The invention discloses a
flue gas desulfurization, denitration and dust removal device and method and belongs to the field of
flue gas treatment by catalytic
cracking. The device comprises a residual heat boiler, a cooler, a washing
tower, a
chimney, a water feeder, a
temperature control valve and a liquid level control valve. A first
flue gas inlet is formed in the top of the residual heat boiler and an
ammonia gas inlet is formed in the upper part of the residual heat boiler; a denitration reactor is arranged in the middle of the residual heat boiler; a
flue gas outlet is formed in the bottom of the residual heat boiler. A second
flue gas inlet and a water inlet are formed in the lower part of the washing
tower; an alkali liquid inlet is formed in the middle of the washing
tower; a liquid and dust remover is arranged at the upper part of the washing tower and a
chimney connector is arranged at the top of the washing tower. The cooler is provided with a
gas phase inlet, a
liquid phase inlet and an outlet. The
flue gas outlet on the residual heat boiler, the
gas phase inlet and the outlet of the cooler, the second flue gas inlet and the
chimney connector of the washing tower, and the chimney are connected in sequence. The
temperature control valve is arranged on a pipeline between the water feeder and the
liquid phase inlet of the cooler; the liquid level control valve is arranged on a pipeline between the water feeder and the water inlet of the washing tower. The device disclosed by the invention can be used for carrying out desulfurization, denitration and dust removal treatment on flue gas from an FCC device.