Commercial ceramic candle filters were exposed to harsh environments to determine the effects of alkali and steam on their long-term durability. Ceramic candle filters are composed of relatively coarse aggregates fixed by a ceramic bond. The filters studied include a clay-bonded, granular aluminosilicate candle and three types of clay-bonded, granular SiC candles. The alkali, steam, and steam-alkali corrosion of these commercial ceramic candle filters was examined at temperatures ranging from 450 to 1225°C and pressures up to 1000 psi. Results indicate that the aluminosilicate candle filters perform better than filters made from granular SiC. The SiC filters show binder degradation in steam as well as in alkali-containing environments at temperatures as low as 700°C, with oxidation of the SiC occurring in the steam environments at higher temperatures. Sodium and potassium contaminants in the steam atmospheres accelerate the degradation of both types of filter material. / Master of Science

One or the characteristics of all anthracite coal, with its low volatile content, is its ability to burn completely in a small volume. Another characteristic and disadvantage of local, semi-anthracite coal is its high ash content. It is the authors' belief that local, semi-anthracite coal can be burned most effectively for domestic heating if the furnace design allows for these characteristics. With these facts in mind, it was decided that the Anthratube had excellent possibilities as a domestic unit for burning local coal. The Anthratube, by its compactness, takes full advantage of the first characteristic; with its ash-removing grate, it overcomes to a great extent the disadvantage of the second characteristic. The purpose of this thesis was, then, to determine whether or not various sizes of local, semi-anthracite coal from the Merrimac seam could be successfully burned in the Anthratube. The coal used for this investigation was obtained from the Great Valley Anthracite Corporation located at McCoy, Virginia. 1. Pea size, local coal can be burned very successfully in the Anthratube. Overall boiler efficiencies of the unit with this size coal are high over a wide range of loads. Of the sizes of coal burned, pea size is most suitable for the Anthratube. 2. Buckwheat size, local coal canoe burned in the Anthratube with good results. The overall boiler efficiencies obtained with this size of coal are good, although not as high as those obtained with the pea coal. 3. The performance of the Anthratube with rice size, local coal is inferior to that achieved with pea and buckwheat sizes. The output of the unit is seriously limited when using this size. 4. Culm size, local coal cannot be burned in the Anthratube. / M.S.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2016 / Stringent worldwide emissions legislation, the drive to lower carbon emissions, together with the ever increasing demand to preserve the environment has led to a considerable demand for cleaner and more efficient coal combustion technologies. A primary technology for the reduction of emissions of oxides of nitrogen (NOx) is the installation of low NOx coal combustion burners. Extensive research into various burner characteristics and, in particular, the aerodynamic characteristics required to improve combustion performance of low NOx coal burners has been extensively undertaken and is ongoing. In this work the aerodynamic behaviour of a full-scale, aerodynamically staged, single low-NOx coal burner was numerically investigated. The objective of the study was to develop a single low NOx burner CFD model in Ansys Fluent, to better characterize and understand the flame shape in terms of the temperature profile achieved. CFD serve as an additional tool to assist with plant optimization, design proposals and occurrence investigations. To have confidence in the single burner coal combustion CFD model, the results of the model were compared to data obtained from an existing operational low NOx burner on site during a pre-defined load condition. To further improve on the theoretical CFD combustion model, drop tube furnace (DTF) experiments have been done to calculate the single rate Arrhenius kinetic parameters (pre-exponential factor and activation energy) for coal devolatilization and char combustion of the specific South African coal used. The combustion CFD simulations showed with a lower than design air flow through the burner, a reduced amount of swirl was achieved. This reduced amount of swirl produces a jet like flame and influences the way in which the combustion species are brought together. Under these operating conditions the flame distance from the burner mouth was predicted to be 1.2 (m). A very promising result was obtained through CFD and compared well with the in-flame temperature measurement obtained through the burner centre-line of approximately 1.4 (m). In an attempt to improve the aerodynamic profile of the burner under the same operating conditions the swirl angle on the tertiary air (TA) inlet was increased. The increased swirl on the TA inlet of the burner showed an improvement on the aerodynamic profile and had a significant impact on the temperature distribution within the flame. The increased swirl resulted in an improved flame distance of approximately 0.5 (m) from the burner mouth. The effect of increased swirl on the temperature profile of the flame displayed the aerodynamic dependence of the low NOx burner on combustion performance. / MT2017