Amine-Phosphonic Acid Absorbent for H2S Selective Removal
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Solution Overview
Problem
Existing absorbents for removing acidic gases from fluid streams, particularly hydrogen sulfide, require high regeneration energy and do not efficiently manage the CO2/H2S ratio, affecting the performance and efficiency of downstream processes like the Claus system.
Innovation Solution
An aqueous solution comprising at least one amine and one organic phosphonic acid, with specific molar ratios, optionally including a carboxylic acid, is used to selectively remove acidic gases, reducing regeneration energy consumption while maintaining absorption capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If aqueous solutions of inorganic or organic bases are used to remove acid gases, then the absorption capacity for acidic gases is improved, but the regeneration energy requirement increases
Solution Approach 1:
The patent changes the chemical parameters of the absorbent by using a buffered amine solution with specific buffer components (carboxylic acid buffers like AMPD, or phosphoric acid buffers) to modify the pH and buffering capacity. This allows the solution to maintain high absorption capacity while reducing the energy required for regeneration by controlling the chemical equilibrium during absorption and desorption cycles
Solution Approach 2:
The patent creates a composite absorbent system combining amine (primary, secondary, or tertiary) with buffer components (carboxylic acids or phosphoric acid) in specific concentrations. This composite formulation synergistically enhances absorption capacity through the buffering action while reducing regeneration energy by preventing excessive pH increase during acid gas absorption
2Manufacturing precision
If tertiary amines like MDEA are used for selective H2S removal, then H2S selectivity is improved, but the absorption rate of CO2 decreases
Solution Approach 1:
The patent introduces buffer components (carboxylic acid buffers or phosphoric acid buffers) as intermediaries that facilitate the absorption process. These buffers act as mediators that enhance the overall absorption rate by maintaining optimal pH conditions and providing additional absorption mechanisms, while the tertiary amine component continues to provide selective H2S removal through kinetic selectivity
Solution Approach 2:
The patent modifies the chemical parameters of the absorbent by adding buffer components that change the pH buffering capacity and chemical equilibrium conditions. This allows the system to maintain high H2S selectivity through the amine's kinetic selectivity while improving the overall absorption rate through the buffer's contribution to acid gas uptake
3Productivity
If primary or secondary amines like MEA or DEA are used, then the absorption rate is improved, but H2S selectivity decreases
Solution Approach 1:
The patent changes the composition parameters by using tertiary amines (which provide kinetic selectivity for H2S) in combination with buffer components. This parameter change maintains high absorption rate through the buffer's contribution while preserving H2S selectivity through the amine's kinetic properties, avoiding the need to use primary or secondary amines that would lose selectivity
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 solution effectively reduces regeneration energy requirements and achieves efficient selective removal of H2S, optimizing the CO2/H2S ratio for improved process efficiency and calorific value in gas streams.
Implementation Method 1
When acid gases dissolve in the absorbent, ions form with the bases. The absorbent can be regenerated by relaxing to a lower pressure and/or stripping, whereby the ionic species react back to acid gases and/or are stripped off using steam.
Implementation Method 2
When acid gases dissolve in the absorbent, ions form with the bases.
Data Source
Figure 1
AI summary
An absorbent for removing acid gases from a fluid flow comprises an aqueous solution of a) at least one amine and b) at least one phosphonic acid, wherein the molar ratio of b) to a) ranges between 0.0005 and 1.0. For example, the phosphonic acid is 1-hydroxyethane-1, 1-diphosphonic acid. Compared to absorbents based on amines or amine/promoter combinations, the absorbent requires less regeneration energy without substantially reducing the solution's capacity to absorb acid gases.