CDFU（Cyclonic Dissolved gas Flotation Unit）
Product Detail
1. Technology introduction
CDFU（Cyclonic Dissolved gas Flotation Unit） is a patented technology independently developed by our company. It creatively combines cyclone centrifugal separation technology, ultramicro bubble generation technology, dissolved gas floatation technology and other technologies to achieve efficient and comprehensive removal of a variety of pollutants in a variety of refractory wastewater, with international advanced technology level.
Process Diagram
·Microbubble generation technology
·Dissolved air floatation technology
·Hydrocyclone technology
·Coalescence
·De-emulsification
·Patent product
2. Technical Principle:
The wastewater to be treated is mixed with dissolved gas water. Then, the mixture enters the floatation tank tangentially along the tank wall. Under the effect of dynamic flow and internal structures, a stable cyclonic flow field is rapidly formed. Through centrifugal force generated by the filed, micro-bubbles and oil droplets rapidly collide, adhere and coalesce to form floating oil.
The floating oil gradually rises and enters the inner oil collection cylinder, and then is discharged into the floating oil collection system through the outlet. Meanwhile, the separated exhaust after floating is discharged into the exhaust treatment system. The treated wastewater gradually flows downward from the outlet of the CDFU.
3. Introduction of Cyclonic Centrifugation Technology:
Dissolved air and water mixed with wastewater into the equipment for double tangential swirl, in this process increases the collision probability between bubbles and particles, the centrifugal effect is weak, so it will not cause oil emulsification, and because of the small size of bubbles, strong stability, large specific surface area, so its adsorption of small particles is more efficient; It can ensure that the suspended matter in the effluent has a small median particle size and low content.
Dissolved gas water is mixed with wastewater, and then enters the floatation tank from a bi-tangential angle. Such design significantly increases the cyclonic velocity and centrifugal acceleration. Under the effcet of centrifugal force, micro-bubbles that has large specific surface area will efficiently adsorp small particles. The characteristics of this flow field strengthen the interaction between micro-bubbles and oil droplets, promoting its efficient coalescence towards the central area of the flow field.
4. Technical advantages
a. Short Retention Time:
The oil-water separation process is extremely rapid, with retention time around 1 to 3 minutes (1/6 of traditional equipment).
b. High Efficiency:
The equipment demonstrates effective separation of floating oil and free oil (oil droplets with particle sizes of 30-100㎛), achieving a removal efficiency up to 99%.
c. No Chemical Agents:
Due to the relatively small bubble diameter (D50≈25㎛), the equipment can remove up to 90% of emulsified oil (oil droplets sized 0.1-20㎛), showing an exceptional effect. Remarkably, most emulsified oil can be removed without adding any chemical agents.
d. Less Maintenance and Operation:
The inner structure is simple. Consequently, it is not easily prone to scaling and clogging, particularly in high-salinity environments, which requires less maintenance and less operational costs.
e. Automation:
Under the fluctuation of water volume and oil content, it can still maintain high-precision liquid level and pressure control. The equipment is fully automatically controlled and has high stability in effluent.
f. Small Footprint:
CDFU adopts skid-mounted design which only occupies a small footprint, optimizing the space utilization. The design makes it easier to assemble and construct.
5. Comparisons between Traditional Technology and CDFU
| NO. | Parameter | Conventional dissolved gas floatation | CDFU（Cyclonic Dissolved Gas Flotation Unit） |
| 1 | Scope of Application | Oily wastewater (with suspended solids) | Oily wastewater (with suspended solids) |
| 2 | Retention time | 15~40min | <5min（1/8~1/3 of tradional） |
| 3 | Oil removal efficiency (single stage) | 60%~85% | >90% |
| 4 | Removal rate of suspended solids (single stage) | 50%~70% | >80% |
| 5 | Removal of particle size (> 80%) | ＞5μm | <3μm |
| 6 | Bubble generation mode | Dissolved air pump/other dissolved air mode | Dissolved air pump |
| 7 | Bubble diameter | 5μm~100μm（General uniformity） | 5μm~30μm（Good uniformity） |
| 8 | Aerated way | Partial water return | Partial water return |
| 9 | Pressure consumption | 0.05Mpa~0.1Mpa（Partial water return） | 0.05Mpa~0.1Mpa（Partial water return） |
| 10 | Operation mode | Manual, open | Automatic and closed operation |
| 11 | Dirty oil discharge | Rely on slag scraper, mechanical slag discharge | Pressure oil discharge, slag discharge, no mechanical power |
| 12 | Technical characteristics | Long residence time, large floor area, low flotation efficiency, need to add agents, oil removal and suspended solids effect is unstable. | Compact structure, small footprint (traditional 1/3), emulsified oil and fine suspended matter removal rate is high, no need for chemical agents. |
| 13 | Range of application | Land and other requirements for land cover, weight and other occasions are not high | Especially suitable for oil field or offshore platform containing emulsified oil and fine suspended particles and other difficult to treat sewage |
| 14 | Structure form | Reinforced concrete | Pressure vessel prying equipment |
Related Patents
Application: petroleum refining, electric power, metallurgy, medicine, printing and dyeing, municipal, landfill leachate, river sewage treatment, etc
6. Cases
Case 1:
(2017) Produced water treatment and re-injection of petrochina Changqing Oilfield, the oil content of sewage ≤1500ppm, the treatment capacity 20m³/h, the treatment equipment two-stage CDFU+ walnut shell filter, the oil content of CDFU effluent ≤30ppm, SS≤30ppm, the oil content of filter effluent ≤10ppm, SS≤10ppm, Median particle size ≤5μm.
Pic 1. On-spot equipment two-stage CDFU+ walnut shell filter Pic 2. Inlet water, Primary outlet water, Secondary outlet water
Case 2:
(2019) Petrochina Dushanzi Petrochemical electric desalting sewage treatment, sewage oil content ≤2000ppm, treatment capacity 100m³/h, treatment equipment two-stage CDFU, water oil content ≤10ppm.
Pic 3.: Two-stage CDFU of on-site equipment Pic 4. Second-level CDFU discharge water; first-level CDFU discharge water; inlet water;
Case 3:
(2021) Sinopec conventional gas field produced liquid (condensate) treatment, sewage oil content ≤500ppm, treatment capacity 30m³/h, treatment equipment first-level CDFU, water oil content ≤20ppm (indicator requirement 50ppm).
Pic 5. Single-stage CDFU of field equipment Pic 6. Influent vs. Effluent
