Simulated concentration profiling of amine transformation products in the quaternary solvent system of (carbon dioxide + triethanolamine / 2-amino-2-methyl-1-propanol + piperazine + water)

College

Gokongwei College of Engineering

Department/Unit

Chemical Engineering

Document Type

Conference Proceeding

Source Title

76th PIChE National Convention

Publication Date

2015

Abstract

In the light of global climate change fears, wide range of technologies currently exist for separation, capture, and storage of carbon dioxide (CO₂) are being deployed rapidly and widely. The process of post-combustion amine based CO₂ capture relies on large scale use of aqueous amine solution. In such operations, it is associated with minor release of amine through the cleaned exhaust gas, as degraded solvent, as accidental spills, and amine transformation products in both liquid waste streams and atmosphere along with the treated flue gas. Thus, an understanding of the potential environmental impacts of amine solvents used in carbon capture and storage (CCS) is important as more of these technologies are moving to the pilot stage of development and will be more regularly operated. However, the evaluation of such impacts is complicated by several issues, including the early stage of technology and solvent development, the limited number of pilot facilities, the proprietary nature of many of the solvents, and the lack of validated sampling and analytical methods to determine the amount, type, and impacts of solvent degradation and by-products, within the technology, the liquid waste stream, and in the atmosphere after emission. It is clear that solvents with otherwise promising performance mat have challenges and considerable inherent problem due to the by-product formation, of which often neglected. In this regard, it is also necessary to study the concentration profiles of the by-products formed in aid of treating liquid waste streams. The study includes chemistry and reaction mechanism of amine transformation products.

The studied quaternary systems were generally written as CO₂-amine-PZ-H₂O, where amine could be TEA or AMP. PZ corresponds to piperazine, TEA to triethanolamine, and AMP to 2-amino-2-methyl-1-propanol. The chemical reactions of CO₂ with AMP, as –hindered amine is governed by the zwitterion mechanism, and with TEA, a tertiary amine is described by base-catalyzed hydration were carefully derived. The thermodynamic equilibrium constants for the considered reactions and the Henry’s constants for CO₂ were acquired from available data in literatures and assumed to be only temperature dependent, pressure independent, and are based on the mole fraction scale. The calculation was carried out using the electrolyte non-random two liquid (NRTL) model in a rigorous rate-based non-equilibrium process simulation on Aspen Plus® 8.6. the results yield reasonable predictions on product concentration profiled. The components behave according to their expected trends and the results are very promising.

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Disciplines

Chemical Engineering

Keywords

PIChE National Convention (76th : 2015 : Puerto Princesa; Palawan; Philippines)

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