The operation of a demethanizer being used to cryogenically separate high carbon dioxide content hydrocarbon feed into liquid ethane essentially free of both methane and carbon dioxide with simultaneous production of overhead gas comprising methane and carbon dioxide without carbon dioxide icing to foul equipment by virtue of maintaining pressure at which non-gaseous carbon dioxide remains dissolved in liquid hydrocarbon, can be improved by intentionally injecting a dehydrated methane-rich stripping gas to the bottom of the demethanizer. At temperatures below about -80.degree. F., the addition of a stream such as dehydrated inlet gas stabilizes the demethanizer operation by making the carbon dioxide to ethane ratio of the liquid bottoms product less sensitive to temperature fluctuations in the reboiler system heating the bottoms. In this manner, product recovery is increased while acceptable carbon dioxide as well as methane content can be maintained. Such a method is compatible with closed-loop control of the reboiler temperature based on gas chromatography measurements.