| 摘要 |
PROBLEM TO BE SOLVED: To optimally control the injection amt. of sodium carbonate into calcium ion-containing water to suppress increase in cost. SOLUTION: In a method for controlling the injection amt. of sodium carbonate which is injected in calcium ion-containing water 1 so as to remove calcium ions, the concn. (Ca2) of calcium ions in calcium ion-containing water 1 after a predetermined injection amt. of sodium carbonate is injected is detected and the corrected injection amt. of sodium carbonate is set on the basis of the concn. (Ca2) and sodium carbonate is injected in calcium ion-containing water 1 in the corrected injection amt. In this case, by introducing the ion concn. (Ca2) in calcium ion-containing water 1 after sodium carbonate is injected as a control variable, when inorg. carbon or the like is contained in calcium ion- containing water 1, feedback control considering the influcence of inorg. carbon or the like becomes possible.
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