Buffered Aqueous Gas Capture Process
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Solution Overview
Problem
Conventional methods for capturing target gases from dilute gas streams, such as carbon dioxide from atmospheric air or flue gas, are inefficient and require high temperatures, making them economically and energetically costly.
Innovation Solution
A process involving an aqueous solution with a buffer species and a catalyst to enrich target gases by transferring them from a gas stream to an aqueous solution, followed by processing to shift the chemical equilibrium and liberate the target gas, using techniques like membrane separation and gas stripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional methods (calcium hydroxide causticization, Benfield Process) are used to capture target gases from dilute gas streams, then the target gas can be captured, but the process requires high temperatures (at least 100°C, typically 900°C in kiln) making it energetically costly and economically inefficient
Solution Approach 1:
The invention changes the chemical parameters of the absorbent system by using a buffer species (weak acid or weak base) instead of strong alkali metals. This parameter change allows the system to operate at lower temperatures while achieving effective target gas capture, thereby reducing energy consumption while maintaining gas concentration capability
Solution Approach 2:
The buffer species acts as an intermediary substance that mediates between the target gas and the absorbent system. The buffer species forms intermediate chemical complexes that enable efficient gas absorption at lower temperatures, avoiding the need for high-temperature kiln processing while still achieving effective gas capture and concentration
2Quantity of substance
If conventional high-temperature causticization processes are used, then target gas capture is achieved, but the process becomes economically costly and complex
Solution Approach 1:
The buffer species serves as an intermediary that simplifies the overall process by enabling direct absorption at lower temperatures. This eliminates the need for complex high-temperature kiln operations and multi-step causticization processes, thereby reducing device complexity while maintaining effective target gas concentration
Solution Approach 2:
The invention replaces the mechanical/thermal system (high-temperature heating and kiln processing) with a chemical system based on buffer species interactions. This substitution achieves the same target gas capture function through chemical equilibrium and buffer capacity rather than thermal energy input, simplifying the overall process architecture
3Device complexity
If dilute aqueous solutions are used for gas absorption, then the process is simple, but the target gas concentration in the aqueous phase is insufficient requiring complex processing
Solution Approach 1:
The invention changes the chemical parameters of the aqueous solution by introducing a buffer species that shifts the equilibrium to favor higher dissolved target species concentration. This parameter change allows the system to maintain simplicity while achieving sufficient concentration for effective gas capture
Solution Approach 2:
The buffer species creates localized chemical environments with different properties - regions of high buffer capacity that promote target gas dissolution. This local quality enhancement allows the overall process to remain simple while achieving high dissolved target species concentration in specific zones of the absorption system
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
This method effectively enriches target gases, increasing their concentration by up to several orders of magnitude, making it economically viable and reducing energy requirements compared to traditional methods.
Implementation Method 1
contacting a gas including a target species with an aqueous solution including a buffer species, such that some of the target species is transferred from the gas to the aqueous solution. The target species forms a dissolved target species in the aqueous solution.
Implementation Method 2
a membrane fluidically coupled to the gas absorber and adapted to separate a buffer species in the aqueous buffer solution from a dissolved target species
Implementation Method 3
a gas stripper, a membrane distillation unit, or both are fluidically coupled to the membrane and configured to shift a chemical equilibrium between the dissolved target species and the target species to liberate the target species
Implementation Method 4
The aqueous solution may further include a catalyst for increasing the rate of transfer of the target species from the gas to the aqueous solution.
Data Source
AI summary
Capturing a target gas includes contacting a gas mixture including a target species with an aqueous solution including a buffer species, and transferring some of the target species from the gas mixture to the aqueous solution. The target species forms a dissolved target species in the aqueous solution, and the aqueous solution is processed to yield a first aqueous stream and a second aqueous stream, where the equilibrium partial pressure of the target species over the second aqueous stream exceeds the equilibrium partial pressure of the target species over the first aqueous stream. At least some of the dissolved target species in the second aqueous stream is converted to the target species, and the target species is liberated from the second aqueous stream. The target species can be collected and/or compressed for subsequent processing or use.