Research Outputs (Chemical and Metallurgical Engineering)

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Browsing Research Outputs (Chemical and Metallurgical Engineering) by Author "Sheridan, C."

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    Critical evaluation of the chemical composition of acid mine drainage for the development of statistical correlations linking electrical conductivity with acid mine drainage concentrations
    (Elsevier, 2022-05-06) Smith, J.; Sheridan, C.; van Dyk, L.; Harding, K.G.
    The design an effective treatment processes for the remediation of acid mine drainage (AMD) requires an understanding of the composition of the AMD water. The pH and elemental composition of AMD waters are site specific and are dependent on the regional geology, and environmental factors. To establish the chemical and physical characteristics of two AMD sites located in the Mpumalanga coal mining region, South Africa, samples were taken between February 2018 to April 2019. These data were compared against regulatory legislation, and the potential health effects of exposure indicated. Strong correlations were noted between parameters and statistical evaluation demonstrated that electrical conductivity (EC) could be a useful correlative for prediction of total acidity, dissolved iron, and sulfur concentrations in acidic AMD waters. From these findings, empirical correlations were used to derive regression equations which were used to derive the EC values corresponding to the respective water quality limits for TDS, dissolved iron, and sulfur to provide a rapid method for testing compliance. Given the site specificity of AMD composition, this approach is intended as a proof of concept for the development of a methodology for adaption at other AMD sites. The regression equations should not be considered as universal to all AMD sites and EC should also not be used as a replacement for more complete chemical analysis.
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    Feasibility assessment of the production of bioethanol from lignocellulosic biomass pretreated with acid mine drainage (AMD)
    (Elsevier, 2020-09-01) Burman, N.W.; Sheridan, C.; Harding, K.G.
    A techno-economic evaluation of a lignocellulosic bioethanol facility that uses acid mine drainage for the pre-treatment of weeping love grass (Eragrostis curvula) was performed. Both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) reactor configurations were evaluated. Results were compared to an evaluation of the same process with biomass pre-treated with dilute H2SO4. Capital and operating costs were estimated and a simple economic evaluation was conducted. It was found that all scenarios made a loss except for biomass pre-treated with H2SO4 in the SHF reactor configuration, although the high capital cost resulted in a payback period of 80.7 years, which is unfeasible. SHF was found to produce more ethanol at a lower capital cost than SSF, indicating that it is more economically feasible. Incorporating the remediation of AMD into a simultaneous process could help improve process economics. It is thus recommended that a techno-economic evaluation be conducted on a process that produces bioethanol through SHF and simultaneously remediates AMD
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    Modelling of Low Temperature Dilute Sulfuric Acid Pre-treatment of South African Grass
    (Elsevier, 2018-12-01) Burman, N.W.; Sheridan, C.; van Dyk, L.; Harding, K.G.
    Dilute acid hydrolysis is an effective method of pre-treatment of lignocellulosic biomass. Although there are many studies modelling this pre-treatment at high temperature (120–210 °C), no studies were found modelling this reaction at low temperature. In this study, a long grass species was pre-treated with dilute sulfuric acid (pH 1, 2 & 3) at low temperatures (35 °C, 65 °C, 90 °C). The hydrolysis of xylan was found to obey a bi-phasic model in which there are two fractions of xylan, with significantly different hydrolysis rates. The rates of hydrolysis of the fast reacting fraction was found to obey Arrhenius type temperature dependence (Ea = 155.06 kJ/mol, A0 = 1.65 × 1019/min), which agrees with findings of similar studies at higher temperatures. A negligible rate of hydrolysis was determined for the slow fraction which differs from previous studies. The proportion of the slow reacting fraction (50%) which is lower than previously determined (55%–100%).