Performance evaluation of combustion of palm kernel shell and coconut husk blend in a pilot scale grate furnace

Abstract

Pollution resulting from the use of stereotypical fuels for energy generation has been a great menace to the air we breathe. Co-combustion of biomass fuels has proved effective against the deficiencies associated with burning of individual biomass on its own. This study aimed at investigating the combustion of Palm Kernel Shell (PKS) and Coconut Husk (CH) blend in a grate furnace. The proximate and ultimate analyses of the mix of PKS and CH were determined using ASTM 3174-76 method. Combustion tests were carried out with a 2 kW grate furnace where the effect of temperature distribution, flue gas emissions (CO₂, CO and NO₂) and combustion efficiency were measured. All the experimental tests were performed using varied primary-secondary air ratio of (40:60). The temperature distribution at different positions (H1, H2, H3, H4 and H5) in the combustion unit using PKS and CH blend (PKS-CH) ratio of 100:00, 70:30, 60:40 and 50:50 were measured. Temperature data were recorded for a period of 50 minutes after a stable bed temperature of 248.7 °C was reached. The results indicated that highest temperature immediately above the grate (H1) was 720.9 °C for 60:40 fuel proportions. A more significant temperature difference of 356.4 ^oC between the bed temperature and H1 temperature was recorded for 70:30 fuel proportions. The average deviation from temperatures at H1 to H5 at 50 minutes of experiment was approximately 122 °C. For each co-combustion fuel option, combustion efficiency increases with time following the same pattern as CO₂ emission. The combustion efficiency was maximum (62.11%) at 70:30 PKS-CH ratios, which conversely showed a low CO emission of 302 ppm