In a process for separating "heavy" impurities such as hydrogen sulfide from crude carbon dioxide comprising significant quantities of "light" impurities such as non-condensable gases, involving at least one heat pump cycle using as working fluid a fluid from the "heavy" impurity separation, the "light" impurities are removed from carbon dioxide-enriched gas generated in the "heavy" impurity separation. The carbon dioxide-enriched gas, or a compressed carbon dioxide-enriched gas produced therefrom, is at least partially condensed by indirect heat exchange against intermediate liquid also generated in the "heavy" impurity separation. Total and specific energy consumption is reduced compared to conventional processes in which "light" impurities are removed from carbon dioxide product gas.