No description available.

No description available.

A deep-bed drying model simulating the drying of peanuts in a fixed bed is required for designing energy-efficient and automatically controlled dryers. A deep-bed drying model consists of a thin-layer drying model to calculate the moisture release from the material and a set of mass and energy balances. An experimental setup was constructed to determine drying rates of Virginia-type peanuts under 14 different drying air conditions. Selected empirical and semi-theoretical models available for modeling thin-layer drying rates were fitted to the collected data using nonlinear regression techniques. The modified Page's model and the two-term exponential model fitted the data better than other models considered. A deep-bed drying model PEATECH based on four coupled partial differential equations consisting of four variables, air temperature, peanut temperature, air humidity, and peanut moisture content was developed. Validation of the model was accomplished by using the data collected from 36 deep-bed drying experiments conducted using three laboratory dryers during 1987, 1988, and 1989. PEATECH predicted the variables within a peanut bed with an accuracy of less than ± 6%. The energy saving potential of exhaust-air recirculation was established by conducting simulated experiments using a modified version of PEATECH. / Ph. D.

A study based on a statistically designed set of experiments (Box-Behnken design) has been conducted to determine the optimum conditions for advanced physical fine coal cleaning using microbubble column flotation. The dependent variables in these experiments were mass yield and product quality (ash, sulfur and btu), while the independent variables were feed solids content, collector dosage, frother dosage, feed rate, aeration rate, and wash water rate. The most important operating parameters in order of significant were found to be aeration rate, feed rate, frother dosage and wash water rate. The test data were found to fall along a single grade-recovery curve and just below the ideal separation curve predicted by release analysis, provided that a sufficient bias flow was maintained. The test results also demonstrated that various combinations of operating conditions can be utilized to achieve the same level of metallurgical performance. In order to develop an improved understanding of the behavior of column flotation cells, a simulation package was developed by incorporating guidelines developed from the parametric test data. Simulations were carried out by examining the effects of key parameters on the performance of a column flotation cell. The parameters that were found to have the most significant influence included column length/diameter ratio, aeration rate, feed rate, feed solids content, and pulp bubble size. It was also found that limitations arising from the carrying capacity of the froth phase can greatly impact the performance of large-scale flotation columns. It is believed that this simulator will be useful for the design, control, optimization and scale-up of column flotation. / Master of Science

No description available.

No description available.

Vibrofluidized microreactor systems have been developed for studies of unsteady-state Fischer-Tropsch synthesis. This development is aimed at preventing carbon deposition on a fused-iron catalyst in a novel reactor called the “heat-tray.” This reactor involves a supernatant gas flowing over a shallow fluidized bed of catalyst particles. Three systems were built: (1) a vibrofluidized-bed microreactor system for obtaining baseline carbon deposition infonnation under industrially important reaction conditions; (2) a sliding-plug vibrofluidized-bed microreactor system for rapid switching of feed gases in the F-T synthesis; and (3) a cold-flow microreactor model for studying the gas mixing characteristics of the sliding-plug vibrofluidized-bed microreactor. The results show that catalyst defluidization occurred under steady-state synthesis conditions below 395°C using a feed gas of H₂/CO ratio of 2:1 or less. Above 395°C, the probability of hydrocarbon chain growth (α) on the fused-iron catalyst was low enough (α < 0.50) to prevent accumulation of high-molecular-weight species that cause defluidization. Carbon deposition was rapid above 395°C when a feed gas of H₂/CO ratio of 2:1 or less was used. Spent catalyst fractions in the form of free-flowing catalyst and "bugdust" were quantitatively analyzed for carbon and iron. Mössbauer spectroscopic analysis of free-flowing catalyst showed mainly Hägg carbide (x-Fe₅C₂) and magnetite (Fe₃O₄) with a smaller fraction present as α-Fe. Scanning electron microscopic analysis of the bugdust revealed a mass of highly porous, fine particles with a high carbon content (18-30 wt%). Cold-flow microreactor model studies show that rapid (on the order of seconds), quantitative switching of feed gases over a vibrofluidized-bed of catalyst could be achieved. Vibrofluidization of the catalyst bed induced little backmixing of feed gas over the investigated flow-rate range of 417 to 1650 actual mm³/s. Further, cold-flow microreactor model studies showed intense solid mixing when a -150+300 µ bed of fused-iron catalyst was vibrofluidized at 24 cycles per second with a peak-to-peak amplitude of 4 mm. The development of this microreactor system has provided an easy way of accurately determining integral fluid-bed kinetics in a laboratory reactor. Further, the unique ability of the microreactor system to rapidly switch feed gases over an intensely-mixed solid has important applications in chemical kinetics and reaction engineering. / Ph. D.

Relationships between laundry practices, detergent knowledge, perception of water quality, and satisfaction with laundry results were determined in this study. The mail survey method was used to obtain information from Virginia Extension Homemakers in April 1986. Only respondents who did laundry in their own home or apartment were used. Two hundred and seventy-six respondents, from a sample of 370 homemakers, met the criterion. Spearman's rho correlation coefficient was used to determine if relationships existed between the variables. Low correlations were found between the variables; therefore, definite conclusions regarding relationships between the variables could not be made. Some discrepancies between actual and recommended laundry practices were found. Data also revealed a lack of knowledge regarding functions of detergent ingredients and proper use with specific water conditions, and some lack of awareness and misperceptions of water quality were detected. However, satisfaction with laundry results was generally good, and most homemakers seemed relatively pleased. The findings suggested that educational programs should emphasize information about detergent formulations and water characteristics. More information on recommended laundry practices and how they should be modified according to water conditions and detergent use also was needed. / M.S.

The hardwood sawmill industry is faced with a decreasing availability of high quality timber, and declining log quality. Ways to improve the technology are needed so that this lower quality resource can be better utilized. The hydraulic linear positioner is one such new technology. The objective of this research is to quantitatively determine the impact of hydraulic linear positioners on the production efficiency of hardwood sawmills by an analysis of: 1) lumber grade yields; 2) log value; 3) sawing time; and 4) sawing variation attributed to the linear positioners, using Factory Grade No. 2 red oak logs sawn into lumber by full-infinite taper and conventional sawing patterns. The results of this study indicate: 1) Hydraulic linear positioners in a hardwood sawmill can improve the production efficiency by a little over one percent (the positioners alone), and by up to 11 percent when including the contribution of the hardware and software with the positioners. 2) Selecting the opening face and using the full-infinite taper setout capabilities of the positioners did not improve the lumber grade yield from the logs used in this study. 3) Opening face selection and taper setout increase sawing time and thereby reduce the log value when based upon a $/log/operating minute. Such practices can reduce the production efficiency by up to $17 per log per operating minute. / Master of Science

Study objectives were 1) to identify successful mechanized thinning and prelogging systems currently operating in the South, 2) to document system characteristics contributing to their success, and 3) to determine which factors affect levels of residual stand damage from thinning operations. The first objective was accomplished by a South-wide industry survey. The latter two objectives were realized through in-depth field studies of selected systems. The survey indicated three system types used on small-tree operations. Feller-buncher/grapple skidder/hydraulic loader systems comprised the majority of operations described. No predictable relationships between system type and tree size were apparent, so examples of the most common type were chosen for detailed study. Three thinning and three prelogging systems were selected, covering a range of ownership patterns and physiographic regions. Information was obtained pertaining to each system's application; crew organization and background; equipment spread and descriptions; performance; and special considerations provided by landowners or timber buyers. Residual stand damage cruises were conducted at each thinning operation's job site. Case-by-case analyses and comparisons between systems based on economic and productivity criteria resulted in a number of recommendations. These suggestions represented system characteristics seen as keys to the success of the operations studied. The recommendations focused on desirable contractor and crew characteristics, equipment selection decisions, job layout, minimization of residual stand damage, and methods of landowner/timber buyer support for small-tree operations. / M.S.