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Huayin City Air Floater Related Principles Parameters
Air floatation equipment operating regulations and application classification
Electrolytic air floatation: During the operation, the micro-bubbles such as hydrogen, oxygen, and liquefied gas are continuously generated in the two electrode areas by means of electrode solution. Suspended particles in the wastewater adhere to the air bubbles and float to the surface of the water and are removed. The process is simple, the equipment is small, but the power consumption is large.
Air floatation equipment operating procedures
1, check before starting:
1) Check that all valves are in normal operation.
2) Check that the tank level is in normal working condition.
3) Check that the electrical equipment is in a normal working condition.
2, boot steps
1) Equipped with adding flocculant, with good medicine, start stirring system.
2) Start the air compressor, open the intake valve, and adjust the intake pressure to 0.2 MPa.
3) Turn on the water pump of the container and fill the water in the container tank. Adjust the water level of the container tank to about 1/3 of the level gauge of the container tank. At this time, the pressure of the container tank should reach 0.4 MPa. After the container feed pump works normally for 3-10 minutes, Only start the air float pump.
4) Adjust the dosing amount, influent amount, and container volume to ensure the quality of the effluent according to changes in effluent quality.
5) According to the generation of scum, control the sluice gate, adjust the scum level to the slag scraper sludge requirements, and start the slag scraper.
6) After starting the machine, check the air-floating water and drainage system to achieve the balance of water in and out, and ensure that the air-float works normally.
3, shutdown steps
1) Turn off the slag scraper.
2) Close the air float pump.
Air flotation principle
(1) Air is introduced into the water to produce fine air bubbles, so that the fine suspension in the water adheres to the air bubbles, and floats together with the air bubbles to the surface of the water to form scum, which can achieve the purpose of removing suspended solids in water and improving water quality.
(2) Factors Affecting Air Flotation and Measures to Improve Air Flotation Effect
The smaller the diameter of bubbles, the greater the number, the better the effect of air flotation; inorganic salts in water will accelerate the collapse and merger of bubbles and reduce the effect of air flotation; adding coagulant will promote the aggregation of suspended solids and make them adhere to the air bubbles. Floating; floatation agent can be added to convert the surface of the hydrophilic particles into hydrophobic substances and adhere to the bubbles, with the bubbles floating up.
2. Classification and application of air floatation
(1) Classification:
Electrolytic air floatation: During the operation, the micro-bubbles such as hydrogen, oxygen, and liquefied gas are continuously generated in the two electrode areas by means of electrode solution. Suspended particles in the wastewater adhere to the air bubbles and float to the surface of the water and are removed. The process is simple, the equipment is small, but the power consumption is large.
Dispersed air flotation: It is the process of air flotation in the form of tiny air bubbles after the air passes through a micropore diffuser or a micropore tube or an impeller.
Advantages: simple and easy.
Disadvantages: Large air bubbles and poor air flotation.
Dissolved air floatation:
Including pressurized dissolved air flotation and dissolved air vacuum flotation. Pressurized dissolved air flotation is air dissolved in water under pressure conditions and precipitation at atmospheric pressure. (more commonly used at home and abroad)
Dissolved air vacuum air floatation is air dissolved in water under normal pressure or pressure conditions, and it is precipitated under negative pressure conditions.
(2) (Air floatation) Scope of application:
Separation of suspended and emulsified oils
Secondary sedimentation tank that can replace activated sludge process for solid-liquid separation of aeration tank outflow mixture
Separable useful substances in industrial wastewater (such as pulp)
Separable substances (such as metal ions, surface active substances, etc.) existing in molecular or ionic state
3. Pressure dissolved gas floatation
(1) System composition: including dissolved air system, air release device, air floatation tank
(2) Classification of process flow:
Complete Dissolved Gas Process Partial Dissolved Gas Process Reflow Pressurized Dissolved Gas Process
(3) Dissolved air:
Suction method of pump suction pipe, dissolving method of pump pressure pipe jet, and combination of water pump and air compressor
(4) Advantages of pressurized dissolved air flotation:
Under pressure, the water in the water has large solubility and can provide enough dissolved air to meet different air floatation requirements;
The sudden decompression release produces bubbles with small diameter (20-100), uniform particle size, stable microbubble floating, little disturbance to the liquid, and is especially suitable for solid-liquid separation of loose flocs and fine particles;
The process is simple and easy to maintain and manage.
(5) Form of air floatation tank:
Advection air flotation tank:
The wastewater to be treated enters the contact area from the lower part of one end of the pool. The microbubbles and the wastewater are uniformly mixed, and the suspended particles are adhered to the bubbles. After the wastewater enters the air flotation separation zone through the partition to separate, the pollutants in the water together with the bubbles Float to the surface of the water and scrape off the scraping equipment.
The principle of air floatation
(1) Air is introduced into the water to produce fine air bubbles, so that the fine suspension in the water adheres to the air bubbles, and floats together with the air bubbles to the surface of the water to form scum, which can achieve the purpose of removing suspended solids in water and improving water quality.
(2) Factors Affecting Air Flotation and Measures to Improve Air Flotation Effect
The smaller the diameter of bubbles, the greater the number, the better the effect of air flotation; inorganic salts in water will accelerate the collapse and merger of bubbles and reduce the effect of air flotation; adding coagulant will promote the aggregation of suspended solids and make them adhere to the air bubbles. Floating; floatation agent can be added to convert the surface of hydrophilic particles into hydrophobic substances and adhere to the bubbles.
2. Classification and application of air floatation
(1) Classification:
Electrolytic air floatation: During the operation, the micro-bubbles such as hydrogen, oxygen, and liquefied gas are continuously generated in the two electrode areas by means of electrode solution. Suspended particles in the wastewater adhere to the air bubbles and float to the surface of the water and are removed. The process is simple, the equipment is small, but the power consumption is large.
Dispersed air flotation: It is the process of air flotation in the form of tiny air bubbles after the air passes through a micropore diffuser or a micropore tube or an impeller.
Advantages: simple and easy.
Disadvantages: Large air bubbles and poor air flotation.
Dissolved air floatation:
Including pressurized dissolved air flotation and dissolved air vacuum flotation. Pressurized dissolved air flotation is air dissolved in water under pressure conditions and precipitation at atmospheric pressure. (more commonly used at home and abroad)
Dissolved air vacuum air floatation is air dissolved in water under normal pressure or pressure conditions, and it is precipitated under negative pressure conditions.
(2) (Air floatation) Scope of application:
Separation of suspended and emulsified oils
Secondary sedimentation tank that can replace activated sludge process for solid-liquid separation of aeration tank outflow mixture
Separable useful substances in industrial wastewater (such as pulp)
Separable substances (such as metal ions, surface active substances, etc.) existing in molecular or ionic state
3. Pressure dissolved gas floatation
(1) System composition: including dissolved air system, air release device, air floatation tank
(2) Classification of process flow:
Complete Dissolved Gas Process Partial Dissolved Gas Process Reflow Pressurized Dissolved Gas Process
(3) Dissolved air:
Suction method of pump suction pipe, dissolving method of pump pressure pipe jet, and combination of water pump and air compressor
(4) Advantages of pressurized dissolved air flotation:
Under pressure, the water in the water has large solubility and can provide enough dissolved air to meet different air floatation requirements;
The sudden decompression release produces bubbles with small diameter (20-100), uniform particle size, stable microbubble floating, little disturbance to the liquid, and is especially suitable for solid-liquid separation of loose flocs and fine particles;
The process is simple and easy to maintain and manage.
(5) Form of air floatation tank:
Advection air flotation tank:
The wastewater to be treated enters the contact area from the lower part of one end of the pool. The microbubbles and the wastewater are uniformly mixed, and the suspended particles are adhered to the bubbles. After the wastewater enters the air flotation separation zone through the partition to separate, the pollutants in the water together with the bubbles Float to the surface of the water and scrape off the scraping equipment.
Advantages: shallow pool, low cost, simple structure, easy management
Disadvantages: The volumetric efficiency of the separation zone is not high.
Vertical air flotation tank:
Advantages: The contact area is in the middle of the pool, the water flow is scattered around, and the hydraulic condition is better than the advection type.
Disadvantages: The structure is more complicated.
(6) Design parameters:
Effective water depth, surface load, water flow rise velocity at the upper and lower ends of the contact zone, flow velocity at the downside of the separation zone, gas-solid ratio, actual amount of air in the air flotation process, reflux ratio, and the diameter of the microbubbles released by the reduced pressure.
4. Advantages and Disadvantages of Air Floatation (Compared to Precipitation)
(1) Advantages:
During the flotation process, the dissolved oxygen in the water is increased, the scum is oxygen-containing, non-corrosive, and is favorable for subsequent treatment; the surface of the floating pond is high in load, the hydraulic retention time is short, the depth of the pool is shallow, and the volume is small; the moisture content of the dross is low, and the slag discharge is convenient. When the flocculant is added to treat the waste water, the required dosage is less.
(2) Disadvantages:
The power consumption is much more than that of the precipitation method per cubic meter of waste water, which consumes 0.02-0.04 KWh more, and the operating cost is higher;
When the concentration of suspended solids in wastewater is high, the decompression release device is easily clogged and the management is complicated.
5. Application of air floatation in wastewater treatment
In the petrochemical, textile, printing and dyeing, machinery and chemical industry, ship recycling and food and other industries waste water treatment applications, in addition to shower waste water and urban sewage treatment applications have increased.
(1) for oily wastewater treatment
(2) Feather cleaning wastewater treatment
The parameters of a floatation tank selected by a certain sporting goods factory for treating the feather cleaning wastewater are: dissolved air pressure 0.4 MPa, reflux ratio 30%, and HRT 60 min. After flotation, COD, BOD, and SS in the wastewater are greatly reduced to meet emission requirements.
3) Close the container water pump.
4) Close the air compressor.
5) Check all valves to normal shutdown.
4, matters needing attention
1) The tank level should be maintained after adjustment and should not be adjusted frequently.
2) According to the quality of the effluent, the dosage, the amount of water, and the amount of water in the container can be adjusted in time.
3) Regularly grease the bearings, chains, sprockets, gears, racks, and slides (about ten days) and perform inspections three months.
What are the precautions for daily operation and management of air floatation?
(1) During the inspection, observe the water level in the dissolved gas tank through the observation hole. It is necessary to ensure that the water level does not submerge the filler layer and affect the effect of the dissolved gas; and it is not less than 0.6m to prevent large amounts of undissolved air in the center of the outflow.
(2) Observe the condition of the pool surface during the inspection. If the scum surface of the contact area is found uneven and the local water flow is drastically violent, it may be that the individual releaser is blocked or detached, and it needs to be repaired and replaced in time. If the scum surface of the separation zone is found to be uneven and large bubbles often bulge out on the surface, this indicates that the air bubbles and the impetus floccules do not adhere well and the amount of dosing or changing the type of coagulant needs to be adjusted.
(3) When the lower water temperature in winter affects the coagulation effect, in addition to the measure of increasing the dosage, the method of increasing the amount of reflux water or increasing the pressure of the dissolved gas may be used to increase the number of microbubbles and the adhesion thereof to the floccules. In order to compensate for the increase of the viscosity of the water flow, the flotation performance of the floccule with air is reduced and the water quality of the water is ensured.
(4) In order not to affect the quality of the effluent, it is necessary to raise the water level in the slag during the slag scraping. Therefore, it is necessary to pay attention to the accumulation of operating experience, sum up the thickness and moisture content of the scum, and run the scumming machine to remove the scum periodically to establish the actual situation. Scraping system.
(5) According to the change of the flocculation of the reaction tank, the scum of the flotation tank separation zone and the quality of the effluent water, timely adjust the dosage of the coagulant, and at the same time constantly check the operation of the dosing tube to prevent blockage (especially in the winter). Before the air flotation is commissioned, the first step is to use a compressed air or high-pressure water to repeatedly purge and clean the pipes and dissolved gas tanks until there are no easily contaminated particles. Then install the dissolved gas releaser. A check valve is installed on the intake pipe to prevent pressure water from flowing back into the air compressor. Before commissioning, check the direction of the check valve on the pipe connecting the dissolving tank and the air compressor to the dissolving tank. In actual operation, after the outlet pressure of the air compressor is greater than the pressure of the dissolved air tank, the valve on the compressed air pipeline is opened and air is injected into the dissolved air tank.
What are the precautions when using pressure dissolved air float?
The operating management precautions for air float debugging are:
(1) Before commissioning the inflow, firstly use compressed air or high-pressure water to repeatedly purge and clean the pipeline and the dissolved gas tank until there are no particles that are easily clogged and then install the dissolved gas releaser.
(2) A check valve is installed on the intake pipe to prevent pressure water from flowing back into the air compressor. Before commissioning, check the direction of the check valve on the pipe connecting the dissolving tank and the air compressor to the dissolving tank. In actual operation, after the outlet pressure of the air compressor is greater than the pressure of the dissolved air tank, the valve on the compressed air line is opened to inject air into the dissolved air tank.
(3) First debug the pressure dissolved gas system and the dissolved gas release system with clean water. After the system is operating normally, inject sewage into the reaction tank.
(4) The outlet valve of the pressure dissolved gas tank must be fully opened to prevent the water flow from being blocked at the outlet valve, so that the air bubbles are released in advance and the merger becomes larger.
(5) Control air floatation tank water outlet adjustment valve or adjustable jaw plate, stabilize the air floatation tank water level 5~10cm below the settling tank mouth. After the water level is stable, use the inlet and outlet water valve to adjust and measure the treated water volume until reaching the design water volume.
(6) After scum accumulates to 5 to 8 cm, the slag scraper is started to perform slag scraping. At the same time, it is checked whether scraping slag and slag discharge are normal and whether the effluent quality is affected.
Air floatation equipment process and operation
This article gives you a detailed introduction of the process and operation of the air floatation equipment. Air flotation equipment pressure dissolved gas and jet dissolved air flotation and water purification method is widely used in domestic sewage treatment in recent years. The practice has proved that it has the advantages of small footprint, investment in the province, quick start, good treatment effect, low energy consumption and easy operation.
Air floatation equipment working principle:
The working principle of the air flotation equipment is to form a saturated gas carrier in the dissolved air tank under a certain pressure (0.35 ~ 0.45 Mpa), and a large amount of fine air bubbles are obtained by a sudden decompression of the release device, and the viscosity is rapidly adhered. Attached to floating particles in the water, emulsified oils, baths, and flocculated flocculations, the floc weight is less than that of water, and it is forced to float on the surface of the water to obtain solid-liquid separation.
In the complex combination of highly difficult wastewater treatment processes, air flotation is accompanied by aeration, resulting in a reduction in surface activity and organic concentration, resulting in a significant reduction in oxygen consumption and further purification of the wastewater. Provides water quality that is conducive to compliance.
The main advantages of air flotation equipment:
Compared with general sedimentation, air flotation equipment has the following advantages:
1. The water production per unit area increases by 4 to 5 times, and the floor space can be reduced by 70%.
2. The residence time of water in purification can be shortened by 80%, and slag discharge is convenient. The water content of the residue body is low, and its volume is only 1/4 of the sedimentation tank.
3, coagulant dosage can be reduced by 30%, can be opened and stopped according to industrial production conditions, easy management. Compared with similar products, this product has the following advantages:
A. Low power consumption, consume 0.1kw/h of electricity per ton of water (100T/h as an example), easy to operate, easy to further automation.
B. Operation is stable, air flotation performance is good, catching ability is strong, and purification effect is further improved. LSQF cancels air compressor and air storage system and eliminates noise.
C. It can work with the pressure of the return pump. According to different water quality conditions, the required gas-water ratio can be arbitrarily called out within the pressure of 0.35~0.45Mpa at any time.
Air flotation equipment operation process:
1, the air floater debugging:
a Fill the air flotation tank with clean water, open the inlet and outlet valves and release valve of the return pump, and turn off the inlet and suction valves of the jet.
b start the return pump;
c. In the dissolving tank, fill the water until the pressure of the pump rises to between 0.45 and 0.65 MPa. Slowly open the inlet valve of the ejector, adjust the pressure in the tank to 0.45-0.5 MPa, and slightly open the intake valve into the micro air. The tank pressure is adjusted to between 0.35 and 0.42 MPa.
d After the dissolved gas system is stabilized, the release device emits a large number of bubbles and can be ready for operation. The entire process takes approximately 15 minutes.
e Under normal circumstances, only two steps 2) and 4) should be performed each time the machine is turned on; start the return pump to stabilize the dissolved gas system.
2. Air floatation equipment operation:
a Open the inlet and outlet valves of the clean water tank return pump and close the inlet, outlet and suction valves of the jet.
b Turn on the return pump.
c. In the dissolved gas tank water injection to the pump's own pressure to 0.45 - 0.65MPa, slowly open the inlet valve of the jet, adjust the pressure in the tank to 0.45 - 0.5MPa, micro-open intake valve into the trace air, The tank pressure was adjusted to between 0.30 and 0.42 MPa.
d Open the lift pump in the sump and inject waste water into the floater.
e Add a proper amount of coagulant to the dissolving enamel, dissolve it with fresh water, open the valve of the dissolving barrel, and drip into the coagulant to mix with the waste water in the reaction area of ​​the air floater.
f When the air floater is turned on for a period of time, the air floater has scum floating on the water surface. When the scum reaches a thickness of 5-10 cm, the scum scraper is started to scrape the scum into the slag tank.
3, air floating equipment shutdown:
a Turn off the sewage lift pump and stop lifting the wastewater.
b Close the outlet valve of the air floater, but the air floater will continue to operate for 10-15 minutes.
c Scrape the scum in the air floater and close the return pump.
Air flotation separation technology refers to air and water under a certain pressure conditions, so that the gas is dissolved into the water to a maximum extent, and strive to be in a saturated state, and then the formed pressure dissolved gas water is released by decompression to generate a large number of microscopic bubbles , Sufficient contact with the suspended floes in the water, so that the suspended floc in water adheres to the microbubbles, floats to the surface with the bubbles, forms scum and scrapes the scum, thus purifying the water.
Process flow:
The raw water flows into the bottom center pipe through flocculation and mixing. The scum on the surface of the water is collected by a skimmer and then discharged into the central sludge tank and discharged to a matching sludge treatment device. The sludge that sinks in the bottom of the pool is scraped. The mud boards are collected and discharged into the mud tanks. The clear water is collected and discharged by the central water collection agency. The flocculated raw water refers to the flocculating agent PAC or PAM (PAC is 400-1000 mg/1, PAM is about 1/5 of PAC) added to the raw water, and the flocculation reaction is effective for 10-15 minutes to form raw water. The specific dose and flocculation time and flocculation effect must be determined experimentally.
The main structure:
The JQF high-efficiency shallow air flotation unit integrates flocculation, air flotation, slag slag, sedimentation, and mud scraping. It is cylindrical in shape, compact in structure, and shallow in the pool. The main body of the device consists of five major components: a pool body, a rotating water distribution mechanism, a frame mechanism, a water collection mechanism, and the like. The inlet, outlet and scum discharge outlets are all concentrated in the central area of ​​the tank body. The water distribution mechanism, water collection mechanism and dissolved air release mechanism are all closely connected with the frame and rotate around the center of the pool body. The device provides a complete set of equipment assembly and a control system, through the combination of centralized control and decentralized control, so that the equipment can reach a good running state.
The basic principle of air floatation:
1. The relationship between floatation and air floatation surface loading with air floccules;
When the floccules adhering to the air bubbles float in the water, they will be macroscopically affected by external forces such as gravity G buoyancy F. The speed with air floccules floating can be derived from Newton's second law. The speed of flotation depends on the difference in density between water and air floccules, the diameter (or characteristic diameter) of air floccules, and the temperature and flow state of water. If the proportion of air bubbles in the air-bearing flocks is larger, the density of the air-bearing flocks will be smaller, and the characteristic diameter thereof will be correspondingly increased. This change of the two will enable the floating speed to be greatly improved.
However, in the actual water flow, the size of the air-bearing batting varies in size, and the resistance caused by it changes constantly. At the same time, the external force also changes in the air-buoying, and thus the bubble forming body and the floating speed also constantly change. The specific floating speed can be determined experimentally. The floating surface load can be determined based on the measured floating speed value. The determination of the floating speed must be based on the requirements of the effluent.
2. The adhesion of floccules to air bubbles in water;
As mentioned before, there are basically two types of floes and particulate monomers that are the main targets for the separation of pollutants from water by air flotation. In the air flotation process, bubbles can bind to the flocculant and the particle monomers in three ways: bubble jacking, bubble wrap, and gas particle adsorption. Obviously, the strength of the binding and adhesion between them, that is, the degree of firmness of the combination of gas and particles (including flocculants) is not only related to the shape of the particles and flocs, but also more important to the water and gas. Grain, three-phase interface properties. The content of the active agent in the water, the hardness in the water, and the concentration of the suspended matter are all closely related to the adhesive strength of the air bubbles. The quality of air flotation is fundamentally related to this. In practical applications, water must be adjusted.
3. The formation and characteristics of bubbles in water;
The size and strength of the bubbles formed depend on the various conditions of use and the surface tension of water at the time of air release. (Surface tension is a pair of forces that are equal in magnitude and direction and are opposite to each other, acting on the contact portions of the surface layers, respectively, and its direction of action is always tangent to the liquid surface.
(1) The smaller the bubble radius, the greater the additional pressure in the bubble, and the greater the probability of collision of air molecules in the bubble with the bubble film. Therefore, to obtain a stable microbubble, the bubble film strength must be guaranteed.
(2) Small bubbles, fast buoyancy, little disturbance to the water body, and it will not crash the floccules. And can increase the probability of collision of bubbles and granules. However, it is not that the finer the air bubbles, the finer the air bubbles affect the floating speed, and thus the size of the air flotation tank and the construction cost. In addition, the addition of a certain amount of surfactant can effectively reduce the surface tension coefficient of water and enhance the bubble film fastness, and r also becomes smaller.
(3) The addition of high-solubility inorganic salts to water can weaken the bubble film and cause the bubbles to be easily broken or large.
4. The role and influence of surfactants and coagulants in flotation separation;
(1) Effect of surface active substances:
If there is a lack of surface active substances in the water, the small bubbles always have the tendency to break through the bubble wall and the large bubble, thereby destroying the stability of the air floating body. At this point it is necessary to add foaming agent to the water in order to ensure the stability of the air bubbles in the air floating operation. Most of the so-called foaming agents are surfactants composed of polar and non-polar molecules. The molecular structure of the surfactant is generally represented by 0. The round end indicates the polar group, which is easily soluble in water and extends into water. (Because water is a strong polar molecule); the tail represents a non-polar group, which is a hydrophobic group that stretches into a bubble. Due to the repulsion of the same number of charges, thereby preventing the merger and burst of bubbles, and enhancing the stability of the foam, most of the surfactants are also foaming agents.
When airfloats are used to treat wastewaters with low levels of organic contaminants, bubble dispersibility and foam stability may be necessary (for example, air-floating filtration of drinking water). However, when the concentration exceeds a certain limit, the surface tension of the water increases, the surface tension of the water is severely emulsified, and the surface potential increases, and the water contains the same charged surface active material as the polluting particle. Turning to the opposite side, in spite of the strong bubbling phenomenon, the foam is stable; however, the adhesion of air and a grain is not good, and the air flotation effect becomes low. Therefore, how to grasp the good content of surface active substances in water has become one of the important issues that need to be addressed in air flotation treatment.
(2) The charged floc produced by adding coagulant:
For the industrial wastewater containing finely dispersed hydrophilic particulate impurities (such as pulp, slime, etc.), when the flotation process is used, in addition to applying the aforementioned electrolyte coagulant to perform the surface electricity neutralization method, it may also be applied to water. The addition of a flotation agent (or presence in water) can also change the hydrophilic surface of the particles to be hydrophobic and adhere to the bubbles. When the polar end of the flotation agent (also a surface active compound composed of amphiphilic molecules) is adsorbed on the surface of the hydrophilic particles, the non-polar end faces toward the water, so that the substance having the hydrophilic surface is converted into Hydrophobic, so that it can adhere to air bubbles and float with it to the surface.
There are many types of flotation agent, whether it can work when used, the first is whether its polar end can be attached to the surface of hydrophilic pollutants, and the strength of its binding with bubbles depends on its non-polarity. The length of the end chain. For example, the flotation agent used to separate the pulverized coal in coal washing wastewater is phenol-free light oil, medium oil, diesel oil, kerosene or pine oil.