Systems and methods for isolating substantially pure carbon dioxide from flue gas

A method for isolating substantially pure carbon dioxide from flue gas produced by a natural gas fired combustion boiler of a multi-unit residential or commercial building that is operably engaged to provide steam upon demand from at least one unit within the multi-unit residential or commercial building using domestic water to provide the steam for hot water, and/or steam supplied radiant building heater, the method comprising:

• upon demand for hot water or building heat by the at least one of the multi-unit residential or commercial building occupants, initiating natural gas combustion within the residential or commercial combustion boiler to produce flue gas and provide the flue gas to an exhaust conduit;
• using the residential or commercial combustion boiler to receive water from a domestic water supply and generate hot water for use by the building occupants and/or steam to provide radiant heat for the building;
• after initiating natural gas combustion, removing tramp air from the exhaust conduit;
• using building water supply to operate a condensing heat exchanger to cool the flue gas and provide a flue gas having less than 3% water;
• compressing the cooled flue gas to lower the water content of the flue gas to less than 1%;
• drying the compressed and cooled flue gas using a desiccant dryer to provide substantially dry flue gas having less than 10 ppm water;
• providing the substantially dry flue gas having less than 10 ppm water to a pressure swing adsorption assembly and removing N2 from the substantially dry flue gas to provide substantially N2 free CO2;
• and
• liquifying the substantially N2 free flue gas CO2 to form substantially pure carbon dioxide.