Thermal Conversion of Mixed Wastes From Biodiesel Manufacturing for Production of Fuel Gas

Thermochemical conversion process has become a viable technology for managing excess waste from various industries while producing value added fuel products. In the work reported here, distribution of products (solid, liquid, and gas) by thermal conversion of wastes from biodiesel production process which are extracted physic nut and palm shell mixed with glycerol waste was carried out using a medium scale tubular reactor with feeding rate of 5 g/min. Several important operating parameters were studied including the proportion of each waste (100:0 – 70:30), reaction temperature (700 – 900°C) and air to fuel ratio (AF) 0.0 – 0.6. It was found that when the temperature increased, the quantity of solid and liquid product decreased while gas product increased. For conversion to CO₂, CO, C_xH_y and H₂, when the temperature increased, CO₂ decreased while yields of CO, CH₄ and H₂ increased. Greater conversion to CO₂, CO, H₂ with AF increased from 0.0 to 0.3. Higher AF from 0.3 to 0.6 resulted in lesser CO and H₂ while conversion to CO₂ increased. On the other hand, C_xH_y decreased when AF changed from 0.0 to 0.6. The maximum heating values of gas product in this study are 3.48 MJ/m³ and 2.27 MJ/m³ for glycerol waste mixed with physic nut waste and palm shell waste, respectively (both at 30% glycerol wastes and reaction temperature of 900°C). The maximum of mole ratio of H₂ to CO obtained is 0.59 for physic nut and 0.37 for palm shell mixed wastes. Relatively high C_xH_y, low product gas heating value and H₂ to CO ratio indicated the need for further product upgrading before using as raw material for other advanced fuel production processes such as Fisher-Tropsch, DME, or methanol syntheses beside direct heat and power utilization.