Evaluating a Chinese Firm's 17,000 m³/d Circulating Water Treatment Scheme for an Uzbek Refinery

Question: I saw that a Chinese company called SINOKLE won a refinery circulating water treatment project in Uzbekistan, with a treatment capacity of17000 m³/d, using a coalescing pressure deoiler, and with effluent oil and suspended solids both held below25mg/L. I would like to ask friends in the industry whether there is anything technically noteworthy about this project.

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Answer：

Having worked in industrial water treatment for a few years, let me offer some brief thoughts on this case.

First, a piece of background that tends to be overlooked:A refinery's circulating cooling water system is a hidden heavy consumer of energy. Many people assume that a refinery's energy consumption is dominated by its columns and reactors, but in fact the electricity consumed by the circulating water system accounts for more than 40% of the plant's total auxiliary power consumption. And deterioration of circulating water quality——chiefly the accumulation of oil and suspended solids——directly lowers the heat transfer coefficient of exchangers, forcing the system to increase circulation volume or run at reduced load, which pushes the energy consumption curve upward.

So the refining industry takes control of circulating water quality seriously. But taking it seriously does not make it easy.

The Contest Between Technical Routes for Circulating Water Deoiling

Traditionally, refineries have taken three routes to remove oil from circulating water:

① Gravity separation (API/CPI oil separation basin): the oil-water mixture flows slowly through a basin and the density difference lets the oil float up. The advantages are a simple structure and tolerance of shock loads; the drawbacks are an enormous footprint and essentially no effect on emulsified oil and very fine droplets (< 50μm). Treatment tops out at around50-100 mg/L and goes no further.

② Flotation (DAF/IAF）: large numbers of microbubbles are injected into the water, the bubbles adhere to oil droplets and rise together, and a scraper removes the scum. It can handle smaller droplets, but it needs a dissolved-air system, a dosing system and a scraping system, so there is more equipment, higher energy consumption and more complex operation and maintenance.

③ Chemical demulsification+ coagulation and sedimentation: demulsifiers and coagulants are dosed to break emulsified oil"apart"and then flocculate and settle it. The results can be quite good, but chemicals are a continuous consumable and the cost is not low; more troublesome still, the process generates sludge containing both oil and chemicals, which is hazardous waste, and disposing of it costs money again.

Summed up, the three routes come down to this: either the equipment is complex and expensive to run, or the chemicals cost money and generate hazardous waste, or the precision is insufficient and compliance is hard to reach.

How Exactly Does a Coalescing Pressure Deoiler Work

The coalescing pressure deoiler that SINOKLE used on this project takes a fourth technical route——purely physical coalescing separation。

The core principle is not complicated: driven by pressure (typically 0.2-0.5 MPa), oily water passes through a coalescing cartridge whose interior is a fibrous medium with a special surface treatment. As small oil droplets travel through the gaps between fibres, they are captured on the fibre surfaces and merge. Once countless micron-scale droplets have gathered and grown on the fibres to millimetre scale, buoyancy is sufficient to overcome the resistance of the flow, the droplets detach from the fibres and rise rapidly inside the separation chamber, and are finally discharged from the oil collection zone at the top.

Two key points here are worth expanding on:

First, selection of the coalescing cartridge. You cannot simply stuff in a wad of fibre and expect coalescence. The fibre diameter, surface wettability (oleophilic and hydrophobic), porosity and specific surface area of the cartridge all directly affect coalescing efficiency and pressure drop. In a duty such as circulating water that contains solid suspended matter, the cartridge must also serve a filtration function——it has to"coalesce"the oil out while also"intercept"the suspended solids, and it must not clog too quickly. That places considerable demands on cartridge material and structural design.

Second, system integration. How two units run in parallel, how automatic oil discharge is controlled, how the backwash cycle is set, how fluctuations in inlet oil content are handled——all of these questions surface during on-site commissioning. Delivering stably means the integration design passed the test.

17000 m³/d Where This Sits Within the Industry

Within refinery circulating water side-stream treatment (sidestream treatment), this throughput qualifies aslarge-scale plant class。

A refinery's circulating water flow is usually on the order of tens of thousands of tonnes/per hour, but side-stream treatment generally takes2%-5%。17000 m³/d of the circulation volume. Converted, that is roughly708 m³/h, and assuming a side-stream ratio of3% and working backwards, the corresponding main circulating water flow is around23000 m³/h ,——which already represents the circulating water system of a medium-to-large refinery.

Effluent oil and suspended solids both held below < 25 mg/Lis not a startling figure on its own, but achieving it stably at17000 m³/d of throughput is another matter entirely. Once you scale up, uniformity of velocity distribution, cartridge service life and oil discharge cycle all become the points where real projects tend to come unstuck.

Where the Greater Value of This Project Lies

My view is this:this is not a"sold two units"trading story, but a milestone in technical validation.

The Central Asian market——Uzbekistan, Kazakhstan and Turkmenistan——is rich in oil and gas resources and its refining and chemical capacity is far from small, yet environmental infrastructure is generally weak. Many refineries in these countries are still at the stage of"separating oil and water by gravity and meeting water quality limits by dilution". If Chinese environmental equipment can prove itself in these markets, the ceiling is high.

This SINOKLE project ran the full chain from design and manufacturing to installation and commissioning, accumulating a set of reusable engineering experience along the"Belt and Road"route.17000 m³/d of operating data is a technical calling card for entering the Central Asian energy and chemical water treatment market.

In the end, when industrial equipment goes global, the most valuable thing is not"what it can do", but"where it has been done and what the data looks like"。