Abstract: A venturi scrubber for scrubbing a gas stream to remove undesired gaseous and particulate components. The device includes a scrubber vessel having an external wall, an upper inlet for admitting the gas stream, and a collecting reservoir at the bottom of the vessel for collecting scrubbing liquid. An internal wall extends from the upper part of the external wall to define an axial converging passage for receiving and converging the gas stream from the inlet. An adjoined downwardly extending venturi passage receives the downwardly flowing gas stream from the converging passage, the internal wall abounding the venturi passage terminating above the liquid level at the reservoir; and an annular space is thereby defined between the internal and external walls. An outlet duct for the scrubbed gas stream intersects the annular space at the upper part of the space.

Abstract: A method for removing the oxy-anions of selenium from FGD scrubber purge water. The purge water is contacted with free hydroxyl radicals to effect oxidation of reduced forms of sulfur to sulfate and the destruction of sulfur-nitrogen compounds present in the purge water. The purge water is then subjected to chemical reduction and co-precipitation of selenium with an amount of ferrous ions effective to remove the oxy-anions of selenium in the liquid in less than 30 minutes of reaction time. The resultant ferrous-selenium solids generated are separated and stabilized to elemental selenium in a separate reaction vessel.

Abstract: A process is provided for removing vapor phase selenium species produced by the combustion of selenium and sulfur-containing fuel of the kind used to generate electric power in conjunction with a flue gas desulfurization process. In one process embodiment the flue gas leaving the combustion system is humidified by the injection of atomized water or a dilute alkaline slurry at a selected location upstream of the flue gas desulfurization system to cool the flue gas from a temperature of about 300.degree. F. to a temperature of about 280.degree. F. so as to enhance the selenium removal efficiency. In another process embodiment the flue gas leaving the combustion system is first humidified to cool the flue gas from a temperature of about 300.degree. F. to a temperature of about 200.degree. F. so as to enhance the selenium removal efficiency, and then an alkaline sorbent material is injected into the humidified flue gas.

Abstract: An efficient and cost-effective flue gas desulfurization apparatus for removing sulfur dioxide from waste gases is provided. The apparatus employs a substantially solids-free clear liquor scrubbing liquid and an, organic acid additive capable of maintaining a process pH of 4.5 to 6.0 under inhibited oxidation conditions in the absorber to accomplish sulfur dioxide removal while avoiding scale formation and encrustation. Calcium sulfite relative saturation is controlled to a desired low optimum level by maintaining the circulating calcium ion concentration at a corresponding, optimum low level. A smaller thickener unit area is required to produced calcium sulfite crystals with optimum settling and dewatering characteristics. A reactor system that promotes the formation of small, efficiently dewatered calcium sulfite solids is also provided.

Abstract: An efficient and cost-effective flue gas desulfurization process for removing sulfur dioxide from waste gases is provided. The process employs a substantially solids-free clear liquor scrubbing liquid and an organic acid additive capable of maintaining a process pH of 4.5 to 6.0 under inhibited oxidation conditions in the absorber to accomplish sulfur dioxide removal while avoiding scale formation and encrustation. Calcium sulfite relative saturation is controlled to a desired low optimum level by maintaining the circulating calcium ion concentration at a corresponding optimum low level. A smaller thickener unit area is required to produce calcium sulfite crystals with optimum settling and dewatering characteristics. A reactor system that promotes the formation of small, efficiently dewatered calcium sulfite solids is also provided.

Abstract: A flue gas desulfurization process and system employing a clear scrubbing liquor and an organic acid buffer conducted under forced oxidation conditions to produce a usable gypsum by-product without scrubber scaling and abrasion is provided. Calcium ion concentration and chloride concentration are suppressed to improve limestone utilization, reduce the consumption of organic acids and improve crystal growth. The FGD system includes a limestone reactor for precipitating gypsum separate from the scrubber system which allows the recovery of pure carbon dioxide and a clarifier/softener tank which allows the production of gypsum-free clear scrubbing liquor and a drier gypsum filter cake.