Circulating Fluidized Bed Boiler

A circulating fluidized bed boiler comprising:

• a rectangular furnace which is horizontally enclosed by a front wall, a back wall and two sidewalls, wherein the common width of the front wall and the back wall is larger than the common width of the sidewalls;
• multiple particle separators, connected to the upper portion of each of the front wall and the back wall, for separating particles from a stream of flue gas and particles discharged from the furnace, wherein each particle separator comprises a gas outlet for discharging cleaned flue gas from the particle separator;
• a flue gas duct system connected to the gas outlets of the particle separators for conducting cleaned flue gas to a back pass,
• wherein the multiple particle separators are arranged in multiple pairs of particle separators, wherein each pair of particle separators includes a front separator arranged adjacent to the front wall and a back separator arranged adjacent to the back wall, and in that the flue gas duct system comprises multiple cross over ducts, each cross over duct connecting the gas outlet of a front separator of a pair of particle separators, across and over the furnace, to the gas outlet of the back separator of the same pair of particle separators, and to the back pass, which back pass is arranged on the back wall side of the furnace, outside of the back separators.