Radiant boiler for pressurized oxy-combustion and method of radiant trapping to control heat flux in high temperature particle-laden flows at elevated pressure

A boiler comprising:

• a shell surrounding a vertical centerline, the shell defining an inner surface having an inner diameter and an inner length extending between an upper upstream end and a lower downstream end, wherein the directionality of the stream is defined with respect to combustion gas flow, the inner surface defining a hollow interior, the boiler having a pre-combustion zone, a combustion zone downstream from the pre-combustion zone, and a post-combustion zone downstream from the combustion zone, the shell being tapered outward along its length as it extends from the upper upstream end toward the lower downstream end in at least a portion of the combustion zone;
• an oxidizer inlet in fluid communication with the pre-combustion zone;
• a fuel nozzle for introducing fuel into the combustion zone;
• a tube assembly comprising a plurality of boiler tubes mounted in the hollow interior of the shell for transferring heat to fluid flowing through the tube assembly;
• and
• a flue duct in fluid communication with the post-combustion zone for transporting flue gases from the hollow interior;
• wherein the combustion zone and post-combustion zone of the boiler are encircled by a plurality of boiler tubes positioned interior to the shell.