Recirculation Loop pH Control With a Compensation Tank

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Solution Overview

Problem

Conventional continuous flow systems for treating process liquids face challenges in maintaining precise control over critical parameters like pH, especially in virus inactivation, due to long response times of sensors and difficulties in detecting and correcting deviations, leading to potential product loss and disruption in bioprocesses.

Innovation Solution

A recirculation loop system with a compensation tank, sensors, and controlled circulation flow, allowing for precise measurement and adjustment of liquid parameters, including pH, through a recirculation loop with a compensation tank, sensors, and controlled circulation flow, enabling precise measurement and adjustment of liquid parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If feedback control is used to maintain pH within allowable range, then process control is improved, but detection reliability deteriorates due to long sensor response time

Engineering Contradiction:
Improveprocess controlVSAvoidpH detection reliability
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The system performs preliminary action by continuously recirculating the process liquid through the compensation tank before measurement, allowing the liquid to be pre-adjusted and stabilized. The recirculation pump ensures that the liquid spends sufficient time in the compensation tank for the pH to be correctly adjusted before reaching the sensor, effectively compensating for the sensor's slow response time.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The compensation tank acts as an intermediary between the pH adjustment point and the sensor. It provides a buffer zone where the liquid can be pre-treated and stabilized before measurement, decoupling the fast-acting pH control from the slow-responding sensor and enabling reliable feedback control.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Device complexity

If pH adjustment is performed immediately downstream of mixing point, then process simplicity is improved, but detection reliability deteriorates due to short dwell time

Engineering Contradiction:
Improveprocess simplicityVSAvoidpH measurement reliability
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The system performs preliminary action by extending the dwell time in the compensation tank before measurement. The recirculation pump ensures that the liquid spends sufficient time in the compensation tank for the pH to be correctly adjusted and stabilized before reaching the sensor, effectively compensating for the short dwell time in the mixing region.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system segments the flow path into distinct regions: the mixing point where pH adjustment occurs, the compensation tank where the liquid is held and recirculated for sufficient dwell time, and the sensor measurement point. This segmentation allows each region to perform its specific function optimally without compromising the others.

Inventive Principle:
Principle #1Segmentation

3Measurement precision

If recirculation loop is added to improve measurement stability, then measurement precision is improved, but device complexity increases

Engineering Contradiction:
Improveliquid parameter measurement stabilityVSAvoidsystem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The compensation tank serves multiple functions: it acts as a mixing chamber, a holding tank for sufficient dwell time, a buffer for pH adjustment, and a recirculation loop for continuous processing. By making this single component multi-functional, the system achieves improved measurement precision without proportionally increasing device complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The recirculation loop is designed to be self-regulating, where the pump continuously circulates the liquid through the compensation tank based on the feedback from the pH sensor. The system automatically adjusts the recirculation flow to maintain pH within the allowable range without requiring external intervention, reducing operational complexity.

Inventive Principle:
Principle #25Self-service

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 system ensures stable and precise measurement of liquid parameters, reduces product loss, and maintains process stability by allowing for real-time adjustments, thereby enhancing the efficiency and reliability of continuous bioprocesses.

Implementation Method 1

a recirculation loop (110) comprising a compensation tank (111) having an inlet and an outlet and a circulation line (112) connecting the inlet and outlet of the compensation tank to one another, wherein the circulation line (112) comprises a pump (113) for generating a circulation flow

Methodology Applied
Scientific EffectPump: Pump

Implementation Method 2

at least one sensor (114) for determining at least one liquid parameter

Methodology Applied
Scientific EffectpH measurement:

Data Source

PatentEP4711439A1Flow system with recirculation loop
Publication Date: 2026.03.18 SARTORIUS STEDIM BIOTECH GMBH
  • EP4711439A1 patent drawingFigure 1
  • EP4711439A1 patent drawingFigure 2
  • EP4711439A1 patent drawingFigure 3

AI summary

The present invention relates to a flow system for the continuous treatment of a process liquid. The flow system comprises a recirculation loop comprising a compensation tank having an inlet and an outlet, a circulation line connecting the inlet and outlet of the compensation tank to one another, at least one sensor for determining at least one liquid parameter, supply lines for the process liquid and at least one treatment liquid which are connected to the recirculation loop, and discharge lines for treated process liquid and waste streams connected to the recirculation loop.