The invention relates to a semi-
tower type medium-temperature separation
biomass circulating fluidized bed boiler, composed of a front shaft, a middle gas-
solid separating and recycled material returning unit, and a
tail flue, wherein the front vertical well comprises a
hearth, a
convection shaft and a
smoke reversing chamber; the middle gas-
solid separating and recycled material returning unit comprises a gas-
solid separating device, a returning riser and a returning device; a super-heater, an
economizer and an air pre-heater are arranged along a
smoke flowing direction in the
tail flue; a lower portion of the
hearth is provided with 2 to 3
layers of secondary air along a height direction; an upper portion of the
hearth is provided with a
convection heated surface in the
convection shaft; the hearth, the convection shaft, the
smoke reversing chamber, the gas-solid separating device, the returning riser and the returning device compose a main circulation loop. According to the invention, adaptability of fuels is wide;
combustion efficiency is high; abrasion and
corrosion for the heated surface is poor; temperature of the smoke at an inlet of the gas-solid separating device is within a range of 400-750 degrees centigrade so as to effectively prevent slagging,
slag hanging, dusts gathering, ashes blocking,
bed materials blocking and returning device blocking in the boiler.