Methods and devices for combusting a carbonaceous fuel in an oxy-combustion fluidized bed reactor involving controlling the local oxygen content within the oxy-combustion reactor to specified levels. The carbonaceous fuel and an oxygen-containing gas are introduced into a fluidized bed reactor and eluted through a fluidized bed of an inert material, dolomite or a combination thereof to combust the fuel and oxygen to produce at least CO.sub.2 and steam. The oxygen-containing gas is a mixture of oxygen, recycled CO.sub.2 and steam and has sufficient oxygen added to the recycled CO.sub.2 and steam that the mixture contains 7-20 mole % oxygen. The carbonaceous fuel and the oxygen-containing gas are introduced into the fluidized bed at a location in sufficiently close proximity to each other to avoid producing a reducing atmosphere at the location. At least a portion of the produced CO.sub.2 and steam are recycled to the reactor.

A modular combustion system for flexible energy generation is provided. The system comprises a plurality of combustion boilers, at least one oxidizer supply unit providing an oxidizer stream to the combustion boilers, at least one feeder to provide fuel to the combustion boilers, at least one particle removal unit to remove particles from a flue gas output stream from the combustion boilers, and a pollution removal unit to remove pollutant gases from the flue gas output stream. A process for flexible energy generation using the modular combustion system is disclosed that includes providing an oxidizer stream to a plurality of combustion boilers with at least one oxidizer supply unit, providing fuel to the plurality of combustion boilers with at least one feeder, removing particles from a flue gas output stream from the plurality of combustion boilers with at least one particle removal unit, and removing pollutant gases from a particle-free flue gas output stream with at least one pollution removal unit. A system for controlling wall heat flux in a pressurized coal combustion environment is disclosed that includes at least one burner; and at least one low-mixing, axial-flow boiler.

A combustion system includes a combustion chamber for generating energy. The system includes a first inlet for supplying an oxidant into the chamber and a second inlet for supplying a fuel into the chamber. The system also includes a third inlet in fluid communication with the first inlet for supplying oxygen into the chamber. The system further includes a fourth inlet for supplying hydrogen into the chamber. A circulation line is used to deliver a flue gas from the chamber to the first inlet.

A modular pressurized combustion system for flexible energy generation is provided. The system comprises a plurality of pressurized combustion boilers, at least one compressor configured to provide pressurized oxidizer gas to each of the plurality of pressurized combustion boilers in parallel, and at least one feeder configured to provide fuel to each of the plurality of pressurized combustion boilers in parallel. The system further comprises a flue gas input unit configured to provide recycled flue gas to each of the plurality of pressurized combustion boilers in series, at least one pressurized heat recovery unit configured to receive a flue gas output stream from each of the plurality of pressurized combustion boilers, and at least one particle filter configured to filter a flue gas output stream from the pressurized heat recovery unit. The system also comprises an integrated pollutant removal unit.