METHOD FOR PREVENTING SCALE OF MULTIEFFECT SEA WATER DESALTING DEVICE

摘要

PURPOSE:To economically obtain fresh water from the sea water by heating the deaerated sea water, which is added with an acid to lower its pH, continuously adding the acid thereto to maintain the water a =pH2 for a short period of time and adding an alkali thereto where the temp. of the concd. sea water attains =110 deg.C. CONSTITUTION:The acid is added to the sea water to lower its pH and to obtain the deaerated sea water of pH 7 to 8. The acid is continuously added to the deaerated sea water which is heated by continuous preheaters until the temp. rises to =90 deg.C, by which the pH thereof is maintained at =5.5. The amt. of the acid to be added is intermittently increased to maintain the pH of the deaerated sea water of =90 deg.C at =2 for a short period of time. Further, the alkali is added to the concn. sea water to increase the pH thereof to =6.5 where the temp. of the sea water concd. by evaporation of a part of the water in the deaerated sea water attains =110 deg.C. The number of the effect stages is increased as compared with the conventional method and the economy is improved.