A high-salinity wastewater double-oxidation treatment system and method

Abstract

The application discloses a high-salinity wastewater double-oxidation treatment system and method, and belongs to the field of water treatment, comprising a DS catalytic oxidation device and a LDO low-temperature wet oxidation device connected in sequence; a water distributor is arranged at the bottom of the inner cavity of the DS catalytic oxidation device, and a separator is arranged at the top of the inner cavity of the DS catalytic oxidation device; the DS catalytic oxidation and the LDO low-temperature wet oxidation two-stage oxidation technology are coupled, so that the total removal rate of organic matters reaches more than 80%, the effluent can directly enter an evaporator to recycle salt, or can continue to enter a high-pressure reverse osmosis membrane to continue concentration; meanwhile, the combined process has lower operation cost, the coupling design of the two-stage oxidation also reduces the cost and implementation scale of the wet oxidation, improves the quality of the recycled salt, effectively reduces the operation risk of the evaporator, prolongs the cleaning cycle, and the subsequent device is a high-pressure reverse osmosis membrane concentration process, which can effectively reduce membrane pollution, improve the operation cycle of the membrane, and prolong the service life of the membrane.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a dual oxidation treatment system and method for high-salinity wastewater. Background Technology

[0002] With the rapid development of industry, the petrochemical, coal chemical, pharmaceutical, and printing and dyeing industries generate large amounts of high-salt organic wastewater. Due to its high salt content, high risk of secondary pollution, and complex composition, this wastewater poses a serious threat to the environment. Conventional biological treatment technologies are insufficient to meet its treatment requirements, and the high-salt environment also inhibits the activity of conventional biological bacteria. In the field of zero wastewater discharge, after continuous concentration by RO and NF membranes, the TDS and COD concentrations of wastewater increase significantly. If COD is not effectively removed, it will not only affect the quality of subsequent evaporation and crystallization products (such as sodium sulfate), but also cause great harm to the stable operation of the evaporator.

[0003] Existing advanced oxidation processes (such as ozone oxidation and Fenton oxidation) and high-temperature wet oxidation processes have many significant limitations in treating high-salinity organic wastewater:

[0004] In terms of treatment capacity, these processes are difficult to adapt to high-salt environments (such as wastewater with TDS concentration ≥ 30000 mg / L). High salinity will interfere with the reaction process, resulting in a significant decrease in the efficiency of organic matter removal, and thus failing to meet the treatment requirements of high-salt organic wastewater.

[0005] In terms of energy consumption, high-temperature wet oxidation processes need to operate under harsh conditions of high temperature and high pressure (200-340℃ and 5.0MPa), resulting in huge energy consumption. Although some advanced oxidation processes (such as Fenton oxidation) have relatively mild reaction conditions, a large amount of oxidant needs to be added in order to achieve a certain treatment effect, which indirectly increases energy consumption and treatment costs.

[0006] In terms of equipment wear and tear, the high-temperature and high-pressure reaction environment will cause serious corrosion to the equipment, which will not only shorten the service life of the equipment, but also require frequent maintenance and replacement, increasing operating costs and operational risks. At the same time, the harsh operating conditions place extremely high demands on the materials of the equipment, further increasing the initial investment costs.

[0007] In terms of processing costs, on the one hand, the high energy consumption and high equipment maintenance costs of high-temperature wet oxidation directly increase the cost; on the other hand, processes such as Fenton oxidation require the addition of large amounts of oxidants and chemical reagents, ozone oxidation requires the consumption of a large amount of electricity to produce ozone, and some processes may use precious metal catalysts (such as Pt, Pd, etc.), all of which lead to high processing costs.

[0008] Furthermore, these processes struggle to achieve efficient and sustained deep degradation when treating complex, high-salt organic wastewater, resulting in low COD removal rates. This fails to meet the influent water quality requirements of subsequent processes such as evaporation crystallization and membrane concentration, thereby affecting the quality of the final product (such as crystalline salt) and the stable operation of subsequent equipment. Summary of the Invention

[0009] The purpose of this invention is to provide a dual oxidation treatment system and method for high-salt wastewater, in order to solve the problems of excessive energy consumption, equipment corrosion, large oxidant dosage, high treatment costs, reduced removal efficiency due to salt and toxicity interference, and difficulty in efficient and sustained deep degradation of COD in the treatment of high-salt, high-COD organic wastewater by single ambient temperature and pressure oxidation or high temperature and high pressure wet oxidation.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a dual oxidation treatment system for high-salinity wastewater, comprising a DS catalytic oxidation device and an LDO low-temperature wet oxidation device connected in sequence;

[0011] A water distributor is installed at the bottom of the inner cavity of the DS catalytic oxidation device, and a separator is installed at the top of the inner cavity of the DS catalytic oxidation device. A circulation pump is installed on the outside of the DS catalytic oxidation device, which can transport wastewater from the top of the inner cavity of the DS catalytic oxidation device to the bottom of the inner cavity of the DS catalytic oxidation device. The DS catalytic oxidation device is filled with DS oxidation catalyst.

[0012] The top effluent from the DS catalytic oxidation unit flows sequentially through the first-stage heat exchanger, the second-stage heat exchanger, the catalytic reactor, and the oxidation reactor in the LDO low-temperature wet oxidation unit. The first-stage heat exchanger, the second-stage heat exchanger, the catalytic reactor, and the oxidation reactor are connected by pipelines.

[0013] Furthermore, the DS catalytic oxidation device operates at a temperature of 40-50℃ and a pH of 6-8, while the LDO low-temperature wet oxidation device operates at a temperature of 130℃, a pressure of 0.5MPa, and a pH of 6-8.

[0014] Furthermore, the high-temperature inlet of the first-stage heat exchanger is connected to the outlet of the LDO low-temperature wet oxidation unit, and the second-stage heat exchanger is externally supplied with steam for heating.

[0015] Furthermore, the operating conditions of the LDO low-temperature wet oxidation device are a temperature of 130°C and a pressure of 0.5 MPa.

[0016] Furthermore, the oxidant used in the DS catalytic oxidation device (1) is 27.5% H2O2.

[0017] Furthermore, the catalytic reactor and the oxidation reactor are respectively filled with a catalyst and an oxidant. The LDO catalyst has a particle size of 3-5 mm, and the oxidant in the oxidation reactor is 27.5% H2O2.

[0018] The DS oxidation catalyst uses sulfuric acid-modified waste tire carbon material.

[0019] The preparation process of the sulfuric acid modified waste tire carbon material is as follows: the waste tire carbon is sieved through a 200-mesh sieve, soaked in 6M sulfuric acid, stirred at low speed for 2 hours, washed with deionized water until pH neutral, and then dried at 120℃ for 6 hours to obtain the sulfuric acid modified waste tire carbon material.

[0020] A method for treating high-salinity wastewater using a dual oxidation system includes the following steps:

[0021] DS catalytic oxidation stage: In the DS catalytic oxidation unit, under normal pressure / micro-pressure, temperature 40-50℃, and pH 6-8 conditions, 27.5% H2O2 is added to the wastewater as an oxidant and DS catalytic oxidation catalyst. The wastewater enters the unit through a water distributor and is completely mixed and reacted with the catalyst. After the reaction, it is separated by a separator. Part of the effluent enters the LDO low-temperature wet oxidation unit, and part of the water is returned by a circulation pump.

[0022] LDO Low-Temperature Wet Oxidation Stage: The effluent from the DS catalytic oxidation stage is preheated by the first-stage heat exchanger and the second-stage heat exchanger and then sent to the LDO low-temperature wet oxidation unit. Under the conditions of approximately 130°C, 0.5MPa, and pH 6-8, 27.5% H2O2 is added as an oxidant, and the water is then treated sequentially by the catalytic reactor and the oxidation reactor.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This low-temperature wet oxidation coupled with salt separation wastewater treatment system and method, by coupling two-stage oxidation technologies of DS catalytic oxidation and LDO low-temperature wet oxidation, not only achieves a total organic matter removal rate of over 80%, but also efficiently treats high-salt wastewater with a TDS concentration ≥30000 mg / L. Furthermore, the effluent can be directly fed into an evaporator or high-pressure membrane for further concentration. Simultaneously, the combined process has lower operating costs. The coupled design of the two-stage oxidation reduces the cost and scale of wet oxidation, improves salt quality while increasing organic matter removal rate, reduces evaporator operating risks, extends cleaning cycles, and effectively reduces membrane fouling if a subsequent membrane concentration process is employed. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a high-salt wastewater oxidation treatment system.

[0026] In the diagram: 1. DS catalytic oxidation unit; 11. Water distributor; 12. Separator; 13. Circulation pump; 2. LDO low-temperature wet oxidation unit; 21. First-stage heat exchanger; 22. Second-stage heat exchanger; 23. Catalytic reactor; 24. Oxidation reactor. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments.

[0028] The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of protection of the present invention. The conditions in the embodiments can be further adjusted according to specific conditions, and simple improvements to the method of the present invention under the premise of the concept of the present invention are all within the scope of protection claimed by the present invention.

[0029] Please see Figure 1 The present invention provides a dual oxidation treatment system for high-salt wastewater, including a DS catalytic oxidation device 1 and an LDO low-temperature wet oxidation device 2.

[0030] Under normal temperature or slightly elevated temperature conditions, most recalcitrant substances are removed by combining a DS oxidation catalyst with an oxidant (such as hydrogen peroxide). The DS oxidation catalyst uses waste tires as raw material, undergoing chemical modification. The waste tire char is sieved (200 mesh), soaked in 6M sulfuric acid, stirred at low speed for 2 hours, washed with deionized water until pH neutral, and then dried at 120℃ for 6 hours to obtain sulfuric acid-modified waste tire char material. This catalyst, rich in oxygen-containing functional groups and containing metal ions, exhibits excellent catalytic performance. Simultaneously, the recycling of waste tires is beneficial to environmental protection and resource regeneration. Compared to precious metal catalysts (such as Pt, Pd, Au, etc.), modified waste tire char is inexpensive and reduces the need for subsequent treatment of heavy metals in water bodies. The incoming water is mixed with the internal circulating water through the water distributor 11 inside the DS catalytic oxidation unit 1. After the reaction inside the DS catalytic oxidation unit 1, the catalyst and water are separated in the separator 12. The catalyst remains in the DS catalytic oxidation unit 1 to continue to participate in the reaction. Part of the effluent is internally circulated through the circulation pump 13, and the other part enters the subsequent LDO low-temperature wet oxidation unit 2 to continue the reaction.

[0031] The DS catalytic oxidation unit 1 can pre-oxidize high-salt wastewater, reducing the COD load on the subsequent LDO low-temperature wet oxidation unit 2. The LDO low-temperature wet oxidation unit 2 can generate a large number of hydroxyl radicals at lower temperatures and pressures, improving the COD removal rate. After catalytic oxidation by the DS catalytic oxidation unit 1, the concentration of salt and recalcitrant macromolecular organic matter entering the LDO low-temperature wet oxidation unit 2 is relatively reduced, effectively reducing harsh reaction conditions such as high temperature and high pressure, and correspondingly reducing equipment corrosion and energy consumption. By using the DS catalytic oxidation unit 1 and the LDO low-temperature wet oxidation unit 2 in combination, the dosage of catalyst and oxidant can be flexibly adjusted according to changes in the organic matter concentration of the wastewater, adapting to high TDS conditions (TDS concentration ≥ 30000 mg / L). The entire process produces no secondary waste residue or increase in heavy metal ions, maintaining the cleanliness of the system.

[0032] The LDO low-temperature wet oxidation unit 2 uses relatively low temperature and pressure (130℃ and 0.5MPa) to further oxidize and decompose residual recalcitrant organic matter in the water through the LDO catalyst packing in the catalytic reactor 23 and the oxidant in the oxidation reactor 24. The wastewater entering the LDO low-temperature wet oxidation unit 2 is preheated in two stages. The first-stage heat exchanger 21 uses the effluent from the LDO low-temperature wet oxidation unit 2 to maximize the utilization of the unit's waste heat and reduce the heat energy supply. The second-stage heat exchanger 22 uses externally supplied steam as a supplement to the first-stage preheating to ensure that the influent meets the reaction conditions of the LDO low-temperature wet oxidation unit 2. The LDO low-temperature wet oxidation unit 2 uses a series connection of the catalytic reactor 23 and the oxidation reactor 24 to achieve the full degradation of organic matter.

[0033] Low-temperature wet oxidation coupled with desalination is a wastewater treatment method.

[0034] DS catalytic oxidation unit 1: The reaction is carried out under normal / micro-pressurized conditions, using 27.5% H2O2 as the oxidant, and adding DS oxidation catalyst. The reaction temperature is controlled at 40-50℃, pH 6-8, and water is introduced through water distributor 11, ensuring complete mixing of the catalyst and water. DS catalytic oxidation unit 1 achieves a COD removal rate of 40-50%. For the catalyst, without adding new carbon-based modification materials, using only H2O2 oxidant with low activity sites, the COD removal rate is only about 10%. Adding a metal Pt catalyst achieves a COD removal rate of about 30%. Modified waste tire carbon materials, due to their excellent oxidation functional groups, are conducive to inducing H2O2 to generate highly active ·OH groups, achieving a COD removal rate of 40-50%. Using H2O2 as the oxidant, compared to ozone (O3) and persulfate systems, has advantages such as cost savings, fewer byproducts, and clean and environmentally friendly treatment. This invention is the first to couple 27.5% H2O2 with modified waste tire carbon in a DS catalytic oxidation unit, achieving excellent COD removal efficiency (40-50%). After catalytic mixing, the mixture is separated by a separator. One portion directly enters the LDO low-temperature wet oxidation unit 2, while the other portion is returned to the DS catalytic oxidation unit 1 via a circulating pump 13 to continue catalytic oxidation and provide hydraulic power to the reactor, thus homogenizing the hydraulic conditions inside the reactor.

[0035] LDO Low-Temperature Wet Oxidation Unit 2: Wastewater from the DS catalytic oxidation unit 1 is heated by effluent heat circulation and hot steam before entering the LDO low-temperature wet oxidation unit 2. The temperature is set at approximately 130℃, 0.5MPa, and pH 6-8. The oxidant used is also 27.5% hydrogen peroxide. The pH and oxidant type are consistent with the previous reaction, which is beneficial for stabilizing the water pH, reducing the consumption of chemicals for pH adjustment, and saving costs. The LDO low-temperature wet oxidation unit 2 is a two-stage series process. The catalytic reactor 23 contains LDO catalyst packing, and the oxidation reactor 24 contains the oxidant. The LDO catalyst particle size is 3-5mm, and the oxidant is 27.5% hydrogen peroxide. The catalyst packing amount in the two tanks is determined by the different water quality treatment requirements. The LDO low-temperature wet oxidation unit 2 can achieve a COD removal rate of 60-80%.

[0036] Taking a coal chemical plant's zero-discharge high-salt organic wastewater as an example:

[0037] The temperature of the DS catalytic oxidation unit 1 was set to 50℃ and the pH was controlled at 7; the temperature of the LDO low-temperature wet oxidation unit 2 was set to 130℃ and the pH was controlled at 7. The wastewater COD was approximately [value missing], and the results of the treatment using the above process are shown in the table below:

[0038] 1 1280 742 42 223 70.1 82.6 2 1390 727 47.7 205 71.8 85.3 3 406 226 44.3 75 66.8 81.5 4 575 276 52 99 63.8 82.8 5 827 468 43.4 132 71.8 84 6 935 483 48.3 154 68 83.5

[0039] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description, and these obvious variations or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims

1. A high-salinity wastewater oxidation treatment system, characterized in that: It includes a DS catalytic oxidation unit (1) and an LDO low-temperature wet oxidation unit (2) connected in sequence. The bottom of the inner cavity of the DS catalytic oxidation device (1) is provided with a water distributor (11), and the top of the inner cavity of the DS catalytic oxidation device (1) is provided with a separator (12). A circulation pump (13) is provided on the outside of the DS catalytic oxidation device (1). The circulation pump (13) can transport the wastewater at the top of the inner cavity of the DS catalytic oxidation device (1) to the bottom of the inner cavity of the DS catalytic oxidation device (1). The DS catalytic oxidation device (1) is filled with DS oxidation catalyst. The DS oxidation catalyst uses sulfuric acid-modified waste tire carbon material. The preparation process of the sulfuric acid modified waste tire carbon material is as follows: the waste tire carbon is sieved through a 200-mesh sieve, soaked in 6M sulfuric acid, stirred at low speed for 2 hours, washed with deionized water until pH neutral, and then dried at 120℃ for 6 hours to obtain the sulfuric acid modified waste tire carbon material. The DS catalytic oxidation device (1) is filled with oxidant H2O2; The top effluent from the DS catalytic oxidation device (1) flows sequentially through the first-stage heat exchanger (21), the second-stage heat exchanger (22), the catalytic reactor (23), and the oxidation reactor (24) in the LDO low-temperature wet oxidation device (2). The first-stage heat exchanger (21), the second-stage heat exchanger (22), the catalytic reactor (23), and the oxidation reactor (24) are connected by pipes.

2. The high-salinity wastewater dual oxidation treatment system according to claim 1, characterized in that: The DS catalytic oxidation device (1) operates at a temperature of 40-50℃ and a pH of 6-8, while the LDO low-temperature wet oxidation device (2) operates at a temperature of 130℃, a pressure of 0.5MPa, and a pH of 6-8.

3. The high-salinity wastewater dual oxidation treatment system according to claim 1, characterized in that: The high-temperature inlet of the first-stage heat exchanger (21) is connected to the outlet of the LDO low-temperature wet oxidation device (2), and the second-stage heat exchanger (22) is connected to external steam for heating.

4. The high-salinity wastewater dual oxidation treatment system according to claim 1, characterized in that: The oxidant used in the DS catalytic oxidation device (1) is 27.5% H2O2.

5. The high-salinity wastewater dual oxidation treatment system according to claim 4, characterized in that: The catalytic reactor (23) is filled with LDO catalyst, and the oxidation reactor (24) is filled with oxidant.

6. The high-salinity wastewater dual oxidation treatment system according to claim 5, characterized in that: The LDO catalyst has a particle size of 3-5 mm.

7. The high-salinity wastewater double oxidation treatment system according to claim 6, characterized in that: The oxidant in the oxidation reactor (24) is the same type and concentration as the oxidant in the DS catalytic oxidation device (1).

8. A method for treating high-salinity wastewater by oxidation, using the high-salinity wastewater oxidation treatment system according to any one of claims 1-7, characterized in that, Includes the following steps: DS catalytic oxidation stage: In the DS catalytic oxidation device (1), under normal or slightly pressurized conditions, temperature of 40-50℃ and pH of 6-8, 27.5% H2O2 is added to the wastewater as an oxidant and DS oxidation catalyst. The wastewater enters the device through the water distributor (11) and is completely mixed and reacted with the catalyst. After the reaction, it is separated by the separator (12). Part of the effluent enters the LDO low-temperature wet oxidation device (2), and part of the water is returned to the DS catalytic oxidation device (1) by the circulating pump (13) to continue the reaction. LDO low-temperature wet oxidation stage: The effluent from the DS catalytic oxidation stage is preheated by the first-stage heat exchanger (21) and the second-stage heat exchanger (22) and then sent to the LDO low-temperature wet oxidation device (2). Under the conditions of temperature 130℃, pressure 0.5MPa and pH 6-8, 27.5% H2O2 is added as an oxidant and then reacted in the catalytic reactor (23) and the oxidation reactor (24) in sequence.

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