1. Overview of petrochemical sludge

1.1 Source of petrochemical sludge

Petrochemical sludge refers to the oily solid waste produced in the process of petroleum exploitation, transportation, refining and oily sewage treatment. In the process of ground oil treatment system and oily sewage treatment, oily sludge will be produced. The oily sludge will also be produced in oil transfer station, oil tank, settling tank, sewage tank, etc. The “three sludge” produced in sewage treatment mainly includes bottom mud of oil separator (tank), scum of flotation tank and residual activated sludge of biochemical tank.

1.2 Characteristics of petrochemical sludge

The volume of oily sludge is huge, if it is discharged without any treatment, it will not only occupy a large amount of farmland, but also pollute the surrounding soil, water and air. The oily sludge contains a large number of pathogenic bacteria, parasites (eggs), copper, zinc, chromium, mercury and other heavy metals, salts, polychlorinated biphenyls, dioxins, radionuclides and other toxic and harmful substances that are difficult to degrade. The oily sludge has been listed as hazardous solid waste.

Petrochemical sludge has the characteristics of great varieties, complex properties, high oil content, serious emulsification, fine particles and high viscosity, so it is difficult to be dewatered by traditional dewatering machines.

2. Petrochemical sludge dewatering technology with the core of multi-disc screw press dehydrator

Multi-disc screw press dehydrator is mainly composed of multiple fixed rings, floating rings and spiral shafts. It has the advantages of compact structure, convenient operation and stable operation.

The main body of the dehydrator is composed of the filter body and the spiral shaft. The filter body can be divided into two parts: concentration zone and dehydration zone. When the sludge is fed into the concentration zone, it will be concentrated by the movement of fixed rings and floating rings. The liquid phase (water) will be discharged, and the solid phase (concentrated sludge) will be pushed to the dehydration zone. In the dehydration zone, the space in the filter chamber will be constantly reduced, the internal pressure of sludge will be constantly enhanced, with the addition of back pressure of the back pressure plate, the concentrated sludge will be dewatered and discharged out of the machine.

The fixed rings and floating rings are used in the multi-disc screw press dehydrator instead of filter cloth. Under the rotating action of the screw shaft, the floating rings move continuously with the respect to the fixed rings, thus realizing the continuous self-cleaning process and avoiding the problem of blockage commonly existing in the traditional dehydrators.

In addition, due to the movement of the fixed rings and floating rings, the velocity of the fluid in the filter gap changes with the viscosity of the material. The higher the viscosity of the material is, the faster the velocity of the fluid is, the more obvious the dewatering effect is. Therefore, the multi-disc screw press dehydrator has the advantages of strong anti oily sludge capacity, good dewatering effect, no blockage, self-cleaning, clean and environmental protection, no odor, no secondary pollution. So it is especially suitable for dewatering treatment of viscous sludge in petrochemical industry.

3. Conclusion

The practical operation shows that the dewatering technology of the multi-disc screw press dehydrator is stable and effective in petrochemical industry, after dewatering, the water content will be 75%-85%. At present, it has been widely used in many petrochemical enterprises. In view of the experience of operation process, the system has a very good application prospect in the petrochemical industry.