PURPOSE: To permit withdrawal operation with a smaller number of personnel in a shorter period by sucking and removing the packing material in a column through a vacuum hose inserted into the manhole of the column.

CONSTITUTION: The vacuum hose 4 is inserted through the manhole 1a of the reaction column into the column and the aperture at the top end of the hose is directed toward a catalyst which is the packing material A in the column. A blower of a vacuum device 3 is then operated to suck the packing material into a separator. The packing material is separated from the air in the separator and is stored in a storage tank. The withdrawal operation is executed in the shorter period according to the above-mentioned method; in addition, the cost is reduced without the need for an installation such as scaffolding by the conventional method.