Optimization of Calorific Value of Densified Bush Mango Shell and Palm Pressed Fibre Briquettes

Energy value of biomass materials can be enhanced through composition, densification and process parameter manipulation. In this study, biomass briquettes of bush mango shell (BMS) and palm pressed fibre (PPF) compositions were evaluated and its calorific values optimized. The effects of biomass concentration, dwelling/compaction time and compression pressure on calorific value were investigated for briquette samples in the compositions of BMS: PPF ratios of 100:0, 75:25, 50:50, 25:75, and 0:100) as sample A, B, C, D and E respectively. An empirical prediction model of the combustion property of the briquettes was developed and optimized using response surface methodology. It was observed across the samples that as bush mango shell composition increased, the calorific value improved significantly from 12.4kJ/kg to 18.65kJ/kg. Increase in dwelling time and pressure also showed slight increase in calorific value of the briquette samples. An optimum calorific value of 19.03 kJ/kg for briquette sample B (75:25 biomass ratio) was realized at dwelling time of 40 minutes and pressure of 25MPa as adequately predicted by a reduced second order model. The model prediction accuracy was over 98% (Pred. R2 of 0.9858) with Coefficient of Variance of 0.64% and Adeq. Precision value of 63.936. Thus, Sample B briquettes possess improved combustion properties with burning rate of 0.472g/min at optimum conditions hence suitable for adoption by investors in renewable energy sector.