RESISTIVITY CONTROLLING APPARATUS FOR ULTRAPURE WATER AND CONTROLLING OF ULTRAPURE WATER

摘要

PROBLEM TO BE SOLVED: To make a control mechanism unnecessary and make a resistivity controlling apparatus compact by dividing ultrapure water fed according to consumption at a definite ratio, feeding either one to a film module to produce a small flow amount of water in which carbon dioxide or ammonia gas is dissolved and joining the water with a large flow amount of original ultrapure water. SOLUTION: It is preferable that carbon dioxide or ammonia gas permeation rate (cm3/cm2.sec.cm Hg) of a hollow fiber film is kept to >=1×10-5 and <=10 and film raw material is poly-4-methylpentene-1. In a hollow fiber film module 11, ultrapure water raw water is divided through a distributing part 15 into a hollow fiber film part 20 and bypass piping 19 at a fixed flow ratio. A small flow amount of ultrapure water in which carbon dioxide or ammonia gas is dissolved is produced in a range of a previously assumed fluctuating flow rate by the hollow fiber film part 20 and gas concentration in the ultrapure water is kept in nearly definite value which is >=90% of equilibrium concentration determined by gas pressure and water temperature. The water in which a gas is dissolved is mixed with ultrapure water raw water derived from by-pass piping 19 in a joining part 16 and ultrapure water controlled in resistivity is obtained from the outlet 18.