The present invention provides a fuel incinerating system comprising a fuel injector, a multi-stage fuel-air mixing device comprising a plurality of fuel intake tubes stacked vertically and configured to provide annular gaps between one or more of the vertically stacked fuel intake tubes to entrain ambient air to form a fuel-air mixture; and a combustor in communication with the fuel-air mixing device and defining a combustion chamber and in communication with an ignition source. The combustor is configured to impede flow of the fuel-air mixture through the combustion chamber to achieve a desired retention time of the fuel-air mixture within the combustion chamber to achieve substantially complete combustions of the fuel.