A method for treating semicoke wastewater

Abstract

The present application belongs to the technical field of water treatment, and relates to a processing method of semi-coke wastewater. The processing method is aimed at the characteristics of high content of coke powder, high concentration of chemical oxygen demand and high content of phenol in the semi-coke wastewater. The wastewater is subjected to multi-stage processing, and the processing technological process is chemical separation, reverse reaction, centrifugal separation, pyrolysis, acid precipitation and reuse. The method removes phenol by extraction, separates and recycles coke powder in the wastewater, solves the problems of coke powder blocking equipment and reducing the efficiency of reagent application caused by the three-phase emulsification of coke powder-separating agent-water, and realizes the resource utilization of phenolic compounds and coke powder.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for treating semi-coke wastewater. Background Technology

[0002] Semi-coke wastewater is generated during the low-temperature carbonization (approximately 550-650℃) processing of coal. It contains recalcitrant organic pollutants such as phenol, tar, and coke dust. This wastewater is complex, containing phenol concentrations of 15,000-20,000 mg / L and a chemical oxygen demand (COD) of approximately 80,000. It also contains a large amount of coke dust, making it difficult to separate by filtration.

[0003] Existing treatment methods all involve single removal methods, which are combined to remove pollutants sequentially.

[0004] For semi-coke wastewater, conventional treatment methods typically include two stages: phenol and ammonia recovery pretreatment and biological treatment. The phenol and ammonia recovery pretreatment unit not only serves as a safety net for the subsequent biological treatment system, directly impacting its operation, but also determines the recovery of valuable resources from the semi-coke wastewater, making it crucial for successful wastewater treatment. Traditional phenol and ammonia recovery processes for semi-coke wastewater often employ a combination of stripping distillation and extraction. Acid removal and ammonia removal often utilize stripping, leveraging the different solubilities of acidic gases and ammonia, as well as the principle of decreased solubility at high temperatures, to remove and recover acidic gases from the wastewater. In the extraction process for phenol removal, traditional extractants include organic extractants such as ethyl acetate, diisopropyl ether, methyl isobutyl ketone (MIBK), and tributyl phosphate (TBP).

[0005] To achieve the above objectives, CN107434335B adds a pre-extraction oil removal treatment before stripping deacidification and deammoniation to control the clogging of the stripping tower; by using a highly efficient compound extractant to reduce the solubility of the extractant in water, the wastewater after extraction treatment needs to be evaporated again, thus reducing operating energy consumption; by combining the purification treatment of the phenol-rich organic phase after pre-extraction oil removal with alkaline washing treatment, the acidic gases extracted from the phenol-rich organic phase can be removed, and the extractant, light oil, and heavy oil in the phenol-rich organic phase can be separated to ensure the purity of crude phenol.

[0006] However, the aforementioned technologies have excessively high requirements for pre-extraction wastewater and present problems with cumbersome and lengthy petroleum tar treatment processes. Furthermore, the technologies only extract phenol and do not analyze or treat the coke powder components commonly found in semi-coke wastewater to avoid the impact of coke powder in actual production. Semi-coke wastewater contains ultrafine coke powder, accounting for approximately 1.4% of the wastewater mass, mostly in nanoscale powder form. Taking a daily flow of 2000 t / d of semi-coke wastewater as an example, the amount of coke powder carried is as high as 28 t / d, which cannot be removed by filtration, coagulation, and sedimentation processes. This easily causes blockages in equipment pipelines, especially in packed towers, greatly reducing treatment efficiency. Simultaneously, the coke powder mixes with the crude phenol recovered by existing technologies, affecting the quality of the crude phenol and resulting in resource waste.

[0007] Based on the aforementioned deficiencies, this application provides a novel method for treating semi-coke wastewater, which addresses the characteristics of high coke powder content, high chemical oxygen demand (COD) concentration, and high phenol content, thereby overcoming the shortcomings of existing technologies and improving wastewater treatment efficiency. Summary of the Invention

[0008] This invention addresses the shortcomings of existing technologies by developing a novel method for treating semi-coke wastewater. It not only realizes the resource utilization of coke powder and phenol in the wastewater but also improves the efficiency of wastewater treatment. The treatment process includes chemical separation, reverse reaction, centrifugal separation, pyrolysis, acid precipitation, and reuse.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A method for treating semi-coke wastewater, characterized by comprising the following steps:

[0011] (1) Chemical separation: Adjust the pH of the wastewater to 1-4, add a separating agent, and after the reaction is completed, let it stand to separate into layers to obtain a double-layer solution, wherein the lower layer is the aqueous phase and the upper layer is the separated phase; the separating agent includes a complexing agent, a co-solvent and a diluent, and by volume ratio, the complexing agent and the co-solvent are 10-40% and 10-20% respectively, and the remainder is a diluent;

[0012] (2) Reverse reaction: Add an alkaline solution to the separated phase. After the reaction is completed, allow the mixture to stand and separate into three layers to obtain a three-layer solution. The lower layer is the first recovery phase, the middle layer is the coke powder enrichment phase, and the upper layer is the separating agent regeneration phase.

[0013] (3) Centrifugal separation: The above-mentioned coke powder enriched phase is centrifuged to obtain three phases, wherein the lower solid phase is a solid, the middle liquid phase is the second recovery phase, and the upper liquid phase is the regenerated phase of the separating agent;

[0014] (4) Pyrolysis: The solids described in step (3) are pyrolyzed and separated to recover the regenerated phase of the separating agent and the coke powder respectively;

[0015] (5) Acid precipitation: After mixing the first recovery phase described in step (2) and the second recovery phase described in step (3), add an acidic solution. After the reaction is completed, let it stand and separate into layers. The upper layer is phenol and the lower layer is a salt-containing recovery phase. The salt-containing recovery phase is treated as hazardous waste.

[0016] (6) Reuse: The regenerated phase of the separating agent in steps (2), (3) and (4) is recycled and applied to step (1) as a separating agent.

[0017] The inventors discovered that the main pollutants in semi-coke wastewater are tar, phenol, and coke powder. Since the coke powder is an ultrafine powder that cannot be filtered, most existing technologies do not treat the coke powder and avoid its influence. Therefore, this application first uses chemical separation to extract the wastewater. The main components of the resulting upper separated phase include separating agent, phenol, coke powder, light oil, and organic matter. All the coke powder enters the separated phase and is evenly distributed.

[0018] The inventors discovered that adjusting the pH of the semi-coke wastewater to 1-4 before extraction enhances the extraction effect. This allows phenolic compounds in the wastewater to exist in the form of phenolic hydroxyl groups. The solubility of heavy oil, light oil, and coal tar decreases under acidic conditions, facilitating effective contact with coke powder and ensuring uniform distribution in the separating agent during extraction. Simultaneously, the binding force of phenolic pollutants to the separating agent forms large molecular complexes, resulting in maximum steric hindrance in the separated phase, ensuring a uniform and stable distribution of coke powder. If the pH is greater than 4, phenolic compounds exist in the form of sodium phenolate, significantly reducing their binding force with the separating agent and decreasing the extraction effect. If the pH is less than 1, the solubility of heavy oil, light oil, and coal tar is extremely low, causing the coke powder in the wastewater to adsorb and clump together, hindering extraction and dispersion. Furthermore, strong acidity affects the quality of the alkaline solution required for the subsequent reverse reaction.

[0019] The separating agent includes a complexing agent, a co-solvent, and a diluent. By volume ratio, the complexing agent and the co-solvent are 10-40% and 10-20%, respectively, with the remainder being a diluent. If the proportion of the complexing agent is too low, the number of phenolic compounds extracted at the same extraction ratio will be reduced, resulting in poor extraction effect. If the proportion is too high, other components will account for a smaller proportion, more complexes will be formed during extraction, and problems such as agglomeration and stratification will occur. If the co-solvent is too low, the extractant will easily stratify. If the co-solvent is too high, it will affect the reverse reaction effect.

[0020] To improve the complexation extraction effect of phenolic pollutants in wastewater, preferably, in step (1), a complexing agent with a strong complexing effect on phenolic hydroxyl groups is used, the complexing agent including one or more of N503, tributyl phosphate, and N-lauro(trialkylmethyl)amine; the cosolvent helps to uniformly disperse the complexing agent, which improves both the utilization rate of the complexing agent and the reaction rate, preferably using a cosolvent with strong compatibility, including at least one of 2-heptadecyl alcohol, sec-octanol, and isochetol; the diluent is at least one of inexpensive and readily available aviation kerosene or diesel oil.

[0021] Furthermore, in order to ensure the stability and completeness of the extraction binding during the chemical separation process, the reaction time between the separating agent and the wastewater is 5-45 min; preferably 30 min.

[0022] The inventors discovered that after chemical separation in step (1), the pollutants are mainly concentrated in the separation phase. In step (2), by adding an alkaline solution to the separation phase to carry out a reverse reaction, a three-layer solution can be obtained, consisting of a lower layer being the first recovery phase, a middle layer being the coke powder enrichment phase, and an upper layer being the separating agent regeneration phase. Phenol in the separation phase is dissolved in the alkaline solution in the form of sodium phenolate and is located in the lower first recovery phase. The main components of the first recovery phase, in addition to sodium phenolate, also include sodium hydroxide and coal tar. Coke powder has adsorption properties and easily adsorbs the extractant and coal tar, so it is in the middle layer during the separation process. The components of the separating agent regeneration phase are similar to those of the initial separating agent and are located in the upper layer.

[0023] Preferably, the alkaline solution can be any inorganic alkali, such as a 6-32 wt% sodium hydroxide solution, and the volume ratio of the separated phase to the alkaline solution is (4-10):1; preferably 8:1; preferably a high-concentration sodium hydroxide solution, preferably 16-20 wt%. In the reverse reaction process, by controlling the concentration of the alkaline solution and its volume ratio to the separated phase, the entire mixed liquid can reach a certain alkalinity, which enhances the organic combination of phenol and the added sodium hydroxide solution in the separated phase, increases the ion concentration of the solution, and improves the density of the recovered phase. However, if the content of the alkaline solution is too high, it will lead to a high salt concentration in the recovered phase, which is easy to precipitate and block the pipeline. If it is too low, it will lead to an increase in the amount of recovered phase, and the low concentration will affect the concentration of phenol extracted in the subsequent process.

[0024] Furthermore, considering the solubility of sodium phenolate in the recovery phase, the temperature during the reaction in step (2) is controlled at 20-60℃; preferably 50-55℃. By increasing the temperature to ensure the solubility of phenol, the distribution of coke powder in the recovery phase can be reduced while minimizing the amount of recovery phase.

[0025] The inventors discovered that by centrifugation, coke powder can be separated from the coke powder enrichment phase. The lower solid phase mainly consists of coke powder and a regenerated phase of the separating agent adsorbed by the coke powder. The second recovery phase is mainly a recovery phase adsorbed by the coke powder enrichment phase, and its composition is similar to that of the first recovery phase. The upper liquid phase is the regenerated phase of the separating agent.

[0026] In step (3), the separating agent and the recovered phase are incompatible. The centrifugation speed needs to be sufficient to break the adsorption force of the coke powder, so that a large amount of the separating agent and the recovered phase are separated from the coke powder enriched phase. The centrifugation speed is preferably 2000-8000 r / min, and the time is 2-10 min; preferably 2500 r / min, centrifugation for 3 min. If the centrifugation speed is too low or the time is too short, the stratification will be indistinct, and the coke powder will be partially distributed in the middle layer and mixed with the second recovered phase. If the centrifugation speed is too high or the time is too long, salt will be deposited in some of the recovered phase and mixed with the coke powder, reducing the purity of the coke powder.

[0027] The inventors discovered that the solids separated in step (3) contain a regenerated phase of the separating agent. In order to ensure that the components of the separating agent are consistent with the original ratio, this application selects to control the pyrolysis temperature in step (4) to 180-420℃, preferably 320-370℃. If the pyrolysis temperature is too low, the separating agent will remain in the coke powder. If it is too high, some components of the separating agent may become ineffective and resources may be wasted.

[0028] The inventors discovered that the main components of the first recovery phase in step (2) and the second recovery phase in step (3) are sodium phenolate. After mixing, the pH is adjusted to 0.5-2 by adding an acidic solution, which completely converts sodium phenolate into phenol. By utilizing the large difference in solubility between phenol and sodium phenolate, phenol is precipitated, thus obtaining a layered solution with an upper layer of phenol and a lower layer of salt-containing recovery phase. The salt-containing recovery phase is treated as hazardous waste. However, if the pH is too low, it will lead to resource waste; if it is too high, some sodium phenolate will not react and cannot precipitate, resulting in a reduction in resource utilization. The temperature during the reaction process is controlled at 20-60℃, preferably 40-50℃. The reaction time is 20-60 min, preferably 30-45 min. If the temperature is too high, phenol and water will be miscible and cannot be separated. If the temperature is too low, the high-concentration phenol solution is prone to coagulation into lumps. The acidic solution can be any inorganic acid, such as hydrochloric acid or sulfuric acid.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] (1) The method of the present invention removes phenol by extraction and separates and recycles coke powder in wastewater, which solves the problems of equipment blockage by coke powder and reagent loss and reduced reagent utilization efficiency caused by three-phase emulsification of coke powder-separating agent-water, and realizes high-quality resource recovery of phenolic compounds and coke powder.

[0031] (2) After complexation extraction, the coke powder in the wastewater is back-extracted, and the separating agent and coke powder are recovered by centrifugation combined with pyrolysis. The resulting coke powder solid can be used as a resource product, and the quality of the recovered coke powder is high.

[0032] (3) Compared with the existing technology, the extraction method is only for the recovery of phenol and cannot solve the many problems caused by coke powder to the extraction process. This application has lower requirements for wastewater before extraction and does not need to separate tar (petroleum light oil and heavy oil) through oil separation treatment, so that the entire process can be reduced to a certain extent. This technology is not a single extraction technology, but a process flow that separates phenol and coke powder at the same time. Attached Figure Description

[0033] Figure 1 Here is a process flow diagram of a method for treating semi-coke wastewater according to the present invention: Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] <Example 1>

[0036] The wastewater was taken from the semi-coke wastewater production workshop of a coal chemical plant in Xinjiang. The water quality was as follows: COD=75376mg / L, pH=8, phenol=18032mg / L.

[0037] The specific processing steps are as follows:

[0038] (1) Take 500ml of water sample, add hydrochloric acid to adjust pH=2, add 200ml of separating agent; the separating agent ratio is 80ml of tributyl phosphate, 40ml of 2-octanol, and 80ml of aviation kerosene; after stirring for 30 minutes, place it in a separatory funnel and let it stand for 10 minutes before separating the liquid. The lower layer is the wastewater after extraction, which contains a small amount of coke powder. The test data are COD=11194mg / L, phenol=565mg / L, and pH=0.5. The upper layer is the separation phase, which is about 214ml, and the coke powder is evenly dispersed in the separation phase.

[0039] (2) Place the separated phase in a 500ml beaker, add 26ml of 32% sodium hydroxide solution, heat to 50℃, stir for 30min, then place in a separatory funnel and let stand for 10min to separate the phases. The lower layer is the first recovery phase with a volume of 51ml. The solution has a pH of 14, COD of 641820mg / L, and phenol concentration of 174670mg / L. The middle layer is the coke powder enrichment phase. The upper layer is the regenerated phase of the separating agent.

[0040] (3) Take the coke powder enriched phase from step (2) into a centrifuge tube and separate it using centrifugation. Set the centrifugation speed to 2500 r / min and the centrifugation time to 3 min. After centrifugation, take out the centrifuge tube. In the centrifuge tube, there is an upper clear separation agent regeneration phase, a middle layer of the second recovery phase, where COD=642200 mg / L and phenol=176000 mg / L, and a lower layer of solid coke powder.

[0041] (4) Place the solid coke powder from step (3) in a small pyrolysis furnace, heat it to 370°C, fill the front end with nitrogen gas, and cool water absorbs the separating agent at the rear end. Pyrolysis treatment is performed to obtain coke powder and the regenerated phase of the separating agent respectively.

[0042] (5) After mixing the first recovery phase in step (2) and the second recovery phase in step (3), place them in a beaker, add hydrochloric acid to adjust the pH to 0.5, heat to 50°C, stir for 30 min, place in a separatory funnel and let stand for 10 min to separate the layers. The lower layer is the salt recovery phase with COD = 288945 mg / L and phenol = 40133 mg / L, and the upper layer is the phenol solution.

[0043] (6) Reuse: The regenerated phase of the separating agent in steps (2), (3) and (4) is recycled and applied to step (1) as a separating agent.

[0044] In this embodiment, the coke powder content recovered in step (4) is 98%, and the phenol content recovered in step (5) is 95%, which is a qualified product, and the phenol recovery amount is 7341mg.

[0045] <Example 2>

[0046] The wastewater source is the same as in Example 1.

[0047] The specific processing steps are as follows:

[0048] (1) Take 500 ml of water sample, add hydrochloric acid to adjust pH=4, and add 100 ml of separating agent; the separating agent ratio is 30 ml of N-lauro(trialkylmethyl)amine, 10 ml of 2-octanol, and 60 ml of aviation kerosene; stir for 30 minutes, place in a separatory funnel and let stand for 10 minutes before separating. The lower layer is the wastewater after extraction, which contains a small amount of coke powder. The test data are COD=25836 mg / L, phenol=1265 mg / L, and pH=0.5. The upper layer is the separating phase, about 210 ml, in which coke powder is evenly dispersed.

[0049] (2) Place the separated phase in a 500ml beaker, add 26ml of 32% sodium hydroxide solution, heat to 50℃, stir for 30min, then place in a separatory funnel and let stand for 10min to separate the phases. The lower layer is the first recovery phase with a volume of 50ml. The solution has pH=14, COD=611560mg / L, and phenol=206300mg / L. The middle layer is the coke powder enrichment phase. The upper layer is the separation agent regeneration phase.

[0050] (3) Take the coke powder enriched phase from step (2) into a centrifuge tube and separate it using centrifugation. Set the centrifugation speed to 8000 r / min and the centrifugation time to 2 min. After centrifugation, take out the centrifuge tube. In the centrifuge tube, there is an upper clear separating agent regeneration phase, a middle layer of the second recovery phase, in which COD=612200 mg / L and phenol=206000 mg / L, and a lower layer of solid coke powder.

[0051] (4) In step (3), the solid coke powder is placed in a small pyrolysis furnace and heated to 400°C. Nitrogen gas is introduced at the front end and cooling water is used to absorb the separating agent at the rear end. The pyrolysis process is used to obtain coke powder and the regenerated phase of the separating agent respectively.

[0052] (5) After mixing the first recovery phase in step (2) and the second recovery phase in step (3), place them in a beaker, add hydrochloric acid to adjust the pH to 2, heat to 60°C, stir for 40 min, place in a separatory funnel and let stand for 10 min to separate the layers. The lower layer is the salt recovery phase with COD=178945mg / L and phenol=45142mg / L, and the upper layer is the phenol solution.

[0053] (6) Reuse: The regenerated phase of the separating agent in steps (2), (3) and (4) is recycled and applied to step (1) as a separating agent.

[0054] In this embodiment, the coke powder content recovered in step (4) is 98.2%, and the phenol content recovered in step (5) is 95.6%, which are qualified products, and the phenol recovery amount is 8621mg.

[0055] <Example 3>

[0056] The wastewater source is the same as in Example 1.

[0057] The specific processing steps are as follows:

[0058] (1) Take 500ml of water sample, add hydrochloric acid to adjust pH=1, and add 200ml of separating agent; the separating agent ratio is 60ml of N-lauro(trialkylmethyl)amine, 40ml of 2-octanol, and 100ml of aviation kerosene; stir for 30 minutes, place in a separatory funnel and let stand for 10 minutes before separating. The lower layer is the wastewater after extraction, which contains a small amount of coke powder. The test data are COD=12188mg / L, phenol=610mg / L, and pH=0.5. The upper layer is the separating phase, about 215ml, in which coke powder is evenly dispersed.

[0059] (2) Place the separated phase in a 500ml beaker, add 70ml of 6% sodium hydroxide solution, heat to 50℃, stir for 30min, then place in a separatory funnel and let stand for 10min to separate the phases. The lower layer is the first recovery phase with a volume of 100ml. The solution has pH=14, COD=315940mg / L, and phenol=87900mg / L. The middle layer is the coke powder enrichment phase. The upper layer is the separation agent regeneration phase.

[0060] (3) Take the coke powder enriched phase from step (2) into a centrifuge tube and separate it using centrifugation. Set the centrifugation speed to 5500 r / min and the centrifugation time to 2 min. After centrifugation, take out the centrifuge tube. In the centrifuge tube, there is an upper clear separating agent regeneration phase, a middle layer of the second recovery phase, in which COD=312890 mg / L and phenol=87820 mg / L, and a lower layer of solid coke powder.

[0061] (4) In step (3), the solid coke powder is placed in a small pyrolysis furnace and heated to 320°C. Nitrogen gas is introduced at the front end and cooling water is used to absorb the separating agent at the rear end. The pyrolysis process is used to obtain coke powder and the regenerated phase of the separating agent respectively.

[0062] (4) After mixing the first recovery phase in step (2) and the second recovery phase in step (3), place them in a beaker, add hydrochloric acid to adjust the pH to 0.5, heat to 30°C, stir for 25 min, place in a separatory funnel and let stand for 10 min to separate the layers. The upper layer is phenol solution and the lower layer is salt recovery phase with COD = 194119 mg / L and phenol = 40256 mg / L.

[0063] (6) Reuse: The regenerated phase of the separating agent in steps (2), (3) and (4) is recycled and applied to step (1) as a separating agent.

[0064] In this embodiment, the coke powder content recovered in step (4) is 99%, and the phenol content recovered in step (5) is 94.9%, which is a qualified product, and the phenol recovery amount is 5097mg.

[0065] <Example 4>

[0066] The wastewater source is the same as in Example 1.

[0067] The specific processing steps are as follows:

[0068] (1) Take 500ml of water sample, add hydrochloric acid to adjust pH=3, and add 200ml of separating agent; the separating agent ratio is 60ml of tributyl phosphate, 40ml of isocetyl alcohol, and 100ml of aviation kerosene; stir for 30 minutes, place in a separatory funnel and let stand for 10 minutes before separating. The lower layer is the wastewater after extraction, which contains a small amount of coke powder. The test data are COD=12836mg / L, phenol=466mg / L, and pH=0.5. The upper layer is the separating phase, about 214ml, in which coke powder is evenly dispersed.

[0069] (2) Place the separated phase in a 500ml beaker, add 26ml of 32% sodium hydroxide solution, heat to 35℃, stir for 30min, then place in a separatory funnel and let stand for 10min to separate the phases. The lower layer is the first recovery phase with a volume of 50ml. The solution has pH=14, COD=625400mg / L, and phenol=155660mg / L. The middle layer is the coke powder enrichment phase. The upper layer is the separation agent regeneration phase.

[0070] (3) Take the coke powder enriched phase from step (2) into a centrifuge tube and separate it using centrifugation. Set the centrifugation speed to 2000 r / min and the centrifugation time to 2 min. After centrifugation, take out the centrifuge tube. In the centrifuge tube, there is a clear upper layer of separating agent regeneration phase, a middle layer of second recovery phase, of which COD=642350 mg / L, phenol=154260 mg / L, and a lower layer of solid coke powder.

[0071] (4) In step (3), the solid coke powder is placed in a small pyrolysis furnace and heated to 220°C. Nitrogen gas is introduced at the front end and cooling water is used to absorb the separating agent at the rear end. The pyrolysis process is used to obtain coke powder and the regenerated phase of the separating agent respectively.

[0072] (5) After mixing the first recovery phase in step (2) and the second recovery phase in step (3), place them in a beaker, add hydrochloric acid to adjust the pH to 1.5, heat to 55°C, stir for 40 min, place in a separatory funnel and let stand for 10 min to separate the layers. The lower layer is the salt recovery phase with COD = 273349 mg / L and phenol = 45210 mg / L, and the upper layer is the phenol solution.

[0073] (6) Reuse: The regenerated phase of the separating agent in steps (2), (3) and (4) is recycled and applied to step (1) as a separating agent.

[0074] In this embodiment, the coke powder content recovered in step (4) is 98.2%, and the phenol content recovered in step (5) is 95.6%, which is a qualified product, and the phenol recovery amount is 5909mg.

[0075] <Example 5>

[0076] The wastewater source is the same as in Example 1.

[0077] The specific processing steps are as follows:

[0078] (1) Take 500ml of water sample, add hydrochloric acid to adjust pH=2, and add 200ml of separating agent; the separating agent ratio is 80ml N503, 40ml isocetyl alcohol, and 80ml aviation kerosene; stir for 30 minutes, place in a separatory funnel and let stand for 10 minutes before separating. The lower layer is the wastewater after extraction, which contains a small amount of coke powder. The test data are COD=12389mg / L, phenol=502mg / L, and pH=0.5. The upper layer is the separating phase, about 214ml, in which coke powder is evenly dispersed.

[0079] (2) Place the separated phase in a 500ml beaker, add 26ml of 32% sodium hydroxide solution, heat to 55℃, stir for 30min, then place in a separatory funnel and let stand for 10min to separate the phases. The lower layer is the first recovery phase with a volume of 49ml. The solution has pH=14, COD=629870mg / L, and phenol=175820mg / L. The middle layer is the coke powder enrichment phase. The upper layer is the separation agent regeneration phase.

[0080] (3) Take the coke powder enriched phase from step (2) into a centrifuge tube and separate it using centrifugation. Set the centrifugation speed to 2500 r / min and the centrifugation time to 3 min. After centrifugation, take out the centrifuge tube. In the centrifuge tube, there is an upper clear separating agent regeneration phase, a middle layer of the second recovery phase, in which COD=625412 mg / L and phenol=176012 mg / L, and a lower layer of solid coke powder.

[0081] (4) In step (3), the solid coke powder is placed in a small pyrolysis furnace and heated to 370°C. Nitrogen gas is introduced at the front end and cooling water is used to absorb the separating agent at the rear end.

[0082] (5) After mixing the first recovery phase in step (2) and the second recovery phase in step (3), place them in a beaker, add hydrochloric acid to adjust the pH to 1, heat to 30°C, stir for 20 min, place in a separatory funnel and let stand for 10 min to separate the layers. The lower layer is the salt recovery phase with COD=317636mg / L and phenol=55210mg / L, and the upper layer is the phenol solution.

[0083] In this embodiment, the coke powder content of the resource recovery in step (4) is 98.3%, and the phenol content of the resource recovery in step (5) is 95.6%, which is a qualified product, and the phenol recovery amount is 6323mg.

[0084] <Example 6>

[0085] The wastewater source was the same as in Example 1, except that the complexing agent used was trioctylphosphine oxide; other experimental conditions remained unchanged, and the data detected in each step are as follows:

[0086] (1) In the wastewater after the lower layer extraction, COD=54110mg / L, phenol=12200mg / L, pH=0.5.

[0087] (2) In the first recovery phase in the lower layer, the solution volume is 35 ml, pH=14, COD=212600 mg / L, and phenol=58320 mg / L;

[0088] (3) In the second recovery phase of the middle layer, COD = 206224 mg / L and phenol = 57650 mg / L.

[0089] (5) The lower layer is a salt recovery phase with COD=170618mg / L and phenol=42150mg / L.

[0090] In this embodiment, the coke powder content recovered in step (4) is 98.2% and the phenol content recovered in step (5) is 95.2%, which are qualified products. However, due to the use of trioctylphosphine oxide as a complexing agent, the extraction effect is extremely low. Therefore, the COD and phenol values ​​of the wastewater after extraction are high, and the amount of phenol precipitated after back-extraction is 605 mg, resulting in a low yield.

[0091] <Example 7>

[0092] The wastewater source is the same as in Example 1. The difference from Example 1 is that in step (2), the solution temperature was not increased during the reaction process, and the reaction temperature was 18°C. Other experimental conditions remained unchanged. The specific data detected in each step are as follows:

[0093] (2) In the first recovery phase in the lower layer, the solution volume is 36 ml, pH=14, COD=230450 mg / L, and phenol=65320 mg / L;

[0094] (3) In the second recovery phase of the middle layer, COD = 228560 mg / L and phenol = 64980 mg / L.

[0095] (5) The lower layer is a salt recovery phase with COD=213518mg / L and phenol=54150mg / L.

[0096] In this embodiment, the coke powder content recovered in step (4) is 98.3%, the phenol content recovered in step (5) is 95.2%, the phenol quality standard is qualified, and the phenol recovery amount is 811 mg. The reason is that the reverse reaction temperature is low, the back-extraction effect is poor, and the phenol content in the recovered phase is lower than in other embodiments. Therefore, the amount of phenol precipitated after acid adjustment in step 5 is very small.

[0097] <Example 8>

[0098] The wastewater source is the same as in Example 1. The difference from Example 1 is that in step (3), the centrifugal speed can be 1800 r / min, and other test conditions remain unchanged. The specific data detected in each step are as follows:

[0099] (3) In the second recovery phase of the middle layer, COD = 602500 mg / L and phenol = 160256 mg / L;

[0100] (5) The lower layer is a salt recovery phase with COD=288560mg / L and phenol=43224mg / L.

[0101] In this embodiment, the recovered coke powder had a content of 85%, which is considered a qualified product; the phenol content was 95.2%, meeting the phenol quality standard; and the phenol recovery amount was 6261 mg. This was because the centrifugation speed was relatively low, leaving some residual recovered phase in the coke powder, which could potentially affect purity.

[0102] <Example 9>

[0103] The wastewater source is the same as in Example 1. The difference from Example 1 is that in step (4), the pyrolysis temperature is 450℃, and other test conditions remain unchanged. The specific data detected in each step are as follows:

[0104] (5) The lower layer is a salt recovery phase with COD=286362mg / L and phenol=41560mg / L.

[0105] In this embodiment, the coke powder content recovered in step (4) is 98.3%, and the phenol content recovered in step (5) is 96%, both of which are qualified products, and the phenol recovery amount is 7121 mg. However, increasing the temperature will cause the separating agent in the coke powder to become ineffective, which may have an adverse effect on the reuse and extraction of the separating agent.

[0106] <Example 10>

[0107] The wastewater source is the same as in Example 1. The difference from Example 1 is that in step (5), hydrochloric acid is added to adjust the pH to 2.5, while other experimental conditions remain unchanged. The specific data detected in each step are as follows:

[0108] (5) The lower layer is a salt recovery phase with COD=390466mg / L and phenol=82680mg / L.

[0109] In this embodiment, the coke powder content recovered in step (4) is 97.6%, and the phenol content recovered in step (5) is 96.1%, which are qualified products. The amount of phenol recovered is 4921 mg. Due to the excessively high pH, ​​only a portion of the sodium phenolate in the recovered phase precipitates as phenol, resulting in a large amount of sodium phenolate present and a lower resource recovery efficiency.

[0110] <Example 11>

[0111] The wastewater source is the same as in Example 1. The difference from Example 1 is that in step (5), hydrochloric acid is added to adjust the pH to 0.3, while other experimental conditions remain unchanged. The specific data detected in each step are as follows:

[0112] (5) The lower layer is a salt recovery phase with COD=243195mg / L and phenol=23156mg / L.

[0113] In this embodiment, the coke powder content recovered in step (4) is 98.5%, and the phenol content recovered in step (5) is 97%, which are qualified products, and the phenol recovery amount is 8105mg. However, due to the excessively low pH, hydrochloric acid resources are wasted, and the cost increases.

[0114] <Comparative Example 1>

[0115] The wastewater source is the same as in Example 1. The difference from Example 1 is that in step (1), hydrochloric acid is added to adjust the pH to 5, while other experimental conditions remain unchanged. The specific data detected in each step are as follows:

[0116] (1) In the wastewater after the lower layer extraction, the detection data were COD=59620mg / L, phenol=13900mg / L, and pH=5;

[0117] (2) In the first recovery phase in the lower layer, the solution volume is 35 ml, pH=14, COD=157560 mg / L, and phenol=61320 mg / L;

[0118] (3) In the second recovery phase of the middle layer, COD = 142,800 mg / L and phenol = 61,320 mg / L;

[0119] (5) The lower layer is a salt recovery phase with COD=115674mg / L and phenol=45210mg / L.

[0120] The recycled coke powder in this example had a content of 98.2% and a phenol content of 95.2%, which are considered qualified products. The phenol recovery amount was 861 mg. After adjusting the pH to 5, the COD of the effluent from step 1 was 59620 mg / L and the phenol content was 13900 mg / L, which are much higher than those in Example 1. This is because the phenol content in the wastewater is high, and it exists in the form of sodium phenolate, which greatly reduces the binding force with the separating agent, reduces the extraction effect, and does not completely achieve resource recovery. However, the phenol and coke powder produced by the reaction both meet the standards.

[0121] <Comparative Example 2>

[0122] The wastewater source is the same as in Example 1. The difference from Example 1 is that in step (1), hydrochloric acid is added to adjust the pH to 0.5, while other experimental conditions remain unchanged. The specific data detected in each step are as follows:

[0123] (1) In the wastewater after the lower layer extraction, the detection data were COD=58420mg / L, phenol=12900mg / L, and pH=0.5;

[0124] (2) In the first recovery phase in the lower layer, the solution volume is 49 ml, pH=14, COD=301650 mg / L, and phenol=112320 mg / L;

[0125] (3) In the second recovery phase of the middle layer, COD=301520mg / L and phenol=112250mg / L;

[0126] (5) The lower layer is a salt recovery phase with COD=130570mg / L and phenol=46520mg / L.

[0127] In this embodiment, the recovered coke powder content was 55%, which was substandard; the phenol content was 95%, which was qualified, and the phenol recovery amount was 3520 mg. After adjusting the pH to 0.5, the COD of the effluent from step 1 was 59620 mg / L, and the phenol content was 12900 mg / L, values ​​much higher than in other embodiments, indicating poor treatment effect. The reason is that the increased acidity caused the binding force between the separating agent and phenolic substances in the wastewater to be less than the binding force between phenols and acids. Therefore, some phenols were not completely extracted, resulting in a large amount of tar and heavy oil residue in the coke powder, affecting the quality of the coke powder.

[0128] <Comparative Example 3>

[0129] The wastewater source is the same as in Example 1. The difference from Example 1 is that in step (1), the separating agent ratio is 90 ml of tributyl phosphate, 30 ml of 2-octanol, and 80 ml of aviation kerosene. Other test conditions remain unchanged. The specific data detected in each step are as follows:

[0130] (1) In the wastewater after the lower layer extraction, COD=55560mg / L, phenol=13652mg / L, pH=2;

[0131] (2) In the first recovery phase in the lower layer, the solution volume is 52 ml, pH=14, COD=588160 mg / L, and phenol=138258 mg / L;

[0132] (3) In the second recovery phase of the middle layer, COD=588152mg / L and phenol=136650mg / L;

[0133] (5) The lower layer is a salt recovery phase with COD=279012mg / L and phenol=43200mg / L.

[0134] The coke powder recovered in this embodiment had a content of 98.5% and a phenol content of 95.9%, which is considered a qualified product. The phenol recovery was 4085 mg. The COD of the effluent from Step 1 was 55560 mg / L, and the phenol content was 13652 mg / L, values ​​higher than in other embodiments, indicating poor treatment performance. This is because, with the increased proportion of the complexing agent, some of the complexing agent combined with organic matter during extraction, forming an overcapacity phenomenon. This caused it to precipitate from the separating agent and dissolve in the aqueous phase, resulting in a higher COD value in the aqueous phase than in the normal extract. Furthermore, clumping and viscosity appeared in the separated phase, and the phenol recovery decreased, but this did not affect the overall quality.

[0135] <Comparative Example 4>

[0136] The wastewater source is the same as in Example 1. The difference from Example 1 is that in step (1), the separating agent ratio is 15 ml of tributyl phosphate, 50 ml of 2-octanol, and 135 ml of aviation kerosene. Other test conditions remain unchanged. The specific data detected in each step are as follows:

[0137] (1) In the wastewater after the lower layer extraction, COD=65200mg / L, phenol=14765mg / L, pH=2;

[0138] (2) In the first recovery phase in the lower layer, the solution volume is 35 ml, pH=14, COD=201760 mg / L, and phenol=56230 mg / L;

[0139] (3) In the second recovery phase of the middle layer, COD = 201760 mg / L and phenol = 55560 mg / L;

[0140] (5) The lower layer is a salt recovery phase with COD=122048mg / L and phenol=45128mg / L.

[0141] In this example, the recovered coke powder content was 98.3% and the phenol content was 96%, which is considered a qualified product. The phenol recovery rate was 415 mg. This is because the COD of the extracted water increased from 1119 mg / L to 65200 mg / L, and the phenol concentration increased from 565 mg / L to 14765 mg / L. The comparison shows that a low complexing agent content weakens the extraction effect, resulting in higher wastewater component values ​​and an extremely low phenol recovery rate.

[0142] The above are merely specific embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for treating semi-coke wastewater, characterized in that, Includes the following steps: (1) Chemical separation: Adjust the pH of the wastewater to 1-4, add a separating agent, and after the reaction is completed, let it stand to separate into layers to obtain a double-layer solution, wherein the lower layer is the aqueous phase and the upper layer is the separated phase; the separating agent includes a complexing agent, a co-solvent and a diluent; by volume ratio, the complexing agent and the co-solvent are 10-40% and 10-20% respectively, and the remainder is a diluent; (2) Reverse reaction: Add an alkaline solution to the separated phase. After the reaction is completed, allow the mixture to stand and separate into three layers to obtain a three-layer solution. The lower layer is the first recovery phase, the middle layer is the coke powder enrichment phase, and the upper layer is the separating agent regeneration phase. (3) Centrifugal separation: The above-mentioned coke powder enriched phase is centrifuged to obtain three phases, wherein the lower solid phase is a solid, the middle liquid phase is the second recovery phase, and the upper liquid phase is the regenerated phase of the separating agent; (4) Pyrolysis: The solids described in step (3) are pyrolyzed and separated to recover the regenerated phase of the separating agent and the coke powder respectively; (5) Acid precipitation: After mixing the first recovery phase described in step (2) and the second recovery phase described in step (3), add an acidic solution. After the reaction is completed, let it stand and separate into layers. The upper layer is phenol and the lower layer is a salt-containing recovery phase. The salt-containing recovery phase is treated as hazardous waste. (6) Reuse: The regenerated phase of the separating agent in steps (2), (3), and (4) is recycled back to step (1) as a separating agent; In step (1), the complexing agent includes one or more of N503, tributyl phosphate, and N-lauro(trialkylmethyl)amine; the cosolvent includes at least one of 2-heptadecyl alcohol, sec-octanol, and isohexadecanol; and the diluent is at least one of aviation kerosene or diesel fuel. In step (2), the temperature of the reaction is controlled at 20-60℃.

2. The processing method according to claim 1, characterized in that, In step (1), the volume ratio between the separating agent and the wastewater is 1:(1-5).

3. The processing method according to claim 1, characterized in that, In step (1), the reaction time between the separating agent and the wastewater is 5-45 min.

4. The processing method according to claim 1, characterized in that, In step (2), the alkaline solution is an optional inorganic alkaline solution; the volume ratio of the separated phase to the alkaline solution is (4-10):

1.

5. The processing method according to claim 1, characterized in that, In step (3), the centrifugation speed is 2000-8000 r / min and the centrifugation time is 2-10 min.

6. The processing method according to claim 1, characterized in that, In step (4), the temperature of the pyrolysis separation is controlled at 180-420℃.

7. The processing method according to claim 1, characterized in that, In step (5), the acidic solution is an optional inorganic acid solution, used to adjust the pH of the solution to 0.5-2.

8. The processing method according to claim 7, characterized in that, In step (5), the temperature of the reaction is controlled at 20-60℃ and the time is 20-60min.

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