A method for treating chemical waste

Abstract

The present application relates to a kind of processing method of waste containing hydrogen cyanide and ammonia, it includes: the wastewater containing hydrogen cyanide and ammonia and the waste gas containing hydrogen cyanide and ammonia are introduced into absorption tank respectively, and hydrogen peroxide solution is added to the absorption tank, adjust pH to obtain the liquid with pH value of 6 to 11;The liquid is transported to oxidation reactor, the reaction temperature of the oxidation reactor is controlled at 40 to 60 ℃, and the total residence time of the liquid in the oxidation reactor is 150 to 270 minutes, to oxidize hydrogen cyanide into ammonia and carbon dioxide;Ammonia in the liquid is removed by gas stripping method.The method can safely and efficiently reduce hydrogen cyanide and ammonia in waste gas and wastewater, efficiently and significantly oxidize hydrogen cyanide into carbon dioxide and ammonia without or with low by-product, without using heavy metal catalyst.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of chemical waste treatment. In particular, the present invention relates to a method for treating waste containing low concentrations of hydrogen cyanide. BACKGROUND

[0002] In industrial production processes, the nitrogen content of raw materials exceeding the expected level can easily lead to the production of by-products such as hydrogen cyanide, ammonia, etc. Such pollutants will eventually enter the wastewater and exhaust gas system. In order to meet the environmental impact assessment (EIA) limits or the acceptable standards of the plant wastewater treatment facility, it is necessary to develop efficient purification methods to reduce the content of hydrogen cyanide and ammonia in the emissions. Various purification methods are known in the prior art to treat wastewater or exhaust gas containing hydrogen cyanide and / or ammonia.

[0003] CN 111356656 A discloses a method for treating wastewater containing cyanide compounds and metal compounds, converting the cyanide compounds into carbon dioxide and nitrogen gas, mixing the wastewater with a chlorine solution and an alkaline reagent in a single oxidation step to obtain a mixture, the alkaline reagent being added in an amount such that the pH of the mixture remains between 8.8 and 9.5, and the chlorine solution being added in an amount such that the redox potential of the mixture remains between 150 mV and 450 mV. This method is accompanied by the generation of residues, which requires additional solid waste treatment, and requires precise regulation of the pH and redox potential, increasing the complexity of the operation, and the chlorine-containing oxidizing agent introduced by this method can increase the risk of equipment corrosion and potential secondary pollution of gaseous substances containing chlorine.

[0004] CN 102921285 B discloses a method for treating exhaust gas containing hydrogen cyanide and ammonia, which uses hydrogen peroxide and excess oxygen as oxidizing agents, and in a spray absorption tower, the hydrogen cyanide and ammonia are oxidized by the spray liquid and excess air to generate CO2 and N2. However, this method relies on heavy metal ions as catalysts, which can cause secondary pollution caused by heavy metals, etc. risks, and the cost of the catalyst is high and requires additional treatment process to separate the heavy metals. In addition, the storage of oxygen also requires special supporting facilities, such as pressurized gas storage devices or refrigerated liquid storage devices.

[0005] CN 210825526 U discloses a combined high-efficiency sodium cyanide wastewater treatment device, which proposes to use a photocatalytic device instead of a traditional catalyst, and the cyanide-containing wastewater is oxidized and decomposed into non-toxic substances by the dual action of the photocatalytic device and H2O2 in the oxidation reaction tank. Although this device avoids the use of traditional heavy metal catalysts, its device is complex, and the photocatalytic device it relies on significantly increases energy consumption, and the maintenance cost of the optical components is high, and the penetration of ultraviolet light is controlled by water quality, affecting the stability of the treatment.

[0006] Current treatment methods mostly focus on the independent treatment of a single medium (wastewater or waste gas), lacking solutions for simultaneously treating gases and liquids containing HCN, or for simultaneously treating multiple streams of liquids with different HCN concentrations. Summary of the Invention

[0007] One object of the present invention is to overcome at least one disadvantage of the prior art, and in particular to provide a treatment method with low or no secondary pollutants, avoiding the use of heavy metal catalysts and gases, to safely and efficiently reduce hydrogen cyanide and ammonia in waste gas and wastewater. This object is achieved by the method of the present invention.

[0008] On one hand, the present invention provides a method for treating waste containing hydrogen cyanide and ammonia, characterized in that the treatment method includes the following steps:

[0009] (1) Wastewater containing hydrogen cyanide and ammonia is pumped to an absorption tank, and hydrogen peroxide solution and pH adjuster are added to the absorption tank to obtain a liquid with a pH value of 6 to 11.

[0010] (2) The waste gas containing hydrogen cyanide and ammonia is introduced into the absorption tank, and the hydrogen cyanide and ammonia in the waste gas are absorbed by the liquid obtained in step (1).

[0011] (3) The liquid obtained in step (2) is transported to an oxidation reactor, the reaction temperature of which is controlled at 40 to 60°C, and the total residence time of the liquid in the oxidation reactor is 150 to 270 minutes, so as to oxidize cyanide into ammonia and carbon dioxide.

[0012] (4) The liquid treated in step (3) is transported to a deammoniation unit, where ammonia is removed from the liquid by air stripping, and the liquid is heated to decompose the remaining hydrogen peroxide, so that the concentration of ammonia in the treated liquid is reduced to no more than 80 mg / L and the concentration of hydrogen cyanide is reduced to no more than 5 mg / L.

[0013] The total amount of hydrogen peroxide added in the method is in a mass ratio of 20:1 to 50:1 to the total amount of initial hydrogen cyanide in the wastewater and the waste gas.

[0014] On the other hand, the present invention provides a processing apparatus system using the processing method of the present invention, the connection relationship of which is attached. Figure 1 It is shown schematically.

[0015] The treatment method and treatment device system of the present invention enable the safe and efficient reduction of hydrogen cyanide and ammonia in waste gas and wastewater, efficiently and significantly oxidizing cyanide to carbon dioxide and ammonia with little or no byproducts and without the use of heavy metal catalysts, and removing the generated ammonia as well as the ammonia initially contained in the waste gas and wastewater. Attached Figure Description

[0016] Figure 1 A schematic diagram of a treatment plant system using the method of the present application is shown.

[0017] Reference signs are explained as follows:

[0018] Treatment plant system 10; grey water buffer tank 101; second flash tank (i.e. grey water flash tank) 102; second gas phase 1021; second liquid phase 1022; first flash tank (i.e. acidic wastewater flash tank) 103; first gas phase 1031; first liquid phase 1032; absorption tank 104; gas-liquid mixer 1041; pH adjuster 1042; hydrogen peroxide 1043; recycle line 1044; hydrogen cyanide and ammonia containing wastewater 1045; hydrogen cyanide and ammonia containing offgas 1046; multi-stage oxidation reactor 105; primary oxidation reactor 105a; secondary oxidation reactor 105b; deaminating device 106; incineration flare 1061; catalytic oxidation device 1062; higher concentration downstream wastewater treatment device 2a, lower concentration downstream wastewater treatment device 2b; second wastewater (i.e. grey water) 3; first wastewater (i.e. acidic wastewater) 4.

[0019] Figure 2 A plot of the change in HCN concentration in the wastewater in Example 1 is shown.

[0020] Figure 3 A plot of the change in HCN concentration in the wastewater in Example 2 is shown.

[0021] Figure 4 A plot of the change in HCN concentration in the wastewater in Example 3 is shown. DETAILED DESCRIPTION

[0022] The application is described in more detail in the following paragraphs. For the avoidance of doubt, any feature of one aspect of the application can be employed with any other aspect of the application. Unless explicitly stated otherwise, each aspect described is combinable with any other aspect or aspects. In particular, any feature indicated as being preferred is combinable with any other feature or features indicated as being preferred.

[0023] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective range, and the recited endpoints. It is to be understood that any specific numerical value stated or implied by an indicated measurement can be associated with any explicit numerical limitation implying that specific value.

[0024] All references cited in this specification are hereby incorporated by reference in their entirety.

[0025] In the context of the present application, unless otherwise defined, all terms used in this application, including technical and scientific terms, have the meaning commonly understood by one of ordinary skill in the art to which this application belongs.

[0026] The term "comprising" as used herein is synonymous with "including", "containing", and "comprehending", and is inclusive or open-ended and does not exclude additional, unrecited elements, components, or process steps.

[0027] All percentages are weight / weight percentages, unless otherwise specified.

[0028] Except in the operating and comparative examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials and / or conditions of material s, physical properties of materials and / or use are to be understood as modified in all instances by the term "about".

[0029] The term "hydrogen cyanide" as used herein refers to hydrogen cyanide (HCN) and cyanide in liquid phase, and hydrogen cyanide (HCN) in gas phase. The cyanide content herein is calculated as hydrogen cyanide (HCN). The hydrogen cyanide content can be determined using any known detection method in the art, for example according to standard HG / T 5544-2019.

[0030] The term "ammonia" as used herein refers to ammonia (NH3) and NH4 + in liquid phase, and ammonia gas in gas phase. The NH4 + content herein is calculated as ammonia (NH3). The ammonia content can be determined using any known detection method in the art.

[0031] The term "first wastewater comprising hydrogen cyanide and ammonia" as used herein is interchangeable with "first wastewater", and refers to sour water from upstream reactions, which typically comprises a higher hydrogen cyanide content, which is subjected to a flash operation to obtain a first liquid phase, the hydrogen cyanide content in the first liquid phase is typically 5 to 100 mg / L. Since the lower concentration downstream wastewater treatment device 2b has a lower tolerance concentration for hydrogen cyanide, the first liquid phase needs to be subjected to an oxidation treatment before it can be delivered to the lower concentration downstream wastewater treatment device 2b.

[0032] The term "second wastewater comprising hydrogen cyanide" as used herein refers to soot water from flue gas filtration, which is subjected to a flash operation to obtain a second liquid phase. Since the higher concentration downstream wastewater treatment device 2a has a higher tolerance concentration for hydrogen cyanide, and the hydrogen cyanide content in the second liquid phase is typically lower than 20 mg / L, it can already meet the downstream treatment concentration requirement, thus the liquid phase does not need to be subjected to further oxidation treatment, and can be directly delivered to the higher concentration downstream wastewater treatment device 2a.

[0033] It can be seen that the treatment system according to the present application can simultaneously treat different kinds of wastewater with different components according to the treatment capacity of the downstream wastewater treatment device, thereby improving the flexibility and integration of chemical wastewater treatment.

[0034] The term "flash" or "flash evaporation" as used herein means an operation process commonly understood in chemical industry, which refers to an operation process of preheating a liquid under high pressure, then reducing the pressure and sending it into a flash tank to cause boiling evaporation and escape of dissolved gas in the instant of pressure reduction. By the flash evaporation optionally used in the present application, the cavitation of the pump caused by the escape of a large amount of gas during the pumping of the acidic wastewater and / or grey water with a large amount of dissolved gas can be avoided. The operating pressure and temperature of the flash can be routinely set by those skilled in the art.

[0035] The term "waste containing hydrogen cyanide and ammonia" as used herein includes wastewater containing hydrogen cyanide and ammonia and off-gas containing hydrogen cyanide and ammonia.

[0036] The "wastewater containing hydrogen cyanide and ammonia" as used herein is used interchangeably with "the wastewater", which refers to wastewater with an initial hydrogen cyanide content of not higher than 100 mg / L and an initial ammonia content of not higher than 2500 mg / L. In an embodiment of the present application, the wastewater containing hydrogen cyanide and ammonia can be the first liquid phase obtained by flash evaporation of the first wastewater containing hydrogen cyanide and ammonia.

[0037] The "off-gas containing hydrogen cyanide and ammonia" as used herein is used interchangeably with "the off-gas", which refers to off-gas with an initial hydrogen cyanide content of not higher than 0.0028 mole% and an initial ammonia content of not higher than 0.0021 mole%. In an embodiment of the present application, the off-gas containing hydrogen cyanide and ammonia can be the first gas phase obtained by flash evaporation of the first wastewater containing hydrogen cyanide and ammonia or a mixture of the first gas phase and the second gas phase obtained by flash evaporation of the second wastewater containing hydrogen cyanide.

[0038] The "absorption tank" as used herein refers to a container for absorbing the off-gas containing hydrogen cyanide and ammonia, buffering the wastewater containing hydrogen cyanide and ammonia, and facilitating the mixing of the two.

[0039] In an embodiment of the present application, a treatment method of waste containing hydrogen cyanide and ammonia is provided, characterized in that the treatment method comprises the following steps:

[0040] (1) introducing the wastewater containing hydrogen cyanide and ammonia into an absorption tank, and adding hydrogen peroxide solution and a pH adjusting agent into the absorption tank to obtain a liquid with a pH value of 6 to 11 by mixing,

[0041] (2) introducing the off-gas containing hydrogen cyanide and ammonia into the absorption tank, and absorbing the hydrogen cyanide and ammonia in the off-gas by the liquid obtained in step (1),

[0042] (3) transferring the liquid obtained in step (2) to an oxidation reactor, controlling the reaction temperature of the oxidation reactor at 40 to 60°C, and controlling the total residence time of the liquid in the oxidation reactor at 150 to 270 minutes, to oxidize hydrogen cyanide to ammonia and carbon dioxide,

[0043] (4) transferring the liquid treated in step (3) to an ammonia removal device, removing ammonia in the liquid by gas stripping, and heating the liquid to decompose the remaining hydrogen peroxide, so that the concentration of ammonia in the treated liquid is reduced to not higher than 80 mg / L and the concentration of hydrogen cyanide is reduced to not higher than 5 mg / L,

[0044] wherein the mass ratio of the total amount of hydrogen peroxide added in the process to the total amount of initial hydrogen cyanide in the waste water and the waste gas is 20:1 to 50:1,

[0045] the initial hydrogen cyanide content in the waste water is not higher than 100 mg / L, and the initial ammonia content in the waste water is not higher than 2500 mg / L;

[0046] the initial hydrogen cyanide content in the waste gas is not higher than 0.0028 mol%, and the initial ammonia content in the waste gas is not higher than 0.0021 mol%.

[0047] In one embodiment of the present application, the pH of the liquid obtained in step (1) can be 6 to 10, 6 to 9, 6 to 8, 6 to 7, 7 to 9, 7 to 8, 8 to 11, 8 to 9, or 9 to 10. In a preferred embodiment, the pH of the liquid obtained in step (1) can be 6 to 9. In another preferred embodiment, the pH of the liquid obtained in step (1) can be 8 to 11.

[0048] In one embodiment of the present application, the hydrogen peroxide solution added in step (1) and / or (3) has a concentration of at least 10 wt%, preferably at least 20 wt%, for example at least 25, 27.5, or 30 wt%.

[0049] In one embodiment of the present application, hydrogen peroxide solution can be added to the oxidation reactor in step (3). In a specific embodiment, the oxidation reactor in step (3) can be a single oxidation reactor, or a multi-stage oxidation reactor, preferably a multi-stage oxidation reactor, for example a two-stage, three-stage, four-stage or more-stage oxidation reactor, more preferably a multi-stage oxidation reactor in series. In a specific embodiment, hydrogen peroxide solution can be added to part or all of the multi-stage oxidation reactor in step (3).

[0050] In one embodiment of the present application, the mass ratio of the total amount of hydrogen peroxide added in the process to the total amount of initial hydrogen cyanide in the waste water and the waste gas is from 20:1 to 50:1. For example, the molar ratio can be from 30:1 to 50:1, from 30:1 to 45:1, from 30:1 to 35:1, from 35:1 to 40:1, or from 40:1 to 45:1, etc. In one embodiment of the present application, the mass ratio of the total amount of hydrogen peroxide added in the process to the total amount of initial hydrogen cyanide in the waste water and the waste gas is from 30:1 to 45:1. In a particular embodiment, the amount of hydrogen peroxide added to the absorption tank is at least 50%, 60%, 70%, 80%, or at least 90% of the total amount of hydrogen peroxide, preferably, the amount of hydrogen peroxide added to the absorption tank is 100% of the total amount of hydrogen peroxide. In a particular embodiment, the amount of hydrogen peroxide added to the oxidation reactor is less than 50%, 40%, 30%, 20%, 10%, 8%, 6%, 4%, 2%, or less than 1% of the total amount of hydrogen peroxide.

[0051] In one embodiment of the present application, the oxidation reactor in step (3) is a multi-stage oxidation reactor, and the total residence time of the liquid obtained in step (2) in the multi-stage oxidation reactor is from 165 to 180 minutes. In a particular embodiment, the oxidation reactor in step (3) is a two-stage, three-stage or higher stage oxidation reactor, and the total residence time of the liquid obtained in step (2) in the multi-stage oxidation reactor is from 165 to 180 minutes. The residence time can be, for example, from 150 to 270, from 150 to 225, from 150 to 200, from 150 to 180, from 150 to 170, from 150 to 165, from 165 to 225, from 165 to 200, from 165 to 180 minutes, from 165 to 175 minutes, from 165 to 170 minutes, preferably from 165 to 180 minutes.

[0052] In one embodiment of the present application, the reaction temperature in step (3) is from 40 to 60°C, for example, from 40 to 59, from 40 to 57, from 40 to 55, from 45 to 55, or from 40 to 50°C, etc. In a particular embodiment, the reaction temperature in step (3) is from 40 to 55°C. A high temperature alarm can be provided in the oxidation reactor of the present application, and the oxidation reactor is cooled to below 60°C when the reactor temperature is higher than 60°C. The cooling can be performed by any conventional means known in the art, for example, by a heat exchanger, a refrigerator, etc. For example, the cooling can be performed by adding hydrogen peroxide solution to the oxidation reactor, wherein the amount of hydrogen peroxide solution added is such that the mass ratio of the total amount of hydrogen peroxide added in the process of the present application to the total amount of initial hydrogen cyanide in the waste water and the waste gas meets the definition in the process of the present application.

[0053] In one embodiment of the present application, step (2) comprises absorbing hydrogen cyanide and ammonia in the waste gas with liquid drawn from the bottom of the absorption tank at a gas-liquid mixer. In a preferred embodiment, the gas-liquid mixer can be a venturi-type ejector.

[0054] In one embodiment of the present application, the pH adjusting agent added in step (1) is any conventional pH adjusting agent known in the art, including acidic pH adjusting agents and basic pH adjusting agents, as long as it will not be oxidized by hydrogen peroxide, such as dilute sulfuric acid, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and the like. In a specific embodiment, the pH adjusting agent is selected from the group consisting of dilute sulfuric acid, sodium hydroxide, and potassium hydroxide.

[0055] In one embodiment of the present application, the hydrogen peroxide solution added in step (1) is acidic hydrogen peroxide. In a specific embodiment, the hydrogen peroxide solution added in step (1) can be reduced to a pH value of 5 or less, preferably 4 or less, such as 3 to 5, 3 to 4, and the like, by the acidic pH adjusting agent.

[0056] In a specific embodiment of the present application, the pH adjusting agent is selected from the group consisting of dilute sulfuric acid, sodium hydroxide, and potassium hydroxide, and adding the hydrogen peroxide solution and the pH adjusting agent to the absorption tank in step (1) comprises mixing dilute sulfuric acid with the hydrogen peroxide solution before adding to the liquid drawn from the bottom of the absorption tank to the gas-liquid mixer, and / or adding sodium hydroxide or potassium hydroxide directly to the absorption tank.

[0057] In one embodiment of the present application, no catalyst is added in the treatment method. In particular, no catalyst is added in steps (1) to (4) of the treatment method.

[0058] In one embodiment of the present application, the treatment method further comprises recycling or transporting the gas collected from the ammonia removal device in step (4) to a catalytic oxidation device and / or an incineration flare.

[0059] In a specific embodiment of the present application, no catalyst is added in steps (1) to (4) of the treatment method, and the treatment method further comprises transporting the gas collected from the ammonia removal device in step (4) to a catalytic oxidation device.

[0060] In one embodiment of the present application, the hydrogen cyanide and ammonia containing waste water in step (1) and the hydrogen cyanide and ammonia containing waste gas in step (2) of the treatment method are provided by:

[0061] transporting a first waste water containing hydrogen cyanide and ammonia to a first flash tank for flashing to obtain a first gas phase and a first liquid phase,

[0062] the second liquid phase having a hydrogen cyanide concentration of not more than 20 mg / L,

[0063] the first liquid phase being the hydrogen cyanide and ammonia containing wastewater in step (1), and the first and second gas phases being mixed as the hydrogen cyanide and ammonia containing waste gas in step (2),

[0064] wherein the first wastewater contains an initial hydrogen cyanide concentration higher than the initial hydrogen cyanide concentration contained in the second wastewater.

[0065] In a further embodiment of the present application, the treatment method additionally comprises the following steps:

[0066] (5) the liquid obtained in step (4) is fed to a lower concentration downstream wastewater treatment device,

[0067] (6) the second liquid phase is fed to a higher concentration downstream wastewater treatment device, and

[0068] (7) the gas obtained from the oxidation reactor in step (3) is combined with the gas obtained from the deamination device in step (4) and fed to a catalytic oxidation device and / or an incineration flare.

[0069] In an embodiment of the present application, the initial hydrogen cyanide content in the wastewater is not more than 100 mg / L, and the initial ammonia content in the wastewater is not more than 2500 mg / L. For example, the initial hydrogen cyanide content in the wastewater is not more than 80, 60, 50, 40, 20, or not more than 10 mg / L, and the initial ammonia content in the wastewater is not more than 2000, 1500, 1000, 500, 300, or not more than 100 mg / L.

[0070] The initial hydrogen cyanide content in the waste gas is not more than 0.0028 mole%, and the initial ammonia content in the waste gas is not more than 0.0021 mole%. For example, the initial hydrogen cyanide content in the waste gas is not more than 0.0025, 0.0020, 0.0015, or not more than 0.0010 mole%, and the initial ammonia content in the waste gas is not more than 0.0020, 0.0015, or not more than 0.0010 mole%.

[0071] In an embodiment of the present application, the concentration of the liquid hydrogen cyanide obtained in step (3) or (4) is less than 5 mg / L. In case the concentration of the liquid hydrogen cyanide obtained in step (3) or (4) is detected to be 5 mg / L or more, the liquid is recycled to the absorption tank to be subjected to the treatment method of the present application again.

[0072] The present application further provides a treatment apparatus system using the treatment method of the present application.

[0073] In one embodiment of the present application, as shown in Figure 1 The treatment apparatus system 10 comprises an absorption tank 104, a multi-stage oxidation reactor 105 and a deamination device 106.

[0074] In one embodiment, the treatment apparatus system 10 can further comprise a grey water buffer tank 101, a second flash tank 102 and a first flash tank 103 to provide the absorption tank 104 with the hydrogen cyanide and ammonia containing wastewater 1045 and the hydrogen cyanide and ammonia containing off-gas 1046.

[0075] In one embodiment, the absorption tank 104 can be equipped with a gas-liquid mixer 1041 to introduce the hydrogen cyanide and ammonia containing off-gas 1046 into the absorption tank 104. The absorption tank 104 can be further equipped with a circulation pipeline 1044 to mix and circulate the liquid in the absorption tank 104. A pH adjuster 1042 and / or hydrogen peroxide 1043 can be added to the circulating liquid in the circulation pipeline 1044 and then introduced into the absorption tank 104. For example, the hydrogen peroxide 1043 can be added to the circulating liquid in the circulation pipeline 1044 after mixing with an acidic pH adjuster and then introduced into the absorption tank 104. Alternatively, the pH adjuster 1042, in particular a basic pH adjuster, can be directly introduced into the absorption tank 104. It is understood that the hydrogen peroxide can be more stable and less decomposed when it is in an acidic condition before mixing with the wastewater to be treated. After the hydrogen peroxide is mixed with the wastewater to be treated, an alkaline condition is beneficial to the catalytic-free oxidation reaction of hydrogen cyanide by hydrogen peroxide.

[0076] In one embodiment, the multi-stage oxidation reactor 105 can comprise a primary oxidation reactor 105a and a secondary oxidation reactor 105b connected in series. The secondary oxidation reactor 105b can further comprise more stages of oxidation reactors connected in series, such as a tertiary oxidation reactor (not shown in the figure), a quaternary oxidation reactor (not shown in the figure) and so on, to extend the residence time. Optionally, the hydrogen peroxide 1043 can be added to the multi-stage oxidation reactor 105.

[0077] In one embodiment, the deamination device 106 can be a deamination tower, the top of which can be connected with a flare stack and / or a device for catalytic oxidation treatment.

[0078] In one specific embodiment of the present application, the treatment method of the present application comprises the following steps:

[0079] (1) pumping the hydrogen cyanide and ammonia containing wastewater 1045 into the absorption tank 104 and adding the pH adjuster 1042 and the hydrogen peroxide 1043 to the absorption tank 104 to mix a liquid with a pH value of 6 to 11, preferably 8 to 10,

[0080] (2) introducing the waste gas 1046 containing hydrogen cyanide and ammonia into the absorption tank 104, and absorbing hydrogen cyanide and ammonia in the waste gas 1046 by the liquid obtained in step (1),

[0081] (3) transporting the liquid obtained in step (2) into the oxidation reactor, controlling the reaction temperature of the oxidation reactor 105 at 40 to 60°C, preferably 40 to 55°C, and the total residence time of the liquid in the oxidation reactor 105 is 150 to 270 minutes, preferably 165 to 180 minutes, to oxidize hydrogen cyanide into ammonia and carbon dioxide, optionally adding hydrogen peroxide into the oxidation reactor 105a and / or 105b,

[0082] (4) transporting the liquid treated in step (3) into the deamination device 106, removing ammonia in the liquid by stripping method, and heating the liquid to decompose the remaining hydrogen peroxide, so that the concentration of ammonia in the treated liquid is reduced to not higher than 80 mg / L and the concentration of hydrogen cyanide is reduced to not higher than 5 mg / L,

[0083] wherein the mass ratio of the total amount of hydrogen peroxide added in the method to the total amount of initial hydrogen cyanide in the waste water 1045 and the waste gas 1046 is 20:1 to 50:1, preferably 30:1 to 50:1.

[0084] In a further embodiment, no catalyst is added in steps (1) to (4).

[0085] In a further embodiment, step (2) comprises absorbing hydrogen cyanide and ammonia in the waste gas 1046 with the liquid drawn from the bottom of the absorption tank 104 at the gas-liquid mixer 1041, wherein the gas-liquid mixer 1041 can be a venturi-type ejector.

[0086] In a further embodiment, in step (1), the pH adjuster 1042 is selected from dilute sulfuric acid, sodium hydroxide and potassium hydroxide, and adding the pH adjuster 1042 and the hydrogen peroxide 1043 into the absorption tank 104 comprises mixing dilute sulfuric acid with the hydrogen peroxide 1043 and then adding into the liquid drawn from the bottom of the absorption tank 104 to the gas-liquid mixer 1041, and / or directly adding sodium hydroxide or potassium hydroxide into the absorption tank 104.

[0087] In a further embodiment, the waste water 1045 containing hydrogen cyanide and ammonia and the waste gas 1046 containing hydrogen cyanide and ammonia are provided by:

[0088] transporting the first waste water 4 containing hydrogen cyanide and ammonia into the first flash tank 103 for flash evaporation, obtaining a first gas phase 1031 and a first liquid phase 1032,

[0089] the second liquid phase 1022 has a hydrogen cyanide concentration no higher than 20 mg / L,

[0090] the first liquid phase 1032 is used as a hydrogen cyanide and ammonia containing wastewater 1045, and the first gas phase 1031 and the second gas phase 1021 are mixed as a hydrogen cyanide and ammonia containing exhaust gas 1046 in step (2),

[0091] wherein the first wastewater 4 contains a higher initial hydrogen cyanide concentration than the second wastewater 3.

[0092] In another embodiment, the hydrogen cyanide and ammonia containing wastewater 1045 and the hydrogen cyanide and ammonia containing exhaust gas 1046 are provided by:

[0093] the first wastewater 4 containing hydrogen cyanide and ammonia is fed to a first flash tank 103 for flash evaporation to obtain a first gas phase 1031 and a first liquid phase 1032,

[0094] the second wastewater 3 containing hydrogen cyanide is fed to a second flash tank 102 for flash evaporation to obtain a second gas phase 1021 and a second liquid phase 1022, the second liquid phase 1022 having a hydrogen cyanide concentration no higher than 20 mg / L,

[0095] the first liquid phase 1032 is used as a hydrogen cyanide and ammonia containing wastewater 1045, and the second gas phase 1021 is fed to the side of the first flash tank 103 and mixed with the first gas phase 1031 from the top of the first flash tank 103 to a gas liquid mixer 1041 as a hydrogen cyanide and ammonia containing exhaust gas 1046 in step (2).

[0096] wherein the first wastewater 4 contains a higher initial hydrogen cyanide concentration than the second wastewater 3.

[0097] In a further embodiment, the treatment method of the present application additionally comprises the following steps:

[0098] (5) feeding the liquid obtained in step (4) to a lower concentration downstream wastewater treatment device 2b,

[0099] (6) feeding the second liquid phase 1022 to a higher concentration downstream wastewater treatment device 2a, and

[0100] (7) feeding the gas obtained in step (3) from the oxidation reactor 105b and the gas obtained in step (4) from the deamination device 106 to a combustion flare 1061 and / or a catalytic oxidation device 1062 after being combined.

[0101] In a further embodiment, the hydrogen cyanide content of the hydrogen cyanide and ammonia containing waste water 1045 is not higher than 100 mg / L and the ammonia content is not higher than 2500 mg / L; and / or

[0102] The hydrogen cyanide content of the hydrogen cyanide and ammonia containing waste gas 1046 is not higher than 0.0028 mole% and the ammonia content is not higher than 0.0021 mole%.

[0103] Examples

[0104] For further understanding of the present application, the preferred embodiments of the present application are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not limitations to the claims of the present application, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement ways, and are all included in the protection scope of the present application.

[0105] The hydrogen cyanide content in the examples of the present application is detected according to the method specified in the People's Republic of China Chemical Industry Standard HG / T 5544-2019 “Determination of Cyanide Content in Cyanide Containing Waste Water”.

[0106] The waste water sample used in the examples is waste water containing 100 mg / L of sodium cyanide (content calculated as HCN) and 2500 mg / L of NH4HCO3 (content calculated as NH3).

[0107] Example 1. Effect of oxidation reaction temperature on HCN oxidation efficiency

[0108] Sodium hydroxide (1 M) is added to the waste water sample at the absorption tank to adjust the pH value of the waste water to 9, and hydrogen peroxide (H2O2 content 27.5%) is added according to a H2O2 / HCN molar ratio of 30:1, and the HCN concentration of the liquid discharged from the oxidation reactor is detected at different time points under continuous stirring conditions at an oxidation reactor temperature of 40, 45, 50, 55, 60 or 65°C, and the results are shown in Figure 2 It should be understood that after further proceeding with the subsequent deamination treatment, the HCN concentration in the liquid will not be higher than the HCN concentration of the liquid discharged from the oxidation reactor.

[0109] As shown in Figure 2 At different temperature conditions, the HCN concentration decreases significantly over time, especially within the first 15 to 30 minutes. As the reaction temperature increases, the rate of decrease of HCN concentration over time increases, and the oxidation reaction speed accelerates. However, as the reaction temperature increases, the decay rate of HCN oxidation reaction speed increases greatly.

[0110] From Figure 2It can be seen that at 40°C, the HCN concentration decreased to 4.89 mg / L at 255 minutes. At 45°C, the HCN concentration decreased to 4.39 mg / L at 165 minutes. At 50°C, the HCN concentration decreased to 3.75 mg / L at 165 minutes. At 55°C, the HCN concentration decreased to 4.13 mg / L at 165 minutes.

[0111] However, as the temperature was further increased, although the HCN concentration decreased rapidly in the initial stage, the rate of the oxidation reaction decreased rapidly in the later stage. At 60°C, the HCN concentration decreased to 6.27 mg / L at 165 minutes and to 4.85 mg / L at 225 minutes. At 65°C, the HCN concentration decreased to 8.12 mg / L at 165 minutes. It is believed that as the temperature increased, the rate of the HCN oxidation reaction increased, and the rate of the decomposition of H2O2 also increased greatly, resulting in a rapid decrease in the concentration of H2O2 in the liquid phase, thereby affecting the efficiency of the oxidation reaction of HCN.

[0112] Example 2. Effect of pH on the efficiency of the oxidation of HCN

[0113] Sodium hydroxide (1 M) was added to the wastewater sample at the absorption tank to adjust the pH of the wastewater to 8, 9, 10 or 11, and hydrogen peroxide (H2O2 content 27.5%) was added at a H2O2 / HCN molar ratio of 30:1, and the concentration of HCN in the liquid discharged from the oxidation reactor was detected at different time points under the condition of continuous stirring at a temperature of 45°C, and the results are shown in Figure 3 It should be understood that after further subsequent deamination treatment, the HCN concentration in the liquid will not be higher than the HCN concentration in the liquid discharged from the oxidation reactor.

[0114] As shown in Figure 3 the rate of decrease of the HCN concentration varied greatly under different pH conditions. At pH = 8, the HCN concentration decreased to 9.85 mg / L at 165 minutes and to 4.93 mg / L at 210 minutes. At pH = 9, the HCN concentration decreased to 4.39 mg / L at 165 minutes. At pH = 10, the HCN concentration decreased to 4.57 mg / L at 165 minutes. At pH = 11, the HCN concentration decreased to 6.19 mg / L at 165 minutes. It is believed that as the pH increased, the rate of decomposition of H2O2 increased, resulting in a decrease in the concentration of H2O2 in the liquid phase, thereby affecting the efficiency of the oxidation reaction of HCN.

[0115] Example 3. Effect of the H2O2 / HCN molar ratio on the efficiency of the oxidation of HCN

[0116] To the wastewater sample at the absorption tank, sodium hydroxide (1 M) was added to adjust the pH of the wastewater to 9, and hydrogen peroxide (H202 content 27.5%) was added at H202 / HCN molar ratios of 20:1, 30:1, 45:1 and 50:1. The HCN concentration of the liquid discharged from the oxidation reactor was measured at different time points under continuous stirring conditions at a temperature of 45°C, and the results are shown in Figure 4 It should be understood that after further subsequent deamination treatment, the HCN concentration in the liquid will not be higher than the HCN concentration of the liquid discharged from the oxidation reactor.

[0117] As shown in Figure 4 The reduction rate of HCN concentration varies greatly under different H202 / HCN molar ratios. Under a molar ratio of 20, the HCN concentration decreased to 22.14 mg / L at 165 minutes and to 5.15 mg / L at 270 minutes. Under a molar ratio of 30, the HCN concentration decreased to 4.39 mg / L at 165 minutes. Under a molar ratio of 45, the HCN concentration decreased to 2.95 mg / L at 165 minutes. Under a molar ratio of 50, the HCN concentration decreased to 2.87 mg / L at 150 minutes.

Claims

1. A method for treating waste containing hydrogen cyanide and ammonia, characterized in that, The treatment method comprises the following steps: (1) pumping the wastewater containing hydrogen cyanide and ammonia into an absorption tank, and adding hydrogen peroxide solution and a pH adjuster into the absorption tank, and mixing to obtain a liquid with a pH value of 6 to 11, (2) introducing the waste gas containing hydrogen cyanide and ammonia into the absorption tank, and absorbing hydrogen cyanide and ammonia in the waste gas by the liquid obtained in step (1), (3) transporting the liquid obtained in step (2) into an oxidation reactor, controlling the reaction temperature of the oxidation reactor at 40 to 60℃, and the total residence time of the liquid in the oxidation reactor is 150 to 270 minutes, so as to oxidize hydrogen cyanide into ammonia and carbon dioxide, (4) transporting the liquid treated in step (3) into a deamination device, removing ammonia in the liquid by gas stripping, and heating the liquid to decompose the remaining hydrogen peroxide, so that the concentration of ammonia in the treated liquid is reduced to not higher than 80 mg / L and the concentration of hydrogen cyanide is reduced to not higher than 5 mg / L, wherein the molar ratio of the total amount of hydrogen peroxide added in the method to the total amount of initial hydrogen cyanide in the wastewater and the waste gas is 30:1 to 50:1, wherein no catalyst is added in steps (1) to (4) of the treatment method, wherein the hydrogen cyanide content of the wastewater containing hydrogen cyanide and ammonia is not higher than 100 mg / L and the ammonia content is not higher than 2500 mg / L.

2. The method of claim 1, wherein, The pH value of the liquid obtained in step (1) is 8 to 10.

3. The method of claim 1, wherein, In step (3), hydrogen peroxide solution is added into the oxidation reactor.

4. The method of claim 1, wherein, The oxidation reactor in step (3) is a multi-stage oxidation reactor, and the total residence time of the liquid obtained in step (2) in the multi-stage oxidation reactor is 165 to 180 minutes.

5. The method of claim 1, wherein, The reaction temperature in step (3) is 40 to 55℃.

6. The method of claim 1, wherein, Step (2) comprises absorbing hydrogen cyanide and ammonia in the waste gas with the liquid drawn from the bottom of the absorption tank at a gas-liquid mixer, wherein the gas-liquid mixer is a Venturi tube ejector.

7. The method of claim 6, wherein, The pH adjuster is selected from dilute sulfuric acid, sodium hydroxide and potassium hydroxide, and adding hydrogen peroxide solution and a pH adjuster into the absorption tank in step (1) comprises mixing dilute sulfuric acid with hydrogen peroxide solution and then adding into the liquid drawn from the bottom of the absorption tank to the gas-liquid mixer, and / or directly adding sodium hydroxide or potassium hydroxide into the absorption tank.

8. The method according to any one of claims 1 to 7, characterized in that, The wastewater containing hydrogen cyanide and ammonia in step (1) and the waste gas containing hydrogen cyanide and ammonia in step (2) are provided by: transporting first wastewater containing hydrogen cyanide and ammonia to a first flash tank for flash evaporation to obtain a first gas phase and a first liquid phase, transporting second wastewater containing hydrogen cyanide to a second flash tank for flash evaporation to obtain a second gas phase and a second liquid phase, the hydrogen cyanide concentration of the second liquid phase is not higher than 20 mg / L, mixing the first gas phase and the second gas phase as the waste gas containing hydrogen cyanide and ammonia in step (2), wherein the initial hydrogen cyanide concentration contained in the first wastewater is higher than the initial hydrogen cyanide concentration contained in the second wastewater.

9. The method of claim 8, wherein, The treatment method comprises the following steps: (5) transporting the liquid obtained in step (4) to a lower concentration downstream wastewater treatment device, (6) transporting the second liquid phase to a higher concentration downstream wastewater treatment device, and (7) transporting the gas obtained from the oxidation reactor in step (3) and the gas obtained from the deamination device in step (4) after being combined to a catalytic oxidation device and / or an incineration flare.

10. The method according to any one of claims 1 to 7, wherein the hydrogen cyanide content of the waste gas containing hydrogen cyanide and ammonia is not higher than 0.0028 mol% and the ammonia content is not higher than 0.0021 mol%.

10. The method according to any one of claims 1 to 7, wherein the hydrogen cyanide content of the waste gas containing hydrogen cyanide and ammonia is not higher than 0.0028 mol% and the ammonia content is not higher than 0.0021 mol%.

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