Tertiary Amine Absorbent Composition for Selective H2S Removal
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Solution Overview
Problem
Existing gas deacidification processes face challenges such as insufficient H₂S absorption selectivity relative to CO₂, slow CO₂ or COS absorption kinetics, high energy consumption for solvent regeneration, thermal stability issues, corrosivity, foaming, and operational instability due to liquid-liquid phase separation of absorbent solutions.
Innovation Solution
Aqueous absorbent solution comprising a specific combination of pentamethyldipropylenetriamine (PMDPTA) and N-methyldiethanolamine (MDEA), optionally with piperazine as an activator, which maintains a monophasic form under operating conditions, enhancing cyclic absorption capacity, CO₂ absorption kinetics, chemical stability, and reducing foaming and corrosivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional amine solutions are used for acid gas removal, then H2S absorption capacity is achieved, but H2S absorption selectivity relative to CO2 is insufficient
Solution Approach 1:
The patent uses a composite amine system combining hindered secondary amine (e.g., N-methyldiethanolamine) with tertiary amine (e.g., N-methyl-diisopropylamine or pentamethyldipropylenetriamine). This composite approach leverages the fast H2S reaction kinetics of hindered secondary amines while the tertiary amine provides high H2S absorption capacity, achieving both high capacity and selectivity simultaneously
Solution Approach 2:
The patent introduces piperazine as an activator component that locally enhances CO2 reaction rates at specific sites in the absorbent solution. This localized activation improves overall CO2 absorption kinetics without compromising the H2S selectivity provided by the hindered secondary amine structure
2Quantity of substance
If amine concentration is increased to improve absorption capacity, then cyclic absorption capacity increases, but energy consumption for regeneration increases
Solution Approach 1:
The patent optimizes the amine concentration parameters to achieve high cyclic absorption capacity while managing regeneration energy. By carefully selecting amine types and concentrations (e.g., specific ratios of hindered secondary to tertiary amines), the system achieves high capacity without proportionally increasing regeneration energy requirements
3Reliability
If absorbent solution is thermally regenerated, then solvent is deacidified, but energy consumption is high
Solution Approach 1:
The patent modifies the thermal regeneration parameters by optimizing reboiler temperature and pressure conditions. The specific amine composition allows effective regeneration at optimized temperature ranges, reducing the energy input required while maintaining reliable solvent deacidification
4Quantity of substance
If absorbent solution contacts acidic compounds, then acid gas absorption occurs, but foaming and operational instability occur
Solution Approach 1:
The patent incorporates small amounts of antifoaming agents (e.g., silicon-based compounds or organic esters) into the absorbent solution. These short-lived additives effectively suppress foam formation during operation without interfering with the acid gas absorption mechanism, maintaining operational stability
5Duration of action of moving object
If absorbent solution is used for extended periods, then continuous operation is achieved, but thermal stability decreases
Solution Approach 1:
The patent selects amine components with inherent resistance to thermal degradation and oxidative damage. The hindered secondary amine and tertiary amine combination provides self-protection against degradation, allowing extended continuous operation while maintaining thermal stability and absorbent performance
6Reliability
If absorbent solution absorbs acid gases, then deacidification occurs, but corrosivity increases
Solution Approach 1:
The patent uses a composite amine system where the specific combination of hindered secondary amine and tertiary amine creates a less corrosive environment compared to conventional amines. This composite approach maintains deacidification effectiveness while reducing corrosivity, allowing the use of standard carbon steel equipment
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 achieves selective H₂S removal with reduced CO₂ absorption, improved CO₂ absorption kinetics, lower energy consumption, enhanced chemical stability, and minimizes operational issues like foaming and phase separation, leading to more efficient and cost-effective gas deacidification.
Implementation Method 1
The gas is deacidified by contacting it with the absorbent solution... A chemical solvent is an aqueous solution containing a reagent that reacts preferentially with acidic compounds (H2S, CO2, COS, CS2, etc.) present in the treated gas to form salts
Implementation Method 2
The chemical reactions are reversible, allowing the solvent, now laden with acidic compounds, to be subsequently deacidified, for example, by heating. This releases the acidic compounds as gases
Data Source
Figure 1
AI summary
Disclosed is a method for removing acid compounds from a gaseous effluent, involving bringing, in the absorption column, a gaseous effluent into contact with an absorbent solution comprising water, 20% to 28% by weight of pentamethyldipropylenetriamine, and 5% to 35% by weight of N-methyldiethanolamine.