Date of Award
Doctor of Philosophy
Cyrogenic Tar Sand Separation is a novel technique to access the vast energy potential of the Alberta Tar Sands. In this process tar sand is ground at about -50(DEGREES)C. At this temperature the tar is more brittle and weaker than the sand. Thus, the tar is liberated from the sand and ground to fine particles, which can be separated from the sand. The technical performance of this process was studied, and a general grinding and liberation model was developed, which simulates this and other two component grinding processes.;Four grinding/separation techniques were studied: Fluidized Bed Grinder (a stirred fluidized bed with steel balls) and Spouted Bed grinding combined with tar entrainment, and High Speed Impeller and Ball Mill grinding combined with sieving. The spouted bed gave the highest quality of separation, with a tar purity of 84%, at a tar recovery of 90%. The ball mill gave the lowest separation quality with a tar purity of 60% at 80% tar recovery, and 35% at 90% recovery. A maximum tar recovery of 94%, at a tar purity of 65%, was obtained in the fluidized bed grinder. The spouted bed gave the lowest rate of separation, with a typical processing time of 14 hours to obtain 90% tar recovery, versus 2-7 hours for the other mills. However, proposed modifications should increase this rate substantially.;In the grinding and liberation model, a distinction is made between tar sand agglomerates, containing more than one sand grain, and single sand particles, coated with a thin tar layer. Grinding of each particle type is described by a set of conventional first order rate equations, although with non-normalized breakage distribution functions for the agglomerates. The processes are interconnected by a continuous transfer of agglomerate grinding products to the tar coated sand particles. The simultaneous attrition of the tar layer on the sand particles is described by a fourth order rate equation, as a function of the remaining tar.;Simulation, using this model and experimentally determined parameters, gave an excellent agreement with measured size distributions (from 63-2000 (mu)m) and tar concentrations (as a function of particle size and processing time), and provided substantial insight into the various tar sand separation experiments.
Welmers, Adrianus, "Two Component Grinding And Liberation Model And Experimental Studies Of Cryogenic Tar Sand Separation" (1983). Digitized Theses. 1247.