The plasticity of coal during pyrolysis is of significant importance, since it affects the reactivity, porosity, particle size and the density of the char and thus also the behaviour of the char during further utilisation processes. The main focus of this study was to characterize the chemical and physical changes which the thermally treated coal undergoes, in order to better understand the pyrolysis process of caking and non-caking South African coals. The pyrolysis behaviour of three South African coals with different caking indices was investigated. The coal samples included; (1) Highveld (TWD), a medium rank C coal with a free swelling index (FSI) of 0, (2) Grootegeluk (GG), also a medium rank C coal, with a FSI of 6.5, and (3) Tshikondeni (TSH), a medium rank B coal with the highest FSI of 9. The three coal samples were classified as vitrinite-rich coals consisting of mainly aliphatic structures. Thermogravimetric experiments were used to determine the different temperatures relating to specific percentages of mass loss using set conditions. The pyrolysis process was stopped at various percentages of mass loss (thus at various stages of the reactions) to characterize the chemical structural changes that occurred at the specific mass loss percentages. The results obtained from characterization analyses indicated that the three coals differ in chemical composition and thus were expected to behave differently during pyrolysis. The coal samples consist of different amounts of macerals and minerals according to X-ray Fluorescence (XRF) and X-ray Diffraction (XRD) analyses. The Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT) results indicated that some of the functional groups within the coal samples evolved with the increase in temperature. The highly caking coal (TSH) exhibited the highest aromaticity and ring condensation. The surface areas were determined by CO2 adsorption and an increase in surface area was observed with an increase in temperature. The surface area of the GG and TSH coal-derived char samples decreased at some stage, which is an indication of thermoplastic behaviour and subsequent swelling of the coal samples. Scanning electron microscopy (SEM) images confirm the plastic stage of caking coals at specific temperatures and volatile matter release via the multiple bubble mechanism. All these results are given and discussed extensively in this dissertation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015

Mozambique has vast forestry resources and also considerable biomass waste material such as bagasse, rice husks, sawdust, coconut husks and shells, cashew nut shell and lump charcoal waste. The potential of the total residues from the agricultural sector and the forest industry is estimated to be approximately 13 PJ. This amount of energy covers totally the production of charcoal which amounted to approximately 12.7 PJ in 2006. Although biomass is an attractive renewable source of energy, it is generally difficult to handle, transport, storage and use due to its lower homogeneity, its lower energy density and the presence of non-combustible inorganic constituents, which leads to different problems in energy conversion units such as deposition, sintering, agglomeration, fouling and corrosion. Therefore, a pretreatment of the biomass to solve these problems could lead to a change of current biomass utilization situation. The aim of this study is to convert Mozambican woody biomass residue into a solid biochar that resembles low-grade coal. In this work the current energy situation in Mozambique has been reviewed, and the available and potential renewable sources including residues from agricultural crops and forest industry as energy have been assessed. It was found that the country is endowed with great potential for biofuel, solar, hydro and wind energy production. However, the production today is still far from fulfilling the energy needs of the country, and the majority of people are still not benefiting from these resources. Charcoal and firewood are still the main sources of energy and will continue to play a very important role in the near future. Additionally, enormous amounts of energy resources are wasted, especially in the agricultural sector. These residues are not visible on national energy statistics. The chemical composition and the fuelwood value index (FVI) showed that by failing to efficiently utilise residues from Afzelia quanzensis, Millettia stuhlmannii and Pterocarpus angolensis, an opportunity to reduce some of the energy related problems is missed. An evaluation of effect of a mild wet torrefaction pretreatment showed that the chemical composition of the biochar is substantially different than the feedstock. The use of diluted acid as catalysts improves the biochar quality, namely in terms of the energy density and ash characteristics; however, the increment of the S content in the final product should be considered for market acceptance (because the fuels have a maximum allowance for S concentration). The thermal behaviour of the untreated and treated biomass was also investigated. The pyrolytic products of umbila and spruce were affected by the treatment and catalyst in terms of yield and composition of the vapours. / <p>QC 20150202</p>

Student Number : 0420699F - MSc Dissertation - School of Physics - Faculty of Science / This dissertation presents for the first time the conditions for the synthesis of VO2 by ultrasonic nebula-spray pyrolysis (UNSP) from a precursor solution of NH4VO3+VCl3 optimized as follows: a carrier gas of argon at a flow rate of 11 liters per minute, a furnace temperature of 400 to 700oC. This work also incorporates thermodynamic variables of Tpr-P-V into the equations that relate the mean diameter of droplets, D, to frequency of the exciting ultrasound waves, f, the density of the precursor solution, #26; and the surface tension, #27;, previously worked on independently by Lang and Jokanovic. The incorporation results in the diameters of the droplets (and consequently the collected grains) being smaller as p and Tpr are increased in a non- linear form. The variable V, however, increases the diameter of the droplets as it is allowed to increase. This study shows the departures many authors find of the theory from experiment but it also shows that the departure does not lie in the equations but rather on post- synthesis and annealing effects. From X-ray diffraction, scanning electron microscopy (SEM) and Raman spectroscopy, this study shows that as furnace temperature is increased the morphology of the sample surfaces for both VO2 and WO3 transforms from amorphous to crystalline, from spherical grains to plate-like structures, with grain mean diameter increasing non-linearly in some cases and decreasing non-linearly in other cases confirming previous findings, the latter enjoying the majority vote. In Raman spectra of the as- obtained WO3, asymmetric broadening of the Raman peaks was observed in some samples and a phonon confinement model was employed in the size distribution prediction. These findings prompted the re- workout of the phonon confinement model. In this dissertation an equation has been derived based on the Faucet-Campbell equation of the PC model. The new equation relates the ratio of neighboring peaks in a material’s Raman spectrum to the mean diameter of the grains. The present modification allows the PCM model to predict the grain size beyond the current limiting range of 0 to 100 nm. Analysis of the experimental data using this equation unveils two different equations- one for particles of size below 100 nm and the other equation for particles with larger that 100 nm. Also this analysis has enabled the present study to evaluate the phonon dispersion relations for WO3.

Call number: LD2668 .T4 1986 H47 / Master of Science / Mechanical and Nuclear Engineering

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Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Microfiche copy available in Archives and Engineering. / Vita. / Bibliography: leaves 414-423. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by John Milan Lavoie, Jr. / Ph.D.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Includes bibliographical references. / by Michael Tully Klein. / Sc.D.

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / Bibliography: leaves 194-198. / by Philip C. Lewellen. / M.S.

In this work, an investigation on the fraction of tyre pyrolysis oil with a similar distillation range to that of automotive diesel (150 – 360 oC) was carried out to determine its suitability as an alternative or additive to petro-diesel fuel. The quality of this oil was evaluated by comparing its key properties to the requirements of South African National Standards for Automotive diesel fuel (SANS-342) and to conventional automotive diesel fuel. The viscosity, density, copper strip corrosion of this fuel were found to be within the acceptable limits set by SANS while sulphur content and flash point were out of their respective set limits. In addition, mixing rule equations for predicting viscosity and density for both pure and blends of the oil as a function of temperature were developed and evaluated. The equations were found to be suitable due to their low Absolute Percentage Deviation. Engine performance tests were carried out with blends of Distilled Tyre Pyrolysis Oil (DTPO) and petro-diesel fuel in a single cylinder air cooled diesel engine. The performance, emission and combustion characteristics of the diesel engine while running on these blends were evaluated and subsequently, a comparative analysis was performed with conventional petro-diesel fuel as the reference fuel. It was found that, the engine could run with up to 60% (DTPO) without any problem. Beyond this level the engine became unstable. The power and torque were similar at low and medium speeds. However, at high speeds, the power dropped with increase in DTPO in the blend. Fuel consumption was very comparable for all the test fuels. Carbon monoxide and unburned hydrocarbons were higher for the blends compared to petro-diesel fuel but oxides of Nitrogen were lower. The peak pressure for petro-diesel fuel was marginally higher than that of the blends. Present results indicate that, petro-diesel fuel can be blended with up to 60% DTPO and produce acceptable performance. Testing the diesel engine under different operating conditions is a time consuming and expensive process that also requires the use of specialised equipment which may not be readily available. An Artificial Neural Network (ANN) model based on a back-propagation learning algorithm was developed to predict engine performance and emissions separately, based on fuel blend and speed. The performance and accuracy of the model were evaluated by comparing experimental and ANN predicted results. The ANN was able to predict both engine performance and emissions with acceptable levels of accuracy. The values of correlation coefficient between experimental and predicted data being greater than 0.99. From this work, it can be implied that engine emission and performance can be predicted using neural network-based mode, consequently, it will be able to do further investigations without running laboratory experiments. Energy recovery from waste is an interesting field for engineers and scientists. It is hoped that this work will prompt new research ideals on how tyre pyrolysis oil can be improved for use as diesel engine fuel and building better models for diesel engine performance and emissions