Process Breakdown: How to Choose a Desalter Wastewater Treatment Scheme
For desalter wastewater treatment, choosing the right process is half the battle. What many refineries agonise over is not"whether to treat it", but "how exactly to treat it". This article breaks down the two process routes in SINOKLE's overall solution and provides a parameter comparison to help you make a quick judgement.
I. Core Equipment: Two Patented Technologies
High-Efficiency Coalescing Oil Remover: it exploits the wetting and coalescing properties of special coalescing media, so that fine emulsified oil droplets repeatedly collide and merge as they pass through the media layer. Small droplets grow into large ones, break free from the constraint of the colloid and asphaltene interfacial film, and are separated by buoyancy. Its core value lies in"demulsification".
CDFUCyclonic Dissolved Air Flotation: it couples cyclonic separation with dissolved air flotation in a single unit. Air is dissolved and released under sealed, pressurised conditions to generate high-density micro-bubbles that adhere to oil droplets and float them rapidly for separation. Its core value is "advanced oil removal", and the unit runs automatically in a fully sealed, pressurised manner, making it safe and environmentally friendly.
II. Applicable Scenarios and Process Flow of the Two Schemes
Scheme 1 (high oil content, severe emulsification): coalescing oil remover + CDFUcombined with cyclonic dissolved air flotation. It suits desalter wastewater with high oil content and severe emulsification. The flow is as follows: the wastewater first enters the coalescing oil remover for demulsification and coalescence, where most of the free oil is separated, and then entersCDFUfor advanced oil removal, with the two stages working in synergy, step by step.
Scheme 2 (low oil content): two stages ofCDFUcyclonic dissolved air flotation units. It suits scenarios with relatively low oil content. The flow is as follows: the wastewater passes successively through two stages ofCDFU, achieving advanced oil removal stage by stage, with a simpler process and a smaller footprint.
III. Comparison of Key Parameters
To make selection easier, let us first place the key parameters of the two schemes side by side (data are based on an influent oil content of0.5%-5%):
Comparison Item | Scheme 1 (High Oil Content) | Scheme 2 (Low Oil Content) |
Applicable scenario | High oil content, severe emulsification | Influent oil content0.5%~5% |
Process configuration | Coalescing oil remover + CDFU | Two-stageCDFUunit |
Effluent oil content | Less than50mg/L | Less than50mg/L |
Oil removal rate | Above 90% | Above 90% |
Water content of recovered crude oil | Less than1% | Less than1% |
Chemical dosing | None (purely physical) | None (purely physical) |
Operating mode | Sealed, pressurised, automatic operation | Sealed, pressurised, automatic operation |
IV. Multi-Dimensional Comparison with Conventional Processes
Placing the new scheme and conventional processes in the same table makes the differences more intuitive. It should be noted that the conventional processes listed are by no means worthless; each still has value under specific operating conditions. However, when facing desalter wastewater with severe emulsification and large fluctuations, their weaknesses become fairly obvious.
Comparison Item | Gravity settling | Cyclonic oil removal | Membrane filtration | Coalescence+CDFUscheme |
Emulsified oil removal | Weak | Average | Fairly strong but prone to clogging | Strong |
Operating cost | Large footprint, low efficiency | Sensitive to fluctuations | High membrane replacement cost | No chemicals, low O&M cost |
Equipment footprint | Large | Medium | Medium | Small |
Level of automation | Low | Medium | Medium | High (sealed, pressurised, automatic) |
Installation without shutdown | Difficult to achieve | Difficult to achieve | Difficult to achieve | Can be installed and commissioned online |
Oil recovery | Difficult to recover | Average recovery quality | Difficult to recover | Crude oil water content<1%, can be sent back for refining |
V. Operation and Maintenance Features
Beyond separation performance, site teams care even more about operation and maintenance. Several features of this solution are worth highlighting: no chemical dosing at any point, which eliminates chemical preparation, storage and reagent costs; sealed, pressurised operation with no odour and no leakage on site, making it safe and environmentally friendly; and a skid-mounted design that allows rapid positioning after delivery and online installation and commissioning while the desalter unit stays in production, which is very friendly to refineries running continuously. The equipment is highly automated, operating parameters are regulated automatically, and daily work is mainly routine inspection, so the manpower burden is light.
VI. Conclusions and Selection Recommendations
The selection logic is actually quite clear. If the water is severely emulsified with large fluctuations in oil content, give priority to the combined process of Scheme 1, using coalescence first to break the emulsion and flotation to finish the job, which offers stronger resistance to shock loads. If the influent oil content remains stable withinthe range of 0.5%-5%, the two-stageCDFUof Scheme 2 is already sufficient, with a simpler process and a smaller footprint.
It is also advisable to carry out a water quality survey before selection: continuously monitor the peak oil content, degree of emulsification and fluctuation range over a period of time, then make a comprehensive judgement together with the available site area and the retrofit window. Scheme 1 has strong shock resistance and suits units with large water quality fluctuations and severe emulsification; Scheme 2 has a simpler process and a smaller footprint and suits scenarios with relatively stable influent. Whichever is chosen, it is recommended to consider the storage and re-refining route of the recovered crude oil at the same time, so that the"treatment" and "recovery" accounts are calculated together.
