Effects of Bio-Based Additives on Fuel Pellet Quality from Oat Hull: Optimization of Additive Concentration and Process Conditions

Conversion of low value agricultural residue into biofuels especially fuel pellet, is a promising technique and this fuel pellet can be used for combustion, co-combustion in boilers and furnace for generation of heat and power in household applications and in industries. Bio-based additives such as mustard meal and bio-oil derived from softwood via pyrolysis has been used as binder for formulation of oat hull pellets. Central composite design was used to find the different conditions of formulation as well as to optimize the formulation for high quality pellet. Three parameters including the concentration (wt%) of mustard meal (10-20), bio-oil (5-15) and moisture content (8-12) were used as input factors while the response factors were durability index, hardness, relaxed density and moisture uptake rate of fuel pellet. The highest durability, density and energy content was found for pellet formed from 15% of bio-oil, 10% of mustard meal and 8% of water. Pyrolysis bio-oil is the most influential factor that significantly affected pellet properties. Moreover, pelletization operating conditions were also optimized using compression force (3000 -4500N), die temperature (90-110°C) and relaxation time (15-60s). The pellet quality improved with higher die temperature and compression force but the effect of holding time is insignificant.