| 摘要 |
<p>PURPOSE:To reduce steam consumption remarkably by adding H2SO4 to the supernatant liquid discharged from a gypsum separation stage, to adjust the concn. to 0.5-5%, introducing the supernatant liq. to an acid decomposing tank where the COD component is decomposed without forcibly degassing generated SO2. CONSTITUTION:The supernatant liquid 22 from a gypsum separation stage 4 is led to a sulphuric acid mixing tank 11 where H2SO4 is added to attain 0.5-5% H2SO4 concn., then the liquid is led to a steam mixing device 12 where the liq. is heated with steam 32 to 95-130 deg.C. The hot supernatant liquid 22 contg. added H2SO4 31 is led to a sufficiently insulated decomposing tank 13 where it is decomposed under a pressure above the saturated vapor pressure of the supernatant liquid 22. COD components contained in the liquid such as dithionic acid, S-N compds., etc. are removed in this stage without degassing generated SO2 forcibly from the decomposition tank 13, and the treated liquid 22' in the acid decomposition stage is then cooled to <=ca.80 deg.C. Then, it is led to a cooling stage where it is reused for replenishing water of the cooling stage 1.</p> |
