5 - 8.0, and repeat Step S1 in a cycle.

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