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- South African Journal of Chemical Engineering
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- Volume 20, Issue 1, 2015
South African Journal of Chemical Engineering - Volume 20, Issue 1, 2015
Volume 20, Issue 1, 2015
Source: South African Journal of Chemical Engineering 20, pp 1 –15 (2015)More Less
-criteria decision analysis (MCDA) techniques were applied to choose a biogas digester technology and a site from a list of potential alternatives for an anaerobic digestion (AD) system utilising the organic fraction of municipal solid waste (OFMSW) based on a case study at the University of Johannesburg's Doornfontein campus in South Africa. The simple multi-attribute rating technique (SMART) and analytic hierarchy process (AHP) techniques of MCDA were used to select a suitable biodigester model and site respectively. From a list of 14 biodigester technologies to be established at 1 of 3 potential sites in the study area, the most preferred model was the Puxin digester to be sited near the Aurum ladies' residence within the school campus to supply biogas for heating purposes.
Source: South African Journal of Chemical Engineering 20, pp 16 –29 (2015)More Less
Removal of nickel (II) and copper (II) from aqueous solutions using NaBH4 as a reducing agent was studied. Reduction crystallization was achieved in a batch reactor at 65°C using seeded experiments. The effect of using different molar ratios of [Ni2+] : [BH4 -] namely; 1:1, 1:0.25 and 1:0.1 and seeding materials on the rate of reduction was also investigated. The results obtained showed that NaBH4 is an effective reducing agent for the removal of Ni2+ and Cu2+ from effluents. Using a molar ratio of 1:0.1 of [Ni2+]: [BH4 -] and Fe and Ni as a seeding material over 99% metal removal was achieved. Ni as a seeding material yielded the best results as it is autocatalytic although there was no significant difference in the rate of reduction compared to that obtained when Fe was used as a seeding material.
Source: South African Journal of Chemical Engineering 20, pp 30 –43 (2015)More Less
A mechanistic model describing the mass and momentum exchange in bubble columns is proposed that is based on the observations that the gas distribution in a bubble column is not uniform across the column and that as a consequence large liquid recirculation cells are formed in such columns. The model provides insight into the mechanism of mass and momentum exchange in bubble columns and predicts turbulent viscosities in bubble columns that are similar to those reported in the literature. It also predicts axial and radial dispersion coefficients that are of the same order of magnitude as the reported data. Whereas the model is based on a description of the underlying physical phenomena, its validity and extrapolation is expected to be more reliable than that of empirical correlations.
Source: South African Journal of Chemical Engineering 20, pp 44 –60 (2015)More Less
Air pollution, which is a threat to human health and to the natural environment, is growing worldwide day by day and the regulations for air pollutants made us to investigate an alternative method to control the emissions from industries, which is of low cost, simple design and of high performance. Plate scrubbers are medium level energy wet scrubbers which have enormous advantages in various chemical process industries for simultaneous removal of particulate matter and gas pollutants from effluent gas streams. A sieve plate scrubber has been modelled and installed in the lab scale. This paper presents the hydrodynamics of the three stage plate column wet scrubber which will be used to clean the synthesis gas by removing particulate matter and gaseous pollutants simultaneously. Experimental study has been done for the pressure drop (P) measurement at different liquid-gas ratios. The highest plate scrubber pressure drop is 1456 Pa, which is obtained at gas flow rate (QG) of 15.134x10-3 Nm3/s and liquid flow rate (QL) of 48.183x10-6 m3/s with 7.5x10-3 kg/m3 inlet fly ash loading (Si) and it is a medium value when compared to other type of scrubbers. The effect of different variables such as inlet flow rates of air and liquid, and inlet fly ash loading on the hydrodynamics was keenly observed. A model has been suggested for the prediction of pressure drop for which the values from the experimental study and predicted values matched with attainable standard deviation and percentage error.
Orthogonal collocation solution of non-linear coupled-partial differential equations in fixed bed adsorption columnSource: South African Journal of Chemical Engineering 20, pp 61 –80 (2015)More Less
The mathematical model for the adsorption of lead ions onto ETS-10 particles has been developed. The resulting material balance equations in fixed bed adsorption column are nonlinear coupled partial differential equations. These equations were solved by using orthogonal collocation technique which converts them to ordinary differential equations. The resulting ordinary differential equations have been solved by using ode15s of MATLAB which uses variable order, variable step Gear method. The model was found to be robust and the results were compared with the experimental results reported in literature. After validation of the model, simulations were carried out using the present model for a systematic parametric study. The effects of various important such as flow rate, bed height, inlet adsorbate concentration, pore diffusivity and particle diameter on breakthrough curve were studied in detail. Also the concentration of adsorbate in the pores of the adsorbent particle was found out.