A horizontal centrifuge, method and system of use, recovers weighting materials from a returned drilling fluid slurry. A clean fluid is delivered, through a clean fluid pipe arranged axially at the hub, to solids discharge ports. The clean fluid is directed radially and circumferentially outwardly at the discharge ports for mixing homogeneously with the recovered weighting materials from forming a reconstituted weighted drilling mud. The reconstituted weighted drilling mud can then be delivered to a rig mud tank for use in a drilling operation. In the system, a drilling fluid and low gravity solids, which are separated from the weighting materials in the horizontal centrifuge, being a first centrifuge, are directed to a second centrifuge which is capable of removing the low gravity solids, thereby producing a clean fluid. The clean fluid is recycled to the first centrifuge for delivery through the clean fluid pipe.

The invention relates to a decanter centrifuge with a rotating bowl (1) provided with at least one solids discharge port (11) and at least one clarified liquid discharge port (15) and a screw conveyor (2) disposed coaxially within said rotating bowl rotated in the same direction with a differential rotational speed, where a feed suspension to be separated is introduced into a ring shaped space formed between said rotating bowl (1) and said screw conveyor (2) through a central feed pipe fixed to the end of the screw conveyor and supported in at least one bearing and can be separated by centrifugal force into a solid and a liquid phase so that said solid phase is discharged from said solid discharge port and said liquid phase is discharged from said clarified liquid discharging apparatus. According to the present invention it is characterized by a liquid phase conduit (4) arranged in the hollow shaft of the rotating bowl (1) guiding the liquid phase outside of the bearings (16, 18), a liquid phase discharge valve (14) provided outside the bearing on the side facing away from the bowl (1) and screw (2) and a sealing (6) at the end of the feed pipe (10) surrounded by the liquid phase conduit. So it is possible to pressurize the system and to use the pressure from the feed pump to support the cake transport in the solids transporting part of the bowl, thereby eliminating the need for variable speed conveyor control and equipment.

A solid bowl screw centrifuge includes a housing and a rotor rotatably mounted in the housing. The centrifuge has a rotatable drum having an axis of rotation, the drum having a cylindrical section having a length L.sub.1 and a conical section having a length L.sub.2. The centrifuge also has a first inlet for feeding a suspension to be processed into the drum and a liquid outlet arranged in the cylindrical section of the drum and a solids outlet arranged in the conical section of the drum. A screw is arranged in the drum and rotatable at a differential speed relative to the rotatable drum, the drum and the screw together forming the rotor. The centrifuge also a second inlet for supplying an additive to a solid phase within the drum.

Accelerators and conveyor bodies for a decanter centrifuge are discussed. A decanter centrifuge may have a bowl forming a sedimentation chamber with a cake discharge and a centrate discharge; a screw conveyor within the sedimentation chamber, the screw conveyor having a conveyor body and a flight, the conveyor body defining a feed chamber; and an accelerator within the feed chamber for increasing the angular velocity of a feed mixture prior to entering the sedimentation chamber, the accelerator comprising an impeller with plural vanes, the plural vanes being releasably mounted to the conveyor body and sized to pass through an axial end of the conveyor body.