Oily Sludge Dewatering Equipment and Technology (1)

Oily sludge is mainly produced in oil fields and refineries. For example, in the dewatering of crude oil, there are a large amount of oily sludge at the bottom of dewatering tanks, oil storage tanks and waste oil tanks.

There are also a large amount of oily sludge in the oil separator tanks, flotation tanks, aeration tanks, etc. The composition of these sludge is very complex, generally composed of oil in water (O/W), water in oil (W/O) and suspended solids, and they are fully emulsified, with high viscosity and difficult to settle.

In recent years, the treatment of oily wastewater and oily sludge has attracted much attention, which has promoted the development of oily wastewater treatment, oily sludge dewatering, oil removal equipment and related treatment technologies.

1. Oily Sludge and Its Treatment Process

Oily sludge particles are small and flocculent, with a small density difference (oil and water density are close), high water content (generally around 96%), strong water holding capacity. The mud, oil, and water are wrapped together and fully emulsified, with high viscosity and difficult to settle. Oily sludge has poor stability, is easy to corrupt and produce bad odor, and pollutes the air environment.

At present, the main processes of oily sludge treatment are as follows:

(1) Concentration-chemical conditioning-dewatering.

(2) Concentration-digestion-chemical conditioning-dewatering.

(3) Concentration-digestion-chemical conditioning-dewatering-pressing.

(4) Concentration-chemical conditioning-dewatering-incineration.

(5) Concentration-digestion-chemical conditioning-dewatering-incineration.

(6) Concentration-chemical conditioning-dewatering-melting.

It can be seen that the three treatment units of concentration, chemical conditioning and dewatering are necessary for the oily sludge treatment system.

2. Sludge Concentration Treatment

2.1 Gravity Thickening Method

Gravity thickening method relies on the gravity of solid matter in sludge to settle and compact, which is a free settling process. Sludge thickening tanks are mainly used in this method.

2.2 Flotation Concentration Method

The air flotation concentration method is based on the principle of dissolved air flotation. Excess air is dissolved in a pressure dissolved air tank, and then a large number of tiny bubbles are released by sudden decompression. The bubbles attach to the sludge particles, reducing their density and forcing them to float. The sludge is concentrated on the surface. The flotation concentration method is suitable for activated sludge with a relative density close to 1. Flotation tanks are mainly used in this method.

2.3 Centrifugal Concentration Method

There is a density difference between the solid and liquid in the sludge. Under the action of the centrifugal force or negative pressure, the solid particles will settle rapidly. Centrifuges and cyclones are mainly used in this method.

2.4 Rotary Drum Concentration and Filtration Method

The rotary drum concentration and filtration device is mainly composed of a flocculation reactor, a rotary drum, an upper drum, a filter screen, a frame, a water collection tank, a transmission device and a water sprayer. The sludge to be treated will be sent to the flocculation reactor through the inlet together with the flocculant.

The motor of the flocculation reactor drives the agitator to rotate, so that the sludge will be fully agglomerated under the action of the flocculant, and then to sent to the rotary drum through the feed pipe. There is a filter screen outside the rotary drum (the water sprayer washes the filter screen for a certain period of time to prevent the filter screen from being blocked), and there are spiral blades on the central axis.

The driving motor drives the rotary drum to rotate (the speed is adjustable within a certain range), so that the sludge is gradually concentrated in the process of moving forward, and the filtrate flows out from the filtrate outlet.

The concentrated sludge is finally discharged from the sludge outlet. Compared with gravity concentration, it has the following advantages: short concentration time, high concentration efficiency, stable and reliable concentration effect, stable sludge concentration, wide applicable concentration range.