Barite recovery decanting centrifuge

Jan. 13, 2013 - PRLog -- A Decanting Centrifuges so named because it Decants, or removes, free liquid from separated solids. A decanting centrifuge consists of a conveyor screw inside a rotating bowl. Decanting centrifuges operate on the principle of exposing the process fluid to increased “G-forces”, thus accelerating the settling rate of solids in the fluid. A rotating bowl creates high G-forces and forms a liquid pool inside the bowl.

GN centrifuge: http://www.gnsolidscontrol.com/decanting-centrifuge/

The free liquid and finer solids flow toward the larger end of the centrifuge and are removed through the effluent overflow weirs. The larger solids settle against the bowl wall, forming a layer. These solids are pushed by a screw conveyor across a drainage deck, or beach.

Dewatering actually takes place on the beach, with the decanted solids discharged through a series of underflow ports. A gear box changes the relative speed of the conveyor to the bowl, causing them to rotate at slightly different rates. This speed differential is required to convey and discharge solids. The bowl and conveyor are rotated at speeds between 1500 and 4000 rpm depending on bowl diameter. This rotation develops centrifugal force sufficient to settle solids along the inner surface of the bowl wall. A gearbox is used to rotate the conveyor and bowl at slightly different speeds (slower or faster). This speed differential conveys and discharges solids from the machine.

Mud, (sometimes diluted with water), is pumped into the conveyor hub through the feed tube. As the conveyor rotates, centrifugal force pushes the feed mud out the feed ports into the bowl. The heavy, coarse particles in the mud are forced against the inner surface of the bowl, where the scraping motion of the conveyor blades moves them toward the solids discharge ports. A drainage deck, called the beach, is where dewatering of the solids actually takes place. The deliquified solids are then discharged through a series of underflow ports.

The light, fine solids tend to remain in suspension in the pools between the conveyor flights and are carried out the overflow ports along with the liquid phase of the mud. The operating principle is similar to that of the cyclone, but it is mechanical rotation rather than fluid head which induces the centrifugal force required to accelerate the particle settling rate. Residence time of fluid in the bowl and a more “gentle” separation environment differentiate separation in a centrifuge from that of a cyclone.

Centrifuges make the finest cut of any separation device used on the rig, usually 2–5 microns.

Bowl sizes in common oilfield applications include diameters of 14”, 15”, 18”, and 24”. Larger 24” diameter units generally have the highest liquid throughput and solids tonnage capacity. In unweighted mud applications, feed mud capacity can range from 25–250 gpm, depending on unit capability and fluid requirements. Solids tonnage rates range from 1.25 tons/hour to 8 tons/hour. In weighted mud applications, feed mud capacity rarely exceeds 25 GPM. Total liquid throughput may be as high as 40 GPM, including dilution liquid. Dilution liquid is required to compensate for increasing viscosity, generally associated with increasing mud weight, in order to maintain satisfactory separation efficiency. The raw mud feed rate is substantially decreased as mud weight increases.

In field operation, the decanting centrifuge is fitted with a housing over the bowl, liquid and solids collection hoppers, skid, feed slurry pump, raw mud and dilution liquid connections, power source, meters and controls.

For more info, please contact GN Solids Control Co.,Ltd.
http://www.gnsolidscontrol.com/contact/