pH Control in Decarbonated Water via Conductivity Feedback
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Solution Overview
Problem
Existing methods for adjusting the pH of decarbonated water to a neutral range (6 to 8) are challenging due to the poor time response of glass electrode pH meters and the high pH buffering action of carbonic acid, making it difficult to control the amount of alkali or acid added effectively.
Innovation Solution
Using an electrical conductivity meter to control the amount of alkali or acid added to decarbonated water by calculating the target electrical conductivity based on the initial conductivity and pH changes, allowing for rapid adjustment to a neutral pH range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a glass electrode pH meter is used to adjust the pH of decarbonated water, then the pH measurement can be performed, but the time response is poor and the controllability is low
Solution Approach 1:
The patent changes the measurement parameter from pH (which has poor time response in decarbonated water) to electrical conductivity (which has excellent time response). The control system measures electrical conductivity and uses a pre-established relationship between conductivity and pH to determine the appropriate alkali addition amount, thereby achieving fast response while maintaining measurement accuracy.
2Stability of the object's composition
If alkali is added to adjust the pH of decarbonated water to neutral, then the pH can be controlled to 6-8, but the pH changes significantly with very small amounts of alkali due to lack of buffering action
Solution Approach 1:
The patent implements a feedback control system where electrical conductivity is continuously measured after alkali addition. The control system compares the measured conductivity with the target conductivity (corresponding to pH 6-8) and adjusts the alkali addition amount accordingly. This feedback mechanism enables precise control despite the high sensitivity of decarbonated water pH to alkali addition.
Solution Approach 2:
The patent uses electrical conductivity as an intermediary parameter to control pH adjustment. Instead of directly measuring and controlling pH (which is difficult due to high sensitivity), the system measures conductivity and uses the established conductivity-pH relationship to indirectly control pH, thereby improving controllability.
3Measurement precision
If two-stage RO membranes are used to remove electrolytes including carbonic acid and hardness components, then water quality of 5 MΩ·cm or more can be achieved, but the process complexity increases
Solution Approach 1:
The patent performs preliminary decarbonation using a membrane degasifier before the RO treatment. By removing carbonic acid in advance, the need for two-stage RO membranes is eliminated, and a single RO membrane can achieve the required water quality of 5 MΩ·cm or more. This preliminary action simplifies the overall process while maintaining high water quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The electrical conductivity meter's high responsiveness enables precise and rapid control of pH adjustments, overcoming the limitations of glass electrode pH meters and achieving stable pH control in decarbonated water.
Implementation Method 1
controlling the amount of the alkali or the acid added using an electrical conductivity meter
Implementation Method 2
RO (Reverse Osmosis) membrane device
Implementation Method 3
SS and Al are completely removed using the decontaminating membrane
Data Source
AI summary
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.