- A-Z Publications
- South African Journal of Chemical Engineering
- Previous Issues
- Volume 20, Issue 3, 2015
South African Journal of Chemical Engineering - Volume 20, Issue 3, 2015
Volume 20, Issue 3, 2015
Investigation of the effects of tray downcomer design on the efficiency of a vibrating plate extractorSource: South African Journal of Chemical Engineering 20, pp 1 –10 (2015)More Less
The effectiveness of different tray designs was studied in liquid-liquid extraction using a vibrating plate extraction (VPE) column. The effect of these tray designs and agitation levels on the dispersed phase holdup, drop size distribution and Sauter mean diameter was investigated. Two different sieve tray designs (Type 1 - cylindrical downcomers and Type 2 - straight segment downcomer) were tested. It was found that the Type 1 was more efficient than Type 2. It had a higher dispersed phase holdup and lower Sauter mean diameter with the highest percentage of solute being extracted (95.05%).
Source: South African Journal of Chemical Engineering 20, pp 11 –26 (2015)More Less
The speed and stability of anaerobic digestion depends mainly on the particle size of the input material. In this paper, particle sizes of 500μm, 250μm, 100μm and 25μm were investigated to evaluate the effects of particle size on biogas production and identify the most suitable size that would improve the efficiency of anaerobic digestion. The study was conducted using anaerobic digestion batch scale tests and gas chromatography to investigate the quality of the gas produced and the optimum particle size to maximise methane production. Prior digestion, the distributions of particle sizes of all samples were determined using single and double pass distribution techniques. 59%, 53%, 33% and 39% of CD, CM, PM and SW were recovered, respectively. In both techniques, the weight of the feed recovered reduced as the sieve became smaller. Decreasing the particle size of the feedstock significantly increased the amount of biogas. At 25μm particle size, 583ml, 569ml, 538ml and 398ml of methane was produced on the 4th day of gas production for CD, PM, CM and SW, respectively. At optimal particle size (25μm) methane was 3 - 30 % higher as compared to that of 100μm, 250μm and 500μm particle size in mesophillic batch digestion tests.
Source: South African Journal of Chemical Engineering 20, pp 27 –40 (2015)More Less
Natural dyes, from botanical sources, for colouring textiles is fast achieving a niche market in the textile industry necessitating optimised scaled-up extraction processes. The extraction of a natural dye, Badie, from the stem bark of the Bridelia ferruginea plant by leaching via an aqueous solvent in a batch stirred tank reactor is reported. The inner bark of the plant tissue with a plate-like morphology retained on a 5 mm mesh size with effective thickness of 500 microns, a liquid solid ratio of 5 mL/g and an effective leaching time of 2 h resulted in an optimum yield of 21% without encumbering the process with limitations in pressure drop during filtration. We identified from infrared and UV spectroscopic analysis that the dye has similar functional features of a flavonol. The effective diffusion coefficient was determined to be 1.6×10-10 m2/s. The formation of pigments by complexation with a variety of cations: Al3+, Zn2+, Cu2+, Fe2+, Ba2+, Ca2+, Mg2+, Mn2+, Cr6+ to extend the range of colours of the pigments is reported. Thus, simplified model derived for this work to optimise contact time in the design and operation of a commercial scale extraction and enhance value is reported.