To surely control the acid concn. of a pickling soln. and the soln. level in a circulating tank by discharging acid or supplying water respectively at a specified rate when the analyzed acid concn. is lower than the lower limit or higher than the upper limit.
Acid is supplied, water is supplied or acid is discharged by using a pickling tank and a circulating tank to control the acid concn. of the pickling tank. The target acid concn. and the target level of a pickling soln. in the circulating tank are preset. When the analyzed acid concn. is lower than the lower limit based on the analyzed concn. and measured level, the acid is discharged or supplied by the amts. obtained from equations I and II, and, when the analyzed concn. is higher than the upper limit, the acid is discharged or supplied by the amt. obtained from equations III and IV. In the equations. Cpo is the analyzed concn. before control, Cpmis the target acid concn., Cpp is the concn. of the acid supplied, and Hpp is the specific gravity of the supplied acid. Consequently, the unit requirements of the acid and water are lowered.
YOSHIOKA MASAHIRO
TAKECHI SHINICHI
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