A method for co-disposal of coking wastewater and steel slag

Abstract

The present application belongs to the technical field of waste environmental protection treatment, and provides a method for coking wastewater and steel slag collaborative treatment, comprising: S1, detecting the alkalinity of the converter steel slag discharged from the converter; S2, adding a dephosphorizing agent to the high-alkalinity steel slag and stirring to react; using a slagging treatment on the solid solution after the stirring reaction to obtain phosphorus-free slag and phosphorus iron; S3, cooling and crushing the low-alkalinity steel slag, and then performing magnetic separation to obtain phosphorus-containing slag and magnetic iron; mixing the magnetic iron with carbon powder to form balls to obtain high-iron balls, medium-iron balls and micro-iron balls; S4, performing biochemical treatment on the coking wastewater to obtain coking biochemical wastewater; adjusting the pH of the coking biochemical wastewater, and then sequentially passing through the high-iron balls, medium-iron balls and micro-iron balls; and obtaining purified water. The present application fully utilizes the advantages of multiple processes of steel and iron, realizes collaborative purification of steel slag and coking wastewater, and does not produce new waste slag and wastewater.

Description

Technical Field

[0001] This invention relates to a wastewater and waste residue treatment method, specifically a method for the co-treatment of wastewater and waste residue generated in the steel industry, belonging to the field of waste environmental protection treatment technology. Background Technology

[0002] After biological treatment, coking wastewater is generally dark yellow in color, with a COD of 100–400 mg / L, while the discharge requirement is <60 mg / L. To reduce COD, the conventional approach is to use advanced oxidation methods, such as ozone, Fenton, and electrocatalysis, but these methods are all too costly.

[0003] Furthermore, my country has a massive steel slag discharge, with annual increases exceeding 100 million tons. Currently, steel slag disposal primarily focuses on cement production, which suffers from low added value and low utilization rate (only about 40%). With the revision of GB175-2023 "General Portland Cement," it is clearly stated that from June 1, 2024, steel slag will no longer be allowed as a blending material in general Portland cement. The safe, efficient, and proper disposal of steel slag has become a major bottleneck restricting the green and sustainable development of my country's steel industry. Steel slag is rich in iron resources, with iron oxides accounting for 15%–25%, but it also contains a large amount of harmful elements (phosphorus) found in steel materials, limiting its internal recycling potential. Developing steel slag dephosphorization technology to overcome the constraints of internal steel smelting could significantly reduce steel slag emissions, eliminating the need for building material production and achieving source reduction and resource recycling.

[0004] For the treatment of coking wastewater effluent after biochemical treatment, in addition to deep oxidation, iron-carbon micro-electrolysis has also been proven to be an effective treatment method. For example, the "Deep Treatment Method and System for Coking Wastewater" disclosed in Chinese Patent CN105948338A mainly addresses the problem that existing coking wastewater treatment processes cannot meet discharge requirements. The deep treatment method and system for coking wastewater described in this invention first subjectes the coking wastewater, after biochemical treatment, to microwave radiation treatment, followed by iron-carbon micro-electrolysis catalytic reduction treatment, further heterogeneous Fenton catalytic oxidation treatment, and then coagulation sedimentation treatment and microfiltration treatment, ultimately meeting discharge requirements. However, this method, due to the use of microwave treatment technology, suffers from relatively high operating costs. Chinese patent CN102627367A discloses a method for deep treatment of coking wastewater. This method mainly includes the following steps: The first step is column packing, where waste iron filings are first soaked in dilute sulfuric acid and dilute NaOH solution respectively, and coke is crushed and mixed evenly with iron filings in a volume ratio of 10:1 before being packed into an iron-carbon column; the second step is acidification treatment of the coking wastewater after secondary biological treatment; the third step is adding flocculant to the acidified wastewater; the fourth step is column permeation, where the liquid enters from the bottom of the iron-carbon column and flows out from the top; the fifth step is neutralization followed by sedimentation; and the sixth step is repeating the operations from steps two to five with the supernatant from step five. This method has the advantages of simple operation and low cost, but the most significant problem is the unstable treatment effect.

[0005] Regarding steel slag dephosphorization technology, Chinese patent CN117778669A discloses "A Method for Gasification Dephosphorization of Converter Final Slag and Recycling of Dephosphorized Slag." This method involves adding a carbonaceous dephosphorizing agent to the converter slag for gasification dephosphorization, and the dephosphorized slag can be recycled back to the sintering process. This method can effectively remove phosphorus and achieve steel slag recycling. However, this method suffers from poor dephosphorization effect and inadequate slag-phosphorus separation in practical applications. Chinese patent CN110184399A discloses "A Steel Slag Treatment Method Using a Two-Step Oxidative Desulfurization and Reduction Dephosphorization Method," in which dephosphorization is achieved using gas-based reduction dephosphorization, utilizing a mixture of CO and CO2 to convert phosphorus into phosphorus gas for removal. This method has a good dephosphorization effect, reaching 80%. However, the phosphorus gas produced by this method is highly toxic, posing a risk of personnel poisoning and explosion of the mixed gas. Chinese patent CN110526745A discloses a method for separating phosphorus from dephosphorized steel slag and preparing phosphate fertilizer. The method involves first oxidizing the phosphorus-containing steel slag in a molten state, then cooling it before crushing and leaching to obtain low-phosphorus residue and phosphorus-containing leachate. While this method can effectively remove and recover phosphorus, the large volume of steel slag processed results in high levels of by-product wastewater, leading to increased disposal costs. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for the co-treatment of coking wastewater and steel slag. It utilizes the alkalinity of steel slag and the acidic conditions of coking wastewater to form an in-situ pH buffer system, achieving a coupling of dephosphorization and purification functions through the gradient utilization of steel slag components. Simultaneously, the phosphate and iron in the steel slag undergo a co-precipitation reaction with the phosphates in the coking wastewater to generate stable hydroxyapatite minerals. These minerals contain elements such as iron, calcium, and phosphorus, and have high crystallinity and low solubility. After solid-liquid separation, the minerals are mixed with aluminum powder, iron powder, and calcium oxide, then pelletized and dried for use as a dephosphorizing agent for converter steel slag, achieving a closed-loop recycling of phosphate and iron resources.

[0007] According to a first embodiment of the present invention, a method for co-treating coking wastewater and steel slag is provided.

[0008] A method for co-treating coking wastewater and steel slag, the method comprising the following steps:

[0009] S1. Perform basicity testing on the steel slag discharged from the converter: when the basicity reaches or exceeds B, proceed to step S2; when the basicity is lower than B, proceed to step S3.

[0010] S2. Add dephosphorizing agent and water to the steel slag with an alkalinity of B obtained in step S1, and stir to react; separate the solid solution after stirring reaction by slag removal to obtain phosphorus-free slag and ferrophosphorus.

[0011] S3. Cool and crush converter steel slag with basicity lower than B, and then perform magnetic separation to obtain phosphorus-containing slag and magnetic iron; mix the magnetic iron with carbon powder to form pellets to obtain high-iron pellets, medium-iron pellets, and micro-iron pellets.

[0012] S4. The coking wastewater is subjected to biological treatment to obtain coking biological wastewater; the pH of the coking biological wastewater is adjusted, and then it is passed through high-iron briquette, medium-iron briquette, and micro-iron briquette in sequence to obtain purified water;

[0013] Wherein, the value of B is 1.0-5.0, preferably 1.5-4, and more preferably 1.8-3.

[0014] Preferably, the coking biochemical wastewater is passed sequentially through a device equipped with high-iron briquettes, medium-iron briquettes, and micro-iron briquettes; wherein the waste residue discharged from the device equipped with micro-iron briquettes is used as raw material for the dephosphorizing agent in step S2.

[0015] As a preferred option, the slag phase discharged from the high-speed rail briquetting device is used as the iron raw material.

[0016] As a preferred option, the slag phase discharged from the iron briquetting device is used as the iron raw material.

[0017] Preferably, the dephosphorizing agent in step S2 is prepared by the following method: the waste residue discharged from the device containing micro-iron briquetting pellets is mixed with aluminum powder, iron powder, calcium oxide, carbon powder and silicon oxide, then pelletized and dried to obtain the dephosphorizing agent.

[0018] Preferably, the composition and content of the waste residue discharged from the device containing micro-iron briquettes are detected, and the mixing ratio of the waste residue discharged from the device containing micro-iron briquettes with aluminum powder, iron powder, calcium oxide, carbon powder and silicon oxide is adjusted so that the dephosphorizing agent contains: Al: 3%~15%, Si: 5%~10%, Fe: 5%~15%, C: 5%~10%, Ca: 10%~15%, with the balance being O.

[0019] As a preferred option, in step S2, the solid solution is separated by slag removal to obtain phosphorus-free slag that accounts for 60%–90% of the mass of converter steel slag.

[0020] Phosphorus-free slag is preferred as a feedstock for converters.

[0021] As a preferred option, the ferrophosphate is recycled into steel slag with an alkalinity of 2.0 or above, or used for phosphorus resource utilization.

[0022] As a preferred method, the phosphorus content in the phosphorus-free slag is detected. When the phosphorus content in the phosphorus-free slag is less than 1%, the ferrophosphate is recycled to steel slag with an alkalinity of 2.0 or higher. When the phosphorus content in the phosphorus-free slag is not less than 1%, the ferrophosphate is transported to the phosphorus resource utilization device.

[0023] Preferably, in step S3, the cooling is performed using direct counter-current cooling.

[0024] Preferably, the cooling medium is air.

[0025] Preferably, the cooling rate is 50~100℃ / min.

[0026] Preferably, the temperature of the converter slag after cooling is less than 100°C.

[0027] Preferably, in step S3, the crushing is carried out using a ball mill until the particle size of the converter steel slag is ≤1mm.

[0028] Preferably, the intensity of the magnetic separation is 0.05~0.2 T.

[0029] Preferably, the phosphorus-containing slag obtained in step S3 is transported to a phosphorus resource utilization device.

[0030] Preferably, the iron content in the magnetic iron is ≥85%.

[0031] In this invention, in step S3, the iron content in the high-iron briquette is greater than 80 wt% by adjusting the mixing ratio of magnetic iron and carbon powder.

[0032] In this invention, by adjusting the mixing ratio of magnetic iron and carbon powder, the iron content in the iron briquette is made to be 40-70 wt%.

[0033] In this invention, by adjusting the mixing ratio of magnetic iron and carbon powder, the iron content in the micro iron sphere is made less than 10 wt%.

[0034] In this invention, in step S4, the biochemical treatment is specifically at least one of A / O, A / A / O, and A / O / A, where A is an anoxic process and O is an aerobic process.

[0035] In this invention, the pH of the coking biochemical wastewater is adjusted to 2-4.

[0036] Preferably, in step S4, the coking biochemical wastewater is simultaneously aerated as it passes through high-iron briquette, medium-iron briquette, and micro-iron briquette.

[0037] Preferably, air is used in the aeration process.

[0038] In this invention, the particle size of the dephosphorizing agent is 2~8 mm.

[0039] In this invention, the moisture content of the dephosphorizing agent is less than 3%.

[0040] The principle of the technical solution of this invention is as follows:

[0041] 1. Recycling of Steel Slag: After adding a dephosphorizing agent, the steel slag undergoes slag-phosphorus separation. Following the dephosphorization reaction, the slag separates into layers based on their melting point and density. The upper layer, primarily composed of CaO-SiO2-MgO-Al2O3 slag (60%–90% of the total slag), can be directly used as a slag-forming agent in the next converter, thus achieving the recycling of steel slag. The lower layer, mainly composed of ferrophosphorus (10%–40% of the total slag), can be used for the next converter slag recycling reaction when the phosphorus content is low. Because the two slag phases have significantly different densities, a slag skimmer can be used to separate the reacted steel slag.

[0042] 2. Steel Slag Cooling and Mineral Phase Control and Waste Heat Utilization: Since steel slag contains elemental iron, direct water cooling at high temperatures (>1400℃) carries the risk of hydrogen deposition due to iron displacement from water, potentially leading to an explosion. Therefore, natural cooling to approximately 800-1000℃ is typically used before water cooling. Natural cooling at high temperatures results in the formation of high-hardness calcium ferrite and RO phases (Mohs hardness 5-7), increasing wear and energy consumption during subsequent treatment. This invention utilizes compressed air for counter-current rapid cooling of the steel slag, employing a dry cooling process throughout, thus avoiding the generation of high-strength steel slag and wastewater.

[0043] 3. High-efficiency purification of COD in coking biochemical wastewater: The main COD components of coking wastewater are phenolic compounds, heterocyclic compounds, naphthalenes, and SCN. - For substances like naphthalene, polycyclic aromatic hydrocarbons, and SCN, biochemical treatment can only remove some easily degradable substances, but not those such as naphthalene, polycyclic aromatic hydrocarbons, and SCN. - Suspended solids and other substances are difficult to biodegrade, resulting in COD levels in coking biochemical effluent still ranging from 100 to 400 mg / L. This invention utilizes recovered magnetic iron and carbon powder to separately press briquettes, obtaining high-iron briquettes, medium-iron briquettes, and iron-free briquettes. The high-iron briquettes contain more than 85 wt% iron, the medium-iron briquettes contain 40-70 wt% iron, and the micro-iron briquettes contain no more than 10 wt% iron. First, the coking biochemical effluent, adjusted to acidity, is added to the high-iron briquettes. Under acidic conditions, the briquettes undergo chemical corrosion, and simultaneously, under aeration, ferrous and ferric ions, as well as hydroxyl radicals, are generated. The hydroxyl radicals have strong oxidizing properties, oxidizing the residual COD in the wastewater. Furthermore, the elemental iron and carbon in the briquettes also have catalytic effects, further enhancing the removal effect. Then, when the solution comes into contact with the ferric briquette, the iron in the briquette reduces ferric ions to form ferrous ions. These ferrous ions further reduce some high-valence COD substances to low-valence states. Simultaneously, under aeration, the ferrous ions are oxidized to ferric ions, further purifying the low-valence COD substances. As the reaction proceeds, the pH of the coking biochemical effluent gradually increases, causing precipitation in the ferric briquette section. Through the adsorption and interception effect of the ferric briquette, the removal of suspended COD is further improved, ultimately achieving compliant discharge.

[0044] 4. Use of waste residue for steel slag dephosphorization: After wastewater treatment, fine waste materials and iron-containing precipitates are generated as residues from the water treatment reaction. Disposing of such waste residues is difficult. The steel slag dephosphorization agent of this invention addresses this need by compounding aluminum powder, dephosphorization slag, and waste residue from water treatment with added iron, calcium oxide, carbon powder, and silicon oxide. The final product is an exothermic dephosphorization co-solvent with the following proportions: Al: 3%–15%, Si: 5%–10%, Fe: 5%–15%, C: 5%–10%, Ca: 10%–15%. When this co-solvent is used for steel slag dephosphorization, it mainly utilizes the exothermic oxidation of aluminum powder, the secondary slag formation of calcium and silicon in the dephosphorization slag with the steel slag, the reduction of high-valence phosphorus compounds in the steel slag by carbon in waste iron-carbon materials and waste activated carbon, and the capture of reduced phosphorus in the steel slag by iron in waste iron-carbon materials. Through the compounding process of this invention, most of the phosphorus in steel slag can be converted into elemental phosphorus and a small amount of phosphorus gas at low cost. The main reaction process involved is Ca3(PO4)2(s) + 5 C(s) = 3 CaO(s) + P2(g) + 5 CO (g) Simultaneously, the reduced elemental phosphorus undergoes an alloying reaction with the iron in the converter and the dephosphorizing agent under high-temperature conditions, thus transforming into a stable phosphorus-iron phase. Furthermore, the exothermic effect of the combustion of elemental iron and aluminum in the dephosphorizing agent is utilized to achieve self-heating of the entire steel slag treatment process.

[0045] In this invention, converter slag refers to a byproduct generated during the converter steelmaking process. Its main components are calcium oxide, silicon oxide, and iron oxide, and it contains a certain amount of phosphorus. The basicity of steel slag is an important indicator of its chemical properties, usually determined by measuring the ratio of its main basic oxides (such as CaO) to acidic oxides (such as SiO2 and P2O5). Dephosphorizing agents are chemical agents used to remove phosphorus from steel slag. They react with phosphides in the slag to generate easily separable phosphorus-containing compounds, thereby reducing the phosphorus content of the slag. Slag removal is a physical separation method that uses mechanical or manual methods to separate the slag phase from the liquid phase or solid phases of different densities in a solid solution to obtain the target product. Phosphorus-free slag refers to steel slag with reduced phosphorus content after dephosphorization treatment, which can be recycled as raw material for other industrial processes. Phosphorus-iron refers to an alloy or compound rich in phosphorus and iron formed during the dephosphorization process, which has value in recovering phosphorus and iron resources. Phosphorus-containing slag refers to steel slag that has not undergone dephosphorization treatment or has undergone incomplete dephosphorization. It has a relatively high phosphorus content and usually requires further processing to recover phosphorus resources. Magnetic iron refers to iron-rich substances extracted from steel slag through magnetic separation. It is magnetic and can be used as an iron raw material.

[0046] In this invention, briquetting refers to the process of shaping powdered or granular materials into spherical or block-shaped materials with specific shapes and strength through pressure. High-speed iron briquetting, medium-speed iron briquetting, and low-speed iron briquetting are briquetting products distinguished by their different iron contents.

[0047] In this invention, biochemical treatment is a water treatment method that utilizes microorganisms to degrade organic pollutants. It typically includes anaerobic, anoxic, and aerobic process stages to reduce indicators such as COD and BOD in wastewater.

[0048] This invention provides a method for the co-treatment of coking wastewater and steel slag. This method combines the dephosphorization of steel slag with the deep purification of coking wastewater, achieving comprehensive resource utilization and effective pollutant removal. The method includes a step S1 of detecting the alkalinity of steel slag discharged from the converter. The alkalinity of converter steel slag is an indicator of its chemical activity, and different alkalinities correspond to different treatment paths. For example, the alkalinity of the steel slag can be detected by sampling and using a pH meter or chemical titration. When the detection result shows that the alkalinity of the steel slag reaches or exceeds a preset value B, the steel slag is guided to the subsequent dephosphorization treatment step S2; if the alkalinity is lower than B, the steel slag is guided to step S3, where it is sequentially cooled, crushed, and magnetically separated. The preset value B can be set according to actual process requirements; for example, it can be set to 1.0-5.0, or a narrower range such as 1.5-4, or even 1.8-3.

[0049] In step S2, a dephosphorizing agent and water are added to steel slag with an alkalinity of B or higher, and the mixture is thoroughly stirred to react. The dephosphorizing agent reacts with phosphorus in the steel slag, converting it into a form that is easily separated. For example, calcium oxide or iron oxide can be used as the main components of the dephosphorizing agent. The addition of water helps form a solid solution, promoting the dephosphorization reaction. The stirring reaction can be achieved using a mechanical stirrer to ensure sufficient contact between the dephosphorizing agent, water, and steel slag, improving reaction efficiency. After the reaction is complete, the formed solid solution is separated using a slag removal technique. Slag removal can be carried out manually or mechanically, for example, using a slag remover to separate the upper slag phase from the lower metal phase. Through this separation process, phosphorus-free slag with reduced phosphorus content and phosphorus-rich ferrophosphate can be obtained.

[0050] Step S3 yields phosphorus-containing slag and magnetic iron. The obtained magnetic iron is then mixed with carbon powder for pelletizing. Adding carbon powder controls the iron content of the pellets and optimizes their micro-electrolysis performance in subsequent coking wastewater treatment. The pelletizing process can be completed using a disc pelletizer or a drum pelletizer, producing spherical particles with a specific size and strength. Depending on the mixing ratio of magnetic iron to carbon powder, pellets with different iron contents can be prepared, such as high-iron pellets, medium-iron pellets, and micro-iron pellets.

[0051] In step S4, the coking wastewater is first subjected to biological treatment to remove most of the organic pollutants, resulting in coking biological wastewater. Biological treatment can employ conventional methods such as activated sludge or biofilm processes. Subsequently, the pH value of the coking biological wastewater is adjusted. pH adjustment can be achieved by adding acid or alkali, for example, sulfuric acid or sodium hydroxide solution, to optimize the reaction conditions for subsequent advanced treatment. The pH-adjusted coking biological wastewater then passes sequentially through high-iron briquette, medium-iron briquette, and low-iron briquette. This process utilizes a micro-electrolysis system formed by iron and carbon in the briquette to deeply purify the coking wastewater. Contact between the wastewater and briquettes with different iron contents further degrades and removes residual pollutants. For example, different types of briquettes can be filled into reactors connected in series, allowing the wastewater to flow through them sequentially. After this treatment process, purified water meeting discharge standards can be obtained.

[0052] In this invention, a multi-stage micro-electrolysis system is constructed by sequentially passing biochemically treated coking wastewater through briquettes with different iron contents (high-iron briquettes, medium-iron briquettes, and low-iron briquettes). Compared with existing single iron-carbon micro-electrolysis or high-cost advanced oxidation technologies, the briquette combination in this embodiment can provide stable pollutant removal effects and improve efficiency, while controlling operating costs. Briquettes with different iron contents play different roles in the micro-electrolysis process, achieving optimized control of pollutant degradation, thereby improving the quality of purified water.

[0053] In this invention, the alkalinity of steel slag is detected, and different treatment paths are adopted according to the alkalinity level. For high-alkalinity steel slag, a dephosphorizing agent and water are reacted and then separated by slag skimming to obtain phosphorus-free slag and ferrophosphate, achieving phosphorus removal and recovery. Based on the principle of converter dephosphorization, the dephosphorization reaction generates stable calcium phosphate, and the phosphorus-free slag can be recycled as a valuable converter raw material, meeting the dephosphorization requirements of converter steelmaking, while avoiding the toxicity risks and large amounts of wastewater generated by traditional dephosphorization technologies. For low-alkalinity steel slag, magnetic iron is extracted through cooling, crushing, and magnetic separation processes, and then mixed with carbon powder in a precise ratio to prepare briquettes with different iron contents. This method of converting the iron resources in steel slag into materials for the deep treatment of coking wastewater solves the problem of steel slag storage, increases the added value of steel slag, and provides a low-cost and effective reaction medium for coking wastewater treatment.

[0054] In this invention, "an apparatus containing high-iron briquettes, medium-iron briquettes, and micro-iron briquettes" refers to a container or reactor capable of accommodating different types of briquettes (high-iron briquettes, medium-iron briquettes, and micro-iron briquettes) and allowing coking biochemical wastewater to flow sequentially through each type of briquette. For example, these apparatuses can be designed as multiple reaction towers or reactors connected in series, each tower or reactor filled with the corresponding type of briquette. Wastewater enters from the top of the first tower, flows sequentially through each tower, and exits from the bottom of the last tower. Alternatively, it can be a stratified filter bed or adsorption column, where different types of briquettes are placed in layers within the same container using partitions or screens, and wastewater flows sequentially through each layer of briquettes from top to bottom.

[0055] This invention provides the following specific implementation scheme: Coking biochemical wastewater is first pumped into a reaction tower filled with high-iron briquettes. The bottom of this reaction tower is equipped with a sieve plate to support the briquettes and ensure smooth passage of the wastewater. The wastewater flows from bottom to top or top to bottom through the high-iron briquette layer within the tower, ensuring full contact with the briquettes. Subsequently, the wastewater discharged from the high-iron briquette reaction tower is introduced into a second reaction tower filled with medium-iron briquettes for similar treatment. Finally, the wastewater enters a third reaction tower filled with micro-iron briquettes to complete the final purification process. At the bottom of each reaction tower, a slag discharge port can be provided for periodically or continuously discharging the waste residue or slag phase generated during the reaction process. The waste residue discharged from the reaction tower filled with micro-iron briquettes can be collected and transported to a dephosphorizing agent preparation unit, where it is mixed with aluminum powder, iron powder, calcium oxide, carbon powder, silicon oxide, etc., and then pelletized and dried to prepare the dephosphorizing agent for step S2. The slag discharged from the reaction tower containing high-speed iron briquettes and medium-speed iron briquettes can be collected and sent back to the ironmaking process of the steel plant for reuse as a supplementary iron raw material.

[0056] In this invention, the waste residue discharged from the device containing micro-iron briquettes is the solid residue discharged from the device containing micro-iron briquettes after the coking biochemical wastewater has passed through high-iron briquettes, medium-iron briquettes, and micro-iron briquettes during the coking wastewater treatment process. The waste residue, aluminum powder, iron powder, calcium oxide, carbon powder, and silicon dioxide discharged from the device containing micro-iron briquettes are auxiliary raw materials used in the preparation of the dephosphorizing agent. Aluminum can act as a reducing agent, promoting phosphorus reduction and forming stable compounds with phosphorus, thus aiding in phosphorus removal. Iron powder can increase the iron content of the dephosphorizing agent, facilitating the formation of ferrophosphorus alloys and improving dephosphorization efficiency. Calcium oxide, as an alkaline substance, can react with phosphates to form stable calcium-phosphorus compounds, thereby fixing phosphorus. Carbon, as a reducing agent, promotes phosphorus reduction at high temperatures and helps regulate the reactivity of the dephosphorizing agent. Silicon dioxide can act as a slag-forming agent, adjusting the viscosity of the slag, improving the reaction interface between the dephosphorizing agent and steel slag, and also reacting with some metal oxides to form silicates. The dephosphorizing agent prepared in this scheme is a chemical substance used to remove phosphorus from steel slag. Its function is to separate phosphorus from the steel slag through a chemical reaction with phosphorus and its compounds, thereby reducing the phosphorus content of the steel slag. This scheme uses waste slag discharged from a device equipped with micro-iron briquetting as the basic raw material, supplemented with various functional components such as aluminum powder, iron powder, calcium oxide, carbon powder, and silicon oxide. Through precise mixing, briquetting, and drying processes, a highly efficient and compositionally controllable dephosphorizing agent is prepared. This type of dephosphorizing agent relies on the reducing and electrochemical properties of iron, as well as the flocculation and adsorption effect of iron ions, to form active substances through a micro-battery effect, which react with phosphorus pollutants to achieve the purpose of dephosphorization.

[0057] In this invention, based on the test results and the required content of Al, Si, Fe, C, and Ca in the target dephosphorizing agent, the precise mass of aluminum powder, iron powder, calcium oxide, carbon powder, and silicon oxide that need to be added is calculated. For example, if the iron content in the waste residue is low, the amount of iron powder added needs to be increased.

[0058] In this invention, when the phosphorus content in ferrophosphorus is low or moderate, it can be added to high-alkalinity steel slag to utilize the high-alkalinity environment to promote further phosphorus removal or conversion, thereby achieving internal phosphorus recycling. When the phosphorus content in ferrophosphorus is high or unsuitable for internal recycling, it can be transported to a dedicated phosphorus resource utilization device for the production of phosphate fertilizers, phosphates, or other phosphorus-containing chemicals. When the phosphorus content in the phosphorus-free slag is less than 1%, the ferrophosphorus is recycled to steel slag with an alkalinity of 2.0 or higher. This is a criterion indicating that the dephosphorization effect of the phosphorus-free slag is good. At this time, the phosphorus in the ferrophosphorus may be relatively low, or its reuse may have little impact on the converter steelmaking process. It can be safely recovered into the converter steelmaking process and treated together with the high-alkalinity steel slag to further optimize phosphorus removal or utilization. When the phosphorus content in the phosphorus-free slag is not less than 1%, the ferrophosphate is transported to the phosphorus resource utilization device. This is a judgment condition, indicating that the dephosphorization effect of the phosphorus-free slag may not have reached the best, or the phosphorus content in the ferrophosphate is high. In this case, directly returning it to the furnace may have an adverse effect on the converter steelmaking process. Therefore, sending it to a special phosphorus resource utilization device for treatment can more effectively recover phosphorus resources, avoid burdening the converter steelmaking process, and realize the external high-value utilization of phosphorus.

[0059] In this invention, a counter-flow cooler can be used to cool converter slag with a basicity lower than B. This cooler has multiple sets of guide plates inside. After the slag enters through the feed inlet, it moves downwards along an inclined path under the action of gravity or mechanical force. Simultaneously, cooling air enters from the discharge end of the cooler in the opposite direction, flowing upwards to fully exchange heat with the downward-moving slag. To achieve a cooling rate of 50~100℃ / min, the intake volume and flow rate of the cooling air can be precisely adjusted according to the initial temperature and flow rate of the slag. For example, the air flow rate can be controlled by a variable frequency fan, and the temperature change of the slag can be monitored in real time using a temperature sensor to form a closed-loop control. When the slag leaves the cooler, its temperature is controlled below 100℃, ensuring that it is in a suitable physical state for subsequent crushing and magnetic separation.

[0060] In this invention, "adjusting the mixing ratio of magnetic iron and carbon powder" refers to precisely controlling the iron content in the final briquettes by changing the relative amounts of magnetic iron and carbon powder during briquette preparation. "The iron content in the high-iron briquettes is greater than 80 wt%" refers to the percentage of iron in the high-iron briquettes by mass. This high iron content ensures the briquettes provide strong reducing capacity during wastewater treatment. "The iron content in the medium-iron briquettes is 40-70 wt%" refers to the percentage of iron in the medium-iron briquettes by mass. This moderate iron content allows the briquettes to perform both reduction reactions and other possible adsorption or catalytic effects in wastewater treatment, while maintaining a certain resource value. "The iron content in the micro-iron briquettes is less than 10 wt%" refers to the percentage of iron in the micro-iron briquettes by mass. This low iron content indicates that the briquettes' main function is as a carrier of the adsorbent and to provide a carbon source.

[0061] In this invention, biochemical treatment is a method that utilizes the metabolic activity of microorganisms to degrade organic pollutants in wastewater. In the treatment of coking wastewater, due to its complex composition and the presence of large amounts of recalcitrant organic matter and toxic substances, traditional single-stage biochemical treatment processes may struggle to achieve ideal treatment results. The A / O process (anaerobic / aerobic process) is a common biological nitrogen and phosphorus removal process, where "A" represents the anoxic or anaerobic zone, primarily used for denitrification or anaerobic hydrolysis acidification; and "O" represents the aerobic zone, primarily used for organic matter degradation and nitrification. The A / A / O process (anaerobic / anoxic / aerobic process) adds an anaerobic zone to the A / O process, enabling more effective biological phosphorus and nitrogen removal. The A / O / A process (anoxic / aerobic / anoxic process) further optimizes nitrogen removal through a combination of multiple anoxic and aerobic zones.

[0062] In this invention, pH adjustment is a crucial step in wastewater treatment, affecting the efficiency and stability of subsequent treatment units. Even after biochemical treatment, the pH value of coking biochemical wastewater may still be in a high or low range, which is unfavorable for subsequent deep purification using iron briquetting balls. Adjusting the pH to an acidic range of 2-4 can effectively promote the adsorption, precipitation, or redox reactions of harmful substances in the wastewater by the iron briquetting balls.

[0063] In this invention, the detection standards for steel slag basicity and phosphorus are GB / T 29514-2018. Specific implementation methods include, but are not limited to, using X-ray fluorescence spectrometry, inductively coupled plasma atomic emission spectrometry, or wet chemical analysis for rapid and accurate elemental analysis, with the detection standard being GB / T 29514-2018.

[0064] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0065] 1. Fully leverage the advantages of multiple steelmaking processes to achieve synergistic purification of steel slag and coking wastewater, without generating new waste slag or wastewater.

[0066] 2. The three-stage briquetting process for treating coking biochemical effluent proposed in this invention can achieve tiered purification of difficult-to-treat COD in coking biochemical effluent, ultimately resulting in low-cost treatment.

[0067] 3. This invention provides a low-cost dephosphorization method for steel slag, achieving a reduction in the amount of steel slag. Attached Figure Description

[0068] Figure 1 This is a process flow diagram of a method for the co-treatment of coking wastewater and steel slag according to the present invention. Detailed Implementation

[0069] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0070] Example 1

[0071] A method for co-treating coking wastewater and steel slag, the method comprising the following steps:

[0072] S1. Perform basicity testing on the steel slag discharged from the converter: when the basicity reaches or exceeds B, proceed to step S2; when the basicity is lower than B, proceed to step S3.

[0073] S2. Add dephosphorizing agent and water to the steel slag with an alkalinity of B obtained in step S1, and stir to react; separate the solid solution after stirring reaction by slag removal to obtain phosphorus-free slag and ferrophosphorus.

[0074] S3. Cool and crush converter steel slag with basicity lower than B, and then perform magnetic separation to obtain phosphorus-containing slag and magnetic iron; mix the magnetic iron with carbon powder to form pellets to obtain high-iron pellets, medium-iron pellets, and micro-iron pellets.

[0075] S4. The coking wastewater is subjected to biological treatment to obtain coking biological wastewater; the pH of the coking biological wastewater is adjusted, and then it is passed through high-iron briquette, medium-iron briquette, and micro-iron briquette in sequence to obtain purified water;

[0076] Where: B takes the value of 2.

[0077] Example 2

[0078] Repeat Example 1, except that the coking biochemical wastewater is passed sequentially through a device containing high-iron briquettes, medium-iron briquettes, and micro-iron briquettes; wherein the waste residue discharged from the device containing micro-iron briquettes is used as raw material for the dephosphorizing agent in step S2.

[0079] Example 3

[0080] Example 1 was repeated, except that the slag phase discharged from the high-speed iron briquetting device and the medium-speed iron briquetting device was used as the iron raw material.

[0081] Example 4

[0082] Repeat Example 2, except that the dephosphorizing agent in step S2 is prepared by the following method: the waste residue discharged from the device containing micro-iron briquetting pellets is mixed with aluminum powder, iron powder, calcium oxide, carbon powder, and silicon oxide, then pelletized and dried to obtain the dephosphorizing agent; the composition and content of the waste residue discharged from the device containing micro-iron briquetting pellets are detected, and the mixing ratio of the waste residue with aluminum powder, iron powder, calcium oxide, carbon powder, and silicon oxide is adjusted so that the dephosphorizing agent contains: Al: 3%–15%, Si: 5%–10%, Fe: 5%–15%, C: 5%–10%, Ca: 10%–15%, with the balance being O.

[0083] Example 5

[0084] Repeat Example 2, except that the phosphorus-free slag is used as the raw material for the converter; the phosphorus content in the phosphorus-free slag is detected. When the phosphorus content in the phosphorus-free slag is less than 1%, the ferrophosphate is recycled to steel slag with an alkalinity of 2.0 or higher; when the phosphorus content in the phosphorus-free slag is not less than 1%, the ferrophosphate is transported to the phosphorus resource utilization device.

[0085] Example 6

[0086] Repeat Example 2, except that in step S3, the cooling is achieved by direct counter-current air cooling; the cooling rate is 50~100℃ / min; and the temperature of the converter slag after cooling is less than 100℃.

[0087] Example 7

[0088] Repeat Example 6, except that in step S3, the crushing is carried out using a ball mill until the particle size of the converter steel slag is ≤1mm; the intensity of the magnetic separation is 0.1T; the phosphorus-containing slag obtained in step S3 is transported to the phosphorus resource utilization device; and the iron content in the magnetic iron is ≥85%.

[0089] Example 8

[0090] Repeat Example 2, except that in step S3, the mixing ratio of magnetic iron and carbon powder is adjusted so that the iron content in the high-iron briquette is 85wt%, the iron content in the medium-iron briquette is 50wt%, and the iron content in the micro-iron briquette is 8wt%.

[0091] Example 9

[0092] Repeat Example 1, except that in step S4, the biochemical treatment is specifically an A / O process, where A is an anoxic process and O is an aerobic process.

[0093] Example 10

[0094] Repeat Example 1, except that in step S4, the biochemical treatment is specifically an A / A / O process, where A is an anoxic process and O is an aerobic process.

[0095] Example 11

[0096] Repeat Example 1, except that in step S4, the biochemical treatment is specifically an A / O / A process, where A is an anoxic process and O is an aerobic process.

[0097] Example 12

[0098] Repeat Example 9, except that the pH of the coking biochemical wastewater is adjusted to 2-4.

[0099] Example 13

[0100] Repeat Example 12, except that in step S4, when the coking biochemical wastewater passes through the high-iron briquette, medium-iron briquette, and micro-iron briquette, air is used for aeration simultaneously.

[0101] Example 14

[0102] Example 4 was repeated, except that the particle size of the dephosphorizing agent was 2-8 mm and the moisture content in the dephosphorizing agent was less than 3%.

[0103] Application Examples Process

[0104] A method for co-treating coking wastewater and steel slag, the method comprising the following steps:

[0105] S1. The basicity of the steel slag discharged from the converter is tested: when the basicity reaches or exceeds 2, the steel slag proceeds to step S2; when the basicity is below 2, the steel slag proceeds to step S3.

[0106] S2. Add dephosphorizing agent and water to the steel slag with an alkalinity of 2 or higher obtained in step S1, and stir the reaction thoroughly; separate the solid solution after stirring reaction by slag removal to obtain phosphorus-free slag and ferrophosphorus.

[0107] S3. Cool and crush converter steel slag with an alkalinity lower than 2, and then perform magnetic separation to obtain phosphorus-containing slag and magnetic iron; mix the magnetic iron with carbon powder to form pellets to obtain high-iron pellets, medium-iron pellets, and micro-iron pellets; the iron content in the high-iron pellets is 85 wt%; adjust the mixing ratio of magnetic iron and carbon powder so that the iron content in the medium-iron pellets is 60 wt%; adjust the mixing ratio of magnetic iron and carbon powder so that the iron content in the micro-iron pellets is less than 6 wt%.

[0108] S4. The coking wastewater is treated by A / O biological treatment to obtain coking biochemical wastewater; the pH of the coking biochemical wastewater is adjusted to 3.0, and the coking biochemical wastewater is passed sequentially through a device equipped with high-iron briquette, medium-iron briquette, and micro-iron briquette, while being aerated with air; the waste residue discharged from the device equipped with micro-iron briquette is used as raw material for the dephosphorizing agent in step S2; purified water is obtained.

[0109] Among them: adjusting the mixing ratio of the waste residue discharged from the device containing micro iron briquettes with aluminum powder, iron powder, calcium oxide, carbon powder and silicon oxide, so that the dephosphorizing agent contains: Al 9%, Si 7.6%, Fe 11%, C 8.5%, Ca 13.7%, and the remainder is O.

[0110] Application Example 1

[0111] In a scenario involving the co-processing of wastewater by a coking plant and a steel plant, the steel plant's converter discharges steel slag, while the coking plant generates biochemically treated coking wastewater. This coking biochemical wastewater still contains a high concentration of COD, failing to meet direct discharge standards.

[0112] First, the basicity of the steel slag discharged from the converter is tested. A rapid testing method was used, and one batch of steel slag had a basicity of 4.5, while another batch had a basicity of 0.8. Based on a preset value B (set to 2.0), the steel slag with a basicity of 4.5 is determined to have a basicity at or above B, and proceeds to step S2. The steel slag with a basicity of 0.8 is determined to have a basicity below B, and proceeds to step S3.

[0113] For the steel slag with a basicity of 4.5 entering step S2, a pre-prepared dephosphorizing agent and an appropriate amount of water are added. The steel slag, dephosphorizing agent, and water are stirred thoroughly in a mixing tank for 30 minutes to allow phosphorus to fully react with the dephosphorizing agent and form phosphorus-containing compounds. After the reaction is complete, the formed solid solution is transferred to a slag removal device, and the upper layer of phosphorus-free slag is separated from the lower layer of ferrophosphorus by mechanical slag removal. The phosphorus-free slag obtained after separation has a significantly reduced phosphorus content and can be recycled as a steelmaking raw material. The obtained ferrophosphorus can be further processed to recover phosphorus resources.

[0114] For steel slag with a basicity of 0.8 entering step S3, its temperature is first reduced to below 100℃ by natural air cooling. Then, the cooled steel slag is fed into a crushing device for crushing until the particle size is less than 1mm. The crushed steel slag then enters a magnetic separator, where magnetic separation separates the magnetic iron component (magnetic iron) from the non-magnetic phosphorus-containing slag. The obtained phosphorus-containing slag can be sent to a phosphorus resource recovery unit. The obtained magnetic iron is mixed with carbon powder in different proportions. A portion of the magnetic iron is mixed with a small amount of carbon powder to form high-iron briquettes, another portion is mixed with a medium amount of carbon powder to form medium-iron briquettes, and a third portion is mixed with a larger amount of carbon powder to form micro-iron briquettes, which are then dried.

[0115] Simultaneously, the coking wastewater from the coking plant undergoes biological treatment to obtain coking biochemical wastewater. The pH value of this coking biochemical wastewater is adjusted to, for example, 3.0. Subsequently, this coking biochemical wastewater is introduced into a series of reactor systems. The wastewater first flows through a reactor equipped with high-iron briquettes, then sequentially through a reactor equipped with medium-iron briquettes and a reactor equipped with micro-iron briquettes. During the flow of the wastewater through the briquettes, the iron and carbon in the briquettes form tiny galvanic cells, generating micro-currents that electrochemically degrade organic pollutants in the wastewater. The high-iron briquettes primarily provide iron ions, promoting coagulation and reduction reactions; the medium-iron and micro-iron briquettes, to varying degrees, maintain the continuous micro-electrolysis reaction and may adsorb some pollutants. Through this synergistic effect of the multi-stage briquettes, pollutants such as COD in the coking biochemical wastewater are effectively removed. Finally, the water discharged from the micro-iron briquette reactor is tested, and its water quality indicators meet discharge standards, becoming purified water.

[0116] In this co-processing method, phosphorus in steel slag is effectively removed and recovered, while the iron resources in the steel slag are made into briquettes for the deep purification of coking wastewater. During the purification process, the iron resources in the steel slag are utilized, achieving compliant discharge of the wastewater. The entire process transforms two types of industrial waste into valuable resources and solves their respective pollution problems.

[0117] Application Example 2

[0118] Using the process method described in the application example, 5 kg of converter steel slag with a basicity exceeding 2.0 was taken and mixed with a prepared dephosphorizing agent during the hot process. The main components of the prepared dephosphorizing agent were Al 9%, Si 7.6%, Fe 11%, C 8.5%, Ca 13.7%, and the remainder being oxygen. The fully reacted solid solution was skimmed to obtain phosphorus-free slag and ferrophosphorus. The phosphorus content in the phosphorus-free slag and ferrophosphorus was tested. The phosphorus content in the phosphorus-free slag was 0.1%, and the phosphorus content in the ferrophosphorus was 5%. The phosphorus-free slag was returned to the converter, and the ferrophosphorus continued to circulate to the converter steel slag to adsorb phosphorus in the converter steel slag.

[0119] 5 kg of converter steel slag with a basicity of 1.2 was taken, cooled, and then ground to a particle size ≤0.8 mm using a ball mill. Magnetic separation was then performed under a magnetic field strength of 0.15 T, yielding magnetic iron with a total iron content of 87.7%. Magnetic iron and carbon powder were mixed in a specific ratio to prepare 500 g each of briquettes with iron contents of 85%, 50%, and 6%, resulting in high-iron briquettes, medium-iron briquettes, and micro-iron briquettes. 3 L of coking wastewater after A / O treatment was taken, with a COD of 280 mg / L. The wastewater was sequentially passed through beakers containing high-iron, medium-iron, and micro-iron briquettes, with a residence time of 15 min for each. Air was introduced during the reaction process for aeration. The effluent from the micro-iron device was collected, and its COD content was measured to be 23.27 mg / L.

[0120] Further testing showed that the total phosphorus in the effluent decreased from 12.6 mg / L to 0.21 mg / L, the color removal rate reached 94.3%, and the residual iron ion concentration was 0.38 mg / L, which met the limit requirements of the "Water Pollutant Discharge Standard for Iron and Steel Industry" (GB 13456-2026). Simultaneous analysis of the waste residue after the micro-iron briquetting reaction confirmed that elements such as Al, Fe, and Ca were effectively enriched, fully meeting the quality requirements of the dephosphorizing agent raw materials.

[0121] The dephosphorizing agent preparation process is as follows: using the waste residue after micro-iron briquetting reaction as the base raw material, it is first dried, crushed, and sieved to a particle size ≤0.15 mm. Then, according to the required proportions of Al 9%, Si 7.6%, Fe 11%, C 8.5%, and Ca 13.7%, high-purity aluminum powder (99.9%), electrolytic iron powder (99.5%), active lime (CaO≥92%), and smokeless carbon powder (fixed carbon≥90%) are added and placed in a mixer for uniform stirring for 30 min. Subsequently, it is pressed into Φ10 mm×10 mm cylindrical particles under a pressure of 15 MPa and dried at 200 ℃ for 2 h to finally obtain the dephosphorizing agent product.

[0122] Application Example 3

[0123] Example 2 was repeated, except that the wastewater was not aerated when passing through a beaker containing high-iron pressure briquette, medium-iron pressure briquette and micro-iron pressure briquette in sequence. The water discharged from the micro-iron device was collected and its COD content was tested, which was 69.27 mg / L.

[0124] Comparative Example 1

[0125] Example 2 was repeated, except that the wastewater was passed only through a beaker containing iron-carbon briquettes. The water discharged from this beaker was collected, and its COD content was measured to be 110.32 mg / L. The iron content in the iron-carbon briquettes used was 85%.

[0126] Comparative Example 2

[0127] Example 2 was repeated, except that the wastewater was passed only through a beaker containing an iron-carbon briquette. The water discharged from the beaker was collected, and its COD content was measured to be 154.86 mg / L. The iron content in the iron-carbon briquette used was 50%.

[0128] Comparative Example 3

[0129] Example 2 was repeated, except that the wastewater was passed only through a beaker containing iron-carbon briquettes. The water discharged from this beaker was collected, and its COD content was measured to be 215.67 mg / L. The iron content in the iron-carbon briquettes used was 6%.

Claims

1. A method for co-treating coking wastewater and steel slag, the method comprising the following steps: S1. Perform basicity testing on the steel slag discharged from the converter: when the basicity reaches or exceeds B, proceed to step S2; when the basicity is lower than B, proceed to step S3. S2. Add dephosphorizing agent and water to the steel slag with an alkalinity of B obtained in step S1, and stir to react; separate the solid solution after stirring reaction by slag removal to obtain phosphorus-free slag and ferrophosphorus. S3. Cool and crush converter steel slag with basicity lower than B, and then perform magnetic separation to obtain phosphorus-containing slag and magnetic iron; mix the magnetic iron with carbon powder to form pellets to obtain high-iron pellets, medium-iron pellets, and micro-iron pellets. S4. The coking wastewater is subjected to biological treatment to obtain coking biological wastewater; The pH of the coking biochemical wastewater is adjusted, and then it is passed through high-iron briquette, medium-iron briquette, and micro-iron briquette in sequence to obtain purified water. Wherein, the value of B is 1.0-5.0, preferably 1.5-4, and more preferably 1.8-3.

2. The method according to claim 1, characterized in that: Coking biochemical wastewater sequentially passes through a device equipped with high-iron briquettes, medium-iron briquettes, and micro-iron briquettes; wherein, the waste residue discharged from the device equipped with micro-iron briquettes is used as raw material for the dephosphorizing agent in step S2; and / or The slag phase discharged from the high-speed rail briquetting device and the medium-speed rail briquetting device is used as iron raw material.

3. The method according to claim 2, characterized in that: The dephosphorizing agent mentioned in step S2 is prepared by the following method: the waste residue discharged from the device containing micro iron briquetting pellets is mixed with aluminum powder, iron powder, calcium oxide, carbon powder and silicon oxide, then pelletized and dried to obtain the dephosphorizing agent; Preferably, the composition and content of the waste residue discharged from the device containing micro-iron briquettes are detected, and the mixing ratio of the waste residue discharged from the device containing micro-iron briquettes with aluminum powder, iron powder, calcium oxide, carbon powder and silicon oxide is adjusted so that the dephosphorizing agent contains: Al: 3%~15%, Si: 5%~10%, Fe: 5%~15%, C: 5%~10%, Ca: 10%~15%, with the balance being O.

4. The method according to claims 1-3, characterized in that: In step S2, the solid solution is separated by slag removal to obtain phosphorus-free slag, which accounts for 60%–90% of the mass of the converter steel slag; preferably, the phosphorus-free slag is used as a converter raw material; and / or The ferrophosphate is recycled to steel slag with an alkalinity of 2.0 or above, or used for phosphorus resource utilization. Preferably, the phosphorus content in the phosphorus-free slag is detected. When the phosphorus content in the phosphorus-free slag is less than 1%, the ferrophosphate is recycled to steel slag with an alkalinity of 2.0 or above. When the phosphorus content in the phosphorus-free slag is not less than 1%, the ferrophosphate is transported to the phosphorus resource utilization device.

5. The method according to claims 1-3, characterized in that: In step S3, the cooling is performed using direct counter-current cooling; preferably, the cooling medium is air; and / or Cooling rate is 50~100℃ / min; and / or The temperature of the converter slag after cooling is less than 100℃.

6. The method according to claims 1-3, characterized in that: In step S3, the crushing is performed using a ball mill until the particle size of the converter slag is ≤1mm; and / or The intensity of the magnetic separation is 0.05~0.2 T; and / or The phosphorus-containing slag obtained in step S3 is transported to a phosphorus resource utilization device; and / or The iron content in the magnetic iron is ≥85%.

7. The method according to claims 1-3, characterized in that: In step S3, the mixing ratio of magnetic iron and carbon powder is adjusted so that the iron content in the high-iron briquette is greater than 80 wt%; and / or Adjust the mixing ratio of magnetic iron and carbon powder, so that the iron content in the iron-pressed briquette is 40-70 wt%; and / or The mixing ratio of magnetic iron and carbon powder is adjusted so that the iron content in the micro iron sphere is less than 10 wt%.

8. The method according to claims 1-3, characterized in that: In step S4, the biochemical treatment specifically refers to at least one of A / O, A / A / O, and A / O / A, where A is an anoxic process and O is an aerobic process; and / or Adjust the pH of the coking biochemical wastewater to 2-4.

9. The method according to claims 1-3, characterized in that: In step S4, the coking biochemical wastewater is simultaneously aerated as it passes through high-iron briquette, medium-iron briquette, and micro-iron briquette; preferably, air is used in the aeration process.

10. The method according to claim 3, characterized in that: The particle size of the dephosphorizing agent is 2~8 mm; and / or The moisture content in the dephosphorizing agent is less than 3%.

Images