WO2023207098A1 - Distillation-oxidation treatment system and method for waste liquid from organic acid chemical cleaning of power station boiler - Google Patents

Abstract

Disclosed in the present application are a distillation-oxidation treatment system and method for waste liquid from organic acid chemical cleaning of a power station boiler. The system comprises a distillation system, a crystallization system and an oxidation system, wherein the distillation system comprises a waste liquid conveying pump, waste liquid enters a flash tank via the waste liquid conveying pump and a heater, a vapor phase outlet of the flash tank is connected to a distillate collecting tank via a condenser, and a liquid phase outlet is connected to an inlet of the heater via a concentrated solution conveying pump; the oxidation system comprises an aeration device, a liquid outlet of the aeration device is connected to an advanced oxidation reactor, and a liquid outlet of the advanced oxidation reactor is connected to an effluent collecting tank; and the crystallization system comprises a crystallization separator, the concentrated solution conveying pump is connected to the crystallization separator, a supernatant, resulting from solid-liquid separation by the crystallization separator, is connected to the flash tank via a pipeline, a solid-liquid mixture enters a salt precipitation device, and an outlet of the salt precipitation device is connected to a dehydration apparatus. The present application solves the problems in a traditional flocculation sedimentation method a large amount of used reagents, a large amount of generated solid waste and difficulty in solid waste treatment and recycling.

Description

Distillation-oxidation treatment system and method for organic acid chemical cleaning waste liquid of power station boiler

Cross-references to related applications

This application requires the priority of the Chinese patent application submitted to the State Intellectual Property Office of China on April 28, 2022, with the application number 202210462733.1 and the invention name "Power Station Boiler Organic Acid Chemical Cleaning Waste Liquid Distillation-Oxidation Treatment System and Method", The entire contents of which are incorporated herein by reference.

Technical field

This application relates to the technical field of chemical cleaning waste liquid treatment for power station boilers, and in particular to a distillation-advanced oxidation treatment system and method for organic acid chemical cleaning waste liquid of power station boilers.

Background technique

With the promotion of chemical cleaning technology for thermal equipment in power plants and the continued tightening of environmental protection policies, the treatment of chemical cleaning waste liquid has become a "stuck" problem in the chemical cleaning industry. Organic acid cleaning waste liquid has the characteristics of high COD (30000~80000mg/L), high iron ion content (5000~10000mg/L), high color, high short-term emission (1000~2000t/time), and non-recurring characteristics. Power plants Existing wastewater treatment equipment and technology are difficult to meet the requirements for treatment and reuse.

At present, my country's power plants mainly use the following methods to treat organic acid chemical cleaning waste liquid:

(1) Spray the coal field and put the coal into the furnace for combustion. This method increases the moisture content of pulverized coal, reduces the thermal energy utilization rate of coal used in power plants, and is not conducive to energy saving and consumption reduction. Secondly, the coal yard’s reception capacity is limited, and the spray flow must be controlled. Otherwise, it is easy to cause incomplete adsorption of organic matter by pulverized coal. The waste liquid seeps into the ground and causes serious environmental pollution; on the other hand, due to the limitation of spray flow, the treatment cycle is long (ranging from 3 months to half a year), causing the waste liquid to occupy the waste liquid pool for a long time and affecting the normal production of the power plant.

(2) Flocculation and sedimentation method. This method requires the use of a large amount of flocculation sedimentation and neutralizing agents (such as lime, etc.), produces a large amount of solid waste, and the treated water quality is difficult to meet the first-level discharge standards stipulated in GB 8978-1996 "Integrated Wastewater Discharge Standard".

(3) Advanced oxidation method. Although there are reports in the literature on the treatment of organic acid waste liquid by advanced oxidation methods such as electrocatalytic oxidation and Fenton oxidation, the advanced oxidation method has limited effect on the treatment of organic acid cleaning waste liquid, and has high requirements for waste liquid water quality and poor adaptability. The waste liquid undergoes pretreatment such as flocculation and sedimentation. This method requires the use of a large amount of oxidants, and the treated water quality is difficult to meet the first-level discharge standards stipulated in GB 8978-1996 "Integrated Wastewater Discharge Standards".

(4) In the process of conventional industrial wastewater treatment, distillation is often used to reduce wastewater. However, the distillate usually contains low-boiling organic matter, and its COD is still high, making it difficult to meet emission standards and requiring advanced treatment.

Contents of the invention

In order to solve the problems existing in the above-mentioned prior art, the purpose of this application is to provide a power station boiler organic acid chemical cleaning waste liquid distillation-advanced oxidation treatment system and method, changing the way of solely relying on chemical methods to treat cleaning waste liquid, combining distillation and The advantages of advanced oxidation technology can solve the problems of traditional treatment methods such as large dosage of chemicals, large amounts of solid waste, high cost, and unqualified effluent quality.

In order to achieve the above objectives, this application adopts the following technical solutions:

A power station boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system, including: a distillation system, an oxidation system, and a crystallization system;

The distillation system includes a waste liquid transfer pump, a heater and a flash tank. The outlet of the waste liquid transfer pump is connected to the flash tank after passing through the heater; the vapor phase outlet of the flash tank is connected to the distillate collection tank after passing through a condenser. , the liquid phase outlet of the flash tank is connected to the heater inlet through the concentrate delivery pump;

The oxidation system includes: an aeration device, an advanced oxidation reactor and an effluent collection tank; the liquid outlet of the distillate collection tank is connected to the aeration device through a distillate delivery pump, and the liquid outlet of the aeration device is connected to the advanced oxidation reactor. The liquid outlet of the advanced oxidation reactor is connected to the water collection tank;

The crystallization system includes: a crystallization separator, a salt precipitator and dehydration equipment; the concentrated liquid delivery pump is connected to the crystallization separator. After solid-liquid separation is performed by the crystallization separator, the supernatant liquid is connected to the flash tank through a supernatant liquid pipeline. ; The solid-liquid mixture enters the salt precipitator, and the outlet of the salt precipitator is connected to the dehydration equipment.

As a further improvement of the present application, the flash tank is connected to a dosing pump for adding defoaming agent; the gas outlet of the distillate collection tank is connected to a vacuum pump.

As a further improvement of the present application, the aeration device is connected to the aeration gas source through an aeration gas source pipe, and the aeration device is connected to a first exhaust pipe.

As a further improvement of this application, the advanced oxidation reactor is connected to a liquid oxidant dosing pump, and the advanced oxidation reactor is connected to a gas oxidant source through a gas pipeline; a second exhaust pipe is provided on the top of the advanced oxidation reactor; and the water effluent collection tank Connect the effluent transfer pump to discharge the distillate out of the system.

As a further improvement of this application, the waste liquid includes: chemical cleaning waste liquid of citric acid, formic acid, glycolic acid, EDTA or EDTA salt.

As a further improvement of this application, the heater is an electric heater or a dividing wall heat exchanger, and the heat source is electric heating or high-temperature steam; a gas-liquid separation accessory is provided inside the flash tank; the condenser is a water-cooled or air-cooled condenser.

As a further improvement of this application, the air source of the aeration device is compressed air; the air source of the aeration device is compressed air with a pressure of 0.1 to 0.2MPa; the advanced oxidation device is a bubble tower reactor, a plate tower reactor, Falling film reactor or packed tower reactor; an ultraviolet device is installed inside the advanced oxidation device; the oxidant used in the advanced oxidation reactor is a gas oxidant, a liquid oxidant, or both, the gas oxidant is ozone, and the liquid oxidant is hydrogen peroxide. solution or ammonium persulfate solution.

As a further improvement of this application, the crystallizer is a cyclone separator, and the dehydration equipment is a centrifuge or a filter press.

A method for chemically cleaning a waste liquid distillation-oxidation treatment system with organic acid in a power station boiler, which is characterized by including the following steps:

The organic acid chemical cleaning waste liquid of the power station boiler is transported to the distillation system through the waste liquid transfer pump; after being heated by the heater, the vapor and liquid are separated in the flash tank, and a defoaming agent is added through the dosing pump to control the foam; the vapor phase is condensed The distillate is obtained by condensation in the device, and the distillate is stored in the distillate collection tank; the liquid phase is re-transported to the heater through the concentrate delivery pump for cyclic evaporation;

The distillate entering the distillate collection tank is transported to the oxidation system through the distillate transfer pump; the distillate first enters the aeration device for aeration, and the aeration gas source enters the aeration device, and the low boiling point components in the distillate After aeration, it is discharged out of the system; the aerated distillate enters the advanced oxidation reactor, the liquid oxidant is added to the advanced oxidation reactor through the liquid oxidant dosing pump, and the gas oxidant is introduced; the distillate is decomposed after advanced oxidation The product and excess gaseous oxidant are discharged from the system, and the distillate after advanced oxidation enters the effluent collection tank and is discharged from the system by the effluent delivery pump;

When the liquid phase in the evaporation system is concentrated to the set index, the concentrated liquid is discharged out of the system or enters the crystallization system; after the concentrated liquid entering the crystallization system is separated from solid and liquid by the crystallization separator, the supernatant liquid returns to the flash tank; the solid liquid is returned to the flash tank; The liquid mixture enters the salt precipitator, and the solid-liquid mixture that passes through the salt precipitator enters the dehydration equipment to obtain organic acid salt crystals and organic acid waste liquid saturated liquid.

Optionally, the working pressure of the evaporation system is -0.1~0.1MPa, the waste liquid temperature is 5°C~95°C, after passing through the heater, the liquid temperature entering the flash tank is 30°C~110°C, and the condensate temperature is 5°C~60°C.

Compared with the existing technology, this application changes the way of treating cleaning waste liquid solely by chemical methods, and has the following advantages:

This system includes a distillation system, an oxidation system, and a crystallization system; through the distillation system, the organic acid chemical cleaning waste liquid of the power station boiler is flashed after heating, the vapor-liquid separation, the distillate is stored, and the liquid phase is circulated and evaporated; the distillate is then exposed Gas, low boiling point components in the distillate are discharged after aeration; the aerated distillate undergoes an oxidation reaction; decomposition products and excess gas oxidants are discharged; the concentrated liquid entering the crystallization system is separated from solid and liquid through the crystallization separator Afterwards, the supernatant liquid returns to the flash tank; the solid-liquid mixture enters the salt precipitator, and the solid-liquid mixture that passes through the salt precipitator enters the dehydration equipment to obtain organic acid salt crystals and organic acid waste liquid saturated liquid. The entire process is produced continuously, and each process cooperates with each other to meet the requirements of industrial production. Combining the advantages of distillation and advanced oxidation technology, it solves the problems of traditional treatment methods such as large dosage of chemicals, large amounts of solid waste, high cost, and unqualified effluent quality.

Description of drawings

The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes and proportional dimensions of each component in the drawings are only schematic and are used to help the understanding of the present application, and are not intended to specifically limit the shapes and proportional dimensions of each component of the present application. In the attached picture:

Figure 1 is a schematic diagram of a distillation-oxidation treatment system for organic acid chemical cleaning waste liquid of a power station boiler according to the present application.

Detailed ways

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

It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is said to be "connected" to another element, it may be directly connected to the other element or there may also be an intervening element present. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent exclusive embodiments.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing specific embodiments only and is not intended to limit the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

This application provides a distillation-oxidation treatment system for organic acid chemical cleaning waste liquid of a power station boiler, which includes: a distillation system, an oxidation system, and a crystallization system. The distillation system includes: waste liquid transfer pump 1, heater 2, flash tank 3, dosing pump 4, condenser 5, distillate collection tank 6, vacuum pump 7, distillate transfer pump 8, concentrate transfer pump 14 and the connecting pipes between each equipment (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 37, 38, 39, 40, 41); the oxidation system includes: aeration device 9, advanced Oxidation reactor 10, liquid oxidant dosing pump 11, effluent collection tank 12, effluent transfer pump 13 and connecting pipes (28, 29, 30, 31, 32, 33, 34, 35, 36) between each equipment; among them, the crystallization system It includes: crystallization separator 15, salt precipitator 16, dehydration equipment 17 and connecting pipes (42, 43, 44, 45, 46, 47) between each equipment.

In the distillation system, the heater 2 is an electric heater or a dividing wall heat exchanger, and the heat source is electric heating or high-temperature steam; defoaming agent is added through the dosing pump 4 to control foaming in the flash tank; inside the flash tank 3 Baffles, demisters, cyclone separators and other gas-liquid separation accessories are provided; the condenser 5 is a water-cooled or air-cooled condenser. In the oxidation system, the gas source of the aeration device 9 is compressed air; the advanced oxidation device 10 is a bubble tower reactor, plate tower reactor, falling film reactor or packed tower reactor; the advanced oxidation device 10 is equipped with a UV device inside . In the crystallization system, the crystallizer 15 is a cyclone separator, and the dehydration equipment 17 is a centrifuge or a filter press.

In the distillation system, the system working pressure is -0.1~0.1MPa, the waste liquid temperature is 5°C~95°C. After passing through the heater 2, the liquid temperature entering the flash tank 3 is 30°C~110°C, and the condensate temperature is 5°C~60°C. . In the oxidation system, the gas source of the aeration device 9 is compressed air with a pressure of 0.1 to 0.2MPa; the oxidant used in the advanced oxidation reactor 10 is a gas oxidant, a liquid oxidant, or both. The gas oxidant is ozone, and the liquid oxidant is hydrogen peroxide solution or ammonium persulfate solution.

The organic acid chemical cleaning waste liquid of the power station boiler is heated after entering the distillation system. The low-boiling point chemicals and most of the water are evaporated by heat and condensed into a distillate. The distillate contains some chemicals, and its COD and ammonia are relatively high. After the distillate is treated with aeration and oxidation systems, the COD is reduced to less than 50 mg/L, and the ammonia hydrogen is reduced to less than 15 mg/L, reaching emission standards. The high-boiling point pharmaceuticals that have not been evaporated in the distillation system are directly discharged from the distillation system in the form of concentrated liquid or are processed by the crystallization system and then discharged from the crystallization system in the form of crystals. The concentrated liquid or crystal has low water content and high calorific value, and can be burned with coal in the furnace. This application solves the problems of traditional distillation method distillate water quality COD and ammonia exceeding the standard; solves the problems of low treatment efficiency, harsh treatment conditions, and long treatment cycle of a single advanced oxidation method; solves the problem of traditional flocculation and sedimentation method with large dosage of chemicals and solid solids. The problem is that the amount of waste is large and solid waste is difficult to process and recycle.

The organic acid chemical cleaning waste liquid in the embodiment of the present application includes: citric acid, formic acid, glycolic acid, EDTA, and EDTA salt chemical cleaning waste liquid. We will not explain them one by one here. Only Examples 1 and 2 will be described as representative examples.

Example 1:

The present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a power plant boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system includes: a distillation system, an oxidation system, and a crystallization system.

The distillation system includes: waste liquid transfer pump 1, heater 2, flash tank 3, dosing pump 4, condenser 5, distillate collection tank 6, vacuum pump 7, distillate transfer pump 8, concentrate transfer pump 14 and connecting pipes 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 37, 38, 39, 40, 41 between equipment; waste liquid transfer pump 1, heater 2, flash tank 3 are connected in sequence, the flash tank 3 is connected to the dosing pump 4 for dosing; the gas pipe of the flash tank 3 is connected to the condenser 5, the distillate collection tank 6, and the gas outlet of the distillate collection tank 6. The vacuum pump 7 is used to exhaust the gas, and the liquid pipeline is connected to the oxidation system through the distillate delivery pump 8 .

The liquid pipeline of the flash tank 3 is respectively connected to the outlet of the waste liquid transfer pump 1 and the inlet of the crystallization system through the concentrated liquid transfer pump 14.

The oxidation system includes: aeration device 9, advanced oxidation reactor 10, liquid oxidant dosing pump 11, effluent collection tank 12, effluent transfer pump 13 and connecting pipes 28, 29, 30, 31, 32, 33 between each equipment. 34, 35, 36.

The distillate transfer pump 8 is connected to the aeration device 9, the advanced oxidation reactor 10, the effluent collection tank 12, and the liquid inlet of the effluent transfer pump 13 in sequence; the advanced oxidation reactor 10 is connected to the liquid oxidant dosing pump 11 for dosing. medicine.

The crystallization system includes: crystallization separator 15, salt precipitator 16, dehydration equipment 17 and connecting pipes 42, 43, 44, 45, 46, 47 between each equipment.

The concentrated liquid delivery pump 14 is connected to the crystallization separator 15, the salt precipitator 16, and the dehydration equipment 17 in sequence. After solid-liquid separation in the crystallizer separator 15, the supernatant liquid returns to the flash tank 3 through the pipeline 43.

The organic acid chemical cleaning waste liquid used in this embodiment is citric acid chemical cleaning waste liquid. The working pressure of the distillation system is 0.03MPa, the temperature of the citric acid chemical cleaning waste liquid is 25°C, and the density is 1.020g/cm ³ .

Optionally, the heater 2 is a dividing wall heat exchanger, and the heat source is high-temperature steam (150°C ~ 200°C). After the waste liquid is heated by the heater 2, the temperature of the liquid entering the flash tank 3 is 99.7°C, and the flash evaporation The internal liquid level of tank 3 is controlled at 30% to 50%, and a baffle, demister, and cyclone separator are installed on the top; the amount of defoaming agent is 0.05‰ (mass fraction) of the waste liquid; condenser 5 is water-cooled condensation device, the condensate temperature after vapor phase condensation is 40°C. In the oxidation system, the gas source of the aeration device 9 is compressed air, the pressure is 0.1MPa, and the dosage is 20 times the waste liquid volume (volume); the advanced oxidation device 10 is a bubble tower reactor, and the gas oxidant used is ozone, and the dosage is The amount of liquid waste is 2‰ (mass fraction), the liquid oxidant is 30% hydrogen peroxide solution, and the dosage is 1‰ (mass fraction) of the waste liquid; the advanced oxidation device 10 is equipped with a UV device (UV intensity 0.01 W/cm ² ). In the crystallization system, the crystallizer 15 is a cyclone separator, and the dehydration equipment 17 is a centrifuge.

Based on the above-mentioned treatment method of the organic acid chemical cleaning waste liquid distillation-oxidation system of power station boilers, it includes the following steps:

Step 1: The citric acid chemical cleaning waste liquid of the power station boiler is transported to the distillation system through the waste liquid transfer pump 1. After being heated by the heater 2, the vapor and liquid are separated in the flash tank 3, and a defoaming agent is added through the dosing pump 4 to control the foam. The vapor phase is condensed through the condenser 5 to obtain a distillate, which is stored in the distillate collection tank 6; the liquid phase is re-transported to the heater 2 through the concentrate delivery pump 14 for cyclic evaporation. The upper part of the distillate collection tank 6 is connected to a vacuum pump 7 to adjust the distillation system pressure to 0.03MPa and discharge non-condensable gas.

Step 2: The distillate entering the distillate collection tank 6 is transported to the oxidation system through the distillate transfer pump 8 . The distillate first enters the aeration device 9 for aeration. The aeration gas source enters the aeration device 9 through the pipeline 29. The low boiling point components in the distillate are aerated and discharged from the system through the pipeline 28; the distillate after aeration The effluent enters the advanced oxidation reactor 10, the hydrogen peroxide solution is added to the advanced oxidation reactor 10 through the liquid oxidant dosing pump 11, and the ozone is introduced through the pipeline 31. After the distillate undergoes advanced oxidation, the decomposition products and excess ozone are discharged from the system through pipeline 33. The distillate after advanced oxidation enters the effluent collection tank 12 and is discharged from the system by the effluent delivery pump 13. Table 1 shows this implementation An example of distillate water quality after advanced oxidation.

Step 3: When the liquid phase in the evaporation system is concentrated to the set index [density greater than 1.266g/cm ³ ], the concentrated liquid enters the crystallization system through pipeline 41; the concentrated liquid entering the crystallization system is separated from solid and liquid by the crystallization separator 15 , the supernatant liquid returns to the flash tank 3 through the pipeline 43; the solid-liquid mixture enters the salt precipitator 16, and the solid-liquid mixture after settling the salt enters the dehydration equipment 17 to obtain ferrous citrate, ferric citrate, and ferrous citrate. Ferrous ammonium, ferric ammonium citrate solid mixture and a small amount of citric acid waste liquid saturated liquid, ferrous citrate, ferric citrate, ferrous ammonium citrate, ferric ammonium citrate solid mixture have the characteristics of high calorific value and low water content. Coal is fed into the furnace and burned.

Table 1 Example 1 Distillate water quality after advanced oxidation

project	GB8978-1996 Level 1 Emission Standard	Distillate measurements
Ammonia nitrogen (calculated as N)/(mg/L)	15	5
TOC/(mg/L)	20	5
COD/(mg/L)	100	20

Example 2:

The present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a power plant boiler organic acid chemical cleaning waste liquid distillation-advanced oxidation treatment system includes: a distillation system, an advanced oxidation system, and a crystallization system. The distillation system includes: waste liquid transfer pump 1, heater 2, flash tank 3, dosing pump 4, condenser 5, distillate collection tank 6, vacuum pump 7, distillate transfer pump 8, concentrate transfer pump 14 and connecting pipes 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 37, 38, 39, 40, 41; the oxidation system includes: aeration device 9, advanced oxidation reaction 10, liquid oxidant dosing pump 11, effluent collection tank 12, effluent transfer pump 13 and connecting pipes 28, 29, 30, 31, 32, 33, 34, 35, 36 between each equipment; the crystallization system includes: crystallization separation 15, salt precipitator 16, dehydration equipment 17 and connecting pipes 42, 43, 44, 45, 46, 47 between each equipment; the specific structural connection relationships are the same as those in the embodiment, and the same system is used.

The organic acid chemical cleaning waste liquid used in this embodiment is formic acid-glycolic acid chemical cleaning waste liquid. The working pressure of the distillation system is 0.03MPa, and the temperature of the formic acid-glycolic acid chemical cleaning waste liquid is 25°C. Heater 2 is a dividing wall heat exchanger, and the heat source is high-temperature steam (150°C ~ 200°C). After the waste liquid is heated by heater 2, the temperature of the liquid entering flash tank 3 is 98.7°C. The liquid inside flash tank 3 The position is controlled at 30% to 50%, and a baffle, demister, and cyclone separator are installed on the top; the amount of defoaming agent is 0.05‰ (mass fraction) of the waste liquid amount; condenser 5 is a water-cooled condenser, vapor phase After condensation, the condensate temperature is 40°C. In the oxidation system, the gas source of the aeration device 9 is compressed air, the pressure is 0.1MPa, and the dosage is 20 times the waste liquid volume (volume); the advanced oxidation device 10 is a bubble tower reactor, and the gas oxidant used is ozone, and the dosage is The liquid oxidant is 30% hydrogen peroxide solution, and the dosage is 0.5‰ (mass fraction) of the waste liquid volume; the advanced oxidation device 10 is equipped with an ultraviolet light device (ultraviolet light intensity 0.01 W/cm ² ). In the crystallization system, the crystallizer 15 is a cyclone separator, and the dehydration equipment 17 is a centrifuge.

The treatment method based on the above distillation-oxidation treatment system for organic acid chemical cleaning waste liquid of power station boilers includes the following steps:

Step 1: The formic acid-glycolic acid chemical cleaning waste liquid of the power station boiler is transported to the distillation system through the waste liquid transfer pump 1. After being heated by the heater 2, the vapor and liquid are separated in the flash tank 3, and a defoaming agent is added through the dosing pump 4 to control the foam. The vapor phase is condensed through the condenser 5 to obtain a distillate, which is stored in the distillate collection tank 6; the liquid phase is re-transported to the heater 2 through the concentrate delivery pump 14 for cyclic evaporation. The upper part of the distillate collection tank 6 is connected to a vacuum pump 7 to adjust the distillation system pressure to 0.03MPa and discharge non-condensable gas.

Step 2: The distillate entering the distillate collection tank 6 is transported to the oxidation system through the distillate transfer pump 8 . The distillate first enters the aeration device 9 for aeration. The aeration gas source enters the aeration device 9 through the pipeline 29. The low boiling point components in the distillate are aerated and discharged from the system through the pipeline 28; the distillate after aeration The effluent enters the advanced oxidation reactor 10, the hydrogen peroxide solution is added to the advanced oxidation reactor 10 through the liquid oxidant dosing pump 11, and the ozone is introduced through the pipeline 31. After the distillate undergoes advanced oxidation, the decomposition products and excess ozone are discharged from the system through pipeline 33. The distillate after advanced oxidation enters the effluent collection tank 12 and is discharged from the system by the effluent delivery pump 13. Table 2 shows this implementation An example of distillate water quality after advanced oxidation.

Step 3: The liquid phase in the evaporation system is concentrated to the set index (when the distillate volume reaches more than 95% of the waste liquid volume), the concentrated liquid enters the crystallization system through pipeline 41, and the concentrated liquid entering the crystallization system passes through the crystallization separator 15. After the solid-liquid separation, the supernatant liquid returns to the flash tank 3 through the pipeline 43; the solid-liquid mixture enters the salt precipitator 16, and the solid-liquid mixture after settling the salt enters the dehydration equipment 17 to obtain ferrous formate and ferrous glycolate. , solid mixture of iron formate, iron glycolate and a small amount of saturated liquid of formic acid glycolate. The solid mixture of ferrous formate, ferrous glycolate, iron formate and iron glycolate has the characteristics of high calorific value and low water content, and is burned with the coal in the furnace.

Table 2 Example 2 Distillate water quality after advanced oxidation

project	GB8978-1996 Level 1 Emission Standard	Distillate measurements
Ammonia nitrogen (calculated as N)/(mg/L)	15	3
TOC/(mg/L)	20	10
COD/(mg/L)	100	40

In summary, this application has the following advantages:

1) Compared with the method of spraying the coal field and burning it with the coal into the furnace, this system has the advantages of high processing efficiency, no risk of waste liquid spillage, and low energy consumption.

2) Compared with the flocculation and sedimentation method, the dosage of chemicals is small, the solid waste is produced less, and the effluent water quality reaches the first-level discharge standard stipulated in GB8978-1996 "Integrated Wastewater Discharge Standard".

3) Compared with the single advanced oxidation treatment method, it has lower requirements for waste water quality and strong adaptability. The effluent water quality reaches the first-level discharge standard stipulated in GB8978-1996 "Integrated Wastewater Discharge Standard".

4) Compared with the single distillation method, it solves the problem of high COD and ammonia content in the distillate.

Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art from reading the above description. The scope of the present teachings, therefore, should be determined, not with reference to the above description, but rather with reference to the foregoing claims, along with the full scope of equivalents to which such claims are entitled. For purposes of comprehensiveness, the disclosures of all articles and references, including patent applications and publications, are hereby incorporated by reference. The omission of any aspect of the subject matter disclosed herein from the preceding claims is not intended to be a disclaimer of such subject matter, nor should it be deemed that Applicant has failed to consider such subject matter to be part of the disclosed inventive subject matter.

The above content is a further detailed description of the present application, and it cannot be concluded that the specific implementation mode of the present application is limited to this. For those of ordinary skill in the technical field to which this application belongs, without departing from the concept of the present application, they can also make Several simple deductions or substitutions should be deemed to fall within the protection scope of this application as determined by the submitted claims.

Claims (10)

1. A power station boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system, which is characterized in that it includes: a distillation system, an oxidation system, and a crystallization system;

   The distillation system includes a waste liquid transfer pump (1), a heater (2) and a flash tank (3). The outlet of the waste liquid transfer pump (1) is connected to the flash tank (3) through the heater (2). ; The vapor phase outlet of the flash tank (3) is connected to the distillate collection tank (6) through the condenser (5), and the liquid phase outlet of the flash tank (3) is connected to the heater (2) through the concentrate delivery pump (14) )Inlet connection;

   The oxidation system includes: an aeration device (9), an advanced oxidation reactor (10) and an effluent collection tank (12); the liquid outlet of the distillate collection tank (6) is connected to the aerator via a distillate transfer pump (8) The device (9) is connected, the liquid outlet of the aeration device (9) is connected to the advanced oxidation reactor (10), and the liquid outlet of the advanced oxidation reactor (10) is connected to the water collection tank (12);

   The crystallization system includes: a crystallization separator (15), a salt precipitator (16) and a dehydration equipment (17); the concentrated liquid delivery pump (14) is connected to the crystallization separator (15), and passes through the crystallization separator (15). After solid-liquid separation, the supernatant is connected to the flash tank (3) through the supernatant pipe (43); the solid-liquid mixture enters the salt precipitator (16), and the outlet of the salt precipitator (16) is connected to the dehydration equipment (17).
2. A power station boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system according to claim 1, characterized in that the flash tank (3) is connected to a dosing pump (4) for adding defoaming agent; The gas outlet of the distillate collection tank (6) is connected to a vacuum pump (7).
3. A power station boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system according to claim 1, characterized in that the aeration device (9) is connected to the aeration gas source through an aeration gas source pipe (29), The aeration device (9) is connected to a first exhaust pipe (28).
4. A power station boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system according to claim 1, characterized in that the advanced oxidation reactor (10) is connected to a liquid oxidant dosing pump (11), and the advanced oxidation reaction The reactor (10) is connected to the gas oxidant source through the gas pipeline (31); a second exhaust pipe (33) is provided on the top of the advanced oxidation reactor (10); the water outlet collection tank (12) is connected to the water outlet pump (13) for The distillate is discharged out of the system.
5. A power station boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system according to claim 1, characterized in that the waste liquid includes: chemical cleaning waste liquid of citric acid, formic acid, glycolic acid, EDTA or EDTA salt .
6. A power station boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system according to claim 1, characterized in that the heater (2) is an electric heater or a dividing wall heat exchanger, and the heat source is electric heating or High-temperature steam; the flash tank (3) is equipped with a gas-liquid separation accessory inside; the condenser (5) is a water-cooled or air-cooled condenser.
7. A power station boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system according to claim 1, characterized in that the air source of the aeration device (9) is compressed air; The source is compressed air with a pressure of 0.1~0.2MPa; the advanced oxidation device (10) is a bubble tower reactor, plate tower reactor, falling film reactor or packed tower reactor; the advanced oxidation device (10) is equipped with an ultraviolet light inside Device; the oxidant used in the advanced oxidation reactor (10) is a gas oxidant, a liquid oxidant, or both, the gas oxidant is ozone, and the liquid oxidant is a hydrogen peroxide solution or an ammonium persulfate solution.
8. A power station boiler organic acid chemical cleaning waste liquid distillation-oxidation treatment system according to claim 1, characterized in that the crystallizer (15) is a cyclone separator, and the dehydration equipment (17) is a centrifuge or a filter press. machine.
9. A method based on the organic acid chemical cleaning of the waste liquid distillation-oxidation treatment system of a power plant boiler according to any one of claims 1 to 8, characterized in that it includes the following steps:

   The organic acid chemical cleaning waste liquid of the power station boiler is transported to the distillation system through the waste liquid transfer pump (1); after being heated by the heater (2), the vapor and liquid are separated in the flash tank (3), and passed through the dosing pump (4) Add defoaming agent to control foam; the vapor phase is condensed through the condenser (5) to obtain a distillate, which is stored in the distillate collection tank (6); the liquid phase is re-transported to Circular evaporation is performed in the heater (2);

   The distillate entering the distillate collection tank (6) is transported to the oxidation system through the distillate transfer pump (8); the distillate enters first, and the aeration device (9) performs aeration, and the aeration gas source enters the aeration system. Gas device (9), the low boiling point components in the distillate are aerated and discharged out of the system; the aerated distillate enters the advanced oxidation reactor (10), and the liquid oxidant is added by the liquid oxidant dosing pump (11) In the advanced oxidation reactor (10), the gaseous oxidant is introduced; after the distillate undergoes advanced oxidation, the decomposition products and excess gaseous oxidant are discharged from the system, and the distillate after advanced oxidation enters the effluent collection tank (12) and is transported by the effluent The pump (13) discharges out of the system;

   When the liquid phase in the evaporation system is concentrated to the set index, the concentrated liquid is discharged out of the system or enters the crystallization system; after the concentrated liquid entering the crystallization system is separated from solid and liquid by the crystallization separator (15), the supernatant liquid returns to the flash tank. In (3); the solid-liquid mixture enters the salt precipitator (16), and the solid-liquid mixture that has precipitated salt enters the dehydration equipment (17) to obtain organic acid salt crystals and organic acid waste liquid saturated liquid.
10. According to the method for chemical cleaning of waste liquid distillation and oxidation treatment system of power plant boiler with organic acid according to claim 9, the working pressure of the evaporation system is -0.1~0.1MPa, the temperature of the waste liquid is 5°C~95°C, and after passing through the heater (2), The temperature of the liquid entering the flash tank (3) is 30°C to 110°C, and the temperature of the condensate is 5°C to 60°C.

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