The Physical Chemistry Of The Hot Water Process

Abstract

The roles in the hot waterprocess ofsodium hydroxide, surfac-tants, watersolubleelectrolytesfinesolidsandelectricproper-ties of the bitumenlwater and solidslwater interfaces are examined. Recovery of bitumen from low-to medium-grade oil sands can be increased by ensuring the fine solids remain dis-persed during digestion by adjustment of digestion water salin-ity and pH. Recovery of bitumen from high-grade oil sands appears to be controlled by surfactants which affect bitumen-water interfacial tension and the size of bitumen dropletsformed during the initial separation of the bitumen from sand grains. Processing behaviour of mixtures of oil sands is explained within the framework of these mechanisms. Introduction In the past few years, there has been a renewed effort to under-stand the hot water process which is used by Suncor Inc. and Syn-crude Canada Ltd. to commercially extract bitumen from mined Athabasca oil sand. The process can be considered in terms of two distinct stages; separation of the bitumen from the sand fol-lowed by flotation which encompasses both primary flotation and scavenging. Separation is induced by mixing the oil sand in a conditioning drum with hot water and often a process d ait, usually sodium hydroxide. The conditioned slurry is pumped a primary separation vessel (PSV) where the bitumen froth is skimmed from the surface. The sand tailings which settle in the PSV are removed. The middlings (water) are pumped to a secon-dary recovery vessel where air is introduced through the bottom of the vessel, attaches to some of the suspended bitumen and causes it to float.The amount of sodium hydroxide added to the conditioning stage of the process is the major variable used to maximize recov-ery of bitumen. The addition rate historically has been based on empirical but sometimes imprecise correlations of oil sand grade with processability. Recently Schramm and co-workers proposed that the process could be optimized around the concentration of free surfactants formed due to reactions between sodium hydrox-ide and organic acids in the bitumen, and found in the tailings water(t).Even if the surfactant concentration in the tailings stream of a hot water processing plant could be accurately monitored there would be a delay between the time recovery fell below its opti Current Address: BASF Canada Inc.,Dispersions R&D, Sarnia,Ontario. Keywords: Bitumen recovery, Hot water process, Interfaces, Surfactants, Surfaces. _ mum level and an adjustment to the digestion stage of the process could be made. A model that is used to predict the best operat-ing conditions based upon properties of oil sand that are easily measured either during a coring program or on-line, would be beneficial compared to one which is used in a reactive mode. This paper describes a model for the hot water process based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) and Ionizable Surface Group theories that can be used to predict from concen-trations of inorganic salts in the digestion stage of the process, the conditions for maximizin...

Understanding Water‐Based Bitumen Extraction from Athabasca Oil Sands

“…In other cases, bitumen recovery was not affected up to 150 mM (3450 ppm) of sodium ion addition (in the form of NaHCO 3 ). Although adding NaHCO 3 would increase the slurry pH, a similar function to adding NaOH, this level of sodium addition was much higher than that in the transition/coagulated region (50-75 mM) even in the presence of 0.048 wt.% NaOH (of oil sands) (Takamura and Wallace, 1988).…”

“…Takamura and Chow (1983) ;Takamura, (1985); Takamura and Wallace, (1988) used the micro-disintegration experiment to examine the development and movement of the bitumen/water/sand three-phase contact line on an individual sand grain over a period of time.…”

“…Blending of different oil sands ores is practiced in commercial operations. Another method to improve bitumen recovery is to dilute the oil sands slurry with water to reduce the salinity of the oil sands slurry (Takamura and Wallace, 1988). This approach might not always be feasible in a commercial operation due to water supply issues.…”

On bitumen liberation from oil sands

“…Clark et al (1932) and Clark (1 949) showed that the bitumen recovery was poor under acidic conditions, but was greatly improved for pH above 7. Takamura et al (1983Takamura et al ( , 1988) have shown through a crumbling test that at a pH of 11.8, the bitumen recovery from oil sand is highest. The reason for high bitumen recovery in an alkaline aqueous solution was explained on the basis of disjoining pressure of water between the sand and bitumen.…”

Interaction between Bitumen and Fines in Oil Sands Extraction System: Implication to Bitumen Recovery

“…However, for poor processing ores, many technical challenges exist to achieve a satisfactory bitumen recovery and froth quality. The significant impact of chemical species and fine clays present in the slurry on oil sands ore processability has been recognized both in industrial operations and in laboratory tests (Sandford and Seyer, 1979;Sanford, 1983;Takamura and Wallace, 1988;Smith and Scharmm, 1992;Zhou et al, 1999). The difference in the processability between good and poor processing ores is of great socioeconomic importance.…”