- Title
- Interactions of sulfur(IV) species with aqueous amine solutions and their impact on CO₂ capture in the post combustion capture process
- Creator
- Beyad, Yaser
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2014
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Carbon dioxide (CO₂) capture from flue gas using aqueous amine solutions is considered as one of the mature and most effective techniques among other carbon capture technologies. In addition to CO₂ and depending on the sulfur content of the fossil fuels, different amounts of SO₂ are present in flue gas resulting from the combustion of fuels in thermal power plants. Sulfur dioxide is known to interfere in CO₂ capture in the amine-based post combustion capture (PCC) process from flue gas. The focus of this project is to investigate the interactions of S(IV) species with aqueous amine solutions. The results of this study have been applied to the development of an amine-based PCC technique that is capable of capturing SO₂ in a single stream normally used to capture CO₂. After a brief introduction (Chapter 1), a broad literature review is presented, which covers all of the reactions of S(IV) species in aqueous amine solution (Chapter 2). A comprehensive investigation of S(IV) speciation in aqueous solution over a wide range of pH was conducted by employing ultraviolet spectrophotometric titrations. As a result, the equilibrium constants of the reactions of S(IV) species in aqueous solutions were accurately determined. Further, an additional equilibrium in the solution, the protonation of disulfite, was identified and quantified for the first time. The molar absorption of S(IV) species have also been reported over the studied wavelength range (Chapter 3). A problem was encountered in the data analysis step of the spectrophotometric titration study of S(IV) speciation in aqueous solution. Since high concentrations of sulfite were required to achieve a measurable amount of disulfite formation, the recorded absorbances at some wavelengths exceeded the linear absorption range of the instrument. All such data points were excluded from the analysis. Therefore, an innovative adaptation of the traditional linear regression method was developed in order to use all available information in the analysis while ignoring the missing values. The algorithm is based on the insight that multivariate linear regression can be formulated as a set of individual univariate linear regressions. All available information is used and the calculations are explicit (Chapter 4). In another study the possible interaction of S(IV) species with monoethanolamine (MEA) in aqueous solutions at high temperature was investigated by following the ¹H-NMR spectrum of the solution. The ¹H-NMR spectra did not show any interaction between S(IV) species and the amine. As there is no direct interaction between SO₂ and MEA, the impact of increasing amounts of accumulated SO₂ on the cyclic capacity of the MEA solution in CO₂ capture was modelled. Moreover, the impact of similar conditions on the reaction rate of CO₂ absorption in the solution was simulated (Chapter 5). Finally, based on the understanding of the physical and chemical properties of SO₂ absorption into aqueous amine solutions, an improved CO₂ capture process has been designed that uses a single solvent and is SO₂ tolerant. SO₂ absorption is carried out in the bottom of the absorber column into a bleed stream from the bulk solvent in which a recycle flow allows the absorbent to be near saturation in SO₂. Principles underlying the concept, specifically kinetic selectivity of SO₂ absorption over CO₂ and reactivity with amines, have been studied in the laboratory. There are clear advantages to a CO₂ capture process that is able to restrict the effects of SO₂ to only a fraction of the solvent with minimum disruption to the carbon capture process. In addition, the new design will result in reduced complexity and cost compared to existing options for SO₂ treatment (Chapter 6).
- Subject
- sulfur dioxide; carbon dioxide capture; post combustion capture; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1051192
- Identifier
- uon:15255
- Rights
- Copyright 2014 Yaser Beyad
- Language
- eng
- Full Text
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