Thomas T. Kivevele

An analysis of fuel properties of fatty acid methyl ester from Manketti seeds oil.

The fatty acid methyl esters (FAME)produced from vegetable oils, animal fats, or waste oils known as biodiesel has attracted attention as possible replacement of fossil fuels. The fuel properties of biodiesel are similar to that of conventional petro-diesel and it is more environmentally friendly. This study investigated in detail the fuel properties of biodiesel from less common edible oil produced from Manketti seeds (Schinziophyton rautanenii). Manketti Oil Methyl Ester (MOME) was produced by transesterification process using an alcohol in the presence of a catalyst. The fuel related properties of MOME were determined and compared with the global biodiesel standards such as ASTM 6751 and EN 14214. Also, the effects of different 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) were investigated on oxidation stability, kinematic viscosity and cetane number (CN) of MOME. The results showed that, most of the determined fuel properties fulfilled the minimum requirement of global biodiesel standards. Among antioxidants used in this study, PY and PG were more effective compared to BHA on oxidation stability. Also, addition of antioxidants on MOME showed positive results on CN which was increased and kinematic viscosity was decreased. In summary, biodiesel produced from manketti seeds oil indigenous to Southern Africa can be used as partial substitute of mineral diesel.

Air source heat pump system for drying biomaterial

Need for a more economic method of drying biomaterial, from paper to fruit, in South Africa has for long been sought. This paper explains research into an advanced air source heat pump drying (ASHPD) system, designed, manufactured and installed for drying South African fruit and taking into account local climactic conditions. The effect of ambient temperature and condenser fan speed on the coefficient of performance (COP) of the heat pump (HP) was evaluated, also the influence of drying temperature and air velocity analysed. Using banana slices (the sample fruit selected for this study) results indicated the moisture content of bananas produced in Mpumalanga Province averaged 75.5±1.5% on a wet basis. The COP of the HP was found to be significantly high - an average 4.7. The influence of the evaporator temperature on the COP was important since it assisted in temperature control during the drying process. It was also observed the COP increased with an increase in room temperature. Drying process results indicated for drying South African bananas a possible optimal drying temperature range was 30-40 °C with 1.5 m/s drying air velocity. Generally, the study demonstrated an ASHPD system was suitable for use in South African climatic conditions. Now South Africa has an opportunity to continue research and to design applications for this green and efficient drying technology - especially for drying biomaterial. This could reduce high energy consumption, something all of South Africa is striving towards.

Mungongo Seeds Oil (Schinziophyton rautanenii) as a Potential Source of Bio-Diesel

Biodiesel from mungongo seeds oil (Schinziophyton rautanenii) was investigated in the present study to determine its suitability for use as substitute of petro diesel. The fuel properties of Mungongo Oil Methyl ester (MOME) such as cetane number, kinematic viscosity, oxidative stability, lubricity, cloud point, pour point, cold filter plugging point, flash point, acid value, density, higher heating value, free and total glycerol were determined and compared with global biodiesel standards such as ASTM 6751 and EN 14214. Most of the determined fuel related properties of MOME fulfilled the minimum requirements of ASTM D6751 and EN 14214 biodiesel standards except oxidation stability. The stability of biodiesel is very critical and biodiesel requires antioxidant to meet storage requirements and to ensure fuel quality at all points along the distribution chain. Therefore, 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) were investigated. The result showed that, PY and PG were more effective antioxidants than BHA.

Experimental comparative study of an open and completely closed air source heat pump for drying sub-tropical fruits

Heat pump drying (HPD) is an energy efficient and environmentally friendly drying method. Heat pumps (HPs) deliver more heat during the drying process than the work input to the compressor. The performance of HP and the dryer is significantly affected by the surrounding conditions. Therefore, the present study investigates the performance of an open and completely closed air duct HPD systems. Also, the influence of refrigerant charge and condenser fan speed was evaluated. The results demonstrated that, the completely closed air duct HPD system had slightly higher coefficient of performance (COP) and heating capacity than the open HPD system because of the heat from the moist exhausted air from the dryer were recovered at the evaporator. However, the drying air temperatures for the closed HPD system were lower than that of open system. This was due to the circulation of cold air from the evaporator. Also, COP increased with the increase of refrigerant charge in both systems. But, at high refrigerant charge the COP values for both systems were decreased because of the decrease in heating capacity which was possible due to the accumulation of refrigerant in the condenser. Similar trend of results were observed at high condenser fan speed, this was due to the increased fan power consumption. Therefore, for the system developed, the optimum refrigerant charge was observed to be 1650 grams and 840 rpm of condenser fan speed (60% of the full speed) and the obtained COP values at this point were 3.85 and 3.75 for the closed and open HPD system, respectively.