vapor - liquid contacting apparatuses comprising a primary contacting zone and a secondary contacting zone are disclosed . a representative secondary contacting zone is a secondary absorption zone , such as a finishing zone for subsequent contacting of the vapor effluent from the primary contacting zone to further remove impurities and achieve a desired purity of purified gas exiting the secondary absorption zone . the secondary contacting zone is disposed below the primary contacting zone , such that the secondary contacting zone , which must operate efficiently in removing generally trace amounts of remaining impurities , is more protected from movement than the more elevated , primary or initial contacting stages for bulk impurity removal . the apparatuses are therefore especially beneficial in offshore applications where they are subjected to rocking .