Two Component Grinding And Liberation Model And Experimental Studies Of Cryogenic Tar Sand Separation

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

Organizational persistence and change: A case study of a community college

This longitudinal case study examined the origins, growth, and development of one community college in Michigan, North Central Michigan College (NCMC). The purpose of the study was to understand organizational persistence and change through learning how one organization formed and developed over time. Five eras between 1958 and 1995 were described, and a conceptual frame considered three levels of organizational responsibility: national, state, and local environments; core technology activities; and leadership activities. Core technology activities were further analyzed using eight indicators of centrality and marginality: a) policy, b) number and type of employees, c) dedicated facilities; d) funding source, e) location of program, f) output; g) prestige, and h) legitimacy. The interpretive approach was followed to examine organizational core values. Data collected included various historical documents, interviews, and participant observations. Findings indicated that during the founding era, the unique resort culture and economy in which the College exists set the stage for the development of its core technologies. The founders idealized North Central as a “real college” emphasizing a transfer/liberal arts curriculum. A strong resort-services core was also developed to provide educated employees for medical and business services in the resort economy. These two cores promoted the founding core values and had centrality in the organization. The ensuing eras revealed the continuation of centrality of the two founding core technologies. Several other cores were developed; however, organizational commitment was low, and they were kept marginal, on the periphery of College operations. The study concluded that North Central developed an identity based upon its founding core values. Its identity as a liberal arts transfer institution persisted throughout the study and drove decision-making behavior, causing the College to forego developing in ways contrary to its values. It showed that this educational organization was value- rather than market-driven. Implications for future research, as well as for educational leadership, included using the indicators of centrality and marginality to gauge organizational commitment; using autopoiesis and resource dependency theories to explain persistence and change; and investigating the relationship between organizational core values, financial behavior, and policy- and decision-making

Phosphonium/Phosphate Ionic Liquids as Lubricant Additives: The Synthesis and Testing of Six Novel ILs

In this study, ionic liquids (ILs) are defined as ionic materials with a melting temperature \u3e100oC. ILs are characterized by their organic moieties which prevent crystallization, forcing the liquid phase. ILs are desirable as lubricant additives because of their ability to be fine-tuned by varying the identity of the cation/anion as well as the various organic functional moieties therein. Several novel phosphonium/phosphate ILs have been successfully synthesized via a simple, straightforward process. In this work a series of symmetric and asymmetric anionic phosphodiesters are developed and coordinated with two asymmetric alkyl phosphonium cations. These ILs are tested in SAE 10W30 engine oil for their tribological performance in wear reduction. At a 5 wt.% loading, phosphonium/phosphate ILs can reduce wear by up to 65% of the base oil wear. The correlation between a variety of organic functional moieties and their relative lubricities in SAE 10W30 oil is demonstrated in this work

Mechanism of charge transfer in the discontinuous metal phase of a fluidized bed electrode

From measurements of double layer capacity, collision frequency and contact time during collision, it is concluded that models for charge transfer in the discontinuous phase of fluidized bed electrode that are based on ideal particulate fluidization cannot explain metal phase resistivities, experimentally observed.\ud Based on a literature survey it is shown that not only gas-solid but also liquid-solid fluidization is at least partially aggregative.\ud A preliminary model for charge transfer in the discontinuous phase, based on aggregative fluidization, is derived

Service Learning: A Natural Link to Interdisciplinary Studies

Service learning, which involves young adolescents helping others in their school or community, provides a unique opportunity to integrate curriculum and school activities