Fluidized bed reactor system and a method of operating a fluidized bed reactor system

A method of controlling a reactor system comprising first and second fluidized bed reactors, a flue gas channel in gas flow connection with the first fluidized bed reactor and a product gas channel in gas flow connection with the second fluidized bed reactor, the method comprising the steps of:

• feeding solid fuel and oxygen containing gas to the first fluidized bed reactor so as to form therein a fluidized bed of particles and combusting a first portion of the solid fuel in the fluidized bed of particles with the oxygen containing gas so as to generate heated bed particles and a first stream of flue gas;
• conveying the first stream of flue gas to the flue gas channel;
• transferring heated bed particles including a second portion of the solid fuel at a predetermined heated particles transfer rate from the first fluidized bed reactor to the second fluidized bed reactor;
• feeding fluidizing gas to the second fluidized bed reactor so as to form therein a second fluidized bed of particles;
• and
• transferring bed particles from the second fluidized bed reactor to the first fluidized bed reactor,
• wherein the method comprises first and second operation modes, in which first operation mode the fluidizing gas is oxygen containing gas and the method comprises the steps of:
• combusting a portion of the second portion of the solid fuel in the second fluidized bed of particles so as to generate a second stream of flue gas;
• and
• conveying the second stream of flue gas to the flue gas channel,
• and, in which second operation mode the fluidizing gas comprises steam, CO2, or non-oxygen containing inert gas and the method comprises the steps of:
• pyrolyzing or gasifying a portion of the second portion of the solid fuel in the second fluidized bed of particles so as to generate product gas;
• and
• conveying the product gas to the product gas channel.