Babcock-hitachi Kabushiki Kaisha

Taiki Hashimoto

Hiroshi Kuroda

Masakatsu Nishimura

Shigeru Nozawa

Tsukasa Nishimura

Osamu Kanda

Kenji Shibata

A flue gas desulfurization process by which gypsum can be recovered; the amount of water used therein is small, the effluent is treated in a closed system, the equipment used is minimized, and no scaling occurs; and an apparatus therefor are provided, the process including the following first process and second process: the first process comprising a cooling step of cooling and dedusting a SO.sub.2 -containing flue gas and removing acidic gases, an absorption step of contacting the cooled gas with a slurry containing limestone and lime to absorb and remove SO.sub.x and form CaSO.sub.3, a pH-adjusting step of adding H.sub.2 SO.sub.4 to the resulting slurry, an oxidation step of blowing an oxygen-containing gas in the pH-adjusted slurry to form gypsum, a step of concentrating the resulting gypsum slurry, a step of adjusting the concentration of the resulting slurry, a step of centrifugally separating gypsum, and a step of treating the effluent discharged from the cooling step, and the second process comprising, in the first process, further feeding the slurry of the absorption step to the cooling step where unreacted limestone is reacted with SO.sub.2 to form CaSO.sub.3 .

Flue gas desulfurization process

A flue gas desulfurization process capable of producing a high purity gypsum and also making equipment employed as minimum as possible is provided, which process comprises the steps of cooling and dedusting flue gas containing SO.sub.x ; contacting the cooled gas with a slurry containing limestone to remove SO.sub.x by absorption and also form CaSO.sub.3 ; controlling the pH of the resulting slurry and then blowing air therein to form gypsum; and separating gypsum from the resulting slurry. As a modification of the above process, the slurry of the above second absorption step is further fed to the above first cooling step where unreacted limestone and SO.sub.x are reacted to form CaSO.sub.3.

Limestone-gypsum flue gas desulfurization process

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Kure, Japan

Taiki Hashimoto