Three-phase solid bowl screw centrifuge and method of controlling the separating process

A method of operating a three-phase solid bowl centrifuge, the method steps comprising:

• providing a three-phase solid bowl centrifuge including
• a rotatable drum;
• a screw arranged in the drum;
• a solid material discharge for a solid phase located at a first axial end of the drum;
• two liquid outlets located at a second axial end of the drum, a first of the liquid outlets being for a lighter liquid phase and a second of the liquid outlets being for a heavier liquid phase;
• one of the liquid outlets including a skimmer disk arranged in a skimmer chamber and the other of the liquid outlets formed as an overflow;
• two regulating disks located in front of the skimmer disk and which disks extend radially from an outside of the drum toward an inside of the drum;
• a siphon disk extends radially outwardly from an interior circumference of the skimmer chamber to an exterior circumference of the skimmer chamber, the siphon disk extending between the regulating disks and into the skimmer chamber, the skimmer chamber opening radially inwardly toward the inside of the drum;
• an annular chamber is formed during in operation and is located between the siphon disk and the skimmer disk, the siphon disk and skimmer disks acting as axial boundaries for an axial area, and the annular chamber is further located between an inside radius of the lighter liquid phase in the axial area and an inner wall of the skimmer chamber in the axial area;
• a fluid feed pipe leading into the annular chamber to change a pressure on the annular chamber and to change at least one of a separation zone between the lighter and heavier phases and a pool depth in the drum;
• operating the centrifuge in a separating operation;
• and
• controlling the separating operation by changing a pressure in the annular chamber or by changing the rotational speed of the drum.