Abstract: An apparatus comprising four compartments connected by inlet and outlet valves in tandem. Effluent gases from a high temperature reactor pass through a filtration unit and are directed through the inlet of a first chamber through a perforated pipe placed at the bottom of the chamber. The hot flue gas then flows upward through the liquid/slurry contained in the chambers, such that the carbonaceous impurities are absorbed in the liquid/slurry along with the temperature of the flue gas in stages so as to obtain oxygen without impurities through at least one discharge. Each chamber is provided with a temperature indicating unit, a stirrer unit, inlet and outlet valves, and a discharge unit at the bottom of the chamber.