Browsing by Author "Mbarawa, Makame M."

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Engine performance, exhaust emissions and combustion characteristics of a CI engine fuelled with croton megalocarpus methyl ester with antioxidant
(Elsevier Ltd., 2011-08) Kivevele, Thomas; Kristóf, Lukács; Bereczky, Ákos; Mbarawa, Makame M.
The use of biodiesel as a substitute for petroleum-based diesel has become of great interest for the reasons of combating the destruction of the environment, the price of petroleum-based diesel and dependency on foreign energy sources. But for practical feasibility of biodiesel, antioxidants are added to increase the oxidation stability during long term storage. It is quite possible that these additives may affect the clean burning characteristics of biodiesel. This study investigated the experimental effects of antioxidants on the oxidation stability, engine performance, exhaust emissions and combustion characteristics of a four cylinder turbocharged direct injection (TDI) diesel engine fuelled with biodiesel from croton megalocarpus oil. The three synthetic antioxidants evaluated its effectiveness on oxidation stability of croton oil methyl ester (COME) were 1, 2, 3 tri-hydroxy benzene (Pyrogallol, PY), 3, 4, 5-tri hydroxy benzoic acid (Propyl Gallate, PG) and 2-tert butyl-4-methoxy phenol (Butylated Hydroxyanisole, BHA). The fuel sample tested in TDI diesel engine include pure croton biodiesel (B100), croton biodiesel dosed with 1000 ppm of an effective antioxidant (B100 + PY1000), B20 (20% croton biodiesel and 80% mineral diesel) and diesel fuel which was used as base fuel. The result showed that the effectiveness of the antioxidants was in the order of PY > PG > BHA. The brake specific fuel consumption (BSFC) of biodiesel fuel with antioxidants decreased more than that of biodiesel fuel without antioxidants, but both were higher than that of diesel. Antioxidants had few effects on the exhaust emissions of a diesel engine running on biodiesel. Combustion characteristics in diesel engine were not influenced by the addition of antioxidants in biodiesel fuel. This study recommends PY and PG to be used for safeguarding biodiesel fuel from the effects of autoxidation during storage. Overall, the biodiesel derived from croton megalocarpus oil can be utilized as partial substitute for mineral diesel.
Evaluation of the Oxidation Stability of Biodiesel Produced from Moringa oleifera Oil
(ACS Publications, 2011-10-19) Kivevele, Thomas; Mbarawa, Makame M.; Bereczky, Ákos; Zöldy, Máté
Biodiesel is considered as an alternative fuel to petroleum-based conventional diesel fuel. Dependent upon the raw material, biodiesel can contain more or less unsaturated fatty acids in its composition, which are susceptible to oxidation reactions accelerated by exposure to oxygen and high temperatures. The present study evaluated the oxidative stability of biodiesel produced by methanolysis of Moringa oleifera oil, primarily available on the African continent. The evaluation was conducted by means of the Rancimat instrument, at a temperature of 110 °C, with an air flow of 10 L/h. Moringa oil methyl ester (MOME) displayed an oxidation stability of 5.05 h. Thus, MOME met the oxidative stability requirement in the American Society for Testing and Materials (ASTM) D6751 standard, which prescribes a minimum of 3 h, but did not meet the minimum requirement prescribed in the EN 14214 standard, which is 6 h. Also, this study evaluated the effectiveness of four antioxidants, 1,2,3-trihydroxybenzene [pyrogallol (PY)], 3,4,5-trihydroxybenzoic acid [propyl gallate (PG)], 2-tert-butyl-4-methoxyphenol [butylated hydroxyanisole (BHA)], and 2,6-di-tert-butyl-4-methylphenol [butylated hydroxytoluene (BHT)], on the oxidation stability of MOME. The result showed that the effectiveness of these antioxidants was in the order of PY > PG > BHA > BHT.
Experimental Investigations of Oxidation Stability of Biodiesel Produced from Manketti Seeds Oil (Schinziophyton rautanenii)
(ACS Publications, 2011-04-12) Kivevele, Thomas; Mbarawa, Makame M.
In this study, biodiesel from Manketti seeds oil (Schinziophyton rautanenii) was investigated to determine its suitability for use as a petrodiesel substitute. The fuel-related properties of Manketti oil methyl ester (MOME) were determined and compared to global biodiesel standards. Most of the determined fuel properties of MOME fulfilled the minimum requirements of ASTM D6751 and EN 14214 biodiesel standards. However, MOME did not meet EN 14214 oxidation stability requirements (6 h). The stability of biodiesel is very critical, and biodiesel requires antioxidants to meet storage requirements and to ensure fuel quality at all points along the distribution chain. This study evaluated the effectiveness of three antioxidants: 1,2,3-trihydroxybenzene (pyrogallol, PY), 3,4,5-trihydroxybenzoic acid (propyl gallate, PG), and 2-tert-butyl-4-methoxyphenol (butylated hydroxyanisole, BHA) on the oxidation stability of MOME. The result showed that the effectiveness of these antioxidants was in the order of PY > PG > BHA. Overall, the biodiesel derived from Manketti seeds oil can be used as partial substitute for mineral diesel.
Impact of antioxidant additives on the oxidation stability of biodiesel produced from Croton Megalocarpus oil
(Elsevier Ltd., 2011-06) Kivevele, Thomas; Mbarawa, Makame M.; Bereczky, Ákos; Laza, Tamás; Madarász, J.
The increase in crude petroleum prices, limited resources of fossil fuels and environmental concerns have led to the search of alternative fuels, which promise a harmonious correlation with sustainable development, energy conservation, efficiency and environmental preservation. Biodiesel is well positioned to replace petroleum-based diesel. Biodiesel is a non-toxic, biodegradable and renewable biofuel. But the outstanding technical problem with biodiesel is that, it is more susceptible to oxidation owing to its exposure to oxygen present in the air and high temperature. This happens mainly due to the presence of varying numbers of double bonds in the free fatty acid molecules. This study evaluates oxidation stability of biodiesel produced from Croton megalocarpus oil. Thermal and Oxidation stability of Croton Oil Methyl Ester (COME) were determined by Rancimat and Thermogravimetry Analysis methods respectively. It was found that oxidation stability of COME did not meet the specifications of EN 14214 (6 h). This study also investigated the effectiveness of three antioxidants: 1,2,3 tri-hydroxy benzene (Pyrogallol, PY), 3,4,5-tri hydroxy benzoic acid (Propyl Gallate, PG) and 2-tert butyl-4-methoxy phenol (Butylated Hydroxyanisole, BHA) on oxidation stability of COME. The result showed that the effectiveness of these antioxidants was in the order of PY > PG > BHA.