CFU Compact Flotation in 90 Seconds: A Parameter-by-Parameter Reality Check

The cost of residence time

Oily industrial wastewater shows up in oil extraction, refining, chemicals and mechanical processing, and it is rarely a single pollutant. Floating oil, dispersed oil, emulsified oil and a heavy suspended solids load arrive together. Handled badly, the stream deoxygenates receiving water, compacts soil, and clogs the equipment downstream, which is where the maintenance budget quietly disappears.

Conventional answers each carry a penalty. Air flotation needs 10-15 minutes of residence time and delivers a single-stage oil removal efficiency of only 60%-80%. Gravity separation occupies an unreasonable amount of land and performs poorly on emulsified oil. Chemical demulsification consumes reagents and creates a secondary pollution problem. The common thread is that all three accept a slow separation rate and then build equipment large enough to compensate.

SINOKLE took a different route with the CFU (Compact Flotation Unit), a patented compact enclosed pressurised flotation technology built on cyclone intensification combined with efficient air flotation. The design premise is that separation speed is a function of collision probability, and collision probability can be engineered.

Where the speed comes from

Introducing the cyclone principle into the flotation system changes two variables at once. High-speed hydraulic shearing produces uniform micro-bubbles, while the centrifugal field raises the probability that a bubble meets an oil droplet or a suspended particle, and raises the flotation rate with it. Compared with the hydraulic or mechanical shearing used in conventional units, bubble generation is more stable and the bubble size distribution is tighter, which is what makes the short residence time possible rather than merely claimed.

The enclosed pressurised operating mode adds a second benefit that has nothing to do with speed. Because the vessel is sealed, gas cannot escape, so the safety and environmental hazards of atmospheric flotation disappear. For petroleum and chemical sites with strict area classification, that single detail often decides the purchase.

Structurally, the unit is an integrated skid that combines the cyclone generator, the bubble generator and the separation zone without complex supporting facilities. There are no moving parts inside. Separation is driven by hydrodynamics, so mechanical failure modes are largely designed out, and site installation is measured in days rather than weeks. Waste oil and residue leave through pressure oil discharge and residue discharge, with no mechanical scraping device, which removes a maintenance item and most of the operating noise.

The comparison, item by item

Residence time is the headline: under 90 seconds for the CFU against 10-15 minutes for a conventional unit. Single-stage oil removal efficiency is above 80% against 60%-80%. Single-stage suspended solids removal is above 70% against 50%-70%. Effective removal particle size reaches down to 5 um with a removal rate above 80%, while a conventional unit reaches 10 um at the same efficiency. Footprint is only 1/5 of the conventional system, and operating weight is materially lower, which matters on an offshore deck or a rooftop.

Bubble generation is by high-speed hydraulic shearing rather than hydraulic or mechanical shearing. Control is fully automatic rather than manual or semi-automatic. Waste oil leaves by pressure discharge instead of mechanical scraping. Installation is skid-mounted and quick, against on-site civil construction with a long construction period. Read as a list, the pattern is consistent: every item that normally drives civil cost, maintenance labour or plot area has been traded for hydraulic design.

The operating envelope

CFU technology handles industrial wastewater with an oil content up to 1000 ppm and suspended solids up to 200 mg/L. Treatment capacity reaches 500 m3/h. Medium temperature tolerance is below 80 C. Operating pressure is above 0.1 MPa with a system pressure drop above 0.05 MPa. Air, argon and natural gas are all acceptable gas media, which lets the same unit serve different industries without a redesign.

Three projects, three different pressures

In an oilfield produced water project the raw water carried an oil content of 800 ppm and suspended solids of 180 mg/L. After the CFU stage the effluent oil content fell below 80 ppm and the suspended solids removal rate reached 75%, enough to meet the influent requirement of the next process. The equipment footprint was 1/5 of the conventional air flotation system it replaced, which on an oilfield site is often the constraint that decides whether a upgrade happens at all.

At a petrochemical electric desalting water separation project, the test was shock load rather than average performance. Influent oil content fluctuated by +/- 50%, and the unit still held effluent oil content below 100 ppm with single-stage oil removal above 82%. Annual operating costs fell by more than 600,000 yuan, and the skid-mounted design allowed installation and commissioning in 10 days, 80% shorter than the conventional route, which gave the plant its compliance date back.

In a machining oily wastewater project, the value came from automation rather than separation. Fully automatic operation cut labour costs by more than 70%, no chemicals were added, and the treated water was clear enough for partial recycling. Avoiding reagent cost is one saving; avoiding the secondary pollution that reagents create is the larger one.

When a compact unit is the wrong purchase

A short residence time is not a substitute for residence time when the pollutant is dissolved. CFU removes free and dispersed oil, emulsified oil that can be destabilised hydraulically, and suspended solids. It does not oxidise dissolved organics, so a stream with high soluble COD still needs a downstream oxidation or biological stage. Very high solids loading will also shorten the interval between residue discharges, so upstream screening remains necessary. Within those limits, the trade of footprint and time for hydraulic complexity is usually the right one.