Treatment system for acrylonitrile wastewater

Abstract

The acrylonitrile wastewater treatment system comprises: a hydrolysis ammoniation pool configured to receive acrylonitrile wastewater and treat organic nitrogen in the acrylonitrile wastewater; and the anoxic-aerobic biological treatment unit is positioned at the downstream of the hydrolytic ammoniation tank and is used for receiving the acrylonitrile wastewater treated by the hydrolytic ammoniation tank.

Description

Technical Field

[0001] This application relates to a treatment system for acrylonitrile wastewater. Background Art

[0002] Acrylonitrile is a widely used chemical raw material, mainly used in the production of synthetic fibers (such as acrylic fibers), synthetic resins (such as ABS resins), and synthetic rubbers (such as nitrile rubbers). The wastewater generated during the production of acrylonitrile mainly contains organic substances such as acrylonitrile, acetonitrile, and cyanide, and is a type of toxic petrochemical wastewater containing organic nitrogen that is relatively difficult to treat. The biological treatment method is the secondary core treatment process for petrochemical wastewater treatment in China. Its main function is to treat colloidal and soluble organic pollutants in wastewater, and it has advantages such as low cost, high efficiency, and low secondary pollution. The biological treatment method is mainly divided into aerobic biological treatment and anaerobic biological treatment. The treatment process of acrylonitrile wastewater mostly includes aerobic biological treatment, such as common A / O or multi-stage A / O process units. However, the toxic substances (usually organic nitrogen) in acrylonitrile wastewater will inhibit the specific functions of microorganisms in the aerobic biological treatment unit or have an overall anesthetic effect on them, thus affecting their normal metabolism, resulting in unstable operation of the treatment process and deterioration of the effluent quality. In addition, due to the characteristics of the petrochemical industry, the acrylonitrile wastewater treatment process often faces water impact from upstream production units during operation, affecting the stability of the biological treatment unit, resulting in abnormal or even collapse of its operation, increasing the difficulty of commissioning and operation management of the biological treatment unit of the acrylonitrile wastewater treatment process, and putting pressure on the subsequent advanced treatment process and thus resulting in high treatment costs. It can be seen that the stable and efficient operation of the biological treatment unit has become a key factor in ensuring the stable operation of the overall acrylonitrile wastewater treatment process and reducing costs and increasing efficiency.

[0003] In the conventional A / O biological treatment unit in the acrylonitrile wastewater treatment process, the organic matter that can be degraded by the denitrification reaction occurring in the anoxic section should be easily biodegradable organic matter. The remaining toxic and refractory organic nitrogen in the water enters the subsequent aerobic section. In the aerobic section, although some organic nitrogen may be ammoniated by ammonifying bacteria, the presence of organic nitrogen will also impact nitrifying bacteria at the same time. Once the water volume and water quality from upstream fluctuate, it will lead to an increase in the organic nitrogen entering the aerobic section, strongly inhibiting nitrifying bacteria and destroying their nitrification ability. This is the main reason why most of the current acrylonitrile wastewater treatment processes with only A / O biological treatment units operate poorly. Utility Model Content

[0004] In order to solve the problems existing in the prior art, this application provides a treatment system for acrylonitrile wastewater, including: a hydrolysis and ammonification tank configured to receive acrylonitrile wastewater and treat the organic nitrogen in the acrylonitrile-containing wastewater; an anoxic-aerobic biological treatment unit located downstream of the hydrolysis and ammonification tank and receiving the acrylonitrile wastewater treated by the hydrolysis and ammonification tank.

[0005] Advantageously, the hydrolysis and ammoniation tank comprises: a tank body; an inlet system located at the bottom of the tank body to make the acrylonitrile wastewater flow upward; an outlet system located at the top of the tank body; and a sludge discharge system located between the top and bottom of the tank body.

[0006] Advantageously, the inlet system includes an inlet main pipe located outside the tank body and a plurality of inlet branch pipes laid at the bottom of the tank body. The inlet main pipe receives the acrylonitrile wastewater and is in fluid communication with the plurality of inlet branch pipes to supply the acrylonitrile-containing wastewater to the plurality of inlet branch pipes, and the plurality of inlet branch pipes supply the acrylonitrile-containing wastewater to the bottom of the tank body.

[0007] Advantageously, the plurality of inlet branch pipes include a first group of inlet branch pipes located on one side of the tank body and a second group of inlet branch pipes located on the other side of the tank body. The inlet branch pipes in the first group of inlet branch pipes and the inlet branch pipes in the second group of inlet branch pipes are laid on the bottom of the tank body in an interleaved manner.

[0008] Advantageously, the outlet system includes an outlet well located outside the tank body and a plurality of outlet branch pipes located inside the tank body. The plurality of outlet branch pipes are configured to collect the treated acrylonitrile wastewater and converge the treated acrylonitrile-containing wastewater to an outlet branch channel.

[0009] Advantageously, the outlet system further includes an outlet branch channel provided inside the tank body and an outlet main channel provided outside the tank body. The plurality of outlet branch pipes are connected to the outlet branch channel, and the position of the outlet main channel is lower than that of the outlet branch channel for collecting the wastewater from the outlet branch channel and connecting to the outlet well.

[0010] Advantageously, the sludge discharge system includes a first layer of sludge discharge branch pipes and a second layer of sludge discharge branch pipes provided inside the tank body and a sludge discharge main pipe provided outside the tank body. The height of the second layer of sludge discharge branch pipes is higher than that of the first layer of sludge discharge branch pipes, the height of the first layer of sludge discharge branch pipes is higher than that of the inlet system. The first layer of sludge discharge branch pipes includes a plurality of first branch pipes arranged on a horizontal plane, and the second layer of sludge discharge branch pipes includes a plurality of second branch pipes arranged on a horizontal plane and a plurality of vertical branch pipes vertically extending from one end of the plurality of second branch pipes to form a sludge inlet of the second layer of sludge discharge branch pipes. The first layer of sludge discharge branch pipes and the second layer of sludge discharge branch pipes are in fluid communication with the sludge discharge main pipe.

[0011] Advantageously, the hydrolysis and ammoniation tank is configured to be operable in a first mode and a second mode based on the performance of the acrylonitrile-containing wastewater. In the first mode, only anaerobic sludge is contained in the tank body of the hydrolysis and ammoniation tank to form a sludge bed layer, and above the sludge bed layer are a sludge expansion zone and a clear water zone in sequence.

[0012] In the second mode, anaerobic sludge and fillers are contained in the tank body of the hydrolysis and ammoniation tank. The anaerobic sludge forms a sludge bed layer, a transition zone is located above the sludge bed layer, and a filler layer and a clear water zone are provided in sequence above the transition zone.

[0013] Advantageously, the packing material of the packing layer includes rope-type hanging packing or light suspended packing.

[0014] Advantageously, the hydrolysis and ammoniation tank further includes an antifoaming system, which is arranged above the top of the hydrolysis and ammoniation tank and includes an antifoaming main pipe and a plurality of antifoaming branch pipes extending from the antifoaming main pipe towards the tank body. Through the antifoaming branch pipes, production water is sprayed onto the top of the tank body to eliminate the foam formed on the top of the tank body.

[0015] Advantageously, the treatment system has the following design parameters, such that after treatment, the ammoniation rate is controlled within the range of 70 - 95%, and the COD removal rate is within the range of 10 - 30%:

[0016] Retention time: 8 - 48h,

[0017] Ratio of acrylonitrile wastewater to dilution water: 2:1 - 1:5,

[0018] pH: 6 - 8,

[0019] Temperature: 20 - 42°C

[0020] Dissolved oxygen content in the hydrolysis and ammoniation tank is controlled < 0.5mg / L,

[0021] Redox potential: -100 ~ -350mV,

[0022] Sludge concentration: 5 - 12g / L,

[0023] COD influent load: 0.15 - 0.4kgCOD / kgSS / d,

[0024] Total TKN influent load: 0.01 - 0.04kgTKN / kgSS / d.

[0025] Advantageously, the sludge used to start the hydrolysis and ammoniation tank is anaerobic sludge or aerobic sludge,

[0026] When starting with anaerobic sludge, the COD start-up load is 0.06 - 0.1kgCOD / kgSS / d, and the TKN start-up load is 0.005 - 0.015kgTKN / kgSS / d;

[0027] When starting with aerobic sludge, the COD start-up load is 0.03 - 0.06kgCOD / kgSS / d, and the TKN start-up load is 0.002 - 0.007kgTKN / kgSS / d. Description of the Drawings

[0028] The above and other features and advantages of the exemplary embodiments of the present utility model will become more apparent from the following detailed description in conjunction with the accompanying drawings, and the description and drawings are for exemplary purposes only and do not limit the scope of the present utility model in any way, where:

[0029] Figure 1 A schematic diagram showing a front view of a hydrolytic ammoniation tank of a treatment system according to the present application.

[0030] Figure 2 A schematic diagram showing a bottom view of a hydrolytic ammoniation tank of a treatment system according to the present application.

[0031] Figure 3 A schematic diagram showing a top view of a hydrolytic ammoniation tank of a treatment system according to the present application.

[0032] Figure 4 Another schematic diagram showing a bottom view of a hydrolytic ammoniation tank of a treatment system according to the present application, with the inlet system removed.

[0033] Figure 5 A schematic diagram showing a side view of a hydrolytic ammoniation tank of a treatment system according to the present application.

[0034] Figure 6 A schematic diagram showing a rear view of a hydrolytic ammoniation tank of a treatment system according to the present application. Detailed implementation manners

[0035] In order to make the objectives, technical solutions, and advantages of the technical solutions of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the specific embodiments of the present disclosure. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0036] Compared with the embodiments shown in the drawings, the feasible implementation solutions within the scope of protection of the present disclosure may have fewer components, have other components not shown in the drawings, different components, components arranged differently, or components connected differently, etc. In addition, two or more components in the drawings may be implemented in a single component, or a single component shown in the drawings may be implemented as multiple separate components.

[0037] Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art to which this disclosure pertains. The terms "first", "second" and similar terms used in the specification and claims of this patent application of the disclosure do not denote any order, quantity or importance, but are merely used to distinguish different components. When the number of components is not stated, the number of components may be one or more; similarly, terms such as "a", "the", "said" and the like do not necessarily denote a quantity limitation. Words such as "comprising" or "including" and the like mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. "Upper", "lower", "left", "right" and the like are only used to represent the relative orientation relationship during the use of the device or the orientation relationship shown in the drawings. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0038] To better describe the hydrolysis and ammoniation tank, hereinafter, the direction of the X axis represents the left - right direction, the direction of the Y axis represents the front - back direction, and the direction of the Z axis represents the up - down direction.

[0039] The treatment system of this application includes a hydrolysis and ammoniation tank 1 and an anoxic - aerobic biological treatment unit (not shown). The hydrolysis and ammoniation tank is arranged upstream of the anoxic - aerobic biological treatment unit and is configured to receive acrylonitrile - containing wastewater and perform anaerobic ammoniation and hydrolysis treatment on the organic nitrogen in the acrylonitrile - containing wastewater. The anoxic - aerobic biological treatment unit receives the acrylonitrile - containing wastewater treated by the hydrolysis and ammoniation tank.

[0040] The hydrolysis and ammoniation tank includes a tank body 11; an inlet system located at the bottom of the tank body to make the acrylonitrile - containing wastewater flow upward; an outlet system located at the top of the tank body to receive the treated acrylonitrile - containing wastewater; a sludge discharge system located at a predetermined position between the top and bottom of the tank body; and an antifoaming system located above the top of the tank body. Each mechanism will be introduced separately below.

[0041] The anoxic - aerobic biological treatment unit is commonly used in the art, well - known to those skilled in the art, and is not the focus of this application. Therefore, it will not be elaborated herein.

[0042] Inlet system

[0043] As Figure 2 shown, a schematic diagram showing the bottom view of the hydrolysis and ammoniation tank, and other components are removed for clearly showing the inlet system.

[0044] The water inlet system includes a main water inlet pipe (not shown) located outside the pool body and a plurality of water inlet branch pipes 12 laid at the bottom of the pool body. The main water inlet pipe receives the acrylonitrile-containing wastewater and is in fluid communication with the plurality of water inlet branch pipes to supply the acrylonitrile-containing wastewater to the plurality of water inlet branch pipes, and the plurality of water inlet branch pipes supply the acrylonitrile-containing wastewater to the bottom of the pool body. Each water inlet branch pipe includes a water inlet 121 and a water outlet 122.

[0045] The plurality of water inlet branch pipes include a first group of water inlet branch pipes (the left water inlet branch pipes in Figure 2 ), located on one side of the pool body, and a second group of water inlet branch pipes (the right water inlet branch pipes in Figure 2 ), located on the other side of the pool body. The water inlet branch pipes in the first group of water inlet branch pipes and the water inlet branch pipes in the second group of water inlet branch pipes are laid on the bottom of the pool body in an alternating manner, so that the water outlets of each water inlet branch pipe in the first group of water inlet branch pipes are staggered from the water outlets of each water inlet branch pipe in the second group of water inlet branch pipes.

[0046] Each water inlet branch pipe 12 includes a first water inlet branch pipe 123 and a second water inlet branch pipe 124 connected to each other. The first water inlet branch pipe is in fluid communication with the main water inlet pipe, and the second water inlet branch pipe 124 forms a water outlet. The diameter of the first water inlet branch pipe 123 is different from the diameter of the second water inlet branch pipe 124. Preferably, the diameter of the first water inlet branch pipe 123 is larger than the diameter of the second water inlet branch pipe 124, so as to make the water distribution more uniform. With such an arrangement, the water inlet form is bilateral pulse water inlet, and the two groups of water inlet branch pipes alternate in water inlet, which is achieved by adjusting the pulse switching frequency and the water inlet valve. The first water inlet branch pipe and the second water inlet branch pipe are perforated pipes, that is, holes are drilled on the first water inlet branch pipe and the second water inlet branch pipe.

[0047] The water inlet system further includes a mixing tank 13, and a stirrer 131 is arranged in the mixing tank to stir and mix the acrylonitrile-containing wastewater evenly. The mixing tank is in fluid communication with the main water inlet pipe and supplies the evenly mixed acrylonitrile-containing wastewater to the main water inlet pipe.

[0048] Outlet system

[0049] As Figure 3 shown, it is a schematic diagram showing a top view of the hydrolysis and ammonification tank, and other components are removed for clearly showing the water outlet system.

[0050] The water outlet system includes a water outlet well 24 located outside the pool body and a plurality of water outlet branch pipes 21 located inside the pool body. The plurality of water outlet branch pipes 21 are configured to receive the treated acrylonitrile-containing wastewater and supply the treated acrylonitrile-containing wastewater to the water outlet well.

[0051] The effluent system further includes an effluent branch channel 22 disposed within the pool body and an effluent main channel 23 disposed outside the pool body. A plurality of effluent branch pipes 21 are fluidly connected to the effluent branch channel 22. The position of the effluent main channel 23 is lower than that of the effluent branch channel, and is used to receive the wastewater from the effluent branch channel and is fluidly connected to the effluent well 24.

[0052] The plurality of effluent branch pipes can be arranged in various patterns, Figure 3 and the examples shown are only exemplary.

[0053] Sludge discharge system

[0054] As Figure 4 、 5 and shown in 6, the sludge discharge system of the hydrolysis and ammoniation tank of the present application is shown. In order to better show the sludge discharge system, other components are removed.

[0055] The sludge discharge system includes a first layer of sludge discharge branch pipes 31 and a second layer of sludge discharge branch pipes 32 disposed within the pool body and a sludge discharge main pipe (not shown) disposed outside the pool body. The height of the second layer of sludge discharge branch pipes is higher than that of the first layer of sludge discharge branch pipes, and the height of the first layer of sludge discharge branch pipes is higher than that of the inlet system. When viewed from the Figure 4 top view shown, the first layer of sludge discharge branch pipes 31 coincides with the second layer of sludge discharge branch pipes 32. The plurality of first branch pipes in the first layer of sludge discharge branch pipes 31 include sludge discharge branch pipes extending along the Y-axis, and may also include sludge discharge branch pipes extending along both the Y-axis and the X-axis. That is to say, the plurality of first branch pipes of the first layer of sludge discharge branch pipes 31 extend in the horizontal plane, which is shown in Figure 4 this figure.

[0056] On the horizontal plane, the form of the second layer of sludge discharge branch pipes is the same as that of the first layer of sludge discharge branch pipes. The difference is that the second layer of sludge discharge branch pipes includes a plurality of second branch pipes arranged on the horizontal plane and a plurality of vertical branch pipes 33 vertically extending from one end of the plurality of second branch pipes to form a sludge inlet 34 of the second layer of sludge discharge branch pipes. The first layer of sludge discharge branch pipes and the second layer of sludge discharge branch pipes are fluidly connected to the sludge discharge main pipe.

[0057] Defoaming system

[0058] During the operation of the hydrolysis and ammoniation tank, foam will be generated at the top of the pool body. In order to eliminate these foams, a defoaming system is arranged above the top of the hydrolysis and ammoniation tank, including a defoaming main pipe 41 and a plurality of defoaming branch pipes 42 extending from the defoaming main pipe towards the pool body. Through the defoaming branch pipes, external water is sprayed onto the top of the pool body to eliminate the foam formed on the top of the pool body. The defoaming branch pipes are perforated pipes and are connected to the defoaming main pipe.

[0059] In addition, the hydrolysis and ammonia pool is also equipped with an effluent ammonia nitrogen meter, a sludge concentration meter, and an oxidation-reduction potential meter, and a sludge interface meter is used to control sludge discharge. Hydrogen sulfide alarms and methane concentration alarms are also installed in the hydrolysis and ammonia pool. An underwater agitator must be installed in the hydrolysis and ammonia pool to ensure that the sludge is evenly mixed in the pool and reduce sludge accumulation and dead zones.

[0060] The hydrolysis and amination tank is configured to be able to operate in a first mode and a second mode based on the performance of the acrylonitrile-containing wastewater. In the first mode, only anaerobic sludge is contained in the tank body of the hydrolysis and amination tank to form a sludge bed layer, and a sludge expansion zone and a clear water zone are sequentially arranged above the sludge bed layer. The mud level of the sludge bed layer is 1 / 2 of the tank body height, and above the sludge bed layer, 1 / 4 of the tank body height is a suspended sludge expansion zone, which increases the contact time between sludge and wastewater on the one hand, and promotes sludge sedimentation, reduces sludge loss, and reduces the suspended solids concentration (SS) in the effluent water on the other hand.

[0061] In the second mode, the hydrolysis and ammoniation tank contains anaerobic sludge and anaerobic biofilm in the tank body. The anaerobic sludge forms a sludge bed layer, and the anaerobic biofilm forms a transition zone above the sludge bed layer. A packing layer and a clear water zone are arranged above the transition zone in sequence. The upper part of the tank body is the packing layer, and the height is 1 / 4 of the tank body height. The upper part of the packing layer is the clear water zone. The lower part is the sludge bed layer, and the height is 1 / 4 of the tank body height. A 1 / 4 of the tank body height is reserved between the packing layer and the sludge bed layer as a transition zone to facilitate the retention of suspended flocculent sludge, increase the biomass in the tank, and prolong the contact time between the sludge and the wastewater. The sludge bed layer should be maintained below the packing layer as a whole.

[0062] The filler of the packing layer includes rope-type suspension filler or light suspended filler. The rope-type suspension filler can be made of organic polymer material or organic mixed material. The advantages of rope-type suspension filler are fast biofilm formation speed and large biofilm formation amount.

[0063] Lightweight suspended fillers can be made of organic polymer materials. When using lightweight suspended fillers, a filler interception net must be installed above the filler layer.

[0064] The advantages of lightweight suspended fillers are flexible and convenient operation and no need for a support.

[0065] The treatment system of the present application sets a hydrolysis and amination unit upstream of the anoxic-aerobic biological treatment unit. Through the hydrolysis and amination process, most of the nitrogen-containing organic matter such as acrylonitrile and cyanide in the acrylonitrile-containing wastewater is first converted into ammonia nitrogen, which can effectively reduce the toxicity in the water, improve the stability of the operation of the subsequent biological treatment unit, enhance its impact resistance, and reduce the difficulty of operation management and treatment costs.

[0066] In addition, the operation and process control of the hydrolysis and ammoniation unit are simple, with obvious effects, and it can be flexibly switched between the pure sludge mode (the first mode) and the sludge-film mode (the second mode) to cope with different influent conditions.

[0067] The following takes four embodiments to introduce the process of the treatment system of the present application.

[0068] For the hydrolysis and ammoniation treatment system of acrylonitrile wastewater, the main operating parameters of the hydrolysis and ammoniation process of acrylonitrile wastewater are controlled within the following ranges:

[0069] Retention time: 8 - 48 h,

[0070] Acrylonitrile wastewater : dilution water = 2:1 - 1:5,

[0071] pH: 6 - 8,

[0072] Temperature: 20 - 42 °C,

[0073] The dissolved oxygen content in the hydrolysis and ammoniation tank is controlled to be < 0.5 mg / L,

[0074] Oxidation-reduction potential ORP: -100 ~ -350 mV,

[0075] Sludge concentration: 5 - 12 g / L,

[0076] Chemical oxygen demand COD influent load: 0.15 - 0.4 kgCOD / kgSS / d,

[0077] Total Kjeldahl nitrogen TKN influent load: 0.01 - 0.04 kgTKN / kgSS / d.

[0078] It is necessary to supplement sludge regularly. When the sludge sedimentation performance SV30 value in the tank drops below 30% and the ammoniation rate shows a rapid decline, sludge needs to be supplemented. The sludge supplementation cycle is determined according to the hydraulic retention time, about 1 - 3 months.

[0079] Inoculated sludge:

[0080] The inoculated sludge can be directly started with anaerobic or anoxic floc sludge, with a fast start-up speed. Generally, it takes 1 - 2 weeks to complete the start-up.

[0081] If there is no anaerobic sludge, the secondary sedimentation tank return aerobic sludge can also be used for inoculation and start-up. The start-up speed using aerobic sludge is slower, generally taking 3 - 5 weeks to start.

[0082] Start-up load:

[0083] When starting with anaerobic sludge, the COD start-up load: 0.06 - 0.1 kgCOD / kgSS / d, the TKN start-up load: 0.005 - 0.015 kgTKN / kgSS / d.

[0084] When starting up with aerobic sludge, the COD startup load is 0.03 - 0.06 kg COD / kg SS / d, and the TKN startup load is 0.002 - 0.007 kg TKN / kg SS / d.

[0085] Operation mode:

[0086] Pure sludge system - that is, there is only sludge in the hydrolysis and ammonification tank. The conventional hydrolysis and ammonification tank operates in a pure sludge system. The operating height of the sludge bed level is 1 / 2 of the tank height. Above the sludge bed, 1 / 4 of the tank height is the suspended sludge expansion zone, which on the one hand increases the contact time between the sludge and the wastewater, on the other hand promotes sludge sedimentation, reduces sludge loss, and reduces the SS in the effluent. Above the sludge expansion zone is the clear water area.

[0087] Sludge - film composite system - that is, there are both anaerobic sludge and anaerobic biofilm in the hydrolysis and ammonification tank, forming a sludge - film complex of sludge and biofilm. When the wastewater to be subjected to hydrolysis and ammonification has high biological toxicity, it operates in a sludge - film system. The upper part of the tank is the packing layer, with a height of 1 / 4 of the tank height. Above the packing layer is the clear water area. The lower part is the sludge bed, with a height of 1 / 4 of the tank height. A 1 / 4 of the tank height is left between the packing layer and the sludge bed as a transition zone to facilitate the stay of flocculent sludge in a suspended state, increase the biomass in the tank, and extend the contact time between the sludge and the wastewater. The sludge bed should be maintained below the packing layer as a whole.

[0088] The packing in the upper packing layer can be rope - type hanging packing or lightweight suspended packing.

[0089] The rope - type hanging packing can be made of organic polymer materials or organic mixed materials. The advantages of the rope - type hanging packing are fast film - hanging speed and large film - hanging amount.

[0090] The lightweight suspended packing can be made of organic polymer materials. When using lightweight suspended packing, a packing interception net needs to be installed above the packing layer.

[0091] The advantages of the lightweight suspended packing are flexible and convenient operation and no need for a support.

[0092] Reference range of the treatment effect of the hydrolysis and ammonification treatment system:

[0093] Ammonification rate (ammonification rate = effluent ammonia nitrogen concentration / effluent total nitrogen concentration): 70 - 95%,

[0094] COD removal rate: 10 - 30%.

[0095] Example 1:

[0096] The daily discharge of acrylonitrile wastewater (mixed with some butadiene latex wastewater) from an acrylonitrile production unit in a petrochemical plant is 60 - 140 m3 / h. After being mixed with ethylene oxide, the MTO unit effluent and domestic rainwater in the homogenization tank, the mixture enters the hydrolysis and ammonification tank. The quality of acrylonitrile wastewater is as follows:

[0097]

[0098] Table 1

[0099] The hydrolysis and ammonification tank in the petrochemical plant sewage treatment station is square, made of concrete, with a volume of 6400 m 3 , and there are two of them. In the hydrolysis and ammonification tank, an effluent ammonia nitrogen meter, a sludge concentration meter, an oxidation-reduction potential meter, etc. are installed, and the sludge interface meter is used to control sludge discharge. An underwater stirrer is also installed in the hydrolysis and ammonification tank.

[0100] The main parameters of the hydrolysis and ammonification treatment process for acrylonitrile wastewater are controlled within the following ranges:

[0101] Retention time: 24 h,

[0102] Acrylonitrile: mixture of acrylonitrile and water is about 1:3 - 1:5,

[0103] pH: 6 - 8,

[0104] Temperature: 25 - 28 °C,

[0105] Dissolved oxygen in the hydrolysis and ammonification tank < 0.5 mg / L,

[0106] ORP: -120 ~ -350 mV,

[0107] Sludge concentration: 6 - 8 g / L,

[0108] COD influent load: about 0.25 kgCOD / kgSS / d,

[0109] Total TKN influent load: about 0.03 kgTKN / kgSS / d.

[0110] Inoculated sludge:

[0111] The inoculated sludge is the aerobic sludge refluxed from the secondary sedimentation tank of a municipal sewage treatment plant, and the start-up is successful after 4 - 5 weeks.

[0112] Start-up load:

[0113] TKN load: 0.002 kgTKN / kgSS / d,

[0114] COD load: 0.03 kgCOD / kgSS / d.

[0115] Operation mode:

[0116] It is a pure sludge system, and the operating height of the sludge bed accounts for about 1 / 2 of the height of the pool body. Above the sludge bed, 1 / 4 of the height of the pool body is the suspended sludge expansion zone, and above the sludge expansion zone is the clear water zone.

[0117] The effluent quality of the hydrolysis and ammoniation tank and the effluent indexes and main control parameters of the subsequent two-stage A / O process are as follows:

[0118]

[0119]

[0120] Table 2

[0121] The pH of the first-stage anoxic tank is 7.6, the residence time is 18 h, and the dissolved oxygen in the tank is <0.5 mg / L.

[0122] The residence time of the first-stage aerobic biochemical tank is 24 h, the dissolved oxygen is 3 - 5 mg / L, and the pH is 7.8.

[0123] The pH of the second-stage anoxic tank is 7.8, the residence time is 9 h, and the dissolved oxygen in the tank is <0.5 mg / L.

[0124] The residence time of the second-stage aerobic biochemical tank is 12 h, the dissolved oxygen is 3 - 4 mg / L, the pH is 8.0, and the reflux ratio of the effluent to the first-stage anoxic tank is 4.

[0125] Example 2:

[0126] Similarly, for a petrochemical plant's acrylonitrile production device in Example 1, the daily discharge of acrylonitrile wastewater (mixed with some butadiene latex wastewater) is 60 - 140 m 3 / h. After mixing with the mixed water of ethylene oxide, MTO device and domestic rainwater in the homogenization tank, it enters the hydrolysis and ammoniation tank. The tank body and each system of the hydrolysis and ammoniation tank are the same as those in Example 1. The quality of the original acrylonitrile wastewater is as follows:

[0127]

[0128] Table 3

[0129] The main parameters of the hydrolysis and ammoniation treatment process for acrylonitrile wastewater are controlled within the following ranges:

[0130] Residence time: 24 h,

[0131] Acrylonitrile: methanol wastewater is about 1:3 - 1:5,

[0132] pH: 6 - 8,

[0133] Temperature: 28 - 31 °C,

[0134] The dissolved oxygen in the hydrolysis and ammoniation tank is controlled to be <0.5 mg / L,

[0135] The ORP control is at -100 to -280 mV,

[0136] the sludge concentration is 5 - 6 g / L,

[0137] the COD operating load: 0.4 kg COD / kg SS / d,

[0138] the total TKN operating load: 0.035 kg TKN / kg SS / d.

[0139] Inoculated sludge:

[0140] The inoculated sludge is anaerobic flocculent sludge from the sewage treatment station of a chemical plant and starts successfully after about 2 weeks.

[0141] Startup load:

[0142] The TKN load: 0.008 kg TKN / kg SS / d,

[0143] The COD load: 0.08 kg COD / kg SS / d.

[0144] Operating mode:

[0145] It is a sludge - film composite system - the upper part of the tank body is the packing layer, with a height of 1 / 4 of the tank body height. Above the packing layer is the clear water area. The lower part is the sludge bed layer, with a height of 1 / 4 of the tank body height. A 1 / 4 of the tank body height is left as the transition area between the packing layer and the sludge bed layer.

[0146] The packing in the upper packing layer is rope - type hanging packing.

[0147] The material of the rope - type hanging packing is an organic composite material. The packing diameter is 60 mm, the breaking tensile force > 1000 N, the specific surface area > 0.4 m 2 / g, and the filling rate is 40%. The packing is suspended on a carbon steel bracket with a hanging height of 2 m.

[0148] The effluent quality of the hydrolysis and ammonification tank and the effluent indexes and main control parameters of the subsequent two - stage A / O process are as follows:

[0149]

[0150] Table 4

[0151] The pH of the first - stage anoxic tank is 7.3, the residence time is 16 h, and the dissolved oxygen in the tank < 0.5 mg / L.

[0152] The residence time of the first - stage aerobic biochemical tank is 24 h, the dissolved oxygen is 3 - 5 mg / L, and the pH is 8.

[0153] The pH value of the second-stage anoxic tank is 8, the residence time is 7h, and the dissolved oxygen content in the tank is <0.5mg / L.

[0154] The residence time of the second-stage aerobic biochemical tank is 12h, the dissolved oxygen content is 3-4mg / L, the pH value is 8.2, and the reflux ratio of the effluent back to the first-stage anoxic tank is 3.5.

[0155] Example 3:

[0156] The daily discharge of acrylonitrile wastewater from an acrylonitrile production unit in a petrochemical plant is 40-110m 3 / h. After mixing with the methanol wastewater discharged from the methanol production unit in the equalization tank, it enters the hydrolysis and ammoniation tank. The quality of the original acrylonitrile wastewater is as follows:

[0157]

[0158] Table 5

[0159] The hydrolysis and ammoniation tank of the sewage treatment station in this petrochemical plant is square, made of concrete, with a volume of 2400m 3 , and the number is one. An effluent ammonia nitrogen analyzer, sludge concentration meter, redox potential meter, etc. are installed in the hydrolysis and ammoniation tank, and the sludge interface meter is used to control sludge discharge. Two underwater agitators are also installed in the hydrolysis and ammoniation tank.

[0160] The main parameters of the hydrolysis and ammoniation treatment process for acrylonitrile wastewater are controlled within the following ranges:

[0161] Residence time: 12h,

[0162] Acrylonitrile: methanol wastewater is about 1:1,

[0163] pH: 6-8,

[0164] Temperature: 38-41°C,

[0165] The dissolved oxygen content in the hydrolysis and ammoniation tank is <0.4mg / L,

[0166] ORP: -120~-300mV,

[0167] Sludge concentration: 5-7g / L,

[0168] COD influent load: about 0.21kgCOD / kgSS / d,

[0169] Total TKN influent load: about 0.032kgTKN / kgSS / d.

[0170] Inoculated sludge:

[0171] The inoculated sludge is the aerobic sludge refluxed from the secondary sedimentation tank of a municipal sewage treatment plant + the sludge discharged from the aerobic biochemical treatment unit in this sewage treatment plant, and it is successfully started after about 4 weeks.

[0172] Startup load:

[0173] TKN load: 0.006 kg TKN / kg SS / d,

[0174] COD load: 0.05 kg COD / kg SS / d.

[0175] Operation mode:

[0176] It is a pure sludge system. The operating height of the sludge bed level accounts for about 1 / 2 of the height of the tank body. Above the sludge bed, 1 / 4 of the height of the tank body is the suspended sludge expansion zone, and above the sludge expansion zone is the clear water zone.

[0177] The effluent quality of the hydrolysis and ammonification tank and the effluent indexes and main control parameters of the subsequent two-stage A / O process are as follows:

[0178]

[0179] Table 6

[0180] The pH of the first-stage anoxic tank is 7.2, the retention time is 26 h, and the dissolved oxygen in the tank is <0.5 mg / L.

[0181] The retention time of the first-stage aerobic biochemical tank is 28 h, the dissolved oxygen is 3 - 4 mg / L, and the pH is 7.5.

[0182] The pH of the second-stage anoxic tank is 7.6, the retention time is 12 h, and the dissolved oxygen in the tank is <0.5 mg / L.

[0183] The retention time of the second-stage aerobic biochemical tank is 10 h, the dissolved oxygen is 3 - 4 mg / L, and the pH is 7.9.

[0184] Example 4:

[0185] Similarly, for a petrochemical plant acrylonitrile production device in Example 3, the daily discharge of acrylonitrile wastewater is 40 - 110 m 3 / h. After mixing with the methanol wastewater discharged from the methanol production unit in the homogenization tank, it enters the hydrolysis and ammonification tank. The tank body and each system of the hydrolysis and ammonification tank are the same as those in Example 3. The original acrylonitrile wastewater quality is as follows:

[0186]

[0187] Table 7

[0188] The main parameter control of the hydrolysis and ammonification treatment process for acrylonitrile wastewater is in the following range:

[0189] Retention time: 12 h,

[0190] Acrylonitrile: methanol wastewater is about 1:1,

[0191] pH: 6 - 8,

[0192] Temperature: 39 - 42 °C,

[0193] Dissolved oxygen in the hydrolysis and ammonification tank < 0.4 mg / L,

[0194] ORP: -110 ~ -310 mV,

[0195] Sludge concentration: 5 - 6 g / L,

[0196] COD influent load: approximately 0.25 kg COD / kg SS / d,

[0197] Total TKN influent load: approximately 0.036 kg TKN / kg SS / d.

[0198] Inoculated sludge:

[0199] The inoculated sludge is the dehydrated sludge from the secondary sedimentation tank of a certain municipal wastewater treatment plant and starts successfully after 4 - 5 weeks.

[0200] Start-up load:

[0201] TKN load: 0.007 kg TKN / kg SS / d,

[0202] COD load: 0.06 kg COD / kg SS / d.

[0203] Operation mode:

[0204] It is a sludge-film composite system. The upper part of the tank is the packing layer, with a height of about 1 / 4 of the tank height. Above the packing layer is the clear water area. The lower part is the sludge bed layer, with a height of 1 / 4 of the tank height. A 1 / 4 of the tank height is left as the transition area between the packing layer and the sludge bed layer. The sludge bed layer is maintained below the packing layer.

[0205] The packing in the upper packing layer is lightweight suspended packing, and a packing interception net is installed above the packing layer. The lightweight suspended packing is made of organic polymer materials. The packing filling rate is 45%, the packing shape is a small ball, its specific surface area is 400 m 2 / m 3 , the diameter is 15 mm, and the packing has a skeleton support structure with a pore gap of 5 mm.

[0206] The effluent quality of the hydrolysis and ammonification tank and the effluent indexes and main control parameters of the subsequent two-stage A / O process are as follows:

[0207]

[0208] Table 8

[0209] The pH value of the first-stage anoxic tank is 7.1, the residence time is 20 h, and the dissolved oxygen content in the tank is <0.5 mg / L.

[0210] The residence time of the first-stage aerobic biochemical tank is 20 h, the dissolved oxygen content is 3 - 4 mg / L, and the pH value is 7.3.

[0211] The pH value of the second-stage anoxic tank is 7.5, the residence time is 10 h, and the dissolved oxygen content in the tank is <0.5 mg / L.

[0212] The residence time of the second-stage aerobic biochemical tank is 8 h, the dissolved oxygen content is 3 - 4 mg / L, and the pH value is 7.8.

[0213] For those skilled in the art, it is obvious that the present utility model is not limited to the details of the above-described exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present utility model. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present utility model. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0214] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A system for treating acrylonitrile wastewater, characterized in that: include: A hydrolysis and amination tank configured to receive acrylonitrile wastewater and treat organic nitrogen in the acrylonitrile-containing wastewater; The anoxic-aerobic biological treatment unit is located downstream of the hydrolysis and ammonia treatment tank and receives the acrylonitrile wastewater treated by the hydrolysis and ammonia treatment tank. The hydrolysis and ammoniation tank comprises: Pool body; The water inlet system located at the bottom of the tank body allows the acrylonitrile wastewater to flow upward; The water outlet system is located at the top of the pool; The sludge drainage system located between the top and bottom of the tank; A defoaming system is arranged above the top of the hydrolysis and amination tank.

2. The system for treating acrylonitrile wastewater according to claim 1, characterized in that: The water inlet system includes a water inlet main pipe located outside the tank body and a plurality of water inlet branches laid at the bottom of the tank body. The water inlet main pipe receives acrylonitrile wastewater and is fluidly connected with the plurality of water inlet branches to supply acrylonitrile-containing wastewater to the plurality of water inlet branches. The plurality of water inlet branches supply the acrylonitrile-containing wastewater to the bottom of the tank body.

3. The system for treating acrylonitrile wastewater according to claim 2, characterized in that: The multiple water inlet branches include a first group of water inlet branches located on one side of the pool body and a second group of water inlet branches located on the other side of the pool body. The water inlet branches in the first group of water inlet branches and the water inlet branches in the second group of water inlet branches are laid alternately at the bottom of the pool body.

4. The system for treating acrylonitrile wastewater according to claim 1, characterized in that: The water outlet system includes a water outlet well located outside the pool body and a plurality of water outlet branches located inside the pool body. The plurality of water outlet branches are configured to collect the treated acrylonitrile wastewater and collect the treated acrylonitrile-containing wastewater into the water outlet branch channel.

5. The system for treating acrylonitrile wastewater according to claim 4, characterized in that: The outlet system also includes an outlet branch channel arranged in the pool body and an outlet main channel arranged outside the pool body. Multiple outlet branch pipes are connected to the outlet branch channels. The outlet main channel is located lower than the outlet branch channels and is used to collect wastewater from the outlet branch channels and connect to the outlet well.

6. The system for treating acrylonitrile wastewater according to claim 1, characterized in that: The mud discharge system includes a first-layer mud discharge branch pipe and a second-layer mud discharge branch pipe arranged in the pool body and a mud discharge main pipe arranged outside the pool body. The height of the second-layer mud discharge branch pipe is higher than that of the first-layer mud discharge branch pipe. The height of the first-layer mud discharge branch pipe is higher than that of the water inlet system. The first-layer mud discharge branch pipe includes a plurality of first branch pipes arranged on a horizontal plane. The second-layer mud discharge branch pipe includes a plurality of second branch pipes arranged on a horizontal plane and a plurality of vertical branch pipes vertically extending from one end of the plurality of second branch pipes to form a sludge inlet of the second-layer mud discharge branch pipe. The first-layer mud discharge branch pipe and the second-layer mud discharge branch pipe are fluidly connected to the mud discharge main pipe.

7. The system for treating acrylonitrile wastewater according to claim 1, characterized in that: The hydrolysis and ammoniation tank is configured to be able to operate in a first mode and a second mode based on the properties of the acrylonitrile-containing wastewater. In the first mode, the hydrolysis and ammoniation tank contains only anaerobic sludge to form a sludge bed layer, and above the sludge bed layer are a sludge expansion zone and a clear water zone in sequence. In the second mode, the hydrolysis and ammoniaization tank contains anaerobic sludge and filler in the tank body, the anaerobic sludge forms a sludge bed layer, the transition zone is located above the sludge bed layer, and the filler layer and the clear water zone are arranged in sequence above the transition zone.

8. The system for treating acrylonitrile wastewater according to claim 7, characterized in that: The filler of the filler layer includes rope-type hanging filler or light suspended filler.

9. The system for treating acrylonitrile wastewater according to claim 1, characterized in that: The defoaming system comprises a defoaming main pipe and a plurality of defoaming branch pipes extending from the defoaming main pipe toward the pool body. Process water is sprayed to the top of the pool body via the defoaming branch pipes to eliminate foam formed on the top of the pool body.

10. The system for treating acrylonitrile wastewater according to claim 1, characterized in that: The treatment system has the following design parameters, so that after treatment, the ammoniation rate is controlled within the range of 70-95%, and the COD removal rate is within the range of 10-30%: Duration: 8-48h, The ratio of acrylonitrile wastewater to dilution water: 2:1-1:5, pH: 6-8, Temperature: 20-42℃ The dissolved oxygen content in the hydrolysis and ammoniation tank is controlled to be <0.5mg / L. Oxidation-reduction potential: -100~-350mV, Sludge concentration: 5-12g / L, COD influent load: 0.15-0.4kgCOD / kgSS / d, Total TKN inlet load: 0.01-0.04kgTKN / kgSS / d.

11. The system for treating acrylonitrile wastewater according to claim 10, characterized in that: The sludge used to start the hydrolysis and ammoniation tank is anaerobic sludge or aerobic sludge. When using anaerobic sludge for startup, the COD startup load is 0.06-0.1kgCOD / kgSS / d, and the TKN startup load is 0.005-0.015kgTKN / kgSS / d; When using aerobic sludge for startup, the COD startup load is 0.03-0.06kgCOD / kgSS / d, and the TKN startup load is 0.002-0.007kgTKN / kgSS / d.

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