Hot Washing Technology for Oily Sludge: Process and Benefits

Aug 11, 2026

In every stage of the petroleum industry, such as extraction, refining, transportation, and storage, the generation of oily sludge is an inevitable problem. This kind of sludge not only contains a large amount of crude oil but also a variety of toxic and harmful substances, such as heavy metals and polycyclic aromatic hydrocarbons, posing a serious threat to the environment and human health. Therefore, efficient treatment of oily sludge has become a key task for the sustainable development of the petroleum industry. Hot washing technology for oily sludge, as an important treatment method, has received extensive attention in recent years. KOSUN offers advanced hot washing systems engineered for efficient oily sludge treatment and resource recovery.
 

 
What Is Hot Washing Technology?

Oily sludge hot washing technology, also known as thermal chemical cleaning, is based on the core principle of breaking the adhesion force between oil and solid particles through the synergistic effect of heat and chemical agents, promoting the separation of oil from sludge. During this process, the increase in temperature can reduce the viscosity of the oil, enhance its fluidity, and make it easier for the oil to separate from the solid surface. Meanwhile, chemical cleaning agents, such as surfactants and alkaline substances, can reduce the tension at the oil-water interface, emulsify and disperse oil stains, and further promote the separation of oil.
 
Process Flow of Hot Washing of Oily Sludge

The process flow of hot washing of oily sludge usually includes the following main steps:
 
1. Pretreatment

Firstly, the oily sludge is subjected to pretreatment to remove large impurities such as sand, stones, and branches, in order to prevent damage to subsequent equipment. Meanwhile, through operations such as stirring and crushing, the sludge particles are refined, increasing their contact area with the cleaning agent and enhancing the cleaning effect.
 
2. Hot Washing Reaction

Mix the pre-treated oily sludge with the prepared cleaning agent solution in a certain proportion and place it in the reaction vessel or other heating equipment. During the heating process, parameters such as temperature, stirring speed, and reaction time should be controlled to ensure that the cleaning agent fully reacts with the oil stains, achieving the stripping and emulsification of the oil. Generally speaking, the hot washing temperature is between 60°C and 90°C. The stirring speed depends on the nature of the sludge and the equipment conditions. The reaction time is usually 1 to 3 hours.
 
3. Solid-Liquid Separation

After the reaction is completed, the sludge after cleaning is separated from the cleaning liquid through solid-liquid separation methods such as sedimentation, centrifugation, and filtration. Sedimentation utilizes gravity to cause solid particles to settle at the bottom of a container. Centrifugation accelerates the solid-liquid separation process by generating centrifugal force through high-speed rotation. Filtration retains solid particles through filtering media such as filter screens and filter paper.
 
4. Oil-Water Separation

For the separated cleaning solution, which contains a large amount of emulsified oil and dissolved oil, further oil-water separation is required. Common oil-water separation methods include air flotation, demulsification, and adsorption. Air flotation introduces air or other gases into the cleaning solution, causing oil droplets to adhere to bubbles and float to the liquid surface. Demulsification involves adding demulsifiers to disrupt the emulsified state of oil droplets. Adsorption utilizes adsorbents, such as activated carbon and diatomite, to adsorb the oil in the cleaning solution.
 
5. Post-Treatment

After solid-liquid separation and oil-water separation, the solid residue obtained and the treated water need to undergo post-treatment. If the oil content of solid residues meets the relevant standards, they can be landfilled, incinerated, or comprehensively utilized. If the treated water meets discharge standards, it can be discharged directly; otherwise, further treatment is required.
 

 
Conclusion

Hot washing technology for oily sludge, as an important method for treating oily sludge, has the advantages of a clear principle, mature process flow, and good oil removal effect. In practical applications, this technology has achieved remarkable results. With the continuous development and innovation of technology, hot washing technology will play a more important role in the field of oily sludge treatment, providing strong support for the sustainable development of the petroleum industry. KOSUN is committed to providing high-performance hot washing systems and expert support to help customers achieve their operational and environmental goals.