Abstract: A boiler system for producing steam from water includes a plurality of serially arranged oxy fuel boilers. Each boiler has an inlet in flow communication with a plurality of tubes. The tubes of each boiler form at least one water wall. Each of the boilers is configured to substantially prevent the introduction of air. Each boiler includes an oxy fuel combustion system including an oxygen supply for supplying oxygen having a purity of greater than 21 percent, a carbon based fuel supply for supplying a carbon based fuel and at least one oxy-fuel burner system for feeding the oxygen and the carbon based fuel into its respective boiler in a near stoichiometric proportion. The oxy fuel system is configured to limit an excess of either the oxygen or the carbon based fuel to a predetermined tolerance. The boiler tubes of each boiler are configured for direct, radiant energy exposure for energy transfer. Each of the boilers is independent of each of the other boilers.

Abstract: A method, apparatus, and system and operation of surface equipment to generate steam while reducing the quantity of boiler blowdown and thereby increasing the amount of feedwater that is re-used or re-cycled in generating said steam. The present invention teaches that, on a sustained basis, the blowdown stream at the outlet of a once-through steam generator can be routed to the inlet of a second once-through steam generator that is in series with the first, that blowdown stream can be used to generate additional steam in the second once-through steam generator and further reduce the amount of blowdown, and that this can be accomplished without need of any treatment that reduces hardness or silica levels of the blowdown stream prior to its entering or during its entry into the inlet of the second once-through steam generator.