Specific Heats of Athabasca Oil Sands And Components

Abstract

Abstract We have measured specific heats of high-grade, medium-grade and low-grade samples of Athabasca oil sands over the temperature range 50–300°C. along with specific heats of components (coarse solids, fine solids and bitumen) over this same temperature range. It has been found that the specific heats of oil sands can be represented accurately as appropriate sums of the specific heats of components. Equations for convenient calculatations of all of these specific heats at temperatures to 300°C are given. Introduction Both commercial plants and all pilot plants currently in operation for the production of bitumen from the oil sands and heavy oil deposits in Alberta make use of thermal methods. Both Syncrude and Suncor use the hot water process in their commercial plants that separate bitumen from mined oil sands. Direct coking of mined oil sands has reached the pilot-plant stage. Various pilot-plant operations for in-situ production are based on steam injection or underground combustion or some combination of these methods. We cite a few useful reviews(l-4). Among the parameters needed for proper design and assessment of all thermal methods are specific heats of the material to be heated. We have therefore measured specific heats of samples of Athabasca oil sands having three different compositions. To make our results applicable to a wide range of oil sands having different compositions, we have also measured specific heats of components of oil sands and have demonstrated that the specific heats of whole oil sands can be represented as appropriate sums of specific heats of their components. We have chosen differential scanning calorimetry as our principal method for obtaining specific heats of oil sands and components. This method offers the advantages of being reasonably fast and makes use of instrumentation that is commercially available so that others may conveniently extend our work. On the other hand, it must be noted that there are two problems to consider in connection with measurements made by this method. Most researchers interested in accurate thermodynamic data have regarded differential scanning calorimetry as an unsatisfactory method, largely on the basis of inaccurate data published a decade and more ago. More recently, as a result of improvements in the instruments and greater care in operation, it has been demonstrated that differential scanning calorimetry can yield thermodynamically accurate results, as summarized in several papers(5–11). Because oil sands are obviously non-homogeneous, the small samples ordinarily used in differential scanning calorimetry can lead to misleading results. We have minimized this problem by using larger-than-usual samples (20–55 mg) and by averaging the results obtained on several different calorimetric samples taken from the same bulk sample. In order to obtain a check on the validity of our minimization of this problem of small sample size and non-homogeneity, we have also made a few measurements with larger calorimeters. Experimental Most of our calorimetric measurements of specific heats have been made with a Perkin-Elmer DSC-2 differential scanning calorimeter, with output recorded on a Perkin-Elmer single-channel multi-range thermal analysis recorder.