The utility model provides a be used for downward carminative flue gas turbine expander device, including air intake casing, bearing housing, downward carminative exhaust volute, rotor subassembly, base, quiet bucket ring subassembly. The utility model discloses the infrastructure of make full use of factory building need not increase additional cost, installs the flue gas turbine expander device two layers of factory building, has solved that the factory building is inside to require too high problem, exhaust duct is installed downwards to the exhaust volute, and be convenient for construction and maintenance have reduced bearing structure, easily fixed, rigidity reinforcing, whole device has reduced the height of C. G. Should not produce great beat, and stability is good, the steady of operation has been guaranteed to less inside obturaging and the load of rotor, has improved the operational reliability.