In this work, the co-pyrolysis of coal and algae is explored with special emphasis on decomposition kinetics and the possibility of the existence of synergistic effects. Modelling and kinetics analysis based approaches were used for the investigation of the existence of synergistic effects. The co-pyrolysis kinetics was studied using the model-free, Coats–Redfern integral method. The kinetics were evaluated for 1st and 2nd order reaction models. Results reveal that Scenedesmus microalgae is characterised by a two stage decomposition process that occurs at temperature ranges of 200–400 °C and 500–700 °C with activation energy of 145.5 and 127.3 kJ/mol, respectively. Bituminous coal has a two stage, slow decomposition process that occurs at temperature ranges of 400–700 °C and above 750 °C with an activation energy of 81.8 and 649.3 kJ/mol, respectively. Furthermore, co-pyrolysis of coal and microalgae is characterised by three stages whose kinetics are dominated by the pyrolysis of the individual materials. For the studied range of coal/algae ratios, the three pyrolysis stages occur in the approximate temperature ranges of 200–400 °C, 430–650 °C and above 750 °C, with activation energies in the ranges of 131–138, 72–78 and 864.5–1235 kJ/mol, respectively. Modelling and kinetics study showed that there is strong evidence of interactions between coal and microalgae that manifest as synergistic effects especially in the second and third stages of decomposition.

With escalating fears of climate change reaching irreversible levels, much emphasis has been recently placed on shifting to renewable sources of energy in supporting future economic livelihood. Focusing on South Africa, as Africa's largest energy consumer and producer, our study investigates the short-run and long-run effects of renewable energy on economic growth using linear and nonlinear autoregressive distributive lag (ARDL) models. Working with data availability, our empirical analysis is carried out over the period of 1991-2016, and our results unanimously fail to confirm any linear or nonlinear cointegration effects of the consumption and production of renewable energy on South African economic growth. We view the absence of cointegration relations as an indication of inefficient usage of renewable energy in supporting sustainable growth in South Africa and hence advise policymakers to accelerate the establishment of necessary renewable infrastructure in supporting future energy requirements.

Abstract:This research study contributes

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Wastewater discharged into municipal sewer systems from electroplating process plants contains a heavy load of metal ions and often requires pre-discharge treatment. Treatment of wastewater to reduce the concentration of metal ions employing an adsorption process has been studied using a wide range of adsorbents. In this work, the concentrations of chromium and nickel ions in wastewater samples from a local electroplating shop were found to be above the limits set out by the Bulawayo City Council, and the Environmental Management Agency, a statutory agency under the Ministry of Environment and Tourism, Government of Zimbabwe. Furthermore, the removal of chromium and nickel ions from the wastewater using magnetite as an adsorbent is studied. Magnetite particulate adsorbent used in this experiment has demonstrated to be an effective adsorbent material. At the optimum process operating pH of 4 – 7 the absorbent was able to achieve removal rates of up to 99% for chromium and 98% for nickel. The adsorption processes for chromium and nickel have been proven to be physical in nature using the Dubinin-Radushkevich isotherm model. Also, the adsorption kinetics data fit well with pseudo second-order kinetic model.

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In present work, the thermal decomposition behaviour and kinetics of proteins, carbohydrates and lipids is studied by use of models derived from mass-loss data obtained from thermogravimetric analysis of Scenedesmus microalgae. The experimental results together with known decomposition temperature range values obtained from various literature were used in a deconvolution technique to model the thermal decomposition of proteins, carbohydrates and lipids. The models fitted well (R2 > 0.99) and revealed that the proteins have the highest reactivity followed by lipids and carbohydrates. Generally, the decomposition kinetics fitted well with the Coats-Redfern first and second order kinetics as evidenced by the high coefficients of determination (R2 > 0.9). For the experimental conditions used in this work (i.e. high heating rates), the thermal decomposition of protein follows second order kinetics with an activation energy in the range of 225.3-255.6 kJ/mol. The thermal decomposition of carbohydrate also follows second order kinetics with an activation energy in the range of 87.2-101.1 kJ/mol. The thermal decomposition of lipid follows first order kinetics with an activation energy in the range of 45-64.8 kJ/ mol. This work shows that the thermal decomposition kinetics of proteins, carbohydrates and lipids can be performed without the need of experimentally isolating the individual components from the bulk material. Furthermore, it was shown that at high heating rates, the decomposition temperatures of the individual components overlap resulting in some interactions that have a synergistic effect on the thermal reactivity of carbohydrates and lipids.

The objective of this work is to demonstrate the utilization of the power of simulation tools to perform an exergy analysis of a process. Exergy analysis, being a new and useful thermodynamics tool, will be applied to one of the newest research fields in hydrogen production. One of the many advantages of computer simulation is elimination of the need to construct a pilot plant. Presently, extensive research is underway to come up with the production and use of clean fuels. The research entails performing pilot studies and proof of concept experiments using validated models. The research is further extended to various analyses such as safety, economic sustainability and energy efficiency of the processes involved. The production of hydrogen through thermochemical water splitting processes is one of the newest technologies and is expected to compete with the existing technologies. Among a wide range of thermochemical cycles, the sulfur-iodine (SI) thermochemical cycle process has been proposed as a promising technology for the production of hydrogen. In this research, we demonstrate how a commercial simulator can be used to perform an energy and exergy analysis of the SI water splitting process. Using a commercial simulator, a process flowsheet is developed based on research findings presented by other authors and an energy-exergy analysis is carried out on the process. The method of energy–exergy analysis used in this presentation indicates that an energy and exergy efficiency of 17% and 24% can be attained, respectively, in the conceptual design of the SI cycle.