Gilles Vaitilingom

Development of rape seed oil burners for drying and heating

Abstract IRIBIOM and CIRAD carried out important experiments on the use of rape seed oil as a substitution for domestic fuel in burners. The first objective was to check the ability of rape seed oil as a biofuel in standard commercial burners. The second objective was to define the modifications to apply to standard burners for an efficient combustion with rape seed oil as well as with domestic fuel. Tests were conducted on a fully-monitored 260 kW boiler test-bench. Performance data, temperatures and pressures of the fuels, as well as gaseous emissions (CO, CO2, O2, NOx, SO2, PAH, cetons and aldehydes) were measured for rape seed oils and domestic fuel. Crude, degummed and refined rape seed oils were tested. The optimisation of the combustion was investigated for different spray nozzles by adjusting: (i) the position of the flame stabilizer; (ii) the opening of the air valve; (iii) the temperature at the tip of the spray nozzle (from 80°C to 150°C); and (iv) the rape seed oil injection pressure. Crude industrial rape seed oils led to filter clogging in few minutes. With degummed and refined rape seed oil a new spray nozzle was determined to avoid fouling and coking problems. Performance data and combustion efficiency was equal to that of domestic fuel. The emission values obtained with the optimal adjustments are far below the limits defined by the European norm in force. The high viscosity of rape seed oil causes poor fuel atomization and difficulty for its ignition, additionally the physical and chemical characteristics of vegetable oils lead to imperfect evaporation of droplets that can cause severe deposits in the combustion chamber of the boiler. Therefore it was necessary to heat the oil and raise the injection pressure in the nozzle. The ability of rape seed oil as a biofuel in burners was proved and confirmed by on site durability tests for grain drying and urban heating.