PURPOSE: To reduce the power to heat regenerated gas and the power to cool for gas-contained moisture removal by using the heat of reaction induced by oxygen and hydrogen at a catalytic vessel as a heating source of regenerated gas for a dehumidification tower.

CONSTITUTION: Coarse argon, which is refined and separated by a low temperature separator 1, is boosted to a specified pressure by an argon compressor 2 and fed to a catalytic vessel 3. At the catalytic vessel 3, added oxygen is adapted to react with oxygen contained in coarse argon gas so as to produce moisture. The high temperature denatured argon gas from which oxygen is removed by this reaction, is precooled heating the regenerated gas required to regenerate a dehumidification tower 5 with a preheater. After the argon has been precooled, an argon cooler 4 is adapted to condense and remove the cooled moisture by using the latent heat of refrigerant. Furthermore, after the residual moisture is absorbed and removed by the dehumidification tower 5, it is returned to the low temperature separator 1 again. On the other hand, after the regenerated gas for the dehumidification tower 5 is heated by the preheater 7 in the catalytic vessel, the regenerated gas is heated by a regeneration heater 6 so that it may rise to a specified temperature and supplied to the dehumidification tower 5. This construction reduces the cooling power and the heating power respectively so that the power for an argon sampling facility may be reduced.