Treatment of waste water from flue gas desulphurisation

摘要

In a wet lime process for treating flue gas containing sulphur and nitrogen oxides, the pH of the filtrate 110 remaining after gypsum 109 is separated 108 is adjusted to 3 to 4 with acid 112 and an oxidising agent such as hypochlorite is added 111 to raise the oxidation state of metals such as manganese, and thereafter an alkaline agent 114 is added 116 to adjust the pH value to 7 to 9.5 and precipitate out such metals for solid-liquid separation in a membrane separation tank 117, while retaining magnesium in solution. A reducing agent 115 such as bisulphite may be added to the content of tank 116 to remove residual chlorine.