Heterogeneous catalytic oxidation system for treating organic wastewater

Abstract

The utility model relates to the technical field of industrial wastewater treatment, in particular to a heterogeneous catalytic oxidation system for treating organic wastewater, which comprises an acid regulating unit, a booster pump, a catalytic oxidation reaction unit and a pH (potential of hydrogen) callback pipeline mixer which are communicated in sequence, the catalytic oxidation reaction unit comprises a plurality of heterogeneous catalytic oxidation reactors which are connected in series, and the treatment temperatures and the treatment pressures of the heterogeneous catalytic oxidation reactors are sequentially reduced along the flowing direction of wastewater. The heterogeneous catalytic oxidation reactors connected in series in the system provided by the utility model do not need to be pressurized step by step, are simple and efficient, and have feasibility. The heterogeneous catalytic oxidation reactors are adopted, so that the loss of the catalyst can be avoided, the continuous addition of the catalyst is not needed, the operation cost is reduced, meanwhile, the function of configuring different catalysts in each stage of heterogeneous catalytic oxidation reactor can be realized, and the degradation degree of organic matters and the precise regulation and control of each stage of target products are realized.

Description

Technical Field

[0001] This utility model relates to the field of industrial wastewater treatment technology, specifically to a multiphase catalytic oxidation system for treating organic wastewater. Background Technology

[0002] Catalytic wet oxidation refers to a method that uses oxygen from the air as an oxidant (or other oxidants such as ozone or hydrogen peroxide) under high temperature (180℃-280℃) and high pressure (2-9MPa) conditions, with the aid of a catalyst, to oxidize dissolved or suspended organic matter or reduced inorganic matter in water into harmless substances such as CO2, H2O, and N2. Compared with traditional physical, chemical, and biological treatment methods, this method has advantages such as high efficiency and small footprint, and is particularly suitable for the treatment of high-concentration, recalcitrant organic wastewater. However, despite its many advantages, catalytic wet oxidation still faces some challenges and limitations in practical applications. These mainly include: the technology requires high reaction conditions, needing to be carried out under high temperature and high pressure, which not only increases equipment investment and operating costs but also raises operational difficulty and safety risks. Furthermore, the reaction process consumes a large amount of energy, resulting in significant energy waste. Additionally, the catalysts used are expensive, unstable, easily disintegrated, and have short lifespans, and there are also problems such as the need for excessive addition of oxidants (such as hydrogen peroxide) and low utilization rates.

[0003] In response, Chinese patent document CN107572651B discloses a method and apparatus for multi-stage wet oxidation treatment of industrial wastewater. While this method reduces energy consumption and treatment costs to some extent, researchers have found that the progressively increasing temperature of the wastewater from the primary to the tertiary oxidation reactors is difficult to implement in engineering. Specifically, it is well known to those skilled in the art that "at standard atmospheric pressure, the boiling point of water is 100°C; to raise the water temperature above 100°C, the pressure must be increased accordingly." Therefore, in this design, the pressure from the primary to the tertiary oxidation reactors would inevitably increase sequentially. However, the wastewater cannot flow from a low-pressure area to a high-pressure area on its own. To implement the disclosed scheme, a booster pump must be installed before each oxidation reactor. However, when the booster pump draws water from the low-pressure reactor and pumps it into the high-pressure reactor, the pump inlet is at a high water temperature (especially above 100°C) and low pressure, making it highly susceptible to cavitation, which can damage the booster pump and prevent it from operating normally. In addition, this invention also reveals that it uses a homogeneous method for catalyst addition, i.e., the catalyst is prepared into a solution and added to the wastewater to be treated. After flowing through the primary, secondary, and tertiary catalytic oxidation reactors, it is discharged from the system as precipitated sludge. This not only results in significant catalyst consumption or loss but also requires continuous catalyst addition. Therefore, there is an urgent need to provide a catalytic oxidation system for treating organic wastewater that is easy to implement in engineering and does not require continuous catalyst addition. Utility Model Content

[0004] Therefore, the technical problem to be solved by this utility model is to overcome the shortcomings of existing heterogeneous catalytic oxidation systems for treating organic wastewater, which are difficult to implement in engineering, require continuous addition of catalysts, and have high operating costs, thereby providing a heterogeneous catalytic oxidation system for treating organic wastewater that solves the above problems.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] This invention provides a multiphase catalytic oxidation system for treating organic wastewater. The system includes a pH adjustment unit, a booster pump, a catalytic oxidation reaction unit, and a pH adjustment pipeline mixer connected in sequence. The catalytic oxidation reaction unit comprises several multiphase catalytic oxidation reactors connected in series, with the treatment temperature and pressure decreasing sequentially along the wastewater flow direction. In this invention, the multiphase catalytic oxidation reactor is a reactor with a loading area filled with a solid catalyst (e.g., a fixed-bed reactor; conventional structures will not be described in detail here). That is, the multiphase catalytic oxidation reactor is filled with a solid catalyst, which serves as the core functional unit of the reactor, contacting the solid catalyst with liquid or gaseous reactants to achieve a catalytic conversion reaction. There is no booster pump between adjacent multiphase catalytic oxidation reactors in the catalytic oxidation reaction unit.

[0007] The acid-adjusting unit is used to connect to the inlet pipe of the wastewater to be treated and to adjust the acidity.

[0008] Booster pumps are used to pressurize the wastewater in the acidification unit;

[0009] The catalytic oxidation reaction unit is used to catalytically oxidize heated wastewater.

[0010] The pH adjustment pipeline mixer is used to adjust the pH of the wastewater after the catalytic oxidation reaction unit by adding alkali.

[0011] Preferably, the pH adjustment unit includes a pH adjustment pipeline mixer and an inlet water adjustment tank connected in sequence; wherein, the pH adjustment pipeline mixer includes a mixer body, and an acid inlet, a wastewater inlet and a mixed liquid outlet disposed on the mixer body, for adding acid to adjust the pH of the wastewater; the inlet water adjustment tank includes a storage tank connected to the mixed liquid outlet, and an online pH meter disposed in the storage tank, the storage tank is used to store the wastewater after acid adjustment by the pH adjustment pipeline mixer, and the online pH meter in the storage tank is used to ensure the stability of the inlet water pH.

[0012] Preferably, a preheating heat exchanger is provided between the booster pump and the catalytic oxidation reaction unit to exchange heat with the outlet material of the catalytic oxidation reaction unit; wherein, the cold side of the preheating heat exchanger is connected to the outlet of the booster pump and the inlet of the catalytic oxidation reaction unit, and the hot side of the preheating heat exchanger is connected to the outlet of the catalytic oxidation reaction unit. That is, the cold side flows through the raw wastewater, and the hot side flows through the effluent of the multiphase catalytic oxidation reactor, realizing the recycling of heat. The above temperature control depends on the operating temperature required for the catalytic oxidation reaction.

[0013] Preferably, the preheating heat exchanger includes, but is not limited to, one of the heat exchangers suitable for high temperature, high pressure, and easy fouling applications, such as plate heat exchangers, shell-and-tube heat exchangers, and spiral plate heat exchangers.

[0014] Preferably, when the oxidant participating in the catalytic oxidation reaction in the catalytic oxidation reaction unit is a non-gaseous oxidant, a non-gaseous oxidant dosing pipe mixer is provided at the inlet of at least the first multiphase catalytic oxidation reactor along the wastewater flow direction where the treatment temperature and treatment pressure decrease sequentially. The non-gaseous oxidant dosing pipe mixer is provided with a non-gaseous oxidant dosing port. When using non-gaseous oxidants such as hydrogen peroxide, a non-gaseous oxidant dosing pipe mixer can be provided only at the inlet of the first multiphase catalytic oxidation reactor. Preferably, a non-gaseous oxidant dosing pipe mixer is provided at the inlet of each multiphase catalytic oxidation reactor.

[0015] And / or, when the oxidant participating in the catalytic oxidation reaction in the catalytic oxidation reaction unit is a gaseous oxidant, each multiphase catalytic oxidation reactor is equipped with a gaseous oxidant injection port at the bottom for injecting gaseous oxidant into the wastewater to be treated. When using gaseous oxidants such as oxygen or air, each multiphase catalytic oxidation reactor must be equipped with a gaseous oxidant injection port at the bottom.

[0016] Preferably, the catalytic oxidation reaction unit comprises 2-4 heterogeneous catalytic oxidation reactors connected in series. The number of reaction stages is determined based on the types and degradation patterns of characteristic organic pollutants in the wastewater; generally, the number of stages N is 2-4. For each stage of the heterogeneous catalytic oxidation reactor, a more efficient catalyst is selected. The single-stage reaction time and catalyst loading amount are determined according to the degradation rate of each stage of the heterogeneous catalytic oxidation reactor. More preferably, the catalytic oxidation reaction unit consists of 3 heterogeneous catalytic oxidation reactors connected in series.

[0017] Preferably, there is no booster pump between the various heterogeneous catalytic oxidation reactors in the catalytic oxidation reaction unit;

[0018] And / or, each multiphase catalytic oxidation reactor in the catalytic oxidation reaction unit is further equipped with an online thermometer and an online pressure gauge;

[0019] And / or, each multiphase catalytic oxidation reactor in the catalytic oxidation reaction unit is also equipped with an online oxidant concentration meter. An online oxidant concentration meter and oxidant dosing point are installed at the inlet of each stage of the multiphase catalytic oxidation reactor, allowing for staged dosing as needed. The distribution ratio can be adjusted according to the oxidant consumption at each stage.

[0020] Preferably, at least the inlet of the first multiphase catalytic oxidation reactor in the catalytic oxidation reaction unit along the wastewater flow direction is provided with a heater for heating the wastewater;

[0021] The pH adjustment pipeline mixer is also equipped with an online pH meter; the pH adjustment pipeline mixer is used to adjust the pH of the wastewater after catalytic oxidation to neutral, and the online pH meter is installed to ensure the stability of the effluent pH.

[0022] And / or, a final cooling heat exchanger is also provided before the pH adjustment pipeline mixer to exchange heat with the circulating cooling water, which is used to exchange heat and cool down the effluent from the catalytic oxidation reaction unit with the circulating cooling water; the final cooling heat exchanger is set according to the specific situation of the project. If the downstream directly enters the evaporation crystallization device, it may not be set. If the downstream is connected to other process units, the heat exchanger parameters need to be selected according to the downstream process inlet water temperature requirements.

[0023] Preferably, the heater is a raw water heater; the raw water heater is a device that uses steam to directly mix with water to heat water, with a thermal efficiency of over 98%. The steam and the heated wastewater are mixed through the raw water heater and heated to the temperature required for the catalytic oxidation reaction; the steam is saturated steam, which meets the temperature and pressure requirements of the multiphase catalytic oxidation reactor, and the steam pressure is 0.8-1.8 MPa.

[0024] Preferably, the final cooling heat exchanger includes, but is not limited to, one of the heat exchangers suitable for high temperature and high pressure, and easy fouling applications, such as plate heat exchangers, shell and tube heat exchangers, and spiral plate heat exchangers.

[0025] And / or, when the oxidant participating in the catalytic oxidation reaction in the catalytic oxidation reaction unit includes a gaseous oxidant, a gas-liquid separator is also provided after the final cooling heat exchanger for gas-liquid separation of the effluent from the catalytic oxidation reaction unit. Specifically, if a gaseous oxidant such as oxygen or air is used in the catalytic oxidation reaction unit, a gas separator needs to be installed after the final cooling heat exchanger; however, if a non-gaseous oxidant (such as hydrogen peroxide, added in liquid form) is used, a gas-liquid separator is not required.

[0026] The specific treatment process of the above-mentioned multiphase catalytic oxidation system for treating organic wastewater includes: the wastewater to be treated is introduced into the pH adjustment unit through the wastewater inlet pipe, and acid is added to adjust the pH of the wastewater to be treated; the wastewater after acid adjustment is pressurized by the booster pump and flows sequentially through the heater, the catalytic oxidation reaction unit, and the pH adjustment pipeline mixer before being discharged.

[0027] Preferably, the wastewater pressurized by the booster pump flows through a preheating heat exchanger to exchange heat with the effluent from the catalytic oxidation reaction unit for a temperature increase; after flowing through the preheating heat exchanger, the effluent from the catalytic oxidation reaction unit also flows through a final cooling heat exchanger for a second temperature decrease; the effluent from the catalytic oxidation reaction unit, acting as a heat source, enters the hot side of the preheating heat exchanger to exchange heat with the raw water after the booster pump for a temperature decrease, and then enters the hot side of the final cooling heat exchanger to exchange heat with the circulating cooling water for a second temperature decrease, in order to meet the inlet water temperature requirements of subsequent process units; when using a gaseous oxidant, the wastewater after the second temperature decrease also flows through a gas-liquid separator for gas-liquid separation.

[0028] Preferably, the wastewater is fed with a non-gaseous oxidant (when a non-gaseous oxidant is used) and / or heated at the inlet of each multiphase catalytic oxidation reactor in the catalytic oxidation reaction unit; optionally, the non-gaseous oxidant includes hydrogen peroxide;

[0029] And / or, when a gaseous oxidant is used, each multiphase catalytic oxidation reactor in the catalytic oxidation reaction unit is provided with a gaseous oxidant inlet at the bottom; optionally, the gaseous oxidant is an oxygen-containing gas, which includes air and / or oxygen.

[0030] Preferably, the temperature of the first multiphase catalytic oxidation reactor in the direction of the wastewater flow is 160-200℃, and the pressure is mainly to ensure that the wastewater is in the liquid phase at this temperature. The reaction pressure is controlled according to the reaction temperature, and the pressure is 0.8-1.8MPa. The temperature loss between two adjacent multiphase catalytic oxidation reactors is controlled below 20℃, and the temperature of the effluent from the entire catalytic oxidation reaction unit is controlled above 80℃.

[0031] Preferably, the residence time of the first heterogeneous catalytic oxidation reactor in the catalytic oxidation reaction unit is 10-30 min, and the total residence time of the entire catalytic oxidation reaction unit is 60-120 min. This is because the first-stage heterogeneous catalytic oxidation reactor reacts rapidly, so the residence time is set at 10-30 min. Subsequently, the residence time of each stage is determined based on the project's processing scale and the decomposition patterns of organic matter, with a total residence time of 60-120 min.

[0032] Preferably, the acid used in the acid-adjusting unit includes sulfuric acid and / or hydrochloric acid;

[0033] And / or, the pH of the acid-adjusted wastewater is 2-4;

[0034] And / or, the head of the booster pump is set to 80-180m, and the inlet pressure and flow rate are adjusted by frequency conversion control;

[0035] And / or, the catalyst in the catalytic oxidation reaction unit includes, but is not limited to, at least one of the following: a targeted catalyst for treating wastewater containing heterocyclic compounds, a targeted catalyst for treating wastewater containing aromatic compounds, and a targeted catalyst for treating wastewater containing hydrocarbons; the solid catalyst in each stage of the multiphase catalytic oxidation reactor is determined according to the characteristics of the wastewater quality and the reaction parameters controlled at each stage. For the wastewater quality to be treated in this invention, the preferred catalyst is one independently developed by the applicant, including a targeted catalyst for treating wastewater containing heterocyclic compounds (CN201610217796.5), a targeted catalyst for treating wastewater containing aromatic compounds (CN201610217797.X), a targeted catalyst for treating wastewater containing hydrocarbons (CN201610218965.7), and one or more of various types of commercially available catalysts. This reduces the activation energy of the reaction, thereby reducing the reaction temperature and pressure, making the reaction conditions more moderate, and allowing for precise control of the degree of organic matter degradation and the target products at each stage according to actual treatment requirements.

[0036] And / or, the alkali used in the pH return pipeline mixer includes sodium hydroxide.

[0037] In this invention, the wastewater to be treated is high-concentration, recalcitrant organic wastewater, specifically referring to a high-ratio membrane concentrate obtained from industrial wastewater after biochemical and advanced treatment. This concentrate is characterized by high salt content, high content of recalcitrant organic matter, and complex composition. Its typical water quality is approximately 800-2500 mg / L COD and 35000-150000 mg / L TDS. After front-end treatment, the COD is mostly composed of relatively stable recalcitrant organic matter, such as heterocyclic compounds, benzene series compounds, halogenated hydrocarbons, and hydrocarbons (cyclic hydrocarbons, chain hydrocarbons, etc.). Since H2O2 has higher oxidizing power than air / oxygen, it can more thoroughly oxidize organic matter; therefore, H2O2 is the preferred oxidant. When using hydrogen peroxide as the oxidant, the H2O2 dosage is 3-8 times the COD concentration, using industrial-grade 27.5% hydrogen peroxide. When using oxygen-containing gas as the oxidant, the O2 dosage is 2-10 times the COD concentration.

[0038] In this invention, the multiphase catalytic oxidation reactor is arranged in a multi-stage series configuration, which successively become a first-stage multiphase catalytic oxidation reactor (corresponding to the first multiphase catalytic oxidation reactor in the flow direction of the wastewater to be treated), a second-stage multiphase catalytic oxidation reactor, ..., an N-stage multiphase catalytic oxidation reactor. The incoming water first enters the high-temperature and high-pressure first-stage multiphase catalytic oxidation reactor to obtain the effluent of reaction 1. The effluent of reaction 1 enters the medium-temperature and medium-pressure second-stage multiphase catalytic oxidation reactor to obtain the effluent of reaction 2. The effluent of reaction 2 then enters the subsequent reactors until it enters the low-temperature and low-pressure N-stage multiphase catalytic oxidation reactor to obtain the effluent of reaction N. The first-stage heterogeneous catalytic oxidation reactor operates in a relatively high-temperature and high-pressure environment. The reaction process is mainly in the thermal decomposition stage. Under the action of high temperature and catalyst, complex macromolecular organic compounds undergo ring-opening and chain-breaking, transforming them into more easily decomposed compounds. The higher the temperature in this stage, the faster the reaction rate. The temperature and pressure of the subsequent-stage heterogeneous catalytic oxidation reactor are reduced to some extent. It mainly carries out the local oxidation process, oxidizing and decomposing the ring-opening and chain-breaking organic compounds into small molecule intermediates. Then, the organic compounds are oxidized step by step until they are completely oxidized into carbon dioxide and water. As the degree of degradation deepens, the type of organic matter to be treated changes, and the corresponding activation energy of the reaction gradually decreases.

[0039] In this invention, a gradient distribution from high temperature and high pressure to low temperature and low pressure is formed under the influence of factors such as the structure of the multiphase catalytic oxidation reactor (height-to-diameter ratio, internal components, etc.), catalyst type and filling form, operating conditions (temperature, pressure, liquid rising velocity), reaction heat effect (the oxidation process is an exothermic reaction, and the reaction at the bottom of the reactor is intense), heat transfer (convection, radiation and conduction, etc.) and loss (heat exchange with the outside world), and heat preservation performance.

[0040] In this invention, the solid catalyst filling rate in the multiphase catalytic oxidation reactor is 50% to 80% (filling rate refers to the proportion of catalyst volume to the total reactor volume);

[0041] In this invention, since temperature and pressure are related, the temperature of each reactor is usually controlled, and once the temperature is set, the pressure is basically set as well. In addition, since no booster pump is installed, the reactors at each stage are directly connected in series. As long as the inlet water pressure is sufficient to overcome the resistance of each stage reactor and ensure that water can enter and exit normally, it is sufficient. Therefore, the pressure of each stage reactor is usually not controlled separately.

[0042] The technical solution of this utility model has the following advantages:

[0043] 1. A multiphase catalytic oxidation system for treating organic wastewater, comprising a pH adjustment unit, a booster pump, a catalytic oxidation reaction unit, and a pH adjustment pipeline mixer connected in sequence; the catalytic oxidation reaction unit comprises several multiphase catalytic oxidation reactors connected in series with progressively decreasing treatment temperatures and pressures along the wastewater flow direction. The multiphase catalytic oxidation system provided by this invention adopts a spatially partitioned treatment strategy, forming a gradient distribution from high temperature and high pressure to low temperature and low pressure between the multiphase catalytic oxidation reactors at each stage. The series-connected multiphase catalytic oxidation reactors do not require stepwise pressurization, avoiding cavitation of the booster pump under high temperature and low pressure conditions, thus improving the system's reliability and stability. It is simple, efficient, and feasible. Furthermore, compared to the homogeneous catalyst addition method used in existing technologies (preparing a catalyst solution, adding it to the primary oxidation reactor, and continuously flowing through subsequent secondary and tertiary oxidation reactors, with continuous inflow and outflow, failing to achieve the function of configuring specific catalysts in each stage of the multiphase catalytic oxidation reactor), this invention utilizes a multiphase catalytic oxidation reaction... This invention relates to a device (an apparatus that brings a solid catalyst into contact with liquid or gaseous reactants to achieve a catalytic conversion reaction) for catalytic oxidation. The solid catalyst used in this device does not require continuous addition as a reagent and is not lost during the reaction, reducing operating costs. Furthermore, it allows for the configuration of different types of solid catalysts in each stage of the multiphase catalytic oxidation reactor. This enables the selection of specific solid catalysts with higher degradation efficiency based on the type of characteristic organic pollutants in the wastewater, their degradation patterns, and reaction conditions. This further reduces the activation energy, thereby lowering the reaction temperature and pressure, resulting in milder reaction conditions. The invention also allows for precise control of the degree of organic matter degradation and the target products at each stage according to actual treatment requirements. Therefore, the system provided by this invention, through the setup of multi-stage multiphase catalytic oxidation reactors, enhances the adaptability and flexibility of the reactors. Each stage of the reactor can be customized with appropriate temperature and pressure conditions according to specific reaction stages and thermodynamic requirements, allowing for customized adjustments for different types of wastewater and treatment needs. This system has broad application prospects and significant market value.

[0044] Secondly, the higher the system temperature, the greater the heat loss. This system achieves a gradient distribution from high temperature and high pressure to low temperature and low pressure, significantly reducing the reaction time at high temperature and high pressure, making the overall reaction conditions milder, thus reducing heat loss. Simultaneously, the large amount of heat energy released during oxidation can also be utilized through gradients in each reaction stage. Overall, this invention allows for full utilization of energy throughout the system, improving the overall energy efficiency of the process. Furthermore, in the system provided by this invention, the oxidant is fully utilized in the multi-stage series reactor, especially when hydrogen peroxide is used as the oxidant, which effectively improves the oxidant utilization rate.

[0045] 2. In the multiphase catalytic oxidation system of this invention, no booster pump is required between the multiphase catalytic oxidation reactors at each stage, which simplifies the equipment structure and reduces operating costs.

[0046] 3. In the multiphase catalytic oxidation system of this invention, addressing the lack of adjustment and control measures for the temperature, pressure, and oxidant dosage of each stage of the multiphase catalytic oxidation reactor in existing technologies, a supplementary heater and a non-gaseous oxidant dosing pipeline mixer are installed at the inlet of each stage of the multiphase catalytic oxidation reactor. Online thermometers and online pressure gauges are installed in each stage of the multiphase catalytic oxidation reactor, and an online hydrogen peroxide concentration meter is installed at the outlet of each stage of the multiphase catalytic oxidation reactor. The temperature, pressure, and oxidant dosage of each stage can be controlled as needed, improving processing efficiency, reducing operating energy and reagent consumption, and providing a wider adjustment range and more flexible operation. Attached Figure Description

[0047] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the heterogeneous catalytic oxidation system of Embodiment 1 of this utility model;

[0049] Figure 2 This is a schematic diagram of the heterogeneous catalytic oxidation system of Embodiment 2 of this utility model.

[0050] Figure labels: 1-pH adjustment pipeline mixer, 2-inlet water regulating tank, 3-boost pump, 4-preheating heat exchanger, 5-non-gaseous oxidant dosing pipeline mixer, 6-heater, 7-multiphase catalytic oxidation reactor, 8-final cooling heat exchanger, 9-pH return pipeline mixer, 10-gas-liquid separator, 11-gaseous oxidant injection port. Detailed Implementation

[0051] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0052] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0054] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0055] Example 1

[0056] Wastewater 1: The wastewater treatment and reuse system of a certain semi-coke plant has a recovery rate of about 95%. The final membrane concentrate produced has a COD of about 2200 mg / L and a TDS of about 72000 mg / L. According to the analysis, the organic matter in the membrane concentrate is mainly aromatic compounds, and also contains a certain amount of chromogenic substances, as well as halogenated hydrocarbons, long-chain alkanes and other substances.

[0057] This embodiment provides a multiphase catalytic oxidation system for treating organic wastewater, with the schematic structure shown below. Figure 1As shown, the multiphase catalytic oxidation system consists of a pH adjustment unit (composed of a pH adjustment pipeline mixer 1 and an inlet water adjustment tank 2) connected in sequence, a booster pump 3, a preheating heat exchanger 4, a non-gaseous oxidant dosing pipeline mixer 5, a heater 6 (specifically a raw water heater), a catalytic oxidation reaction unit consisting of three multiphase catalytic oxidation reactors 7 filled with solid catalysts (referred to as the first-stage multiphase catalytic oxidation reactor, the second-stage multiphase catalytic oxidation reactor, and the third-stage multiphase catalytic oxidation reactor in sequence according to the flow direction of the wastewater to be treated), with the catalytic oxidation reaction unit gradually distributed from high temperature and high pressure to low temperature and low pressure in the flow direction of the wastewater to be treated, a final cooling heat exchanger 8, and a pH adjustment pipeline mixer 9. Each stage of the multiphase catalytic oxidation reactor is equipped with an oxidant dosing pipeline mixer 5 and a heater 6.

[0058] Among them, pH adjustment pipeline mixer 1 is used to connect to the inlet pipeline of the wastewater to be treated, and at the same time add acid to adjust the pH of the wastewater;

[0059] The inlet regulating tank 2 is used to store the wastewater after it has been acidified by the pH regulating pipeline mixer 1. The inlet regulating tank 2 is also equipped with an online pH meter to ensure the stability of the inlet pH.

[0060] Booster pump 3 is used to pressurize the wastewater in the acidification unit;

[0061] The preheating heat exchanger 4, specifically a plate heat exchanger, is used to exchange heat and raise the temperature of the pressurized wastewater and the effluent from the catalytic oxidation reaction unit. The cold side of the preheating heat exchanger 4 is connected to the effluent from the booster pump 3, and the hot side of the preheating heat exchanger 4 is connected to the effluent from the catalytic oxidation reaction unit. That is, the cold side flows through the raw wastewater, and the hot side flows through the effluent from the multiphase catalytic oxidation reactor.

[0062] Non-gaseous oxidant dosing pipeline mixer 5 is used to add non-gaseous oxidant to the wastewater to be treated;

[0063] Raw water heater, used to heat wastewater after the addition of non-gaseous oxidant by mixing it with steam;

[0064] The catalytic oxidation reaction unit is used to carry out catalytic oxidation reaction on heated wastewater. Each multiphase catalytic oxidation reactor 7 in the catalytic oxidation reaction unit is also equipped with an online thermometer and an online pressure gauge. At the same time, an online hydrogen peroxide concentration meter is installed at the inlet of each stage of the multiphase catalytic oxidation reactor.

[0065] The final cooling heat exchanger 8, specifically a plate heat exchanger, is used to exchange heat again with the circulating cooling water to cool it down.

[0066] pH adjustment pipeline mixer 9 is used to add alkali to the wastewater after the catalytic oxidation reaction unit to adjust the pH back to neutral. The pH adjustment pipeline mixer 9 is also equipped with an online pH meter to ensure the stability of the effluent pH.

[0067] Based on the characteristic pollutants in wastewater 1, the primary multiphase catalytic oxidation reactor is filled with a targeted catalyst (CN201610217797.X) (referred to as catalyst I) for treating wastewater containing aromatic compounds, and the secondary and tertiary multiphase catalytic oxidation reactors are filled with a targeted catalyst (CN201610218965.7) (referred to as catalyst II) for treating wastewater containing hydrocarbons. The filling rate of solid catalyst in each multiphase catalytic oxidation reactor is 68%.

[0068] This embodiment also provides a heterogeneous catalytic oxidation process for treating organic wastewater, which utilizes the aforementioned heterogeneous catalytic oxidation system to degrade wastewater 1. The specific steps are as follows:

[0069] Wastewater 1 is fed into pH adjustment pipeline mixer 1 through the wastewater inlet pipe, and acid is added to adjust the pH of the wastewater. The acid-adjusted wastewater is stored in inlet regulating tank 2, and then pressurized by booster pump 3. After that, it flows sequentially through the cold side of preheating heat exchanger 4, non-gaseous oxidant dosing pipeline mixer 5, raw water heater, primary multiphase catalytic oxidation reactor, non-gaseous oxidant dosing pipeline mixer 5, raw water heater, secondary multiphase catalytic oxidation reactor, non-gaseous oxidant dosing pipeline mixer 5, raw water heater, tertiary multiphase catalytic oxidation reactor, preheating heat exchanger 4 hot side, final cooling heat exchanger 8 hot side, and pH adjustment pipeline mixer 9 before being discharged.

[0070] The main control parameters are:

[0071] Add hydrochloric acid to the influent to adjust the pH to 3.0, and collect it in the influent conditioning tank;

[0072] The inlet water temperature is approximately 170℃, the average temperature loss per stage is approximately 15℃, and the outlet temperature is approximately 120℃.

[0073] If the inlet water pressure is about 1.0 MPa, the booster pump head is set to 100 m, with frequency conversion control, and 1.0 MPa saturated steam is used.

[0074] Residence time: 20 min for the first-stage multiphase catalytic oxidation reactor, 40 min for the second-stage multiphase catalytic oxidation reactor, and 40 min for the third-stage multiphase catalytic oxidation reactor, for a total residence time of 100 min.

[0075] H2O2 dosage: 5 times the COD concentration, added in stages. The distribution ratio is adjusted according to the online hydrogen peroxide concentration meter at the outlet. The dosage for the first-stage reaction is about 50% of the total H2O2 dosage, the dosage for the second-stage reaction is about 50% of the total H2O2 dosage, and no H2O2 is added for the third-stage reaction.

[0076] After heat exchange, the effluent from the three-stage multiphase catalytic oxidation reactor is adjusted to neutral pH with sodium hydroxide. The final effluent COD is ≤50mg / L, with a removal rate of over 97%. There is no catalyst loss, no need for continuous catalyst addition, and no cavitation phenomenon occurs in the booster pump.

[0077] Example 2

[0078] Wastewater 2: A coal gasification wastewater treatment system uses membrane technology for zero-discharge salt separation. After multi-stage concentration and nanofiltration salt separation, the COD in the nanofiltration concentrate (Na2SO4 side) is about 1200 mg / L and the TDS is about 126000 mg / L. The membrane concentrate is mainly composed of heterocyclic compounds and contains small amounts of halogenated hydrocarbons, long-chain alkanes and other substances.

[0079] The multiphase catalytic oxidation system for treating organic wastewater in this embodiment is the same as in Embodiment 1.

[0080] Based on the water quality characteristics of wastewater 1 above, the first-stage multiphase catalytic oxidation reactor is filled with a targeted catalyst (ZL201610217796.5) (referred to as catalyst III) for treating wastewater containing heterocyclic compounds, and the second-stage and third-stage multiphase catalytic oxidation reactors are filled with a targeted catalyst (CN201610218965.7) (referred to as catalyst II) for treating wastewater containing hydrocarbons. The filling rate of solid catalyst in each stage of the multiphase catalytic oxidation reactor is 73%.

[0081] This embodiment provides a heterogeneous catalytic oxidation process for treating organic wastewater. The difference between this process and Embodiment 1 is that the main control parameters are:

[0082] Add sulfuric acid to the influent to adjust the pH to 3.5, and collect it in the influent conditioning tank;

[0083] The inlet water temperature is approximately 150℃, the single-stage temperature loss is approximately 12℃, and the outlet temperature is approximately 115℃.

[0084] If the inlet water pressure is about 0.8MPa, the booster pump head is set to 80m, with frequency conversion control, and 0.8MPa saturated steam is used.

[0085] Residence time: 15 min for the first-stage multiphase catalytic oxidation reactor, 30 min for the second-stage multiphase catalytic oxidation reactor, and 30 min for the third-stage multiphase catalytic oxidation reactor, for a total residence time of 75 min.

[0086] H2O2 dosage: 4 times the COD concentration, added in stages. The distribution ratio is adjusted according to the online hydrogen peroxide concentration meter at the outlet. The dosage for the first-stage reaction is 60% of the total H2O2 dosage, the dosage for the second-stage reaction is 40% of the total H2O2 dosage, and no H2O2 is added for the third-stage reaction.

[0087] After heat exchange, the effluent from the three-stage multiphase catalytic oxidation reactor is adjusted to neutral pH with sodium hydroxide. The final effluent COD is ≤30mg / L, with a removal rate of over 97%. There is no catalyst loss, no need for continuous catalyst addition, and no cavitation phenomenon occurs in the booster pump.

[0088] Example 3

[0089] This embodiment provides a multiphase catalytic oxidation system for treating organic wastewater, with the schematic structure shown below. Figure 2 As shown, the difference between this multiphase catalytic oxidation system and Example 1 is that all non-gaseous oxidant dosing pipe mixers 5 are removed, and the bottom of the multiphase catalytic oxidation reactors 7 (first-stage multiphase catalytic oxidation reactor, second-stage multiphase catalytic oxidation reactor, and third-stage multiphase catalytic oxidation reactor) is equipped with gaseous oxidant nozzles 11 for injecting oxygen (O2 dosage is 5 times the COD concentration) into the wastewater to be treated. A gas-liquid separator 10 is also provided after the final cooling heat exchanger 8 for gas-liquid separation of the effluent from the final cooling heat exchanger 8. Other conditions are the same as in Example 1.

[0090] After heat exchange, the effluent from the three-stage multiphase catalytic oxidation reactor is adjusted to neutral pH with sodium hydroxide. The final effluent COD is ≤40mg / L, with a removal rate of over 97%. There is no catalyst loss, no need for continuous catalyst addition, and no cavitation phenomenon occurs in the booster pump.

[0091] Comparative Example 1

[0092] This comparative example provides a catalytic oxidation system for treating organic wastewater. The difference between this comparative example and Example 1 is that a homogeneous catalytic reactor (without a solid catalyst) is used for the catalytic oxidation reaction. Specifically, a catalyst solution (ferrous sulfate, 6 mmol / L) is continuously added to the wastewater to be treated. After flowing through the first, second, and third stage catalytic oxidation reactors, the wastewater is discharged from the system as precipitated sludge. Furthermore, the catalytic oxidation reactors 7 are gradually distributed from low temperature and low pressure to high temperature and high pressure according to the flow direction of the wastewater. Specifically, booster pumps 3 are added between the first, second, and third stage catalytic oxidation reactors. Simultaneously, the temperatures of the influent to the first, second, and third stage catalytic oxidation reactors are controlled to 90°C, 190°C, and 240°C, respectively, by controlling the raw water heater. Other conditions are the same as in Example 1. During implementation, this comparative example suffers from booster pump cavitation, leading to pump damage and system malfunction. It also requires continuous catalyst addition, resulting in high operating costs.

[0093] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A heterogeneous catalytic oxidation system for treating organic wastewater, characterized by, The system comprises a pH adjusting unit, a booster pump (3), a catalytic oxidation reaction unit and a pH readjusting pipeline mixer (9) connected in sequence; the catalytic oxidation reaction unit comprises a plurality of multiphase catalytic oxidation reactors (7) connected in series and arranged in sequence in terms of decreasing treatment temperature and treatment pressure along the flow direction of the wastewater.

2. The multiphase catalytic oxidation system of claim 1, wherein, The pH adjusting unit comprises a pH adjusting pipeline mixer (1) and a water inlet adjusting tank (2) connected in sequence; the pH adjusting pipeline mixer (1) comprises a mixer body, an acid liquid inlet, a wastewater inlet and a mixed liquid outlet arranged on the mixer body; the water inlet adjusting tank (2) comprises a storage tank connected with the mixed liquid outlet and an online pH meter arranged in the storage tank.

3. The multiphase catalytic oxidation system of claim 1, wherein, The booster pump (3) and the catalytic oxidation reaction unit are further provided with a preheating heat exchanger (4) for heat exchange with the outlet material of the catalytic oxidation reaction unit; the cold side of the preheating heat exchanger (4) is connected with the outlet of the booster pump (3) and the inlet of the catalytic oxidation reaction unit, and the hot side of the preheating heat exchanger (4) is connected with the outlet of the catalytic oxidation reaction unit.

4. The multiphase catalytic oxidation system of claim 3, wherein, The preheating heat exchanger (4) comprises one of a plate heat exchanger, a shell-and-tube heat exchanger and a spiral plate heat exchanger.

5. The multiphase catalytic oxidation system of claim 1, wherein, An inlet of at least the first multiphase catalytic oxidation reactor (7) in the catalytic oxidation reaction unit is provided with a non-gaseous oxidant adding pipeline mixer (5) provided with a non-gaseous oxidant adding port; And / or, a gaseous oxidant injection port (11) is arranged at the bottom of each multiphase catalytic oxidation reactor (7) in the catalytic oxidation reaction unit.

6. The multiphase catalytic oxidation system of claim 1, wherein, The catalytic oxidation reaction unit comprises 2-4 multiphase catalytic oxidation reactors (7) connected in series.

7. The multiphase catalytic oxidation system of claim 6, wherein, The catalytic oxidation reaction unit is composed of 3 multiphase catalytic oxidation reactors (7) connected in series.

8. The multiphase catalytic oxidation system of claim 1, wherein, An online thermometer and an online pressure gauge are further arranged in each multiphase catalytic oxidation reactor (7) in the catalytic oxidation reaction unit; And / or, an online oxidant concentration gauge is further arranged in each multiphase catalytic oxidation reactor (7) in the catalytic oxidation reaction unit.

9. The multiphase catalytic oxidation system of claim 1, wherein, A heater (6) is arranged at the inlet of at least the first multiphase catalytic oxidation reactor (7) in the catalytic oxidation reaction unit; And / or, an online pH meter is further arranged in the pH readjusting pipeline mixer (9); And / or, a final cooling heat exchanger (8) for heat exchange with circulating cooling water is further arranged before the pH readjusting pipeline mixer (9).

10. The multiphase catalytic oxidation system of claim 9, wherein, The heater (6) is a raw water heater; And / or, the final cooling heat exchanger (8) comprises one of a plate heat exchanger, a shell-and-tube heat exchanger and a spiral plate heat exchanger; And / or, a gas-liquid separator (10) is further arranged after the final cooling heat exchanger (8).

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