Hilary Rutto

Optimization of Production Variables of Biodiesel from Manketti Using Response Surface Methodology

Manketti oil that was used as a feedstock to produce the biodiesel was extracted from manketti nut. An alkali catalyst transesterfication process was adopted. A statistical model was developed to correlate the transesterification process variables to the yield of fatty acid methyl ester (FAME) using a central composite design (CCD) by a response surface methodology. The transesterification process variables were reaction temperature x1, (30°C–65°C), amount of catalyst x2, (0.5–1.5 wt%), amount of methanol in the oil x3, (10–50 wt%), and reaction time (30–90 min). The essential fuel properties such as density, flash point, viscosity, and acid number were measured and compared with other types of biodiesel produced from wild nuts and American Society for Testing and Material (ASTM) standards for biodiesel. From the results, the optimum conditions for the production of FAME obtained were as follows: reaction temperature 55°C, reaction time 53 min, amount of catalyst 1.02 wt%, and amount of methanol in the oil of 32 wt%. The optimum yield of FAME that can be produced was 98.3%. The results show that the important fuel properties of the biodiesel produced in optimum conditions met the biodiesel ASTM standard.

Dissolution of a South African calcium based material using urea: An optimized process

The rate at which limestone dissolves is very important in wet flue gas desulfurization process (FGD). High dissolution rates provide better alkalinity, which is important for sulfur dioxide (SO2) absorption. This study investigates the use of urea to improve the dissolution rate of limestone. The dissolution characteristics have been studied by using a pH-Stat method. The dissolution rate constant was measured according to the shrinking core model with surface control, i.e. (1−(1−X)1/3)=krt. The effect of experimental variables such as temperature, amount of urea, solid to liquid ratio and stirring speed on the dissolution rate of limestone were investigated. Using a central composite design (CCD) of experiments variables, a mathematical model was developed to correlate the experimental variables to the dissolution rate constant. The experimental value was found to agree satisfactorily with predicted dissolution rate constant. The model shows that high temperature and low solid to liquid ratio improves the dissolution rate. The dissolution rate increased slightly with increase in the stirring speed. In the presence of urea the dissolution rate constant increased by 122%. The dissolution reaction follows a shrinking-core model with the chemical reaction control as the rate-controlling step.

Preparation of bagasse ash/CaO/ammonium acetate sorbent and modelling their desulphurization reaction

The influence of siliceous and hydration agents additives on the preparation of calcium-based sorbents for dry flue-gas desulphurization at low temperature was studied. The key reaction variables investigated are: quantity of bagasse ash, hydration temperature, quantity of ammonium acetate and hydration time. Their effect on the surface area of the sorbent was determined and a central composite design was used as a statistical tool. A polynomial model was established to correlate the sorbent preparation parameters to the sorbent surface area. The desulphurization experiments performed with the thermogravimetric analyser indicate higher SO2 removal when bagasse ash and ammonium acetate are used. The kinetics of desulphurization reaction was fitted using the unreacted shrinking core model and the results show that the rate-limiting step was diffusion over the product layer.

Dissolution kinetics of sorbents and effect of additives in wet flue gas desulfurization

Abstract Flue gas desulfurization (FGD) technology has been adopted by a number of power stations for the removal of sulfur dioxide (SO2) from flue gas. The wet FGD system is the most commonly used process because of high SO2 removal efficiency and because of the availability of the sorbent used. This paper emphasizes the wet FGD process and the different types of sorbents used. Sorbent dissolution in the wet FGD process plays a significant role in the overall performance of the system. Factors such as temperature, solid-to-liquid ratio, pH, particle size, and additives can be optimized to improve the dissolution rate in the wet FGD system. Additives such as organic acids and inorganic salts can improve the dissolution rate and the desulfurization efficiency of the sorbent. Dissolution kinetics gives an understanding of the effects of reaction variables on the dissolution rate. The dissolution process is a heterogeneous reaction system consisting of fluid reactants and solid particles. This is best described using the shrinking core model that considers a reducing solid particle size as the reaction takes place.

Leaching kinetics of bottom ash waste as a source of calcium ions

Bottom ash is a waste material from coal-fired power plants, and it is known to contain elements that are potentially toxic at high concentration levels when disposed in landfills. This study investigates the use of bottom ash as a partial substitute sorbent for wet flue gas desulfurization (FGD) processes by focusing on its leaching kinetics in adipic acid. This was studied basing on the shrinking core model that was applied to the experimental data obtained by the authors presented at the International Conference on Industrial, Manufacturing, Automation and Mechanical Engineering, Johannesburg, South Africa, November 27–28, 2013) on dissolution of bottom ash. The leaching rate constant was obtained from different reaction variables, namely, temperature, pH, acid concentration, and solid-to-liquid ratio, that could affect the leaching process. The solid sample of bottom ash was characterized at different leaching periods using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that solid-to-liquid ratio had a significant effect on the leaching rate constant when compared with other variables. The leaching kinetics showed that diffusion through the product layer was the rate-controlling step during leaching, and the activation energy for the process was found to be 18.92 kJ/mol. Implications: The use of coal bottom ash waste as a sorbent substitute in wet flue gas desulfurization (FGD) has both economic and environmental advantages. This is because it is a waste from coal-fired thermal power plant and this study has proven that it can leach out a substantial amount of calcium ions for wet FGD process. This will abate anthropogenic pollution due to landfill disposal of bottom ash wastes and also reduce sulfur dioxide emissions.

The use of impregnated perlite as a heterogeneous catalyst for biodiesel production from marula oil

In this study, biodiesel was produced from marula (Sclerocarya birrea) oil using impregnated perlite with potassium hydroxide (KOH) as a heterogeneous catalyst. The effect of experimental variables such as temperature (°C), reaction time (h), methanol to oil ratio (mass %), and catalyst to oil ratio (mass %) on the transesterification process were investigated. Using a central composite design (CCD), a mathematical model was developed to correlate the experimental variables with the percentage yield of biodiesel. The model showed that optimum conditions for biodiesel production were as follows: catalyst to oil ratio of 4.7 mass %, temperature of 70.4°C, methanol to oil ratio of 29.9 mass %, and reaction time of 3.6 h. The yield of 91.4 mass % of biodiesel was obtained. It was also possible to recycle and reuse the modified perlite up to three times without any significant change in its catalytic activity. The X-ray diffraction (XRD) and the Brunauer-Emmett-Teller (BET) surface area showed no modifications in the perlite structure. The results show that the important fuel properties of marula biodiesel meet the American Society for Testing and Materials (ASTM) biodiesel standard properties.

Dissolution kinetics of South African coal fly ash and the development of a semi-empirical model to predict dissolution

Wet flue gas desulphurization (FGD) is a crucial technology which can be used to abate the emission of sulphur dioxide in coal power plants. The dissolution of coal fly ash in adipic acid is investigated by varying acid concentration (0.05-0.15M), particle size (45- 150μm), pH (5.5-7.0), temperature (318-363K) and solid to liquid ratio (5-15 wt %.) over a period of 60 minutes which is a crucial step in wet (FGD). Characterization of the sorbent was done using X-ray fluorescence (XRF), X-ray diffraction (XRD), Furrier transform infrared (FTIR), scanning electron microscope (SEM) and Branauer-Emmett-Teller (BET) surface area. BET surface area results showed an increase in the specific surface area and SEM observation indicated a porous structure was formed after dissolution. The experimental data was analyzed using the shrinking core model and the diffusion through the product layer was found to be the rate limiting step. The activation energy for the process was calculated to be 10.64kJ/mol.

Formulations, development and characterization techniques of investment casting patterns

Abstract Conventionally, unfilled wax has been used as a universal pattern material for the investment casting process. With increase in demand for accurate dimensions and complex shapes, various materials have been blended with wax to develop more suitable patterns for investment casting in order to overcome performance limitations exhibited by unfilled wax. The present article initially reviews various investigations on the development of investment casting patterns by exploring pattern materials, type of waxes and their limitations, the effect of filler materials and various additives on unfilled wax, wax blends for pattern materials, plastics and polymers for pattern materials and 3D-printed patterns. The superiority of filled and polymer patterns in terms of dimensional accuracy, pattern strength, surface and flow properties over unfilled wax is also discussed. The present use of 3D patterns following their versatility in the manufacturing sector to revolutionize the investment casting process is also emphasized. Various studies on wax characterization such as physical (surface and dimensions), thermal (thermogravimetric analysis and differential scanning calorimetry), mechanical (thermomechanical analysis, tensile stress testing, dynamic mechanical analysis) and rheological (viscosity and shearing properties) are also discussed.

The dissolution kinetics of industrial brine sludge wastes from a chlor-alkali industry as a sorbent for wet flue gas desulphurisation (FGD)

ABSTRACT The disposal of industrial brine sludge waste (IBSW) in chlor-alkali plants can be avoided by utilization of IBSW as a sorbent in wet flue gas desulfurization (FGD). The shrinking core model was used to determine the dissolution kinetics of IBSW, which is a vital step in wet FGD. The effects of solid-to-liquid ratio (m/v), temperature, pH, particle size, and stirring speed on the conversion and dissolution rate constant are determined. The conversion and dissolution rate constant decreases as the pH, particle size, and solid-to-liquid ratio are increased and increases as the temperature, concentration of acid, and stirring speed are increased. The sorbents before and after dissolution were characterized using x-ray fluorescence (XRF), x-ray diffraction (XRD), and scanning electron microscopy (SEM). An activation energy of 7.195 kJ/mol was obtained and the product layer diffusion model was found to be the rate-controlling step. Implications: The use of industrial brine sludge waste as an alternative sorbent in wet flue gas desulfurization can reduce the amounts of industrial wastes disposed of in landfills. This study has proved that the sorbent can contain up to 91% calcium carbonate and trace amounts of sulfate, magnesium, and so on. This can be used as new sorbent to reduce the amount of sulfur dioxide in the atmosphere and the by-product gypsum can be used in construction, as a plaster ingredient, as a fertilizer, and for soil conditioning. Therefore, the sorbent has both economic and environmental benefits.

Desulphurization of Waste Tire Pyrolytic Oil (TPO) Using Photodegradation and Adsorption Techniques

S (Ag) and zinc oxide (ZnO) nanoparticles were simultaneously deposited on a glass substrate using the radio frequency (RF) sputtering technique at different substrate temperatures. Detailed characterization of the co-sputtered Ag/ZnO thin films were performed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS). The synthesized thin films were tested with UV-Vis diffuse reflectance spectroscopy to evaluate their optical properties. The obtained SEM results show a uniform dispersion of Ag nanoparticles within the ZnO matrix. These nanoparticles have average particle size of 20 nm. The optical band gap value had been calculated from UV transmission spectra of Ag/ZnO thin films deposited at various substrate temperatures. This value was observed to be in the visible light range (i.e. 2.7-3.1 eV), which is much smaller than that of pure ZnO (3.37eV). The photocatalytic activity of the produced thin films was evaluated through visible light photo degradation of 2-chlorophenol (2-CP) which, has been used as a pollutant model in water. The synthesized thin films showed enhanced visible light photocatalytic efficiency towards 2-CP degradation at elevated substrate temperature and retained its catalytic efficiency with only 8% loss in efficiency after four reuse cycles. Kinetic parameters involved in the degradation process were investigated by applying pseudo-second-order kinetic model.T study exposes the extent of contaminations and natural disturbance in soil and tobacco (Nicotiana tabacum) crops with potential health and ecological impacts caused by metals contaminated industrial waste water to surrounding environment. By exploring the extent of metals contamination the study find out the role of geochemical, geostatistical and geospatial inter and intra elemental relationship in soil and tobacco crops. By exploring the relation between and soil and Tobacco crops, a total of 51 samples were collected, pass through acid digestion and analyzed for thirteen major and toxic metals through atomic absorption spectroscopy (AAS 700). Geochemical results showed that the concentration of major and toxic elements in target area was exotically higher than the background areas (control area) with possible percentile (%) variations of 65.7, 27.5, 72.8, 7.5, 56.7, 54.26 23.95, 31.56, 39.3, 22.04, 48.92, 34.11 and 42.6 for Chromium, Cadmium, lead, Nickle, Copper, Zinc, Cobalt, Iron, Manganese, Magnesium, Sodium, Calcium and Potassium respectively. Meanwhile transfer ratio from soil to tobacco crops are 1.64, 5.99, 3.39, 7.59, 7.40, 6.01, 9.29, 1.12, 13.72, 16.37, 1.7, 7.72 and 36.56 (%) respectively. By integrating geochemical and geospatial analysis hereby provide a mobility evidence of metals in the environment. Geostatistical techniques provide scientific evidence and magnitude of toxic and major elements in soils and tobacco crops. All the geostatistical techniques are coherent with each other and can +90 % reliable, except enrichment factor, which were not compatible with these methods. However geospatial analysis proved the mobility of metals in environment. Thus geochemical, geostatistical and geospatial analysis show that industrial discharge are responsible for hyper accumulation of major and toxic elements in soils and tobacco crops and their mobility causes severe ecological and health problems. The study recommends the prohibition of tobacco cultivation and processing. It calls for regular supervision of industrial contamination and its instant remediation through national and international agencies thereby reducing soil contaminations through economic feasibility and in a reasonable time frame.V organic compounds (VOCs) have a variety of negative impacts on human health, some (e.g. benzene and formaldehyde) are known to be human carcinogen. There is, therefore, often a pressing requirement to monitor these compounds. However, monitoring them is not straightforward as their concentrations vary with environmental parameters such temperature, barometric pressure, and groundwater movement. Because of this, the sampling frequency that is used at present is ineffective for determining their representative concentration, therefore, a device which can be left in-situ to collect high temporal resolution data has been developed. VOCs are measured by PID; however, PID measures aggregate VOC concentration. Because VOCs have differing toxicities and behaviours, individual identification is required; therefore, a sample must be collected. In order to do this, a sorbent material must be used to transfer the sample to the GC-MS for identification. The sorbent material must be appropriate for the range of VOCs and of sufficient capacity for extended exposure. The objectives of the work are therefore to: (i) select an appropriate sorbent for incorporation into a dual measurement VOC monitoring device, then to use the instrument to (ii) derive an optimum monitoring methodology.