Caustic dosing for primary extraction in oil sands processing

Abstract

Described herein are methods and systems in which the alkaline dosage used for oil sands slurries fed into a primary separation vessel (PSV) is controlled based on a combination of clay content and process water characteristics. The dosage control can include operating within different dosage envelopes that correspond to respective combinations of clay content and dissolved solids content. Enhanced bitumen separation by the PSV and usage of alkaline compounds, such as caustic, can be facilitated by such methods.

1 . A process for producing a bitumen product from oil sands, the process comprising:
 supplying an oil sands slurry comprising the oil sands and process water to a primary separation vessel (PSV) configured to produce a bitumen froth stream, a middlings stream, and a tailings stream;   controlling a dosage of an alkaline compound for addition to the oil sands slurry, comprising:
 determining a clay content of the oil sands slurry; 
 determining a dissolved solids content of the process water; and 
 determining the dosage of the alkaline compound based on the clay content and on the dissolved solids content to achieve a target recovery level of bitumen in the bitumen froth; 
   separating the oil sands slurry in the PSV to form the bitumen froth stream having the target recovery level;   subjecting the bitumen froth stream to froth treatment to produce solvent diluted bitumen and solvent extraction tailings; and   recovering solvent from the solvent diluted bitumen to produce the bitumen product.   
     
     
         2 . The process of  claim 1 , wherein dosing the alkaline compound comprises:
 determining operating envelopes based on the clay content and the dissolved solids content; and   determining the dosage of the alkaline compound for addition to the oil sands slurry according to one of the operating envelopes to achieve the target recovery level of bitumen; and   adding the alkaline compound to the oil sands slurry based on the determined dosage.   
     
     
         3 . The process of  claim 2 , wherein the dosage of the alkaline compound is within a low dosage interval, an intermediate dosage interval, or a high dosage interval, and each one of the low dosage interval, the intermediate dosage interval, and the high dosage interval corresponds to at least one of the operating envelopes. 
     
     
         4 . The process of  claim 3 , wherein:
 when at least one of the clay content and the dissolved solids content is below a lower predetermined clay content threshold and a lower predetermined dissolved solids content threshold, respectively, the dosage of the alkaline compound added to the oil sands slurry is zero; and   when the clay content is above the lower predetermined clay content threshold and the dissolved solids content is above the lower predetermined dissolved solids content threshold, the dosage of the alkaline compound added to the oil sands slurry is within one of the low dosage interval, the intermediate dosage interval, and the high dosage interval.   
     
     
         5 . The process of  claim 4 , wherein when both the clay content and the dissolved solids content are below the lower predetermined clay content threshold and the lower predetermined dissolved solids content threshold, respectively, the dosage of the alkaline compound added to the oil sands slurry is zero. 
     
     
         6 . The process of  claim 4 , wherein when:
 the clay content is within a first clay content range below the lower predetermined clay content threshold; or   the clay content is within a second clay content range and the dissolved solids content is within a first dissolved solids content range below the lower predetermined dissolved solids content threshold; or   the clay content is within a third clay content range and the dissolved solids content is within the first dissolved solids content range below the lower predetermined dissolved solids content threshold;   the dosage of the alkaline compound is zero.   
     
     
         7 . The process of  claim 6 , wherein when:
 the clay content is within the second clay content range and the dissolved solids content is within a second dissolved solids content range; or   the clay content is within the second clay content range and the dissolved solids content is within a third dissolved solids content range; or   the clay content is within the third clay content range and the dissolved solids content is within the second dissolved solids content range; or   the clay content is within a fourth clay content range and the dissolved solids content is within the first dissolved solids content range below the lower predetermined dissolved solids content threshold;   the dosage of the alkaline compound is above zero and within a low dosage interval.   
     
     
         8 . The process of  claim 7 , wherein when:
 the clay content is within the second clay content range and the dissolved solids content is within a fourth dissolved solids content range above a higher predetermined dissolved solids content threshold; or   the clay content is within the third clay content range and the dissolved solids content is within the third dissolved solids content range; or   the clay content is within the fourth clay content range and the dissolved solids content is within the second dissolved solids content range;   the dosage of the alkaline compound is above zero and within an intermediate dosage interval.   
     
     
         9 . The process of  claim 8 , wherein when:
 the clay content is within the third clay content range and the dissolved solids content is within the fourth dissolved solids content range above the higher predetermined dissolved solids content threshold; or   the clay content is within the fourth clay content range and the dissolved solids content is within the third dissolved solids content range; or   the clay content is within a fifth clay content range above a higher predetermined clay content threshold and the dissolved solids content is within the first dissolved solids content range below the lower predetermined dissolved solids content threshold;   the dosage of the alkaline compound is above zero and within a high dosage interval.   
     
     
         10 . The process of  claim 9 , wherein when:
 the clay content is within the fourth clay content range and the dissolved solids content is within the fourth dissolved solids content range above the higher predetermined dissolved solids content threshold;   the dosage of the alkaline compound is above the high dosage interval.   
     
     
         11 . A process for producing a bitumen product from oil sands, the process comprising:
 mining oil sands ore to obtain mined oil sands ore;   crushing the mined oil sands ore in a mixing unit to form crushed ore;   subjecting the crushed ore to sizing and addition of process water to form an oil sands slurry;   supplying the oil sands slurry to a primary separation vessel (PSV);   dosing an alkaline compound for addition into the oil sands slurry based on:
 determining a clay content of the oil sands slurry; 
 determining a dissolved solids content of the process water; 
 adding a dosage of the alkaline compound based on the clay content and the dissolved salt content, wherein: 
 the dosage of the alkaline compound is determined based on the clay content and the dissolved solids content; and 
 the dosage of the alkaline compound is performed based on alkaline dosage intervals corresponding to respective determined combinations of clay content ranges and dissolved solids content ranges; and 
   separating the oil sands slurry in the PSV to form a bitumen froth stream;   subjecting the bitumen froth stream to froth treatment to produce solvent diluted bitumen and solvent extraction tailings; and   recovering solvent from the solvent diluted bitumen to produce the bitumen product.   
     
     
         12 . The process of  claim 11 , wherein during a start-up phase of the process, the process water comprises fresh water and the dissolved solids content is below a lower predetermined dissolved solids content threshold. 
     
     
         13 . The process of  claim 12 , wherein after the start-up phase, the process water comprises recycled process water and the dissolved solids content increases over time such that during a second operating phase of the process, the dissolved solids content exceeds the lower predetermined dissolved solids content threshold. 
     
     
         14 . The process of  claim 13 , wherein the recycled process water is recycled from a tailings pond. 
     
     
         15 . The process of  claim 13 , wherein determining the dissolved solids content of the process water comprises determining the dissolved solids content of the recycled process water. 
     
     
         16 . The process of  claim 13 , wherein during the second operating phase of the process, the process water comprises exclusively recycled process water, and the dissolved solids content of the process water is above the predetermined dissolved solids content threshold. 
     
     
         17 . The process of  claim 11 , further comprising:
 transmitting information related to at least one of the clay content and the dissolved solids content to an analyzer operatively connected to at least one controller; and   automatically dosing the alkaline compound for addition in the oil sands slurry through the at least one controller in response to the at least one of the clay content and the dissolved solids content.   
     
     
         18 . The process of  claim 11 , further comprising determining a water content of the oil sands slurry. 
     
     
         19 . The process of  claim 11 , further comprising supplying dilution water to the oil sands slurry upstream of the PSV. 
     
     
         20 . The process of  claim 11 , wherein the oil sands slurry is a diluted oil sands slurry, the clay content is measured on the diluted oil sands slurry, and the alkaline compound is added to at least one of the diluted oil sands slurry and the PSV. 
     
     
         21 . The process of  claim 11 , wherein determining the clay content comprises obtaining a clay content indicator. 
     
     
         22 . The process of  claim 11 , wherein determining the clay content of the mined ore, the crushed ore, and/or the oil sands slurry is conducted in-line. 
     
     
         23 . A process for producing a bitumen product from oil sands, comprising:
 mixing oil sands ore with process water to produce an oil sands slurry;   supplying the oil sands slurry to a primary separation vessel (PSV);   determining a clay content of the oil sands slurry and a dissolved solids content of the process water of the slurry;   adding an alkaline compound to the oil sands slurry according to an alkaline dosage, wherein:
 during a start-up phase, the dissolved solids content is below a lower dissolved solids content threshold and the alkaline dosage is maintained at zero; 
 during a second operating phase, the dissolved solids content is above the lower dissolved solids content threshold and the alkaline dosage is increased above zero when the clay content is above a lower clay content threshold; 
   separating the oil sands slurry in the PSV to produce a bitumen froth stream, a middlings stream and a tailings stream;   subjecting the bitumen froth stream to froth treatment to produce solvent diluted bitumen and solvent extraction tailings; and   recovering solvent from the solvent diluted bitumen to produce the bitumen product.   
     
     
         24 . The process of  claim 23 , wherein the lower clay content threshold is about 0.8 mg/100 g. 
     
     
         25 . The process of  claim 23 , wherein the lower dissolved solids content threshold is about 1250 mg/L. 
     
     
         26 . The process of any  claim 23 , wherein measuring the clay content comprises using a methylene blue index (MBI) technique, an NIR technique or a K40 technique. 
     
     
         27 . The process of  claim 23 , wherein the predetermined dissolved solids content threshold is a predetermined total dissolved salts threshold. 
     
     
         28 . The process of  claim 23 , wherein during the start-up phase, the process water comprises fresh water. 
     
     
         29 . The method of  claim 23 , wherein after the start-up phase, the process water comprises recycled process water and the dissolved solids content increases over time such that at the second operating phase the dissolved solids content exceeds the lower predetermined dissolved salt content threshold. 
     
     
         30 . The method of  claim 29 , wherein the recycled process water is recycled from a tailings pond.