Abstract: A hybrid combustion system is provided combining advantages of a fluidized bed combustion portion and a pulverized coal combustion portion. The former portion includes a fluidized bed chamber, a coal mill without an air separator, a recycling duct connected to the coal mill, a coal supply duct, and a spray feeder. The fluidized coal combustion portion includes a pulverizing coal mill with air separator, a blowing duct for blowing ground coal, at least one pulverized coal burner and an air recycling duct for recycling combustion air. Fluidized bed combustion takes place in a lower part of the system and pulverized coal combustion takes place above the fluidized bed combustion. Each of the portions may be independently operated of the other. A main combustion chamber is common to both the fluidized bed portion and the pulverized coal portion. A related process is also described.