- Title
- An investigation of the combustion kinetics of coal-microalgae composite
- Creator
- Ejesieme, Obialo Vitus
- Creator
- Dugmore, Gary
- Subject
- Microalgae -- Biotechnology
- Subject
- Biomass energy -- South Africa Coal -- South Africa
- Date Issued
- 2018
- Date
- 2018
- Type
- Thesis
- Type
- Doctoral
- Type
- PhD
- Identifier
- http://hdl.handle.net/10948/34777
- Identifier
- vital:33447
- Description
- Coal mining and handling generate sizeable quantities of ultra-fine coal particles which are heaped as discard material. Use of the ultra-fine coal for co-firing with microalgae biomass appears to be a promising option that would improve combustion of the discard. There is no available traditional biomass binder that can be used to agglomerate, reclaim, and co-fire the discard ultra-fine coal to generate heat. In a recent research, microalgae biomass was identified as an effective natural binder for discard ultra-fine coal. Biomass is a renewable resource, and many have been co-fired on a large scale except microalgae biomass. Researchers have studied co-firing of dry mixed coal-microalgae, however, the kinetics of a wet mix of microalgae biomass and ultra-fine coal, “Coalgae®” patented recently by the Nelson Mandela University needs to be explored. The study aimed at investigating in some detail the oxidation mechanism of coal-microalgae composites. The objective is to understand the impact of microalgae on the kinetic properties of coal which will inform on the application of “Coalgae®”. It involves correlating the small and large-scale combustion properties that will establish the co-firing option on an industrial scenario. The goal is to utilize all grades of discard ultra-fine resource using microalgae biomass as binder and a renewable component which enhances the combustion of coal to supply heat and electricity. The use of microalgae for fuel preparation and upgrading is on the increase due to its high growth potential, reactivity, and ability to store energy more than other biomasses. This research hypothesized that blending of discard ultra-fine coal with live microalgae biomass would improve the kinetic properties of the coal more than expected from linear combination of the dry materials. Thermogravimetric combustion of “Coalgae®” was studied under non-isothermal conditions from 40 °C to 900°C at a heating rate of 15 °C/min and air flow rate of 20 ml/min. The thermogravimetric combustion properties i.e. small-scale was related to the large-scale, John Thompson’s fixed-bed reactor under the above condition. Thermal profiles were transformed into a differential function to reveal overlapped combustion events. The Coat-Redferns kinetic model was applied on the non-de-Ejesieme, O.V. PhD Chemistry (Research), Nelson Mandela Univ. Email: ejevit@yahoo.com , s211266744@live.nmmu.ac.za convoluted reactions set to obtain some of kinetic parameters. The Fraser-Suzuki equation was used to de-convolute the overlapped combustion. Then, rate law combined with Arrhenius equation was used to derive the activation energy E a and pre-exponential factor A, while the integral form of solid states reaction model, g (∝) was applied to deduce the oxidation mechanism. The composite formed a strong and partly renewable blend under controlled temperature conditions, unlike assorted dried biomass mixed with coal. Microalgae biomass upgraded the fuel and kinetics properties of ultra-fine coal more than what was expected from a linear combination. It released heat that promoted the oxidation mechanism of the discard coal. The main effect is that the “Coalgae®” is significantly (p = 0.0570) more reactive than the coal. The co-firing approach is partly renewable and contributes to the utilization of high and low-quality available discard ultra-fine coal. It advances the combustion of coal resources and reduces carbon dioxide, CO2 emission attributed to global warming as well as preserves the natural biomass sources. The combustion of “Coalgae® “will improve economy, environment, and health, heat, and electricity supply to the society.
- Format
- vxi, 225 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
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NMU School of BioMolecular and Chemical Sciences
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