- Title
- CO₂ capture by aqueous diamine solutions
- Creator
- Yu, Bing
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2019
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Aqueous monoamine solvents have been extensively studied for CO₂ absorption to reduce emissions from sources such as industrial power stations. However, to improve the economic viability of carbon capture technologies, solvents with a higher CO₂ absorption capacity and faster kinetics are urgently required. Diamines comprising two amino groups have potentially higher CO₂ absorption capacities and rates than monoamine solvents, such as monoethanolamine, and could be superior liquid absorbents for CO₂ absorption. In this research, we firstly perform the evaluation of the CO₂ absorption performance of various diamines using a bubble column, wetted-wall column and stopped-flow reactor, and we identify the relationships between the diamine molecular structure and the CO₂ absorption performance; Then we further investigate the underlying reaction mechanism between diamine solutions and CO₂ via the stopped-flow kinetic and ¹H/¹³C NMR analysis; Finally, we develop a new integrated absorption-mineralisation (IAM) process for CO₂ sequestration that couples a diamine-based CO₂ absorption and coal fly ash-based diamine regeneration. Based on experimental results from the evaluation of the CO₂ absorption performance of various diamine solvents, we found that all selected diamines have an absorption capacity of more than 0.78 moles of CO₂ per mole of amine under the conditions studied, which far outstrips the capacity of monoamines. The hydroxyl group decreases the rate of CO₂ absorption, while the methyl group and longer chain lengths increase the CO₂ absorption rate and capacity; the tertiary amino group exhibits the lowest kinetic performance. N-methylpropane-1, 3-diamine (MAPA) has both the fastest absorption rate and the highest mass transfer coefficient among all studied diamines in this study. As for those diamines which contain one primary and one tertiary amino group within their molecular structures (1°/3° diamines), the increase of the alkyl spacer between two amino groups within 1°/3° diamines promotes the CO₂ absorption rate, while a large decrease in their reactivities with CO₂ is observed when the tertiary amino group exists in the cyclic structure. In an effort to advance the understanding of diamine solvents-based CO₂ capture, the determination of the kinetic and equilibrium constants for a simple linear diamine N, N-dimethylethylenediamine (DMEDA) is performed. From the kinetic data, the formation of monocarbamic acid (DMEDACOOH) from the reaction of DMEDA with CO₂(aq) is the dominant reaction at high pH > 9.0 (k₇ = 6.99 × 10³ M⁻¹·s⁻¹). Below this pH, the formation of protonated monocarbamic acid (DMEDACOOH₂) via the pathway involving DMEDAH⁺ and CO₂(aq) becomes active and contributes to the kinetics despite the 10⁷-fold decrease in the rate constant between the two pathways. As for the diamine based IAM process, it was found that CaO and CaO rich coal fly ash are effective to regenerate the diamine - 3-Diethylaminopropylamine (DEAPA) by the decomposition of DEAPA carbamate species and the formation of calcium carbonate precipitates. Furthermore, the diamine-based IAM process displays a fast kinetics and a high stability for CO₂ sequestration and can reduce the leachability of some heavy metals in the fly ash. These process properties render this diamine-based IAM process a great potential for carbon capture and sequestration applications. Finally, to further advance the technology of diamine solvents-based CO₂ capture, this research suggests that more work is required in the future regarding the development of some new energy-saving processes or the implementation of more reliable diamine-screening work.
- Subject
- industrial power stations; aqueous monoamine solvents; CO2 absorption; carbon capture; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1409396
- Identifier
- uon:36012
- Rights
- Copyright 2019 Bing Yu
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 11 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 835 KB | Adobe Acrobat PDF | View Details Download |