A gas treatment plant (3) for treating an industrial waste gas comprising carbon dioxide comprises an oxyfuel boiler (100) and a pipe (109; 122; 180) arranged for forwarding the industrial waste gas to the oxyfuel boiler (100) and injecting the industrial waste gas into the oxyfuel boiler (100) to participate in the combustion process occurring in the boiler (100) to cause oxidation of at least a portion of the content of at least one oxidizable substance of the industrial waste gas. The gas treatment plant (3) further comprises a gas cleaning system (108), and a pipe (126) for forwarding a carbon dioxide rich flue gas generated in the boiler (100) to the gas cleaning system (108) for being cleaned therein, such that an at least partly cleaned carbon dioxide rich flue gas is formed.