Method to enhance operation of circulating mass reactor and method to carry out such reactor

A method for enhancing the operation of a circulating mass reactor, in which circulating mass reactor, at least a part of the heat contained by the flue gases formed in the circulating mass reactor is transferred to the fluidized material arranged to circulate in the circulating mass reactor, and which circulating mass reactor comprises

• a fluidized-bed chamber, in the lower part of which is provided a fluidized bed containing fluidized material,
• means for separating fluidized material from the flue gases, and
• a return conduit system, through which the fluidized material can be returned to the fluidized-bed chamber and which includes at least one cooled return conduit, in which a part of the heat energy contained by the fluidized material passing there through is transferred to the heat transfer liquid circulating in the circulating mass reactor by means of heat exchangers fitted in the return conduits,
• wherein
• that for the combustion of fuel taking place in the circulation mass reactor is provided a lower combustion chamber, which comprises a fluidized-bed chamber, and an upper combustion chamber, and a flow conduit connecting them,
• that the flow conduit, the means for separating the fluidized material from the fuel gases and the return conduit system are arranged to be located between the lower combustion chamber and the upper combustion chamber, at least mainly above the lower combustion chamber and below the upper combustion chamber,
• that the lower combustion chamber and the upper combustion chamber are dimensioned in such a way that the combustion of the fuel can be essentially completed before the discharge of the flue gases from the combustion chamber, whereupon the average delay time of the flue gases in the upper combustion chamber is most preferably 0.3-3.0 seconds, and
• that the fluidized material is separated from the flue gases after the upper combustion chamber and guided back to the fluidized-bed chamber through cooled return conduits and/or an uncooled return conduit system in the desired ratio.