| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the consumption of a chemical to be used and a slug throughput by mixing an effluent from a dust removing column after the removal of fly ash with an effluent for an absorption column at a specific ratio, and treating the mixture into a flocculate through adding an alkali agent to adjust the mixture to a specific pH value and further, recovering a high-purity gypsum through solid/liquid separation treatment. SOLUTION: Effluent from a dust removing column 2 (drain from the dust removing column) is caused to pass through a fly ash removal/sedimentation tank 6 to perform the sedimentation/ separation of sludge. Next, an effluent from an a sorption column 1 (slurry for the absorption column) and the drain from the dust removing column 2 are mixed at a mixing ratio of 1:0.5-1:10 in a mixing tank 13. After that, this mixture is introduced into a reaction tank 14 together with part of a separated sludge from a second sedimentation tank 12 and an alkali agent is added to the mixture to adjust it to an pH value of 6-9. Consequently, sludge composed mainly of gypsum is flocculated from the mixture, so that this sludge is separated in a first sedimentation tank 15 and the separated water is partly returned to a desulfurization step, whilst the remainder is sent to a reaction tank 10, a flocculation tank 11 and the second sedimentation tank 12 in that order for treatment ad then calcium is removed form the separated water.</p> |
