Publications

Mixing efficiency in stirred tanks is an important consideration in the design of many industrial processes. Computational fluid dynamics (CFD) techniques have been employed in the present work to study the hydrodynamics in a tank stirred by a Rushton turbine. The effect of the impeller clearance on the velocity field and mixing has been investigated. It has been shown that at a low impeller clearance, the Rushton turbine generates a flow field that evolves from the typical two loops to a single loop flow pattern similar to that of an axial impeller. This single loop flow pattern resulted in an increase in axial flow and a decrease in mixing time at a constant power number. It has been found that a draft tube can be used with a single Rushton turbine, at a low clearance to aid axial flow and mixing, and this resulted in 50% reduction in mixing time. There was a good comparison between laser Doppler velocimetry (LDV) experimental and CFD simulation flow fields, both of which showed that the draft tube improved mixing in the tank by suppressing secondary circulation loops.

Abstract The removal of fluoride from single component aqueous solution using Al3+‐ pretreated low‐silica synthetic zeolites (Al‐Na‐HUD, Al‐HUD, Al‐F9, and Al‐A4) was studied. The effects of adsorbent mass, initial solution pH, and initial concentration on fluoride removal in a batch system were evaluated. Equilibrium data were simulated using simple isotherms such as the Freundlich (F), Langmuir‐Freundlich (LF), Redlich‐Peterson (RP) and Dubinin‐Radushkevitch (DR) isotherms. From the DR model, initial pH effects and desorption studies, it was considered that the fluoride adsorption onto the zeolites proceeded by ion‐exchange or chemisorption mechanism. In interpreting the kinetic results, reaction kinetics (using Elovich equation) and mass transfer processes (both external mass transfer and intraparticle diffusion) were considered. Equilibrium and kinetic results of fluoride adsorption onto the adsorbents demonstrated the following order of performance: Al‐Na‐HUD>Al‐F9> Al‐HUD>Al‐A4.

Engineering education is getting global. This article assesses the present scenario in engineering education, which is undergoing a paradigm shift because of the Internet, innovation, and internationalization. The influence of information technology, industrial development, national politics, and economic policies on internationalization of engineering education has been discussed. Quality control and accreditation practices in some countries have been reviewed, and a link between technology advancement and engineering curricula has been drawn. A stable political and economic system is necessary to retain the highly qualified African engineers who are the drivers of the engineering education toward achieving this goal.

Case, J.M., et al., 2016. The significance of context for curriculum development in engineering education: a case study across three African countries. European Journal of Engineering Education, 41, p.279-292. Website Abstract

Curriculum reform is a key topic in the engineering education literature, but much of this discussion proceeds with little engagement with the impact of the local context in which the programme resides. This article thus seeks to understand the influence of local contextual dynamics on curriculum reform in engineering education. The empirical study is a comparative analysis of the context for curriculum reform in three different chemical engineering departments on the African continent, located in Kenya, Tanzania and South Africa. All three departments are currently engaged in processes of curriculum reform, but the analysis shows how the different contexts in which these efforts are taking place exert strong shaping effects on the processes and outcomes for that reform.

Kilonzi, F.M., et al., 2015. Optimization of transesterifcation of sunflower oil with ethanol using eggshell as heterogeneous catalyst. Chemical and Process Engineering Research, 30, p.24-33. Abstract

Biodiesel is currently mostly produced by homogeneous catalysis. Recently, however, heterogeneous catalysis is being considered as a cheaper alternative to the homogeneous process. Heterogeneous transesterification is considered a green process. The process requires neither catalyst recovery nor aqueous treatment steps and very high yields of ethyl esters can be obtained, close to the theoretical value. However, heterogeneously catalyzed transesterification generally requires more severe operating conditions, and the performance of heterogeneous catalysts is generally lower than that of the commonly used homogeneous catalysts. This study seeks to address this problem by studying the production of biodiesel using eggshells as heterogeneous catalysts. Heterogeneous catalysts can make biodiesel production more energy efficient, and therefore less expensive, by eliminating the need for expensive purification processes that separates the catalyst from reaction products typical in the use of homogeneous catalysts. Matlab was employed for the experimental design, statistical analysis and process modeling. Fatty acid ethyl ester was produced by transesterification of sunflower oil and ethanol using calcined eggshells as a heterogeneous catalyst. To optimize the process, some important variables such as reaction temperature, molar ratio of ethanol to oil and mass weight of catalyst were selected and studied. At the following conditions: 343K of reaction temperature, ethanol to sunflower oil ratio of 9: 1 and 1 mass wt% of catalyst, an optimum fatty acid ethyl ester yield of 92% was obtained, indicating that eggshells have the potential of …

Kumar, A., et al., 2015. Microwave Enhanced Organic Synthesis Green Chemistry- A Study in Transesterification. Proceedings of Sustainable Research and Innovation Conference, p.177–184} url = {http://sri.jkuat.ac.ke/ojs/index.php/proceedings/article/view/293. Abstract

Use of microwaves as an alternate heat source to replace conventional heating has been studied in organic synthesis. Microwave irradiation results in faster reaction rates, cleaner production, thereby reducing energy consumption. This also leads to better environmental impacts and is considered green chemistry. This Paper reviews application of microwave irradiation in transesterification reactions for production of biodiesels. Transesterification of Croton Megalocarpus oil using homogeneous sodium hydroxide catalyst was carried out using conventional heating in a water bath, and in a microwave oven. Synthesis of fatty acid methyl ester (FAME) was studied for the reaction variables catalyst concentration, methanol to oil molar feed ratio and reaction time. Results indicated that reaction time was reduced to about 2% for a similar yield when microwave irradiation was employed instead of convective heating. During convectional heating, a FAME yield of 96% corresponded to a methanol-to-oil molar ratio of 6:1, catalyst of 1 %, temperature of 70oC, and reaction time of 60 minute. During microwave irradiation, a yield of 92% was obtained when methanol-to-oil molar ratio was 9:1, catalyst concentration 0.5 %, and reaction time 1 minute. FAME was analyzed through gas chromatography.

Chirchir, A., et al., 2015. Improved biogas production over immobilised methanogenic consortia. Proceedings of Sustainable Research and Innovation Conference, p.294–303. Website Abstract

Alcohol distilleries produce effluents which are strongly acidic, have high Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD), contain strong odour and are dark brown in colour. They cause detrimental environmental effects if they are freely disposed off to the environment. Adopted anaerobic treatment techniques with associated biogas generation have not proved to be very efficient on high strength distillery effluents as substrates. The improvement on mean product yield, effluent stabilization and sterile air tolerance was explored through microbial immobilization on activated natural zeolite and calcium alginate supports. Three experimental set-ups were performed with the first acting as a control and having no support material whereas the second and third having microbial system immobilized unto activated natural zeolite and calcium alginate supports respectively. At the marginal organic loading of 75 kg/m3 (corresponding to undiluted waste water), the unsupported system showed a low yield of 2.1 X 10-3 m3/kg CODt in biogas, whereas the calcium alginate system registered the highest yield of 84.5 X 10-3 m3/kg CODt . Activated natural zeolite system on the other hand showed a yield of 43.6 X 10-3 m3/kg CODt. Based on the effluent stabilization over the same initial marginal organic loading, activated natural zeolite system demonstrated the highest degree in effluent stabilization of 44.0 % as opposed to the unsupported and the calcium alginate system that registered 24.0 % and 41.3 % respectively. Finally, activated natural zeolite supported system showed the longest tolerance to sterile air exposures of 90 minutes. The unsupported system registered a tolerance of 30 minutes whereas the calcium alginate system demonstrated 60 minutes of oxygen tolerance.

Kumar, A., 2015. TRANSESTERIFICATION OF CROTON MEGALOCARPUS OIL BY HETEROGENEOUS CATALYSIS AND MICROWAVE IRRADIATION – REACTION KINETICS AND PROCESS OPTIMIZATION. Moi University: School of Engineering.

Kiriamiti, {H.K. }, et al., 2014. Comparative Study of Petrodiesel and Biodiesel in Domestic and Engine Use. African Journal of Technology, 1. Abstract

Increased gas emissions from the production and use of petroleum products have negative impact on the environment and more specifically on the flora and fauna. This has necessitated the development of alternative cleaner petroleum substitutes such as biodiesel. In this work, an investigation was carried on a pilot scale batch distillation unit to determine operating parameters that influence the quality of a biodiesel. The parameters studied include reaction temperature, amount of catalyst and alcohol, rate of agitation and reaction time. The biodiesel was produced using the method of transesterification of methanol and sunflower oil with sodium hydroxide as a catalyst. Comparative engine tests on both petrodiesel and biodiesel were performed with a view to ascertain the comparative performance of the two fuels. Over the temperatures considered, the results showed that the transesterification of sunflower oil produced a marked decrease in viscosity and density to a level comparable to those of the petrodiesel. This gave an indication that the biodiesel could be as good as petroleum diesel. Tested on hurricane lumps and pressure stove, it was shown that the biodiesel burned for longer time compared to kerosene and this can be attributed to its low volatility and high calorific value. On blending with kerosene, its capillarity action improved substantially and, on burning, emissions were unnoticed. From the analysis carried out on biodiesel production from sunflower oilseeds, there are indications that the project looks economically viable because the major raw material is readily available at an affordable cost.

Anil Kumar

Associate Professor of Chemical Engineering

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