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 one of the key tasks 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.

Oily sludge hot washing technology, also known as thermal chemical cleaning method, its core principle is to break the adhesion force between oil and solid particles by means of the synergistic effect of heat and chemical agents, and promote 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.

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℃ and 90℃. 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 is a process that utilizes the force of gravity to cause solid particles to settle at the bottom of a container. Centrifugation, on the other hand, accelerates the solid-liquid separation process by generating centrifugal force through high-speed rotation. Filtration is achieved by retaining solid particles through filtering media such as filter screens and filter paper, thereby realizing solid-liquid separation.

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, adsorption, etc. Air flotation is a method that involves introducing air or other gases into the cleaning solution, causing oil droplets to adhere to the bubbles and float to the liquid surface, thereby achieving oil-water separation. The demulsification method involves adding demulsifiers to disrupt the emulsified state of oil droplets, causing them to aggregate and separate. Adsorption method utilizes adsorbents, such as activated carbon and diatomite, to adsorb the oil in the cleaning solution, achieving the purpose of oil-water separation.

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 the discharge standards, it can be discharged directly; otherwise, further treatment is required.

Hot washing technology for oily sludge, as an important method for treating oily sludge, has the advantages of 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.