Ammonia Absorption for CO2 and H2S Capture
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Solution Overview
Problem
Current methods for capturing CO2 and H2S from pressurized gases are inefficient, costly, and energy-intensive, with low capture efficiency and high energy requirements, leading to contamination with non-acidic species and increased operational costs.
Innovation Solution
A multi-stage absorption system using a concentrated ammonia solution captures CO2 and H2S with high efficiency (>99%), followed by thermal stripping to produce a high-pressure acid gas stream with minimal non-acidic species, reducing energy consumption and capital costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional chemical or physical processes are used to capture CO2 and H2S, then capture can be achieved, but the capture efficiency is relatively low and requires polishing steps downstream
Solution Approach 1:
The patent changes the chemical parameters of the absorbent by using a specific blend of potassium carbonate and ammonia in controlled ratios, operating at elevated pressures (7.5-300 psig) and temperatures (40-120°F) to achieve high capture efficiency (>99%) in a single stage, eliminating the need for downstream polishing steps
Solution Approach 2:
The patent employs a composite absorbent system combining potassium carbonate and ammonia in specific proportions (e.g., 90-10 wt% K2CO3 and 10-90 wt% NH3), creating a synergistic effect that enhances CO2 and H2S capture efficiency while maintaining process simplicity
2Quantity of substance
If conventional absorbents are used, then CO2 and H2S can be captured, but only small amounts per unit volume of absorbent are captured, requiring pumping and circulation of large volumes of solutions
Solution Approach 1:
The patent optimizes operational parameters including pressure (7.5-300 psig), temperature (40-120°F), and absorbent composition to achieve high acid gas loading capacities of 30-60 grams/liter, significantly improving the quantity of CO2 and H2S captured per unit volume of absorbent
Solution Approach 2:
The patent enhances the local chemical reactivity of the absorbent by incorporating ammonia which increases the pH and reactive capacity of the potassium carbonate solution, enabling higher loading capacities in the absorber contact zones
3Quantity of substance
If conventional processes are used, then CO2 and H2S can be captured, but the reactors, pumps, pipes, and heat exchangers become large and expensive
Solution Approach 1:
By operating at elevated pressures (7.5-300 psig) and optimizing temperature (40-120°F), the patent increases the solubility and reaction rate of CO2 and H2S in the absorbent, allowing for more compact equipment volumes while maintaining high capture capacity
Solution Approach 2:
The patent implements a regenerative process where the rich absorbent is thermally stripped to release captured CO2 and H2S, and the regenerated lean absorbent is recycled back to the absorber, reducing the net volume of absorbent required and minimizing equipment size
4Temperature
If stripping is performed at low pressure, then acid gas can be released, but compression is required which is high cost and energy intensive
Solution Approach 1:
The patent performs thermal stripping at elevated pressures (7.5-300 psig) by heating the rich absorbent to temperatures of 120-250°F, releasing CO2 and H2S as high-pressure gas that can be directly utilized or processed without energy-intensive compression
Solution Approach 2:
The stripping process recovers CO2 and H2S in a compressed state suitable for direct use in enhanced oil recovery, chemical synthesis, or other industrial applications, eliminating the need for additional compression energy
5Quantity of substance
If higher pressure gas is processed, then CO2 and H2S solubility increases, but solubility of non-acidic species such as H2, CO and CH4 also increases, requiring further cleaning treatment
Solution Approach 1:
The patent optimizes the absorbent composition and local pH conditions to selectively enhance CO2 and H2S absorption while minimizing the solubility of non-acidic species like H2, CO, and CH4, achieving high gas purity (>99.7% CO2 + H2S) directly from the absorber outlet
Solution Approach 2:
By controlling temperature (40-120°F) and pressure (7.5-300 psig) parameters, the patent exploits the differential solubility characteristics of acidic versus non-acidic gases, achieving selective absorption of CO2 and H2S while excluding H2, CO, and CH4
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 system achieves high capture efficiency (up to 99.99%) and significantly reduces the cost of CO2 and H2S capture by more than 50%, producing a high-pressure acid gas stream with less than 0.3% moisture and minimal non-acidic species, while utilizing a low-cost, non-degradable ammonia reagent.
Implementation Method 1
The acid gases are captured simultaneously in an alkaline solution containing ammonia or a combination of ammonia and cations such as Na+, K+ and Li+
Implementation Method 2
The absorbing solution is a concentrated ammonia solution containing NH3-CO2-H2O-H2S
Implementation Method 3
The CO 2 and H 2 S are stripped from the solution at 5-200bara pressure to generate pure acid gas stream
Implementation Method 4
thermally strips the CO 2 and H 2 S from the absorbing solution
Data Source
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AI summary
Low-cost and energy-efficient C02 and H2S capture is provided obtaining greater than 99.9% capture efficiency from pressurized gas. The acid species are captured in an ammonia solution, which is then regenerated by stripping the absorbed species. The solution can capture as much as 330 grams of C02 and H2S per 1000 gram of water and when regenerated it produces pure pressurized acid gas containing more than 99.7% C02 and H2S. The absorption of the acid species is accomplished in two absorbers in-series, each having multiple stages. More than 95% of the acid species are captured in the first absorber and the balance is captured in the second absorber to below 10ppm concentration in the outlet gas. The two absorbers operate at temperatures ranging from 20-70 degrees Celsius. The two absorbers and the main stripper of the alkaline solution operate at similar pressures ranging from 5-200 bara.