Micropile Installation with Spoil Control at Logan Airport - Nicholson ...

DesilterThe desilting process makes use ofsmaller diameter (~4-in) hydrocyclones.In order to maintain the same overallflow rate it is commonly necessary toemploy several hydrocyclones in thedesilting system. Figure 9 is aphotograph of the system used. Similarto the desander, the denser solidcomponents leaving the hydrocyclone aredeposited on a screen with any materialthat passes the screen being recirculated.Many hydrocyclonesCentrifugeHydrocycloneFigure 8. The Desanding system.The final stage of treatment was acentrifuge system that employed a polymerflocculent. In concept, the operation of thecentrifuge is similar to the hydrocyclone inthat it use centrifugal forces to separatedenser materials. However, the centrifugeuses a spinning drum and thus inducesmuch more force than that obtained withthe hydrocyclone. The added polymerflocculent facilitated coagulation of theclay minerals such that the efficiency of thecentrifuge was greatly enhanced. Thecentrifuges employed at Logan is shown inFigure 10.Figure 9. The Desilting SystemFigure 10. The CentrifugesThe complete system is shownschematically in Figure 11 and aphotograph in Figure 12. Several largetanks are incorporated into the system toprovide needed storage for efficientoperation and the ability to accommodatepeak flow conditions. The effectivenessof this system in separating the spoils andin ultimately producing a clear liquid forreuse in the drilling operations is quiteremarkable. The capacity of the systemis such that it can process an incomingspoil stream of 60 gpm, per centrifuge.10