Application of demulsifiers in oily wastewater treatment

Abstract: Treating oily wastewater from oilfields to meet the water quality standards for injection water or effluent discharge is crucial to preventing environmental pollution incidents. For heavily emulsified oily wastewater, the optimal demulsifier should be selected for demulsification and purification. Using a reverse-phase demulsifier can accelerate the treatment of oily wastewater and achieve the desired efficiency in oilfield wastewater treatment.

Keywords: oily wastewater treatment; demulsifier; selection; application

Choosing a suitable demulsifier is crucial for demulsifying oily wastewater. The demulsifier penetrates the oil-water interface film, weakening its strength and facilitating better oil-water separation. The separated crude oil is then processed and incorporated into oilfield production. The optimal demulsifier should be selected in an economical and practical manner to meet the technical requirements of oily wastewater treatment and achieve the desired economic benefits.

1. Overview of Oily Wastewater Treatment

In response to the unique characteristics of oily wastewater from oilfields, separation treatment is implemented to remove oil and suspended particles, thereby improving water quality standards and enabling its use as a source of water for oilfield injection. For the removal of oil droplets during the treatment process, advanced technologies are required, such as air flotation, to separate oil from the wastewater. However, in cases where oil and water form a stable emulsion, demulsifiers are necessary for separation. Therefore, it is essential to select the optimal demulsifier to separate the oil from the wastewater, achieving the desired treatment effect and meeting the technical requirements for oilfield wastewater treatment. Furthermore, by combining this with energy-saving and consumption-reducing technologies in oilfield production, the selection of economical and suitable demulsifiers can lower the cost of oily wastewater treatment, ultimately achieving the goal of cost reduction and efficiency improvement in oilfield production.

Chemical demulsifiers are generally used before oily wastewater enters the oil removal equipment. The agents break down the oil and water, and then the oil in the wastewater is separated and removed by the density difference between the oil and water.

2. Application of demulsifiers in oily wastewater treatment

For oil-water emulsions present in oily wastewater, a demulsifier is needed to break the emulsion before gravity separation can be performed to separate the oil and water. The separated oil droplets are then processed and used to measure oilfield production. Optimal demulsifier selection is crucial to achieve the desired demulsification and separation effect.

2.1 Development of demulsifiers adaptable to various emulsions

Different types of oil-water emulsions require different demulsifiers. For water-in-oil emulsions, where oil is the external phase and water is the internal phase, a lipophilic demulsifier is preferred to improve demulsification efficiency. Conversely, for oil-in-water emulsions, where water is the external phase and oil is the internal phase, a hydrophilic demulsifier is chosen to quickly disrupt the emulsion’s structure, reduce the strength of the interfacial film, and facilitate oil-water demulsification and separation. This, combined with techniques such as flotation for oil removal, achieves the desired treatment of oily wastewater.

This study researches and designs a universal demulsifier for use in oily wastewater treatment. Increasing the molecular weight of the demulsifier, such as using acrylic acid-modified demulsifiers, provides better low-temperature demulsification performance. Therefore, it eliminates the need for heating the oily wastewater; simply adding the demulsifier allows for rapid demulsification and dehydration, saving treatment time and significantly improving oilfield production efficiency.

2.2 Use of nanosphere demulsifier

The application of high-density nanospheres is suitable for treating oily wastewater in an emulsified state, separating and demulsifying the oil and water to produce clear effluent that meets water quality separation requirements. This demulsifier accelerates oil-water separation, contains no metal ions, and therefore does not cause secondary pollution. The nanospheres are cationic organic polymer microspheres with superior reverse demulsification capabilities, effectively separating oil from oily wastewater. They can be used as both reverse demulsifiers and flocculants with outstanding results. They can disrupt the type of oil-in-water crude oil emulsion, shorten oil-water separation time, and are miscible with water, making them one of the most ideal demulsifiers for treating oily wastewater.

2.3 Research and Application of Economical and Highly Efficient Demulsifiers

Based on the water quality standards for oily wastewater, the most economical and applicable demulsifiers are researched and applied, taking into account the type of emulsion in the oily wastewater. Different demulsifiers are selected for oily wastewater from different oilfields; targeted application is essential to achieve the desired demulsification effect. Polymer demulsifiers are widely used, achieving oil-water separation in oily wastewater. Selecting different polymer types and optimizing the most suitable demulsifier improves the water quality standards for oily wastewater treatment, meeting the requirements for oilfield water injection, while simultaneously preventing the discharge of oily wastewater, reducing environmental pollution, and ensuring that oilfield production meets environmental protection technical requirements.

3. Conclusion

This research focuses on the application of demulsifiers in oily wastewater treatment. The goal is to select the optimal type of demulsifier to effectively treat oily wastewater and improve treatment efficiency. This will enhance the quality of the treated water and meet the technical requirements of oilfield production. Furthermore, selecting the best demulsifier ensures economic viability in oilfield wastewater treatment. It aims to achieve optimal demulsification without increasing treatment costs. Otherwise, it could negatively impact the economic benefits of oilfield production and impose high costs on wastewater treatment. Therefore, it is crucial to research and select economically suitable demulsifiers that are tailored to the specific characteristics of oily wastewater from oilfields to achieve the most ideal demulsification effect and better promote the treatment of oily wastewater.