System and Integrated Method For Treatment of Tailings From Bitumen Extraction Process

Abstract

A system and method for treating tailings from a bitumen froth treatment process such as TSRU tailings. The tailings are dewatered to at least 50 wt percent solids content, and then combusted to convert kaolin in the tailings into metakaolin. Calcined fines and heavy minerals may be recovered from the combustion products, namely from the flue gas or bottom ash or both. A trafficable deposit may be formed from the ash when mixed with tailings, such as mature fine tailings (MFT).

What is claimed is: 
     
         1 . A method for treating tailings from a froth treatment process, the tailings comprising sand, clay comprising kaolin, water, and hydrocarbons, the method comprising:
 dewatering the tailings comprising a primary water separation and a secondary water separation to produce dewatered tailings and recovered water, the dewatered tailings having a hydrocarbon content and a solids content to support combustion of the dewatered tailings;   combusting the hydrocarbons in the dewatered tailings in a combustion chamber to cause a dehydration reaction converting kaolin into metakaolin and to produce fly ash and bottom ash; and   recovering calcined fines comprising metakaolin from at least one of the fly ash and the bottom ash.   
     
     
         2 . The method of  claim 1 , wherein the dewatered tailings have a solids content of at least 40 wt percent following the primary water separation. 
     
     
         3 . The method of  claim 1 , wherein combusting occurs at 500° C. to 1000° C. 
     
     
         4 . The method of  claim 1 , further comprising adding fine tailings to the combustion chamber to one of increase the kaolin content and control a maximum combustion temperature, wherein the fine tailings comprise at least one of a middling stream, froth flotation tailings, paraffinic froth treatment tailings prior to dewatering, naphthenic froth treatment tailings, and mature fine tailings. 
     
     
         5 . The method of  claim 4 , wherein the fine tailings stream has been at least partially dewatered or concentrated. 
     
     
         6 . The method of  claim 4 , further comprising adding at least one of water and a substantially hydrocarbon free wet tails to the combustion chamber to control a maximum combustion temperature. 
     
     
         7 . The method of  claim 4 , wherein the combustion is staged to control a maximum combustion temperature. 
     
     
         8 . The method of  claim 1 , wherein the combustion chamber comprises a combustion bed comprising sand and fines and wherein the combustion bed comprises limestone for in-situ sulfur removal. 
     
     
         9 . The method of  claim 1 , wherein the dewatered tailings are fluidized for combustion, with air having an air velocity of between 0.1 m/s and 2.0 m/s. 
     
     
         10 . The method of  claim 1 , further comprising combining the bottom ash and bitumen extraction tailings for solidifying or stabilizing the bitumen extraction tailings. 
     
     
         11 . The method of  claim 1 , further comprising recovering the calcined fines comprising metakaolin from the bottom ash and separating the metakaolin from the calcined fines. 
     
     
         12 . The method of  claim 11 , further comprising one of (i) adding the recovered calcined fines to bitumen extraction tailings for solidifying or stabilizing the bitumen extraction tailings and (ii) adding the recovered calcined fines to cement, cementitious materials or concrete. 
     
     
         13 . The method of  claim 11 , further comprising one of (i) adding the metakaolin separated from the calcined fines to bitumen extraction tailings for solidifying or stabilizing the bitumen extraction tailings and (ii) adding the metakaolin separated from the calcined fines to cement, cementitious materials or concrete. 
     
     
         14 . The method of  claim 1 , further comprising one of (i) adding the fly ash to bitumen extraction tailings for solidifying or stabilizing the bitumen extraction tailings and (ii) adding the fly ash to cement, cementitious materials or concrete. 
     
     
         15 . The method any  claim 1 , further comprising recovering the calcined fines from the fly ash and one of (i) separating the metakaolin from the calcined fines, (ii) adding the recovered calcined fines to bitumen extraction tailings for solidifying or stabilizing the bitumen extraction tailings and (iii) adding the recovered calcined fines to cement, cementitious materials or concrete. 
     
     
         16 . The method of  claim 15 , further comprising one of adding the metakaolin separated from the calcined fines to bitumen extraction tailings for solidifying or stabilizing the bitumen extraction tailings and adding the metakaolin separated from the calcined fines to cement, cementitious materials or concrete. 
     
     
         17 . The method of any  claim 1 , further comprising mixing a tailings stream, a chemical modifier and at least one of the fly ash and the bottom ash to provide a trafficable deposit. 
     
     
         18 . The method of  claim 17 , wherein the chemical modifier one of comprises a sodium silicate solution and is caustic. 
     
     
         19 . The method of  claim 17 , wherein the tailings stream comprises mature fine tailings having substantially 30 wt % solids content. 
     
     
         20 . A system for treating tailings from a froth treatment process, the tailings comprising sand, clay comprising kaolin, water, and hydrocarbons, the system comprising:
 a dewatering unit comprising a primary water separation unit and a secondary water separation unit for removing water from a tailings stream, producing a dewatered tailings stream and a tailings water stream;   a combustion chamber for combusting the dewatered tailings stream, carrying out a chemical reaction whereby kaolin converts to metakaolin, and producing a fly ash and a bottom ash; and   a fly ash recovery unit for recovering calcined fines comprising metakaolin from the fly ash.   
     
     
         21 . The system of  claim 20 , further comprising one of (i) a metakaolin recovery unit for recovering metakaolin from the calcined fines and (ii) a bottom ash recovery unit for recovering metakaolin from the bottom ash. 
     
     
         22 . The system of  claim 20 , wherein one of the primary water separation unit provides thickener underflow having a solids content of at least 40 wt % and the secondary water separation unit provides a high solids content stream having a solids content of at least 50 wt %. 
     
     
         23 . The system of  claim 20 , wherein the secondary water separation unit provides cake having a solids content of at least 60 wt %. 
     
     
         24 . The system of  claim 20 , wherein the dewatering unit comprises a thickener unit for primary water separation and a centrifuge unit for secondary water separation and wherein one of (i) the dewatering unit comprises a thickener unit for primary water separation and a filter unit for secondary water separation and (ii) the dewatering unit comprises a thickener unit for primary water separation and an air drying unit for secondary water separation. 
     
     
         25 . The system of  claim 25 , wherein the air drying unit is configured to deposit the dewatered tailings on the ground for moisture release by evaporation to provide dried material. 
     
     
         26 . The system of  claim 25 , wherein the thickener unit uses at least one of a flocculent, a coagulant, and dilution water to flocculate fine particles for removal and wherein the flocculent and the coagulant are added to the thickener unit at one of a single injection point and multiple injection points. 
     
     
         27 . The system of  claim 26 , wherein the at least one of the flocculent and the coagulant are added upstream of the thickener unit at one or more locations. 
     
     
         28 . The system of any one of  claims 26 , wherein the dilution water comprises one of a portion of primary water from the thickener unit and recovered water from the dewatering unit. 
     
     
         29 . A method for treating tailings from a froth treatment process to provide a trafficable deposit, comprising mixing the tailings with combustion ash and a chemical modifier. 
     
     
         30 . A method for treating TSRU tailings to provide a trafficable deposit, comprising:
 receiving a TSRU tailings stream;   dewatering the TSRU tailings stream to provide cake having at least 50% solid content;   combusting the cake at between about 800° C. and about 900° C., to provide fly ash and bottom ash;   mixing the bottom ash or fly ash or both with the tailings to provide the trafficable deposit.   
     
     
         31 . The method of  30 , further comprising mixing a chemical modifier with the ash and tailings.