CN115636468A - A treatment equipment and treatment method suitable for high-concentration hydrazine wastewater - Google Patents

Abstract

The invention discloses a treatment device suitable for high-concentration hydrazine wastewater, which comprises a reaction tank, a waste liquid pool, a chemical catalysis unit, a gas discharge unit, a micro-nano bubble generation unit and an ozone generation unit, wherein the chemical catalysis unit is communicated with the reaction tank; the reaction tank is provided with a first circulating pipeline, and the micro-nano bubble generating unit is arranged on the first circulating pipeline. The invention relates to a method for treating hydrazine wastewater, which comprises the following steps: conveying the wastewater in the waste liquid pool to a reaction tank, and starting a circulating pump to continuously circulate the wastewater in a first circulating pipeline and the reaction tank; the bubble generator is used for generating micro-nano bubbles in the circulating water; starting an ozone generating device, and injecting ozone into the circulating water through a bubble generator; the circulation time is 15-60 min, the concentration of hydrazine in the circulating water is less than 20mg/kg, the hydrazine reaches the standard and is discharged, otherwise, the hydrazine is discharged back to the waste liquid pool for continuous circulation.

Description

A treatment equipment and treatment method suitable for high-concentration hydrazine wastewater

technical field

The invention belongs to the field of nuclear power production and environmental protection, and specifically relates to a treatment device and a treatment method for continuously treating waste water containing high-concentration hydrazine in a nuclear power plant in a coordinated manner using micro-nano ozone bubbles and chemical catalytic oxidation.

Background technique

Hydrazine (N ₂ H ₄ ) has strong reducibility and ecotoxicity, and direct discharge has long-term potential harm to the environment. The national occupational health standard GBZ2.1-2019 stipulates that the occupational exposure limit is 0.06mg/kg. The EU REACH Act lists hydrazine as a toxic carcinogen, and the occupational exposure limit is 0.1mg/kg in 2019, and will be tightened to 0.01mg/kg in 2020.

Hydrazine is mainly used as an oxygen scavenger and passivator in nuclear power plants. The main sources of high-concentration hydrazine wastewater include process system flushing water, secondary circuit drainage water, steam generator wet maintenance water, etc. During the commissioning of the secondary circuit system of a nuclear power plant, 30-50 mg/kg hydrazine is generally added to the equipment flushing water. During equipment shutdown and maintenance, according to the maintenance time, or desalted water and ammonia are added to adjust the pH value to 10.5, and then add 200mg/kg hydrazine; or the secondary circuit supply water with a pH value of about 9.0, then add 400mg/kg ammonia. Such a high-concentration hydrazine waste liquid is a kind of discharged wastewater with the highest concentration of hydrazine in the liquid effluent of nuclear power plants and a relatively concentrated total amount. It needs professional treatment to meet the discharge requirement of less than 20mg/kg.

At present, the treatment methods of hydrazine-containing wastewater mainly include dilution method, aeration decomposition method and chemical oxidation method. Among them, the dilution method cannot eliminate the harm of hydrazine, and long-term discharge will still cause environmental pollution over time. The degradation rate of hydrazine by the aeration decomposition method is extremely low, and the average degradation coefficient k of hydrazine is only 0.064h ^-1 under oxygen-enriched conditions, and the disposal takes a long time. Selecting a suitable oxidant and using the strong reducing property of hydrazine to carry out oxidative degradation has the advantages of fast speed and high efficiency, and is the most common waste liquid disposal method in nuclear power plants. For example, hydrogen peroxide with 1.76 times the mass of hydrazine can be used to treat waste liquid, and 0.5 mg/kg copper sulfate catalyst can be added to improve the oxidative degradation rate of hydrazine; Sodium hypochlorite disposes of waste faster. For the disposal of a large amount of high-concentration hydrazine waste liquid, it is necessary to choose a storage area with good ventilation conditions and can be idle for a long time. When the oxidant concentration is high, the reaction is violent and the operation is dangerous. The volatilization of hydrazine causes a large number of local accumulations, and there is a risk of personnel poisoning or combustion explosion. Danger.

Ozone and ozone-based advanced oxidation processes have been widely studied and successfully applied in food preservation, sterilization, decolorization and deodorization, sewage treatment and other fields. pollute. Micro-nano bubbles are tiny bubbles with a diameter of 0.2-20 μm, which are completely different from ordinary bubbles. They have the characteristics of large specific surface area, high mass transfer efficiency, long residence time, high interface potential, and increased gas solubility, especially for micro-bubbles in water. Annihilation can also generate hydroxyl radicals with super-oxidizing effects, which can degrade pollutants in water.

Chinese invention patent CN202010577362.2 introduces an ozone bubble generating device for catalytic oxidation sewage treatment, but the structure is complex and the degree of bubble formation is low, so it is not suitable for the treatment of high-cleanness wastewater containing hydrazine in nuclear power plants. Another example is the Chinese invention patent application CN201911116016.8 which discloses a method for treating organic wastewater with hydrogen peroxide-ozone micro-nano bubbles. Micro-nano bubbles are used to improve the utilization rate of ozone, and hydrogen peroxide is added to enhance the oxidation capacity, but no catalyst is added. The efficiency of advanced treatment by air flotation oxidation tank cannot meet the requirements of hydrazine-containing wastewater from nuclear power plants. Due to its unique advantages, ozone micro-nano bubbles have become a research and development hotspot in wastewater treatment, but their application in the treatment of liquid effluents from nuclear power plants has not been reported.

The disclosure of the above background technical content is only used to assist in understanding the inventive concepts and technical solutions of the present invention, and it does not necessarily belong to the prior art of this patent application. In the case of disclosure, the above background technology should not be used to evaluate the novelty and inventiveness of this application.

Contents of the invention

In view of this, in order to overcome the defects of the prior art, the object of the present invention is to provide a treatment equipment and treatment method for nuclear power plant high-concentration hydrazine wastewater.

In order to achieve the above object, the present invention adopts the following technical solutions:

A treatment device suitable for high-concentration hydrazine wastewater, comprising a reaction tank, a waste liquid pool, a chemical catalytic unit connected to the reaction tank, a gas discharge unit, a micro-nano bubble generation unit, and a micro-nano bubble generation unit. An ozone generating unit in unit communication; a first circulation pipeline is arranged on the reaction tank, and the micro-nano bubble generation unit is arranged on the first circulation pipeline. The concentration of high-concentration hydrazine wastewater is at least greater than 30 mg/kg, preferably greater than 100 mg/kg, more preferably greater than 200 mg/kg.

According to some preferred implementation aspects of the present invention, the micro-nano bubble generating unit includes a Venturi bubble generator, and the Venturi bubble generator includes an inlet section, a throat section and an outlet section, and the ozone generating unit is connected to the throat The sections are connected, and there are multiple steps on the outlet section.

According to some preferred implementation aspects of the present invention, the outlet section has a plurality of annular cavities sequentially opened, and the diameters of the plurality of annular cavities increase sequentially from the direction close to the throat section to the direction away from the throat section.

According to some preferred implementation aspects of the present invention, the cross-sectional shape of each annular cavity is rectangle and/or trapezoid. When the cross-section of the ring cavity is trapezoidal, it is preferable to have different inclination angles of the side walls of the ring cavity to enhance the turbulence intensity, further improve the efficiency of the bubble generator, make the size of the bubbles smaller, and further improve the treatment effect of hydrazine in combination with ozone .

According to some preferred implementation aspects of the present invention, an air intake passage through the wall thickness is opened on the periphery of the throat section, and the ozone generating unit communicates with the air intake passage.

According to some preferred implementation aspects of the present invention, the ozone generating unit includes an oxygen cylinder, an ozone generator, and an ozone pipeline, and an end of the ozone pipeline communicates with the air intake passage.

According to some preferred implementation aspects of the present invention, the lower part of the reaction tank is provided with a return water distribution unit, and the return water distribution unit includes a plurality of symmetrically distributed return water distribution pipes, and each return water distribution pipe is arranged along the reaction tank. The radial direction extends from inside to outside and from bottom to top.

According to some preferred implementation aspects of the present invention, a hydrazine monitoring device, a circulation pump, and the micro-nano bubble generating unit are sequentially arranged on the first circulation pipeline, and one end of the first circulation pipeline is connected to the tank of the reaction tank. body, and the other end of the first circulation pipe is in communication with the return water distribution unit.

According to some preferred implementation aspects of the present invention, the lower part of the reaction tank is provided with an ultrasonic generating device, and the ultrasonic generating device is arranged corresponding to the return water distribution unit.

According to some preferred implementation aspects of the present invention, the chemical catalytic unit includes a dosing pipeline connected to the reaction tank, and an oxidant dosing tank and a catalyst dosing tank communicated with the dosing pipeline.

According to some preferred implementation aspects of the present invention, the oxidant is sodium hypochlorite and/or hydrogen peroxide; the catalyst is ferrous sulfate and/or copper sulfate.

According to some preferred implementation aspects of the present invention, a bottom pipe is provided between the bottom of the reaction tank and the waste liquid pool, and a liquid discharge port is arranged on the bottom pipe; between the waste liquid pool and the upper part of the reaction tank An upper pipe is provided for sending the waste water in the waste liquid pool to the reaction tank; a liquid level gauge is provided on the outer wall of the reaction tank.

According to some preferred implementation aspects of the present invention, the gas discharge unit includes a gas pipeline connected between the top of the reaction tank and the waste liquid pool, an air extraction device arranged on the gas pipeline, a gas filter device, and a gas filter located in the waste liquid pool. A gas bubbler in the liquid pool, the gas pipeline is provided with a gas discharge port.

The present invention also provides a method for treating hydrazine wastewater according to the above-mentioned treatment equipment, comprising the steps of:

Transport the wastewater in the waste liquid pool to the reaction tank, start the circulation pump, and make the wastewater circulate continuously in the first circulation pipeline and the reaction tank; the bubble generator is used to generate micro-nano bubbles in the circulating water; The generator injects ozone into the circulating water;

The cycle time is 15 to 60 minutes. If the concentration of hydrazine in the circulating water is less than 20mg/kg, it will be discharged up to the standard, otherwise it will be discharged back to the waste liquid pool to continue the cycle.

According to some preferred implementation aspects of the present invention, the circulating flow rate is greater than or equal to 3 m ³ /h, preferably 5 m ³ /h; the concentration of ozone in the circulating water is 5-55 mg/L. Turn on the ozone generator, the ozone output is 50-300g/h, the ozone concentration in the outlet gas is 60-150mg/L, adjust the flow valve to control the ozone injection (intake flow) 5-50L/min, and use a Venturi bubble generator Generate micronano ozone bubbles in the circulating water, so that the effective ozone concentration in the circulating water reaches 5-55mg/L.

According to some preferred implementation aspects of the present invention, during the cycle, the ultrasonic generating device is turned on for intermittent operation, preferably every 10 minutes for 5 minutes, the ultrasonic power density is 20-35W/cm ² , and the frequency is 20-45KHz, preferably 28Hz.

According to some preferred implementation aspects of the present invention, if the concentration of hydrazine in the wastewater is ≥50 mg/kg, the chemical catalytic unit is opened, and oxidant and/or catalyst are added to the reaction tank; the amount of oxidant added is 0.5 to 1.5 times the mass of hydrazine Concentration, the addition amount of catalyst is to maintain the catalyst concentration of 0.1～0.5mg/kg in the system. Generally (daily low-concentration hydrazine) waste liquid is directly treated with ozone micro-nano bubble technology, and high-concentration hydrazine waste liquid needs to be treated with chemical means. The reaction principle is as follows:

3N ₂ H ₄ +2O ₃ ＝3N ₂ ↑+6H ₂ O

N ₂ H ₄ +2H ₂ O ₂ →N ₂ ↑+4H ₂ O

N ₂ H ₄ +2NaClO→N ₂ ↑+2H ₂ O+2NaCl

According to some preferred implementation aspects of the present invention, during the circulation process, the gas discharge unit is opened, and the pumping flow rate is greater than or equal to 3.0m ³ /h. When the concentration of hydrazine in the circulating water is less than 20mg/kg, the gas at the top of the reaction tank passes through Discharge directly after filtration; if the concentration of hydrazine in the circulating water is greater than or equal to 20mg/kg, then introduce the gas at the top of the reaction tank into the waste liquid pool.

Due to the adoption of the above technical scheme, compared with the prior art, the present invention is beneficial in that: the present invention is suitable for the treatment equipment of high-concentration hydrazine wastewater, which integrates micro-nano ozone bubble generating device and ultrasonic generating device As well as the chemical catalytic reaction device, the waste liquid and ozone gas are fully mixed through the circulating pump and the Venturi bubble generator, and cleaned by ultrasonic intermittent oscillation to generate continuous micro-nano bubbles with a large specific surface area, which greatly improves the gas-liquid contact. area, promotes the decomposition efficiency of hydrazine, and has the advantages of new environmental protection, safety and high efficiency, and simple operation.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

Fig. 1 is the structural representation of the treatment equipment of hydrazine wastewater in the preferred embodiment of the present invention;

Fig. 2 is the structural representation of bubble generator in the preferred embodiment of the present invention;

Fig. 3 is the structural representation of bubble generator in another preferred embodiment of the present invention;

Fig. 4 is the structural representation of bubble generator in another preferred embodiment of the present invention;

Fig. 5 is the result of the simulated decomposition experiment of hydrazine waste liquid under different conditions in the preferred embodiment 2-4 of the present invention;

Fig. 6 is the flowchart of the processing method of hydrazine wastewater in the preferred embodiment of the present invention;

In the drawings, 1-reaction tank, 101-liquid level gauge, 102-ultrasonic device, 103-return water distribution pipe, 104-drainage valve, 105-manhole door; 2-online hydrazine monitoring device; 3-circulation pump; 4-bubble generator; 401-inlet section, 402-throat section, 403-exit section, 404-intake channel, 5-ozone generator, 501-oxygen bottle, 502-ozone flow regulating valve; 6-oxidant plus Medicine tank; 7-catalyst dosing tank; 8-exhaust device; 9-gas filter device; 10-waste liquid pool, 11-gas bubbler, 12-first circulation pipeline, 13-ozone pipeline, 14-addition Medicine pipeline, 15-bottom pipeline, 16-upper pipeline, 17-gas pipeline.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described implementation Examples are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

In order to solve the existing problems such as incomplete dilution and neutralization treatment, large consumption of hazardous chemicals, high operating labor intensity, and difficulty in storage and disposal of waste liquid, the present invention aims at the strong alkalinity and good water quality of waste liquid containing hydrazine in nuclear power plants (wastewater For the characteristics of adding ammonia and hydrazine to high-purity water, which basically does not contain other impurities), discontinuous (high-concentration hydrazine is only used in the unit overhaul and wet maintenance stages), we choose micro-nano ozone bubble advanced oxidation combined with chemical oxidation technology , intermittently turn on ultrasonic self-cleaning, give full play to the synergistic effect of ultrasonic waves and micro-nano bubbles on chemical reactions, greatly improve the treatment efficiency of existing chemical dosing and oxidative decomposition of hydrazine waste liquid, and completely solve the problem of incomplete dilution and neutralization treatment. The consumption of hazardous chemicals is large, the operation labor intensity is high, and the storage and disposal of waste liquid are difficult. On the premise of reducing the consumption of hazardous chemicals, the treatment efficiency of oxidative decomposition of hydrazine can be improved synergistically, and at the same time, no new environmental pollution problems will be generated. The process has the advantages of high efficiency, less consumption, no pollution, and no deposition, and the supporting equipment has the advantages of new type, high efficiency, safety, environmental protection, and simple operation.

The basic principle of the present invention is as follows: ozone is injected into water to make the water have a certain oxidation ability, the Venturi tube type bubble generator makes the ozone bubbles micronano, increases the gas-liquid contact area, promotes the decomposition of hydrazine, and turns on the ultrasonic wave intermittently, which is beneficial to chemical Both the catalytic reaction and the micro-nano ozone bubble oxidation have a synergistic effect, which enhances the mass transfer process of the redox reaction and further improves the decomposition efficiency of hydrazine. The oxidation-reduction reaction of hydrazine with hydrogen peroxide and sodium hypochlorite, under the action of ultrasonic cavitation, water molecules split into hydroxyl radicals, which greatly promotes the oxidative decomposition reaction of hydrazine; the micro-nano ozone bubbles gradually increase in the process of floating in the reaction tank, The larger the particle size, the greater the floating speed. Ultrasonic waves prevent bubbles from gathering after passing through the distribution pipe, and increase the number of microbubbles in the water to a certain extent. In addition, the low-frequency ultrasonic cavitation effect accelerates the peeling off of the sludge attached to the surface of the distribution pipe, which has a better self-cleaning function.

According to the characteristics of high-concentration hydrazine wastewater in nuclear power plants, the treatment process of micro-nano ozone bubble synergistic chemical oxidation and degradation of hydrazine waste liquid mainly includes the following steps: (1) introducing waste liquid into the reaction tank, turning on the circulation pump and The ozone regulating valve uses a Venturi bubble generator to generate micro-nano ozone bubbles to realize the advanced oxidation and decomposition of hydrazine; (2) According to the online monitoring of hydrazine concentration, oxidants and catalysts are selectively added to the reaction tank to accelerate the decomposition of chemical oxidation; ( 3) Intermittently turn on the ultrasonic wave to further accelerate the degradation of waste liquid; (4) During normal operation, the waste liquid is discharged to the atmosphere after the online monitoring of hydrazine monitoring, and the waste gas is purified; under abnormal working conditions, both the waste liquid and the waste gas return To the waste liquid pool, and recycle until it reaches the standard. Compared with the existing hydrogen peroxide and copper sulfate catalytic oxidation treatment process, the micro-nano ozone bubble technology is used for co-treatment, the treatment efficiency is increased by 40%, the hydrogen peroxide consumption is reduced by 50%, the reaction time is shortened to 20min, and the ozone utilization rate is >95%.

Embodiment 1 processing equipment

As shown in Figure 1-2, in the present invention, a bypass hydrazine decomposition treatment device is added downstream of the secondary circuit wastewater discharge main pipe, including a reaction tank, a waste liquid pool, a chemical catalytic unit connected to the reaction tank, a gas discharge unit, a micro-nano The bubble generating unit and the ozone generating unit connected with the micro-nano bubble generating unit; the lower part of the reaction tank is provided with an ultrasonic generating device and a return water distribution unit, and the ultrasonic generating device is set corresponding to the return water distribution unit. A first circulation pipe is arranged on the reaction tank, a bottom pipe is arranged between the bottom of the reaction tank and the waste liquid pool, and a liquid discharge port is arranged on the bottom pipe; an upper pipe is arranged between the waste liquid pool and the upper part of the reaction tank for The waste water in the waste liquid pool is sent to the reaction tank; the outer wall of the reaction tank is provided with a liquid level gauge. The following is a detailed description of each unit and component:

Reaction tank: It is used to provide space for the oxidation and decomposition treatment of hydrazine waste liquid to ensure that the waste water is fully treated to meet the standard. The reaction tank is a cylindrical cylinder, and the upper and lower ends of the elliptical head are welded together with the cylinder. The total volume is 3.0m ³ . There is a DN400 inspection manhole on the top, a suction filter device, and a return valve in the bottom head. The water distribution unit, reaction tank and internal components are all made of stainless steel. A flap liquid level gauge is installed on the side wall of the tank, and a sewage outlet is provided at the bottom.

The first circulation pipeline: the first circulation pipeline leads from the middle position of the reaction tank and returns to the return water distribution unit, that is, one end of the first circulation pipeline communicates with the tank body of the reaction tank, and the other end of the first circulation pipeline connects with the return water distribution unit connected. A hydrazine monitoring device, a circulation pump, and a micro-nano bubble generating unit are sequentially arranged on the first circulation pipeline for circulating the hydrazine wastewater in the reaction tank.

Among them, the circulation pump is used to pressurize the waste liquid in the reaction tank into the micro-nano bubble generating device. The circulation pump is matched with the frequency converter to adjust the circulating water volume. The water intake pipe is arranged in the middle of the reaction tank, and the return pipe is arranged in the bottom head. , circulation flow ≥ 3m ³ /h, preferably 5m ³ /h.

The hydrazine monitoring device monitors the concentration of hydrazine in the circulating water. After the set reaction time is reached, if the residual concentration of hydrazine is still greater than 20mg/kg, the waste liquid will continue to be processed by the circulating pump, or discharged back to the waste liquid pool, and the time will be extended. Decompose naturally over time; when the concentration is less than 20mg/kg, it will be discharged directly.

Micro-nano bubble generating unit: including a Venturi bubble generator. The Venturi bubble generator includes an inlet section, a throat section and an outlet section. The ozone generating unit is connected to the throat section, and the outlet section has multiple steps. An air intake passage through the wall thickness is opened on the circumference of the throat section, and the ozone generating unit communicates with the air intake passage.

The circulation pump pressurizes the waste liquid into the Venturi bubble generator, inhales ozone to generate continuous micro-nano ozone bubbles, and greatly improves the oxidation and decomposition rate of hydrazine.

The outlet section has a plurality of annular cavities successively opened, and the diameters of the plurality of annular cavities increase sequentially from the direction close to the throat section to the direction away from the throat section. The section shape of each annular cavity is rectangle or trapezoid. When the cross-section of the ring cavity is trapezoidal, it is preferable that the inclination angles of the side walls of multiple ring cavities are different to enhance the turbulence intensity and further improve the efficiency of the bubble generator, so that the size of the bubbles is smaller (maintained at 0.2-20 μm), combined with ozone Further enhance the treatment effect of hydrazine.

As shown in Figure 2, the cross-sections of the plurality of annular cavities in this embodiment are rectangular, and the dimensions of each rectangular cross-section are different, that is, the diameters of the annular cavities are different, and gradually increase from the section close to the throat to the section away from the throat. to increase the turbulence intensity. In some other embodiments, the cross-sections of the plurality of annular cavities are trapezoidal, and the side walls of the trapezoidal cross-sections have different inclination angles, and the angle between the side walls and the axis of the generator is from close to the throat to away from the throat. The segments increase gradually, as shown in Figure 3. In yet another embodiment, the cross-section of the ring cavity may be alternately rectangular and trapezoidal to further enhance the effect, as shown in FIG. 4 .

Ozone generating unit: including an oxygen cylinder, an ozone generator and an ozone pipeline, the end of the ozone pipeline communicates with the air intake channel. The ozone generating unit is a device that converts oxygen into ozone by using the principle of high voltage discharge.

Specifically, after the high-voltage alternating current is passed into the high-voltage electrode of the ozone generator, high-purity oxygen is passed into the ozone generator. When the high-voltage alternating current reaches 10-15KV, a blue glow discharge is generated, and the free high-energy ions in the corona are dissociated. Oxygen molecules decompose oxygen molecules into oxygen atoms, and the oxygen atoms aggregate into ozone molecules after collision. The ozone output is 50-300g/h, and the ozone concentration is 60-150mg/L.

Backwater distribution unit: It includes a plurality of symmetrically distributed backwater distribution pipes, and each backwater distribution pipe extends from inside to outside and from bottom to top along the radial direction of the reaction tank. It is preferably three return water distribution pipes evenly distributed, and the angle between adjacent return water distribution pipes is 120°, so that the water flow containing micro-nano ozone bubbles is evenly distributed into the reaction tank, ensuring that the micro-nano bubbles float slowly in the waste liquid, Accelerates the decomposition of hydrazine.

Ultrasonic device: arranged on the inner wall of the lower part of the reaction tank. The frequency of the ultrasonic vibration box is 20-60kHz, preferably 28kHz. On the one hand, it is used to accelerate the chemical reaction, and on the other hand, it cleans the distribution pipe at the bottom to prevent blockage or bubble flow.

Chemical catalysis unit: including a dosing pipeline connected to the reaction tank, an oxidant dosing tank and a catalyst dosing tank connected to the dosing pipeline. The oxidant and catalyst are added through the metering pump, and the dosing amount matches the flow of waste liquid to accelerate the decomposition of hydrazine into non-toxic and harmless nitrogen and water. Preferably, the oxidant is sodium hypochlorite and/or hydrogen peroxide; the catalyst is ferrous sulfate and/or copper sulfate.

Gas discharge unit: including the gas pipeline connecting the top of the reaction tank and the waste liquid pool, the air extraction device arranged on the gas pipeline, the gas filter device and the gas bubbler located in the waste liquid pool, and the gas pipeline is provided with a gas discharge port .

The air extraction device is arranged on the top of the reaction tank. The decomposition products nitrogen, oxygen, and volatilized hydrazine, hydrogen peroxide, ozone, etc. during the treatment process are sucked and purified and blown into the waste liquid pool or discharged to the atmosphere. Specifically, when the online monitoring of hydrazine concentration is qualified, the exhaust gas is directly discharged into the atmosphere after purification; when the hydrazine concentration is unqualified, the exhaust gas is blown into the waste liquid pool to increase the rate of hydrazine decomposition in the waste liquid pool and reduce the consumption of ozone .

The treatment device of the present invention is based on a bubble generating device based on the cavitation effect of a Venturi tube, sucks ozone gas in the throat, and generates an aqueous solution containing ozone micro-nano bubbles along a multi-step diffusion section. The ozone intake rate and circulation pump flow have a more obvious influence on the ozone dissolution rate, and the preferred intake rate is 400m L/min. The size and number of bubbles will be significantly different if the ozone air intake is too large or too small (the size and number of bubbles will be affected when the gas volume changes, and the bubble size cannot be guaranteed when the gas volume is too large). Micro-nano bubbles can significantly improve the mass transfer efficiency of ozone, increase the gas holdup rate of the solution to 8 times, and improve the utilization rate of ozone.

Embodiment 2 processing method

As shown in Figure 6, this embodiment provides a method for treating hydrazine wastewater according to the treatment equipment of Embodiment 1, including the following steps:

Step S1. Discharging the waste liquid in the waste liquid tank into the reaction tank until the predetermined minimum liquid level is reached, the volume is about 1.5-2.5 m ³ , and the treatment process is selected according to the concentration of hydrazine. Below the minimum liquid level, the ultrasonic generating device is interlocked with the circulation pump for protection, and cannot be started; if the maximum liquid level is exceeded, the equipment will alarm, and the drain valve will be opened to reduce to the working liquid level.

When the concentration of hydrazine is ≥50mg/kg, auxiliary chemical oxidation catalysis is required, that is, the chemical catalytic unit needs to be turned on. Oxidant is preferably the hydrogen peroxide of 0.5～1.5 times of hydrazine mass concentration, maintains 0.1～0.5mg/kg copper sulfate concentration (catalyst concentration is calculated according to the volume of liquid to be treated and hydrazine content, maintains and refers to total amount maintenance, according to The total amount can be added at one time, the catalyst is mainly to shorten the reaction time, the less the added amount, the better); if the waste liquid disposal time is tight, the oxidant can be changed to sodium hypochlorite with a mass concentration of 0.5 to 1.5 times hydrazine. The reaction principle is mainly shown in the following formula:

3N ₂ H ₄ +2O ₃ ＝3N ₂ ↑+6H ₂ O

N ₂ H ₄ +2H ₂ O ₂ →N ₂ ↑+4H ₂ O

N ₂ H ₄ +2NaClO→N ₂ ↑+2H ₂ O+2NaCl

Step S2, opening the gas discharge unit

Turn on the exhaust fan, and the exhaust flow rate is ≥3.0m ³ /h. Volatile gases such as hydrazine and hydrogen peroxide, including unreacted ozone gas, and decomposition products such as nitrogen and oxygen generated during the reaction process, accumulate on the top of the reaction tank. When the concentration of hydrazine in the treated circulating water is less than 20mg/kg, the gas at the top of the reaction tank is extracted by the exhaust fan and filtered and discharged into the atmosphere. equal to 20mg/kg), the exhaust gas is introduced into the waste liquid neutralization tank for further treatment.

Step S3, loop processing

Turn on the circulation pump to continuously circulate the waste water in the first circulation pipeline and the reaction tank, with a circulation flow rate ≥ 3m ³ /h.

Turn on the ozone generator, inject ozone into the circulating water through the bubble generator, and the injection amount of ozone is 5-50L/min. The concentration of ozone used is adjusted according to the amount of circulating water and ozone intake, and the concentration of ozone in circulating water is preferably 5-55 mg/L.

The bubble generator is used to generate micro-nano bubbles in circulating water.

The cycle time is 15 to 60 minutes. If the concentration of hydrazine in the circulating water is less than 20mg/kg, it will be discharged up to the standard, otherwise it will be discharged back to the waste liquid pool to continue the cycle.

Step S4, turn on the ultrasonic generating device

During the cycle, turn on the ultrasonic generating device and run intermittently for 5-10 minutes, preferably every 10 minutes for 5 minutes, with an ultrasonic power density of 20-35 W/cm ² and a frequency of 20-45 KHz, preferably 28 Hz.

The above step numbers are only for the convenience of understanding and description. In actual operation, for continuous processing, there is no strict backward order between the steps. For example, steps 3 and 4 are performed synchronously or in no sequence.

Example 2-1

During the shutdown period of thermal equipment in the secondary circuit of nuclear power plants, steam generators need to take wet maintenance measures. The maintenance solution is an ammonia solution with a pH value of 8.5 to 9.2, and then 400 mg/kg of hydrazine is added. Such a high concentration of hydrazine waste liquid needs to be treated jointly with ozone and sodium hypochlorite, and the degradation time is 40 minutes. Only by using the above-mentioned treatment equipment and treatment process can the hydrazine concentration in the hydrazine waste liquid be less than 20mg/L. Discharge requirements. Specifically include the following steps:

Step 1), drain the hydrazine maintenance solution containing 400 mg/kg into the waste liquid pool and then transport it to the reaction tank to reach the working liquid level, with a volume of about 2.0 m ³ .

Step 2), turn on the exhaust fan, the flow rate is ≥3.0m ³ /h, to avoid the accumulation of hydrazine, ammonia, ozone, oxygen, nitrogen and other gases on the top of the reaction tank.

Step 3), turn on the circulation pump, adjust the flow through the frequency converter, meet the minimum flow requirement of the bubble generator ≥ 3m ³ /h, and control the waste liquid circulation flow to 5m ³ /h.

Step 4), turn on the ozone generator, the output of the ozone machine is 300g/h, the ozone mass concentration is 100mg/L, the gas flow rate is controlled by the flow meter to 50L/min, and the ozone can be sucked into the Venturi bubble generator by itself through negative pressure.

Step 5), the Venturi bubble generator based on the cavitation effect fully mixes the waste liquid and ozone gas to produce continuous micro-nano bubbles with a very large specific surface, and enters the waste liquid tank through the distribution pipe along the circulation pipeline to ensure that the bubbles are uniform The distribution greatly improves the mass transfer efficiency, and it is not easy to be blocked and has low energy consumption.

Step 6), open the dosing metering pump, add sodium hypochlorite in the reaction tank according to the mass concentration ratio of 1:1;

N ₂ H ₄ +2NaClO→N ₂ ↑+2H ₂ O+2NaCl

Step 7) After 10 minutes of circulating reaction, turn on the ultrasonic wave at a frequency of 28 Hz, run for 5 minutes, and then run for 5 minutes at intervals of 10 minutes to avoid fouling of the bubble distribution pipe by sludge and reaction by-products, resulting in turbulent water flow and uneven distribution of bubbles.

Step 8), the reaction time is 36 minutes, the online concentration of hydrazine is monitored to reach 19.32 mg/L, and the reaction is continued for 40 minutes, and the concentration of hydrazine drops to 12.4 mg/L, which meets the emission requirements.

Step 9), shut down the ozone generator, close the ozone inlet valve, waste water circulation pump and exhaust fan in turn, open the blowdown valve at the bottom of the reaction tank, and discharge the waste water up to the standard.

The monitoring data in the processing of the present embodiment are shown in Table 1 below:

Table 1 field test data

time (min) Hydrazine concentration (mg/kg) Effective ozone concentration (mg/kg) Sodium hypochlorite (mg/kg) temperature(℃) pH value T₀ 404.4 20 400 22.5 9.9 10 285.8 20 / 25.3 9.6 20 174.2 20 / 28.4 9.5 30 84.5 20 / 29.5 9.3 40 12.4 20 / 30.4 9.1

Example 2-2

The maintenance solution for the secondary circuit of nuclear power plants with high pH value should be desalted water plus ammonia to adjust the pH value to 10.5, and then add 200mg/kg hydrazine. For the strongly alkaline hydrazine waste liquid, use ozone combined with hydrogen peroxide and catalyst to cooperate with the above-mentioned treatment equipment and treatment method for treatment, and the degradation time is less than 40 minutes. Specifically include the following steps:

Step (1), drain the high-pH value maintenance solution containing 206.5 mg/kg hydrazine into the waste liquid pool and then transport it to the reaction tank to reach the working level, with a volume of about 2.0 m ³ .

Step (2), turn on the exhaust fan, with a flow rate of ≥3.0 m ³ /h, to avoid accumulation of hydrazine, ammonia, hydrogen peroxide, ozone, oxygen, nitrogen and other gases on the top of the reaction tank.

Step (3), turn on the circulating pump, adjust the flow rate through the frequency converter to meet the minimum flow rate of the bubble generator ≥ 3m ³ /h, and control the circulating flow rate of the waste liquid to 5 m ³ /h.

Step (4), turn on the ozone generator, open the outlet valve, the output of the ozone machine is 200 g/h, the mass concentration of ozone is 100 mg/L, the gas flow rate is controlled by the flow meter to 33 L/min, and the ozone can be sucked into Venturi by itself through negative pressure in the bubble generator.

Step (5), based on the cavitation effect, the Venturi bubble generator fully mixes the waste liquid and ozone gas to generate continuous micro-nano bubbles with a very large specific surface, and enters the waste liquid tank through the distribution pipe along the circulation pipeline.

Step (6), turn on the metering pump, add hydrogen peroxide and copper sulfate according to the mass concentration ratio of hydrazine in the wastewater to 1:1:0.00005, so that the concentration of hydrogen peroxide in the system is 210 mg/kg, and the concentration of copper ions is 0.2 mg/kg.

N ₂ H ₄ +2H ₂ O ₂ →N ₂ ↑+4H ₂ O

Step (7), after reacting for 10 minutes, turn on the ultrasonic wave with a frequency of 28 Hz, run for 5 minutes first, and then run for 5 minutes at intervals of 10 minutes to avoid fouling of the bubble distribution pipe by sludge and reaction by-products, resulting in turbulent water flow and uneven distribution of bubbles .

Step (8), the reaction time is 40 minutes, which meets the emission requirements, and the reaction time is 60 minutes, and the online concentration of hydrazine is monitored to reach 0.4 mg/L.

Step (9), shut down the ozone generator, close the ozone inlet valve, waste water circulation pump and exhaust fan in turn, open the blowdown valve at the bottom of the reaction tank, and discharge the waste water up to the standard.

The monitoring data in the processing of the present embodiment are shown in Table 2 below:

Table 2 field test data

Example 2-3

For equipment flushing water with a hydrazine concentration of 30-50mg/kg, there is no need to add chemicals during the waste liquid treatment process, and only need to open the ozone micro-nano bubbles for recycling treatment. Specifically include the following steps:

Step (1), discharge the flushing water of the secondary circuit containing 49mg/kg hydrazine into the waste liquid pool and then transport it to the reaction tank. When the working liquid level is reached, the volume is about 2.0m ³ , the ammonia concentration in the wastewater is 5mg/kg, and the pH value is is 9.8.

Step (2), turn on the exhaust fan, with a flow rate of ≥3.0m ³ /h, to avoid accumulation of hydrazine, ammonia, ozone, oxygen, nitrogen and other gases on the top of the reaction tank.

Step (3), turn on the circulating pump, adjust the flow rate through the frequency converter to meet the minimum flow rate of the bubble generator ≥ 3m ³ /h, and control the circulating flow rate of the waste liquid to 4m ³ /h.

Step (4), turn on the ozone generator, open the outlet valve, the output of the ozone machine is 200g/h, the mass concentration of ozone gas is 100mg/L, the gas flow rate is controlled by the flow meter to 40L/min, and the ozone can be sucked into the Venturi by itself through negative pressure Bubble generator.

In step (5), the Venturi-type bubble generator based on the cavitation effect fully mixes the waste liquid and ozone gas to generate continuous micro-nano bubbles with a very large specific surface, and enters the waste liquid tank through the distribution pipe along the circulation pipeline.

3N ₂ H ₄ +2O ₃ ＝3N ₂ ↑+6H ₂ O

Step (6), after reacting for 10 minutes, turn on the ultrasonic wave at a frequency of 28 Hz, run for 5 minutes, and then run for 5 minutes at intervals of 10 minutes to avoid fouling of the bubble distribution pipe by sludge and reaction by-products, resulting in turbulent water flow and uneven distribution of bubbles.

Step (7), the reaction time is 40 minutes, which meets the discharge requirements, and the reaction time is 60 minutes, and the online concentration of hydrazine is monitored to reach 0.4 mg/L.

Step (8), shut down the ozone generator, close the ozone inlet valve, waste water circulation pump and exhaust fan in turn, open the bottom drain valve, and discharge the waste water up to the standard.

Example 2-4

The volume of hydrazine wastewater prepared in the laboratory is 5L, and the initial mass concentration of hydrazine in the waste liquid pool is 100mg/kg. The decomposition rate of hydrazine under three conditions is compared and tested.

Condition 1: Add hydrogen peroxide and copper sulfate according to the mass concentration ratio of 1:1:0.0001. The measured concentration of hydrogen peroxide is 106 mg/kg, and the concentration of copper ions is 0.1 mg/kg. After stirring evenly by hand, take samples every 15 minutes to measure the mass concentration of hydrazine .

Condition 2: Introduce ozone into the Venturi micro-nano bubble generating device and mix it with the hydrazine liquid at the outlet of the circulation pump. The gas-liquid mixture will pass through the fluid oscillator to the bottom of the hydrazine waste liquid pool, and the waste liquid pool is filled with ozone micro-nano bubbles. The solution was transparent and colorless and became white milky. The mass concentration of ozone in the solution was determined by the indigo method to be 100 mg/kg. The air intake rate was controlled to be 250 mL/min. Samples were taken every 15 minutes to measure the mass concentration of hydrazine.

Condition 3: On the basis of keeping consistent with condition 2, add hydrogen peroxide and copper sulfate according to the mass concentration ratio of hydrazine 1:0.5:0.00005, the measured hydrogen peroxide concentration is 54mg/kg, copper ion concentration is 0.06mg/kg, every 15min Samples were taken to determine the mass concentration of hydrazine.

The comparison results of the experimental results under the three conditions are shown in Figure 1. It can be seen from Figure 1 that the combined treatment of hydrazine with hydrogen peroxide + ozone micro-nano bubbles has the highest efficiency, and the concentration of hydrazine is only reduced to 64mg/kg when only hydrogen peroxide is used for 2 hours. , it takes 6h to reach the emission requirement of 20mg/kg. The efficiency of treating waste liquid with ozone micro-nano bubbles has been improved, and the concentration of hydrazine has dropped to 14 mg/kg after 2 hours. However, when the combined treatment process of hydrogen peroxide + ozone micro-nano bubbles was used, the concentration of hydrazine had dropped to 23 mg/kg after 45 minutes, and it had completely decomposed after 1 hour.

The results of the decomposition experiment on hydrazine waste liquid show that the decomposition efficiency of hydrazine waste liquid is "hydrogen peroxide + ozone micro-nano bubbles" > ozone micro-nano bubbles > hydrogen peroxide. Compared with the traditional catalytic decomposition process of hydrogen peroxide, when the concentration of hydrogen peroxide is halved, The use of ozone micro-nano bubbles combined with hydrogen peroxide catalytic decomposition treatment process greatly improves the decomposition efficiency of hydrazine and shortens the complete decomposition time of hydrazine from 6 hours to less than 1 hour.

In fact, if the intake of ozone is increased, the decomposition efficiency of hydrazine will be further improved. However, the ozone intake rate is too fast, which affects the size and distribution of micro-nano bubbles, resulting in unstable properties of ozone micro-nano bubbles in the process of floating and annihilation, affecting the mass transfer and dissolution of ozone, unable to improve the decomposition of hydrazine, and instead causing ozone waste and pollution.

The treatment equipment of the present invention integrates a micro-nano ozone bubble generating device, an ultrasonic generating device, and a chemical catalytic reaction device. Through a circulation pump and a Venturi bubble generator, the waste liquid and ozone gas are fully mixed, and cleaned by ultrasonic intermittent oscillation to produce Continuous micro-nano bubbles with a large specific surface area greatly increase the gas-liquid contact area and promote the decomposition efficiency of hydrazine. It has the advantages of new environmental protection, safety and efficiency, and simple operation. The technical principle of the present invention is, aiming at the characteristics that the p H value of the hydrazine-containing waste liquid of the nuclear power plant is greater than 9.0, it overcomes the shortcomings of hydrogen peroxide self-decomposition consumption under alkaline conditions and the oxidation capacity is reduced, and utilizes the micro-nano ozone bubble specific surface area Large, high mass transfer efficiency, and increased gas dissolution, especially the bubbles can generate hydroxyl radicals (OH) in water, and increase the yield of hydroxyl radicals as the pH of the solution increases, thereby increasing the ozone bubble Oxidative degradation ability of synergistic chemical system to hydrazine.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (18)

1. The treatment equipment for the high-concentration hydrazine wastewater is characterized by comprising a reaction tank, a waste liquid pool, a chemical catalysis unit, a gas discharge unit, a micro-nano bubble generation unit and an ozone generation unit, wherein the chemical catalysis unit is communicated with the reaction tank; the reaction tank is provided with a first circulating pipeline, and the micro-nano bubble generating unit is arranged on the first circulating pipeline.

2. The processing equipment according to claim 1, wherein the micro-nano bubble generating unit comprises a venturi bubble generator, the venturi bubble generator comprises an inlet section, a throat section and an outlet section, the ozone generating unit is communicated with the throat section, and the outlet section is provided with a plurality of steps.

3. The treatment apparatus according to claim 2, wherein the outlet section has a plurality of annular chambers formed therein in sequence, and the diameters of the plurality of annular chambers increase in sequence from a position near the throat section to a position away from the throat section.

4. A treatment plant according to claim 3, characterized in that the cross-sectional shape of each ring chamber is rectangular and/or trapezoidal.

5. The treatment apparatus according to claim 2, wherein the throat section is circumferentially provided with an air inlet passage penetrating the wall thickness, and the ozone generating unit is communicated with the air inlet passage.

6. The treatment apparatus according to claim 5, wherein the ozone generating unit includes an oxygen cylinder, an ozone generator, and an ozone pipe, an end of the ozone pipe communicating with the intake passage.

7. The treatment equipment according to claim 1, wherein a return water distribution unit is arranged at the lower part of the reaction tank, and comprises a plurality of symmetrically distributed return water distribution pipes, and each return water distribution pipe extends from inside to outside and from bottom to top along the radial direction of the reaction tank.

8. The treatment equipment according to claim 7, wherein a hydrazine monitoring device, a circulating pump and the micro-nano bubble generating unit are sequentially arranged on the first circulating pipeline, one end of the first circulating pipeline is communicated with the tank body of the reaction tank, and the other end of the first circulating pipeline is communicated with the return water distribution unit.

9. The treatment equipment according to claim 7, wherein an ultrasonic generating device is arranged at the lower part of the reaction tank, and the ultrasonic generating device is arranged corresponding to the water return distribution unit.

10. The process apparatus of claim 1, wherein the chemical catalytic unit comprises a dosing line communicating to the reaction tank and an oxidant dosing tank and a catalyst dosing tank communicating with the dosing line.

11. The processing apparatus according to claim 10, wherein the oxidant is sodium hypochlorite and/or hydrogen peroxide; the catalyst is ferrous sulfate and/or copper sulfate.

12. The treatment facility according to claim 1, wherein a bottom pipe is provided between the bottom of the reaction tank and the waste liquid tank, and a liquid discharge port is provided on the bottom pipe; an upper pipeline is arranged between the waste liquid pool and the upper part of the reaction tank and is used for conveying the waste water in the waste liquid pool to the reaction tank; and a liquid level meter is arranged on the outer wall of the reaction tank.

13. The treatment equipment according to claim 1, wherein the gas discharge unit comprises a gas pipeline communicated between the top of the reaction tank and the waste liquid pool, an air suction device arranged on the gas pipeline, a gas filtering device and a gas bubbler positioned in the waste liquid pool, and a gas discharge port is arranged on the gas pipeline.

14. A method for treating hydrazine wastewater by using the treatment equipment according to any one of claims 1-13, characterized in that the treatment method comprises the following steps:

conveying the wastewater in the waste liquid pool to a reaction tank, and starting a circulating pump to continuously circulate the wastewater in a first circulating pipeline and the reaction tank; the bubble generator is used for generating micro-nano bubbles in the circulating water; starting an ozone generating device, and injecting ozone into the circulating water through a bubble generator;

the circulation time is 15-60 min, the concentration of hydrazine in the circulating water is less than 20mg/kg, the hydrazine reaches the standard and is discharged, otherwise, the hydrazine is discharged back to the waste liquid pool for continuous circulation.

15. The process according to claim 14, characterized in that the circulation flow rate is greater than or equal to 3m ³ H; the concentration of the ozone in the circulating water is 5-55 mg/L.

16. The treatment method according to claim 14, wherein the ultrasonic generator is turned on to perform intermittent operation during the circulation, and the ultrasonic power density is 20-35W/cm ² The frequency is 20-45 KHz.

17. The treatment method according to claim 14, wherein if the hydrazine concentration in the wastewater is more than or equal to 50mg/kg, the chemical catalysis unit is started, and an oxidant and/or a catalyst are/is added into the reaction tank; the addition of the oxidant is 0.5 to 1.5 times of the mass concentration of hydrazine, and the addition of the catalyst is 0.1 to 0.5mg/kg of the catalyst concentration in the maintenance system.

18. The process of claim 14, wherein during the cycle, the gas discharge unit is turned on and the pumping rate is 3.0m or more ³ When the concentration of hydrazine in the circulating water is less than 20mg/kg, the gas at the top of the reaction tank is directly discharged after being filtered; and if the concentration of the hydrazine in the circulating water is more than or equal to 20mg/kg, introducing gas at the top of the reaction tank into the waste liquid pool.

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