Apparatus for handling and utilizing system gas in a pyro-processing

Abstract

Emission gas to be scrubbed of sulfur dioxide or the like has turbulent flow through a mixing vessel. At a mixing zone in the vessel, comminuted lime is fed into the gas and carried out of the vessel with the gas to a cyclone separator. A substantial portion of the dust from the cyclone is recycled back to the mixing zone of the mixing vessel. The gas from the cyclone is passed through a quench zone and excess dust from the cyclone is introduced into the gas stream for additional sulfur-dioxide removal, and quenching of the gas and dust from the cyclone is accomplished in a quenching zone prior to the gas being utilized in the system. Off-gas from the preheat zone which contains unburned combustibles is burned in a booster heater with the heat being utilized as process heat. Excess preheat off-gas not required for preheat process is delivered to a second combustion furnace for burning the combustibles therein and the heat utilized for drying. From the quench zone the gas passes to two dust separators with the cleansed gas being utilized in up-draft and down-draft drying zones. The dust from the two separators and from the grate is passed to a final dust separator where dust is removed from the gas. Make-up lime is fed to the mixing zone from a suspension calcining furnace, reaching the mixing zone while still heated.