Interaction of fuel spray and air swirl on the combustion of residue oils

Effervescent atomization technology was applied in Waste Lubricant Oils (WLO) combustion. The tests were conducted in a 150 kW prototype boiler with a horizontally oriented cylindrical shape combustion chamber in which the combustion process was studied in terms of the interaction between a swirling air flow and fuel spray pattern. The combustion performance was assessed by continuously monitoring gaseous emissions, particularly carbon monoxide (CO) emission. Two different air feeding strategies were tested, varying in swirl number and six different configurations of the injection nozzle orifice. Three nozzles had a single orifice varying in diameter and discharge end geometry, and the others had three divergent orifice arrangement varying in cone angle and diameter. At the same time, the gas-to-liquid ratio (GLR) of the effervescent atomizer was also investigated, allowing to draw important illations about its influence on the combustion efficiency. The results show that the use of effervescent atomizers allows to burn of WLO, with CO emissions as low as 15 ppm at 8% of oxygen (O2) when using a three orifice of 1 mm with 15 degrees of cone angle nozzle. This result was achieved by applying highintensity combustion air flow swirl. However, the one orifice nozzles with penetrant spray pattern combined with low swirl intensity air flow also produced satisfactory results. With CO emissions of 27 ppm at 8% of O2 with a 1.2 mm single orifice nozzle. Furthermore, it was also demonstrated that the increment of the GLR in a range between 0.25 and 0.35 can be responsible for the reduction of 40 to 50% of the CO emissions when burning WLO.