Browsing by Author "Knoetze, Johannes H."

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    Hydrodynamics of a packed column operated under supercritical conditions
    (AIDIC, 2018) Franken, Hendrik H.; Knoetze, Johannes H.; Schwarz, Cara E.
    ENGLISH ABSTRACT: There is a lack of hydrodynamic data under supercritical conditions, in particular in systems that attempt to isolate hydrodynamics from mass transfer. This paper presents hydrodynamic data focusing on the characterization of flooding. Two different flooding phenomena are identified using the column overheads, pressure drop and liquid hold-up of the system. It is further noted that the saturated fluid properties of density and dynamic viscosity play a significant role in flooding. A density difference of less than 250 kg/m3 between phases and a decrease in liquid viscosity causes a shift from classical gas-liquid flooding to behaviour more analogous to that of liquid-liquid extraction columns.
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    Thermogravimetric study of the pyrolysis characteristics and kinetics of coal blends with corn and sugarcane residues
    (Elsevier, 2013) Aboyade, Akinwale O.; Gorgens, Johann F.; Carrier, Marion; Meyer, Edson L.; Knoetze, Johannes H.
    This paper investigates the non-isothermal thermokinetics of the co-pyrolysis of sugarcane bagasse and corn residue blended with coal. The individual devolatilization behaviour of each of the fuels obtained separately was compared with the behaviour of the biomass blends with coal at various mix ratios. Possible synergistic behaviour that points to the existence of chemical interactions during pyrolysis between the coal and biomass fractions of the blends could thus be quantified. Synergistic interactions in the blends resulted in higher than expected volatile yields. The interactions occurred between 300 °C and 500 °C, corresponding to the end of biomass devolatilization and the start of coal decomposition. Isoconversional kinetic analysis revealed that apparent activation energy values varied between 165–180, 162–190, 160–175, and 225–260 kJ mol− 1 for sugarcane bagasse, corn cobs, corn stover, and coal in the 0.1 to 0.8 conversion range. A comparison of E(α) for single fuels and coal-biomass blends gave further evidence of synergistic behaviour as demonstrated by larger variation in E(α) during the decomposition of the blends, compared to the individual fuels.