Composite Amine Absorbent for H2S Selective Removal
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Solution Overview
Problem
Current methods for removing hydrogen sulfide and carbon dioxide from fluid streams, particularly in natural gas processing, face challenges in achieving high selectivity for hydrogen sulfide while maintaining efficient regeneration and avoiding excessive energy consumption, especially at high acid gas partial pressures.
Innovation Solution
A method involving an absorption step with an aqueous solution of specific amines of the formula (I), optionally combined with tertiary amines, to achieve a selectivity for hydrogen sulfide over carbon dioxide not greater than 8, allowing for high CO2 and H2S coabsorption, followed by regeneration and recycling of the absorbent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If highly sterically hindered secondary amines are used for selective H2S removal, then H2S selectivity is improved, but CO2 absorption capacity deteriorates
Solution Approach 1:
The patent uses a composite absorbent system combining highly sterically hindered secondary amine (providing H2S selectivity) with tertiary amine (providing CO2 absorption capacity). This composite approach allows simultaneous achievement of high H2S selectivity and adequate CO2 absorption, resolving the contradiction between selective H2S removal and CO2 co-absorption
Solution Approach 2:
The patent modifies the chemical composition parameters of the absorbent by specifying precise molar ratio ranges (0.05-0.50 for secondary amine to tertiary amine) and concentration ranges (1-50 wt% for secondary amine, 0.1-10 wt% for tertiary amine). These parameter adjustments optimize the balance between H2S selectivity and CO2 absorption capacity
2Quantity of substance
If total absorption of CO2 and H2S is performed, then CO2 removal is improved, but H2S selectivity deteriorates
Solution Approach 1:
The patent controls the molar ratio of highly sterically hindered secondary amine to tertiary amine within 0.05-0.50 and adjusts concentration parameters to achieve optimal balance. This allows the system to simultaneously absorb both CO2 and H2S while maintaining sufficient H2S selectivity (≥1.0), resolving the contradiction between total absorption and selective removal
3Manufacturing precision
If H2S-selective absorbents are used, then H2S separation is improved, but regeneration energy increases
Solution Approach 1:
The patent optimizes the concentration of highly sterically hindered secondary amine (1-50 wt%) and tertiary amine (0.1-10 wt%) to achieve the right balance between H2S separation efficiency and regeneration energy consumption. By controlling these parameters, the system maintains effective H2S separation while managing regeneration energy requirements
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 approach enables effective separation of hydrogen sulfide with controlled selectivity, allowing for high CO2 absorption while maintaining regeneration energy comparable to H2S-selective absorbents, suitable for natural gas treatment and pipeline gas processing.
Implementation Method 1
When acid gases dissolve in the absorbent, ions form with the bases
Implementation Method 2
CO2 is converted to bicarbonate in a slow reaction with the amine and with water
Implementation Method 3
The absorbent can be regenerated by depressurizing 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 4
stripped off using steam
Data Source
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AI summary
A process for removing hydrogen sulfide and carbon dioxide from a fluid stream comprises (a) an absorption step in which the fluid stream is brought into contact with an absorbent comprising an aqueous solution (i) of an amine of the general formula (I) wherein R1, R2 and R3 are independently selected from C1-4-alkyl and C1-4-hydroxyalkyl; R4 is each independently selected from hydrogen, C1-4-alkyl and C1-4-hydroxyalkyl; R5 is each independently selected from hydrogen, C1-4-alkyl and C1-4-hydroxyalkyl; X represents OH or NH(CR1R2R3); m represents 2, 3, 4 or 5; n represents 2, 3, 4 or 5; and o represents 0 or 1; and optionally (ii) comprising at least one tertiary amine, wherein the molar ratio of (i) to (ii) is greater than 0.05;wherein at least 90% of the hydrogen sulfide is removed from the fluid stream and the selectivity for hydrogen sulfide over carbon dioxide is not greater than 8, yielding a CO2- and H2S-laden absorbent; b) a regeneration step in which at least a partial stream of the CO2- and H2S-laden absorbent is regenerated and a regenerated absorbent is obtained; and c) a recycling step in which at least a partial stream of the regenerated absorbent is recycled back into absorption step a). The process allows for a high degree of hydrogen sulfide removal with simultaneously high coabsorption of carbon dioxide.