Process for treating nitrile-containing wastewater and application thereof

Abstract

The application relates to the field of wastewater treatment processes, in particular to a nitrile-containing wastewater treatment process and application thereof. The nitrile-containing wastewater treatment process comprises the following steps: (1) azeotropic distillation of the nitrile-containing wastewater; (2) hydrolysis treatment of the nitrile-containing wastewater in a pressure kettle. The nitrile-containing wastewater treatment process provided in the application can solve the problems in the existing nitrile-containing wastewater treatment process, the cost is lower than that of the oxidation method and the electrolysis method, the problem that the biological method is not suitable for industrialization is avoided, the operation is simple, and the process has excellent market prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wastewater treatment process, especially to a nitrile-containing wastewater treatment process and application thereof. BACKGROUND

[0002] The wastewater generated in the production process of isobutyronitrile / n-butyl nitrile / pentanitrile contains a certain amount of isobutyronitrile / n-butyl nitrile / pentanitrile. Generally, nitriles are toxic, such as isobutyronitrile, which is a toxic substance. Therefore, the content of isobutyronitrile / n-butyl nitrile / pentanitrile in the wastewater must be controlled within a certain range to meet the discharge standard and ensure biological safety. At present, the treatment methods of nitrile-containing wastewater include oxidation treatment, electrolytic treatment, ion exchange method, biological treatment method or a combination of two or more methods.

[0003] The prior art, patent CN110803818 discloses a novel acetonitrile wastewater treatment method, which mainly recovers acetonitrile in wastewater through distillation operation, and removes acetonitrile residues in wastewater through alkaline hydrolysis reaction. This method needs distillation operation and high concentration of alkali, and is not suitable for large-scale industrialization, and is easy to cause more environmental pollution.

[0004] In other methods, the oxidation treatment method includes ozone and photo-oxidation method, which degrades acetonitrile to remove acetonitrile in acetonitrile-containing industrial wastewater. This method has high treatment cost, low performance-price ratio for treating nitrile-containing wastewater, and is also easy to produce toxic secondary pollutants. On the other hand, the use of biological treatment method can further accelerate the volatilization speed of nitriles, which in turn causes unnecessary pollution, and the biological treatment method cannot decompose and absorb most of the complex wastewater components, and the wastewater treatment effect is very limited.

[0005] Therefore, in order to solve the above problems, the present application provides a nitrile-containing wastewater treatment process, especially for wastewater with high content of isobutyronitrile, n-butyl nitrile and pentanitrile. SUMMARY

[0006] In order to solve the above problems, the present application provides a nitrile-containing wastewater treatment process, the steps comprising: (1) azeotropic distillation of nitrile-containing wastewater; (2) hydrolysis treatment of nitrile-containing wastewater in a pressure kettle.

[0007] As a preferred scheme, the nitrile-containing wastewater is wastewater containing at least one of acetonitrile, isobutyronitrile, n-butyl nitrile and pentanitrile.

[0008] As a preferred scheme, the nitrile-containing wastewater is wastewater containing at least one of isobutyronitrile, n-butyl nitrile and pentanitrile.

[0009] As a preferred scheme, the nitrile content of the nitrile-containing wastewater is 0.1-10%.

[0010] As a preferred solution, the nitrile-containing wastewater has a nitrile content of 2-5%.

[0011] As a preferred solution, the azeotropic distillation of the nitrile-containing wastewater is performed by feeding the nitrile-containing wastewater into a distillation vessel through a metering pump, and performing azeotropic distillation in the distillation vessel under reflux conditions to separate an azeotropic distillate containing nitriles, and collecting a distillate with low nitrile content.

[0012] As a preferred solution, the nitrile-containing wastewater is fed into the distillation vessel through the metering pump in a continuous or intermittent manner.

[0013] As a preferred solution, the nitrile-containing wastewater is fed into the distillation vessel through the metering pump in a continuous manner.

[0014] As a preferred solution, the azeotropic distillation is performed at a temperature of 100-120°C and a pressure of 1-10 MPa.

[0015] As a preferred solution, the azeotropic distillation is performed at a temperature of 104-110°C and a pressure of 1-2 MPa.

[0016] As a preferred solution, the azeotropic distillation is performed at a temperature of 105°C and a pressure of 1.2 MPa.

[0017] As a preferred solution, the hydrolysis treatment of the nitrile-containing wastewater in the pressure vessel is performed by adding the distillate with low nitrile content obtained in step (1) into the pressure vessel, controlling the pressure and temperature of the pressure vessel, and adding a hydrolysis catalyst for hydrolysis treatment.

[0018] As a preferred solution, the pressure of the pressure vessel is 1-10 MPa, and the temperature of the pressure vessel is 120-220°C.

[0019] As a preferred solution, the pressure of the pressure vessel is 1-2 MPa, and the temperature of the pressure vessel is 170-200°C.

[0020] As a preferred solution, the pressure of the pressure vessel is 1 MPa, and the temperature of the pressure vessel is 180°C.

[0021] As a preferred solution, the reaction time of the hydrolysis treatment is 2-24 hours, and further preferably 2-6 hours.

[0022] As a preferred solution, the hydrolysis catalyst is at least one of an inorganic base or an inorganic acid.

[0023] As a preferred scheme, the inorganic base is at least one of sodium hydroxide, potassium hydroxide, ammonia, ammonia gas, dimethylamine, diethylamine, sodium carbonate, potassium carbonate, sodium bicarbonate.

[0024] As a preferred scheme, the inorganic base is at least one of sodium hydroxide, potassium hydroxide, ammonia.

[0025] As a preferred scheme, the inorganic acid is at least one of sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid.

[0026] As a preferred scheme, the inorganic acid is hydrochloric acid.

[0027] As a preferred scheme, the mass ratio of the low nitrile content distillate to the hydrolysis catalyst is 100-120:0.1-3.

[0028] In the present application, by combining the azeotropic distillation and high-pressure hydrolysis treatment process, the treatment effect of the nitrile-containing wastewater, especially the isobutyronitrile, n-butyronitrile and pentanitrile-containing wastewater, is effectively improved, continuous production is realized, the nitrile content in the nitrile-containing wastewater is greatly reduced to 4 ppm or less, and the amount of alkali catalyst is reduced. This is mainly because the azeotropic distillation in the present application can directly reduce the content of nitriles in the distillation stage, and then the distillate is further subjected to hydrolysis of hydrogen ions or hydroxyl ions in a high-temperature and high-pressure environment to realize rapid decomposition of nitriles, and the overall integrated continuous working mode can further help the production of nitrile compounds.

[0029] The second aspect of the present application provides an application of the above-mentioned nitrile-containing wastewater treatment process, including the application of the nitrile-containing wastewater treatment process in a nitrile-containing wastewater treatment device and a nitrile-containing wastewater treatment production line.

[0030] Advantages:

[0031] 1. The nitrile-containing wastewater treatment process provided in the present application can overcome the shortcomings in the existing nitrile-containing wastewater treatment process, has lower cost than the oxidation method and the electrolysis method, avoids the problem that the biological method is not suitable for industrialization, is simple to operate, and has excellent market prospects.

[0032] 2. The nitrile-containing wastewater treatment process provided in the present application uses the combination of azeotropic distillation and high-pressure hydrolysis treatment process, which not only realizes effective treatment of nitrile-containing wastewater, but also realizes continuous production of nitrile-containing wastewater, and reduces equipment and labor costs.

[0033] 3. The nitrile-containing wastewater treatment process provided in the present application uses a high-pressure hydrolysis method, which can effectively control the final content of nitriles in high-content nitrile-containing wastewater to be ≤4 ppm, and can meet various emission standards.

[0034] 4、The nitrile-containing wastewater treatment process provided in the application has less dosage of alkali hydrolysis catalyst, can effectively reduce the corrosion of alkali substances on equipment and the salt concentration in wastewater, and further reduces the maintenance cost.

[0035] 5、The nitrile-containing wastewater treatment process provided in the application can directly reduce the content of nitriles in a large amount in the distillation stage through azeotropic distillation, and then the distillate is further subjected to hydrolysis of hydrogen ions or hydroxyl ions in a high-temperature and high-pressure environment to realize rapid decomposition of nitriles, and the overall integrated continuous working mode can further help the production of nitrile compounds. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the azeotropic distillation related equipment in the nitrile-containing wastewater treatment process of the application.

[0037] In the figure:

[0038] 1-nitrile-containing wastewater, 2-distillation kettle, 3-pressure gauge, 4-thermometer, 5-valve, 6-condenser tube, 7-condensed water. DETAILED DESCRIPTION

[0039] Example 1

[0040] Embodiment 1 The first aspect provides a nitrile-containing wastewater treatment process, which comprises the following steps: (1) azeotropic distillation of nitrile-containing wastewater; (2) hydrolysis treatment of the nitrile-containing wastewater in a pressure kettle.

[0041] The specific operation is as follows in terms of mass parts:

[0042] Step (1): 500 parts of wastewater containing isobutyronitrile are pumped into a distillation kettle through a metering pump, 10 parts of isobutyronitrile are contained in the wastewater, then 300 parts of deionized water are added, and azeotropic distillation is carried out in the distillation container under reflux conditions to separate the azeotropic distillate containing nitriles, and collect the distillate with low nitrile content.

[0043] The nitrile-containing wastewater is continuously fed into the distillation container through the metering pump.

[0044] The temperature of azeotropic distillation is 105°C, and the pressure is 1.2 MPa.

[0045] Step (2): 300 parts of the distillate with low nitrile content obtained in step (1) are added to the pressure kettle, the pressure and temperature of the pressure kettle are controlled, and 1 part of a hydrolysis catalyst is added for hydrolysis treatment.

[0046] The pressure and temperature of the pressure kettle are 1 MPa and 180°C, respectively, and the heat preservation reaction is carried out for 4 hours.

[0047] Hydrolysis catalyst: sodium hydroxide.

[0048] In the implementation process, the azeotropic distillation is carried out as shown in the figure. Figure 1 As shown in the figure, a thermometer 4 and a pressure gauge 3 are respectively arranged on a distillation kettle 2, the distillation kettle 2 is inserted with the nitrile-containing wastewater 1, a condenser pipe 6 is connected to the outside of the distillation kettle 2, a valve 5 is arranged on the pipe to control the opening and closing, and the condenser water 7 is circulated into the condenser pipe 6.

[0049] Example 2

[0050] The specific implementation of the embodiment is the same as that of Example 1, except that:

[0051] In step (1), 500 parts of the wastewater containing isobutyronitrile contains 15 parts of isobutyronitrile.

[0052] Example 3

[0053] The specific implementation of the embodiment is the same as that of Example 2, except that:

[0054] In step (2), the pressure and temperature of the pressure kettle are 1 MPa and 200°C respectively, and the heat preservation reaction is carried out for 4 hours.

[0055] Example 4

[0056] The specific implementation of the embodiment is the same as that of Example 2, except that:

[0057] In step (2), the pressure and temperature of the pressure kettle are 2 MPa and 180°C respectively, and the heat preservation reaction is carried out for 4 hours; the hydrolysis catalyst is ammonia water.

[0058] Example 5

[0059] The specific implementation of the embodiment is the same as that of Example 2, except that: in step (2), the pressure and temperature of the pressure kettle are 1 MPa and 220°C respectively, and the heat preservation reaction is carried out for 4 hours; the hydrolysis catalyst is ammonia water.

[0060] Example 6

[0061] The specific implementation of the embodiment is the same as that of Example 2, except that: in step (2), the pressure and temperature of the pressure kettle are 2 MPa and 180°C respectively, and the heat preservation reaction is carried out for 4 hours.

[0062] Performance evaluation

[0063] Nitrile content: the products obtained in all examples are tested for the final isobutyronitrile content, 10 samples are tested for each example, and the average value of the measured values is recorded in Table 1.

[0064] Table 1

[0065] Example Isobutyronitrile content mg / L Example 1 0.43 Example 2 0.50 Example 3 0.42 Example 4 7.75 Example 5 7.73 Example 6 0.40

Claims

1. A process for treating nitrile-containing wastewater, characterized by: The steps comprise: (1) feeding the nitrile-containing wastewater into a distillation vessel through a metering pump, carrying out azeotropic distillation in the distillation vessel under reflux conditions, separating an azeotropic distillate containing nitriles, and collecting a distillation liquid with low nitrile content; (2) adding the distillation liquid with low nitrile content obtained in step (1) into a pressure kettle, controlling the pressure and temperature of the pressure kettle, and adding a hydrolysis catalyst for hydrolysis treatment; The nitrile-containing wastewater contains at least one of isobutyronitrile, n-butyronitrile and pentanitrile. The azeotropic distillation is carried out at a temperature of 100-120°C and a pressure of 1-10 MPa. The pressure of the pressure kettle is 1-2 MPa, and the temperature of the pressure kettle is 170-200°C. The hydrolysis catalyst is sodium hydroxide.

2. The nitrile-containing wastewater treatment process of claim 1, wherein: The nitrile content of the nitrile-containing wastewater is 0.1-10%.

3. The nitrile-containing wastewater treatment process of claim 1, wherein: The nitrile-containing wastewater is fed into the distillation vessel through a metering pump in a continuous or intermittent manner.

4. Use of a process for the treatment of nitrile-containing waste water according to any one of claims 1 to 3, characterized in that: The application of the nitrile-containing wastewater treatment process in a nitrile-containing wastewater treatment device and a nitrile-containing wastewater treatment production line.

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