PURPOSE: To eliminate danger of boiling of sulfuric acid and to efficiently produce dilute sulfuric acid in a continuous stage by separating concentrated sulfuric acid into two stages and diluting it with dilution water in a mixer and successively cooling it by a cooler.
CONSTITUTION: Concentrated sulfuric acid is supplied to a first mixer 2 by a feed pump 1. On the other hand, industrial water for dilution is pressurized by a pump 3 and thereafter controlled by a control valve 4 for the flow rate of dilution water so that the concentration of sulfuric acid is regulated to about 80-90wt.% and supplied to the first mixer 2. This diluted sulfuric acid is immediately carried to a first cooler 5 and cooled at about 70-80°C therein. The cooled diluted sulfuric acid is sent to a second mixer 6 and diluted by industrial water controlled in flow rate by the control valve 4 for the flow rate of dilution water so that the concentration is regulated to about 70wt.%. Since the temperature of sulfuric acid at a point of this time is raised at about 100-110°C, sulfuric acid is cooled by a second cooler 7.
TAI NOBUO
SATO HIROSHI
ONISHI KATSUHISA
