Two-Vessel Liquid Degassing with Stripping Gas Separation

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Solution Overview

Problem

Existing methods for removing gases from liquids are not cost-effective and efficient, and there is a need for an improved process that can effectively remove both dissolved and undissolved gases in a sustainable manner.

Innovation Solution

A two-vessel process is employed, where a stripping gas is used to form large bubbles in the first vessel, removing dissolved gases, and undissolved stripping gas is removed in the second vessel, with controlled bubbling time and gas flow to enhance contact area and residence time for efficient gas removal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single large expansion vessel is used to remove gases from liquid, then gas removal functionality is provided, but the vessel size becomes excessively large and occupies excessive space

Engineering Contradiction:
Improvegas removal functionalityVSAvoidvessel size
Core Design Contradiction:
ReliabilityVSVolume of stationary object

Solution Approach 1:

The single large expansion vessel is divided into two separate vessels: a first expansion vessel for gas removal and a second expansion vessel for liquid volume accommodation. This segmentation allows each vessel to be optimized for its specific function, with the first vessel being much smaller than a single vessel would need to be to perform both functions.

Inventive Principle:
Principle #1Segmentation

2Reliability

If chemicals are used as gas scavengers to remove gases from liquid, then gas removal is facilitated, but the process becomes less cost-effective and sustainable

Engineering Contradiction:
Improvegas removal efficiencyVSAvoidcost-effectiveness
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The chemical gas scavenging method is replaced with a mechanical/physical system using two expansion vessels. The first vessel uses reduced pressure and bubble formation to remove gases, while the second vessel accommodates volume changes. This mechanical approach eliminates the need for continuous chemical addition, reducing operational costs and improving sustainability.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If the first expansion vessel is made large enough to remove all gases, then gas removal is effective, but the vessel occupies excessive space

Engineering Contradiction:
Improvegas removal effectivenessVSAvoidfirst vessel size
Core Design Contradiction:
ReliabilityVSVolume of stationary object

Solution Approach 1:

The gas removal function is segmented from the volume accommodation function. The first vessel is sized only for effective gas removal under reduced pressure, while the second vessel handles the liquid volume changes. This allows the first vessel to be much smaller than it would need to be if it had to perform both functions alone.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system uses parameter changes (reduced pressure in the first vessel) to enhance gas removal efficiency. By operating the first vessel at reduced pressure, gases are more effectively removed from the liquid, allowing for a smaller vessel size while maintaining effective gas removal.

Inventive Principle:
Principle #35Parameter changes

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 process effectively reduces the amount of dissolved and undissolved gases in the liquid, providing a space-effective and cost-effective solution by utilizing inert gases like nitrogen, with controlled parameters to optimize gas removal.

Implementation Method 1

a portion, such as e.g. a majority, of the dissolved gases in the supply liquid is removed in the first vessel by using a stripping gas, typically by forming relatively large bubbles as the stripping gas removes and replaces the dissolved gas in the liquid

Methodology Applied
Scientific EffectStripping: Sparging

Implementation Method 2

a portion, such as e.g. a majority, of the stripping gas is removed in the second vessel

Methodology Applied
Scientific EffectGravity separation: Gravitation

Implementation Method 3

a portion, such as e.g. a majority, of the stripping gas is removed in the second vessel

Methodology Applied
Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Data Source

PatentEP3831457B1System and process for degassing a liquid
Publication Date: 2025.10.01 HITACHI ENERGY LTD
  • EP3831457B1 patent drawingFigure 1
  • EP3831457B1 patent drawingFigure 2~3
  • EP3831457B1 patent drawingFigure 4~5

AI summary

The present invention relates to a process for removing gases from a liquid. The process comprising the steps of: (S1) introducing a supply liquid to a first vessel to form a liquid volume at a first vessel level inside of the first vessel, (S2) injecting a stripping gas into the liquid volume below the first vessel level to remove at least a portion of the dissolved gas contained in the liquid volume to produce a reduced gas containing liquid including at least a portion of the stripping gas, (S3) introducing the reduced gas containing liquid into a second vessel, (S4) accommodating the liquid from the reduced gas containing liquid in the second vessel to enable at least a portion of the stripping gas to be removed from the liquid to produce a gas treated liquid.