Dewatering unit is actually a mixing system for flocculant fine solids in drilling mud. The real function of dewatering unit is flocculation. After flocculation, very fine particle polymerized into bigger sizes suitable for centrifuge separation.

2 Kinds of chemicals normally be used for flocculation in dewatering unit: PAC & PAM. Chemical is dosed from hopper on top of mixing tank. Normally, customer choose 3-chamber dewatering unit.

Functions of the 3 chambers:

1# Chamber: chemical mixing,

2# Chamber: chemical Slaking,

3# Chamber: after mixing and slaking, the prepared material stocked in 3# chamber for usage.

Chemical transfer pump: suck chemical from 3# chamber and feed to decanter centrifuge.

Decanter centrifuge in dewatering unit: There are 2 feed pipes to dewatering centrifuge: One pipe is chemical feeding pump. Another pipe is screw pump feeding mud to centrifuge. Before the mud enters into centrifuge, it is mixed with flocculation chemicals.

If chemicals request a certain time to mixing thoroughly with mud, bend pipe will be used for centrifuge feeding. In this case, chemicals and mud can be mixed well before centrifuge treated.

After treated by decanter centrifuge: solids phase above 2~5 microns will be discharged from solids side. Water phase collected for further treatment.

After dewatering unit and dewatering centrifuge, fluids phase can be transferred to sewage treatment plant for further treatment. But it cannot be discharged into environment directly. As dewatering unit is a physical separation process. It utilizes flocculation function to make fine particles in bigger size, and then use high speed centrifuge force for separation. There still small amount fine solids (smaller size than 2~5 microns) and other chemical material.