PURPOSE: To provide the title apparatus comprising a plurality of reaction towers each packed with an absorbent which absorbs sulfur compounds in a high-temperature reducing gas, pipes for feeding or discharging a regenerating gas, etc., to or from the reaction towers and specified structures, wherein a plurality of specified instruments are provided in order to control the oxygen concentration of the regenerating gas to thereby ensure the regeneration of the absorbent and to prevent the deterioration of the catalyst.

CONSTITUTION: The title apparatus comprises at least three reaction towers 1, 2 and 3 each packed with an absorbent which absorbs sulfur compounds in a high-temperature reducing gas, pipes for feeding or discharging gases such as a regenerating gas to or from the reaction towers and specified structures, wherein the pipe communicating with the reaction tower 1 in the step of absorption is provided with detectors 82 and 83 for the concentrations of gases of sulfur compounds, a subtractor 84, a multiplier 85, an integrator 86 and a function generator 87, the output signal from the function generator 87 is inputted as a set of the oxygen concentration detector controller 40 to regulate an air or oxygen gas flow control valve 41 to thereby regulate the oxygen concentration of the regenerating gas (21-22-24-25) fed to the reaction tower in the step of regeneration.