Abstract: Substantially pure high pressure steam is produced within a high pressure heat exchanger. Heat for the high pressure heat exchanger is provided from an outlet of an oxy-fuel combustion gas generator which discharges a steam/CO2 mixture at high pressure and temperature. The gas generator combusts oxygen and hydrocarbon fuel and mixes with water which can include contaminates therein in the form of dissolved solids or hydrocarbons. A separator is typically provided downstream of the gas generator and upstream of the heat exchanger and the steam/CO2 mixture is discharged from the gas generator at saturation temperature. A water fraction of the steam/CO2 mixture is discharged from the separator along with dissolved solids in concentrated brine form. The water heated into steam by the heat exchanger can be at least partially water separated within a condenser downstream of the heat exchanger.