High-concentration sodium cyanide wastewater treatment system

Abstract

The utility model discloses a high-concentration sodium cyanide wastewater treatment system, which is characterized in that the whole system is in an under-pressure closed state, no waste gas is generated in the process, the safety can be ensured, cyanogen breaking is carried out through alkaline hydrolysis and hydrogen peroxide oxidation in the reaction process, the cyanogen breaking effect is obvious, the concentration of sodium cyanide in wastewater can be reduced from 20000 mg / L to 0.5 mg / L, and the concentration of sodium cyanide in wastewater can be reduced from 20000 mg / L to 0.5 mg / L. And through two-stage under-pressure heat exchange and one-stage normal-temperature heat exchange in the heat recovery device, waste heat energy is utilized to the maximum extent, and the energy-saving effect is obvious.

Description

Technical Field

[0001] This utility model relates to the field of applied chemical technology, and in particular to a high-concentration sodium cyanide wastewater treatment system. Background Technology

[0002] Sodium cyanide (NaCN) has many important applications in chemical and industrial processes, playing a crucial role in organic chemical synthesis. It is primarily used to synthesize various chemical intermediates, especially organic compounds containing cyano (CN) groups. For example, sodium cyanide is commonly used in the pharmaceutical, pesticide, and plastics industries to synthesize cyano compounds.

[0003] During chemical synthesis, excessive sodium cyanide is added to ensure complete reaction, resulting in wastewater with a high concentration of sodium cyanide (20,000 mg / L). The basic characteristics of sodium cyanide wastewater include high toxicity, high cyanide concentration, high chemical oxygen demand (COD), high dissolved solids content, volatility risk, and potential metal pollution. The high cyanide concentration in the wastewater makes its treatment and remediation very challenging. Effective cyanide reduction technologies are needed to lower the sodium cyanide concentration in the wastewater to a level that meets requirements before other pollutant removal processes can be carried out, ensuring the operational safety and environmental safety of subsequent removal processes.

[0004] Existing technologies include various devices for treating sodium cyanide production wastewater. For example, utility model patent CN218321052U discloses a sodium cyanide production wastewater treatment device. This utility model includes an oxidation reaction tank connected to an H2O2 dosing device, and a catalytic device for catalyzing H2O2 oxidation is installed inside the oxidation reaction tank. The wastewater undergoes a dual process of photocatalysis and H2O2 within the oxidation reaction tank, oxidizing and decomposing the sodium cyanide in the water into non-toxic substances. The effluent meets discharge standards (CN≤0.5mg / L) and is discharged directly without adding other catalysts to the effluent, thus preventing secondary pollution. However, this utility model is only suitable for treating small volumes of sodium cyanide wastewater and cannot handle larger volumes.

[0005] For example, utility model patent CN210825526U discloses a combined high-efficiency sodium cyanide wastewater treatment device. This utility model includes a neutralization tank, a crystallizer, a centrifuge, and an oxidation reactor. The outlet of the neutralization tank is connected to the crystallizer via a pipeline; the crystallizer is connected to the centrifuge, and the liquid outlet of the centrifuge is connected to a waste liquid pipeline and a return liquid pipeline via a main pipeline; the waste liquid pipeline is connected to the oxidation reactor; the return liquid pipeline is connected to the neutralization tank; a sodium cyanide concentration detection sensor is connected to the main pipeline; a first solenoid valve is installed in the waste liquid pipeline, and a second solenoid valve is installed in the return liquid pipeline; the sodium cyanide concentration detection sensor is connected to a controller, which is connected to both the first and second solenoid valves; the oxidation reactor is equipped with an H2O2 dosing port. This device effectively reduces the residual sodium cyanide in the wastewater and solves the problem of large wastewater discharge and residual sodium cyanide during sodium cyanide production. However, this utility model cannot treat high-concentration sodium cyanide wastewater. Summary of the Invention

[0006] Therefore, a high-concentration sodium cyanide wastewater treatment system is needed, which achieves cyanide removal through two steps: alkaline hydrolysis and hydrogen peroxide oxidation, along with a matching heat recovery system. The reaction process does not produce waste gas, the effluent can meet the standard requirement of 0.5 mg / L, and it can also maximize the utilization of waste heat, featuring safety, high efficiency, and energy saving.

[0007] To achieve the above objectives, this utility model provides a high-concentration sodium cyanide wastewater treatment system, including a cyanide breaking treatment device. The cyanide breaking treatment device includes a wastewater collection tank, a wastewater preheating tank, a pressurizing pump, a primary alkaline hydrolysis tower, a hydrogen peroxide premixing tank, a secondary oxidation tower, and an effluent collection tank, which are connected in sequence according to the wastewater treatment process direction.

[0008] The wastewater collection tank is equipped with a wastewater inlet and a wastewater outlet, and receives production wastewater containing sodium cyanide from the front end through the wastewater inlet.

[0009] The wastewater preheating tank is equipped with a pretreatment outlet, a preheating unit, and a pretreatment inlet connected to the wastewater outlet, which is used to adjust the pH of the wastewater and preheat its temperature.

[0010] The booster pump is equipped with a booster outlet and a booster inlet connected to the pretreatment outlet, for pressurizing the wastewater;

[0011] The primary alkaline hydrolysis tower is equipped with an alkaline hydrolysis outlet, a heating unit, and an alkaline hydrolysis inlet connected to the pressurized outlet, for carrying out hydrolysis reactions;

[0012] The hydrogen peroxide premixing tank is equipped with a premixing outlet and a premixing inlet connected to the alkaline hydrolysis outlet, which are used to adjust the pH of the wastewater treated by the first-stage alkaline hydrolysis tower and premix hydrogen peroxide.

[0013] The secondary oxidation tower is provided with a steam inlet, an oxidation outlet, and an oxidation inlet connected to the premixed outlet. The steam inlet is connected to a steam source.

[0014] The effluent collection tank is equipped with a collection inlet connected to the oxidation outlet, used to collect wastewater after cyanide destruction.

[0015] Furthermore, it also includes a heat recovery device, which includes a heat exchanger assembly and a self-regulating pressure reducing valve assembly. The pressurization outlet is connected to the alkaline hydrolysis inlet through the heating pipeline of the heat exchanger assembly, and the oxidation outlet is connected to the collection inlet through the cooling pipeline of the heat exchanger assembly. The self-regulating pressure reducing valve assembly is located between the heat exchanger assembly and the collection inlet.

[0016] Furthermore, the heat exchanger assembly includes a primary preheating heat exchanger and a secondary preheating heat exchanger.

[0017] Furthermore, the wastewater preheating tank is equipped with a heat exchange mechanism, which is located between the heat exchanger assembly and the collection inlet.

[0018] It also includes a hydrogen peroxide feeding high-pressure metering pump, which is connected to the first feeding port.

[0019] Furthermore, it also includes a high-pressure metering pump for liquid alkali feeding, which is connected to the second feeding port.

[0020] Furthermore, the primary preheating heat exchanger and the secondary preheating heat exchanger are shell-and-tube heat exchangers, plate heat exchangers, spiral plate heat exchangers, or finned tube heat exchangers.

[0021] Furthermore, the wastewater preheating tank is provided with a jacket.

[0022] Unlike existing technologies, the relevant reaction equipment in the above-mentioned technical solution (such as the primary alkaline hydrolysis tower and the secondary oxidation tower) are all in a pressurized and closed state, and no waste gas is generated during the entire treatment process, ensuring safety. The reaction process breaks down cyanide through two-stage reactions of alkaline hydrolysis and hydrogen peroxide oxidation, with a significant cyanide reduction effect, which can reduce the concentration of sodium cyanide in wastewater from 20,000 mg / L to 0.5 mg / L. Furthermore, through two-stage pressurized heat exchange and one-stage ambient temperature heat exchange in the heat recovery device, the waste heat energy is utilized to the maximum extent, resulting in significant energy-saving effects. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a high-concentration sodium cyanide wastewater treatment system according to a specific embodiment;

[0024] Figure 2 This is a schematic diagram of the wastewater pretreatment tank of a high-concentration sodium cyanide wastewater treatment system according to a specific embodiment;

[0025] Figure 3 This is a schematic diagram of the wastewater recovery process and heat recovery circuit of a high-concentration sodium cyanide wastewater treatment system according to a specific embodiment;

[0026] Figure 4 This is a partial structural schematic diagram of a high-concentration sodium cyanide wastewater treatment system according to a specific embodiment;

[0027] Figure 5 This is a schematic diagram of another part of the structure of a high-concentration sodium cyanide wastewater treatment system described in a specific embodiment.

[0028] Explanation of reference numerals in the attached figures:

[0029] 10. Wastewater collection tank; 20. Wastewater preheating tank; 201. Pretreatment outlet; 202. Preheating unit; 203. Pretreatment inlet; 30. Booster pump; 40. Primary alkaline hydrolysis tower; 50. Hydrogen peroxide premixing tank; 60. Secondary oxidation tower; 70. Effluent collection tank; Detailed Implementation

[0030] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following description is provided in conjunction with specific embodiments and accompanying drawings.

[0031] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0032] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0033] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0034] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0035] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0036] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0037] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0038] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. Those skilled in the art to which this application pertains can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0039] Please see Figures 1 to 5 This utility model provides a high-concentration sodium cyanide wastewater treatment system, including a cyanide breaking treatment device. The cyanide breaking treatment device includes a wastewater collection tank 10, a wastewater preheating tank 20, a pressurizing pump 30, a primary alkaline hydrolysis tower 40, a hydrogen peroxide premixing tank 50, a secondary oxidation tower 60, and an effluent collection tank 70, which are connected in sequence according to the wastewater treatment process direction.

[0040] Those skilled in the art will understand that the wastewater treatment process direction refers to the flow direction of wastewater from the first process to the last process in the entire process of wastewater treatment, along the order of the processes. In this utility model, it is the direction along the "wastewater collection tank 10 - wastewater preheating tank 20 - pressurizing pump 30 - primary alkaline hydrolysis tower 40 - hydrogen peroxide premixing tank 50 - secondary oxidation tower 60 - effluent collection tank 70".

[0041] The wastewater preheating tank 20 is equipped with a preheating unit for adjusting the pH and preheating the wastewater.

[0042] The primary alkaline hydrolysis tower 40 is equipped with a heating unit and a pressurization unit for carrying out hydrolysis reactions;

[0043] The hydrogen peroxide premixing tank 50 is used to adjust the pH of the wastewater treated by the primary alkaline decomposition tower 40 and to premix hydrogen peroxide.

[0044] The effluent collection tank 70 is used to collect wastewater after cyanide destruction is completed;

[0045] The wastewater collection tank 10 is equipped with a wastewater inlet and a wastewater outlet. The wastewater inlet receives production wastewater containing sodium cyanide from the upstream process. The sodium cyanide concentration in the production wastewater is not less than 20,000 mg / L, i.e., high-concentration sodium cyanide wastewater (hereinafter referred to as wastewater). The wastewater collection tank 10 can regulate water quality by collecting various streams of sodium cyanide wastewater from the production process and mixing wastewater of different concentrations in a proportional manner, so that the wastewater reaches a relatively stable concentration for subsequent treatment. This is beneficial for stabilizing subsequent chemical dosage and reaction time. Furthermore, since the generation of wastewater from various streams in the production process is not continuous and stable, the wastewater collection tank 10 can effectively ensure a continuous inflow of wastewater to the downstream process.

[0046] The wastewater preheating tank 20 is equipped with a pretreatment outlet 201, a preheating unit 202, and a pretreatment inlet 203 connected to the wastewater outlet. After being transferred and adjusted to a suitable water quality in the wastewater collection tank 10, the wastewater is transferred to the wastewater preheating tank 20 through the wastewater outlet and pretreatment inlet for pretreatment. The pretreatment includes pH adjustment and preheating. The pH needs to be adjusted to 12-14 to provide an alkaline environment for the subsequent alkaline hydrolysis reaction. Preheating preheats the wastewater, improving heating efficiency and facilitating a faster alkaline hydrolysis reaction. The top of the wastewater preheating tank 20 is equipped with a liquid alkali inlet 204, and a liquid alkali metering pump 84 is installed at the front end of the liquid alkali inlet 204 for precise input of liquid alkali to adjust the pH of the wastewater.

[0047] The preheating unit can employ electric heating devices, external coil heating devices, etc. Electric heating devices refer to devices that heat the wastewater in the wastewater preheating tank 20 by installing electric heating elements (such as resistance wires, silicon carbide rods, PTC ceramics, etc.) inside or outside the wastewater preheating tank 20, utilizing the heat generated by the current passing through resistance. The heating principle of the external coil heating device is to achieve heat transfer through its external coil structure to heat the wastewater inside the wastewater preheating tank 20. In this process, a heat-conducting medium, such as hot water, steam, or hot oil, is first directly introduced into the external coil. As these media pass through the coil, their heat energy is conducted to the outer surface of the coil, and then further transferred to the outer wall of the wastewater preheating tank 20 through heat conduction, thereby raising the temperature inside the wastewater preheating tank 20. In addition, the wastewater preheating tank 20 can also be heated at a constant temperature by injecting a hot melt medium through its jacket.

[0048] The pressurization pump 30 is equipped with a pressurization outlet and a pressurization inlet connected to the pretreatment outlet, used to pressurize the wastewater. The wastewater, after pretreatment by the wastewater preheating tank 20, is input into the pressurization pump 30 through the pretreatment outlet and the pressurization inlet. The pressurization pump 30 pressurizes the wastewater to about 0.6 MPa, which is beneficial to the subsequent hydrolysis reaction.

[0049] The booster pump 30 can be a commonly used device in existing wastewater treatment processes, such as a high-pressure pump (centrifugal pump, plunger pump, etc.). It typically consists of a pump body, inlet and outlet pipes, a drive unit (including a motor, coupling, reducer, etc.), and internal working parts (such as impeller, piston, plunger, etc.). The working principle of the high-pressure pump involves three main stages: the water inlet stage, where liquid enters the low-pressure area of ​​the pump through the suction pipe; the pressurization stage, where, for centrifugal pumps, the liquid is driven by the impeller to generate centrifugal force and is thrown outward, increasing the pressure, while for positive displacement pumps, such as plunger pumps, the reciprocating motion of the piston or plunger changes the pump chamber space to achieve liquid intake and discharge; and the drainage stage, where the pressurized liquid is discharged under high pressure through the outlet pipe.

[0050] The primary alkaline hydrolysis tower 40 is equipped with an alkaline hydrolysis outlet, a heating unit, and an alkaline hydrolysis inlet connected to the pressurized outlet for hydrolysis reaction. Wastewater pressurized by the pressurized pump 30 is fed into the primary alkaline hydrolysis tower 40 through the pressurized outlet and the alkaline hydrolysis inlet. At this point, the wastewater has a pH of 12-14 and a water pressure of 0.6 MPa. The heating unit controls the temperature inside the tower at 130-160℃. The specific structure of the heating unit can be referred to the aforementioned preheating unit and will not be repeated here. Under strongly alkaline conditions, sodium cyanide undergoes a hydrolysis reaction. Under high temperature and high pressure conditions, the reaction takes 3-4 hours. After the reaction, the concentration of sodium cyanide in the wastewater can be reduced to approximately 1000 mg / L, and the pH will decrease to approximately 6-7. The concentration of sodium cyanide in the wastewater after passing through the primary alkaline hydrolysis tower 40 is significantly reduced.

[0051] The principle of alkaline hydrolysis reaction in cyanide treatment is as follows: In an environment with pH=14, temperature 130-160℃, and pressure 0.6MPa, sodium cyanide (NaCN) wastewater will undergo hydrolysis to generate cyanate (NaOCN) and sodium hydroxide (NaOH). This process is accelerated by the promoting effect of high temperature and strong alkaline environment.

[0052] The hydrogen peroxide premixing tank 50 is equipped with a premixing outlet and a premixing inlet connected to the alkali hydrolysis outlet, used for adjusting the pH and premixing hydrogen peroxide in the wastewater treated by the primary alkali hydrolysis tower 40. The hydrogen peroxide premixing tank also has a first feed port for hydrogen peroxide and a second feed port for liquid alkali. Feeding hydrogen peroxide through the first feed port further adjusts the hydrogen peroxide concentration in the premixing tank to ensure the normal progress of the oxidation reaction. Feeding liquid alkali through the second feed port further adjusts the pH value in the premixing tank to ensure the acid-base environment meets the reaction requirements. Preferably, a high-pressure metering pump 85 for hydrogen peroxide and a high-pressure metering pump 86 for liquid alkali can be separately installed to deliver hydrogen peroxide and liquid alkali into the premixing tank 50, ensuring accurate input and stable system pressure. Wastewater from the hydrolysis reaction in the primary alkaline hydrolysis tower 40 is fed into the hydrogen peroxide premixing tank 50 through the alkaline hydrolysis outlet and the premixing inlet. The pH is then adjusted to 12 again in the hydrogen peroxide premixing tank 50 to facilitate the subsequent oxidation reaction, and 1% hydrogen peroxide is added.

[0053] The secondary oxidation tower 60 is equipped with a steam inlet, an oxidation outlet, and an oxidation inlet connected to the premixed outlet. The steam inlet is connected to a steam source. Wastewater that has undergone pH adjustment and premixing with hydrogen peroxide in the hydrogen peroxide premixing tank 50 is input into the secondary oxidation tower 60 through the premixed outlet and oxidation inlet. Saturated steam (steam pressure not less than 0.6 MPa) is introduced through the steam inlet to control the temperature inside the secondary oxidation tower 60 at approximately 130-160℃ and the pressure at approximately 0.6 MPa. Sodium cyanide undergoes a hydrolysis and oxidation reaction, which takes approximately 2 hours. After the reaction, the concentration of sodium cyanide in the wastewater can be reduced to 0.5 mg / L.

[0054] The principle of hydrogen peroxide oxidation reaction is as follows: after adding 1% hydrogen peroxide, hydrogen peroxide acts as an oxidant to accelerate the oxidation process of sodium cyanide. Under this condition, both the hydrolysis and oxidation processes of sodium cyanide wastewater will occur, and hydrogen peroxide may make the whole process faster and more effective.

[0055] The effluent collection tank 70 is equipped with a collection inlet connected to the oxidation outlet. The effluent collection tank 70 is used to collect the wastewater after the cyanide destruction is completed. After passing the test, the wastewater is transported to the treatment process for removing other pollutants.

[0056] Preferably, the system also includes a heat recovery device, which comprises a heat exchanger assembly and a self-regulating pressure-reducing valve assembly 83. The pressurized outlet is connected to the alkaline hydrolysis inlet via the heating pipeline of the heat exchanger assembly, and the oxidation outlet is connected to the collection inlet via the cooling pipeline of the heat exchanger assembly. The self-regulating pressure-reducing valve assembly is located between the heat exchanger assembly and the collection inlet. Specifically, the heat exchanger assembly includes a primary preheating heat exchanger 81 and a secondary preheating heat exchanger 82. The wastewater treated by the cyanide-breaking treatment device retains a high temperature and pressure, with an outlet temperature of 130-160℃ and a pressure of approximately 0.6MPa. By setting up the heat exchanger assembly, the high-temperature wastewater is connected from the oxidation outlet of the secondary oxidation tower 60 to the cooling pipeline of the heat exchanger assembly. The heat is transferred to the wastewater to be treated in the heating pipeline of the heat exchanger assembly through the heat exchange elements, realizing heat recovery and reuse, reducing treatment costs, and the pressure of the treated wastewater is reduced to atmospheric pressure by the self-regulating pressure-reducing valve assembly for subsequent treatment. Through two-stage high-pressure heat exchange, the heat exchanger can exchange heat under high pressure and features high efficiency, anti-fouling, and easy disassembly and cleaning.

[0057] The self-regulating pressure reducing valve assembly 83 is an automated fluid control device, mainly used for automatically controlling and regulating the pressure in a fluid system to ensure the safe and stable operation of the system. In this invention, it is used to automatically control the pressure reduction of treated wastewater. It typically includes components such as a pressure regulating valve, a safety valve, and a check valve. The pressure regulating valve is the core component of the self-regulating pressure reducing valve assembly 83. Its working principle is to regulate the flow rate of the medium by controlling the opening degree of the opening and closing element in the valve body, thereby reducing the pressure of the medium and maintaining the outlet pressure within a certain range, thus achieving the pressure reduction of wastewater.

[0058] After two stages of high-pressure heat exchange, pressure reduction, and one stage of atmospheric pressure heat exchange, the wastewater temperature is reduced to meet the discharge and collection requirements.

[0059] The heat exchanger assembly is a device composed of multiple heat exchangers, such as a primary preheating heat exchanger 81 and a secondary preheating heat exchanger 82. Both the primary preheating heat exchanger 81 and the secondary preheating heat exchanger 82 can utilize existing technologies for heat exchange, such as shell-and-tube heat exchangers, plate heat exchangers, spiral plate heat exchangers, and finned tube heat exchangers. By setting up two stages of heat exchangers to preheat the wastewater at the front end of the primary alkali decomposition tower 40, the heat from the wastewater treated by the cyanide removal device can be fully reused, reducing treatment costs and improving the heating efficiency of the wastewater.

[0060] Even after pressure reduction, the wastewater still retains residual heat that can be exchanged. Preferably, the wastewater preheating tank 20 is equipped with a heat exchange mechanism, which is located between the heat exchanger assembly and the collection inlet. This heat exchange mechanism can refer to existing heat exchange mechanisms, such as an external coil (i.e., a heat exchange mechanism) installed on the outer wall of the wastewater preheating tank 20. The wastewater is then transported to the effluent collection tank 70 via the external coil, allowing heat in the wastewater to be transferred to the wastewater preheating tank 20, providing heat for the wastewater to be pretreated. The wastewater preheating tank 20 then performs the final heat exchange, eventually reaching the effluent temperature and reducing treatment costs.

[0061] Referring to the accompanying drawings and the above-described high-concentration sodium cyanide wastewater treatment system, this utility model also provides a method for treating sodium cyanide wastewater, comprising the following steps:

[0062] S01: Input the production wastewater containing high concentration of sodium cyanide into the wastewater collection tank 10 and adjust the water quality;

[0063] S02: The high-concentration sodium cyanide wastewater that has been prepared in the wastewater collection tank 10 is transferred to the wastewater preheating tank 20 for pretreatment. The pretreatment involves adding alkali to adjust the pH to 12-14 and turning on the preheating unit to preheat to a certain temperature.

[0064] S03: The pretreated high-concentration sodium cyanide wastewater is transferred to the primary alkaline hydrolysis tower 40. The heating unit is turned on to heat the internal temperature of the primary alkaline hydrolysis tower 40 to the first temperature range. The pressurization unit is turned on to pressurize the wastewater to 0.6MPa. The sodium cyanide in the wastewater undergoes hydrolysis in the primary alkaline hydrolysis tower 40. The reaction time is controlled between 3-4 hours.

[0065] S04: Transfer the wastewater after the hydrolysis reaction is completed to the hydrogen peroxide premixing tank 50, add alkali to adjust the pH to 12, and add 1% hydrogen peroxide;

[0066] S05: Transfer the wastewater after hydrogen peroxide premixing to the secondary oxidation tower 60, and introduce steam with a pressure greater than 0.6 MPa. The temperature inside the tower is controlled within the first temperature range, and the pressure is controlled at 0.6 MPa. The sodium cyanide wastewater undergoes hydrolysis and oxidation reactions for 2 hours.

[0067] S06: The wastewater after the oxidation reaction is completed is transferred to the effluent collection tank 70 for collection.

[0068] Furthermore, step S06 also includes the following sub-steps: S061: The wastewater after the oxidation reaction is subjected to a first heat recovery, and the first heat recovery is used to heat the wastewater that is pumped to the first-stage alkaline decomposition tower 40 by the self-pressurizing pump 30. The wastewater after the cyanide decomposition reaction has an outlet temperature of 130-160℃ and a pressure of about 0.6MPa. The first heat recovery is carried out by high-pressure heat exchange through a two-stage preheating heat exchanger. The heat exchanger group can exchange heat under high pressure and has the characteristics of high efficiency, anti-fouling and easy disassembly and cleaning.

[0069] Preferably, step S06 further includes the following sub-step: S062: After step S061 is completed, the wastewater that has undergone one heat recovery is depressurized and subjected to a second heat recovery. The heat recovered in the second step is used to heat the wastewater in the wastewater preheating tank 20. After passing through two stages of high-pressure heat exchange and an automatic pressure-reducing valve group, the pressure of the wastewater is reduced to the normal pressure. The wastewater temperature is still around 70°C, so it can pass through the atmospheric pressure wastewater preheating tank 20 for heat exchange again, i.e., a second heat recovery, so that its outlet water temperature is around 50°C, which meets the discharge collection requirements.

[0070] Preferably, the temperature range of the first temperature range is 130-160℃. At a pressure of 0.6 MPa, the temperature of the saturated steam is 158℃, which is lower than the saturated steam temperature.

[0071] Because sodium cyanide wastewater reacts under alkaline conditions and does not produce highly toxic hydrogen cyanide, the related reaction equipment of this invention (primary alkaline hydrolysis tower 40, secondary oxidation tower 60, etc.) are all in a pressurized and closed state, producing no waste gas during the process, thus ensuring safety. The reaction process involves two stages of cyanide removal through alkaline hydrolysis and hydrogen peroxide oxidation, resulting in significant cyanide removal efficiency, reducing the concentration of sodium cyanide in the wastewater from 20,000 mg / L to 0.5 mg / L. Furthermore, the heat recovery device utilizes two stages of pressurized heat exchange and one stage of ambient temperature heat exchange to maximize the utilization of waste heat energy, resulting in significant energy savings.

[0072] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection for this utility model. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of this utility model, or equivalent structural or procedural transformations made using the content of this utility model's specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection for this utility model.

Claims

1. A high concentration sodium cyanide wastewater treatment system, characterized by: The device comprises a cyanide breaking treatment device, which comprises a wastewater collecting tank, a wastewater preheating tank, a pressurizing pump, a first alkaline hydrolysis tower, a hydrogen peroxide premixing tank, a second oxidation tower and a water outlet collecting tank connected in sequence according to the wastewater treatment process direction. The wastewater collecting tank is provided with a wastewater inlet and a wastewater outlet, and the wastewater inlet is used to receive the front-end wastewater containing sodium cyanide. The wastewater preheating tank is provided with a pretreatment outlet, a preheating unit and a pretreatment inlet connected with the wastewater outlet, and is used to adjust the pH value and preheat the temperature of the wastewater. The pressurizing pump is provided with a pressurizing outlet and a pressurizing inlet connected with the pretreatment outlet, and is used to pressurize the wastewater. The first alkaline hydrolysis tower is provided with an alkaline hydrolysis outlet, a heating unit and an alkaline hydrolysis inlet connected with the pressurizing outlet, and is used to perform a hydrolysis reaction. The hydrogen peroxide premixing tank is provided with a premixing outlet and a premixing inlet connected with the alkaline hydrolysis outlet, and is used to adjust the pH value and premix the hydrogen peroxide of the wastewater treated by the first alkaline hydrolysis tower, and is further provided with a first feeding port for inputting hydrogen peroxide and a second feeding port for inputting liquid alkali. The second oxidation tower is provided with a steam inlet, an oxidation outlet and an oxidation inlet connected with the premixing outlet, and the steam inlet is connected to a steam source. The water outlet collecting tank is provided with a collecting inlet connected with the oxidation outlet, and is used to collect the wastewater after the cyanide breaking is completed.

2. The high concentration sodium cyanide wastewater treatment system according to claim 1, characterized in that: The device further comprises a heat recovery device, which comprises a heat exchanger group and an automatic pressure reducing valve group, the pressurizing outlet is connected to the alkaline hydrolysis inlet through the heating pipeline of the heat exchanger group, the oxidation outlet is connected to the collecting inlet through the cooling pipeline of the heat exchanger group, and the automatic pressure reducing valve group is arranged between the heat exchanger group and the collecting inlet.

3. The high concentration sodium cyanide wastewater treatment system according to claim 2, characterized in that: The heat exchanger group comprises a first preheating heat exchanger and a second preheating heat exchanger.

4. The high concentration sodium cyanide wastewater treatment system according to claim 3, characterized in that: The wastewater preheating tank is provided with a heat exchange mechanism arranged between the heat exchanger group and the collecting inlet.

5. The high concentration sodium cyanide wastewater treatment system of claim 1, wherein: The device further comprises a hydrogen peroxide feeding high-pressure metering pump connected with the first feeding port.

6. The high concentration sodium cyanide wastewater treatment system of claim 1, wherein: The device further comprises a liquid alkali feeding high-pressure metering pump connected with the second feeding port.

7. The high concentration sodium cyanide wastewater treatment system of claim 3, wherein: The first preheating heat exchanger and the second preheating heat exchanger are tube-shell heat exchangers, plate heat exchangers, spiral plate heat exchangers or finned tube heat exchangers.

8. The high concentration sodium cyanide wastewater treatment system of claim 1, wherein: The wastewater preheating tank is provided with a sandwich layer.

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