The present disclosure relates to systems and methods that are useful for controlling one or more aspects of a power production plant. More particularly, the disclosure relates to power production plants and methods of carrying out a power production method utilizing different fuel chemistries. Combustion of the different fuel mixtures can be controlled so that a defined set of combustion characteristics remains substantially constant across a range of different fuel chemistries.

Disclosed is a mixed combustion system fueled with ammonia, hydrogen and natural gas, which comprises a furnace chamber, a combustor, a heat exchanger, a mixer and a storage tank, the combustor and a conical combustion cavity are installed in the furnace chamber, the storage tank is provided with a first branch pipeline through a conveying pipe to be connected with the heat exchanger, the heat exchanger is connected with an inlet of the mixer, and an outlet of the mixer is connected with a fuel inlet of the combustor; and the conveying pipe is provided with a second branch pipeline connected with an ejector port of a first ejector, the first ejector is installed on a flue gas recirculating pipe connected with a furnace chamber flue gas exhaust pipeline, and the other end of the flue gas recirculating pipe is connected with an auxiliary fuel inlet of the combustor.