Cavitation air floatation Machine(CAF)

1. Use of THAF Vortex Concave Air Flotation Machine

THAF Vortex-Concave Air Flotation Machine is the core product of our company. It is specially designed to remove grease, colloid and suspended matter from industrial and urban sewage. Since its establishment in 1995, Qingtian Company has produced nearly 1,000 vortex-concave air flotation machines of various specifications, which have been applied in sewage treatment fields all over the country, achieved good results, and have been exported to many foreign countries and regions. Among them, the matching vortex aerator is a patented product of our company (patent number: ZL98 2 21723.4). THAF Series Vortex Air Flotation Machine was listed as the national key environmental protection practical technology in 2009 by the State Environmental Protection Administration, and obtained the environmental protection product approval certificate of Shandong Environmental Protection Bureau. According to different wastewater, the removal rate of suspended solids (SS) and grase in the vortex-concave air flotation machine is as high as 95%, and other wastewater indexes also decrease in different degrees. In addition, after adding appropriate chemicals and mixtures to the equipment, COD and BOD can be removed by more than 40% in this pretreatment stage, which is a significant technological revolution to the traditional dissolved air flotation with low equipment operation cost, high work efficiency and simple operation and maintenance.

The vortex-concave air flotation machine produced by Qingtian Company has mature technology, stable performance and reliable quality. Its products are available to major environmental protection design companies, engineering companies and end users, and the price is real and the quality s reliable. THAF Vortex Concave adapts to industries: paint, leather making, oil refining, printing and dyeing, chemistry, dairy processing, fiber production, paper making, food, beverage, slaughter, textile, mechanical processing, municipal sewage.

Air flotatin is the primary treatment in sewage treatment, which belongs to the category of physical treatment. Air flotation machine can only remove most (up to 99%) of suspended matters and a small part of COD and BOD. Strictly speaking, the treated water can't be directly discharged and can't reach the standard, so it can only be used as the pretreatment of secondary and tertiary biochemical treatment. However, in the sewage treatment project, if there is no pretreatment, the raw water will not enter the biochemical treatment process, or it will cause great load to the biochemical treatment process. Therefore, pretreatment is a necessary step in sewage treatment, and the result of pretreatment is directly related to the effect of subsequent biochemical treatment. Therefore, the air flotation machine is an essential universal environmental protection equipment in sewage treatment. In some simple sewage treatment systems, sewage can be directly discharged into the urban pipe network for centralized treatment after sedimentation, air flotation and filtration. It depends on different water quality conditions and requirements of different regions.

THAF vortex-concave flotation can not only help us to treat sewage to the biochemical standard range, but also greatly reduce the subsequent operation cost. Another important aspect is that the by-products produced in wastewater treatment can often be recovered, recycled and sold. For example, in the paper industry, the pulp collected by the air flotation slag scraper can be recycled.

2. Advantages of THAF series vortex-concave air flotation machine

A. Save investment

THAF Vortex-Concave Air Flotation Machine can remove grease, suspended solids, BOD and COD in sewage. Installing this equipment in front of the biochemical secondary sewage treatment plant can greatly reduce the scale of the treatment plant, thus greatly reducing the overall investment cost. Vortex flotation machine does not need pressure vessel, air compressor, circulating pump and dissolved gas release equipment, thus greatly reducing the investment cost of sewage pretreatment.

B. Low operating cost

The whole vortex-concave air flotation machine only needs the power of a few ordinary motors. Low energy consumption, which can't be compared with other air flotation machines. And the maintenance and manual operation are minimal.

C. High efficiency

Contrary to the traditional grease collectors (gravity settling tank and separation tank), the vortex-concave air flotation machine automatically and continuously removes solid sludge from wastewater. The removal and storage of sludge are carried out in a concentrated way, thus reducing the cost of sludge treatment.

D. Simple operation

THAF Vortex-Concave Air Flotation Machine is very easy to operate, and there is no complicated machinery and equipment at all, nor does it need human participation. The whole main machine part consists of only two mechanical parts (aerator and slag scraper), unlike dissolved air flotation machine, which includes many necessary equipment such as pressure vessel, air compressor and circulating pump. And the vortex-concave air flotation machine can be used after installation without debugging or calculating the mixing ratio of air and water.

E. Good working environment

The treatment of wastewater by THAF flotation machine is an aerobic process. The odor problem caused by the original grease collector (gravity settling tank and separation tank) has been well solved. On the other hand, the power of the equipment is very small, and there is only slight motor noise during operation, so there is no noise pollution.

F. Economic benefits

THAF flotation machine has simple design, good matching, and less civil works for the machine, which is very attractive from the investment point of view. Because of its simplicity and integrity, it can be installed on the ground, underground or high, and it takes very little time.

II、 the structure and working principle of vortex-concave air flotation machine.

1. Machine structure of vortex-concave air flotation machine

The whole air flotation machine host system consists of five parts:

a)   Flocculation coagulation zone

b)   Aeration zone

c)   Separation part of flotation machine (standard chain scraper)

d)   Scum collecting tank (self-flowing or optional screw-type solid discharger)

e)   Clear water discharge area (standard handwheel water level regulator)

Note: The front end of the air flotation machine needs to be equipped with a dosing system. At present, domestic air flotation machines commonly use the combination of flocculant PAC and coagulant aid anion PAM (for details, please refer to the instructions of liquid medicine configuration in the annex).

If there is no dosing system at the front end of the air flotation machine, the air flotation effect will be greatly affected, and the equipment can play a greater role with the cooperation of flocculants. It is recommended to use the dosing system. Unless in some special areas, such as just degreasing or oily paint (floating state originally), direct operation without dosing system can be considered.

2. Working principle and process of vortex-concave air flotation machine

The sewage pump lifts the untreated sewage into the coagulation and flocculation tank at the front end of the air flotation machine (if conditions permit, it can also flow into the air flotation machine by itself). It is suggested to set the PAC dosing port in front of the sewage lift pump, so that the PAC liquid medicine can be more fully mixed in the sewage through the high-speed rotation of the impeller of the lift pump. Of course, the PAC dosing port can also be set on the sewage inlet pipe, and it is recommended that it be on the pipe 30-40m away from the air flotation machine, so that the effect is better. The farther the dosing nozzle is from the main machine, the more fully the liquid medicine and sewage can be mixed and reacted.

     At the water inlet of each air flotation machine and the flocculation tank, we set a connecting thread head of the dosing pipeline. However, we don't recommend adding PAC liquid medicine here. The two liquid medicine adding points are only for standby, so it's really impossible to find the adding position far away from the main air flotation machine. Then consider the adding point at the water inlet. The two dosing points can be used as PAM dosing points. It is recommended to use the dosing point in the flocculation tank (the nearest dosing point to the aeration tank).

Mixing with sewage PAC and PAM in flocculation tank can adopt mechanical agitation or baffled flow, both of which have their own advantages and disadvantages. Users can choose the type according to the actual situation. Mechanical stirring type is equipped with two mixers, the rotating speed of which is mostly 30-60RPM, which can mix well, but it consumes energy, and there may be mechanical failures in operation, resulting in high cost. Baffle flow mostly uses three cavities to baffle back and forth, without mechanical equipment and cost, but the mixing effect is not as good as mechanical stirring. However, in some sewage fields, the use of mechanical stirring may break flocs, which is more unfavorable to air flotation.

After mixing and reacting with sewage flocculant, it enters the aeration box equipped with aerator. Vortex aerator is the key equipment of air flotation machine, and its performance directly affects the effluent effect of air flotation machine. The sewage enters the aeration tank from the bottom (the water inlet is above the impeller of the aerator to prevent flocs in sewage from being broken by the impeller rotating at high speed).

And sewage flocs gradually rise along with the water flow in the aeration tank, and are fully mixed with the tiny bubbles generated at the impeller of the vortex aerator. In the floating process, the tiny bubbles will adhere to the suspended solids, and when they reach the water surface, the solid suspended solids will be supported and maintained by these bubbles and float on the water surface of the air flotation separation area.

The working principle of the concave aerator is to use the high-speed rotation of the impeller at the bottom of the aerator main shaft (air conveying pipe) to form a vacuum area at the lower part of the aerator box, so that the air on the liquid surface of the aerator box is continuously sucked into the water vacuum area through the aerator main shaft to fill the gap, and is broken by the high-speed rotating impeller, forming tiny bubbles (with diameters ranging from 30um to 2-3mm, mostly tiny bubbles below 1mm). In the process of rising, microbubbles adhere to flocs such as suspended solids, forming a gas-water mixture.

Due to the imbalance between the gas-water mixture and the liquid, a vertical upward buoyancy is generated, and the suspended solids are brought to the water surface under the action of buoyancy and water flow.

The suspended solids floating on the water surface move from the front end of the separation area to the back end driven by the water flow and the scraper of the slag scraper. The slag scraper is driven by the sprocket drive driven by the stepless speed regulator. The scraper is connected to the chain, and driven by the chain, it moves along the whole liquid surface, scraping the pollutants onto the inclined metal plate (saddle plate), and then pushing them into the slag collecting tank. According to the length of air flotation equipment, multi-page scraper can be configured to ensure timely slag scraping. However, if there are too many scrapers, the chain will be burdened and the failure rate will increase. The speed of the stepless governor can be adjusted within 8-40 revolutions, and it is recommended that the speed be 12RPM (the running linear speed is about 2m/min). Therefore, the proper number of scrapers, proper running speed, and proper slag scraping interval are the keys to ensure the effective operation of the slag scraper.

Most of the slag collecting tanks are designed to be self-flowing, and the height difference at both ends is greater than 400mm, which can ensure that scum can be discharged out of the box smoothly. If the scum density is very high and the fluidity is poor, a screw slag extractor can be arranged, and the horizontal screw hinge can be used to discharge the scum in the slag collecting tank out of the box. The discharged scum can enter the sludge pond or directly into the sludge dewatering equipment for further treatment. If the air flotation equipment is installed overhead on the sludge tank, it can also be drilled in the middle part of the sludge collection tank and directly discharged into the sludge tank at the bottom of the air flotation machine by pipeline, which is more convenient.

Before being discharged, the purified sewage will first pass through the baffle at the back of the air flotation box, and then flow into the overflow trough from below the baffle. A hand-wheel type liquid level regulator is arranged between the overflow tank and the clear water tank to control the water level in the air flotation tank, so as to ensure that the liquid in the air flotation tank will not flow into the slag collection tank.