Systems and techniques for the reclamation from boiler flue gas of all or substantially all gaseous substances for well injection oil recovery. A system can include one or more of a boiler for generating high pressure steam, a high pressure water pump, a tower scrubber, an induced draft fan, an absorber, a separating tank, a heat exchanger, a regenerator, a reboiler, a steam boiler, a water segregator, a carbon dioxide compressor, a purifier, a nitrogen compressor, drying beds, adsorption beds, a carbon dioxide pressurizer, a nitrogen pressurizer and a mixing tank of which: the boiler for generating high pressure steam, the tower scrubber, the absorber, the regenerator and the adsorption beds connect with each other in turn. In addition, the mixing tank connects by pipelines with a gas injection tube of an oil well. Mixed gases of carbon dioxide and nitrogen can be obtained for injection into the oil well, thus gaining favorable results of crude oil output increase as well as environment protection.