| 摘要 |
<p>PURPOSE:To reduce the treating cost by controlling the hydrochloric acid concn. in the waste water from a cooling stage, heating the water to carry out acidolysis, and then neutralizing the water. CONSTITUTION:Since the waste water 21 from the cooling stage contains dithionic acid generated in an absorption stage 2, hydrochloric acid 36 is added by a hydrochloric acid mixer 12 to obtain a 0.2-2% acid soln. The water is then heated to >=95 deg.C by steam 37 in a steam mixer 13, and introduced into a heat-insulated decomposition vessel 14 wherein dithionic acid is decomposed. After acidolysis, the water is introduced into a rough-neutralization stage 7, and the pH is controlled to 2-4 by slaked lime 38 to deposit gypsum. Slaked lime 38 is then added in a pH regulating stage 8 to control the pH to 7-9. As a result, the fluorine is converted into difficulty soluble calcium fluoride which is precipitated and removed.</p> |
