Sewage and waste gas treatment process for acrylonitrile production device

Abstract

The invention discloses an acrylonitrile production device sewage and waste gas treatment process and belongs to the technical field of sewage and waste gas treatment. The method comprises the following steps: (1) a nitrile removal process: adding an alkaline substance into condensate of a quadruple-effect evaporator to adjust the pH value, and reacting to obtain nitrile removal process effluent; introducing a first part of atmospheric emissions of an AOGI waste gas incineration system into the nitrile removal process effluent to adjust the pH value; (2) a cyanide breaking process: enabling the effluent obtained in the step (1) to enter a UV / H2O2 advanced oxidation process, and reacting to obtain cyanide breaking process effluent; all atmospheric emissions of a WWI waste water incineration system and a second part of atmospheric emissions of an AOGI waste gas incineration system are introduced into the cyanide breaking process effluent to adjust the pH value; and (3) treating the effluent in the step (2) through an A / A / O process and a biological filter EBF in sequence, and discharging after reaching the standard. According to the treatment process disclosed by the invention, waste is treated by waste, so that sewage and waste gas generated in the acrylonitrile production device can be stably discharged in a standard reaching manner, and carbon and nitrogen emission reduction of the acrylonitrile production device is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage and waste gas treatment, and specifically relates to a sewage and waste gas treatment process for an acrylonitrile production device. Background Art

[0002] As a common chemical raw material, acrylonitrile is an important monomer for synthetic fibers, synthetic rubbers and synthetic resins, and is widely used in industries such as acrylic fibers, nitrile rubber or latex, and ABS engineering resins. Since the existing acrylonitrile production unit adopts the propylene / ammonia oxidation process to produce acrylonitrile, including reaction, recovery, refining, and four-effect evaporation units, the characteristic compounds contained in the process wastewater are basically organic nitriles, inorganic cyanides and other nitrogen-containing group compounds, which is a significant feature of the process wastewater of the acrylonitrile production unit. The nitrogen element exists in various forms such as -C≡N, five-membered or six-membered nitrogen-containing heterocyclic rings, NH3, -NH2 or nitrogen on -NH-. Whether it is the sewage entering the biochemical unit of the sewage field, or the emissions after waste gas incineration or sewage incineration, they all contain C and N elements, and the emissions from sewage incineration also contain sulfur-containing compounds, such as SO2 and SO3.

[0003] The wastewater generated in the process of refining acrylonitrile is called refined water. In the existing technology, the wastewater from the acrylonitrile process is refined water, which is concentrated and condensed by a four-effect evaporator to form high-concentration wastewater and low-concentration wastewater. Among them, the low-concentration wastewater enters the sewage field, and the high-concentration wastewater will enter the WWI (Waster Water Incinerator) system for incineration to form CO2, water vapor, NOx, SO2, etc. The waste gas generated by the system, containing CO2, CO, N2, unreacted O2 and hydrocarbons, will also form CO2, water vapor, NOx, SO2, etc. after entering the AOGI (Absorber Off Gas Incinerator) system for incineration. Both use natural gas as energy and are discharged after high-temperature incineration. The discharge after incineration must meet the SO2 content of 0-50mg / m 3 , NOx is 0-100mg / m 3 , CO content 0-100mg / m 3 , while other organic characteristic pollutants, such as acrylonitrile < 0.5 mg / m 3 , acetonitrile<50mg / m 3 , hydrogen cyanide <1.9mg / m 3 wait.

[0004] Patent CN103304096A discloses a method for treating acrylonitrile wastewater by ozone catalysis coupled with biological nitrification. The incoming water first enters a regulating tank for water quality adjustment, then flows through a pre-oxidation tower and a catalytic oxidation tower, and then passes through an ozone removal tank to remove residual ozone in the water. Then, ammonia nitrogen is removed through a nitrification tank, and the effluent is discharged from a clear water tank. This invention pre-oxidizes and catalytically oxidizes the effluent from the regulating tank, which increases the operating cycle of the sewage treatment plant, does not fundamentally solve the problem of biodegradability of sewage, and does not reduce the atmospheric emissions of the incinerator tail gas of the acrylonitrile production device.

[0005] Patent CN202529945U relates to a wastewater treatment system for acrylonitrile and acrylic fiber devices; an alkaline hydrolysis treatment device is connected to an acrylonitrile production wastewater discharge pipeline, and an alkaline hydrolysis treatment device is connected to a homogenizer; a coagulation sedimentation or coagulation flotation device A is connected to a polymerization process wastewater discharge pipeline, and a coagulation sedimentation or coagulation flotation device A is connected to a homogenizer; a homogenizer is connected to a good-keeping biological treatment device, and a good-keeping biological treatment device is connected to an advanced oxidation treatment device, and an advanced oxidation treatment device is connected to a hydrolysis acidification-aerobic device or an A / O device; a coagulation sedimentation or coagulation flotation device B is connected to a spinning process wastewater discharge pipeline, and a coagulation sedimentation or coagulation flotation device B is connected to a hydrolysis acidification-aerobic device or an A / O device. The system mixes the pretreated wastewater with the wastewater discharged from other devices that do not require pretreatment for centralized treatment to achieve standard discharge. However, this system is connected in series with alkaline hydrolysis, which cannot achieve the purpose of energy conservation and carbon reduction, nor can it reduce the atmospheric emissions of the exhaust gas from the incinerator of the acrylonitrile production unit. Summary of the invention

[0006] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a wastewater and waste gas treatment process for an acrylonitrile production device, which achieves the goal of treating waste with waste, so that the wastewater and waste gas generated in the acrylonitrile production device can be discharged stably and meet the standards, thereby achieving carbon and nitrogen emission reduction in the acrylonitrile production device.

[0007] In order to achieve the above object, according to one aspect of the present invention, a process for treating wastewater and waste gas from an acrylonitrile production device is provided, comprising the following steps: (1) Nitrile removal process: adding alkaline substances to the condensate of the four-effect evaporator to adjust the pH value to 11-13, reacting for a certain period of time, and obtaining nitrile removal process effluent; introducing the first part of the atmospheric emissions of the AOGI waste gas incineration system into the nitrile removal process effluent to adjust the pH value of the nitrile removal process effluent to 9-11; (2) Cyanide breaking process: the effluent from step (1) enters into a UV / H2O2 advanced oxidation process and reacts for a certain period of time to obtain cyanide breaking process effluent; all the atmospheric emissions from the WWI wastewater incineration system and the second part of the atmospheric emissions from the AOGI waste gas incineration system are introduced into the cyanide breaking process effluent to adjust the pH value of the cyanide breaking process effluent to 7.5-9.0; (3) The effluent from step (2) is treated by the A / A / O process and the biological filter EBF in sequence and can meet the discharge standards.

[0008] In some embodiments, in step (1), the alkaline substance includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0009] In some embodiments, in step (1), the reaction temperature is room temperature and the reaction time is 3-6 hours.

[0010] In some embodiments, in step (1), the first portion of the atmospheric emissions introduced into the AOGI waste gas incineration system is used to adjust the pH value of the effluent from the nitrile removal process to 9.5-10.5.

[0011] In some embodiments, in step (2), the dosage of hydrogen peroxide in the UV / H2O2 advanced oxidation process is 300-700 mg / L.

[0012] In some embodiments, in step (2), the reaction temperature is room temperature and the reaction time is 2-5 hours.

[0013] In some embodiments, in step (2), all of the atmospheric emissions from the WWI wastewater incineration system and the second portion of the atmospheric emissions from the AOGI waste gas incineration system are introduced into the effluent to adjust the pH value of the cyanide destruction process to 8.0-8.5.

[0014] In some embodiments, the volume ratio of the first portion of atmospheric emissions to the second portion of atmospheric emissions of the AOGI waste gas incineration system is (1.5-2.5):1.

[0015] In some embodiments, in step (3), the A / A / O process conditions are: the hydraulic retention time of the anaerobic tank is 15-30 hours, the hydraulic retention time of the anoxic tank is 20-40 hours, and the hydraulic retention time of the aerobic tank is 15-30 hours.

[0016] In some embodiments, in step (3), the hydraulic retention time of the biological filter EBF is 2-4 hours.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a low-cost, low-energy consumption process for treating wastewater and waste gas from an acrylonitrile production unit. At the same time, the atmospheric emission materials from the AOGI waste gas incineration system and the WWI wastewater incineration system are introduced into the process, thereby greatly improving the biodegradability of the wastewater. At the same time, the goal of treating waste with waste, reducing atmospheric emissions from the acrylonitrile production unit, and ensuring that the biochemical unit of the sewage field meets the discharge standards stably is achieved.

[0018] (2) The treatment process of the present invention is simple to operate, low in cost, and the effluent quality can meet the direct discharge water quality requirements of GB31571-2015. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 The present invention is a flowchart of a wastewater and waste gas treatment process for an acrylonitrile production device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0022] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0023] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0024] The sewage of the present invention refers to the sewage generated during the refining of acrylonitrile in an acrylonitrile production device, specifically the condensate of the four-effect evaporator in the acrylonitrile production device, hereinafter referred to as the four-effect evaporator condensate. Nitrogen-containing organic compounds are the significant characteristics of the characteristic pollutants of the four-effect evaporator condensate. Nitrogen elements exist in nitrogen-containing heterocyclic compounds, organic nitrile compounds, inorganic cyanide compounds, etc., resulting in high CODcr (dichromate oxygen demand) and total nitrogen in sewage. Organic nitriles and inorganic cyanides are highly toxic or extremely toxic compounds, which are the main factors leading to the extremely poor biodegradability of the four-effect evaporator condensate, and the BOD5 / COD is only about 0.004.

[0025] The present invention provides a process for treating wastewater and waste gas from an acrylonitrile production device, comprising the following steps: (1) Nitrile removal process: adding alkaline substances to the condensate of the four-effect evaporator to adjust the pH value to 11-13, reacting for a certain period of time, and obtaining nitrile removal process effluent; introducing the first part of the atmospheric emissions of the AOGI waste gas incineration system into the nitrile removal process effluent to adjust the pH value of the nitrile removal process effluent to 9-11; (2) Cyanide breaking process: the effluent from step (1) enters into a UV / H2O2 advanced oxidation process and reacts for a certain period of time to obtain cyanide breaking process effluent; all the atmospheric emissions from the WWI wastewater incineration system and the second part of the atmospheric emissions from the AOGI waste gas incineration system are introduced into the cyanide breaking process effluent to adjust the pH value of the cyanide breaking process effluent to 7.5-9.0; (3) The effluent from step (2) is treated by the A / A / O process and the biological filter EBF in sequence and can meet the discharge standards.

[0026] According to the treatment process of the present invention, in some embodiments, in step (1), the alkaline substance includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. The alkaline substance in the present invention is used to adjust the pH value of the nitrile-containing wastewater, thereby providing necessary conditions for subsequent reactions.

[0027] According to the treatment process of the present invention, in some specific embodiments, in step (1), the alkaline substance can be in the form of an aqueous solution when used, and the mass concentration of the alkaline substance aqueous solution can be 30%-50%.

[0028] Furthermore, in some specific embodiments, in step (1), alkaline substances are added to the condensate of the four-effect evaporator to adjust the pH value to preferably 11.5-12.5.

[0029] According to the treatment process of the present invention, in some embodiments, in step (1), the reaction temperature is room temperature and the reaction time is 3-6 hours. It is understood that the reaction time can be any specific value of 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours or any value within the range of 3-6 hours.

[0030] Furthermore, in some specific embodiments, in step (1), the reaction time is preferably 4-5.5 h.

[0031] In the present invention, in the nitrile removal process, an alkaline substance is added to the condensate of the four-effect evaporator to adjust the pH value, and the reaction is carried out for a certain period of time, so that the organic nitrile in the condensate of the four-effect evaporator can be converted into amide or ammonium carboxylate substances, thereby achieving the goal of converting highly toxic organic nitrile into non-toxic substances.

[0032] Further, according to the treatment process of the present invention, in some specific embodiments, in step (1), the first portion of the atmospheric emissions introduced into the AOGI waste gas incineration system is used to adjust the pH value of the effluent from the nitrile removal process to 9.5-10.5.

[0033] In the present invention, the first part of the atmospheric emissions introduced into the AOGI waste gas incineration system in the nitrile removal process refers to the first part of the atmospheric emissions introduced into the outlet of the nitrile removal process by the AOGI waste gas incineration system, and the pH value of the effluent from the nitrile removal process is adjusted to a specific range by using the acidic gas in the atmospheric emissions. On the one hand, the pH value required by the process can be adjusted well by using the NOx compounds in the waste gas as the main component, and the problem of NOx compounds being discharged and polluting the atmosphere is solved at the same time, and the nitrate nitrogen compounds or nitrite nitrogen compounds formed after entering the sewage can generate nitrogen in the denitrification reaction in the subsequent biochemical system, thereby achieving the purpose of treating waste with waste.

[0034] The present invention has no specific restrictions on the reaction device of the UV / H2O2 advanced oxidation process, and a conventional UV / H2O2 advanced oxidation reaction device in the art can be used. For example, the reaction device may include a reactor body, the reactor body includes but is not limited to a stainless steel tank, a UV lamp is arranged in the center of the reactor body, a quartz glass sleeve is covered on the UV lamp, the upper and lower ends of the tank body are connected by a pipeline, and an electromagnetic metering pump is used to drive the liquid in the tank to flow.

[0035] According to the treatment process of the present invention, in some embodiments, in step (2), the dosage of hydrogen peroxide in the UV / H2O2 advanced oxidation process is 300-700 mg / L.

[0036] According to the treatment process of the present invention, in some embodiments, in step (2), the wavelength of ultraviolet light in the UV / H2O2 advanced oxidation process is 250-260nm, and the irradiation power of the ultraviolet lamp is 0.3-0.6kw·h / m 3 .

[0037] According to the treatment process of the present invention, in some embodiments, in step (2), the reaction temperature is room temperature and the reaction time is 2-5 hours.

[0038] In some specific embodiments, the specific steps of the UV / H2O2 advanced oxidation process may be adding a certain amount of H2O2 to the sewage, mixing it evenly and then sucking it into a reaction tank with a pump, turning on the ultraviolet lamp, and starting the reaction.

[0039] Furthermore, according to the treatment process of the present invention, in some specific embodiments, in step (2), the entire atmospheric emissions of the WWI wastewater incineration system and the second portion of the atmospheric emissions of the AOGI waste gas incineration system are introduced into the effluent to adjust the pH value of the cyanide destruction process to 8.0-8.5.

[0040] In the present invention, the second part of the atmospheric emissions introduced into the WWI wastewater incineration system and the AOGI waste gas incineration system in the cyanide breaking process refers to all the atmospheric emissions of the WWI wastewater incineration system and the remaining part of the AOGI waste gas incineration system after the first part of the atmospheric emissions consumed in the nitrile removal process section are introduced into the outlet of the cyanide breaking process. On the one hand, the NOx and SO3 compounds in the two waste gases can be used to better adjust the pH value required by the process, and at the same time, the residual hydrogen peroxide in the UV / H2O2 advanced oxidation process can undergo redox reaction with SO2, thereby achieving the problem of reducing the residual hydrogen peroxide and avoiding the excessive hydrogen peroxide affecting the subsequent biochemical system; at the same time, the problem of NOx, SO3 and SO2 compounds being emptied and polluted by the atmosphere is solved, and the nitrate nitrogen compounds, nitrite nitrogen compounds and sulfate radicals formed after entering the sewage can generate nitrogen in the denitrification reaction in the subsequent biochemical system or be discharged with the sewage, thereby avoiding the discharge of NOx, SO3 and SO2 compounds into the atmosphere and achieving the purpose of treating waste with waste.

[0041] According to the treatment process of the present invention, in some embodiments, the volume ratio of the first part of the atmospheric emissions to the second part of the atmospheric emissions of the AOGI waste gas incineration system is (1.5-2.5):1.

[0042] According to the treatment process of the present invention, in some embodiments, the BOD5 / COD value of the sewage after being treated with the nitrile removal process and the cyanide destruction process is greater than 0.5, indicating that the treatment process of the present invention can completely remove the difficult-to-degrade, nitrification-inhibiting substances and toxic substances in the sewage, and improve the biodegradability of the sewage.

[0043] In the present invention, the sewage treated by the nitrile removal process and the cyanide breaking process further enters the A / A / O process and the biofilter EBF for treatment. Alternatively, the sewage treated by the nitrile removal process and the cyanide breaking process can enter the A / A / O process and the biofilter EBF for treatment together with other sewage in the plant area, for example, can enter the A / A / O process and the biofilter EBF for treatment together with the circulating water wastewater and the desalted water station sewage in the plant area. The present invention has no particular restrictions on this and can be adjusted according to actual conditions.

[0044] According to the treatment process of the present invention, in some embodiments, in step (3), the A / A / O process conditions are: the hydraulic retention time of the anaerobic tank is 15-30 hours, the hydraulic retention time of the anoxic tank is 20-40 hours, and the hydraulic retention time of the aerobic tank is 15-30 hours.

[0045] In the present invention, the sewage treated in the anoxic tank enters the aerobic tank for nitrification treatment, part of the nitrification effluent is returned to the anoxic tank, the remaining effluent enters the sedimentation tank for sedimentation separation, part of the sludge is returned to the anoxic tank, and the supernatant is discharged as treated effluent to the subsequent process. The present invention can adopt conventional process parameters of the A / A / O process, for example, the return ratio of the nitrification effluent can be 200%-600%, and the return ratio of the sedimentation tank sludge can be 30%-90%.

[0046] In the present invention, the A / A / O process is the abbreviation of Anaerobic-Anoxic-Oxic in English (biological denitrification and phosphorus removal), also known as anaerobic-anoxic-aerobic method. In some specific embodiments, the sewage and the return sludge first enter the anaerobic tank and are completely mixed. After a certain period of anaerobic decomposition, part of the nitrogen-containing compounds are converted into N2 (denitrification) and released, and the polyphosphate microorganisms (polyphosphate bacteria, etc.) in the return sludge release phosphorus to meet the bacteria's demand for phosphorus. Then the sewage flows into the anoxic tank, and the denitrifying bacteria in the pool use the undecomposed carbon-containing organic matter in the sewage as a carbon source to reduce the nitrate ions that flow back through the internal circulation in the aerobic tank to N2 and release. Next, the sewage flows into the aerobic tank, and the ammonia nitrogen in the water undergoes nitrification to generate nitrate ions. At the same time, the organic matter in the water is oxidized and decomposed to supply energy to the phosphorus-absorbing microorganisms. The microorganisms absorb phosphorus from the water, and the phosphorus enters the cell tissue and is enriched in the microorganisms. After precipitation and separation, it is discharged from the system in the form of phosphorus-rich sludge.

[0047] According to the treatment process of the present invention, in some embodiments, in step (3), the hydraulic retention time of the biological filter EBF is 2-4 hours.

[0048] EBF, or engineered bacteria biofilter, forms a fixed bed biofilter by loading bio-enhanced engineered strains into porous materials such as activated carbon and ceramsite to remove COD that is difficult to biodegrade in sewage. In actual operation, the pool is aerated from the bottom, the dissolved oxygen is maintained at 1-6 mg / L, and the water flows from bottom to top through the fixed bed, which can remove most of the difficult to biodegrade COD in the water.

[0049] The present invention has no special limitation on the A / A / O tank and the biological filter EBF, and conventional A / A / O tanks and biological filter EBF in the art can be used.

[0050] The present invention will be described in detail below by way of examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0051] In the present invention, the testing methods of various performance parameters in the embodiments and comparative examples are as follows: Chemical oxygen demand CODcr: dichromate method, tested according to HJ828-2017 standard; Five-day biochemical oxygen demand BOD5: tested according to HJ505-2009 standard; Total organic carbon TOC: tested according to HJ 501-2009 standard; Total nitrogen content TN: tested according to BSEN12260-2003 standard; Ammonia nitrogen NH3-N content: tested according to HJ / T 195-2005 standard; NO3-N content: tested according to HJ / T 198-2005 standard; Total cyanide content: tested according to HJ 484-2009 standard; Total phosphorus content: tested according to DIN EN ISO 6878-2004; Suspended matter content: tested according to GB / T 11901-1989 standard; The contents of acrylonitrile, acrolein, cyanopyridine, succinonitrile and propionitrile are determined in accordance with JY / T 0574-2020 General Rules for Gas Chromatography, and are detected by headspace gas chromatography-mass spectrometry, with 5 mg / L, 10 mg / L and 50 mg / L acrylonitrile solutions as internal standard curves.

[0052] In the present invention, the wastewater to be treated used in the embodiments and comparative examples is the condensate of a four-effect evaporator of an acrylonitrile production device, and the conventional water quality is shown in Table 1.

[0053] Table 1 Conventional water quality of condensate from four-effect evaporator .

[0054] The content of characteristic pollutants in the condensate of the four-effect evaporator was measured by gas chromatography-mass spectrometry, as shown in Table 2.

[0055] Table 2 Characteristic pollutant content in condensate of four-effect evaporator .

[0056] This sewage has low biodegradability and the BOD5 / COD value is too low to be detected.

[0057] Example 1 The process for treating wastewater and waste gas from the acrylonitrile production device described in this embodiment is as follows: Figure 1 The specific steps include: Nitrile removal process: a sodium hydroxide solution with a mass concentration of 48% is added to the condensate of the four-effect evaporator to adjust its pH value to 11.5, and the reaction is carried out at room temperature for 5.5 hours. After the nitrile removal reaction, the pH value drops to 11.1, and the first part of the atmospheric emissions of the AOGI waste gas incineration system is introduced into the effluent of the nitrile removal process to adjust the pH value of the effluent of the nitrile removal process to 10.5.

[0058] Cyanide destruction process: The effluent from the nitrile removal process enters the three-stage UV / H2O2 advanced oxidation process. The ultraviolet light wavelength is 254nm and the ultraviolet lamp irradiation power is 0.4kw·h / m 3 , add 300 mg / L hydrogen peroxide, react at room temperature for 3.5 hours, after the reaction, the pH value drops to 9.4, the hydrogen peroxide residue is about 50 mg / L, and the cyanide breaking process effluent is obtained; all the atmospheric emissions of the WWI wastewater incineration system and the second part of the atmospheric emissions of the AOGI waste gas incineration system are introduced into the cyanide breaking process effluent to adjust the pH value of the cyanide breaking process effluent to 8.3, wherein the volume ratio of the first part of the atmospheric emissions and the second part of the atmospheric emissions of the AOGI waste gas incineration system is 2:1. After testing, the total cyanide content in the cyanide breaking process effluent dropped to below 1 mg / L, and the BOD5 / COD ratio was 0.58.

[0059] The effluent from the cyanide destruction process enters the anaerobic tank, anoxic tank and aerobic tank of the A / A / O biochemical system in turn, where the hydraulic retention time in the anaerobic tank is 30 hours, the hydraulic retention time in the anoxic tank is 30 hours, and the hydraulic retention time in the aerobic tank is 40 hours. The sewage treated in the aerobic tank enters the secondary sedimentation tank for sedimentation and separation, and the nitrification liquid and sludge in the secondary sedimentation tank are returned to the anoxic tank, where the nitrification liquid return ratio is 300%, and the sludge return ratio is 50%. Then the effluent enters the biological filter EBF, and the empty tower hydraulic retention time is 3 hours. The treated effluent is directly discharged.

[0060] After testing, the EBF effluent quality meets the direct discharge water quality requirements of GB31571-2015. The specific data are shown in Table 3.

[0061] Example 2 The process for treating wastewater and waste gas from the acrylonitrile production device described in this embodiment is as follows: Figure 1 The specific steps include: Nitrile removal process: a sodium carbonate solution with a mass concentration of 50% is added to the condensate of the four-effect evaporator to adjust its pH value to 12.5, and the reaction is carried out at room temperature for 4 hours. After the nitrile removal reaction, the pH value drops to 12.3, and the first part of the atmospheric emissions of the AOGI waste gas incineration system is introduced into the effluent of the nitrile removal process to adjust the pH value of the effluent of the nitrile removal process to 9.5.

[0062] Cyanide destruction process: The effluent from the nitrile removal process enters the three-stage UV / H2O2 advanced oxidation process. The ultraviolet wavelength is 260nm and the irradiation power of the ultraviolet lamp is 0.5kw·h / m 3 , add 700 mg / L hydrogen peroxide, react at room temperature for 5 hours, after the reaction, the pH value drops to 9.4, the hydrogen peroxide residue is about 50 mg / L, and the cyanide breaking process effluent is obtained; all the atmospheric emissions of the WWI wastewater incineration system and the second part of the atmospheric emissions of the AOGI waste gas incineration system are introduced into the cyanide breaking process effluent to adjust the pH value of the cyanide breaking process effluent to 8.5, wherein the volume ratio of the first part of the atmospheric emissions and the second part of the atmospheric emissions of the AOGI waste gas incineration system is 2:1. After testing, the total cyanide content in the cyanide breaking process effluent dropped to below 1 mg / L, and the BOD5 / COD ratio was 0.59.

[0063] The effluent from the cyanide destruction process enters the anaerobic tank, anoxic tank and aerobic tank of the A / A / O biochemical system together with an equal amount of circulating water sewage and desalted water station sewage. The hydraulic retention time in the anaerobic tank is 25 hours, the hydraulic retention time in the anoxic tank is 25 hours, and the hydraulic retention time in the aerobic tank is 20 hours. The sewage treated in the aerobic tank enters the secondary sedimentation tank for sedimentation and separation. The nitrification liquid and sludge in the secondary sedimentation tank are returned to the anoxic tank, wherein the nitrification liquid return ratio is 400%, and the sludge return ratio is 70%. Then the effluent enters the biological filter EBF, and the empty tower hydraulic retention time is 4 hours. The treated effluent is directly discharged.

[0064] After testing, the EBF effluent quality meets the direct discharge water quality requirements of GB31571-2015. The specific data are shown in Table 3.

[0065] Table 3 EBF effluent quality in the examples and GB31571-2015 direct discharge quality .

[0066] Comparative Example 1 The nitrile removal and cyanide breaking process of this comparative example is the same as that of Example 1, except that the AOGI waste gas incineration system and the WWI wastewater incineration system atmospheric emission materials of the plant area are not introduced into the nitrile removal and cyanide breaking processes. After testing, the total cyanide content of the effluent from the cyanide breaking process reached 8.9 mg / L, the pH value was 10.1, and the BOD5 / COD was 0.13. Since the biodegradability of the sewage is too low, it cannot be put into the biochemical system for subsequent treatment.

[0067] Comparative Example 2 The nitrile removal process and cyanide destruction process of this comparative example are the same as those of Example 1, except that the tail gas of the WWI wastewater incineration system is introduced into the nitrile removal process, and all the atmospheric emissions of the WWI wastewater incineration system and the atmospheric emissions of the AOGI waste gas incineration system are not introduced into the cyanide destruction process. The specific steps are as follows: Nitrile removal process: add sodium hydroxide solution with a mass concentration of 48% to the condensate of the four-effect evaporator, adjust its pH value to 11.5, react at room temperature for 5.5 hours, and after the nitrile removal reaction, the pH value drops to 11.1, and introduce the tail gas of the WWI wastewater incineration system into the effluent of the nitrile removal process to adjust the pH value of the effluent of the nitrile removal process to 10.3.

[0068] Cyanide destruction process: The effluent from the nitrile removal process enters the three-stage UV / H2O2 advanced oxidation process. The ultraviolet light wavelength is 254nm and the ultraviolet lamp irradiation power is 0.6kw·h / m 3 , add 300mg / L hydrogen peroxide, react at room temperature for 3.5 hours, after the reaction, the pH value drops to 9.4, the hydrogen peroxide residue is about 50mg / L, and the cyanide breaking process effluent is obtained. After testing, the total cyanide content in the effluent of the cyanide breaking process is 15.0mg / L, and its BOD5 / COD value has not increased, and it has not reached the water quality entering the biochemical unit of the sewage field, so it cannot be put into the biochemical system for subsequent treatment.

[0069] Comparative Example 3 This comparative example uses the traditional stripping tower process to treat the wastewater from the acrylonitrile production unit, but does not use the nitrile removal process and cyanide destruction process; the atmospheric emissions from the AOGI waste gas incineration system and the WWI wastewater incineration system are treated using the traditional stripping tower process. After testing, the pH value of the stripping tower effluent dropped to 4.9, and NOx was found in the tail gas collection system of the sewage field, indicating that the tail gas cannot be completely absorbed by the stripping tower effluent.

[0070] It can be seen from Example 1 and Comparative Example 3 that the conventional four-effect evaporation + stripping tower process is used to treat the wastewater and waste gas of the acrylonitrile production device in Comparative Example 3, and the treatment effect is not good. This is because the pH value of the water discharged from the stripping tower is basically neutral, and it cannot absorb the acidic gas well. It is also impossible to achieve the goal of treating waste with waste, reducing the atmospheric emissions of the acrylonitrile production device, and ensuring the stable and standard discharge of the biochemical unit of the sewage field proposed in the present invention.

[0071] It can be seen from Example 1 and Comparative Example 1 that the AOGI waste gas incineration system and the WWI waste water incineration system atmospheric emission materials of the plant area are not introduced into the nitrile removal and cyanide breaking processes in Comparative Example 1, and the total cyanide content of the effluent from the cyanide breaking process reaches 8.9mg / L, and BOD5 / COD is 0.13. Due to the low biodegradability of sewage, it is impossible to put it into the biochemical system for subsequent treatment. It can be seen from Example 1 and Comparative Example 2 that the tail gas of the WWI waste water incineration system is introduced into the nitrile removal process of Comparative Example 2, and all atmospheric emissions of the WWI waste water incineration system and the atmospheric emissions of the AOGI waste gas incineration system are not introduced into the cyanide breaking process, and the total cyanide content of the effluent from the cyanide breaking process is 15.0mg / L, and its BOD5 / COD value is not improved when detected, and the water quality of the biochemical unit entering the sewage field is not reached, so it is impossible to put it into the biochemical system for subsequent treatment. Therefore, after the nitrile removal and cyanide destruction process treatment of the present invention, the atmospheric emissions of the AOGI waste gas incineration system and the WWI wastewater incineration system of the plant are introduced into the process, and the difficult-to-degrade, nitrification-inhibiting substances and toxic substances in the condensate of the four-effect evaporator are removed, and the BOD5 / COD is greatly improved, so that the biodegradability of the treated sewage is significantly improved, and the goals of treating waste with waste, reducing the atmospheric emissions of the acrylonitrile production device and ensuring that the biochemical unit of the sewage field is stably discharged up to the standard are achieved.

[0072] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A process for treating wastewater and waste gas from an acrylonitrile production plant, characterized in that: The steps include: (1) Nitrile removal process: adding alkaline substances to the condensate of the four-effect evaporator to adjust the pH value to 11-13, reacting for a certain period of time, and obtaining nitrile removal process effluent; introducing the first part of the atmospheric emissions of the AOGI waste gas incineration system into the nitrile removal process effluent to adjust the pH value of the nitrile removal process effluent to 9-11; (2) Cyanide breaking process: the effluent from step (1) enters into a UV / H2O2 advanced oxidation process and reacts for a certain period of time to obtain cyanide breaking process effluent; all the atmospheric emissions from the WWI wastewater incineration system and the second part of the atmospheric emissions from the AOGI waste gas incineration system are introduced into the cyanide breaking process effluent to adjust the pH value of the cyanide breaking process effluent to 7.5-9.0; (3) The effluent from step (2) is treated by the A / A / O process and the biological filter EBF in sequence and can meet the discharge standards.

2. The process for treating wastewater and waste gas from an acrylonitrile production plant according to claim 1, characterized in that: In step (1), the alkaline substance includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

3. The process for treating wastewater and waste gas from an acrylonitrile production device according to claim 1, characterized in that: In step (1), the reaction temperature is room temperature and the reaction time is 3-6 hours.

4. The process for treating wastewater and waste gas from an acrylonitrile production device according to claim 1, characterized in that: In step (1), the first portion of the atmospheric emissions introduced into the AOGI waste gas incineration system is used to adjust the pH value of the effluent from the nitrile removal process to 9.5-10.

5.

5. The process for treating wastewater and waste gas from an acrylonitrile production device according to claim 1, characterized in that: In step (2), the dosage of hydrogen peroxide in the UV / H2O2 advanced oxidation process is 300-700 mg / L.

6. The process for treating wastewater and waste gas from an acrylonitrile production device according to claim 1, characterized in that: In step (2), the reaction temperature is room temperature and the reaction time is 2-5 hours.

7. The process for treating wastewater and waste gas from an acrylonitrile production device according to claim 1, characterized in that: In step (2), the entire atmospheric emissions from the WWI wastewater incineration system and the second portion of atmospheric emissions from the AOGI waste gas incineration system are introduced into the effluent to adjust the pH value of the cyanide destruction process to 8.0-8.

5.

8. The process for treating wastewater and waste gas from an acrylonitrile production device according to claim 1, characterized in that: The volume ratio of the first part of atmospheric emissions and the second part of atmospheric emissions of the AOGI waste gas incineration system is (1.5-2.5):

1.

9. The process for treating wastewater and waste gas from an acrylonitrile production device according to claim 1, characterized in that: In step (3), the A / A / O process conditions are: the hydraulic retention time of the anaerobic tank is 15-30 hours, the hydraulic retention time of the anoxic tank is 20-40 hours, and the hydraulic retention time of the aerobic tank is 15-30 hours.

10. The process for treating wastewater and waste gas from an acrylonitrile production device according to claim 1, characterized in that: In step (3), the hydraulic retention time of the biological filter EBF is 2-4h.

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