Treatment of thick fine tailings including chemical immobilization, polymer flocculation and dewatering

Abstract

A process for the treatment of thick fine tailings that include constituents of concern (CoCs) and suspended solids is provided. The process includes subjecting the thick fine tailings to treatments including chemical immobilization of the CoCs, polymer flocculation of the suspended solids, and dewatering. The chemical immobilization can include the addition of compounds enabling the insolubilization of the CoCs. Subjecting the thick fine tailings to chemical immobilization and polymer flocculation can facilitate production of a reclamation-ready material, which can enable disposing of the material as part of a permanent aquatic storage structure (PASS).

1 . A process for treating tailings, comprising:
 adding a flocculant to an in-line flow of material comprising tailings to produce a flocculating material;   subjecting the flocculating material to shear conditioning to form a conditioned flocculated material;   conveying the conditioned flocculated material to a pit under shear rate and energy conditions that are lower than those of the shear conditioning used to form the conditioned flocculated material; and   discharging the conditioned flocculated material into the pit to enable water separation.   
     
     
         2 . The process of  claim 1 , wherein the shear conditioning is pipeline shear conditioning provided to put the conditioned flocculated material in a water release zone upon discharging into the pit, thereby producing a water component and a solids-enriched component comprising flocculated solids. 
     
     
         3 . The process of  claim 2 , wherein the pipeline shear conditioning is performed to:
 produce a gel-state material having increased yield stress; and then   produce the conditioned flocculated material having an ungelled state and a decreased yield stress compared to the gel-state material.   
     
     
         4 . The process of  claim 2 , wherein the conditioned flocculated material being in the water release zone results in an initial clay-to-water ratio (CWR) in the solids-enriched component of at least 0.55 or at least 0.65. 
     
     
         5 . The process of  claim 1 , wherein the conveying of the conditioned flocculated material to the pit is performed under non-turbulent flow conditions. 
     
     
         6 . The process of  claim 1 , further comprising forming a permanent aquatic storage structure (PASS) from the conditioned flocculated material that is discharged in the pit, the PASS comprising:
 a water cap formed by the water released from the conditioned flocculated material; and   a consolidating solids-rich lower stratum below the water cap, formed by settling and consolidation of the conditioned flocculated material.   
     
     
         7 . The process of  claim 1 , wherein the in-line flow of material comprises chemically immobilized contaminants of concern. 
     
     
         8 . The process of  claim 1 , wherein the flocculant comprises an anionic polymer flocculant. 
     
     
         9 . The process of  claim 8 , wherein the anionic polymer flocculant comprises a sodium-based or calcium-based polyacrylamide-polyacrylate co-polymer with high molecular weight. 
     
     
         10 . A process for treating fine tailings, comprising:
 adding in-line a coagulant to a fine tailings flow to cause coagulation and to form a coagulated tailings material flow;   adding in-line a flocculant to the coagulated tailings material flow to produce a flocculating tailings material flow;   subjecting the flocculating tailings material flow to shear conditioning to produce a conditioned flocculated tailings material;   dewatering the conditioned flocculated tailings material to form:
 water; and 
 a solid-enriched component comprising flocculated solids. 
   
     
     
         11 . The process of  claim 10 , wherein the shear conditioning is pipeline shear conditioning that is conducted to increase a yield stress of the flocculating tailings material flow to a maximum where the flocculating tailings material flow presents gel-like characteristics, and then to reduce the yield stress and effect floc breakdown to form the conditioned flocculated tailings material in a water release zone. 
     
     
         12 . The process of  claim 10 , further comprising conveying the conditioned flocculated tailings material under shear rate and energy conditions that are lower than those of the shear conditioning. 
     
     
         13 . The process of  claim 12 , wherein the conveying of the conditioned flocculated tailings material is performed under non-turbulent flow conditions. 
     
     
         14 . The process of  claim 10 , wherein the dewatering comprises:
 continuously depositing the conditioned flocculated tailings material onto a sub-aerial deposition area to allow an initial water release from the conditioned flocculated tailings material and to start forming the solids-enriched component.   
     
     
         15 . The process of  claim 14 , wherein the sub-aerial deposition area is a pit and the process further comprises forming a permanent aquatic storage structure (PASS) from the conditioned flocculated tailings material that is discharged in the pit, the PASS comprising:
 a water cap formed by the water released from the conditioned flocculated tailings material; and   a consolidating solids-rich lower stratum below the water cap, formed by settling and consolidation of the solid-enriched component.   
     
     
         16 . The process of  claim 14 , wherein the sub-aerial deposition area has a sloped base to facilitate release water draining from the solids-enriched component. 
     
     
         17 . The process of  claim 16 , wherein the sub-aerial deposition area is a sloped sub-aerial beach and the process further comprises forming a thin lift via deposition of the conditioned flocculated tailings material flow to allow water to drain from the thin lift and form the solid-enriched component. 
     
     
         18 . The process of  claim 17 , wherein the thin lift is a lower thin lift and the process further comprises stacking at least one additional thin lift on a top of the lower thin lift once the lower thin lift is dewatered, to form multiple thin lifts. 
     
     
         19 . The process of  claim 18 , wherein each thin lift is a 2 cm lift. 
     
     
         20 . The process of  claim 10 , comprising further dewatering of the solid-enriched component via freeze-thaw mechanism. 
     
     
         21 . The process of  claim 10 , comprising further dewatering of the solid-enriched component via evaporation mechanism, 
     
     
         22 . The process of  claim 10 , comprising further dewatering of the solid-enriched component via permeation mechanism. 
     
     
         23 . The process of  claim 10 , wherein the conditioned flocculated tailings material has a target floc size that is greater than 100 pm upon discharge. 
     
     
         24 . The process of  claim 23 , wherein the target floc size is greater than 150 pm. 
     
     
         25 . The process of  claim 23 , wherein the target floc size is greater than 200 pm. 
     
     
         26 . The process of  claim 23 , wherein the target floc size is greater than 250 pm.