Roadmap Towards Clean Coal Technology for Sustainable Power Sector in South Africa

South Africa has sufficient coal resources to meet future demand. However, using this local energy resource presents several environmental compliance concerns. The export market's need for high-quality coal results in a decline in coal quality, which results in increased environmental regulation non-compliance. In this study, five samples of coal covering a wide range of qualities obtained from mine stockpiles supplying power plants were collected, and standardized processes were used to prepare them for various analyses. Based on the results of coal characterization and resultant emissions, a wide range of technology options should be made available for different types of coal, and all these technologies are presented in the current study. Therefore, South Africa will likely have to take a hybrid approach to reduce emissions and address electricity supply and demand issues. South Africa's ageing electricity generation infrastructure, sluggish economic development, and water shortages support this. In order to find solutions that will satisfy the demands of coal users for dependable, tried-and-true technology while also meeting environmental criteria, various limitations were used to sort through the available technologies. The coal roadmap proposes three possible routes, ranging from business-as-usual physical methods to chemical methods and biological methods. Such processing methods could drastically reduce power sector SO2 emissions if they are commercially feasible. This roadmap outlines the challenges that the power sector must overcome and provides an overview of potential treatment initiatives for the power sector that South Africa may implement over the coming years

Performance Evaluation of AOP/Biological Hybrid System for Treatment of Recalcitrant Organic Compounds

Process water from nuclear fuel recovery unit operations contains a variety of toxic organic compounds. The use of decontamination reagents such as CCl4 together with phenolic tar results in wastewater with a high content of chlorophenols. In this study, the extent of dehalogenation of toxic aromatic compounds was evaluated using a photolytic advanced oxidation process (AOP) followed by biodegradation in the second stage. A hard-to-degrade toxic pollutant, 4-chlorophenol (4-CP), was used to represent a variety of recalcitrant aromatic pollutants in effluent from the nuclear industry. A UV-assisted AOP/bioreactor system demonstrated a great potential in treatment of nuclear process wastewater and this was indicated by high removal efficiency (>98%) under various 4-CP concentrations. Adding hydrogen peroxide (H2O2) as a liquid catalyst further improved biodegradation rate but the effect was limited by the scavenging of OH• radicals under high concentrations of H2O2

Performance evaluation of microbial desulphurization of Waterberg steam coal as a pre-combustion technique

The current study evaluates pre-combustion microbial desulphurization of medium – sulphur type coal containing total sulphur (1.45 wt. %) and pyritic sulphur (≥ 0.51 wt. %) in a laboratory scale. Coal samples used in the current study were supplied by one of South African Power Utility, Eskom power station as received from the nearby Waterberg coalfield in Limpopo in South Africa... After a stipulated hydraulic retention time (HRT), the coal samples were filtered, washed, dried and analyzed for total sulphur, ash content and calorific values. The calorific value of the coal significantly improved from 20.42 MJ/Kg to 24.16 MJ/Kg on the 5th day. The process removed up to 72 % of the total sulphur content in the coal samples at an HRT of day 9th. Furthermore, ash content reduced by 16 %. This study provides a novel breakthrough of an alternative microbial desulphurization process of Waterberg steam coal as a pre-treatment technique in order to meet stringent environmental emissions standards for SO2.This work was partially funded by University of Pretoria Postgraduate Support Bursary and National Research Foundation (NRF) Funding for Rated Researchers (IFRR) Grant No. IFR170214222643 awarded to Professor Evans M. N. Chirwa of the University of Pretoria.http://www.aidic.it/cetam2019Chemical Engineerin

Effect of Isokinetic Sampling on Combustion Airflow and Heat Energy Produced in 600 Mw Coal-Fired Boiler

The focus of this research is to study the effect of isokinetic sampling of the secondary airflow on the energy input to the fuel-fired boiler. The relocation of the secondary airflow test ports from horizontal to vertical transverse sampling was implemented after the observation that the airflow in the duct was not constant. Additionally, the methods are used to ensure that the airflow particle inlet velocity to the sampling nozzle is the same as the duct velocity. The pressure was measured using the S-type pitot tube on four boiler levels at the full load capacity of the boiler. At 100% fuel-fired boiler capacity, the energy equation accurately projected the kinetics of pressure drop. It was established that the decrease in pressure results in increased airflow. The continuity principle supports the claim that these outcomes are due to the secondary air's increased velocity as it passes through the constricted duct area, which causes a decrease in pressure. These findings improve our understanding of how isokinetic sampling affects combustion airflow and heat energy, which can guide its future application in coal-fired boilers

Possible Diamond-Like Nanoscale Structures Induced by Slow Highly-Charged Ions on Graphite (HOPG)

The interaction between slow highly-charged ions (SHCI) of different charge states from an electron-beam ion trap and highly oriented pyrolytic graphite (HOPG) surfaces is studied in terms of modification of electronic states at single-ion impact nanosizeareas. Results are presented from AFM/STM analysis of the induced-surface topological features combined with Raman spectroscopy. I-V characteristics for a number of different impact regions were measured with STM and the results argue for possible formation of diamond-like nanoscale structures at the impact sites

Modelling performance evaluation of microbial desulphurization of Waterberg steam coal in CSTR

The first part of this study used microbial desulphurization process as a pre-combustion technique for sulphur content reduction in Waterberg steam coal. This is simulated at the laboratory scale where Continuously Stirred Tank Reactor (CSTR) acts as a biological reaction chamber. Experimental tests were performed by varying coal particle size distribution of -0.85 mm, +1.00 mm, +2.30 mm and 4.60 mm in order to determine the influence and optimum condition for desulphurization process. The second part of this study deals with developing a model based on reaction kinetics, simulate microbial desulphurization process in CSTR system and validate the model under various experimental conditions. Kinetics study and parameter estimations were evaluated and optimized using the Simulation Programme for Aquatic Systems (AQUASIM) 2.0 Software. The average kinetic parameters in the bioreactor were determined for both without inhibition: kd = 1.65 x 10-3 (h-1), Ks = 1.23 x 10-4 mgL-1, X0 = 523 mgL-1 and χ2 = 0.524 and with inhibition, KI = 371 mgL-1 for finer coal particle size. Equally important, these kinetic parameters were determined by means of optimization. Consideration should be given that the developed model may be applied to only wider range of sulphur content range studied.This work was partially funded by University of Pretoria Postgraduate Support Bursary and National Research Foundation (NRF) Funding for Rated Researchers (IFRR) Grant No. IFR170214222643 awarded to Professor Evans M. N. Chirwa of the University of Pretoria.The University of Pretoria Postgraduate Support Bursary and National Research Foundation (NRF) Funding for Rated Researchers.http://www.aidic.it/cetam2020Chemical Engineerin

Skills training through hands-on practical activities in civil technology – a case study of three technical schools in South Africa

Skills training for Civil Technology learners in South African schools, is an aspect entrenched in the Civil Technology policy document in order to produce skilled personnel for a sustainable economy. Practical activities through the Practical Assessment Task (PAT) are national requirements for all practical-based subjects from grades 10–12 in South African schools. The purpose of this study was to investigate the status of Civil Technology practical activities in three South African schools in the Eastern Cape Province. Purposive sampling was used to identify 41 learners and 3 teachers to participate in the study. Questionnaires, semi-structured interviews and observation as data collection methods were instruments used to collect data. The study has found that learners exit grade 12 without basic practical hands-on skills. Civil Technology practical activities were found to be inadequately offered in the three schools investigated. Educators should be well-trained by higher education institutions (HEIs) to conduct practical activities with learners so that these learners are equipped with marketable skills in order to contribute to a sustainable economy after grade 12. Technology teacher education and training should include regular exposure and visits to relevant industries in order for teachers to keep abreast with the latest technological developments. The supply of equipment to schools should be coupled with routine maintenance of the equipment.https://doi.org/10.4102/td.v10i3.18

Characteristics of thermal coal used by power plants in Waterberg Region of South Africa

The current study evaluate the key characteristics of coal used by power stations in the Waterberg region of South Africa as a future alternative to South Africa’s well known depletion coal reserves. Eight coals samples used in the current study were supplied by one of South African Power Utility, Eskom power station as received from the nearby Waterberg coalfield in Limpopo, South Africa. Conventional characterization such as proximate and ultimate analysis as well as determination of sulphur forms in coal samples were carried out as per ASTM and ISO standards. The study revealed coal as medium sulphur type coal with pyritic and organic sulphurs accounting for the bulk of the total sulphur. Maceral analyses of coal showed that vitrinite is the dominant maceral (up to 51.8 vol.%), whereas inertinite, liptinite and reactive semifusinite occurred in proportions of 22.6 vol.%, 2.9 vol.% and 5.3 vol.% respectively. The ratio of fixed carbon to volatile matter, commonly referred to as fuel ration which indicates the combustion characteristics of the coal was determined. A correlation between forms of sulphur and total sulphur in medium sulphur Waterberg coals was also established.http://www.aidic.it/cetam2018Chemical Engineerin

Desulphurization of medium sulphur Waterberg steam coal in a batch operated scale : microbial solution

The current study evaluates pre-combustion microbial desulphurization of medium – sulphur type coal containing total sulphur (1.45 wt.%) and pyritic sulphur (≥ 0.51 wt. %) in a laboratory scale. Coal samples used in the current study were supplied by one of South African Power Utility, Eskom power station as received from the nearby Waterberg coalfield in Limpopo in South Africa. Coal samples were size fractioned using 13.2, 9.5, 8.0, 6.3, 5.6, 4.7, 2.36, 2.00, 1.00, 0.85 mm and below using automatic screens shaker. Coal sample containing particle size in the range of − 0.85 mm was used in the experiments with bacteria isolated from the native coal mine site. After a stipulated hydraulic retention time (HRT), the coal samples were filtered, washed, dried and used for total sulphur and calorific value analysis. The calorific value of the coal significantly improved from 20.42 MJ/Kg to 24.16 MJ/Kg on the 5th day.The process removed up to 41% of the total sulphur content in the coal samples at a HRT of 8 days. This study provides a novel breakthrough of an alternative microbial desulphurization process of Waterberg steam coal as a further pre-treatment technique in order to meet stringent environmental emissions standards for SO2.University of Pretoria Postgraduate Support Bursary and National Research Foundation (NRF) Funding for Rated Researchers (IFRR) Grant No. IFR170214222643 awarded to Professor Evans M. N. Chirwa of the University of Pretoria.http://www.aidic.it/cetam2018Chemical Engineerin

Recent and Prospects of Synthesis and Application of Metal-Organic Frameworks (MOFs) in Water Treatment: A Review

Wastewater treatment is designed to eradicate toxic pollutants emanating from the industrial effluent to the surface and underground water. The efficiency and limitations of most of the existing water treatment techniques such as coagulation/flocculation, photocatalysis, membrane technologies and adsorption in the remediation of toxic pollutants have been established. However, the success reported for each of these techniques is usually associated with the efficiency and environmental friendliness of water treatment products applied. MOFs-based products are one of the materials serving as an alternative to chemically synthesized products, and their application as water treatment products has been reported extensively but not systematically documented. In this review, authors endeavoured to comprehensively provide insights into the recent MOFs-based product synthesis for different applications, especially in water treatment. The key factors influencing the synthesis of MOFs, including choice of metal ions, organic linkers, and synthesis conditions, along with the latest developments in scalable and cost-effective fabrication techniques are discussed. The synthesis routes, their limitation and their performances as an adsorbent, photocatalyst and additives in membrane fabrication in the removal of toxic pollutants from water are elaborated. The prospects in the large-scale production of MOFs-based water treatment products for real industrial applications are critically reviewed in this study. Overall, a well-curated synthesis and application of MOFs in water treatment is hereby generated from the best resources accessible through the literature