Liquid recovery system

Abstract

A system and process for removing solids from raw, untreated liquid that combines mechanical techniques, such as via shakers, hydrocyclones and/or centrifuges, with an additive technique for removal of smaller solids. The additive is selected according to the application. In drilling mud applications, preferred additive embodiments are polyaluminum chloride or polyacrylamide flocculants. Preferably, liquid additive precursors are pre-mixed separately and are then blended before injection into the solids removal process. Some embodiments provide an externally-actuated rack and pinion mud screen lock for simplified screen lockdown on shakers. Some embodiments provide a separate preliminary processing and feed system for pretreatment of the raw, untreated liquid.

I claim: 
     
         1 . A method for removing solids from an untreated liquid, the method comprising the steps of:
 (a) passing the untreated liquid through at least two treatment shakers to yield a first treated liquid;   (b) passing the first treated liquid through at least two hydrocyclones to yield a second treated liquid;   (c) adding a particle-removing additive to the second treated liquid to yield a third treated liquid; and   (d) passing the third treated liquid through at least two centrifuges to yield a fourth treated liquid.   
     
     
         2 . The method of  claim 1 , in which the particle-removing additive in step (c) includes at least one flocculant selected from the group consisting of:
 (1) a polyaluminum chloride; and   (2) a polyacrylamide;   and in which the particle-removing additive is pre-mixed with a precursor liquid prior to addition to the second treated liquid.   
     
     
         3 . The method of  claim 1 , in which the particle-removing additive in step (c) is a blend of at least two compounds, wherein each compound is pre-mixed with its own precursor liquid prior to blending together. 
     
     
         4 . The method of  claim 3 , in which at least one of the compounds includes a flocculant selected from the group consisting of:
 (1) a polyaluminum chloride; and   (2) a polyacrylamide.   
     
     
         5 . The method of  claim 1 , in which, prior to step (a), a preliminary liquid passes through a separate preliminary processing and feed system (PPFS) to yield the untreated liquid, the PPFS including at least one pretreatment shaker. 
     
     
         6 . The method of  claim 5 , in which the PPFS further includes at least one input tank for receiving the preliminary liquid, and at least one pretreated liquid holding tank for receiving the untreated liquid. 
     
     
         7 . The method of  claim 6 , in which at least one of the input tank and the pretreated liquid holding tank are located at least partially below grade level. 
     
     
         8 . The method of  claim 6 , in which at least one auger delivers the preliminary liquid from the input tank to the pretreatment shaker. 
     
     
         9 . The method of  claim 8 , in which at least one auger is a progressive pitch auger with a smaller pitch deployed near the input tank and a larger pitch deployed near the pretreatment shaker. 
     
     
         10 . The method of  claim 1 , in which at least one treatment shaker provides an externally-actuated screen lock, the screen lock comprising:
 a wedge, the wedge providing a rack disposed on a generally upward-facing side thereof;   a lug, the lug rigidly fixed to the treatment shaker at a predetermined lug location inside the pretreatment shaker;   a pinion, the pinion having an elongate central axial pinion shaft, the pinion shaft received inside a corresponding hole through the treatment shaker such that the pinion is located inside the treatment shaker and the pinion shaft is rotatable from outside the treatment shaker;   wherein the pinion engages the rack such that rotation of the pinion against the rack displaces the wedge laterally;   such that when the wedge is interposed between the lug and a screen resting atop a screen frame, rotation of the pinion shaft from outside the pretreatment shaker compresses the screen against the screen frame.   
     
     
         11 . The method of  claim 1 , wherein said method is continuous. 
     
     
         12 . The method of  claim 5 , wherein said method is continuous. 
     
     
         13 . The fourth treated liquid product of the process according to  claim 1 . 
     
     
         14 . The fourth treated liquid product of the process according to  claim 2 .