1 Overview of oily sludge
Oily slag is a kind of oily waste. It is in the process of oil-containing wastewater treatment in the air flotation unit produced by the end of the waste, for a variety of particles, water and bubbles formed by the coagulation of the mass, semi-solid state, mobility, and its main components are a variety of chemicals, a variety of surfactants and flocculants, emulsified oil, dispersed oil, heavy oil components, fine sand and a large number of secondary clay minerals, a variety of substances cohesive together, emulsified flocculation serious, and its settling performance Very poor, difficult to separate and clean.
Oil-containing sludge viscosity is high, containing small particles, system stability, filtration specific resistance, most of the waste particles are “oily solids” (such as asphaltenes, gums and paraffins, etc.), the quality is soft, it is difficult to dewater by gravity concentration. Oil-containing slag with high water content, oil content is relatively low, water content in 96% or more, sometimes up to 99%, but the oil content is relatively low, generally between 0.5% ~ 5.O%.

2 oil-containing slag treatment technology status
In the oil mining, oil refining and processing, usually produces a large number of oily wastewater, oily wastewater treatment for this type of treatment, are generally “oil + flotation + gas flotation + biochemical treatment” of the old three sets of technology. Which in the “air flotation” unit in addition to emulsified oil in the process will produce a large number of oily sludge. Oily sludge composition is extremely complex, containing a large number of aging crude oil, wax, asphaltene, colloids, suspended solids, etc., but also includes the production process of coagulants, corrosion inhibitors and other chemicals.
As the oil sludge has been included in China’s “National Hazardous Waste List” (2016 Ministry of Environmental Protection, National Development and Reform Commission Decree No. 1), it is a hazardous waste, and the “National Cleaner Production Promotion Law” and the “Solid Waste Environmental Pollution Prevention and Control Law” also require the harmless treatment of oil-containing sludge. At present, most of the refineries have adopted the sludge into the coking unit back to refining or centralized incineration or blending treatment. However, due to the large amount of sludge and high water content, back to refining or incineration is bound to consume a lot of heat, which directly leads to high energy consumption. Therefore, the oil slick must be dewatered and reduced before harmless or resource disposal. At present, the domestic Zhenhai Refining, Luoyang Petrochemical, Shanghai Petrochemical, Jinan Petrochemical and other centrifugal three-phase separator for dewatering, but the effect is not very satisfactory, mainly as follows: slag in the oil, water is difficult to separate the water content of oil-containing slag is more between 75% to 85%; at the same time, the centrifugal equipment frequently failures, high operating and maintenance costs. Therefore, there is an urgent need for an efficient oil sludge dewatering disposal method to realize the oil sludge reduction, harmless and resource treatment.

3 Technology Introduction
Oily sludge is a kind of hazardous waste in the petrochemical industry, which is the end waste produced by the gas flotation unit of oily wastewater. For a variety of particles, water and air bubbles formed by the coagulation mass, semi-solid state, with mobility; its main components are a variety of chemicals, surfactants and flocculants, emulsified oil, dispersed oil, heavy oil components, fine sand and a large number of secondary clay minerals; its quantitative treatment is a petrochemical industry, an environmental problem.
The water content of oil sludge is high, generally above 95%, sometimes as high as 99%; the oil content is relatively low, generally between 0.5% and 5%; the sand content is 1-3%.
Nanjing Bidun Environmental Protection Technology Co., Ltd. has successfully researched and developed highly efficient treatment technology and complete sets of equipment for oil slick, realizing three-phase separation of oil, water and solids from the oil slick:
After treatment of oily slag
Water (oil <50ppm) oil (water <1%) solid (solid content >30%) depth treatment solid content of up to 90%
If the slag is calculated according to 1% solid content, the rate of dewatering and oil removal can reach 97%, and the volume can be reduced by 96%.
3m3/h industrialized application test device has been successfully tested in Sinopec Jinling Branch.