No description available.

No description available.

No description available.

The purpose of this study was to determine whether the fluctuations of concentration in the exit stream for a RTD were statistically random. A 460ml one inlet, one outlet CSTR (Continuous Stirred Tank Reactor) was set up to perform the RTD (Residence Time Distribution) test. A electrical conductivity probe capable of measuring concentration variations in volume elements of the order of 3.00 x 10⁻⁵ml was used to detect the tracer {sodium chloride) response. Flow rates ranging from 52 (ml/min) to 213 (ml/min) and agitation speeds from 0.00 rpm to 200 rpm were covered. The C-curve (concentration curve) was found to be reproducible to within ± 5 % at agitation speed greater than 20 rpm. The fluctuations for a C-curve were extracted and standard deviation was used to characterize these fluctuations. The fluctuations were found to be not random statistically and the standard deviation of fluctuation was reproducible to within ± 8%. / M.S.

The gasification of carbonaceous fuel materials offers significant potential for the production of both energy and chemical products. Advancement of gasification technologies may be expedited through the use of computational fluid dynamics, as virtual reactor design offers a low cost method for system prototyping. To that end, a series of numerical studies were conducted to identify a computational modeling strategy for the simulation of coal gasification in fluidized bed reactors. The efforts set forth by this work first involved the development of a validatable hydrodynamic modeling strategy for the simulation of sand and coal fluidization. Those fluidization models were then applied to systems at elevated temperatures and polydisperse systems that featured a complex material injection geometry, for which no experimental data exists. A method for establishing similitude between 2-D and 3-D multiphase systems that feature non-symmetric material injection were then delineated and numerically tested. Following the development of the hydrodynamic modeling strategy, simulations of coal gasification were conducted using three different chemistry models. Simulated results were compared to experimental outcomes in an effort to assess the validity of each gasification chemistry model. The chemistry model that exhibited the highest degree of agreement with the experimental findings was then further analyzed identify areas of potential improvement. / Ph. D.

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Fluidized-bed combustion residue (FBCR) results from mixing coal with limestone during the combustion process. This by-product may be used as a liming agent. A grazing trial was conducted on an acidic mine soil to compare FBCR to dolomitic limestone and no amendment (control). Six steers per treatment were grazed rotationally on three replications (rep) of three .8 ha pastures. Both materials increased soil pH similarly, and reduced plant uptake of Fe, Zn, Mn, and Ni similarly. Calcium concentration increased in forages by both amendments, Mg increased with limestone and S with FBCR application. Cell wall components decreased, while ash and lignin increased with both amendments. Serum mineral levels of cattle were normal except Cu was low. Animal tissues reflected differences in mineral concentration observed in forages. Hay harvested from one rep was used in a mineral balance trial with 18 wethers. Apparent digestibility of dry matter, crude protein and fiber components, and N retention were not affected by treatment. Control animals were in negative Ca balance. Apparent absorption of Mg was higher (P < .01) for limestone treatment animals; S absorption was higher for the FBCR group; and, Zn absorption was higher for controls. Serum mineral levels of sheep were normal except Cu was low. No appreciable accumulation of heavy metals occurred in forage or animal tissues. Low Cu levels observed for all treatment groups indicate a problem inherent of the study site. FBCR appears to be a safe and efficient soil pH amendment. / Master of Science

Numerical modeling and prediction techniques are used to determine pressure drop, minimum fluidization velocity and segregation for bubbling fluidized beds. The computational fluid dynamics (CFD) code Multiphase Flow with Interphase eXchange (MFIX) is used to study a two-stage reactor geometry with a binary mixture. MFIX is demonstrated to accurately predict pressure drop versus inlet gas velocity for binary mixtures. A new method is developed to predict the pressure drop versus inlet gas velocity and minimum fluidization velocity for multi-component fluidized beds. The mass accounting in the stationary system (MASS) method accounts for the changing bed composition during the fluidization process by using a novel definition for the mass fractions of the bed not yet fluidized. Published experimental data for pressure drop from single-, binary- and ternary-component fluidized bed systems are compared to MFIX simulations and the MASS method, with good agreement between all three approaches. Minimum fluidization velocities predicted using correlations in the literature were compared with the experimental data, MFIX, and the MASS method. The predicted minimum fluidization velocity from the MASS method provided very good results with an average relative error of ±4%. The MASS method is shown to accurately predict when complex multi-component systems of granular material will fluidize. The MASS method and MFIX are also used to explore the occurrence and extent of segregation in multi-component systems. The MASS method and MFIX are both shown to accurately predict the occurrence and extent of segregation in multi-component systems. / Master of Science

The effect of the solid-circulation rate and pattern as well as the air-gap size on heat-transfer coefficients between a horizontal, cylindrical heater and vibrated beds of Master Beads (spherical alumina) and glass spheres was studied. Solid piles were observed to form at specific bed locations. Solid-circulation paths were directed from the shallowest toward the deepest region of the vibrated bed. For beds in which the solid pile formed above the heating surface, local solid-circulation loops were observed above and below the heater. Air gaps developed at the top and bottom of the cylindrical heater. Heat-transfer coefficients of 140-350 W/m²K in beds of glass spheres and 180-480 W/m²K in beds of Master Beads were determined for a temperature difference of 30°C between the heater and vibrated bed. The trends in the behavior of the heat-transfer coefficient could be explained in terms of a model that accounted for the air-gap size and particle renewal in the layer closest to the heater. Increased solid-circulation rates improved the heat-transfer performance until larger air-gap sizes eventually compromised any increase in solid circulation. The expansion of the interlayer spacing of H-Magadiite (a layered silicic acid) by the introduction of pillars containing silicon atoms was investigated. A trisiloxane and two trichloroorganosilane compounds were used as the pillaring agents. The interlayer space of H-Magadiite was successfully expanded by pillaring with trichloroorganosilanes. The minimum dimensions of the pores that access the interlayer space of the pillared compounds were determined as being 6.2 Å and 9.5 Å (dimensions at perpendicular directions). Pillaring of H-Magadiite at low pH and temperatures close to 0 °C yielded the highest surface areas, e.g., increasing the surface area from 35 to 130-200 m²/g. The pillared compounds were found to be thermally stable up to temperatures of 650°C. / Ph. D.

Ceramic candle filters were subjected to 500 hour high temperature/ high pressure (HTHP) exposure tests to examine their extended durability in simulated coal pressurized-fluidized bed combustion (PFBC) environments. The candle filter materials analyzed included two SiC filters, one with clay binder and one with a minimal amount of clay binder, a cordierite filter, a mullite candle filter and an aluminosilicate refractory concrete filter. Exposure testing conditions included a range of temperature from 700-850°C and a pressure ranging from 1.7-1.8 MPa. The HTHP tests included exposing the ceramic filter materials to steam and steam-alkali environments. The presence of alkali significantly accelerated the deterioration of the filters. The results of the analysis show that significant crushing strength losses were exhibited by the SiC filters after exposure to HTHP alkali-steam conditions at temperatures as low as 700°C. The expansive and destructive cristobalite phase developed in the SiC filters after most of the treatments. The cordierite candle filter showed a decrease in crushing strength associated with grain growth after each high temperature exposure but few other signs of deterioration were detected. The mullite candle filter and the refractory concrete candle filter showed the least amount of change in crushing strength and overall the most candle stability. / Master of Science