Method for removing high-concentration scroll dyeing wastewater based on advanced oxidation

Abstract

This invention discloses a method for treating high-concentration dyeing wastewater based on advanced oxidation, comprising the following steps: S1: preparation of a catalyst for the reaction; S2: loading the catalyst; S3: preparing the wastewater treatment process; S4: testing the treated wastewater; S5: re-treating the wastewater. This method for treating high-concentration dyeing wastewater based on advanced oxidation can oxidize sulfides in the wastewater to sulfates with an oxidation efficiency approaching 100%. It significantly reduces the acid consumption for subsequent recovery of naphthenic acids or phenols and pH adjustment, avoids catalyst poisoning in the secondary reactor, and does not destroy recoverable naphthenic acids and phenols in the wastewater during the oxidation reaction. Furthermore, the quality of the recovered products is greatly improved, and the discharged tail gas does not contain malodorous gases such as H2S. The content of volatile phenols and other pollutants is also significantly reduced, while energy consumption is low.

Description

Technical Field

[0001] This invention relates to the field of dyeing wastewater treatment, and particularly to a method for treating high-concentration dyeing wastewater based on advanced oxidation. Background Technology

[0002] Dyeing wastewater is wastewater discharged from printing and dyeing, wool dyeing and finishing, and silk factories that process cotton, linen, chemical fibers and their blended products, as well as silk. The volume and quality of dyeing wastewater vary depending on the type of fiber and the processing technology. Among them, the wastewater from printing and dyeing factories has a large volume. Dyeing wastewater is characterized by large volume, high content of organic pollutants, high alkalinity, and large variation in water quality, and is one of the difficult industrial wastewaters to treat.

[0003] Existing technologies for treating dyeing wastewater cannot guarantee oxidation efficiency and do not have a recycling effect, which can easily lead to energy waste. Furthermore, the residual exhaust gas discharged will affect the environment, and the content of pollutants such as volatile phenols will increase. At the same time, the overall energy consumption of the equipment is high, and it cannot be guaranteed that the wastewater discharge will meet the standards. Summary of the Invention

[0004] The main objective of this invention is to provide a method for treating high-concentration dyeing wastewater based on advanced oxidation, which can effectively solve the problems in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for treating high-concentration dyeing wastewater based on advanced oxidation includes the following steps:

[0007] S1: Preparation of the catalyst for the reaction: r-Al2O3 was used directly as the support. It was calcined at 500-750℃ for 3 hours and then ground into particles of 180-250 μm to form the support. The r-Al2O3 support was impregnated with an equal volume of nickel nitrate solution in an 80℃ hot water bath. The solution was evaporated by drying at 110℃ for 10 hours. The support was then calcined at 650℃ for 4 hours. The r-Al2O3 support was then impregnated with an equal volume of nickel nitrate aqueous solution in an 80℃ hot water bath. The solution was evaporated by drying at 110℃ for 10 hours. The support was then calcined at 650℃ for 4 hours. The catalyst was prepared by mixing an equal volume of nickel nitrate solution and an equal volume of nickel nitrate aqueous solution.

[0008] S2: Catalyst loading treatment: The prepared catalyst is made into 20-60 mesh particles and filled into a quartz tube reactor with an inner diameter of 6 mm. The catalyst loading is 60 mg. The catalyst is dried in a water bath and then dried at 100 °C overnight. Then it is calcined in air at 400 °C for 10 h to complete the overloading.

[0009] S3: Wastewater treatment process preparation: This includes two stages of treatment. The first stage is a mild wet air oxidation process, which oxidizes Na2S and organic sulfur in the alkaline wastewater to SO42- at around 100℃ and a reaction pressure of 0.2-3.5MPa. The second stage is a catalytic wet oxidation process, where the temperature is controlled between 200℃ and 300℃ and the pressure is controlled at 5.0MPa. Pure oxygen aeration is used, and the prepared catalyst is used for catalytic wet oxidation. The alkaline wastewater will first pass through a sedimentation separator to remove oil before entering a storage tank. Then, it will be pumped and pressurized to the first-stage mild wet oxidation reactor to remove sulfides. Part of the liquid will be recycled and gradually enter the second-stage catalytic wet oxidation reactor to degrade residual phenols and most of the CODcr.

[0010] S4: Testing the treated wastewater: For the removal of heavy metal ions in wastewater containing copper, zinc, and bare acid or alkali, a precipitant is added to convert copper, zinc, and nickel ions into precipitates with the lowest solubility. NaOH is used as the precipitant. The pH of the treated wastewater is monitored and automatically adjusted to 8.0-9.0 under the control of a pH meter by adding acid and alkali reagents. The wastewater is also treated by adding calcium ion reagent to react and generate calcium hydroxide precipitate.

[0011] S5: After monitoring, the wastewater enters the chlorine equalization tank from the workshop again for homogenization. Then, it is pumped into the grate reaction tank by a lift pump at a controlled flow rate for sedimentation. After sedimentation, it enters the oxygen sedimentation tank for sludge-water separation. The settled sludge enters the integrated sludge tank for filter pressing. The effluent from the sedimentation enters the integrated reaction tank for secondary reaction. Alternatively, the wastewater enters the equalization tank from the workshop for homogenization. Then, it is pumped into the reaction tank by a lift pump at a controlled flow rate for chemical reaction. The effluent from the sedimentation enters the inclined plate sedimentation tank for sludge-water separation. The settled sludge enters the bare sludge tank for filter pressing. The effluent from the sedimentation enters the integrated reaction tank for secondary reaction, thus completing the oxidation treatment of the wastewater.

[0012] Preferably, if the alkaline residue wastewater contains naphthenic acid and phenol, sulfuric acid is used for acidification and recovery, and the pH value is adjusted. At the same time, in order to maintain the reaction temperature and pressure, high-pressure steam needs to be introduced into the jacket of the sleeve-type reaction tower to regulate the temperature, and an air compressor is used for aeration inside to maintain the oxygen partial pressure and the total operating pressure. The heat in the treatment process is recovered and utilized using a heat exchange device.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] This treatment method can oxidize sulfides in wastewater to sulfates with an oxidation efficiency of nearly 100%. It can significantly reduce the acid consumption in subsequent recovery of naphthenic acids or phenols and pH adjustment processes. It can also avoid catalyst poisoning in the secondary reactor. The oxidation reaction does not destroy the recoverable naphthenic acids and phenols in the wastewater, and the quality of the recovered products is greatly improved. The residual exhaust gas does not contain malodorous gases such as H2S, and the content of volatile phenols and other pollutants is greatly reduced. At the same time, the energy consumption is low, and the heat generated by the oxidation of alkaline sludge wastewater with a CODcr concentration of tens of thousands can be recovered and utilized to maintain most of the heat energy required for the entire system. In addition, the wastewater is monitored and treated again to ensure that the harmful substances in the wastewater do not exceed the standards, and the wastewater discharge meets the standards. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.

[0016] This invention relates to a method for treating high-concentration dyeing wastewater based on advanced oxidation, comprising the following steps:

[0017] S1: Preparation of the catalyst for the reaction: r-Al2O3 was used directly as the support. It was calcined at 500-750℃ for 3 hours and then ground into particles of 180-250 μm to form the support. The r-Al2O3 support was impregnated with an equal volume of nickel nitrate solution in an 80℃ hot water bath. The solution was evaporated by drying at 110℃ for 10 hours. The support was then calcined at 650℃ for 4 hours. The r-Al2O3 support was then impregnated with an equal volume of nickel nitrate aqueous solution in an 80℃ hot water bath. The solution was evaporated by drying at 110℃ for 10 hours. The support was then calcined at 650℃ for 4 hours. The catalyst was then prepared by mixing an equal volume of nickel nitrate solution and an equal volume of nickel nitrate aqueous solution.

[0018] S2: Catalyst loading treatment: The prepared catalyst is made into 20-60 mesh particles and filled into a quartz tube reactor with an inner diameter of 6 mm. The catalyst loading is 60 mg. The catalyst is dried in a water bath, then dried at 100 °C overnight, and then calcined in air at 400 °C for 10 h to complete the overloading.

[0019] S3: Wastewater treatment process preparation: This includes two stages of treatment. The first stage is a mild wet air oxidation process, conducted at approximately 100℃ and a reaction pressure of 0.2-3.5 MPa, oxidizing Na2S and organic sulfur in the alkaline residue wastewater to SO42-. The second stage is a catalytic wet oxidation process, with the temperature controlled between 200℃ and 300℃ and the pressure controlled at 5.0 MPa. Pure oxygen aeration is used, and a prepared catalyst is employed for catalytic wet oxidation. The alkaline residue wastewater at this stage first passes through a settling separator to remove oil before entering a storage tank, and then is pumped... The feed liquid is pressurized and sent to the primary mild wet oxidation reactor to remove sulfides. Part of the feed liquid is recycled and gradually enters the secondary catalytic wet oxidation reactor to degrade residual phenols and most of the CODcr. If the alkaline residue wastewater contains naphthenic acids and phenols, sulfuric acid is used for acidification and recovery, and the pH value is adjusted. At the same time, in order to maintain the reaction temperature and pressure, high-pressure steam needs to be introduced into the jacket of the sleeve-type reaction tower to regulate the temperature. An air compressor is used for aeration inside to maintain the oxygen partial pressure and the total operating pressure. The heat in the process is recovered and utilized using a heat exchange device.

[0020] S4: Testing the treated wastewater: For the removal of heavy metal ions in wastewater containing copper, zinc, and bare acid or alkali, a precipitant is added to convert copper, zinc, and nickel ions into precipitates with minimal solubility. NaOH is used as the precipitant. The pH of the treated wastewater is monitored and automatically adjusted to 8.0-9.0 under the control of a pH meter by adding acid and alkali reagents. The wastewater is further treated by adding calcium ion reagent to react and generate calcium hydroxide precipitate.

[0021] S5: After monitoring, the wastewater enters the chlorine equalization tank from the workshop again for homogenization. Then, it is pumped into the grate reaction tank by a lift pump at a controlled flow rate for sedimentation. After sedimentation, it enters the oxygen sedimentation tank for sludge-water separation. The settled sludge enters the integrated sludge tank for filter pressing. The effluent from the sedimentation enters the integrated reaction tank for secondary reaction. Alternatively, the wastewater enters the equalization tank from the workshop for homogenization. Then, it is pumped into the reaction tank by a lift pump at a controlled flow rate for chemical reaction. The effluent from the sedimentation enters the inclined plate sedimentation tank for sludge-water separation. The settled sludge enters the bare sludge tank for filter pressing. The effluent from the sedimentation enters the integrated reaction tank for secondary reaction, thus completing the oxidation treatment of the wastewater.

[0022] The treated pollutants were tested, and the test results are as follows:

[0023]

[0024] This demonstrates that wastewater treated with ozone using this method can have most of its impurities removed.

[0025] This treatment method can oxidize sulfides in wastewater to sulfates with an oxidation efficiency of nearly 100%. It can significantly reduce the acid consumption in subsequent recovery of naphthenic acids or phenols and pH adjustment processes. It can also avoid catalyst poisoning in the secondary reactor. The oxidation reaction does not destroy the recoverable naphthenic acids and phenols in the wastewater, and the quality of the recovered products is greatly improved. The residual exhaust gas does not contain malodorous gases such as H2S, and the content of volatile phenols and other pollutants is greatly reduced. At the same time, the energy consumption is low, and the heat generated by the oxidation of alkaline sludge wastewater with a CODcr concentration of tens of thousands can be recovered and utilized to maintain most of the heat energy required for the entire system. In addition, the wastewater is monitored and treated again to ensure that the harmful substances in the wastewater do not exceed the standards, and the wastewater discharge meets the standards.

[0026] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for treating high-concentration dyeing wastewater based on advanced oxidation, characterized in that: The following steps are included: S1: Preparation of the catalyst for the reaction: r-Al2O3 was used directly as the support. It was calcined at 500-750℃ for 3 hours and then ground into particles of 180-250 μm to form the support. The r-Al2O3 support was impregnated with an equal volume of nickel nitrate solution in an 80℃ hot water bath. The solution was evaporated by drying at 110℃ for 10 hours. The support was then calcined at 650℃ for 4 hours. The r-Al2O3 support was then impregnated with an equal volume of nickel nitrate aqueous solution in an 80℃ hot water bath. The solution was evaporated by drying at 110℃ for 10 hours. The support was then calcined at 650℃ for 4 hours. The mixture was then mixed with an equal volume of nickel nitrate aqueous solution. The catalyst was thus prepared. S2: Catalyst loading treatment: The prepared catalyst is made into 20-60 mesh particles and filled into a quartz tube reactor with an inner diameter of 6 mm. The catalyst loading is 60 mg. The catalyst is dried in a water bath and then dried at 100 °C overnight. Then it is calcined in air at 400 °C for 10 h to complete the overloading. S3: Wastewater treatment process preparation: This includes two stages of treatment. The first stage is a mild wet air oxidation process, which oxidizes Na2S and organic sulfur in the alkaline residue wastewater to SO4 at around 100℃ and a reaction pressure of 0.2-3.5MPa. 2- The second stage is catalytic wet oxidation, with the temperature controlled between 200℃ and 300℃ and the pressure controlled at 5.0MPa. Pure oxygen aeration is used, and the prepared catalyst is used for catalytic wet oxidation. The alkaline residue wastewater will first pass through a sedimentation separator to remove oil before entering a storage tank. Then, it will be pumped and pressurized to the first-stage mild wet oxidation reactor to remove sulfides. Part of the feed liquid will be recycled and gradually enter the second-stage catalytic wet oxidation reactor to degrade the residual phenols and most of the CODcr. S4: Testing the treated wastewater: For the removal of heavy metal ions in wastewater containing copper, zinc, and bare acid or alkali, a precipitant is added to convert copper, zinc, and nickel ions into precipitates with the lowest solubility. NaOH is used as the precipitant. The pH of the treated wastewater is monitored and automatically adjusted to 8.0-9.0 under the control of a pH meter by adding acid and alkali reagents. The wastewater is also treated by adding calcium ion reagent to react and generate calcium hydroxide precipitate. S5: After monitoring, the wastewater enters the chlorine equalization tank from the workshop again for homogenization. Then, it is pumped into the grate reaction tank by a lift pump at a controlled flow rate for sedimentation. After sedimentation, it enters the oxygen sedimentation tank for sludge-water separation. The settled sludge enters the integrated sludge tank for filter pressing. The sedimented effluent enters the integrated reaction tank for secondary reaction. Alternatively, the wastewater enters the equalization tank from the workshop for homogenization. Then, it is pumped into the reaction tank by a lift pump at a controlled flow rate for chemical reaction. The effluent enters the inclined plate sedimentation tank for sludge-water separation. The settled sludge enters the bare sludge tank for filter pressing. The sedimented effluent enters the integrated reaction tank for secondary reaction, thus completing the oxidation treatment of the wastewater. If the alkaline residue wastewater contains naphthenic acid and phenol, sulfuric acid is used for acidification and recovery, and the pH value is adjusted. At the same time, in order to maintain the reaction temperature and pressure, high-pressure steam needs to be introduced into the jacket of the sleeve-type reaction tower to regulate the temperature. An air compressor is used for aeration inside to maintain the oxygen partial pressure and the total operating pressure. The heat in the treatment process is recovered and utilized using a heat exchange device.

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