Oily sludge treatment technology

Oily sludge refers to a mixture of oil, water, solid particles and other pollutants generated during the process of oil extraction, refining, storage, transportation and use. It is very challenging to handle due to its high oil content, high toxicity and high viscosity. The following are several main technologies for the treatment of oily sludge: 1. Pyrolysis treatment Pyrolysis technology uses high temperature, oxygen-free or anoxic conditions to cause the organic matter in the oily sludge to undergo pyrolysis reactions and convert them into oil, gas, combustible gas, tar and solid residue (semi-coke or biochar). Pyrolysis equipment includes pyrolysis furnace, oil and gas condensation separation system, flue gas purification system and other components. The pyrolysis process can not only greatly reduce the volume of sludge, but also recover valuable energy, while converting harmful organic matter into relatively harmless solid residues, realizing resource utilization and harmlessness. 2. Chemical hot washing Chemical hot washing is to add chemical agents (such as surfactants, alkali solution, etc.) to the oily sludge and heat it to destroy the emulsified state in the sludge, so that the oil droplets gather and separate. The washed oil-water mixture is separated into oil and water by an oil-water separator (such as gravity sedimentation, centrifugal separation or membrane separation equipment). Chemical hot washing is suitable for treating oily sludge with severe oil-water emulsification, but the cost of chemical agents and the disposal of waste liquid after treatment need to be considered. 3. Biological treatment Biological treatment uses microorganisms to degrade organic matter in oily sludge. It mainly includes aerobic biological treatment (such as activated sludge method, biofilm method, sequencing batch reactor, etc.) and anaerobic biological treatment (such as anaerobic digestion, two-phase digestion, anaerobic fermentation, etc.). Biological treatment is suitable for oily sludge with high organic content and low toxicity, and can also produce clean energy (biogas) and biofertilizer. 4. Mechanical dehydration, such as belt filter press, plate and frame filter press, screw press, centrifugal dehydrator, etc., is used to deeply dehydrate the oily sludge after preliminary treatment. Most of the water in the sludge is removed by physical pressure or centrifugal force to reduce the water content and form a mud cake that is convenient for subsequent treatment or disposal. Mechanical dehydration is usually the last step in the oily sludge treatment process to ensure that the sludge meets the moisture content standards required for subsequent disposal such as landfill, incineration, and resource utilization. 5. Thermal evaporation treatment Thermal evaporation treatment uses high-temperature steam or hot air to heat the oily sludge to evaporate the water in it and separate the oil from the solid particles. The evaporated water vapor is recovered by condensation, and the oil and solid residue are further processed. The thermal evaporation method is suitable for treating oily sludge with high moisture content and low oil content. 6. Solidification/stabilization By adding a solidifying agent (such as cement, lime, gypsum, etc.) or a stabilizer (such as biological enzymes, modified clay, etc.), the harmful substances in the oily sludge are fixed or converted, reducing their mobility and bioavailability, making it easier to landfill safely or use it as a building base material. The solidification/stabilization method is suitable for treating oily sludge containing harmful substances such as heavy metals and difficult-to-degrade organic matter. 7. Incineration For oily sludge containing high concentrations of harmful substances or not suitable for resource utilization, an incinerator can be used for high-temperature incineration. During the incineration process, organic matter is completely oxidized into carbon dioxide and water, inorganic matter is retained in the form of ash, and harmful substances are destroyed by high temperature, achieving maximum reduction and harmlessness. The heat generated by incineration can be recycled, but a complete flue gas purification system is required to ensure that emissions meet standards. In summary, there are various technologies for treating oily sludge, including pyrolysis, chemical heat washing, biological treatment, mechanical dehydration, thermal evaporation, solidification/stabilization, incineration, etc. In practical applications, it is often necessary to select or combine different methods and technologies according to the specific properties, treatment objectives and environmental protection requirements of the oily sludge to build an efficient, economical and environmentally friendly oily sludge treatment system.