Ionic Liquid Absorption Medium for Corrosion-Free Gas Dehumidification

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Solution Overview

Problem

Current absorption media for dehumidifying moist gas mixtures, particularly in air conditioning systems and absorption chillers, face issues with corrosion, salt crystallization, poor absorption capability, and low heat transfer efficiency, especially when using ionic liquids and traditional aqueous solutions with aluminum components.

Innovation Solution

A process utilizing a liquid absorption medium comprising a mixture of dialkylimidazolium-based ionic liquids and specific salts, which reduces surface tension and contact angle with metal surfaces, enhancing wetting performance and heat transfer capabilities, thereby improving dehumidification efficiency and reducing equipment complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If aqueous solutions of lithium bromide, lithium chloride or calcium chloride are used as liquid absorption media, then dehumidification capability is achieved, but corrosion towards aluminium and other materials occurs necessitating expensive specific materials of construction

Engineering Contradiction:
Improvedehumidification capabilityVSAvoidcorrosion
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the chemical composition parameters of the absorption medium by using ionic liquids with specific cations (imidazolium, pyridinium, ammonium) and anions (halides, pseudohalides, carboxylates, phosphates, sulfonates) instead of traditional aqueous lithium bromide or calcium chloride solutions. This parameter change eliminates corrosion while maintaining dehumidification capability.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The invention uses composite ionic liquid formulations combining specific cation-anion pairs to create an absorption medium that simultaneously provides dehumidification capability and corrosion resistance. The composite nature of the ionic liquid (combining organic cation with inorganic or organic anion) allows tuning of both functional and protective properties.

Inventive Principle:
Principle #40Composite materials

2Object-affected harmful factors

If ionic liquids are used as absorption media, then corrosion resistance is improved, but absorption capability and heat transfer efficiency are poor

Engineering Contradiction:
Improvecorrosion resistanceVSAvoidabsorption capability
Core Design Contradiction:
Object-affected harmful factorsVSProductivity

Solution Approach 1:

The invention optimizes parameters including ionic liquid concentration (20-80 wt%), temperature ranges for absorption and desorption, and pressure conditions to maximize both absorption capability and heat transfer efficiency while maintaining corrosion resistance. Specific parameter ranges are identified for different ionic liquid compositions.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The invention applies different ionic liquid compositions to different functional zones: highly absorbent ionic liquids in the absorption section and ionic liquids with superior heat transfer properties in the heat exchange sections. This local optimization allows each zone to perform its specific function at maximum efficiency.

Inventive Principle:
Principle #3Local quality

3Reliability

If traditional drying media are used, then dehumidification is achieved, but equipment complexity and drying medium quantity are high

Engineering Contradiction:
ImprovedehumidificationVSAvoidequipment complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates unnecessary equipment components by using ionic liquids that can be directly applied to aluminium heat exchange surfaces without requiring additional protective coatings, barriers, or complex material systems. This simplification reduces both equipment complexity and drying medium quantity.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The ionic liquid serves multiple functions simultaneously: it acts as the absorption medium for water removal, provides corrosion protection for aluminium components, enhances heat transfer efficiency, and eliminates the need for separate protective material systems. This multi-functionality reduces overall equipment complexity.

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

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 proposed solution achieves improved heat transfer and dehumidification efficiency by lowering surface tension and contact angle with metal surfaces, leading to increased dehumidification capacity and reduced energy consumption in air conditioning systems and absorption chillers.

Implementation Method 1

contacting the moist gas mixture G with a liquid absorption medium AVE... at least partially absorbs water from the moist gas mixture G

Methodology Applied
Scientific EffectAbsorption: Absorption (physical)

Implementation Method 2

at least partially removing water from the liquid absorption medium AVE1... regeneration of the water-laden drying medium by heating to a temperature at which the water is desorbed again

Methodology Applied
Scientific EffectDesorption: Desorption

Data Source

PatentEP3925687B1Process for dehumidifying moist gas mixtures
Publication Date: 2023.06.21 EVONIK OPERATIONS GMBH
  • EP3925687B1 patent drawingFigure 1
  • EP3925687B1 patent drawingFigure 2
  • EP3925687B1 patent drawing

AI summary

The invention relates to a process for dehumidifying a moist gas mixture. The invention further relates to an apparatus for dehumidifying a moist gas mixture and to the use of said apparatus in the process according to the invention. The invention also relates to the absorption medium used in the process and the apparatus.