Continuous pH Adjustment With Split-Flow Feedback Control
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Solution Overview
Problem
Existing pH adjustment methods in continuous processes are slow, prone to overshooting the target pH value, and lack resilience against sudden changes in process liquid composition and flow rate, leading to adverse reactions and increased salt load.
Innovation Solution
A method that adjusts pH in a continuous process by mixing process and treatment liquids with a controlled second flow rate composed of a predetermined and variable portion, using sensors to determine liquid parameters and dynamic control to maintain the pH within the allowable range, reducing or avoiding overshoots and salt introduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If treatment liquid is added slowly to avoid pH overshoot, then pH control precision is improved, but pH adjustment speed deteriorates
Solution Approach 1:
The system performs preliminary action by continuously measuring pH and predicting future pH trends before overshoot occurs. The controller uses this predictive information to preemptively adjust the treatment liquid flow rate, preventing overshoot while maintaining faster adjustment speeds compared to reactive control methods.
Solution Approach 2:
The system implements continuous feedback by monitoring pH in real-time and using this information to dynamically adjust the treatment liquid flow rate. The feedback loop enables the controller to respond to pH changes immediately, balancing precision and speed by adjusting flow rate based on current pH status and trend.
2Device complexity
If pH measurement is performed at outlet far from treatment liquid introduction point, then measurement position is simplified, but control response time deteriorates due to substantial delay
Solution Approach 1:
The system uses continuous real-time pH feedback from the outlet measurement to immediately adjust treatment liquid flow rate. This closed-loop control compensates for the transport delay by continuously updating the control action based on current pH status, maintaining effective control despite the spatial separation between injection and measurement points.
Solution Approach 2:
The controller dynamically adjusts the treatment liquid flow rate based on real-time pH measurements and process conditions. This dynamic control adapts to changing pH trends and flow rates, optimizing the response time by varying the injection rate rather than using a fixed rate, thereby compensating for the measurement delay.
3Speed
If treatment liquid is added quickly to achieve fast pH adjustment, then pH adjustment speed is improved, but pH overshoot increases causing detrimental effects
Solution Approach 1:
The system performs preliminary action by continuously monitoring pH and predicting future pH values based on current trends. This allows the controller to anticipate when the target pH will be reached and preemptively reduce the treatment liquid flow rate, preventing overshoot while maintaining fast adjustment speeds throughout most of the neutralization process.
Solution Approach 2:
The treatment liquid flow rate is dynamically adjusted throughout the neutralization process. The system starts with higher flow rates for rapid pH change when far from the target, then smoothly transitions to lower flow rates as the target pH approaches, optimizing both speed and precision through continuous adaptation of the injection rate.
4Device complexity
If known pH adjustment methods are used, then process simplicity is maintained, but resilience against sudden changes in process liquid composition and flow rate deteriorates
Solution Approach 1:
The controller dynamically adapts the treatment liquid flow rate in response to sudden changes in process liquid composition or flow rate. By continuously monitoring pH and adjusting the injection rate in real-time, the system maintains resilience against process variations without requiring complex pre-programming or multiple fixed-rate pumps.
Solution Approach 2:
The continuous pH feedback mechanism enables the system to automatically respond to unexpected changes in process conditions. When process liquid composition or flow rate changes suddenly, the pH measurement detects the deviation and the controller adjusts the treatment liquid flow rate accordingly, providing inherent resilience against process variations.
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
Enables quicker and more accurate pH adjustment with improved resilience against process liquid variations, minimizing adverse reactions and salt load, while maintaining process stability and product quality.
Implementation Method 1
a treatment liquid (usually acid or base) is added to the entire batch of process fluid until a target pH value is reached
Implementation Method 2
continuously monitoring the pH value of the process liquid batch and controlling the amount of treatment liquid added, for example by means of a dynamic controller such as a proportional-integral-derivative (PID) controller
Data Source
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AI summary
The invention relates to a method for adjusting the pH of a process liquid in a continuous process, comprising: (a.) providing the process liquid in a first volume flow having a first flow rate (f1), (b.) providing at least one treatment liquid in a second volume flow having a second flow rate (f2), (c.) mixing the at least one treatment liquid with the process liquid to produce a pH-adjusted process liquid, wherein the second flow rate is composed of a predetermined portion (fp) and a variable portion (fv), and wherein the variable portion (fv) is controlled based on at least one liquid parameter (pHa) of the pH-adjusted process liquid.