Coking wastewater treatment method based on gas ratio combined precipitation

Abstract

The invention discloses a coking wastewater treatment method based on gas ratio combined precipitation, which comprises the following steps: adding an acidic reagent and PAM (polyacrylamide) into coking wastewater, and removing small molecular weight toxic substances, specifically thiocyanide and cyanide, and large molecular weight toxic substances, specifically more than ternary phenol and tar in the wastewater through a gas ratio combined precipitation device, the method comprises the following steps: treating the coking wastewater through a GDiAR-F anaerobic reactor, removing three-element or less phenol and macromolecular COD (Chemical Oxygen Demand) through a GDiAR-F anaerobic reactor, removing micromolecular COD, ammonia nitrogen, TN (Total Nitrogen) and TP (Total Phosphorus) in the wastewater through a secondary A / O (Anaerobic / Oxic) device, and finally enabling the effluent to reach the standard, thereby completing the comprehensive and efficient treatment The coking wastewater is treated by adopting a gas ratio combination precipitation device, a GDiAR-F anaerobic reactor and a secondary A / O device, so that the effluent of the coking wastewater is stably discharged in a standard reaching manner. The method does not need to add activated carbon, is simple to operate and low in cost, can greatly reduce the operating cost of each ton of wastewater, and achieves the direct emission standard of Emission Standard of Pollutants in Coking Industry, thereby having wide development potential.

Description

Technical Field

[0001] This invention relates to the field of coking wastewater treatment, and specifically to a method for treating coking wastewater based on gas-to-water ratio sedimentation. Background Technology

[0002] Coking wastewater refers to high-concentration coking wastewater generated during the high-temperature dry distillation of coal, coal gas purification, coal-to-coke production, and the refining and recovery of chemical products. Its properties and composition are mainly affected by many factors such as the properties of raw coal, the production process of the products, and the coal gas purification process. Its main components include phenolic compounds, high concentrations of ammonia nitrogen, and recalcitrant polycyclic aromatic hydrocarbons and heterocyclic compounds, such as indole, naphthalene, and quinoline.

[0003] Currently, there are reports on methods for treating coking wastewater. For example, Chinese patent CN201910887752.7 discloses a method and system for treating coking wastewater, specifically disclosing a process of pretreatment, biochemical treatment, and advanced treatment to ultimately achieve the treatment of coking wastewater meeting the requirements of the "Emission Standard of Pollutants for Coking Chemical Industry" (GB16171-2012). However, the biotoxicity of the (toxic substances) in the biochemically treated wastewater in this method inhibits microbial activity, leading to system instability, poor resistance to shock loads, and sludge bulking problems. The inhibition of microbial activity by biotoxicity is mainly manifested in the following two aspects: 1) Toxic substances with small molecular weights, such as SCN-, CN-, fluorides, and heavy metals. These pollutants can penetrate the cell wall of microorganisms and directly enter the cell membrane, causing electrolyte imbalance in the cell membrane and ultimately damaging the cell nucleus, thus leading to microbial poisoning.

[0004] 2) Toxic substances with large molecular weights, such as phenols and naphthalenes. Prolonged contact with the cell wall can corrode it, causing it to dissolve and thus poisoning microorganisms.

[0005] Chinese patent CN201811198870.9 discloses a method for treating coking wastewater from chemical plants, specifically employing a combination of oil separation, biological treatment (high-load aeration + A / O), and activated carbon adsorption. However, this method has high operating costs, averaging 14-27 yuan per ton of wastewater. Furthermore, the activated carbon is difficult to regenerate after adsorption, and the quality of the coking wastewater fluctuates greatly with changes in coal quality, making stable operation of the wastewater system difficult, with approximately three system failures per year. Summary of the Invention

[0006] In view of the technical problems existing in the background art, the purpose of the present invention is to provide a method for treating coking wastewater based on gas ratio sedimentation.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A first aspect of the present invention provides a coking wastewater treatment system based on gas-to-air ratio sedimentation, comprising an oil separator, an equalization tank, a gas-to-air ratio sedimentation device, and a GDiAR (Gas-to-Air Separation) system. ® -F anaerobic reactor unit and secondary A / O device; wherein The oil separator is used to isolate oil from the raw coking wastewater. The equalization tank is used to homogenize and equalize the volume of the oil-separated wastewater and to adjust the water temperature to 45℃~55℃. The gas-to-water separation and sedimentation device includes a first gas-to-water separation and sedimentation unit for reducing the content of low molecular weight toxic substances and a second gas-to-water separation and sedimentation unit for reducing the content of high molecular weight toxic substances; the first gas-to-water separation and sedimentation unit includes a cyanide removal device; the second gas-to-water separation and sedimentation unit includes a scrubbing tower and an air flotation device. The GDiAR ® -F anaerobic reaction unit, used for anaerobic degradation and removal of ternary and smaller phenols and COD, including GDiAR. ® -F anaerobic reactor and anaerobic inlet tank; The secondary A / O device is used to remove the remaining COD, ammonia nitrogen, TN, and TP from the wastewater after anaerobic treatment, so that the final effluent meets the standards.

[0008] A second aspect of the present invention provides a method for treating coking wastewater based on gas-to-water ratio co-precipitation using the above-described system, comprising the following steps: S1. The raw coking wastewater is separated from the oil in the oil separator and then flows by gravity into the equalization tank for collection. S2. Homogenize and equalize the volume in the equalization tank, and adjust the water temperature to 45℃~55℃. Then pump the water effluent from the equalization tank into the air ratio sedimentation device. S3. Add acidic reagent to the cyanide removal device of the first unit of gas-liquid separation and sedimentation, adjust the pH to 4-6, so that the cyanide and thiocyanate in the wastewater form complexes, then add PAM to form precipitates, and then separate the precipitates into mud and water. The concentration of thiocyanate and cyanide in the effluent after separation is ≤10mg / l. S4. Pump the effluent from the first unit of air-to-water separation and sedimentation in step S3 into the scrubbing tower of the second unit of air-to-water separation and sedimentation. In the scrubbing tower, the phenols with ternary components or more in the wastewater are fully mixed with carbon dioxide and nitrogen and reacted. Then, the wastewater enters the flotation device, and the phenols with ternary components or more in the wastewater and tar are separated and removed from the wastewater by the flotation device. S5, the effluent from the second unit of gas-liquid separation and sedimentation enters GDiAR ® The -F anaerobic reactor unit uses the GDiAR®-F anaerobic reactor to anaerobicly degrade ternary and smaller phenols and COD in wastewater, resulting in volatile phenols ≤20mg / l and COD ≤800mg / l in the effluent.

[0009] The effluent from the S6 and GDiAR®-F anaerobic reactors enters the secondary A / O unit. The secondary A / O unit removes residual COD, ammonia nitrogen, TN, and TP from the wastewater, resulting in effluent that meets the standards.

[0010] Preferably, the acidic reagent is a combination of ferrous sulfate, ferrous chloride and copper chloride. By combining the above three acidic reagents with PAM, the cyanide and thiocyanate levels in coking wastewater can be effectively reduced to ≤10mg / l.

[0011] The present invention has the following beneficial effects: (1) In this invention, acidic reagents and PAM are first added to coking wastewater, and thiocyanates and cyanides, as well as phenols and tar of ternary or higher compounds, are removed from the wastewater through a gas-to-water separation and sedimentation device; then, GDiAR is used to remove these substances. ® The -F anaerobic reactor removes ternary and smaller phenols and COD from the wastewater, followed by a secondary A / O unit to remove small-molecule COD, ammonia nitrogen, TN, and TP. These steps work synergistically, ensuring the final effluent meets the direct discharge standards of the "Emission Standard for Pollutants from Coking Industry" (GB16171-2012), thus achieving comprehensive and efficient treatment of coking wastewater. Specifically, for low-molecular-weight toxic substances (such as SCN-, CN-, etc.), this invention employs a complexation method, transforming them into large-molecule complexes that cannot penetrate cell walls. For high-molecular-weight toxic substances (such as phenols, naphthalene, etc.), this invention uses an air flotation device, allowing microorganisms to decompose these toxic substances for a longer period than cell wall corrosion, thereby reducing toxicity and degrading pollutants. Once the effects of toxic substances are addressed, pollutants can be readily degraded by microorganisms, thus solving the fundamental problem.

[0012] (2) This invention does not require the addition of activated carbon, is simple to operate, and has low cost. The total operating cost per ton of wastewater, excluding depreciation, can be as low as 9 yuan / ton, which is about half the operating cost of traditional processes, thus solving the problem of high operating costs of existing coking wastewater treatment processes. (3) The Prussian blue precipitate, tar, biogas and other substances obtained by the treatment method of the present invention have certain utilization value and can be comprehensively utilized.

[0013] (4) This invention achieves carbon reduction while degrading pollutants and reduces ESG emission indicators. The final effluent meets environmental protection requirements. This is an innovative treatment method for the current coking industry and therefore has broad development potential. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of a coking wastewater treatment method based on gas-to-water ratio sedimentation. Figure 2 A schematic diagram of the process for the secondary A / O unit; Figure 3 Images of raw water, anaerobic effluent, and final effluent from the secondary A / O unit; Figure 4 For GDiAR ® - Images of the influent and effluent from the F-type anaerobic reactor; Detailed Implementation In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention may be implemented in other embodiments without these specific details.

[0016] Example 1 Reference Figure 1 and Figure 2 A coking wastewater treatment system based on gas-to-air ratio sedimentation includes an oil separator, an equalization tank, a gas-to-air ratio sedimentation device, and a GDiAR (Gas-to-Air Separation) system. ® -F anaerobic reactor unit and secondary A / O device; wherein (1) Oil separator The coking (phenol and ammonia) raw water is pressure-sent from the workshop to the wastewater treatment station. After passing through the oil separator, most of the oil is separated, and then it flows by gravity into the equalization tank for collection.

[0017] (2) Equalization tank The wastewater after oil separation is homogenized and its volume is equalized in the equalization tank, which is simultaneously agitated by a stirrer and then covered. A pipeline is led from the effluent pump of the equalization tank into the air-water separation and settling unit. The water temperature is adjusted to 45℃~55℃.

[0018] (3) Gas ratio settling device The gas-to-water separation and sedimentation unit comprises a first unit and a second unit. Effluent is pumped from the equalization tank into the first unit to reduce the content of low-molecular-weight toxic substances (such as thiocyanate and cyanide). This unit includes a cyanide removal device, which performs pH adjustment, cyanide removal, and fluoride removal in this area. Specifically, acidic reagents, namely ferrous sulfate, ferrous chloride, and copper chloride, are added to the cyanide removal device, and the pH is adjusted to 4-6. This causes the cyanide and thiocyanate in the wastewater to form complexes, which further react with PAM to form Prussian blue precipitate. This precipitate, classified as solid waste, can be used in the dye industry to turn waste into treasure, achieving comprehensive utilization. Furthermore, the formation of complexes does not affect the normal metabolism of microorganisms. After treatment in this unit, the concentration of thiocyanate and cyanide in the effluent is ≤10mg / l. Then, a booster pump is added to pump the effluent from the first air-to-water separation unit to the second air-to-water separation unit for further treatment. This unit includes a scrubbing tower and a micronaphthalene flotation (MNA) device. This unit is used to reduce the content of high molecular weight toxic substances (such as phenols with more than three molecular weight components and tar). Specifically, the effluent from the first air-to-water separation unit first enters the scrubbing tower for treatment. In this area, phenols with more than three molecular weight components in the effluent are fully mixed with carbon dioxide and nitrogen and react. Then, it enters the MNA flotation device to remove organic pollutants such as phenols with more than three molecular weight components, naphthalene, indole, quinoline, suspended solids (SS), and tar. The removed organic pollutants are collected in a sludge tank. After solid separation, the clear effluent flows by gravity to the anaerobic influent tank. The COD composition of the clear effluent is acetic acid and propionic acid, and the alkalinity is 1000–1500 mg / l.

[0019] (4) GDiAR ® -F Anaerobic Reactor GDiAR ® -F anaerobic reactor unit includes anaerobic influent tank and GDiAR ® -F anaerobic reactor composition, via GDiAR ® The -F anaerobic reactor unit anaerobicly degrades COD and phenols in wastewater, ensuring that the effluent meets the requirements of volatile phenols ≤20mg / l and COD ≤800mg / l.

[0020] Specifically, the wastewater effluent after treatment in the second unit of gas separation and sedimentation flows by gravity into the anaerobic influent tank. In the anaerobic influent tank, nutrients, alkali, and trace elements are added, while the wastewater temperature is controlled at 35℃~38℃ to provide the necessary environment for subsequent anaerobic treatment. Then, the wastewater is sent to GDiAR via an anaerobic feed pump. ® Anaerobic degradation is carried out in the -F anaerobic reactor, and the feed flow rate of the anaerobic reactor is controlled by frequency conversion to maintain a stable input flow rate.

[0021] GDiAR ®The -F anaerobic reactor is equipped with an anaerobic circulation pump that continuously recirculates a portion of the wastewater from the top of the reactor back to the inlet pipe. This wastewater mixes with the inlet water before entering the reactor. The large volume of circulation ensures a high upward flow velocity, guaranteeing effective mixing within the reactor. The flow rate, pH, and temperature of the circulating water are continuously monitored.

[0022] In GDiAR ® In the -F anaerobic reactor, ternary and smaller organic pollutants such as phenols and COD in the wastewater are converted into biogas by anaerobic sludge, thereby purifying the wastewater. The anaerobic wastewater, anaerobic sludge, and biogas are then transported to a reactor located in the GDiAR... ® The three-phase separation module at the top of the reactor separates the wastewater, and the treated effluent overflows from the reactor and flows by gravity into the anaerobic sedimentation tank for sedimentation treatment. The sludge is returned to the GDiAR. ® In the -F anaerobic reactor, the supernatant flows by gravity into the subsequent secondary A / O unit. This unit is designed to provide carbon source and alkalinity for subsequent processes, significantly reducing the operating costs of coking wastewater.

[0023] The GDiAR®-F anaerobic reactor produces biogas during the removal of ternary and smaller phenols and COD, which is collected at the top of the reactor. Biogas falls under the category of biogas (BNG) and, after purification, can be used for various purposes, including: biogas steam production, biogas power generation, replacing some coke oven gas in production, and liquefied natural gas (LNG) production after further purification. As green methane, it achieves carbon emission reduction and contributes to ESG emission reduction targets. (4) Secondary A / O device The secondary A / O unit includes a primary A / O unit (comprising a primary anaerobic tank and a primary anoxic tank) and a secondary A / O unit (comprising a secondary anoxic tank and a secondary anaerobic tank). This secondary A / O unit further removes COD from the wastewater, while simultaneously ensuring that ammonia nitrogen, total nitrogen, and total phosphorus levels meet required standards.

[0024] Specifically, after effluent from the anaerobic sedimentation tank, the wastewater flows by gravity into the secondary A / O unit. A sludge pump at the bottom of the anaerobic sedimentation tank returns the sludge to the anaerobic reactor. Biogas is produced in the anaerobic reactor; the amount of biogas produced depends on the amount of COD removed during anaerobic treatment. The more COD removed, the more biogas produced. The biogas is then processed in the GDiAR (Gas Dioxide) reactor. ® - The biogas collected at the top of the anaerobic reactor has considerable economic value and can be utilized in many ways.

[0025] After effluent from the anaerobic sedimentation tank, it enters the secondary A / O unit along with other wastewater. Because the COD of the anaerobic effluent is greatly reduced, and the COD composition is mainly acetic acid and propionic acid, it can be used as a carbon source for the subsequent secondary A / O unit. Therefore, the biological retention time will be greatly shortened to 60 hours, and the effluent from the secondary A / O sedimentation tank will meet the discharge standards.

[0026] This invention also provides a method for treating coking wastewater based on gas-to-earth sedimentation using the above-described system, employing gas-to-earth sedimentation + GDiAR. ® - An anaerobic reactor combined with a secondary A / O unit treats coking wastewater, ensuring that the final coking wastewater effluent consistently meets discharge standards. Specifically, this includes the following steps: S1. The raw coking wastewater (its physicochemical parameters are shown in Table 1) is separated from most of the oil in an oil separator, and then flows by gravity into an equalization tank for collection. S2. Homogenize and equalize the volume in the equalization tank, and adjust the water temperature to 45℃~55℃. Then pump the water effluent from the equalization tank into the air ratio sedimentation device. S3. Ferrous sulfate, ferrous chloride, and copper chloride are added to the cyanide removal unit of the first gas-liquid separation and precipitation unit to adjust the pH to 4-6, causing cyanide and thiocyanate in the wastewater to form complexes. Then, PAM is added for precipitation to obtain Prussian blue precipitate. The obtained Prussian blue precipitate is separated from the water. After this step, the concentration of thiocyanate and cyanide in the effluent is ≤10mg / l. The obtained Prussian blue precipitate (which is solid waste) can be recycled and applied to the dye industry to turn waste into treasure.

[0027] S4. The effluent from the first unit of air-to-water separation and sedimentation in step S3 is pumped into the scrubbing tower of the second unit of air-to-water separation and sedimentation. In the scrubbing tower, the phenols with ternary components or higher in the wastewater are fully mixed with carbon dioxide and nitrogen and react. After the reaction is complete, the wastewater enters the flotation unit. The flotation unit separates and removes the phenols with ternary components or higher and the tar from the wastewater. The phenols with ternary components or higher are discharged from the bottom of the flotation unit (the phenols formed are crude phenols, which have certain utilization value and can be recycled). The effluent (the main components of COD in which are acetic acid and propionic acid, and the alkalinity is 1000-1500 mg / L) overflows from the top of the flotation unit. The tar (which is a resource and can be comprehensively utilized) is scraped off from the top of the flotation unit by the slag scraping system. S5, the effluent from the second unit of gas-liquid separation and sedimentation enters GDiAR ®In the -F anaerobic reactor unit, ternary and smaller phenols and COD in the wastewater are anaerobicly degraded using the GDiAR®-F anaerobic reactor, resulting in volatile phenols ≤20mg / l and COD ≤800mg / l in the effluent. The parameters of the effluent are shown in Table 2. This step provides carbon source and alkalinity for subsequent processes, avoids the addition of carbon source reagents, saves on alkalinity reagents, and greatly reduces the operating cost of coking wastewater.

[0028] Biogas is generated during the removal of ternary and smaller phenols and COD using the GDiAR®-F anaerobic reactor. Biogas falls under the category of BNG (Biogas Non-Gross Gas) and can be comprehensively utilized after purification. It can be used for: biogas steam production, biogas power generation, biogas to replace part of the coke oven gas in production, and biogas purification to produce LNG. It is green methane, which achieves carbon emission reduction and is beneficial to ESG emission reduction targets.

[0029] S6. The effluent from the GDiAR®-F anaerobic reactor is passed through a secondary A / O unit to remove residual COD, ammonia nitrogen, TN, and TP, resulting in final effluent that meets the direct discharge standards in the "Emission Standard of Pollutants for Coking Industry" (GB16171-2012). Specific indicators are shown in Table 3. This step does not require the addition of activated carbon, saving on activated carbon reagent costs.

[0030] The above treatment process also revealed that the initial color of the raw water was dark brown. After each treatment step, the effluent from the anaerobic treatment turned green, and the A / O terminal effluent became clear with a slight yellow tint (see...). Figure 3 The anaerobic influent is reddish-brown, and the effluent turns green after anaerobic treatment (see...). Figure 4 ).

[0031] Table 1. Raw water parameters

[0032] Table 2. Water parameters obtained from the GDiAR®-F anaerobic reactor unit

[0033] Table 3. Parameters of effluent from the secondary A / O unit

Claims

1. A system for treatment of coking wastewater based on air ratio combustion, characterized in that, The device comprises an oil separation tank, a regulating tank, a gas ratio combined settling device, and a GDiAR ® The device comprises an anaerobic reaction unit and a secondary A / O device. The oil separation tank is used for separating oil in the coking wastewater raw water. The adjusting tank is used for homogenizing and equalizing the wastewater after oil separation and adjusting the water temperature to 45-55 DEG C. The air ratio coagulation and sedimentation device comprises an air ratio coagulation and sedimentation first unit for reducing the content of small molecular weight toxic substances and an air ratio coagulation and sedimentation second unit for reducing the content of large molecular weight toxic substances; the air ratio coagulation and sedimentation first unit comprises a cyanide removal device; the air ratio coagulation and sedimentation second unit comprises a washing tower and an air flotation device; the small molecular weight toxic substances comprise thiocyanide and cyanide; the large molecular weight toxic substances comprise phenol and tar with three or more than three. The GDiAR ® - An anaerobic reaction unit for anaerobically degrading and removing phenol and COD of three or less, including the GDiAR ® - An anaerobic reactor and an anaerobic influent tank; The secondary A / O device is used for removing the residual COD, ammonia nitrogen, TN and TP in the wastewater after anaerobic treatment, so that the final effluent meets the standard.

2. A method for treatment of coking wastewater based on air ratio combustion using the system of claim 1, characterized by, The method comprises the following steps: S1, separating oil in the coking wastewater raw water through the oil separation tank, and then flowing into the adjusting tank for collection; S2, homogenizing and equalizing and adjusting the water temperature to 45-55 DEG C in the adjusting tank, and then pumping the effluent of the adjusting tank into the air ratio coagulation and sedimentation device; S3, adding an acidic reagent into the cyanide removal device of the air ratio coagulation and sedimentation first unit to adjust the pH to 4-6, so that the cyanide and thiocyanide in the wastewater form a complex, then adding PAM to form a precipitate, and then separating the precipitate from the wastewater, and the concentration of the cyanide and thiocyanide in the effluent after separation is less than or equal to 10 mg / l; S4, pumping the effluent after the treatment of the air ratio coagulation and sedimentation first unit in step S3 into the washing tower of the air ratio coagulation and sedimentation second unit, fully mixing and reacting the phenol with three or more than three in the wastewater with carbon dioxide and nitrogen in the washing tower, and then entering the air flotation device, and separating and removing the phenol with three or more than three and tar in the wastewater through the air flotation device; S5, the effluent after being treated by the second unit is introduced into GDiAR ® -F anaerobic reaction unit, the phenol and COD of three or less than three in the wastewater are treated by GDiAR®-F anaerobic reactor, so that the volatile phenol in the effluent is ≤20 mg / l, and the COD is ≤800 mg / l. S6, pumping the effluent after the treatment of the GDiAR®-F anaerobic reaction unit into the secondary A / O device, removing the residual COD, ammonia nitrogen, TN and TP in the wastewater through the secondary A / O device, and obtaining the effluent meeting the standard.

3. The method of treating coking wastewater according to claim 2, characterized in that, The acidic reagent is a combination of ferrous sulfate, ferrous chloride and copper chloride.

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