PURPOSE:To remove ammonia and acidic gas efficiently and obtain treated ammonia water having no adverse effect upon equipment for activated sludge in the subsequent steps, by treating surplus ammonia water in a specified two- step process. CONSTITUTION:Surplus ammonia water produced in a coke oven 8 is led into a vacuum ammonia water stripper 7 via a dry main 9 and a tar decanter 10 for stripping under reduced pressure through utilization of heat of circulated hot ammonia water to remove ammonia and acidic gas. Resulting condensed liquid at the top of the tower is refluxed to the dry main 9 via a condensate tank 13 and the treated ammonia water is discharged through a heat exchanger 15. The surplus ammonia water should pref. be treated with alkali for removal of formed precipitates and filtered for removal of oil before it is fed into the vacuum stripper. Preferred vacuum stripper is multi-layer tower filled with a filler having a low level of pressure loss.
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