ABSTRACT
This research investigates the use of palm kernel shell as a supplementary fuel with coal in high efficiency coal boilers for a cleaner and an improved coal usage as well as adding value to waste.
Coal was obtained from Ankpa coal field in Kogi State while Palm Kernel Shell was obtained locally in an oil processing mill. Both fuel samples were prepared separately for pelleting and further analysis. Seven fuel pellets lettered A to G were produced using a piston-type pelleting machine: 100% palm kernel shell, 100% coal and coal combined with palm kernel shell at varying masses having mix ratios: 10 %, 20 %, 30 %, 40 % and 50 % respectively. This provided basis for a comprehensive study. The produced fuel pellets were characterized: moisture content, calorific value, proximate and ultimate analyses in order to define the fuels’ property (characteristics). An oven, an oxygen bomb calorimeter, a precision balance and a muffle furnace were used in the experimental study. Aspen Hysys: a process simulation software was used to test the performance of the fuel pellets on a simple steam cycle.
The calorific values of the seven fuel pellets were 21714.74 kJ/kg, 28430.26 kJ/kg, 26449.16 kJ/kg, 25508.01 kJ/kg, 25017.95 kJ/kg, 22046.31 kJ/kg and 20811.92 kJ/kg respectively. The moisture contents of the pellets were 4.69 %, 4.38 %, 4.49 %, 4.80 %, 4.09 %, 4.60 % and 4.10 % respectively. The ash content obtained were 13.61 %, 14.89 %, 11.89 %, 11.15 %, 11.51 %, 11.88 % and 16.77 % respectively. Also, sulphur content showed 0.84 %, 0.76 %, 0.67 %, 0.70 %, 0.73 %, 0.82 % and 0.88 % respectively. Key parameters such as the calorific value, moisture content, ash and sulphur content obtained from this study were compared with the results of other similar research work. The moisture content result from this study is reduced compared with other similar studies. The calorific value result also showed a significant increase compared with other similar studies due to the presence of coal in the pellets. The percentage ash and sulphur contents obtained in this study were in the recommended range of: 5 - 40% for ash and 0.5 - 0.8% for sulphur as reported by (Bureau of Energy Efficiency: Fuels and Combustion, 2013). The products of combustion specifically greenhouse gases, cycle efficiency and estimated power generation per fuel sample were key indices taken into consideration in choosing the most suitable fuel at the end of the performance simulation. Sample D with mix ratio 80-20 came out the best fuel blend having a CO2 emission of 1844.198854 Kgmol/h, an SO2 emission of 8.830612928 kgmol/h, a cycle efficiency of 0.41 and an estimated power of 104, 076 kW. It was concluded that coal blended with palm kernel shell preferable at a mix ratio of 80-20 has a suitable heating value for steam generation which promotes a cleaner coal usage with a significant reduction in the emission levels of greenhouse gases.
