Column flotation cells have become increasingly popular in the coal industry due to their ability to improve flotation selectivity. The improvement can be largely attributed to the use of froth washing, which minimizes the nonselective entrainment of ultrafine minerals matter into the froth product. Unfortunately, the practice of adding wash water in conventional flotation machines has been largely unsuccessful in industrial trials. In order to better understand the causes of these failures, a detailed in-plant test program was undertaken to evaluate the use of froth washing at an operating coal preparation plant. The tests included detailed circuit audits (solid and liquid mass balances), salt tracer studies, and release analyses. The data collected from these tests have been used to develop criteria that describe when and how froth washing may be successfully applied in industrial flotation circuits. A second series of tests was developed to look at other alternatives to froth washing and their effectiveness. This involved two-staged flotation circuitry. A two-staged approach was developed because the existing flotation cells did not have enough residence time to support froth washing. The process owner wanted to evaluate possible alternatives to column cell flotation. The testing included release analysis testing as well as a detailed series of tests with percent solids control to the secondary flotation unit. / Master of Science

The fundamental requirement for a coal preparation plant is to transform low value run-of-mine (ROM) material into high value marketable products. The significant aspect relative to the plant is that any gain in efficiency flows almost entirely to the "bottom line" for the operation. The incremental quality concept has gained wide acceptance as the best method to optimize the overall efficiency of the various cleaning circuits. Simply stated, the concept requires that all the cleaning circuits operate as near as possible to the same incremental quality. To ensure optimal efficiency, a plant that receives ROM feed from multiple sources must develop a strategy to operate at the same incremental quality, which yields wide ranges in product qualities from the individual ROM coals. In order to provide products that meet contract specifications, clean coal stockpiles can be utilized to accept coals with various qualities, such as "premium," "low," and "filler" qualities, with shipments formulated from the stockpiles to meet product specifications. A more favorable alternative is raw coal blending to produce the specified clean coal qualities. This study will review the incremental quality concept and present case studies in applying the concept to meet product specifications. / Master of Science

A new processing technique, known as hydrophobic displacement, was explored as a means of simultaneously removing both mineral matter and surface moisture from coal in a single process. Previous thermodynamic analysis suggests that coal moisture will be spontaneously displaced by any oil with a contact angle greater than ninety degrees in water. Based on these results, six methods of hydrophobic displacement were evaluated: hand shaking, screening, air classification, centrifugation, filtration, and displacement. In the first five methods hydrophobic displacement took place during the cleaning stage. A recyclable non-polar liquid (i.e. pentane) was used to agglomerate coal fines followed by a physical separation step to remove the coal agglomerates from the mineral-laden slurry. Bench-scale tests were performed to identify the conditions required to create stable agglomerates. Only the last method, displacement, did not utilized agglomeration and performed hydrophobic displacement during dewatering, not cleaning. A procedure was also developed for determining moisture content from evaporation curves so that the contents of water and pentane remaining in a sample could be accurately distinguished. Two primary coal samples were evaluated in the test program, i.e., dry pulverized 80 mesh x 0 clean coal and 100 mesh x 0 flotation feed. These samples were further screened or aged (oxidized) to provide additional test samples. The lowest moisture, 7.5%, was achieved with centrifugation of the pulverized 80 mesh x 0 clean coal sample. Centrifugation provided the most reliable separation method since it consistently produced low moisture, high combustible recoveries, and high ash rejections. Hand shaking produced the next lowest moisture at 16.2%; however, the low moistures were associated with a drop in combustible recovery. There was also a great deal of error in this process due to its arbitrary nature. Factors such as oxidation, size distribution, and contact angle hysteresis influenced the concentrate moistures, regardless of the method utilized. / Master of Science

The erosion damage to stator and rotor blades associated with flow containing particulates in turbines is investigated. The main parameters studied are blade leading edge thickness, blade turning angle, turbine inlet temperature, particle size, and particle densities. The computer programs used in the investigation are based on inviscid flow theory. Flow velocities relative to blades ranged up to sonic values. Results predict that decreasing flow turning angles and increasing blade leading edge thicknesses are the most effective ways to reduce erosion damage caused by impacting particles. Decreasing particle sizes and densities can also significantly reduce erosion rates. The erosion model uses the brittle and ductile mode response exhibited by materials subjected to particle impacts to predict the total erosion damage. The accuracy for small (1 micron) particles is questionable since some of these particles will have long residence times in the boundary layers, causing deposition rather than erosion. / Master of Science

The potential for improved selectivity has made column flotation cells a popular choice for upgrading fine coal. Unfortunately, recent production data from full-scale column plants indicate that many industrial installations have failed to meet original expectations in terms of clean coal recovery. Theoretical studies performed using a simple dispersion model showed that this inherent shortcoming could be largely minimized by reconfiguring the columns to operate in series as a cell-to-cell circuit. Follow-up field data showed that this low-cost modification increased flotation recovery as predicted by the dispersion model. This study presents the key findings obtained from the field investigation and provides generic guidelines for designing multi-stage column circuits. / Master of Science

To understand the behavior and performance of a new 100 kW pilot scale pressurized oxy-coal reactor, radiation measurements of the flame have been made using a Fourier Transform Infrared (FTIR) spectrometer. From these radiation measurements, gas temperatures were obtained using integrated spectral infrared (ISIR) emission from the CO2 and water vapor of the combustion product gases. Radiative emission from the product gases in the reactor were collected through a quartz window 1.524 m downstream of the burner. An optical probe focused culminated emission from the combustion chamber into a silica fiber which transported the radiative signal to the spectrometer. The method produced both wall and gas temperatures as well as total integrated intensity. Values for wall temperature ranged from 1150 to 1450K and gas temperatures ranged from 1150 to 1680K. The wall and gas temperature measurement trends were consistent with expected trends with periods of increasing and decreasing fuel flow rates. Temperatures could not be verified by independent measurements, but the absolute uncertainty of the gas temperature was estimated to be +100 and -50 K in the worst case, with the largest source of uncertainty being due to window fouling. These temperature and integrated intensity values were compared to measurements taken using thermocouple and radiometers at the same axial location on the reactor.

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