| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a by-product salt refined from a salt water obtained by washing-treating the gas containing hydrogen chloride by washing water containing sodium hydroxide, in which the quality is raised to the grade which can be utilized as an antifreezing agent. <P>SOLUTION: The refining method of a by-product salt includes: a first calcium magnesium removing process 35 in which carbon dioxide and sodium hydroxide are added to a raw salt water, and carbonate of calcium and magnesium is deposited, and which carries out the separation removing; a concentration process 36 which condenses the salt water and forms a concentration raw salt water after the first calcium magnesium removing process 35; a second calcium magnesium removing process 37 in which carbon dioxide and sodium hydroxide are added to the concentration raw salt water, and carbonate of calcium and magnesium is deposited, and which carries out the separation removing; a crystallization process 38 in which a by-product salt is deposited from the concentration raw salt water, and which forms a salt slurry; and a dehydration process 39 which dehydrates the salt slurry and obtains the by-product salt, wherein the calcium weight concentration in the by-product salt is made at most 0.1%, and the magnesium weight concentration is made at most 0.1%. <P>COPYRIGHT: (C)2012,JPO&INPIT |
