In many cases the recovered solids from the hydrocyclone are fed to a dewatering shaker that is outfitted with as fine a screen as possible. It is extremely important to remember to use separate compartments and centrifugal pumps for each size hydrocyclone. Each stage of hydrocyclone should be sized out to process 125 to 150 percent of the volumetric circulating and dry tonnage rate to allow them to work more efficiently and reduce the likelihood of plugging. Cleaned fluid should always be discharged downstream.
The trenchless industry is seeing an increased demand for high-speed centrifuges to help remove colloidal size solids that can wreak havoc on a mud system if they are not removed. A centrifuge is a high speed, high “G” force rotating bowl and scroll assembly capable of separation down to 5 to 7 microns without chemical enhancement.
In this process, slurry is fed through a feed tube into the rotating bowl, where centrifugal force propels the ultra-fine solids outward against the interior wall of the bowl. A rotating conveyor in the center of the bowl drives the recovered solids toward the solids discharge ports, where they are expelled into a chute. Liquid is retained in the pool and discharged through the liquid discharge ports at the opposite end of the bowl.
If desired, polymer injection or “dewatering” units can be integrated with centrifuges to remove solids down to 0um. Polymer injected in between the feed pump and inlet of the centrifuge will flocculate the reactive ultra-fine solids, forming a heavy enough mass for the centrifuge to capture. If done properly, the result can be a semi-clear effluent that may be more readily disposed of or returned to the system. This can help drastically reduce or eliminate expensive drilling mud disposal.
