Method for controlling pH by electrical conductivity

Patent metadata

Field	Value
Publication number	US-11130688-B2
Application number	US-201716476731-A
Country	US
Kind code	B2
Filing date	Sep 15, 2017
Priority date	Jan 30, 2017
Publication date	Sep 28, 2021
Grant date	Sep 28, 2021

Abstract

Provided is a method for controlling a pH to a neutral range (pH 6 to 8) by adding an alkali or an acid to decarbonated water, including controlling the amount of the alkali or the acid added using an electrical conductivity meter. The decarbonated water is, for example, water obtained by decarbonating industrial water or groundwater so that the concentration of carbonic acid is 10 ppm or less. The method may further have a step of producing pure water by RO treatment of the decarbonated water with a pH adjusted to 6 to 8 by the pH control.

First claim

The invention claimed is:

1. A method for controlling a pH to a neutral range by adding an alkali or an acid to decarbonated water, comprising:
controlling an amount of the alkali or the acid added using an electrical conductivity meter,
a step of measuring the pH and electrical conductivity EC 1 [mS/m] of the decarbonated water;
a step of calculating electrical conductivity EC 2 [mS/m] of the water after the addition of the alkali or the acid according to the following formula; and
a step of adding the alkali or the acid so that the electrical conductivity after the addition of the alkali or the acid is the calculated EC 2 [mS/m]:
Electrical conductivity EC 2 [mS/m]=Electrical conductivity EC 1 [mS/m]+(ΔEC/ΔpH) [mS/m]×(Target pH−pH of decarbonated water),

wherein (ΔEC/ΔpH) is a ratio of an electrical conductivity relative to pH.

2. The method for controlling a pH according to claim 1 , wherein the decarbonated water is water obtained by decarbonating industrial water or groundwater so that the concentration of carbonic acid is 10 ppm or less.

3. The method for controlling a pH according to claim 1 , further comprising a step of producing pure water by RO treatment of the decarbonated water with a pH adjusted to 6 to 8 by the pH control.

4. The method for controlling a pH according to claim 1 , wherein ΔEC/ΔpH of the decarbonated water is experimentally determined in advance.

Assignees

• Kurita Water Ind Ltd

Inventors

• Iwasaki Mamoru
• Ikuno Nozomu

Classifications

• B01D61/026

  comprising multiple reverse osmosis steps · CPC title

• B01D61/12

  Controlling or regulating · CPC title

• B01D19/0068

  General arrangements, e.g. flowsheets (B01D19/0063 takes precedence) · CPC title

• B01D2311/12

  Addition of chemical agents · CPC title

• B01D2311/18

  pH control · CPC title