Chilled Solvent Contactors for Natural Gas H2S Removal
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Solution Overview
Problem
Current membrane separation technologies for natural gas streams require significant amounts of amine solvent to remove hydrogen sulfide (H2S) and carbon dioxide (CO2), with inefficiencies in reaction temperatures and contact times leading to high solvent circulation and CO2 reaction rates.
Innovation Solution
The method involves using a membrane separation system to create a partially-treated gas stream and a permeate stream, which are then cooled before being contacted with chilled lean solvent streams containing hindered amines in separate contactors, optimizing H2S selectivity and reducing CO2 reaction rates by chilling the solvent and minimizing contact time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amine solvent is used to remove H2S and CO2 from natural gas stream, then H2S removal efficiency is improved, but solvent circulation quantity increases significantly
Solution Approach 1:
The patent applies parameter changes by cooling the amine solvent to lower temperatures (e.g., 40-80°F) to alter its reaction characteristics. This temperature reduction slows down the CO2 reaction rate while maintaining H2S removal efficiency, thereby reducing the required solvent circulation quantity by up to an order of magnitude
Solution Approach 2:
The system dynamically adjusts the solvent temperature and contact time parameters to optimize performance. By controlling the solvent temperature and limiting contact time, the system achieves selective H2S removal while minimizing CO2 reaction, thus reducing overall solvent requirements
2Reliability
If contact time between gas stream and amine solvent is increased, then H2S removal is improved, but CO2 reaction increases
Solution Approach 1:
The patent applies partial action by providing only enough contact time for the amine solvent to remove H2S effectively, but not enough time for significant CO2 reaction to occur. This optimized contact time allows selective H2S removal while minimizing unwanted CO2 absorption
Solution Approach 2:
The system changes the temperature parameter to lower it, which slows down the CO2 reaction rate. This temperature reduction allows shorter contact times to be used without compromising H2S removal efficiency, thereby preventing excessive CO2 reaction
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 significantly reduces the solvent flow required for separation, enhancing H2S selectivity and minimizing CO2 interaction, thereby reducing the overall solvent usage by up to an order of magnitude.
Implementation Method 1
Membranes work by preferentially permeating the acid gas (e.g., CO2 and H2S) through the membrane to a lower pressure, which cools both the process gas and permeate
Implementation Method 2
The amines achieve selective H2S removal by reacting more quickly with H2S than CO2. At colder temperatures (50-80 °F) the reactions with CO2 slow down significantly and the reaction becomes even further selective towards H2S
Data Source
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AI summary
A method of separating impurities from a natural gas stream. CO2 and H2S are separated from the natural gas stream in a membrane separation system, thereby creating a partially -treated gas stream and a permeate gas stream, both of which are at a lower temperature than the natural gas stream. The partially-treated gas stream is contacted with a first lean solvent stream in a first contactor to separate H2S from the partially -treated gas stream, thereby producing a first rich solvent stream and a fully -treated gas stream. The permeate gas stream is contacted with a second lean solvent stream in a second contactor to separate H2S therefrom to produce a second rich solvent stream and a CO2 gas stream. H2S and CO2 are removed from the first and second rich solvent streams, thereby producing the first and second lean solvent streams.